US20150346866A1 - Touch panel - Google Patents

Abstract

To increase the detection sensitivity of a touch panel, provide a thin touch panel, provide a foldable touch panel, or provide a lightweight touch panel. A display element and a capacitor forming a touch sensor are provided between a pair of substrates. Preferably, a pair of conductive layers forming the capacitor each have an opening. The opening and the display element are provided to overlap each other. A light-blocking layer is provided between a substrate on the display surface side and the pair of conductive layers forming the capacitor.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• One embodiment of the present invention relates to a touch panel.
• Note that one embodiment of the present invention is not limited to the above technical field. One embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, an electronic appliance, a lighting device, an input device, an input/output device, a method for driving any of them, and a method for manufacturing any of them.
• In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A semiconductor element such as a transistor, a semiconductor circuit, an arithmetic device, and a memory device are each an embodiment of a semiconductor device. An imaging device, a display device, a liquid crystal display device, a light-emitting device, an electro-optical device, a power generation device (including a thin film solar cell, an organic thin film solar cell, and the like), and an electronic appliance may each include a semiconductor device.
• 2. Description of the Related Art
• Recent display devices are expected to be applied to a variety of uses and become diversified. For example, a smartphone and a tablet with a touch panel are being developed as portable information terminals.
• Patent Document 1 discloses a flexible active matrix light-emitting device in which an organic EL element and a transistor serving as a switching element are provided over a film substrate.
REFERENCEPatent Document
• [Patent Document 1] Japanese Published Patent Application No. 2003-174153
SUMMARY OF THE INVENTION
• What is desirable is a touch panel in which a display panel is provided with a function of inputting data with a finger, a stylus, or the like touching a screen as a user interface.
• Furthermore, it is demanded that an electronic appliance using a touch panel is reduced in thickness and weight. Therefore, a touch panel itself is required to be reduced in thickness and weight.
• For example, in a touch panel, a touch sensor can be provided on the viewer side (the display surface side) of a display panel.
• In a touch panel where a capacitive touch sensor is provided so as to overlap with the display surface side of a display panel, when the distance between a pixel or a wiring of the display panel and an electrode or a wiring of the touch sensor is reduced, the touch sensor is likely to be influenced by noise caused when the display panel is driven by the touch sensor, which results in a reduction of the detection sensitivity of the touch panel in some cases.
• One object of one embodiment of the present invention is to improve detection sensitivity of a touch panel. Another object is to provide a thin touch panel. Another object is to provide a foldable touch panel. Another object is to provide a lightweight touch panel. Another object is to provide a touch panel with high reliability.
• Another object is to provide a novel input device. Another object is to provide a novel input/output device.
• Note that the descriptions of these objects do not disturb the existence of other objects. In one embodiment of the present invention, there is no need to achieve all the objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
• One embodiment of the present invention is a touch panel including a first substrate, a second substrate, a first conductive layer, a second conductive layer, a first light-emitting element, a second light-emitting element, and a light-blocking layer. The first conductive layer has a first opening, and the second conductive layer has a second opening. The first conductive layer and the second conductive layer form a capacitor. The first opening and the first light-emitting element overlap with each other in a region. The second opening and the second light-emitting element overlap with each other in a region. The first conductive layer and the light-blocking layer overlap with each other in a region. The second conductive layer and the light-blocking layer overlap with each other in a region. The first light-emitting element and the second light-emitting element are positioned between the first substrate and the second substrate in a region. The first conductive layer and the second conductive layer are positioned between the first light-emitting element or the second light-emitting element and the second substrate in a region. The light-blocking layer is positioned between the first conductive layer or the second conductive layer and the second substrate in a region.
• In the above embodiment, a CR value of the first conductive layer or the second conductive layer is preferably greater than 0 s and less than or equal to 1×10⁻⁴s.
• In the above embodiment, an aperture ratio of the first conductive layer or the second conductive layer is preferably greater than or equal to 20% and less than 100% in a region.
• In the above embodiment, it is preferable that the touch panel include a third conductive layer, the third conductive layer be provided closer to the first substrate than the first conductive layer or the second conductive layer, and a distance between the first conductive layer and the third conductive layer or a distance between the second conductive layer and the third conductive layer be greater than or equal to 25 nm and less than or equal to 50 μm in a region.
• In the above embodiment, it is preferable that the touch panel include a third light-emitting element, the third light-emitting element is positioned between the first substrate and the second substrate in a region, and the third light-emitting element and the first opening overlap with each other in a region.
• In the above embodiment, it is preferable that the touch panel include a fourth light-emitting element, the fourth light-emitting element is positioned between the first substrate and the second substrate in a region, and the fourth light-emitting element and the second opening overlap with each other in a region.
• In the above embodiment, it is preferable that the touch panel include an insulating layer, the first conductive layer and the second conductive layer overlap with each other in a region, and the insulating layer is positioned between the first conductive layer and the second conductive layer in a region.
• In the above embodiment, it is preferable that the touch panel include a fourth conductive layer, a fifth conductive layer, and an insulating layer. Here, the fourth conductive layer and the light-blocking layer overlap with each other in a region, the fifth conductive layer and the light-blocking layer overlap with each other in a region, the fifth conductive layer and the second conductive layer overlap with each other in a region, the insulating layer is positioned between the first conductive layer and the fifth conductive layer in a region, the insulating layer is positioned between the second conductive layer and the fifth conductive layer in a region, and the insulating layer is positioned between the fourth conductive layer and the fifth conductive layer in a region. The insulating layer has a third opening and a fourth opening. The first conductive layer and the fifth conductive layer are electrically connected to each other through the third opening. It is preferable that the fourth conductive layer and the fifth conductive layer be electrically connected to each other through the fourth opening.
• It is preferable that the touch panel further include a fifth light-emitting element. At this time, it is preferable that the fourth conductive layer have a fifth opening, the fifth light-emitting element is positioned between the first substrate and the second substrate in a region, and the fifth opening and the fifth light-emitting element overlap with each other in a region.
• One embodiment of the present invention can improve the detection sensitivity of a touch panel. Alternatively, a thin touch panel can be provided. Alternatively, a foldable touch panel can be provided. Alternatively, a lightweight touch panel can be provided. Alternatively, a touch panel with high reliability can be provided.
• Alternatively, a novel input device can be provided. Alternatively, a novel input/output device can be provided. Note that the description of these effects does not disturb the existence of other effects. One embodiment of the present invention does not necessarily achieve all the effects listed above. Other effects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIGS. 1A and 1B show a structure example of a touch panel module of an embodiment.
• FIGS. 2A to 2C show a structure example of a touch sensor of an embodiment.
• FIGS. 3A to 3C show structure examples of a touch sensor of an embodiment.
• FIGS. 4A and 4B show structure examples of a touch sensor of an embodiment.
• FIGS. 5A and 5B show structure examples of a touch sensor of an embodiment.
• FIG. 6 shows a structure example of a touch sensor of an embodiment.
• FIGS. 7A to 7G show structure examples of a touch panel of an embodiment.
• FIG. 8 shows a structure example of a touch panel of an embodiment.
• FIGS. 9A to 9E show structure examples of a touch panel of an embodiment.
• FIGS. 10A and 10B show a structure example of a touch panel of an embodiment.
• FIGS. 11A and 11B show a structure example of a touch panel of an embodiment.
• FIGS. 12A and 12B show a structure example of a touch panel of an embodiment.
• FIG. 13 shows a structure example of a touch panel of an embodiment.
• FIG. 14 shows a structure example of a touch panel of an embodiment.
• FIG. 15 shows a structure example of a touch panel of an embodiment.
• FIGS. 16A and 16B are a block diagram and a timing chart of a touch sensor of an embodiment.
• FIG. 17 is a circuit diagram of a touch sensor of an embodiment.
• FIGS. 18A to 18G each illustrate an electronic appliance of an embodiment.
• FIGS. 19A to 19I illustrate electronic appliances of an embodiment.
• FIG. 20 shows a structure of a touch panel of an example.
• FIGS. 21A to 21C are photographs of a touch panel of an example.
• FIG. 22 shows measurement results of parasitic capacitance and parasitic resistance of a touch panel of an example.
DETAILED DESCRIPTION OF THE INVENTION
• Embodiments will be described in detail with reference to drawings. Note that the present invention is not limited to the description below, and it is easily understood by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Accordingly, the present invention should not be interpreted as being limited to the content of the embodiments below.
• Note that in the structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description of such portions is not repeated. Further, the same hatching pattern is applied to portions having similar functions, and the portions are not especially denoted by reference numerals in some cases.
• Note that in each drawing described in this specification, the size, the layer thickness, or the region of each component is exaggerated for clarity in some cases. Therefore, embodiments of the present invention are not limited to such a scale.
• Note that in this specification and the like, ordinal numbers such as “first”, “second”, and the like are used in order to avoid confusion among components and do not limit the number.
• Note that the terms “film” and “layer” can be interchanged with each other depending on the case or circumstances. For example, the term “conductive layer” can be changed into the term “conductive film” in some cases. Also, the term “insulating film” can be changed into the term “insulating layer” in some cases.
Embodiment 1
• In this embodiment, a structure example of a touch panel of one embodiment of the present invention will be described with reference to drawings. In the description below, a capacitive touch sensor is used as a touch sensor of a touch panel.
• Note that in this specification and the like, a touch panel has a function of displaying or outputting an image or the like on or to a display surface and a function of a touch sensor capable of sensing contact or proximity of an object such as a finger or a stylus on or to the display surface. Therefore, the touch panel is an embodiment of an input/output device.
• In this specification and the like, a structure in which a connector such as a flexible printed circuit (FPC) or a tape carrier package (TCP) is attached to a substrate of a touch panel, or a structure in which an integrated circuit (IC) is directly mounted on a substrate by a chip on glass (COG) method is referred to as a touch panel module or simply referred to as a touch panel in some cases.
• A capacitive touch sensor that can be used for one embodiment of the present invention includes a capacitor. The capacitor can have a structure in which a dielectric is provided between a first conductive layer and a second conductive layer. At this time, part of the first conductive layer and part of the second conductive layer each function as an electrode of the capacitor. The other part of the first conductive layer and the other part of the second conductive layer may each function as a wiring.
• Examples of the capacitive touch sensor are a surface capacitive touch sensor and a projected capacitive touch sensor. Examples of the projected capacitive touch sensor are a self-capacitive touch sensor, a mutual capacitive touch sensor, and the like, which differ mainly in the driving method. The use of a mutual capacitive type is preferable because multiple points can be sensed simultaneously.
• A touch panel of one embodiment of the present invention includes, between a pair of substrate, a display element and a capacitor included in a touch sensor. Thus, a thin and lightweight touch panel can be obtained.
• It is preferable that a pair of conductive layers included in the capacitor each have an opening. It is preferable that the opening and the display element overlap with each other. Such a structure enables extraction of light emitted from the display element to the outside through the opening, and therefore, the pair of conductive layers included in the capacitor do not necessarily have a light-transmitting property. That is, a material such as metal or alloy that has lower resistance than a light-transmitting conductive material can be used as a material for the pair of conductive layer included in the capacitor. This reduces the influence of detection signal delay or the like and increases the detection sensitivity of the touch panel. Furthermore, such a structure can be applied to large-sized display devices such as televisions as well as portable devices.
• Since the pair of conductive layers can be formed of a low-resistance material, each of the conductive layers can have an extremely small line width. That is, a surface area of each of the conductive layers when seen from the display surface side (in a plan view) can be reduced. As a result, the influence of noise caused by driving a pixel is suppressed, which increases detection sensitivity. Furthermore, even when the capacitor included in the touch sensor and the display element included in the pixel are provided close to each other and between the two substrates, a reduction in detection sensitivity can be suppressed. Thus, the thickness of the touch panel can be reduced. In particular, in the case where a flexible material is used for the pair of substrates, a flexible touch panel that is thin and lightweight can be obtained.
• In the case of using a projected capacitive type, the product of resistance and capacitance (also referred to as a CR value or a time constant) of the first conductive layer is preferably as small as possible. Similarly, the CR value of the second conductive layer is preferably as small as possible.
• For example, in the case of using a projected mutual capacitive type, a pulse voltage is supplied to one of the conductive layers, and a current flowing in the other conductive layer is sensed. At this time, as the CR value of the conductive layer where current sensing is performed is smaller, a change in current due to the presence or absence of a touch motion can be increased more. Furthermore, as the CR value of the conductive layer supplied with the pulse voltage is smaller, delay in the waveform of the pulse voltage is suppressed more and detection sensitivity can be increased more.
• In the case of using a projected self-capacitive type, a pulse voltage is applied to each of the pair of conductive layers, and a current flowing in each of the conductive layers is sensed. Therefore, as the CR value of each of the conductive layers is smaller, detection sensitivity can be increased more.
• For example, the CR value of the first conductive layer or the second conductive layer is greater than 0 s and less than or equal to 1×10⁻⁴s, preferably greater than 0 s and less than or equal to 5×10⁻⁵s, more preferably greater than 0 s and less than or equal to 5×10⁻⁶s, still more preferably greater than 0 s and less than or equal to 5×10⁻⁷s, still more preferably greater than 0 s and less than or equal to 2×10⁻⁷s. In particular, when the CR value is 1×10⁻⁶s or less, high detection sensitivity can be achieved while the influence of noise is suppressed.
• The first conductive layer or the second conductive layer preferably has a mesh shape having a plurality of openings. At this time, the aperture ratio of the first conductive layer or the second conductive layer (the proportion of the opening area of the first conductive layer or the second conductive layer per unit area) is preferably higher than at least the aperture ratio of the pixel included in the touch panel. When the aperture ratio of the first conductive layer or the second conductive layer is higher than the aperture ratio of the pixel, blocking of light emitted from the pixel by the first conductive layer or the second conductive layer can be suppressed. When the aperture ratio is increased by increasing the size of the opening, the area where the object overlaps with the first conductive layer or the second conductive layer is reduced, and therefore, detection sensitivity is reduced in some cases. In view of this, the aperture ratio and an opening pattern are preferably set so that the opening area is smaller than the area of the object.
• For example, the aperture ratio of the first conductive layer or the second conductive layer is preferably higher than or equal to 20% and lower than 100%, more preferably higher than or equal to 30% and lower than 100%, still more preferably higher than or equal to 50% and lower than 100%.
• The touch panel of one embodiment of the present invention has high detection sensitivity and is less influenced by noise caused when a display panel is driven. Therefore, the thickness of the touch panel itself can be reduced. For example, the distance between the pair of substrates included in the touch panel can be reduced to 50 nm or more and 100 μm or less, preferably 200 nm or more and 50 μm or less, more preferably 500 nm or more and 20 μm or less. When a flexible substrate is used for the pair of substrates at this time, a flexible touch panel strong against bending can be obtained.
• In particular, the distance between the first conductive layer or the second conductive layer and a conductive layer closer to the substrate provided with the display element than the first conductive layer or the second conductive layer is set to, for example, greater than or equal to 25 nm and less than or equal to 50 μm, preferably greater than or equal to 50 nm and less than or equal to 10 μm, more preferably greater than or equal to 50 nm and less than or equal to 5 μm.
• Furthermore, a light-blocking layer is preferably provided between the substrate on the display surface side and the pair of electrodes included in the capacitor. The light-blocking layer may have a function of suppressing color mixing between adjacent pixels. When the light-blocking layer is closer to the display surface than the pair of electrodes, reflection of external light by the pair of electrodes is prevented, and the pair of electrodes is prevented from being visually recognized from the display surface side. Thus, the touch panel can have high display quality.
• The light-blocking layer and the pair of electrodes included in the capacitor are preferably provided between adjacent pixels when seen from the display surface side (in a plan view). Furthermore, the width of each of the pair of electrodes included in the capacitor is preferably smaller than the width of the light-blocking layer or the interval between the two adjacent pixels.
• A more specific structure example of one embodiment of the present invention is described below with reference to drawings.
Structure Example
• FIG. 1A is a schematic perspective view of atouch panel module10 of one embodiment of the present invention.FIG. 1B is a developed view of the schematic perspective view of thetouch panel module10. In the touch panel module, atouch sensor module20 and adisplay panel30 are provided to overlap with each other.
• In thetouch sensor module20, asubstrate21 is provided with anFPC41. Furthermore, atouch sensor22 is provided on a surface on thedisplay panel30 side of thesubstrate21. Thetouch sensor22 includes aconductive layer23, aconductive layer24, and aconductive layer25. Furthermore, thetouch sensor module20 includes awiring29 which electrically connects these conductive layers to theFPC41. TheFPC41 has a function of supplying a signal from the outside to thetouch sensor22. Furthermore, theFPC41 has a function of outputting a signal from thetouch sensor22 to the outside. Note that the substrate without theFPC41 is also simply referred to as a touch sensor, or referred to as a touch sensor substrate or a touch sensor panel.
• Thetouch sensor22 includes a plurality ofconductive layers23, a plurality ofconductive layers24, and a plurality ofconductive layers25. Each of theconductive layers23 has a shape extending in one direction. The plurality ofconductive layers23 are arranged in a direction crossing the extending direction. Each of theconductive layers24 is positioned between two adjacentconductive layers23. Each of theconductive layer25 electrically connects twoconductive layers24 adjacent in the direction crossing the extending direction of the conductive layers23. That is, the plurality ofconductive layers24 arranged in the direction crossing the extending direction of theconductive layers23 are electrically connected to each other with the plurality ofconductive layers25.
• Here, there is a region where theconductive layer23 and theconductive layer25 overlap with each other. Theconductive layer23, theconductive layer25, and an insulating layer which is provided therebetween and functions as a dielectric form acapacitor11. Therefore, theconductive layer23 and theconductive layer25 partly function as the pair of electrodes of thecapacitor11.
• Note that here, the plurality ofconductive layers24 are electrically connected to each other with theconductive layer25. Alternatively, it is possible to employ a structure in which theconductive layer24 has a shape extending in one direction like theconductive layer23, an insulating layer is provided between theconductive layer23 and theconductive layer24, and theconductive layer25 is not provided. In this case, part of theconductive layer24 functions as one electrode of thecapacitor11.
• Note that, for example, a low-resistance material is preferably used as a material of conductive films such as theconductive layer23, theconductive layer24, and theconductive layer25, i.e., a wiring and an electrode in the touch panel. As an example, metal such as silver, copper, or aluminum may be used. Alternatively, a metal nanowire including a number of conductors with an extremely small width (for example, a diameter of several nanometers) may be used. Examples of such a metal nanowire include an Ag nanowire, a Cu nanowire, and an Al nanowire. In the case of using an Ag nanowire, light transmittance of 89% or more and a sheet resistance of 40 ohm/square or more and 100 ohm/square or less can be achieved. Note that because such a metal nanowire provides high transmittance, the metal nanowire may be used for an electrode of the display element, e.g., a pixel electrode or a common electrode.
• In thedisplay panel30, adisplay portion32 is provided over asubstrate31. Thedisplay portion32 includes a plurality ofpixels33 arranged in a matrix. Eachpixel33 preferably includes a plurality of sub-pixels. Each sub-pixel includes a display element. Acircuit34 electrically connected to thepixel33 in thedisplay portion32 is preferably provided over thesubstrate31. For example, a circuit functioning as a gate driver circuit can be used for thecircuit34. AnFPC42 has a function of supplying a signal from the outside to at least one of thedisplay portion32 and thecircuit34. An IC functioning as a source driver circuit is preferably mounted on thesubstrate31 or theFPC42. The IC can be mounted on thesubstrate31 by a COG method or a COF method. Alternatively, theFPC42, a TAB, a TCP, or the like on which an IC is mounted can be attached to thesubstrate31. Note that an object in which an IC or a connector such as an FPC is mounted on thedisplay panel30 can be referred to as a display panel module.
• The touch panel module of one embodiment of the present invention can output positional information based on the change in capacitance by thetouch sensor22 at the time of a touch motion. Furthermore, thedisplay portion32 can display an image.
[Structural Example of Touch Sensor]
• FIG. 2A is a schematic top view (schematic plan view) of part of thetouch sensor22.FIG. 2B is an enlarged schematic top view of a region surrounded by dashed-dotted line inFIG. 2A.
• As shown inFIGS. 2A and 2B, it is preferable that theconductive layer23 be partly narrowed so that the width of a portion crossing theconductive layer25 is small. Thus, the capacitance of thecapacitor11 can be reduced. In the case of using a self-capacitive touch sensor, the detection sensitivity can be increased more as the capacitance of thecapacitor11 is smaller.
• Furthermore, it is preferable to provide, between theconductive layer23 and theconductive layer24 which are adjacent to each other, aconductive layer26 which is electrically insulated from theseconductive layers23 and24. Theconductive layer26 can suppress the formation of a thin portion of thetouch sensor22. For example, in the case where theconductive layer23 and theconductive layer24 are formed over the same flat surface, theconductive layer26 formed in a manner similar to that of theconductive layer23 and theconductive layer24 can increase coverage of a thin film formed after the formation of these conductive layers; thus, a surface can be planarized. Furthermore, owing to the uniform thickness of thetouch sensor22, luminance unevenness of light emitted from the pixels through thetouch sensor22 can be reduced, so that the touch panel can achieve high display quality.
• FIG. 2C shows the case where theconductive layer23 and theconductive layer24 are formed over different flat surfaces and theconductive layer25 is not provided. At this time, theconductive layer26 may be formed over the flat surface over which theconductive layer23 or theconductive layer24 is formed, or may be formed over a flat surface different from the flat surface over which theconductive layer23 or theconductive layer24 are formed. Note that theconductive layer26 is not necessarily provided if not necessary.
• FIG. 3A shows an example of a circuit diagram of thetouch sensor22 including a plurality ofconductive layers23 and a plurality ofconductive layers24. InFIG. 3A, sixconductive layers23 and sixconductive layers24 are shown for simplicity, but the number of theconductive layers23 and the number of theconductive layers24 are not limited thereto.
• Onecapacitor11 is formed between one of theconductive layers23 and one of the conductive layers24. Therefore,capacitors11 are arranged in a matrix.
• In the case of a projected self-capacitive type, a pulse voltage is applied to each of theconductive layers23 and24 so that theconductive layers23 and24 are scanned, and the value of a current flowing in theconductive layer23 or theconductive layer24 at this time is sensed. The amount of current is changed when an object approaches, and therefore, positional information of the object can be obtained by sensing the difference between the values. In the case of a projected mutual-capacitive type, a pulse voltage is applied to one of theconductive layers23 and24 so that one of theconductive layers23 and24 is scanned, and a current flowing in the other is sensed to obtain positional information of the object.
• The CR value of theconductive layer23 or theconductive layer24 is greater than 0 s and less than or equal to 1×10⁻⁴s, preferably greater than 0 s and less than or equal to 5×10⁻⁵s, more preferably greater than 0 s and less than or equal to 5×10⁻⁶s, still more preferably greater than 0 s and less than or equal to 5×10⁻⁷s, still more preferably greater than 0 s and less than or equal to 2×10⁻⁷s.
• Each of theconductive layers23 and24 preferably has a lattice shape or a mesh shape having a plurality of openings.FIG. 3B shows an example of a top surface shape of part of theconductive layer23.
• Theconductive layer23 shown inFIG. 3B has a lattice shape in which a distance P1 is provided in a lateral direction and a distance P2 is provided in a longitudinal direction. The distance P1 and the distance P2 are almost the same inFIG. 3B, but may be different from each other. For example, the distance P2 in a longitudinal direction may be larger than the distance P1 in a lateral direction as shown inFIG. 3C, or the distance P2 in a longitudinal direction may be smaller than the distance P1 in a lateral direction. The same can be said for theconductive layer24.
• The aperture ratio of theconductive layer23 or the conductive layer24 (the proportion of the opening area in theconductive layer23 or theconductive layer24 per unit area) is preferably higher than or equal to 20% and lower than 100%, more preferably higher than or equal to 30% and lower than 100%, still more preferably higher than or equal to 50% and lower than 100% in a region.
• The aperture ratio can be easily calculated from the distance P1, the distance P2, and the width of the conductive layer. Alternatively, when a region R is assumed to be a periodic unit inFIG. 3B, the aperture ratio can be calculated from the ratio of the area of the region R to the area of theconductive layer23 included in the region R. Here, the region R is a periodic unit of a periodic pattern of theconductive layer23. By arranging regions R longitudinally and laterally in a periodic manner, the pattern of theconductive layer23 can be formed.
• In each of theconductive layer23 and theconductive layer24, the line width of a lattice is preferably greater than or equal to 50 nm and less than or equal to 100 μm, more preferably greater than or equal to 1 μm and less than or equal to 50 μm, still more preferably greater than or equal to 1 μm and less than or equal to 20 μm. The lattice having such a narrow line width allows adjacent pixels to be close to each other in the case where the opening overlaps with the pixel as described later. Consequently, the touch panel can have higher resolution and higher aperture ratio.
• FIG. 4A is an enlarged schematic top view of a region indicated by a dashed-dotted line inFIG. 2B.
• As shown inFIG. 4A, each of theconductive layers23 and24 preferably has a lattice shape (also referred to as a mesh shape). That is, each of theconductive layers23 and24 preferably has a plurality of openings (anopening23aand anopening24a). When the opening and the pixel are provided to overlap with each other as described later, light emitted from the display element in the pixel is not blocked by theconductive layer23 and theconductive layer24, or a reduction in the luminance of light due to the transmission through theconductive layer23 and theconductive layer24 does not occur. As a result, thetouch sensor22 can be used in the touch panel without a reduction in the aperture ratio of the pixel and the light extraction efficiency. It is preferable that theconductive layer25 similarly have a shape not overlapping with the pixel.
• In the structure shown inFIG. 4A, theconductive layer24 and theconductive layer25 are electrically connected to each other throughopenings27 formed in an insulating layer positioned between theconductive layer24 and theconductive layer25. Thecapacitor11 is formed in a portion where theconductive layer23 and theconductive layer25 overlap with each other.
• As shown inFIG. 4A, the shape of theconductive layer25 crossing theconductive layer23 preferably has two or more portions shaped like strips whose long sides extend in a direction crossing theconductive layer23. The plurality of strip-like portions can reduce contact resistance between theconductive layer24 and theconductive layer25. Furthermore, electrical connection between theconductive layer25 and theconductive layer24 can be kept even when part of theconductive layer25 is broken or a contact failure occurs in a portion where theconductive layer25 and theconductive layer24 are connected to each other. Defects like the break and the contact failure might occur particularly when the touch panel is used while being bent; therefore, theconductive layer25 preferably has the above-described shape.
• FIG. 4B shows an example of increasing the area where theconductive layer23 and theconductive layer25 overlap with each other. In the example, theconductive layer25 overlaps with theconductive layer23 not only in the portion where theconductive layer23 and theconductive layer25 cross each other but also in another portion, whereby the capacitance of thecapacitor11 can be increased. The capacitance of thecapacitor11 can be changed as appropriate by adjusting the area where theconductive layer23 and theconductive layer25 overlap with each other or the dielectric constant or the thickness of the insulating layer, for example.
• Furthermore, in the example shown inFIG. 4B, theconductive layer26 shown inFIGS. 2A to 2C is provided. As shown inFIG. 4B, a plurality of island-like patterns may be provided as theconductive layer26.
• FIG. 5A shows an example where theconductive layer25 is not provided in the structure shown inFIG. 4A. InFIG. 5A, theconductive layer23 and theconductive layer24 are provided to overlap with each other.FIG. 5B shows an example where theconductive layer25 is not provided in the structure shown inFIG. 4B.
• FIG. 6 shows an example of a boundary portion between theconductive layer23 and theconductive layer24. As shown inFIG. 6, an opening22asurrounded by part of theconductive layer23 and part of theconductive layer24 may be formed in the boundary portion. Such a structure can significantly reduce the distance between theconductive layer23 and theconductive layer24 and can increase mutual capacitance therebetween. In particular, in the case of using a mutual capacitive type, the distance between the two conductive layers is preferably reduced to increase mutual capacitance.
[Arrangement Example of Opening of Conductive Layer and Pixel]
• FIGS. 7A to 7G,FIG. 8, andFIGS. 9A to 9E are schematic views each showing the positional relationship between a pixel, sub-pixels included in the pixel, and theconductive layer23 which are seen from the display surface side. Note that although theconductive layer23 is shown inFIGS. 7A to 7G,FIG. 8, andFIGS. 9A to 9E as an example, the same applies to theconductive layer24 and theconductive layer25.
• In the example shown inFIG. 7A, thepixel33 includes a sub-pixel33R, asub-pixel33G, and a sub-pixel33B. For example, the sub-pixel33R, thesub-pixel33G, and the sub-pixel33B have a function of expressing red color, green color, and blue color, respectively. Note that the number and the colors of the sub-pixels included in thepixel33 are not limited thereto.
• The sub-pixels included in thepixel33 each have a display element. Typical examples of the display element include light-emitting elements such as organic EL elements; liquid crystal elements; display elements (electronic ink) that perform display by an electrophoretic method, an electronic liquid powder (registered trademark) method, or the like; MEMS shutter display elements; and optical interference type MEMS display elements. The sub-pixel may have a transistor, a capacitor, a wiring that electrically connects the transistor and the capacitor, and the like in addition to the display element.
• Furthermore, this embodiment can be used in a transmissive liquid crystal display, a transflective liquid crystal display, a reflective liquid crystal display, a direct-view liquid crystal display, or the like. In the case of a transflective liquid crystal display or a reflective liquid crystal display, some or all of pixel electrodes function as reflective electrodes. For example, some or all of pixel electrodes are formed to contain aluminum, silver, or the like. In such a case, a memory circuit such as an SRAM can be provided under the reflective electrodes, leading to lower power consumption. A structure suitable for employed display elements can be selected from among a variety of structures of pixel circuits.
• In the structure shown inFIG. 7A, one opening23ain theconductive layer23 is provided to overlap with three sub-pixels, i.e., the sub-pixel33R, thesub-pixel33G, and the sub-pixel33B. In this manner, the opening23ain theconductive layer23 is preferably provided to overlap with onepixel33. In other words, thepixels33 and the openings in the lattice of theconductive layer23 are preferably provided at the same intervals. Such a structure allows the peripheral portions of thepixels33 to have the same structures (e.g., the structures of films in the pixels and in the periphery of the pixels, the thicknesses of the films, and the unevenness of surfaces thereof), leading to a reduction in display unevenness.
• Note that two ormore pixels33 and oneopening23amay overlap with each other as shown inFIG. 8, for example.
• FIG. 7B shows an example where oneopening23aand one sub-pixel overlap with each other. When theconductive layer23 is provided between two sub-pixels in onepixel33 in a plan view, the wiring resistance of theconductive layer23 can be reduced. Consequently, the detection sensitivity of the touch panel can be increased.
• FIG. 7C shows an example where thepixel33 further includes a sub-pixel33Y in the structure shown inFIG. 7A. For example, a pixel capable of expressing yellow color can be used for the sub-pixel33Y. Instead of the sub-pixel33Y, a pixel capable of expressing white color may be used. When thepixel33 includes sub-pixels of more than three colors, power consumption can be reduced.
• FIG. 7D shows an example where oneopening23aand one sub-pixel overlaps with each other, i.e., an example where theconductive layer23 is provided between two adjacent sub-pixels in a plan view. Note that a structure in which two of the four sub-pixels overlap with one opening23amay be employed, although not shown.
• In the examples shown inFIGS. 7A to 7D, sub-pixels of each color are arranged in a stripe pattern. Alternatively, as shown inFIGS. 7E to 7G, sub-pixels of two colors may be alternated in one direction, for example. In a structure shown inFIG. 7E, thepixel33 including four sub-pixels and oneopening23aoverlap with each other. In a structure shown inFIG. 7F, two adjacent sub-pixels and oneopening23aoverlap with each other. In a structure shown inFIG. 7G, one sub-pixel and oneopening23aoverlap with each other.
• Furthermore, the sub-pixels included in thepixel33 may differ in size (e.g., the area of a region contributing to display). For example, the size of the sub-pixel of blue color with a relatively low luminosity factor can be set large, whereas the size of the sub-pixel of green or red color with a relatively high luminosity factor can be set small.
• FIGS. 9A and 9B each show an example where the size of the sub-pixel33B is larger than the size of the sub-pixel33R and the size of the sub-pixel33G. In the examples shown here, the sub-pixel33R and the sub-pixel33G are alternated. However, sub-pixels of each color may be arranged in a stripe pattern as shown inFIG. 7A and other drawings, and may have different sizes from each other.
• FIG. 9A shows a structure in which thepixel33 including three sub-pixels and oneopening23aoverlap with each other.FIG. 9B shows a structure in which oneopening23aand onesub-pixel33B overlap with each other and another opening23aand two sub-pixels (the sub-pixel33R and the sub-pixel33G) overlap with each other.
• Alternatively, pixel structures as those shown inFIGS. 9C to 9E can be employed. Here, a column of the sub-pixels33B arranged in a stripe pattern is provided between columns in each of which sub-pixels33R and33G are alternated. Furthermore, onesub-pixel33B is provided between one sub-pixel33R and onesub-pixel33G.
• In the structure shown inFIG. 9C, six sub-pixels (using two sub-pixels for each color) overlap with one opening23a. In a structure shown inFIG. 9D, three sub-pixels (using one sub-pixel for each color) overlap with one opening23a. In a structure shown inFIG. 9E, one sub-pixel and oneopening23aoverlap with each other. Note that the pixel structure is not limited to the structures described here, and a structure in which two or more adjacent sub-pixels and oneopening23aoverlap with each other may be employed.
• Note that although the positional relationship between theconductive layer23 and the sub-pixels is described here, the same applies to theconductive layer24 and theconductive layer25. That is, in the touch panel of one embodiment of the present invention, the opening23ain theconductive layer23 overlaps with one or more sub-pixels in a region and theopening24ain theconductive layer24 overlaps with one or more of the other sub-pixels in a region. Since each sub-pixel includes the display element as described above, it can be said that the opening23aand theopening24aeach have a region overlapping with one or more display elements.
[Stacked-Layer Structure Included in Touch Panel]
• FIG. 10A is a schematic top view of part of the touch panel when seen from the display surface side. InFIG. 10A, theconductive layer23, theconductive layers24, theconductive layer25, a light-blockinglayer53, coloring layers52R,52G, and52B, and the like are shown.
• FIG. 10B is a developed schematic view of a stacked-layer structure ofFIG. 10A. As shown inFIG. 10B, the light-blockinglayer53, theconductive layer23, theconductive layers24, an insulatinglayer28, theconductive layer25, the coloring layers52R,52G, and52B, and displayelements51 are provided between thesubstrate21 and thesubstrate31.
• Note that hereinafter, each of the coloring layers52R,52G, and52B is also simply referred to as acoloring layer52 in the case of describing common points of the coloring layers52R,52G, and52B without distinguishing them.
• Eachcoloring layer52 has a function of transmitting light in a particular wavelength range. Here, thecoloring layer52R transmits red light, thecoloring layer52G transmits green light, and the coloring layer52B transmits blue light. One of thedisplay elements51 and one of the coloring layers52 are provided to overlap with each other, whereby only light in a particular wavelength range in light emitted from the display element can be transmitted to thesubstrate21 side.
• The light-blockinglayer53 has a function of blocking visible light. The light-blockinglayer53 is provided to overlap with a region between two adjacent coloring layers52. In the example shown inFIGS. 10A and 10B, the light-blockinglayer53 has an opening provided to overlap with thedisplay element51 and thecoloring layer52.
• As shown inFIG. 10B, the light-blockinglayer53 is preferably provided closer to thesubstrate21 than theconductive layer23, theconductive layers24, and theconductive layer25. That is, the light-blockinglayer53 is preferably provided closer to the display surface than these conductive layers. Furthermore, the light-blockinglayer53, theconductive layer23, theconductive layers24, and theconductive layer25 preferably overlap with each other in a region. Such a structure allows theconductive layer23, theconductive layers24, and theconductive layer25 to be less recognized visually by a user because these conductive layers are hidden by the light-blockinglayer53 when seen from the display surface side. Such a structure is effective particularly when theconductive layer23, theconductive layers24, and theconductive layer25 are formed using a material reflecting visible light such as metal or alloy.
• In the structure shown inFIG. 10B, theconductive layer23, theconductive layer25, and the insulatinglayer28 provided therebetween form thecapacitor11. Furthermore, the twoconductive layers24 between which theconductive layer23 is provided are electrically connected to theconductive layer25 through theopenings27 formed in the insulatinglayer28.
• Each of theconductive layer23, theconductive layer24, and theconductive layer25 is preferably provided between twoadjacent display elements51 in a plan view. Furthermore, each of theconductive layer23, theconductive layer24, and theconductive layer25 is preferably provided between two adjacent coloring layers52 in a plan view. Note that in the case where the area of thecoloring layer52 or the area of thedisplay element51 is larger than the opening area in the light-blockinglayer53, part of theconductive layer23, theconductive layer24, or theconductive layer25 may overlap with thedisplay element51 or thecoloring layer52 in a region.
• Note that in the example shown here, thecoloring layer52 is provided closer to thesubstrate31 than theconductive layer23 or the like; however, thecoloring layer52 may be provided closer to thesubstrate21 than theconductive layer23 or the like.
• In the example shown inFIGS. 10A and 10B, the twoconductive layers24 between which theconductive layer23 is provided are electrically connected to each other with theconductive layer25. However, theconductive layer25 is not necessarily provided as described above.
• FIGS. 11A and 11B show a structure example of the case where theconductive layer25 and theopening27 are not provided inFIGS. 10A and 10B. As shown inFIG. 11B, theconductive layer23, theconductive layer24, and the insulatinglayer28 provided therebetween form thecapacitor11.
• The above is the description of the stacked-layer structure.
[Cross-Sectional Structure Example]
• A cross-sectional structure example of thetouch panel module10 is described below.
[Cross-Sectional Structure Example 1]
• FIG. 12A is a schematic cross-sectional view of a touch panel module of one embodiment of the present invention. In the touch panel module shown inFIG. 12A, a capacitor of a touch sensor and a display element are provided between a pair of substrates, and therefore, the thickness of the touch panel module can be reduced.
• The touch panel module has a structure in which thesubstrate21 and thesubstrate31 are bonded to each other with anadhesive layer220. Theconductive layer23, theconductive layer24, theconductive layer25, and the insulatinglayer28 which form a touch sensor, acontact portion253, thecoloring layer52, the light-blockinglayer53, and the like are provided on thesubstrate31 side of thesubstrate21. Atransistor201, atransistor202, atransistor203, a light-emittingelement204, acontact portion205, and the like are provided on thesubstrate21 side of thesubstrate31.
• An insulatinglayer212, an insulatinglayer213, an insulatinglayer214, an insulatinglayer215, an insulatinglayer216, an insulatinglayer217, an insulatinglayer218, aspacer219, aconductive layer225, and the like are provided over thesubstrate31 with anadhesive layer211 provided therebetween.
• The light-emittingelement204 is provided over the insulatinglayer217. The light-emittingelement204 includes afirst electrode221, anEL layer222, and a second electrode223 (seeFIG. 12B). Anoptical adjustment layer224 is provided between thefirst electrode221 and theEL layer222. The insulatinglayer218 is provided to cover end portions of thefirst electrode221 and theoptical adjustment layer224.
• InFIG. 12A, thetransistor201 for controlling current and thetransistor202 for controlling switching are provided in thepixel33. One of a source and a drain of thetransistor201 is electrically connected to thefirst electrode221 through theconductive layer225.
• InFIG. 12A, thetransistor203 is provided in thecircuit34.
• In the example illustrated inFIG. 12A, thetransistors201 and203 each have a structure in which a semiconductor layer where a channel is formed is provided between two gate electrodes. Such transistors can have a higher field-effect mobility and thus have higher on-state current than other transistors. Consequently, a circuit capable of high-speed operation can be obtained. Furthermore, the area occupied by a circuit portion can be reduced. The use of the transistor having high on-state current can reduce signal delay in wirings and can suppress display unevenness even in a display panel or a touch panel in which the number of wirings is increased because of increase in size or resolution.
• Note that the transistor included in thecircuit34 and the transistor included in thepixel33 may have the same structure. Transistors included in thecircuit34 may have the same structure or different structures. Transistors included in thepixel33 may have the same structure or different structures.
• The light-emittingelement204 has a top-emission structure and emits light to thesecond electrode223 side. Thetransistors201 and202, a capacitor, a wiring, and the like are provided to overlap with the light-emitting region of the light-emittingelement204. Thus, an aperture ratio of thepixel33 can be increased.
• Thespacer219 is provided over the insulatinglayer218 and has a function of adjusting the distance between thesubstrate31 and thesubstrate21. InFIG. 12A, thespacer219 and anovercoat267 of thesubstrate21 are provided with a gap therebetween. Alternatively, as shown inFIG. 13, components such as theovercoat267 on thesubstrate21 side may be in contact with thesecond electrode223 over thespacer219 in a region. Furthermore, as shown inFIG. 13, thespacer219 may also be provided outside thepixel33, e.g., in a region overlapping with thecircuit34 or in a peripheral portion of thesubstrate21 or thesubstrate31. Although thespacer219 is formed on thesubstrate31 side in the structure described here, thespacer219 may be formed on thesubstrate21 side. For example, thespacer219 may be provided on an insulatinglayer266, theovercoat267, thecoloring layer52, or the like.
• As shown inFIG. 14, aspherical spacer226 may be used instead of thespacer219. A light-transmitting material or a light-absorbing material may be used for thespherical spacer226. Although a material such as silica can be used for thespacer226, an elastic material such as an organic resin or rubber is preferably used. InFIG. 14, thespacer226 having elasticity is deformed and seems to be pressed from above and below.
• An insulatinglayer262, the light-blockinglayer53, an insulatinglayer264, theconductive layer23, theconductive layer24, the insulatinglayer28, theconductive layer25, the insulatinglayer266, thecoloring layer52, and the like are provided on thesubstrate31 side of thesubstrate21 with anadhesive layer261 provided between thesubstrate21 and them. Furthermore, theovercoat267 covering thecoloring layer52 may be provided.
• The light-blockinglayer53 is provided closer to thesubstrate31 than the insulatinglayer262. The light-blockinglayer53 has the opening, and the opening is provided to overlap with the light-emitting region of the light-emittingelement204.
• As examples of a material that can be used for the light-blockinglayer53, carbon black, a metal oxide, and a composite oxide containing a solid solution of a plurality of metal oxides can be given. Stacked films containing the material of thecoloring layer52 are preferably used for the light-blockinglayer53. For example, a material containing an acrylic resin can be used for each coloring layer, and a stacked-layer structure of a film containing the material of thecoloring layer52R transmitting red light and a film containing the material of the coloring layer52B transmitting blue light can be employed. Formation of thecoloring layer52 and the light-blockinglayer53 using the same material can reduce a manufacturing cost because the same manufacturing apparatus can be used.
• As examples of a material that can be used for thecoloring layer52, a metal material, a resin material, and a resin material containing a pigment or dye can be given.
• The insulatinglayer264 is provided to cover the light-blockinglayer53. The insulatinglayer264 may have a function of a planarization film. In the case where a material with low heat resistance is used for the light-blockinglayer53, an organic insulating material is preferably used for the insulatinglayer264 because a layer with high planarity can be formed at a low temperature. Alternatively, an inorganic insulating material is preferably used for the insulatinglayer264 because the insulatinglayer264 can function as an etching stopper at the time of processing theconductive layer23 and theconductive layer24.
• Each of theconductive layer23 and theconductive layer24 is provided to cover part of the insulatinglayer264. Each of theconductive layer23 and theconductive layer24 overlaps with the light-blockinglayer53 in a region. InFIG. 12A, the example where theconductive layer24 is provided in part of a region of thepixel33 is shown. The opening24ain theconductive layer24 overlaps with the light-emittingelement204 in a region. In thepixel33, theconductive layer24 is provided to surround the light-emitting region of the light-emittingelement204. Therefore, theconductive layer24 may overlap with, for example, thespacer219, the insulatinglayer218, theconductive layer225, thetransistor201, thetransistor202, or a wiring electrically connected to thetransistor201 or202 in a region. The same applies to theconductive layer23 and theconductive layer25.
• In the example shown inFIG. 12A, theconductive layer23 and theconductive layer24 are processed using the same conductive film. Since theconductive layer23 and theconductive layer24 are formed over the entire display region, formation of the conductive layers in the same step can reduce display unevenness.
• The insulatinglayer28 has a function of a dielectric of thecapacitor11. In the example shown inFIG. 12A, an inorganic insulating material is used for the insulatinglayer28. When the insulatinglayer28 is formed using an inorganic insulating material, the insulatinglayer28 having a uniform thickness can be formed easily, and furthermore, the insulatinglayer28 can be thinner than the case of using an organic insulating material. Therefore, variation in the capacitances of thecapacitors11 can be reduced. Like the insulatinglayer264, the insulatinglayer28 can function as an etching stopper at the time of processing theconductive layer25. Note that the insulatinglayer28 may be formed using an organic insulating material. In this case, a material with low heat resistance can be used for components between thesubstrate21 and the insulatinglayer28, and therefore, the range of choices of materials thereof can be expanded.
• Theconductive layer25 is provided to cover part of the insulatinglayer28. Theconductive layer25 is provided to overlap with the light-blockinglayer53. Part of theconductive layer25 overlaps with theconductive layer23 in a region. Theconductive layer25 has a function of electrically connecting the twoconductive layers24 between which theconductive layer23 is provided, through the openings formed in the insulatinglayer28.
• The insulatinglayer266 is provided to cover theconductive layer25 and the insulatinglayer28, and thecoloring layer52 is provided to cover part of the insulatinglayer266. Theovercoat267 may be provided to cover thecoloring layer52.
• It is preferable that the insulatinglayer266 have a function of a planarization layer and be formed using an organic insulating material. Alternatively, an inorganic insulating material having high planarity may be used. A flat surface provided by the insulatinglayer266 can reduce a variation in the thickness of thecoloring layer52. Thus, the touch panel can have high display quality.
• When a flexible substrate is used for at least one of thesubstrates21 and31, the touch panel can be thin and lightweight. When a flexible substrate is used for each of thesubstrates21 and31, the touch panel can be flexible.
• A color filter method is employed in the touch panel shown inFIGS. 12A and 12B. For example, a structure where pixels of three colors of red (R), green (G), and blue (B) express one color can be employed for thecoloring layer52. In addition, a pixel of white (W) or yellow (Y) may be used for the structure.
• An EL layer that emits white light is preferably used as theEL layer222 of the light-emittingelement204. By using the light-emittingelement204, it is not necessary to separately form the EL layers222 expressing different colors in pixels. Therefore, the cost can be reduced, and the high resolution is achieved easily. Furthermore, by varying the thickness of theoptical adjustment layer224 in pixels, light with a wavelength suitable for each pixel can be extracted, which increases color purity. Note that the EL layers222 expressing different colors may be separately formed in pixels, in which case theoptical adjustment layer224 is not necessarily used.
• An opening is provided in the insulating layers and the like in a region overlapping with thecontact portion205 provided over thesubstrate31, and thecontact portion205 and theFPC41 are electrically connected to each other with aconnection layer260 provided in the opening. Furthermore, an opening is provided in the insulating layers and the like in a region overlapping with thesubstrate21, and thecontact portion253 and theFPC42 are electrically connected to each other through aconnection layer210 provided in the opening.
• Note that as shown inFIG. 13 orFIG. 14, a structure in which theFPC41 and theconnection layer260 do not overlap with thesubstrate21 and the insulating layer and the like provided for thesubstrate21 may be employed. Similarly, in the structures shown inFIG. 13 andFIG. 14, theFPC42 and theconnection layer210 do not overlap with thesubstrate31 and the insulating layer and the like provided for thesubstrate31.
• In the structure shown inFIG. 12A, thecontact portion205 has a conductive layer formed by processing a conductive film that is also used for the source electrode and the drain electrode of the transistor. Furthermore, thecontact portion253 has a stacked-layer structure of a conductive layer formed by processing a conductive film that is also used for theconductive layer23 and theconductive layer24, and a conductive layer formed by processing a conductive film that is also used for theconductive layer25. The contact portion preferably has a stacked-layer structure of a plurality of conductive layers as described above because electric resistance can be reduced and mechanical strength can be increased.
• Furthermore,FIG. 12A shows a cross-sectional structure of acrossing portion206 where a wiring formed by processing the conductive film used for forming the gate electrode of the transistor and a wiring formed by processing the conductive film used for forming the source electrode and the drain electrode of the transistor cross each other.
• As theconnection layer210 and theconnection layer260, any of various anisotropic conductive films (ACF), anisotropic conductive pastes (ACP), or the like can be used.
• A material in which impurities such as water or hydrogen do not easily diffuse is preferably used for the insulatinglayer212 and the insulatinglayer262. That is, the insulatinglayer212 and the insulatinglayer262 can each function as a barrier film. Such a structure can effectively suppress diffusion of the impurities to the light-emittingelement204 and the transistors even in the case of using a material permeable to moisture for thesubstrate21 and thesubstrate31, and a highly reliable touch panel can be achieved.
• Here, the distance between one of theconductive layer23 and the conductive layer24 (or the conductive layer25) which is positioned closer to the display panel (i.e., the substrate side on which the display element is provided) than the other and a conductive layer which is the closest to the one of theconductive layer23 and the conductive layer24 (or the conductive layer25) of the conductive layers provided closer to the display panel than the one of theconductive layer23 and the conductive layer24 (or the conductive layer25) is preferably greater than or equal to 25 nm and less than or equal to 100 μm, more preferably greater than or equal to 50 nm and less than or equal to 10 μm, still more preferably greater than or equal to 50 nm and less than or equal to 5 μm.
• In the example shown inFIG. 12A, thesecond electrode223 of the light-emittingelement204 corresponds to the conductive layer which is the closest to theconductive layer24 in a region of thepixel33 of the conductive layers provided closer to the display panel than theconductive layer24. Here, the distance between theconductive layer24 and thesecond electrode223 is denoted by D. As the distance D is shorter, a distance between the pair of substrates can be reduced more, and the thickness of the touch panel can be reduced more. In particular, when flexible substrates are used as the pair of substrates, the touch panel can be flexible and strong against bending.
• Note that the conductive layer which is the closest to theconductive layer23 or24 of the conductive layers provided closer to the display panel than theconductive layer23 or24 is not limited to thesecond electrode223 and may be a conductive layer other than thesecond electrode223. For example, in the case where another conductive layer is provided between thesecond electrode223 and theconductive layer23 or24, the distance between the conductive layer and theconductive layer23 or24 is set within the above-described range. For example, a conductive layer can be provided on the insulatinglayer266 so that theadhesive layer220 can be formed on a surface with higher wettability of higher adhesion.
[Components]
• The above components are described below.
• The transistor includes a conductive layer functioning as the gate electrode, the semiconductor layer, a conductive layer functioning as the source electrode, a conductive layer functioning as the drain electrode, and an insulating layer functioning as a gate insulating layer.FIG. 12A shows the case where a bottom-gate transistor is used.
• Note that there is no particular limitation on the structure of the transistor included in the touch panel of one embodiment of the present invention. For example, a forward staggered transistor or an inverted staggered transistor may be used. A top-gate transistor or a bottom-gate transistor may be used. A semiconductor material used for the transistor is not particularly limited, and for example, an oxide semiconductor, silicon, or germanium can be used.
• There is no particular limitation on the crystallinity of a semiconductor material used for the transistor, and an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single-crystal semiconductor, or a semiconductor partly including crystal regions) may be used. It is preferable that a semiconductor having crystallinity be used, in which case deterioration of the transistor characteristics can be suppressed.
• As a semiconductor material for the semiconductor layer of the transistor, an element of Group 14, a compound semiconductor, or an oxide semiconductor can be used, for example. Typically, a semiconductor containing silicon, a semiconductor containing gallium arsenide, an oxide semiconductor containing indium, or the like can be used.
• An oxide semiconductor is preferably used as a semiconductor in which a channel of the transistor is formed. In particular, an oxide semiconductor having a wider band gap than silicon is preferably used. A semiconductor material having a wider band gap and a lower carrier density than silicon is preferably used because off-state current of the transistor can be reduced.
• For example, the oxide semiconductor preferably contains at least indium (In) or zinc (Zn). The oxide semiconductor more preferably contains an In—M-Zn-based oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).
• As the semiconductor layer, it is particularly preferable to use an oxide semiconductor film including a plurality of crystal parts whose c-axes are aligned substantially perpendicular to a surface on which the semiconductor layer is formed or the top surface of the semiconductor layer and having no grain boundary between adjacent crystal parts.
• There is no grain boundary in such an oxide semiconductor; thus, generation of a crack in an oxide semiconductor film which is caused by stress when a display panel is bent is prevented. Therefore, such an oxide semiconductor can be preferably used for a flexible touch panel which is used in a bent state, or the like.
• Moreover, the use of such an oxide semiconductor for the semiconductor layer makes it possible to provide a highly reliable transistor in which a change in the electrical characteristics is suppressed.
• Charge accumulated in a capacitor through a transistor can be held for a long time because of the low off-state current of the transistor. When such a transistor is used for a pixel, operation of a driver circuit can be stopped while a gray scale of an image displayed in each display region is maintained. As a result, a display device with an extremely low power consumption can be obtained.
• Alternatively, silicon is preferably used as a semiconductor in which a channel of a transistor is formed. Although amorphous silicon may be used as silicon, silicon having crystallinity is particularly preferable. For example, microcrystalline silicon, polycrystalline silicon, single crystal silicon, or the like is preferably used. In particular, polycrystalline silicon can be formed at a lower temperature than single crystal silicon and has higher field effect mobility and higher reliability than amorphous silicon. When such a polycrystalline semiconductor is used for a pixel, the aperture ratio of the pixel can be improved. Even in the case where pixels are provided at extremely high resolution, a gate driver circuit and a source driver circuit can be formed over a substrate over which the pixels are formed, and the number of components of an electronic appliance can be reduced.
• As conductive layers such as a gate, a source, and a drain of the transistor and a wiring and an electrode in the touch panel, a single-layer structure or a stacked-layer structure using any of metals such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, and tungsten, or an alloy containing any of these metals as its main component can be used. For example, a single-layer structure of an aluminum film containing silicon, a two-layer structure in which an aluminum film is stacked over a titanium film, a two-layer structure in which an aluminum film is stacked over a tungsten film, a two-layer structure in which a copper film is stacked over a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is stacked over a titanium film, a two-layer structure in which a copper film is stacked over a tungsten film, a three-layer structure in which a titanium film or a titanium nitride film, an aluminum film or a copper film, and a titanium film or a titanium nitride film are stacked in this order, a three-layer structure in which a molybdenum film or a molybdenum nitride film, an aluminum film or a copper film, and a molybdenum film or a molybdenum nitride film are stacked in this order, and the like can be given. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may be used. Copper containing manganese is preferably used because controllability of a shape by etching is increased.
• As a light-transmitting conductive material, a conductive oxide such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium is added, or graphene can be used. Alternatively, a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, or titanium, or an alloy material containing any of these metal materials can be used. Alternatively, a nitride of the metal material (e.g., titanium nitride) or the like may be used. In the case of using the metal material or the alloy material (or the nitride thereof), the thickness is set small enough to be able to transmit light. Alternatively, a stack of any of the above materials can be used as the conductive layer. For example, a stack of indium tin oxide and an alloy of silver and magnesium is preferably used because the conductivity can be increased.
• Examples of an insulating material that can be used for the insulating layers, theovercoat267, thespacer219, and the like include a resin such as acrylic or epoxy resin, a resin having a siloxane bond, and an inorganic insulating material such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, or aluminum oxide.
• As described above, the light-emitting element is preferably provided between a pair of insulating films with low water permeability. Thus, an impurity such as water can be prevented from entering the light-emitting element, leading to prevention of a decrease in the reliability of the light-emitting device.
• As an insulating film with low water permeability, a film containing nitrogen and silicon (e.g., a silicon nitride film or a silicon nitride oxide film), a film containing nitrogen and aluminum (e.g., an aluminum nitride film), or the like can be used. Alternatively, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or the like can be used.
• For example, the water vapor transmittance of the insulating film with low water permeability is lower than or equal to 1×10⁻⁵[g/(m²·day)], preferably lower than or equal to 1×10⁻⁶[g/(m²·day)], further preferably lower than or equal to 1×10⁻⁷[g/(m²·day)], still further preferably lower than or equal to 1×10⁻⁸[g/(m²·day)].
• For the adhesive layers, a curable resin such as a heat curable resin, a photocurable resin, or a two-component type curable resin can be used. For example, a resin such as an acrylic resin, a urethane resin, an epoxy resin, or a resin having a siloxane bond can be used.
• TheEL layer222 includes at least a light-emitting layer. In addition to the light-emitting layer, theEL layer222 may further include one or more layers containing any of a substance with a high hole-injection property, a substance with a high hole-transport property, a hole-blocking material, a substance with a high electron-transport property, a substance with a high electron-injection property, a substance with a bipolar property (a substance with a high electron- and hole-transport property), and the like.
• For theEL layer222, either a low molecular compound or a high molecular compound can be used, and an inorganic compound may be used. Each of the layers included in theEL layer222 can be formed by any of the following methods: an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, a coating method, and the like.
• In the case where a light-emitting element emitting white light is used as the light-emittingelement204, theEL layer222 preferably contains two or more kinds of light-emitting substances. For example, light-emitting substances are selected so that two or more light-emitting substances emit complementary colors to obtain white light emission. Specifically, it is preferable to contain two or more selected from light-emitting substances emitting light of red (R), green (G), blue (B), yellow (Y), orange (0), and the like and light-emitting substances emitting light containing two or more of spectral components of R, G, and B. The light-emittingelement204 preferably emits light with a spectrum having two or more peaks in the wavelength range of a visible light region (e.g., 350 nm to 750 nm). An emission spectrum of a material emitting light having a peak in the wavelength range of a yellow light preferably includes spectral components also in the wavelength range of a green light and a red light.
• More preferably, a light-emitting layer containing a light-emitting material emitting light of one color and a light-emitting layer containing a light-emitting material emitting light of another color are stacked in theEL layer222. For example, the plurality of light-emitting layers in theEL layer222 may be stacked in contact with each other or may be stacked with a separation layer therebetween. For example, a separation layer may be provided between a fluorescent layer and a phosphorescent layer.
• The separation layer can be provided to prevent an energy transfer by the Dexter mechanism (particularly triplet energy transfer) from a phosphorescent material or the like in an excited state which is generated in the phosphorescent layer to a fluorescent material or the like in the fluorescent layer. The thickness of the separation layer may be approximately several nanometers, specifically 0.1 nm or more and 20 nm or less, 1 nm or more and 10 nm or less, or 1 nm or more and 5 nm or less. The separation layer contains a single material (preferably a bipolar material) or a plurality of materials (preferably, a hole-transport material and an electron-transport material).
• The separation layer may be formed using a material contained in the light-emitting layer in contact with the separation layer. This facilitates the manufacture of the light-emitting element and reduces the drive voltage. For example, in the case where the phosphorescent layer contains a host material, an assist material, and the phosphorescent material (a guest material), the separation layer may contain the host material and the assist material. In other words, the separation layer includes a region which does not contain the phosphorescent material, while the phosphorescent layer includes a region containing the phosphorescent material. Thus, the separation layer and the phosphorescent layer can be separately deposited depending on the presence of the phosphorescent material. Furthermore, such a structure enables the separation layer and the phosphorescent layer to be deposited in the same chamber, which leads to a reduction in manufacturing cost.
• The light-emittingelement204 may be a single element including one EL layer or a tandem element in which a plurality of EL layers are stacked with a charge generation layer therebetween.
[Manufacturing Method Example]
• Here, a method for manufacturing a flexible touch panel is described.
• For convenience, a structure including a pixel and a circuit, a structure including an optical member such as a color filter, or a structure including a touch sensor is referred to as an element layer. An element layer includes a display element, for example, and may include a wiring electrically connected to the display element or an element such as a transistor used in a pixel or a circuit in addition to the display element.
• Here, a support body (e.g., thesubstrate21 or the substrate31) with an insulating surface where an element layer is formed is referred to as a base material.
• As a method for forming an element layer over a flexible base material provided with an insulating surface, there are a method in which an element layer is formed directly over a base material, and a method in which an element layer is formed over a supporting base material that has stiffness and then the element layer is separated from the supporting base material and transferred to the base material.
• In the case where a material of the base material can withstand heating temperature in a process for forming the element layer, it is preferable that the element layer be formed directly over the base material, in which case a manufacturing process can be simplified. At this time, the element layer is preferably formed in a state where the base material is fixed to the supporting base material, in which case transfer thereof in an apparatus and between apparatuses can be easy.
• In the case of employing the method in which the element layer is formed over the supporting base material and then transferred to the base material, first, a separation layer and an insulating layer are stacked over the supporting base material, and then the element layer is formed over the insulating layer. Next, the element layer is separated from the supporting base material and then transferred to the base material. At this time, a material is selected that would causes separation at an interface between the supporting base material and the separation layer, at an interface between the separation layer and the insulating layer, or in the separation layer.
• For example, it is preferable that a stacked layer of a layer including a high-melting-point metal material, such as tungsten, and a layer including an oxide of the metal material be used as the separation layer, and a stacked layer of a plurality of layers, such as a silicon nitride layer and a silicon oxynitride layer be used over the separation layer. The use of the high-melting-point metal material is preferable because the degree of freedom of the process for forming the element layer can be increased.
• The separation may be performed by application of mechanical power, by etching of the separation layer, by dripping of a liquid into part of the separation interface to penetrate the entire separation interface, or the like. Alternatively, separation may be performed by heating the separation interface by utilizing a difference in thermal expansion coefficient.
• The separation layer is not necessarily provided in the case where separation can occur at an interface between the supporting base material and the insulating layer. For example, glass is used as the supporting base material and an organic resin such as polyimide is used as the insulating layer, a separation trigger is formed by locally heating part of the organic resin by laser light or the like, and separation is performed at an interface between the glass and the insulating layer. Alternatively, a metal layer may be provided between the supporting base material and the insulating layer formed of an organic resin, and separation may be performed at the interface between the metal layer and the insulating layer by heating the metal layer by feeding a current to the metal layer. In that case, the insulating layer formed of an organic resin can be used as a base material.
• Examples of such a base material having flexibility include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, a polyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, a polyamide resin, a cycloolefin resin, a polystyrene resin, a polyamide imide resin, and a polyvinyl chloride resin. In particular, it is preferable to use a material with a low thermal expansion coefficient, and for example, a polyamide imide resin, a polyimide resin, PET, or the like with a thermal expansion coefficient lower than or equal to 30×10⁻⁶/K can be suitably used. A substrate in which a fibrous body is impregnated with a resin (also referred to as prepreg) or a substrate whose thermal expansion coefficient is reduced by mixing an inorganic filler with an organic resin can also be used.
• In the case where a fibrous body is included in the above material, a high-strength fiber of an organic compound or an inorganic compound is used as the fibrous body. The high-strength fiber is specifically a fiber with a high tensile elastic modulus or a fiber with a high Young's modulus. Typical examples thereof include a polyvinyl alcohol based fiber, a polyester based fiber, a polyamide based fiber, a polyethylene based fiber, an aramid based fiber, a polyparaphenylene benzobisoxazole fiber, a glass fiber, and a carbon fiber. As the glass fiber, glass fiber using E glass, S glass, D glass, Q glass, or the like can be used. These fibers may be used in a state of a woven fabric or a nonwoven fabric, and a structure body in which this fibrous body is impregnated with a resin and the resin is cured may be used as the flexible substrate. The structure body including the fibrous body and the resin is preferably used as the flexible substrate, in which case the reliability against bending or breaking due to local pressure can be increased.
• Alternatively, glass, metal, or the like that is thin enough to have flexibility can be used as the base material. Alternatively, a composite material where glass and a resin material are attached to each other may be used.
• In the structure shown inFIG. 12A, for example, a first separation layer and the insulatinglayer262 are formed in this order over a first supporting base material, and then components in a layer over the first separation layer and the insulatinglayer262 are formed. Separately, a second separation layer and the insulatinglayer212 are formed in this order over a second supporting base material, and then upper components are formed. Next, the first supporting base material and the second supporting base material are bonded to each other using theadhesive layer220. After that, separation at an interface between the second separation layer and the insulatinglayer212 is conducted so that the second supporting base material and the second separation layer are removed, and then thesubstrate31 is bonded to the insulatinglayer212 using theadhesive layer211. Further, separation at an interface between the first separation layer and the insulatinglayer262 is conducted so that the first supporting base material and the first separation layer are removed, and then thesubstrate21 is bonded to the insulatinglayer262 using theadhesive layer261. Note that either side may be subjected to separation and attachment first.
• The above is the description of a manufacturing method of a flexible touch panel.
[Cross-Sectional Structure Example 2]
• FIG. 15 is a cross-sectional structure example whose structure is partly different from that ofFIG. 12A. Note that descriptions of the portions already described are omitted and different portions are described below.
• In the example shown inFIG. 15, theconductive layer25 is not provided. Theconductive layer24 is provided to cover part of the insulatinglayer28. Theconductive layer23 and theconductive layer24 overlap with each other in a region, and thecapacitor11 is formed in the region.
• FIG. 15 also shows a cross-sectional structure of a connection portion272 in which theconductive layer24 is electrically connected to a wiring formed by processing the conductive film used for forming theconductive layer23 through an opening formed in the insulatinglayer28.
• In the example shown inFIG. 15, theEL layer222 is separately formed in each pixel. TheEL layer222 can include a light-emitting layer containing a light-emitting material emitting light of one color. In the light-emittingelement204 shown inFIG. 15, theoptical adjustment layer224 shown inFIG. 12B is not included. Furthermore, thecoloring layer52 is not provided inFIG. 15. In this manner, the structure of the light-emitting element can be simplified in the case where theEL layer222 of the light-emittingelement204 is separately formed in each pixel to obtain light emission with high color purity from the light-emittingelement204.
• Here, the distance between one of theconductive layer23 and theconductive layer24 which is positioned closer to the display panel than the other and a conductive layer which is the closest to the one of theconductive layers23 and24 of the conductive layers provided closer to the display panel than the one of theconductive layers23 and24 is preferably greater than or equal to 25 nm and less than or equal to 100 μm, more preferably greater than or equal to 50 nm and less than or equal to 10 μm, still more preferably greater than or equal to 50 nm and less than or equal to 5 μm.
• In the example shown inFIG. 15, thesecond electrode223 of the light-emittingelement204 corresponds to the conductive layer which is the closest to theconductive layer24 of the conductive layers provided closer to the display panel than theconductive layer24. Here, as the distance D between theconductive layer24 and thesecond electrode223 is shorter, a distance between the pair of substrates can be reduced more, and the thickness of the touch panel can be reduced more. In particular, when a flexible substrate is used as the pair of substrates, the touch panel can be flexible and strong against bending.
• The above is the description of the cross-sectional structure example 2.
• Though this embodiment shows the structure including two substrates, i.e., the substrate supporting the touch sensor and the substrate supporting the display element, the structure is not limited thereto. For example, a structure with three substrates where a display element is sandwiched between two substrates and the substrate supporting a touch sensor is bonded thereto can be employed. Alternatively, a structure with four substrates where a display element sandwiched between two substrates and a touch sensor sandwiched between two substrates are bonded to each other can be employed.
• This embodiment can be combined with any of the other embodiments disclosed in this specification as appropriate.
Embodiment 2
• In this embodiment, an example of a method for operating the touch panel of one embodiment of the present invention is described with reference to drawings.
[Example of Sensing Method of Sensor]
• FIG. 16A is a block diagram illustrating the structure of a mutual capacitive touch sensor.FIG. 16A illustrates a pulsevoltage output circuit601 and acurrent sensing circuit602. Note that inFIG. 16A, six wirings X1 to X6 represent theelectrodes621 to which a pulse voltage is applied, and six wirings Y1 to Y6 represent theelectrodes622 that detect changes in current.FIG. 16A also illustrates acapacitor603 that is formed where theelectrodes621 and622 overlap with each other. Note that functional replacement between theelectrodes621 and622 is possible.
• The pulsevoltage output circuit601 is a circuit for sequentially applying a pulse voltage to the wirings X1 to X6. By application of a pulse voltage to the wirings X1 to X6, an electric field is generated between theelectrodes621 and622 of thecapacitor603. When the electric field between the electrodes is shielded, for example, a change occurs in the capacitor603 (mutual capacitance). The approach or contact of a sensing target can be sensed by utilizing this change.
• Thecurrent sensing circuit602 is a circuit for detecting changes in current flowing through the wirings Y1 to Y6 that are caused by the change in mutual capacitance in thecapacitor603. No change in current value is detected in the wirings Y1 to Y6 when there is no approach or contact of a sensing target, whereas a decrease in current value is detected when mutual capacitance is decreased owing to the approach or contact of a sensing target. Note that an integrator circuit or the like is used for sensing of current values.
• FIG. 16B is a timing chart showing input and output waveforms in the mutual capacitive touch sensor illustrated inFIG. 16A. InFIG. 16B, sensing of a sensing target is performed in all the rows and columns in one frame period.FIG. 16B shows a period when a sensing target is not sensed (not touched) and a period when a sensing target is sensed (touched). Sensed current values of the wirings Y1 to Y6 are shown as the waveforms of voltage values.
• A pulse voltage is sequentially applied to the wirings X1 to X6, and the waveforms of the wirings Y1 to Y6 change in accordance with the pulse voltage. When there is no approach or contact of a sensing target, the waveforms of the wirings Y1 to Y6 change in accordance with changes in the voltages of the wirings X1 to X6. The current value is decreased at the point of approach or contact of a sensing target and accordingly the waveform of the voltage value changes.
• By detecting a change in mutual capacitance in this manner, the approach or contact of a sensing target can be sensed.
• It is preferable that the pulsevoltage output circuit601 and thecurrent sensing circuit602 be mounted on a substrate in a housing of an electronic appliance or on the touch panel in the form of an IC. In the case where the touch panel has flexibility, parasitic capacitance might be increased in a bent portion of the touch panel, and the influence of noise might be increased. In view of this, it is preferable to use an IC to which a driving method less influenced by noise is applied. For example, it is preferable to use an IC to which a driving method capable of increasing a signal-noise ratio (S/N ratio) is applied.
• AlthoughFIG. 16A is a passive matrix type touch sensor in which only thecapacitor603 is provided at the intersection of wirings as a touch sensor, an active matrix type touch sensor including a transistor and a capacitor may be used.FIG. 17 is a sensor circuit included in an active matrix type touch sensor.
• The sensor circuit includes thecapacitor603 andtransistors611,612, and613. A signal G2 is input to a gate of thetransistor613. A voltage VRES is applied to one of a source and a drain of thetransistor613, and one electrode of thecapacitor603 and a gate of thetransistor611 are electrically connected to the other of the source and the drain of thetransistor613. One of a source and a drain of thetransistor611 is electrically connected to one of a source and a drain of thetransistor612, and a voltage VSS is applied to the other of the source and the drain of thetransistor611. A signal G1 is input to a gate of thetransistor612, and a wiring ML is electrically connected to the other of the source and the drain of thetransistor612. The voltage VSS is applied to the other electrode of thecapacitor603.
• Next, the operation of the sensor circuit will be described. First, a potential for turning on thetransistor613 is supplied as the signal G2, and a potential with respect to the voltage VRES is thus applied to the node n connected to the gate of thetransistor611. Then, a potential for turning off thetransistor613 is applied as the signal G2, whereby the potential of the node n is maintained.
• Then, mutual capacitance of thecapacitor603 changes owing to the approach or contact of a sensing target such as a finger, and accordingly the potential of the node n is changed from VRES.
• In reading operation, a potential for turning on thetransistor612 is supplied as the signal G1. A current flowing through thetransistor611, that is, a current flowing through the wiring ML is changed in accordance with the potential of the node n. By sensing this current, the approach or contact of a sensing target can be sensed.
• It is preferred that thetransistors611,612, and613 each include an oxide semiconductor in a semiconductor layer where a channel is formed. In particular, by using an oxide semiconductor in a semiconductor layer where a channel of thetransistor613 is formed, the potential of the node n can be held for a long time and the frequency of operation (refresh operation) of resupplying VRES to the node n can be reduced.
• At least part of this embodiment can be implemented in combination with any of the embodiments described in this specification as appropriate.
Embodiment 3
• In this embodiment, electronic appliances and lighting devices that can be fabricated according to one embodiment of the present invention will be described with reference toFIGS. 18A to 18G andFIGS. 19A to 19I.
• The touch panel of one embodiment of the present invention has flexibility. Therefore, a touch panel of one embodiment of the present invention can be used in electronic appliances and lighting devices having flexibility. Furthermore, according to one embodiment of the present invention, electronic appliances and lighting devices having high reliability and resistance against repeated bending can be manufactured.
• Examples of electronic appliances include a television set (also referred to as a television or a television receiver), a monitor of a computer or the like, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also referred to as a mobile phone device), a portable game machine, a portable information terminal, an audio reproducing device, a large game machine such as a pinball machine, and the like.
• The touch panel of one embodiment of the present invention has flexibility and therefore can be incorporated along a curved inside/outside wall surface of a house or a building or a curved interior/exterior surface of a car.
• An electronic appliance of one embodiment of the present invention may include a touch panel and a secondary battery. It is preferable that the secondary battery is capable of being charged by contactless power transmission.
• As examples of the secondary battery, a lithium ion secondary battery such as a lithium polymer battery (lithium ion polymer battery) using a gel electrolyte, a lithium ion battery, a nickel-hydride battery, a nickel-cadmium battery, an organic radical battery, a lead-acid battery, an air secondary battery, a nickel-zinc battery, and a silver-zinc battery can be given.
• The electronic appliance of one embodiment of the present invention may include a touch panel and an antenna. When a signal is received by the antenna, the electronic appliance can display an image, data, or the like on a display portion. When the electronic appliance includes a secondary battery, the antenna may be used for contactless power transmission.
• FIG. 18A illustrates an example of a mobile phone. Themobile phone7400 is provided with adisplay portion7402 incorporated in ahousing7401,operation buttons7403, anexternal connection port7404, aspeaker7405, amicrophone7406, and the like. Note that themobile phone7400 is manufactured by using the touch panel of one embodiment of the present invention for thedisplay portion7402. In accordance with one embodiment of the present invention, a highly reliable mobile phone having a curved display portion can be provided at a high yield.
• When thedisplay portion7402 of themobile phone7400 illustrated inFIG. 18A is touched with a finger or the like, data can be input into themobile phone7400. Further, operations such as making a call and inputting a letter can be performed by touch on thedisplay portion7402 with a finger or the like.
• With theoperation buttons7403, power ON or OFF can be switched. In addition, types of images displayed on thedisplay portion7402 can be switched; switching images from a mail creation screen to a main menu screen.
• FIG. 18B illustrates an example of a wrist-watch-type portable information terminal Aportable information terminal7100 includes ahousing7101, adisplay portion7102, aband7103, abuckle7104, anoperation button7105, an input/output terminal7106, and the like.
• Theportable information terminal7100 is capable of executing a variety of applications such as mobile phone calls, e-mailing, reading and editing texts, music reproduction, Internet communication, and a computer game.
• The display surface of thedisplay portion7102 is bent, and images can be displayed on the bent display surface. Furthermore, thedisplay portion7102 includes a touch sensor, and operation can be performed by touching the screen with a finger, a stylus, or the like. For example, by touching anicon7107 displayed on thedisplay portion7102, an application can be started.
• With theoperation button7105, a variety of functions such as time setting, power ON/OFF, ON/OFF of wireless communication, setting and cancellation of manner mode, and setting and cancellation of power saving mode can be performed. For example, the functions of theoperation button7105 can be set freely by setting the operating system incorporated in theportable information terminal7100.
• Theportable information terminal7100 can employ near field communication that is a communication method based on an existing communication standard. In that case, for example, mutual communication between theportable information terminal7100 and a headset capable of wireless communication can be performed, and thus hands-free calling is possible.
• Moreover, theportable information terminal7100 includes the input/output terminal7106, and data can be directly transmitted to and received from another information terminal via a connector. Charging through the input/output terminal7106 is possible. Note that the charging operation may be performed by wireless power feeding without using the input/output terminal7106.
• Thedisplay portion7102 of theportable information terminal7100 includes the touch panel of one embodiment of the present invention. According to one embodiment of the present invention, a highly reliable portable information terminal having a curved display portion can be provided with a high yield.
• FIGS. 18C to 18E illustrate examples of a lighting device.Lighting devices7200,7210, and7220 each include astage7201 provided with anoperation switch7203 and a light-emitting portion supported by thestage7201.
• Thelighting device7200 illustrated inFIG. 18C includes a light-emittingportion7202 having a wave-shaped light-emitting surface, and thus has good design.
• A light-emittingportion7212 included in thelighting device7210 illustrated inFIG. 18D has two convex-curved light-emitting portions symmetrically placed. Thus, all directions can be illuminated with thelighting device7210 as a center.
• Thelighting device7220 illustrated inFIG. 18E includes a concave-curved light-emittingportion7222. This is suitable for illuminating a specific range because light emitted from the concave-curved light-emittingportion7222 is collected to the front of thelighting device7220.
• The light-emitting portion included in each of thelighting devices7200,7210, and7220 are flexible; thus, the light-emitting portion may be fixed on a plastic member, a movable frame, or the like so that an emission surface of the light-emitting portion can be bent freely depending on the intended use.
• Note that although the lighting device in which the light-emitting portion is supported by the stage is described as an example here, a housing provided with a light-emitting portion can be fixed on a ceiling or suspended from a ceiling. Since the light-emitting surface can be curved, the light-emitting surface is curved to have a depressed shape, whereby a particular region can be brightly illuminated, or the light-emitting surface is curved to have a projecting shape, whereby a whole room can be brightly illuminated.
• Here, the light-emitting portions each include the touch panel of one embodiment of the present invention. In accordance with one embodiment of the present invention, a highly reliable lighting device having a curved light-emitting portion can be provided at a high yield.
• FIG. 18F illustrates an example of a portable touch panel. Atouch panel7300 includes ahousing7301, adisplay portion7302,operation buttons7303, adisplay portion pull7304, and acontrol portion7305.
• Thetouch panel7300 includes a rolledflexible display portion7302 in thecylindrical housing7301.
• Thetouch panel7300 can receive a video signal with thecontrol portion7305 and can display the received video on thedisplay portion7302. In addition, a battery is included in thecontrol portion7305. Moreover, a terminal portion for connecting a connector may be included in thecontrol portion7305 so that a video signal or power can be directly supplied from the outside with a wiring.
• By pressing theoperation buttons7303, power ON/OFF, switching of displayed videos, and the like can be performed.
• FIG. 18G illustrates atouch panel7300 in a state where thedisplay portion7302 is pulled out with thedisplay portion pull7304. Videos can be displayed on thedisplay portion7302 in this state. Further, theoperation buttons7303 on the surface of thehousing7301 allow one-handed operation. Theoperation buttons7303 are provided not in the center of thehousing7301 but on one side of thehousing7301 as illustrated inFIG. 18F, which makes one-handed operation easy.
• Note that a reinforcement frame may be provided for a side portion of thedisplay portion7302 so that thedisplay portion7302 has a flat display surface when pulled out.
• Note that in addition to this structure, a speaker may be provided for the housing so that sound is output with an audio signal received together with a video signal.
• Thedisplay portion7302 includes the touch panel of one embodiment of the present invention. According to one embodiment of the present invention, a lightweight and highly reliable touch panel can be provided with a high yield.
• FIGS. 19A to 19C illustrate a foldableportable information terminal310.FIG. 19A illustrates theportable information terminal310 that is opened.FIG. 19B illustrates theportable information terminal310 that is being opened or being folded.FIG. 19C illustrates theportable information terminal310 that is folded. Theportable information terminal310 is highly portable when folded. When theportable information terminal310 is opened, a seamless large display region is highly browsable.
• Adisplay panel316 is supported by threehousings315 joined together by hinges313. By folding theportable information terminal310 at a connection portion between twohousings315 with thehinges313, theportable information terminal310 can be reversibly changed in shape from an opened state to a folded state. The touch panel according to one embodiment of the present invention can be used for thedisplay panel316. For example, a touch panel that can be bent with a radius of curvature of greater than or equal to 1 mm and less than or equal to 150 mm can be used.
• Note that in one embodiment of the present invention, a sensor that senses whether the touch panel is in a folded state or an unfolded state and supplies sensing data may be used. The operation of a folded portion (or a portion that becomes invisible by a user by folding) of the touch panel may be stopped by a control device through the acquisition of data indicating the folded state of the touch panel. Specifically, display of the portion may be stopped, and furthermore, sensing by the touch sensor may be stopped.
• Similarly, the control device of the touch panel may acquire data indicating the unfolded state of the touch panel to resume displaying and sensing by the touch sensor.
• FIGS. 19D and 19E each illustrate a foldableportable information terminal320.FIG. 19D illustrates theportable information terminal320 that is folded so that adisplay portion322 is on the outside.FIG. 19E illustrates theportable information terminal320 that is folded so that thedisplay portion322 is on the inside. When theportable information terminal320 is not used, theportable information terminal320 is folded so that anon-display portion325 faces the outside, whereby thedisplay portion322 can be prevented from being contaminated or damaged. The touch panel in one embodiment of the present invention can be used for thedisplay portion322.
• FIG. 19F is a perspective view illustrating an external shape of theportable information terminal330.FIG. 19G is a top view of theportable information terminal330.FIG. 19H is a perspective view illustrating an external shape of aportable information terminal340.
• Theportable information terminals330 and340 each function as, for example, one or more of a telephone set, a notebook, and an information browsing system. Specifically, theportable information terminals330 and340 each can be used as a smartphone.
• Theportable information terminals330 and340 can display characters and image information on its plurality of surfaces. For example, threeoperation buttons339 can be displayed on one surface (FIGS. 19F and 19H). In addition,information337 indicated by dashed rectangles can be displayed on another surface (FIGS. 19F,19G, and19H). Examples of theinformation337 include notification from a social networking service (SNS), display indicating reception of an e-mail or an incoming call, the title of an e-mail or the like, the sender of an e-mail or the like, the date, the time, remaining battery, and the reception strength of an antenna. Alternatively, theoperation buttons339, an icon, or the like may be displayed in place of theinformation337. AlthoughFIGS. 19F and 19G illustrate an example in which theinformation337 is displayed at the top, one embodiment of the present invention is not limited thereto. The information may be displayed, for example, on the side as in theportable information terminal340 illustrated inFIG. 19H.
• For example, a user of theportable information terminal330 can see the display (here, the information337) with theportable information terminal330 put in a breast pocket of his/her clothes.
• Specifically, a caller's phone number, name, or the like of an incoming call is displayed in a position that can be seen from above theportable information terminal330. Thus, the user can see the display without taking out theportable information terminal330 from the pocket and decide whether to answer the call.
• A touch panel of one embodiment of the present invention can be used for adisplay portion333 mounted in each of ahousing335 of theportable information terminal330 and ahousing336 of theportable information terminal340. According to one embodiment of the present invention, a highly reliable touch panel having a curved display portion can be provided with a high yield.
• As in aportable information terminal345 illustrated inFIG. 19I, data may be displayed on three or more surfaces. Here,data355,data356, anddata357 are displayed on different surfaces.
• The touch panel of one embodiment of the present invention can be used for adisplay portion358 included in ahousing354 of theportable information terminal345. According to one embodiment of the present invention, a highly reliable touch panel having a curved display portion can be provided with a high yield.
• At least part of this embodiment can be implemented in combination with any of the embodiments described in this specification as appropriate.
Example
• In this example, a foldable touch panel of one embodiment of the present invention was fabricated. This example also describes the results of performing evaluation of a time constant and performing a folding test on the touch panel.
[Fabrication of Touch Panel]
• In this example, an in-cell touch panel in which a touch sensor was formed in a counter substrate (a substrate on the display surface side) of a flexible display panel was fabricated. An electrode of the touch sensor had a metal-mesh structure to reduce the load capacitance formed between the touch sensor and the display panel. Thus, the whole touch panel can be thin enough to be freely folded by a user. In addition, because of the small load capacitance, the influence of noise from the display panel to the touch sensor can be suppressed, so that defects such as false detection and detection failure can be suppressed.
• As a method for driving the in-cell touch panel fabricated in this example, a projected mutual capacitive type was employed.
• The touch panel having the cross-sectional structure shown inFIGS. 12A and 12B was fabricated in this example. As the mesh pattern of the touch sensor, the pattern shown inFIG. 6 was used.
• FIG. 20 shows a structure of the touch panel fabricated in this example. A schematic view of the touch panel is shown in the center ofFIG. 20, a cross-sectional structure of the touch panel is shown in the left side thereof, and an enlarged view of a bent portion of the touch panel is shown in the right side thereof. The touch panel includes a display portion (denoted by Display) having flexibility and an FPC. In the structure of the touch panel, two flexible substrates were bonded to each other with an adhesive layer, and a passivation layer was provided on each of the facing surfaces of the flexible substrates. An FET layer (denoted by FET) and an organic EL element (denoted by OLED) were formed over the passivation layer over one of the flexible substrates. A touch sensor and a color filter were formed over the passivation layer over the other of the flexible substrates. As shown inFIG. 20, the touch panel fabricated in this example can be folded so that its display surface has a convex curve and a concave curve.
• First, a separation layer, the passivation layer, the FET layer, and the organic EL element were formed over a glass substrate.
• As a transistor (e.g., the transistor201) included in the FET layer, a transistor including an oxide semiconductor as a semiconductor where a channel is formed was used. Here, a crystalline oxide semiconductor having c-axis alignment in a direction perpendicular to a film surface (CAAC-OS: c-axis aligned crystalline-oxide semiconductor) was used as the oxide semiconductor in this example.
• A CAAC-OS is a crystalline oxide semiconductor having c-axis alignment of crystals in a direction substantially perpendicular to the film surface. It has been found that oxide semiconductors have a variety of crystal structures other than a single-crystal structure. An example of such structures is a nano-crystal (nc) structure, which is an aggregate of nanoscale microcrystals. The crystallinity of a CAAC-OS structure is lower than that of a single-crystal structure and higher than that of an nc structure. Moreover, since the CAAC-OS does not have a grain boundary, a stable and uniform film can be formed over a large area, and stress that is caused by bending a flexible light-emitting device does not easily make a crack in a CAAC-OS film.
• In—Ga—Zn-based oxide was used as the oxide semiconductor material in this example.
• As a pixel electrode (the first electrode221), alloy containing silver with extremely high reflectivity was used. A transparent electrode layer (the optical adjustment layer224) was formed over the pixel electrode and the thickness thereof varied as appropriate depending on the structure of the sub-pixel to produce a microcavity effect.
• As the organic EL element, a top-emission white EL element was used. The organic EL element had a tandem structure in which a blue light-emitting unit and a yellow light-emitting unit were stacked.
• Furthermore, a separation layer, the passivation layer, a light-blocking layer, a touch sensor electrode, and the color filter were formed over another glass substrate. In order to suppress reflection of light by the touch sensor electrode, the light-blocking layer was provided between the touch sensor electrode and the passivation layer.
• Then, the two substrates were bonded to each other with the adhesive layer. The distance (cell gap) between the substrates was set to approximately 5 μm. Then, separation of each substrate was made to occur between the separation layer and the passivation layer, and the flexible substrates were attached. The flexible substrates were plastic substrates each having a thickness of approximately 20 μm.
• In this manner, the touch panel was fabricated. Table 1 shows the specifications of a display device, and Table 2 shows the specifications of the touch sensor.

• TABLE 1
  Specifications of 8.67 inch OLED Display

  	Screen diagonal	8.67 inch
  	Driving method	Active Matrix
  	Number of effective pixels	1080 × RGBY × 1920
  	Pixel pitch	0.100 mm × 0.100 mm
  	Pixel density	254 ppi
  	Aperture ratio	0.46%
  	Pixel arrangement	RGBY checker
  	Pixel circuit	6Tr + 1C/cell
  	Source driver	COF
  	Scan driver	Integrated

• TABLE 2
  Specifications of 8.67 inch Touch Sensor

  	Screen diagonal	8.67 inch
  	Driving method	Projection capacitance
  		(Mutual capacitance)
  	Sensor structure	Metal mesh
  	Number of sensor units	48(T) × 27(R)
  	Sensor unit pitch	4.00 mm × 4.00 mm

• The pixel included in the touch panel fabricated in this example included four RGBY sub-pixels. The use of the Y (yellow) sub-pixel increased current efficiency and reduced chromaticity variation depending on the viewing angle more than the case of using a white sub-pixel.
• For the touch sensor, 48 transmitting electrodes were arranged in the longitudinal direction of the display portion and 27 receiving electrodes were arranged in the lateral direction thereof with 4 mm pitches. A matrix of 40×40 pixels in the display portion corresponds to one unit of the touch sensor.
[Touch Panel]
• FIGS. 21A to 21C are photographs of the fabricated touch panel.FIG. 21A shows a state where the display panel is unfolded.FIG. 21B shows a state where the display panel is folded in three.FIG. 21C shows a state where the display panel is touched while folded. It was demonstrated that a touch on each of a flat surface portion, a convex curved portion, and a concave curved portion of the surface of the touch panel was detected appropriately.
• Since the pixels are arranged in the openings in the mesh of the touch sensor electrode, providing the touch sensor does not significantly affect the light extraction efficiency.
[Evaluation of Time Constant]
• Next, the parasitic capacitance and resistance between the receiving electrode of the fabricated touch panel and the display panel were measured with varying frequency. An LCR meter (4275A manufactured by Agilent Technologies, Inc.) was used for the measurement.
• FIG. 22 shows the measurement results. The vertical axis on the left side, the vertical axis on the right side, and the horizontal axis inFIG. 22 represent parasitic capacitance, parasitic resistance, and frequency, respectively. The number of measurements was six. As shown inFIG. 22, with 10 kHz measurement frequency, the parasitic capacitance was approximately 910 pF, and the parasitic resistance was approximately 1.3 kΩ. The time constant was calculated to be approximately 1.2 μs. This value is small but not so small as to cause failure of touch detection.
• [Folding test]
• Next, the results of performing a folding test on the fabricated touch panel are described. In the folding test, an operation of folding and unfolding the touch panel with a curvature radius of 5 mm or 3 mm was performed once every two seconds, and the operation was repeated 100,000 times. The folding and unfolding operation was performed under two different conditions: inward folding (the display surface faces inward) and outward folding (the display surface faces outward). Even after the folding and unfolding operation was performed 100,000 times, normal display and touch detection were achieved.
• These results show that the touch panel of one embodiment of the present invention is a foldable touch panel with high reliability, high visibility, and low power consumption. This touch panel will lead to a novel mobile device.
• This application is based on Japanese Patent Application serial no. 2014-112316 filed with Japan Patent Office on May 30, 2014, Japanese Patent Application serial no. 2014-128409 filed with Japan Patent Office on Jun. 23, 2014, and Japanese Patent Application serial no. 2014-242912 filed with Japan Patent Office on Dec. 1, 2014, the entire contents of which are hereby incorporated by reference.

Claims (18)

1. A touch panel comprising:

a first substrate;

a second substrate;

a first conductive layer having a first opening;

a second conductive layer having a second opening; and

a first light-emitting element and a second light-emitting element between the first substrate and the second substrate,

wherein the first conductive layer and the second conductive layer form a capacitor,

wherein the first opening and whole of the first light-emitting element overlap with each other,

wherein the second opening and whole of the second light-emitting element overlap with each other, and

wherein the first conductive layer and the second conductive layer are positioned between the second substrate and at least one of the first light-emitting element and the second light-emitting element.

2. The touch panel according toclaim 1, wherein a time constant of at least one of the first conductive layer and the second conductive layer is greater than 0 s and less than or equal to 1×10⁻⁴s.

3. The touch panel according toclaim 1, wherein an aperture ratio of at least one of the first conductive layer and the second conductive layer is greater than or equal to 20% and less than 100%.

4. The touch panel according toclaim 1, further comprising:

a third conductive layer provided closer to the first substrate than at least one of the first conductive layer and the second conductive layer,

wherein at least one of a first distance between the first conductive layer and the third conductive layer and a second distance between the second conductive layer and the third conductive layer is greater than or equal to 25 nm and less than or equal to 50 nm.

5. The touch panel according toclaim 1, further comprising:

a first insulating layer,

wherein the first conductive layer and the second conductive layer overlap with each other, and

wherein the first insulating layer is positioned between the first conductive layer and the second conductive layer.

6. The touch panel according toclaim 1, further comprising:

a fourth conductive layer; and

a second insulating layer having a third opening,

wherein the fourth conductive layer and the second conductive layer overlap with each other,

wherein the second insulating layer is positioned between the first conductive layer and the fourth conductive layer,

wherein the second insulating layer is positioned between the second conductive layer and the fourth conductive layer, and

wherein the first conductive layer and the fourth conductive layer are electrically connected to each other through the third opening.

7. The touch panel according toclaim 1, further comprising:

a light-blocking layer between the second substrate and at least one of the first conductive layer and the second conductive layer,

wherein the first conductive layer and the light-blocking layer overlap with each other, and

wherein the second conductive layer and the light-blocking layer overlap with each other.

8. A module comprising:

the touch panel according toclaim 1; and

at least one of a flexible printed circuit and a tape carrier package.

9. An electronic appliance comprising:

the touch panel according toclaim 1; and

at least one of a battery, an antenna, a housing, an operation button, an external connection port, a speaker, and a microphone.

10. A touch panel comprising:

a first substrate;

a second substrate;

a first conductive layer having a first opening;

a second conductive layer having a second opening; and

a first light-emitting element and a second light-emitting element between the first substrate and the second substrate,

wherein the first conductive layer and the second conductive layer form a capacitor,

wherein the first opening and both of whole of the first light-emitting element and whole of the second light-emitting element overlap with each other, and

wherein the first conductive layer and the second conductive layer are positioned between the second substrate and at least one of the first light-emitting element and the second light-emitting element.

11. The touch panel according toclaim 10, wherein a time constant of at least one of the first conductive layer and the second conductive layer is greater than 0 s and less than or equal to 1×10⁻⁴s.

12. The touch panel according toclaim 10, wherein an aperture ratio of at least one of the first conductive layer and the second conductive layer is greater than or equal to 20% and less than 100%.

13. The touch panel according toclaim 10, further comprising:

a third conductive layer provided closer to the first substrate than at least one of the first conductive layer and the second conductive layer,

wherein at least one of a first distance between the first conductive layer and the third conductive layer and a second distance between the second conductive layer and the third conductive layer is greater than or equal to 25 nm and less than or equal to 50 μm.

14. The touch panel according toclaim 10, further comprising:

a first insulating layer,

wherein the first conductive layer and the second conductive layer overlap with each other, and

wherein the first insulating layer is positioned between the first conductive layer and the second conductive layer.

15. The touch panel according toclaim 10, further comprising:

a fourth conductive layer; and

a second insulating layer having a third opening,

wherein the fourth conductive layer and the second conductive layer overlap with each other,

wherein the second insulating layer is positioned between the first conductive layer and the fourth conductive layer,

wherein the second insulating layer is positioned between the second conductive layer and the fourth conductive layer, and

wherein the first conductive layer and the fourth conductive layer are electrically connected to each other through the third opening.

16. The touch panel according toclaim 10, further comprising:

a light-blocking layer between the second substrate and at least one of the first conductive layer and the second conductive layer,

wherein the first conductive layer and the light-blocking layer overlap with each other, and

wherein the second conductive layer and the light-blocking layer overlap with each other.

17. A module comprising:

the touch panel according toclaim 10; and

at least one of a flexible printed circuit and a tape carrier package.

18. An electronic appliance comprising:

the touch panel according toclaim 10; and

at least one of a battery, an antenna, a housing, an operation button, an external connection port, a speaker, and a microphone.

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