US20220317790A1 - Touch panel and method for manufacturing touch panel - Google Patents

Abstract

A touch panel capable of performing display and sensing along a curved surface or a touch panel that maintains high detection sensitivity even when it is curved along a curved surface is provided. A flexible display panel is placed along a curved portion included in a surface of a support. A first film layer is attached along a surface of the display panel by a bonding layer. Second to n-th film layers (n is an integer of 2 or more) are sequentially attached along a surface of the first film layer by bonding layers. A flexible touch sensor is attached along a surface of the n-th film layer by a bonding layer.

Description

TECHNICAL FIELD
• One embodiment of the present invention relates to a display device, and particularly to a flexible display device capable of performing display along a curved surface. One embodiment of the present invention also relates to a touch panel, and particularly to a flexible touch panel capable of being placed along a curved surface. Furthermore, one embodiment of the present invention relates to an electronic device having a display portion.
• Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, 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, a method for driving any of them, and a method for manufacturing any of them.
BACKGROUND 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 appliances.
• 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.
[Reference]
• Patent Document 1: Japanese Published Patent Application No. 2003-174153
DISCLOSURE OF INVENTION
• It is expected that placing a touch panel along a curved surface of a housing in an electronic device will provide an unprecedented function and application for the electronic device. For this reason, what is desirable is a touch panel in which a display device thinned to have flexibility is provided with a function of inputting data with a finger or the like touching a screen as a user interface.
• An object of one embodiment of the present invention is to provide a touch panel capable of performing display and sensing along a curved surface. Another object of one embodiment of the present invention is to provide a touch panel that maintains high detection sensitivity even when it is curved along a curved surface. Another object of one embodiment of the present invention is to provide an electronic device capable of performing display and sensing along a curved surface. Another object of one embodiment of the present invention is to provide an electronic device in which the detection sensitivity of a touch panel is high even in a curved portion.
• Another object of one embodiment of the present invention is to provide a novel display device, a novel touch sensor, a novel touch panel, or a novel electronic device.
• Note that the description of these objects does not disturb the existence of other objects. In one embodiment of the present invention, there is no need to achieve all the objects. Objects other than the above objects will be apparent from and can be derived from the description of the specification and the like.
• One embodiment of the present invention is a method for manufacturing a touch panel, including the following steps: placing a flexible display panel along a curved portion included in a surface of a support; attaching a film layer along a surface of the display panel by a bonding layer; and attaching a flexible touch sensor along a surface of the film layer by a bonding layer.
• Another embodiment of the present invention is a method for manufacturing a touch panel, including the following steps: placing a flexible display panel along a curved portion included in a surface of a support; attaching a first film layer along a surface of the display panel by a bonding layer; sequentially attaching second to n-th film layers (n is an integer of 2 or more) along a surface of the first film layer by bonding layers; and attaching a flexible touch sensor along a surface of the n-th film layer by a bonding layer.
• The method preferably includes a step of sequentially attaching (n+1)th to m-th film layers (m is an integer of n+1 or more) along a surface of the touch sensor after the step of attaching the touch sensor.
• Another embodiment of the present invention is a touch panel including a display panel, first to n-th film layers (n is an integer of 2 or more), and a touch sensor that are sequentially stacked. A surface of the touch panel is a curved surface maintained even when the touch panel is not supported by a support.
• In the touch panel, it is preferred that the display panel have a thickness of 1 μm to 300 μm, that the touch sensor have a thickness of 1 μm to 300 μm, and that each of the first to n-th film layers have a thickness of 1 μm to 300 μm.
• In the touch panel, it is preferred that any adjacent two of the display panel, the first to n-th film layers, and the touch sensor be attached to each other by a bonding layer, and that the bonding layer have a thickness of 300 nm to 300 μm.
• One embodiment of the present invention can provide a touch panel capable of performing display and sensing along a curved surface. Another embodiment of the present invention can provide a touch panel whose detection sensitivity is high even when it is curved along a curved surface.
• Another embodiment of the present invention can provide a novel display device (display panel), touch sensor, or touch panel. 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. 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 DRAWINGS
• In the accompanying drawings:
• FIGS.1A1 and1A2 illustrate a structure example of an electronic device, andFIGS. 1B and 1C illustrate a structure example of a touch panel;
• FIGS. 2A and 2B illustrate structure examples of a touch panel;
• FIG. 3 illustrates a structure example of a touch panel;
• FIGS.4A1,4A2,4B1,4B2,4C1,4C2, and4D illustrate an example of a method for manufacturing a touch panel;
• FIGS.5A1,5A2,5B1,5B2,5C1, and5C2 illustrate structure examples of an electronic device;
• FIG. 6 illustrates a structure example of a touch sensor;
• FIGS. 7A to 7C illustrate structure examples of a touch sensor;
• FIG. 8 illustrates a structure example of a display panel;
• FIG. 9 illustrates a configuration example of a circuit applicable to a display panel;
• FIGS. 10A and 10B illustrate structure examples of a display panel;
• FIG. 11 illustrates a structure example of a display panel;
• FIGS. 12A and 12B illustrate structure examples of an electronic device, andFIGS. 12C to 12E illustrate structure examples of a lighting device;
• FIGS. 13A to 13D illustrate structure examples of an electronic device;
• FIG. 14 illustrates a stacked-layer structure in Example 3;
• FIG. 15 is a photograph of a touch panel in Example 3;
• FIGS. 16A and 16B are a circuit diagram and a timing chart in Example 1;
• FIGS. 17A and 17B are circuit diagrams in Example 1;
• FIGS. 18A and 18B show input-output characteristics in Example 1;
• FIG. 19 shows results of calculating output characteristics of circuits in Example 1;
• FIG. 20A is a photograph showing a display panel in measurement andFIG. 20B shows results of measuring electromagnetic noise in Example 1;
• FIG. 21 is a schematic top diagram of a test element in Example 2;
• FIG. 22 shows results of measuring resistance in Example 2; and
• FIGS. 23A and 23B show output characteristics of a touch sensor in Example 2.
BEST MODE FOR CARRYING OUT THE INVENTION
• Embodiments will be described in detail with reference to the 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. In some cases, the same hatching pattern is used for portions having similar functions, and the portions are not denoted by reference numerals.
• 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 and second are used in order to avoid confusion among components and do not limit the number.
(Embodiment 1)
• In this embodiment, a touch panel of one embodiment of the present invention and examples of electronic devices having the touch panel will be described with reference to drawings.
[Structure Example]
• FIGS.1A1 and1A2 are schematic perspective diagrams of anelectronic device10. FIG.1A1 illustrates the front surface, right side surface, and top surface of theelectronic device10. FIG.1A2 illustrates the back surface, left side surface, and top surface of theelectronic device10. Note that the side A and the side B of the line A-B in FIGS.1A1 and1A2 are the front side and the back side of theelectronic device10, respectively.
• Theelectronic device10 is provided with atouch panel100 capable of display on a surface of ahousing101. Thetouch panel100 is positioned along surfaces of parts of regions in the top, front, and back surfaces of thehousing101 among six faces of the top, back, front, bottom, right side, and left side surfaces. In thehousing101, at least the surfaces where thetouch panel100 is positioned have curved portions.
• FIG. 1B is a schematic cross-sectional diagram along the line A-B in FIGS.1A1 and1A2. A region including the surface with a curved portion of thehousing101 is cut along the line A-B.
• Thetouch panel100 is provided along a surface of asupport103. The surface of thesupport103 has a curved portion. A light-transmittingexterior component102 is provided to cover thetouch panel100. The light-transmittingexterior component102 is preferably used at least in a region of thehousing101 that overlaps with a display portion of thetouch panel100. Thesupport103 and theexterior component102 may be part of thehousing101.
• The curved portion of the surface of thesupport103 is preferably a surface that can be made by transforming a plane without stretching or compressing (i.e., a developable surface).
• Thesupport103 has a function of maintaining the shape of thetouch panel100. For thesupport103, a material with higher stiffness than at least the touch panel100 (e.g., resin, glass, or metal) can be used.
• As thesupport103, it is possible to use a support for determining the shape of thetouch panel100 in an example of manufacturing steps of thetouch panel100 that is described later. Note that thesupport103 is not necessarily provided when it is not required in thehousing101, or thesupport103 may be part of thehousing101.
• For theexterior component102, a light-transmitting material (e.g., glass or an organic material such as acrylic) can be used. Since a surface of theexterior component102 serves as a touch surface, theexterior component102 is preferably an insulator. A high dielectric constant material is preferably used for theexterior component102, in which case the detection sensitivity of thetouch panel100 can be increased.
• When a surface of thetouch panel100 functions as a touch surface, it is possible that theexterior component102 is not provided and the surface of thetouch panel100 is exposed. In this case, the surface of thetouch panel100 is preferably coated with a material having high hardness.
• FIG. 1C is an enlarged schematic cross-sectional diagram of a region surrounded by dashed lines inFIG. 1B.FIG. 2A is a schematic diagram showing that the components illustrated inFIG. 1C are separated from each other.
• Thetouch panel100 includes adisplay panel111, atouch sensor112, and a plurality of film layers113. Thedisplay panel111 and thetouch sensor112 are stacked so that thedisplay panel111 is placed on thesupport103 side and thetouch sensor112 is placed on theexterior component102 side. Furthermore, n film layers113 (n is an integer of 2 or more) are sandwiched between thedisplay panel111 and thetouch sensor112. Here, among the film layers sandwiched between thedisplay panel111 and thetouch sensor112, the film layer nearest to thedisplay panel111 is referred to as a film layer113(1), the film layer next nearest to thedisplay panel111 is referred to as a film layer113(2), and the film layer nearest to thetouch sensor112 is referred to as a film layer113(n). In the following description, the term “film layer113” is used when the film layers are not distinguished from each other.
• Two film layers113 are preferably bonded to each other with abonding layer114 as shown inFIG. 1C and the like. Similarly, bonding of the film layer113(1) and thedisplay panel111 as well as bonding of the film layer113(n) and thetouch sensor112 is preferably performed with bonding layers114.
• Thedisplay panel111 is flexible and is provided along the surface of thesupport103. The film layer113(1) is provided along a surface of thedisplay panel111. The film layer113(2) is provided along a surface of the film layer113(1). Similarly, the film layer113(n) is provided along a surface of the film layer113(n−1). Thetouch sensor112 is provided along a surface of the film layer113(n).
• The plurality of film layers113 sandwiched between thedisplay panel111 and thetouch sensor112 in such a manner can increase the distance between thedisplay panel111 and thetouch sensor112, thereby decreasing parasitic capacitance between a wiring or an electrode included in thedisplay panel111 and that included in thetouch sensor112. This prevents the detection sensitivity of thetouch sensor112 from being decreased by adverse effects on thetouch sensor112 of noise that occurs when thedisplay panel111 is driven.
• As compared to the case where a spacer, which is a single component, is sandwiched between thedisplay panel111 and thetouch sensor112 to increase the distance therebetween, the use of the plurality of film layers113 makes noise from thedisplay panel111 likely to be scattered between the film layers113, resulting in a reduction in the effect of noise on thetouch sensor112 in some cases.
• The thickness of thedisplay panel111 ranges preferably from 1 μm to 300 μm, for example, more preferably from 3 μm to 200 μm, still more preferably from 5 μm to 100 μm. Typically, the thickness of thedisplay panel111 is preferably approximately 50 μm.
• The thickness of thetouch sensor112 ranges preferably from 1 μm to 300 μm, more preferably from 3 μm to 200 μm, still more preferably from 5 μm to 100 μm. Typically, the thickness of thetouch sensor112 is preferably approximately 50 μm.
• If thedisplay panel111 or thetouch sensor112 has a thickness of less than 1 μm, insufficient mechanical strength of thedisplay panel111 or thetouch sensor112 contributes to damage. On the other hand, if thedisplay panel111 or thetouch sensor112 has a thickness of more than 500 μm, the flexibility decreases and stress applied to thedisplay panel111 or thetouch sensor112 increases because the difference between the inner diameter and outer diameter of the curved portion increases. Thus, a substrate included in thedisplay panel111 or thetouch sensor112 or a wiring, an element, or the like provided over the substrate might be damaged.
• The thickness of thefilm layer113 can be set as appropriate in accordance with the number of layers to be stacked, the radius of curvature of a curved surface, or the like. Specifically, the thickness of thefilm layer113 is 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less, still more preferably 150 μm or less, yet still more preferably 100 μm, even yet still more preferably 50 μm and is 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more. As thefilm layer113 is thinner, thefilm layer113 can be more easily provided along a curved surface with a smaller radius of curvature; however, the number of stacked layers increases to increase the distance between thedisplay panel111 and thetouch sensor112, which might result in a complicated fabrication process. If thefilm layer113 has a thickness of more than 500 μm, a wrinkle, a crack, or the like might occur on the surface of thefilm layer113 depending on the radius of curvature of the curved surface of thesupport103.
• The thickness of thebonding layer114 is 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less, still more preferably 50 μm or less and is 300 nm or more, preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more.
• For thefilm layer113 and thebonding layer114, a low dielectric constant material is preferably used. Thefilm layer113 formed using a low dielectric constant material can reduce the number of stacked film layers113 as well as parasitic capacitance between thetouch sensor112 and thedisplay panel111. For example, thefilm layer113 and thebonding layer114 are preferably formed using a material with a dielectric constant in the range of 2.0 to 10.0, preferably 2.0 to 5.0, more preferably 2.0 to 4.5, still more preferably 2.0 to 4.0.
• The material used for thefilm layer113 and thebonding layer114 preferably has high visible light transmittance. It is preferable to use a material with transmittance of visible light (e.g., light in the wavelength range of 400 nm to 700 nm) of 70% or more, preferably 80% or more, more preferably 85% or more, still more preferably 90% or more.
• For thefilm layer113, an insulating material with a light-transmitting property, for example, an organic insulating material or an inorganic insulating material can be used. Moreover, a material used for thefilm layer113 may be in a sheet form, have viscosity, or be obtained by drying and solidifying a viscous material. Furthermore, thefilm layer113 may have a stacked-layer structure using at least two organic insulating materials, at least two inorganic insulating materials, or a combination of an organic insulating material and an inorganic insulating material.
• Examples of a material used for thefilm layer113 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, for example, a polyamide imide resin, a polyimide resin, or PET, which has a thermal expansion coefficient of 30×10⁻⁶/K or lower. It is also possible to use 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.
• 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 modulus of elasticity or a fiber with a high Young's modulus. Typical examples 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 a flexible substrate. The structure body including the fibrous body and the resin is preferably used as a flexible substrate, in which case the reliability against bending and damage due to local pressure can be increased.
• For thebonding layer114, a viscous material or a curable resin such as a heat curable resin, a photocurable resin, or a two-component curable resin can be used. For instance, an acrylic resin, a urethane resin, an epoxy resin, a silicone resin, or a resin having a siloxane bond can be used.
• When thefilm layer113 is formed using a viscous material, a material for thebonding layer114 can be used, in which case thebonding layer114 can be omitted.
• When thefilm layer113 is thinner, the radius of curvature of the curved surface of thesupport103 can be reduced as described above. When the radius of curvature is large, a relativelythick film layer113 can be used.
• Here, when the thickness of thefilm layer113 is T and the smallest radius of curvature of thesupport103 is R, the thickness of thefilm layer113 can be set so that T|R is, for example, 0.2 or less, preferably 0.1 or less, more preferably 0.05 or less. For example, T|R is 0.025 when the curvature radius R is 4 mm and the thickness T of thefilm layer113 is 100 μm.
• In reality, the radius of curvature of thecurved film layer113 increases according to the thicknesses of thedisplay panel111 and thebonding layer114; thus, the allowable thickness of thefilm layer113 can be larger than the aforementioned upper limit. The film layer113(1), which is placed nearest to thedisplay panel111, has the smallest allowable thickness.
• The plurality of film layers113 are preferably films of the same material and with the same thickness for lower fabrication cost. Alternatively, the film layers113 closer to thetouch sensor112 may be thicker.
• As illustrated inFIG. 2B, a material combining thefilm layer113 and thebonding layer114 may be used. For example, an adhesive film in which anadhesive bonding layer114 is provided on at least one surface of thefilm layer113 may be used. In this case, the film layer113(n) closest to thetouch sensor112 or the film layer113(1) closest to thedisplay panel111 is preferably a film in which thebonding layer114 is provided on opposite sides of thefilm layer113 so that it can be bonded to thetouch sensor112 or thedisplay panel111.
• As illustrated inFIG. 3, between thetouch sensor112 and theexterior component102, at least onefilm layer113 may be provided so that eachfilm layer113 is sandwiched between the bonding layers114. Such afilm layer113 can easily adjust the distance between thetouch sensor112 and theexterior component102 serving as a touch surface, and the detection sensitivity of thetouch panel100 can be optimized easily without changing the design of a circuit for driving thetouch panel100.
• FIG. 3 illustrates a structure where twofilm layers113 are sandwiched between theexterior component102 and thetouch sensor112. Here, among the film layers sandwiched between theexterior component102 and thetouch sensor112, thefilm layer113 nearest to theexterior component102 is referred to as a film layer113(m) (m is an integer of n+1 or more), and thefilm layer113 nearest to thetouch sensor112 is referred to as a film layer113(n+1).
[Manufacturing Method Example]
• An example of a method for manufacturing thetouch panel100 will be described with reference to FIGS.4A1,4A2,4B1,4B2,4C1,4C2, and4D.
• First, thesupport103 is prepared. Thesupport103 can be used as a component incorporated in thehousing101 later. Alternatively, thesupport103 serving as a mold may be used when a different support is used to mount thetouch panel100 in thehousing101 or when part of thehousing101 is used as a support.
• Then, thedisplay panel111 is placed to be curved along a surface of the support103 (FIGS.4A1 and4A2). At this time, thesupport103 and thedisplay panel111 are preferably fixed with an adhesive, a pressure-sensitive adhesive, or the like. When thetouch panel100 is detached from thesupport103 later, it is preferable to use an adhesive or a pressure-sensitive adhesive with which separation is easily performed.
• Next, thefilm layer113 is attached along a surface of thedisplay panel111 with the bonding layer114 (not shown) (FIGS.4B1 and4B2). At this time, to cover the entire surface of thedisplay panel111, thefilm layer113 is preferably attached so that its end portion is placed outside thedisplay panel111.
• The step of attaching thefilm layer113 in such a manner is repeated the number of times equal to the number of the film layers113, whereby a stacked-layer structure of the film layers113 can be obtained.
• Then, thetouch sensor112 is attached along a surface of the film layer113 (specifically the film layer113(n)) with the bonding layer114 (not shown) (FIGS.4C1 and4C2).
• When another film layer is provided along a surface of thetouch sensor112 as illustrated inFIG. 3, it is provided in the same manner as thefilm layer113.
• FIG. 4D illustrates a state where thetouch panel100 is detached from thesupport103. The form of thetouch panel100 can be maintained even after thetouch panel100 is detached from thesupport103.
• Thetouch panel100 can be manufactured through these steps.
• If thedisplay panel111, the n film layers113, and thetouch sensor112 are sequentially stacked along a flat surface to form a touch panel and the touch panel is curved along thesupport103, external force occurs in the direction where thetouch sensor112, which is the most distant from thesupport103, is particularly pulled along the curve; thus, thetouch sensor112 might be damaged.
• In contrast, by using the method of sequentially providing thedisplay panel111, the n film layers113, and thetouch sensor112 on the surface of thesupport103, stress applied to thedisplay panel111 and thetouch sensor112 when they are curved is reduced, and a substrate included in thedisplay panel111 or thetouch sensor112 or a wiring, an element, and the like provided over the substrate can be prevented from being damaged. Thus, the highlyreliable touch panel100 can be provided.
• When thedisplay panel111, the film layers113, and thetouch sensor112 are curved along the curved surface, stress applied to them increases depending on their thickness. However, the thickness of each of thedisplay panel111, the n film layers113, and thetouch sensor112 is sufficiently small, so that no defect is caused by stress due to their thickness.
• If a flat-plate touch panel is curved, the touch panel cannot maintain the curved form without a support and returns to a flat-plate shape. In contrast, the curved shape of thetouch panel100 fabricated according to this manufacturing method example can be maintained even when thetouch panel100 is detached from the support103 (is not supported by the support103) as illustrated inFIG. 4D.
• If a flat-plate touch panel is curved and fixed to a support, stress is applied to the touch panel all the time, which might decrease long-term reliability. In contrast, thetouch panel100 fabricated with this manufacturing method example maintains its curved form, so that unintentional stress is not applied to thetouch panel100 and thetouch panel100 with high reliability can be obtained as a result.
• When this manufacturing method example is used, the number of film layers113 stacked to increase the distance between thedisplay panel111 and thetouch sensor112 is unlimited, and the touch panel can keep its curved form without problems even in the case where the number of stacked film layers113 is extremely large and the distance between thedisplay panel111 and thetouch sensor112 increases. In contrast, in the case where a flat-plate touch panel is curved, thetouch sensor112 is damaged even when the distance between thedisplay panel111 and thetouch sensor112 is large.
• By using this manufacturing method example, stress applied to thedisplay panel111, thetouch sensor112, and the like due to bending can be extremely small, so that the allowable radius of curvature at the time of bending thetouch panel100 can be extremely small. Furthermore, the distance between thedisplay panel111 and thetouch sensor112 can be sufficiently large when thetouch panel100 is bent with a small radius of curvature, resulting in higher detection sensitivity of thetouch panel100.
• In the above description, the display surface (the side where thetouch sensor112 is provided) of thetouch panel100 has a convex curve; alternatively, the display surface can have a concave surface.
[Electronic Devices]
• FIGS.5A1,5A2,5B1,5B2,5C1, and5C2 illustrate examples of an electronic device in which the position of thetouch panel100 is different from that in FIGS.1A1 and1A2. In FIGS.5A1 and5A2, thetouch panel100 is provided over most of the back surface of thehousing101. In FIGS.5B1 and5B2, thetouch panel100 extends from the right side surface to the left side surface across the front surface. In FIGS.5C1 and5C2, thetouch panel100 extends from the back surface to the back surface across the right side surface, front surface, and left side surface.
• Without limitation to the above structures, the electronic device can be configured so that thetouch panel100 is provided along a curved surface of the housing in various different manners. Although the surface of the housing is convex in the above examples, the surface may be concave or may have a shape including both a convex and a concave, such as a wave shape.
• At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification as appropriate.
(Embodiment 2)
• This embodiment will explain examples of a touch sensor and a display panel used in the touch panel of one embodiment of the present invention.
[Touch Sensor]
• FIG. 6 is a schematic perspective diagram of thetouch sensor112.FIGS. 7A to 7C are schematic cross-sectional diagrams along lines C-D and E-F inFIG. 6.
• As thetouch sensor112, a capacitive touch sensor can be used, for example. Examples of a capacitive touch sensor are a surface capacitive touch sensor and a projected capacitive touch sensor. Examples of a projected capacitive touch sensor are a self-capacitive touch sensor and a mutual capacitive touch sensor, which differ mainly in the driving method. The use of a mutual capacitive touch sensor is preferable because multiple points can be sensed simultaneously. An example of using a projected capacitive touch sensor will be described below.
• Thetouch sensor112 includes a plurality ofelectrodes221 and a plurality ofelectrodes222 between aflexible substrate201 and aflexible substrate202. Theelectrode221 is electrically connected to one of a plurality ofwirings211. Theelectrode222 is electrically connected to one of a plurality ofwirings212. Thewirings211 and212 are extended to the periphery of thesubstrate201 and electrically connected to a flexible printed circuit (FPC)205.
• Theelectrode221 has a shape extending in one direction. Each of theelectrodes222 is provided between twoelectrodes221. Twoelectrodes222 between which theelectrode221 is placed are electrically connected to each other by awiring223 that intersects with theelectrode221. Adielectric layer224 is provided between thewiring223 and theelectrode221, so that a capacitor is formed. In thetouch sensor112, the plurality ofelectrodes222 are electrically connected by thewirings223 and arranged in one direction, and the plurality ofelectrodes221 are arranged in the direction intersecting with the direction of theelectrodes222; thus, capacitors are arranged in a matrix.
• Theelectrode221, theelectrode222, and thewiring223 preferably have a light-transmitting property. As shown inFIG. 6, theelectrodes221 and222 preferably have a shape with which hardly any space is generated therebetween. Moreover, a dummy electrode including the same conductive film as theelectrode221, theelectrode222, or thewiring223 may be provided at the space between theelectrodes221 and222. Reducing a space between theelectrodes221 and222 as much as possible in such a manner can reduce transmittance unevenness. As a result, unevenness in luminance of light transmitted through thetouch sensor112 can be reduced.
• 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.
• Theelectrodes221 and222 and thewiring223 can be formed in such a manner that a light-transmitting conductive material is deposited on thesubstrate201 by sputtering and then an unnecessary portion is removed by any of various patterning techniques such as photolithography. Graphene may be formed by CVD or by application of a solution in which graphene oxide is dispersed and subsequent reduction of graphene oxide.
• Thewiring212 is electrically connected to theelectrode222. Thewiring212 is provided so that its surface is exposed at the periphery of thesubstrate201, and can be electrically connected to theFPC205 through aconnection layer255. Note that thewiring211 electrically connected to theelectrode221 can have a similar structure.
• For thewirings211 and212, a metal material such as aluminum, gold, platinum, silver, nickel, titanium, tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or an alloy material containing any of these metal materials can be used.
• For theconnection layer255, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like can be used.
• In the cross-sectional structure example inFIG. 7A, theelectrode221 and theelectrode222 are formed over an insulatinglayer220. Thesubstrate201 and the insulatinglayer220 are attached to each other with abonding layer231 placed therebetween. Thesubstrate202 and thesubstrate201 provided with the electrodes and the like are attached to each other with abonding layer232.
• Thebonding layer231 and thebonding layer232 have a light-transmitting property. A thermosetting resin or an ultraviolet curable resin can be used; for example, an acrylic resin, a urethane resin, an epoxy resin, or a resin having a siloxane bond can be used.
• Aprotection layer235 is preferably provided on a surface of thesubstrate202. Theprotection layer235 can be referred to as a ceramic coat and has a function of protecting the surface of thesubstrate202 when thetouch sensor112 is operated with a finger, a stylus, or the like. The provision of theprotection layer235 is particularly preferred when theexterior component102 is not provided. Theprotection layer235 can be formed using an inorganic insulating material such as silicon oxide, aluminum oxide, yttrium oxide, or yttria-stabilized zirconia (YSZ) by sputtering, a sol-gel method, or the like. Aerosol deposition is particularly preferably employed to form theprotection layer235, in which case a high-density film can be formed at low temperature and mechanical strength can be increased as a result.
• Theprotection layer235 is provided at least on the touch surface.FIG. 7A shows the case where theprotection layer235 is provided on the surface of thesubstrate202; alternatively, theprotection layer235 may be provided on a surface of thesubstrate201.
• It is possible that thebonding layer231 is not provided.FIG. 7B illustrates a structure where the insulatinglayer220 is provided on a top surface of thesubstrate201.FIG. 7C illustrates a structure where the insulatinglayer220 is also omitted and theelectrode221, theelectrode222, and the like are provided over thesubstrate201.
• The above is the description of the touch sensor.
[Display Panel]
• FIG. 8 is a schematic perspective diagram of thedisplay panel111.
• Thedisplay panel111 includes adisplay portion491 including a plurality of pixels and awiring457 for supplying a signal and power to thedisplay portion491. The pixel included in thedisplay portion491 is preferably provided with a transistor and a display element. Typical examples of the display element include an organic EL element, a liquid crystal element, electronic ink, electronic liquid powder, and an electrophoretic element.
• InFIG. 8, thedisplay panel111 includes adriver circuit493 in addition to thedisplay portion491. As thedriver circuit493, a circuit functioning as a scan line driver circuit or a signal line driver circuit, for example, can be used.
• When thedriver circuit493 serves as a scan line driver circuit, a circuit (circuit A) shown inFIG. 9 can be used. The circuit A inFIG. 9 includes transistors M1 to M15. Each of the transistors preferably contains an oxide semiconductor as a semiconductor in which a channel is formed. The transistor containing an oxide semiconductor exhibits ultralow off-state current. The use of such a transistor in the circuit can reduce shoot-through current compared with a CMOS circuit containing low-temperature polysilicon, and noise generated from the circuit can be reduced. Consequently, the detection sensitivity of thetouch panel100 can be increased.
• AnFPC495 is electrically connected to thewiring457 inFIG. 8. A signal and power for driving thedisplay panel111 can be supplied from theFPC495 through thewiring457.
• FIG. 8 illustrates an example where anIC470 is mounted on theFPC495 by COF. As theIC470, an IC functioning as a scan line driver circuit or a signal line driver circuit can be used. Note that it is possible that theIC470 is not provided when thedisplay panel111 includes circuits serving as a scan line driver circuit and a signal line driver circuit and when circuits serving as a scan line driver circuit and a signal line driver circuit are externally provided and a signal for driving thedisplay panel111 is input through theFPC495.
[Cross-Sectional Structure Example 1]
• An example of a cross-sectional structure of thedisplay panel111 will be described below. Here, thedisplay panel111 is a light-emitting device using an organic EL element.
• FIG. 10A is a schematic cross-sectional diagram along lines G-H, I-J, and K-L inFIG. 8. The display panel illustrated inFIG. 10A is a top-emission display panel fabricated by separately depositing light-emitting layers of different colors.
• The display panel illustrated inFIG. 10A includes thedisplay portion491, thedriver circuit493, and theFPC495. An organic EL element and transistors included in thedisplay portion491 and thedriver circuit493 are sealed with asubstrate420, asubstrate428, and abonding layer407.
• The display panel inFIG. 10A includes thesubstrate420, abonding layer422, an insulatinglayer424, atransistor455, an insulatinglayer463, an insulatinglayer465, an insulatinglayer405, an organic EL element450 (alower electrode401, anEL layer402, and an upper electrode403), thebonding layer407, thesubstrate428, and awiring457. Thesubstrate428, thebonding layer407, and theupper electrode403 transmit visible light.
• In thedisplay portion491 of the display panel inFIG. 10A, thetransistor455 and theorganic EL element450 are provided over thesubstrate420 with thebonding layer422 and the insulatinglayer424 placed therebetween. Theorganic EL element450 includes thelower electrode401 over the insulatinglayer465, theEL layer402 over thelower electrode401, and theupper electrode403 over theEL layer402. Thelower electrode401 is electrically connected to a source electrode or a drain electrode of thetransistor455. Thelower electrode401 preferably reflects visible light. An end portion of thelower electrode401 is covered with the insulatinglayer405.
• Thedriver circuit493 includes a plurality of transistors.FIG. 10A illustrates one of the transistors in thedriver circuit493.
• Thewiring457 is electrically connected to an external input terminal through which a signal (e.g., a video signal, a clock signal, a start signal, or a reset signal) or a potential from the outside is transmitted to thedriver circuit493. Here, theFPC495 is provided as the external input terminal as an example.
• To prevent an increase in the number of fabrication steps, thewiring457 is preferably formed using the same material and the same step as those of the electrode or the wiring in the display portion or the driver circuit. Here, an example is described in which thewiring457 is formed using the same material and the same step as those of the source and drain electrodes of the transistor.
• The insulatinglayer463 has an effect of suppressing diffusion of impurities into a semiconductor included in the transistor. As the insulatinglayer465, an insulating film having a planarization function is preferably used to reduce surface unevenness due to the transistor.
[Cross-Sectional Structure Example 2]
• FIG. 10B illustrates a cross-sectional structure of the display panel different from the above. The display panel illustrated inFIG. 10B is a bottom-emission display panel fabricated using a color filter method.
• The display panel inFIG. 10B includes thesubstrate420, thebonding layer422, the insulatinglayer424, atransistor454, thetransistor455, the insulatinglayer463, acoloring layer432, the insulatinglayer465, aconductive layer435, an insulatinglayer467, the insulatinglayer405, the organic EL element450 (thelower electrode401, theEL layer402, and the upper electrode403), thebonding layer407, thesubstrate428, and thewiring457. Thesubstrate420, thebonding layer422, the insulatinglayer424, the insulatinglayer463, the insulatinglayer465, the insulatinglayer467, and thelower electrode401 transmit visible light.
• In thedisplay portion491 of the display panel inFIG. 10B, the switchingtransistor454, thecurrent control transistor455, and theorganic EL element450 are provided over thesubstrate420 with thebonding layer422 and the insulatinglayer424 placed therebetween. Theorganic EL element450 includes thelower electrode401 over the insulatinglayer467, theEL layer402 over thelower electrode401, and theupper electrode403 over theEL layer402. Thelower electrode401 is electrically connected to the source electrode or the drain electrode of thetransistor455 through theconductive layer435. An end portion of thelower electrode401 is covered with the insulatinglayer405. Theupper electrode403 preferably reflects visible light. The display panel includes, over the insulatinglayer463, thecoloring layer432 overlapping with theorganic EL element450.
• Thedriver circuit493 includes a plurality of transistors.FIG. 10B illustrates two of the transistors included in thedriver circuit493.
• Thewiring457 is electrically connected to an external input terminal through which a signal or a potential from the outside is transmitted to thedriver circuit493. Here, thewiring457 is formed using the same material and the same step as those of theconductive layer435.
• The insulatinglayer463 has an effect of suppressing diffusion of impurities into a semiconductor included in the transistor. As the insulatinglayer465 and the insulatinglayer467, an insulating film having a planarization function is preferably used to reduce surface unevenness due to the transistors and the wirings.
[Cross-Sectional Structure Example 3]
• FIG. 11 illustrates a cross-sectional structure of the display panel different from the above. The display panel illustrated inFIG. 11 is a top-emission display panel fabricated using a color filter method.
• The display panel inFIG. 11 includes thesubstrate420, thebonding layer422, the insulatinglayer424, thetransistor455, the insulatinglayer463, the insulatinglayer465, the insulatinglayer405, the organic EL element450 (thelower electrode401, theEL layer402, and the upper electrode403), thebonding layer407, a light-blocking layer431, thecoloring layer432, anovercoat453, an insulatinglayer226, abonding layer426, thesubstrate428, and thewiring457. Thesubstrate428, thebonding layer426, the insulatinglayer226, theovercoat453, thebonding layer407, and theupper electrode403 transmit visible light.
• In the structure ofFIG. 11, an insulatinglayer496 is provided over the insulatinglayer405. Providing the insulatinglayer496 serving as a spacer over the insulatinglayer405 prevents the distance between the substrates from being smaller than the predetermined distance.
• In thedisplay portion491 of the display panel inFIG. 11, thetransistor455 and theorganic EL element450 are provided over thesubstrate420 with thebonding layer422 and the insulatinglayer424 placed therebetween. Theorganic EL element450 includes thelower electrode401 over the insulatinglayer465, theEL layer402 over thelower electrode401, and theupper electrode403 over theEL layer402. Thelower electrode401 is electrically connected to the source electrode or the drain electrode of thetransistor455. An end portion of thelower electrode401 is covered with the insulatinglayer405. Thelower electrode401 preferably reflects visible light. Moreover, the display panel includes thecoloring layer432 overlapping with theorganic EL element450 with thebonding layer407 therebetween, and the light-blocking layer431 overlapping with the insulatinglayer405 with thebonding layer407 therebetween.
• Thedriver circuit493 includes a plurality of transistors.FIG. 11 illustrates one of the transistors in thedriver circuit493.
• Thewiring457 is electrically connected to an external input terminal through which a signal or a potential from the outside is transmitted to thedriver circuit493. Here, as an example, theFPC495 is provided as the external input terminal, and thewiring457 is formed using the same material and the same step as those of the source and drain electrodes of thetransistor455. Aconnector497 over the insulatinglayer226 is connected to thewiring457 through an opening provided in the insulatinglayer226, theovercoat453, thebonding layer407, the insulatinglayer465, and the insulatinglayer463. Theconnector497 is connected to theFPC495. TheFPC495 and thewiring457 are electrically connected through theconnector497.
[Manufacturing Method Example]
• Here, a method for manufacturing a flexible touch sensor or a flexible display panel will be described.
• Here, a component including a pixel and a driver circuit or a component including an optical component such as a color filter in a display panel, or a component including an electrode and a wiring in a touch sensor is referred to as an element layer for convenience. An element layer includes a display element, for example, and may also include a wiring electrically connected to the display element and an element used in a pixel or a circuit, such as a transistor.
• Furthermore, a support provided with an insulating surface where an element layer is formed is referred to as a base.
• As a method for forming an element layer over a flexible base, there are a method in which an element layer is formed directly on a base; and a method in which an element layer is formed over a supporting base that is different a base and has stiffness, and then the element layer is separated from the supporting base and transferred to the base.
• When the material of the base can withstand heating temperature in the process for forming the element layer, the element layer is preferably formed directly on the base, in which case the manufacturing process can be simplified. At this time, the element layer is preferably formed in a state where the base is fixed to the supporting base, in which case transfer of the element layer 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 and then transferred to the base, first, a separation layer and an insulating layer are stacked over the supporting base, and then the element layer is formed over the insulating layer. Then, the element layer is separated from the supporting base and then transferred to the base. In this case, materials are selected so that separation occurs at the interface between the supporting base and the separation layer, at the interface between the separation layer and the insulating layer, or in the separation layer. With such a method, the element layer can be formed at temperatures higher than the upper temperature limit of the base, which improves the reliability.
• It is preferred that the separation layer have a stacked-layer structure using a layer containing a high-melting-point metal material (e.g., tungsten) and a layer containing an oxide of the metal material, and a layer in which a plurality of layers such as a silicon nitride layer and a silicon oxynitride layer are stacked be formed over the separation layer as the insulating layer. By using a high-melting-point metal material, a high-temperature process can be performed to form the element layer, resulting in high reliability. Impurities contained in the element layer can be further reduced, and the crystallinity of a semiconductor or the like included in the element layer can be further increased.
• Examples of the separation include peeling off by application of mechanical power, removal of the separation layer by etching, or separation by dripping of a liquid into part of the separation interface to penetrate the entire separation interface. Alternatively, the separation may be performed by heating the separation interface by utilizing a difference in coefficient of thermal expansion.
• The separation layer is not necessary when separation can be performed at the interface between the supporting base and the insulating layer. For example, it is possible that glass is used as the supporting base, an organic resin such as polyimide is used for the insulating layer, a starting point of separation is set by locally heating the organic resin with laser light or the like, and separation is performed at the interface between the glass and the insulating layer. Alternatively, it is possible that a layer containing a material with high thermal conductivity (e.g., a metal or a semiconductor) is provided between the supporting base and the insulating layer containing an organic resin, and this layer is heated by current so that separation easily occurs, and then separation is performed. In this case, the insulating layer containing an organic resin can also be used as the base.
• Examples of a material of the flexible base 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, polytetrafluoroethylene (PTFE), 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, for example, a polyamide imide resin, a polyimide resin, or PET, which has a thermal expansion coefficient of 30×10⁻⁶/K or lower. It is also possible to use 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.
• 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 modulus of elasticity or a fiber with a high Young's modulus. Typical examples 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 a flexible substrate. The structure body including the fibrous body and the resin is preferably used as a flexible substrate, in which case the reliability against bending and damage due to local pressure can be increased.
[Examples of Materials]
• Next, materials and the like that can be used for the display panel will be described. Note that the description of the components already described in this embodiment is omitted.
• As a light-emitting element, a self-luminous element can be used, and an element whose luminance is controlled by current or voltage is included in the category of the light-emitting element. For example, a light-emitting diode (LED), an organic EL element, or an inorganic EL element can be used.
• There is no particular limitation on the structure of the transistors in the display panel. 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. There is no particular limitation on a semiconductor material used for the transistors, and for example, silicon, germanium, or an oxide semiconductor may be used.
• There is no particular limitation on the state of a semiconductor material used for the transistors, 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. A semiconductor having crystallinity is preferably used, in which case deterioration of the transistor characteristics can be suppressed.
• Here, for the transistors, a polycrystalline semiconductor such as polycrystalline silicon is preferably used. Polycrystalline silicon can be formed at lower temperature than single crystal silicon and has higher field-effect mobility and higher reliability than amorphous silicon. The use of such a polycrystalline semiconductor in pixels increases the aperture ratio of the pixels. Furthermore, by using a polycrystalline semiconductor, a gate driver circuit and a source driver circuit can be formed over a substrate where pixels are provided even when the pixel density is quite high; thus, the number of components included in an electronic device can be decreased.
• Furthermore, an oxide semiconductor is preferably used for the transistor. For example, an oxide semiconductor having a wide 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 the 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 In-M-Zn-based oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).
• As the oxide semiconductor, for example, any of the following can be used: indium oxide, tin oxide, zinc oxide, In—Zn-based oxide, Sn—Zn-based oxide, Al—Zn-based oxide, Zn—Mg-based oxide, Sn-Mg-based oxide, In—Mg-based oxide, In—Ga-based oxide, In—Ga—Zn-based oxide (also referred to as IGZO), In—Al—Zn-based oxide, In—Sn—Zn-based oxide, Sn—Ga—Zn-based oxide, Al—Ga—Zn-based oxide, Sn—Al—Zn-based oxide, In—Hf—Zn-based oxide, In—Zr—Zn-based oxide, In—Ti—Zn-based oxide, In—Sc—Zn-based oxide, In—Y—Zn-based oxide, In—La—Zn-based oxide, In—Ce—Zn-based oxide, In—Pr—Zn-based oxide, In—Nd—Zn-based oxide, In—Sm—Zn-based oxide, In—Eu—Zn-based oxide, In—Gd—Zn-based oxide, In—Tb—Zn-based oxide, In—Dy—Zn-based oxide, In—Ho—Zn-based oxide, In—Er—Zn-based oxide, In—Tm—Zn-based oxide, In—Yb—Zn-based oxide, In—Lu—Zn-based oxide, In—Sn—Ga—Zn-based oxide, In—Hf—Ga—Zn-based oxide, In—Al—Ga—Zn-based oxide, In—Sn-Al—Zn-based oxide, In—Sn—Hf—Zn-based oxide, and In—Hf—Al—Zn-based oxide.
• Here, an In—Ga—Zn-based oxide means an oxide containing In, Ga, and Zn as its main components, and there is no particular limitation on the ratio of In, Ga, and Zn. The In—Ga—Zn-based oxide may contain another metal element in addition to In, Ga, and Zn.
• An oxide semiconductor film is classified roughly into a single crystal oxide semiconductor film and a non-single-crystal oxide semiconductor film. The non-single-crystal oxide semiconductor film includes any of a c-axis aligned crystalline oxide semiconductor (CAAC-OS) film, a polycrystalline oxide semiconductor film, a microcrystalline oxide semiconductor film, an amorphous oxide semiconductor film, and the like. Note that the CAAC-OS film is an oxide semiconductor film including a plurality of c-axis aligned crystal parts.
• As the semiconductor layer, it is particularly preferable to use an oxide semiconductor film which includes a plurality of crystal parts with c-axes aligned perpendicular to a surface where the semiconductor layer is formed or the top surface of the semiconductor layer and in which the adjacent crystal parts have no grain boundary. Such an oxide semiconductor without grain boundary prevents a crack of an oxide semiconductor film from being caused by stress generated when a flexible device fabricated according to one embodiment of the present invention is bent. Consequently, such an oxide semiconductor is preferably used for a flexible display device that is bent when used.
• The use of such materials for the semiconductor layer makes it possible to provide a highly reliable transistor in which a change in the electrical characteristics is suppressed.
• In addition, the low off-state current of a transistor using such an oxide semiconductor enables long-term retention of charge stored in a capacitor through the transistor. The use of such a transistor in a pixel allows a driver circuit to stop while the luminance of an image displayed on a display region is maintained. Thus, an electronic device with ultralow power consumption can be provided.
• Various wirings and electrodes in a touch panel as well as a gate, source, and drain of a transistor are formed with a single-layer structure or a stacked-layer structure using a metal 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. For example, it is possible to employ 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; or 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. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may be used. Copper containing manganese is preferably used because the shape controllability of etching is increased.
• A light-emitting element included in the display panel includes a pair of electrodes and an EL layer between the pair of electrodes. One of the pair of electrodes functions as an anode and the other functions as a cathode.
• The light-emitting element may have any of a top emission structure, a bottom emission structure, and a dual emission structure. A conductive film that transmits visible light is used as the electrode through which light is extracted. A conductive film that reflects visible light is preferably used as the electrode through which light is not extracted.
• A conductive film that transmits visible light can be formed using, for example, indium oxide, indium tin oxide (ITO), indium zinc oxide, zinc oxide, or zinc oxide to which gallium is added. It is also possible to use a film that is formed of a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, or titanium; an alloy containing any of these metal materials; or a nitride of any of these metal materials (e.g., titanium nitride) when the film is thin enough to have a light-transmitting property. Alternatively, a stack of any of the above materials can be used as the conductive film. For example, a stacked film of ITO and an alloy of silver and magnesium is preferably used, in which case the conductivity can be increased. Further alternatively, graphene or the like may be used.
• For the conductive film that reflects visible light, a metal material such as aluminum, gold, platinum, silver, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or an alloy containing any of these metal materials can be used, for example. Lanthanum, neodymium, germanium, or the like may be added to the metal material or the alloy. Furthermore, an alloy containing aluminum (an aluminum alloy) such as an alloy of aluminum and titanium, an alloy of aluminum and nickel, or an alloy of aluminum and neodymium; or an alloy containing silver such as an alloy of silver and copper, an alloy of silver, copper, and palladium, or an alloy of silver and magnesium can be used for the conductive film. An alloy of silver and copper is preferable because of its high heat resistance. When a metal film or a metal oxide film is stacked on an aluminum alloy film, oxidation of the aluminum alloy film can be suppressed. Examples of a material for the metal film or the metal oxide film are titanium and titanium oxide. Alternatively, the conductive film that transmits visible light and a film containing any of the above metal materials may be stacked. For example, a stacked film of silver and ITO or a stacked film of an alloy of silver and magnesium and ITO can be used.
• The electrodes can be formed by an evaporation method or a sputtering method. Alternatively, a discharging method such as an ink-jet method, a printing method such as a screen printing method, or a plating method may be used.
• When a voltage higher than the threshold voltage of the light-emitting element is applied between the lower electrode and the upper electrode, holes are injected to the EL layer from the anode side and electrons are injected to the EL layer from the cathode side. The injected electrons and holes are recombined in the EL layer, so that a light-emitting substance contained in the EL layer emits light.
• The EL layer includes at least a light-emitting layer. In addition to the light-emitting layer, the EL layer may also 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 high electron- and hole-transport properties), and the like.
• For the EL layer, either a low molecular compound or a high molecular compound can be used, and an inorganic compound may also be used. The layers included in the EL layer 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.
• The light-emitting element is preferably provided between a pair of insulating films with a high gas barrier property. Thus, impurities such as water can be prevented from entering the light-emitting element, leading to prevention of a decrease in the reliability of the display panel.
• Examples of the insulating layer with a high gas barrier property include a film containing nitrogen and silicon, such as a silicon nitride film or a silicon nitride oxide film, and a film containing nitrogen and aluminum, such as an aluminum nitride film. Alternatively, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or the like may be used.
• For example, the moisture vapor transmission rate of the insulating film with a high gas barrier property is 1×10⁻⁵g/m²·day or less, preferably 1×10⁻⁶g/m²·day or less, more preferably 1×10⁻⁷g/m²·day or less, still more preferably 1×10⁻⁸g/m²·day or less.
• A flexible material is used for the flexible substrate. For example, an organic resin or a glass material that is thin enough to have flexibility can be used. Furthermore, a material that transmits visible light is used for a substrate of the display panel from which light emission is extracted. A metal substrate or the like may be used in the case where the flexible substrate does not need to transmit visible light.
• An organic resin with a lower specific gravity than glass is preferably used for the flexible substrate, in which case the display panel can be lightweight as compared to the case of using glass.
• Examples of a material having flexibility and a light-transmitting property 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, for example, a polyamide imide resin, a polyimide resin, or PET. It is also possible to use 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.
• In the case where a fibrous body is included in the material having flexibility and a light-transmitting property, 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 modulus of elasticity or a fiber with a high Young's modulus. Typical examples 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 a flexible substrate. The structure body including the fibrous body and the resin is preferably used as a flexible substrate, in which case the reliability against bending and damage due to local pressure can be increased.
• To improve the light extraction efficiency, the refractive index of the material having flexibility and a light-transmitting property is preferably high. For example, a substrate obtained by dispersing an inorganic filler having a high refractive index into an organic resin can have a higher refractive index than the substrate formed of only the organic resin. In particular, an inorganic filler having a particle diameter as small as 40 nm or less is preferred because such a filler can maintain optical transparency.
• To obtain flexibility and bendability, the thickness of a metal substrate ranges preferably from 10 μm to 200 μm, more preferably from 20 μm to 50 μm. Since the metal substrate has high thermal conductivity, heat generated due to light emission of a light-emitting element can be efficiently released.
• There is no particular limitation on a material of the metal substrate, but it is preferable to use, for example, aluminum, copper, nickel, or an alloy such as an aluminum alloy or stainless steel.
• The flexible substrate may have a structure in which a hard coat layer (e.g., a silicon nitride layer) by which a device surface is protected from damage, a layer (e.g., an aramid resin layer) that can disperse pressure, or the like is stacked over a layer of any of the above-mentioned materials. Furthermore, to suppress a decrease in the lifetime of the functional element (in particular, the organic EL element) due to moisture and the like, an insulating film with low water permeability described later may be included.
• The flexible substrate may be formed by stacking a plurality of layers. When a glass layer is used, barrier properties against water and oxygen can be improved and thus a reliable display panel can be provided.
• For example, a flexible substrate in which a glass layer, a bonding layer, and an organic resin layer are stacked from the side closer to an organic EL element can be used. The thickness of the glass layer ranges from 20 μm to 200 μm, preferably from 25 μm to 100 μm. With such a thickness, the glass layer can have both high barrier properties against water and oxygen and flexibility. The thickness of the organic resin layer ranges from 10 μm to 200 μm, preferably from 20 μm to 50 μm. By providing such an organic resin layer on the outer side of the glass layer, occurrence of a crack or a break in the glass layer can be suppressed and mechanical strength can be increased. With the substrate using such a composite material of a glass material and an organic resin, a highly reliable flexible display panel can be provided.
• For the bonding layer, any of a variety of curable adhesives, for example, a light curable adhesive such as a UV curable adhesive, a reactive curable adhesive, a thermal curable adhesive, and an anaerobic adhesive can be used. Examples of these adhesives include an epoxy resin, an acrylic resin, a silicone resin, a phenol resin, a polyimide resin, an imide resin, a polyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, and an ethylene vinyl acetate (EVA) resin. In particular, a material with low moisture permeability, such as an epoxy resin, is preferred. Alternatively, a two-component-mixture-type resin may be used. Further alternatively, an adhesive sheet or the like may be used.
• Furthermore, the resin may include a drying agent. For example, a substance that adsorbs moisture by chemical adsorption, such as oxide of an alkaline earth metal (e.g., calcium oxide or barium oxide), can be used. Alternatively, a substance that adsorbs moisture by physical adsorption, such as zeolite or silica gel, may be used. The drying agent is preferably included because it can prevent impurities such as moisture from entering the functional element, thereby improving the reliability of the display panel.
• It is preferable to mix a filler with a high refractive index or a light-scattering material into the resin, in which case the efficiency of light extraction from the light-emitting element can be improved. For example, titanium oxide, barium oxide, zeolite, or zirconium can be used.
• The above is the description of the display panel.
• Note that in this specification and the like, a display element, a display device which is a device including a display element, a light-emitting element, and a light-emitting device which is a device including a light-emitting element can employ various modes or can include various elements. Examples of a display element, a display device, a light-emitting element, and a light-emitting device include an element and a device having a display medium whose contrast, luminance, reflectance, transmittance, or the like is changed by electromagnetic action, such as an EL element (e.g., an EL element including organic and inorganic materials, an organic EL element, and an inorganic EL element), an LED (e.g., a white LED, a red LED, a green LED, and a blue LED), a transistor (a transistor that emits light depending on current), an electron emitter, a liquid crystal element, electronic ink, an electrophoretic element, a grating light valve (GLV), a plasma display panel (PDP), a display element using micro electro mechanical system (MEMS), a digital micromirror device (DMD), a digital micro shutter (DMS), an interferometric modulator display (IMOD), an electrowetting element, a MEMS shutter display element, an optical-interference-type MEMS display element, a piezoelectric ceramic display, and a carbon nanotube. An example of a display device having EL elements is an EL display. Examples of a display device including electron emitters are a field emission display (FED) and an SED-type flat panel display (SED: surface-conduction electron-emitter display). An example of a display device including liquid crystal elements includes a liquid crystal display (e.g., a transmissive liquid crystal display, a transflective liquid crystal display, a reflective liquid crystal display, a direct-view liquid crystal display, and a projection liquid crystal display). An example of a display device having electronic ink, electronic liquid powder, or electrophoretic elements is electronic paper. In a transflective liquid crystal display or a reflective liquid crystal display, some of 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 SRAM can be provided under the reflective electrodes, leading to lower power consumption.
• In this specification and the like, it is possible to employ an active matrix method in which an active element (a non-linear element) is included in a pixel or a passive matrix method in which an active element is not included in a pixel.
• In the active matrix method, as an active element, not only a transistor but also a variety of active elements, for example, a metal insulator metal (MIM) or a thin film diode (TFD) can be used. These elements are manufactured with a small number of steps, resulting in low manufacturing cost or high yield. Furthermore, since these elements are small, the aperture ratio can be increased, leading to low power consumption and high luminance.
• Since an active element is not used in a passive matrix method, the number of manufacturing steps is small, so that the manufacturing cost can be reduced or the yield can be improved. Furthermore, since an active element is not used, the aperture ratio can be improved, so that power consumption can be reduced or higher luminance can be achieved.
• At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification as appropriate.
(Embodiment 3)
• In this embodiment, electronic devices and lighting devices that can include the touch panel, the touch sensor, the display panel, or the light-emitting device of one embodiment of the present invention will be described with reference toFIGS. 12A to 12E andFIGS. 13A to 13D.
• Examples of electronic devices include a television set (also referred to as a television or a television receiver), a monitor of a computer or the like, a camera such as a digital camera and a digital video camera, a digital photo frame, a mobile phone (also referred to as a cellular phone or mobile phone device), a portable game machine, a portable information appliance, an audio reproducing device, and a large game machine such as a pachinko machine.
• The device manufactured according to 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.
• FIG. 12A illustrates an example of a mobile phone. Amobile phone7400 is provided with adisplay portion7402 incorporated in ahousing7401, anoperation button7403, anexternal connection port7404, aspeaker7405, amicrophone7406, and the like. Themobile phone7400 is manufactured using the display device manufactured according to one embodiment of the present invention for thedisplay portion7402. According to one embodiment of the present invention, a highly reliable mobile phone having a curved display portion can be provided with high yield.
• When thedisplay portion7402 of themobile phone7400 inFIG. 12A is touched with a finger or the like, data can be input to themobile phone7400. Operations such as making a call and inputting letters can be performed by touch on thedisplay portion7402 with a finger or the like.
• With theoperation button7403, the power can be turned on and off. Furthermore, types of images displayed on thedisplay portion7402 can be switched; for example, the image can be switched from a mail creation screen to a main menu.
• FIG. 12B illustrates an example of a wrist-watch-type portable information appliance. Aportable information appliance7100 includes ahousing7101, adisplay portion7102, aband7103, abuckle7104, anoperation button7105, an input/output terminal7106, and the like.
• Theportable information appliance7100 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. 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, an application can be started by touching anicon7107 displayed on thedisplay portion7102.
• With theoperation button7105, a variety of functions such as time setting, power on/off, on/off control 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 the operation system incorporated in theportable information appliance7100.
• Theportable information appliance7100 can employ near field communication, which is a communication method based on an existing communication standard. In that case, for example, hands-free calling is achieved with mutual communication between theportable information appliance7100 and a headset capable of wireless communication.
• Since theportable information appliance7100 includes the input/output terminal7106, data can be directly transmitted to and received from another information appliance 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 appliance7100 includes the display panel manufactured according to one embodiment of the present invention. According to one embodiment of the present invention, a highly reliable portable information appliance having a curved display portion can be provided with a high yield.
• FIGS. 12C to 12E illustrate examples of lighting devices.Lighting devices7200,7210, and7220 each include astage7201 provided with anoperation switch7203 and a light-emitting portion supported by thestage7201.
• Thelighting device7200 illustrated inFIG. 12C includes a light-emittingportion7202 with a wave-shaped light-emitting surface and thus has an elaborate design.
• A light-emittingportion7212 included in thelighting device7210 inFIG. 12D 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. 12E includes a concave-curved light-emittingportion7222. This is suitable for illuminating a specific range because light emitted from the light-emittingportion7222 is collected at the front of thelighting device7220.
• The light-emitting portion included in each of thelighting devices7200,7210, and7220 is flexible; accordingly, the light-emitting portion may be fixed on a plastic member, a movable frame, or the like so that a light-emitting surface of the light-emitting portion can be bent freely depending on the intended use.
• Although the lighting devices in which the light-emitting portion is supported by the stage are described as an example, 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 can be bent concavely so that a particular region is brightly illuminated, or bent convexly so that the whole room is brightly illuminated.
• When the light-emitting portion includes a touch panel, it is possible to achieve a novel lighting device where the color of light and luminance can be changed (light can be controlled) by touch on the light-emitting portion.
• FIG. 13A is a perspective view illustrating the external shape of aportable information appliance330.FIG. 13B is a top view of theportable information appliance330.FIG. 13C is a perspective view illustrating the external shape of aportable information appliance340.
• Theportable information appliances330 and340 function as one or more of a telephone set, an electronic notebook, and an information browsing system, for example. Specifically, each of theportable information appliances330 and340 can be used as a smartphone.
• Theportable information appliances330 and340 can display letters and image data on their plurality of surfaces. For example, threeoperation buttons339 can be displayed on one surface (FIGS. 13A and 13C). Furthermore,information337 indicated by dashed rectangles can be displayed on another surface (FIGS. 13B and 13C). Examples of theinformation337 include an alert for an incoming email, social networking service (SNS) message, and call; the title and sender of an email and SNS massage; the date, the time, remaining battery, and the reception strength of an antenna. On the position where theinformation337 is displayed, theoperation button339, an icon, or the like may be displayed instead of theinformation337. AlthoughFIGS. 13A and 13B show the example in which theinformation337 is displayed at the top, one embodiment of the present invention is not limited to this example. For instance, theinformation337 may be displayed on the side as in theportable information appliance340 inFIG. 13C.
• For example, a user can see the display (here, the information337) with theportable information appliance330 put in a breast pocket.
• Specifically, a caller's phone number, name, or the like of an incoming call is displayed at a position that can be observed from above theportable information appliance330. Thus, the user can see the display without taking out theportable information appliance330 from the pocket and decide whether to answer the phone.
• As adisplay portion333 included in ahousing335 of theportable information appliance330 and ahousing336 of theportable information appliance340, the display device fabricated according to one embodiment of the present invention can be used. According to one embodiment of the present invention, a highly reliable display device having a curved display portion can be provided with high yield.
• As in aportable information appliance345 illustrated inFIG. 13D, information may be displayed on at least three surfaces. Here, as an example,information355,information356, andinformation357 are displayed on different surfaces.
• As adisplay portion358 included in ahousing351 of theportable information appliance345, the display device fabricated according to one embodiment of the present invention can be used. According to one embodiment of the present invention, a highly reliable display device having a curved display portion can be provided with high yield.
• The touch panel, the touch sensor, the display panel, or the light-emitting device of one embodiment of the present invention can be used for the display portion in the electronic device and the light-emitting portion in the lighting device shown above. Consequently, it is possible to achieve a thin, light, and versatile electronic device with high detection sensitivity.
• At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification as appropriate.
EXAMPLE 1Electromagnetic Noise of Display Panel
• In this example, a display panel of one embodiment of the present invention was fabricated. Moreover, the results of examining electromagnetic noise from the display panel are shown.
• As has been described, in the case where electromagnetic noise generated when the display panel operates affects a touch sensor, the detection sensitivity of the touch sensor might be decreased. For this reason, reducing electromagnetic noise caused by the display panel is effective in increasing the detection sensitivity of the touch sensor.
• One of the factors in electromagnetic noise from the display panel is electromagnetic noise from a gate driver circuit (scan line driver circuit). A circuit functioning as a shift register is suitable for the gate driver circuit.
• Changing the waveform of an input signal such as a clock signal is an effective way to reduce electromagnetic noise from a shift register circuit. Specifically, as an input signal, a signal not with an ideal square wave but with a gentle potential gradient on the rising and falling edges is used. An input signal is preferably close to a sine wave, in which case electromagnetic noise can be further reduced. Examples of a method for generating such a waveform from a square wave include using a delay circuit or the like and adding a capacitor to a wiring. Preferably, such a waveform may be generated by decreasing the current supply capability of a signal generator circuit.
• FIG. 16A illustrates a shift register circuit of one embodiment of the present invention. The circuit illustrated inFIG. 16A is a circuit extracted in part from the circuit inFIG. 9. Transistors M21 to M28 included in the circuit ofFIG. 16A are preferably transistors in which the above-described oxide semiconductor is contained in a channel formation region.FIG. 16B is a timing chart. When the circuit inFIG. 16A is driven using input signals with waveforms shown inFIG. 16B, for example, generation of electromagnetic noise in the circuit can be prevented. The shift register circuit of one embodiment of the present invention has lower shoot-through current than a shift register circuit using a CMOS circuit described later, partly because it is composed of transistors with the same conductivity type. If a circuit with the same configuration is formed using transistors in which amorphous silicon, low-temperature polysilicon, or the like is used for a semiconductor layer, it is necessary to add a capacitor to a node N1 to prevent leakage current. As a result, current required for charging and discharging is increased, which may increase power consumption as compared to the case of using the oxide semiconductor.
• Here, the case where a CMOS circuit in which an n-channel transistor and a p-channel are combined as shown inFIG. 17A is used in a shift register circuit is considered.FIG. 17B illustrates an example of a shift register circuit (circuit B) using the CMOS circuit.
• The assumption is made that each transistor inFIGS. 17A and 17B contains silicon such as low-temperature polysilicon in a semiconductor layer in which a channel is formed.FIG. 18A shows an example of input-output characteristics of the CMOS circuit inFIG. 17A. In the CMOS circuit having the transistor in which silicon is used for the semiconductor layer, as shown inFIG. 18B, a shoot-through current flows when input voltage is inverted. This means that when a signal not with an ideal square wave but with a gentle potential gradient on the rising and falling edges is used as an input signal, power consumption due to shoot-through current is further increased.
• Power consumption (charge consumption) of the circuit A inFIG. 9 and that of the circuit B inFIG. 17B with varying rise time of an input signal were calculated for comparison. When a high-level potential at which the input signal is saturated is 100%, the rise time refers to time it takes for a potential level to increase from 10% to 90%.
• FIG. 19 shows the calculation results. In the circuit B, power consumption increases as the rise time of the input signal becomes longer. In contrast, in the circuit A, power consumption is almost constant regardless of the length of the rise time of the input signal.
• A flexible display panel using the circuit illustrated inFIG. 9 as a gate driver was fabricated. The display panel was a top-emission organic EL panel using a color filter method. Transistors included in pixels and the driver circuit of the organic EL panel were formed using CAAC-OS for a semiconductor layer. The thickness of the display panel was approximately 50 μm.
• Electromagnetic noise emitted from the fabricated flexible display panel was measured by a spectrum analyzer while an image was displayed.FIG. 20A shows the panel at the time of measurement. The intensity of electromagnetic noise was measured with a spectrum analyzer probe placed directly above the gate driver. The measurement was performed under two conditions: when a signal input to the gate driver has a square wave and when the input signal has a waveform with gentle rising. For the latter condition, a capacitor was added to an input terminal of the display panel to increase the rise time of the signal from approximately 50 ns to approximately 800 ns. Although a capacitor is added in this example, addition of a resistor produces a similar effect; that is, source-sink current of a transistor for outputting a signal in an external control circuit for driving the organic EL panel can be reduced.
• FIG. 20B shows the measurement results. As compared to the case of the input signal with a square wave (indicated by a dashed line), electromagnetic noise emitted from the display panel was reduced in the case where the input signal has a waveform with gentle rising (indicated by a solid line). Furthermore, a reduction of current flowing to VDD inFIG. 9 by approximately 20% was found.
• At least part of this example can be implemented in combination with any of the embodiments described in this specification as appropriate.
EXAMPLE 2
• In this example, a change in resistance of a transparent conductive film that can be used in a touch panel and a touch sensor of one embodiment of the present invention was measured at the time of bending. Then, a touch sensor of one embodiment of the present invention was fabricated, and a change in its output signal between two states (when the touch sensor was bent and when it was not bent) was measured.
Bending Test of Transparent Conductive Film
• FIG. 21 is a schematic top diagram of a test element fabricated to perform a bending test on the transparent conductive film. The test element includes, over a flexible substrate, two metal wirings and a transparent electrode electrically connected to the metal wirings. The metal wirings are electrically connected to respective ends of the transparent electrode and an FPC. The transparent electrode has a rectangular shape with a length L of 75 mm and a width W of 300 μm. As the transparent electrode, an indium tin oxide film containing silicon with a thickness of approximately 230 nm was used. As the metal wiring, a tungsten film with a thickness of approximately 200 nm was used.
• The bending test was performed by bending the flexible substrate in a direction parallel to the longitudinal direction of the transparent electrode as shown inFIG. 21. The resistance of the test element was measured with a varying radius of curvature of the flexible substrate.
• FIG. 22 shows the measurement results. The vertical axis and the horizontal axis ofFIG. 22 represent the resistance and the inverse of the radius of curvature, respectively.FIG. 22 shows that the resistance does not change even when the radius of curvature is reduced. That is, the resistance of the transparent conductive film does not change even with a radius of curvature of 4 mm or less or approximately 2 mm. Accordingly, this transparent conductive film is suitably used in a flexible touch sensor, a flexible display panel, and a flexible touch panel.
Bending Test of Touch Sensor
• A flexible touch sensor using the above transparent conductive film as a pair of electrodes was fabricated. The touch sensor was a mutual capacitive touch sensor. The thickness of the touch sensor was approximately 50 μm. The transmittance of the flexible touch sensor ranged from 80% to 85%.
• Next, a signal output from the fabricated touch sensor was measured when the touch sensor was laid flat and when it was bent at 180° with a radius of curvature of 4 mm.
• FIGS. 23A and 23B show the measurement results. Specifically,FIG. 23A shows the results measured when the touch sensor is laid flat, andFIG. 23B shows the results measured when the touch sensor is bent. InFIGS. 23A and 23B, a solid line indicates the results obtained when an object does not touch the touch sensor, and a dashed line indicates the results obtained when an object touches the touch sensor. The flat touch sensor and the bent touch sensor output substantially the same signals, and this fact demonstrates that the touch sensor can operate properly in either state.
• At least part of this example can be implemented in combination with any of the embodiments described in this specification as appropriate.
EXAMPLE 3
• In this example, a touch panel was manufactured with the method for manufacturing a touch panel in one embodiment of the present invention.
• The touch panel was manufactured with the manufacturing method example inEmbodiment 1.FIG. 14 illustrates a stacked-layer structure of the fabricated touch panel. Here, the display panel was a top-emission organic EL panel using a color filter method. Transistors included in pixels and a driver circuit of the organic EL panel were formed using CAAC-OS for a semiconductor layer. The touch sensor was a mutual capacitive touch sensor. The display panel and the touch sensor each had a thickness of approximately 50 μm. The film layer was a PET film with a thickness of approximately 50 μm. The bonding layer was a silicone resin film with a thickness of approximately 25 μm.
• As the support, an epoxy resin having curved opposite edges with a radius of curvature of 4 mm was used. According to the manufacturing method described inEmbodiment 1, the touch panel was fabricated along the opposite side surfaces and the top surface of the support.
• FIG. 15 is a photograph of the fabricated touch panel. In the application shown inFIG. 15, text data is displayed on a region of the top surface of the support and can be scrolled up and down by operating a slider displayed on a region of the side surface of the support. It was demonstrated that multi-touch operation was achieved in the regions at the side surface and the top surface of the support. Providing the control portion at the side of the panel in this manner is convenient for one-handed holding and operation of a mobile device.
• At least part of this example can be implemented in combination with any of the embodiments described in this specification as appropriate.
EXPLANATION OF REFERENCE
• 10: electronic device,100: touch panel,101: housing,102: exterior component,103: support,111: display panel,112: touch sensor,113: film layer,114: bonding layer,201: substrate,202: substrate,205: FPC,211: wiring,212: wiring,220: insulating layer,221: electrode,222: electrode,223: wiring,224: dielectric layer,226: insulating layer,231: bonding layer,232: bonding layer,235: protection layer,255: connection layer,330: portable information appliance,333: display portion,335: housing,336: housing,337: information,339: operation button,340: portable information appliance,345: portable information appliance,351: housing,355: information,356: information,357: information,358: display portion,401: lower electrode,402: EL layer,403: upper electrodes,405: insulating layer,407: bonding layer,420: substrate,422: bonding layer,424: insulating layer,426: bonding layer,428: substrate,431: light-blocking layer,432: coloring layer,435: conductive layer,450: organic EL element,453: overcoat,454: transistor,455: transistor,457: wiring,463: insulating layer,465: insulating layer,467: insulating layer,470: IC,491: display portion,493: driver circuit,495: FPC,496: insulating layer,497: connector,7100: portable information appliance,7101: housing,7102: display portion,7103: band,7104: buckle,7105: operation button,7106: input/output terminal,7107: icon,7200: lighting device,7201: stage,7202: light-emitting portion,7203: operation switch,7210: lighting device,7212: light-emitting portion,7220: lighting device,7222: light-emitting portion,7400: mobile phone,7401: housing,7402: display portion,7403: operation button,7404: external connection port,7405: speaker,7406: microphone
• This application is based on Japanese Patent Application serial no. 2013-249280 and no. 2014-104981 filed with Japan Patent Office on Dec. 2, 2013 and May 21, 2014, respectively, the entire contents of which are hereby incorporated by reference.

Claims (15)

1. An electronic device comprising a curved display portion, the electronic device comprising:

a substrate comprising a curved portion;

a transistor over the substrate;

an organic EL element electrically connected to the transistor;

a film layer comprising an organic material over the organic EL element;

a bonding layer over the film layer;

a touch sensor over the bonding layer; and

an exterior component over the touch sensor,

wherein at least part of the exterior component is configured to serve as a housing of the electronic device,

wherein an end portion of the film layer comprises a region provided outside of an end portion of the touch sensor, and

wherein the curved portion of the substrate is not supported by a support.

2. The electronic device according toclaim 1,

wherein the film layer comprises a plurality of inorganic insulating layers.

3. The electronic device according toclaim 1,

wherein the film layer comprises an inorganic insulating layer and an organic insulating layer.

4. The electronic device according toclaim 1,

wherein the electronic device is a mobile phone.

5. The electronic device according toclaim 1,

wherein the electronic device is a wrist-watch-type portable information appliance.

6. An electronic device comprising a curved display portion, the electronic device comprising:

a substrate;

a transistor over the substrate;

an organic EL element electrically connected to the transistor;

a film layer comprising an organic material over the organic EL element;

a bonding layer over the film layer;

a touch sensor over the bonding layer; and

an exterior component over the touch sensor,

wherein at least part of the exterior component is configured to serve as a housing of the electronic device,

wherein an end portion of the film layer comprises a region provided outside of an end portion of the touch sensor,

wherein the film layer comprises a curved portion, and

wherein the curved portion of the film layer is not supported by a support.

7. The electronic device according toclaim 6,

wherein the film layer comprises a plurality of inorganic insulating layers.

8. The electronic device according toclaim 6,

wherein the film layer comprises an inorganic insulating layer and an organic insulating layer.

9. The electronic device according toclaim 6,

wherein the electronic device is a mobile phone.

10. The electronic device according toclaim 6,

wherein the electronic device is a wrist-watch-type portable information appliance.

11. An electronic device comprising a curved display portion, the electronic device comprising:

a substrate;

a transistor over the substrate;

an organic EL element electrically connected to the transistor;

a film layer comprising an organic material over the organic EL element;

a bonding layer over the film layer;

a touch sensor over the bonding layer; and

an exterior component over the touch sensor,

wherein at least part of the exterior component is configured to serve as a housing of the electronic device,

wherein an end portion of the film layer comprises a region provided outside of an end portion of the touch sensor,

wherein the film layer comprises a curved portion, and

wherein the substrate is not supported by a support in a region overlapping with the curved portion of the film layer.

12. The electronic device according toclaim 11,

wherein the film layer comprises a plurality of inorganic insulating layers.

13. The electronic device according toclaim 11,

wherein the film layer comprises an inorganic insulating layer and an organic insulating layer.

14. The electronic device according toclaim 11,

wherein the electronic device is a mobile phone.

15. The electronic device according toclaim 11,

wherein the electronic device is a wrist-watch-type portable information appliance.

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