US20070189667A1 - Display element and display device using the same - Google Patents

Abstract

A display element is provided with a light source and a waveguide that propagates a light emitted from the light source, wherein the light propagated in the waveguide is extracted to outside from a waveguide lateral face, and wherein the light is extracted out of the waveguide from the waveguide lateral face by changing a shape of the waveguide lateral face.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is a Division of application Ser. No. 10/533,663, filed May 3, 2005, which is a National Stage of PCT/JP2003/014047, which applications are incorporated herein by reference.
TECHNICAL FIELD
• The present invention relates to display elements and display devices using these display elements in which display is carried out by extracting light propagated by a waveguide from a lateral face of the waveguide.
BACKGROUND ART
• Display devices in which light propagated by a waveguide is extracted from a lateral face of the waveguide are disclosed in JP H7-287176A (particularly pages 6-7 and FIGS.1 to20) and JP H11-202222A (particularly pages 3-4, paragraph (0010), andFIG. 2) for example. These display devices are provided with actuator portions that are connected to light extraction portions and made of a ceramic piezoelectric film. Rest and displacement of the actuator portion is carried out by applying a voltage to the actuator portion such that the light extraction portion comes in contact with or moves away from the light waveguide, thereby extracting leakage light in a controlled manner.
• Display devices that use the above system have been implemented as large size display panels. A commercialized example of these is presented in a CeramVision/CeramBoard brochure (fifth page, lower left column) at the following Internet address: http://www.ngk.co.jp/ELE/product/07/index.html (accessed on Jul. 25, 2002).
• With traditional displays, light that is totally reflected and propagated within the waveguide is made to leak to the outside from a lateral face of the waveguide by bringing the waveguide and the light extraction portion together to a distance less than the wavelength of the light. That is, so called evanescent waves are extracted (particularly see paragraph (0009) of JP H7-287176A and claim1 of JP H11-202222A). As shown in drawings such asFIGS. 1 and 4 of JP H7-287176A, the extraction of light from a lateral face of the waveguide is controlled by whether or not a flat surface of a displacement transmission portion (light extraction portion) is made to come into contact with a planar waveguide.
• Furthermore,FIG. 3 of JP H11-202222A shows the transmissivity of light when evanescent light of light that is totally reflected by a total reflection surface is extracted at an extraction surface that has been brought in to proximity with the total reflection surface. According to this, transmissivity of approximately 50% is shown for light that has an incident angle in the range of 50° to 80° to the total reflection surface when the distance between the total reflection surface and the extraction surface is in the range of 0.1 to 0.05 μm.
• Furthermore, for example, a display device is disclosed in “Waveguide Panel Display Using Electromechanical Spatial Modulators,” X. Zhou, E. Gulari, SID98 Digest, 1998, pages 1,022 to 1,025, in which an electrostatic actuator, in which a metal electrode film is formed on a polyimide film, is used as the actuator portion and an LED is used as the light source. In this display device, in contrast to the light extraction portion's width of 0.23 mm, the thickness of the waveguide is 0.5 mm. Furthermore, a surface of the waveguide is an ITO film, and the surface of the light extraction portion that comes into contact with the ITO film is made by forming a film doped with titanium dioxide particles, which affect the diffusion properties of the polyimide, on an electrode, such that this film becomes a composite material harder than polyimide.
• The above-described conventional display device has low efficiency in extracting from the waveguide the light that is propagated in the waveguide. Moreover, unless the light extraction portion exerts a large pressure on the waveguide, the extracted light has insufficient brightness and is uneven.
DISCLOSURE OF INVENTION
• The present invention has been devised to solve these issues, and it is an object thereof to provide a display element and a display device in which light propagated in a waveguide can be extracted with high efficiency from a lateral face of the waveguide.
• A display element according to the present invention is provided with a light source and a waveguide that propagates a light emitted from the light source, wherein the light propagated in the waveguide is extracted to the outside from a waveguide lateral face, and wherein the light is extracted out of the waveguide from the waveguide lateral face by changing a shape of the waveguide lateral face.
BRIEF DESCRIPTION OF DRAWINGS
• FIG. 1 is a cross-sectional view showing a structure of a display element according to Embodiment 1 of the present invention.
• FIG. 2 is a perspective view showing a structure of a display device according to Embodiment 1 of the present invention.
• FIG. 3 is a block diagram showing a structure of a display device according to Embodiment 1 of the present invention.
• FIG. 4 is a cross-sectional view showing a structure of a display element according toEmbodiment 2 of the present invention.
• FIG. 5 is a cross-sectional view showing a structure of a display element according toEmbodiment 3 of the present invention.
• FIG. 6 is a perspective view showing a structure of a display device according toEmbodiment 3 of the present invention.
• FIG. 7 is a block diagram showing a structure of a display device according toEmbodiment 3 of the present invention.
• FIG. 8 is a cross-sectional view showing a structure of a display element according toEmbodiment 4 of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
• A display device according to the present invention extracts, from a lateral face of a waveguide, light that is propagated in the waveguide by changing the shape of the waveguide lateral face, and therefore is capable of extracting propagated light with high efficiency. This makes possible a display that is bright and uniform.
• Furthermore, it is preferable that the display element is further provided with a plurality of actuators that change a shape of the waveguide, wherein the shape of the waveguide lateral face is changed by selectively operating the actuators to extract the light out of the waveguide from the waveguide lateral face. In this way, light propagated in the waveguide can be extracted with high efficiency.
• Furthermore, it is preferable that the waveguide is provided with a core and a cladding formed along one lateral face of the core, wherein the actuators are attached to the cladding and a shape of the waveguide lateral face is changed by deforming the actuators. In this way, light propagated in the waveguide can be extracted with high efficiency.
• Furthermore, it is preferable that the light is extracted out of the waveguide by deforming at least a portion of the core of the waveguide. In this way, light can be extracted precisely.
• Furthermore, it is preferable that the actuators are attached to the waveguide lateral face, and a shape of the waveguide lateral face is changed by deforming the actuators. In this way, light can be extracted easily.
• Furthermore, it is preferable that the actuators are provided with a piezoelectric element, and a shape of the waveguide lateral face is changed by deforming the piezoelectric element by applying a voltage to the piezoelectric element. In this way, actuators that operate at high speed can be formed and therefore high precision video display can be supported.
• Furthermore, it is preferable that the actuators are provided with a first electrode film arranged at the waveguide lateral face, a piezoelectric element layered on the electrode film, and a second electrode film layered on the piezoelectric element, wherein the shape of the waveguide lateral face is changed by deforming the piezoelectric element by applying a voltage between the first electrode film arranged at the waveguide lateral face and the second electrode film layered on the piezoelectric element. In this way, high efficiency light extraction can be achieved with small external pressure.
• Furthermore, it is preferable that the actuators are provided with a convex portion, and a shape of the waveguide lateral face is changed by applying pressure to the waveguide lateral face with the convex portion. In this way, high efficiency light extraction can be achieved easily.
• Furthermore, the actuators are provided with: an electrode film arranged at the waveguide lateral face, and an external electrode film that is in opposition to and adjacent to the waveguide, wherein the shape of the waveguide lateral face is changed by an electrostatic force produced by applying a voltage between the external electrode film and the electrode film. In this way, high efficiency light extraction can be achieved easily.
• The external electrode film is provided with a convex portion at the waveguide lateral face, and a shape of the waveguide lateral face is changed by the convex portion of the external electrode film applying pressure to the waveguide lateral face by using the electrostatic force. In this way, actuators that operate at high speed can be formed and therefore high precision video display can be supported.
• Furthermore, it is preferable that the light is extracted out of the waveguide by deforming at least a portion of the core of the waveguide. In this way, light can be extracted precisely.
• Furthermore, it is preferable that at least a portion of the waveguide is made of an elastic material. In this way, high efficiency light extraction is possible with small external pressure.
• Furthermore, it is preferable that at least a portion of the waveguide is made of a transparent gel. In this way, high efficiency light extraction is possible with small external pressure.
• Furthermore, it is preferable that the actuators are formed for each pixel. This makes possible a display using an active matrix.
• Furthermore, it is preferable that the waveguide is provided with a waveguide electrode film on the waveguide lateral face, an opposing electrode film that opposes the waveguide electrode film, and particles arranged between the waveguide electrode film and the opposing electrode film, wherein, by applying a voltage between the waveguide electrode film and the opposing electrode film, the particles and the waveguide electrode film are brought into contact such that the light is extracted out of the waveguide from the waveguide lateral face. With such a structure, the particles and the waveguide can be integrated by bringing the particle into contact with the waveguide electrode film, and the light can be extracted out of the waveguide from the waveguide lateral face by changing the shape of the waveguide lateral face. In this way, high efficiency light extraction is possible by applying only a very uniform and small pressure.
• Furthermore, it is preferable that the light is extracted out of the waveguide by deforming at least a portion of the core of the waveguide. In this way, light can be extracted precisely.
• Furthermore, it is preferable that the particle is electrically charged. In this way, it is possible to control the particle with an electrostatic force and therefore control can be achieved easily.
• Furthermore, it is preferable that the particle has a magnetic property. In this way, it is possible to control the particle with an electrostatic force and therefore control can be achieved easily.
• Furthermore, it is preferable that a surface tension of the waveguide electrode film and a surface tension of a surface of the particles are different from each other. In this way, it is easy to cause the particles to contact the waveguide electrode film. For this reason, contact and non-contact of the particles can be controlled with a low voltage.
• Furthermore, a coating material is applied to the waveguide electrode film. In this way, it is easy to cause the particles to contact the waveguide electrode film. For this reason, contact and non-contact of the particles can be controlled with a low voltage.
• Furthermore, it is preferable that the waveguide electrode film and the opposing electrode film are provided for each pixel. This makes possible display using an active matrix.
• Furthermore, the particle is fluorescent. In this way, it is possible to extract light of various wavelengths by varying the wavelength of the light from the light source.
• Furthermore, the light source emits ultraviolet light. In this way, it is possible to achieve RGB display even when the light source is one type of LED.
• Furthermore, the light source is a 3-color LED or a 3-color laser. In this way, the number of waveguides can be reduced.
• Furthermore, it is preferable that the display device according to the present embodiment is provided with: the above-described display element, the light source drive circuit for driving the light source, an actuator drive circuit for driving the actuator, and a control circuit that controls the light source drive circuit and the actuator drive circuit. In this way, it is possible to achieve a display device capable of higher luminance and uniform display with lower power consumption.
• Furthermore, it is preferably provided with the above-described display element, the light source drive circuit for driving the light source, a particle drive circuit for applying a voltage between the waveguide electrode film and the opposing electrode film, and a control circuit that controls the light source drive circuit and the particle drive circuit. In this way, it is possible to achieve a display device capable of higher luminance and uniform display with lower power consumption.
• Furthermore, it is preferably provided with the above-described display element and an active matrix element that controls the respective actuators. This achieves a display device using an active matrix.
• Furthermore, it is preferably provided with the above-described display element and an active matrix element that controls respective voltages between the waveguide electrode films and the opposing electrode films. This achieves a display device using an active matrix.
• Furthermore, the active matrix elements may be a TFT or a TFD.
• The following is a description of more specific examples of embodiments according to the present invention with reference to the accompanying drawings.
Embodiment 1
• The following is a description of a display element and a display device according to an embodiment of the present invention with reference to the accompanying drawings.FIG. 1 is a cross-sectional view showing a structure of a display element1 according to Embodiment 1 of the present invention. The display element1 is provided with alight source2, awaveguide3 that propagates the light emitted from thelight source2, and a plurality ofactuators4 that change the form of thewaveguide3.
• Thewaveguide3 is provided with acore3a,through which light propagates, and acladding3b.Thecladding3bis arranged along the surface on one side of thecore3a.Cladding is not arranged on the surface on the opposite side from thecladding3bsuch that air acts as the cladding there. A sheet of silicone gel, which is an extremely soft material, with a thickness of 100-μm for example may be used as thecore3a,through which light propagates. A transparent fluoric polymer for example with a low refractive index may be used as thecladding3b.Thecore3ais coated with thecladding3bto a thickness of 10 μm.
• Thelight source2 is arranged at an end portion of thewaveguide3 and thelight source2 is arranged with an orientation such that the light emitted from thelight source2 is coupled into thewaveguide3. It is preferable that a 3-color LED for example is used as thelight source2. The 3-color LED can have a structure in which RGB 3-color LED chips are accommodated in a single lamp, with each color independently controlled.. In conventional flat panel displays using LCD or PDP, the pixels of the three RGB colors are separated in a stripe form. However, in Embodiment 1, by using a 3-color LED, the light of the three colors R, G, and B can be input to asingle waveguide3, and therefore it is possible for asingle waveguide3 to emit any of the three colors R, G, and B. It should be noted that it is preferable for aprism2ato be placed and optically coupled at an incident location of thewaveguide3 to facilitate entrance of the light from thelight source2 even when thewaveguide3 is thin.
• Theactuators4 are provided with apiezoelectric element4a,andelectrode films4band4cthat are arranged respectively on opposite sides of thepiezoelectric element4a.Theactuators4 are attached at a lateral face on thecladding3bside of thewaveguide3. Thepiezoelectric element4amay be polyvinylidene fluoride (PVDF) for example, on which a plurality of theelectrode films4band theelectrode film4care formed by applying on both sides thereof a silver paste for example. Theactuators4 are attached with an adhesive at a lateral face, that is, thecladding3b,of thewaveguide3. Theelectrode films4bhave a width of 70 μm and are formed in a striped pattern with a pitch of 90 μm. It should be noted that these stripes are formed extending vertically with respect to the paper plane inFIG. 1. Four of these stripes ofelectrode films4bconstitute asingle actuator4. Furthermore, theelectrode film4cfacing theelectrode films4bis a continuous coating that spreads uniformly on thewaveguide3 and is shared by a plurality ofactuators4.
• The following is a description of how light is extracted from a lateral face of thewaveguide3 of the display element1 shown inFIG. 1. Positive and negative voltages are alternately applied to the four stripes ofelectrode films4bof theactuators4 arranged at thewaveguide3. In this way, thepiezoelectric film4acontracts in locations of theelectrode films4bsupplied with a positive voltage, and thepiezoelectric film4alengthens in locations of theelectrode films4bsupplied with a negative voltage. Since the length of thecladding3bis prescribed and does not change, theactuators4 alternately project up and down as shown inFIG. 1. That is, theactuators4 become wave shaped. This makes thecladding3bchange to the same shape as theactuators4 and the surface of thecore3aon thecladding3bside is also deformed.
• The lengths of thecladding3band thepiezoelectric film4aare the same when no voltage is applied, and therefore theactuators4 assume a planar shape.
• In this way, it is possible to change the form of the lateral face of thewaveguide3 by selectively controlling the voltage that is applied between theelectrode films4band theelectrode film4c.
• Light of a desired color emitted from thelight source2 is propagated in thewaveguide3. Here; when concavity and convexity are produced in desired locations on the surface of thecore3aon thecladding3bside in thewaveguide3 by selectively applying voltages, a portion of the light propagated in thewaveguide3, for example, alight2cshown as a dot-dash line, undergoes a change of angle with respect to the surface of thecore3a,and therefore is emitted out of thewaveguide3 from a lateral face (the side on which actuators4 of thewaveguide3 are not arranged) of thewaveguide3 after being totally reflected. Furthermore, alight2b,which is shown by a broken line, is transmitted through thecore3aand thecladding3bdue to the changed form of thewaveguide3 and is then reflected by thesilver electrode film4csuch that it is scatter-reflected and emitted out of thewaveguide3 from a lateral face of thewaveguide3.
• In this way, by controlling the application of voltages to control the color of emitted light from thelight source2 that is incident on thewaveguide3, it is possible to extract light at a desired position and of a desired color from the lateral face (display surface1a) of thewaveguide3 of the display element1 and carry out display.
• Furthermore, the greater the voltage applied to theactuators4, the greater the change in form of thewaveguide3. Increases in the luminance of the extracted light were observed according to measurements along with gradual increases in applied voltages starting from zero. Luminance was saturated when the voltage applied was ±30 volts and it was possible to extract 80% or more of the light from thelight source2 that was incident on thewaveguide3.
• Alight source2 that provides high directivity for emitted light is preferable for extracting light efficiently. In thewaveguide3 of thedisplay surface1ainFIG. 1, the total reflection angle at the interface between the core3aand the air is 60°. Accordingly, when the angle (incident angle) of the light propagated in thewaveguide3 with respect to the normal line of the display surface la is smaller than 41.8°, which is the critical angle, light leaks from thewaveguide3. Conversely, when the incident angle is large and the travel direction of the light is close to parallel to thewaveguide3, total reflection occurs repetitively in thecore3aand the spacing between locations of such total reflection becomes extremely large such that locations in which light extraction is desired are passed over, thus tending to reduce efficiency and produce uneven luminance.
• For these reasons, it is preferable that the incident angle of light emitted from thelight source2 to thewaveguide3 is larger than the critical angle of 41.8° but close to the critical angle of 41.8° with a light of high directivity. For example, when thelight source2 is an LED, the directivity can be varied according to the shape of the lens that is molded, and therefore the half-value width of the emitted light angle distribution of the 3-color LED serving as thelight source2 was set at approximately 10°.
• It should be noted that it is possible to use alight source2 other than an LED. For example, it is possible to use alight source2 in which directivity has been improved by arranging a micro-lens array on an organic EL panel and it is also possible to use a semiconductor laser as thelight source2.
• When thewaveguide3 is too thick, the light propagated inside thewaveguide3 undergoes repetitive total reflection at thedisplay surface1a(the interface between thewaveguide3 and the air) and the spacing between locations of total reflection becomes extremely large. For this reason, the propagated light may pass over the arranged locations (pixels) of theactuators4, thus bringing about light beams that cannot be extracted. Therefore, it is preferable that thewaveguide3 is not too thick.
• Specifically, setting the thickness D of thewaveguide3 inFIG. 1 at not greater than ½ of the length L (the length of theactuators4 in the propagation direction of light in the waveguide3) of the portions of thewaveguide3 that are made to change form by theactuators4 is preferable in terms of efficient extraction.
• The thickness of thewaveguide3 is determined according to the number of pixels and the size of the display area. In the display element1, the length L of the portions of thewaveguide3 that are made to change form by theactuators4 corresponds to the length of one pixel in the horizontal direction (propagation direction of light in the waveguide3). For example, the display size of adisplay device100 using the display element1 described below is that of a HDTV in the range of 60 to 100 inches. In this case for example, the size of a single pixel is approximately in the range of 230.6 μm (vertical)×691.8 μm (horizontal) to 384.3 μm (vertical)×1,153 μm (horizontal). It should be noted that here vertical is the length in the perpendicular direction with respect to the propagation direction of length in thewaveguide3 and horizontal is the length in the propagation direction of light in thewaveguide3. The thickness D of thewaveguide3 here is preferably not greater than 345.9 μm and not greater than 576.5 μm. The thickness D of thewaveguide3 is preferably not greater than ½ of the length L (the length of theactuators4 in the propagation direction of light in the waveguide3) of the portions of thewaveguide3 that are made to change form by theactuators4.
• On the other hand, when thewaveguide3 is too thin, the angles at which light can be propagated in thewaveguide3 are limited such that the propagated light is close to single mode, and therefore the amount of propagated light is reduced. Furthermore, it is difficult to provide incident light when thewaveguide3 is too thin. For this reason, it is preferable that the thickness of thecore3ais at least 30 μm or more.
• The following is a description of adisplay device100 according to Embodiment1 with reference toFIG. 2.FIG. 2 is a perspective view showing a structure of thedisplay device100 according to Embodiment 1. With the above-described display element1 vertical with respect to the propagation direction of light in thewaveguide3, thedisplay device100 can be configured by arranging in a row a plurality of the display elements1 such that the display surfaces la are on the same side. As shown inFIG. 2, with thedisplay device100 of Embodiment 1, thewaveguides3 of the display elements1 are arranged in an array of n rows in the row direction (X direction) of the screen. Here, n is a natural number. Therespective light sources2 are arranged at end portions of thewaveguides3 andactuators4 for m lines are arranged in a line direction (Y direction), which is the direction in whichwaveguides3 extend. The number of pixels of thedisplay device100 is n×m pixels.
• Adisplay device100 according to Embodiment 1 operates theactuators4 in line sequence to change the form of the lateral face of thewaveguide3 and thereby change the direction in which light conveyed in thewaveguide3 by total reflection is reflected, thus extracting light from within thewaveguide3 and causing the light emission from thedisplay surface1a.
• Adisplay device100 with this configuration is capable of displaying a given image by controlling the application of voltages to the various chips for the 3-color LEDs serving as thelight sources2 for thewaveguides3 that extend in the row direction of the display plane (XY plane), based on the color and luminance information of the pixels on the lines for which extraction is selected with theelectrode films4band theelectrode film4c.
• A block diagram showing a configuration of thedisplay device100 of Embodiment 1 is shown inFIG. 3.FIG. 3 illustrates a specific configuration for actually operating thedisplay device100. In addition to the above, thedisplay device100 is provided with a lightsource drive circuit50 for driving thelight sources2, anactuator drive circuit51 for driving theactuators4 by applying voltages to theelectrode film4band4c,and acontrol circuit52 that synchronizes these circuits, inputs signals, and displays images. Thecontrol circuit52 inputs luminance information of the colors RGB of pixels in lines selected by theactuator drive circuit51 to the driver LSI of the lightsource drive circuit50, and the lightsource drive circuit50 inputs applied voltages corresponding to the luminance information to thelight sources2 to enable full color image display.
• Since 3-color LEDs are used as thelight sources2, it is possible to make light of three colors incident on asingle waveguide3. This makes it possible to display light of three colors with a single display element1, that is, with one line. With conventional display devices such as liquid crystal displays and PDPs, a pixel is configured by three sub-pixels of the three primary colors R, G, and B. However, with the display device using thewaveguide3 of Embodiment 1, it is not necessary to divide thewaveguides3 that extend in the row direction for each color and the three primary colors can be incident on asingle waveguide3, and therefore it is possible to reduce the number of waveguides3 (display elements1), thus providing the effect of reduced costs.
• Uniformly bright planar display could be confirmed by sequentially applying voltages of ±30V to theactuators4 in the display elements1 of thedisplay device100. With conventional structures in which light is extracted using evanescent waves, it has not been possible to reduce to zero the distance between the waveguide and the light extraction surface due to the influence of submicron size particulates that exist in multitude even in clean rooms. For this reason, it has not been easy to achieve high extraction efficiency even when pressing the light extraction surface against the waveguide with considerable force.
• However, with the display elements1 of thedisplay device100 of Embodiment 1, by using soft waveguides, light is extracted by causing the waveguides to change form with small external force, thus changing the reflection direction of light propagated in the waveguides. For this reason, it was possible to achieve a higher extraction efficiency than using extraction of evanescent waves.
• Furthermore, high speed operation is possible since piezoelectric elements are used in theactuators4. For this reason, high-speed scanning is possible, thus also supporting high-definition image display.
Embodiment 2
• The following is a description of a display element11 according toEmbodiment 2 of the present invention with reference toFIG. 4. In the display element11 ofEmbodiment 2 and the display element1 of Embodiment 1, the actuators are different. Other than that the structure is substantially the same and therefore members having the same function will be given the same numerical symbol and description thereof will be omitted.
• As shown inFIG. 4, the display element11 ofEmbodiment 2 is provided with alight source2, awaveguide3 that propagates the light emitted from thelight source2, andactuators14 that change the form of thewaveguide3. Thelight source2 and thewaveguide3 are the same as in the display element1 of Embodiment 1. Thelight source2 is a 3-color LED for example, and the light emitted by thelight source2 propagates in thewaveguide3. Thewaveguide3 is provided with acore3aand acladding3b,and since thecore3ais exposed on the opposite side of thecladding3b,the air acts as cladding. It should be noted that inEmbodiment 2, thecore3ais a flat sheet of a 100 μm thickness and is made of a silicone gel material, while thecladding3bis a transparent fluoric resin with a film thickness of 5 μm.
• Theactuators14 are provided with anelectrode film14aarranged on a lateral face of thewaveguide3, a polycarbonate insulationthin film14bof a thickness of 0.1 μm for example that is applied to theelectrode film14a,asubstrate14dmade of 0.15 mm thick PET film arranged in opposition to the insulationthin film14b,andexternal electrode films14c,which are formed on thesubstrate14don the insulationthin film14bside and have a concavo-convex shape. There are a plurality of the concavo-convex shapedexternal electrode films14con thesubstrate14d,and asingle actuator14 is configured for eachexternal electrode film14c.Theelectrode film14ais formed on the entire surface of the waveguide3 (cladding3b) and is common with respect to theactuators14.
• A method for manufacturing the above-describedwaveguide3 and theactuators14 is to coat thecladding3bon thecore3afor example, then further apply a silver paste with screen printing for example on the surface of thecladding3bto form theelectrode film14a.Further still, a polycarbonate is applied to theelectrode film14ato form the insulationthin film14b.Then, an indented concavo-convex portion14eis formed by being pressed formed in a striped pattern on the surface of thesubstrate14d,which is made of a 0.15 mm thick PET film. The concavo-convex portion14ehas a cross-sectional depth of 3 μm for example and a pitch of 30 μm. The aluminumexternal electrode films14care formed on the concavo-convex portion14eby carrying out aluminum deposition for example. Finally, thesubstrate14dand thewaveguide3 are arranged so as to oppose each other.
• The following is a description of the operation of the thus-structured display element11.
• When no voltage is applied between theelectrode film14aand theelectrode film14b,only the convex portions of the concavo-convex shapedexternal electrode films14cand the insulationthin film14dare connected at the end portions of the display element11 shown inFIG. 4. For this reason, the lateral face of thewaveguide3 is flat. However, by applying a voltage between theelectrode film14aand theexternal electrode films14c,an electrostatic force is produced therebetween such that these are attracted to each other. Due to this, as shown in the central area of the display element11 shown inFIG. 4, theelectrode film14aand theexternal electrode film14ccling toward each other and theelectrode film14aand theexternal electrode film14care deformed to the same concavo-convex shape. Furthermore, theelectrode film14ais adhering to thewaveguide3, and therefore thecladding3band the surface of thecore3aare deformed to the same concavo-convex shape as theexternal electrode films14c.That is, the lateral face of thewaveguide3 changes shape. It should be noted that thecore3ais particularly soft and therefore changes shape greatly. In this way, light that is being propagated while being totally reflected in thewaveguide3 can be extracted to the outside from the lateral face of thewaveguide3. As in Embodiment 1, a light12cthat is being propagated while being totally reflected in thewaveguide3 by the surfaces of thecore3acan be leaked to the outside from the lateral face of thewaveguide3 by deforming the lateral face on one side of thewaveguide3.
• That is, when desired locations of the surface of thecore3aare made to deform to a concavo-convex shape, of the light that has been propagated in thewaveguide3, the light12cshown by the one-dot dash line for example, is emitted out of thewaveguide3 from the lateral face (the side on which theactuators4 of thewaveguide3 are not arranged) of thewaveguide3 after being totally reflected since the angle of the surface of thecore3achanges. Furthermore, there is also light for example that penetrates thecore3aand thecladding3band is then reflected by thesilver electrode film14asuch that it is scatter-reflected and emitted out of thewaveguide3 from a lateral face of thewaveguide3.
• In this way, by controlling the application of voltages to control the color of emitted light from thelight source2 that is incident on thewaveguide3, it is possible to extract light at a desired position and of a desired color from the lateral face (display surface1a) of thewaveguide3 of the display element1 and carry out display.
• When sequential line scanning actually is carried out by introducing incident light to thewaveguide3 from the 3-colorLED light source2, applying +10V as a selective voltage between theelectrode film14aand theexternal electrode film14c,and applying 0V to a non-selective location, a uniformly bright display is achieved from the lateral face (display surface1a) of thewaveguide3. Even at low voltages, it is possible to extract to the outside almost all the incident light of thelight source2, thus achieving a display element1 with high power efficiency.
• A display device can be configured in the same way as thedisplay device100 by arranging in a row a plurality of the display elements11 shown inFIG. 4 vertical with respect to the propagation direction of light in thewaveguide3, such that the display surfaces la are on the same side, as shown inFIG. 2. The number of pixels when n rows of the display elements11 are arranged in the row direction of the screen andactuators14 for m lines are arranged in the direction (line direction) in which thewaveguides3 extend is n×m pixels.
• The method for achieving extraction from the lateral face (display surface1a) of thewaveguide3 to carry out image display is the same as for thedisplay device100 of Embodiment 1, and therefore will not be further explained. Only the structure of the actuators is different between the display device of Embodiment 1 and the display device ofEmbodiment 2, and the rest of the structure is substantially the same.
• Furthermore, in order to actually operate the display device ofEmbodiment 2, it is sufficient to provide, as shown inFIG. 3, a lightsource drive circuit50 for driving thelight sources2, anactuator drive circuit51 for driving operating theactuators14 by applying voltages to theelectrode films14aand14c,and acontrol circuit52 that synchronizes these circuits, inputs signals, and displays images.
• Since a light modulation medium is sandwiched between line electrodes and row electrodes in conventional XY matrix-type flat display elements, it was difficult to increase the size of the devices due to the occurrence of crosstalk. However, with the display devices ofEmbodiment 1 and 2, there is no electrical connection between the drive circuits of the lines and rows, and therefore crosstalk essentially does not occur and, moreover, it is easy to increase the size of devices since the structure is simple. Moreover, since it is not particularly necessary to provide ITO, which requires high temperature processing and because the structure is simple, it is possible to achieve thin flexible display devices that resemble film. Furthermore, LEDs or the like with high light-emission efficiency are used as the light source, and therefore it is possible to achieve high light extraction efficiency with low power actuators, such that power consumption also can be reduced.
• As described above, with a display element and a display device according toEmbodiment 1 and 2, by using a soft waveguide, it is possible to achieve a innovative display that has a large thin screen capable of being, hung or attached on a wall and that has high light emission efficiency and low power consumption.
• It should be noted that inembodiments 1 and 2, an example of silicone gel as thecore3aof thewaveguide3 was described, but a transparent material that easily deforms and shows so called rubber elasticity, for example urethane based rubber will achieve the same effect. A material with a Young's modulus smaller than 10⁶N/m²may be used as thecore3a.
• Furthermore, inembodiments 1 and 2, theentire core3awas structured with the same material, but it is sufficient for the surface of thecore3aof thewaveguide3 to be easily deformable, and therefore the surface on the side of thewaveguide3 may be structured with a hard material such as an ordinary plastic while only locations to be deformed are structured as layers arranged by a soft layer. Furthermore, it is also possible to use awaveguide3 in which only thecore3ais structured without thecladding3bsuch that the cladding on both sides is air. Furthermore, to facilitate handling, it is possible to use awaveguide3 in which cladding is provided on both sides of thecore3a.
• It should be noted that inembodiments 1 and 2 a simple matrix type display device was shown in which thewaveguides3 were arrayed according to the number of rows and a plurality of 3-colorLED light sources2 were arranged, but the type of light source and the type of actuator, as well as the structure of the positioning of these is in no way limited to this. Any structure by which it is possible to achieve high extraction efficiency with low power by deforming asoft waveguide3 may be used. For example, a structure is possible in which thewaveguide3 is made of a single flat sheet with a singlelight source2 arranged in an XY matrix with a number ofactuators4 or14 according to the number of pixels. In this case, an active element that, drives theactuators4 or14 are added to each actuator and driven for each pixel such that gradation is carried out by controlling the time in which the core deforms. A TFT (thin flat transistor) or a TFD (thin flat diode) may be used as the active element.
• With the display element and the display device according toembodiments 1 and 2, the light extraction efficiency is improved in display elements and display devices that use a technique in which light propagated in thewaveguide3 is extracted from the lateral face of the waveguide, which enables greater luminance with reduced power consumption as well as improved uniformity of display. Furthermore, it is possible to achieve sheet-shaped thin display devices regardless of the screen size even for large screens exceeding100 inches and small screens for mobile applications.
Embodiment 3
• The following is a description of a display element according toEmbodiment3 of the present invention with reference toFIG. 5.FIG. 5 is a cross-sectional view showing a structure of adisplay element21 according toEmbodiment 3. As shown inFIG. 5, thedisplay element21 is provided with alight source22, awaveguide23, an opposingelectrode film25 that opposes thewaveguide23, andparticles26 arranged near thewaveguide23.
• Thewaveguide23 is provided with a core23athat propagates light, acladding23b,andwaveguide electrode films23c.A sheet of acrylic resin for example, which is an extremely soft material, with a thickness of 100-μm is used as the core23a.Furthermore, a transparent fluoric polymer that has a low refractive index is coated as thecladding23bto a thickness of 10 μm on a surface on one side of the core23a.Thewaveguide electrode films23care ITO and are attached directly with an adhesive on a surface on the opposite side of the core23afrom thecladding23b.Thecladding23bis arranged on one surface only of the core23aand a plurality of thewaveguide electrode films23care arranged on the reverse surface. Thewaveguide electrode films23care ITO and a plurality of these are arranged in the direction in which thewaveguide23 extends. The length W of thewaveguide electrode film23cin the propagation direction of light in thewaveguide23 is 300 μm for example. The cladding on the opposite side of thecladding23bis air. Furthermore, thewaveguide electrode films23care a portion of the core and the light propagated in thewaveguide23 is also totally reflected by the interface of thewaveguide electrode films23cand the air. It should be noted that this also may be a structure in which nocladding23bis provided.
• Thelight source22 is arranged at an end portion of thewaveguide23 and thelight source22 is arranged with an orientation such that the light emitted from thelight source22 is coupled into thewaveguide23. It is preferable that aprism22ais placed and optically coupled at an incident location of thewaveguide23. It should be noted that thelight source22 may be the same as thelight source2 in Embodiment 1 and it is preferable that a 3-color LED is used for example.
• Alight source22 that has high directivity is preferable to enable efficient extraction of light from thewaveguide23. In thewaveguide23, the total reflection angle at the interface between the core23aand the air is 60°. The state of light propagation in thewaveguide23 is shown conceptually in the cross-sectional view ofFIG. 5.
• When the incident angle (angle with respect to the normal line of thedisplay surface21a) to thewaveguide23 of the light22bshown as a broken line emitted from thelight source22 is smaller than 41.8°, which is the critical angle inEmbodiment 3, the light22bleaks from thewaveguide23. Conversely, when the incident angle is greater than the critical angle of 41.8° as with the light22cshown by the dot-dash line, the travel path of the light22cis close to parallel to thewaveguide23. In this way, total reflectance occurs repetitively in the core23aand thewaveguide electrode film23cand the spacing between locations of such total reflectance becomes extremely large such that locations in which light extraction is desired are passed over, thus tending to reduce efficiency and produce uneven luminance. Furthermore, as illustrated inFIG. 3 of JP H7-287176A, the extraction ratio of evanescent waves becomes smaller and efficiency is reduced. For these reasons, it is preferable that the incident angle of light emitted from thelight source22 to thewaveguide23 is larger than the critical angle of 41.8° but close to the critical angle of 41.8° with alight source22 of high directivity. For example, when thelight source22 is an LED, the directivity can be varied according to the shape of the lens that is molded, and is therefore preferable. That is why, inEmbodiment 3, a 3-color LED in which the half value width of the emitted light angle distribution is set to 10° is used as thelight source22.
• It should be noted that, other than an LED, it is also possible to use a light source whose directivity has been improved by arranging a micro-lens array on an organic EL panel, as thelight source22, and it is also possible to use a semiconductor laser. By using 3-color LED as thelight source22, it is easier to make light of three colors incident on asingle waveguide23. With conventional displays such as liquid crystal displays and PDPs, a pixel is configured by three sub-pixels of the three primary colors R, G, and B, but by configuring a pixel as described above, it is not necessary to divide thewaveguides23 that extend in the row direction for each color and the three primary colors can be incident on asingle waveguide23. Therefore it is possible to reduce the number ofwaveguides23, thus providing the effect of reduced costs.
• The opposingelectrode film24 is arranged in opposition to thewaveguide23. The opposingelectrode film24 is ITO for example, and is deposited on asubstrate25 of an acrylic resin. The spacing between thewaveguide electrode film23cand the opposingelectrode film24 is 35 μm for example.
• Particles26 are arranged in the vicinity of thewaveguide23. Theparticles26 are positioned between thewaveguide electrode film23cand the opposingelectrode film24, are made of an acrylic resin, and are electrically charged. The mean particle size of theparticles26 is 6 μm for example. Theparticles26 are filled into the space between thewaveguide electrode film23cand the opposingelectrode film24 to a filling rate of 20%. It should be noted that the filling rate is the ratio of the volume occupied by the particles per unit of volume. The volume occupied by theparticles26 can be obtained by multiplying the number ofparticles26 per unit of volume by the volume per particle that is obtained from the mean particle size of theparticles26.
• When applying a voltage of 70V for example so that the selectedwaveguide electrode film23cbecomes negative and the opposingelectrode film24 becomes positive, theparticles26 contact the surface of thewaveguide electrode film23c.In this way, theparticles26 and thewaveguide23 become integrated. That is, theparticles26 become a portion of a lateral face of thewaveguide23 and the shape of the lateral face of thewaveguide23 on the side of thewaveguide electrode film23cis changed.
• Light of a desired color emitted from thelight source22 is propagated in thewaveguide23. Here, by selectively applying voltages to thewaveguide electrode film23cand the opposingelectrode film24, the shape of the lateral face of thewaveguide23 on the side of thewaveguide electrode film23cis changed by theparticles26. By changing the shape of thewaveguide23, the state of propagation changes and the light that has been propagated in thewaveguide23 leaks outside from the waveguide lateral face of thewaveguide23. By setting the refractive index of theparticles26 to approximate the refractive index of the core23aor thecladding23b,it is possible to extract light to the outside from theparticles26. It is preferable that the refractive index of theparticles26 for example is substantially equivalent to the refractive index of the core23a.
• In this way, light leaks from the contacting portions of theparticles26 and thewaveguide electrode film23c,and therefore light can be extracted in the direction of theacrylic resin substrate25 such that thesubstrate25 can be made a display screen.
• On the other hand, when a voltage of 70V is applied to reverse the electric field, that is, such that thewaveguide electrode film23cbecomes positive and the opposingelectrode film24 becomes negative, theparticles26 move away from thewaveguide electrode film23c.For this reason, the light being propagated inside thewaveguide23 cannot be extracted as leaked light and is guided as it is within thewaveguide23, and therefore display is not conducted.
• In this way, since light is extracted from the lateral face of thewaveguide23 by bringingindividual particles26 into contact with thewaveguide electrode film23c,the contact surface area is small and it is not necessary to have contact within the entire surface such as with conventional flat shaped piezoelectric elements. For this reason, a very uniform small pressure can be applied to thewaveguide23 and, moreover, the pressure can be applied electrostatically to make control possible. It should be noted that in the above description chargedparticles26 were used, but instead of these it is also possible to use particles that are magnetic and to control contact and non-contact of theparticles26 to the surface of thewaveguide23 by controlling a magnetic field between the opposingelectrode film24 and thewaveguide electrode film23c.
• Furthermore,particles26 made of an acrylic resin containing rhodamine, which is a fluorochrome, may be used as theparticles26. In this case, the light extracted from the lateral face of thewaveguide23 when using a green LED that emits a 520 nm wavelength light as thelight source22 was observed to be an orange light with a wavelength of 580 nm. In this way, by selectively usingparticles26 that contain a fluorochrome or a fluorescent substance, and anLED light source22 that corresponds to the excitation wavelength of the fluorochrome or the fluorescent substance, it is possible to extract light, of various wavelengths. Furthermore, by using an ultraviolet light LED as thelight source22 and by using the fluorescent substances used in PDPs as theparticles26, it is possible to achieve display of RGB even when using a single color LED as thelight source22.
• The following is a description of adisplay device300 according toEmbodiment 3 with reference toFIG. 6.FIG. 6 is a perspective view showing a structure of thedisplay device300 according toEmbodiment 3. Thedisplay device300 can be configured by arranging a plurality of the above-describeddisplay elements21 in a row vertically with respect to the propagation direction of light in thewaveguide23. As shown inFIG. 6, with thedisplay device300 ofEmbodiment 3, thewaveguides23 of thedisplay elements21 are arranged in an array of n rows in the row direction (X direction) of the screen. It should be noted that n is a positive integer. Thelight sources22 are arranged respectively at end portions of thewaveguides23. At the lateral face of thewaveguide23, theelectrode films23cfor m lines are arranged in the line direction (Y direction), which is the direction in which waveguides23 extend. The opposingelectrode film24 for thedisplay elements21 is common and is arranged such that it covers all thewaveguides23 of thedisplay elements24. Furthermore, also thewaveguide electrode films23cof the same line are shared by therespective waveguides23 and cover the lines thereof. The number of pixels of thedisplay device300 is n×m pixels.
• With thedisplay device300 ofEmbodiment 3, theparticles26 are made to undergo contact or non-contact to thewaveguide electrode film23cby controlling, line by line, the voltages applied between thewaveguide electrode film23cand the opposingelectrode film24 such that light propagated in thewaveguide23 by total reflection is extracted from a lateral face of thewaveguide23 and emitted toward the opposingelectrode film24.
• Adisplay device300 configured in this way is capable of displaying a given image by controlling the application of voltages to the various chips for the 3-color LEDs for thewaveguides23 that extend in the row direction of the display plane (XY plane), based on the color and luminance information of the pixels on the lines for which extraction is selected with thewaveguide electrode film23cand the opposingelectrode film24.
• A block diagram showing a configuration of thedisplay device300 ofEmbodiment 3 is shown inFIG. 7.FIG. 7 illustrates a specific configuration for actually operating thedisplay device300. In addition to the above, thedisplay device300 is provided with a lightsource drive circuit60 for driving thelight sources22, aparticle drive circuit61 for making theparticles26 undergo contact or non-contact with thewaveguide electrode film23cby applying voltages to thewaveguide electrode film23cand the opposingelectrode film24, and acontrol circuit62 that synchronizes these circuits, inputs signals, and displays images. Thecontrol circuit62 inputs luminance information of the colors RGB of pixels in lines selected by theparticle drive circuit61 to the driver LSI of the lightsource drive circuit60, and the lightsource drive circuit60 inputs applied voltages corresponding to the luminance information to thelight sources22 to enable full color image display.
• Since 3-color LEDs are used as thelight sources22, it is possible to make light of three colors incident on a single waveguide33. This makes it possible to display light of three colors with asingle display element21, that is, with one line. With conventional display devices such as liquid crystal displays and PDPs, a pixel is configured by three sub-pixels of the three primary colors R, G, and B. However, with the display device using thewaveguide23 ofEmbodiment 3, it is not necessary to divide thewaveguides3 that extend in the row direction for each color and the three primary colors can be incident on asingle waveguide23. Therefore it is possible to reduce the number of waveguides23 (display elements21), thus providing the effect of reduced costs.
Embodiment 4
• The following is a description of adisplay element31 according toEmbodiment 4 of the present invention with reference toFIG. 8. Thedisplay element31 according toEmbodiment 4 is a structure in which acoating material37 that has a relatively large surface tension is applied on thewaveguide23 of thedisplay element21 according toEmbodiment 3, on the side on which thewaveguide electrode film23cis arranged. Specifically, the surface tension of thecoating material37 is preferably not less than 50 mN/m. Thecoating material37 covers the core23aand thewaveguide electrode film23csuch that thecoating material37 is a portion of the core, and the light propagated in thewaveguide23 is also totally reflected by the interface of thecoating material37 and the air. Since the same function is indicated for portions other than thecoating material37, the same numerical symbols will be used and their further description will be omitted.
• Thecoating material37 is a glycerin for example with a surface tension of 63.4 mN/m and is applied to have a thickness of approximately 2 μm. Furthermore, it is preferable that a material with a small surface tension is used for theparticles26. Specifically, the surface tension of theparticles26 is preferably not more than 30 mN/m.
• Adisplay element31 was actually formed using theparticles26 made of Teflon (registered trademark) with a surface tension of 18.4 mN/m, for example. The mean particle size of theparticles26 was set at 6 μm and the filling rate of theparticles26 in the space between thewaveguide electrode film23cand the opposingelectrode film24 was set at 20%. A voltage of 50V was applied so that thewaveguide electrode film23cof the selected line became negative and the opposingelectrode film24 became positive. In this way, theparticles26 came in contact with the surface of thewaveguide electrode film23cand the leaked light from the contact portion was extracted toward thesubstrate25. On the other hand, a voltage of 50V was applied to reverse the electric field, namely so that thewaveguide electrode film23cbecame positive and the opposingelectrode film24 became negative. In this way, since theparticles26 move away from the surface of thewaveguide electrode film23c,the light from thelight source22 propagated in thewaveguide23 cannot be extracted as leaked light. In this case, display and non-display can be switched by a small voltage in thedisplay element31 ofEmbodiment 4. This is because the surface tension of the glycerin, which is thecoating material37 is sufficiently larger than the surface tension of the Teflon (registered trademark) of theparticles26. In this way, the so called springiness at the contact surface between theparticles26 and thecoating material37 becomes greater. Springiness is a physical phenomenon in which springing occurs without thecoating material37 spreading against surface of theparticles26. That is, the greater the springiness between theparticles26 and thecoating material37, the greater the rebound at contact between theparticles26 and thewaveguide electrode film23c.For this reason, theparticles26 can be made to move away more easily from thewaveguide electrode film23c.Accordingly, contact and non-contact between theparticles26 and, thewaveguide electrode film23 can be controlled with a low voltage.
• In this way, by providing thecoating material37 with a different surface tension from theparticles26 on the surface of the core23aand thewaveguide electrode film23c,it is possible to reduce the voltage required to control contact of theparticles26. It should be noted that the surface tension of theparticles26 may be different from the surface tension of the surface of the waveguide23 (thewaveguide electrode film23c). However, generally the structure is such that the surface tension of theparticles26 is smaller than the surface tension of the surface of thewaveguide23.
• A display device can be configured in the same way as thedisplay device300 by arranging in a row a plurality of thedisplay elements31 shown inFIG. 8 vertical with respect to the propagation direction of light in thewaveguide23, such that the display surfaces21aare on the same side, as shown inFIG. 6. When n rows of thedisplay elements31 are arranged in the row direction of the screen and thewaveguide electrode film23cfor m lines are arranged in the direction (line direction) in which thewaveguides3 extend the number of pixels is n×m pixels.
• The method for achieving extraction of a desired light from the lateral face (display surface21a) of thewaveguide23 to carry out image display is the same as for thedisplay device300 ofEmbodiment 3, and therefore its explanation will be omitted. A point of difference between the display device ofEmbodiment 4 and the display device of Embodiment 5 is that thecoating material37 is arranged on a surface of thewaveguide23 and otherwise the structures are substantially the same.
• Furthermore, in order to actually operate the display device ofEmbodiment 4, as shown inFIG. 7, it is possible to provide a lightsource drive circuit60 for driving thelight sources22, aparticle drive circuit61 for making theparticles26 undergo contact or non-contact to thewaveguide electrode film23cby applying voltages to thewaveguide electrode film23cand the opposingelectrode film24, and acontrol circuit62 that synchronizes these circuits, inputs signals, and displays images.
• With the display devices ofEmbodiment 3 and 4, display of a given image was achieved by controlling the application of voltages to the various chips for the 3-color LEDs serving as thelight sources22 for thewaveguides23 that extend in the row direction of the display plane (XY plane), based on the color and luminance information of the pixels on the lines for which extraction is selected with thewaveguide electrode film23cand the opposingelectrode film24. However, the configuration of the type of light source and the positioning for example is not limited to these. For example, a structure is possible in which thewaveguide electrode film23cand the opposingelectrode film24 are arranged in an XY matrix corresponding to the number of pixels. In this case, each pixel may be driven by connecting an active element to thewaveguide electrode film23cand the opposingelectrode film24. A TFT or a TFD may be used as the active element for example.
• With the display element and the display device according toembodiments 3 and 4, the light extraction efficiency is improved by controlling contact of the particles in a display device making use of a technique in which light is guided from an end face of the waveguide and light is extracted from a surface of core of the waveguide, thus making it possible to achieve higher luminance with lower power consumption. Furthermore, the uniformity of display is improved. Withembodiments 3 and 4, it is possible to achieve sheet-shaped thin display devices regardless of the screen size even for large screens exceeding 100 inches and small screens for mobile applications.
• The present inventors produced a display device in which light is extracted from a waveguide with a structure that is the same as the conventional structure of the previously mentioned “Waveguide Panel Display Using Electromechanical Spatial Modulators,” X. Zhou, E. Gulari, SID98 Digest, 1998, pages 1,022 to 1,025. However, it was evident that luminance was low and brightness is increased as thickness is reduced in conventional structures in which the thickness of the waveguide is thicker than the pixel width (width of propagation direction of light).
• The reason for this is that the distance between locations of total reflection in the waveguide in which propagated light undergoes repetitive total reflection at the interface between the core and the air is dependent on the thickness of the waveguide. For example, for total reflection at a reflection angle of 45°, the distance between locations of total reflection is double the width of the waveguide. And for this reason the thickness of the waveguide must be not greater than ½ of the width of the pixels in the light propagation direction. If not, the distance between locations of total reflection becomes greater than the pixel width and the reflected light passes over the pixels such that extraction from the waveguide lateral face cannot be achieved.
• Accordingly, from the point of view of extraction efficiency, the thickness of the waveguide in the display element of embodiments 1 to 4 is preferably less than ½ of the pixel width and, moreover, in consideration of the angle distribution of the incident light, it is more preferably thinner still. It should be noted that, specifically, the pixel width is the length of theelectrodes4 and14 in the longitudinal direction of thewaveguide3 inFIGS. 1 and 2 for the display elements ofembodiments 1 and 2, and is the length in the longitudinal direction of thewaveguide electrode film23corwaveguide23 inFIGS. 5 and 6 forembodiments 3 and 4.
• For example, when the thickness of thewaveguide3 and23 is set at ¼ or less than the pixel width, then light with a reflection angle of 60° or less also becomes extractable. When light of an LED with high directivity is incident on such a waveguide, it is possible to extract almost all the incident light. On the other hand, when thewaveguides3 and23 are too thin, single mode is approached, at which the angles at which light can be propagated in thewaveguide3 and23 are limited. This reduces the amount of light that can be transmitted. Moreover, since it becomes difficult to introduce incident light when thewaveguide3 and23 are too thin, it is preferable that the thickness of thewaveguide3 and23 are at least 30 μm.
• It should be noted that a 3-color laser (RGB) for example may be used for thelight sources2 and22 of the display elements according to embodiments 1 to 4.
INDUSTRIAL APPLICABILITY
• A display element and a display device of the present invention can be used in sheet-shaped thin display devices regardless of the screen size even for large screens and small screens for mobile applications.

Claims (21)

1. A display element comprising a light source and a waveguide that comprises a deformable core and propagates a light emitted from the light source, wherein the light propagated in the waveguide is extracted to outside the display element from a waveguide lateral face,

the display element further comprising a plurality of actuators that deform a shape of the waveguide,

wherein the actuators are attached to the waveguide lateral face,

wherein the shape of the waveguide lateral face is changed by deformation of the actuators, and

wherein the actuators are operated selectively to deform a surface shape of at least a portion of the core on the waveguide lateral face to a concavo-convex shape, and the surface of the core deformed to the concavo-convex shape reflects the light propagated in the waveguide toward a direction that extracts the light out of the display element from the waveguide lateral face.

2. (canceled)

3. The display element according toclaim 1, wherein the waveguide comprises a cladding formed along one lateral face of the core,

wherein the actuators are attached to the cladding and the shape of the waveguide lateral face is changed by deforming the actuators.

4. (canceled)

5. (canceled)

6. The display element according toclaim 1, wherein the actuators comprise a piezoelectric element, and

wherein the shape of the waveguide lateral face is changed by deforming the piezoelectric element by applying a voltage to the piezoelectric element.

7. The display element according toclaim 1, wherein the actuators comprise: a first electrode film arranged at the waveguide lateral face,

a piezoelectric element layered on the first electrode film, and

a second electrode film layered on the piezoelectric element,

wherein the shape of the waveguide lateral face is changed by deforming the piezoelectric element by applying a voltage between the first electrode film arranged at the waveguide lateral face and the second electrode film layered on the piezoelectric element.

8. The display element according toclaim 1, wherein the actuators comprise a convex portion, and

wherein the shape of the waveguide lateral face is changed by applying pressure to the waveguide lateral face with the convex portion.

9. The display element according toclaim 1, wherein the actuators comprise: an electrode film arranged at the waveguide lateral face, and

an external electrode film that is in opposition to and adjacent to the waveguide,

wherein the shape of the waveguide lateral face is changed by an electrostatic force produced by applying a voltage between the external electrode film and the electrode film.

10. The display element according toclaim 9, wherein the external electrode film comprises a convex portion at the waveguide lateral face, and a shape of the waveguide lateral face is changed by the convex portion of the external electrode film applying pressure to the waveguide lateral face by using the electrostatic force.

11. (canceled)

12. The display element according toclaim 1, wherein at least a portion of the waveguide comprises an elastic material.

13. The display element according toclaim 1, wherein at least a portion of the waveguide comprises a transparent gel.

14. The display element according toclaim 1, wherein the actuators are formed for each of a plurality of pixels.

15-23. (canceled)

24. The display element according toclaim 1, wherein the light source is a 3-color LED or a 3-color laser.

25. A display device comprising:

the display element according toclaim 1,

a light source drive circuit for driving the light source,

an actuator drive circuit for driving the actuators, and

a control circuit that controls the light source drive circuit and the actuator drive circuit.

26. (canceled)

27. A display device comprising:

the display element according toclaim 14, and

an active matrix element that controls the respective actuators.

28. (canceled)

29. The display device according toclaim 27, wherein the active matrix element is a TFT or a TFD.

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