Light guide plate

Abstract

A single light guide plate enables clear display. [Solution] The light guide plate of the embodiment is a light guide plate that has a substantially rectangular shape in plan view, with a collection of reflective elements having reflective surfaces that reflect light incident from the end face in the direction of observation on the surface side formed on the back side, in which light of the three primary colors is incident from two adjacent sides, two of the three primary colors are incident from one of the two sides, and two colors of light, the remaining one of the three primary colors and one color common to the one side, are incident from the other side, the incident light of each of the three primary colors is substantially parallel in the plan view, the incident light of the common color is incident at a common angle of approximately 45 degrees with respect to the incident side in the plan view, the incident light of the other two colors of the common color is incident at a substantially right angle with respect to the incident side in the plan view, and each reflective element reflects only light of a specific color in the direction of observation on the surface side.

Description

Technical Field

[0001] The present invention relates to a light guide plate.

Background Art

[0002] Light emission display with a specific design by a light guide plate is a widely implemented technology. Usually, it only displays a fixed design by a single-color light source.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a method of displaying colors with a light guide plate, there is a method of stacking three light guide plates and individually emitting images decomposed into three colors of R (red), G (green), and B (blue), and overlapping them. However, in this method, due to the thickness of the light guide plate, the positions (heights) of the images to be displayed are different, so the images are shifted when viewed from an oblique direction. Also, using three light guide plates increases the cost. Patent Document 1 discloses that color display can be achieved by arranging reflection elements of a shape that allows light of different colors to be incident from three sides of a single light guide plate and reflects only the light from each direction. However, with the configuration of Patent Document 1, it is difficult to practically realize the shape of the reflection element that efficiently reflects only the light from one direction out of the incident lights from three directions.

[0005] Therefore, an object of the present invention is to enable clear display with a single light guide plate.

Means for Solving the Problems

[0006] (1) A light guide plate according to one aspect of the present invention is a light guide plate having a substantially rectangular shape in plan view, wherein a collection of reflective elements having reflective surfaces that reflect light incident from the end face in the direction of observation on the surface side is formed on the back side, wherein light of three primary colors is incident from two adjacent sides, two of the three primary colors are incident from one of the two sides, and two colors of light are incident from the other of the two sides, the remaining one of the three primary colors and one color common to the one side, the incident light of each of the three primary colors is substantially parallel in the plan view, the incident light of the common color is incident at a common angle of approximately 45 degrees with respect to the incident side in the plan view, the other two colors of the common color are incident at a substantially right angle with respect to the incident side in the plan view, and each reflective element reflects only light of a specific color in the direction of observation on the surface side.

[0007] (2) In the embodiment described in (1) above, the light guide plate has an upper and lower two-layer structure, and the two sides on the light-receiving side of either layer of the upper and lower two-layer structure have a stepped structure in plan view, and the incident light of the common one color is incident from the light-receiving surface that has the same angle in the stepped structure in plan view, and the incident light of the other two colors may be incident from each side of the light-receiving part that does not have the stepped structure in plan view.

[0008] (3) In the embodiment described in (1) or (2) above, the divergence angle of the incident light of each color may be ±20 degrees or less with respect to the principal optical axis of the incident light in the plan view.

[0009] (4) In any of the embodiments described in (1) to (3) above, a focusing lens may be provided between the light guide plate and the light source.

[0010] (5) In any of the embodiments described in (1) to (4) above, specular reflection treatment may be applied to the surfaces of the light guide plate that are along the two sides other than the incident side.

[0011] (6) A light guide plate according to one aspect of the present invention is a light guide plate having a substantially rectangular shape in plan view, wherein a collection of reflective elements having a reflective surface that reflects light incident from the end face in the direction of observation on the surface side is formed on the back side, wherein three types of light are incident from two adjacent sides, two of the three types of light are incident from one of the two sides, and two types of light are incident from the other of the two sides, the remaining one of the three types and one common to the one side, and each of the three types of incident light is substantially parallel in the plan view, the common one type of incident light is incident at a common incident angle of approximately 45 degrees with respect to the incident side in the plan view, and the other two types of incident light are incident at approximately right angles with respect to the incident side in the plan view, and each reflective element reflects only a specific type of light in the direction of observation on the surface side, and the emission of light from the three types of reflective elements is individually controlled by individually controlling the three types of incident light.

[0012] (7) In the embodiment described in (6) above, the light guide plate has an upper and lower two-layer structure, and the two sides on the light-receiving side of either layer of the upper and lower two-layer structure have a stepped structure in plan view, and the one common type of incident light is incident from the light-receiving surface that has the same angle in the stepped structure in plan view, and the other two types of incident light may be incident from each side of the light-receiving portion that does not have the stepped structure in plan view.

[0013] (8) In the embodiment described in (6) or (7) above, the divergence angle of each type of incident light may be ±20 degrees or less with respect to the principal optical axis of the incident light in the plan view.

[0014] (9) In any of the embodiments described in (6) to (8) above, a focusing lens may be provided between the light guide plate and the light source.

[0015] (10) In any of the embodiments described in (6) to (9) above, specular reflection treatment may be applied to the surfaces of the light guide plate that are along the two sides other than the incident side. [Effects of the Invention]

[0016] According to the light guide plate of this aspect, clear display can be achieved with a single light guide plate.

Brief Description of the Drawings

[0017] [Figure 1] Plan view of the display device of the first embodiment. [Figure 2] Side view of the light guide plate of the first embodiment. [Figure 3] Plan view of the first layer of the light guide plate. [Figure 4] Plan view of the second layer of the light guide plate. [Figure 5] Explanation diagram of the principle of each color emission. [Figure 6] Plan view of the display device of the second embodiment. [Figure 7] Plan view of the light guide plate of the third embodiment. [Figure 8] Explanation diagram of Shape Example 1 of the reflection element. [Figure 9] Explanation diagram of Shape Example 2 of the reflection element. [Figure 10] Explanation diagram of Shape Example 3 of the reflection element. [Figure 11] Explanation diagram of Shape Example 4 of the reflection element. [Figure 12] Explanation diagram of Shape Example 5 of the reflection element. [Figure 13] Explanation diagram of Shape Example 6 of the reflection element.

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described based on each drawing. An X-Y-Z coordinate system is described in each drawing as necessary. In this specification, each direction is defined and described along these coordinate systems. Note that the behavior of light rays in an actual light guide plate is three-dimensional including the Z-axis direction, and is more complicated than the description content in the plan view in this specification. However, regarding the basic principle of color display, the description by the plan view is sufficient, so it is expressed in that way. The drawings used in the following description may show the characteristic parts enlarged for convenience in order to make the characteristics easy to understand, and the dimensional ratios of each component are not necessarily the same as the actual ones.

[0019] <First Embodiment> Referring to Figures 1 to 4, the display device 100 comprises a light guide plate 1, light sources 3R, 3G, and 3B, and a focusing lens 4.

[0020] The light guide plate 1 has a collection of reflective elements 2 on its back side (-Z side), each having a reflective surface 2a that reflects light incident from the end faces (-Y side end face, +X side end face) in the front side observation direction (+Z direction). The light guide plate 1 is approximately rectangular in plan view (viewed from the Z direction). Note that the term "approximately rectangular" includes not only squares and rectangles, but also shapes in which at least a part of each side has an uneven shape, a stepped shape, a curved shape, etc.

[0021] In the light guide plate 1, light of the three primary colors (R, G, B) is incident from two adjacent sides (the -Y side and the +X side). From one of the two sides (the -Y side), light of two of the three primary colors (R, G) is incident. From the other side (the +X side), light of the remaining primary color (B) and one color common to the other side (R) is incident, for a total of two colors (R, B).

[0022] The incident light of each of the three primary colors is approximately parallel when viewed from a planar perspective. In this specification, approximately parallel light is defined as light with an incident angle distribution of ±20 degrees or less.

[0023] The incident light of the common color (R) is incident at a common angle of approximately 45 degrees to the incident side (the -Y side and the +X side) in a plan view. The incident light of the other two colors (G, B) of the common color is incident at approximately right angles to the incident side in a plan view. Each reflecting element 2 reflects only light of a specific color in the direction of observation towards the surface.

[0024] The light guide plate 1 has a two-layer structure, upper and lower. Two sides of either layer of the upper and lower layer have a stepped structure in plan view. The common single-color incident light (R) enters from the light-entering surface that has the same angle in the stepped structure in plan view. The other two colors of incident light (G, B) enter from the respective sides of the light-entering area that do not have a stepped structure in plan view.

[0025] The light guide plate 1 has a two-layer structure, consisting of two layers made of transparent material. The light guide plate 1 comprises a first layer 10 located on the +Z side and not containing the reflective element 2, and a second layer 20 located on the -Z side and containing the reflective element 2.

[0026] The reflective element 2 has a concave shape with a reflective surface 2a that reflects light incident from the end faces (-Y side end face, +X side end face) in the surface-side observation direction (+Z direction). The reflective element 2 is a notch (recess) formed on the -Z surface of the light guide plate 1. The reflective surface 2a is formed on the side of the reflective element 2 facing the light sources 3R, 3G, and 3B. Light R, G, B irradiated from the light sources 3R, 3G, and 3B enters the light guide plate 1 from the end faces and passes through the interior of the light guide plate 1. Furthermore, this light R, G, B is reflected by the reflective surface 2a of the reflective element 2 and emitted as reflected light on the +Z side in the display area 100A, where it is perceived by the observer.

[0027] For example, the light guide plate 1 is integrally formed by bonding the -Z plane of the first layer 10 and the +Z plane of the second layer 20 together. The light guide plate 1 may also be integrally molded using a mold. In the example shown in the figure, the light guide plate 1 has two layers, but an adhesive layer may be provided between the first layer 10 and the second layer 20 to increase the adhesion between these two layers. The second layer 20 does not have to be made of only one type of material; for example, it may be a structure consisting of two layers of different resin materials. In other words, the number of layers of the light guide plate 1 may be three or more. Even when the number of layers of the light guide plate 1 is two or three or more, the incident light propagates freely between the layers.

[0028] As shown in Figure 3, the light guide plate 1 has a two-layer structure, with the first layer 10 having a stepped structure in plan view on two sides 11 and 12 (the -Y side and the +X side) on the light-receiving side. The first layer 10 has a stepped structure that combines a flat surface, a first inclined surface, and a second inclined surface (light-receiving surface).

[0029] The first side 11 of the first layer 10 includes, as a step-like structure, a flat portion 11a along the XZ plane, a first inclined surface 11b inclined at an angle of approximately 45 degrees with respect to the XZ plane, and a second inclined surface 11c (light-receiving surface) that is approximately perpendicular to the first inclined surface 11b and inclined at an angle of approximately 45 degrees with respect to the XZ plane. The shape formed by combining the first inclined surface 11b and the second inclined surface 11c on the first side 11 of the first layer 10 is a triangular shape (V-shape) protruding to the -Y side. The multiple V-shapes protruding to the -Y side are formed in a step-like shape with equal intervals in a plan view. Note that the intervals do not necessarily have to be equal, and the intervals (sizes) may differ slightly in each step (the same applies to the explanation of equal intervals below).

[0030] The second side 12 of the first layer 10 includes, as a stepped structure, a flat portion 12a along the YZ plane, a first inclined surface 12b inclined at an angle of approximately 45 degrees with respect to the YZ plane, and a second inclined surface 12c (light-receiving surface) that is approximately perpendicular to the first inclined surface 12b and inclined at an angle of approximately 45 degrees with respect to the YZ plane. The shape formed by combining the first inclined surface 12b and the second inclined surface 12c on the second side 12 of the first layer 10 is a triangular shape (V-shape) protruding towards the +X side. Multiple V-shapes protruding towards the +X side are formed in a stepped shape with equal intervals when viewed from above.

[0031] Light sources 3R are provided on the second inclined surfaces 11c and 12c (light-receiving surfaces) of the first side 11 and the second side 12, respectively, via a condensing lens 4. The light sources 3R are arranged at equal intervals along each side 11 and 12 (when viewed from the direction normal to the second inclined surfaces 11c and 11c). LEDs (Light Emitting Diodes) or the like can be used as the light sources 3R.

[0032] In the example shown in the figure, a chip-shaped monochromatic LED emitting red light (R) is provided as the light source 3R. In the example shown in the figure, red light (R) is incident on each of the first side 11 and the second side 12 from the second inclined surfaces 11c and 12c (light-receiving surfaces) at the same incident angle αR (approximately 45 degrees with respect to the XZ and YZ planes) in the -X and +Y directions, and is approximately parallel to the light source.

[0033] As shown in Figure 4, the light guide plate 1 has a two-layer structure, with the second layer 20 having light-receiving sections on two sides 21 and 22 (the -Y side and the +X side) that do not have a stepped structure in plan view. In other words, the second layer 20 has the same structure as a normal light guide plate in plan view.

[0034] The first edge 21 of the second layer 20 is planar along the XZ plane. The second edge 22 of the second layer 20 is planar along the YZ plane. Light sources 3G and 3B are provided on the respective planes (light-receiving surfaces) of the first edge 21 and second edge 22 of the second layer 20 via a condensing lens 4. The light sources 3G and 3B are arranged at equal intervals along each edge 21 and 22 (when viewed from the Y or X direction). LEDs or the like can be used as light sources 3G and 3B.

[0035] In the example shown in the figure, a chip-shaped monochromatic LED emitting green light (G) is provided on the first side 21, and a chip-shaped monochromatic LED emitting blue light (B) is provided on the second side 22, as light sources 3G and 3B. In the example shown in the figure, at the first side 21, green light (G) is incident from the light-receiving surface at an incidence angle αG (approximately 90 degrees with respect to the XZ plane) in the +Y direction and is approximately parallel to the XZ plane. On the other hand, at the second side 22, blue light (B) is incident from the light-receiving surface at an incidence angle αB (0 degrees with respect to the XZ plane, i.e., parallel to the XZ plane) in the -X direction and is approximately parallel to the XZ plane.

[0036] The display area 100A of the light guide plate 1 has numerous dot-like, fine concave reflective elements 2, each having a reflective surface 2a that reflects light incident from the end face in the direction of observation towards the surface. In the display area 100A, a specific design is displayed when the light sources 3R, 3G, and 3B are illuminated. The angle and shape of the reflective surface 2a of the reflective elements 2 are set so that light of a specific color is reflected in the direction of observation towards the surface. In other words, the angle and shape of the reflective surface 2a of the reflective elements 2 are set so that light other than light of a specific color is not reflected in the direction of observation towards the surface.

[0037] If the reflective surface 2a is a plane, by setting it to an angle that is directly opposite to the light of the set color in a planar view, other colors of light incident at angles 45 or 90 degrees different will not be reflected, or will be reflected in a direction other than the surface observation direction, so that only the set color is observed by the observer. By arranging reflective elements 2 corresponding to each color in a predetermined area with appropriate size and density, it is possible to adjust the emission intensity of each color and make that area emit light of any desired color.

[0038] Figure 5 is used to explain the principle of emission of each color. In Figure 5, the R, G, and B arrows indicate the direction of light entry for each color. The rectangles within the dashed lines of areas A, B, and C, representing the RGB color borders, indicate the reflective elements 2R, 2G, and 2B that receive light of each color and reflect that light in the forward direction (+Z direction). The reflective elements 2R, 2G, and 2B of each color either do not reflect colors other than their corresponding color, or they reflect light in an oblique direction other than forward, so they do not emit light in the forward direction.

[0039] In area A, the reflective elements 2R, 2G, and 2B of each color are evenly distributed, so it emits white light in the forward direction. In area B, the dimensions (size) of reflective element 2G are smaller than those of the other reflective elements 2R and 2B, resulting in weaker green emission and a strong purple-tinged white emission. In area C, the density of reflective element 2 of G is smaller than that of the other reflective elements 2R and 2B. Therefore, similar to area B, the green emission is weaker, and it emits a white light with a strong purple tint. Basically, the emission color of a given area can be controlled by adjusting the size or density of the reflective elements 2R, 2G, and 2B present in that area. It should be noted that this explanation assumes that the intensity of the three primary colors of light incident on each area is equal, that each area is sufficiently far from the observation position, that individual reflective elements are not perceived, and that each area is perceived as a single unit with average brightness and color.

[0040] The above explanation assumed that the reflective surface 2a of reflective element 2 is a plane and that the incident light is parallel to the plane in view. However, if this were actually the case, the direction of reflection of the light reflected by the reflective surface 2a of reflective element 2 would be limited. In this case, the field of view in which the luminescent design can be observed in the intended color would also be limited to an extremely narrow range, which is undesirable. Conversely, if the reflective surface 2a of reflective element 2 is curved and its curvature is too large, or if the divergence angles θR, θG, and θB of the incident light are too large, unwanted colors will be mixed into the light reflected in the observation direction by the reflective surface 2a of reflective element 2. In this case, there is a high possibility that the resulting color will differ from the design, which is undesirable. For the designed color to be observed within a reasonably wide field of view, the shape of the reflective surface 2a and the setting of the angle distribution of the incident light are crucial.

[0041] In this embodiment, the difference in the angle of incidence of the principal optical axes of R, G, and B in a plan view is 45 degrees or 90 degrees (in the example shown in the figure, the difference in the angle of incidence of the principal optical axes of G and B in a plan view is 90 degrees). If the distribution of the angle of incidence is ±22.5 degrees or more, then when the difference in the angle of incidence is 45 degrees, there will be different colored light components with the same angle of incidence, making it impossible to independently design the emission intensity of each color, which is undesirable.

[0042] Since it is not possible to completely control the angle of entry of LED light with lenses or the like, it is desirable to effectively limit the distribution of entry angles to ±20 degrees or less. In this embodiment, the divergence angles θR, θG, and θB of the incident light of each color are ±20 degrees or less with respect to the principal optical axis of the incident light in a plan view. In other words, the distribution of entry angles for each color is limited to ±20 degrees or less. The beam angle of an LED light is defined as twice the angle at which the brightness decreases from the center (central axis) to half (the sum of the values ​​for both the left and right sides). For example, if the beam angle is ±20 degrees, it does not mean that there is absolutely no light at angles exceeding that (e.g., +30 degrees).

[0043] The closer the incoming light angle distribution is to parallel light (closer to 0 degrees) at 20 degrees or less, the easier it is to separate each color, resulting in clearer color reproduction. However, as mentioned above, this has the drawback of narrowing the field of view, so an incoming light angle distribution of around ±10 degrees is most practical.

[0044] For example, an LED without a lens typically has a beam angle of about 120 degrees. When this light enters a light guide plate, the beam angle of the incident light within the plate becomes about ±40 degrees. Therefore, in order to reduce the distribution of the incident light angle to ±20 degrees or less, it is necessary to place a focusing lens between the LED and the light guide plate.

[0045] In this embodiment, a condensing lens 4 is provided between the light guide plate 1 and the light sources 3R, 3G, and 3B. Multiple condensing lenses 4 are provided corresponding to the light sources 3R, 3G, and 3B (the same number as the light sources 3R, 3G, and 3B). In the example shown in the figure, there are a total of 12 condensing lenses 4 on the two light-receiving sides 11 and 12 of the first layer 10, and a total of 18 condensing lenses 4 on the two light-receiving sides 21 and 22 of the second layer 20. The number of condensing lenses 4 is not limited to the above and can be changed according to the design specifications. The number of light sources 3R, 3G, and 3B can also be changed according to the design specifications, similar to the number of condensing lenses 4 shown.

[0046] In this embodiment, the surfaces of the light guide plate 1 along the two sides (the +Y side and the -X side) that are not the incident side are treated with specular reflection. For example, the surfaces along the two sides 13 and 14 of the first layer 10 opposite to the light-receiving side, and the surfaces along the two sides 23 and 24 of the second layer 20 opposite to the light-receiving side are treated with specular reflection by vapor deposition or reflective film application. Alternatively, a mirror plate may be installed externally at a position close to the two sides 23 and 24.

[0047] <Effects and Effects> As described above, the light guide plate 1 of this embodiment is a light guide plate that has a substantially rectangular shape in plan view, with a collection of reflective elements 2 having a reflective surface 2a that reflects light incident from the end face in the direction of observation on the surface side formed on the back side. In the light guide plate 1, light of the three primary colors is incident from two adjacent sides, two of the three primary colors are incident from one of the two sides, and two colors of light are incident from the other of the two sides, the remaining one of the three primary colors and one color common to the other side. The incident light of each of the three primary colors is substantially parallel in plan view, the incident light of the common color is incident at a common angle of incidence of approximately 45 degrees with respect to the incident side in plan view, and the incident light of the other two colors of the common color is incident at a substantially right angle with respect to the incident side in plan view, and each reflective element 2 reflects only the light of a specific color in the direction of observation on the surface side. This configuration makes it possible to display clear color with a single light guide plate 1.

[0048] Conventionally, one method for displaying color using light guide plates involves stacking three light guide plates and individually emitting light from images separated into the three primary colors R (red), G (green), and B (blue), then stacking these images. However, in this method, the position (height) of the displayed images differs due to the thickness of the light guide plates, resulting in image misalignment when viewed from an oblique angle (Problem 1). Furthermore, the use of three light guide plates increases costs (Problem 2). Patent Document 1 (Japanese Patent No. 6394765) discloses a method for achieving color display using a single light guide plate, where light of different colors is incident from three sides, and reflective elements are arranged to reflect only the light from each respective direction. However, in the configuration of Patent Document 1, it is practically difficult to realize a shape for reflective elements that efficiently reflects only the light from one of the three incident directions (Problem 3). In contrast, the light guide plate 1 of this embodiment, being a single light guide plate 1, avoids the problem of image distortion when viewed from an oblique direction. Furthermore, it is possible to reduce costs compared to using multiple light guide plates. Moreover, since two colors are incident from each of the two sides on the light-receiving side, the shape of the reflective element 2 can be practically realized. Thus, the light guide plate 1 of this embodiment can solve all of the above problems 1 to 3.

[0049] In this embodiment, the light guide plate 1 has a two-layer structure, and the two light-receiving sides of either layer of the two-layer structure have a stepped structure in plan view. The incident light of one common color enters from the light-receiving surface that has the same angle in the stepped structure in plan view, while the incident light of the other two colors enters from each side of the light-receiving area that does not have a stepped structure in plan view. With this configuration, the stepped structure allows two colors to be incident simultaneously from each of the two sides on the light-receiving side, thus enabling clear color display with a single light guide plate 1.

[0050] In this embodiment, the divergence angles θR, θG, and θB of the incident light of each color are ±20 degrees or less with respect to the principal optical axis of the incident light in a plan view. With this configuration, compared to cases where the light angle distribution exceeds ±20 degrees, the separation of each color becomes easier, enabling clearer color reproduction.

[0051] In this embodiment, a focusing lens 4 is provided between the light guide plate 1 and the light sources 3R, 3G, and 3B. With this configuration, the angle of incidence of light from light sources 3R, 3G, and 3B can be adjusted with the focusing lens 4, making it easy to create nearly parallel light.

[0052] In this embodiment, the two sides of the light guide plate 1 that are not the incident side are treated with specular reflection. In this configuration, light reflected from the two sides that are not the incident side strikes the reflective surface 2a of reflective element 2 from the opposite direction to the light coming from the incident side. In addition, by having the reflective surface 2a of reflective element 2 installed on both the front and back sides, the effects of suppressing color changes due to changes in viewpoint and improving brightness can be obtained.

[0053] <Second Embodiment> Next, a second embodiment will be described. In the first embodiment described above, an example was described in which the light guide plate 1 has a two-layer structure (specifically, in an example in which two sides on the light-receiving side of one of the two layers of the two-layer structure have a stepped structure in plan view, and incident light of one common color enters from the light-receiving surface that has the same angle in the stepped structure in plan view, while incident light of the other two colors enters from each side of the light-receiving part that does not have a stepped structure in plan view). In contrast, the second embodiment differs from the first embodiment in that the light guide plate does not have a two-layer structure. This second embodiment will be described with reference to Figure 6.

[0054] Figure 6 is a plan view of the display device 200 according to the second embodiment. In the components of the light guide plate 201 of the second embodiment, components that are identical in appearance to those of the first embodiment are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0055] The light guide plate 201 of the second embodiment has a single-layer structure, and the light incident from the two sides on the light-receiving side and its configuration are the same as in the first embodiment (except for the arrangement of light sources 203G and 203B). The light guide plate 201 intermittently provides a stepped structure in plan view, enabling both colors to be incident simultaneously from each of the two sides on the light-receiving side. This enables color display in the display area 200A, similar to that of the first embodiment.

[0056] In the example shown in the figure, the light guide plate 201 has a stepped structure intermittently provided in plan view on two sides 211 and 212 (the -Y side and the +X side) on the light-receiving side. The light guide plate 201 has a stepped structure that combines a flat surface, a first inclined surface, and a second inclined surface (light-receiving surface).

[0057] The first side 211 of the light guide plate 201 has a stepped structure and includes a flat portion 211a along the XZ plane, a first inclined surface 211b inclined at an angle of approximately 45 degrees with respect to the XZ plane, and a second inclined surface 211c (light-receiving surface) that is approximately perpendicular to the first inclined surface 211b and inclined at an angle of approximately 45 degrees with respect to the XZ plane. In the first side 211, the combined shape of the first inclined surface 211b and the second inclined surface 211c forms a triangular shape (V-shape) protruding to the -Y side. Multiple V-shapes protruding to the -Y side are arranged at equal intervals in a plan view. In the first side 211 of the second embodiment, the flat portion 211a is interposed between two adjacent V-shapes in the X direction or next to a V-shape, thereby forming an intermittent stepped shape.

[0058] The second side 212 of the light guide plate 201 has a stepped structure and includes a flat portion 212a along the YZ plane, a first inclined surface 212b inclined at an angle of approximately 45 degrees with respect to the YZ plane, and a second inclined surface 212c (light-receiving surface) that is approximately perpendicular to the first inclined surface 212b and inclined at an angle of approximately 45 degrees with respect to the YZ plane. In the second side 212, the combined shape of the first inclined surface 212b and the second inclined surface 212c forms a triangular shape (V-shape) protruding towards the +X side. Multiple V-shapes protruding towards the +X side are arranged at equal intervals in a plan view. In the second embodiment, the second side 212 is formed in an intermittent stepped shape by interposing the flat portion 212a between two adjacent V-shapes in the Y direction or next to a V-shape.

[0059] Light sources 203R are provided on the second inclined surfaces 211c and 212c (light-receiving surfaces) of the first and second sides 211 and 212 of the light guide plate 201, respectively. The light sources 203R are arranged at equal intervals on each side (when viewed from the direction normal to the second inclined surfaces 211c and 212c). As the light sources 203R, bullet-shaped LEDs or the like can be used to make the incident light approximately parallel. Alternatively, as in the first embodiment, a combination of an LED and a focusing lens 4 may be used.

[0060] In the example shown in the figure, a bullet-shaped monochromatic LED emitting red light (R) is provided as a light source 203R on each of the second inclined surfaces 211c and 212c (light-receiving surfaces). In the example shown in the figure, red light (R) is incident on each of the first side 211 and second side 212 from the second inclined surfaces 211c and 212c (light-receiving surfaces) at the same incident angle (approximately 45 degrees with respect to the XZ and YZ planes) in the -X and +Y directions, and is approximately parallel to the surface.

[0061] Light sources 203B and 203G are provided on the adjacent V-shaped planar portions 211a and 212a (light-receiving surfaces) of the first and second sides 211 and 212 of the light guide plate 201, respectively. The light sources 203B and 203G are arranged at equal intervals along each side 211 and 212 (when viewed from the Y or X direction). As light sources 203B and 203G, bullet-shaped LEDs or the like can be used to make the incident light approximately parallel. Alternatively, as in the first embodiment, a combination of an LED and a focusing lens 4 may be used.

[0062] In the example shown in the figure, a bullet-shaped monochromatic LED emitting blue light (B) is provided on the first side 211, and a bullet-shaped monochromatic LED emitting green light (G) is provided on the second side 212, as light sources 203B and 203G. In the example shown in the figure, blue light (B) is incident from the planar portion 211a (light-receiving surface) on the first side 211, with an incidence angle of 90 degrees in the +Y direction (approximately 90 degrees with respect to the XZ plane) and becoming approximately parallel light. On the other hand, green light (G) is incident from the planar portion 212a (light-receiving surface) on the second side 212, with an incidence angle of 0 degrees in the -X direction (parallel to the XZ plane) and becoming approximately parallel light.

[0063] In the second embodiment as well, specular reflection treatment may be applied to the surfaces of the light guide plate 201 along the two sides 213 and 214 (the +Y side and the -X side) that are not the incident side. For example, specular reflection treatment may be applied to the surfaces of the light guide plate 201 along the two sides 213 and 214 that are opposite to the light-receiving side by vapor deposition or reflective film application.

[0064] As described above, the light guide plate 201 of the second embodiment has a single-layer structure and has a stepped structure that is intermittently provided in a plan view on the two sides on the light-receiving side (the -Y side and the +X side). With this configuration, the light guide plate 201 does not have a two-layer structure, making it easier to manufacture.

[0065] <Third Embodiment> Next, a third embodiment will be described. In the above-described embodiment, an example was given in which the light guide plate has a stepped structure in plan view. In contrast, the third embodiment differs from the above embodiment in that the light guide plate 301 does not have a stepped structure in plan view. This third embodiment will be described with reference to Figure 7.

[0066] Figure 7 is a plan view of the light guide plate 301 of the third embodiment. In the components of the light guide plate 301 of the third embodiment, components that are the same as those in the above-described embodiments are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0067] The light guide plate 301 of the third embodiment has a two-layer structure, including a rectangular first layer 310 in plan view, and a second layer 320 having an incident side 321 at a 45-degree angle to two adjacent sides 311 and 312 of the first layer 310. This makes it possible to simultaneously incident two colors from each of the two light-receiving sides 311 and 312, enabling color display in the display area 300A similar to that of the above-described embodiment.

[0068] In the example shown in the figure, red light (R) is incident from the incident edge 321 (light-receiving surface) of the second layer 320, with the same incident angle (approximately 45 degrees with respect to the XZ and YZ planes) in both the -X and +Y directions, and is approximately parallel to the light. Blue light (B) is incident from the first edge 311 (light-receiving surface) of the first layer 310, with an incident angle of 90 degrees (approximately 90 degrees with respect to the XZ plane) in the +Y direction, and is approximately parallel to the light. Green light (G) is incident from the second edge 312 (light-receiving surface) of the first layer 310, with an incident angle of 0 degrees (parallel to the XZ plane) in the -X direction, and is approximately parallel to the light.

[0069] As described above, the light guide plate 301 of the third embodiment has a two-layer structure, comprising a first layer 310 which is rectangular in plan view, and a second layer 320 which has an incident side 321 at a 45-degree angle to two adjacent sides 311 and 312 of the first layer 310. This configuration eliminates the need for a stepped structure in plan view, thus simplifying the fabrication of the light guide plate 301.

[0070] <Variation> Next, a modified example of the embodiment will be described. For example, the display area of ​​the light guide plate is not limited to displaying color; it may also display monochrome. The display mode in the display area of ​​the light guide plate can be changed according to the design specifications.

[0071] For example, regarding the incidence direction of the three primary colors, it is not limited to G (green light) and B (blue light) being incident transversely or downward (incident in the -X direction or +Y direction in the above embodiment), and R (red light) being incident obliquely on two common sides (incident in the -X and +Y directions in the above embodiment), but other combinations are also possible. For example, another combination is possible where R (red light) is incident downward, G (green light) is incident transversely, and B (blue light) is incident obliquely. Furthermore, other combinations of the incidence directions of the three primary colors described above may be adopted. The manner in which the three primary colors are incident can be changed according to the design specifications.

[0072] Next, we will describe examples of reflective element shapes. Figure 8 is an explanatory diagram of example 1 of the shape of the reflective element. Figure 9 is an explanatory diagram of example 2 of the shape of the reflective element. In the components of the reflective element in each example, components that are the same as those in the embodiments described above are denoted by the same reference numerals, and their detailed descriptions are omitted. As shown in Figures 8 and 9, the shape of the reflective element may be a triangular cross-section. For example, as shown in Figure 8, the reflective element may be formed in the shape of a triangular prism and have reflective surfaces 2a on the two sides that form the vertices of the triangle. As shown in Figure 9, the reflective element may be triangular when viewed from a first direction (front view) and include a curved shape when viewed from a direction perpendicular to the first direction (plan view and side view), and may have reflective surfaces 2a on the surfaces including the curved shape.

[0073] For example, if incident light strikes a rectangular light guide plate at a 45-degree angle, and the incident light reaches the opposite end face without hitting the light-emitting area or the reflective element, then if the light guide plate material is a common acrylic or polycarbonate, the critical angle is exceeded, resulting in total internal reflection. The light that has undergone total internal reflection twice at the end face reaches the light-emitting area again at an angle directly opposite to that of the incident light. Therefore, considering the reflectivity, it is desirable for the reflective surface of the reflective element to have reflective surfaces in two directions: one on the side facing the incoming light and another on the side facing the opposite direction of the incoming light. Thus, a reflective element with a triangular cross-section, as shown in Figures 8 and 9, is desirable. Furthermore, if the incident angle is 0 or 90 degrees instead of 45 degrees, the reflected light at the end face will not be strong, but it is possible to increase the amount of reflected light by applying a reflective treatment to the end face or by installing a reflector externally. For this reason, a reflective element with a triangular cross-section, as shown in Figures 8 and 9, is desirable.

[0074] Figure 10 is an explanatory diagram of example 3 of the shape of the reflective element. Figure 11 is an explanatory diagram of example 4 of the shape of the reflective element. Figure 12 is an explanatory diagram of example 5 of the shape of the reflective element. Figure 13 is an explanatory diagram of example 6 of the shape of the reflective element. In the components of the reflective element in each example, components that are the same as those in the embodiments described above are denoted by the same reference numerals, and their detailed descriptions are omitted. As shown in Figures 10 to 13, the shape of the reflective element may be other than a triangular cross-section (for example, a trapezoidal cross-section or a semicircular cross-section). For example, as shown in Figure 10, the reflective element may be trapezoidal when viewed from a first direction (front view), rectangular when viewed from a direction perpendicular to the first direction (plan view and side view), and have a reflective surface 2a on the hypotenuse of the trapezoid. As shown in Figure 11, the reflective element may be trapezoidal when viewed from a first direction (front view), and include a curved shape when viewed from a direction perpendicular to the first direction (plan view and side view), and may have a reflective surface 2a on the surface including the curved shape. As shown in Figure 12, the reflective element may be formed in a semi-cylindrical shape, and may have a reflective surface 2a on the surface forming a semicircle. As shown in Figure 13, the reflective element may be semicircular when viewed from a first direction (front view), and include a curved shape when viewed from a direction perpendicular to the first direction (plan view and side view), and may have a reflective surface 2a on the surface including the curved shape. Furthermore, the shape of the reflective element is not limited to the above and can be changed according to the design specifications.

[0075] The above explanation pertains to color displays, but the present invention is not limited thereto. Color displays are obtained by simultaneously and independently emitting three different images of R, G, and B, which are separated into three colors. However, by using the technology of the present invention, it is also possible to independently emit three completely different types of images. In other words, it is possible to obtain three switching images by individually lighting up three different types of images. In this case, the incoming light color does not need to be limited to a specific color.

[0076] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and additions, omissions, substitutions, and other modifications of the configuration are possible without departing from the spirit of the invention, and the above-described modifications can be combined as appropriate. [Explanation of Symbols]

[0077] 1…Light guide plate, 2,2R,2G,2B…Reflective element, 2a…Reflective surface, 3R,3G,3B…Light source, 4…Concentrating lens, 10…First layer, 11,12…Incident side, 11c,12c…Light-receiving surface, 13,14…Side not on the incident side, 20…Second layer, 21,22…Incident side, 23,24…Side not on the incident side, 201…Light guide plate, 203R,203G,203B…Light source, 211,212…Incident side, 211c,212c…Light-receiving surface, 213,214…Side not on the incident side, 301…Light guide plate, 310…First layer, 311,312…Incident side, 320…Second layer, 321…Incident side, αR,αG,αB…Angle of incidence, θR,θG,θB…Broadening angle

Claims

1. In a light guide plate having a roughly rectangular shape in plan view, a collection of reflective elements having reflective surfaces that reflect light incident from the end face in the direction of observation towards the front surface is formed on the back side, Light of the three primary colors is incident from two adjacent sides, Light from two of the three primary colors enters from one of the two aforementioned sides. From the other of the two sides, light of two colors is incident: the remaining color from the three primary colors and one color common to the other side. The incident light of each of the three primary colors is approximately parallel in the plan view. The aforementioned common single-color incident light is incident at a common angle of incidence of approximately 45 degrees with respect to the incident side in the plan view. The two other incident light colors, which are the same as the one common color, are incident at approximately a right angle to the side from which the light is incident in the plan view. Each reflective element is characterized by reflecting only light of a specific color in the direction of observation on the surface side. light guide plate.

2. The light guide plate has a two-layer structure, upper and lower. The two light-receiving sides of either of the two layers of the aforementioned upper and lower structure have a stepped structure in plan view. The aforementioned common single-color incident light enters from light-receiving surfaces that have the same angle in the stepped structure when viewed from above. The other two colors of incident light are characterized in that they are incident from each side of the light-receiving portion that does not have the stepped structure in a plan view. The light guide plate according to claim 1.

3. The divergence angle of the incident light of each color is characterized in that, in the plan view, it is ±20 degrees or less with respect to the principal optical axis of the incident light. The light guide plate according to claim 1 or 2.

4. A focusing lens is provided between the light guide plate and the light source, characterized in that The light guide plate according to claim 1 or 2.

5. The light guide plate is characterized in that a specular reflection treatment is applied to the surfaces along the two sides other than the incident side. The light guide plate according to claim 1 or 2.

6. In a light guide plate having a roughly rectangular shape in plan view, a collection of reflective elements having reflective surfaces that reflect light incident from the end face in the direction of observation towards the front surface is formed on the back side, Three types of light enter from two adjacent sides, Two of the three types of light are incident on one of the two sides. From the other of the two sides, a total of two types of light are incident: the remaining one of the three types and one type common to the other side. Each of the three types of incident light is substantially parallel in the plan view. The aforementioned common type of incident light is incident at a common incident angle of approximately 45 degrees with respect to the incident side in the plan view. The two other types of incident light, which are the one common type, are incident at approximately right angles to the incident side in the plan view. Each reflective element reflects only a specific type of light in the direction of observation on the surface side. This method is characterized by individually controlling the emission of light from three types of reflective elements by individually controlling three types of incident light. light guide plate.

7. The light guide plate has a two-layer structure, upper and lower. The two light-receiving sides of either of the two layers of the aforementioned upper and lower structure have a stepped structure in plan view. The aforementioned common type of incident light enters from the light-receiving surface that has the same angle in the stepped structure when viewed from above. The other two types of incident light are characterized in that they are incident from each side of the light-receiving portion that does not have a stepped structure in a plan view. The light guide plate according to claim 6.

8. The divergence angle of each type of incident light is characterized in that, in a plan view, it is ±20 degrees or less with respect to the principal optical axis of the incident light. The light guide plate according to claim 6 or 7.

9. A focusing lens is provided between the light guide plate and the light source, characterized in that The light guide plate according to claim 6 or 7.

10. The light guide plate is characterized in that a specular reflection treatment is applied to the surfaces along the two sides other than the incident side. The light guide plate according to claim 6 or 7.

Images