Backlight and display device

Abstract

To eliminate unevenness of luminance.SOLUTION: A backlight 12 includes: a light guide plate 16 in which a thickness is larger on a second end surface 24 than on a first end surface 22; a laser 28 which may emit a laser beam toward the first end surface 22 of the light guide plate 16; and a reflection plate 26 facing the second end surface 24. The laser beam entering the first end surface 22 is reflected on a surface 18, a rear surface 20, and the reflection plate 26 to be propagated into the light guide plate 16 and emitted from the surface 18. The surface 18 has a plurality of protruding or recessed line parts 32 in an area where the laser beam is reflected. The plurality of line parts 32 extend in a first direction D1 in a direction between the first end surface 22 and the second end surface 24 and are located adjacent to each other in a second direction D2 orthogonal to the first direction D1. The line part 32 includes a curved surface formed by translating a straight line L parallel to an axis A extending in the first direction D1 around the axis A. Tips in the first direction D1 of the adjacent line parts 32 are not aligned.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a backlight and a display device. [Background technology]

[0002] When a laser is used as the light source for an edge-lit backlight, the light has high directivity, so it cannot be reflected upwards at positions close to the light source, and the surface-emitting area becomes distant from the light source. Therefore, two light guide plates are used, with lasers placed on opposite sides of each other (Patent Document 1). Alternatively, in a backlight that uses a wedge-shaped light guide plate with different thicknesses on both ends and an inclined bottom surface, light that enters from one end surface is reflected by the other end surface, and the returning light is reflected by the bottom surface and travels upwards. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-238484 A Summary of the Invention [Problem to be solved by the invention]

[0004] Backlights can cause stripes (stripe-like uneven brightness) along the light's direction of travel due to the high directivity of light. To prevent uneven brightness, it is desirable to prevent other types of uneven brightness from occurring.

[0005] An object of the present invention is to eliminate uneven luminance. [Means for solving the problem]

[0006] The backlight includes a light guide plate including a front surface and a back surface, a first end surface connecting one end of the front surface and one end of the back surface, and a second end surface connecting the other end of the front surface and the other end of the back surface, the thickness between the front surface and the back surface being greater at the second end surface than at the first end surface, and the back surface being inclined with respect to the front surface, a laser capable of emitting laser light toward the first end surface of the light guide plate, and a reflector facing the second end surface, and the laser light incident on the first end surface is reflected by the front surface, the back surface, and the second end surface. the laser light is reflected by the reflector, propagates inside the light guide plate, and exits from the surface, the surface has a plurality of convex or concave line portions in an area where the laser light is reflected, the plurality of line portions extend in a first direction which is a direction between the first end face and the second end face, and are adjacent to each other in a second direction perpendicular to the first direction, each of the plurality of line portions includes a curved surface formed by translating a straight line parallel to an axis extending in the first direction around the axis, and the tips of adjacent line portions in the first direction are not aligned.

[0007] The backlight includes a light guide plate having a front surface and a back surface, a first end surface connecting one end of the front surface and one end of the back surface, and a second end surface connecting the other end of the front surface and the other end of the back surface, the thickness between the front surface and the back surface being greater at the second end surface than at the first end surface, and the back surface being inclined with respect to the front surface, a laser capable of emitting laser light toward the first end surface of the light guide plate, and a reflector facing the second end surface, and the laser light incident on the first end surface is reflected by the front surface, the back surface, and the first end surface of the light guide plate. the laser light is reflected by the first end face and the second end face, propagates inside the light guide plate, and exits from the surface, the surface having a plurality of convex or concave line portions in an area where the laser light is reflected, the plurality of line portions extending in a first direction which is a direction between the first end face and the second end face and adjacent to each other in a second direction perpendicular to the first direction, each of the plurality of line portions including a curved surface formed by translating a straight line parallel to an axis extending in the first direction around the axis, and each end of the plurality of line portions is tapered.

[0008] The display device includes a backlight and a display panel disposed so as to face the surface of the light guide plate. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of a display device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the display device shown in FIG. [Diagram 3] FIG. 3 is a plan view of the backlight shown in FIG. [Figure 4] 4 is a cross-sectional view of the light guide plate taken along line IV-IV in FIG. [Diagram 5] FIG. 1 is a plan view of a backlight according to a related art. [Figure 6] FIG. 13 is a plan view of a backlight according to another related art. [Figure 7] 4 is a cross-sectional view of a light guide plate according to a first modified example of the first embodiment. FIG. [Figure 8] FIG. 11 is a plan view of a backlight according to Modification 2 of the first embodiment. [Figure 9] FIG. 11 is a plan view of a backlight according to a second embodiment. [Figure 10] 10 is a cross-sectional view of the light guide plate shown in FIG. 9 taken along line XX. [Figure 11] FIG. 11 is a cross-sectional view of a light guide plate according to a first modified example of the second embodiment. [Figure 12] FIG. 13 is a cross-sectional view of a light guide plate according to Modification 2 of the second embodiment. [Figure 13] FIG. 13 is a perspective view of the line portion shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and the present invention should not be construed as being limited to the description of the embodiment exemplified below.

[0011] In order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, elements having the same functions as those explained in the previous drawings may be given the same reference numerals, and duplicate explanations may be omitted.

[0012] Furthermore, in the detailed description of the present invention, when defining the positional relationship between a certain component and another component, "above" and "below" do not only mean a component being located directly above or below another component, but also include a component being located between the other components, unless otherwise specified.

[0013] [First embodiment] 1 is a perspective view of a display device 1 according to a first embodiment. The display device 1 is a head-mounted display that is worn on the head like goggles or glasses, allowing a user to enjoy virtual reality (VR). An image display area 2 is, for example, an octagon.

[0014] Fig. 2 is a schematic cross-sectional view of the display device 1 shown in Fig. 1. The display device 1 has a display panel 10 (e.g., a liquid crystal display panel). The left and right display panels 10 correspond to the two eyes. A backlight 12 is disposed on the rear side of the display panel 10. An optical sheet 14 is interposed between the display panel 10 and the backlight 12.

[0015] The backlight 12 has a light guide plate 16. The material is an acrylic resin, and the refractive index is, for example, 1.492 to 1.496. The light guide plate 16 includes a front surface 18 and a back surface 20. The display panel 10 faces the front surface 18. The light guide plate 16 includes a first end surface 22 connecting one end of the front surface 18 and one end of the back surface 20. The light guide plate 16 includes a second end surface 24 connecting the other end of the front surface 18 and the other end of the back surface 20. The thickness between the front surface 18 and the back surface 20 is larger at the second end surface 24 than at the first end surface 22. The back surface 20 is inclined with respect to the front surface 18. A reflector 26 faces the second end surface 24. A pair of light guide plates 16 are arranged symmetrically.

[0016] The backlight 12 has a laser 28. The laser 28 can emit laser light (e.g., polarized light) toward the first end face 22 of the light guide plate 16. The laser light incident on the first end face 22 is reflected by the front face 18, the back face 20, and the reflector 26, propagates inside the light guide plate 16, and is emitted from the front face 18. A reflecting sheet 30 is provided under the back face 20, and is configured to reflect the light that has passed through the back face 20.

[0017] FIG. 3 is a plan view of the backlight 12 shown in FIG. 2. FIG. 4 is a cross-sectional view of the light guide plate 16 of FIG. 3 taken along line IV-IV. The surface 18 has a plurality of line portions 32 in the region where the laser light is reflected. As shown in FIG. 2, when the laser light is reflected in a plurality of regions, the plurality of line portions 32 are closer to the second end face 24 than to the first end face 22. Each of the line portions 32 is convex. The plurality of line portions 32 extend in a first direction D1, which is a direction between the first end face 22 and the second end face 24. The plurality of line portions 32 are adjacent to each other in a second direction D2 perpendicular to the first direction D1. Each of the line portions 32 includes a curved surface (e.g., a cylindrical surface) that is formed by translating a straight line L parallel to the axis A that extends in the first direction D1 around the axis A. The curved surface is a convex curved surface. The laser light is reflected and diffused by the curved surface.

[0018] Each line portion 32 has, at its tip, an end face perpendicular to the axis A. The tips of adjacent line portions 32 do not align in the first direction D1. The tips do not align on either side of the first direction D1.

[0019] 5 is a plan view of a backlight according to the related art. Unlike the present embodiment, there are no line portions on the light guide plate 116. Therefore, due to the straightness of the laser light, a striped pattern appears along the traveling direction of the laser light.

[0020] 6 is a plan view of a backlight according to another related technique. As in the present embodiment, the light guide plate 116A has a plurality of line portions 132. Since the laser light is reflected and diffused by the curved surfaces of the line portions 132, the striped pattern shown in FIG. 5 disappears. However, since the tips of adjacent line portions 132 are aligned, brightness unevenness along the tips is visible. In contrast, in the present embodiment, as shown in FIG. 3, the tips of adjacent line portions 32 in the first direction D1 are not aligned, so there is no brightness unevenness.

[0021] [Modification 1 of the first embodiment] 7 is a cross-sectional view of a light guide plate according to Modification 1 of the first embodiment. The curved surface of line portion 32A is a concave curved surface. In other words, line portion 32A of this modification has an inverted shape of line portion 32 of the first embodiment.

[0022] [Modification 2 of the first embodiment] FIG. 8 is a plan view of a backlight according to Modification 2 of the first embodiment. This modification is different from the first embodiment in the planar shape. That is, the light guide plate 16 shown in FIG. 3 is rectangular, whereas the light guide plate 16B in FIG. 8 is a pentagon with the corners of the rectangle cut off. This makes it possible to avoid the nose 36 when applied to a head mounted display. The cut end face is jagged and is composed of a plurality of end faces that are parallel to the first end face 22B but at different distances from the first end face 22B.

[0023] [Second embodiment] Fig. 9 is a plan view of a backlight according to a second embodiment. Fig. 10 is a cross-sectional view of the light guide plate shown in Fig. 9 taken along line XX. The line portion 232 includes a curved surface (cylindrical surface) formed by translating a straight line L1 parallel to an axis A extending in a first direction D1 around the axis A. The curved surface constitutes a portion of the line portion 232 other than the end portion 234.

[0024] This embodiment differs from the first embodiment in the shape of the end 234 (e.g., both ends) of the line portion 232. The end 234 of each line portion 232 is tapered. The end 234 is tapered on either side of the first direction D1. The end 234 is tapered in width in the second direction D2. The end 234 is tapered in height in a third direction D3 perpendicular to the first direction D1 and the second direction D2. The end 234 is a curved surface (conical surface) obtained by translating a straight line L2 that is not parallel to the axis A and extends in the first direction D1 around the axis A. The end 234 is composed of a convex curved surface. The contents of the first embodiment are applicable to other details.

[0025] [Modification 1 of the second embodiment] 11 is a cross-sectional view of a light guide plate according to Modification 1 of the second embodiment. Each line portion 232A is concave. End portion 234A of each line portion 232A is formed of a concave curved surface. In other words, line portion 232A of this modification has an inverted shape of line portion 232 of the second embodiment.

[0026] [Modification 2 of the second embodiment] Fig. 12 is a cross-sectional view of a light guide plate according to Modification 2 of the second embodiment. Fig. 13 is a perspective view of the line portion shown in Fig. 12. In this modification, end 234B of line portion 232B is a curved surface formed by translating curve L3, which is non-parallel to axis A and extends in first direction D1, around axis A.

[0027] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configurations described in the embodiments can be replaced with substantially the same configurations, configurations that provide the same effects, or configurations that can achieve the same purpose.

[0028] [Overview of the embodiment] (1) A light guide plate 16 including a front surface 18 and a back surface 20, including a first end surface 22 connecting one end of the front surface 18 to one end of the back surface 20, and a second end surface 24 connecting the other end of the front surface 18 to the other end of the back surface 20, wherein a thickness between the front surface 18 and the back surface 20 is greater at the second end surface 24 than at the first end surface 22, and the back surface 20 is inclined with respect to the front surface 18, a laser 28 capable of emitting laser light toward the first end surface 22 of the light guide plate 16, and a reflector 26 opposed to the second end surface 24, wherein the laser light incident on the first end surface 22 is reflected by the front surface 18, the back surface 20, and the first end surface 24. a backlight 12 in which the laser light is reflected by the reflector 26, propagates inside the light guide plate 16, and exits from the surface 18, the surface 18 having a plurality of convex or concave line portions 32 in the area where the laser light is reflected, the plurality of line portions 32 extending in a first direction D1 which is the direction between the first end face 22 and the second end face 24 and adjacent to each other in a second direction D2 perpendicular to the first direction D1, each of the plurality of line portions 32 including a curved surface formed by translating a straight line L parallel to an axis A extending in the first direction D1 around the axis A, and the tips of adjacent ones of the plurality of line portions 32 in the first direction D1 are not aligned.

[0029] Stripes along the traveling direction of the laser light are eliminated by the line portions 32. In addition, since the tips of adjacent line portions 32 are not aligned, there is no unevenness in brightness.

[0030] (2) The backlight 12 according to (1), in which the tips are not aligned on either side of the first direction D1.

[0031] (3) The backlight 12 according to (1) or (2), wherein each of the plurality of line portions 32 has an end face perpendicular to the axis A.

[0032] (4) The backlight 12 according to any one of (1) to (3), wherein each of the plurality of line portions 32 is convex, and the curved surface is a convex curved surface.

[0033] (5) The backlight according to any one of (1) to (3), wherein each of the plurality of line portions 32A is concave, and the curved surface is a concave curved surface.

[0034] (6) A light guide plate 216 including a front surface 218 and a back surface 220, including a first end surface 222 connecting one end of the front surface 218 and one end of the back surface 220, and including a second end surface 224 connecting the other end of the front surface 218 and the other end of the back surface 220, wherein a thickness between the front surface 218 and the back surface 220 is greater at the second end surface 224 than at the first end surface 222, and the back surface 220 is inclined with respect to the front surface 218, a laser 228 capable of emitting laser light toward the first end surface 222 of the light guide plate 216, and a reflector 226 facing the second end surface 224, wherein the laser light incident on the first end surface 222 is reflected by the front surface 218, a backlight having a first end surface and a second end surface, the first end surface being a first direction D1, the second end surface being a direction between the first end surface and the second end surface, and the second end surface being a direction between the first end surface and the second end surface, the second end surface being a direction between the first end surface and the second end surface, the second end surface being a direction between the first end surface and the second end surface, the second end surface being a direction between the first end surface and the second end surface, the second end surface being a direction between the first end surface and the second end surface,

[0035] (7) The backlight according to (6), wherein the end 234 is tapered on either side in the first direction D1.

[0036] (8) The backlight according to (6) or (7), wherein the end 234 is tapered in width in the second direction D2.

[0037] (9) The backlight according to any one of (6) to (8), wherein the end 234 is tapered in a height in a third direction D3 perpendicular to the first direction D1 and the second direction D2.

[0038] (10) The backlight according to any one of (6) to (9), wherein each of the plurality of line portions 232 is convex, and the end portion 234 is configured as a convex curved surface.

[0039] (11) The backlight according to any one of (6) to (9), wherein each of the plurality of line portions 232A is concave, and the end portion 234A is configured as a concave curved surface.

[0040] (12) A display device 1 having a backlight 12 according to any one of (1) to (11) and a display panel 10 arranged to face the surface 18 of the light guide plate 16. [Explanation of symbols]

[0041] 1 display device, 2 display area, 10 display panel, 12 backlight, 14 optical sheet, 16 light guide plate, 16B light guide plate, 18 front surface, 20 rear surface, 22 first end surface, 22B first end surface, 24 second end surface, 26 reflector, 28 laser, 30 reflector sheet, 32 line portion, 32A line portion, 36 nose, 116 light guide plate, 116A light guide plate, 132 line portion, 216 light guide plate, 218 front surface, 220 rear surface, 222 first end surface, 224 second end surface, 226 reflector, 228 laser, 232 line portion, 232A line portion, 232B line portion, 234 end portion, 234A end portion, 234B end portion, A axis, D1 first direction, D2 second direction, D3 3rd direction, L straight line, L2 straight line, L3 curve.

Claims

1. a light guide plate including a front surface and a back surface, including a first end surface connecting one end of the front surface and one end of the back surface, and a second end surface connecting the other end of the front surface and the other end of the back surface, the thickness between the front surface and the back surface being greater at the second end surface than at the first end surface, and the back surface being inclined with respect to the front surface; a laser capable of emitting laser light toward the first end surface of the light guide plate; a reflector facing the second end surface; having the laser light incident on the first end surface is reflected by the front surface, the back surface, and the reflector, propagates inside the light guide plate, and is emitted from the front surface; the surface has a plurality of convex or concave line portions in an area where the laser light is reflected, The plurality of line portions extend in a first direction between the first end surface and the second end surface and are adjacent to each other in a second direction perpendicular to the first direction. Each of the plurality of line portions includes a curved surface formed by translating a straight line parallel to an axis extending in the first direction around the axis, The backlight has adjacent line portions whose tips in the first direction are not aligned with each other.

2. 2. The backlight according to claim 1, The backlight, wherein the tips are not aligned on either side of the first direction.

3. 2. The backlight according to claim 1, Each of the plurality of line portions has an end face perpendicular to the axis.

4. 2. The backlight according to claim 1, Each of the plurality of line portions is convex, The backlight, wherein the curved surface is a convex curved surface.

5. 2. The backlight according to claim 1, Each of the plurality of line portions is concave, The backlight, wherein the curved surface is a concave curved surface.

6. a light guide plate including a front surface and a back surface, including a first end surface connecting one end of the front surface and one end of the back surface, and a second end surface connecting the other end of the front surface and the other end of the back surface, the thickness between the front surface and the back surface being greater at the second end surface than at the first end surface, and the back surface being inclined with respect to the front surface; a laser capable of emitting laser light toward the first end surface of the light guide plate; a reflector facing the second end surface; having the laser light incident on the first end surface is reflected by the front surface, the back surface, and the reflector, propagates inside the light guide plate, and is emitted from the front surface; the surface has a plurality of convex or concave line portions in an area where the laser light is reflected, The plurality of line portions extend in a first direction between the first end surface and the second end surface and are adjacent to each other in a second direction perpendicular to the first direction. Each of the plurality of line portions includes a curved surface formed by translating a straight line parallel to an axis extending in the first direction around the axis, A backlight in which each end of the plurality of line portions is tapered.

7. 7. The backlight according to claim 6, The backlight, wherein the edges are tapered on either side of the first direction.

8. 7. The backlight according to claim 6, The end portion is tapered in width in the second direction.

9. 7. The backlight according to claim 6, The end portion is tapered in height in a third direction perpendicular to the first direction and the second direction.

10. 7. The backlight according to claim 6, Each of the plurality of line portions is convex, The end portion of the backlight is configured as a convex curved surface.

11. 7. The backlight according to claim 6, Each of the plurality of line portions is concave, The end portion of the backlight is formed of a concave curved surface.

12. A backlight according to any one of claims 1 to 11; a display panel disposed opposite the surface of the light guide plate; A display device having the above configuration.

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