Back light and display device

Abstract

To improve luminance.SOLUTION: A back light 10 includes: a light guide plate 14 having an end surface 16 serving as a light incidence surface and a plate surface 18 serving as a light emission surface; a first prism sheet 22 which has a flat surface 24 directly facing the plate surface 18 and a first prism surface 26 located at the side opposite to the flat surface 24 and in which the first prism surface 26 has a plurality of first grooves 28 and the first grooves 28 are located adjacent to each other in a first direction D1 and extend in a second direction D2; and a second prism sheet 30 which overlaps with the first prism sheet 22 and has a second prism surface 32 directly facing the first prism surface 26 and a flat surface 36 located at the side opposite to the second prism surface 32 and in which the second prism surface 32 has a plurality of second grooves 34 and the second grooves 34 are located adjacent to each other in the first direction D1 and extend in the second direction D2. Peaks of luminosity exist in two directions excluding a vertical direction VD in light distribution characteristics on a first vertical surface P1 extending in the vertical direction VD and the first direction D1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A display that separates light into left and right and displays different images in two directions is known (Patent Document 1). To enable such a display, a backlight with light distribution characteristics that produce peaks of luminous intensity in two directions is required. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2008-538154 Summary of the Invention [Problem to be solved by the invention]

[0004] Edge-lit backlights, in which light is incident from the edge of the light guide plate, are expected to achieve even greater brightness.

[0005] The present invention aims to improve brightness in two directions. [Means for solving the problem]

[0006] The backlight comprises a light source, a light guide plate having an end face which is an incident surface of light from the light source and a plate surface which is an exit surface of the light, a first prism sheet which overlaps the light guide plate and has a flat surface directly facing the plate surface and has a first prism surface opposite the flat surface, the first prism surface having a plurality of first grooves, the plurality of first grooves being adjacent to the first direction and extending in a second direction, the first direction and the second direction being perpendicular to each other, and a second prism sheet which overlaps the first prism sheet and has a second prism surface directly facing the first prism surface and has a flat surface opposite to the second prism surface, the second prism surface having a plurality of second grooves, the plurality of second grooves being adjacent to the first direction and extending in the second direction, and the light distribution characteristics on a vertical direction perpendicular to the first direction and the second direction and on a first vertical plane extending in the first direction have peaks of luminous intensity in two directions except the vertical direction.

[0007] The display device includes a backlight and a display panel that is arranged so that the light emitted from the backlight is incident on the rear surface of the display panel. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view of the backlight according to the embodiment. [Figure 2] 2 is a cross-sectional view of the backlight shown in FIG. 1 taken along line II-II. [Figure 3] FIG. 2 is a partial enlarged view of the first prism sheet and the second prism sheet. [Figure 4] 4 is a cross-sectional view of the backlight shown in FIG. 1 taken along line IV-IV. [Figure 5] FIG. 4 is a diagram illustrating light distribution characteristics of a backlight according to the embodiment. [Figure 6] FIG. 10 is a cross-sectional view of a backlight according to a reference technique. [Figure 7] FIG. 10 is a diagram illustrating the light distribution characteristics of light emitted from a light guide plate of the reference technology. [Figure 8] FIG. 10 is a diagram showing the light distribution characteristics of light emitted from a diffusion sheet of the reference technology. [Figure 9] 1 is a schematic diagram of a display device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments 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 embodiments exemplified below.

[0010] In order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part schematically 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 assigned the same reference numerals, and duplicate explanations may be omitted.

[0011] 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 being located directly above or directly below a certain component, but also include cases where there are other components interposed between them, unless otherwise specified.

[0012] FIG. 1 is a plan view of a backlight according to this embodiment. FIG. 2 is a cross-sectional view of the backlight shown in FIG. 1 taken along line II-II. The backlight 10 has light sources 12 (e.g., lasers). The light sources 12 include a pair of light sources 12. The light sources 12 are configured to emit light. The light sources 12A of a first group are aligned in a first direction D1, and the light sources 12B of a second group are aligned in the first direction D1. There is a gap between the light sources 12A of the first group and the light sources 12B of the second group in a second direction D2 that is perpendicular to the first direction D1.

[0013] The backlight 10 has a light guide plate 14. The light guide plate 14 has an end surface 16 which is the incident surface of light from the light source 12. The backlight 10 is of an edge light type (side light type). The light source 12 is adjacent to the light guide plate 14 in the second direction D2. A pair of light sources 12 are adjacent to both sides of the light guide plate 14 in the second direction D2. This allows light to be incident in opposite directions, thereby reducing brightness variations due to distance from the light source 12. The light guide plate 14 has a plate surface 18 which is the light exit surface. On the opposite side to the plate surface 18 is a reflective sheet 20 which directs light toward the exit surface.

[0014] The backlight 10 has a first prism sheet 22. The first prism sheet 22 overlaps the light guide plate 14. The first prism sheet 22 has a flat surface 24 that directly faces the plate surface 18. No diffusion sheet is interposed between the first prism sheet 22 and the light guide plate 14.

[0015] The first prism sheet 22 has a first prism surface 26 on the side opposite to the flat surface 24. The first prism surface 26 has a plurality of first grooves 28. The plurality of first grooves 28 are adjacent to each other in the first direction D1 and extend in the second direction D2. Each of the plurality of first grooves 28 is a V-groove.

[0016] The backlight 10 has a second prism sheet 30. The second prism sheet 30 overlaps the first prism sheet 22. The second prism sheet 30 has a second prism surface 32 directly facing the first prism surface 26. The second prism surface 32 has a plurality of second grooves 34. The plurality of second grooves 34 are adjacent to each other in the first direction D1 and extend in the second direction D2. Each of the plurality of second grooves 34 is a V-groove. The second prism sheet 30 has a flat surface 36 on the side opposite the second prism surface 32.

[0017] 3 is a partially enlarged view of the first prism sheet 22 and the second prism sheet 30. Each of the multiple first grooves 28 includes a pair of first inclined surfaces 38. The pair of first inclined surfaces 38 are plane-symmetric. The reference plane of the plane symmetry is a second vertical plane P2 extending in the vertical direction VD and the second direction D2. Each of the multiple second grooves 34 includes a pair of second inclined surfaces 40. The pair of second inclined surfaces 40 are plane-symmetric. The reference plane of the plane symmetry is the second vertical plane P2 extending in the vertical direction VD and the second direction D2.

[0018] The first exterior angle α1 (e.g., 120 degrees) formed by the pair of first inclined surfaces 38 is equal to or greater than the second exterior angle α2 (e.g., 90 degrees) formed by the pair of second inclined surfaces 40. The difference between the first exterior angle α1 and the second exterior angle α2 is equal to or greater than 20 degrees and equal to or less than 40 degrees.

[0019] The first prism surface 26 has a first ridge portion 42 between adjacent pairs of the multiple first grooves 28. A first interior angle β1 of the first ridge portion 42 is the same as the first exterior angle α1. The second prism surface 32 has a second ridge portion 44 between adjacent pairs of the multiple second grooves 34. A second interior angle β2 of the second ridge portion 44 is the same as the second exterior angle α2.

[0020] 4 is a cross-sectional view of the backlight 10 shown in FIG. 1 taken along line IV-IV. The backlight 10 includes a third prism sheet 46. The third prism sheet 46 has a lower surface 48 that directly faces the flat surface 36 of the second prism sheet 30. The third prism sheet 46 has a third prism surface 50 on the side opposite the lower surface 48. The third prism surface 50 has a plurality of third grooves 52. The plurality of third grooves 52 extend in a first direction D1 and are adjacent in a second direction D2. The backlight 10 includes a dual brightness enhancement film 54 that directly faces the third prism surface 50 of the third prism sheet 46.

[0021] Fig. 5 is a diagram showing the light distribution characteristics of the backlight 10 according to this embodiment. In the light distribution characteristics on the first vertical plane P1 extending in the vertical direction VD and the first direction D1 shown in Fig. 2, there are peaks of luminous intensity in two directions except for the vertical direction VD. The angle in the vertical direction VD is 0 degrees. The angles in the two directions are angles greater than or equal to +30 degrees and angles less than or equal to -30 degrees.

[0022] 6 is a cross-sectional view of a backlight according to the reference technology. The first prism sheet 22 of the embodiment is replaced with a diffusion sheet 56. The rest of the configuration is the same as the embodiment. Note that when the second outer angle α2 of the second prism sheet 30 is set to 90 degrees, the backlight according to the reference technology has the highest luminous intensity at its peak.

[0023] 7 is a diagram showing the light distribution characteristics of light emitted from the light guide plate 14 of the reference technology. The luminous intensity of the light emitted from the light guide plate 14 is uniform over a range of ±30 degrees or more.

[0024] 8 is a diagram showing the light distribution characteristics of the light emitted from the diffusion sheet 56 of the reference technology. The luminous intensity of the light emitted from the diffusion sheet 56 is high near 0 degrees.

[0025] In contrast, the backlight 10 according to the embodiment has a first prism sheet 22 instead of a diffusion sheet 56, and therefore, as shown in Fig. 5, there are luminous intensity peaks in two directions, improving brightness in both directions. In a simulation in which the first outer angle α1 was 120 degrees and the second outer angle α2 was 90 degrees, the luminous intensity of the embodiment was 1.03 when the luminous intensity of the reference technology was 1.0. Alternatively, in a simulation in which both the first outer angle α1 and the second outer angle α2 were 90 degrees, the luminous intensity of the embodiment was 1.02.

[0026] 9 is a schematic diagram of a display device according to this embodiment. The display device has a backlight 10. The display device has a display panel 58 (e.g., a liquid crystal display panel) arranged so that light emitted from the backlight 10 enters from the backside.

[0027] [Outline of the embodiment] (1) a light source 12, a light guide plate 14 having an end face 16 which is an incident face of light from the light source 12 and a plate face 18 which is an exit face of the light, a first prism sheet 22 which overlaps the light guide plate 14 and has a flat face 24 directly facing the plate face 18 and has a first prism face 26 on the opposite side to the flat face 24, the first prism face 26 having a plurality of first grooves 28 which are adjacent to a first direction D1 and extend in a second direction D2, the first direction D1 and the second direction D2 being orthogonal to each other, and a first prism sheet 22 which overlaps the first prism sheet 22; a second prism sheet (30) having a second prism surface (32) directly opposed to the first prism surface (26), and a flat surface (36) on the opposite side to the second prism surface (32), the second prism surface (32) having a plurality of second grooves (34), the plurality of second grooves (34) being adjacent to the first direction (D1) and extending in the second direction (D2), and wherein the backlight (10) has peaks of luminous intensity in two directions except for the vertical direction (VD), in light distribution characteristics on a vertical direction (VD) perpendicular to the first direction (D1) and the second direction (D2) and on a first vertical plane (P1) extending in the first direction (D1).

[0028] The first prism surface 26 reduces the light in the vertical direction VD, thereby improving the brightness in two directions.

[0029] (2) The backlight 10 according to (1), wherein the plurality of first grooves 28 and the plurality of second grooves 34 are V-grooves.

[0030] (3) A backlight 10 as described in (1), wherein each of the plurality of first grooves 28 includes a pair of first inclined surfaces 38, and each of the plurality of second grooves 34 includes a pair of second inclined surfaces 40.

[0031] (4) In the backlight 10 described in (3), the pair of first inclined surfaces 38 are plane-symmetric, the pair of second inclined surfaces 40 are plane-symmetric, and the reference plane of the plane symmetry is a second vertical plane P2 extending in the vertical direction VD and the second direction D2.

[0032] (5) The backlight 10 according to (3), wherein the first outer angle α1 formed by the pair of first inclined surfaces 38 is equal to or larger than the second outer angle α2 formed by the pair of second inclined surfaces 40.

[0033] (6) The backlight 10 according to (5), wherein the difference between the first outer angle α1 and the second outer angle α2 is 20 degrees or more and 40 degrees or less.

[0034] (7) In the backlight 10 described in (1), the light source 12 is adjacent to the light guide plate 14 in the second direction D2.

[0035] In the backlight 10 described in (8) and (7), the light source 12 includes a pair of light sources 12, the pair of light sources 12 being adjacent to each other on both sides of the light guide plate 14 in the second direction D2.

[0036] (9) The backlight 10 described in (1) further includes a third prism sheet 46 having a lower surface 48 directly facing the flat surface 36 of the second prism sheet 30, a third prism surface 50 on the opposite side of the lower surface 48, the third prism surface 50 having a plurality of third grooves 52, the plurality of third grooves 52 extending in the first direction D1 and adjacent to the second direction D2.

[0037] (10) The backlight 10 according to (9), further comprising a dual brightness enhancement film 54 directly facing the third prism surface 50 of the third prism sheet 46 .

[0038] (11) The backlight 10 according to (1), wherein the angle of the vertical direction VD is 0 degrees, and the angles in the two directions are an angle of +30 degrees or more and an angle of -30 degrees or less.

[0039] (12) A display device having a backlight 10 according to any one of (1) to (11) and a display panel 58 arranged so that the light emitted from the backlight 10 is incident on the back surface.

[0040] The present invention is not limited to the above-described embodiments and various modifications are possible. For example, the configurations described in the embodiments can be replaced with substantially the same configurations, configurations that achieve the same effects, or configurations that can achieve the same objectives. [Explanation of symbols]

[0041] 10 backlight, 12 light source, 14 light guide plate, 16 end face, 18 plate surface, 20 reflective sheet, 22 first prism sheet, 24 flat surface, 26 first prism surface, 28 first groove, 30 second prism sheet, 32 second prism surface, 34 second groove, 36 flat surface, 38 first inclined surface, 40 second inclined surface, 42 first ridge portion, 44 second ridge portion, 46 third prism sheet, 48 bottom surface, 50 third prism surface, 52 third groove, 54 dual brightness enhancement film, 56 diffusion sheet, 58 display panel, D1 first direction, D2 second direction, P1 first vertical surface, P2 second vertical surface, VD vertical direction.

Claims

1. A light source and a light guide plate having an end surface which is an incident surface of light from the light source and a plate surface which is an exit surface of the light; a first prism sheet that overlaps the light guide plate and has a flat surface directly facing the plate surface, and a first prism surface on the opposite side to the flat surface, the first prism surface having a plurality of first grooves that are adjacent to each other in a first direction and extend in a second direction, the first direction and the second direction being perpendicular to each other; a second prism sheet overlapping the first prism sheet, having a second prism surface directly facing the first prism surface and a flat surface on the opposite side to the second prism surface, the second prism surface having a plurality of second grooves, the plurality of second grooves being adjacent to each other in the first direction and extending in the second direction; and A backlight having a light distribution characteristic in a vertical direction perpendicular to the first direction and the second direction and on a first vertical plane extending in the first direction, in which luminous intensity peaks exist in two directions excluding the vertical direction.

2. 2. The backlight according to claim 1, The backlight, wherein the plurality of first grooves and the plurality of second grooves are V-grooves.

3. 2. The backlight according to claim 1, Each of the plurality of first grooves includes a pair of first inclined surfaces, Each of the plurality of second grooves includes a pair of second inclined surfaces.

4. 4. The backlight according to claim 3, the pair of first inclined surfaces are plane-symmetric, the pair of second inclined surfaces are plane-symmetric, The reference plane of plane symmetry is a second vertical plane extending in the vertical direction and the second direction.

5. 4. The backlight according to claim 3, A backlight, wherein a first outer angle formed by the pair of first inclined surfaces is equal to or larger than a second outer angle formed by the pair of second inclined surfaces.

6. 6. The backlight according to claim 5, The backlight has a difference between the first outer angle and the second outer angle of 20 degrees or more and 40 degrees or less.

7. 2. The backlight according to claim 1, The light source is a backlight adjacent to the light guide plate in the second direction.

8. 8. The backlight according to claim 7, the light source includes a pair of light sources; The pair of light sources are backlights adjacent to each other on both sides of the light guide plate in the second direction.

9. 2. The backlight according to claim 1, a third prism sheet having a lower surface directly facing the flat surface of the second prism sheet and a third prism surface on the opposite side to the lower surface, the third prism surface having a plurality of third grooves, the plurality of third grooves extending in the first direction and adjacent to each other in the second direction.

10. 10. The backlight according to claim 9, The backlight further includes a dual brightness enhancement film directly facing the third prism surface of the third prism sheet.

11. 2. The backlight according to claim 1, the vertical angle is 0 degrees; The angles in the two directions are an angle of +30 degrees or more and an angle of -30 degrees or less.

12. A backlight according to any one of claims 1 to 11; a display panel arranged so that the light emitted from the backlight is incident on the rear surface; A display device having:

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