Luminaire and display device

Abstract

To suppress emission of light to the outside of a limited angle range, and to improve luminance of emission light in a direction inclined with respect to a front direction.SOLUTION: A luminaire 12 includes a first light source 13, a first light guide plate 14, a first sheet 18, a second light source 24, and a second light guide plate 25. The first sheet 18 has at least: two first light shielding parts 18C disposed by having an interval in a first direction including a direction toward the first light guide plate 14 from the first light source 13 and for shielding light; and a first light transmission part 18D disposed between the two first light shielding parts 18C and for transmitting light. On a second opposite main surface 25C of the second light guide plate 25, a first inclined surface 28A and a second inclined surface 29A of the inclination standing toward a second LED 24 side from the opposite side from the second LED 24 in the first direction are provided. In the first inclined surface 28A, an angle with respect to the first direction is a first angle θ1 larger than 27°, and in the second inclined surface 29A, an angle with respect to the first direction is a second angle θ2 larger than the first angle θ1 and smaller than 58°.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a lighting device and a display device. [Background technology]

[0002] Conventionally, an example of a lighting device is known, which is described in Patent Document 1 below. The lighting device described in Patent Document 1 operates in at least two operation modes, namely, a free-view mode and a limited-view mode. The lighting device includes a backlight system. A light guide plate is disposed in front of the backlight system, and a light source is disposed along the side of the light guide plate. The light guide plate has a resin matrix in which diffusing particles made of a polymer are dispersed, and has a light transmittance of at least 80%. In the free-view mode, the light source is turned on and the backlight system is turned off. In the limited-view mode, the backlight system is turned on and the light source is turned off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2017 / 0069236 Summary of the Invention [Problem to be solved by the invention]

[0004] The light guide plate provided in the lighting device described in the above Patent Document 1 contains diffusion particles, so in the limited viewing mode, the light emitted from the backlight system and incident on the light guide plate is diffused by the diffusion particles. Therefore, in the limited viewing mode, light is likely to be emitted outside the limited angle range, and it is difficult to emit light only within the limited angle range. In addition, since the light transmittance of the light guide plate is high, at least 80%, in the free viewing mode, the light from the light source is not sufficiently diffused in the process of passing through the light guide plate. Therefore, in the free viewing mode, there is a problem that the brightness of the emitted light in a direction inclined relative to the front direction is insufficient.

[0005] The technology described in this specification was developed based on the above circumstances, and aims to suppress the emission of light outside a limited angular range and to improve the brightness of light emitted in a direction tilted relative to the forward direction. [Means for solving the problem]

[0006] (1) A lighting device according to the technology described in this specification includes a first light source, a first light guide plate having at least a part of an outer peripheral end surface that faces the first light source and is a first end surface through which light is incident, one main surface being a first main surface that emits light, and the other main surface being a second main surface, a first sheet having one main surface that faces the first main surface and is a third main surface through which light is incident and is disposed to face the first main surface, and the other main surface being a fourth main surface through which light is output, a second light source, and a second light guide plate having at least a part of an outer peripheral end surface that faces the second light source and is a second end surface through which light is incident, one main surface being a fifth main surface that emits light, and the other main surface being a sixth main surface disposed to face the fourth main surface. the first sheet has at least two first light-shielding portions arranged at an interval in a first direction including a direction from the first light source to the first light guide plate to block light, and a first light-transmitting portion arranged between the two first light-shielding portions to transmit light, and the sixth main surface of the second light guide plate is provided with a first inclined surface and a second inclined surface that are inclined rising from a side opposite to the second light source in the first direction toward the second light source, and the first inclined surface has an angle with respect to the first direction that is greater than 27°, and the second inclined surface has an angle with respect to the first direction that is greater than the first angle and less than 58°.

[0007] (2) In addition to the above-mentioned (1), the lighting device may further include a third inclined surface on the sixth main surface of the second light guide plate, the third inclined surface being inclined upward from the second light source side toward an opposite side in the first direction.

[0008] (3) In addition to the above-mentioned (2), the lighting device may further include a fourth inclined surface arranged opposite the second inclined surface with a gap therebetween, and the fourth inclined surface may have a third angle, which is an angle with respect to the first direction, of 40° or more.

[0009] (4) In addition to the above-mentioned (3), the lighting device may further include the fourth inclined surface having the third angle of 65° or more.

[0010] (5) In addition to the above-mentioned (3), the lighting device may further include the fourth inclined surface having the third angle of 67° or more.

[0011] (6) In addition to any one of (2) to (5) above, the lighting device may further include a fourth inclined surface arranged facing the second inclined surface with a gap therebetween, and a fifth inclined surface arranged facing the first inclined surface with a gap therebetween, and the fifth inclined surface may have a fourth angle, which is an angle with respect to the first direction, that is equal to a third angle, which is an angle of the fourth inclined surface with respect to the first direction.

[0012] (7) In addition to any one of (2) to (5) above, the lighting device may further include a fourth inclined surface arranged opposite the second inclined surface with a gap therebetween, and a fifth inclined surface arranged opposite the first inclined surface with a gap therebetween, and a fourth angle of the fifth inclined surface which is an angle with respect to the first direction may be smaller than a third angle which is an angle of the fourth inclined surface with respect to the first direction.

[0013] (8) In addition to the above (7), the lighting device may further include a fifth angle, which is an angle with respect to the first direction, that is, the first inclined surface and the fourth inclined surface are arranged at an interval in the first direction, the third inclined surface includes a sixth inclined surface located between the first inclined surface and the fourth inclined surface, and the sixth inclined surface has a fifth angle with respect to the first direction that is equal to the fourth angle.

[0014] (9) A display device related to the technology described in this specification includes an illumination device described in any one of (1) to (8) above, and a display panel that performs display using light from the illumination device. Effect of the Invention

[0015] According to the technology described in this specification, it is possible to suppress the emission of light outside a limited angle range and to improve the luminance of light emitted in a direction inclined relative to the front direction. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a side cross-sectional view of a liquid crystal display device according to a first embodiment. [Diagram 2] 1 is a side cross-sectional view of a backlight device provided in a liquid crystal display device according to a first embodiment. [Diagram 3] 1 is a front cross-sectional view of a backlight device according to a first embodiment. [Figure 4] FIG. 2 is a perspective view of a first light guide plate constituting the backlight device according to the first embodiment, viewed from the first opposite principal surface side. [Diagram 5] FIG. 1 is a bottom view showing a configuration of a first opposite principal surface of a first light guide plate according to a first embodiment; [Figure 6] FIG. 1 is a side cross-sectional view of a second light guide plate constituting a backlight device according to a first embodiment. [Figure 7] FIG. 1 is a bottom view showing a configuration of a second opposite principal surface of a second light guide plate according to a first embodiment; [Figure 8] 1 is a graph showing a relationship between a position in the X-axis direction in a second light guide plate according to embodiment 1 and a width dimension of a first inclined surface, a width dimension of a fourth inclined surface, a width dimension of a third plane, a width dimension of a second inclined surface, and a width dimension of a fifth inclined surface. [Figure 9] 10 is a graph showing the relationship between the position in the X-axis direction of the second light guide plate in the first embodiment and the height dimension of the sixth light guide plate lens and the height dimension of the seventh light guide plate lens. [Figure 10] Graph showing light distribution when the first inclined surface and the second inclined surface are changed in Demonstration Experiment 1 according to the first embodiment. [Figure 11]1 is a graph showing a light distribution when the first LED is turned on and the second LED is turned off in Comparative Example 1 of Comparative Experiment 1 according to Embodiment 1. [Figure 12] 1 is a graph showing a light distribution when the second LED is turned on and the first LED is turned off in Comparative Example 1 of Comparative Experiment 1 according to Embodiment 1. [Figure 13] 1 is a graph showing a light distribution when the first LED and the second LED are both turned on in Comparative Example 1 of Comparative Experiment 1 according to Embodiment 1. [Figure 14] 1 is a graph showing a light distribution when the first LED is turned on and the second LED is turned off in Example 1 of Comparative Experiment 1 according to Embodiment 1. [Figure 15] 1 is a graph showing a light distribution when the second LED is turned on and the first LED is turned off in Example 1 of Comparative Experiment 1 according to the first embodiment. [Figure 16] 1 is a graph showing a light distribution when the first LED and the second LED are both turned on in Example 1 of Comparative Experiment 1 according to Embodiment 1. [Figure 17] FIG. 1 is a diagram for explaining an angle in the X-axis direction with respect to the forward direction in a liquid crystal display device installed in front of a passenger seat of a passenger vehicle according to embodiment 1. [Figure 18] 1 is a side cross-sectional view of a second light guide plate according to a second embodiment. [Figure 19] Graph showing light distribution when the fourth inclined surface and the fifth inclined surface are changed in Demonstration Experiment 2 according to the second embodiment. [Figure 20] 13 is a graph showing a light distribution when the first LED is turned on and the second LED is turned off in Example 2 of Comparative Experiment 2 according to the second embodiment. [Figure 21] 13 is a graph showing a light distribution when the second LED is turned on and the first LED is turned off in Example 2 of Comparative Experiment 2 according to the second embodiment. [Figure 22] 13 is a graph showing the light distribution when the first LED and the second LED are both turned on in Example 2 of Comparative Experiment 2 according to the second embodiment. [Figure 23] 11 is a side cross-sectional view of a second light guide plate according to a third embodiment. [Figure 24]11 is a front cross-sectional view of a second light guide plate according to a third embodiment. [Diagram 25] Graph showing light distribution when the fourth inclined surface is changed in Demonstration Experiment 3 according to the third embodiment. [Figure 26] Graph showing an enlarged portion of FIG. 25 in Demonstration Experiment 3 according to the third embodiment. [Figure 27] Table showing experimental results of Demonstration Experiment 3 according to the third embodiment [Figure 28] 13 is a graph showing the light distribution when the first LED is turned on and the second LED is turned off in Example 3 of Comparative Experiment 3 according to the third embodiment. [Figure 29] 13 is a graph showing a light distribution when the second LED is turned on and the first LED is turned off in Example 3 of Comparative Experiment 3 according to the third embodiment. [Diagram 30] 13 is a graph showing the light distribution when the first LED and the second LED are both turned on in Example 3 of Comparative Experiment 3 according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] <Embodiment 1> The first embodiment will be described with reference to Fig. 1 to Fig. 17. In this embodiment, a liquid crystal display device (display device) 10 is illustrated. Note that the X-axis, Y-axis, and Z-axis are shown in a part of each drawing, and each axis direction is drawn to be the direction shown in each drawing. Also, the up-down direction is based on Fig. 2 and Fig. 3, and the upper side of each drawing is the front side and the lower side of each drawing is the back side.

[0018] 1, the liquid crystal display device 10 includes a liquid crystal panel (display panel) 11 that displays an image, and a backlight device (illumination device) 12 that is disposed on the rear side of the liquid crystal panel 11 and irradiates light used for display toward the liquid crystal panel 11. In this embodiment, an in-vehicle liquid crystal display device 10 is illustrated. The in-vehicle liquid crystal display device 10 is mounted, for example, in a car navigation system that displays maps and the like as images, a multifunction display that displays the operating status of devices such as an air conditioner in addition to maps and the like as images, an instrument panel that displays gauges and warnings as images, and an infotainment system that displays television images and audio information in addition to maps and the like as images.

[0019] The liquid crystal panel 11 has a plate-like main surface parallel to the X-axis and Y-axis directions, and the normal direction (thickness direction) of the main surface coincides with the Z-axis direction. The central part of the main surface of the liquid crystal panel 11 is a display area capable of displaying an image, and the frame-like peripheral end part surrounding the display area is a non-display area. The liquid crystal panel 11 has a pair of substrates and a liquid crystal layer sealed between the pair of substrates. Of the pair of substrates constituting the liquid crystal panel 11, the one disposed on the front side is a CF substrate (opposing substrate), and the one disposed on the back side is an array substrate (TFT substrate). The CF substrate is provided with color filters exhibiting R (red), G (green), B (blue), etc., and a light-shielding portion (black matrix) that separates adjacent color filters. The array substrate (TFT substrate) is provided with at least gate wiring and source wiring that are perpendicular to each other, switching elements (e.g., TFTs) connected to the gate wiring and source wiring, and pixel electrodes that are connected to the switching elements and form pixels. An alignment film is provided on each inner surface of the array substrate and the CF substrate constituting the liquid crystal panel 11. A polarizing plate is attached to each outer surface of the array substrate and the CF substrate constituting the liquid crystal panel 11.

[0020] Next, a description will be given of the backlight device 12. As shown in Fig. 1, the backlight device 12 at least includes a first LED (first light source) 13, a first light guide plate 14 that guides light from the first LED 13, a reflective sheet 15 arranged on the back side (opposite the light output side) of the first light guide plate 14, a first prism sheet 16 arranged on the front side (light output side) of the first light guide plate 14, and a second prism sheet 17 arranged on the front side of the first prism sheet 16.

[0021] As shown in FIG. 1, the first LED 13 is substantially block-shaped, and one of a pair of surfaces along the Y-axis direction and the Z-axis direction is the first light-emitting surface 13A that emits light. The first LED 13 is arranged in a row at intervals along the Y-axis direction. The first LED 13 is mounted on an LED substrate. The first LED 13 is configured by sealing an LED chip on a substrate portion mounted on the LED substrate with a sealing material. The LED chip provided in the first LED 13 emits monochromatic light, for example, blue light. The sealing material provided in the first LED 13 has a phosphor dispersed therein. The phosphor contained in the sealing material includes a yellow phosphor, a green phosphor, a red phosphor, and the like. The first LED 13 provided with such an LED chip and sealing material emits white light as a whole.

[0022] The first light guide plate 14 is made of a synthetic resin material (e.g., acrylic resin such as PMMA) that has a refractive index sufficiently higher than that of air and is almost transparent. As shown in FIG. 1, the first light guide plate 14 is plate-shaped, and its main surface is parallel to the main surface of the liquid crystal panel 11. The main surface of the first light guide plate 14 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface coincides with the Z-axis direction. The first light guide plate 14 is arranged along the X-axis direction (first direction) with respect to the first LED 13, and is arranged along the Z-axis direction with respect to the liquid crystal panel 11 and each prism sheet 16, 17. The first light guide plate 14 is arranged on one side in the X-axis direction with respect to the first LED 13 (the right side in FIG. 1). One end surface of the outer peripheral end surface of the first light guide plate 14 is a first light-entering end surface (first end surface) 14A that faces the first light-emitting surface 13A of the first LED 13. The first light-entering end surface 14A is a surface parallel to the first light-emitting surface 13A of the first LED 13, and the light emitted from the first light-emitting surface 13A is incident on the first light-incoming end surface 14A. Therefore, the first LED 13 is arranged on only one side of the first light guide plate 14 in the X-axis direction, and the first light guide plate 14 and the first LED 13 constitute a one-side light-incoming backlight unit. Of the pair of main surfaces in the first light guide plate 14, the front main surface facing the first prism sheet 16 is the first light guide plate light-outgoing main surface (first main surface) 14B that outputs light guided inside. Of the pair of main surfaces in the first light guide plate 14, the back main surface facing the reflection sheet 15 is the first opposite main surface (second main surface) 14C located on the opposite side to the first light guide plate light-outgoing main surface 14B. The first light guide plate 14 has a function of guiding the light emitted from the first LED 13 toward the first light guide plate 14 through the first light-entering end surface 14A, propagating the light inside, and then raising the light so as to face the front side (light-emitting side) along the Z-axis direction and emitting the light. The detailed structure of the first light guide plate 14 will be described later. The normal direction of the first light-entering end surface 14A coincides with the X-axis direction (the arrangement direction of the first LED 13 and the first light guide plate 14).

[0023] 1, the reflection sheet 15 is disposed so that its principal surface is parallel to each principal surface of the liquid crystal panel 11 and the first light guide plate 14, and covers the first opposite principal surface 14C of the first light guide plate 14. The reflection sheet 15 has excellent light reflectivity, and can efficiently direct light leaking from the first opposite principal surface 14C of the first light guide plate 14 toward the front side, i.e., the light output principal surface 14B of the first light guide plate. The reflection sheet 15 has an outer shape that is slightly larger than the first light guide plate 14, and is disposed so as to overlap almost the entire area of ​​the first opposite principal surface 14C.

[0024] 1, the first prism sheet 16 and the second prism sheet 17 are in the form of sheets, and their respective main surfaces are parallel to the respective main surfaces of the liquid crystal panel 11 and the first light guide plate 14. The first prism sheet 16 and the second prism sheet 17 have their main surfaces parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surfaces coincides with the Z-axis direction. The first prism sheet 16 and the second prism sheet 17 are laminated on the front side of the first light guide plate 14, and have a function of imparting a predetermined optical effect to the light emitted from the first light guide plate light output main surface 14B of the first light guide plate 14 and emitting the light.

[0025] As shown in Fig. 1, the first prism sheet 16 has a sheet-like first base material 16A and a first prism 16B provided on the main surface (light output main surface) of the front side (light output side) of the first base material 16A. The first base material 16A is made of a substantially transparent synthetic resin, specifically, a crystalline transparent resin material such as PET (polyethylene terephthalate). In manufacturing the first base material 16A, the raw material crystalline transparent resin material is stretched in a biaxial stretching process to form a sheet-like shape, which is suitable for reducing manufacturing costs. The first prism 16B is made of a substantially transparent ultraviolet curable resin material, which is a type of photocurable resin material. In manufacturing the first prism sheet 16, for example, an uncured ultraviolet-curable resin material is filled in a mold for molding, and the first base material 16A is placed on the open end of the mold so that the uncured ultraviolet-curable resin material is arranged in contact with the main surface on the front side. In this state, when ultraviolet rays are irradiated onto the ultraviolet-curable resin material through the first base material 16A, the ultraviolet-curable resin material is cured, and the first prism 16B is integrally provided with the first base material 16A. The ultraviolet-curable resin material constituting the first prism 16B is, for example, an acrylic resin such as PMMA. The refractive index of the ultraviolet-curable resin material constituting the first prism 16B is preferably in the range of 1.49 to 1.52, and most preferably 1.49.

[0026] As shown in Fig. 2, the first prism 16B is provided in a shape that protrudes from the main surface of the first base material 16A toward the front side (the side opposite to the first light guide plate 14) along the Z-axis direction. The first prism 16B has a cross-sectional shape cut along the X-axis direction that is substantially triangular (substantially mountain-shaped) and extends linearly along the Y-axis direction (second direction), and a plurality of the first prisms 16B are continuously arranged side by side along the X-axis direction (first direction) on the main surface of the first base material 16A with almost no space therebetween. The first prism 16B has a pair of inclined surfaces 16B1 and 16B2. Of the pair of inclined surfaces 16B1 and 16B2 of the first prism 16B, the one on the first LED 13 side in the X-axis direction is referred to as the first prism inclined surface 16B1, and the one on the opposite side is referred to as the second prism inclined surface 16B2. The first prism slope 16B1 has an inclination that rises from the first LED 13 side (left side in FIG. 2) in the X-axis direction of the first prism sheet 16 to the opposite side (right side in FIG. 2). Of the light incident on the first prism 16B, the light traveling mainly in a direction toward the first LED 13 in the X-axis direction hits the first prism slope 16B1 and is refracted. The second prism slope 16B2 has an inclination that rises from the opposite side from the first LED 13 side in the X-axis direction of the first prism sheet 16 (right side in FIG. 2) to the first LED 13 side (left side in FIG. 2). Of the light incident on the first prism 16B, the light traveling mainly in a direction away from the first LED 13 in the X-axis direction hits the second prism slope 16B2 and is refracted. Most of the light refracted by the pair of inclined surfaces 16B1 and 16B2 of the first prism 16B is selectively tilted in the X-axis direction and collected.

[0027] As shown in FIG. 2, the first prism 16B has a larger inclination angle (third base angle) θ6 of the first prism slope 16B1 relative to the X-axis direction than the inclination angle (fourth base angle) θ7 of the second prism slope 16B2 relative to the X-axis direction. That is, the cross-sectional shape of the first prism 16B is an asymmetric scalene triangle. Specifically, the inclination angle θ6 of the first prism slope 16B1 relative to the X-axis direction is preferably in the range of 50° to 60°, and most preferably 55°. On the other hand, the inclination angle θ7 of the second prism slope 16B2 relative to the X-axis direction is preferably in the range of 35° to 50°, and most preferably 45°. Moreover, the angle (second apex angle) θ8 formed by the pair of inclined surfaces 16B1, 16B2 in first prism 16B is preferably in the range of 70° to 95°, and most preferably 80°. The multiple first prisms 16B aligned along the Y-axis direction all have approximately the same height, width, and inclination angle of each of the inclined surfaces 16B1, 16B2 with respect to the X-axis direction, and the arrangement intervals between adjacent first prisms 16B are also approximately constant and equally spaced.

[0028] As shown in FIG. 1, the second prism sheet 17 has a sheet-like second base material 17A and a second prism 17B provided on the main surface (light output main surface) of the front side (light output side) of the second base material 17A. The second base material 17A is made of a nearly transparent synthetic resin, specifically, for example, the same crystalline transparent resin material as the first base material 16A, such as PET. The second prism 17B is made of a nearly transparent ultraviolet curable resin material, which is a type of photocurable resin material. The manufacturing method of the second prism sheet 17 is the same as the manufacturing method of the first prism sheet 16 described above. The ultraviolet curable resin material constituting the second prism 17B is, for example, an acrylic resin such as PMMA, and its refractive index is set higher than that of the material of the first prism 16B, for example, about 1.61.

[0029] As shown in FIG. 2, the second prism 17B is provided in a shape that protrudes from the main surface of the second base material 17A toward the front side (opposite side from the first prism sheet 16 side) along the Z-axis direction. The cross section of the second prism 17B cut along the X-axis direction is substantially triangular (substantially mountain-shaped) and extends linearly along the Y-axis direction, and a plurality of the second prisms 17B are continuously arranged side by side along the X-axis direction on the main surface of the second base material 17A with almost no space therebetween. The second prism 17B has a pair of inclined surfaces 17B1 and 17B2. Of the pair of inclined surfaces 17B1 and 17B2 in the second prism 17B, the one on the first LED 13 side in the X-axis direction is referred to as the third prism inclined surface 17B1, and the one on the opposite side is referred to as the fourth prism inclined surface 17B2. The third prism inclined surface 17B1 has an inclination that rises from the first LED 13 side (left side in FIG. 2) in the X-axis direction of the second prism sheet 17 toward the opposite side (right side in FIG. 2). The third prism slope 17B1 is refracted by light that mainly travels toward the first LED 13 in the X-axis direction among the light incident on the second prism 17B. The fourth prism slope 17B2 has an inclination that rises from the opposite side of the second prism sheet 17 from the first LED 13 side in the X-axis direction (the right side in FIG. 2) toward the first LED 13 side (the left side in FIG. 2). The fourth prism slope 17B2 is refracted by light that mainly travels away from the first LED 13 in the X-axis direction among the light incident on the second prism 17B. Most of the light refracted by the pair of slopes 17B1 and 17B2 of the second prism 17B is selectively raised in the X-axis direction and condensed.

[0030] As shown in FIG. 2, the second prism 17B has the same inclination angle (fifth base angle) θ9 of the third prism slope 17B1 with respect to the X-axis direction and the same inclination angle (sixth base angle) θ10 of the fourth prism slope 17B2 with respect to the X-axis direction. That is, the second prism 17B has a symmetrical cross-sectional shape of an isosceles triangle. In addition, the inclination angles θ9 and θ10 of the third prism slope 17B1 and the fourth prism slope 17B2 with respect to the X-axis direction are smaller than the inclination angle θ6 of the first prism slope 16B1 with respect to the X-axis direction. Specifically, the inclination angles θ9 and θ10 of the third prism slope 17B1 and the fourth prism slope 17B2 with respect to the X-axis direction are preferably in the range of 40° to 50°, and most preferably 45°. In contrast, the angle (third apex angle) θ11 between the pair of inclined surfaces 17B1, 17B2 in the second prism 17B is preferably in the range of 80° to 100°, and is most preferably 90°, i.e., a right angle. The second prisms 17B arranged along the Y-axis direction are all substantially identical in height, width, and inclination angle of each surface 17B1, 17B2 with respect to the X-axis direction, and the arrangement intervals between adjacent second prisms 17B are also substantially constant and arranged at equal intervals. In addition, it is preferable that the height and arrangement interval of the second prism 17B are different from those of the first prism 16B, respectively, in order to suppress the occurrence of interference fringes called moire.

[0031] The first prism sheet 16 and the second prism sheet 17 configured as described above provide the following actions and effects. That is, most of the light emitted from the first light guide plate light-emitting main surface 14B of the first light guide plate 14 and incident on the first prism sheet 16 is refracted by hitting the second prism slope 16B2 of the first prism 16B, and is either emitted while being raised or directed toward the first prism slope 16B1. Here, the inclination angle θ6 of the first prism 16B with respect to the X-axis direction is larger than the inclination angle θ7 of the second prism 17B, so that the light incident on the first prism sheet 16 is less likely to hit the first prism slope 16B1 compared to a hypothetical case in which the angles are the same or the magnitudes of the angles are reversed. When the incident light of the first prism sheet 16 strikes the first prism inclined surface 16B1 of the first prism 16B, it tends to be emitted as side lobe light (stray light) without being raised when it leaves the first prism 16B. Therefore, if it becomes difficult for the incident light of the first prism sheet 16 to directly strike the first prism inclined surface 16B1 of the first prism 16B, the generation of side lobe light is suppressed, and as a result, the light utilization efficiency is improved.

[0032] Most of the light that leaves the first prism sheet 16 and enters the second prism sheet 17 is refracted by the fourth prism slope 17B2 of the second prism 17B, and either leaves while rising or travels toward the third prism slope 17B1. Since the inclination angle θ7 of the second prism 17B relative to the X-axis direction is smaller than the inclination angle θ6 of the first prism 16B, the light that is refracted by the fourth prism slope 17B2 and travels toward the third prism slope 17B1 is more likely to be returned to the first prism sheet 16 side by the third prism slope 17B1, compared to a case where the angles are the same or the magnitudes of the angles are reversed. As a result, the amount of light returned from the second prism sheet 17 to the first prism sheet 16 side (hereinafter referred to as retrolight) increases. This retroreflected light is reflected within the backlight device 12 and reaches the second prism sheet 17 again, where it is raised by one of the pair of inclined faces 17B1, 17B2 of the second prism 17B before being emitted, improving the light utilization efficiency. Since the optical path of the retroreflected light from the second prism sheet 17 to the emission is complicated, the rising angle given by the second prism 17B is also diversified, thereby improving the viewing angle characteristics. As a result, the viewing angle characteristics and brightness are improved.

[0033] Next, the detailed structure of the first light guide plate 14 will be described. As shown in FIG. 2 and FIG. 3, the first light guide plate 14 is provided with a first light guide plate lens 21, a second light guide plate lens 22, and a third light guide plate lens 23. As shown in FIG. 3, the first light guide plate lens 21 is provided on the first light guide plate light output main surface 14B of the first light guide plate 14. The first light guide plate lens 21 extends along the X-axis direction, and a plurality of first light guide plate lenses 21 are arranged side by side along the Y-axis direction. In this embodiment, the first light guide plate lens 21 is a so-called lenticular lens. The first light guide plate lens 21 is a convex lens that protrudes from the first light guide plate light output main surface 14B to the front side. In detail, the first light guide plate lens 21 has a semicircular cross section cut along the Y-axis direction and a semicircular shape that extends linearly along the X-axis direction, and its surface is a first arc-shaped surface 21A. When the angle that the tangent at the base end of first arcuate surface 21A makes with respect to the Y-axis direction is defined as the "contact angle," the contact angle of first light guide plate lens 21 is, for example, about 62°. The contact angles, width dimensions (arrangement intervals), and height dimensions of the multiple first light guide plate lenses 21 aligned along the Y-axis direction are all substantially the same. To provide first light guide plate lens 21 configured as described above integrally with first light guide plate 14, for example, first light guide plate 14 may be manufactured by injection molding, and a transfer shape for transferring first light guide plate lens 21 may be formed in advance on a molding surface of the molding die for molding first light guide plate light output main surface 14B.

[0034] As shown in FIG. 3, the second light guide plate lens 22 is provided on the first opposite principal surface 14C of the first light guide plate 14. The second light guide plate lens 22 extends along the X-axis direction, and a plurality of second light guide plate lenses 22 are arranged side by side along the Y-axis direction. In this embodiment, the second light guide plate lens 22 is a convex prism protruding from the first opposite principal surface 14C to the rear side. More specifically, the second light guide plate lens 22 has a cross-sectional shape cut along the Y-axis direction that is substantially triangular (substantially mountain-shaped) and extends linearly along the X-axis direction. The second light guide plate lens 22 has a width dimension (dimension in the Y-axis direction) that is constant over the entire length in the X-axis direction. The second light guide plate lens 22 has a cross-sectional shape that is substantially an isosceles triangle, and has a pair of first light guide plate inclined surfaces 22A. The apex angle of the second light guide plate lens 22 is preferably an obtuse angle (an angle exceeding 90°), specifically, in the range of 100° to 150°, and most preferably 140°. The second light guide plate lenses 22 arranged along the Y-axis direction all have approximately the same apex angle, width (arrangement interval), and height. In this embodiment, the arrangement interval of the second light guide plate lenses 22 is greater than the arrangement interval of the first light guide plate lenses 21. To provide the second light guide plate lenses 22 configured in this manner integrally with the first light guide plate 14, for example, the first light guide plate 14 may be manufactured by injection molding, and a transfer shape for transferring the second light guide plate lenses 22 may be formed in advance on a molding surface of the molding die for molding the first light guide plate light-emitting main surface 14B.

[0035] According to the first light guide plate 14 having such a configuration, the light propagating in the first light guide plate 14 is repeatedly reflected by hitting the first arc-shaped surfaces 21A of the first light guide plate lenses 21 on the first light guide plate light output main surface 14B side in the Z-axis direction, and proceeds in a zigzag manner approximately along the X-axis direction, as shown in Fig. 3. On the other hand, the light propagating in the first light guide plate 14 is repeatedly reflected by hitting the pair of first light guide plate inclined surfaces 22A of the second light guide plate lenses 22 on the first opposite main surface 14C side in the Z-axis direction, and proceeds in a zigzag manner approximately along the X-axis direction. As a result, the spread of the light propagating in the first light guide plate 14 in the Y-axis direction is limited, so that unevenness in brightness is less likely to occur between the vicinity of the first LED 13 and its surroundings in the Y-axis direction.

[0036] As shown in FIG. 2, the third light guide plate lens 23 is provided on the first opposite principal surface 14C of the first light guide plate 14. A plurality of the third light guide plate lenses 23 are arranged in a line at intervals along the X-axis direction. The third light guide plate lenses 23 protrude from the first opposite principal surface 14C toward the rear side along the Z-axis direction. The third light guide plate lens 23 has a second light guide plate inclined surface 23A arranged on the opposite side to the first LED 13 side in the X-axis direction (the right side in FIG. 2), a third light guide plate inclined surface 23B arranged on the first LED 13 side in the X-axis direction (the left side in FIG. 2), and a fourth light guide plate inclined surface 23C located between the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B. The second light guide plate inclined surface 23A has an inclination that rises from the first LED 13 side in the X-axis direction of the first light guide plate 14 (the left side in FIG. 2) toward the opposite side (the right side in FIG. 2). The third light guide plate inclined surface 23B has an inclination that rises from the side opposite to the first LED 13 side in the X-axis direction in first light guide plate 14 (the right side in FIG. 2) toward the first LED 13 side (the left side in FIG. 2). The fourth light guide plate inclined surface 23C has an inclination that rises from the first LED 13 side (the left side in FIG. 2) in the X-axis direction in first light guide plate 14 toward the opposite side (the right side in FIG. 2).

[0037] As shown in FIG. 2, the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B can reflect the light propagating in the first light guide plate 14 and raise it toward the front side at an angle close to the Z-axis direction, thereby promoting emission from the first light guide plate light output main surface 14B. In detail, the second light guide plate inclined surface 23A mainly functions to reflect and raise the light traveling away from the first LED 13 in the X-axis direction. On the other hand, the third light guide plate inclined surface 23B mainly functions to reflect and raise the light traveling toward the first LED 13 in the X-axis direction. The second light guide plate inclined surface 23A has a gradient such that the distance from the first light guide plate light output main surface 14B (a portion where the third light guide plate lens 23 is not installed) becomes smaller as it moves away from the first LED 13 in the X-axis direction. The second light guide plate inclined surface 23A has an inclination angle with respect to the X-axis direction of about 8°, for example. Third light guide plate slope 23B has a gradient in which the distance from first light guide plate main light output surface 14B increases in the X-axis direction as it moves away from first LED 13, that is, a gradient opposite to that of second light guide plate slope 23A. Third light guide plate slope 23B has a steep slope with an inclination angle of, for example, about 80° with respect to the X-axis direction that is close to vertical and larger than the inclination angle of second light guide plate slope 23A.

[0038] 2, 4, and 5, the multiple third light guide plate lenses 23 aligned along the X-axis direction are designed so that their height dimension (dimension in the Z-axis direction) and length dimension (dimension in the X-axis direction) increase as they move away from the first LED 13 in the X-axis direction. More specifically, when a third light guide plate lens 23 close to the first LED 13 in the X-axis direction is compared with a third light guide plate lens 23 far from the first LED 13 in the X-axis direction, the latter has larger areas of the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B than the former. As a result, on the side closer to the first LED 13 in the X-axis direction, light is less likely to strike the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B of the third light guide plate lens 23, suppressing light output, but on the side farther from the first LED 13 in the X-axis direction, light is more likely to strike the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B of the third light guide plate lens 23, promoting light output. As a result, the amount of light output from the first light guide plate light output main surface 14B is uniform between the first LED 13 side and the opposite side in the X-axis direction.

[0039] As shown in FIG. 2, the end of the fourth light guide plate inclined surface 23C on the opposite side to the first LED 13 side in the X-axis direction (the right side in FIG. 2) is connected to the second light guide plate inclined surface 23A, and the end of the fourth light guide plate inclined surface 23C on the first LED 13 side in the X-axis direction (the left side in FIG. 2) is connected to the third light guide plate inclined surface 23B. The fourth light guide plate inclined surface 23C has a gradient such that the distance from the first light guide plate light output main surface 14B (the portion where the third light guide plate lens 23 is not installed) increases as it moves away from the first LED 13 in the X-axis direction. In other words, the fourth light guide plate inclined surface 23C has the same gradient as the third light guide plate inclined surface 23B. The fourth light guide plate inclined surface 23C has an inclination angle with respect to the X-axis direction of, for example, about 1.4°, which is smaller than the inclination angles of the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B. The fourth light guide plate inclined surface 23C having such a configuration reflects the light traveling in the first light guide plate 14 so as to move away from the first LED 13, thereby directing the light toward the first light guide plate light output main surface 14B, but the angle of incidence of the light with respect to the first light guide plate light output main surface 14B does not exceed the critical angle. Therefore, the light is totally reflected by the first light guide plate light output main surface 14B and is guided away from the first LED 13. This makes it difficult for the light emitted from the first light guide plate light output main surface 14B to be biased toward the first LED 13 in the X-axis direction. As described above, the first light guide plate 14 is configured so that the inclination angle with respect to the X-axis direction increases in the order of the fourth light guide plate inclined surface 23C, the second light guide plate inclined surface 23A, and the third light guide plate inclined surface 23B. Further, the multiple fourth light guide plate inclined surfaces 23C aligned along the X-axis direction are designed to have a smaller length dimension in the X-axis direction as they move away from the first LED 13. This is because the length dimension of third light guide plate lens 23 increases as it moves away from first LED 13 in the X-axis direction, and the range occupied by third light guide plate lens 23 increases.

[0040] The third light guide plate lens 23 configured as above is disposed between two adjacent second light guide plate lenses 22 in the Y-axis direction, as shown in Fig. 3 to Fig. 5. Therefore, the third light guide plate lenses 23 are disposed so as to be alternately arranged with the second light guide plate lenses 22 in the Y-axis direction. The third light guide plate lenses 23 have a maximum protruding dimension (height dimension) from the first opposite principal surface 14C that is smaller than the same protruding dimension of the second light guide plate lenses 22. Therefore, even the third light guide plate lens 23 located farthest from the first LED 13 in the X-axis direction does not protrude further back than the second light guide plate lenses 22.

[0041] Incidentally, the in-vehicle liquid crystal display device 10 may be installed, for example, in front of the passenger seat of a passenger vehicle. In this case, for example, while the passenger vehicle is running, it may be required to limit the viewing angle so that the display image of the liquid crystal display device 10 is viewable from the passenger seat but not viewable from the driver's seat. Furthermore, for example, while the passenger vehicle is stopped, it may be required not to limit the viewing angle so that the display image of the liquid crystal display device 10 is viewable from both the passenger seat and the driver's seat. Note that the in-vehicle liquid crystal display device 10 is installed in a position in which the X-axis direction is approximately the same as the horizontal direction and the Y-axis direction is parallel to the vertical direction. In order to meet such a demand, the backlight device 12 according to this embodiment includes at least a first louver (first sheet) 18 arranged on the front side of the second prism sheet 17, a second LED (second light source) 24, and a second light guide plate 25 arranged on the front side of the first louver 18, in addition to the above-mentioned configurations, as shown in FIG. 1. Furthermore, in order to prevent reflection on the windshield of the vehicle, the backlight device 12 according to this embodiment includes a second louver 30 disposed on the front side of the second light guide plate 25. The second louver 30 will be described later.

[0042] The configuration of the first louver 18 will be described with reference to FIG. 1 and FIG. 2. As shown in FIG. 1, the first louver 18 has a sheet-like shape with its main surface parallel to the main surfaces of the liquid crystal panel 11 and the first light guide plate 14. The main surface of the first louver 18 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface coincides with the Z-axis direction. The first louver 18 has a function of limiting the output angle range of light in the X-axis direction. The first louver 18 has a first light-entering main surface (third main surface) 18A on the back side and a first light-exiting main surface (fourth main surface) 18B on the front side. The first light-entering main surface 18A faces the main surface of the front side (light-exiting side) of the second prism sheet 17. The first light-exiting main surface 18B faces a second opposite main surface 25C of the second light guide plate 25 described later.

[0043] As shown in FIG. 2, the first louver 18 has a first light-shielding portion 18C that blocks light and a first light-transmitting portion 18D that transmits light. The first light-shielding portion 18C is made of a light-shielding resin material (light-shielding material) that is, for example, black and blocks light. The first light-shielding portion 18C is in a layered shape extending along the Y-axis direction and the Z-axis direction, and a plurality of the first light-transmitting portions 18C are arranged side by side at intervals in the X-axis direction. The first light-transmitting portion 18D is made of a light-transmitting resin material (light-transmitting material) that is almost transparent and transmits light. The first light-transmitting portion 18D is in a layered shape extending along the Y-axis direction and the Z-axis direction, and a plurality of the first light-transmitting portions 18D are arranged side by side at intervals in the X-axis direction. The plurality of first light-shielding portions 18C and first light-transmitting portions 18D are arranged side by side alternately and repeatedly in the X-axis direction. Therefore, a first light transmitting portion 18D is interposed between two adjacent first light shielding portions 18C spaced apart in the X-axis direction, and a first light shielding portion 18C is interposed between two adjacent first light transmitting portions 18D spaced apart in the X-axis direction. Light incident on the first light entering main surface 18A of the first louver 18 passes through the first light transmitting portion 18D arranged between two adjacent first light shielding portions 18C in the X-axis direction, and is emitted from the first light emitting main surface 18B. The emission angle in the X-axis direction of the light emitted from the first light emitting main surface 18B is limited by the two adjacent first light shielding portions 18C in the X-axis direction. Note that the emission angle of the light emitted from the first light emitting main surface 18B is not limited by the first louver 18 in the Y-axis direction. The emission angle range in the X-axis direction of the light emitted from the first light-emitting main surface 18B is defined by two straight lines that diagonally connect the ends in the Z-axis direction of the two first light-shielding portions 18C that sandwich the first light-transmitting portion 18D. The emission angle range in the X-axis direction of the light transmitted through the first light-transmitting portion 18D changes according to the ratio of the width W1 and height H1 of the first light-transmitting portion 18D. The first louver 18 has a pair of sheet carriers that sandwich and support the first light-shielding portions 18C and the first light-transmitting portions 18D from the front and back sides. The sheet carriers are made of a translucent resin material that is almost transparent and transmits light. The sheet carriers extend over the entire area of ​​the first louver 18 and hold the first light-shielding portions 18C and the first light-transmitting portions 18D collectively.

[0044] Specifically, as shown in FIG. 2, the ratio of the width W1 of the first light-transmitting portion 18D divided by the height H1 of the first louver 18 is equal to "tan 10°". In this way, the maximum absolute value of the angle that the light passing through the first light-transmitting portion 18D makes with respect to the Z-axis direction is 10°. As compared to the case where the ratio of the width of the first light-transmitting portion 18D divided by the height is larger than "tan 10°", the emission angle range of the light emitted from the backlight device 12 is sufficiently narrowed. This is suitable for restricting the viewing angle so that the display image of the liquid crystal display device 10 is visible from the passenger seat while the display image of the liquid crystal display device 10 is not visible from the driver's seat. Also, as compared to the case where the ratio of the width of the first light-transmitting portion 18D divided by the height is smaller than "tan 10°", the amount of light blocked by the first light-shielding portion 18C is reduced, improving the light utilization efficiency.

[0045] The configuration of the second LED 24 and the second light guide plate 25 will be described with appropriate use of FIG. 1 to FIG. 3, FIG. 6, and FIG. 7. FIG. 6 is an enlarged cross-sectional view of the second light guide plate 25, one of the components of the backlight device 12. FIG. 7 is a bottom view showing the main surface on the back side of the second light guide plate 25. As shown in FIG. 1, the second LED 24 is substantially block-shaped, and one of a pair of surfaces along the Y-axis direction and the Z-axis direction is the second light-emitting surface 24A that emits light. The second LED 24 is arranged in a line at intervals along the Y-axis direction. The second LED 24 is mounted on an LED board. The second LED 24 is configured by sealing an LED chip on a board portion mounted on the LED board with a sealing material. The LED chip provided in the second LED 24 emits a single color light, for example, blue light. A phosphor is dispersed and blended in the sealing material provided in the second LED 24. The phosphor contained in the encapsulant includes a yellow phosphor, a green phosphor, a red phosphor, etc. The second LED 24 including such an LED chip and encapsulant emits white light as a whole.

[0046] The second light guide plate 25 is made of a synthetic resin material (e.g., acrylic resin such as PMMA) that has a refractive index sufficiently higher than that of air and is almost transparent. As shown in FIG. 1, the second light guide plate 25 is plate-shaped, and its main surface is parallel to the main surface of the liquid crystal panel 11, etc. The main surface of the second light guide plate 25 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface coincides with the Z-axis direction. The second light guide plate 25 is arranged along the X-axis direction (first direction) with respect to the second LED 24, and is arranged along the Z-axis direction with respect to the liquid crystal panel 11 and the first louver 18, etc. The second light guide plate 25 is arranged on the other side in the X-axis direction (left side in FIG. 1) with respect to the second LED 24. In other words, the positional relationship between the second light guide plate 25 and the second LED 24 in the X-axis direction is opposite to the positional relationship between the first light guide plate 14 and the first LED 13 in the X-axis direction. In this way, since the first LED 13 and the second LED 24 are disposed in a dispersed manner in the X-axis direction, heat is unlikely to build up even if the first LED 13 and the second LED 24 are each turned on.

[0047] As shown in FIG. 1, one end surface of the outer peripheral end surface of the second light guide plate 25 is a second light-entering end surface (second end surface) 25A facing the second light-emitting surface 24A of the second LED 24. The second light-entering end surface 25A is a surface parallel to the second light-emitting surface 24A of the second LED 24, and the light emitted from the second light-emitting surface 24A is incident on the second light guide plate 25. Therefore, the second LED 24 is arranged only on one side in the X-axis direction in the second light guide plate 25, and the second light guide plate 25 and the second LED 24 constitute a one-side light-entering type backlight unit. Of the pair of main surfaces of the second light guide plate 25, the main surface on the front side facing the second louver 30 described later is the second light guide plate light-exiting main surface (fifth main surface) 25B that emits light guided inside. Of the pair of main surfaces in the second light guide plate 25, the rear main surface facing the first louver 18 is a second opposite main surface (sixth main surface) 25C located on the opposite side to the second light guide plate light output main surface 25B. The second light guide plate 25 is arranged such that the second opposite main surface 25C faces the first light output main surface 18B of the first louver 18 in the Z-axis direction. The second light guide plate 25 introduces light emitted from the second LEDs 24 toward the second light guide plate 25 from the second light input end surface 25A, and propagates the light inside, and then can emit the light by raising it from the second light guide plate light output main surface 25B along the Z-axis direction toward the liquid crystal panel 11 on the front side (light output side). In addition, second light guide plate 25 can introduce light emitted from first louver 18 from second opposite principal surface 25C, and emit the light from second light guide plate light exit principal surface 25B toward second louver 30 (liquid crystal panel 11) on the front side. The normal direction of second light incident end surface 25A coincides with the X-axis direction (the arrangement direction of second LED 24 and second light guide plate 25).

[0048] As shown in FIG. 2 and FIG. 3, the second light guide plate 25 is provided with a fourth light guide plate lens 26, a fifth light guide plate lens 27, a sixth light guide plate lens (first lens) 28, and a seventh light guide plate lens (second lens) 29. As shown in FIG. 3, the fourth light guide plate lens 26 is provided on the second light guide plate light output main surface 25B of the second light guide plate 25. The fourth light guide plate lens 26 extends along the X-axis direction, and a plurality of fourth light guide plate lenses 26 are arranged side by side along the Y-axis direction. In this embodiment, the fourth light guide plate lens 26 is a so-called lenticular lens. The fourth light guide plate lens 26 is a convex lens that protrudes from the second light guide plate light output main surface 25B to the front side. In detail, the fourth light guide plate lens 26 has a semicircular cross section cut along the Y-axis direction and a semicircular shape that extends linearly along the X-axis direction, and its surface is a second arc-shaped surface 26A. When the angle that the tangent at the base end of the second arcuate surface 26A makes with respect to the Y-axis direction is defined as the "contact angle," the contact angle of the fourth light guide plate lens 26 is, for example, about 30°. The contact angles, width dimensions (arrangement intervals), and height dimensions of the multiple fourth light guide plate lenses 26 aligned along the Y-axis direction are all substantially the same. To provide the fourth light guide plate lens 26 configured as described above integrally with the second light guide plate 25, for example, the second light guide plate 25 may be manufactured by injection molding, and a transfer shape for transferring the fourth light guide plate lens 26 may be formed in advance on a molding surface of the molding die for molding the second light guide plate light output main surface 25B.

[0049] As shown in FIG. 3, the fifth light guide plate lens 27 is provided on the second opposite principal surface 25C of the second light guide plate 25. The fifth light guide plate lens 27 extends along the X-axis direction, and a plurality of fifth light guide plate lenses 27 are arranged side by side along the Y-axis direction. In this embodiment, the fifth light guide plate lens 27 is a convex prism protruding from the second opposite principal surface 25C to the rear side. More specifically, the fifth light guide plate lens 27 has a cross-sectional shape cut along the Y-axis direction that is substantially triangular (substantially mountain-shaped) and extends linearly along the X-axis direction. The fifth light guide plate lens 27 has a width dimension (dimension in the Y-axis direction) that is constant over the entire length in the X-axis direction. The fifth light guide plate lens 27 has a cross-sectional shape that is substantially an isosceles triangle, and has a pair of fifth light guide plate inclined surfaces 27A. The apex angle of the fifth light guide plate lens 27 is preferably an obtuse angle (an angle exceeding 90°), specifically, in the range of 100° to 150°, and most preferably 140°. The fifth light guide plate lens 27 has a width dimension in the Y-axis direction of, for example, about 0.126 mm. The arrangement interval of the fifth light guide plate lenses 27 arranged along the Y-axis direction (the interval between the vertices of two fifth light guide plate lenses 27 arranged along the Y-axis direction) is, for example, about 0.175 mm. The fifth light guide plate lenses 27 arranged along the Y-axis direction all have substantially the same apex angle, width dimension (arrangement interval), and height dimension. In this embodiment, the arrangement interval of the fifth light guide plate lenses 27 is larger than the arrangement interval of the fourth light guide plate lenses 26. To integrally provide the fifth light guide plate lens 27 having such a configuration with the second light guide plate 25, for example, the second light guide plate 25 is manufactured by injection molding, and a transfer shape for transferring the fifth light guide plate lens 27 may be formed in advance on a molding surface for molding the second opposite principal surface 25C of the molding die.

[0050] The sixth light guide plate lens 28 and the seventh light guide plate lens 29 are provided on the second opposite principal surface 25C of the second light guide plate 25, as shown in FIG. 2. The sixth light guide plate lens 28 and the seventh light guide plate lens 29 protrude from the second opposite principal surface 25C toward the rear side along the Z-axis direction. The sixth light guide plate lens 28 and the seventh light guide plate lens 29 are arranged alternately and repeatedly at intervals along the X-axis direction. The sixth light guide plate lens 28 has a first inclined surface 28A arranged on the opposite side to the second LED 24 side in the X-axis direction (left side in FIG. 2). The seventh light guide plate lens 29 has a second inclined surface 29A arranged on the opposite side to the second LED 24 side in the X-axis direction. Both the first inclined surface 28A and the second inclined surface 29A have an inclination that rises from the second LED 24 side (right side in FIG. 2) in the X-axis direction of the second light guide plate 25 toward the opposite side (left side in FIG. 2). First inclined surface 28A has a gradient such that the thickness of sixth light guide plate lens 28 is continuously and gradually reduced in the X-axis direction from the second LED 24 side toward the opposite side. Similarly, second inclined surface 29A has a gradient such that the thickness of seventh light guide plate lens 29 is continuously and gradually reduced in the X-axis direction from the second LED 24 side toward the opposite side.

[0051] As shown in FIG. 2, the sixth light guide plate lens 28 and the seventh light guide plate lens 29 each have a third inclined surface 31 disposed on the second LED 24 side in the X-axis direction. The third inclined surface 31 has an inclination that rises from the side opposite to the second LED 24 side in the X-axis direction in the second light guide plate 25 toward the second LED 24 side. The third inclined surface 31 includes a fourth inclined surface 28B provided on the sixth light guide plate lens 28 and a fifth inclined surface 29B provided on the seventh light guide plate lens 29. The fourth inclined surface 28B is disposed at a position on the sixth light guide plate lens 28 toward the second LED 24 side in the X-axis direction with a gap therebetween with respect to the first inclined surface 28A. The fourth inclined surface 28B provided on the sixth light guide plate lens 28 is disposed opposite the second inclined surface 29A provided on the seventh light guide plate lens 29 with a gap therebetween. The fourth inclined surface 28B has a gradient such that the thickness of the sixth light guide plate lens 28 increases continuously and gradually in the X-axis direction from the second LED 24 side toward the opposite side. The fifth inclined surface 29B is disposed at a position on the seventh light guide plate lens 29 that is spaced apart from the second inclined surface 29A toward the second LED 24 side in the X-axis direction. The fifth inclined surface 29B of the seventh light guide plate lens 29 is disposed facing the first inclined surface 28A of the sixth light guide plate lens 28 with a gap therebetween. The fifth inclined surface 29B has a gradient such that the thickness of the seventh light guide plate lens 29 increases continuously and gradually in the X-axis direction from the second LED 24 side toward the opposite side.

[0052] As shown in FIG. 2, the sixth light guide plate lens 28 has a first plane 28C located between the first inclined surface 28A and the fourth inclined surface 28B. The seventh light guide plate lens 29 has a second plane 29C located between the second inclined surface 29A and the fifth inclined surface 29B. The first plane 28C and the second plane 29C are both parallel to the X-axis direction and the Y-axis direction. In addition, on the second opposite main surface 25C of the second light guide plate 25, a third plane 32 is provided between the sixth light guide plate lens 28 and the seventh light guide plate lens 29 adjacent to each other with a gap in the X-axis direction. The third plane 32 is a plane parallel to the X-axis direction and the Y-axis direction. A plurality of third planes 32 are arranged with a gap in the X-axis direction on the second opposite main surface 25C of the second light guide plate 25. Between two adjacent third flat surfaces 32 spaced apart in the X-axis direction, there is interposed a sixth light guide plate lens 28 or a seventh light guide plate lens 29. The detailed configurations, functions and effects of each of these inclined surfaces 28A, 29A, 31 (28B, 29B) and each of the flat surfaces 28C, 29C, 32 will be described in detail later.

[0053] Next, the configuration of the second louver 30 will be described with reference to FIG. 1 and FIG. 3. As shown in FIG. 1, the second louver 30 has a sheet-like shape with its main surface parallel to the main surfaces of the liquid crystal panel 11 and the second light guide plate 25. The main surface of the second louver 30 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface coincides with the Z-axis direction. The second louver 30 has a function of limiting the output angle range of light in the Y-axis direction. The second louver 30 has a second light-entering main surface 30A on the back side and a second light-exiting main surface 30B on the front side. The second light-entering main surface 30A faces the second light-exiting main surface 25B of the second light guide plate 25. The second light-exiting main surface 30B faces the main surface on the back side of the liquid crystal panel 11. That is, the second louver 30 is disposed on the front side of the second light guide plate 25 and on the back side of the liquid crystal panel 11.

[0054] As shown in FIG. 3, the second louver 30 has a second light-shielding portion 30C that blocks light and a second light-transmitting portion 30D that transmits light. The second light-shielding portion 30C is made of a light-shielding resin material (light-shielding material) that is, for example, black and blocks light. The second light-shielding portion 30C is layered and extends along the X-axis direction and the Z-axis direction, and a plurality of the second light-transmitting portions 30C are arranged side by side at intervals in the Y-axis direction. The second light-transmitting portion 30D is made of a light-transmitting resin material (light-transmitting material) that is almost transparent and transmits light. The second light-transmitting portion 30D is layered and extends along the X-axis direction and the Z-axis direction, and a plurality of the second light-transmitting portions 30D are arranged side by side at intervals in the Y-axis direction. A plurality of the second light-shielding portions 30C and the second light-transmitting portions 30D are arranged side by side in an alternating manner in the Y-axis direction. Therefore, a second light transmitting portion 30D is interposed between two adjacent second light shielding portions 30C spaced apart in the Y-axis direction, and a second light shielding portion 30C is interposed between two adjacent second light transmitting portions 30D spaced apart in the Y-axis direction. Light incident on the second light entering principal surface 30A of the second louver 30 passes through the second light transmitting portion 30D arranged between two adjacent second light shielding portions 30C in the Y-axis direction, and is emitted from the second light emitting principal surface 30B. The emission angle in the Y-axis direction of the light emitted from the second light emitting principal surface 30B is limited by the two adjacent second light shielding portions 30C in the Y-axis direction. Note that the emission angle of the light emitted from the second light emitting principal surface 30B is not limited by the second louver 30 in the X-axis direction. The range of the emission angle in the Y-axis direction of the light emitted from the second light-emitting main surface 30B is defined by two straight lines that diagonally connect the ends in the Z-axis direction of the two second light-shielding parts 30C that sandwich the second light-transmitting part 30D. The range of the emission angle in the Y-axis direction of the light transmitted through the second light-transmitting part 30D changes according to the ratio of the width to the height of the second light-transmitting part 30D. In the second louver 30, the ratio of the width of the second light-transmitting part 30D divided by the height is greater than the ratio of the width W1 of the first light-transmitting part divided by the height H1 in the first louver 18. Specifically, in the second louver 30, the ratio of the width W of the second light-transmitting part 30D divided by the height is, for example, "tan 55°" or more. In addition, the second louver 30 has a pair of sheet carriers that sandwich and support the second light-shielding parts 30C and the second light-transmitting parts 30D from the front side and the back side. The sheet carrier is made of a translucent resin material that is almost transparent and transmits light.The sheet carrier extends over the entire area of ​​the second louver 30 and collectively holds the plurality of second light-shielding portions 30C and the plurality of second light-transmitting portions 30D.

[0055] When the liquid crystal display device 10 is installed in a passenger vehicle, the use of such second louvers 30 can limit the emission angle range of light emitted from the liquid crystal panel 11 in the vertical direction. This makes it possible to reduce the occurrence of reflection of the displayed image on the windshield.

[0056] Next, the first inclined surface 28A and the second inclined surface 29A of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 will be described in detail. First, as shown in FIG. 6, the angle that the first inclined surface 28A of the sixth light guide plate lens 28 makes with respect to the X-axis direction is defined as a "first angle θ1", and the angle that the second inclined surface 29A of the seventh light guide plate lens 29 makes with respect to the X-axis direction is defined as a "second angle θ2". The first inclined surface 28A has a first angle θ1 that is greater than 27° and smaller than the second angle θ2. The second inclined surface 29A has a second angle θ2 that is greater than the first angle θ1 and smaller than 58°. In this embodiment, specifically, the first inclined surface 28A has a first angle θ1 of, for example, about 32°. The second inclined surface 29A has a second angle θ2 of, for example, about 54°.

[0057] According to this configuration, as shown in FIG. 6, the light emitted from the second LED 24 and incident on the second light-entering end surface 25A of the second light guide plate 25 hits the first inclined surface 28A and the second inclined surface 29A while propagating through the second light guide plate 25, and is mostly reflected there. The light reflected by the first inclined surface 28A and the second inclined surface 29A is raised toward the front side, and is encouraged to be emitted from the second light guide plate light-emitting main surface 25B. Here, the traveling direction of the light reflected by the first inclined surface 28A and the second inclined surface 29A depends on the angle of the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction. Specifically, for example, when the angle that either the first inclined surface 28A or the second inclined surface 29A makes with respect to the X-axis direction is set to 45°, the reflected light is raised so as to travel along the Z-axis direction (the normal direction of the second light guide plate light-emitting main surface 25B, the front direction). For example, when the angle that either the first inclined surface 28A or the second inclined surface 29A makes with respect to the X-axis direction is less than 45°, the reflected light tends to easily travel toward the side opposite the second LED 24 side in the X-axis direction (the left side in FIG. 6) with respect to the Z-axis direction. For example, when the angle that either the first inclined surface 28A or the second inclined surface 29A makes with respect to the X-axis direction is more than 45°, the reflected light tends to easily travel toward the second LED 24 side in the X-axis direction (the right side in FIG. 6) with respect to the Z-axis direction.

[0058] In this embodiment, the first angle θ1 is set to about 32° and is less than 45°, so that the light reflected by the first inclined surface 28A tends to travel toward the opposite side of the second LED 24 side in the X-axis direction (the side going away from the second LED 24) when it is emitted from the second light guide plate light emitting main surface 25B with respect to the Z-axis direction. On the other hand, the second angle θ2 is set to about 54° and is more than 45°, so that the light reflected by the second inclined surface 29A tends to travel toward the second LED 24 side (the side approaching the second LED 24) in the X-axis direction with respect to the Z-axis direction when it is emitted from the second light guide plate light emitting main surface 25B. Therefore, when the second LED 24 is turned on, it is possible to supply emitted light with a luminance angle distribution in which the peak luminance of the emitted light is unevenly distributed on the opposite side of the second LED 24 side in the X-axis direction and on the second LED 24 side in the X-axis direction. This not only ensures sufficient brightness of the emitted light in a direction inclined with respect to the Z-axis direction, but also widens the emission angle range of the emitted light, which is preferable for achieving a wide viewing angle.

[0059] The closer the first angle θ1 and the second angle θ2 are to 45°, the more the reflected light from the first inclined surface 28A and the second inclined surface 29A tends to travel in a direction closer to the Z-axis direction. Specifically, in this embodiment, the first angle θ1 of the first inclined surface 28A is greater than 27° and closer to 45°, so that when the light reflected from the first inclined surface 28A is emitted from the second light guide plate light output main surface 25B, it travels in a direction closer to the Z-axis direction compared to when the first angle θ1 is 27° or less. On the other hand, the second inclined surface 29A has a second angle θ2 smaller than 58° and closer to 45°, so that when the light reflected from the second inclined surface 29A is emitted from the second light guide plate light output main surface 25B, it travels in a direction closer to the Z-axis direction compared to when the second angle θ2 is 58° or more. Therefore, when both the first LED 13 and the second LED 24 are turned on, the luminance angle distribution of the light emitted from the second light guide plate light output principal surface 25B tends to have lower luminance toward the wider angle side in the Z-axis direction, making it difficult for localized drops in luminance to occur. As a result, it is possible to achieve a wider viewing angle while making it difficult for luminance unevenness to occur.

[0060] According to this embodiment, for example, while the passenger car is running, as shown in FIG. 1, the first LED 13 is turned on and the second LED 24 is turned off. Then, the angle range of the light emitted from the second light guide plate light output main surface 25B of the second light guide plate 25 is limited by the first light blocking portion 18C of the first louver 18, so that it is difficult for the light to be emitted outside the limited angle range. Therefore, if the first LED 13 is turned on and the second LED 24 is turned off, the backlight device 12 selectively emits light within the limited angle range, so that the display image of the liquid crystal display device 10 can be viewed from the passenger seat, but the display image of the liquid crystal display device 10 cannot be viewed from the driver's seat. On the other hand, for example, while the passenger car is stopped, both the first LED 13 and the second LED 24 are turned on. Then, the light emitted from the second light guide plate light output main surface 25B of the second light guide plate 25 includes the light of the first LED 13 whose angle range is limited by the first louver 18, and the light of the second LED 24 whose peak brightness has a brightness angle distribution biased to the side opposite to the second LED 24 side in the X-axis direction and to the second LED 24 side. Therefore, when both the first LED 13 and the second LED 24 are turned on, in addition to the light in the limited angle range, the backlight device 12 emits light whose peak brightness has a brightness angle distribution biased to the side opposite to the second LED 24 side in the X-axis direction and to the second LED 24 side, so that the display image of the liquid crystal display device 10 can be viewed from both the driver's seat and the passenger seat, and in particular, the display image can be viewed with a wide viewing angle from the passenger seat. In this way, by controlling the drive of the second LED 24 according to the driving situation of the passenger car, it is possible to adjust whether or not the display image can be viewed from the driver's seat.

[0061] Next, the third inclined surface 31 provided on the sixth light guide plate lens 28 and the seventh light guide plate lens 29 will be described in detail. First, as shown in FIG. 6, among the third inclined surfaces 31, the angle that the fourth inclined surface 28B provided on the sixth light guide plate lens 28 makes with respect to the X-axis direction is defined as the "third angle θ3", and the angle that the fifth inclined surface 29B provided on the seventh light guide plate lens 29 makes with respect to the X-axis direction is defined as the "fourth angle θ4". The fourth inclined surface 28B has a third angle θ3 in the range of, for example, 3° to 10°, specifically about 3°. The fifth inclined surface 29B has a fourth angle θ4 in the range of, for example, 3° to 10°, specifically about 3°. In this embodiment, the third angle θ3 of the fourth inclined surface 28B and the fourth angle θ4 of the fifth inclined surface 29B are equal. According to this configuration, when the light traveling in the second light guide plate 25 so as to approach the second LED 24 in the X-axis direction hits the fourth inclined surface 28B and the fifth inclined surface 29B, which are the third inclined surface 31, and is refracted, the light travels toward the opposite side of the second LED 24 in the X-axis direction with respect to the Z-axis direction. This can further improve the brightness of the emitted light in the direction inclined with respect to the Z-axis direction. In addition, when the light traveling in the second light guide plate 25 so as to move away from the second LED 24 in the X-axis direction hits the third inclined surface 31, the fourth inclined surface 28B, and the fifth inclined surface 29B, the light is guided further away from the second LED 24. This makes it difficult for the emitted light from the second light guide plate light output main surface 25B to be biased toward the second LED 24 in the X-axis direction.

[0062] Next, the first plane 28C, the second plane 29C, and the third plane 32 will be described in detail. As shown in Fig. 6, the first plane 28C, the second plane 29C, and the third plane 32 are parallel to the X-axis direction and the Y-axis direction, and their normal directions coincide with the Z-axis direction. Light that is emitted from the first light guide plate light-emitting principal surface 14B of the first light guide plate 14 and enters the second opposite principal surface 25C of the second light guide plate 25 travels without being refracted even if it hits any of the first plane 28C, the second plane 29C, and the third plane 32. Therefore, compared to a configuration in which the first inclined surface 28A and the fourth inclined surface 28B are directly connected without passing through the first plane 28C, or in which the second inclined surface 29A and the fifth inclined surface 29B are directly connected without passing through the second plane 29C, or in which the sixth light guide plate lens 28 and the seventh light guide plate lens 29 that are adjacent in the X-axis direction are directly connected without passing through the third plane 32, it is possible to suppress the generation of side lobe light that travels in a direction inclined toward the opposite side to the second LED 24 in the X-axis direction with respect to the Z-axis direction.

[0063] As shown in Figs. 6 and 7, the sixth light guide plate lenses 28 and the seventh light guide plate lenses 29 arranged along the X-axis direction each have height dimensions (dimensions along the Z-axis direction) H2 and H3 that increase as they move away from the second LED 24 in the X-axis direction, but are designed to have constant arrangement pitches (arrangement intervals) P1 and P2 in the X-axis direction. The width dimensions (dimensions along the X-axis direction) W2 and W6 of the first inclined surface 28A and the second inclined surface 29A each increase as they move away from the second LED 24 in the X-axis direction. The width dimensions (dimensions along the X-axis direction) W3 and W7 of the fourth inclined surface 28B and the fifth inclined surface 29B each increase as they move away from the second LED 24 in the X-axis direction, and the rate of increase is higher than the rate of increase of the first inclined surface 28A and the second inclined surface 29A. The width dimensions (dimensions along the X-axis direction) W4 and W8 of the first flat surface 28C and the second flat surface 29C are constant regardless of their positions in the X-axis direction. The width dimension (dimension in the X-axis direction) W5 of the third plane 32 becomes smaller as it gets farther from the second LED 24 in the X-axis direction. The arrangement pitch P1 in the X-axis direction of the sixth light guide plate lens 28 is the sum of the width dimension W2 of the first slope 28A, the width dimension W3 of the fourth slope 28B, the width dimension W4 of the first plane 28C, and the width dimension W5 of the third plane 32. The arrangement pitch P2 in the X-axis direction of the seventh light guide plate lens 29 is the sum of the width dimension W6 of the second slope 29A, the width dimension W7 of the fifth slope 29B, the width dimension W8 of the second plane 29C, and the width dimension W5 of the third plane 32.

[0064] Specific values ​​of width dimension W2 of first inclined surface 28A, width dimension W6 of second inclined surface 29A, width dimension W3 of fourth inclined surface 28B, width dimension W7 of fifth inclined surface 29B, and width dimension W5 of third flat surface 32 change according to the positions in the X-axis direction of sixth light guide plate lens 28 and seventh light guide plate lens 29 in second light guide plate 25, as shown in Fig. 8. Fig. 8 is a graph in which the horizontal axis represents the position in the X-axis direction in second light guide plate 25 (unit: mm) and the vertical axis represents the width dimensions W2, W3, W5, W6, W7 (unit: mm) of first inclined surface 28A, second inclined surface 29A, fourth inclined surface 28B, fifth inclined surface 29B, and third flat surface 32. 8 is the position of second light-entering end surface 25A of second light guide plate 25, and the position of 300 mm is the position of the end surface opposite to second light-entering end surface 25A of second light guide plate 25. The solid line shown in FIG. 8 is a graph of width dimensions W2, W6 of first inclined surface 28A and second inclined surface 29A, the dashed line is a graph of width dimensions W3, W7 of fourth inclined surface 28B and fifth inclined surface 29B, and the dashed line is a graph of width dimension W5 of third plane 32. When second light guide plate 25 has a length dimension of, for example, 300 mm, the specific numerical values ​​of height dimensions H2, H3 of sixth light guide plate lens 28 and seventh light guide plate lens 29 change according to the positions of sixth light guide plate lens 28 and seventh light guide plate lens 29 in second light guide plate 25 in the X-axis direction, as shown in FIG. FIG. 9 is a graph in which the horizontal axis represents the position in the X-axis direction on second light guide plate 25 (unit: mm) and the vertical axis represents the height dimensions H2, H3 (unit: mm) of sixth light guide plate lens 28 and seventh light guide plate lens 29.

[0065] Specifically, when the length dimension (dimension in the X-axis direction) of the second light guide plate 25 is, for example, 300 mm, the arrangement pitches P1, P2 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 in the X-axis direction are both constant, for example, about 0.114 mm. The width dimensions W4, W8 of the first plane 28C and the second plane 29C are both constant, for example, about 0.017 mm. According to FIG. 8, the width dimensions W2, W6 of the first slope 28A and the second slope 29A vary, for example, in the range of 0.003 mm to 0.004 mm. According to FIG. 8, the width dimensions W3, W7 of the fourth slope 28B and the fifth slope 29B vary, for example, in the range of 0.037 mm to 0.063 mm. According to FIG. 8, the width dimension W5 of the third plane 32 varies, for example, in the range of 0.003 mm to 0.032 mm. 9, the height dimensions H2, H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 vary within a range of, for example, 0.002 mm to 0.0034 mm. In this manner, the height dimensions H2, H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are secured to a minimum value of about 0.002 mm (2 μm). This ensures sufficient ease in manufacturing the second light guide plate 25 by resin molding. In order to ensure that the minimum values ​​of the height dimensions H2, H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are about 0.002 mm, it is preferable that the third angle θ3 of the fourth inclined surface 28B and the fourth angle θ4 of the fifth inclined surface 29B are each 3° or more. In addition, the first angle θ1 of the first inclined surface 28A, the second angle θ2 of the second inclined surface 29A, the third angle θ3 of the fourth inclined surface 28B, and the fourth angle θ4 of the fifth inclined surface 29B are each constant regardless of the position in the X-axis direction on the second light guide plate 25.

[0066] The sixth light guide plate lens 28 and the seventh light guide plate lens 29 configured as described above are arranged to be sandwiched between two fifth light guide plate lenses 27 adjacent to each other in the Y-axis direction, as shown in Figs. 3 and 7. Therefore, the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are arranged to be alternately arranged with the fifth light guide plate lens 27 in the Y-axis direction. The sixth light guide plate lens 28 and the seventh light guide plate lens 29 have maximum values ​​of their height dimensions (projection dimensions from the second opposite principal surface 25C) H2 and H3 both smaller than the height dimension of the fifth light guide plate lens 27. Therefore, even the sixth light guide plate lens 28 and the seventh light guide plate lens 29 located on the farthest side from the second LED 24 in the X-axis direction do not protrude further back than the fifth light guide plate lens 27.

[0067] Here, in order to obtain knowledge regarding how the light distribution changes when the first angle θ1 and the second angle θ2, which are angles that the first inclined surface 28A and the second inclined surface 29A of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 of the second light guide plate 25 make with respect to the X-axis direction, are changed, a demonstration experiment 1 was performed. In this demonstration experiment 1, a backlight device 12 having the same configuration as that described in the previous paragraph is used, except for the configurations of the sixth light guide plate lens 28 and the seventh light guide plate lens 29. In the demonstration experiment 1, the angles that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction are made equal, and the angles are changed in the range of 36° to 60°. In detail, in the demonstration experiment 1, the angles that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction are set to 36°, 40°, 44°, 48°, 50°, 54°, and 60°. In the backlight device 12 in which the angles that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction are changed in this manner, the second LED 24 was turned on, and the brightness of the emitted light was measured with the first LED 13 turned off, and a graph was created showing the light distribution (brightness angular distribution) in the X-axis direction.

[0068] The experimental results of the light distribution in the demonstration experiment 1 are shown in Fig. 10. In the graph of the light distribution shown in Fig. 10, the horizontal axis represents the angle (unit: "°") in the X-axis direction with respect to the front direction (Z-axis direction), and the vertical axis represents the luminance (unit: "cd / m 210, "- (minus)" means the left side in the X-axis direction with respect to the reference angle of 0° (front direction) when viewing backlight device 12 from the front, and "+ (plus)" means the right side in the X-axis direction with respect to the reference angle of 0° (front direction) when viewing backlight device 12 from the front.

[0069] The experimental results of the demonstration experiment 1 will be described. According to Fig. 10, when the angle that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction is in the range of 36° to 60°, the angle at which the peak brightness is reached is "-" when the angle is 36°, 40°, and 44°, and when the angle is 48°, 50°, 54°, and 60°, the angle at which the peak brightness is reached is "+". In detail, when the angle that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction is 44°, the angle at which the peak brightness is reached is closest to 0°, so that it can be inferred that when the angle that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction is 45°, the angle at which the peak brightness is reached is almost 0°. Therefore, if the angle that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction is smaller than 45°, the angle at which the peak brightness is obtained will be "-", and if the angle that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction is larger than 45°, the angle at which the peak brightness is obtained will tend to be "+".

[0070] According to FIG. 10, it can be said that the absolute value of the angle at which the peak luminance is reached tends to be smaller (closer to 0°) as the angle that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction is closer to 45°. According to FIG. 10, it can be seen that when the angles that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction are 36° and 54°, the angle at which the peak luminance is reached is about ±20°. Also, according to FIG. 10, it can be said that the peak luminance tends to be higher as the angles that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction are smaller. Also, if the light emitted at an angle in the range of −80° to −50° with respect to the front direction with respect to the X-axis direction is defined as “side lobe light”, it can be said that the amount of side lobe light is minimum when the angle that the first inclined surface 28A and the second inclined surface 29A make with respect to the X-axis direction is 44°, and the amount of side lobe light tends to increase whether the angle is larger or smaller than 44°.

[0071] Next, in order to verify the superiority of the backlight device 12 and the liquid crystal display device 10 according to the present embodiment, the following Comparative Experiment 1 was conducted. This Comparative Experiment 1 was conducted using the following Example 1 and Comparative Example 1 to obtain knowledge regarding how the light distribution changes when only the first LED 13 is turned on, when only the second LED 24 is turned on, and when both the first LED 13 and the second LED 24 are turned on. Example 1 is a backlight device 12 having the same configuration as that described before the above-mentioned Demonstration Experiment 1, in which the first angle θ1 of the first inclined surface 28A of the sixth light guide plate lens 28 is set to 32°, and the second angle θ2 of the second inclined surface 29A of the seventh light guide plate lens 29 is set to 54°. Comparative Example 1 is similar to the backlight device 12 having the same configuration as that described before Demonstration Experiment 1, except that the first angle θ1 of the first inclined surface 28A of the sixth light guide plate lens 28 is set to 27° and the second angle θ2 of the second inclined surface 29A of the seventh light guide plate lens 29 is set to 58°. Specifically, in Comparative Experiment 1, using Example 1 and Comparative Example 1, the luminance of the emitted light was measured in the case where the first LED 13 was turned on and the second LED 24 was turned off, the case where the second LED 24 was turned on and the first LED 13 was turned off, and the case where both the first LED 13 and the second LED 24 were turned on, and a graph of the light distribution (luminance angle distribution) in the X-axis direction was created.

[0072] The experimental results of the light distribution in Comparative Experiment 1 are shown in Fig. 11 to Fig. 16. In the graphs of the light distribution shown in Fig. 11 to Fig. 16, the horizontal axis represents the angle (unit: "°") in the X-axis direction with respect to the front direction (Z-axis direction), and the vertical axis represents the luminance (unit: "cd / m 2 "). The positive and negative symbols attached to the angles on the horizontal axis in Figs. 11 to 16 have the same meaning as the symbols attached to the horizontal axis of the graph in Fig. 11. Figs. 11 to 13 show the experimental results of Comparative Example 1. Figs. 14 to 16 show the experimental results of Example 1. Figs. 11 and 14 show the light distribution when the first LED 13 is turned on and the second LED 24 is turned off. Figs. 12 and 15 show the light distribution when the second LED 24 is turned on and the first LED 13 is turned off. Figs. 13 and 16 show the light distribution when both the first LED 13 and the second LED 24 are turned on.

[0073] The experimental results of Comparative Experiment 1 will be described. First, according to the light distribution in Fig. 11 and Fig. 14, when the first LED 13 was turned on and the second LED 24 was turned off, the peak luminance was almost 0° and the emission angle range was about ±10° in both Comparative Example 1 and Example 1. It can be said that this result reflects the fact that the emission angle range of the light emitted from the first light guide plate 14 as the first LED 13 was turned on is limited to about ±10° by the first louver 18.

[0074] Next, according to the light distribution of FIG. 12, which is the experimental result of Comparative Example 1, when the second LED 24 is turned on and the first LED 13 is turned off, there are two peak luminances, one near -40° and one near +20°. It is presumed that the light emitted near -40° is light reflected by the first inclined surface 28A, and the light emitted near +20° is light reflected by the second inclined surface 29A. According to the light distribution of FIG. 15, which is the experimental result of Example 1, when the second LED 24 is turned on and the first LED 13 is turned off, there are three peak luminances, one near -60°, one near -20°, and one near +20°. It is presumed that the light emitted near -20° is light reflected by the first inclined surface 28A, and the light emitted near +20° is light reflected by the second inclined surface 29A. Also, it is presumed that the emitted light near -60° is, for example, light that is refracted at the second inclined surface 29A and transmitted through the second inclined surface 29A, and is refracted when entering the fourth inclined surface 28B, and reaches the second light guide plate light-emitting main surface 25B and is emitted (side lobe light). Thus, according to the light distribution in Fig. 12 and Fig. 15, when the second LED 24 is turned on, it can be said that emitted light is emitted with an orientation distribution in which the peak luminance of the emitted light is unevenly distributed on the side opposite to the second LED 24 side in the X-axis direction and on the second LED 24 side in the X-axis direction.

[0075] The orientation distribution of FIG. 13, which is the experimental result of Comparative Example 1, is a combination of the light distribution of FIG. 11 and the light distribution of FIG. 12, and the orientation distribution of FIG. 16, which is the experimental result of Example 1, is a combination of the light distribution of FIG. 14 and the light distribution of FIG. 15. According to the light distribution of FIG. 13, which is the experimental result of Comparative Example 1, when the first LED 13 and the second LED 24 are both turned on, the peak luminance exists at approximately 0°, near -40°, and near +20°, and the luminance is the highest at approximately 0°. However, according to the light distribution of FIG. 13, which is the experimental result of Comparative Example 1, when the first LED 13 and the second LED 24 are both turned on, the luminance falls locally at approximately -15° between the luminance peak at approximately 0° and the luminance peak near -40°, and the luminance falls locally at approximately +15° between the luminance peak at approximately 0° and the luminance peak near +20°. 13, the luminance near -15° is lower than the peak luminance near -40°, and the luminance near +15° is lower than the peak luminance near +20°. Therefore, in Comparative Example 1, in the visible range of ±20°, a local luminance drop occurs only near ±15°, resulting in poor viewing angle performance.

[0076] In contrast, according to the light distribution of Fig. 16, which is the experimental result of Example 1, when both the first LED 13 and the second LED 24 are turned on, the peak luminance exists at approximately 0° and near -60°, and the luminance is the highest at approximately 0°. According to the light distribution of Fig. 16, which is the experimental result of Example 1, when both the first LED 13 and the second LED 24 are turned on, it can be seen that the luminance tends to decrease continuously from the luminance peak at approximately 0° to ±20°, and no change occurs in which the luminance increases along the way. In other words, in Example 1, it can be said that localized luminance reduction is avoided in the viewing range of ±20°, and excellent viewing angle performance is obtained.

[0077] FIG. 17 is shown to supplement the explanation of the graphs shown in FIG. 11 to FIG. 16. FIG. 17 is a diagram for explaining the angle in the X-axis direction with respect to the front direction of the liquid crystal display device 10 installed in front of the passenger seat in a passenger car in which the driver's seat is located on the left side of the passenger seat. FIG. 17 shows a light-blocking range (+10° to +90°, -10° to -90°) blocked by the first louver 18, a driver's seat visible range (-20° to -50°) which is the visible range when the liquid crystal display device 10 is viewed from the driver's seat located on the left side of the passenger seat, a passenger's seat visible range (-20° to +20°) which is the visible range when the liquid crystal display device 10 is viewed from the passenger's seat located on the right side of the driver's seat and in front of the liquid crystal display device 10, and an emission range (-80° to -50°) of side lobe light that is emitted to a range outside both the driver's seat visible range and the passenger's seat visible range on the driver's seat side.

[0078] 11, 14 and 17, in both Comparative Example 1 and Example 1, when the first LED 13 is turned on and the second LED 24 is turned off, the peak luminance is approximately 0° and the emission angle range is approximately ±10°, so that it can be said that the display image of the liquid crystal display device 10 is almost unrecognizable from the driver's seat, while the display image of the liquid crystal display device 10 can be well-recognized from the passenger seat located at 0°. According to Figs. 12, 15 and 17, in both Comparative Example 1 and Example 1, when the second LED 24 is turned on and the first LED 13 is turned off, the display image of the liquid crystal display device 10 cannot be well-recognized, particularly from the passenger seat. According to Figs. 13 and 17, in Comparative Example 1, when both the first LED 13 and the second LED 24 are turned on, the luminance is 50 cd / m2 over the entire range in both the passenger seat visibility range of -20° to +20° and the driver's seat visibility range of -50° to -20°. 2Since the above is ensured, the display image of the liquid crystal display device 10 can be viewed from both the driver's seat and the passenger seat, but the viewing angle is narrower in the passenger seat due to a local decrease in luminance existing near ±15°. According to Fig. 16 and Fig. 17, in Example 1, when the first LED 13 and the second LED 24 are both turned on, the luminance is 50 cd / m2 or less over the entire range in both the passenger seat visibility range of -20° to +20° and the driver's seat visibility range of -50° to -20°. 2 As a result, the image displayed on the liquid crystal display device 10 can be seen from both the driver's seat and the passenger seat. In particular, since there is no local decrease in luminance in the passenger seat visible range, it can be said that a wide viewing angle is achieved in the passenger seat.

[0079] As described above, the backlight device (illumination device) 12 of this embodiment includes a first LED (first light source) 13, a first light guide plate 14 having at least a part of an outer peripheral end face that faces the first LED 13 and serves as a first light incident end face (first end face) 14A into which light is incident, one main face of which serves as a first light guide plate light exiting main face (first main face) 14B that emits light, and the other main face of which serves as a first opposite main face (second main face) 14C, a first louver (first sheet) 18 that is disposed facing the light plate light output main surface 14B and serves as a first light entering main surface (third main surface) 18A into which light is incident and has the other main surface serving as a first light exiting main surface (fourth main surface) 18B from which light is output; a second LED (second light source) 24; and a second light guide plate light output main surface 14B that is disposed facing the light plate light output main surface 14B and serves as a second light entering end surface (second end surface) 25A into which light is incident and has one main surface serving as a second light exiting main surface (fourth main surface) 18B from which light is output. and a second light guide plate 25 having a first main surface (fifth main surface) 25B facing the first light emitting main surface 18B and a second opposite main surface (sixth main surface) 25C arranged facing the first light emitting main surface 18B. The first louver 18 includes at least two first light blocking portions 18C arranged at an interval in a first direction including a direction from the first LED 13 to the first light guide plate 14 to block light, and a first light transmitting portion 18D arranged between the two first light blocking portions 18C to transmit light. The second opposite main surface 25C of the second light guide plate 25 is provided with a first inclined surface 28A and a second inclined surface 29A that rise from the side opposite the second LED 24 in the first direction toward the second LED 24 side, and the first inclined surface 28A has a first angle θ1 with respect to the first direction that is greater than 27°, and the second inclined surface 29A has an angle with respect to the first direction that is greater than the first angle θ1 and less than 58°.

[0080] In this way, the light emitted from the first LED 13 and incident on the first light-entering end surface 14A of the first light guide plate 14 propagates through the first light guide plate 14, is emitted from the first light-exiting main surface 14B of the first light guide plate, and is incident on the first light-entering main surface 18A of the first louver 18. The light incident on the first light-entering main surface 18A of the first louver 18 passes through the first light-transmitting portion 18D arranged between the two first light-shielding portions 18C, and is emitted from the first light-exiting main surface 18B. The emission angle of the light emitted from the first light-exiting main surface 18B is limited by the two first light-shielding portions 18C. When the light emitted from the first light-exiting main surface 18B is incident on the second opposite main surface 25C of the second light guide plate 25, it is emitted from the second light-exiting main surface 25B of the second light guide plate. The light emitted from the second light guide plate's light-emitting principal surface 25B is unlikely to be emitted outside the limited angular range because the angular range is limited by the first light-shielding portion 18C of the first louver 18. This makes it possible to selectively emit light within the limited angular range centered on the normal direction of the second light guide plate's light-emitting principal surface 25B, i.e., the front direction, by turning on the first LED 13 and turning off the second LED 24.

[0081] At least a part of the light emitted from the second LED 24 and incident on the second light-entering end surface 25A of the second light guide plate 25 hits the first inclined surface 28A and the second inclined surface 29A provided on the second opposite main surface 25C during the process of propagating through the second light guide plate 25, and is reflected or transmitted there. The traveling direction of the light reflected by the first inclined surface 28A and the second inclined surface 29A depends on the angle of the first inclined surface 28A and the second inclined surface 29A with respect to the first direction. The light reflected by the first inclined surface 28A, which has an angle of the first angle θ1 with respect to the first direction smaller than the second angle θ2, tends to travel toward the opposite side to the second LED 24 side in the first direction with respect to the front direction when it is emitted from the light-emitting main surface 25B of the second light guide plate. On the other hand, the light reflected by the second inclined surface 29A, which has an angle θ2 with respect to the first direction that is larger than the first angle θ1, tends to travel toward the second LED 24 side in the first direction with respect to the front direction when it is emitted from the second light guide plate light emitting main surface 25B. Therefore, when the second LED 24 is turned on, it is possible to supply emitted light with a luminance angle distribution in which the peak luminance of the emitted light is unevenly distributed on the side opposite to the second LED 24 side with respect to the first direction and on the second LED 24 side with respect to the first direction. This not only ensures sufficient luminance of the emitted light in a direction inclined with respect to the front direction, but also expands the emission angle range of the emitted light, which is suitable for achieving a wide viewing angle.

[0082] Moreover, since the first inclined surface 28A has a first angle θ1 larger than 27°, when the light reflected by the first inclined surface 28A is emitted from the second light guide plate light output main surface 25B, the light proceeds in a direction closer to the front direction compared to the case where the first angle θ1 is 27° or less. Since the second inclined surface 29A has a second angle θ2 smaller than 58°, when the light reflected by the second inclined surface 29A is emitted from the second light guide plate light output main surface 25B, the light proceeds in a direction closer to the front direction compared to the case where the second angle θ2 is 58° or more. Therefore, when the first LED 13 and the second LED 24 are both turned on, the luminance angle distribution of the light emitted from the second light guide plate light output main surface 25B tends to have lower luminance toward the wide angle side with respect to the front direction, and localized luminance drops are less likely to occur along the way. As a result, it is possible to achieve a wide viewing angle while making it difficult for luminance unevenness to occur.

[0083] In addition, the second opposite main surface 25C of the second light guide plate 25 is provided with a third inclined surface 31 that is inclined and rises from the second LED 24 side toward the opposite side in the first direction. When the light traveling in the second light guide plate 25 so as to approach the second LED 24 in the first direction hits the third inclined surface 31 and is refracted, the light travels toward the opposite side of the second LED 24 in the first direction with respect to the front direction. This can further improve the brightness of the emitted light in the direction inclined with respect to the front direction. In addition, when the light traveling in the second light guide plate 25 so as to move away from the second LED 24 in the first direction hits the third inclined surface 31 and is refracted, the light is guided so as to move further away from the second LED 24. This makes it difficult for the emitted light from the second light guide plate light output main surface 25B to be biased toward the second LED 24 side in the first direction.

[0084] Moreover, the liquid crystal display device (display device) 10 according to this embodiment includes the above-described backlight device 12, and a liquid crystal panel (display panel) 11 that performs display using light from the backlight device 12. According to the liquid crystal display device 10 configured in this manner, in the backlight device 12, emission of light outside a limited angle range is suppressed, and the luminance of the emitted light in a direction inclined with respect to the front direction is improved. In addition, the emission angle range of the emitted light is expanded to achieve a wide viewing angle, and luminance unevenness is less likely to occur, so that a display with excellent display quality can be realized.

[0085] <Embodiment 2> A second embodiment will be described with reference to Fig. 18 to Fig. 22. In this second embodiment, the configuration of the third inclined surface 131 and the like are changed. Note that a duplicated description of the structure, action, and effects similar to those of the first embodiment will be omitted.

[0086] As shown in FIG. 18, the third inclined surface 131 of the second light guide plate 125 according to this embodiment has an angle of 40° or more with respect to the X-axis direction (first direction). The fourth inclined surface 128B included in the third inclined surface 131 has a third angle θ103, which is an angle with respect to the X-axis direction, of 40° or more, for example, about 65°. The fifth inclined surface 129B included in the third inclined surface 131 has a fourth angle θ104, which is an angle with respect to the X-axis direction, of 40° or more, for example, about 65°. Therefore, the fourth inclined surface 128B and the fifth inclined surface 129B are configured so that the third angle θ103 and the fourth angle θ104 are equal. Note that, similarly to the above-mentioned embodiment 1, the first inclined surface 128A has a first angle θ101 of about 32°, and the second inclined surface 129A has a second angle θ102 of about 54°. Furthermore, the second opposite principal surface 125C of the second light guide plate 125 according to this embodiment does not have the third plane 32 (see FIG. 6) described in the first embodiment. Therefore, in this embodiment, the first inclined surface 128A and the second inclined surface 129A are directly connected to each other.

[0087] As shown in Fig. 18, when the light emitted from the second LED 24 and introduced into the second light guide plate 125 hits the second inclined surface 129A while propagating through the second light guide plate 125, most of the light is reflected, but some of the light passes through the second inclined surface 129A. The light that passes through the second inclined surface 129A is refracted by the second inclined surface 129A and enters the fourth inclined surface 128B facing the second inclined surface 129A, where it is refracted and directed toward the second light guide plate light output principal surface 125B. Here, since the third angle θ103 of the fourth inclined surface 128B is set to be 40° or more as described above, the incident light can be angled so that most of the light that passes through the second inclined surface 129A and reaches the second light guide plate light output principal surface 125B by being refracted by the fourth inclined surface 128B is totally reflected by the second light guide plate light output principal surface 125B. In this way, most of the light that is refracted at the fourth inclined surface 128B and then reaches the second light guide plate light-emitting principal surface 125B can be totally reflected and travel toward the second opposite principal surface 125C. This makes it possible to reduce side lobe light that is emitted from the second light guide plate light-emitting principal surface 125B and travels in a direction inclined toward the opposite side to the second LED 24 in the X-axis direction with respect to the front direction.

[0088] On the other hand, when the first LED 13 is turned on while the second LED 24 is turned off (see FIG. 1), the light emitted from the first light guide plate light-emitting main surface 14B of the first light guide plate 14 passes through the first light-transmitting portion 18D of the first louver 18, and then is incident on the first inclined surface 128A, the second inclined surface 129A, and the third inclined surface 131 provided on the second opposite main surface 125C of the second light guide plate 125, as shown in FIG. 18. Among these, the light incident on the fourth inclined surface 128B included in the third inclined surface 131 is refracted by the fourth inclined surface 128B in a direction according to the third angle θ103. In this embodiment, since the third angle θ103 is set to about 65°, 65° or more, it is possible to reduce the ratio of light traveling in the opposite direction from the second LED 24 side in the X-axis direction (the left side in FIG. 18) in the light emitted from the second light guide plate light output main surface 125B, compared to the case where the third angle θ103 is less than 65°. In particular, the ratio of light traveling in a direction at 45° to the X-axis direction among the light traveling in the opposite direction from the second LED 24 side in the X-axis direction in the light emitted from the second light guide plate light output main surface 125B can be set to 2.5% or less. This makes it difficult to effectively view the light that is emitted outside the angle range limited by the first light-shielding portion 18C of the first louver 18 (see FIG. 2).

[0089] In addition, when the first LED 13 is turned on while the second LED 24 is turned off (see FIG. 1), the light emitted from the first louver 18 is incident on the fourth inclined surface 128B and the fifth inclined surface 129B provided on the second opposite principal surface 125C of the second light guide plate 125. Then, the light incident on the fourth inclined surface 128B is refracted by the fourth inclined surface 128B in a direction according to the third angle θ103, and the light incident on the fifth inclined surface 129B is refracted by the fifth inclined surface 129B in a direction according to the fourth angle θ104. In this embodiment, the fourth angle θ104 of the fifth inclined surface 129B is set to be equal to the third angle θ103 of the fourth inclined surface 128B, so that the degree of refraction given to each light incident on the fourth inclined surface 128B and the fifth inclined surface 129B from the first louver 18 side is equal. This makes it less likely that the direction of travel of each light that enters the fourth inclined surface 128B and the fifth inclined surface 129B from the first louver 18 side and is refracted by the fourth inclined surface 128B and the fifth inclined surface 129B will vary when it exits from the second light guide plate light output main surface 125B.

[0090] Here, in order to obtain knowledge regarding how the light distribution changes when the third angle θ103 and the fourth angle θ104, which are angles that the fourth inclined surface 128B and the fifth inclined surface 129B of the sixth light guide plate lens 128 and the seventh light guide plate lens 129 of the second light guide plate 125 make with respect to the X-axis direction, are changed, a demonstration experiment 2 was performed. In the demonstration experiment 2, a backlight device 12 having the same configuration as that described in the previous paragraph is used, except for the configurations of the sixth light guide plate lens 128 and the seventh light guide plate lens 129. In the demonstration experiment 2, the angles that the first inclined surface 128A and the second inclined surface 129A make with respect to the X-axis direction are made equal and fixed at 54°, and then the angles that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction are made equal and the angles are changed within a range of 3° to 60°. Specifically, in Demonstration Experiment 2, the angles that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction were set to 3°, 10°, 20°, 40°, and 60°. In the backlight device 12 in which the angles that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction were changed in this manner, the second LED 24 was turned on in the backlight device 12, and the luminance of the emitted light was measured with the first LED 13 turned off, and a graph of the light distribution (luminance angle distribution) in the X-axis direction was created.

[0091] The experimental results of the light distribution in the demonstration experiment 2 are shown in Fig. 19. In the graph of the light distribution shown in Fig. 19, the horizontal axis represents the angle (unit: "°") in the X-axis direction with respect to the front direction (Z-axis direction), and the vertical axis represents the luminance (unit: "cd / m 2 The positive and negative symbols attached to the angles on the horizontal axis in FIG. 19 have the same meanings as the symbols attached to the horizontal axis of the graph in FIG. 10 described in Demonstration Experiment 1 of the first embodiment.

[0092] The experimental results of the demonstration experiment 2 will be described. It can be seen from Fig. 19 that the amount of side lobe light (light emitted at an angle in the X-axis direction with respect to the front direction in the range of -80° to -50°) changes depending on the angle that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction. Specifically, when the angle that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction is set to 20° or less, the luminance of the side lobe light is 20 cd / m2 When the angle that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction is 40° or more, the luminance of the side lobe light tends to be higher than 10 cd / m 2 It can be seen that the luminance of the side lobe light is lower than that of the fourth inclined surface 128B and the fifth inclined surface 129B. It can also be seen that the luminance of the side lobe light does not change significantly whether the angle that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction is 40° or 60°. Therefore, it can be said that the side lobe light can be effectively reduced if the angle that the fourth inclined surface 128B and the fifth inclined surface 129B make with respect to the X-axis direction is 40° or more.

[0093] Next, in order to verify the superiority of the backlight device 12 and the liquid crystal display device 10 according to this embodiment, Comparative Experiment 2 was performed similarly to Comparative Experiment 1 of Embodiment 1. In Comparative Experiment 2, the following Example 2 was used. Example 2 is a backlight device 12 having the same configuration as that described before the above-mentioned Demonstration Experiment 2, in which the first inclined surface 128A has a first angle θ101 of 32°, the second inclined surface 129A has a second angle θ102 of 54°, the fourth inclined surface 128B has a third angle θ103 of 65°, and the fifth inclined surface 129B has a fourth angle θ104 of 65°. In comparative experiment 2, using Example 2, the luminance of the emitted light was measured in the cases where the first LED 13 was turned on and the second LED 24 was turned off, where the second LED 24 was turned on and the first LED 13 was turned off, and where both the first LED 13 and the second LED 24 were turned on, and a graph was created showing the light distribution (luminance angular distribution) in the X-axis direction.

[0094] The experimental results of the light distribution in Comparative Experiment 2 are shown in Fig. 20 to Fig. 22. In the graphs of the light distribution shown in Fig. 20 to Fig. 22, the horizontal axis represents the angle (unit: "°") in the X-axis direction with respect to the front direction (Z-axis direction), and the vertical axis represents the luminance (unit: "cd / m 2"). The positive and negative symbols attached to the angles on the horizontal axis in Figs. 20 to 22 have the same meaning as the symbols attached to the horizontal axis of the graph in Fig. 10 explained in Demonstration Experiment 1 of Embodiment 1. Figs. 20 to 22 are experimental results of Example 2. Fig. 20 shows the light distribution when the first LED 13 is turned on and the second LED 24 is turned off. Fig. 21 shows the light distribution when the second LED 24 is turned on and the first LED 13 is turned off. Fig. 22 shows the light distribution when both the first LED 13 and the second LED 24 are turned on.

[0095] The experimental results of Comparative Experiment 2 will be described while appropriately comparing them with the experimental results of Comparative Experiment 1 (FIGS. 11 to 16). First, according to the light distribution in FIG. 20, which is the experimental result of Example 2, when the first LED 13 is turned on and the second LED 24 is turned off, the peak luminance is approximately 0° and the emission angle range is about ±10°. This result is generally similar to the experimental result of Example 1 of Comparative Experiment 1 (see FIG. 14).

[0096] Next, according to the light distribution in Fig. 21 which is the experimental result of Example 2, when the second LED 24 is turned on and the first LED 13 is turned off, there are two peak luminances, one near -20° and one near +20°. It is presumed that the light emitted near -20° is light reflected by the first inclined surface 128A, and the light emitted near +20° is light reflected by the second inclined surface 129A. Compared to the experimental result of Example 1 of Comparative Experiment 1 (see Fig. 15), the light distribution in Fig. 21 which is the experimental result of Example 2 shows high luminance in the range of -40° to +40°, but significantly low luminance in the range of -80° to -50°.

[0097] The orientation distribution of Fig. 22, which is the experimental result of Example 2, is a combination of the light distribution of Fig. 20 and the light distribution of Fig. 21. According to the light distribution of Fig. 22, when both the first LED 13 and the second LED 24 are turned on, the peak luminance is at approximately 0°, and, except for a part (in the range of -60° to -80°), the luminance tends to decrease as the absolute value of the angle increases (as it moves away from 0° on the horizontal axis of Fig. 22). Compared to the experimental result of Example 1 of Comparative Experiment 1 (see Fig. 16), the light distribution of Fig. 22, which is the experimental result of Example 2, has high luminance in the range of -40° to +40°, but significantly low luminance in the range of -80° to -50°. This is presumably because in Example 2, the light transmitted through second inclined surface 129A is refracted by fourth inclined surface 128B having third angle θ103 of 65°, and most of the light is totally reflected by second light guide plate light output principal surface 125B, so that side lobe light emitted in the range of -80° to -50° is significantly reduced and light emitted in the range of -50° to +40° is increased. Also, in Example 2, like Example 1, localized brightness reduction is avoided in the visible range of ±20° (visible range from the passenger seat in FIG. 17), and it can be said that excellent viewing angle performance is obtained.

[0098] As described above, according to this embodiment, the third inclined surface 131 includes the fourth inclined surface 128B arranged to face the second inclined surface 129A with a gap therebetween, and the fourth inclined surface 128B has a third angle θ103, which is an angle with respect to the first direction, of 40° or more. The light transmitted through the second inclined surface 129A is refracted by the second inclined surface 129A and enters the fourth inclined surface 128B facing the second inclined surface 129A, where it is refracted and directed toward the second light guide plate light output principal surface 125B. Since the fourth inclined surface 128B has a third angle θ103 of 40° or more, the incident light can be angled so that most of the light reaching the second light guide plate light output principal surface 125B is totally reflected by the second light guide plate light output principal surface 125B. In this way, most of the light that is refracted at the fourth inclined surface 128B and then reaches the second light guide plate light-emitting main surface 125B can be totally reflected and travel toward the second opposite main surface 125C. This makes it possible to reduce side lobe light that is emitted from the second light guide plate light-emitting main surface 125B and travels in a direction inclined toward the opposite side to the second LED 24 in the first direction with respect to the front direction.

[0099] Moreover, the fourth inclined surface 128B has a third angle θ103 of 65° or more. When the first LED 13 is turned on with the second LED 24 turned off, the light emitted from the first light guide plate light output main surface 14B of the first light guide plate 14 passes through the first light transmitting portion 18D of the first louver 18 and is incident on the first inclined surface 128A, the second inclined surface 129A, and the fourth inclined surface 128B provided on the second opposite main surface 125C of the second light guide plate 125. Of these, the light incident on the fourth inclined surface 128B is refracted in a direction according to the third angle θ103. If the third angle θ103 is 65° or more, the ratio of light traveling in the direction opposite to the second LED 24 side in the first direction to the light emitted from the second light guide plate light output main surface 125B can be reduced compared to the case where the third angle θ103 is less than 65°. In particular, the ratio of light traveling in a direction at 45° to the first direction to the light emitted from the second light guide plate light output main surface 125B among the light traveling in the direction opposite to the second LED 24 side in the first direction can be reduced to 2.5% or less. This makes it difficult to effectively view the light emitted outside the angle range limited by the first light blocking portion 18C of the first louver 18.

[0100] The third inclined surface 131 also includes a fourth inclined surface 128B arranged opposite the second inclined surface 129A with a gap therebetween, and a fifth inclined surface 129B arranged opposite the first inclined surface 128A with a gap therebetween, and the fifth inclined surface 129B has a fourth angle θ104, which is an angle with respect to the first direction, that is equal to a third angle θ103, which is the angle of the fourth inclined surface 128B with respect to the first direction. When the first LED 13 is turned on while the second LED 24 is turned off, the light emitted from the first light guide plate light-emitting main surface 14B of the first light guide plate 14 passes through the first light-transmitting portion 18D of the first louver 18 and is incident on the first inclined surface 128A, the second inclined surface 129A, the fourth inclined surface 128B, and the fifth inclined surface 129B provided on the second opposite main surface 125C of the second light guide plate 125. Of these, the light incident on the fourth inclined surface 128B is refracted in a direction according to the third angle θ103, and the light incident on the fifth inclined surface 129B is refracted in a direction according to the fourth angle θ104. Here, since the fourth angle θ104 of the fifth inclined surface 129B is set to be equal to the third angle θ103 of the fourth inclined surface 128B, the degree of refraction imparted to each light beam incident on the fourth inclined surface 128B and the fifth inclined surface 129B from the first louver 18 side is equal. As a result, the light beams incident on the fourth inclined surface 128B and the fifth inclined surface 129B from the first louver 18 side and refracted by the fourth inclined surface 128B and the fifth inclined surface 129B are less likely to vary in their traveling direction when they are emitted from the second light guide plate light output principal surface 125B.

[0101] <Embodiment 3> A third embodiment will be described with reference to Fig. 23 to Fig. 30. In this third embodiment, the configurations of sixth light guide plate lens 228 and seventh light guide plate lens 229, etc. are changed from those of the second embodiment. Note that redundant descriptions of structures, actions, and effects similar to those of the second embodiment will be omitted.

[0102] As shown in FIG. 23, the sixth light guide plate lens 228 according to this embodiment has a sixth slope 33 located between the first slope 228A and the fourth slope 228B in the X-axis direction (first direction) in addition to the first slope 228A and the fourth slope 228B. The sixth slope 33 has an inclination that rises from the opposite side (left side of FIG. 23) to the second LED 24 side (right side of FIG. 23) in the X-axis direction toward the second LED 24 side. That is, the sixth slope 33 is included in the third slope 231. The sixth light guide plate lens 228 has the fourth slope 228B and the sixth slope 33 included in the third slope 231. The sixth slope 33 has a gradient such that the thickness of the sixth light guide plate lens 228 is continuously and gradually increased from the second LED 24 side toward the opposite side in the X-axis direction. The sixth inclined surface 33 has a fifth angle θ5, which is an angle with respect to the X-axis direction, of, for example, about 1.4°. In contrast, the fourth inclined surface 228B has a third angle θ203 that is 67° or more, for example, about 67°. In this embodiment, the first inclined surface 228A has a first angle θ201 that is, for example, about 33°. Moreover, the sixth light guide plate lens 228 according to this embodiment is not provided with the first plane 28C (see FIG. 6) described in the first embodiment.

[0103] As shown in FIG. 23, the seventh light guide plate lens 229 according to this embodiment does not have the second plane 29C (see FIG. 6) described in the first embodiment, and the second inclined surface 229A and the fifth inclined surface 229B are directly connected to each other. The fifth inclined surface 229B has a fourth angle θ204 of, for example, about 1.4°. Therefore, the fifth inclined surface 229B has a fourth angle θ204 smaller than the third angle θ203. The fifth inclined surface 229B and the sixth inclined surface 33 have the same fourth angle θ204 and fifth angle θ5, which are angles formed with respect to the X-axis direction. As in the first embodiment described above, the second inclined surface 229A has a second angle θ202 of about 54°.

[0104] 23, the sixth light guide plate lens 228 and the seventh light guide plate lens 229 have the same arrangement pitches P201, P202 in the X-axis direction, which are, for example, about 0.045 mm. The sixth light guide plate lens 228 has a height dimension (projection dimension from the second opposite principal surface 225C) H202, which is, for example, about 0.0054 mm. In addition, the sixth light guide plate lens 228 has a height dimension H4 from the upper end position of the first inclined surface 228A (the intersection position of the first inclined surface 228A and the fifth inclined surface 229B) to the lower end position of the first inclined surface 228A (the intersection position of the first inclined surface 228A and the sixth inclined surface 33) which is, for example, about 0.0021 mm. Seventh light guide plate lens 229 has a height dimension H203 from second opposite principal surface 225C that is smaller than height dimension H202 of sixth light guide plate lens 228 and is set to, for example, about 0.0043 mm. Furthermore, in seventh light guide plate lens 229, height dimension H5 from the upper end position of fifth slope 229B (intersection position of first slope 228A and fifth slope 229B) to the lower end position of fifth slope 229B (intersection position of second slope 229A and fifth slope 229B) is set to, for example, about 0.001 mm.

[0105] When the first LED 13 is turned on while the second LED 24 is turned off (see FIG. 1), the light emitted from the first light guide plate light output main surface 14B of the first light guide plate 14 passes through the first light transmitting portion 18D of the first louver 18 and enters the second opposite main surface 225C of the second light guide plate 225. In the second opposite main surface 225C, the light incident on the fourth inclined surface 228B is refracted in a direction according to the third angle θ203. In this embodiment, the third angle θ203 is set to about 67°, which is 67° or more. Therefore, compared to the case where the third angle θ203 is 65° or more and less than 67°, the ratio of the light directed toward the opposite side to the second LED 24 side in the X-axis direction in the light emitted from the second light guide plate light output main surface 225B can be further reduced. In particular, among the light traveling in the direction opposite to the second LED 24 in the X-axis direction, the proportion of light traveling at an angle of 45° to the X-axis direction in the light emitted from the second light guide plate light-emitting main surface 225B can be set to 2.3% or less. This makes it more difficult for light that is emitted outside the angle range limited by the first light-shielding portion 18C of the first louver 18 to be visually recognized.

[0106] In addition, when the first LED 13 is turned on while the second LED 24 is turned off, in the second opposite principal surface 225C, the light incident on the fourth inclined surface 228B is refracted in a direction according to the third angle θ203, and the light incident on the fifth inclined surface 229B is refracted in a direction according to the fourth angle θ204. In this embodiment, since the fourth angle θ204 of the fifth inclined surface 229B is smaller than the third angle θ203 of the fourth inclined surface 228B, the degree of refraction imparted to the light incident on the fifth inclined surface 229B from the first light guide plate 14 side is smaller than the degree of refraction imparted to the light incident on the fourth inclined surface 228B. As a result, light that enters from the first light guide plate 14 side and is refracted by the fifth inclined surface 229B is less likely to travel outside the angular range limited by the first light-shielding portion 18C of the first louver 18 when it exits from the second light guide plate light-exiting main surface 225B.

[0107] In addition, when the first LED 13 is turned on while the second LED 24 is turned off, in the second opposite principal surface 225C, the light incident on the fifth inclined surface 229B is refracted in a direction according to the fourth angle θ204, and the light incident on the sixth inclined surface 33 is refracted in a direction according to the fifth angle θ5. In this embodiment, since the fifth angle θ5 of the sixth inclined surface 33 is equal to the fourth angle θ204, the degrees of refraction imparted to the lights incident on the fifth inclined surface 229B and the sixth inclined surface 33 are equal and smaller than the degree of refraction imparted to the light incident on the fourth inclined surface 228B. As a result, each light that enters from the first light guide plate 14 side and is refracted by the fifth inclined surface 229B and the sixth inclined surface 33 is less likely to travel outside the angular range limited by the first light-shielding portion 18C of the first louver 18 when it exits from the second light guide plate light output main surface 225B.

[0108] 24, the width dimension of the fifth light guide plate lens 227, which is the dimension in the Y-axis direction, is larger than the width dimension (0.126 mm) of the fifth light guide plate lens 27 described in the first embodiment, and is, for example, about 0.165 mm. The arrangement interval of the plurality of fifth light guide plate lenses 227 arranged along the Y-axis direction (the interval between the vertices of two fifth light guide plate lenses 227 arranged along the Y-axis direction) is the same as the arrangement interval of the fifth light guide plate lenses 27 described in the first embodiment, and is, for example, about 0.175 mm. The apex angle of the fifth light guide plate lens 227 is smaller than the apex angle (140°) of the fifth light guide plate lens 27 described in the first embodiment, and is, for example, about 120°. Here, the occupancy rate of the width dimension of the fifth light guide plate lens 227 in the arrangement interval is about 94% when expressed as a percentage obtained by dividing the width dimension (0.165 mm) by the arrangement interval (0.175 mm). The higher the occupancy rate of the width dimension of fifth light guide plate lens 227 in the arrangement interval, the lower the occupancy rate of sixth light guide plate lens 228 and seventh light guide plate lens 229 in second opposite principal surface 225C of second light guide plate 225. On the other hand, the occupancy rate of the width dimension (0.126 mm) of fifth light guide plate lens 27 described in embodiment 1 in the arrangement interval (0.175 mm) is about 72%. Therefore, in this embodiment, the occupancy rate of sixth light guide plate lens 228 and seventh light guide plate lens 229 in second opposite principal surface 225C of second light guide plate 225 is lower than in embodiment 1. As a result, when the first LED 13 is turned on with the second LED 24 turned off, the probability that the light from the first louver 18 will be refracted by the slopes 33, 228A, 228B, 229A, 229B decreases, so that when the light is emitted from the second light guide plate light output main surface 225B, it is less likely to travel outside the angle range restricted by the first light blocking portion 18C of the first louver 18. The fifth light guide plate lens 227 has an apex rounded to form an arc shape, and the radius of curvature is, for example, about 0.0875 mm.

[0109] Next, in order to obtain knowledge regarding how the light distribution changes when the third angle θ203, which is the angle that the fourth inclined surface 228B of the sixth light guide plate lens 228 of the second light guide plate 225 makes with respect to the X-axis direction, is changed, a demonstration experiment 3 was performed. In this demonstration experiment 3, a backlight device 12 having the same configuration as that described in the previous paragraph, except for the configuration of the sixth light guide plate lens 228, is used. In the demonstration experiment 3, the third angle θ203 of the fourth inclined surface 228B was changed in the range of 60° to 75°. More specifically, in the demonstration experiment 3, the third angle θ203 of the fourth inclined surface 228B was set to 60°, 65°, 67°, 70°, and 75°. In the backlight device 12 in which the third angle θ203 of the fourth inclined surface 228B was changed in this manner, the first LED 13 was turned on, and the luminance of the emitted light was measured with the second LED 24 turned off, and a graph of the light distribution (luminance angle distribution) in the X-axis direction was created. Then, the ratio of light at each angle of -25°, -35°, and -45° in the orientation distribution in the X-axis direction was calculated. In the calculation, the peak luminance at each angle of -25°, -35°, and -45° was divided by the overall peak luminance (relative luminance "1"). Here, the significance of calculating the ratio of light at each angle of -25°, -35°, and -45° is to provide an index regarding whether or not the side lobe light (light emitted in the range of -80° to -50°) is easily visible. That is, in order for the side lobe light to be difficult to be visible, the ratio of light at -25° is preferably 5% or less, the ratio of light at -35° is preferably 3% or less, and the ratio of light at -45° is preferably 2.5% or less. In this way, the reference value at which the side lobe light is difficult to be visible tends to be lower as the angle in the orientation distribution in the X-axis direction increases.

[0110] The experimental results of the demonstration experiment 3 are as shown in Fig. 25 to Fig. 27. Fig. 25 is a graph showing the light distribution when the third angle θ203 of the fourth inclined surface 228B is set to 60°, 65°, 67°, 70°, and 75°. In the graph relating to the light distribution shown in Fig. 25, the horizontal axis represents the angle (unit: "°") in the X-axis direction with respect to the front direction (Z-axis direction), and the vertical axis represents the relative luminance (unitless). Fig. 26 is a graph in Fig. 25 in which the range of the horizontal axis from 0° to -70° and the range of the vertical axis from 0 to 0.1 are enlarged. The positive and negative symbols attached to the angle on the horizontal axis in Figs. 25 and 26 have the same meaning as the symbols attached to the horizontal axis of the graph in Fig. 10 described in the demonstration experiment 1 of the first embodiment. FIG. 19 is a table showing the relationship between the third angle θ203 (unit: °) and the ratio (unit: %) of light at angles of -25°, -35°, and -45° in the orientation distribution in the X-axis direction.

[0111] The experimental results of the demonstration experiment 3 will be described. According to Fig. 25 to Fig. 27, when the third angle θ203 of the fourth inclined surface 228B is 60°, the ratio of light at -25° and -35° is less than the respective reference values ​​(5%, 3%), but the ratio of light at -45° is greater than the reference value (2.5%). In contrast, when the third angle θ203 of the fourth inclined surface 228B is 65°, 67°, 70°, and 75°, the ratio of light at -25°, -35°, and -45° is less than the respective reference values. In particular, when the third angle θ203 of the fourth inclined surface 228B is 65°, the ratio of light at -45° is equal to the reference value (2.5%), whereas when the third angle θ203 of the fourth inclined surface 228B is 67°, 70°, and 75°, the ratio of light at -45° is smaller than the reference value (2.3%). Therefore, it can be said that if the third angle θ203 of the fourth inclined surface 228B is set to 67° or more, the side lobe light is less likely to be clearly visible.

[0112] Next, in order to verify the superiority of the backlight device 12 and the liquid crystal display device 10 according to this embodiment, Comparative Experiment 3 was performed similarly to Comparative Experiment 1 of the first embodiment. In Comparative Experiment 3, the following Example 3 was used. Example 3 is a backlight device 12 having the same configuration as that described before the above-mentioned Demonstration Experiment 3, and the first inclined surface 228A has a first angle θ201 of 33°, the second inclined surface 229A has a second angle θ202 of 54°, the fourth inclined surface 228B has a third angle θ203 of 67°, the fifth inclined surface 229B has a fourth angle θ204 of 1.4°, and the sixth inclined surface 33 has a fifth angle θ5 of 1.4°. In Comparative Experiment 3, using Example 3, the luminance of the emitted light was measured in the cases where the first LED 13 was turned on and the second LED 24 was turned off, where the second LED 24 was turned on and the first LED 13 was turned off, and where both the first LED 13 and the second LED 24 were turned on, and a graph was created showing the light distribution (luminance angular distribution) in the X-axis direction.

[0113] The experimental results of the light distribution in Comparative Experiment 3 are shown in Fig. 28 to Fig. 30. In the graphs of the light distribution shown in Fig. 28 to Fig. 30, the horizontal axis represents the angle (unit: "°") in the X-axis direction with respect to the front direction (Z-axis direction), and the vertical axis represents the luminance (unit: "cd / m 2 "). The positive and negative symbols attached to the angles on the horizontal axis in Figs. 28 to 30 have the same meaning as the symbols attached to the horizontal axis of the graph in Fig. 10 explained in Demonstration Experiment 1 of Embodiment 1. Figs. 28 to 30 show the experimental results of Example 3. Fig. 28 shows the light distribution when the first LED 13 is turned on and the second LED 24 is turned off. Fig. 29 shows the light distribution when the second LED 24 is turned on and the first LED 13 is turned off. Fig. 30 shows the light distribution when both the first LED 13 and the second LED 24 are turned on.

[0114] The experimental results of Comparative Experiment 3 will be described while appropriately comparing them with the experimental results of Comparative Experiment 2 (FIGS. 20 to 22). First, according to the light distribution in FIG. 28, which is the experimental result of Example 3, when the first LED 13 is turned on and the second LED 24 is turned off, the peak luminance is almost 0° and the emission angle range is about ±10°. This result is generally similar to the experimental result of Example 1 of Comparative Experiment 1 (see FIG. 14).

[0115] Next, according to the light distribution of FIG. 29, which is the experimental result of Example 3, when the second LED 24 is turned on and the first LED 13 is turned off, there are two peak luminances, one near -20° and one near +20°. It is presumed that the light emitted near -20° is light reflected by the first inclined surface 228A, and the light emitted near +20° is light reflected by the second inclined surface 229A. Compared with the experimental result of Example 2 of Comparative Experiment 2 (see FIG. 21), the light distribution of FIG. 29, which is the experimental result of Example 3, has a slightly lower luminance in the range of -40° to +40°, and a lower luminance in the range of -80° to -50° than in the range of -40° to +40°. In particular, Example 3 has a significantly lower luminance in the range of -80° to -70°.

[0116] The light distribution in Fig. 30, which is the experimental result of Example 3, is a combination of the light distribution in Fig. 28 and the light distribution in Fig. 29. According to the light distribution in Fig. 30, when both the first LED 13 and the second LED 24 are turned on, the peak luminance is present at approximately 0°, and the luminance tends to decrease as the absolute value of the angle increases over the entire angle range (as it moves away from 0° on the horizontal axis in Fig. 29). Compared with the experimental result of Example 2 of Comparative Experiment 2 (see Fig. 22), the light distribution in Fig. 30, which is the experimental result of Example 3, has a slightly lower luminance in the range of -40° to +40°, and a lower luminance in the range of -80° to -50° than in the range of -40° to +40°, and in particular, the luminance is significantly decreased in the range of -80° to -70°. This is presumably because in Example 3, the light transmitted through the second inclined surface 229A is refracted by the fourth inclined surface 228B having the third angle θ203 of 67°, and most of the light is totally reflected by the second light guide plate light output principal surface 225B, reducing the side lobe light emitted in the range of -80° to -50°. In addition, since the fourth angle θ204 and the fifth angle θ5 of the fifth inclined surface 229B and the sixth inclined surface 33 are both about 1.4°, which is close to 0°, the refraction effect imparted by the fifth inclined surface 229B and the sixth inclined surface 33 when the light from the first louver 18 enters the second opposite principal surface 225C of the second light guide plate 225 is very small, which is presumably also contributing to the reduction of the side lobe light emitted in the range of -80° to -50°. It is also believed that the high occupancy rate of the width dimension of fifth light guide plate lenses 227 in the arrangement interval, which is about 94%, also contributes to this. Note that the reason why the brightness is somewhat low in the range of -40° to +40° is that the fourth angle θ204 of fifth inclined surface 229B is about 1.4°, which is extremely small compared to the third angle θ203 of fourth inclined surface 228B, so that the light traveling from the side opposite to the second LED 24 side in the X-axis direction in second light guide plate 225 to the second LED 24 side is difficult to be tilted up by fifth inclined surface 229B.

[0117] As described above, according to this embodiment, the fourth inclined surface 228B has the third angle θ203 of 67° or more. When the first LED 13 is turned on while the second LED 24 is turned off, the light emitted from the first light guide plate light output main surface 14B of the first light guide plate 14 passes through the first light transmitting portion 18D of the first louver 18 and is incident on the first inclined surface 228A, the second inclined surface 229A, and the fourth inclined surface 228B provided on the second opposite main surface 225C of the second light guide plate 225. Of these, the light incident on the fourth inclined surface 228B is refracted in a direction according to the third angle θ203. If the third angle θ203 is 67° or more, the ratio of the light traveling in the direction opposite to the second LED 24 side in the first direction to the light emitted from the second light guide plate light output main surface 225B can be further reduced compared to the case where the third angle θ203 is 65° or more and less than 67°. In particular, the ratio of the light traveling in the direction of 45° to the first direction to the light emitted from the second light guide plate light output main surface 225B among the light traveling in the direction opposite to the second LED 24 side in the first direction can be reduced to 2.3% or less. This makes it more difficult for the light emitted outside the angle range limited by the first light blocking portion 18C of the first louver 18 to be visually recognized.

[0118] The third inclined surface 231 includes a fourth inclined surface 228B arranged to face the second inclined surface 229A with a gap therebetween, and a fifth inclined surface 229B arranged to face the first inclined surface 228A with a gap therebetween, and the fifth inclined surface 229B has a fourth angle θ204, which is an angle with respect to the first direction, smaller than a third angle θ203, which is an angle with respect to the first direction, of the fourth inclined surface 228B. When the first LED 13 is turned on with the second LED 24 turned off, the light emitted from the first light guide plate light output main surface 14B of the first light guide plate 14 passes through the first light transmitting portion 18D of the first louver 18 and enters the first inclined surface 228A, the second inclined surface 229A, the fourth inclined surface 228B, and the fifth inclined surface 229B provided on the second opposite main surface 225C of the second light guide plate 225. Among these, the light incident on the fourth inclined surface 228B is refracted in a direction according to the third angle θ203, and the light incident on the fifth inclined surface 229B is refracted in a direction according to the fourth angle θ204. Here, since the fourth angle θ204 of the fifth inclined surface 229B is smaller than the third angle θ203 of the fourth inclined surface 228B, the degree of refraction given to the light incident on the fifth inclined surface 229B from the first light guide plate 14 side is smaller than the degree of refraction given to the light incident on the fourth inclined surface 228B. As a result, the light incident from the first light guide plate 14 side and refracted by the fifth inclined surface 229B is less likely to travel outside the angle range limited by the first light-shielding portion 18C of the first louver 18 when it is emitted from the second light guide plate light-emitting main surface 225B.

[0119] The first inclined surface 228A and the fourth inclined surface 228B are disposed at an interval in the first direction, and the third inclined surface 231 includes a sixth inclined surface 33 located between the first inclined surface 228A and the fourth inclined surface 228B, and the sixth inclined surface 33 has a fifth angle θ5, which is an angle with respect to the first direction, equal to the fourth angle θ204. When the first LED 13 is turned on with the second LED 24 turned off, the degrees of refraction imparted to the light incident on the fifth inclined surface 229B and the sixth inclined surface 33 become equal and smaller than the degree of refraction imparted to the light incident on the fourth inclined surface 228B. As a result, each light that enters from the first light guide plate 14 side and is refracted by the fifth inclined surface 229B and the sixth inclined surface 33 is less likely to travel outside the angular range limited by the first light-shielding portion 18C of the first louver 18 when it exits from the second light guide plate light output main surface 225B.

[0120] <Other embodiments> The technology disclosed in this specification is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included in the technical scope.

[0121] (1) The specific values ​​of the first angles θ1, θ101, θ201, the second angles θ2, θ102, θ202, the third angles θ3, θ103, θ203, the fourth angles θ4, θ104, θ204, and the fifth angle θ5 can be changed appropriately to values ​​other than those mentioned above.

[0122] (2) In the configuration described in the first embodiment, the third plane 32 may be omitted.

[0123] (3) In the configurations described in the first and second embodiments, the first plane 28C and the second plane 29C may be omitted.

[0124] (4) In the configurations described in the second and third embodiments, a third plane 32 may be provided.

[0125] (5) In the configuration described in the third embodiment, the third angle θ203 may be equal to the fourth angle θ204. In the configuration described in the third embodiment, the fourth angle θ204 may be equal to the third angle θ203.

[0126] (6) In the configuration described in embodiment 3, the fourth angle θ204 and the fifth angle θ5 may be different.

[0127] (7) In the configuration described in embodiment 3, a first plane 28C and a second plane 29C may be provided.

[0128] (8) In the configuration described in the third embodiment, the sixth inclined surface 33 may be replaced with a flat surface.

[0129] (9) In the configuration described in the third embodiment, a flat surface may be provided in place of the fifth inclined surface 229B.

[0130] (10) The specific arrangement of the sixth light guide plate lenses 28, 128, 228 and the seventh light guide plate lenses 29, 129, 229 may be changed as appropriate. For example, the sixth light guide plate lenses 28, 128, 228 and the seventh light guide plate lenses 29, 129, 229 may be arranged alternately in such an order that the sixth light guide plate lenses 28, 128, 228 are arranged in succession, and then the seventh light guide plate lenses 29, 129, 229 are arranged in succession.

[0131] (11) The specific numerical values ​​of the arrangement pitches P1, P2, P201, and P202 in the X-axis direction of the sixth light guide plate lenses 28, 128, and 228 and the seventh light guide plate lenses 29, 129, and 229 can be appropriately changed to values ​​other than those mentioned above.

[0132] (12) The specific values ​​of the width dimensions W2 to A8 and height dimensions H2, H3, H202, H203 of the inclined surfaces and flat surfaces of the sixth light guide plate lenses 28, 128, 228 and the seventh light guide plate lenses 29, 129, 229 can be appropriately changed to values ​​other than those mentioned above.

[0133] (13) The specific materials used for the first light guide plate 14 and the second light guide plates 25, 125, and 225 can be changed as appropriate.

[0134] (14) The specific values ​​of the contact angle, inclination angle, and the like of each of the light guide plate lenses 21 to 23 provided on the first light guide plate 14 can be changed as appropriate.

[0135] (15) The positional relationship in the X-axis direction of the second LED 24 with respect to the second light guide plate 25, 125, 225 may be the same as the positional relationship in the X-axis direction of the first LED 13 with respect to the first light guide plate 14. In other words, the first LED 13 and the second LED 24 may be disposed on the same side in the X-axis direction.

[0136] (16) It is also possible to omit either or both of first light guide plate lens 21 and second light guide plate lens 22 provided in first light guide plate 14.

[0137] (17) The specific values ​​of the contact angle of the fourth light guide plate lens 26 provided on the second light guide plate 25, 125, 225 and the apex angle of the fifth light guide plate lens 27, 227, etc., can be changed as appropriate.

[0138] (18) It is also possible to omit either or both of the fourth light guide plate lens 26 and the fifth light guide plate lens 27, 227 provided in the second light guide plate 25, 125, 225.

[0139] (19) The thickness of the first light guide plate 14 may be decreased as it becomes farther from the first LED 13, and the first opposite principal surface 14C may be inclined.

[0140] (20) The thickness of the second light guide plate 25, 125, 225 may be smaller as it becomes farther away from the second LED 24, and the second opposite principal surface 25C, 125C, 225C may be inclined.

[0141] (21) The specific values ​​of the inclination angles and apex angles of the prism inclined surfaces 16B1, 16B2, 17B1, and 17B2 of the prisms 16B and 17B of the prism sheets 16 and 17 can be changed as appropriate. The specific materials used for the base materials 16A and 17A of the prism sheets 16 and 17 can be changed as appropriate. Similarly, the specific materials used for the prisms 16B and 17B can also be changed as appropriate.

[0142] (22) The specific cross-sectional shape of each of the prisms 16B, 17B of each of the prism sheets 16, 17 may be changed as appropriate. In this case, for example, any of the prism slopes 16B1, 16B2, 17B1, 17B2 of each of the prisms 16B, 17B may be curved to have a plurality of inclination angles.

[0143] (23) In the first louver 18, the specific value of the ratio (tan θ) obtained by dividing the width of the first translucent portion 18D by its height can be changed appropriately to a value other than tan 10°, for example, tan 12.5°, tan 15°, tan 17.5°, etc.

[0144] (24) The second louver 30 may be omitted.

[0145] (25) Instead of the first LED 13 and the second LED 24, a light source such as an organic EL (Electro Luminescence) may be used.

[0146] (26) A reflective polarizing sheet may be attached to the rear (outer) main surface of the array substrate constituting the liquid crystal panel 11 instead of the polarizing plate. The reflective polarizing sheet has a polarizing layer having a specific polarization axis (transmission axis), a multilayer film in which layers having different refractive indexes are alternately stacked, a protective layer, and the like. The polarizing layer has a polarization axis and an absorption axis perpendicular to the polarization axis, and can selectively transmit linearly polarized light parallel to the polarization axis and can convert circularly polarized light into linearly polarized light along the polarization axis. The polarization axis of this polarizing layer is perpendicular to the polarization axis of the polarizing plate attached to the outer main surface of the CF substrate. The multilayer film has a multilayer structure and has a reflection characteristic in which the reflectance for s waves contained in light is generally higher than the reflectance for p waves. By providing the multilayer film, the reflective polarizing sheet can reuse the s waves that would otherwise be absorbed by the polarizing layer by reflecting them to the rear side, thereby improving the light utilization efficiency (and therefore the brightness).

[0147] (27) It is also possible to use a prism sheet having prisms provided on the light-entering principal surface side instead of the first prism sheet 16 and the second prism sheet 17. This prism sheet is arranged such that the light-entering principal surface faces the first light-guide plate light-exiting principal surface 14B of the first light guide plate 14, and the light-exiting principal surface faces the first light-entering principal surface 18A of the first louver 18, and a plurality of prisms are arranged along the X-axis direction on the light-entering principal surface. Even when such a prism sheet is used, it is possible to supply light with less side lobe light to the first louver 18, and it is possible to ensure a sufficient amount of light transmitted through the first light-transmitting portion 18D.

[0148] (28) The in-vehicle liquid crystal display device 10 may be installed in a position other than in front of the passenger seat of a passenger vehicle. For example, it may be installed in a position between the passenger seat and the driver's seat. As the position of the liquid crystal display device 10 is changed, the required angular range of the viewing angle is also changed, so that the configurations of the first louver 18, the sixth light guide plate lenses 28, 128, 228, and the seventh light guide plate lenses 29, 129, 229, etc. may be changed accordingly. [Explanation of symbols]

[0149] 10... liquid crystal display device (display device), 11... liquid crystal panel (display panel), 12... backlight device (illumination device), 13... first LED (first light source), 14... first light guide plate, 14A... first light incident end surface (first end surface), 14B... first light guide plate light exiting main surface (first main surface), 14C... first opposite main surface (second main surface), 18... first louver (first sheet), 18A... first light incident main surface (third main surface), 18B... first light exiting main surface (fourth main surface), 18C... first light blocking portion, 18D... first light transmitting portion, 24... second LED (second light source), 25, 125, 225... second light guide plate, 25A... second light incident end surface ( 25B, 125B, 125B... second light guide plate light output main surface (fifth main surface), 25C, 125C, 225C... second opposite main surface (sixth main surface), 28A, 128A, 228A... first inclined surface, 28B, 128B, 228B... fourth inclined surface, 29A, 129A, 229A... second inclined surface, 29B, 129B, 229B... fifth inclined surface, 31, 131, 231... third inclined surface, 33... sixth inclined surface, θ1, θ101, θ201... first angle, θ2, θ102, θ202... second angle, θ3, θ103, θ203... third angle, θ4, θ104, θ204... fourth angle, θ5... fifth angle

Claims

1. A first light source; a first light guide plate in which at least a part of an outer peripheral end surface is a first end surface facing the first light source and into which light is incident, one main surface is a first main surface from which light is emitted, and the other main surface is a second main surface; a first sheet having one main surface serving as a third main surface facing the first main surface and through which light is incident, and the other main surface serving as a fourth main surface through which light is emitted; A second light source; a second light guide plate having at least a part of an outer peripheral end surface serving as a second end surface facing the second light source and receiving light therethrough, one main surface serving as a fifth main surface for emitting light, and the other main surface serving as a sixth main surface arranged facing the fourth main surface, the first sheet has at least two first light-shielding portions that are spaced apart from each other in a first direction including a direction from the first light source toward the first light guide plate and that block light, and a first light-transmitting portion that is arranged between the two first light-shielding portions and that transmits light; The sixth main surface of the second light guide plate is provided with a first inclined surface and a second inclined surface that are inclined from a side opposite to the second light source in the first direction toward the second light source, The first inclined surface has a first angle with respect to the first direction that is greater than 27°, The second inclined surface has an angle with respect to the first direction that is larger than the first angle and smaller than 58°.

2. The lighting device according to claim 1 , wherein the sixth main surface of the second light guide plate is provided with a third inclined surface that is inclined upward from the second light source side toward an opposite side in the first direction.

3. The third inclined surface includes a fourth inclined surface disposed opposite the second inclined surface with a gap therebetween, The lighting device according to claim 2 , wherein a third angle of the fourth inclined surface relative to the first direction is equal to or greater than 40°.

4. The lighting device according to claim 3 , wherein the third angle of the fourth inclined surface is equal to or greater than 65°.

5. The lighting device according to claim 3 , wherein the third angle of the fourth inclined surface is equal to or greater than 67°.

6. The third inclined surface includes a fourth inclined surface arranged to face the second inclined surface with a gap therebetween, and a fifth inclined surface arranged to face the first inclined surface with a gap therebetween, The lighting device according to claim 2 , wherein a fourth angle, which is an angle of the fifth inclined surface with respect to the first direction, is equal to a third angle, which is an angle of the fourth inclined surface with respect to the first direction.

7. The third inclined surface includes a fourth inclined surface arranged to face the second inclined surface with a gap therebetween, and a fifth inclined surface arranged to face the first inclined surface with a gap therebetween, The lighting device according to claim 2 , wherein a fourth angle, which is an angle of the fifth inclined surface with respect to the first direction, is smaller than a third angle, which is an angle of the fourth inclined surface with respect to the first direction.

8. the first inclined surface and the fourth inclined surface are arranged at an interval in the first direction, the third slope includes a sixth slope located between the first slope and the fourth slope, The lighting device according to claim 7 , wherein a fifth angle of the sixth inclined surface relative to the first direction is equal to the fourth angle.

9. The lighting device according to any one of claims 1 to 5, a display panel that performs display using light from the illumination device.

Images