Illumination device and display device

Abstract

The present invention provides an illumination device and a display device which suppress light emission outside a limited angle range and improve the brightness of emitted light in a direction inclined with respect to the front direction. The lighting device (12) comprises 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) at least comprises two first light shielding parts (18C) and a first light transmitting part (18D), and a 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) which are inclined. Both the first inclined surface (28A) and the second inclined surface (29A) rise in the first direction from the side opposite the second LED (24) toward the second LED (24) side, the angle of the first inclined surface (28A) with respect to the first direction is set to a first angle (theta1) greater than 27 DEG, and the angle of the second inclined surface (29A) with respect to the first direction is set to a second angle (theta2) greater than the first angle (theta1) and less than 58 DEG.

Description

Technical Field

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

[0002] Conventionally, as an example of a lighting device, there is known a lighting device described in the following Patent Document 1. The lighting device described in Patent Document 1 operates in at least two operation modes, namely, a free view mode and a restricted view mode. The lighting device includes a backlight system. A light guide plate is arranged in front of the backlight system, and a light source is arranged along the side of the light guide plate. The light guide plate has diffusion particles composed of a polymer dispersed in a resin matrix 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 restricted view mode, the backlight system is turned on and the light source is turned off. Prior art literature Patent Literature

[0003] Patent Document 1: U.S. Patent Application Publication No. 2017 / 0069236 Summary of the invention Technical Problems to be Solved by the Invention

[0004] The light guide plate of the lighting device described in the above-mentioned patent document 1 contains diffusion particles, so in the restricted field of view mode, the light emitted from the backlight system and incident on the light guide plate is diffused by the diffusion particles. Therefore, in the restricted field of view mode, it is easy to generate light that is emitted outside the restricted angle range, and there is a problem that it is difficult to emit light only within the restricted angle range. In addition, since the transmittance of the light guide plate is as high as at least 80%, in the free field of view mode, the light from the light source will not be fully diffused in the process of transmitting through the light guide plate. Therefore, in the free field of view mode, there is a problem of insufficient brightness of the emitted light in the direction inclined relative to the front direction.

[0005] The technology described in this specification has been accomplished based on the above situation, and its purpose is to suppress light from being emitted outside a limited angle range and to increase the brightness of light emitted in a direction inclined with respect to the front direction. Solutions to the problem

[0006] (1) An illumination device related to the technology described in this specification comprises: a first light source; a first light guide plate, at least a portion of its outer peripheral end surface is set as a first end surface opposite to the first light source and for light incidence, and one principal surface of the first light guide plate is set as a first principal surface for light emission, and the other principal surface is set as a second principal surface; a first sheet material, one principal surface of which is set as a third principal surface arranged toward the first principal surface and for light incidence, and the other principal surface is set as a fourth principal surface for light emission; a second light source; and a second light guide plate, at least a portion of its outer peripheral end surface is set as a second end surface opposite to the second light source and for light incidence, and one principal surface of the second light guide plate is set as a fifth principal surface for light emission, and the other principal surface is set as a sixth principal surface arranged toward the fourth principal surface, The first sheet material comprises at least: two first light-shielding portions, which are arranged at intervals in a first direction including a direction from the first light source toward the first light guide plate and block light; and a first light-transmitting portion, which is arranged between the two first light-shielding portions and transmits light, and the sixth main surface of the second light guide plate is provided with an inclined first slope and a second slope, and the inclination of the first slope and the second slope is to rise from the side opposite to the second light source toward the second light source side in the first direction, and the angle of the first slope relative to the first direction is set to a first angle greater than 27°, and the angle of the second slope relative to the first direction is set to a second angle greater than the first angle and less than 58°.

[0007] (2) In addition, the lighting device described above may be configured such that, based on the configuration described above (1), the sixth principal surface of the second light guide plate is provided with an inclined third slope, wherein the inclination of the third slope is such that it rises from the second light source side toward the opposite side of the second light source side in the first direction.

[0008] (3) In addition, the lighting device described above may be configured in accordance with (2) above, wherein the third inclined plane includes a fourth inclined plane, the fourth inclined plane is arranged opposite to the second inclined plane with a distance therebetween, and an angle of the fourth inclined plane relative to the first direction, i.e., a third angle, is set to be greater than 40°.

[0009] (4) In addition, in the lighting device described above in (3), the third angle of the fourth inclined surface may be set to be greater than or equal to 65°.

[0010] (5) In addition, in the lighting device described above in (3), the third angle of the fourth inclined surface may be set to be greater than or equal to 67°.

[0011] (6) In addition, the above-mentioned lighting device can also be based on any one of the above-mentioned (2) to (5), wherein the third inclined plane contains a fourth inclined plane and a fifth inclined plane, the fourth inclined plane is arranged opposite to the second inclined plane with a distance therebetween, the fifth inclined plane is arranged opposite to the first inclined plane with a distance therebetween, and the angle of the fifth inclined plane relative to the first direction, i.e., the fourth angle, is set to be equal to the angle of the fourth inclined plane relative to the first direction, i.e., the third angle.

[0012] (7) In addition, the above-mentioned lighting device can also be based on any one of the above-mentioned (2) to (5), wherein the third inclined plane contains a fourth inclined plane and a fifth inclined plane, the fourth inclined plane is arranged opposite to the second inclined plane with a distance therebetween, the fifth inclined plane is arranged opposite to the first inclined plane with a distance therebetween, and the angle of the fifth inclined plane relative to the first direction, i.e., the fourth angle, is set to be smaller than the angle of the fourth inclined plane relative to the first direction, i.e., the third angle.

[0013] (8) In addition, the above-mentioned lighting device can also be based on the above-mentioned (7), wherein the first inclined plane and the fourth inclined plane are arranged at intervals in the first direction, the third inclined plane contains a sixth inclined plane, and the sixth inclined plane is located between the first inclined plane and the fourth inclined plane, and the angle of the sixth inclined plane relative to the first direction, that is, the fifth angle, is set to be equal to the fourth angle.

[0014] (9) A display device according to the technology described in this specification includes: the lighting device described in any one of (1) to (8) above; and a display panel that performs display using light from the lighting device. Effects of the Invention

[0015] According to the technology described in this specification, it is possible to suppress the emission of light outside the limited angle range, and to increase the brightness of the light emitted in a direction inclined with respect to the front direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a side cross-sectional view of the liquid crystal display device according to Embodiment 1. Figure 2 It is a side cross-sectional view of a backlight device included in the liquid crystal display device according to Embodiment 1. Figure 3 It is a front cross-sectional view of the backlight device according to the first embodiment. Figure 4 This is a perspective view of a first light guide plate constituting the backlight device according to Embodiment 1, as viewed from the first opposite principal surface side. Figure 5 This is a bottom view showing the structure of the first opposite main surface of the first light guide plate according to the first embodiment. Figure 6 It is a side cross-sectional view of a second light guide plate constituting the backlight device according to the first embodiment. Figure 7 This is a bottom view showing the structure of the second opposite main surface of the second light guide plate according to the first embodiment. Figure 8 It is a curve chart showing the relationship between the position of the second light guide plate involved in embodiment 1 in the X-axis direction and the width dimension of the first slope, the width dimension of the fourth slope, the width dimension of the third plane, the width dimension of the second slope and the width dimension of the fifth slope. Fig. 9 Graph showing the relationship between the position of the second light guide plate in the X-axis direction and the height of the sixth light guide plate lens and the height of the seventh light guide plate lens according to Embodiment 1. FIG. Fig.10 This is a graph related to light distribution when the first slope and the second slope are changed in the demonstration experiment 1 according to the first embodiment. Fig.11 This is a graph relating to 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. Fig.12 This is a graph relating to 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. Fig.13 This is a graph relating to light distribution when the first LED and the second LED are lit together in Comparative Example 1 of Comparative Experiment 1 according to Embodiment 1. Fig.14 This is a graph relating to 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. Fig.15 This is a graph relating to 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 Embodiment 1. Fig.16 This is a graph relating to light distribution when the first LED and the second LED are lit together in Example 1 of Comparative Experiment 1 according to Embodiment 1. Fig.17 This is a diagram for explaining an angle of the liquid crystal display device installed in front of the front passenger seat of the passenger car according to the first embodiment in the X-axis direction with respect to the front direction. Fig.18 It is a side sectional view of the second light guide plate involved in Embodiment 2. Fig.19This is a graph related to light distribution when the fourth slope and the fifth slope are changed in the demonstration experiment 2 according to the second embodiment. Fig. 20 This is a graph relating to 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 Embodiment 2. Fig.21 This is a graph relating to 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 Embodiment 2. Fig. 22 This is a graph relating to light distribution when the first LED and the second LED are lit together in Example 2 of Comparative Experiment 2 according to Embodiment 2. Fig.23 It is a side sectional view of the second light guide plate involved in Embodiment 3. Fig.24 This is a front cross-sectional view of the second light guide plate involved in Embodiment 3. Fig.25 This is a graph related to the light distribution when the fourth slope is changed in the demonstration experiment 3 according to the third embodiment. Fig.26 In the empirical experiment 3 of implementation mode 3, Fig.25 A graph of a portion of . Fig. 27 This is a table showing the experimental results of the demonstration experiment 3 according to the third embodiment. Fig.28 This is a graph relating to 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 Embodiment 3. Fig.29 This is a graph relating to 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 Embodiment 3. Fig.30 This is a graph relating to light distribution when the first LED and the second LED are lit together in Example 3 of Comparative Experiment 3 according to Embodiment 3. DETAILED DESCRIPTION

[0017] <Implementation Method 1> according to Figures 1 to 17 Embodiment 1 is described. In this embodiment, a liquid crystal display device (display device) 10 is exemplified. In some drawings, the X-axis, Y-axis, and Z-axis are shown, and the directions of the axes are drawn in the directions shown in the drawings. In addition, the up and down directions are shown in FIG. Figure 2 and Figure 3As a reference, the upper side of the figure is set as the front side, and the lower side of the figure is set as the back side.

[0018] like Figure 1 As shown, 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 arranged on the back side of the liquid crystal panel 11 and irradiates light for display toward the liquid crystal panel 11. In this embodiment, an example of a vehicle-mounted liquid crystal display device 10 is provided. The vehicle-mounted liquid crystal display device 10 is mounted on, for example, a car navigation system that displays a map or the like as an image, a multi-function display that displays the operating status of equipment such as an air conditioner as an image on the basis of a map or the like, an instrument panel that displays instruments, warnings, etc. as an image, and an information system that displays a TV image, audio information, etc. as an image on the basis of a map or the like.

[0019] The liquid crystal panel 11 is a plate-shaped panel whose main surface is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The central side portion of the main surface of the liquid crystal panel 11 becomes a display area capable of displaying images, and the peripheral end side portion of the frame-shaped portion surrounding the display area becomes 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. The substrate arranged on the surface side of the pair of substrates constituting the liquid crystal panel 11 is a CF substrate (opposing substrate), and the substrate arranged on the back side is an array substrate (TFT substrate). Color filters such as R (red), G (green), and B (blue), a shading portion (black matrix) separating adjacent color filters, etc. are provided on the CF substrate. The array substrate (TFT substrate) is provided with at least mutually orthogonal gate wiring and source wiring, a switching element (such as TFT) connected to the gate wiring and the source wiring, and a pixel electrode connected to the switching element to form a pixel. In addition, an alignment film is provided on each inner surface of the array substrate and the CF substrate constituting the liquid crystal panel 11. In addition, polarizing plates are respectively mounted on the outer surfaces of the array substrate and the CF substrate constituting the liquid crystal panel 11 .

[0020] Next, the backlight device 12 will be described. Figure 1 As shown, the backlight device 12 comprises at least: a first LED (first light source) 13; a first light guide plate 14, which guides the light from the first LED 13; a reflective sheet 15, which is arranged on the back side (opposite to the light emitting side) of the first light guide plate 14; a first prism sheet 16, which is arranged on the surface side (light emitting side) of the first light guide plate 14; and a second prism sheet 17, which is arranged on the surface side of the first prism sheet 16.

[0021] like Figure 1As shown, the first LED 13 is roughly block-shaped, and one of the pairs of faces along the Y-axis direction and the Z-axis direction becomes the first light-emitting surface 13A that emits light. A plurality of first LEDs 13 are arranged at intervals along the Y-axis direction. The first LED 13 is mounted on an LED substrate. The first LED 13 is configured such that an LED chip is sealed with a sealing material on a substrate portion mounted on the LED substrate. The LED chip provided by the first LED 13 emits, for example, monochromatic blue light. Phosphors are dispersed in the sealing material provided by the first LED 13. The phosphors contained in the sealing material include yellow phosphors, green phosphors, red phosphors, and the like. The first LED 13 having such an LED chip and a sealing material emits white light as a whole.

[0022] The first light guide plate 14 is made of a synthetic resin material (such as acrylic resin such as PMMA) having a refractive index sufficiently higher than that of air and being substantially transparent. Figure 1 As shown, the first light guide plate 14 is formed in a plate shape, and its main surface is parallel to the main surface of the liquid crystal panel 11. In addition, 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 is consistent with the Z-axis direction. The first light guide plate 14 is arranged along the X-axis direction (first direction) relative to the first LED 13, and is arranged along the Z-axis direction relative to the liquid crystal panel 11 and each prism sheet 16, 17. The first light guide plate 14 is arranged on one side of the X-axis direction (the first direction) relative to the first LED 13. Figure 1 on the right side). One of the outer peripheral end faces of the first light guide plate 14 is a first light incident end face (first end face) 14A opposite to the first light emitting surface 13A of the first LED 13. The first light incident end face 14A is a face parallel to the first light emitting surface 13A of the first LED 13, and the first light incident end face 14A is incident with light emitted from the first light emitting surface 13A. Therefore, it can be said that in the first light guide plate 14, the first LED 13 is arranged only on one side in the X-axis direction, and the first light guide plate 14 and the first LED 13 together constitute a single-side light incident type backlight unit. The main surface on the surface side opposite to the first prism sheet 16 of the pair of main surfaces of the first light guide plate 14 becomes the first light guide plate light emitting main surface (first main surface) 14B from which the light guided inside is emitted. The main surface on the back side opposite to the reflective sheet 15 of the pair of main surfaces of the first light guide plate 14 is the first opposite main surface (second main surface) 14C located on the side opposite to the first light guide plate light emitting main surface 14B. Furthermore, the first light guide plate 14 has a function of introducing light emitted from the first LED 13 toward the first light guide plate 14 from the first light incident end surface 14A and causing the light to propagate inside and then be emitted upward in the Z-axis direction toward the surface side (light-exiting side). The detailed structure of the first light guide plate 14 will be described later. In addition, the normal direction of the first light incident end surface 14A is consistent with the X-axis direction (the arrangement direction of the first LED 13 and the first light guide plate 14).

[0023] like Figure 1 As shown, the reflective sheet 15 is arranged in such a manner that its main surface is parallel to the main surfaces of the liquid crystal panel 11 and the first light guide plate 14 and covers the first opposite main surface 14C of the first light guide plate 14. The reflective sheet 15 has excellent light reflectivity and can efficiently direct the light leaking from the first opposite main surface 14C of the first light guide plate 14 toward the surface side, that is, the light emitting main surface 14B of the first light guide plate. The reflective sheet 15 has an outer shape that is one circle larger than the first light guide plate 14, and is arranged to overlap with the first opposite main surface 14C in substantially the entire area.

[0024] like Figure 1 As shown, the first prism sheet 16 and the second prism sheet 17 are formed in a sheet shape, and their respective main surfaces are parallel to the main surfaces of the liquid crystal panel 11 and the first light guide plate 14. In addition, the main surfaces of the first prism sheet 16 and the second prism sheet 17 are parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The first prism sheet 16 and the second prism sheet 17 are stacked on the surface side of the first light guide plate 14, and have the function of giving a predetermined optical effect to the light emitted from the first light guide plate light emitting main surface 14B of the first light guide plate 14 so that it can be emitted.

[0025] like Figure 1 As shown, the first prism sheet 16 has a first substrate 16A and a first prism 16B. The first substrate 16A is in sheet form, and the first prism 16B is arranged on the main surface (light emitting main surface) of the surface side (light emitting side) of the first substrate 16A. The first substrate 16A is made of a substantially transparent synthetic resin, specifically, a crystalline transparent resin material such as PET (polyethylene terephthalate). During the manufacture, the first substrate 16A is formed into a sheet by stretching the crystalline transparent resin material as the raw material by a biaxial stretching process, which is preferred from the perspective of achieving a reduction in manufacturing costs. The first prism 16B is made of a substantially transparent ultraviolet curing resin material, which is a type of photocurable resin material. When manufacturing the first prism sheet 16, for example, an uncured ultraviolet curable resin material is filled into a molding mold, and the first substrate 16A is attached to the open end of the mold, so that the uncured ultraviolet curable resin material is arranged in contact with the main surface on the surface side. If ultraviolet rays are irradiated to the ultraviolet curable resin material through the first substrate 16A in this state, the ultraviolet curable resin material is cured, and the first prism 16B is integrated with the first substrate 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 set in the range of 1.49 to 1.52, and most preferably set to 1.49.

[0026] like Figure 2 As shown, the first prism 16B is arranged in a manner that protrudes from the main surface of the first substrate 16A along the Z-axis direction toward the surface side (the opposite side of the first light guide plate 14 side). The cross-sectional shape of the first prism 16B cut along the X-axis direction is formed into a roughly triangular shape (roughly mountain-shaped) and extends straightly along the Y-axis direction (the second direction). In the main surface of the first substrate 16A, a plurality of first prisms 16B are arranged continuously and substantially without intervals along the X-axis direction (the first direction). The first prism 16B has a pair of inclined surfaces 16B1 and 16B2. Among the pair of inclined surfaces 16B1 and 16B2 of the first prism 16B, the inclined surface located on the first LED 13 side in the X-axis direction is set as the first prism inclined surface 16B1, and the inclined surface on the opposite side is set as the second prism inclined surface 16B2. The first prism inclined surface 16B1 has a protruding portion from the first LED 13 side ( Figure 2 ) to the opposite side ( Figure 2 The light incident on the first prism 16B, which mainly travels in the direction close to the first LED 13 in the X-axis direction, is refracted by the first prism inclined surface 16B1. The second prism inclined surface 16B2 has a first prism sheet 16 on the opposite side from the first LED 13 side in the X-axis direction ( Figure 2 The right side of the LED 13 ( Figure 2 The light incident on the first prism 16B that mainly travels in the direction away from the first LED 13 in the X-axis direction is refracted by the second prism inclined surface 16B2. Most of the light refracted by the pair of inclined surfaces 16B1 and 16B2 in the first prism 16B is selectively focused upward in the X-axis direction.

[0027] Moreover, if Figure 2As shown, in the first prism 16B, when the inclination angle (third base angle) θ6 of the first prism bevel 16B1 relative to the X-axis direction and the inclination angle (fourth base angle) θ7 of the second prism bevel 16B2 relative to the X-axis direction are compared, the former is larger than the latter. That is to say, the first prism 16B is an unequal-sided triangle with an asymmetric cross-sectional shape. Specifically, the inclination angle θ6 of the first prism bevel 16B1 relative to the X-axis direction is preferably in the range of 50° to 60°, with 55° being the most preferred. In contrast, the inclination angle θ7 of the second prism bevel 16B2 relative to the X-axis direction is preferably in the range of 35° to 50°, with 45° being the most preferred. In addition, in the first prism 16B, the angle (second vertex angle) θ8 formed by a pair of bevels 16B1 and 16B2 is preferably set in the range of 70° to 95°, with 80° being the most preferred. In addition, for the multiple first prisms 16B arranged along the Y-axis direction, their height dimensions, width dimensions, inclination angles of each inclined surface 16B1 and 16B2 relative to the X-axis direction, etc. are all approximately the same, and the arrangement intervals between adjacent first prisms 16B are also approximately fixed and arranged at equal intervals.

[0028] like Figure 1 As shown, the second prism sheet 17 has a second substrate 17A and a second prism 17B, the second substrate 17A is in sheet form, and the second prism 17B is arranged on the main surface (light emitting main surface) of the surface side (light emitting side) of the second substrate 17A. The second substrate 17A is made of a substantially transparent synthetic resin, specifically, a crystalline transparent resin material such as PET, which is the same as the first substrate 16A. The second prism 17B is made of a substantially transparent ultraviolet curing 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 curing resin material constituting the second prism 17B is an acrylic resin such as PMMA, and its refractive index is higher than the refractive index of the material of the first prism 16B, for example, set to about 1.61.

[0029] like Figure 2As shown, the second prism 17B is arranged in a manner that protrudes from the main surface of the second substrate 17A along the Z-axis direction toward the surface side (the opposite side of the first prism sheet 16). The cross-sectional shape of the second prism 17B cut along the X-axis direction is formed into a roughly triangular shape (roughly mountain-shaped) and extends straightly along the Y-axis direction, and a plurality of second prisms 17B are arranged continuously and substantially without intervals along the X-axis direction in the main surface of the second substrate 17A. The second prism 17B has a pair of inclined surfaces 17B1 and 17B2. Among the pair of inclined surfaces 17B1 and 17B2 of the second prism 17B, the inclined surface located on the first LED 13 side in the X-axis direction is set as the third prism inclined surface 17B1, and the inclined surface on the opposite side is set as the fourth prism inclined surface 17B2. The third prism inclined surface 17B1 has a protruding portion from the first LED 13 side ( Figure 2 ) to the opposite side ( Figure 2 The light incident on the second prism 17B, which mainly travels in the direction close to the first LED 13 in the X-axis direction, is refracted by the third prism inclined surface 17B1. The fourth prism inclined surface 17B2 has a side opposite to the first LED 13 side in the X-axis direction of the second prism sheet 17 ( Figure 2 The right side of the LED 13 ( Figure 2 The light incident on the second prism 17B that mainly travels in the direction away from the first LED 13 in the X-axis direction is refracted by the fourth prism inclined surface 17B2. Most of the light refracted by the pair of inclined surfaces 17B1 and 17B2 in the second prism 17B is selectively focused upward in the X-axis direction.

[0030] Moreover, if Figure 2As shown, in the second prism 17B, the inclination angle (fifth base angle) θ9 of the third prism bevel 17B1 relative to the X-axis direction is set to be the same as the inclination angle (sixth base angle) θ10 of the fourth prism bevel 17B2 relative to the X-axis direction. In other words, the second prism 17B is an isosceles triangle with a symmetrical cross-sectional shape. On this basis, the inclination angles θ9 and θ10 of the third prism bevel 17B1 and the fourth prism bevel 17B2 relative to the X-axis direction are smaller than the inclination angle θ6 of the first prism bevel 16B1 relative to the X-axis direction. Specifically, the inclination angles θ9 and θ10 of the third prism bevel 17B1 and the fourth prism bevel 17B2 relative to the X-axis direction are preferably in the range of 40° to 50°, with 45° being the most preferred. In contrast, the angle (third vertex angle) θ11 formed by a pair of inclined surfaces 17B1 and 17B2 of the second prism 17B is preferably set in the range of 80° to 100°, and is most preferably set to 90°, that is, a right angle. In addition, for the multiple second prisms 17B arranged along the Y-axis direction, their height dimensions, width dimensions, and the inclination angles of each inclined surface 17B1 and 17B2 relative to the X-axis direction are all approximately the same, and the arrangement intervals between adjacent second prisms 17B are also approximately fixed and arranged at equal intervals. In addition, the height dimension and arrangement interval of the second prism 17B are different from the height dimension and arrangement interval of the first prism 16B, but this is preferred from the perspective of suppressing the generation of interference fringes called moiré.

[0031] According to the first prism sheet 16 and the second prism sheet 17 constructed as described above, the following functions and effects can be obtained. That is, for 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, most of it is irradiated to the second prism bevel 16B2 of the first prism 16B and refracted, and is emitted while rising, or is directed toward the first prism bevel 16B1. Here, since the inclination angle θ6 of the first prism 16B with respect to the X-axis direction is greater than the inclination angle θ7 of the second prism 17B with respect to the X-axis direction, the light incident on the first prism sheet 16 is less likely to be irradiated to the first prism bevel 16B1 than the case where the same angle or the size of the angle is set to an opposite relationship. If the incident light of the first prism sheet 16 is irradiated to the first prism bevel 16B1 of the first prism 16B, it will not rise when emitted from the first prism 16B, but tends to be easily emitted as side lobe light (stray light). Therefore, if the incident light of the first prism sheet 16 is less likely to directly hit the first prism slope 16B1 of the first prism 16B, the generation of side lobe light can be suppressed, and as a result, the light utilization efficiency is improved.

[0032] Most of the light emitted from the first prism sheet 16 and incident on the second prism sheet 17 is refracted by the fourth prism inclined surface 17B2 of the second prism 17B, and is emitted while rising, or is directed toward the third prism inclined surface 17B1. Here, since the inclination angle θ7 of the second prism 17B with respect to the X-axis direction is smaller than the inclination angle θ6 of the first prism 16B with respect to the X-axis direction, the light refracted by the fourth prism inclined surface 17B2 and directed toward the third prism inclined surface 17B1 is more likely to return to the first prism sheet 16 side through the third prism inclined surface 17B1 than the case where the same angle or the size of the angle is set to an opposite relationship. As a result, the amount of light (hereinafter referred to as returning light) returning from the second prism sheet 17 to the first prism sheet 16 side increases. The returning light reaches the second prism sheet 17 again by reflection in the backlight device 12, and rises and exits through any one of a pair of inclined surfaces 17B1 and 17B2 in the second prism 17B, thereby improving the light utilization efficiency. Since the optical path of the returning light from the second prism sheet 17 to the return becomes complicated, the rising angle given by the second prism 17B also becomes diversified, thereby improving the viewing angle characteristics. As described above, it is possible to achieve an improvement in the viewing angle characteristics and brightness.

[0033] Next, the detailed structure of the first light guide plate 14 is described. Figure 2 and Figure 3 As shown, a first light guide plate lens 21, a second light guide plate lens 22 and a third light guide plate lens 23 are provided on the first light guide plate 14. Figure 3 As shown, the first light guide plate lens 21 is arranged on the first light guide plate light emitting 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 them are arranged along the Y-axis direction. In the present embodiment, the first light guide plate lens 21 is a so-called double convex lens. The first light guide plate lens 21 is convex and protrudes from the first light guide plate light emitting main surface 14B to the surface side. Specifically, the first light guide plate lens 21 is formed into a semi-cylindrical shape whose cross-sectional shape cut along the Y-axis direction is semicircular and extends straight along the X-axis direction, and its surface is a first arc-shaped surface 21A. When the angle formed by the tangent at the base end of the first arc-shaped surface 21A and the Y-axis direction is set as the "contact angle", the contact angle of the first light guide plate lens 21 is set to, for example, about 62°. The contact angles, width dimensions (arrangement intervals) and height dimensions of the plurality of first light guide plate lenses 21 arranged along the Y-axis direction are all substantially the same. To integrally set the first light guide plate lens 21 of this structure on the first light guide plate 14, for example, the first light guide plate 14 can be manufactured by injection molding, and a transfer shape for transferring the first light guide plate lens 21 can be pre-formed on the molding surface for molding the main light emitting surface 15B in the molding mold.

[0034] like Figure 3As shown, the second light guide plate lens 22 is arranged on the first opposite main 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 them are arranged along the Y-axis direction. In the present embodiment, the second light guide plate lens 22 is a convex prism protruding from the first opposite main surface 14C to the back side. Specifically, the second light guide plate lens 22 is formed so that the cross-sectional shape cut along the Y-axis direction is roughly triangular (roughly mountain-shaped) and extends straight along the X-axis direction. The width dimension (dimension in the Y-axis direction) of the second light guide plate lens 22 is fixed over the entire length range in the X-axis direction. The cross-sectional shape of the second light guide plate lens 22 is roughly an isosceles triangle, and the second light guide plate lens 22 has a pair of first light guide plate inclined surfaces 22A. The vertex angle of the second light guide plate lens 22 is preferably set to an obtuse angle (an angle exceeding 90°), specifically, in the range of 100° to 150°, and most preferably 140°. The vertex angles, width dimensions (arrangement intervals), and height dimensions of the plurality of second light guide plate lenses 22 arranged along the Y-axis direction are all substantially the same. In this embodiment, the arrangement intervals of the second light guide plate lenses 22 are greater than the arrangement intervals of the first light guide plate lenses 21. To integrally set the second light guide plate lenses 22 of such a configuration on the first light guide plate 14, for example, the first light guide plate 14 can be manufactured by injection molding, and a transfer shape for transferring the second light guide plate lenses 22 can be formed in advance on the molding surface for molding the light emitting main surface 15B in the molding mold thereof.

[0035] According to the first light guide plate 14 constructed in this way, Figure 3 As shown, for the light propagating in the first light guide plate 14, on the side of the first light guide plate light emitting main surface 14B in the Z-axis direction, it is repeatedly reflected by irradiating the first arc-shaped surface 21A of each first light guide plate lens 21, and moves roughly in a zigzag shape along the X-axis direction. On the other hand, for the light propagating in the first light guide plate 14, on the side of the first opposite main surface 14C in the Z-axis direction, it is repeatedly reflected by irradiating a pair of first light guide plate inclined surfaces 22A of each second light guide plate lens 22, and moves roughly in a zigzag shape along the X-axis direction. As a result, the expansion of the light propagating in the first light guide plate 14 in the Y-axis direction is limited, so it is not easy to produce uneven brightness between the vicinity of the first LED 13 and its surroundings in the Y-axis direction.

[0036] like Figure 2 As shown, the third light guide plate lens 23 is disposed on the first opposite main surface 14C of the first light guide plate 14. A plurality of third light guide plate lenses 23 are arranged at intervals along the X-axis direction. The third light guide plate lens 23 protrudes from the first opposite main surface 14C toward the back side along the Z-axis direction. The third light guide plate lens 23 has: a second light guide plate inclined surface 23A, which is disposed on the opposite side of the first LED 13 side in the X-axis direction ( Figure 2The third light guide plate inclined surface 23B is arranged on the side of the first LED 13 in the X-axis direction ( Figure 2 and a fourth light guide plate inclined surface 23C, which is 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 a first light guide plate 14 in the X-axis direction from the first LED 13 side ( Figure 2 to the left side) to the opposite side ( Figure 2 The third light guide plate inclined surface 23B has an inclination rising from the opposite side (the right side) of the first LED 13 side in the X-axis direction of the first light guide plate 14. Figure 2 The right side of the LED 13 ( Figure 2 The fourth light guide plate inclined surface 23C has an inclination rising from the first LED 13 side (the left side) in the X-axis direction of the first light guide plate 14. Figure 2 to the left side) to the opposite side ( Figure 2 right side) with an ascending slope.

[0037] like Figure 2 As shown, the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B reflect the light propagating in the first light guide plate 14, and make it rise toward the surface side in a manner close to the Z-axis direction, thereby promoting the emission from the first light guide plate light emitting main surface 14B. Specifically, the second light guide plate inclined surface 23A mainly plays the role of reflecting the light traveling in a manner away from the first LED 13 in the X-axis direction so as to make it rise. On the other hand, the third light guide plate inclined surface 23B mainly plays the role of reflecting the light traveling in a manner close to the first LED 13 in the X-axis direction so as to make it rise. The second light guide plate inclined surface 23A has a slope that the farther away from the first LED 13 in the X-axis direction, the smaller the distance from the first light guide plate light emitting main surface 14B (the part where the third light guide plate lens 23 is not provided). The inclination angle of the second light guide plate inclined surface 23A relative to the X-axis direction is, for example, about 8°. The third light guide plate inclined surface 23B has a slope in which the distance from the first light guide plate light emitting main surface 14B increases as it moves away from the first LED 13 in the X-axis direction, i.e., a slope opposite to that of the second light guide plate inclined surface 23A. The third light guide plate inclined surface 23B is formed to have an inclination angle of about 80° with respect to the X-axis direction, which is close to a vertical slope and is larger than the inclination angle of the second light guide plate inclined surface 23A.

[0038] In addition, if Figure 2 , Figure 4 and Figure 5As shown, the plurality of third light guide plate lenses 23 arranged along the X-axis direction are designed so that the further away from the first LED 13 in the X-axis direction, the greater the height dimension (dimension in the Z-axis direction) and the length dimension (dimension in the X-axis direction) increase. In more detail, when the third light guide plate lens 23 close to the first LED 13 in the X-axis direction is compared with the third light guide plate lens 23 far away from the first LED 13 in the X-axis direction, the latter has a larger area of ​​the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B than the former. Thus, although on the side close to the first LED 13 in the X-axis direction, the light is difficult to be irradiated on 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 and the light emission is suppressed, on the side far away from the first LED 13 in the X-axis direction, the light is easily irradiated on 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 to promote the light emission. As a result, the amount of light emitted from the light emitting main surface 14B of the first light guide plate is made uniform on the first LED 13 side and the opposite side in the X-axis direction.

[0039] like Figure 2 As shown, in the fourth light guide plate inclined surface 23C, the side opposite to the first LED 13 side in the X-axis direction ( Figure 2 The end portion of the right side of the LED 13 in the X-axis direction is connected to the inclined surface 23A of the second light guide plate. Figure 2The end of the fourth light guide plate inclined surface 23C (on the left side) is connected to the third light guide plate inclined surface 23B. The fourth light guide plate inclined surface 23C has a slope in which the distance from the first light guide plate light emitting main surface 14B (the portion where the third light guide plate lens 23 is not provided) increases as it is further away from the first LED 13 in the X-axis direction. In other words, the fourth light guide plate inclined surface 23C is formed to have the same slope as the third light guide plate inclined surface 23B. The inclination angle of the fourth light guide plate inclined surface 23C relative to the X-axis direction is, for example, set to 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 constructed in this way reflects the light traveling in the first light guide plate 14 in a manner away from the first LED 13, thereby directing the light toward the first light guide plate light emitting main surface 14B side, but the incident angle of the light relative to the first light guide plate light emitting main surface 14B does not exceed the critical angle. Therefore, the light is totally reflected by the main light emitting surface 14B of the first light guide plate, and is guided to be farther away from the first LED 13. As a result, the emitted light emitted from the main light emitting surface 14B of the first light guide plate is not easily deflected to the side of the first LED 13 in the X-axis direction. As described above, the first light guide plate 14 is constructed in such a way that the inclination angle relative 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. In addition, the plurality of fourth light guide plate inclined surfaces 23C arranged along the X-axis direction are designed so that the length dimension becomes smaller as they are farther away from the first LED 13 in the X-axis direction. This is because the length dimension of the third light guide plate lens 23 becomes larger as it is farther away from the first LED 13 in the X-axis direction, and the occupied range of the third light guide plate lens 23 becomes larger.

[0040] like Figures 3 to 5 As shown, the third light guide plate lens 23 of the above-mentioned structure is configured to be sandwiched between two adjacent second light guide plate lenses 22 in the Y-axis direction. Therefore, the third light guide plate lens 23 is configured to be alternately and repeatedly arranged with the second light guide plate lenses 22 in the Y-axis direction. The maximum value of the protruding dimension (height dimension) of the third light guide plate lens 23 protruding from the first opposite main surface 14C is smaller than the protruding dimension of the second light guide plate lens 22 also protruding from the first opposite main surface 14C. Therefore, even if the third light guide plate lens 23 is located on the side farthest from the first LED 13 in the X-axis direction, it will not protrude to the back side more than the second light guide plate lens 22.

[0041] However, the vehicle-mounted liquid crystal display device 10 is sometimes arranged, for example, to be located in front of the front passenger seat of a passenger car. In this case, for example, while the passenger car is driving, it is sometimes required to limit the viewing angle so that the display image of the liquid crystal display device 10 can be visually recognized from the front passenger seat, but the display image of the liquid crystal display device 10 cannot be visually recognized from the driver's seat. Furthermore, for example, while the passenger car is stopped, it is sometimes required not to limit the viewing angle so that the display image of the liquid crystal display device 10 can be visually recognized from both the front passenger seat and the driver's seat. In addition, the vehicle-mounted liquid crystal display device 10 is set in a posture where the X-axis direction is roughly consistent with the horizontal direction and the Y-axis direction is parallel to the vertical direction. In order to respond to such requirements, Figure 1 As shown, the backlight device 12 involved in this embodiment, in addition to the above-mentioned components, further includes at least a first grid (first sheet) 18 arranged on the surface side of the second prism sheet 17, a second LED (second light source) 24, and a second light guide plate 25 arranged on the surface side of the first grid 18. In addition, the backlight device 12 involved in this embodiment includes a second grid 30 arranged on the surface side of the second light guide plate 25 in order to prevent reflection on the windshield of the passenger car. The second grid 30 will be described later.

[0042] use Figure 1 and Figure 2 The structure of the first grid 18 is described below. Figure 1 As shown, the main surface of the first grid 18 is parallel to the main surfaces of the liquid crystal panel 11 and the first light guide plate 14, and is in the shape of a sheet. In addition, the main surface of the first grid 18 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The first grid 18 has the function of limiting the range of the emission angle of light in the X-axis direction. The first grid 18 has a first light incident main surface (third main surface) 18A on the back side and a first light emitting main surface (fourth main surface) 18B on the surface side. The first light incident main surface 18A is opposite to the main surface of the surface side (light emitting side) of the second prism sheet 17. The first light emitting main surface 18B is opposite to the second opposite main surface 25C of the second light guide plate 25 described later.

[0043] like Figure 2As shown, the first grille 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, for example, a light-shielding resin material (light-shielding material) that is black and blocks light. The first light-shielding portion 18C is in the form of a layer extending along the Y-axis direction and the Z-axis direction, and a plurality of the first light-transmitting portions 18D are arranged 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 substantially transparent and transmits light. The first light-transmitting portion 18D is in the form of a layer extending along the Y-axis direction and the Z-axis direction, and a plurality of the first light-transmitting portions 18D are arranged at intervals in the X-axis direction. A plurality of the first light-shielding portions 18C and the first light-transmitting portions 18D are arranged alternately and repeatedly in the X-axis direction. Therefore, the first light-transmitting portion 18D is between two first light-shielding portions 18C that are adjacent to each other at intervals in the X-axis direction, and the first light-shielding portion 18C is between two first light-transmitting portions 18D that are adjacent to each other at intervals in the X-axis direction. The light incident on the first light incident principal surface 18A of the first grating 18 is transmitted through the first light-transmitting portion 18D arranged between the two first light-shielding portions 18C adjacent in the X-axis direction, and is emitted from the first light-emitting principal surface 18B. The emission angle of the emitted light from the first light-emitting principal surface 18B in the X-axis direction is limited by the two first light-shielding portions 18C adjacent in the X-axis direction. In addition, the emission angle of the emitted light from the first light-emitting principal surface 18B in the Y-axis direction is not limited by the first grating 18. The emission angle range of the emitted light from the first light-emitting principal surface 18B in the X-axis direction is defined by two straight lines that obliquely connect the ends of the two first light-shielding portions 18C sandwiching the first light-transmitting portion 18D in the Z-axis direction. The emission angle range of the transmitted light of the first light-transmitting portion 18D in the X-axis direction varies according to the ratio of the width W1 to the height H1 of the first light-transmitting portion 18D. In addition, the first grid 18 has a pair of sheet carriers that sandwich and carry the plurality of first light shielding portions 18C and the plurality of first light transmitting portions 18D from the front side and the back side. The sheet carriers are made of a substantially transparent light-transmitting resin material. The sheet carriers extend over the entire area of ​​the first grid 18 and hold the plurality of first light shielding portions 18C and the plurality of first light transmitting portions 18D together.

[0044] Specifically, if Figure 2As shown, the ratio of the width W1 of the first light-transmitting portion 18D in the first grille 18 divided by the height H1 is equal to "tan10°". In this way, the absolute value of the maximum value of the angle formed by the light passing through the first light-transmitting portion 18D relative to the Z-axis direction is 10°. Assuming that the range of the emission angle of the emitted light of the backlight device 12 is sufficiently narrowed compared to the case where the ratio of the width of the first light-transmitting portion 18D divided by the height is greater than "tan10°". As a result, the display image of the liquid crystal display device 10 can be visually recognized from the passenger seat, but the display image of the liquid crystal display device 10 cannot be visually recognized from the driver's seat, which is preferred in terms of limiting the viewing angle. In addition, assuming that the ratio of the width of the first light-transmitting portion 18D divided by the height is less than "tan10°", the amount of light shielded by the first light-shielding portion 18C is reduced, and the light utilization efficiency is improved.

[0045] Appropriate use Figures 1 to 3 , Figure 6 and Figure 7 , describing the structure of the second LED 24 and the second light guide plate 25. Figure 6 It is an enlarged cross-sectional view of the second light guide plate 25 among the components of the backlight device 12 . Figure 7 2 is a bottom view showing the main surface of the back side of the second light guide plate 25. Figure 1 As shown, the second LED 24 is roughly block-shaped, and one of the pair of faces along the Y-axis direction and the Z-axis direction becomes the first light-emitting surface 13A that emits light. A plurality of second LEDs 24 are arranged at intervals along the Y-axis direction. The second LED 24 is mounted on an LED substrate. The second LED 24 is configured such that an LED chip is sealed with a sealing material on a substrate portion mounted on the LED substrate. The LED chip possessed by the second LED 24 emits, for example, monochromatic blue light. Phosphors are dispersed in the sealing material possessed by the second LED 24. The phosphors contained in the sealing material include yellow phosphors, green phosphors, red phosphors, and the like. The second LED 24 having such an LED chip and a sealing material emits white light as a whole.

[0046] The second light guide plate 25 is made of a synthetic resin material (such as acrylic resin such as PMMA) having a refractive index sufficiently higher than that of air and being substantially transparent. Figure 1 As shown, the second light guide plate 25 is formed in a plate shape, and its main surface is parallel to the main surface of the liquid crystal panel 11. In addition, 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 is consistent with the Z-axis direction. The second light guide plate 25 is arranged along the X-axis direction (first direction) relative to the second LED 24, and is arranged along the Z-axis direction relative to the liquid crystal panel 11 and the first grid 18. The second light guide plate 25 is arranged on the other side of the X-axis direction (the first direction) relative to the second LED 24. Figure 1That is, 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, the first LED 13 and the second LED 24 are dispersedly arranged in the X-axis direction, so even if the first LED 13 and the second LED 24 are lit separately, heat is difficult to accumulate.

[0047] like Figure 1 As shown, one of the outer peripheral end faces of the second light guide plate 25 becomes the second light incident end face (second end face) 25A opposite to the second light emitting surface 24A of the second LED 24. The second light incident end face 25A is a face parallel to the second light emitting surface 24A of the second LED 24, and the second light incident end face 25A is incident with the light emitted from the second light emitting surface 24A. Therefore, it can be said that in the second light guide plate 25, the second LED 24 is arranged only on one side in the X-axis direction, and the second light guide plate 25 and the second LED 24 together constitute a single-side light incident type backlight unit. The main surface of the surface side of the pair of main surfaces of the second light guide plate 25 that is opposite to the second grid 30 described later becomes the second light guide plate light emitting main surface (fifth main surface) from which the light guided inside is emitted. 25B. The main surface on the back side opposite to the first grid 18 among the pair of main surfaces of the second light guide plate 25 is a second opposite main surface (sixth main surface) 25C located on the side opposite to the second light guide plate light emitting main surface 25B. The second opposite main surface 25C of the second light guide plate 25 is arranged toward the first light emitting main surface 18B of the first grid 18 in the Z-axis direction. Moreover, the second light guide plate 25 is capable of introducing light emitted from the second LED 24 toward the second light guide plate 25 from the second light incident end surface 25A, and after the light propagates inside, it is emitted upwardly from the second light guide plate light emitting main surface 25B along the Z-axis direction toward the liquid crystal panel 11 on the surface side (light emitting side). In addition, the second light guide plate 25 is capable of introducing the outgoing light from the first grid 18 from the second opposite main surface 25C, and causing the light to be emitted from the second light guide plate light emitting main surface 25B toward the second grid 30 (liquid crystal panel 11) on the surface side. Furthermore, the normal direction of the second light incident end surface 25A coincides with the X-axis direction (the arrangement direction of the second LEDs 24 and the second light guide plate 25 ).

[0048] like Figure 2 as well as Figure 3 As shown, 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 are provided on the second light guide plate 25. Figure 3As shown, the fourth light guide plate lens 26 is arranged on the second light guide plate light emitting 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 them are arranged along the Y-axis direction. In the present embodiment, the fourth light guide plate lens 26 is a so-called double convex lens. The fourth light guide plate lens 26 is convex and protrudes from the second light guide plate light emitting main surface 25B to the surface side. Specifically, the fourth light guide plate lens 26 is formed into a semi-cylindrical shape whose cross-sectional shape cut along the Y-axis direction is semicircular and extends straight along the X-axis direction, and its surface is a second arc-shaped surface 26A. When the angle formed by the tangent at the base end of the second arc-shaped surface 26A and the Y-axis direction is set as the "contact angle", the contact angle of the fourth light guide plate lens 26 is set to, for example, about 30°. The contact angles, width dimensions (arrangement intervals) and height dimensions of the plurality of fourth light guide plate lenses 26 arranged along the Y-axis direction are all substantially the same. To integrally set the fourth light guide plate lens 26 of this structure on the second light guide plate 25, for example, the second light guide plate 25 can be manufactured by injection molding, and a transfer shape for transferring the fourth light guide plate lens 26 can be pre-formed on the molding surface of the molding mold for molding the second light guide plate main light emitting surface 25B.

[0049] like Figure 3As shown, the fifth light guide plate lens 27 is arranged 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 them are arranged along the Y-axis direction. In the present embodiment, the fifth light guide plate lens 27 is a convex prism protruding from the second opposite principal surface 25C to the back side. Specifically, the fifth light guide plate lens 27 is formed so that the cross-sectional shape cut along the Y-axis direction is roughly triangular (roughly mountain-shaped) and extends straight along the X-axis direction. The width dimension (dimension in the Y-axis direction) of the fifth light guide plate lens 27 is fixed over the entire length range in the X-axis direction. The cross-sectional shape of the fifth light guide plate lens 27 is roughly an isosceles triangle, and the fifth light guide plate lens 27 has a pair of fifth light guide plate inclined surfaces 27A. The vertex angle of the fifth light guide plate lens 27 is preferably set to an obtuse angle (an angle exceeding 90°), specifically, in the range of 100° to 150°, and most preferably 140°. The width dimension of the fifth light guide plate lens 27 as a dimension in the Y-axis direction is, for example, about 0.126 mm. The arrangement interval of the plurality of 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 vertex angles, width dimensions (arrangement intervals) and height dimensions of the plurality of fifth light guide plate lenses 27 arranged along the Y-axis direction are all substantially the same. In the present embodiment, the arrangement interval of the fifth light guide plate lenses 27 is greater than the arrangement interval of the fourth light guide plate lenses 26. To integrally set the fifth light guide plate lenses 27 of this construction on the second light guide plate 25, for example, the second light guide plate 25 can be manufactured by injection molding, and a transfer shape for transferring the fifth light guide plate lenses 27 can be pre-formed on a molding surface for molding the second opposite main surface 25C in the molding mold.

[0050] like Figure 2 As shown, the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are arranged on the second opposite main surface 25C of the second light guide plate 25. The sixth light guide plate lens 28 and the seventh light guide plate lens 29 protrude from the second opposite main surface 25C toward the back side along the Z-axis direction. A plurality of the sixth light guide plate lenses 28 and the seventh light guide plate lenses 29 are arranged alternately and repeatedly at intervals along the X-axis direction. The sixth light guide plate lens 28 has a side (opposite to the side of the second LED 24) arranged in the X-axis direction. Figure 2 The seventh light guide plate lens 29 has a second slope 29A disposed on the opposite side of the second LED 24 in the X-axis direction. The first slope 28A and the second slope 29A both have a first slope 28A and a second slope 29A disposed on the opposite side of the second LED 24 in the X-axis direction of the second light guide plate 25. Figure 2 to the right side) toward the opposite side ( Figure 2The first inclined surface 28A is formed to have a slope that causes the thickness of the sixth light guide plate lens 28 to increase gradually from the second LED 24 side toward the opposite side in the X-axis direction. Similarly, the second inclined surface 29A is formed to have a slope that causes the thickness of the seventh light guide plate lens 29 to increase gradually from the second LED 24 side toward the opposite side in the X-axis direction.

[0051] like Figure 2 As shown, 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 opposite side of the second LED 24 side in the X-axis direction of the second light guide plate 25 toward the second LED 24 side. The third inclined surface 31 includes a fourth inclined surface 28B provided in the sixth light guide plate lens 28 and a fifth inclined surface 29B provided in the seventh light guide plate lens 29. The fourth inclined surface 28B is disposed at a position spaced apart from the first inclined surface 28A toward the second LED 24 side in the X-axis direction in the sixth light guide plate lens 28. The fourth inclined surface 28B of the sixth light guide plate lens 28 is disposed opposite to the second inclined surface 29A of the seventh light guide plate lens 29 with an interval. The fourth inclined surface 28B is formed to have a slope that causes the thickness of the sixth light guide plate lens 28 to increase continuously and gradually from the second LED 24 side toward the opposite side thereof in the X-axis direction. The fifth inclined surface 29B is arranged at a position spaced apart from the second inclined surface 29A in the seventh light guide plate lens 29 on the second LED 24 side in the X-axis direction. The fifth inclined surface 29B of the seventh light guide plate lens 29 is arranged opposite to the first inclined surface 28A of the sixth light guide plate lens 28 at a distance. The fifth inclined surface 29B is formed to have a slope that gradually increases the thickness of the seventh light guide plate lens 29 from the second LED 24 side toward the opposite side in the X-axis direction.

[0052] like Figure 2As shown, 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 planes parallel to the X-axis direction and the Y-axis direction. In addition, in 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 at intervals 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 at intervals in the X-axis direction on the second opposite main surface 25C of the second light guide plate 25. The sixth light guide plate lens 28 or the seventh light guide plate lens 29 is located between two third planes 32 adjacent to each other at intervals in the X-axis direction. The detailed structures, functions and effects of the inclined surfaces 28A, 29A, 31 (28B, 29B) and the flat surfaces 28C, 29C, 32 will be described in detail later.

[0053] Next, use Figure 1 as well as Figure 3 The structure of the second grid 30 is described below. Figure 1 As shown, the main surface of the second grid 30 is parallel to the main surfaces of the liquid crystal panel 11 and the second light guide plate 25, and is in a sheet shape. In addition, the main surface of the second grid 30 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The second grid 30 has the function of limiting the emission angle range of the light in the Y-axis direction. The second grid 30 has a second light incident main surface 30A on the back side and a second light emitting main surface 30B on the surface side. The second light incident main surface 30A is opposite to the second light guide plate light emitting main surface 25B of the second light guide plate 25. The second light emitting main surface 30B is opposite to the main surface on the back side of the liquid crystal panel 11. That is, the second grid 30 is located on the surface side of the second light guide plate 25, and is configured to be located on the back side of the liquid crystal panel 11.

[0054] like Figure 3As shown, the second grid 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, for example, a light-shielding resin material (light-shielding material) that is black and blocks light. The second light-shielding portion 30C is in the form of a layer extending along the X-axis direction and the Z-axis direction, and a plurality of the second light-transmitting portions 30D are arranged at intervals in the Y-axis direction. The second light-transmitting portions 30D are made of a light-transmitting resin material (light-transmitting material) that is substantially transparent and transmits light. The second light-transmitting portions 30D are in the form of a layer extending along the X-axis direction and the Z-axis direction, and a plurality of the second light-transmitting portions 30D are arranged at intervals in the Y-axis direction. Multiple second light-shielding portions 30C and multiple second light-transmitting portions 30D are arranged alternately and repeatedly in the Y-axis direction. Therefore, the second light-transmitting portion 30D is between two second light-shielding portions 30C that are adjacent to each other at intervals in the Y-axis direction, and the second light-shielding portion 30C is between two second light-transmitting portions 30D that are adjacent to each other at intervals in the Y-axis direction. The light incident on the second light incident main surface 30A of the second grating 30 is transmitted through the second light-transmitting portion 30D arranged between the two second light-shielding portions 30C adjacent in the Y-axis direction, and is emitted from the second light-emitting main surface 30B. The emission angle of the emitted light from the second light-emitting main surface 30B in the Y-axis direction is limited by the two second light-shielding portions 30C adjacent in the Y-axis direction. In addition, the emission angle of the emitted light from the second light-emitting main surface 30B in the X-axis direction is not limited by the second grating 30. The emission angle range of the emitted light from the second light-emitting main surface 30B in the Y-axis direction is defined by two straight lines that obliquely connect the ends of the two second light-shielding portions 30C sandwiching the second light-transmitting portion 30D in the Z-axis direction. The emission angle range of the transmitted light of the second light-transmitting portion 30D in the Y-axis direction varies according to the ratio of the width to the height of the second light-transmitting portion 30D. The ratio of the width of the second light-transmitting portion 30D in the second grid 30 divided by the height is greater than the ratio of the width W1 of the first light-transmitting portion in the first grid 18 divided by the height H1. Specifically, the ratio of the width W of the second light-transmitting portion 30D in the second grid 30 divided by the height is, for example, "tan55°" or more. In addition, the second grid 30 has a pair of sheet carriers that clamp and carry the plurality of second light-shielding portions 30C and the plurality of second light-transmitting portions 30D from the front side and the back side. The sheet carrier is made of a light-transmitting resin material that is substantially transparent and transmits light. The sheet carrier extends over the entire area of ​​the second grid 30 and holds the plurality of second light-shielding portions 30C and the plurality of second light-transmitting portions 30D together.

[0055] When the liquid crystal display device 10 is mounted in a passenger car, the use of such a second grille 30 can limit the emission angle range of light emitted from the liquid crystal panel 11 to the vertical direction. This makes it difficult for the display image to be reflected 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 are described in detail. Figure 6 As shown, the angle formed by the first inclined surface 28A of the sixth light guide plate lens 28 relative to the X-axis direction is set to "first angle θ1", and the angle formed by the second inclined surface 29A of the seventh light guide plate lens 29 relative to the X-axis direction is set to "second angle θ2". The first angle θ1 of the first inclined surface 28A is greater than 27° and less than the second angle θ2. The second angle θ2 of the second inclined surface 29A is greater than the first angle θ1 and less than 58°. In the present embodiment, specifically, the first angle θ1 of the first inclined surface 28A is set to, for example, about 32°. The second angle θ2 of the second inclined surface 29A is set to, for example, about 54°.

[0057] According to this composition, Figure 6 As shown, for the light emitted from the second LED 24 and incident on the second light-entering end face 25A of the second light guide plate 25, it is irradiated to the first inclined surface 28A and the second inclined surface 29A during the propagation in the second light guide plate 25, where most of it is reflected. The light reflected by the first inclined surface 28A and the second inclined surface 29A rises toward the surface side, promoting the emission from the main light-emitting surface 25B of the second light guide plate. Here, the traveling direction of the light reflected by the first inclined surface 28A and the second inclined surface 29A becomes a direction corresponding to the angle of the first inclined surface 28A and the second inclined surface 29A relative to the X-axis direction. Specifically, for example, when the angle between the first inclined surface 28A and the second inclined surface 29A and the X-axis direction is 45°, the reflected light rises in a manner of traveling along the Z-axis direction (the normal direction of the main light-emitting surface 25B of the second light guide plate, the front direction). For example, when the angle between the first slope 28A and the second slope 29A with respect to the X-axis direction is less than 45°, the reflected light tends to be directed toward the side opposite to the second LED 24 side in the X-axis direction with respect to the Z-axis direction ( Figure 6 For example, when the angle between the first slope 28A and the second slope 29A relative to the X-axis direction exceeds 45°, the reflected light tends to be directed toward the second LED 24 side in the X-axis direction ( Figure 6 ) on the right side of the road.

[0058] In the present embodiment, since the first angle θ1 is about 32°, which is less than 45°, 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 away from the second LED 24) relative to the Z-axis direction when it is emitted from the second light guide plate light emitting main surface 25B. On the other hand, the second angle θ2 is set to about 54°. Since it exceeds 45°, the light reflected by the second inclined surface 29A tends to travel toward the second LED 24 side in the X-axis direction (the side close to the second LED 24) relative to the Z-axis direction when it is emitted from the second light guide plate light emitting main surface 25B. Therefore, if the second LED 24 is turned on, it is possible to provide an output light having a brightness angle distribution in which the peak brightness associated with the output light is biased toward the opposite side of the second LED 24 side in the X-axis direction and the second LED 24 side in the X-axis direction, respectively. Thus, in addition to being able to fully ensure the brightness of the output light in the direction inclined relative to the Z-axis direction, it is also possible to expand the output angle range of the output light to achieve a wide viewing angle, which is preferred.

[0059] Moreover, the closer the first angle θ1 and the second angle θ2 are to 45°, the more the reflected light of the first inclined surface 28A and the second inclined surface 29A tends to move closer to the Z-axis direction. Specifically, in the present embodiment, since the first angle θ1 of the first inclined surface 28A is an angle greater than 27° and close to 45°, when the light reflected by the first inclined surface 28A is emitted from the second light guide plate light emitting main surface 25B, it moves in a direction closer to the Z-axis direction compared to the case where the first angle θ1 is set to be less than 27°. On the other hand, since the second angle θ2 of the second inclined surface 29A is an angle less than 58° and close to 45°, when the light reflected by the second inclined surface 29A is emitted from the second light guide plate light emitting main surface 25B, it moves in a direction closer to the Z-axis direction compared to the case where the second angle θ2 is assumed to be greater than 58°. Therefore, if both the first LED 13 and the second LED 24 are turned on, the angular distribution of brightness associated with the light emitted from the main light emitting surface 25B of the second light guide plate shows a tendency that the brightness decreases as the light approaches the wide angle side relative to the Z-axis direction, and it is difficult for a local decrease in brightness to occur in the middle. As described above, it is possible to achieve a wide viewing angle while making it difficult for brightness non-uniformity to occur.

[0060] According to this embodiment, Figure 1As shown, for example, while the passenger car is traveling, the first LED 13 is turned on and the second LED 24 is turned off. In this way, the angle range of light emitted from the second light guide plate light emitting main surface 25B of the second light guide plate 25 is limited by the first light shielding portion 18C of the first grille 18, and it is difficult to emit light outside the limited angle range. Therefore, if the first LED 13 is turned on and the second LED 24 is turned off, light is selectively emitted from the backlight device 12 to the limited angle range, so although the display image of the liquid crystal display device 10 can be visually recognized from the passenger seat, the display image of the liquid crystal display device 10 cannot be visually recognized from the driver's seat. In contrast, for example, while the passenger car is stopped, both the first LED 13 and the second LED 24 are turned on. Thus, the light emitted from the second light guide plate light emitting 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 grid 18; and the light of the second LED 24 whose peak brightness is respectively biased toward the opposite side of the second LED 24 side and the second LED 24 side in the X-axis direction. Therefore, if both the first LED 13 and the second LED 24 are turned on, the backlight device 12 emits light whose peak brightness is respectively biased toward the opposite side of the second LED 24 side and the second LED 24 side in the X-axis direction in addition to the light emitted from the limited angle range, so that in addition to enabling the driver's seat and the passenger seat to visually recognize the display image of the liquid crystal display device 10, the display image can be visually recognized from the passenger seat light viewing angle in particular. In this way, by controlling the driving of the second LED 24 according to the driving condition of the passenger car, it is possible to adjust whether the display image can be visually recognized from the driver's seat.

[0061] Next, the third inclined surface 31 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 will be described in detail. Figure 6As shown, the angle formed by the fourth inclined surface 28B included in the sixth light guide plate lens 28 in the third inclined surface 31 with respect to the X-axis direction is set as "third angle θ3", and the angle formed by the fifth inclined surface 29B included in the seventh light guide plate lens 29 in the third inclined surface 31 with respect to the X-axis direction is set as "fourth angle θ4". The third angle θ3 of the fourth inclined surface 28B is, for example, in the range of 3° to 10°, specifically, about 3°. The fourth angle θ4 of the fifth inclined surface 29B is, for example, in the range of 3° to 10°, specifically, about 3°. In the present embodiment, the third angle θ3 of the fourth inclined surface 28B is equal to the fourth angle θ4 of the fifth inclined surface 29B. According to such a configuration, for light that travels in the second light guide plate 25 in a manner close to the second LED 24 in the X-axis direction, if it is irradiated by the fourth inclined surface 28B and the fifth inclined surface 29B as the third inclined surface 31 and refracted, it travels toward the opposite side of the second LED 24 side in the X-axis direction relative to the Z-axis direction. Thus, the brightness of the light emitted in the direction inclined relative to the Z-axis direction can be further improved. In addition, if the light traveling in the second light guide plate 25 in the X-axis direction in a manner away from the second LED 24 is refracted by the fourth inclined surface 28B and the fifth inclined surface 29B as the third inclined surface 314, it is guided in a manner further away from the second LED 24. Thus, the light emitted from the second light guide plate light emitting main surface 25B is not easily deflected to the second LED 24 side in the X-axis direction.

[0062] Next, the first plane 28C, the second plane 29C, and the third plane 32 are described in detail. Figure 6 As shown, 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 the normal direction thereof is consistent with the Z-axis direction. Even if 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 second opposite main surface 25C of the second light guide plate 25 is irradiated on any one of the first plane 28C, the second plane 29C and the third plane 32, it travels without being refracted. Therefore, compared with the case where the first inclined surface 28A and the fourth inclined surface 28B are directly connected without the first plane 28C in between, the case where the second inclined surface 29A and the fifth inclined surface 29B are directly connected without the second plane 29C in between, and the case where the sixth light guide plate lens 28 and the seventh light guide plate lens 29 adjacent in the X-axis direction are directly connected without the third plane 32 in between, the generation of side lobe light that travels in a direction inclined toward the opposite side of the second LED 24 side in the X-axis direction relative to the Z-axis direction can be suppressed.

[0063] like Figure 6 as well as Figure 7As shown, the plurality of sixth light guide plate lenses 28 and the plurality of seventh light guide plate lenses 29 arranged along the X-axis direction are designed so that the further away from the second LED 24 in the X-axis direction, the greater the height dimensions (dimensions in the Z-axis direction) H2 and H3 are, but the arrangement pitches (arrangement intervals) P1 and P2 in the X-axis direction are constant. The width dimensions (dimensions in the X-axis direction) W2 and W6 of the first inclined surface 28A and the second inclined surface 29A are both larger as they are further away from the second LED 24 in the X-axis direction. The width dimensions (dimensions in the X-axis direction) W3 and W7 of the fourth inclined surface 28B and the fifth inclined surface 29B are both larger as they are further away from the second LED 24 in the X-axis direction, and their increasing rates are higher than those of the first inclined surface 28A and the second inclined surface 29A. The width dimensions (dimensions in the X-axis direction) W4 and W8 of the first plane 28C and the second plane 29C are set to be constant regardless of the position in the X-axis direction. The width dimension (dimension in the X-axis direction) W5 of the third plane 32 is smaller as it is further away from the second LED 24 in the X-axis direction. The arrangement pitch P1 of the sixth light guide plate lenses 28 in the X-axis direction is the sum of the width dimension W2 of the first inclined surface 28A, the width dimension W3 of the fourth inclined surface 28B, the width dimension W4 of the first plane 28C, and the width dimension W5 of the third plane 32. The arrangement pitch P2 of the seventh light guide plate lenses 29 in the X-axis direction is the sum of the width dimension W6 of the second inclined surface 29A, the width dimension W7 of the fifth inclined surface 29B, the width dimension W8 of the second plane 29C, and the width dimension W5 of the third plane 32.

[0064] The specific values ​​of the width dimension W2 of the first inclined surface 28A, the width dimension W6 of the second inclined surface 29A, the width dimension W3 of the fourth inclined surface 28B, the width dimension W7 of the fifth inclined surface 29B, and the width dimension W5 of the third plane 32 are determined according to the positions of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 in the second light guide plate 25 in the X-axis direction, as shown in FIG. Figure 8 Changes as shown. Figure 8 It is a curve graph with the horizontal axis representing the position in the X-axis direction of the second light guide plate 25 (in "mm") and the vertical axis representing the width dimensions W2, W3, W5, W6, and W7 (in "mm") of the first slope 28A, the second slope 29A, the fourth slope 28B, the fifth slope 29B, and the third plane 32. Figure 8 The reference position (0 mm) of the horizontal axis is the position of the second light incident end surface 25A of the second light guide plate 25, and the position of 300 mm is the position of the end surface of the second light guide plate 25 on the opposite side to the second light incident end surface 25A. Figure 8The solid line is a graph of the width dimensions W2 and W6 of the first inclined surface 28A and the second inclined surface 29A, the dotted line is a graph of the width dimensions W3 and W7 of the fourth inclined surface 28B and the fifth inclined surface 29B, and the single-point dashed line is a graph of the width dimension W5 of the third plane 32. When the length dimension of the second light guide plate 25 is set to 300 mm, for example, the specific values ​​of the height dimensions H2 and H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are determined according to the positions of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 in the second light guide plate 25 in the X-axis direction, as shown in FIG. Fig. 9 Changes as shown. Fig. 9 The horizontal axis is the position of the second light guide plate 25 in the X-axis direction (unit: "mm"), and the vertical axis is the height dimensions H2 and H3 (unit: "mm") of the sixth light guide plate lens 28 and the 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 set to 300 mm, for example, the arrangement pitches P1 and P2 in the X-axis direction of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are both constant at about 0.114 mm, for example. The width dimensions W4 and W8 of the first plane 28C and the second plane 29C are both constant at about 0.017 mm, for example. Figure 8 The width dimensions W2 and W6 of the first inclined surface 28A and the second inclined surface 29A vary within a range of 0.003 mm to 0.004 mm, for example. Figure 8 The width dimensions W3 and W7 of the fourth inclined surface 28B and the fifth inclined surface 29B vary within a range of 0.003 mm to 0.004 mm, for example. Figure 8 The width dimension W5 of the third plane 32 varies within a range of, for example, 0.003 mm to 0.032 mm. Fig. 9 , the height dimensions H2 and H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 vary, for example, in the range of 0.002 mm to 0.0034 mm. In this way, the minimum values ​​of the height dimensions H2 and H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are ensured to be about 0.002 mm (2 μm). As a result, the ease of manufacturing the second light guide plate 25 by resin molding can be fully ensured. In order to ensure that the minimum values ​​of the height dimensions H2 and H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are about 0.002 mm, it is preferred to set the third angle θ3 of the fourth inclined surface 28B and the fourth angle θ4 of the fifth inclined surface 29B to be greater than 3°, respectively. 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 set to be constant, regardless of the position of the second light guide plate 25 in the X-axis direction.

[0066] like Figure 3 as well as Figure 7 As shown, the sixth light guide plate lens 28 and the seventh light guide plate lens 29 of the above-mentioned structure are arranged between two adjacent fifth light guide plate lenses 27 in the Y-axis direction. Therefore, the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are arranged in a manner of alternating and repeating arrangement with the fifth light guide plate lens 27 in the Y-axis direction. The maximum values ​​of each height dimension (protruding dimension protruding from the second opposite main surface 25C) H2 and H3 of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are both smaller than the height dimension of the fifth light guide plate lens 27. Therefore, even if the sixth light guide plate lens 28 and the seventh light guide plate lens 29 are located on the side farthest from the second LED 24 in the X-axis direction, they will not protrude to the back side more than the fifth light guide plate lens 27.

[0067] Here, in order to obtain insights into how the light distribution changes when the angles formed by the first bevel 28A and the second bevel 29A of the sixth light guide plate lens 28 and the seventh light guide plate lens 29 of the second light guide plate 25 relative to the X-axis direction, i.e., the first angle θ1 and the second angle θ2, are changed, an empirical experiment 1 was conducted. In this empirical experiment 1, except for the structure of the sixth light guide plate lens 28 and the seventh light guide plate lens 29, a backlight device 12 with the same structure as described previously in this paragraph was used. In empirical experiment 1, the angles formed by the first bevel 28A and the second bevel 29A relative to the X-axis direction were equal, and the angles were changed within the range of 36° to 60°. In detail, in empirical experiment 1, the angles formed by the first bevel 28A and the second bevel 29A relative to the X-axis direction were set to 36°, 40°, 44°, 48°, 50°, 54°, and 60°. When the second LED 24 is turned on and the first LED 13 is turned off in the backlight device 12 in which the angle between the first slope 28A and the second slope 29A relative to the X-axis direction is changed as described above, the brightness related to the emitted light is measured and a curve graph related to the light distribution (brightness angle distribution) in the X-axis direction is prepared.

[0068] The experimental results related to light distribution in empirical experiment 1 are as follows: Fig.10 As shown. Fig.10 In the graph related to light distribution shown in the figure, the horizontal axis is the angle of the X-axis direction relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Fig.10 The positive and negative signs "-(minus)" in the angle of the horizontal axis indicate that the backlight device 12 is viewed from the front with respect to the reference 0°. (front direction) and on the left side in the X-axis direction d, and "+ (positive)" indicates the right side in the X-axis direction relative to 0° (front direction) serving as a reference when the backlight device 12 is viewed from the front.

[0069] The experimental results of empirical experiment 1 are described. Fig.10 , when the angle formed by the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is 36°, 40°, and 44° in the range of 36° to 60°, the angle at which the peak brightness is obtained becomes "-", and when the angle formed by the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is 48°, 50°, 54°, and 60°, the angle at which the peak brightness is obtained becomes "+". Specifically, when the angle formed by the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is 44°, the angle at which the peak brightness is obtained is closest to 0°, so it can be inferred that if the angle formed by the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is 45°, the angle at which the peak brightness is obtained becomes approximately 0°. Therefore, it can be said that the following tendency is presented: if the angle formed by the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is less than 45°, the angle at which the peak brightness is obtained becomes "-", and if the angle formed by the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is greater than 45°, the angle at which the peak brightness is obtained becomes "+".

[0070] according to Fig.10 , it can be said that the following tendency is presented: the closer the angle between the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is to 45°, the smaller the absolute value of the angle at which the peak brightness is obtained (the closer it is to 0°). Fig.10 It can be seen that the angles formed by the first inclined surface 28A and the second inclined surface 29A relative to the X-axis direction are 36° and 54°. When the brightness reaches the peak value, the angle is about ±20°. Fig.10 , it can be said that the following tendency is presented: the smaller the angle between the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction, the higher the peak brightness. In addition, when light emitted in the range of -80° to -50° with respect to the front direction in the X-axis direction is defined as "side lobe light", when the angle between the first inclined surface 28A and the second inclined surface 29A with respect to the X-axis direction is 44°, the amount of side lobe light is the smallest, and it can be said that the following tendency is presented: whether it is greater than 44° or less than 44°, the amount of side lobe light increases.

[0071] Next, in order to verify the advantages of the backlight device 12 and the liquid crystal display device 10 involved in this embodiment, the following comparative experiment 1 was performed. In this comparative experiment 1, the following Example 1 and Comparative Example 1 were used to obtain insights into 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 with the same structure as that described before the above-mentioned empirical experiment 1, and 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 the same as the backlight device 12 with the same structure as the backlight device described before the empirical 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 brightness associated with each emitted light was measured when the first LED 13 was turned on and the second LED 24 was turned off, when the second LED 24 was turned on and the first LED 13 was turned off, and when both the first LED 13 and the second LED 24 were turned on, and a curve graph associated with the light distribution in the X-axis direction (brightness angle distribution) was prepared.

[0072] Compare the experimental results related to light distribution in Experiment 1. Figures 11 to 16 As shown. Figures 11 to 16 In the graph related to light distribution shown in the figure, the horizontal axis is the angle of the X-axis direction relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Figures 11 to 16 The positive and negative signs of the angles on the horizontal axis are Fig.11 The symbols marked on the horizontal axis of the curve graph have the same meaning. Figures 11 to 13 This is the experimental result of Comparative Example 1. Figures 14 to 16 This is the experimental result of Example 1. Fig.11 and Fig.14 The light distribution when the first LED 13 is turned on and the second LED 24 is turned off is shown. Fig.12 and Fig.15 The light distribution when the second LED 24 is turned on and the first LED 13 is turned off is shown. Fig.13 and Fig.16 The light distribution when the first LED 13 and the second LED 24 are turned on together is shown.

[0073] The experimental results of comparative experiment 1 are described. First, according to Fig.11 and Fig.14 In the light distribution, when the first LED 13 is turned on and the second LED 24 is turned off, in either Comparative Example 1 or Example 1, the peak brightness is approximately 0°, and the emission angle range is approximately ±10°. It can be said that this result reflects that the light emitted from the first light guide plate 14 accompanying the lighting of the first LED 13 passes through the first grid 18, so that the emission angle range is limited to approximately ±10°.

[0074] Next, according to the experimental results of Comparative Example 1 Fig.12 In the light distribution of Example 1, when the second LED 24 is turned on and the first LED 13 is turned off, there are two peak brightnesses near -40° and near +20°. It is estimated that the light emitted near -40° is the light reflected by the first inclined surface 28A, and the light emitted near +20° is the light reflected by the second inclined surface 29A. Fig.15 The light distribution has three peak brightnesses near -60°, -20°, and +20° when the second LED 24 is turned on and the first LED 13 is turned off. It is speculated that the light emitted near -20° is the light reflected by the first slope 28A, and the light emitted near +20° is the light reflected by the second slope 29A. In addition, it is speculated that the light emitted near -60° is, for example, light refracted by the second slope 29A and transmitted through the second slope 29A, and when it is incident on the fourth slope 28B, it is refracted and reaches the second light guide plate main light emitting surface 25B and is emitted (side lobe light). In this way, according to Fig.12 and Fig.15 It can be said that when the second LED 24 is turned on, the peak brightness of the emitted light is biased toward the opposite side of the second LED 24 side in the X-axis direction and the second LED 24 side in the X-axis direction.

[0075] As the experimental results of Comparative Example 1 Fig.13 The light distribution is a synthesis of Fig.11 Light distribution and Fig.12 The light distribution content is as the experimental results of Example 1 Fig.16 The light distribution is a synthesis of Fig.14 Light distribution and Fig.15 The light distribution of the content. According to the experimental results of comparative example 1 Fig.13 The light distribution of the first LED 13 and the second LED 24 is such that the peak brightness exists at about 0°, -40°, and +20°, and the highest brightness is at about 0°. Fig.13In the light distribution of the first LED 13 and the second LED 24, when both are turned on, the brightness is locally reduced near -15° between the brightness peak of approximately 0° and the brightness peak of approximately -40°, and the brightness is locally reduced near +15° between the brightness peak of approximately 0° and the brightness peak of approximately +20°. That is, in Fig.13 In the light distribution, the brightness near -15° is lower than the peak brightness near -40°, and the brightness near +15° is lower than the peak brightness near +20°. Therefore, in Comparative Example 1, within the visual recognition range of ±20°, only a local brightness reduction occurs near ±15°, resulting in a problem of poor viewing angle performance.

[0076] In contrast, according to the experimental results of Example 1, Fig.16 The light distribution of the embodiment 1 is such that when both the first LED 13 and the second LED 24 are turned on, the peak brightness exists near approximately 0° and -60°, and the brightness is highest at approximately 0°. Fig.16 From the light distribution, it can be seen that when both the first LED 13 and the second LED 24 are turned on, the brightness shows a tendency to continuously decrease from the brightness peak of approximately 0° to ±20°, and no change such as the brightness becoming higher occurs in the middle. That is, in Example 1, in the visual recognition range of ±20°, the occurrence of local brightness reduction is avoided, and it can be said that excellent viewing angle performance is obtained.

[0077] To supplement Figures 11 to 16 The illustration of the coordinate graph shown shows Fig.17 . Fig.17 This is a diagram for explaining an angle of the liquid crystal display device 10 provided in front of the passenger seat with respect to the front direction in the X-axis direction in a passenger car in which the driver's seat is located on the left side with respect to the passenger seat. Fig.17 The figure shows the shading range (+10° to +90°, -10° to -90°) blocked by the first grille 18, the driver's seat observation range (-20° to -50°) which is the observation range when observing the liquid crystal display device 10 from the driver's seat located on the left side relative to the passenger seat, the passenger seat observation range (-20° to +20°) which is the observation range when observing the liquid crystal display device 10 from the passenger seat located on the right side relative to the driver's seat and in front of the liquid crystal display device 10, and the emission range (-80° to -50°) of light emitted to the range deviating from either the driver's seat observation range and the passenger seat observation range on the driver's seat side.

[0078] according to Fig.11 , Fig.14 and Fig.17In either Comparative Example 1 or Example 1, if the first LED 13 is turned on and the second LED 24 is turned off, the peak brightness is approximately 0°, and the emission angle range is approximately ±10°. Therefore, it can be said that the display image of the liquid crystal display device 10 is almost invisible from the driver's seat, and the display image of the liquid crystal display device 10 can be well visually recognized from the passenger seat at 0°. Fig.12 , Fig.15 and Fig.17 In any of Comparative Example 1 and Example 1, if the second LED 24 is turned on and the first LED 13 is turned off, the image displayed by the liquid crystal display device 10 cannot be visually recognized well, especially in the passenger seat. Fig.13 and Fig.17 In Comparative Example 1, if both the first LED 13 and the second LED 24 are turned on, the brightness is ensured to be 50 cd / m throughout the entire area in both the -20° to +20° passenger seat visual recognition range and the -50° to -20° driver seat visual recognition range. 2 As described above, the display image of the liquid crystal display device 10 can be visually recognized from both the driver's seat and the passenger seat, but the viewing angle at the passenger seat becomes narrower due to the local brightness reduction near ±15°. Fig.16 and Fig.17 In Example 1, if both the first LED 13 and the second LED 24 are turned on, the brightness is ensured to be 50 cd / m throughout the entire area in both the -20° to +20° passenger seat visual recognition range and the -50° to -20° driver seat visual recognition range. 2 As described above, the display image of the liquid crystal display device 10 can be visually recognized from both the driver's seat and the passenger seat. In particular, there is no local brightness reduction in the passenger seat visual recognition range, so 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, at least a portion of its outer peripheral end surface is a first light incident end surface (first end surface) 14A that is opposite to the first LED 13 and for light to be incident, and one main surface is a first light guide plate light emitting main surface (first main surface) for emitting light. 14B, the other main surface is the first opposite main surface (second main surface) 14C; a first grid (first sheet) 18, one main surface of which is the first light incident main surface (third main surface) 18A arranged toward the first light guide plate light emitting main surface 14B and incident light, and the other main surface is the first light emitting main surface (fourth main surface) 18B for emitting light; a second LED (second light source) 24; and a second light guide plate 25, at least a portion of its outer peripheral end surface is a second light incident end surface (second end surface) 25A opposite to the second LED 24 and for incident light, one main surface is the second light guide plate light emitting main surface (fifth main surface) 25B for emitting light, and the other main surface is the second opposite main surface (sixth main surface) 25C arranged toward the first light emitting main surface 18B, wherein the first grid 1 8 at least comprises: two first light shielding portions 18C which are arranged at intervals in a first direction including a direction from the first LED 13 toward the first light guide plate 14 and shield light; and a first light transmitting portion 18D which is arranged between the two first light shielding portions 18C and transmits light, and an inclined first inclined surface 28A and a second inclined surface 29A are provided on a second opposite main surface 25C of the second light guide plate 25, the inclination of the first inclined surface 28A and the second inclined surface 29A is to rise from the side opposite to the second LED 24 toward the second LED 24 side in the first direction, the angle of the first inclined surface 28A relative to the first direction is set to a first angle θ1 greater than 27°, and the angle of the second inclined surface 29A relative to the first direction is set to a second angle θ2 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 incident end surface 14A of the first light guide plate 14 propagates in the first light guide plate 14, and is emitted from the first light guide plate light emitting main surface 14B and is incident on the first light incident main surface 18A of the first grid 18. The light incident on the first light incident main surface 18A of the first grid 18 is transmitted through the first light-transmitting portion 18D arranged between the two first light shielding portions 18C, and is emitted from the first light emitting main surface 18B. The emission angle of the emitted light from the first light emitting main surface 18B is limited by the two first light shielding portions 18C. If the emitted light from the first light emitting 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 guide plate light emitting main surface 25B. The angle range of the light emitted from the second light guide plate light emitting main surface 25B is limited by the first light shielding portion 18C of the first grid 18, so it is difficult to be emitted outside the limited angle range. Thus, if the first LED 13 is turned on and the second LED 24 is turned off, light can be selectively emitted into an angle range limited around the normal direction of the second light guide plate light emitting main surface 25B, that is, the front direction.

[0081] 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, at least a part of which is irradiated by the first inclined surface 28A and the second inclined surface 29A provided on the second opposite main surface 25C during the process of propagating in 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 is a direction corresponding to the angle of the first inclined surface 28A and the second inclined surface 29A relative to the first direction. The light reflected by the first inclined surface 28A, which is set at the first angle θ1 smaller than the second angle θ2 relative to the first direction, tends to travel toward the opposite side of the second LED 24 side in the first direction relative to the front direction when it is emitted from the second light guide plate light-emitting main surface 25B. On the other hand, the light reflected by the second inclined surface 29A, which is set at the second angle θ2 larger than the first angle θ1 relative to the first direction, tends to travel toward the second LED 24 side in the first direction relative to the front direction when it is emitted from the second light guide plate light-emitting main surface 25B. Therefore, if the second LED 24 is turned on, the peak brightness of the emitted light is biased toward the opposite side of the second LED 24 side in the first direction and the second LED 24 side in the first direction. In this way, in addition to being able to fully ensure the brightness of the emitted light in the direction inclined relative to the front direction, the emission angle range of the emitted light can be expanded to achieve a wide viewing angle, which is preferred.

[0082] Moreover, since the first angle θ1 of the first bevel 28A is greater than 27°, when the light reflected by the first bevel 28A is emitted from the second light guide plate main light emitting surface 25B, it moves toward a direction closer to the front direction, compared with the case where the first angle θ1 is set to be less than 27°. Since the second angle θ2 of the second bevel 29A is less than 58°, when the light reflected by the second bevel 29A is emitted from the second light guide plate main light emitting surface 25B, it moves toward a direction closer to the front direction, compared with the case where the second angle θ2 is assumed to be greater than 58°. Therefore, if both the first LED 13 and the second LED 24 are turned on, the angular distribution of brightness associated with the emitted light from the second light guide plate main light emitting surface 25B shows a tendency that the brightness becomes lower the closer to the wide-angle side relative to the front direction, and it is difficult to produce a local decrease in brightness in the middle. As described above, it is possible to achieve a wide viewing angle while making it difficult for brightness non-uniformity to occur.

[0083] In addition, a third inclined surface 31 that rises from the second LED 24 side toward the opposite side thereof in the first direction is provided on the second opposite main surface 25C of the second light guide plate 25. For light that travels in the second light guide plate 25 in a manner approaching the second LED 24 in the first direction, if it is irradiated with the third inclined surface 31 and refracted, it travels to the opposite side of the second LED 24 side in the first direction relative to the front direction. Thus, the brightness of the emitted light in a direction inclined relative to the front direction can be further improved. In addition, for light that travels in the second light guide plate 25 in a manner away from the second LED 24 in the first direction, if it is irradiated with the third inclined surface 31 and refracted, it is guided in a manner further away from the second LED 24. Thus, the emitted light emitted from the light emitting main surface 25B of the second light guide plate is not easily deflected to the second LED 24 side in the first direction.

[0084] In addition, the liquid crystal display device (display device) 10 involved in this embodiment includes the backlight device 12 described above and a liquid crystal panel (display panel) 11 that displays using the light from the backlight device 12. According to the liquid crystal display device 10 configured in this way, in the backlight device 12, the emission of light outside the limited angle range is suppressed, the brightness of the emitted light in the direction inclined relative to the front direction is improved, and the emission angle range of the emitted light is expanded to achieve a wide viewing angle and is less likely to produce uneven brightness, thereby achieving a display with excellent display quality.

[0085] <Implementation Method 2> according to Figures 18 to 22 Embodiment 2 will be described. In this Embodiment 2, a case where the configuration of the third inclined surface 131 is changed is described. In addition, about the structure, operation, and effect similar to the above-mentioned first embodiment, the repeated description is omitted.

[0086] like Fig.18As shown, the angle formed by the third inclined surface 131 of the second light guide plate 125 involved in the present embodiment with respect to the X-axis direction (first direction) is set to be greater than 40°. The angle formed by the fourth inclined surface 128B included in the third inclined surface 131 with respect to the X-axis direction, that is, the third angle θ103, is set to be greater than 40°, for example, it is set to be about 65°. The angle formed by the fifth inclined surface 129B included in the third inclined surface 131 with respect to the X-axis direction, that is, the fourth angle θ104, is set to be greater than 40°, for example, it is set to be about 65°. Therefore, the fourth inclined surface 128B and the fifth inclined surface 129B are configured so that the third angle θ103 is equal to the fourth angle θ104. In addition, similarly to the above-mentioned embodiment 1, the first angle θ101 of the first inclined surface 128A is about 32°, and the second angle θ102 of the second inclined surface 129A is about 54°. In addition, the third plane 32 described in embodiment 1 is not provided on the second opposite main surface 125C of the second light guide plate 125 involved in the present embodiment (refer to Figure 6 ). Therefore, in the present embodiment, the first inclined surface 128A and the second inclined surface 129A are directly connected.

[0087] like Fig.18 As shown, for the light emitted from the second LED 24 and introduced into the second light guide plate 125, if it irradiates the second inclined surface 129A during the process of propagating in the second light guide plate 125, most of the reflected light passes through the second inclined surface 129A. The light that passes through the second inclined surface 129A is refracted at the second inclined surface 129A and is incident on the fourth inclined surface 128B facing the second inclined surface 129A, and is refracted at the fourth inclined surface 128B toward the second light guide plate light output main surface 125B. Here, as described above, the third angle θ103 of the fourth inclined surface 128B is set to be greater than 40°, so that by passing through the second inclined surface 129A and being refracted by the fourth inclined surface 128B, the incident light can be given an angle in such a way that most of the light reaching the second light guide plate light output main surface 125B is totally reflected by the second light guide plate light output main surface 125B. In this way, most of the light reaching the second light guide plate light emitting main surface 125B after being refracted at the fourth inclined surface 128B can be totally reflected and travel toward the second opposite main surface 125C. Thus, the side lobe light traveling in a direction inclined toward the opposite side of the second LED 24 side in the X-axis direction relative to the front direction after being emitted from the second light guide plate light emitting main surface 125B can be reduced.

[0088] On the other hand, when the first LED 13 is turned on while the second LED 24 is turned off (see Figure 1 ), if the light emitted from the first light guide plate light emitting main surface 14B of the first light guide plate 14 is transmitted through the first light-transmitting portion 18D of the first grid 18, then Fig.18As shown, the light 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. Among them, the light incident on the fourth inclined surface 128B included in the third inclined surface 131 is refracted by the fourth inclined surface 128B to the direction corresponding to the third angle θ103. In this embodiment, the third angle θ103 is greater than 65°. Since it is set to be greater than 65°, compared with the case where the third angle θ103 is less than 65°, the light incident on the opposite side (the side facing the second LED 24) in the X-axis direction can be made to be greater than the side facing the second LED 24 in the X-axis direction. Fig.18 In particular, the ratio of the light traveling in the direction of 45° relative to the X-axis direction among the light on the opposite side of the second LED 24 in the X-axis direction to the light exiting from the second light guide plate light exiting main surface 125B can be set to 2.5% or less. Therefore, the light exiting to the first light shielding portion 18C (refer to Figure 2 ) Light outside the limited angle range is not easily visually discernible.

[0089] In addition, when the first LED 13 is turned on while the second LED 24 is turned off (see Figure 1 ), the light emitted from the first grating 18 is incident on 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. Thus, the light incident on the fourth inclined surface 128B is refracted by the fourth inclined surface 128B to a direction corresponding to the third angle θ103, and the light incident on the fifth inclined surface 129B is refracted by the fifth inclined surface 129B to a direction corresponding to the fourth angle θ104. In the present embodiment, the fourth angle θ104 of the fifth inclined surface 129B is equal to the third angle θ103 of the fourth inclined surface 128B, and therefore the same degree of refraction is imparted to each light incident on the fourth inclined surface 128B and the fifth inclined surface 129B from the first grating 18 side. Therefore, when each light incident on the fourth inclined surface 128B and the fifth inclined surface 129B from the first grid 18 side and refracted by the fourth inclined surface 128B and the fifth inclined surface 129B is emitted from the second light guide plate light emitting main surface 125B, the traveling direction is not easily deviated.

[0090] Here, in order to obtain insights into how the light distribution changes when the angles formed by the fourth bevel 128B and the fifth bevel 129B of the sixth light guide plate lens 128 and the seventh light guide plate lens 129 of the second light guide plate 125 relative to the X-axis direction, that is, the third angle θ103 and the fourth angle θ104, are changed, an empirical experiment 2 was conducted. In this empirical experiment 2, except for the structure of the sixth light guide plate lens 128 and the seventh light guide plate lens 129, a backlight device 12 having the same structure as that described previously in this paragraph was used. In empirical experiment 2, the angles formed by the first bevel 128A and the second bevel 129A relative to the X-axis direction were made equal, and the angles were fixed at 54°, and the angles formed by the fourth bevel 128B and the fifth bevel 129B relative to the X-axis direction were made equal, and the angles were changed within the range of 3° to 60°. Specifically, in the empirical experiment 2, the angles formed by the fourth inclined surface 128B and the fifth inclined surface 129B 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 formed by the fourth inclined surface 128B and the fifth inclined surface 129B with respect to the X-axis direction were changed as described above, the second LED 24 was turned on and the first LED 13 was turned off, the brightness related to the emitted light was measured, and a graph related to the light distribution (brightness angle distribution) in the X-axis direction was prepared.

[0091] The experimental results related to light distribution in empirical experiment 2 are as follows: Fig.19 As shown. Fig.19 In the graph related to light distribution shown in the figure, the horizontal axis is the angle of the X-axis direction relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Fig.19 The positive and negative signs of the angles on the horizontal axis are the same as those described in the empirical experiment 1 of the implementation mode 1. Fig.10 The symbols marked on the horizontal axis of the curve graph have the same meaning.

[0092] The experimental results of empirical experiment 2 are described. Fig.19 It can be seen that the amount of side lobe light (light emitted at an angle of -80° to -50° in the X-axis direction relative to the front direction) varies according to the angle formed by the fourth inclined surface 128B and the fifth inclined surface 129B relative to the X-axis direction. Specifically, if the angle formed by the fourth inclined surface 128B and the fifth inclined surface 129B relative to the X-axis direction is less than 20°, the brightness of the side lobe light is greater than 20 cd / m 2The smaller the angle between the fourth inclined surface 128B and the fifth inclined surface 129B and the X-axis direction, the higher the brightness of the side lobe light. It can be seen that if the angle between the fourth inclined surface 128B and the fifth inclined surface 129B and the X-axis direction is greater than 40°, the brightness of the side lobe light is lower than 10 cd / m 2 In addition, it can be seen that when the angle between the fourth inclined surface 128B and the fifth inclined surface 129B with respect to the X-axis direction is 40° or 60°, the brightness of the side lobe light does not change much. Therefore, it can be said that if the angle between the fourth inclined surface 128B and the fifth inclined surface 129B with respect to the X-axis direction is greater than 40°, the side lobe light can be well reduced.

[0093] Next, in order to verify the advantages of the backlight device 12 and the liquid crystal display device 10 involved in this embodiment, a comparative experiment 2 similar to the comparative experiment 1 of the embodiment 1 was conducted. In this comparative experiment 2, the following Example 2 was used. Example 2 is a backlight device 12 having the same structure as that described before in the above-mentioned empirical experiment 2, and the first angle θ101 of the first inclined surface 128A is set to 32°, the second angle θ102 of the second inclined surface 129A is set to 54°, the third angle θ103 of the fourth inclined surface 128B is set to 65°, and the fourth angle θ104 of the fifth inclined surface 129B is set to 65°. In the comparative experiment 2, Example 2 was used, and the brightness related to each emitted light was measured when the first LED 13 was turned on and the second LED 24 was turned off, when the second LED 24 was turned on and the first LED 13 was turned off, and when both the first LED 13 and the second LED 24 were turned on, and a graph related to the light distribution (brightness angle distribution) in the X-axis direction was prepared.

[0094] Compare the experimental results related to light distribution in Experiment 2. Figure 20 to Figure 22 As shown. Figure 20 to Figure 22 In the graph related to light distribution shown in the figure, the horizontal axis is the angle of the X-axis direction relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Figure 20 to Figure 22 The positive and negative signs of the angles on the horizontal axis are the same as those described in the empirical experiment 1 of the implementation mode 1. Fig.10 The symbols marked on the horizontal axis of the curve graph have the same meaning. Figure 20 to Figure 22 This is the experimental result of Example 2. Fig. 20 The light distribution when the first LED 13 is turned on and the second LED 24 is turned off is shown. Fig.21 The light distribution when the second LED 24 is turned on and the first LED 13 is turned off is shown. Fig. 22 The light distribution when the first LED 13 and the second LED 24 are turned on together is shown.

[0095] The experimental results of comparative experiment 2 are similar to those of comparative experiment 1 ( Figures 11 to 16 ) will be described while comparing. First, according to the experimental results of Example 2 Fig. 20 The light distribution of the embodiment 1 of the comparative experiment 1 (see Fig.14 ) are roughly the same.

[0096] Next, according to the experimental results of Example 2 Fig.21 The light distribution of the embodiment 1 of the comparative experiment 1 (refer to Fig.15 ) compared to the experimental results of Example 2 Fig.21 The brightness of the light distribution increases in the range of -40° to +40°, and decreases significantly in the range of -80° to -50°.

[0097] As the experimental results of Example 2 Fig. 22 The light distribution is a synthesis of Fig. 20 Light distribution and Fig.21 The content of light distribution. Fig. 22 The light distribution shows that when both the first LED 13 and the second LED 24 are turned on, the peak brightness is almost at 0°, except for a part (in the range of -60° to -80°), the larger the absolute value of the angle (in Fig. 22 The further away from 0° on the horizontal axis, the lower the brightness. Fig.16 ) compared to the experimental results of Example 2 Fig. 22 The brightness of the light distribution becomes higher in the range of -40° to +40°, and becomes significantly lower in the range of -80° to -50°. The reason is speculated to be that in Example 2, the light transmitted through the second inclined surface 129A is refracted by the fourth inclined surface 128B whose third angle θ103 is set to 65°, whereby most of the light is totally reflected by the second light guide plate main light emitting surface 125B. Therefore, the side lobe light emitted in the range of -80° to -50° is significantly reduced, and the light emitted in the range of -50° to +40° is increased. In addition, similar to Example 1, Example 2 avoids the visual recognition range of ±20° ( Fig.17There is a local reduction in brightness within the visual range of the front passenger seat, which can be said to achieve excellent viewing angle performance.

[0098] As described above, according to the present embodiment, the third inclined surface 131 includes the fourth inclined surface 128B disposed opposite to the second inclined surface 129A at a distance, and the angle of the fourth inclined surface 128B relative to the first direction, that is, the third angle θ103, is set to be greater than 40°. The light transmitted through the second inclined surface 129A is refracted at the second inclined surface 129A and incident on the fourth inclined surface 128B facing the second inclined surface 129A, and is refracted at the fourth inclined surface 128B and directed toward the second light guide plate light output main surface 125B. The third angle θ103 of the fourth inclined surface 128B is set to be greater than 40°, so that most of the light reaching the second light guide plate light output main surface 125B can be given an angle in a manner that most of the light reaching the second light guide plate light output main surface 125B is totally reflected by the second light guide plate light output main surface 125B. In this way, most of the light reaching the second light guide plate light output main surface 125B after being refracted at the fourth inclined surface 128B can be totally reflected and travel toward the second opposite main surface 125C. Thus, the side lobe light emitted from the light emitting main surface 125B of the second light guide plate and traveling in a direction inclined toward the opposite side of the second LED 24 side in the first direction relative to the front direction can be reduced.

[0099] In addition, the third angle θ103 of the fourth inclined surface 128B is set to be greater than 65°. 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, if it passes through the first light-transmitting portion 18D of the first grid 18, 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. Among them, the light incident on the fourth inclined surface 128B is refracted in a direction corresponding to the third angle θ103. In addition, if the third angle θ103 is set to be greater than 65°, the ratio of the light on the opposite side of the second LED 24 side in the first direction to the light emitted from the second light guide plate light-emitting main surface 125B can be reduced compared to the case where the third angle θ103 is less than 65°. In particular, the ratio of the light traveling in the direction of 45° relative to the first direction among the light on the opposite side of the second LED 24 in the first direction to the light emitted from the light emitting main surface 125B of the second light guide plate can be set to be 2.5% or less. Therefore, the light emitted outside the angle range limited by the first light shielding portion 18C of the first grid 18 is effectively made difficult to be visually recognized.

[0100] In addition, the third inclined surface 131 includes a fourth inclined surface 128B disposed opposite to the second inclined surface 129A at a distance and a fifth inclined surface 129B disposed opposite to the first inclined surface 128A at a distance, and a fourth angle θ104 of the fifth inclined surface 129B relative to the first direction is equal to a third angle θ103 of the fourth inclined surface 128B relative to the first direction. When the first LED 13 is turned on while the second LED 24 is turned off, 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 grid 18, and then enters 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. Among them, the light incident on the fourth inclined surface 128B is refracted to the direction corresponding to the third angle θ103, and the light incident on the fifth inclined surface 129B is refracted to the direction corresponding to the fourth angle θ104. Here, the fourth angle θ104 of the fifth inclined surface 129B is equal to the third angle θ103 of the fourth inclined surface 128B, so the degree of refraction given to each light incident on the fourth inclined surface 128B and the fifth inclined surface 129B from the first grating 18 side is equal. Therefore, when each light incident on the fourth inclined surface 128B and the fifth inclined surface 129B from the first grating 18 side and refracted by the fourth inclined surface 128B and the fifth inclined surface 129B is emitted from the second light guide plate light emitting main surface 125B, the traveling direction is not easily deviated.

[0101] <Implementation Method 3> according to Figures 23 to 30 Embodiment 3 is described. Embodiment 3 shows a case where the configurations of the sixth light guide plate lens 228 and the seventh light guide plate lens 229 are changed from those of Embodiment 2. In addition, repeated descriptions of the same configurations, functions, and effects as those of Embodiment 2 are omitted.

[0102] like Fig.23 As shown, the sixth light guide plate lens 228 of this embodiment has a first inclined surface 228A and a fourth inclined surface 228B, and further has a sixth inclined surface 33 located between the first inclined surface 228A and the fourth inclined surface 228B in the X-axis direction (first direction). The sixth inclined surface 33 has a first inclined surface 228A and a second inclined surface 228B in the X-axis direction (first direction). Fig.23 The opposite side ( Fig.23The sixth bevel 33 is included in the third bevel 231. The sixth light guide plate lens 228 has a fourth bevel 228B and a sixth bevel 33 included in the third bevel 231. The sixth bevel 33 is formed to have a slope that causes the thickness of the sixth light guide plate lens 228 to increase continuously and gradually from the second LED 24 side toward the opposite side in the X-axis direction. Moreover, the angle formed by the sixth bevel 33 relative to the X-axis direction, i.e., the fifth angle θ5, is set to, for example, about 1.4°. In contrast, the third angle θ203 of the fourth bevel 228B is greater than 67°, for example, set to about 67°. In the present embodiment, the first angle θ201 of the first bevel 228A is set to, for example, about 33°. In addition, the first plane 28C described in Embodiment 1 is not provided on the sixth light guide plate lens 228 involved in the present embodiment (refer to Figure 6 ).

[0103] like Fig.23 As shown, the seventh light guide plate lens 229 involved in this embodiment does not have the second plane 29C described in Embodiment 1 (see Figure 6 ), and the second inclined surface 229A and the fifth inclined surface 229B are directly connected. The fourth angle θ204 of the fifth inclined surface 229B is set to about 1.4°, for example. Therefore, the fourth angle θ204 of the fifth inclined surface 229B is smaller than the third angle θ203. In addition, the angles formed by the fifth inclined surface 229B and the sixth inclined surface 33 relative to the X-axis direction, that is, the fourth angle θ204 and the fifth angle θ5 are equal. In addition, similarly to the above-mentioned embodiment 1, the second angle θ202 of the second inclined surface 229A is about 54°.

[0104] like Fig.23As shown, the arrangement pitches P201 and P202 of the sixth light guide plate lens 228 and the seventh light guide plate lens 229 in the X-axis direction are equal to each other, for example, set to about 0.045 mm. The height dimension H202 of the sixth light guide plate lens 228 (the protruding dimension protruding from the second opposite main surface 225C) is set to about 0.0054 mm, for example. In addition, the height dimension H4 of the sixth light guide plate lens 228 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) is set to about 0.0021 mm, for example. The height dimension H203 of the seventh light guide plate lens 229 from the second opposite main surface 225C is smaller than the height dimension H202 of the sixth light guide plate lens 228, for example, set to about 0.0043 mm. In addition, the height dimension H5 from the upper end position of the fifth slope 229B (the intersection position of the first slope 228A and the fifth slope 229B) to the lower end position of the fifth slope 229B (the intersection position of the second slope 229A and the fifth slope 229B) in the seventh light guide plate lens 229 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 Figure 1 ), if 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 grid 18, it is incident on the second opposite main surface 225C of the second light guide plate 225. On the second opposite main surface 225C, the light incident on the fourth inclined surface 228B is refracted in a direction corresponding to the third angle θ203. In addition, in the present embodiment, the third angle θ203 is set to be greater than 67°. Since it is set to be greater than 67°, compared with the case where the third angle θ203 is assumed to be greater than 65° and less than 67°, the ratio of the light on the opposite side of the second LED 24 side in the X-axis direction to the light emitted from the second light guide plate light emitting main surface 225B can be further reduced. In particular, among the light on the opposite side of the second LED 24 side in the X-axis direction, the ratio of the light traveling in the direction of 45° with the X-axis direction to the light emitted from the second light guide plate light emitting main surface 225B can be set to be less than 2.3%. Therefore, light emitted outside the angle range limited by first light shielding portion 18C of first grating 18 is more effectively made less likely to be visually recognized.

[0106] In addition, when the first LED 13 is turned on while the second LED 24 is turned off, on the second opposite main surface 225C, the light incident on the fourth inclined surface 228B is refracted in a direction corresponding to the third angle θ203, and the light incident on the fifth inclined surface 229B is refracted in a direction corresponding to the fourth angle θ204. In the present embodiment, the fourth angle θ204 of the fifth inclined surface 229B is smaller than the third angle θ203 of the fourth inclined surface 228B, so 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. Therefore, when the light incident on the first light guide plate 14 side and refracted by the fifth inclined surface 229B is emitted from the second light guide plate light exit main surface 225B, it is difficult to travel outside the angle range limited by the first light shielding portion 18C of the first grid 18.

[0107] In addition, when the first LED 13 is turned on while the second LED 24 is turned off, on the second opposite main surface 225C, the light incident on the fifth inclined surface 229B is refracted in a direction corresponding to the fourth angle θ204, and the light incident on the sixth inclined surface 33 is refracted in a direction corresponding to the fifth angle θ5. In the present embodiment, since the fifth angle θ5 of the sixth inclined surface 33 is equal to the fourth angle θ204, the degree of refraction given to each light incident on the fifth inclined surface 229B and the sixth inclined surface 33 is equal and smaller than the degree of refraction given to the light incident on the fourth inclined surface 228B. Therefore, each light incident from the first light guide plate 14 side and refracted by the fifth inclined surface 229B and the sixth inclined surface 33 is difficult to travel outside the angle range limited by the first light shielding portion 18C of the first grid 18 when it is emitted from the second light guide plate light exit main surface 225B.

[0108] In addition, if Fig.24As shown, the width dimension of the fifth light guide plate lens 227 as a 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 Embodiment 1, and is set to about 0.165 mm, for example. 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 lens 27 described in Embodiment 1, and is set to about 0.175 mm, for example. In addition, the vertex angle of the fifth light guide plate lens 227 is smaller than the vertex angle (140°) of the fifth light guide plate lens 27 described in Embodiment 1, and is set to about 120°, for example. Here, if the occupancy rate of the width dimension of the fifth light guide plate lens 227 in the arrangement interval is expressed as a percentage obtained by dividing the width dimension (0.165 mm) by the arrangement interval (0.175 mm), it is about 94%. The following tendency is shown: the higher the occupancy rate of the width dimension of the fifth light guide plate lens 227 in the arrangement interval, the lower the occupancy rate of the sixth light guide plate lens 228 and the seventh light guide plate lens 229 in the second opposite main surface 225C of the second light guide plate 225. On the other hand, the occupancy rate of the width dimension (0.126 mm) of the fifth light guide plate lens 27 described in Embodiment 1 in the arrangement interval (0.175 mm) is about 72%. Therefore, in this embodiment, compared with Embodiment 1, the occupancy rate of the sixth light guide plate lens 228 and the seventh light guide plate lens 229 in the second opposite main surface 225C of the second light guide plate 225 becomes lower. Thus, when the first LED 13 is turned on while the second LED 24 is turned off, the probability of the light from the first grid 18 being refracted by the inclined surfaces 33, 228A, 228B, 229A, and 229B is reduced, so when the light is emitted from the second light guide plate light emitting main surface 225B, it is difficult to travel outside the angle range limited by the first light shielding portion 18C of the first grid 18. In addition, the fifth light guide plate lens 227 is rounded in an arc-shaped manner at the top, and its curvature radius is, for example, about 0.0875 mm.

[0109] Next, in order to gain insights into how the light distribution changes when the third angle θ203, which is the angle formed by the fourth inclined surface 228B of the sixth light guide plate lens 228 of the second light guide plate 225 relative to the X-axis direction, changes, an empirical experiment 3 was conducted. In this empirical experiment 3, except for the structure of the sixth light guide plate lens 228, a backlight device 12 having the same structure as that described previously in this paragraph was used. In empirical experiment 3, the third angle θ203 of the fourth inclined surface 228B was varied within the range of 60° to 75°. In detail, in empirical experiment 3, the third angle θ203 of the fourth inclined surface 228B was set to 60°, 65°, 67°, 70°, and 75°. In the state where the first LED 13 is turned on and the second LED 24 is turned off in the backlight device 12 in which the third angle θ203 of the fourth inclined surface 228B is changed as described above, the brightness related to the emitted light is measured, and a curve graph related to the light distribution (brightness angle distribution) in the X-axis direction is produced. On this basis, the ratio of light at each angle of -25°, -35°, and -45° in the light distribution in the X-axis direction is calculated respectively. When calculating, the peak brightness at each angle of -25°, -35°, and -45° is divided by the overall peak brightness (relative brightness is "1"). Here, the significance of calculating the ratio of light at each angle of -25°, -35°, and -45° is to provide an indicator of whether the side lobe light (light emitted in the range of -80° to -50°) is easy to visually identify. That is, in order to make the side lobe light difficult to be visually recognized, 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 larger the angle in the light distribution in the X-axis direction, the lower the reference value at which the side lobe light is difficult to be visually recognized.

[0110] The experimental results of empirical experiment 3 are as follows Figure 25 to Figure 27 shown. Fig.25 2 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°. Fig.25 In the graph related to light distribution shown, the horizontal axis is the angle (unit: "°") of the X-axis direction relative to the front direction (Z-axis direction), and the vertical axis is the relative brightness (unitless). Fig.26 Yes Fig.25 The horizontal axis ranges from 0° to -70° and the vertical axis ranges from 0 to 0.1, which are enlarged in the graph. Fig.25 and Fig.26 The positive and negative signs of the angles on the horizontal axis are the same as those described in the empirical experiment 1 of the implementation mode 1. Fig.10 The symbols marked on the horizontal axis of the curve graph have the same meaning. Fig. 272 is a table showing the relationship between the third angle θ203 (unit: "°") and the ratio of light at each angle of -25°, -35°, and -45° in the light distribution in the X-axis direction (unit: "%).

[0111] The experimental results of empirical experiment 3 are described below. Figure 25 to Figure 27 It can be seen that when the third angle θ203 of the fourth inclined surface 228B is 60°, the ratios of light at -25° and -35° are below the respective reference values ​​(5%, 3%), and the ratio of light at -45° is greater than the reference value (2.5%). In contrast, it can be seen that when the third angle θ203 of the fourth inclined surface 228B is 65°, 67°, 70°, and 75°, the ratios of light at -25°, -35°, and -45° are all below the respective reference values. In particular, compared to the case where the ratio of light at -45° is equal to the reference value (2.5%) when the third angle θ203 of the fourth inclined surface 228B is 65°, the ratio of light at -45° becomes a value (2.3%) less than the reference value when the third angle θ203 of the fourth inclined surface 228B is 67°, 70°, and 75°. 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 difficult to be visually recognized well.

[0112] Next, in order to verify the advantages of the backlight device 12 and the liquid crystal display device 10 involved in this embodiment, a comparative experiment 3 similar to the comparative experiment 1 of the embodiment 1 was conducted. In this comparative experiment 3, the following embodiment 3 was used. Embodiment 3 is a backlight device 12 with the same structure as that described before the above-mentioned empirical experiment 3, and the first angle θ201 of the first inclined surface 228A is set to 33°, the second angle θ202 of the second inclined surface 229A is set to 54°, the third angle θ203 of the fourth inclined surface 228B is set to 67°, the fourth angle θ204 of the fifth inclined surface 229B is set to 1.4°, and the fifth angle θ5 of the sixth inclined surface 33 is set to 1.4°. In comparative experiment 3, using Example 3, the brightness associated with each emitted light is measured when the first LED 13 is turned on and the second LED 24 is turned off, when the second LED 24 is turned on and the first LED 13 is turned off, and when both the first LED 13 and the second LED 24 are turned on, a curve graph associated with the light distribution in the X-axis direction (brightness angle distribution) is prepared.

[0113] Compare the experimental results related to light distribution in Experiment 3. Figures 28 to 30 As shown. Figures 28 to 30 In the graph related to light distribution shown in the figure, the horizontal axis is the angle of the X-axis direction relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Figures 28 to 30The positive and negative signs of the angles on the horizontal axis are the same as those described in the empirical experiment 1 of the implementation mode 1. Fig.10 The symbols marked on the horizontal axis of the curve graph have the same meaning. Figures 28 to 30 This is the experimental result of Example 3. Fig.28 The light distribution when the first LED 13 is turned on and the second LED 24 is turned off is shown. Fig.29 The light distribution when the second LED 24 is turned on and the first LED 13 is turned off is shown. Fig.30 The light distribution when the first LED 13 and the second LED 24 are turned on together is shown.

[0114] The experimental results of comparative experiment 3 are similar to those of comparative experiment 2 ( Figure 20 to Figure 22 ) will be described while comparing. First, according to the experimental results of Example 3 Fig.28 The light distribution of the first LED 13 is turned on and the second LED 24 is turned off. The peak brightness is approximately 0° and the emission angle range is about ±10°. This result is similar to the experimental results of Example 1 of Comparative Experiment 1 (refer to Fig.14 ) are roughly the same.

[0115] Next, according to the experimental results of Example 3 Fig.29 The light distribution of the embodiment 2 of the comparative experiment 2 (refer to Fig.21 ) compared to the experimental results of Example 3. Fig.29 The brightness of the light distribution of Example 3 decreases slightly in the range of -40° to +40°, and in the range of -80° to -50°, the brightness becomes lower than that in the range of -40° to +40°. In particular, the brightness of Example 3 decreases significantly in the range of -80° to -70°.

[0116] As the experimental results of Example 3 Fig.30 The light distribution is a synthesis of Fig.28 Light distribution and Fig.29 The content of light distribution. Fig.30 The light distribution of the first LED 13 and the second LED 24 is turned on, and the peak brightness exists at approximately 0°, and the larger the absolute value of the angle (in Fig.29 The further away from 0° on the horizontal axis, the lower the brightness. Fig. 22) compared to the experimental results of Example 3. Fig.30 The brightness of the light distribution is slightly lower in the range of -40° to +40°, and lower in the range of -80° to -50° than in the range of -40° to +40°, especially in the range of -80° to -70°, where the brightness is significantly reduced. The reason is presumed to be that in Example 3, the light transmitted through the second inclined surface 229A is refracted by the fourth inclined surface 228B whose third angle θ203 is set to 67°, so that most of the light is totally reflected by the main light emitting surface 225B of the second light guide plate, and thus the side lobe light emitted to the range of -80° to -50° is reduced. On this basis, if 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°, since they are values ​​close to 0°, it is inferred that when the light from the first grid 18 is incident on the second opposite main surface 225C of the second light guide plate 225, the refraction effect given by the fifth inclined surface 229B and the sixth inclined surface 33 is extremely small, which also helps to reduce the side lobe light emitted to the range of -80° to -50°. In addition, it is inferred that it also helps to make the width dimension of the fifth light guide plate lens 227 account for as much as 94% of the arrangement interval. In addition, the reason why the brightness is slightly low in the range of -40° to +40° can be speculated to be that if the fourth angle θ204 of the fifth slope 229B is about 1.4°, it is extremely small compared to the third angle θ203 of the fourth slope 228B, so the light traveling from the opposite side of the second LED 24 side to the second LED 24 side in the X-axis direction in the second light guide plate 225 is difficult to rise through the fifth slope 229B.

[0117] As described above, according to the present embodiment, the third angle θ203 of the fourth inclined surface 228B is set to be greater than or equal to 67°. 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 grid 18, and then enters 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. Among them, the light incident on the fourth inclined surface 228B is refracted in a direction corresponding to the third angle θ203. Moreover, if the third angle θ203 is set to be greater than or equal to 67°, the ratio of the light on the opposite side of the second LED 24 side in the first direction to the light emitted from the second light guide plate light-emitting main surface 225B can be further reduced compared to the case where the third angle θ203 is greater than or equal to 65° and less than 67°. In particular, the ratio of the light traveling in the direction of 45° relative to the first direction among the light on the opposite side of the second LED 24 in the first direction to the light emitted from the light emitting main surface 225B of the second light guide plate can be set to 2.3% or less. Therefore, it is more effective to make the light emitted outside the angle range limited by the first light shielding portion 18C of the first grid 18 less visually recognizable.

[0118] In addition, the third inclined surface 231 includes a fourth inclined surface 228B disposed opposite to the second inclined surface 229A at a distance and a fifth inclined surface 229B disposed opposite to the first inclined surface 228A at a distance, and a fourth angle θ204, which is an angle of the fifth inclined surface 229B relative to the first direction, is smaller than a third angle θ203, which is an angle of the fourth inclined surface 228B relative to the first direction. When the first LED 13 is turned on while the second LED 24 is turned off, 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 grid 18, and then 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 them, the light incident on the fourth inclined surface 228B is refracted in a direction corresponding to the third angle θ203, and the light incident on the fifth inclined surface 229B is refracted in a direction corresponding to the fourth angle θ204. Here, the fourth angle θ204 of the fifth inclined surface 229B is smaller than the third angle θ203 of the fourth inclined surface 228B, so 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. Therefore, when the light incident on the first light guide plate 14 side and refracted by the fifth inclined surface 229B is emitted from the second light guide plate light emitting main surface 225B, it is difficult to travel outside the angle range limited by the first light shielding portion 18C of the first grid 18.

[0119] In addition, the first inclined surface 228A and the fourth inclined surface 228B are arranged at intervals 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 angle of the sixth inclined surface 33 relative to the first direction, that is, the fifth angle θ5, is equal to the fourth angle θ204. When the first LED 13 is turned on in a state where the second LED 24 is turned off, the refraction degree given to each light incident on the fifth inclined surface 229B and the sixth inclined surface 33 is equal and smaller than the refraction degree given to the light incident on the fourth inclined surface 228B. Therefore, each light incident from the first light guide plate 14 side and refracted by the fifth inclined surface 229B and the sixth inclined surface 33 is difficult to travel outside the angle range limited by the first light shielding portion 18C of the first grid 18 when it is emitted from the light emitting main surface 225B of the second light guide plate.

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

[0121] (1) first angle θ1, θ101, θ201, second angle θ2, θ102, θ202, third angle θ3, θ103, θ203, fourth angle θ4, θ104, The specific numerical values ​​of θ204 and the fifth angle θ5 can be changed as appropriate in addition to those described above.

[0122] (2) In the configuration described in Embodiment 1, the third plane 32 may be omitted.

[0123] (3) In the configurations described in Embodiments 1 and 2, the first plane 28C and the second plane 29C may be omitted.

[0124] (4) In the configurations described in Embodiments 2 and 3, a third plane 32 may be provided.

[0125] (5) In the configuration described in Embodiment 3, the third angle θ203 may be equal to the fourth angle θ204. In the configuration described in Embodiment 3, 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 from each other.

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

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

[0129] (9) In the configuration described in Embodiment 3, a flat surface may be provided instead 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 can be changed as appropriate. For example, a plurality of sixth light guide plate lenses 28, 128, 228 and a plurality of seventh light guide plate lenses 29, 129, 229 may be arranged alternately in the order that a plurality of sixth light guide plate lenses 28, 128, 228 are arranged in succession and a plurality of 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 of the sixth light guide plate lenses 28, 128, and 228 and the seventh light guide plate lenses 29, 129, and 229 in the X-axis direction can be changed as appropriate in addition to the above.

[0132] (12) The specific numerical values ​​of the width dimensions W2 to A8 and the height dimensions H2, H3, H202, H203 of each inclined surface and each flat surface of the sixth light guide plate lens 28, 128, 228 and the seventh light guide plate lens 29, 129, 229 can be changed as appropriate in addition to the above.

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

[0134] (14) Specific numerical values ​​such as the contact angle and the tilt angle of each of the light guide plate lenses 21 to 23 included in the first light guide plate 14 may be changed as appropriate.

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

[0136] (16) Either or both of the first light guide plate lens 21 and the second light guide plate lens 22 included in the first light guide plate 14 may be omitted.

[0137] (17) Specific numerical values ​​of the contact angle of the fourth light guide plate lens 26 included in the second light guide plate 25 , 125 , 225 , the apex angle of the fifth light guide plate lens 27 , 227 , and the like can be changed as appropriate.

[0138] (18) Either or both of the fourth light guide plate lens 26 and the fifth light guide plate lens 27 or 227 included in the second light guide plate 25 , 125 , or 225 may be omitted.

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

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

[0141] (21) The specific values ​​of the inclination angles, vertex angles, etc. of the prism slopes 16B1, 16B2, 17B1, 17B2 of the prisms 16B, 17B of the prism sheets 16, 17 can be changed as appropriate. The specific materials of the substrates 16A, 17A used in the prism sheets 16, 17 can be changed as appropriate. Similarly, the specific materials used in the prisms 16B, 17B can also be changed as appropriate.

[0142] (22) The specific cross-sectional shape of each prism 16B, 17B included in each prism sheet 16, 17 can be changed appropriately. In this case, for example, any one of the prism inclined surfaces 16B1, 16B2, 17B1, 17B2 of each prism 16B, 17B may be curved to have a plurality of inclination angles.

[0143] (23) In the first grid 18, the specific value of the ratio (tanθ) of the width divided by the height of the first light-transmitting portion 18D can be appropriately changed other than tan10°, and can be, for example, tan12.5°, tan15°, tan17.5°, etc.

[0144] (24) The second grid 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 polarizer may be installed on the main surface of the back side (outer side) of the array substrate constituting the liquid crystal panel 11 instead of the polarizer. The reflective polarizer includes a polarizing layer having a specific polarization axis (transmission axis), a multilayer film in which layers with different refractive indices are alternately stacked, a protective layer, etc. The polarizing layer has a polarization axis and an absorption axis orthogonal to the polarization axis, thereby selectively transmitting linear polarization parallel to the polarization axis and converting circular polarization into linear polarization along the polarization axis. The polarization axis of the polarizing layer is orthogonal to the polarization axis of the polarizing plate installed on the outer main surface of the CF substrate. The multilayer film is a multilayer structure, and the multilayer film has a reflection characteristic in which the reflectivity of the s-wave contained in the light is roughly higher than the reflectivity of the p-wave. The reflective polarizer has a multilayer film, so that the s-wave originally absorbed by the polarizing layer can be reused by reflecting it to the back side, which can improve the utilization efficiency of light (more specifically, brightness).

[0147] (27) A prism sheet arranged on the light incident principal surface side may be used in place of the first prism sheet 16 and the second prism sheet 17. The prism sheet is configured such that the light incident principal surface is opposite to the first light guide plate light emitting principal surface 14B of the first light guide plate 14 and the light emitting principal surface is opposite to the first light incident principal surface 18A of the first grid 18, and a plurality of prism sheets are arranged along the X-axis direction on the light incident principal surface. Even when such a prism sheet is used, light with less side lobe light can be supplied to the first grid 18, and the amount of light transmitted by the first light transmitting portion 18D can be sufficiently ensured.

[0148] (28) The vehicle-mounted liquid crystal display device 10 may also be installed at a position other than in front of the front passenger seat of the passenger car. For example, it may be installed at a position between the front passenger seat and the driver's seat. As the configuration of the liquid crystal display device 10 is changed, the required angle range of the viewing angle also changes. Therefore, it is sufficient to change the first grid 18, the sixth light guide plate lens 28, 128, 228, and the seventh light guide plate lens 29, 129, 229 accordingly. Description of Reference Numerals

[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 face (first end face), 14B…First light guide plate light emitting main face (first main face), 14C…First opposite main face (second main face), 18…First grid (first sheet), 18A…First light incident main face (third main face), 18B…First light emitting main face (fourth main face), 18C…First light shielding portion, 18D…First light transmitting portion, 24…Second LED (second light source), 25, 125, 225…Second light guide plate, 25A…Second light incident end face (second end face ), 25B, 125B, 125B…the second light guide plate light emitting main surface (fifth main surface), 25C, 125C, 225C…the second opposite main surface (sixth main surface), 28A, 128A, 228A…the first inclined plane, 28B, 128B, 228B…the fourth inclined plane, 29A, 129A, 229A…the second inclined plane, 29B, 129B, 229B…the fifth inclined plane, 31, 131, 231…the third inclined plane, 33…the sixth inclined plane, θ1, θ101, θ201…the first angle, θ2, θ102, θ202…the second angle, θ3, θ103, θ203…the third angle, θ4, θ104, θ204…the fourth angle, θ5…the fifth angle.

Claims

1. A lighting device, characterized in that: include: The first light source; A first light guide plate, wherein at least a portion of its outer peripheral end surface is set as a first end surface opposite to the first light source and for light incidence, and one principal surface of the first light guide plate is set as a first principal surface for light emission, and the other principal surface is set as a second principal surface; A first sheet, one main surface of which is set as a third main surface arranged toward the first main surface and for light to enter, and the other main surface of which is set as a fourth main surface for light to exit; Second light source; as well as a second light guide plate, wherein at least a portion of its outer peripheral end surface is set as a second end surface that is opposite to the second light source and for light to be incident on, and one principal surface of the second light guide plate is set as a fifth principal surface for light to be emitted, and the other principal surface is set as a sixth principal surface arranged toward the fourth principal surface, The first sheet material has at least: two first light shielding portions, which are arranged at intervals in a first direction including a direction from the first light source toward the first light guide plate and shield light; as well as a first light-transmitting portion, which is disposed between the two first light-shielding portions and transmits light; The sixth main surface of the second light guide plate is provided with an inclined first inclined surface and a second inclined surface, wherein the first inclined surface and the second inclined surface are inclined to rise from the side opposite to the second light source toward the second light source side in the first direction. An angle of the first inclined surface relative to the first direction is set to a first angle greater than 27°, and an angle of the second inclined surface relative to the first direction is set to a second angle greater than the first angle and less than 58°.

2. The lighting device according to claim 1, characterized in that: The sixth main surface of the second light guide plate is provided with an inclined third slope, and the inclination of the third slope is to rise from the second light source side toward the opposite side of the second light source side in the first direction.

3. The lighting device according to claim 2, characterized in that: The third inclined surface includes a fourth inclined surface, and the fourth inclined surface is arranged opposite to the second inclined surface with a gap therebetween. The third angle, that is, the angle of the fourth inclined surface relative to the first direction, is set to be greater than 40°.

4. The lighting device according to claim 3, characterized in that: The third angle of the fourth inclined surface is set to be greater than 65°.

5. The lighting device according to claim 3, characterized in that: The third angle of the fourth inclined surface is set to be greater than 67°.

6. The lighting device according to any one of claims 2 to 5, characterized in that: The third inclined surface includes a fourth inclined surface and a fifth inclined surface, the fourth inclined surface is arranged to face the second inclined surface with a gap, and the fifth inclined surface is arranged to face the first inclined surface with a gap, The fourth angle, an angle of the fifth inclined surface relative to the first direction, is set equal to the third angle, an angle of the fourth inclined surface relative to the first direction.

7. The lighting device according to any one of claims 2 to 5, characterized in that: The third inclined surface includes a fourth inclined surface and a fifth inclined surface, the fourth inclined surface is arranged to face the second inclined surface with a gap, and the fifth inclined surface is arranged to face the first inclined surface with a gap, The fourth angle, which is an angle of the fifth inclined surface relative to the first direction, is set to be smaller than the third angle, which is an angle of the fourth inclined surface relative to the first direction.

8. The lighting device according to claim 7, characterized in that: The first inclined surface and the fourth inclined surface are arranged at intervals in the first direction. The third inclined plane includes a sixth inclined plane, the sixth inclined plane is located between the first inclined plane and the fourth inclined plane, and an angle of the sixth inclined plane relative to the first direction, ie, a fifth angle, is set equal to the fourth angle.

9. A display device, characterized in that: include: The lighting device according to any one of claims 1 to 5; A display panel performs display using the light from the lighting device.

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