Lighting devices and display devices

Abstract

The present invention provides a lighting device and a display device for achieving uniform brightness distribution. The lighting device (12) comprises: a first sheet (18) having a first light incident principal surface (18A), a first light emitting principal surface (18B), two first light shielding portions (18C) spaced apart in a first direction, and a first light transmitting portion (18D) disposed between the two first light shielding portions (18C); a second sheet (19) having a second light incident principal surface (19A) opposite to the first light emitting principal surface (18B), a second light emitting principal surface (19B), and a first lens (19C); and a third sheet (20) having a third light incident principal surface (20A) opposite to the second light emitting principal surface (19B), two second light shielding portions (20C) spaced apart in the first direction on the third light emitting principal surface (20B), and a second light transmitting portion (20D) disposed between the two second light shielding portions (20C).

Description

Technical Field

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

[0002] As an example of an illumination device included in a liquid crystal display device, a planar illumination device described in Patent Document 1 is known. The planar illumination device described in Patent Document 1 includes an optical path changing unit that changes the direction of light propagation, located on at least one of the incident and exit surfaces of a louver, at a position opposite the end face of the light-blocking member. The optical path changing unit, located on the incident surface side of the louver, changes the direction of light that enters the end face of the light-blocking member of the louver from a light source and is absorbed, and then guides the light to the light-transmitting layer of the louver.

[0003] Prior art literature

[0004] Patent Literature

[0005] Japanese Patent Publication No. 2016-110854 Summary of the Invention

[0006] Technical problems to be solved by the present invention

[0007] In the planar lighting device described in Patent Document 1, if the louver is used to excessively restrict the light emission angle to prevent sidelobe light, there is a concern that the brightness distribution of the emitted light may become uneven. Specifically, while the brightness of the emitted light is high in the center of the planar lighting device, it may be significantly lower at the two end portions.

[0008] The technology described in this specification has been accomplished based on the above-mentioned circumstances, and its purpose is to achieve uniform brightness distribution.

[0009] Technical solutions to technical problems

[0010] (1) An illumination device related to the technology described in this specification comprises: a first sheet having a first light incident principal surface along a first direction, a first light emitting principal surface along the other side of the first direction, two first light shielding portions spaced apart in the first direction, and a first light transmitting portion disposed between the two first light shielding portions; a second sheet having a second light incident principal surface along the first direction and opposite to the first light emitting principal surface, a second light emitting principal surface along the other side of the first direction, and a first light transmitting portion disposed between the two first light shielding portions. a first lens; and a third piece, which has a main surface along the first direction and on the side opposite to the second light-emitting main surface, namely the third light-incident main surface, a main surface along the other side of the first direction, namely the third light-emitting main surface, two second light-shielding portions arranged at intervals in the first direction, and a second light-transmitting portion arranged between the second two light-shielding portions, the first lens has an inclined first inclined surface, which stands upright from the end side of the second piece in the first direction to the center side; in the third piece, the ratio of the width of the second light-transmitting portion divided by the height is greater than the ratio of the width of the first light-transmitting portion divided by the height.

[0011] The above-mentioned lighting device can also be constructed based on the above (1), wherein a plurality of the first lenses are arranged in the first direction, and the plurality of the first lenses include a central side lens and an end side lens, and the end side lens is located in the second piece at a position closer to the end side in the first direction than the central side lens, and the angle formed by the first inclined surface of the end side lens relative to the first direction is greater than the angle formed by the first inclined surface of the central side lens relative to the first direction.

[0012] In the lighting device described above in (2), each of the plurality of first lenses may have an inclined second slope rising from the center of the second sheet in the first direction toward the end.

[0013] Based on the above (3), the above-mentioned lighting device can also be constructed as follows: the angle formed by the first inclined surface and the second inclined surface of the central side lens, that is, the vertex angle, is equal to the vertex angle of the end side lens, and the angle formed by the second inclined surface of the end side lens relative to the first direction is smaller than the angle formed by the second inclined surface of the central side lens relative to the first direction.

[0014] Based on the above (4), the above-mentioned lighting device can also be constructed as follows: the angle formed by the first inclined surface of the plurality of first lenses relative to the first direction is in the range of 0° to 24°, and the angle formed by the second inclined surface relative to the first direction is in the range of 46° to 70°.

[0015] The above-mentioned lighting device can also be constructed based on any one of the above (1) to (5), wherein the first lens is arranged on the second light incident principal surface, and the second light emitting principal surface of the second piece is installed on the third light incident principal surface of the third piece.

[0016] The above-mentioned lighting device can also be constructed based on any one of the above (1) to (5), wherein the first lens is arranged on the second light-emitting principal surface, and the second light-incident principal surface of the second piece is installed on the first light-emitting principal surface of the first piece.

[0017] The above-mentioned lighting device can also be constructed based on any one of the above (1) to (7), wherein the lighting device has: a first light source; a first light guide plate, which is arranged along the first direction relative to the first light source; a first prism sheet, which is arranged on the light-emitting side relative to the first light guide plate, and has a first prism, a plurality of the first prisms are arranged along the first direction and extend along a second direction, and the second direction is orthogonal to both the first direction and the normal direction of the main surface of the first light guide plate; and a second prism sheet, which is arranged on the light-emitting side relative to the first prism sheet, and has a second prism, a plurality of the second prisms are arranged along the first direction and extend along the second direction, at least a portion of the outer peripheral end surface of the first light guide plate is a first light incident end surface opposite to the first light source, and one main surface is a fourth light exit end surface for emitting light. main surface, the main surface of the light-emitting side of the second prism sheet is arranged opposite to the first light-incident main surface of the first sheet, the first prism has: an inclined third oblique surface, which stands from the first light source side of the first direction of the first prism sheet to its opposite side; and an inclined fourth oblique surface, which stands from the side opposite to the first light source in the first direction of the first prism sheet to the first light source side, the second prism has: an inclined fifth oblique surface, which stands from the first light source side of the first direction of the second prism sheet to its opposite side; and an inclined sixth oblique surface, which stands from the side opposite to the first light source in the first direction of the second prism sheet to the first light source side, the angle formed by the fifth oblique surface in the second prism relative to the first direction is smaller than the angle formed by the third oblique surface in the first prism relative to the first direction.

[0018] The above-mentioned lighting device can also be constructed as follows based on the above (8), wherein the lighting device has: a second light source; and a second light guide plate, which is arranged along the first direction relative to the second light source, at least a portion of the outer peripheral end surface of the second light guide plate is a second light incident end surface opposite to the second light source, the main surface on one side is a fifth light emitting main surface for emitting light, and the main surface on the other side is an opposite main surface opposite to the third light emitting main surface and provided with a second lens, the second lens having an inclined seventh inclined surface, which stands from the side of the second light guide plate opposite to the second light source in the first direction toward the second light source.

[0019] A display device related to the technology described in this specification includes: the lighting device described in any one of (1) to (9) above; and a display panel that uses light from the lighting device to perform display.

[0020] Beneficial effects

[0021] According to the technology described in this specification, it is possible to achieve uniform brightness distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a side cross-sectional view of the liquid crystal display device according to the first embodiment.

[0023] Figure 2 This is a side cross-sectional view of a backlight device included in a liquid crystal display device.

[0024] Figure 3 It is a front cross-sectional view of the backlight device.

[0025] Figure 4 This is a perspective view of the first light guide plate constituting the backlight device as viewed from the first opposite main surface side.

[0026] Figure 5 It is a bottom view showing the structure of the first opposite main surface of the first light guide plate.

[0027] Figure 6 1 is a side sectional view showing a first louver, a linear Fresnel lens sheet, and a second louver constituting the backlight device.

[0028] Figure 7 Graph showing the relationship between the position of the linear Fresnel lens sheet in the X-axis direction and the tilt angle θ1 and the tilt angle θ2 of the first lens.

[0029] Figure 8 This is a table showing the experimental results of Comparative Experiment 1.

[0030] Figure 9 This is a graph showing the experimental results of the experimental experiment 1 when the inclination angle θ2 is 40° to 59°. Figure 10This is a graph showing the experimental results of the experimental experiment 1 when the inclination angle θ2 is 60° to 80°.

[0031] Figure 11 This is a graph showing the relationship between the ratio of light and the tilt angle θ2 in the angle range of −20° to −45° in Experiment 1.

[0032] Figure 12 This is a diagram for explaining the angle of the X-axis direction relative to the front direction in a liquid crystal display device installed in front of the passenger seat of a passenger car.

[0033] Figure 13 It is a side sectional view of a backlight device according to a second embodiment.

[0034] Figure 14 It is a side sectional view of a backlight device according to a third embodiment.

[0035] Figure 15 It is a side sectional view of a backlight device according to a fourth embodiment.

[0036] Figure 16 This is a side cross-sectional view of a liquid crystal display device according to a fifth embodiment. DETAILED DESCRIPTION

[0037] <First embodiment>

[0038] pass Figures 1 to 12 The first embodiment is described. In this embodiment, a liquid crystal display device (display device) 10 is illustrated. In addition, the X-axis, Y-axis, and Z-axis are shown in a portion of each drawing, and the directions of each axis are described in a manner such that the directions are the directions shown in each drawing. In addition, the up and down directions are shown in the following manner. Figure 2 and Figure 3 as a reference, and the upper side of the same figure is set as the front side, and the lower side of the same figure is set as the back side.

[0039] like Figure 1 As shown, the liquid crystal display device 10 includes a liquid crystal panel (display panel) 11 that displays images, and a backlight device (illumination device) 12 that is disposed on the back side of the liquid crystal panel 11 and irradiates the liquid crystal panel 11 with light used for display. In this embodiment, a vehicle-mounted liquid crystal display device 10 is illustrated. Vehicle-mounted liquid crystal display devices 10 are, for example, mounted on car navigation systems that display maps and other images, multi-function displays that display the operating status of equipment such as air conditioners in addition to maps, instrument panels that display instruments and warnings in addition to images, and information display systems that display television images, audio information, and other information in addition to maps.

[0040] The main surface of the liquid crystal panel 11 is in the shape of a plate parallel to the X-axis and the Y-axis, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis. The central side portion of the main surface of the liquid crystal panel 11 serves as a display area capable of displaying images, and the frame-shaped outer peripheral end portion surrounding the display area serves as a non-display area. The liquid crystal panel 11 comprises a pair of substrates and a liquid crystal layer enclosed between the pair of substrates. Of the pair of substrates constituting the liquid crystal panel 11, the substrate disposed on the front side is a CF substrate (counter substrate), and the substrate disposed on the back side is an array substrate (TFT substrate). The CF substrate is provided with color filters such as R (red), G (green), and B (blue), or a light shielding portion (black matrix) separating adjacent color filters. The array substrate (TFT substrate) is provided with at least mutually orthogonal gate wiring and source wiring, switching elements (such as TFTs) connected to the gate wiring and source wiring, and pixel electrodes connected to the switching elements to form pixels. In addition, alignment films are provided on the inner surfaces of each of the array substrate and CF substrate constituting the liquid crystal panel 11. Furthermore, polarizing plates are attached to respective outer surfaces of the array substrate and the CF substrate constituting the liquid crystal panel 11 .

[0041] Next, the backlight device 12 will be described. Figure 1 As shown, the backlight device 12 includes at least: a first LED (first light source) 13; a first light guide plate 14 that guides light from the first LED 13; a reflective sheet 15 disposed on the back side (light-exiting side) of the first light guide plate 14; a first prism sheet 16 disposed on the front side (light-exiting side) of the first light guide plate 14; and a second prism sheet 17 disposed on the front side of the first prism sheet 16. The backlight device 12 is a single-side incident edge-light type, in which light from the first LED 13 enters the first light guide plate 14 only from one side.

[0042] like Figure 1 As shown, the first LED 13 is roughly block-shaped, and one of the pair of surfaces along the Y-axis direction and the Z-axis direction is 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 by sealing an LED chip with a sealing material on a substrate portion mounted on the LED substrate. The LED chip of the first LED 13 emits, for example, monochromatic blue light. Phosphors are dispersed in the sealing material of 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 sealing material emits white light as a whole.

[0043] The first light guide plate 14 is made of a substantially transparent synthetic resin material (eg, acrylic resin such as PMMA) having a refractive index sufficiently higher than that of air. Figure 1As shown, the first light guide plate 14 is plate-shaped, and its main surface is parallel to the main surface of the liquid crystal panel 11. 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. One of the outer peripheral end surfaces of the first light guide plate 14 is a first light incident end surface 14A opposite to the first light-emitting surface 13A of the first LED 13. The first light incident end surface 14A is a surface parallel to the first light-emitting surface 13A of the first LED 13, and light emitted from the first light-emitting surface 13A is incident on the first light incident end surface 14A. Of the pair of main surfaces of the first light guide plate 14, the main surface on the front side opposite to the first prism sheet 16 is the first light guide plate light emitting main surface (fourth light emitting main surface) 14B from which light guided internally 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 14C located on the side opposite to the light emitting main surface 14B of the first light guide plate. Moreover, the first light guide plate 14 has the following functions: to introduce light emitted from the first LED 13 to the first light guide plate 14 from the first light incident end surface 14A, and to make the light rise and emit along the Z-axis direction toward the surface side (light emitting side) after propagating inside. The detailed structure of the first light guide plate 14 will be described again 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).

[0044] like Figure 1 As shown, the reflective sheet 15 is positioned so that its principal surface is parallel to the principal surfaces of the liquid crystal panel 11 and the first light guide plate 14, and covers the first opposite principal surface 14C of the first light guide plate 14. The reflective sheet 15 has excellent light reflectivity, effectively directing light leaking from the first opposite principal surface 14C of the first light guide plate 14 toward the front side, i.e., the first light guide plate's light-emitting principal surface 14B. The reflective sheet 15 is slightly larger than the first light guide plate 14 and is positioned to overlap substantially the entire area of the first opposite principal surface 14C.

[0045] like Figure 1 As shown, the first prism sheet 16 and the second prism sheet 17 are sheet-shaped, with their respective principal surfaces being parallel to the principal surfaces of the liquid crystal panel 11 and the first light guide plate 14. Furthermore, the principal surfaces of the first prism sheet 16 and the second prism sheet 17 are parallel to the X-axis and the Y-axis, and the normal direction (thickness direction) of the principal surfaces is aligned with the Z-axis. The first prism sheet 16 and the second prism sheet 17 are stacked on the front side of the first light guide plate 14 and have the function of imparting a predetermined optical effect to light emitted from the first light guide plate light-emitting principal surface 14B of the first light guide plate 14, thereby causing it to be emitted.

[0046] like Figure 1As shown, the first prism sheet 16 includes: a sheet-like first substrate 16A; and a first prism 16B, which is provided on the main surface (light-emitting main surface) of the front side (light-emitting side) of the first substrate 16A. The first substrate 16A is formed of a substantially transparent synthetic resin, specifically, a crystalline transparent resin material such as PET (polyethylene terephthalate). When manufacturing the first substrate 16A, it is preferable to form the first substrate 16A into a sheet by stretching the crystalline transparent resin material as the raw material using a biaxial stretching process, which is preferable in terms 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, uncured UV-curable resin material is filled into a molding mold. The first substrate 16A is placed at the open end of the mold, so that the uncured UV-curable resin material contacts the main surface on the front side. In this state, when the UV-curable resin material is irradiated with ultraviolet light through the first substrate 16A, the UV-curable resin material is cured, and the first prism 16B is integrally formed with the first substrate 16A. The UV-curable resin material constituting the first prism 16B is, for example, an acrylic resin such as PMMA. The refractive index of the UV-curable resin material constituting the first prism 16B is preferably in the range of 1.49 to 1.52, and most preferably 1.49.

[0047] like Figure 2 As shown, the first prism 16B is provided in a form protruding from the main surface of the first substrate 16A along the Z-axis direction toward the front side (the side opposite to the first light guide plate 14 side). The cross-sectional shape of the first prism 16B cut along the X-axis direction is roughly triangular (roughly mountain-shaped), and extends straight along the Y-axis direction (second direction). On the main surface of the first substrate 16A, along the X-axis direction (first direction), a plurality of them are arranged continuously without intervals. The first prism 16B has a pair of inclined surfaces 16B1 and 16B2. Among the pair of inclined surfaces 16B1 and 16B2 in the first prism 16B, the inclined surface on the first LED 13 side in the X-axis direction is the first prism inclined surface (third inclined surface) 16B1, and the inclined surface on the opposite side is the second prism inclined surface (fourth inclined surface) 16B2. The first prism inclined surface 16B1 has a plurality of inclined surfaces 16B1 and 16B2. Figure 2 to the left side) to the opposite side ( Figure 2 The light incident on the first prism 16B mainly travels in the direction close to the first LED 13 in the X-axis direction and is refracted by the first prism inclined surface 16B1. The second prism inclined surface 16B2 has a side opposite to the first LED 13 side in the X-axis direction of the first prism sheet 16 ( Figure 2 right side) toward the first LED 13 side ( Figure 2 The light incident on first prism 16B, primarily traveling in the X-axis direction away from first LED 13, is refracted by second prism inclined surface 16B2. Most of the light refracted by the pair of inclined surfaces 16B1 and 16B2 in first prism 16B selectively rises in the X-axis direction and is focused.

[0048] Moreover, if Figure 2 As shown, when comparing the inclination angle (third base angle) θ4 of the first prism bevel 16B1 of the first prism 16B with respect to the X-axis direction and the inclination angle (fourth base angle) θ5 of the second prism bevel 16B2 with respect to the X-axis direction, the former is larger than the latter. That is, the cross-sectional shape of the first prism 16B is an asymmetric shape, formed as an isosceles triangle. Specifically, the inclination angle θ4 of the first prism bevel 16B1 with respect 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 θ5 of the second prism bevel 16B2 with respect to the X-axis direction is preferably in the range of 35° to 50°, with 45° being the most preferred. In addition, the angle (second vertex angle) θ6 formed by a pair of bevels 16B1 and 16B2 in the first prism 16B is preferably in the range of 70° to 95°, with 80° being the most preferred. Furthermore, the height and width dimensions of the plurality of first prisms 16B arranged along the Y-axis direction, the inclination angles of the inclined surfaces 16B1 and 16B2 relative to the X-axis direction, etc. are all substantially the same, and the arrangement intervals between adjacent first prisms 16B are also substantially constant and arranged at equal intervals.

[0049] like Figure 1 As shown, the second prism sheet 17 includes: a sheet-like second substrate 17A; and a second prism 17B, which is provided 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 formed of a substantially transparent synthetic resin. Specifically, it is made of 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, for example, an acrylic resin such as PMMA, and its refractive index is higher than that of the material of the first prism 16B, for example, about 1.61.

[0050] like Figure 2As shown, the second prism 17B is provided in a form protruding from the main surface of the second substrate 17A along the Z-axis direction toward the front side (the side opposite to the first prism sheet 16). The cross-sectional shape of the second prism 17B cut along the X-axis direction is roughly triangular (roughly mountain-shaped), and extends in a straight line along the Y-axis direction. On the main surface of the second substrate 17A, along the X-axis direction, a plurality of them are arranged continuously without any intervals. The second prism 17B has a pair of inclined surfaces 17B1 and 17B2. Among the pair of inclined surfaces 17B1 and 17B2 in the second prism 17B, the inclined surface on the first LED 13 side in the X-axis direction is the third prism inclined surface (fifth inclined surface) 17B1, and the inclined surface on the opposite side is the fourth prism inclined surface (sixth inclined surface) 17B2. The third prism inclined surface 17B1 has a plurality of inclined surfaces 17B1 and 17B2. Figure 2 to the left side) 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 side of the second prism sheet 17 in the X-axis direction and opposite to the first LED 13) Figure 2 right side) toward the first LED 13 side ( Figure 2 The light incident on second prism 17B, primarily traveling in the X-axis direction away from first LED 13, is refracted by fourth prism inclined surface 17B2. Light refracted by the pair of inclined surfaces 17B1 and 17B2 in second prism 17B is mostly selectively directed upward in the X-axis direction and focused.

[0051] Moreover, if Figure 2As shown, the inclination angle θ7 (fifth base angle) formed by the third prism inclined surface 17B1 of the second prism 17B with respect to the X-axis direction and the inclination angle θ8 (sixth base angle) formed by the fourth prism inclined surface 17B2 with respect to the X-axis direction are the same. That is, the cross-sectional shape of the second prism 17B is symmetrical, forming an isosceles triangle. Moreover, the inclination angles θ7 and θ8 of the third prism inclined surface 17B1 and the fourth prism inclined surface 17B2 with respect to the X-axis direction are smaller than the inclination angle θ4 of the first prism inclined surface 16B1 with respect to the X-axis direction. Specifically, the inclination angles θ7 and θ8 of the third prism inclined surface 17B1 and the fourth prism inclined surface 17B2 with respect 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) θ9 formed by the pair of inclined surfaces 17B1 and 17B2 in the second prism 17B is preferably in the range of 80° to 100°, with 90°, i.e., a right angle, being the most preferred. Furthermore, the height, width, and inclination angles of the surfaces 17B1 and 17B2 relative to the X-axis of the plurality of second prisms 17B arranged along the Y-axis are all substantially the same. Adjacent second prisms 17B are also arranged at substantially constant and evenly spaced intervals. Furthermore, it is preferable that the height and spacing of the second prisms 17B differ from those of the first prisms 16B in order to suppress the generation of interference fringes known as moiré patterns.

[0052] 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, most of the light emitted from the first light guide plate light-emitting main surface 14B of the first light guide plate 14 and incident on the first prism sheet 16 hits the second prism bevel 16B2 of the first prism 16B and is refracted, rising and emerging, or heading towards the first prism bevel 16B1. Here, the inclination angle 04 of the first prism 16B relative to the X-axis direction is greater than the same inclination angle 05 of the second prism 17B. Therefore, compared with the case where the angles are the same or the angles are in an opposite relationship, the light incident on the first prism sheet 16 is less likely to hit the first prism bevel 16B1. If the incident light of the first prism sheet 16 hits the first prism bevel 16B1 of the first prism 16B, it has a tendency not to rise when exiting the first prism 16B and is 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 inclined surface 16B1 of the first prism 16B, the generation of side lobe light is suppressed, and as a result, the light utilization efficiency is improved.

[0053] Most of the light emitted from the first prism sheet 16 and incident on the second prism sheet 17 hits and is refracted by the fourth prism inclined surface 17B2 of the second prism 17B, then rises and exits, or travels toward the third prism inclined surface 17B1. Since the inclination angle θ5 of the second prism 17B with respect to the X-axis is smaller than the same inclination angle θ4 of the first prism 16B, 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 via the third prism inclined surface 17B1 than if the angles were the same or opposite. As a result, the amount of light returning from the second prism sheet 17 to the first prism sheet 16 (hereinafter referred to as "return light") increases. This return light, after reflecting within the backlight unit 12 or other factors, reaches the second prism sheet 17 again, rises and exits via one of the pair of inclined surfaces 17B1 and 17B2 of the second prism 17B, thereby improving light utilization efficiency. The optical path of the returning light before it exits the second prism sheet 17 is complicated, and thus the rising angles given by the second prism 17B are diversified, thereby improving the viewing angle characteristics.

[0054] Next, the detailed structure of the first light guide plate 14 will be described. Figure 2 as well as 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 provided 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 the first light guide plate lenses 21 are arranged along the Y-axis direction. In this embodiment, the first light guide plate lens 21 is a so-called double convex lens. The first light guide plate lens 21 is formed as a convex shape protruding from the first light guide plate light emitting main surface 14B to the front side. Specifically, the cross-sectional shape of the first light guide plate lens 21 cut along the Y-axis direction is semicircular and semi-cylindrical extending in a straight line 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 relative to the Y-axis direction is set as the "contact angle", the contact angle of the first light guide plate lens 21 is, 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 roughly the same. When the first light guide plate lens 21 of such a structure is set integrally with the first light guide plate 14, the first light guide plate 14 is manufactured in advance by injection molding, for example, and the molding surface for molding the main light emitting surface 14B of the first light guide plate in the molding mold is pre-formed with a transfer shape for transferring the first light guide plate lens 21.

[0055] like Figure 3The second light guide plate lens 22 is provided on the first opposite principal surface 14C of the first light guide plate 14. The second light guide plate lens 22 extends along the X-axis direction, and a plurality of the second light guide plate lenses 22 are arranged along the Y-axis direction. In this embodiment, the second light guide plate lens 22 is a convex prism that protrudes from the first opposite principal surface 14C toward the back. Specifically, the cross-sectional shape of the second light guide plate lens 22 cut along the Y-axis direction is roughly triangular (roughly mountain-shaped), and it extends in a straight line along the X-axis direction. The width dimension (dimension in the Y-axis direction) of the second light guide plate lens 22 is constant along the entire length of the X-axis direction. The cross-sectional shape of the second light guide plate lens 22 is roughly an isosceles triangle, and it has a pair of first light guide plate inclined surfaces 22A. The vertex angle of the second light guide plate lens 22 is preferably an obtuse angle (an angle exceeding 90°), specifically preferably in the range of 100° to 150°, and most preferably 140°. The vertex angle, width dimension (arrangement spacing), and height dimension of the plurality of second light guide plate lenses 22 arranged along the Y-axis direction are all roughly the same. In this embodiment, the arrangement intervals of the second light guide plate lenses 22 are larger than the arrangement intervals of the first light guide plate lenses 21. To integrally arrange the second light guide plate lenses 22 configured in this manner with the first light guide plate 14, the first light guide plate 14 can be manufactured in advance by, for example, injection molding, and a transfer shape for transferring the second light guide plate lenses 22 can be preformed on the molding surface of the mold used to mold the first opposite principal surface 14C.

[0056] According to the first light guide plate 14 of such a configuration, Figure 3 As shown, the light propagating in the first light guide plate 14 hits the first arc-shaped surface 21A of each first light guide plate lens 21 on the side of the first light guide plate light emitting main surface 14B in the Z-axis direction and is repeatedly reflected, and moves in a zigzag pattern roughly along the X-axis direction. On the other hand, the light propagating in the first light guide plate 14 hits the first light guide plate inclined surface 22A of each pair of second light guide plate lenses 22 on the side of the first opposite main surface 14C in the Z-axis direction and is repeatedly reflected, and moves in a zigzag pattern roughly 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 difficult to produce uneven brightness between the vicinity of the first LED 13 and its surroundings in the Y-axis direction.

[0057] like Figure 2 As shown, the third light guide plate lens 23 is provided 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 along the Z-axis direction. The third light guide plate lens 23 has: a side (opposite to the side of the first LED 13) arranged in the X-axis direction. Figure 2 The second light guide plate inclined surface 23A is arranged on the right side of the X-axis direction; the first LED13 side ( Figure 2and a fourth light guide plate inclined surface 23C located between the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B. The second light guide plate inclined surface 23A has a first LED 13 side ( Figure 2 to the left side) toward the opposite side ( Figure 2 The third light guide plate inclined surface 23B has a side (opposite to the first LED 13 side) in the X-axis direction of the first light guide plate 14. Figure 2 right side) toward the first LED 13 side ( Figure 2 The fourth light guide plate inclined surface 23C has an inclined surface from the first LED 13 side ( Figure 2 to the left side) to the opposite side ( Figure 2 The right side of the upright tilt.

[0058] like Figure 2 It indicates that the light propagating in the first light guide plate 14 is reflected by the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B, and rises toward the surface side at an angle close to the Z-axis direction, thereby promoting the emission from the first light guide plate main light-emitting surface 14B. In detail, the second light guide plate inclined surface 23A mainly plays the role of reflecting and rising the light traveling away from the first LED 13 in the X-axis direction. On the other hand, the third light guide plate inclined surface 23B mainly plays the role of reflecting and rising the light traveling close to the first LED 13 in the X-axis direction. The second light guide plate inclined surface 23A has a slope that becomes smaller as it moves away from the first LED 13 in the X-axis direction. 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 that increases as the distance from the first light guide plate main light output surface 14B increases in the X-axis direction as the distance from the first LED 13 increases. This slope is, in other words, the opposite slope to the second light guide plate inclined surface 23A. The inclination angle of the third light guide plate inclined surface 23B relative to the X-axis direction is, for example, a steep slope of approximately 80°, close to vertical, and is greater than the inclination angle of the second light guide plate inclined surface 23A.

[0059] 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 their height dimension (dimension in the Z-axis direction) and length dimension (dimension in the X-axis direction). More specifically, when comparing the third light guide plate lenses 23 closer to the first LED 13 in the X-axis direction with the third light guide plate lenses 23 farther from the first LED 13 in the X-axis direction, the areas of the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B of the third light guide plate lenses 23 are larger than those of the third light guide plate lenses 23 farther from the first LED 13 in the X-axis direction. As a result, while light is less likely to strike the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B of the third light guide plate lenses 23 on the side closer to the first LED 13 in the X-axis direction, thus suppressing light emission, light is more likely to strike the second light guide plate inclined surface 23A and the third light guide plate inclined surface 23B of the third light guide plate lenses 23 on the side farther from the first LED 13 in the X-axis direction, thus promoting 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.

[0060] like Figure 2 As shown, the side of the fourth light guide plate inclined surface 23C opposite to the first LED 13 side in the X-axis direction ( Figure 2 The end portion of the right side of the light guide plate is connected to the second light guide plate inclined surface 23A, and the first LED13 side in the X-axis direction ( Figure 2The end portion 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 that increases as it is further away from the first LED 13 in the X-axis direction and away from the first light guide plate main light emitting surface 14B (the portion where the third light guide plate lens 23 is not provided). In other words, the fourth light guide plate inclined surface 23C has 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, 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 side of the first light guide plate main light emitting surface 14B, but the incident angle of the light relative to the first light guide plate main light emitting 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 further away from the first LED 13. As a result, the outgoing light from the main light-emitting surface 14B of the first light guide plate is difficult to deviate 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 multiple fourth light guide plate inclined surfaces 23C arranged along the X-axis direction are designed to have a smaller length dimension as they are further away from the first LED 13 in the X-axis direction. This is because the longer the length dimension of the third light guide plate lens 23 is, the further away from the first LED 13 in the X-axis direction, and the larger the range occupied by the third light guide plate lens 23.

[0061] like Figures 3 to 5 As shown, the third light guide plate lens 23 of the above-described configuration is arranged so as to be sandwiched between two adjacent second light guide plate lenses 22 in the Y-axis direction. Therefore, the third light guide plate lenses 23 are arranged in a manner that alternates and repeats with the second light guide plate lenses 22 in the Y-axis direction. The maximum protrusion dimension (height dimension) of the third light guide plate lens 23 from the first opposite principal surface 14C is smaller than the same protrusion dimension of the second light guide plate lens 22. Therefore, even if the third light guide plate lens 23 is located farthest from the first LED 13 in the X-axis direction, it does not protrude further to the rear than the second light guide plate lens 22.

[0062] However, the vehicle-mounted liquid crystal display device 10 is sometimes installed, for example, in front of the front passenger seat of a passenger car. In this case, it is sometimes required to limit the viewing angle so that the image displayed by the liquid crystal display device 10 can be visually recognized from the front passenger seat and cannot be visually recognized from the driver's seat. In order to respond to such a request, Figure 1As shown, in addition to the above-mentioned structures, the backlight device 12 of this embodiment also has at least a first louver (first piece) 18 arranged on the front side of the second prism sheet 17, a linear Fresnel lens sheet (second piece) 19 arranged on the front side of the first louver 18, and a second louver (third piece) 20 arranged on the front side of the linear Fresnel lens sheet 19.

[0063] Appropriate use Figure 1 、 Figure 2 and Figure 6 The configurations of the first louver 18 , the linear Fresnel lens sheet 19 , and the second louver 20 will be described. Figure 6 FIG is an enlarged cross-sectional view of the first louver 18, the linear Fresnel lens sheet 19, and the second louver 20 among the components of the backlight device 12. Figure 1 As shown, the main surfaces of the first louver 18, linear Fresnel lens sheet 19, and second louver 20 are parallel to the main surfaces of the liquid crystal panel 11 and the first light guide plate 14, and are all sheet-shaped. Furthermore, the main surfaces of the first louver 18, linear Fresnel lens sheet 19, and second louver 20 are parallel to the X-axis and Y-axis directions, and the normal direction (thickness direction) of the main surfaces is aligned with the Z-axis direction. The first louver 18 and second louver 20 function to limit the emission angle range of light in the X-axis direction. The linear Fresnel lens sheet 19 functions to selectively focus light in the X-axis direction.

[0064] like Figure 1 As shown, the first louver 18 has a first light-entering principal surface 18A on the inner side and a first light-emitting principal surface 18B on the outer side. The first light-entering principal surface 18A is opposite to the principal surface on the light-emitting side of the second prism sheet 17. The first light-emitting principal surface 18B is opposite to the second light-entering principal surface 19A of the linear Fresnel lens sheet 19 described later. Figure 2As shown, the first louver 18 includes a first light-blocking portion 18C that blocks light and a first light-transmitting portion 18D that allows light to pass. The first light-blocking portion 18C is made of, for example, a black, light-blocking resin material (light-blocking material). The first light-blocking portion 18C is in the form of a layer extending along the Y-axis and Z-axis directions, and a plurality of the first light-transmitting portions 18D are arranged at intervals in the X-axis direction. The first light-transmitting portions 18D are made of a substantially transparent, light-transmitting resin material (light-transmitting material). The first light-transmitting portions 18D are in the form of a layer extending along the Y-axis and Z-axis directions, and a plurality of the first light-transmitting portions 18D are arranged at intervals in the X-axis direction. The plurality of first light-blocking portions 18C and the plurality of first light-transmitting portions 18D are arranged alternately and repeatedly in the X-axis direction. Therefore, a first light-transmitting portion 18D is located between two first light-blocking portions 18C that are adjacent to each other at intervals in the X-axis direction, and a first light-blocking portion 18C is located 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 main surface 18A of the first louver 18 passes through the first light-transmitting portion 18D arranged between the two first light-shielding portions 18C adjacent to each other in the X-axis direction, and is emitted from the first light-emitting main surface 18B. The emission angle in the X-axis direction of the emitted light from the first light-emitting main surface 18B is limited by the two first light-shielding portions 18C adjacent to each other in the X-axis direction. In addition, the emission angle in the Y-axis direction of the emitted light from the first light-emitting main surface 18B is not limited by the first louver 18. The emission angle range in the X-axis direction of the emitted light from the first light-emitting main surface 18B is defined by two straight lines connecting the respective ends in the Z-axis direction of the two first light-shielding portions 18C sandwiching the first light-transmitting portion 18D obliquely relative to each other. The emission angle range in the X-axis direction of the transmitted light of the first light-transmitting portion 18D varies according to the ratio of the width W1 to the height H1 of the first light-transmitting portion 18D (refer to Figure 6 The first louver 18 also includes a pair of sheet carriers that sandwich and support the plurality of first light-blocking portions 18C and the plurality of first light-transmitting portions 18D from the front and back sides. The sheet carriers are made of a substantially transparent, light-transmitting resin material. The sheet carriers extend over the entire area of the first louver 18 and hold the plurality of first light-blocking portions 18C and the plurality of first light-transmitting portions 18D.

[0065] like Figure 1As shown, the linear Fresnel lens sheet 19 has a second light-entering principal surface 19A on the back side and a second light-emitting principal surface 19B on the front side. The second light-entering principal surface 19A is opposite to the first light-emitting principal surface 18B of the first louver 18. The second light-emitting principal surface 19B is opposite to the third light-entering principal surface 20A of the second louver 20 described later. The linear Fresnel lens sheet 19 has a flat substrate 19D and a first lens 19C arranged on the principal surface (second light-emitting principal surface 19B) on the front side of the substrate 19D. The linear Fresnel lens sheet 19 is made of a substantially transparent synthetic resin. Specifically, the entire linear Fresnel lens sheet 19 is made of an acrylic resin material such as PMMA. In addition, the substrate 19D of the linear Fresnel lens sheet 19 can also be made of PET, and the first lens 19C can be made of an ultraviolet-curable resin material. In this case, similar to the manufacturing method of the first prism sheet 16, etc., uncured ultraviolet curing resin material is filled into a molding mold, and by placing the substrate 19D at the open end of the mold, the uncured ultraviolet curing resin material is arranged in a form in contact with the main surface of the front side. In this state, the ultraviolet curing resin material is irradiated with ultraviolet rays through the substrate 19D, and the first lens 19C can be set integrally on the substrate 19D.

[0066] like Figure 1 As shown, the first lens 19C protrudes from the substrate 19D toward the front side along the Z-axis direction. The cross-section of the first lens 19C cut along the X-axis direction is a triangle, and extends in a straight line along the Y-axis direction. The width dimension (dimension in the X-axis direction) of the first lens 19C is constant over the entire length in the Y-axis direction. A plurality of first lenses 19C are arranged along the X-axis direction in the substrate 19D. The height of the plurality of first lenses 19C varies depending on the position of the substrate 19D in the X-axis direction. Specifically, the lens located at the end side of the substrate 19D in the X-axis direction (the end side lens 19CE described later) among the plurality of first lenses 19C protrudes from the substrate 19D to a greater height than the lens located at the center side (the center side lens 19CC described later). The closer the plurality of first lenses 19C are from the center position of the substrate 19D in the X-axis direction to the two end positions, the more gradually the protrusion height from the substrate 19D increases. The plurality of first lenses 19C are symmetrical with the center position of the substrate 19D in the X-axis direction as the center. In this manner, the plurality of first lenses 19C are so-called “linear Fresnel lenses”.

[0067] like Figure 1 and Figure 2As shown, the first lens 19C has a pair of inclined surfaces 19C1 and 19C2. Among the pair of inclined surfaces 19C1 and 19C2 of the first lens 19C, the inclined surface on the end side of the linear Fresnel lens sheet 19 in the X-axis direction is the first inclined surface 19C1, and the inclined surface on the center side is the second inclined surface 19C2. The first inclined surface 19C1 has an inclination rising from the end side of the linear Fresnel lens sheet 19 in the X-axis direction toward the center side. The second inclined surface 19C2 has an inclination rising from the center side of the linear Fresnel lens sheet 19 in the X-axis direction toward the end side. It is located closer to the first LED 13 side than the center position of the linear Fresnel lens sheet 19 in the X-axis direction ( Figure 1 The first lens 19C on the left side of the lens 19C has a first inclined surface 19C1 located relative to the top. Figure 1 On the left side, the second inclined surface 19C2 is located Figure 1 Located on the right side of the first LED 13 and closer to the center of the linear Fresnel lens sheet 19 in the X-axis direction ( Figure 1 The first lens 19C on the right side of the lens 19C has a first inclined surface 19C1 located relative to the top. Figure 1 On the right side, the second inclined surface 19C2 is located Figure 1 In addition, Figure 2 3 , the first lens 19C is shown, which is located closer to the first LED 13 than the center position of the linear Fresnel lens sheet 19 in the X-axis direction.

[0068] like Figure 2 As shown, light incident on the first lens 19C, upon refracting upon striking the first inclined surface 19C1, travels toward the center of the linear Fresnel lens sheet 19 in the X-axis direction. In other words, the first inclined surface 19C1 imparts an anisotropic refractive effect, selectively focusing light in the X-axis direction. Because the first lens 19C includes the second inclined surface 19C2 in addition to the first inclined surface 19C1, manufacturing the linear Fresnel lens sheet 19 facilitates processing of multiple first lenses 19C compared to assuming that the second inclined surface 19C2 is perpendicular to the X-axis direction. Conversely, light incident on the first lens 19C, upon refracting upon striking the second inclined surface 19C2, travels toward the edge of the linear Fresnel lens sheet 19 in the X-axis direction, tending to be emitted as sidelobe light (stray light). In contrast, the inclination angle θ1 of the first inclined surface 19C1 of the first lens 19C relative to the X-axis (angle, first base angle) is smaller than the inclination angle θ2 of the second inclined surface 19C2 relative to the X-axis (angle, second base angle). Therefore, most of the light incident on the first lens 19C strikes the first inclined surface 19C1 and is focused, while very little strikes the second inclined surface 19C2. Thus, the cross-sectional shape of the first lens 19C is asymmetrical, forming an isosceles triangle.

[0069] like Figure 2As shown, the second venetian blind 20 has a third light-entering principal surface 20A on the back side and a third light-emitting principal surface 20B on the front side. The third light-entering principal surface 20A is opposite to the second light-emitting principal surface 19B of the linear Fresnel lens sheet 19. The second venetian blind 20 has a second light-blocking portion 20C that blocks light and a second light-transmitting portion 20D that allows light to pass. The second light-blocking portion 20C is, for example, made of a light-blocking resin material (light-blocking material) that is black and blocks light. The second light-blocking portion 20C is in the form of a layer extending along the Y-axis direction and the Z-axis direction, and a plurality of the second light-transmitting portions 20D are arranged at intervals in the X-axis direction. The second light-transmitting portions 20D are in the form of a layer extending along the Y-axis direction and the Z-axis direction, and a plurality of the second light-transmitting portions 20D are arranged at intervals in the X-axis direction. The plurality of second light-blocking portions 20C and the plurality of second light-transmitting portions 20D are arranged alternately and repeatedly in the X-axis direction. Therefore, the second light-transmitting portion 20D is located between two second light-shielding portions 20C that are adjacent to each other and spaced apart in the X-axis direction, and the second light-shielding portion 20C is located between two second light-transmitting portions 20D that are adjacent to each other and spaced apart in the X-axis direction. Light incident on the third light-entering principal surface 20A of the second louver 20 passes through the second light-transmitting portion 20D disposed between the two second light-shielding portions 20C that are adjacent to each other in the X-axis direction, and is emitted from the third light-emitting principal surface 20B. The emission angle in the X-axis direction of the light emitted from the third light-emitting principal surface 20B is limited by the two second light-shielding portions 20C that are adjacent to each other in the X-axis direction. In addition, the emission angle in the Y-axis direction of the light emitted from the third light-emitting principal surface 20B is not limited by the second louver 20. The emission angle range in the X-axis direction of the light emitted from the third light-emitting principal surface 20B is defined by two straight lines that connect the respective ends of the two second light-shielding portions 20C that sandwich the second light-transmitting portion 20D in the Z-axis direction in a diagonally opposite manner. The X-axis angular range of light emitted by the second light-transmitting portions 20D varies depending on the ratio of the width W2 to the height H2 of the second light-transmitting portions 20D. Furthermore, the second Venetian blind 20 includes a pair of sheet carriers that sandwich and support the plurality of second light-blocking portions 20C and the plurality of second light-transmitting portions 20D from the front and back sides. The sheet carriers are made of a substantially transparent, light-transmitting resin material. The sheet carriers extend across the entire area of the second Venetian blind 20 and collectively support the plurality of second light-blocking portions 20C and the plurality of second light-transmitting portions 20D.

[0070] like Figure 6As shown, the ratio of the width W1 of the first light-transmitting portion 18D of the first louver 18 divided by the height H1 is smaller than the ratio of the width W2 of the second light-transmitting portion 20D divided by the height H2. According to this structure, the maximum absolute value of the angle formed by the light passing through the first light-transmitting portion 18D relative to the Z-axis direction (the normal direction of the first light-emitting principal surface 18B) is smaller than the maximum absolute value of the angle formed by the light passing through the second light-transmitting portion 20D relative to the Z-axis direction (the normal direction of the third light-emitting principal surface 20B). As a result, the light emitted from the first light-emitting principal surface 18B and incident on the second light-entering principal surface 19A of the linear Fresnel lens sheet 19 includes a large amount of light close to the Z-axis direction. Therefore, the light refracted by the first inclined surface 19C1 of the first lens 19C of the linear Fresnel lens sheet 19 is effectively given directivity toward the center side of the X-axis direction. Furthermore, light incident on first light incident principal surface 18A of first louver 18 passes through second prism sheet 17, reducing side lobe light and including regressive light, thereby improving utilization efficiency. Consequently, a sufficient amount of light is transmitted through first light-transmitting portion 18D, while the amount of light blocked by first light-blocking portion 18C is reduced. This is advantageous for achieving, for example, improved brightness of light emitted from backlight device 12.

[0071] On the other hand, Figure 6As shown, the ratio of the width W2 of the second light-transmitting portion 20D of the second louver 20 divided by the height H2 is greater than the ratio of the width W1 of the first light-transmitting portion 18D divided by the height H1. According to this structure, the maximum absolute value of the angle formed by the light passing through the second light-transmitting portion 20D relative to the Z-axis direction (the normal direction of the third light-emitting main surface 20B) is greater than the maximum absolute value of the angle formed by the light passing through the first light-transmitting portion 18D relative to the Z-axis direction (the normal direction of the first light-emitting main surface 18B). Thus, the situation in which the light imparted with anisotropic refractive effect by the linear Fresnel lens sheet 19 is excessively restricted in its exit angle by the second louver 20 is avoided. Thus, the exit light from the third light-emitting main surface 20B fully reflects the anisotropic refractive effect imparted by the linear Fresnel lens sheet 19. Therefore, the brightness of the exit light is uniformized in the central side portion and the two end side portions in the X-axis direction of the third light-emitting main surface 20B. In this way, the brightness distribution of the exit light of the backlight device 12 is uniformized. The outgoing light of the backlight device 12 of this embodiment is uniformly distributed in brightness, based on the fact that the outgoing angle range is limited by the second louver 20. Therefore, when the liquid crystal display device 10 of this embodiment is set to be located in front of the front passenger seat of a passenger car, the display image of the liquid crystal display device 10 cannot be visually recognized from the driver's seat, and the display image of uniform brightness can be visually recognized from the front passenger seat regardless of the position of the screen of the liquid crystal display device 10 in the X-axis direction. In addition, the outgoing angle of the outgoing light from the third light-emitting main surface 20B is limited by the two second shading portions 20C. Therefore, even if side lobe light is generated by the second inclined surface 19C2 of the first lens 19C, it is blocked by the second shading portion 20C of the second louver 20, making it difficult to be emitted from the third light-emitting main surface 20B. As a result, the side lobe light that may be generated in the outgoing light of the backlight device 12 can be sufficiently reduced.

[0072] Specifically, if Figure 6 As shown, the ratio of the width W1 of the first light-transmitting portion 18D divided by its height H1 is equal to tan10°. Consequently, the maximum absolute value of the angle formed by light passing through the first light-transmitting portion 18D with respect to the Z-axis direction is 10°. Compared to a case where the ratio of the width to the height of the first light-transmitting portion 18D is greater than tan10°, the light supplied to the linear Fresnel lens sheet 19 contains a greater amount of light incident at a preferred angle of incidence on the first inclined surface 19C1 of the first lens 19C. Consequently, the first inclined surface 19C1 of the first lens 19C effectively imparts directivity toward the center of the X-axis direction to the light emitted from the linear Fresnel lens sheet 19. Furthermore, compared to a case where the ratio of the width to the height of the first light-transmitting portion 18D is less than tan10°, the amount of light blocked by the first light-blocking portion 18C is reduced, improving light utilization efficiency.

[0073] like Figure 6As shown, the ratio of the width W2 of the second light-transmitting portion 20D of the second louver 20 divided by the height H2 is equal to "tan 45°." Thus, the absolute value of the maximum angle formed by the light passing through the second light-transmitting portion 20D relative to the Z-axis direction is 45°. Compared to a case where the ratio of the width of the second light-transmitting portion 20D divided by the height is greater than "tan 45°," sidelobe light can be reduced. Furthermore, compared to a case where the ratio of the width of the second light-transmitting portion 20D divided by the height is less than "tan 45°," the light imparted with anisotropic refraction by the linear Fresnel lens sheet 19 is less likely to have its exit angle excessively restricted by the second louver 20. This allows for a more uniform brightness distribution of the light exiting the second louver 20.

[0074] The detailed structure of the linear Fresnel lens sheet 19 will be described. Figure 6 As shown, the plurality of first lenses 19C arranged along the X-axis are configured such that the inclination angle θ1 of the first inclined surface 19C1 relative to the X-axis direction varies depending on the position in the X-axis direction. Specifically, the plurality of first lenses 19C include a central lens 19CC and an end lens 19CE located closer to the end of the central lens 19CC in the X-axis direction in the linear Fresnel lens sheet 19. When any first lens 19C arranged at a position other than the two ends in the X-axis direction among the plurality of first lenses 19C is referred to as a "central lens 19CC," the first lens 19C located closer to the end of the central lens 19CC in the X-axis direction is referred to as an "end lens 19CE." Furthermore, the angle θ1E formed by the first inclined surface 19C1 of the end lens 19CE relative to the X-axis direction is greater than the angle θ1C formed by the first inclined surface 19C1 of the central lens 19CC relative to the X-axis direction. With this structure, the anisotropic refractive effect imparted to light by the first inclined surface 19C1 of the end lens 19CE is stronger than the anisotropic refractive effect imparted by the first inclined surface 19C1 of the center lens 19CC. That is, light emitted from the end portion of the second light-emitting principal surface 19B of the linear Fresnel lens sheet 19 in the X-axis direction has a stronger directivity toward the center of the X-axis direction than light emitted from the center portion in the X-axis direction. In the second louver 20, which receives light emitted from the second light-emitting principal surface 19B, excessive restriction of the emission angle of the emitted light is avoided. Consequently, the brightness of the emitted light in the center and both end portions of the third light-emitting principal surface 20B of the second louver 20 in the X-axis direction is more uniform.

[0075] like Figure 6As shown, the vertex angles (first vertex angles) θ3 of the plurality of first lenses 19C arranged along the X-axis direction are the same. That is, the vertex angle θ3C of the central side lens 19CC is equal to the vertex angle θ3E of the end side lens 19CE. According to such a structure, when the linear Fresnel lens sheet 19 is manufactured by resin molding, the processing of the mold used for molding becomes easy. In addition, the plurality of first lenses 19C are configured so that the inclination angle θ2 of the second inclined surface 19C2 relative to the X-axis direction changes according to the position in the X-axis direction. The angle θ2E formed by the second inclined surface 19C2 of the end side lens 19CE relative to the X-axis direction is smaller than the angle θ2C formed by the second inclined surface 19C2 of the central side lens 19CC relative to the X-axis direction. According to this structure, the side lobe light generated by the second inclined surface 19C2 of the end side lens 19CE tends to be more than the side lobe light generated by the second inclined surface 19C2 of the central side lens 19CC. In contrast, the emission angle of the light emitted from the third light-emitting main surface 20B is limited by the two second light-shielding portions 20C of the second louver 20 , thereby sufficiently reducing side lobe light caused by the second inclined surface 19C2 of the end-side lens 19CE.

[0076] like Figure 6 As shown in , the vertex angle θ3 of the plurality of first lenses 19C is constant at 110°. In the plurality of first lenses 19C, the inclination angle θ1 of the first inclined surface 19C1 relative to the X-axis direction ranges from 0° to 24°, and the inclination angle θ2 of the second inclined surface 19C2 relative to the X-axis direction ranges from 46° to 70°. Specifically, among the plurality of first lenses 19C, in the first lens 19C located at the center of the linear Fresnel lens sheet 19 in the X-axis direction (center side lens 19CC), the inclination angle θ1 (θ1C) of the first inclined surface 19C1 relative to the X-axis direction is approximately 0°, the inclination angle θ2 (θ2C) of the second inclined surface 19C2 relative to the X-axis direction is approximately 70°, and the vertex angle θ3 (θ3C) is 110°. In contrast, among the multiple first lenses 19C, in the first lenses 19C located at both ends of the linear Fresnel lens sheet 19 in the X-axis direction (end side lenses 19CE), the inclination angle θ1 (θ1E) of the first inclined surface 19C1 relative to the X-axis direction is approximately 24°, the inclination angle θ2 (θ2E) of the second inclined surface 19C2 relative to the X-axis direction is approximately 46°, and the vertex angle θ3 (θ3E) is 110°.

[0077] The relationship between the position of the linear Fresnel lens sheet 19 in the X-axis direction and the tilt angle θ1 and the tilt angle θ2 of the first lens 19C is as follows: Figure 7 shown. Figure 7 The graph has the horizontal axis representing the position of the linear Fresnel lens sheet 19 in the X-axis direction (unit: mm), and the vertical axis representing the tilt angle θ1 and the tilt angle θ2 (unit: degrees). Figure 7The reference position (0 mm) of the horizontal axis is the center position in the X-axis direction. Figure 7 The solid line is a graph of the tilt angle θ1, and the dotted line is a graph of the tilt angle θ2. Figure 7 In FIG. 1 , a linear Fresnel lens sheet 19 having a length of 300 mm in the X-axis direction is illustrated. Figure 7 In the plurality of first lenses 19C, the inclination angle θ1 of the first inclined surface 19C1 with respect to the X-axis direction changes so as to continuously and gradually decrease as it moves from the center position in the X-axis direction toward the end positions. In the plurality of first lenses 19C, the inclination angle θ2 of the second inclined surface 19C2 with respect to the X-axis direction changes so as to continuously and gradually increase as it moves from the center position in the X-axis direction toward the end positions.

[0078] If the angle θ1 formed by the first inclined surface 19C1 with the X-axis direction is greater than 24°, and the angle θ2 formed by the second inclined surface 19C2 with the X-axis direction is less than 46°, there is a possibility that the second light-blocking portion 20C of the second louver 20 will have excessive side lobe light that is difficult to block. Furthermore, if the angle θ1 formed by the first inclined surface 19C1 with the X-axis direction is less than 0°, and the angle θ2 formed by the second inclined surface 19C2 with the X-axis direction is greater than 70°, there is a possibility that the second light-blocking portion 20C of the second louver 20 will have excessive side lobe light that is difficult to block. Regarding this point, as described above, if the angle θ1 formed by the first inclined surface 19C1 with the X-axis direction is within the range of 0° to 24°, and the angle θ2 formed by the second inclined surface 19C2 with the X-axis direction is within the range of 46° to 70°, side lobe light that is difficult to block by the second light-blocking portion 20C of the second louver 20 can be sufficiently suppressed.

[0079] To verify the superiority of the backlight device 12 and the liquid crystal display device 10 of this embodiment, the following Comparative Experiment 1 was conducted. In this Comparative Experiment 1, the backlight device 12 having the configuration described in the preceding section was used as Example 1, and a backlight device having the linear Fresnel lens sheet 19 and the second louver 20 removed from Example 1 was used as Comparative Example 1. In Comparative Experiment 1, the luminance of light emitted from each of the backlight devices of Comparative Example 1 and Example 1 was measured with the first LED 13 illuminated. The relative luminance percentage (in "%) was calculated, and a graph representing the luminance distribution in terms of shading was created. A graph of the light distribution in the X-axis direction (luminance angular distribution) was also created. In this Comparative Experiment 1, the luminance of light emitted from three different locations in the backlight device in the X-axis direction (the center, the right end, and the left end) was measured, and three graphs were created for each of Comparative Example 1 and Example 1. Furthermore, in Comparative Experiment 1, the percentage (unit: "%) of the ratio of the minimum brightness divided by the maximum brightness in the calculated relative brightness was calculated. The larger the percentage value of the calculated ratio, the more uniform the brightness distribution, and the smaller the percentage value, the less uniform the brightness distribution.

[0080] Comparison of the experimental results of Experiment 1 Figure 8 As shown in the table. Figure 8 In the figure, from the top, there are shown a graph of the light distribution in the X-axis direction in Comparative Example 1 and Example 1, a graph of the brightness distribution in Comparative Example 1 and Example 1, and a percentage of the ratio of the minimum brightness to the maximum brightness in Comparative Example 1 and Example 1. Figure 8 In the light distribution diagram shown, 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 relative brightness (unit: "%). The relative brightness on the vertical axis is a percentage value with the maximum brightness as the reference (100%). Among the positive and negative signs marked on the angle of the horizontal axis, "- (negative)" indicates the left side of the X-axis direction relative to the reference, i.e., 0° (front direction), when observing the backlight device from the front, and "+ (positive)" indicates the right side of the X-axis direction relative to the reference, i.e., 0° (front direction), when observing the backlight device from the front. In addition, Figure 8 The diagram of the light distribution shown in FIG. 1 shows an example. In this example, when observing the backlight device from the front, the light distribution of the light emitted from the center portion in the X-axis direction is represented as "C", the light distribution of the light emitted from the right end portion in the X-axis direction is represented as "R", and the light distribution of the light emitted from the left end portion in the X-axis direction is represented as "L". Figure 8 In the diagram of brightness distribution shown in , the brightness is represented by shades. Figure 8The brightness distribution diagram shown shows the position in the X-axis direction (unit: "mm") and the position in the Y-axis direction (unit: "mm"). The reference position (0mm) of the X-axis direction is the center position of the X-axis direction. In addition, the positive and negative signs shown in the X-axis direction have the same meaning as the signs marked on the horizontal axis of the graph. Figure 8 In addition to the diagram of brightness distribution, a diagram of brightness shades is also shown. Figure 8 The relative brightness values (100% and 0%) corresponding to the examples are shown in FIG.

[0081] The experimental results of comparative experiment 1 are described below. Figure 8 In the light distribution diagram, Comparative Example 1 shows that the three light distributions (L, C, and R) overlap, with their respective peak brightness at 0°, near the front direction. This means that when the backlight device of Comparative Example 1 is viewed from the front, the center of the X-axis reaches peak brightness, but the right and left ends of the X-axis have brightness lower than the peak brightness. In fact, when the backlight device is viewed from the front, the center of the X-axis is at an angle of approximately 0°, while the right and left ends of the X-axis are at angles of approximately ±10°. Therefore, in Comparative Example 1, the relative brightness at the right and left ends of the X-axis is approximately 30% to 40%. The brightness distribution of Comparative Example 1 reflects this light distribution. Although the relative brightness is high, close to 100%, near the center of the X-axis (0mm), it is low, around 30% to 40% near the two end positions of the X-axis (150mm). In addition, the ratio of the minimum brightness divided by the maximum brightness of Comparative Example 1 is as low as 14%.

[0082] In contrast, in Example 1, the light distribution of L is offset toward the "+" angle, and the light distribution of R is offset toward the "-" angle, relative to the light distribution of C. The peak brightness of the light distribution of C is near 0°. The peak brightness of the light distribution of L is near +10°. The peak brightness of the light distribution of R is near -15°. This means that when the backlight device of Example 1 is viewed from the front, the brightness at the center, right end, and left end in the X-axis direction is close to the peak brightness. In other words, it can be said that the light emitted from the right and left ends of the backlight device in the X-axis direction is angled so as to travel toward the center in the X-axis direction. Furthermore, at angles with an absolute value of 45° or greater, the relative brightness is sufficiently suppressed. This light distribution is reflected in the brightness distribution of Example 1, with a high relative brightness of nearly 100% near the center position in the X-axis direction (0 mm) and a high relative brightness of approximately 70% to 80% near the two ends in the X-axis direction (150 mm). Furthermore, the ratio of the minimum brightness divided by the maximum brightness in Example 1 was 75%, significantly higher than that in Comparative Example 1. These experimental results indicate that the linear Fresnel lens sheet 19 included in the backlight device 12 of Example 1 achieves uniform brightness distribution, while the second louver 20 suppresses the generation of side lobe light having an absolute value of 45° or greater.

[0083] Next, in order to obtain knowledge about how the light distribution changes when the inclination angle θ2 of the second inclined surface 19C2 of the first lens 19C of the linear Fresnel lens sheet 19 relative to the X-axis direction changes, an empirical experiment 1 was conducted. In this empirical experiment 1, a backlight device 12 having the same structure as that described previously in this paragraph was used, except for the structure of the first lens 19C. In the empirical experiment 1, the inclination angle θ1 of the first inclined surface 19C1 of the first lens 19C relative to the X-axis direction was fixed to 15°, and the inclination angle θ2 of the second inclined surface 19C2 relative to the X-axis direction was changed in the range of 40° to 80°. The reason for fixing the inclination angle θ1 to 15° is to set the peak brightness of the emitted light to about +10° and reproduce the light distribution of L among the three light distributions of Example 1 of the above-mentioned comparative experiment 1 (refer to Figure 8In other words, the tilt angle θ2 shown in Experiment 1 is the tilt angle θ2 of the second inclined surface 19C2 of the first lens 19C located near the left end of the linear Fresnel lens sheet 19, among the plurality of first lenses 19C arranged along the X-axis direction. Specifically, in Experiment 1, the tilt angle θ2 is 40°, 44°, 45°, 46°, 47°, 48°, 49°, 50°, 53°, 55°, 56°, 57°, 58°, 59°, 60°, 61°, 63°, 64°, 65°, 66°, 67°, 68°, 69°, 70°, 71°, 72°, 75°, 78°, and 80°. In the backlight device 12 with the tilt angle θ2 varied in this manner, the brightness of the emitted light with the first LED 13 illuminated was measured, and a graph of the light distribution along the X-axis (brightness angle distribution) was created. Based on this, the ratio of light within the angle range of -20° to -45° in the X-axis light distribution at all the aforementioned tilt angles θ2 was calculated. This calculation was performed by dividing the peak brightness within the angle range of -20° to -45° by the overall peak brightness (relative brightness "1").

[0084] The experimental results of light distribution in experimental 1 are as follows: Figure 9 and Figure 10 shown. Figure 9 The experimental results are shown when the tilt angle θ2 is between 40° and 59°. Figure 10 The experimental results are shown when the tilt angle θ2 is between 60° and 80°. Figure 9 and Figure 10 The horizontal axis of the light distribution diagram shown is the angle of the X-axis relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the relative brightness (unitless). The relative brightness of the vertical axis is the relative value with the maximum brightness as the reference (1). The positive and negative signs marked on the horizontal axis angle are the same as the Figure 8 The symbols marked on the horizontal axis of the graph have the same meaning. Figure 9 and Figure 10 The numerical values of the tilt angle θ2 corresponding to each graph are recorded in . The experimental results related to the ratio of light in the angle range of -20° to -45° in the experimental experiment 1 are as follows Figure 11 shown. Figure 11 In the graph of the ratio of light in the angle range of -20° to -45°, the horizontal axis is the tilt angle θ2 (unit is "°"), and the vertical axis is the percentage of the ratio of light in the angle range of -20° to -45° (unit is "%). Figures 9 to 11 The diagram shown shows Figure 12 . Figure 12 This is a diagram for explaining the angle of the liquid crystal display device 10 installed in front of the passenger seat of a passenger car with respect to the front direction X-axis direction. Figure 12 The figure shows the angle (+10°) at which the outgoing light of the backlight device 12 from the empirical experiment 1 reaches peak brightness, the shading range (+45° to +90°, -45° to -90°) blocked by the second blind 20, and the visual recognition range (-20° to -50°) when visually recognizing the liquid crystal display device 10 from the driver's seat located on the left side relative to the passenger seat.

[0085] The experimental results of empirical experiment 1 are explained. Figure 9 In the range of 40° to 50°, the larger the value of the tilt angle θ2, the larger the absolute value of the angle generated by the side lobe light. Specifically, when the tilt angle θ2 is 40°, the peak brightness of the side lobe light is around -35°, while when the tilt angle θ2 is 50°, the peak brightness of the side lobe light is around -75°. In the range of 50° to 59°, the larger the value of the tilt angle θ2, the smaller the absolute value of the angle generated by the side lobe light. Specifically, when the tilt angle θ2 is 53°, the peak brightness of the side lobe light is around -65°, while when the tilt angle θ2 is 59°, the peak brightness of the side lobe light is around -50°.

[0086] according to Figure 10 , within the range of 60° to 66°, the larger the value of the tilt angle θ2, the larger the absolute value of the angle generated by the side lobe light tends to become. Specifically, when the tilt angle θ2 is 60°, the peak brightness of the side lobe light is around -55°, while when the tilt angle θ2 is 65°, the peak brightness of the side lobe light is around -80°. Within the range of 66° to 80°, the larger the value of the tilt angle θ2, the smaller the absolute value of the angle generated by the side lobe light tends to become. Specifically, when the tilt angle θ2 is 66°, the peak brightness of the side lobe light is around -80°, while when the tilt angle θ2 is 80°, the peak brightness of the side lobe light is around -25°.

[0087] according to Figure 11 It can be seen that when the tilt angle θ2 is less than 45° and greater than 71°, the ratio of light in the angle range of -20° to -45° increases sharply. In contrast, when the tilt angle θ2 is in the range of 46° to 70°, the ratio of light in the angle range of -20° to -45° can be kept below 4%. Figure 12The shading range of the second venetian blind 20 is the angle range of +45° to +90° and the angle range of -45° to -90°, and the side lobe light existing in these angle ranges cannot be visually recognized from the driver's seat. Therefore, the light in the angle range of -20° to -45° becomes the side lobe light that can be visually recognized from the driver's seat located to the left of the front passenger seat. Therefore, if the ratio of the light in the angle range of -20° to -45° can be made low, specifically, below 4%, the display image of the liquid crystal display device 10 can be almost impossible to visually recognize from the driver's seat. According to Figure 11 According to the experimental results, if the tilt angle θ2 is set to the range of 46° to 70°, the ratio of light in the angle range of -20° to -45° is reduced to less than 4%, which can effectively prevent the visual recognition of the displayed image from the driver's seat. Here, because the vertex angle θ3 of the first lens 19C is fixed at 110°, if the tilt angle θ1 of the first inclined surface 19C1 relative to the X-axis direction is in the range of 0° to 24°, it can be said that the ratio of light in the angle range of -20° to -45° can be set to less than 4%. In addition, it can be inferred that when the tilt angle θ2 is lower than 40°, most of the light incident on the first lens 19C is refracted by the second inclined surface 19C2 and becomes sidelobe light. Therefore, the sidelobe light becomes excessive, and the light in the angle range of -20° to -45° also increases significantly.

[0088] As described above, the backlight device (illumination device) 12 of this embodiment comprises: a first louver (first sheet) 18, which has a main surface along one side of the first direction, namely, a first light-entering main surface 18A, a main surface along the other side of the first direction, namely, a first light-emitting main surface 18B, two first light-shielding portions 18C arranged at intervals in the first direction, and a first light-transmitting portion 18D arranged between the two first light-shielding portions 18C; a linear Fresnel lens sheet (second sheet) 19, which has a main surface on the side opposite to the first light-emitting main surface 18B along the first direction, namely, a second light-entering main surface 19A, a main surface along the other side of the first direction, namely, a second light-emitting main surface 19B, and a first light-transmitting portion 18D arranged on the second light-entering main surface 19A or the second light-emitting main surface 19B of the first lens 19C; and a second louver (third piece) 20, which has a main surface on the side opposite to the second light-emitting main surface 19B along the first direction, namely the third light-incident main surface 20A, a main surface on the other side along the first direction, namely the third light-emitting main surface 20B, two second light-shielding portions 20C arranged at intervals in the first direction, and a second light-shielding portion 20D arranged between the two second light-shielding portions 20C, the first lens 19C has an inclined first inclined surface 19C1 rising from the end side in the first direction toward the center side of the linear Fresnel lens piece 19, and the ratio of the width W2 of the second light-transmitting portion 20D of the second louver 20 divided by the height H2 is greater than the ratio of the width W1 of the first light-transmitting portion 18D divided by the height H1.

[0089] Light incident on the first light-entering principal surface 18A of the first louver 18 passes through the first light-transmitting portion 18D disposed between the two first light-shielding portions 18C and is emitted from the first light-emitting principal surface 18B. The emission angle of the light emitted from the first light-emitting principal surface 18B is limited by the two first light-shielding portions 18C. When the light emitted from the first light-emitting principal surface 18B is incident on the second light-entering principal surface 19A of the linear Fresnel lens sheet 19, it is refracted by the first inclined surface 19C1 of the first lens 19C and is emitted from the second light-emitting principal surface 19B. The first inclined surface 19C1 has an inclination that rises from the end side in the first direction toward the center side of the linear Fresnel lens sheet 19, thereby imparting an anisotropic refractive effect directed toward the center side in the first direction to the light emitted from the second light-emitting principal surface 19B. When light emitted from the second light-emitting principal surface 19B enters the third light-incident principal surface 20A of the second louver 20, it passes through the second light-transmitting portion 20D disposed between the two second light-shielding portions 20C and is emitted from the third light-emitting principal surface 20B. The emission angle of the light emitted from the third light-emitting principal surface 20B is limited by the two second light-shielding portions 20C.

[0090] Here, the ratio of the width W1 of the first light-transmitting portion 18D divided by the height H1 is smaller than the ratio of the width W2 of the second light-transmitting portion 20D divided by the height H2. Due to this configuration, the maximum absolute value of the angle formed by light passing through the first light-transmitting portion 18D with respect to the normal to the first light-emitting principal surface 18B is smaller than the maximum absolute value of the angle formed by light passing through the second light-transmitting portion 20D with respect to the normal to the third light-emitting principal surface 20B. Consequently, the light emitted from the first light-emitting principal surface 18B and incident on the second light-entering principal surface 19A of the linear Fresnel lens sheet 19 includes a significant amount of light oriented near the normal to the first light-emitting principal surface 18B. Consequently, light refracted by the first inclined surface 19C1 of the first lens 19C of the linear Fresnel lens sheet 19 is efficiently imparted with directivity toward the center in the first direction.

[0091] On the other hand, the ratio of the width W2 of the second light-transmitting portion 20D of the second louver 20 divided by the height H2 is greater than the ratio of the width W1 of the first light-transmitting portion 18D divided by the height H1. According to this configuration, the maximum absolute value of the angle formed by the light passing through the second light-transmitting portion 20D relative to the normal direction of the third light-emitting main surface 20B is greater than the maximum absolute value of the angle formed by the light passing through the first light-transmitting portion 18D relative to the normal direction of the first light-emitting main surface 18B. This prevents the light, which is imparted with anisotropic refraction by the linear Fresnel lens sheet 19, from being excessively restricted in its exit angle by the second louver 20. As a result, the light emitted from the third light-emitting main surface 20B fully reflects the anisotropic refraction imparted by the linear Fresnel lens sheet 19, and thus the brightness of the emitted light is uniformed in the central side portion and the two end side portions in the first direction of the third light-emitting main surface 20B. Furthermore, the emission angle of the light emitted from the third light-emitting main surface 20B is limited by the two second light-shielding portions 20C, thereby reducing side lobe light that may be generated in the light emitted from the backlight device 12 .

[0092] Furthermore, a plurality of first lenses 19C are arranged in the first direction. The plurality of first lenses 19C include a central lens 19CC and an end lens 19CE located closer to the end of the central lens 19CC in the first direction in the linear Fresnel lens sheet 19. An angle θ1E formed by a first inclined surface 19C1 of the end lens 19CE with respect to the first direction is greater than an angle θ1C formed by the first inclined surface 19C1 of the central lens 19CC with respect to the first direction. In the linear Fresnel lens sheet 19, the first inclined surface 19C1 of the end lens 19CE located closer to the end of the central lens 19CC in the first direction imparts a stronger anisotropic refractive effect on light than the first inclined surface 19C1 of the central lens 19CC located closer to the center of the end lens 19CE in the first direction. That is, the light emitted from the end portions in the first direction of the second light-emitting principal surface 19B of the linear Fresnel lens sheet 19 has a stronger directivity toward the center in the first direction than the light emitted from the center portion in the first direction. In the second louver 20, upon which the light emitted from the second light-emitting principal surface 19B is incident, excessive restriction of the emission angle of the emitted light is avoided. Therefore, the brightness of the light emitted from the center portion and both end portions in the first direction of the third light-emitting principal surface 20B of the second louver 20 is more uniform.

[0093] Furthermore, each of the multiple first lenses 19C includes an inclined second slope 19C2 extending from the center of the linear Fresnel lens sheet 19 in the first direction toward the end. This facilitates processing of the multiple first lenses 19C during the manufacture of the linear Fresnel lens sheet 19, compared to assuming that the second slope 19C2 is a perpendicular surface perpendicular to the first direction. Conversely, light refracted by the second slope 19C2 toward the end in the first direction may potentially become sidelobe light. In this regard, since the emission angle of the light emitted from the third light-emitting principal surface 20B is limited by the two second light-shielding portions 20C of the second louver 20, the sidelobe light caused by the second slope 19C2 can be significantly reduced.

[0094] Furthermore, the angle formed between the first inclined surface 19C1 and the second inclined surface 19C2 of the center lens 19CC, namely the vertex angle θ3C, is equal to the vertex angle θ3E of the end lens 19CE. The angle θ2E formed by the second inclined surface 19C2 of the end lens 19CE with respect to the first direction is smaller than the angle θ2C formed by the second inclined surface 19C2 of the center lens 19CC with respect to the first direction. Thus, since the vertex angle θ3C of the center lens 19CC and the vertex angle θ3E of the end lens 19CE are equal, the processing of the mold used for molding becomes easier, for example, when the linear Fresnel lens sheet 19 is manufactured by resin molding. By making the vertex angle θ3 of the center lens 19CC and the end lens 19CE equal, the angle θ2E formed by the second inclined surface 19C2 of the end lens 19CE with respect to the first direction is smaller than the angle θ2C formed by the second inclined surface 19C2 of the center lens 19CC with respect to the first direction. Therefore, there is a tendency for the side lobe light generated by the second inclined surface 19C2 of the end lens 19CE to be greater than the side lobe light generated by the second inclined surface 19C2 of the center lens 19CC. In contrast, the emission angle of the light emitted from the third light-emitting main surface 20B is limited by the two second light-shielding portions 20C of the second louver 20, thereby significantly reducing the side lobe light generated by the second inclined surface 19C2 of the end lens 19CE.

[0095] Furthermore, in the plurality of first lenses 19C, the angle θ1 formed by the first inclined surface 19C1 with respect to the first direction is set to be in the range of 0° to 24°, and the angle θ2 formed by the second inclined surface 19C2 with respect to the first direction is set to be in the range of 46° to 70°. If the angle θ1 formed by the first inclined surface 19C1 with respect to the first direction is greater than 24°, and the angle θ2 formed by the second inclined surface 19C2 with respect to the first direction is less than 46°, there will be an excess of side lobe light that is difficult for the second light shielding portion 20C of the second louver 20 to block. If the angle θ1 formed by the first inclined surface 19C1 with respect to the first direction is less than 0°, and the angle θ2 formed by the second inclined surface 19C2 with respect to the first direction is greater than 70°, there will be an excess of side lobe light that is difficult for the second light shielding portion 20C of the second louver 20 to block. Regarding this point, as described above, in the multiple first lenses 19C, if the angle θ1 formed by the first inclined surface 19C1 relative to the first direction is set to the range of 0° to 24°, and the angle θ2 formed by the second inclined surface 19C2 relative to the first direction is set to the range of 46° to 70°, the side lobe light that is difficult to be blocked by the second shading portion 20C of the second shutter 20 can be fully suppressed.

[0096] In addition, it is provided with: a first LED (first light source) 13; a first light guide plate 14 arranged in a first direction relative to the first LED 13; a first prism sheet 16, which is the first prism sheet 16 arranged on the light-emitting side relative to the first light guide plate 14, and has a plurality of first prisms 16B arranged in the first direction and extending in a second direction, the second direction being orthogonal to both the first direction and the normal direction of the main surface of the first light guide plate 14; and a second prism sheet 17, which is the second prism sheet 17 arranged on the light-emitting side relative to the first prism sheet 16, and has a plurality of second prisms 17B arranged in the first direction and extending in the second direction, in the first light guide plate 14, at least a part of its outer peripheral end surface is the first light incident end surface 14A opposite to the first LED 13, one main surface is the first light-emitting main surface (fourth light-emitting main surface 14B) of the first light guide plate from which light is emitted, and the main surface of the light-emitting side of the second prism sheet 17 is aligned with the first light incident main surface 17B of the first louver 18 8A are arranged relative to each other, the first prism 16B has: an inclined first prism bevel (third bevel) 16B1 rising from the first LED 13 side of the first direction of the first prism sheet 16 to its opposite side; and an inclined second prism bevel (fourth bevel) 16B2 rising from the side of the first direction of the first prism sheet 16 opposite to the first LED 13 to the first LED 13 side, the second prism 17B has: an inclined third prism bevel (fifth bevel) 17B1 rising from the first LED 13 side of the first direction of the second prism sheet 17 to its opposite side; and an inclined fourth prism bevel (sixth bevel) 17B2 rising from the side of the first direction of the second prism sheet 17 opposite to the first LED 13 to the first LED 13 side, the angle θ7 formed by the third prism bevel 17B1 in the second prism 17B with respect to the first direction is smaller than the angle θ4 formed by the first prism bevel 16B1 in the first prism 16B with respect to the first direction.

[0097] Light emitted from the first LED 13 and incident on the first light-entering end surface 14A of the first light guide plate 14 propagates within the first light guide plate 14, exits from the first light guide plate's main light-emitting surface 14B, and enters the first prism sheet 16. Most of the light entering the first prism sheet 16 hits the second prism bevel 16B2 of the first prism 16B, is refracted, and then rises and exits, or is directed toward the first prism bevel 16B1. Here, in the first prism 16B, the angle θ4 formed by the first prism bevel 16B1 with respect to the first direction is greater than the angle θ7 formed by the third prism bevel 17B1 of the second prism 17B with respect to the first direction. Therefore, compared to a case where the angles are the same or the angles are set to be opposite in magnitude, the light entering the first prism sheet 16 is less likely to hit the first prism bevel 16B1 of the first prism 16B. If the incident light on the first prism sheet 16 strikes the first prism inclined surface 16B1 of the first prism 16B, it tends to be emitted as side lobe light when exiting the first prism 16B. Therefore, if the incident light on the first prism sheet 16 is less likely to directly strike the first prism inclined surface 16B1 of the first prism 16B, the generation of side lobe light is suppressed, resulting in improved light utilization efficiency.

[0098] Most of the light emitted from the first prism sheet 16 and incident on the second prism sheet 17 hits the fourth prism slope 17B2 of the second prism 17B and is refracted, rising and emitted, or heading toward the third prism slope 17B1.

[0099] Here, because the angle θ7 formed by the third prism oblique surface 17B1 of the second prism 17B with respect to the first direction is smaller than the angle θ4 formed by the first prism oblique surface 16B1 of the first prism 16B with respect to the first direction, light refracted by the sixth hypotenuse and directed toward the third prism oblique surface 17B1 is more likely to return to the first prism sheet 16 via the third prism oblique surface 17B1 than if the angles were equal or opposite. As a result, the amount of light (hereinafter referred to as "return light") that returns from the second prism sheet 17 to the first prism sheet 16 increases. This return light, through reflection within the backlight device 12 and other factors, reaches the second prism sheet 17 again, ascending through the third prism oblique surface 17B1 or the fourth prism oblique surface 17B2 of the second prism 17B and exiting, thereby improving light utilization efficiency. Furthermore, the optical path of the return light before exiting the second prism sheet 17 is complicated, and the ascending angle imparted by the second prism 17B is diversified, thereby improving viewing angle characteristics.

[0100] Light emitted from the second prism sheet 17 enters the first main light-entering surface 18A of the first louver 18. The light incident on the first main light-entering surface 18A has less sidelobe light and is more efficiently utilized due to the reentrant light. This ensures that a sufficient amount of light is transmitted through the first light-transmitting portion 18D, while reducing the amount of light blocked by the first light-blocking portion 18C. This improves the brightness of the light emitted by the backlight device 12.

[0101] Furthermore, the liquid crystal display device (display device) 10 of this embodiment includes the backlight device 12 described above and a liquid crystal panel (display panel) 11 that performs display using light from the backlight device 12. With the liquid crystal display device 10 thus configured, the brightness distribution of light emitted from the backlight device 12 is made uniform, thereby achieving a display with excellent display quality.

[0102] <Second embodiment>

[0103] pass Figure 13 The second embodiment will be described. In this second embodiment, a case where the arrangement of the linear Fresnel lens sheet 119 is changed will be described. Regarding the same structure, operation, and effects as those of the first embodiment, repeated descriptions will be omitted.

[0104] like Figure 13 As shown, the linear Fresnel lens sheet 119 of this embodiment is arranged with the first lens 119C facing the rear side, that is, toward the first louver 118. Specifically, the first lens 119C is disposed on the second light-entering principal surface 119A of the linear Fresnel lens sheet 119. The second light-exiting principal surface 119B of the linear Fresnel lens sheet 119, which is not formed with the first lens 119C, faces the second louver 120. Even with this configuration, the same functions and effects as those of the first embodiment described above can be achieved.

[0105] <Third embodiment>

[0106] pass Figure 14 The third embodiment is described. In the third embodiment, the linear Fresnel lens sheet 219 is modified from the second embodiment. The same configuration, operation, and effects as those of the second embodiment will be omitted from repeated description.

[0107] like Figure 14As shown, the second main light-emitting surface 219B of the linear Fresnel lens sheet 219 in this embodiment is attached to the third main light-entering surface 220A of the second louver 220. During attachment, for example, adhesive can be interposed between the third main light-entering surface 220A of the second louver 220 and the second main light-emitting surface 219B of the linear Fresnel lens sheet 219. This ensures that the third main light-entering surface 220A of the second louver 220 and the second main light-emitting surface 219B of the linear Fresnel lens sheet 219 maintain close contact across their entire area, avoiding the presence of an air layer (a portion not in close contact) between them. This prevents light incident on the third main light-entering surface 220A of the second louver 220 from being refracted by this air layer, making visual unevenness less noticeable. In addition, it is possible to avoid a gap between the third light incident principal surface 220A of the second louver 220 and the second light emitting principal surface 219B of the linear Fresnel lens sheet 219 , and thus is also suitable for achieving overall thinning.

[0108] As described above, according to this embodiment, the first lens 219C is arranged on the second light-entering principal surface 219A, and the second light-emitting principal surface 219B of the linear Fresnel lens sheet 219 is attached to the third light-entering principal surface 220A of the second louver 220. If the linear Fresnel lens sheet 219 is not attached to the second louver 220, and the second light-emitting principal surface 219B and the third light-entering principal surface 220A, which are opposed to each other, are partially in close contact, a difference in the direction of light travel occurs between the closely contacted and non-closely contacted portions, which may be visually perceived as unevenness. In this regard, by attaching the second light-emitting principal surface 219B of the linear Fresnel lens sheet 219, where the first lens 219C is not arranged, to the third light-entering principal surface 220A of the second louver 220, this unevenness can be avoided. Furthermore, this is also suitable for achieving a thinner design.

[0109] <Fourth embodiment>

[0110] pass Figure 15 The fourth embodiment is described. In the fourth embodiment, the linear Fresnel lens sheet 319 is modified from the first embodiment. The same structure, operation, and effects as those of the first embodiment will be omitted from repeated description.

[0111] like Figure 15As shown, the second main light-entering surface 319A of the linear Fresnel lens sheet 319 of this embodiment is attached to the first main light-emitting surface 318B of the first louver 318. During installation, for example, adhesive can be placed between the first main light-emitting surface 318B of the first louver 318 and the second main light-entering surface 319A of the linear Fresnel lens sheet 319. In this way, the first main light-emitting surface 318B of the first louver 318 and the second main light-entering surface 319A of the linear Fresnel lens sheet 319 are maintained in close contact over the entire area, avoiding the presence of an air layer (a portion not in close contact) between them. This prevents light incident on the first main light-emitting surface 318B of the first louver 318 from being refracted by the aforementioned air layer, making it difficult to visually detect unevenness. In addition, it is possible to avoid a gap between the first light-emitting principal surface 318B of the first louver 318 and the second light-incident principal surface 319A of the linear Fresnel lens sheet 319 , and thus is also suitable for achieving overall thinning.

[0112] As described above, according to this embodiment, the first lens 319C is arranged on the second light-emitting principal surface 319B, and the second light-entering principal surface 319A of the linear Fresnel lens sheet 319 is attached to the first light-emitting principal surface 318B of the first louver 318. If the linear Fresnel lens sheet 319 is not attached to the first louver 318, if the second light-entering principal surface 319A and the first light-emitting principal surface 318B, which are opposed to each other, are partially in close contact, a difference in the direction of light travel will occur between the closely contacting portion and the non-closely contacting portion, potentially causing this difference to be visually perceived as unevenness. In this regard, the second light-entering principal surface 319A of the linear Fresnel lens sheet 319, where the first lens 319C is not arranged, is attached to the first light-emitting principal surface 318B of the first louver 318, thereby avoiding the aforementioned unevenness. Furthermore, this is also suitable for achieving a thinner design.

[0113] <Fifth embodiment>

[0114] pass Figure 16 The fifth embodiment will be described. In the fifth embodiment, the configuration of the backlight device 412 is modified from that of the first embodiment. Repetitive descriptions of the same structures, functions, and effects as those of the first embodiment will be omitted.

[0115] like Figure 16As shown, the backlight device 412 of this embodiment includes: a second LED (second light source) 24; and a second light guide plate 25, which is arranged along the X-axis direction (first direction) relative to the second LED 24. The second LED 24 is roughly block-shaped, and one of the pairs of faces along the Y-axis direction and the Z-axis direction is a second light-emitting surface 24A 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 to seal the LED chip on a substrate portion mounted on the LED substrate through a sealing material. The LED chip of the second LED 24 emits, for example, monochromatic blue light. Phosphors are dispersed in the sealing material of the second LED 24. The phosphors contained in the sealing material include yellow phosphors, green phosphors, red phosphors, etc. The second LED 24 having such an LED chip and sealing material emits white light as a whole.

[0116] The second light guide plate 25 is made of a substantially transparent synthetic resin material (eg, acrylic resin such as PMMA) that has a refractive index sufficiently higher than that of air. Figure 16 As shown, the second light guide plate 25 is in a plate shape, and its main surface is parallel to the main surface of the liquid crystal panel 411. 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 relative to the second LED 24. Figure 16. That 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 414 and the first LED 413 in the X-axis direction. Thus, the first LED 413 and the second LED 24 are configured so as not to overlap with each other. The second light guide plate 25 is arranged at a position overlapping with the back side in the Z-axis direction relative to the liquid crystal panel 411, and is arranged at a position overlapping with the front side of the second louver 420. One of the outer peripheral end faces of the second light guide plate 25 is a second light incident 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 light emitted from the second light emitting surface 24A is incident on the second light incident end face 25A. Of the pair of main faces in the second light guide plate 25, the main face on the front side opposite to the liquid crystal panel 411 is the second light guide plate light emitting main face 25B that emits light guided internally. The main surface on the back side opposite to the second louver 420 among the pair of main surfaces in the second light guide plate 25 is a second opposite main surface 25C located on the side opposite to the second light guide plate light emitting main surface 25B. 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 internally, it rises and exits from the second light guide plate light emitting main surface 25B along the Z-axis direction toward the liquid crystal panel 411 on the front side (light emitting side). In addition, the second light guide plate 25 is capable of introducing the outgoing light from the second louver 420 from the second opposite main surface 25C, and causing the light to exit from the second light guide plate light emitting main surface 25B toward the liquid crystal panel 411 on the front side. In addition, the normal direction of the second light incident end surface 25A is consistent with the X-axis direction (the arrangement direction of the second LED 24 and the second light guide plate 25).

[0117] like Figure 16 As shown, a fourth light guide plate lens 26, a fifth light guide plate lens 27 and a sixth light guide plate lens 28 are provided on the second light guide plate 25. The fourth light guide plate lens 26 is provided 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 is arranged in a plurality along the Y-axis direction, and is a so-called double convex lens. The specific structure of the fourth light guide plate lens 26 is roughly the same as that of the first light guide plate lens 421, and the detailed description is the same as that described in the first embodiment (refer to Figure 3 ). In addition, the contact angle of the fourth light guide plate lens 26 can be smaller than the contact angle of the first light guide plate lens 421, for example, it can be set to about 30°. The fifth light guide plate lens 27 is arranged on the second opposite main surface 25C of the second light guide plate 25. The fifth light guide plate lens 27 is a convex prism extending along the X-axis direction, arranged in parallel along the Y-axis direction, and protruding from the second opposite main surface 25C to the back side. The specific structure of the fifth light guide plate lens 27 is the same as that of the second light guide plate lens 22 described in the first embodiment (refer to Figure 2 ) are roughly the same, and detailed description is omitted.

[0118] like Figure 16 As shown, the sixth light guide plate lens 28 is provided on the second opposite main surface 25C of the second light guide plate 25. A plurality of the sixth light guide plate lenses 28 are arranged at intervals along the X-axis direction. The sixth light guide plate lens 28 protrudes from the second opposite main surface 25C toward the back side along the Z-axis direction. The sixth light guide plate lens 28 has a side (opposite to the second LED 24 side) arranged in the X-axis direction. Figure 16 The sixth light guide plate inclined surface (seventh inclined surface) 28A, the second LED 24 side ( Figure 16 The sixth light guide plate inclined surface 28A has a first plane 28C located between the sixth light guide plate inclined surface 28A and the seventh light guide plate inclined surface 28B. The sixth light guide plate inclined surface 28A has a first plane 28C located between the second LED 24 side ( Figure 16 to the right side) toward the opposite side ( Figure 16 The seventh light guide plate inclined surface 28B has a side opposite to the second LED 24 side in the X-axis direction of the second light guide plate 25 ( Figure 16 Left side) toward the second LED24 side ( Figure 16 The first plane 28C is parallel to the X-axis and Y-axis directions. Furthermore, a second plane 29 is provided between two adjacent sixth light guide plate lenses 28 in the X-axis direction. Thus, the sixth light guide plate lenses 28 and the second plane 29 are arranged alternately and repeatedly along the X-axis direction.

[0119] like Figure 16As shown, the sixth light guide plate inclined surface 28A reflects light propagating within the second light guide plate 25 and, by rising toward the front, promotes emission from the second light guide plate's main light-emitting surface 25B. Specifically, the sixth light guide plate inclined surface 28A primarily reflects and elevates light traveling away from the second LED 24 in the X-axis direction within the second light guide plate 25. The inclination angle of the sixth light guide plate inclined surface 28A relative to the X-axis direction is, for example, 40° or less, preferably approximately 27°. When the inclination angle of the sixth light guide plate inclined surface 28A relative to the X-axis direction is 40° or less, light can be directed in a direction that is inclined toward the side opposite to the second LED 24 in the X-axis direction relative to the front direction. Therefore, light emitted from the second light guide plate's main light-emitting surface 25B, which faces the side opposite to the second LED 24 in the X-axis direction relative to the Z-axis direction (the normal to the second light guide plate's main light-emitting surface 25B), contains a greater amount of light than light facing the side opposite to the second LED 24 in the X-axis direction. Therefore, when the second LED 24 is illuminated, the emitted light can have a brightness angle distribution in which the peak brightness of the emitted light is biased toward the side opposite the second LED 24 in the X-axis direction. In a vehicle-mounted liquid crystal display device 410 installed in front of the front passenger seat of a passenger vehicle, the second LED 24 is preferably positioned on the side opposite the driver's seat in the X-axis direction. Thus, for example, while the passenger vehicle is in motion, by illuminating the first LED 413 and extinguishing the second LED 24, the image displayed on the liquid crystal display device 410 can be visually recognized from the front passenger seat, but not from the driver's seat. In contrast, when the passenger vehicle is stopped, by illuminating both the first LED 413 and the second LED 24, the image displayed on the liquid crystal display device 410 can be visually recognized from either the driver's seat or the front passenger seat. In this way, by controlling the driving of the second LED 24 according to the vehicle's driving conditions, whether the displayed image is visually recognized from the driver's seat can be adjusted.

[0120] Meanwhile, the seventh light guide plate inclined surface 28B can reflect light traveling toward the second LED 24 in the X-axis direction and direct it upward, or reflect light traveling within the second light guide plate 25 away from the second LED 24 in the X-axis direction and direct it further away from the second LED 24. The inclination angle of the seventh light guide plate inclined surface 28B relative to the X-axis direction is, for example, approximately 3°, which is smaller than the inclination angle of the sixth light guide plate inclined surface 28A. Furthermore, the plurality of sixth light guide plate lenses 28 arranged along the X-axis direction are designed so that their height (Z-axis dimension) increases as they move away from the second LED 24 in the X-axis direction, while maintaining a constant arrangement pitch in the X-axis direction. The length of the sixth light guide plate inclined surface 28A increases slightly as they move away from the second LED 24 in the X-axis direction. The length of the seventh light guide plate inclined surface 28B increases as they move away from the second LED 24 in the X-axis direction, with the rate of increase being higher than that of the sixth light guide plate inclined surface 28A. The length of the first flat surface 28C remains constant regardless of its position in the X-axis direction. The length of the second flat surface 29 decreases as it moves away from the second LED 24 in the X-axis direction. Furthermore, the inclination angles of the sixth light guide plate slope 28A and the seventh light guide plate slope 28B relative to the X-axis direction are constant regardless of their positions in the X-axis direction.

[0121] As described above, according to this embodiment, there is a second LED (second light source) 24 and a second light guide plate 25 arranged along the first direction relative to the second LED 24, at least a portion of the outer peripheral end surface of the second light guide plate 25 is a second light incident end surface 25A opposite to the second LED 24, one main surface is the second light guide plate light emitting main surface (fifth light emitting main surface) 25B for emitting light, and the other main surface is the second opposite main surface (opposite main surface) 25C opposite to the third light emitting main surface 420B and provided with a sixth light guide plate lens (second lens) 28, the sixth light guide plate lens 28 has an inclined sixth light guide plate inclined surface (seventh inclined surface) 28A that stands from the side of the second light guide plate 25 opposite to the second LED 24 in the first direction toward the second LED 24 side.

[0122] Light emitted from the second LED 24 and incident on the second light-entry end surface 25A of the second light guide plate 25 propagates within the second light guide plate 25. It then strikes the sixth light guide plate inclined surface 28A of the sixth light guide plate lens 28 provided on the second opposite principal surface 25C. The light striking the sixth light guide plate inclined surface 28A is reflected and emitted from the second light guide plate light-emitting principal surface 25B. The sixth light guide plate inclined surface 28A is inclined, rising from the side of the second light guide plate 25 opposite to the second LED 24 in the first direction toward the second LED 24. The light emitted from the second light guide plate light-emitting principal surface 25B contains more light directed toward the side opposite to the second LED 24 in the first direction relative to the normal to the second light guide plate light-emitting principal surface 25B than toward the side toward the second LED 24 in the first direction. Therefore, when the second LED 24 is illuminated, the emitted light has a brightness angular distribution in which the peak brightness of the emitted light is shifted toward the side opposite to the second LED 24 in the first direction.

[0123] <Other Implementation Methods>

[0124] 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.

[0125] (1) In the configurations described in the first to fourth embodiments, a third louver may be provided at a position where the front side of the second louvers 20, 120, and 220 is the back side of the liquid crystal panel 11. The third louver includes at least two third light-shielding portions spaced apart in the Y-axis direction perpendicular to the X-axis direction, and a third light-transmitting portion disposed between the two third light-shielding portions. The third louver can limit the Y-axis emission angle of the emitted light. This prevents the displayed image from being reflected on the windshield of a passenger vehicle.

[0126] (2) In the configuration described in the fifth embodiment, the third louver described in (1) above may be provided at a position where the front side of the second light guide plate 25 is the back side of the liquid crystal panel 411 .

[0127] (3) In the configuration described in the third embodiment, the linear Fresnel lens sheet 219 and the second louver 220 may be integrally molded. In this case, uncured ultraviolet curable resin material is filled into a molding die, and the second louver 220 is placed at the open end of the die, so that the uncured ultraviolet curable resin material contacts the main surface on the front side. In this state, the ultraviolet curable resin material is irradiated with ultraviolet light through the second louver 220, thereby integrally providing the linear Fresnel lens sheet 219 and the second louver 220.

[0128] (4) In the configuration described in the fourth embodiment, the linear Fresnel lens sheet 319 and the first louver 318 may be integrally molded. In this case, uncured ultraviolet curable resin material is filled into a molding die, and the first louver 318 is placed at the open end of the die. The uncured ultraviolet curable resin material is arranged so as to contact the main surface on the front side. In this state, the ultraviolet curable resin material is irradiated with ultraviolet light through the first louver 318, thereby enabling the linear Fresnel lens sheet 319 and the first louver 318 to be integrally provided.

[0129] (5) In the configuration described in the fifth embodiment, the positional relationship of the second LED 24 relative to the second light guide plate 25 in the X-axis direction may be the same as the positional relationship of the first LED 13 , 413 relative to the first light guide plates 14 , 414 in the X-axis direction.

[0130] (6) The plurality of first lenses 19C, 119C, 219C, 319C included in the linear Fresnel lens sheet 19, 119, 219, 319 may include a plurality of first lenses 19C, 119C, 219C, 319C having the same angle θ1 of the first inclined surface 19C1 relative to the X-axis direction (angle θ2 of the second inclined surface 19C2 relative to the X-axis direction). In other words, the angle θ1 of the first inclined surface 19C1 relative to the X-axis direction (angle θ2 of the second inclined surface 19C2 relative to the X-axis direction) may be different for all first lenses 19C, 119C, 219C, 319C.

[0131] (7) The specific values of the angles of the first lens elements 19C, 119C, 219C, and 319C of the linear Fresnel lens sheets 19, 119, 219, and 319 (the angle θ1 of the first inclined surface 19C1 relative to the X-axis, the angle θ2 of the second inclined surface 19C2 relative to the X-axis, and the vertex angle θ3 formed between the first inclined surface 19C1 and the second inclined surface 19C2) can be varied as appropriate. In this case, the angle θ1 of the first inclined surface 19C1 relative to the X-axis is preferably within the range of 0° to 24°, and the angle θ2 of the second inclined surface 19C2 relative to the X-axis is preferably within the range of 46° to 70°, but may also be outside these ranges. Furthermore, while setting the angle θ1 of the first inclined surface 19C1 relative to the X-axis direction to within the range of 0° to 24° and the angle θ2 of the second inclined surface 19C2 relative to the X-axis direction to within the range of 46° to 70°, the value of the vertex angle θ3 formed by the first inclined surface 19C1 and the second inclined surface 19C2 can be set to a value other than 110° (e.g., 80°, 90°, 100°, 120°, etc.). Furthermore, it is also possible to set the angle θ1 of the first inclined surface 19C1 relative to the X-axis direction to outside the range of 0° to 24°, set the angle θ2 of the second inclined surface 19C2 relative to the X-axis direction to outside the range of 46° to 70°, and set the vertex angle θ3 formed by the first inclined surface 19C1 and the second inclined surface 19C2 to outside the range of 110° (e.g., 80°, 90°, 100°, 120°, etc.). Furthermore, the specific material used for the linear Fresnel lens sheets 19 , 119 , 219 , and 319 may be changed as appropriate.

[0132] (8) The specific values of the contact angle, tilt angle, etc. of each light guide plate lens 21 to 23, 421 included in the first light guide plate 14, 414 can be changed as appropriate. The specific material used for the first light guide plate 14, 414 can be changed as appropriate.

[0133] (9) The specific values of the contact angles, tilt angles, etc. of the light guide plate lenses 26 to 28 included in the second light guide plate 25 described in the fifth embodiment may be changed as appropriate. The specific material used for the second light guide plate 25 may be changed as appropriate.

[0134] (10) Either or both of the first light guide plate lens 21 , 421 and the second light guide plate lens 22 included in the first light guide plate 14 , 414 may be omitted.

[0135] (11) Either or both of the fourth light guide plate lens 26 and the fifth light guide plate lens 27 included in the second light guide plate 25 may be omitted.

[0136] (12) The thickness of the first light guide plate 14 or 414 may decrease as it becomes farther away from the first LED 13 or 413 , and the first opposite main surface 14C may be inclined.

[0137] (13) The thickness of the second light guide plate 25 described in the fifth embodiment may decrease as it becomes farther away from the second LED 24 , and the second opposite main surface 25C may be inclined.

[0138] (14) The specific values of the inclination angles, vertex angles, etc. of the prism slopes 16B1, 16B2, 17B1, and 17B2 of the prisms 16B and 17B included in the prism sheets 16 and 17 can be appropriately changed. The specific materials used for the base materials 16A and 17A of the prism sheets 16 and 17 can also be appropriately changed. Similarly, the specific materials used for the prisms 16B and 17B can also be appropriately changed.

[0139] (15) The specific cross-sectional shape of each prism 16B, 17B included in each prism sheet 16, 17 may be changed as appropriate. In this case, for example, any of the prism inclined surfaces 16B1, 16B2, 17B1, 17B2 in each prism 16B, 17B may be curved with a plurality of inclination angles.

[0140] (16) In the first louver 18, 118, 318, the specific value of the ratio (tanθ) of the width of the first light-transmitting portion 18D divided by the height can be appropriately changed other than tan10°, for example, it can be set to tan12.5°, tan15°, tan17.5°, etc.

[0141] (17) In the second louvers 20, 120, 220, and 420, the specific value of the ratio (tanθ) of the width of the second light-transmitting portion 20D divided by the height can be appropriately changed other than tan45°, for example, to tan50°.

[0142] (18) Instead of the first LEDs 13 and 413 and the second LED 24 , a light source such as an organic EL (ElectroLuminescence) may be used.

[0143] (19) The configuration described in the fifth embodiment may be combined with the configurations described in the second to fourth embodiments.

[0144] (20) Instead of a polarizing plate, 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, 411. The reflective polarizing plate comprises: a polarizing layer having a specific polarization axis (transmission axis), a multilayer film formed by alternating layers of layers with different refractive indices, a protective layer, etc. The polarizing layer has a polarization axis and an absorption axis perpendicular to the polarization axis, thereby selectively allowing linear polarized light parallel to the polarization axis to pass through and converting circularly polarized light into linear polarized light along the polarization axis. The polarization axis of the polarizing layer is perpendicular to the polarization axis of the polarizing plate installed on the main surface outside the CF substrate. The multilayer film is a multilayer structure having a reflective characteristic in which the reflectivity of the s-wave contained in the light is substantially higher than the reflectivity of the p-wave. By having a multilayer film, the reflective polarizing plate can improve the efficiency of light utilization (and thus the brightness) by reflecting the s-wave absorbed by the polarizing layer to the back side for reuse.

[0145] (21) A prism sheet having prisms disposed on the light incident principal surface side may be used in place of the first prism sheet 16 and the second prism sheet 17. This prism sheet is configured such that the light incident principal surface faces the first light guide plate light exit principal surface 14B of the first light guide plate 14 or 414, and the light exit principal surface faces the first light incident principal surface 18A of the first louver 18, 118, or 318. A plurality of prisms are arranged along the X-axis on the light incident principal surface. Even when such a prism sheet is used, light with little side lobe light can be supplied to the first louver 18, 118, or 318, and a sufficient amount of light transmitted through the first light-transmitting portion 18D can be ensured.

[0146] (22) The vehicle-mounted liquid crystal display device 10, 410 can be installed at a position other than in front of the passenger seat of a passenger car. For example, it can be installed at a position between the passenger seat and the driver's seat. As the configuration of the liquid crystal display device 10, 410 is changed, the required angle range of the viewing angle also changes. Therefore, the various structures of the first louver 18, 118, 318, the linear Fresnel lens sheet 19, 119, 219, 319, and the second louver 20, 120, 220, 420 (such as the ratio of the width to the height of each light-transmitting portion 18D, 20D, the inclination angle of each inclined surface 19C1, 19C2 of the first lens 19C, 119C, 219C, 319C, etc.) can be changed accordingly.

[0147] (23) In addition to vehicle-mounted applications, the liquid crystal display device 10 or 410 can also be used in devices requiring a limited viewing angle, such as ATMs (Automatic Teller Machines), laptop computers, and tablet computers. When the application of the liquid crystal display device 10 or 410 changes, the required viewing angle range also changes. Therefore, the configuration of the first louver 18, 118, 318, linear Fresnel lens sheet 19, 119, 219, 319, and second louver 20, 120, 220, 420 (such as the ratio of the width to the height of each light-transmitting portion 18D or 20D, and the inclination angle of each inclined surface 19C1 or 19C2 of the first lens 19C, 119C, 219C, or 319C) can be changed accordingly.

[0148] Description of Reference Numerals

[0149] 10, 410…Liquid crystal display device (display device); 11, 411…Liquid crystal panel (display panel); 12, 412…Backlight device (illumination device); 13, 413…First LED (first light source); 14, 414…First light guide plate; 14A…First light incident end surface; 14B…First light guide plate main light exit surface (fourth light exit surface); 16…First prism sheet; 16B…First prism; 16B1…First prism oblique surface (third oblique surface); 16B2…Second prism oblique surface 17…Second prism sheet; 17B…Second prism; 17B1…Third prism inclined surface (fifth inclined surface); 17B2…Fourth prism inclined surface (sixth inclined surface); 18, 118, 318…First louver (first sheet); 18A…First light incident principal surface; 18B…First light emitting principal surface; 18C…First light shielding portion; 18D…First light transmitting portion; 19, 119, 219, 319…Linear Fresnel lens sheet (second sheet); 19A, 119A, 219 A, 319A…Second principal light incident surface; 19B, 119B, 219B, 319B…Second principal light exit surface; 19C, 119C, 219C, 319C…First lens element; 19C1…First inclined surface; 19C2…Second inclined surface; 19CC…Center lens element; 19CE…End lens element; 20, 120, 220, 420…Second louver (third element); 20A, 220A…Third principal light incident surface; 20B, 420B…Third principal light exit surface; 20C… Second light-shielding portion; 20D…second light-transmitting portion; 24…second LED (second light source); 25…second light guide plate; 25A…second light-entering end face; 25B…second light-emitting principal surface (fifth light-emitting principal surface) of the second light guide plate; 25C…second opposite principal surface (opposite principal surface); 28…sixth light guide plate lens (second lens); 28A…sixth light guide plate inclined surface (seventh inclined surface); H1…height; H2…height; W1…width; width…W2; angle…θ1; θ2…angle; θ3…vertex angle.

Claims

1. A lighting device, characterized in that: It has: a first sheet having a first light incident principal surface on one principal surface along a first direction, a first light emitting principal surface on the other principal surface along the first direction, two first light shielding portions spaced apart in the first direction, and a first light transmitting portion disposed between the two first light shielding portions, wherein a plurality of the first light shielding portions and a plurality of the first light transmitting portions are alternately and repeatedly arranged in the first direction; a second lens having a principal surface along the first direction and opposite to the first light emitting principal surface, namely, a second light incident principal surface; a principal surface along the first direction, namely, a second light emitting principal surface; and a plurality of first lenses arranged on the second light incident principal surface or the second light emitting principal surface; as well as The third sheet has a main surface along the first direction and opposite to the second light-emitting main surface, namely, a third light-incident main surface; a main surface along the other side of the first direction, namely, a third light-emitting main surface; two second light-shielding portions arranged at intervals in the first direction; and a second light-transmitting portion arranged between the two second light-shielding portions, wherein a plurality of the second light-shielding portions and a plurality of the second light-transmitting portions are alternately and repeatedly arranged in the first direction. The first lens has an inclined first slope that rises from an end side of the second lens in the first direction toward a center side. In the third sheet, a ratio of the width of the second light-transmitting portion divided by its height is greater than a ratio of the width of the first light-transmitting portion divided by its height.

2. The lighting device according to claim 1, characterized in that A plurality of first lenses are arranged in the first direction. The plurality of first lenses include a center lens and an end lens, wherein the end lens is located in the second sheet closer to the end side in the first direction than the center lens. An angle formed by the first inclined surface of the end-side lens with respect to the first direction is larger than an angle formed by the first inclined surface of the center-side lens with respect to the first direction.

3. The lighting device according to claim 2, characterized in that Each of the plurality of first lenses has an inclined second slope surface rising from the center side toward the end side of the second lens in the first direction.

4. The lighting device according to claim 3, characterized in that The angle formed by the first inclined surface and the second inclined surface of the central side lens, that is, the vertex angle, is equal to the vertex angle of the end side lens. An angle formed by the second inclined surface of the end side lens with respect to the first direction is smaller than an angle formed by the second inclined surface of the center side lens with respect to the first direction.

5. The lighting device according to claim 4, characterized in that An angle formed by the first inclined surfaces of the plurality of first lenses relative to the first direction is in a range of 0° to 24°, and an angle formed by the second inclined surfaces relative to the first direction is in a range of 46° to 70°.

6. The lighting device according to any one of claims 1 to 5, characterized in that: The first lens is arranged on the second light incident principal surface, The second light-emitting main surface of the second sheet is mounted on the third light-incident main surface of the third sheet.

7. The lighting device according to any one of claims 1 to 5, characterized in that: The first lens is arranged on the second light-emitting principal surface, The second light incident principal surface of the second sheet is mounted on the first light emitting principal surface of the first sheet.

8. The lighting device according to any one of claims 1 to 5, characterized in that: The lighting device comprises: a first light source; a first light guide plate arranged along the first direction relative to the first light source; a first prism sheet, disposed on a light-emitting side relative to the first light guide plate, comprising a plurality of first prisms arranged along the first direction and extending along a second direction, the second direction being orthogonal to both the first direction and a normal direction to a principal surface of the first light guide plate; as well as a second prism sheet, which is arranged on the light-emitting side relative to the first prism sheet, and has a plurality of second prisms arranged along the first direction and extending along the second direction; At least a portion of the outer peripheral end surface of the first light guide plate is a first light incident end surface opposite to the first light source, and one main surface is a fourth light emitting main surface for emitting light. The main surface of the second prism sheet on the light-emitting side is arranged opposite to the first light-incident main surface of the first sheet. The first prism has: an inclined third slope rising from the first light source side of the first prism sheet in the first direction to the opposite side thereof; and an inclined fourth oblique surface rising from a side of the first prism sheet opposite to the first light source in the first direction toward the first light source, The second prism has: an inclined fifth oblique surface rising from the first light source side of the second prism sheet in the first direction to the opposite side thereof; and an inclined sixth inclined surface, which stands from the side of the second prism sheet opposite to the first light source in the first direction toward the first light source, An angle formed by the fifth inclined surface in the second prism relative to the first direction is smaller than an angle formed by the third inclined surface in the first prism relative to the first direction.

9. The lighting device according to claim 8, characterized in that The lighting device comprises: Second light source; as well as a second light guide plate arranged along the first direction relative to the second light source, At least a portion of the outer peripheral end surface of the second light guide plate is a second light incident end surface opposite to the second light source, one principal surface is a fifth light emitting principal surface for emitting light, and the other principal surface is an opposite principal surface opposite to the third light emitting principal surface and provided with a second lens. The second lens has an inclined seventh slope that stands from a side of the second light guide plate opposite to the second light source in the first direction toward the second light source.

10. A display device, characterized in that: It includes: The lighting device according to any one of claims 1 to 9; as well as A display panel that performs display using the light from the lighting device.

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