Lighting devices and display devices

Abstract

Provided are an illumination device and a display device that suppress the emission of light outside a limited angle range and improve the brightness of light emitted in a direction inclined relative to the front direction. The illumination device (12) comprises: a first light source (13); a first light guide plate (14) having a first end surface (14A) opposite to the first light source (13), a first main surface (14B), and a second main surface (14C); a first sheet (18) having a third main surface (18A) and a fourth main surface (18B) arranged toward the first main surface (14B); a second light source (24); and a second light guide plate (25) having a second end surface (25A) opposite to the second light source (24), a fifth main surface (25B), and a sixth main surface (25C) arranged toward the fourth main surface (18B).

Description

Technical Field

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

[0002] Conventionally, as an example of a lighting device, there is a device described in the following Patent Document 1. The lighting device described in Patent Document 1 operates in at least two operating modes, namely, a free view mode and a restricted view mode. The lighting device includes a backlight system. A light guide plate is arranged in front of the backlight system, and a light source is arranged along the side of the light guide plate. The light guide plate has a light transmittance of at least 80% by dispersing diffusion particles composed of a polymer in a resin matrix. In the free view mode, the backlight system is turned on and the light source is turned off. In the restricted view mode, the light source is turned on and the backlight system is turned off.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: U.S. Patent Application Publication No. 2017 / 0069236 Summary of the Invention

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

[0007] The light guide plate included in the lighting device described in Patent Document 1 contains diffusing particles. Therefore, in the restricted field of view mode, light emitted from the light source and incident on the light guide plate is diffused by the diffusing particles. Therefore, in the restricted field of view mode, light is easily emitted outside the restricted angle range, and there is a problem that it is difficult to emit light within the restricted angle range. In addition, the light transmittance of the light guide plate is at least as high as 80%. Therefore, in the free field of view mode, the light from the backlight system is not fully diffused during the process of passing through the light guide plate. Therefore, in the free field of view mode, there is a problem of insufficient brightness of the emitted light in a direction inclined relative to the front direction.

[0008] The technology described in this specification has been accomplished based on the above circumstances, and its purpose is to suppress the emission of light outside a limited angle range and to increase the brightness of the emitted light in a direction oblique to the front direction.

[0009] Technical solutions to technical problems

[0010] (1) The lighting device related to the technology described in this specification comprises: a first light source; a first light guide plate, at least a portion of its outer peripheral end surface is opposite to the first light source and is provided as a first end surface for light incidence, one principal surface of which is a first principal surface for light emission, and the other principal surface is a second principal surface; a first sheet, one principal surface of which is a third principal surface arranged toward the first principal surface and provided as light incidence, and the other principal surface is a fourth principal surface for light emission; a second light source; and a second light guide plate, at least a portion of its outer peripheral end surface is provided as a second end surface opposite to the second light source and provided as light incidence, The principal surface of one side is the fifth principal surface for emitting light, and the principal surface of the other side is the sixth principal surface arranged toward the fourth principal surface. The first sheet has at least: two first light-shielding portions, which are arranged at intervals in a first direction including a direction from the first light source toward the first light guide plate and block light; and a first light-transmitting portion, which is arranged between the two first light-shielding portions and allows light to pass through. The sixth principal surface of the second light guide plate is provided with a first lens, which has an inclined first slope rising from the side of the first direction opposite to the second light source toward the second light source side.

[0011] (2) In addition, the lighting device described above, in accordance with (1) above, may be configured such that the angle formed by the first inclined surface relative to the first direction is within a range of 27° to 40°.

[0012] (3) In addition, the lighting device described above, in addition to (1) or (2), may be configured such that the first lens has a second inclined surface that rises from the second light source in the first direction toward the opposite side.

[0013] (4) In addition, the lighting device described above, in accordance with (3) above, may be configured such that the angle formed by the second inclined surface relative to the first direction is within a range of 3° to 10°.

[0014] (5) In addition, the above-mentioned lighting device can also be constructed based on the above-mentioned (3) or (4), wherein the first lens has a first plane along the first direction, and the first plane is located between the first inclined surface and the second inclined surface in the first direction.

[0015] (6) In addition, the above-mentioned lighting device can also be constructed based on any one of the above-mentioned (3) to (5), wherein a plurality of the first lenses are arranged in the first direction, and a second plane along the first direction is provided on the sixth main surface of the second light guide plate, and the second plane is located between two adjacent first lenses in the first direction.

[0016] (7) In addition, the above-mentioned lighting device can also be constructed based on the above-mentioned (1) or (2), wherein the first lens has a first plane along the first direction, the first plane is arranged adjacent to the first inclined surface in the first direction, a plurality of first lenses are arranged in the first direction, and among the three first lenses included in the plurality of first lenses and arranged continuously in the first direction, the first inclined surface possessed by the first lens located in the center of the first direction is connected to the first plane possessed by the first lens adjacent to the side opposite to the second light source in the first direction, and the first plane possessed by the first lens located in the center of the first direction is connected to the first inclined surface possessed by the first lens adjacent to the second light source side in the first direction.

[0017] (8) In addition, the above-mentioned lighting device can also be constructed based on any one of the above-mentioned (1) to (7), wherein a second lens extending along the first direction is provided on the fifth main surface of the second light guide plate, and a plurality of the second lenses are arranged along a second direction orthogonal to both the first direction and the normal direction of the main surface of the first light guide plate.

[0018] (9) In addition, the above-mentioned lighting device can also be constructed based on any one of the above-mentioned (1) to (8), wherein a third lens extending along the first direction is provided on the sixth main surface of the second light guide plate, and a plurality of the third lenses are arranged at intervals along the second direction, 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 plurality of the first lenses are arranged in a manner alternating with the third lenses in the second direction.

[0019] (10) In addition, based on the above (9), the above-mentioned lighting device can also be constructed as follows: the multiple third lenses include a central side third lens and an end side third lens that is located on the end side of the second direction more than the central side third lens on the sixth principal surface; the multiple first lenses include a central side first lens and an end side first lens that is located on the end side of the second direction more than the central side first lens on the sixth principal surface; the size of the end side third lens in the second direction is smaller than the size of the central side third lens in the second direction, and the size of the end side first lens in the second direction is larger than the size of the central side first lens in the second direction.

[0020] (11) In addition, the above-mentioned lighting device can also be constructed based on any one of the above-mentioned (1) to (10), wherein a plurality of the first lenses are arranged in the first direction, and the plurality of first lenses include: a first lens on one side, which has a gentle slope as the first slope; and a first lens on the other side, which has a steep slope as the first slope, and the steep slope has a larger angle relative to the first direction than the gentle slope.

[0021] (12) In addition, the lighting device described above may be configured based on any one of the above (1) to (11), and may include: a first prism sheet, one main surface of which is arranged opposite to the first main surface, and having a first prism sheet, a plurality of which are arranged along the first direction, and having a first prism extending along 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; and a second prism sheet, which is located on the side opposite to the first light guide plate relative to the first prism sheet, and having a second prism, a plurality of which are arranged along the first direction, and extending along the second direction, the first prism having: an inclined third slope, The second prism comprises: a first prism sheet having a first light source side extending from the first direction of the first prism sheet to the opposite side thereof; and a fourth slant extending from the first direction of the first prism sheet to the opposite side thereof; the second prism comprises: a fifth slant extending from the first light source side extending from the first direction of the second prism sheet to the opposite side thereof; and a sixth slant extending from the first direction of the second prism sheet to the opposite side thereof; the angle formed by the fifth slant in the second prism relative to the first direction is smaller than the angle formed by the third slant in the first prism relative to the first direction.

[0022] (13) In addition, the above-mentioned lighting device can also be constructed based on any one of the above-mentioned (1) to (12), comprising: a second sheet, one main surface of which is opposite to the fourth main surface and is set as the seventh main surface for light incidence, and the other main surface is set as the eighth main surface for light emission; and a third sheet, one main surface of which is opposite to the eighth main surface and is set as the ninth main surface for light incidence, and the other main surface is opposite to the sixth main surface and is set as the tenth main surface for light emission, the second sheet has a fourth lens, the fourth lens is arranged on the seventh main surface or the eighth main surface, the third sheet has at least: two second light-shielding portions, which are arranged at intervals in the first direction and block light; and a second light-transmitting portion, which is arranged between the two second light-shielding portions and allows light to pass through, the fourth lens has an inclined seventh inclined surface, which stands from the end side of the first direction in the second sheet toward the center side, and in the third sheet, 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.

[0023] (14) In addition, the above-mentioned lighting device can also be constructed based on any one of the above-mentioned (1) to (13), wherein the first light source is arranged on one side of the first direction relative to the first light guide plate, and the second light source is arranged on the other side of the first direction relative to the second light guide plate.

[0024] (15) A display device related to the technology described in this specification includes: an illumination device described in any one of (1) to (14) above; and a display panel that uses light from the illumination device to perform display.

[0025] Beneficial effects

[0026] According to the technology described in this specification, it is possible to suppress the emission of light outside a limited angle range, and to increase the brightness of light emitted in a direction oblique to the front direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a side cross-sectional view of the liquid crystal display device according to the first embodiment.

[0028] Figure 2 This is a side cross-sectional view of a backlight device included in a liquid crystal display device.

[0029] Figure 3 It is a front cross-sectional view of the backlight device.

[0030] 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.

[0031] Figure 5 It is a bottom view showing the structure of the first opposite main surface of the first light guide plate.

[0032] Figure 6 It is a side cross-sectional view of the second light guide plate constituting the backlight device.

[0033] Figure 7 It is a bottom view showing the structure of the second opposite main surface of the second light guide plate.

[0034] Figure 8 Graph showing the relationship between the position of the second light guide plate in the X-axis direction and the width W2 of the sixth light guide plate inclined surface, the width W3 of the seventh light guide plate inclined surface, and the width W5 of the second flat surface.

[0035] Figure 9 Graph showing the relationship between the position of the second light guide plate in the X-axis direction and the height of the sixth light guide plate lens.

[0036] Figure 10 This is a graph showing the light distribution when the inclination of the sixth light guide plate is changed in Experiment 1.

[0037] Figure 11 This is a graph of light distribution when the first LED is turned on and the second LED is turned off in the experimental experiment 2.

[0038] Figure 12 This is a graph of light distribution when the second LED is turned on and the first LED is turned off in the experimental experiment 2.

[0039] Figure 13 This is a graph of light distribution when both the first LED and the second LED are turned on in Demonstration Experiment 2.

[0040] Figure 14 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.

[0041] Figure 15 This is a table showing the experimental results of Comparative Experiment 1.

[0042] Figure 16 This is a graph showing the light distribution of the reference example, comparative examples 1 to 3, and example 1 in comparative experiment 1.

[0043] Figure 17 Graph showing light distribution when the inclination angle θ3 of the inclined surface of the seventh light guide plate is changed in Experiment 3.

[0044] Figure 18 It will Figure 17 A magnified portion of the chart.

[0045] Figure 19This is a graph showing the relationship between the inclination angle θ3 of the inclined surface of the seventh light guide plate and the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction in Experiment 3.

[0046] Figure 20 This is a graph showing the relationship between the apex angle θ1 of the fifth light guide plate lens and the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction in Experiment 4.

[0047] Figure 21 This is a graph showing the relationship between the vertex angle θ1 and the brightness at 0° in the light distribution in the X-axis direction in Experiment 4.

[0048] Figure 22 This is a graph showing the relationship between the contact angle θc of the fourth light guide plate lens and the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction in Experiment 5.

[0049] Figure 23 This is a graph showing the relationship between the contact angle θc of the fourth light guide plate lens and the brightness at 0° in the light distribution in the X-axis direction in Experiment 5.

[0050] Figure 24 This is a side cross-sectional view of a liquid crystal display device according to a second embodiment.

[0051] Figure 25 is a side sectional view of a backlight device.

[0052] Figure 26 It is a front cross-sectional view of a second light guide plate according to the third embodiment.

[0053] Figure 27 Graph showing the relationship between the position of the second light guide plate in the Y-axis direction and the width of the fifth light guide plate lens.

[0054] Figure 28 This is a table showing the experimental results of comparative experiment 2.

[0055] Figure 29 This is a graph showing the light distribution at the center position in the Y-axis direction of Example 2 and Example 3 in Comparative Experiment 2.

[0056] Figure 30 It is a side sectional view of the second light guide plate of the fourth embodiment.

[0057] Figure 31 This is a graph of light distribution when the first LED is turned on and the second LED is turned off in Demonstration Experiment 6.

[0058] Figure 32This is a graph of light distribution when the second LED is turned on and the first LED is turned off in Demonstration Experiment 6.

[0059] Figure 33 This is a graph of light distribution when both the first LED and the second LED are turned on in Demonstration Experiment 6.

[0060] Figure 34 It is a side cross-sectional view of the second light guide plate of the fifth embodiment.

[0061] Figure 35 It is a front cross-sectional view of a second light guide plate and an anisotropic diffusion sheet according to the sixth embodiment.

[0062] Figure 36 It is a front cross-sectional view of a second light guide plate according to the seventh embodiment. DETAILED DESCRIPTION

[0063] <First embodiment>

[0064] pass Figures 1 to 23 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.

[0065] 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.

[0066] 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 .

[0067] Next, the backlight device 12 will be described. Figure 1 As shown, the backlight device 12 comprises at least: a first LED (first light source) 13; a first light guide plate 14 for guiding light from the first LED 13; a reflective sheet 15 arranged on the back side (light-emitting side) of the first light guide plate 14; a first prism sheet 16 arranged on the front side (light-emitting side) of the first light guide plate 14; and a second prism sheet 17 arranged on the front side of the first prism sheet 16.

[0068] 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.

[0069] 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 in the shape of a plate, and its main surface is parallel to the main surface of the liquid crystal panel 11. In addition, the main surface of the first light guide plate 14 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The first light guide plate 14 is arranged along the X-axis direction (first direction) relative to the first LED 13, and is arranged along the Z-axis direction relative to the liquid crystal panel 11 and each prism sheet 16, 17. The first light guide plate 14 is arranged on one side of the X-axis direction (the first direction) relative to the first LED 13. Figure 1 on the right side). One of the outer peripheral end faces of the first light guide plate 14 is the first light incident end face (first end face) 14A opposite to the first light emitting surface 13A of the first LED 13. The first light incident end face 14A is a face parallel to the first light emitting surface 13A of the first LED 13, and the light emitted from the first light emitting surface 13A is incident on the first light incident end face 14A. Therefore, it can be said that the first LED 13 is arranged only on a single side in the X-axis direction in the first light guide plate 14, and the first light guide plate 14 and the first LED 13 together constitute a single-side light-incoming type backlight unit. The main surface on the front side opposite to the first prism sheet 16 of the pair of main surfaces of the first light guide plate 14 is the first light guide plate light-emitting main surface (first main surface) 14B from which the 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 (second main surface) 14C located on the side opposite to the first light guide plate light-emitting main surface 14B. The first light guide plate 14 has the following function: it guides light emitted from the first LED 13 into the first light guide plate 14 through the first light incident end surface 14A, propagates the light internally, and then rises along the Z-axis toward the front side (light output side) for emission. The detailed structure of the first light guide plate 14 will be described later. Furthermore, the normal direction of the first light incident end surface 14A coincides with the X-axis direction (the direction in which the first LED 13 and the first light guide plate 14 are arranged).

[0070] 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.

[0071] like Figure 1As 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.

[0072] like Figure 1 As 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.

[0073] like Figure 2As 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.

[0074] Moreover, if Figure 2As 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 θ4 of the first prism 16B with respect to the X-axis direction is greater than the same inclination angle θ7 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.

[0079] 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 slope 17B2 of the second prism 17B, then rises and exits, or travels toward the third prism slope 17B1. Since the inclination angle θ7 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 slope 17B2 and directed toward the third prism slope 17B1 is more likely to return to the first prism sheet 16 via the third prism slope 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 and returning to the second prism sheet 17, travels upward and exits via one of the pair of slopes 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 in which the distance from the first light guide plate main light-emitting surface 14B (the portion where the third light guide plate lens 23 is not provided) becomes smaller the further 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 light output main surface 14B increases in the X-axis direction, that is, a slope opposite to that of 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] However, the vehicle-mounted liquid crystal display device 10 is sometimes arranged, for example, in front of the front passenger seat of a passenger car. In this case, for example, while the passenger car is driving, it is sometimes required to limit the viewing angle so that the display image of the liquid crystal display device 10 can be visually confirmed from the front passenger seat and the display image of the liquid crystal display device 10 cannot be visually confirmed from the driver's seat. Furthermore, for example, while the passenger car is stopped, it is sometimes required not to limit the viewing angle so that the display image of the liquid crystal display device 10 can be visually confirmed from both the front passenger seat and the driver's seat. In addition, the vehicle-mounted liquid crystal display device 10 is set in a posture where the X-axis direction is roughly consistent with the horizontal direction and the Y-axis direction is parallel to the vertical direction. In order to respond to such requirements, Figure 1 As shown, in addition to the above-mentioned components, the backlight device 12 of this embodiment further includes at least a first louver (first sheet) 18 disposed on the front side of the second prism sheet 17, a second LED (second light source) 24, and a second light guide plate 25 disposed on the front side of the first louver 18. Furthermore, to prevent reflections of passenger vehicles on the windshield, the backlight device 12 of this embodiment includes a second louver 30 disposed on the front side of the second light guide plate 25. The second louver 30 will be described later.

[0089] use Figure 1 and Figure 2 The structure of the first louver 18 is described below. Figure 1 As shown, the main surface of the first louver 18 is parallel to the main surfaces of the liquid crystal panel 11 and the first light guide plate 14, and is in the shape of a sheet. In addition, the main surface of the first louver 18 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The first louver 18 has the function of limiting the range of the output angle of light in the X-axis direction. The first louver 18 has a first light-entering main surface (third main surface) 18A on the inner side and a first light-emitting main surface (fourth main surface) 18B on the front side. The first light-entering main surface 18A is opposite to the main surface on the front side (light-emitting side) of the second prism sheet 17. The first light-emitting main surface 18B is opposite to the second opposite main surface 25C of the second light guide plate 25 described later.

[0090] like Figure 2The 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 through. The first light-blocking portion 18C is made of, for example, a light-blocking resin material (light-blocking material) that is black and blocks light. The first light-blocking portion 18C is in the form of a layer extending along the Y-axis direction and the Z-axis direction, and a plurality of the first light-transmitting portions 18D are arranged at intervals in the X-axis direction. The first light-transmitting portions 18D are in the form of a layer extending along the Y-axis direction and the Z-axis direction, and a plurality of the first light-transmitting portions 18D are arranged at intervals in the X-axis direction. The plurality of first light-blocking portions 18C and the first light-transmitting portions 18D are arranged alternately and repeatedly in the X-axis direction. Therefore, the first light-transmitting portion 18D is located between two first light-blocking portions 18C that are adjacent to each other and spaced apart in the X-axis direction, and the first light-blocking portion 18C is located between two first light-transmitting portions 18D that are adjacent to each other and spaced apart 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 in the X-axis direction, and is emitted from the first light-emitting main surface 18B. The emission angle of the light emitted from the first light-emitting main surface 18B in the X-axis direction is limited by the two first light-shielding portions 18C adjacent in the X-axis direction. In addition, the emission angle of the light emitted from the first light-emitting main surface 18B in the Y-axis direction is not limited by the first louver 18. The emission angle range of the light emitted from the first light-emitting main surface 18B in the X-axis direction is defined by two straight lines that connect the respective ends of the two first light-shielding portions 18C sandwiching the first light-transmitting portion 18D in the Z-axis direction in a diagonally opposite manner. The emission angle range of the light transmitted by the first light-transmitting portion 18D in the X-axis direction varies according to the ratio of the width W1 to the height H1 of the first light-transmitting portion 18D. 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 collectively support the plurality of first light-blocking portions 18C and the plurality of first light-transmitting portions 18D.

[0091] Specifically, if Figure 2Indicates that the ratio of the width W1 of the first light-transmitting portion 18D of the first louver 18 divided by the height H1 is equal to "tan10°". In this way, the absolute value of the maximum angle formed by the light passing through the first light-transmitting portion 18D relative to the Z-axis direction is 10°. Assuming that the ratio obtained by dividing the width of the first light-transmitting portion 18D by the height is greater than "tan10°", the emission angle range of the outgoing light of the backlight device 12 is sufficiently narrowed. Therefore, it is preferable in terms of limiting the viewing angle so that the display image of the liquid crystal display device 10 can be visually confirmed from the passenger seat, but the display image of the liquid crystal display device 10 cannot be visually confirmed from the driver's seat. In addition, compared with the case where the ratio obtained by dividing the width of the first light-transmitting portion 18D by the height is less than "tan10°", the amount of light blocked by the first light-blocking portion 18C is reduced, and the light utilization efficiency is improved.

[0092] Appropriate use Figures 1 to 3 、 Figure 6 and Figure 7 The configuration of the second LED 24 and the second light guide plate 25 will be described. Figure 6 It is an enlarged cross-sectional view of the second light guide plate 25 among the components of the backlight device 12 . Figure 7 2 is a bottom view showing the main surface of the back side of the second light guide plate 25. Figure 1 As shown, the second LED 24 is roughly block-shaped, and one of a pair of surfaces along the Y-axis direction and the Z-axis direction is set as 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 a structure in which an LED chip is sealed on a substrate portion mounted on the LED substrate using a sealing material. The LED chip possessed by the second LED 24 emits, for example, monochromatic blue light. Phosphors are dispersed and combined in the sealing material possessed by 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.

[0093] 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 1 As shown, the second light guide plate 25 is in the shape of a plate, and its main surface is parallel to the main surface of the liquid crystal panel 11 and the like. In addition, the main surface of the second light guide plate 25 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The second light guide plate 25 is arranged along the X-axis direction (first direction) relative to the second LED 24, and is arranged along the Z-axis direction relative to the liquid crystal panel 11 and the first blind 18 and the like. The second light guide plate 25 is arranged on the other side of the X-axis direction (the first direction) relative to the second LED 24. Figure 1That is, the positional relationship between the second light guide plate 25 and the second LED 24 in the X-axis direction is opposite to the positional relationship between the first light guide plate 14 and the first LED 13 in the X-axis direction. Thus, the first LED 13 and the second LED 24 are dispersed in the X-axis direction. Therefore, even if the first LED 13 and the second LED 24 are both turned on, heat is less likely to accumulate.

[0094] like Figure 1 As shown, one of the outer peripheral end surfaces of the second light guide plate 25 serves as a second light incident end surface (second end surface) 25A, which is opposite the second light-emitting surface 24A of the second LED 24. The second light incident end surface 25A is parallel to the second light-emitting surface 24A of the second LED 24, and light emitted from the second light-emitting surface 24A enters this second light incident end surface 25A. Therefore, it can be said that the second LED 24 is disposed only on one side of the second light guide plate 25 in the X-axis direction, and the second light guide plate 25 and the second LED 24 together constitute a single-side light-incoming backlight unit. Of the pair of principal surfaces of the second light guide plate 25, the front principal surface facing the second louver 30, described later, serves as the second light guide plate light-emitting principal surface (fifth principal surface) 25B, from which light guided internally is emitted. Of the pair of principal surfaces of the second light guide plate 25, the rear principal surface facing the third louver 20 serves as the second opposite principal surface (sixth principal surface) 25C, located opposite the second light guide plate light-emitting principal surface 25B. The second opposite main surface 25C of the second light guide plate 25 is configured in a manner that faces the first light emitting main surface 18B of the first louver 18 in the Z-axis direction. Moreover, the second light guide plate 25 is capable of introducing light emitted from the second LED 24 toward the second light guide plate 25 from the second light incident end surface 25A, and after the light propagates 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 11 on the front side (light emitting side). In addition, the second light guide plate 25 is capable of introducing the exit light from the first louver 18 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 second louver 30 (liquid crystal panel 11) 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).

[0095] like Figure 2 and Figure 3 As shown, a fourth light guide plate lens (second lens) 26, a fifth light guide plate lens (third lens) 27, and a sixth light guide plate lens (first lens) 28 are provided on the second light guide plate 25. Figure 3As shown, 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 a plurality of them are arranged along the Y-axis direction. In this embodiment, the fourth light guide plate lens 26 is a so-called double convex lens. The fourth light guide plate lens 26 is convex and protrudes from the second light guide plate light emitting main surface 25B to the front side. Specifically, the fourth light guide plate lens 26 is a semi-cylindrical shape having a semicircular cross-section cut along the Y-axis direction and extending in a straight line along the X-axis direction, and its surface is a second arc-shaped surface 26A. When the angle formed by the tangent of the base end of the second arc-shaped surface 26A relative to the Y-axis direction is set as the "contact angle", the contact angle θc of the fourth light guide plate lens 26 is, for example, about 30°. The contact angle θc, width dimension (arrangement interval) and height dimension of the plurality of fourth light guide plate lenses 26 arranged along the Y-axis direction are all substantially the same. In order to set the fourth light guide plate lens 26 constructed in this way as a whole with the second light guide plate 25, for example, it is only necessary to manufacture the second light guide plate 25 by injection molding, and pre-form a transfer shape for transferring the fourth light guide plate lens 26 on the molding surface used to mold the second light guide plate main light emitting surface 25B in the molding mold.

[0096] like Figure 3 Indicates that 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 extends along the X-axis direction, and a plurality of them are arranged along the Y-axis direction. In this embodiment, the fifth light guide plate lens 27 is a convex prism protruding from the second opposite main surface 25C to the back side. In detail, the cross-sectional shape of the fifth light guide plate lens 27 cut along the Y-axis direction is roughly triangular (roughly mountain-shaped), and extends in a straight line along the X-axis direction. The width dimension (dimension in the Y-axis direction) of the fifth light guide plate lens 27 is constant over the entire length in the X-axis direction. The cross-sectional shape of the fifth light guide plate lens 27 is roughly an isosceles triangle, and has a pair of fifth light guide plate inclined surfaces 27A. The vertex angle θ1 of the fifth light guide plate lens 27 is preferably an obtuse angle (an angle exceeding 90°), specifically preferably in the range of 100° to 150°, and most preferably 140°. The plurality of fifth light guide plate lenses 27 arranged along the Y-axis have substantially the same vertex angle θ1, width (arrangement spacing), and height. In this embodiment, the arrangement spacing of the fifth light guide plate lenses 27 is greater than the arrangement spacing of the fourth light guide plate lenses 26. To integrally incorporate the fifth light guide plate lenses 27 thus configured into the second light guide plate 25, for example, by manufacturing the second light guide plate 25 by injection molding, it is sufficient to pre-form a transfer shape for transferring the fifth light guide plate lenses 27 onto the molding surface of the second opposite principal surface 25C in the mold used for molding the fifth light guide plate lenses 27.

[0097] like Figure 2As 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 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 2 The sixth light guide plate inclined surface (first inclined surface) 28A, the second LED 24 side ( Figure 2 The sixth light guide plate inclined surface 28A has a first plane 28D 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 28D located between the second LED 24 side ( Figure 2 to the right side) toward the opposite side ( Figure 2 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 2 Left side) toward the second LED24 side ( Figure 2 The first plane 28D 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.

[0098] like Figure 2 As shown, the sixth light guide plate inclined surface 28A reflects the light propagating in the second light guide plate 25 and promotes the light to be emitted from the second light guide plate main light emitting surface 25B by rising toward the front side. Specifically, the sixth light guide plate inclined surface 28A mainly acts to reflect and rise the light traveling away from the second LED 24 in the X-axis direction in the second light guide plate 25. Specifically, as shown in FIG. Figure 6As shown, the inclination angle (angle) θ2 of the sixth light guide plate inclined surface 28A relative to the X-axis direction is, for example, less than 40°, preferably about 27°. If the inclination angle θ2 of the sixth light guide plate inclined surface 28A relative to the X-axis direction is less than 40°, the light can be made to rise in a direction inclined toward the side opposite to the second LED 24 side in the X-axis direction relative to the front direction. Therefore, in the outgoing light from the second light guide plate main light-emitting surface 25B, the light on the side opposite to the second LED 24 side in the X-axis direction relative to the Z-axis direction (the normal direction of the second light guide plate main light-emitting surface 25B) contains more light than the light on the second LED 24 side in the X-axis direction. Therefore, if the second LED 24 is turned on, it is possible to provide outgoing light with a brightness angle distribution in which the peak brightness of the outgoing light is biased toward the side opposite to the second LED 24 side in the X-axis direction. In the vehicle-mounted liquid crystal display device 10 installed in front of the front passenger seat of a passenger car, the second LED 24 is preferably arranged on the side opposite to the driver's seat side in the X-axis direction.

[0099] According to such a configuration, for example, during the travel of a passenger car, Figure 1 As shown, the first LED 13 is illuminated and the second LED 24 is deactivated. Thus, the angular range of light emitted from the second light guide plate main light exit surface 25B of the second light guide plate 25 is limited by the first light shielding portion 18D of the first louver 18, making it difficult for light to be emitted outside the limited angular range. Therefore, when the first LED 13 is illuminated and the second LED 24 is deactivated, light is selectively emitted from the backlight device 12 into the limited angular range. Therefore, while the image displayed on the liquid crystal display device 10 can be visually recognized from the passenger seat, the image displayed on the liquid crystal display device 10 cannot be visually recognized from the driver's seat. In contrast, for example, when the passenger car is stopped, both the first LED 13 and the second LED 24 are illuminated. Thus, the light emitted from the second light guide plate main light exit surface 25B of the second light guide plate 25 includes: light from the first LED 13, whose angular range is limited by the first louver 18; and light from the second LED 24, whose peak brightness is biased toward the side of the X-axis direction opposite to the side of the second LED 24, with a brightness angle distribution. Therefore, when both the first LED 13 and the second LED 24 are illuminated, the backlight device 12 emits light having a brightness angle distribution with a peak brightness shifted toward the side opposite to the second LED 24 in the X-axis direction, in addition to the light emitted within the restricted angle range. This allows the image displayed on the liquid crystal display device 10 to be visually recognized from both the driver's seat and the passenger seat. In this way, by controlling the driving of the second LED 24 according to the driving conditions of the passenger vehicle, it is possible to adjust whether the displayed image can be visually recognized from the driver's seat.

[0100] On the other hand, Figure 2As shown, the seventh light guide plate inclined surface 28B can reflect the light traveling close to the second LED 24 in the X-axis direction and make it rise, or reflect the light traveling in the second light guide plate 25 away from the second LED 24 in the X-axis direction and further guide it away from the second LED 24. Specifically, as Figure 6 As shown, the inclination angle (angle) θ3 of the seventh light guide plate inclined surface 28B relative to the X-axis direction is, for example, in the range of 3° to 10°, preferably approximately 3°. The inclination angle θ3 of the seventh light guide plate inclined surface 28B is smaller than the inclination angle θ2 of the sixth light guide plate inclined surface 28A. With the seventh light guide plate inclined surface 28B thus configured, light traveling through the second light guide plate 25 toward the second LED 24 in the X-axis direction is refracted by the seventh light guide plate inclined surface 28B and then travels toward the side of the light guide plate 25 opposite to the front direction in the X-axis direction from the second LED 24. This further improves the brightness of light emitted in a direction oblique to the front direction. Furthermore, light traveling through the second light guide plate 25 away from the second LED 24 in the X-axis direction is refracted by the seventh light guide plate inclined surface 28B and then further away from the second LED 24. This makes it less likely that light emitted from the second light guide plate's main light-emitting surface 25B will deviate toward the second LED 24 in the X-axis direction.

[0101] like Figure 2 As shown, first plane 28D and second plane 29 are parallel to the X-axis and Y-axis directions, and their normals are aligned with the Z-axis. Light emitted from first light guide plate light-emitting principal surface 14B of first light guide plate 14 and incident on second opposite principal surface 25C of second light guide plate 25 travels with little or no refraction even if it strikes either first plane 28D or second plane 29. Therefore, compared to a configuration where sixth light guide plate inclined surface 28A and seventh light guide plate inclined surface 28B are directly connected without passing through first plane 28D, or where two sixth light guide plate lenses 28 adjacent in the X-axis direction are directly connected without passing through second plane 29, the generation of sidelobe light that travels in a direction inclined relative to the front direction toward the side of the X-axis direction opposite to the second LED 24 can be suppressed.

[0102] like Figure 6 and Figure 7As shown, the plurality of sixth light guide plate lenses 28 arranged along the X-axis are designed such that their height dimension (Z-axis dimension) H2 increases as they are further away from the second LED 24 in the X-axis direction, while maintaining a constant arrangement pitch (arrangement interval) P1 in the X-axis direction. The width dimension (X-axis dimension) W2 of the sixth light guide plate inclined surface 28A increases slightly as they are further away from the second LED 24 in the X-axis direction. The width dimension (X-axis dimension) W3 of the seventh light guide plate inclined surface 28B increases as they are further away from the second LED 24 in the X-axis direction, with a rate of increase higher than that of the sixth light guide plate inclined surface 28A. The width dimension (X-axis dimension) W4 of the first plane 28D remains constant regardless of its position in the X-axis direction. The width dimension (X-axis dimension) W5 of the second plane 29 decreases as it is further away from the second LED 24 in the X-axis direction. The arrangement pitch P1 of the sixth light guide plate lenses 28 in the X-axis direction is the sum of the width W2 of the sixth light guide plate slope 28A, the width W3 of the seventh light guide plate slope 28B, the width W4 of the first plane 28D, and the width W5 of the second plane 29.

[0103] When the length dimension (dimension in the X-axis direction) of the second light guide plate 25 is set to 300 mm, for example, the arrangement pitch P1 of the sixth light guide plate lenses 28 in the X-axis direction is constant at, for example, about 0.114 mm, and the width dimension W4 of the first plane 28D is constant at, for example, about 0.017 mm. When the length dimension (dimension in the X-axis direction) of the second light guide plate 25 is set to 300 mm, for example, the specific values of the width dimension W2 of the sixth light guide plate inclined surface 28A, the width dimension W3 of the seventh light guide plate inclined surface 28B, and the width dimension W5 of the second plane 29 are determined according to the position of the sixth light guide plate lenses 28 in the X-axis direction in the second light guide plate 25. Figure 8 Changes as shown. Figure 8 It is a graph in which the horizontal axis is the position of the second light guide plate 25 in the X-axis direction (unit: "mm"), and the vertical axis is the width dimensions W2, W3, and W5 (unit: "mm") of the sixth light guide plate inclined surface 28A, the seventh light guide plate inclined surface 28B, and the second plane 29. Figure 8 The reference position (0 mm) of the horizontal axis is the position of the second light incident end surface 25A of the second light guide plate 25, and the position of 300 mm is the position of the end surface of the second light guide plate 25 on the side opposite to the second light incident end surface 25A. Figure 8 The solid line is a graph showing the width dimension W2 of the sixth light guide plate inclined surface 28A, the dotted line is a graph showing the width dimension W3 of the seventh light guide plate inclined surface 28B, and the dashed line is a graph showing the width dimension W5 of the second plane 29. When the length dimension of the second light guide plate 25 is set to 300 mm, for example, the specific value of the height dimension H2 of the sixth light guide plate lens 28 is determined according to the position of the sixth light guide plate lens 28 in the X-axis direction in the second light guide plate 25. Figure 9 Changes as shown. Figure 9 The horizontal axis is the position of the second light guide plate 25 in the X-axis direction (unit: "mm"), and the vertical axis is the height dimension H2 (unit: "mm") of the sixth light guide plate lens 28. Figure 9 , the height dimension H2 of the sixth light guide plate lens 28 is ensured to be approximately 0.002 mm (2 μm) at a minimum value. In this way, the ease of resin molding of the second light guide plate 25 can be fully ensured. In order to ensure that the minimum value of the height dimension H2 of the sixth light guide plate lens 28 is approximately 0.002 mm, it is preferred to set the inclination angle θ3 of the seventh light guide plate inclined surface 28B relative to the X-axis direction to be greater than 3°. In addition, the inclination angle θ2 of the sixth light guide plate inclined surface 28A relative to the X-axis direction and the inclination angle θ3 of the seventh light guide plate inclined surface 28B relative to the X-axis direction are respectively constant regardless of the position of the second light guide plate 25 in the X-axis direction.

[0104] like Figure 3 and Figure 7 As shown, the sixth light guide plate lenses 28 configured as described above are arranged between two adjacent fifth light guide plate lenses 27 in the Y-axis direction. Therefore, the sixth light guide plate lenses 28 are arranged alternately with the fifth light guide plate lenses 27 in the Y-axis direction. The maximum value of the height dimension H2 (the protrusion dimension from the second opposite main surface 25C) of the sixth light guide plate lenses 28 is smaller than the height dimension of the fifth light guide plate lenses 27. Therefore, even in the sixth light guide plate lens 28 located farthest from the second LED 24 in the X-axis direction, it does not protrude further to the rear than the fifth light guide plate lens 27.

[0105] Next, use Figure 1 and Figure 3 The structure of the second louver 30 will be described. Figure 1 As shown, the main surface of the second venetian blind 30 is parallel to the main surfaces of the liquid crystal panel 11 and the second light guide plate 25, and is in the shape of a sheet. In addition, the main surface of the second venetian blind 30 is parallel to the X-axis direction and the Y-axis direction, and the normal direction (thickness direction) of the main surface is consistent with the Z-axis direction. The second venetian blind 30 has the function of limiting the range of the output angle of light in the Y-axis direction. The second venetian blind 30 has a second light-entering main surface 30A on the back side and a second light-emitting main surface 30B on the front side. The second light-entering main surface 30A is opposite to the second light guide plate light-emitting main surface 25B of the second light guide plate 25. The second light-emitting main surface 30B is opposite to the main surface on the back side of the liquid crystal panel 11. That is, the second venetian blind 30 is located on the front side of the second light guide plate 25 and is configured on the back side of the liquid crystal panel 11.

[0106] like Figure 3The second louver 30 includes a second light-blocking portion 30C that blocks light and a second light-transmitting portion 30D that allows light to pass through. The second light-blocking portion 30C is made of, for example, a black light-blocking resin material (light-blocking material) that blocks light. The second light-blocking portion 30C is in the form of a layer extending along the X-axis and Z-axis directions, and a plurality of the second light-transmitting portions 30D are arranged at intervals along the Y-axis direction. The second light-transmitting portions 30D are made of a substantially transparent light-transmitting resin material (light-transmitting material) that is translucent and transmits light. The second light-transmitting portions 30D are in the form of a layer extending along the X-axis and Z-axis directions, and a plurality of the second light-transmitting portions 30D are arranged at intervals along the Y-axis direction. Each plurality of second light-blocking portions 30C and second light-transmitting portions 30D are arranged alternately and repeatedly in the Y-axis direction. Therefore, a second light-transmitting portion 30D is located between two second light-blocking portions 30C that are adjacent to each other at intervals along the Y-axis direction, and a second light-blocking portion 30C is located between two second light-transmitting portions 30D that are adjacent to each other at intervals along the Y-axis direction. Light incident on the second light-entering main surface 30A of the second louver 30 passes through the second light-transmitting portion 30D disposed between two second light-shielding portions 30C adjacent in the Y-axis direction, and is emitted from the second light-emitting main surface 30B. The emission angle in the Y-axis direction of the light emitted from the second light-emitting main surface 30B is limited by the two second light-shielding portions 30C adjacent in the Y-axis direction. In addition, the emission angle in the X-axis direction of the light emitted from the second light-emitting main surface 30B is not limited by the second louver 30. The emission angle range in the Y-axis direction of the light emitted from the second light-emitting main surface 30B is defined by two straight lines connecting the respective ends in the Z-axis direction of the two second light-shielding portions 30C sandwiching the second light-transmitting portion 30D in a diagonally opposite manner. The emission angle range in the Y-axis direction of the light transmitted by the second light-transmitting portion 30D varies according to the ratio of the width to the height of the second light-transmitting portion 30D. The ratio of the width of the second light-transmitting portion 30D of the second Venetian blind 30 divided by its height is greater than the ratio of the width W1 of the first light-transmitting portion 18D of the first Venetian blind 18 divided by its height H1. Specifically, the ratio of the width W of the second light-transmitting portion 30D of the second Venetian blind 30 divided by its height is, for example, "tan55°" or greater. Furthermore, the second Venetian blind 30 includes a pair of sheet carriers that sandwich and support the plurality of second light-blocking portions 30C and the plurality of second light-transmitting portions 30D 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 30 and collectively hold the plurality of second light-blocking portions 30C and the plurality of second light-transmitting portions 30D.

[0107] When the liquid crystal display device 10 is installed in a passenger car, using such a second louver 30 can limit the emission angle range of light emitted from the liquid crystal panel 11 to the vertical direction, thereby reducing the reflection of the display image on the windshield.

[0108] To understand how light distribution changes when the inclination angle θ2 of the sixth light guide plate inclined surface 28A of the sixth light guide plate lens 28 of the second light guide plate 25 relative to the X-axis direction is varied, Experiment 1 was conducted. In Experiment 1, a backlight device 12 having the same configuration as described previously in this paragraph was used, except for the configuration of the sixth light guide plate lens 28. In Experiment 1, the inclination angle θ2 of the sixth light guide plate inclined surface 28A of the sixth light guide plate lens 28 relative to the X-axis direction was varied within a range of 27° to 40°. Specifically, in Experiment 1, the inclination angle θ2 was set to 27°, 30°, 32°, 34°, 36°, 38°, and 40°. In the backlight device 12 with the inclination angle θ2 thus varied, the brightness of the emitted light was measured when the second LED 24 was on and the first LED 13 was off, and a graph of the light distribution (brightness angle distribution) in the X-axis direction was created.

[0109] The experimental results of light distribution in empirical experiment 1 are as follows: Figure 10 shown. Figure 10 In the light distribution graph shown, the horizontal axis is the angle of the X-axis relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Figure 10 The positive and negative signs marked on the horizontal axis angle are "-(negative)" indicating that the angle is on the left side of the X-axis direction relative to the reference 0° (front direction) when the backlight device 12 is observed from the front, and "+(positive)" indicating that the angle is on the right side of the X-axis direction relative to the reference 0° (front direction) when the backlight device 12 is observed from the front.

[0110] The experimental results of empirical experiment 1 are explained. Figure 10 , when the inclination angle θ2 is in the range of 27° to 40°, the angle at which the peak brightness is achieved is "-". That is, when the second LED 24 is turned on, the light emitted from the second light guide plate 25 becomes a light distribution that is biased to the left side of the X-axis direction, that is, the side opposite to the second LED 24 side. Moreover, the larger the inclination angle θ2 is, the closer the angle at which the peak brightness is to 0°. On the contrary, the smaller the inclination angle θ2 is, the further away the angle at which the peak brightness is from 0°, and there is a tendency for the absolute value of "-" to become larger. In addition, there is a tendency for the rate of change of the angle to become larger as the inclination angle θ2 becomes smaller. Specifically, when the inclination angle θ2 is 40°, the peak brightness is around -5°, when the inclination angle θ2 is 30°, the peak brightness is around -30°, and when the inclination angle θ2 is 27°, the peak brightness is around -45°.

[0111] Based on the experimental results of Experiment 1, the tilt angle θ2 can be appropriately determined within the range of 27° to 40°, depending on the relative position of the liquid crystal display device 10 and the person viewing the liquid crystal display device 10. For example, in a passenger vehicle with the driver's seat located to the left of the passenger seat, if the liquid crystal display device 10 is positioned in front of the passenger seat, the visual range for viewing the liquid crystal display device 10 from the driver's seat is approximately -20° to -50°. In this case, a tilt angle θ2 of approximately 27° allows peak brightness to be efficiently directed toward the driver's seat at approximately -45°.

[0112] Next, in a backlight device 12 equipped with a second light guide plate 25 having a sixth light guide plate inclined surface 28A with an inclination angle θ2 of 27° relative to the X-axis, a second empirical experiment 2 was conducted to determine how the light distribution changes when only the first LED 13 is illuminated, only the second LED 24 is illuminated, and both the first LED 13 and the second LED 24 are illuminated. In this empirical experiment 2, using the backlight device 12 equipped with a second light guide plate 25 having a sixth light guide plate inclined surface 28A with an inclination angle θ2 of 27°, the luminance of emitted light was measured for each of the following cases: the first LED 13 was illuminated and the second LED 24 was off; the second LED 24 was illuminated and the first LED 13 was off; and both the first LED 13 and the second LED 24 were illuminated. A graph of the light distribution (luminance angular distribution) in the X-axis direction was then generated.

[0113] The experimental results of light distribution in empirical experiment 2 are as follows: Figures 11 to 13 shown. Figures 11 to 13 In the light distribution graph shown, the horizontal axis is the angle of the X-axis relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Figures 11 to 13 The positive and negative signs of the angles of the horizontal axis are the same as Figure 10 The symbols marked on the horizontal axis of the graph have the same meaning. Figure 11 The light distribution when the first LED 13 is turned on and the second LED 24 is turned off is shown. Figure 12 The light distribution when the second LED 24 is turned on and the first LED 13 is turned off is shown. Figure 13 Indicates the light distribution when both the first LED 13 and the second LED 24 are turned on. Figures 11 to 13 In FIG. 1 , the dotted line indicates an angle (−45°) at which the peak brightness is achieved when the second LED 24 is turned on in the second light guide plate 25 in which the inclination angle θ2 of the sixth light guide plate inclined surface 28A is 27°.

[0114] The experimental results of empirical experiment 2 are explained. Figure 11 The light distribution has a peak brightness of approximately 0° and an emission angle range of approximately ±10°. This result can be said to reflect that the light emitted from the first light guide plate 14 is limited to an emission angle range of approximately ±10° by the first louver 18 as the first LED 13 is turned on. Figure 11 It can be seen that there is almost no outgoing light near -45°. Figure 12 The light distribution of is consistent with the light distribution when the inclination angle θ2 is set to 27° in the experimental experiment 1. Figure 12 The light distribution is biased to the left side in the X-axis direction, that is, to the side opposite to the second LED 24 side, so that the peak brightness is around -45°, and the emission angle range is about -80° to 0°. Figure 13 The light distribution is Figure 11 Light distribution and Figure 12 That is, Figure 13 In the light distribution, the peak brightness exists around 0° and -45°.

[0115] To supplement Figures 11 to 13 The diagram shown indicates Figure 14 . Figure 14 This is a diagram for explaining the angle of the X-axis direction relative to the front direction of the liquid crystal display device 10 installed in front of the passenger seat of a passenger car. Figure 14 The figure shows the shading range (+10° to +90°, -10° to -90°) of the first blind 18, the visual confirmation range (-20° to -50°) when the liquid crystal display device 10 is visually confirmed from the driver's seat on the left side relative to the passenger seat, and the peak brightness (-45°) when the tilt angle θ2 is set to 27°. Figure 11 and Figure 14 If the first LED 13 is turned on and the second LED 24 is turned off, the peak brightness is approximately 0°, and the emission angle range is approximately ±10°. Therefore, it can be said that the display image of the liquid crystal display device 10 is almost impossible to visually confirm from the driver's seat, and the display image of the liquid crystal display device 10 can be visually confirmed well from the passenger seat at 0°. Figure 12 and Figure 14 If the second LED 24 is turned on and the first LED 13 is turned off, the peak brightness is around -45° and the emission angle range is around -80° to 0°. Therefore, it can be said that the image displayed on the liquid crystal display device 10 is almost impossible to be visually confirmed from the passenger seat at 0°, and the image displayed on the liquid crystal display device 10 can be visually confirmed well from the driver's seat. Figure 13 and Figure 14If both the first LED 13 and the second LED 24 are turned on, the peak brightness exists near approximately 0° and -45°, so it can be said that the display image of the liquid crystal display device 10 can be visually confirmed well from both the driver's seat and the passenger seat.

[0116] Next, to verify the superiority of the backlight device 12 and the liquid crystal display device 10 according to this embodiment, the following comparative experiment 1 was conducted. In this comparative experiment 1, a backlight device 12 having the following configuration was used as Example 1: the contact angle θc of the fourth light guide plate lens 26 of the second light guide plate 25 was set to 49°, the apex angle θ1 of the fifth light guide plate lens 27 was set to 110°, the inclination angle θ2 of the sixth light guide plate inclined surface 28A of the sixth light guide plate lens 28 was set to 27°, and the inclination angle θ3 of the seventh light guide plate inclined surface 28B was set to 40°. In the second light guide plate 25 of Example 1, the contact angle θc of the fourth light guide plate lens 26, the apex angle θ1 of the fifth light guide plate lens 27, and the inclination angle θ3 of the seventh light guide plate inclined surface 28B were intentionally different from those of the second light guide plate 25 of the backlight device 12 described previously in this paragraph, and were set to produce a significant amount of sidelobe light. The reason is to make it easier to understand the differences from Comparative Examples 1 to 3 described below. In Comparative Experiment 1, a backlight device having a structure in which the sixth light guide plate lens 28 is removed from the second light guide plate 25 of Example 1 is set as Comparative Example 1. In Comparative Experiment 1, a backlight device having a structure in which the fourth light guide plate lens 26 is removed from the second light guide plate 25 of Example 1 is set as Comparative Example 2. In Comparative Experiment 1, a backlight device having a structure in which the fourth light guide plate lens 26 and the fifth light guide plate lens 27 are removed from the second light guide plate 25 of Example 1 is set as Comparative Example 3. In Comparative Experiment 1, a backlight device having a structure in which the fourth light guide plate lens 26, the fifth light guide plate lens 27, and the sixth light guide plate lens 28 are removed from the second light guide plate 25 of Example 1 is set as a reference example. The second light guide plate of the reference example is a flat plate whose two main surfaces are flat. In comparative experiment 1, the first LED 13 is turned on in each backlight device of the reference example, comparative examples 1 to 3, and embodiment 1, the brightness of the emitted light when the second LED 24 is off is measured, the peak brightness is calculated, and a graph of the light distribution in the X-axis direction (brightness angle distribution) is prepared. The peak brightness is a relative value with the peak brightness of the reference example as a benchmark (100%). On this basis, the ratio of light at each angle of -25°, -35°, and -45° in the light distribution in the X-axis direction of the reference example, comparative examples 1 to 3, and embodiment 1 is calculated respectively. When calculating, the peak brightness at each angle of -25°, -35°, and -45° is divided by the overall peak brightness (relative brightness "1").

[0117] Comparison of the experimental results of Experiment 1 Figure 15 as well as Figure 16 shown. Figure 15This is a table showing the experimental results of Comparative Experiment 1. Figure 15 In the figure, from the top, the structure of the second light guide plate (the presence or absence of each light guide plate lens 26 to 28), the ratio of light at each angle of -25°, -35°, and -45° in the light distribution in the X-axis direction (in "%), and the percentage of peak brightness (in "%) are shown. Figure 16 Graphs showing light distributions of a reference example, comparative examples 1 to 3, and example 1. Figure 16 In the graph of light distribution shown, the horizontal axis represents the angle of the X-axis direction relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis represents the relative brightness (unit: "%). Figure 16 The positive and negative signs of the angles on the horizontal axis are the same as Figure 10 The symbols marked on the horizontal axis of the graph have the same meaning.

[0118] The experimental results of comparative experiment 1 are explained. Figure 15 and Figure 16 In the reference example, the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction is the lowest, and the peak brightness is the highest. The reason for this is presumably that the second light guide plate in the reference example is a flat plate with both main surfaces being flat, and therefore the light emitted from the first light guide plate 14 side is hardly refracted. In comparative example 3, the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction is the highest, and in comparative example 2, the ratio of light at angles of -25°, -35°, and -45° is the second highest. Although comparative examples 2 and 3 both have the sixth light guide plate lens 28, they do not have the fourth light guide plate lens 26. It is speculated that when light emitted from the first LED 13 enters the second opposite principal surface 25C of the second light guide plate 25, it is refracted by the sixth light guide plate inclined surface 28A and the seventh light guide plate inclined surface 28B of the sixth light guide plate lens 28, tending to produce sidelobe light that is significantly inclined relative to the front direction. This tendency is reflected in the experimental results of Comparative Examples 2 and 3. The difference between Comparative Examples 2 and 3 lies in the presence or absence of the fifth light guide plate lens 27. In Comparative Example 2, which includes the fifth light guide plate lens 27, the occupancy rate of the sixth light guide plate lens 28 on the second opposite principal surface 25C is lower than in Comparative Example 3 after the fifth light guide plate lens 27 is provided. Therefore, it is speculated that in Comparative Example 2, the generation of sidelobe light caused by the sixth light guide plate inclined surface 28A and the seventh light guide plate inclined surface 28B of the sixth light guide plate lens 28 is suppressed. In contrast, the peak brightness of Comparative Example 2 is the lowest at 39%. This is presumably because the light-collecting function of the fourth light guide plate lens 26 is impaired, and thus the light cannot be sufficiently directed forward.

[0119] according to Figure 15 and Figure 16In the light distribution in the X-axis direction, the ratio of light at angles of -25°, -35°, and -45° in Comparative Example 1 is second only to that of the reference example. The reason for this is presumably that Comparative Example 1 does not have the sixth light guide plate lens 28, and thus does not generate side lobe light caused by the sixth light guide plate inclined surface 28A and the seventh light guide plate inclined surface 28B of the sixth light guide plate lens 28. Figure 15 and Figure 16 In Example 1, the ratio of light at angles of 20°, -35°, and -45° is second only to Comparative Example 1. In other words, Example 1 exhibits more sidelobe light than Comparative Example 1, but exhibits less sidelobe light than Comparative Examples 2 and 3. It is speculated that, similar to Comparative Example 2, the inclusion of the fifth light guide plate lens 27 in Example 1 reduces the occupancy ratio of the sixth light guide plate lens 28 on the second opposite principal surface 25C, resulting in less sidelobe light than in Comparative Example 3. It is speculated that the inclusion of the fourth light guide plate lens 26 in Example 1 allows sufficient light to rise in the forward direction, and that a portion of the light is totally reflected back toward the first light guide plate 14, generating regressive light that includes light at angles close to the forward direction. This results in higher peak brightness and fewer sidelobe light than in Comparative Example 2. Furthermore, while Comparative Example 1 achieved excellent experimental results second only to those of the reference example in Comparative Experiment 1, the lack of the sixth light guide plate lens 28 prevented the emission of nearly all light from the second LED 24.

[0120] Next, in order to gain knowledge about how the light distribution changes when the inclination angle θ3 of the seventh light guide plate inclined surface 28B of the sixth light guide plate lens 28 of the second light guide plate 25 relative to the X-axis direction is changed, Experiment 3 was conducted. In Experiment 3, a backlight device 12 having the same structure as described previously in this paragraph was used, except for the structure of the sixth light guide plate lens 28. In Experiment 3, the inclination angle θ3 of the seventh light guide plate inclined surface 28B of the sixth light guide plate lens 28 relative to the X-axis direction was varied within a range of 1° to 60°. Specifically, in Experiment 3, the inclination angle θ3 was set to 1°, 3°, 5°, 10°, 20°, 30°, 40°, 50°, and 60°. In addition, the inclination angle θ2 of the sixth light guide plate inclined surface 28A relative to the X-axis direction was constant at 27°. In the backlight device 12 with the tilt angle θ3 varied in this manner, the first LED 13 is illuminated, and the brightness of the emitted light with the second LED 24 off is measured. A graph of the light distribution along the X-axis (brightness angle distribution) is created. Based on this, the ratio of light at angles of -25°, -35°, and -45° in the X-axis light distribution for all of the aforementioned tilt angles θ3 is calculated. This calculation is performed by dividing the peak brightness at each of the angles -25°, -35°, and -45° by the overall peak brightness (relative brightness "1").

[0121] The experimental results of empirical experiment 3 are as follows Figures 17 to 19 shown. Figure 17 Graphs showing light distribution when the inclination angle θ3 is set to 1°, 3°, 5°, 10°, 20°, 30°, 40°, 50°, and 60°. Figure 17 In the graph of light distribution shown, the horizontal axis represents the angle (unit: "°") of the X-axis direction relative to the front direction (Z-axis direction), and the vertical axis represents relative brightness (unitless). Figure 18 It will Figure 17 The graph is an enlarged graph of the range of 0° to -60° on the horizontal axis and the range of 0 to 0.2 on the vertical axis. Figure 19 This is a graph showing the relationship between the tilt angle θ3 and the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction. Figure 19 In the figure, the horizontal axis represents the tilt angle θ3 (in degrees), and the vertical axis represents the ratio of light at angles of -25°, -35°, and -45° in the X-axis light distribution (in percent). To minimize the visual perception of sidelobe light, the ratio of light at -25° is preferably 5% or less, the ratio of light at -35° is preferably 3% or less, and the ratio of light at -45° is preferably 2.5% or less. Thus, the larger the angle in the X-axis light distribution, the lower the baseline value for making sidelobe light less visually perceptible.

[0122] The experimental results of empirical experiment 3 are explained. Figures 17 to 19 When the tilt angle θ3 is 20°, 30°, and 40°, the ratio of light at -25° in the light distribution in the X-axis direction exceeds 5%. When the tilt angle θ3 is 30°, 40°, 50°, and 60°, the ratio of light at -35° in the light distribution in the X-axis direction exceeds 3%. When the tilt angle θ3 is 50° and 60°, the ratio of light at -45° in the light distribution in the X-axis direction exceeds 2.5%. Furthermore, it can be seen that the reference values of the ratio of light at each angle of -25°, -35°, and -45° in the light distribution in the X-axis direction are all satisfied when the tilt angle θ3 is 1°, 3°, 5°, and 10°. Therefore, it can be said that as long as the tilt angle θ3 is within the range of 1° to 10°, the side lobe light can be made difficult to be fully visually recognized. Within the range of 1° to 10°, the smaller the tilt angle θ3, the lower the proportion of light at angles of -25°, -35°, and -45° in the X-axis light distribution. Therefore, a tilt angle θ3 of 1° or 3° is most preferred for minimizing visual detection of sidelobe light. Since manufacturing the sixth light guide plate lens 28 with a tilt angle θ3 of 1° is difficult, a tilt angle θ3 of 3° is most preferred for ease of manufacturing.

[0123] Next, in order to gain knowledge about how the light distribution changes when the vertex angle θ1 of the fifth light guide plate lens 27 of the second light guide plate 25 is changed, an empirical experiment 4 was conducted. In this empirical experiment 4, a backlight device 12 having the same structure as that described previously in empirical experiment 1 was used, except for the structure of the fifth light guide plate lens 27. In empirical experiment 1, the vertex angle θ1 formed by a pair of fifth light guide plate inclined surfaces 27A of the fifth light guide plate lens 27 was changed within the range of 90° to 150°. Specifically, in empirical experiment 4, the vertex angle θ1 was set to 90°, 100°, 110°, 120°, 130°, 140°, and 150°. In the backlight device 12 in which the vertex angle θ1 was changed in this manner, the brightness of the emitted light was measured in the state where the first LED 13 was lit. Based on the measured brightness data of the emitted light, the ratio of light at angles of -25°, -35°, and -45° in the X-axis light distribution for all vertex angles θ1 is calculated. The calculation is performed by dividing the peak brightness at angles of -25°, -35°, and -45° by the overall peak brightness (relative brightness "1").

[0124] The experimental results of light distribution in empirical experiment 4 are as follows: Figure 20 and Figure 21 shown. Figure 20 This is a graph showing the relationship between the vertex angle θ1 and the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction. Figure 20 In the figure, the horizontal axis is the vertex angle θ1 (unit: "°"), and the vertical axis is the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction (unit: "%). Figure 21 This is a graph showing the relationship between the vertex angle θ1 and the brightness at 0° (front brightness) in the light distribution in the X-axis direction. Figure 21 In the figure, the horizontal axis is the vertex angle θ1 (unit is "°"), and the vertical axis is the brightness (unit is "cd / m 2 ”).

[0125] The experimental results of Experiment 4 are explained. Figure 19 In comparison, in Experiment 4 Figure 20 In the figure, it can be seen that even if the vertex angle θ1 is changed, the ratio of light at each angle of -25°, -35°, and -45° in the light distribution in the X-axis direction does not change much. In other words, it can be said that no matter what value the vertex angle θ1 of the fifth light guide plate lens 27 is, the influence on the light emitted from the first light guide plate 14 side does not change much. On the other hand, according to Figure 21It can be seen that the larger the vertex angle θ1, the higher the front brightness, and the smaller the vertex angle θ1, the lower the front brightness. This is presumably because the smaller the vertex angle θ1, the greater the refraction of the light emitted from the first light guide plate 14 side by the fifth light guide plate inclined surface 27A, resulting in a greater inclination relative to the front direction and an angle.

[0126] Next, to gain knowledge about how the light distribution changes when the contact angle θc of the fourth light guide plate lens 26 of the second light guide plate 25 is varied, Experiment 5 was conducted. In Experiment 5, a backlight device 12 having the same configuration as described in Experiment 1 was used, except for the configuration of the fourth light guide plate lens 26. In Experiment 1, the contact angle θc of the fourth light guide plate lens 26 was varied within a range of 15° to 58°. Specifically, in Experiment 5, the contact angle θc was set to 15°, 20°, 30°, 40°, 48°, and 58°. In the backlight device 12 with the contact angle θc thus varied, the brightness of the emitted light was measured when the first LED 13 was illuminated. Based on the measured brightness data of the emitted light, the ratios of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction were calculated for all contact angles θc. In the calculation, the peak brightness at each angle of -25°, -35°, and -45° is divided by the overall peak brightness (relative brightness "1").

[0127] The experimental results of light distribution in experimental 5 are as follows: Figure 22 and Figure 23 shown. Figure 22 This is a graph showing the relationship between the contact angle θc and the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction. Figure 22 In the graph, the horizontal axis represents the contact angle θc (unit: "°"), and the vertical axis represents the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction (unit: "%). Figure 23 This is a graph showing the relationship between the contact angle θc and the brightness (front brightness) at 0° in the light distribution in the X-axis direction. Figure 23 In the figure, the horizontal axis is the contact angle θc (unit is "°"), and the vertical axis is the brightness (unit is "cd / m 2 ”).

[0128] The experimental results of empirical experiment 5 are explained. Figure 22It can be seen that the larger the contact angle θc is, the lower the ratio of light at angles of -25°, -35°, and -45° in the light distribution in the X-axis direction tends to be. It is speculated that this is because the larger the contact angle θc is, the more the majority of the light emitted from the first light guide plate 14 side is reflected and returned to the first light guide plate 14 side, thereby generating more return light. As a result, more light at an angle close to 0° in the front direction can be emitted. In addition, Figure 22 Compared with Experiment 3 Figure 19 In comparison, it can be said that the rate of change of the ratio of light at each angle of -25°, -35°, and -45° in Experiment 5 is relatively low. Figure 23 It can be seen that the larger the contact angle θc is, the higher the front brightness is, and the smaller the contact angle θc is, the lower the front brightness is. Figure 22 The reason is the same as that described in , and it is presumed that a larger contact angle θc can generate more returning light.

[0129] As described above, the backlight device (illumination device) 12 of the present embodiment comprises: a first LED (first light source) 13; a first light guide plate 14, at least a portion of its outer peripheral end surface is opposite to the first LED 13 and is a first light incident end surface (first end surface) 14A on which light is incident, one main surface of which is the first light guide plate light emitting main surface (first main surface) 14B from which light is emitted, and the other main surface is the first opposite main surface (second main surface) 14C; a first louver (first sheet) 18, one main surface of which is the first light incident main surface (third main surface) 18A arranged toward the first light guide plate light emitting main surface 14B and on which light is incident, and the other main surface is the first light emitting main surface (fourth main surface) 18B from which light is emitted; a second LED (second light source) 24; and a second light guide plate 25, at least a portion of its outer peripheral end surface is opposite to the second LED 24 and on which light is incident. Two light-entering end faces (second end faces) 25A, one main face is the second light guide plate light-emitting main face (fifth main face) 25B for emitting light, and the other main face is the second opposite main face (sixth main face) 25C arranged toward the first light-emitting main face 18B, the first louver 18 has at least: two first light-shielding portions 18C, which are arranged at intervals in a first direction and block light, and the first direction includes the direction from the first LED 13 toward the first light guide plate 14; and a first light-transmitting portion 18D, which is arranged between the two first light-shielding portions 18C and allows light to pass through, and a sixth light guide plate lens (first lens 28) is provided on the second opposite main face 25C of the second light guide plate 25, and the sixth light guide plate lens 28 has an inclined sixth light guide plate inclined surface (first inclined surface) 28A that stands from the side opposite to the second LED 24 in the first direction toward the second LED 24 side.

[0130] In this way, the light emitted from the first LED 13 and incident on the first light incident end surface 14A of the first light guide plate 14 propagates within the first light guide plate 14, and is emitted from the first light emitting main surface 14B of the first light guide plate and is incident on the first light incident main surface 18A of the first louver 18. 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 and is emitted from the first light emitting main surface 18B. The emission angle of the light emitted from the first light emitting main surface 18B is limited by the two first light-shielding portions 18C. If the light emitted from the first light emitting main surface 18B is incident on the second opposite main surface 25C of the second light guide plate 25, it is emitted from the second light guide plate light emitting main surface 25B. The light emitted from the second light guide plate light emitting main surface 25B is difficult to be emitted outside the limited angle range because the angle range is limited by the first light-shielding portion 18C of the first louver 18. Thus, by lighting the first LED 13 and turning off the second LED 24 , light can be selectively emitted into a limited angle range.

[0131] 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 in the normal direction of the second light guide plate light-emitting principal surface 25B—that is, toward the side opposite to the second LED 24 in the first direction relative to the front direction—than light directed toward the side opposite to 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. This makes it possible to sufficiently ensure the brightness of light emitted in a direction oblique to the front direction.

[0132] Furthermore, the angle θ2 formed by the sixth light guide plate inclined surface 28A with respect to the first direction is set to be within a range of 27° to 40°. If the angle formed by the sixth light guide plate inclined surface 28A with respect to the first direction is greater than 40°, light refracted by the sixth light guide plate inclined surface 28A may be more likely to be emitted at an angle close to the front direction, or at an angle toward the second LED 24 side in the first direction. If the angle formed by the sixth light guide plate inclined surface 28A with respect to the first direction is less than 27°, light refracted by the sixth light guide plate inclined surface 28A may be emitted at an angle excessively inclined with respect to the front direction. As described above, by setting the angle θ2 formed by the sixth light guide plate inclined surface 28A with respect to the first direction within a range of 27° to 40°, a larger amount of light can be emitted at an angle appropriately inclined with respect to the front direction, toward the side opposite to the second LED 24 side in the first direction. This further improves the brightness of light emitted in a direction inclined with respect to the front direction.

[0133] In addition, the sixth light guide plate lens 28 has an inclined seventh light guide plate slope (second slope) 28B that rises from the second LED 24 in the first direction toward the opposite side thereof. Light traveling in the second light guide plate 25 in a manner close to the second LED 24 in the first direction, if it hits the seventh light guide plate slope 28B and is refracted, will travel to the side opposite to the second LED 24 side in the first direction relative to the front direction. Thus, the brightness of the emitted light in a direction inclined relative to the front direction can be further improved. In addition, light traveling in the second light guide plate 25 in a manner away from the second LED 24 in the first direction, if it hits the seventh light guide plate slope 28B and is refracted, will be guided further away from the second LED 24. Thus, the emitted light from the second light guide plate light-emitting main surface 25B is difficult to deviate toward the second LED 24 side in the first direction.

[0134] Furthermore, the angle θ3 formed by the seventh light guide plate inclined surface 28B relative to the first direction is in the range of 3° to 10°. First, if light emitted from the first light guide plate light emitting main surface 14B of the first light guide plate 14 and incident on the second opposite main surface 25C of the second light guide plate 25 hits the seventh light guide plate inclined surface 28B and is refracted, it may be emitted as side lobe light that travels in a direction inclined relative to the front direction toward the side opposite to the second LED 24 side in the first direction. Assuming that the angle formed by the seventh light guide plate inclined surface 28B with respect to the first direction is greater than 10°, the side lobe light described above becomes excessive. Assuming that the angle formed by the seventh light guide plate inclined surface 28B with respect to the first direction is less than 3°, it is difficult to form the sixth light guide plate lens 28 having the seventh light guide plate inclined surface 28B with such an angle. In this regard, as described above, by setting the angle θ3 of the seventh light guide plate inclined surface 28B with respect to the first direction to be in the range of 3° to 10°, the above-mentioned side lobe light can be sufficiently reduced while ensuring ease of forming the sixth light guide plate lens 28 .

[0135] Furthermore, the sixth light guide plate lens 28 is located between the sixth light guide plate inclined surface 28A and the seventh light guide plate inclined surface 28B in the first direction and has a first flat surface 28D extending along the first direction. Light emitted from the first light guide plate light-emitting principal surface 14B of the first light guide plate 14 and incident on the second opposite principal surface 25C of the second light guide plate 25 travels with little refraction even when it strikes the first flat surface 28D. Therefore, compared to a configuration where the sixth light guide plate inclined surface 28A and the seventh light guide plate inclined surface 28B are directly connected without passing through the first flat surface 28D, the generation of side lobe light that travels in a direction oblique to the side opposite to the second LED 24 side in the first direction relative to the front direction can be suppressed.

[0136] Furthermore, a plurality of sixth light guide plate lenses 28 are arranged in the first direction, and a second flat surface 29 extending along the first direction is provided on the second opposite principal surface 25C of the second light guide plate 25, between two adjacent sixth light guide plate lenses 28 in the first direction. Light emitted from the first light guide plate light-emitting principal surface 14B of the first light guide plate 14 and incident on the second opposite principal surface 25C of the second light guide plate 25 is substantially unrefracted even when it strikes the second flat surface 29. Therefore, compared to a configuration in which two adjacent sixth light guide plate lenses 28 in the first direction are directly connected without intervening the second flat surface 29, the generation of sidelobe light that travels in a direction oblique to the side opposite to the second LED 24 side in the first direction relative to the front direction can be suppressed.

[0137] In addition, a fourth light guide plate lens (second lens) 26 is provided on the second light guide plate light emitting main surface 25B of the second light guide plate 25. A plurality of the fourth light guide plate lenses (second lens) 26 are arranged along a second direction orthogonal to both the first direction and the normal direction of the main surface of the first light guide plate 14, and extend along the first direction. If the incident angle of light propagating in the second light guide plate 25 and reaching the second light guide plate light emitting main surface 25B exceeds the critical angle relative to the fourth light guide plate lens 26, the fourth light guide plate lens 26 imparts a focusing effect in the second direction and emits the light. Light whose incident angle relative to the fourth light guide plate lens 26 does not exceed the critical angle is totally reflected by the fourth light guide plate lens 26 and returns to the second opposite main surface 25C. When it is also totally reflected by the second opposite main surface 25C, it reaches the second light guide plate light emitting main surface 25B again. In this way, the light in the second light guide plate 25 is repeatedly totally reflected between the fourth light guide plate lens 26 and the second opposite main surface 25C, and is emitted from the second light guide plate light emitting main surface 25B after traveling along the first direction, so that the emitted light is difficult to deviate toward the second LED 24 side in the first direction.

[0138] Furthermore, a fifth light guide plate lens (third lens) 27 is provided on the second opposite principal surface 25C of the second light guide plate 25. A plurality of fifth light guide plate lenses (third lenses) 27 are arranged at intervals along a second direction perpendicular to both the first direction and the normal direction of the principal surface of the first light guide plate 14, extending along the first direction. A plurality of sixth light guide plate lenses 28 are arranged in a manner alternating with the fifth light guide plate lenses 27 in the second direction. Most of the light that propagates within the second light guide plate 25 and reaches the second opposite principal surface 25C has an incident angle with the fifth light guide plate lens 27 that does not exceed the critical angle, and is therefore totally reflected by the fifth light guide plate lens 27 and directed toward the second light guide plate light exit principal surface 25B. Furthermore, if this light is also totally reflected by the second light guide plate light exit principal surface 25B, it will again reach the second opposite principal surface 25C. In this way, light within the second light guide plate 25 is repeatedly totally reflected between the fifth light guide plate lens 27 and the second light guide plate light exiting main surface 25B, traveling along the first direction before exiting from the second light guide plate light exiting main surface 25B. This makes it difficult for the exiting light to deflect toward the second LED 24 in the first direction. Furthermore, on the second opposing main surface 25C, the sixth light guide plate lens 28 and the fifth light guide plate lens 27 are alternately arranged in the second direction. Therefore, the occupancy rate of the sixth light guide plate lens 28 on the second opposing main surface 25C is reduced compared to a case where the fifth light guide plate lens 27 is not provided. The sixth light guide plate lens 28 can refract a portion of the exiting light from the first light exiting main surface 18B of the first light guide plate 14, generating sidelobe light. Therefore, by reducing the occupancy rate of the sixth light guide plate lens 28 on the second opposing main surface 25C, sidelobe light can be reduced.

[0139] In addition, there are a first prism sheet 16 and a second prism sheet 17, the main surface of one side of the first prism sheet 16 is arranged opposite to the main light-emitting surface 14B of the first light guide plate, and has a plurality of first prisms 16B arranged along the first direction and extending along the second direction orthogonal to both the first direction and the normal direction of the main surface of the first light guide plate 14, the second prism sheet 17 is arranged on the side opposite to the first light guide plate 14 relative to the first prism sheet 16, and has a plurality of second prisms 17B arranged along the first direction and extending along the second direction; 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 the opposite side thereof; and A prism sheet 16 has a second prism bevel (fourth bevel) 16B2 inclined upward from the side opposite to the first LED 13 in the first direction thereof toward the side of the first LED 13, and a second prism 17B has: a third prism bevel (fifth bevel) 17B1 inclined upward from the side opposite to the first LED 13 in the first direction of the second prism sheet 17 toward its opposite side; and a fourth prism bevel (sixth bevel) 17B2 inclined upward from the side opposite to the first LED 13 in the first direction of the second prism sheet 17 toward the side of the first LED 13, and an angle θ7 formed by the third prism bevel 17B1 in the second prism 17B relative to the first direction is smaller than an angle θ4 formed by the first prism bevel 16B1 in the first prism 16B relative to the first direction.

[0140] 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 strikes the second prism bevel 16B2 of the first prism 16B and is refracted, rising and exiting, or heading 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 opposite in magnitude, the light entering the first prism sheet 16 is less likely to strike 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.

[0141] Most of the light that exits the first prism sheet 16 and enters the second prism sheet 17 hits and is refracted by the fourth prism slope 17B2 of the second prism 17B, then rises and exits, or travels toward the third prism slope 17B1. Here, the angle θ7 formed by the third prism slope 17B1 of the second prism 17B with respect to the first direction is smaller than the angle θ4 formed by the first prism slope 16B1 of the first prism 16B with respect to the first direction. Therefore, compared to a case where the angles are the same or opposite, the light refracted by the sixth slope and directed toward the third prism slope 17B1 is more likely to return to the first prism sheet 16 via the third prism slope 17B1. 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. The returning light is reflected within the backlight unit 12 and reaches the second prism sheet 17 again. It is then raised by the third prism inclined surface 17B1 or the fourth prism inclined surface 17B2 of the second prism 17B and emitted, thereby improving light utilization efficiency. In addition, the optical path of the returning light before being emitted from the second prism sheet 17 is complicated, and the rising angle given by the second prism 17B is also diversified, thereby improving viewing angle characteristics.

[0142] Light exiting the second prism sheet 17 enters the first principal light-entering surface 18A of the first louver 18. The light entering the first principal light-entering surface 18A has fewer side lobes, resulting in higher utilization efficiency due to the return light. This ensures a sufficient amount of light passing through the first light-transmitting portion 18D, while minimizing 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.

[0143] Furthermore, the first LED 13 is arranged on one side in the first direction relative to the first light guide plate 14, and the second LED 24 is arranged on the other side in the first direction relative to the second light guide plate 25. Thus, the first LED 13 and the second LED 24 are dispersed in the first direction, so even if the first LED 13 and the second LED 24 are individually lit, heat is unlikely to accumulate.

[0144] 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 thus configured liquid crystal display device 10, the backlight device 12 suppresses light from being emitted outside a limited angular range, thereby increasing the brightness of light emitted in a direction oblique to the front direction, thereby achieving a display with excellent display quality.

[0145] <Second embodiment>

[0146] pass Figure 24 or Figure 25The second embodiment will be described. In this second embodiment, the configuration of the backlight device 112 is modified. Repetitive descriptions of the same structures, functions, and effects as those of the first embodiment will be omitted.

[0147] like Figure 24 As shown, the backlight device 112 of this embodiment includes at least a linear Fresnel lens sheet (second sheet) 19, which is positioned on the front side of the first louver 118; and a third louver (third sheet) 20, which is positioned on the front side of the linear Fresnel lens sheet 19 and on the back side of the second light guide plate 125. The principal surfaces of the linear Fresnel lens sheet 19 and the third louver 20 are parallel to the principal surfaces of the first louver 118 and the second light guide plate 125, and both are sheet-shaped. Furthermore, the principal surfaces of the linear Fresnel lens sheet 19 and the third louver 20 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 linear Fresnel lens sheet 19 functions to selectively focus light in the X-axis direction. Like the first louver 118, the third louver 20 functions to limit the range of light emission angles in the X-axis direction.

[0148] like Figure 24 As shown, the linear Fresnel lens sheet 19 has a third light-entering principal surface (seventh principal surface) 19A on the back side and a third light-emitting principal surface (eighth principal surface) 19B on the front side. The third light-entering principal surface 19A is opposite to the first light-emitting principal surface 118B of the first louver 118. The third light-emitting principal surface 19B is opposite to the fourth light-entering principal surface 20A of the third louver 20 described later. The linear Fresnel lens sheet 19 has a flat substrate 19D and a linear Fresnel lens (fourth lens) 19C arranged on the principal surface (third 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 can be 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 linear Fresnel lens 19C can be made of an ultraviolet-curable resin material. In this case, similar to the manufacturing method of the first prism sheet 116, 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, ultraviolet rays are irradiated on the ultraviolet curing resin material through the substrate 19D, and the linear Fresnel lens 19C can be set integrally on the substrate 19D.

[0149] like Figure 24As shown, the linear Fresnel lens 19C protrudes from the substrate 19D toward the front side along the Z-axis direction. The cross-sectional shape of the linear Fresnel lens 19C cut along the X-axis direction is a triangle, and it extends in a straight line along the Y-axis direction. The width dimension (dimension in the X-axis direction) of the linear Fresnel lens 19C is constant over the entire length in the Y-axis direction. A plurality of linear Fresnel lenses 19C are arranged along the X-axis direction in the substrate 19D. The height and other factors of the plurality of linear Fresnel lenses 19C vary depending on the position of the substrate 19D in the X-axis direction. Specifically, the linear Fresnel lens located at the end side of the substrate 19D in the X-axis direction (the linear Fresnel lens 19CE described later) among the plurality of linear Fresnel lenses 19C protrudes from the substrate 19D to a greater height than the linear Fresnel lens located at the center side (the linear Fresnel lens 19CC described later). The linear Fresnel lenses 19C gradually increase in height from the center of the substrate 19D in the X-axis direction toward the ends. The linear Fresnel lenses 19C are symmetrical about the center of the substrate 19D in the X-axis direction. Thus, the linear Fresnel lenses 19C are so-called "linear Fresnel lenses."

[0150] like Figure 24 As shown, the linear Fresnel lens 19C has a pair of inclined surfaces 19C1 and 19C2. Among the pair of inclined surfaces 19C1 and 19C2 of the linear Fresnel lens 19C, the inclined surface on the end side of the linear Fresnel lens sheet 19 in the X-axis direction is set as the first inclined surface (seventh inclined surface) 19C1, and the inclined surface on the center side is set as 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 to 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 to the end side. Compared with the center position of the linear Fresnel lens sheet 19 in the X-axis direction, the second inclined surface 19C2 is located on the side of the first LED 113 ( Figure 24 The linear Fresnel lens 19C is on the left side of the lens, and the first inclined surface 19C1 is located relative to the top. Figure 24 On the left side, the second inclined surface 19C2 is located Figure 24 Compared to the center position of the linear Fresnel lens sheet 19 in the X-axis direction, it is located on the opposite side of the first LED 113 ( Figure 24 The linear Fresnel lens 19C is on the right side of the lens, and the first inclined surface 19C1 is located relative to the top. Figure 24 On the right side, the second inclined surface 19C2 is located Figure 24 In addition, Figure 25 2 shows a linear Fresnel lens 19C located closer to the first LED 113 than the center position of the linear Fresnel lens sheet 19 in the X-axis direction.

[0151] like Figure 24As shown, light incident on the linear Fresnel 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. Specifically, the first inclined surface 19C1 imparts an anisotropic refractive effect that selectively focuses light in the X-axis direction. Since the linear Fresnel lens 19C includes the second inclined surface 19C2 in addition to the first inclined surface 19C1, it is easier to process multiple linear Fresnel lenses 19C during the manufacture of the linear Fresnel lens sheet 19 than if the second inclined surface 19C2 were perpendicular to the X-axis direction. Conversely, light incident on the linear Fresnel 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 (angle, first base angle) θ10 of the first inclined surface 19C1 of the linear Fresnel lens 19C relative to the X-axis is smaller than the inclination angle (angle, second base angle) θ11 of the second inclined surface 19C2 relative to the X-axis. Consequently, most of the light incident on the linear Fresnel lens 19C strikes the first inclined surface 19C1, where it is focused, while less light strikes the second inclined surface 19C2. Thus, the cross-sectional shape of the linear Fresnel lens 19C is asymmetrical, forming an isosceles triangle.

[0152] like Figure 24As shown, the third louver 20 has a fourth light-entering principal surface (ninth principal surface) 20A on the back side and a fourth light-emitting principal surface (tenth principal surface) 20B on the front side. The fourth light-entering principal surface 20A is opposite to the third light-emitting principal surface 19B of the linear Fresnel lens sheet 19. The third louver 20 has a third light-blocking portion (second light-blocking portion) 20C that blocks light and a third light-transmitting portion (second light-transmitting portion) 20D that allows light to pass. The third light-blocking portion 20C is, for example, made of a light-blocking resin material (light-blocking material) that is black and blocks light. The third 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 third light-transmitting portions 20C are arranged at intervals in the X-axis direction. The third light-transmitting portion 20D is made of a light-transmitting resin material (light-transmitting material) that is substantially transparent and translucent. The third light-transmitting portion 20D is in the form of a layer extending along the Y-axis direction and the Z-axis direction, and a plurality of the third light-transmitting portions 20D are arranged at intervals in the X-axis direction. A plurality of third light-shielding portions 20C and a plurality of third light-transmitting portions 20D are arranged alternately and repeatedly in the X-axis direction. Therefore, the third light-transmitting portion 20D is located between two third light-shielding portions 20C that are adjacent to each other and spaced apart in the X-axis direction, and the third light-shielding portion 20C is located between two third light-transmitting portions 20D that are adjacent to each other and spaced apart in the X-axis direction. Light incident on the fourth light-entering principal surface 20A of the third louver 20 passes through the third light-transmitting portion 20D disposed between the two third light-shielding portions 20C that are adjacent to each other in the X-axis direction, and is emitted from the fourth light-emitting principal surface 20B. The emission angle of the light emitted from the fourth light-emitting principal surface 20B in the X-axis direction is limited by the two third light-shielding portions 20C that are adjacent to each other in the X-axis direction. In addition, the emission angle of the light emitted from the fourth light-emitting principal surface 20B in the Y-axis direction is not limited by the third louver 20. The emission angle range in the X-axis direction of the emitted light from the fourth light-emitting main surface 20B is defined by two straight lines that connect the respective ends in the Z-axis direction of the two third light-shielding portions 20C that sandwich the third light-transmitting portion 20D obliquely relative to each other. The emission angle range in the X-axis direction of the transmitted light of the third light-transmitting portion 20D varies according to the ratio of the width W6 to the height H3 of the third light-transmitting portion 20D. In addition, the third venetian blind 20 has a pair of sheet carriers that sandwich and support each of the multiple third light-shielding portions 20C and the third light-transmitting portion 20D from the front and back sides. The sheet carrier is made of a translucent resin material that is substantially transparent and transmits light. The sheet carrier extends throughout the entire area of the third venetian blind 20 and holds each of the multiple third light-shielding portions 20C and the third light-transmitting portion 20D together.

[0153] like Figure 25 As shown, in the third louver 20, the ratio of the width W6 of the third light-transmitting portion 20D divided by the height H3 is greater than the ratio of the width W1 of the first light-transmitting portion 118D divided by the height H1 (refer to Figure 3). According to this structure, the maximum absolute value of the angle formed by the light passing through the third light-transmitting portion 20D relative to the Z-axis direction (the normal direction of the fourth 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 118D relative to the Z-axis direction (the normal direction of the first light-emitting main surface 118B). Thus, it is avoided that the light imparted with anisotropic refraction by the linear Fresnel lens sheet 19 is excessively restricted in its exit angle by the third louver 20. Thus, the exiting light from the fourth light-emitting main surface 20B fully reflects the anisotropic refraction imparted by the linear Fresnel lens sheet 19. Therefore, the brightness of the exiting light is uniformed in the central side portion and the two end side portions in the X-axis direction of the fourth light-emitting main surface 20B. In this way, the brightness distribution of the exiting light of the backlight device 112 is uniformed. For the exiting light of the backlight device 112 of this embodiment, the brightness distribution is uniformed on the basis of limiting the exit angle range by the third louver 20. Therefore, when the liquid crystal display device 110 of this embodiment is set to be located in front of the passenger seat of a passenger car, the display image of the liquid crystal display device 110 cannot be visually confirmed from the driver's seat, and regardless of the position of the screen of the liquid crystal display device 110 in the X-axis direction, the display image of uniform brightness can be visually confirmed from the passenger seat. In addition, the emission angle of the outgoing light from the fourth light-emitting main surface 20B is limited by the two third shading portions 20C. Therefore, even if side lobe light is generated by the second inclined surface 19C2 of the linear Fresnel lens 19C, it is blocked by the third shading portion 20C of the third louver 20, making it difficult to be emitted from the fourth light-emitting main surface 20B. As a result, the side lobe light that may be generated in the outgoing light of the backlight device 112 can be sufficiently reduced.

[0154] like Figure 25 As shown, in the third venetian blind 20, the ratio of the width W6 of the third light-transmitting portion 20D divided by the height H3 is equal to "tan45°". In this way, the absolute value of the maximum angle formed by the light passing through the third light-transmitting portion 20D relative to the Z-axis direction is 45°. Assuming that the side lobe light can be reduced compared to the case where the ratio of the width of the third light-transmitting portion 20D divided by the height is greater than "tan45°". In addition, assuming that the light given anisotropic refraction by the linear Fresnel lens sheet 19 is less likely to have its exit angle excessively restricted by the third venetian blind 20, as compared to the case where the ratio of the width of the third light-transmitting portion 20D divided by the height is less than "tan45°". As a result, the brightness distribution of the light emitted from the third venetian blind 20 can be made uniform.

[0155] The detailed structure of the linear Fresnel lens sheet 19 will be described. Figure 25As shown, the plurality of linear Fresnel lenses 19C arranged along the X-axis direction are configured such that the inclination angle θ10 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 linear Fresnel lenses 19C include a central linear Fresnel lens 19CC and an end linear Fresnel lens 19CE located closer to the end of the central linear Fresnel lens 19CC in the X-axis direction within the linear Fresnel lens sheet 19. When any linear Fresnel lens 19C arranged at a position other than the two ends in the X-axis direction among the plurality of linear Fresnel lenses 19C is referred to as a "central linear Fresnel lens 19CC," the linear Fresnel lens 19C located closer to the end of the central linear Fresnel lens 19CC in the X-axis direction is referred to as an "end linear Fresnel lens 19CE." Furthermore, the angle θ10E formed by the first inclined surface 19C1 of the end-side linear Fresnel lens 19CE with respect to the X-axis direction is greater than the angle θ10C formed by the first inclined surface 19C1 of the center-side linear Fresnel lens 19CC with respect to the X-axis direction. With this configuration, the anisotropic refractive effect imparted to light by the first inclined surface 19C1 of the end-side linear Fresnel lens 19CE is stronger than the anisotropic refractive effect imparted to light by the first inclined surface 19C1 of the center-side linear Fresnel lens 19CC. In other words, light emitted from the end-side portion of the third light-emitting principal surface 19B of the linear Fresnel lens sheet 19 in the X-axis direction has a stronger directivity toward the center in the X-axis direction than light emitted from the center-side portion in the X-axis direction. In the third louver 20 for incident light emitted from the third main light-emitting surface 19B, the brightness of the emitted light is more uniform in the central side portion and the two end side portions in the X-axis direction of the fourth main light-emitting surface 20B of the third louver 20 in order to avoid excessive restriction of the emission angle of the emitted light.

[0156] like Figure 25As shown, the vertex angles (first vertex angles) θ12 of the plurality of linear Fresnel lenses 19C arranged along the X-axis direction are identical. That is, the vertex angle θ12C of the center-side linear Fresnel lens 19CC is equal to the vertex angle θ12E of the end-side linear Fresnel lens 19CE. This configuration facilitates the processing of the mold used for molding when manufacturing the linear Fresnel lens sheet 19 by resin molding. Furthermore, the plurality of linear Fresnel lenses 19C are configured such that the inclination angle θ11 of the second inclined surface 19C2 relative to the X-axis direction changes depending on the position in the X-axis direction. The angle θ11E formed by the second inclined surface 19C2 of the end-side linear Fresnel lens 19CE relative to the X-axis direction is smaller than the angle θ11C formed by the second inclined surface 19C2 of the center-side linear Fresnel lens 19CC relative to the X-axis direction. With this configuration, the sidelobe light generated by the second inclined surface 19C2 of the end-side linear Fresnel lens 19CE tends to be greater than the sidelobe light generated by the second inclined surface 19C2 of the center-side linear Fresnel lens 19CC. In contrast, the two third light-shielding portions 20C of the third louver 20 limit the angle of emission of light from the fourth light-emitting principal surface 20B, thereby significantly reducing the sidelobe light generated by the second inclined surface 19C2 of the end-side linear Fresnel lens 19CE.

[0157] like Figure 25 As shown, the vertex angle θ12 of the plurality of linear Fresnel lenses 19C is constant at 110°. The tilt angle θ10 of the first inclined surface 19C1 of the plurality of linear Fresnel lenses 19C relative to the X-axis direction ranges from 0° to 24°, and the tilt angle θ11 of the second inclined surface 19C2 relative to the X-axis direction ranges from 46° to 70°. Specifically, the linear Fresnel lens 19C located at the center of the linear Fresnel lens sheet 19 in the X-axis direction (central linear Fresnel lens 19CC) among the plurality of linear Fresnel lenses 19C has a tilt angle θ10 (θ10C) of approximately 0° relative to the X-axis direction of the first inclined surface 19C1, a tilt angle θ11 (θ11C) of approximately 70° relative to the X-axis direction of the second inclined surface 19C2, and a vertex angle θ12 (θ12C) of 110°. In contrast, the first inclined surface 19C1 of the linear Fresnel lens 19C (end side linear Fresnel lens 19CE) located at both ends of the linear Fresnel lens sheet 19 in the X-axis direction among the multiple linear Fresnel lenses 19C has an inclination angle θ10 (θ10E) of approximately 24° relative to the X-axis direction, the second inclined surface 19C2 has an inclination angle θ11 (θ11E) of approximately 46° relative to the X-axis direction, and the vertex angle θ12 (θ12E) is 110°.

[0158] The tilt angles θ10 and θ11 of the linear Fresnel lenses 19C vary as follows depending on the position of the linear Fresnel lens sheet 19 in the X-axis direction. Specifically, the tilt angles θ10 of the first inclined surfaces 19C1 of the linear Fresnel lenses 19C with respect to the X-axis direction decrease continuously and gradually as they move from the center position in the X-axis direction toward the ends. The tilt angles θ11 of the second inclined surfaces 19C2 of the linear Fresnel lenses 19C with respect to the X-axis direction increase continuously and gradually as they move from the center position in the X-axis direction toward the ends.

[0159] If the angle θ10 formed by the first inclined surface 19C1 with the X-axis direction is greater than 24°, and the angle θ11 formed by the second inclined surface 19C2 with the X-axis direction is less than 46°, there is a possibility that excessive side lobe light, which is difficult to block by the third light-blocking portion 20C of the third louver 20, may occur. Furthermore, even if the angle θ10 formed by the first inclined surface 19C1 with the X-axis direction is less than 0°, and the angle θ11 formed by the second inclined surface 19C2 with the X-axis direction is greater than 70°, there is a possibility that excessive side lobe light, which is difficult to block by the third light-blocking portion 20C of the third louver 20, may occur. As described above, in the plurality of linear Fresnel lenses 19C, if the angle θ10 formed by the first inclined surface 19C1 with the X-axis direction is within the range of 0° to 24°, and the angle θ11 formed by the second inclined surface 19C2 with the X-axis direction is within the range of 46° to 70°, side lobe light, which is difficult to block by the third light-blocking portion 20C of the third louver 20, can be sufficiently suppressed.

[0160] As described above, according to the present embodiment, there are provided: a linear Fresnel lens sheet (second sheet) 19, a principal surface of one side of which is opposite to the first light-emitting principal surface 118B and is set as the third light-entering principal surface (seventh principal surface) 19A for light incidence, and a principal surface of the other side is set as the third light-emitting principal surface (eighth principal surface) 19B for light emission; and a third louver (third sheet) 20, a principal surface of one side of which is opposite to the third light-emitting principal surface 19B and is set as the fourth light-entering principal surface (ninth principal surface) 20A for light incidence, and a principal surface of the other side is opposite to the second opposite principal surface 125C and is set as the fourth light-emitting principal surface (tenth principal surface) 20B for light emission, the linear Fresnel lens sheet 19 has a main surface arranged on the third light-entering principal surface 19A or The linear Fresnel lens (fourth lens) 19C of the third light-emitting main surface 19B, the third louver 20 at least has: two third light-shielding portions (second light-shielding portions) 20C arranged at intervals in the first direction and blocking light; and a third light-transmitting portion (second light-transmitting portion) 20D arranged between the two third light-shielding portions 20C and allowing light to pass therethrough, the linear Fresnel lens 19C has an inclined first inclined surface (seventh inclined surface) 19C1 rising from the end side in the first direction toward the center side of the linear Fresnel lens sheet 19, and in the third louver 20, the ratio of the width W6 of the third light-transmitting portion 20D divided by the height H3 is greater than the ratio of the width W1 of the first light-transmitting portion 118D divided by the height H1.

[0161] When light emitted from the first light-emitting principal surface 118B of the first louver 118 is incident on the third light-incident principal surface 19A of the linear Fresnel lens sheet 19, it is refracted by the first inclined surface 19C1 of the linear Fresnel lens 19C and emitted from the third light-emitting principal surface 19B.

[0162] The first inclined surface 19C1 is inclined from the end side in the first direction toward the center side of the linear Fresnel lens sheet 19, thereby imparting anisotropic refraction to the light emitted from the third light-emitting principal surface 19B, directed toward the center side in the first direction. When light emitted from the third light-emitting principal surface 19B is incident on the fourth light-entering principal surface 20A of the third louver 20, it passes through the third light-transmitting portion 20D disposed between the two third light-shielding portions 20C and is emitted from the fourth light-emitting principal surface 20B. The emission angle of the light emitted from the fourth light-emitting principal surface 20B is limited by the two third light-shielding portions 20C. The light emitted from the fourth light-emitting principal surface 20B is incident on the second opposite principal surface 125C of the second light guide plate 125.

[0163] Here, the ratio of the width W1 of the first light-transmitting portion 118D of the first louver 118 divided by its height H1 is smaller than the ratio of the width W6 of the third light-transmitting portion 20D divided by its height H3. With this configuration, the maximum absolute value of the angle formed by light passing through the first light-transmitting portion 118D with respect to the normal to the first light-emitting principal surface 118B is smaller than the maximum absolute value of the angle formed by light passing through the third light-transmitting portion 20D with respect to the normal to the fourth light-emitting principal surface 20B. Consequently, the light emitted from the first light-emitting principal surface 118B and incident on the third light-incident principal surface 19A of the linear Fresnel lens sheet 19 contains a greater proportion of light directed toward the normal to the first light-emitting principal surface 118B. Consequently, light refracted by the first inclined surface 19C1 of the linear Fresnel lens 19C of the linear Fresnel lens sheet 19 is effectively imparted with directivity toward the center of the first direction.

[0164] On the other hand, the ratio of the width W6 of the third light-transmitting portion 20D of the third louver 20 divided by the height H3 is greater than the ratio of the width W1 of the first light-transmitting portion 118D divided by the height H1. According to this configuration, the maximum absolute value of the angle formed by the light passing through the third light-transmitting portion 20D relative to the normal direction of the fourth light-emitting principal surface 20B is greater than the maximum absolute value of the angle formed by the light passing through the first light-transmitting portion 118D relative to the normal direction of the first light-emitting principal surface 118B. This prevents the light, which has been anisotropically refracted by the linear Fresnel lens sheet 19, from being excessively restricted in its exit angle by the third louver 20. As a result, the light emitted from the fourth light-emitting principal surface 20B fully reflects the anisotropic refractive effect imparted by the linear Fresnel lens sheet 19, and thus the brightness of the emitted light is uniform in the central portion and both end portions of the fourth light-emitting principal surface 20B in the first direction. Furthermore, the emission angle of the light emitted from the fourth light-emitting main surface 20B is limited by the two third light-shielding portions 20C, thereby reducing side lobe light that may be generated in the light emitted from the backlight device 112 .

[0165] <Third embodiment>

[0166] pass Figures 26 to 29 The third embodiment is described. In the third embodiment, the configuration of the fifth light guide plate lens 227 is modified from the first embodiment. Repetitive descriptions of the same structures, functions, and effects as those of the first embodiment will be omitted.

[0167] like Figure 26As shown, in this embodiment, the plurality of fifth light guide plate lenses 227 arranged along the Y-axis direction on the second opposite principal surface 225C of the second light guide plate 225 are configured so that their width dimensions (dimensions in the Y-axis direction) vary. Specifically, the plurality of fifth light guide plate lenses 227 include a central fifth light guide plate lens (central third lens) 227C and an end fifth light guide plate lens (end third lens) 227E located further in the Y-axis direction than the central fifth light guide plate lens 227C in the second light guide plate 225. When any of the plurality of fifth light guide plate lenses 227 arranged at a position other than the two ends in the Y-axis direction is designated as the "central fifth light guide plate lens 227C," the fifth light guide plate lens 227 located further in the Y-axis direction than the "central fifth light guide plate lens 227C" is designated as the "end fifth light guide plate lens 227E."

[0168] Furthermore, the width dimension (dimension in the Y-axis direction) W7 of the end-side fifth light guide plate lens 227E is smaller than the width dimension W8 of the center-side fifth light guide plate lens 227C. Thus, the occupancy rate of the end-side fifth light guide plate lens 227E in the end-side portion of the second opposite principal surface 225C in the Y-axis direction is lower than the occupancy rate of the center-side fifth light guide plate lens 227C in the center-side portion in the Y-axis direction. As a result, the closer one gets from the center side in the Y-axis direction of the second light guide plate 225 to the end side, the less light travels straight along the X-axis direction due to repeated total reflection between the end-side fifth light guide plate lens 227E and the second light guide plate light-emitting principal surface 225B, and the easier it is for light to reach the end of the second light guide plate 225 in the Y-axis direction.

[0169] The specific value of the width of the fifth light guide plate lens 227 is determined by the position of the fifth light guide plate lens 227 in the Y-axis direction of the second light guide plate 225. Figure 27 Changes as shown. Figure 27 The horizontal axis is a graph in which the position of the second light guide plate 25 in the Y-axis direction (unit: "mm") and the vertical axis is a graph in which the width dimension of the fifth light guide plate lens 227 (unit: "mm") is represented. Figure 27 The reference position (0 mm) of the horizontal axis is the center position of the second light guide plate 225 in the Y-axis direction, and the positions of ±60 mm are the two end positions of the second light guide plate 225 in the Y-axis direction. Figure 27 The solid line shown is the fifth light guide plate lens 27 of the first embodiment (see Figure 3 ), and the dotted line is a graph of the width dimension of the fifth light guide plate lens 227 of this embodiment. Furthermore, the vertex angle θ1 of the fifth light guide plate lens 227 is constant regardless of the position in the Y-axis direction.

[0170] according to Figure 27The width dimensions of the plurality of fifth light guide plate lenses 227 are approximately constant in the central portion (range of +20 mm to -20 mm) of the second light guide plate 225 in the Y-axis direction. In contrast, the width dimensions of the plurality of fifth light guide plate lenses 227 at the two end portions (range of +60 mm to +20 mm and range of -60 mm to -20 mm) of the second light guide plate 225 in the Y-axis direction continuously and gradually decrease as they approach the two end positions in the Y-axis direction. Specifically, among the plurality of fifth light guide plate lenses 227, the fifth light guide plate lens 227 located in the central portion (central fifth light guide plate lens 227C) of the second light guide plate 225 in the Y-axis direction has the largest width dimension W8, while the fifth light guide plate lenses 227 located at the two end positions in the Y-axis direction (end fifth light guide plate lens 227E) have the smallest width dimension W7.

[0171] In this way, along with the plurality of fifth light guide plate lenses 227 formed as described above, the plurality of sixth light guide plate lenses 228 arranged on the second opposite principal surface 225C of the second light guide plate 225 are formed. Figure 26 As shown, the width dimension (dimension in the Y-axis direction) varies. Specifically, the plurality of sixth light guide plate lenses 228 include a central sixth light guide plate lens (central first lens) 228C and an end sixth light guide plate lens (end first lens) 228E located closer to the end in the Y-axis direction than the central sixth light guide plate lens 228C in the second light guide plate 225. When any sixth light guide plate lens 228 disposed at a position other than the ends in the Y-axis direction among the plurality of sixth light guide plate lenses 228 is designated as the "central sixth light guide plate lens 228C," the sixth light guide plate lens 228 located closer to the end in the Y-axis direction than the "central sixth light guide plate lens 228C" becomes the "end sixth light guide plate lens 228E."

[0172] Furthermore, the width dimension (dimension in the Y-axis direction) W9 of the end-side sixth light guide plate lens 228E is greater than the width dimension W10 of the center-side sixth light guide plate lens 228C. That is, in the center portion of the second opposite principal surface 225C of the second light guide plate 225 in the Y-axis direction, as the occupancy ratio of the fifth light guide plate lens 227 (center-side fifth light guide plate lens 227C) increases, the occupancy ratio of the sixth light guide plate lens 228 (center-side sixth light guide plate lens 228C) decreases. Conversely, in the end portions in the Y-axis direction, as the occupancy ratio of the fifth light guide plate lens 227 (end-side fifth light guide plate lens 227E) decreases, the occupancy ratio of the sixth light guide plate lens 228 (end-side sixth light guide plate lens 228E) increases. As a result, the amount of light reflected by the sixth light guide plate inclined surface 228A of the sixth light guide plate lens 228E on the end side in the Y-axis direction of the second light guide plate 225 and emitted from the second light guide plate light output main surface 225B increases. As a result, the brightness of the light emitted from the center and both end portions of the second light guide plate light output main surface 225B in the Y-axis direction is uniform.

[0173] Specifically, according to Figure 27 In the Y-axis central portion (range of +20 mm to -20 mm) of the second light guide plate 225, the widths of the plurality of fifth light guide plate lenses 227 are substantially constant, and therefore the widths of the plurality of sixth light guide plate lenses 228 are also substantially constant. In contrast, in the Y-axis end portions (ranges of +60 mm to +20 mm and -60 mm to -20 mm) of the second light guide plate 225, the widths of the plurality of fifth light guide plate lenses 227 decrease continuously and gradually as they approach the Y-axis end positions. Therefore, the widths of the plurality of sixth light guide plate lenses 228 increase continuously and gradually as they approach the Y-axis end positions. Among the multiple sixth light guide plate lenses 228, the sixth light guide plate lens 228 located at the central side portion of the second light guide plate 225 in the Y-axis direction (the central side sixth light guide plate lens 228C) has the smallest width dimension W10, while the sixth light guide plate lens 228 located at both end positions in the Y-axis direction (the end side sixth light guide plate lens 228E) has the largest width dimension W9.

[0174] To verify the superiority of the backlight device 12 of this embodiment and the liquid crystal display device 10, the following Comparative Experiment 2 was conducted. In this Comparative Experiment 2, the backlight device 12 having the configuration described in the first embodiment was used as Example 2, and the backlight device 12 having the configuration described in the previous stage of Comparative Experiment 2 was used as Example 3. In Comparative Experiment 2, the first LED 13 of each backlight device of Example 2 and Example 3 was illuminated, and the luminance of the emitted light with the second LED 24 off was measured. A graph was created to represent the luminance distribution using shades, and a graph was created to show the light distribution distribution along the Y axis (luminance angle distribution). Furthermore, in Comparative Experiment 2, the percentage (unit: "%) of the ratio of the minimum luminance divided by the maximum luminance of the calculated luminance was calculated. The percentage of the calculated ratio indicates that a larger value indicates a higher uniformity of the luminance distribution, while a smaller value indicates a lower uniformity of the luminance distribution.

[0175] Comparison of the experimental results of Experiment 2 Figure 28 as well as Figure 29 As shown. Figure 28 In the figure, from the top, the brightness distribution diagrams in Example 2 and Example 3 and the percentage of the ratio of the minimum brightness divided by the maximum brightness in Example 2 and Example 3 are shown. Figure 28 In the diagram showing the brightness distribution, high and low brightness are expressed by shades. Figure 28 In addition to the diagram of brightness distribution, a legend related to brightness shades is also shown (the minimum brightness is grayscale 0 and the maximum brightness is grayscale 255). Figure 28 The relative brightness values (100% and 0%) corresponding to the examples are shown in FIG. Figure 29 The center position of the Y axis direction of Example 2 and Example 3 ( Figure 28 The luminance distribution diagram is shown in the figure of the AA line. Figure 29 In the figure, the horizontal axis is the angle of the Y-axis relative to the front direction (Z-axis direction) (unit: "°"), and the vertical axis is the brightness (unit: "cd / m 2 ”). Figure 29 The positive and negative signs marked on the angle of the horizontal axis are "-(negative)" indicating the left side of the Y-axis direction relative to the reference 0° (front direction) when the backlight device is observed from the front, and "+(positive)" indicating the right side of the Y-axis direction relative to the reference 0° (front direction) when the backlight device is observed from the front.

[0176] The experimental results of comparative experiment 2 are described. Figure 28 as well as Figure 29It can be seen that, compared with Examples 2 and 3, the brightness in the center portion in the Y-axis direction is equivalent, but the brightness in Example 3 is higher than that in Example 2 at the two end portions in the Y-axis direction, and the difference in brightness with the center portion is smaller. At the same time, the ratio of minimum brightness divided by maximum brightness is as high as 83% in Example 3, while it is as low as 70% in Example 2. The reason for this experimental result is believed to be that in Example 3, the occupancy rate of the fifth light guide plate lens 227 (end-side fifth light guide plate lens 227E) is lower, and the occupancy rate of the sixth light guide plate lens 228 (end-side sixth light guide plate lens 228E) is higher at the two end portions in the Y-axis direction of the second opposite main surface 225C of the second light guide plate 225. In Example 3, at both end portions of the second light guide plate 225 in the Y-axis direction, the amount of light traveling straight along the X-axis direction is reduced due to repeated total reflection between the fifth light guide plate lens 227 (end-side fifth light guide plate lens 227E) and the second light guide plate main light exit surface 225B. This reduces the amount of light that easily reaches the end portion of the second light guide plate 225 in the Y-axis direction and is reflected by the sixth light guide plate inclined surface 228A of the sixth light guide plate lens 228 (end-side sixth light guide plate lens 228E), increasing the amount of light that exits from the second light guide plate main light exit surface 225B. Based on the above, it is speculated that in Example 3, the brightness of light emitted from the central portion and both end portions of the second light guide plate main light exit surface 225B in the Y-axis direction is uniform.

[0177] As described above, according to this embodiment, a plurality of fifth light guide plate lenses (third lenses) 227 include a central side fifth light guide plate lens (central side third lens) 227C, and an end side fifth light guide plate lens (end side third lens) 227E located on the second opposite main surface 25C closer to the end side in the second direction than the central side fifth light guide plate lens 227C, and a plurality of sixth light guide plate lenses 228 include a central side sixth light guide plate lens (central side first lens) 228C, and an end side sixth end side light guide plate lens (end side first lens) 228E located on the second opposite main surface 225C closer to the end side in the second direction than the central side sixth light guide plate lens 228C, the size of the end side fifth light guide plate lens 227E in the second direction is smaller than the size of the central side fifth light guide plate lens 227C in the second direction, and the size of the end side sixth light guide plate lens 228E in the second direction is larger than the size of the central side sixth light guide plate lens 228C in the second direction. The occupancy rate of the end-side fifth light guide plate lens 227E at the end portion of the second opposing principal surface 225C in the second direction is lower than the occupancy rate of the central-side fifth light guide plate lens 227C at the center portion in the second direction. Consequently, the closer one moves from the center side of the second light guide plate 225 in the second direction to the end, the less light travels in the first direction due to repeated total reflections between the end-side fifth light guide plate lens 227E and the second light guide plate light exiting principal surface 225B, making it easier for light to reach the end portion of the second light guide plate 225 in the second direction. Meanwhile, the occupancy rate of the end-side sixth light guide plate lens 228E at the end portion of the second opposing principal surface 225C in the second direction is higher than the occupancy rate of the central-side sixth light guide plate lens 228C at the center portion in the second direction. Consequently, at the end portion of the second light guide plate 225 in the second direction, the amount of light reflected by the sixth light guide plate inclined surface 228A of the end-side sixth light guide plate lens 228E and emitted from the second light guide plate light exiting principal surface 225B increases. As a result, the brightness of the outgoing light is made uniform in the central side portion and the end side portions in the second direction of the light-emitting main surface 225B of the second light guide plate.

[0178] <Fourth embodiment>

[0179] use Figures 30 to 33 The fourth embodiment is described. In this fourth embodiment, the configuration of the sixth light guide plate lens 328 is modified from the first embodiment. Repetitive descriptions of the same structures, functions, and effects as those of the first embodiment will be omitted.

[0180] like Figure 30 As shown, a plurality of two types of sixth light guide plate lenses 328 are provided on the second light guide plate 325 of this embodiment. Figure 30The second light guide plate 325 shown in the figure has a second LED 24 arranged on the right side of the figure. The plurality of sixth light guide plate lenses 328 arranged along the X-axis direction include a sixth light guide plate lens (one first lens) 328α having a gentle slope 328Aα, which serves as the sixth light guide plate slope 328A, and a sixth light guide plate lens (the other first lens) 328β having a steep slope 328Aβ, which serves as the sixth light guide plate slope 328A. The angle θ2β of the steep slope 328Aβ of the other sixth light guide plate lens 328β relative to the X-axis direction is greater than the angle θ2α of the gentle slope 328Aα of the one sixth light guide plate lens 328α relative to the X-axis direction. Specifically, the angle θ2α of the gentle slope 328Aα of the one sixth light guide plate lens 328α relative to the X-axis direction is, for example, approximately 27°. The steep slope 328Aβ of the other sixth light guide plate lens 328β forms an angle θ2β of about 58° with respect to the X-axis direction. The sixth light guide plate lenses 328α and 328β are alternately arranged one after another in the X-axis direction.

[0181] According to such a configuration, when the light emitted from the second LED 24 and propagating in the second light guide plate 325 is reflected (refracted) by the sixth light guide plate inclined surface 328A, i.e., the gentle inclined surface 328Aα, of one sixth light guide plate lens 328α, it is easy to be directed to the side opposite to the second LED 24 side in the X-axis direction relative to the front direction ( Figure 30 On the other hand, if the light emitted from the second LED 24 and propagating in the second light guide plate 325 is reflected (refracted) by the sixth light guide plate inclined surface 328A, i.e., the steep inclined surface 328Aβ of the sixth light guide plate lens 328β, it is easy to move toward the second LED 24 side in the X-axis direction ( Figure 30 Therefore, if the second LED 24 is turned on, the peak brightness of the emitted light can be provided to the side opposite to the second LED 24 side in the X-axis direction and the second LED 24 side in the X-axis direction.

[0182] Next, in the backlight device 12 of this embodiment, in order to obtain knowledge about how the light distribution changes when only the first LED 13 is turned on, when only the second LED 24 is turned on, and when both the first LED 13 and the second LED 24 are turned on, a demonstration experiment 6 was conducted. In this demonstration experiment 6, using the backlight device 12 having the second light guide plate 325 described previously in this paragraph, the brightness of the emitted light was measured when the first LED 13 was turned on and the second LED 24 was turned off, when the second LED 24 was turned on and the first LED 13 was turned off, and when both the first LED 13 and the second LED 24 were turned on, a graph of the light distribution (brightness angle distribution) in the X-axis direction was created.

[0183] The experimental results of light distribution in empirical experiment 6 are as follows: Figures 31 to 33 shown. Figures 31 to 33 In the light distribution graph 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: "%). Figure 31 The peak brightness of the image is taken as the relative value to the reference (100%). Figures 31 to 33 The positive and negative signs of the angles of the horizontal axis are the same as Figure 10 The symbols marked on the horizontal axis of the graph have the same meaning. Figure 31 The light distribution when the first LED 13 is turned on and the second LED 24 is turned off is shown. Figure 32 The light distribution when the second LED 24 is turned on and the first LED 13 is turned off is shown. Figure 33 The light distribution when both the first LED 13 and the second LED 24 are turned on is shown.

[0184] The experimental results of empirical experiment 6 are explained. Figure 31 The peak brightness is approximately 0°, and the emission angle range is about ±10°. This result is consistent with the experimental results of Experiment 2. Figure 11 Same. Figure 32 In the light distribution, there are two peak brightnesses near -40° and near +20°. It can be inferred that the light emitted near -40° is reflected by the gentle slope 328Aα of the sixth light guide plate lens 328α on one side, and the light emitted near +20° is reflected by the steep slope 328Aβ of the sixth light guide plate lens 328β on the other side. Figure 32 It can be said that if the second LED 24 is turned on, the peak brightness of the emitted light is shifted to the side opposite to the second LED 24 side in the X-axis direction and the emitted light in the light distribution distribution of the second LED 24 side in the X-axis direction. Figure 33 The light distribution is Figure 31 Light distribution and Figure 32 That is, in Figure 33 In the light distribution, peak brightness occurs at approximately 0°, near -40°, and near +20°, with the highest brightness occurring at approximately 0°. Therefore, if both the first LED 13 and the second LED 24 are illuminated, the image displayed on the liquid crystal display device 10 can be more clearly seen from both the driver's seat and the passenger seat.

[0185] As described above, according to this embodiment, a plurality of sixth light guide plate lenses 328 are arranged in the first direction. The plurality of sixth light guide plate lenses 328 include: one sixth light guide plate lens (one first lens) 328a having a gently inclined surface 328Aα as the sixth light guide plate inclined surface 328A; and another sixth light guide plate lens (the other first lens) 328β having a steeply inclined surface 328Aβ as the sixth light guide plate inclined surface 328A having a larger angle with respect to the first direction than the gently inclined surface 328Aα. Light refracted by the gently inclined surface 328Aα of the sixth light guide plate inclined surface 328A of one sixth light guide plate lens 328α tends to travel toward the side of the first direction opposite to the second LED 24 side relative to the front direction. On the other hand, light refracted by the steeply inclined surface 328Aβ of the sixth light guide plate inclined surface 328A of the other sixth light guide plate lens 328β tends to travel toward the second LED 24 side relative to the front direction in the first direction. Therefore, when the second LED 24 is turned on, outgoing light having a brightness angle distribution in which the peak brightness of the outgoing light is shifted to the side opposite to the second LED 24 side in the first direction and to the second LED 24 side in the first direction can be supplied.

[0186] <Fifth embodiment>

[0187] pass Figure 34 The fifth embodiment is described. In the fifth embodiment, the configuration of the sixth light guide plate lens 428 is modified from the first embodiment. Repetitive descriptions of the same structures, functions, and effects as those of the first embodiment will be omitted.

[0188] like Figure 34 As shown, the second light guide plate 425 of this embodiment is not provided with the seventh light guide plate inclined surface 28B and the second flat surface 29 described in the first embodiment on the second opposite main surface 425C (see Figure 2 ) structure. At the same time, the two sixth light guide plate lenses 428 adjacent to each other in the X-axis direction are not connected to each other via the second plane 29. Therefore, the height of the plurality of sixth light guide plate lenses 428 arranged along the X-axis direction gradually decreases as they move away from the second LED 24 in the X-axis direction, and conversely, the height gradually increases as they move closer to the second LED 24 in the X-axis direction. In addition, relative to Figure 34 The second light guide plate 425 shown in the figure has the second LED 24 arranged on the right side.

[0189] Specifically, the following description will be given of the three sixth light guide plate lenses 428 arranged continuously in the X-axis direction among the plurality of sixth light guide plate lenses 428 arranged in the X-axis direction. Among the three sixth light guide plate lenses 428 arranged continuously in the X-axis direction, the sixth light guide plate inclined surface 428A of the sixth light guide plate lens 428 located in the center in the X-axis direction is aligned with the side opposite to the second LED 24 in the X-axis direction ( Figure 34 The first plane 428D of the sixth light guide plate lens 428 located in the center of the X-axis direction is connected to the first plane 428D of the sixth light guide plate lens 428 located in the center of the X-axis direction on the side of the second LED 24 in the X-axis direction ( Figure 34 The sixth light guide plate bevel 428A of the sixth light guide plate lens 428 adjacent to the second light guide plate lens 428 (on the right side of the second light guide plate 425) is connected. In this way, a portion of the sixth light guide plate lens 428 is formed in the second opposite main surface 425C of the second light guide plate 425, and the seventh light guide plate bevel 28B and the second plane 29 described in the first embodiment do not exist, and only the sixth light guide plate bevel 428A and the first plane 428D exist. Moreover, the occupancy rate of the first plane 428D is higher than the occupancy rate of the sixth light guide plate bevel 428A. When the first LED 13 is turned on and the second LED 24 is turned off, the light irradiated from the side of the first light guide plate 14 will hardly be refracted even if it hits the first plane 428D. By increasing the occupancy rate of the first plane 428D, it is difficult to generate side lobe light when the first LED 13 is turned on and the second LED 24 is turned off.

[0190] As described above, according to this embodiment, the sixth light guide plate lens 428 is arranged adjacent to the sixth light guide plate inclined surface 428A in the first direction and has a first flat surface 428D along the first direction. A plurality of sixth light guide plate lenses 428 are arranged in the first direction. Among the three sixth light guide plate lenses 428 included in the plurality of sixth light guide plate lenses 428 and arranged continuously in the first direction, the sixth light guide plate inclined surface 428A of the sixth light guide plate lens 428 located in the center in the first direction is connected to the first flat surface 428D of the sixth light guide plate lens 428 adjacent to the side opposite the second LED 24 in the first direction. Furthermore, the first flat surface 428D of the sixth light guide plate lens 428 located in the center in the first direction is connected to the sixth light guide plate inclined surface 428A of the sixth light guide plate lens 428 adjacent to the second LED 24 side in the first direction. The three sixth light guide plate lenses 428 arranged continuously in the first direction are configured such that the mutually adjacent sixth light guide plate inclined surfaces 428A are directly connected to the first flat surface 428D. Therefore, the plurality of sixth light guide plate lenses 428 do not have inclined surfaces extending from the second LED 24 in the first direction toward the side opposite thereto. If the sixth light guide plate lenses 428 had inclined surfaces extending from the second LED 24 in the first direction toward the side opposite thereto, light emitted from the first light guide plate light exiting principal surface 14B of the first light guide plate 14 and incident on the second opposite principal surface 425C of the second light guide plate 425 could potentially strike the inclined surfaces and be refracted, thereby emitting sidelobe light that travels in a direction inclined relative to the front direction toward the side opposite to the second LED 24 in the first direction. In this regard, the plurality of sixth light guide plate lenses 428 do not have inclined surfaces extending from the second LED 24 in the first direction toward the side opposite thereto, thereby reducing the generation of such sidelobe light.

[0191] <Sixth embodiment>

[0192] pass Figure 35 The sixth embodiment is described. In the sixth embodiment, an anisotropic diffusion sheet 31 is used instead of the second louver 30 of the first embodiment. Repetitive descriptions of the same structure, operation, and effects as those of the first embodiment will be omitted.

[0193] like Figure 35 As shown, an anisotropic diffusion sheet 31 is disposed on the front side of the second light guide plate 525 in this embodiment to replace the second louver 30 described in the first embodiment (see FIG. Figure 3). The anisotropic diffuser 31 is a so-called double convex lens sheet. The anisotropic diffuser 31 has a substrate 31A and a convex cylindrical lens 31B protruding from the main surface of the surface side of the substrate 31A. The cross-sectional shape of the cylindrical lens 31B cut along the Y-axis direction is semicircular and semi-cylindrical extending linearly along the X-axis direction, and its surface is a third arc-shaped surface 31B1. A plurality of cylindrical lenses 31B are arranged along the Y-axis direction on the main surface of the surface side of the substrate 31A. The contact angles, width dimensions (arrangement intervals) and height dimensions of the plurality of cylindrical lenses 31B arranged along the Y-axis direction are all approximately the same. If the light incident on the cylindrical lens 31B hits the third arc-shaped surface 31B1 and is refracted, it rises at an angle close to the front direction. The third arcuate surface 31B1 of the cylindrical lens 31B has curvature in the Y-axis direction but no curvature in the X-axis direction, thus selectively focusing light only in the Y-axis direction (anisotropic focusing). By using such an anisotropic diffuser 31 and adjusting the contact angle of the third arcuate surface 31B1 of the cylindrical lens 31B, the range of light emission angles in the Y-axis direction can be limited. This can prevent reflections of the displayed image onto the windshield.

[0194] <Seventh embodiment>

[0195] pass Figure 36 The seventh embodiment is described. In the seventh embodiment, the configuration of the fifth light guide plate lens 627 is modified from the first embodiment. Repetitive descriptions of the same structures, functions, and effects as those of the first embodiment will be omitted.

[0196] like Figure 36 As shown, the fifth light guide plate lens 627 of the present embodiment is a so-called double convex lens. The cross-sectional shape of the fifth light guide plate lens 627 cut along the Y-axis direction is semicircular and semi-cylindrical extending linearly along the X-axis direction, and its surface is a fourth arc-shaped surface 627B. Even the fifth light guide plate lens 627 with such a structure can obtain the same function and effect as the above-mentioned first embodiment. In addition, compared with the above-mentioned first embodiment, the fourth arc-shaped surface 627B of the fifth light guide plate lens 627 is opposite to the first light emitting main surface 618B of the first louver 18 arranged on the back side (at Figure 36 As a result, uneven contact between the second light guide plate 625 and the first louver 18 is less likely to occur, and therefore, uneven brightness of the emitted light is less likely to occur.

[0197] <Other Implementation Methods>

[0198] The technology disclosed in this specification is not limited to the embodiments described above and illustrated in the drawings, and for example, the following embodiments are also included in the technical scope.

[0199] (1) The values of the sixth light guide plate lens 28, 228, 328, 428 of the second light guide plate 25, 125, 225, 325, 425, 625 can be changed appropriately. For example, the angle θ2 formed by the sixth light guide plate inclined surface 28A, 228A, 328A, 428A with respect to the X-axis direction is preferably changed within the range of 27° to 40°, but it can also be outside this range. In addition, the width dimension W2 of the sixth light guide plate inclined surface 28A, 228A, 328A, 428A can also be set to be constant regardless of the position in the X-axis direction. The angle θ3 formed by the seventh light guide plate inclined surface 28B with respect to the X-axis direction is preferably changed within the range of 3° to 10°, but it can also be outside this range. The width dimension W3 of the seventh light guide plate inclined surface 28B can also be set to be constant regardless of the position in the X-axis direction. The widths W4 and W5 of the first planes 28D and 428D and the second planes 29 of the sixth light guide plate lenses 28, 228, 328, and 428 may be values other than those shown in the first embodiment. Furthermore, the arrangement pitch P1 of the sixth light guide plate lenses 28, 228, 328, and 428 may be varied depending on the position in the X-axis direction.

[0200] (2) The width W4 of the first plane 28D or 428D of the sixth light guide plate lens 28, 228, 328, or 428 may vary depending on the position in the X-axis direction. Furthermore, the width W5 of the second plane 29 may be constant regardless of the position in the X-axis direction.

[0201] (3) Specific values such as the contact angle θc of the fourth light guide plate lens 26 and the apex angle θ1 of the fifth light guide plate lens 27 , 227 , 627 included in the second light guide plate 25 , 125 , 225 , 325 , 425 , and 625 may be changed as appropriate.

[0202] (4) The specific material used for the second light guide plates 25, 125, 225, 325, 425, and 625 may be changed as appropriate.

[0203] (5) The specific values of the contact angle, tilt angle, etc. of each light guide plate lens 21 to 23 included in the first light guide plate 14 can be changed as appropriate. The specific material used for the first light guide plate 14 can be changed as appropriate.

[0204] (6) The positional relationship of the second LED 24 relative to the second light guide plate 25, 125, 225, 325, 425, 625 in the X-axis direction may be the same as the positional relationship of the first LED 13, 113 relative to the first light guide plate 14 in the X-axis direction. In other words, the first LED 13, 113 and the second LED 24 may be arranged on the same side in the X-axis direction.

[0205] (7) Either or both of the first light guide plate lens 21 and the second light guide plate lens 22 included in the first light guide plate 14 may be omitted.

[0206] (8) Either or both of the fourth light guide plate lens 26 and the fifth light guide plate lens 27 , 227 , 627 included in the second light guide plate 25 , 125 , 225 , 325 , 425 , and 625 may be omitted.

[0207] (9) The thickness of the first light guide plate 14 may decrease as it becomes farther away from the first LEDs 13 and 113 , and the first opposite main surface 14C may be inclined.

[0208] (10) The thickness of the second light guide plate 25, 125, 225, 325, 425, or 625 may decrease as it becomes farther away from the second LED 24, and the second opposite main surface 25C, 125C, 225C, or 425C may be inclined.

[0209] (11) The specific values of the inclination angles, vertex angles, etc. of the prism bevels 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 of the substrates 16A and 17A used in the prism sheets 16 and 17 can be appropriately changed. Similarly, the specific materials used in the prisms 16B and 17B can be appropriately changed.

[0210] (12) 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 have a curved shape with a plurality of inclination angles.

[0211] (13) In the first louvers 18 and 118 , 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°, and can be, for example, tan12.5°, tan15°, tan17.5°, etc.

[0212] (14) In the configuration described in the second embodiment, the third light-entering principal surface 19A of the linear Fresnel lens sheet 19 may be mounted in contact with the first light-emitting principal surface 118B of the first louver 118. In this case, the linear Fresnel lens sheet 19 may be integrally formed with the first louver 118.

[0213] (15) In the configuration described in the second embodiment, the linear Fresnel lens sheet 19 may be provided with the front and back directions reversed. That is, the linear Fresnel lens 19C may be provided on the third light incident principal surface 19A of the linear Fresnel lens sheet 19.

[0214] (16) In the configuration described in (15) above, the third light-emitting principal surface 19B of the linear Fresnel lens sheet 19 may be mounted in contact with the fourth light-entering principal surface 20A of the third louver 20. In this case, the linear Fresnel lens sheet 19 and the third louver 20 may be integrally formed.

[0215] (17) In the configuration described in the second embodiment, the plurality of linear Fresnel lenses 19C included in the linear Fresnel lens sheet 19 may include a plurality of linear Fresnel lenses 19C having the same angle θ10 relative to the first inclined surface 19C1 in the X-axis direction (angle θ11 relative to the second inclined surface 19C2 in the X-axis direction). In other words, the angle θ10 relative to the first inclined surface 19C1 in the X-axis direction (angle θ11 relative to the second inclined surface 19C2 in the X-axis direction) may be different for all the linear Fresnel lenses 19C.

[0216] (18) In the configuration described in the second embodiment, the specific values of the various angles of the linear Fresnel lens 19C included in the linear Fresnel lens sheet 19 (angle θ10 of the first inclined surface 19C1 relative to the X-axis direction, angle θ11 of the second inclined surface 19C2 relative to the X-axis direction, and vertex angle θ12 formed between the first inclined surface 19C1 and the second inclined surface 19C2) can be appropriately changed. In this case, the angle θ10 of the first inclined surface 19C1 relative to the X-axis direction is preferably within the range of 0° to 24°, and the angle θ11 of the second inclined surface 19C2 relative to the X-axis direction is preferably within the range of 46° to 70°, but may be outside these ranges. Furthermore, while setting the angle θ10 of the first inclined surface 19C1 relative to the X-axis to within the range of 0° to 24° and the angle θ11 of the second inclined surface 19C2 relative to the X-axis to within the range of 46° to 70°, the vertex angle θ12 formed between 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, by setting the angle θ10 of the first inclined surface 19C1 relative to the X-axis to outside the range of 0° to 24° and the angle θ11 of the second inclined surface 19C2 relative to the X-axis to outside the range of 46° to 70°, the vertex angle θ12 formed between 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, the specific material used for the linear Fresnel lens sheet 19 can be appropriately modified.

[0217] (19) In the configuration described in the second embodiment, in the third louver 20 , the specific value of the ratio (tanθ) of the width of the third light-transmitting portion 20D divided by the height can be appropriately changed other than tan45°, for example, to tan50°.

[0218] (20) The configuration described in the second embodiment may be combined with the configurations described in the third to seventh embodiments.

[0219] (21) In the configuration described in the third embodiment, the specific rate of change of the width of the center side fifth light guide plate lens 227C (center side sixth light guide plate lens 228C) and the width of the end side fifth light guide plate lens 227E (end side sixth light guide plate lens 228E) according to the position in the Y-axis direction, etc., except Figure 27 The data other than those shown can also be changed as appropriate.

[0220] (22) In the configuration described in the fourth embodiment, the specific arrangement of the two types of sixth light guide plate lenses 328 may be modified as appropriate. For example, a plurality of sixth light guide plate lenses 328α on one side may be arranged successively, followed by a plurality of sixth light guide plate lenses 328β on the other side, with the plurality of sixth light guide plate lenses 328α on one side and the plurality of sixth light guide plate lenses 328β on the other side being arranged successively.

[0221] (23) In the configuration described in the fourth embodiment, in addition to the above, the specific values of the angle θ2α formed by the gently inclined surface 328Aα of the sixth light guide plate lens 328α on one side relative to the X-axis direction and the angle θ2β formed by the steep inclined surface 328Αβ of the sixth light guide plate lens 328β on the other side relative to the X-axis direction can be appropriately changed.

[0222] (24) The configuration described in the fifth embodiment may be combined with the configuration described in the fourth embodiment.

[0223] (25) The cylindrical lenses 31B included in the anisotropic diffusion sheet 31 described in the sixth embodiment may be configured to extend in a serpentine shape along the X-axis direction.

[0224] (26) The second louver 30 or the anisotropic diffusion sheet 31 may also be removed.

[0225] (27) Instead of the first LEDs 13 and 113 and the second LED 24, a light source such as an organic EL (ElectroLuminescence) may be used.

[0226] (28) Instead of a polarizer, 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. The reflective polarizer 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 mounted 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 polarizer 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.

[0227] (29) A prism sheet having prisms disposed on the light incident principal surface side may be used in place of the first prism sheet 16, 116 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, and the light exit principal surface faces the first light incident principal surface 18A of the first louvers 18, 118. 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 louvers 18, 118, and a sufficient amount of light can be transmitted through the first light-transmitting portion 18D.

[0228] (30) The vehicle-mounted liquid crystal display device 10, 110 can be installed at a position other than in front of the front passenger seat of the passenger car. For example, it can also be installed at a position between the front passenger seat and the driver's seat. As the configuration of the liquid crystal display device 10, 110 changes, the angle range of the required viewing angle also changes. Therefore, it is sufficient to change the first blind 18, 118, the third blind 20, and the sixth light guide plate lens 28, 228, 328, 428 and other components (the ratio of the width to the height of each light-transmitting portion 18D, 30D, the inclination angle of each inclined surface 28A, 28B of the sixth light guide plate lens 28, 228, 328, 428, etc.) accordingly. In addition, in the configuration described in the second embodiment, in addition to the above, it is sufficient to change the configurations of the linear Fresnel lens sheet 19 and the third louver 20 (the ratio of the width to the height of the third light-transmitting portion 20D, the inclination angles of the inclined surfaces 19C1 and 19C2 of the linear Fresnel lens 19C, etc.).

[0229] (31) In addition to vehicle-mounted applications, the liquid crystal display devices 10 and 110 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 devices 10 and 110 is changed, the required viewing angle range is also changed. Therefore, the configurations of the first louver 18 and 118, the third louver 20, and the sixth light guide plate lenses 28, 228, 328, and 428 (such as the ratio of the width to the height of each light-transmitting portion 18D and 30D, and the inclination angles of the inclined surfaces 28A and 28B of the sixth light guide plate lenses 28, 228, 328, and 428) can be changed accordingly. In addition, in the configuration described in the second embodiment, in addition to the above, it is sufficient to change the configurations of the linear Fresnel lens sheet 19 and the third louver 20 (such as the ratio of the width to the height of the light-transmitting portion 20D, the inclination angles of the inclined surfaces 19C1 and 19C2 of the linear Fresnel lens 19C, etc.).

[0230] Description of Reference Numerals

[0231] 10, 110…Liquid crystal display device (display device); 11…Liquid crystal panel (display panel); 12, 112…Backlight device (illumination device); 13, 113…First LED (first light source); 14…First light guide plate; 14A…First light incident end surface (first end surface); 14B…First light emitting principal surface (first principal surface); 14C…First opposite principal surface (second principal surface); 16, 116…First prism sheet; 16B…First prism; 16B1…First prism inclined surface (third inclined surface); 16B2…Second prism inclined surface (fourth inclined surface); 17…Second prism sheet; 17B…Second prism; 17B1…Third prism inclined surface (fifth inclined surface); 17B2…Fourth prism inclined surface (sixth inclined surface); 1 8, 118…first louver (first sheet); 18A…first principal light incident surface (third principal surface); 18B, 118B, 618B…first principal light emitting surface (fourth principal surface); 18C…first light shielding portion; 18D, 118D…first light transmitting portion; 19…linear Fresnel lens sheet (second sheet); 19A…third principal light incident surface (seventh principal surface); 19B…third principal light emitting surface (eighth principal surface); 19C…linear Fresnel lens (fourth lens); 19C1…first inclined surface (seventh inclined surface); 20…third louver (third sheet); 20A…fourth principal light incident surface (ninth principal surface); 20B…fourth principal light emitting surface (tenth principal surface); 20C…third light shielding portion (second light shielding portion); 20D…third light transmitting portion (the 2nd light-transmitting portion); 24…second LED (second light source); 25, 125, 225, 325, 425, 625…second light guide plate; 25A…second light incident end surface (second end surface); 25B, 225B…second light guide plate light emitting principal surface (fifth principal surface); 25C, 125C, 225C, 425C…second opposite principal surface (sixth principal surface); 26…fourth light guide plate lens (second lens); 27, 227, 627…fifth light guide plate lens (third lens); 28, 228, 328, 428…sixth light guide plate lens (first lens); 28A, 228A, 328A, 428A…sixth light guide plate inclined surface (first inclined surface); 28B…seventh light guide plate inclined surface (second inclined surface); 2 8D, 428D…first plane; 29…second plane; 227C…center-side fifth light guide plate lens (center-side third lens); 227E…end-side fifth light guide plate lens (end-side third lens); 228C…center-side sixth light guide plate lens (center-side first lens); 228E…end-side sixth light guide plate lens (end-side first lens); 328α…one side sixth light guide plate lens (one side first lens); 328β…other side sixth light guide plate lens (other side first lens); 328Aα…gentle slope; 328Aβ…steep slope; H1…height; H3…height; W1…width; W6…width; W7…width dimension (dimension in the second direction); W8…width dimension (dimension in the second direction);W9…width dimension (dimension in the second direction); W10…width dimension (dimension in the second direction); θ2…angle; θ3…angle; θ4…angle; θ7…angle.

Claims

1. A lighting device, characterized in that: It has: a first light source; A first light guide plate, at least a portion of its outer peripheral end surface facing the first light source and serving as a first end surface for light incidence, one principal surface serving as a first principal surface for light emission, and the other principal surface serving as a second principal surface; a first sheet having one principal surface as a third principal surface disposed toward the first principal surface and configured to be incident on light, and another principal surface as a fourth principal surface for emitting light; Second light source; as well as The second light guide plate has at least a portion of its outer peripheral end surface as a second end surface facing the second light source and configured as a light incident surface, one principal surface of which is a fifth principal surface for emitting light, and the other principal surface of which is a sixth principal surface arranged toward the fourth principal surface. The first sheet has at least: two first light shielding portions arranged at intervals in a first direction including a direction from the first light source toward the first light guide plate and configured to shield light; as well as a first light-transmitting portion disposed between the two first light-shielding portions and allowing light to pass therethrough; The sixth main surface of the second light guide plate is provided with a first lens having a first inclined surface rising from the side opposite to the second light source in the first direction toward the second light source. A third lens extending along the first direction is provided on the sixth principal surface of the second light guide plate, wherein a plurality of the third lenses are arranged at intervals along a second direction, wherein the second direction is orthogonal to both the first direction and the normal direction of the principal surface of the first light guide plate. A plurality of first lenses are arranged alternately with the third lenses in the second direction. The plurality of third lenses include a central third lens and an end third lens located on the sixth principal surface further to the end side in the second direction than the central third lens. The plurality of first lenses include a central first lens and an end first lens located on the sixth principal surface further to the end side in the second direction than the central first lens. The dimension of the third lens on the end side in the second direction is smaller than the dimension of the third lens on the center side in the second direction. The dimension of the end-side first lens in the second direction is larger than the dimension of the center-side first lens in the second direction.

2. The lighting device according to claim 1, characterized in that An angle formed by the first inclined surface relative to the first direction is in a range of 27° to 40°.

3. The lighting device according to claim 1 or 2, characterized in that: The first lens has a second inclined surface that rises from the second light source in the first direction toward the opposite side.

4. The lighting device according to claim 3, characterized in that An angle formed by the second inclined surface relative to the first direction is in a range of 3° to 10°.

5. The lighting device according to claim 3, characterized in that The first lens has a first plane along the first direction, and the first plane is located between the first inclined surface and the second inclined surface in the first direction.

6. The lighting device according to claim 3, characterized in that A plurality of first lenses are arranged in the first direction. A second plane along the first direction is provided on the sixth principal surface of the second light guide plate, and the second plane is located between two adjacent first lenses in the first direction.

7. The lighting device according to claim 1 or 2, characterized in that: The first lens has a first plane along the first direction, and the first plane is arranged adjacent to the first inclined surface in the first direction. A plurality of first lenses are arranged in the first direction. Among the three first lenses included in the plurality of first lenses and arranged continuously in the first direction, the first inclined surface of the first lens located at the center in the first direction is connected to the first flat surface of the first lens adjacent to the side opposite to the second light source in the first direction, and the first flat surface of the first lens located at the center in the first direction is connected to the first inclined surface of the first lens adjacent to the second light source side in the first direction.

8. The lighting device according to claim 1 or 2, characterized in that: The fifth principal surface of the second light guide plate is provided with second lenses extending along the first direction. A plurality of second lenses are arranged along a second direction perpendicular to both the first direction and the normal direction of the principal surface of the first light guide plate.

9. The lighting device according to claim 1 or 2, characterized in that: A plurality of first lenses are arranged in the first direction. The plurality of first lenses include: The first lens on one side has a gentle slope as the first slope; and The other first lens has a steep slope as the first slope, and the steep slope has a larger angle with respect to the first direction than the gentle slope.

10. The lighting device according to claim 1 or 2, characterized in that: have: a first prism sheet having one principal surface facing the first principal surface, the first prism sheet including a plurality of first prisms arranged along the first direction and having first prisms extending along a second direction, the second direction being orthogonal to both the first direction and a normal direction of the principal surface of the first light guide plate; as well as a second prism sheet located on the side opposite to the first light guide plate relative to the first prism sheet and having a plurality of second prisms arranged along the first direction and extending along the second direction; 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.

11. The lighting device according to claim 1 or 2, characterized in that: have: a second sheet having one principal surface facing the fourth principal surface and serving as a seventh principal surface on which light is incident, and another principal surface serving as an eighth principal surface from which light is emitted; and The third sheet has one principal surface facing the eighth principal surface and serving as a ninth principal surface for incident light, and the other principal surface facing the sixth principal surface and serving as a tenth principal surface for emitting light. The second lens has a fourth lens, and the fourth lens is arranged on the seventh principal surface or the eighth principal surface. The third piece has at least: two second light shielding portions, which are spaced apart in the first direction and shield light; as well as a second light-transmitting portion disposed between the two second light-shielding portions and allowing light to pass therethrough; The fourth lens has an inclined seventh slope that rises from the end side of the second lens in the first direction toward the center side. In the third sheet, a ratio of a width of the second light-transmitting portion divided by a height is greater than a ratio of a width of the first light-transmitting portion divided by a height.

12. The lighting device according to claim 1 or 2, characterized in that: The first light source is arranged on one side of the first direction relative to the first light guide plate. The second light source is arranged on the other side of the first direction relative to the second light guide plate.

13. A display device, characterized in that: It has: The lighting device according to any one of claims 1 to 12; and A display panel performs display using the light from the lighting device.

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