Illumination device and display device

Abstract

To improve emission efficiency.SOLUTION: A lighting device comprises: a first light guide plate having a first side face, a second side face located at a side opposite to the first side face in a first direction, a first main face, and a first opposing face located at a side opposite to the first main face in a second direction intersecting with the first direction; and a first light source opposing the first side face, and emitting first P-polarization light to the first side face. The first side face is inclined to the first main face and the first opposing face, and the first light source is inclined to a first linear line which is vertical to the first side face.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to a lighting device and a display device.

Background Art

[0002] For example, a display device such as a liquid crystal display device includes a display panel having pixels and a lighting device such as a backlight that illuminates the display panel. The lighting device includes a light source that emits light and a light guide plate irradiated with light from the light source. Light from the light source enters the light guide plate from the side surface of the light guide plate, propagates through the light guide plate, and exits from an exit surface corresponding to one main surface of the light guide plate.

[0003] For example, as described in Patent Document 1, a configuration in which two light guide plates are stacked is also known. However, in a conventional lighting device, there is a problem that some light leaks from the light guide plate before entering the light guide plate from the side surface and exiting from the exit surface, resulting in a decrease in the exit efficiency.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present embodiment is to provide a lighting device and a display device capable of improving the emission efficiency.

Means for Solving the Problems

[0006] The lighting device according to one embodiment includes a first light guide plate having a first side surface, a second side surface located on the opposite side of the first side surface in the first direction, a first main surface, and a first opposing surface located on the opposite side of the first main surface in a second direction intersecting the first direction, and a first light source facing the first side surface and emitting first P-polarized light to the first side surface. The first side surface is inclined with respect to the first main surface and the first opposing surface, and the first light source is inclined with respect to a first straight line perpendicular to the first side surface.

[0007] The display device according to another embodiment includes the lighting device according to any one of (1) to (14) and a display panel that displays an image, and the display panel faces the first main surface.

Brief Description of the Drawings

[0008]

Figure 1

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[0009] Hereinafter, embodiments will be described with reference to the drawings. Note that the disclosure is merely an example, and for those that can be easily conceived by a person skilled in the art with appropriate modifications while maintaining the gist of the invention, they are naturally included in the scope of the present invention. Also, for the purpose of making the description clearer, the drawings may be presented schematically compared to the embodiments, but they are merely examples and do not limit the interpretation of the present invention. Further, in this specification and each figure, components that exhibit the same or similar functions as those previously described with respect to the existing figures may be assigned the same reference numerals, and detailed descriptions that are redundant may be omitted.

[0010] In the embodiment, as an example of the display device DSP, a transmissive liquid crystal display device is disclosed. Also, as an example of the lighting device, a lighting device used as the backlight of a transmissive liquid crystal display device is disclosed. Note that the main configurations disclosed in this embodiment are applicable to a liquid crystal display device having a reflective function that reflects external light in addition to the transmissive function and utilizes this reflected light for display, an electronic paper type display device having electrophoretic elements, etc., a display device applying MEMS (Micro Electro Mechanical Systems), or a display device applying electrochromism. Further, the main configurations disclosed in this embodiment are also applicable to lighting devices used for purposes other than backlights.

[0011] (First Embodiment) FIG. 1 is an exploded perspective view showing a configuration example of a display device DSP according to the present embodiment. In FIG. 1, a direction X, a direction Y (first direction), and a direction Z (second direction) are shown. The direction X, the direction Y, and the direction Z are orthogonal to each other, but may intersect at an angle other than 90 degrees. The direction X and the direction Y correspond to directions parallel to the main surface of the substrate constituting the liquid crystal display device (hereinafter, may be simply referred to as a display device) DSP, and the direction Z corresponds to the thickness direction of the display device DSP. In this specification, the direction from the first substrate SUB1 to the second substrate SUB2 is referred to as "upper side" (or simply up), and the direction from the second substrate SUB2 to the first substrate SUB1 is referred to as "lower side" (or simply down). When referring to "the second layer above the first layer" and "the second layer below the first layer", the second layer may be in contact with the first layer or may be separated from the first layer. It is assumed that there is an observation position for observing the display device DSP on the tip side of the arrow indicating the direction Z, and viewing from this observation position toward the X-Y plane defined by the direction X and the direction Y is referred to as a plan view. The X-Z plane is defined by the direction X and the direction Z. The Y-Z plane is defined by the second direction and the direction Z. Also, the "lengths in the direction X and the direction Y of a predetermined substance, object, or region" may be referred to as "width", and the "length in the third direction of a predetermined substance, object, or region" may be referred to as "thickness" or "height".

[0012] The display device DSP includes a display panel PNL, an illumination device IL, an IC chip 1, and a wiring substrate 2.

[0013] The display panel PNL includes a first substrate SUB1 and a second substrate SUB2. The first substrate SUB1 and the second substrate SUB2 face each other. A display function layer (in this embodiment, the liquid crystal layer LC described later) is provided between each of the substrates SUB1 and SUB2. The display panel PNL has a display area DA and a non-display area NDA. The display area DA is an area for displaying an image. The display area DA is located substantially at the center of the area where the first substrate SUB1 and the second substrate SUB2 face each other. The non-display area NDA is an area where no image is displayed and is located outside the display area DA. The display panel PNL includes, for example, a plurality of pixels PX arranged in a matrix in the display area DA.

[0014] The IC chip 1 and the wiring board 2 may read signals from the display panel PNL, but mainly function as signal sources for supplying signals to the display panel PNL. The IC chip 1 and the wiring board 2 are located in the non-display area NDA. In the example shown in FIG. 1, the IC chip 1 and the wiring board 2 are mounted on a mounting portion MT of the first substrate SUB1 that extends outside one substrate side edge (or sometimes referred to as the substrate end) of the second substrate SUB2. The wiring board 2 is, for example, a flexible printed circuit board that can be bent. The IC chip 1 may be provided on the wiring board 2.

[0015] The lighting device IL illuminates the display panel PNL. The lighting device IL includes a light guide plate LG1, a light guide plate LG2, a plurality of light sources LS1, and a plurality of light sources LS2. The light guide plate LG2, the light guide plate LG1, the first substrate SUB1, and the second substrate SUB2 are arranged in the order described toward the tip side of the arrow in the direction Z.

[0016] The light guide plate LG1 is an insulating substrate such as a glass substrate or a plastic substrate. The light guide plate LG1 is formed of a material containing an acrylic resin, for example, an acrylic substrate. The light guide plate LG1 is formed in a flat plate shape parallel to the X-Y plane. The light guide plate LG1 has a main surface 1A facing the display panel PNL, a facing surface 1B located on the opposite side of the main surface 1A in the Z direction, a side surface SF1, and a side surface SF2 located on the opposite side of the side surface SF1 in the Y direction. The main surface 1A and the facing surface 1B are, for example, parallel to the X-Y plane and are provided parallel to each other. Note that the main surface 1A and the facing surface 1B may be non-parallel to each other. The side surface SF1 and the side surface SF2 face each other in the Y direction. The side surface SF1 is, for example, non-parallel to the X-Z plane. The side surface SF2 is, for example, parallel to the X-Z plane. The side surface SF1 and the side surface SF2 are, for example, provided non-parallel to each other. Note that the side surface SF1 and the side surface SF2 may be parallel to the X-Z plane and provided parallel to each other. The light guide plate LG1 has a thickness T1. The thickness T1 is the length from the facing surface 1B to the main surface 1A in the Z direction.

[0017] The plurality of light sources LS1 are arranged at intervals in the X direction. In the example shown in FIG. 1, the plurality of light sources LS1 face the side surface SF1. Also, the plurality of light sources LS1 are arranged along the side surface SF1 at intervals in the X direction.

[0018] The light guide plate LG2 is an insulating substrate such as a glass substrate or a plastic substrate. The light guide plate LG2 is formed of, for example, the same material as the light guide plate LG1. Note that the light guide plate LG2 does not necessarily have to be formed of the same material as the light guide plate LG1. The light guide plate LG2 is formed of a substrate material containing an acrylic resin, for example, an acrylic substrate. The light guide plate LG2 is formed in a flat plate shape parallel to the X-Y plane. The light guide plate LG2 has a main surface 2A facing the opposing surface 1B, an opposing surface 2B located on the opposite side of the main surface 2A in the Z direction, a side surface SF3 aligned with the side surface SF1 in the Z direction, and a side surface SF4 located on the opposite side of the side surface SF3 in the Y direction and aligned with the side surface SF2 in the Z direction. The main surface 2A and the opposing surface 2B are, for example, parallel to the X-Y plane and are provided parallel to each other. Note that the main surface 2A and the opposing surface 2B may not be parallel to each other. The side surface SF3 and the side surface SF4 face each other in the Y direction. The side surface SF3 is, for example, parallel to the X-Z plane. The side surface SF4 is, for example, non-parallel to the X-Z plane. The side surface SF3 and the side surface SF4 are, for example, provided non-parallel to each other. Note that the side surface SF3 and the side surface SF4 may be parallel to the X-Z plane and provided parallel to each other. The light guide plate LG2 has a thickness T2. The thickness T2 is the length from the opposing surface 2B to the main surface 2A in the Z direction.

[0019] The plurality of light sources LS2 are arranged at intervals in the X direction. In the example shown in FIG. 1, the plurality of light sources LS2 face the side surface SF4. Also, the plurality of light sources LS2 are arranged along the side surface SF4 with an interval in the X direction.

[0020] The light sources LS1 and LS2 are, for example, laser light sources such as semiconductor lasers that emit polarized laser light. Note that the light sources LS1 and LS2 are not limited to those that emit laser light, and may be, for example, light emitting diodes.

[0021] The light sources LS1 and LS2 may each include a plurality of light-emitting elements that emit light of different colors. For example, the light sources LS1 and LS2 each include three light-emitting elements that emit red, green, and blue light. When including three light-emitting elements that emit red, green, and blue light, the light sources LS1 and LS2 can obtain light of a mixed color (e.g., white) of these colors.

[0022] FIG. 2 is a plan view of the lighting device IL shown in FIG. 1. As shown in FIG. 2, the lighting device IL has a first region A1, a second region A2, and a boundary BO between the first region A1 and the second region A2. The first region A1 has a length LN10 in the direction Y, and the second region A2 has a length LN20 in the direction Y. The length LN10 and the length LN20 may be the same. Note that the length LN10 and the length LN20 do not have to be the same. "Same", "identical", "equivalent", and "coincident" include not only the case where physical quantities, materials, or configurations (structures) of a plurality of target objects, spaces, or regions are exactly the same, but also the case where they are slightly different to the extent that they can be regarded as substantially the same. In the example shown in FIG. 2, the light guide plates LG1 and LG2 are respectively located over the entire first region A1 and the entire second region A2. That is, the main surface 1A, the opposing surface 1B, the main surface 2A, and the opposing surface 2B shown in FIG. 2 are respectively located in the first region A1 and the second region A2. The side surfaces SF1 and SF3 are located in the first region A1, and the side surfaces SF2 and SF4 are located in the second region A2. The boundary BO corresponds to the middle between the side surfaces SF1 and SF2 and the middle between the side surfaces SF3 and SF4, respectively. For example, the boundary BO corresponds to the middle between the foremost end portion on the side opposite to the tip side of the arrow in the direction Y of the side surface SF1 and the foremost end portion on the tip side of the arrow in the direction Y of the side surface SF2. For example, the boundary BO corresponds to the middle between the foremost end portion on the side opposite to the tip side of the arrow in the direction Y of the side surface SF3 and the foremost end portion on the tip side of the arrow in the direction Y of the side surface SF4.

[0023] The light source LS1 emits light in the emission direction DL1 toward the side surface SF1. The intensity of the light emitted by the light source LS1 is highest on the optical axis AX1, and the emission direction DL1 is parallel to the optical axis AX1. The light source LS2 emits light in the emission direction DL2 toward the side surface SF4. The intensity of the light emitted by the light source LS2 is highest on the optical axis AX2, and the emission direction DL2 is parallel to the optical axis AX2.

[0024] Figure 3 is a cross-sectional view of the display device DSP shown in Figure 1. As shown in Figure 3, the display panel PNL further includes a liquid crystal layer LC, a seal SE, a polarizing plate PL1, and a polarizing plate PL2.

[0025] The liquid crystal layer LC and the seal SE are located between the first substrate SUB1 and the second substrate SUB2. The seal SE adheres the first substrate SUB1 and the second substrate SUB2 and encloses the liquid crystal layer LC between the first substrate SUB1 and the second substrate SUB2.

[0026] The polarizing plate PL1 is adhered to the lower surface of the first substrate SUB1. The polarizing plate PL2 is adhered to the upper surface of the second substrate SUB2. The polarization axis of the polarizing plate PL1 and the polarization axis of the polarizing plate PL2 are, for example, orthogonal to each other.

[0027] The lighting device IL further includes a reflective layer P1, a reflective layer P2, a diffusion sheet DS, a prism sheet PS, and a reflective sheet RS. Note that a plurality of, for example, two prism sheets PS may be provided stacked in the direction Z.

[0028] The diffusion sheet DS is located between the display panel PNL and the light guide plate LG1. The diffusion sheet DS diffuses the light incident on the diffusion sheet DS to equalize the luminance of the light. The prism sheet PS is located between the diffusion sheet DS and the light guide plate LG1. The prism sheet PS, for example, condenses the light emitted from the main surface 1A of the light guide plate LG1 in the direction Z. The prism sheet PS is composed of a plurality of prisms arranged continuously in the direction Y. The plurality of prisms of the prism sheet PS protrude toward the main surface 1A in the direction Z. The prism of the prism sheet PS has a triangular cross-sectional shape parallel to the Y-Z plane. The cross-sectional shapes parallel to the Y-Z plane of the respective prisms of the prism sheet PS are in a similar relationship with each other. Hereinafter, the base angle of the prism of the prism sheet PS may also be referred to as the reverse prism base angle. The reflection sheet RS faces the opposing surface 2B of the light guide plate LG2. The reflection sheet RS, for example, reflects the light leaking from the inside of the light guide plate LG2 and re-incides it on the light guide plate LG2.

[0029] In the lighting device IL, the side surface SF1 is an inclined surface extending in a direction between the opposite side of the tip of the arrow in the direction Y and the tip side of the arrow in the direction Z. In other words, the side surface SF1 is an inclined surface that goes from the inside to the outside in the direction Y as it goes from the lower side to the upper side in the direction Z. In FIG. 3, the main surface 1A extends to the opposite side of the tip of the arrow in the direction Y from the opposing surface 1B. Note that the side surface SF1 may be an inclined surface extending in a direction between the opposite side of the tip of the arrow in the direction Y and the opposite side of the tip of the arrow in the direction Z. In other words, the side surface SF1 may be an inclined surface that goes from the inside to the outside in the direction Y as it goes from the upper side to the lower side in the direction Z. In FIG. 3, the opposing surface 1B may extend to the opposite side of the tip of the arrow in the direction Y from the main surface 1A.

[0030] The side surface SF1 is inclined at an acute angle with respect to the main surface 1A and at an obtuse angle with respect to the opposing surface 1B. In other words, the side surface SF1 is inclined at an acute angle with respect to the main surface 1A. Also, the side surface SF1 is inclined at an obtuse angle with respect to the opposing surface 1B. For example, the side surface SF1 is inclined at an angle smaller than 90° and larger than 90° (degrees) - Brewster angle with respect to the main surface 1A. Note that the side surface SF1 may be inclined at an obtuse angle with respect to the main surface 1A and at an acute angle with respect to the opposing surface 1B. In other words, the side surface SF1 may be inclined at an obtuse angle with respect to the main surface 1A. Also, the side surface SF1 may be inclined at an acute angle with respect to the opposing surface 1B. For example, the side surface SF1 may be inclined at an angle larger than 0° and smaller than 90° (degrees) - Brewster angle with respect to the main surface 1A.

[0031] In the lighting device IL, the side surface SF4 is an inclined surface extending in a direction between the tip side of the arrow in the direction Y and the tip side of the arrow in the direction Z. In other words, the side surface SF4 is an inclined surface that extends from the inner side to the outer side in the direction Y as it goes from the lower side to the upper side in the direction Z. In FIG. 3, the main surface 2A extends to the tip side of the arrow in the direction Y more than the opposing surface 2B. Note that the side surface SF4 may be an inclined surface extending in a direction between the tip side of the arrow in the direction Y and the side opposite to the tip of the arrow in the direction Z. In other words, the side surface SF4 is an inclined surface that extends from the inner side to the outer side in the direction Y as it goes from the upper side to the lower side in the direction Z. In FIG. 3, the opposing surface 2B may extend to the arrow side in the direction Y more than the main surface 2A.

[0032] The side surface SF4 is inclined at an acute angle with respect to the main surface 2A and at an obtuse angle with respect to the opposing surface 2B. In other words, the side surface SF4 is inclined at an acute angle with respect to the main surface 2A. Also, the side surface SF4 is inclined at an obtuse angle with respect to the opposing surface 2B. For example, the side surface SF4 is inclined at an angle smaller than 90° and larger than 90° - Brewster angle with respect to the main surface 2A. Note that the side surface SF4 may be inclined at an obtuse angle with respect to the main surface 2A and at an acute angle with respect to the opposing surface 2B. In other words, the side surface SF4 may be inclined at an obtuse angle with respect to the main surface 2A. Also, the side surface SF4 may be inclined at an acute angle with respect to the opposing surface 2B. For example, the side surface SF4 may be inclined at an angle larger than 0° and smaller than 90° - Brewster angle with respect to the main surface 2A.

[0033] The reflective layer P1 and the reflective layer P2 are each a layer including a plurality of prisms, which will be described in detail later.

[0034] The reflective layer P1 is located on the facing surface 1B. The reflective layer P1 extends in the Y direction from the second region A2 beyond the boundary BO to a predetermined position between the boundary BO and the side surface SF1. Note that the reflective layer P1 may extend within the second region A2. The reflective layer P1 has an end portion E10 on the tip side of the arrow in the Y direction and an end portion E11 on the opposite side of the end portion E10 in the Y direction. The end portion E10 is located between the boundary BO and the side surface SF2. The end portion E10 is located on the side surface SF2 side between the boundary BO and the side surface SF2. The end portion E10 is close to the side surface SF2. For example, the end portion E10 overlaps with the side surface SF2. Note that the end portion E10 may not overlap with the side surface SF2. The end portion E11 is located between the side surface SF1 and the boundary BO. The end portion E11 is located on the boundary BO side between the side surface SF1 and the boundary BO. The end portion E11 is located in the vicinity of the boundary BO. Note that the end portion E11 may be located between the side surface SF2 and the boundary BO. The end portion E11 may be located on the boundary BO side between the side surface SF2 and the boundary BO. For example, the end portion E10 corresponds to the position of the prism closest to the side surface SF2 among the plurality of prisms (prism PA described later) included in the reflective layer P1. For example, the end portion E11 corresponds to the position of the prism closest to the side surface SF1 among the plurality of prisms (prism PA described later) included in the reflective layer P1.

[0035] The reflective layer P2 is located on the opposing surface 2B. The reflective layer P2 extends from the second region A2 beyond the boundary BO to a predetermined position between the boundary BO and the side surface SF4. Note that the reflective layer P2 may extend within the second region A2. The reflective layer P2 has an end E20 and an end E21 on the opposite side of the end E20. The end E20 is located between the side surface SF3 and the boundary BO. The end E20 is located on the side of the side surface SF3 between the side surface SF3 and the boundary BO. The end E20 is close to the side surface SF3. For example, the end E20 overlaps with the side surface SF3. Note that the end E20 may not overlap with the side surface SF3. The end E21 is located between the boundary BO and the side surface SF4. The end E21 is located on the side of the boundary BO between the boundary BO and the side surface SF4. The end E21 is located in the vicinity of the boundary BO. Note that the end E21 may be located between the side surface SF3 and the boundary BO. The end E21 may be located on the side of the boundary BO between the side surface SF3 and the boundary BO. For example, the end E20 corresponds to the position of the prism closest to the side surface SF3 among the plurality of prisms (prism PB described later) included in the reflective layer P2. For example, the end E21 corresponds to the position of the prism closest to the side surface SF4 among the plurality of prisms (prism PB described later) included in the reflective layer P2.

[0036] The reflective layer P1 and the reflective layer P2 overlap in the Z direction in the vicinity of the boundary BO and the boundary BO. Note that the reflective layer P1 and the reflective layer P2 may not overlap in the Z direction in the vicinity of the boundary BO and the boundary BO.

[0037] The light source LS1 is away from the side surface SF1. The emission direction DL1 of the light source LS1 is a direction that intersects a line parallel to the center line extending in the direction Y passing through the center of the thickness T1 of the light guide plate LG1. The light source LS2 is away from the side surface SF4. The emission direction DL2 of the light source LS2 is a direction that intersects a line parallel to the center line extending in the direction Y passing through the center of the thickness T2 of the light guide plate LG2.

[0038] The light L1 emitted from the light source LS1 is incident on the light guide plate LG1 from the side surface SF1 without being completely or almost reflected at the interface between the side surface SF1 and the air layer, and is refracted at the side surface SF1. Among the light L1 incident on the light guide plate LG1, the light traveling toward the opposing surface 1B is reflected (e.g., total reflection) at the interface between the light guide plate LG1 and the air layer. Also, among the light L1 incident on the light guide plate LG1, the light traveling toward the main surface 1A is reflected (e.g., total reflection) at the interface between the light guide plate LG1 and the air layer. Thus, in the region within the first region A1 where the reflective layer P1 is not provided, the light L1 travels within the light guide plate LG1 toward the tip side of the arrow in the direction Y while being repeatedly reflected (e.g., total reflection) at the main surface 1A and the opposing surface 1B. The angle of the total reflection condition is a fixed value calculated by subtracting the critical angle calculated based on the refractive index of the light guide plate LG1 and the refractive index of the air layer from 90°. When the light guide plate LG1 is formed of, for example, glass, it is 48°. When the angle formed by the light and the main surface or the opposing surface is less than or equal to the angle of the total reflection condition, the light is totally reflected at the main surface or the opposing surface. On the other hand, when the angle formed by the light and the main surface or the opposing surface is greater than the angle of the total reflection condition, the light is taken out from the main surface or the opposing surface, which is the emission surface, outside the total reflection condition.

[0039] Among the light L1 traveling within the light guide plate LG1, the light traveling toward the reflective layer P1 is reflected by the prism of the reflective layer P1 and its traveling direction can be changed. The light reflected by the prism of the reflective layer P1 exits from the main surface 1A outside the total reflection condition of the main surface 1A. The light exiting from the main surface 1A illuminates the display panel PNL through the prism sheet PS and the diffusion sheet DS. That is, in the region within the first region A1 where the reflective layer P1 is not provided (or the region near the side surface SF1), the light L1 incident from the side surface SF1 is suppressed from exiting the light guide plate LG1 toward the display panel PNL.

[0040] Similarly, the light L2 emitted from the light source LS2 is incident on the light guide plate LG2 from the side surface SF4 without being completely or almost reflected at the interface between the side surface SF4 and the air layer, and is refracted at the side surface SF4. Among the light L2 incident on the light guide plate LG2, the light traveling toward the opposing surface 2B is reflected (e.g., totally reflected) at the interface between the light guide plate LG2 and the air layer. Also, among the light L2 incident on the light guide plate LG2, the light traveling toward the main surface 2A is reflected (e.g., totally reflected) at the interface between the light guide plate LG2 and the air layer. Thus, in the region within the second region A2 where the reflective layer P2 is not provided, the light L2 travels within the light guide plate LG2 on the side opposite to the tip of the arrow in the direction Y while being repeatedly reflected (e.g., totally reflected) at the main surface 2A and the opposing surface 2B.

[0041] Among the light L2 traveling within the light guide plate LG2, the light L2 traveling toward the reflective layer P2 is reflected by the prism of the reflective layer P2 and its traveling direction can be changed. The light reflected by the prism of the reflective layer P2 exits from the main surface 2A outside the total reflection condition of the main surface 2A. The light exiting from the main surface 2A illuminates the display panel PNL through the light guide plate LG1, the prism sheet PS, and the diffusion sheet DS. That is, in the region within the second region A2 where the reflective layer P2 is not provided (or the region near the side surface SF4), the light L2 incident from the side surface SF4 is suppressed from exiting the light guide plate LG2 toward the display panel PNL.

[0042] The display panel PNL is mainly illuminated by the light L2 from the light source LS2 in the first region A1. The display panel PNL is mainly illuminated by the light L1 from the light source LS1 in the second region A2.

[0043] Generally, the light from a plurality of light sources arranged at intervals travels inside the light guide plate while diffusing, but these lights do not mix sufficiently in the vicinity of the light sources. Therefore, in a display device that uses such light as illumination light, there is a possibility that streak-like luminance unevenness or chromaticity deviation due to the difference in intensity is visually recognized when the display area is viewed in plan view. The difference in the intensity of the illumination light is reduced as the position away from the light source increases.

[0044] In the example shown in FIG. 3, in the region within the first region A1 where the reflective layer P1 is not provided, the light L1 incident from the side surface SF1 is confined within the light guide plate LG1, and the incidence to the display panel PNL is suppressed. In the first region A1, although the light L1 from the light source LS1 hardly enters the display panel PNL, the light L2 from the light source LS2 illuminates the display panel PNL. The second region A2 is separated from the side surface SF1 by a distance sufficient for the lights L1 to mix with each other. Therefore, in the second region A2, it is possible to suppress a decrease in display quality (lighting quality) due to unevenness in luminance and chromaticity shift of the illumination light.

[0045] Similarly, in the region within the second region A2 where the reflective layer P2 is not provided, the light L2 incident from the side surface SF3 is confined within the light guide plate LG2, and the incidence to the display panel PNL is suppressed. In the second region A2, although the light L2 from the light source LS2 hardly enters the display panel PNL, the light L1 from the light source LS1 illuminates the display panel PNL. The first region A1 is separated from the side surface SF4 by a distance sufficient for the lights L2 to mix with each other. Therefore, in the first region A1, it is possible to suppress a decrease in display quality (lighting quality) due to unevenness in luminance and chromaticity shift of the illumination light.

[0046] Furthermore, the reflective layer P1 extends to the first region A1 beyond the boundary BO, and the reflective layer P2 extends to the second region A2 beyond the boundary BO. For this reason, it is possible to avoid a situation where the luminance level of the emitted light of the lighting device IL decreases in the vicinity of the boundary BO. When the end portion E11 of the reflective layer P1 and the end portion E21 of the reflective layer P2 are respectively located at the boundary BO, there is a possibility that the luminance level of the emitted light of the lighting device IL decreases in the vicinity of the boundary BO.

[0047] FIG. 4 is a perspective view showing an example of the configuration of the reflective layer P1 and the reflective layer P2. FIG. 4 corresponds to FIG. 3. FIG. 4 shows only the configuration necessary for the description. In the example shown in FIG. 4, the reflective layer P1 has a plurality of prisms PA (first prisms). In the reflective layer P1, the plurality of prisms PA are intermittently arranged in the Y direction. The reflective layer P2 has a plurality of prisms PB (second prisms). In the reflective layer P2, the plurality of prisms PB are intermittently arranged in the Y direction. The plurality of prisms PA are provided on the opposing surface 1B. The plurality of prisms PB are provided on the opposing surface 2B. For example, the prism PA is integrally formed with the light guide plate LG1. Similarly, the prism PB is integrally formed with the light guide plate LG2.

[0048] The prism PA protrudes from the opposing surface 1B toward the main surface 2A. In other words, the prism PA protrudes in a direction opposite to the tip side of the arrow in the Z direction. The prism PA has a triangular cross-sectional shape parallel to the Y-Z plane and extends in the X direction. For example, the cross-sectional shapes parallel to the Y-Z plane of the respective prisms PA are in a similar relationship to each other. The prism PA has an inclined surface SL1 (first inclined surface), an inclined surface SL2 (second inclined surface), a reference surface BL1, and a vertex VT1. The height HA of the prism PA is the height of the prism PA in the normal direction of the reference surface BL1 (opposing surface 1B) and corresponds to the length in the Z direction from the reference surface BL1 to the vertex VT1.

[0049] In the prism PA, the inclined surface SL1 is located on the side surface SF2 side, and the inclined surface SL2 is located on the side surface SF1 side. The reference surface BL1 is located on the same plane as the opposing surface 1B. The vertex VT1 corresponds to the point where the inclined surface SL1 and the inclined surface SL2 intersect.

[0050] A plurality of vertices VT1 are arranged at equal intervals LG30 in the Y direction. The interval LG30 is, for example, 0.1 mm. In the example shown in FIG. 4, the angle α1 formed by the inclined surface SL1 and the reference surface BL1 is equal to the angle α2 formed by the inclined surface SL2 and the reference surface BL1. Note that the angle α1 corresponds to one of the interior angles in the cross-section of the prism PA, and the angle α2 corresponds to one of the interior angles different from the angle α1 in the cross-section of the prism PA. The angles α1 and α2 may be referred to as the prism angles of the prism PA. The cross-section of the prism PA is an isosceles triangle. Note that the cross-section of the prism PA does not have to be an isosceles triangle.

[0051] In the example shown in FIG. 4, the height HA of each of the plurality of prisms PA decreases as it goes from the side surface SF2 toward the side surface SF1. That is, the height HA of each of the plurality of prisms PA increases for the prism PA farther from the light source LS1. Note that the height HA of each of the plurality of prisms PA may be the same. In the Y direction, as going from the end E11 toward the end E10, the ratio of the prism PA (reference surface BL1) per unit area in the X-Y plane increases, and the ratio of the opposing surface 1B per unit area in the X-Y plane decreases. On the other hand, when the light traveling in the light guide plate LG1 travels to the prism PA of the reflection layer P1 and is emitted from the light guide plate LG1, the amount of light of the light traveling in the light guide plate LG1 decreases. Thereby, the illumination device IL can irradiate the display panel PNL with illumination light having a uniform luminance distribution in the second region A2.

[0052] The prism PB protrudes from the opposing surface 2B toward the reflection sheet RS. In other words, the prism PB protrudes toward the side opposite to the tip side of the arrow in the Z direction. The prism PB has a triangular cross-sectional shape parallel to the Y-Z plane and extends in the X direction. For example, the cross-sectional shapes parallel to the Y-Z plane of the respective prisms PB are in a similar relationship with each other. The prism PB has an inclined surface SL3 (third inclined surface), an inclined surface SL4 (fourth inclined surface), a reference surface BL2, and a vertex VT2. The height HB of the prism PB is the height of the prism PB in the normal direction of the reference surface BL2 (opposing surface 2B) and corresponds to the length in the Z direction from the reference surface BL2 to the vertex VT2.

[0053] In the prism PB, the inclined surface SL3 is located on the side surface SF4 side, and the inclined surface SL4 is located on the side surface SF3 side. The reference plane BL2 is located on the same plane as the opposing surface 2B. The vertex VT2 corresponds to the point where the inclined surface SL3 and the inclined surface SL4 intersect.

[0054] A plurality of vertices VT2 are arranged at equal intervals LG30 along the direction Y. In the example shown in FIG. 4, the angle α3 formed by the inclined surface SL3 and the reference plane BL2 is equal to the angle α4 formed by the inclined surface SL4 and the reference plane BL2. Note that the angle α3 corresponds to one of the interior angles in the cross section of the prism PB, and the angle α4 corresponds to one of the interior angles different from the angle α3 in the cross section of the prism PB. The angles α3 and α4 may be referred to as the prism angles of the prism PB. The cross section of the prism PB is an isosceles triangle. Note that the cross section of the prism PB does not have to be an isosceles triangle.

[0055] In the example shown in FIG. 4, the height HB of each of the plurality of prisms PB decreases as it goes from the side surface SF3 toward the side surface SF4. That is, the height HB of each of the plurality of prisms PB increases as the prism PB is farther from the light source LS2. Note that the height HB of each of the plurality of prisms PB may be the same at times. In the direction Y, as it goes from the end portion E21 toward the end portion E20, the ratio of the prism PB (reference plane BL2) per unit area in the X - Y plane increases, and the ratio of the opposing surface 2B per unit area in the X - Y plane decreases. On the other hand, when the light traveling in the light guide plate LG2 travels to the prism PB of the reflection layer P2 and is emitted from the light guide plate LG2, the amount of light of the light traveling in the light guide plate LG2 decreases. Thereby, the illumination device IL can irradiate the display panel PNL with illumination light having a uniform luminance distribution in the first region A1.

[0056] FIG. 5 is a schematic diagram showing an example of the change in reflectance of S-polarized light and P-polarized light incident from air onto a light guide plate with respect to the incident angle of these S-polarized light and P-polarized light. In FIG. 5, the vertical axis represents the reflectance of light, and the horizontal axis represents the incident angle of light [° (degrees)]. FIG. 5 shows the change in the reflectance of this P-polarized light with respect to the incident angle of P-polarized light incident from air onto a light guide plate formed of the same material as the light guide plates LG1 and LG2 (hereinafter, may also be referred to as the change in the reflectance of P-polarized light incident from air onto the light guide plate) Rp1, and the change in the reflectance of this S-polarized light with respect to the incident angle of S-polarized light incident from air onto a light guide plate formed of the same material as the light guide plates LG1 and LG2 (hereinafter, may also be referred to as the change in the reflectance of S-polarized light incident from air onto the light guide plate) Rs1. P-polarized light corresponds to the component of light whose electric vector vibrates in the plane of incidence. S-polarized light corresponds to the component of light whose electric vector vibrates perpendicular to the plane of incidence.

[0057] In the example shown in FIG. 5, the change in the reflectance of P-polarized light incident from air onto the light guide plate Rp1 decreases as the incident angle of P-polarized light incident from air onto the light guide plate goes from 0° to 55.9°. That is, as the incident angle of P-polarized light incident from air onto the light guide plate becomes from 0° to 55.9°, the reflectance of P-polarized light incident from air onto the light guide plate becomes smaller.

[0058] In the example shown in FIG. 5, when the incident angle of P-polarized light incident from air onto the light guide plate is 55.9°, the change in the reflectance of P-polarized light incident from air onto the light guide plate Rp1 becomes 0. That is, when the incident angle of P-polarized light incident from air onto the light guide plate is 55.9°, the reflectance of P-polarized light incident from air onto the light guide plate becomes 0. In other words, when the incident angle of P-polarized light incident from air onto the light guide plate is 55.9°, the P-polarized light incident from air onto the light guide plate is not reflected at all at the boundary between air and the light guide plate and is all incident from air onto the light guide plate. Thus, the incident angle at which the reflectance (or reflection intensity) of P-polarized light becomes 0 (0%) is called the Brewster angle. In the example shown in FIG. 5, when P-polarized light is incident from air onto the light guide plate, the Brewster angle is 55.9°.

[0059] In the example shown in FIG. 5, the change Rp1 in the reflectance of P-polarized light incident from air onto the light guide plate increases as the incident angle of the P-polarized light incident from air onto the light guide plate becomes larger than 55.9°. That is, as the incident angle of the P-polarized light incident from air onto the light guide plate becomes larger than 55.9°, the reflectance of the P-polarized light incident from air onto the light guide plate increases.

[0060] Further, when the incident angle of the P-polarized light incident from air onto the light guide plate is in the range of 49.0° or more and 62.0° or less, the reflectance of the P-polarized light from air to the light guide plate becomes 0.005 (0.5%) or less. In other words, when the incident angle of the P-polarized light incident from air onto the light guide plate is in the range of 49.0° or more and 62.0° or less, the P-polarized light incident from air onto the light guide plate is almost not reflected at the boundary between air and the light guide plate and is almost incident from air onto the light guide plate.

[0061] In the example shown in FIG. 5, the change Rs1 in the reflectance of S-polarized light incident from air onto the light guide plate increases as the incident angle of the S-polarized light incident from air onto the light guide plate becomes larger than 0°. That is, as the incident angle of the S-polarized light incident from air onto the light guide plate becomes larger than 0°, the reflectance of the S-polarized light incident from air onto the light guide plate increases. In other words, as the incident angle of the S-polarized light incident from air onto the light guide plate becomes larger than 0°, the ratio of the S-polarized light incident from air onto the light guide plate that is reflected at the boundary between air and the light guide plate increases.

[0062] FIG. 6 is a schematic diagram showing an example of P-polarized light incident from air onto the light guide plate LG10. FIG. 6 shows a light guide plate LG10 formed of the same material as the light guide plates LG1 and LG2. The light guide plate LG10 is formed in a flat plate shape parallel to the X-Y plane. The light guide plate LG10 has an upper main surface 10A, an opposing surface 10B located on the opposite side of the main surface 10A in the Z direction, and a side surface SF10. The main surface 10A and the opposing surface 10B are, for example, parallel to the X-Y plane and are provided parallel to each other. Note that the main surface 10A and the opposing surface 10B may be non-parallel to each other. The side surface SF10 is, for example, parallel to the X-Z plane. FIG. 6 shows P-polarized light L10 incident from air onto the light guide plate LG10.

[0063] In the example shown in FIG. 6, the P-polarized light L10 is incident on the light guide plate LG10 from the air at an incident angle of 55.9°. In other words, the P-polarized light L10 is incident on the side surface SF10 of the light guide plate LG10 from the air at an incident angle of 55.9° with respect to the straight line perpendicular to the side surface SF10. As shown by the change Rp1 in the reflectance of the P-polarized light incident on the light guide plate from the air in FIG. 5, when the P-polarized light L10 is incident on the side surface SF10 from the air at an incident angle (Brewster angle) of 55.9°, the P-polarized light L10 is all incident on the light guide plate LG10 without being reflected by the side surface SF10. In other words, when the P-polarized light L10 is incident on the side surface SF10 at an angle of 55.9° with respect to the straight line perpendicular to the side surface SF10, the P-polarized light L10 is all incident on the light guide plate LG10 without being reflected by the side surface SF10.

[0064] FIG. 7 is a schematic diagram showing an example of the change in the reflectance of S-polarized light and P-polarized light with respect to the incident angle of the S-polarized light and P-polarized light incident from the light guide plate to the air. In FIG. 7, the vertical axis represents the light reflectance, and the horizontal axis represents the light incident angle [°]. FIG. 7 shows the change in the reflectance of this P-polarized light with respect to the incident angle of the P-polarized light incident from the light guide plate to the air (hereinafter, may also be referred to as the change in the reflectance of the P-polarized light incident from the light guide plate to the air) Rp2, and the change in the reflectance of this S-polarized light with respect to the incident angle of the S-polarized light incident from the light guide plate to the air (hereinafter, may also be referred to as the change in the reflectance of the S-polarized light incident from the light guide plate to the air) Rs2, which are formed of the same material as the light guide plates LG1 and LG2.

[0065] In the example shown in FIG. 7, the change Rp2 in the reflectance of the P-polarized light incident from the light guide plate to the air decreases as the incident angle of the P-polarized light incident from the light guide plate to the air goes from 0° to 33.5°. That is, as the incident angle of the P-polarized light incident from the light guide plate to the air becomes from 0° to 33.5°, the reflectance of the P-polarized light incident from the light guide plate to the air becomes smaller.

[0066] In the example shown in FIG. 7, when the incident angle of the P-polarized light incident from the light guide plate into the air is 33.5°, the change in the reflectance Rp2 of the P-polarized light incident from the light guide plate into the air becomes 0. That is, when the incident angle of the P-polarized light incident from the light guide plate into the air is 33.5°, the reflectance of the P-polarized light incident from the light guide plate into the air becomes 0. In other words, when the incident angle of the P-polarized light incident from the light guide plate into the air is 33.5°, the P-polarized light incident from the light guide plate into the air is all incident from the light guide plate into the air without being reflected at all at the boundary between the light guide plate and the air. In the example shown in FIG. 6, when P-polarized light is incident from the light guide plate into the air, the Brewster angle is 33.5°.

[0067] In the example shown in FIG. 7, the change in the reflectance Rp2 of the P-polarized light incident from the light guide plate into the air increases as the incident angle of the P-polarized light incident from the light guide plate into the air becomes larger than 33.5°. That is, as the incident angle of the P-polarized light incident from the light guide plate into the air becomes larger than 33.5°, the reflectance of the P-polarized light incident from the light guide plate into the air increases.

[0068] Also, when the incident angle of the P-polarized light incident from the light guide plate into the air is in the range of 30.0° or more and 35.5° or less, the reflectance of the P-polarized light incident from the light guide plate into the air becomes 0.005 or less. In other words, when the incident angle of the P-polarized light incident from the light guide plate into the air is in the range of 30.0° or more and 35.5° or less, the P-polarized light incident from the light guide plate into the air is almost incident from the light guide plate into the air without being reflected at the boundary between the light guide plate and the air.

[0069] In the example shown in FIG. 7, the change in the reflectance Rs2 of the S-polarized light incident from the light guide plate into the air increases as the incident angle of the S-polarized light incident from the light guide plate into the air becomes larger than 0°. That is, as the incident angle of the S-polarized light incident from the light guide plate into the air becomes larger than 0°, the reflectance of the S-polarized light incident from the light guide plate into the air increases. In other words, as the incident angle of the S-polarized light incident from the light guide plate into the air becomes larger than 0°, the ratio of the S-polarized light incident from the light guide plate into the air reflected at the boundary between the light guide plate and the air increases.

[0070] FIG. 8 is a schematic diagram showing an example of P-polarized light incident from the light guide plate LG10 into air. FIG. 8 shows the light guide plate LG10. FIG. 8 shows the P-polarized light L11 incident from the light guide plate LG10 into air.

[0071] In the example shown in FIG. 8, the P-polarized light L11 is incident from the light guide plate LG10 into air at an incident angle = 33.5°. In other words, the P-polarized light L11 is incident on the main surface 10A from the light guide plate LG10 into air at an incident angle = 33.5° with respect to the straight line perpendicular to the main surface 10A. As shown by the change Rp2 in the reflectance of the P-polarized light incident from the light guide plate in FIG. 8 into air, when the P-polarized light L11 is incident on the main surface 10A from the light guide plate LG10 at an incident angle (Brewster angle) = 33.5°, the P-polarized light L11 is all incident on air without being reflected at the main surface 10A. In other words, when the P-polarized light L10 is incident on the main surface 10A at an angle = 33.5° with respect to the straight line perpendicular to the main surface 10A, the P-polarized light L11 is all incident on air without being reflected at the main surface 10A.

[0072] FIG. 9 is a cross-sectional view showing a configuration example of the illumination device ILc of the comparative example. As shown in FIG. 9, the illumination device ILc of the comparative example has a third region A3, a fourth region A4, and a boundary BOc between the third region A3 and the fourth region A4. The length in the Y direction of the third region A3 and the length in the Y direction of the fourth region A4 are the same. Note that the length in the Y direction of the third region A3 and the length in the Y direction of the fourth region A4 do not have to be the same.

[0073] The illumination device ILc includes a diffusion sheet DS, a prism sheet PS, a light guide plate LG3, a plurality of light sources LS3, a reflective layer P3, a light guide plate LG4, a plurality of light sources LS4, a reflective layer P4, and a reflective sheet RS. The reflective sheet RS, the reflective layer P4, the light guide plate LG4, the reflective layer P3, the light guide plate LG3, the prism sheet PS, and the diffusion sheet DS are arranged in the described order toward the tip side of the arrow in the Z direction.

[0074] The diffusion sheet DS is located on the light guide plate LG3. The prism sheet PS is located between the diffusion sheet DS and the light guide plate LG3. The prism sheet PS, for example, condenses the light emitted from the light guide plate LG3 in the direction Z.

[0075] The light guide plate LG3 is an insulating substrate such as a glass substrate or a plastic substrate. The light guide plate LG3 is formed of, for example, the same material as the light guide plates LG1 and LG2. The light guide plate LG3 is formed in a flat plate shape parallel to the X-Y plane. The light guide plate LG3 has a main surface 3A facing the display panel PNL, an opposing surface 3B located on the opposite side of the main surface 3A in the direction Z, a side surface SF5, and a side surface SF6 located on the opposite side of the side surface SF5 in the direction Y. The main surface 3A and the opposing surface 3B are, for example, parallel to the X-Y plane and are provided parallel to each other. Note that the main surface 3A and the opposing surface 3B may not be parallel to each other. The side surfaces SF5 and SF6 are, for example, parallel to the X-Z plane and are provided parallel to each other. Note that the side surfaces SF5 and SF6 may be provided non-parallel to each other.

[0076] The light guide plate LG3 is located in the entire area of the third region A3 and the entire area of the fourth region A4. That is, the main surface 3A and the opposing surface 3B shown in FIG. 9 are located in the third region A3 and the fourth region A4. The side surface SF5 is located in the third region A3, and the side surface SF6 is located in the fourth region A4. The boundary BOc corresponds to the middle of the side surface SF5 and the side surface SF6.

[0077] The plurality of light sources LS3 are arranged at intervals in the direction X. In the example shown in FIG. 9, the plurality of light sources LS3 face the side surface SF5. Also, the plurality of light sources LS3 are arranged along the side surface SF5 at intervals in the direction X.

[0078] The light source LS3 is away from the side surface SF5. The light source LS3 emits the light L3 in the emission direction DL3 toward the side surface SF5. The emission direction DL3 of the light source LS3 is a direction that intersects a line parallel to the center line extending in the direction Y passing through the center of the thickness of the light guide plate LG3.

[0079] The reflective layer P3 is a layer including a plurality of prisms, which will be described in detail later. The reflective layer P3 is located on the opposing surface 3B. The length of the reflective layer P3 in the direction Y is 70.6 mm. The reflective layer P3 extends from the fourth region A4 across the boundary BOc to a predetermined position between the boundary BOc and the side surface SF5 in the direction Y. Note that the reflective layer P3 may extend within the fourth region A4. The reflective layer P3 has an end portion E30 on the tip side of the arrow in the direction Y and an end portion E31 on the side opposite to the end portion E10 in the direction Y. The end portion E30 is 0.66 mm away from the side surface SF6 on the side opposite to the tip side of the arrow in the direction Y. The end portion E31 is located between the side surface SF5 and the boundary BOc. The end portion E31 is located on the boundary BOc side between the side surface SF5 and the boundary BOc. The end portion E31 is located in the vicinity of the boundary BOc. Note that the end portion E31 may be located between the boundary BOc and the side surface SF6. For example, the end portion E30 corresponds to the position of the prism closest to the side surface SF6 among the plurality of prisms (prism PC described later) included in the reflective layer P3. For example, the end portion E31 corresponds to the position of the prism closest to the side surface SF5 among the plurality of prisms (prism PC described later) included in the reflective layer P3.

[0080] The light guide plate LG4 is an insulating substrate such as a glass substrate or a plastic substrate. The light guide plate LG4 is formed of, for example, the same material as the light guide plate LG3. Note that the light guide plate LG4 may not be formed of the same material as the light guide plate LG3. The light guide plate LG4 is formed in a flat plate shape parallel to the X-Y plane. The light guide plate LG4 has a main surface 4A facing the opposing surface 3B, an opposing surface 4B located on the side opposite to the main surface 4A in the direction Z, a side surface SF7 aligned with the side surface SF5 in the direction Z, and a side surface SF8 located on the side opposite to the side surface SF7 in the direction Y and aligned with the side surface SF6 in the direction Z. The main surface 4A and the opposing surface 4B are, for example, parallel to the X-Y plane and are provided parallel to each other. Note that the main surface 4A and the opposing surface 4B may not be parallel to each other. The side surface SF7 and the side surface SF8 face each other in the direction Y. The side surface SF7 and the side surface SF8 are, for example, parallel to the X-Z plane and are provided parallel to each other. Note that the side surface SF7 and the side surface SF8 may not be provided parallel to each other.

[0081] The light guide plate LG4 is located in the entire third region A3 and the entire fourth region A4. That is, the main surface 4A and the opposing surface 4B shown in FIG. 9 are located in the third region A3 and the fourth region A4. The side surface SF7 is located in the third region A3, and the side surface SF8 is located in the fourth region A4. The boundary BOc corresponds to the middle of the side surface SF7 and the side surface SF8.

[0082] The plurality of light sources LS4 are arranged at intervals in the direction X. In the example shown in FIG. 1, the plurality of light sources LS4 face the side surface SF8. Further, the plurality of light sources LS4 are arranged along the side surface SF8 at intervals in the direction X.

[0083] The light source LS4 is away from the side surface SF8. The light source LS4 emits the light L4 in the emission direction DL4 toward the side surface SF8. The emission direction DL4 of the light source LS4 is a direction that intersects a line parallel to the center line extending in the direction Y passing through the center of the thickness of the light guide plate LG4.

[0084] The light sources LS3 and LS4 are laser light sources such as semiconductor lasers that emit polarized laser light, for example. Note that the light sources LS3 and LS4 are not limited to those that emit laser light, and may be light emitting diodes, for example.

[0085] The light sources LS3 and LS4 may each include a plurality of light emitting elements that emit light of different colors. For example, the light sources LS3 and LS4 each include three light emitting elements that emit red, green, and blue light. When including three light emitting elements that emit red, green, and blue light, the light sources LS3 and LS4 can obtain light of a mixed color (for example, white) of these colors.

[0086] The reflective layer P4 is a layer including a plurality of prisms, which will be described in detail later. The reflective layer P4 is located on the opposing surface 4B. The length of the reflective layer P4 in the direction Y is 70.6 mm. The reflective layer P4 extends in the direction Y from the third region A3 beyond the boundary BOc to a predetermined position between the boundary BOc and the side surface SF8. Note that the reflective layer P4 may extend into the fourth region A4. The reflective layer P4 has an end E40 on the side opposite to the tip side of the arrow in the direction Y, and an end E41 on the side opposite to the end E40 in the direction Y. The end E40 is 0.66 mm away from the side surface SF7 toward the tip side of the arrow in the direction Y. The end E41 is located between the boundary BOc and the side surface SF8. The end E41 is located on the boundary BOc side between the boundary BOc and the side surface SF8. The end E41 is located in the vicinity of the boundary BOc. Note that the end E41 may be located between the boundary BOc and the side surface SF7. For example, the end E40 corresponds to the position of the prism closest to the side surface SF7 among the plurality of prisms (prism PD described later) included in the reflective layer P4. For example, the end E41 corresponds to the position of the prism closest to the side surface SF8 among the plurality of prisms (prism PD described later) included in the reflective layer P4.

[0087] The reflective layer P3 and the reflective layer P4 overlap in the direction Z at the boundary BOc and in the vicinity of the boundary BOc. Note that the reflective layer P3 and the reflective layer P4 may not overlap in the direction Z at the boundary BOc and in the vicinity of the boundary BOc.

[0088] The reflective sheet RS faces the opposing surface 4B of the light guide plate LG4. The reflective sheet RS, for example, reflects the light leaked from within the light guide plate LG4 and causes it to enter the light guide plate LG4 again. Note that the reflective sheet RS may not be provided.

[0089] The light L3 emitted from the light source LS3 enters the light guide plate LG3 from the side surface SF5 without being reflected at the interface between the side surface SF5 and the air layer, and is refracted at the side surface SF5. Among the light L3 that has entered the light guide plate LG3, the light traveling toward the opposing surface 3B is reflected at the interface between the light guide plate LG3 and the air layer. Also, among the light L3 that has entered the light guide plate LG3, the light traveling toward the main surface 3A is reflected at the interface between the light guide plate LG3 and the air layer. Thus, in the region within the third region A3 where the reflective layer P3 is not provided, the light L3 travels within the light guide plate LG3 toward the tip side of the arrow in the direction Y while being repeatedly reflected at the main surface 3A and the opposing surface 3B.

[0090] Among the light L3 traveling within the light guide plate LG3, the light traveling toward the reflective layer P3 is reflected by the prism of the reflective layer P3 and its traveling direction can be changed. The light reflected by the prism of the reflective layer P3 exits from the main surface 3A, deviating from the total reflection condition of the main surface 3A. The light exiting from the main surface 3A is irradiated through the prism sheet PS and the diffusion sheet DS. That is, in the region within the third region A3 where the reflective layer P3 is not provided (or the region near the side surface SF5), the light L3 incident from the side surface SF5 is suppressed from exiting the light guide plate LG3.

[0091] Similarly, the light L4 emitted from the light source LS4 enters the light guide plate LG4 from the side surface SF8 without being reflected at the interface between the side surface SF8 and the air layer, and is refracted at the side surface SF8. Among the light L4 that has entered the light guide plate LG4, the light traveling toward the opposing surface 4B is reflected at the interface between the light guide plate LG4 and the air layer. Also, among the light L4 that has entered the light guide plate LG4, the light traveling toward the main surface 4A is reflected at the interface between the light guide plate LG4 and the air layer. Thus, in the region within the fourth region A4 where the reflective layer P4 is not provided, the light L4 travels within the light guide plate LG4 toward the side opposite to the tip side of the arrow in the direction Y while being repeatedly reflected at the main surface 4A and the opposing surface 4B.

[0092] Among the light L4 traveling inside the light guide plate LG4, the light L4 traveling toward the reflection layer P4 can have its traveling direction changed by being reflected by the prisms of the reflection layer P4. The light reflected by the prisms of the reflection layer P4 exits from the main surface 4A by violating the total reflection condition of the main surface 4A. The light exiting from the main surface 4A illuminates through the light guide plate LG3, the prism sheet PS, and the diffusion sheet DS.

[0093] FIG. 10 is a perspective view showing an example of the configurations of the reflection layer P3 and the reflection layer P4 corresponding to the illumination device ILc of FIG. 9. FIG. 10 corresponds to FIG. 9. FIG. 10 shows only the configurations necessary for the description. In the example shown in FIG. 10, the reflection layer P3 has a plurality of prisms PC. In the reflection layer P3, the plurality of prisms PC are intermittently arranged in the direction Y. The reflection layer P4 has a plurality of prisms PD. In the reflection layer P4, the plurality of prisms PD are intermittently arranged in the direction Y. The plurality of prisms PC are provided on the opposing surface 3B. The plurality of prisms PD are provided on the opposing surface 4B. For example, the prism PC is integrally formed with the light guide plate LG3. Similarly, the prism PD is integrally formed with the light guide plate LG4.

[0094] The prism PC protrudes from the opposing surface 3B toward the main surface 4A. In other words, the prism PC protrudes toward the side opposite to the tip side of the arrow in the direction Z. The prism PC has a triangular cross-sectional shape parallel to the Y-Z plane and extends in the direction X. For example, the cross-sectional shapes parallel to the Y-Z plane of each prism PC are in a similar relationship with each other. The prism PC has an inclined surface SL5, an inclined surface SL6, a reference plane BL3, and a vertex VT3. The height HC of the prism PC is the height of the prism PC in the normal direction of the reference plane BL3 (opposing surface 3B) and corresponds to the length in the direction Z from the reference plane BL3 to the vertex VT3.

[0095] In the prism PC, the inclined surface SL5 is located on the side of the side surface SF6, and the inclined surface SL6 is located on the side of the side surface SF5. The reference plane BL3 is located on the same plane as the opposing surface 3B. The vertex VT3 corresponds to the point where the inclined surface SL5 and the inclined surface SL6 intersect.

[0096] The plurality of vertices VT3 are arranged at equal intervals LG32 in the Y direction. The interval LG32 is, for example, 0.1 mm. In the example shown in FIG. 10, the angle formed by the inclined surface SL5 and the reference surface BL3 is 15°, and the angle formed by the inclined surface SL6 and the reference surface BL3 is 35°. The angle formed by the inclined surface SL5 and the inclined surface SL6 is 130°. The R at the tip of the vertex VT3 is 0.015 mm.

[0097] In the example shown in FIG. 10, the height HC of each of the plurality of prisms PC is constant. Note that the height HC of each of the plurality of prisms PC may decrease from the side surface SF6 toward the side surface SF5. That is, the height HC of each of the plurality of prisms PC may increase as the prism PC is farther from the light source LS3.

[0098] The prism PD protrudes from the opposing surface 4B toward the reflection sheet RS. In other words, the prism PD protrudes toward the side opposite to the tip side of the arrow in the Z direction. The prism PD has a triangular cross-sectional shape parallel to the Y-Z plane and extends in the X direction. For example, the cross-sectional shapes parallel to the Y-Z plane of the respective prisms PD are in a similar relationship to each other. The prism PD has an inclined surface SL7, an inclined surface SL8, a reference surface BL4, and a vertex VT4. The height HD of the prism PD is the height of the prism PD in the normal direction of the reference surface BL4 and corresponds to the length in the Z direction from the reference surface BL4 to the vertex VT4.

[0099] In the prism PD, the inclined surface SL7 is located on the side surface SF8 side, and the inclined surface SL8 is located on the side surface SF7 side. The reference surface BL4 is located on the same plane as the opposing surface 4B. The vertex VT4 corresponds to the point where the inclined surface SL7 and the inclined surface SL8 intersect.

[0100] The plurality of vertices VT4 are arranged at equal intervals LG32 in the Y direction. In the example shown in FIG. 10, the angle formed by the inclined surface SL7 and the reference surface BL4 is 15°, and the angle formed by the inclined surface SL8 and the reference surface BL4 is 35°. The angle formed by the inclined surface SL7 and the inclined surface SL8 is 130°. The R at the tip of the vertex VT4 is 0.015 mm.

[0101] In the example shown in FIG. 10, the height HD of each of the plurality of prisms PD is constant. Note that the height HC of each of the plurality of prisms PD may decrease from side surface SF7 toward side surface SF8. That is, the height HC of each of the plurality of prisms PD may increase for the prism PD farther from the light source LS4.

[0102] FIG. 11 is a diagram showing an example of changes in the luminance of the illumination device ILc in FIG. 9 with respect to the distance x in the direction Y when P-polarized light and S-polarized light are incident. In FIG. 11, the vertical axis represents the luminance of the illumination device ILc, and the horizontal axis represents the distance x [mm] from the side surfaces SF5 and SF7 of the illumination device ILc to the tip side of the arrow in the direction Y. In FIG. 11, there are shown the change in the luminance of the illumination device ILc with respect to the distance x when P-polarized light is emitted from the light sources LS3 and LS4 in the illumination device ILc including the reflection sheet RS (hereinafter, may also be referred to as the change in the luminance of the illumination device ILc including the reflection sheet RS when P-polarized light is emitted) LMp1, the change in the luminance of the illumination device ILc with respect to the distance x when P-polarized light is emitted from the light sources LS3 and LS4 in the illumination device ILc not including the reflection sheet RS (hereinafter, may also be referred to as the change in the luminance of the illumination device ILc not including the reflection sheet RS when P-polarized light is emitted) LMp2, the change in the luminance of the illumination device ILc with respect to the distance x when S-polarized light is emitted from the light sources LS3 and LS4 in the illumination device ILc including the reflection sheet RS (hereinafter, may also be referred to as the change in the luminance of the illumination device ILc including the reflection sheet RS when S-polarized light is emitted) LMs1, and the change in the luminance of the illumination device ILc with respect to the distance x when S-polarized light is emitted from the light sources LS3 and LS4 in the illumination device ILc not including the reflection sheet RS (hereinafter, may also be referred to as the change in the luminance of the illumination device ILc not including the reflection sheet RS when S-polarized light is emitted) LMs2. In FIG. 11, the change in the luminance LMp1 of the illumination device ILc including the reflection sheet RS when P-polarized light is emitted, the change in the luminance LMp2 of the illumination device ILc not including the reflection sheet RS when P-polarized light is emitted, the change in the luminance LMs1 of the illumination device ILc including the reflection sheet RS when S-polarized light is emitted, and the change in the luminance LMs2 of the illumination device ILc not including the reflection sheet RS when S-polarized light is emitted each include the luminance due to the light reflected by the reflection layer P3 and the luminance due to the light reflected by the reflection layer P4.

[0103] In the example shown in FIG. 11, the luminance change LMp1 of the illumination device ILc including the reflection sheet RS when emitting P-polarized light is greater than the luminance change LMs1 of the illumination device ILc including the reflection sheet RS when emitting S-polarized light and the luminance change LMs2 of the illumination device ILc not including the reflection sheet RS when emitting S-polarized light. In other words, the luminance of the illumination device ILc including the reflection sheet RS when emitting P-polarized light from the light sources LS3 and LS4 is greater than the luminance of the illumination device ILc including the reflection sheet RS when emitting S-polarized light from the light sources LS3 and LS4 and the luminance of the illumination device ILc not including the reflection sheet RS when emitting S-polarized light from the light sources LS3 and LS4.

[0104] The luminance change LMp2 of the illumination device ILc not including the reflection sheet RS when emitting P-polarized light is substantially the same as the luminance change LMs1 of the illumination device ILc including the reflection sheet RS when emitting S-polarized light. In other words, the luminance of the illumination device ILc not including the reflection sheet RS when emitting P-polarized light from the light sources LS3 and LS4 is substantially the same as the luminance of the illumination device ILc including the reflection sheet RS when emitting S-polarized light from the light sources LS3 and LS4.

[0105] The luminance change LMs1 of the illumination device ILc including the reflection sheet RS when emitting S-polarized light is greater than the luminance change LMs2 of the illumination device ILc not including the reflection sheet RS when emitting S-polarized light. In other words, the luminance of the illumination device ILc including the reflection sheet RS when emitting S-polarized light from the light sources LS3 and LS4 is greater than the luminance of the illumination device ILc not including the reflection sheet RS when emitting S-polarized light from the light sources LS3 and LS4.

[0106] In each of the luminance change LMp1 of the illumination device ILc including the reflection sheet RS when emitting P-polarized light and the luminance change LMp2 of the illumination device ILc not including the reflection sheet RS reflected when emitting P-polarized light, the luminance due to the light reflected by the reflection layer P4 and the luminance due to the light reflected by the reflection layer P3 are substantially the same. That is, for P-polarized light, the interface reflection of the emitted light is small.

[0107] In the luminance change LMs1 of the lighting device ILc including the reflection sheet RS when emitting S-polarized light, the luminance due to the light reflected by the reflection layer P4 and the luminance due to the light reflected by the reflection layer P3 are almost the same. However, in the luminance change LMs2 of the lighting device ILc without the reflection sheet RS when emitting S-polarized light, the luminance due to the light reflected by the reflection layer P4 is smaller than the luminance due to the light reflected by the reflection layer P3. That is, for S-polarized light, the interface reflection is large when the emitted light reflected by the reflection layer P4 passes through the light guide plate LG3. As described above, it is desirable to use P-polarized light rather than S-polarized light as the light emitted from the light sources of the lighting devices, for example, the lighting devices IL and ILc.

[0108] FIG. 12 is a cross-sectional view showing an example of the arrangement of the light source LS1 with respect to the light guide plate LG1 of the lighting device IL shown in FIG. 3. According to the study by the inventors of the present application, when the two reverse prism bottom angles of the prism of the prism sheet PS are set to 61.3°, the refractive index n of the light guide plate indicates 1.5, the angle of the total reflection condition of the incident light indicates 48 degrees, and the emission angle δ of the incident light indicates 6.5°, by setting the angle between the incident light and the main surface and the opposing surface of the light guide plate to 26.5°, setting the bottom angle α1 of the prisms PA and PB to 15°, and further setting the apex angles of the prism PA and the prism PA to 130°, it is possible to improve the emission efficiency of the lighting device IL to 90%.

[0109] In the example shown in FIG. 12, the light source LS1 emits P-polarized light L1. In the example shown in FIG. 12, the light source LS1 is arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG1 such that, in the Y-Z plane, the incident angle is in the vicinity of the Brewster angle (hereinafter, may also be referred to as the Brewster approximation angle) at which the reflectance with respect to the side surface SF1 is 0.005 or less, for example, the Brewster approximation angle = 56° and P-polarized light is incident. In other words, the light source LS1 is arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG1 such that, in the Y-Z plane, P-polarized light is incident at an angle of = 56° on the main surface 1A side with respect to the straight line (perpendicular line) perpendicular to the side surface SF1 at which the reflectance with respect to the side surface SF1 is 0.005 (0.5%) or less. Note that the light source LS1 may be arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG1 such that, in the Y-Z plane, P-polarized light is incident on the side surface SF1 at the Brewster angle = 55.9°. In other words, the light source LS1 may be arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG1 such that, in the Y-Z plane, P-polarized light is incident at an angle of = 55.9° on the main surface 1A side with respect to the straight line perpendicular to the side surface SF1.

[0110] In the example shown in FIG. 12, the light source LS1 is arranged so as to protrude (or deviate) to the tip side of the arrow in the second direction Y from the main surface 1A. In other words, the light source LS1 is located on the tip side of the arrow in the Y direction from the main surface 1A. The light source LS1 is arranged to a position at a distance HL1 from the main surface 1A of the light guide plate LG1 on the tip side of the arrow in the Z direction. The emission part LSP1 of the light source LS1 that emits P-polarized light L1 is located above the center line parallel to the main surface 1A and the opposing surface 1B and passing through the centers of the heights of the main surface 1A and the opposing surface 1B in the Z direction.

[0111] In FIG. 12, the side surface SF1 is formed to be inclined at an angle of = 82.9° with respect to the main surface 1A and at an angle of = 97.1° with respect to the opposing surface 1B in the Y-Z plane. In other words, the side surface SF1 is formed to be inclined at an angle of = 82.9° with respect to the main surface 1A in the Y-Z plane. Also, the side surface SF1 is formed to be inclined at an angle of = 97.1° with respect to the opposing surface 1B in the Y-Z plane.

[0112] In the example shown in FIG. 12, the light source LS1 emits P-polarized light L1 at a Brewster's approximation angle of 56° from the main surface 1A side toward the side surface SF1 in the Z direction. The P-polarized light L1 emitted from the light source LS1 enters the side surface SF1 at a Brewster's approximation angle of 56° from the main surface 1A side in the Z direction. In other words, the P-polarized light L1 emitted from the light source LS1 enters the side surface SF1 at an angle of 56° with respect to the straight line perpendicular to the side surface SF1 from the main surface 1A side in the Z direction. The P-polarized light L1 incident on the light guide plate LG1 from the air is refracted at a refraction angle of 33.6° at the boundary between the air and the side surface SF1 and travels at an angle of 26.5° with respect to the opposing surface 1B. In other words, the P-polarized light L1 incident on the light guide plate LG1 from the side surface SF1 is refracted at an angle of 33.6° toward the opposing surface 1B side with respect to the straight line perpendicular to the side surface SF1 at the side surface SF1 and travels at 26.5° with respect to the opposing surface 1B.

[0113] FIG. 13 is a cross-sectional view showing an example of the arrangement of the light source LS2 with respect to the light guide plate LG2 of the illumination device IL shown in FIG. 3. In the example shown in FIG. 13, the light source LS2 emits P-polarized light L2. In the example shown in FIG. 13, the light source LS2 is arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG2 such that P-polarized light is incident at a Brewster's approximation angle at which the reflectance with respect to the side surface SF4 is 0.005 (0.5%) or less in the Y-Z plane, for example, a Brewster's approximation angle of 56°. In other words, the light source LS2 is arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG2 such that P-polarized light is incident at an angle of 56° with respect to the straight line perpendicular to the side surface SF4 toward the main surface 1A side in the Y-Z plane where the reflectance with respect to the side surface SF4 is 0.005 or less. Note that the light source LS2 may be arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG2 such that P-polarized light is incident on the side surface SF4 at a Brewster's angle of 55.9° in the Y-Z plane. In other words, the light source LS2 may be arranged on the tip side of the arrow in the Z direction with respect to the light guide plate LG2 such that P-polarized light is incident at an angle of 55.9° with respect to the straight line perpendicular to the side surface SF4 toward the main surface 1A side in the Y-Z plane.

[0114] In the example shown in FIG. 13, the light source LS2 is arranged so as to protrude (or deviate) to the side opposite to the tip of the arrow in the third direction Y from the main surface 2A. In other words, the light source LS2 is located on the tip side of the arrow in the direction Y from the main surface 2A. The light source LS2 is arranged up to a position at a distance HL1 from the main surface 2A of the light guide plate LG2 toward the tip side of the arrow in the direction Z. The light emitting portion LSP2 of the light source LS2 that emits the P-polarized light L2 is located above the center line parallel to the main surface 2A and the opposing surface 2B in the direction Z, passing through the centers of the heights of the main surface 2A and the opposing surface 2B of the light guide plate LG2.

[0115] In FIG. 13, the side surface SF4 is formed to be inclined at an angle = 82.9° with respect to the main surface 2A and at an angle = 97.1° with respect to the opposing surface 2B in the Y-Z plane. In other words, the side surface SF4 is formed to be inclined at an angle = 82.9° with respect to the main surface 2A in the Y-Z plane. Also, the side surface SF4 is formed to be inclined at an angle = 97.1° with respect to the opposing surface 2B in the Y-Z plane.

[0116] In the example shown in FIG. 13, the light source LS2 emits the P-polarized light L2 at the Brewster's approximation angle = 56° from the main surface 2A side toward the side surface SF4 in the direction Z. The P-polarized light L2 emitted from the light source LS2 is incident on the side surface SF1 at the Brewster's approximation angle = 56° from the main surface 2A side in the direction Z. In other words, the P-polarized light L2 emitted from the light source LS2 is incident on the side surface SF4 at an angle = 56° on the main surface 2A side with respect to the straight line perpendicular to the side surface SF4 in the direction Z. The P-polarized light L2 incident from the air on the light guide plate LG2 is refracted at a refraction angle of 33.6° at the boundary between the air and the side surface SF4 and travels at an angle = 26.5° with respect to the opposing surface 2B. In other words, the P-polarized light L2 incident on the light guide plate LG2 from the side surface SF4 is refracted at an angle = 33.6° on the opposing surface 2B side with respect to the straight line perpendicular to the side surface SF4 at the side surface SF4 and travels at 26.5° with respect to the opposing surface 2B.

[0117] According to the present embodiment, the lighting device IL includes a light guide plate LG1, a light guide plate LG2, a plurality of light sources LS1, and a plurality of light sources LS2. The light guide plate LG1 has a main surface 1A facing the display panel PNL, an opposing surface 1B located on the opposite side of the main surface 1A in the direction Z, a side surface SF1, and a side surface SF2 located on the opposite side of the side surface SF1 in the direction Y. The side surface SF1 and the side surface SF2 face each other in the direction Y. The side surface SF1 is non-parallel to the X-Z plane. The side surface SF2 is parallel to the X-Z plane. The side surface SF1 and the side surface SF2 are provided non-parallel to each other. The side surface SF1 is an inclined surface that faces outward from the inside in the direction Y as it goes from the lower side to the upper side in the direction Z. The side surface SF1 is formed to be inclined at an angle of = 82.9° with respect to the main surface 1A. The light guide plate LG2 has a main surface 2A facing the opposing surface 1B, an opposing surface 2B located on the opposite side of the main surface 2A in the direction Z, a side surface SF3 aligned with the side surface SF1 in the direction Z, and a side surface SF4 located on the opposite side of the side surface SF3 in the direction Y and aligned with the side surface SF2 in the direction Z. The side surface SF3 and the side surface SF4 face each other in the direction Y. The side surface SF3 is parallel to the X-Z plane. The side surface SF4 is non-parallel to the X-Z plane. The side surface SF3 and the side surface SF4 are provided non-parallel to each other. The side surface SF4 is an inclined surface that faces outward from the inside in the direction Y as it goes from the lower side to the upper side in the direction Z. The side surface SF4 is formed to be inclined at an angle of = 82.9° with respect to the main surface 2A.

[0118] A plurality of light sources LS1 face the side surface SF1. The light source LS1 emits P-polarized light L1. The light source LS1 is arranged on the tip side of the arrow in the direction Z rather than the light guide plate LG1 so that P-polarized light is incident at the Brewster approximation angle = 56° at which the reflectance with respect to the side surface SF1 is 0.005 or less. A plurality of light sources LS2 face the side surface SF4. The light source LS2 emits P-polarized light L2. The light source LS2 is arranged on the tip side of the arrow in the direction Z rather than the light guide plate LG2 so that P-polarized light is incident at the Brewster approximation angle = 56° at which the reflectance with respect to the side surface SF4 is 0.005 or less. Therefore, the lighting device IL can improve the light emission efficiency from the light guide plates LG1 and LG2 of the light emitted from the light sources LS1 and LS2. Therefore, the display device DSP can also improve the light emission efficiency.

[0119] Next, a modified example according to the first embodiment and display devices DSP and lighting devices IL of other embodiments will be described. In the modified examples and other embodiments described below, the same parts as the display device DSP and the lighting device IL of the first embodiment described above are given the same reference numerals, and the detailed description thereof is omitted or simplified, and the description will be centered on the parts different from the display device DSP and the lighting device IL of the first embodiment. In addition, even in the modified examples and other embodiments, the same effects as those of the above-described embodiment can be obtained.

[0120] (Modified Example 1) In the lighting device IL according to the first modified example, the configurations of the light sources LS1 and LSF2 are different from those of the lighting device IL of the first embodiment. FIG. 14 is a cross-sectional view showing an example of the arrangement of the light source LS1 with respect to the light guide plate LG1 of the lighting device IL according to the first modified example. In the example shown in FIG. 14, the light source LS1 is arranged on the opposite side of the tip of the arrow in the Z direction with respect to the light guide plate LG1 such that P-polarized light is incident at the Brewster approximation angle of 56° with a reflectance of 0.005 (0.5%) or less with respect to the side surface SF1 in the Y-Z plane. In other words, the light source LS1 is arranged on the opposite side of the tip of the arrow in the Z direction with respect to the light guide plate LG1 such that P-polarized light is incident at an angle of 56° on the opposing surface 1B side with respect to a straight line perpendicular to the side surface SF1 with a reflectance of 0.005 or less with respect to the side surface SF1 in the Y-Z plane. Note that the light source LS1 may be arranged on the opposite side of the tip of the arrow in the Z direction with respect to the light guide plate LG1 such that P-polarized light is incident at the Brewster angle of 55.9° with respect to the side surface SF1 in the Y-Z plane. In other words, the light source LS1 may be arranged on the opposite side of the tip of the arrow in the Z direction with respect to the light guide plate LG1 such that P-polarized light is incident at an angle of 55.9° on the opposing surface 1B side with respect to a straight line perpendicular to the side surface SF1 in the Y-Z plane.

[0121] In the example shown in FIG. 14, the light source LS1 is arranged so as to protrude (or deviate) to the opposite side of the tip of the arrow in the second direction Y from the opposing surface 1B. In other words, the light source LS1 is located on the opposite side of the tip of the arrow in the Y direction from the opposing surface 1B. The light source LS1 is arranged to a position at a distance HL1 from the opposing surface 1B of the light guide plate LG1 on the opposite side of the tip of the arrow in the Z direction. The emitting portion LSP1 of the light source LS1 that emits P-polarized light L1 is located below the center line parallel to the main surface 1A and the opposing surface 1B passing through the centers of the heights of the main surface 1A and the opposing surface 1B of the light guide plate LG1 in the Z direction.

[0122] In FIG. 14, the side surface SF1 is formed to be inclined at an angle of 97.1° with respect to the main surface 1A and at an angle of 82.9° with respect to the opposing surface 1B in the Y-Z plane. In other words, the side surface SF1 is formed to be inclined at an angle of 82.9° with respect to the opposing surface 1B in the Y-Z plane. Also, the side surface SF1 is formed to be inclined at an angle of 97.1° with respect to the main surface 1A in the Y-Z plane.

[0123] In the example shown in FIG. 14, the light source LS1 emits P-polarized light L1 at a Brewster's approximation angle of 56° from the side of the facing surface 1B toward the side surface SF1 in the direction Z. The P-polarized light L1 emitted from the light source LS1 is incident on the side surface SF1 at a Brewster's approximation angle of 56° from the side of the facing surface 1B in the direction Z. The P-polarized light L1 incident on the light guide plate LG1 from the air is refracted at a refractive angle of 33.6° at the boundary between the air and the side surface SF1 and travels at an angle of 26.5° with respect to the main surface 1A. In other words, the P-polarized light L1 incident on the light guide plate LG1 from the side surface SF1 is refracted at an angle of 33.6° toward the main surface 1A side with respect to a straight line perpendicular to the side surface SF1 at the side surface SF1 and travels at 26.5° with respect to the main surface 1A.

[0124] FIG. 15 is a cross-sectional view showing an example of the arrangement of the light source LS2 with respect to the light guide plate LG2 of the lighting device IL according to the first modification. In the example shown in FIG. 15, the light source LS2 is arranged on the side opposite to the tip of the arrow in the direction Z with respect to the light guide plate LG2 such that P-polarized light is incident at a Brewster's approximation angle of 56° with a reflectance of 0.005 or less with respect to the side surface SF4 in the Y-Z plane. In other words, the light source LS2 is arranged on the side opposite to the tip of the arrow in the direction Z with respect to the light guide plate LG2 such that P-polarized light is incident at an angle of 56° toward the facing surface 1B side with respect to a straight line perpendicular to the side surface SF4 with a reflectance of 0.005 (0.5%) or less with respect to the side surface SF4 in the Y-Z plane. Note that the light source LS2 may be arranged on the side opposite to the tip of the arrow in the direction Z with respect to the light guide plate LG2 such that P-polarized light is incident on the side surface SF4 at a Brewster's angle of 55.9°. In other words, the light source LS2 may be arranged on the side opposite to the tip of the arrow in the direction Z with respect to the light guide plate LG2 such that P-polarized light is incident at an angle of 55.9° toward the facing surface 1B side with respect to a straight line perpendicular to the side surface SF4 in the Y-Z plane.

[0125] In the example shown in FIG. 15, the light source LS2 is disposed so as to protrude (or deviate) to the side opposite to the tip of the arrow in the second direction Y with respect to the opposing surface 2B. In other words, the light source LS2 is located on the side opposite to the tip of the arrow in the direction Y with respect to the opposing surface 2B. The light source LS2 is disposed to a position separated by a distance HL1 from the opposing surface 2B of the light guide plate LG2 to the side opposite to the tip of the arrow in the direction Z. The light emitting portion LSP2 of the light source LS2 that emits the P-polarized light L2 is located below the center line parallel to the main surface 2A and the opposing surface 2B in the direction Z, passing through the centers of the heights of the main surface 2A and the opposing surface 2B of the light guide plate LG2.

[0126] In FIG. 15, the side surface SF4 is formed to be inclined at an angle = 82.9° with respect to the opposing surface 2B and at an angle = 97.1° with respect to the main surface 2A in the Y-Z plane. In other words, the side surface SF4 is formed to be inclined at an angle = 82.9° with respect to the opposing surface 2B in the Y-Z plane. Also, the side surface SF4 is formed to be inclined at an angle = 97.1° with respect to the main surface 2A in the Y-Z plane.

[0127] In the example shown in FIG. 15, the light source LS2 emits the P-polarized light L2 at a Brewster's approximation angle = 56° from the opposing surface 2B side toward the side surface SF4 in the direction Z. The P-polarized light L2 emitted from the light source LS2 is incident on the side surface SF4 at a Brewster's approximation angle = 56° from the opposing surface 2B side in the direction Z. The P-polarized light L2 incident from the air on the light guide plate LG2 is refracted at a refraction angle of 33.6° at the boundary between the air and the side surface SF4 and travels at an angle = 26.5° with respect to the main surface 2A. In other words, the P-polarized light L2 incident on the light guide plate LG2 from the side surface SF4 is refracted at an angle = 33.6° toward the main surface 2A side with respect to the straight line perpendicular to the side surface SF4 at the side surface SF4 and travels at 26.5° with respect to the main surface 2A. Even in such a modification 1, there is the same effect as that of the first embodiment.

[0128] (Second Embodiment) The display device DSP according to the second embodiment is different from the display device DSP of the first embodiment in the configuration of the light sources LS1 and LS2 of the illumination device IL and the light guide plates LG1 and LG2 of the illumination device IL.

[0129] FIG. 16 is a cross-sectional view of the display device DSP according to the second embodiment. For example, the side surface SF1 is inclined at an angle greater than 0° and less than the 90° - Brewster angle with respect to the main surface 1A. Also, for example, the side surface SF4 is inclined at an angle greater than 0° and less than the 90° - Brewster angle with respect to the main surface 2A.

[0130] The light L1 emitted from the light source LS1 is not reflected at all or is hardly reflected at the interface between the side surface SF1 and the air layer, enters the light guide plate LG1 from the side surface SF1, and is refracted at the side surface SF1. Among the light L1 incident on the light guide plate LG1, the light traveling toward the main surface 1A is reflected (e.g., totally reflected) at the interface between the light guide plate LG1 and the air layer. Also, among the light L1 incident on the light guide plate LG1, the light traveling toward the opposing surface 1B is reflected (e.g., totally reflected) at the interface between the light guide plate LG1 and the air layer. In this way, the light L1 travels toward the tip side of the arrow in the direction Y within the light guide plate LG1 while being repeatedly reflected (e.g., totally reflected) at the main surface 1A and the opposing surface 1B in the region where the reflection layer P1 is not provided within the first region A1.

[0131] Similarly, the light L2 emitted from the light source LS2 is not reflected at all or is hardly reflected at the interface between the side surface SF4 and the air layer, enters the light guide plate LG2 from the side surface SF4, and is refracted at the side surface SF4. Among the light L2 incident on the light guide plate LG2, the light traveling toward the main surface 2A is reflected (e.g., totally reflected) at the interface between the light guide plate LG2 and the air layer. Also, among the light L2 incident on the light guide plate LG2, the light traveling toward the opposing surface 2B is reflected (e.g., totally reflected) at the interface between the light guide plate LG2 and the air layer. In this way, the light L2 travels on the side opposite to the tip of the arrow in the direction Y within the light guide plate LG2 while being repeatedly reflected (e.g., totally reflected) at the main surface 2A and the opposing surface 2B in the region where the reflection layer P2 is not provided within the second region A2.

[0132] FIG. 17 is a cross-sectional view showing an example of the arrangement of the light source LS1 with respect to the light guide plate LG1 of the lighting device IL according to the second embodiment. In the example shown in FIG. 17, the light source LS1 is arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at a Brewster approximation angle at which the reflectance with respect to the side surface SF1 is 0.005 (0.5%) or less, for example, Brewster approximation angle = 56°. In other words, the light source LS1 is arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at an angle of = 56° on the main surface 1A side with respect to a straight line perpendicular to the side surface SF1 at which the reflectance with respect to the side surface SF1 is 0.005 or less. Further, the light source LS1 is arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at an angle of = 4.1° with respect to the center line passing through the center of the light guide plate LG1 and parallel to the main surface 1A and the opposing surface 1B.

[0133] Note that the light source LS1 may be arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident on the side surface SF1 at a Brewster angle = 55.9°. In other words, the light source LS1 may be arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at an angle of = 55.9° on the main surface 1A side with respect to a straight line perpendicular to the side surface SF1.

[0134] In the example shown in FIG. 17, the light source LS1 is arranged between the main surface 1A and the opposing surface 1B in the direction Z. In other words, the light source LS1 is arranged between the heights of the main surface 1A and the opposing surface 1B in the direction Z. The light source LS1 is arranged in the range from the opposing surface 1B to a position at a distance HL2 away from the tip of the arrow in the opposite direction of the direction Z from the main surface 1A. The light source LS1 is arranged in the direction Z so as to be inclined downward at an angle of = 4.1° with respect to the center line passing through the centers of the heights of the main surface 1A and the opposing surface 1B of the light guide plate LG1 and parallel to the main surface 1A and the opposing surface 1B. The light emitting portion LSP1 of the light source LS1 that emits P-polarized light L1 is located below the center line passing through the centers of the heights of the main surface 1A and the opposing surface 1B of the light guide plate LG1 and parallel to the main surface 1A and the opposing surface 1B in the direction Z.

[0135] In FIG. 17, the side surface SF1 is inclined at an angle of = 29.9° with respect to the main surface 1A and at an angle of = 150.1° with respect to the opposing surface 1B in the Y-Z plane. In other words, the side surface SF1 is inclined at an angle of = 29.9° with respect to the main surface 1A in the Y-Z plane. Also, the side surface SF1 is inclined at an angle of = 150.1° with respect to the opposing surface 1B in the Y-Z plane.

[0136] In the example shown in FIG. 17, the light source LS1 emits P-polarized light L1 at a Brewster's approximation angle of = 56° from the opposing surface 1B side toward the side surface SF1 in the direction Z. The P-polarized light L1 emitted from the light source LS1 is incident on the side surface SF1 at a Brewster's approximation angle of = 56° from the opposing surface 1B side in the direction Z. In other words, the P-polarized light L1 emitted from the light source LS1 is incident on the side surface SF1 at an angle of = 56° on the main surface 1A side with respect to the straight line perpendicular to the side surface SF1 in the direction Z. The P-polarized light L1 incident on the light guide plate LG1 from the air is refracted at a refraction angle of = 33.6° at the boundary between the air and the side surface SF1 and travels at an angle of = 26.5° with respect to the main surface 1A. In other words, the P-polarized light L1 incident on the light guide plate LG1 from the side surface SF1 is refracted at an angle of = 33.6° on the opposing surface 1B side with respect to the straight line perpendicular to the side surface SF1 at the side surface SF1 and travels at 26.5° with respect to the main surface 1A.

[0137] FIG. 18 is a cross-sectional view showing an example of the arrangement of the light source LS2 with respect to the light guide plate LG2 of the lighting device IL according to the second embodiment. In the example shown in FIG. 18, the light source LS2 emits P-polarized light L2. In the example shown in FIG. 18, the light source LS2 is arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident at a Brewster approximation angle at which the reflectance with respect to the side surface SF4 is 0.005 (0.5%) or less, for example, Brewster approximation angle = 56° in the Y-Z plane. In other words, the light source LS2 is arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident at an angle of = 56° on the main surface 2A side with respect to a straight line perpendicular to the side surface SF4 at which the reflectance with respect to the side surface SF4 is 0.005 or less in the Y-Z plane. Further, the light source LS2 is arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at an angle of = 4.1° with respect to the center line passing through the center of the light guide plate LG2 and parallel to the main surface 2A and the opposing surface 2B in the Y-Z plane.

[0138] Note that the light source LS2 may be arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident on the side surface SF4 at a Brewster angle = 55.9°. In other words, the light source LS2 may be arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident at an angle of = 55.9° on the opposing surface 2B side with respect to a straight line perpendicular to the side surface SF4 in the Y-Z plane.

[0139] In the example shown in FIG. 18, the light source LS2 is arranged between the main surface 2A and the opposing surface 2B in the direction Z. In other words, the light source LS2 is arranged between the heights of the main surface 2A and the opposing surface 2B in the direction Z. The light source LS2 is arranged in a range from the opposing surface 2B to a position at a distance HL2 away from the tip of the arrow in the opposite direction in the direction Z from the main surface 2A. The light source LS2 is arranged to be inclined downward at an angle of = 4.1° with respect to the center line passing through the centers of the heights of the main surface 2A and the opposing surface 2B of the light guide plate LG2 and parallel to the main surface 2A and the opposing surface 2B in the direction Z. The emission part LSP2 of the light source LS2 that emits P-polarized light L1 is located below the center line passing through the centers of the heights of the main surface 2A and the opposing surface 2B of the light guide plate LG2 and parallel to the main surface 2A and the opposing surface 2B in the direction Z.

[0140] In FIG. 18, the side surface SF4 is inclined at an angle = 29.9° with respect to the main surface 2A and at an angle = 150.1° with respect to the opposing surface 2B in the Y-Z plane. In other words, the side surface SF4 is inclined at an angle = 29.9° with respect to the main surface 2A in the Y-Z plane. Also, the side surface SF4 is inclined at an angle = 150.1° with respect to the opposing surface 2B in the Y-Z plane.

[0141] In the example shown in FIG. 18, the light source LS2 emits P-polarized light L2 at a Brewster's approximation angle = 56° from the opposing surface 2B side toward the side surface SF4 in the direction Z. The P-polarized light L2 emitted from the light source LS2 is incident on the side surface SF4 at a Brewster's approximation angle = 56° from the opposing surface 2B side in the direction Z. In other words, the P-polarized light L2 emitted from the light source LS2 is incident on the side surface SF4 at an angle = 56° on the main surface 2A side with respect to the straight line perpendicular to the side surface SF4 from the opposing surface 2B side in the direction Z. The P-polarized light L2 incident on the light guide plate LG2 from the air is refracted at a refraction angle of 33.6° at the boundary between the air and the side surface SF4 and travels at an angle = 26.5° with respect to the main surface 2A. In other words, the P-polarized light L2 incident on the light guide plate LG2 from the side surface SF4 is refracted at an angle = 33.6° on the opposing surface 2B side with respect to the straight line perpendicular to the side surface SF4 at the side surface SF4 and travels at 26.5° with respect to the main surface 2A.

[0142] Even in such a second embodiment, there are the same effects as those of the first embodiment and Modification 1. In addition, the thickness of the lighting device IL according to the second embodiment can be made smaller than the thickness of the lighting device IL according to the first embodiment.

[0143] (Modification 2) In the lighting device IL according to Modification 2 of the second embodiment, the configurations of the light sources LS1 and LS2 are different from those of the lighting devices IL of the first embodiment, Modification 1, and the second embodiment.

[0144] FIG. 19 is a cross-sectional view showing an example of the arrangement of the light source LS1 with respect to the light guide plate LG1 of the lighting device IL according to Modification 2. In the example shown in FIG. 19, the light source LS1 is arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at a Brewster approximation angle at which the reflectance with respect to the side surface SF1 is 0.005 (0.5%) or less, for example, the Brewster approximation angle = 56°. In other words, the light source LS1 is arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at an angle of 56° on the opposing surface 1B side with respect to a straight line perpendicular to the side surface SF1 at which the reflectance with respect to the side surface SF1 is 0.005 or less. Further, the light source LS1 is arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident at an angle of 4.1° with respect to the center line passing through the center of the light guide plate LG1 and parallel to the main surface 1A and the opposing surface 1B.

[0145] Note that the light source LS1 may be arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident on the side surface SF1 at a Brewster angle = 55.9°. In other words, the light source LS1 may be arranged in the Y-Z plane at a position away from the tip of the arrow in the direction Y with respect to the side surface SF1 such that P-polarized light is incident on the opposing surface 1B side at an angle of 55.9° with respect to a straight line perpendicular to the side surface SF1.

[0146] In the example shown in FIG. 19, the light source LS1 is arranged between the main surface 1A and the opposing surface 1B of the light guide plate LG1 in the direction Z. In other words, the light source LS1 is arranged between the heights of the main surface 1A and the opposing surface 1B in the direction Z. The light source LS1 is arranged in the range from a position at a distance HL2 from the opposing surface 1B toward the tip side of the arrow in the direction Z to the main surface 1A. The light source LS1 is arranged in the direction Z so as to be inclined upward at an angle of 4.1° with respect to the center line passing through the centers of the heights of the main surface 1A and the opposing surface 1B of the light guide plate LG1 and parallel to the main surface 1A and the opposing surface 1B. The emission part LSP1 of the light source LS1 that emits the P-polarized light L1 is located above the center line passing through the centers of the heights of the main surface 1A and the opposing surface 1B of the light guide plate LG1 and parallel to the main surface 1A and the opposing surface 1B in the direction Z.

[0147] In FIG. 19, the side surface SF1 is inclined at an angle = 150.1° with respect to the main surface 1A and at an angle = 29.9° with respect to the opposing surface 1B in the Y-Z plane. In other words, the side surface SF1 is inclined at an angle = 150.1° with respect to the main surface 1A in the Y-Z plane. Also, the side surface SF1 is inclined at an angle = 29.9° with respect to the opposing surface 1B in the Y-Z plane.

[0148] In the example shown in FIG. 19, the light source LS1 emits P-polarized light L1 at a Brewster's approximation angle = 56° from the main surface 1A side toward the side surface SF1 in the direction Z. The P-polarized light L1 emitted from the light source LS1 enters the side surface SF1 at a Brewster's approximation angle = 56° from the main surface 1A side in the direction Z. In other words, the P-polarized light L1 emitted from the light source LS1 enters the side surface SF1 at an angle = 56° from the main surface 1A side in the direction Z with respect to a straight line perpendicular to the side surface SF1 toward the opposing surface 1B side. The P-polarized light L1 incident on the light guide plate LG1 from the air is refracted at a refraction angle = 33.6° at the boundary between the air and the side surface SF1 and travels at an angle = 26.5° with respect to the opposing surface 1B. In other words, the P-polarized light L1 incident on the light guide plate LG1 from the side surface SF1 is refracted at an angle = 33.6° at the side surface SF1 with respect to a straight line perpendicular to the side surface SF1 toward the main surface 1A side and travels at 26.5° with respect to the opposing surface 1B.

[0149] FIG. 20 is a cross-sectional view showing an example of the arrangement of the light source LS2 with respect to the light guide plate LG2 of the illumination device IL according to the second modification. In the example shown in FIG. 20, the light source LS2 is arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident at a Brewster approximation angle at which the reflectance with respect to the side surface SF4 is 0.005 (0.5%) or less, for example, the Brewster approximation angle = 56° in the Y-Z plane. In other words, the light source LS2 is arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident at an angle of = 56° on the opposing surface 2B side with respect to a straight line perpendicular to the side surface SF4 at which the reflectance with respect to the side surface SF4 is 0.005 or less in the Y-Z plane. Further, the light source LS2 is arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident at an angle of = 4.1° with respect to the center passing through the center of the light guide plate LG2 and parallel to the main surface 2A and the opposing surface 2B in the Y-Z plane.

[0150] Note that the light source LS2 may be arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident on the side surface SF4 at a Brewster angle = 55.9°. In other words, the light source LS2 may be arranged at a position away from the tip side of the arrow in the direction Y with respect to the side surface SF4 such that P-polarized light is incident at an angle of = 55.9° on the opposing surface 2B side with respect to a straight line perpendicular to the side surface SF4.

[0151] In the example shown in FIG. 20, the light source LS2 is arranged between the main surface 2A and the opposing surface 2B in the direction Z. In other words, the light source LS2 is arranged between the heights of the main surface 2A and the opposing surface 2B in the direction Z. The light source LS2 is arranged in the range from a position at a distance HL2 away from the opposing surface 2B toward the tip side of the arrow in the direction Z to the main surface 2A. The light source LS2 is arranged to be inclined upward at an angle of = 4.1° with respect to the center line passing through the centers of the heights of the main surface 2A and the opposing surface 2B of the light guide plate LG2 and parallel to the main surface 2A and the opposing surface 2B in the direction Z. The emission part LSP2 of the light source LS2 that emits the P-polarized light L1 is located above the center line passing through the centers of the heights of the main surface 2A and the opposing surface 2B of the light guide plate LG2 and parallel to the main surface 2A and the opposing surface 2B in the direction Z.

[0152] In FIG. 20, the side surface SF4 is inclined at an angle = 150.1° with respect to the main surface 2A and at an angle = 29.9° with respect to the opposing surface 2B in the Y-Z plane. In other words, the side surface SF4 is formed by being inclined at an angle = 29.9° with respect to the main surface 2A in the Y-Z plane. Also, the side surface SF4 is formed by being inclined at an angle = 150.1° with respect to the opposing surface 2B in the Y-Z plane.

[0153] In the example shown in FIG. 20, the light source LS2 emits P-polarized light L2 at a Brewster's approximation angle = 56° from the main surface 2A side toward the side surface SF4 in the direction Z. The P-polarized light L2 emitted from the light source LS2 is incident on the side surface SF4 at a Brewster's approximation angle = 56° from the main surface 2A side in the direction Z. In other words, the P-polarized light L2 emitted from the light source LS2 is incident on the side surface SF4 at an angle = 56° from the opposing surface 2B side with respect to the straight line perpendicular to the side surface SF4 in the direction Z. The P-polarized light L2 incident from air on the light guide plate LG2 is refracted at a refraction angle of 33.6° at the boundary between air and the side surface SF4 and travels at an angle = 26.5° with respect to the opposing surface 2B. In other words, the P-polarized light L2 incident on the light guide plate LG2 from the side surface SF4 is refracted at an angle = 33.6° from the side surface SF4 toward the main surface 2A side with respect to the straight line perpendicular to the side surface SF4 and travels at 26.5° with respect to the opposing surface 2B. Even in such a second embodiment, there are the same effects as those in the first embodiment and Modification 1.

[0154] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention and are also included in the invention described in the claims and its equivalent scope.

Description of Reference Numerals

[0155] LG1…Light guide plate, 1A, 2A…Main surfaces, 1B, 2B…Opposite surfaces, SF1, SF2, SF3, SF4…Side surfaces, PA, PB, PC, PD…Prisms, SL1, SL2, SL3, SL4, SL5, SL6, SL7, SL8…Inclined surfaces, LS1, LS2, LS3, LS4…Light sources, DL1, DL2, DL3, DL4…Emission directions, AX1, AX2…Optical axes, L1, L2, L3, L4, L10, L11…Light.

Claims

1. A first light guide plate having a first side surface, a second side surface located on the opposite side of the first side surface in a first direction, a first main surface, and a first opposing surface located on the opposite side of the first main surface in a second direction intersecting the first direction; A first light source facing the first side surface and emitting first P-polarized light with respect to the first side surface; The first side surface is inclined with respect to the first main surface and the first opposing surface; The first light source is inclined with respect to a first straight line perpendicular to the first side surface; The first light source is located on the second direction side of the first main surface; The first light source is inclined toward the first main surface side with respect to the first straight line in the second direction; The first P-polarized light is incident on the first side surface at 56° with respect to the first straight line from the first main surface side in the second direction, a lighting device.

2. The first side surface is inclined at 82.9° with respect to the first main surface and inclined at 97.1° with respect to the first opposing surface, the lighting device according to claim 1.

3. A first light guide plate having a first side surface, a second side surface located on the opposite side of the first side surface in a first direction, a first main surface, and a first opposing surface located on the opposite side of the first main surface in a second direction intersecting the first direction; A first light source facing the first side surface and emitting first P-polarized light with respect to the first side surface; The first side surface is inclined with respect to the first main surface and the first opposing surface; The first light source is inclined with respect to a first straight line perpendicular to the first side surface; The first light source is disposed between the heights of the first main surface and the first opposing surface in the second direction, a lighting device.

4. The first light source is inclined toward the first main surface side with respect to the first straight line in the second direction, the lighting device according to claim 3.

5. The first P-polarized light is incident on the first side surface at Brewster's angle with respect to the first straight line from the first main surface side in the second direction, the lighting device according to claim 4.

6. The first P-polarized light is incident on the first side surface at 56° with respect to the first straight line from the first main surface side in the second direction, the lighting device according to claim 4.

7. The first side surface is inclined at 29.9° with respect to the first main surface and inclined at 150.1° with respect to the first opposing surface, the lighting device according to claim 6. Claim 8: A first light guide plate having a first side surface, a second side surface located on the opposite side of the first side surface in a first direction, a first main surface, and a first opposing surface located on the opposite side of the first main surface in a second direction intersecting the first direction; A first light source facing the first side surface and emitting first P-polarized light to the first side surface; A first layer located on the second side surface side in the first direction and including a first prism provided on the first opposing surface; The first side surface is inclined with respect to the first main surface and the first opposing surface; The first light source is inclined with respect to a first straight line perpendicular to the first side surface. An illumination device. Claim 9 An illumination device according to any one of claims 1 to 8; A display panel for displaying an image; The display panel faces the first main surface. A display device.

Images