JP2018045990A - Lighting device and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device which radiates light of a favorable luminance distribution from an emission surface of a light guide plate, and a display device.SOLUTION: A lighting device includes a light guide plate, a first light source and a plurality of prisms. The light guide plate has a first side surface, a first main surface, and a second main surface on the opposite side of the first main surface. The first light source radiates light along a first irradiation direction to the first side surface of the light guide plate. The plurality of prisms are provided on the second main surface. The second main surface has a first region and a second region arranged side by side along the first irradiation direction. The plurality of prisms include a plurality of first prisms in the first region and a plurality of second prisms in the second region. In a cross-sectional view, a first virtual line connecting the apexes of the plurality of first prisms is inclined with respect to the first main surface. In a cross-sectional view, a distance between the second region and the first main surface is longer than a distance between the first region and the first main surface.SELECTED DRAWING: Figure 4

Description

  Embodiments described herein relate generally to a lighting device and a display device.

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

  If uneven brightness occurs on the exit surface of the light guide plate, the quality of the image displayed on the display panel may be lowered. For example, when the viewing angle of light emitted from the light source is narrow, there is a possibility that desired luminance cannot be obtained in a region close to the light source on the exit surface of the light guide plate. In this case, light with sufficient luminance cannot be supplied to the display panel in a region near the light source on the emission surface.

JP 2004-38108 A JP 2011-238484 A

  The objective in 1 aspect of this indication is to provide the illuminating device and display apparatus which irradiate the light of favorable brightness | luminance distribution from the output surface of a light-guide plate.

  An illumination device according to an embodiment includes a light guide plate, a first light source, and a plurality of prisms. The light guide plate has a first side surface, a first main surface, and a second main surface opposite to the first main surface. The first light source irradiates light on the first side surface of the light guide plate along a first irradiation direction. The plurality of prisms are provided on the second main surface. The second main surface has a first region and a second region that are sequentially arranged along the first irradiation direction. The plurality of prisms include a plurality of first prisms in the first region and a plurality of second prisms in the second region. In a cross-sectional view, a first imaginary line connecting vertices of the plurality of first prisms is inclined with respect to the first main surface. In a cross-sectional view, the distance between the second region and the first main surface is longer than the distance between the first region and the first main surface.

FIG. 1 is a perspective view illustrating a schematic configuration of a display device according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the display device according to the first embodiment. FIG. 3 is a schematic plan view of the illumination device according to the first embodiment. FIG. 4 is a schematic cross-sectional view of the light guide plate according to the first embodiment. FIG. 5 is an enlarged cross-sectional view of the first prism according to the first embodiment. FIG. 6 is an enlarged cross-sectional view of the second prism according to the first embodiment. FIG. 7 is a diagram illustrating a luminance distribution of the light guide plate according to the comparative example. FIG. 8 is a diagram illustrating a luminance distribution of a light guide plate according to another comparative example. FIG. 9 is a schematic cross-sectional view of a light guide plate according to the comparative example of FIG. FIG. 10 is a diagram illustrating an example of a luminance distribution of the light guide plate according to the first embodiment. FIG. 11 is a diagram illustrating an example of adjusting the density of the second prism according to the first embodiment. FIG. 12 is a diagram showing the luminance distribution of the light guide plate with the density adjusted as shown in FIG. FIG. 13 is a diagram illustrating an example of adjusting the shape of the second prism according to the first embodiment. FIG. 14 is a diagram illustrating a schematic configuration of the illumination device according to the second embodiment. FIG. 15 is a diagram illustrating an example of a luminance distribution of the light guide plate according to the second embodiment. FIG. 16 is a diagram illustrating a schematic configuration of the illumination device according to the third embodiment. FIG. 17 is a diagram illustrating an example of a luminance distribution of the light guide plate according to the third embodiment. FIG. 18 is a diagram illustrating a schematic configuration of a lighting device according to a modification of the third embodiment. FIG. 19 is a schematic cross-sectional view of the light guide plate according to the fourth embodiment. FIG. 20 is a diagram illustrating a schematic cross-section of the light guide plate according to the fifth embodiment. FIG. 21 is a diagram illustrating a schematic cross-section of the illumination device according to the sixth embodiment. FIG. 22 is a schematic cross-sectional view of a part of the lighting apparatus according to the seventh embodiment. FIG. 23 is a schematic cross-sectional view of a part of the lighting apparatus according to the eighth embodiment. FIG. 24 is a schematic cross-sectional view of a light guide plate according to the ninth embodiment. FIG. 25 is an enlarged cross-sectional view of a part of the light guide plate shown in FIG.

Several embodiments will be described with reference to the drawings.
It should be noted that the disclosure is merely an example, and those skilled in the art can easily conceive of appropriate changes while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, the drawings may be schematically represented in comparison with actual modes in order to clarify the description, but are merely examples, and do not limit the interpretation of the present invention. In each drawing, the reference numerals may be omitted for the same or similar elements arranged in succession. In addition, in the present specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are denoted by the same reference numerals, and redundant detailed description may be omitted.

  In each embodiment, a transmissive liquid crystal display device is disclosed as an example of the display device. In addition, a backlight of a liquid crystal display device is disclosed as an example of a lighting device. However, each embodiment does not prevent application of the individual technical ideas disclosed in each embodiment to other types of display devices and lighting devices. Other types of display devices include, for example, a liquid crystal display device having a reflection type function that reflects external light and uses the reflected light for display in addition to a transmission type function, and a micro electro mechanical system (MEMS). A display device having a mechanical display panel in which the shutter functions as an optical element is assumed. As another type of lighting device, for example, a front light disposed on the front surface of the display device is assumed. Further, the lighting device may be used for an application different from the lighting of the display device.

[First Embodiment]
FIG. 1 is a perspective view illustrating a schematic configuration of a display device 1 according to the first embodiment. The display device 1 can be used for various devices such as a smartphone, a tablet terminal, a mobile phone terminal, a personal computer, a television receiver, an in-vehicle device, a game machine, and a wearable terminal.

  The display device 1 includes a display panel 2, a lighting device 3 as a backlight, a driving IC chip 4 that drives the display panel 2, and flexible circuit boards FPC1 and FPC2 that transmit control signals to the display panel 2 and the lighting device 3. And. For example, the flexible circuit boards FPC1 and FPC2 are connected to a control module that controls operations of the display panel 2 and the lighting device 3.

  The display panel 2 includes a first substrate SUB1 (array substrate) and a second substrate SUB2 (counter substrate) facing the first substrate SUB1. The display panel 2 has a display area DA for displaying an image. The display panel 2 includes, for example, a plurality of pixels PX arranged in a matrix in the display area DA.

  The illumination device 3 includes a first light source LS1, a second light source LS2, and a light guide plate LG facing the first substrate SUB1. The first light source LS1 is opposed to one side surface of the light guide plate LG, and the second light source LS2 is opposed to the other side surface of the light guide plate LG. In FIG. 1, each of the light sources LS1 and LS2 is shown one by one, but actually, a plurality of first light sources LS1 and a plurality of second light sources LS2 are provided (see FIG. 3).

  As shown in FIG. 1, a first direction X, a second direction Y, and a third direction Z are defined. Each direction X, Y, Z is orthogonal to each other, for example. In the present disclosure, viewing the display device 1 from a direction parallel to the third direction Z is referred to as a plan view. Further, viewing the cross section of the display device 1 parallel to the XZ plane is referred to as a cross sectional view. In the example of FIG. 1, each of the substrates SUB1 and SUB2 and the light guide plate LG has a long side along the first direction X and a short side along the second direction Y, and the shape in plan view is rectangular. . However, the shape of each of the substrates SUB1 and SUB2 and the light guide plate LG is not limited to this, and the shape in plan view may be another shape such as a square or a circle.

  FIG. 2 is a schematic cross-sectional view of the display device 1 parallel to the XZ plane. The display panel 2 further includes a sealing material SL and a liquid crystal layer LC. Each of the substrates SUB1 and SUB2 is bonded with a sealing material SL. The liquid crystal layer LC is sealed between the sealing material SL and each of the substrates SUB1 and SUB2.

  A first polarizing plate PL1 is attached to the lower surface of the first substrate SUB1 (the surface facing the light guide plate LG). A second polarizing plate PL2 is attached to the upper surface of the second substrate SUB2 (the surface that does not face the first substrate SUB1). The polarization axes of the polarizing plates PL1 and PL2 are orthogonal to each other.

  The light guide plate LG includes a first main surface 51 facing the display panel 2, a second main surface 52 opposite to the first main surface 51, a first side surface 53, and a second main surface opposite to the first side surface 53. And a side surface 54. The first light source LS1 faces the first side surface 53, and the second light source LS2 faces the second side surface 54. An optical element such as a lens is further arranged between the first light source LS1 and the first side surface 53 and between the second light source LS2 and the second side surface 54, and the width and angle of light from each of the light sources LS1 and LS2 are adjusted. Also good.

  The first light source LS1 irradiates the first side surface 53 with diffused light having a spread centering on the first irradiation direction DL1. The second light source LS2 irradiates the second side surface 54 with diffused light having a spread centering on the second irradiation direction DL2. The irradiation directions DL1 and DL2 are, for example, opposite directions and are parallel to the first direction X. As the light emitting elements of the light sources LS1 and LS2, for example, laser light sources such as semiconductor lasers that emit polarized laser light can be used. The light emitting elements of the light sources LS1 and LS2 are not limited to those emitting laser light, and for example, light emitting diodes can be used.

  Each of the light sources LS1 and LS2 may include a plurality of light emitting elements that emit light of different colors. For example, if each of the light sources LS1 and LS2 includes three light emitting elements that emit red, green, and blue light, light of a mixed color of these colors (for example, white) can be obtained.

  The display device 1 includes a prism sheet PS between the display panel 2 and the light guide plate LG. Further, the display device 1 includes a diffusion sheet DS (diffusion layer) between the prism sheet PS and the display panel 2. For example, the prism sheet PS includes a large number of prisms extending in parallel with the second direction Y. These prisms are formed, for example, on the lower surface of the prism sheet PS (the surface facing the light guide plate LG). However, these prisms may be formed on the upper surface (surface facing the display panel 2) of the prism sheet PS.

  In FIG. 2, an example of an optical path of light emitted from the first light source LS1 is indicated by a broken line, and an example of an optical path of light emitted from the second light source LS2 is indicated by a one-dot chain line. The light emitted from the first light source LS1 enters the light guide plate LG from the first side surface 53, propagates through the light guide plate LG while being reflected by the main surfaces 51 and 52, and eventually deviates from the total reflection condition of the first main surface 51. Then, the light is emitted from the first main surface 51. The light emitted from the second light source LS2 enters the light guide plate LG from the second side surface 54, propagates through the light guide plate LG while being reflected by the main surfaces 51 and 52, and eventually deviates from the total reflection condition of the first main surface 51. Then, the light is emitted from the first main surface 51. As described above, the first main surface 51 corresponds to an emission surface from which light is emitted.

  The prism sheet PS converts the light emitted from the first main surface 51 into light substantially parallel to the third direction Z. Here, “light substantially parallel to the third direction Z” is not only light that is strictly parallel to the third direction Z, but also when the inclination with respect to the third direction Z is emitted from the first main surface 51. Compared with the light, the light converted by the prism sheet PS is sufficiently small. From the viewpoint of maintaining the polarization of light from each of the light sources LS1, LS2, it is preferable that the prism of the prism sheet PS is formed on the lower surface. The light that has passed through the prism sheet PS is diffused by the diffusion sheet DS and applied to the display panel 2. Even when the viewing angle of the light passing through the prism sheet PS is narrow, the viewing angle can be widened by diffusing the light with the diffusion sheet DS.

  In addition, when the light from each light source LS1, LS2 reaches the display panel 2 in a sufficiently polarized state, the first polarizing plate PL1 may be omitted. When the first polarizing plate PL1 is omitted, for example, by increasing the translucency of the substrates SUB1 and SUB2, a so-called transparent liquid crystal display device in which the background of the display device 1 can be seen can be obtained.

  FIG. 3 is a schematic plan view of the illumination device 3. In the example of this figure, eight first light sources LS1 are arranged along the first side surface 53, and eight second light sources LS2 are arranged along the second side surface 54. The intensity of light emitted from the first light source LS1 is highest on the first optical axis AX1, and the intensity of light emitted from the second light source LS2 is highest on the second optical axis AX2.

  The light sources LS1 and LS2 are arranged alternately in the second direction Y as shown in the figure. That is, the first optical axis AX1 of light emitted from the first light source LS1 in the first irradiation direction DL1 and the second optical axis AX2 of light emitted from the second light source LS2 in the second irradiation direction DL2 are in the second direction Y. They are offset from each other. The first optical axis AX1 and the second optical axis AX2 may be aligned in the second direction Y.

  FIG. 4 is a schematic cross-sectional view of the light guide plate LG parallel to the XZ plane. The first main surface 51 of the light guide plate LG is a plane parallel to the first direction X and the second direction Y. The second major surface 52 has a first area A1, a second area A2, and a third area A3. As shown in the plan view of FIG. 3, the first region A1 is provided closer to the first side surface 53 from one end to the other end in the second direction Y of the light guide plate LG. The third region A3 is provided closer to the second side surface 54 from one end to the other end in the second direction Y of the light guide plate LG. The second region A2 is provided between the first region A1 and the third region A3 from one end to the other end in the second direction Y of the light guide plate LG. The first region A1, the second region A2, and the third region A3 are arranged in this order along the first irradiation direction DL1. As an example, in the first direction X, the width of the first region A1 is equal to the width of the third region A3. In the first direction X, the width of the second area A2 is smaller than the width of each area A1, A3. However, the widths of the areas A1 and A3 may be different, and the width of the second area A2 may be greater than or equal to the widths of the areas A1 and A3.

  As shown in FIG. 4, the first region A <b> 1 and the third region A <b> 3 are inclined with respect to the first main surface 51. The second region A2 is parallel to the first major surface 51. “Parallel” here is an angle that is sufficiently smaller than the angle at which each of the regions A1 and A3 is inclined with respect to the first main surface 51, and the second region A2 is inclined with respect to the first main surface 51 ( In the case of being substantially parallel to the first main surface 51).

  A plurality of prisms P are provided on the second main surface 52. The plurality of prisms P include a plurality of first prisms P1 in the first region A1, a plurality of second prisms P2 in the second region A2, and a plurality of third prisms P3 in the third region A3. . Each prism P1, P2, P3 extends in the second direction Y. The cross-sectional shape of the first prism P1 is, for example, uniform in the second direction Y, but may be different. The same applies to the second prism P2 and the third prism P3.

  For example, the first prism P1 and the second prism P2 have different shapes. Also, the third prism P3 and the second prism P2 have different shapes. The first prism P1 and the third prism P3 may have the same shape (including a symmetric shape).

  For example, the first prisms P1 and the second prisms P2 are arranged with different densities. Further, the third prisms P3 and the second prisms P2 are also arranged at different densities. Each first prism P1 and each third prism P3 may be arranged with the same density.

  In cross-sectional view, a line connecting the vertices of the plurality of first prisms P1 is the first imaginary line VL1, a line connecting the vertices of the plurality of second prisms P2 is the second imaginary line VL2, and the vertices of the plurality of third prisms P3. A line segment connecting the two is called a third virtual line VL3. In the example of FIG. 4, each of the virtual lines VL1, VL2, and VL3 is a straight line. However, each virtual line VL1, VL2, VL3 may be at least partially bent or curved.

The first imaginary line VL1 is inclined at the first angle θ1 with respect to the first major surface 51. The third imaginary line VL3 is inclined at the third angle θ3 with respect to the first major surface 51. Each angle θ1, θ3 is an acute angle. As an example, the first angle θ1 and the third angle θ3 are substantially equal (θ1≈θ3). However, the first angle θ1 and the third angle θ3 may be different (θ1 ≠ θ3).
The second virtual line VL2 is inclined with respect to the virtual lines VL1 and VL3. The second angle θ2 formed by the second virtual line VL2 and the first main surface 51 is smaller than the respective angles θ1 and θ3 (θ2 <θ1, θ3). In the example of FIG. 4, the second virtual line VL <b> 2 is parallel to the first major surface 51. Here, “parallel” includes not only the case where the second angle θ2 is zero, but also the case where the angle is sufficiently smaller than the angles θ1 and θ3 (when substantially parallel to the first main surface 51).

  Here, the thickness of the light guide plate LG in the first region A1 (the distance between the first region A1 and the first main surface 51) is D1, and the thickness of the light guide plate LG in the second region A2 (the second region A2 and the first region). The distance between the first main surface 51 and the first main surface 51 is defined as D2, and the thickness of the light guide plate LG in the third region A3 (the distance between the third region A3 and the first main surface 51) is defined as D3. The distance D1 increases from the first side surface 53 toward the boundary between the regions A1 and A2. The distance D3 increases from the second side surface 54 toward the boundary between the regions A2 and A3. In the example of FIG. 4, the distance D2 is constant.

  In such a shape, the distance D2 is longer than the distance D1 at any position in the first region A1 (D2> D1). The distance D2 is longer than the distance D3 at any position in the third region A3 (D2> D3).

  FIG. 5 is an enlarged cross-sectional view of the first prism P1. The first prism P1 has a first inclined surface 11 and a second inclined surface 12, and has a triangular cross section. The angle of the apex angle formed by the inclined surfaces 11 and 12 is θa. The angle formed by the second major surface 52 and the first inclined surface 11 in the first region A1 is θb. The angle formed by the second major surface 52 and the second inclined surface 12 in the first region A1 is θc. The width of the first prism P1 in the first direction X is Dp1, and the interval between the adjacent first prisms P1 in the first direction X is Tp1. The height of the first prism P1 is H1.

  In the example of FIG. 5, the angle θa is an obtuse angle, the angles θb and θc are acute angles, and θa> θc> θb holds. As an example, the first inclined surface 11 is parallel to the first main surface 51. In this case, the angle θb is equal to the angle θ1 described above. The first prisms P1 formed in the first region A1 may all have the same shape, or at least some of the first prisms P1 may have different shapes.

Each third prism P3 formed in the third region A3 has the same configuration as the first prism P1 described above.
As the first prism P1 and the third prism P3 increase, the amount of light emitted from the first main surface 51 can be increased. In general, the luminance of the exit surface tends to decrease at the end of the light guide plate. In view of these, as shown in FIG. 4, the density of the first prism P1 in the first region A1 may be increased from the boundary between the regions A1 and A2 toward the first side surface 53. Similarly, the density of the third prism P3 in the third region A3 may be increased from the boundary between the regions A2 and A3 toward the second side surface 54.

  Here, the density of the first prisms P1 can be defined as the number of first prisms P1 per unit length, for example. Alternatively, the density of the first prism P1 can be expressed by a ratio between the width Dp1 of the first prism P1 and the interval Tp1 between the adjacent first prisms P1. The same applies to the density of the third prism P3.

Further, the apex angle θa and the height H1 of the first prism P1 may be increased from the boundary between the regions A1 and A2 toward the first side surface 53. In this case, the density of the first prism P1 in the first region A1 may be constant.
Similarly, the apex angle and height of the third prism P3 may be increased from the boundary between the regions A2 and A3 toward the second side surface 54. In this case, the density of the third prism P3 in the third region A3 may be constant.

  Note that the density, angle, and height adjustments described above are not necessarily applied to all the first prisms P1 and the third prisms P3. For example, the density, angle, and height may be different in a part of each first prism P1. Similarly, the density, angle, and height may be different in a part of each third prism P3.

  FIG. 6 is an enlarged cross-sectional view of the second prism P2. The second prism P2 has a first inclined surface 21 and a second inclined surface 22, and has a triangular cross section. The apex angle formed by the inclined surfaces 21 and 22 is θd. The angle formed by the second major surface 52 and the first inclined surface 21 in the second region A2 is θe. The angle formed between the second major surface 52 and the second inclined surface 22 in the second region A2 is θf. The width of the second prism P2 in the first direction X is Dp2, and the interval between the adjacent second prisms P2 in the first direction X is Tp2. The height of the second prism P2 is H2.

  In the example of FIG. 6, the angle θd is an obtuse angle, the angles θe and θf are acute angles, and θd> θe and θf are established. The angle θe and the angle θf are, for example, the same angle (θe = θf). The angle θd and the height H2 of each second prism P2 formed in the second region A2 may all be the same, or may be different in at least a part of each second prism P2. Further, the density of each second prism P2 may be constant, or may be different in at least a part of each second prism P2.

  Here, the density of the second prisms P2 can be defined as the number of second prisms P2 per unit length, for example. Alternatively, the density of the second prism P2 can be expressed by a ratio between the width Dp2 of the second prism P2 and the interval Tp2 between the adjacent second prisms P2.

According to the structure of the light guide plate LG of the present embodiment, the luminance unevenness of the light emitted from the first main surface 51 can be suppressed, and the display panel 2 can be irradiated with light having a good luminance distribution. This effect will be described with reference to FIGS.
FIG. 7 is a diagram illustrating a luminance distribution on the exit surface of the light guide plate LGA according to the comparative example. The light guide plate LGA is a flat plate having a constant thickness from one end (left side in the figure) to the other end (right side in the figure) on the light source side. That is, the shape of the light guide plate LGA corresponds to a shape having the third region A3 and not having the first region A1 and the second region A2 in the light guide plate LG shown in FIG. Nine light sources are arranged along the left end in the figure. In this comparative example, the brightness of the exit surface increases as the distance from the light source increases. In the region close to the light source, a stripe pattern in which the high luminance portion and the low luminance portion are repeated along the second direction Y is generated.

  FIG. 8 is a diagram showing a luminance distribution on the exit surface of a light guide plate LGB according to another comparative example. FIG. 9 is a schematic cross-sectional view of the light guide plate LGB. As shown in FIG. 9, the light guide plate LGB has a shape in which the thickness increases from the left end toward the center C in the first direction X, and the thickness decreases from the center C toward the right end. That is, the shape of the light guide plate LGB corresponds to a shape having the first region A1 and the third region A3 in the light guide plate LG shown in FIG. 4 and not having the second region A2. A plurality of light sources LS are arranged on each of the left end and the right end. The light guide plate LGB has the same prisms as the first prism P1 and the third prism P3 described above, but is omitted in FIG.

  The light of the light source LS disposed at the left end of the light guide plate LGB is mainly reflected by the prism in the third region A3 and emitted from the emission surface. The light from the light source LS arranged at the right end of the light guide plate LGB is mainly reflected by the prism in the first region A1 and emitted from the emission surface. Therefore, as shown in FIG. 8, in this comparative example, the luminance reduction near the light source as shown in FIG. 7 does not occur. However, the light reflected by the prisms in the vicinity of the boundaries between the regions A1 and A3 is not easily emitted from directly above the vicinity of the boundary, and is emitted from a position away from the vicinity of the boundary. As a result, the luminance of the exit surface is greatly reduced in the vicinity of the center C in the first direction X (near the boundary between the regions A1 and A3).

  FIG. 10 is a diagram showing a luminance distribution of the emission surface (first main surface 51) in the light guide plate LG according to the present embodiment. In the example of this figure, since the second region A2 is provided between the regions A1 and A3, the luminance does not decrease near the center. That is, the second prism P2 in the second region A2 emits light from the light sources LS1 and LS2 also from the exit surface (first main surface 51) near the center, so that uneven brightness as shown in FIG. 9 is suppressed. ing.

  In the luminance distribution of FIG. 10, there is a slight decrease in luminance at the boundaries between the regions A1 and A2 and the boundaries between the regions A2 and A3. The density and shape of the second prism P2 may be adjusted to suppress this decrease in luminance.

  FIG. 11 is a diagram illustrating an example of adjusting the density of the second prism P2. A line indicated by a one-dot chain line is the center C of the second region A2 in the first direction X. The density of each second prism P2 increases from the center C toward the boundary between the regions A1 and A2. Further, the density of each second prism P2 increases from the center C toward the boundary between the regions A2 and A3. In this example, the width Dp2 and the apex angle θd of each second prism P2 are constant, and the density is adjusted by increasing the interval Tp2 between the adjacent second prisms P2 closer to the center C. Yes. When the density of the second prism P2 is increased at the boundaries between the areas A1 and A2 and at the boundaries between the areas A2 and A3, more light can be emitted from the emission surface at these boundaries.

  FIG. 12 is a diagram showing the luminance distribution of the exit surface (first main surface 51) of the light guide plate LG in which the density of the second prism P2 is adjusted as shown in FIG. In this example, the luminance does not decrease as shown in FIG. 10 at the boundaries between the areas A1 and A2 and at the boundaries between the areas A2 and A3. Therefore, it can be seen that a better luminance distribution can be obtained by adjusting the density of the second prism P2.

  FIG. 13 is a diagram illustrating an example of adjusting the shape of the second prism P2. In this example, the angle θd of each second prism P2 decreases from the center C toward the boundary between the regions A1 and A2. Further, the angle θd of each second prism P2 decreases from the center C toward the boundary between the regions A2 and A3. The width Dp2 and the interval Tp2 are constant over the entire second region A2. Accordingly, the height H2 of each second prism P2 increases from the center C toward the boundary between the regions A1 and A2. Similarly, the height H2 of each second prism P2 increases from the center C toward the boundary between the regions A2 and A3.

  When the angle θd of the second prism P2 is increased at the boundaries between the areas A1 and A2 and at the boundaries between the areas A2 and A3, the inclined surfaces 21 and 22 shown in FIG. 6 become steep. Therefore, the light reflected by the inclined surfaces 21 and 22 reaches the first main surface 51 at an angle closer to vertical, and is likely to be emitted from the first main surface 51. Further, when the height H2 is increased, the areas of the inclined surfaces 21 and 22 are increased. Therefore, more light is reflected toward the first main surface 51 by the inclined surfaces 21 and 22. For these reasons, by adjusting the angle θd and the height H2, more light can be emitted from the emission surface at the boundaries between the regions A1 and A2 and at the boundaries between the regions A2 and A3. Therefore, even when the shape of the second prism P2 is adjusted as shown in FIG. 13, a good luminance distribution can be obtained as in the case of adjusting the density.

According to the present embodiment described above, it is possible to obtain a good luminance distribution of the first main surface 51 by providing the second region A2 on the light guide plate LG. Moreover, the display quality of the display apparatus 1 can be improved by using the illuminating device 3 provided with such a light-guide plate LG.
In addition, various suitable effects described above can be obtained from this embodiment.

[Second Embodiment]
A second embodiment will be described. The configurations and effects not particularly mentioned are the same as those in FIG. 4 of the first embodiment.
FIG. 14 is a diagram illustrating a schematic configuration of the illumination device 3 according to the second embodiment. The illumination device 3 includes a first reflecting member 60 in addition to the first light source LS1, the second light source LS2, and the light guide plate LG. The first reflecting member 60 is a sheet material made of, for example, a metal material, and faces the second main surface 52 of the light guide plate LG. The first reflecting member 60 reflects the light leaked from the second main surface 52 of the light guide plate LG toward the light guide plate LG. In addition, the prism group in the 2nd main surface 52 is abbreviate | omitted.

  The first reflecting member 60 has a first portion 61 that faces the first region A1, a second portion 62 that faces the second region A2, and a third portion 63 that faces the third region A3. . In the present embodiment, each of the portions 61 to 63 extends on the same XY plane. The first portion 61 is not parallel to the first region A1. The second portion 62 is parallel to the second region A2. The third portion 63 is not parallel to the third region A3.

  FIG. 15 is a diagram illustrating a luminance distribution on the exit surface of the light guide plate LG in the configuration of the second embodiment. As can be seen from this luminance distribution, even when the first reflecting member 60 is provided, a good luminance distribution can be obtained as in the first embodiment. Further, when the first reflecting member 60 is provided, the light leaking from the second main surface 52 of the light guide plate LG can be reused, so that the luminance of the first main surface 51 can be increased as a whole.

[Third Embodiment]
A third embodiment will be described. About the structure and effect which are not mentioned especially, it is the same as that of each above-mentioned embodiment.
FIG. 16 is a diagram illustrating a schematic configuration of the illumination device 3 according to the third embodiment. This illuminating device 3 is provided with the 1st reflection member 60 similarly to 2nd Embodiment. In FIG. 16, the center C of the second region A2 in the first direction X is indicated by a one-dot chain line.

  The first reflecting member 60 has a first portion 61 and a second portion 62. The first portion 61 faces all of the first region A1 and half of the second region A2 closer to the first region A1 than the center C. The second portion 62 faces all of the third region A3 and half of the second region A2 closer to the third region A3 than the center C. The first portion 61 is parallel to the first region A1 and non-parallel to the second region A2. The second portion 62 is parallel to the third region A3 and non-parallel to the second region A2.

  FIG. 17 is a diagram illustrating the luminance distribution of the exit surface of the light guide plate LG in the configuration of the third embodiment. As in FIG. 15, a good luminance distribution can be obtained. Furthermore, the uniformity of the luminance distribution is increased compared to FIG. Therefore, it is preferable to arrange the first reflecting member 60 in parallel with the first region A1 and the third region A3 as in the present embodiment. As shown in FIG. 18, the second portion 62 may be formed in parallel with the second region A2.

[Fourth Embodiment]
A fourth embodiment will be described. About the structure and effect which are not mentioned especially, it is the same as that of each above-mentioned embodiment.
FIG. 19 is a diagram illustrating a schematic cross-section of a part of the light guide plate LG according to the fourth embodiment. Here, illustration of each prism P1, P2, P3 is abbreviate | omitted. As illustrated, in the light guide plate LG, the second main surface 52 is curved in the second region A2. If the second region A2 is configured in this way, the change of the second main surface 52 at the boundary between the regions A1 and A2 and the boundary between the regions A2 and A3 becomes smooth. Therefore, the change in the luminance distribution on the first main surface 51 also becomes smooth, and a local decrease in luminance can be prevented.

[Fifth Embodiment]
A fifth embodiment will be described. About the structure and effect which are not mentioned especially, it is the same as that of each above-mentioned embodiment.
FIG. 20 is a diagram illustrating a schematic cross-section of a part of the light guide plate LG according to the fifth embodiment. As illustrated, the light guide plate LG has a plurality of inclined surfaces A2a, A2b, A2c, and A2d in the second region A2. The inclined surfaces A2a, A2b, A2c, and A2d are arranged in this order from the boundary between the regions A1 and A2 toward the boundary between the regions A2 and A3. Each inclined surface A2a, A2b, A2c, A2d extends in parallel to the second direction Y, for example, in the illustrated cross-sectional shape.

The inclined surface A2a is inclined with respect to the XY plane at an angle different from that of the first region A1. The inclined surface A2b is inclined with respect to the XY plane at an angle different from that of the inclined surface A2a. The inclined surface A2c is inclined with respect to the XY plane at an angle different from that of the inclined surface A2b. The inclined surface A2d is inclined with respect to the XY plane at an angle different from that of the inclined surface A2c and the third region A3. Here, illustration of the second prism P2 is omitted, but the second prism P2 is formed on each of the inclined surfaces A2a, A2b, A2c, A2d.
20 shows an example in which the inclined surfaces A2a, A2b, A2c, and A2d are arranged in the first direction X, but a plurality of inclined surfaces arranged in the second direction Y may be formed in the second region A2. . Further, the number of inclined surfaces is not limited to four, but may be two or three, or may be five or more. Further, the second region A2 may include a surface parallel to the XY plane in addition to the inclined surface.

[Sixth Embodiment]
A sixth embodiment will be described. About the structure and effect which are not mentioned especially, it is the same as that of each above-mentioned embodiment.
FIG. 21 is a diagram illustrating a schematic cross-section of the illumination device 3 according to the sixth embodiment. The illumination device 3 includes a light guide plate LG, a first light source LS1, and a first reflecting member 60. The illumination device 3 does not include the second light source LS2. The second main surface 52 of the light guide plate LG has a first area A1 and a second area A2. Although not shown here, a plurality of first prisms P1 are formed in the first region A1, and a plurality of second prisms P2 are formed in the second region A2.

  The distance D1, which is the thickness of the light guide plate LG in the first region A1, increases from the first side surface 53 toward the boundary between the regions A1 and A2. In the example of FIG. 21, the distance D2, which is the thickness of the light guide plate LG in the second region A2, is constant. Similar to the first embodiment, the distance D2 is longer than the distance D1 at any position in the first region A1 (D2> D1).

  The first reflecting member 60 has a first portion 61 that faces the first region A1 and a second portion 62 that faces the second region A2. The first portion 61 is parallel to the first region A1, and the second portion 62 is parallel to the second region A2. As shown in FIG. 14, the first portion 61 and the first region A1 do not have to be parallel. Further, as shown in FIG. 16, the second portion 62 and the second region A2 may not be parallel.

  The lighting device 3 further includes a second reflecting member 70. The second reflecting member 70 is a sheet material made of, for example, a metal material, and faces the second side surface 54 of the light guide plate LG. The second reflecting member 70 is parallel to the second side surface 54.

  In FIG. 21, an example of an optical path of light emitted from the first light source LS1 is indicated by a broken line. The light emitted from the first light source LS1 enters the light guide plate LG from the first side surface 53. If the first area A1 is inclined as shown in FIG. 21, the light is irradiated to the first area A1 at a shallow angle, so that it is difficult to deviate from the total reflection conditions of the main surfaces 51 and 52. Therefore, the light propagates through the light guide plate LG while being reflected by the main surfaces 51 and 52 and reaches the second side surface 54. Although this light can be emitted from the second side surface 54, it is reflected by the second reflecting member 70 and enters the light guide plate LG again. The light that has returned to the light guide plate LG is reflected by the first prism P1 in the first area A1 and the second prism P2 in the second area A2, and deviates from the total reflection condition of the first main surface 51 from the first main surface 51. Exit.

  If the second region A <b> 2 is not provided, the luminance of the light reflected by the second reflecting member 70 is greatly reduced in the vicinity of the second side surface 54, and luminance unevenness may occur on the first main surface 51. On the other hand, when the second region A2 is provided, it is possible to suppress such luminance unevenness and improve the uniformity of the luminance distribution of the first main surface 51 as in the first embodiment.

[Seventh Embodiment]
A seventh embodiment will be described. About the structure and effect which are not mentioned especially, it is the same as that of each above-mentioned embodiment.
FIG. 22 is a schematic cross-sectional view of a part of the illumination device 3 according to the seventh embodiment. The illumination device 3 includes a light guide plate LG, a first light source LS1, and a first reflecting member 60.
In the present embodiment, the first side surface 53 includes an incident surface 53a and an end surface 53b. The incident surface 53a is inclined with respect to the first main surface 51 at an angle θin. The angle θin is an acute angle larger than the first angle θ1 that is an inclination angle of the first virtual line VL1 with respect to the first main surface 51 (θ1 <θin <90 °). The end surface 53b is a plane parallel to the YZ plane, for example.
In the example of FIG. 22, the incident surface 53a is a flat surface, but may be a curved surface. Further, the first side surface 53 may not have the end surface 53b.

  A first irradiation direction DL <b> 1, which is a direction in which the first light source LS <b> 1 emits light, is inclined with respect to the first main surface 51. That is, in the present embodiment, the first irradiation direction DL1 does not coincide with the first direction X in a cross-sectional view. However, in the plan view, the first irradiation direction DL1 and the first direction X coincide.

  The first light source LS1 overlaps the light guide plate LG in the thickness direction (third direction Z) of the light guide plate LG. In the example of FIG. 22, all of the first light sources LS1 overlap the light guide plate LG, but a part of the first light sources LS1 may overlap the light guide plate LG.

Even if it is the above structure, the effect similar to each above-mentioned embodiment can be acquired. Further, by arranging the first light source LS1 in the space below the light guide plate LG, it is possible to reduce the size of the illumination device 3 to the display device 1 and to narrow the frame area.
Note that the same configuration as the first side surface 53 and the first light source LS1 disclosed in the present embodiment can be applied to the second side surface 54 and the second light source LS2.

[Eighth Embodiment]
An eighth embodiment will be described. About the structure and effect which are not mentioned especially, it is the same as that of each above-mentioned embodiment.
FIG. 23 is a schematic cross-sectional view of a part of the illumination device 3 according to the eighth embodiment. The illumination device 3 includes a light guide plate LG, a first light source LS1, and a first reflecting member 60. The configurations of the above-described embodiments can be applied to the light guide plate LG and the first reflecting member 60.
The first light source LS1 overlaps the light guide plate LG in the thickness direction (third direction Z) of the light guide plate LG. In the example of FIG. 23, all of the first light sources LS1 overlap the light guide plate LG, but a part of the first light sources LS1 may overlap the light guide plate LG.

  Furthermore, the illumination device 3 includes a bent body 80 disposed in the vicinity of the first side surface 53 of the light guide plate LG. The bent body 80 shown in FIG. 23 is a prism having a triangular shape in the XZ cross section and extending in the second direction Y. Specifically, the bent body 80 has a first surface 81, a second surface 82, and a third surface 83. As an example, one bending body 80 may be provided for each of the plurality of first light sources LS1 arranged in the second direction Y as shown in FIG. One bending body 80 may be provided for each of the two or more first light sources LS1, or one bending body 80 may be provided for all the first light sources LS1.

  The first surface 81 has an incident area 81a and an emission area 81b. The incident area 81a faces the first light source LS1. The emission region 81b faces the first side surface 53 of the light guide plate LG. In the example of FIG. 23, the first surface 81 is parallel to the third direction Z, but may be inclined with respect to the third direction Z. The second surface 82 and the third surface 83 are inclined at a predetermined angle with respect to the first surface 81. The angle formed by the second surface 82 and the first surface 81 and the angle formed by the third surface 83 and the first surface 81 may be the same or different.

  The light emitted from the first light source LS1 enters the bent body 80 from the incident region 81a. The incident light is reflected by the second surface 82, further reflected by the third surface 83, and emitted from the emission region 81b. The emitted light is irradiated on the first side surface 53 of the light guide plate LG along the first irradiation direction DL1, and propagates through the light guide plate LG while being reflected by the main surfaces 51 and 52 of the light guide plate LG. Thus, in the present embodiment, the optical path of the light emitted from the first light source LS1 is bent in the first irradiation direction DL1 by the bent body 80 and enters the light guide plate LG.

  Even if it is the above structure, the effect similar to each above-mentioned embodiment can be acquired. Further, by using the bent body 80 as in the present embodiment, the degree of freedom of the arrangement position of the first light source LS1 is increased. Therefore, for example, by arranging the first light source LS1 in the space below the light guide plate LG as shown in FIG. 23, it is possible to reduce the size of the illumination device 3 to the display device 1 and to narrow the frame area.

23 shows an example in which the bending body 80 is a prism, the bending body 80 may be a reflecting member (mirror member) having a shape corresponding to the second surface 82 and the third surface 83.
The bent body 80 may be configured to reflect the light from the first light source LS1 only once and irradiate the first side surface 53, or to reflect the light from the first light source LS1 three times or more and irradiate the first side surface 53. It may be.
The first side surface 53 may include an incident surface 53a inclined with respect to the first main surface 51 as shown in FIG. In this case, the bending body 80 may be configured to bend the optical path of the light from the first light source LS1 so that the incident surface 53a is irradiated with light.
As described above, the configuration described in the vicinity of the first light source LS1 in the present embodiment can be similarly applied to the second light source LS2 side.

[Ninth Embodiment]
A ninth embodiment will be described. About the structure and effect which are not mentioned especially, it is the same as that of each above-mentioned embodiment.
FIG. 24 is a schematic cross-sectional view of a light guide plate LG according to the ninth embodiment. In the example of this figure, the thickness of the light guide plate LG gradually decreases from the center C in the first direction X toward the first side surface 53 and the second side surface 54. A plurality of prisms PA are provided on the second main surface 52 of the light guide plate LG. The light guide plate LG as a whole has a line-symmetric shape with respect to the center C, but is not limited to this example.

FIG. 25 is an enlarged cross-sectional view of a part of the light guide plate LG shown in FIG. In the example of this figure, eight prisms PA (PA1 to PA8) are provided from the first side surface 53 to the center C. However, the number of prisms PA provided from the first side surface 53 to the center C is not limited to eight.
The prism PA has a first inclined surface 13 and a second inclined surface 14 and has a triangular cross section. The angle formed by the first inclined surface 13 and the second main surface 52 is α. The angle formed by the second inclined surface 14 and the second main surface 52 is β. In the example of FIG. 25, no interval is provided between adjacent prisms PA. In such a case, for example, the surface connecting the tips of the valleys between the adjacent prisms PA can be defined as the second main surface 52. An interval may be provided between adjacent prisms PA.

In the example of FIG. 25, the prisms PA1 to PA4 have the same shape. The first inclined surfaces 13 of the prisms PA <b> 1 to PA <b> 4 are parallel to the first main surface 51.
On the other hand, the prisms PA5 to PA8 have different shapes from the prisms PA1 to PA4, and the prisms PA5 to PA8 also have different shapes. Specifically, the angle α of the prisms PA5 to PA8 is larger as the prism PA is closer to the center C. Thereby, the first inclined surfaces 13 of the prisms PA <b> 5 to PA <b> 8 are inclined at an angle that forms an acute angle with respect to the first main surface 51. Also, the heights of the prisms PA5 to PA8 are larger than the heights of the prisms PA1 to PA4, and the prism PA closer to the center C is larger. The angles β of the prisms PA1 to PA8 are the same, for example, but may be different.

Here, attention is focused on the first virtual line VL11 connecting the vertices of the prisms PA1 to PA4 and the second virtual line VL12 connecting the vertices of the prisms PA7 and PA8. The first imaginary line VL11 is inclined at the first angle θ11 with respect to the first major surface 51. The second imaginary line VL12 is inclined at the second angle θ12 with respect to the first major surface 51.
The prisms PA1 to PA4 are all the same height. On the other hand, because the angles α of the prisms PA7 and PA8 are different, the height of the prism PA8 is larger than the height of the prism PA7 in the example of FIG. Therefore, the second angle θ12 is larger than the first angle θ11 (θ12> θ11). From another viewpoint, the second virtual line VL12 in the region (second region) where the prisms PA7 and PA8 are provided is the first virtual line VL11 in the region (first region) where the prisms PA1 to PA4 are provided. It is inclined with respect to it.

Note that although the prisms PA7 and PA8 are focused here, even if the second virtual line VL12 is defined by focusing on the prisms PA4 and PA5, the prisms PA5 and PA6, and the prisms PA6 and PA7, the second virtual line is defined. VL12 is inclined with respect to the first virtual line VL11.
The same configuration as that of the prism PA provided between the first side surface 53 and the center C can be applied to the prism PA provided between the second side surface 54 and the center C.

  In the configuration of the present embodiment, the angle α is larger as the prism PA is closer to the center C, so that the light reflected by the first inclined surface 13 is easily emitted from the first main surface 51. Therefore, it is possible to suppress a reduction in luminance near the center C as shown in FIG.

  As described above, all lighting devices and display devices that can be implemented by a person skilled in the art based on the lighting device and display device described as the embodiment of the present invention as long as they include the gist of the present invention. It belongs to the scope of the invention.

  In the scope of the idea of the present invention, those skilled in the art can conceive various modifications, and these modifications are also considered to be within the scope of the present invention. For example, those in which the person skilled in the art has appropriately added, deleted, or changed the design of the above-described embodiments, or those in which processes have been added, omitted, or changed conditions are also included in the present invention. As long as the gist is provided, it is included in the scope of the present invention.

  Further, regarding other operational effects brought about by the aspects described in the respective embodiments, those that are apparent from the description of the present specification or that can be appropriately conceived by those skilled in the art are naturally understood to be brought about by the present invention. Is done.

  DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 2 ... Display panel, 3 ... Illuminating device, SUB1 ... 1st board | substrate, SUB2 ... 2nd board | substrate, LC ... Liquid crystal layer, DA ... Display area, LG ... Light guide plate, PS ... Prism sheet, DS ... Diffusion Sheet, 51 ... 1st main surface, 52 ... 2nd main surface, 53 ... 1st side surface, 54 ... 2nd side surface, A1-A3 ... 1st-3rd area | region, P1-P3 ... 1st-3rd prism, LS1 ... 1st light source, LS2 ... 2nd light source, VL1-VL3 ... 1st-3rd imaginary line, 60 ... 1st reflection member, 61-63 ... 1st-3rd part, 70 ... 2nd reflection member.

Claims (15)

A light guide plate having a first side surface, a first main surface, and a second main surface opposite to the first main surface;
A first light source that irradiates the first side surface of the light guide plate along a first irradiation direction;
A plurality of prisms provided on the second main surface,
The second main surface has a first region and a second region arranged in order along the first irradiation direction,
The plurality of prisms includes a plurality of first prisms in the first region and a plurality of second prisms in the second region,
In a cross-sectional view, a first imaginary line connecting vertices of the plurality of first prisms is inclined with respect to the first main surface,
In cross-sectional view, the distance between the second region and the first main surface is longer than the distance between the first region and the first main surface.
Lighting device. A second imaginary line connecting vertices of the plurality of second prisms is inclined with respect to the first imaginary line;
The lighting device according to claim 1. The second imaginary line is parallel to the first main surface,
The lighting device according to claim 2. The light guide plate has a second side opposite to the first side;
A second light source that emits light to the second side surface of the light guide plate;
The second main surface has the first region, the second region, and the third region arranged in order along the first irradiation direction,
The plurality of prisms includes a plurality of third prisms in the third region,
4. The cross-sectional view according to claim 1, wherein a distance between the second region and the first main surface is longer than a distance between the third region and the first main surface in a cross-sectional view. Lighting device. The first prism and the second prism have different shapes.
The lighting device according to any one of claims 1 to 4. The plurality of first prisms and the plurality of second prisms are arranged at different densities.
The lighting device according to any one of claims 1 to 4. In at least some of the plurality of second prisms, the density of the second prisms, the apex angle of the second prisms, or the height of the second prisms are different from each other.
The lighting device according to any one of claims 1 to 6. In at least a part of the plurality of second prisms, the density of the second prisms or the height of the second prisms is greater on the boundary side between the first region and the second region.
The lighting device according to claim 7. In at least some of the plurality of second prisms, the apex angle of the second prism is smaller on the boundary side between the first region and the second region,
The lighting device according to claim 7 or 8. The first light source is a laser light source that emits laser light.
The lighting device according to any one of claims 1 to 9. A first reflecting member facing the second main surface;
The first reflecting member includes a first portion facing the first region, and a second portion facing the second region,
The first portion is parallel to the first region;
The lighting device according to any one of claims 1 to 10. The light guide plate has a second side surface facing the first side surface,
A second reflecting member facing the second side surface and reflecting the light of the first light source emitted from the second side surface toward the second side surface;
The lighting device according to any one of claims 1 to 3. The first irradiation direction is inclined with respect to the first main surface;
The first side surface has an incident surface on which light from the first light source is incident,
The incident surface is inclined with respect to the first main surface at an acute angle larger than an angle with which the first imaginary line is inclined with respect to the first main surface.
The lighting device according to any one of claims 1 to 12. In the thickness direction of the light guide plate, at least a part of the first light source overlaps the light guide plate.
The lighting device according to claim 13. The lighting device according to any one of claims 1 to 14,
A display panel that faces the first main surface of the light guide plate of the lighting device and displays an image using light emitted from the first main surface;
A display device comprising:

Images