In-vehicle display device

Abstract

The present invention improves the brightness unevenness near the light source. Zenka Efficient light guiding Board Used In-vehicle display device provide 。 [Solution] The in-vehicle display device includes a light emitter, a light guide plate 1, and a liquid crystal panel. The light guide plate 1 is luminous body A light incident surface 13 through which light enters and a light exit surface 14 through which light exits. , out It has a light surface 14 and an opposing reflective surface 15. , anti Shooting surface 15 is against The reflecting surface prism 16 And, against Reflection surface prism 16 Is in Extends in a direction perpendicular to the light direction Insert Light Direction 2nd Arranged at 1 pitch P1 The 1 prism element 11e and extending in the light incident direction Insert Orthogonal to the light direction 2nd Arranged at 2 pitch P2 The 2 prism elements 12e and , th Peak height H1 of prism element 11e Is in Increases from the light surface 13 in the direction of light incidence The liquid crystal panel has a light emitter arranged opposite the light incident surface 13, and displays the image using the light from the light guide plate.

Description

[Technical Field]

[0001] The present invention provides In-vehicle display device It is related to. [Background technology]

[0002] Generally, a transmission type display device such as a liquid crystal display device uses a surface illumination device called a backlight device that illuminates the back of the liquid crystal display unit. Backlight devices are broadly divided into direct-type and edge-light type, with edge-light type being the most commonly used type for thin backlight devices. Edge-lit backlight devices use a light guide plate, and LEDs (light-emitting diodes) serving as light sources are arranged along one edge of the plate-shaped light guide plate. The light guide plate is made of a material such as a translucent resin, and light entering the light guide plate from the light source propagates through the light guide plate. The light guide plate has a mechanism for reflecting and scattering the incident light, and the light that enters the light guide plate is emitted toward the liquid crystal display device.

[0003] Backlight devices often use a light guide plate with convex or concave dots. The light diffused by the dots on the light guide plate is then focused onto the LCD display by a prism sheet. The dots can be made more dense as they move away from the light input side, allowing for adjustment of brightness uniformity. However, since the dots do not have a light alignment function, it is difficult to improve the front brightness of the liquid crystal display. To improve the front brightness, a light guide plate provided with prisms having alignment properties is known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-81094 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-38748 [Patent Document 3] Japanese Patent Application Publication No. 2020-119678 [Patent Document 4] Japanese Patent Application Publication No. 2022-129946 Summary of the Invention [Problem to be solved by the invention]

[0005] Light guide plates using prisms can achieve high directivity and high brightness, but because they use a light collection process that does not involve diffusion, it is difficult to improve brightness unevenness around the light source (LED). In recent years, in order to meet the ever-increasing demand for higher image quality in liquid crystal display devices, there has been a demand for light guide plates that can further improve brightness unevenness.

[0006] The present invention provides a light guide that can improve brightness unevenness near a light source. Board Used In-vehicle display device The purpose is to provide the following. [Means for solving the problem]

[0007] According to the present invention In-vehicle display device teeth, The display device includes a light emitter, a light guide plate, and a liquid crystal panel, The light guide plate is the light emitter a light-entering surface 13 through which light from the outside enters, a light-exiting surface 14 through which light exits, and a reflecting surface 15 opposed to the light-exiting surface 14, The reflecting surface 15 has a reflecting surface prism 16, The reflecting surface prism 16 is a plurality of first prism elements 11e extending in a direction perpendicular to the light incident direction and arranged at a first pitch P1 along the light incident direction; a plurality of second prism elements 12e extending in the light incident direction and arranged at a second pitch P2 along a direction perpendicular to the light incident direction; The peak height H1 of the plurality of first prism elements 11e tends to increase along the light incident direction from the light incident surface 13. It is given as the sum of a typical value and a variation that randomly fluctuates within a predetermined range, The light emitter is disposed opposite the light incident surface, The liquid crystal panel displays information using the light from the light guide plate. It is characterized by:

[0008] Such a configuration In-vehicle display device By doing so, light entering from the light entrance surface propagates inside the light guide plate, is reflected to the light exit surface by the reflecting surface prisms provided on the reflecting surface, and is emitted from the light exit surface. The reflecting surface prisms are provided with first and second prism elements extending in directions perpendicular to each other, and the density of the first prism elements tends to increase along the direction of light entrance, making it possible to increase brightness and improve brightness unevenness near the light source.

[0009] According to the present invention In-vehicle display device teeth, The display device includes a light emitter, a light guide plate, and a liquid crystal panel, The light guide plate is the light emitter a light-entering surface 13 through which light from the outside enters, a light-exiting surface 14 through which light exits, and a reflecting surface 15 opposed to the light-exiting surface 14, The reflecting surface 15 has a reflecting surface prism 16, The reflecting surface prism 16 is a plurality of first prism elements 11e extending in a direction perpendicular to the light incident direction and arranged at a first pitch P1 along the light incident direction; a plurality of second prism elements 12e extending in the light incident direction and arranged at a second pitch P2 along a direction perpendicular to the light incident direction; the peak height of the first prism element is given by the sum of a typical value that tends to increase along the light incident direction from the light incident surface and a variation that randomly fluctuates within a predetermined range, The peak heights of the second prism elements tend to decrease along the light incident direction from the light incident surface. death, The light emitter is disposed opposite the light incident surface, The liquid crystal panel displays information using the light from the light guide plate. It is characterized by:

[0010] Such a configuration In-vehicle display deviceBy doing so, the peak height of the second prism element decreases from the light incident surface along the light incident direction, thereby increasing the area occupied by the first prism and improving the brightness uniformity along the light incident direction.

[0011] In addition, the present invention In an in-vehicle display device, The peak height H1 of the plurality of first prism elements 11e is a typical value that tends to increase along the light incident direction from the light incident surface; Random fluctuation within a given range is given by the sum of the change in .

[0012] Such a configuration In-vehicle display device By doing so, the density of the first prism elements changes randomly, making it possible to improve localized brightness unevenness.

[0013] In addition, the present invention In-vehicle display device In the above configuration, the first prism element has a first inclined surface and a second inclined surface; The first inclined surface is located closer to the light incident surface than the second inclined surface. the first inclined surface is inclined at a first inclination angle with respect to a direction parallel to the light incident direction, the second inclined surface is inclined at a second inclination angle with respect to a direction parallel to the light incident direction, The first inclined surface and the second inclined surface may contact each other at a predetermined contact angle.

[0014] In addition, the present invention In-vehicle display device In the above configuration, The second slope may have a curved surface.

[0015] In addition, the present invention In-vehicle display device In the above configuration, The contact angle may be in the range of 2 to 9°.

[0016] Such a configuration In-vehicle display device This makes it possible to improve brightness unevenness and flexibly respond to various required uses and specifications.

[0017] In addition, the present invention In-vehicle display device In the above configuration, The first tilt angle θ1 may be greater than the second tilt angle θ2.

[0018] By using the first prism element with such a configuration, it is possible to set a wide angular range over which the emitted light spreads.

[0019] In addition, the present invention In-vehicle display device In the above configuration, The second tilt angle θ2 may be greater than the first tilt angle θ1.

[0020] By using the first prism element with such a configuration, it is possible to increase the angle of the emitted light and narrow the angular range over which the light spreads.

[0021] In addition, the present invention In-vehicle display device In the above configuration, The first pitch P1 may vary randomly within a predetermined range.

[0022] By using the first prism element with such a configuration, localized brightness unevenness can be improved.

[0023] According to the present invention In-vehicle display device teeth, before a reflection sheet 3 disposed opposite the reflection surface 15; a first prism sheet (20) disposed opposite the light exit surface (14); The first prism sheet 20 has first prism sheet elements 20e that protrude from the light exit surface 14 and extend in a direction perpendicular to the light incident direction. It is characterized by:

[0024] Such a configuration In-vehicle display device This makes it possible to improve the brightness unevenness near the light source. In-vehicle display device can be obtained.

[0025] According to the present invention In-vehicle display device teeth, before a reflection sheet 3 disposed opposite the reflection surface 15; a first prism sheet 20 disposed opposite the light exit surface 14; a second prism sheet 30 disposed opposite the first prism sheet 20; The first prism sheet 20 has a first prism sheet element 20e that protrudes in the light emission direction and extends in a direction perpendicular to the light incidence direction, The second prism sheet 30 has second prism sheet elements 30e that protrude in the light emission direction and extend in a direction perpendicular to the light incidence direction, The first prism sheet 20 is located between the second prism sheet 30 and the light exit surface 14 .

[0026] Such a configuration In-vehicle display device This makes it possible to improve the brightness unevenness near the light source. In-vehicle display device can be obtained. [Effects of the Invention]

[0027] According to the present invention, it is possible to improve the brightness unevenness in the vicinity of the light source. Board Used In-vehicle display device can be provided. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1(A) is a perspective view showing a schematic view of a light guide plate 1 of embodiment 1, FIG. 1(B) is a partial cross-sectional view in the AA direction showing the shape of a first prism 11, and FIG. 1(C) is a partial cross-sectional view in the BB direction showing the shape of a second prism 12. [Figure 2] Figure 2(A) is a perspective view showing a schematic representation of only the first prism 11 on the reflecting surface 15 of the light guide plate 1, Figure 2(B) is a perspective view showing a schematic representation of only the second prism 12 on the reflecting surface 15 of the light guide plate 1, and Figure 2(C) shows the distance dependence in the Y-axis direction of the peak height H1 of each first prism element 11e. [Figure 3]Figure 3(A) is a plan view schematically showing a part of the reflecting surface prism 16 as seen from the reflecting surface 15 side of the light guide plate 1, Figure 3(B) is a cross section of the light guide plate 1 taken along line AA, Figure 3(C) is a cross section of the light guide plate 1 taken along line BB, and Figure 3(D) is a cross section of the light guide plate 1 taken along line CC. [Figure 4] Figure 4(A) is a diagram for explaining the geometric configuration of the cross section of the first prism element 11e, Figure 4(B) is a diagram for explaining the geometric configuration of the cross section of the first comparative prism element 91e of Comparative Example 1, and Figure 4(C) is a diagram showing the effect of the second inclined surface Sb11 having a curved surface. [Figure 5] FIG. 5 shows a comparison of the evaluation results of the uneven image, normal luminance, and light distribution characteristics of the light emitted from the light output surface 14 of the light guide plate 1 of Example 1 and Comparative Example 1. [Figure 6] FIG. 6(A) shows a schematic cross-sectional shape of the first prism 11 of the light guide plate 1 of embodiment 2, FIG. 6(B) is a diagram for explaining the cross-sectional geometric configuration of the first prism element 11e, and FIG. 6(C) is a diagram comparing the optical characteristics of the first prism 11 of embodiment 1 and embodiment 2. [Figure 7] FIG. 7(A) is a graph showing the Y-coordinate dependency of the Michelson contrast of the LED image when Example 2 and Comparative Examples 2 and 3 are used, and FIG. 7(B) shows the LED image. [Figure 8] 8(A) and 8(B) are schematic diagrams showing a part of a cross section of a first prism 11 of a light guide plate 1 according to Modification 1 and Modification 2 of Embodiment 2, respectively. [Figure 9] FIG. 9 illustrates the dependence of optical properties on the contact angle α, where FIG. 9(A) shows the dependence of peak angle on the contact angle α, FIG. 9(B) shows the dependence of peak luminance and luminance loss on the contact angle α, and FIG. 9(C) shows the conditions and results used in the optical simulation. [Figure 10]10(A) is a plan view schematically showing the configuration of the light guide plate 1 of embodiment 3, FIG. 10(B) is a cross-sectional view along line AA, FIG. 10(C) is a cross-sectional view along line BB, FIG. 10(D) is a graph schematically showing the dependence of peak height H1 and peak height H2 in the Y-axis direction when the Typ value, which is the central value of the peak height H1 of the first prism 11, is changed, and FIG. 10(E) is a graph schematically showing the dependence of peak height H1 and peak height H2 in the Y-axis direction when the Typ value, which is the central value of the peak height H1 of the first prism 11, is constant. [Figure 11] 11A and 11B are cross-sectional views schematically showing configuration example 1 and configuration example 2 of a backlight device 100 to which the light guide plate 1 is applied. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are not intended to limit the scope of the present invention. Furthermore, the same or similar components will be designated by the same reference numerals, and their description may be omitted.

[0030] Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "horizontal," "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are not to be construed as being bound by strict meanings, but rather as including a range within which similar functions can be expected.

[0031] (Embodiment 1) The light guide plate 1 of the first embodiment will be described below. FIG. 1(A) is a perspective view showing a schematic view of a light guide plate 1 of embodiment 1, FIG. 1(B) is a partial cross-sectional view in the AA direction showing the shape of a first prism 11, and FIG. 1(C) is a partial cross-sectional view in the BB direction showing the shape of a second prism 12. Figure 2(A) is a perspective view showing a schematic representation of only the first prism 11 on the reflecting surface 15 of the light guide plate 1, Figure 2(B) is a perspective view showing a schematic representation of only the second prism 12 on the reflecting surface 15 of the light guide plate 1, and Figure 2(C) shows the distance dependence in the Y-axis direction of the peak height H1 of each first prism element 11e. The Z-axis direction is the thickness direction of the light guide plate 1, and is the direction from the light guide plate 1 toward the liquid crystal panel (not shown). The Y-axis direction is the direction from the light emitter 2 (LED) toward the light incident surface 13, and is the light incident direction in which the emitted light enters the light guide plate 1 and travels (straight) through the light guide plate 1. The X-axis direction is perpendicular to the Z-axis and Y-axis directions, and is parallel to the light incident surface 13.

[0032] As shown in FIG. 1(A), a light emitter 2 (specifically, an LED) serving as a light source is disposed opposite a light entrance surface 13, which is one of the peripheral end surfaces of a rectangular plate-shaped light guide plate 1. Light emitted from the light emitter 2 is incident on the light entrance surface 13 of the light guide plate 1 parallel to the Y-axis direction in FIG. 1(A). A liquid crystal panel (not shown) is disposed opposite a light exit surface 14, which is one of the plate surfaces of the light guide plate 1 (in the +Z-axis direction in FIG. 1(A)). The multiple light emitters 2 are disposed side by side in the X-axis direction. Furthermore, a reflective sheet 3 is disposed on the reflective surface 15 side of the light guide plate 1 (in the −Z axis direction in FIG. 1(A)). The light emitters 2 can be appropriately selected depending on the application and purpose, and are fixed opposite the light incident surface 13 by a known method, with a plurality of light emitters 2 arranged in the X-axis direction.

[0033] The light guide plate 1 further has an opposing surface 17 that faces the light incident surface 13 in the Y-axis direction, and side end surfaces 18 that face each other in the X-axis direction. The light that enters the light guide plate 1 from the light incident surface 13 is reflected by the reflective sheet 3 and by each end surface of the light guide plate 1 (the reflective surface 15, the opposing surface 17, and the side end surfaces 18), and is thereby efficiently propagated within the light guide plate 1.

[0034] 1(A), (B), and (C), the light guide plate 1 has a rectangular main body 10 having a certain thickness, and a reflecting surface prism 16 provided on a reflecting surface 15 of the main body 10. The reflecting surface prism 16 is composed of a first prism 11 and a second prism 12. The first prism 11 and the second prism 12 are each composed of a plurality of first prism elements 11e and second prism elements 12e that protrude from the main body 10 in the -Z axis direction (i.e., the direction from the light output surface 14 toward the reflecting surface 15). The light guide plate 1 is made of a known material, for example, a synthetic resin material (such as polycarbonate resin or acrylic resin) that has a refractive index that is sufficiently higher than that of air, is nearly transparent, and has excellent light transmissivity. The lengths of the light guide plate 1 in the X-axis direction and the Y-axis direction are, for example, about 200 to 300 mm, but are not limited to this.

[0035] The thickness of the light guide plate 1 is set according to the thickness of the light emitter 2 (specifically, the LED). If the thickness is thinner than the thickness of the light emitter 2, the loss of incident light increases, so it is preferable that the thickness is equal to or greater than the thickness of the light emitter 2. For example, in the case of a mobile terminal such as a notebook PC (for example, the typical size of a mobile PC is 13 to 17 inches), a thin LCD panel is required. The thickness of the LED, which is the light emitter 2, is generally 0.4 to 0.6 mm, and the thickness of the light guide plate 1 can also be preferably set to 0.4 to 0.6 mm. Note that the typical size of a mobile PC is 13 to 17 inches. In the case of an in-vehicle liquid crystal panel, a high-brightness LED with a thickness of 1 to 2 mm is required as the light emitter 2. Therefore, the thickness of the light guide plate 1 can be preferably set to 1.5 to 3 mm. Furthermore, displays have become larger in recent years, and liquid crystal panels of 10 to 17 inches are sometimes used, or in the case of pillar-to-pillar displays where the CID and passenger display are integrated, 20 inches or more.

[0036] As shown in FIGS. 1A and 2A, the first prism elements 11e extend in a direction perpendicular to the light incident direction (parallel to the X-axis direction). The first prism elements 11e are arranged in the Y-axis direction. Specifically, as shown in FIG. 2A, the first prism elements 11e are arranged in multiple rows of first prism elements 11e1, 11e2, 11e3, ... 11e in a direction parallel to the light incident direction (parallel to the Y-axis direction). L are arranged in parallel. As shown in Figures 1(A) and 2(B), the second prism elements 12e extend in a direction parallel to the light incident direction. The second prism elements 12e are arranged in a direction perpendicular to the light incident direction. Specifically, as shown in Figure 2(B), the second prism elements 12e are arranged in a plurality of rows of second prism elements 12e1, 12e2, 12e3, ... 12e in a direction perpendicular to the light incident direction. N are arranged in parallel.

[0037] The first prism element 11e and the second prism element 12e are arranged so as to intersect perpendicularly and are superimposed on each other. As will be described later, the height at the position of the reflecting surface prism 16 (i.e., position coordinates (x, y)), i.e., the distance from the main body 10, is configured to be the greater of the height of the first prism 11 and the height of the second prism 12.

[0038] 1(B), each of the first prism elements 11e has a first inclined surface Sa11 and a second inclined surface Sb11. The first inclined surface Sa11 is located closer to the light incident surface 13 than the second inclined surface Sb11. A first ridge line RL11, which is the boundary line where the first inclined surface Sa11 and the second inclined surface Sb11 meet, extends linearly parallel to the X-axis. The peak height H1 of the first prism element 11e is the distance from the first ridge line RL11 to the main body 10, and is the maximum value of the distance between the first prism element 11e and the main body 10 (i.e., the peak value of the cross section in the Y-axis direction). The first inclined surface Sa11 is composed of a flat surface having an inclination angle θ1 (referred to as the first inclination angle) with respect to the Y-axis direction (i.e., the surface of the main body 10 in the -Z-axis direction), and the second inclined surface Sb11 is composed of a curved surface having a radius of curvature R1 (e.g., a curved surface with an arc-shaped cross section). The inclination angle θ1 is preferably in the range of 30° to 80°. If the inclination angle θ1 is smaller than 30°, the probability that the propagating light will hit the first inclined surface Sa11 increases, causing an angle change away from the critical angle, increasing the risk that not all light will be emitted and brightness will decrease. The first pitch P1, which is the peak-to-peak distance between adjacent first prism elements 11e, i.e., the distance in the Y-axis direction between each first ridge line RL11, is constant. The first pitch P1 is determined depending on the pixel pitch of the liquid crystal panel, and is preferably set to a value that does not cause moire. On the other hand, the peak height H1 of each first prism 11 varies depending on the position in the Y-axis direction from the light incident surface 13, that is, the distance y, as will be described later (see FIG. 3).

[0039] 1(C), each of the second prism elements 12e has a third inclined surface Sa12 and a fourth inclined surface Sb12. The third inclined surface Sa12 and the fourth inclined surface Sb12 are formed by flat surfaces having an inclination angle β with respect to the X-axis direction. The third inclined surface Sa12 and the fourth inclined surface Sb12 meet at the second ridge line RL12 and form an isosceles triangle in a cross section taken along the X axis. Preferably, the third inclined surface Sa12 and the fourth inclined surface Sb12 may be connected so that their tips form a gently curved surface with a radius of curvature R2. The cross section of the second prism element 12e may also be arc-shaped, i.e., the third inclined surface Sa12 and the fourth inclined surface Sb12 may be shaped to form an arc. The peak height H2 of second prism element 12e from main body 10 (the distance from the surface of main body 10 to second ridge line RL12) is constant. Note that peak height H2 is the maximum distance from main body 10 to second prism element 12e. The peak-to-peak distance of the second prism elements 12e, that is, the second pitch P2 which is the distance in the X-axis direction between the peak positions of adjacent second prism elements 12e, is constant.

[0040] 2(C) shows the distance dependency in the Y-axis direction of the peak height H1 of each first prism element 11e. The vertical axis represents the peak height H1. The horizontal axis represents the distance in the Y-axis direction from the light incident surface 13, specifically the peak position of the second prism element 12e, i.e., the position of the first ridge line RL11. In Figure 2(C), Typ, shown by the solid line, indicates the behavior of the typical value of H1. The peak height H1 varies within a range of +10% and -10% of the Typ value, with the Typ value at the center. The amount of variation in peak height H1 is set to a random value within the range of +10% and -10%. If peak height H1 is treated as a function of the length y in the Y-axis direction, it is expressed as follows: H1(y)=Typ(y)+Δ (Equation 1) Here, y is a discrete value determined by the first pitch P1 of the first prism elements 11e. Typ(y) is a function that monotonically increases with y. As shown in Fig. 2(C), Typ(y) may have a constant region near the light emitter 2, but is set so that the peak height H1 of the first prism element 11e tends to increase in the direction away from the light incident surface 13 and toward the opposing surface 17. The amount of change Δ may be set by, for example, using a computer random function to set a random value f between -0.1 and +0.1, and multiplying this by the Typ value, i.e., Δ=f*Typ. Note that, for example, the Typ value closest to the light incident surface 13 (i.e., Typ(y=0)) can be used as Typ. Because the amount of change Δ is set using the random value f, it is generated with approximately equal probability without bias within the range of +10% and -10% of Typ.

[0041] The peak heights H1 and H2 are preferably 0.002 mm or greater. If they are smaller than this, mold processing and injection molding become difficult, and there is a risk of deformation of the prism shape (such as rounded tips). The peak heights H1 and H2 are preferably about 0.05 mm, a range within which processing is relatively easy. The shorter the first pitch P1 and second pitch P2, the narrower the pitch of the moiré fringes, and the less noticeable they tend to be, so shorter pitches are preferable. Considering the above-mentioned processability, the first pitch P1 and second pitch P2 are preferably about 0.04 to 0.15 mm. The second tilt angle θ2 of the first prism 11 can be appropriately set depending on the required output angle. The tilt angle β of the second prism 12 is preferably in the range of 15 to 40°. If the tilt angle β is 40° or more, the light collection becomes too strong, making it difficult to eliminate LED unevenness on the light entrance side. If the tilt angle β is 15° or less, the light becomes nearly flat, and the diffusion function becomes poor. Furthermore, the width of second prism 12 (corresponding to the occupied area, which is the area of ​​the region functioning as second prism 12) is set appropriately within a range that achieves uniformity in brightness. As the width of second prism 12 increases, the area of ​​the region functioning as first prism 11 decreases, and therefore the amount of emitted light decreases. Conversely, as the width of second prism 12 decreases, the amount of emitted light increases. Therefore, by adjusting these parameters, it is possible to achieve the amount of emitted light required for light guide plate 1.

[0042] Fig. 3(A) is a plan view schematically showing a part of the reflecting surface prism 16 as seen from the reflecting surface 15 side of the light guide plate 1, Fig. 3(B) is a cross section of the light guide plate 1 taken along line AA, Fig. 3(C) is a cross section of the light guide plate 1 taken along line BB, and Fig. 3(D) is a cross section of the light guide plate 1 taken along line CC. The lines AA and BB each correspond to the position of the first ridge line RL11. For ease of understanding, the peak height H1 of each first prism element 11e is exaggerated in Fig. 3. In Figs. 3(B), (C), and (D), the dotted lines indicate part of the shape of second prism element 12e.

[0043] As described above, the peak height H1 of each first prism element 11e varies randomly, so the peak height H1 of the first ridge line RL11 shown in Figure 3(B) is different from the peak height H1 of the first ridge line RL11 shown in Figure 3(C). Therefore, the reflecting surface prism 16 is configured so that a first prism 11 having a plurality of first prism elements 11e with different peak heights H1 intersects with a second prism 12 having a plurality of second prism elements 12e. The height hr of the reflecting surface prism 16 at any position on the reflecting surface 15 is a function of the position coordinates (x, y) of the reflecting surface 15. For example, the origin of the x coordinate can be set at the end of the reflecting surface 15 in the X-axis direction, and the origin of the y coordinate can be set at the end of the reflecting surface 15 in the Y-axis direction, which is the position of the end of the light incident surface 13.

[0044] The height of the first prism 11 at the position coordinates (x, y) where the first prism elements 11e are arranged in parallel in the Y-axis direction at a first pitch P1 is defined as h1(x, y). Because the first prism elements 11e have a constant shape in the X-axis direction, h1(x, y) is a function of y only and can be expressed as h1(y). The height of the second prism 12 at the position coordinates (x, y) where the second prism elements 12e are arranged in parallel in the X-axis direction at a second pitch P2 is defined as h2(x, y). Because the second prism elements 12e have a constant shape in the Y-axis direction, h2(x, y) is a function of x only and can be expressed as h2(x).

[0045] The height hr of the reflecting surface prism 16 at the position coordinates (x, y) is set to be the greater of the height h1 of the first prism 11 and the height h2 of the second prism 12. That is, when [height h1 of the first prism 11]≧[height h2 of the second prism 12], [height hr of the reflecting surface prism 16]=[height h1 of the first prism 11], and when [height h1 of the first prism 11]<[height h2 of the second prism 12], [height hr of the reflecting surface prism 16]=[height h2 of the second prism 12]. That is, the height hr of the reflecting surface prism 16 at the position coordinates is set to the higher value between the height h1 of the first prism 11 and the height h2 of the second prism 12. Therefore, hr(x, y)=max[h1(y), h2(x)].

[0046] 3A, each of the first prism elements 11e and the first ridge line RL11 extends intermittently in the X-axis direction. That is, in the reflecting surface prism 16, there are portions that function as first prisms 11 and portions that function as second prisms 12, and these portions appear alternately in the X-axis direction. In addition, in Figure 3(A), since the peak height H2 of the second prism element 12e is set higher than the peak height H1 of the first prism element 11e, it can be seen that the second ridge line RL12 of the second prism element 12e extends continuously in the Y-axis direction.

[0047] FIG. 3 shows an example in which the height h1 of the first prism 11 in the cross section taken along line AA is greater than the height h1 of the first prism 11 in the cross section taken along line BB. As shown in FIG. 3(B), the first ridge line RL11 of the first prism element 11e is located at a peak height H1, and the exposed width of the first ridge line RL11 is Wa. As shown in FIG. 3(C), the first ridge line RL11' of the adjacent first prism element 11e' is at a position of peak height H1', ​​and the exposed width of the first ridge line RL11 is Wa'. Since second prism element 12e has third inclined surface Sa12 and fourth inclined surface Sb12, when peak height H1 is greater than peak height H1', ​​width Wa is greater than width Wa'.

[0048] 3(C), the cross section along line CC is located away from the first ridge line RL11' of the first prism element 11e', and the height h1 of the first prism element 11e' at this position is smaller than the peak height H1'. Therefore, the width Wb of the exposed surface of the first prism element 11e' is smaller than the width Wa'.

[0049] In this way, the height h1 of the first prism elements 11e changes in the Y-axis direction, and therefore the exposed width of the first prism elements 11e also changes. This is why Figure 3(A) shows a shape in which the width is narrowest at the boundary between adjacent first prism elements 11e.

[0050] The first region a1 where the surface of the first prism element 11e is exposed functions as the first prism 11, and the other second region a2 where the surface of the second prism element 12e is exposed functions as the second prism 12.

[0051] As described above, by combining the first prism element 11e with the second prism element 12e, the exposed width of the first prism element 11e varies depending on the height h1 of the first prism element 11e. Because the typical value of peak height H1 is larger on the opposing surface 17 side than on the light incident surface 13 side, the area of ​​the first region a1 that functions as the first prism 11 also becomes larger. Therefore, the first region a1 becomes denser (i.e., the prism concentration increases) as it moves away from the light incident surface 13 and toward the opposing surface 17 side, which has the effect of improving reflectance. As a result, the uniformity of brightness in the light incident direction improves, and brightness unevenness near the light incident surface 13 is alleviated. Furthermore, the peak height H1 of the first prism element 11e varies randomly within a predetermined range, and the width of the first region a1 also varies randomly. That is, the density of the first prism 11 varies randomly locally. As a result, it is possible to improve local brightness unevenness.

[0052] The effect of the curved second inclined surface Sb11 will be described below with reference to FIG. Figure 4(A) is a diagram for explaining the geometric configuration of the cross section of the first prism element 11e, Figure 4(B) is a diagram for explaining the geometric configuration of the cross section of the first comparative prism element 91e of Comparative Example 1, and Figure 4(C) is a diagram showing the effect of the second inclined surface Sb11 having a curved surface. For ease of understanding, FIGS. 4A and 4B show only the shapes of the first prism element 11e and the first comparative prism element 91e.

[0053] In the cross section shown in FIG. 4A, the vertex of the first prism element 11e corresponding to the position of the first ridge line RL11 is defined as point P, and the point corresponding to the position where the second slope Sb11 contacts the main body 10 is defined as point Q. The line connecting points P and Q is defined as line Ln1 (shown by a dashed line in the figure), and the tangent line of the second slope Sb11 at point P is defined as line Ln2 (shown by a chain line in the figure). The inclination angle θ2 (referred to as the second inclination angle) of the curved second slope Sb11 is defined as the angle between the Y-axis direction and line Ln1, and the contact angle α is defined as the angle between line Ln1 and line Ln2. That is, the contact angle α is defined as the angle at which the second slope Sb11 contacts the first slope Sa11. To achieve the effect of the second slope Sb11, the contact angle α is set to 2° or more. The contact angle α is preferably set in the range of 2 to 9°. The inclination angle θ2 of the second inclined surface Sb11 is set to be smaller than the inclination angle θ1 of the first inclined surface Sa11 (θ2<θ1).

[0054] The first comparative prism element 91e has a fifth inclined surface Sa91 on the light incident surface 13 side and a sixth inclined surface Sb91 on the opposing surface 17 side. The fifth inclined surface Sa91 and the sixth inclined surface Sb91 are configured as flat surfaces having inclination angles γ1 and γ2 with respect to the Y-axis direction.

[0055] Fig. 4(C) shows the results of calculating the Michelson contrast Cm to evaluate brightness unevenness. In Fig. 4(C), the dotted line shows the results of Example 1, and the solid line shows the results of Comparative Example 1. The dashed-dotted line shows the reference value (0.03). As Example 1, a sample was used in which the inclination angle θ1 of the first inclined surface Sa11 was 35°, the contact angle α of the second inclined surface Sb11 was 3.5°, and the radius of curvature R1 was 0.9 mm, and as Comparative Example 1, a sample was used in which the inclination angle γ1 of the fifth inclined surface Sa91 was 35°, and the inclination angle γ2 of the sixth inclined surface Sb91 was 5°. The Michelson contrast Cm was calculated by Cm=(Lmax-Lmin) / (Lmax+Lmin), where Lmax is the maximum value of luminance and Lmin is the minimum value of luminance. As is clear from FIG. 4(C), Example 1 has a lower Michelson contrast value than Comparative Example 1, and it can be seen that the luminance unevenness in the vicinity of the light entrance surface 13 in particular is greatly improved.

[0056] Fig. 5 compares the evaluation results of the unevenness image, normal luminance, and light distribution characteristics of light emitted from the light output surface 14 of the light guide plate 1 of Example 1 and Comparative Example 1. From the unevenness image in Fig. 5, it can be seen that the unevenness of Example 1 is improved compared to Comparative Example 1. The evaluation results shown in Fig. 5 were obtained using the backlight device 100 shown in Fig. 11(A). Furthermore, the distance that satisfies the standard of less than 0.03 at which unevenness becomes invisible is 9.9 mm in Comparative Example 1, but 5.5 mm in Example 1, which confirms that the area where unevenness occurs is shortened and optical performance is improved. It was confirmed that the brightness and light distribution characteristics of Example 1 and Comparative Example 1 were equivalent.

[0057] <Embodiment 2> The light guide plate 1 of the second embodiment will be described below with reference to FIGS. FIG. 6(A) shows a schematic cross-sectional shape of the first prism 11 of the light guide plate 1 of embodiment 2, FIG. 6(B) is a diagram for explaining the cross-sectional geometric configuration of the first prism element 11e, and FIG. 6(C) is a diagram comparing the optical characteristics of the first prism 11 of embodiment 1 and embodiment 2.

[0058] In a backlight device 100 incorporating a light guide plate 1, it may be required to improve the brightness in a specific direction depending on the application. For this reason, it may be required to adjust the peak angle of light emitted from the light-emitting surface 14 of the light guide plate 1. The light guide plate 1 of the first embodiment can emit light at an optimal incident angle for a backlight that uses a prism sheet. The light guide plate 1 of the second embodiment can increase the angle of the emitted light. For example, the light guide plate 1 of embodiment 1 has a peak angle at 70 to 75 degrees when the front is 0 degrees, and can be suitably used when a prism sheet is used to direct light toward the front, as in the backlight device 100 shown in Figures 11(A) and 11(B) described below. On the other hand, the light guide plate 1 of embodiment 2 can be suitably used in a backlight device 100 that requires control of the output angle using only the light guide plate 1, without using a prism sheet.

[0059] As shown in FIG. 6A, each first prism element 11e has a first slope Sa11 on the left side of the figure, i.e., on the light incident surface 13 side, and a second slope Sb11 on the right side of the figure, i.e., on the opposing surface 17 side. The first prism elements 11e are arranged in the Y-axis direction at a predetermined first pitch P1 and extend in the X-axis direction. The first slope Sa11 is a flat surface, and the second slope Sb11 is a curved surface having a radius of curvature R1 (e.g., a curved surface with an arc-shaped cross section). The distance from the main body 10 to the first ridge RL11 is the peak height H1. The peak height H1 and first pitch P1 of the first prism elements 11e, and the peak height H2 and second pitch P2 of the second prism elements 12e are the same as those in the first embodiment.

[0060] As shown in FIG. 6(B), the first slope Sa11 has an inclination angle θ1 with respect to the Y-axis direction, and the second slope Sb11 has an inclination angle θ2. In the case of the second inclined surface Sb11 of the second embodiment, the inclination angle θ2 is set to be larger than the inclination angle θ1 (θ2>θ1).

[0061] The larger the inclination angle θ2, the greater the change in angle of the light reflected by the second inclined surface Sb11, making it possible to adjust the reflected light to a desired peak angle. On the other hand, a small inclination angle θ1 is desirable, preferably 3° or less. As the inclination angle θ1 increases, the angle change away from the critical angle when the propagating light within the light guide plate 1 hits the first inclined surface Sa11 becomes greater, increasing the risk that not all light will be able to be emitted, resulting in reduced brightness. Therefore, a value of 10° or less is desirable. Based on the application and specifications of the LCD device, it is possible to set the optimal tilt angle θ1, tilt angle θ2, contact angle α, and curvature radius R1 through optical simulation in accordance with the required output angle and brightness. Note that the contact angle α can be determined by the tilt angle θ2 and curvature radius R1.

[0062] For example, the inclination angle θ2 can be set according to the emission peak required for the backlight device 100 in which the light guide plate 1 is used (for example, determined by the specifications of the liquid crystal display device incorporating the backlight device 100), and can be determined by optical simulation. The contact angle α is uniquely determined from the determined inclination angle θ2 and the radius of curvature R1. Figure 9 illustrates the dependence of optical properties on contact angle α, where Figure 9(A) shows the dependence of peak angle on contact angle α, Figure 9(B) shows the dependence of peak luminance and luminance loss on contact angle α, and Figure 9(C) shows the conditions and results of the optical simulation. Note that luminance loss was defined as luminance at an angle of 70°, at which the observer finds it difficult to see. The conditions under which peak luminance is greater than luminance loss were determined to be favorable. As shown in Figure 9(A), the peak angle decreases as the contact angle α increases. As shown in Figure 9(B), when the contact angle α is 1° and 10°, the luminance loss is greater than the peak luminance. Therefore, it is determined that the contact angle α is preferably 2 to 9°.

[0063] 6(C) shows the angle of reflected light by the first prism element 11e and the light distribution of light emitted from the light output surface 14. It can be seen that the angle of the emitted light is higher in the case of embodiment 2 compared to embodiment 1. That is, it can be seen that embodiment 1 allows the angle range over which light spreads to be set wide, while embodiment 2 allows the angle range over which light spreads to be set narrow. The angle range can be set depending on the intended use.

[0064] Fig. 7 is a diagram verifying the luminance unevenness improvement effect of the light guide plate 1 of embodiment 2, and shows a comparison of light unevenness images from Example 2 and Comparative Examples 2 and 3. Fig. 7(A) is a graph showing the Y-coordinate dependency of the Michelson contrast of the LED image (luminance of the light output surface 14 of the light guide plate 1) when Example 2 and Comparative Examples 2 and 3 are used, and Fig. 7(B) shows the LED image. The conditions for Example 2 are: tilt angle θ1=2°, contact angle α=5.5°, radius of curvature R1=0.03 mm, and second prism 12 is present. The conditions for Comparative Examples 2 and 3 are that the tilt angle γ1=2° and the tilt angle γ2=36°, and Comparative Example 2 does not have the second prism 12, while Comparative Example 3 has the second prism 12. From Figures 7(A) and (B), when comparing the distance <0.03, at which unevenness becomes invisible, it can be seen that the distance is about 9 mm for Comparative Examples 2 and 3, while it is about 6 mm for Example 2, and the area where unevenness occurs is shortened.

[0065] In the second embodiment as well, the width in the X-axis direction over which the first prism elements 11e on the opposing surface 17 side are exposed is wider than the width in the X-axis direction over which the first prism elements 11e on the light incident surface 13 side are exposed. In other words, the density of the first prisms 11 on the opposing surface 17 side is higher. As in the first embodiment, this contributes to improving the uniformity of the luminance of the light emitted from the light exit surface 14.

[0066] <Modification> 8(A) and 8(B) are schematic diagrams showing a portion of a cross section of a first prism 11 of a light guide plate 1 according to Modifications 1 and 2 of Embodiment 2, respectively. The first prism elements 11e are arranged continuously in the Y-axis direction so as to be in contact with each other. The first prism elements 11e are also arranged continuously in the Y-axis direction so as not to expose the surface of the main body 10.

[0067] FIG. 8A shows a first modification in which the length of the first pitch P1, which is the interval between the first prism elements 11e, is made variable. i It is written as follows. In the second embodiment, the length of the first pitch P1 is constant. However, in the first modification, each first pitch P1 i is not constant, but varies randomly within a predetermined range around a predetermined center value. For example, if numbers are assigned to the first prism elements 11e in order from the first prism element 11e closest to the light incident surface 13 toward the opposing surface 17, the first pitch P1 of the kth first prism element 11e at any position will be k is a constant central value <p1>is given by the following formula, with P1 k = <p1>+Δ' (Equation 2) Here, the variation Δ′ is preferably a random number in the range of 0.01 mm to −0.01 mm. <p1>The value is set by randomly varying it based on the above. For example, set a random value f', <p1>and product, i.e., Δ'=f'* <p1>It may be set by: The peak height H1 is the same as in the second embodiment. Each first pitch P1 of Modification 1 k By randomly varying the density of the first prism 11, the density of the first prism 11 varies locally randomly, and it is possible to improve local luminance unevenness.

[0068] 8(B) shows another modified example 2 of the second embodiment, in which there is no random variation in the peak height H1. That is, in Equation 1, the variation Δ is set to 0. Since the peak height H1 is higher on the opposing surface 17 side away from the light emitter 2 compared to the light incident surface 13 side, the prism concentration of the first prism can be increased, improving the uniformity of brightness in the Y-axis direction. In the second modification, the design and manufacture of each first prism element 11e becomes easier. Any of the embodiments and modifications can be selected appropriately depending on the application, etc. The above-mentioned modifications 1 and 2 can also be applied to other embodiments.

[0069] <Embodiment 3> In the first and second embodiments, the peak height H2 of the second prism 12 is set to a constant value. In embodiment 3, the peak height H2 is changed in the Y-axis direction, and the area of ​​the region that functions as the first prism 11 (corresponding to the first region a1) (i.e., the area occupied by the first prism 11) is changed, thereby improving the uniformity of brightness in the Y-axis direction. 10(A) is a plan view schematically showing the configuration of the light guide plate 1 of embodiment 3, FIG. 10(B) is a cross-sectional view taken along line AA, FIG. 10(C) is a cross-sectional view taken along line BB, FIG. 10(D) is a graph schematically showing the dependence of peak height H1 and peak height H2 in the Y-axis direction when the Typ value, which is the central value of the peak height H1 of the first prism 11, is changed, and FIG. 10(E) is a graph schematically showing the dependence of peak height H1 and peak height H2 in the Y-axis direction when the Typ value, which is the central value of the peak height H1 of the first prism 11, is constant. FIG. 10(D) shows an example in which the peak height H1 of the first prism 11 changes according to Equation 1. The peak height H1 of the first prism 11 shown in FIGS. 10(D) and 10(E) varies randomly within a predetermined range with respect to a Typ value which is the central value.

[0070] As shown in FIGS. 10(D) and 10(E), the peak height H2 of the second prism element 12e is set to increase with increasing distance from the light incident side in the Y-axis direction. 10(B) and 10(C), the width w of the first prism element 11e on the light incident side (position of line AA) is smaller than the width w' of the first prism element 11e at a position away in the Y-axis direction (position of line BB). In other words, as shown in FIG. 10(A), the area occupied by the first prism 11 increases with increasing distance from the light incident side. Therefore, the peak height H2 of the second prism 12 tends to decrease along the light incident direction from the light incident surface 13 toward the opposing surface 17, and the width of the first prism element 11e is increased (i.e., the area occupied by the first prism 11 increases). As a result, the diffusion effect of the first prism element 11e can be enhanced, and brightness uniformity can be improved.

[0071] In the embodiment shown in Figure 10(D), the Y-axis direction dependence of the occupied area of ​​the first prism 11 can be adjusted by the Y-axis direction dependence of the peak height H1 of the first prism element 11e and the peak height H2 of the second prism element 12e. In the embodiment shown in FIG. 10(E), the dependency of the occupied area of ​​the first prism 11 in the Y-axis direction can be adjusted by the dependency of the peak height H2 of the second prism element 12e in the Y-axis direction. In the embodiment shown in Figure 10(D), the occupied area of ​​the first prism 11 is adjusted using two parameters, peak height H1 and peak height H2, resulting in a complex configuration, but providing a greater degree of freedom in adjusting the occupied area of ​​the first prism 11.

[0072] The region where [height h1 of the first prism 11]≧[height h2 of the second prism 12] is the region (first region a1) that functions as the first prism 11. The region where [height h1 of the first prism 11]<[height h2 of the second prism 12] is the region (second region a2) that functions as the second prism 12. The first prism 11 and the second prism 12 are integrally formed from the same material, but in Figures 10(B) and (C), for ease of understanding, the area that functions as the first prism 11 and the area that functions as the second prism 12 are distinguished and shown as the first prism element 11e and the second prism element 12e, respectively.

[0073] <Backlight device> The light guide plate 1 of any of the above embodiments (including the modified examples) can be applied to the backlight device 100. 11A and 11B are cross-sectional views schematically showing configuration example 1 and configuration example 2 of a backlight device 100 to which the light guide plate 1 is applied. 11, the white arrow indicates the direction of light incident from the light emitter 2 to the light guide plate 1, the solid black arrow indicates the path of light passing through the light guide plate 1 and the prism sheets (first and second prism sheets 20, 30) toward the liquid crystal panel (not shown), and the dotted black arrow indicates the path of light reflected by the reflective sheet 3 toward the light guide plate 1. The liquid crystal panel is disposed above the backlight device 100 in the drawing (in the +Z-axis direction).

[0074] The backlight device 100 shown in FIG. 11(A) simply totally reflects light at the inclined surface of a single prism sheet and directs it toward the front, thereby achieving higher directivity. On the other hand, the backlight device 100 shown in FIG. 11(B) has a complex configuration using two prism sheets. The process of gradually refracting and directing the light with the two prism sheets includes the action of returning some of the light toward the light guide plate 1, so the effect of improving brightness unevenness is greater than that of the backlight device 100 shown in FIG. 11(A). In both cases, the optimal incident angle at which the prism sheet focuses light toward the front is approximately 70 to 75°, and the light guide plate 1 of embodiment 1 can be preferably used, but is not limited to this.

[0075] Configuration example 1 of the backlight device 100 shown in FIG. 11(A) has a first prism sheet 20 on the Z-axis direction (upward in FIG. 11(A), on the extension side of the traveling direction of the emitted light) of the light-emitting surface 14 of the main body 10. The first prism sheet 20 is interposed between a liquid crystal panel (not shown) and the main body 10. The first prism sheet 20 is made of a known material and can be manufactured by a known method. For example, the first prism sheet 20 is made of a material with a refractive index of 1.49 to 1.52.

[0076] The first prism sheet 20 has first prism sheet elements 20e each having an inverted triangular cross section and protruding toward the light output surface 14, and a first prism sheet substrate 20s that supports a plurality of first prism sheet elements 20e. The first prism sheet element 20e is provided on the light guide plate 1 side of the first prism sheet substrate 20s. The first prism sheet element 20e has two inclined planes Sa20 and Sb20 inclined with respect to the Y-axis direction, and a ridge line RL20 (ie, a line connecting the vertices of a triangle) corresponding to the line where the two inclined planes meet. Each ridge line RL20 extends in the X-axis direction, and each first prism sheet element 20e is arranged in a row in the Y-axis direction, with their ends in contact with each other. That is, each first prism sheet element 20e (or inclined planes Sa20 and Sb20) is arranged in a direction perpendicular to the first prism element 11e (or first inclined surface Sa11 and second inclined surface Sb11).

[0077] The pitch of the first prism sheet elements 20e corresponds to the pixel pitch of the liquid crystal panel or the first pitch P1 and second pitch of the light guide plate 1, and is set to a pitch that does not cause moire. The inclination angles of the inclined planes Sa20 and Sb20 can be any known inclination angle. For example, the inclination angles of the inclined planes Sa20 and Sb20 can be set to 56.5 to 57.5 degrees so that the apex angle is 65 to 67 degrees. The inclination angles of the inclined planes Sa20 and Sb20 can be set to different values ​​so that the cross section is an asymmetric triangle.

[0078] The first prism sheet 20 has the function of reflecting the light emitted from the light guide plate 1 and directing it toward the liquid crystal panel (not shown), thereby increasing the brightness as viewed from the Z-axis direction (see the solid black arrow in FIG. 11(A)). This provides high directivity to the light emitted from the backlight device 100, and also enables high brightness. Therefore, the light incident on the light guide plate 1 from the light emitter 2 (see the white arrow in FIG. 11(A)) can be effectively utilized for, for example, a liquid crystal panel. Light traveling downward (in the −Z-axis direction) from the light guide plate 1 is directed toward the light guide plate 1 by the reflective sheet 3 (see the dotted black arrow in FIG. 11(A)).

[0079] The backlight device 100 may be configured with a two-layer prism sheet (see, for example, Patent Document 3). Configuration example 2 of the backlight device 100 shown in Figure 11(B) has a first prism sheet 20 and a second prism sheet 30 in the Z-axis direction (upward in Figure 11(B), on the extension side of the direction in which the emitted light is emitted) of the light output surface 14 of the main body 10. The first prism sheet 20 and the second prism sheet 30 are interposed between a liquid crystal panel (not shown) and the main body 10. As described above, the first prism sheet 20 and the second prism sheet 30 are made of known materials and can be manufactured by known methods.

[0080] The first prism sheet 20 has first prism sheet elements 20e each having a triangular cross section and a first prism sheet substrate 20s that supports a plurality of first prism sheet elements 20e. The first prism sheet elements 20e protrude from the first prism sheet substrate 20s in the light emission direction. The first prism sheet element 20e is provided on the opposite side of the first prism sheet substrate 20s to the light guide plate 1 (on the liquid crystal panel side). The first prism sheet element 20e has two inclined planes Sa20 and Sb20 inclined with respect to the Y-axis direction. A ridge line RL20 where the two inclined planes meet extends in the X-axis direction, and each of the first prism sheet elements 20e (or the inclined planes Sa20 and Sb20) is disposed in a direction perpendicular to the first prism element 11e (or the first inclined plane Sa11 and the second inclined plane Sb11). The first prism sheet elements 20e are arranged consecutively in the Y-axis direction so as to be in contact with one another.

[0081] The second prism sheet 30 is arranged in the Z-axis direction of the first prism sheet 20 (above in Figure 11 (B), on the extension side of the direction in which the emitted light travels) and is interposed between the first prism sheet 20, the liquid crystal panel, and the main body 10. Similar to the first prism sheet 20, the second prism sheet 30 has second prism sheet elements 30e with triangular cross sections and a second prism sheet substrate 30s that supports a plurality of second prism sheet elements 30e. The second prism sheet elements 30e protrude from the second prism sheet substrate 30s in the light emission direction. The second prism sheet element 30e has two inclined planes Sa30 and Sb30 inclined with respect to the Y-axis direction, and a ridge line RL30 where the two inclined planes meet extends in the X-axis direction. Each second prism sheet element 30e (or the inclined planes Sa30 and Sb30) is disposed in a direction perpendicular to the first prism element 11e (or the first inclined plane Sa11 and the second inclined plane Sb11).

[0082] Light emitted from the light exit surface 14 of the light guide plate 1 is reflected by the first prism sheet 20 and the second prism sheet 30, and directed in the Z-axis direction (towards the liquid crystal panel) (see the solid black arrow in Figure 11(B)). High directivity and high brightness can be obtained for the light emitted from the backlight device 100. The two prism sheets, the first prism sheet 20 and the second prism sheet 30, make it possible to optimize the viewing angle characteristics of the light emitted from the backlight device 100. [Industrial Applicability]

[0083] According to the present invention, it is possible to provide a light guide plate that can improve brightness unevenness around a light source. A backlight device using this light guide plate can contribute to the provision of a high-brightness, high-image-quality transmissive display device, and has high industrial applicability. [Explanation of symbols]

[0084] 1 Light guide plate 2. Light source 3 Reflective sheet 10 Main body 11 First Prism 11e First prism element 12 Second Prism 12e Second prism element 13 Light entrance surface 14 Idemitsu surface 15 Reflective surface 16 Reflective surface prism 17 Opposite Surface 18 Side end face 18 20 First prism sheet 20e First prism sheet element 91e First comparison prism element H1 Peak height H2 peak height P1 First pitch P2 2nd pitch RL11 First Ridge RL12 2nd Ridge RL20, RL30 ridgeline Sa11 1st slope Sb11 Second slope Sa12 3rd slope Sb12 4th slope Sa91 5th slope Sb91 6th slope Sa20, Sb20 inclined plane θ1 1st inclination angle θ2 2nd inclination angle Δ, Δ' change amount β, γ1, γ2 Tilt angle

Claims

1. A light emitting device comprising a light guide plate and a liquid crystal panel, The light guide plate is a light-entering surface through which light from the light-emitting body enters, a light-exiting surface through which light exits, and a reflecting surface facing the light-exiting surface; the reflecting surface comprises a reflecting surface prism; The reflecting surface prism is a plurality of first prism elements extending in a direction perpendicular to the light incident direction and arranged at a first pitch along the light incident direction; a plurality of second prism elements extending in the light incident direction and arranged at a second pitch along a direction perpendicular to the light incident direction; the peak heights of the plurality of first prism elements are given by the sum of a typical value that tends to increase along the light incident direction from the light incident surface and a variation that randomly varies within a predetermined range, The light emitter is disposed opposite the light incident surface, The liquid crystal panel displays information using the light from the light guide plate.

1. An in-vehicle display device comprising:

2. A light emitting device comprising a light guide plate and a liquid crystal panel, The light guide plate is a light-entering surface through which light from the light-emitting body enters, a light-exiting surface through which light exits, and a reflecting surface facing the light-exiting surface; the reflecting surface comprises a reflecting surface prism; The reflecting surface prism is a plurality of first prism elements extending in a direction perpendicular to the light incident direction and arranged at a first pitch along the light incident direction; a plurality of second prism elements extending in the light incident direction and arranged at a second pitch along a direction perpendicular to the light incident direction; the peak height of the first prism element is given by the sum of a typical value that tends to increase along the light incident direction from the light incident surface and a variation amount that randomly fluctuates within a predetermined range, the peak heights of the second prism elements tend to decrease along the light incident direction from the light incident surface; The light emitter is disposed opposite the light incident surface, The liquid crystal panel displays information using the light from the light guide plate.

1. An in-vehicle display device comprising:

3. the first prism element has a first inclined surface and a second inclined surface; the first inclined surface is located closer to the light incident surface than the second inclined surface, the first inclined surface is inclined at a first inclination angle with respect to a direction parallel to the light incident direction, the second inclined surface is inclined at a second inclination angle with respect to a direction parallel to the light incident direction, 3. The in-vehicle display device according to claim 1, wherein the first inclined surface and the second inclined surface are in contact with each other at a predetermined contact angle.

4. 4. The in-vehicle display device according to claim 3, wherein the second inclined surface has a curved surface.

5. 4. The in-vehicle display device according to claim 3, wherein the contact angle is in the range of 2 to 9 degrees.

6. 4. The in-vehicle display device according to claim 3, wherein the first tilt angle is greater than the second tilt angle.

7. 4. The in-vehicle display device according to claim 3, wherein the second tilt angle is greater than the first tilt angle.

8. 3. The in-vehicle display device according to claim 1, wherein the first pitch varies randomly within a predetermined range.

9. A light source device comprising: a reflective sheet disposed opposite the reflective surface; and a first prism sheet disposed opposite the light output surface; 3. The in-vehicle display device according to claim 1, wherein the first prism sheet has first prism sheet elements that protrude from the light exit surface and extend in a direction perpendicular to the light incident direction.

10. A light source device comprising: a reflective sheet disposed opposite the reflective surface; a first prism sheet disposed opposite the light output surface; and a second prism sheet disposed opposite the first prism sheet; the first prism sheet has first prism sheet elements that protrude in a light emission direction and extend in a direction perpendicular to a light incidence direction; the second prism sheet has second prism sheet elements that protrude in the light emission direction and extend in a direction perpendicular to the light incidence direction; 3. The in-vehicle display device according to claim 1, wherein the first prism sheet is positioned between the second prism sheet and the light exit surface.

Images