Backlight device and liquid crystal display device

Abstract

The present invention provides a backlight device and a liquid crystal display device with improved uniformity of brightness distribution. [Solution] The backlight device 200 includes a light source, a light guide plate 120 having a side surface facing the light source, a first main surface 126 that emits light from the light source, and a second main surface 128 opposite to the first main surface 126. The light guide plate 120 has a recess 130 located on the second main surface 128. When the recess 130 is viewed in cross-section perpendicular to the second main surface 128, the side surface of the recess that is continuous with the bottom surface of the recess 130 is inclined at an obtuse angle with respect to the bottom surface.

Description

Technical Field

[0001] The present disclosure relates to a backlight device and a liquid crystal display device.

Background Art

[0002] A liquid crystal display device having a camera provided on the back surface of a liquid crystal display panel is known. For example, Patent Document 1 discloses an electronic device including a camera, a liquid crystal panel having a display portion overlapping the camera, a light guide plate having a through hole, and a light source facing the side surface of the light guide plate. The camera is provided in the through hole of the light guide plate. Further, in Patent Document 2, a hole (recess) is formed in a light guide plate of a backlight that irradiates light on a liquid crystal display panel, and an imaging device is provided in the hole of the light guide plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, since a through hole is provided in the light guide plate, it is difficult for the light emitted from the light source to be guided inside the light guide plate beyond the through hole of the light guide plate. As a result, on the opposite side of the light source across the through hole, the luminance of the light guide plate decreases, and the luminance distribution of the light guide plate becomes non-uniform. Further, in Patent Document 2, although the hole in the light guide plate does not penetrate the light guide plate, the thickness of the light guide plate becomes thinner at the hole portion. Therefore, also in the configuration of Patent Document 2, it is difficult for the light emitted from the light source to be guided inside the light guide plate beyond the through hole of the light guide plate, and on the opposite side of the light source across the through hole, the luminance of the light guide plate decreases.

[0005] This disclosure is made in view of the above circumstances and aims to provide a backlight device and a liquid crystal display device with improved uniformity of brightness distribution. [Means for solving the problem]

[0006] The backlight device relating to the first aspect of this disclosure is Light source and The light guide plate comprises a side facing the light source, a first main surface that emits light from the light source, and a second main surface opposite to the first main surface. The light guide plate has a recess disposed on the second main surface, When the recess is viewed in cross-section perpendicular to the second main surface, the side surface of the recess that is continuous with the bottom surface of the recess is inclined at an obtuse angle with respect to the bottom surface.

[0007] The liquid crystal display device relating to the second aspect of this disclosure is The above backlight device and The light guide plate comprises a liquid crystal display panel having a display area for displaying display elements, which is disposed on the first main surface of the light guide plate. When viewed from above, the recess of the light guide plate overlaps with the display area of ​​the liquid crystal display panel. [Effects of the Invention]

[0008] According to this disclosure, the recess is arranged on the second main surface of the light guide plate, and the side surface of the recess that is continuous with the bottom surface of the recess is inclined at an obtuse angle with respect to the bottom surface of the recess, thereby increasing the uniformity of the luminance distribution. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a liquid crystal display device according to Embodiment 1. [Figure 2] This is a plan view showing the light source, light guide plate, optical sheet, and lower chassis of a backlight device according to Embodiment 1. [Figure 3] This is a plan view showing a light guide plate according to Embodiment 1. [Figure 4]It is a cross-sectional view of the light guide plate shown in Fig. 3 as viewed along the line A-A. [Figure 5] It is a schematic diagram for explaining the light guiding of light in a light guide plate in which the entire recess is recessed in a cylindrical shape. [Figure 6] It is a schematic diagram for explaining the light guiding of light in the light guide plate according to Embodiment 1. [Figure 7] It is a plan view showing the dimensions of the light guide plate in the simulation according to Embodiment 1. [Figure 8] It is a cross-sectional view showing the dimensions of the light guide plate in the simulation according to Embodiment 1. [Figure 9] It is a cross-sectional view showing the dimensions of the light guide plate in the simulation according to Comparative Example 1. [Figure 10] It is a cross-sectional view showing the dimensions of the light guide plate in the simulation according to Comparative Example 2. [Figure 11] It is a cross-sectional view showing the dimensions of the light guide plate in the simulation according to Comparative Example 3. [Figure 12] It is a diagram showing the luminance distribution of the emission surface in the simulation according to Embodiment 1. [Figure 13] It is a diagram showing the luminance distribution of the emission surface in the simulation according to Comparative Example 1. [Figure 14] It is a diagram showing the luminance distribution of the emission surface in the simulation according to Comparative Example 2. [Figure 15] It is a diagram showing the luminance distribution of the emission surface in the simulation according to Comparative Example 3. [Figure 16] It is a diagram showing the luminance distribution on the line of the emission surface in the simulation according to Embodiment 1 and Comparative Examples 1 to 3. [Figure 17] It is a plan view showing the region of the simulation according to Embodiment 1. [Figure 18] It is a cross-sectional view showing the region of the simulation according to Embodiment 1. [Figure 19] It is a diagram showing the relationship between the angle of the side surface of the recess and the ratio of the light rays guiding light beyond the recess according to Embodiment 1. [Figure 20]It is a cross-sectional view showing a liquid crystal display device according to Embodiment 2. [Figure 21] It is a plan view showing a light guide plate according to Embodiment 2. [Figure 22] It is a cross-sectional view of the light guide plate shown in FIG. 21 as viewed along the line B-B. [Figure 23] It is a schematic diagram for explaining light guiding in a light guide plate according to Embodiment 2. [Figure 24] It is a cross-sectional view showing the dimensions of a light guide plate in a simulation according to Embodiment 2. [Figure 25] It is a diagram showing the luminance distribution on the emission surface in a simulation according to Embodiment 2. [Figure 26] It is a diagram showing the luminance distribution on a line of the emission surface in a simulation according to Embodiment 2 and Comparative Examples 1 to 3. [Figure 27] It is a diagram showing the relationship between the angle of the side surface of the convex portion, the angle of the side surface of the concave portion, and the ratio of the light rays that guide light beyond the concave portion according to Embodiment 2. [Figure 28] It is a diagram showing the relationship between the diameter of the bottom surface of the convex portion and the ratio of the light rays that guide light beyond the concave portion according to Embodiment 3. [Figure 29] It is a diagram showing the luminance distribution on a line of the emission surface according to Embodiment 3. [Figure 30] It is a diagram showing the luminance distribution on a line of the emission surface according to Embodiment 3. [Figure 31] It is a cross-sectional view showing a concave portion and a lens of an imaging device according to a modification.

Mode for Carrying Out the Invention

[0010] Hereinafter, a backlight device and a display device according to an embodiment will be described with reference to the drawings.

[0011] <Embodiment 1> Referring to Figures 1 to 19, the backlight device 200 and the liquid crystal display device 500 according to this embodiment will be described. As shown in Figure 1, the liquid crystal display device 500 comprises a backlight device 200, a liquid crystal display panel 300, and an imaging device 400. The backlight device 200 comprises a light source 110, which will be described later, and a light guide plate 120. The liquid crystal display panel 300 has a display area 302 for displaying display elements (characters, images, etc.) and a frame area 304 surrounding the display area 302. The imaging device 400 has a lens part 410 and a main body part 420. In this specification, the longitudinal direction (to the right of the paper) of the liquid crystal display device 500 in Figure 1 will be described as the +X direction, the short direction (towards the back of the paper) as the +Y direction, and the direction perpendicular to the +X and +Y directions (towards the top of the paper, towards the user) as the +Z direction. Note that in Figure 1, the hatching of the optical sheet 160, which will be described later, has been omitted for ease of understanding. In the following diagrams, hatching may be omitted in some cases.

[0012] First, the backlight device 200 will be described. The backlight device 200 functions as a means of illuminating the liquid crystal display panel 300 of the liquid crystal display device 500. As shown in Figures 1 and 2, the backlight device 200 comprises a light source 110, a light guide plate 120, a reflective sheet 150, an optical sheet 160, a lower chassis 170, and an upper chassis 180.

[0013] The light source 110 of the backlight device 200 is, for example, a white LED (Light Emitting Diode) element. As shown in Figure 2, multiple light sources 110 are arranged facing each other on the +Y side surface 122 of the light guide plate 120. Light emitted from the multiple light sources 110 enters the light guide plate 120 from the side surface 122 of the light guide plate 120.

[0014] The light guide plate 120 of the backlight device 200 is a plate-shaped member formed in a rectangular shape that is long in the X direction. The light guide plate 120 emits light incident from the light source 110 toward the liquid crystal display panel 300. As shown in Figures 1 and 2, the light guide plate 120 has a first main surface 126 toward the liquid crystal display panel 300 toward the light incident from the light source 110, and a second main surface 128 opposite to the first main surface 126. The light guide plate 120 also has four sides, including a side surface 122 facing the light source 110 and a side surface 124 opposite to side surface 122. Hereafter, the first main surface 126 will also be referred to as the emission surface 126, the side surface 122 facing the light source 110 as the incidence surface 122, and the side surface 124 opposite to side surface 122 as the anti-incident surface 124.

[0015] As shown in Figures 1 to 3, the light guide plate 120 has a recess 130 in the area 128a of the second main surface 128 that corresponds to the display area 302 of the liquid crystal display panel 300. As shown in Figure 1, the tip 412 of the lens portion 410 of the imaging device 400 is positioned in the recess 130.

[0016] In the recess 130, the upper part 134 (the -Y side of the recess 130) is concave in a cylindrical shape, and the bottom part 132 (the +Y side of the recess 130) is concave in a mortar shape (frustoconical shape). In other words, as shown in Figure 4, when the recess 130 is viewed in cross-section perpendicular to the second main surface 128, the side surface 138 of the recess 130, which is continuous with the bottom surface 136 of the recess 130, is inclined at an obtuse angle with respect to the bottom surface 136. As will be described later, it is preferable that the inclination φ of the side surface 138 of the recess 130 with respect to the bottom surface 136 of the recess 130 is 150° or more.

[0017] The light guide plate 120 is formed from a light-transmitting resin (for example, polycarbonate). In one example of the light guide plate 120, a diffusion layer (not shown) is printed in a predetermined pattern as dots on the second main surface 128, excluding the recesses 130, in order to guide light through the light guide plate 120 and emit it from the first main surface 126.

[0018] As shown in Figure 1, the reflective sheet 150 of the backlight device 200 is provided on the second main surface 128 of the light guide plate 120. The reflective sheet 150 reflects the light emitted from the second main surface 128 of the light guide plate 120 back towards the light guide plate 120. The reflective sheet 150 is provided with a through hole 152 through which the lens portion 410 of the imaging device 400 passes.

[0019] As shown in Figures 1 and 2, the optical sheet 160 of the backlight device 200 is provided on the first main surface 126 of the light guide plate 120. The optical sheet 160 is a diffusion sheet, a prism sheet, a polarizing reflective sheet, etc.

[0020] The lower chassis 170 of the backlight device 200 has a box shape. The lower chassis 170 is made of resin or metal. As shown in Figure 1, the lower chassis 170 houses the light source 110, the light guide plate 120, the reflective sheet 150, and the optical sheet 160 inside. A through hole 174 is provided in the bottom 172 of the lower chassis 170 for the lens portion 410 of the imaging device 400 to pass through.

[0021] The upper chassis 180 of the backlight device 200 has a frame shape. As shown in Figure 1, the upper chassis 180 has a projection 182 extending into the frame. The liquid crystal display panel 300 is mounted on the projection 182. The upper chassis 180 is formed from, for example, synthetic resin.

[0022] Here, the effects of this embodiment will be explained. For example, in the light guide plate 720 shown in Figure 5, where the entire recess 130 is cylindrical (the side surface 138 continuous with the bottom surface 136 is perpendicular to the bottom surface 136), the width Din for guiding light L1 from the incident surface 122 side into the light guide plate 120 on the recess 130 becomes narrower. As the width Din becomes narrower, the amount of light guided to the region SR on the opposite side of the recess 130 of the light guide plate 720, as viewed from the incident surface 122 side, decreases. As a result, the luminance Lu in the region SR on the opposite side of the recess 130 of the light guide plate 720 decreases, and the luminance distribution of the light guide plate 720 (exit surface 126) becomes non-uniform.

[0023] On the other hand, in this embodiment, when the recess 130 is viewed in cross-section perpendicular to the second main surface 128, the side surface 138 of the recess 130, which is continuous with the bottom surface 136 of the recess 130, is inclined at an obtuse angle with respect to the bottom surface 136, so the width Din widens as shown in Figure 6. As a result, the amount of light guided to the region SR of the light guide plate 120 increases, and the luminance Lu in the region SR of the light guide plate 120 increases, thereby improving the uniformity of the luminance distribution of the light guide plate 120 (emitting surface 126).

[0024] The following describes the specific effects of this embodiment based on a ray tracing simulation (Synopsys's LightTools lighting analysis software). First, the light source 110, light guide plate 120, etc., used in the simulation of this embodiment will be described.

[0025] As shown in Figure 7, the light guide plate 120 measures 190 mm (X direction) x 120 mm (Y direction), and the center line C1 of the recess 130 is located 90 mm in the -Y direction from the incident surface 122 and 130 mm in the +X direction from the left side surface. In addition, 28 white LED elements (not shown) are arranged as the light source 110 at a 6.5 mm pitch, facing the incident surface 122.

[0026] As shown in Figure 8, the thickness D1 of the light guide plate 120 above the recess 130 is 1.5 mm, and the thickness D2 of the light guide plate 120 is 3 mm. The depth DP1 of the recess 130 is 1.5 mm, the depth DP2 of the bottom 132 of the recess 130 is 0.5 mm, and the depth DP3 of the top 134 is 1.0 mm. Furthermore, the diameter DA1 of the recess 130 is 18 mm. The angle φ of the side surface 138 of the recess 130 that is continuous with the bottom surface 136 is 170°. In this simulation, a light absorber (not shown) is placed in the recess 130 instead of the lens section 410 of the imaging device 400.

[0027] A dot-shaped diffusion layer (not shown) is provided on the second main surface 128, excluding the recess 130. As the pattern of the diffusion layer, a pattern that produces a uniform brightness distribution on the light guide plate in a light guide plate without the recess 130 (hereinafter referred to as pattern A) is used.

[0028] Next, we will describe the light guide plates 820, 840, and 860 that were simulated as Comparative Examples 1 to 3. The size and thickness of the light source 110 and the light guide plates 820, 840, and 860 in the simulations of Comparative Examples 1 to 3 are the same as those in the simulation of this embodiment.

[0029] In the light guide plate 820 of Comparative Example 1, as shown in Figure 9, a cylindrical through-hole 822 is provided instead of the recess 130. The position of the through-hole 822 is the same as the position of the recess 130 in the embodiment, and the diameter of the through-hole 822 is the same as the diameter DA1 of the recess 130 in the embodiment. A light absorber is also placed in the through-hole 822. In Comparative Example 1 as well, pattern A is used as the pattern of the diffusion layer.

[0030] In the light guide plate 840 of Comparative Example 2, as shown in Figure 10, a cylindrical recess 842 is provided on the first main surface 126. The position of the recess 842 is the same as that of the recess 130 in the embodiment. The diameter of the recess 842 is also the same as the diameter DA1 of the recess 130 in the embodiment. The depth of the recess 842 is 1.5 mm, and the thickness of the light guide plate 840 below the recess 842 is 1.5 mm. In Comparative Example 2 as well, pattern A is used as the pattern of the diffusion layer. A light absorber is placed in the recess 842.

[0031] In the light guide plate 860 of Comparative Example 3, as shown in Figure 11, a cylindrical recess 862 is provided on the second main surface 128. The position of the recess 862 is the same as that of the recess 130 in the embodiment. The diameter of the recess 862 is also the same as the diameter DA1 of the recess 130 in the embodiment. The depth of the recess 862 is 1.5 mm, and the thickness of the light guide plate 860 above the recess 862 is 1.5 mm. In Comparative Example 3 as well, pattern A is used as the pattern of the diffusion layer. A light absorber is placed in the recess 862.

[0032] The luminance distribution of the emission surface 126 (first main surface 126) was simulated for the light guide plate 120 of the above embodiment and the light guide plates 820 to 860 of Comparative Examples 1 to 3.

[0033] Figures 12 to 15 show the luminance distribution of the embodiment and comparative examples 1 to 3, respectively. In Figures 12 to 15, brighter areas indicate higher luminance Lu. In addition, the hatched areas in Figures 12 to 15 have a light absorber and no diffuse layer in the recess 130, so the luminance Lu is zero. The following figures illustrate this similarly.

[0034] Figure 16 shows the brightness distribution along a straight line (the y1-y1 line shown in Figures 12-15) that extends parallel to the Y-axis from the incident surface 122 to the anti-incident surface 124 (from the +Y side to the -Y side) and passes through the center of the recesses 130, 842, 862 or the through hole 822, when the exit surface 126 of the embodiment and comparative examples 1-3 is viewed from above.

[0035] As shown in Figures 12 to 16, the luminance Lu in region SR of the light guide plate 120 in the embodiment is higher than the luminance Lu in region SR of the light guide plates 820 to 860 in Comparative Examples 1 to 3. Furthermore, the uniformity of the luminance distribution of the light guide plate 120 in the embodiment is improved compared to the uniformity of the luminance distribution of the light guide plates 820 to 860 in Comparative Examples 1 to 3.

[0036] As described above, when the recess 130 is viewed in cross-section perpendicular to the second main surface 128, the side surface 138 of the recess 130, which is continuous with the bottom surface 136 of the recess 130, is inclined at an obtuse angle with respect to the bottom surface 136. This increases the luminance Lu of the SR region and improves the uniformity of the luminance distribution of the light guide plate 120.

[0037] Next, the relationship between the angle φ of the side surface 138 of the recess 130 and the proportion of light rays that pass beyond the recess 130 was simulated. Specifically, the relationship between the ratio Rt of the number of light rays passing through region R2 (Figures 17 and 18) in the light guide plate 120 immediately after the recess 130 and the angle φ was simulated, as viewed from the incident surface 122 (side surface 122) side, with respect to the number of light rays passing through region R1 (Figures 17 and 18) in the light guide plate 120 immediately before the recess 130, and the angle φ. Except for the value of the angle φ of the side surface 138, the configuration of the light guide plate 120 in this simulation is the same as the configuration of the light guide plate 120 in the aforementioned simulation.

[0038] Figure 19 shows the relationship between the angle φ of the side surface 138 and the ratio Rt of the number of light rays passing through region R2 to the number of light rays passing through region R1. As shown in Figure 19, when the angle θ of the side surface 144 is 150° or more, the ratio Rt increases sharply. That is, by making the angle θ of the side surface 144 150° or more, the number of light rays (amount of light) that guide beyond the recess 130 can be increased. Therefore, it is preferable that the angle φ of the side surface 138 is 150° or more.

[0039] Next, the liquid crystal display device 500 will be described. As shown in Figure 1, the liquid crystal display device 500 comprises the backlight device 200 described above, a liquid crystal display panel 300, and an imaging device 400. Here, the liquid crystal display panel 300 and the imaging device 400 will be described.

[0040] The liquid crystal display panel 300 of the liquid crystal display device 500 is mounted on a protrusion 182 of the upper chassis 180 of the backlight device 200. The liquid crystal display panel 300 is, for example, a known transmissive transverse electric field type liquid crystal display panel. The liquid crystal display panel 300 is actively matrix driven by a TFT (Thin Film Transistor). The liquid crystal display panel 300 modulates light from the backlight device 200 to display display elements (characters, images, etc.). The liquid crystal display panel 300 has a display area 302 and a bezel area 304. The display area 302 is an area in which pixels are arranged in a matrix and display elements can be displayed. The display area 302 corresponds to the area 128a of the second main surface 128 of the light guide plate 120. The bezel area 304 is an area in which wiring, drive circuits, etc., are arranged.

[0041] The imaging device 400 of the liquid crystal display device 500 captures an image of the object to be captured through the liquid crystal display panel 300. The imaging device 400 has a lens section 410 and a main body section 420. The lens section 410 passes through a through hole 174 in the lower chassis 170 and a through hole 152 in the reflective sheet 150, and the tip 412 of the lens section 410 is positioned in a recess 130 in the light guide plate 120. The lens section 410 houses a lens system for forming an image of the object to be captured onto an image sensor (for example, a CCD (Charge Coupled Device) image sensor). The main body section 420 is located on the rear side (-Z side) of the lower chassis 170. The main body section 420 houses the image sensor, circuit board, etc.

[0042] As described above, in the backlight device 200, when the recess 130 of the light guide plate 120 is viewed in cross-section perpendicular to the second main surface 128, the side surface 138 of the recess 130, which is continuous with the bottom surface 136 of the recess 130, is inclined at an obtuse angle with respect to the bottom surface 136. This increases the luminance Lu of the region SR of the light guide plate 120, thereby improving the uniformity of the luminance distribution of the light guide plate 120. Furthermore, since the backlight device 200 emits highly uniform light, the liquid crystal display device 500 can achieve highly uniform display.

[0043] <Embodiment 2> In Embodiment 1, the first main surface 126 of the light guide plate 120 is flat. The light guide plate 120 may have a protrusion 140 on the first main surface 126.

[0044] As shown in Figure 20, the liquid crystal display device 500 of this embodiment includes a backlight device 200, a liquid crystal display panel 300, and an imaging device 400, similar to the liquid crystal display device 500 of Embodiment 1. Furthermore, the backlight device 200 of this embodiment includes a light source 110, a light guide plate 120, a reflective sheet 150, an optical sheet 160, a lower chassis 170, and an upper chassis 180, similar to the backlight device 200 of Embodiment 1. The configuration of the backlight device 200 and the liquid crystal display device 500 of this embodiment is the same as that of Embodiment 1, except for the configuration of the light guide plate 120 and the optical sheet 160. Here, the light guide plate 120 and the optical sheet 160 of this embodiment will be described.

[0045] As shown in Figure 20, the light guide plate 120 of this embodiment has a protrusion 140 on its first main surface 126. The configuration of the light guide plate 120 of this embodiment is the same as that of the light guide plate 120 of Embodiment 1, except for the protrusion 140. The protrusion 140 of the light guide plate 120 of this embodiment will now be described.

[0046] When the light guide plate 120 of this embodiment is viewed from above, as shown in Figure 21, the outer circumference 140a of the convex portion 140 surrounds the concave portion 130. The convex portion 140 also has a frustoconical shape. As shown in Figure 22, when the convex portion 140 is viewed in cross-section perpendicular to the first main surface 126, it has a trapezoidal shape, and the side surface 144 of the convex portion 140 is inclined at an acute angle (inclination θ) with respect to the bottom surface 142 of the convex portion 140.

[0047] In this embodiment, when viewed from above, the outer circumference 140a of the convex portion 140 surrounds the concave portion 130, so the thickness D1 of the light guide plate 120 above the concave portion 130 becomes thicker. As the thickness D1 of the light guide plate 120 above the concave portion 130 increases, as shown in Figure 23, the amount of light L2 guided from the incident surface 122 side to the anti-incident surface 124 side within the light guide plate 120 increases, and the amount of light guided to the region SR on the opposite side of the concave portion 130 of the light guide plate 120, as viewed from the incident surface 122 side, increases. Furthermore, the light L2 is reflected by the side surface 144 of the convex portion 140 and guided to region SR. As a result, the amount of light guided to region SR of the light guide plate 120 increases further, and the luminance Lu in region SR of the light guide plate 120 increases further, so the uniformity of the luminance distribution of the light guide plate 120 (exit surface 126) can be further improved.

[0048] As shown in Figure 20, the optical sheet 160 of this embodiment has through holes 162 corresponding to the protrusions 140. The other configurations of the optical sheet 160 of this embodiment are the same as those of the optical sheet 160 of Embodiment 1.

[0049] The specific effects of this embodiment will be explained below based on a ray tracing simulation. The configuration of the light source 110 and the light guide plate 120 in the simulation of this embodiment is the same as in the simulation of Embodiment 1, except for the dimensions of the recess 130 and the protrusion 140. First, the dimensions of the recess 130 and the configuration of the protrusion 140 used in the simulation of this embodiment will be explained.

[0050] Similar to Embodiment 1, in the recess 130, the upper part 134 (the -Y side of the recess 130) is cylindrically recessed, and the bottom part 132 (the +Y side of the recess 130) is mortar-shaped (frustoconical). The center line C1 of the recess 130 is located 90 mm in the -Y direction from the incident surface 122 and 130 mm in the +X direction from the left side surface.

[0051] Also, similar to Embodiment 1, the thickness D2 of the light guide plate 120 is 3 mm. The thickness D1 of the light guide plate 120 above the recess 130 is 1.5 mm.

[0052] In this embodiment, as shown in Figure 24, the depth DP1 of the recess 130 is 2.0 mm. Of the recess 130, the depth DP2 of the bottom 132 is 0.5 mm, and the depth DP3 of the top 134 is 1.5 mm.

[0053] The diameter DA1 of the recess 130 is 18 mm, as in Embodiment 1. The angle φ of the side surface 138 of the recess 130 that is continuous with the bottom surface 136 of the recess 130 is also 170°, as in Embodiment 1. In this simulation as well, a light absorber is placed in the recess 130.

[0054] The center line C2 of the frustoconical convex portion 140 coincides with the center line C1 of the concave portion 130, and the diameter DA2 of the base surface 142 of the convex portion 140 is 21 mm. The height H1 of the convex portion 140 is 0.5 mm, and the inclination θ of the side surface 144 of the convex portion 140 is 10°. Since the inclination φ of the side surface 138 of the concave portion 130 is 170°, the side surface 138 of the concave portion 130 and the side surface 144 of the convex portion 140 are parallel.

[0055] The luminance distribution of the light guide plate 120 of this embodiment was simulated on the emission surface 126 (first main surface 126). Figure 25 shows the luminance distribution of the light guide plate 120 of this embodiment. Figure 26 shows the luminance distribution on a straight line (on the y1-y1 line shown in Figures 13-15 and 25) that extends parallel to the Y axis from the incident surface 122 side to the anti-incident surface 124 side (from the +Y side to the -Y side) and passes through the center of the recesses 130, 842, 862 or through holes 822, when the emission surface 126 of this embodiment and comparative examples 1-3 of Embodiment 1 are viewed from above.

[0056] As shown in Figures 25 and 26, the luminance Lu in region SR of the light guide plate 120 in this embodiment is higher than the luminance Lu in region SR of the light guide plates 820 to 860 in Comparative Examples 1 to 3. Furthermore, the uniformity of the luminance distribution of the light guide plate 120 in this embodiment is improved compared to the uniformity of the luminance distribution of the light guide plates 820 to 860 in Comparative Examples 1 to 3.

[0057] Next, the relationship between the angle φ of the side surface 138 of the recess 130 and the angle θ of the side surface 144 of the protrusion 140 in the light guide plate 120, and the proportion of light rays that guide beyond the recess 130 was simulated. Specifically, similar to the simulation in Embodiment 1, the relationship between the ratio Rt of the number of light rays passing through region R2 in the light guide plate 120 immediately after the protrusion 140 to the number of light rays passing through region R1 in the light guide plate 120 immediately before the protrusion 140, viewed from the incident surface 122 (side surface 122), and the angle φ and angle θ was simulated. The side surface 138 of the recess 130 and the side surface 144 of the protrusion 140 were assumed to be parallel. Furthermore, except for the values ​​of the angle φ of the side surface 138 and the angle θ of the side surface 144, the configuration of the light guide plate 120 in this simulation is the same as the configuration of the light guide plate 120 in the aforementioned simulation.

[0058] Figure 27 shows the relationship between the angle θ of side surface 144, the angle φ of side surface 138, and the ratio Rt of the number of rays passing through region R2 to the number of rays passing through region R1. As shown in Figure 27, the ratio Rt increases sharply when the angle θ of side surface 144 is 40° or less, and the angle φ of side surface 138 is 140° or more. Therefore, when side surface 144 and side surface 138 are parallel, it is preferable to set the angle θ of side surface 144 to 40° or less, or the angle φ of side surface 138 to 140° or more.

[0059] As described above, in this backlight device 200, similar to the backlight device 200 of Embodiment 1, when the recess 130 of the light guide plate 120 is viewed in cross-section perpendicular to the second main surface 128, the side surface 138 of the recess 130 that is continuous with the bottom surface 136 of the recess 130 is inclined at an obtuse angle with respect to the bottom surface 136. This increases the luminance Lu of the region SR of the light guide plate 120 and improves the uniformity of the luminance distribution of the light guide plate 120. In the backlight device 200 of this embodiment, the outer circumference 140a of the convex portion 140 of the light guide plate 120 surrounds the recess 130 of the light guide plate 120 in plan view, and when the convex portion 140 is viewed in cross-section, the convex portion 140 has a trapezoidal shape. This further increases the luminance Lu of the region SR of the light guide plate 120 and further improves the uniformity of the luminance distribution of the emission surface 126. Furthermore, since the backlight device 200 emits highly uniform light, the liquid crystal display device 500 can achieve highly uniform display.

[0060] <Embodiment 3> In Embodiment 2, the outer circumference 140a of the protrusion 140 of the light guide plate 120 surrounds the recess 130 of the light guide plate 120. That is, the diameter DA2 of the bottom surface 142 of the protrusion 140 is larger than the diameter DA1 of the recess 130 (DA2 > DA1). It is preferable that the diameter DA2 is larger than the diameter DA1.

[0061] Figure 28 shows the relationship between the ratio Rt of the number of light rays passing through region R2 in the light guide plate 120 immediately after the protrusion 140 and the number of light rays passing through region R1 in the light guide plate 120 immediately before the protrusion 140, as viewed from the incident surface 122 (side surface 122) side, and the diameter DA2 of the bottom surface 142 of the protrusion 140. Figures 29 and 30 show the luminance distribution along the line of the exit surface 126 in the light guide plate 120 of Embodiment 2. The luminance distribution in Figures 29 and 30 is the luminance distribution along a straight line that extends parallel to the Y axis from the incident surface 122 side to the anti-incident surface 124 side (+Y side to -Y side) and passes through the center of the recess 130, when the exit surface 126 is viewed from above.

[0062] Figures 28 to 30 are based on simulations using pattern B as the diffusion layer pattern, with the inclination θ of the side surface 144 of the convex portion 140 set to 10° and the angle φ of the side surface 138 of the concave portion 130 set to 170°, or the inclination θ of the side surface 144 of the convex portion 140 set to 20° and the angle φ of the side surface 138 of the concave portion 130 set to 160°, and the diameter DA2 of the bottom surface 142 of the convex portion 140 being varied. Other simulation conditions are the same as those for the simulation in Embodiment 2. The diameter DA1 of the concave portion 130 is 18 mm (DA1 = 18 mm).

[0063] As shown in Figure 28, the larger the diameter DA2 of the bottom surface 142 of the convex portion 140 is than the diameter DA1 of the concave portion 130, the more light rays can be guided beyond the concave portion 130. Therefore, it is preferable that the diameter DA2 is larger than the diameter DA1.

[0064] Furthermore, as shown in Figures 29 and 30, even if the diameter DA2 is made larger, the brightness Lu of the region SR can be increased, and the brightness distribution of the light guide plate 120 can be made uniform. In the case where the optical sheet 160 has through holes 162 corresponding to the protrusions 140, as in the backlight device 200 of Embodiment 2, the size of the through holes 162 of the optical sheet 160 increases with the size of the diameter DA2, so if the diameter DA2 is too large, there is a risk that the brightness Lu around the recesses 130 will decrease. The size of the diameter DA2 is appropriately selected according to the application, required specifications, etc.

[0065] <Variation> While embodiments have been described above, this disclosure can be modified in various ways without departing from its essence.

[0066] For example, in this embodiment, the outer shape of the light guide plate 120 is rectangular when viewed from above. However, the outer shape of the light guide plate 120 is not limited to a rectangle when viewed from above.

[0067] The shape of the upper part 134 of the recess 130 is not limited to a cylindrical shape. For example, the shape of the upper part 134 of the recess 130 may be a prism shape. The bottom part 132 of the recess 130 only needs to have a side surface 138 of the recess 130 that is continuous with the bottom surface 136 of the recess 130 inclined at an obtuse angle with respect to the bottom surface 136. For example, the shape of the bottom part 132 may be a truncated pyramidal shape, depending on the shape of the upper part 134.

[0068] In this embodiment, a diffusion layer for emitting light from the light source 110 is provided on the second main surface 128 of the light guide plate 120, excluding the recess 130. The light guide plate 120 only needs to be provided with a configuration for emitting light from the light source 110. For example, a fine prism may be provided on the second main surface 128 of the light guide plate 120, excluding the recess 130.

[0069] In this embodiment, the tip portion 412 of the lens portion 410 of the imaging device 400 is positioned in the recess 130 of the light guide plate 120. As shown in Figure 31, it is preferable that the effective aperture DE of the lens 413 located on the imaging target side of the lens portion 410 does not overlap with the side surface 138 of the recess 130. This allows the imaging device 400 to image the target while suppressing the effects of light refraction or reflection caused by the side surface 138 which is inclined with respect to the second main surface 128. In the second embodiment, it is also preferable that the effective aperture DE of the lens 413 located on the imaging target side of the lens portion 410 does not overlap with at least one of the side surface 138 of the recess 130 and the side surface 144 of the convex portion 140.

[0070] At least a portion of the imaging device 400 is placed in the recess 130 of the light guide plate 120. For example, the entire imaging device 400 may be placed in the recess 130.

[0071] Other components besides the imaging device 400 may be placed in the recess 130 of the light guide plate 120; for example, various sensors may be placed in the recess 130.

[0072] While preferred embodiments have been described above, this disclosure is not limited to these specific embodiments, and includes the invention described in the claims and its equivalents. [Explanation of Symbols]

[0073] 110 Light source, 120 Light guide plate, 122 Side, incident surface, 124 Side, anti-incident surface, 126 First main surface, exit surface, 128 Second main surface, 128a Area, 130 Recess, 132 Bottom, 134 Top, 136 Bottom surface, 138 Side, 140 Convex part, 140a Outer circumference, 142 Bottom surface, 144 Side, 150 Reflective sheet, 152 Through hole, 160 Optical sheet, 162 Through hole, 170 Lower chassis, 172 Bottom, 174 Through hole, 180 Upper chassis, 182 Protruding part, 200 Backlight device, 300 Liquid crystal display panel, 302 Display area, 304 Frame area, 400 Imaging device, 410 Lens part, 412 Tip part, 413 Lens, 420 Main body, 500 liquid crystal display device, 720 light guide plate, 820 light guide plate, 822 through hole, 840 light guide plate, 842 recess, 860 light guide plate, 862 recess, C1, C2 center line, L1, L2 light, Lu luminance, D1, D2 thickness, Din width, DA1, DA2 diameter, DE effective aperture, DP1, DP2, DP3 depth, H1 height, Rt ratio, SR, R1, R2 area, θ, φ angle

Claims

1. Light source and The light guide plate comprises a side facing the light source, a first main surface that emits light from the light source, and a second main surface opposite to the first main surface. The light guide plate has a recess arranged on the second main surface, When the recess is viewed in cross-section perpendicular to the second main surface, the side surface of the recess that is continuous with the bottom surface of the recess is inclined at an obtuse angle with respect to the bottom surface. Backlight device.

2. The light guide plate has a protrusion arranged on the first main surface, When viewed from above, the outer circumference of the convex portion surrounds the concave portion. When the protrusion is viewed in cross-section perpendicular to the first main surface, the protrusion has a trapezoidal shape. The backlight device according to claim 1.

3. The first main surface of the light guide plate is provided with at least one optical sheet, The at least one optical sheet has through holes corresponding to the protrusions of the light guide plate. The backlight device according to claim 2.

4. The inclination of the side surface of the recess with respect to the bottom surface of the recess is 150° or more. The backlight device according to claim 1.

5. A backlight device according to any one of claims 1 to 4, The light guide plate is disposed on the first main surface and comprises a liquid crystal display panel having a display area for displaying display elements, When viewed from above, the recess of the light guide plate overlaps the display area of ​​the liquid crystal display panel. LCD display device.

6. At least a part of the imaging device is placed in the recess of the light guide plate. The liquid crystal display device according to claim 5.

Images