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 and a light guide plate 120 having a side 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 and a protrusion 140 located on the first main surface 126, the outer circumference of which surrounds the recess 130 when viewed from above. When the protrusion 140 is viewed in cross-section perpendicular to the first main surface 126, the protrusion 140 has a trapezoidal shape.

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 and a convex portion disposed on the first main surface, whose outer circumference surrounds the recess when viewed from above. When the protrusion is viewed in cross-section perpendicular to the first main surface, the protrusion has a trapezoidal shape.

[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 light guide plate has a recess positioned on the second main surface and a convex portion positioned on the first main surface from which light from the light source is emitted, with its outer circumference surrounding the recess when viewed from above. When the convex portion is viewed in cross-section, it has a trapezoidal shape, thus enabling high 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]It 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 line A-A. [Figure 5] It is a schematic diagram for explaining light guiding in a light guide plate having only concave portions. [Figure 6] It is a schematic diagram for explaining light guiding in a light guide plate according to Embodiment 1. [Figure 7] It is a plan view showing the dimensions of a light guide plate in a simulation according to Embodiment 1. [Figure 8] It is a cross-sectional view showing the dimensions of a light guide plate in a simulation according to Embodiment 1. [Figure 9] It is a cross-sectional view showing the dimensions of a light guide plate in a simulation according to Comparative Example 1. [Figure 10] It is a cross-sectional view showing the dimensions of a light guide plate in a simulation according to Comparative Example 2. [Figure 11] It is a cross-sectional view showing the dimensions of a light guide plate in a simulation according to Comparative Example 3. [Figure 12] It is a diagram showing the luminance distribution of an emission surface in a simulation according to Embodiment 1. [Figure 13] It is a diagram showing the luminance distribution of an emission surface in a simulation according to Comparative Example 1. [Figure 14] It is a diagram showing the luminance distribution of an emission surface in a simulation according to Comparative Example 2. [Figure 15] It is a diagram showing the luminance distribution of an emission surface in a simulation according to Comparative Example 3. [Figure 16] It is a diagram showing the luminance distribution on a line of an emission surface in a simulation according to Embodiment 1 and Comparative Examples 1 to 3. [Figure 17] It is a diagram showing the luminance distribution of an emission surface in a simulation according to Embodiment 1. [Figure 18] It is a diagram showing the luminance distribution of an emission surface in a simulation according to Comparative Example 1. [Figure 19]The figure showing the luminance distribution of the emission surface in the simulation according to Comparative Example 2. [Figure 20] The figure showing the luminance distribution along the line of the emission surface in the simulation according to Embodiment 1 and Comparative Examples 1 and 2. [Figure 21] The plan view showing the region of the simulation according to Embodiment 1. [Figure 22] The cross-sectional view showing the region of the simulation according to Embodiment 1. [Figure 23] The figure showing the relationship between the angle of the side surface of the convex portion and the ratio of the light rays that are guided through the concave portion according to Embodiment 1. [Figure 24] The cross-sectional view showing the light guide plate according to Embodiment 2. [Figure 25] The cross-sectional view showing the dimensions of the light guide plate in the simulation according to Embodiment 2. [Figure 26] The figure showing the luminance distribution of the emission surface in the simulation according to Embodiment 2. [Figure 27] The figure showing the luminance distribution along the line of the emission surface in the simulation according to Embodiment 2 and Comparative Examples 1 to 3. [Figure 28] The figure showing the luminance distribution of the emission surface in the simulation according to Embodiment 2. [Figure 29] The figure showing the luminance distribution along the line of the emission surface in the simulation according to Embodiment 2 and Comparative Examples 1 and 2. [Figure 30] The figure 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 are guided through the concave portion according to Embodiment 2. [Figure 31] The figure showing the relationship between the diameter of the bottom surface of the convex portion and the ratio of the light rays that are guided through the concave portion according to Embodiment 3. [Figure 32] The figure showing the luminance distribution along the line of the emission surface according to Embodiment 3. [Figure 33] The figure showing the luminance distribution along the line of the emission surface according to Embodiment 3. [Figure 34]This figure shows the relationship between the diameter of the bottom surface of the protrusion and the proportion of light rays that pass through the recess, according to Embodiment 3. [Figure 35] This figure shows the brightness distribution along the line of the emission surface according to Embodiment 3. [Figure 36] This figure shows the brightness distribution along the line of the emission surface according to Embodiment 3. [Figure 37] This is a cross-sectional view showing a modified example, specifically the convex portion and the lens of the imaging device. [Modes for carrying out the invention]

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

[0011] <Embodiment 1> Referring to Figures 1 to 23, 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 (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 is 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 (described later) is 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. The recess 130 is cylindrical. 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] As shown in Figures 1 to 4, the light guide plate 120 has a protrusion 140 on its first main surface 126. When the light guide plate 120 is viewed from above, as shown in Figure 3, the outer circumference 140a of the protrusion 140 surrounds the recess 130. The protrusion 140 has a frustoconical shape and a trapezoidal shape when viewed in cross-section perpendicular to the first main surface 126 (Figures 1 and 4). In addition, the side surface 144 of the protrusion 140 is inclined at an acute angle with respect to the bottom surface 142 of the protrusion 140. As will be described later, it is preferable that the inclination θ of the side surface 144 of the protrusion 140 with respect to the bottom surface 142 of the protrusion 140 is 30° or less.

[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. The optical sheet 160 is provided with through holes 162 corresponding to the protrusions 140.

[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 having only a recess 130 as shown in Figure 5, the thickness D1 of the light guide plate 720 above the recess 130 becomes thinner. As the thickness D1 becomes thinner, the amount of light L1 guided through the light guide plate 720 from the incident surface 122 side to the anti-incident surface 124 side decreases, and 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 (output surface 126) becomes non-uniform.

[0023] On the other hand, in this embodiment, when viewed from above, the outer circumference 140a of the convex portion 140 surrounds the recess 130, so the thickness D1 of the light guide plate 120 above the recess 130 becomes thicker. As the thickness D1 of the light guide plate 120 above the recess 130 increases, as shown in Figure 6, 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 recess 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, and the luminance Lu in region SR of the light guide plate 120 increases, so the uniformity of the luminance distribution of the light guide plate 120 (output surface 126) can be improved.

[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 cylindrical 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 D2 of the light guide plate 120 is 3 mm, the depth DP1 of the recess 130 is 2.0 mm, and the diameter DA1 of the recess 130 is 18 mm. The thickness D1 of the light guide plate 120 above the recess 130 is 1.5 mm. In this simulation, a light absorber (not shown) is placed in the recess 130 instead of the lens portion 410 of the imaging device 400.

[0027] Furthermore, 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°.

[0028] A dot-shaped diffusion layer (not shown) is provided on the second main surface 128, excluding the recess 130. As the diffusion layer pattern, a pattern that generates a uniform luminance distribution on the light guide plate in a light guide plate that does not have recesses 130 or protrusions 140 (hereinafter referred to as pattern A) and a pattern optimized to increase the luminance Lu of the region SR on the emission surface 126 so that the luminance distribution becomes uniform (hereinafter referred to as pattern B) are used.

[0029] 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.

[0030] 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, patterns A and B are used as the patterns of the diffusion layer.

[0031] 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, and no protrusions are provided. The position of the recess 842 is the same as the position 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, patterns A and B are used as the diffuser layer patterns. A light absorber is placed in the recess 842.

[0032] 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, and no protrusions are provided. The position of the recess 862 is the same as the position of the recess 130 in the embodiment. The diameter of the recess 862 is 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, pattern A is used as the pattern of the diffusion layer. A light absorber is placed in the recess 862.

[0033] 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.

[0034] Figures 12 to 15 show the luminance distribution of the embodiment and comparative examples 1 to 3, respectively, using pattern A as the pattern of the diffusion layer. In Figures 12 to 15, the brighter the area, the higher the luminance Lu. Also, in Figures 12 to 15, the hatched areas have a light absorber and the diffusion layer is not provided in the recess 130, so the luminance Lu is zero. The following figures also illustrate this similarly.

[0035] Figure 16 shows the brightness distribution on 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 through holes 822, when the exit surface 126 of Embodiment (Pattern A) and Comparative Examples 1-3 (Pattern A) are viewed from above.

[0036] 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.

[0037] Figures 17 to 19 show the luminance distribution of the embodiment and comparative examples 1 and 2, respectively, using pattern B as the diffusion layer pattern. Figure 20 shows the luminance distribution of the embodiment (pattern B) and comparative examples 1 and 2 (pattern B) when the exit surface 126 is viewed from above, along a straight line (the y1-y1 line shown in Figures 17 to 19) 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 or through holes 822.

[0038] As shown in Figures 17 and 20, in the light guide plate 120 of the embodiment, the uniformity of the brightness distribution can be further improved by optimizing the pattern of the diffusion layer. On the other hand, in Comparative Examples 1 and 2, as shown in Figures 18 to 20, even when the pattern of the diffusion layer is optimized, the brightness Lu in the SR region is low, and sufficient uniformity cannot be obtained.

[0039] As described above, the light guide plate 120 has a recess 130 positioned on the second main surface 128 and a protrusion 140 positioned on the first main surface 126 (emitting surface 126) with its outer circumference 140a surrounding the recess 130, and the protrusion 140 has a trapezoidal shape when viewed in cross-section, so the luminance Lu of the region SR can be increased and the uniformity of the luminance distribution of the light guide plate 120 can be improved.

[0040] Next, the relationship between the angle θ of the side surface 144 of the protrusion 140 and the proportion of light rays that guide beyond the recess 130 was simulated. Specifically, the relationship between the ratio Rt of the number of light rays passing through region R2 (Figures 21 and 22) in the light guide plate 120 immediately after the protrusion 140 and the number of light rays passing through region R1 (Figures 21 and 22) immediately before the protrusion 140, as viewed from the incident surface 122 (side surface 122), and the angle θ was simulated. Except for the value of 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. The pattern of the diffusion layer is pattern A.

[0041] Figure 23 shows the relationship between the angle θ of the side surface 144 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 23, when the angle θ of the side surface 144 is 30° or less, the ratio Rt increases sharply. In other words, by making the angle θ of the side surface 144 30° or less, the number of light rays (amount of light) that guide beyond the recess 130 can be increased. Therefore, it is preferable that the angle θ of the side surface 144 be 30° or less.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] As described above, in the backlight device 200, the outer circumference 140a of the protrusion 140 of the light guide plate 120 surrounds the recess 130 of the light guide plate 120 in a plan view, and when the protrusion 140 is viewed in cross-section, the protrusion 140 has a trapezoidal shape, thus improving the uniformity of the brightness distribution on the emission surface 126 (first main surface 126). Furthermore, since the backlight device 200 emits highly uniform light, the liquid crystal display device 500 can achieve highly uniform display.

[0046] <Embodiment 2> In Embodiment 1, the recess 130 of the light guide plate 120 is cylindrical. The bottom 132 of the recess 130 may be mortar-shaped (frustoconical).

[0047] 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. The light guide plate 120 of this embodiment will now be described.

[0048] The configuration of the light guide plate 120 in this embodiment is the same as that of the light guide plate 120 in Embodiment 1, except for the configuration of the recess 130. The recess 130 of the light guide plate 120 in this embodiment will now be described.

[0049] The recess 130 in this embodiment, like the recess 130 in Embodiment 1, is provided in the region 128a of the second main surface 128 that corresponds to the display area 302 of the liquid crystal display panel 300. In this embodiment, the upper part 134 (the -Y side of the recess 130) of the recess 130 is cylindrically recessed, and the bottom part 132 (the +Y side of the recess 130) is mortar-shaped (frustoconical). In other words, as shown in Figure 24, 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 a result, the width Din for guiding light L2 from the incident surface 122 into the light guide plate 120 on the recess 130 is widened, further increasing the amount of light guided to the region SR on the opposite side of the recess 130 of the light guide plate 720 when viewed from the incident surface 122. Since the amount of light guided to region SR is further increased, the luminance Lu in region SR of the light guide plate 120 can be further increased, and the uniformity of the luminance distribution of the light guide plate 120 (exit surface 126) can be further improved.

[0050] 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 recess 130. First, the configuration of the recess 130 of the light guide plate 120 used in the simulation of this embodiment will be explained.

[0051] In the simulation, the upper part 134 of the recess 130 is cylindrical, and the bottom part 132 of the recess 130 is frustoconical. The depth DP1 of the recess 130 is 2.0 mm, as in Embodiment 1. As shown in Figure 25, the depth DP2 of the bottom part 132 of the recess 130 is 0.5 mm, and the depth DP3 of the upper part 134 is 1.5 mm. 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 is 170°. Since the inclination θ of the side surface 144 of the convex part 140 is 10°, the side surface 138 of the recess 130 and the side surface 144 of the convex part 140 are parallel. In this simulation as well, a light absorber is placed in the recess 130 instead of the lens portion 410 of the imaging device 400. Furthermore, the center line C1 of the recess 130 and the center line C2 of the convex portion 140 coincide.

[0052] The luminance distribution of the light guide plate 120 of this embodiment described above was simulated on the exit surface 126 (first main surface 126). Figure 26 shows the luminance distribution of the light guide plate 120 of this embodiment, using pattern A as the pattern of the diffusion layer. Figure 27 shows the luminance distribution of the light guide plate 120 of this embodiment (pattern A) and comparative examples 1 to 3 (pattern A) of Embodiment 1, when viewed from above, along a straight line (on the y1-y1 line shown in Figures 13 to 15 and 26) 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.

[0053] As shown in Figures 26 and 27, 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.

[0054] Figure 28 shows the luminance distribution of the light guide plate 120 of the embodiment, using pattern B as the pattern of the diffusion layer. Figure 29 shows the luminance distribution of the output surface 126 of this embodiment (pattern B) and comparative examples 1 and 2 (pattern B) of Embodiment 1, when viewed from above, along a straight line (on the y1-y1 line shown in Figures 17, 18, and 28) 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 or through holes 822.

[0055] As shown in Figures 28 and 29, in the light guide plate 120 of this embodiment, the uniformity of the luminance distribution can be further improved by optimizing the pattern of the diffusion layer. On the other hand, in Comparative Examples 1 and 2, even when the pattern of the diffusion layer is optimized, the luminance Lu in the SR region is low, and sufficient uniformity cannot be obtained.

[0056] 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 made parallel. Also, except for the values ​​of the angle φ of side surface 138 and the angle θ of 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. The pattern of the diffusion layer is pattern A.

[0057] Figure 30 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 30, 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.

[0058] As described above, in this backlight device 200, similar to the backlight device 200 of Embodiment 1, the outer circumference 140a of the protrusion 140 of the light guide plate 120 surrounds the recess 130 of the light guide plate 120 in a plan view, and when the protrusion 140 is viewed in cross-section, the protrusion 140 has a trapezoidal shape, thus improving the uniformity of the brightness distribution on the emission surface 126 (first main surface 126). In this backlight device 200, 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, so the brightness Lu of the region SR of the light guide plate 120 can be further increased, further improving the uniformity of the brightness distribution on the emission surface 126. In addition, since the backlight device 200 emits highly uniform light, the liquid crystal display device 500 can achieve highly uniform display.

[0059] <Embodiment 3> In Embodiment 1 and 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.

[0060] Figure 31 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 32 and 33 show the luminance distribution along the line of the exit surface 126 in the light guide plate 120 of Embodiment 1. The luminance distribution in Figures 32 and 33 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.

[0061] Figures 31 to 33 are based on simulations using pattern B as the diffusion layer pattern, with the inclination θ of the side surface 144 of the protrusion 140 set to 10° or 20°, and the diameter DA2 of the bottom surface 142 of the protrusion 140 varied. Other simulation conditions are the same as those for the simulation in Embodiment 1. The diameter DA1 of the recess 130 is 18 mm (DA1 = 18 mm).

[0062] As shown in Figure 31, 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.

[0063] Furthermore, as shown in Figures 32 and 33, 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 1, the size of the through holes 162 of the optical sheet 160 increases with the size of the diameter DA2. Therefore, if the diameter DA2 is too large, there is a risk that the brightness Lu around the recesses 130 will decrease. Accordingly, the size of the diameter DA2 is appropriately selected according to the application, required specifications, etc.

[0064] Figure 34 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 35 and 36 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 35 and 36 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.

[0065] Figures 34 to 36 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).

[0066] As shown in Figure 34, in the light guide plate 120 of Embodiment 2, the larger the diameter DA2 of the bottom surface 142 of the protrusion 140 is than the diameter DA1 of the recess 130, the more light rays can be guided beyond the recess 130. Therefore, it is preferable that the diameter DA2 is larger than the diameter DA1.

[0067] Furthermore, as shown in Figures 35 and 36, 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.

[0068] <Variation> While embodiments have been described above, this disclosure can be modified in various ways without departing from its essence.

[0069] 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.

[0070] In Embodiment 1, the recess 130 of the light guide plate 120 is cylindrical. However, in Embodiment 1, the shape of the recess 130 is not limited to a cylindrical shape. For example, the shape of the recess 130 may be a rectangular prism.

[0071] In Embodiment 2, 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.

[0072] 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.

[0073] 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. In Embodiment 1, as shown in Figure 37, 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 144 of the convex portion 140. This allows the imaging device 400 to image the target while suppressing the effects of light refraction or reflection caused by the side surface 144 which is inclined with respect to the first main surface 126. In Embodiment 2, 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 at least one of the side surface 144 of the convex portion 140 and the side surface 138 of the recess 130.

[0074] 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.

[0075] 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.

[0076] 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]

[0077] 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 disposed on the second main surface and a protrusion disposed on the first main surface, the outer circumference of which surrounds the recess when viewed from above. When the protrusion is viewed in cross-section perpendicular to the first main surface, the protrusion has a trapezoidal shape. Backlight device.

2. 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. 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 1.

4. The inclination of the side surface of the protrusion with respect to the bottom surface of the protrusion is 30° or less. 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