Liquid crystal display device

Abstract

To provide a display device with high definition and high contrast by accurate local dimming.SOLUTION: A liquid crystal display device includes a display panel and a backlight. The backlight includes a light source and an optical sheet group. The light source includes a light source substrate 61, and an LED 60 disposed on the light source substrate 61. The light source is sectioned into segments in a plan view. In the segment, at least one LED 60 exists. The segment is surrounded by a multilayer structure of a lower reflection wall 80 and an upper reflection wall 90.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a display device having a backlight, and more particularly to a display device that uses local dimming to enable a high contrast screen. [Background technology]

[0002] In a liquid crystal display device, a TFT substrate on which pixel electrodes and thin film transistors (TFTs) are formed in a matrix and an opposing substrate are disposed opposite the TFT substrate, with a liquid crystal layer sandwiched between the TFT substrate and the opposing substrate. Images are formed by controlling the light transmittance of the liquid crystal molecules for each pixel.

[0003] On the other hand, in an organic EL display device, pixels each having a light-emitting element made of an organic EL layer, a driving TFT, a switching TFT, etc. are formed in a matrix, and an image is formed by controlling the light emission intensity of the organic EL layer for each pixel. Since an organic EL display device is a self-emitting element, it has excellent image contrast.

[0004] However, because the pixel size can be made smaller in LCD devices, LCD devices have superior definition. Therefore, local dimming has been developed as a method for improving the contrast of LCD devices. Prior art related to local dimming is, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-074264 Summary of the Invention [Problem to be solved by the invention]

[0006] Display devices for VR (Virtual Reality) and medical use require images with higher resolution and contrast. When using local dimming in such display devices, more precise control of the local dimming is also required.

[0007] In order to perform local dimming more effectively and improve contrast in such a display device, it is necessary, for example, to reduce the area of ​​the segment that serves as the unit of local dimming and to prevent the light of each segment from reaching adjacent segments.

[0008] Furthermore, if the area of ​​a segment is reduced, it becomes difficult to place multiple LEDs in the segment. On the other hand, if only one LED is placed in each segment, it becomes difficult to uniform the brightness distribution, and the LED can be seen from the screen side. If a diffusion sheet is placed to address this issue, for example, the diffusion sheet will cause the light from each segment to leak into adjacent segments.

[0009] An object of the present invention is to solve such problems, to effectively perform local dimming, and to realize a high-definition, high-contrast screen in a display device having a backlight. [Means for solving the problem]

[0010] The present invention is intended to solve the above problems, and the main specific means are as follows.

[0011] (1) A liquid crystal display device having a display panel and a backlight, the backlight having a light source and a group of optical sheets, the light source having a light source substrate and an LED arranged on the light source substrate, the light source being divided into segments when viewed in a plane, each segment having at least one of the LEDs, and the segment being surrounded by a laminated structure of a lower reflective wall and an upper reflective wall 90.

[0012] (2) The liquid crystal display device according to (1), wherein the LED is covered with a transparent resin.

[0013] (3) The liquid crystal display device according to (2), wherein the thickness of the transparent resin is equal to or greater than the height of the lower reflecting wall.

[0014] (4) The liquid crystal display device according to (1), wherein the width of the lower reflecting wall is equal to or greater than the height of the lower reflecting wall.

[0015] (5) The liquid crystal display device according to (1), wherein the width of the upper reflecting wall is equal to or greater than the height of the upper reflecting wall.

[0016] (6) The liquid crystal display device according to (1), wherein the lower reflection wall and the upper reflection wall are formed of a silicone resin containing a reflective pigment.

[0017] (7) The liquid crystal display device according to (2), wherein the transparent resin is made of a silicone resin.

[0018] (8) The liquid crystal display device described in (2), characterized in that a group of optical sheets is arranged on the upper reflective wall, and the area surrounded by the transparent resin, the upper reflective wall, and the group of optical sheets forms a space. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a plan view of a liquid crystal display device. [Diagram 2] FIG. 1 is a cross-sectional view of a liquid crystal display device. [Diagram 3] FIG. 11 is a plan view showing an example of a segment in a liquid crystal display device in a local dimming operation. [Figure 4] FIG. 11 is a plan view of Comparative Example 1 in which four LEDs are arranged in a segment. [Diagram 5] FIG. 11 is a cross-sectional view of Comparative Example 1 in which four LEDs are arranged in a segment. [Figure 6]FIG. 13 is a plan view of Comparative Example 2 in which one LED is arranged in a segment. [Figure 7] FIG. 11 is a cross-sectional view of Comparative Example 2 in which one LED is arranged in a segment. [Figure 8] FIG. 11 is a plan view showing a segment of Comparative Example 3. [Figure 9] FIG. 11 is a cross-sectional view showing a segment of Comparative Example 3. [Figure 10] FIG. 2 is a plan view showing a segment according to the first embodiment of the present invention. [Figure 11] FIG. 2 is a cross-sectional view showing a segment according to the first embodiment of the present invention. [Figure 12] FIG. 11 is a cross-sectional view showing another configuration for producing the effects of the first embodiment. [Figure 13] 1A to 1C are cross-sectional views showing a first process for realizing the structure of Example 1. [Figure 14] FIG. 4 is a cross-sectional view showing a second process. [Figure 15] FIG. 4 is a cross-sectional view showing a third process. [Figure 16] FIG. 11 is a cross-sectional view showing a fourth process. [Figure 17] FIG. 11 is a cross-sectional view showing a fifth process. [Figure 18] FIG. 11 is a cross-sectional view showing a sixth process. [Figure 19] FIG. 13 is a cross-sectional view showing a seventh process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be described in detail below with reference to examples. EXAMPLES

[0021] Fig. 1 is a plan view showing an example of a liquid crystal display device. In Fig. 1, a TFT substrate 100 and a counter substrate 200 are bonded with a sealant 16, and liquid crystal is sandwiched between them. A display area 14 is formed in an area where the TFT substrate 100 and the counter substrate 200 overlap. In the display area 14, scanning lines 11 extend in the horizontal direction (x direction) and are arranged in the vertical direction (y direction). Video signal lines 12 extend in the vertical direction and are arranged in the horizontal direction. Pixels 13 are formed in an area surrounded by the scanning lines 11 and the video signal lines 12.

[0022] 1, the portion where the TFT substrate 100 does not overlap with the counter substrate 200 is a terminal region 15. A flexible wiring board 17 is connected to the terminal region 15 in order to supply power and signals to the liquid crystal display panel. A driver IC that drives the liquid crystal display panel is mounted on the flexible wiring board 17. A backlight is disposed on the rear side of the TFT as shown in FIG.

[0023] Fig. 2 is a cross-sectional view of a liquid crystal display device. In Fig. 2, a backlight 20 is disposed on the back surface of a liquid crystal display panel 10. The liquid crystal display panel 10 has the following configuration. That is, a counter substrate 200 on which a black matrix and a color filter are formed is disposed opposite a TFT substrate 100 on which pixel electrodes, common electrodes, TFTs, scanning lines, video signal lines, etc. are formed. The TFT substrate 100 and the counter substrate 200 are bonded to each other at their peripheries by a sealant 16, and liquid crystal 300 is enclosed inside.

[0024] The liquid crystal molecules are initially aligned by alignment films formed on the TFT substrate 100 and the counter substrate 200. When a voltage is applied between the pixel electrode and the common electrode, the liquid crystal molecules rotate, and an image is formed by controlling the light from the backlight 20 for each pixel. Since the liquid crystal 300 can only control polarized light, a lower polarizer 101 is disposed below the TFT substrate 100, and only the polarized light is incident on the liquid crystal 300. The light modulated by the liquid crystal 300 is analyzed by the upper polarizer 201, and the image is visually recognized.

[0025] In Fig. 2, a backlight 20 is disposed on the back surface of a liquid crystal display panel. The backlight 20 has a configuration in which a light guide plate 40 is disposed on a light source 30, and an optical sheet group 50 is disposed on the light guide plate 40. Fig. 2 is an example, and the light guide plate 40 is not essential. For example, Example 1 described in this specification describes an example in which the light guide plate 40 is not used.

[0026] The light guide plate 40 in Fig. 2 is made of a transparent resin and serves to properly set the distance between the light source 30 and the liquid crystal display panel 10. The light guide plate 40 in Fig. 2 also serves to homogenize the light from the LED, which is a point light source, by reflecting the light incident on the light guide plate 40 at the interface.

[0027] A group of optical sheets 50 is disposed on the light guide plate 40. The group of optical sheets 50 may include a prism sheet, a diffusion sheet, or the like. In addition, in order to obtain white light using a blue LED or the like as a light source, a color conversion sheet in which phosphor is dispersed in a resin sheet or a sheet using quantum dots may be used. Also, in order to improve the efficiency of using light from the backlight 20, a polarizing reflection sheet may be used. The type of optical sheet to be used or the number of such optical sheets to be used is determined by the display device.

[0028] When an image is displayed on a liquid crystal display device, the bright areas transmit the backlight and the dark areas block the backlight. The contrast of the image is defined by the ratio of the bright areas to the dark areas. In liquid crystal display devices, the dark areas are formed by blocking the light from the backlight using liquid crystals. However, the liquid crystals do not completely block the backlight, and some light leaks through. This reduces the contrast.

[0029] Local dimming makes it possible to display deep black by not irradiating the backlight on dark areas. Therefore, a high contrast can be achieved. FIG. 3 is an example of a liquid crystal display device showing a form of local dimming. FIG. 3 is a plan view of the liquid crystal display device, and the configuration is the same as that explained in FIG. 1. In FIG. 3, the display area 14 is divided by segments 141. The dotted lines in FIG. 3 indicate the boundaries of the segments 141, but this is shown for convenience, and the liquid crystal display panel does not have such boundaries. The light sources in the backlight are arranged at positions corresponding to the respective segments.

[0030] In Fig. 3, segment (4, 2) is a bright area, and segment (5, 2) is a dark area. With local dimming, the light source in segment (4, 2), i.e., the LED, is turned on, and the light source in segment (5, 2), i.e., the LED, is not turned on. Then, the black formed in segment (5, 2) is a deep black display, and high contrast is achieved.

[0031] However, since there are no boundaries between the segments, depending on the luminance distribution of the segments, for example, the light from segment (4, 2) may reach segment (5, 2). If this happens, the backlight will also illuminate segment (5, 2) which should display black, and the effect of local dimming will not be fully achieved.

[0032] 4 and 5 are comparative examples showing the configuration of a backlight for reducing such problems. FIG. 4 is a plan view showing the arrangement of LEDs 60, which are light sources, in each segment 141 in a backlight. Hereinafter, the light source will be expressed as LEDs 60. In FIG. 4, each segment 141 is divided by a dotted line. However, this dotted line is for convenience only, and there are no actual dividers. The size of each segment is 4 mm square or less, and in the case of FIG. 5, it is, for example, 2 mm square. The size of the segments 141 in the following examples is similar.

[0033] 4, four LEDs 60 are arranged in each segment 141. That is, by arranging four LEDs 60 in a segment 141, the brightness of each LED can be reduced. As a result, the amount of light leaking into adjacent segments can also be reduced.

[0034] Fig. 5 is a cross-sectional view of a backlight in Comparative Example 1. In Fig. 5, LEDs 60 are arranged on a light source substrate 61, and transparent resin 62 is formed to cover the LEDs 60. A blue LED is used for the LEDs 60. For example, an acrylic resin or a silicone resin is used for the transparent resin 62. The transparent resin 62 is for protecting the LEDs 60 and the electrodes and wiring formed on the light source substrate 61. The dotted lines drawn on the light source substrate 61 in Fig. 5 indicate the boundaries of segments for the sake of convenience.

[0035] The light guide plate 40 is disposed on the transparent resin 62. The light guide plate 40 is transparent, but has the function of reflecting light incident on the light guide plate 40 at the interface and homogenizing the light from the LEDs 60. The color conversion sheet 6 is disposed on the light guide plate 40. The color conversion sheet 51 is a transparent resin sheet in which phosphors that receive blue light and emit yellow light are dispersed, and the light that passes through the color conversion sheet 51 becomes white light. The thickness of the color conversion sheet 51 is, for example, 50 to 70 microns.

[0036] A prism sheet 52 is disposed on the color conversion sheet 51. The prism sheet 52 is made up of prisms with triangular cross sections extending in the y direction and arranged in the x direction. The role of the prism sheet 52 is to improve the light utilization efficiency by directing the light emitted in an oblique direction from the main surface of the color conversion sheet 51 in a direction perpendicular to the main surface of the color conversion sheet 51. In FIG. 5, there is only one prism sheet 52, but a prism sheet having a prism array extending in a direction perpendicular to the prism array of the prism sheet 52 in FIG. 5 may be added. The thickness of the prism sheet is, for example, 50 microns for the thickness of the prism array portion (i.e., the height of the prism) and 70 microns for the thickness of the base material portion, totaling about 120 microns.

[0037] In the configurations of Figures 4 and 5, four LEDs 60 are arranged per segment. Therefore, the brightness of each LED 60 can be reduced, and light leakage to adjacent segments can be reduced. However, arranging four LEDs 60 per segment may be problematic in terms of cost. Also, when the size of the segments is reduced, arranging multiple LEDs in each segment may be problematic in terms of space.

[0038] 6 and 7 show Comparative Example 2 in which one LED 60 is arranged in each segment 141. Fig. 6 is a plan view showing the arrangement of LEDs 60, which are light sources, in each segment 141 in a backlight. In Fig. 6, each segment 141 is divided by a dotted line. However, this dotted line is for convenience only, and there is no actual division.

[0039] 6, one LED 60 is disposed in each segment 141. The luminance of the entire segment 141 is covered by one LED 60, so the luminance of the LED 60 is much higher than that of Comparative Example 1. Furthermore, if the luminance of the LED 60, which is a point light source, is high, a portion with high luminance will be generated in the portion corresponding to the LED when viewed from the screen side. To address this, it is necessary to dispose a diffusion sheet 53 in the optical sheet group 50, as will be described later.

[0040] Fig. 7 is a cross-sectional view of a backlight in Comparative Example 2. In Fig. 7, LEDs 60 are arranged on a light source substrate 61, and transparent resin 62 is formed to cover the LEDs 60. The configuration of the light source is the same as that in Fig. 5, except that there is only one LED 60 per segment.

[0041] A light guide plate 40 is disposed on a transparent resin 62. The role of the light guide plate 40 is the same as that described in Comparative Example 1. A color conversion sheet 51 is disposed on the light guide plate 40. The role of the color conversion sheet 51 is the same as that described in Comparative Example 1. In FIG. 7, a diffusion sheet 53 is disposed on the color conversion sheet 51. The diffusion sheet 53 is for diffusing the light from the light source 60 to make the brightness uniform. The thickness of the diffusion sheet 53 is, for example, 50 to 70 microns.

[0042] That is, since segment 141 has only one LED 60, it is necessary to increase the brightness of LED 60 in order to supply sufficient light to entire segment 141. If this is done, the part on the screen corresponding to LED 60 will appear to shine like a dot. Hereinafter, this dot-like shine will also be referred to as a bright spot. The role of diffusion sheet 53 is to diffuse light so that the bright spot corresponding to LED 60 is not visible.

[0043] However, because this diffusion sheet 53 diffuses light, it also has the effect of diffusing the light from the LEDs 60 to adjacent segments. In other words, the configuration in Fig. 7 has the problem that the light from the LEDs 60 leaks to adjacent segments not only through the transparent resin 62 covering the LEDs 60, the light guide plate 40, and the color conversion sheet 51, but also through the diffusion sheet 53. The configuration and function of the prism sheet in Fig. 7 are the same as those explained in Fig. 5.

[0044] 8 and 9 show the configuration of a backlight according to Comparative Example 3. FIG. 8 is a plan view showing the arrangement of LEDs 60, which are light sources, in each segment 141 in the backlight. In Comparative Example 3, the LEDs 60 are also blue LEDs. In FIG. 8, each segment 141 is separated by partition plates 70. Partition plates 70 are made of thin resin plates arranged in a crisscross pattern. The size of each segment 141 is 4 mm square or less, for example 2 mm square.

[0045] 8, one LED 60 is arranged in each segment 141. Therefore, although the brightness of the LED 60 is high, the configuration of Example 1 has a small amount of light leaking from the LED 60 to adjacent segments, as will be described later, and therefore the brightness of the LED can be made smaller than that of the comparative example 2.

[0046] FIG. 9 is a cross-sectional view of a backlight in Comparative Example 3. In FIG. 9, LEDs 60 are arranged on a light source substrate 61. In FIG. 9, a protective film 63 is formed to cover the wiring and electrodes formed on the light source substrate 61. This configuration is significantly different from Comparative Examples 1 and 2. That is, in the configuration of Comparative Example 3, the LEDs 60 are not covered with a transparent resin 62, and the emission area of ​​light from the LEDs 60 exists above the protective film 63. Therefore, the protective film 63 does not need to be transparent. That is, in Example 1, the transparent resin 62 in Comparative Examples 1 and 2 does not exist.

[0047] 9, the protective film 63 is formed of, for example, a white resin, and the higher the reflectance, the better. Such a resin can be formed of, for example, a silicone resin. That is, a part of the light emitted from the LED 60 is reflected by the partition plate 70 and the light guide plate 40 and enters the protective film 63 side, but if the reflectance of the protective film 63 is high, this light can be reflected again and directed toward the liquid crystal display panel.

[0048] In Fig. 9, a partition plate 70 is present at the boundary between the segments, and this partition plate 70 is disposed on top of the protective film 63. The partition plate 70 is made of white PET (Polyethylene terephthalate). Light emitted obliquely from the LEDs 60 is reflected by the partition plate 70 and directed toward the light guide plate 40. A transparent light guide plate 40 is disposed on top of the partition plate 70. The light incident on the light guide plate 40 is reflected within the light guide plate 40, reducing uneven brightness caused by the presence of the partition plate 70.

[0049] In Comparative Examples 1 and 2, light from the LED 60 leaks through the transparent resin 62 that covers the LED to adjacent segments, but in Comparative Example 3, as shown in FIG. 9, the light emitted from the LED 60 is reflected by the partition plate 70 and does not leak to adjacent segments.

[0050] In FIG. 9, a color conversion sheet 51 is disposed on the light guide plate 40. The configuration and function of the color conversion sheet 51 are the same as those described in Comparative Example 1. A diffusion sheet 53 is disposed on the color conversion sheet 51. The role of the diffusion sheet 53 is to make the bright spots of the LEDs 60 invisible from the screen side. However, since the light from the LEDs 60 is diffused by the diffusion sheet 53, this diffused light leaks into adjacent segments. Incidentally, in FIG. 9, the partition plate 70 prevents light from leaking into adjacent segments, so the intensity of the light from the LEDs 60 can be reduced, and the effect of the light diffused by the diffusion sheet 53 on adjacent segments can be reduced accordingly.

[0051] In Fig. 9, prism sheet 52 is disposed on diffusion sheet 53, similarly to Comparative Examples 1 and 2. The configuration and action of prism sheet 52 are also similar to those described in Comparative Examples 1 and 2. Note that the optical sheet group in Fig. 9 is an example, and other optical sheets may be used.

[0052] The partition plate 70 is made by combining white PET plates with a thickness of about 0.2 mm in a crisscross pattern. Segments 141 are formed in the area surrounded by the partition plate 70. The size of the segment 141 is, for example, 2 mm square, and the height of the partition plate 70 is, for example, 1 mm.

[0053] The problem with Comparative Example 3 is that it requires the partition plate 70 in the form of parallel crosses. That is, it requires costs for manufacturing the partition plate and for mounting the partition plate.

[0054] Figures 10 and 11 show the configuration of a backlight according to Example 1 of the present invention. Figure 10 is a plan view showing the arrangement of LEDs 60, which are light sources, in each segment 141 in the backlight. In this example, the LEDs 60 are blue LEDs. In Figure 10, each segment 141 is partitioned by a lower reflective wall 80 and an upper reflective wall 90 that are stacked in two stages. The size of each segment 141 is 4 mm square or less, for example 2 mm square.

[0055] 10, one LED 60 is arranged in each segment 141. Therefore, although the brightness of the LED 60 is high, in the configuration of Example 1, as will be described later, the amount of light leaking from the LED 60 to adjacent segments is small, so that the brightness of the LED can be made smaller than that in Comparative Example 2.

[0056] Fig. 11 is a cross-sectional view of the backlight in Example 1. Each segment is separated by a lower reflective wall 80. In Fig. 11, in each segment, LEDs 60 are arranged on a light source substrate 61. A transparent resin 62 is formed to cover the LEDs 60, wiring, electrodes, etc.

[0057] 11, a transparent resin 62 is formed to cover the LEDs 60, wiring, electrodes, etc. formed on a light source substrate 61. The transparent resin 62 also covers the side surface of the lower reflecting wall 80, but the transparent resin 62 is almost the same as the upper surface of the lower reflecting wall 80. An upper reflecting wall 90 is formed overlapping the lower reflecting wall 80. The layered structure of the lower reflecting wall 80 and the upper reflecting wall 90 serves as a partition between the segments.

[0058] For example, a silicone resin is used for the transparent resin 62. The lower reflective wall 80 and the upper reflective wall 90 used as partitions are formed from a silicone resin containing a highly reflective white pigment.

[0059] 11, color conversion sheet 51 is disposed on top of upper reflecting wall 90. The configuration and function of color conversion sheet 51 are the same as those explained in Comparative Example 1. The area surrounded by upper reflecting wall 90, transparent resin 62, and color conversion sheet 51 forms a space. Light leaving LED 60 is reflected by lower reflecting wall 80 etc. within transparent resin 62, or refracted, reflected etc. at the interface between transparent resin 62 and space 95, and light going in various directions is emitted from transparent resin 62.

[0060] Part of the light incident on the space 95 is reflected by the upper reflecting wall 90, and is further reflected or refracted at the interface between the space 95 and the color conversion sheet 51, resulting in the light being mixed further and traveling in various directions. Therefore, the light guide plate 40 used in the comparative examples 1 to 3 is not used in FIG. 11. Also, the distance between the LED 60, which is the light source, and the liquid crystal display panel 10 can be adjusted by changing the height of the lower reflecting wall 80 or the upper reflecting wall 90. However, the conductive film 40 may be used in this embodiment as well, if necessary.

[0061] In FIG. 11, a prism sheet 52 is placed on a color conversion sheet 51. The role of the prism sheet 52 is as explained in Comparative Example 1 and the like. In FIG. 11, a diffusion sheet is not used. In the configuration of FIG. 11, the action of the lower reflection wall 80 and the upper reflection wall 90 can reduce light leakage to adjacent segments, so that it is possible to keep the light output of the LEDs 60 low compared to Comparative Example 2 and the like. However, a diffusion sheet can also be used as necessary. In the configuration of FIG. 11, the light intensity of the LEDs 60 can be reduced, so even if a diffusion sheet is used, the effect on adjacent segments can be kept low.

[0062] The feature of FIG. 11 is that the partitions of each segment are formed with a two-layer structure of a lower reflection wall 80 and an upper reflection wall 90. In FIG. 11, the thickness h2 of the transparent resin 62 is greater than the height h3 of the LEDs 60. The lower reflection wall 80 reflects light from the LEDs 60 that is heading toward an adjacent segment within the transparent resin 62. Furthermore, the upper reflection wall 90 reflects light that is heading toward an adjacent segment in the space 95. Therefore, the configuration of FIG. 11 can efficiently prevent light leakage into adjacent segments.

[0063] A configuration that can have the same effect as that in FIG. 11 is shown in FIG. 12. In FIG. 12, the partitions of each segment are configured with only one stage of reflecting wall 85. The other configurations are the same as those in FIG. 11. In the configuration of this embodiment, it is important to accurately set the height h1 of the reflecting wall 85 and the thickness h2 of the transparent resin 62 in order to obtain certain optical characteristics. However, since both the transparent resin 62 and the reflecting wall 85 are made of resin, it is difficult to accurately set the dimensions as in FIG. 12 in terms of the process. To accurately realize the configuration as in FIG. 12, accurate process control is required, which ultimately increases the manufacturing cost.

[0064] In the first embodiment of the present invention, the partitions of the segments are formed by laminating the lower reflecting wall 80 and the upper reflecting wall 90, so that the necessary dimensions, i.e., the heights of the lower reflecting wall 80 and the upper reflecting wall 90 and the thickness of the transparent resin 62, can be stably and accurately set without requiring a complicated process. Figures 13 to 19 show an example of a process for realizing the configuration of the light source of the first embodiment. The LEDs 60 are omitted in Figures 13 to 19.

[0065] Fig. 13 shows the first process, in which the lower reflective wall 80 is applied to the light source substrate 61 by screen printing or with a dispenser or the like. The height h4 of the lower reflective wall 80 at this time is greater than the height h2 shown in Fig. 11. Also, the width w2 of the lower reflective wall 80 at this time is smaller than the width w1 of the lower reflective wall 80 shown in Fig. 11. A compression step will be performed in a later process, so the dimensions are set taking this into consideration. After the lower reflective wall 80 is applied, it is dried and provisionally cured.

[0066] 14 shows the second process, in which transparent resin is poured into each segment. The viscosity of the transparent resin is appropriately controlled to level the surface so that it is almost flush with the lower reflective wall 80 after drying. The transparent resin 62 is then dried and temporarily cured. In this state, the height of the lower reflective wall 80 and the thickness of the transparent resin 62 are h4, and the width of the lower reflective wall 80 is w2.

[0067] FIG. 15 is a cross-sectional view showing the third process in which pressure is applied from above to the lower reflection wall 80 and the transparent resin 62 by the pressure plate 500. In the state shown in FIG. 15, the lower reflection wall 80 and the transparent resin 62 are not yet in a provisionally cured state, so when pressure is applied, their thickness decreases. However, the width of the lower reflection wall 80 increases as a result of the pressure being applied. FIG. 16 is a cross-sectional view showing the fourth process after the lower reflection wall 80 and the transparent resin 62 are crushed by the pressure plate 500. In this state, baking is performed to thermally cure the lower reflection wall 80 and the transparent resin 62. After the thermal curing is completed, the height h2 and width w1 of the lower reflection wall 80 and the thickness h2 of the transparent resin 62 are the same as in FIG. 11.

[0068] Fig. 17 is a cross-sectional view showing the fifth process in which the upper reflection wall 90 is applied by screen printing or a dispenser or the like onto the hardened lower reflection wall 80. The shape of the upper reflection wall 90 in Fig. 17 is the same as the shape of the lower reflection wall 80 in Fig. 13. In the state shown in Fig. 17, the upper reflection wall 90 is dried and temporarily hardened.

[0069] 18 shows the sixth process, in which pressure is applied to the upper reflective wall 90 in the partially cured state by a pressure plate 500. At this time, since the lower reflective wall 80 and the transparent resin 62 are completely solidified, the height does not change, and only the upper reflective wall 90 in the partially cured state is crushed. As a result, the height of the upper reflective wall 90 decreases.

[0070] 19 is a cross-sectional view showing the seventh process in which the upper reflective wall 90 is compressed to a predetermined size and then thermally cured. As a result, the lower reflective wall 80, the transparent resin 62, and the upper reflective wall 90 all finish curing and assume a stable shape. The states of the lower reflective wall 80, the transparent resin 62, and the upper reflective wall 90 in FIG. 19 are the same as those in FIG. 11.

[0071] In the above process, the dimensions are determined by compressing the lower reflecting wall 80 and the transparent resin 62 in a partially cured state with a pressure plate, so that the thickness or height can be determined accurately and reproducibly. In FIG. 19, the dimensions of both the lower reflecting wall 80 and the upper reflecting wall 90 are determined by squashing them with a pressure plate 500. When squashed, the height of both the lower reflecting wall 80 and the upper reflecting wall 90 decreases from h4 to h2, and the width increases from w2 to w1. As a result, in the lower reflecting wall 80 or the upper reflecting wall 90, the width w1 is often greater than the height h2.

[0072] 14, when the transparent resin 62 is applied, if the viscosity of the transparent resin 62 is high, the thickness of the transparent resin 62 may slightly exceed the height of the lower reflection wall 80. In this case, a small gap is generated between the lower reflection wall 80 and the upper reflection wall 90, but since the upper reflection wall 90 with width w1 is disposed above this gap, light leakage is unlikely to become a major problem.

[0073] In the above description, the lower reflecting wall 80 and the upper reflecting wall 90 are described as having the same height and width, but this is not limited thereto, and one of the walls may be made taller than the other, if necessary.

[0074] In this embodiment, the height of the lower reflection wall 80 and the thickness h4 of the transparent resin 62 are reduced to the height and thickness h2 after compression by applying pressure from above with the pressure plate 500 in the third process, but the height of the lower reflection wall 80 and the thickness of the transparent resin may be created to h2 in the first and second processes. In this case, the pressure applied by the pressure plate 500 in the third process is only enough to flatten the surface of the transparent resin 62.

[0075] As described above, by using the present invention, local dimming can be effectively performed, and a liquid crystal display device with high contrast can be manufactured. [Explanation of symbols]

[0076] 10...display panel, 11...scanning line, 12...video signal line, 13...pixel, 14...display area, 15...terminal area, 16...sealing material, 17...flexible wiring board, 20...backlight, 30...light source, 40...light guide plate, 50...optical sheet group, 51...color conversion sheet, 52...prism sheet, 53...diffusion sheet, 60...blue LED, 61...light source substrate, 62...transparent resin, 63...white protective film, 70...partition plate, 80...lower reflecting wall, 90...upper reflecting wall, 95...space, 100...TFT substrate, 101...lower polarizing plate, 141...segment, 200...opposite substrate, 201...upper polarizing plate, 300...liquid crystal, 500...pressure plate

Claims

1. A display device having a display panel and a backlight, The backlight includes a light source and an optical sheet group. The light source includes a light source substrate and an LED disposed on the light source substrate, The light source is divided into segments in a plan view, At least one of the LEDs is present in the segment; The liquid crystal display device is characterized in that the segments are surrounded by a laminated structure of a lower reflecting wall and an upper reflecting wall (90).

2. 2. The liquid crystal display device according to claim 1, wherein the LED is covered with a transparent resin.

3. 3. The liquid crystal display device according to claim 2, wherein the thickness of the transparent resin is equal to or greater than the height of the lower reflection wall.

4. 2. The liquid crystal display device according to claim 1, wherein the width of the lower reflective wall is equal to or greater than the height of the lower reflective wall.

5. 2. The liquid crystal display device according to claim 1, wherein the width of the upper reflecting wall is equal to or greater than the height of the upper reflecting wall.

6. 2. The liquid crystal display device according to claim 1, wherein the lower reflection wall and the upper reflection wall are made of a silicone resin containing a reflective pigment.

7. 3. The liquid crystal display device according to claim 2, wherein the transparent resin is made of a silicone resin.

8. 3. The liquid crystal display device according to claim 2, wherein a group of optical sheets is arranged on the upper reflecting wall, and an area surrounded by the transparent resin, the upper reflecting wall and the group of optical sheets forms a space.

9. 8. The liquid crystal display device according to claim 7, wherein the group of optical sheets includes a color conversion sheet.

10. 8. The liquid crystal display device according to claim 7, wherein the group of optical sheets includes a prism sheet.

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