JP5363874B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device using an LED as a backlight, and more particularly to a relatively large liquid crystal display device used in a TV or the like that is thin and consumes less power.

  In a liquid crystal display device, there are a TFT substrate in which pixel electrodes and thin film transistors (TFTs) are formed in a matrix, and a counter substrate in which color filters are formed at locations corresponding to the pixel electrodes of the TFT substrate, facing the TFT substrate. The liquid crystal is sandwiched between the TFT substrate and the counter substrate. An image is formed by controlling the light transmittance of the liquid crystal molecules for each pixel.

  Liquid crystal display devices are used in various fields because they can be made thin and light. Since the liquid crystal itself does not emit light, a backlight is disposed on the back of the liquid crystal display panel. A fluorescent tube has been used as a backlight in a liquid crystal display device having a relatively large screen such as a television. However, LEDs (Light Emitting Diodes) have started to be used in order to make the liquid crystal display device thinner or to increase the color display area.

  There are two types of backlight light source arrangements: a direct type that places the light source directly under the liquid crystal display panel and a sidelight type that places the light source on the side of the light guide plate. In order to increase the brightness of the screen, a direct light source has been often used.

  Although it has been performed by a conventional cathode ray tube TV or the like, it is not always necessary to make the screen brightness uniform in the application of the TV or the like, and the peripheral luminance can be made smaller than the central luminance. In “Patent Document 1”, a fluorescent tube is used as a light source of a direct type backlight, and the density of the dot pattern formed on the reflection surface is changed between the center and the periphery, whereby the brightness of the screen periphery is changed from the brightness of the screen center. A configuration for reducing the size is also described. In addition, “Patent Document 1” describes a configuration in which the brightness of a screen is adjusted by using an LED as a light source of a direct type backlight and changing the density of the LED depending on a place.

  In “Patent Document 2”, in a relatively small liquid crystal display device, a sidelight type backlight is used, and the density of LEDs arranged on the side of the light guide plate is changed between the vicinity of the center and the vicinity of the periphery. It describes that the brightness of the screen is adjusted.

  “Patent Document 3” describes a configuration in which a plurality of seamless light guide plates are formed in a first direction in a sidelight type light guide plate. The light guide plate described in “Patent Document 3” is a single light guide plate that is continuous in a second direction perpendicular to the first direction.

JP WO2004 / 038283 JP 2002-75038 A JP 2001-93321 A

  The direct type backlight can easily increase the brightness of the screen, but it is difficult to reduce the thickness of the liquid crystal display device. FIG. 18 is a schematic cross-sectional view of a liquid crystal display device having a direct-type backlight using LED as a light source. The LED 30 is disposed on the back cover 90. In the direct type backlight, a diffusion plate 60, a diffusion sheet, and the like are used, but are omitted in FIG.

  In FIG. 18, the distance d from the bottom of the LED 30 to the lower side of the liquid crystal display panel needs to be about 25 mm to 35 mm. In FIG. 18, if the distance d between the liquid crystal display panel 10 and the LED 30 is reduced while the pitch P of the LEDs 30 is kept constant, uneven brightness occurs. In order to reduce the distance d, the pitch P of the LEDs 30 needs to be reduced so that the luminance unevenness does not occur. However, reducing the pitch P of the LEDs 30 means that the number of LEDs 30 needs to be increased, which is a problem in terms of manufacturing cost.

  FIG. 19 is a schematic cross-sectional view of a sidelight type liquid crystal display device. In FIG. 19, the light guide plate 50 is disposed on the back cover 90, and the LEDs 30 are disposed on the side surfaces of the light guide plate 50. Light from the LED 30 is directed toward the liquid crystal display panel 10 by the light guide plate 50. Actually, a diffusion sheet or the like exists between the liquid crystal display panel 10 and the light guide plate 50, but is omitted in FIG.

  In FIG. 19, the distance d from the lower side of the light guide plate 50 to the lower side of the liquid crystal display panel 10 is 10 to 15 mm, which can be made smaller than in the case of a direct type backlight. However, since the light of the LED 30 is incident from the side of the light guide plate 50, the light use efficiency is lower than that of the direct type. In order to obtain the same screen brightness as that of the direct light type as shown in FIG. 19, the number of LEDs 30 must be increased as compared with the case of the direct light type.

  For example, in a 42-inch liquid crystal display device, in order to obtain a predetermined brightness, a direct-type backlight requires 500 LEDs 30. On the other hand, in order to obtain the same brightness on the same screen, it is necessary to use 700 LEDs 30 when using a sidelight type backlight. That is, in the sidelight system, the thickness of the liquid crystal display device can be reduced, but the number of LEDs 30 must be increased, and the power consumption of the LEDs 30 increases.

  An object of the present invention is to reduce the thickness of a liquid crystal display device without increasing the number of LEDs and without increasing power consumption as compared with a direct type backlight.

  The present invention overcomes the above problems, and specific means are as follows.

  (1) A liquid crystal display device having a liquid crystal display panel and a backlight, wherein the backlight has a rectangular light guide plate in which rectangular light guide plate blocks are arranged in a matrix, and corresponds to the light guide plate block The number of LEDs arranged in the light guide plate block in the center of the light guide plate is larger than the number of LEDs arranged in the light guide plate block in the periphery of the light guide plate. A liquid crystal display device.

  (2) The liquid crystal display device according to (1), wherein the light guide plate is formed by a plurality of divided light guide plates having a plurality of light guide plate blocks.

  (3) The liquid crystal display device according to (1), wherein the light guide plate in which the light guide plate blocks are arranged in a matrix is integrally formed.

  (4) The liquid crystal display device according to (1), wherein the LEDs are arranged in a wiring board shape, and an integrated reflection sheet is arranged on the wiring board.

  (5) A liquid crystal display device having a liquid crystal display panel and a backlight, wherein the backlight has a rectangular light guide plate in which rectangular light guide plate blocks are arranged in a matrix, and corresponds to the light guide plate block The number of LEDs arranged in the light guide plate block along the short axis and the long axis of the light guide plate is the number of the short axis at the center of the short axis and the center of the long axis. The number of LEDs arranged in the light guide plate block along the short side and the long side of the light guide plate more than the end portion and the long axis end portion is the same.

  (6) A liquid crystal display device having a liquid crystal display panel and a backlight, wherein the backlight has a rectangular light guide plate in which rectangular light guide plate blocks are arranged in a matrix, and corresponds to the light guide plate block The number of LEDs arranged in the light guide plate block at the center of the light guide plate is larger than the number of LEDs arranged in the light guide plate block at the four corners of the light guide plate. Liquid crystal display device.

  (7) A liquid crystal display device having a liquid crystal display panel and a backlight, the backlight having a rectangular light guide plate in which rectangular light guide plate blocks are arranged in a matrix, and corresponding to the light guide plate block LEDs are arranged, and the number of LEDs arranged in the light guide plate block along the short side and the long side of the light guide plate is the center of the short side and the center of the long side. The number of LEDs arranged in the light guide plate block along the short axis and the long axis of the light guide plate more than the end portions and the end portions of the long sides is the same.

  According to the present invention, a light guide plate having light guide plate blocks arranged in a matrix is used, and the number of LEDs corresponding to the light guide plate blocks arranged in the peripheral portion is larger than the number of LEDs corresponding to the light guide plate blocks in the center. By reducing the number, the number of LEDs used for the backlight can be reduced and the power consumption of the backlight can be reduced without recognizing a decrease in luminance for human vision.

  Further, according to the present invention, since the light guide plate is constituted by the light guide plate blocks arranged in a matrix, the thickness of the backlight can be reduced. Furthermore, according to the present invention, since the light guide plate is constituted by the light guide plate blocks arranged in a matrix, it is possible to perform brightness region control.

It is a general-view figure of a liquid crystal display device. 1 is an exploded perspective view of Example 1. FIG. It is a perspective view of a division | segmentation light-guide plate. 1 is an exploded sectional view of Example 1. FIG. 1 is a detailed cross-sectional view of Example 1. FIG. It is a schematic diagram which shows the relationship between a light-guide plate block and LED. It is a top view which shows the relationship between the position of the light-guide plate block by a 1st example, and the number of LED. It is a top view which shows the relationship between the position of the light-guide plate block by the 2nd example, and the number of LED. It is a top view which shows the relationship between the position of the light-guide plate block by the 3rd example, and the number of LED. It is a top view which shows the leakage of the light from the specific light-guide plate block to the adjacent light-guide plate block. It is a top view which shows area | region control of a brightness. 3 is an exploded perspective view of Example 2. FIG. 6 is a perspective view of a light guide plate of Example 2. FIG. It is sectional drawing which shows the relationship between the light-guide plate of Example 2, and LED. It is sectional drawing which shows the example of the relationship between a light-guide plate and a reflective sheet. 6 is a cross-sectional view showing the position of a reflection sheet in Example 3. FIG. 6 is an exploded perspective view of Example 3. FIG. It is sectional drawing of a direct type | mold backlight. It is sectional drawing of a sidelight type backlight.

  Hereinafter, the contents of the present invention will be described in detail using examples.

  FIG. 1 is a liquid crystal TV showing an example in which the liquid crystal display device according to the present invention is used. In FIG. 1, the display frame 2 leaves the display screen 1 and surrounds the periphery of the liquid crystal display panel. A backlight 3 is disposed on the back surface of the liquid crystal display panel. The backlight 3 shown in FIG. 1 has a configuration having a light guide plate having a plurality of light guide plate blocks and LEDs arranged in each light guide plate block.

  FIG. 2 is an exploded perspective view of the liquid crystal display panel 10 and the backlight from which the display frame and the like are removed in the liquid crystal display device shown in FIG. In FIG. 2, a TFT substrate 11 on which a display area in which TFTs and pixel electrodes are arranged in a matrix, scanning lines, video signal lines and the like and an opposite substrate 12 on which color filters and the like are formed are bonded with an adhesive (not shown). Are bonded through. A liquid crystal (not shown) is sandwiched between the TFT substrate 11 and the counter substrate 12.

  A lower polarizing plate 14 is attached to the lower side of the TFT substrate 11, and an upper polarizing plate 13 is attached to the upper side of the counter substrate 12. A state in which the TFT substrate 11, the counter substrate 12, the lower polarizing plate 14, and the upper polarizing plate 13 are bonded together is referred to as a liquid crystal display panel 10. A backlight is disposed on the back surface of the liquid crystal display panel 10. The backlight is formed of a light source unit and various optical components.

  In FIG. 2, the LEDs 30 are arranged on the wiring board 40 in the light source unit. The arrangement density of the LEDs 30 is different between the vicinity of the center of the wiring board 40 and the vicinity of the periphery. This is because the luminance is intentionally reduced in the peripheral portion of the display screen. A light guide plate 50 having a light guide plate block 51 is disposed on the wiring substrate 40 on which the LEDs 30 are disposed. The LEDs 30 arranged on the wiring board 40 correspond to the respective light guide plate blocks 51.

  The light guide plate 50 shown in FIG. 2 is formed of four rectangular light guide plates 53. The shape of the divided light guide plate 53 is shown in FIG. FIG. 3A is a perspective view of the divided light guide plate 53. In the divided light guide plate 53, four light guide plate blocks 51 are formed. 3B is a cross-sectional view taken along the line KK of FIG. 3A, and is a cross-sectional shape of the groove 52 that forms the boundary of the light guide plate block 51 formed in the divided light guide plate 53. Each light guide plate block 51 is partitioned by a groove 52. Each light guide plate block 51 functions as an independent light guide plate by the groove 52. As shown in FIG. 3B, the shape of the groove 52 is substantially V-shaped, and the depth dd is about 0.5 mm.

  Returning to FIG. 2, three diffusion sheets 15 are disposed on the light guide plate 50. Since each diffusion sheet 15 is as thin as about 60 μm, the three diffusion sheets 15 are actually placed on the light guide plate 50. Fine irregularities are formed on the surface of the diffusion sheet 15, and this diffuses light from the light guide plate 50. Further, the fine irregularities on the surface have a role of a kind of prism, and also have a function of directing light incident obliquely on the diffusion sheet 15 toward the liquid crystal display panel 10.

  The number of the diffusion sheets 15 is an example, and may be one, two, or more than three as necessary. In addition to the diffusion sheet 15, a prism sheet may be disposed if necessary. The prism sheet has a function of improving the luminance of the screen by directing light from the backlight incident from an oblique direction toward the liquid crystal display panel 10.

  The liquid crystal display panel 10 is disposed on the uppermost diffusion sheet 15. Even after the assembly, the liquid crystal display panel 10 and the diffusion sheet 15 are spaced apart by, for example, about 50 μm. This is to prevent the diffusion sheet 15 and the lower polarizing plate 14 from being rubbed and scratched.

  4 is an exploded cross-sectional view of the liquid crystal display device shown in FIG. In FIG. 4, the liquid crystal display panel 10 and the three diffusion sheets 15 are as described in FIG. In FIG. 4, a light guide plate 50 is disposed below the diffusion sheet 15. The light guide plate 50 is formed of four divided light guide plates 53. As described with reference to FIG. 3, each divided light guide plate 53 further includes four light guide plate blocks 51.

  Each divided light guide plate 53 has a wedge-shaped cross section, and has a thick part and a thin part. The thick part is about 3 mm, and the thin part is less than 1 mm. Since the thin part of the divided light guide plate 53 enters the step formed in the thick part of the previously arranged split light guide plate 53, the appearance looks like a single light guide plate 50.

  In FIG. 4, the light guide plate 50 is placed on the wiring board 40 having the LEDs 30. The LEDs 30 are arranged on the side surfaces of the thick sections of the divided light guide plates 53. Light from the LED 30 that has entered from the side surface on the thick side of the light guide plate 50 changes its direction toward the liquid crystal display panel 10 and exits within the light guide plate 50.

  FIG. 5 is a cross-sectional view showing a state in which the components shown in FIG. 4 are assembled. FIG. 5 shows a cross section of one light guide plate block 51 of the divided light guide plates 53. In FIG. 5, the LEDs 30 arranged on the wiring board 40 are arranged on the thick side surface of the light guide plate block 51. The LEDs 30 are combined for each divided light guide plate 53. There is no need to combine each LED 30 or each light guide plate block 51.

  In FIG. 5, the light from the LED 30 incident from the side surface of the light guide plate block 51 is reflected by, for example, the lower surface of the light guide plate block 51 and travels toward the liquid crystal display panel 10. However, since the lower surface of the light guide plate block 51 is a diffusing surface, the light incident from the LED 30 is directed in various directions, but most is directed to the method of the liquid crystal display panel 10.

  In order to direct the light from the LED 30 toward the liquid crystal display panel 10 efficiently, the lower surface of the light guide plate block 51 needs to have a predetermined inclination. Therefore, when the light guide plate 50 is large, the surface of the light guide plate 50 on which the LEDs 30 are arranged becomes thick. In the present invention, since the light guide plate 50 is divided, the thickness can be reduced.

  FIG. 6 is a schematic diagram showing the relationship between the light guide plate block 51 and the LEDs 30. FIG. 6A is a schematic cross-sectional view, and FIG. 6B is a perspective view. In FIG. 6A, the cross section of the light guide plate block 51 is simplified and described as being triangular. The LED 30 is disposed on the thick side of the side surface of the light guide plate block 51. For the sake of clarity, FIG. 6A shows that the LED 30 is separated from the side surface of the light guide plate block 51. In practice, however, the LED 30 is a light guide plate in order to increase the utilization efficiency of light from the LED 30. It is arranged as close to the side surface of the block 51 as possible.

  In FIG. 6B, two LEDs 30 represented by solid lines and two LEDs 30 represented by dotted lines are arranged on the side surface of the light guide plate 50, for a total of four LEDs 30. In the present invention, by changing the number of LEDs 30 arranged for each light guide plate block 51, the brightness of the screen is inclined so as not to feel unnaturalness to human vision. The number of LEDs 30 used is reduced.

  For example, four LEDs 30 are arranged for the light guide plate block 51 near the center of the screen, and for example, two LEDs 30 indicated by dotted lines are removed from the light guide plate block 51 around the screen, and the solid line Only the two LEDs 30 shown are arranged. The number of LEDs 30 is set according to the size of the screen, the size of the light guide plate block 51, and the intended luminance gradient of the screen.

  Also in the conventional cathode ray tube TV, the brightness is different between the screen center and the screen periphery. According to the result of investigating the relationship between screen brightness and human vision in the case of a TV using the liquid crystal display panel 10, if the brightness around the screen is about 60% of the brightness at the center of the screen, human beings In the visual perception, brightness nonuniformity is not recognized.

  7 to 9 are examples of the number of LEDs 30 arranged in each light guide plate block 51. FIG. 7 shows an example in which the light guide plate 50 is divided into 16 parts. In FIG. 7, the vertical lines indicate the boundaries of the divided light guide plates 53, and the horizontal lines indicate the grooves 52 between the light guide plate blocks 51. In FIG. 7, two LEDs 30 are arranged in the light guide plate block 51 arranged in the periphery. On the other hand, three LEDs 30 are arranged in the central four light guide plate blocks 51.

  In FIG. 7, the region where the two LEDs 30 are arranged in the light guide plate block 51 is hatched. The luminance in this part is smaller than the luminance in the central part. In FIG. 7, it seems that the boundary between the light guide plate block 51 in which three LEDs 30 are arranged and the light guide plate block 51 in which two LEDs 30 are arranged seems to have a level difference in brightness. As will be described, since there is a light leak between the light guide plate blocks 51, there is no luminance step.

  In FIG. 7, two LEDs 30 are all disposed in the light guide plate block 51 corresponding to the line AA. In addition, two LEDs 30 are all disposed in the light guide plate block 51 corresponding to the line BB. On the other hand, the light guide plate block 51 corresponding to the line C-C has two light guide plate blocks 51 on both sides and three LEDs 30 in the central light guide plate block 51.

  In other words, the same number of LEDs 30 are arranged in the light guide plate block 51 along the short side or the long side of the light guide plate 50. On the other hand, in the light guide plate block 51 along the long axis or the short axis of the light guide plate 50, the number of LEDs 30 is arranged more in the central portion of the long axis or the short axis than in the end portion of the long axis or the short axis. ing. Here, the light guide plate block 51 along the major axis or the minor axis of the light guide plate 50 includes the light guide plate block 51 sandwiching the major axis or the minor axis.

Although the luminance around the screen is reduced by the arrangement of the LEDs 30 as shown in FIG. 7, if the luminance around the screen is 60% or more of the luminance at the center of the screen, it hardly affects human vision. On the other hand, by reducing the number of LEDs 30 in the peripheral light guide plate block 51, the component cost of the LEDs 30 can be reduced and the power consumption of the backlight can also be reduced.
FIG. 8 shows an example of a TV having a larger screen than that in FIG. 7, and is an example in which the light guide plate 50 is divided into 36 parts. In FIG. 8, the vertical lines indicate the boundaries of the divided light guide plates 53, and the horizontal lines indicate the grooves 52 between the light guide plate blocks 51. In FIG. 8, two LEDs 30 are arranged in the light guide plate block 51 arranged in the periphery and one inside thereof. On the other hand, three LEDs 30 are arranged in the central four light guide plate blocks 51.

  In FIG. 8, the area where the two LEDs 30 are arranged in the light guide plate block 51 is hatched. The luminance in this part is smaller than the luminance in the central part. Also in FIG. 8, there is almost no difference in luminance between the hatched portion around the screen and the center portion of the screen, as will be described later.

  In FIG. 8, two LEDs 30 are all arranged in the light guide plate block 51 corresponding to the DD line, and two LEDs 30 are all arranged in the light guide plate block 51 corresponding to the EE line. Yes.

By reducing the number of LEDs 30 in the peripheral light guide plate block 51, the component cost of the LEDs 30 can be reduced, and the power consumption of the backlight can also be reduced. In the example of FIG. 8, the cost is reduced and the power consumption is reduced by reducing the components of the LED 30 as the screen is larger than in the case of FIG. 7.
FIG. 9 shows an example of a TV having the same screen size as that in FIG. 8, but the luminance distribution of the screen is changed from that in FIG. Also in FIG. 9, the light guide plate 50 is divided into 36 parts. In FIG. 9, the vertical lines indicate the boundaries of the divided light guide plates 53, and the horizontal lines indicate the grooves 52 between the light guide plate blocks 51. In FIG. 9, two LEDs 30 are arranged for the four light guide plate blocks 51 corresponding to the four corners of the light guide plate 50, with respect to the light guide plate blocks 51 near the center, near the long axis, and near the short axis. The three LEDs 30 are arranged.

  In FIG. 9, the region where the two LEDs 30 are arranged in the light guide plate block 51 is hatched. The luminance in this part is smaller than the luminance in the central part. Also in FIG. 8, there is almost no difference in luminance between the hatched portion around the screen and the center portion of the screen, as will be described later.

  In FIG. 9, the light guide plate block 51 corresponding to the FF line and the light guide plate block 51 corresponding to the GG line include two light guide plate blocks 51 on both sides, and the light guide plate block 51 in the center portion. Three LEDs 30 are arranged. On the other hand, three LEDs 30 are all disposed in the light guide plate block 51 corresponding to the DD line.

  In other words, the same number of LEDs 30 are arranged in the light guide plate block 51 along the short axis or the long axis of the light guide plate 50. On the other hand, in the light guide plate block 51 along the long side or the short side of the light guide plate 50, the number of the LEDs 30 is arranged more in the central portion of the long side or the short side than in the end portion of the long side or the short side. ing. Here, the light guide plate block 51 along the major axis or the minor axis of the light guide plate 50 includes the light guide plate block 51 sandwiching the major axis or the minor axis.

  In FIG. 9, the number of LEDs 30 of the light guide plate block 51 corresponding to the screen corner portion is reduced. Although the reduction effect is small compared to the case of FIG. 8, the reduction effect of the component cost and power consumption of the LED 30 is large compared to the case where the present invention is not used.

  The above is an example of the division of the light guide plate 50, and other divisions than those shown in FIG. 7 or FIG. 8 may be used depending on the size of the screen and the necessity of fine screen control. Moreover, although arrangement | positioning of LED30 was given as an example only in the case of two pieces and three pieces in each light-guide plate block 51, you may arrange | position one piece or four pieces or more as needed.

  FIG. 10 shows an example of luminance when the LED 30 of only one light guide plate block 55 is illuminated in the light guide plate 50 divided into blocks. As shown in FIG. 10, although only one light guide plate block 55 is actually illuminated, the peripheral light guide plate block 56 is also brightened. This is because light leaks from the light guide plate block 55 to the other light guide plate block 56.

  Due to the presence of such light leakage, as shown in FIGS. 7 to 9, there is a luminance step at the boundary between the light guide plate block 51 with two LEDs 30 and the light guide plate block 51 with three LEDs 30. It never happens. Therefore, even when white is displayed on the screen, luminance unevenness does not occur.

  In the present invention, since the brightness can be controlled for each light guide plate block 51, the brightness area can be controlled. The brightness area control is, for example, a control method in which the LED 30 is turned on in a bright part of the screen, but the LED 30 is not turned on in a dark part.

  Such area control can be performed by storing video information in a frame memory, identifying bright and dark areas on the screen, and lighting the LEDs 30 only in areas corresponding to the bright areas. By performing brightness area control, it is possible to reduce power consumption and improve contrast.

  On the other hand, since the light guide plate block 51 is used in the present invention, the fineness of the light guide plate block 51 and the brightness area control can be a problem. FIG. 11 is an explanatory diagram showing how the light guide plate block 51 affects an actual image when brightness area control is performed. FIG. 11A shows an image actually desired to be displayed. FIG. 11A shows a case where a bright portion 70, for example, the moon is displayed on a dark background.

  FIG. 11B shows an example of the luminance of the backlight when brightness area control is performed corresponding to the image of FIG. In FIG.11 (b), LED30 of the light-guide plate block 51 of the part corresponding to the moon of a screen is lighted. FIG. 11C shows the correspondence between the image and the luminance of the backlight that performs brightness area control. The light guide plate block 51 corresponding to the moon on the screen is bright. As shown in FIG. 11C, appropriate brightness can be obtained by lighting the LEDs 30 of the plurality of light guide plate blocks 51 corresponding to the bright portions.

  In the first embodiment, the light guide plate 50 is formed using a divided light guide plate 53 having a plurality of light guide plate blocks 51. On the other hand, all the light guide plate blocks 51 can be formed on one light guide plate 50. FIG. 12 is a perspective view of the liquid crystal display device when the light guide plate block 51 is one. FIG. 12 is the same as FIG. 2 except for the light guide plate 50. In FIG. 12, the light guide plate 50 is formed with four light guide plate blocks 51 in the y direction and four in the x direction.

  FIG. 13 is a perspective view of the integrated light guide plate 50. In FIG. 13, a groove 52 indicating the boundary of the light guide plate block 51 extends in the x direction. The shape of the groove 52 is the same as that shown in FIG. A dotted line extending in the y direction is a portion where the thickness is reduced in the light guide plate block 51, and a boundary of the light guide plate block 51 is formed in this portion. Each light guide plate block 51 has a wedge-shaped cross section. For example, a thick portion is about 3 mm and a thin portion is less than 1 mm.

  The boundary of each light guide plate block 51 is formed by the thinned region of the groove 52 extending in the x direction or the light guide plate block 51 extending in the y direction. Any boundary is a specific light guide plate block. Since the light from 51 is not completely blocked, the light of a specific light guide plate block 51 leaks to the adjacent light guide plate block 51. This action eliminates the luminance step between the light guide plate blocks 51 and forms a smooth luminance distribution.

  FIG. 14 is a cross-sectional view showing a state in which the wiring board 40 having the light guide plate 50 and the LEDs 30 in the present embodiment is assembled. Although the optical sheet and the liquid crystal display panel 10 are disposed on the light guide plate 50 shown in FIG. 14, they are omitted in FIG. In FIG. 14, the LED 30 is arranged on the side surface of the thick portion of the light guide plate block 51 having a wedge-shaped cross section.

  As shown in FIG. 14, the light guide plate block 51 having a wedge-shaped cross section is connected to the previous light guide plate block 51 in the thinner plate thickness. Since this connection portion exists, the light from the LED 30 leaks to the previous light guide plate block 51, and the brightness between the light guide plate blocks 51 is prevented from changing abruptly. As shown in FIG. 12, a large number of LEDs 30 are attached to the wiring board 40. However, since all the light guide plate blocks 51 are integrally formed, the combination of the light guide plate 50 and the LEDs 30 can be performed only once. I can do it.

  In Example 1 and Example 2, it has been described on the assumption that the reflection sheet 80 is attached to the lower surface of the light guide plate block 51, that is, the inclined surface as shown in FIG. The reflection sheet 80 is formed of a sheet coated on one side with a highly reflective metal such as Al, and reflects light directed downward from the light guide plate 50 toward the liquid crystal display panel 10.

  In FIG. 15, since the reflection sheet 80 is attached to the lower surface of each light guide plate block 51, the number of steps for attaching the reflection sheet 80 is large. The reflection sheet 80 is attached to each row after the light guide plate 50 is formed. However, since the reflection sheet 80 is attached to the inclined surface with the concave portion, the mechanism for attaching becomes complicated and the attaching accuracy is a problem. Become.

  In this embodiment, as shown in FIG. 16, the reflection sheet 80 is arranged not on the light guide plate 50 but on the wiring board 40 on which the LEDs 30 are mounted. A reflective sheet 80 shown in FIG. 16 is a single sheet having a hole in a portion corresponding to the LED 30. The reflective sheet 80 shown in FIG. 16 may be before the LED 30 is attached to the wiring board 40 or after it is attached. In FIG. 16, the reflection sheet 80 is bonded to the wiring board 40 with an adhesive material. According to the present embodiment, the surface on which the reflection sheet 80 is pasted is a flat surface, so that the pasting accuracy can be ensured.

  FIG. 17 is an exploded perspective view of the liquid crystal display device when the wiring substrate 40 with the reflection sheet 80 attached is used. In FIG. 17, the circuit portion of the wiring board 40 is covered with the reflection sheet 80, but the LED 30 is exposed to the light guide plate 50 side through a hole formed in the reflection sheet 80. Other configurations in FIG. 17 are the same as those described in FIG. 2 or FIG.

  As described above, according to the present embodiment, since the reflection sheet 80 can be formed by one sheet, the number of steps for attaching can be reduced. Furthermore, since the reflection sheet 80 is attached to a flat surface, a complicated attaching mechanism is not required.

  DESCRIPTION OF SYMBOLS 1 ... Display screen, 2 ... Display frame, 3 ... Backlight, 10 ... Liquid crystal display panel, 11 ... TFT substrate, 12 ... Opposite substrate, 13 ... Upper polarizing plate, 14 ... Lower polarizing plate, 15 ... Diffusion sheet, 30 ... LED, 40 ... Wiring board, 45 ... Dark part, 50 ... Light guide plate, 51 ... Light guide plate block, 52 ... Groove, 53 ... Divided light guide plate, 55 ... Bright block, 56 ... Light leaked block, 70 ... Bright image 80 ... Reflective sheet, 90 ... Back cover.

Claims (3)

A liquid crystal display device having a liquid crystal display panel and a backlight,
The backlight has a rectangular light guide plate in which rectangular light guide plate blocks are arranged in a matrix, and LEDs are arranged corresponding to the light guide plate blocks,
A plurality of the light guide plate blocks are integrally formed in the arrangement direction of the LEDs arranged corresponding to the light guide plate blocks, thereby causing light leakage between the adjacent light guide plate blocks. And
The number of LEDs arranged in the light guide plate block along the short axis and the long axis of the light guide plate is the center of the short axis and the center of the long axis. More than the number of LEDs at the end,
The number of LED arrange | positioned at the light-guide plate block along the short side and long side of the said light-guide plate is the same, The liquid crystal display device characterized by the above-mentioned. A liquid crystal display device having a liquid crystal display panel and a backlight,
The backlight has a rectangular light guide plate in which rectangular light guide plate blocks are arranged in a matrix, and LEDs are arranged corresponding to the light guide plate blocks,
A plurality of the light guide plate blocks are integrally formed in the arrangement direction of the LEDs arranged corresponding to the light guide plate blocks, thereby causing light leakage between the adjacent light guide plate blocks. And
The number of LED arrange | positioned at the said light-guide plate block in the center of the said light-guide plate is more than the number of LED arrange | positioned at the said light-guide plate block in the four corners of the said light-guide plate, The liquid crystal display device characterized by the above-mentioned. A liquid crystal display device having a liquid crystal display panel and a backlight,
The backlight has a rectangular light guide plate in which rectangular light guide plate blocks are arranged in a matrix, and LEDs are arranged corresponding to the light guide plate blocks,
A plurality of the light guide plate blocks are integrally formed in the arrangement direction of the LEDs arranged corresponding to the light guide plate blocks, thereby causing light leakage between the adjacent light guide plate blocks. And
The number of LEDs arranged in the light guide plate block along the short side and the long side of the light guide plate is the end of the short side and the length of the long side at the center of the short side and the center of the long side. More than the number of LEDs at the end,
The liquid crystal display device according to claim 1, wherein the number of LEDs arranged in the light guide plate block along the short axis and the long axis of the light guide plate is the same.

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