JP2012118439A - Video display apparatus - Google Patents

Abstract

In a video display device having a backlight unit in which a plurality of LED light source plates each having a plurality of LED elements are arranged to form a backlight light source, the backlight unit can be operated even if the on / off state of the LEDs varies from place to place. The diffuser plate is positioned at a predetermined position.
An image display device includes a plurality of substrates each having a plurality of LED light emitting elements mounted in a row, a light guide plate disposed on an upper surface of the substrate, and a chassis that accommodates the plurality of substrates and the light guide plate. 10, a diffusion plate 60 disposed on the top surface of the light guide plate, a plurality of optical sheets disposed on the top surface of the diffusion plate, and a liquid crystal panel disposed on the top surface of the optical sheet. The chassis 10 has an outer frame portion 18, and has a pin 13 in the vicinity of the center portion which is a lower side when the video display device of the outer frame portion 18 is used. The diffusion plate 60 is formed with a groove 62 into which the pin 13 is inserted.
[Selection] Figure 4

Description

  The present invention relates to a video display device, and more particularly to a video display device suitable for a large television.

  An example of a conventional liquid crystal display device is described in Patent Document 1. The liquid crystal display device described in this publication includes a main frame formed on the optical sheet on which the first and second openings are placed, and a sub-frame that covers the outer peripheral side wall of the main frame and has a window formed at the center. And a frame. Then, the positioning and fixing of the optical sheet is improved to enlarge the display screen and reduce the thickness of the apparatus, and the first small protrusion protruding upward corresponding to the first opening is formed on the top surface of the base. A second small protrusion protruding downward corresponding to the second opening is provided on the back surface of the frame, and the first opening of the optical sheet is inserted into the first small protrusion and the second small protrusion is inserted into the second opening. Thus, the optical sheet is positioned and fixed.

  Another example of a display device having a conventional backlight unit is described in Patent Document 2. In the display device described in this publication, in order to enable a design in consideration of both thermal expansion of optical sheets and positioning accuracy with respect to the backlight chassis, a lamp is provided by interposing optical sheets on the back side of the display panel. A backlight chassis is housed. A positioning unit for positioning the optical sheets at a predetermined position with respect to the mounting surface is provided on the mounting surface on which the optical sheets of the backlight chassis are mounted. It is in a position corresponding to approximately the center of the long side.

  An example of a backlight unit using an LED as a light source is described in Patent Document 3. In the backlight device described in this publication, the luminance distribution is improved by arranging a substrate in which a plurality of LEDs are arranged in the horizontal direction in a plurality of rows in the vertical direction.

  Furthermore, in order to easily distinguish the order and front and back of the optical sheets constituting the backlight unit, the edge of the upper optical sheet is more suitable than the edge of the lower optical sheet on the outer periphery of the optical sheet. Patent Document 4 describes that a sheet arrangement identifying unit configured by retreating a gap is provided. In this publication, it is recommended that the sheet arrangement identification means is arranged at least on one side or corner of the outer periphery of the optical sheet, and that the two sheet arrangement identification means are formed in different sizes or / and shapes. ing. It is also described that the sheet arrangement identification means is arranged outside the image display area of the liquid crystal panel.

JP 2005-091821 A International Publication No. 2006/070646 JP 2010-192395 A JP 2006-071685 A

  In the conventional liquid crystal device described in Patent Document 1, since the optical sheet is fixed to one side of the main frame, generation of wrinkles due to thermal deformation of the optical sheet is prevented in the direction connecting the fixed end and the free end. However, the optical sheet is fixed in the direction connecting both ends of the fixed end, and wrinkles may occur due to thermal deformation of the optical sheet.

  In addition, in this patent document 1, since the linear light source is arrange | positioned at the outer peripheral part at frame shape, a light source can only make the back surface of a liquid crystal uniform bright or dark. Therefore, non-uniform temperature distribution or the like is unlikely to occur. On the other hand, recently, the screen has been clarified by partially turning on and off the light source in accordance with the screen displayed on the liquid crystal. As a result, partial brightness adjustment is performed, the amount of heat generated by the light source varies depending on the position of the liquid crystal screen, and the thermal deformation of the optical sheet varies from place to place. In order to absorb this deformation as much as possible, it is required to eliminate the binding point of the optical sheet.

  Patent Document 2 also describes that a tubular lamp is used as a backlight light source, and the thermal distortion of the optical sheet in the uniformed backlight is considered. Therefore, even if the optical sheet is positioned at the positioning portion at the center of the long side and pressed in four rounds, there is little risk of wrinkling due to thermal deformation in the optical sheet. However, no consideration is given to the case where the above-described backlight light source is partially turned on / off.

  Further, in Patent Document 3, partial LED emission / stop is possible, but no consideration is given to achieving both absorption and positioning of the thermal deformation of the optical sheet by the backlight.

  Further, in Patent Document 4, one of the sheet arrangement identification means is necessarily a rectangular cutout, and the further provided sheet arrangement identification means is rectangular or triangular. In other words, in order to clarify the stacking order of sheets and the front and back regardless of the position of the operator, two sheet notches are required in principle, and a rectangular shape is provided so that the operator can easily identify them. Is mandatory. By using two locations, the portion that does not contribute to the image on the sheet increases. In other words, the area that can be used for video is reduced.

  Further, as shown in FIG. 3 which is a typical embodiment, a right angle portion or an acute angle portion remains in the notched portion. This right angle or acute angle portion may damage other sheets. Further, in the process of notching, there is a possibility that a crack may be generated from a recessed portion formed on the inner side of the sheet for some reason. It is desirable that each sheet is formed with a rounded portion so as not to form corners as much as possible, and it should be avoided that sharp corners remain on the sheet.

  The present invention has been made in view of the above-described problems of the prior art, and the object thereof is an image display device having a backlight unit in which a plurality of LED light source plates in which a plurality of LED elements are arranged are arranged in a plurality of rows to serve as a backlight light source. Even if the on / off state of the LED differs from place to place, the diffuser plate of the backlight unit is positioned at a predetermined position, and the distance between each optical sheet and the liquid crystal panel or diffuser plate is held at a predetermined distance. . Another object is to improve the assembly of the backlight unit and increase the display range.

  In order to achieve the above object, the present invention is characterized by a plurality of substrates each having a plurality of LED light emitting elements mounted in a row, a light guide plate disposed on an upper surface of the substrate, the plurality of substrates and the light guide plate, An image display device comprising: a chassis for housing the light guide plate; a diffusion plate disposed on the top surface of the light guide plate; a plurality of optical sheets disposed on the top surface of the diffusion plate; and a liquid crystal panel disposed on the top surface of the optical sheet. The chassis has an outer frame portion, and when the video display device of the outer frame portion is used, the chassis has a pin in the vicinity of the center portion, and the pin is inserted into the diffusion plate. The groove is formed.

  And in this feature, it is preferable to provide a bent portion which is a cut portion of the outer frame portion and is bent at a position adjacent to the pin in the outer frame portion, and the bent portion of the outer frame portion is formed. More preferably, another bent portion is formed on the same side as the bent side and outside the bent portion in the width direction.

  In the above feature, the diffusion plate is formed with holes at positions corresponding to the plurality of LED light emitting elements, and the LED light emitting elements are preferably positioned in the holes, and the pins are diffused. You may arrange | position in the position different from the center position of the outer-frame part of a board, and may serve as the front-and-back determination means of the said diffusion plate.

  Further, each of the plurality of optical sheets is formed with a front / back discriminating portion having a shape in which only one of the four corners of the rectangular sheet is cut into a triangle, and the front / back discriminating portion is disposed close to the diffusion plate. The cut-out amount of the optical sheet may be reduced as the number of the front and back discriminating portions formed on the plurality of optical sheets is substantially constant in the length of one side of the triangle in any of the optical sheets. You may change the notch amount of a some optical sheet by changing the length of a side with each optical sheet. The front and back discriminating portions formed by the plurality of optical sheets may have obtuse angles at both ends.

  According to the present invention, the diffusing plate positioning means is provided substantially at the center of the lower side of the chassis of the video display device, and the diffusing plate holding means is provided adjacent to the positioning means on the lower side of the chassis. Even if the LED of the configured backlight light source is turned on / off for each location, the distance from the optical sheet, the liquid crystal panel, and the diffusion plate can be maintained at a predetermined distance. Further, the assemblability of the backlight unit can be improved and the display range can be increased.

Sectional drawing of the principal part of one Example of the video display apparatus concerning this invention. The disassembled perspective view except the liquid crystal panel of the video display apparatus shown in FIG. The enlarged perspective view of the A section of Drawing 3, the AA sectional view, and the BB sectional view. FIG. 4 is a perspective view and a top view showing a combination of the chassis and the diffusion plate shown in FIG. 3. The 3rd page figure which shows the detail of the front and back identification part of the various sheets used for a backlight unit. The top view of the LED light source plate used for the liquid crystal display device shown in FIG.

  Hereinafter, an embodiment of a video display device 150 including the backlight unit 200 according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a video display device 150 according to the present invention, and FIG. 2 is an exploded perspective view of a backlight unit 200 part extracted from the video display device 150 shown in FIG. FIG.

  In this embodiment, a liquid crystal television having a large screen of about 40 inches will be described as an example. However, the present invention is not limited to such a liquid crystal television, and may be applied to any video display device 150 having a large screen. it can. However, the video display device 150 is based on the premise that the long side is arranged in the horizontal direction and the short side is arranged in the vertical direction. Although various substrates, drivers, power supply devices and the like necessary for the video display device 150 are not shown in the drawing, they are arranged on the rear side of the chassis 10 and on the lower side in FIG. In the following description, the upper and lower sides are set based on the state of FIG.

  In FIG. 1, a metal chassis 10 is arranged at the lowest level. Since the chassis 10 is a structural member and is required to hold the liquid crystal panel 110 disposed in the foreground without distortion, a steel plate of about 1 to 3 mm is pressed to have a width of 1000 mm × length of 600 mm. Form to the extent. A frame is formed around the chassis 10, and through holes or screw holes are formed in the frame portion to attach mold frames 100 to 103, which will be described in detail later.

  As shown in FIG. 2, the bottom surface of the chassis 10 is formed with a plurality of rows, two rows in FIG. In order to hold the LED light source plate 30 in the chassis 10 via the insulating sheet 20 formed slightly smaller than the recess shape, a recess is formed. On the upper surface of the insulating sheet 20, an LED light source plate 30 in which the LED elements 32 are arranged in a row is disposed corresponding to the recesses of the chassis 10. Further, on the upper surface of the LED light source plate 30, a reflecting plate 40 having holes formed at positions corresponding to the positions of the LED elements 32 is disposed.

  On the upper surface of the reflection plate 40, a light guide plate 50 in which a hole 52 is formed at a position corresponding to the position of the LED element 32 is disposed. When the LED element 32 enters the hole 52 of the light guide plate 50, light emission from the LED element 32 progresses from the lower side to the upper side (from the left side to the right side in FIG. 1) so-called side view type. .

  The light guide plate 50 is made of a material such as acrylic, and has a flag pattern that suppresses uneven brightness by surface processing. Further, when the video display screen is divided into several blocks and the light emission of the LED element 32 is controlled for each block, the light emission spread is suppressed so that the light emission for each block does not affect each other.

  For surface processing or the like, the light guide plate 50 has a shape divided into a plurality of pieces, and a plurality of LED light source plates 30 are attached to each light guide plate 50. Further, the bottom surface of the light guide plate 50 is positioned at a position where the bottom surface convex portion of the chassis 10 is in contact via the reflective sheet 40.

  A diffusion plate 60 is disposed on the upper surface of the light guide plate 50 at a predetermined interval. The diffusing plate 60 is slightly smaller than the outer periphery of the chassis 10 and is sized to be placed on the frame portion 18 formed on the outer peripheral portion of the chassis 10. Details of the positioning of the diffusion plate 60 to the frame portion 18 of the chassis 10 will be described later.

  A plurality of optical sheets are placed on the upper surface of the diffusion plate 60. In this embodiment, the optical sheets are the diffusion sheet 70, the prism sheet 80, and the polarization reflection sheet 90 from the side closer to the diffusion plate 60, and these are sheets having the same size and area as the diffusion plate 60. . The thickness of the diffusing plate 60 is about several millimeters, and the thickness of each of the optical sheets 70 to 90 is about several millimeters of commas.

  When the optical sheets 70 to 90 are placed and positioned on the upper surface of the diffusion plate 60 in a prescribed order, the plastic mold frames 100 to 103 are placed on the chassis 10 according to the long side and the short side of the optical sheets 70 to 90, respectively. Secure to the side of the. Here, projections 104 and 105 are formed on the mold frames 100 to 103, and the projections 104 and 105 are inserted into the holes 15 provided in the chassis 10.

  In this embodiment, the protrusions 104 and 105 are formed on the mold frames 100 to 103, but a through hole may be formed on the mold frames 100 to 103 and a screw hole may be formed on the side surface of the chassis 10 for screwing. Since the mold frames 100 to 103 are L-shaped in cross section, the diffusion plate 60 and the optical sheets 70 to 90 are sandwiched between the frame portion 18 of the chassis 10 and the lateral sides of the mold frames 100 to 103. The reflector unit 30 to the optical sheet 90 constitute the backlight unit 200.

  When the optical sheets 70 to 90 are held in the chassis 10, a separately assembled liquid crystal panel 1110 is placed on the upper surface thereof. A substrate 112 is attached to one end side of the liquid crystal panel 10. A connector 114 is attached to the surface of the substrate 12 for external connection. The width of the substrate 114 is formed within the range of the height of the video apparatus 150 (the height in the state of FIG. 1), and is accommodated in a metal frame 120 for holding the liquid crystal panel 110. . The four peripheral portions of the liquid crystal panel 110 are fixed and held by a frame-shaped frame 120. After attaching various substrates and a power supply unit to the back surface of the chassis 10 and applying a cover, the video display device 150 is used with the left side of FIG.

  Next, positioning of the diffusion plate 60, which is a characteristic configuration of the present invention, will be described with reference to FIGS. FIG. 3 is a detailed view of part A of FIG. 2 and shows a part of the chassis 10 included in the video display device 150. 3A is a perspective view of the central portion of the lower side of the chassis 10, FIG. 3B is a sectional view taken along line BB, and FIG. 3C is a sectional view taken along line CC. 4 is a diagram of the combination of the chassis 10 and the diffusion plate 60, and is a diagram corresponding to FIG. FIG. 4A is a perspective view thereof, and FIG. 4B is a plan view thereof.

  As shown in FIG. 2, the lower side when the frame portion 18 of the chassis 10 is used has three notches 11 at intervals and a bent portion 12 obtained by bending the notch 11. Is formed. Further, a pin 13 is attached to substantially the center of the frame portion 18 in the width direction. A through-hole is formed in the frame portion 18, and the pin 13 is fitted into the hole and crimped from the back surface. Since the pin 13 is used for positioning, the tolerance of the position in the width direction is several hundred μm or less. On the other hand, the bent portion 12 that acts as a register is cut with a round shape so as to form a smooth curved surface in the width direction after being cut at the corner of the frame portion 15 and bent.

  A positioning groove 62 having a width corresponding to the diameter of the pin 13 is formed in a portion placed on the frame portion 18 at the center portion in the width direction of the lower side when the diffusion plate 60 is used. When the backlight unit 200 is assembled, the right and left positions of the diffusion plate 60 are positioned by fitting the pins 13 into the positioning grooves 62. Further, the position of the diffusion plate 62 in the short side direction is positioned when the long side of the diffusion plate 60 contacts the bent portion 12. Here, since the bent portion 12 is a curved surface, the curved surface of the bent portion 12 and the flat surface of the diffusion plate 60 are in contact with each other.

  By the way, while the video display device 150 is used, the light emission state of the LED 42 as the backlight changes according to the image, and the heat generation state also changes for each part of the video display device 150 accordingly. In the present video display device 150, the diffusion plate 60 and the optical sheets 70 to 90 are made of resin. Therefore, when the LED 42 emits light, a large strain is generated compared to the metal chassis 10 and the frame 120, and the diffusion plate 60 and the optical sheet 70. If the peripheral part of ~ 90 is fixedly held, there is a possibility that a distorted image is formed.

  Therefore, in the present invention, even if the diffusing plate 60 and the optical sheets 70 to 90 are displaced due to a temperature change, the structure is such that the elongation escapes with reference to the pin 13. That is, the diffusion plate 60 can be displaced by sliding along the bent portion 12 in the width direction, and can be extended and displaced in the vertical direction with respect to the bent portion 12 in the vertical direction. The mold frames 100 to 103 only hold the optical sheet 90 from the upper surface, and do not hinder the displacement of the diffusion plate 60 and the optical sheets 70 to 90 in the sliding direction. Thereby, the bad influence to the image by the distortion of the optical sheet 60 or the diffusion plates 70-90 can be prevented.

  In the above embodiment, the pin 13 is formed at the center in the width direction, and the bent portion 12 is formed at three appropriate locations in the width direction. However, the bent portion is formed at the center portion in the width direction and at two equally spaced positions from the center. You may make it provide adjacent to a bending part. In this case, since the pin is not in the center, the front and back of the diffusion plate can be determined. That is, when the front and back sides of the diffusion plate are arranged in reverse, the diffusion plate protrudes from the chassis. In addition, although the bending part is provided in three places, it is also possible to increase / decrease suitably according to the magnitude | size of the image of a video display apparatus.

  Incidentally, the backlight unit 200 included in the video display device 150 is configured by laminating a plurality of transparent or translucent optical sheets 70 to 90. At the time of assembling the backlight unit 200, it is necessary for an operator to definitely stack these stacking surfaces, directions, and orders. In a large image display device, since the optical sheets 70 to 90 reach 1 m square, means for easily finding the front, back, top, bottom, and order of the optical sheets 70 to 90 is required. Therefore, in the present invention, the front and back discriminating portions as shown in FIG.

  FIG. 5 is a partial view of a plurality of optical sheets included in the backlight unit 200 shown in FIG. 2, FIG. 5A is a plan view showing a plurality of optical sheets stacked, and FIG. The lower side view and FIG. 5 (c) are right side views thereof.

Each of the diffusing plate 60 and the optical sheets 70 to 90 is formed with notches 64, 72, 82, and 92 at locations located in the lower right corner when in use. And the shape is a triangle. That is, the rectangular diffuser plate 60 with the corners subjected to R processing is dropped from the right corner to the left by w ₆₄ and from the right corner in the vertical direction by h to form the front / back discriminating portion 64 that is a slope. At that time, the corners are α degrees and β degrees (α, β> 90 degrees), respectively.

Similarly, the diffusion sheet 70 located on the upper surface of the diffusion plate 60 is also provided with a front and back discriminating portion 72 that is a slope by dropping the corners by w _{72 in} the width direction and h in the vertical direction at the lower right corner. In the prism sheet 80 located on the upper surface of the diffusion sheet, the front and back discriminating part 82 is dropped in the width direction by w _{82 in} the width direction and h in the vertical direction. Further, the polarization reflection sheet 90 located on the upper surface is arranged in the width direction. The front / back discriminating part 92 is formed by dropping a corner by w _{92 in} the vertical direction.

Here, in the front and back discriminating portions formed on the diffusion plate 60 and the optical sheets 70 to 90, the notch length in the vertical direction is common to h, and only the notch length w in the width direction is changed. Then, the notch length w that is closest to the chassis 10, that is, the one that is far from the liquid crystal panel 110 is minimized, and the notch length w in the width direction is increased as it approaches the liquid crystal panel. In this embodiment, w ₆₄ <w ₇₂ <w ₈₂ <w ₉₂ .

  When the notch length w is set in this way, as shown in FIG. 5A, when the diffusion plate 60 and the optical sheets 70 to 90 formed of a transparent or translucent material are stacked, the stacked state of each sheet Can be easily confirmed visually. Further, during assembly of the backlight unit 200, an operator can reliably identify a missing sheet or an incorrect front / back by the presence / absence of the front / back discriminating portions 64, 72, 82, 92.

  It should be noted that even the front / back discriminating portion formed on the optical sheet closest to the liquid crystal panel 110 located at the top is not located within the image range 130. In this way, by setting the front / back discriminating section, it is possible to perform assembly without mistakes in the stacking order and front / back of the optical sheets without providing an extra mechanism. In addition, since only one place is cut off as the front / back discriminating portion, a reduction in the effective area of the optical sheet or the diffusion plate can be reduced as much as possible. This is because the front and back discriminating part is formed in the holding part of the mold frame.

  In the above embodiment, the length in the width direction is changed with the length in the vertical direction h being constant, but the length in the width direction may be changed to be constant by changing the length in the length direction. It should be noted that both the length in the vertical direction and the width direction may be changed, but it may be difficult to see, so only one of them may be changed. In any case, the corner formed by the corner drop becomes an obtuse angle, and it is possible to avoid the occurrence of cracks and the risk of damaging other sheets. Furthermore, although the notch is the lower right corner, it is not limited to the lower right corner, and can be any one of four rectangular corners depending on the design of the liquid crystal display device. Therefore, the design likelihood of the liquid crystal display device is increased.

  In the above embodiment, one diffusion plate and three optical sheets are used. However, the combination of the diffusion plate and the optical sheet is not limited to this, and the number of optical sheets may be larger. Further, when other identifying means is provided on the diffusion plate, a cutout may be provided only on the optical sheet. In any case, if it is provided only at one corner of the rectangular sheet, the number of processing steps and the number of parts that cannot be used as an image are small, and the stacking order and the front and back can be reliably determined.

  Next, the LED light source plate 30 on which the LED light emitting element 32 is mounted will be described with reference to FIG. FIG. 6 is a plan view of the LED light source plate 30. On the surface of the LED light source plate 30, a plurality of circuit pattern portions 34 identified by white color or a color close to white are formed in a line, and the LED light emitting element 32 is arranged at substantially the center of the circuit pattern portion 34. Has been. The LED light source plate 30 is held by the light guide plate 50 by attaching fixtures 52 and 53 to the attachment holes 36 formed at both ends.

  Here, when the assembly operator attaches the LED light emitting element 32 and attaches the LED light source plate 30 to the light guide plate 30, it is difficult to instantaneously determine which direction the LED light emitting element 32 should be set. There is. In preparation for such a case, the LED light source plate 30 is provided with a light emission direction instruction mark 38 for indicating the light emission direction corresponding to each LED light emitting element 32. Thereby, the assembly property of the LED light emitting element 32 and the LED light source plate 340 is improved.

DESCRIPTION OF SYMBOLS 10 ... Chassis, 11 ... Notch part, 12 ... Holding means (bending part), 13 ... Positioning means (pin), 15 ... Hole, 18 ... (Outside) frame part, 20 ... Insulating sheet, 30 ... LED light source plate ( (Light emitting means), 32 ... LED light emitting element, 34 ... circuit pattern portion, 36 ... mounting hole, 38 ... light emission direction instruction mark, 40 ... reflector, 50 ... light guide plate, 52 ... hole, 60 ... diffuser plate, 62 ... positioning Groove 64, front / back discriminating portion (notched portion), 70 ... diffusion sheet, 72 ... front / back discriminating portion (notched portion), 80 ... prism sheet, 82 ... front / back discriminating portion (notched portion), 90 ... polarized light reflection Sheet, 92 ... Front / back discriminating part (notch part), 100-103 ... Mold frame, 104, 105 ... Projection, 110 ... Liquid crystal panel, 112 ... Flexible substrate, 114 ... Connector, 120 ... Frame, 150 ... Video display device, 200 ... Backlight unit.

Claims (8)

  A plurality of substrates each having a plurality of LED light emitting elements mounted in a row, a light guide plate disposed on the top surface of the substrate, a chassis for housing the plurality of substrates and the light guide plate, and disposed on the top surface of the light guide plate A diffusion plate, a plurality of optical sheets disposed on the upper surface of the diffusion plate, and a liquid crystal panel disposed on the upper surface of the optical sheet, wherein the chassis has an outer frame portion, A video display having a pin in the vicinity of a central portion which is a lower side when using the video display device of the outer frame portion, and a groove into which the pin is inserted is formed in the diffusion plate. apparatus.   The video display device according to claim 1, wherein a bent portion that is formed by cutting and bending a part of the outer frame portion is provided at a position adjacent to the pin in the outer frame portion.   The video display device according to claim 2, wherein another bent portion is formed on the same side as the side where the bent portion of the outer frame portion is formed, and on the outer side in the width direction than the bent portion. .   The image display according to claim 2, wherein the diffusion plate has holes formed at positions corresponding to the plurality of LED light emitting elements, and the LED light emitting elements are positioned in the holes. apparatus.   The video display device according to claim 1, wherein the pin is disposed at a position different from a center position of an outer frame portion of the diffusion plate, and also serves as a front / back determination unit of the diffusion plate.   Each of the plurality of optical sheets is formed with a front / back discriminating portion having a shape in which only one of the four corners of the rectangular sheet is cut into a triangle, and the front / back discriminating portion is disposed close to the diffusion plate. The video display device according to claim 1, wherein the cutout amount is smaller.   The front and back discriminating part formed on the plurality of optical sheets has a substantially constant length of one side of the triangle in any optical sheet, and by changing the length of the other side in each optical sheet, The video display device according to claim 6, wherein the cutout amounts of the plurality of optical sheets are changed.   The image display apparatus according to claim 7, wherein the front and back discriminating portions formed by the plurality of optical sheets have obtuse angles at both ends.

Images