JP2011216274A - Backlight unit and liquid crystal display device including the same - Google Patents

Abstract

To provide a backlight unit that prevents as much as possible undulation of an optical sheet group caused by heat generation of a linear light source.
A light guide plate, a diffusion sheet, which is an optical sheet, a prism sheet, and a polarizing sheet are accommodated in this order from the bottom of the housing in a rectangular housing, and are disposed on at least one side surface of the light guide plate. A front frame 78 which is a backlight unit having a configuration in which an LED array unit which is a linear light source is installed along the longitudinal direction of the side surface, and which is fastened to a flange portion 14 which is a peripheral portion of the housing 12. The front frame 78 holds the periphery of the optical sheets 38, 40, 42 so as to be slidable with respect to the light guide plate 36.
[Selection] Figure 2

Description

  The present invention relates to a backlight unit and a liquid crystal display device using the same, and more particularly to an edge light type backlight unit and the like.

In recent years, as liquid crystal display devices such as liquid crystal televisions have become widespread, the demand for backlight units equipped therein has been further expanded.
The backlight unit is roughly classified into an edge light type and a direct type, but from the viewpoint of reducing the thickness of the entire apparatus, an edge light type is often used.

  The edge light system has a rectangular housing, and has a configuration in which a reflection sheet, a light guide plate, and optical sheets such as a diffusion sheet, a prism sheet, and a polarizing sheet are housed in this order from the bottom of the housing. It is common. A light source is disposed on one side surface of the light guide plate, and the optical sheet group is fixed by pressing a peripheral portion of the optical sheet group against the light guide plate by a front frame fastened to the housing.

  Conventionally, cold cathode fluorescent lamps have been often used as the light source. Recently, however, LEDs are being replaced from the viewpoints of power saving, longer life, and further reduction in thickness. That is, a linear light source in which a large number of LEDs are arranged in the longitudinal direction of an elongated printed wiring board is arranged along the one side surface.

JP 2006-310058 A

  By the way, in recent years, liquid crystal televisions and the like tend to have larger screens. Therefore, in order to realize a large screen, it is necessary to increase the power input to the LEDs in order to obtain a required luminance, or to increase the number of LEDs constituting the linear light source. However, this causes a problem that the amount of heat generated by the entire linear light source is increased, and undulation or the like occurs in each of the sheets constituting the optical sheet group due to the influence of the heat.

  In view of the above-described problems, the present invention provides a backlight unit that prevents as much as possible the undulation of an optical sheet caused by heat from a linear light source, and a liquid crystal display device including such a backlight unit. The purpose is to provide.

  In order to achieve the above object, a backlight unit according to the present invention includes a rectangular housing in which a light guide plate and an optical sheet are accommodated in this order from the bottom of the housing, and are linear on at least one side surface of the light guide plate. A backlight unit having a configuration in which a light source is installed along the longitudinal direction of the side surface, the backlight unit having a front frame fastened to a peripheral portion of the casing, and the front frame is formed of the optical sheet. The peripheral portion is slidably held between the light guide plate and the light guide plate.

  In addition, when the optical sheet slides, there is provided a regulating means for regulating the slide range so that the edge of the optical sheet does not move into the opening window of the front frame. To do.

  Further, the front frame has a pressing member that protrudes from an inner surface facing the peripheral portion of the light guide plate and presses the light guide plate toward the bottom of the housing. An inner surface, a light guide plate, and a gap are defined.

Here, the front frame and the casing are fastened by screws, rivets or other fastening means, and the fastening means is positioned in the vicinity of the pressing member.
In order to achieve the above object, a liquid crystal display device according to the present invention includes a liquid crystal display panel and the backlight unit disposed on the back surface of the liquid crystal display panel.

  According to the backlight unit having the above configuration, since the peripheral portion of the optical sheet is slidably held between the light guide plate and the front frame, a linear light source installed on one side surface of the light guide plate is provided. The waviness of the optical sheet caused by the influence of the heat generated can be prevented as much as possible. That is, conventionally, since the peripheral edge of the optical sheet is pressed and restrained by the light guide plate by the front frame as described above, the expansion of the restrained region is suppressed. For this reason, a difference in expansion occurs between the area near the front frame and, as a result, the undulation of the optical sheet occurs near the front frame. According to the present invention, the peripheral edge of the optical sheet slides. This is because the degree of expansion difference as described above can be reduced because it is held freely.

It is a disassembled perspective view of the backlight unit which concerns on embodiment. It is a fragmentary sectional view of the said backlight unit. It is a fragmentary sectional view of the said backlight unit. It is the schematic diagram which planarly viewed only the optical sheet and press pin in the said backlight unit. It is a fragmentary sectional view of the said backlight unit. It is sectional drawing of the liquid crystal television which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an exploded perspective view of a backlight unit 10 according to an embodiment. In addition, the scale between each member is not unified in all the figures including this figure.

  As shown in FIG. 1, the backlight unit 10 has a casing 12 that is rectangular (in this example, a horizontally long rectangle) and has a flat box shape. The housing 12 is formed by pressing a steel plate such as stainless steel. The periphery of the opening of the housing 12 is formed in a flange portion 14 having a rectangular frame shape. The flange portion 14 is provided with screw holes 16, 18, 20, and 22 for fastening a front frame 78 described later. In addition, the bottom portion 24 of the housing 12 is formed with a portion that protrudes one step higher by drawing. This is mainly for increasing the rigidity of the housing 12. Furthermore, a plurality of (four in this example) columnar pins 26, 28, 30, and 32 are erected from the bottom 24 of the housing 12. The role of the positioning pins 26, 28, 30, 32 will be described later.

  The casing 12 includes a reflection sheet 34, a light guide plate 36, a diffusion sheet 38, a prism sheet 40, and a polarizing sheet 42 (hereinafter, these three sheets are collectively referred to as “optical sheet”). An optical sheet group 44 is housed in this order from the bottom 24.

For the reflection sheet 34, for example, a polyethylene terephthalate (PET) sheet is used.
The light guide plate 36 is made of polycarbonate (PC), for example, and is a daylighting element for causing incident light to be emitted from the light emission surface on the reflection sheet 34 side main surface facing the light emission surface (one side main surface). A dot pattern (not shown) is printed. As a lighting element, a light scattering element such as a light scattering structure formed by printing, molding, etc. and a prism shape, or formed inside the light guide plate with respect to the main surface facing the light exit surface of the light guide plate However, the present invention is not particularly limited. In addition to this, an optical element that changes the light guiding direction can also be used as the daylighting element.

For the diffusion sheet 38, for example, a PET film or a PC film is used.
The prism sheet 40 is formed, for example, by forming a regular prism pattern with an acrylic resin on one side of a polyester sheet material. For the polarizing sheet 42, for example, a polyethylene naphthalate film is used.

  The thicknesses of the reflection sheet 34, the light guide plate 36, the diffusion sheet 38, the prism sheet 40, and the polarizing sheet 42 are, for example, 0.33 [mm], 4 [mm], 0.16 [mm], and 0.3 [mm, respectively. ], 0.3 [mm].

  Moreover, the reflection sheet 34, the light guide plate 36, and the optical sheets 38, 40, and 42 are all rectangular in shape, and all have the same size. Here, “having a rectangular shape as a whole” means that the shape is a square, except for a local notch which will be described later. Therefore, from any of the reflection sheet 34, the light guide plate 36, and the optical sheets 38, 40, and 42, a square in which all four sides are straight lines can be considered. Therefore, in the present specification, when referring to the inside of the rectangular shape of the reflecting sheet 34, the light guide plate 36, and the optical sheets 38, 40, and 42 that are generally rectangular, the inside of the rectangular shape in which all the four sides are straight lines. Shall.

  In each of the reflection sheet 34, the light guide plate 36, and the optical sheets 38, 40, and 42, cutout portions 46A to 46E cut in an “U” shape inwardly from end edges corresponding to both short sides thereof, Notch parts 48A-48E, notch parts 50A-50E, and notch parts 52A-52E are established. In a state where the reflection sheet 34, the light guide plate 36, and the optical sheets 38, 40, and 42 are overlaid, the notches 46A to 46E, the notches 48A to 48E, the notches 50A to 50E, and the notches 52A to 52E. Each communicates.

  Further, in each of the optical sheets 38, 40, 42, notches 54A to 54C, notches 56A to 56C, which are cut in an “U” shape inwardly from end edges corresponding to both short sides thereof, Notch parts 58A-58C and notch parts 60A-60C are established. In a state where the optical sheets 38, 40, and 42 are overlapped, the cutout portions 54A to 54C, the cutout portions 56A to 56C, the cutout portions 58A to 58C, and the cutout portions 60A to 60C are respectively formed on the optical sheets 38, 40. , 42 communicate in the stacking direction.

  In the assembly process of the backlight unit 10, each of the reflection sheet 34, the light guide plate 36, and the optical sheets 38, 40, and 42 has a notch 46A to 46E, a notch 48A to 48E, and a notch 50A to 50E. The notches 52 </ b> A to 52 </ b> E are accommodated in the corresponding positioning pins 26, 28, 30, 32, and are accommodated in the housing 12. In this case, the notch portions 46D, 48D, 50D, and 52D provided in the light guide plate 36 and the corresponding positioning pins 26, 28, 30, and 32 are arranged in the vertical and horizontal directions in the housing 12 of the light guide plate 36. Functions as positioning means. Each of the optical sheets 38, 40, and 42 is laminated on the positioned light guide plate 36 so as to overlap the light guide plate 36 using an unillustrated assembly jig.

LED array units 62, 64, 66, and 68, which are linear light sources, are provided so as to face each of both side surfaces corresponding to both long sides of the light guide plate 36. The LED array units 62, 64, 66, and 68 have the same configuration. The LED array units 62 and 64 are formed by mounting a plurality of white LEDs 62B and 64B in the longitudinal direction of the elongated metal base printed wiring boards 62A and 64A. The LED array units 66 and 68 are the same.
The LED array units 62, 64, 66, and 68 are held by heat sinks 70, 72, 74, and 76, respectively.

The heat sinks 70, 72, 74, 76 are made of an aluminum drawing material (angle material) having a substantially “L” -shaped cross section.
The LED array units 62, 64, 66, and 68 are attached to the LED array units 62, 64, 66, and 68 by a heat conductive double-sided tape (not shown) on the back surface of the metal base printed wiring boards 62A, 64A, 66A, and 68A. Being held.

  The actual assembly order is that the heat sinks 70, 72, 74, 76 holding the LED array units 62, 64, 66, 68 are each fixed to the bottom of the housing 12 with screws (not shown), and then the reflective sheet 34. The light guide plate 36, the diffusion sheet 38, the prism sheet 40, and the polarizing sheet 42 are accommodated in the housing 12 in this order.

  Thereafter, the front frame 78 having a square shape (rectangular shape in this example) is fastened to the flange portion 14 which is the peripheral portion of the housing 12 by screws 80, 82, 84 and 86. The front frame 78 fixes the light guide plate 36 to the casing bottom 24 in the thickness direction, and holds the periphery of the optical sheets 38, 40, 42 slidably between the light guide plate 36 as will be described later. To do.

FIG. 2 shows a sectional view of the screw 86 and the vicinity thereof in the assembled backlight unit 10.
As described above, the front frame 78 is fastened with the flange portion 14 of the housing 12 and the screw 86. The front frame 78 has a pressing pin 88 that is a pressing member protruding from the inner surface 78A facing the peripheral edge of the light guide plate 36. The pressing pin 88 lightly presses the light guide plate 36 and restrains it in the thickness direction. Here, the size T1 of the gap between the main surface 36A of the light guide plate 36 and the inner surface 78A of the front frame 78 in the fastening state is larger than the total thickness T2 of the optical sheets 38, 40, 42 by a predetermined size ( T1> T2). For this reason, the optical sheets 38, 40, 42 can slide in the direction along the main surface 36 </ b> A of the light guide plate 36 within a range described later.

  Here, the pressing pin 88 also serves as a spacer for ensuring at least the T1 between the main surface 36A of the light guide plate 36 and the inner surface 78A of the front frame 78. That is, as described above, since the casing 12 is manufactured by press molding, there is a possibility that the inclination of the flange portion 14 may vary due to its processing accuracy. Therefore, if the pressing pin 88 is not provided, the inner edge of the front frame 78 may press the optical sheets 38, 40, and 42 when the screw 86 is completely tightened depending on the direction of inclination of the flange portion 14. Accordingly, if the movement of the peripheral portions of the optical sheets 38, 40, 42 in the direction along the main surface 36A of the light guide plate 36 is constrained, the above-described problem of the related art occurs. On the other hand, when the pressing pin 88 is provided, the size of the gap between the main surface 36A of the light guide plate 36 and the inner surface 78A of the front frame 78 does not become shorter than the height from the inner surface 78A of the pressing pin 88. .

  The flange portion 14 and the front frame 78 lightly press the optical sheet 38, 40, 42 toward the light guide plate 36 by the inner edge of the front frame 78 when the screw 86 is tightened without the pressing pin 88. It can also be intentionally formed in such a shape. Thus, the tip of the pressing pin 88 is surely brought into contact with the light guide plate 36 to press the light guide plate 36, and the size of the gap between the main surface 36A of the light guide plate 36 and the inner surface 78A of the front frame 78 is the above. This is because it becomes T1 (height from the inner surface 78A of the pressing pin 88). However, in any case, there is no difference that the pressing pin 88 functions as a spacer.

  Further, as in this example, the pressing pin 88 is preferably positioned in the vicinity of the screw 86. This is because it is possible to effectively prevent the inner edge of the front frame 78 from pressing the optical sheets 38, 40, 42 toward the light guide plate 36 by tightening the screws 86. In addition to the pressing pin 88, the pressing pin is also provided in the vicinity of the screws 80, 82, and 84 (the pressing pins 83, 85, and 87 (FIG. 4)).

The number and position of screws for fastening the front frame 78 to the housing 12 and the number and position of the pressing pins are not limited to the above example, and can be appropriately increased or decreased.
Further, the pressing member is not limited to the pressing pin, and for example, may be constituted by a rib (pressing rib) formed integrally with the front frame 78 and extending from the inner surface 78A.

  The size T1 of the gap between the inner surface 78A of the front frame 78 and the main surface of the light guide plate 36 is maintained not only at the position shown in FIG. 2 (the short side portion of the front frame 78) but also over the entire circumference thereof. Yes. For example, FIG. 3 shows a partial cross-sectional view cut at a position where the LED module 66 (FIG. 1) exists (long side portion of the front frame 78). In this figure, the LED module 66 is not cut.

  Here, the difference dT (= T1-T2) between T1 and T2 is that the optical sheets 38, 42 at both ends of the laminated optical sheets 38, 40, 42 are the inner surface 78A of the front frame 78 and the main surface of the light guide plate 36, respectively. It is preferable to have such a size that a so-called slidable contact state is reached. This is because such a dimensional relationship can prevent the optical sheets 38, 40, 42 from floating from the main surface of the light guide plate 36 as much as possible.

  On the other hand, in order to ensure sufficient slidability, dT can be set larger. By setting dT to be larger, it is possible to cope with the case where the thickness of the optical sheets 38, 40, and 42 to be used is slightly changed in the manufacture of the product. However, when the total thickness of the optical sheets 38, 40, and 42 is considerably smaller than dT, the following problems may occur. That is, since the backlight unit 10 is used upright, the lower sides of the optical sheets 38, 40, 42 may abut against the inner wall of the housing 12 in the upright state. In this case, since the optical sheets 38, 40, and 42 are as thin as several hundred μm as described above, the lower side portion may be bent like a bow (buckling) due to its own weight on the lower side portion. If this curved portion reaches the inside of the front frame 78, it causes uneven brightness.

  Therefore, it is preferable to integrate the end portions that are the lower sides of the optical sheets 38, 40, and 42 in the use state (the standing state) of the backlight unit 10. The term "integrated" means that the end portions of the optical sheets 38, 40, 42 are in close contact with each other, and the optical sheets 38.40, 42 do not slide relative to each other at the end portions, or Say that state. For example, in a state where a plurality of optical sheets 38, 40, 42 (three in this example) are overlapped, the end portion is covered with an adhesive tape, or the end portion is melt bonded by thermocompression bonding or ultrasonic welding. To include. In addition, it cannot be overemphasized that the form of integration is not restricted to the above-mentioned thing, In short, what is necessary is just the form which the edge part of the some optical sheet was united.

  In this way, by integrating the end portions of the optical sheets 38, 40, and 42, so-called waist is strengthened at the end portions, so that the curved state as described above can be prevented as much as possible.

In addition, it is preferable that the end portion to be integrated is in a range hidden by the front frame 78 in consideration of deterioration of optical characteristics of the optical sheets 38, 40, and 42 due to integration.
As shown in FIG. 3, long side peripheral portions of the reflection sheet 34, the light guide plate 36, and the optical sheets 38, 40, 42 are supported on the bottom of the housing 12 via a heat sink 74. The LED 66B is disposed opposite to the side surface of the light guide plate 36, and light emitted from the LED 66B enters from the side surface.

  The LED 66B generates heat during lighting, and the optical sheets 38, 40, and 42 tend to expand under the influence of the heat. In particular, the portion of the optical sheet close to the LED module tends to stretch well. Conventionally, since the peripheral edge portion of the optical sheet is pressed and restrained by the light guide plate by the front frame, expansion of the restrained region is suppressed. Therefore, a difference in expansion occurs between the area near the front frame and, as a result, the optical sheet undulates near the front frame. When undulation occurs, uneven brightness occurs in this portion.

  On the other hand, in the present embodiment, since the peripheral portions of the optical sheets 38, 40, 42 are slidably held, the degree of expansion difference as described above can be reduced, so that the swell is prevented as much as possible. it can.

  Since the optical sheet 38, 40, 42 is only slidably held along the main surface of the light guide plate 36, the entire optical sheet 38, 40, 42 slides relative to the front frame 78. For this reason, it is necessary to prevent the optical sheets 38, 40, 42 from sliding so that the edge of the optical sheet 38, 40, 42 is viewed from the opening window of the front frame 78, that is, the edge does not move into the opening window of the front frame 78. It is necessary to do so. In this example, the restricting means for restricting the slide are the pressing pins 83, 85, 87, 88, the corresponding notches 54A to 54C, the notches 56A to 56C, the notches 58A to 58C, It is comprised by the notch parts 60A-60C.

  Here, the relationship in plan view of the optical sheet (38, 40, 42) and the pressing pins 83, 85, 87, 88 will be described with reference to FIG. FIG. 4 is a schematic view of only the optical sheet (38, 40,) 42 and the pressing pins 83, 85, 87, 88 viewed in plan. In FIG. 4, for the sake of convenience, the optical sheets 38, 40, and 42 are only the polarizing sheet 42, and the notches 54A to 54C, the notches 56A to 56C, the notches 58A to 58C, and the notches 60A to 60A. Each of 60C is indicated by only a number (54, 56, 58, 60). In the drawing, a two-dot chain line indicates the inner edge of the front frame 78, that is, the opening window 90. Further, an orthogonal coordinate system is set in which the X axis is parallel to the long side of the aperture window 90 and the Y axis is parallel to the short side, and the X axis direction is the horizontal direction and the Y axis direction is the vertical direction.

The dimensional relationships between the pressing pins 83, 85, 87, and 88 and the corresponding notches 54, 56, 58, and 60 are all the same. FIG. 4 shows a state in which the pressing pins 83, 85, 87, 88 are located in the middle of the notches 54, 56, 58, 60, respectively. Exactly middle means a state in which the center of the semicircle at the bottom of the notches 54, 56, 58, 60 coincides with the center of the cylindrical pressing pins 83, 85, 87, 88.
In this state, the size of the clearance (clearance) in the Y-axis direction between the pressing pins 83, 85, 87, and 88 and the notches 54, 56, 58, and 60 is d1, and the clearance (clearance) in the X-axis direction. Let the magnitude be d2. The distance in the Y-axis direction between the long side of the opening window 90 and the long side of the optical sheet 42 is D1, and the shortest distance in the X-axis direction between the short side of the opening window 90 and the notches 54, 56, 58, 60 is D2. And In such a case, in this example, the dimensions of each part are determined so that d1, d2, D1, and D2 have a relationship of D1> d1 and D2> d2. Due to this relationship, even if the optical sheet 42 is slid until the inner periphery of the notches 54, 56, 58, 60 abuts against the pressing pins 83, 85, 87, 88, the short edge of the optical sheet 42 has the opening window 90. The edge of the optical sheet does not move into the opening window 90.

FIG. 5 is a partial cross-sectional view of the backlight unit 10 cut at the position of the positioning pin 32 (FIG. 1).
As shown in FIG. 5, the positioning pin 32 that is a columnar member standing from the bottom of the housing 12 passes through the notches 52 </ b> A to 52 </ b> E.

  Here, the dimensional relationship between the positioning pins 26, 28, 30, 32 and the notches 46D, 48D, 50D, 52D of the light guide plate 36 is as follows. That is, the clearances between the positioning pins 26, 28, 30, 32 and the corresponding notches 46D, 48D, 50D, 52D are extremely small. Specifically, with the notches 46D, 48D, 50D, and 52D fitted into the positioning pins 26, 28, 30, and 32, the light guide plate 36 is almost fully struck in the vertical and horizontal directions with respect to the housing 12. The clearance is set to a certain level (see FIG. 5). This is because it is necessary to accurately position the side surface (light introduction surface from the LED array) of the light guide plate 36 with respect to the light emission surface of each LED. On the other hand, there is a considerable gap between the positioning pin 32 and the inner periphery of the notches 52A to 52E, but this gap is simply the positioning pins 26, 28, 30, 32 of the optical sheets 38, 40, 42. It is provided so as not to interfere with storage.

  Further, the positioning pin 32 protrudes larger than the uppermost polarizing sheet 42. This is to prevent the optical sheets 38, 40, 42 from inadvertently getting on the tip of the positioning pin 32 when the front frame 78 is attached to the housing 12. That is, when the protrusion height of the positioning pin 32 from the uppermost polarizing sheet 42 is low, even if the optical sheets 38, 40, 42 are positioned just superimposed on the light guide plate 36, in the direction along the surface. When an external force is unexpectedly applied, the optical sheets 38, 40, 42 may ride on the positioning pins 32. If the front frame 78 is fastened to the housing 12 in such a state, the optical sheets 38, 40, and 42 may be damaged. Accordingly, the positioning pin 32 is secured to a height from the main surface (upper surface) of the uppermost polarizing sheet 42, and the optical sheets 38, 40, 42 are once positioned and then run on the positioning pin 32. Is prevented from occurring. The end portion of the positioning pin 32 that has been raised is provided with a recess 92 in the front frame 78 and is housed (entered) into the recess 92. Or it is good also as not only the recessed part 92 but opening a through-hole (not shown) and inserting the said edge part into the said through-hole.

  FIG. 6 shows a liquid crystal television 100 as an example of a liquid crystal display device including the backlight unit 10 having the above configuration. FIG. 6 is a cross-sectional view showing a schematic configuration of the liquid crystal television 100. The liquid crystal television 100 includes a liquid crystal display panel 102 and a backlight unit 10 disposed on the back surface of the liquid crystal display panel 102, and the liquid crystal display panel 102 and the backlight unit 10 are housed in a housing 104. ing.

As described above, the backlight unit according to the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described form, and may be, for example, the following form.
(1) In the above embodiment, when the optical sheet is slid, its edge is not looked into from the opening window of the front frame (so that the edge is not moved into the opening window of the front frame). The restricting means for restricting the slide range includes notches 54A to 54C, notches 56A to 56C, notches 58A to 58C, notches 60A to 60C provided on the optical sheet, and corresponding pressing pins. However, the present invention is not limited to this, and a projection (rib) may be provided on the light guide plate side (inner surface) of the front frame to restrict the movement of the optical sheet. Alternatively, the following may be used. That is, the gap between the casing (inner wall) and other members existing in the vertical and horizontal directions of the optical sheet and the edge of the optical sheet may be set to a predetermined size. Here, the predetermined size refers to, for example, the edge and the inner wall of the optical sheet that are in the other direction even if the optical sheet slides in one direction in the longitudinal direction until the edge contacts the inner wall of the housing, for example. The gap is sufficiently short so that it cannot be seen through the opening window of the front frame (so that it does not move into the opening window). The same applies to the horizontal direction.
(2) In the above embodiment, the notches 46A to 46E, 48A to 48E, 50A to 50E, and 52A to 52E are all formed in a “U” shape, but are not limited thereto. A U-shape may be used. Further, the positioning pin is not limited to a cylindrical shape, and may be an elliptical column shape or a prism shape.
(3) Although the LED array unit is arranged on the two side surfaces of the light guide plate, the present invention is not limited to this, and the present invention can also be applied to a backlight unit configured to arrange the LED array unit only on one side surface of the light guide plate. It is.
(4) In the above embodiment, the front frame and the housing are fastened with screws, but the fastening means is not limited to this, and for example, rivets may be used. Alternatively, welding may be used.

  The backlight unit according to the present invention can be suitably used as a planar light source disposed on the back surface of a liquid crystal panel of a liquid crystal display device such as a liquid crystal television.

DESCRIPTION OF SYMBOLS 10 Backlight unit 12 Housing | casing 36 Light guide plate 38 Diffusion sheet 40 Prism sheet 42 Polarizing sheet 62A-68A LED array unit 78 Front frame

Claims (5)

A back having a configuration in which a light guide plate and an optical sheet are housed in this order from the bottom of the housing in a rectangular housing, and a linear light source is disposed along at least one side surface of the light guide plate along the longitudinal direction of the side surface. A light unit,
Having a front frame fastened to the periphery of the housing;
The said front frame is holding | maintaining the peripheral part of the said optical sheet slidably between the said light-guide plates, The backlight unit characterized by the above-mentioned.   A restriction means is provided for restricting the slide range so that an edge of the optical sheet does not move into the opening window of the front frame when the optical sheet slides. Item 2. The backlight unit according to Item 1. The front frame has a pressing member that protrudes from the inner surface facing the peripheral portion of the light guide plate and presses the light guide plate toward the bottom of the housing;
The backlight unit according to claim 1, wherein the inner surface of the front frame, the light guide plate, and a gap are defined by the pressing member. The front frame and the housing are fastened by screws, rivets or other fastening means,
The backlight unit according to claim 3, wherein the fastening means is positioned in the vicinity of the pressing member. A liquid crystal display panel;
The backlight unit according to any one of claims 1 to 4, which is disposed on a back surface of the liquid crystal display panel;
A liquid crystal display device comprising:

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