JP2008112663A - Backlight unit and liquid crystal display having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit which prevents the deformation of a reflection sheet 12 caused by friction between the reflection sheet 12 and a frame 13 even if the frame 13 shifts when the backlight unit shakes or drops, and in which the reflection sheet 12 is placed between the frame 13 and the lower case 11 to reduce a warp of the reflection sheet 12 caused by a difference in a linear expansion coefficient between the reflective sheet 12 and a lower case 11. <P>SOLUTION: The backlight unit includes an LED 141, a guide plate 15 having a side face on which light from the LED 141 is incident and an upper face from which incident light is emitted, the reflection sheet 12 disposed below the guide plate 15, the frame 13 which has a frame shape and encircles the guide plate 15, and the lower case 11 which is of a box shape with an open top and a side wall, has a bottom face bearing the reflection sheet 12 laid thereon, and encircles the frame 13 with the side wall. The reflection sheet 12 has a cutout 12a, and the frame 13 has a projection 13a in a range narrower than the cutout 12a, in which range the projection projects higher than the thickness of the reflection sheet 12 and is in contact with the bottom face of the lower case 11. The frame 13 is not superposed on the reflection sheet 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight unit in which a reflection sheet is laid on the inner bottom surface of a lower case and a liquid crystal module using the backlight unit.

  Liquid crystal display devices are characterized by light weight, thinness, and low power consumption, and are used in many electronic devices. Many of the liquid crystal display devices have a backlight unit that emits light from behind the liquid crystal panel. For this reason, the display can be seen without relying on outside light, and the display screen can be brightened.

A backlight of a general liquid crystal display device has a light guide plate disposed on the back surface of the liquid crystal panel, a light source such as a fluorescent discharge tube or an LED is disposed on an end surface of the light guide plate, and light incident from the side surface of the light guide plate is transmitted to the liquid crystal panel. It is the structure which radiate | emits to the back side. And in order to raise the brightness | luminance of a liquid crystal panel, the reflection sheet is arrange | positioned on the bottom face of the light-guide plate. Further, a frame-like frame body is provided on the periphery of the light guide plate to hold the light guide plate, the light source or the optical sheet, and to shape the lead wire of the light source (see Patent Document 1). And these are accommodated in a case.
JP-A-2005-173302

  There are usually two methods for arranging the reflection sheet. One is a method in which the entire reflection sheet fits completely in the frame of the frame (see FIG. 10, where the reference numerals in FIG. 10 are the same as those in the embodiments described later), and the other is the frame. (See FIG. 11 or Patent Document 1. Note that the reference numerals in FIG. 11 are the same as those in the embodiments described later).

  The method of putting the entire reflection sheet into the frame of the frame is that when a gap is generated between the frame and the case due to vibration / dropping, the reflection sheet enters the gap and the position of the reflection sheet is greatly displaced. There's a problem.

The method of laying the reflective sheet under the frame body is that the reflective sheet is sandwiched between the frame body and the housing, and the central part of the reflective sheet receives frictional movement force due to the movement of the light guide plate due to vibration and dropping. There is a problem of deformation. Further, when the liquid crystal display device is used in a vehicle, quality assurance of −40 ° C. to 85 ° C. is required. However, when the linear expansion coefficient of the reflective sheet and the housing is greatly different, for example, the reflective sheet has a linear expansion coefficient of 7 × 10 was -5 ^/ ° C. of PET (polyethylene terephthalate), when the housing is in the linear expansion coefficient of 1.9 × 10 -5 ^/ ° C. stainless, reflective sheet housing by Ju置a frame to the reflective sheet When sandwiched between the body and the frame, there is a problem that the reflection sheet warps due to the difference in linear expansion coefficient.

  The present invention is a backlight unit in which the reflection sheet does not move into the gap even if a gap is generated between the frame and the case due to vibration, dropping, etc., and the reflection sheet is not sandwiched between the frame and the case. Supply.

In order to solve the above-mentioned problems, in the backlight unit according to claim 1 of the present invention, the reflective sheet has a notch, and protrudes higher than the thickness of the reflective sheet in a range narrower than the notch. The frame is provided with a convex portion that comes into contact with the bottom surface of the lower case, and the frame is not placed on the reflection sheet.

  In the backlight unit according to claim 2 of the present invention, the frame body has an engaging portion that engages with the lower case, and the convex portion is provided in the vicinity of the engaging portion. It is characterized by.

  Further, in the invention of the backlight unit according to claim 3 of the present invention, the gaps to the frame body in the front, back, left, and right directions of the reflective sheet at the notch portions are in front of the reflective sheet. -It is characterized by being larger than the respective gaps to the lower case in the rear, left and right directions.

  Further, the invention of the backlight unit according to claim 4 of the present invention is that the respective gaps to the frame body in the front, rear, left and right directions of the reflective sheet at the notch are in front of the reflective sheet. -It is larger than the value obtained by adding the respective gaps to the lower case in the rear, front, right and left directions of the frame body in the respective gaps to the lower case in the rear, left and right directions. .

  Moreover, the invention of the backlight unit according to claim 5 of the present invention is characterized in that the light guide plate does not overlap the reflective sheet.

  The invention of a liquid crystal display device according to claim 6 of the present invention has a liquid crystal panel, and the backlight unit according to claims 1 to 5 is used to irradiate the liquid crystal panel with light. To do.

  According to the first aspect of the present invention, the reflective sheet has a notch, and the frame body is provided with a convex portion protruding in a narrower range than the notch, and the frame body does not overlap the reflective sheet. Thereby, since the frame is not placed on the reflection sheet, the reflection sheet is not deformed by friction with the frame even if the frame moves due to vibration drop. Since the reflection sheet is movable without being sandwiched between the frame and the lower case, the reflection sheet is not warped due to the difference in linear expansion coefficient from the lower case.

  According to claim 2 of the present invention, since the convex portion is provided in the vicinity of the engaging portion that engages with the lower case, it engages with the abutting portion on the bottom surface of the lower case and the side surface of the lower case. The distance between the parts becomes smaller, and the attachment of the frame is stabilized.

  According to claim 3 of the present invention, the gaps to the frame in the front, rear, left, and right direction of the reflective sheet at the notch are the front, rear, left, and right of the reflective sheet. Greater than the respective gap to the lower case in the direction. Therefore, the back-and-forth movement of the reflection sheet in the front-rear and left-right directions is prevented from abutting the reflection sheet and the frame body by the end of the reflection sheet abutting against the side wall of the lower case. As a result, even if the reflection sheet floats due to vibration and dropping and a gap is generated between the frame and the casing, the reflection sheet does not enter the gap. Further, since the reflection sheet does not come into contact with the frame, deformation of the reflection sheet due to dropping / vibration or heat can be reduced.

  According to a fourth aspect of the present invention, the gaps to the frame in the front, rear, left and right directions of the reflective sheet at the notch are the front, rear, left and right sides of the reflective sheet. It is larger than the value obtained by adding the respective gaps to the lower case in the rear, front, right and left directions of the frame body to the respective gaps to the lower case in the direction. Therefore, regardless of the fitting position of the frame body and the lower case, the reflection sheet is prevented from abutting between the reflection sheet and the frame body in the longitudinal and lateral movements. As a result, even if the reflection sheet floats due to vibration and dropping and a gap is generated between the frame and the casing, the reflection sheet does not enter the gap. Further, since the reflection sheet does not come into contact with the frame, deformation of the reflection sheet due to dropping / vibration or heat can be reduced.

  According to claim 5 of the present invention, the light guide plate does not overlap the reflective sheet. Thereby, since the light guide plate does not prevent the reflection sheet from moving, deformation of the reflection sheet can be reduced. Further, even if the light guide plate moves due to dropping or vibration, the light guide plate and the reflection sheet are not rubbed and damaged.

  According to claim 6 of the present invention, a backlight unit having the above-described effects can be applied to a liquid crystal display device.

  Hereinafter, the best embodiment of the present invention will be described with reference to the drawings. However, the embodiment shown below exemplifies a backlight unit for embodying the technical idea of the present invention, and is not intended to identify the present invention as this backlight unit. Other embodiments within the scope of the claims are equally applicable.

  1 is an exploded perspective view of a liquid crystal display device having a backlight unit according to an embodiment of the present invention, FIG. 2 is an exploded perspective view seen from the back side of the liquid crystal panel, and FIG. 3 is a plan view. 4 is a cross-sectional view taken along line AA ′ of FIG. 3, FIG. 5 is a cross-sectional view taken along line BB ′ of FIG. 3, and FIG. 6 is a perspective view showing a frame.

  The backlight unit 10 of the present invention is a unit that irradiates light to the liquid crystal panel 20. The lower case 11 has a reflection sheet 12, a frame 13, a flexible printed circuit board 14 having a plurality of LEDs 141 that are light sources, PMMA (polymethyl methacrylate). ) Of the light guide plate 15, the diffusion sheet 16, the lens sheet 17 in the X direction, and the lens sheet 18 in the Y direction. The light source may be a fluorescent discharge tube instead of the LED 141.

  The liquid crystal display device 1 of the present invention has a configuration in which the backlight unit 10 is disposed on the back surface of the liquid crystal panel 20 and is sandwiched between the upper case 30 and the lower case 11.

  The lower case 11 has a box shape with the upper part opened. A reflective sheet 12 is laid on the bottom surface of the lower case 11. A plurality of notches are provided at the edge of the reflection sheet 12. As shown in FIG. 7, this notch has two notches 12a to 12d on the left and right, three notches 12e to 12g on the back, and one notch 12h on the front. As shown in FIG. 6, the frame body 13 has a frame shape and has convex portions 13 a to 13 h that protrude into the regions of the notches 12 a to 12 h of the reflection sheet 12.

  Here, the gap between the reflection sheet 12 and the frame body 13 will be described. FIG. 7 is a schematic plan view showing a gap between the reflection sheet 12 and the frame body 13, and FIG. 8 is a schematic plan view showing a gap between the reflection sheet 12 and the frame body 13 in a state where the reflection sheet 12 is shifted to the lower right side. FIG. 9 is a schematic plan view showing a gap between the reflection sheet 12 and the frame body 13 in a state in which the reflection sheet 12 is moved to the lower right side and the frame body 13 is moved to the upper left side.

The height of the convex portions 13 a to 13 g of the frame body 13 exceeds the thickness of the reflective sheet 12, and the convex portions 13 a to 13 g are in contact with the lower case 11. As a result, as shown in FIG. 5, a gap Z <b> 1 is formed between the reflection sheet 12 and the frame 13 in the height direction. As shown in FIG. 7, the reflective sheet 12 and the frame 13 are provided with gaps YF1, YB1, XL1, and XR1 in the front, rear, left, and right directions, respectively, and the reflective sheet 12 and the lower case 11 are front, rear, and left. A gap of YF2, YB2, XL2, XR2 is provided in the right direction. As a result, the frame body 13 does not overlap the reflective sheet 12 (herein, “overlay” means that the frame body 13 is placed in a state where the movement is prevented), so that the frame body 13 is moved by the vibration drop. Also, the reflection sheet 12 is not deformed by friction with the frame 13. Since the reflection sheet 12 is movable without being sandwiched between the frame 13 and the lower case 11, the reflection sheet 12 is not warped due to a difference in linear expansion coefficient from the lower case 11. The convex portion 13h of the frame body covers the shear surface 11h (11h in FIG. 2) of the lower case 11, and the flexible printed board 14 of the light source and the flexible printed board (not shown) of the liquid crystal panel 20 are the lower case. 11 is in contact with the shearing surface 11h to protect it from damage.

  The gaps YF1, YB1, XL1, and XR1 to the front, rear, left, and right frame 13 of the reflection sheet 12 are the gaps to the lower case 11 in the front, rear, left, and right directions of the reflection sheet 12, respectively. It is larger than YF2, YB2, XL2, and XR2. Thereby, even if the reflection sheet 12 largely fluctuates due to vibration, dropping, etc., the reflection sheet 12 will not be sandwiched between the frame 13 and the lower case 11 by contacting the lower case 11, Further, the frame 13 does not prevent the reflection sheet 12 from moving (see FIG. 8). Thereby, deformation of the reflection sheet can be reduced.

The frame 13 is made of polycarbonate, and the lower case 11 is made of stainless steel. The liquid crystal display device is designed so as to endure in an environment of −40 ° C. to 85 ° C. in consideration of being mounted on a vehicle. Therefore, considering the difference between the linear expansion coefficient 7 × 10 ⁻⁵ / ° C. of the frame 13 and the linear expansion coefficient 1.9 × 10 ⁻⁵ / ° C. of the lower case 11, the front, rear, left, Respective gaps YF3, YB3, XL3, XR3 to the lower case 11 in the right direction are provided. There is a possibility that the frame body 13 may loosen due to this gap.

  Therefore, the gaps YF1, YB1, XL1, and XR1 to the frame 13 in the front, back, left, and right directions of the reflection sheet 12 are further directed to the lower case 11 in the front, back, left, and right directions of the reflection sheet 12. Are larger than the values YF2 + YB3, YB2 + YF3, XL2 + XR3, XR2 + XL3, which are obtained by adding the gaps to the lower case 11 in the rear, front, right, and left directions of the frame body 13. Thereby, even if the position of the frame body 13 and the lower case 11 is shifted due to vibration or dropping, the reflective sheet 12 is not sandwiched between the frame body 13 and the lower case 11, and the frame body 13 is not attached to the reflective sheet 12. Is not prevented (see FIG. 9). Thereby, deformation of the reflection sheet can be reduced.

  The frame 13 is provided with a diffusion sheet 16, a lens sheet 17 in the X direction, a lens sheet 18 in the Y direction, and a flexible printed circuit board 14 having a light source LED 141 and a light guide plate 15. The flexible printed circuit board 14 is adhered to the light guide plate 15 with double-sided tape. The light guide plate 15 is supported by the frame body 13 by fitting the convex portions 15 m to 15 p of the light guide plate 15 and the concave portions 13 m to 13 p of the frame body 13. As shown in FIG. 5, the light guide plate 15 and the reflection sheet 12 have a gap Z2. As described above, since the light guide plate 15 is not placed on the reflection sheet 12, even if the light guide plate moves due to dropping or vibration, the light guide plate and the reflection sheet are not rubbed to damage each other. Further, since the reflection sheet 12 is not sandwiched between the light guide plate 15 and the lower case 11, deformation of the reflection sheet 12 due to a difference in linear expansion coefficient can be reduced.

  Three convex portions 18q to 18s (one of the tail q on the left and two tails r and s on the right) and three concave portions 13q to 13s of the frame 13 (the tail q on the left) The diffusion sheet 16, the X-direction lens sheet 17, and the Y-direction lens sheet 18 are supported by the frame body 13 by fitting one, two tails r and s on the right.

Seven convex portions 13t to 13z (two tails t and u on the left, two tails v and w on the right, and three tails x, y, and z on the back) provided on the side wall of the frame 13; Recesses 11t to 11z provided on the side wall of the lower case 11 (two tails t and u on the left, two tails v and w on the right, and three tails x, y, and z on the back) are engaged. As a result, the frame 13 and the lower case 11 are engaged. The projecting portions 13a to 13g for contact of the frame 13 are disposed in the vicinity of the projecting portions 13t to 13z for engagement. Thus, since the contact portion with the bottom surface of the lower case 11 is close to the engaging portion with the side surface of the lower case 11, the holding of the frame body is stabilized. For example, the abutment protrusion 13d shown in FIG. 5 prevents the frame body from moving downward, and the engagement protrusion 13w prevents the frame body from moving upward. If the convex portion 13d and the convex portion 13w are separated from each other, the dimensional accuracy between the upper and lower sides to be blocked is deteriorated, or the dimension between the upper and lower sides to be blocked by the deformation of the frame body 13 and the lower chassis 11 is greatly shifted. Cannot be matched or engagement is weak.

  The upper case 30 is made of stainless steel, and has a box shape that is open at the bottom and has a large square hole at the top. Six convex portions 11a to 11f (two tails a and b on the left, two tails c and d on the right, two tails e and f on the back) provided on the side wall of the lower case 11 and the upper case Six recesses 30a to 30f (two tails a and b on the left, two tails c and d on the right, and two tails e and f on the back) provided on the side wall of 30 are respectively engaged. Thus, the lower case 11 and the upper case 51 are engaged.

  In the configuration of the liquid crystal display device 1 described above, light emitted from the LED 141 is transmitted through the light guide plate 15, the reflection sheet 12, the light guide plate 15, the diffusion sheet 16, the lens sheet 17 in the X direction, and the lens sheet 18 in the Y direction. 20 is irradiated.

1 is an assembled perspective view of a liquid crystal display device having a backlight unit according to an embodiment of the present invention. It is the assembly perspective view seen from the back side. It is a top view. FIG. 4 is a cross-sectional view taken along the line A-A ′ of FIG. 3. FIG. 4 is a B-B ′ sectional view of FIG. 3. It is a perspective view which shows a frame. It is a schematic plan view which shows the clearance gap between a reflection sheet and a frame, the case used as the reflection sheet, and a frame and a lower case. It is a schematic plan view which shows the clearance gap between a reflective sheet and a frame when the position of a reflective sheet deviates. It is a schematic plan view which shows the clearance gap between a reflective sheet and a frame when the position of a reflective sheet and a frame offsets. It is sectional drawing which shows the attachment method of the conventional reflection sheet. It is sectional drawing which shows the attachment method of the other conventional reflective sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Backlight unit 11 Lower case 12 Reflective sheet 12a-12h Notch part (frame body)
13 Frame 13a-13h Convex part (frame)
14 Flexible printed circuit board 141 LED
15 Light guide plate 16 Diffusion sheet 17 Lens sheet (X direction)
18 Lens sheet (Y direction)
20 LCD panel 30 Upper case

Claims (6)

A light guide plate having a light source, a light guide plate having a side surface on which light from the light source is incident, and a top surface from which incident light is emitted, a reflection sheet disposed below the light guide plate, and having a frame shape, the light guide plate. In a backlight unit having a frame body that surrounds the optical plate, and a lower case that is open at the top and has a side wall and the reflection sheet is laid on the bottom surface and surrounds the frame body with the side wall,
The reflective sheet has a notch, the frame includes a convex portion that protrudes higher than the thickness of the reflective sheet in a range narrower than the notch and contacts the bottom surface of the lower case, and the frame is A backlight unit characterized by not being placed on the reflection sheet. The backlight unit according to claim 1, wherein the frame includes an engaging portion that engages with the lower case, and the convex portion is provided in the vicinity of the engaging portion. The gaps to the frame in the front, back, left, and right directions of the reflective sheet at the notch portions are larger than the gaps to the lower case in the front, back, left, and right directions of the reflective sheet. The backlight unit according to claim 1, wherein the backlight unit is large. Respective gaps to the front, rear, left, and right frame of the reflective sheet at the notch are respectively spaced to the lower case in the front, rear, left, and right directions of the reflective sheet. The backlight unit according to claim 1, wherein the backlight unit is larger than a value obtained by adding respective gaps to the lower case in the rear, front, right, and left directions of the frame. The liquid crystal module according to claim 1, wherein the light guide plate does not overlap the reflective sheet. A liquid crystal display device comprising a liquid crystal panel, wherein the liquid crystal panel is irradiated with light using the backlight unit according to claim 1.

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