JP2001091947A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with which the display defects occurring in the misalignment, bending, etc., of an optical sheet are decreased and reliability is improved. SOLUTION: The liquid crystal display device has a liquid crystal display panel and surface light source unit 20 laminated and arranged on a resin frame 30. The surface light source unit 20 has a tubular light source 25, a light transmission plate 22 which is mounted at the frame so as to face the liquid crystal display panel and introduces the light from the light source to the liquid crystal display panel, and the optical sheet 24 which is arranged in superposition on the light transmission plate and faces the liquid crystal display panel. The optical sheet has a first pawl part 50 which projects from one short side and is fixed to the frame and a second pawl part 52 which projects from the other short side. A long hole 54 is formed in the second pawl part. The frame has a recess 58 which is fitted with the second pawl part and the base surface of the recess is projectingly provided with a positioning projection inserted into the long hole of the second pawl part to permit the relative displacement of the second pawl part and the frame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display having a surface light source unit.

[0002]

2. Description of the Related Art In recent years, flat display devices typified by liquid crystal display devices have been used as various display devices such as televisions, computers, and car navigation systems, taking advantage of features such as thinness, light weight, and low power consumption. .

[0003] For example, a liquid crystal display device generally includes a light transmissive liquid crystal display panel in which a liquid crystal layer is held between a pair of substrates, and a surface light source unit disposed on one surface of the liquid crystal display panel. And The liquid crystal display panel and the surface light source unit are mounted on a substantially rectangular resin frame.
A rectangular frame-shaped metal bezel is mounted on the liquid crystal display panel. Thereby, the liquid crystal display panel and the surface light source unit are held in a state sandwiched between the resin frame and the bezel. Further, the liquid crystal display device includes a drive circuit board for supplying a signal for driving the liquid crystal display panel. The drive circuit board is attached to the resin frame in a state facing the back surface of the surface light source unit in order to achieve a narrow frame.

Generally, a surface light source unit includes a light guide plate and a tubular light source provided to face one side edge of the light guide plate. Also, a reflection sheet is provided below the light guide plate,
A plurality of optical sheets, such as a diffusion sheet and a prism sheet, are provided on the emission surface side for the purpose of controlling light emission characteristics.

[0005]

In the liquid crystal display having the above structure, the light guide plate and the tubular light source in the surface light source unit are mounted on a resin frame. In the optical sheet, the claw provided on one side is fixed to the resin frame using a double-sided tape, and the other side is not fixed.
However, in this case, when a mechanical stress acts on the liquid crystal display device, the optical sheet is displaced, which causes a display defect. Therefore, a structure having low vibration resistance and shock resistance is obtained.

Therefore, if a structure is adopted in which a claw is added to the other side of the optical sheet and this claw is fixed to the resin frame with a double-sided tape, vibration resistance and shock resistance can be improved. However, in this case, the optical sheet is distorted or warped due to the difference in thermal expansion between the optical sheet and the resin frame supporting the optical sheet, resulting in a structure that is weak against thermal stress.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a liquid crystal display device in which display defects due to a displacement or bending of an optical sheet are reduced and reliability is improved. is there.

[0008]

In order to achieve the above object, a flat display device according to the present invention comprises a substantially rectangular liquid crystal display panel having an effective display area, and a liquid crystal display panel arranged opposite to the liquid crystal display panel. A substantially rectangular surface light source unit, a substantially rectangular frame on which the liquid crystal display panel and the surface light source unit are mounted, and an opening corresponding to an effective display area of the liquid crystal display panel. A substantially rectangular frame-shaped bezel holding the liquid crystal display panel and the surface light source unit between the frame and the frame, the surface light source unit facing the tubular light source and the liquid crystal display panel. A light guide plate mounted on the frame and guiding light from the light source to the liquid crystal display panel, and an optical sheet interposed between the light guide plate and the liquid crystal display panel Has, the optical sheet,
A first fixing portion provided on one side facing each other and fixed to the frame; and a second fixing portion provided on the other side, wherein the frame engages with the second fixing portion. ,
It is characterized in that the second fixing portion is provided with a positioning portion which is displaceably positioned along a predetermined direction passing through the first and second fixing portions.

Further, according to the liquid crystal display device of the present invention, the positioning portion is formed in the frame and has the recess in which the second fixing portion is mounted, and the positioning portion protrudes from the bottom of the recess. And the second fixing portion has an elongated hole through which the engagement protrusion is inserted and which extends in the predetermined direction.

According to the liquid crystal display device configured as described above, even when mechanical stress such as vibration or impact acts on the optical sheet, the optical sheet is moved by the first and second claws engaged with the frame. The light guide plate is held at a predetermined position. In addition, even when a thermal stress acts due to a temperature rise and a thermal expansion difference occurs between the optical sheet, the frame, and the light guide plate, the relative thermal displacement between the second claw portion and the frame absorbs the thermal expansion difference. As a result, it is possible to prevent the optical sheet from being bent or displaced due to thermal stress.

As a result, it is possible to obtain a highly reliable liquid crystal display device capable of eliminating a display defect due to a positional shift, bending, warping or the like of the optical sheet and capable of displaying a good image.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display according to an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the liquid crystal display device is disposed such that an effective display area has a rectangular shape with a diagonal of 11.3 inches and a light transmission type liquid crystal display panel 10, which is overlapped on the back side of the liquid crystal display panel 10. A substantially rectangular surface light source unit 20;
The liquid crystal display panel and the surface light source unit are mounted on a substantially rectangular resin frame 30. A rectangular frame-shaped metal bezel 40 is placed over the periphery of the liquid crystal display panel 10, and the bezel is joined to the frame 30. Therefore, the liquid crystal display panel 10 and the surface light source unit 20 are held between the frame 30 and the bezel 40. The bezel 40 is formed of, for example, 0.2 mm thick stainless steel.

The liquid crystal display panel 10 includes a rectangular array substrate 12, a counter substrate 14, and a liquid crystal layer (not shown) sealed between these substrates. A drive circuit including a large number of display pixels, switching elements, wirings, and an analog sample-and-hold circuit (not shown) is formed on the array substrate 12, and has an effective display area 11 indicated by a broken line in FIG. Further, a drive circuit board 16 including a digital-to-analog conversion circuit (DAC) is connected to the array substrate 12 via a flexible printed circuit (FPC) 15. The drive circuit board 16 includes a surface light source unit 20
Is arranged on the back side.

As shown in FIGS. 1 and 2, the surface light source unit 20 is a side edge type surface light source unit.
A rectangular light guide plate 22 made of acrylic resin, a reflection sheet 23 adhered to the lower surface of the light guide plate, and a plurality of optical sheets 24 provided on the upper surface of the light guide plate 22, that is, the emission surface.
And Further, the surface light source unit 20 includes a tubular light source 25 provided to face one side surface of the light guide plate 22,
And a reflector 26 having a U-shaped cross section which covers the tubular light source and is fitted and held at the edge of the light guide plate 22. The light guide plate 22, the tubular light source 25, and the reflection plate 26 to which the reflection sheet 23 is attached are fitted in the frame 30 and held at predetermined positions.

The optical sheet 24 includes, for example, two diffusion sheets and one prism sheet.
They are provided in order from the side. These optical sheets 24 are formed in a rectangular shape having substantially the same dimensions as the planar shape of the light guide plate 22, and are arranged in the frame 30 so as to overlap the light guide plate 22.

Each optical sheet 24 serves as a first fixing portion.
Rectangular first claw portion 50 protruding from the middle portion of one of the short sides
And a second claw 52 having a rectangular shape protruding from a substantially middle portion of the other short side as a second fixing portion. A long hole 54 is formed at the center of the second claw 52. As will be described later, the elongated hole 54 extends along the longitudinal direction of the optical sheet, that is, the direction X connecting the first and second claws, in consideration of the thermal expansion difference between the optical sheet 24 and the frame 30. I have.

On the other hand, as shown in FIGS. 1 to 3, a pair of short side walls of the frame 30 are provided with a first engagement recess 56 into which the first claw 50 of the optical sheet 24 is fitted, and a second engagement recess 56. 2
Second engagement recesses 58 into which the claws 52 fit are formed. At the center of the bottom surface of the second engagement recess 58, a cylindrical positioning projection 60 is provided so as to project therefrom.

The first claw 50 of the optical sheet 24 is fitted into the first engagement recess 56 of the frame 30 and is attached to the first engagement recess 56 by the double-sided tape 62. Further, the second claw 52 is provided with the positioning protrusion 6.
0 is inserted through the long hole 54, and the second
It is fitted in the engagement recess 58. Here, the longitudinal dimension of the long hole 54 is formed sufficiently larger than the diameter of the positioning protrusion 60 so as to allow the relative movement between the optical sheet 24 and the frame 30 due to thermal expansion or the like. Also,
The width dimension of the long hole 54 is formed slightly larger than the diameter of the positioning projection 60. Further, the longitudinal direction of the long hole 54 is in the direction of thermal expansion of the optical sheet, that is, the first claw portion and the second claw portion are fixed to the first claw portion 50 which is a fixed end of the optical sheet 24.
It matches the direction X connecting the claw portion 52.

As a result, the optical sheet 24 is
2 is positioned at a predetermined position with respect to the frame 2, and is disposed in the frame 30. Even if a thermal stress causes a difference in thermal expansion between the optical sheet and the frame, the oblong hole 54 This difference in thermal expansion can be absorbed by the positioning projection 60 and the positioning projection 60.

Further, a second engaging recess 58 is provided in the frame 30.
Is fixed so as to cover the second claw portion 52 of the optical sheet 24 with a gap. A through hole 65 is formed at the center of the holding plate 64, and the tip of the positioning protrusion 60 is inserted into the through hole. The holding plate 64 prevents the second claw portion 52 of the optical sheet 24 from coming off the second engagement recess 58 and the positioning protrusion 60 of the frame 30. The positioning projection 60, the second engagement recess 58, and the holding plate 64 of the frame 30 constitute a positioning portion in the present invention.

As shown in FIGS. 1, 2 and 4, the tubular light source 25 and the reflector 26 extend along the longitudinal direction of the frame 30 and the light guide plate 22, and are fitted between the light guide plate 22 and the frame. Have been. The reflection plate 26 is formed by forming a reflection film made of silver on the inner surface of a molded product of stainless steel, for example.

Further, holders 66 are attached to both ends of the tubular light source 25, and a thin ground cable 70 and a relatively thick hot cable 72 extend from these holders. A connector 74 is attached to the extension ends of these cables 70 and 72.

An outlet 76 for drawing the ground cable 70 and the hot cable 72 to the outside is provided at a corner of the frame 30 adjacent to one end of the tubular light source 25. In addition, the frame 30 is provided with a pair of locking projections 78 projecting into the outlet 76 and facing each other with a gap therebetween. Further, between the locking projections 78, the locking projections 78 are slightly separated from the outlet. A positioned positioning rib 80 is provided.

Then, the ground cable 70 and the hot cable 72 are respectively caught by the locking projections 78,
It is held at a predetermined position with respect to the outlet 76. Also,
The positioning ribs 80 are located between the ground cable 70 and the hot cable 72, and regulate the movement of the cables so that these cables do not come off the locking projections 78, respectively. Therefore, the ground cable 70 and the hot cable 72 are reliably drawn out through the outlet without being displaced from the outlet 76.

The distance between the pair of locking projections 78 and the positioning ribs 80 is adjusted according to the thickness of the cable. That is, the distance between the locking projection 78 on which the thick hot cable 72 is hooked and the positioning rib is set larger than the distance between the locking projection 78 on which the thin ground cable 70 is hooked and the positioning rib.

As can be clearly understood from FIG.
The positioning rib 80 extends to the vicinity of the bezel 40 and also functions as a receiving surface of the bezel. Thereby, the receiving area of the bezel 40 in the vicinity of the outlet 76 increases, and it is possible to prevent deformation of the bezel in this portion.

On the other hand, as shown in FIG. 2, FIG. 4 to FIG. 6, the ground cable 70 of the tubular light source 25 is drawn out from the end of the tubular light source which is separated from the outlet 76, and the outer surface of the reflecting plate 26. It extends along the longitudinal direction of the reflection plate 26 and is led to the outlet 76 in a state of being sandwiched between the gap and the inner surface of the frame 30.

The ground cable 70 is connected to the reflection plate 2.
In order not to come off between 6 and the frame 30,
It is held by a metal clip 82 bent substantially in an L shape. This metal clip 82 is
0 is attached to the frame 30 from the back side, and is fastened together with the bezel 40 to the frame 30 by screws 84.
The metal clip 82 is connected to the reflection plate 26 and the frame 30.
The claw portion 82 a is inserted into a gap between the frame 30 and the claw portion 82 a, the claw portion 82 a being in contact with the outer surface of the reflection plate 26, and sandwiching the ground cable 70 with the frame 30.

The metal clips 82 are provided at a plurality of positions, for example, at three positions at intervals in the direction in which the ground cable 70 extends. By holding the ground cable 70 with these metal clips 82, even if the gap between the frame and the reflection plate varies due to a manufacturing error of the frame 30, the reflection plate 26, or the like, the ground cable 70 is connected to the reflection plate 26. And frame 3
It can be prevented from deviating from zero and can be held in a predetermined position. Therefore, at the time of assembling, it is possible to eliminate the possibility that the ground cable 70 may be disturbed or cut off from the gap.

At the same time, the metal clip 82 and the screw 84
, The reflector 26 and the bezel 40 can be electrically connected, and the generation of inverter noise caused by the tubular light source 25 can be reduced.

According to the liquid crystal display device configured as described above, in the surface light source unit 20, the optical sheet 24 installed on the light guide plate 22 has the first pair of short sides opposed to each other.
And a second claw 50, 52, the first claw is fixed to the frame 30 by a double-sided tape 62, and the second claw is
The optical sheet is attached to a first claw portion, which is a fixed end, so as to be relatively movable in a thermal expansion direction. Therefore, even when mechanical stress such as vibration or impact acts on the optical sheet 24, the optical sheet 24 can be reliably held at a predetermined position with respect to the light guide plate 22. Further, even when a thermal stress acts due to the temperature rise and a difference in thermal expansion occurs between the optical sheet 24 and the frame 30 and the light guide plate 22, the second thermal expansion is performed.
The long hole 54 of the claw portion 52 and the positioning protrusion 60 of the frame 30
Thus, the difference in thermal expansion can be absorbed, and as a result, bending, displacement and the like of the optical sheet due to thermal stress can be prevented.

As a result, it is possible to provide a highly reliable liquid crystal display device which can eliminate display defects such as uneven brightness due to displacement, bending, warpage and the like of the optical sheet and can display good images. . Further, according to the above configuration,
The positioning accuracy of the optical sheet is improved, and the display quality can be improved.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, the number and type of optical sheets can be changed as needed. Further, the shapes and arrangement positions of the first and second fixing portions provided on the optical sheet are not limited to the above-described embodiment, and can be changed as necessary.

[0034]

As described above in detail, according to the present invention, it is possible to provide a liquid crystal display device with reduced display defects due to misalignment or deflection of an optical sheet and improved reliability.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a frame and a surface light source unit of the liquid crystal display device.

FIG. 3 is a perspective view showing a positioning portion between the optical sheet of the surface light source unit and the frame.

FIG. 4 is a view showing a cable derived from a tubular light source in the liquid crystal display device and a cable outlet portion.

FIG. 5 is a perspective view showing the cable and a metal clip for holding the cable.

FIG. 6 is a sectional view taken along line AA in FIG. 5;

FIG. 7 is a cross-sectional view corresponding to FIG. 6, showing a state where the metal clip and the bezel are jointly fastened to the frame with screws.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display panel 16 ... Drive circuit board 20 ... Surface light source unit 22 ... Light guide plate 23 ... Reflection sheet 24 ... Optical sheet 25 ... Tubular light source 26 ... Reflection plate 30 ... Frame 50 ... 1st nail part 52 ... 2nd nail part 54 ... long hole 56 ... first engagement recess 58 ... second engagement recess 60 ... positioning protrusion 62 ... double-sided tape 64 ... holding plate 70 ... ground cable 72 ... hot cable 76 ... outlet 78 ... locking protrusion 80 … Positioning rib 82… Metal clip

Continued on the front page (72) Inventor Tsutomu Masuda 7-1 Nisshin-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term in Toshiba Electronic Engineering Co., Ltd. (Reference) 2H091 FA23Z FA41Z LA02 5G435 AA12 AA14 BB12 BB15 EE05 EE07 EE27 EE29 FF03 FF08 FF08 FF12 GG24 GG42 KK03

Claims (6)

[Claims] 1. A substantially rectangular liquid crystal display panel having an effective display area, a substantially rectangular surface light source unit disposed to face the liquid crystal display panel, and the liquid crystal display panel and the surface light source unit mounted thereon. A substantially rectangular frame, and an opening corresponding to an effective display area of the liquid crystal display panel. The liquid crystal display panel and the surface light source unit are attached to the frame. A substantially rectangular frame-shaped bezel held, wherein the surface light source unit is mounted on the frame so as to face the tubular light source and the liquid crystal display panel, and guides light from the light source to the liquid crystal display panel. Light plate, an optical sheet interposed between the light guide plate and the liquid crystal display panel,
Wherein the optical sheet has a first fixed portion provided on one side facing each other and fixed to the frame, and a second fixed portion provided on the other side. A liquid crystal display, comprising: a positioning portion which engages with the second fixing portion and positions the second fixing portion so as to be displaceable along a predetermined direction passing through the first and second fixing portions. apparatus. 2. The method according to claim 1, wherein the positioning portion is formed in the frame and has a recess in which the second fixing portion is mounted.
An engagement projection protruding from the bottom of the recess, and the second fixing portion has an elongated hole through which the engagement projection is inserted and which extends in the predetermined direction. The liquid crystal display device according to claim 1, wherein: 3. The first fixing portion has a first claw protruding from the one side of the optical sheet, and the second fixing portion has a second claw protruding from the other side of the optical sheet. 3. The liquid crystal display device according to claim 2, wherein the elongated hole extends along a direction connecting the first and second claw portions. 4. 4. The liquid crystal according to claim 3, wherein said frame is provided with another concave portion to which said first claw portion of said optical sheet is engaged and which is affixed with a double-sided tape. Display device. 5. The optical sheet according to claim 1, wherein the optical sheet is formed in a rectangular shape having the pair of sides as short sides, and the tubular light source is disposed along a long side of the optical sheet. The liquid crystal display device according to any one of claims 1 to 4. 6. The surface light source unit includes a reflector covering the tubular light source and mounted in the frame, wherein the tubular light source is led out from one end thereof, and is provided between the reflector and the frame. And a claw that is inserted into the gap between the reflector and the frame to hold the cable, and that is screwed to the frame and that the reflector is The liquid crystal display device according to claim 5, further comprising a metal clip that electrically connects the bezel to the bezel.