JP2001117097A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reduction of display quality by suppressing light leakage from a gap at a tip edge of a light source side of a light transmission plate. SOLUTION: A both side adhesive light shielding member 20 is disposed between a tip edge 2a of the surface of the light transmission plate 2 and a tip edge 5a of a reflection plate 5 to fix the light transmission plate 2 to the reflection plate 5. Thereby, the light passing from a fluorescent lamp 4 through an edge 2b of the light transmission plate 2 is interrupted by the light shielding member 20 and the light passing to the end surface of an optical sheet 12 is also interrupted, accordingly no light leaks from the gap between a frame 21 and the light transmission plate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a transmission type liquid crystal display device provided with an edge light type illumination device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been attracting attention for their features of low power consumption, light weight, and thinness, and their application fields are expanding. For example, in a monitor for consumer video, a monitor for industrial equipment, and a display panel of a personal digital assistant, a transmissive liquid crystal display device is often used for a display portion thereof.

[0003] The transmissive liquid crystal display device comprises a panel-like liquid crystal display element and an edge light type illuminating device arranged on the back side thereof. FIG. 7 shows the structure of a conventional lighting device. A light guide plate 2 made of an acrylic resin, a polycarbonate resin, or the like is disposed behind the liquid crystal display element 1, a dot-like diffusion pattern is formed on the back surface thereof by molding or printing, and a reflection sheet 3 that covers the entire back surface is disposed. You. A tubular fluorescent lamp 4 as a light source is arranged on the side of the light guide plate 2 so as to face this end face. The fluorescent lamp 4 is held by a holder (not shown) and is three-way except for the direction facing the light guide plate 2. Are surrounded by the reflection plate 5.
The edge 5a of the reflection plate 5 extends toward the light guide plate 2, the front edge 5a is overlapped with the edge 2a on the surface of the light guide plate 2, and the rear edge 5a of the reflection sheet 3 is It overlaps with the edge 3a. Then, a resin frame 6 and a metal frame 7 are provided so as to cover the reflection plate 5, and the reflection plate 5 is fixed to the resin frame 6, and the edge 6 of each frame 6, 7 is provided.
a and 7a are respectively closer to the light guide plate 2 than the edge 5a of the reflection plate 5.
Extending toward the center of the building.

On the surface of the light guide plate 2, a diffusion plate 8, a condenser lens sheet 9, a light deflection selective reflection / transmission sheet 10, and a protection diffusion sheet 11 are laminated in this order from the bottom. here,
These are sheets or films having some optical effects such as a diffusion effect, a light condensing effect, and a light reflection selective reflection / transmission, respectively.
Call. The end face of the resin frame 6 is the optical sheet 1
2 and a gap is formed between the resin frame 6 and the optical sheet 12 in consideration of variations during assembly and dimensional errors. Also, even if there is no gap in the design,
Gaps may occur due to variations during assembly and dimensional errors. In the figure, reference numeral 13 denotes an edge 3a of the reflection sheet 3.
It is a light absorbing material provided in.

Accordingly, the light emitted from the light guide plate 2 is made uniform in brightness by the optical sheet 12 and guided to the effective display area of the liquid crystal display element 1. In addition, the optical sheet 1
No. 2 is not limited to a laminate of a plurality of sheets as described above, and may be used alone.

[0006]

By the way, in the liquid crystal display device having the above structure, if the light of the fluorescent lamp leaks directly from the gap between the frame and the light guide plate, when the light is viewed obliquely,
Bright lines due to the edge of the light guide plate appear on the liquid crystal display element,
The reflection by the incident light on the end face of the optical sheet, especially the condensing lens sheet is observed. As a result, image unevenness appears on the liquid crystal display element.

[0007] Components such as a light guide plate, an optical sheet, and a frame used in a liquid crystal display device may have molding variations or warpage of individual components. Warping may occur due to local pressing. Due to such variations and warpage of the components, a gap equal to or larger than the design value is generated at a place where the components are overlapped or arranged close to each other.

Further, many of the light guide plates, optical sheets and frames are liable to generate thermal distortion, and the components may be deformed in a wave shape by the heat of the fluorescent lamp with the use of the liquid crystal display device. Due to this deformation, a gap larger than an allowable range is generated between parts.

Then, light leaks from such a gap, and the display quality of the liquid crystal display device is impaired by the light leak.
Therefore, as shown in FIG. 8, a portion A where the display quality is deteriorated, such as a bright line or uneven brightness observed as a bright and dark pattern, appears at an end of the liquid crystal display element 1 near the fluorescent lamp 4.

[0010] Also, on the rear surface of the light guide plate, a gap exceeding the allowable range is generated between the reflection sheet and the reflection plate due to variations and warpage of components or deformation due to heat, and light leaks from this gap. This also causes uneven brightness that looks like light leakage near the fluorescent lamp.

On the other hand, the components and structure of the liquid crystal display device are designed so that an appropriate gap between the components can be obtained and thermal deformation hardly occurs. However, it is difficult to maintain the designed gap due to molding variations and warpage of each part, which is a manufacturing problem, and it is also difficult to suppress deformation due to heat within a desired range. In particular, as the size of the liquid crystal display device increases in recent years, the influence of molding variations and warpage of each component increases, and each component also tends to be deformed, resulting in a noticeable decrease in display quality.

Also, with respect to light leakage from the back surface of the light guide plate, the metal frame is subjected to drawing processing and the reflection plate is pressed against the reflection sheet to suppress the occurrence of voids or to prevent the light from being reflected at the edge of the reflection sheet. This is dealt with by providing a light-absorbing material by bonding, coating, or the like. However, the frame for holding the light source and the like must have a structure in which two types of members are combined, and there are problems in cost and manufacturing. Further, even if a light absorbing material is provided on the reflection sheet, it does not make sense if a gap is formed between the reflection plate and the reflection sheet.

Prior art techniques for preventing the deterioration of display quality occurring at the end of the liquid crystal display element near the light source are disclosed in, for example, JP-A-8-327828, JP-A-8-82716, and JP-A-9-329710. No., JP-A-5-88
172, JP-A-10-133204, JP-A-9-274185, and JP-A-6-308494. However, the structure of the liquid crystal display device described in these prior arts is different from the above structure in which the frame covers the edge of the light guide plate and the edge of the reflection sheet, and there is a gap between the optical sheet and the frame. Because of the difference, even if the prior art is applied to the above structure as it is, light leakage from the gap cannot be suppressed.

In view of the above, it is an object of the present invention to provide a liquid crystal display device with high display quality by suppressing light leakage from a gap at a light source side edge of a light guide plate.

[0015]

According to the present invention, a light source is disposed on a side of a light guide plate, and the light source is surrounded on three sides except for a direction in which the light source faces the light guide plate. The front edge of the light guide plate is overlapped with the edge of the front surface of the light guide plate, the back edge is overlapped with the edge of the reflection sheet on the back surface of the light guide plate,
A frame is provided so as to cover the reflector, and the front edge of the frame is closer to the edge of the light guide plate with respect to the lighting device extending toward the center of the light guide plate than the front edge of the reflector plate. A light-shielding member is provided on the light-emitting device to prevent light leakage from a gap between the frame and the light guide plate.

That is, by providing a light-blocking member between the front-side edge of the light guide plate and the reflection plate arranged so as to overlap with the light guide plate, a gap is not formed between the light guide plate and the reflection plate. Blocks light leaking through the gap between the frame and the light guide plate.

Alternatively, by arranging a light shielding member on the surfaces of the frame and the optical sheet, light passing through the gap between the light guide plate and the frame is blocked by the light shielding member, thereby preventing light leakage from the gap.

Further, instead of separately providing a light shielding member, a frame may be formed so that an edge of the frame is bent to form a light shielding portion so as to cover an end surface of the reflection plate and close a gap between the frame and the optical sheet. Similarly, there is an advantage that light leakage from the gap can be prevented, and the work of attaching the light shielding member is unnecessary.

Therefore, such a light-shielding member can exert its effect particularly on a lighting device having a structure in which there is a gap between the frame, the light guide plate, and the optical sheet on the surface.

Furthermore, light leakage members are provided between the light guide plate and the reflection sheet and between the reflection sheet and the reflection plate for light leakage from the back surface side of the light guide plate. And displace them along. Accordingly, the light blocking area on the back surface side of the light guide plate is increased, and light leakage from the back surface side of the light guide plate can be prevented.

[0021]

(First Embodiment) FIG. 1 shows an illumination device in a liquid crystal display device according to a first embodiment. Since the present lighting device has basically the same structure as the conventional lighting device, a configuration for suppressing light leakage will be described. That is, the light blocking member 20 is provided between the front edge 2a of the light guide plate 2 and the front edge 5a of the reflection plate 5 to prevent light leaking through the gap between the frame 21 and the light guide plate 2. Note that, unlike the conventional case, the frame 21 has an integrated structure surrounding three sides of the reflection plate 5. Further, the back surface side end surface of the reflection plate 5 may protrude toward the center from the back surface side end surface of the frame 21.

The light-shielding member 20 is formed of a light-shielding double-sided adhesive tape colored in dark color having a light-absorbing property such as black. The light path from the fluorescent lamp 4 to the edge 2b of the end face of the light guide plate 2 and the end face of the optical sheet 12 are provided. The position and the size are set so as to block the optical path directly reaching. Further, as the light shielding member 20, a highly reflective metal foil such as silver or aluminum, a resin sheet on which the highly reflective metal film is formed, or a dark colored resin sheet such as a light absorbing black is used. It may be attached to the light guide plate 2 and the reflection plate 5 with an agent.

By arranging the light-shielding member 20 in this manner, the liquid crystal display element 1 is not affected by the bright line due to the edge 2b of the light guide plate 2 and the reflection due to the incident light on the end face of the optical sheet 12, especially the condensing lens sheet 10. It will not appear any more, and a decrease in display quality can be prevented.

When the front edge 5a of the reflection plate 5 is adhered to the frame 21, the frame 21 is warped due to, for example, molding failure of the frame 21, and a gap is formed between the reflection plate 5 and the light guide plate 2. Although this occurs, the warpage of the frame 21 can be corrected because the reflection plate 5 and the light guide plate 2 are fixed. Therefore, no gap is formed between the reflection plate 5 and the light guide plate 2, and light leakage from the gap can be eliminated.

(Second Embodiment) FIG. 2 shows a lighting device of the present embodiment. The present illuminating device has basically the same structure as the conventional one, but extends from the front side edge 21a of the frame 21 of an integral structure surrounding three sides of the reflector 5 to the front side edge 12a of the optical sheet 12, A light-blocking member 22 for preventing light leaking through a gap between the frame 21 and the light guide plate 2 is provided.

The light-shielding member 22 is provided between the fluorescent lamp 4 and the optical path passing through the edge 2 b of the end face of the light guide plate 2 and the optical sheet 12.
The position and size are set so as to block the optical path that passes through the optical sheet 12 and exits from the end face of the optical sheet 12.

The material of the light shielding member 22 is, for example, a darkly colored resin sheet having a light absorbing property such as black. This resin sheet is attached to the frame 21 and the optical sheet 1
2 and is pressed and fixed by the liquid crystal display element 1. Thereby, the warpage of the frame 21 can be corrected. Further, the light-shielding member 22 is attached to the surfaces of the frame 21 and the optical sheet 12 as a dark one-sided adhesive tape. Thereby, the displacement of the optical sheet 12 can be prevented. Here, a conductive resin is used as the resin sheet, a conductive metal film is formed on the surface side of the single-sided adhesive tape, or a conductive metal foil is attached to the frame 21 and the optical sheet 12 with an adhesive. By providing the light-blocking member 22 with conductivity by attaching it, an effect of reducing inverter noise to the liquid crystal display element 1 can be obtained.

As described above, the light-blocking member 22 can prevent the generation of a gap due to the warpage of the frame 21, and can eliminate light leakage therefrom. In addition, when the liquid crystal display element 1 is viewed obliquely, the light blocking member 22
, The optical path connecting the fluorescent lamp 4 and the edge 2b of the light guide plate 2 and the optical path from the fluorescent lamp 4 to the end face of the optical sheet 12 are blocked, so that no uneven brightness occurs.
Therefore, a decrease in display quality can be prevented.

(Third Embodiment) FIG. 3 shows a lighting device of the present embodiment. The present illuminating device has basically the same structure as the conventional one, except that light shielding members 23 and 24 are provided between the light guide plate 2 and the reflection sheet 3 and between the reflection sheet 3 and the reflection plate 5, respectively. I have.

The first light guide between the light guide plate 2 and the reflection sheet 3
The light shielding member 23 is disposed near the end face of the light guide plate 2 and is located between the reflection sheet 3 and the reflection plate 5.
Are arranged near the edge of the reflection plate 5, and each light shielding member 23,
Reference numeral 24 is arranged along the back surface of the light guide plate 2 so as not to overlap with each other.

The light-shielding members 23 and 24 are formed of a light-shielding double-sided adhesive tape colored in dark color having a light-absorbing property such as black, and fix the light guide plate 2 and the reflection sheet 3 and the reflection sheet 3 and the reflection plate 5 respectively. . Further, as the light shielding members 23 and 24, a dark resin sheet may be used and attached between the light guide plate 2 and the reflection sheet 3 and between the reflection sheet 3 and the reflection plate 5 with an adhesive.

By arranging the light shielding members 23 and 24 in this manner, it is possible to prevent the light transmitted through the reflection sheet 3 from leaking to the back surface side of the light guide plate 2, and to thereby eliminate the uneven brightness. In addition, the first light-blocking member 23 can reduce bright lines from the edge on the rear surface side of the light guide plate 2, thereby preventing a reduction in display quality.

From the beginning, the light guide plate 2 is provided with the reflection sheet 3.
Is attached by the first light-blocking member 23, the assembling work of the liquid crystal display device can be performed efficiently. In addition, since the sheet is delivered in a state where the reflection sheet 3 is set in advance, there is no mistake in which the front and back of the reflection sheet 3 are mistaken.

Further, by disposing the light shielding members 23 and 24 in a shifted manner, as shown in FIG. The thickness can be reduced, and the thickness of the liquid crystal display device can be reduced. In addition, the area of the light-blocking region is increased, and light leakage can be reliably prevented. Furthermore, the clearance between the light guide plate 2 and the reflection sheet 3 and the clearance between the reflection sheet 3 and the reflection plate 5 are also reduced, so that each component is less likely to bend. If the clearance is large, deformation due to heat, which is likely to occur, can be suppressed. Prevent outbreak.

(Fourth Embodiment) FIG. 5 shows an illumination device of the present embodiment. This lighting device has basically the same structure as that of the conventional one, however, in order to prevent light leaking through a gap between the light guide plate 2 and the frame 21 having an integral structure surrounding three sides of the reflection plate 5, the surface of the frame 21 is The side edge 21a is bent so as to cover the end surface of the reflection plate 5. That is, the L-shaped light shielding portion 25 is formed on the edge 21 a of the frame 21. The light-shielding portion 25 is in contact with the end surface of the reflection plate 5, and the lower end of the light-shielding portion 25 extends along the surface of the light guide plate 2.
It is bent toward. When the light-shielding portion 25 comes into contact with the surface edge 2 a of the light guide plate 2 and comes close to the optical sheet 12, the gap between the frame 21 and the optical sheet 12 is closed.

As described above, the edge 21a of the frame 21 is formed so as to block the optical path passing from the fluorescent lamp 4 through the edge 2b of the end face of the light guide plate 2 and the optical path directly reaching the end face of the optical sheet 12, thereby providing a light guide. Edge 2b of light plate 2
Cannot be visually recognized from the outside, and light does not enter the end surface of the optical sheet 12. As a result, there is no light leaking from the gap between the frame 21 and the light guide plate 2, and the liquid crystal display element 1 has a bright line due to the edge 2 b of the light guide plate 2 and light incident on the end face of the optical sheet 12, particularly the end face of the condenser lens sheet 10. Reflection does not appear, so that deterioration of display quality can be prevented. And
Even if the frame 21 is warped, the light-shielding portion 25 is always present in the gap between the frame 21 and the light guide plate 2, so that light leakage from here can be prevented.

When the gap between the frame 21 and the optical sheet 12 is slightly wide, as shown in FIG. 6, the lower end of the light shielding portion 25 is bent toward the optical sheet 12 without making contact with the surface of the light guide plate 2. By doing so, it is possible to close the gap between the frame 21 and the optical sheet 12 without contacting the light guide plate 2 and prevent light leakage.

When the frame 21 is made of metal, it may be formed into the above-mentioned shape by drawing, and it is possible to reduce the thickness while securing the strength. further,
The heat radiation effect is enhanced, the influence of heat can be reduced, and the waving of the optical sheet 12 can be suppressed.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention. First,
The lighting devices of the second and fourth embodiments may be combined with the light shielding members of the third embodiment.

[0040]

As is apparent from the above description, according to the present invention, light leaking directly from the light source to the outside can be blocked by providing a light shielding member around the edge of the light guide plate. Therefore, even if voids are generated due to molding variations and warpage of each component, and even deformation due to heat, light leakage from here can be prevented, and uneven brightness appearing near the light source of the liquid crystal display element is suppressed, and good display quality is obtained. A liquid crystal display device can be provided.

If an adhesive material is used for the light-shielding member, the components can be fixed to each other, and the warpage of the components can be suppressed and the deformation can be prevented. Thereby, a high-quality liquid crystal display device with high assembling accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a lighting device according to a first embodiment.

FIG. 2 is a cross-sectional view of a lighting device according to a second embodiment.

FIG. 3 is a cross-sectional view of a lighting device according to a third embodiment.

FIG. 4 is an enlarged view of a rear side edge of the light guide plate.

FIG. 5 is a sectional view of a lighting device according to a fourth embodiment.

FIG. 6 is a cross-sectional view of a lighting device according to another embodiment.

FIG. 7 is a cross-sectional view of a conventional lighting device.

FIG. 8 is a plan view of a liquid crystal display device with reduced display quality.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2 Light guide plate 3 Reflection sheet 4 Fluorescent lamp 5 Reflection plate 12 Optical sheet 20 Light shielding member 21 Frame

Claims (7)

[Claims] 1. A light guide plate disposed on a back side of a liquid crystal display element, a light source disposed on an end face of the light guide plate, a reflector surrounding the light source, a reflection sheet covering a back surface of the light guide plate, An optical sheet disposed on a surface of the light guide plate, and the light guide plate;
A frame that holds a light source and a reflector, wherein the front and back edges of the reflector overlap the front and back edges of the light guide plate, and the front end of the frame is closer than the front end of the reflector. A light-shielding member is provided to extend and face the optical sheet, and between a surface-side edge of the light guide plate and the reflection plate, to prevent light leaking through a gap between the frame and the light guide plate. A liquid crystal display device characterized by the above-mentioned. 2. The liquid crystal display device according to claim 1, wherein the light-shielding member is a light-shielding double-sided adhesive tape, and the frame and the reflection plate are adhered. 3. A light guide plate disposed on the back side of the liquid crystal display element, a light source disposed on an end face of the light guide plate, a reflector surrounding the light source, a reflection sheet covering the back surface of the light guide plate, An optical sheet disposed on a surface of the light guide plate, and the light guide plate;
A frame that holds a light source and a reflector, wherein the front and back edges of the reflector overlap the front and back edges of the light guide plate, and the front end of the frame is closer than the front end of the reflector. A liquid crystal display device comprising: a light-shielding member that extends and faces the optical sheet and that is provided on a surface of the frame and the optical sheet to prevent light leaking through a gap between the frame and the light guide plate. . 4. The liquid crystal display device according to claim 3, wherein the light shielding member is made of a conductive light shielding material, and is attached to the frame and the optical sheet. 5. A light guide plate disposed on a back surface side of a liquid crystal display element, a light source disposed on an end surface of the light guide plate, a reflector surrounding the light source, a reflection sheet covering a back surface of the light guide plate, An optical sheet disposed on a surface of the light guide plate, and the light guide plate;
A frame that holds a light source and a reflector, wherein the front and back edges of the reflector overlap the front and back edges of the light guide plate, and the front end of the frame is closer than the front end of the reflector. A light-shielding member extending between the light guide plate and the reflection sheet and between the reflection sheet and the reflection plate to prevent light leaking through a gap between the frame and the light guide plate, the light shielding member being opposed to the optical sheet; Wherein each light shielding member is arranged to be shifted along the back surface of the light guide plate. 6. A light-shielding member between the light guide plate and the reflection sheet is disposed closer to an end face of the frame than a light-shielding member between the reflection sheet and the reflection plate, and each light-shielding member is a light-shielding double-sided adhesive tape. The liquid crystal display device according to claim 5, wherein: 7. A light guide plate disposed on the back side of the liquid crystal display element, a light source disposed on an end face of the light guide plate, a reflector surrounding the light source, a reflection sheet covering the back surface of the light guide plate, An optical sheet disposed on a surface of the light guide plate, and the light guide plate;
A frame that holds a light source and a reflector, wherein the front and back edges of the reflector overlap the front and back edges of the light guide plate, and the front end of the frame is closer than the front end of the reflector. An edge of the frame is bent so as to cover the end face of the reflector in order to prevent light leaking through a gap between the frame and the light guide plate. Liquid crystal display device.