JP2007305449A - Surface light source, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-weight, thin backlight unit for a flat panel display device that is reduced in cost by forming a light source into a surface light source to facilitate luminance increase by only using a thin optical sheet group, without having to use a thick, heavy and high-cost diffusion plate is not used. <P>SOLUTION: This surface light source is provided with a housing having a bottom surface for supporting the light source thereto, and having an opening on an upper surface thereof facing to the bottom surface; a frame body fitted to the upper surface of the housing; an optical sheet 1 fixed to the housing or the frame body that covers the opening of the housing or an opening of the frame body; and an optical sheet 2 supported by the optical sheet 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a surface light source and a liquid crystal display device. More specifically, the present invention relates to a surface light source composed of only an optical sheet without using a diffusion plate having a thickness of about 2 mm, and a liquid crystal display device using the surface light source.

  Since liquid crystal display devices have characteristics such as thinness, light weight and low power consumption, they are rapidly spreading as display devices for information equipment and video equipment. In order to further promote the spread of liquid crystal display devices, there are demands for reduction in thickness and weight and reduction in cost of members. In order to satisfy these demands, it is particularly important to reduce the thickness and weight of the backlight unit that accounts for about half of the thickness and cost of the liquid crystal display device, that is, to reduce the thickness and weight of the surface light source.

  In a surface light source of a liquid crystal display device, particularly a surface light source called a direct-type surface light source, a plurality of fluorescent tubes arranged side by side are bright and a space between adjacent fluorescent tubes is dark (tube unevenness). In order to make the tube unevenness uniform, a diffusive diffusion plate having a high turbidity, which is usually about 2 mm thick and kneaded with cross-linked organic particles or silica is used (Patent Document 1). This diffuser plate not only has a function of making light uniform, but also has a function of supporting other optical sheets having functions such as diffusibility and light collecting property.

  However, this diffusion plate is as thick as about 2 mm, heavy, and expensive. In order to reduce the thickness and weight of the surface light source and further reduce the cost, it is important to reduce the thickness of the diffusion plate or not to use the diffusion plate.

On the other hand, in recent years, a study of replacing the diffusion plate with a thin film sheet has been underway.
JP 2004-29091 A

  However, if the diffusion plate is made thinner or the diffusion plate is eliminated, it becomes impossible to support other optical sheets that have been conventionally supported by the diffusion plate. Also, when a thin film sheet is used as an alternative to a diffuser plate, the thin film sheet alone is not self-supporting, so simply installing the thin film sheet will cause the sheet to bend and support other optical sheets. Can not. An object of the present invention is to provide a surface light source that has a thickness and can be made uniform with only a thin optical sheet group without using a heavy diffuser, and is lightweight, thin, and cost-effective. And

The present invention employs the following means in order to solve such problems. That is, the surface light source of the present invention is
A housing having a bottom surface for supporting the light source and having an opening on the top surface facing the bottom surface;
At least one optical sheet 1 fixed to the housing and covering an opening of the housing;
At least one optical sheet 2 supported by the optical sheet 1, and
And a frame body fitted into the upper surface of the housing.

Moreover, the surface light source of another aspect of the present invention is:
A housing having a bottom surface for supporting the light source and having an opening on the top surface facing the bottom surface;
A frame fitted into the upper surface of the housing;
At least one optical sheet 1 fixed to the frame and covering the opening of the frame;
And at least one optical sheet 2 supported by the optical sheet 1.

  Furthermore, the present invention is a liquid crystal display device using such a surface light source.

  According to the present invention, it is possible to provide a surface light source that can be made uniform with light only by a thin optical sheet group, is light and thin, and costs are reduced, without using a diffuser plate that is thick and heavy. Further, only one optical sheet group may be attached to the housing or the frame, and the remaining optical sheet group may be simply installed so as to be supported by the optical sheet, and the work efficiency can be greatly improved. .

  Hereinafter, preferred embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment.

  The present invention has the above-mentioned problem, that is, a thick optical sheet group that is thick, heavy, and does not use a high-cost diffuser plate, and can achieve uniform light, a light weight, a thin shape, and a low cost. It was discovered by earnestly examining the surface light source. That is, the present invention includes a housing having a bottom surface for supporting a light source and having an opening on an upper surface facing the bottom surface, and at least one optical sheet fixed to the housing and covering the opening of the housing. 1, at least one optical sheet 2 supported by the optical sheet 1, and a frame fitted into the upper surface of the housing, or a bottom surface that supports the light source. A housing having an opening on the top surface facing the bottom surface; a frame body fitted into the top surface of the housing; and at least one optical sheet 1 fixed to the frame body and covering the opening of the frame body And a surface light source having a configuration including at least one optical sheet 2 supported by the optical sheet 1, and has found that the above problem can be solved.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. Here, FIG. 1 is a cross-sectional view showing an example of the configuration of a surface light source for a liquid crystal display device in an embodiment of the present invention.

  As shown in FIG. 1, the surface light source of the present invention includes, for example, a light source 6 such as a fluorescent tube, a casing 5 having a reflection member such as a reflection sheet on the inner surface, a frame 3 that can be fitted into an opening of the casing, An optical sheet 1 solidified on the frame 3 so as to cover the opening of the frame 3, a fixture 4 for solidifying the optical sheet 1 on the frame 3, and an optical sheet 2 supported on the optical sheet 1. Has been. In FIG. 1, the optical sheet 1 is fixed to the frame 3, but may be fixed to the housing 5 so as to cover the opening of the housing 5. Further, the optical sheet 1 need not completely cover the opening of the frame 3 or the opening of the housing 5. The frame 3 can be integrated with the liquid crystal panel.

  Each of the optical sheet 1 and the optical sheet 2 according to the present invention may be composed of one optical sheet or a plurality of optical sheets. In order to make the light from the light source 6 uniform and further improve the brightness, the optical sheet 2 is preferably composed of at least two optical sheets. The optical sheet 1 according to the present invention is preferably fixed to the frame 3 or the housing 5 by using the fixing tool 4. By fixing using the fixing tool 4, the optical sheet 1 can be attached to the frame 3 in a tensioned state without sagging or distortion in order to support the optical sheet 2. The fixing tool 4 is usually attached to the outer edge portion of the optical sheet at a position where it does not obstruct the light path of the optical sheet, as many members as necessary. Here, it is preferable that at least a part of the fixture 4 is made of an elastic material. Examples of the material of the fixture 4 include a spring, a rubber material, and a highly elastic plastic material. When the optical sheet 2 is loaded, the optical sheet 1 can be kept in a tension state without sagging or distorting. As long as it is not limited to these. By using an elastic material for at least a part of the fixture 4, the elastic body absorbs thermal expansion and contraction of the optical sheet due to heating caused by the light source and changes in the external environment, and an effect of suppressing the occurrence of sagging and distortion is obtained.

  In the present invention, it is preferable that the optical sheet 1 is provided closer to the bottom surface side (side closer to the light source 6) of the housing 5 than the optical sheet 2, and the optical sheet 2 is sandwiched between the optical sheet 1 and the frame body 3. By setting it as such a structure, it can support only with a thin optical sheet group.

  In particular, when the optical sheet 1 is fixed to the frame body 3, the optical sheets 1 and 2 can be integrated with the frame body 3, so that the assembly work of the surface light source is simplified and the work efficiency is improved. Also contribute.

The shape of the optical sheet used for the surface light source can be used in any shape and size. In general, when the shape of the liquid crystal display device is taken into consideration, it is preferably a substantially rectangular shape.
The optical sheets 1 and 2 according to the present invention are a group consisting of a diffusion sheet, a prism sheet, a polarization-selective reflection / transmission sheet, or an electromagnetic wave shielding sheet, and a function-integrated optical sheet having two or more characteristics of these optical sheets. It is preferable that the optical sheet is selected from:

The thickness of the optical sheet 1 according to the present invention takes into consideration both the characteristics that it is possible to maintain a tension state without using the fixture 4 without sagging or distortion, and that it is lightweight, thin, and cost-effective. Is preferably 5 μm or more and 1000 μm or less, more preferably 10 μm or more and 500 μm or less, and particularly preferably 30 μm or more and 300 μm or less.
The size of the liquid crystal display device of the present invention is not particularly limited. In order to effectively reduce the thickness and weight of the display device and further reduce the cost of members, it is used for monitors for personal computers and televisions, and is 15 inches. The above screen size is preferable.

Sectional drawing which shows an example of a structure of the surface light source of this invention

Explanation of symbols

1 Optical sheet 1
2 Optical sheet 2
3 Frame 4 Fixture 5 Housing 6 Light source

Claims (7)

A housing having a bottom surface for supporting the light source and having an opening on the top surface facing the bottom surface;
An optical sheet 1 fixed to the housing and covering an opening of the housing;
An optical sheet 2 supported by the optical sheet 1, and
A surface light source comprising: a frame body fitted into an upper surface of the housing.   The surface light source according to claim 1, wherein the optical sheet 1 is fixed to the housing via an elastic body. A housing having a bottom surface for supporting the light source and having an opening on the top surface facing the bottom surface;
A frame fitted into the upper surface of the housing;
An optical sheet 1 fixed to the frame and covering the opening of the frame;
An area light source comprising: an optical sheet 2 supported by the optical sheet 1.   The surface light source according to claim 3, wherein the optical sheet 1 is fixed to the frame body through an elastic body.   5. The surface according to claim 1, wherein the optical sheet 1 is provided closer to the bottom surface of the housing than the optical sheet 2, and the optical sheet 2 is sandwiched between the optical sheet 1 and the frame body. light source.   The surface light source according to claim 1, wherein the optical sheet 1 has a thickness of 5 μm or more and 1000 μm or less.   The liquid crystal display device using the surface light source in any one of Claims 1-6.

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