JPH0320716A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a back light having a uniform luminance even when the back light type liquid crystal display device is used over a long period of time in an atmosphere of high humidity by forming the small projections to prevent tight adhesion on the opposite surfaces of a light transmission body and a reflecting plate of the above-mentioned display device. CONSTITUTION:The light radiated from a linear source 1 enters the light trans mission body 2 and repeats reflections and diffusions between this body and the reflecting plate 3 of the bottom plate. The rear surface of the liquid crystal display element is irradiated with this light through a diffusion plate 4. The small projections 5 of a prescribed height are provided at prescribed intervals on the reflecting plate 3. The contact of the reflecting plate 3 and the light transmission body 2 is obviated by providing the projections 5. Such an incident that the spacings are filled with water does not arise even if the water film of a very small thickness is generated on the surface of the reflecting plate 3 after the long-term use in the atmosphere of the high humidity. The back light having the uniform luminance is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a liquid crystal display that maintains a uniform amount of incident light from the back of the liquid crystal display element even when used for a long period of time in a high humidity atmosphere. Regarding equipment.

[Prior Art] Backlight type liquid crystal display devices are widely used as display devices that are bright and easy to view, and have a small depth relative to the screen size. If a normal light source is placed directly behind the liquid crystal display device as a backlight for a backlight type liquid crystal display device, problems arise such as the depth becomes large and it is difficult to obtain uniform brightness on the display surface.

As a countermeasure to this problem, a light source placed on the side of the liquid crystal display element, a light guide body that guides the light from the light source and illuminates the liquid crystal display element uniformly from the back side, and a light guide body placed on the back side of the light guide body. A backlight equipped with a reflecting plate that reflects the light emitted from the light guide and makes it enter the light guide again has come to be used (Japanese Utility Model Publication No. 52-1277931). In this backlight light guide, the light from the light source that enters from the side is diffused little by little toward the back side of the liquid crystal display element in order to illuminate the back side of the liquid crystal display element, and the remaining light is diffused and emitted. As the light is reflected repeatedly, the amount of light gradually decreases as it travels further through the light guide.

The light guide is usually made of plastic material in order to form the desired shape of the surface facing the liquid crystal display element, as well as from the viewpoint of weight and cost. Aluminum is used because of its cost.

[Problems to be Solved by the Invention] However, in the backlight type liquid crystal display device as described above, special attention is not paid to the surfaces of the respective members on the side where the light guide and the reflection plate face each other. Instead, they were usually only finished in what is called a flat surface. If flat surfaces that have been finished without special care come into contact, the two parts will touch in some places, but in other places there will be slight undulations in the surfaces,
Due to the curvature, etc., an extremely small air layer remains. If such a liquid crystal display device is used for a long period of time in a high humidity atmosphere, the tiny gaps between the light guide and the reflector will become filled with water, even in areas where the above air layer remains. This results in areas where the In the case where there is a thin air layer in the gap between the light guide and the reflector and the place where the gap is filled with water, the amount of light incident on the light guide is greater in the latter case, resulting in brighter light. In the end, between the light guide and the reflector, there are areas where they are in direct contact, areas where there is a layer of water in between, and areas where an air layer remains, which reduces the brightness of the display surface. This causes unevenness and makes the display look ugly.

The present invention solves the problems of conventional backlight type liquid crystal display devices, and provides a liquid crystal display device that does not cause uneven display brightness even when used for a long period of time in a high humidity atmosphere. The purpose is to provide

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a backlight type liquid crystal display device including a light guide and a reflector.
It was decided to form small protrusions on the opposing surfaces of either the light guide or the reflector to prevent them from coming into close contact with each other.

[Function] If the light guide and the reflector can be truly brought into close contact with each other over the entire surface, no problem will occur.Although it is not technically impossible to do so, it requires a large amount of man-hours. Not possible considering the price. In addition, the light guide and the reflector are bonded together using a transparent adhesive having an appropriate refractive index.
It is conceivable to fill the gap between the two with a hardened adhesive, but this is also undesirable in terms of man-hours and costs.

According to the present invention, by providing small protrusions on either the light guide or the reflector so that even when used for a long time in a high humidity atmosphere, a thin air layer always exists between the two, it is possible to It is clear that a display with uniform brightness can be seen over the entire display surface of a liquid crystal display device at a reasonable cost.

[Embodiment] FIG. 1 is a side sectional view of a backlight section according to an embodiment of the present invention. Linear light tX1 For example, light emitted from a cold cathode discharge tube with a small tube diameter enters the light guide 2 and is repeatedly reflected and diffused between the bottom reflector 3 and passes through a diffuser plate 4 (not shown). Illuminates the back side of the liquid crystal display element. This bottom reflector 3
Small protrusions 5 with a height of 0.2 m are sparsely provided at intervals of 20 mm.

If the diameter of the peak of the protrusion is 0.3 mm or less, the reflectance of light in that area does not appear to change, so the tips of the protrusions on the reflector are in contact with the light guide. However, it is not noticeable and there is no problem. Also, the distance between the protrusions is 20lln
If the spacing is within a reasonable distance, the reflector and light guide will not come into contact even with an extremely simple finishing method. Note that 6 is a side reflection plate.

In this way, even if you continue to use it for a long time in a high humidity atmosphere, even if a microscopic water film forms on the surface of the light guide or reflector, both will be protected. There will be no situation where the gap between the two is filled with water. Therefore, even if the backlight is used for a long period of time in a high humidity atmosphere, a backlight with uniform brightness can be obtained.

[Effects of the Invention] As described above, according to the present invention, a liquid crystal display device that does not cause uneven display brightness even when used for a long period of time in a high humidity atmosphere can be obtained.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a backlight section according to an embodiment of the present invention. Construction: line light source, 2: light guide, 3: bottom reflector, 4: diffuser plate, 5: small protrusion, 6: side reflector. 1st Figure 4 1 Line Death Rider 2 Ichicho Mitsuki 3 Ichijo Ukisugi Vs.

Claims (1)

[Claims] 1. A light source placed on the side of the liquid crystal display element, a light guide for guiding the light from the light source and uniformly illuminating the liquid crystal display element from the back side, and a light guide placed on the back side of the light guide. In a backlight type liquid crystal display device equipped with a reflector that reflects light emitted from the light guide and re-injects it into the light guide, a light guide and a reflector are provided on the surfaces of either the light guide or the reflector that face each other. A liquid crystal display device characterized in that a small protrusion is formed that prevents the adhesion of the liquid crystal display device.