JPH02132702A - Back light - Google Patents

Abstract

PURPOSE:To make the efficiency of a light conductor the optimum by specifying the thickness of the light conductor to a bulb diameter of an applicable lamp. CONSTITUTION:White paint 5 is applied tightly on acryle at three side surfaces and the bottom surface of acrylic light conductor 2 of a thickness (t), so light generated from a lamp 1 of a bulb diameter D gets into the acryle to be reflected at a white painted surface without leaking externally, and a diffusion plate 4 is installed on the top surface of acryle. The light is used for a flat light source from the acryle top surface through the diffusion plate 4. In this case, for securing the minimum required efficiency for a light conductor, it is set as t/D>=1.2. The optimum light conductor thickness can thus be obtained with the weight added, thereby a thin back light of a good efficiency can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a pack light, which is a liquid crystal backlight, and in which a transparent resin light guide and a fluorescent lamp are placed on the sides of the backlight serve as a planar light source.

[Conventional technology]

Conventionally, a system has been proposed in which a transparent resin such as acrylic is used as a light guide, and the area other than the lamp light introduction part is treated with white paint or sandpaper, etc., and used as a flat light source. For example, Japanese Utility Model Application Publication No. 12203/1983 can be mentioned.

[Problem to be solved by the invention]

The above conventional technology does not take into account the so-called light guide efficiency, which is how much light is introduced into the light guide and how much light is used as a flattened light source in relation to the amount of light emitted by the light source. There was a problem in using it with optimal body efficiency.

An object of the present invention is to optimize the efficiency of the light guide by defining the thickness of the light guide with respect to the tube diameter of the lamp used.

[Means to solve the problem]

In order to achieve the above object, in the present invention, the thickness of the side surface of the light guide is made larger than the outer diameter of the fluorescent lamp installed on the side of the light guide.

At this time, as the thickness of the light guide increases, the efficiency of the light guide increases, but the weight of the light guide increases as the thickness increases, so the thickness of the light guide must be determined based on this balance.

[Effect]

As the thickness of the light guide increases, the efficiency of introducing light emitted from the lamp increases, so naturally the efficiency of the light guide increases. However, even if the thickness is increased beyond a certain level, as the incident angle of the incident light increases, more light is reflected than the light that enters the light guide, so the light guide efficiency does not change and the light guide weight will only become larger and the benefits will disappear.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained.

FIG. 1 shows a backlight according to the present invention, in which (a) is a plan view and (b) is a sectional view. A straight tube fluorescent lamp 1 is placed on the side of an acrylic light guide 2, and a reflector 3 is placed around the lamp.
is fixed to acrylic 2. The three sides and bottom of the acrylic light guide are coated with white paint 5 in close contact with the acrylic, and the light emitted from the lamp enters the acrylic.
To prevent reflection from the white painted surface and leakage to the outside, a diffuser plate 4 (manufactured by Mitsubishi Rayon, Acrylite S #422, transmittance 73%) is installed on the top surface of the acrylic.

Light is passed from the top surface of the acrylic through the diffuser plate 14 and used as a planar light source. At this time, in Fig. 1, the dimensions of the light emitting part are LXH, the thickness is t, and the lamp has an outer diameter of φ8 (
When the wall thickness is 0.5t), it becomes. FIG. 2 shows the light guide efficiency expressed by the above formula.

As shown in Figure 2, the light guide efficiency increases with t/D, but becomes almost constant above t/D = 1.5.
If it exceeds 2.0, the efficiency will actually deteriorate. In other words, the minimum efficiency required for a light guide is considered to be 50%, and therefore t/D≧1.2.6 Also, the upper limit is t/D considering the efficiency of increasing the weight of the light guide. ≦2.0
is desirable.

Further, FIG. 5 shows another embodiment, and shows a modification of the cross-sectional shape of the light guide. It has been found that the light guide efficiency is not affected by such a cross-sectional shape of the light guide. At this time, the thickness t of the light guide is defined by the thickness of the side surface adjacent to the lamp.

〔Effect of the invention〕

According to the present invention, it is possible to provide an optimal light guide thickness for the outer diameter of the lamp used in a light guide type backlight, taking into account the overlap area. This allows for a thin and efficient backlight.

[Brief explanation of the drawing]

Fig. 1 is a plan view and a cross-sectional view showing the schematic structure of a backlight according to an embodiment of the present invention, Fig. 2 is a relationship curve of light guide efficiency due to changes in light guide thickness with respect to lamp tube diameter, and Fig. 3
The figure is a sectional view showing the shape of a light guide according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Fluorescent lamp, 2... Light guide, 3... Reflector, 4... Expansion board, 5... White paint. Tomi 1 Figure (cL 冫(b)

Claims (1)

[Claims] 1. In a backlight system that has a straight tube fluorescent lamp and a transparent resin light guide and emits light from one side, the thickness t of the light guide at the part where the straight tube fluorescent lamp touches or is placed close to it. and the lamp tube diameter D is at least t≧
A backlight characterized by being 1.2D.