JPS635302A - Light guide - Google Patents

Abstract

PURPOSE:To obtain illumination having no unevenness in intensity of illumination, by reflecting rays of light from light sources by means of a spherical reflecting surface and plane reflecting surface and leading the rays of light in a prescribed direction. CONSTITUTION:When rays of light from tubular light sources 4 and 5 are reflected in a wide angle by means of a spherical reflecting surface 2, the reflecting surface 2 receives the rays of light from the light sources 4 and 5 and rays of light which are totally reflected by a transparent plate 6. Therefore, it is considered that light source centers exist at the centers O1 and O2 of the light sources 4 and 5 and mirror images 4' and 5' and the rays of light which are regarded as those emitted from the center O1 in the directions A1 and A2 are reflected in the directions Am and An by the spherical reflecting surface 2. Moreover, rays of light which are directly projected on a plane reflecting surface 3 or those projected on the surface 3 after they are reflected by the surface 2 exist against the rays of light which are directly reflected toward the plate 6 from the surface 2, but those rays of light also advance toward the transparent plate 6 after they are reflected by the spherical reflecting surface 2 as shown by the light routes B1 Bm and B2 Bn. Therefore, illumination of uniform intensity of illumination can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to the structure of a light guide used in a bank light of a liquid crystal display or the like.

<Prior art> Display devices include those that display by emitting their own light, such as light-emitting diodes and electroluminescent displays, and those that do not emit light themselves, such as liquid crystal displays, that do not emit light by themselves, but have light transmittance or reflection. Some devices display patterns by controlling the rate of illumination to modulate natural light or light emitted from other illumination sources. The latter would therefore require lighting means.

The display mode of most liquid crystal displays utilizes the optical anisotropy of liquid crystal, and in the case of color display devices, the amount of light is further reduced by a polarizing plate or a color filter, so it is not suitable for general indoor use. , the provision of lighting means is an essential requirement.

FIG. 2 shows a cross-sectional structure of a conventional light guide used in a liquid crystal display. The light guide 12 has a large number of strip-shaped reflective surfaces A and strip-shaped non-reflective surfaces B alternately formed at a constant pitch on the - side surface.

Tubular light g11 arranged at one end of this light guide 12
The incident light from 1 is reflected by the reflective surface A, and surface illumination is obtained by this reflected light. In the figure, 0 is the center of the light source, which is the design origin of the light guide, and 11' is the mirror image of the tubular light source 11.

<Problems to be solved by the invention> Conventionally, as shown in FIG. 2, a light guide has alternating strip-shaped reflective surfaces A and strip-shaped non-reflective surfaces B, thereby making the brightness of brightness uniform over the entire surface. In order to achieve this, an enlarged V&transmission plate made of opalescent glass or synthetic resin plate having a light scattering effect is provided. In this case, if the projection Y width in the horizontal direction in the figure of the band-shaped reflective surface A is a, and the same (projection width of the band-shaped non-reflective surface B is b), the average brightness of the bright and dark stripes of the band-shaped reflective surface is In order to eliminate the influence, conventional methods have been taken such as increasing the diffusion effect of the diffuser plate or increasing the ratio of a in the ratio a:b of the projected width of the reflective surface and the non-reflective surface. For example, 30-50% by diffusion plate
This leads to a certain degree of reduction in brightness, and furthermore, there are drawbacks such as an increase in the thickness of the light guide shape.

<Means for Solving the Problems> The light guide according to the present invention includes a plurality of spherical reflecting surfaces arranged at predetermined intervals and a planar reflecting surface connecting the spherical reflecting surfaces. have

Effect> The light guide according to the present invention reflects light from a light source on a spherical reflective surface and a planar reflective surface and guides it in a predetermined direction.

<Example> FIG. 1 shows a cross-sectional configuration of a lighting device equipped with a light guide of this example. The light guide l has a structure in which a plurality of spherical reflective surfaces 2 protruding downward in the figure are uniformly arranged at predetermined intervals, and each spherical reflective surface 2 is connected by a planar reflective surface 3. have The surfaces of the spherical reflective surface 2 and the planar reflective surface 3 are coated with a reflective layer to increase reflectance. The light guide 1 has a symmetrical structure. A tubular light source 4 is provided at both left and right ends of the light guide 1.
．． 5 are placed respectively. 2111i1 tubular light source 4
．． A transparent plate 6 is arranged between the light guides 1 and 5 at a position facing the reflective surface 2°3 of the light guide 1.
A diffusion plate 7 is disposed outside the transparent plate 6 if necessary depending on the degree of diffusion. In addition, in the figure, 4' and 5' are tubular light sources 4.
．． 5, and 01 and 02 are the centers of the light sources, which are the design origins of the light guide l.

Now, consider the case where light from the tubular light source 4.5 is reflected at a wide angle by the spherical reflecting surface 2. The spherical reflective surface 2 is a light source 4
, 5 and the light totally reflected by the transparent plate 6. Therefore, the light source center is considered to be at the center 01°02 of the tubular light sources 4, 5 and the mirror images 4', 5', and the light that is considered to be emitted from the light source center 01 is reflected on the spherical reflective surface 2 in the figure. Light in the AI and A2 directions is reflected in the Am and An directions.

In addition, with respect to the light that is directly reflected toward the transparent plate 6 on the above-mentioned spherical reflective surface 2, the light that directly hits the planar reflective surface 3 or is reflected by the spherical reflective surface 2 and is reflected on the planar reflective surface. 3
There is also light that falls on the optical path B IB m,
After being reflected by the spherical reflecting surface 2, it heads toward the transparent plate 6, as indicated by B2-Bn.

In this way, in the light guide 1, since the spherical reflecting surface 2 itself has a diffuse reflection effect, uniform brightness of the light can be obtained.

<Effects of the Invention> As explained above, in the present invention, a large number of spherical reflective surfaces are uniformly arranged, and light from a light source is reflected by the spherical reflective surfaces and guided in a predetermined direction. Therefore, the incident light is directly diffusely reflected by the spherical reflecting surface, and the same effect as using a diffuser plate can be obtained. Therefore, it is possible to omit the diffuser plate or use a diffuser plate with low diffusivity, and since illumination with uniform brightness can be obtained, the light guide can be made thinner and the brightness can be increased.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the cross-sectional structure of a lighting device equipped with a light guide according to an embodiment of the present invention, and FIG. 2 is a diagram showing the structure of a conventional light guide. 1... Light guide 2... Spherical reflective surface 3... Planar reflective surface 4.5... Tubular light source

Claims (1)

[Claims] a plurality of spherical reflective surfaces arranged at predetermined intervals;
A light guide comprising a planar reflective surface connecting the spherical reflective surfaces, and wherein light from a light source is reflected by the spherical reflective surface and the planar reflective surface and guided in a predetermined direction.