JPH0547922U - Surface light source - Google Patents

Abstract

(57) [Summary] [Object] The present invention aims to achieve uniform brightness in a surface light source device using a light guide. A surface light source device in which a light guide body that allows light from a light source to enter from at least two opposing end surfaces and a diffuser plate disposed on the front surface side thereof is arranged, and a large number of cones or pyramids are provided on the back surface of the light guide body. The recess was formed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a surface light source device used for a backlight of a liquid crystal display panel or the like.

[0002]

[Prior Art]

 A conventional surface light source device using a light guide has a structure as shown in FIG. This apparatus includes a linear light source 1 such as a cold cathode tube, a light guide 2 arranged with the incident end face 2a in close proximity to the light source 1, and a diffusion plate 3 provided on the surface of the light guide 2. It is composed of a reflection surface 4 formed on the back surface of the light guide 2. The light from the light source 1 enters the light guide 2 through the incident end face 2a, is repeatedly reflected by the front surface and the back surface of the light guide, and travels to the other end side. In the meantime, the light emitted from the surface of the light guide 2 passes through the diffusion plate 3 and becomes diffused light.

[0003]

[Problems to be solved by the device]

 The diffused light needs to be uniform at all points on the surface of the diffuser plate 3. Therefore, various measures are taken.

It is an object of the present invention to provide a surface light source device using a light guide, which has a simple structure and has a uniform luminance distribution on a diffusion plate.

[0005]

[Means for Solving the Problems]

 The surface light source device of the present invention is configured by using the light guide as described above, and has a large number of minute pyramids and conical recesses formed on the back surface of the light guide. The size is different depending on the place so that a uniform luminance distribution can be obtained on the diffusion surface.

Particularly, the surface light source device of the present invention does not have one light source as in the conventional example, but has two light sources in which light sources are respectively arranged near the opposite end faces of the light guide body, or a light guide body. It is effective for an apparatus having four light sources in which light sources are arranged on all four end faces.

[0007]

【Example】

 Next, an embodiment of the surface light source device of the present invention will be described.

FIG. 1 shows a two-light type embodiment of the surface light source device of the present invention. In the figure, 1 is a linear light source, 2 is a light guide, 3 is a diffusing plate, and 4 is a reflecting surface, which are basically the same as the conventional surface light source device shown in the figure. However, this embodiment is different from that shown in FIG. 3 in that it is of a two-lamp type and that light is made incident from both end surfaces 1a and 1b and that a recess 5 is formed on the lower surface of the light guide 2. ing.

FIG. 2 is an enlarged sectional view of the light guide 2 of the surface light source device of the present invention.

The recess 5 formed in the light guide 2 shown in FIG. 2 is preferably pyramidal or conical.

Similar to the conventional example, the light guide 2 of this embodiment advances when light from the light source enters from the incident end faces 2a and 2b while reflecting on the front and back surfaces. In the meantime, a part of the light goes out of the light guide from the surface, becomes diffused light through the diffusion plate 3, and this diffused light becomes the illumination light of the surface light source.

Here, since the concave portion 5 is formed on the bottom surface of the light guide body 2, light is subjected to an action such as total reflection by the concave portion 5. As a result, the light emitted from the surface of the light guide is different from that of the light guide in which the recess is not formed. Therefore, by controlling the size of the recesses 5 formed on the back surface of the light guide 2, the number of recesses per unit area, the shape of the recesses such as the inclination angle of the recesses with respect to the back surface, the diffusion plate 3 is reached. It is possible to control the distribution of light, and thereby make the brightness distribution on the surface of the diffuser plate uniform.

Although this embodiment is a two-lamp type surface light source device, four end faces corresponding to four sides of a quadrangle of a light guide having a quadrangular surface are incident end faces, and each of the incident end faces is respectively A four-lamp system in which a linear light source is arranged may be used. As a result, a brighter surface light source device can be obtained.

Further, although it can be applied to a one-lamp type surface light source device as shown in FIG. 3, it is more preferable to apply the idea of the present invention to a two-lamp type and a four-lamp type from the viewpoint of brightness and the like.

The light guide used in this embodiment and the like is generally made of transparent synthetic resin. Therefore, the light guide having the concave portion 5 according to the present invention can be extremely easily manufactured by a method such as injection molding.

[0016]

[Effect of the device]

 INDUSTRIAL APPLICABILITY The surface light source device of the present invention has a simple structure in which a recess is formed on the back surface of the light guide body, and the brightness of the diffusion surface can be uniform.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a light guide used in the above embodiment.

FIG. 3 is a cross-sectional view of a conventional surface light source device using a light guide.

[Explanation of symbols]

1 light source, 2 light guide, 3 diffuser plate, 4 reflector plate, 5
Recess

Claims (1)

[Scope of utility model registration request] 1. A light guide body made of a transparent plate having a rectangular shape,
A large number of concave portions each having a conical shape or a pyramid shape on the back surface of the light guide body, the linear light sources being respectively arranged on at least two opposing end surfaces of the light guide body, and a diffusion plate arranged on the front surface of the light guide body. A surface light source device formed with.