JP2995556B2 - Light guide and surface light source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide and a surface light source device using the light guide.

[0002]

2. Description of the Related Art Heretofore, as a method of forming a rough surface on a surface of a synthetic resin molded product such as a synthetic resin plate, a method of spraying sand on the surface of the molded product to form irregularities on the surface is known.

As another method, there is a method of forming a molded article having a rough surface by forming irregularities in a mold for forming the molded article in advance, and molding the molded article using the mold having the irregularities.

An example of a molded product having such a rough surface is a light guide used in a surface light source device.

In a surface light source device using this light guide, a light guide 12 made of a plate-shaped transparent body is arranged in proximity to a linear light source 11 such as a cold-cathode tube in a configuration as shown in FIG. A diffusion plate 13 is provided on the surface of the light guide 12 and a reflection surface 14 is provided on the back surface thereof.
Is arranged.

In the surface light source device having the structure shown in FIG. 2, the light from the linear light source 11 is made to enter the light guide 12 from the incident end face 12a, and the interior is totally reflected by the upper and lower faces while the other end face is being reflected. 12b, during which light within the total reflection angle exits from the light guide surface to the diffusion plate 13b.
Through the light to become diffused light. This diffused light becomes illumination light from the surface light source device.

In the surface light source device using such a light guide 12, the back surface of the light guide is set so that the diffused light emitted from the diffusion plate 13 has a uniform brightness on the surface of the diffusion plate. The surface is made to have a rough surface with fine irregularities so that light reflected on the back surface becomes diffused light. It is desirable that the rough surface is not diffused much near the incident end face so that the diffused light emitted from the diffuser plate 13 becomes uniform, and that the ratio of the diffused light gradually increases as the distance from the incident end face increases.

For this reason, it is desirable that the rough surface has a structure as shown in FIG. That is, in FIG.
A large number of rough surface portions (hereinafter, referred to as miniaturized portions) having a small area indicated by are formed, and the number is changed depending on locations. For example, in FIG. 3, the number of the miniaturized portions 15 is small on the incident end side 12a, and increases as the distance from the incident end side 12a increases.

The pattern having the rough surface may be formed on the back surface of the light guide 12.

[0010]

A plate-like molded product having a diffuse reflection surface having a specific pattern as described above is formed by, for example, injection molding using a mold having a rough surface formed by sandblasting. In the case of forming, it is difficult to form the rough surface portion of the mold, and it is particularly difficult to accurately form a specific pattern as shown in FIG.

According to the present invention, a light guide having a diffuse reflection surface, such as a light guide having a specific pattern and requiring high accuracy, exhibits optical characteristics as designed, and such a light guide is provided. It is an object of the present invention to provide a used surface light source device exhibiting a very uniform luminance distribution.

[0012]

SUMMARY OF THE INVENTION A light guide according to the present invention has a specific pattern formed by partitioning a large number of miniaturized portions having fine irregularities on the back surface, and a portion corresponding to the pattern is formed. It is characterized by being molded from a synthetic resin material using a mold roughened by electric discharge machining. or,
The surface light source device of the present invention is a light guide made of a transparent member, a linear light source arranged near one end face of the light guide, and a reflection member arranged on the back side of the light guide. A light source device having at least a specific pattern formed by partitioning a large number of miniaturized portions consisting of fine irregularities on the back surface of the light guide, and the light guide is in the pattern It is characterized in that a corresponding portion is formed of a synthetic resin material using a mold whose surface is roughened by electric discharge machining.

According to the present invention, the rough surface provided on the mold used for molding the light guide can be formed in an accurate shape and a pattern corresponding to the shape of the convex portion of the electrode. Is formed by electric discharge machining, so that very fine irregularities can be formed.

Therefore, by forming an electrode plate having a convex portion having the same surface shape as the pattern of the diffuse reflection surface formed on the light guide and processing the mold, a light guide having an accurate pattern can be formed. It becomes possible to do.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing a state in which a metal mold used for molding the light guide of the present invention is subjected to electric discharge machining. In the figure, reference numeral 1 denotes a metal mold, and 2 denotes an electrode when performing electric discharge machining. On the electrode 2, for example, a large number of convex portions 2a (as many as the number of the rough surface portions 15) are formed on the diffuse reflection surface having the pattern shown in FIG. Have been.

As shown in FIG. 1 above, if the electric discharge machining is performed after the mold 1 and the electrode 2 are arranged to face each other, the mold 1
Only the portion of the surface 1a facing the convex portion 2a of the electrode 2 is processed to form a pattern. Each of the miniaturized portions 15 of this pattern has a very rough surface with extremely fine irregularities formed by electric discharge machining.

When a light guide using a synthetic resin plate, for example, a transparent resin material, is formed by an injection molding method or the like using the mold formed as described above, the surface of the light guide will be formed. A pattern as shown in FIG. 3 is formed by partitioning a large number of miniaturized portions 15 having fine irregularities.

Therefore, for example, when the mold formed by the method of the above embodiment is used as a mold for molding a light guide, a light guide having a pattern as shown in FIG. 3 is obtained. If this light guide is arranged as shown in FIG. 2 with the surface on which the pattern is formed downward, a surface light source device can be formed.

As described above, in the description of the embodiment, the mold for molding the light guide of the surface light source device has been described. However, the present invention can be applied to other molded products, and particularly the distribution and the pattern. It is extremely effective if applied to the production of a mold for molding a molded article having a complicated rough surface.

The electric discharge machining used in the method of the present invention is performed by defining a current, a single pulse, and the like. For example, the current value is 3 to 7 amperes, and the duration of one pulse is 5 to 20 microseconds. The roughness of each rough surface formed on the mold can be controlled by appropriately selecting the conditions during the electric discharge machining.

[0022]

According to the light guide of the present invention, a portion corresponding to a pattern provided on the light guide is formed by using a metal mold whose surface is roughened by electric discharge machining, so that an accurate optical characteristic as designed can be obtained. It has a pattern. Further, the surface light source device of the present invention uses a light guide formed by using a mold whose surface corresponding to the pattern provided on the light guide is roughened by electric discharge machining. The light guide thus obtained has an accurate pattern showing the optical characteristics as designed, so that an extremely uniform luminance distribution can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a state where an electric discharge machining is performed on a mold used for molding the light guide of the present invention.

FIG. 2 is a conceptual diagram showing an example of the surface light source device of the present invention.

FIG. 3 is a diagram showing an example of a rough surface pattern formed on the back surface of the light guide of the present invention.

[Explanation of symbols]

 Reference Signs List 1 mold 2 electrode 3 convex part 15 miniaturized part

Claims (2)

(57) [Claims] 1. A mold having a specific pattern formed by partitioning a large number of miniaturized portions made of fine irregularities on a back surface, and a portion corresponding to the pattern being roughened by electric discharge machining. A light guide formed of a synthetic resin material. 2. A light guide comprising a transparent member, at least a linear light source disposed near one end face of the light guide, and a reflecting member disposed on the back side of the light guide. A surface light source device having a specific pattern formed by partitioning a large number of miniaturized portions formed of fine irregularities on the back surface of the light guide, and a portion corresponding to the pattern in which the light guide corresponds to the pattern. A surface light source device characterized in that the surface light source device is formed of a synthetic resin material using a mold whose surface is roughened by electric discharge machining.