JPH0533129U - Surface light source - Google Patents

Abstract

(57) [Summary] [Object] To provide a surface light source that is thin, has high brightness, and is easy to prevent moire. A surface light source characterized in that a large number of prism elements are arranged on a light emitting surface side of the surface light source with a convex portion facing outward.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source used for back lighting of liquid crystal display elements and various kinds of display lamps.

[0002]

[Prior Art]

 As surface light sources, electroluminescent lamps, direct surface light sources that combine a fluorescent lamp and a reflector, and edge lights that combine a fluorescent lamp and a light guide plate are used.

From the viewpoint of space saving, it is required for these surface light sources to reduce the thickness and to have high brightness for improving the performance of the light source. For this reason, it is proposed in JP-A-2-17 and JP-A-2-84618 to provide a prism and a lens element. These proposals regulate the angle of emitted light so that the light is concentrated in the direction normal to the emission surface.

However, even by these proposals, the effect of obtaining a thin surface light source with sufficiently high brightness is not yet sufficiently expressed, and the prism elements and lens elements and the liquid crystal display element for the pixels and the display are arranged. There was a drawback that moire was likely to occur between the pattern and.

[0005]

[Problems to be solved by the device]

 An object of the present invention is to provide a surface light source that is thin, has high brightness, and is easy to prevent moire.

[0006]

[Means for Solving the Problems]

 The present invention provides a surface light source characterized in that a large number of prism elements are arranged on the exit surface side of the surface light source with the convex portions facing outward. The prism element has a triangular prism shape, a quadrangular pyramid or a hexagonal pyramid, a cone or an elliptic cone with a bottom surface cut into a quadrangle or a regular hexagon, a triangular prism configured to form a concentric polygon, a circle, or a circle. It may be a large number of concentrically arranged elliptical triangular prisms, or a large number of densely arranged triangular prisms, or a light diffusing function. Good.

[0007]

【Example】

 Hereinafter, the present invention will be described in more detail with reference to examples.

FIG. 1 is the most basic embodiment of the present invention, and shows a schematic sectional view in which a prism element is arranged in an edge light. In FIG. 1, 1 is a fluorescent lamp, 2 is a light cover and a reflection plate, 3 is a light guide plate, and 4 is an array of prism elements. A schematic view of only the prism portion is shown in FIG.

The prism is formed by processing a transparent material such as MMA or polycarbonate by a method such as hot pressing, roll extrusion or template polymerization. The refractive index of these materials is 1. Since it is 4 to 1.6, the apex angle of the prism is preferably 60 to 95 degrees.

A polycarbonate resin having a refractive index of 1.6, an apex angle of 90 degrees, a length of 130 mm, and a width of 0. When a 35 mm prism element is combined with an edge light having a length of 215 mm and a width of 130 mm, the brightness in the normal direction of the exit surface is set to 100% and gradually decreases to 83% at around 35 degrees and then 45 degrees. Then, it was drastically decreased to about 7%, and the effect of controlling the emission angle of the present invention was remarkably recognized. The average luminance in the normal direction was increased by about 50% as compared with the case where the prism element of the present invention was not used. When this surface light source was used as a backside illumination light source for a liquid crystal display device of PC-9801NV, the display quality was good not only in the normal direction of the device but also in the oblique direction inclined by 35 degrees or more. This prism element had an isosceles triangular cross section.

When the same prisms are combined with the convex portions of the prisms facing downward toward the light emission surface side of the surface light source as disclosed in JP-A Nos. 2-17 and 2-84618, the prisms are aligned in the normal direction. On the other hand, a peak of brightness appeared at around 45 degrees, and the effect of restricting the emission angle was not so clear, and the brightness in the normal direction was only about 20% higher than when the prism element was not used. When this surface light source was used as a backside illumination light source of a liquid crystal display device of PC-9801NV, moire occurred and the display quality was not good.

3 and 4 are examples using prism elements having a quadrangular pyramid shape and a hexagonal pyramid shape. In the configuration of FIG. 1, the emission angle is regulated only in one direction, but with this configuration, the emission angle can be regulated in two or more directions, and the brightness can be increased by about 20%. At this time, the sizes of the surfaces of the prism elements do not necessarily have to be equal.

For example, when used as a backside illumination light source of a liquid crystal display element, generally, the observable angle in the up-down direction may be narrow with respect to the left-right direction. That is, in the case of the quadrangular pyramid-shaped prism element of FIG. 3, the vertical side of the bottom surface is a rectangle or a parallelogram. In the case of FIG. 4 as well, the bottom surface is not a regular hexagon but a vertically shorter one.

Also in the case of the conical or elliptical cone-shaped prism element array shown in FIG. 5, it is possible to make the angle regulation strongly act in the vertical direction by forming an ellipse with the short side in the vertical direction. ..

FIG. 6 shows an array of prism elements in which triangular prisms are molded in a ring shape, and these ring-shaped prisms having different sizes are combined in a concentric shape. Even when the prism array shown in FIGS. 1 to 5 is used, when moire occurs, it can be an effective moire preventing means.

FIG. 7 shows an example in which prism elements having a triangular prism shape are arranged in a polygonal shape. By arranging in an ellipse or a rectangle with a short vertical direction, it is possible to make the angle regulation strong in the vertical direction.

It is also possible to further combine the prism arrays of FIG. 6 or FIG. 7 to form an array as shown in FIG. Can be used to prevent moire. Not only the prism arrays of FIGS. 6 and 7 but also any combination with the prism elements of FIGS. 1 to 5 are possible. It is necessary to decide the balance between the effect and the ease of manufacturing.

It is effective to use a light diffusion plate when defects such as the shape of the prism and the light guide plate and the reflection plate are conspicuous. Further improvement in performance can be achieved by adding a light diffusing function to the prism element for ease of processing, improvement of durability, reduction of thickness, etc. The light diffusing function is added to the prism by dispersing a small amount of pigment such as barium sulfate in the prism material or applying a light diffusing paint. The coating material can be applied to either or both of the bottom surface and the inclined surface of the prism.

[0019]

[Effect of the device]

 According to the present invention, it is possible to provide a surface light source that is thin, has high brightness, and is easy to prevent moire, and has great utility in the fields of back lighting of liquid crystal display devices and various display lamps.

[Brief description of drawings]

FIG. 1 is a sectional view of a surface light source provided with a prism element of the present invention,

2 is a schematic view of a prism arranged in FIG. 1,

FIG. 3 is a plan view and a sectional view of a prism element used in the present invention,

FIG. 4 is a plan view and a sectional view of a prism element used in the present invention,

FIG. 5 is a plan view and a sectional view of a prism element used in the present invention,

FIG. 6 is a plan view and a sectional view of a prism element used in the present invention,

FIG. 7 is a plan view and a sectional view of a prism element used in the present invention,

FIG. 8 is a plan view of a prism element used in the present invention.

[Explanation of symbols]

In the figure, 1 is a fluorescent lamp, 2 is a light cover and a reflection plate, 3 is a light guide plate, and 4 is a prism element.

Claims (8)

[Scope of utility model registration request] 1. A surface light source characterized in that a large number of prism elements are arranged on the light emitting surface side of the surface light source with the convex portions facing outward. 2. The surface light source according to claim 1, wherein the prism element has a triangular prism shape. 3. The surface light source according to claim 1, wherein the prism element is a quadrangular pyramid or a hexagonal pyramid. 4. The surface light source according to claim 1, wherein the prism element has a shape obtained by cutting the bottom surface of a cone or an elliptic cone into a quadrangular shape or a regular hexagonal shape. 5. The surface light source according to claim 1, wherein the prism element is formed by forming a triangular prism into a concentric polygon. 6. The surface light source according to claim 1, wherein the prism element is a large number of concentric triangular prisms formed in a circular or elliptical shape. 7. A prism element is one in which a plurality of triangular prisms are arranged concentrically or a large number of concentric triangular prisms formed in a circle or an ellipse are arranged. The surface light source according to claim 1, wherein: 8. The surface light source according to claim 1, wherein the prism element has a light diffusing function.