JPH0385586A - Diffusion plate - Google Patents

Abstract

PURPOSE:To brighten the diffusion plate and to uniformize the luminance distribution thereof by constituting the diffusion plate by superposing and disposing diffusion plate body and a transparent plate formed with many circular conical projections on the surface on the side opposite from a light source. CONSTITUTION:The diffusion plate is constituted of the light source 1, a reflecting plate 2 and the diffusion plate body 3 consisting of a milky white plate or embossed plate, etc., dispersed with the diffused grains of inorg. matter. The circular conical projections 11 are formed on the surface of the planar transparent body 10 disposed in front of the milky white plate 3 on the side opposite from the light source. The light diffused by the milky white plate 3 is, therefore, refracted by the slopes of the circular conical projections 11 of the transparent plate 10 and is then passed therethrough. Since this refraction is the refraction toward the center line direction of the circular conical projections, the refraction is the direction where directivity is provided in the diffused light. Further, the refractive effect is imparted to the rays emitted from any directions of the circular conical projections 11 and, therefore, the varying of the visual fields with the directions is obviated. The brighter diffusion plate is obtd. in this way and the luminance distribution is uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-efficiency diffusion plate for a lighting device suitable for use as a backlight in a display device using liquid crystal, for example.

[Prior Art] A lighting device suitable for use as a conventional backlight has a reflector plate 2 disposed on the back side of the light source 1 and a reflector plate 2 disposed on the back side of the light source 1 as shown in FIG. (opposite side of board 2)
It is composed of a milky-white plate 3 placed in the. This type of lighting device is illuminated by the light emitted from the light source 1 and directly reaching the milky white plate 3, or by the light from the light source 1 that is reflected by the reflecting plate 2 and reaching the milky white plate 3, and by the diffused light from the milky white plate 3. However, this diffused light is required to have a uniform luminance distribution on the surface of the milky white plate 3 and to be bright. Therefore, mainly for the purpose of increasing brightness, the fourth
As shown in the figure, a Fresnel plate-like transparent plate with a serrated cross section is placed in front of the milky white plate 3, and the diffused light is given a certain directivity from the milky white plate 3 to parallel to the plate surface. The light is made brighter by directing wasted light that would otherwise be emitted at a close, large angle toward the front.

Note that FIG. 5 uses a linear light source such as a fluorescent tube as the light source 1, and other aspects are substantially the same as FIG. 4.

[Problems to be Solved by the Invention] Such conventional illumination devices have different viewing angles depending on the viewing direction, that is, different viewing angles depending on the horizontal direction of the drawing and the direction perpendicular to the drawing, which is not preferable because the brightness distribution is not uniform.

The present invention is a diffuser plate for a lighting device configured as in the conventional example, which is configured to give a certain directivity to the diffused light, and which is bright and has a uniform luminance distribution when used in the lighting device. The purpose is to provide the following. That is, the objective is to make the component light of a relatively wasted large angle emitted from the opalescent plate brighter by directing it forward using the conical projection.

[Means for Solving the Problems] The diffuser plate of the present invention is used in an illumination device composed of a diffuser plate such as a milky-white plate placed in front of a light source, and a large number of microscopic particles are arranged in front of the light source. The present invention is characterized in that a transparent plate-like body is provided with a conical projection or has a conical projection on the front surface and is disposed in front of the diffuser plate main body to form a diffuser plate as a whole.

Since the diffuser plate of the present invention has a conical projection as described above, the diffused light emitted from the milky white portion of the lighting device is given appropriate directivity depending on the angle of the apex of the cone. Further, this directivity and its degree are constant at all angles when viewed from any angle. Therefore, by using the diffuser plate of the present invention, the brightness can be increased and the brightness on the diffuser plate can be made uniform.

[Example] Next, an example of the diffusion plate of the present invention will be described based on the drawings.

FIG. 1 is a sectional view showing a state in which a diffuser plate according to an embodiment of the present invention is placed in front of a lighting device. In this figure, the lighting device includes a light source 1) a reflector 2. It is composed of a diffusion plate main body 3 made of a milky white plate, a grained plate, etc. in which inorganic diffusion particles are dispersed, and is substantially the same as that shown in FIG. 4 or FIG. 5.

Reference numeral 10 denotes a plate-shaped transparent body placed in front of the milky white plate 3 constituting the main body of the diffuser plate of the present invention, and its surface (the surface opposite to the light source)
A conical protrusion 1) as shown in FIGS. 2 and 3 is formed on the surface.

If this diffuser plate is used as a diffuser plate of a lighting device as shown in FIG. Pass this from.

Since this refraction is in the direction of the center line of the conical projection, it gives directionality to the diffused light, that is, it gives directionality to the direction perpendicular to the plate surface of the diffuser plate, resulting in bright light. Moreover, since the refraction effect described above is applied to the light rays emitted from any part of the conical protrusion, the field of view does not differ depending on the direction, resulting in a uniform brightness distribution.

Since the degree of directivity of this diffuser plate differs depending on the angle θ of the conical protrusion 1), it is preferable to set this angle θ to an appropriate value depending on the lighting device used and the purpose of use. Considering the refractive index of the material of the diffuser plate (glass, plastic), a value within the range of 0° and θ<60° is appropriate.

In this embodiment, the value of θ of the conical projection at the center of the diffuser plate is smaller than that of the conical projection at the periphery. In other words, θ1 minus θ2. This is because generally the center tends to be high brightness, so the degree of directivity is reduced in this part and the spread of the diffused light is increased compared to other areas, making the overall brightness distribution uniform. .

When used in a lighting device in which the brightness of the diffused light is approximately the same in the center and the periphery, it can be made sufficiently bright and uniform even if the conical protrusions of the same shape are arranged uniformly.

As a method of adjusting the degree of directivity, in addition to changing the angle (or angle θ) of the apex of the conical projection, it is also possible to change the density of the conical projection. By making the center small, it is possible to have an effect similar to that of the embodiment.

Furthermore, the conical projections may be arranged vertically and horizontally as shown in Figures 2 and 3, or may be arranged diagonally or completely irregularly. Polymerization is carried out through an air layer.

[Effects of the Invention] The diffuser plate of the present invention can be made brighter by imparting a certain degree of homogeneity to the light of the diffuser plate, and can have uniform brightness without causing differences in viewing angle depending on the viewing direction. If used in a lighting device such as a backlight for a liquid crystal display, it can be made into a bright lighting device with a similar brightness.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a lighting device in which the diffuser plate of the present invention is arranged, FIG. 2 is a perspective view of a transparent plate in the diffuser plate of the present invention, and FIG. 3 is a view taken along line III-III in FIG. The enlarged sectional views, FIGS. 4 and 5, are sectional views of a lighting device using a conventional diffuser plate. 1--light source, 2--reflector, 3--milky white plate, l
O...Transparent plate, 1)...Conical projection

Claims (2)

[Claims] (1) In an illumination device consisting of a light source and a diffuser plate disposed in front of the light source, the diffuser plate includes a diffuser body and a transparent plate having a large number of conical protrusions formed on the surface opposite to the light source. A diffusion plate characterized by being formed by superimposing a diffusion plate and a plate. (2) Claim (1) wherein the angle of the apex of the conical projection at the center of the transparent plate is different from the angle of the apex of the other conical projections.
) diffuser plate.