JPH05188207A - Irregular reflection plate for back illumination - Google Patents

Abstract

PURPOSE:To provide an irregular reflection plate for back illumination which can evenly uniformalize the quantity of the light with which a diffusion plate is irradiated. CONSTITUTION:The irregular reflection plate for back illumination irregularly reflecting the light from a light source 12 in the direction of the diffusion plate 16 is so constituted as to have the sectional shape expressed by y=A when y=xcot (x/A), xnot equal to 0, if the max. depth of the irregular reflection plate 15 from the light source 12 is designated as A in the orthogonal coordinates where the distance in the development direction of the diffusion plate 16 from the light source 12 with the light source 12 as an origin is x and the distance up to the irregular reflection surface 15 of the irregular reflection plate 14 is y.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffuse reflection plate for back lighting of a display device which illuminates a diffuser plate by illuminating light from the back and displays pictures, characters, numbers, etc. on the diffuser plate.

[0002] For example, a liquid crystal display (LCD) generally needs back lighting for illuminating light from the back to obtain sufficient brightness. Further, in an advertisement display in which a picture, a character, etc. are drawn on the diffuser plate, a method of displaying the picture, the character, etc. on the diffuser plate by back lighting is adopted.

Therefore, there is a demand for a diffused reflection plate for back lighting, which can make the amount of light applied to the diffusion plate uniform.

[0004]

2. Description of the Related Art Conventionally, various diffuser plate shapes for illuminating a diffuser plate by irradiating light from the back are known in various sectional shapes shown in FIGS. In these figures, 2 is an elongated light source such as a fluorescent lamp, 4a to 4d are diffuse reflection plates, and 6 is a diffusion plate.

The diffuse reflection plate 4a of FIG. 3 has a planar shape, and the diffuse reflection surface of the diffuse reflection plate 4d of FIG. 6 has a circular arc cross section. The irregular reflection surfaces of the irregular reflection plates 4b and 4c shown in FIGS. 4 and 5 have a special shape for irregularly reflecting light to the diffusion plate 6 as uniformly as possible.

[0006]

However, in the above-described diffuse reflection plate shape, the light emitted from the light source 2 is diffusely reflected by the diffuse reflection plate and is applied to the diffusion plate 6.
There is a problem that the amount of light applied to the diffusion plate is not uniform and the brightness is uneven when the diffusion plate is viewed from the front.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a diffused reflection plate for back irradiation capable of making the amount of light irradiated on the diffusion plate uniform. That is.

[0008]

In order to solve the above-mentioned problems, the present invention is a diffuse reflection plate for back lighting which diffuses light from a light source in the direction of the diffuser plate, and the diffuser plate from the light source with the light source as the origin. In Cartesian coordinates, where x is the distance in the developing direction and y is the distance to the diffuse reflection surface of the diffuse reflection plate, and y is the maximum depth of the diffuse reflection surface from the light source, y = xcot (x
/ A) (where x ≠ 0), and when x = 0, a diffuse reflection plate for back lighting having a cross-sectional shape represented by y = A is provided.

[0009]

The method of deriving the above-mentioned mathematical formula will be described with reference to FIG. FIG. 1 is an orthogonal coordinate system in which the light source is at the origin, the distance from the light source in the developing direction of the diffusion plate is x, and the distance from the diffuse reflection plate to the diffuse reflection surface is y.

In order for the amount of diffused reflection light per unit area viewed from the front of the display surface to be constant, the distance in the x-axis direction from FIG. 1 should be proportional to θ. Therefore, x = cθ (c is a constant) (1) y = xcotθ = cθcotθ (2) Since θ = x / c, y = xcot (x / c) (where x ≠ 0) (3) ) When x = 0, y is equal to the maximum depth A of the reflection plate. Therefore, when x = 0, y = A (4)

[0011]

[Equation 1]

Here, if x → 0,

[0013]

[Equation 2]

Therefore,

[0015]

[Equation 3]

From equation (4), when x = 0, y = A and the reflector must be a continuous curved surface.

[0017]

[Equation 4]

Therefore, y = xcot (x / A) (9) is obtained. By employing the diffuse reflection plate having the cross-sectional shape of the above formula (9), the diffuser plate can be illuminated uniformly and evenly from the back.

[0019]

Embodiments of the present invention will be described below with reference to FIG. In FIG. 2, reference numeral 12 is a light source such as a fluorescent lamp that extends in the direction perpendicular to the paper surface, and 14 is a diffuse reflection plate for back lighting, whose sectional shape of the diffuse reflection surface 15 is specified by the curve of the above-described formula (9).

Reference numeral 16 is a diffuser plate on which character figures and the like are drawn, and is arranged so as to extend in the lateral direction from the light source 12. Although not shown in particular, the front side of the light source 12 is shielded so that the light source 12 cannot be directly seen from the front side when the diffusion plate 16 is observed.

In FIG. 2, when the maximum depth A of the irregular reflection surface 15 from the light source 12 is 10 cm, the dimensions of the main points of the irregular reflection surface 15 are calculated. Since x = Aθ, the distance from the light source 12 to the point 15b where the irregular reflection surface 15 intersects the diffuser plate 16 is 10 × π / 2 = 5π = 15.708 cm.

Further, by increasing θ by 10 °, L in FIG.
_If we find ₅₁ , L _52, ... L ₅₈ , they are all equal,
It is 1.7453 cm. From this, the irregular reflection surface 15
It is understood that the light diffusely reflected by the light reaches the diffuser plate 16 uniformly.

[0023]

According to the diffused reflection plate for back lighting of the present invention, there is an effect that the diffused reflection light amount applied to the diffusion plate can be made uniform.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating the principle of the present invention.

FIG. 2 is a sectional view of an embodiment of the present invention.

FIG. 3 is a sectional view of a conventional example.

FIG. 4 is a sectional view of another conventional example.

FIG. 5 is a sectional view of still another conventional example.

FIG. 6 is a sectional view of still another conventional example.

[Explanation of symbols]

 12 light source 14 diffuse reflection plate 15 diffuse reflection surface 16 diffuser plate

Claims (1)

[Claims] 1. A diffuse reflection plate for back lighting, which diffuses light from a light source (12) in the direction of a diffuser plate (16), wherein the diffuser plate (16) is expanded from the light source (12) as an origin. In Cartesian coordinates where the directional distance is x and the distance to the diffuse reflection surface (15) of the diffuse reflection plate (14) is y, and the maximum depth from the light source (12) of the diffuse reflection surface (15) is A, y = xcot (X / A) (where x ≠ 0), and when x = 0, a diffuse reflection plate for back lighting having a cross-sectional shape represented by y = A.