JPH10197724A - Surface light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the surface light emission of high luminance by forming the surface of a light transmission plate to be a fine wave surface. SOLUTION: The surface of the light transmission plate 1 of a surface light emitting device obtained by arranging a linear light source 2 on one side surface of the transparent light transmission plate 1, providing a light diffusing transmitting part 3 on the back of the plate 1, and arranging a light scattering reflecting plate 4 on the back surface is formed to be the fine wave surface 6. The surface 6 on the surface of the plate 1 focuses and emits light scattered and reflected on the surface side of the plate 1 by the part 3 and the plate 4 in a direction close to a perpendicular to the plate 1. That is, since the surface of the plate 1 is the wave surface 6, a light beam scattered and reflected on the surface side of the plate 1 by the part 3, etc., is refracted so that an angle formed with the perpendicular to the plate becomes smaller than that obtained before light emission when the light beam is emitted from the inside of the plate 1 to an air layer. As to the arraying direction of wave on the surface 6, a direction in parallel with the light source 2, and a direction perpendicular to the light source 2, etc., for example, and moire is prevented from occurring when a liquid crystal display device is arranged in a front surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge light type surface light emitting device used for a backlight of a thin and lightweight color liquid crystal TV.

[0002]

2. Description of the Related Art Conventionally, as a surface light emitting device of the edge light type, a line light source 2 is arranged on one side of a transparent light guide plate 1 having a smooth surface 13, and a side reflector 5 is arranged on the other side. In some cases, a light diffusion / transmission portion 3 is provided on the back surface of the light guide plate 1, and a light scattering / reflecting plate 4 is provided on the back surface (see FIG. 5). In this surface light emitting device, the light from the linear light source 2 enters the light guide plate 1 from the side surface and is guided to the central portion of the light guide plate 1 while repeating internal reflection. Were scattered and reflected by the light scattering / reflecting plate 4, and uniformly emitted from the surface of the light guide plate 1.

[0003]

However, when a surface light emitting device is used for a backlight of a color liquid crystal TV, high luminance is required, whereas in the conventional surface light emitting device,
When the light beam 7 scattered and reflected on the light guide plate 1 surface side by the light diffusion / transmission unit 3 and the like is emitted from the inside of the light guide plate 1 to the air layer 8, refraction such that the angle with respect to the perpendicular to the light guide plate 1 becomes larger than before the emission (See FIG. 6), the front luminance of the surface emitting device could not be sufficiently obtained.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a high-luminance surface emitting device.

[0005]

In order to achieve the above object, the present invention provides a transparent light guide plate having a linear light source disposed on at least one side surface thereof, a light diffusion / transmission portion provided on a back surface of the light guide plate, and a back surface thereof. In the surface emitting device in which the light scattering reflector is disposed, the surface of the light guide plate is formed to have a fine wavefront.

Further, in the above configuration, the wavelength, the wave height, and the radius of curvature at the wave apex of the wave cross section of the wave front are each configured to be less than 30 μm.

Further, in the above-mentioned structure, the wavefront is formed such that the wave-shaped cross section has a straight portion between the wave peak and the wave trough.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the surface light emitting device according to the present invention, FIG. 2 is a diagram showing a change in the course of light rays on the surface of the light guide plate of the present invention, and FIG. FIG. 4 is a sectional view showing another embodiment of the surface emitting device according to the present invention. 1 is a light guide plate, 2 is a line light source, 3 is a light diffusion and transmission part, 4 is a light scattering reflection plate, 5 is a side reflection plate, 6 is a wavefront, 7 is a light beam, 8 is an air layer, 9 is a wavelength, and 10 is a wave height. , 1
1 indicates a vertex, and 12 indicates a light diffusion sheet.

In the surface light emitting device of the present invention, a linear light source 2 is disposed on one side surface of a transparent light guide plate 1, a light diffusion / transmission portion 3 is provided on the back surface of the light guide plate 1, and a light scattering / reflection plate 4 is provided on the back surface. In the arranged surface light emitting device, the surface of the light guide plate 1 is formed with a fine wavefront 6 (see FIG. 1).

The light guide plate 1 is a transparent rectangular plate resin plate having a thickness of about 1 mm to 5 mm. In particular, a wedge-shaped cross section whose thickness decreases as the distance from the line light source 2 increases is preferable. As a material of the light guide plate 1, a resin such as acrylic, polycarbonate, polystyrene, acrylic styrene, or polyvinyl chloride may be used. Light guide plate 1
Is preferably polished to a smooth surface.

The wavefront 6 on the surface of the light guide plate 1 reflects the light scattered and reflected toward the front surface of the light guide plate 1 by the light diffusion / transmission portion 3 and the light scattering / reflecting plate 4 on the back surface thereof in a direction close to a perpendicular to the light guide plate 1. It is focused and emitted. That is, since the surface of the light guide plate 1 is the wavefront 6, the light rays 7 scattered and reflected toward the surface of the light guide plate 1 by the light diffusion / transmission unit 3 and the like are reflected.
When the light is emitted from the inside to the air layer 8, the light is refracted so that the angle between the light guide plate 1 and the perpendicular to the light guide plate 1 becomes smaller than before the emission (FIG. 2)
reference). The arrangement direction of the waves on the wavefront 6 includes, for example, a direction parallel to the line light source 2 and a direction perpendicular to the line light source 2, so that moiré does not occur when the liquid crystal device is arranged on the front surface. Wavelength 9 of the wavefront section of the wavefront 6,
The radius of curvature at the wave height 10 and the wave peak 11 is 3
It is preferably less than 0 μm (see FIG. 3). This is because when these dimensions are 30 μm or more, the roughness of the surface of the light guide plate 1 becomes more conspicuous than the light emitting surface side of the surface light emitting device.
Further, the corrugated section may have a straight portion between the crest and the trough. As a method of forming the surface of the light guide plate 1 on the corrugated surface 6, for example, there is a method of performing injection molding by providing irregularities on the inner wall surface of an injection mold used for molding the light guide plate 1.

As the line light source 2, a cathode ray tube such as a hot cathode ray tube or a cold cathode ray tube is used. Further, the light guide plate 1 of the linear light source 2
The light source reflector is disposed so as to cover the surface on the opposite side to the light guide plate 1 of the linear light source 2 so that light from the surface on the opposite side to the light guide plate 1 is reflected toward the light guide plate 1 so that light can be used efficiently. Is preferred.

The light diffusing and transmitting section 3 is provided with a light guide plate 1 from the linear light source 2.
The light guided to the inside is scattered and reflected, and a part of the light is directed toward the surface of the light guide plate 1.
Light is distributed uniformly by forming a gradation pattern that increases the area ratio at a location away from the light source. In order to change the area ratio of the light diffusion transmission part 3, the light diffusion transmission part 3 is formed by dots having an arbitrary shape, and the dot size is changed or the number of dots is changed depending on the position. The shape of the dot is not particularly limited,
Any shape such as a round dot, a square dot, and a chain dot may be used. Further, it may be formed in stripes instead of dots. The light diffusion transmission part 3 is formed by a printing method such as gravure printing, offset printing, screen printing, a transfer method, and a simultaneous molding transfer method using a mat ink containing a particulate transparent substance such as calcium carbonate or silica. Further, when the light guide plate 1 is formed, the light diffusion / transmission portion 3 may be formed by forming irregularities exhibiting a gradation pattern on the back surface of the light guide plate 1.

The light scattering / reflecting plate 4 scatters and transmits light in the light diffusion / transmission portion 3 and cannot return to the light guide plate 1.
The light is reflected to the side so that light can be used efficiently. As the light scattering reflector 4, (1) a white polyethylene terephthalate film, (2) a white painted or white printed aluminum plate, or the like can be used.

Further, the linear light sources 2 may be arranged on two or more side surfaces of the light guide plate 1. For example, they are arranged on one or two sets of two opposite sides, or on two adjacent sides or three adjacent sides. As the shape of the linear light source 2, in addition to a straight shape, an L-shaped shape extending over two adjacent sides and a U-shaped shape extending over three adjacent sides can be used, and these may be used in combination.

Further, a side reflector 5 may be arranged on the side of the light guide plate 1 where the line light source 2 is not arranged (see FIG. 4). The side reflection plate 5 reflects light that has been emitted from the side surface of the light guide plate 1 and has not been returned to the light guide plate 1 side so that the light can be used efficiently. As the side reflector 5,
(1) white polyethylene terephthalate film,
(2) white painted or white printed aluminum plate,
(3) a metal plate or a metal foil having a mirror surface, (4) a coating layer or a printing layer of white ink, (5) a vapor deposition layer, and the like can be used.

A light diffusion sheet 12 is provided on the surface of the light guide plate 1.
(See FIG. 4). The light diffusion sheet 12
This is for diffusing the light emitted from the surface of the light guide plate 1 to prevent the dots of the light diffusion / transmission portion 3 from being conspicuous. As the light diffusion sheet 12, (1) a film coated with a light diffusion substance, (2) a film having a diffusive property itself,
(3) A milky white resin plate or the like can be used.

The light scattering / reflecting plate 4 or the side reflecting plate 5 can be replaced by a case for a surface light emitting device whose inner surface is coated with a white paint.

[0020]

[Example] Length 240mm, width 170mm, thickness 1.5m
A light guide plate made of a wedge-shaped acrylic resin plate of m to 3 mm is used, and a cold cathode ray tube having a tube length of 240 mm and a diameter of 2.6 mm is arranged as a line light source on one side having a thickness of 3 mm. A white polyethylene terephthalate film (E60L, manufactured by Toray Industries, Inc.) was disposed as a side reflection plate on the side where no is disposed. On the surface of the light guide plate, a wavefront in which a number of fine waves are arranged in a direction parallel to the line light source is formed, and the wavelength of the waveform cross section is 25 μm and the wave height is 15 μm.
m, the radius of curvature at the peak of the wave is 5 μm. Also,
On the back surface of the light guide plate, a light diffusion / transmission portion composed of a large number of dots is provided by a screen printing method using a mat ink containing silica in an acrylic resin. Further, a white polyethylene terephthalate film (E60L manufactured by Toray Industries, Inc.) is arranged as a light scattering reflector on the back surface of the light guide plate, and a resin film (D121 manufactured by Tsujimoto Electric Works) coated with a light diffusing substance on the surface of the light guide plate is lighted. A surface emitting device was obtained by disposing as a diffusion sheet.

This surface light emitting device was capable of emitting high-luminance surface light, and was sufficient for use in a backlight of a color liquid crystal TV.

[0022]

Since the present invention has the above-described structure,
It has the following effects.

That is, the light scattered and reflected on the light guide plate surface side by the light diffusion transmitting portion and the light scattering reflection plate on the back surface is focused and emitted in a direction close to a perpendicular to the light guide plate by the fine wavefront of the light guide plate surface. Therefore, high-luminance surface light emission can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a surface emitting device according to the present invention.

FIG. 2 is a diagram showing a change in the course of a light beam on the light guide plate surface of the present invention.

FIG. 3 is a diagram showing a waveform cross section on the surface of the light guide plate.

FIG. 4 is a sectional view showing another embodiment of the surface emitting device according to the present invention.

FIG. 5 is a cross-sectional view showing a surface emitting device according to a conventional technique.

FIG. 6 is a diagram showing a change in the path of a light beam on the surface of a light guide plate according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light-guide plate 2 Line light source 3 Light-diffusion transmission part 4 Light-scattering reflection plate 5 Side-surface reflection plate 6 Wave surface 7 Light 8 Air layer 9 Wavelength 10 Wave height 11 Apex 12 Light diffusion sheet 13 Smooth surface

Claims (3)

[Claims] 1. A surface light emitting device in which a linear light source is disposed on at least one side surface of a transparent light guide plate, a light diffusion / transmission portion is provided on a back surface of the light guide plate, and a light scattering reflector is disposed on the back surface. Is formed on a fine wavefront. 2. The surface emitting device according to claim 1, wherein the wavelength, the wave height, and the radius of curvature at the peak of the wave of the wave cross section of the wavefront are each less than 30 μm. 3. The surface light emitting device according to claim 1, wherein the wavefront has a straight section between a wave crest and a wave trough.