JPH08146230A - Surface light emitting device - Google Patents

Abstract

PURPOSE: To obtain high-luminance light emission by chamfering an angular part between the surface of a light transmission plate and a side surface where a linear light source is arranged so that light made incident on the light transmission plate once may be reflected and guided to the inner part of the light transmission plate. CONSTITUTION: In this surface light emitting device, the linear light source 2 is arranged on the side surface of the transparent light transmission plate 1 having outside dimension larger than a display area 9. A rectangular plate material is used as the light transmission plate 1, a chamfer part 7 is formed by chamfering the angular part between the surface of the plate 1 and the side surface where the light source 2 is arranged so that the light made incident on the plate 1 once may be reflected and guided to the inner part of the plate 1. The shape of the chamfer part 7 is a flat surface or a crosssection curved surface (projected surface or recessed surface), and the angle and dimension are properly set in accordance with the thickness of the plate 1, the size of the light source 2, a distance between the plate 1 and the light source 2 and other conditions. Acrylic, polycarbonate, polystyrene or acrylic styrene is used as the material of the plate 1.

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 emitting device used for thin and lightweight laptop personal computers, word processors, liquid crystal TV backlights and the like.

[0002]

2. Description of the Related Art Conventionally, a linear light source 2 is arranged on a side surface of a transparent light guide plate 1, a light diffusion / transmission part 3 is provided on the back surface of the light guide plate 1, and a light diffusion / transmission part 3 of the light guide plate 1 is provided. The edge light system in which the rear surface reflection plate 4 is arranged on the front surface, the light diffusion plate 5 is arranged on the surface of the light guide plate 1, and the light source reflection plate 6 is arranged so as to cover the side of the linear light source 2 opposite to the light guide plate 1. The surface emitting device is used as a backlight of a liquid crystal display device (see FIG. 8).

In this surface emitting device, the end portion of the light guide plate 1 on the side of the linear light source 2 is strong light which is incident from the linear light source 2 into the light guide plate 1 and is emitted to the side of the light diffusion plate 5 as it is, or the linear light source 2. Due to the strong light that is incident on the inside of the light guide plate 1 and is once reflected by the back surface reflection plate 4 and then emitted to the light diffusion plate 5 side, it becomes too bright as compared with other places. However, in the past, the light guide plate 1
Since the distance from the side surface to the display area 9 was sufficiently secured, the abnormal light emitting portion did not appear in the display area 9.

[0004]

However, recently, with the downsizing of word processors, personal computers and the like, it has become necessary to meet the technical demand for making the outer dimensions of the light guide plate closer to the dimensions of the display area. As a result, the distance from the side surface of the light guide plate 1 to the display area 9 cannot be sufficiently secured, the line light source 2 side in the display area 9 exhibits an abnormally high brightness, and the linear light source 2 has a linear shape along the tube axis direction. The brightness unevenness was 10 (see FIG. 9).

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a surface emitting device which makes the outer dimensions of the light guide plate as close as possible to the dimensions of the display area and which is uniform and has high brightness.

[0006]

To achieve the above object, in a surface emitting device of the present invention, a linear light source is arranged on the side surface of a transparent light guide plate, and a light diffusion / transmission part is provided on the back surface of the light guide plate. In the surface emitting device, the chamfered portion is formed by chamfering the corner between the surface of the light guide plate and the side surface on which the linear light source is arranged so that the light once incident on the light guide plate is reflected and guided to the back of the light guide plate. Configured to be formed.

Further, the surface emitting device of the present invention is a surface emitting device in which a linear light source is arranged on the side surface of a transparent light guide plate and a light diffusion / transmission part is provided on the back surface of the light guide plate, and the light is once incident on the light guide plate. The reflected light is reflected and guided to the back of the light guide plate,
The chamfered portion is formed by chamfering the corner between the back surface of the light guide plate and the side surface on which the linear light source is arranged.

In each of the above constructions, a specular reflector may be arranged so as to cover the chamfered portion.

Embodiments of the surface emitting device of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the surface emitting device according to the present invention, and FIGS. 2 to 7 are sectional views showing other embodiments of the surface emitting device according to the present invention. 1 is a light guide plate, 2 is a linear light source, 3 is a light diffusion / transmission part, 4 is a back reflection plate, 5 is a light diffusion plate, 6 is a light source reflection plate, 7 is a chamfered part, 8 is a specular reflection plate,
Reference numerals 9 respectively indicate the display areas.

The surface emitting device shown in FIG. 1 has a display area 9
A linear light source 2 is arranged on the side surface of a transparent light guide plate 1 having a larger outer dimension.

A rectangular flat plate material having a thickness of about 1.5 to 3 mm is used as the light guide plate 1, and the light guide plate 1 is configured so that light that once enters the light guide plate 1 is reflected and guided to the back of the light guide plate 1. 1
A chamfered portion 7 is formed by chamfering a corner portion between the front surface and the side surface on which the linear light source 2 is arranged. The shape of the chamfered portion 7 may be a flat surface or a curved surface in cross section (convex surface or concave surface), and the angle and size thereof are the thickness of the light guide plate 1, the size of the linear light source 2, the light guide plate 1 and the linear light source. 2 is set as appropriate according to the distance and other conditions. The material of the light guide plate 1 is not particularly limited as long as it is a substance that allows light to pass efficiently, and for example, a resin such as acrylic, polycarbonate, polystyrene, acrylic styrene, polyvinyl chloride, or glass can be used. . Moreover, it is preferable that all the side surfaces of the light guide plate 1 are finished to be smooth.

A linear light source 2 is arranged on the side surface of 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 having a diameter of 2 to 3 mm is used. In addition, the line light source 2
The shape of is straight, L over two adjacent sides
It is possible to use a U-shaped one or a U-shaped one extending over the three adjacent sides. Further, a plurality of linear light sources 2 may be arranged.

A light diffusion / transmission part 3 is formed on the back surface of the light guide plate 1. The light diffusion / transmission part 3 scatters and reflects the light guided from the linear light source 2 into the light guide plate 1, and directs a part of the light toward the surface side of the light guide plate 1. The light is evenly distributed by increasing the area ratio of the portion distant from the linear light source 2. In order to change the area ratio of the light diffusing and transmitting portion 3, the light diffusing and transmitting portion 3 is formed of dots having an arbitrary shape, and the size of the dots is changed or the number of dots is changed depending on the position. The shape of the dot is not particularly limited, and may be any shape such as round dot, square dot, chain dot. Also, instead of dots, it may be formed in stripes. As a method of forming the light diffusing and transmitting portion 3, there are a printing method such as screen printing using a matte ink, a transfer method, and a method in which the back surface of the light guide plate 1 is made uneven. As matte ink,
If an ink containing a particulate transparent substance such as calcium carbonate or silica having a refractive index substantially equal to or lower than that of the light guide plate 1 is used, the light diffusivity can be further improved.

A back reflector 4 is arranged on the surface of the light guide plate 1 on which the light diffusion / transmission part 3 is provided. Back reflector 4
Is to reflect the light that could not be returned into the light guide plate 1 in the light diffusion / transmission part 3 to the light guide plate 1 side so that the light can be used efficiently. As the material of the back reflector 4, for example, the following materials are preferable. (1) A film or plate in which a white pigment is mixed in a resin. (2) White painted or white printed aluminum plate. (3) A metal plate having a mirror surface, a metal foil such as aluminum, or a film or plate obtained by vapor deposition of a metal such as aluminum or silver. Also,
The inner surface of the case that houses the light guide plate 1 and the linear light source 2 may be painted or printed in white to form the back reflector 4.

A light diffusing plate 5 is arranged on the surface of the light guide plate 1. The light diffusing plate 5 is for diffusing the light emitted from the surface of the light guide plate 1 and smoothing the luminance distribution. For example, the following materials are preferable as the material of the light diffusion plate 5. (1) A film or plate coated with a light diffusing substance. (2) A film or plate having a light diffusing property by itself. (3) A milky white resin film or plate. The light diffusing plate 5 is arranged closer to the light guide plate 1 than the light diffusing plate 5 is in close contact with the light guide plate 1, so that total reflection is ensured inside the light guide plate 1. Light guide plate 1
There is little loss inside and light can be reflected sufficiently. The light diffusion plate 5 may be formed in a plurality of layers.

A light source reflector 6 is arranged so as to cover the surface of the linear light source 2 opposite to the light guide plate 1. The light source reflection plate 6 reflects the light from the surface of the linear light source 2 opposite to the light guide plate 1 to the light guide plate 1 side so that the light can be used efficiently. As the material of the light source reflector 6, the same material as the back reflector 4 may be used. The distance between the linear light source 2 and the light source reflection plate 6 may be kept uniform by interposing a spacer therebetween.

The present invention is not limited to the above, and for example, the chamfered portion 7 is formed by chamfering the corner between the back surface of the light guide plate 1 and the side surface on which the linear light source 2 is arranged. The chamfering may be performed on both the corners between the front surface of the light guide plate 1 and the side surface on which the linear light source 2 is arranged, and the corners on the back surface of the light guide plate 1 and the side surface on which the linear light source 2 is arranged. Then, the chamfered portions 7 may be formed on each (see FIG. 3).

Further, according to the present invention, the thickness of the light guide plate 1 may be reduced as the distance from the linear light source 2 is increased (see FIGS. 4 to 6).

Further, in the present invention, a specular reflector 8 may be provided so as to cover the surfaces of the chamfered portions 7 on the front surface and the back surface (see FIG. 7). Most of the light reaching the chamfered portion 7 is reflected, but a part of the light is refracted and emitted from the light diffusion plate 5 side. The specular reflection plate 8 reflects the light, which is not reflected by the chamfered portion 7 of the light guide plate 1 and is to be emitted as it is, to the light guide plate 1 side by the mirror surface thereof to further improve the light efficiency. As a material for the specular reflection plate 8, for example, a metal plate having a mirror surface, a metal foil such as aluminum, or a film or plate obtained by vapor-depositing metal such as aluminum or silver is preferable.

Although the surface emitting device shown in FIGS. 1 to 7 is provided with the back reflector 4, the light diffuser 5 and the light source reflector 6, these may be omitted.

A side reflector may be arranged on any of the side surfaces of the light guide plate 1 where the linear light source 2 is not arranged. The side reflector reflects the light emitted from the side surface of the light guide plate 1 toward the light guide plate 1 side so that the light can be used efficiently. As the material of the side reflector, the same material as the back reflector 4 may be used.

[0023]

The surface emitting device of the present invention, having the above structure, has the following effects.

That is, most of the strong light that once enters the light guide plate and reaches the chamfer is reflected deep inside the light guide plate at the chamfer.

Therefore, at the end of the light guide plate on the linear light source side, the light emitted from the light diffusion plate side is reduced. Also,
The light reflected to the back of the light guide plate is scattered and reflected at each light diffusion / transmission part, and is emitted from the light diffusion plate side of the light guide plate.

[0026]

[Example] A transparent wedge-shaped acrylic resin plate having a length of 220 mm, a width of 160 mm, a minimum thickness of 1.5 mm, and a maximum thickness of 3 mm is used as a light guide plate whose outer dimensions are close to the dimensions of the display area, and the side surface having the maximum thickness is used. The corner with the back surface of the light guide plate was chamfered.

A pipe length is provided on the side surface where the thickness of the light guide plate is maximum.
A cold cathode ray tube having a diameter of 220 mm and a diameter of 3 mm was arranged as a line light source.

A large number of circular dots are screen-printed on the back surface of the light guide plate using a matte ink containing silica in an acrylic resin, so that a gradation pattern having a large area ratio at a position distant from the line light source from the line light source side. The light diffusing and transmitting portion having

A white polyethylene terephthalate film (E60L manufactured by Toray Industries, Inc.) was arranged as a back reflector on the surface of the light guide plate on which the light diffusion / transmission part was provided.

On the surface of the light guide plate, a resin film (100S manufactured by Kimoto Co.) coated with a light diffusing substance was arranged as a light diffusing plate.

Further, a white polyethylene terephthalate film (E60L manufactured by Toray Industries, Inc.) was arranged as a light source reflection plate so as to cover the surface of the linear light source opposite to the light guide plate, to obtain a surface emitting device.

When the brightness of the surface emitting device obtained as described above was measured, it was found to be more uniform and higher in brightness than the conventional surface emitting device.

[0033]

Since the surface emitting device of the present invention has the above-described structure and operation, the following effects can be obtained.

That is, at the end portion of the light guide plate on the side of the linear light source, the light emitted from the side of the light diffusion plate decreases, so that even if the outer dimensions of the light guide plate are brought close to the dimensions of the display area, the linear light source in the display area is displayed. Abnormal light emission does not occur on the side, and uniform light emission can be obtained.

Further, the light reflected to the back of the light guide plate is scattered and reflected at each light diffusion / transmission part and is emitted from the light diffuser plate side of the light guide plate, so that it is generally higher than the conventional surface emitting device. Luminous emission can be obtained.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing another embodiment of the surface emitting device according to the present invention.

FIG. 3 is a sectional view showing another embodiment of the surface emitting device according to the present invention.

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

FIG. 5 is a sectional view showing another embodiment of the surface emitting device according to the present invention.

FIG. 6 is a sectional view showing another embodiment of the surface emitting device according to the present invention.

FIG. 7 is a sectional view showing another embodiment of the surface emitting device according to the present invention.

FIG. 8 is a cross-sectional view showing a conventional surface emitting device.

FIG. 9 is a plan view showing a light emitting surface of a conventional surface light emitting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Line light source 3 Light diffusing / transmitting part 4 Back reflecting plate 5 Light diffusing plate 6 Light source reflecting plate 7 Chamfering part 8 Specular reflecting plate 9 Display area 10 Brightness unevenness

Claims (3)

[Claims] 1. A surface light emitting device in which a linear light source is disposed on a side surface of a transparent light guide plate, and a light diffusion / transmission part is provided on a back surface of the light guide plate, and the light that has once entered the light guide plate is reflected to the light guide plate. A surface emitting device, characterized in that a chamfered portion is formed by chamfering a corner between the surface of the light guide plate and the side surface on which the linear light source is arranged so as to be guided to the back. 2. A surface light emitting device in which a linear light source is arranged on the side surface of a transparent light guide plate and a light diffusion / transmission part is provided on the back surface of the light guide plate, and the light that has once entered the light guide plate is reflected and the light guide plate is reflected. A surface emitting device, characterized in that a chamfered portion is formed by chamfering a corner between the back surface of the light guide plate and the side surface on which the linear light source is arranged so as to be guided to the back. 3. The surface emitting device according to claim 1, wherein a specular reflector is arranged so as to cover the chamfered portions on the front surface and the back surface.