JPH0996813A - Illuminator, backlight and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize luminance distribution and to restrain the occurrence of the interference fringe of light by providing a light control plate disposed on the light emitting surface side of a light transmission means and radiating the light in a specified direction and a double refraction plate disposed on the light emitting surface side of the light control plate. SOLUTION: A fluorescent lamp 2 being a light source 2 is disposed on the side surface 1a side of a nearly square light transmission plate 1 being the light transmission means, and a reflection mirror 3 is disposed to surround the lamp 2. A reflector 4 is disposed on the back surface 1b of the plate 1. Then, the light control plate 5 capable of radiating the light mainly in the specified direction is disposed on the light emitting surface 1c side of the plate 1. Furthermore, the double refraction plate 6, for example, a plate-like calcite is disposed on the light emitting surface side of the light control plate 5. An inverter circuit being a lighting means 8 supplying high frequency power to the lamp 2 is attached to a case main body 7 in which the plate 1, the lamp 2, the mirror 3, the reflector 4, the light control plate 5 and a light diffusing plate 6 are housed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device, a backlight and a liquid crystal display device using the backlight.

[0002]

2. Description of the Related Art This type of backlight is a U.S. Pat. S. Pa
It is disclosed in Japanese Patent No. 5,396,350 (tentative example) and the like. A liquid crystal display device using this backlight will be described with reference to FIG.

FIG. 4 is a side view of a liquid crystal display device. The backlight used for this is provided with a light control plate having a plurality of condenser lenses formed on the light exit surface side of the light guide plate, and a liquid crystal display plate is provided close to the light control plate. There is.

[0004]

Referring to the ray trace in FIG. 4, the light incident on the liquid crystal display plate is large around the condenser lens and small at the central portion.

Therefore, although the light emitted from the light guide plate is condensed by the condenser lens, the absolute brightness on the surface of the light control plate is improved, but there is a problem that the brightness distribution is difficult to be uniform. In addition, the uneven brightness distribution on the surface of the light control plate is
Optical interference fringes may be generated on the surface of the liquid crystal display panel.

Therefore, it is an object of the present invention to provide an illumination device having a uniform luminance distribution, a backlight, and a liquid crystal display device in which generation of optical interference fringes is suppressed when a light control plate is used.

[0007]

According to a first aspect of the present invention, there is provided a light guiding means having a side surface, a back surface and a light emitting surface; a light source disposed on a side surface side of the light guiding means; and a light emitting surface side of the light guiding means. And a birefringent plate disposed on the light emitting surface side of the light control plate, the light control plate being capable of emitting light mainly in a predetermined direction.

The light guide means means for conveying the light incident from the light source in the light emitting surface direction. The light source is, for example, a discharge lamp such as a fluorescent lamp, a light bulb, or the like. Further, the light control plate is configured by forming a plurality of lenses that can mainly emit light in a predetermined direction and that controls, for example, the emission direction of light. The birefringent plate is, for example, calcite.

According to the present invention, since light is mainly emitted from each part of the light control plate in a predetermined direction, the brightness on the surface of the light control plate is not uniform, but the light is divided into two components having different speeds by the birefringent plate. . Therefore, the brightness on the birefringent plate is made uniform.

According to a second aspect of the present invention, a light guide plate having a side surface, a back surface and a light exit surface; a light source arranged on the side surface side of the light guide plate; a reflecting mirror arranged so as to surround the light source; A light control plate disposed on the light emitting surface side of the light plate and capable of mainly emitting light in a predetermined direction; a birefringent plate disposed on the light emitting surface side of the light control plate; disposed on the back surface of the light guide plate And a reflector that is formed.

The light guide plate is made of, for example, a transparent acrylic resin having an excellent visible light transmittance. Further, the reflector has a role of efficiently returning the light leaking from the light guide plate to the light guide plate, and there are, for example, a white sheet-shaped one, an ink-printed one, and the like.

The present invention has the same operation as the invention of claim 1.

According to a third aspect of the present invention, a light guide plate having a side surface, a back surface and a light exit surface; a light source arranged on the side surface side of the light guide plate; a reflecting mirror arranged so as to surround the light source; A light control plate disposed on the light emitting surface side of the light plate and capable of mainly emitting light in a predetermined direction; a birefringent plate disposed on the light emitting surface side of the light control plate; disposed on the back surface of the light guide plate And a case body that accommodates a light guide plate, a light source, a reflecting mirror, a reflector, a light diffusion plate, and a light control plate.

The case main body may be formed of plastic or the like, and may be integral or divided into several parts.

According to the present invention, in addition to the operation of the first aspect of the present invention, the respective members are sequentially arranged on the case body to improve the efficiency of assembly.

According to a fourth aspect of the present invention, a light guide plate having a side surface, a back surface and a light emitting surface; a light source arranged on the side surface side of the light guide plate; a reflecting mirror arranged so as to surround the light source; A light control plate disposed on the light emitting surface side of the light plate and capable of mainly emitting light in a predetermined direction; a birefringent plate disposed on the light emitting surface side of the light control plate; disposed on the back surface of the light guide plate A reflector, a case body that accommodates a light guide plate, a light source, a reflecting mirror, a reflector, a light diffusing plate, and a light control plate; and lighting means that is provided in the case body and supplies high-frequency power to the light source It has.

The lighting means is, for example, an inverter circuit or the like.

According to the present invention, in addition to the action of the invention of claim 3, the wiring led out from the lighting means can be efficiently routed and assembled.

According to a fifth aspect of the present invention, in the backlight according to any one of the second to fourth aspects, the birefringent plate is
It is made of calcite.

The present invention has the same operation as the invention of claim 1.

A sixth aspect of the present invention includes the backlight according to any one of the second to fifth aspects; and a liquid crystal display plate disposed on the light emitting surface side of the birefringent plate.

According to the present invention, the screen of the liquid crystal display plate becomes clearer.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a backlight which is a lighting device of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG.

FIG. 1 is an exploded perspective view of the backlight, and FIG. 2 is a side view of an essential part. In FIG.
Is a substantially rectangular light guide plate as a light guide means, and the side surface 1
a, a back surface 1b and a light emitting surface 1c. This side 1a
On the side, a fluorescent lamp which is the light source 2 is arranged, and the reflecting mirror 3 is arranged so as to surround the fluorescent lamp 2.
A reflector 4 is provided on the back surface 1b of the light guide plate 1.

On the light emitting surface 1c side of the light guide plate 1, there is provided a light control plate 5 which can mainly emit light in a predetermined direction. In the present embodiment, the angle θ of the light control plate 5 in the predetermined direction is set to 20 ° with respect to the vertical direction of the light control plate 5.

Further, a birefringent plate 6, for example, a plate-shaped calcite is disposed on the light emitting surface side of the light control plate 5.

The light guide plate 1, the fluorescent lamp 2, the reflecting mirror 3, the reflector 4, the light control plate 5, the light diffusing plate 6 and the case body 7 to be housed are provided with a lighting means for supplying high frequency power to the fluorescent lamp 2. The inverter circuit which is 8 is installed.

Next, each component described above will be described in detail below.

The light guide plate 1 introduces the light emitted from the fluorescent lamp 2 from the side surface 1a and emits the light from the light emitting surface 1c side.
The light guide plate 1 is made of a transparent acrylic resin having an excellent visible light transmittance, and has outer dimensions of 150 mm in width and 100 m in length.
m, the thickness is 4 which is larger than the outer diameter of the fluorescent lamp 2.
It is formed in a flat plate shape of mm and a substantially square shape.

Although the light emitting surface 1c is processed to be flat, a conical small hole is formed in the back surface 1b facing the light emitting surface 1c, and its size increases as the distance from the fluorescent lamp 2 increases. You may make it large. By doing so, the uniformity of the brightness of the light emitting surface 1c is further improved. Further, the conical small hole may be formed by pressing a heated conical mold against the acrylic resin surface, cutting by a drilling machine, or formed by the mold during molding of the light guide plate. Good.

Further, the light guide plate 1 has a cutout portion 1d formed by cutting out a portion of the fluorescent lamp 2 where the bent portion 2a is arranged. The shape of the cut portion 1d may be a straight line or a curve having a radius of curvature of 0.5 mm to 10 mm. This excision part 1d
It is preferable to apply a paint for reflection or to dispose a member having a reflection function on the light guide plate 1. By preventing the light from entering the light guide plate 1 from this portion, the brightness of the light emitted from the light emitting surface 1c is made uniform. Can be

That is, at the bent portion 2a of the fluorescent lamp 2, since the light emitted from the fluorescent lamp 2 enters the light guide plate 1 from both side surfaces 1a, the brightness becomes high. Therefore, if a coating material for reflection is applied to the cutout portion 1d of the light guide plate 1 or a member having a reflection function is arranged, the light incident on the light guide plate 1 becomes a light of a straight line portion and is emitted from the light guide plate 1. The brightness distribution of light becomes more uniform. The excision part 1d
With a polygonal shape, the fluorescent lamp 2 can be relatively close to the side surface 1a of the light guide plate 1.

In the fluorescent lamp 2, a phosphor coating is formed on the inner surface of a cylindrical bulb made of soft glass and having an outer diameter of 3 mm (inner diameter of 2 mm) and a total length of 160 mm, and electrodes are arranged at both ends thereof to seal rare gas and mercury. Airtightly seal. After that, fix one end of the valve and free the other end to rotate at a low speed to heat the part to be bent, heat it for a predetermined time, stop the rotation and bend the other end to the right angle Approximately 6m radius of curvature with one side 70mm and the other 90mm
The L-shaped fluorescent lamp 2 is completed by forming the L-shaped fluorescent lamp 2.

The fluorescent lamp 2 may be either a hot cathode type or a cold cathode type, but since the fluorescent lamp 2 used for the backlight has good starting characteristics and low power consumption, it is preferable. Cold cathode fluorescent lamps are preferred.

The reflecting mirror 3 is constructed such that a reflecting sheet is attached to its inner surface, and surrounds the fluorescent lamp 2. In addition,
The reflection sheet is formed by vapor-depositing silver on the surface of a transparent film and coating the surface with a white paint mainly containing barium oxide or the like. This white paint prevents light from leaking from the silver deposition portion.

The reflector 4 is arranged in contact with the entire back surface 1b of the light guide plate 1. Similar to the light guide plate 1, the reflector 4 has an outer dimension of 150 mm in width and 100 mm in length.

A white sheet is used as the reflector 4 in order to reflect a large amount of light leaked from the light guide plate 1 toward the light guide plate 1, but a silver vapor deposition sheet may be used.

The light control plate 5 has a light-entering surface 5b in which a plurality of V-shaped groove portions 5a are arranged vertically and horizontally at a pitch of 0.8 mm, and a convex portion having a curved surface which bulges outward facing the groove portion 5a. It is composed of a light emitting surface 5d formed in 5c.

Light incident from various points on the convex portion 5c is emitted from the light emitting surface 5d within a predetermined direction of θ within about 20 °, so that the light is condensed and the absolute brightness on the surface of the light control plate is improved. However, the distribution tends to be non-uniform.

The birefringent plate 6 is arranged on the light emitting surface 5d side of the light control plate 5, and is such that a light beam is divided into two components having different velocities by the birefringent plate. Therefore, the brightness on the birefringent plate 6 is remarkably made uniform.

The case body 7 is integrally molded with a synthetic resin such as a polycarbonate resin, and has an outer shape of a substantially quadrangle (vertical length: about 90 mm, horizontal length: about 120 mm). The light guide plate 1, the fluorescent lamp 2, the reflecting mirror 3, A portion for housing the reflector 4, the light control plate 5, and the birefringent plate 6 is formed, and a portion for mounting the lighting means 8 is also formed around the portion.

The lighting means 8 is an inverter circuit for generating high frequency power, and in the present embodiment, supplies a substantially sinusoidal power of 40 KHz to the fluorescent lamp 2. By providing the lighting means 8 in the case body 7, the wiring connection between the fluorescent lamp 2 and the lighting means 8 can be facilitated. Further, the backlight can be easily miniaturized.

Next, a liquid crystal display device showing a second embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a side view of the liquid crystal display device. In the figure, the liquid crystal display device includes the backlight of the first embodiment and a liquid crystal display plate 9 arranged on the birefringent plate 6 side. Therefore, the brightness on the liquid crystal display plate 9 is improved, and the optical interference fringes on the liquid crystal display plate are suppressed, resulting in further sharpening.

[0045]

According to the invention of claim 1, the uniformity of the luminance distribution on the surface of the birefringent plate is remarkably improved, and the outer dimensions can be made relatively thin.

The invention of claim 2 has the same effect as the invention of claim 1.

According to the invention of claim 3, in addition to the effect of the invention of claim 1, since each member is sequentially arranged in the case body, the assembling efficiency is improved. In the invention of claim 4, the effect of the invention of claim 3 is provided. In addition to this, the routing of the wiring derived from the lighting means and the efficiency of assembly are improved.

The invention of claim 5 has the same effect as the invention of claim 1.

According to the sixth aspect of the present invention, the optical interference fringes on the liquid crystal display plate are less likely to occur, and the external dimensions can be made relatively thin.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a backlight according to a first embodiment of the present invention.

FIG. 2 is a side view of the main part of the same.

FIG. 3 is a side view of a liquid crystal display device showing a second embodiment of the present invention.

FIG. 4 is a side view of a conventional backlight.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light guide plate 2 ... Light source 3 ... Reflector 4 ... Reflector 5 ... Light control plate 6 ... Birefringent plate 7 ... Case main body 8 ... Lighting means 9 ... Liquid crystal display plate

Claims (6)

[Claims] 1. A light guide means having a side surface, a back surface and a light exit surface; a light source arranged on the side surface side of the light guide means; a light source arranged on the light exit surface side of the light guide means, and mainly emits light in a predetermined direction. An illuminating device comprising: a light control plate capable of emitting light; and a birefringent plate disposed on the light emitting surface side of the light control plate. 2. A light guide plate having a side surface, a back surface, and a light exit surface; a light source arranged on the side surface side of the light guide plate; a reflecting mirror arranged so as to surround the light source; and a light exit surface side of the light guide plate. And a birefringent plate disposed on the light emitting surface side of the light control plate; and a reflector disposed on the back surface of the light guide plate. A backlight comprising: 3. A light guide plate having a side surface, a back surface, and a light exit surface; a light source arranged on the side surface side of the light guide plate; a reflecting mirror arranged so as to surround the light source; and a light exit surface side of the light guide plate. And a birefringent plate disposed on the light emitting surface side of the light control plate; and a reflector disposed on the back surface of the light guide plate. A case main body for accommodating a light guide plate, a light source, a reflecting mirror, a reflector, a light diffusion plate and a light control plate; 4. A light guide plate having a side surface, a back surface and a light exit surface; a light source arranged on the side surface side of the light guide plate; a reflecting mirror arranged so as to surround the light source; a light exit surface side of the light guide plate. A light control plate that is mainly arranged to emit light in a predetermined direction; a birefringent plate that is arranged on the light emitting surface side of the light control plate; and a reflector that is arranged on the back surface of the light guide plate. A light guide plate, a light source, a reflecting mirror, a reflector, a light diffusing plate and a light control plate; and a lighting means arranged in the case main body for supplying high frequency power to the light source. Backlight characterized by. 5. The backlight according to claim 2, wherein the birefringent plate is made of calcite. 6. A liquid crystal display comprising: the backlight according to claim 2; and a liquid crystal display plate disposed on the light exit surface side of the birefringent plate. apparatus.