JPH0990362A - Illumination light, back light and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an illuminate device with which a luminance distribution is made uniform, a back light and a liquid crystal display device with which the occurrence of light interference fringes is controlled by disposing a light control plate which radiates light mainly in a prescribed direction on the light exit surface side of a light transmission means and disposing a light diffusion plate on the light exit surface side of this light control plate. SOLUTION: The light transmission plate 1 is introduced with the light radiated from a fluorescent lamp 2 from its flank 1a and radiates the light from the light exit surface 1c side. The incident light is emitted within nearly 20 deg. of θ which is the prescribed direction. The light emitted from the respective points with an increase in the distance from the surface of the light control plate is corrected of the points where the luminance is low and, therefore, the luminance is made relatively uniform. The light diffusion plate 6 is arranged by having 6 to 10mm spacing from the light control plate 5 on the light exit surface side of the light control plate 5. The light diffusion plate which varies in the surface roughness of its front and rear surfaces is used. The light diffusion plate is arranged on the light control plate 5 by positioning the surface which is not rough in the surface roughness on the light exit surface side and directing the rough surface upward. The luminance distribution of the light is made further uniform if plural sheets of the light diffusion plates 6 are used.

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. 6 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 traces in FIG. 6, 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. A light control plate that is mainly arranged to emit light in a predetermined direction; and a light diffusing plate that is arranged on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm from the light control plate. And;

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. Furthermore, the average distance between the light control plate and the light diffusion plate is 6 mm to 10 m.
m is enough.

In the present invention, since light is mainly emitted in predetermined directions from various parts of the light control plate, the brightness of the surface of the light control plate is
Although the light is non-uniform, the light emitted from each part as the distance is increased corrects the low brightness part. Therefore, according to the experiment, the brightness becomes relatively uniform when the light is separated by about 6 mm. Further, although the uniformity of the brightness is improved when the distance is increased, there is a problem that the absolute brightness is lowered and the external dimension is further increased. Therefore, the upper limit is approximately 10 mm.

Further, since the light diffusing plate is arranged with the above-mentioned gap being provided between the light diffusing plate and the light control plate, the uniformity of the brightness on the light diffusing plate is significantly improved.

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 light control plate disposed on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm And a reflector disposed on the back surface of the light guide plate.

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 that of the first aspect of the invention.

According to a third 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 light control plate disposed on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm A light diffuser plate; a reflector disposed on the back surface of the light guide plate; and a case body that accommodates the light guide plate, the light source, the reflecting mirror, the reflector, the light diffuser plate, and the light control plate. .

The case body is molded of, for example, 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 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 light control plate disposed on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm A light diffusing plate; a reflector disposed on the back surface of the light guide plate; a case body accommodating the light guide plate, a light source, a reflecting mirror, a reflector, a light diffusing plate and a light control plate; Lighting means for supplying high frequency power to the light source.

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

According to the present invention, in addition to the operation of the third aspect of the invention, it is possible to efficiently route and assemble the wiring led out from the lighting means.

According to a fifth aspect of the present invention, in the third or fourth aspect, the angle of the light control plate in the predetermined direction is within about 20 ° with respect to the vertical direction of the light control plate.

According to the present invention, since light is emitted from each position of the light control plate within a range of 20 °, the brightness of the surface of the light control plate is experimentally shown to be relatively uniform when the distance is about 6 mm. come. Further, although the uniformity of the brightness is improved when the distance is increased, there is a problem that the absolute brightness is lowered and the external dimension is further increased. Therefore, the upper limit is approximately 10 mm
It is.

According to a sixth 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 light control plate disposed on the light emitting surface side of the light control plate with a gap of 8 mm to 10 mm A light diffusing plate; a liquid crystal display plate having elements arranged in a matrix arranged on the light emitting surface side of the light diffusing plate; and a reflector arranged on the back surface of the light guide plate. There is.

According to the present invention, according to the experiment, the light interference fringes, which are generated when the light emitted from various parts of the light control plate passes through the elements arranged in a matrix form, are observed. If the gap between and is about 8 mm, it is less likely to occur. Further, if the distance is increased, optical interference fringes are less likely to occur, but there is a problem that absolute brightness is lowered and external dimensions are increased. Therefore, the upper limit is about 10 mm.

According to a seventh 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 arranged on the light emitting surface side of the light plate and capable of mainly emitting light in a predetermined direction; and a light control plate arranged on the light emitting surface side of the light control plate with a gap of 6 mm to 8 mm. A light diffusing plate; a liquid crystal display plate having elements arranged in a staggered arrangement on the light emitting surface side of the light diffusing plate; and a reflector disposed on the back surface of the light guide plate. There is.

In the present invention, instead of the liquid crystal display panel having the elements arranged in a matrix as in the sixth aspect of the invention, the elements are arranged in a staggered manner. According to experiments, the above-mentioned optical interference fringes are The gap between the light control plate and the light diffusion plate is approximately 6 m
When it is set to about m, it hardly occurs. Further, the optical interference fringes become more difficult to see as the distance increases, but the absolute luminance decreases, so the upper limit is approximately 8 mm.

[0026]

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 longitudinal sectional view of a main 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, the light diffusion plate 6 is provided on the light emitting surface side of the light control plate 5 with a gap of 6 mm to 10 mm from the light control plate 5.
Are arranged.

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 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.

The light guide plate 1 also 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 of the bulb 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 as the fluorescent lamp 2 used for the backlight, the rising characteristics are good and low power consumption is preferred, so Cold cathode fluorescent lamps are preferred.

The reflecting mirror 3 encloses the fluorescent lamp 2 while attaching the reflecting sheet 3b along the inner surface of the reflecting mirror body 3a whose inside is curved. The reflective sheet 3b 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 bulging 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. Then, as the distance from the surface of the light control plate increases, the light emitted from each part corrects the low brightness part, so that the brightness becomes relatively uniform. In the present embodiment, the angle θ of the light control plate 5 in the predetermined direction is approximately 20 ° with respect to the vertical direction of the light control plate 5.

The light diffusing plate 6 is arranged on the light emitting surface 5d side of the light control plate 5 and has different surface roughnesses on the front and back surfaces. In this case, a surface having a non-rough surface is positioned on the light emitting surface 5d side, and the rough surface is directed upwards.
It is placed on top. If a plurality of light diffusion plates 6 are used, the brightness distribution of the light emitted from the light exit surface can be made more uniform. Further, since the light diffusing plate 6 is arranged so as to leave this gap with the light control plate 5, the uniformity of the brightness on the light diffusing plate 5 is significantly improved.

The case body 7 is integrally molded with a synthetic resin such as a polycarbonate resin, and has a substantially quadrangular outer shape (length 90 mm, width 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 light diffusion 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 FIGS.

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 light diffusion plate side.

FIG. 4 is a schematic view of an essential part showing elements arranged in a matrix on the liquid crystal display panel 9, and FIG.
FIG. 3 is a schematic diagram of a main part showing elements arranged in a staggered pattern on the liquid crystal display panel 9.

When each of the liquid crystal display plates 9 having such two different types of elements is used, the light on the liquid crystal display plate 9 is adjusted by adjusting the gap between the light control plate 5 and the light diffusion plate 6. An experiment was conducted on the generation of interference fringes. At this time, the gap between the light control plate 5 and the light diffusion plate 6 having a large effect was obtained by taking into consideration the absolute brightness on the light diffusion plate 6.

The results are shown below. The circles are good because the optical interference fringes are hard to see and the brightness is sufficient. △ is a little worse than the evaluation of ○. × indicates that the optical interference fringes are clearly visible, or the external dimension is relatively thick.

[Gap (mm)] [Evaluation in matrix] [Evaluation in zigzag] 0 × × 1 × × 2 × × 3 × × 4 × △ 5 × △ 6 △ ○ 7 △ ○ 8 ○ ○ 9 ○ △ 10 ○ △ 11 × × 12 × × Therefore, when using the elements arranged in a matrix in the liquid crystal display panel 9 of FIG. 4, according to experiments,
The gap between the light control plate and the light diffusion plate is approximately 8 mm to 10 m.
m is good.

Further, when the elements arranged in a zigzag manner are used in the liquid crystal display panel 9 of FIG. 5, the gap is preferably about 6 mm to 8 mm.

[0053]

According to the first aspect of the present invention, the uniformity of the luminance distribution on the surface of the light diffusion 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 the respective members are sequentially arranged in the case body, the assembly 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 invention, optical interference fringes are less likely to occur on the liquid crystal display plate, and the external dimensions can be made relatively thin.

The invention of claim 7 has the same effect as the invention of claim 6.

[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 likewise a longitudinal sectional view of an essential part.

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

FIG. 4 is a schematic view of a main part of a liquid crystal display panel showing elements arranged in a matrix.

FIG. 5 is a schematic view of a main part of a liquid crystal display panel showing elements arranged in a staggered manner.

FIG. 6 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 ... Light diffuser plate 7 ... Case body 8 ... Lighting means 9 ... Liquid crystal display plate

Claims (7)

[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. A light control plate capable of emitting light; and a light diffusing plate disposed on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm from the light control plate. Lighting equipment. 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. A light control plate that is mainly arranged to emit light in a predetermined direction; and a light diffusing plate that is arranged on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm from the light control plate. And a reflector disposed on the back surface of the light guide plate. 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. A light control plate that is mainly arranged to emit light in a predetermined direction; and a light diffusing plate that is arranged on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm from the light control plate. And; a reflector disposed on the back surface of the light guide plate; and a case body that accommodates the light guide plate, the light source, the reflection mirror, the reflector, the light diffusion plate, and the light control plate; Backlight. 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; and a light diffusing plate that is arranged on the light emitting surface side of the light control plate with a gap of 6 mm to 10 mm from the light control plate. And; a reflector disposed on the back surface of the light guide plate; a case body that accommodates the light guide plate, a light source, a reflecting mirror, a reflector, a light diffuser plate, and a light control plate; A backlight comprising: a lighting means for supplying electric power; 5. The backlight according to claim 3, wherein the angle of the light control plate in the predetermined direction is within about 20 ° with respect to the vertical direction of the light control plate. 6. A light guide plate having a side surface, a back surface and a light emitting surface; a light source arranged on a side surface side of the light guide plate; a reflecting mirror arranged so as to surround the light source; a light emitting surface side of the light guide plate. A light control plate which is mainly arranged to emit light in a predetermined direction; and a light diffusing plate which is arranged on the light emitting surface side of the light control plate with a gap of 8 mm to 10 mm from the light control plate. A liquid crystal display plate having elements arranged in a matrix arranged on the light exit surface side of the light diffusion plate; and a reflector provided on the back surface of the light guide plate. Liquid crystal display device. 7. A light guide means 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; and a light emitting surface of the light guide plate. A light control plate disposed on the side of the light control plate and capable of mainly emitting light in a predetermined direction; and a light diffusion plate disposed on the light emitting surface side of the light control plate with a gap of 6 mm to 8 mm from the light control plate. A liquid crystal display panel having elements arranged in a zigzag pattern, the liquid crystal display panel being disposed on the light emitting surface side of the light diffusing plate; and the reflector being disposed on the back surface of the light guide plate. Liquid crystal display device.