JPH0843636A - Illumination device and liquid crystal display device - Google Patents

Abstract

PURPOSE:To enhance luminance over the entire surface of an effective light emission region without generating bright lines and to obtain an illumination device reduced in size by providing an end region of a light transmission plate where the light scattering layer on the other main surface thereof is not formed or the end region which does not face the light scattering layer on a light reflection member with a light absorption layer. CONSTITUTION:A light scattering layer 9 is formed as a regulating means for enhancing luminance in a plane shape on the other main surface of the light transmission plate 4. A light absorption layer 16 is directly formed at the end region where the light scattering layer 9 on the other main surface is not formed in the spacing D4 from the end face of the light transmission plate 4 where the bright lines are liable to arise in correspondence to the part within this spacing D4. Since the light transmission plate is provided with the light absorption layer 16 in such a manner, the light emitted from a fluorescent lamp 5 is so suppressed by the light transmission layer 16 that the light quantity does not increase in the region of the spacing D4. The luminance is enhanced over the entire surface of the effective light emission region 11 by a combination of the light scattering layer 9 and the light reflection member 7 when the light beams from two pieces of the fluorescent lamps 5 are made incident on the light transmission plate 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device that irradiates light on a surface, and also relates to a liquid crystal display device equipped with the illuminating device.

[0002]

2. Description of the Related Art A liquid crystal display device is equipped with an illuminating device for irradiating a planar display portion with light. For example, in a liquid crystal display device of a time division system or an active matrix system, a backlight system is adopted in order to improve its visibility.

FIG. 3 is a schematic cross-sectional view of the liquid crystal display device 1 of that type, and FIG. 4 is a schematic cross-sectional view of the main part thereof. As shown in the figure, the liquid crystal display device 1 is composed of a liquid crystal panel 2 and a lighting device 3, and the lighting device 3 is a two-lamp type in which a long cylindrical fluorescent lamp 5 is placed on an end surface of a rectangular light guide plate 4. The edge light method. A diffusion plate 6 is provided on one main surface of the light guide plate 4, and a plate-shaped light reflecting member 7 is provided on the other main surface. Moreover, a reflector 8 made of Al or the like is provided so as to cover each long cylindrical fluorescent lamp 5.

On the other main surface of the light guide plate 4, dot-shaped printing containing glass beads of white or milky white, which are distributed in a high density on almost the entire surface as an adjusting means for increasing the brightness in a planar manner. The light scattering layer 9 that is a pattern is formed.

In the liquid crystal display device 1 having such a configuration, the effective display area 10 which is an area where the liquid crystal panel 2 actually displays an image is set, and the effective display area 10 has the same size at a position corresponding to the effective display area 10. The effective light emitting area 11 is determined.

When the light emitted from the two fluorescent lamps 5 enters the light guide plate 4, the combination of the light-scattering layer 9 and the light-reflecting member 7 enhances the brightness over the entire surface of the effective light-emitting region 11 and makes it uniform. The light is emitted with the amount of light.

[0007]

However, it is required that the liquid crystal display device 1 having the above-mentioned configuration be made thinner and lighter and that the components other than the effective display region 10 be made smaller, and the end face of the light guide plate 4 and the diffuser plate are required. Although the distance D1 (for example, 4 mm) from the end face of No. 6 is made small, on the other hand, there is a problem that a bright line is generated in the effective display area 10. This bright line is a line of light visually recognized in the effective display area 10,
It occurs because the distance from the effective light emitting region 11 to the fluorescent lamp 5 is shortened.

In order to solve this problem, the applicant of the present application has proposed a liquid crystal display device 12 having a structure shown in FIG. 5 (see Japanese Patent Laid-Open No. 5-88172). 3 and 4 in the figure.
The same members as those in FIG.

FIG. 5 is a schematic cross-sectional view of the main part of the liquid crystal display device 12. According to the lighting device 3a, the distance D2 (for example, 15 mm) between the end surface of the light guide plate 4 and the end surface of the diffusion plate 6 is used. The exposed region 13 of the light guide plate 4 which is not covered with the reflector 8 in a partial region on one main surface of the light guide plate 4 to be exposed.
(Space D3) is provided, and in this exposed region 13, a light absorbing member 14 formed by mixing black pigment or dye into polyester resin is provided.
The light absorbing member 14 suppresses the irradiation light of the fluorescent lamp 5 so that the light amount does not become large near the end surface of the diffusion plate 6 (the end portion of the effective light emitting region 11).

However, the above proposed liquid crystal display device 1
In No. 2, the problem of bright lines in the effective display area 10 was solved, but if the distance D3 between the exposed areas 13 is reduced (for example, 0 to 1 mm) in order to reduce the distance D2 to reduce the size of the liquid crystal display device 12. However, it is difficult to set the distance D3 with high precision due to the narrow region, and when the light absorbing member 14 is attached and provided at a predetermined position, high mounting precision is required.

Therefore, the present invention has been completed in view of the above circumstances, and an object thereof is to increase the brightness over the entire surface of the effective light emitting region without causing a bright line and to emit a uniform amount of light. It is an object of the present invention to provide a high quality and highly reliable lighting device capable of improving the manufacturing efficiency and the manufacturing yield because a highly accurate design is not required.

Another object of the present invention is to provide a lighting device in which the components other than the effective light emitting region are further reduced in size, and the size and weight of the lighting device are reduced.

Yet another object of the present invention is to provide a small-sized liquid crystal display device having such a high quality and highly reliable lighting device mounted thereon and having a uniform display surface.

[0014]

According to a first aspect of the present invention, there is provided a lighting device having a light-scattering layer formed in a dot pattern to scatter light on the other main surface of a light guide plate which emits light from one main surface, A light-reflecting member is provided on the light-scattering layer, a long light source is provided on the end surface of the light guide plate, and the end surface region on the other main surface of the light guide plate where the light-scattering layer is not formed, or It is characterized in that a light absorbing layer is provided in an end region which does not face the light scattering layer on the light reflecting member.

According to a second aspect of the present invention, there is provided a liquid crystal display device in which a liquid crystal panel is arranged on one main surface of the illuminating device of the first aspect.

[0016]

According to the illuminating device of the first aspect, in the light guide plate which emits light from the one main surface, the light absorbing layer is provided in the end region on the other main surface where the light scattering layer is not formed. Alternatively, the light absorption layer is provided on the end portion region of the light reflection member that does not face the light scattering layer. With these configurations, the light absorbing layer is directly formed on the light guide plate instead of the conventional structure in which the light absorbing member is surrounded by the light guide plate. Therefore, the light absorbing layer is guided by dot printing or the like. It can be arranged with high precision as in the case of forming on an optical plate.

Further, by providing this light absorbing layer, it is possible to increase the luminance over the entire surface of the effective light emitting region without generating a bright line and to emit a uniform amount of light.

Moreover, since high precision design is not required, the manufacturing efficiency and the manufacturing yield can be improved.

Furthermore, by forming the light absorption layer directly on the light guide plate by dot printing or the like, the positional accuracy of the formation is improved, and thus the light absorption layer can be formed as required with a size as small as possible. The components other than the effective light emitting region can be further reduced, and as a result, it is possible to achieve thinning and weight reduction as well as size reduction.

According to a second aspect of the present invention, there is provided a liquid crystal display device comprising a liquid crystal panel disposed on one main surface of the illuminating device according to the first aspect, whereby bright lines are not generated in the effective display area. It is possible to achieve high performance and miniaturization without display unevenness.

[0021]

【Example】

(Example 1) A liquid crystal display device 15 of the present invention will be described with reference to FIG. This drawing is a schematic cross-sectional view of the main part of the liquid crystal display device 15. The same members as those in FIGS. 3 and 4 are designated by the same reference numerals.

According to FIG. 1, the liquid crystal display device 15 comprises a liquid crystal panel 2 and an illuminating device 3b. The illuminating device 3b places a long cylindrical fluorescent lamp 5 on the end face of a rectangular light guide plate 4. It is a two-lamp type edge light system.

The light guide plate 4 is a rectangular plate made of polymethylmethacrylate (PMMA) having a thickness of 4 mm. A diffusion plate 6 made of PET or polycarbonate (PC) is provided on one main surface of the light guide plate 4, and the other is provided. A light reflection member 7 made of a low-foamed film of white polyester is provided on the main surface. Moreover, a long cylindrical fluorescent lamp 5 (cold cathode tube or hot cathode tube having a tube diameter of 3.8 mm) is arranged along the end surface of the light guide plate 4, and a PET sheet is provided with silver on the outer periphery of the fluorescent lamp 5. The reflector 8 is formed by vapor deposition.

The liquid crystal panel 2 is patterned 2
The glass substrates are bonded together with an adhesive, then cut out with a predetermined size, and liquid crystal is sealed. The area of the liquid crystal panel 2 where an image is actually displayed is set as the effective display area 10. This effective display area 10
At the same position corresponding to, there is an effective light emitting region 11 of the same size.

On the other main surface of the light guide plate 4, dot-shaped printing containing glass beads of white or milky white color distributed in a high density in a large number on almost the entire surface as a means for adjusting the brightness in a planar manner. The light scattering layer 9 that is a pattern is formed. The light amount tends to decrease as the distance from the fluorescent lamp 5 increases, but the light scattering layer 9 prevents the decrease.

Then, with respect to the distance D4 from the end surface of the light guide plate 4 where the bright line is likely to occur, an end region on the other main surface where the light scattering layer 9 is not formed corresponding to a portion within the distance D4. The light absorption layer 16 is directly formed on the surface. This light absorption layer 1
6 is a black ink containing carbon or the like printed in dots.

Thus, according to the liquid crystal display device 15 having the above structure, since the light absorption layer 16 is provided, the light absorption layer 16 prevents the irradiation light of the fluorescent lamp 5 from increasing in the area of the interval D4. I was able to suppress it. When the light emitted from the two fluorescent lamps 5 is incident on the light guide plate 4, the effective light emitting region 1 is formed by the combination of the light scattering layer 9 and the light reflecting member 7.
It was possible to increase the brightness over the entire surface of No. 1 and emit a uniform amount of light.

Moreover, since the light absorption layer 16 is formed on the light guide plate 4 by dot printing, the light absorption layer 16 can be arranged with high accuracy, and the manufacturing efficiency and the manufacturing yield can be improved.

Further, by forming the light absorption layer 16 directly on the light guide plate 4 by dot printing or the like, the positional accuracy of the formation is improved, and according to experiments by the present inventors, from the end face of the light guide plate 4, The distance D4 can be reduced to 4 mm.

Example 2 Referring to FIG. 2, the liquid crystal display device 1 of this example is shown.
7 will be described. This drawing is a schematic cross-sectional view of the main part of the liquid crystal display device 17, and the same members as those in FIG. 1 are designated by the same reference numerals.

In the liquid crystal display device 15 of FIG. 1, the light absorption layer 1
6 is provided on the light guide plate 4, the light absorption layer 16 is provided on the light reflection member 7 in the liquid crystal display device 17 of FIG.
a.

Thus, also in the liquid crystal display device 17 having the above structure, the light absorption layer 16a can suppress the irradiation light of the fluorescent lamp 5 from increasing in the area of the interval D4, and the light absorption layer 16a can suppress the effective light emission. The brightness was increased over the entire surface of the region 11, and the light could be emitted with a uniform light amount. In addition, by directly forming the light absorption layer 16a on the light reflection member 7 by dot printing or the like, the positional accuracy of the formation is increased, and according to experiments by the present inventors, the distance D4 from the end surface of the light guide plate 4 is determined. Was reduced to 4 mm.

The present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the scope of the present invention. For example, in this embodiment, the light absorption layer 16 is directly and discontinuously formed on the light guide plate 4 by dot printing or the like, but similar effects can be obtained by forming the light absorption layer 16 in a continuous layered form. Further, in this embodiment, the two-light type edge light system is used. However, the same operation and effect can be obtained by the one-light type edge light system in which only one long light source is arranged for the light guide plate 4. can get. Further, a prism plate made of PC may be further formed on the diffusion plate 6 in order to enhance the brightness.

[0034]

As described above, according to the first aspect of the invention, in the light guide plate which emits light from the one main surface, the light absorption layer is provided on the other main surface in the end region where the light scattering layer is not formed. Since the light absorption layer is provided in the end region that does not face the light scattering layer on the light reflection member, this light absorption layer can be formed on the light guide plate or the light reflection member with high precision by dot printing or the like.
This allowed the desired size to be formed with the smallest possible dimensions. Therefore, the components other than the effective light emitting region can be further reduced, and as a result, the manufacturing efficiency and the manufacturing yield can be improved, and further, the lighting device can be provided which is thin and lightweight, and is also downsized.

Moreover, in the present invention, by providing the above-mentioned light absorption layer, it is possible to prevent the generation of bright lines, increase the brightness over the entire effective light emitting region, and emit a uniform amount of light. A highly reliable lighting device could be provided.

According to the second aspect of the present invention, by mounting the above-mentioned illumination device, it is possible to provide a high-quality and highly reliable small-sized liquid crystal display device having a uniform display surface.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a lighting device of an embodiment.

FIG. 2 is a schematic cross-sectional view of a lighting device of an example.

FIG. 3 is a schematic cross-sectional view of a liquid crystal display device.

FIG. 4 is a schematic cross-sectional view of a conventional lighting device.

FIG. 5 is a schematic cross-sectional view of a conventional lighting device.

[Explanation of symbols]

 2 Liquid crystal panels 3, 3a, 3b Illumination device 4 Light guide plate 5 Fluorescent lamp 6 Diffuser 7 Light reflecting member 9 Light scattering layer 10 Effective display area 11 Effective light emitting area 16, 16a Light absorbing layer

Claims (2)

[Claims] 1. A light-scattering layer formed in a dot pattern to scatter light is formed on the other main surface of a light guide plate which emits light from one main surface, and a light-reflecting member is disposed on the light-scattering layer. ,
In a lighting device in which a long light source is provided on an end surface of the light guide plate, the light guide plate is opposed to an end region where the light scattering layer is not formed on the other main surface of the light guide plate or a light scattering layer on the light reflecting member. An illuminating device characterized in that a light absorbing layer is provided in an end region that does not exist. 2. A liquid crystal display device in which a liquid crystal panel is arranged on one main surface of the illuminating device of claim 1.