JPH09292529A - Illuminator and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a bright line and luminance irregularity from occurring on an effective light emitting area by adjusting the distribution density of the dot-like pattern of a light absorbing layer so that luminance in the vicinity of the end part of the effective light emitting area is uniformized. SOLUTION: A light scattering layer 9 is formed on a light transmission plate 4 by which light is emitted from the effective light emitting area 11, an optical reflector 7 is disposed on the layer 9, a fluorescent lamp 5 is provided on the end face of the plate 4, and the belt-like light absorbing layer 13 constituted of the dot-like pattern is further provided on the plate 4; and the distribution density of the dot-like pattern of the layer 13 is adjusted in order to uniformize the luminance in the vicinity of the end part of the area 11.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art There are various types of display devices in which a lighting device for irradiating light on a surface is mounted. For example, in the field of time division type or active matrix type liquid crystal display devices, their visibility is improved. A backlight system is used to measure the brightness. Further, particularly in a color liquid crystal display device, the panel transmittance is extremely low as compared with a monochrome liquid crystal display device, so that a thin illumination device with higher brightness is required.

FIG. 3 shows a backlight type liquid crystal display device 1.
FIG. 4 is a schematic cross-sectional view of FIG. 4, and FIG. The liquid crystal display device 1 includes a liquid crystal panel 2 and a lighting device 3. The lighting device 3 is a two-light type edge light system in which a long cylindrical fluorescent lamp 5 is arranged on an end surface of a rectangular light guide plate 4. . 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. Further, a reflector 8 made of Al or the like is provided so as to cover the fluorescent lamp 5. Then, a dot-shaped print pattern containing a white or milky white system and containing glass beads is provided on the other main surface of the light guide plate 4 to form the light scattering layer 9. According to the light scattering layer 9, a large number of dots are distributed over the entire surface with a high density, and the light scattering layer 9 serves as an adjusting means for increasing the brightness.

According to the liquid crystal display device 1, an effective display area 10 which is an area where the liquid crystal panel 2 actually displays an image is set, and an effective light emitting area having the same size as that of the effective display area 10 is set. 11 is provided.

When the light emitted from the two fluorescent lamps 5 is incident on 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.

[0006]

However, in the liquid crystal display device 1 having the above-described structure, it is required to reduce the thickness and weight of the liquid crystal display device 1 and to further reduce the size of the components other than the effective display region 10, and the end face of the light guide plate 4 is required. Although the distance D1 (for example, 4 mm) between the end face of the diffuser plate 6 and
On the other hand, there is a problem that bright lines are generated in the effective display area 10. This bright line is a light ray visually recognized in the effective display area 10, and is generated because the distance from the effective light emitting area 11 to the fluorescent lamp 5 is shortened.

In order to solve this problem, in the end region where the light scattering layer 9 is not formed on the other main surface of the light guide plate 4 or at the end which does not face the light scattering layer 9 on the light reflecting member 7. It has been proposed to provide a light absorbing layer which is patterned in a dot shape with a black ink containing carbon or the like in a partial area and absorbs an extra bright line by the light absorbing layer (see Japanese Patent Laid-Open No. 8-43636). ).

However, it has been found that the proposed liquid crystal display device still does not solve the bright line problem to a satisfactory degree. That is, due to the heat generation of the fluorescent lamp 5, temperature unevenness is generated in the plane of the device, and this temperature unevenness is particularly remarkable in the brightness generation region closest to the fluorescent lamp 5, and this causes uneven brightness. Occurs (because the threshold voltage of the liquid crystal partially changes due to such temperature unevenness, the transmittance of the liquid crystal changes), and thus the brightness problem is satisfied simply by providing the light absorption layer. It turned out that it could not be resolved to the extent possible.

Moreover, even if a uniform brightness is obtained over the entire display surface immediately after the fluorescent lamp 5 is turned on, if the lighting time becomes long, heat is conducted to the liquid crystal display surface due to the heat generated by the fluorescent lamp 5, whereby the negative type The above liquid crystal display device has a problem that the transmittance is high in a high temperature region and the brightness is high in the high temperature region.

Therefore, the present invention has been completed in view of the above circumstances, and an object thereof is to prevent generation of bright lines more effectively and to emit a uniform amount of light over the entire surface of an effective light emitting region. It is to provide a lighting device.

Another object of the present invention is to provide a long-term reliable lighting device in which the influence of heat generation of a long light source is reduced to prevent the generation of bright lines for a long period of time.

Still another object of the present invention is to provide a high-performance, high-reliability and small-sized liquid crystal display device equipped with the lighting device of the present invention.

[0013]

The lighting device of the present invention comprises:
On the other main surface of the light guide plate that emits light from the effective light emitting area of the one main surface, a light scattering layer formed in a dot pattern is formed to scatter light, and a light reflecting member is disposed on this light scattering layer.
A strip-shaped light is formed by providing a long light source on the end surface of the light guide plate, straddling a side of the effective light emitting region closest to the long light source, and having a dot pattern on both sides of the side. The absorption layer is provided on the other main surface of the light guide plate or on the light reflection member, and the distribution density of the dot-shaped pattern of the light absorption layer is adjusted to make the brightness near the end of the effective light emitting region uniform. To do.

The liquid crystal display device of the present invention is characterized in that a liquid crystal panel having an effective display region corresponding to the effective light emitting region is arranged on one main surface of the illuminating device of the present invention.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a liquid crystal display device 12 according to the present invention.
2 is a schematic cross-sectional view of an essential part showing a size relationship of the density of the dot pattern of the light absorption layer 13 provided in the liquid crystal display device 12. FIG. In the liquid crystal display device 12 of the same figure, the same members as those of the liquid crystal display device 1 shown in FIGS. 3 and 4 are designated by the same reference numerals.

According to the liquid crystal display device 12, the liquid crystal panel 2 and the lighting device 3a are incorporated in a pair of metal cases (not shown), and the lighting device 3a has a thickness of 3 mm. Along the end surface of the light guide plate 4 made of polymethylmethacrylate, two tube diameters 2.6 as long light sources.
mm cold cathode type fluorescent lamp 5 is arranged, and aluminum or PET on which silver is vapor-deposited on the outer periphery of the fluorescent lamp 5.
A light source-made reflection plate 8 is provided. The light source reflection plate 8 has a reflection surface whose cross-sectional shape is curved along the longitudinal direction of the fluorescent lamp 5.

A light diffusing plate 6 made of PET or polycarbonate (PC) is provided on one main surface of the light guide plate 4, and a dot-like light scattering layer 9 is formed on the other main surface. The dot-shaped light-scattering layer 9 is printed with a pattern containing glass beads (titanium oxide added) exhibiting a white to milky white system as a means for adjusting the brightness in a planar manner so that a large number of them are distributed at high density. It was formed in. A white polyethylene terephthalate light reflection plate 7 is provided on the dot-shaped light scattering layer.

The liquid crystal panel 2 is patterned 2
A structure in which a sheet of glass substrates is attached with a sealant, and then cut out with a predetermined size and liquid crystal is enclosed, and an area for displaying an image in the liquid crystal panel 2 is referred to as an effective display area 10. At the same position corresponding to the display area 10, there is an effective light emitting area 11 of the same size.

In order to reduce the size of the liquid crystal display device 12 having the above structure, the end face of the light guide plate 4 and the effective light emitting region 1 are used.
When the distance from 1 is decreased, the bright line generation region 14 (width D2) is formed along the end face. Further, in the bright line generation region 14, a uniform bright line is generated at the beginning of lighting, but there is a brightness uneven region 15 (width D3) in which brightness unevenness occurs due to heat generation of the fluorescent lamp 5 over time.

Therefore, in the present invention, the light absorption layer 1 extends over the bright line generation region 14 and the brightness unevenness region 15.
3 is formed to absorb an extra bright line. The light absorption layer 13 is patterned in a dot shape with a black ink containing carbon or the like, and extends over the side of the effective light emitting region 11 and has a band shape on both sides of the side.

Further, the bright line generation area 14 and the uneven brightness area 1
The region 16 in which 5 and 5 are overlapped is the other region 1 on both sides thereof.
It can be seen that more bright lines are generated as compared with Nos. 7 and 18, and therefore the light absorption rate of the region 16 is changed to those of the regions 17 and 18.
It is set higher than the above, so that uneven brightness does not occur. In order to obtain such a high light absorptance, the density of the dot pattern may be increased or the dot area may be increased.

Thus, according to the liquid crystal display device 12 having the above-described structure, when the light absorption layer 13 having the dot pattern is formed, the density of the dot pattern is adjusted so that the luminance near the end of the effective light emitting region 11 is uniform. I was able to.

Next, another embodiment of the present invention will be described with reference to FIG. This figure is a schematic cross-sectional view of a main part of a liquid crystal display device 19 of the present invention, and the same members as those of the liquid crystal display device 12 of FIG.

In the illuminating device 3a of the liquid crystal display device 12, the light absorbing layer 13 is provided on the light guide plate 4, whereas in the illuminating device 3b of the liquid crystal display device 19, a similar light reflecting plate 7 is provided. The light absorption layer 13a is formed.

Even in the illuminating device 3b or the liquid crystal display device 19 having this structure, in the region where the bright line generating region and the uneven brightness region are overlapped, the light absorption rate is higher than that of the other regions on both sides thereof. As a result, uneven brightness does not occur, and the brightness near the end of the effective light emitting region 11 can be made uniform.

[0026]

EXAMPLES Next, the present inventor measured the brightness as follows using the illumination device 3a having the above-mentioned configuration. As shown in the plan view of the illumination device 3a in FIG. 6, the surface is numbered 9
When individual parts were designated, the brightness of each part was measured, and the average value of these was calculated, the results shown in FIG. 7 were obtained. Further, when the luminance was similarly measured for the conventional lighting device 3 of FIG. 3, the result as shown in FIG. 8 was obtained. The unit of the numerical value of each luminance is cd / m ² .

As is apparent from these figures, in the present invention (FIG. 7), the 9-point average luminance is 67.7 cd / m.
It is ² , but the difference is small compared to this. However, in the comparative example (FIG. 8), the brightness is significantly higher at the edge portion than the 9-point average brightness, and it is recognized as uneven brightness.

The present invention is not limited to the above embodiment, and various modifications and improvements can be made without departing from the scope of the present invention. For example, although the light guide plate 4 is a flat plate in the above-described embodiment, a single-light type backlight illuminating device using a wedge-shaped light guide plate may be used instead.

[0029]

As described above, according to the illuminating device of the present invention, the effective light emitting region is formed in a dot pattern on both sides of the side that is closest to the elongated light source. By providing a band-shaped light absorbing layer on the other main surface of the light guide plate or on the light reflecting member, and adjusting the density of the dot-shaped pattern of the light absorbing layer to make the brightness near the edge of the effective light emitting region uniform. Thus, it is possible to provide a high-quality and small-sized illuminating device capable of preventing the generation of bright lines and uneven brightness, thereby increasing the brightness over the entire surface of the effective light emitting region and emitting a uniform amount of light.

Further, according to the illumination device of the present invention, by arranging it under the optimum conditions while adjusting it to a portion where bright lines do not occur, the influence of the heat generation of the elongated light source is reduced, and It was possible to provide a lighting device with long-term reliability that prevented the generation of bright lines over a period of time.

Further, according to the liquid crystal display device of the present invention, by disposing the liquid crystal panel having the effective display area corresponding to the effective light emitting area on one main surface of the illuminating device of the present invention, high reliability is achieved. Moreover, a small liquid crystal display device could be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a liquid crystal display device according to an embodiment.

FIG. 2 is a schematic enlarged cross-sectional view of a main part of the liquid crystal display device of the embodiment.

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

FIG. 4 is a schematic cross-sectional view of a main part of a conventional liquid crystal display device.

FIG. 5 is a schematic cross-sectional view of a main part of a liquid crystal display device according to another embodiment.

FIG. 6 is an explanatory diagram showing a luminance measurement portion of the illumination device.

FIG. 7 is a diagram showing a change with time in luminance of the illumination device of the embodiment.

FIG. 8 is a diagram showing a temporal change in luminance of a conventional lighting device.

[Explanation of symbols]

 2 Liquid crystal panel 3a, 3b Illumination device 4 Light guide plate 5 Fluorescent lamp 6 Light diffusing plate 7 Light reflecting plate 8 Reflecting plate 9 Light scattering layer 10 Effective display area 11 Effective light emitting area 12, 19 Liquid crystal display device 13, 13a Light absorbing layer 14 Bright line generation area 15 Brightness unevenness area

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 that emits light from an effective light emitting region of one main surface, and a light-reflecting member is formed on the light-scattering layer. In a lighting device comprising a light source and a long light source provided on the end surface of the light guide plate, a dot shape is formed on both sides of the side across the side closest to the long light source in the effective light emitting region. A patterned band-shaped light-absorbing layer is provided on the other main surface of the light guide plate or on the light-reflecting member, and the distribution density of the dot-shaped pattern of the light-absorbing layer is made uniform in order to make the brightness near the edge of the effective light emitting region uniform. A lighting device characterized by being adjusted. 2. A liquid crystal display device in which a liquid crystal panel having an effective display region corresponding to an effective light emitting region is arranged on one main surface of the illuminating device of claim 1.