JPH1039299A - Light irradiation device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power of a light source lighting a light transmission plate while maintaining high luminance and without lowering luminous efficiency, and to make a light irradiation device small in size and light in weight, and to reduce the energy for the device, and also to uniformize the display luminance of a liquid crystal display device. SOLUTION: An L-shape fluorescent tube 13 consisting of a first light source and a second light source shorter than the first side 15a and the second side 15b of a light transmission plate 14 are provided at the first angle part 14c of the light transmission plate 14 and also the arrangement density of light scattering patterns 17 of overlapping areas C of the light transmission plate 14 where illuminations from both light sources are overlapped is made lower as compared with that of surrounding areas A', B'. Thus, the lowering of powers of fluorescent tubes 13 is realized and, moreover, the display diginity of this device is enhanced by uniformizing outgoing intensities from the light transmission plate 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light irradiation device for irradiating an image display device such as a liquid crystal television and a personal computer.
Further, the present invention relates to a liquid crystal display device having a light irradiation device for efficiently irradiating an image display element.

[0002]

2. Description of the Related Art In a liquid crystal display device, a light source such as a fluorescent tube is provided on a side surface, and light emitted from a light guide plate illuminated by the light source irradiates and transmits a liquid crystal display element from the back to display an image. Among the irradiation devices, the amount of light entering the light guide plate is large,
In order to obtain high luminance while consuming low power, conventionally, as disclosed in Japanese Patent Application Laid-Open No. Hei 2-232468, an L-shaped fluorescent tube lamp is provided along the entire length of two sides of a light guide plate. A light irradiation device was used.

[0003]

However, in the above-mentioned conventional apparatus, the light guide plate is irradiated with an L-shaped fluorescent tube lamp having at least one side substantially equal in length to one side of the light guide plate. Although high brightness can be obtained, the power consumption cannot be reduced sufficiently due to the long length of the L-shaped fluorescent tube, and further energy saving of the light irradiation device has been hindered. In particular, there has been a demand for the development of a light irradiation device that can be incorporated into a portable size liquid crystal display device that needs to be thin and light and requires low power consumption and that can achieve low power consumption and high brightness. .

Therefore, in order to reduce the power consumption of the light source, the diameter of the fluorescent tube has been reduced or the tube current has been reduced. However, despite the necessity of applying a fluorescent material to the inside of the fluorescent tube, the diameter of the tube is currently reduced to about 2 mm, which is close to the manufacturing limit. In addition, there is a new problem that the tube voltage is increased by reducing the diameter of the fluorescent tube.

Although the tube current is currently set to about 6 to 3 mmA, the tube current must be 3 mA in order to maintain the stability of discharge.
It is required that the current be about mA or more, and furthermore, since it has a negative resistance characteristic, an attempt to lower the current will cause a further increase in the tube voltage, thereby causing a problem that the discharge becomes more unstable. Was. Furthermore, the fluorescent tube is 20-50k
It is excited by a high-frequency current of about Hz, and a leakage current is generated to the outside through the floating capacitance in the vicinity. This leakage current increases with an increase in the tube voltage, and the luminous efficiency is reduced as compared with the power consumption. There was also a problem that it would end up.

In addition, fluorescent materials generally used for fluorescent tubes are highly temperature-dependent, and although the luminous efficiency is highest at a temperature of about 60 to 70 ° C., the fluorescent substance is required to reduce power consumption. If the tube current is reduced, the power consumption per unit area of the fluorescent tube is reduced, and the temperature of the fluorescent material applied to the tube wall is lowered. As a result, the luminous efficiency of the fluorescent tube is reduced. Was reduced. For this reason, although the power consumption of the fluorescent tube must be reduced, there is a contradiction that the power consumption per unit length of the fluorescent tube must be maintained.

Accordingly, the present invention solves the above-mentioned problems, and a light irradiating device capable of realizing a high luminance and low power consumption of a light source without causing a decrease in luminous efficiency. It is an object to provide a liquid crystal display device using the device.

[0008]

According to the present invention, as a means for solving the above-mentioned problems, a flat light guide plate made of a light-transmitting material and having adjacent first and second sides is provided. A first light source, which is shorter than the first side and illuminates a first region of the light guide plate along the corner of one side, and a corner of the second side adjacent to the first light source; The second of the light guide plate
A second light source shorter than said second side illuminating an area of
Light that is dispersedly arranged on the light guide plate and has a lower arrangement density in an overlapping region of the first region and the second region than a region irradiated by only the first light source or only the second light source. And a scattering pattern.

According to another aspect of the present invention, there is provided a liquid crystal display device having electrodes and having a liquid crystal composition sealed in a gap between electrode substrates opposed to each other, and a liquid crystal display device substantially equivalent to the liquid crystal display device. A liquid crystal display device having a light guide plate having a shape, a light source for irradiating the light guide plate, and a light irradiating device for irradiating transmitted light on the back of the liquid crystal display element, the light irradiating device being formed of a light scattering pattern dispersedly arranged on the light guide plate The light guide plate is made of a light-transmitting material, is a flat plate shape having an adjacent first side and a second side, and the light source is in contact with a corner of the first side and the first side of the light guide plate. A first light source that is shorter than the first side and illuminates a region of the light guide plate that is adjacent to the first light source and is adjacent to a corner of the second side and illuminates a second region of the light guide plate; And a second light source shorter than side 2; Arrangement density of over emissions is compared with the area irradiated only by said first light source or only the second light source, the first region and the overlapping region of the second region is low.

With the above structure, the present invention achieves energy saving by adjusting the arrangement density of the light scattering pattern by reducing the diameter of the fluorescent tube and shortening the light source without reducing the tube current. As a result, it is possible to eliminate uneven brightness in the light guide plate due to the shortening of the light source, and realize a light-emitting device having an energy-saving type and uniform brightness without lowering the luminous efficiency of the light source and a liquid crystal display device using the light-emitting device. It is assumed that.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. Liquid crystal display device 10
On the back surface of a liquid crystal display element 11 having electrodes (not shown) and a liquid crystal composition (not shown) sealed between opposing transparent substrates, L condensed by a reflecting mirror 12 is provided. A light irradiation device 16 is provided for irradiating the liquid crystal display element 11 with light from a fluorescent tube 13 which is a V-shaped light source via a light guide plate 14.

The light guide plate 14 is in the form of a rectangular flat plate made of optically transparent resin such as acrylic or polycarbonate or optical glass, all six surfaces of which are mirror-finished to transmit / refract / permit light. Reflection is possible. The light exit surface 14 of the light guide plate 14 facing the diffusion sheet 19
The light scattering pattern 17 is formed on the opposite surface 14b of FIG.

The fluorescent tube 13 is connected to one of the first light guide plates 14.
, Which are shorter than the first side 15a and the second side 15b forming the first corner 14c.
The first light source 13a having a length a and the second light source having a length b are formed into an L-shape, and are in contact with a part of the first side 15a and a part of the second side 15b, respectively. This makes the first
The light source 13a of FIG.
Area A, and the second light source 13b illuminates the second area B of the light guide plate 14, as indicated by hatching in FIG.

The angle of incidence of the incident light on the light guide plate is determined by the refractive index of the light guide plate. In the case of acrylic resin which is usually used as a light guide plate material, the incident angle α is about 21 °.

The light scattering pattern 17 has a uniform light emission intensity because the light emission intensity from the light guide plate 14 is proportional to the product of the amount of light propagating through the light guide plate 14 and the light scattering pattern 17. For this purpose, the first light source 13 shown in FIG.
a and the second region B, which are illuminated by both the light source 13a and the second light source 13b and have a large amount of light propagating relative to their surroundings.
In the overlapping region C, the arrangement density is low and the first light source 1
3A or the second light source 13b, which is illuminated only by one of the light sources 3a and the area A 'with a small propagation light amount around the overlapping area C;
B 'is arranged so that the arrangement density is high. Further, on the back surface of the opposite surface 14b of the light guide plate 4 on which the light scattering pattern 17 is provided, there is provided a reflection sheet 18 as a reflection means for reflecting light leaked from the opposite surface 14b to the light emitting surface 14a.

The density of the light reflection pattern is controlled by adjusting the size of the reflection dots or the number of the reflection dots per unit area. That is, when dots having the same diameter are arranged, the dot arrangement density per unit area in the region C may be smaller than the density in other regions, and when the number of dots per unit area is not changed, the region C It is sufficient that the number of dots per unit area in is smaller than the number in other areas.
It goes without saying that these two methods may be used in combination.

Further, since the incident light is attenuated in accordance with the distance from the light source, the density of the light reflection pattern may be increased as the distance from the light source increases.

When the fluorescent tube 13 is turned on by the light irradiating device 16 having such a configuration, the light guide plate 14 has the first side 15a and the second side 15b at the first corner 14c. Light from the direction is incident on the light guide plate 14, and the light incident on the light guide plate 14 has a low degree of scattering in the overlapping region C where the light scattering patterns 17 are arranged at low density, and the light scattering pattern 17 has high density. Are scattered with a high degree of scattering in the surrounding areas A ′ and B ′, and propagate in the direction of the arrow x while repeating total reflection on the upper and lower surfaces of the light guide plate 14.

As a result, irradiation light having substantially uniform intensity is emitted from the entire surface of the light guide plate 14 to the liquid crystal display element 11 side.

According to this structure, the entire surface of the light guide plate 14 is controlled by the first light source 13a and the second light source 13b which are shorter than the first side 15a and the second side 15b at the first corner 14c. By illuminating with the L-shaped fluorescent tube 13, the power consumption can be remarkably reduced without causing high luminance and a decrease in luminous efficiency.
By arranging the light scattering pattern 17 of the overlapping area C receiving the illumination from 3a and 13b at a lower density than the light scattering patterns of the surrounding areas A 'and B', the difference in the amount of incident light in the light guide plate 14 is reduced. Regardless, since the emission intensity from the light guide plate 14 can be maintained uniformly over the entire surface, the liquid crystal display device 10
The brightness of the image displayed in is uniform over the entire surface,
A small, lightweight, energy-saving portable light irradiation device and a liquid crystal display device using the light irradiation device can be put to practical use, and the display quality of the liquid crystal display device can be further improved.

Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The light irradiation device 28 according to the second embodiment includes a first light guide plate 14
A notch is formed at the corner 14c of the light guide plate 13 and the fluorescent tube 13 is fitted therein, and the fluorescent tube 13 is disposed so as to wrap the fluorescent tube 13 within the surface of the light guide plate 14. 14 is illuminated from two directions.

With this structure, although the reflecting mirror 12 is slightly protruded from the surface of the light guide plate 14, the fluorescent tube 13 is formed.
Are enclosed in the light guide plate 14, the frame portion other than the actual display area of the light irradiation device 28 can be reduced in comparison with the first embodiment, and the liquid crystal display device can be made more portable.

Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is different from the first embodiment in that a plurality of fluorescent tubes are provided in the first embodiment, and the other parts are the same as those in the first embodiment. Are denoted by the same reference numerals, and description thereof is omitted. The light irradiation device 24 according to the third embodiment includes:
Opposite first and second corners 1 on a diagonal line of light guide plate 14
4c and 14d are provided with L-shaped fluorescent tubes 13, respectively.
The inside of the light guide plate 14 is illuminated from four directions of the first to fourth sides 15a to 15d with the fluorescent tube 13 as short as possible.

With such a configuration, the light guide plate 14 can be
Since the light can be illuminated from four directions with twice the amount of light as in the first embodiment, the entire surface of the light guide plate 14 can be illuminated more uniformly, and the frame area can be increased without increasing the frame area. Thus, the luminance of irradiation light emitted from the light guide plate 14 can be improved.

The present invention is not limited to the above embodiment, but can be changed without departing from the spirit of the present invention. For example, the shape of the light guide plate is not limited, and the material for forming the light guide plate is not limited. It is optional and its refractive index is not limited. First and second light sources for illuminating the light guide plate from two directions.
May be separate.

[0026]

As described above, according to the present invention, a light guide plate is illuminated from two directions by a light source shorter than each side thereof, and the light guide plate is formed on the light guide plate in accordance with the amount of illumination of the light guide plate by the light source. By adjusting the arrangement density of light scattering patterns
Smaller, lighter, and energy-saving type because it is a tube light source that is shorter than before and achieves high brightness and low power consumption without lowering the luminous efficiency, and can obtain a substantially uniform output layer degree over the entire light guide plate. Portable light irradiating device and a liquid crystal display device using this light irradiating device, and the image quality of the liquid crystal display device can be made uniform.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a light irradiation device according to a first embodiment of the present invention.

FIG. 2 is a schematic side view showing the liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a first region of the light guide plate according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a second region of the light guide plate according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an overlapping area of the light guide plate according to the first embodiment of the present invention.

FIG. 6 is a schematic plan view showing an arrangement density of light scattering patterns on the light guide plate according to the first embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view taken along line 5D-D 'of FIG. 5, showing the arrangement density of light scattering patterns on the light guide plate according to the first embodiment of the present invention.

FIG. 8 is a schematic plan view showing a light irradiation device according to a second embodiment of the present invention.

FIG. 9 is a schematic plan view showing a light irradiation device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 11 ... Liquid crystal display element 13 ... Fluorescent tube 14 ... Light guide plate 16 ... Light irradiation device 17 ... Light scattering pattern 18 ... Reflection sheet

Claims (10)

[Claims] 1. A flat light guide plate made of a light transmitting material and having adjacent first and second sides, and a first region of the light guide plate along a corner of the first side. A first light source that is shorter than the first side and illuminates a second region of the light guide plate adjacent to the first light source and along a corner of the second side. A second light source shorter than a side, and the first region and the second region dispersed in the light guide plate, compared to a region illuminated by only the first light source or only the second light source. And a light scattering pattern having a low arrangement density in an overlapping region of the light irradiation device. 2. The light irradiation device according to claim 1, wherein the first light source and the second light source are provided inside the light guide plate. 3. The method according to claim 1, wherein the first light source comprises a first tubular light source,
The light irradiation device according to claim 1, wherein the second light source comprises a second tubular light source. 4. The first tubular light source and the second tubular light source,
The light irradiation device according to claim 3, wherein the light irradiation device is an integral L-shaped tubular light source. 5. The light irradiation device according to claim 1, wherein the light guide plate has a reflection means on a back surface of the light scattering pattern. 6. A liquid crystal display device having electrodes and having a liquid crystal composition sealed in a gap between electrode substrates facing each other, a light guide plate having substantially the same shape as the liquid crystal display device, and irradiating the light guide plate. A light irradiating device comprising a light source and a light scattering pattern dispersedly arranged on the light guide plate and irradiating transmitted light on the back surface of the liquid crystal display element, wherein the light guide plate is made of a light transmitting material, A first plate having a first side and a second side adjacent to each other, wherein the light source is arranged along a corner of the first side and illuminates a first region of the light guide plate; A first light source that is short and a second light source that is adjacent to the first light source, is adjacent to a corner of the second side, and illuminates a second area of the light guide plate and is shorter than the second side. , The arrangement density of the light scattering pattern is only the first light source The liquid crystal display device, wherein the only the second light source by comparison to area irradiated, said first region and overlapping region of the second region is narrow. 7. The liquid crystal display device according to claim 6, wherein the first light source and the second light source are provided inside the light guide plate. 8. The first light source comprises a first tubular light source,
The liquid crystal display device according to claim 6, wherein the second light source comprises a second tubular light source. 9. The first tubular light source and the second tubular light source,
The liquid crystal display device according to claim 8, wherein the liquid crystal display device is an integral L-shaped tubular light source. 10. The liquid crystal display device according to claim 6, wherein the light guide plate has a reflection means on a back surface of the light scattering pattern.