JPH0894847A - Surface light source element and liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain a high-luminance edge light system surface light source element by coating a nearly half outer peripheral area of a long light source on an opposite side to a light transmission plate with a light reflection layer and disposing a reflection member having a light reflection surface whose cross- sectional shape is curved in the longitudinal direction of the long light source. CONSTITUTION: The long cylindrical light source 13 is disposed along one end face of the minor axis of the light transmission plate 10, and a reflector 14 being a reflection member where silver is vapor-deposited is provided on the outer periphery of the light source 13. Furthermore, the nearly half area positioned on the opposite side to the plate 10 on the outer periphery of the light source 13 is coated with the light reflection layer 15. The layer 15 consists of a film sheet where silver is vapor-deposited, and a fluorescent lamp is coated with the layer 15 by adhesive agent. Since the layer 15 is just near to the light source 13 and its arranged position is closer to the plate 10, the reflected light on the layer 15 is most easily made incident on the end face of the plate 10 in a state where the repetitive reflection after that is little. Thus, much light is introduced to the plate 10, so that high luminance is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source element for irradiating light in a plane and a liquid crystal display device equipped with the surface light source element.

[0002]

2. Description of the Related Art A liquid crystal display device of a time division system or an active matrix system employs a backlight system in order to improve its visibility. In particular, a color liquid crystal display device has an extremely low panel transmittance as compared with a monochrome liquid crystal display device, and thus a thin illuminating device with high brightness is required.

FIG. 5 shows an example of a liquid crystal display device 1 equipped with this thin lighting device. A rectangular light guide plate 3 is arranged on a liquid crystal panel 2, and a fluorescent lamp 4 is placed on an end face of the light guide plate 2. It is a light type edge light system (Japanese Patent Laid-Open No. 51-8).
8042, JP-A-64-57240, JP-A 2-1
7, JP-A-4-10913, JP-A-6-67025.
No.).

According to FIG. 1, a diffuser plate 5 is provided on one main surface of the light guide plate 3, and a long cylindrical fluorescent lamp 4 is arranged along a pair of opposite sides of the light guide plate 3, and further. Reflecting plate 6, so as to cover the other main surface and fluorescent lamp 4, respectively.
The light source reflector 7 is provided.

According to the above liquid crystal display device 1, the irradiation light of the fluorescent lamp 4 directly projects the light guide plate 3, or a part of the irradiation light is reflected by the light source reflection plate 7, and the reflected light is also reflected. The light guided to the light guide plate 3 and introduced into the light guide plate 3 is reflected by the reflection plate 6 and irradiates the liquid crystal panel 2 through the diffusion plate 5.

[0006]

However, although the liquid crystal display device 1 having the above-described structure can obtain high brightness by the edge light type illumination device, it is still sufficiently satisfying the recent demands. High brightness is not obtained.

Therefore, as a result of further in-depth research by the inventor of the liquid crystal display device 1 having the above structure, the device 1
As shown in FIG. 6, which is an enlarged view of the main part of FIG. 6, when a part of the irradiation light of the long cylindrical fluorescent lamp 4 projects the light source reflection plate 7,
The reflected light from the reflector 7 returns to the fluorescent lamp 4,
The light is reflected on the outer surface, and the reflected light is further reflected by the light source reflector plate 7.
The number of light paths for projecting light again and then entering the fluorescent lamp 4 increases, and the amount of light gradually attenuates due to such repeated reflections. Therefore, the amount of light introduced into the light guide plate 3 decreases, which is high. It was found that the brightness could not be obtained.

Therefore, an object of the present invention is to provide an edge light type surface light source device which achieves high brightness.

A further object of the present invention is to provide a high-performance liquid crystal display device equipped with a high brightness surface light source element.

[0010]

According to a surface light source element of claim 1, an elongated light source is arranged on one end surface of a light guide plate having a light reflection means on one main surface, and the elongated light source is provided. A light reflecting layer is coated on a substantially semi-peripheral region on the side opposite to the light guide plate, and a reflecting member having a light reflecting surface whose cross-sectional shape is curved is disposed along the longitudinal direction of the elongated light source, It is characterized in that light is emitted from the other main surface side of the light guide plate.

A liquid crystal display device according to a second aspect of the invention is characterized in that a liquid crystal panel is disposed on the other main surface side of the surface light source element having the above-mentioned structure via a light diffusing plate.

[0012]

According to the surface light source element of the present invention, the elongated light source has a structure in which the light reflection layer is coated on substantially the half region of the elongated light source located on the opposite side to the light guide plate. For example, almost half of the irradiation light of the elongated light source reaches the light reflection layer, and this light reflection layer is close to the light irradiation source, and its arrangement position is crossed along the longitudinal direction of the elongated light source. The light guide plate is closer to the light guide plate than the conventional reflection member having a light reflection surface whose surface shape is curved.

Therefore, the light reflected by the light reflecting layer is most likely to be incident on the end face of the light guide plate with a small amount of repeated reflection thereafter, and the light attenuation is reduced accordingly.
Therefore, a large amount of light is introduced into the light guide plate, so that high brightness can be obtained.

According to the second aspect, it is possible to provide a high-performance and high-performance liquid crystal display device having the surface light source element of the present invention.

[0015]

FIG. 1 shows a cross section of a liquid crystal display device 9 in which an edge light type thin lighting device 8 which is a surface light source element of the present invention is arranged on a liquid crystal panel 2. FIG. It is a figure.

According to this liquid crystal display device 9, the thickness is 4 mm.
The light guide plate 10 made of Toray Co., Ltd., which is a low-foaming film of white polyester, is provided on one main surface of the rectangular light guide plate 10 made of polymethylmethacrylate (PMMA), and the other main surface is made of PET or polycarbonate. (P
A light diffusing plate 12 made of C) is provided, and the light guide plate 10 is also provided.
The long cylindrical light source 13 (tube diameter 3.8
mm cold-cathode type or hot-cathode type fluorescent lamp), and a light source 13 is provided with a reflection plate 14 which is a reflection member on which silver is vapor-deposited. As shown in FIG. 2, the reflecting plate 14 has a reflecting surface 14a whose transverse cross section is curved along the longitudinal direction of the elongated cylindrical light source 13.

In addition, on one main surface of the light guide plate 10, a printing pattern (not shown) containing glass beads having a white or milky white color in which titanium oxide is added to almost the entire surface as a means for adjusting the brightness in a planar manner. ) Are formed so as to be distributed in a high density, and a reflection plate 11 is further provided on the lower surface thereof. With this configuration, the brightness of the lighting device 8 is increased, and the light reflected by the reflection plate 11 is More light can be emitted to the liquid crystal panel 2 side.

Furthermore, in this embodiment, a product name B manufactured by Sumitomo 3M Co., Ltd. is provided between the light diffusion plate 12 and the liquid crystal panel 2.
The prism sheet (not shown) of EF100 is interposed,
The brightness is further increased.

Further, in the present invention, the light reflecting layer 15 is further coated on a substantially half region of the outer periphery of the elongated cylindrical light source 13 located on the opposite side of the light guide plate 10. The light-reflecting layer 15 consisted of a silver-deposited film sheet and was coated on the fluorescent lamp with an adhesive formed on this film sheet.

Thus, according to the illumination device 8 having the above structure,
Since the light reflection layer 15 is located directly close to the elongated cylindrical light source 13 and the position of the light reflection layer 15 is further closer to the light guide plate 10, the reflected light on the light reflection layer 15 remains less reflected repeatedly thereafter. The light is most likely to be incident on the end surface of the light guide plate 10, whereby a large amount of light is introduced into the light guide plate 10, and thus high brightness is obtained.

The inventor of the present invention measured the luminance (in-plane average luminance) using the lighting device 8 and found that it was 4710c.
It was d / m ² . On the other hand, in the case of the conventional illuminating device of the liquid crystal display device 1 which does not have the light reflecting layer 15 and has the same other configuration, the luminance was 4250 cd / m ² . Therefore, it is understood that the illumination device 8 of the present invention has obtained high brightness.

Next, a lighting device 8a of another embodiment will be described in detail with reference to FIGS. The same members as those shown in FIGS. 1 and 2 are designated by the same reference numerals.

FIG. 3 is an example of a liquid crystal display device 9a equipped with the lighting device 8a, and FIG. 4 is an enlarged cross-sectional view of a main part of the lighting device 8a. As shown in these figures, the light guide plate 10
This is a one-lamp type edge light system in which the long cylindrical light source 13 is placed only on one end surface of the light guide plate 10. The long cylindrical light source 13 is arranged along one end surface of the light guide plate 10, A light reflection layer 15 is coated on a substantially half region of the outer periphery of the cylindrical light source 13 located on the opposite side of the light guide plate 10. An end face reflection plate 16 made of PET or the like is provided on the other end face of the light guide plate 10.

Thus, also in the illuminating device 8a having the above-mentioned structure, since the light reflecting layer 15 is located immediately adjacent to the elongated cylindrical light source 13 and the arrangement position thereof is further closer to the light guide plate 10, a large amount of light is emitted to the light guide plate 10. The light introduced and incident on the light guide plate 10 is reflected by the light reflection plate 11, or the light reaching the other end face of the light guide plate 10 is reflected by the end face reflection plate 16 and a large amount of light is emitted. Illuminates the liquid crystal panel 2 through the diffusion plate 12, and as a result, high brightness was obtained.

The present inventor uses the illumination device 8a to
The luminance (in-plane average luminance) was measured and found to be 2710
It was cd / m ² . On the other hand, in the case of the conventional lighting device which does not have the light reflecting layer 15 and has the same structure as the lighting device 8a in other respects, the luminance was 2210 cd / m ² . Therefore, it is understood that the illumination device 8a of the present invention can obtain high brightness.

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 the above embodiment, the case where the surface light source element of the present invention is mounted on the liquid crystal display device is illustrated, but it is also mounted on other devices requiring surface irradiation (EL display, plasma display, CRT display, etc.). it can. Alternatively, in the above-described embodiment, the light source is arranged along the minor axis one end surface of the light guide plate, but the light source may be arranged along the major axis one end surface of the light guide plate.

[0027]

As described above, according to the surface light source element of the first aspect, the elongated light source is covered with the light reflection layer in a substantially half region located on the opposite side to the light guide plate on the outer periphery thereof. Therefore, almost half of the irradiation light from the long light source reaches the light reflection layer,
Moreover, this light reflecting layer becomes closer to the light irradiation source,
The arrangement position is further closer to the light guide plate, which reduces the light attenuation, and a large amount of light is introduced into the light guide plate accordingly, resulting in high brightness, and as a result, for color liquid crystal display or monochrome liquid crystal. A transparent or semi-transmissive type high-luminance edge light type surface light source element for display can be provided.

According to a second aspect of the present invention, a high-performance liquid crystal display device having a high brightness is provided by mounting the surface light source element of the present invention,
For example, a color liquid crystal display device and a monochrome liquid crystal display device could be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid crystal display device of an example.

FIG. 2 is a cross-sectional view of the main parts of the lighting device of the embodiment.

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

FIG. 4 is a cross-sectional view of a main part of a lighting device according to another embodiment.

FIG. 5 is a schematic cross-sectional view of a conventional liquid crystal display device.

FIG. 6 is a sectional view of a main part of a conventional lighting device.

[Explanation of symbols]

 2 Liquid Crystal Panels 8 and 8a Illuminating Device 10 Light Guide Plate 12 Light Diffusing Plate 13 Long Cylindrical Light Source 11, 14 Reflecting Plate 15 Light Reflecting Layer 16 End Face Reflecting Plate

Claims (2)

[Claims] 1. A long light source is disposed on one end surface of a light guide plate having a light reflecting means provided on one main surface, and light is reflected in a substantially semi-peripheral region of the long light source opposite to the light guide plate. A reflecting member having a light reflecting surface covering the layer and having a cross-sectional shape curved along the longitudinal direction of the elongated light source is arranged to emit light from the other main surface side of the light guide plate. Surface light source element. 2. A liquid crystal display device in which a liquid crystal panel is arranged on the other main surface side of the surface light source element of claim 1 with a light diffusing plate interposed.