JPH07325223A - Surface light source element and liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a surface light source element having high illuminance by covering a long-sized light source with a reflection member having a reflection surface having two curved cross sectional shapes along the longitudinal direction thereof, thereby increasing the quantity of the light introduced into a light transmission plate. CONSTITUTION:An illumination device 8 of this liquid crystal display device is constituted by providing the main surface of the rectangular light transmission plate 10 made of a polymethyl methacrylate with the reflection plate 11 and a light diffusion plate 12. The long-sized cylindrical light source 13 is disposed along one end of the light transmission plate 10 and the outer periphery of the light source 13 is provided with the reflection plate 14. The reflection plate 14 has the reflection surface 14a having the two curved cross sectional shapes along the longitudinal direction of the light source 13. The main surface of the light transmission plate 10 is provided with printing patterns contg. milky white glass beads added with titanium oxide and further, the rear surface thereof is provided with the reflection plate 11 and, therefore, the illuminance of the illumination device 8 is enhanced and the light reflected by the reflection plate 11 is emitted more to the liquid crystal panel side.

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 which is mounted on a liquid crystal display device or the like and irradiates light in a plane shape, and a liquid crystal display device which is 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. Especially in color liquid crystal display devices, compared to monochrome liquid crystal display devices,
Since the panel transmittance is extremely low, a high-luminance thin lighting device is required.

FIG. 3 shows an example of a liquid crystal display device 1 equipped with this thin illuminating device. A rectangular light guide plate 3 is arranged on a liquid crystal panel 2, and a fluorescent lamp 4 is placed on the 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 diffusing plate 5 is further 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, Further, a reflection plate 6 and a light source reflection plate 7 are provided so as to cover the other main surface and the fluorescent lamp 4, respectively.

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 insufficient for the recent demand for high brightness. Not satisfied.

Therefore, as a result of further diligent research conducted by the present inventor on the liquid crystal display device 1 having the above-mentioned structure, as shown in the enlarged view of the main part of FIG. When the portion projects the light source reflection plate 7, the reflection plate 7
It was found that the reflected light in (1) returns to the fluorescent lamp 4 and is absorbed (a in the figure), and thereby the light introduced into the light guide plate 3 decreases, and accordingly high brightness cannot be obtained.

Therefore, an object of the present invention is to provide an edge light type surface light source device which achieves higher 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 another aspect of the surface light source element of the present invention, a long light source is provided on one end surface of a light guide plate having a reflecting means provided on one main surface thereof, and the long light source is long. A reflecting member having two curved reflecting surfaces having a cross-sectional shape along the direction is arranged so 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 claim 1, the long light source is covered with a reflecting member having a reflecting surface having two curved cross sections along the longitudinal direction thereof. When the linear light source projects the curved reflecting surface, the reflected light does not return to the elongated light source and is introduced into the light guide plate by that amount, so that higher 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 structure in which the surface light source element of the above invention is mounted.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cross section of a liquid crystal display device 9 in which an edge-light type thin lighting device 8 according to the present invention is arranged on a liquid crystal panel 2, and FIG.

According to this liquid crystal display device 9, the thickness is 4 mm.
Of the rectangular light guide plate 10 made of polymethylmethacrylate (PMMA) is provided with a reflection plate 11 of a low foaming film of white polyester manufactured by Toray Industries, Inc., which is the reflection means, and PET or polycarbonate is provided on the other main surface. A (PC) light diffusing plate 12 is provided, and a long cylindrical light source 13 (tube diameter 3.8) is provided along one end face of the light guide plate 10.
mm cold-cathode tube) and a light-reflecting plate 14 vapor-deposited with silver is also provided on the outer periphery of the light source 13.

As shown in FIG. 2, the reflecting plate 14 has a reflecting surface 14a having two curved cross sections 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, whereby the brightness of the illumination 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 of EF100 is interposed to further increase the brightness.

According to the illuminating device 8 having the above structure, the reflecting plate 1
4 has a reflecting surface 14a having two curved cross-sectional shapes along the longitudinal direction of the elongated cylindrical light source 13, the light source 13 projects the curved reflecting surface 14a (b in the figure). The reflected light (c in the figure) does not return to the light source 13,
Since it was introduced into the light guide plate 11, higher brightness was obtained.

The present inventor measured the luminance (in-plane average luminance) using this illuminating device 8 and obtained the results shown in Table 1. In addition, in the same table, an illumination device of the conventional liquid crystal display device 1 is shown as a comparative example.

[0021]

[Table 1]

As is clear from the results of the table, it is understood that the illuminating device 8 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-described embodiment, the case where the surface light source element of the present invention is mounted on the liquid crystal display device is illustrated, but the surface light source element can also be mounted on other devices requiring surface irradiation. For example, it can be mounted on devices such as EL displays, plasma displays, CRT displays, and the like.

[0024]

As described above, according to the surface light source element of the first aspect, the cross-sectional shape is 2 along the longitudinal direction of the elongated light source.
It covers a reflecting member having two curved reflecting surfaces, and when the curved reflecting surface is projected, the reflected light does not return to the elongated light source and is introduced to the light guide plate by that amount, High brightness was obtained. Therefore, a transmissive or semi-transmissive high-luminance edge light type surface light source element for color liquid crystal display or monochrome liquid crystal display can be provided.

According to a second aspect of the present invention, a high-performance liquid crystal display device having a high brightness by the structure in which the surface light source element of the invention is mounted,
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 embodiment.

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 conventional liquid crystal display device.

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

[Explanation of symbols]

 2 liquid crystal panel 8 illuminating device 10 light guide plate 11 reflecting plate 12 light diffusing plate 13 cylindrical light source 14 reflecting plate 14a curved reflecting surface

Claims (2)

[Claims] 1. A long light source is disposed on one end surface of a light guide plate having a reflecting means provided on one main surface thereof, and a reflection having two curved cross-sectional shapes along the longitudinal direction of the long light source. A surface light source element in which a reflecting member having a surface is arranged and light is emitted from the other main surface side of the light guide plate. 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.