JPH08152623A - Back light unit for liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a back light unit for the liquid crystal display device which excellently evades trouble such as the decrease in illuminance due to a leak current and is low in manufacturing cost, and lightweight, compact, and simple. CONSTITUTION: This back light unit includes a light guide plate 3, >=1 light source 5 which is provided on >=1 flank side of the light guide 3, a diffuse reflection part 9 which disperses light made incident on the light guide plate 3 to constitute a nearly uniform light emission diffusion surface, and a lamp holder 13 equipped with a reflection cover surface 13a for the light source which is formed of a high-reflectivity mold material by injection molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit for a liquid crystal display device.

[0002]

2. Description of the Related Art Since a liquid crystal display device is a passive element in which liquid crystal does not emit light by itself, a separate light source is required from the viewpoint of easy viewing. Therefore, a liquid crystal display device is usually composed of a liquid crystal display unit (liquid crystal panel) and a backlight unit, and both units are manufactured separately and then placed on the back side of the liquid crystal display unit to illuminate from the back side (back side). Is
A backlight unit is attached.

Such a backlight unit has a lamp for emitting light and a light guide plate for irradiating the light of the lamp incident from the side uniformly on the entire panel surface of the liquid crystal display unit. Consists of On the side opposite to the light guide plate of the lamp, while covering the lamp, a curved surface (reflective cover surface) like a vertically divided cylinder so that the light of the lamp can enter the light guide plate without waste. A lamp holder for a light source having a complicated shape is attached.

This lamp holder is formed by bending a metal (alloy) plate material, and then mounted so as to cover the lamp.

[0005]

However, the above metal lamp holder is not preferable because the leakage current is large and therefore the brightness of the backlight unit is significantly lowered. That is, specifically, when this metal lamp holder is used, it is recognized that the current value drops by about 3 to 5% as compared with the case of a single lamp.

In view of the above, it is an object of the present invention to provide a backlight unit that is inexpensive to manufacture, lightweight, compact and simple, and that is capable of satisfactorily avoiding the inconvenience such as the decrease in brightness due to the leakage current.

[0007]

In order to solve the above-mentioned problems, a backlight unit for a liquid crystal display device according to the present invention is provided with a light guiding means and one or more side surfaces of the light guiding means. And a homogenizing means for dispersing the light incident on the light guiding means to form a substantially uniform light emitting diffusion surface, and a reflective cover part for the light source formed by injection molding of a highly reflective molding material. It is a structural feature that it includes a provided holder.

Preferably, a light diffusing member for increasing the amount of diffusion is attached to the light emitting diffusion surface side of the light guide means. Further, a light reflection member for increasing the amount of emitted light is attached to the side of the light guide means opposite to the light emission diffusion surface side. Further, the uniformizing means includes a predetermined uneven surface physically or chemically formed on the upper surface, the lower surface or both surfaces of the light guide means.

[0009]

When the lamp holder for the light source is formed by injection molding of the highly reflective molding material, the leakage current is substantially eliminated and the brightness is improved accordingly. Moreover, a lamp holder having a complicated shape can be manufactured inexpensively and easily.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment of a backlight unit of a liquid crystal display device according to the present invention. The illustrated backlight unit 1 is provided therein with a light guide means, for example, a rectangular flat plate-shaped light guide plate 3 (shown by a broken line in FIG. 2). However, such a solid light guide plate 3
Instead of, a gas layer (not shown) made of a predetermined gas (including air) can be used as the light guiding means.

On one side (left side) of the light guide plate 3, a round rod-shaped lamp 5 (for example, a cold cathode tube) is arranged in parallel. A light diffusing plate 7 for increasing the diffusion amount is additionally provided on the upper side (light emitting diffusion surface side) of the light guide plate 3, and a diffuse reflection portion for improving the brightness distribution is provided on the lower surface (the upper surface or both surfaces) of the light guide plate 3. (Uniformizing means) 9 is provided. The irregular reflection portion 9 can be formed by additionally performing silk printing or cutting on the light guide plate 3, but a predetermined uneven surface is partially formed in advance on an injection mold (not shown) for forming the light guide plate. By engraving, it is convenient that the light guide plate can be formed and configured at one time during manufacturing (molding).

A light reflection plate 11 for increasing the amount of emitted light is attached below the light guide plate 3 (diffuse reflection section 9). The light guide plate 3
The shape of is not limited to that shown in the figure, and a cross section having a concave shape, a convex shape, a U shape, a V shape, a wedge shape (both sides), or the like can be adopted. Further, the lamp 5 is provided on one side of the light guide plate 3, but it may be provided on the other side instead of or in addition to it, and the lamp 5 may be composed of a plurality of lamps. .

By the way, the lamp holder 1 for covering the lamp 5
3 is formed by injection molding a high reflection molding material. As the high reflection molding material, for example, polycarbonate (PC) or a material obtained by adding ABS resin thereto can be used. More practically, for example, S3100 (PC manufactured by Daicel Chemical Industries, Ltd.) / A
BS) may be used. In addition, titanium white, calcium carbonate, a fluorescent material, etc. may be added separately, and acrylic beads, balloons, etc. may be added to promote the high brightness described later.

The lamp holder 13 is provided with a curved surface (reflection cover surface) 13a formed by vertically dividing a cylindrical body so that the light of the lamp 5 can enter the light guide plate 3 without waste. Incidentally, in FIG. 2, parts other than the reflection cover surface are omitted. Further, instead of such a curved surface 13a, a multi-sided portion (not shown) including a plurality of flat surfaces can be used.

In the backlight unit 1 of the present embodiment having the above-mentioned structure, since the lamp holder 13 is formed by injection molding of the high reflection molding material, the leakage current (thus, the decrease in brightness) is substantially eliminated. You can That is, specifically, in the current value comparison experiment, the current value in the structure of the present embodiment is approximately the same as that in the case of the lamp alone (about 5 mA), and the structure of the present embodiment has no adverse electrical effect. It was recognized that there was no (no reduction in brightness).

The lamp holder 13 having a complicated shape can be manufactured in large quantities at a low cost and easily at one time, which is extremely preferable.

[0017]

As described above, according to the present invention, it is possible to realize a rational and economical backlight unit that does not cause electrical inconvenience.

[Brief description of drawings]

FIG. 1 is an overall external perspective view of an embodiment of a backlight unit according to the present invention.

FIG. 2 is a side sectional view of a main part of the backlight unit of this embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Backlight unit 3 ... Light guide plate 5 ... Lamp 7 ... Light diffusion plate 9 ... Diffuse reflection part 11 ... Light reflection plate 13 ... Lamp holder 13a ... Reflection cover surface

Claims (4)

[Claims] 1. A light guide means (3), one or more light sources (5) that can be provided on one or more side surfaces of the light guide means (3), and light incident on the light guide means (3). A holder (1) provided with a homogenizing means (9) capable of forming a substantially uniform light emitting diffusion surface and a light source reflective cover portion (13a) formed by injection molding of a highly reflective molding material.
3), and a backlight unit for a liquid crystal display device. 2. The backlight unit according to claim 1, wherein a light diffusing member (7) for increasing the amount of diffusion is attached to the light emitting surface of the light guide means (3). 3. The light reflecting member (11) for increasing the amount of emitted light is attached to the side of the light guide means (3) opposite to the side of the light emitting diffusion surface. Backlight unit. 4. The uniformizing means (9) includes a predetermined uneven surface physically or chemically formed on the upper surface, the lower surface or both surfaces of the light guiding means (3). Backlight unit described in.