JPH07318935A - Back light unit for liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide an inexpensively manufactured, light in weight, compact, and simple back light unit for a liquid crystal display device free from such inconvenience as the lowering of illuminance caused by leaked current. CONSTITUTION:This back light unit 1 for the liquid crystal display device includes a light guide means 3, one or more light sources 5 provided on the one or more side surfaces of the means 3, a uniformizing means constituting a nearly uniform light emitting diffusing surface by dispersing the light made incident on the means 3, and a supporting base 7 housed with the means 3 and the light source 5; and the base 7 has a reflecting cover part 7a for the light source which is integrally formed with a supporting base main body.

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
The backlight unit is connected and fixed.

An example of such a backlight unit is shown in FIG. The illustrated backlight unit 21 includes a round rod-shaped lamp 25 for emitting light, a flat light guide plate 23 for irradiating the light of the lamp 25 on the entire panel surface of the liquid crystal display unit without unevenness, and a housing for these. And a support base 27 for On the side of the lamp 25 opposite to the light guide plate 23, a reflective cover 29 having a curved shape like a vertically divided cylinder is attached so that the light of the lamp 25 can enter the light guide plate 23 without waste. To be The reflection cover 29 is formed by bending a rectangular metal (alloy) plate material, and then attached to the support base 27.

[0004]

However, in the structure type in which the metallic reflection cover 29 is separately manufactured and attached, the leakage current is large and therefore the brightness of the backlight unit is significantly lowered, which is not preferable. That is, specifically, in the case of the structure in which the reflection cover 29 formed by bending a metal plate is attached to the support base 27, it is recognized that the current value is reduced by about 3 to 5% as compared with the case of the lamp alone.

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

[0006]

In order to solve the above-mentioned problems, the present invention provides a light guide means, one or more light sources which can be provided on one or more side surfaces of the light guide means, and a light guide means. A backlight unit for a liquid crystal display device, comprising: a homogenizing unit that can disperse light to form a substantially uniform light-emitting diffusion surface; and a support base that can accommodate a light guide unit and a light source. Is characterized in that it has a reflection cover portion for the light source, which is integrally formed with the support base body portion.

Preferably, the reflection cover portion is integrally formed by injection molding of a highly reflective molding material. In addition, a light diffusing member for increasing the amount of diffusion is attached on 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 guiding means.

[0009]

The reflecting cover for the light source is integrally formed with the support base body, so that the number of parts, the number of assembling steps and the weight are reduced. Further, when the reflection cover portion is integrally formed by injection molding of a highly reflective molding material, the leakage current is substantially eliminated, and the brightness is improved accordingly.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a main part of an embodiment of a backlight unit of a liquid crystal display device according to the present invention. In the illustrated backlight unit 1, a light guide unit, for example, a rectangular flat plate-shaped light guide plate 3 is provided inside the backlight unit 1. However,
Instead of such a solid light guide plate 3, a gas layer (not shown) made of a predetermined gas (including air) can be used as the light guide 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 diffusion plate for increasing the amount of diffusion is attached above the light guide plate 3 (on the side of the light emission diffusion surface), and a lower surface (the upper surface or both surfaces) of the light guide plate is used for improving the brightness distribution. The diffuse reflection part (uniformizing means) is provided, and the light reflection plate for increasing the light emission amount is attached below the light guide plate (random reflection part), but it is not shown in the drawing. This irregular reflection portion is provided by the light guide plate 3
Although it can be formed by additionally performing silk printing or cutting on the surface, it can be formed by partially engraving a predetermined uneven surface in advance on the injection mold (not shown) for forming the light guide plate. It is convenient because it can be formed and configured at once when manufacturing (molding) an optical plate. Further, the shape of the light guide plate 3 is not limited to that shown in the drawing, and a cross section having a concave shape, a convex shape, a U shape, a V shape, a piece (both) wedge shape, or the like can be adopted. Further, although the lamp 5 is provided on one side of the light guide plate 3, 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. .

A box-shaped support base 7 having an open top for housing the light guide plate 3, the lamp 5 and the like is integrally formed by injection molding a high reflection molding material. Examples of the highly reflective molding material include polycarbonate (PC) and
A resin added with ABS resin may be used, but more practically, for example, S manufactured by Daicel Chemical Industries, Ltd. may be used.
3100 (PC / ABS) can be used. In addition, titanium white, calcium carbonate, fluorescent material, etc. are added separately,
Furthermore, acrylic beads, balloons, etc. may be added to promote the high brightness described later.

This support base 7 is provided with a side (reflective cover) 7a in the shape of a single concave lens on the side (left side) where the lamp is arranged.
The inner surface 7b of the reflective cover portion 7a is a curved surface portion (reflective cover surface) 7b that concentrically and partially surrounds the lamp in the lateral direction. Instead of the curved surface portion 7b, a multi-sided portion (not shown) including a plurality of flat surfaces can be used.

In the backlight unit 1 of this embodiment having the above-mentioned structure, the reflection cover portion 7a has the support base 7a.
Since it is formed integrally with the main body, it is extremely rational and economical in manufacturing and assembling. Further, when the reflection cover portion 7a is integrally formed by injection molding of a high reflection molding material, it is possible to substantially eliminate the leakage current (thus reducing the luminance). 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).

[0015]

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 a perspective view of a main part of an embodiment of a backlight unit according to the present invention.

FIG. 2 is a perspective view of a backlight unit to which a reflection cover is separately attached.

[Explanation of symbols]

 1 ... Backlight unit 3 ... Light guide plate 5 ... Lamp 7 ... Support 7a ... Reflective cover

Claims (5)

[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 backlight unit for a liquid crystal display device including a homogenizing means capable of forming a substantially uniform light-emitting diffusion surface and a support base (7) capable of accommodating the light guide means (3) and the light source (5) ( 1) The backlight unit, wherein the support base (7) has a reflection cover part (7a) for the light source, which is integrally formed with the support base body portion. 2. The backlight unit according to claim 1, wherein the reflective cover portion is integrally formed by injection molding of a highly reflective mold material. 3. The backlight unit according to claim 1, wherein a light diffusing member for increasing the amount of diffusion is additionally provided on the light emitting diffusion surface side of the light guide means. 4. The backlight unit according to claim 1, wherein a light reflection member for increasing the amount of emitted light is attached to the side of the light guide means opposite to the side of the light emission diffusion surface. 5. The backlight unit according to claim 1, wherein 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. .