JPH06308491A - Back light device and liquid crystal display device unit it - Google Patents

Abstract

PURPOSE:To provide the back light device in which a bent fluorescent lamp can approach a light transmission plate, light incident efficiency is made high and also which can be miniaturized; and the liquid crystal display device using it. CONSTITUTION:The planar light transmission plate 1, the bent fluorescent lamp 2 provided oppositely over the adjacent end faces of the light transmission plate 1, and a light diffusing board provided on the front surface of the light transmission plate 1 are provided; a chamfered part 10 is provided on the corner part of the light transmission plate 1. Since the chamfering is performed on the corner part of the light transmission plate 1, the corner part of the light transmission plate 1 is not made to abut on the bent part 2a of the bent fluorescent lamp 2, so that the straight line part 2b of the lamp 2 can approach the end face of the light transmission plate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device using a light guide plate and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art In a liquid crystal display device, a backlight device is usually installed on the back surface of a liquid crystal display plate, and the liquid crystal display plate is back illuminated by light emitted from the backlight device.

An example of a conventional liquid crystal display device is shown in FIGS. 4 and 5.
In the figure, 1 is a light guide plate,
It is formed of a transparent or milky white light transmissive plate such as acrylic resin, and has a rectangular flat plate shape. Two L-shaped fluorescent lamps 2, 2 are arranged on the side of the light guide plate 1. The fluorescent lamps 2 and 2 are
It is excellent in luminous efficiency and can obtain uniform brightness over a predetermined length, so it is suitable for the light source of this type of backlight device,
Hot cathode fluorescent lamps and cold cathode fluorescent lamps are used. Such fluorescent lamps 2 and 2 are covered with lamp covers 3 and 3 as shown in FIG. 4, and the lamp covers 3 and 3 reflect the light emitted from the fluorescent lamps 2 and 2. It has a function of directing the light guide plate 1 toward the end surface. A reflection plate 5 is provided on the back surface of the light guide plate 1.
Reflects the light transmitted through the light guide plate 1 and directs it to the front side.
A light diffusing plate 6 having a milky white color such as acrylic resin is provided on the front surface of the light guide plate 1, and the light diffusing plate 6 diffuses light to reduce uneven brightness. A liquid crystal display plate 7 is installed on the front surface of the light diffusion plate 6.

In the liquid crystal display device having such a structure, when the fluorescent lamps 2 and 2 as light sources are turned on to emit light, the light emitted from the fluorescent lamps 2 and 2 directly
Further, the light is reflected by the lamp covers 3 and 3 and faces the end surface of the light guide plate 1, and thus enters the inside of the light guide plate 1 from this end surface. Inside the light guide plate 1, light travels while repeating total reflection on each surface, and is reflected by the reflection plate 5 provided on the back surface, so that it is eventually emitted toward the front surface. In this way, the light traveling toward the front surface is diffused by the light diffusing plate 6, and the diffused light illuminates the back surface of the liquid crystal display plate 7. Therefore, the liquid crystal display panel 7 is illuminated by the light from the back surface, and a predetermined display can be displayed on the front surface.

In the backlight device of the liquid crystal display device as described above, if the light is taken in from the entire surface around the light guide plate 1, the amount of light radiated forward is increased and the brightness is increased. For this reason, conventionally, the straight tube type fluorescent lamps have been arranged so as to face the two facing end faces, respectively. However, recently, a backlight device having higher brightness has been demanded. As shown in FIG. 2, a device is proposed in which two L-shaped fluorescent lamps 2 and 2 are used to take in light from the entire peripheral surface of the flat light guide plate 1.

[0006]

However, when the L-shaped fluorescent lamp 2 as described above is used, it is difficult to bend the bent portion 2a of the fluorescent lamp 2 made of a straight glass tube at a right angle. Even if the bent portion 2a having a large curvature is brought close to the corner of the light guide plate 1, the straight portions 2b, 2
There is a problem that b is separated from the end faces of the light guide plates 1 which are adjacent to each other. In this case, the lamp 2
Since a large gap is formed between the light guide plate 1 and the light guide plate 1, there is a disadvantage that the light emitted from the lamp 2 is lost, the amount of light entering the light guide plate 1 is reduced, and the planar brightness is reduced. Further, since the fluorescent lamps 2 and 2 are separated from the light guide plate 1, there is a drawback that the size of the entire device is increased.

The present invention has been made in view of the above circumstances. An object of the present invention is to allow a bent fluorescent lamp to be brought close to a light guide plate, thereby increasing the light incident efficiency and reducing the size. It is intended to provide a backlight device capable of achieving the above and a liquid crystal display device using the same.

[0008]

According to a first aspect of the present invention, there is provided a flat light guide plate which transmits light, a fluorescent lamp provided opposite to an end face of the light guide plate, and a front face of the light guide plate. A light diffusing plate provided, wherein the fluorescent lamp is a backlight device using a curved fluorescent lamp facing a plurality of adjacent end faces of the light guide plate and facing the end faces. It is characterized in that a chamfer is formed at a corner of the light plate. According to a second aspect of the present invention, there is provided a flat light guide plate that transmits light, a fluorescent lamp provided to face an end surface of the light guide plate, and a light diffusion plate provided on the front surface of the light guide plate. In a backlight device using a fluorescent lamp having a bent shape facing the end faces of a plurality of adjacent end faces of the light guide plate, the fluorescent lamp is provided inside a bent portion of the bent portion of the fluorescent lamp. It is characterized in that a concave portion is formed. The invention of claim 3 is characterized in that the backlight device according to claim 1 or 2 is installed on the back surface of a liquid crystal display panel.

[0009]

In the backlight device according to the first aspect, since the chamfered portion is provided at the corner of the light guide plate, the corner of the light guide plate does not come into contact with the bent portion of the bent fluorescent lamp, and the straight portion of the lamp is guided. It is possible to approach the end face of the light plate. In the backlight device according to claim 2, since the concave portion is formed inside the bent portion of the fluorescent lamp, the corner portion of the light guide plate does not contact, and the bent portion can be bent with a small curvature. Therefore, the straight part of the lamp can be brought close to the end face of the light guide plate. Therefore, in any of the backlight devices, the fluorescent lamp can be brought close to the light guide plate, the light incident efficiency can be increased, and the size can be reduced. Further, according to the liquid crystal display device of the present invention, a liquid crystal display having a high plane brightness can be realized.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the first embodiment shown in FIG. In this embodiment, most of the configuration is shown in FIG.
The liquid crystal display device may have the same structure as that of the liquid crystal display device shown in FIG. 5, and in FIG.
That is, the L-shaped fluorescent lamp 2 provided around the light guide plate 1 has a bent portion 2a facing a corner portion of the light guide plate 1 and having a predetermined curvature, and is continuous with the bent portion 2a. The light guide plate 1 is provided with linear portions 2b, 2b facing the end faces adjacent to each other. A chamfer 10 is formed at a corner of the light guide plate 1. The chamfered portion 10 of this embodiment is C-face processed and chamfered in the range of C0.5 to C20.

With this structure, since the chamfered portion 10 is formed at the corner of the light guide plate 1, the L-shaped fluorescent lamp 2 is provided.
The bent portion 2a does not come into contact with the corner of the light guide plate 1, and the bent portion 2a can be brought closer to the corner of the light guide plate 1 by this amount. As a result, the straight portion 2 of the fluorescent lamp 2 is
b and 2b can be brought close to the adjacent end faces of the light guide plate 1.

Therefore, the gap between the fluorescent lamp 2 and the light guide plate 1 can be reduced, and the light emitted from the fluorescent lamp 2 is effectively incident on the end face of the light guide plate 1, that is, the incident efficiency is high. Since the amount of light incident on the light guide plate 1 increases, the planar brightness on the front side increases. As a result, the planar brightness of the liquid crystal display device is increased, and clear liquid crystal display is possible.

Further, since the fluorescent lamps 2 and 2 approach the light guide plate 1, there is an advantage that the size of the entire device can be reduced. Furthermore, since a large curvature of the bent portion 2a can be secured, there is no concern that the phosphor coating will deteriorate or come off. That is, when the curvature of the bent portion 2a is reduced, the phosphor coating formed on the inner surface is deteriorated,
It may come off. That is, in the case of a bent type fluorescent lamp, a fluorescent film is formed on the inner surface of a straight tube type glass tube in advance, and this is softened by heating to be bent. , The phosphor coating on the inner surface may fall off. With such a lamp,
Ultraviolet rays are emitted from the peeled portion of the phosphor coating, and the ultraviolet rays are applied to the light guide plate 1, so that the light guide plate 1 may be deteriorated by the ultraviolet rays.

Therefore, it is desirable that the bent portion 2a has a large curvature. In the case of the above embodiment, since the chamfered portion 10 is provided at the corner of the light guide plate 1, the straight portions 2b, 2b can be brought close to the light guide plate 1 even if the curvature of the bent portion 2a is kept large. Therefore, the phosphor coating is not peeled off, and the light guide plate 1 is not likely to be deteriorated by ultraviolet rays.

FIG. 2 shows a second embodiment of the present invention. In this example, the chamfered portion 20 is curved, that is, R-shaped. The radius of curvature in this case, R is R0.5
The range of to R20 is good. Even in this case, the same effect as that of FIG. 1 can be obtained.

FIG. 3 shows a third embodiment of the present invention. In this embodiment, the concave portion 30 is formed inside the bent portion 2a of the bent fluorescent lamp 2 inside the bent portion. By forming such a recess 30, it is possible to avoid the contact of the corners of the light guide plate 1, and it is also possible to sharply bend the light guide plate 1 largely to reduce the curvature. Therefore, the straight portions 2b, 2b can be brought close to the end surface of the light guide plate 1.

In the case of the above embodiment, an example using two L-shaped fluorescent lamps has been described.
The case where only the book is used may be used, and the fluorescent lamp is not limited to the L-shape, and the fluorescent lamp is substantially U-shaped and surrounds the end faces of the light guide plate 1 in the three directions.
It can be implemented even if it is bent and formed in a letter shape. Further, the above-described backlight device is not limited to being used as the backlight of the liquid crystal display board 7, but can be used for a signboard for display or the like.

[0018]

As described above, according to the present invention, in the backlight device according to claim 1, since the chamfered portion is formed at the corner portion of the light guide plate, the corner portion of the light guide plate is a bent fluorescent lamp. The straight portion of the lamp can be brought closer to the end surface of the light guide plate. In the backlight device according to claim 2, since the concave portion is formed inside the bent portion of the fluorescent lamp, the corners of the light guide plate do not come into contact with each other.
Moreover, the bent portion can be bent with a small curvature, and therefore the straight portion of the lamp can be brought close to the end surface of the light guide plate. Therefore, in any of the backlight devices, the fluorescent lamp can be brought close to the light guide plate, the light incident efficiency can be increased, and the size can be reduced.
Further, the liquid crystal display device of the present invention has an advantage that a liquid crystal display having a high plane brightness can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention and showing an arrangement of a corner portion of a light guide plate of a liquid crystal display device and a bent portion of an L-shaped fluorescent lamp.

FIG. 2 is a view showing a second embodiment of the present invention and showing an arrangement of a corner portion of a light guide plate of a liquid crystal display device and a bent portion of an L-shaped fluorescent lamp.

FIG. 3 is a view showing a second embodiment of the present invention and showing an arrangement of a corner portion of a light guide plate of a liquid crystal display device and a bent portion of an L-shaped fluorescent lamp.

FIG. 4 is a sectional view schematically showing the structure of a conventional liquid crystal display device.

FIG. 5 is a plan view showing a positional relationship between a light guide plate and an L-shaped fluorescent lamp in a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light guide plate 2 ... Fluorescent lamp 2a ... Bent part 2b ... Straight part 6 ... Light diffusing plate 7 ... Liquid crystal display plate 10 ... C chamfer 20 ... R chamfer 30 ... Recess.

Claims (3)

[Claims] 1. A flat light guide plate that transmits light, a fluorescent lamp provided to face an end surface of the light guide plate, and a light diffusion plate provided on the front surface of the light guide plate. In the backlight device using a fluorescent lamp having a bent shape facing the end faces of a plurality of adjoining end faces of the light guide plate, the fluorescent lamp has chamfered portions formed at corners of the light guide plate. Backlight device characterized by. 2. A flat light guide plate that transmits light, a fluorescent lamp provided to face an end surface of the light guide plate, and a light diffusion plate provided on the front surface of the light guide plate. In the backlight device using a fluorescent lamp having a bent shape facing the end surfaces of the light guide plate across a plurality of adjacent end surfaces of the light guide plate, a recess is formed inside the bent portion of the fluorescent lamp. A backlight device characterized by being formed. 3. A liquid crystal display device, wherein the backlight device according to claim 1 or 2 is installed on the back surface of a liquid crystal display plate.