JPH10228020A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a backlight equally to the life of a liquid crystal display board itself without exchanging a light source by constituting the backlight of the proper number of light sources. SOLUTION: A light guide plate 2 for guiding light from plural light sources to the liquid crystal display board is provided at the back of the liquid crystal display board, and plural light sources are arranged around the light transmission plate 2. Three fluorescent lamps 7, 71 and T2 are arranged in a circle along one side of the plate 2. The lamps 7, 71 and 72 are connected with a switching mechanism for switching and setting optional one lamp to a specified illumination position. As a method for switching plural lamps, for example, three lamps 7, 71 and 72; not only manual operation but also various switching systems such as constitution where they are automatically alternately switched at the time of supplying power, constitution where they are switched in a fixed cycle in a state where the power is supplied, or constitution where they are simultaneously switched in the case of switching a display screen as a whole are adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a backlight at the back of a liquid crystal display panel.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of various information processing devices such as word processors, liquid crystal display devices have been widely adopted as image output devices. In a liquid crystal display device that is assumed to be used indoors, on the back of the liquid crystal display panel,
A backlight such as a fluorescent lamp or an incandescent lamp is provided.

[0003]

The lifetime of a liquid crystal display panel is 30,000 hours or more, whereas the lifetime of a fluorescent lamp, for example, is approximately 10,000 hours, and the lifetime of a backlight is extremely short. Therefore, conventionally, a backlight is exchangeably equipped. However, this has a problem that the mechanism is complicated and the cost is increased.

An object of the present invention is to provide a liquid crystal display device that can extend the life of the backlight to the same as the life of the liquid crystal display panel itself without replacing the backlight.

[0005]

In a liquid crystal display device having a backlight at the back of the liquid crystal display panel (1), the backlight comprises a light guide plate (2) having a reflector (22) at the back, and a light guide plate (2). Arranged around the light guide plate (2), each is constituted by a plurality of light sources each independently emitting a light amount necessary for illuminating the liquid crystal display panel, and these light sources are arranged with a plurality of rod-shaped lamps in parallel and close to each other, It is characterized in that any one rod-shaped lamp is connected to a switching mechanism for switching and moving to a predetermined illumination position and lighting.

Further, in the above configuration, a light guide plate (2) for guiding light from a plurality of light sources to the liquid crystal display panel (1) is provided on the back of the liquid crystal display panel (1), and the plurality of light sources are , Placed around the light guide plate (2). The light guide plate (2) includes a reflector (22) on the back. The light source is configured by arranging a plurality of rod-shaped lamps in parallel and close to each other, and is linked to a switching mechanism for switching an arbitrary one of the rod-shaped lamps to a predetermined illumination position and lighting them.

[0007]

A plurality of light sources are selectively turned on by a switching circuit, and the liquid crystal display panel is illuminated with a sufficient amount of light by light from a single light source. Since the light sources are turned on with a time lag, the lifetime of the backlight constituted by the plurality of light sources is the sum of the lifetimes of the light sources.

[0008]

According to the liquid crystal display device of the present invention, by constructing the backlight from an appropriate number of light sources, the life of the backlight can be made equal to the life of the liquid crystal display panel itself without replacing the light source. Can be extended to A plurality of rod-shaped lamps are arranged in parallel with each other as a light source, and when the illuminance of the lamp decreases, a new lamp moves to an illumination position and is lit by manual or automatic operation of a switching mechanism. There is an advantage that the switching of the data becomes easy.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. As shown in FIG.
A liquid crystal display panel (1) is arranged in a flat casing (10), and a backlight having a light guide plate (2) and two upper and lower fluorescent lamps (3) and (4) is provided at the back thereof. ing.

[0010] These two fluorescent lamps (3) and (4) are light guide plates.
The mounting brackets (31) and (41) are fixed to the upper and lower ends of (2), respectively.

As shown in FIG. 2, the light guide plate (2) covers the surface of a transparent resin plate (21) made of acryl, and a translucent diffusion sheet (23) is arranged on the light guide plate (2). A reflection plate (22) is arranged on the back of the device.

Each of the mounting brackets (31) and (41) has a substantially cylindrical main body covering the outer peripheral surface of the fluorescent lamps (3) and (4), and a light guide plate (2).
It opens to the end face of. A light reflecting surface is formed on the inner surface of the cylindrical main body, and plays a role of condensing light from the fluorescent lamps (3) and (4) toward the light guide plate (2).

The two fluorescent lamps (3) and (4) are connected to a power source (6) via a changeover switch (5) as shown in FIG. 3, and any one of the two fluorescent lamps is manually operated by the changeover switch (5). Only one fluorescent lamp can be turned on.

Thus, of the two fluorescent lamps (3) and (4),
When one of the lamps is turned on, the light from the fluorescent lamp is guided into the light guide plate (2) shown in FIG. 2, and the inside of the light guide plate (2) is reflected by the reflection plate (22) and the diffusion sheet (23). While being reflected and diffused,
The light reaches the end on the other fluorescent lamp side, and in this process, the light transmitted through the diffusion sheet (23) uniformly irradiates the entire surface of the liquid crystal display panel (1).

When one of the fluorescent lamps reaches the end of its service life, the other fluorescent lamp is used by switching the changeover switch (5). Therefore, the fluorescent lamp can be continuously used for a period twice as long as the life of one fluorescent lamp, and the replacement of the fluorescent lamp is not required during this period.

Therefore, as compared with a conventional liquid crystal display device in which the fluorescent lamp can be replaced, the mechanism is simplified and the cost can be reduced.

As shown in FIG. 4, for example, as shown in FIG. 4, a light guide plate (2) is provided in order to further reduce the bias in the amount of light caused by turning on only one of the two fluorescent lamps (3) and (4).
The reflection plate (22) can be subjected to a surface treatment for reducing the amount of light reflected on the liquid crystal display panel (1) in the area near each fluorescent lamp.

In the example shown in FIG. 4, the light reflecting surface is formed to have a symmetrical saw-tooth cross-section, and the rising angle of the saw-tooth surface is larger in the vicinity of the fluorescent lamp indicated by A and C in FIG. By approaching 90 degrees, the light reflection direction (indicated by a chain line in the figure) is removed from the liquid crystal display panel (1). As a result, the amount of light in the region near the fluorescent lamp is reduced, and a uniform illumination effect can be obtained over the entire surface of the liquid crystal display panel.

In the above embodiment, the backlight is constituted by two fluorescent lamps. However, it is also possible to arrange three or more fluorescent lamps, whereby the life of the backlight can be further extended.

FIG. 5 shows three fluorescent lamps (7), (71) and (72) arranged in a circle along one side of the light guide plate (2). These fluorescent lamps are optional. Is connected to a switching mechanism (not shown) for switching and setting one of the two to a predetermined illumination position. Of course, the switching mechanism can be constituted by various known mechanisms.

The description of the above embodiments is for the purpose of illustrating the present invention and should not be construed as limiting the invention described in the appended claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

For example, switching of a plurality of fluorescent lamps
Not only manual operation but also various switching methods, such as a configuration that switches automatically and automatically when the power is turned on, a configuration that switches at a fixed cycle in the power-on state, and a configuration that switches at the same time when the entire display screen is switched. Can be adopted.

If a plurality of fluorescent lamps need to be simultaneously turned on for illuminating the liquid crystal display panel, a plurality of light sources composed of the plurality of fluorescent lamps are provided, and the plurality of light sources are switched. Will do.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a liquid crystal display device.

FIG. 2 is an enlarged sectional view taken along the line AA-A of FIG.

FIG. 3 is a diagram showing a configuration example of a switching circuit to be connected to two fluorescent lamps.

FIG. 4 is an enlarged cross-sectional view of each region of a reflector constituting a light guide plate.

FIG. 5 is a perspective view showing an embodiment according to the present invention.

[Explanation of symbols]

 (1) LCD panel (2) Light guide plate (3) Fluorescent lamp (4) Fluorescent lamp (5) Changeover switch

Claims (1)

[Claims] 1. A liquid crystal display device having a backlight at the back of a liquid crystal display panel (1), the backlight comprising a light guide plate (2) having a reflector (22) at the back, and a light guide plate (2). ), Each of which is constituted by a plurality of light sources each of which independently emits a light amount necessary for illuminating the liquid crystal display panel, and these light sources arrange a plurality of rod-shaped lamps in parallel and close to each other,
A liquid crystal display device, wherein the liquid crystal display device is connected to a switching mechanism for switching and lighting any one rod-shaped lamp to a predetermined illumination position.