JPH0634971A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the unbalance of brightness and lighting defects by housing the lead wires of the plural light sources which are disposed on the flanks of a light transmission plate and are provided with the lead wires respectively having the lengths approximately equal to each other into housing parts in such a manner that the lead wires of the one light source do not overlap on the lead wires of the other light source. CONSTITUTION:An illuminating means 2 consists of the light transmission plate 21 and the plural light sources disposed on the flanks of the light transmission plate 21. The lead wires 221, 222 are led out of respective both ends of the linear light sources 22, such as cold cathode ray tubes and are so adjusted that the lengths from the light source ends on the terminal leading out sides of the respective light sources 22 are equal to each other. Further, a frame body 3 consisting of resin molded parts constituting an outside frame by holding and housing a light source 1 and the illuminating means 2 together with a frame 4 consisting of a metallic plate, etc., is provided with the housing parts 31 for housing the lead wires of the one light source 22 in such a manner that these lead wires do not overlap on the lead wires of the other light source 22. As a result, there is no need for considering the interference of the lead wires with each other and therefore, the impedances of the two light sources are nearly equal even if the lead wires are led out of any of the upper, lower and central lead wire leading out parts.

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 lighting means.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device, as shown in Japanese Patent Laid-Open No. 3-194515, a liquid crystal cell and an illuminating means arranged on the back surface thereof are housed in a frame for modularization. It was In order to make the entire module thinner, the illuminating means is configured by arranging a linear light source composed of a fluorescent lamp or a cold cathode tube on the side surface of the light guide plate laminated on the liquid crystal cell, and the light source is an inverter transformer or the like. Lighting is driven by.

[0003]

When a plurality of such light sources are used, since the light source is thin and the display device is small and light in weight, there is a slight difference in conditions such as a difference in lead wire length. The light source may have different brightness or may not light up. For example, when two cold cathode tubes are arranged on two side surfaces of the light guide plate and lead wires are led out from one corner of the liquid crystal display device and driven by an inverter, the lead wires of the light source near that corner are more than those of other light sources. It has a short lead wire. For example, if the light source is arranged on the long side of the display of the size of B5 plate, the difference in the length of the lead wire exceeds 10 cm, and the light source is placed on the short side of the display of the size of A4 plate. When arranged, the difference in lead wire length is 30
It will reach up to cm. Due to such a difference in length, the impedance to the drive circuit is different, and the load condition of the cold cathode tube is different when lighting and during lighting.Therefore, when lighting, the short lead wire lights first and after lighting. As the temperature rises, the light source becomes brighter, and the light source of the long lead wire symmetrically delays or cannot be lighted, and the brightness does not increase after lighting. Such an imbalance in the brightness of the light source directly affects not only the nonuniformity of the display screen but also the display density, the contrast, or the easiness of distinguishing the display content, which is not preferable.

[0004]

The present invention has been made in view of the above points, and supports an illuminating means arranged on the back surface of a liquid crystal cell with a plurality of light sources arranged on the side surface of a light guide plate. The frame body is provided with an accommodating portion for accommodating the lead wire of at least one light source of the lead wires of substantially the same length provided in each light source so as not to overlap the lead wire of the other light source.

[0005]

[Function] Since the lead wires have the same length and it is not necessary to consider mutual interference, there are few luminance imbalances and lighting defects.
In addition, the degree of freedom of the place where the lead wire is taken out is increased.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention. In the figure, reference numeral 1 is a simple matrix type super twisted nematic field effect (STN) liquid crystal cell, which may be taped as required. A film-supported drive element 12 called automated bonding (TAB) is attached around the liquid crystal 1 by an anisotropic conductive film or the like.

Reference numeral 2 denotes an illuminating means comprising a light guide plate 21 and a plurality of light sources 22 arranged on the side surface of the light guide plate 21, which is arranged on the back surface of the liquid crystal cell 1. In particular, the light guide plate 21 is the liquid crystal cell 1.
It is preferable that the layers are laminated with a certain gap. The light guide plate 21 is made of, for example, a flat plate made of acrylic resin, but a light diffusion plate may be attached to the surface as necessary, or spots or bubbles for light diffusion may be mixed inside, or the bottom surface or the side surface. A reflector may be attached to the above. Further, the light source 22 is a linear light source such as a cold cathode tube, and when two light sources are used, it is preferable to arrange them on the opposite long sides or opposite short sides of the light guide plate 21 so that light can be efficiently emitted to the opposite side surfaces of the light guide plate. It is more preferable to wind the reflection sheet around the light source 22 in a non-contact state for guiding. Lead wires 221 and 222 are led out from both ends of the light source 22, and the lengths from the light source end portions on the terminal lead-out side are adjusted to be equal in each of the light sources 22.

Reference numeral 3 denotes a supporting frame made of a resin molded product or the like, which constitutes an outer frame of the liquid crystal display device by holding and accommodating the liquid crystal 1 and the illuminating means 2 together with the frame 4 made of a metal plate or the like. 3 has at least a concave-convex surface for storage so as to support the illuminating means 2, and may have any color scheme if there is no problem with glare around the display surface, but if there is a problem of light leakage or glare. Is molded to have a black or dark color, while the frame 4 has a through hole exposing at least the effective display surface of the liquid crystal cell 1.
Further, as shown in FIG. 2, the frame body 3 is provided with an accommodating portion 31 for accommodating the lead wire of at least one light source 22 so as not to overlap the lead wire of the other light source 22, and the accommodating portion 31 is, for example, 3 on the top, bottom and center of the short side of the LCD
A guide groove 31 that allows the lead wire to meander and accommodate corresponding to the upper and lower sides of the lead wire lead-out portion 32 provided at the place
It is preferable to provide a protrusion that contacts the bent portion of the lead wire or the lead wire. If it is difficult to provide such a groove or protrusion, a recess or a through hole for accommodating the lead wire bent in a plane must be provided. 2 shows that when the guide groove 311 is provided, the lead wires 221 and 2 are
A method of housing the lead wire when the lead wire 22 is led out from the lead wire lead-out portion 32 on the lower side of the drawing is shown by a chain double-dashed line. When the central lead wire lead-out portion 32 is used, no lead wire is stored in any of the housing portions 31, and when the lead wire lead-out portion 32 on the upper side of the drawing is used, it is stored in the upper lead wire housing portion 31 of FIG. The lead wires 221 and 222 of the upper light source 22 may be housed.

[0009]

As described above, according to the present invention, since the lead wires have the same length and the mutual interference does not have to be taken into consideration, the lead wire can be led out from any of the lead wire lead-out portions of the upper, lower, and center portions.
The impedances of the two light sources are almost equal, and therefore the brightness imbalance and the lighting failure are reduced. For example, in the liquid crystal display device, which has a delay in lighting due to different lead wires, a brightness difference of several candela occurs and the screen While the unevenness of the illuminance was noticeable, the illuminance difference was not noticeable in the visual observation in the above-mentioned examples.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part of a frame body according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal 2 Illuminating means 21 Light guide plate 22 Light source 221 Lead wire 222 Lead wire 3 Frame body 4 Frame

Claims (1)

[Claims] 1. A liquid crystal cell, a light guide plate and a plurality of light sources arranged on a side surface of the light guide plate, and an illuminating unit arranged on the back surface of the liquid crystal cell, and a frame body for supporting at least the illuminating unit. Each of the light sources has a lead wire of substantially the same length, and the frame body is provided with a housing portion for housing the lead wire of at least one light source so as not to overlap the lead wire of the other light source. A liquid crystal display device characterized by the above.