JPH07120756A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the compact liquid crystal display device with back illumination with which the non-light emitting part of a radiation type light emitting illuminating light source of inexpensive and uniform surface light emission does not restrict the outside shape of the device by forming reflection patterns in such a manner that the reflectivity near the non-light emitting part of the tubular light source of a light transmission plate is higher than the reflectivity near the light emitting part. CONSTITUTION:This liquid crystal display device is provided with the light transmission plate 23 for introducing the light from the light emitting part 24a via a light introducing end 23a to a liquid crystal display plate 19 and a module cover 26 housing this liquid crystal display plate 19 so as to expose the display surface of the liquid crystal display plate 19. The reflection patterns are so arranged that the tubular length 1 of the tubular light source 24 is smaller than the length L along the tube of the tubular light source 24 of the module cover 6 and that the region in proximity to the non-light emitting part 24b of the light transmission plate 23 has the higher reflectivity than the reflectivity of the region in proximity to the light emitting part 24a. As a result, the darkening near the non-light emitting part 24b exclusive of the light emitting part 24a of the tubular light source 24 of the light transmission plate 23 and the part along the direction orthogonal with the longitudinal direction of the tubular light source 24 therefrom is prevented.

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 planar light emitting illumination on its rear surface and a light guide plate for the planar light emitting illumination.

[0002]

2. Description of the Related Art In recent years, transmissive or semi-transmissive liquid crystal display devices have been widely used for display devices such as word processors and sonal computers. In such liquid crystal display devices, illumination is usually provided on the back surface of a liquid crystal display plate. It is arranged.
For example, a light bulb has been used as the illumination for the back surface in the past, but recently, a discharge type such as a fluorescent lamp or a cold cathode discharge tube has been used.

As a lighting method, generally, a light source is arranged directly below the rear surface of the liquid crystal display plate, or a light source is arranged directly below the liquid crystal display section without arranging the light source in the lateral direction of the liquid crystal display section. There is known a method (sidelight method) of producing a planar light emitting illumination by using a light guide plate such as acrylic. here,
The sidelight system is disclosed in, for example, Japanese Patent Laid-Open No. 61-
It is described in Japanese Patent Laid-Open No. 99187 and Japanese Patent Laid-Open No. 63-62104.

By the way, such a discharge type illumination light source is generally tubular, and a discharge electrode is disposed at the end of the tube as a feature of the discharge type illumination light source. The emission brightness is extremely low. Therefore, conventionally, the portion of the tube end where the emission brightness is extremely low has not been used as a surface emitting light source.

[0005]

FIG. 2 is a plan view showing an example of a conventional liquid crystal display device. In the figure, a light-introducing end portion 2a of a light guide plate 2 made of, for example, rectangular acrylic is arranged adjacent to a light emitting portion 1a of a light source 1 made of, for example, a cold cathode fluorescent lamp, and light from the light source 1 is used for liquid crystal display plate 3 It is structured to irradiate. Here, the light guide plate 2 may be, for example, Japanese Patent Application Laid-Open No.
As described in Japanese Patent Laid-Open No. 3-62105, milk-white printing (not shown) is performed so that the density (reflectance) increases from one end side to the other end side. Further, the length of the light introducing end portion 2a of the light guide plate 2 is determined by the light source 1
The length of the light emitting portion 1a is substantially the same as that of the light source 1, that is, shorter than the length of the light source 1, and the non-light emitting portion 1b of the light source 1 protrudes from the substantially rectangular shape.

Since the protruding portion significantly restricts the outer shape of the product defined by the module cover 4, it is desirable that the light source 1 be housed in a substantially rectangular shape of the surface emitting illumination.

FIG. 3 is a plan view showing another example of the conventional liquid crystal display device, and the portions corresponding to those in FIG. 2 are designated by the same reference numerals. As can be seen from the figure, the shape of the light guide plate 2 is
By making only the light-introducing end portion 2a the same length as the light-emitting portion 1a of the light source 1 and widening it from here in a wedge shape, it is possible to fit the outer shape of the product in a substantially rectangular shape. However, due to the presence of wedge-shaped parts that cannot be used for back lighting,
The outer shape of the product is inevitably larger than that in the case of FIG. 2, and the processing cost of the light guide plate 2 is also high.

The present invention has been made in view of such conventional circumstances.

[0009]

SUMMARY OF THE INVENTION According to the present invention, first and second substrates having electrodes formed on one main surface are combined so that their one main surface sides face each other, and the first and second substrates are connected to each other. A discharge type tubular light source having a liquid crystal display plate formed by sandwiching liquid crystal in a gap, a non-light emitting portion at a tube end, and a light emitting portion sandwiched by the non-light emitting portion, and being substantially parallel to the tubular light source, A light guide plate having a light introducing end portion arranged in the vicinity of the tubular light source and guiding light from the light emitting portion to the liquid crystal display plate via the light introducing end portion; and a display screen of the liquid crystal display plate. In a liquid crystal display device including a module cover that houses the liquid crystal display plate so as to be exposed, the tube length of the tubular light source is smaller than the length along the tube length of the tubular light source of the module cover, The area close to the non-light emitting portion is close to the light emitting portion. It is characterized in that the reflective pattern is positioned so as to increase the reflectivity than the region.

Here, the display screen means a display range in which an observer can actually observe, and an outer frame is defined by a module cover, for example.

[0011]

According to the present invention, the shape of the reflection pattern formed on the light guide plate is smaller than that of the tubular light source near the light emitting portion at the center of the tube.
By increasing the reflectance in the vicinity of the non-luminous portion of the tube end of the tubular light source, the vicinity of the non-luminous portion other than the luminous portion of the tubular light source in the light guide plate and the portion along the direction orthogonal to the longitudinal direction of the tubular light source from here Can be prevented from darkening. As a result, the entire discharge type light source can be housed in a substantially rectangular shape without impairing the display characteristics.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing an embodiment of the present invention. FIG. 1 (a) is a schematic plan view as seen from the display surface side, and FIG. 1 (b) is an A- line in FIG. 1 (a). FIG. 6C is a schematic cross-sectional view of the surface A ′ as seen from the direction of the arrow, and FIG. 6C is a schematic view showing a printed pattern in the vicinity of the non-light-emitting portion of the tubular light source in the light guide plate of the present invention.

1A and 1B, electrodes 12, 13 made of, for example, ITO (indium tin oxide) are formed on one main surface of the first and second substrates 10, 11 made of, for example, glass. Is formed, and alignment films 14 and 15 made of, for example, polyimide are formed so as to cover the film. Then, on one of the first and second substrates 10 and 11, for example, one main surface of the first substrate 10, an adhesive made of, for example, a thermosetting epoxy resin is formed in a frame shape in which a portion to be a liquid crystal injection port is opened. The agent 16 is printed on the first and second substrates 1
Spacers 17 made of, for example, glass fibers are scattered on the other main surface of 0 and 11, for example, one main surface of the second substrate 11. Subsequently, the first and second substrates 10 and 11 are combined so that their main surfaces are opposed to each other, and then the liquid crystal 18 is injected from the liquid crystal injection port.
The liquid crystal 18 is held in the gap between 0 and 11. Then, by sealing the liquid crystal inlet, the predetermined liquid crystal display board 1
9 is obtained. Subsequently, the polarizing plate 20 is attached to the other main surface side of the first and second substrates 10 and 11.

A liquid crystal drive circuit board 21 is arranged on the other main surface side of the first substrate 1, and the liquid crystal display board 19 and the liquid crystal drive circuit board 21 are connected by a connecting means 22 such as a flexible cable. It is electrically connected. And, between the liquid crystal display board 19 and the liquid crystal drive circuit board 21,
A light guide plate 23 made of, for example, an acrylic plate is arranged, and a discharge type tubular light source 24 made of, for example, a cold cathode tube is provided in the vicinity of the light introducing end 23a of the light guide plate 23. Further, the length L of the display screen in the direction parallel to the light introducing end 23a is equal to or more than the length l of the tubular light source 24, for example, L> l,
A reflection pattern 25 is formed on the surface of the light guide plate 23 facing the liquid crystal drive circuit board 21 by milk white printing, for example. This reflection pattern 25 is shown in FIG.
As shown in, the area of each reflection pattern 25 is made larger in the vicinity of the light emitting portion 24a at the center of the tube of the tubular light source 24 than in the vicinity of the non-light emitting portion 24b at the tube end, and as a whole,
The area of each reflection pattern 25 increases as the distance from the tubular light source 24 increases. The liquid crystal display plate 19, the liquid crystal drive circuit board 21, the light guide plate 23, and the tubular light source 24 are integrated by a module cover 26,
A predetermined liquid crystal display device is configured.

In this embodiment, a predetermined reflection pattern 24 is formed on the light guide plate 23 so that the reflectance near the non-light emitting portion 24b of the tubular light source 24 is higher than the reflectance near the light emitting portion 24a. Therefore, even when the length of the effective light emitting portion in the direction parallel to the light introduction end portion 23a is made equal to the length of the tubular light source 24, the vicinity of the non-light emitting portion 24b is the light emitting portion 24.
It can be prevented from becoming dark as compared with the vicinity of a. Therefore, it is possible to fit the outer shape of the liquid crystal display device into a substantially rectangular shape.
Further, by changing the shape of each reflection pattern 25 according to the distance from the tubular light source 24, variations in printing accuracy and stripes due to moire are prevented.

It has been described above that the liquid crystal display panel has a one-layer cell structure, but it goes without saying that it may have a multi-layer cell structure having two or more layers.

[0018]

According to the present invention, a reflective pattern is formed on the light guide plate so that the reflectance near the non-light emitting portion of the tubular light source is higher than the reflectance near the light emitting portion. Thus, it is possible to obtain a compact liquid crystal display device with a back illumination, in which the non-light emitting portion of the radiant emission illumination light source does not become a restriction on the outer shape of the device.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic view showing an example of a conventional liquid crystal display device.

FIG. 3 is a schematic view showing another example of a conventional liquid crystal display device.

[Explanation of symbols]

 10 ... 1st board 11 ... 2nd board 12, 13 ... Electrode 18 ... Liquid crystal 19 ... Liquid crystal display 23 ... Light guide plate 23a ... Light introduction end 24 ... Tubular light source 24a ... Light emitting part 24b ... Non-light emitting part 25 ... Reflection pattern

Claims (5)

[Claims] 1. A combination of first and second substrates having electrodes formed on one main surface such that one main surface side faces each other,
A discharge type tubular light source having a liquid crystal display plate having a liquid crystal sandwiched between the first and second substrates, a non-light emitting portion at a tube end, and a light emitting portion sandwiched by the non-light emitting portion, A light guide plate that is substantially parallel to the tubular light source and that has a light introducing end portion that is arranged close to the tubular light source, and that guides light from the light emitting portion to the liquid crystal display plate through the light introducing end portion; In a liquid crystal display device comprising a module cover that houses the liquid crystal display plate so that the display screen of the liquid crystal display plate is exposed, the tube length of the tubular light source is longer than the tube length of the tubular light source of the module cover. Also, the liquid crystal display device is characterized in that a reflection pattern is arranged so that a region of the light guide plate that is close to the non-light emitting portion has a higher reflectance than a region of the light guide plate that is close to the light emitting portion. 2. A liquid crystal display device, wherein the reflection pattern according to claim 1 is formed by printing. 3. A liquid crystal display device according to claim 1, wherein an area of the reflection pattern increases as the distance from the tubular light source increases. 4. A liquid crystal display device, wherein the tubular light source according to claim 1 is a cold cathode tube. 5. The liquid crystal display device according to claim 1, further comprising a liquid crystal drive circuit board that drives the liquid crystal display plate,
A liquid crystal display device, characterized in that the light guide plate is disposed between a substrate and the liquid crystal drive circuit substrate.