JPH0882716A - Liquid crystal display - Google Patents

Abstract

PURPOSE: To eliminate loss in the light quantity from a light source by fixing in between the edge of a reflection sheet for the light source and a light guide body edge facing to a diffusion plate with a dark double-coated adhesive tape and fixing the edge of the reflection sheet for the light source and the light guide body edge facing to the reflection plate with a double-coated adhesive tape. CONSTITUTION: A cold cathode tube 9 disposed along the one side edge of a light-guide plate 6 is surrounded with a reflection sheet 10 for the light source. The one of two ends of the reflection sheet 10 toward a diffusion plate 8 is fixed to the light-guide body with a dark double-coated adhesive tape 8a. The other end near a reflection plate 7 is fixed to the plate 7 with a normal double- coated adhesive tape 9b. The dark double-coated adhesive tape 8a consists of a polyethylene terephthalate(PET) film as the base film which is colored into black or other light-absorbing color with a pigment or dye, and a tacky adhesive material applied on both surfaces of the base film. The base film is not limited to PET, and an adhesive can be used instead of the tacky adhesive material.

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, and more particularly to a liquid crystal display device having a light source structure capable of reducing the reduction of the effective display area and obtaining uniform brightness over the entire effective area.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used as display devices for displaying various images.

Liquid crystal display devices are classified into a simple matrix type and an active matrix type, depending on the pixel selection method.

A simple matrix type liquid crystal display device is one in which liquid crystal such as STN is sealed between two sets of intersecting electrodes, and pixels are formed at the intersections of the electrodes.

On the other hand, an active matrix type liquid crystal display device has a nonlinear element (switching element) corresponding to each of a plurality of pixel electrodes arranged in a matrix.
Is provided. Theoretically, the liquid crystal in each pixel is always driven (duty ratio 1/1), so the active method has better contrast than the simple matrix method that employs the time-division driving method. It is becoming an indispensable technology for equipment. A typical example of the switching element is a thin film transistor (TFT).

However, even the recent simple matrix type liquid crystal display device can display a high quality color image by improving its driving system or liquid crystal structure.

In these liquid crystal display devices, a so-called backlight, which irradiates light from the back surface of a liquid crystal panel composed of the liquid crystal display element, is generally incorporated.

This backlight is formed by laminating a light diffusing plate (hereinafter, simply referred to as a diffusing plate), a light guide and a reflecting plate made of a transparent material such as an acrylic plate, and at least one side of the light guiding plate. A linear light source arranged along the light source is provided, and the light from the linear light source is guided by the light guide toward the liquid crystal display element to form a surface light source.

As the linear light source, a cold cathode fluorescent lamp (cold cathode fluorescent fluorescent lamp, usually called CFL) is generally used, and the light of the cold cathode fluorescent lamp is provided in the periphery except the area facing the light guide. A light source reflection sheet for efficiently introducing light into the light guide is installed.

FIG. 4 is an explanatory view of the arrangement structure of the backlight and the liquid crystal display element of the liquid crystal display device. 4 is a liquid crystal display element, 6 is a light guide plate, 6b is a diffusion pattern, 6c is an end face reflection tape, and 7 is A reflection plate, 8 is a diffusion plate, 9 is a cold cathode tube as a linear light source, 9a is a power supply cable, 10 is a light source reflection sheet, and 15 is a mounting hole.

As shown in the figure, a cold cathode tube 9 and a light source reflection sheet 10 arranged around the cold cathode tube are installed at one end of a light guide plate 6 which constitutes a backlight.

The light source reflection sheet 10 and the light guide 6 are fixed by using a double-sided adhesive tape. Then, a reflection plate 7 is laminated on the lower surface and a diffusion plate 8 is laminated on the upper surface, and the liquid crystal display element 4 is mounted thereon.

The structure in which the backlight and the liquid crystal display element are combined is fixed in a mounting hole 15 between an upper frame and an intermediate frame (not shown).

5A and 5B are explanatory views of a constitutional example of a backlight installed in a conventional liquid crystal display device. FIG. 5A is a sectional view of an essential part, and FIG. 5B is a display area with respect to a distance from a light source side. FIG. 5 is an explanatory diagram of a luminance change in FIG.

In the figure, 6 is a light guide, 6a is a light incident end surface, 6b is a diffusion pattern formed on the surface of the light guide on the side of the reflection plate by printing or the like, 7 is a reflection plate, 7a is a dark tape, 8 Is a diffusion plate, 9 is a light source reflection sheet, 9b and 9b are double-sided adhesive tapes, and 10 is a cold cathode tube. Usually, as a means for fixing the light source reflection sheet 9 to the light guide 6, a double-sided adhesive tape 9a,
9b is used.

That is, as shown in FIG. 3A, a dark (black) tape 7a is installed at a portion indicated by an arrow A to suppress the generation of a bright portion on the light source side. As described above, the effective display area is enlarged.
However, since the dark (black) tape 7a is installed in addition to the double-sided tapes 9a and 9b, the thickness of the liquid crystal display device increases.

As a prior art relating to the fixing of this type of light source reflection sheet to a light guide, Japanese Patent Laid-Open No. 4-324821 can be cited.

[0018]

In the above-mentioned conventional liquid crystal display device, the double-sided adhesive tapes 9a and 9b are non-transparent due to the use of a non-woven fabric substrate or the like. Abnormally bright due to the fixed part with double-sided adhesive tape. The amount of the light emitted is not utilized as effective luminance and becomes a loss of light, and the light of the mounting portion is further reflected on the reflection plate 7 to be seen from an oblique upper portion as shown by an arrow A.

For this reason, in the light guide, it is necessary to increase the distance R between the light source and the light emitting surface (effective display window) used to avoid the influence of the attached light emission, and the effective display area becomes small. there were.

In particular, in a portable liquid crystal display device, the reduction of the effective area must be avoided in order to reduce the size. However, it has been difficult for the above-mentioned conventional techniques to efficiently use the light emitted from the light source to illuminate the liquid crystal display element.

An object of the present invention is to solve the problems of the prior art and to absorb light without causing the light source reflection sheet in a light source device (backlight) for a liquid crystal display device to be attached to the surface of the light guide body. It is to provide a fixed liquid crystal display device.

[0022]

In order to achieve the above object, the present invention provides a light guide plate, a linear light source disposed on at least one end face of the light guide plate, and a region of the linear light source facing the light guide plate. Except for the light source reflection sheet installed around, a diffusion plate laminated on one surface of the light guide plate, a reflection plate laminated on the other surface of the light guide, and arranged facing the diffusion plate side. In the liquid crystal display device including at least the liquid crystal display element, the edge of the light source reflection sheet is overlapped with the one end face side both side edges of the light guide, and the edge of the light source reflection sheet is overlapped. The light guide plate was fixed between the diffusion plate side edges with a double-sided adhesive tape of dark color, and the light source reflection sheet and the light guide plate side edge were fixed with double-sided adhesive tape. It is characterized by

[0023]

By using the dark-colored double-sided tape for fixing the light source reflection tape and the light guide plate, the light of the fixed portion is reflected on the reflection plate 7 as described with reference to FIG. It is not necessary to set a large distance R to the display window), and a large effective display area can be set.

Further, since the number of adhesive tapes required for fixing the conventional light guide and the light source reflection sheet can be reduced by one, the number of manufacturing steps can be reduced and the thickness of the liquid crystal display device as a whole can be reduced. In particular, it is suitable for reducing the size and thickness of a portable liquid crystal display device.

[0025]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a developed perspective view for explaining the overall structure of the liquid crystal display device according to the present invention, in which 1 is an upper frame and 2 is a top frame.
Is a lower frame, 3 is a liquid crystal display window (display area), 4 is a liquid crystal display element, 5 is a printed circuit board, 6 is a light guide plate, 7 is a reflection plate, 8 is a diffusion plate, 9 is a cold cathode tube, and 10 is a light source reflection. A sheet, 11 is an intermediate frame, 12 is a light-shielding spacer, 13 is a spacer, and 14 is a lamp cover.

In the figure, a backlight composed of a light guide plate 6, a reflecting plate 7, a diffusing plate 8, a cold cathode tube 9 and a light source reflecting sheet 10 is laminated under the liquid crystal display element 4, and these liquid crystal display elements are stacked. The backlight and the backlight are set on the intermediate frame 11, and are sandwiched and fixed by the upper frame 1 and the lower frame 2.

Cut and raised piece 16 formed on the upper frame 1
Contacts the ground pad 17 formed on the printed circuit board 5, and the claw 18 engages with a claw receiver 19 formed on the lower frame 2 to fix the upper frame 1 and the lower frame 2. Also,
The upper frame 1 and the liquid crystal display element 4 are adhesive spacers 1.
Fixed at 3.

A cutout portion 20 formed in the lower frame 2,
Reference numeral 21 is provided at a position symmetrical to a line orthogonal to the central portion of the backlight, and cutout portions 22 and 23 are provided in the longitudinal direction of the cold cathode tube 9. Further, notches 24 and 25 are provided in the lower portions of both ends of the cold cathode tube 9.

The upper frame 1 is, for example, a steel plate having a thickness of 0.8 mm, and the lower frame 2 is a steel plate or has a considerable thickness, for example, 0.5 m.
Composed of m-thick aluminum.

In the figure, the liquid crystal display device is sandwiched and fixed by the upper frame 1 and the lower frame 2 in the arrangement relationship shown in the figure. A cold cathode tube 9 which is a linear light source is installed on one end side of the intermediate frame 11, and light emitted from the cold cathode tube 9 is directed to the light guide plate 6 side by the light source reflection sheet 10.

The light-shielding spacer 12 is the intermediate frame 1.
The effective display area is defined by being interposed between the liquid crystal display element 4 and the light guide body 6 which constitutes the backlight installed in the recess formed in 1.

The light guide plate 6 and the light source reflection sheet 10 constituting the backlight are fixed by using a double-sided adhesive tape whose edge on the diffusion plate side of the light guide 6 is dark. The edge of the light guide plate 6 on the side of the reflection plate and the light source reflection sheet are fixed by using an ordinary double-sided adhesive tape.

2A and 2B are explanatory views of the structure of the backlight portion in the first embodiment of the liquid crystal display device according to the present invention. FIG. 2A is a sectional view of the main part, and FIG. 2B is a distance from the light source side and display. It is explanatory drawing of the change of the brightness | luminance in an area | region.

As shown in (a), a light source reflection sheet 10 is installed around the cold cathode tubes 9 arranged along one end side edge of the light guide plate 6. Of the both edges of the light source reflection sheet 10, the edge on the side of the diffusion plate 8 is a dark double-sided adhesive tape 8.
It is fixed via a. Further, it is fixed to the reflection plate 7 by an ordinary double-sided adhesive tape 9b.

In this embodiment, the dark color double-sided adhesive tape 8 is used.
A is attached to a position outside the dot pattern 6b printed on the light guide plate 6 on the side of the reflection plate 7.

With this structure, as shown in FIG. 6B, the bright portion on the light source side of the display area is reduced, the light distribution becomes flat, and the effective display area can be made large. it can.

The dark-colored double-sided tape 8a is made of a polyethylene terephthalate (PET) film, which is colored with a pigment or a dye in black or other light-absorbing color, as a base.
Although the pressure-sensitive adhesive is applied to both surfaces of the substrate, the substrate is not limited to the above PET, and an adhesive may be used instead of the pressure-sensitive adhesive.

3A and 3B are explanatory views of the structure of the backlight portion for explaining the second embodiment of the liquid crystal display device according to the present invention. FIG. 3A is a sectional view of the main part and FIG. 3B is from the light source side. FIG. 6 is an explanatory diagram of the distance and the change in luminance in the display area.

In this embodiment, a dot pattern 6b printed on the light guide plate 6 on the reflection plate 7 side is further extended to the light source side, and a dark double-sided adhesive tape 8a is provided on the dot pattern 6 side.
It has the same configuration as that of the first embodiment except that it is attached so as to overlap b.

According to this embodiment, the printed dot pattern 6b and the light reflection suppressing effect of the dark color double-sided adhesive tape 8a are superimposed, and the luminance distribution can be further flattened.

According to the configuration of each embodiment of the present invention described above,
It is possible to suppress the occurrence of a light-luminance portion on the light source side of the light guide plate, and to achieve thinning and weight reduction.

As described above, by fixing the light source reflection sheet 10 to the light guide plate 6 by the fixing means as described above, an increase in the distance between the display region 3 and the cold cathode tube 9 is suppressed, and the portable type or the like is used. It is possible to provide a miniaturized liquid crystal display device.

Further, in FIG. 1, the both ends of the cold cathode fluorescent lamp 9 are the parts that cause a decrease in luminance due to a decrease in temperature, and in the range where the temperature distribution of the liquid crystal display element can be kept uniform, It is necessary to keep the temperature high. Therefore, the notches 24 and 25 are provided to prevent the deterioration of the brightness while making the temperature distribution of the liquid crystal display element uniform.

Further, the weight of the lower frame 2 is reduced by the cutouts 20 and 21 provided at positions symmetrical with respect to the line orthogonal to the center of the cold cathode tube over the effective display area of the liquid crystal display element, and the liquid crystal display is displayed. The temperature distribution of the element can be made uniform.

[0046]

As described above, according to the present invention, the effective display area can be expanded because there is no loss due to the amount of light emitted from the light source shining at unnecessary points or absorbing the light. . Therefore, it is not necessary to increase the area of the light guide plate excessively, and it is possible to configure a high-intensity backlight which is optimal for downsizing such as a portable type, and it is possible to provide a liquid crystal display device having an excellent function.

[Brief description of drawings]

FIG. 1 is a developed perspective view illustrating an overall configuration of a liquid crystal display device according to the present invention.

FIG. 2 is an explanatory diagram of a structure of a backlight portion in the first embodiment of the liquid crystal display device according to the present invention.

FIG. 3 is an explanatory diagram of a structure of a backlight portion for explaining a second embodiment of the liquid crystal display device according to the present invention.

FIG. 4 is an explanatory diagram of an arrangement structure of a backlight and a liquid crystal display element of a liquid crystal display device.

FIG. 5 is an explanatory diagram of a configuration example of a backlight installed in a conventional liquid crystal display device.

[Explanation of symbols]

 1 Upper Frame 2 Lower Frame 3 Liquid Crystal Display Window (Display Area) 4 Liquid Crystal Display Element 5 Printed Circuit Board 6 Light Guide Plate 6b Printed Dot Pattern 7 Reflector 8 Diffuser 8a Dark Sided Adhesive Tape 9 Cold Cathode Tube 9a, 9b Double Sided Adhesive Tape 10 Light source reflection sheet 11 Intermediate frame 12 Light-shielding spacer 13 Spacer 14 Lamp cover.

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[Procedure amendment]

[Submission date] August 3, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

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[Fig. 2]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

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[Figure 5]

Claims (1)

[Claims] 1. A light guide plate, a linear light source disposed on at least one end surface of the light guide plate, a light source reflection sheet installed around the linear light source except for a region facing the light guide plate, and a light guide plate of the light guide plate. In a liquid crystal display device comprising at least a diffusion plate laminated on one surface, a reflection plate laminated on the other surface of the light guide, and a liquid crystal display element arranged facing the diffusion plate side, the light source The edges of the reflection sheet are overlapped with both edges of the one end face side of the light guide, and the both sides of the overlapped light source reflection sheet and the edge of the light guide with the diffuser plate are dark-colored. The liquid crystal display device is characterized in that it is fixed with an adhesive tape, and a space between the edge of the light source reflection sheet and the edge of the light guide on the side of the reflection plate is fixed with a double-sided adhesive tape.