JP2000010499A - Back light device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back light device provided with a projecting part for disposing a clearance for the required number of sheets of diffusion plates between a light transmission plate and a frame at the outer edge on the light exit surface side of the light transmission plate in order to solve problems, such as insufficiency of protection to the diffusion plates and the occurrence of flawing during an assembly stage leading to a decrease of a yield or the occurrence of deformation in the process of use leading to the degradation in performance. SOLUTION: The back light device 1 provided with the projecting part 4b for disposing the clearance for the required number of sheets of the diffusion plates 3 between the light transmission plate 4 and the frame 2 at the outer edge of the light exit surface side 4a of the light transmission plate is constituted. The degradation in the performance heretofore caused by the defective articles arising from the flawing of the diffusion plates as the diffusion plates are held between the frame 2 and the light transmission plate 4 at the time of assembly because of lack of the place provided with the diffusion plates 3 or the deformation of prism cuts as the diffusion plates are compressed by the thermal expansion of the light transmission plate 4 during the course of the use is thus averted by providing the device with the projecting part 4b thereby assuring the dimensions for the light transmission plate 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device used for illuminating a liquid crystal display device used as a display screen of a portable computer or the like with transmitted light from the back.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the structure of a conventional backlight device 90 of this type. This backlight device 90 is made of a transparent resin in the form of a thick plate and has a white paint on the back side. A light guide plate 91 having a reflection surface 91a formed by printing or the like; a film-shaped diffusion plate 92 provided on the light exit surface 91b side of the light guide plate 91; , And a cold cathode fluorescent lamp, a reflecting mirror, and the like, which are arranged on a plate-thick surface of the light guide plate 91 (not shown).

The frame 93 is formed in a thin box shape of metal or the like, and has a window 93a corresponding to the light exit surface 91b of the light guide plate 91, and an opening 93b on the side surface. When assembling the backlight device 90, for example, two diffusion plates 9 are formed through the opening 93b on the side surface.
2 and then the light guide plate 91 is inserted through the same opening 93b.

[0004]

However, in the above-described backlight device 90 having the conventional configuration, the light guide plate 9 is mounted on the frame 93 in which the diffusion plate 92 is already inserted.
When the light guide plate 91 is inserted, the diffusion plate 92 rubs against the frame 93 with the insertion of the light guide plate 91, so that a scratch often occurs.

[0005] These scratches impair the diffusion performance of the surface of the diffusion plate 92, and when the liquid crystal display device or the like is illuminated from the back, the scratches appear as white or black streaks. Must be removed by a process inspection or the like, which complicates the production process, reduces the yield, and impairs the productivity.

[0006] Further, since the diffusion plate 92 has an extremely fine prism cut or the like on its surface, the above-mentioned prism cut may be damaged or deformed by the stress when the light guide plate 91 is inserted. May occur. In this case, unevenness in the diffusivity is caused to cause unevenness in brightness on the display surface, and there is also a problem that display quality is deteriorated.

Further, the stress on the diffusion plate 92 is also caused by the thermal expansion of the light guide plate 91 due to a temperature rise during use and the diffusion plate 92 being sandwiched between the light guide plate 91 and the frame 93. The degree of deformation of the prism cut gradually increases, and a problem of so-called deterioration, in which a decrease in luminance, a decrease in uniformity of brightness, etc. progresses with the elapse of use time, also arises, and solving these points is an issue. It has become something.

[0008]

According to the present invention, as a specific means for solving the above-mentioned conventional problems, a film-shaped diffusion plate and a thin frame provided with an opening on a side surface are provided from the opening. In a backlight device in which a thick light guide plate is inserted, a gap corresponding to the required number of the diffusion plates is provided between an outer edge of the light guide plate and a frame on the light emission surface side. It is an object of the present invention to solve the conventional problem by providing a backlight device characterized by including a unit.

[0009]

Next, the present invention will be described in detail based on an embodiment shown in the drawings. 1 and FIG.
Is a backlight device according to the present invention. The backlight device 1 includes a frame 2 formed in a thin box shape having an opening 2a on a side surface, and a film-shaped diffusion plate 3 made of, for example, two sheets. And a light guide plate 4 formed of a transparent member in the form of a thick plate as in the conventional example.

A window 2b is formed corresponding to the light exit surface 4a of the light guide plate 4 of the frame 2.
Light from a cold cathode fluorescent lamp (not shown) provided on the thick surface of the light guide plate 4 is radiated from the window portion 2b as a uniform surface light source, and is installed so as to cover the front surface of the window portion 2b. The liquid crystal display device and the like to be illuminated with the transmitted light from the back is also the same as the conventional example.

Here, in the present invention, the light guide plate 4 is provided with the convex portions 4.
b, and the convex portion 4b is provided on the light emitting surface 4a side of the light guide plate 4 on the front end side of the insertion into the frame 2,
And, it is provided as a narrow ridge shape having a substantially U-shape over three sides, two sides parallel to the insertion direction. The height provided is the same as that obtained by integrating the thickness of the diffusion plate 3 by the required number, or slightly higher.

When assembling the backlight device 1 using the light guide plate 4 configured as described above, first, the diffusion plate 3
Is set to have an area corresponding to the light emitting surface 4a surrounded by the convex portion 4b, and the necessary number of sheets are stacked on the light emitting surface 4a, and then the light guide plate 4 and the opening 2a are connected to the frame 2 through the opening 2a. Insert inside.

In this way, when the light guide plate 4 is inserted, on the surface on the light emission surface 4a side of the light guide plate 4, the frame 2 comes into contact with the apex of the projection 4b, and the light emission The dimension set as the height of the projection 4b is secured as a gap between the surface 4a and the inner surface of the frame 2.

Therefore, the diffusion plate 3 has a size smaller than the height of the projections 4b even when a predetermined number of the diffusion plates 3 are stacked.
In addition, since the light guide plate 4 is inserted into the frame 2 together with the light guide plate 4, there is no rubbing with the light guide plate 4 and the displacement of the diffuser plate 3, which tends to occur during assembly due to this, can be prevented. It will be.

Further, since the necessary and sufficient dimensions are ensured by the projections 4b, even when the light guide plate 4 undergoes thermal expansion due to a temperature rise during use, for example, the diffusion plate 3 can be mounted on the frame 2
And the light guide plate 4 does not receive excessive stress. Therefore, the deformation of the prism cut of the diffusion plate 3 caused by the stress does not occur, and the performance does not deteriorate during the use process.

Further, according to the present invention, the projection 4b is
The three sides of the front end side of insertion into the frame 2 and the two sides parallel to the insertion direction are provided in a substantially U-shape, so that the rear end side in the insertion direction is released. Therefore, even if the light guide plate 4 is bent or bent by the diffusion plate 3, the light guide plate 4 can be connected to the frame 2.
It can be replaced from the rear end side without taking it out, and the process for correction is also simplified.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the convex portion 4c is provided in a frame shape around four sides of the light emitting surface 4a of the light guide plate 4. The height of the projection 4c is the same as in the previous embodiment.
Therefore, the diffusion plate 3 cannot be replaced after the assembly, but on the other hand, the positioning of the diffusion plate 3 is ensured, so that the diffusion plate 3 does not fall off during use.

FIG. 4 shows still another embodiment of the present invention. In this embodiment, the projections 4d are formed as bosses provided at the four corners of the light guide plate 4. In the case of this embodiment, the accuracy of positioning with respect to the diffusion plate 3 and the like are lower than those of the previous embodiments, but since the configuration is simple, the configuration of the light guide plate 4 is simplified and the implementation is inexpensive. There are advantages that can be done.

Since the light guide plate 4 is required to have high accuracy in flatness, smoothness, etc., in order to prevent sink marks or the like during molding, the area of the cross section must be changed as much as possible. It is preferable to have no shape. Therefore,
In this embodiment, since the convex portion 4d can be minimized,
There is an advantage in that the precision is not impaired by the occurrence of sink marks or the like.

[0020]

As described above, according to the present invention, at the outer edge of the light guide plate on the light emitting surface side, there is provided a projection for providing a required number of gaps of the diffusion plate between the light guide plate and the frame. In the past, there was no space for the installation of the diffuser plate because the backlight device was used, and this caused the frame and the light guide plate to be caught between the frame and the light guide plate during assembly, resulting in defective products. Although the prism cut was deformed due to the thermal expansion of the light guide plate in the process of use and the prism cut was deformed and the performance was reduced, the projections were provided to secure the dimensions for installing the diffusion plate. Thus, the occurrence of scratches or deformation is eliminated, and this type of backlight device has extremely excellent effects in improving the productivity and performance.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a backlight device according to the present invention in a partially exploded state.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view showing another embodiment of the backlight device according to the present invention in a main part.

FIG. 4 is a perspective view showing still another embodiment of the backlight device according to the present invention in a main part.

FIG. 5 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Backlight device 2 ... Frame 2a ... Opening 2b ... Window 3 ... Diffusion plate 4 ... Light guide plate 4a ... Light emission surface 4b, 4c, 4d ... Convex part

Claims (1)

[Claims] 1. A backlight device in which a film-like diffuser plate and a thick plate-like light guide plate are inserted through a thin frame having an opening on a side surface thereof from the opening, and the light guide plate emits light. A backlight device, wherein a projection is provided at an outer edge on a surface side to provide a gap corresponding to a required number of the diffusion plates between the frame and the frame.