JP2002328239A - Light transmission plate and illumination unit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of bright-lines by concentration of rays at the corner of a light transmission plate. SOLUTION: The corner C1 on at least the rear surface side of the light transmission plate 1 which guides the light from a light source 2 from the side 1c and emits the light to a front surface side 1a is right angled or the corner C1 at least at its rear surface side 1b is rounded (R) within 0.1 mm or is chamfered (C) within 0.1 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light guide plate used for a display device such as a liquid crystal panel and an illumination unit using the same.

[0002]

2. Description of the Related Art In recent years, display devices for information devices such as notebook personal computers and word processors, and display devices for video devices such as portable televisions, video movies, and car navigation systems have become lighter and smaller and thinner. Liquid crystal display devices have been widely used because of their low power consumption and low power consumption. Many of these liquid crystal display devices have a configuration in which illumination light is applied from behind a display element by a built-in illumination unit in order to realize a bright display screen.

In this lighting unit, an edge light system (also referred to as a light guide plate system) in which a light guide plate is placed on the back surface of a display panel and a light source is disposed on an end surface of the light guide plate has been proposed to reduce the thickness and uniformity of luminance of a light emitting surface. It has a feature of being superior, and an edge light method is often adopted as a method of a liquid crystal unit of a liquid crystal display device used for a notebook personal computer or the like, giving priority to thinness. In liquid crystal display devices used in portable televisions and car navigation systems, etc., in order to achieve both thinness and brightness,
In many cases, an edge light method using two or more fluorescent discharge tubes, or an edge light method using an L-shaped fluorescent discharge tube or a U-shaped fluorescent discharge tube is used.

FIG. 4 shows a liquid crystal display device L using an edge light type illumination unit using a conventional fluorescent discharge tube 2.
It shows an example of D, and is composed of a lighting unit UT and a liquid crystal display device LD in which a liquid crystal panel 5 and the like are mounted on the lighting unit UT. The illumination unit UT includes a light guide plate 1 that illuminates the liquid crystal panel 5, and a reflection sheet 3 that is arranged along the back surface of the light guide plate 1 and reflects light from the fluorescent discharge tube 2 toward the liquid crystal panel 5.

[0005]

However, the corner portion C1 of the conventional light guide plate 1 has a relatively large chamfer (C).
And a circular arc (R shape), but the light ray emitted from the light source 2 is concentrated at that portion, and the bright line is generated. There was a problem that display quality was impaired.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light guide plate for preventing the generation of bright lines due to the concentration of light rays at corners, and an illumination unit using the same.

[0007]

According to a first aspect of the present invention, there is provided a light guide plate for guiding light from a light source from the side to emit light to a front surface side. The corner portion on the side is a right angle.

According to the present invention, since the corner portion on the back surface side of the light guide plate is at a right angle, the corner portion does not become a planar lens, so that the light emitted from the light source is not concentrated. This will prevent the generation of bright lines.

According to a second aspect of the present invention, there is provided a light guide plate for guiding light from a light source from the side and emitting the light to the front surface side, wherein at least a corner portion on the rear surface side is a radius (R).
It is characterized by being within 0.1 mm or chamfering (C) within 0.1 mm.

According to the present invention, by setting the corner portion on the back surface side of the light guide plate to the above range, the corner portion is hardly formed like a planar lens, and the bright line on the front surface side of the light guide plate is reduced. The occurrence is actually suppressed to such an extent that there is almost no effect.

[0011] The lighting unit according to claim 3 of the present invention comprises:
In a lighting unit including a light source and a light guide plate that guides light from the light source from the side and emits the light to the front surface side, at least a corner of the light guide plate on the back surface side is at a right angle.

According to the present invention, since the corners of the light guide plate are at right angles, the corners do not look like planar lenses, so that light emitted from the light source is not concentrated, and the generation of bright lines is reduced. Will be prevented.

[0013] The lighting unit according to claim 4 of the present invention comprises:
In a lighting unit including a light source and a light guide plate that guides light from the light source from the side and emits the light to the front side, at least a corner portion on the back surface side of the light guide plate has a radius (R) within 0.1 mm or a chamfer (C). ) It is characterized by being within 0.1 mm.

According to the present invention, by setting the corner portion on the back surface side of the light guide plate to the above range, the corner portion is hardly like a planar lens, and the bright line on the irradiation surface side of the illumination unit is provided. Is suppressed to such an extent that there is almost no effect in practice.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the present embodiment comprises a lighting unit UT and a liquid crystal display device LD in which a liquid crystal panel 5 and the like are mounted on the lighting unit UT. The lighting unit UT is an edge light type lighting unit (backlight device), and includes a light source 2, a light guide plate 1 that is arranged close to the light source 2 and guides light from the light source 2, and a back surface of the light guide plate 1. A reflection sheet 3 arranged along 1b;
A reflector that includes the light source and reflects light from the light source toward the incident end face;

The light guide plate 1 is disposed close to the fluorescent discharge tube 2 and guides light from the fluorescent discharge tube 2, and has optimal optical characteristics represented by transmittance and refractive index required for light transmission. It is formed of a material such as acrylic or polycarbonate.

The corner C1 of the back side 1b of the light guide plate 1, that is, the back side 1b of the light guide plate 1 and one side 1c
Is a right angle (90 degree angle).
In a liquid crystal display device LD including a conventional lighting unit (backlight device), as shown in FIG. 4, if the corner portion C1 of the light guide plate 1 has an arc shape (R shape) or a chamfer, this arc shape is obtained. The light from the light source 1 concentrates at the corner C1 because the chamfered portion acts in the same way as the lens, and as a result, the concentrated light becomes a bright line, appears on the display of the liquid crystal display device LD, and impairs the display quality. It is. But,
When the corner C1 on the back surface 1c of the light guide plate 1 is at a right angle as in the present embodiment, the corner C1 does not become planar (one point in cross section), and acts like a lens. , And the generation of bright lines on the surface side of the light guide plate 1 hardly occurs. As a result, the display quality of the liquid crystal display device LD is improved.

Here, as shown in FIG. 2, the radius R of the corner C1 on the back surface side 1b of the light guide plate 1 may be within R0.1 mm. Further, as shown in FIG.
The chamfer C of the corner portion C1 on the back surface side may be within 0.1 mm. By setting the corner portion C1 of the back surface side 1b of the light guide plate 1 in the above range, the corner portion C1 hardly acts as a planar shape, and almost no bright line is generated on the front surface side 1a of the light guide plate 1.

The surface side (outgoing surface side) 1a of the light guide plate 1 includes a flat surface (also called a flat type) and a saw-toothed prism processed (also called a wedge type). In the flat type, the corner C on the back side 1b
It is preferable that not only 1 but also the corner C2 on the exit surface side 1a be a right angle or within the above-mentioned set range (see FIG. 1).

As the reflection sheet 3, a white resin film having a high reflectance is used. The reflection sheet 3 has a role of returning light that goes out from the back surface of the light guide plate 1 back into the light guide plate 1 and increasing illumination light emitted from the light emitting surface.

The reflector 4 allows the light of the light source 2 to be efficiently incident on the incident end face of the light guide plate 1, and is bent in a U-shaped cross section or a U-shaped cross section so as to surround the light source 2, and is formed on one side ( The lower end is disposed so as to cover the back surface of the reflection sheet 3.

In the illumination unit UT having such a configuration, the liquid crystal display panel 5 is disposed on the irradiation surface side (upper side in the drawing), and a rear cover or a metal front frame is attached to the liquid crystal display device UT. Become. In the liquid crystal display device LD, the light emitted from the light source 2 is directly or condensed by the reflector 4 and guided to the light guide plate 1, and is emitted from the emission surface on the front surface side. The liquid crystal display panel 5 is transmitted evenly.
The characters and images projected on the display surface of are displayed.

As described above, in the present embodiment, the lighting unit U
Although the description has been made using the liquid crystal display device LD in which the liquid crystal display panel 5 and the like are mounted on T, the present invention is also applicable to display devices and the like other than the liquid crystal display device LD. Applicable.

[0025]

According to the light guide plate of the present invention, since the corners of the light guide plate are at right angles, it is possible to eliminate the concentration of light rays that would become bright lines on the exit surface side of the light guide plate.

In the lighting unit according to the present invention, since the corners of the light guide plate are at right angles, the concentration of light rays that become bright lines is eliminated, and the display quality of a display device such as a liquid crystal display device is improved.

[0027]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a lighting unit according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a lighting unit according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a lighting unit according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional lighting unit.

[Explanation of symbols]

 Reference Signs List 1 light guide plate 1a front side 1b back side 1c side 2 light source 5 liquid crystal panel C1 back side corner C2 front side corner θ1, θ2 corner angle

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court II (reference) // F21Y 103: 00 F21Y 103: 00

Claims (4)

[Claims] 1. A light guide plate which guides light from a light source from the side and emits the light to the front surface, wherein at least a corner portion on the back surface is a right angle. 2. A light guide plate which guides light from a light source from the side and emits the light to the front side, wherein at least a corner portion on the back side is within 0.1 mm of a radius (R) or within 0.1 mm of a chamfer (C). A light guide plate, characterized in that: 3. An illumination unit comprising a light source and a light guide plate for guiding light from the light source from the side and emitting the light to the front surface side, wherein at least a corner of the light guide plate on the rear surface side is at a right angle. unit. 4. An illumination unit comprising a light source and a light guide plate arranged close to the light source to guide light from the light source, wherein at least the back surface corner of the light guide plate has a radius (R) of 0.1 mm or less. Or chamfering (C) 0.1mm
A lighting unit characterized by being within.