JPH07128526A - Light transmission plate device - Google Patents

Abstract

PURPOSE:To effectively randomly reflect the light falling onto the opposite surfaces and flanks of a light transmission plate and to further improve luminance by composing the reflection plate to be disposed at the end face, exclusive of the light introducing end face, of the light transmission plate of a foam. CONSTITUTION:This light introducing plate device has the light transmission plate 11, of which the one surface is formed as a light emitting surface 11a and the other surface as a reflection surface 11b. A light source 15 is adjacently arranged outside the light introducing end face 14 of the light transmission plate 11 and the end face, exclusive of the light introducing end face 4 is provided with the reflection plate 20 for reflecting the light of the light source 15. Since the reflection plate 20 is composed of the foam, the surface of the reflection plate 20 has an intricately rugged surface as the surface of the reflection plate 20 is the section of the bubble in the foam. The irregularly reflected light irregularly reflected by the reflection plate 20 has a higher ratio of falling onto the irregular reflection part disposed on the reflection surface 11b than the specularly reflected light and part of the light diffused and emits light on the light emitting surface 11a. Then, the luminance of the light emitting surface 11a is eventually improved.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a liquid crystal backlight,
The present invention relates to a light guide plate device used for a backlight for signs such as advertisements and a lighting device.

[0002]

2. Description of the Related Art In a light guide plate device, as shown in FIG. 7, a light guide plate 1 made of a transparent resin is provided with a light diffusing plate 2 made of, for example, a polycarbonate film having irregularities on a light emitting surface 1a, and a reflecting surface. 1b is provided with a first reflection plate 3 made of a white film such as polyethylene terephthalate, and a rod-shaped light source 5 is arranged adjacent to the outside of the light-introducing end face 4 of the light guide plate 1 so that the light from the light source 5 does not leak to the outside. There is a lamp reflector 6 arranged so as to cover 5 and the light introducing end face 4.

The reflecting surface 1b of the light guide plate 1 is made of silica, titanium oxide or the like so that the light entering the light guide plate 1 from the light source 5 can be effectively reflected by the reflecting surface 1b and emitted by the light emitting surface 1a. An irregular reflection section 7 formed by dot-printing ink containing a diffusing agent is provided. In addition, an end surface of the light guide plate 1 other than the light introducing end surface 4, that is, a facing surface (hereinafter, simply referred to as “opposing surface”) 8a of the light introducing end surface 4 and both side surfaces (hereinafter, simply referred to as “side surface”) 8b of the light guide plate 1 are provided. , 8b are provided with a second reflecting plate 9 for reflecting the light hitting the surfaces 8a, 8b back into the light guide plate 1. As the second reflector 9, a metal vapor deposition film in which a metal such as silver or aluminum is vapor deposited on a polyester film is generally used.

[0004]

In such a light guide plate device, the light from the light source 5 is incident from the light introducing end face 4 and is diffusely reflected when hitting the irregular reflection portion 7, and the irregular reflection light is diffused.
Diffuse light emission at. Further, the light hitting the facing surface 8a or the side surface 8b is reflected by the second reflecting plate 9, and when the reflected light hits the irregular reflection portion 7, it is diffusely reflected and diffused by the diffuser plate 2 to emit light.

Here, when the second reflector 9 is a metal vapor deposition film, since it reflects specularly with a constant reflection angle, the ratio of the reflected light to the irregular reflection portion 7 depends on the reflection angle and the position of the irregular reflection portion 7. Decided. This means that only a part of the light hitting the facing surface 8a or the side surface 8b of the light guide plate 1 is diffusely reflected by the diffuse reflection portion 7, and thus it is not possible to contribute to the improvement of the brightness. In particular, the area ratio of the irregular reflection portion 7 (the area ratio of the irregular reflection portion 7 to the entire area of the reflection surface 1b) becomes remarkable in the vicinity of the light introduction end face 4. It is also possible to increase the area ratio of the irregular reflection portion 7 in order to effectively diffuse the specular reflection light from the second reflection plate 9, but the area ratio of the irregular reflection portion 7 is irrespective of the distance from the light source 5. Since it is selected from the viewpoint that the luminance of 1a should be uniform, the area ratio of the irregular reflection portion 7 cannot be increased unnecessarily.

The present invention has been made in view of the above technical background.
It is an object of the present invention to provide a light guide plate device in which the light hitting the facing surface and the side surface of the light guide plate is effectively diffused by changing the configuration of the second reflecting plate to further improve the brightness.

[0007]

SUMMARY OF THE INVENTION The inventor of the present invention uses the light that strikes the facing surface and the side surface of the light guide end surface of the light guide plate as the second light.
The present invention has been completed by paying attention to the fact that the diffuse reflection by the reflection plate results in higher brightness than the case of specular reflection. That is, the light guide plate device of the present invention includes the light guide plate 11 having one surface as the light emitting surface 11a and the other surface as the reflecting surface 11b, and the light source 15 is disposed adjacent to the outside of the light introducing end surface 14 of the light guide plate 11. The light source 15 is provided on an end face other than the light introducing end face 14.
In the light guide plate device provided with the reflection plate 20 that reflects the light, the reflection plate 20 is made of foam.

[0008]

Function: Reflector 2 used in the light guide plate device of the present invention
Since 0 is made of foam, the surface of the reflection plate 20 is a cross section of the bubbles in the foam and has a complicated uneven surface. Therefore, when the light incident on the light guide plate 11 strikes the end faces other than the light-introducing end face 14, that is, the reflecting plate 20 provided on the facing face or the side face, it is diffusely reflected by the uneven surface of the reflecting plate 20 surface. The diffuse reflection light diffusely reflected by the reflecting plate 20 hits the diffuse reflection portion provided on the reflection surface 11b at a higher rate than the specular reflection light, and a part of the light diffusely emits on the light emitting surface 11b. Therefore, the light emitting surface 11
This leads to an improvement in brightness in a. Furthermore, light that has not been reflected by the surface of the reflector 20 and has proceeded to the inside can also be diffusedly reflected by the bubbles inside the foam, which contributes to an increase in reflectance and an improvement in brightness.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the light guide plate device of the present invention. In this light guide plate device, a diffusion plate 12 is provided on a light emitting surface 11a of a transparent resin light guide plate 11, a first reflecting plate 13 is provided on a reflecting surface 11b, and a light introducing end surface 1 of the light guide plate 11 is provided.
4 A rod-shaped light source 15 is arranged adjacent to the outside, and a lamp reflector 16 is arranged so as to cover the light source 15 and the light introducing end face 14 so that the light of the light source 15 does not leak to the outside. In order to make the light incident on the light guide plate 11 from the light source 15 effectively be emitted on the light emitting surface 11a, the reflecting surface 11b of the light guide plate,
An irregular reflection section 17 is provided by dot-printing an ink containing a diffusing agent such as silica or titanium oxide. Also,
End surfaces of the light guide plate 11 other than the light introducing end surface 14, that is, the facing surface 18a and both side surfaces 18b of the light introducing end surface 14,
A second reflector 20 is provided on 8b.

The second reflector 20 is made of various foams such as polyester foam, polystyrene foam and polyurethane foam. The foaming form may be either continuous foaming or independent foaming. Although it becomes opaque due to the presence of many and complex bubbles 20a, it is preferable to use a white foam in order to increase the reflectance. The second reflection plate 20 may be provided on the light guide plate 11 as it is by an appropriate method, or may be combined with a protective film for reinforcement. For example, in the light guide plate device shown in FIG. 2, both surfaces of the second reflection plate 20 are sandwiched by the first protective film 22 and the second protective film 23, and the adhesive 21 is applied onto the first protective film 22 to form an adhesive. The second reflection plate 20 is attached to the light guide plate 11 by 21. In this case, the first protective film 2
As 2, a transparent film of polyester, polycarbonate, or the like is used because it is necessary to transmit light.
The second protective film may be of the same type as the first protective film, or may be of a different type. In addition, the second reflector 20 is attached to the protective films 22 and 23.
When used in combination with, the total thickness of the second reflector 20 and the protective films 22 and 23 is preferably 200 μm or less from the viewpoint of device miniaturization. As the adhesive 21, a transparent adhesive such as an acrylic adhesive is used.

In the light guide plate device having the second reflection plate 20 having such a structure, the facing surface 18a of the light guide plate 11 is formed.
And the light which hits the side surface 18b is reflected as follows. That is, since the surface of the second reflection plate 20 has a complicated uneven surface in the cross section of the large number of bubbles 20a forming the foamed body, most of the incident light is diffusely reflected here. Further, the light that has propagated to the inside without being reflected on the surface is also reflected at the interfaces of many bubbles 20a existing inside. Therefore, the reflection of the second reflection plate 20 as a whole is diffuse reflection in which light is reflected at various angles. In the device shown in FIG. 2, the adhesive 2 is provided between the second reflection plate 20 and the light guide plate 11.
Although the first protective film 22 and the first protective film 22 are present, there is no problem because light passes through them.

As a result of the diffused reflection of the light striking the second reflection plate 20 in this manner, the following effects are obtained. That is, as shown in FIG. 3, the light diffusely reflected by the second reflection plate 20 (shown by the solid line in FIG. 3) has a high proportion of hitting the irregular reflection portion 17. On the other hand, when the light is specularly reflected by the second reflection plate (shown by a dotted line in FIG. 3), the probability of hitting the irregular reflection section 17 is low because the reflection angle is constant. This is
When the second reflection plate 20 is made of foam, compared with the case where the second reflection plate 20 is made of a metal deposition film, the second reflection plate 20
This means that the proportion of the light that hits the diffuse reflection portion 17 is diffusely reflected by the diffuse reflection portion 17, and further, the diffuse reflection light of the second reflection plate 20 can be directly emitted on the light emitting surface 11b, which means that the brightness is increased. It should be noted that, even if a white film having an uneven surface is diffusely reflected, it is difficult to reflect the light that has not been reflected on the surface and has proceeded to the inside of the second reflection plate 20, that is, the reflectance is slightly different. The second reflector 20 made of foam is superior in that it is inferior and that the foam can more easily produce a more complicated uneven surface.

Next, the effects of the present invention will be described based on specific examples. The light guide plate device having the configuration of FIG. 2 was used as an example of the present invention. Here, the second reflector 20
Is composed of a white polyester film. The first protective film 22 and the second protective film 23 sandwiching both sides of the second reflector 20 are both transparent polyester films. Second reflector 20 and protective film 2
The total thickness of 2 and 23 is 200 μm. With respect to such a light guide plate device, the brightness was measured at 25 points on the effective light emitting surface, and the result is displayed in FIG. The brightness average of 25 points is 1
It was 252 cd / m ² .

On the other hand, as a conventional example, the luminance was measured at 25 points on the effective light emitting surface of a light guide plate device using a metal vapor deposition film having a thickness of 100 μm for the second reflecting plate. The measured brightness is displayed in FIG. The brightness average of 25 points is 1
It was 161 cd / m ² . As a comparative example, the brightness was measured at 25 points on the effective light emitting surface of a light guide plate device using a single unfoamed white polyester film having a thickness of 200 μm for the second reflecting plate. The measurement results are shown in FIG. The average brightness at 25 points was 1205 cd / m ² .

As can be seen from the above results, the product of this embodiment in which the second reflector is made of foam has a brightness as high as 8% as compared with the conventional product in which the second reflector is specularly reflected. became. In addition, the brightness is 4% compared to the comparative example product that diffusely reflects.
Has improved. This means that since the foam has a more complicated uneven surface, diffuse reflection is performed more efficiently, and light that is not reflected on the surface can also be diffusely reflected by the bubbles inside the foam in this example product. Thought to be due to.

In the above embodiment, all the end surfaces of the light guide plate other than the light introduction end surface, that is, both side surfaces and the opposing surface are provided with the second surface.
Although the reflection plate is provided, the brightness is improved to some extent even if it is provided only on the facing surface.

[0017]

According to the light guide plate device of the present invention, since the reflecting plate provided on the end surface other than the light introducing end surface of the light guide plate is made of foam, the light hitting the end surface can be diffusely reflected. Therefore, the light striking the end face can not only be directly emitted on the light emitting surface, but also is hardly reflected by the arrangement of the irregular reflection portion and is diffusely reflected by the irregular reflection portion, and the irregular reflection light is emitted on the light emission surface. Therefore, the brightness can be improved.

Further, the reflector made of foam is excellent in that it can reflect the light that has not been reflected on the surface and has proceeded to the inside, that is, the reflectance, as compared with a simple white film which is not foamed. It is also preferable from the viewpoint of manufacturing that a complicated uneven surface can be easily obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view (a) and a plan view (b) of a light guide plate device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of the vicinity of a second reflection plate of the light guide plate device of this embodiment.

FIG. 3 is a diagram for explaining the operation of the light guide plate device according to the present embodiment.

FIG. 4 is a diagram showing a result of measuring the luminance of the light guide plate device according to the present embodiment.

FIG. 5 is a diagram showing a result of measuring the luminance of a conventional light guide plate device.

FIG. 6 is a diagram showing a result of measuring a luminance of a light guide plate device of a comparative example.

FIG. 7 is a side sectional view (a) and a plan view (b) of a conventional light guide plate device.

[Explanation of symbols]

 11 Light guide plate 11a Light emitting surface 11b Reflecting surface 14 Light introducing end surface 15 Light source 17 Diffuse reflecting portion 20 Second reflecting plate

Claims (1)

[Claims] 1. A light guide plate (11), one surface of which is a light emitting surface (11a) and the other surface of which is a reflecting surface (11b), the light guide plate (11) being located outside a light introducing end surface (14). Light source (1
5) Adjacent to each other, and a reflection plate (20) for reflecting the light of the light source (15) is provided on an end surface other than the light introduction end surface (14), wherein the reflection plate (20) is a foam. A light guide plate device comprising: