JP2562315Y2 - Light diffusion plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a light diffusion plate suitable for use as a backlight of a liquid crystal panel or the like.

[Problems to be solved by conventional technology and device]

2. Description of the Related Art In a lighting device serving as a surface light source for a backlight such as a liquid crystal, a diffusion plate is used to diffuse light from the light source and irradiate uniform light from behind the liquid crystal. Sixth
FIG. 1 shows a configuration example of a conventional lighting device.
Is a light source composed of a pair of linear fluorescent lamps, 2 is a curved reflector formed near the light source 1, and 3 is a light source 1.
This is a diffuser plate that is flatly formed on both sides for projecting the direct light from the LCD and the indirect light reflected by the reflector 2 onto, for example, a liquid crystal panel P as an illuminated body. The diffusion plate 3 diffuses light passing therethrough by the action of diffusion particles mixed therein.

However, in the case of the configuration of FIG. 6, it can be said that the illumination light having uniform luminance characteristics is obtained as a surface light source by the diffusion plate 3, but if the distance between the light source 1 and the diffusion plate 3 is small, As is clear from FIG. 7 showing the luminance characteristics,
The brightness of the portion corresponding to the light source 1 is significantly increased locally. Therefore, there is a problem with such uneven luminance characteristics as a surface light source.

The present invention has been made in view of the above circumstances, and has as its object to provide a light diffusing plate suitable for this type of lighting device capable of uniformly illuminating an object to be illuminated.

[Means and actions for solving the problem]

The light diffusing plate according to the present invention includes a diffusing plate body whose only surface opposite to the light source side is a textured surface, and a cover that is in close contact with the textured surface of the diffusion plate body.

Therefore, the light that enters the diffusion plate body from the light source side and is irradiated to the illuminated body side is diffused by passing through the inside of the diffusion plate body, and the diffused light is further diffused and irregularly reflected by the textured surface, and the light Since the luminance characteristics on the diffusion plate are made more uniform, illumination light without unevenness on the illuminated object can be obtained. In addition, according to the present invention, the textured surface of the diffusion plate main body and the flat cover are brought into close contact with each other, so that the air layer is entirely dispersed between the diffusion plate main body and the cover. It exists in a state.

Therefore, the light emitted from the light source first enters the diffusion plate main body from the light source side surface of the diffusion plate main body, and is diffused and diffused by the diffusion particles mixed in the diffusion plate main body. From the surface, the light is once emitted to the air layer or directly incident to the cover.

The light emitted from the diffusion plate body to the air layer is emitted in various directions with the traveling direction being bent at the interface between the textured surface and the air surface, and is directly incident on the cover from the diffusion plate body. Light is refracted or reflected variously at the contact portion between the textured surface of the diffusion plate body and the cover.

Furthermore, of the light emitted to the air layer, the light directed to the cover is variously refracted or reflected at the interface between the air layer and the planar cover.

The light reflected at the interface between the air layer and the cover and the light reflected at the contact portion between the textured surface of the diffuser body and the cover are returned to the diffuser body again, and Some light is reflected by the textured surface of the diffuser body, and some other light is re-entered into the diffuser body and diffused particles in the diffuser body and the light source side surface of the diffuser body A part of the light is returned to the cover side again by being reflected at the interface between the air layer and the air layer, and the refraction and reflection as described above are repeated in the middle of the light.

Through such refraction and reflection, the light emitted from the light source is greatly disturbed in its progress and dispersed over a wide range.

Therefore, according to the present invention, the luminance distribution can be made more uniform as compared with the conventional diffusion plate.

In addition, according to the present invention, since a flat cover is provided on the diffusion plate main body whose entire surface opposite to the light source has been textured, light transmitted through the diffusion plate main body is reflected by the textured surface. The traveling direction of the flat cover varies, but at the stage of transmission through the flat cover, only light having an incident angle with respect to the flat cover within a certain range is incident on the flat cover. Then, only light that passes through the planar cover and is within a certain range of an incident angle with respect to the interface with air is emitted to the outside, while light not emitted to the outside is reflected and returned. Further, part of the light is reflected by the textured surface of the diffusion plate body, the diffusion particles in the diffusion plate body, the interface between the plane of the diffusion plate body and the air layer, and returns to the cover side again. The light is further refracted or reflected repeatedly until the incident angle with respect to the flat cover falls within a certain range. Also,
Light that is emitted from the textured surface of the diffuser body in a direction in which the angle of incidence on the flat cover is out of a certain range is reflected back, and some of the light is incident on the flat cover. The refraction or reflection is repeated as described above until the angle is within a certain range, and the traveling direction is changed, so that the light travels in a required direction.

Therefore, according to the present invention, it is possible to eliminate the emission of light in a direction that is not absolutely necessary for irradiating the object, and to irradiate the illumination object with increased light use efficiency.

Also, in the present invention, the entire surface of the diffusion plate main body on the side opposite to the light source is a textured surface and the cover is flat, so even if the diffusion plate main body and the cover are overlaid and fixed integrally,
The air layer can be present in such a state that the air layer is entirely dispersed between the diffusion plate body and the cover, and the air layer generated between the diffusion plate body and the cover is partially biased, It is possible to prevent large variations in the formation of the air layer.

That is, according to the present invention, a substantially uniform light diffusing effect can be obtained over the entire surface of the light diffusing plate, and the width of variation of the light diffusing effect for each product can be reduced.

In the present invention, if the cover is made of a diffusion plate,
Light incident on the inside of the cover plate while being dispersed over a wide range is further diffused, so that the luminance distribution can be further uniformed.

Further, according to the present invention, when the brightness is more important than the uniformity of the luminance distribution, the cover can be formed of a transparent plate.

In the conventional diffusion plate, when the transparent plate and the diffusion plate main body are overlapped and fixed integrally, a thin air layer is formed between the transparent plate and the diffusion plate main body, and the Newton ring may be visually recognized. Therefore, it is inevitable that a certain distance or more must be provided between the transparent plate and the diffusion plate main body, and it cannot be applied to a thin surface light source device.

In this regard, according to the present invention, since the entire surface of the diffusion plate body on the cover side is textured, even if the cover and the diffusion plate body are overlapped and fixed integrally, the gap between the cover and the diffusion plate body is The thickness of the air layer is random in the entire area between the cover and the diffuser body, and the Newton ring is not visible.

Therefore, according to the present invention, since the cover and the diffusion plate main body can be overlapped and fixed integrally, the cover can be used for a thin surface light source device, and the light diffusion plate itself can be easily manufactured.

〔Example〕

Hereinafter, a first embodiment of the light diffusing plate according to the present invention will be described with reference to FIGS. 1 to 3. In the drawing, reference numerals 1 and 2 denote a light source and a reflection plate configured in the same manner as in the conventional example, and 3 'denotes a diffusion plate body in which the entire surface opposite to the light source 1 is formed as a textured surface 3'a. Reference numeral 4 denotes a flat cover made of a diffusion plate formed in the same manner as in the conventional example. The liquid crystal panel P to be illuminated is arranged on the opposite side of the cover 4 from the light source 1, and the cover 4 is in close contact with the above-mentioned textured surface 3'a (the gap g = 0 in FIG. 2). The diffusion plate body 3 '
In addition, diffused particles mixed at a predetermined ratio are uniformly distributed inside the cover 4.

Since the light diffusing plate according to the present invention is configured as described above, the light source light incident on the diffusing plate body 3 'via the light source 1 and the reflecting plate 2 is diffused while passing through the inside of the diffusing plate body 3'. Further, after that, the diffused light is dispersed when emitted from the embossed surface 3'a toward the cover 4, and a part of the light is diffusely reflected to the inner surface side and then dispersed and emitted again. Uniform illumination light is obtained over the entire area 3 '. The illumination light further reaches the liquid crystal panel P via the cover 4, but the surface luminance is further uniformed by the diffusion effect of the cover 4 to provide illumination light without unevenness. That is, the light emitted from the light source 1 first enters the diffusion plate main body 3 'from the light source side surface of the diffusion plate main body, and is diffused by diffusion particles mixed in the diffusion plate main body 3'. From the embossed surface 3'a, the light is once emitted to the air layer or directly incident on the cover 4.

The light emitted from the diffusion plate body 3 'to the air layer is emitted in various directions with the traveling direction being bent at the interface between the embossed surface 3'a and the air layer, while the light is directly emitted from the diffusion plate body 3'a. The light incident on the cover 4 is applied to the textured surface 3'a of the diffusion plate body 3 '.
The light is variously refracted or reflected at the contact portion between the cover and the cover 4.

Further, of the light emitted to the air layer, the light directed to the cover 4 is variously refracted or reflected at the interface between the air layer and the flat cover 4.

The light reflected at the interface between the air layer and the cover 4 and the light reflected at the contact portion between the textured surface 3'a of the diffusion plate main body 3 'and the cover 4 are returned to the diffusion plate main body 3' again, Part of the returned light is reflected by the textured surface 3'a of the diffusion plate main body 3 ', and another part of the light is re-entered into the diffusion plate main body 3', and is diffused. Some of the light is returned to the cover 4 again due to, for example, the diffusion particles in the inside or the reflection at the interface between the light source side surface of the diffusion plate main body 3 ′ and the air layer. And refraction and reflection are repeated.

Through such refraction and reflection, the light emitted from the light source 1 is greatly disturbed in its progress and dispersed over a wide range.

Therefore, according to the present invention, the luminance distribution can be made more uniform as compared with the conventional diffusion plate.

Further, according to the present invention, since the flat cover 4 is provided on the diffusion plate main body 3 ′ whose entire surface opposite to the light source 1 has been textured, light transmitted through the diffusion plate main body 3 ′ Although the traveling direction of the light varies due to the textured surface 3 ′ a, only light having an incident angle with respect to the flat cover 4 within a certain range is transmitted to the flat cover 4 at the stage of transmission through the flat cover 4.
Incident. Then, only the light transmitted through the flat cover 4 and within a certain range of the incident angle with respect to the interface with the air is emitted to the outside, while the light not emitted to the outside is reflected and returned. Further, part of the light is generated by the textured surface 3'a of the diffusion plate main body 3 ', the diffusion particles in the diffusion plate main body 3', and the interface between the plane of the diffusion plate main body 3 'and the air layer. The light is reflected, returns to the cover 4 side, and is further repeatedly refracted or reflected until the incident angle with respect to the flat cover 4 falls within a certain range. Light emitted from the textured surface 3'a of the diffusion plate main body 3 'in a direction in which the angle of incidence on the flat cover 4 is out of a certain range is reflected and returned, and a part of the light is reflected. Is refracted or reflected as described above until the incident angle with respect to the flat cover 4 is within a certain range, and the traveling direction is changed to become light traveling in a required direction.

Therefore, according to the present invention, since the traveling direction of the light emitted to the outside of the cover is corrected to a direction within a certain range, the emission of the light in the direction necessary for irradiating the target object is eliminated. Thus, it is possible to irradiate the illumination target object with increased light use efficiency.

Also, in the present invention, the entire surface of the diffusion plate main body 3 'on the side opposite to the light source is a textured surface 3'a and the cover 4 is flat, so that the diffusion plate main body 3' and the cover 4 are overlapped and integrated. , The air layer can exist between the diffusion plate main body 3 ′ and the cover 4 in a state of being dispersed as a whole between the diffusion plate main body 3 ′ and the cover 4. It is possible to prevent the air layer from being partially biased and the air layer from one product to another from having large variations.

That is, according to the present invention, a substantially uniform light diffusing effect can be obtained over the entire surface of the light diffusing plate, and the width of variation of the light diffusing effect for each product can be reduced.

Further, since the cover and the diffusion plate main body can be overlapped and integrally fixed, the cover can be used for a thin surface light source device, and the light diffusion plate itself can be easily manufactured. The luminance characteristic of the illuminating light with respect to the liquid crystal panel P thus obtained is the third.
As shown in the figure, there is almost no peak characteristic corresponding to the light source 1 and the brightness is uniform as a whole. Therefore, the liquid crystal panel P can exhibit excellent performance as a display device of this type due to the uniformed backlight.

As described above, the illumination light can be made uniform by the diffusion plate main body 3 'itself. However, by providing the cover 4 made of the diffusion plate in close contact, the uniformity can be achieved with almost no reduction in luminance. Further, since the cover 4 exerts a dust-proofing effect on the grained surface 3'a, it is possible to completely eliminate a decrease in luminance and luminance unevenness which may be caused by dust adhering to the grained surface 3'a.

Note that the example shown in FIG. 4 shows a case where the textured surface 3'a of the diffusion plate main body 3 'is arranged on the light source 1 side and the cover 4 is adhered to the textured surface 3'a. The luminance characteristics according to this example are shown in FIG. 5, but the degree of uniformity of the luminance of the illumination light in this case is inferior to the luminance characteristic of FIG. 3 according to the above-described embodiment. Is not preferred. Therefore, the optimal condition for obtaining illumination light having uniform luminance characteristics is that the textured surface 3'a of the diffusion plate main body 3 'is arranged on the side opposite to the light source 1 and the diffusion plate is in close contact with the textured surface 3'a. It turns out that it is to arrange a cover that is.

As a second embodiment, although not shown, the cover 4 in the example of FIG. 1 may be formed of a transparent flat plate made of a synthetic resin or the like. Even in this case, illumination light with uniform luminance characteristics can be obtained without any particular decrease in luminance. In the conventional diffusion plate, when the transparent plate and the diffusion plate main body are overlapped and fixed integrally, a thin air layer is formed between the transparent plate and the diffusion plate main body, and the Newton ring may be visually recognized. Therefore, it is inevitable that a certain distance or more must be provided between the transparent plate and the diffusion plate main body, and it cannot be applied to a thin surface light source device.

In this regard, according to the present invention, the cover 4 of the diffusion plate main body 3 'is provided.
Even if the cover 4 and the diffusion plate main body 3 'are overlaid and fixed together, the air layer formed between the cover 4 and the diffusion plate main body 3' is covered with the cover 4 The thickness is random in the entire area between the diffusion plate body 3 'and the Newton ring is not visible. Incidentally, also in the second embodiment, the cover 4 can achieve a dustproof effect on the grained surface 3'a.

In each of the above embodiments, the light source 1 and the reflection plate 2 allow the light from the light source to enter the diffusion plate main body 3 ′. You may do so. Also, the liquid crystal panel P has been described as an example of the illuminated body, but the present invention can be applied to various apparatuses such as a fluoroscopic apparatus and a drafting apparatus.

[Effect of the invention]

As described above, the light diffusion plate according to the present invention has advantages such as obtaining bright illumination light without luminance unevenness as this kind of surface light source and being excellent as a backlight or the like. More specifically, the light diffusion effect of the light diffusion plate can be increased, and the variation in the light diffusion effect can be reduced, the light use efficiency can be increased, and the surface light source device can be made thinner. , And the manufacturing of the diffusion plate itself is facilitated.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an example of a lighting device using the light diffusing plate according to the present invention, FIG. 2 is a partial longitudinal sectional view of the light diffusing plate of FIG. 1, and FIG. FIGS. 4 and 5 are partial longitudinal sectional views showing a modification of the light diffusing plate and graphs showing the luminance characteristics of the illumination light.
6 and 7 are a longitudinal sectional view of a conventional lighting device and a graph showing its luminance characteristics. 1 light source 2 reflector plate 3 'diffuser body 3'
a: Textured surface, 4: Cover, P: Illuminated object.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-43783 (JP, A) Full-open sho 61-14411 (JP, U) Full-open sho-56-47529 (JP, U) Real-open sho 63- 82224 (JP, U) Japanese Utility Model Showa 57-195182 (JP, U) Japanese Utility Model Showa 61-66312 (JP, U) Japanese Utility Model Showa 63-29123 (JP, U)

Claims (3)

(57) [Scope of request for utility model registration] A diffuser disposed between the light source and the object to be illuminated and capable of uniformly diffusing light emitted from the light source to the object to be illuminated; A light diffusing plate, comprising: a diffusion plate main body whose entire surface opposite to the side is textured; and a flat cover arranged so as to be in close contact with the textured surface. 2. The light diffusion plate according to claim 1, wherein said cover is a diffusion plate. 3. The light diffusing plate according to claim 1, wherein said cover is a transparent plate.