JPH01112202A - Light diffusing device - Google Patents

Abstract

PURPOSE:To reduce the loss of the quantity of a light with thin device and a small wattage of a light source and to obtain a light diffusing effect of good uniformity by forming most of a base material with a transparent layer and forming a light diffusing layer on one surface and forming an intermediate layer whose property is intermediate between the transparent layer and the light diffusing layer and forming a reflection layer with a silver thin film layer. CONSTITUTION:Most of a base material 1 consists of a transparent layer 2, and a light diffusing layer 3 is formed on its surface, namely, the light diffusion exit face side, and an intermediate layer 4 whose property is optically intermediate between properties of the diffusing layer 3 and the transparent layer 2 is formed between the diffusing layer 3 and the transparent layer 2. Light in the transparent layer 2 is diffused and projected from the exit face to the outside of the base material 1 more satisfactorily than the absence of the intermediate layer 4. A reflection layer 5 is formed on the rear face of the base material 1, and light sources 10 and 11 are arranged along end faces 8 and 9, and end faces other than end faces facing light sources 10 and 11 are subjected to the light scattering reflection treatment, and thus, the luminance is improve about 1.5-1.8 times as high as an aluminium light diffuser with the thin device and a small wattage of light sources without changing the shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light diffusing device. This type of light diffusion device is used as a surface light source to uniformly illuminate a relatively wide area by receiving light from a light source, and is used as a lighting means for display devices such as advertising lights. Recently, it has been used as a backside illumination means for liquid crystal display devices.

[Prior Art] As a light diffusing device, a light diffusing plate such as a ground glass plate or a milky white glass plate is generally widely used. These are usually used with a light source placed a predetermined distance away from the back side of a light diffusing plate.

Incidentally, in recent years, there has been a demand for downsizing of devices, particularly in liquid crystal display devices, etc., and it is also desired that lighting means be downsized. Therefore, it has become common practice to arrange a light source close to the end face of the diffuser plate and use the end face as a light entrance surface. However, simply arranging a light source on the end face of the ground glass plate or the opalescent glass plate does not provide uniform brightness over the entire surface of the diffuser plate. For this reason,
For example, Japanese Patent Publication No. 58-17957 and Utility Model Publication No. 58
As shown in Publication No. 25405, the back surface is roughened in a hairline shape from the end face on the light source side to the end face (or edge) facing the end face to provide directivity for light transmission within the diffuser plate. It has been proposed to improve the brightness of the diffuser plate at the opposite end surface and to obtain uniform brightness over the entire surface by gradually reducing the thickness of the diffuser plate toward the opposite end surface.

However, this method requires very fine and precise processing on the surface of the transparent substrate, so there are two difficulties in production and cost, and this is not completely satisfactory considering the need for lower cost devices. There wasn't.

In order to solve these problems, the present inventors previously proposed that a transparent light-diffusing layer is formed on all surfaces except at least a part of at least one end surface of a transparent substrate. All light diffusing layers except at least part of the surface
a light diffusing plate on which a light shielding layer is formed; a light reflecting layer on the back side of a transparent substrate; proposed a light diffusing plate in which a light-shielding layer is formed on all the light-diffusing areas except at least a part of the surface of the transparent substrate.
Old name and Utsukai Showa 60-26002 ji"). As a result,
Although considerable improvements have been made, further detailed studies have shown that in these light diffusing plates, some of the incident light is reflected at the light diffusing irradiation surface [11] and is absorbed within the diffusing plate, particularly by the light-shielding layer. It was found that there was a loss of light.

As a means to solve the problem in item 1, the present inventors proposed a light diffusion device as disclosed in Japanese Patent Application Laid-open No. 61-55684. This device is a light diffusion device in which a light diffusion layer is formed on the surface of a base material, and a light reflection layer is formed on the back surface of the base material. By forming a layer having intermediate properties between the transparent layer and the transparent layer, the loss of the amount of light from the light source is small and a light diffusion effect with good uniformity is achieved.

[Problems to be Solved by the Invention] However, as the size of liquid crystal displays has increased, it has become necessary to maximize the surface brightness emitted from the light diffusing device with minimum power consumption (minimum luminous flux). is requested. Meeting this requirement depends on how much light energy, which is determined by the lamp used, can be emitted from the diffusing surface, and it has been desired to provide a light diffusing device that can achieve this.

[Means for Solving the Problems] An object of the present invention is to further improve the light diffusing device as disclosed in Japanese Patent Application Laid-Open No. 61-55684, and reduce the amount of light from the light source while keeping the device thin and the wattage of the light source small. An object of the present invention is to provide a light diffusing device that can achieve a light diffusing effect with little loss and good uniformity.

In the above 11 targets, at least one side end of the base material is the incident surface of the light flux, and one blood perpendicular or substantially perpendicular to this is the exit surface, and optically corresponds to the exit surface. In a light diffuser in which a reflective layer is formed on a surface to reflect a light beam toward an exit surface, - the base material is mostly formed of a transparent layer, and a light diffusing layer is formed on one surface thereof, and A light diffuser characterized in that an intermediate layer having intermediate properties between the transparent layer and the light diffusing layer is formed between the transparent layer and the light diffusing layer, and -11 the reflective layer is formed of a silver thin film layer. achieved.

That is, the present inventors have already proposed JP-A-61-55.
As a result of intensive study to further improve each component of No. 684, we came to invent a light diffusing device having the following configuration. In other words, regarding the light diffusion layer, the structure of the proposed invention is the best, but after considering the reflective surface, which is formed directly or close to the back surface of the base material, which is another component, Surprisingly, we found a difference between an aluminum thin film, which is commonly used as a reflective material, and a silver thin film, which is unimaginable based on the material's inherent reflectance (Note). By using a silver thin film for the reflective layer, a light diffusing device that can achieve the above object was completed.

(Note 1) The refractive index of both is
Thin Film (Vacuum Deposition
ofThirrFilms) J (Author: L, Ho11and) Publisher: Chapman End Hall Co., Ltd.
nd Hall Ltd. 1966), p. 322, r Visible light (450~&[1
0 nm) As read from the graph of Reflectivity J, A°C: 88-93% Ag: 93-97%.

Hereinafter, the light diffusing device of the present invention will be explained in detail based on the drawings.

FIG. 1 is a perspective view of an embodiment of the light diffuser of the present invention in use, FIG. 2 is a sectional view taken along line II-II', and FIG. 3 is a sectional view taken along line I-1'.

1 to 3, reference numeral 1 is a base material, the base material I is mostly composed of a transparent layer 2, and the surface, that is, the light diffusing and exiting surface side (the upper surface side in FIG. 2) is Layer 3 is formed. Furthermore, an intermediate layer 4 having optical properties intermediate between them is formed between the diffusion layer 3 and the transparent layer 2. That is, the base material 1 consists of a transparent layer 2, a diffusion layer 3, and an intermediate layer 4. By forming the diffusion layer 3 and the intermediate layer 4 on the surface of the base material 1, that is, on the light diffusion/emission surface side, the intermediate layer 4
Compared to the case where there is no transparent layer, the light in the transparent layer 2 is better diffused and irradiated from the exit surface to the outside of the base material 1.

Further, a reflective layer 5 is provided on the back surface of the base material I (lower surface side in FIG. 2). Furthermore, along each end face 8.9 of the substrate 1 a light source 10.11 is arranged. Base material 1
The end faces other than the end faces facing the light sources 10 and 11 are subjected to light scattering and reflection treatment. 7 is a light source 10. 6 in FIG. 3 is a light scattering and reflective layer provided on the other end surface of the base material I.

The base material 1 can be formed by appropriately treating the surface of a material with good translucency, or by adding a diffusion layer 3 and an intermediate layer 4 to the surface when molding the material. As a method for forming such a base material, the method disclosed in Japanese Unexamined Patent Publication No. 61-55684 can be applied.

The thickness of the diffusion layer 3 of the base material 1 is, for example, about 0.05 to 1 mm.
The thickness of the intermediate layer 4 is, for example, about 0.01 to 0.0
It is about 2 mm.

The base material 1 is usually in the shape of a flat plate, and its planar shape is usually rectangular as shown in the figure, but it is not limited to this, and can be appropriately deformed depending on the shape of the device used. It is. Although the thickness is usually uniform over the entire surface, it is not necessarily limited to this, and for example, the thickness may be formed so that the thickness gradually decreases from the end surface on the light source side to the opposite end surface, or the overall shape may be arched. Modifications such as making it into a shape are possible. The size and thickness of the base material 1 are not particularly limited and are determined depending on the purpose. Furthermore, the first
Although the figure shows a configuration in which light sources 10.11 are arranged at both ends 8.9 of the base material l, one end surface 10 or 1 of the base material l
It is clear that a configuration in which a light source is disposed only at one point can also be adopted.

The light-reflecting layer 5 is usually formed by vapor-depositing silver onto the base material 1, but it is not limited to directly forming a thin silver film. It may be formed by sticking or being close to each other.

Note that the light scattering and reflective layer 6 may be any reflective material that has a good reflectance as usual.

[Examples] Examples will be described below, but these are, of course, examples of embodiments of the present invention, and it goes without saying that the present invention is not limited thereto.

(Example-1) 1.5% by weight of rutile-type titane oxide was triblended into an acrylic resin pellet (Hibet HBS [registered trademark] manufactured by Mitsubishi Rayon Co., Ltd.), and a film with a thickness of 75 μm was formed using an ordinary extruder. The film is spread on an inorganic glass flat plate without air bubbles, tentatively dyed with methyl methacrylate, and then cells are formed with the glass plate using a spacer in the usual manner, and during this clearance, methyl methacrylate is A semi-polymerized sill was injected and polymerized and solidified in a conventional manner to obtain a resin with a thickness of 5 mm.

A plate measuring 61'mm x 56mm was cut from this plate, and two sides of the 61mm were flame polished. A silver sputtered film (
Substrate: 2-axis rotating polyester film Tetraite'SAG (registered trademark) manufactured by Oike Kogyo Co., Ltd. was attached using a transparent adhesive glue so that the silver side was on the acrylic resin plate. Next, a retroreflective sheet with transparent adhesive glue (Sparklite [registered trademark] manufactured by Unideka) was attached to the two unpolished sides of the 61 mm x 56 mm panel.

(Comparative Example-1) An aluminum thin film was directly formed on the white side of a plate having a light-diffusing layer prepared in the same manner as in Example 1 by vacuum evaporation using a normal method (transparent light was almost invisible to the naked eye). After that, a panel was produced in the same manner as in Example 1.

(Example-2) The light diffusing layer created in the same manner as Example-1 was divided by 1,000 and 1
225 mm x 164 from 0 mm thick acrylic resin plate
A root of 1 mm in size was cut and two 225 mm sides were flame-polished, and on the opposite white side (light diffusion layer) of the acrylic resin plate, spread Silver Suba Ntafilm with adhesive in the same manner as in Example-1. did. A milky white acrylic resin plate (manufactured by Wangling Rayon Co., Ltd., #6132 mm) cut to the same size was laminated on the white side of the acrylic resin plate, and two sides of 164 mm were covered with a retroreflective sheet.

(Comparative Example-2) A panel was created in exactly the same manner as Comparative Example-1, except that an aluminum vapor-deposited thin film was directly formed instead of the silver sputtered film of Example-2.

(Experiment details) The following light sources were arranged for the above four samples, and the surface brightness was measured at the center of the diffused irradiation surface.

Kuwatari Pu 2 Bu Example-1, Comparative Example-1 Lamp FLE manufactured by Erebam Co., Ltd.
-8,902 lamps Example-2, Comparative example-2, Matsushita Electric Corporation fluorescent lamp Ft,
-8D 2 lamps and Tokyo Optical Co., Ltd. Dobcon [registered trademark] BM-5 viewing angle l.

(Experimental results) Luminance Cd/m2 Lamp example-117
40FLE-8,902 lamp comparison example-11160FLE-
8,902 lights Example-2+420 FL-
8D 2-lamp comparative example - 2860FL-8D 2-lamp The lamp was placed in close contact with the polished end face, and was covered with aluminum foil to form a flefter.

[Effects of the Invention] As can be seen from the above experimental results, the light diffuser of the present invention does not require any changes in shape, even though there is a demand for a thinner light source lamp with a lower wattage. To,
A brightness ratio of about 1.5 to 1.8 times was achieved compared to a conventional light diffuser using aluminum.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the light diffuser of the present invention, FIG. 2 is a sectional view taken along the line 1--2, and FIG. 33 is a sectional view taken along the line 1-1'. 1: Base material, 2: Transparent layer, 3: Diffusion layer, 4: Intermediate layer, 5:
Light reflective layer made of silver, 6: Light scattering reflective layer, 7: Reflector, 10, 11: Light source lamp agent Patent attorney Yamashita
Johei

Claims (3)

[Claims] (1) At least one side end of the base material is the incident surface of the light beam, one surface perpendicular or substantially perpendicular to this is the exit surface, and the light beam is emitted to a surface that optically corresponds to the exit surface. In a light diffuser in which a reflective layer that reflects on the surface side is formed, the base material is mostly formed of a transparent layer, and a light diffusing layer is formed on one surface of the base material, and the transparent layer and the light A light diffuser characterized in that an intermediate layer having properties intermediate between these layers is formed between the light diffuser and the diffusion layer, and the reflective layer is formed of a silver thin film layer. (2) The light diffuser according to claim 1, characterized in that another light diffuser plate is brought into contact with the exit side surface. (3) The light diffuser according to claim 1, wherein the silver thin film layer is directly formed on the base material by vapor deposition. (3) The light diffuser according to claim 1, wherein the silver thin film layer is placed in contact with the base material.