JPH03180887A - Surface light source device - Google Patents

Abstract

PURPOSE:To thin a device and to make brightness uniform by using a diffusing resin sheet obtained by laminating and integrating a resin film having specified distribution in light transmitting ability on a resin sheet layer as a surface plate. CONSTITUTION:The surface plate 2 consists of the light diffusing region sheet which has uniform thickness in substance and is obtained by laminating and integrating the resin film 21 having the light transmitting ability so that brightness distribution may be made uniform on the resin sheet layer 23. By interposing a distribution layer 22 between the film 21 and the sheet layer 23, durability by water or solvent is enhanced. Owing to the existence of the diffusing resin sheet used as the surface plate 2, the brightness is made uniform and the device is thinned. Then, the durability of the surface plate 2 is constitutionally enhanced, thereby obtaining the device excellent in practicality.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface light source device for use in internally illuminated signboards, displays, guide lights, lighting equipment, liquid crystal display devices, and the like.

Surface light source devices incorporating a point light source or a line light source are widely used in internally illuminated signboards, liquid crystal displays, lighting equipment, and the like. Such devices generally have a reflective layer on the bottom of the housing, a built-in fluorescent lamp, and a diffuser plate on the front. However, if the depth of such a device is sufficiently large, the atb problem will not occur. However, if the depth is reduced and the device is made thinner, the image of the fluorescent lamp will be visible to the naked eye, resulting in a lack of uniformity.

To this end, it is conceivable to improve the diffusion performance of the diffusion plate, but if this is done, the light transmittance will inevitably decrease and the entire surface will become dark.

(Problems to be Solved by the Invention) In order to improve these points, a light diffusing plate made of a transparent base material mixed with a light diffusing agent) is used to increase the thickness of the part where the light intensity is high to reduce the unevenness of light. It is known to use a removal member (Japanese Unexamined Patent Publication No. 63-74004).

However, changing the light refraction and the thickness of the scattering plate in accordance with the light intensity requires setting each time depending on the shape and size of the device and the distance between the light sources and the light source. The manufacturing cost of the mold to be manufactured is high and it cannot be said to be practical.

In view of these circumstances, the present invention provides a thin and uniform brightness by using a diffusive resin sheet of substantially uniform thickness, which is made by laminating resin films with a distribution of light diffusivity, as a face plate. The present invention aims to provide a surface light source device.

(Means for Solving the Problems) In other words, the gist of the present invention is to provide a surface light source device in which a light source is built in a housing and a face plate is attached to the illumination surface. A surface light source device characterized by using a diffusive resin sheet that is laminated and integrated.

None The transmittance applied to the resin film with a distribution of light transmittance according to the present invention refers not only to the distribution of transmittance due to the light absorption property, but also to the distribution layer due to the difference in the degree of light diffusivity, and the combination of both. distribution.

The present invention will be explained in more detail below.

Fig. 1 shows an example of a surface light source device of the present invention, in which (1) is a housing made of synthetic resin or the entire area, etc.;
) is a face plate constituting the illumination surface, and (3) is a linear light source.

Of these, the housing (1) has a bottom plate (11) and a side plate (
12), and the inner surface is a reflective surface made of aluminum, silver, etc.

The face plate (2) is the most characteristic feature of the present invention, and is made of a diffusive resin sheet in which a film is laminated and integrated with a resin sheet layer. An example of this is shown in Figure @2, where (
21) is a resin film, (22) is a distribution layer for imparting light diffusing properties, and (23) is a resin sheet layer. This distribution NI (22) is preferable when placed between the resin film (21) and the resin sheet layer (23) because it has high durability against water, solvents, etc., and can also withstand friction during cleaning the casing. I see you.

As the resin film (21) used for this face plate, films of polyester, polyvinyl chloride, polystyrene, etc. can be used, but acrylic resin films are particularly suitable. This acrylic resin film can be obtained by polymerizing alkyl methacrylate as a main component, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, or propyl methacrylate alone, or by copolymerizing two or more of these. Mention may be made of films made of polymers. Even if the polymer consists of a copolymerized polymer by adding other copolymer components such as acrylate, vinyl acetate, vinyl chloride, styrene, acrylonitrile, methacrylatetrile, etc., if necessary, it is also possible to use an ultraviolet absorber, A coloring agent, a heat stabilizer, a plasticizer, a degree of polymerization regulator, a release agent, and an antistatic agent can be added as necessary.

These resin films have a distribution of light transmittance, which is caused by carbon, gold powder, inorganic,
Although it can be partially dyed with a light absorbing agent made of organic dyes and pigments or a light diffusing agent made of inorganic or organic transparent fine particles, it is more preferable to dye one side of the film with a paint containing a light diffusing agent. ! Alternatively, use a coating tube or one with printing on both sides. Coating or printing in this way
It is advantageous that one or both sides of the film can be arbitrarily selected to provide variations in light diffusivity. Examples of the light diffusing agent used at this time include titanium oxide, magnesium oxide, barium sulfate, and the like.

The material for the resin sheet layer (25) constituting the face plate is as follows:
Synthetic resins such as polycarbonate, polystyrene, polyvinyl chloride, and acrylic may be used, with acrylic resin being particularly suitable. Examples of this acrylic resin include methyl methacrylate resin sheets,
Also mentioned are sheets consisting of methyl methacrylate alone or a copolymer of methyl methacrylate with a polymerization coefficient of 50 or more and other copolymerizable monoethylenically unsaturated compounds and/or polyfunctional compounds. Here, monoethylenically unsaturated compounds include, for example, methacrylic acid esters, chloroethyl esters, styrene, etc., and polyfunctional compounds include, for example, glycolyl dimethacrylate, diallyl methacrylate, trimethylolpropane trimethacrylate, etc. Examples include methacrylic acid esters such as methacrylate and neopentyl glycol dimethacrylate.

The residue sheet E*(2'z,) contains light-diffusing inorganic transparent fine particles and/or transparent polymer beads having a refractive index different from that of the tree. It is also possible to use a material with an additive added.In this case, it is desirable to use a material with a total light transmittance of 15 to 50 or more and a shape factor of brightness distribution of 116 or more.
Yes. Here, the shape factor of the brightness distribution refers to the transmitted light distribution of light incident perpendicularly to the sheet (the ratio of the spread of diffuse transmitted light in the direction parallel to the sheet to the transmitted light perpendicular to the sheet). If this coefficient is α6 or more, at least one acrylic resin film with a distribution of light diffusion or transparency is laminated on one or both sides of the resin sheet layer and integrated. Regarding the diffusive resin sheet of the present invention, if the transmittance at a place with high transmittance and the place with low transmittance is '!, 1, 'r24, and the reflectance is R11, R2elI, then light is If there is no component to absorb, the approximate result is 'I'1+R, T2-1-R, and 100qb, and the unevenness of the reflectance distribution is smaller than the unevenness of the transmittance distribution, so when the light source is turned off or the light Undesirable unevenness during application of a diffusing agent or during printing has a negative effect.

As the inorganic transparent fine particles contained in this resin sheet layer, fine particles of silica, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, calcium phosphate, etc. are used.

The transparent polymer beads used are preferably styrene or polymer beads made by copolymerizing styrene and methyl methacrylate in the presence of a crosslinking monomer, but this is not limiting. are ultraviolet absorbers, colorants,
Heat-resistant stabilizers, plasticizers, polymerization degree regulators, release agents, sooty combustible agents, antistatic agents, etc. are required.To integrate the resin sheet layer with the resin sheet layer, adhesives or heat fusion methods are used. be done. Furthermore, when an acrylic resin film is used as the resin film and an acrylic resin is used as the resin sheet layer, the film is integrated by being partially swollen or dissolved by the monomer or partial polymer that is the raw material of the acrylic resin. As a result, the distribution of the coated layer or printed layer provided on the film is not impaired, and it is possible to form a close-fitting one-piece structure, making it easy to apply.

(Example) Hereinafter, embodiments of the present invention will be explained in detail.

The evaluation items for this example were measured as follows.

・Total light transmittance...Measured in accordance with JIS K7105.

・Total light reflectance... Same as above ・Glossiness... Same as above ・Surface brightness... Guidance light equipment technical standards, TIL550
This was carried out in accordance with 2.

[Production of acrylic resin film with distributed light transmittance]

Methyl methacrylate 601J (f14, butyl acrylate 39g74, and 2-(5.
A copolymer film (thickness 75μ) consisting of methyl-2-hydroxyphenyl)benzotriazole 1fr″ik4
), using white ink containing titanium oxide fine particles as the main component, gravure printing was performed to create a linear pattern with a dark center in the center and a blurred pattern with slow waves of # on the sides, as shown in Figure 4. Printed. When the total light transmittance of the obtained film in the XY cross section was measured, the results were as shown in FIG. That is, in FIG. 5, a is the total light transmittance of this film.

[Production of acrylic resin diffusion sheet]

First, methyl methacrylate monomer was prepolymerized to produce a methyl methacrylate partial polymer containing approximately 20 parts of methyl methacrylate polymer. Add to this the azozuisoptylonitrile 0.05 weight [4, dioctyl sulfosuccinate sodium salt nooi weight f4 as a stripping agent and ultraviolet Is@2-(5-methyl-2-hydroxyphenyl)benzotriazole o as an absorbent. , o o s
``IiIi'' was dissolved in a small amount, and further, 50 times F4 of polystyrene particles and 11.14 times F4 of titanium oxide particles were added as a dispersing agent.

Next, prepare a pair of molds in which the acrylic resin film obtained above was pasted on one of the metal mold surfaces by pouring methyl methacrylate in advance, and inject the above mixture into the rIJl of the metal mold to determine the thickness after polymerization. The surrounding area was clamped so that there were two towers. Then, according to the conventional method of cast polymerization, the first stage polymerization was performed by immersing it in hot water at 60 °C for 2 hours, and then the second stage polymerization was performed by leaving it in hot air at 120 °C for 2 hours to complete the polymerization. . After cooling in a cabinet at room temperature, the acrylic resin diffusion sheet was removed from the mold, and it was found to be a good product with integrated lamination of acrylic resin films with a distribution of light transmittance.

When the optical properties of the obtained sheet were evaluated (measured at a location corresponding to the X-Y cross section in Figure 1), the results shown in Figure 6 were obtained, confirming that it satisfies the requirements for the sheet. Ta.

[Production of surface light source device]

When the acrylic resin diffusion sheet obtained above was used as a face plate and attached to a surface light source device having the dimensions shown in Fig. 3, and the surface brightness in the X-Y cross section was measured, the results shown in Fig. 7 were obtained. It was found that the invention example was even better.

The light source used at this time was a 20W fluorescent lamp with a diameter of 28 cm. As a comparative example, a diffusion sheet of the above-mentioned cylindrical plate except for the acrylic resin film with a distribution of light diffusivity was used, and b1 and other components had the same structure as above. The measured total light transmittance of only the diffuser 5/-t used in the comparative example was linear at about 30%, as shown in Figure 5.

(Effects of the Invention) Since the present invention has the four-hole configuration detailed above, the presence of the diffusive resin sheet used for the face plate provides uniform brightness and allows for a thinner face plate. Because of its structure, it has the advantage of being highly durable and providing a highly practical device.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the device of the present invention with the face plate removed, Fig. 2 is an enlarged sectional view of the face plate at that time;
Figure 7 is used in an example of the present invention, Figure 5 is a cross-sectional view of the device, Figure 4 is a perspective view of a resin film with a distribution of light transmittance, Figure 5 is a graph showing its optical performance, Figure 6 is a graph showing the optical characteristics of the face plate,
FIG. 7 is a graph showing the surface brightness of the face plate applied to the device. (1) l... Housing (2)... Face plate (5)... Light source

Claims (1)

[Claims] 1. In a surface light source device in which a light source is built in a housing and a face plate is attached to the illumination surface, the face plate has a substantially uniform thickness and a light source is provided so that the luminance distribution is uniform. 1. A surface light source device characterized by using a diffusive resin sheet in which a resin film having a distribution of transmittance is laminated and integrated with a resin sheet layer. 2. The surface light source device according to claim 1, wherein an acrylic resin film is used as the resin film. 3. Claim 1, characterized in that the resin film is an acrylic resin film coated or printed with a paint containing a light diffusing agent on one or both sides to give it distribution.
The surface light source device described in Section 1. 4. Claim 1, characterized in that the face plate is attached so that the resin film with distributed light transmittance is on the outside.
The surface light source device according to item 1, 2 or 3. 5. The surface light source device according to claim 1, 2, 3, or 4, wherein a light diffusing agent is added to the resin sheet layer of the face plate.