Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Utilizing plasma – electric – electromagnetic – particulate – or...
Patent
1990-02-22
1992-06-23
Lowe, James
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Utilizing plasma, electric, electromagnetic, particulate, or...
264 16, 264 17, 264 22, 264102, 264160, 264334, B27D 1100
Patent
active
051240890
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a transmissive screen for use in a video projector, and a manufacturing method thereof.
A transmissive screen for use in a video projector is generally composed of a Fresnel lens and a lenticular lens, and contains a diffusing agent made, for example, of SiO.sub.2 in order to have a diffusing property. The Fresnel lens has a function in which a diverged light from a projection lens is refracted toward a viewer. This Fresnel lens has a lens surface formed on one side of a methacrylic resin plate in which a number of concentric V letter-shaped grooves are formed. A non-lens surface is formed on the other side of the methacrylic resin plate. In general, a hot-press molding method is employed to produce a Fresnel lens screen. According to the hot-press molding method, a methacrylic resin plate of 3 to 5 mm thick is sandwiched between a metal mold in which V letter-shaped grooves opposite to the configuration of the Fresnel lens are concentrically engraved on a copper plate of 1 to 3 mm thick. A calendered metal plate is also provided. The assemble is heated and molded with a pressure. Thus the Fresnel lens screen is produced. A lenticular lens screen is produced similarly.
According to the aforementioned prior-art manufacturing method, in order to form one surface of a Fresnel lens, one surface of the engraved metal mold is needed, and many metal molds are required to mass-produce a Fresnel lens. The metal mold costs 1,500,000 to 2,500,000 yen per one plane, and is expensive. Further, the metal mold needs a large number of planes, and the a metal mold cost increases a cost of the product. A life span of the metal mold provides a press-process of about 800 to 1000 times, which means a metal mold cost of 1,500 to 2,500 yen per plane. In the molding-process, a methacrylic resin plate provided as material must be heated, softened and placed in a condition that it can be molded. A molding temperature must be selected to be high in a range of from 140.degree. to 170.degree. C., and a molding time needs 1.5 to 2 hours per plane. Further, the Fresnel lens screen molded by the hot-press molding method must be released from the metal mold at a high temperature of 80.degree. to 100.degree. C., otherwise it can not be released from the mold without difficulty. If the molded Fresnel lens screen is not uniformly released from the mold, this causes a failure product. Furthermore, the metal mold is heated a very high temperature so that the life span of the metal mold is short, which causes a cost of a product to be increased much more. In addition, the prior-art Fresnel lens screen is thick, which causes a problem of the occurrence of multiple images.
SUMMARY OF THE INVENTION
The present invention is to provide a transmissive screen and a manufacturing method thereof in which the above-described problems can be solved.
A method for manufacturing a transmissive screen according to the present invention comprises the processes of coating a UV-curable resin 12 on one side surface of a back film 13 or a mold 10 in which a lens surface of opposite shape is formed, irradiating ultraviolet rays 7 on the UV-curable resin 12 between the back film 13 and the mold 10, and releasing a molded transmissive screen 11 from the mold 10. A light source 8 for irradiating the ultraviolet rays 7 may be a metal halide lamp, a high pressure mercury lamp, an Xe lamp or the like.
According to the above-mentioned processes, the transmissive screen 11 of this invention can be obtained.
Further, the transmissive screen 11 according to this invention is comprised of the lens made of the UV-curable resin 12 which has a lens surface 15 formed on its one surface and the back film 13 deposited on the other surface of this lens.
The present invention provides a transmissive projector having the above-described transmissive screen 11.
According to the present invention, the UV-curable resin is utilized as a host material of the screen, whereby a molding time can be reduced and a continuous mass-production is made possible.
REFERENCES:
patent: 4294782 (1981-10-01), Froehlig
patent: 4415509 (1983-11-01), Toyooka et al.
patent: 4512631 (1985-04-01), Van Breenen
Inoue Takuji
Ogino Toyohiro
Ohkoshi Akio
Yokota Toshikazu
Lowe James
Sony Corporation
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