| 摘要 |
PURPOSE:To reduce the generation of Moire fringes by a method wherein a Fresnel lens plate base is formed by pressing a polyvinyl chloride-based resin sheet and, after that, the surface of said Fresnel lens plate base is matted by annealing the base at a temperature in the lower region within the softening temperature range of the resin composition. CONSTITUTION:A resin sheet is formed by extruding resin composition, the major component of which is partially cosslinked polyvinyl chloride-based resin. Next, in order to form a Fresnel lens having the predetermined shape, said resin sheet is press-worked by being pinched between a mirror plate and a Fresnel lens forming mold, the shape of the inner surface of which is the reverse of said shape of the Fresnel lens, in order to obtain a Fresnel lens plate base, one side of which is a plane and on the other side of which a Fresnel lens is formed. Next, the surface of the resultant base is matted by annealing the base at a temperature in the lower region among the softening temperatures of said resin composition in order to obtain a Fresnel lens plate. Thus, the generation of Moire fringes can be reduced, when the Fresnel lens plate is used as a projection screen. |
