| 摘要 |
PROBLEM TO BE SOLVED: To obtain an inexpensive optical element, such as triangular prism array, which has high total ray transmittance, an adequate light diffusion effect and good transferability of a surface relief shape of a thin type by constituting the element of crystalline high polymer. SOLUTION: This optical element consists of a crystalline high polymer. Some of the crystalline high polymers which are hitherto considered inadequate as the surface type relief optical element are adequately usable according to conditions and one of these high polymers is a propylene-ethylene random copolymer. This propylene-ethylene random copolymer is, thereupon, adopted for the material of the surface relief type optical element, such as triangular prism array 1 or Fresnel lens, and is molded by injection molding or injection compression molding. The cutting defects in a later stage do not occur any more and the dealing with the metal molds for product part of one piece of the products is merely necessitated. A maintenance cost is reduced and the molding time is short and, therefore, the manufacturing cost is low. |
