| 摘要 |
PURPOSE:To inexpensively mass-produce the titled Fresnel plate, by irradiating ultraviolet rays from the coated surface or back in a range of irradiation angles, within which the incident light on the molded resin plate exceeds the critical angle at the inside of the Fresnel vertical surface. CONSTITUTION:A water soluble photosetting type photosensitive resin 2 is applied to the Fresnel-formed surface of a Fresnel plate 1 which is formed from a transparent resin plate by heating and pressing with metallic molds for Fresnel forming. Then, by irradiating parallel ultraviolet rays on the Fresnel plate 1 in accordance with the inclined angle of the Fresnel inclined surface in such a way that the ultraviolet rays made incident on the Fresnel plate 1 from the Fresnel inclined surface can be irradiated beyond the critical angle at the inside of the vertical surface 4, the photosensitive resin of the inclined surface 3 only is exposed and hardened so as to form a hardened film 5 on the Fresnel inclined surface 3. Thereafter, a light absorbing coating material 6 is applied to the whole formed surface of the plate 1 and hardened. After hardening the coating material 6, the hardened film 5 is dissolved with an organic solvent, such as alcoholic solvent, etc., and the coating material 6 on the inclined surface 3 is removed. Thus a Fresnel plate which is provided with a light absorbing layer 7 on its Fresnel vertical surface only is obtained.
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