PURPOSE: To prevent the loss of a diffraction grating at the time of heat sealing by a method wherein the resin in a molten state is pressed between a nip roll and a cooling roll in order to form a relief diffraction grating on the resin surface and a radiation curable resin layer is formed and cured on the light reflecting layer of this diffraction grating forming surface.
CONSTITUTION: The resin 11 in a molten state is extrusion molded into the form of a sheet from a melt extrusion machine 3 and, during the subsequent passage around a cooling roll 2, pressed under a nip roll 4 to be formed into a diffraction grating. To make this diffraction grating brighter, it is necessary to form a light reflecting layer 12 on the diffraction grating forming surface. A radiation caruble resin 13 is provided to retain the irregular surface of the light reflecting layer 12 at the time of heat sealing. By way of example, the radiation curable resin may be a bifunctional acrylic monomer or oligomer alone or in mixture with an additive such as sensitizer as required. This method permits an efficient method to be employed to form a relief type diffraction grating and the diffraction grating to be retained at a heat sealing part.
HOSHINO KAZUHISA
ARAI KAZUNARI
