In a known method to produce an optical film for use as optical medium in light guide plates, light diffusion plates, lenses, etc., a film is pressed against a surface having a fine asperity pattern of an original plate to transfer the fine asperity pattern of the original plate onto a surface of the film. A long resin film is used as the film, and a portion having a predetermined length of the long film which is as a processing film is supplied intermittently onto a surface having a fine asperity pattern of a transfer plate (mold), and the processing film is pressed against the surface of the transfer plate to transfer the pattern to the surface of the processing film. After completion of the transfer, the processing film formed the pattern referred as a processed film is pulled in the direction of the length of the surface of the transfer plate to provide peel off the processed film from the surface of the transfer plate. Then, as the processing film peeled is taken up, a new processing film having a predetermined length is supplied onto the surface of the transfer plate. Such processes to produce optical products are proposed in Patent Literatures 1 and 2.
This generally known method has a peeling step to peel off the processed film from the surface of the transfer plate and a supply step to supply the new processing film having a predetermined length onto the surface of the transfer plate. There is a case that the peeling step is called as a mold release step, since a film having a pattern is released from a surface formed a pattern, that is, a mold. This generally known method can suffer problems as described below.
In the peeling step, or the mold release step, therefore, depending on the characteristics of a film used or depletion of a mold releasing agent on a surface of a mold, the film can adhere to the mold surface to damage the mold surface, leaving flaws, or mold release marks, on a transfer surface of the film.
In the supply step, a thickness and characteristics of the film can have influence on a formation of crease on the film supplied onto the mold surface.
In addition, a film supplied onto a heated mold surface can soften in local portions at increased temperatures before being pressed against the surface of the transfer plate, and softened portions can be stretched under the tension applied to the film, leading to local undulation caused on the patterned surface. Such local undulation can be caused significantly in low-rigidity or thin films.
Patent Literature 1: JP 2005-199455 A
Patent Literature 2: JP 2005-310286 A