| 摘要 |
PURPOSE:To obtain the thermoplastic resin film with periodically varied thickness most effectively by cooling a thermoplastic resin melt-extruded into a film form by means of a cooling drum whose rotation is periodically changed. CONSTITUTION:A molten thermoplastic resin is extruded through a die slit into a film form and then placed on a rotating cooling drum to cool and solidify it in order to obtain the film, where the cooling drum is driven by a motor provided with a speed controller from which a periodically varying electric signal is applied to the speed detection circuit of the motor to periodically change the rotation of the cooling drum. The film thus obtained is useful in the fields of utilizing the transmissivity of specific light rays, interleaving the film with undulatory surface between two films, etc. |
