PURPOSE: To improve the coating properties and slitting properties by using a biaxially oriented polyester film having a local slack area rate of a specific value or less as a base film of a transfer material for a printer used in a thermal recording system using an electrothermal recorder such as a thermal printer.
CONSTITUTION: As a thermal transfer film, a biaxially oriented polyester film having a local slack area rate of 10% or less is used. The polyester uses ethylene glycol as main starting material. The polyester film preferably has centerline mean roughness of one side surface of a range of 0.02 to 1μm. Fine particles inert for the polyester are mixed in any step of the extruding step before forming the film from the polyester manufacturing step. As the inert fine particle, kaolin can be, for example, used. The mean particle size of the inert compound is normally 0.1 to 10μm of equivalent spherical diameter, or preferably selected from a range of 0.3 to 3μm.
HOUZEKI YOSHITAKA
SUZUKI TAKASHI
