| 摘要 |
PROBLEM TO BE SOLVED: To improve plate wear, film rolling properties, perforation sensitivity and resolving degree at the time of printing by using a biaxially oriented polyester film which shows specific values in terms of melting point, coefficient of thermal contraction and modulus of tensile elasticity. SOLUTION: In a biaxially oriented polyester film for screen process printing employed for a thermal stenciling method, a biaxially oriented polyester film is used which has a coefficient of thermal contraction 8 times or more the coefficient of thermal contraction at 65 deg.C, at a melting point of 170-240 deg.C, a modulus of tensile elasticity of at least, 200kg/mm<2> in both longitudinal and width directions and a thickness of 0.5-7μm. When manufacturing this kind of polyester film, first a polymer is supplied to a known melt extrusion device, then is heated at temperatures or higher than the melting point of this polymer, and this molten polymer is extruded from a slit-like die. Further, this molten polymer is quenched and solidified so that its temperatures are below the glass transition temperature level on a rotary cooling drum to obtain substantially amorphous unoriented sheet. Finally this sheet is biaxially stretched into a film. |
