| 摘要 |
PROBLEM TO BE SOLVED: To prepare a polyester film having extremely good followingness with a substrate, preventing a generation of a defect in a circuit and useful as a supporting layer for a photoresist film by blending a specific polyester with a specified lubricant. SOLUTION: This polyester film comprises a copolyester including a lubricant (e.g. silica) having $2.5μm average particle diameter and having 210-250 deg.C melting temperature and formed to have 0.09-0.16 plane orientation coefficient. Moreover, the L5 values of the films in the machine and transverse directions are preferably each 1-65g/mm and, for example, the objective film is obtained by melting the copolyester including the lubricant, extruding the molten copolyester from a die to form a film shape, further biaxially orienting the resultant film and heat-setting the oriented film. |
