公开(公告)号：US20240018316A1

公开(公告)日：2024-01-18

申请号：US17619613

申请日：2021-03-08

Applicant: UNITIKA LTD.

Inventor： Hiroshi Ashihara ,  Takayoshi Okuzu ,  Ken Akamatsu ,  Akiko Kurosawa ,  Goro Araki ,  Akito Kajita

IPC: C08J5/18 ,  C08G63/183 ,  B29C48/00 ,  B29C48/08

CPC classification number: C08J5/18 ,  C08G63/183 ,  B29C48/022 ,  B29C48/08 ,  B29C48/0018 ,  B29K2067/003

Abstract: A polyester film includes a polyester (A) composed mainly of polybutylene terephthalate and a polyester (B) composed mainly of polyethylene terephthalate,



wherein a mass ratio (A/B) between the polyesters (A) and (B) is 70/30 to 55/45, a dry heat shrinkage rate (B) through heat treatment at 200° C. for 15 minutes is 35% or less in any of four directions (0°, 45° 90° and 135°) on the film surface, a difference between a maximum value and a minimum value of these dry heat shrinkage rates is 5% or less, a thickness variation in the four directions is 10% or less, and a crystallization index shown in DSC measurement is 25 to 55 J/g.