| abstract |
PURPOSE:To enable biaxial orientation, and to satisfy heat-shrinkable characteristics by bringing crystallite size constituting a film composed of polybutylene terephthalate or polyester mainly comprising said polybutylene terephthalate and the degree of face orientation to specific values. CONSTITUTION:The title film consists of polybutylene terephthalate or polyester mainly comprising said polybutylene terephthalate, and is synthesized by combining the esterification reaction or ester exchange reaction of terephthalic acid or terephthalic acid dimethyl and 1,4-butanediol and a de-glycol reaction. Polybutylene terephthalate group polyester having high molecular weight is used preferably, and it is desirable that intrinsic viscosity at 25 deg.C in the mixed solvent of phenol/tetrachloroethane at the weight ratio of 1/1, etc. is concretely brought to 0.7 or more, preferably 0.8 or more. Crystallite size and the degree of face orientation measured through an X-ray diffraction method must be brought respectively to 35-80Angstrom and 85% or more in the film. It is desirable that flat method co-biaxial orientation and heat treatment are combined as the manufacture of the biaxially oriented film. |