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AssigneeToyobo Co., Ltd.
InventorsTsutomu Isaka, Hiroshi Nagano, Tetsushi Murakami, Koichi Matsunami, Yukio Yamane
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A transparent polyester film having excellent printability, flexing resistance and pinhole resistance and further excellent interlaminar strength, which is made from a polymer mixture or blend comprising (i) a polyester consisting essentially of a residue of dibasic acids wherein at least 80 % by mol is terephthalic acid and a residue of at least one glycol and (ii) a block copolyester consisting of a crystalline polyester (hard) segment having a high melting point and a soft polymer segment having a low melting point and a number average molecular weight of 400 to 8,000, said soft polymer segment having a low melting point being contained in an amount of 0.5 to 10 % by weight on the basis of the whole weight of the polymer mixture or blend, and said crystalline polyester segment having a melting point of at least 170.degree. C when a polymer is produced by the monomers composing the segment alone and said soft polymer segment having a melting or softening point of 100.degree. C or lower.
A stretched polyester film made from a polymer blend comprising (i) a polyester consisting essentially of a residue of dibasic acids wherein at least 80% by mole thereof is terephthalic acid and a residue of at least one glycol and (ii) a block copolyester consisting of a crystalline polyester segment having a high melting point and a soft polymer segment having a low melting point and a number average molecular weight of 400 to 8,000, said soft polymer segment having a low melting point being present in an amount of 0.5 to 10% by weight on the basis of the whole weight of the mixed polymer, and said crystalline polyester segment having a melting point of at least 170.degree. C. when a polymer is produced by the monomers composing this segment alone and said soft polymer segment having a melting or softening point of 100.degree. C. or lower, said film being drawn at least uniaxially in a ratio of 1.2 to 6.
Dependencies are inferred from the claim text.