| 摘要 |
PURPOSE:To obtain a base film for a magnetic recording medium capable of performing high-density recording, by molding a polyester comprising dicarboxylic acid units, glycol units and hydroxycarboxylic acid units into a film and stretching this film. CONSTITUTION:A liquid crystal aromatic polyester film comprising an aromatic polyester composed of dicarboxylic acid units of formula I, glycol units of formula II and hydroxycarboxylic acid units of formula III and having the properties including a modules >=3 GPa, a coefficient of thermal expansion <=5X10<-5>/ deg.C, a coefficient of moisture expansion <=9X10<-6>/% RH, an anisotropy of modulus <=2 and an anisotropy of thermal expansion <=2. In the formulas, at least 60% of R groups are bivalent 6-16C aromatic hydrocatbon groups other than a 1,4-phenylene group, or the like and R2 is a bivalent 1-20C aliphat ic hydrocarbon group or the like. In order to obtain a film which can meet said property values from said polyester, the polyester is molded into a film, which is biaxially stretched, and the stretched film is heat-set. |
