| 摘要 |
PURPOSE:To obtain film for floppy disk excellent in dimensional stability and flatness by a method wherein polyester film having specified physical properties is used. CONSTITUTION:Polyester film concerned has a thermal expansion coefficient of (1.7+ or -0.8)X10<-5>/ deg.C and a shrinkage coefficient of 0.03% or less after treatment at 60 deg.C under 80% RH for 72 hours. If the film, which does not satisfy said values of coefficients, is used, the track density can not increase, since the difference between the thermal expansion coefficient of a heat and that of the film is too large and, in addition, its dimensional stability is poor. The film concerned satisfies equations 1 - 6. If nalpha is below 1.492, the dimensional stability of the film not satisfying the equation (1) becomes poor and if nalpha exceeds 1.505, its strength lowers. If DELTAP exceeds 0.168, the dimensional stability of the film not satisfying the equation (2) becomes poor and if DELTAP is below 0.160, its strength is poor. If n is below 1.605, the dimensional stability of the film not satisfying the equation (3) becomes poor and if n exceeds 1.609, the film easily breaks. If X1 is below 5%, the dimensional stability of the film not satisfying the equation (4) becomes poor and if X1 exceeds 15%, its strength is poor. If X100 is below 60Angstrom , the dimensional stability of the film not satisfying the equation (5) becomes poor and if X100 exceeds 68Angstrom , its strength and flatness become poor. If rho is below 1.395, the dimensional stability of the film not satisfying the equation (6) becomes poor and, if rho exceeds 1.405, its flatness and strength become poor. |
