| 摘要 |
PROBLEM TO BE SOLVED: To improve surface properties such as abrasion resistance, scratch resistance, and cutting resistance by making the intrinsic viscosity of at least one side of a thin surface layer greater by a specified quantity then that of a thick inner layer. SOLUTION: In a thermoplastic resin layer in which the intrinsic viscosityηs of at least one side of a thin surface layer is greater by at least 0.05 than thatηe of a thick inner layer, it is requisite for surface properties such as abrasion resistance and cutting resistance that the molecular weight of the surface layer is greater than that of the inner layer. When the difference in the intrinsic viscosityηvalues is under 0.05, or when there is no difference in the intrinsic viscosityηvalues, the desired surface properties can hardly be obtained. Good surface properties can not be obtained in a single layer sheet having high intrinsic viscosityη. The surface of a tough surface layer alone is vulnerable to scratching; however, the existence of the thin layer having high intrinsic viscosityηallows scratching energy to be absorbed in the thickness direction of the sheet.
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