| 摘要 |
PURPOSE:To provide a surface protective film which has an adhesive layer with high initial bond strength and prevents contamination of adherends, prepared by forming a foamed pressure-sensitive adhesive layer on a thin base sheet. CONSTITUTION:A foamed pressure-sensitive adhesive is prepared by adding 10pts.wt. or lower, pref. 0.01-5pts.wt. foaming agent (e.g. toluenesulfonylhydrazide) to 100pts.wt. pressure-sensitive adhesive material obtained by adding tackifier resin, softener, filler, age resistor, etc., to a base material such as acrylic rubber, natural rubber, polyisobutylene rubber or acrylic copolymer. The surface protective film covered with a foamed pressure sensitive adhesive layer having a fine cellular structure in the size of 0.1-30mum at an expansion ratio of less than 2.7, pref. 1.05-2, is obtained by applying the above adhesive in the thickness of 5-50mum to the surface of a thin plastic film (e.g. polyethylene film) of 3-150mum thickness so that it may have a contact area of 50% or higher.
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