Adhesive film

Abstract

An adhesive film with excellent cuttability with respect to both a base layer and a surface layer or layers laminated thereon is provided, without significant formation of adhesive burrs in various shearing processes. The adhesive film includes a support member and an adhesive layer laminated on at least one side of the support member. The adhesive layer has a laminate structure having a base layer made of a resin-based adhesive and laminated on the surface of the support member and a surface layer made of a resin-based adhesive and laminated on the base layer. The base layer is non-directional and has lengthwise and widthwise shearing strengths of 2 g to 2000 g (200 mm/min, 25 mm) in the thickness range of 2 μm to 60 μm. The base layer has a shearing strength of 1.5 to 200 times the shearing strength of the surface layer.

What is claimed is: 
     
         1 . An adhesive film characterized by being produced by laminating a non-directional base layer comprising resin and having lengthwise and widthwise shearing strengths of 2 g to 2000 g (200 mm/minute, width 25 mm) in the thickness range of 2 μm to 60 μm with a surface layer comprising resin-based adhesive. 
     
     
         2 . The adhesive film according to  claim 1 , characterized in that the base layer has a shearing strength of 1.5 to 200 times the shearing strength of the surface layer. 
     
     
         3 . The adhesive film according to  claim 1 , characterized in that the surface layer has a gel fraction of 0% to 80%, the base layer has a gel fraction of 30% to 100% and the ratio in gel fraction between the base layer and the surface layer is 80 or less relative to 100 of the base layer. 
     
     
         4 . The adhesive film according to  claim 1 , characterized in that the surface layer has a glass transition point (Tg) of −80° C. to 5° C., while the base layer has a glass transition point (Tg) of 0° C. to 260° C. 
     
     
         5 . The adhesive film according to  claim 3 , characterized in that the surface layer is formed on each of the side of the base layer. 
     
     
         6 . The adhesive film according to  claim 4 , characterized in that the surface layer is formed on each of the side of the base layer. 
     
     
         7 . The adhesive film according to  claim 1 , characterized in that it has a gradient resulting from chemical equilibrium-due crosslinking in the interface between the base layer and the surface layer. 
     
     
         8 . The adhesive film according to  claim 1 , characterized in that 20% to 100% of the respective constituents of the base layer and the surface layer are constituted of the same monomer or polymer compositions except for the differences in molecular weight and in intermolecular crosslinking agent species. 
     
     
         9 . The adhesive film according to  claim 1 , characterized in that the resin constituting the base layer is higher in molecular weight than the resin constituting the surface layer. 
     
     
         10 . The adhesive film according to  claim 1 , characterized in that the resin constituting the base layer is higher in degree of crosslinking as compared with the resin forming the surface layer. 
     
     
         11 . The adhesive film according to  claim 1 , characterized in that the surface layer has a thickness of 0.1 μm to 50 μm and the base layer has a thickness of 2 μm to 60 μm. 
     
     
         12 . The adhesive film according to  claim 5 , characterized in that the surface layer on one side thereof and the surface layer on the other side thereof are formed of different adhesives. 
     
     
         13 . The adhesive film according to  claim 6 , characterized in that the surface layer on one side thereof and the surface layer on the other side thereof are formed of different adhesives. 
     
     
         14 . The adhesive film according to  claim 5 , characterized in that the surface layer on one side thereof and the surface layer on the other side thereof are formed of adhesives differing in adhesive power. 
     
     
         15 . The adhesive film according to  claim 6 , characterized in that the surface layer on one side thereof and the surface layer on the other side thereof are formed of adhesives differing in adhesive power. 
     
     
         16 . The adhesive film according to  claim 1 , characterized in that the elongation percentage of the surface layer is 200% or more. 
     
     
         17 . The adhesive film according to  claim 1 , characterized in that the elongation percentage of the base layer is 300% or less.