Cover film

Abstract

A cover film including, at least, (A) a substrate layer, (B) an intermediate layer, (C) a release layer and (D) a heat seal layer is provided. The release layer (C) includes a resin composition which includes (a) a styrene-based resin composition and (b) an ethylene-α-olefin random copolymer, with the content of the copolymer (b) in the release layer being 20 to 50 mass %, and which has a Vicat softening temperature of 55 to 80° C., while the heat seal layer (D) includes an acrylic resin having a glass transition temperature of 55 to 80° C. By the cover film, a carrier tape of polystyrene or the like can be so heat-sealed even in a short time as to achieve sufficient peel strength. Further, the resulting heat-sealed carrier tape exhibits little variation in peel strength, so that when peeling, few components fly out of the carrier tape.

1 . A cover film comprising at least, in order, a substrate layer (A), an intermediate layer (B), a peel layer (C) and a heat seal layer (D), wherein
 the peel layer (C) comprises a resin composition comprising a styrenic resin composition (a) having a styrene-diene block copolymer as a main component, and an ethylene-α-olefin random copolymer (b), the ethylene-α-olefin random copolymer occupying 20 to 50 mass % of the peel layer, and having a Vicat softening temperature of 55 to 80° C.; and   the heat seal layer (D) comprising an acrylic resin with a glass transition temperature of 55 to 80° C.   
     
     
         2 . The cover film according to  claim 1 , wherein the thickness of the substrate layer (A) after drying is 12 to 20 μm, the thickness of the intermediate layer (B) after drying is 10 to 40 μm, the thickness of the peel layer (C) after drying is 5 to 20 μm, and the total thickness of the cover film after drying is 45 to 65 μm. 
     
     
         3 . The cover film according to  claim 1 , wherein the heat seal layer (D) comprises 100 to 700 parts by mass of conductive microparticles of one of tin oxide, zinc oxide and zinc antimonate having a mass-average particle size of 1.0 μm or less, with respect to 100 parts by mass of the resin constituting the heat seal layer (D). 
     
     
         4 . The cover film according to  claim 1 , wherein the heat seal layer (D) comprises 40 to 100 parts by mass of a cationic polymer-type anti-static agent having a quaternary ammonium salt on a side chain, with respect to 100 parts by mass of the resin constituting the heat seal layer (D).