Biaxially oriented multilayer film

Abstract

A biaxially oriented multilayer film, able to prevent gaps between the film and a package containing a product or wrinkles and to wrap in a predetermined way while preventing smell from being transferred to the product, comprised of a base layer formed by a propylene-based polymer and surface layers formed by a propylene-based resin on the two surfaces of the base layer, wherein a heat shrinkage rate R1 in a length direction and a heat shrinkage rate R2 in a width direction when heating at 120° C. for 15 minutes: R 1=( L 1 H −L 2 H )/ L 1 H . . .   (a) R 2=( L 1 W −L 2 W )/ L 1 W . . .   (b) 0.08≦R1≦0.20 . . .   (c) 0.08≦R2≦0.20 . . .   (d) | R 1− R 2|≦0.05 . . .   (e) where, L1 H : length before shrinkage in length direction, L2 H : length after shrinkage in length direction, L1 W : length before shrinkage in width direction, L2 W : length after shrinkage in width direction

What is claimed is  
     
         1 . A biaxially oriented multilayer film comprised of a base layer formed by a propylene-based polymer and surface layers formed by a propylene-based resin on the two surfaces of the base layer, wherein 
 a heat shrinkage rate R1 in a length direction and a heat shrinkage rate R2 in a width direction when heating at 120° C. for 15 minutes:      R 1=( L 1 H   −L 2 H )/ L 1 H  . . .   (a)  R 2=( L 1 W   −L 2 W )/ L 1 W  . . .   (b) 0.08≦R1≦0.20 . . .   (c) 0.08≦R2≦0.20 . . .   (d) | R 1 −R 2|0.05 . . .   (e)    where,    L1 H : length before shrinkage in length direction,    L2 H : length after shrinkage in length direction,    L1 W : length before shrinkage in width direction,    L2 W : length after shrinkage in width direction    
     
     
         2 . A biaxially oriented multilayer film as set forth in  claim 1 , wherein the base layer contains 80 to 95 parts by weight of a propylene-based polymer and 5 to 20 parts by weight of a hydrocarbon resin.  
     
     
         3 . A biaxially oriented multilayer film as set forth in  claim 2 , wherein the hydrocarbon resin contained in the base layer is a petroleum resin having a softening point of 130 to 150° C.  
     
     
         4 . A biaxially oriented multilayer film as set forth in  claim 1 , wherein a total peak area detected in a retention time of 10 minutes to 50 minutes when measuring components heated and volatilizing at 160° C. for 15 minutes by gas chromatography is not more than 30 pA·s.  
     
     
         5 . A biaxially oriented multilayer film as set forth in  claim 3 , wherein the hydrocarbon resin contained in the base layer is a dicyclopentadiene-based petroleum resin having a softening point of 130 to 150° C.  
     
     
         6 . A biaxially oriented multilayer film as set forth in  claim 1 , wherein a dynamic coefficient of friction μ1 of film measured by JIS K 7125 is not more than 0.3 and a dynamic coefficient of friction 2 of film measured by JIS K 7125 with a measurement speed of 25 mm/min is not less than 0.15.  
     
     
         7 . A biaxially oriented multilayer film as set forth in  claim 1 , wherein the time when a saturated charging voltage on at least one surface of the film is reduced to half is not more than 200 sec.