Patent ID: 7314905

Claim:
A drawn film which is a single layer film of a layer (A) that is obtained by monoaxial drawing a three-layer sheet having the structure of (B)/(A)/(B) from 7 to 10 times, and subsequently peeling the layers (A) and (B) from each other, the layer (A) comprising a copolymer that is made from 4-methyl-1-pentene and at least one comonomer of ethylene or an α-olefin having 3 to 20 carbon atoms with the proviso that the α-olefin is not 4-methyl-1-pentene, wherein the copolymer comprises 80% or more by mole of 4-methyl-1-pentene units and said layer does not substantially comprise wax or organic silicone compound, wherein the peel area of the film is from 70 to 100% wherein the peel area is determined by overlapping layer (A) on a copper foil having roughened surfaces, placing the drawn film and copper foil between metal plates with cushions, pressing by means of a press at 185° C. and 36 kg/cm 2 for 30 minutes, cooling to 25° C., and picking up one end of the film, and peeling the film continuously at a rate of 100 mm/minute and a peel angle of 90°, the peel angle being an angle between the roughened copper foil and the film; and the thermal coefficient of contraction of the film is from 26 to 30% along the direction in which is the film is drawn.