| abstract |
The present invention provides a biaxially stretched sheet which is obtained by biaxially stretching an acrylonitrile-styrene copolymer, wherein the content of the acrylonitrile unit in the copolymer is 10 to 40% by mass, and the weight average molecular weight of the copolymer It is 100,000 to 250,000, and the polydispersity is 2.0 to 2.5. The biaxial extension of the biaxially stretched sheet has a surface magnification of 4 to 10 times, and the maximum directional relaxation stress in the MD direction and the TD direction is 0.2 to 0.6 MPa, respectively. The absolute value (| ab |) of the difference between the maximum alignment relaxation stress (a) in the MD direction and the maximum alignment relaxation stress (b) in the TD direction is 0.3 MPa or less, and the sulfur content in the biaxially stretched sheet is 0 ppm or more. Up to 100ppm, the volatile matter content is 200~2000ppm. |