| abstract |
The present invention provides a biaxially stretched sheet which is obtained by biaxially stretching an acrylonitrile-styrene copolymer, and the content of the acrylonitrile unit in the copolymer is 10 to 40% by mass, and the weight average of the copolymer The molecular weight is 100,000 to 250,000, the polydispersity is 2.0 to 2.5, the biaxial extension of the biaxially stretched sheet is 4 to 10 times, and the maximum directional relaxation stress in the MD and TD directions is 0.2 to 0.6 MPa, respectively. The absolute value (|ab|) of the difference between the maximum orientation 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 100 to 300 ppm. The content of volatile substances is 200~2000ppm. |