| abstract |
The invention provides a biaxially stretched sheet, which is formed by biaxially stretching an acrylonitrile-styrene copolymer, and the content of acrylonitrile units in the copolymer is 10-40% by mass. The weight-average molecular weight of the film is 100,000-250,000, the polydispersity is 2.0-2.5, the biaxially stretched area ratio of the biaxially stretched sheet is 4-10 times, and the maximum orientation relaxation stress in the MD direction and the TD direction is respectively 0.2-0.6MPa, the absolute value of the difference between the maximum orientation relaxation stress (a) in the MD direction and the maximum orientation relaxation stress (b) in the TD direction (︱a‑b︱) is 0.3MPa or less, biaxially stretched sheet The sulfur content in the glass is 100-300ppm, and the volatile matter content is 200-2000ppm. |