| 摘要 |
PROBLEM TO BE SOLVED: To provide a release film extremely reduced in thermal deformation at the time of heat treatment and excellent in subsequent cutting or punching processability in molding various resin sheets, resin films or ceramic sheets. SOLUTION: A release film has a film consisting of polyethylene naphthalate as a substrate film and, in the substrate film, a refractive index (nz) in a thickness direction is 1.49-1.53, a surface orientation coefficient (NS) is 0.23-0.27 and the sum of tear propagation resistance in a film roll taking-up direction and the direction vertical thereto is 4 N/mm or less.
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