Patent ID: 7585446

Claim:
A method of producing a film from a dope containing a polymer or a molten polymer, said dope or said molten polymer being discharged from a die onto a running support and peeled as said film from said support, said film being dried or cooled to have a predetermined thickness t (μm), said method comprising steps of: decompressing by a decompressing apparatus in upstream side of said running support from said dope or said molten polymer that is discharged from said die; and wherein when a predetermined value to the decompression is P 0 (unit; Pa) and the different between said predetermined value P 0 and a measured value after the decompression is a pressure fluctuation Pv, said pressure fluctuation Pv satisfies following formula, |Pv|≦ 1.5 |K| ( K= ( t×|P 0 |) 1/2 /100) wherein said decompressing apparatus includes a decompression chamber, a decompression regulating section for regulating an inner pressure of said decompression chamber, and a pipe connecting said decompression chamber and said decompression regulating section; and wherein said pipe is provided with a vibration damping device for damping a vibration which causes the change of said inner pressure.