Method Of Manufacture Of Polytetrafluoroethylene Stretched Film, And Polytetrafluoroethylene Stretched Film

Polytetrafluoroethylene stretched film, which is manufactured by the polytetrafluoroethylene stretched film manufacturing method having the following steps (I) and (II),

• (I) a step in which a resin composition obtained by mixing an emulsion of polytetrafluoroethylene (A) with a number average molecular weight of 5×106 or more and an emulsion of polytetrafluoroethylene (B) with a number average molecular weight of 1×106 to 4×106 so that the solid content ratio (A/B) of the polytetrafluoroethylene (A) and the polytetrafluoroethylene (B) is 99/1 to 10/90 is subjected to compression molding in a melted state under a reduced-pressure atmosphere to obtain a film and
• (II) a step in which said film is melt stretched,
• wherein said melt stretching is biaxial stretching,
• said step (I) has a step (I-1) in which said resin composition is pressed at the first pressure V1 (0.01-100 MPa) for 1-100 minutes in a state where it has been heated to a temperature T1 (15-150° C.) under a reduced-pressure atmosphere, and a step (I-2) in which the heated and pressed resin composition in said step (I-1) is further heated at a temperature T2 (330-420° C.) to a melted state, and compression molded at second pressure V2 (0.01-100 MPa) for 1-100 minutes under a reduced-pressure atmosphere,
• said reduced-pressure atmosphere in said steps (I) and (II) is 10 Torr or less, and
• the difference of said second pressure V2 and said first pressure V1 (V2−V1) ranges between about 0 0.1-99 MPa., and
• in which haze is 45% or less, and tensile strength at break is 30 MPa or more.