Method for manufacturing resin film for thin film-capacitor and the film therefor
The present invention provides a method for manufacturing a film for a film capacitor making it possible to produce a film for a film capacitor which has a thickness of 10 μm or less and which is excellent in a heat resistance and a voltage resistance at a high thickness accuracy by using a polyetherimide resin and provides as well a film for a film capacitor. The above manufacturing method comprises the steps of: feeding a molding material 1 containing a polyetherimide resin into an extruding machine 10, extruding a film 50 for a film capacitor immediately downward from a lip part 21 at a tip of a T dice 20 thereof, interposing the film 50 for a film capacitor between a pressing roll 31 and a cooling roll 33 to cool it and winding up the cooled film 50 for a film capacitor having a thickness of 10 μm or less on a winding equipment 40 , wherein assuming that a shear rate of the molten molding material 1 in the lip part 21 of the T dice 20 is set to γ [/s] and that a circumferential speed of the cooling roll 33 is set to V [m/s], a ratio V/γ [m] of a circumferential speed V of the cooling roll 33 to a shear rate γ of the molding material 1 falls in a range of 3.0×10 −2 to 90×10 −2 [m].
1. A method for manufacturing a film for a film capacitor, comprising the steps of:
feeding a molding material into an extruding equipment,
extruding a film for a film capacitor downward from a lip part of a T die tip thereof,
interposing the above extruded film for a film capacitor between a pressing roll and a cooling roll to cool it, and
winding up the above cooled film for a film capacitor having a thickness of 10 μm or less on a winding equipment,
wherein the molding material comprises a polyetherimide resin that is mixed with a fluorocarbon resin,
wherein a ratio V/y of the circumferential speed V [m/s] of the cooling roll to the shear rate y [/s] of the molten molding material in the lip part of the T die is 3.0×10 −2 to 90×10 −2 [m] and
wherein the method excludes biaxial stretching.
2. The method for manufacturing a film for a film capacitor as described in claim 1 , wherein a clearance of the lip part in the T die is set to 0.11 to 1.00 mm, and a temperature of the cooling roll falls in a range of a glass transition point of the polyetherimide resin −100° C. to +50° C.
3. A film for a film capacitor produced by the method for manufacturing a film for a film capacitor as described in claim 1 or 2 .
4. The method for manufacturing a film for a film capacitor as described in claim 1 , wherein a melt viscosity of the fluorocarbon resin is 120,000 poise or less.