Polyethylene-2,6-naphthalate film for capacitor

Claim 2

A polyethylene-2,6-naphthalate film for plastic film capacitors having a Young's modulus of not smaller than 600 kg/mm2 both in the machine direction and in the transverse direction and a degree of crystallinity of not smaller than 40 %.

Claim 3

A polyethylene-2,6-naphthalate film for plastic film capacitors according to Claim 1, wherein said capacitor is a chip type film capacitor.

Claim 4

A polyethylene-2,6-naphthalate film for plastic film capacitors according to Claim 1, wherein the thickness of said film is not greater than 2.5 µm.

Claim 5

A polyethylene-2,6-nachthalate film for plastic film capacitors according to Claim 1, wherein said film is produced by a method comprising the steps of: melt-extruding polyethylene-2,6-naphthalate which contains 0.01 to 1 wt% of inactive fine particles having a primary particle diameter of 0.001 to 10 µm and has an intrinsic viscosity of not smaller than 0.40 into a film, stretching the film by 1.1 to 3.5 times in the machine direction at a temperature of 120 to 170°C, stretching the film by 2.5 to 5.0 times in the transverse direction at a temperature of 120 to 180°C, heatsetting the film at a temperature of 130 to 240°C while subjecting the film to relaxation by 1 to 30 % in the transverse direction, re-stretching the film by 1.2 to 4.0 times in the machine direction at a temperature of 140 to 200°C, heatsetting the film at a temperature of 240°C to the melting point while re-stretching the film by 1.03 to 1.5 times in the transverse direction, and winding said film while subjecting the film to relaxation by 1 to 10 % in the machine direction and in the transverse direction.

Claim 6

A process for producing a polyethylene-2,6-naphthalate film for plastic film capacitors having a Young's modulus of not smaller than 600 kg/mm both in the machine direction and in the transverse direction and a degree of crystallinity of not smaller than 40 %, comprising the steps of: melt-extruding polyethylene-2,6-naphthalate which contains 0.01 to 1 wt% of inactive fine particles having a primary particle diameter of 0.001 to 10 µm and has an intrinsic viscosity of not smaller than 0.40 into a film, stretching the film by 1.1 to 3.5 times in the machine direction at a temperature of 120 to 170°C, stretching the film by 2.5 to 5.0 times in the transverse direction at a temperature of 120 to 180°C, heatsetting the film at a temperature of 130 to 240°C while subjecting the film to relaxation by 1 to 30 % in the transverse direction, re-stretching the film by 1.2 to 4.0 times in the machine direction at a temperature of 140 to 200°C, heatsetting the film at a temperature of 240°C to the melting point while re-stretching the film by 1.03 to 1.5 times in the transverse direction,and winding the film while subjecting the film to relaxation by 1 to 10 % in the machine direction and in the transverse direction.

Claim 7

A process for producing a polyethylene-2,6-naphthalate film for plastic film capacitors having a Young's modulus of not smaller than 600 kg/mm both in the machine direction and in the transverse direction and a degree of crystallinity of not smaller than 40 %, comprising the steps of: melt-extruding polyethylene-2,6-naphthalate which contains 0.01 to 1 wt% of inactive fine particles having a primary particle diameter of 0.001 to 10 µm and has an intrinsic viscosity of not smaller than 0.40 into a film, stretching the film by 1.1 to 3.5 times in the machine direction at a temperature of 120 to 170°C, stretching the film by 2.5 to 5.0 times in the transverse direction at a temperature of 120 to 180°C, heatsetting the film at a temperature of 130 to 240°C while subjecting the film to relaxation by 1 to 30 % in the transverse direction, re-stretching the film by 1.2 to 4.0 times in the machine direction at a temperature of 140 to 200°C, heatsetting the film at a temperature of 240°C to the melting point while re-stretching the film by 1.03 to 1.5 times in the transverse direction,and winding the film while subjecting the film to relaxation by 1 to 10 % in the machine direction and in the transverse direction.

Claim 8

A process according to Claim 5, wherein said inactive fine particles are at least one of fine particles selected from the group consisting of kaolin, talc, silica, magnesium carbonate, calcium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, lithium fluoride, Ca, Ba, Zn and Mn salts of terephthalic acid and carbon blacks.