Biaxially oriented polyester film and flexible disk
AssigneeTeijin Limited
InventorsToshikazu Uchida, Toshifumi Osawa
Life of this patent
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Abstract
A biaxially oriented polyester film which has a difference between refractive index on the front side and refractive index on the rear side of the film of 0 to 0.002, a heat shrinkage factor of 0 to 0.6% when it is heated at 105° C. for 30 minutes under no load, a Young's modulus of 4,609 MPa (470 kg/mm2) or more and a difference between the maximum value and the minimum value of Young's modulus on the film plane of 981 MPa (100 kg/mm2) or less, a center line average roughness on the film plane of 2 to 10 nm, and a static friction coefficient of 0.55 or less. A flexible disk having excellent electromagnetic conversion characteristics can be produced by forming an adhesive layer on both sides of the film and a magnetic layer on the adhesive layer.
Claims22
A biaxially oriented polyester film which has:
- (A) a difference between the refractive index on the front side and the refractive index on the rear side of the film of 0 to 0.002;
- (B) a heat shrinkage factor of 0 to 0.6% when it is heated at 105° C. for 30 minutes under no load;
- (C) a Young's modulus of 4,609 MPa (470 kg/mm2) or more and a difference between the maximum value and the minimum value of Young's modulus on the film plane of 981 MPa (100 kg/mm2) or less;
- (D) a center line average roughness on the film plane of 2 to 10 nm;
- and
- (E) a static friction coefficient of 0.55 or less, which biaxially oriented polyester film contains 0.1 to 0.5 wt % of first inert fine particles having an average particle diameter of 0.01 to 0.5 μm and 0.001 to 0.1 wt % of second inert fine particles having an average particle diameter of 0.1 to 1.0 μm which is larger than the average particle diameter of the first inert fine particles;
- and wherein the first inert fine particles and the second inert fine particles are of the same chemical specifies and differ from each other in the particles diameter peak value of the distribution curve of the first inert fine particles and the second inert fine particles.
Dependencies are inferred from the claim text.