Laminated polyester film for magnetic recording medium comprising specific particles
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United States of America Patent
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Jan 18, 1994
Grant Date -
N/A
app pub date -
Sep 3, 1992
filing date -
Sep 3, 1991
priority date (Note) -
Expired
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Abstract
A laminated polyester film for a magnetic recording medium which has a first polyester layer (A) containing inorganic particles (a) having a Moh's hardness of at least 8 and a specific average particle size and inactive particles (b) having a Moh's hardness of less than 8 and a specific average particle size larger than that of the particle (a) and a second polyester layer (B) containing inactive particles (c) having a Moh's hardness of less than 8 and a specific average particle size, wherein a content of the particles (a) is from 0.25 to 5% by weight based on the weight of the polyester in the layer (A) and less than 0.15% by weight of the whole weight of the polyester in the layers (A) and (B), the contents of the particles (b) and (c) are each 0.05 to 2.0% by weight of the polyester in the layers (A) and (B), respectively, and exposed surfaces of the layers (A) and (B) have coefficients of friction and surface roughness (Ra) which satisfy the specific conditions.
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