High density magnetic recording medium
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United States of America Patent
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May 18, 1993
Grant Date -
N/A
app pub date -
Dec 27, 1991
filing date -
Dec 28, 1990
priority date (Note) -
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Abstract
A novel high density magnetic recording medium is disclosed. Said medium comprises a polyester film formed of a plurality of layers laminated by coextrusion and oriented by stretching, which simultaneously satisfies the conditions of the following relations (1) to (4); a back coat layer which is provided on the rougher surface side of said polyester film layer and whose surface roughness simultaneously satisfies the conditions of the following relations (5) and (6); and a magnetic film layer provided on the less rough surface side of said polyester film. Ra.sup.A .ltoreq.0.008 (1) 0.005.ltoreq.Ra.sup.B .ltoreq.0.02 (2) 0.005.ltoreq.Ra.sup.B -Ra.sup.A .ltoreq.0.015 (3) 9.ltoreq.F.sub.5 .ltoreq.30 (4) 0.015.ltoreq.Ra.sup.C .ltoreq.0.040 (5) 0.003.ltoreq.Ra.sup.C -Ra.sup.B .ltoreq.0.35 (6) wherein Ra.sup.A stands for centerline average roughness (.mu.m) of the less rough surface side of the polyester film; Ra.sup.B stands for centerline average roughness (.mu.m) of the rougher surface side of the polyester film; Ra.sup.C stands for centerline average roughness (.mu.m) of the surface of the back coat layer; and F.sub.5 stands for the tensile strength in kilograms per square millimeter at 5% elongation in the longitudinal direction of the polyester film.
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