Patent ID: 7531252

Claim:
A magnetic recording medium comprising a magnetic layer on at least one surface of a film formed from an aromatic polyamide, the film being characterized in that the heat shrinkage ratio in the transverse direction of the film subjected to heat treatment under a condition of no tension for 30 mm. at 180° C. is from 1.0 to 2.5%, and wherein the film: (1) satisfies the following equations (1)-(4) simultaneously, with αMD (×10 −6 /° C.) and αTD (×10 −6 /° C.) being coefficient of thermal expansion in the longitudinal and the transverse direction, respectively, and βMD (×10 −6 /% RH) and βTD (×10 −6 /% RH) being coefficient of hygroscopic expansion in the longitudinal and the transverse direction, respectively, −7 ≦αMD≦ 6 (1) α MD− 10 ≦αTD≦αMD− 3 (2) −10 ≦βMD≦ 10 (3) β MD −10 ≦βTD≦βMD− 3 (4); and (2) satisfies the following equations (5) and (6) simultaneously, with EMD (GPa) and ETD (GPa) being Young's moduli in the longitudinal and the transverse direction, respectively, 8≦EMD≦16 (5) EMD×0.7≦ETD≦EMD×1.7 (6); and wherein the magnetic-recording medium satisfies the following equations (7)-(10) simultaneously, with α′MD (×10 −6 /° C.) and α′TD (×10 −6 /° C.) being coefficients of thermal expansion in the longitudinal and the transverse directions, respectively, and β′MD (×10 −6 /% RH) and β′TD (×10 −6 /% RH) being coefficients of hygroscopic expansion in the longitudinal and the transverse directions, respectively, −5 ≦α′MD ≦10 (7) −5 ≦α′MD−α′TD ≦5 (8) −10 ≦β′MD ≦7 (9) −5 ≦β′MD−β′TD ≦5 (10).