Magnetic recording medium

Abstract

A magnetic recording medium including a nonmagnetic substrate and a magnetic layer, wherein the nonmagnetic substrate is made from a polyethylene naphthalate and has a thickness of 6.5 μm or smaller, and the magnetic recording medium has a creep deformation of 0.30% or less in a longitudinal direction of the magnetic recording medium under a tensile stress of 15.7 MPa applied in the longitudinal direction at 60° C. for 50 hours.

Description

Claims

1. A magnetic recording medium comprising a nonmagnetic substrate and a magnetic layer, wherein the nonmagnetic substrate is made from a polyethylene naphthalate and has a thickness of 6.5 μm or smaller, and the magnetic recording medium has a creep deformation of 0.30% or less in a longitudinal direction of the magnetic recording medium under a tensile stress of 15.7 MPa applied in the longitudinal direction at 60° C. for 50 hours.

2. The magnetic recording medium according to claim 1, wherein the magnetic layer has a roughness average Ra of from 1 to 3 nm.

3. The magnetic recording medium according to claim 1, wherein the magnetic layer has a roughness average Ra of from 1.2 to 2.8 nm.

4. The magnetic recording medium according to claim 1, wherein the magnetic layer has a roughness average Ra of from 1.5 to 2.8 nm.

5. The magnetic recording medium according to claim 1, wherein the nonmagnetic substrate has a creep deformation of 0.30% or less in a longitudinal direction of the nonmagnetic substrate under a tensile stress of 15.7 MPa applied in the longitudinal direction at 60° C. for 50 hours.

6. The magnetic recording medium according to claim 5, wherein the creep deformation of the nonmagnetic substrate is 0.20% or less.

7. The magnetic recording medium according to claim 5, wherein the creep deformation of the nonmagnetic substrate is 0.15% or less.

8. The magnetic recording medium according to claim 1, further comprising a nonmagnetic layer between the nonmagnetic substrate and the magnetic layer.

9. The magnetic recording medium according to claim 8, wherein the nonmagnetic layer contains nonmagnetic powder and a binder.

10. The magnetic recording medium according to claim 1, wherein the creep deformation is 0.20% or less.

11. The magnetic recording medium according to claim 1, wherein the creep deformation is 0.15% orless.

12. The magnetic recording medium according to claim 1, wherein the nonmagnetic substrate has a thickness of from 3.0 to 6.0 μm.

13. The magnetic recording medium according to claim 1, wherein the nonmagnetic substrate has a thickness of from 3.0 to 5.5 μm.

14. The magnetic recording medium according to claim 1, wherein the nonmagnetic substrate is heat-treated at a temperature lower than a glass transition temperature of the substrate by 25° C. or more, before the magnetic layer is provided above the nonmagnetic substrate.

15. The magnetic recording medium according to claim 1, wherein the nonmagnetic substrate is heat-treated at a temperature lower than a glass transition temperature of the substrate by 30° C. or more, before the magnetic layer is provided above the nonmagnetic substrate.