Magnetic recording medium and process of production thereof

Abstract

An aspect of the present invention provides a magnetic recording medium comprising following layers in this order on at least one surface of a nonmagnetic support: a nonmagnetic layer including a nonmagnetic powder and a binder; and a magnetic layer including a magnetic powder and a binder, wherein the nonmagnetic support has an enthalpy relaxation (ΔH) equal to or more than 0.5 J/g and equal to or less than 2.0 J/g. According to the aspect of the present invention, a magnetic recording medium is provided that is superior in electromagnetic conversion (e.g., with a high S/N ratio for surface recording density) and running durability (e.g., with a small number of dropouts and a low error rate).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a production process diagram to describe a method of producing the magnetic recording medium according to the present invention; and

FIG. 2 shows a schematic sectional view of the magnetic recording medium according to the present invention.

Claims

1. A magnetic recording medium comprising following layers in this order on at least one surface of a nonmagnetic support: a nonmagnetic layer including a nonmagnetic powder and a binder; anda magnetic layer including a magnetic powder and a binder, wherein the nonmagnetic support has an enthalpy relaxation (ΔH) equal to or more than 0.5 J/g and equal to or less than 2.0 J/g.

2. The magnetic recording medium according to claim 1, wherein the magnetic powder is one of a ferromagnetic hexagonal ferrite powder having an average plate size equal to or more than 5 nm and equal to or less than 40 nm and a fine ferromagnetic metal powder having an axial length as average length equal to or more than 20 nm and equal to or less than 60 nm.

3. A method of producing a magnetic recording medium having a nonmagnetic layer including a nonmagnetic powder and a binder and a magnetic layer including a magnetic powder and a binder in this order on at least one surface of a nonmagnetic support, the method comprising: a thermal relaxation step of allowing the nonmagnetic support to have an enthalpy relaxation (ΔH) equal to or more than 0.5 J/g and equal to or less than 2.0 J/g.

4. The method of producing a magnetic recording medium according to claim 3, wherein the magnetic powder used in the method is one of a ferromagnetic hexagonal ferrite powder having an average plate size equal to or more than 5 nm and equal to or less than 40 nm and a fine ferromagnetic metal powder having an axial length as average length equal to or more than 20 nm and equal to or less than 60 nm.

5. The method of producing a magnetic recording medium according to claim 3, wherein in the thermal relaxation step, the nonmagnetic support is kept in a temperature range equal to or more than Tg (° C.) −40° C. and equal to or less than Tg (° C.) −1° C., and wherein said Tg (° C.) represents the glass transition temperature of a resin forming the nonmagnetic support.

6. The method of producing a magnetic recording medium according to claim 4, wherein in the thermal relaxation step, the nonmagnetic support is kept in a temperature range equal to or more than Tg (° C.) −40° C. and equal to or less than Tg (° C.) −1° C., andwherein said Tg (° C.) represents the glass transition temperature of a resin forming the nonmagnetic support.

7. The method of producing a magnetic recording medium according to claim 3, wherein the thermal relaxation step has a period of time equal to or more than 1 hour and equal to or less than 14 days.

8. The method of producing a magnetic recording medium according to claim 6, wherein the thermal relaxation step has a period of time equal to or more than 1 hour and equal to or less than 14 days.

9. The method of producing a magnetic recording medium according to claim 3, wherein the thermal relaxation step is carried out before at least one of the nonmagnetic layer and the magnetic layer is formed.

10. The method of producing a magnetic recording medium according to claim 4, wherein the thermal relaxation step is carried out before at least one of the nonmagnetic layer and the magnetic layer is formed.

11. The method of producing a magnetic recording medium according to claim 5, wherein the thermal relaxation step is carried out before at least one of the nonmagnetic layer and the magnetic layer is formed.

12. The method of producing a magnetic recording medium according to claim 6, wherein the thermal relaxation step is carried out before at least one of the nonmagnetic layer and the magnetic layer is formed.

13. The method of producing a magnetic recording medium according to claim 8, wherein the thermal relaxation step is carried out before at least one of the nonmagnetic layer and the magnetic layer is formed.

14. The method of producing a magnetic recording medium according to claim 3, wherein the nonmagnetic support is formed of one of biaxially oriented polyethylene terephthalate and biaxially oriented polyethylene naphthalate as main component.

15. The method of producing a magnetic recording medium according to claim 4, wherein the nonmagnetic support is formed of one of biaxially oriented polyethylene terephthalate and biaxially oriented polyethylene naphthalate as main component.

16. The method of producing a magnetic recording medium according to claim 5, wherein the nonmagnetic support is formed of one of biaxially oriented polyethylene terephthalate and biaxially oriented polyethylene naphthalate as main component.

17. The method of producing a magnetic recording medium according to claim 7, wherein the nonmagnetic support is formed of one of biaxially oriented polyethylene terephthalate and biaxially oriented polyethylene naphthalate as main component.

18. The method of producing a magnetic recording medium according to claim 9, wherein the nonmagnetic support is formed of one of biaxially oriented polyethylene terephthalate and biaxially oriented polyethylene naphthalate as main component.

19. The method of producing a magnetic recording medium according to claim 13, wherein the nonmagnetic support is formed of one of biaxially oriented polyethylene terephthalate and biaxially oriented polyethylene naphthalate as main component.