Magnetic recording medium and process of producing the same

Abstract

A magnetic recording medium including a substrate, a nonmagnetic layer containing nonmagnetic powder and a binder, and a magnetic layer containing ferromagnetic powder and a binder, in this order, wherein the nonmagnetic layer has a thickness of from 0.5 to 2.5 μm, a specific surface area of from 20 to 120 m2/ml, a pore volume of from 0.15 to 0.40 ml/ml, and a median pore radius of from 3 to 16 nm, and the nonmagnetic layer has particles having an average particle diameter of from 4 to 14 nm on a magnetic layer side.

Description

Claims

1. A magnetic recording medium comprising: a substrate;a nonmagnetic layer containing nonmagnetic powder and a binder; anda magnetic layer containing ferromagnetic powder and a binder, in this order,wherein the nonmagnetic layer has a thickness of from 0.5 to 2.5 μm, a specific surface area of from 20 to 120 m2/ml, a pore volume of from 0.15 to 0.40 ml/ml, and a median pore radius of from 3 to 16 nm, and the nonmagnetic layer has particles having an average particle diameter of from 4 to 14 nm on a magnetic layer side.

2. The magnetic recording medium according to claim 1, wherein the particles has an average particle diameter of from 5 to 14 nm.

3. The magnetic recording medium according to claim 1, wherein the particles has an average particle diameter of from 5 to 13 nm.

4. The magnetic recording medium according to claim 1, wherein the nonmagnetic layer has pores filled with the particles having an average particle diameter of from 4 to 14 nm.

5. The magnetic recording medium according to claim 1, wherein the magnetic layer has a thickness of from 25 to 150 nm.

6. The magnetic recording medium according to claim 1, wherein the magnetic layer has a thickness of from 25 to 100 nm.

7. The magnetic recording medium according to claim 1, wherein the magnetic layer has a thickness of from 25 to 90 nm.

8. The magnetic recording medium according to claim 1, wherein the average particle diameter of the particles is not larger than a desorption pore radius D90 of the nonmagnetic layer.

9. The magnetic recording medium according to claim 1, wherein the average particle diameter of the particles is not larger than the (desorption pore radius D10+desorption pore radius D90)/2 of the nonmagnetic layer.

10. The magnetic recording medium according to claim 1, which is for use in recording signals and reproducing the recorded signals using a giant magnetoresistive head having a read track width of 1 μm or smaller.

11. The magnetic recording medium according to claim 1, wherein the nonmagnetic layer has a thickness of from 0.5 to 2.0 μm.

12. The magnetic recording medium according to claim 1, wherein the nonmagnetic layer has a thickness of from 0.6 to 2.0 μm.

13. A process for producing a magnetic recording medium including a substrate, a nonmagnetic layer containing nonmagnetic powder and a binder, and a magnetic layer containing ferromagnetic powder and a binder in this order, the process comprising: applying a coating composition containing a nonmagnetic powder and a binder on a substrate to form a nonmagnetic layer having a thickness of from 0.5 to 2.5 μm, a specific surface area of from 20 to 120 m2/ml, a pore volume of from 0.15 to 0.40 ml/ml, and a median pore radius of from 3 to 16 nm;applying a dispersion containing particles having an average particle diameter of from 4 to 14 nm on the nonmagnetic layer; andapplying a coating composition containing ferromagnetic powder and a binder on the nonmagnetic layer onto which the dispersion is applied, to form a magnetic layer.

14. The process according to claim 13, wherein the dispersion contains 2% to 15% by weight of the particles which have an average diameter of not greater than the desorption pore radius D90 of the nonmagnetic layer.