Magnetic recording medium and magnetic recording and reproducing methods

• US 20040265643A1
• Filed: 06/22/2004
• Published: 12/30/2004
• Est. Priority Date: 06/23/2003
• Status: Abandoned Application

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Ejiri, Kiyomi
• Application Number:
  US10/872,520
• Publication Number:
  US 20040265643A1
• Time in Patent Office: Days
• US Class Current: 428/837
• CPC Class Codes: G11B 5/584 for track following on tapes
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/733 characterised by the addition of non-magnetic particles base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/7356 comprising non-magnetic particles in the back layer, e.g. particles of TiO2, ZnO or SiO2
• CPC Class Codes: G11B 5/73927 Polyester substrates, e.g. polyethylene terephthalate

Abstract

A magnetic recording medium comprising a magnetic layer, a flexible support and a back coat layer in this order, wherein a density of spines on the back coat layer having a height of 100 nm or more measured with an atomic force microscope is from 50 to 200 in 90 μm square, and a thermal shrinkage factor in a machine direction after preservation at 70° C. 5% RH for 48 hours is 0.4% or less.

Claims

1. A magnetic recording medium comprising a magnetic layer, a flexible support and a back coat layer in this order, wherein a density of spines on the back coat layer having a height of 100 nm or more measured with an atomic force microscope is from 50 to 200 in 90 μ

m square, and a thermal shrinkage factor in a machine direction after preservation at 70°

C. 5% RH for 48 hours is 0.4% or less.

2. The magnetic recording medium according to claim 1, which is used in a recording and reproducing system having a reproducing track breadth of from 2 to 15 μ

m

3. The magnetic recording medium according to claim 1, which is used in a recording and reproducing system having a reproducing track breadth of from 2 to 10 μ

m

4. The magnetic recording medium according to claim 1, further comprising a nonmagnetic layer containing nonmagnetic powder and a binder so that the magnetic layer, the nonmagnetic layer and the flexible support are in this order, wherein the magnetic layer has a thickness of from 30 to 150 nm.

5. The magnetic recording medium according to claim 4, wherein the magnetic layer has a thickness of from 50 to 120 nm.

6. The magnetic recording medium according to claim 1, wherein coated layers including the magnetic layer provided on a side of the support opposite to a side of the support on which the back coat layer is provided have a glass transition point of from 100 to 200°

C.

7. The magnetic recording medium according to claim 1, wherein the flexible support is a polyester film having a Young'"'"'s modulus in a machine direction of 5,880 MPa or more.

8. The magnetic recording medium according to claim 1, wherein the back coat layer contains nonmagnetic powder and a binder.

9. The magnetic recording medium according to claim 8, wherein the nonmagnetic powder contains a carbon black.

10. The magnetic recording medium according to claim 9, wherein the carbon black has an average primary particle size of 50 nm or less.

11. The magnetic recording medium according to claim 9, wherein the carbon black has an average primary particle size of from 10 to 40 nm.

12. The magnetic recording medium according to claim 1, wherein the back coat layer has a glass transition temperature of from 80 to 180°

C.

13. The magnetic recording medium according to claim 1, wherein the back coat layer has a glass transition temperature of from 90 to 160°

C.

14. A method comprising recording and reproducing the magnetic recording medium according to claim 1 with a reproducing track breadth of from 2 to 15 μ

m.

15. The method according to claim 14, wherein the reproducing track breadth is from 2 to 10 μ

m.