Magnetic recording medium

• US 20020122339A1
• Filed: 11/21/2001
• Published: 09/05/2002
• Est. Priority Date: 11/21/2000
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Takano, Hiroaki, Suzuki, Masaki, Kunikata, Masanosuke
• Granted Patent: US 6,686,022 B2
• Time in Patent Office: Days
• US Class Current: 365/200
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/7085 non-magnetic abrasive particles
• CPC Class Codes: Y10T 428/24975 No layer or component greater than 5 mils thick
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/257 Iron oxide or aluminum oxide
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

Provided is a particulate magnetic recording medium with good output at high frequency, yielding a low coefficient of friction, and having good running properties, in particular, a magnetic recording medium affording good electromagnetic characteristics and good repeat durability in recording and reproducing at a high-density. The magnetic recording medium comprises a lower layer comprising a nonmagnetic powder and a binder and an upper magnetic layer comprising a ferromagnetic powder, a binder and at least one abrasives provided on a nonmagnetic support in this order. The number of abrasive particles present on said magnetic layer surface satisfied the relation 0.2≦X≦1.2 (particles/μm²). When the number of pairs of abrasive particles satisfying the relation L≦2K (where K denotes the mean particle diameter of the abrasive and L denotes the distance from the center of gravity of one of the abrasive particles to the center of gravity of the other abrasive particle) is denoted as Y (particles/μm²), Y/X is equal to or less than 2.

Claims

1. A magnetic recording medium comprising a lower layer comprising a nonmagnetic powder and a binder and an upper magnetic layer comprising a ferromagnetic powder, a binder and at least one abrasives provided on a nonmagnetic support in this order, wherein the number of abrasive particles present on said magnetic layer surface satisfied the relation 0.2≦

X≦

1.2 (particles/μ

m²), and when the number of pairs of abrasive particles satisfying the relation L≦

2K (where K denotes the mean particle diameter of the abrasive and L denotes the distance from the center of gravity of one of the abrasive particles to the center of gravity of the other abrasive particle) is denoted as Y (particles/μ

m²), Y/X is equal to or less than 2.

2. The magnetic recording medium according to claim 1 wherein said abrasive has the mean particle diameter ranging from 0.1 to 0.6 μ

m.

3. The magnetic recording medium according to claim 1 wherein said magnetic layer has a thickness ranging from 0.05 to 0.6 μ

m.

4. The magnetic recording medium according to claim 1 wherein said abrasive has a mean particle diameter falling within the range of 0.3 to 2 times the thickness of the magnetic layer.

5. The magnetic recording medium according to claim 1 wherein said lower layer has a thickness ranging from 0.5 to 2.0 μ

m.

6. The magnetic recording medium according to claim 1 wherein said magnetic layer has a coercivity ranging from 159 to 239 KA/m.

7. The magnetic recording medium according to claim 1 wherein said ferromagnetic powder is a ferromagnetic metal powder chiefly of Fe.

8. The magnetic recording medium according to claim 7 wherein said ferromagnetic metal powder has a major axis length of 0.05 to 0.19 μ

m.

9. The magnetic recording medium according to claim 7 wherein said ferromagnetic metal powder has a crystalline size ranging from 100 to 230 Angstroms.

10. The magnetic recording medium according to claim 7 wherein said ferromagnetic metal powder has a coercivity Hc of 79 to 316 KA/m and an σ

s of 1.26 to 2.26×

10<sup>−

4</sup> Wb·

m/kg.

11. The magnetic recording medium according to claim 7 wherein said ferromagnetic metal powder has a specific surface area ranging from 35 to 60 m²/g and a pH equal to or higher than 7.

12. The magnetic recording medium according to claim 1 wherein said ferromagnetic powder is a hexagonal ferrite ferromagnetic powder.

13. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has a plate diameter of 40 nm or less.

14. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has a coercivity Hc of 79 to 316 KA/m.

15. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has a σ

s ranging from 45 to 75 A·

m²/kg.

16. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has a σ

s ranging from 50 to 70 A·

m²/kg.

17. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has a plate diameter/thickness ratio ranging from 2 to 15.

18. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has a plate diameter/thickness ratio ranging from 3 to 8.

19. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has an average particle volume ranging from 2,000 to 12,000 nm³.

20. The magnetic recording medium according to claim 12 wherein said hexagonal ferrite ferromagnetic powder has an average particle volume ranging from 3,000 to 10,000 nm³.