Magnetic recording medium comprising a magnetic layer having specific thickness, surface roughness and friction coefficient

• US 6,921,592 B2
• Filed: 12/03/2003
• Issued: 07/26/2005
• Est. Priority Date: 10/31/2000
• Status: Expired due to Term

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Hitachi Maxell Limited (Maxell, Ltd.)
• Inventors: Yoshida, Kenichiro, Yoshimoto, Norihisa, Makita, Yoshiyuki, Tani, Masakazu
• Primary Examiner(s): Le, H. Thi
• Application Number:
  US10/725,413
• Publication Number:
  US 20040166373A1
• Time in Patent Office: 601 Days
• Field of Search: 428/694.BR, 428/694.BP, 428/900
• US Class Current: 428/845.5
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/735 characterised by the back layer 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 5/7368 Non-polymeric layer under the lowermost magnetic recording layer base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/78 Tape carriers
• CPC Class Codes: Y10S 428/90 Magnetic feature

Abstract

A magnetic recording medium comprising a non-magnetic support, at least one primer layer formed on one surface of the non-magnetic support, a magnetic layer formed on the primer layer, and a backcoat layer formed on the other surface of the non-magnetic support, wherein the magnetic layer has a thickness of 0.30 μm or less and a centerline average surface roughness Ra of 3.2 nm or less, and (P₁−P₀) is 30 nm or less and (P₁-P₂₀) is 5 nm or less in which P₀ is an averaged height of projections of the magnetic layer, and P₁, P₂, - - - and P₂₀ are heights of the highest, the second highest, - - - and the 20th highest projections of the magnetic layer, respectively.

Claims

1. A magnetic recording medium comprising a non-magnetic support, at least one primer layer formed on one surface of the non-magnetic support, a magnetic layer formed on the primer layer, and a backcoat layer formed on the other surface of the non-magnetic support, wherein the primer layer has a thickness of 0.3 to 3.0 μ

m, the magnetic layer has a thickness of 0.30 μ

m or less and a centerline average surface roughness Ra of 3.2 nm or less, and a ratio of μ

_mSL to μ

_mSUS [(μ

_mSL)/(μ

_mSUS)] is from 0.7 to 1.3 and a ratio of μ

_mSL to μ

_BSUS [(μ

_mSL)/(μ

_BSUS)] is from 0.8 to 1.5, wherein μ

_mSL is a coefficient of friction between said magnetic layer and a slider material, μ

_mSUS is a coefficient of friction between said magnetic layer and stainless steel (SUS

     304), and μ

_BSUS is a coefficient of friction between the backcoat layer and stainless steel (SUS

     304).

2. The magnetic recording medium according to claim 1, which is recorded and read with a reading head comprising a magnetoresistance effect element.

3. The magnetic recording medium according to claim 1, wherein said magnetic layer has a coercive force of 120 to 320 kA/m, and a product of a residual magnetic flux density in the machine direction of said magnetic layer and a thickness of said magnetic layer is from 0.0018 Tμ

m to 0.06 Tμ

m.

4. The magnetic recording medium according to claim 1, wherein said non-magnetic support has a Young'"'"'s modulus in a machine direction of at least 6.08 GPa (at least 600 kg/mm²), and a ratio of a Young'"'"'s modulus MD in the machine direction to a Young'"'"'s modulus TD in a transverse direction (MD/TD) is from 0.6 to 1.8.