MAGNETIC RECORDING MEDIUM

• US 20090087689A1
• Filed: 09/29/2008
• Published: 04/02/2009
• Est. Priority Date: 09/28/2007
• Status: Abandoned Application

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Oyanagi, Masahito, Doushita, Hiroaki
• Application Number:
  US12/240,284
• Publication Number:
  US 20090087689A1
• Time in Patent Office: Days
• US Class Current: 428/844.800
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/7021 containing a polyurethane or a polyisocyanate
• CPC Class Codes: G11B 5/71 characterised by the lubricant

Abstract

The magnetic recording medium comprises a magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support. In the magnetic recording medium, a number of protrusions equal to or greater than 10 nm in height on the magnetic layer surface, as measured by an atomic force microscope, ranges from 50 to 500/1,600 μm², the binder comprises a polyurethane resin with a weight average molecular weight ranging from 100,000 to 200,000, and the magnetic layer further comprises a carbonic ester having a molecular weight ranging from 360 to 460.

Claims

1. A magnetic recording medium comprising a magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support, wherein

a number of protrusions equal to or greater than 10 nm in height on the magnetic layer surface, as measured by an atomic force microscope, ranges from 50 to 500/1,600 μ

m²,

the binder comprises a polyurethane resin with a weight average molecular weight ranging from 100,000 to 200,000, and

the magnetic layer further comprises a carbonic ester having a molecular weight ranging from 360 to 460.

2. The magnetic recording medium according to claim 1, wherein the carbonic ester is a carbonic ester denoted by general formula (1).

[In general formula (1), R¹ and R² each independently denote a saturated hydrocarbon group.]

3. The magnetic recording medium according to claim 1, wherein one of R¹ and R² denotes a saturated hydrocarbon group having a branched structure.

4. The magnetic recording medium according to claim 1, wherein, among R¹ and R², one denotes a saturated hydrocarbon group having a branched structure and the other denotes a saturated hydrocarbon group having a linear structure.

5. The magnetic recording medium according to claim 3, wherein the branched structure is present at a β

position in the saturated hydrocarbon group.

6. The magnetic recording medium according to claim 1, wherein one of R¹ and R² denotes 2-methylpropyl group, 2-methylbutyl group or 2-ethylhexyl group.

7. The magnetic recording medium according to claim 1, wherein the polyurethane resin comprises the following polyurethane resin (A) and/or the following polyurethane resin (B).

Polyurethane resin (A):

A polyurethane resin with a weight average molecular weight ranging from 100,000 to 200,000 in the form of a reaction product of a polyether polyol;

a short-chain diol having a bridged hydrocarbon structure denoted by the following (a) and/or a bridged hydrocarbon structure denoted by the following (b); and

an organic diisocyanate.

Polyurethane resin (B);

A polyurethane resin with a weight average molecular weight ranging from 100,000 to 200,000 in the form of a reaction product of a polyester polyol having a weight average molecular weight ranging from 100,000 to 200,000, comprising an aliphatic dibasic acid and an aliphatic diol not having a cyclic structure but comprising a branched alkyl side chain;

an aliphatic diol having a branched alkyl side chain with a total carbon number of equal to or more than 3; and

an organic diisocyanate.