MAGNETIC RECORDING MEDIUM

• US 20100081011A1
• Filed: 09/29/2009
• Published: 04/01/2010
• Est. Priority Date: 09/29/2008
• Status: Abandoned Application

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: NAKAMURA, Kenichi
• Application Number:
  US12/569,071
• Publication Number:
  US 20100081011A1
• Time in Patent Office: Days
• US Class Current: 428/832
• 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 5/73913 Composites or coated substrates
• CPC Class Codes: G11B 5/73937 Substrates having an organic polymer comprising a ring structure

Abstract

A magnetic recording medium includes, in the following order: a backcoat layer; a nonmagnetic support; a nonmagnetic layer containing a nonmagnetic powder and a binder; and a magnetic layer containing a ferromagnetic powder and a binder, wherein the backcoat layer contains particles having an average primary particle size D50 of from 0.05 to 1.0 μm and forming substantially no aggregates nor agglomerates in the backcoat layer.

Claims

1. A magnetic recording medium comprising, in the following order:

a backcoat layer;

a nonmagnetic support;

a nonmagnetic layer comprising a nonmagnetic powder and a binder; and

a magnetic layer comprising a ferromagnetic powder and a binder,

wherein the backcoat layer comprises particles having an average primary particle size D50 of from 0.05 to 1.0 μ

m and forming substantially no aggregates nor agglomerates in the backcoat layer.

2. The magnetic recording medium according to claim 1, wherein the particles have an average primary particle size D50 of from 0.1 to 0.6 μ

m.

3. The magnetic recording medium according to claim 1, wherein the particles are spherical particles having a particle size distribution D25/D75 of 2.0 or smaller.

4. The magnetic recording medium according to claim 3, wherein the particle size distribution D25/D75 is 1.5 or smaller.

5. The magnetic recording medium according to claim 3, wherein the particles have the particle size distribution D25/D75 adjusted to 2.0 or smaller by classification.

6. The magnetic recording medium according to claim 1, wherein the particles are polymer particles having a crosslinked structure.

7. The magnetic recording medium according to claim 1, wherein the particles are polymer particles comprising at least one component selected from the group consisting of an acrylic compound, styrene, divinylbenzene, benzoguanamine, melamine, formaldehyde, butadiene, acrylonitrile, and chloroprene.

8. The magnetic recording medium according to claim 1, wherein the particles are thermoplastic and have a glass transition temperature or a softening temperature of from 20°

to 160°

C.

9. The magnetic recording medium according to claim 1, wherein the particles are polymer particles obtained by seed emulsion polymerization in which a crosslinkable or polymerizable monomer is added to an aqueous dispersion of seed particles, adsorbed by the seed particles, and allowed to polymerize.

10. The magnetic recording medium according to claim 1, wherein the particles are inorganic particles mainly comprising silicon dioxide.

11. The magnetic recording medium according to claim 1, wherein the backcoat layer is free from carbon black having a specific surface area less than 30 m²/g.

12. The magnetic recording medium according to claim 1, wherein the magnetic layer, the nonmagnetic layer, and the backcoat layer have a total residual solvent content of from 0.1 to 25 mg/g.

13. The magnetic recording medium according to claim 1, having a lower indentation hardness on a side of the backcoat layer than on a side of the magnetic layer.

14. The magnetic recording medium according to claim 1, wherein the nonmagnetic support is one of a support mainly comprising an aromatic polyamide and a support having a nonmagnetic layer of a metal or a metallic inorganic compound formed on at least one side thereof by vapor deposition.