Magnetic recording medium comprising two magnetic layers of hexagonal ferrite magnetic particles and binder wherein the easy axes of the particle is specified

• US 5,419,938 A
• Filed: 06/30/1993
• Issued: 05/30/1995
• Est. Priority Date: 07/03/1992
• Status: Expired due to Fees

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Tokuoka, Yasumichi, Yokoyama, Kenji, Koga, Keiji, Kagotani, Tsuneo
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US08/083,498
• Time in Patent Office: 699 Days
• Field of Search: 428/694 BH, 428/694 BM, 428/329, 428/212, 428/64, 428/900, 427/131, 360/135
• US Class Current: 428/839.3
• CPC Class Codes: G11B 5/716 characterised by two or more magnetic layers
• CPC Class Codes: G11B 5/845 in a magnetic field
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/257 Iron oxide or aluminum oxide

Abstract

A magnetic recording medium includes a coated type of magnetic layer containing magnetic powders substantially made up of hexagonal ferrite particles and a binder, and has the values of

SQR.sub.x ≧0.50

SQR.sub.y ≦0.35

where SQR_x is the squareness ratio of said magnetic layer in the recording track direction, and SQR_y is the intra-surface squareness ratio of said magnetic layer in the direction perpendicular to the recording track direction, and has also the value of

α≧3%

where α is given by

α=I(006)×100/I(%)

where I is the peak intensities, I(hkl), of the (hkl) planes of said magnetic layer upon X-ray diffraction, defined by

I=I(006)+I(110)+I(107)+I(114)

Claims

1. A magnetic recording medium comprising a substrate, a first magnetic layer coated thereon having at least one recording track, and a second magnetic layer coated on the first magnetic layer, said magnetic layers being composed essentially of magnetic hexagonal ferrite particles and binder, and wherein the easy axes of the magnetic particles in the first magnetic layer in a zone adjacent to the surface of the substrate are oriented substantially in the recording track direction, and the easy axes of the magnetic particles in the second magnetic layer in a zone adjacent to the surface of the medium are oriented substantially perpendicular to the second layer'"'"'s surface, and the easy axis of the magnetic particles changes in a continuous manner from substantially in the recording track direction to substantially in the perpendicular direction between said zones,said magnetic recording medium having the values of

View Dependent Claims (2, 3, 4, 5, 6)

2. A magnetic recording medium according to claim 1, wherein the coercive force in the recording track direction is at least 1,000 Oe.

3. A magnetic recording medium according to claim 1, wherein said hexagonal ferrite particles are Ba ferrite particles.

4. A magnetic recording medium according to claim 1, wherein said substrate is rigid.

5. A magnetic recording medium as set forth in claim 1, said medium being disc shaped and having a circumferential recording track.

6. A magnetic recording medium according to claim 1, wherein said magnetic material is formed by forming a first layer of magnetic coating, applying a magnetic field to said first magnetic layer in the recording track direction for orientation, followed by drying;

then forming a second magnetic layer on the first magnetic layer; and

applying a magnetic field to the first and second magnetic layers in the perpendicular direction for orientation.