Perpendicular magnetic recording medium

• US 4,966,821 A
• Filed: 06/27/1989
• Issued: 10/30/1990
• Est. Priority Date: 07/17/1986
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited, Ricoh Research Institute Of General Electronics Co., Ltd. (Ricoh Company Limited)
• Original Assignee: Ricoh Company Limited, Ricoh Research Institute Of General Electronics Co., Ltd. (Ricoh Company Limited)
• Inventors: Ryu, Shinei, Koh, Futoyoshi, Kawashima, Ikue, Kumano, Masafumi
• Primary Examiner(s): Thibodeau, Paul J.
• Application Number:
  US07/372,307
• Time in Patent Office: 490 Days
• Field of Search: 428/694, 428/900, 428/928, 428/678, 428/681, 428/611
• US Class Current: 428/830
• CPC Class Codes: G11B 5/00 Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor G11B11/00 and G11B13/00 take precedence
• CPC Class Codes: G11B 5/66 the record carriers consisting of several layers
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/12465 having magnetic properties, or preformed fiber orientation coordinate with shape

Abstract

A perpendicular magnetic recording medium is disclosed, which comprises a substrate, a soft magnetic layer formed on the substrate, a lower recording layer having a coercive force of Hcl formed on the soft magnetic layer, and an upper recording layer having a coercive force of Hcu, with the coercive ratio of Hcu/Hcl being in the range of 1.4 to 3.3, that is, 1.4≦Hcu/Hcl≦3.3.

Claims

1. A perpendicular magnetic recording medium comprising:

a substrate;

a soft magnetic layer formed on said substrate;

a lower recording layer having a coercive force of Hcl formed on said soft magnetic layer; and

an upper recording layer having a coercive force of Hcu, with the coercive ratio of Hcu/Hcl being in the range of 1.4 to 3.3.

2. The perpendicular magnetic recording medium as claimed in claim 1, wherein said coercive ratio of Hcu/Hcl is in the range of 1.7 to 2.5.