# US 5,346,758 A · Magnetic coating composition and magnetic recording medium

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- Number: US 5,346,758 A
- Document ID: US5346758A
- Status: Granted
- Kind: A
- Application number: 06/935,083
- Filed: 1986-11-24
- Granted: 1994-09-13
- Earliest claimed: 1984-03-01
- Assignees: Daikin Industries, Ltd.
- Inventors: Yoshiyuki Shibuya; Shigeo Daimon; Kazuo Okamura
- Web page: https://patentgrep.com/patent/US5346758A

## CPC

- G11B 5/70668: {containing a dopant}
- Y10S 428/90: Magnetic feature
- Y10T 428/25: Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
- Y10T 428/256: Heavy metal or aluminum or compound thereof
- Y10T 428/257: Iron oxide or aluminum oxide
- Y10T 428/2991: Coated
- Y10T 428/30: Self-sustaining carbon mass or layer with impregnant or other layer
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A magnetic coating composition comprising acicular particles containing iron carbide and a main magnetic material.

## Claims

### Claim 1

A magnetic coating composition comprising a main magnetic material selected from the group consisting of magnetic iron oxide particles, cobalt-modified iron oxide particles, chromium dioxide particles and metallic iron particles, and acicular particles containing iron carbide produced by contacting acicular particles of iron oxyhydroxide or iron oxide with carbon monoxide or with a mixture of carbon monoxide and hydrogen, said acicular particles being up to 2 .mu.m in average particles size (long axis or length) and having an average axial ratio of from about 3 to about 20 of primary particles.

### Claim 2 (depends on 1)

A composition as defined in claim 1, wherein said acicular particles are contained in an amount of about 0.5 to about 20% by weight based on the weight of said main magnetic material.

### Claim 3 (depends on 1)

A composition as defined in claim 1, wherein said acicular particles are contained in an amount of about 1 to about 10% by weight based on the weight of said main magnetic material.

### Claim 4 (depends on 1)

A composition as defined in claim 1, wherein said acicular particles are 0.1 to 2.0 .mu.m in average particles size.

### Claim 5 (depends on 4)

A composition as defined in claim 4, wherein said average particle size is 0.1 to 1.0 .mu.m.

### Claim 6 (depends on 1)

A magnetic recording medium comprising a substrate coated with a magnetic coating composition as claimed in claim 1.

### Claim 7

In a magnetic recording medium comprising a substrate coated with a magnetic coating composition having magnetic particles dispersed in a binder, the improvement wherein the magnetic powder is a mixture of (a) magnetic metal particles, and (b) magnetic iron carbide particles and/or magnetic particles containing iron oxide and iron carbide with the weigh ratio of (a) to (b) being in the range between 99.5:0.5 and 80:20.

### Claim 8 (depends on 7)

The magnetic recording medium of claim 7, wherein the iron carbide has the formula Fe.sub.x C wherein x is a number of at least 2.

### Claim 9 (depends on 7, 8)

The magnetic recording medium of claims 7 or 8, wherein all of the magnetic iron carbide particles are acicular.

### Claim 10 (depends on 7)

The magnetic recording medium of claim 7, wherein the magnetic particles are a mixture of (a) magnetic metal particles and (b) magnetic iron carbide particles.

### Claim 11 (depends on 7)

The magnetic recording medium of claim 7, wherein the magnetic particles are a mixture of (a) magnetic metal particles and (b) magnetic particles containing iron oxide and iron carbide.