# US 4,395,447 A · Medium for recording

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- Number: US 4,395,447 A
- Document ID: US4395447A
- Status: Granted
- Kind: A
- Application number: 06/256,316
- Filed: 1981-04-22
- Granted: 1983-07-26
- Earliest claimed: 1980-05-08
- Inventors: Yoshiro Nakamatsu
- Web page: https://patentgrep.com/patent/US4395447A

## CPC

- G11B 5/016: using magnetic foils
- G11B 5/012: Recording on, or reproducing or erasing from, magnetic disks (G11B17/00, G11B19/00 take precedence)
- G11B 5/845: in a magnetic field
- Y10S 428/90: Magnetic feature
- Y10T 428/24612: Composite web or sheet
- 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 video disc includes a magnetic material applied thereon in such a manner that the orientation of said magnetic material is gradually intensified from the outermost track of the video disc to the innermost track thereof, starting from zero orientation at the outermost track.

## Claims

### Claim 1

A recording medium comprising:
(a) a recording disc,
(b) a magnetic coating on said disc and with said coating having a thickness which decreases from a maximum to a minimum radially inwardly from the outer periphery toward the center of said disc to provide correspondingly increasing recording density from the outer periphery toward the center of said disc, said coating containing magnetic particles,
(c) said magnetic particles being oriented relative to the surface of said disc generally inversely to the change in thickness of said coating and being essentially non-oriented at the periphery of said disc in the area of maximum coating thickness and increasing in orientation radially inwardly toward the center of said disc to a maximum uniform orientation in the area of minimum coating thickness, to thereby provide an essentially constant output for the recording medium from the disc periphery radially inwardly to the inner termination of said magnetic coating.

### Claim 2 (depends on 1)

The recording medium of claim 1 wherein the resolution thereof adjacent the area of minimum coating thickness and maximum uniform orientation is about 90%.

### Claim 3

In the manufacture of a recording medium comprising a recording disc provided with a magnetic coating on said disc and with said coating containing magnetic particles, the steps of:
(a) coating said disc with said magnetic coating so that the latter has a thickness which decreases from a maximum to a minimum radially inwardly from the outer periphery toward the center of said disc to provide correspondingly increasing recording density from the outer periphery toward the center of said disc,
(b) and causing said magnetic particles on said coated disc to be oriented relative to the surface of said disc generally inversely to the change in thickness of said coating so that said particles are essentially non-oriented at the periphery of said disc in the area of maximum coating thickness and increase in orientation radially inwardly toward the center of said disc to a maximum uniform orientation in the area of minimum coating thickness to provide a recording medium having an essentially constant output from the disc periphery radially inwardly to the inner termination of said magnetic coating.