MR. PRAVIN S PATEL, B.S.
Pharmacy at Washington Blvd, Los Angeles, CA

4224381, Sep 23, 1980

Oct 19, 1978

5/918729

Pravin K. Patel - Los Angeles CA
David H. Johnston - Redondo Beach CA
John Makaeff - late of Los Angeles CA

Poly Disc Systems, Inc. - Torrance CA

B32B 1508

428652

A new and improved magnetic recording disk can be prepared by interposing between an aluminum substrate disk and a recording alloy layer a support layer located on the substrate disk and a shield layer located between the support layer and the recording layer. The support layer is a hard, semi-crystalline nickel alloy layer having magnetic properties which is of such a character that if it is contacted by a recording head during the use of the disk it will tend to form a powder which will not interfere with subsequent use of the disk or recording head. The shield layer is of a nonmagnetic metal and serves to reflect signals from the recording head so that they do not reach the support layer. The support layer is created by forming an electroless nickel alloy deposit in the substrate and subsequently heating this deposit at a temperature which will not cause warpage of the substrate but which cause the deposit to change to a desired physical form while concurrently causing diffusion of nickel into the substrate. Such diffusion has the effect of increasing the amount of the alloying element in the support layer and firmly bonding the support layer to the substrate.

4522848, Jun 11, 1985

Apr 28, 1983

6/489370

Pravin K. Patel - Los Angeles CA

H01F 1002

427131

A magnetic recording disk is constructed wherein a disk substrate is overlayed with at least one non-recording layer. A recording layer is then overlayed on the non-recording layer with the thickness of the recording layer at those areas corresponding to the inner track zone located toward the central hub area of the disk being thinner than the intermediate track zone radially displaced outwardly from the inner track zone toward the periphery of the recording disk.

4124736, Nov 7, 1978

Oct 29, 1974

5/518461

Pravin K. Patel - Los Angeles CA
David H. Johnston - Redondo Beach CA
John Makaeff - Los Angeles CA

Poly-Disc Systems, Inc. - Torrance CA

H01F 1000

428622

It is known to manufacture a recording member having a substrate supporting a magnetic recording alloy on a surface and to locate a protective covering on the surface of the alloy remote from the substrate. An improved protective covering for use in this combination comprises a barrier layer located on the surface of the recording alloy and an oxide layer located on the surface of the barrier layer remote from the recording alloy. The barrier layer preferably consists of a nonmagnetic material. The oxide layer is also nonmagnetic and is sufficiently thick to protect the magnetic alloy layer against surface abrasion. The barrier layer isolates the oxide layer from the magnetic recording layer so as to preserve the character and uniformity of the magnetic recording layer as the oxide layer is created.