Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
1995-03-21
2004-10-12
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Record medium
Disk
C428S141000, C428S690000
Reexamination Certificate
active
06804085
ABSTRACT:
FIELD OF THE INVENTION
This invention relates, in an electromagnetic data-storage (information storage and retrieval) system, to the contact (communication) interface between the recording surface of a rigid information storage magnetic recording medium (device), such as a disk, and a read/write head (or transducer) structure which operates in substantially continuous dynamic contact with the medium's surface during reading and writing operations. In particular, the invention focuses upon both the structural characteristics of such a contact interface, and upon the process and methodology of preparing and creating that interface. From another point of view, the invention disclosed herein also relates to a contact recording electromagnetic information storage and retrieval system, also called a read/write system, wherein several important features interact. This system includes, inter alia, a rigid magnetic recording medium, or device, having a surface associated with an adjacent information storage layer, an elongate flexure, a transducer portion joined to, and carried/supported/biased by, that flexure including read/write pole structure embedded within a circumsurrounding, medium-contacting wear pad, and a contact interface in the region of contact between the transducer/wear pad/medium surface which meets the criteria of other features of the present invention. This invention also pertains to the surface structure, per se, of a rigid recording medium.
The term “recording surface” is employed herein as a verbal artifact, widely recognized in the art, to refer collectively to a solid-material structure, typically a layered structure, including the usual information-storage magnetic-recording-layer substructure (typically one or two layers), and the normal protective overcoat (if any) provided on the “transducer side” of the magnetic-recording-layer substructure.
While, to the naked eye, the recording surface of a modern rigid recording medium, such as a rigid disk, appears to be absolutely flat and smooth, on a microscopic level, such a surface is, in truth, inherently irregular, to different degrees of irregularity depending upon the associated surface-preparation technique(s). As will become very apparent from the explanatory and descriptive material which follows hereinbelow, our creation and development of the present invention has involved, largely, an exploration of the microscopic surface irregularity in such a setting. Given this situation, we view the interface surface structure discussed and claimed herein—the landscape, so to speak—in terms of topography and peaks and valleys, etc.
BACKGROUND AND SUMMARY OF THE INVENTION
As has just been expressed above in the “Field of the Invention” section, the novel system, medium and interface of the present invention, and the associated creational processing and methodology, exist in relation to, and in the regime of, contact recording, and in the context of a contact recording system including other important interactive and cooperative structural elements and features. This is a regime which represents a substantial departure from the conventional art of the standard “flying”, take-off-and-landing-type systems—a departure which has been pioneered and led by the Censtor Corporation of San Jose, Calif.
While the contributions of the present invention clearly offer utility in a variety of rigid-medium systems, we describe and illustrate those contributions herein particularly in the setting of rigid-disk recording—a setting wherein the invention has been found to proffer great immediate commercial promise.
Most of the pioneering and significant work in this field is disclosed and illustrated in the following, listed U.S. patents and pending U.S. patent applications, and it is our intent, as is now expressed, to have the full disclosure contents of each and every one of these listed patents and patent applications fully incorporated herein by reference:
(a) U.S. Pat. No. 4,751,598, issued Jun. 14, 1988;
(b) U.S. Pat. No. 4,860,139, issued Aug. 22, 1989;
(c) U.S. Pat. No. 5,041,932, issued Aug. 20, 1991;
(d) U.S. Pat. No. 5,073,242, issued Dec. 17, 1991;
(e) U.S. Pat. No. 5,111,351, issued May 5, 1992;
(f) U.S. Pat. No. 5,163,218, issued Nov. 17, 1992;
(g) U.S. Pat. No. 5,174,012, issued Dec. 29, 1992;
(h) U.S. Pat. No. 5,063,712, issued Nov. 12, 1991;
(i) U.S. Pat. No. 4,757,402, issued Jul. 12, 1988;
(j) U.S. Pat. No. 4,636,894, issued Jan. 13, 1987;
(k) U.S. Pat. No. 4,423,450, issued Dec. 27, 1983;
(l) U.S. patent application Ser. No. 08/191,967, filed Feb. 4, 1994;
(m) U.S. patent application Ser. No. 07/992,886, filed Dec. 14, 1992;
(n) U.S. patent application Ser. No. 07/990,005, filed Dec. 10, 1992;
(o) U.S. patent application Ser. No. 07/989,170, filed Dec. 10, 1992;
(p) U.S. patent application Ser. No. 07/806,577, filed Dec. 21, 1991;
(q) U.S. patent application Ser. No. 07/966,095, filed Oct. 22, 1992;
(r) U.S. patent application Ser. No. 08/011,890, filed Feb. 1, 1993; and
(s) U.S. patent application Ser. No. 08/338,394, filed Nov. 14, 1994.
As is recognized in the leading work done by the Censtor Corporation, contact reading and writing offers the most intimate working relationship between a read/write head and a rigid magnetic recording surface. Such intimacy, for a given head geometry, offers the maximum possible linear recording density and signal output level. However, and focussing illustrative attention hereinafter throughout on rigid disk recording, contact operation introduces, significantly, the issue of wear which takes place within the head/disk interface. And, while wear involves both head wear and media wear, in contact operation, it is head wear that is far the more important issue, and is the key factor which decides the usable lifetime of a given recording system. Accordingly, the primary focus of the work leading to the present invention has been solving the problem of head wear.
Accepting the fact that some wear often occurs wherever there is relative motion between two bodies in contact, the challenge of maintaining head wear within acceptable limits in the setting of contact recording is fundamentally one of tribology. Thus, a functional thrust of the present invention has been to establish a contact, head/disk interface which will lead to a head-wear characteristic, or performance, offering a system having, as an illustration, a usable lifetime of five years, under conditions of continuous (24-hours-per-day, everyday) operation.
In the interface proposed by the present invention, the read/write head is embedded, and exposed in a disk-contacting face, within a tiny-footprint (typically about 20-&mgr;m by 20-&mgr;m) contact, or wear, pad. In such a setting, pad wear must be less than about 5-&mgr;m total height change for most read/write transducers. For wear-pad lateral dimensions of 20-&mgr;m by 20-&mgr;m mentioned in the illustration above, this corresponds to a volumetric wear rate of less than about 2000-&mgr;m
3
over the total intended interface lifetime of about 5-years. Such a volume of wear, of course, must be scaled accordingly to accommodate different wear-pad dimensions, as well as to account for the presence of multiple disk-contacting wear pads. The single-pad head geometry tested in one embodiment of the present invention was capable of tolerating the wear volume just mentioned (about 2000-&mgr;m
3
) without degradation of read/write performance.
In point of fact, we have discovered that an interface constructed in accordance with the teachings of this invention can lead to as low a figure as 0.1-&mgr;m of vertical wear for over 5-years of continuous-duty operation in a 48-mm disk drive system. When a limited duty cycle of less than 24-hours-per-day is taken into consideration—a duty cycle which typifies the operation of small disk drive systems, head-wear life projections extend far beyond the 5-year satisfactory performance mark.
Preferably, a plurality of the asperities that are within the 100-&mgr;m squared area, rise at least 5-nm from an interposed recess within a 10-&mg
Azarian Michael H.
Baldwinson Michael A.
Berding Keith R.
Chun Kaynam
Garrettson Garrett A.
Evans Jefferson
Kolisch & Hartwell, P.C.
Seagate Technology LLC
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