Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1998-12-11
2003-12-16
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S064200, C428S065100, C428S426000, C428S690000, C360S135000
Reexamination Certificate
active
06663938
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the texturing of magnetic data storage media, and more particularly to the texturing of dedicated transducing head contact zones (also called landing zones) of such media to reduce friction and improve wear, while also minimizing system resonance.
Laser textured magnetic disks, particularly those textured over areas designed for contact with data transducing heads, are known to reduce friction and improve wear characteristics as compared to mechanically textured disks. Traditional laser texturing involves focusing a laser beam onto a disk substrate surface at multiple locations, forming at each location a depression surrounded by a raised rim as disclosed in U.S. Pat. No. 5,062,021 (Ranjan) and U.S. Pat. No. 5,108,781 (Ranjan). An alternative, as disclosed in International Publications No. WO 97/07931 and No. WO 97/43079, is to use a laser beam to form domes or nodules, rather than rims. In some cases, each of the domes is surrounded by a raised rim. The features can have either circular or elliptical profiles.
Collectively, the texturing features form a texture pattern or distribution throughout the head contact zone. A particularly preferred pattern is a spiral, formed by rotating the disk at a controlled angular speed while moving a laser radially with respect to the disk. The laser is pulsed to form the individual texturing features. For example, the disk can be rotated to provide a circumferential speed of about one meter per second. Then, operating the laser at 50,000 pulses per second provides a 20 micron circumferential pitch, i.e. distance between adjacent texturing features. The radial speed of the laser controls the radial pitch or spacing between adjacent turns of the spiral, which also can be about 20 microns.
Although this approach has been highly successful in terms of reducing dynamic friction and improving the wear characteristics of dedicated transducing head contact zones, the regular, repeating pattern of the laser texture features produces strong input excitations based on the fundamental frequency of the circumferential pitch, including higher order harmonics. When the excitation frequencies coincide with natural frequencies of the slider or its gimbal and support system, resonance occurs which results in a high amplitude acoustic energy signal, which can increase the difficulty of determining the glide avalanche breaking point (a disk/transducing head spacing value) and yield a false indication that the disk has failed a glide test.
Several previously proposed media texturing alternatives address these difficulties to a degree. For example, the aforementioned International Publication Number WO 97/43079 includes the observation that mechanically textured disks, as compared to laser textured disks, produce less acoustic energy during head take-off and landing. A noise-reducing texturing alternative is discussed therein; namely, rows of rims connected to one another at their ends, as shown in
FIG. 15
of the publication. In International Application Serial No. PCT/US98/05283 entitled “Low Resonance Texturing of Magnetic Media,” filed Mar. 13, 1998, resonance-reducing texturing is disclosed in the form of elongate circumferential ridges, most notably a continuous ridge in the shape of a spiral throughout the transducing head contact region. Although these alternatives afford considerable reduction in noise during head take-off and landing, there remains a need for noise-reducing texturing arrangements compatible with substantial spacing between adjacent texturing features. These arrangements frequently are preferred due to lower manufacturing costs and better potential for producing a uniform roughness throughout the head contact zone.
According to another alternative approach, the contact zone is textured with an irregular sequence of spaced-apart texturing features forming a substantially circumferential, spiral path. Multiple turns of the spiral path define a uniform radial pitch. By contrast, the circumferential pitch is irregular, determined according to a pseudo random function in which the actual spacing intervals vary about a nominal interval, over a range comparable to but generally less than the nominal interval. This approach is disclosed in International Application Serial No. PCT/US98/05340 entitled “Magnetic Media with Randomly Positioned Texturing Features,” filed Mar. 18, 1998. While this approach has been found quite useful in minimizing resonance effects, the manufacturing advantages afforded by texture patterns of constant radial and circumferential pitch underline the desire for texturing approaches that minimize resonance effects without the need for random spacing intervals. More particularly, randomizing circumferential pitch involves additional control equipment, e.g., a random signal generator or means to accelerate and decelerate a rotating substrate disk. Also, care must be taken to assure that a texture pattern, although randomized, has a substantially constant average feature density across a slider contact area.
Therefore, it is an object of the present invention to provide a substrate texturing process in which resonance effects are minimized without randomizing the spacing between adjacent texturing features, in particular without randomizing circumferential pitch within an annular contact zone.
Another object is to provide a substrate for a magnetic data recording medium, in which multiple texturing features formed within a contact zone of the substrate are specially shaped to reduce resonance effects.
A further object is to provide a process for forming multiple texturing features on the substrate surface of a substrate for a data recording medium, in which the texturing features exhibit fast roll-off profiles, more particularly bell-shaped profiles that more effectively diminish higher order harmonics excitation.
Yet another object is to provide a data recording medium with a dedicated transducer contact zone textured to minimize the occurrence of false failure episodes during glide avalanche testing.
SUMMARY OF THE INVENTION
To achieve these and other objects, there is provided a substrate for a magnetic data storage medium of the type including a data zone for storing data and a contact zone textured for a contact with a data transducing head maintained apart from the data zone by an air bearing during use of the data storage medium. The substrate includes a substrate body having a substantially planar substrate surface including a data zone and a contact zone. The substrate body is adapted for movement substantially parallel to the substrate surface in a predetermined direction with respect to a data transducing head. Multiple texturing features are formed in the contact zone, and are projected outwardly from the substrate surface. Each of the texturing features has bell-shaped profiles taken in planes substantially perpendicular to the substrate surface and oriented in the predetermined direction. The texturing features further have diameters, taken in the predetermined direction, of at least about three microns.
As used in this application, the term “bell-shaped profile” refers primarily to the smoothness of the profile, and to the nature of its changing slope. In particular, for a texturing feature projected upwardly from a horizontal surface, the slope is zero (representing a horizontal segment) at the point of maximum texturing feature height. The profile curves in both directions away from the maximum height point, in both cases with the slope smoothly increasing, until a maximum slope is reached along a medial region between the horizontal surface and the height of the texturing feature. Then, on both sides the curve continues its downward course, but with a smoothly decreasing slope, thus to create at the bottom of the profile an outward flare.
Preferably the maximum height point is at the center of the profile, with the profile being symmetrical about the maximum height point. In fact, most preferably each profile represents a Gaussian curve, i.e.,
Cheng Yuh-Jen
Ku Chiao-Ping
Kuo David S.
Marchon Bruno
Wang Li-Ping
Castillo Jesus Del
Minisandram Raghunath S.
Resan Stevan A.
Seagate Technology LLC
LandOfFree
Media contact zone with bell-shaped texturing features does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Media contact zone with bell-shaped texturing features, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Media contact zone with bell-shaped texturing features will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3180942