Data storage media

Abstract

The data storage media comprises, in a preferred embodiment, a homogenous or non-homogenous plastic substrate that can be formed in situ with the desired surface features disposed thereon on one or both sides, a data storage layer such as a magneto-optic material also on one or both sides, and an optional protective, dielectric, and / or reflective layers. The substrate can have a substantially homogenous, tapered, concave, or convex geometry, with various types and geometries of reinforcement employed to increase stiffness without adversely effecting surface integrity and smoothness.

Description

[0001] This application is a continuation application of U.S. patent application Ser. No. 09 / 502,968 filed Feb. 11, 2000, and also claims the benefit of the filing date of U.S. Provisional Application Ser. Nos. 60 / 120,101 filed Feb. 12, 1999, Attorney Docket Nos. GP2-0001 and 8CN-8803PA; 60 / 134,585 filed May 17, 1999, Attorney Docket No. 8CN-8807PA; 60 / 137,883 filed Jun. 7, 1999, Attorney Docket No. 8CU-5845PA; 60 / 137,884 filed Jun. 7, 1999, Attorney Docket Nos. 8CU-5846PA; and 60 / 146,248 filed Jul. 29, 1999, Attorney Docket No. 8CN-8826PA and GP2-0018; the entire contents of each application are hereby incorporated by reference.BACKGROUND OF INVENTION[0002] Optical, magnetic and magneto-optic media are primary sources of high performance storage technology that enables high storage capacity coupled with a reasonable price per megabyte of storage. Areal density, typically expressed as billions of bits per square inch of disk surface area (Gbits per square inch (Gbits / in .sup.2)), is...

AI Technical Summary

Benefits of technology

[0034] As with the axial displacement, due to the small stand-off distances employed and the deleterious effect of surface roughness on carrier-to-noise ratio, the substrate should have a high surface quality, particularly in the area of the storage media where the data is stored, and should be substantially flat to inhibit damage to the read / write device or surface of the storage media, and to enable accurate data deposit and retrieval. Preferably, the substrate has at least a portion of its surface with an average surface roughness ((R.sub.a) as measured by atomic force microscopy) of less than about 100 Angstroms (.ANG.), preferably with a roughness of less than about 10 .ANG., and more preferably with a roughness of less than about 5 .ANG.. (Roughness is typically an average of a 10 .mu. by 10 .mu. area of the substrate.) The microwaviness of the surface, which is typically an average of a 1 mm by 1 mm area, can be up to about 100 .ANG., with up to about 10 .ANG. preferred, and up to about 5 .ANG. especially preferred. With respect to the flatness (also known as "run-out"), a substantially flat substrate essentially free of ridges or valleys is especially preferred. A run-out of up to about 100 .mu. can be employed, with a run-out of up to about 10 .mu. preferred, and a run-out up to about 5 .mu. especially preferred. (Flatness is typically an average of the area of the entire disk.)

[0086] One unexpected result of the storage media described herein that contain a rigid substrate, e.g., an aluminum substrate, with a plastic resin embossed with surface features, was retention of head slap performance as compared to conventional storage media. Conventional aluminum media are typically coated, e.g., with nickel phosphide, to improve the surface hardness for polishing and to resist damage to the polished surface by contact with the head. Plastic resins are generally softer than the aluminum surface coating and would be expected to limit the head slap resistance of the storage media; however, storage media described herein containing plastic films unexpectedly exhibited no observed diminished slap resistance. This unexpected result is believed to depend somewhat on the thickness of the plastic film and plastic films having higher thickness are expected to have diminished head slap resistance. Thus, in an especially preferred embodiment, the head slap resistance of a coated aluminum substrate having a plastic film, preferably containing surface features, is substantially equivalent to the head slap resistance of the coated aluminum substrate not containing the plastic film. Similar head slap results can be obtained with other rigid substrates such as glass.

Problems solved by technology

Furthermore, the physical characteristics of the storage media when in use can also affect the ability to store and retrieve data; i.e. the axial displacement of the media, if too great, can inhibit accurate retrieval of data and / or damage the read / write device.

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