Browse Prior Art Database

Optical Recording Disc System and Memory Medium

IP.com Disclosure Number: IPCOM000045951D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 5 page(s) / 54K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+5]

Abstract

An energy-absorbing medium comprises a substrate coated with a textured surface in the form of dendrites, cones, pyramids, pinnacles, projections, etc. which are in turn coated thinly with an energy-absorbing material selected from the elements in the Group VII, IB portion of the periodic chart, or elements selected from Al, C, Te, a semiconductor (Si, Ge) or a dye.

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Optical Recording Disc System and Memory Medium

An energy-absorbing medium comprises a substrate coated with a textured surface in the form of dendrites, cones, pyramids, pinnacles, projections, etc. which are in turn coated thinly with an energy-absorbing material selected from the elements in the Group VII, IB portion of the periodic chart, or elements selected from Al, C, Te, a semiconductor (Si, Ge) or a dye.

Method I

The method of forming an optical storage medium comprises:(a) depositing a random mask of a material upon the surface of a substrate, (b) etching the surface through the mask preferably by means of a reactive gas etching process such as plasma or ion beam etching, and then (c) depositing an energy- absorbing film onto the etched surface.

Method II

Alternatively, the method of forming an optical storage medium comprises:
(a) implanting high energy ions in a substrate medium or exposing the medium with photons or electrons to leave tracks in the medium, (b) employing wet chemical etching to produce a roughened surface by preferentially etching the damaged tracks, and (c) application of a thin coating of an energy-absorbing material upon the roughened surface.

Preferably, the substrate is composed of a polymer, such as polymethylmethacrylate (PMMA). A roughened texture is provided on the surface of PMMA by depositing a few angstroms (l-3) of copper or employing some copper in a reactive ion etching system operated with oxygen to promote roughening. Other metals can be employed instead of copper.

An earlier article µ*Ù describes writing with a laser beam upon an optical storage medium coated with pinnacles coated with a thin metal film which is highly absorbing of light, with the smoothed areas being more able to reflect or transmit light. The microscopically rough areas may be made from materials such as plastics. It is suggested that the pinnacled light-absorbing surface structures may be formed by dendritic growth.

U.S. Patent 4,l60,045 describes a process of forming such a surface on silicon (for solar cells) by depositing discontinuous islands of indium on the surface of the silicon to form a mask about 500-l000 angstroms thick. Then the coated surface is bombarded with an argon ion beam which sputters the islands of indium and the silicon between the islands. The islands are removed. The result is a series of small sharp cones and pyramids of silicon, which is then coated with an antireflection layer or a protective coating. Alternatives to Si are Ge, lead tin telluride, indium antimonide, etc.

Method III

Another method of fabricating the microtextured surface of the storage medium involves ion bombardment of the surface of a polymer. For example,

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oxygen ions from a plasma gun are accelerated to an energy of 250-500 eV and then neutralized by a flood of electrons. The energetic beam is then directed to the surface of a polymer on which the beam will etch microdendrites. The surface may be covered...