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Highly Compatible Write-Once and Reversible Optical Recording Media

IP.com Disclosure Number: IPCOM000038538D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Barton, RW: AUTHOR [+4]

Abstract

Write-once and reversible phase-change optical recording media usually are made with very different active layers. As a result, two separate production processes are required to produce the two media. Significant simplification, with attendant cost savings, may be realized when the production process of the write-once media can be made very similar to those used to produce reversible media. We disclose here write-once and reversible media with such characteristics. Write-once media based on a phase-change approach are well known. These media crystallize extremely fast so that short laser pulses, >30 ns to 200 ns in duration, can _ crystallize the material and record data. Usually, recording is accomplished by selectively crystallizing areas in an amorphous track.

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Highly Compatible Write-Once and Reversible Optical Recording Media

Write-once and reversible phase-change optical recording media usually are made with very different active layers. As a result, two separate production processes are required to produce the two media. Significant simplification, with attendant cost savings, may be realized when the production process of the write-once media can be made very similar to those used to produce reversible media. We disclose here write-once and reversible media with such characteristics. Write-once media based on a phase-change approach are well known. These media crystallize extremely fast so that short laser pulses, >30 ns to 200 ns in duration, can _ crystallize the material and record data.

Usually, recording is accomplished by selectively crystallizing areas in an amorphous track. To erase (crystallize), the media is exposed to laser radiation with sufficient duration, which can be significantly shorter than 1 ms. To record (amorphize), short laser pulses, typically >50 ns, are used. _ Such short heating pulses, combined with the proper thermal design of the disk structure to enable very fast cool- down, quench selected areas on the disk into the amorphous state. Information is typically encoded in amorphous areas in a crystalline track. Fast-crystallizing media can be used for either write-once or reversible applications. Whether a disk is write-once or reversible simply depends on the required quench rate of the material relative to the maximum cooling rate of the disk structure. Laser re-amorphization can be precluded by minor adjustments of the disk structure (to reduce the maximum cooling rate) or of the media composition (to change the required quench rate). Furthermore, only minimal drive modifications will be required to use either type of disk. Three implementations of the above ideas are described below. GeTe is an extremely fast-erasing material which is made reversible in the following structure: 500A Al/2kA ZnS/750...