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Browse Prior Art Database

Optical Recording Media

IP.com Disclosure Number: IPCOM000041533D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Levin, RH: AUTHOR

Abstract

Organic cholesteric liquid crystals are the active medium of an optical recording disk. A one-micron-thick layer of a counterclockwise twisted, helical cholesteric-phase medium reflects about 100% of right circularly polarized light, and transmits left circularly polarized light, when the wavelength of light approximates the helical pitch. This property allows for either reflective or transmissive reading of a data track. The liquid crystal layer is written by the use of a laser beam. The beam's heat melts the liquid crystal. When the beam is turned off (i.e., the heat is removed), local cooling results in formation of the crystal's scattering phase.

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Optical Recording Media

Organic cholesteric liquid crystals are the active medium of an optical recording disk. A one-micron-thick layer of a counterclockwise twisted, helical cholesteric- phase medium reflects about 100% of right circularly polarized light, and transmits left circularly polarized light, when the wavelength of light approximates the helical pitch. This property allows for either reflective or transmissive reading of a data track. The liquid crystal layer is written by the use of a laser beam. The beam's heat melts the liquid crystal. When the beam is turned off (i.e., the heat is removed), local cooling results in formation of the crystal's scattering phase. Thereafter, the polarization of a reflected (or transmitted) lower-energy reading laser beam from the written scattered phase area is very different from that which is reflected from (or transmitted through) an unwritten cholesteric crystal phase area. The disk can be erased, and full-surface restored to the cholesteric phase, by the application of an audio or other high frequency field. If archival permanence is required, a higher energy laser can be used to write the disk, thus photochemically destroying the cholesteric phase and locking written areas of the layer permanently into the scattering phase.

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