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Smectic a Liquid-Crystal Light Valves for Electrophotographic Printheads

IP.com Disclosure Number: IPCOM000037915D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-30
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Yang, KH: AUTHOR

Abstract

Smectic A Liquid-Crystal (SALC) light valves can be constructed for use in high speed electrophotographic printhead applications. The smectic A LC has to be biased at a suitable elevated temperature so that the radiation and the conduction losses of the SALC printhead are fast enough to compensate the heating of few watts due to the operation of the SALC light valve. Smectic A LC with suitable smectic A-to-isotropic-transition temperature can be obtained from eutectic mixtures of LC compounds.

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Smectic a Liquid-Crystal Light Valves for Electrophotographic Printheads

Smectic A Liquid-Crystal (SALC) light valves can be constructed for use in high speed electrophotographic printhead applications. The smectic A LC has to be biased at a suitable elevated temperature so that the radiation and the conduction losses of the SALC printhead are fast enough to compensate the heating of few watts due to the operation of the SALC light valve. Smectic A LC with suitable smectic A-to-isotropic-transition temperature can be obtained from eutectic mixtures of LC compounds.

The size of the focal conic of a SALC is dependent on the biased temperature of the SALC. Results indicate that the size of the focal conic is larger than 2 mM at 43oC or higher which is 5oC below the smectic A-to-nematic transition temperature. At this bias temperature, if the SALC medium is confined in a cell with cell-spacing less than 2 mM the focal conic texture is suppressed because of the boundary effect, and a well-aligned state such as homogeneous(H) or homeotropic state will be formed. There are several means to suppress the growth of focal conic textures. These are surface alignment by oblique evaporation at high incident angle and/or choosing a smectic A LC which has no nematic meso-phase between the smectic A and the isotropic phases.

A transparent conducting indium-tin-oxide (ITO) on polymeric or glass substrates can be used as the pel heating electrode. Each pel is driven by a driver. To...