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Browse Prior Art Database

Temperature Control of a Projection Display Cell

IP.com Disclosure Number: IPCOM000061112D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Cox, AR: AUTHOR [+3]

Abstract

A heater assembly for bringing a miniature liquid-filled display cell to operating temperature employs a PTC (positive temperature coefficient) material as the heating element. Accurate operating temperature control is provided by an associated thermistor temperature sensor but the self-limiting characteristics of the PTC material are relied on to prevent thermal runaway in the event of control circuit failure. The heater assembly is mounted in a heat sink beneath the cell from which it is largely insulated by a plastic insulator material. In normal operation the heat sink prevents overheating of the cell under illumination by a projection lamp. A heater assembly 10 and display cell 11 are shown in the drawing together with a heat sink 12.

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Temperature Control of a Projection Display Cell

A heater assembly for bringing a miniature liquid-filled display cell to operating temperature employs a PTC (positive temperature coefficient) material as the heating element. Accurate operating temperature control is provided by an associated thermistor temperature sensor but the self-limiting characteristics of the PTC material are relied on to prevent thermal runaway in the event of control circuit failure. The heater assembly is mounted in a heat sink beneath the cell from which it is largely insulated by a plastic insulator material. In normal operation the heat sink prevents overheating of the cell under illumination by a projection lamp. A heater assembly 10 and display cell 11 are shown in the drawing together with a heat sink 12. The display cell 11 is an electrochromic cell and consists of a display chip 15 under a conductive solution 16 containing an electrochromic species. Images formed on an array of electrodes on the chip surface by deposition of the species in colored form are projected by illumination through a glass cover 17. The heat sink 12 is provided to prevent overheating of the solution under projector illumination. The electrochromic display will only operate satisfactorily within a narrow temperature range above ambient temperature. Thus, a heater 10 is necessary to bring the cell quickly up to temperature at power- on. The heater 10 is mounted directly beneath the chip 15 and is separated...