Smectic liquid crystal device with temperature control system

• US 4,763,992 A
• Filed: 04/28/1987
• Issued: 08/16/1988
• Est. Priority Date: 11/15/1983
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takada, Yoshihiro, Hosono, Nagao
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/045,769
• Time in Patent Office: 476 Days
• Field of Search: 350/350 S, 350/331 T, 350/351, 350/346, 355/3 R
• US Class Current: 349/72
• CPC Class Codes: G02F 1/133382 Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell

Abstract

An image forming apparatus comprising: a light signal generator which comprises an exposure light source and a light-path switching means capable of interrupting the transmission of light rays at arbitrary portions of the cross-sectional area of the path of the light rays emitted from the light source, and an image-bearing member so disposed as to be illuminated with light signals from said light signal generator, wherein the light signal generator comprises: the light-path switching means which in turn comprises scanning lines, data lines and a ferroelectric liquid crystal material having an operational temperature range in which the ferroelectric liquid crystal material behaves as a ferroelectric liquid crystal and driven by selective application of signals to the scanning lines and the data lines so as to assume either one of light-transmitting state and light-interrupting state, and temperature control means for controlling the temperature of the liquid crystal material within the operational temperature range by means of at least one of heating means and cooling means.

Claims

1. A liquid crystal device comprising:

(a) a light source for emitting light rays;

(b) a light-path switching means disposed in the path of said light rays emitted from said light source;

said light-path switching means comprising a shutter array including a plurality of shutter means;

each shutter means comprising a pair of opposed electrodes and ferroelectric liquid crystal material sandwiched therebetween;

(c) a temperature sensor for detecting the temperature of the ferroelectric liquid crystal material and for generating an output response thereto;

(d) a temperature raising means for raising the temperature of the ferroelectric liquid crystal material, said temperature raising means comprising a resistance heater disposed in a thermally insulating body;

(e) a temperature controlling means which, during the operation of said shutter means, is for receiving said output from the temperature sensor, for comparing said detected temperature with a predetermined operational temperature range and a predetermined temperature above said operational temperature range, for restoring the temperature of the ferroelectric liquid crystal material when the detected temperature is outside said operational temperature range by causing the temperature raising means to raise the temperature of the ferroelectric crystal material until said detected temperature is above said predetermined temperature above the operational temperature range and thereafter to allow the ferroelectric liquid crystal material to cool to a temperature within said operational temperature range, and for causing the temperature raising means to maintain the temperature of the ferroelectric liquid crystal material within said operational temperature range;

said operational temperature range being the range wherein the ferroelectric liquid crystal material assumes a chiral smectic phase.

2. A Liquid crystal device according to claim 1 wherein the liquid crystal in said chiral smectic phase is disposed in a layer thin enough to release its spiral structure in the absence of an electric field.

3. A liquid crystal device according to claim 1 wherein said chiral smectic phase is a chiral smectic C phase or H phase.

4. A liquid crystal device according to claim 1, wherein said ferroelectric liquid crystal assumes a smectic A phase at said predetermined temperature above said operational temperature.

5. A liquid crystal device according to claim 1 further comprising a cooling means for cooling the temperature of the ferroelectric liquid crystal material.

6. A liquid crystal device comprising:

(a) a light source for emitting light rays;

(b) a light-path switching means disposed in the path of said light rays emitted from said light source;

said light-path switching means comprising a shutter array including a plurality of shutter means;

each shutter means comprising a pair of opposed electrodes and ferroelectric liquid crystal material sandwiched therebetween;

(c) a temperature sensor for detecting the temperature of the ferroelectric liquid crystal material and for generating an output response thereto;

(d) a temperature raising means for raising the temperature of the ferroelectric liquid crystal material, said temperature raising means comprising a resistance heater disposed in a thermally insulating body;

(e) a temperature controlling means which, during the operation of said shutter means, is for receiving said output from the temperature sensor, for comparing said detected temperature with a predetermined operational temperature range and a predetermined temperature above said operational temperature range, for restoring the temperature of the ferroelectric liquid crystal material when the detected temperature is outside said operational temperature range by causing the temperature raising means to raise the temperature of the ferroelectric crystal material until said detected temperature is above said predetermined temperature above the operational temperature range and thereafter to allow the ferroelectric liquid crystal material to cool to a temperature within said operational temperature range, and for causing the temperature raising means to raise the temperature of the ferroelectric liquid crystal material and to allow the ferroelectric liquid crystal material to cool so as to maintain the temperature of the ferroelectric liquid crystal material within said operational temperature range;

said operational temperature range being the range wherein the ferroelectric liquid crystal material assumes a chiral smectic phase.

7. A liquid crystal device according to claim 6 wherein the liquid crystal in said chiral smectic phase is disposed in a layer thin enough to release its spinal structure in the absence of an electric field.

8. A liquid crystal device according to claim 6 wherein said chiral smectic phase is a chiral smectic C or H phase.

9. A liquid crystal device according to claim 6, wherein said ferroelectric liquid crystal assumes a smectic A phase at said predetermined temperature above said operational temperature.

10. A liquid crystal device according to claim 6, further comprising a cooling means for cooling the temperature of the ferroelectric liquid crystal material.