US 4,907,859 AGranted

Liquid crystal device and image forming apparatus utilizing liquid crystal device

AssigneeCanon Kabushiki Kaisha

InventorsYoshihiro Takada, Nagao Hosono

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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.

Claims20

Dependent claims

An electro-optical switching apparatus for forming an image comprising:

(a) a light source for emitting light rays;
(b) a light-path switching means comprising
(i) a first base plate having scanning lines,
(ii) a second base plate having data lines,
(iii) a ferroelectric liquid crystal disposed between the first and second base plates,
(iv) a driving means for driving the ferroelectric liquid crystal by selective application of signals to the scanning lines and the data lines so as to cause the ferroelectric liquid crystal to assume either one of light-transmitting state and light-interrupting state;
(c) a temperature sensor for detecting the temperature of the ferroelectric liquid crystal and for generating an output response therefrom;
(d) a heating means for raising the temperature of the ferroelectric liquid crystal, said heating means comprising a resistance heater disposed on one of the base plates;
and
(e) a temperature-controlling means which, during the operation of said light-path switching means, receives said output from the temperature sensor for comparing the detected temperature with a predetermined operational temperature within a temperature range providing a ferroelectric liquid crystal phase, for restoring the temperature of the ferroelectric liquid crystal when the detected temperature is lower than the predetermined operational temperature by causing the heating means to raise the temperature of the ferroelectric liquid crystal until said detected temperature is above said predetermined temperature and thereafter cooling the ferroelectric liquid crystal to a temperature below said predetermined temperature, and for causing the heating means to maintain the temperature of the ferroelectric liquid crystal to be substantially constant.

7 more elements

An electro-optical switching apparatus for forming an image, comprising:

(a) a light for emitting light rays;
(b) a light-path switching means comprising
(i) a first base plate having scanning lines,
(ii) a second base plate having data lines,
(iii) a ferroelectric liquid crystal disposed between the first and second base plates, and
(iv) a driving means for driving the ferroelectric liquid crystal by selective application of signals to the scanning lines and the data lines so as to cause the ferroelectric liquid crystal to assume either one of light-transmitting state and light-interrupting state;
(c) a temperature sensor for detecting the temperature of the ferroelectric liquid crystal and for generating an output response therefrom;
(d) a heating means for raising the temperature of the ferroelectric liquid crystal, said heating means comprising a resistance heater disposed on the base plate;
and
(e) a temperature controlling means which, during the operation of said light-path switching means, receives said output from the temperature sensor for comparing said detected temperature with a predetermined operational temperature within a temperature range providing a ferroelectric liquid crystal phase, for restoring the temperature of the ferroelectric liquid crystal when the detected temperature is lower than the predetermined operational temperature by causing the heating means to raise the temperature of the ferroelectric liquid crystal until said detected temperature is above said predetermined temperature and thereafter cooling the ferroelectric liquid crystal to a temperature below said predetermined temperature and then heating the ferroelectric liquid crystal to a temperature above said predetermined temperature, and for causing the heating means to maintain the temperature of the ferroelectric liquid crystal to be substantially constant.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/205,685Filed 25 May 1988 · division
Priority: JP 58-21572415 Nov 1983
Granted: 13 Mar 1990
Term ends: Not estimatedThe source records don’t support an estimate.

Classification2 codes

G02F 1/133382
Constructional arrangements; Manufacturing methods: heating or cooling of liquid crystal cells other than for activation, e.g. circuits or…
G02F
Optical devices or arrangements for the control of light by modification of