EP0197743A2
Expired / Lapsed
EP
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Addressing liquid crystal cells
Assignee: STC PLC
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Filing: 1986-04-01
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Granted: —
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Expires: 2006-04-01
Abstract
Abstract A method of addressing a matrix addressed ferroelectric liquid crystal cell is described that uses parallel entry of balanced bipolar data pulses on one set of electrodes to co-operate with serial entry of balanced bipolar strobe pulses on the other set of electrodes. The pulse profiles include zero voltage steps between certain positive- and negative-going voltage excursions.
Inventors
- 👤 Peter John Ayliffe
- 👤 Anthony Bernard Davey
- 👤 Johannes Karel Zelisse
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 16:59
CPC Classifications
G; G09; G09G; G09G3/00; G09G3/20; G09G3/34; G09G3/36; G09G3/3611; G09G3/3622; G09G3/3629; G09G2310/00; G09G2310/06; G09G2310/065; G09G2320/00; G09G2320/02; G09G2320/0209
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
139 words
A method of addressing a matrix-array type liquid crystal cell with a ferroelectric liquid crystal layer whose pixels are defined by the areas of overlap between the members of a first set of electrodes on one side of the liquid crystal layer and the members of a second set on the other side of the layer, characterised in that the cell is addressed on a line-by-line basis by applying strobe pulses serially to the members of the first set while data pulses are applied in parallel to the members of the second set, that the strobe and data pulse waveforms are balanced bipolar pulses, and that the addressing of any given pixel by the co-operative action of a strobe pulse of a data pulse waveform. includes a zero voltage step during at least a part of the strobe pulse.
Claim 2
Independent Claim
139 words
A method of addressing a matrix-array type liquid crystal cell with a ferroelectric liquid crystal layer whose pixels are defined by the areas of overlap between the members of a first set of electrodes on one side of the liquid crystal layer and the members of a second set on the other side of the layer, characterised in that the cell is addressed on a line-by-line basis by applying strobe pulses serially to the members of the first set while data pulses are applied in parallel to the members of the second set, that the strobe and data pulse waveforms are balanced bipolar pulses, and that the addressing of any given pixel by the co-operative action of a strobe pulse of a data pulse waveform. includes a zero voltage step during at least a part of the strobe pulse.
Claim 3
Dependent Claim
129 words
A method as claimed in claim 1, characterised in that the strobe and data pulse waveforms each include a zero voltage portion, a positive-going voltage excursion and a negative-going voltage excursion, and that the waveforms are such that when a strobe pulse is synchronised with a data pulse of one data significance the strobe pulse positive-going excursion coincides with the negative-going excursion of the data pulse while the negative-going excursion of the strobe pulse coincides with the zero voltage portion of the data pulse, and such that when the data pulse is of the other data significance the strobe pulse negative-going excursion coincides with the positive-going excursion of the data pulse while the positive-going excursion of the strobe pulse coincides with the zero voltage portion of the data pulse.
Claim 4
Dependent Claim
27 words
A method as claimed in claim 2, characterised in that the positive- and negative-going voltage excursions of a strobing pulse are separated by its zero voltage portion.
Claim 5
Dependent Claim
58 words
A method as claimed in claim 2 or 3, characterised in that the strobe and data pulse waveforms are such that when a strobe pulse is synchronised with a data pulse of either data significance there are zero voltage dwell times for each waveform that precede and follow each voltage excursion of the strobe and data pulse waveforms.
Claim 6
Dependent Claim
44 words
A method as claimed in claim 2, 3 or 4, characterised in that the positive- and negative-going voltage excursions of each balanced bipolar data pulse are asymmetric, the excursion of one polarity having 'm' times the amplitude of the other and 1/m the duration.
Claim 7
Dependent Claim
71 words
A method as claimed in claim 1, characterised in that the strobe and data pulse waveforms are such that whenever they co-operate to produce, across at least a portion of the liquid crystal layer, a switching stimulus in the form of a unidirectional potential difference sufficient to effect switching, then that switching stimulus is immediately preceded by and immediately followed with periods for which the potential difference is held at zero.
Claim 8
Dependent Claim
50 words
A method as claimed in claim 1, characterised in that the addressing of any given pixel by the co-operative action of a strobe pulse and a data pulse the positive- and negative-going excursions of the data pulse entirely precede the strobe pulse, or entirely follow it, according to data significance.
Claim 9
Dependent Claim
33 words
A method as claimed in claim 7, characterised in that the data pulses of both data significances and the strobing pulses all incorporate zero voltage steps between their positive- and negative-going voltage excursions.
Claim 10
Dependent Claim
42 words
A method as claimed in claim 7 or 8, characterised in that the data pulses of both data significances and the strobing pulses all make positive-going excursions to the same common voltage +V and negative-going excursions to the same common voltage -V.
Claim 11
Dependent Claim
37 words
A method as claimed in claim 7 or 8, characterised in that the positive- and negative-going excursions of each data pulse are asymmetric, one part having 'm' times the amplitude of the other and 1/m the duration.
Claim 12
Dependent Claim
83 words
A method as claimed in claim 1, characterised in that in the addressing of any given pixel by the co-operative action of a strobe pulse and a data pulse the data pulse is composed of two halves one of which immediately precedes the strobe pulse and the other of which immediately follows the strobe pulse, and that the half which immediately follows the strobe pulse also functions as the half which immediately precedes the strobing pulse of the next line to be strobed.
Claim 13
Dependent Claim
33 words
A method as claimed in claim 11, characterised in that the data pulses of both data significances and the strobing pulses all incorporate zero voltage steps between their. positive- and negative-going voltage excursions.
References Cited (Backward Citations)
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