US5684503A
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Method of driving a liquid crystal display device
Assignee: BOE Technology Group Co Ltd
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Filing: 1994-02-18
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Granted: 1997-11-04
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Expires: 2014-02-18
Abstract
Abstract A method of driving a liquid crystal that has a memory capability, wherein a reset voltage is initially applied to the liquid crystal during a reset period, to bring about a Frederick's transition in the liquid crystal. During a subsequent selection period, a selection voltage that is selected on the basis of a critical value that brings about one of two metastable states in the liquid crystal is applied to the liquid crystal, and, during a nonselection period that follows the selection period, a nonselection voltage that is less than or equal to a threshold value that maintains two metastable states is applied to the liquid crystal. A delay period is provided between the reset period and the selection period, in order to gain effective timing for applying the selection voltage to the liquid crystal after the application of the reset voltage has been turned off. This shortens the length of the selection period, and hence the write time.
Inventors
- 👤 Hiroaki Nomura
- 👤 Yuzuru Sato
- 👤 Akira Inoue
- 👤 Takaaki Tanaka
- 👤 Kenichi Momose
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 17:30
CPC Classifications
G; G09; G09G; G09G3/00; G09G3/20; G09G3/34; G09G3/36; G09G3/3611; G09G3/3622; G09G3/3629; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G09G3/3674; G09G3/3681; G09G3/3685; G09G3/3692; G09G2300/00; G09G2300/04; G09G2300/0469; G09G2300/0478; G09G2300/0482; G09G2300/0486; G09G2310/00; G09G2310/06; G09G2310/061; G09G2310/065; G09G2320/00; G09G2320/02; G09G2320/0247; G09G2320/04; G09G2320/041; G09G2320/10
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
217 words
A method of driving a liquid crystal display device that uses a chiral nematic liquid crystal medium wherein liquid crystal molecules interposed between two substrates have a predetermined angle of twist in an initial state and said chiral nematic liquid crystal medium has two metastable states differing from said initial states as relaxation states achieved after a voltage that brings about a Frederick's transition has been applied in said initial state, said method comprising the steps of: a) during a reset period, applying to said liquid crystal medium a reset voltage greater than or equal to a threshold value that brings about said Fredericks' transition; b) during a first selection period after said reset period, applying to said liquid crystal medium a selection voltage selected on the basis of a critical value which brings about one of said two metastable states; c) during a nonselection period following said first selection period, applying to said liquid crystal medium a nonselection voltage less than or equal to a threshold value which maintains said two metastable states; and d) during a delay period between said reset period and said first selection period, applying to said liquid crystal medium a delay voltage that is less than or equal to said critical value which brings about one of said two metastable states.
Claim 2
Independent Claim
217 words
A method of driving a liquid crystal display device that uses a chiral nematic liquid crystal medium wherein liquid crystal molecules interposed between two substrates have a predetermined angle of twist in an initial state and said chiral nematic liquid crystal medium has two metastable states differing from said initial states as relaxation states achieved after a voltage that brings about a Frederick's transition has been applied in said initial state, said method comprising the steps of: a) during a reset period, applying to said liquid crystal medium a reset voltage greater than or equal to a threshold value that brings about said Fredericks' transition; b) during a first selection period after said reset period, applying to said liquid crystal medium a selection voltage selected on the basis of a critical value which brings about one of said two metastable states; c) during a nonselection period following said first selection period, applying to said liquid crystal medium a nonselection voltage less than or equal to a threshold value which maintains said two metastable states; and d) during a delay period between said reset period and said first selection period, applying to said liquid crystal medium a delay voltage that is less than or equal to said critical value which brings about one of said two metastable states.
Claim 3
Dependent Claim
87 words
The method of claim 1, wherein the length of said delay period is set in such a manner that said selection voltage is applied to said liquid crystal medium at a time in the vicinity of a transition point to said two metastable states, after backflow has occurred and a number of said liquid crystal molecules positioned at the approximate center between said substrates have relaxed into one of said metastable states from a homeotropic orientation state directly after the application of said reset voltage has ended.
Claim 4
Dependent Claim
65 words
The method of claim 1, further comprising the steps of: e) during an interval period, applying said nonselection voltage to said liquid crystal medium; f) during a second selection period, applying said selection voltage to said liquid crystal medium, wherein said interval period follows said first selection period and said second selection period follows said interval period; and g) optionally repeating steps e) and f).
Claim 5
Dependent Claim
220 words
The method of claim 1, wherein said liquid crystal display device comprises a plurality of row electrodes formed on a first one of said two substrates, each of said row electrodes being supplied with a row electrode signal, and a plurality of column electrodes formed on a second one of said two substrates, each of said column electrodes being supplied with a column electrode signal; intersections between said row electrodes and said column electrodes forming pixels; and the voltage of a difference signal between said row electrode signal and said column electrode signal is applied to said liquid crystal medium corresponding to each of said pixels; wherein said difference signal includes within one frame said first selection period that is set to be shifted for each of said row electrodes, said nonselection period following thereafter, said reset period set before said selection period, and said delay period inserted between said reset period and said first selection period; wherein said row electrode signal is at a reset potential during said reset period, a selection potential during said first selection period, and a nonselection potential during said delay period and said nonselection period; and wherein said column electrode signal is set to data potential which includes either an ON selection potential or OFF selection potential in synchronism with said first selection period.
Claim 6
Dependent Claim
83 words
The method of claim 4, wherein the length of said delay period is such that said selection voltage is applied to said liquid crystal medium at a time in the vicinity of a transition point to said two metastable states, after backflow has occurred and a number of said liquid crystal molecules positioned at the approximate center between said substrates have relaxed into one of said metastable states from a homeotropic orientation state directly after the application of said reset voltage has ended.
Claim 7
Dependent Claim
27 words
The method of claim 5, wherein when a unit time equivalent to said first selection period is termed 1H, said delay period is set to be (1H/2)×n.
Claim 8
Dependent Claim
130 words
The method of claim 4, further comprising the steps of: e) during an interval period, applying said nonselection voltage to said liquid crystal medium; f) during a second selection period, applying said selection voltage to said liquid crystal medium wherein said interval period follows said first selection period and said second selection period follows said interval period; g) optionally repeating steps e) and f); h) setting said row electrode signal to said selection potential in said first selection period, to said nonselection potential in said interval period, and back to said selection potential in said second selection period; and i) setting said column electrode signal to said data potential, in both of said first and second selection periods, to drive the same pixel repeatedly within the period of one frame.
Claim 9
Dependent Claim
94 words
The method of claim 7, wherein the lengths of said delay period and said interval period are each set in such a manner that said selection voltage is applied to said liquid crystal display device at a time in the vicinity of a transition point to said two metastable states, after back flow has occurred and a number of said liquid crystal molecules positioned at the approximate center between said substrates have relaxed into one of said metastable states from a homeotropic orientation state directly after the application of said reset voltage has ended.
Claim 10
Dependent Claim
31 words
The method of claim 8, wherein when a unit time equivalent to each of said first and second selection periods is termed 1H, said interval period is set to be (1H)×m.
Claim 11
Dependent Claim
31 words
The method of claim 8, wherein when a unit time equivalent to each of said first and second selection periods is termed 1H, said delay period is set to be (1H/2)×n.
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