US4214819A
Expired / Lapsed
US
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Electro-optical modulator
Assignee: Merck Patent GmbH
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Filing: 1978-10-27
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Granted: 1980-07-29
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Expires: 1998-10-27
Abstract
Abstract The optically active medium of an electro-optical cell sandwiched between a pair of crossed polarizers is a thin layer of liquid crystal with a positive dielectric anisotropy and a negative anisotropy of the diamagnetic susceptibility. The medium is positioned between two planar transparent electrodes across which a potential difference establishes, in the liquid crystal layer, an electric field perpendicular to the electrode layers. A magnet is provided for establishing in the medium a magnetic field that has a predetermined orientation relative to the electric field. When both fields are parallel, the threshold voltage of the cell is increased. The presence of such a magnetic field, when the electric field is switched off, reduces the turn-off time of the cell. When the fields are perpendicular to each other, the color of the display can be controlled in accordance with the magnitude of the magnetic field.
Inventors
- 👤 Ludwig Pohl
- 👤 Rudolf Eidenschink
- 👤 Joachim Krause
- 👤 Georg Weber
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 05:35
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/137; G02F1/13768; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
81 words
An electro-optical modulator comprising: (a) a liquid crystal cell having a thin layer of liquid crystal material with a positive DKA and a negative DMA positioned between two transparent electrode layers across which a potential difference establishes in the liquid crystal layer an electric field perpendicular to the electrode layers; (b) crossed polarizers sandwiching the cell; and (c) means for establishing a magnetic field in the liquid crystal layer having a predetermined direction relative to the direction of the electric field.
Claim 2
Dependent Claim
81 words
An electro-optical modulator comprising: (a) a liquid crystal cell having a thin layer of liquid crystal material with a positive DKA and a negative DMA positioned between two transparent electrode layers across which a potential difference establishes in the liquid crystal layer an electric field perpendicular to the electrode layers; (b) crossed polarizers sandwiching the cell; and (c) means for establishing a magnetic field in the liquid crystal layer having a predetermined direction relative to the direction of the electric field.
Claim 3
Dependent Claim
17 words
An electro-optical modulator according to claim 1 wherein the magnetic field is parallel to the electric field.
Claim 4
Dependent Claim
17 words
An electro-optical modulator according to claim 1 wherein the magnetic field is perpendicular to the electric field.
Claim 5
Dependent Claim
17 words
An electro-optical modulator according to claim 1 wherein the magnetic field is produced by a permanent magnet.
Claim 6
Dependent Claim
22 words
An electro-optical modulator according to claim 1 wherein the magnetic field is produced by an electromagnet whose field strength can be varied.
Claim 7
Dependent Claim
51 words
An electro-optical modulator according to claim 2 wherein the magnetic field is produced by two transparent magnetic layers, each of which is located between a respective one of the transparent electrode layers and the liquid crystal layer, the magnetic field being perpendicular to both the magnetic layers and the electrode layers.
Claim 8
Dependent Claim
50 words
An electro-optical modulator according to claim 2 wherein the magnetic field is produced by two transparent magnetic layers, each of which cooperates with the crystal layer and sandwiches a respective one of the transparent electrode layers, the magnetic field being perpendicular to both the magnetic layers and the electrode layers.
Claim 9
Dependent Claim
39 words
An electro-optical modulator according to claim 6 wherein each of the magnetic layers is provided with electric conductor paths, the flow of control current through such conductor paths serving to rotate the direction of the magnetic field by 90°.
Claim 10
Dependent Claim
39 words
An electro-optical modulator according to claim 7 wherein each of the magnetic layers is provided with electric conductor paths, the flow of control current through such conductor paths serving to rotate the direction of the magnetic field by 90°.
Claim 11
Dependent Claim
35 words
An electro-optical modulator according to claim 1, wherein the liquid crystal contains at least one trans,transcyclohexylcyclohexane of the formula ##STR2## wherein X is --R, --OR or --OCOR and R is alkyl of 1-12 carbon atoms.
Claim 12
Dependent Claim
23 words
A display element adapted for use in calculators, clocks, television sets or electronic data-processing units comprising an electro-optical modulator according to claim 1.
Claim 13
Independent Claim
79 words
A method for reducing the turn-off time of a positive DKA liquid crystal cell in which a layer of liquid crystal material is sandwiched between transparent electrodes by which an electrical field can be established in the liquid crystal material to switch the cell to its display mode, which comprises employing a liquid crystal material having a negative DMA and establishing a magnetic field parallel to the electric field therein during at least a portion of the turn-off time.
Claim 14
Independent Claim
79 words
A method for reducing the turn-off time of a positive DKA liquid crystal cell in which a layer of liquid crystal material is sandwiched between transparent electrodes by which an electrical field can be established in the liquid crystal material to switch the cell to its display mode, which comprises employing a liquid crystal material having a negative DMA and establishing a magnetic field parallel to the electric field therein during at least a portion of the turn-off time.
Claim 15
Independent Claim
104 words
A method for improving the contrast by reducing undesired "crosstalk" of a matrix-addressed liquid crystal display in which a layer of positive DKA liquid crystal material is sandwiched between transparent electrodes, consisting of a multiplicity of parallel horizontal conductor rows, and a multiplicity of parallel vertical conductor columns, respectively, by which the liquid crystal material at the crosspoint of any horizontal row with any vertical column can be separately triggered to its display mode, which comprises employing a liquid crystal material having negative DMA, and establishing at the adjacent untriggered crosspoints a magnetic field parallel to the electric field established at said triggered crosspoint.
Claim 16
Independent Claim
104 words
A method for improving the contrast by reducing undesired "crosstalk" of a matrix-addressed liquid crystal display in which a layer of positive DKA liquid crystal material is sandwiched between transparent electrodes, consisting of a multiplicity of parallel horizontal conductor rows, and a multiplicity of parallel vertical conductor columns, respectively, by which the liquid crystal material at the crosspoint of any horizontal row with any vertical column can be separately triggered to its display mode, which comprises employing a liquid crystal material having negative DMA, and establishing at the adjacent untriggered crosspoints a magnetic field parallel to the electric field established at said triggered crosspoint.
References Cited (Backward Citations)
US3364433A
Cited
US4066334A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-07-29 | 1984-01-28 | 1984-07-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-07-29 | 1988-01-28 | 1988-07-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-07-29 | 1992-01-28 | 1992-07-29 | $7700.00 | Window Closed / Lapsed |