US3690745A - Electro-optical devices using lyotropic nematic liquid crystals - Google Patents

Electro-optical devices using lyotropic nematic liquid crystals Download PDF

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US3690745A
US3690745A US16078A US3690745DA US3690745A US 3690745 A US3690745 A US 3690745A US 16078 A US16078 A US 16078A US 3690745D A US3690745D A US 3690745DA US 3690745 A US3690745 A US 3690745A
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phenyl
substrate
nematic
lyotropic
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Derick Jones
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Texas Instruments Inc
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Texas Instruments Inc
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/42—Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40
    • C09K19/50—Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40 containing steroidal liquid crystal compounds

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  • ABSTRACT A display device in which a thin layer of a lyotropic nematic mesomorphic composition is utilized to diffuse light from a source toward an observer by applying a suitable voltage, for example, 20 volts for a 1 mil layer.
  • a suitable voltage for example, 20 volts for a 1 mil layer.
  • One form of the device transmits light through the layer.
  • a second form of the device uses light diffused and reflected to the observer.
  • a preferred lyotropic nematic mesomorphic composition includes three compounds of the structural formulas 12 Claims, 3 Drawing Figures Patented Sept. 12, 1972 FIG. 2
  • the isotropic liquid is generally the state referred to when the term liquid is used.
  • the majority of organic and inorganic compounds will transform from a solid, or a crystalline solid, to the isotropic liquid state upon reaching a particular temperature peculiar to a given solid.
  • the smectic mesophase is a turbid viscous state which has certain properties similar to those found in soaps.
  • the nematic mesophase is a turbid state, but is also a mobile state.
  • the nematic mesophase frequently appears to be threaded when viewed between crossed polaroids.
  • the cholesteric mesophase is a turbid and mobile phase which exhibits optical characteristics quite different from those of the smectic and nematic mesophases.
  • compositions exhibiting a mesomorphic phase are thermotropic.
  • the mesophase is exhibited when a suitable compound is heated to a temperature above that at which its crystal lattice is stable, i.e., above its initial melting temperature.
  • a suitable compound which is both smectogenic and nematogenic is heated, the compound will change from the crystalline state to the smectic mesophase at a first given temperature.
  • the compound will suddenly change states, giving rise to the nematic mesophase.
  • the nematic mesophase of the composition will yield suddenly to give the isotropic liquid.
  • These transition temperatures are reversible, but upon reversal are sometimes accompanied by supercooling.
  • Compositions can exhibit one or more of the smectic, nematic and cholesteric mesophases.
  • a second type of mesomorphism to be distinguished from thermotropic mesomorphism is lyotropic mesomorphism.
  • Lyotropic mesomorphism is exhibited when certain solvents are added to certain other compositions. As the solvent is added intermediate states arise which exhibit mesomorphic properties. An excess of solvent will cause the lyotropic mesophase to pass over to a true solution. Lyotropic mesomorphic compounds also exhibit smectic and nematic properties. A number of known compositions will exhibit the lyotropic mesophase using water or other compounds as a solvent.
  • mesomorphic state including the smectic, nematic and cholesteric mesophases and the distinction between the lyotropic mesophase and the thermotropic mesophase, refer to G. W. Gray, Molecular Structure and the Properties of Liquid Crystals, Academic Press, lnc., New York, 1962.
  • mesophases are commonly referred to as liquid crystals or as exhibiting liquid crystallinity.
  • the patent states that the optical scattering effect can only be observed when the mesomorphic layer is both nematic and thermotropic and is less than one-half millimeter in thickness.
  • no organic nematic thermotropic compound is disclosed which has or exhibits a mesophase below the temperature of 45 C.
  • normal room temperature is well below the lower limits of 45 C.
  • nematic mesomorphic composition which can be utilized as an electro-optical display screen operable at temperatures normally encountered in habitable structures, i. e., temperatures near 25 C. It is furthermore desirable to possess a compound which will scatter light without maintaining an exact elevated temperature environment around the compound.
  • This invention therefore provides an electro-optical display device including a first optically transmissive substrate and a first optically transmissive and electrically conductive coating on a face of the first substrate, a second substrate and an electrically conductive coating on a face of the second substrate, the substrates positioned such that the coatings are adjacent and substantially equidistantly spaced, and a light source means positioned to direct light toward the substrates, and means for impressing a voltage gradient between the coatings, the improvement comprising a lyotropic nematic mesomorphic composition occupying the space between the coatings, the composition having a threshold electrical field which when exceeded will cause it to scatter light.
  • the lyotropic nematic mesomorphic composition is preferably organic and is preferably nematogenic at room temperature.
  • the invention also provides a method for displaying light from a light source comprising the steps of directing a light beam at an angle toward a thin layer of a lyotropic nematic mesomorphic composition, and impressing a threshold voltage across the thin layer sufficient to cause the composition to scatter light.
  • FIG. 1 is an exploded schematic view of a display device utilizing the composition of the present invention
  • FIG. 2 is a side view of a device similar to that shown in FIG. 1;
  • FIG. 3 is a side view of another embodiment of the display device of the present invention.
  • Substrate 10 shown partially broken away, is optically transmissive and has deposited thereon a coating 14 of a material which is optically transmissive and electrically conductive.
  • Optically transmissive substrate 12 has coated thereon a plurality of electrically isolated electrodes 16, 18, 20, 22, 24, 26 and 28. These electrodes are also optically transmissive and electrically conductive.
  • Each of the electrodes 16 through 28 has attached thereto a lead 30 which is optically transmissive and which has been electrically insulated by an optically transmissive insulating composition.
  • Each of the leads 30 is attached at the edge of substrate 12 to conventional electrical leads which in turn are connected to switches 34 through 46 which correspond respectively to electrodes 16 through 28.
  • Switches 34 through 46 are connected in parallel to a source 48 of electrical energy which is connected in series to electrically conductive coating 14.
  • a thin layer 50 of a lyotropic nematic mesomorphic composition Interposed between substrates l0 and 12 is a thin layer 50 of a lyotropic nematic mesomorphic composition.
  • the thin layer 50 is shown separated from the substrates l0 and 12; however, in operation, the thin layer 50 is intimately contacting the coating 14 and the electrodes 16 through 28.
  • the layer 50 also, of course, contacts that portion of substrate 12 not containing an electrode.
  • a light source 52 Positioned behind substrate 12 is a light source 52 which directs a light beam at an angle toward the rear face of substrate 12.
  • the source of light 52 can be any conventional source including an incandescent source.
  • the light beam is electrically connected to a suitable source 58 of electrical energy.
  • a nonreflective light absorbing substrate 60 Positioned behind and spaced from the substrate 12 is a nonreflective light absorbing substrate 60 preferably a dull black in color.
  • FIG. 2 differs from FIG. 1 in that only one electrode of electrodes 16 through 28 is illustrated.
  • the display device is shown enclosed in casing 70.
  • Like numerals are used where applicable.
  • the thin layer 50 of a lyotropic nematic mesomorphic composition contacts the electrically conductive coating 14 and electrode 20.
  • switch 36 When switch 36 is closed a voltage gradient is impressed through the layer 50 between electrode 20 and that portion of coating 14 corresponding thereto. This will cause the portion of layer 50 through which the voltage gradient is impressed to diffuse light coming from light source 52.
  • light beam 72 is shown being diffused toward the eye 74 of an observer.
  • a second light beam 76 which passes through the portion of the lyotropic nematic mesomorphic composition across which no voltage gradient is impressed without being diffused.
  • substrate is provided to eliminate internal reflections from light source 52 and also to eliminate stray room light which might interfere with the display characteristics of the display screen.
  • optically transmissive substrate 10 and optically transmissive and electrically conductive coating 14 are constructed the same as above.
  • a light source 80 connected to a suitable electrical energy source 82, is positioned exterior of the casing to direct light beams 84 and 86 toward the lyotropic nematic mesomorphic layer 50.
  • substrate 88 need not be optically transmissive.
  • Contacting substrate 88 is a reflective coating 90 onto which an electrode 20 is placed. Similar to the foregoing embodiment, the electrode 20 is electrically connected through switch 36 and energy source 48 to coating 14.
  • light from source 80 strikes the lyotropic nematic mesomorphic layer 50 through which a voltage is impressed, is diffused, and is reflected back toward observer 92 by reflective coating 90.
  • light beam 84 not traversing a portion of the layer 50 across which an electrical field is being impressed is reflected by coating 90 away from observer 92.
  • the observer 92 will see a display corresponding only to the size and shape of electrode 20.
  • Light source 80 need not be an artificial source such as shown but can be any available source including sunlight.
  • the electrical energy or impressed voltage across the layer 50 must be sufficiently large to reach or exceed the threshold voltage at which the lyotropic nematic mesomorphic composition will scatter light. It has been found that for layers having a thickness of 1 mil the threshold voltage for most compositions occurs at around 8 volts, while best results are obtained with a voltage on the order of 20 volts. For best results it has been found that the layer should be relatively thin, preferably less than 20 mils thick with a layer less than 4 mils giving most preferred and optimum results.
  • the substrates 10 and 12 can be composed of any suitable material which is optically transmissive, for example, various types of glass, fused quartz, transparent varieties of corundum and transparent plastics or resins.
  • optically transmissive includes both transparent and translucent materials.
  • the coating and electrodes which are both electrically conductive and optically transmissive, such as coatings l4 and electrodes 16 through 28, can be composed of layers of indium oxide or tin oxide deposited on the surface of the respective substrates. If a reflective surface is desired, a thin layer of a metallic material such as silver or aluminum can be deposited on a substrate such as coating 90 on substrate 88. It is to be understood, of course, with reference to FIG. 3 that the reflective coating 90 can be placed either at the front or rear of the substrate 88, but if placed on the front of substrate 88 as shown in FIG. 3, a reflective and conductive coating must be electrically isolated from the electrode 20 to give the desired display effect. An alternate means of producing the desired reflection is to eliminate the coating 90 and compose the electrode 20 of a suitable reflective material. So doing would achieve the same result as that illustrated.
  • Lyotropic nematic mesomorphic compositions which can be utilized with the present invention will include a solvent and a solute.
  • the types of molecules which will form the required lyotropic mesophase are usually of an elongated, relatively straight and in some cases flattened structure. This shape favors the parallel arrangement of molecules characteristic of the nematic mesophase.
  • these compounds preferably are nematogenic at room temperature, for example in the range of from to 30 C.
  • Exemplary solutes are as follows:
  • n-butyl Preferred solute molecules are those compounds (a) and above, and more preferably a mixture of about 80 weight percent (a) and about 20 weight percent (c).
  • Suitable solvent molecules for use with the present invention can be of the general formula:
  • HSQ-GIEN-QA Hz-(C H2) 2-0 n3
  • solvent (m) is mixed with 40 mole percent of the aforementioned preferred mixture of (a) and (c) to yield a lyotropic nematic mesomorphic composition which exhibits the nematic mesophase within the temperature range as follows:
  • Solid Nematic Isotropic liquid Other molecules exhibiting the long straight flattened structure and having a melting point preferably below room temperature can also be utilized within the purview of the present invention.
  • an electro-optical display device including a first optically transmissive substrate and a first optically transmissive and electrically conductive coating on a face of the first substrate, a second substrate and an electrically conductive coating on a face of the second substrate, the substrates positioned such that the coatings are adjacent and substantially equidistantly spaced, a light source means positioned to direct light toward the substrates, and means for impressing a voltage gradient between the coatings, the improvement comprising a lyotropic nematic mesomorphic composition occupying the space between the coatings, the composition having a threshold electrical field which when exceeded will cause it to scatter light.
  • composition is organic and includes a Shiff base solvent and a liquid crystalline solute.
  • composition is nematogenic at temperatures in the range of from 15 to 30 C.
  • composition comprises a mixture of:

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US16078A 1970-03-03 1970-03-03 Electro-optical devices using lyotropic nematic liquid crystals Expired - Lifetime US3690745A (en)

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3815972A (en) * 1972-08-09 1974-06-11 Olivetti & Co Spa Low voltage liquid crystal display
US3876286A (en) * 1972-06-14 1975-04-08 Werk Fernsehelektronik Veb Use of nematic liquid crystalline substances
US3880767A (en) * 1970-11-06 1975-04-29 Rockwell International Corp Nematic liquid-crystal compositions
US3956167A (en) * 1973-05-17 1976-05-11 Beckman Instruments, Inc. Liquid crystal compositions and devices
US3960752A (en) * 1972-10-24 1976-06-01 Eastman Kodak Company Liquid crystal compositions
US3960749A (en) * 1971-02-09 1976-06-01 International Liquid Xtal Company Liquid-crystal mixtures for use in liquid-crystal displays
US3965029A (en) * 1974-02-04 1976-06-22 Kent State University Liquid crystal materials
US4030812A (en) * 1975-06-16 1977-06-21 Minnesota Mining And Manufacturing Company Lyotropic birefringent films
US4038200A (en) * 1972-08-07 1977-07-26 Texas Instruments Incorporated Lyotropic nematic liquid crystals for use in electro-optical display devices
US4038199A (en) * 1972-08-07 1977-07-26 Texas Instruments Incorporated Lyotropic nematic liquid crystals for use in electro-optical display devices
US4173544A (en) * 1975-12-19 1979-11-06 Bbc Brown Boveri & Company Limited Novel alkylsubstituted N-benzylideneanilines and liquid crystal compositions containing same
EP0323008A3 (en) * 1987-10-09 1990-02-28 Director-General Of Agency Of Industrial Science And Technology Liquid crystal cell

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3499112A (en) * 1967-03-31 1970-03-03 Rca Corp Electro-optical device
US3499702A (en) * 1967-12-05 1970-03-10 Rca Corp Nematic liquid crystal mixtures for use in a light valve

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3499112A (en) * 1967-03-31 1970-03-03 Rca Corp Electro-optical device
US3499702A (en) * 1967-12-05 1970-03-10 Rca Corp Nematic liquid crystal mixtures for use in a light valve

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3880767A (en) * 1970-11-06 1975-04-29 Rockwell International Corp Nematic liquid-crystal compositions
US3960749A (en) * 1971-02-09 1976-06-01 International Liquid Xtal Company Liquid-crystal mixtures for use in liquid-crystal displays
US3876286A (en) * 1972-06-14 1975-04-08 Werk Fernsehelektronik Veb Use of nematic liquid crystalline substances
US4038200A (en) * 1972-08-07 1977-07-26 Texas Instruments Incorporated Lyotropic nematic liquid crystals for use in electro-optical display devices
US4038199A (en) * 1972-08-07 1977-07-26 Texas Instruments Incorporated Lyotropic nematic liquid crystals for use in electro-optical display devices
US3815972A (en) * 1972-08-09 1974-06-11 Olivetti & Co Spa Low voltage liquid crystal display
US3960752A (en) * 1972-10-24 1976-06-01 Eastman Kodak Company Liquid crystal compositions
US3956167A (en) * 1973-05-17 1976-05-11 Beckman Instruments, Inc. Liquid crystal compositions and devices
US3965029A (en) * 1974-02-04 1976-06-22 Kent State University Liquid crystal materials
US4030812A (en) * 1975-06-16 1977-06-21 Minnesota Mining And Manufacturing Company Lyotropic birefringent films
US4173544A (en) * 1975-12-19 1979-11-06 Bbc Brown Boveri & Company Limited Novel alkylsubstituted N-benzylideneanilines and liquid crystal compositions containing same
EP0323008A3 (en) * 1987-10-09 1990-02-28 Director-General Of Agency Of Industrial Science And Technology Liquid crystal cell
US5045227A (en) * 1987-10-09 1991-09-03 Director-General Of Agency Of Industrial Science And Technology Liquid crystal cell

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