WO2001012752A1 - Electro-optical composition - Google Patents

Electro-optical composition Download PDF

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Publication number
WO2001012752A1
WO2001012752A1 PCT/GB2000/003187 GB0003187W WO0112752A1 WO 2001012752 A1 WO2001012752 A1 WO 2001012752A1 GB 0003187 W GB0003187 W GB 0003187W WO 0112752 A1 WO0112752 A1 WO 0112752A1
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WO
WIPO (PCT)
Prior art keywords
composition
particles
liquid crystalline
electro
crystalline material
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PCT/GB2000/003187
Other languages
French (fr)
Inventor
Wilson Che Kei Poon
Jason Crain
Steven Paul Meeker
Original Assignee
The University Court, The University Of Edinburgh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Publication of WO2001012752A1 publication Critical patent/WO2001012752A1/en

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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
    • C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
    • C09K19/54—Additives having no specific mesophase characterised by their chemical composition
    • 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
    • C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
    • C09K19/54—Additives having no specific mesophase characterised by their chemical composition
    • C09K19/542—Macromolecular compounds

Definitions

  • This invention relates to compositions which exhibit switchable electro- optical properties, to processes for their production, to electro-optical devices comprising the compositions and to the use of particles for improving the handling of a liquid crystalline material.
  • liquid crystalline materials in electro-optical devices are, of course, well-known. They exhibit electro-optical properties as a result of the alignment of their molecules when exposed to an electrical field, such as when a thin film is disposed between two electrically conducting plates across which a potential difference is applied.
  • a composite material formed from a binary emulsion of a thermotropic liquid crystal and a non-liquid crystalline organic compound is disclosed in WO 99/00464.
  • the material is a mutual dispersion of a polymer and the liquid crystal, which contains more than 50% of the polymer component (and therefore less than 50% of the optically active liquid crystal).
  • the polymer is present in the material as generally irregular particles.
  • the material, which is in the form of a solid film, is said to be highly adhesive to glass or plastic supports and is prepared by cross- linking to form a polymer matrix containing the particles.
  • thermotropic liquid crystalline polymer A blend of a thermotropic liquid crystalline polymer and an organic compound is described in US 4867538.
  • the blend is a mixture of the polymer and the compound.
  • the compound is not in the form of discrete particles.
  • the compositions are solid and no unusual physical properties are ascribed to them.
  • EP-A-0334176 describes a composition of a polymer matrix that exhibits a non-linear optical response containing a silver colloid. The compositions are formed as films by spin coating from solution and there is no mention of their physical properties.
  • Electro-optical displays including colloid-disperse systems with light controlling qualities are taught in GB-A-2090011.
  • the electro-optical compositions need to be sealed within a cell before they can be used in the displays.
  • Liquid crystalline materials can be difficult to handle and to process. For this reason, as described in GB-A-2090011 , for example, they are generally sealed within a cell having rigid walls. There exists a need for an electro-optical composition which can be more readily handled and processed.
  • the present invention aims to alleviate the problems associated with the processing and handling of switchable electro-optical materials.
  • the invention is based on the finding that certain compositions containing liquid crystalline materials, which can be considered as being composite materials, can be produced in a form which is a soft solid at room temperature.
  • composition which exhibits electro-optical properties and is a soft solid at 25°C comprising a dispersion of particles in a liquid crystalline material.
  • the composition may be a solid which is, at room temperature, sufficiently soft to be moulded into different shapes by hand and sufficiently rigid to be capable of being cut with a knife and to retain its cut shape for at least 10 minutes at room temperature.
  • compositions typically have storage moduli G' at 25 °C of greater than 1 ,000 Pa, more preferably 1,000 to 500,000 Pa.
  • the storage modulus G' and the yield stress ⁇ ys of the compositions may be determined by conventional methods.
  • compositions of the invention in spite of being soft solids, retain their switchable electro-optical properties.
  • the film when a thin film of a composition is placed between a pair of electrodes at room temperature, the film changes from being birefringent when viewed through cross polarisers using an optical microscope to exhibiting no birefringence on application of a potential difference across the cell.
  • the liquid crystalline material in the composition becomes homeotropically aligned on application of the potential difference.
  • the particles used in the composition are preferably of a relatively small size.
  • the particles have a size in the range of from lOOnm to 1000 nm, more preferably 200 nm to 800 nm.
  • the particles are substantially spherical in shape (ie the particles generally appear to be regular spheres when viewed under a microscope).
  • the particles may have a refractive index within ⁇ 0.05 of one of the refractive indices of the liquid crystalline material.
  • the particles may be made from any suitable material but are preferably of a polymer.
  • a suitable polymer is poly(methyl methacrylate) (PMMA).
  • the particles are desirably non- agglomerated.
  • they preferably comprise a stabilising compound on their surface.
  • the stabilising compound may be a polymer, such as a poly(hydroxycarboxylic acid) for example, which is chemically grafted onto the surface of the particles.
  • the polymer is preferably a poly(hydroxy C ⁇ 2 -C 2 o carboxylic acid) eg, poly(12-hydroxystearic acid).
  • Stabilised PMMA particles may be obtained by conventional methods such as, for example, those described in L Antl et al, "The Preparation of Poly (Methyl Methacrylate) latices in Non-aqueous Media” , Colloids and Surfaces, Volume 17, pages 67-78 (1986).
  • the particles are preferably present in the composition in an amount of from 2% to 50% by volume of the composition with the balance being the liquid crystalline material and, optionally, other additives such as agents which stabilise the composition. At levels of particles in the composition below 2% by volume, the composition tends to lose its advantageous physical properties. At levels of particles above 50% by volume, the physical properties and the switchable electro-optical properties of the compositions are expected to become inferior. More preferred levels of particles in the compositions of the invention are from 2% to 30% by volume, such as from 5% to 20% by volume for example.
  • the liquid crystalline material may, for example, be selected from any of the known organic thermotropic liquid crystalline compounds, including cholesterics, for example.
  • the liquid crystalline material may have a smectic phase and/or a nematic phase.
  • suitable examples of liquid crystalline materials include relatively low molecular mass compounds (ie, having a molecular mass of less than about 1000 Daltons) which have an isotropic-nematic transition temperature higher than about 30°C, preferably in the range of 35°C to 100°C.
  • An example of a class of suitable liquid crystalline compounds are the alkyl cyanobiphenyls, such as, for example 4-n-pentyl-4'-cyanobiphenyl.
  • the liquid crystalline material is not polymeric.
  • the present invention provides a switchable electro- optical device comprising a composition of the invention and means for optically switching the composition.
  • the device may be a flat panel display.
  • Means for optically switching liquid crystalline materials in electro-optical devices are, of course, well-known.
  • the conventional means may be used in devices which comprise the compositions of the invention.
  • compositions have significant advantages when they are used as the electro-optical material in conventional electro-optical devices. As a result of their properties of being soft solids at room temperature and of being capable of being cut with a knife at room temperature, then- handling is greatly improved compared to conventional liquid crystalline materials. Thus, when the compositions of the invention are being processed for use in an electro-optical device, they may simply be cut and moulded to the required size. Thus, the need for handling liquid materials and the provision of sealed cells to contain them can be avoided in preparing an electro-optical device.
  • compositions of the invention can be used to produce an electro-optical device which comprises an optically switchable display that is flexible.
  • a composition of the invention may be provided as a thin film sandwiched between two flexible sheets which are capable of applying a potential difference across the composition.
  • the present invention provides a process for preparing a composition of the invention which comprises forming a homogenous dispersion of particles in a liquid crystalline material at a temperature above the isotropic-nematic transition temperature of the material and then cooling the dispersion.
  • the dispersion is cooled to room temperature, although it may be cooled to below room temperature if desired.
  • the homogenous dispersion of the particles may be formed at a temperature of from about 40°C to 60°C, although the actual temperature used in any given case will depend on the particular liquid crystalline material which is used and its isotropic-nematic transition temperature.
  • the dispersion is prepared by a method comprising sonicating and tumbling a mixture of the particles and the liquid crystalline material.
  • This method may be carried out in a heated vessel, such as an oven.
  • tumbling it is meant that the mixture is caused to fall repeatedly under the influence of gravity, preferably during rotation in a rotating vessel.
  • the method allows the formation of a substantially homogenous dispersion of the particles in the liquid crystalline material.
  • the present invention provides the use of particles for improving the handling of a liquid crystalline material.
  • the handling may be improved by converting the material to a soft solid.
  • Suitable soft solids can be moulded by hand and cut with a knife at room temperature.
  • the particles used in the fourth aspect of the invention are particles used in the composition of the invention which are described above in detail.
  • the particles were prepared according to the method of Antl et al, Colloids and Surfaces, Volume 17, pages 67-78 (1986). Thus suspended, these particles behave as nearly- perfect hard spheres.
  • the solvent was evaporated off to provide dry particles, which were then redispersed in liquid crystal 4-n-pentyl-4'- cyanobiphenyl (5CB) at 44 ⁇ 2°C by sonicating and slowly tumbling in an oven. At this temperature, pure 5CB is in its isotropic phase
  • Optical cells (10 ⁇ m thick) with ITO electrodes were prepared. The glass surfaces were coated with silicon oxide, for homogenous surface alignment of the liquid crystal. The cells were filled with ⁇ « 10% composites, and observed through crossed polarizers using an optical microscope. The samples appeared birefringent. On application of a voltage of about 2V across the cell, the entire liquid crystal composite becomes homeotropically aligned (ie no birefringence).

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Liquid Crystal Substances (AREA)

Abstract

A composition which exhibits switchable electro-optical properties and is soft solid at 25 °C comprises a dispersion of particles in a liquid crystalline material. The particles may be substantially spherical particles of a polymer such as PMMA having a size of about 100 to 1000 nm. The composition may be produced by forming a homogenous dispersion of particles in a liquid crystalline material at a temperature above the isotropic-nematic transition temperature of the material and then cooling the dispersion. The composition has the advantages of improved hanlding and flexibility and may be used in electro-optical devices such as flat panel displays.

Description

ELECTRO-OPTICAL COMPOSITION
This invention relates to compositions which exhibit switchable electro- optical properties, to processes for their production, to electro-optical devices comprising the compositions and to the use of particles for improving the handling of a liquid crystalline material.
The use of liquid crystalline materials in electro-optical devices is, of course, well-known. They exhibit electro-optical properties as a result of the alignment of their molecules when exposed to an electrical field, such as when a thin film is disposed between two electrically conducting plates across which a potential difference is applied.
A composite material formed from a binary emulsion of a thermotropic liquid crystal and a non-liquid crystalline organic compound is disclosed in WO 99/00464. The material is a mutual dispersion of a polymer and the liquid crystal, which contains more than 50% of the polymer component (and therefore less than 50% of the optically active liquid crystal). The polymer is present in the material as generally irregular particles. The material, which is in the form of a solid film, is said to be highly adhesive to glass or plastic supports and is prepared by cross- linking to form a polymer matrix containing the particles.
A blend of a thermotropic liquid crystalline polymer and an organic compound is described in US 4867538. The blend is a mixture of the polymer and the compound. The compound is not in the form of discrete particles. The compositions are solid and no unusual physical properties are ascribed to them. EP-A-0334176 describes a composition of a polymer matrix that exhibits a non-linear optical response containing a silver colloid. The compositions are formed as films by spin coating from solution and there is no mention of their physical properties.
Electro-optical displays including colloid-disperse systems with light controlling qualities are taught in GB-A-2090011. The electro-optical compositions need to be sealed within a cell before they can be used in the displays.
Sequeria and Hill, Journal of Rheology, Volume 42, pages 203 to 213, 1998 describe the Theological properties of particle suspensions in liquid crystalline media. The suspensions were formed by mixing a low molecular weight thermotropic liquid crystal, N-(4-methoxybenzylidine)- 4-butylaniline, with 31.5 volume % zeolite particles. The physical data given in the paper indicates that thin films made of this suspension do not have sufficient flexural rigidity to support their own weight. Thus, the suspension had a yield stress τys of about 8 Pa at room temperature (25 °C) and a storage modulus G' of about 1.5 Pa at the same temperature. There is no mention in the paper of any electro-optical properties of the composition.
Liquid crystalline materials can be difficult to handle and to process. For this reason, as described in GB-A-2090011 , for example, they are generally sealed within a cell having rigid walls. There exists a need for an electro-optical composition which can be more readily handled and processed. The present invention aims to alleviate the problems associated with the processing and handling of switchable electro-optical materials.
The invention is based on the finding that certain compositions containing liquid crystalline materials, which can be considered as being composite materials, can be produced in a form which is a soft solid at room temperature.
According to the invention in its first aspect, there is provided a composition which exhibits electro-optical properties and is a soft solid at 25°C comprising a dispersion of particles in a liquid crystalline material.
It was unexpected that such a composition could be obtained which is a soft solid but retains switchable electro-optical properties. The composition may be a solid which is, at room temperature, sufficiently soft to be moulded into different shapes by hand and sufficiently rigid to be capable of being cut with a knife and to retain its cut shape for at least 10 minutes at room temperature.
The compositions typically have storage moduli G' at 25 °C of greater than 1 ,000 Pa, more preferably 1,000 to 500,000 Pa. The storage modulus G' and the yield stress τys of the compositions may be determined by conventional methods.
The compositions of the invention, in spite of being soft solids, retain their switchable electro-optical properties. Thus, when a thin film of a composition is placed between a pair of electrodes at room temperature, the film changes from being birefringent when viewed through cross polarisers using an optical microscope to exhibiting no birefringence on application of a potential difference across the cell. Thus, the liquid crystalline material in the composition becomes homeotropically aligned on application of the potential difference.
The particles used in the composition are preferably of a relatively small size. Desirably, the particles have a size in the range of from lOOnm to 1000 nm, more preferably 200 nm to 800 nm. Preferably, the particles are substantially spherical in shape (ie the particles generally appear to be regular spheres when viewed under a microscope).
If it is desired that the particles should not interfere with the optical properties of the liquid crystalline material, which may not be the case for all applications of the compositions of the invention, the particles may have a refractive index within ± 0.05 of one of the refractive indices of the liquid crystalline material.
The particles may be made from any suitable material but are preferably of a polymer. A suitable polymer is poly(methyl methacrylate) (PMMA).
In order to obtain a homogeneous dispersion of the particles in the isotropic phase of the liquid crystalline material, the particles are desirably non- agglomerated. So as to inhibit or prevent agglomeration of the particles, they preferably comprise a stabilising compound on their surface. The stabilising compound may be a polymer, such as a poly(hydroxycarboxylic acid) for example, which is chemically grafted onto the surface of the particles. The polymer is preferably a poly(hydroxy Cι2-C2o carboxylic acid) eg, poly(12-hydroxystearic acid). Stabilised PMMA particles may be obtained by conventional methods such as, for example, those described in L Antl et al, "The Preparation of Poly (Methyl Methacrylate) latices in Non-aqueous Media" , Colloids and Surfaces, Volume 17, pages 67-78 (1986).
The particles are preferably present in the composition in an amount of from 2% to 50% by volume of the composition with the balance being the liquid crystalline material and, optionally, other additives such as agents which stabilise the composition. At levels of particles in the composition below 2% by volume, the composition tends to lose its advantageous physical properties. At levels of particles above 50% by volume, the physical properties and the switchable electro-optical properties of the compositions are expected to become inferior. More preferred levels of particles in the compositions of the invention are from 2% to 30% by volume, such as from 5% to 20% by volume for example.
The liquid crystalline material may, for example, be selected from any of the known organic thermotropic liquid crystalline compounds, including cholesterics, for example. The liquid crystalline material may have a smectic phase and/or a nematic phase. Suitable examples of liquid crystalline materials include relatively low molecular mass compounds (ie, having a molecular mass of less than about 1000 Daltons) which have an isotropic-nematic transition temperature higher than about 30°C, preferably in the range of 35°C to 100°C. An example of a class of suitable liquid crystalline compounds are the alkyl cyanobiphenyls, such as, for example 4-n-pentyl-4'-cyanobiphenyl. Preferably, the liquid crystalline material is not polymeric. In a second aspect, the present invention provides a switchable electro- optical device comprising a composition of the invention and means for optically switching the composition. The device may be a flat panel display.
Means for optically switching liquid crystalline materials in electro-optical devices are, of course, well-known. The conventional means may be used in devices which comprise the compositions of the invention.
The compositions have significant advantages when they are used as the electro-optical material in conventional electro-optical devices. As a result of their properties of being soft solids at room temperature and of being capable of being cut with a knife at room temperature, then- handling is greatly improved compared to conventional liquid crystalline materials. Thus, when the compositions of the invention are being processed for use in an electro-optical device, they may simply be cut and moulded to the required size. Thus, the need for handling liquid materials and the provision of sealed cells to contain them can be avoided in preparing an electro-optical device.
As a consequence of the physical properties of the compositions of the invention, they can be used to produce an electro-optical device which comprises an optically switchable display that is flexible. For example, a composition of the invention may be provided as a thin film sandwiched between two flexible sheets which are capable of applying a potential difference across the composition.
In a third aspect, the present invention provides a process for preparing a composition of the invention which comprises forming a homogenous dispersion of particles in a liquid crystalline material at a temperature above the isotropic-nematic transition temperature of the material and then cooling the dispersion. Typically, the dispersion is cooled to room temperature, although it may be cooled to below room temperature if desired. The homogenous dispersion of the particles may be formed at a temperature of from about 40°C to 60°C, although the actual temperature used in any given case will depend on the particular liquid crystalline material which is used and its isotropic-nematic transition temperature.
Preferably, the dispersion is prepared by a method comprising sonicating and tumbling a mixture of the particles and the liquid crystalline material. This method may be carried out in a heated vessel, such as an oven. By tumbling, it is meant that the mixture is caused to fall repeatedly under the influence of gravity, preferably during rotation in a rotating vessel. The method allows the formation of a substantially homogenous dispersion of the particles in the liquid crystalline material.
In a fourth aspect, the present invention provides the use of particles for improving the handling of a liquid crystalline material. The handling may be improved by converting the material to a soft solid. Suitable soft solids can be moulded by hand and cut with a knife at room temperature.
Preferably, the particles used in the fourth aspect of the invention are particles used in the composition of the invention which are described above in detail.
The following non-limiting examples illustrate the present invention.
Examples Sample preparation
The particles used were nearly-monodisperse polymethylmethacrylate (PMMA) spheres, sterically-stabilised with chemically-grafted poly- 12- hydroxystearic acid, radius R=250 nm, initially dispersed in cis-decalin at approximately 30% volume fraction. The particles were prepared according to the method of Antl et al, Colloids and Surfaces, Volume 17, pages 67-78 (1986). Thus suspended, these particles behave as nearly- perfect hard spheres. The solvent was evaporated off to provide dry particles, which were then redispersed in liquid crystal 4-n-pentyl-4'- cyanobiphenyl (5CB) at 44 ± 2°C by sonicating and slowly tumbling in an oven. At this temperature, pure 5CB is in its isotropic phase
(isotropic-nematic transition temperature TIN « 35 °C). Particle-liquid crystal composites with particle volume fractions of 5 % , 10% and 20% were prepared. In all cases, when the mixture was cooled from about
44°C to room temperature (25°C), a waxy solid resulted.
Rheology
To quantify the mechanical properties of the composite, small-amplitude oscillatory viscoelastic measurements were performed at 1Hz, strain amplitude 2% , and a constant cooling rate of 3.5°C per minute. In the isotropic phase (temperature T > 35°C) the sample behaves as a fluid eg storage modulus G' about 0.01 Pa and loss modulus G" about 0.1 Pa for the 5 % particle composite. Close to the pure 5CB isotropic-nematic transition temperature (TIN « 35 °C) a sudden increase in both storage and loss moduli was observed, and the sample became a viscoelastic solid eg for a 5 % composite the storage modulus G' suddenly increases by four orders of magnitude to about 100 Pa, gradually increasing to > 1000 Pa as the temperature is further decreased. The low-temperature G' is an increasing function of particle volume fraction φ, reaching a value of about 105 Pa for the φ = 20% composite.
Electro-optical switching
Optical cells (10 μm thick) with ITO electrodes were prepared. The glass surfaces were coated with silicon oxide, for homogenous surface alignment of the liquid crystal. The cells were filled with φ « 10% composites, and observed through crossed polarizers using an optical microscope. The samples appeared birefringent. On application of a voltage of about 2V across the cell, the entire liquid crystal composite becomes homeotropically aligned (ie no birefringence).

Claims

1. Composition which exhibits electro-optical properties and is a soft solid at 25 °C comprising a dispersion of particles in a liquid crystalline material.
2. Composition as claimed in Claim 1 ,
Figure imgf000011_0001
the particles have a size in the range of from 100 to 1000 nm.
3. Composition as claimed in Claim 1 , wherein the particles have a size in the range of from 200 to 800 nm.
4. Composition as claimed in any one of Claims 1 to 3, wherein the particles are capable of transmitting light and have a refractive index within 0.05 of the refractive index of the liquid crystalline material.
5. Composition as claimed in any one of Claims 1 to 4, wherein the particles are substantially spherical.
6. Composition as claimed in any one of Claims 1 to 5, wherein the particles are of a polymer.
7. Composition as claimed in Claim 6, wherein the polymer is polyme thy lmethacry late.
8. Composition as claimed in any one of Claims 1 to 7, wherein a stabilising compound is present on the surface of the particles.
. Composition as claimed in Claim 8, wherein the stabilising compound is a poly(hydroxycarboxylic acid) chemically grafted onto the surface of the particles.
10. Composition as claimed in Claim 9, wherein the stabilising polymer is poly(12-hydroxystearic acid).
11. Composition as claimed in any one of Claims 1 to 10 comprising from 2% to 50% by volume of the particles.
12. Composition as claimed in Claim 11 comprising from 5 % to 20% by volume of the particles.
13. Composition as claimed in any one of Claims 1 to 12, wherein the liquid crystalline material is 4-n-pentyl-4'-cyanobiphenyl.
14. Composition as claimed in any one of Claims 1 to 13 which has a storage modulus G' at 25° C of greater than 1,000 Pa.
15. Composition as claimed in Claim 14, which has a storage modulus G' at 25°C of from 1 ,000 to 500,000 Pa.
16. Electro-optical device comprising a composition according to any of Claims 1 to 15 and means for optically switching said composition.
17. Electro-optical device as claimed in Claim 16 which is a flat panel display.
18. Electro-optical device as claimed in Claim 16 or Claim 17 which comprises an optically switchable display that is flexible.
19. Process for producing the composition of any of Claims 1 to 15 which comprises forming a homogenous dispersion of particles in a liquid crystalline material at a temperature above the isotropic- nematic transition temperature of the material and then cooling the dispersion.
20. Process as claimed in Claim 19, wherein the dispersion is prepared by a method comprising sonicating and tumbling a mixture of the particles and the material.
21. Use of particles for improving the handling of a liquid crystalline material.
22. Use as claimed in Claim 21 wherein the particles have the features mentioned in any of Claims 2 to 12.
PCT/GB2000/003187 1999-08-18 2000-08-18 Electro-optical composition WO2001012752A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63297491A (en) * 1987-05-29 1988-12-05 Matsushita Electric Ind Co Ltd Liquid crystal composite composition
JPH02202986A (en) * 1989-02-02 1990-08-13 Dainippon Ink & Chem Inc Liquid crystal device
DE4317081A1 (en) * 1993-05-21 1994-11-24 Nematel Dr Rudolf Eidenschink Liquid-crystalline medium

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63297491A (en) * 1987-05-29 1988-12-05 Matsushita Electric Ind Co Ltd Liquid crystal composite composition
JPH02202986A (en) * 1989-02-02 1990-08-13 Dainippon Ink & Chem Inc Liquid crystal device
DE4317081A1 (en) * 1993-05-21 1994-11-24 Nematel Dr Rudolf Eidenschink Liquid-crystalline medium

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Section Ch Week 198903, Derwent World Patents Index; Class A89, AN 1989-020692, XP002152544 *
DATABASE WPI Section Ch Week 199038, Derwent World Patents Index; Class A85, AN 1990-287214, XP002152545 *
EIDENSCHINK R ET AL: "STATIC SCATTERING IN FILLED NEMATIC: NEW LIQUID CRYSTAL DISPLAY TECHNIQUE", ELECTRONICS LETTERS,GB,IEE STEVENAGE, vol. 27, no. 13, 20 June 1991 (1991-06-20), pages 1195 - 1196, XP000213768, ISSN: 0013-5194 *
V. SEQUEIRA, D.A. HILL: "particle suspensions in liquide crystalline media: rheology, structure, and dynamic interactions", JOURNAL OF RHEOLOGY, vol. 42, no. 1, 1998, pages 203 - 213, XP000961798 *

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