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WO1997038349A1 - Materiaux et dispositifs pour orienter des cristaux liquides - Google Patents

Materiaux et dispositifs pour orienter des cristaux liquides Download PDF

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Publication number
WO1997038349A1
WO1997038349A1 PCT/GB1997/000745 GB9700745W WO9738349A1 WO 1997038349 A1 WO1997038349 A1 WO 1997038349A1 GB 9700745 W GB9700745 W GB 9700745W WO 9738349 A1 WO9738349 A1 WO 9738349A1
Authority
WO
WIPO (PCT)
Prior art keywords
liquid crystal
polymer
layer
alignment
alignment layer
Prior art date
Application number
PCT/GB1997/000745
Other languages
English (en)
Inventor
Julian Hollingshurst
John William Goodby
Ian Charles Sage
Guy Peter Bryan-Brown
Original Assignee
The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland
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
Publication date
Application filed by The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland filed Critical The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland
Priority to JP9535937A priority Critical patent/JPH11508063A/ja
Priority to GB9724101A priority patent/GB2315877B/en
Priority to EP97907225A priority patent/EP0830634A1/fr
Publication of WO1997038349A1 publication Critical patent/WO1997038349A1/fr

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G02F1/133711—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by organic films, e.g. polymeric films
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G02F1/13378—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation
    • G02F1/133788—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation by light irradiation, e.g. linearly polarised light photo-polymerisation

Definitions

  • This invention relates to materials and methods for achieving alignment of liquid crystal materials on a solid surface, and to devices made using these methods.
  • Liquid crystal devices commonly comprise a layer of a liquid crystal material contained between two cell walls. These walls carry electrode structures for applying an electric field across the layer so that the layer may be switched between different molecular arrangements, e.g. between light transmitting and light blocking states. Many devices carry surface mounted structures such as thin film transistors; these are used in active matrix displays. Most devices also have a surface alignment treatment on the cell walls which impart a preferred molecular alignment direction to contacting liquid crystal molecules.
  • An object of this invention is to provide means of achieving a defined surface alignment of a liquid crystal material on a surface, which does not require mechanical rubbing or other physical contact which may damage the surface or structures on it.
  • a further objective of the invention is to provide means by which the pretilt angle and surface anchoring energy may be altered without the need for mechanical rubbing or contact.
  • Homeotropic alignment refers to an alignment in which the unique optical axis of a liquid crystal phase, especially a nematic liquid crystal phase, is held perpendicular to the adjacent surface.
  • Planar alignment sometimes referred to as homogeneous alignment, refers to alignment in which the unique optic axis of the liquid crystal phase lies parallel to the adjacent surface. Planar alignment may also impose a direction in which the optic axis of the liquid crystal lies, in the plane of the adjacent surface.
  • Tilted planar alignment or tilted homogenous alignment refer to alignment in which the liquid crystal unique optic axis lies at an angle, termed the pretilt angle from the plane of the adjacent surface.
  • the pretilt angle may be as small as a fraction of one degree, or as large as several tens of degrees.
  • Tilted homeotropic alignment refers to an alignment in which the optic axis of the liquid crystal lies tilted away from the normal to the adjacent surface. This deviation is again termed a pretilt angle.
  • said alignment geometries are chosen and used in combination to achieve specific optical and electro-optic properties from the device and may be combined in new ways or with new liquid crystalline fluids to provide new types of devices.
  • a disadvantage of this method is that the mechanical rubbing process may cause damage to structures on the surface, for example to the elements of an active switching matrix fabricated on the surface.
  • a further disadvantage is that a static electric charge may be generated during the rubbing process, and may damage the surface or structures on the surface or connected to it.
  • a planar alignment or tilted planar alignment may also be achieved by evaporating a variety of inorganic substances onto the surface from an oblique angle if incidence.
  • a disadvantage of this method is that it requires slow and costly vacuum processing.
  • the resulting evaporated layer may show a high capacity to absorb contaminants onto itself from the environment or from other materials used in construction of the device. These contaminants may adversely affect the operation of the device.
  • a homeotropic alignment can be obtained by depositing a surfactant, for example, a quaternary ammonium salt onto the surface from solution in a suitable solvent.
  • a surfactant for example, a quaternary ammonium salt
  • a disadvantage of this treatment is that the resistivity of the liquid crystal device may be lowered by the surfactant, and the resulting alignment may also show poor stability.
  • a photoactive polymer or polymer mixture comprising or containing at least one polymer of structure
  • BP in which C represents a carbon atom
  • A is selected from H, Cl, F, CN, CO 2 R, OCOR, OR, where R is a straight chain or branched alkyl group having 1 to 15 carbon atoms, X and Y are independently selected from the same groups as A, subject to at least one of X and Y on each C atom being selected from F and H B is a linking group comprising a single bond, or a chain of from 1 to 15 methylene groups in which one or more non-adjacent methylenes may be replaced by O, C0 2 , OCO,
  • P is a photoactive group selected from cinnamate or anthracene groups substituted with at least one group selected from F, Cl, CN, CF 3 , OCF 3l Br.
  • the total interfacial energy of the polymer surface is within 3.0 erg per square centimetre of the liquid crystal surface energy, and in the range 35 to 50 ergs per square centimetre.
  • n is conventionally known as the number of repeat units and may typically be in the range 4-1000. Preferably n is in the range 20-300. a is 1.
  • the polymer used may be a single polymer or a mixture of polymers.
  • one or more polymers of structure 1 may be mixed together or may be mixed with other photoactive polymers in order to adjust the interfacial energy of the polymer surface.
  • the types of polymer included in the current invention may be any of the known types of polymer including homo and co polymers.
  • the interfacial energy of the surface may be measured by examining the contact angles made between the surface and reference liquids, according to the method described by Shohei Naemura, PhD Thesis, University of Kyoto, 1982.
  • Suitable polymers include derivatives of poly(vinyl cinnamate), poly(2- cinnamoyloxyethylacrylate) and poly(2-(anthracene-5-carboxy)ethyl) acrylate.
  • a method of providing an alignment layer on a surface of a liquid crystal cell wall includes the step of depositing a layer of a polymer containing at least one polymer of structure I on the surface, followed by exposure to actinic light, and controlling the exposure time and/or intensity of light used to provide a selected value of pretilt in a liquid crystal placed in contact with the exposed layer.
  • a liquid crystal device comprises a layer of a liquid crystal material contained between two cell walls both carrying electrodes structures and surface treated to provide an alignment to liquid crystal molecules;
  • the surface treatment is a layer of the polymer of structure 1 and exposed to actinic light.
  • Figure 1 is a plan view of a liquid crystal device
  • Figure 2 is a cross sectional view of Figure 1.
  • the device of Figures 1 , 2 comprises a liquid crystal cell 1 formed by two cell walls 2, 3 spaced typically 1 to 15 ⁇ m apart by a spacer ring 4 to contain a layer 5 of a liquid crystal material.
  • the inside faces of both walls 2, 3 are coated with a indium tin oxide layer 6, 7 forming transparent electrodes.
  • the electrodes may be of sheet like form covering the complete wall, or formed into e.g. strip electrodes to provide an array of addressable electrode intersections.
  • the walls are also coated with an aligning layer 8, 9 of polymer. These layers provide both an alignment direction, indicated by A, and A b as orthogonally arranged. If the material 5 is nematic then the device may be the known twisted nematic device. In this case polarisers 10, 11 are used to distinguish between the device voltage ON and OFF states.
  • the liquid crystal material may be nematic, cholesteric, or smectic material.
  • the device may be used as a display device, e.g. displaying alpha numeric information, or an x,y matrix displaying information.
  • the device may operate as a shutter to modulate light transmission, e.g. as a spatial light modulator, or as a privacy window.
  • the alignment layer may be produced as described, by way of example only, in the following examples:
  • Poly(vinyl 4-chlorocinnamate) was prepared by reaction of 4-chloroacryloyl chloride with poly(vinyl alcohol) in pyridine at room temperature overnight. The product was recovered by removal of the pyridine on a rotary evaporator, washed with water, and purified by successive dissolution in dichloromethane followed by precipitation from ethyl alcohol until the colour was pale yellow.
  • a solution of poly(vinyl 4-chlorocinnamate) was dissolved in propylene glycol methyl ether acetate at a concentration of 6%.
  • the solution was deposited by spinning onto an indium tin oxide coated glass substrate at 3000rpm for 6 seconds.
  • Samples of the substrate were exposed to linearly polarised light from a helium cadmium laser source providing radiation at a wavelength of 325nm. After exposure, the samples were assembled into cells and these were filled with liquid crystal mixture E7 (available from Merck).
  • the tilt angle in each cell was measured by determining the symmetry point of the optical interference pattern which resulted from rotating the cell in a beam of light of wavelength 633nm, between crossed polarising filters. The results obtained are tabulated below:
  • a liquid crystal cell was constructed having one wall surface coated with the alignment polymer of example 3, exposed to 0 5J/m 2 of 325nm linear polarised light, liquid crystal molecules align perpendicular to the polarisation direction
  • the other wall surface was coated with Probimide 32, a polyimide commercially available from Ciba-Geigy chemicals, and mechanically rubbed, liquid crystal molecules align along the rubbing direction
  • the cell was assembled with the alignment direction on the two walls mutually perpendicular The walls were spaced apart using plastic bead spacers by a distance of 6 ⁇ m
  • the cell was filled with the commercially available liquid crystal mixture ZLI-2293 doped with 0 8% S-811 , both materials obtained from E Merck, Darmstadt The resulting electro-optic response showed a steep switching characteristic with no intrusion of an undesirable stripe characteristic

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Liquid Crystal (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

L'invention concerne une couche d'orientation pour un dispositif à cristaux liquides, qui comprend ou qui contient un polymère de structure (I), dans laquelle: C représente un atome de carbone; A est choisi parmi H, Cl, F, CN, CO2R, OCOR ou OR, où R est un groupe alkyle à chaîne droite ou ramifiée ayant de 1 à 15 atomes de carbone, X et Y sont indépendamment choisis dans les mêmes groupes que A, au moins un X et un Y sur chaque atome C étant choisis entre F et H; B est un groupe de liaison comprenant une liaison unique ou une chaîne constituée de 1 à 15 groupes méthylène dans lesquels un ou plusieurs méthylènes non adjacents peuvent être remplacés par O, CO2 ou OCO; P est un groupe photoactif choisi dans des groupes cinnamate ou anthracène substitués par au moins un groupe choisi parmi F, Cl, CN, CF3, OCF3 ou Br, la tension interfaciale de la surface du polymère étant inférieure ou égale à 3,0 ergs par centimètre carré de la tension interfaciale du cristal liquide et se situant entre 35 et 50 ergs par centimètre carré. L'invention concerne également un procédé destiné à fournir un couche d'orientation sur la surface d'une paroi de cellule de cristal liquide, qui comprend les étapes suivantes: déposition sur la surface d'une couche d'un polymère contenant au moins un polymère comme décrit ci-dessus, irradiation par lumière actinique polarisée et régulation du temps d'exposition et/ou de l'intensité de la lumière utilisée pour fournir une valeur sélectionnée de pré-inclinaison dans un cristal liquide placé en contact avec la couche exposée. La couche d'orientation formée comme indiqué ci-dessus peut être utilisée pour obtenir une ou deux couches d'orientation sur les deux parois d'une cellule de cristal liquide. La cellule peut incorporer un matériau constitué d'un cristal liquide nématique, cholestérique ou smectique.
PCT/GB1997/000745 1996-04-03 1997-03-19 Materiaux et dispositifs pour orienter des cristaux liquides WO1997038349A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP9535937A JPH11508063A (ja) 1996-04-03 1997-03-19 液晶配向物質および装置
GB9724101A GB2315877B (en) 1996-04-03 1997-03-19 Liquid crystal alignment materials and devices
EP97907225A EP0830634A1 (fr) 1996-04-03 1997-03-19 Materiaux et dispositifs pour orienter des cristaux liquides

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9607059.4 1996-04-03
GBGB9607059.4A GB9607059D0 (en) 1996-04-03 1996-04-03 Liquid crystal alignment materials and devices

Publications (1)

Publication Number Publication Date
WO1997038349A1 true WO1997038349A1 (fr) 1997-10-16

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PCT/GB1997/000745 WO1997038349A1 (fr) 1996-04-03 1997-03-19 Materiaux et dispositifs pour orienter des cristaux liquides

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Country Link
EP (1) EP0830634A1 (fr)
JP (1) JPH11508063A (fr)
GB (1) GB9607059D0 (fr)
WO (1) WO1997038349A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999049360A1 (fr) * 1998-03-20 1999-09-30 Rolic Ag Couche d'orientation de cristaux liquides

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001042278A (ja) * 1999-08-03 2001-02-16 Minolta Co Ltd 液晶素子
CN107849330B (zh) * 2015-05-20 2021-11-02 日产化学工业株式会社 聚合物组合物、液晶取向剂、液晶取向膜、具有该液晶取向膜的基板及具有该液晶取向膜的液晶表示元件
KR102540421B1 (ko) * 2015-05-20 2023-06-05 닛산 가가쿠 가부시키가이샤 중합체 조성물, 액정 배향제, 액정 배향막, 그 액정 배향막을 갖는 기판 및 그 액정 배향막을 갖는 액정 표시 소자

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0611786A1 (fr) * 1993-02-17 1994-08-24 F. Hoffmann-La Roche Ag Couche d'orientation pour cristaux liquides
DE4417409A1 (de) * 1993-05-20 1994-11-24 Gold Star Co Thermostabiles Photopolymermaterial zur Ausrichtung von Flüssigkristallen
GB2281977A (en) * 1993-09-18 1995-03-22 Gold Star Co Orientation film for a liquid crystal display
EP0742471A2 (fr) * 1995-05-10 1996-11-13 Stanley Electric Co., Ltd. Agencement d'orientation des cristaux liquides sans frottage

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0611786A1 (fr) * 1993-02-17 1994-08-24 F. Hoffmann-La Roche Ag Couche d'orientation pour cristaux liquides
DE4417409A1 (de) * 1993-05-20 1994-11-24 Gold Star Co Thermostabiles Photopolymermaterial zur Ausrichtung von Flüssigkristallen
GB2281977A (en) * 1993-09-18 1995-03-22 Gold Star Co Orientation film for a liquid crystal display
EP0742471A2 (fr) * 1995-05-10 1996-11-13 Stanley Electric Co., Ltd. Agencement d'orientation des cristaux liquides sans frottage

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DYADUYSHA A ET AL: "PECULIARITY OF AN OBLIQUE LIQUID CRYSTAL ALIGNMENT INDUCED BY A PHOTOSENSITIVE ORIENTAT", JAPANESE JOURNAL OF APPLIED PHYSICS, vol. 34, no. 8A, 1 August 1995 (1995-08-01), pages L1000 - L1002, XP000600431 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999049360A1 (fr) * 1998-03-20 1999-09-30 Rolic Ag Couche d'orientation de cristaux liquides
EP1642953A1 (fr) * 1998-03-20 2006-04-05 Rolic AG Couche d'orientation à cristaux liquides
KR100660050B1 (ko) * 1998-03-20 2006-12-21 롤리크 아게 액정 매질용 배향층 제조용 재료, 당해 재료를 포함하는 액정 매질용 배향층, 당해 배향층을 함유하는 광학 또는 전자-광학 장치 및 당해 배향층의 제조방법
JP2009025828A (ja) * 1998-03-20 2009-02-05 Rolic Ag 液晶配向層
US9321962B2 (en) 1998-03-20 2016-04-26 Rolic Ag Liquid crystal orientation layer

Also Published As

Publication number Publication date
GB9607059D0 (en) 1996-06-05
JPH11508063A (ja) 1999-07-13
EP0830634A1 (fr) 1998-03-25

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