EP0830634A1 - Materiaux et dispositifs pour orienter des cristaux liquides - Google Patents
Materiaux et dispositifs pour orienter des cristaux liquidesInfo
- Publication number
- EP0830634A1 EP0830634A1 EP97907225A EP97907225A EP0830634A1 EP 0830634 A1 EP0830634 A1 EP 0830634A1 EP 97907225 A EP97907225 A EP 97907225A EP 97907225 A EP97907225 A EP 97907225A EP 0830634 A1 EP0830634 A1 EP 0830634A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- liquid crystal
- polymer
- layer
- alignment
- alignment layer
- Prior art date
- Legal status (The legal status 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 status listed.)
- Withdrawn
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
Landscapes
- 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)
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.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9607059 | 1996-04-03 | ||
GBGB9607059.4A GB9607059D0 (en) | 1996-04-03 | 1996-04-03 | Liquid crystal alignment materials and devices |
PCT/GB1997/000745 WO1997038349A1 (fr) | 1996-04-03 | 1997-03-19 | Materiaux et dispositifs pour orienter des cristaux liquides |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0830634A1 true EP0830634A1 (fr) | 1998-03-25 |
Family
ID=10791566
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP97907225A Withdrawn EP0830634A1 (fr) | 1996-04-03 | 1997-03-19 | Materiaux et dispositifs pour orienter des cristaux liquides |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0830634A1 (fr) |
JP (1) | JPH11508063A (fr) |
GB (1) | GB9607059D0 (fr) |
WO (1) | WO1997038349A1 (fr) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1999049360A1 (fr) * | 1998-03-20 | 1999-09-30 | Rolic Ag | Couche d'orientation de cristaux liquides |
JP2001042278A (ja) * | 1999-08-03 | 2001-02-16 | Minolta Co Ltd | 液晶素子 |
WO2016186190A1 (fr) * | 2015-05-20 | 2016-11-24 | 日産化学工業株式会社 | Composition de polymères, agent d'alignement de cristaux liquides, film d'alignement de cristaux liquides, substrat comprenant ledit film d'alignement de cristaux liquides, et élément d'affichage à cristaux liquides comprenant ledit film d'alignement de cristaux liquides |
WO2016186189A1 (fr) * | 2015-05-20 | 2016-11-24 | 日産化学工業株式会社 | Composition polymère, agent d'alignement de cristaux liquides, film d'alignement de cristaux liquides, substrat comprenant ledit film d'alignement de cristaux liquides et élément d'affichage à cristaux liquides comprenant ledit film d'alignement de cristaux liquides |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5539074A (en) * | 1993-02-17 | 1996-07-23 | Hoffmann-La Roche Inc. | Linear and cyclic polymers or oligomers having a photoreactive ethene group |
JP2777056B2 (ja) * | 1993-05-20 | 1998-07-16 | エルジー電子株式会社 | 液晶セルの配向物質 |
KR970000356B1 (ko) * | 1993-09-18 | 1997-01-08 | 엘지전자 주식회사 | 액정표시소자(lcd)용 광 폴리머 배향막 형성방법 |
JP2773795B2 (ja) * | 1995-05-10 | 1998-07-09 | スタンレー電気株式会社 | 液晶配向構造の製造方法及び液晶表示装置 |
-
1996
- 1996-04-03 GB GBGB9607059.4A patent/GB9607059D0/en active Pending
-
1997
- 1997-03-19 JP JP9535937A patent/JPH11508063A/ja active Pending
- 1997-03-19 EP EP97907225A patent/EP0830634A1/fr not_active Withdrawn
- 1997-03-19 WO PCT/GB1997/000745 patent/WO1997038349A1/fr not_active Application Discontinuation
Non-Patent Citations (1)
Title |
---|
See references of WO9738349A1 * |
Also Published As
Publication number | Publication date |
---|---|
JPH11508063A (ja) | 1999-07-13 |
WO1997038349A1 (fr) | 1997-10-16 |
GB9607059D0 (en) | 1996-06-05 |
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Legal Events
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17P | Request for examination filed |
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RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: QINETIQ LIMITED |
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17Q | First examination report despatched |
Effective date: 20020207 |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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18D | Application deemed to be withdrawn |
Effective date: 20020618 |