The Secretary of State for Defence in Her Britannic Majesty's Government

Zbd Displays Limited

Qinetiq Limited

Hewlett-packard Development Company, L.p.

The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and Northern Ireland

The Secretary of State for Defense in Her Britannic Majesty's Government of the United Kingdom of Great Britain and Northern Ireland

Guy Peter Bryan-Brown

John Clifford Jones

Damien Gerard McDonnell

Carl Vernon Brown

Emma Louise Wood

Ian Charles Sage

Michael John Towler

Ian Robert Mason

Victor Chaklam Hui

Richard M Amos

Jonathan Rennie Hughes

William James Feast

Alistair Graham

Kathryn E Foster

Philip T Worthing

David Walker

Martin S Bancroft

The invention relates to a method of patterning a layer formed from a fixable material such as photopolymer on a surface in a desired pattern. The method involves coating selected areas of the substrate with an adhesion promoter and subsequently coating the fixable material. The fixable material is then fixed, for instance by curing by exposure to UV radiation. The adhesion promoter is adapted to have a surface energy which is designed to adhere to the substrate or selected areas thereof and also to the fixed material such that fixed material may be easily removed from areas of the substrate not coated with adhesion promoter but retained in areas where the adhesion promoter has bonded to the substrate.

Method for patterning a surface using selective adhesion

A photopolymer mixture is capable of use for a liquid crystal alignment layer. An alignment layer is formed from such a photopolymer mixture. The mixture comprises at least two polymerisable materials which are blended together in proportion so as to give a predetermined, preferably low, surface energy. A low surface energy, e.g., less than 4&#xd7;10N/m, can result in an alignment layer which imparts a particular orientation to liquid crystal molecules with out requiring any post-cure treatments. The polymerisable materials may be monomers, oligomers, or diluents that form long chain molecules when cured, and the mixture may contain additives to lower the overall surface energy.

Liquid crystal alignment layer

A method and apparatus for forming a patterned layer having a surface profile that provides relief structures within an electronic device. The method comprises the steps of taking a carrier film () having an inverse of the required surface profile formed on one side thereof, taking a layer of fixable material () located on a substrate (), laminating the carrier film () and substrate () such the carrier film causes the required surface profile to be formed in the layer of fixable material with a predetermined offset, and then fixing the fixable material. Lamination may be performed using rollers () or a vacuum process. The process is designed to ensure that the offset can be kept as low as possible, preferably to within 150 nm.

Embossing method and apparatus

A bistable nematic liquid crystal device cell is provided with a surface alignment grating on at least one cell wall and a surface treatment on the other wall. Such treatment may be a homeotropic alignment or a planar alignment with or without an alignment direction, and zero or a non zero pretilt. The surface profile on the monograting is asymmetric with its groove height to width selected to give approximately equal energy within the nematic material in its two allowed alignment arrangements. The monograting may be formed by a photolithographic process or by embossing of a plastics material. The cell is switched by dc pulses coupling to a flexoelectric coefficient in the material, or by use of a two frequency addressing scheme and a suitable two frequency material. Polarisers either side of the cell distinguish between the two switched states. The cell walls may be rigid or flexible, and are coated with electrode structures, e.g. in row and column format giving an x,y matrix of addressable pixels on the cell.

Liquid crystal device exhibiting zernithal bistability and a cell wall for such a device

Liquid crystal devices are described that exhibit bistable, tri-stable or other multistable operation. The stable liquid crystal configurations are attained using a surface alignment grating () on the internal surface of at least one cell wall (). The surface profile of the surface alignment grating comprises three or more defect sites per grating period and permit the liquid crystal molecules to adopt any one of two or more stable pretilt angles in the same azimuthal plane. Application of a suitable voltage causes the liquid crystal material to switch between the stable configurations.

Liquid crystal device

A bistable nematic liquid crystal device is addressed by application of a row waveform to successive row electrodes of an x, y matrix of pixels whilst one of two data waveforms are applied to each column electrode. The row waveform has a period of two or more time slots (ts), with two dc pulses of opposite amplitude for causing a switching to a dark state, and two dc pulses of opposite amplitude for causing a switching to a light state. The data waveforms have the same period as the strobe with dc pulses of opposite amplitude and combine with the strobe pulses to switch the device. The device can be addressed in two field periods, one field switching to a dark state, the other field switching to a light state. Alternatively, the device can be blanked to the dark state then selectively switched to the light state. When blanking is used, the row waveform has blanking de pulses placed a short time before selective switching to reduce overall addressing time. Zero voltage pulses may be used within the two or more time slot period of the strobe and data waveforms; these reduce rms. voltages appearing at the pixels and enhance contrast ratio.

Addressing bistable nematic liquid crystal devices

Liquid crystal devices are formed by a layer of a liquid crystal material enclosed between two cell walls, both carrying electrode structures, and one or both walls treated to align molecules of the liquid crystal material. Most alignment treatment give alignment and surface pretilt with a strong azimuthal and zenithal anchoring energy to contacting liquid crystal molecules. The invention reduces at least one of the azimuthal zenithal or translational anchoring energy to improve switching characteristics and optical performance by allowing movement of liquid crystal molecules at or close to the cell wall. The reduction of anchoring energy may be achieved by an oligomer or short chain polymer which is either spread on the surface or added to the liquid crystal material. The size of oligomer or short chain polymer is low enough that it does not appreciably phase separate from the liquid crystal material. The polymer layer has the characteristics of having imperfect solubility in the liquid crystal material used in the device, of having a physical affinity for the surface of the substrate, and of retaining a substantially liquid like surface at the polymer/liquid crystal interface. The polymer may be formed by polymerisation of reactive low molecular weight materials in solution in the liquid crystal fluid. The resulting solution or dispersion of polymer in liquid crystal is then filled into the cell, and the polymer is allowed to coat the substrate surfaces.

Liquid crystal device alignment

A first layer of photoresist material, sensitive to radiation of a first wavelength, has a second layer of photoresist material, sensitive to radiation of a second wavelength, deposited thereon. A pattern of radiation of the second wavelength is then formed on the second layer of photoresist material which is subsequently treated with a solvent, in which the first layer of photoresist material is insoluble, to develop a first periodic profile. The first layer of photoresist material is then exposed to radiation of the first wavelength through the first periodic profile and treated to develop a second periodic profile. By directing the radiation of the second wavelength through the first periodic profile at an angle to normal to the first material photoresist material a blaze profile may be obtained.

Process for making a periodic profile

Bistable nematic liquid crystal device

A liquid crystal device comprises a cell ( ) formed by a layer ( ) of nematic or long pitch cholesteric liquid crystal material contained between two cell walls ( ). One wall ( ) carries a surface treatment giving a first azimuthal alignment direction with or without a surface pretilt to liquid crystal molecules. The other wall ( ) carries a surface treatment capable of separately providing both a preferred, substantially homeotropic alignment of the adjacent liquid crystal, and a defined azimuthal second alignment direction to the adjacent liquid crystal dependant upon liquid crystal molecular arrangement. The first and second alignment directions are approximately orthogonal. Polarisers ( ) may be arranged on either side of the cells walls with their polarization axes parallel or perpendicular to the two azimuthal directions. In addition one or more birefringent compensator layers ( ) are disposed on one side or on both sides of the cell ( ). The compensator layers ( ) may be formed of aligned polymer layers, or aligned liquid crystal material, either in a liquid form in a cell, or dispersed in a polymer sheet, or sheets of quartz or calcite slices. The device operates between two different voltage levels, one level (V ) providing a non twisted liquid crystal molecular arrangement, the other and higher voltage (V ) providing a twisted molecular arrangement.

A liquid crystal device comprises a layer of nematic or long pitch cholesteric liquid crystal material contained between two cell walls. One wall (A) carries a surface treatment giving a first azimuthal alignment direction with or without a surface pretilt to liquid crystal molecules. The other wall (B) carries a surface treatment ( ) capable of separately providing both a preferred, substantially homeotropic alignment of the adjacent liquid crystal, and a defined azimuthal second alignment direction to the adjacent liquid crystal dependent upon liquid crystal molecular arrangement. The first and second alignment directions are approximately orthogonal. Polarisers may be arranged on either side of the cell walls with their polarisation axes parallel or perpendicular to the two azimuthal directions. Alternatively an amount of dichroic dye may be incorporated in the liquid crystal material, and the device operated with one or two polarisers. The device operates between two different voltage levels, one level providing a non twisted liquid crystal molecular arrangement, the other and higher voltage providing a twisted molecular arrangement.

A bistable nematic liquid crystal device cell (,) is provided with a surface alignment grating on at least one cell wall (,) and a surface treatment on the other wall (,). Such treatment may be a homeotropic alignment or a planar alignment with or without an alignment direction, and zero or a non zero pretilt. The surface profile on the monograting is asymmetric with its grove height to width selected to give approximately equal energy within nematic material (,) in its two allowed alignment arrangements. The monograting may be formed by a photolithographic process or by embossing of a plastics material. The cell (,) is switched by dc pulses coupling to a flexoelectric coefficient in the material (,), or by use of a two frequency addressing scheme and a suitable two frequency material. Polarizers (,&prime;) either side of the cell (1) distinguish between the two switched states. The cell walls (,) may be rigid or flexible, and are coated with electrode structures (,), e.g. in row and column format giving an x,y matrix of addressable pixels on the cell (,).

In order to reduce the effects of impact on liquid crystal devices a polymer network is introduced into ferroelectric liquid crystal cells. A liquid crystal device comprises two spaced cell walls each bearing electrode structures and treated on at least one facing surface with an alignment layer, a layer of a smectic liquid crystal material enclosed between the cell walls, characterised in that the liquid crystal material contains a small amount of monomer. The liquid crystal material may also contain a photoinitiator. The monomer material may be cured to produce the polymer networks the curing many be carried out in the presence of an electric or magnetic field. Further, the monomer may be cured in an isotropic or liquid crystal phase.

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Malvern, United Kingdom

Guy Peter Bryan-Brown