Cambridge Enterprise Limited

Dow Corning Corporation

Huan Xu

William Alden Crossland

Anthony Bernard Davey

Terry Clapp

Jonathan Hannington

Russell Keith King

Martin Grasmann

Fumito Nishida

Omar Farooq

Harry J Coles

Mykhaylo Pivnenko

Oliver Hadeler

Joo-Nyung Jang

Daping Chu

Steven Robson

Russel Keith King

Mikhael Pivnenko

Jonathan Paul Hannington

Anthony Bemard Davey

Mike Pivnenko

Terry Victor Clapp

Martin Grassman

Harry James Coles

A liquid crystal smectic A composition that can be switched by the application of different electric fields across it between a first stable state (left hand block in FIG.) and at least one second stable state (right hand block in FIG.) in which the composition is less ordered than in the first state. The radiation transmission properties of the first and second states are different. The composition comprises: (A) a liquid crystal material that has a positive dielectric anisotropy and that is a uniformly aligned smectic A structure when in the first state; (B) an ionic dopant giving a negative conductivity anisotropy in the liquid crystal material so that it is capable of disrupting the smectic A structure of the first state when subject to an electric field that causes the dopant to migrate through the composition, thereby causing the composition to switch into said at least one second state, and (C) optically anisotropic pigment particles having positive dielectric anisotropy dispersed in the composition, the largest dimension of the pigment particles being in the range of 10 nm to 1 &#x3bc;m. The composition, when in the first relatively stable state, is capable of undergoing smectic dynamic scattering due to electro-hydrodynamic instability under the influence of a sufficiently low frequency AC field, thereby disordering the liquid crystals and the pigment particles and thereby discouraging the pigment particles from aggregating together. The composition is suitable for use in displays and is especially resistant to degradation by ambient light and so can be used in outside applications.

Smectic A compositions for use in optical devices

The present, invention relates to liquid crystal compositions having a smectic A structure for use in an optical device in which the composition is sandwiched between a pair of electrodes (-). In essence the composition includes a siloxane oligomer (component (a)) which may be seen to construct a layered SmA system of particular spacing and 'strength'. Within this structure a low molar mass nematic mesogen (component (c)) is provided that may be considered to be that of a 'plasticiser' which moderates the layer &#x201c;strength&#x201d;, while simultaneously providing tuneability to the properties of the composition, e.g. its refractive index or dielectric anisotropy. The addition of a side chain liquid crystal polysiloxane (component (d)) allows such systems to be further moderated since they can be considered as binding together the la&#x3e;&#xbe;rs, both within a given layer and between layers. An ionic dopant (component (b)) is also included in the composition that migrates through the composition when low frequency electric fields are applied to the composition by the electrodes, thereby disrupting the order to the composition. Order in the composition can be restored by applying a higher frequency field that does not allow the dopant time to migrate significantly. Chromophores may also be included in the formulation.

Liquid crystal formulations and structures for smectic A optical devices

A liquid crystal formulation is described. The liquid crystal formulation comprises a first oligosiloxane-modified nano-phase segregating liquid crystalline material; and at least one additional material selected from a second oligosiloxane-modified nano-phase segregating liquid crystalline material, non-liquid crystalline oligosiloxane-modified materials, organic liquid crystalline materials, or non-liquid crystalline materials, wherein the liquid crystal formulation has an I&#x2192;SmA*&#x2192;SmC* phase transition, with a SmC* temperature range from about 15&#xb0; C. to about 35&#xb0; C., a tilt angle of about 22.5&#xb0;&#xb1;6&#xb0; or about 45&#xb0;&#xb1;6&#xb0;, a spontaneous polarization of less than about 50 nC/cm2., and a rotational viscosity of less than about 600 cP. Devices containing liquid crystal formulations are also described. The device has a stable bookshelf geometry, bistable switching, and isothermal electric field alignment, a response time of less than 500 &#x3bc;s when switched between two stable states, and an electric drive field of less than about 30 V/&#x3bc;m.

Oligosiloxane modified liquid crystal formulations and devices using same

A liquid crystal formulation is described. The liquid crystal formulation comprises a first oligosiloxane-modified nano-phase segregating liquid crystalline material; and at least one additional material selected from a second oligosiloxane-modified nano-phase segregating liquid crystalline material, non-liquid crystalline oligosiloxane-modified materials, organic liquid crystalline materials, or organic non-liquid crystalline materials, wherein the liquid crystal formulation is nano-phase segregated in the SmC* phase, has an I&#x2192;SmC* phase transition, with a SmC* temperature range from about 15&#xb0; C. to about 35&#xb0; C., has a tilt angle of about 22.5&#xb0;&#xb1;6&#xb0; or about 45&#xb0;&#xb1;6&#xb0;, and has a spontaneous polarization of less than about 50 nC/cm2, and a rotational viscosity of less than about 600 cP. Devices containing liquid crystal formulations are also described. The device has a stable bookshelf geometry, bistable switching, and isothermal electric field alignment, a response time of less than 500 &#x3bc;s when switched between two stable states, and an electric drive field of less than about 30 V/&#x3bc;m.

A liquid crystal electro-optic device. The liquid crystal electro-optic device comprises at least one liquid crystal cell comprising: a pair of substrates having a gap therebetween; a pair of electrodes, the pair of electrodes positioned on one of the substrates or one electrode positioned on each substrate; and a ferroelectric, oligosiloxane liquid crystal material disposed in the gap between the pair of substrates, the ferroelectric, oligosiloxane liquid crystal material exhibiting an I-&#x2666; SmC* phase sequence wherein the liquid crystal electro-optic device is bistable in operation. The invention also involves a method for making a liquid crystal electro-optic device.

Bistable ferroelectric liquid crystal devices

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Cambridge, United Kingdom

Huan Xu