Patent ID: 8999195
Filing Date: 2015-04-07
Classification: C09K,G02F

Abstract:
1. A liquid crystal smectic A composition that can be switched by the application of different electric fields across it between a first stable state and at least one second stable state in which the composition is less ordered than in the first state, the radiation transmission properties of the first and second states being different at at least one wavelength, the composition comprising: (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 smectic A composition 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 the 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 μm wherein the composition, when in the first 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.