| abstract |
The present invention relates to a liquid crystal composition having a smectic A structure for use in an optical device, interposed between a pair of electrodes 12-15. Essentially, the composition comprises siloxane oligomers (component (a)) which can be seen in constructing the layered SmA system at specific intervals and "strengths". Within this structure, low molecular weight nematic mesogens (components), which can be considered to be "plasticizer" components that can control layer "strength" while simultaneously controlling the properties of the composition, such as the refractive index or dielectric anisotropy of the composition. c)) is provided. The addition of side chain liquid crystal polysiloxane (component (d)) can be considered to combine the layers together in both the layers presented and between the layers, thus allowing this system to be further adjusted. Also included in the composition is an ionic dopant (component (b)), which travels through the composition when a low frequency electric field is applied to the composition by an electrode, thereby disrupting the regularity to the composition. Regularity in the composition can be restored by applying a high frequency electric field that does not allow time for the dopant to move significantly. In addition, chromophores may be included in the formulation. |