Patent FR-2956489-A1 (FR)
Title: Fabrication of an electro-optical cell comprising first and second plates of optically transparent material, comprises processing first and second alignment layers according to the first and second alignment directions respectively
Inventor: DE BOUGRENET JEAN-LOUIS
IPC: G02F1/1337
Filed: 2010-02-15
Abstract: The process for fabrication of an electro-optical cell comprising a first plate (302) and a second plate (303) of optically transparent material, comprises processing a first alignment layer (304) and a second alignment layer (305) according to the first and second alignment directions respectively, where torsion angle alpha is formed between the first and second directions such that 5[deg] less than alpha less than theta , and theta is an angle associated with liquid crystal molecules (306). The electro-optical cell has a thickness based on liquid crystal molecules between the plates. The process for fabrication of an electro-optical cell comprising a first plate (302) and a second plate (303) of optically transparent material, comprises processing a first alignment layer (304) and a second alignment layer (305) according to the first and second alignment directions respectively, where torsion angle alpha is formed between the first and second directions such that 5[deg] less than alpha less than theta , and theta is an angle associated with liquid crystal molecules (306). The electro-optical cell has a thickness based on liquid crystal molecules between the plates. The first and second alignment layers have anchor energy greater than or equal to a predetermined threshold such that the liquid crystal molecules are located in a common interface between the first and second alignment layer respectively. The material based on the liquid crystal molecules includes ferroelectric liquid crystal material, anti-ferroelectric liquid crystal material, polymer stabilized ferroelectric liquid crystal material, and polymer stabilized anti-ferroelectric liquid crystal material. Each of the first and second alignment layers comprises a photopolymerizable material. The processing of the first and second alignment layers comprises exposing the first alignment layer to UV radiation in a first direction of polarization to form the first direction of alignment, and exposing the second alignment layer to UV radiation in a second direction of polarization to form the second direction of alignment, where the radiation energy is more than 500x 10 ->3>Jm ->2>. The processing step is performed by a surface treatment technique with the anchoring energy of greater than 0.33x 10 ->3>Jm ->2>. The process further comprises depositing a liquid crystal pre-polymer on one of the first and second alignment layers, radiating the liquid crystal pre-polymer by UV radiation under nitrogen atmosphere, injecting a material based of liquid crystal molecules in the electro-optical cell, and progressively cooling the injected liquid crystal molecules for 2 hours under an electric field of 1 V/mu m at a frequency of 1 kHz. The first and second alignment layers are made of polyimide, and silicon oxide deposited by evaporation to form an angle of 20-25[deg] with the plate along a direction of orientation of liquid crystal molecules. An independent claim is included for an electro-optical cell.