Method for producing an improved liquid cystal device, and resulting device
AssigneeNemoptic
InventorsSandrine Lamarque-Forget, Julien Roux, Ivan N. Dozov, Philippe R. Martinot-Lagarde
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Abstract
The present invention relates to a method of making nematic liquid crystal devices, characterized by the fact that low energy zenith anchoring of the liquid crystal is obtained over at least one of the confinement plates by the steps consisting in: depositing a polymer or copolymer based on PVC onto a substrate; stabilizing the polymer deposit; and defining an azimuth orientation for the deposit to induce controlled azimuth anchoring of the liquid crystal.
Claims17
1/ A method of making nematic liquid crystal devices, the method being characterized by the fact that it comprises the steps consisting in:
- depositing a polymer or copolymer based on PVC onto a substrate;
- stabilizing the polymer deposit;
- and
- defining an azimuth orientation for the deposit to induce controlled azimuth anchoring of the liquid crystal;
- in order to obtain low energy zenith anchoring for the liquid crystal over at least one of its confinement plates.
2/ A method according to claim 1, characterized in that the stabilization implements exposure to ultraviolet light.
3/ A method according to claim 1 or claim 2, characterized in that the stabilization implements one or more annealing steps.
4/ A method according to any one of claims 1 to 3, characterized in that the stabilization uses one or more annealing steps performed before and/or after exposure.
5/ A method according to any one of claims 1, 2, 3, or 4, characterized by the fact that the polymer is selected from the group comprising PVC and a copolymer of PVC and PVAc.
6/ A method according to any one of claims 1, 2, 3, or 4, characterized by the fact that the polymer is a terpolymer based on PVC-PVAc.
7/ A method according to claim 6, characterized by the fact that the polymer is a terpolymer based on PVC-PVAc in which the third monomer is hydroxypropyl acrylate or vinyl alcohol.
8/ A method according to any one of claims 1 to 7 in combination with claim 3 or claim 4, characterized by the fact that the heating step(s) is/are performed at temperatures below the melting point (mp) of the polymer.
9/ A method according to any one of claims 1 to 8 taken in combination with claim 3 or claim 4, characterized by the fact that the heating step(s) is/are performed for a duration of about 1 h 30.
10/ A method according to any one of claims 1 to 9 taken in combination with claim 2, characterized by the fact that the exposure step is performed using ultraviolet light having a wavelength lying in the range 180 nm to 400 nm.
11/ A method according to any one of claims 1 to 10, characterized by the fact that the step consisting in defining controlled azimuth anchoring of the liquid crystal is performed by the fact that the polymer of the invention (PVC and PVC-PVAc copolymers) is rubbed with a textile-covered roller.
12/ A method according to any one of claims 1 to 10, characterized by the fact that the step consisting in defining controlled azimuth anchoring of the liquid crystal is performed by depositing the polymer on a substrate that has already been made anisotropic by special treatment such as:
- another brushed or stretched polymer;
- evaporated SiO or other oxide;
- a grating (etched, printed, or photoinduced).
13/ A method according to any one of claims 1 to 12, characterized by the fact that the polymer is deposited on the substrate by centrifuging.
14/ A method according to any one of claims 1 to 13, characterized by the fact that the polymer is deposited in solution in a solvent based on ketone, such as methyl ethyl ketone or dimethyl formamide.
15/ A bistable nematic liquid crystal device using at least one anchoring layer with low zenith energy made using the method according to any one of claims 1 to 14.
16/ A device according to claim 15, characterized by the fact that the polymer is selected from the group comprising:
- PVC, a copolymer of PVC and PVAc, a terpolymer based on PVC and PVAc.
17/ A device according to claim 15 or claim 16, characterized by the fact that the anchoring layer having low zenith energy is deposited on an electrode that is transparent or reflecting.