Composite photoalignment layer
A composite photoalignment layer for aligning liquid crystal molecules includes: a monomeric material; a photoinitiator or a thermal initiator; and an azo dye material. A method for preparing a composite photoalignment layer for aligning liquid crystal molecules includes: mixing, in solution form, a monomeric material, a photoinitiator or a thermal initiator, and an azo dye material; coating the mixed solution onto a substrate to form a thin film; exposing the thin film to polarized light; and, with a thermal initiator, heating the thin film to polymerize the monomeric material and form a solid thin film.
1. A method for preparing a composite photoalignment layer for aligning liquid crystal molecules, comprising:
mixing, in solution form, a monomeric material, a photoinitiator, and an azo dye material, wherein the monomeric material comprises liquid crystal monomers;
coating the mixed solution onto a substrate to form a thin film; and
exposing the thin film to polarized light to form a solid thin film;
wherein exposing the thin film is a single step exposure that provides both alignment and polymerization for the composite photoalignment layer.
2. The method according to claim 1 , wherein the polarized light is from a polarized light source having one or more major wavelength components.
3. The method according to claim 1 , wherein exposing the thin film is performed under environmental humidity conditions in the range of 50%-75% relative humidity.
4. The method according to claim 3 , wherein exposing the thin film is performed under environmental humidity conditions in the range of 55%-70% relative humidity.
5. The method according to claim 1 , wherein the liquid crystal monomers are liquid crystalline reactive mesogens.
6. The method according to claim 1 , wherein mixing, in solution form, the monomeric material, the photoinitiator, and the azo dye material comprises:
mixing the monomeric material and the azo dye material; and
adding the photoinitiator to the mixture of the monomeric material and the azo dye material.
7. The method according to claim 6 , wherein the monomeric material and the azo dye material are mixed at relative concentrations of 50:50.
8. The method according to claim 7 , wherein the photoinitiator is added to the mixture of the monomeric material and the azo dye material at a concentration of 10% wt/wt of the monomeric material.
9. The method according to claim 7 , wherein the photoinitiator is added to the mixture of the monomeric material and the azo dye material at a concentration within the range of 1% wt/wt of the monomeric material to 30% wt/wt of the monomeric material.
10. The method according to claim 1 , wherein the photoinitiator and the azo dye material have matching absorption bands.
11. The method according to claim 1 , wherein a phase mask is used during exposure of the thin film to the polarized light to rotate a plane of impinging light.
12. The method according to claim 11 , wherein the phase mask provides two or more alignment domains for the composite photoalignment layer.