US 12,276,884 B1
Electrically switchable liquid crystal grating cell based on photoalignment with an amplitude mask
Yuechu Cheng, Hong Kong (CN); and Abhishek Kumar Srivastava, Hong Kong (CN)
Assigned to The Hong Kong University of Science and Technology, Hong Kong (CN)
Filed by The Hong Kong University of Science and Technology, Hong Kong (CN)
Filed on Oct. 31, 2023, as Appl. No. 18/498,148.
Int. Cl. G02F 1/1347 (2006.01); G02F 1/1337 (2006.01); G02F 1/135 (2006.01)
CPC G02F 1/133769 (2021.01) [G02F 1/1355 (2021.01); G02F 2201/305 (2013.01); G02F 2202/09 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A method for manufacturing a switchable liquid crystal grating cell, the method comprising:
coating a substrate with a conductive layer;
spin-coating the substrate with a photoalignment material to establish a photoalignment layer on the conductive layer;
exposing the photoalignment layer to a first polarized UV light polarized in a first direction to achieve a uniform orientation of liquid crystal molecules of the photoalignment layer;
contacting an amplitude mask with the photoalignment layer of the substrate to expose non-masked areas of the photoalignment layer;
irradiating the photoalignment layer with a second polarized UV light polarized in a second direction which is arranged at a predetermined angle to the first direction so as to reorient the non-masked areas of the photoalignment layer to thereby result in a switchable liquid crystal grating part with an alignment pattern on the photoalignment layer with first and second types of domain, the first type of domain having a first uniform alignment direction, the second type of domain having a second uniform alignment direction that is reoriented at the predetermined angle to the first direction, wherein the predetermined angle is 85° to 95°, and wherein the amplitude mask is formed with alternating light-transmitting and opaque stripes with a predetermined period for defining the non-masked areas, the predetermined period being selected to be a small period within 2 μm to 6 μm such that using the amplitude mask with the small period to fabricate the switchable liquid crystal grating part leads to the switchable liquid crystal grating part with a high diffraction efficiency;
arranging a pair of the switchable liquid crystal grating parts, wherein two photoalignment layers in the pair of switchable liquid crystal grating parts face each other, and the alignment patterns of the photoalignment layer on the top surface of the lower switchable liquid crystal grating part shift by half a pitch or less than half a pitch relative to the other alignment patterns of the photoalignment layer on the bottom surface of the upper switchable liquid crystal grating part such that electrical stability of the switchable liquid crystal grating cell as manufactured is significantly enhanced; and
infusing a nematic liquid crystal between the pair of switchable liquid crystal grating parts to obtain the switchable liquid crystal grating cell.