High contrast ratio of a vertically aligned liquid crystal cell using photocrosslinking alignment |
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Authors: | Hyun-Wuk Kim Kyung-Soo Choi Jin-Yool Kim Tae-Min Kim Jong-Duk Kim |
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Institution: | Thin Film and Interface Group, Department of Physics, University of Exeter, Stocker Road , Exeter, EX4 4QL, England |
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Abstract: | A photo-induced alignment layer for LCDs has been successfully fabricated using the polarized UV photoreaction of a photo-crosslinkable polymer with the incident UV light at some angle with respect to the cell normal. The surface alignment and electro-optic properties were investigated for various UV exposure times. The homeotropic alignment layer showed a discrete anisotropic dichroic ratio, its surface morphology became smoother as the UV exposure time increased, and the LCs were arranged in a perpendicular direction to the PUVL direction with a proper pretilt angle. The cell showed no defects under cross-polarized microscopy and the contrast ratio was as high as 550:1 in transmittance. The contrast ratio pattern was found to be very similar to that of dichroic ratio as a function of UV exposure time and depended upon the frequency change to some degree. The response time was also investigated. |
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