Self Vertically-Aligned Liquid Crystal Cells Polymerized of the Monomers in the Liquid Crystal Layer and Its Monomer Materials

<p>This report introduces the fabrication method of a self vertically-aligned (VA) liquid crystal (LC) cells (S-VA cells) by exposure of unpolarized ultraviolet (UV) to the cells including mixtures of the LC material and the monomers carrying alkyl group. The monomers for inducing the vertical alignment with high long-term reliability were also focused on here. First, the mixture of the LC material and the monomer was injected into the empty cell without forming a conventional alignment layer on substrates. The UV was then exposed to the cell from the normal direction, and then the self vertical alignment was obtained due to formation of the self-aligned layer (SAL). Two monomers for the S-VA cells were developed, acrylic acid 4’-octyloxy-biphenyl-4-yl ester (AOBE) and acrylic acid 4-(4’-octyloxy-biphenyl-4-yloxy)-butyl ester (AOBBE). The monomer AOBE induced the vertical alignment by the exposure of the UV without addition of a radical-produced monomer since AOBE generates the radicals by the photo-Fries rearrangement. However, voltage holding ratio (VHR) was seriously decreased by the exposure of the UV, and the S-VA cell fabricated by the monomer AOBE showed low level of long-term reliability under backlight exposure. On the other hand, the monomer AOBBE needs the radical-produced monomer for obtaining the vertical alignment because AOBBE does not generate the radicals by the photo-Fries rearrangement. The monomer 1,2-bis-(4-methacryloxy-phenyl)-2,2-dimethoxy-ethane-1-one (BMPDEO) was used as the radical-produced monomer. The VHR was maintained relatively high level by the exposure of the UV, and the S-VA cells fabricated by the monomers AOBBE and BMPDEO showed high level of long-term reliability.</p>