Photoalignment

Fig. 23. Illustration of the nonplanarity at the photoalignment mark required for photolithography. This nonplanarity can be lost if the W deposited thickness prior to W CMP is too large or if nonplanarity exists but is insufficient due to the step abruptness having been smeared out. For the former, the surface at the alignment mark will be planarized after CMP for the tatter, after metal deposition, the image of the alignment mark can be obscured by noise due to the grainy metal surface.

K. Ichimura, K. Photoalignment of Liquid-Crystal Systems. Chem. Rev. 100, 1847 (2000). Ichimura, K., Seki, T, Kawanishi, Y., Suzuki, Y., Sakuragi, M., and Tamaki, T. Photocontrol of Liquid Crystal Alignment by Command Surfaces , in Photoreactive Materials for Ultrahigh Density Optical Memory. M. Irie, Ed., Elsevier Amsterdam, (1994), p. 55. 

Ichimura, K. Photoalignment of liquid-crystal systems. Chem. Rev., 100, 1847 (2000). 

V. Strehmel, B. Stiller, B. Strehmel, A. M. Sarker, and D. C. Neckers, Fluorinated Distyrylbenzenes Containing Copolymers for Photoinduced Formation of Anisotropic Materials as Photoalignment Layers for Liquid Crystals. In Photoinitiated Polymerization, Vol. 847, K. D. Belfield and J. V. Crivello, Eds., American Chemical Society, Washington, DC, 2003, p. 482. 

The liquid crystalline characteristics of cinnamate esters have been examined and novel azo bearing systems have been made based on 4-[N-ethyl-N-(2-methacryloyloxyethyl)]amino-4 -(2-cinnamoyloxyethylcarbonyl)-2 -(nitroazoben-zene). Poly[4-(2-methacryloylethoxy)azobenzene] has been found to be valuable for the photocontrol of liquid crystalline alignment as have polymers with benzylidene phthalimidine side chains. Poly(methyl methacrylates) with o-cinnamate side chains undergo polarisation isomerisation resulting in photoalign-... 

---