Nanoparticle-doped polyimide for controlling the pretilt angle of liquid crystals devices

The pretilt angles of liquid crystal molecules can be controlled by using conventional polyimide (PI) alignment material doped with different concentrations of Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles, which have been observed to spontaneously induce vertical alignment. The addition of POSS in the homogenous PI changes the surface energy of the alignment layer and generates a variable pretilt angle. Experimental results demonstrate that the pretilt angle. p is a function of the POSS concentration, and can be tuned continuously over the range of 0 degrees<90 degrees. The polar anchoring energy of POSS/PI alignment layer is almost constant regardless of the POSS concentration. This technique is very simple and is compatible with methods familiar in the current LCD industry. (C) 2010 Optical Society of America