Homogeneous alignment

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In liquid crystals homogeneous alignment, sometimes called planar alignment, is the state of alignment where molecules align in parallel to a substrate. The opposite method is homeotropic alignment.{{Citation |last=Jones |first=Lesley Parry |title=Alignment Properties of Liquid Crystals |date=2012 |work=Handbook of Visual Display Technology |pages=1390–92 |editor-last=Chen |editor-first=Janglin |url=http://link.springer.com/10.1007/978-3-540-79567-4_86 |access-date=2025-01-08 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |language=en |doi=10.1007/978-3-540-79567-4_86 |isbn=978-3-540-79566-7 |editor2-last=Cranton |editor2-first=Wayne |editor3-last=Fihn |editor3-first=Mark|url-access=subscription }}

For planar alignment - polyimides can be used. One of the popular ones is PI-2555.

The surface has to be rubbed by paper or by a velvet or similar cloth in order to make the alignment axis parallel to the rubbing. However the exact mechanism of this alignment is not entirely clear.