Study of Anthraquinone Type Dichroic Dyes with Positive Yellow and Red Colour for Liquid Crystal Colour Display

Eight positive yellow colour dyes, 1,5-dihydroxy-2,p-alkoxyphenylanthraquinone and 1,5-dihydroxy-3-p-alkoxyphenylanthraquinone type, and two red colour positive dyes, 1-amino-4-hydroxy-2-phenylthioanthraquinone and 1-amino-4-hydroxy-2-benzyloxyanthraquinone type were prepared. The order parameters of dye moleculars in liquid crystal were determined. The transition energy and dipole moment of dye molecules in ground and excited state were calculated with CAMTC-ppp procedure. The results show that the order parameter (S) of dye molecules in liquid crystal increases with the decrease of angles between dipole moments of molecules in ground and excited states.