Optically variable ink with polarizing effect STEP
An optically variable semi-transparent ink which changes its color at different angles of illumination and observation. It contains liquid crystal pigments with periodic spiral molecular structure. Ink color depends on the lead of the spiral and angle of illumination. Color changing effect is achieved due to interference. Incident light reflected from the ink interacts with the spiral of a liquid crystal molecule and becomes polarized.
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Latvia. Travel document (2015):
a - page 1, general view, STEP element location; b - observation of optically variable ink properties: color changing effect at different angles of illumination and observation; c - STEP element at a right angle of observation and illumination; d — the same image at an acute angle of observation and illumination; e - ink structure: liquid crystal pigments; f - view through a polarizing filter (dark area on the right) proves that the reflected light is polarized