Clevertex - Grado Zero Espace Srl

chiral nematic phase is its ability to selectively reflect light of wavelengths equal to the pitch length, so
that a colour will be reflected when the pitch is equal to the corresponding wavelength of light in the
visible spectrum. When the chiral nematic phase is cooled down, the helix has the tendency to
unwind. This means that the length of the pitch increases and another wavelength will be reflected.
When the temperature continues to decrease and the smectic phase is not reached yet, the colour will
pass through the infrared. When the temperature rises again, all changes are reversible. The effect of
temperature can best be explained by comparing the spiral staircase with a spring. Temperature
changes cause the spring to contract or to stretch. A ‘spring’ in stretched position will reflect another
light than a ‘spring’ in contracted position and hence it has another colour.
It is this class of liquid crystals that is used in the textile industry. Using this variety of liquid crystals, it
is possible to achieve significant changes in appearance over narrow temperature ranges (5-15°C)
and to detect small variations in temperature (