
CLC Pigments
The Cholesteric liquid crystal (CLC) pigments are made up
of CLC films rather CLC polymers. The polymers are typically cross linked
materials which have their molecules "locked" during the
cholesteric phase. Now this enables the unique and brilliant optical
properties of a liquid crystal to be exploited to the hilt in a solid
pigment. Each of the flake in the pigment is a piece of microfilm in a
platelet form. It has dimensions of around 5 micron in thickness.
Cholesteric liquid crystal or CLC polymer film is kind of naturally
reflective polarizer. If the center wavelength is set in a way, to be within
the visible spectra, then it is possible to create color travel effects
through a circular polarized reflection. A typical structure of CLC
structure is given below:


For enabling a good special effect pigment, that is to be
derived from a CLC (cholesteric liquid crystal technology), some sort of
modification needs to be done to several properties of CLCs
| Cholesteric Liquid Crystals | Requirements for Pigment application |
| Periodic structure (facilitates color travel) | Temperature Insensitive (Color Fixed) |
| Thermochromic (change of color with temperature) | Fairly Durable Properties wrt temperature, chemical resistance needed |
| Alignment is needed | Good processing i.e. ease in manufacture is needed |
| Highly aromatic nature |
Optical Properties of CLC Pigments
The Optical properties of CLC pigments can be best described with the help of the diagram that is given below. It is to be undersood here, that quite unlike the metal interference systems, CLCs can develop their color reflection through a single layer only.


Colour travelling properties of CLC Pigments
CLC pigments show very good blue-shifting color travel as illustrated in this graphical representation.

The Optical properties of CLC pigments can be best described with the help of the diagram that is given below. It is to be undersood here, that quite unlike the metal interference systems, CLCs can develop their color reflection through a single layer only.


CLC pigments show very good blue-shifting color travel as illustrated in this graphical representation.

- Unlike the interference type systems, CLC pigments are basically
circular polarized that can create a secondary detection mechanism that
is very simple.
- In the case of CLC based flakes, center wavelength can be adjusted
with ease thus enabling a vast set of custom products.
- CLC pigments are produced by using a continuous film based
polymerization, this allows for considerable cut in expenditure as
compared to vacuum deposition technologies.
- Owing to the periodic structure of CLC films, CLC pigments has in it
a strong color travel effect.
- As CLC pigments are manufactured using polymeric material, and their
optical properties mostly determined by CLC mixtures only. Features like
control of band width color fine-tuning, special wavelength design, etc.
becomes relatively easier as compared to those using traditional
interference technology.
- Every CLC pigment comes with circular polarization, that facilitates simple detection mechanisms like opposite handedness extinction. This features is unique to CLC pigments.
- Light that is reflected from a CLC is circularly polarized, this
effect finds very popular application in security and machine read
applications.

- CLC pigments are increasingly applied as a deterrence for counterfeit in banknotes, securing documents, and in authentication processes to protect brand and products.
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