CLC PIGMENTS DYES The Cholesteric liquid crystal (CLC) pigments are fabricated with 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: Key Properties of CLCs 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 CrystalsRequirements 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 neededGood processing i.e. ease in manufacture is needed
Highly aromatic nature
Optical Properties of CLC Pigments
A diagram can betterly describe the optical properties of CLC pigments, such as : It is to be understood here, that quite unlike the metal interference systems, CLCs can develop their color reflection through a single layer only.
Color travelling properties of CLC Pigments
CLC pigments show very good blue-shifting color travel as illustrated in this graphical representation.
Advantages of CLC Pigments
*.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.
*.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.
*.Every CLC pigment comes with circular polarization, that facilitates simple detection mechanisms like opposite handedness extinction. This features is unique to CLC pigments.
*.Owing to the periodic structure of CLC films, CLC pigments has in it a strong color travel effect. Application of CLC pigments CLC pigments are increasingly applied as a deterrence for counterfeit in banknotes, securing documents, and in authentication processes to protect brand and products. Light that is reflected from a CLC is circularly polarized, this effect finds very popular application in security and machine read applications.
Gen Next Developments:-
*.A Multilayer CLC system
*.Doping of the CLC pigment
*.Very High process speeds of 100 ft/min
*.Smart Pigments that has controlled shape
*.Ultrathin CLC pigments
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