faq

liquid crystal inks

What is Thermochromic Liquid Crystal?
Liquid Crystal inks and coatings are optically active mixtures of organic chemicals that react to changes in temperature by changing color.
How do Liquid Crystals work?
They show colours by selectively reflecting incident white light. They should be viewed against non-reflecting backgrounds (ideally black which is totally absorbing) for best visualisation of the colours.
Liquid Crystal mixtures change colour from colourless (or black if printed onto a black background) to red at a specific formulated temperature and, as the temperature is increased, the liquid crystal changes through other colours of the visible spectrum in sequence (orange, yellow, green, blue, and violet).
Eventually it will turn colourless (black) again at a higher temperature still. The colour changes are reversible, and on cooling the colour change sequence reverses back again.
What standard Liquid Crystal inks can be supplied from stock?
HAND TOUCH and STRESS formulations are available from stock. (Hand Touch formulation is: R25C5W = red start 25°C bandwidth 5°C . Blue start 30°C)
All other microencapsulated Liquid crystal inks and sprayable coatings are manufactured to order.
What is bandwidth?
Bandwidth is defined as the difference between the temperature at which a red colour starts to appear, and the temperature at which a blue colour starts to appear.
What range of temperatures can be supplied ?
Liquid Crystal mixtures can be produced with colour-change properties evident over a wide temperature range; red start temperatures can be made to vary from -30°C to 120°C and bandwidths from 1.0°C to 20°C. However for most practical purposes the working temperature range is 0°C to 50°C. Below 0°C, response times increase significantly to the point where utilisation becomes slow.
What are the response times of Liquid Crystals to temperature changes? How quickly do they change colour?
At ambient temperatures (around 15 to 25°C), the colour change generally only takes a few tens of milliseconds to take effect. Response times are greater at lower temperatures, and are the same in both the heating and cooling cycles.
Do Liquid crystals exhibit hysteresis?
Hysteresis is not usually noticeable in most temperature-sensitive Liquid Crystal mixtures. (More details can be given).
Are Liquid Crystals UV stable?
Most Liquid Crystals are very sensitive to UV light and exposure should be avoided. However, for applications requiring some degree of UV stability, protection can be achieved by using materials with UV absorbing properties in combination with the Liquid Crystals whenever possible (e.g. in overcoats, laminations etc.).
How do I print Liquid Crystals?
Liquid Crystal Inks should be printed by screen printing method. Using a screen mesh between 77T and 90T will generally give the best results.
Ensure that no solvent residues are either in the equipment, or in the air (from open containers or other print/production processes nearby).
What chemicals are Liquid Crystals incompatible with?
Liquid crystal mixtures are essentially oils and are very sensitive to contact with common organic solvents, oils and waxes, particularly low molecular weight materials. These have small molecules which can penetrate the microcapsule walls and destroy the highly ordered molecular structure of the Liquid Crystal which is what gives them their unique colour change properties. At all times, care must be taken to ensure that solvents and oils do not contaminate Liquid Crystal products.
Do Liquid Crystal products contain any heavy metals?
No - they do not contain any heavy metals.
What is the shelf life of the TLC products?
A shelf life of at least 6 months is guaranteed for all Liquid crystal products provided that they are stored correctly. All Liquid Crystal products are sensitive to UV light and elevated exposure will cause degradation. This will initially result in loss of temperature calibration and color brightness and eventually lead to complete loss of thermochromic functionality.