Colour shifting liquid crystals for authentication and brand protection

Idvac Ltd, a specialist in advanced vacuum and thin film technology, has been investigating the properties of some Liquid Crystals (LCs) for packaging and security applications.

LCs are molecules which have properties between those of conventional liquids and those of solid crystals. They can be aligned by an applied electric field or other methods which change their optical properties.

Lately the company has seen a dramatic increase in the development of products containing colour shift features using different techniques. Colour shift effect can be used for brand protection, anti-counterfeiting and smart packaging in multiple industries, including pharmaceuticals.

In recent work Idvac has developed a colour shift effect on a flexible film such as PET using LCs and without the use of structural embossing, inks or pigments. The product exhibits an aesthetically appealing colour shift effect from red to green depending on the angle of viewing, it claims.

The LCs can be applied using different coating techniques including printing. After application on a flexible film, the LCs coating is dried and UV cured to become solid at room temperature. The colour shift film produced is transparent and can be recognised in transmitted and reflected visible light.

This new development has the following features:

• Single layer application of LCs on PET film using standard wet coating application methods such as printing.
• The LC colour shift film can be transparent or semi-transparent.
• Fast colour change from red to green.
• The LCs colour shift film is bright and has saturated colours.
• The LCs colour shift effect is easy to observe from a distance and from a multiple viewing angles under standard lighting conditions.
• The effect can be combined with other security features such as a holographic security pattern and a tamper evident layer to make unique products.
• The LCs colour shift effect can be applied on high refractive index (HRI) coated films for extra reflectance and colours.
• The LCs colour shift film can be laminated on Idvac vacuum metallised black coated films to achieve a Green/Deep Blue colour shift.
• The LC colour shifting film exhibits some polarizing effect when rotated from one angle to another under polarized light.
• The production of the LCs colour shift film does not require vacuum metallizing equipment.

Idvac is based in Manchester Science Park, England and has over 25 years of experience in the holographic and 40 years in advanced vacuum coating technology markets including UK, Europe, USA, Asia and Far East, to improve the image, brand and durability of their products. The company develops new processes and supplies process know-how and retrofits to convert standard vacuum metallizers to produce unique coatings.