Sustainable Materials for Inkless Digital Printing

BA327K – Sustainable Materials for Inkless Digital Printing and Plastics Coloration (Project Number: 100711) – Public domain abstract
Datalase Ltd has developed a novel method of coloration and printing that is based on a colour generating material technology, produced from a raw material derived from sustainable castor oil. The material is a unique type of organic pigment that is initially colourless, but upon exposure to light undergoes a permanent transformation into an intensely coloured form. Datalase, in conjunction with its partners Innovia Films, Tullis Russell Coaters and P&G have successfully demonstrated that these pigments can be:
i. Formulated into liquid inks and/or coatings and applied to substrates.
ii. Incorporated directly into thermoplastic parts using moulding processes.
Exposure of the substrates containing the unique pigments to light causes the colour change reactions to occur which consequently brings about substrate printing and coloration. This process forms the basis of ‘inkless digital printing’. In ‘inkless digital printing’ liquid inks or other consumables such as: solvents, toners, ribbons or cartridges are not required at the actual point of printing. Also, the light emitting print engine which complements these pigments can operate with essentially minimal maintenance for prolonged periods, whereas rival inkjet technology requires constant attention to prevent nozzles from clogging. Datalase has also demonstrated that the pigments can be produced in a form which is initially unreactive. The pigment can then be converted into its light reactive form, only in the areas where printing or colouration is required, in situ within the substrate just prior to printing or coloration.
The pigments are unique in that they can not only produce colour and variations in depth of a single colour, they can also produce several chromatically different colours as well. A single pigment can produce blue, magenta, red, orange and yellow colours. The specific colour formed is determined by the intensity of the incident light and the total exposure time. Consequently, a substrate containing one of these pigments can be printed in a wide gamut of different shades and hues. A single, sustainably sourced, light activated pigment can therefore replace many traditional, petrochemically derived dyes and pigments. This further reduces the overall carbon footprint of the printing or colouration process.
A consortium was formed specifically to initiate a work programme to accelerate the development of the pigments and their successful application to substrates. The main aim was to produce pigments and substrates for use in inkless digital printing that satisfied the requirements and specifications of the target market opportunities. Molecular design and laboratory synthesis of the pigments and initial substrate testing was performed by Datalase. Innovia Films supplied the expertise for coating the pigments onto biaxially orientated polypropylene films, and Tullis Russell Coaters supplied the expertise for coating onto paper based substrates. P&G performed additional substrate testing.
The project successfully delivered a series of light reactive, sustainably sourced pigments suitable for use in both inkless digital printing and plastics colouration processes. The pigments were readily formulated into water based inks that were applied to the chosen substrates using flexographic and gravure printing techniques. The pigments were also successfully injection moulded directly into polyethylene and polypropylene parts. The substrates were then used, in combination with the complementary light emitting print engine, to demonstrate multi-colour inkless digital printing. Extensive testing then showed that the substrates had sufficient background and colour fastness to meet the requirements of the initial target market opportunities. Further work will be undertaken to take the first generation products to market. Further development work will also be undertaken to expand the colour palette achievable with these pigments and substrates, and also to increase stability to the levels required by high volume, market opportunities that have more stringent fastness requirements.