Woodbury and Lippmann: A new approach to continuous tone and full colour non-impact printing

Our society has an unsatisfiable hunger for images. The UK printing industry is the 5th biggest in the world with a turnover of £13.5 billion employing c.122 000 people. The internet is now the main platform for advertising, with 39% of advertising expenditure, print comes second with 32% and is fast growing. A historic development, the CMYK halftone process and the ruled glass screen patented by Frederick Ives, has led to the reproduction of almost all present day images as pixelated CMYK prints. Historic processes, such as those invented by Woodbury and Lippmann produce prints far superior to anything which is commercially available at the present time. Those processes have been largely forgotten as they were not commercially competitive. The applicant, with her expertise in colloidal chemistry, optics and 3D printing, aims to lift those technologies from obscurity to the forefront of modern developments. The new incarnations of old printing technologies will allow production of high quality prints for advertising, packaging, fashion and, at the same time, include impossible to replicate security features.

By transferring the principals of historic, high quality, continuous tone printing processes to non-impact printing, the processes will be freed from dimensional restrictions and restrictions of shape and material of the substrate. Woodburytype was the first, and still is the only photomechanical process that can reproduce truly continuous tone. A topographic print of pigmented gelatin layers, the image is generated by the absorption of light in those layers. The applicant aims to generate the layers by an additive process, for example ink jet printing, instead of an imprint from a plate. With especially formulated inks and modified printers which allow multipath printing, the continuous tone print can then be generated on a multitude of substrates and shapes. Combining this new process with Lippmann photography will lead to a full colour, non-pixelated printing process with in-built security features. Lippmann photography does not contain any dyes or pigments, but still reproduce the biggest colour gamut possible on the basis of interference colours like the ones observed on the surface of soap bubbles. Light is selectively reflected by resonance cavities which makes the print change colour under different viewing angles. This characteristic cannot be copied by simple means and can therefore be exploited as a security feature. In classic Lippmann photography, the reflective layers of the cavities consist of very fine metallic silver grains separated by layers of gelatin. The layers are generated by a direct photographic process making Lippmann photography a one-off method. In collaboration with industrial partners, the applicant aims to formulate two inks, one transparent and the other reflective and aims to print a hybrid Lippmann/ Woodburytype by non-impact methods. The hybrid type will have no dimensional restrictions and can be customized. On an ID card or driving license, a Lippmann/Woodburytype could be included as an owner specific security feature. Creating the cavities by direct print will be a challenge, but materials exist which can be printed and organize themselves in periodic structures: chiral liquid crystals for example. Liquid crystals interact with light and are the active layer in most displays today. In chiral liquid crystals the molecules are organized in helical structures. When the spacing of the helix fulfils a specific condition, colour is generated. The final print will consist of a variety of liquid crystal and containment layers which will have additional functionality. An electric or magnetic field can switch the liquid crystal, i.e. the print is rewritable which can be exploited as a security feature. By hosting the fellowship at the Centre for Fine Print research, an ideal combination of printing and material expertise is achieved guaranteeing the success of the project.

This fellowship seeks to contribute a radical alternative, and cross-disciplinary approach, to the physical output of pixel based photograph and/or image creation that has potential to impact several industries and to grow and strengthen the research and capability at UWEs Centre for Fine Print Research.

Manufacturers of functional chemicals
Providing new, cutting edge research to the UK print industry will turn it into the vanguard of technology. The fellowship will impact industry at different points. From the start a close collaboration with Siltech (material suppliers) is planned. Suppliers are always searching for new application of their products and are ready to modify existing products to be first in a new market. Coming from an industrial background, the applicant has a track record of working with industrial material suppliers for the development of new speciality materials in a rapid feedback cycle. Collaborating in the proposed research will enable Siltech to be world leading in novel materials. Engaging with the printing industry early on, will not only allow them to overcome conservative attitudes, but will give them the chance to explore this new printing technology for their applications and beyond. The fellow aims to build prototypes of printers able to print non-pixelated
topographic prints, but will rely on industrial partners or a spin-off company to take the prototypes to reliable products which will print in a quality not seen in a 100 years. The addition of functional materials will soften the difference between print and display. The fellowship is not aiming to create a bistable display but a print which could be a low energy alternative to electronic billboards for example and regain the printing industry territory lost. This will have an impact on the engineering industry since new writing devices have to be built, from handheld to large format.

Packaging and security printing industries
Lippmann photography is one reproduction technology that will be explored, that uses the same principals as holography. The image is generated by selective reflection of light and looks therefore different depending on the viewing angle. This characteristic is exploited in holograms used as security features on credit cards or packaging, because they cannot be copied. At present those holograms are the same for a run of credit cards or product packaging. The ability to print interference structures directly will allow the manufacturer to customize these security features, or even individualize for each customer. Fake pharmaceuticals are a major problems all over the world. Pharmaceutical packaging could have Lippmann prints which contain information such as; country of production, town and country of destination, production date, sell by date, etc. visible for the user, and in connection with the appropriate data infrastructure. This would be impossibly hard to fake. The suggested introduction of liquid crystals to the printing process turns the print rewritable, and can also make it temperature sensitive. Rewritable prints can be used as security features too, for example every time a product passes a transportation hub a mark is added or changed. The ability to rewrite image information on smart cards could be an important tool for industries ranging from the financial to the medical sectors. More ambitious are rewritable images on fashion items. Depending on the mood of the wearer colour or image content could be changed. At the same time, exploiting the temperature sensitivity of the liquid crystal, a print on a t-shirt could change colour when the wearer was exposed to a certain amount of sunshine and remind the wearer to seek shade.

Women are well represented in the arts but still less so in in the sciences. By demonstrating that art and science can work together, this fellowship aims to attract more women into engineering, physics and material sciences.