Adventures in lithography

Klein, Susanne; Fuller, Harrie

Abstract

Lithography is the most important industrial printing process for non-textile printing. Liquid crystal is ubiquitous in display technology. What happens when the two are combined? The adventure begins.
Lithography was invented in 1796 by Alois Senefelder. It is a so-called planography where the plate is neither relief nor intaglio, but the image transfer is based on the immiscibility of water and oil. Senefelder marked a levelled limestone with oil, fat or wax and ‘etched’ the unprotected parts of the stone with a mixture of acid and gum arabic [1], a method still used in hand printing. The modern industrial version is called offset printing where the plate is a photosensitive aluminium plate and the image is first transferred onto a soft rubber blanket and from there to the final substrate, in most cases paper, but the soft blanket allows transfers to any kind of substrates as long as the ink sticks. The ink is still oil based as it was at the time of Senefelder.
Our ink is special. It is a linseed oil suspension of Merck Spectraval pigments, mica plates which generate structural colour when printed on a black substrate and invisible when printed on white. The come in red, green, blue and white and allow so-called RGB printing. The thin plates are polydispersed and have a diameter ranging from 5 to 25 μm (see Figure 1). Already very low weight percentage of suspended pigment, less then 1wt% show Schlieren texture. When used in lithographic inks, the weight percentage is between 30 and 50wt% leading to a heigh viscosity paste which keeps the sheer alignment generated by the pressure exerted during the transfer of the ink from plate to blanket and then to the substrate. We will discuss the conditions under which successful RGB printing happens, from printing press pressure to paper surface.
References
[1] A. Senefelder and Lessing J. Rosenwald Collection (Library of Congress), Vollständiges Lehrbuch der Steindrukerey ... belegt mit den nöthigen Musterblättern, nebst einer vorangehenben ausführlichen Geschichte dieser Kunst. München,: K. Theinemann, 1818, pp. xiv, 370 p.

• Presentation Conference Type: Conference Paper (unpublished)
• Conference Name: Annual Conference of the British Liquid Crystal Society
• Start Date: Jun 21, 2021
• End Date: Jun 24, 2021
• Deposit Date: Jul 1, 2021
• Keywords: Lithography, Liquid Crystal
• Public URL: https://uwe-repository.worktribe.com/output/7502627
• Additional Information: Only a book of abstracts was sent out to participants.