Printing braille with expandable printing inks in screen printing technique

Taktilni elementi in brajica so osnovno orodje za komunikacijo slepih in slabovidnih. Z namenom preučiti možnost izdelave odtisov s pomočjo modificirane tehnike sitotiska in ugotoviti, ali je mogoče izdelati taktilno zaznavne odtise, primerljive upodobitvam drugih tehnik, kot tudi obojestranske odtise brajice, je nastala raziskava tega magistrskega dela. Namen raziskave je bil natisniti brajico s pomočjo modificirane tehnike sitotiska in uporabe posebnih ekspandirajočih sitotiskarskih barv, ki vsebujejo temperaturno občutljive mikrosfere. Slednje pri ustreznih temperaturnih in časovnih pogojih ekspandirajo in na površini tiskovnih substratov tvorijo taktilno zaznavne odtise. V raziskavi smo uporabili tri tiskovne substrate različnih gramatur in dve ekspandirajoči sitotiskarski barvi. S preliminarno analizo sta bila določena primerna čas in temperatura ekspanzije, z izbranimi meritvami in analizami pa so bili vrednoteni tiskovni materiali in izdelani odtisi. Poleg vrednotenja lastnosti odtisov smo slednje izpostavili tudi taktilnim (simulaciji branja) in fizičnim obremenitvam (obremenitev je bila izvedena s težo drugih odtisov in knjig na knjižni polici v času petih mesecev) in po določenem času ovrednotili njihove spremembe. Določevali smo predvsem spremembe višine in oblike odtisnjenih brajevih pik. Rezultati so pokazali, da je tisk brajice s pomočjo sitotiska in izbranih ekspandirajočih sitotiskarskih barv enostavno izvedljiv, da dosežene višine odtisov brajevih pik ustrezajo predpisanim standardnim vrednostim (in jih celo presegajo) ter da se njihova višina ob taktilni in fizični obremenitvi ne zmanjša do te mere, da bi besedilo postalo neberljivo. Analiza je pokazala, da na rezultate višine, oblike in kakovosti odtisnjenih brajevih pik vpliva predvsem pravilna določitev časa in temperature ekspanzije. Namreč, predolgi časi in previsoke temperature ekspandiranja povzročijo preveliko ekspanzijo, ki vodi do deformacij brajevih pik in odstopanj od predpisanih vrednosti. Na podlagi rezultatov je bilo mogoče tudi dokazati, da je s pravilno določenim vrstnim redom tiskanja, sušenja in ekspandiranja mogoče dokaj enostavno izvesti tudi obojestranski tisk.Tactile elements and Braille are basic communication tools for blind and visually impaired people. This master’s thesis examines the possibility of producing prints by using a modified screen printing technique, with the aim to establish whether it is possible to produce tactile perceptible prints comparable to those produced by other techniques as well as suitable double-sided prints. To this end, modified screen printing technique and special expandable screen printing inks, containing temperature sensitive microspheres, which expand and form tactile perceptions on the surface of the printing substrates, when exposed to appropriate temperatures in the adequate time interval, were used to print Braille. Three printing substrates of different grammage and two expandable screen printing inks were used in the research. The preliminary analysis determined the appropriate time interval and temperature required for the expansion, and enabled the printed materials and the prints to be evaluated using the data from the selected measurements and analyses. In addition to evaluating the properties of the prints, the prints themselves were subjected to tactile recognition (reading simulation) and physical weights (they were weighted down by other prints and books on the bookshelf, where they remained for five months). After a certain time period the changes that took place were evaluated with the primary aim of determining the changes in the height and the shape of the printed Braille dots. The study shows that printing Braille by using a screen printing technique and selected expandable screen printing inks is easily doable and that the achieved height of Braille dots corresponds to, or even exceeds, the prescribed standard values. The study also shows that when subject to tactile recognition and physical weights, the height of Braille dots in not reduced to such an extent so as to make the text unreadable. The analysis shows that the results relative to the height, the shape, and the quality of printed Braille dots are primarily influenced by the correct determination of the time interval and the temperature of the expansion. Namely, too long time intervals and excessive expansion temperatures cause excessive expansion, which leads to the deformation of Braille dots and causes departure from the prescribed values. The results also demonstrate that, double-sided printing can easily be achieved if the correct sequencing of printing, drying and expanding is followed