Studija indirektne elektrofotografije

Indirektno elektrofotografsko otiskivanje tehnički je vrlo je složen proces. On u sebi implementira 6 zasebnih faza koje se izvode sinkronizirano. To su nabijanje, osvjetljavanje, razvijanje, prvi transfer, drugi transfer i čišćenje. U ovome radu istraživan je utjecaj svake pojedine faze na kvalitetu višebojne reprodukcije, pri čemu su se koristili i parametri koji nisu standardni za proizvodni tisak. Rezultati utjecaja pojedinih faza elektrofotografskog tiska na konačnu reprodukciju prikazani su u gamutnom obliku (konstrukcija definirana s ECI formom od 378 polja), i kao CIE LAB ΔE razlika između kalibracije i eksperimentalnog otiska. U početnoj fazi istraživan je utjecaj skorotrona na formiranje budućih slobodnih površina. Pritom nastale promjene gamuta su minimalne (ΔVsimb=13,3, ΔVsplen=8,6 i ΔVarco= 4,1 prostorne jedinice). Uz to vrijedi pravilo: što niži napon skorotrona to veći volumen gamuta. Promjena rastriranih površina pritom je veća u odnosu na pune tonove. Kod istraživanja utjecaja laserske glave, uočeno je da rasterska točka doživljava veliku promjenu. Povećavanjem snage lasera rasterski elementi se povećavaju i postaju tamniji. Puni tonovi se ne mijenjaju značajnije, te gamutni doživljavaju slijedeće promjene: ΔVsimb=10,3, ΔVsplen=13,2 i ΔVarco=2,9 prostorne jedinice. Razvijački proces (razvijački bubanj i povratni valjci) utječu na maksimalnu promjenu obojenja gamuta (ΔVsim = 301,5 odnosno ΔVsimb=210 prostorne jedinice). Primjenom viših napona, ostvaruje se i veći nanos bojila. Djelovanje razvijačkog bubnja utječe na veću promjenu punih tonova, dok se u slučaju povratnih valjaka postiže veća promjena u rasteru. Ekstremnim povećanjem napona “squeegee” valjka ostvaruje se samo manja degradacija gamutnog volumena (ΔVsimb=17,2, ΔVsplen=22,3 i ΔVarco= 9,4 prostorne jedinice). Pri izvođenju transfernog postupka, varirana su dva parametra: temperatura ofsetnog cilindra i napon ofsetnog cilindra. Porastom temperature raste i viskozitet bojila, Ëime se povećava i volumen gamuta (ΔVsimb=44,8, ΔVsplen=49,3 i ΔVarco= 31,9 prostorne jedinice). Viši napon ofsetnog cilindra osigurava bolji transfer. Promjena napona od 200V uzrokovat će najveći porast gamuta (ΔVsimb=37,7, ΔVsple=14,3 i ΔVarco=11,5 prostorne jedinice). Na kraju istraživanja, promatran je utjecaj gustoće bojila na konačnu reprodukciju. Porast koncentracije pigmenata ostvaruje tamniji otisak. Tijekom varijacije boje, nastali gamuti nisu očekivano veliki (ΔVsimb=60,2, ΔVsplen=36,6 i ΔVarco= 57,3 prostorne jedinice). Pri istraživanju elektrofotografskog procesa korištene su 3 različite tiskovne podloge: Simbol (sjajni papir za umjetnički tisak namijenjen otiskivanju u klasičnom ofsetu), Splendogel (naravni papir s premazom za digitalni tisak) i Arcoprint (naravni papir za klasični ofsetni tisak). Površinska svojstva papira pokazala su da imaju presudnu ulogu pri postizanju kvalitetne reprodukcije. Splendogel i Simbol papir zbog premazane površine najbolje se ponašaju u ekstremnim uvjetima, što nije slučaj za naravni papir Arcoprint

Kvaliteta digitalnih otisaka uvjetovana starenjem tiskovne podloge

Papir, najviše korištena tiskovna podloga u tiskarstvu, podložan je mnogim degradacijskim promjenama. U tim procesima sudjeluju reakcije kisele i alkalne hidrolize, oksidacije ili pak termolize. Najčešća reakcija je ipak hidrolitička degradacija molekula celuloze, kao najvažnije konstitucijske specije u građi papira. Spomenuti mehanizmi izmjenjuju se u procesu prirodnog starenja. Premda individualne vrijednosti ovih reakcija variraju, pretpostavlja se da su vrijednosti degradacijskih procesa povezane s temperaturom. Stoga se smatra da bi rezultati ubrzanog starenja mogli koristiti za stvaranje zaključka o mehanizmu i zakonitostima u uvjetima prirodnog starenja. Takav pristup omogućava praćenje i studiranje posljedica spomenutih pojava na papiru kao i na otisku. Tiskovne podloge uvrštene u istraživanje su: papir za umjetnički tisak, naravni papir i reciklirani papir. Za otiskivanje su korištene slijedeće tehnike otiskivanja: elektrofotografija (Indigo E-print 1000, Xerox DC 50) i Ink Jet (Epson 1200+). Papiri i otisci ubrzano su ostareni. Daljnja istraživanja raena su na novim otiscima, ubrzano ostarenim i otiscima načinjenim na papiru koji je prethodno ubrzano ostaren. Praćena je kvaliteta reprodukcije, te mehanička i optička svojstva otisaka. Kolorne vrijednosti 100% otisnutih procesnih boja (CMY) starenjem se takoer smanjuju. Promjene su najuočljivije na Ink Jet i Xerox otiscima što je specijalno naglašeno na papirima za umjetnički tisak. Vizualnom kontrolom “metodom prosječnog promatrača” potvrđeni su aparativno dobiveni rezultati. Istraživanja su u znanstvenom pogledu doprinos pojašnjenju optičkih i mehaničkih promjena, te kvalitete reprodukcije u funkciji starenja. Istraživanja su interesantna i u primjeni, posebno u povećanju kvalitete određenog grafičkog proizvoda

Press - world milestone and Croatia

The machine printing and rapid cultural development in Europe begins with the discovery of metal lettering at the end of the 15th century. This printing technique has been named the letterpress printing and is one of the greatest inventions of mankind. The development of printing was one of the main indicators of the development of individual countries. We believe that today in the world and in Europe the Croatian development of that age is significantly neglected. This paper presents European development and development in Croatia. This paper will contribute to a more accurate evaluation of Croatian printing and cultural level of that time by displaying Croatian achievements of that era, the printing staff, printed works and printing houses, throughout European and Croatian development of printing

The Possibility of Increasing the Achromatic Tone Values of FOGRA 51 Standards Achieved by the Modification of in Line Pre-Treatment of the Printing Substrate

For high-quality black & white printing realized with an electrophotography printing machine, it is necessary to prepare the printing substrate. For optimal adhesion of the black liquid electrophotography ink to the printing substrate, it is necessary to apply additional treatment to meet ideal substrate surface tension by means of corona treatment and/or coating with fluid for regulating the surface tension (primer). This paper examines the influence of the corona power and the thickness of used fluid for the regulation of surface tension on the achromatic digital reproduction quality. Within the electrophotography printing process, this implies determining the differences in the colour gamut volume, the structure of characteristic screening elements, the amplitude-modulated screening, and the increase in the number of colour separations. The results show that the optimal colour tone values, colour gamut, and dot gain, high quality of digital prints will be realized without the use of the fluid for the regulation of surface tension and without activation of the corona power. That confirms that the FOGRA values for industrial standards can be used for quality electrophotography printing

Do Braille Cells Influence Legibility of Texts for the Sighted?

Labels as a graphic product are important for information in declarations, especially for languages of smaller nations. Labels are increasingly required together with their ever more complicated technical performance, one of them being the desire to adapt the text to blind or partially sighted users. We therefore tested the possibility of using a declaration text in black with overprinted Braille cells with no or minor influence on legibility. The research was performed by analyzing the influence of printed cells on the achromatic halftone reproduction. The prints of the text and the overprinted Braille cells were made with a UV LED inkjet printer. Two different typefaces in two different sizes suitable for labelling were tested. The color properties were determined colorimetrically and the differences in the typographic tonal density of typefaces were measured with an image analysis. The legibility research was performed with the help of observers who read the plain printed text and the printed text in combination with overprinted Braille cells made with varnish. The results showed that an appropriate typeface and type size can reduce the influence of overprinted Braille on text legibility

Influence of the Varnishing "Surface" Coverage on Optical Print Characteristics

Varnishing is often used to protect or decorate the print, but it can also influence the print’s colour appearance. Therefore, varnishing should enhance the print role, while colour change should be kept as low as possible. The aim of this paper is to evaluate inkjet UV LED varnishing by estimating optical print characteristics. Prepared offset prints were UV LED varnished in different surface coverage values (SCV) with a matte and gloss finish. The prints were evaluated by measuring gloss and colour coordinates. Secondly, varnishing was performed in a different SCV, which enabled assessing the optimal SCV, i.e. the most cost-efficient varnishing. The printing process was conducted in a standardized and controlled laboratory environment, regulated via the ISO 12647-2:2013 norm to ensure that the black colour was reproduced in the standard tolerance. The results showed that the colour difference is negligible (stays in the ISO tolerances), regardless of the varnishing SCV. On the other hand, the optimal printing gloss is at the SCV of 100%

Influence of UV curing varnish coating on surface properties of paper

U svrhu postizanja boljih svojstava tiskovne je podloge moguće oplemenjivati na različite načine. U ovom radu analizira se mogućnost oplemenjivanja s različitom površinskom pokrivenošću lakova koji se suše UV zračenjem, pri čemu su korištena tri karakteristična papira (papir za umjetnički tisak gloss, offsetni papir i kalandriran papir). Primijenjene metode su bazirane na mjerenju optičkih svojstava lakom impregnirane površine (obojenje, sjaj i glatkoća), kao i na određivanju fizikalnog svojstva upojnosti. Dvojne osobine papirnih podloga dobivaju se nanosom UV laka koji suši LED svjetlošću. Rezultati istraživanja pokazuju da se kod gloss premazanog papira upojnost smanjuje nanosom UV laka, dok se kod nepremazanih papira (offsetni, kalandrirani) upojnost povećava. Nanos laka s manjom površinskom pokrivenošću (33 % UV laka) nije relevantntna za upojnost i optička svojstva naravnih papira. Značajne promjene u hrapavosti i optičkim svojstava postižu se 66 % nanosom, što je posebice vidljivo kod papira za umjetnički tisak.In order to achieve better properties of the printing substrates their improving is possible in various ways. In this article the possibility of the substrate improving is analyzed with different surface coverage of varnishes cured by UV radiation, where three characteristic kinds of paper were used (fine art glossy paper, offset paper and calendered paper). The applied methods are based on measuring the optical properties with the varnish impregnated surface (colouring, gloss, smoothness), as well as determining the physical property of absorbency. Double properties of the printing substrates are obtained by the layer of UV varnish which is cured by LED light. The investigation results show that the absorbency decreases on gloss coated paper by the application of UV varnish coating, while it increases on uncoated paper (offset and calendered paper). The varnish coating with smaller coverage (33 % UV varnish) is not relevant for the absorbency and for optical properties of the natural paper. Important changes in roughness and optical properties are achieved with 66 % coating which is especially visible on fine art paper

The influence of pre-treatment by priming on the CMY reproduction quality printed with ElectroInk

In order to achieve high-quality colour prints by using an electrophotography printing machine, it is necessary to prepare the printing substrate. Additional treatment may be needed to achieve the better substrate surface tension for optimally attaching the liquid electrophotography ink to the fine art paper. To ensure good adhesion of the ink to the printing substrate, a pre-treatment by application of surface tension regulating fluids (priming) may be used. In this paper, we will determine the possibility of realization of the CMY prints and the possibility of achieving an increased range of tone value in electrophotography digital printing. Based on the results, the new possible values of reproduced CMY tones will be determined so that a higher print quality can be achieved. The application of primers changes the optical properties of the paper printing substrate, which directly affects the colour reproduction. An additional 100 % increase of primer application will result in total colour changes of ΔEC (0,5g/m2 & 1g/m2) = 0,06, ΔEM (0,5g/m2 & 1g/m2) = 0,42, ΔEY (0,5g/m2 & 1g/m2) = 0,08. In this scenario, 1 g/m2 application of primer will produce the most intense full tones and therefore the highest quality prints for all three ElectroInk process colours

Label legibility influenced by different number of white ink layers

Različit broj otisnutih slojeva bijele boje utječe na čitljivost otisaka. U ovom radu testirana je mogućnost postizanja najbolje čitljivosti otisnutog teksta na etiketi, zajedno sa analizom tipografskih svojstava i ostvarenih kolornih promjena. Otisci otisnuti na UV tintnom pisaču imaju mogućnost ostvarivanja većeg broja istih separacija (tri sloja bijele). Pritom su varirana tri tipa i četiri veličine pisma (karakteristična za etiketne deklaracije). Kolorne promjene su određene kolorimetrijski, te izračunom tipografske optičke gustoće slova primjenom slikovne analize. Ispitivanje čitljivosti je izvršena uz pomoć ispitanika koji su čitali tekst u kombinaciji: bijela podloga – crni tekst i crna podloga – bijeli tekst. Rezultati pokazuju da bez obzira na ostvarene kolorimetrijske promjene i različitu kvalitetu tipografske reprodukcije, najbolja čitljivost je ostvarena tiskom u dva sloja.A different number of white ink layers printed with the inkjet technology can influence the legibility of prints. Therefore, we tested how to achieve best legibility of printed text and labelling information, considering the changes in colorimetric and typographic properties. The prints were made with an inkjet printer and three different numbers of white ink layers were used. Three different typefaces in four different sizes, appropriate for labelling, were tested. The colour differences were determined colorimetrically and the differences in the typographic tonal density of typefaces were measured with an image analysis. The legibility research was performed with the help of observers who read the printed text in the combination of white ink on black paper and black ink on white paper. The results led to the conclusion that with regard to the colorimetric and typographic quality and effectiveness, the legibility was the best at two layers of white ink

Effect of Aging on the Microstructure and Optical Properties of Translucent ZrO 2 Ceramics

Svrha: Tržište dentalnih materijala u punom je zamahu kad je riječ o razvoju i plasiranju translucentnih cirkonij-oksidnih keramika. Cilj ovog istraživanja bio je ispitati utjecaj protokola starenja na mikrostrukturu, kolorne parametre i translucenciju nove generacije monolitne cirkonij-oksidne keramike. Materijal i postupci: Translucentna cirkonij-oksidna keramika KATANA-Zirconia STML s različitim načinima obrade površine (bez obrade, glazirana, polirana) testirana je u sklopu dvaju protokola starenja (hidrotermalna degradacija u autoklavu na 134 °C, 2 bara, 3 h i kemijska degradacija u 4-postotnoj octenoj kiselini na 80 °C tijekom 16 h) kako bi se ispitao fazni sastav rendgenskom difrakcijskom analizom, a kolorni parametri ∆E, ∆L i ∆C spektrofotometrijski. Iz parametara L*,a* i b* na crnoj i bijeloj podlozi izračunat je parametar translucencije (TP). Rezultati: Postupci starenja, bez obzira na način obrade površine, nisu potaknuli tetragonsko-monoklinsku faznu transformaciju, ali se kod svih testiranih uzoraka pri hidrotermalnoj degradaciji u autoklavu dogodila potpuna transformacija miješane tetragonsko-kubične strukture u tetragonsku strukturu. Značajnu kolornu promjenu ∆E pokazali su svi polirani te glazirani uzorci pri kemijskoj degradaciji. Svjetlina ∆L značajno se promijenila na poliranim uzorcima koji su starjeli u autoklavu. Na svim ispitanim uzorcima zabilježena je promjena ∆C u obliku žućenja koja nije statistički značajna. Pri primjeni obaju protokola starenja, translucencija se na uzorcima nije značajno promijenila. Zaključak: Starenje ne rezultira pojavom monoklinske faze u uzorcima, bez obzira na način završne obrade površine. Dominira tetragonsko-kubična mikrostruktura. Glaziranje površine translucentne cirkonij-oksidne keramike pridonosi manjim kolornim promjenama i promjenama svjetline u odnosu prema poliranju površine. Translucencija translucentne cirkonij-oksidne keramike stabilna je bez obzira na starenje i način obrade površine.Objectives: The development and placement of translucent zirconia ceramics on the dental materials market is in full swing. This research aimed to investigate how aging protocols affect the microstructure, color parameters and translucency of a new-generation monolithic zirconia ceramic. Material and methods: Translucent zirconia ceramics KATANA-Zirconia STML with different surface treatments (as sintered - control, glazed, polished) was tested using two aging protocols (hydrothermal degradation in autoclave at 134 °C and 2 bars for three hours, chemical degradation in four-percent acetic acid at 80 °C for 16 hours) in order to examine phase composition using X-ray diffraction analysis and ΔE, ΔL and ΔC color parameters through spectrophotometry. The translucency parameter (TP) was calculated using parameters L*, a* and b* on a black and white surface. Results: Regardless of the surface treatment, aging protocols did not cause a tetragonal-to-monoclinic phase transformation, although hydrothermal degradation in the autoclave transformed the hybrid tetragonal-cubic structure of all specimens to a tetragonal one. All polished and glazed specimens during chemical degradation demonstrated a significant color change ΔE. Lightness ΔL significantly changed in polished specimens aged in the autoclave. In all specimens, ΔC underwent a change manifested through statistically insignificant yellowing. None of the aging protocols altered the translucency of specimens. Conclusions: Aging, regardless of the final surface treatment, did not manifest a monoclinic phase in the specimens. A tetragonal-cubic microstructure dominates. Unlike polishing, glazing the surface of translucent zirconia ceramics contributed to minor changes in color, lightness and chromaticity. The translucency of translucent zirconia ceramics remains stable regardless of aging and surface treatment