Studija indirektne elektrofotografije

Majnarić, Igor (2007) Studija indirektne elektrofotografije. Dissertation (PhD) thesis. Grafički fakultet. [Mentor: Bolanča, Stanislav].

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Abstract

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.

Item Type:	Dissertation (PhD) thesis
Mentor name:	Bolanča, Stanislav
Thesis Committee:	Bolanča, Zdenka and Bolanča, Stanislav and Golubović, Adrijano and Parac-Ostrman, Đurđica and Mrvac, Nikola
Defence date:	20 April 2007
Abstract in english:	Technically, the indirect electrophotographic printing is a very complicated job. It implements 6 separate phases performed synchronically. They are charging, exposing, developing, the first transfer, the second transfer and cleaning. The influence of each phase on the quality of the multicolour reproduction has been researched in this work and the parameters which are not the standard ones for the production printing were used in it. The influence results of particular phases of electrophotographic printing process on the final reproduction have been presented in the gamut form (construction defined by ECI form of 378 patches) as well as the CIE LAB ΔE difference between calibration and the experimental print. In the starting phase, the influence of scorotron on the formation of the future free surfaces has been researched. The changes in gamut which appeared, were minimal ones (ΔVsimb=13,3, ΔVsplen=8,6 i ΔVarco= 4,1 space unit). The valid rule in this case is: the less scorotron voltage, the greater gamut volume. The change of the screen surfaces is greater in relation to the full tones. In investigating the influence of the laser head, it was noticed that the screen dot is subdued to great change. By increasing the laser strength, the screen elements become greater and darker. Full tones do not change considerably, and gamuts have the following changes: ΔVsimb=10,3, ΔVsple=13,2 i ΔVarco= 2,9 space unit. The developing process (developing drum and the squeegee rollers) influence the maximal change of the gamut inking (ΔVsimb= 301,5 ; ΔVsimb=210 space unit). By application of higher voltages, the greater application of the ink is achieved. The activity of the developing drum influences the greater change of the full tones, while in the case of the squeegee rollers greater change is achieved in screen. By the extreme increase of the voltage of the squeegee rollers, only smaller degradation of the gamut volume is achieved (ΔVsim=17,2, ΔVsple=22,3 i ΔVarc= 9,4 space unit) During the transferring process, two parameters varied: the temperature of the offset cylinder and the voltage of the offset cylinder. The increase of temperature causes the increase of the ink viscosity, which increases the gamut volume (ΔVsim=44,8, ΔVsple=49,3 i ΔVarc=31,9 space unit). The higher voltage of the offset cylinder ensures the better transfer. The change in voltage of 200V will cause the greatest gamut increase (ΔVsimb=37,7, ΔVsplen=14,3 i ΔVarco=11,5 space unit). At the end of the research the influence of the ink density on the final reproduction has been observed. The concentration increase of the pigment results in darker impression. During the colour variations, the gamuts ware not expected to be great (ΔVsimb=60,2, ΔVsplen=36,6 i ΔVarco=57,3 space unit). In investigation of the electrophotographic process, three different substrates were used: Simbol (glossy fine art paper for printing in classical offset), Splendogel (natural coated paper for digital printing) and Arcoprint (natural paper for classical offset printing). The surface properties of paper showed that they have decisive role in achieving the reproduction quality. Splendogel and Simbol papers with their coatings behave better in extreme conditions which is not the case in the application of the natural paper Arcoprint.
Uncontrolled Keywords:	Ektrofotografija, nabijanje, osvjetljavanje, razvijanje, transfer, gamutna reprodukcija
Keywords in english:	Electrophotography, charging, exposing, developing, transfer, gamut reproduction
Subjects:	TECHNICAL SCIENCES > Graphic Technology
Institution:	Grafički fakultet
City:	Zagreb
Number of Pages:	148
Callnumber:	655.39.062 maj d
Inventory number:	8251
Status:	Unpublished
Date Deposited:	15 Nov 2013 21:47
Last Modified:	24 Oct 2014 11:02
URI:	http://eprints.grf.unizg.hr/id/eprint/1420

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