Printability and Ink-Coating Interactions in Inkjet Printing

Inkjet is a digital printing process where the ink is ejected directly onto a substrate from a jet device driven by an electronic signal. Most inkjet inks have a low viscosity and a low surface tension, which put high demands on the coating layer’s porosity and absorbency characteristics. The aim of...

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Main Author: Svanholm, Erik
Format: Doctoral Thesis
Language:English
Published: Karlstads universitet, Fakulteten för teknik- och naturvetenskap 2007
Subjects:
Online Access:http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-572
http://nbn-resolving.de/urn:isbn:91-7063-104-2
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spelling ndltd-UPSALLA1-oai-DiVA.org-kau-5722013-01-08T13:04:24ZPrintability and Ink-Coating Interactions in Inkjet PrintingengSvanholm, ErikKarlstads universitet, Fakulteten för teknik- och naturvetenskapFakulteten för teknik- och naturvetenskap2007coatinginkjetprint qualityprintabilitypigmentsilicapolyvinyl alcoholcolorantink absorptionChemical engineeringKemiteknikInkjet is a digital printing process where the ink is ejected directly onto a substrate from a jet device driven by an electronic signal. Most inkjet inks have a low viscosity and a low surface tension, which put high demands on the coating layer’s porosity and absorbency characteristics. The aim of this study has been to gain an increased knowledge of the mechanisms that control the sorption and fixation of inkjet inks on coated papers. The focus has been on printability aspects of high print quality (although not photographic quality) laboratory-coated inkjet papers for printers using aqueous-based inks. Papers coated solely with polyvinyl alcohol (PVOH) and starch presented excellent gamut values and good print sharpness over the uncoated substrate, due to good film-forming characteristics observed by light microscopy and ESCA. ESEM analyses showed the complexity and variation of PVOH surface structures, which has probably explained the wide scatter in the colour-to-colour bleed results. Pure PVOH coatings also gave a surface with high gloss variations (2-8 times greater than that of commercial inkjet papers), prolonged ink drying time, and cracked prints when using pigmented inks. When an amorphous silica gel pigment (with broad pore size distribution) was used in combination with binder, a new structure was formed with large pores in and between the pigments and a macro-roughness generated by the large particles. The inkjet ink droplets could quickly penetrate into the large pores and the time for surface wicking was reduced, which was beneficial for the blurriness. However, the macro-roughness promoted bulk spreading in the coarse surface structure, and this tended to increase the line width. Finally, when the ink ends up within the coating, the colorant is partly shielded by the particles, and this reduced the gamut area to some extent. The binder demand of the silica pigments was strongly related to their pore size distributions. Silica gel required two to three times the amount of binder compared to novel surfactant-templated mesoporous silica pigments (with small pores and narrow pore size distribution). This finding was attributed to the significant penetration of PVOH binder into the pores in the silica gel, thereby, increasing its binder demand. Furthermore, this binder penetration reduced the effective internal pore volume available for rapid drainage of the ink vehicle. Consequently, the surfactant-templated pigments required significantly lower amounts of binder, and gave improvements in print quality relative to the commercial pigment. Doctoral thesis, comprehensive summaryinfo:eu-repo/semantics/doctoralThesistexthttp://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-572urn:isbn:91-7063-104-2Karlstad University Studies, 1403-8099 ; 2007:2application/pdfinfo:eu-repo/semantics/openAccess
collection NDLTD
language English
format Doctoral Thesis
sources NDLTD
topic coating
inkjet
print quality
printability
pigment
silica
polyvinyl alcohol
colorant
ink absorption
Chemical engineering
Kemiteknik
spellingShingle coating
inkjet
print quality
printability
pigment
silica
polyvinyl alcohol
colorant
ink absorption
Chemical engineering
Kemiteknik
Svanholm, Erik
Printability and Ink-Coating Interactions in Inkjet Printing
description Inkjet is a digital printing process where the ink is ejected directly onto a substrate from a jet device driven by an electronic signal. Most inkjet inks have a low viscosity and a low surface tension, which put high demands on the coating layer’s porosity and absorbency characteristics. The aim of this study has been to gain an increased knowledge of the mechanisms that control the sorption and fixation of inkjet inks on coated papers. The focus has been on printability aspects of high print quality (although not photographic quality) laboratory-coated inkjet papers for printers using aqueous-based inks. Papers coated solely with polyvinyl alcohol (PVOH) and starch presented excellent gamut values and good print sharpness over the uncoated substrate, due to good film-forming characteristics observed by light microscopy and ESCA. ESEM analyses showed the complexity and variation of PVOH surface structures, which has probably explained the wide scatter in the colour-to-colour bleed results. Pure PVOH coatings also gave a surface with high gloss variations (2-8 times greater than that of commercial inkjet papers), prolonged ink drying time, and cracked prints when using pigmented inks. When an amorphous silica gel pigment (with broad pore size distribution) was used in combination with binder, a new structure was formed with large pores in and between the pigments and a macro-roughness generated by the large particles. The inkjet ink droplets could quickly penetrate into the large pores and the time for surface wicking was reduced, which was beneficial for the blurriness. However, the macro-roughness promoted bulk spreading in the coarse surface structure, and this tended to increase the line width. Finally, when the ink ends up within the coating, the colorant is partly shielded by the particles, and this reduced the gamut area to some extent. The binder demand of the silica pigments was strongly related to their pore size distributions. Silica gel required two to three times the amount of binder compared to novel surfactant-templated mesoporous silica pigments (with small pores and narrow pore size distribution). This finding was attributed to the significant penetration of PVOH binder into the pores in the silica gel, thereby, increasing its binder demand. Furthermore, this binder penetration reduced the effective internal pore volume available for rapid drainage of the ink vehicle. Consequently, the surfactant-templated pigments required significantly lower amounts of binder, and gave improvements in print quality relative to the commercial pigment.
author Svanholm, Erik
author_facet Svanholm, Erik
author_sort Svanholm, Erik
title Printability and Ink-Coating Interactions in Inkjet Printing
title_short Printability and Ink-Coating Interactions in Inkjet Printing
title_full Printability and Ink-Coating Interactions in Inkjet Printing
title_fullStr Printability and Ink-Coating Interactions in Inkjet Printing
title_full_unstemmed Printability and Ink-Coating Interactions in Inkjet Printing
title_sort printability and ink-coating interactions in inkjet printing
publisher Karlstads universitet, Fakulteten för teknik- och naturvetenskap
publishDate 2007
url http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-572
http://nbn-resolving.de/urn:isbn:91-7063-104-2
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