This thesis concerns paper and ink interactions related to inkjet printing. The
main purpose of this work was to gain a deeper understanding in which
parameters control the flow of ink into papers and how the ink interacts with the
paper surface. The overall objective was to find key parameters to optimize the
print quality in inkjet printing. Characterization of paper-surfaces in terms of porosity, surface roughness and
surface energy was made. Objective and subjective measurements were used for
print quality evaluation. Light microscopy imaging and SEM was used to see how
ink interacts with the paper surface in a printed image. A high speed camera was
used to study the absorption of picolitre sized inkjet droplets into fine papers.
An initial study on the effect of paper properties on print quality was made.
Result indicated that there were small differences in print quality for pilot papers
with different composition (in a specific parameter window) and the commercial
paper COLORLOK® reproduced a noticeable high colour gamut compared to the
other samples.Research was made to see how surface fixation can affect the print quality for
printouts made with pigmented ink. Surface fixation promotes retention of the
pigmented colorant in the outermost surface layer of the paper and has been
denoted “colorant fixation” in this thesis.
It was shown that applying colorant fixation onto a paper surface before
printing can increase the detail reproduction in a printed image. Different
concentrations of calcium chloride were applied onto the paper surface on fullscale
produced non-commercial papers. Test printing was made with a SoHo
(Small office/Home office) printer using pigmented ink and results showed that
using calcium chloride as surface treatment can lead to aggregation of pigments at
the surface resulting in a higher detail reproduction.
Fast absorption of the carrier liquid into the paper and fast fixation of
colourants on the surface is important in inkjet printing to avoid colour to colour
bleeding. These demands will be more pronounced when the printing speed
increases. It is important to understand which parameters affect the absorption process to
be able to control the mechanisms and to optimize the print quality.
A study of absorption of picolitre size inkjet droplets into fine paper was made
in this work. Theoretical equations describing fluid absorption into capillaries were
tested and compared with experimental results. The result showed that the time
dependence in the Lucas-Washburn (L-W) equation fits fairly well to data whereas
the L-W equation overestimates the penetration depth.
The results are directly applicable to paper and printing industry and can be
used as a base for future studies of absorption of picolitre sized droplets into
porous materials and for studies of aggregation of colloidal particles on surfaces.
Sundsvall: Kopieringen Mittuniversitetet , 2011. , 28 p.