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Abstract This licentiate thesis comprises two studies dealing with the fusing step in electrophotographic printing. The first study addresses the development,of amethod,for monitoring wetting/spreading of single toner particles in-situ ona,heated substrate. The method,employs,imaging,from above and thus makes it possible to use,toner particles of r...
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Citations
... It is more likely that the colour difference signal from a pair of samples of very low reflectance is masked by the effect of flare light under high levels of illumination, and that the signal to noise ratio in this condition is not high enough to permit reliable observer judgements. Johnson and Birkenshaw [24] showed that the Bartleson-Breneman equations predict a greater rate of change in the perceived lightness of dark stimuli as illuminance increases, but that when the effect of flare is included this rate of change decreases significantly. ...
... In recent years debate about the surface free energy of solids has become greater, producing some important advances in the understanding of this subject. A product of these advances, however, is the continuous discovery of the limits of models developed [24][25]. ...
... The ranked cloudiness was generally more frequent in paperboard with unbleached back sides that caused brightness variations of the unprinted substrate, see fig 8. Other variables affecting cloudiness or similar artefacts are according to Xeikon transfer currents, substrate surface potential (U2 1 ) and the roughness of the substrate. Pettersson [24] claims that cloudiness and speckles can occur when the U2 level is too low and transfer currents are too high or too low. ...
We have investigated the effect of mechanical properties of flexographic post-printing forms on stress variation generated during the moment of printing, and how it affects banding in printing of corrugated board. A laboratory flexograhpic printing press and a stress sensor were used for the stress measurements and printing trails. It was shown in the results that the various stress variations generated due to the printing forms mechanical properties hade a strong correlation with the banding, a greater variance in stress also generated a higher degree of banding.
... It is more likely that the colour difference signal from a pair of samples of very low reflectance is masked by the effect of flare light under high levels of illumination, and that the signal to noise ratio in this condition is not high enough to permit reliable observer judgements. Johnson and Birkenshaw [24] showed that the Bartleson-Breneman equations predict a greater rate of change in the perceived lightness of dark stimuli as illuminance increases, but that when the effect of flare is included this rate of change decreases significantly. ...
... In recent years debate about the surface free energy of solids has become greater, producing some important advances in the understanding of this subject. A product of these advances, however, is the continuous discovery of the limits of models developed [24][25]. ...
... The ranked cloudiness was generally more frequent in paperboard with unbleached back sides that caused brightness variations of the unprinted substrate, see fig 8. Other variables affecting cloudiness or similar artefacts are according to Xeikon transfer currents, substrate surface potential (U2 1 ) and the roughness of the substrate. Pettersson [24] claims that cloudiness and speckles can occur when the U2 level is too low and transfer currents are too high or too low. ...
Print mottle, i.e. unwanted reflectance variation patterns, is perhaps one of the factors most detrimental to general print quality, and it is therefore important that it is evaluated in a proper and understandable manner. Several models have, over the years, been developed to evaluate mottle instrumentally. Today, there is also an ISO Standard for evaluating print mottle. The theoretical foundation of this standard is not however entirely reassuring. This paper attempts to examine a number of different print mottle evaluation models, including ISO 13660, conceptually and to compare the extents to which they correlate with visual print mottle assessment. Results suggest that three aspects of stochastic monochrome print mottle must be considered in any attempt to evaluate print mottle instrumentally: the amplitude of the variation, the coarseness of the variation, and the mean reflectance level of the print. The way in which this is carried out is however somewhat less crucial. We question whether an ISO standard for print mottle evaluation should indeed be based on a specific model such as the one described in ISO 13660. A standard based on a rigorous visual assessment of artificially created mottle would perhaps serve a better purpose.
