Separation of off-set ink components during absorption into pigment coating structures

Rousu, Sanna; Gane, Patrick; Spielmann, D.; Eklund, D.

doi:10.3183/npprj-2000-15-05-p527-535

Cited by 41 publications

(61 citation statements)

References 6 publications

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“…Additionally, depending on their polarity, liquids will adsorb onto polymer-dispersed pigment surfaces according to their presented surface area, and, depending on solubility index match, will diffuse into latex binder polymer networks Van Gilder and Purfeest (1994); Rousu et al (2002); Rousu et al (2000a); Rousu et al (2000bRousu et al ( , 2001Rousu et al ( , 2003. These effects will combine with capillarity and inertia, discussed above, to define the distribution of ink and fountain solution components within the coating layer.…”

Section: Liquid Uptake Into Coating Structuresmentioning

confidence: 97%

Relating Liquid Location as a Function of Contact Time Within a Porous Coating Structure to Optical Reflectance

Gane

Koivunen

2010

Transp Porous Med

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Refractive index differences between a first and a second fluid can be utilised to obtain information about the location and amount of the fluids in a porous medium in the case where the light absorption coefficient of the skeletal material is small and the light scattering coefficient high using optical measurement methods. An example of such a medium is an air-filled paper coating, and the fluid that of a printing ink liquid phase absorbing into the coating during printing. We examined capillary absorption of mineral oil, used in offset printing ink, into model coatings compressed from dispersed mineral pigments with a range of latex binder levels, and established a porosity-normalised relationship for light reflectance change as a function of absorbed mass of the liquid established at a given time after initial contact with the liquid. The results suggest a significant change in reflectance due to the absorption, and progressive absorption behaviour of the liquid in the coatings can be monitored by the change in reflectance following a newly established relationship derived from the observational data. The findings support the concept of a preferred pathway flow for the wetting front, defined by differential pore size and connectivity, and a longer time saturation front flow lagging behind the wetting front, which theoretically at the limit of infinite time coincides with the wetting front, the time constant of the approach being related to the permeability of the porous network.

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Section: Liquid Uptake Into Coating Structuresmentioning

confidence: 97%

Relating Liquid Location as a Function of Contact Time Within a Porous Coating Structure to Optical Reflectance

Gane

Koivunen

2010

Transp Porous Med

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“…Ink penetration has a great impact on the print result (Rousu et al, 2000;Yang, Lenz and Kruse, 2001). Ink penetration is explained by explaining the following terms: ink components, separation effect, penetrability of different substrates, and ink drying and absorption.…”

Section: Ink Penetrationmentioning

confidence: 99%

“…This specific form of physical drying is called "setting". The absorption process is thus an interaction between ink and printing substrate (Rousu et al, 2000). The absorption rate is dependent on the diameter and the number of the pores and the viscosity of the ink vehicle.…”

Section: Ink Drying and Absorptionmentioning

confidence: 99%

Automated CtP Calibration for Offset Printing : Dot gain compensation, register variation and trapping evaluation

Hauck

2015

Linköping Studies in Science and Technology. Dissertations

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Although offset printing has been and still is the most common printing technology for color print productions, its print productions are subject to variations due to environmental and process parameters. Therefore, it is very important to frequently control the print production quality criteria in order to make the process predictable, reproducible and stable. One of the most important parts in a modern industrial offset printing is Computer to Plate (CtP), which exposes the printing plate. One of the most important quality criteria for printing is to control the dot gain level. Dot gain refers to an important phenomenon that causes the printed elements to appear larger than their reference size sent to the CtP. It is crucial to have the dot gain level within an acceptable range, defined by ISO 12647-2 for offset printing. This is done by dot gain compensation methods in the Raster Image Processor (RIP). Dot gain compensation is however a complicated task in offset printing because of the huge number of parameters affecting dot gain. Another important quality criterion affecting the print quality in offset is the register variation caused by the misplacement of printing sheet in the printing unit. Register variation causes tone value variations, gray balance variation and blurred image details. Trapping is another important print quality criterion that should be measured in an offset printing process. Trapping occurs when the inks in different printing units are printed wet-on-wet in a multi-color offset printing machine. Trapping affects the gray balance and makes the resulting colors of overlapped inks pale. In this dissertation three different dot gain compensation methods are discussed. The most accurate and efficient dot gain compensation method, which is noniterative, has been tested, evaluated and applied using many offset printing workflows. To further increase the accuracy of this method, an approach to effectively select the correction points of a RIP with limited number of correction points, has also been proposed. Correction points are the tone values needed to be set in the RIP to define a dot gain compensation curve. To fulfill the requirement of having the register variation within the allowed range, it has to be measured and quantified. There have been two novel models proposed in this dissertation that determine the register variation value. One of the models is based on spectrophotometry and the other one on densitometry. The proposed methods have been evaluated by comparison to the industrial image processing based register variation model, which is expensive and not available in most printing companies. The results of all models were ii comparable, verifying that the proposed models are good alternatives to the image processing based model. The existing models determining the trapping values are based on densitometric measurements and quantify the trapping effect by a percentage value. In this dissertation, a novel trapping model is proposed that quantifies the trapping effect by a c...

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“…The two liquids were chosen so as to isolate polar and non-polar effects, which are frequently represented in the fluid phases of a variety of different inks, for example water-based and oil-based inkjet, fountain solution and offset ink diluent, respectively. Whilst we accept that reference to practical inks and formulations using two pure liquids omits the effects of the retained ink surface layers, we wish to draw attention to the fact that differences in effective surface chemistry will lead to differential adsorption as well as absorption, and as such will promote chromatographic separation of ink components, as has already been demonstrated for offset inks (Rousu et al 2001) also including the effect of polymer binder. By highlighting that there are apparent differences associated with pore size, we can be confident in predicting chromatography according to pore size and associated surface chemistry, and not only by the traditional effects of size exclusion.…”

Section: Introductionmentioning

confidence: 97%

“…The rate and volume of liquid absorption is dependent on the porous network structure of the coating layer established via coating pigment particle packing in the presence of binders, such as latex. The timescale of absorption falls under the description of network pore structure imbibition theory Schoelkopf et al 2000a,b) and the nature of the chemical surface encountered by the liquid, together with diffusional effects (Rousu et al 2001(Rousu et al , 2002. The printing process manifests timescales of phenomena from nanoseconds through milliseconds, up to minutes and hours depending on ink and coating chemistry.…”

Section: Introductionmentioning

confidence: 99%

Competitive Absorption of Polar and Non-Polar Liquids into Latex Bound Porous Structures of Fine Ground Calcium Carbonate

Ridgway¹,

Schoelkopf²,

Gane

2010

Transp Porous Med

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Fine calcium carbonate is frequently used as coating pigment, e.g. in paints, paper and board. Emulsion polymer latex provides a typical binder incorporated in such coatings. Exposure of the resulting porous structure to liquid, depending on latex concentration level, results in ab-and adsorption as the liquid is drawn into the structure by capillarity and the nature of the relative surface chemistry of the pores. Previous work has shown that typical coating structures act to separate oil components according to their surface energy characteristics and solubility index in respect to pigment surface and intra-latex diffusion. This study considers water and alkane (hexadecane) as model liquids. Absorption rate into compressed tablets of ground calcium carbonate is observed with and without the presence of latex. Polyacrylate dispersant used in manufacture renders the pigment surface both hydrophilic and hygroscopic and, therefore, controls the differential dynamic wetting characteristics of the porous structure for either polar or non-polar liquid. In competition with hexadecane saturating the pore structure of a latex-free sample, polar water is seen to displace the non-polar liquid instantaneously, causing disintegration of the packed porous structure. In the presence of latex binder, however, the structurally destructive pressure this creates is contained, and retardation of the polar water is observed. The required pre-wetting action of water vapour diffusion on the polyacrylate pigment surface is considered to be an integral part of the successful competition between oil and water in the offset printing process, as non-polar oil absorbs steadily into a water pre-saturated structure.

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Separation of off-set ink components during absorption into pigment coating structures

Cited by 41 publications

References 6 publications

Relating Liquid Location as a Function of Contact Time Within a Porous Coating Structure to Optical Reflectance

Relating Liquid Location as a Function of Contact Time Within a Porous Coating Structure to Optical Reflectance

Automated CtP Calibration for Offset Printing : Dot gain compensation, register variation and trapping evaluation

Competitive Absorption of Polar and Non-Polar Liquids into Latex Bound Porous Structures of Fine Ground Calcium Carbonate

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