Modeling the effect of ink spread and ink penetration on tone reproduction

In ink jet printing when ink is printed on top of the paper, two effects occur that have an effect on the dot that is printed. One effect is that the ink spreads out laterally and the other is that the ink penetrates into the paper. A tone reproduction model was developed that mathematically modeled the effects ink spread and ink penetration have on tone reproduction. Since the optical behavior of ink penetration is very complex, the model only included characteristics that were expected to be significant. This model was built from the foundation of another tone reproduction model which mathematically modeled the optical effect of halftone patterns as a probability. The model was tested using test samples consisting of gray scales produced by thermal ink jet. These samples were produced by varying certain conditions that are thought to affect ink penetration and ink spread and simulate other ink jet environments such as different inks, different papers, and different printers. Microdensitometry equipment was used to obtain data from the samples and the model was analyzed on how well it fit the data

Laser driven variable dot size thermal wax transfer printing

A digital image hardcopy device has been designed using a laser exposure mechanism, a pigmented wax /resin donor ink sheet, and an opaque receiver sheet. The writing system relies on image-wise thermal mass transfer of molten ink to the receiver in order to produce high resolution output. With the receiver media and a specially designed donor ribbon being held to a platen through vacuum pressure, a pulsed solid-state diode pumped near IR NdrYAG laser provides the energy necessary to complete the thermal transfer process. By varying pulse width, dot size variation is possible. A mathematical model was developed to explain the physics of the imaging process and aid further experimentation. In order to maximize photothermal conversion and transfer efficiency while maintaining environmental friendliness, a water/ alcohol based multi-layer donor ribbon was designed. Digital image analysis techniques and processing algorithms were developed specifically to provide a reliable quantification scheme for all variables. A randomized four factor central composite design provided a statistically robust means by which to map measured image quality. Response surface methods of factorial experimental design afforded a means to model the ribbon design space. Utilization of the Downhill Simplex Method (Nelder and Mead, 1965) yielded the optimum point on the estimated image quality response surface. The optimum point represented the final donor ribbon composition. It is primarily the continuously variable dot size capability and high thermal efficiency of the developed system that sets this research apart from other published works related to laser driven thermal transfer

Gloss Development of Spray-coated Systems

A spray-coated system involves any substrate on which a liquid coating is applied in a drop-wise fashion. Inkjet printing is the controlled application of drops to print a surface and is the focus of this work. The gloss of the printed substrate is an important attribute of print quality. Print gloss depends on a number of factors, such as ink and media properties. Non-uniform gloss in different regions of a printed image can cause a decrease in quality of a printed sample. However, a good understanding of the gloss development of spray-coated systems is not available in the literature. Several combinations of inkjet inks and media were characterized in terms of physical properties. Both pigmented and dye-based inks were used with absorbing microporous coated media. These ink/media combinations were printed with an inkjet printer and the final gloss measured. A laser system was used to measure the gloss every millisecond right after printing, around 20 ms after drop impact. Some media were modified with chemicals or other treatments to modify physical and chemical properties. Fiber swelling in paper-based media was found to lower gloss in those media which contain fibers that can contact water. This reduction in gloss occurred one second after printing. Media with protected paper fibers do not exhibit this gloss reduction. Plastic-based media with porous coatings obtained the final gloss at 0.1 seconds. Inks can be destabilized by ions on the media surface that leads to low gloss. Some inks were not sensitive to ions on the media. Light color inks were found to have high gloss values at 50% fill compared to 100% fill while most other inks have the opposite behavior. This phenomenon is likely due to the secondary reflection at the ink/media interface; light is able to transmit through the ink layer and reflect at the media surface

Taguchi's Grey Relationship Analysis (GRA) for Comparing the Performance of Various Inkjet Printheads for Tone Value Increase on Uncoated Paper Substrates

Digital technologies in printing attract more attention among the printers in recent years. All around the world, inkjet technology is used by both home and commercial printers. New applications for inkjet printing have emerged as the technology has developed, including the printing of high-quality periodicals and the packaging sector. This state-of-the-art technology, particularly Inkjet, has undergone extensive testing and refinement to ensure high quality prints High-quality printing often makes use of gloss coated sheets. Yet the high price of gloss coated paper limits its usefulness to certain types of work. Since then, it has been clear that uncoated papers are the best option for this task. The print quality would be different from that of glossy coated paper because of the roughness, porosity, and unevenness of the surface. Tone Value Increase (TVI) on uncoated paper printed with various inkjet printheads is an intriguing topic for investigation. Therefore, effective TVI is crucial. Multiple commercial inkjet printheads were tested for their TVI performance on uncoated paper and the results were compared using a novel statistical approach Taguchi's Grey Relational Analysis (GRA). The use of this statistical method yielded fruitful results in our study

In-situ resonant band engineering of solution-processed semiconductors generates high performance n-type thermoelectric nano-inks.

Thermoelectric devices possess enormous potential to reshape the global energy landscape by converting waste heat into electricity, yet their commercial implementation has been limited by their high cost to output power ratio. No single "champion" thermoelectric material exists due to a broad range of material-dependent thermal and electrical property optimization challenges. While the advent of nanostructuring provided a general design paradigm for reducing material thermal conductivities, there exists no analogous strategy for homogeneous, precise doping of materials. Here, we demonstrate a nanoscale interface-engineering approach that harnesses the large chemically accessible surface areas of nanomaterials to yield massive, finely-controlled, and stable changes in the Seebeck coefficient, switching a poor nonconventional p-type thermoelectric material, tellurium, into a robust n-type material exhibiting stable properties over months of testing. These remodeled, n-type nanowires display extremely high power factors (~500 µW m-1K-2) that are orders of magnitude higher than their bulk p-type counterparts

Composition-Processing-Property Relationships of 3D-Printed Graphene-Egain-Poly(ethylene Oxide) Composites

Direct-ink-writing is an effective manufacturing method to process polymer composites as it has been shown to be capable of controlling material microstructure in each deposited filament. Particularly, nanofillers are known to align under the influence of shear and extensional deformation of the composite inks. Comprehensive understanding of this phenomenon relies heavily not only on ink rheology but also the interaction between the ink and the nozzle To address them, this study includes direct-ink-write of unique polymer composites and extensive study of shear and extensional experiments to elucidate how the ink composition, process induced shear stresses and strain rates along with the presence of wall slip influence the microstructure and electrical conductivity of the printed structures

N-colour separation methods for accurate reproduction of spot colours

In packaging, spot colours are used to print key information like brand logos and elements for which the colour accuracy is critical. The present study investigates methods to aid the accurate reproduction of these spot colours with the n-colour printing process. Typical n-colour printing systems consist of supplementary inks in addition to the usual CMYK inks. Adding these inks to the traditional CMYK set increases the attainable colour gamut, but the added complexity creates several challenges in generating suitable colour separations for rendering colour images. In this project, the n-colour separation is achieved by the use of additional sectors for intermediate inks. Each sector contains four inks with the achromatic ink (black) common to all sectors. This allows the extension of the principles of the CMYK printing process to these additional sectors. The methods developed in this study can be generalised to any number of inks. The project explores various aspects of the n-colour printing process including the forward characterisation methods, gamut prediction of the n-colour process and the inverse characterisation to calculate the n-colour separation for target spot colours. The scope of the study covers different printing technologies including lithographic offset, flexographic, thermal sublimation and inkjet printing. A new method is proposed to characterise the printing devices. This method, the spot colour overprint (SCOP) model, was evaluated for the n-colour printing process with different printing technologies. In addition, a set of real-world spot colours were converted to n-colour separations and printed with the 7-colour printing process to evaluate against the original spot colours. The results show that the proposed methods can be effectively used to replace the spot coloured inks with the n-colour printing process. This can save significant material, time and costs in the packaging industry

Modeling and Halftoning for Multichannel Printers: A Spectral Approach

Printing has been has been the major communication medium for many centuries. In the last twenty years, multichannel printing has brought new opportunities and challenges. Beside of extended colour gamut of the multichannel printer, the opportunity was presented to use a multichannel printer for ‘spectral printing’. The aim of spectral printing is typically the same as for colour printing; that is, to match input signal with printing specific ink combinations. In order to control printers so that the combination or mixture of inks results in specific colour or spectra requires a spectral reflectance printer model that estimates reflectance spectra from nominal dot coverage. The printer models have one of the key roles in accurate communication of colour to the printed media. Accordingly, this has been one of the most active research areas in printing. The research direction was toward improvement of the model accuracy, model simplicity and toward minimal resources used by the model in terms of computational power and usage of material. The contribution of the work included in the thesis is also directed toward improvement of the printer models but for the multichannel printing. The thesis is focused primarily on improving existing spectral printer models and developing a new model. In addition, the aim was to develop and implement a multichannel halftoning method which should provide with high image quality. Therefore, the research goals of the thesis were: maximal accuracy of printer models, optimal resource usage and maximal image quality of halftoning and whole spectral reproduction system. Maximal colour accuracy of a model but with the least resources used is achieved by optimizing printer model calibration process. First, estimation of the physical and optical dot gain is performed with newly proposed method and model. Second, a custom training target is estimated using the proposed new method. These two proposed methods and one proposed model were at the same time the means of optimal resource usage, both in computational time and material. The third goal was satisfied with newly proposed halftoning method for multichannel printing. This method also satisfies the goal of optimal computational time but with maintaining high image quality. When applied in spectral reproduction workflow, this halftoning reduces noise induced in an inversion of the printer model. Finally, a case study was conducted on the practical use of multichannel printers and spectral reproduction workflow. In addition to a gamut comparison in colour space, it is shown that otherwise limited reach of spectral printing could potentially be used to simulate spectra and colour of textile fabrics

Test Targets 8.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Publishing is both a journey and a destination. In the case of Test Targets, the act of creating and editing content, paginating and managing digital assets, represents the journey. The hard copy is the result or destination that readers can see and touch. Like the space exploration program, everyone saw the spacecraft that landed on the moon. It was the rocket booster that made the journey from the earth to the moon possible. This article portrays the process of capturing ideas in the form of digital data. It also describes the process of managing digital assets that produces the Test Targets publication