Inkjet Ink Research Articles

Wetting of Inkjet Polymer Droplets on Porous Alumina Substrates.

The resolution of inkjet printing technology is determined by wetting and evaporation processes after the jet drop contacts the substrate. Here, the wetting of different picoliter solubilized polymer droplets jetting onto one-end-closed porous alumina was investigated. The selected polymers are commonly used in inkjet ink. The synergistic effects of the hierarchical structure and substrate surface modification were used to control the behavior of polymer-based ink drops. A model that invokes the effect of surface tension was applied to calculate the amount of polymer solution penetrating into the pores. The calculation corroborates experimental observations and shows that the volume of polymer solution in the pores increases with an increase in pore radius and depth, resulting in less solution remaining on the substrate surface. The structure of the porous substrate coupled with intrinsic polymer properties and surface modifications all contribute to the resolution that can be achieved via inkjet printing.

Improving Dispersibility of Pigment in Inkjet Ink by Using Synergist

Improving Dispersibility of Pigment in Inkjet Ink by Using Synergist

Anionically surface treated inkjet and flexographic inks and their deinkability

Prerecycling of water-based flexographic ink and water-based thermal inkjet inks was explored. Model laboratory formulated water-based flexographic and commercial water-based thermal inkjet inks were used in experiments using solely wet or dry inks. The goal was to optimize ink detachment during repulping and at the same time assure its minimal ink redeposition. Ink’s behavior was examined under a wide pH range. An alkaline environment is desirable for complete ink detachment from the printed substrate, whereas the benefit of an acid environment is the agglomeration of the pigment in water-based ink. Deinking would be most efficient if executed in two steps: first, alkaline to detach most of the alkaline water-based ink and second, acidic to maintain detached ink coagulated. Acidic pH has the ability to agglomerate the pigment, once it is detached and present in deinking waters. However, such a recycling protocol is likely not achievable in current recycling plants.

Inkjet ink behaviors and its implication in adsorption deinking

ABSTRACTThe deinking process of inkjet deinking was evaluated by following INGEDE Method 11 and the influence of the pulping chemistry was studied. The inkjet ink behavior during pulping and papermaking was also investigated to distinguish between redeposited ink and bound ink, which has shown that redeposited ink is the major concern during paper recycling. In order to prevent the ink redeposition, adsorption has been used to improve inkjet removal during pulping. Chitosan was selected as an effective adsorbent, and the ISO brightness was improved by 5 points compared with flotation deinking.

Application of Vinylcarbonates as Low-Toxic Monomers in Digital Inkjet Inks

During the last decade, the research on digital inks has seen a strong increase with the focus to bring this technique into new markets. In this regard, many experts predict huge market potential for ink-jet inks for printing on food packaging, textiles and garments. However, commercially available inks contain noxious substances or solvents, which limit or completely prevent their application in these specific fields. Especially, UV- curable inks that offer unique advantages such as instantaneous drying, the absence of VOCs, good adhesion on substrates and excellent film forming properties consist of precarious monomers mainly based on (meth)acrylates.[1]One remarkable drawback of (meth)acrylates is their comparably high irritancy and even cytotoxicity in their uncured state.[2] This disadvantageous behaviour can be mainly attributed to the reactivity of the acrylate double bond towards Michael Addition reactions with amino- or thiol- groups of proteins or DNA. This fact together with the incomplete curing behavior of (meth)acrylates prevents their usability for substrates which are in contact with food or the human body.Recently, several radical curable functionalities such as vinylcarbonates, vinylesters and vinylcarbamates have been introduced as interesting alternatives to (meth)acrylate based resins providing a significant lower cytotoxicity.[3,4]The focus of this work was to evaluate vinylcarbonates as reactive building blocks in UV- curable digital inks in order to overcome the health issues which are related to (meth)arylates. For that purpose, a multitude of vinylcarbonate monomers was synthesized and studied regarding their reactivity, conversion and printability.Although, the viscosity and surface tension of these monomers are appropriate for ink-jet printing, the curing speed is far too low for high speed printing processes. One possibility to circumvent this limitation is to use thiol-vinylcarbonate formulations offering reactivities and double bond conversions (DBC) similar to those of acrylates. For that purpose, a multifunctional thiol was synthesized providing low odour and also an appropriate low viscosity facilitating the formulation of pigmented ink-jet inks. These basic digital inks offer an excellent jetting behaviour (see Figure 1) together with good film forming properties and adhesion on PET. Ongoing experiments concentrate on the storage stability of this system to allow the implementation of these thiol-vinylcarbonate inks in industrial printing processes. <fig position="float" id="s119_f.1"> <label>Figure 1</label> <caption>Top left: images of the formed droplets 50 μs after actuation; top right: single droplet test; bottom: print on photo paper (Epson photo paper glossy)[5]</caption> <graphic mime-subtype="tif" xlink:href="Images\s119_f01.tif" xmlns:xlink="http://www.w3.org/1999/xlink"/> </fig&gt

Development of inks suitable for the manufacturing of micro-scale polyurethane foams

We herein present the development of inkjet inks that have the capability of producing micro-scale polyurethane foams. Inkjet technology can be used as an additive manufacturing tool using small amounts of liquids to form a desired structure. Furthermore, in situ chemical reactions can be carried out using this particular printing technique. In order to achieve suitable printing inks, viscosity properties were taken as the key limiting factor choosing the ink components. Poly(ethylene glycol) 200 was selected as the main polyol for the reactive inks. Glycerol ethoxylate, also known as star-PEG, was selected as the crosslinking agent due to its three primary hydroxyl groups as well as its good compatibility with PEG200. Variation in star-PEG content was investigated by means of rheometric and tensiometric measurements. For the reactive isocyanate compound, 1,6-hexamethylene diisocyanate (HDI) was chosen due to its high reactivity and low viscosity. Polyurethane foams (PUF) were prepared in bulk to validate the foam recipe. Small droplets of the inks were then tested by manually placing two drops on top of each other. It was shown that in the absence of mechanical mixing the gelling and blowing reaction still take place. Furthermore, catalytic influences on the reactions were investigated using a central composite experimental design combined with FTIR-ATR spectroscopy. In order to evaluate the spectra, a deconvolution of the Amid I and Amid II area was conducted. The results were evaluated using an analysis of variance to gain models.

Inkjet Printing of Graphene Inks for Wearable Electronic Applications

Inkjet printing of graphene-based conductive inks is an encouraging research approach in the field of printed electronics as both the benefits of inkjet printing and extraordinary electronic, optical and mechanical properties of graphene can be exploited [1]. Inkjet printing is one of the most promising techniques for the fabrication of wearable electronics due to number of advantages over conventional manufacturing techniques such as digital and additive patterning, reduction in material waste, deposition of controlled amount of materials and compatibility with various substrates [2]. In addition, graphene is a single atom thick two-dimensional closely packed honeycomb lattice of sp2 carbon allotropes, which has been focus of mass investigations in recent years because of its unique physical and chemical properties [3].Currently silver nanoparticles (NPs) as inkjet printing inks are the most reported and utilised conductive inks because of their excellent electrical conductivity and strong antioxidant characteristics [4]. However higher concentration of NPs and higher sintering temperatures are required in order to obtain continuous metallic phase, with numerous percolation paths between metal particles within the printed pattern [5], which increased processing cost and limited the choice of substrates to be printed because of their heat sensitivity. Inkjet printing of reduced graphene oxide (rGO) are reported in several studies as a popular choice to fabricate wearable devices due its advantages such as readily dispersible in water and high volume production at lower cost [6]. However large number of unreduced oxygen-containing functional groups and inter-sheet junctions between the graphene domains limits the conductivity achieved with rGO [7]. In order to overcome the limitations associated with rGO inkjet inks, pristine graphene inks were developed and printed.Herein we report exfoliation of pristine graphene dispersions produced in gram scale quantities based on literature review [8, 9]. Liquid phase exfoliation method was used by shear mixing in the presence of a polymer stabilizer, ethyl cellulose which enhances the ink stability as well as printing performance [2, 10]. To formulate ink for inkjet printing graphene/ethyl cellulose powder was directly dispersed in a mixture of solvents by bath sonication. Then the formulated inks were successfully inkjet printed onto textile substrate in order to fabricate an Electro-Oculogram (EOG) device for healthcare applications, Figure 1. <fig position="float" id="s121_f.1"> <label>Figure 1</label> <caption>Graphene printed electrodes on textile substrates for bio-sensing without requiring a fixed connection to the body</caption> <graphic mime-subtype="tif" xlink:href="Images\s121_f01.tif" xmlns:xlink="http://www.w3.org/1999/xlink"/> </fig&gt

Preparation and Properties of Blue Edible Inkjet Ink Based on Chitosan Oligochitosan

Different formulations of blue edible inkjet inks were prepared in this study using chitosan oligochitosan as a binder. The properties of different formulations of the ink were analysed by measuring conductivity, surface tension, viscosity, and antimicrobial properties. Chromaticity and density experiments were also conducted on the blue inkjet inks. Results show that the quality of the printed matter was improved considerably, including enhanced resolution, antimicrobial resistance, and reduced graphic burrs, after the addition of chitosan oligosaccharide.

Synthesis, characterization and ultrafiltration of reactive dyes. Application by exhaustion and/or ink-jet printing—II

Three novel vinyl sulfone reactive dyes of various metallic salts (Na, K, Li) have been synthesized by coupling 1-amino-phenyl-4-beta hydroxyethyl sulfone sulfate ester with 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid (H-acid). The reactive dyes were then purified using ultrafiltration (UF). The ultrafiltrated dyes of the various metallic salts were characterized by their spectrophotometrical data using Ultra Violet-visible (UV-vis), Fourier transform infra-red and optical emission spectroscopy, X-ray diffraction, and elemental analysis. The purity of the dyes was checked by Thin Layer Chromatography (TLC). The solubility characteristics of the various salts of the ultrafiltrated reactive dyes were assessed and compared with the non-ultrafiltrated reactive dyes of the same salts. The dyes were characterized and applied to cotton, wool, and nylon 66 by exhaustion (dyeing). Novel water-based reactive ink-jet inks were prepared with the ultrafiltrated reactive dyes of the various metallic salts. Their suitability for digital printing applications was examined by using a digital printer on suitably pretreated cotton samples. Color and fastness properties measurements were performed for both the dyed and digitally printed samples. K/S values of the dyed samples were higher than those of the digitally printed ones, whereas K/S values of the samples dyed with the ultrafiltrated dyes were much higher than those of the non-ultrafiltrated dyes. The other coloristic co-ordinates L*, a*, b*, C*, and ho were in line with strength changes of the dyes before and after UF. The dyed and digitally printed samples had excellent wash and good light fastness properties. UF slightly improved the fastness properties of the dyed samples.

Dispenser printed capacitive proximity sensor on fabric for applications in the creative industries

This paper reports a planar capacitive proximity sensor fully dispenser printed on a standard polyester woven fabric using conductive ink. Dispenser printing is a new digital printing technique offering the advantages of complete geometric design flexibility and the ability to direct write multilayer devices without requiring bespoke tooling. A dispenser printer is also capable of printing a wide range of ink viscosities encompassing those of inkjet and screen printable inks. Previous research has demonstrated the principle of using proximity sensors for human interaction but none of them are fabricated directly on fabric. In this research, the proximity sensor is dispenser printed directly onto the fabric with an optimised loop electrode design which uses 76% less conductive ink while still offering 90% of the detection range when compared with a standard filled electrode design. The loop design also has the highest detection coefficient (maximum detection distance versus the conductive area of the sensor) of 0.23 compared with 0.06 and 0.1 for the investigated filled and spiral designs, respectively. In addition, the ratio of the track width to the width of the entire sensor is investigated showing 1/16 as being the most suitable ratio for the proximity sensor printed on fabric. Proximity sensors with loop widths ranging from 10mm to 400mm are evaluated. The maximum detection distance is 400mm when the largest sensor is used and the linearity of the sensing circuit is 0.79.

Product design: Metal nanoparticle‐based conductive inkjet inks

A systematic procedure that provides an efficient workflow for formulating conductive inks is developed. Qualitative product attributes of the inkjet ink are first identified and transformed into quantitative product specifications. Ingredients are then selected based on heuristics, mechanistic, and empirical models to meet the product specifications. Printability checks based on theoretical criteria are used to ensure that stable droplets can in principle be formed and coalesced properly to form a printed line of ink. Then, the conductive ink is prepared and printed to evaluate the performance of the inkjet ink experimentally. An example of preparing a copper ink for inkjet printing is used to illustrate the systematic procedure. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2740–2753, 2016

A benchmark study of commercially available copper nanoparticle inks for application in organic electronic devices

A set of three commercial copper nanoparticle based inkjet inks has been benchmarked with respect to their potential to form conducting printed structures for future applications in organic electronic devices. Significant differences were observed in terms of jetting properties, spreading behaviour and line formation on a number of relevant substrates. The inks' stabilities against oxidation were investigated, inkjet printed patterns were subjected to photonic flash sintering and their electrical properties characterized. As a result, optimized conditions for printing and post-deposition processing were determined. Photonic flash sintering, which is a roll-to-roll compatible manufacturing process, allowed a significant reduction in sintering time. Flash sintering was performed in the presence of air, thereby excluding the necessity for processing under inert atmosphere. One product was identified which showed satisfactory performances regarding all tested features: stable jet formation, well-defined definition of the printed structures and high electrical conductivity (20% of the value of bulk Cu). The obtained results can be considered as a promising step towards the future application of Cu inks in organic electronic devices.

Evaluation of the Forensic Utility of Scanning Electron Microscopy-Energy Dispersive Spectroscopy and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry for Printing Ink Examinations.

Improvements in printing technology have exacerbated the problem of document counterfeiting, prompting the need for analytical techniques that better characterize inks for forensic analysis and comparisons. In this study, 319 printing inks (toner, inkjet, offset, and Intaglio) were analyzed directly on the paper substrate using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). As anticipated, the high sensitivity of LA-ICP-MS pairwise comparisons resulted in excellent discrimination (average of ~ 99.6%) between different ink samples from each of the four ink types and almost 100% correct associations between ink samples known to originate from the same source. SEM-EDS analysis also resulted in very good discrimination for different toner and intaglio inks (>97%) and 100% correct association for samples from the same source. SEM-EDS provided complementary information to LA-ICP-MS for certain ink types but showed limited utility for the discrimination of inkjet and offset inks.

A Novel Forensic Tool for the Characterization and Comparison of Printing Ink Evidence: Development and Evaluation of a Searchable Database Using Data Fusion of Spectrochemical Methods

A searchable printing ink database was designed and validated as a tool to improve the chemical information gathered from the analysis of ink evidence. The database contains 319 samples from printing sources that represent some of the global diversity in toner, inkjet, offset, and intaglio inks. Five analytical methods were used to generate data to populate the searchable database including FTIR, SEM-EDS, LA-ICP-MS, DART-MS, and Py-GC-MS. The search algorithm based on partial least-squares discriminant analysis generates a similarity "score" used for the association between similar samples. The performance of a particular analytical method to associate similar inks was found to be dependent on the ink type with LA-ICP-MS performing best, followed by SEM-EDS and DART-MS methods, while FTIR and Py-GC-MS were less useful in association but were still useful for classification purposes. Data fusion of data collected from two complementary methods (i.e., LA-ICP-MS and DART-MS) improves the classification and association of similar inks.

A study on the thermal sintering process of silver nanoparticle inkjet inks to achieve smooth and highly conducting silver layers

Silver nanoparticle inkjet inks are commonly used to print electrically conductive patterns, such as sensors or electrodes in organic light emitting diodes (OLEDs) or organic photovoltaic devices (OPVs). After printing, a sintering step is required to transform the printed layer into an electrically conductive one. Gaining more insight into the occurring phenomena during this post‐treatment step is necessary when applying different kinds of inkjet ink. Therefore, in this work the commercially available silver nanoparticle inkjet ink Metalon JS‐B30G from Novacentrix is characterised during the different stages in the printing and thermal sintering sequence. The pre‐printing and post‐sintering characterisation proves that the inkjet ink used has got the right material parameters, such as viscosity and particle size. Silver layers with sheet resistances of 40 mΩ/sq were obtained with an average roughness lower than 10 nm. The experiments performed show the different stages during the thermal sintering procedure. Based on this, suitable thermal sintering parameters are defined leading to application of these conductive silver layers in OLEDs.

Vinylcarbonates as low-toxic monomers for digital ink-jet inks: Promising alternatives to acrylate based systems

Abstract The last decade has seen a significant increase in research on UV curable digital inks for industrial printing applications with the focus to expand this technique into new markets. However, most of the commercially available inks are based on acrylic monomers, which provide a significant toxicological behavior limiting their applicability in promising fields, e.g. printing on food packaging materials. In this study, a variety of biocompatible monomers based on vinylcarbonate building blocks were evaluated regarding their application in UV curable digital inks. Although, the viscosity and surface tension of these monomers is appropriate for ink-jet printing, the curing speed is far too low for high speed printing processes. In order to circumvent this limitation, thiol-vinylcarbonate formulations were prepared that offer reactivities and double bond conversions (DBC) similar to those of acrylates. For that purpose, a multifunctional thiol was synthesized providing both, low odor and an appropriate low viscosity facilitating the formulation of basic ink-jet inks, which offer excellent jetting behavior, together with good film forming properties and adhesion on PET. Although there are some challenges regarding stability, in particular for pigmented formulations, this system represents a promising alternative to commercially available acrylate based inks.

One-step inkjet printing of tungsten oxide-poly(3,4-ethylenedioxythiophene):polystyrene sulphonate hybrid film and its applications in electrochromic devices

Hybrid film comprised tungsten oxide and poly (3,4-ethylenedioxythiophene):polystyrene sulphonate (WO3–PEDOT:PSS) was developed by applying one-step inkjet printing from an office inkjet printer. The WO3 nanoparticles were synthesized from commercial crystalline WO3 powder through a wet ball-milling process, which is a simple, environmentally friendly, and cost-effective method of using water as a green solvent and low-energy milling. The WO3–PEDOT:PSS inkjet ink was prepared by dispersing the as-milled WO3 and PEDOT:PSS in n-propanol and deionized water. The inkjet-printed WO3–PEDOT:PSS thin films show marked improvements of cathodic electrochromism over WO3 films: the transmittance change of 20% at 550nm (visible region) and 35% at 900nm (infrared region) along with the response time of 5.67/0.30s in their colored/bleached state, and the electrochromic coloration efficiency of 27.86cm2/C at 550nm and 69.64cm2/C at 900nm.

Disperse inkjet inks with a new antibacterial agent as additive: Properties and application to polyester and polyamide fibres

Two water based disperse inkjet inks for polyester textile printing with antibacterial properties were prepared. The antibacterial activity was due to the presence of polyhexamethylene bisguanidine (PHMBG). The surface tension, pH, viscosity and conductivity of all inks formulations were monitored over a period of time for the evaluation of ink stability and suitability. The inks were used for application on polyester and polyamide samples by exhaustion (dyeing) and wash, light fastness and colour measurements were made on the dyed samples. The optimum application level required to give long lasting antimicrobial protection was determined by carrying out a series of antimicrobial testing.

The effect of multilayer polyelectrolyte coating on inkjet ink water fastness and rub resistance

The effect of multilayer polyelectrolyte coating on inkjet ink water fastness and rub resistance

Robust Design of a Particle-Free Silver-Organo-Complex Ink with High Conductivity and Inkjet Stability for Flexible Electronics.

Currently, silver-nanoparticle-based inkjet ink is commercially available. This type of ink has several serious problems such as a complex synthesis protocol, high cost, high sintering temperatures (∼200 °C), particle aggregation, nozzle clogging, poor shelf life, and jetting instability. For the emerging field of printed electronics, these shortcomings in conductive inks are barriers for their widespread use in practical applications. Formulating particle-free silver inks has potential to solve these issues and requires careful design of the silver complexation. The ink complex must meet various requirements, such as in situ reduction, optimum viscosity, storage and jetting stability, smooth uniform sintered films, excellent adhesion, and high conductivity. This study presents a robust formulation of silver-organo-complex (SOC) ink, where complexing molecules act as reducing agents. The 17 wt % silver loaded ink was printed and sintered on a wide range of substrates with uniform surface morphology and excellent adhesion. The jetting stability was monitored for 5 months to confirm that the ink was robust and highly stable with consistent jetting performance. Radio frequency inductors, which are highly sensitive to metal quality, were demonstrated as a proof of concept on flexible PEN substrate. This is a major step toward producing high-quality electronic components with a robust inkjet printing process.