Effects on print quality of varying acrylic binder types in water-based flexographic ink formulations

The ink industry is one of the world's largest markets due to the increasing demand for printing inks for the packaging industry. Flexography printing is a well-known promising technology for large-area printing due to its high printing speed and roll-to-roll capability to print economically on a variety of surfaces and is used in nearly in all areas of packaging printing. Water-based inks are considered non-toxic, odourless, and more environmentally friendly options compared to solvent-based inks. Therefore, in this article, the goal was to develop new water-based ink formulation with different acrylic binders for flexographic printing on commercial solid bleached sulphate (SBS) board. Five inks were formulated with four different acrylic binders and compared to a commercially available ink to study their performance. The developed inks were investigated with regard to their print qualities and print characteristics. It was found that the binder type influenced some print quality while the effect was not significant for others. Using flexography printed cyan inks, the ink formulated with the highest molecular weight had the lowest print density and the largest tonal value increase (TVI) observed between 40 and 60 tone values. The same ink had the largest mottle values and variation in topography. For values of print contrast and delta gloss at 75°, although differences were observed between average values, data had inconclusive variation and spread around averages, where no conclusive trends or effects of acrylic binder type on these response factors were observed. Print chroma and dot roundness results were equally close for all printed samples.     

Spray-coated nanoscale conductive patterns based on in situ sintered silver nanoparticle inks

Nanoscale patterns with high conductivity based on silver nanoparticle inks were fabricated using spray coating method. Through optimizing the solution content and spray operation, accurate nanoscale patterns consisting of silver nanoparticles with a square resistance lower than 1 Ω /cm² were obtained. By incorporating in situ sintering to substitute the general post sintering process, the time consumption could be significantly reduced to one sixth, qualifying it for large-scale and cost-effective fabrication of printed electronics. To testify the application of spray-coated silver nanoparticle inks, an inverted polymer solar cell was also fabricated, which exhibited a power conversion efficiency of 2.76%.     

纳米金属喷墨导电墨水研究进展

喷墨印刷电子技术是电子及微电子行业未来的一种高效、绿色环保型生产技术。本文详细阐述了纳米金属喷墨导电墨水的制备及性能研究、墨滴控制、涂层后处理与应用4个方面的研究进展,说明了纳米金属喷墨导电墨水是未来喷墨印刷电子研究的关键技术之一,指出了纳米金属喷墨导电墨水目前存在的不足,如固含量与稳定性之间的矛盾、导电性能不理想等。并对喷墨印刷电子技术的发展提出了展望,指出其在RFID天线、印刷线路板、印刷电子产业领域有广阔的应用前景。     

Photochromic ink formulation for digital inkjet printing and colour measurement of printed polyester fabrics

The application of a series of commercial photochromic dyes to polyester fabric by a digital inkjet printing method was investigated. Solvent‐based ink systems using the dyes were formulated. The inks were characterised in terms of their physical properties which are related to the jettability of the inks, and finally the prints were fixed onto polyester fabrics by thermal fixation. Colour measurement of the printed fabrics was used to measure their degree of photocoloration, fading rate, fatigue resistance, and storage stabilities. The measured properties of the inkjet‐printed fabrics were compared with the same properties of the same dyes applied to polyester fabrics by dyeing methods. The printed fabrics demonstrated inferior performance in terms of the degree of photocoloration, superior performance in the case of background colours, a higher rate of fading, and a lower fatigue resistance compared with that shown by the same dyes applied to polyester fabric by dyeing methods.     

Transparent conductive grids via direct writing of silver nanoparticle inks

Transparent conductive grids are patterned by direct writing of concentrated silver nanoparticle inks. This maskless, etch-free patterning approach is used to produce well-defined, two-dimensional periodic arrays composed of conductive features with center-to-center separation distances of up to 400 μm and an optical transmittance as high as 94.1%.     

Screen printing of silver nanoparticle suspension for metal interconnects

Silver nanoparticle suspensions were synthesized by chemical reduction method using a formaldehyde reductant. Polyvinyl pyrrolidone (PVP) of two different molecular weights (M.W.=8,000 and 29,000) was used as a stabilizer for the suspensions. PVP of a smaller molecular weight could produce silver suspensions of nanoparticle size around 20 nm. Water-based conductive silver inks with different silver concentrations were prepared and tested for suitability for screen printing. We have successfully printed silver metal lines on glass substrates using a 400 mesh screen-mask with 60wt.% silver ink prepared in this study. Curing at a low temperature of 200 °C for an hour was found sufficient to reach the lowest resistivity value with the synthesized ink. For a line with a width and thickness of 0.5 mm and 2.12 μm, respectively, it exhibited a resistivity of 3.3×10⁻⁵ Ω·cm, which could serve as conducting lines for various electronic applications.     

Antibacterial flexographic ink containing silver nanoparticles

The current work deals with the effects of incorporation of silver nanoparticles on the antibacterial and the thermal properties of a flexographic ink. The stable and uniform dispersion of silver nanoparticles in the ink were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal properties of the pure and nanoparticle loaded ink films were also evaluated using TGA and DSC techniques. The results from this study proved acceptable dispersion characteristics, wherein, the flexographic ink showed a significant antibacterial activity against Gram-positive and Gram-negative bacteria     

New printing inks with barrier performance for packaging applications: Design and investigation

Barrier properties of packaging materials against moisture and oxygen penetration are of high relevance. Enhanced protection of existing materials against weather conditions can be achieved by application of printed coatings. To improve barrier performance of packaging materials, new inks for obtaining printed coatings with a layered structure were developed and investigated. The proposed ink compositions for flexographic printing on paper substrates are based on an environmentally friendly acrylic binder and contain inorganic fillers with platelet particles incorporated in the polymer matrix. Coatings based on the developed printing inks demonstrate significantly decreased water vapour permeability compared to traditional polymer inks. The effect of decreased permeability was investigated considering inks rheological behaviour, the coating structure, mechanical properties, surface energy and water uptake for different ink formulations. The developed inks provide variable optical properties including coatings with a relatively high transparency. The development of the functional barrier inks contributes to saving natural resources by prolonging life performance of packaging materials and goods.     

Electrohydrodynamic pulsed-inkjet characteristics of various inks containing aluminum particles

As nano-sized silver particles are prohibitively expensive, lower cost materials (e.g., micro-sized aluminum) are sought for the manufacture of conducting electrodes. Inks containing various aluminum weight percentages are dot-printed onto a stainless-steel substrate with an electrohydrodynamic (EHD) inkjet, which is superior to thermal and piezoelectric inkjets for inks containing larger particles because it ejects drops smaller than the nozzle diameter. Various ink solvents (ethanol, octanol, and diethylene glycol) are formulated with aluminum particles from 1 to 10 wt%. EHD inkjet characteristics such as drop-separation distance, drop size, drop-to-substrate impact velocity, and required voltage are reported. The ink's thermo-fluid properties are the primary factors controlling drop characteristics and printing quality.     

Ionic liquids as performance additives for water‐based printing inks

For the first time, the use of ionic liquids as additives for printing inks in order to improve the wettability of the printing base by the ink is presented. The aim of this work was to study the influence of ionic liquids on the selected properties of water‐based printing ink and the prints. The contact angles of the printing inks on the printing base were measured. Modified flexographic inks were laboratory printed on polypropylene plastic film. The impact of small amounts of various ionic liquids on printing ink colour was examined in terms of the optical density of the full‐tone area, the colour parameters (L*, a*, b*, CIE), the total colour difference, and the gloss of the dried ink film. The influence of ionic liquids on the ink contact angle, the optical density, and the L*a*b* coordinates is discussed. In general, the investigated ionic liquids improve the wettability of water‐based flexographic printing ink, with an acceptable total colour difference. The optical density is increased for printing inks containing ionic liquids in comparison with the original flexographic printing ink, Process.     

反应喷墨打印技术及其在功能材料领域的研究进展

反应喷墨打印技术作为喷墨打印电子技术的重要分支,因其可以在沉积材料的同时可得到器件而受到人们的广泛关注.本文详细阐述了反应喷墨打印技术在功能材料制备领域,特别是在金属材料、高分子材料、无机材料等方面的研究进展,说明了反应喷墨打印用墨水是未来喷墨印刷电子研究的关键技术之一,简要介绍了反应喷墨打印技术与三维打印的联系,指出其在金属电路、有机发光二极管等印刷电子产业领域有广阔的应用前景.     

Inkjet printing of polyvinyl alcohol multilayers for additive manufacturing applications

Here we demonstrate that inkjet printing technology is capable of producing polyvinyl alcohol (PVOH) multilayer structures. PVOH water‐based inks were formulated with the addition of additives such as humectant and pigments. The intrinsic properties of the inks, such as surface tension, rheological behavior, pH, wetting, and time stability were investigated. The ink's surface tension was in the range 30–40 mN/m. All formulated inks displayed a pseudoplastic (non‐Newtonian shear thinning and thixotropic) behavior at low‐shear rates and a Newtonian behavior at high‐shear rates; were neutral solutions (pH7) and demonstrated a good time stability. A proprietary 3D inkjet printing system was utilized to print polymer multilayer structures. The morphology, surface profile, and the thickness uniformity of inkjet printed multilayers were evaluated by optical microscopy and FT‐IR microscopy. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43572.     

Inkjet printing of 3D metal–insulator–metal crossovers

The inkjet deposition of a single functional material on a substrate is well developed, however, little attention has been paid to the sequential printing of different functional elements to generate complex 3D structures. The successful all additive manufacture of electronics circuits requires the printing of features such as crossovers and interconnections, the passive elements in electronics where metal–insulator–metal must be sequentially deposited with retained function. We describe the inkjet printing of both a commercial silver nanoparticle metal and a cationic/thermally cured epoxy insulator, SU8, and discuss the role of print strategy and surface treatment on retaining functionality. The issues to be addressed in the successful all inkjet printing of such features are discussed.     

Novel Insights into Inkjet Printed Silver Nanowires Flexible Transparent Conductive Films

Silver nanowire (AgNWs) inks for inkjet printing were prepared and the effects of the solvent system, wetting agent, AgNWs suspension on the viscosity, surface tension, contact angle between ink droplet and poly(ethylene) terephthalate (PET) surface, and pH value of AgNWs ink were discussed. Further, AgNWs flexible transparent conductive films were fabricated by using inkjet printing process on the PET substrate, and the effects of the number printing layer, heat treatment temperature, drop frequency, and number of nozzle on the microstructures and photoelectric properties of AgNWs films were investigated in detail. The experimental results demonstrated that the 14-layer AgNWs printed film heated at 60 °C and 70 °C had an average sheet resistance of 13 Ω∙sq⁻¹ and 23 Ω∙sq⁻¹ and average transparency of 81.9% and 83.1%, respectively, and displayed good photoelectric performance when the inkjet printing parameters were set to the voltage of 20 V, number of nozzles of 16, drop frequency of 7000 Hz, droplet spacing of 15 μm, PET substrate temperatures of 40 °C and nozzles of 35 °C during printing, and heat treatment at 60 °C for 20 min. The accumulation and overflow of AgNWs at the edges of the linear pattern were observed, which resulted in a decrease in printing accuracy. We successfully printed the heart-shaped pattern and then demonstrated that it could work well. This showed that the well-defined pattern with good photoelectric properties can be obtained by using an inkjet printing process with silver nanowires ink as inkjet material.     

The morphology, electrical conductivity and vapour sensing ability of inkjet-printed thin films of single-wall carbon nanotubes

Thin films containing single-wall carbon nanotubes (SWCNTs) have been prepared using the inkjet printing (IJP) technique. Atomic force microscopy (AFM) has been used to investigate the morphology of these layers. The inkjet printed films consisted of small, randomly-oriented islands of nanotubes, the topography of which was dependent on the nature of the substrate surface. The in-plane electrical characteristics of the films were measured at room temperature. The current versus voltage data exhibited non-linear behaviour, which could be fitted to the theoretical model for Poole-Frenkel conductivity. Preliminary measurements are also reported on the use of the thin layers to detect alcohol vapour.     

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     

The fabrication and characterization of inkjet-printed polyaniline nanoparticle films

This paper reports on the fabrication and characterization of electrodes modified with conducting polymer nanoparticle films, produced via inkjet printing. The polyaniline nanoparticle formulations were deposited via a desktop inkjet printer onto screen-printed carbon-paste electrodes (SPE), polyethylene terephthalate (PET) and gold-PET and their morphology studied at a range of length scales using profilometry, scanning electron microscopy and atomic force microscopy. The deposited films were found to form continuous polymer films depending upon film thickness, which was in turn dependent on the number of prints performed. The inkjet-printed films exhibited a smooth morphology on the SPEs at the micro-dimensional scale, as a result of the aggradation and coalescing of the nanoparticles upon deposition. The resulting modified electrodes were both conductive and electroactive, possessing good reversible polyaniline electrochemistry. Such a combination of materials and processing offers the potential of producing a range of low cost, solid state devices such as sensors, actuators and electrochromic devices.     

Usability of cellulose-based binder in water-based flexographic ink

Packaging must have a good commercial appearance and is generally obtained by ink transferred to its substrate. It is important that the ink used in packaging printing is produced from environmentally friendly and sustainable raw materials as well as being suitable for the printing system. The increasing demand in the field of printed packaging and the scarcity of resources to meet this demand have accelerated the search for new sources for inks. For this purpose, inks produced in the laboratory using a modified cellulose-based binder, a commercial acrylic resin and a commercial soybean protein were compared with a commercial ink. As a result of the study, it was determined that the printability properties of the ink obtained by using the modified cellulose-based binder were better than the ink obtained with commercial soybean protein. It was determined that it showed printability properties close to the ink produced with commercial acrylic binders. By using modified cellulose-based water-based flexographic ink instead of other commonly used binders, more environmentally friendly sustainable inks can be produced.     

Method for controlling surface energies of paper substrates to create paper-based printed electronics

The creation of practical paper-based electronics requires secured conductivity with conductive silver tracks fabricated on a paper substrate. Various paper properties were explored for obtaining the key parameters intimately related to printed circuit qualities. A comparison of the resistance of silver tracks printed by ink-jet with a tetradecane-based ink of silver nanoparticles among four substrates—photo-quality ink-jet paper, matte-type ink-jet paper, coated offset paper, and uncoated laboratory sheets—implied the importance of pore size, porosity, surface roughness, and surface energy. Paper surface layers with small pore sizes and high porosities produced highly conductive, narrow silver tracks because of quick ink absorption, as observed in the photo-quality ink-jet paper. The surface roughness induced a high resistance to peel-off force at the expense of conductivity, and this improvement in the peel-off resistance is considered to be achieved because of the anchor effect of silver nanoparticle inks which fell into dents present on the rough paper surfaces. The widths of the silver tracks were significantly reduced by controlling the surface energies of the paper sheets. This tendency was remarkable, especially for uncoated laboratory sheets, and thus the conductivities of the silver tracks were successfully improved.     

Printability of functional inks on multilayer curtain coated paper

Printability of functional inks on multilayer curtain coated substrates was investigated. The inks represent those commonly used to produce solution processable electronic devices, such as organic transistors. The substrate, which combines sufficient barrier and printability properties for printed functional devices, was manufactured utilizing high speed curtain coating technique. The coating structure consists of a mineral pigment layer coated on top of a barrier layer. The combination of the two layers allows for controlling the absorption of ink solvents. By adjusting the thickness, porosity and surface energy of the top-coating the printability can be tuned for various functional inks. Focus was set on printing conducting silver and carbon inks, both with nano- and micrometer sized particles, as well as printing of an organic semiconductor, poly(3-hexylthiophene). The pore volume in the top-coating determined the spreading of the micrometer sized silver ink as well as the amount semiconductor per area required, whereas the pore size was the determining factor regarding penetration of the nano-sized silver ink. As a proof of concept hygroscopic insulator field effect transistors were printed on the multi-layer curtain coated paper using a custom-built roll to roll hybrid printer.