Eifion Jewell

The effect of exposure to inks and solvents on squeegee performance

SummariesThe squeegee in screen printing forces ink into the screen and the screen into contact with the substrate. The squeegee, which is manufactured from polyurethane, has a major influence on screen printing quality. This paper summarises an experimental programme into the durability of squeegees when exposed to inks and solvents. The softer the squeegee the more il was affected by exposure to any ink or solvent with the increases in mass of up to 14%, increases in volume of up to 12%, and reductions in elastic modulus of up to 80%. The low boiling point cleaner and solvent ink had the greatest effect of all the liquids tested. Distortion of the samples during solvent absorption caused small errors in the measurement of the volume and elastic modulus of the samples. The measurement in the increase in mass of the sample provided the most reliable method for estimating any ink/squeegee compatibility problems. Relaxation in the air returned the squeegee to its original mass. No clear relationship could be established between the surface roughness of the sample and the change in squeegee properties.Exposure to ultraviolet (UV) ink increased the mass of the sample with time. Unlike exposure to solvent-based inks, the effect of UV exposure was cumulative with relaxation between exposures doing little to reduce the mass of the squeegee. Relaxation of the squeegee over a two-week period of time under room temperature conditions did little to reduce the mass back to its original level. A printing experiment with an ‘inked’ and new squeegee showed that a two-hour exposure caused a hard squeegee to act like a medium and resulted in a 0.05 increase in printed density. Finite element modelling of a ‘compound’ squeegee showed that the change in modulus had a significant effect on the deformation of the squeegee tip.RésuméDans le cadre de la sérigraphie c’est le squeegee qui force l’encre à pénétrer la claie et la claie à entrer en contact avec le substrat. Le squeegee, qui est fabriqué de polyuréthane, a une influence majeure sur la qualité des impressions sérigraphiques. Cet article résume un programme expérimental conçu pour examiner la durabilité des squeegees quand ils sont exposés aux encres et aux solvants. Plus le squeegee était souple plus il était affecté par son exposition à n’importe quel encre ou solvant, avec des accroissements de la masse de jusqu’à 14%, des accroissements du volume de jusqu’à 12% et des diminutions du module élastique de jusqu’à 80%. Parmi toutes le liquides testées, l’encre au solvant et le produit de nettoyage à point d’ébullition bas avaient le plus grand effet. La déformation des échantillons pendant l’absorption des solvants a causé de petites erreurs en ce qui concerne la mesure du volume et du module élastique des échantillons. La mesure de l’accroissement de la masse de l’échantillon représentait la méthode la plus fiable d’évaluer des problèmes dans le domaine de la compatibilité squeegee/encre. Une diminution [de la pression] de l’air a restitué le squeegee à sa masse originale. On ne pouvait pas établir un clair rapport entre la rugosité de la surface de l’échantillon et les variations des propriétés du squeegee.Au fil du temps, l’exposition à l ’encre UV a augmenté la masse de l’échantillon. Contrairement au cas de l’exposition aux encres au solvant, l’effet de l’exposition UV était cumulatit et les relâchements entre expositions n’ont pas fait grand-chose pour réduire la masse du squeegee. L’inactivité du squeegee pendant une période de deux semaines à température ambiante n’a pas fait grand-chose pour réduire la masse à son niveau original. Une expérience d’impression avec un squeegee enduit d’encre et un squeegee neut a démontré qu’une exposition de deux heures a provoqué un squeegee dur à agir en tant que médium et a abouti à un accroissement de la densité d’impression de 0.05. Le modelage par élément fini d’un squeegee composé a montré que le tait de changer le module a eu un effet signifiant sur la détormation du bout du squeegee.ZusammenfassungDer Rakel wird im Siebdruck eingesetzt, um Tinten und Farben in den Sieb, und den Sieb in Kontakt mit dem Substrat zu bringen. Der polyurethanrakel hat einen grossen Einfluß auf die Druckqualität. Diese Arbeit faßt ein experimentelles Programm zusammen, die Haltbarkeit des Rakels under Aussetzung zu Lösungsmitteln und Druckfarben zu bewerten. Je weicher der Rakel, desto stärker wurde er von Druckfarben und Lösungsmitteln angegriffen, mit dem Effekt daß die Masse des Rakels um bis zu 14% zunahm, das Volumen um 12% zunahm, und die Elastizität um bis zu 80% abnahm. Der leicht flüchtige Reiniger und lösungsmittelreiche Farben hatten den größten Effekt. Die Distortion der Proben durch Lösungsmitteladsorption verursachte kleine Fehler bei der Messung des Volumens und der Elastizität der Proben. Die Gewichtszunahme stellte sich als die zuverlässigste Methode heraus, Inkompatibilitätsprobleme zwischen Rakel und Farben vorherzusagen. Nach einiger Zeit and der frischen Luff kehrte der Rakel zu seinem Originalgewicht zurück. Wir stellten keine klare Verbindung zwischen der Oberflächenaufrauhung der Rakelprobe und der Veränderungen der Rakeleigenschaften fest.UV-Druckfarben hatten auch den Effekt, mit der Zeit das Gewicht des Rakels zu erhöhen. Im Gegensatz zu lösungsmittelhaltigen Farben war der UV-Effekt kummulativ, und Zeit an der Frischluff hatte kaum einen Effekt auf das Rakelgewicht, selbst über einen Zeitraum von zwei Wochen bei Raumtemperatur. Ein Druckexperiment, einen von Farben angegriffenen Rakel mit einem neuen Rakel zu vergleichen, zeigte, daß sich das angegriffene Rakel nach zwei Stunden Druckzeit wie ein Medium verhält und die Druckdichte um 0.05 erhöht. Ein finites Elementmodell eines “compound” Rakels zeigte daß die Veränderung des Modulus einen deutlichen Effekt auf die Deformierung der Rakelspitze hatte.

Viscosity control in the screen printing of ceramic transfers

SummariesThis paper describes an experimental investigation into process parameter effects and viscosity variation on colour control in the printing of ceramic transfers. This has been achieved through the completion of controlled experiments and monitoring of a commercial production run. The findings indicate that process parameter adjustments have only a small impact on print quality, the most dominant term being ink viscosity variation through solvent evaporation. Through determination of the dependence of colour change on viscosity change, coupled with the dependence of viscosity on solvent addition, it has been possible to establish a strategy for solvent addition. This was found to be most sensitive at low solvent addition levels and this identifies the need for close viscosity control to ensure consistent colour quality. The methodology that has been established in this work is also applicable to other ink systems where significant carrier loss is experienced during a printing run.RésuméCet article décrit une enquête expérimentale sur les effets des paramètres de procédé et des variations de viscosité, sur le contrôle de la couleur dans le domaine des décalcomanies pour céramiques. Ce but a été atteint grace à la réalisation des expériences contrôlés et à la surveillance de l’opération d’une chaîne de fabricatiion commerciale. Les résultats indiquent que les ajustements des paramètres de procédé n’ont que peu d’ influence sur la qualité de l’impression. L’élément qui a le plus grand impact est la variation de viscosité due à l’évaporation du solvant. Grace à la détermination du fait que le changement de la couleur dépendait de la variation de viscosité et que la viscosité dépendait de l’addition du solvant, il fut possible d’établir une stratégie vis à vis de l’addition du solvant. Il a été trouvé que cette stratégie était au plus sensible quand les niveaux du solvant étaient bas. Cela indique le besoin de bien contrôler la viscosité afin d’assurer une qualité de couleur qui soit invariable. La méthodologie qui a été étabolie au cours de ce travail a des applications dans le cadre d’autres systèmes d’encre où il y a des pertes notables de l’élément porteur de l’encre pendant un tirage.ZusammenfassungDiese Arbeit beschäftigt sich mit der experimenteller Erforschung des Effekts verschiedener in Prozessparameter und Viskositäten auf die Farbkontrolle beim Drucken von keramischen Transfers. Dieses wurde erreicht durch ein kontrolliertes Experiment und durch die Beobachtung eines kommerziellen Produktionsdurchlaufes. Unsere Ergebnisse zeigen, daß die Veränderung der Prozeßparameter nur einen geringen Einfluß auf die Druckqualität hat. Ein wesentlich größeren Einfluß hatte die Veränderung der Farbviskosität durch die Verdunstung des Lösungsmittels. Wir ermittelten wie die Farbveränderung von der Viskosität abhängt, und wie wiederrum die Viskosität von der Zugabe von Lösungsmitteln abhängt. So gelang es uns, eine Strategie für die korrekte Beigabe von Lösungsmitteln zu entwickeln. Wir fanden daß die Viskositätskontrolle bei geringem Lösungsmittelzusatz besonders empfindlich war, das heißt daß die Viskosität besonders gut kontrolliert werden muß um eine gleichbleibende Farbqualität zu erreichen. Diese Methode kann auch in anderen Drucksystemen verwendet werden, wo ein deutlicher Verlust des Farbträgers während des Druckvorganges zu erwarten ist.

The impact of carbon content and mesh on the characteristics of screen printed conductive structures

Purpose – The purpose of this paper is to carry out a comprehensive experimental investigation into the role of screen and conductive carbon material formulation on line conductivity and printing capability in the screen printing process, to provide design knowledge and further understanding of the screen printing for printed carbon.Design/methodology/approach – A full factorial experiment was carried out where six carbon materials were printed through ten screens to a polyester substrate under a set of standard conditions.Findings – Material characterization showed that viscosity and the corresponding viscous and elastic material modulli increased with solids content and that the elastic properties at low shear are significant. The solids carbon content materials were unable to produce the minimum printable line features possible with the low carbon materials. Increasing the solids contents reduced the final cured line resistance, reduced the printed line width, increased the film thickness, increased th...

An investigation into screen printing using UV process colour inks

SummariesThis paper presents the results from a comprehensive exploration of printing sequence based on dot gain, colour gamut and grey balance characteristics for screen printing. The tests involved designing a test image and this included the successful incorporation of a novel feature to explore grey balance. This allowed the three process colours, cyan, magenta and yellow, to be varied independently. The results confirmed the excellent repeatability of the process when printing a conventional UV ink. The results also showed the small impact of increasing the ink base up to 30% on tone gain and the colour range was not affected by the printing sequence.The results showed that print sequence had a major effect on the grey balance, and this was traced to the effect of a gasket on the stencil, and that half-tone dots from the first print effectively generated a rough surface that affects the gasket formed by the stencil. The results show that tonal reproduction and colour range measurements are not appropriate quality indicators. For precision screen printing, quality measurement should be made on the image, and that separation and screen preparation needs to account for process settings and the printing sequence used.RésuméCet exposé présente les résultats à partir d’une exploration compréhensive de la séquence d’impressions basée sur le gain de points, la gamme de couleurs et la mise au point du gris, pour sérigraphie. Les essais comprennent également la conception d’une image d’essai qui a renfermé avec succès une nouvelle caractéristique à l’exploration du rapport gris. Ceci a permis aux trois couleurs du procédé, cyan, magenta et jaune, de se varier indépendamment. Le résultats ont confirmé que la répétition du procédé donne d’excellents résultats lors de l’impression avec une encre d’imprimerie UV de convention. Les résultats démontraient aussi que le faible effet de l’augmentation de l’encre jusqu’a 30% sur le gain de points et sur la gamme de couleur n’était pas altéré par la séquence d’impressionLes résultats ont démontré que la séquence avait un effet important sur la mise au point du rapport gris, imputable à l’effet de cloisonnage du pochoir, et que les points demi-teinte à partir de la première impression ont créé une surface rugueuse qui a un effet sur le cloisonnage du pochoir. Les résultats démontrent que la réproduction tonale et les mesures de la gamme de couleurs ne sont pas convenables en tant qu’indicateurs de qualité. Les mesures de qualité de sérigraphie de précision doivent être effectués sur l’image. La séparation et la préparation du tamis dovient déterminer les ajustements du procédé et la séquence d’impression utilisée.ZusammenfassungDiese Arbeit zeigt die Ergebnisse einer umfassenden Analyse von Drucksequenzen basierend auf den Punkt Gain, Farbgamut und Graubalance-Werten von Screen Printing. Die Analyse basiert auf dem Entwurf eines Testbildes und beinhalted eine neuartige Methode um die Graubalance-Werte zu ermitteln. Dadurch konnten die drei Prozessfarben, Cyan, Magenta und Gelb, individuell variiert werden. Die Ergebnisse bestätigten die hervorragende Wiederholbarkeit des Prozesses unter Verwendung einer konventionellen UV-Druckfarbe. Die Ergebnisse zeigten auch den kleinen Einfluss erzielt mit der Anhebung der Tintenbasis um bis zu 30% auf die Tonstärke. Die Farpalette wurde durch die Drucksequenz nicht beeinflusst.Die Ergebnisse zeigten weiter daß die Drucksequenz einen starken Einfluss auf die Graubalance hatte. Dies wurde auf den Effekt der Dichtung auf die Matritze zurückgeführt, und darauf daß Halb-Ton Punkte vom ersten Druckvorgang eine rauhe Oberfläche generierten, das die von der Matritze produzierten Dichtung beeinflusst. Die Ergebnisse zeigten auch daß Ton-Reproduktion und Farbpalette nicht angemessene Qualitätsindikatoren sind. Für Präzisions-Screen Printing sollte die Qualität am Bild gemessen werden, und die Trennung und Vorbereitung des Screens sollte beachtet werden für die Prozess-Einstellungen und die verwendete Drucksequenz.

Printed silver circuits for FMCG packaging

Purpose – Printed flexible circuits that combined conventional silicon technology will enable the realisation of many value added products such as smart packaging for the fast moving consumer goods (FMCG) industry. This paper aims to describe an investigation into integrating silicon and printable circuits for the FMCG packaging industry and this would allow products with features such as brand protection, time temperature indicators, customer feedback and visual product enhancement. Responding to interest from the FMCG packaging industry, an investigation was carried out which investigated the printing conductive silver ink on common packaging substrates. Design/methodology/approach – Standard IC mounting patterns were screen printed using two conductive silver materials (one high silver content traditional paste and one lower silver content gel polymer) to four plastic and three paper substrates which represent common FMCG substrates (HDPE, BOPP, PET and three paper substrates). Materials were character...

Homogeneous and highly controlled deposition of low viscosity inks and application on fully printable perovskite solar cells

Abstract The fully printed, hole-transporter-free carbon perovskite solar cell structure incorporating a triple mesoscopic layer has emerged as a possible frontrunner for early industrialisation. It is an attractive structure because it can be fabricated by the simple sequential screen printing and sintering of titania, zirconia, and carbon. The device is finalised by manual dropping of a perovskite precursor solution onto the carbon which subsequently infiltrates. This stage in device fabrication is inhomogeneous, ineffective for large areas, and prone to human error. Here we introduce an automated deposition and infiltration system using a robotic dispenser and mesh which delivers the perovskite precursor uniformly to the carbon surface over a large area. It has been successfully used to prepare perovskite solar cells with over 9% efficiency. Cells, prepared by this robotic mesh deposition, showed comparable performance to reference cells, made by standard drop deposition, confirming this approach to be effective and reliable. X-ray diffraction and Raman spectroscopy were used to confirm the uniformity of the deposition over a large area.

Improved Manufacturing Performance of Screen Printed Carbon Electrodes through Material Formulation.

Printed carbon graphite materials are the primary common component in the majority of screen printed sensors. Screen printing allows a scalable manufacturing solution, accelerating the means by which novel sensing materials can make the transition from laboratory material to commercial product. A common bottleneck in any thick film printing process is the controlled drying of the carbon paste material. A study has been undertaken which examines the interaction between material solvent, printed film conductivity and process consistency. The study illustrates that it is possible to reduce the solvent boiling point to significantly increase process productivity while maintaining process consistency. The lower boiling point solvent also has a beneficial effect on the conductivity of the film, reducing the sheet resistance. It is proposed that this is a result of greater film stressing increasing charge percolation through greater inter particle contact. Simulations of material performance and drying illustrate that a multi layered printing provides a more time efficient manufacturing method. The findings have implications for the volume manufacturing of the carbon sensor electrodes but also have implications for other applications where conductive carbon is used, such as electrical circuits and photovoltaic devices.

Development of measurement techniques to characterize the optical properties of transparent films with application in in-mould decoration

This paper details the development of appropriate techniques for quantifying and comparing the optical properties of transparent polymer films used in in-mould decoration (IMD) and the effects of heat and strain on these properties. Currently there are no approved methods for optical characterization of transparent films, with most techniques being based on reflectance measurement of printed materials for the graphic arts industry. Original experimentation was therefore required in order to characterize the optical properties of transparent polymer films used in IMD or similar applications and to predict the changes in appearance during the forming process. A range of measurement techniques was utilized to characterize the films and their interaction with light in terms of light scattering and transmission. As a result of the investigation, the optical properties of these films can now be quantified and the changes due to the different mechanisms of softening and crystallization can be separately distinguished.

Characterising the discharge cycle of CaCl 2 and LiNO 3 hydrated salts within a vermiculite composite scaffold for thermochemical storage

Transpired solar collectors (TSC) are an efficient means of building heating but due to the demand / use mismatch their capabilities are maximised when paired with a suitable storage technology. The Hydration and / dehydration of inorganic salts provides an appropriate energy storage medium which is compatible with the air temperature provided by a conventional TSC (<70 C). The study reports on technical appraisal of materials which are compatible with building scale energy storage installations. Two salts (CaCl2, and LiNO3) were impregnated into porous vermiculite to form a salt in matrix (SIM). Their performance during the discharge portion of the cycle at high packing density was examined using a laboratory scale reactor. Reactor and exit temperature increases were considerably lower than those predicted from first principles. Peak reactor temperature rises of only 14 C were observed with a reduction in temperature output from this initial peak over 60 hours. Poor salt utilization resulting from deliquescence near the reactor inlet was identified as being the source of the reduced performance. Changes in reactor size, orientation and cycling between input periods of moist and dry air did not improve reactor performance. The investigation has identified that moist air transit through the packed SIM reactor column is limited to approximately 100 mm AC CE PT ED M AN US CR IP T from the air inlet. This has implications for reactor design and the operation of any practical building scale installation. Predictions of building scale energy storage capabilities based on simple scaling of laboratory test considerably under estimate the volume and complexity of equipment required.

Bi directional flexible electroluminescent mouldable lamps fabricated by screen printing

We formed the GEnetics of Nephropathy–an International Effort (GENIE) consortium to examine previously reported genetic associations with diabetic nephropathy (DN) in type 1 diabetes. GENIE consists of 6,366 similarly ascertained participants of European ancestry with type 1 diabetes, with and without DN, from the All Ireland-Warren 3-Genetics of Kidneys in Diabetes U.K. and Republic of Ireland (U.K.-R.O.I.) collection and the Finnish Diabetic Nephropathy Study (FinnDiane), combined with reanalyzed data from the Genetics of Kidneys in Diabetes U.S. Study (U.S. GoKinD). We found little evidence for the association of the EPO promoter polymorphism, rs161740, with the combined phenotype of proliferative retinopathy and end-stage renal disease in U.K.-R.O.I. (odds ratio [OR] 1.14, P = 0.19) or FinnDiane (OR 1.06, P = 0.60). However, a fixed-effects meta-analysis that included the previously reported cohorts retained a genome-wide significant association with that phenotype (OR 1.31, P = 2 × 10−9). An expanded investigation of the ELMO1 locus and genetic regions reported to be associated with DN in the U.S. GoKinD yielded only nominal statistical significance for these loci. Finally, top candidates identified in a recent meta-analysis failed to reach genome-wide significance. In conclusion, we were unable to replicate most of the previously reported genetic associations for DN, and significance for the EPO promoter association was attenuated.