Ink Drying Research Articles

Theoretical Modeling of Catalyst Layers for Polymer Electrolyte Fuel Cells with Different Fabrication Processes and Analysis of the Morphologies

Polymer electrolyte fuel cells (PEFCs) have attracted much attention as power sources for automobiles and stationary cogeneration systems. For further cost reduction of PEFCs, it is necessary to optimize catalyst layer (CL) structure to reduce Pt loadings. The CL is a porous structure typically consisting of Pt, carbon, ionomer, and pores, and needs to effectively form conductive pathways for electrons, H+, and gas to the surface of the Pt catalyst. However, even with state-of-the-art techniques1), the CL structure has not yet been optimized, because it remains difficult to modify flexibly the morphologies and to analyze them accurately due to the heterogeneous nanoscale structure. In particular, effects of CL fabrication processes such as spraying, bar coating, and freeze drying of catalyst ink on the morphology of CL have not been sufficiently investigated2). Hence, this research focuses on the modeling and analyses of the morphology of CLs by use of computational techniques3). Three types of different fabrication processes are modelled and compared with each other. The model CLs are characterized numerically by analyzing the morphologies with a newly developed algorithm. From the results, the effects of CL structures on the cell performance and overvoltages are discussed. CL Modeling process: First, 100 types of carbon aggregates were designed by connecting 25 primary particles, each of which is a perfect sphere 30 nm in diameter. The aggregates are randomly chosen and packed in the analysis domain (600 nm × 600 nm × 1.2 um) at a space resolution of 2 nm, until the total volume fraction of carbon reaches 0.5. In this process, three types of filling methods were prepared (Fig. 1a). In the 3D random filling model, aggregates were placed in 3D random positions. In the accumulated model, aggregates were accumulated from bottom to top of the analysis domain. In the arranged model, aggregates were placed from the bottom edge and lined up from bottom to top. After fabrication of the carbon structure, 4 nm Pt particles were loaded on the carbon surface until the Pt loading was equivalent to 0.3 mg/cm2 at a Pt/carbon weight ratio of 1.0, and ionomer was covered on the surface of both Pt and carbon until the ionomer/carbon weight ratio was equivalent to 1.0. The CL morphologies such as pore size distributions (PSDs), Pt inter-particle distances, ionomer coating thickness distributions, ionomer coverage on the Pt surface, and tortuosity of pore, ionomer, and carbon were measured by the computational algorithm. Results: Fig. 1 shows the fabrication processes and model CLs in each filling method. Fig. 2 and Fig. 3 show the PSDs and tortuosity of pore, carbon, and ionomer in each model. In the 3D random filling, the mean pore size was 58 nm and the tortuosities of pore, carbon, and ionomer were 2.3, 7.3, and 6.5, respectively. The CL structure appears sparse, and the mean ionomer covering-thickness was lower than those of the accumulated CL and the arranged CL. As the result, the pore tortuosity was lower and both carbon and ionomer tortuosity were higher than those of the other CLs and indicated higher O2 diffusivity and lower conductivity of H+ and electron. In the accumulated model, larger pores (> 100 nm) were probably formed due to a steric hindrance effect of the accumulated aggregates. In the arranged model, the CL structure appears dense, and the mean pore size was lower than the others. Accordingly, the pore tortuosity of the arranged CL was higher, and both carbon and ionomer tortuosity were lower than the others, assuming higher conductivity of H+ and electrons and lower O2 diffusivity. These results indicate that the fabrication process has a significantly influence on the CL morphologies, and there are trade-off relationships between H+, electrons, and O2 diffusion in each structure. In order to balance these parameters, further CL models, such as oriented pillars and cubic frames, have been developed and their characteristics discussed. This work was partially supported by funds for the “Superlative, Stable, and Scalable Performance Fuel Cell (SPer-FC)” Project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Black phosphorus ink formulation for inkjet printing of optoelectronics and photonics

Black phosphorus is a two-dimensional material of great interest, in part because of its high carrier mobility and thickness dependent direct bandgap. However, its instability under ambient conditions limits material deposition options for device fabrication. Here we show a black phosphorus ink that can be reliably inkjet printed, enabling scalable development of optoelectronic and photonic devices. Our binder-free ink suppresses coffee ring formation through induced recirculating Marangoni flow, and supports excellent consistency (< 2% variation) and spatial uniformity (< 3.4% variation), without substrate pre-treatment. Due to rapid ink drying (< 10 s at < 60 °C), printing causes minimal oxidation. Following encapsulation, the printed black phosphorus is stable against long-term (> 30 days) oxidation. We demonstrate printed black phosphorus as a passive switch for ultrafast lasers, stable against intense irradiation, and as a visible to near-infrared photodetector with high responsivities. Our work highlights the promise of this material as a functional ink platform for printed devices.

Homogeneous Surface Profiles of Inkjet-Printed Silver Nanoparticle Films by Regulating Their Drying Microenvironment

Obtaining homogeneous surface profiles of inkjet-printed silver nanoparticle films (SNFs) is severely hampered by the classical coffee-ring phenomenon. Traditional approaches to suppress the coffee-ring effect are achieved by improving the uniformity of liquid evaporation rate or introducing inward Marangoni force during ink drying. However, these existing methods involve extra chemicals, treatments, or equipment that will definitely increase the production cost or reduce conductivity. In this study, we demonstrate an inexpensive and efficient method to obtain uniform surface profiles of inkjet-printed SNFs by rationally regulating the drying microenvironment. To this end, a number of surface profiles of printed dots and lines, such as concave, convex, and flat, were first obtained via this method. The underlying principle of this method was then investigated by analytical calculations based on the simplified vapor diffusion model. Consequently, homogeneous surface profiles of inkjet-printed SNFs were ach...

Low band‐gap CuIn(S,Se)2 thin film solar cells using molecular ink with 9.5% efficiency

Vacuum free, solution based routes to the preparation of chalcopyrite absorbers for solar cells promise options in device design and manufacturing that are not provided by the standard vacuum based approaches. In order to fully exploit these options, the precursor should contain neither nanoparticles nor hazardous chemicals, and it should be stable under ambient conditions. In this contribution we report on CuIn(S,Se)2 thin film preparation based on spin coating of an air stable molecular ink containing metal chlorides and thiourea in organic solvents. Several key parameters directly influencing the performance of the resulting solar cells have been identified. Wetting of the glass/Mo substrate has been adjusted by varying the concentration of ethylene glycol butyl ether in the ink. Before annealing in Ar/Se at atmospheric pressure, several cycles of ink deposition and drying can be used to increase the thickness of the precursor stack. Careful balancing of ink concentration, number of precursor deposition cycles, and annealing temperature profile will transform the multi‐layer precursor into a sufficiently thick, continuous, large grained film as required for high quantum efficiency, and good red response of the cells. These optimizations aimed at high photo current have already led to an efficiency of 9.5%.

38-3:Invited Paper: Solution Printing for OLED Televisions

DuPont Displays recently leveraged its nozzle printing experience to develop high performance inkjet materials with a focus on mass production challenges. We will discuss the status of key developments in ink containment, pixel wetting and drying, integrated process/material considerations, ink formulation and rheology, particularly for HIL/HTL materials. A summary of the latest printed performance metrics and future material considerations will be discussed.

Effect of Nano-Silver Ink Composition and Drying Behavior on Its Adhesion on Glass Substrate

The adhesion of silver colloids to a glass substrate was investigated in this study. The silver colloids first added nano-TiO2 particle by varying solid content and changed pH to 10 to make sure the solution dispersion well. The adhesion of silver colloids to the glass substrate after sintering was then measured according to both ASTM D4541 and ASTM 3359 standards. The results indicated that adhesion increased proportionally with TiO2 solid content; however, this enhancement effect was lessened when the solid content was above 8wt%. Sintering temperature was also beneficial in increasing adhesion to the substrate; however, the electrical resistance of the silver colloids after sintering increased with degree of solid content. This implied that TiO2 solid content simultaneously made adhesion and electrical resistance increased. Consequently, values of TiO2 solid content and sintering temperature were optimal when adhesion and electrical resistivity were balanced. Ultimately, using commercial software Origin to fit the TiO2 solid content and sintering temperature to get the optimum value of adhesion and electrical resistivity.

Roll-to-roll infrared (IR) drying and sintering of an inkjet-printed silver nanoparticle ink within 1 second

The scheme shows the experimental setup of roll-to-roll infrared drying and sintering of inkjet-printed silver layers on flexible polymer substrates.

Memories of the Ottoman Empires Entry into the First World War

The Ottoman Empire's entry into the First World War and how it occurs in a process and the conditions under which the subject is extremely important in terms of recent history. Because the First World War, six centuries has resulted in the liquidation of the Ottoman Empire. From the Armistice more ink drying and Sevre paved the way for foreign occupation and intervention has led to the Turkish War of Independence. An independent state under the debris of destroyed large Turkey, under the leadership of Ataturk many years with great dedication and achievement are established by the National Struggle. It is therefore that the Ottoman Empire's entry into the war, perhaps more than the war itself were discussed. Today we rotate back to relive the events is not possible. But good to analyze what happened , they take lessons from this day to try to make the right decisions is the duty of the Turkish nation. Already Republic of Turkey, The lessons of these events have taken, II. World War didn‟t enter

Determination of color changes of inks on the uncoated paper with the offset printing during drying using artificial neural networks

This study attempts to determinate color changes based on time in inks applied on the surface of wood-free uncoated paper with offset printing during drying. This study consists of two main cases: (1) Experimental analysis: By preparing a test page according to the 12647-2 principle with an offset printing system, test prints were applied to 120 g/m2 wood-free uncoated paper using an ECI 2002 CMYK test chart. Each press was measured being subject to process every 15 min in the first 2 h, then hour by hour between 2 and 12 h, then 4---4 h between 12 and 24 h, and then 6---6 h between 24 and 48 h. CIELAB and reflectance values between 380 and 720 nm of the target, 1,485 colors of the test chart were obtained. To see the drying and color changes of the ink on paper, changes were determined by printing on the paper and applying artificial neural network (ANN) to spectrophotometer data at the stated time intervals. (2) Empirical analysis: The use of the ANN has been proposed as numerical approach to get of empirical equations of color changes in inks applied on the surface of wood-free uncoated paper with offset printing during drying. Based on the outputs of the study, ANN model can be used to estimate the effects of digital proofing systems used in color management on print quality with high confidence with the use of the acquired equations without experimental study. In the study, as colors are defined in terms of wave length, in case, all wave lengths are taken into consideration, certain wave length changes have been taken into consideration.

The influence of printing inks on work conditions and environment: Application of ecological colour

This paper analyses the influence of content of printing inks (and different materials used in their production) on work surrounding and the environment, with the special review on eco inks usage. Printing ink presents dispersive system made of number of different components (pigments, vehicle, adhesive materials, aid materials etc.), which all brought together give specific properties suitable for the printing. During production, ink components are put under intensive homogenization and create a paste of specific consistency. Printing inks contain different kinds of organic and inorganic matter, which can be emitted to the air, soil and water, sometimes causing long-lasting damages to the environment. Beside that, toxic and dangerous vapors from inks violate quality of working surrounding and present the threat for employees in printing facilities. Pigment gives color in printing process and presents the most important constituent of the printing ink. Pigment usually contains different heavy metals, while some oils contained in inks, present distillation derivates of crude petroleum and are dangerous substances which might be cancerous. From the aspect of environmental protection, optimal content of printing ink is unavailable to determine, because each printing technique dictates its own demands in printing - quality and printing speed (connected with the properties of ink drying). Thus, the possibility of substitution dangerous substances in printing inks by less dangerous or harmless is limited. Printing process is sensitive to the paper and ink properties, the way of paper production was done and the origin of other repro materials in printing industry. It is the fact that 'eco inks' can't achieve the same results and quality in printing as traditional inks. In that reason, some other measures can be also effective in protecting employees and the environment from the harmful effect of printing inks constituents. Uprising the consciousness of employees and the management of the printeries, conducting of preventive measures and measures for occupational safety present the main moto for socially and environmentally responsible printing business. The highest responsibility in preserving lives and the environment is on the state itself - to implement laws, to concern about their enforcement and to encourige and stimulate printeries to use recycled materials and eco inks.

Relating ink solvent-coating component thermal properties to smearing and development of abrasion resistance in ink jet printing

Abstract The target of this study was to identify the interactions of the compounds of printing ink and paper coating colour and their effects on the inkjet print quality. Interactions between inkjet ink solvent components and their interaction with paper coating compounds are considered significant for the final print quality. Especially, ink solvent properties play an important role in inkjet ink drying. The methods used to study these interactions are thermogravimetry (TGA) and differential scanning calorimetry (DSC), and results are analysed for correlations with print quality. The experimental material consists of both commercial and model inkjet inks, paper coating colour compounds and commercial papers. To visualize the thermal data and to combine the TGA and DSC measurements in a single plot, a representation has been used, in which the specific gravimetric (TGA) and specific energy (DSC) ratios, m1/m2 and E1/E2, corresponding to the mass loss and energy consumed per unit mass of sample, in the temperature regions T &lt; 100°C and 100°C &lt; T &lt; 220°C, respectively, are plotted against each other. The determined ratios differed greatly between different model solvents and ink series. The thermal behaviour of the solvents is seen to be relevant for predicting inkjet print quality.

A review of modified surfaces for high speed inkjet coating

There are many interaction phenomena occurring between inks and the printed surface during the inkjet ink setting and drying process on coated papers. First, the ink wets the surface and then absorption into the capillary network occurs. After milliseconds, the colourant and solvent/diluent parts of the ink separate. Wetting of the coating surface, and the interior of the capillary network, depends on the relative surface energies of the components being brought into contact, and their interaction may include selective adsorption. Additionally, diffusion phenomena occur a few seconds after the ink arrives at the surface, which may be vapour dependent or liquid–liquid and liquid–solute concentration dependent. The final ink drying and polymerization can last for hours. The interactions have a direct connection to the final print quality. The most important properties of the coated surface are the porous structure parameters – pore size, amount and the network they form – and the chemical nature. In the beginning, at the first contact of the ink with the surface, the chemical properties of the coating layer and the ink dominate. As the mobile ink components penetrate deeper into the coating structure, the pore structure becomes more important. In some cases, depending on the nature of the binder (water soluble and/or emulsion polymer-based), the ink diluent or solvent may enter the intermolecular structure of the binder of the coating layer by diffusion, and the binder often swells as a result. A more hydrophilic binder in contact with water-based ink swells more than the one that is less hydrophilic. The most important control parameters in designing inkjet print surfaces, from the point of view of ink spreading and penetration, are the porosity, permeability, thickness/bulk, sizing (hydrophobizing), moisture content, temperature, and capillary structure of paper. Depending on whether an ink is dye-based or pigment-based, a main aspect that affects the print quality is the distribution and permanence of the colourant. The aim, in the inkjet ink setting process, apart from providing a dried ink surface, is to fix the colourant part of ink at or in the uppermost layer of the coating whilst allowing the diluent/solvent part of ink to penetrate deeper into the structure. Proper colourant fixation produces high optical print density, bright colour tones, high sharpness, low bleeding, low print-through, and high rub and wet resistance.

Inkjet Printing of Swathe-Free Displays

Visible swathes are an unwanted artefact of the inkjet printing process used in the production process for displays, and the reduction or elimination of swathes is crucial to producing displays of high quality. Causes of swathing such as physical swathes due to dried film asymmetry at swathe joins and drop volume variability have been identified and are described.As a result significant developments have been made in these areas. New ink formulations have significantly reduced the occurrence of physical swathe joins caused during the drying of inks, and print process and strategy, for example through the use of interlacing, have enabled very high quality displays to be produced with the inkjet printing process at CDT.

Fabrication of a Gated Cold Cathode Using the Inkjet Embedding Method

We proposed the inkjet embedding method for fabrication of a gated cold cathode. In fabrication of the gated cold cathode, a conventional photolithography and a newly developed system for inkjet printing were used for the gate aperture opening and the ink embedding, respectively. It was found that the surface free energy control before embedding of the ink, the ink drying, and separation between the gate electrode and the ink are the key steps to successful fabrication of the gated cold cathode. We also demonstrated the field electron emission from the gated cold cathode. The turn-on voltage was about 40 V, and an anode current of about 3 µA was obtained at the gate voltage of 120 V.

Growth and design of deep-UV (240–290 nm) light emitting diodes using AlGaN alloys

Solid-state light sources emitting at wavelengths less than 300 nm would enable technological advances in many areas such as fluorescence-based biological agent detection, non-line-of-sight communications, water purification, and industrial processing including ink drying and epoxy curing. In this paper, we present our recent progress in the development of LEDs with emission between 237 and 297 nm.We will discuss growth and design issues of deep-UV LEDs, including transport in Si-doped AlGaN layers. The LEDs are designed for bottom emission so that improved heat sinking and light extraction can be achieved by flip chipping. To date, we have demonstrated 2.25 mW of output power at 295 nm from 1 mm×1 mm LEDs operated at 500 mA. Shorter wavelength LEDs emitting at 276 nm have achieved an output power of 1.3 mW at 400 mA. The heterostructure designs that we have employed have suppressed deep level emission to intensities that are up to 330×lower than the primary quantum well emission.

Using Ultrasonic Energy to Improve the Ink Drying Process: A Feasibility Study

It has recently been proposed to use ultrasonic energy to dry ink jet printed materials. This work presents the results of a feasibility study of such technology. Both calculations and experiments show that direct heat transfer may be of significant influence only for MHz range ultrasonic frequencies. Thus, any attempt to use ultrasonic energy to speed drying on non-absorbing substrates should involve moving to MHz frequencies, and this move may prove useful.

Effect of Paper Properties on Print Quality of Ink Jet Printer

The interactions of ink jet inks with the substrate are very complex and dependent on various parameters. Since aqueous-based inks are most popular, this work is concentrated on aqueous-based inks in drop-on-demand printer. The rapid growth of ink jet printers has created a rapid expansion of ink jet paper market. However, it requires proper understanding of ink drying and ink-paper interaction. Wide variation of print quality is expected due to variation of ink formulation and paper properties. The print quality is highly dependent on paper properties specifically on its smoothness and absorption characteristics. In this study, the smoothness and absorption properties of different grades of papers are measured. A Bristow tester is used to study ink-paper interaction and drying time at different circumferential speeds. It has been seen that the paper properties have a significant effect on print quality. The study shows that the smoothness and the absorption characteristics of paper affects ink-paper interaction and finally the Image quality of printer.

The effect of process parameters on product quality of rotogravure printing

This paper describes an experimental investigation into the process parameter effects on product quality in rotogravure printing. A production printing press was instrumented for the measurement of parameters including strategic temperatures, speeds and web tension. Through-the-run analysis was used to evaluate the fluctuation of the press parameters and the product quality. The trials indicated the parameters where process control is important and allowed the elimination of several parameters, including ink drying, from the main experimental programme. The parameters selected for the main experiments were those most often used for control purposes, or those that were varied between print jobs. Orthogonal array experiments were used, as these allow the simultaneous variation of several parameters and the investigation of interactions between parameters. The experiments were performed using a typical commercial print run once the production of saleable copy had been completed. The analysis of the print quality was carried out in the image areas using spectrophotometry. The experiments highlighted the sensitivity of the process to changes in ink viscosity and the non-linearity of the response. Doctor blade setting was also found to be important, whereas blade load and impression pressure had negligible impact. No interactions were found between any of the parameters investigated. For viscosity change, analysis of the printed image confirmed the importance of hydrodynamic mechanisms, but it was not possible to isolate ink dilution. For doctor blade angular setting, hydrodynamic behaviour appears secondary to cell transport and release mechanisms. This latter mechanism requires further investigation in order to establish a clear understanding.

Simultaneous convective heat and mass transfer in impingement ink drying

Effective and economical drying of the ink is essential in the printing, packaging and converting industries. In evaporative drying, high heat and mass transfer rates are commonly achieved by means of high velocity impinging air jets To provide data for dryer designer a programme of research has been implemented to study the heat and mass transfer processes which underlie the drying of thin ink rims The heat transfer situation under impinging air jets is outlined and some experimental results are presented. Optimization of nozzle arrays for impinging air jets is analysed for practical applications. A non-contact infra-red technique for continuously monitoring the ink drying process is described and drying curves for an ink based on a single solvent (4-Methyl-2-pentanol-MIBC) are presented. Heat and mass transfer theory has been used to predict dry ing limes in the constant rate drying period These predictions have been compared with experimentally determined doing times This research has served to confirm the fundamental importance of the dry ing curve as a basis for dryer design.

Drying of Water-Based Inks on Plain Paper

Previous studies in ink-jet printing have considered ink penetration into paper or ink evaporation to be effective in the drying process. In the present study, a unified approach that allows for simultaneous evaporation and penetration during the drying process was applied. To this end, penetration rates were measured experimentally using a Bristow tester. In addition, evaporation rates were determined from a theoretical evaporation model that contained no adjustable parameters. It was found that for plain paper used in the office environment, the rate of penetration was at least 20 &#xD7; higher than the rate of evaporation. Accordingly, ink drying is determined mainly by penetration, and penetration curves alone are sufficient to predict the dry time or ink disappearance on a plain paper surface. In practice, this is illustrated by ink-jet print quality on plain papers of various sizing treatments. The sizing level needs to be adjusted according to the desired ink-jet image. That is, full-color printing requires penetration rates sufficient to accommodate each of the process inks applied without color bleed or other ink-to-ink interaction processes. This may be at expense of character and line print deterioration due to fiber swelling in mono-color printing.