Modeling and Optimizing Industrial Inkjet Printhead for Printable Electronics Fabrication

The major challenge in printable electronics fabrication is to effectively and accurately control a drop-on-demand (DoD) inkjet printhead for high printing quality. In this work, an optimal prediction model, constructed with the lumped element modeling (LEM) and the artificial bee colony (ABC) algorithm, was proposed to efficiently predict the combination of waveform parameters for obtaining the desired droplet properties. For acquiring higher simulation accuracy, a modified dynamic lumped element model (DLEM) was proposed with time-varying equivalent circuits, which can characterize the nonlinear behaviors of piezoelectric printhead. The proposed method was then applied to investigate the influences of various waveform parameters on droplet volume and velocity of nano-silver ink, and to predict the printing quality using nano-silver ink. Experimental results show that, compared with two-dimension manual search, the proposed optimal prediction model perform efficiently and accurately in searching the appropriate combination of waveform parameters for printable electronics fabrication.

In order to rival the quality of silver halide photographs, digital printing systems need to satisfy issues of high print quality as well as image stability. Our research and development efforts have focused on thermal dye transfer and ink jet printing systems, with extraordinarily good results in each system.Discussion will focus on the chelate reaction between dye molecules and metal ions in the thermal dye transfer printing system, which has greatly improved the image stability issues, well in excess of original targets.As for ink jet printing, attention was paid to improving the print quality. These efforts led to the world's first production of micro porous printing media with an RC-paper base. The combination of the printing media and dye inks brings the expected print quality together with other features such as quick drying cased by high ink-absorption speed, resistance to water.Work on improving image stability in ink jet systems will also be discussed.

Acoustic Inkjet Printing (AIP) is suitable for jetting a small drop when compared with other available methods because the drop size depends not on the nozzle area but on the frequency of acoustic beam that enables ejection from free liquid surface.For inkjet printing, drop modulation is the major technology being effective to realize both high image quality and high print speed. In the previous reports regarding AIP, multiple droplets were fired at the same location on paper for gray scale of image.1 This method could enhance image quality at the sacrifice of print speed.Here we propose a method of drop size modulation in AIP to achieve both high image quality and high print speed. It has been proved that the drop size is modulated by a second harmonic on fresnel lens without changing the liquid level and other dimensions. This report also shows that calculations and experiments ascertained drop modulation by the second harmonic.

SEIKO EPSON Corporation has successfully developed the original ink jet printing technology MACH. MACH has overcome all defects of the conventional piezo ink jet technology and realized high printing quality and high printing speed. In this paper, history, principle, features of MACH and other effective means for high printing quality and high printing speed are described.

Interactions of ink colourants with chemically modified paper surfaces concerning inkjet print improvement

Performance Improvement of Professional Printing Systems: from theory to practice Markets demand continuously for higher quality, higher speed, and more energy-efficient professional printers. In this thesis, control strategies have been developed to improve the performance of both professional inkjet and laser printers. Drop-on-Demand (DoD) inkjet printing is considered as one of the most promising printing technologies. It offers several advantages including high speed, quiet operation, and compatibility with a variety of printing media. Nowadays, it has been used as low-cost and efficient manufacturing technology in a wide variety of markets. Although the performance requirements, which are imposed by the current applications, are tight, the future performance requirements are expected to be even more challenging. Several requirements are related to the jetted drop properties, namely, drop velocity, drop volume, drop velocity consistency, productivity, and reliability. Meeting the performance requirements is restricted by several operational issues that are associated with the design and operation of inkjet printheads. Major issues that are usually encountered are residual vibrations in and crosstalk among ink channels. This results in a poor printing quality for high-speed printing. Given any arbitrary bitmap, the main objective is to design actuation pulses such that variations in the velocity and volume of the jetted drops are minimized. Several model-based feedfoward control techniques using an existing model are implemented to generate appropriate input pulses for the printhead. Although the implementation of the model-based techniques shows a considerable improvement of the printhead performance compared with the current performance, further improvements are still necessary. We observe that besides the pulse shape the state of the ink surface at the nozzle plate (speed, position) at the start of the pulse influences the drop velocity considerably. This state at firing depends also on previous pixels in the bitmap of the image. Consequently, any pulse design has to guarantee almost the same initial state when firing a drop. Based on these facts, a model-free optimization scheme is developed to minimize the drop velocity variations taking into account the bitmap information. Experimental results show the effectiveness of the optimized pulses. Laser printing systems are highly depending on the appropriate combination of several design factors so as to become functional in a desired working range. The physical printing process involves multiple temperature set points at different places, precise electro-magnetic conditions, transfer of toner through certain pressures and layouts, and many other technical considerations. In the laser printing system there are several challenging issues and unknown disturbances. They originate from different sources, such as the printer itself (unknown phenomena appear, disturbances that are not foreseen, wear, contamination, failures, bugs), the environment of the system (power supply variations, temperature, humidity, vibrations), and the printing media (weight, coating, thermal properties, humidity characteristics, and initial temperature). These issues have a negative effect on the stability and performance of the laser printing system. The objective is to design a control scheme to achieve printing quality requirements and a high productivity. Good printing quality means that the fusing temperature should track a certain reference signal at different operating conditions. Based on the printing system behavior, we propose two different control schemes to cope with the large parameter variations and disturbances, namely, a Model Reference Adaptive Controller (MRAC) and a nonlinear (scheduled) observer-based output feedback control scheme. Both control techniques yield considerable performance improvements compared with the present industrial controller.

Inkjet printers are the most commonly owned printers because of their low cost, high printing quality, and ease of use. The four major inkjet printer manufacturers are Canon, Epson, Hewlett-Packard, and Lexmark. The inkjet printer business has adopted the “bait and hook” business strategy, offering the basic printer product at a low (possibly below cost) price while charging a higher price for their proprietary ink cartridges. Table 1 shows the pricing of different ink jet printers and ink cartridges from the four major manufacturers. With technology advancement, inkjet printers have improved in quality and reduced in price. As seen in Table 1, the printer (being more technologically complex to make than the ink cartridge) is relatively inexpensive. This is a business tactic used to attract more people to buy the printer. The manufacturers are trying to improve their overall profit margin by charging higher prices than they would have normally done for their proprietary ink cartridges. The setting of printer and cartridge prices must therefore be closely linked and studied, as they affect the overall profitability and survival of the printer company. According to LYRA research (http://www.lyra. com/), the total revenue from inkjet printers and ink cartridges exceeded $45 billion in 2006. I.T. Strategies (http://www.it-strategies.com/) expects the inkjet printer market to grow to $58 billion by 2009. It expects the largest segment of the revenue to come from ink cartridges, with the revenue rising from $20 billion in 2004 to $33 billion in 2009. The printer business is very lucrative, and it is crucial for the survival of a company that produces printers to use a “good and flexible” business decision tool to price the printer and ink cartridges. Allan Table 1 Sample Inkjet Printer and Cartridge Prices

One of the major digital printing technologies used for production printing is dry-toner electrophotography. The main technical challenge is print quality and many researches have been done to improve it in the recent years. In our study, dry-toner color electrophotography was compared to conventional offset printing. A Xerox iGen3 press and a Heidelberg Speedmaster press were used. The substrates used were different uncoated and coated paper stocks. The GATF 11x17 Four-Color Test Form was printed on the papers by both printing presses. Print quality, such as color gamut, dot gain, print contrast, and trapping, were evaluated and compared. Higher dot gains were found on Speedmaster than on iGen3 except for black color. Higher print contrast values were found for iGen3 than for Speedmaster except for black color. Wider color gamuts were achieved on iGen3 than on Speedmaster, especially on uncoated papers. With high print quality, it is expected that more production printing will be done by dry-toner color electrophotography.

The drop-on-demand (DOD) inkjet printing technology has been widely used in many fields and several types of droplet generators are developed. This paper presents the design, fabrication and tests of a piezoelectric bend mode drop-on-demand inkjet printhead with interchangeable nozzle. A disk-type PZT is actuated to push the liquid out of inkjet printhead by a function generator, and a droplet is formed because of surface tension. The interchangeable nozzle design enables the same printhead to be fitted with nozzles of different orifice size, thus a clogged nozzle can be easily removed for cleaning or replacement. An experimental platform for micro-droplet jetting is built in this paper. The droplet formation is recorded by a CCD camera as pictures, which can be used to measure the droplet dimension. The experiments are carried out by using the self-developed bend mode piezoelectric inkjet printing system. The influence of the drive parameters on the droplet quality is also studied by dispensing water.

A thermal ink jet (TIJ) printhead suitable for high speed and high quality printing has been developed. The printhead has been fabricated by dicing the bonded wafer, which consists of a bubble generating heater plate and a Si channel plate. The Si channel plate consists of an ink chamber and an ink inlet formed by KOH etching, and a nozzle formed by ICP RIE. The nozzle formed by ICP RIE has squeezed structures, which contribute to high-energy efficiency of drop ejector and therefore successful ejection of small ink drop. These two wafers are directly bonded by using electrostatic bonding of full-cured polyimide to Si. With these technologies, we have fabricated a 1 long printhead with 832 nozzles having 800 dots per inch (dpi) resolution and a 4 pl. ink drop volume.

The human visual system has an exceptional ability to detect systematic print mottle. One type of systematic print mottle is banding on printed corrugated board, resulting in a disturbing print defect. A new method that quantifies banding on printed corrugated board is proposed. The method is based on spatial frequency analysis, and the degree of banding is determined using a band‐pass filter range adapted to fit the flute wavelength and orientation of the acquired image of the printed board. The results for B‐flute corrugated board gave a correlation coefficient of 0.98 between the technical measurements and the subjective ratings. Methods of quantifying the banding on the different types of corrugated board available on the market are discussed. Copyright © 2005 John Wiley & Sons, Ltd.

Paper for ink jet printing has to obtain optimal printing runnability, printability, and printing quality Therefore, it must have some specific properties that ensure optimal drying time, mechanical stability of a print, and its light and water resistance. The paper surface should enable the printing ink to be dried as fast as possible. The aim of the applied research was to determine how an ink jet color print on paper changes with time immediately after printing, and how long it takes for the color print to stabilize. Color differences ΔE ab were measured that appeared on print after a certain amount of time with regards to values attained immediately after printing. The influence of paper on colorimetric properties and optical density of a print was analyzed by measuring some structural, surface, and sorption properties. The values attained show that the paper surface should enable wetting and ink penetration in paper structure. The biggest changes in colorimetric properties of the print became visible during 1 h after printing; however, color print finally stabilizes only after 96 h. Research results confirmed the importance of paper sorption properties for obtaining high-quality ink jet color prints.

Coatings based on hydroxypropylated starch (HPS) provide extraordinary print density with dye-based inkjet inks, but their suitability for pigment-based inks can be limited due to inadequate carrier medium (water) absorption and colorant fixation. In the present work, HPS-based coatings were tailored for both a pigmentbased and a dye-based ink by adding silicate minerals or acid clay (both Lewis and Brönstedt acid sites present in the acid clay). Substrate-ink interaction and colorant distribution were investigated via uncoated gloss and print quality indicators such as print density, ink bleeding tendency and delta gloss after printing with desktop printers. Three-dimensional z-stack CLSM images taken from printed samples revealed substantial differences in ink holdout and penetration characteristics between the studied materials. Pigment-filled HPS coatings showed up to 60% increase in print density compared to uncoated reference substrate and an increase of up to 35% compared to plain HPS coating with dyebased inks. In case of pigment-based ink, the increase was 17% between plain HPS coating and acid-clay-filled HPS coating. In addition, a combination of HPS and silicate mineral decreased ink bleeding substantially, but lower print gloss compared to substrate initial gloss was observed with the majority of experimental coatings. It was found that the pigment type affects substantially the unprinted gloss, which is naturally high in the case of pure HPS coating, but also the observed drastic difference in substrate permeability may explain the differences in print quality. The findings suggest that coating morphology, together with chemical interactions between starch and mineral and coated substrate and ink, has a key role in achieving high gloss and good print quality.

Drop-on-demand (DoD) ink-jet printing is an efficient technology for depositing picoliter drops on various printing surfaces. DoD technology is compatible with various liquids and does not require contacting the printing media. DoD inkjet printing combines several advantages including high speed, quiet operation, and compatibility with a variety of printing surfaces. Moreover, DoD printing can make patterns without any additional lithographic process. Ink-jet printing can reduce the number of processing steps compared to conventional patterning processes, which results in a lower production cost. Therefore, DoD ink-jet technology is applied in many engineering and scientific applications (see Figure 1), such as the formation of the conductive tracks for printed circuit boards, color filters in flat panel displays and plasma displays, polymer light-emitting diode displays, organic transistors, and the construction of DNA microarrays [1]-[5].

Inkjet technology has been integrated into manufacturing processes due to (1) efficient material usage (environmentally friendly), (2) direct write process (an additive process), (3) speedy set-up (digital printing and no masks needed), (4) large area printing, (5) high productivity by increasing number nozzles and jetting frequency, (6) non contact printing for sensitive substrate, (7) print heads and jetting materials tailored for specific applications and (8) ultimately low capital investment. Also piezoelectric inkjet print heads have dominated in drop-on-demand (DOD) industrial and commercial market for last two decades, because they offer high jetting frequency, long life expectancy, and the ability to jet a wide range of fluids. Emerging market opportunities in production of flat panel display, solar cell, printed circuit boards and printed electronics will require highly flexible, reliable and robust design piezoelectric inkjet print heads. This paper focuses on some recent developments and some unique features such as high reliability, accurate orifice manufacture, replaceable orifice - chamber plates, inert print head bodies, individual orifice jetting performance calibration, and a highly flexible design to adapt to a wide range of drop volumes and jetting fluids. Trident's print heads (256Jet-D) has currently been released to meet these applications.