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Handbook of Industrial Inkjet Printing

A Full System Approach

Edited by Werner Zapka

Volume 1 & 2

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Introduction

Werner Zapka*

XaarJet Limited, Advanced Application Technology, Drottning Kristinas väg 61, 114 28 Stockholm, Sweden

This handbook is meant to tackle those “lab-to-fab” transition problems that often prevent efficient and fast implementation of inkjet applications in industry, for example, on the manufacturing floor. Implementation can be accelerated with proper knowledge, planning, and execution.

This Handbook of Industrial Inkjet Printing therefore provides a detailed analysis of inkjet technology, covering all key areas of the total technology chain of industrial inkjet printing. It thus gives support and guidance to technical personnel to approach the integration of inkjet technology following a “fully engineered system approach.”

Before describing the setup of this handbook, we provide a few introductory comments:

Successful implementing of industrial inkjet printing applications requires knowledge and expertise in various areas of technology, especially in mastering the important interfaces. The simplified sketch in Figure 1 is just one approach to describe those key technology areas and interfaces. Basic requirements are the adaptations of both ink-to-printhead and ink-to-substrate. The latter typically benefits from preprocessing of the substrate, while postprocesses are needed for drying, curing, or sintering. Having access to appropriate metrology technology is necessary to precisely measure those parameters that control proper performance of fluids, print quality, and reliability under heavy duty printing. Data flow has to be considered especially with high-duty, high-volume applications. With machine integration – a key function in any industrial inkjet implementation – several tasks have to be included in a system solution complying with the end user's requests on throughput, productivity, performance, and economics. To enlarge the application area and/or improve performance, it is often helpful to consider “hybrid solutions,” that is, combinations of inkjet with other technologies.

Figure depicting various technology areas (printhead, ink, substrate, post processing, machine integration, pre processing, data flow, hybrid technologies, ) that are interfaced to assess industrial inkjet printing under a full system approach.

Figure 1 Various technology areas have to be interfaced to assess industrial inkjet printing under a full system approach.

In the following, we assess all these topics. Far away from giving a complete overview, we instead let experts from companies active in those areas above describe their and their companies' technical expertise and experience. Those who plan an industrial inkjet application will benefit from this handbook in identifying important tasks of the authors' specific applications, and will get an idea how to approach and structure a plan for a specific project of their own. The reader is invited to approach the authors and companies for further information or support in their planning phase (see the contact details in each individual chapter).

In this handbook, we provide Parts One to Eleven, starting with general considerations about the pros and cons of inkjet technology. Thereafter, we address all the topics in Figure 1, including inks, inkjet printheads, substrates, metrology, and data flow. Then, we focus on machine integration and pre- and postprocesses. Thereafter, we move to application and integration by way of addressing print strategies, application developments, and successful implementations and case studies.

Part One: Pros and Cons of Inkjet Technology

For the engineers to select the appropriate printing technique for their specific application, it is essential to understand the technical capabilities, advantages, as well as disadvantages of those various printing methods.

The two printing techniques that appear to be most suitable for applications in industry, and which are expected to grow fast are inkjet printing and screen printing.

In our introductory Part One, we therefore focus on comparing the advantages and disadvantages of inkjet printing and screen printing. Chapter 1 comprises the pros and cons of inkjet technology as seen by the authors of this handbook. In Chapter 2 Gunter Hübner, an expert in screen printing, gives his view on the comparison of screen printing and inkjet technology with a focus on the recent advances of screen printing.

Once the decision toward inkjet is made, it is time for the engineer or the reader to understand the technical complexity of inkjet printing, and to learn from the experts about the various topics, issues, problems, and solutions, as they are presented in the following Parts Two to Eleven.

Part Two: Inks

This part comprises 10 chapters provided by authors from different ink manufacturers. SunChemical gives an overview of industrial inkjet inks, before focusing on UV inks. BASF cover photoinitiators for UV inks and radiation sources for UV curing and UV radiation measurement. AGFA addresses low-migration UV inks, with applications in food packaging (e.g., see KHS Chapter 47). Ceramic inks are described by Colorobbia. Fujifilm covers aqueous ink, and Sawgrass describes sublimation inks. Silver nanoparticle inks are covered by two companies, by Clariant and by Harima. OLED inks are described by Fraunhofer IAP.

Several other chapters deal with silver-nano inks, namely, metrology in Chapter 25 (TNO-Holst), photonic sintering in Chapter 32 (NovaCentrix), and applications in Chapters 35 (TNO-Holst), Chapter 36 (HSG-IMAT), and Chapter 37 (M-SOLV).

Part Three: Inkjet Printhead Technology

Although there are more inkjet printhead technology companies out there, we here focus on the most common state-of-the art printhead types for industrial inkjet printing. A variety of piezo-based printheads are used in industrial applications, both as binary and gray scale, with or without recirculation, with bulk PZT or thin film PZT MEMS printheads. Authors from Fujifilm Dimatix, Konica Minolta, Xaar, and Memjet all describe their respective printhead technologies in detail. Bubble Jet inkjet printheads are described by Hewlett Packard, and KODAK covers its specific continuous jet STREAM technique. To help understand how the various inkjet printhead types perform in industrial applications, the authors refer to specific chapters in Part Eleven of this handbook.

Part Four: Substrates

A few different substrates as required in applications of industrial inkjet printing are addressed here, namely, coated paper, polymeric substrates, and glass substrates, for example, touch screen and displays.

Part Five: Metrology

Industrial inkjet applications, often in-line processes, require high and long-term reliability in order to provide productivity and high manufacturing yield. Precise and statistical measurements of critical fluid, print, and product parameters are therefore necessary to control and monitor performance. Part Five presents state-of-the-art methods to measure complex fluid rheology, monitor “printhead health” during operation, detect missing drops during heavy-duty printing, and monitor electrical conductivity of printed tracks during sintering. Summing up, the total control of the behavior of drops on substrates is of paramount importance to successful printing.

Part Six: Data Flow

A short chapter describes the importance of data handling with the example of an HP Inkjet Web Press, where high-quality single-pass web printing is enabled by various features at press start and during operation.

Part Seven: Machine Integration

Machine integration is central to any implementation of industrial inkjet printing, as is obvious from Figure 1. All interfaces are handled by the integrator. We therefore strongly suggest studying the chapters in Part Seven before planning a new implementation project. The authors give advice on which project tasks to conduct, in which sequence, which should be done in parallel, and so on. There are several different kinds of integrators. VdW Consulting typically supports the user onsite, Notion Systems is an example of integrators who build equipment for/with customers. Besides, there are larger industry companies that are capable of acting as their own integrator. Several examples of their machine integration and successful implementations are presented in Part Eleven.

Part Eight: Pre- and Postprocesses

Of key importance for any inkjet application is an optimum match of ink-to-printhead and ink-to-substrate to provide an as large as possible operational window for the application process. Pretreatment of the substrate surface is often used to improve the ink-to-substrate performance, while various posttreatment techniques are used for drying, curing, or sintering the inkjet-printed structures. Plasma pretreatment is described by Gerhard Liebel (PINK), UV LED curing by Dirk Exner (Phoseon), E-beam curing by Urs Läuppi (COMET), and photonic sintering by Vahid Akhavan (NovaCentrix).

Part Nine: Printing Strategies

To match the performance characteristics of printheads, setting ink and substrate requirements by the specific application is a highly complex task. The concepts and strategies to adapt inkjet printing to industrial application requirements are described in this part to address this task.

Part Ten: Application Development

Inkjet printing is making ground in ever new industrial application areas, and the authors in this part present concepts and approaches toward implementations. Concepts for inkjet printing onto curved surfaces, for example, are of key importance for “direct-to-shape printing” applications. Other important areas are 3D printing and the newly evolving inkjet printing in Life Sciences. Further conceptual applications in this part deal with inkjet printing of metal–nanoparticle inks for printed electronics applications.

Part Eleven: Successful Implementations and Case Studies

Several successful implementations of industrial inkjet printing are described in detail in this part. The authors describe key technology tasks and problems they have tackled and solved. In case studies, the reader can join the author from machine concept to a complete solution in different application spaces such as digital multicolor direct decoration of cylindrical plastic bottles with high speed and high image quality, digital décor printing in the laminate industry, industrial inkjet in decorative web print applications, and single-pass inkjet printing for ceramic tile decoration.

Several “hybrid” solutions are presented, wherein inkjet technology and other techniques are joined in highly complementary fashion to provide solutions that are well beyond the capabilities and limitations of the individual techniques.

With the Graphium and the Gallus Labelfire, two such hybrid label presses are described from machine concept to machine solution. Two other hybrids described are inkjet + laser hybrid processing, an enabling technology for reliable production of fine interconnects in large area electronics/displays, and the hybrid of inkjet and nanoimprint lithography, which provides nanometer pattern resolution combined with high-throughput.

Glossary

The glossary provides a broad set of industrial inkjet terms defined to help the neophyte or cross-disciplinarian to hit the ground running in industrial inkjet terminology and concepts.

Note

Part One
Pros and Cons of Inkjet Technology

1
Pros and Cons of Inkjet Technology in Industrial Inkjet Printing

Werner Zapka

XaarJet Limited, Advanced Application Technology, Drottning Kristinas väg 61, 114 28 Stockholm, Sweden

During the recent decade, inkjet technology has made large inroads into the industrial domain.

Fairs like DRUPA, Fesba, Drinktech, and many more demonstrate the strong advance of digital and specifically of industrial inkjet printing. In fact, inkjet has become a mature technology for graphical applications. Even in functional printing like printed electronics, 3D, and bio/pharma/medical applications, there have been successful implementations of inkjet technology.

The potential user of inkjet technology will find it useful in assessing the pros and cons of inkjet technology. We have, therefore, compiled here the views of the contributors of this handbook and have listed the advantages as well as disadvantages of inkjet, which still need improvement. Pros of inkjet technology:

Cons of inkjet technology:

The goal of this handbook is to provide all the advantageous features of inkjet to the reader and to address solutions for the challenges exemplified by the “cons” above. It is obvious that a close cooperation of technology experts throughout the field is paramount for the development and implementation of industrial inkjet applications in a fast and successful fashion.

In the following chapters, we will discuss whether or not inkjet is the appropriate technology for specific applications, and we will also compare inkjet with competing analog technologies.

We conclude this chapter with an example of a successful introduction of inkjet technology into industry. Alberto Annovi from TecnoFerrari describes the transfer of the decoration of ceramic tiles from analog screen printing to digital inkjet printing:

At the time when the first tile was printed by an inkjet printer (Spain, 1998), the ceramic tile industry almost exclusively used the well-established screen printing technique for the tile decoration process.

The competition at that time was mainly on prices, which prompted the major manufacturers to adopt a “big volumes model” with bigger and bigger batches and to save cost by way of developing their own inks internally. Small ceramic tile manufacturers with their low volumes therefore had difficulties to enter or be competitive in the market.

In this scenario, the first inkjet applications were not really successful: The possibility of obtaining high-resolution designs and a good gamut starting from just a few colors (CMYK) were not compensating for the poor reliability of the available printers in such difficult manufacturing environment and the high cost for the printers and the inks. A further technical problem was the limited color fastness of the inks during high-temperature postprocessing of the tiles.

However, the advance of oil-based pigmented inks in 2006 changed the situation: Their cost was significantly lower, their thermal stability and color fastness were much higher, and the jetting process was of higher reliability. More printhead manufacturers entered the market, thus adding competition and reducing the printer prices.

A further move toward inkjet was the 2008 crisis, which impacted the ceramic tile market and specifically hit the major manufacturers, because their “big volumes model” was no longer efficient.

Small factories were now able to buy inkjet printers and started to be competitive in the market since the cost of inkjet technology (printers, printheads, and inks) was essentially the same for everyone. It was neither possible nor cost-effective even for the major manufacturers to develop an inkjet printer or an ink internally.

In parallel, some new developments in presses, glazers, and packaging were made that enabled the production of bigger tile sizes (over 60 cm), and noncontact inkjet printing thus became advantageous over a screen/roller, pushing a big thin tile passing over two belts.

In the past 8 years, inkjet printing has grown fast to become the dominant technique, thanks to strong competition between manufacturers of printheads, inks, and printer machines. Nowadays, inkjet technology has almost saturated the ceramic tile manufacturing (in some countries like Italy and Spain, more than 95% of production lines are digitalized), but still there are few thousands production lines to populate with new printers worldwide.

The challenge now for a ceramic tile manufacturer is to design a new product faster than his competitor and to create greater diversification by mixing press, roller, and inkjet printing.

The tile size has increased recently, and now it is possible to produce big slabs (over 200 cm) and their decoration process can only be inkjetted.

The inkjet technology is still unable to produce a good “materic effect” (surface structure and 3D effect) due to limited particle sizes that can be jetted. This is why tiles printed by inkjet are sometimes considered “flat” compared to those produced with conventional screen printing. To produce “materic” effect by way of inkjet printing or by hybrid techniques of inkjet and analog techniques is therefore a “new frontier” in inkjet development for ceramic tile manufacturing. See TecnoFerrari's chapter 45 (paragraph 3.2) for details on this further technology step.

And some inkjet “pros and cons” specific for the decoration of ceramic tiles:

Inkjet pros:

Inkjet cons:

For further information regarding the comparison between inkjet and screen technology, see Chapter 2.