Roll-to-Roll Manufacturing E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 689

Veröffentlichungsjahr: 2018

Beschreibung

A single-volume resource featuring state-of-the art reviews of key elements of the roll-to-roll manufacturing processing methodology

Roll-to-roll (R2R) manufacturing is an important manufacturing technology platform used extensively for mass-producing a host of film-type products in several traditional industries such as printing, silver-halide photography, and paper. Over the last two decades, some of the methodologies and know-how of R2R manufacturing have been extended and adapted in many new technology areas, including microelectronics, display, photovoltaics, and microfluidics. This comprehensive book presents the state-of-the-art unit operations of the R2R manufacturing technology, providing a practical resource for scientists, engineers, and practitioners not familiar with the fundamentals of R2R technology.

Roll-to-Roll Manufacturing: Process Elements and Recent Advances reviews new developments in areas such as flexible glass, display, and photovoltaics and covers a number of process innovations implemented recently to extend and improve the capabilities of traditional R2R lines. It covers such topics as: coating and solidification processes, in-line vacuum deposition, drying, web handling and winding, polymer film substrates, novel hybrid composite films, flexible solar cells and more.  Additionally, this book:

• Examines key elements (unit operations) of the R2R technology, and discusses how these elements are utilized and integrated to achieve desired process efficiencies in a host of applications.
• Illustrates several established and novel application areas where R2R processing is utilized in current or future products.
• Discusses process design methodology and key advantages of R2R manufacturing technology over batch or sheet-to-sheet operations.

Roll-to-Roll Manufacturing: Process Elements and Recent Advances is an ideal book for undergraduate and graduate students in various science and engineering disciplines, as well as for scientists, engineers, and technical and business leaders associated in any way with the development, commercialization, and manufacture of a variety of film products.

Leseprobe

Roll‐to‐Roll Manufacturing

Process Elements and Recent Advances

Edited by

Jehuda Greener, Glen Pearson, and Miko Cakmak

This edition first published 2018© 2018 John Wiley & Sons, Inc.

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The right of Jehuda Greener, Glen Pearson, and Miko Cakmak to be identified as the editors of this work has been asserted in accordance with law.

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Library of Congress Cataloging‐in‐Publication Data

Names: Greener, Jehuda, editor. | Pearson, Glen Hamilton, 1948– editor. | Cakmak, Mukerrem, editor.Title: Roll‐to‐roll manufacturing : process elements and recent advances / edited by Jehuda Greener, Glen Pearson, Miko Cakmak.Description: Hoboken, NJ : John Wiley & Sons, 2018. | Includes bibliographical references and index. |Identifiers: LCCN 2017043485 (print) | LCCN 2017052231 (ebook) | ISBN 9781119163800 (pdf) | ISBN 9781119163817 (epub) | ISBN 9781119162209 (cloth)Subjects: LCSH: Manufacturing processes–Technological innovations. | Flexible electronics–Processing.Classification: LCC TS183 (ebook) | LCC TS183 .R65 2018 (print) | DDC 670.42–dc23LC record available at https://lccn.loc.gov/2017043485

Cover Design: WileyCover Images: Courtesy of Miko Cakmak; © Iaremenko Sergii/Shutterstock

For Helena, Maya, Eli, Karen, Emre, and Gulgun

Preface

Roll‐to‐roll (R2R) manufacturing is a well‐established manufacturing technology platform used for over a century in many mature industries, such as printing, paper consumables and silver‐halide photography, to produce two‐dimensional, film‐like products on a mass scale. The main appeal of this technology and the reason for its widespread use is its high throughput capability combined with a low manufacturing cost. The last two decades have seen a strong resurgence of this technology as it is being extended and adapted in many new technology areas, including microelectronics, display and photovoltaics, in an attempt to leverage some of the tangible benefits of R2R manufacturing, especially its low cost, in a new lineup of innovative products.

This volume mainly aims to review the state‐of‐the‐art and shed a new light on R2R technology, to familiarize a new generation of researchers and practitioners with many aspects of this technology as it is being applied in an ever‐growing number of industries and product categories. Some key elements of R2R manufacturing are reviewed by highly experienced experts in the field, with emphasis on practical, hands‐on application principles. We also introduce the reader to a number of novel extensions and upgrades of R2R technology, designed to meet new and challenging requirements in the new generation of products.

Although we do not attempt to cover all aspects and possible variants of this widely used manufacturing tool, we sincerely hope that this volume will provide a solid foundation for students, practitioners and researchers already involved in R2R operations or those contemplating this process option in future development programs.

November 2017Jehuda Greener,Glen Pearson,Miko Cakmak

1Roll‐to‐Roll Manufacturing: An Overview

Jehuda Greener

J. Greener Consulting, Rochester, NY, USA

1.1 Introduction

Roll‐to‐roll (R2R) manufacturing is an important manufacturing technology platform widely used for a host of applications and product categories, spanning many industries. These cover the gamut from traditional and mature technologies such as printing and silver halide photography to more novel application areas including flexible microelectronics [1–4], thin flexible batteries [5, 6], photovoltaics [7–10], and display [11–13]. A typical R2R production line, with standard coating, drying, and lamination steps, is depicted in Figure 1.1. This particular line, however, represents only one specialized process layout from within a multitude of manufacturing processes that can be broadly classified as R2R operations. A common thread in all these diverse manufacturing operations is that in all cases relatively thin and flat, film‐type two‐dimensional (2D) structures are processed continuously on a flexible moving web that is conveyed at some fixed speed between two or more rotating rollers. The web comprises an inert and flexible substrate on which a layer (or layers) of a functional material is applied by some means. The functional layer possesses some desired physical/chemical property that has special utility to its intended application. Many types of functional layers are applied in R2R operations reflecting the wide variety of applications utilizing this manufacturing platform. These include chemically sensitized layers used in traditional photography, ink layers used in various printing lines, optically refractive, diffusive, or collimating layers used in optical films for liquid crystal displays, photovoltaic layers used in flexible solar cells, barrier layers used in various packaging applications and magnetic layers used in magnetic tape, to name just a few. The functional layers are often flat and featureless films applied by some common coating method onto a moving substrate. However, in some application areas, the functional layers can be patterned by standard printing methods or by various novel photolithographic, embossing [14], or other patterning techniques. The various printing techniques fall under the general category of additive patterning, while some photolithographic techniques, where excess material is removed, are generally classified as subtractive patterning methods. The patterned functional layers are designed to enable a particular function such as light collimation (as in the case of prism films used in liquid crystal displays [15]) or special fluid management (as in the case of microfluidic films [16]), and are either directly printed or replicated onto the moving substrate from a master roll or belt having a corresponding relief (“negative”) pattern. A wide variety of micro‐ and nano‐patterning methods are highly compatible with a continuous web, R2R‐type operation and have been described at length in the literature [17, 18]. Various printing methods such as inkjet printing, flexography, and screen printing are used extensively for producing patterned functional layers in R2R operations [19–22]. Patterning of the functional layer can also be achieved by self‐assembly of block copolymers [23].

Figure 1.1 Typical roll‐to‐roll production line.

In addition to the functional layers, the final film structure often comprises additional so‐called ancillary layers whose function is secondary to the intended application, but these layers are critical to the effective processability and successful function of the film product. Examples of ancillary layers include adhesion promoting layers, sometimes referred to as “primers” or “subbing layers,” that ensure good adhesion of the functional layer or an ancillary layer to the substrate or to another layer [24], antistatic layers [25] that dissipate static charges during conveyance and final use, various protective layers such as “hard coats” that protect the functional layers from environmental or mechanical damage [26], slip layers used to minimize friction during conveyance and end use, and barrier layers used to minimize contact with ambient gases, especially oxygen and water. (Barrier layers could be classified as functional layers if the main function of the film product is to minimize contact with ambient gasses, e.g., in packaging applications.)

The substrate layer itself is often polymeric or paper‐based although it could also be a metal foil or inorganic glass [27, 28]. Aside from being flexible, this layer serves as a physical foundation and carrier1 for the functional layer(s), which is often mechanically not sufficiently sturdy to withstand on its own mechanical deformations applied during the R2R manufacturing process or during its functional lifetime use. Thus, substrate materials must be generally dimensionally, mechanically, and environmentally stable under the conditions the film product is expected to withstand over its functional lifetime in order to ensure a durable and useful product. Some mechanical stiffness and rigidity are usually attained by making the substrate layer considerably thicker than the functional layer(s) and by ensuring that its glass transition temperature and melting point are well above the product’s processing or application temperature ranges. Although the bending stiffness of the film is significantly increased with an increase in thickness of the substrate layer, there is a myriad of factors that go into selecting the thickness and type of the substrate layer; the thickness is mostly dictated by product design considerations, but it can also adversely impact material cost, web conveyance, and winding, so proper selection of substrate thickness and type is critical to product performance, manufacturability, and cost. For many optical applications, the optical properties of the substrate such as transmittance, birefringence, and color are often critical to the performance of the film product [27] and must be carefully considered in selecting the appropriate substrate material for the application at hand. Otherwise, the substrate is expected to interfere as little as possible with the performance of the functional layer.

The origins of R2R manufacturing technology can be traced to the tail end of the Industrial Revolution in the second half of the 19th Century. In fact, the emergence of two traditional industries, printing and photography, is closely linked to advances and innovations in R2R manufacturing during the Industrial Revolution. A major boost to the evolution of mass printing was prompted by the invention of the rotary printing press in the 1840s by Richard Hoe [29]. Combining this invention with the earlier inventions of rolled paper and the steam engine made it possible to cost‐effectively print large areas of paper continuously, thus launching mass‐circulation newspapers and laying the foundation to the modern publishing industry. Similarly, the history of silver halide photography parallels and coincides with the emergence and evolution of R2R manufacturing. In the mid‐19th Century, photographic plates were produced in a batch process by coating light‐sensitive emulsions on glass. Consequently, silver halide photography was relatively expensive and out of reach of the average consumer. In the early 1880s, George Eastman and the newly founded Kodak (later to be named Eastman Kodak) Company developed a novel manufacturing process that facilitated the coating of light‐sensitive materials on flexible substrates using a R2R operation that helped launch the mass production of photographic film [30]. The first step in the development of the R2R manufacturing process of photographic film was to coat photographic emulsions on a rolled paper substrate based on key inventions by William Walker and George Eastman [30]. This was followed by replacing paper with a clear cellulose nitrate substrate first proposed and patented by H. Reichenbach, one of Eastman’s early collaborators (see Figure 1.2), based on an earlier invention by H. Goodwin of a process for making cellulose nitrate film [31]. These pioneering developments in the manufacturing of photographic film led to the popularization of photography, making it accessible to the average consumer as well as creating a demand for cameras, film processing, and printing equipment and related consumer products. Indeed, many of the early developments and innovations in R2R manufacturing technology in the late 19th Century and first half of the 20th Century were prompted and driven by the fast growth of the photographic and printing industries but especially by the exacting demands of the photographic industry that required precise deposition of up to 24 thin light‐sensitive layers on a fast‐moving web as well as creating the need for advanced finishing methods and novel substrate technologies [32].

Figure 1.2 Drawing of a roll‐to‐roll coating process in Reichenbach’s 1889 patent.

Today, many wide‐ranging industries, including printing, paper, packaging, and photography, among others, benefit directly from the operational and cost advantages of the R2R manufacturing technology platform. Many focused attempts to adapt and extend R2R processing practices to various new technology areas, particularly in microelectronics, display, and photovoltaics, are currently underway in many research groups around the world [1–4, 7–13]. Some common operational features of R2R processes are highlighted in Section 1.2 followed by a general discussion of cost and environmental, health, and safety considerations in Sections 1.3 and 1.4.

1.2 R2R Operation Overview

R2R operations are as varied and diverse as the markets and product categories they serve, but they share many underlying common features and operational principles. Figure 1.1 represents a typical R2R production line with conventional coating, drying, and lamination steps, but a more generic schematic layout of a R2R operation is shown in Figure 1.3. In this schematic a flexible web is conveyed between two rollers while passing through various process (converting) steps. An unprocessed web, comprising an uncoated or pre‐coated substrate, is fed from a supply station (unwinder) wherein the raw or partially processed substrate is unwound from a supply roller and fed into the R2R machine (dashed frame). The raw substrate then undergoes a series of consecutive process (converting) steps (S1, S2, …) while being conveyed at a controlled speed through the R2R machine.

Figure 1.3 Generic roll‐to‐roll operation with five converting steps (S1–S5), one tension roller (T), and two conveyance rollers (C).

The web, consisting of a substrate and deposited layers, is driven through the R2R machine by the winder and its conveyance is facilitated by a number of conveyance rollers or idlers (C) placed along its path. Tension in the conveyed web is controlled by the winder but is typically adjusted by one or more tension rollers (T) distributed within the R2R machine to insure flatness, planarity, and defect‐free conveyance throughout the operation. We note that a single R2R line could have more than one unwinder if the operation comprises lamination or interleaving steps, as illustrated in Figure 1.1, but the line is always terminated by a single winder. The only exception here is for the case where the incoming substrate is protected by a sacrificial protective layer (“release liner”), which must be peeled off using a separate winder before the substrate is processed in the R2R machine.

Five converting steps are illustrated in the schematic layout of Figure 1.3, though the number of steps is arbitrary and usually greater than 1. A wide variety of converting steps are used in R2R operations, most of which involve the deposition and posttreatment of thin layers of some functional and ancillary materials on the moving substrate. Indeed, typical converting steps can be categorized by two main classes: (i) film‐forming steps whereby a thin material layer(s) is deposited on the moving substrate and (ii) film enhancement steps whose function is mainly to consolidate, modify, and improve the performance of the deposited layer(s). Examples of common R2R film‐forming steps include wet coating [33, 34], vacuum deposition [35, 36], printing [20, 21, 37], solvent casting, extrusion casting, and lamination, while typical film enhancement steps include drying [33, 34, 38], radiation curing [39–41], thermal curing, calendering, micro‐ or nano‐patterning [14, 17, 18], heat treatment, Corona discharge treatment [42], annealing, chemical treatment, cleaning, interleaving, and so on. Some steps may require a special environment (temperature, humidity, vacuum, nitrogen blanket, etc.) so the web moving through the corresponding station must be properly enclosed, which may present some challenges as discussed later. Figure 1.3 underscores the modular nature of R2R operations whereby converting steps (modules) can be added or removed from the production line as dictated by the special requirements of the film product.

As the web is conveyed at a constant speed through all converting steps, it is important to select a speed (equivalent to residence time) that satisfies all process elements to allow an overall robust operation. In this sense we say that the process steps are coupled and the final line speed is constrained by the slowest process step. This is the so‐called rate‐determining step for the R2R operation. If this is not possible, that is, if one or more steps must operate at very different speeds from the rest, the operation must be split into more than one line, each operating at different speed, or the web needs to run multiple times through the same line at different speeds. Such a “multi‐pass” (or “multi‐line”) operation is, of course, costlier than a single‐pass operation and must be avoided if possible. Indeed, as discussed in Section 1.3, the selection of line speed is dictated not only by quality and operational considerations but also by cost considerations. Another factor, aside from line speed, that would require multi‐line or multi‐pass operation is process environment; for example, addition of vacuum deposition steps to a R2R line. Generally, confining a fast moving web in a vacuum atmosphere may be particularly challenging when combined with atmospheric pressure process steps, which may necessitate splitting the operation into an atmospheric pressure line and a vacuum deposition line.

Line speeds in R2R operations vary widely depending on the type of film being processed, the quality requirements, and the number of converting steps along the R2R line. For mature and commoditized technologies such as printing and various paper products, line speeds of up to 2000 m/min are not uncommon. But for more specialized application areas and advanced technologies with film products having complex and exacting layer structures with tight registration requirements, speeds of less than 10 m/min are often used. As discussed in