Flexible Flat Panel Displays
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Flexible Flat Panel Displays
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Overview
A complete treatment of the entire lifecycle of flexible flat panel displays, from raw material selection to commercialization
In the newly revised Second Edition of Flexible Flat Panel Displays, a distinguished team of researchers delivers a completely restructured and comprehensive treatment of the field of flexible flat panel displays. With material covering the end-to-end process that includes commercial and technical aspects of the technology, the editors have included contributions that introduce the business, marketing, entrepreneurship, and intellectual property content relevant to flexible flat panel displays.
This edited volume contains a brand-new section on case studies using the Harvard Business School format that discusses current and emerging markets in flexible displays, such as an examination of the use of electronic ink and QD Vision in commercial devices.
From raw material selection to device prototyping, manufacturing, and commercialization, each stage of the flexible display business is discussed in this insightful new edition. The book also includes:
- Thorough introductions to engineered films for display technology and liquid crystal optical coatings for flexible displays
- Comprehensive explorations of organic TFT foils, metallic nanowires, adhesives, and self-healing polymer substrates
- Practical discussions of flexible glass, AMOLEDs, cholesteric displays, and electronic paper
- In-depth examinations of the encapsulation of flexible displays, flexible batteries, flexible flat panel photodetectors, and flexible touch screens
Perfect for professionals working in the field of display technology with backgrounds in science and engineering, Flexible Flat Panel Displays is also an indispensable resource for professionals with marketing, sales, and technology backgrounds, as well as senior undergraduates and graduate students in engineering and materials science.
Product Details
| ISBN-13: | 9781118751114 |
|---|---|
| Publisher: | Wiley |
| Publication date: | 02/13/2023 |
| Series: | Wiley Series in Display Technology |
| Edition description: | 2nd ed. |
| Pages: | 416 |
| Product dimensions: | 6.69(w) x 9.61(h) x 1.11(d) |
About the Author
Dirk J. Broer, is a Polymer Chemist specialized in polymer structuring and self-organizing polymer networks. This entails the development of polymers with new functionalities and integrating them into devices to meet industrial and societal challenges in the fields of sustainable energy, water-management, healthcare and personal comfort.
Gregory P. Crawford, PhD, is President of Miami University, USA, and Professor of Physics. His research interests include liquid crystal and polymer materials for display and biotechnology applications. He is the editor of the first edition of Flexible Flat Panel Displays (2005).
Read an Excerpt
Flexible Flat Panel Displays
John Wiley & Sons
Copyright © 2005 John Wiley & Sons, LtdAll right reserved.
ISBN: 0-470-87048-6
Chapter One
Flexible Flat Panel Display Technology
Gregory P. Crawford
Division of Engineering, Brown University, Providence RI
1.1 Introduction
The manufacturing of flat panel displays is a dynamic and continuously evolving industry. Improvements of flat panel displays are made rapidly as technology improves and new discoveries are made by display scientists and engineers. The cathode ray tube and active matrix liquid crystal display (LCD) recently celebrated their 100th and 25th anniversary, respectively. The arrival of portable electronic devices has put an increasing premium on durable, lightweight and inexpensive display components. In recent years, there has been significant research investment in the development of a flexible display technology. Figure 1.1 shows the evolution away from the bulky CRT display to the thin active matrix LCD for desktop applications, and the much anticipated paper-like flexible flat panel display of the future. To enable a flexible flat panel display, a flexible substrate must be used to replace conventional glass substrates, which can be either plastic or thin glass. Flexible flat panel display technologies offer many potential advantages, such as very thin profiles, lightweight and robust display systems, the ability to flex, curve, conform,roll, and fold a display for extreme portability, high-throughput manufacturing, wearable displays integrated in garments and textiles, and ultimate engineering design freedom (e.g. odd-shaped displays) as shown in Figure 1.2(a). Many of these potential advantages have been the principal driving force behind much of the effort and resources dedicated towards the development of flexible flat panel display configurations.
There are also many new compelling product categories enabled by the promise of plastic display technology. An electronic newspaper, for example, could eventually update headlines throughout the day. If plastic displays on televisions and computers could become analogous to fabric or paper, they would no longer dominate our physical and aesthetic worlds. We could make them fade from sight when not in service. The television could simply disappear into a painting or tapestry. Your PDA could roll up into a pen that you could stick into your shirt pocket. Instead of adapting our aesthetic sensibilities to incorporate technology into our lives, technology could better reflect our imagination and creativity.
The broad definition of a flexible flat panel display is as follows (Slikkerveer 2003):
A flat panel display constructed of thin (flexible) substrates that can be bent, flexed, conformed, or rolled to a radius of curvature of a few centimeters without losing functionality.
Defining a flexible display is akin to defining modern art (Slikkerveer 2003). Because the diversity of the application space for flexible display technology is so vast, it is hard to propose an all-encompassing definition. The term "flexible display" means different things to different people. Flexible displays may only be flexed once during their lifetime; for example, during manufacturing to create a permanently conformed display. For a rollable display application, however, the display may be rolled and unrolled more than 100 times per day.
The ability to flex a display has fascinated researchers for many years, only today they are being seriously considered for a number of applications and moving closer to the marketplace (Howard 2004; Ong 2004; Kinkade 2004; Hogan 2003; Hellemans 2000; Savage 1999). One of the primary reasons for the increased interest is that many of the necessary enabling technologies for flexible displays are maturing to the extent where reasonable-looking prototypes are being produced by many research and development organizations. As illustrated in Figure 1.2(b), the convergence and evolution of technologies such as flexible substrates, barrier layers, conducting layers, electro-optic materials, optical and functional thin film materials, and thin film transistors (TFTs) is making possible new flexible display concepts.
Flexible display technology can potentially result in many compelling applications not satisfied by a rigid glass-based display. Figure 1.3 shows several artistic renditions of flexible display concepts, such as a large-area, wall-sized reflective screen for use in a conference room setting that could be rolled away when not in use (a), a small portable rollable display (b), an irregular-shaped display used in the steering wheel of an automobile (c), a conformed display integrated in an automobile filling up the entire dashboard (d), a wristband display that is permanently conformed throughout its lifetime (e), and a switchable mask for children, also permanently conformed. Also, there may be a temptation to believe flexible displays will replace glass-based displays for many other applications. While this may be possible at some point in the future, it will be difficult for flexible displays to compete solely on cost alone in the inexpensive and small display module market (e.g. super twisted nematic displays) or in the high-end, high-performance market such as desktop and laptop screens. For the time being, flexible displays will most likely enter the marketplace in a unique way where their positive attributes are clearly capitalized on. The market outlook for flexible displays is surveyed in Chapter 25.
Flexible flat panel display technology constitutes an eclectic research field and potentially large industry in the future. Its highly interdisciplinary range combines basic principles from engineering, physics, chemistry, and manufacturing. The following chapters will provide a comprehensive overview of this exciting and multidisciplinary field.
1.2 Manufacturing
Although it may be somewhat of an overstatement, the words "holy grail" are often used to describe the flat panel display community desire to achieve a commercialized flexible display technology (Kincade 2004). One reason why these words are often used is because flexible displays, in principle, are amendable to a roll-to-roll manufacturing process which would be a revolutionary change from current batch process manufacturing (Chapter 21). Figure 1.4 shows a simple conceptual illustration of a roll-to-roll manufacturing process where display materials are deposited on indium-tin-oxide (ITO) coated plastic substrates, processed, and rolled back up.
As compared to a batch process, which handles only one component at a time, roll-to-roll processing represents a dramatic deviation from current manufacturing practices. If and when roll-to-roll manufacturing technology matures for display processing, it promises to reduce capital equipment costs, reduce display part costs, significantly increase throughput, and it may potentially eliminate component supply chain issues if all processes are performed with roll-to-roll techniques. Although batch processing can still be employed to manufacture flexible flat panel displays, many researchers and technologists believe that roll-to-roll manufacturing will ultimately be implemented.
1.3 Enabling Technologies
The technology of flexible displays includes many components and supporting technologies. Anticipating a new market opportunity, the display industry has been developing display materials targeted specifically at flexible flat panel display requirements. These technologies must be compatible and converge to enable a truly flexible display. The necessary technologies include robust flexible substrates, conducting transparent conducting oxides and/or conducting polymers, electro-optic and reflecting materials, inorganic and organic electronics, and packaging technologies. In addition, many processes must also be developed and optimized in concert with the materials development, such as roll-to-roll manufacturing, coating technology, and printing. In reality, these components and processes cannot be optimized independently since a flexible display is a complex system of linked components that must be co-developed in order to function efficiently. It should be made clear that not all technologies described in this book will survive the flexible flat panel race. Since the field is still racing towards commercialization at a rapid pace, it is not at all clear which technologies will win and ultimately become commercialized. The book provides an overview of nearly all the technologies competing in the flexible display landscape, and each topic area provides several solutions for the specific needs of a flexible flat panel display.
1.3.1 Flexible Substrates
There are two choices for flexible substrates, which include polymeric and thin glass. Since the flexible substrate represents the fundamental starting component for the display, flexible substrates arguably face the greatest challenges in terms of compatibility with all of the other necessary display layers that need to be integrated onto them. Chapter 2 focuses on polymer films engineered for flexible display technologies. A number of issues are discussed such as process temperature limitations as a function of polymer type, optical properties, thermal properties, and surface smoothness properties. One of the biggest challenges for polymeric substrates is the process temperature required by subsequent display layers (Lueder 2002). It is highly unlikely that flexible displays in the foreseeable future will be completely organic, but rather they will be a hybrid of inorganic and organic layers and components. However, the process temperatures for many inorganic layers have been decreasing (Chapter 5) and the thermal stability of polymer substrates has greatly improved (Chapter 2). This represents one example where technologies are converging in an optimal way to enable flexible displays.
The other solution for flexible substrates is organic based (Chapter 3). Glass has the ultimate barrier properties and is resistant to display process temperature and chemicals, but it lacks the flexibility and ease of handling found in polymeric substrates. Chapter 3 discusses a glass manufacturing process which can process thin glass down to 30 mm thicknesses. In order to improve mechanical stability for flexibility and processing, a polymeric layer is deposited on the glass. This hybrid solution enables one to capitalize on the positive attributes of glass, as well as to enable it to be more flexible and process handling friendly.
1.3.2 Barrier Layers
When polymeric substrates are employed in flexible display applications, a barrier layer is required to protect the enclosed functional materials and layers from oxygen and water permeation (Chapter 4). Oxygen and water permeation through a flexible substrate is of particular importance to organic light-emitting diode (OLED) devices (Chapter 15). Although single-layer barrier layers do provide the packaged materials with some protection, it appears that multiple layers are necessary for OLED applications for long-term stability. Chapter 4 discloses an inorganic/organic hybrid multilayer solution to create a barrier layer that is beginning to satisfy the demanding requirements of an OLED material.
1.3.3 Inorganic Conducting Layersan dMechanical Properties
Indium tin oxide (ITO) is the typical conducting layer used in display technologies. However, the process temperatures required for ITO on glass to obtain low sheet resistance and high optical throughput properties is incompatible with plastic substrates. Therefore lower-temperature processes have to be developed for ITO in order for it to be considered for flexible display applications (Chapter 5). Although ITO has excellent sheet resistance and optical properties, it does have one shortcoming in the flexible display realm. When ITO is deposited on a polymeric substrate, it can crack (buckle) under tensile (compressive) strain. For a flexible display application, ITO cracking can cause catastrophic failure (Chapter 6). Because of the importance of ITO in display applications, there is significant emphasis on the mechanics of ITO in this book (Chapters 6 and 7). The mechanics of ITO on polymeric substrates is becoming better understood in flexible display applications. In addition, the models and fundamentals learned by studying ITO on polymeric substrates can also be applied to other components, such as inorganic thin film transistors (TFTs) on plastic.
1.3.4 Organic Conducting Layersan dMechanical Properties
Conducting polymers are also being considered for flexible display applications (Chapter 8). Although their sheet resistance and optical properties are not as attractive as ITO, they do have exceptional mechanical properties (Chapter 9) and low process temperatures. Chapter 8 describes the fundamentals of the underlying chemistry of conducting polymers and Chapter 9 investigates the mechanics of conducting polymers as compared to ITO. As ITO and conducting polymer technology compete for the conducting substrate solution, there is a new conducting substrate technology based on nanotechnology. Flexible and transparent electrodes have been formed from carbon nanotube dispersions in combination with wet coating processes and printing techniques (Arthur et al. 2004).
1.3.5 Optical Coatings
Optical coatings will play an important role in flexible flat panel displays. Many optical films that are used on conventional glass-based displays will be applicable to flexible display configurations. Polarizers, retarders, color filters, antireflection films, and alignment layers for liquid crystals are discussed in Chapter 10. This is an area of research and development that has not been specifically targeted towards the flexible display field, but it does constitute a crucial set of elements in certain flexible display configurations. For example, the paintable LCDs presented in Chapter 18 require thin film polarizers. Additionally, when super twisted nematic (STN) displays are used in a flexible configuration, they require thin film polarizers, retarders, color filters, and backlights (Slikkerveer et al. 2004).
1.3.6 Thin Film Transistors
For many electro-optic materials, such as OLEDs (Chapter 15), polymer-dispersed liquid crystals (Chapter 16), paintable LCDs (Chapter 18), electrophoretics (Chapter 19) and Gyricon materials (Chapter 20), an active matrix backplane will be required for high resolution. Considerable work is being dedicated to developing various processes to print and pattern organic electronics on polymeric substrates (Chapters 11, 12, 13). There is also significant research and development in developing processes for inorganic TFTs on foil (Chapter 14) and polymer substrates (Chapter 24). The failure mechanisms of TFTs on flexible substrates are also critical to the future success of flexible displays, as discussed in Chapter 14. The success of TFTs for plastic substrates to date has been an enabler for flexible flat panel displays and constitutes a very vital component. They have enabled the development of high-resolution prototypes.
1.3.7 Electro-Optic Materials
The various types of electro-optic materials for flexible display applications essentially fall into three categories - emissive, reflective, and transmissive - analogous to the categories for glass-based displays. For emissive applications, OLED materials are being developed that can be small molecule or high molecular weight (Chapter 15). In order to have a truly low-power display, a reflection mode of operation will have to be implemented on flexible substrates. Polymer-dispersed liquid crystals (Chapter 16), chiral liquid crystal dispersions (Chapter 17), encapsulated electrophoretics (Chapter 19), and bichromic ball composites (Chapter 20) all operate in the reflective mode. For electronic book and surrogate paper applications, an efficient reflective mode display is critical to eliminate the need for a power-hungry backlight. Chapter 19 discloses a unique process to paint liquid crystals onto a flexible substrate. Although this technique currently uses a transmissive display mode, the process may be applicable to other materials that can operate in reflection.
(Continues...)
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Table of Contents
Series Editor’s Foreword xvList of Contributors xvii
1 Introduction 1 Darran R. Cairns, Gregory P. Crawford, and Dirk J. Broer
1.1 Toward Flexible Mobile Devices 1
1.2 Flexible Display Layers 2
1.3 Other Flexible Displays and Manufacturing 2
2 Engineered Films for Display Technology 5 W.A. MacDonald
2.1 Introduction 5
2.2 Factors Influencing Film Choice 5
2.2.1 Application Area 5
2.2.2 Physical Form/Manufacturing Process 6
2.2.3 Film Property Set 7
2.2.3.1 Polymer Type 7
2.2.3.2 Optical Clarity 9
2.2.3.3 Birefringence 10
2.2.3.4 The Effect of Thermal Stress on Dimensional Reproducibility 10
2.2.3.5 Low-bloom Films 11
2.2.3.6 Solvent and Moisture Resistance 12
2.2.3.7 The Effect of Mechanical Stress on Dimensional Reproducibility 16
2.2.3.8 Surface Quality 18
2.3 Summary of Key Properties of Base Substrates 19
2.4 Planarizing Coatings 21
2.5 Examples of Film in Use 23
2.6 Concluding Remarks 24
Acknowledgments 25
3 Liquid Crystal Optical Coatings for Flexible Displays 27 Owain Parri, Johan Lub, and Dirk J. Broer
3.1 Introduction 27
3.2 LCN Technology 27
3.3 Thin-film Polarizers 29
3.3.1 Smectic Polarizers 29
3.3.2 Cholesteric Polarizers 32
3.4 Thin-film Retarders 34
3.4.1 Reactive Mesogen Retarders 35
3.4.2 Chromonic Liquid Crystal-based Retarders 37
3.4.3 Liquid Crystal Alignment and Patterned Retarders 37
3.5 Color Filters 41
3.6 Conclusion 43
4 Large Area Flexible Organic Field-effect Transistor Fabrication 47 Zachary A. Lamport, Marco Roberto Cavallari, and Ioannis Kymissis
4.1 Introduction 47
4.2 Substrates 48
4.3 Photolithography 49
4.4 Printing for Roll-to-roll Fabrication 52
4.4.1 Inkjet Printing 52
4.4.2 Gravure and Flexographic Printing 55
4.4.3 Screen Printing 56
4.4.4 Aerosol Jet Printing 56
4.4.5 Contact Printing 58
4.4.6 Meniscus Dragging 60
4.5 Conclusions 62
5 Metallic Nanowires, Promising Building Nanoblocks for Flexible Transparent Electrodes 67 Jean-Pierre Simonato
5.1 Introduction 67
5.2 TEs Based on Metallic Nanowires 68
5.2.1 Metallic Nanowires, New Building Nanoblocks 68
5.2.2 Random Network Fabrication 69
5.2.3 Optical Characterization 70
5.2.4 Electrical Characterization 71
5.2.5 Mechanical Aspect 73
5.3 Application to Flexible Displays 73
5.3.1 Touch Screens 73
5.3.2 Light-emitting Diodes Displays 74
5.3.3 Electrochromic Flexible Displays 76
5.3.4 Other Displays 77
5.4 Conclusions 78
6 Optically Clear Adhesives for Display Assembly 85 Albert I. Everaerts
6.1 Introduction 85
6.2 OCA Definition and General Performance Specifications 86
6.3 Application Examples and Challenges 89
6.3.1 Outgassing Tolerant Adhesives 90
6.3.2 Anti-whitening Adhesives 91
6.3.3 Non-corrosive OCAs 92
6.3.4 Compliant OCAs for High Ink-step Coverage and Mura-free Assembly of LCD Panels 94
6.3.5 Reworkable OCAs 102
6.3.6 Barrier Adhesives 103
6.4 Summary and Remaining Challenges 104
7 Self-healing Polymer Substrates 107 Progyateg Chakma, Zachary A. Digby, and Dominik Konkolewicz
7.1 Introduction 107
7.2 General Classes of Self-healing Polymers 108
7.2.1 Types of Dynamic Bonds in Self-healing Polymers 109
7.2.2 Supramolecularly Crosslinked Self-healing Polymers 109
7.2.2.1 Hydrogen Bonding 110
7.2.2.2 π–π Stacking 110
7.2.2.3 Ionic Interactions 111
7.2.3 Dynamic-covalently Crosslinked Self-healing Polymers 111
7.2.3.1 Cycloaddition Reactions 111
7.2.3.2 Disulfides-based Reversible Reactions 112
7.2.3.3 Acylhydrazones 113
7.2.3.4 Boronate Esters 113
7.3 Special Considerations for Flexible Self-healing Polymers 114
7.4 Incorporation of Electrically Conductive Components 115
7.4.1 Metallic Conductors 115
7.4.2 Conductive Polymers 116
7.4.3 Carbon Materials 118
7.4.4 Polymerized Ionic Liquids 119
7.5 Additional Possibilities Enabled by Three-dimensional Printing 119
7.6 Concluding Remarks 121
8 Flexible Glass Substrates 129 Armin Plichta, Andreas Habeck, Silke Knoche, Anke Kruse, Andreas Weber, and Norbert Hildebrand
8.1 Introduction 129
8.2 Display Glass Properties 129
8.2.1 Overview of Display Glass Types 129
8.2.2 Glass Properties 130
8.2.2.1 Optical Properties 130
8.2.2.2 Chemical Properties 130
8.2.2.3 Thermal Properties 131
8.2.2.4 Surface Properties 132
8.2.2.5 Permeability 133
8.3 Manufacturing of Thin “Flexible’’ Glass 134
8.3.1 Float and Downdraw Technology for Special Glass 134
8.3.2 Limits 135
8.3.2.1 Thickness Limits for Production 135
8.3.2.2 Surface Quality Limits for Production 136
8.4 Mechanical Properties 137
8.4.1 Thin Glass and Glass/Plastic Substrates 137
8.4.2 Mechanical Test Methods for Flexible Glasses 137
8.5 Improvement in Mechanical Properties of Glass 140
8.5.1 Reinforcement of Glass Substrates 140
8.5.1.1 Principal Methods of Reinforcement 141
8.5.1.2 Materials for Reinforcement Coatings 141
8.6 Processing of Flexible Glass 142
8.6.1 Cleaning 143
8.6.2 Separation 143
8.7 Current Thin Glass Substrate Applications and Trends 144
8.7.1 Displays 145
8.7.2 Touch Panels 145
8.7.3 Sensors 145
8.7.4 Wafer-level Chip Size Packaging 146
9 Toward a Foldable Organic Light-emitting Diode Display 149 Meng-Ting Lee, Chi-Shun Chan, Yi-Hong Chen, Chun-Yu Lin, Annie Tzuyu Huang, Jonathan HT Tao, and Chih-Hung Wu
9.1 Panel Stack-up Comparison: Glass-based and Plastic-based Organic Light-emitting Diode 149
9.1.1 Technology for Improving Contrast Ratio of OLED Display 151
9.2 CF–OLED for Achieving Foldable OLED Display 153
9.2.1 Mechanism of the AR coating in CF–OLED 154
9.2.2 Optical Performance of CF–OLED 155
9.3 Mechanical Performance of CF–OLED 157
9.3.1 Bi-directional Folding Performance and Minimum Folding Radius of SPS Cf–oled 159
9.4 Touch Panel Technology of CF–OLED 160
9.5 Foldable Application 162
9.5.1 Foldable Technology Summary 162
9.5.1.1 Polymer Substrates and Related Debonding Technology 162
9.5.1.2 Alternative TFT Types to LTPS 162
9.5.1.3 Encapsulation Systems to Protect Devices against Moisture 163
9.5.2 Novel and Next-generation Display Technologies 163
10 Flexible Reflective Display Based on Cholesteric Liquid Crystals 167 Deng-Ke Yang, J. W. Shiu, M. H. Yang, and Janglin Che
10.1 Introduction to Cholesteric Liquid Crystal 167
10.2 Reflection of CLC 169
10.3 Bistable CLC Reflective Display 171
10.4 Color Design of Reflective Bistable CLC Display 173
10.4.1 Mono-color Display 173
10.4.2 Full-color Display 173
10.5 Transitions between Cholesteric States 175
10.5.1 Transition from Planar State to Focal Conic State 175
10.5.2 Transition from Focal Conic State to Homeotropic State 177
10.5.3 Transition from Homotropic State to Focal Conic State 177
10.5.4 Transition from Homeotropic State to Transient Planar State 178
10.5.5 Transition from Transient Planar State to Planar State 179
10.6 Driving Schemes 181
10.6.1 Response to Voltage Pulse 181
10.6.2 Conventional Driving Scheme 183
10.6.3 Dynamic Driving Scheme 183
10.6.4 Thermal Driving Scheme 185
10.6.5 Flow Driving Scheme 186
10.7 Flexible Bistable CLC Reflective Display 187
10.8 Bistable Encapsulated CLC Reflective Display 188
10.9 Production of Flexible CLC Reflective Displays 189
10.9.1 Color e-Book with Single-layered Structure 191
10.9.2 Roll-to Roll E-paper and Applications 195
10.10 Conclusion 202
11 Electronic Paper 207 Guofu Zhou, Alex Henzen, and Dong Yuan
11.1 Introduction 207
11.2 Electrophoretic Display 210
11.2.1 Development History and Working Principle 210
11.2.2 Materials 212
11.2.2.1 Colored Particles/Pigments 212
11.2.2.2 Capsule Shell Materials 213
11.2.2.3 Suspending Medium (Mobile Phase) 213
11.2.2.4 Charge Control Agents 213
11.2.2.5 Stabilizers 213
11.2.3 Device Fabrication 214
11.2.4 Flexible EPD 215
11.3 Electrowetting Displays 216
11.3.1 Development History and Working Principle 216
11.3.2 Materials 218
11.3.2.1 Absorbing (Dyed) Hydrophobic Liquid 218
11.3.3 Device Fabrication 220
11.3.4 Flexible EWD 221
11.4 Other E-paper Display Technologies and Feasibility of Flexibility 222
11.4.1 Pcd 222
11.4.2 Lpd 223
11.5 Cholesteric (Chiral Nematic) LCDs 224
11.6 Electrochromic Displays 224
11.7 MEMS Displays 226
12 Encapsulation of Flexible Displays: Background, Status, and Perspective 229 Lorenza Moro and Robert Jan Visser
12.1 Introduction 229
12.2 Background 230
12.3 Multilayer TFE Technology 234
12.3.1 Multilayer Approach 234
12.3.2 Inorganic Layer Deposition Techniques 237
12.3.3 Organic Layer Deposition Techniques 238
12.4 Current Technology Implementation 242
12.5 Future Developments 246
12.6 Conclusions 249
Acknowledgments 250
13 Flexible Battery Fundamentals 255 Nicholas Winch, Darran R. Cairns, and Konstantinos A. Sierros
13.1 Introduction 255
13.2 Structural and Materials Aspects 256
13.2.1 Shape 257
13.2.2 One-dimensional Batteries 257
13.2.3 Two-dimensional Planar Batteries 258
13.2.4 Solid versus Liquid Electrolyte 259
13.2.5 Carbon Additives 259
13.3 Examples of Flexible Batteries 260
13.4 Future Perspectives 266
14 Flexible and Large-area X-ray Detectors 271 Gerwin Gelinck
14.1 Introduction 271
14.2 Direct and Indirect Detectors 272
14.3 Thin-film Photodiode Sensors for Indirect-conversion Detectors 273
14.3.1 Performance Parameters 273
14.3.2 Photodiode Materials on Plastic Substrates 275
14.3.2.1 Amorphous Silicon 275
14.3.2.2 Organic Semiconductor Materials 275
14.4 TFT Array 277
14.4.1 Pixel Architecture and Transistor Requirements 277
14.4.2 Flexible Transistor Arrays 278
14.5 Medical-grade Detector 282
14.6 Summary and Outlook 283
15 Interacting with Flexible Displays 287 Darran R. Cairns and Anthony S. Weiss
15.1 Introduction 287
15.2 Touch Technologies in Non-Flexible Displays 287
15.2.1 Resistive Touch Sensors 287
15.2.2 4-Wire Resistive 288
15.2.3 5-Wire Resistive 289
15.2.4 Capacitive Sensing 290
15.2.5 Surface Capacitive 291
15.2.6 Projected Capacitive 291
15.2.7 Infrared Sensing 293
15.2.8 Surface Acoustic Wave 293
15.2.9 Bending Wave Technologies 294
15.3 Touch Technologies in Flexible Displays 294
15.4 Summary 299
16 Mechanical Durability of Inorganic Films on Flexible Substrates 301 Yves Leterrier
16.1 Introduction 301
16.2 Flexible Display Materials 302
16.2.1 Property Contrast between Coating and Substrate Materials 302
16.2.2 Determination of Mechanical Properties of Inorganic Coatings 302
16.3 Stress and Strain Analyses 304
16.3.1 Intrinsic, Thermal, and Hygroscopic Stresses and Strains 304
16.3.2 Strain Analysis of Multilayer Films under Bending 307
16.3.3 Critical Radius of Curvature 308
16.4 Failure Mechanics of Brittle Films 309
16.4.1 Damage Phenomenology under Tensile and Compressive Loading 309
16.4.2 Experimental Methods 310
16.4.3 Fracture Mechanics Analysis 311
16.4.4 Role of Internal Stresses 312
16.4.5 Influence of Film Thickness on Critical Strain 312
16.5 Durability Influences 313
16.5.1 Influence of Temperature 313
16.5.2 Fatigue 314
16.5.3 Corrosion 315
16.6 Toward Robust Layers 317
16.7 Final Remarks 317
Acknowledgments 318
Nomenclature 318
17 Roll-to-roll Production Challenges for Large-area Printed Electronics 325 Dr. Grzegorz Andrzej Potoczny
17.1 Introduction 325
17.2 Infrastructure 327
17.3 Equipment 328
17.4 Materials 329
17.5 Processing 331
17.6 Summary 334
18 Direct Ink Writing of Touch Sensors and Displays: Current Developments and Future Perspectives 337 Konstantinos A. Sierros and Darran R. Cairns
18.1 Introduction 337
18.2 DIW and Ink Development 338
18.3 Applications of DIW for Displays and Touch Sensors 343
18.4 Future Challenges and Opportunities 347
19 Flexible Displays for Medical Applications 351 Uwadiae Obahiagbon, Karen S. Anderson, and Jennifer M. Blain Christen
19.1 Introduction 351
19.1.1 Flexible Displays in Medicine 351
19.1.2 A Brief Historical Perspective 351
19.1.3 Application of Flexible Displays for Biochemical Analysis 352
19.1.4 OLEDs and Organic Photodiodes as Optical Excitation Sources and Detectors 352
19.1.5 Device Integration 354
19.1.6 Fluorescence, Photoluminescence Intensity, and Decay-time Sensing 355
19.2 Flexible OLEDs for Oxygen Sensors 356
19.3 Glucose Sensing Using Flexible Display Technology 358
19.4 POC Disease Diagnosis and Pathogen Detection Using Flexible Display Optoelectronics 359
19.5 Flexible Display Technology for Multi-analyte Sensor Array Platforms 364
19.5.1 Integrated LOC and Flexible Display Devices 364
19.5.2 Multiplexed Sensor Platforms 364
19.6 Medical Diagnostic Displays 366
19.7 Wearable Health Monitoring Devices Based on Flexible Displays 366
19.7.1 Monitoring Vital Signs Using Flexible Display Technology 367
19.7.2 Flexible Display Technology for Phototherapy 369
19.7.3 Smart Clothing Using Flexible Display Technology 370
19.8 Competing Technologies, Challenges, and Future Trends 371
19.9 Conclusion 372
Acknowledgment 373
Conflicts of Interest 373
Index 379