Advances in Flexible Electronics Displays

132 Pages·4.097 MB·English

by  Pira International Ltd

Advances in Flexible Electronics Displays
Wolfgang Bock
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© Copyright
Pira International Ltd 2005
ISBN 1 85802 368 2
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Contents
4
List of tables v
List of figures vi
Executive summary ix
1
Applications 27
Substitute or added-value products 28
OLED viewfinders 28
Introduction 1 E-ink wearables 28
Targets 1 Shirt-pocket devices 29
Context 1 Radical innovation 29
Acknowledgements 2 Paper and ink 29
2
Real paper e-displays 30
Dynamic display functions 33
Displays in e-publishing 34
E-books instead of paper 34
From rigid to flexible 3 Enhanced real paper 36
Printable versus flexible 4 Textile displays 38
Printing on rigid and flexible surfaces 4 Signage 40
Small molecules versus large molecules4 Paradigm-changing innovation 41
Elements and structures 4 Audio 41
Display elements 5 E-wallpaper 41
Flexible elements 6 Greetings cards 42
Rigid technologies 7 Playing cards 44
Electromechanical displays 7 Conformal displays 45
Projection displays 8 Power sources 45
Cathode ray tubes 8 Conformal displays in toys 45
5
Plasma displays 9
Field-emissive displays 9
LED displays 10
Liquid crystal displays 11
Cholesteric displays 13 Printing and other deposition
Electroluminescent displays 14 methods 47
Original and adapted technologies 15 Requirements 47
Flexible elements 15 Basic performance goals 47
Backplanes 21 Deposition requirements 48
Mobile and rich media 22 Roll-to-roll 53
3
Materials influence processes 56
Substrates 57
Glass 58
Paper 58
SWOT analysis 23 Polymer foils 58
Strengths 23 Barrier issues 59
Weaknesses 24 Textiles 63
Opportunities 25 Inks 63
Threats 26 Printing inks 63
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Advances inFlexible Electronics Displays
Contents
Film parameters 65 Aggressive-innovative 86
Printing processes 65 Scientific breakthrough 88
Sheet-fed versus R2R 67 Engineering-led 88
Dynamic plate printing 68 Integration 89
Legacy contact presses 70 Resources-limited innovation 90
Other processes 79 Risk-averse 90
CVD 79 Engineering-led substitution 92
Dipping 79 Structurally innovating 93
Spin coating 79 Unconventional 93
7
Sputtering 79
Finishing 80
Specific issues 81
6
Companies and contact details 95
Appendices 113
Approaches to innovation 85 A Selling proposition 113
Aggressive-conservative 85 B Augmented paper publishing 117
Page iv © Copyright Pira International Ltd 2005
List of tables
5.1 Performance of industrial printing 5.3 WVTR and OTR for some polymers
processes 49 and coatings 62
5.2 Substrate properties 57
Page v © Copyright Pira International Ltd 2005
List of figures
2.1 Extreme Photonix demonstrator 6 4.7 Integrated display, input system and
2.2 Segmented alphanumeric printed power system all printed on paper 33
display 6 4.8 Sustainpack milk carton 34
2.3 PM display architecture 7 4.9 Sony Librié 35
2.4 Iridigm micromechanics mimic 4.10 E-book scroll in a mobile phone 36
butterfly wing iridescence by using 4.11 A musical jacket 39
interference 8 4.12 France Telecom’s woven or knitted
2.5 Electrowetting display 8 fibre display 39
2.6 Simplified plasma display 9 4.13 Elumin8 patterns 41
2.7 Field-emissive display 10 4.14 GE’s wallpaper matrix 42
2.8 Simplified crystalline LED display 4.15 Greetings card or letter
element 11 personalisation 43
2.9 Principle of an elementary nematic 4.16 An electrochromic curtain for
LCD display 12 greetings cards and pictures 43
2.10 Samsung prototype for a plastic 4.17 SqueezeMe toy from Enable Arts 46
plane LCD display 12 5.1 A simple pattern to measure printing
2.11 Principle of a Magink cholesteric resolution 49
display 13 5.2 Very uniform inkjet films 50
2.12 Magink display performance 13 5.3 Inkjet was used to make this smooth,
2.13 Principle of an electroluminescent highly conductive silver film 50
display 14 5.4 DuPont Teijin’s Teonex 65
2.14 Gyricon displays 15 exemplifies progress in plastic
2.15 Gyricon signage in a hotel 16 substrates 59
2.16 E-Ink display 17 5.5 A multilayer food package barrier 60
2.17 Kodak’s cholesteric display 18 5.6 OLED packaging 60
2.18 OLED element 19 5.7 Examples of OLED packaging 61
2.19 Philishave PLED display 19 5.8 Ink parameters for conventional use
2.20 Sony OLED 19 and polymer electronics 64
2.21 Sony Clié VZ 90 20 5.9 Taxonomy of legacy printing
2.22 Viologen display principle 20 processes 66
2.23 NTERA’s electrochromic displays 21 5.10 Schematic arrangement in R2R 67
2.24 Electrochromic transistor and display 5.11 The Nilpeter 3300, a medium-sized
element 21 R2R press 67
2.25 AMOLED architecture 22 5.12 Inkjet: continuous versus DoD 68
4.1 Bendable e-ink display 5.13 High-performance inkjetting lines 69
demonstrators 27 5.14 Simplified thermosublimation
4.2 Display-enabled credit card 28 engine 70
4.3 OLED viewfinder in a camera 28 5.15 Letterpress 71
4.4 An e-ink wearable 29 5.16 Flexo process 71
4.5 Genealogy of the PAELLA project 32 5.17 Offset process 73
4.6 Acreo’s 40-pixel matrix 5.18 Gravure and gravure stamp action75
electrochromic paper substrate 5.19 Intaglio plate made by hand 76
display 32 5.20 Intaglio label printed as a relief 76
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Advances inFlexible Electronics Displays
List of figures
5.21 Basic screen printing 77 5.27 The Labratester gravure and flexo
5.22 Rotary screen press 78 printer 82
5.23 Pad printing 78 6.1 Batman centrepiece with conductive
5.24 Philips’ Wave system for soft ink touchpads plus integrated voice
lithography 79 chip and batteries 91
5.25 Planing as a patterning method 80 B.1 Anoto pen 119
5.26 Inline bonding machine for silicon
electronics 81
Page vii © Copyright Pira International Ltd 2005

Executive summary
Advances in organic chemistry, along with some radically new ideas on how to exhibit
information, have begun to realise the promise of flexible electronic displays, which can
be bent into cylindrical shapes, or even conformed to surfaces.
Such progress in chemistry has occurred along three rather distinct lines:
(cid:1) Small-molecule OLED(organic light-emitting diode) displays embody a somewhat
more mature technology and are manufactured by evaporation methods and
patterning processes.
(cid:1) Large molecule OLEDs(a.k.a. PLEDs) use compopunds that can be processed in
solution, i.e. they can be deposited by printing processes.
(cid:1) E-Inkis one technology that has made it to the market where a particular process –
electrophoresis – has been implemented in a very small capsule or bead. These beads
can then be assembled into a flexible sheet, incorporating in particular a flexible part
backplane that drives the beads individually, resulting in a flexible display. More
exotic ideas have been mooted along structurally similar lines; thus plasma sphere
displays have been proposed.
All three lines postulate a flexible backplane. In the current state of the art, all of the fast
processing such as the logic addressing rows and columns in a matrix display, still has to
be done in silicon, generally in classically crystalline silicon.
How to use this book This book is mainly aimed at innovative customers of the printing and polymer electronics
industries, and aims to create some bridges between these two very different fields. As
these may be product, marketing or even organisational innovators that do not necessarily
have a technical background, the technical side has been kept simple.
Flexible electronics displays is a very dynamic area so this book strives to support
users of internet search engines by providing clean semantics – an area where the
interests of buzzword inventors and researchers appear to be in clear conflict.
Although this nascent technology has been accompanied by much hype, the
fundamental enthusiasm seems justified due to the potential of these technologies in
product innovation, mobility and cost.Even small-molecule displays offer significant
advances in colour rendition, lower power consumption, cost and weight reduction, and
potential conformability to curved surfaces (compared to an LCD display). In addition, the
large-molecule variant promises at least some of the speed, simplicity and economics of
printing. Conventional electronics (including display production) is based on crystal
semiconductors, which have to be manufactured in highly controlled, hideously expensive
environments using processes that are slow. In contrast, flexible displays technology
comprises variants that can be printed at room temperature and pressure, perhaps even
using high-speed printing processes borrowed from the conventional printing industry.
Also, at least for the inkjet technology variants, there is the promise of almost
unlimited flexibility, as the patterns to be printed can be changed almost at whim. Finally,
the 21st century is generally deemed to be the ‘age of materials’ and materials are key to
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Advances inFlexible Electronics Displays
Executive summary
this new industry, as are media/information technologies. This confluence has attracted
much interdisciplinary talent.
The flexible-display pioneers – their distant cousins from the flat-panel display
industry – have investigated most of the old TV technologies, those that have succeeded
such as the cathode ray tube (CRT) and those that have so far failed such as the field-
emission display. Some of these have been adapted, resulting in the (rigid) plasma display,
and pointing to a potential flexible plasma sphere display. Others have recuscitated nearly
defunct technologies, such as Motorola’s most recent development of field-emissive
displays technology. Moreover, under competitive pressure, there has been an almost
straight progression from glass-pane LCD to – potentially – bendable plastic-pane LCDs,
and an interesting newcomer, E-Ink.
A number of totally new technologies have been developed or proposed: these
include the Bragg reflection cholesteric displays pioneered by Magink; the low-end
electrochromic displays proposed by Acreo; the interference-reflection micropixels of
Iridigm (now part of Qualcomm); and the E-Ink and Gyricon displays. Some of these are
potentially flexible; others are flexible already.
But the potentially most momentus development has been led from Europe and in
particular from the UK. This concerns printable flexible displays. The ubiquitous inorganic
LED display has led to organic LEDs, such as the printable OLEDs/PLEDs developed by
Philips and others.
Here, the advantages promised by flexible displays are dwarfed by another promise:
to use printing technology to produce displays at very high speed and very low cost.
Every display is an heterostructure, as it involves a minimum of two electrodes and
some optically active material. Impressive progress has been achieved in actually
producing such devices using inkjet printing, such as in packaging them in such a way
as to prevent water or oxygen ingress, which would corrupt them. Life times in the tens of
thousands of hours have been achieved – not as good as inorganic display devices, but
useful in product terms.
Such progress in inkjet has led to renewed interest in revisiting standard high-speed
printing processes, which – in contrast to inkjet – rely on contact between a printing
stamp and the substrate. These processes include offset, gravure, flexo, pad and screen
printing, as well as more exotic variants such as electrostatic printing. These processes are
currently being analysed by a number of parties, including the so-called ‘organic
electronics’ cluster of research projects currently being funded by the European
Commission.
It is not clear whether in adapting these technologies, the printable electronics
industry will ever achieve the speed and area throughput of large paper printing presses.
Indeed it is almost obvious that such speed is unnecessary in the present state of the art.
However, even if printing speeds lagged behind by one or two orders of magnitude this
would constitute a major advance compared with much current electronic device
production.
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