24-06-2014, 03:54 PM
The role of paper in the future of printed electronics
[attachment=65273]
ABSTRACT
Paper is the raw material for much of the output of home and
commercial printing. Printing methods that were developed for
and matured in commercial printing are now being applied for
electronic device fabrication in applications areas such as printed
electronics, printed displays and photovoltaic devices.
Over the years digital methods have made significant inroads
into printing and one significant technology in this is inkjet.
This paper examines the potential use of paper substrates in
printed electronics and the technical issues involved. The paper
uses inkjet printing to illustrate these technical issues. However,
much of what is discusses also applies to other printing methods
INTRODUCTION
The use of paper as the substrate in printing processes can be
considered to be a mature technology. However, there are now
new applications being developed that, while using the existing
technologies require substantial modifications to make them a
realistic option in the market place. One of these is printed
electronics, the ability to print electronic components and
complete devices onto substrates.
These devices are now beginning to appear and the market
research listed in this paper suggests that we are now on the cusp
of widespread application.
Paper would appear to have a place in this new technology but in
order to understand this and optimise products for these
applications the printing characteristics must be re-examined,
particularly considering fluid – paper interactions.
One of the key strengths of paper as a substrate for printed
electronics is its widespread acceptance for many existing
applications. The future may well lie in mixed documents,
containing both conventional print and printed electronics. One
technology that looks ideally suited to this is inkjet printing and
this printing method is used by way of illustration in this paper.
This paper first of all outlines the reasons why printing is being
considered as an electronics fabrication method and some of the
substrates and techniques being tested. It then looks at the
components of a printing system using inkjet as an example in
order to identify the areas needing technological development.
Finally, it examines fluid – substrate interactions, the key issue
facing the use of paper in this market.
Why print electronics?
Printed electronics for our purposes includes the creation of
electronic or opto-electronic circuitry using some kind of printing
method. There are a number of applications benefits to printing
electronics.
1. It is a ready route to flexible components. Examples of
these include flexible displays for mobile devices and
“electronic papers”. Here printing competes with
vapour deposition and will probably be cost
competitive for many devices. This is because vapour
deposition has the expense of large vacuum chambers
and printing could be capable of the assembly of
devices using multiple technologies (batteries, aerials,
memory, interconnects etc).
2. It allows electronics to be readily integrated as a part of
other printed media by printing them on the same
press. This gives access to products such as novelty
cards, Radio Frequency Identification (RFID) and
smart packaging. There is already significant interest in
this from the packaging sector as there are many
potential applications here. It is interesting to note that
in all these cases the printed item would combine both
conventional printing and printed electronics.
3. Printing is much faster than traditional wafer
fabrication. One estimate puts this speed difference as
4 orders of magnitude per device. This speed difference
is the key to low cost production and is the facilitator of
disposable electronics such as electronic tickets,
rudimentary examples of which already exist using
conventional printing.1
4. Printing has a lower capital investment cost than other
fabrication means. It is estimated that a printed
electronics plant will cost $30 million, just a fraction of
a $3 billion conventional silicon fabrication plant.2
Printing substrates and techniques
So far, commercial activity for printed electronics has largely
been confined to glass and a narrow range of plastic substrates.
Glass will continue to be an important substrate for printed
electronics in rigid displays due to its excellent optical and
mechanical properties.7 Substrates for printed electronics are and
will probably continue to be dominated by plastics, in particular
PEN because of its greater dimensional and thermal stability.8
For smart packaging and other applications paper is seen as
potentially useful. Printing on paper is very logical and it would
seem to be essential to the emergence of a significant smart
packaging sector. By 2013, it is forecast that paper substrates for
printable electronics will reach $0.5 billion in annual sales.9 This
looks likely to consist of specialist coated papers, for the
technical reasons outlined in Section 5.
Virtually every traditional printing mode (screen printing,
flexographic, gravure) has been or is currently being used for
creating circuitry of some kind.1 In the future all of these are
likely to co-exist in the printed electronics market and the choice
will be determined by the normal parameters such as run length,
feature size and variable data requirements. Conventional
printing systems such as flexographic, offset and gravure are best
suited to mass production and this will likely continue in printed
electronics. Screen printing also has a place and some early
commercial electronics printing activity such as the creation of
RFID and novelties is being done in this way.
Fluid – substrate interactions
The various aspects of ink and media interactions must be
revisited for printed electronics, particularly when considering
paper as the substrate. However, previous knowledge from
conventional printing is still applicable here.14
When a drop of inkjet ink is printed on media it has been shown
that there are 3 phases in the process of forming the final printed
dot
The challenges remaining
Printed electronics looks set to happen. At the time of writing the
majority of printing is still done by conventional printing
methods. These methods will continue to be important in the
longer term, particularly for high volume, low cost mechanisms
that will be necessary for disposable electronics. However, to
make this happen costs will have to be reduced. Lower cost
functional inks and substrates will need to be produced with the
correct price / performance ratios.
There are further challenges for the newer digital technologies.
The fluid / substrate interactions covered in Section 5 are one
major issue. The registration of successive layers is another
problem to be faced, particularly as substrates such as paper tend
to swell, cockle and shrink during the printing and drying
Conclusions
Controlling the morphology of the printed dots or elements is key
to making paper substrates work for printed electronics.
Amorphous or irregular structures such as those exhibited by
plain and cast coated papers in Figure 3 are unlikely to be of use
in anything other than the most coarsely printed electronic
component. However, dot shapes such as that exhibited by the
polymer coated product in Figure 3 are likely to be much more
acceptable.
This polymer coated material is an example of the sort of
complex multilayer coated products that have evolved for the
highest print quality in photo printing. It is this knowledge and
technology that looks set to become important in the new
applications.
It is normal to see demonstration prints of printed electronics on
photographic grade inkjet papers. These give excellent image
quality but because of the resin coated base do not withstand the
sintering temperatures of silver laden ink. However, they do
point to the sort of technologies that will be needed in the future
of paper in printed electronics
[attachment=65273]
ABSTRACT
Paper is the raw material for much of the output of home and
commercial printing. Printing methods that were developed for
and matured in commercial printing are now being applied for
electronic device fabrication in applications areas such as printed
electronics, printed displays and photovoltaic devices.
Over the years digital methods have made significant inroads
into printing and one significant technology in this is inkjet.
This paper examines the potential use of paper substrates in
printed electronics and the technical issues involved. The paper
uses inkjet printing to illustrate these technical issues. However,
much of what is discusses also applies to other printing methods
INTRODUCTION
The use of paper as the substrate in printing processes can be
considered to be a mature technology. However, there are now
new applications being developed that, while using the existing
technologies require substantial modifications to make them a
realistic option in the market place. One of these is printed
electronics, the ability to print electronic components and
complete devices onto substrates.
These devices are now beginning to appear and the market
research listed in this paper suggests that we are now on the cusp
of widespread application.
Paper would appear to have a place in this new technology but in
order to understand this and optimise products for these
applications the printing characteristics must be re-examined,
particularly considering fluid – paper interactions.
One of the key strengths of paper as a substrate for printed
electronics is its widespread acceptance for many existing
applications. The future may well lie in mixed documents,
containing both conventional print and printed electronics. One
technology that looks ideally suited to this is inkjet printing and
this printing method is used by way of illustration in this paper.
This paper first of all outlines the reasons why printing is being
considered as an electronics fabrication method and some of the
substrates and techniques being tested. It then looks at the
components of a printing system using inkjet as an example in
order to identify the areas needing technological development.
Finally, it examines fluid – substrate interactions, the key issue
facing the use of paper in this market.
Why print electronics?
Printed electronics for our purposes includes the creation of
electronic or opto-electronic circuitry using some kind of printing
method. There are a number of applications benefits to printing
electronics.
1. It is a ready route to flexible components. Examples of
these include flexible displays for mobile devices and
“electronic papers”. Here printing competes with
vapour deposition and will probably be cost
competitive for many devices. This is because vapour
deposition has the expense of large vacuum chambers
and printing could be capable of the assembly of
devices using multiple technologies (batteries, aerials,
memory, interconnects etc).
2. It allows electronics to be readily integrated as a part of
other printed media by printing them on the same
press. This gives access to products such as novelty
cards, Radio Frequency Identification (RFID) and
smart packaging. There is already significant interest in
this from the packaging sector as there are many
potential applications here. It is interesting to note that
in all these cases the printed item would combine both
conventional printing and printed electronics.
3. Printing is much faster than traditional wafer
fabrication. One estimate puts this speed difference as
4 orders of magnitude per device. This speed difference
is the key to low cost production and is the facilitator of
disposable electronics such as electronic tickets,
rudimentary examples of which already exist using
conventional printing.1
4. Printing has a lower capital investment cost than other
fabrication means. It is estimated that a printed
electronics plant will cost $30 million, just a fraction of
a $3 billion conventional silicon fabrication plant.2
Printing substrates and techniques
So far, commercial activity for printed electronics has largely
been confined to glass and a narrow range of plastic substrates.
Glass will continue to be an important substrate for printed
electronics in rigid displays due to its excellent optical and
mechanical properties.7 Substrates for printed electronics are and
will probably continue to be dominated by plastics, in particular
PEN because of its greater dimensional and thermal stability.8
For smart packaging and other applications paper is seen as
potentially useful. Printing on paper is very logical and it would
seem to be essential to the emergence of a significant smart
packaging sector. By 2013, it is forecast that paper substrates for
printable electronics will reach $0.5 billion in annual sales.9 This
looks likely to consist of specialist coated papers, for the
technical reasons outlined in Section 5.
Virtually every traditional printing mode (screen printing,
flexographic, gravure) has been or is currently being used for
creating circuitry of some kind.1 In the future all of these are
likely to co-exist in the printed electronics market and the choice
will be determined by the normal parameters such as run length,
feature size and variable data requirements. Conventional
printing systems such as flexographic, offset and gravure are best
suited to mass production and this will likely continue in printed
electronics. Screen printing also has a place and some early
commercial electronics printing activity such as the creation of
RFID and novelties is being done in this way.
Fluid – substrate interactions
The various aspects of ink and media interactions must be
revisited for printed electronics, particularly when considering
paper as the substrate. However, previous knowledge from
conventional printing is still applicable here.14
When a drop of inkjet ink is printed on media it has been shown
that there are 3 phases in the process of forming the final printed
dot
The challenges remaining
Printed electronics looks set to happen. At the time of writing the
majority of printing is still done by conventional printing
methods. These methods will continue to be important in the
longer term, particularly for high volume, low cost mechanisms
that will be necessary for disposable electronics. However, to
make this happen costs will have to be reduced. Lower cost
functional inks and substrates will need to be produced with the
correct price / performance ratios.
There are further challenges for the newer digital technologies.
The fluid / substrate interactions covered in Section 5 are one
major issue. The registration of successive layers is another
problem to be faced, particularly as substrates such as paper tend
to swell, cockle and shrink during the printing and drying
Conclusions
Controlling the morphology of the printed dots or elements is key
to making paper substrates work for printed electronics.
Amorphous or irregular structures such as those exhibited by
plain and cast coated papers in Figure 3 are unlikely to be of use
in anything other than the most coarsely printed electronic
component. However, dot shapes such as that exhibited by the
polymer coated product in Figure 3 are likely to be much more
acceptable.
This polymer coated material is an example of the sort of
complex multilayer coated products that have evolved for the
highest print quality in photo printing. It is this knowledge and
technology that looks set to become important in the new
applications.
It is normal to see demonstration prints of printed electronics on
photographic grade inkjet papers. These give excellent image
quality but because of the resin coated base do not withstand the
sintering temperatures of silver laden ink. However, they do
point to the sort of technologies that will be needed in the future
of paper in printed electronics