UV/EB and Printed Electronics
The benefits of energy-curable technologies are leading to new opportunities in photovoltaics and printed electronics.
By David Savastano
There is tremendous interest in the potential market for printed electronics (PE), and the reasons are fairly clear: By combining the manufacturing of electronics with printing, companies will be able to mass produce products at a much faster rate and lower unit cost.
Roll-to-roll processing of printed elctronics. (Photo courtesy of PolyIC)
One key PE segment is the photovoltaic (PV) market. Companies are already successfully printing solar cells on flexible substrates, and the potential for the market is huge. PV manufacturers are looking for new ways to improve their products, and energy curable technologies such as UV and EB are well positioned to play key roles in the marketplace.
“We are getting more and more inquiries in just the last year, anywhere from thin film photovoltaics to concentrated PV,” said Patrick Peach, business manager – solar energy products for Red Spot Paint & Varnish Co.
UV is already developing a position in the PE and PV markets. Radiation curing has been used on printed circuit boards for many years, and is already playing a role in areas such as photovoltaics and printed electronics.
Dr. Mike Idacavage, principal research fellow for Cytec Industries and president of RadTech International NA, said that he can see UV and EB as one of the key enabling technologies for printed electronics.
“UV conductive inks lend themselves well to PE and PV systems,” Dr. Idacavage said. “There is a lot of really interesting research being done in our industry. For example, work is being done at universities and start-up companies using carbon nanotubes as flexible conductive inks. Another intriguing opportunity is developing UV curable flexible adhesives, which have a different set of demands from rigid applications.”
As for EB, Dr. Idacavage noted that EB does not usually use photoinitiators, so there is less chance of having unreacted fragments that could cause problems in highly sensitive systems.
Josh Rosenheck, technical market manager, graphic arts/functional coatings for Lubrizol Advanced Materials, Inc., noted that his company is seeing more requests for additives from printed electronics manufacturers.
“UV is an area that people are becoming more curious, and we are starting to see a lot more interest, particularly in our hyperdispersant lines,” Mr. Rosenheck noted. “Companies are coming to us looking to enhance their products and improve their processes.”
UV equipment manufacturers are also active in the PV market.
“We are very active in the marketplace, and we’ve seen no slowdown in interest, which is quite telling considering the slowdown in other industrial markets,” said David Harbourne, president of Fusion UV Systems. “There is a lot of activity in the development of roll-to-roll production of photovoltaics.”
UV and EB offer numerous advantages when it comes to printing. They are “green” technologies, as they emit no volatile organic compounds (VOCs). Because of the ability to cure instantly, throughput is increased, and costly dryers are eliminated.
“UV can offer a lot of potential to these new technologies, whether it’s conductive inks, encapsulants or adhesives, while reducing the carbon footprint for manufacturers because they are eliminating the drying oven and the emissions,” said Michael Kelly, president of Allied PhotoChemical
“The inherent advantage of UV is throughput and energy cost reductions as well as reducing emissions,” Mr. Peach noted.
Another benefit is the low drying temperature of UV and EB. Because roll-to-roll production would use film substrates, the PV cells would be very flexible, which is ideal for numerous applications. Mr. Harbourne noted that UV and EB curing is best suited for these film substrates.
“It is likely that most of these film substrates will be heat-sensitive, and UV is a very cool process for drying,” Mr. Harbourne said.
Josh Oliver, manager, UV/EB specialty applications for Sartomer, said that most of the motivation for printed electronics manufacturers’ interest in UV and EB is cure speed and economics.
“The holy grail is grid parity and reducing the price of energy to $1 or $2 per watt, and UV and EB has to show that it is a way to get closer to that goal,” Mr. Oliver said. “We’ve had photovoltaic companies come to us and ask how we can help them. There is also a lot of interest in the display side. UV is faster, uses less energy and imparts great physical properties.”
UV and EB suppliers are looking for ways to provide PE manufacturers with more functional products that will handle multiple functions.
Dr. Idacavage said that developing UV products with multiple functionalities is a promising area. “Another area of interest is combining multiple functions, for example, a UV adhesive that has light management properties, or a conductive ink that acts as a barrier,” Dr. Idacavage noted.
“It’s a matter of adding the functionality the PV industry needs,” Mr. Peach said. “There’s a tremendous need for product improvement as manufacturers look to increase efficiency, manufacturing and functionality. There is opportunity for improvement in areas such as weatherability, yellowing under high heat, and we are working on adding functionality, such as creating anti-reflective characteristics as well as self-cleaning properties.”