David Savastano, Editor02.23.11
As printed electronics (PE) moves from lab to production, methods of manufacturing PE systems are being analyzed. There are advantages and disadvantages inherent in each printing and deposition process.
Much like other processes, gravure printing has numerous advantages for the field of printed electronics, as well as limitations. Gravure allows the ability to print fine resolutions, which is key to conductivity, and offers high ink transfer volume. It is also a high-speed printing process, which makes it ideal for high volume applications. The perception of gravure as being only suitable for high volumes is a key limitation, though.
There are a number of important printed electronic applications where gravure is already playing an important role. Organic light emitting diodes (OLED) for displays and lighting is an important market. Gravure has shown its viability for RFID, as Avery Dennison RFID utilized gravure for UHF RFID label antennas, and Omron uses gravure printing ink as the resist layer for its RFID tags. Transistors, circuits and interconnects are areas where gravure could excel.
Certainly, solar cells could be a sizable market, and work is being conducted on the university and research center levels. For example, “Gravure Printed Flexible Organic Photovoltaic Modules” was a collaboration between researchers at VTT Technical Research Centre of Finland, IMEC, University of Oulu and CEA-INES RDI. As another example, “Gravure Printing for Three Subsequent Solar Cell Layers of Inverted Structures on Flexible Substrates,” written at Centre for Plastic Electronics, Department of Physics, Imperial College of Science, Technology and Medicine in the UK, noted that inverted organic photovoltaic devices have been fabricated by gravure printing on a flexible substrate.
Interest in Gravure
With the advantages that gravure offers, it is no surprise that industry leaders are seeing increasing interest among manufacturers as to how gravure can benefit the PE field.
“The interest in gravure printing is slowly building up as more and more research groups in both industry and academia realize its potential as a simple, commercially viable fast printing method for solvent-based printed electronics,” said Dr. Anoop Menon, senior research scientist for Add-Vision, Inc., a leading developer of organic light-emitting-polymer display technology (P-OLED) for low resolution displays and backlighting applications. “We are aware of serious efforts in the US, UK and Japan in this area.”
Dr. Menon noted that Add-Vision opted for gravure printing to reduce the consumption of expensive light emitting polymer materials, to develop a high throughput process, which would be commercially viable and scalable for mass production and to improve the film uniformity and overall performance of the OLEDs.
“Interest in gravure for PE is strong and growing in relation to an increased understanding of gravure’s inherent benefits,” said Eric Serenius, vice president of Daetwyler R&D. “These benefits include the simplicity of the process, the ability to transfer a variable amount of ink volume, the robustness of the image carrier and its resistance to harsh solvents that are used for printed electronics and its capability to print long runs at high speeds. Additionally, there is an increased awareness of scalable R&D/laboratory tools, such as the AccuPress, which have accelerated growth. Also, influential leaders such as Vivek Subramanian have also fostered awareness and growth.
“Gravure is very well suited for high demand products such as photovoltaics (PV) and indium tin oxide (ITO) replacement,” Serenius added. “Many PE applications targeted for screen printing can be handled by gravure due to its inherent ability to deliver a high volume of ink. Unlike screen, gravure is capable of transferring high volumes of ink even at fine resolutions and can be easily controlled using gravure’s third dimension of depth to benefit printing of thin conductive lines; the ink deposition is not just defined by x and y, but also the depth, z. This third dimension is applicable to all types of functional ink deposition and is a tool that is very effective in controlling the film thickness. Thus gravure works well not only for applications like PV and ITO replacement but also for printing of OLED inks and thin conductive interconnects for circuits.”
“Gravure is making its way in printed electronics for sure,” said Dr. Erika Rebrosova of CAPE - Center for the Advancement of Printed Electronics at Western Michigan University, which is using the AccuPress in its laboratories. “Polyera published a paper in Nature in 2009 where they printed organic transistors by gravure. Universities that do research in gravure include us; some reports are seen from UC Berkley, VTT in Finland and Imperial College in the UK.”
“We have seen a lot of interest in gravure,” said John Lettow, president of Vorbeck Materials, which manufacturers Vor-Ink, a graphene-based conductive gravure ink. “I think that gravure and flexography will be where the high-volume applications are produced, and as a result, both flexo and gravure are highly sought after. We see gravure as an area where major manufacturers will be playing. We see primary opportunities being RFID antennas as well as high volume consumer applications.”
Gravure’s ability to produce extremely fine resolutions at high speeds is potentially an important advantage for printed electronics manufacturers.
“The major advantages of gravure are the range of ink volumes and viscosities, both coarse and ultra-fine resolutions, direct transfer of ink, stability of ink carrier, long run-length durability and its ability to print on a wide variety of flexible as well as rigid substrates,” Serenius said. “Gravure also has the unique capability of being able to print different ink film thickness using the same image carrier.”
Dr. Menon said that gravure is a simple and robust process that bridges the gap between traditional publishing and printed electronics, thus stirring interest in traditional publishing firms. He added that Add-Vision has developed a strong partnership with Daetwyler R&D to create world’s first commercial scale sheetfed gravure printer for printing OLEDs, which is adaptable to a roll to roll printing scenario and is broadly compatible with light emitting polymer inks.
Lettow noted that gravure printing combines high output with lower cost due to less ink consumption.
“For manufacturers, the main advantages of gravure are line speed and ink usage, which is generally less than screen printing,” Lettow said. “Gravure can be printed in very thin layers while maintaining high conductivity.”
Lettow said that graphene-based inks offer numerous benefits for printed electronics manufacturers. “One of the key advantages we offer is that using carbon-based conductive gravure inks, we can print layers not nearly as thick as screen while maintaining conductivity. This makes graphene inks a viable alternative to silver inks at a very good cost point.”
Gravure has its limitations. Dr. Menon said more work needs to be done on gravure to make it advantageous for more PE projects.
“The tools and peripheral technologies around gravure need to be adapted to this new materials set as printed electronics has requirements and constraints that are unique as compared to the graphic arts industry,” Dr. Menon said. “We cannot change our artwork on the fly and new cylinders must be engraved for each design change. This design change cost is not significant in large volumes, but can be a factor for small R&D efforts.”
Another disadvantage has been the size of the equipment itself, but Serenius said that is being overcome by new technologies.
Along those lines, Daetwyler R&D has developed unique products that have been specifically designed to meet the requirements for printed electronics: the µStar for microengraving precision cylinders, capable of engraving very fine 3D micro-structures to widths of less than 5 µm and depth control of less than 200 nm;, and the AccuPress for multi-layer microgravure printing, a customizable sheetfed gravure printer, designed for high accuracy layer-to-layer printing required for PE applications for both the lab and limited production runs.
“Gravure limitations have historically been the large scale equipment requirements, but this has changed with the availability of smaller printing units such as the AccuPress,” Serenius noted. “With precision engraving and cell shapes that optimize the transfer of ink on the substrates, the issues such as missing dots and edge definition can be positively monitored.”
Overall, gravure has a strong story to tell when it comes to producing printed electronics systems. For example, Serenius said that near-term, Daetwyler R&D sees opportunities for gravure in accelerated research and dense multi-layer applications.
Long-term, Serenius said that intelligent packaging will become common-place, incorporating technologies such as self-powering photovoltaics, sensors for quality monitoring, displays for information and advertising and RFID.
“Gravure is well suited for these and many other similar applications,” Serenius added.
“Due to high cost of the active materials in printed electronics, gravure printing has a strong advantage over other printing methods such as flexographic printing or screen printing,” Dr. Menon said. “Material use efficiency over 90% is easily achievable with gravure. Also, AVI and its partners are developing pilot scale equipment specifically for printed electronics. This will enable large manufacturers to build pilot scale production facilities.
“There will be large publishing firms entering the printed electronics world to use existing infrastructure to create electronic applications within traditional printing,” Dr. Menon added. “This may be signage, labeling, advertisements, packaging, etc. There will be consumer electronics firms from traditional information displays manufacturing, who realize the advantages of using thin, flexible low cost devices in their applications gaining advantage on form factor and power consumption. This will trigger a whole new application space for printed electronic devices such as Add-Vision OLEDs.”
There are a number of important printed electronic applications where gravure is already playing an important role. Organic light emitting diodes (OLED) for displays and lighting is an important market. Gravure has shown its viability for RFID, as Avery Dennison RFID utilized gravure for UHF RFID label antennas, and Omron uses gravure printing ink as the resist layer for its RFID tags. Transistors, circuits and interconnects are areas where gravure could excel.
Certainly, solar cells could be a sizable market, and work is being conducted on the university and research center levels. For example, “Gravure Printed Flexible Organic Photovoltaic Modules” was a collaboration between researchers at VTT Technical Research Centre of Finland, IMEC, University of Oulu and CEA-INES RDI. As another example, “Gravure Printing for Three Subsequent Solar Cell Layers of Inverted Structures on Flexible Substrates,” written at Centre for Plastic Electronics, Department of Physics, Imperial College of Science, Technology and Medicine in the UK, noted that inverted organic photovoltaic devices have been fabricated by gravure printing on a flexible substrate.
Interest in Gravure
With the advantages that gravure offers, it is no surprise that industry leaders are seeing increasing interest among manufacturers as to how gravure can benefit the PE field.
“The interest in gravure printing is slowly building up as more and more research groups in both industry and academia realize its potential as a simple, commercially viable fast printing method for solvent-based printed electronics,” said Dr. Anoop Menon, senior research scientist for Add-Vision, Inc., a leading developer of organic light-emitting-polymer display technology (P-OLED) for low resolution displays and backlighting applications. “We are aware of serious efforts in the US, UK and Japan in this area.”
Dr. Menon noted that Add-Vision opted for gravure printing to reduce the consumption of expensive light emitting polymer materials, to develop a high throughput process, which would be commercially viable and scalable for mass production and to improve the film uniformity and overall performance of the OLEDs.
“Interest in gravure for PE is strong and growing in relation to an increased understanding of gravure’s inherent benefits,” said Eric Serenius, vice president of Daetwyler R&D. “These benefits include the simplicity of the process, the ability to transfer a variable amount of ink volume, the robustness of the image carrier and its resistance to harsh solvents that are used for printed electronics and its capability to print long runs at high speeds. Additionally, there is an increased awareness of scalable R&D/laboratory tools, such as the AccuPress, which have accelerated growth. Also, influential leaders such as Vivek Subramanian have also fostered awareness and growth.
“Gravure is very well suited for high demand products such as photovoltaics (PV) and indium tin oxide (ITO) replacement,” Serenius added. “Many PE applications targeted for screen printing can be handled by gravure due to its inherent ability to deliver a high volume of ink. Unlike screen, gravure is capable of transferring high volumes of ink even at fine resolutions and can be easily controlled using gravure’s third dimension of depth to benefit printing of thin conductive lines; the ink deposition is not just defined by x and y, but also the depth, z. This third dimension is applicable to all types of functional ink deposition and is a tool that is very effective in controlling the film thickness. Thus gravure works well not only for applications like PV and ITO replacement but also for printing of OLED inks and thin conductive interconnects for circuits.”
“Gravure is making its way in printed electronics for sure,” said Dr. Erika Rebrosova of CAPE - Center for the Advancement of Printed Electronics at Western Michigan University, which is using the AccuPress in its laboratories. “Polyera published a paper in Nature in 2009 where they printed organic transistors by gravure. Universities that do research in gravure include us; some reports are seen from UC Berkley, VTT in Finland and Imperial College in the UK.”
“We have seen a lot of interest in gravure,” said John Lettow, president of Vorbeck Materials, which manufacturers Vor-Ink, a graphene-based conductive gravure ink. “I think that gravure and flexography will be where the high-volume applications are produced, and as a result, both flexo and gravure are highly sought after. We see gravure as an area where major manufacturers will be playing. We see primary opportunities being RFID antennas as well as high volume consumer applications.”
Gravure’s ability to produce extremely fine resolutions at high speeds is potentially an important advantage for printed electronics manufacturers.
Dr. Menon said that gravure is a simple and robust process that bridges the gap between traditional publishing and printed electronics, thus stirring interest in traditional publishing firms. He added that Add-Vision has developed a strong partnership with Daetwyler R&D to create world’s first commercial scale sheetfed gravure printer for printing OLEDs, which is adaptable to a roll to roll printing scenario and is broadly compatible with light emitting polymer inks.
Lettow noted that gravure printing combines high output with lower cost due to less ink consumption.
“For manufacturers, the main advantages of gravure are line speed and ink usage, which is generally less than screen printing,” Lettow said. “Gravure can be printed in very thin layers while maintaining high conductivity.”
Lettow said that graphene-based inks offer numerous benefits for printed electronics manufacturers. “One of the key advantages we offer is that using carbon-based conductive gravure inks, we can print layers not nearly as thick as screen while maintaining conductivity. This makes graphene inks a viable alternative to silver inks at a very good cost point.”
Gravure has its limitations. Dr. Menon said more work needs to be done on gravure to make it advantageous for more PE projects.
“The tools and peripheral technologies around gravure need to be adapted to this new materials set as printed electronics has requirements and constraints that are unique as compared to the graphic arts industry,” Dr. Menon said. “We cannot change our artwork on the fly and new cylinders must be engraved for each design change. This design change cost is not significant in large volumes, but can be a factor for small R&D efforts.”
Another disadvantage has been the size of the equipment itself, but Serenius said that is being overcome by new technologies.
Along those lines, Daetwyler R&D has developed unique products that have been specifically designed to meet the requirements for printed electronics: the µStar for microengraving precision cylinders, capable of engraving very fine 3D micro-structures to widths of less than 5 µm and depth control of less than 200 nm;, and the AccuPress for multi-layer microgravure printing, a customizable sheetfed gravure printer, designed for high accuracy layer-to-layer printing required for PE applications for both the lab and limited production runs.
“Gravure limitations have historically been the large scale equipment requirements, but this has changed with the availability of smaller printing units such as the AccuPress,” Serenius noted. “With precision engraving and cell shapes that optimize the transfer of ink on the substrates, the issues such as missing dots and edge definition can be positively monitored.”
Overall, gravure has a strong story to tell when it comes to producing printed electronics systems. For example, Serenius said that near-term, Daetwyler R&D sees opportunities for gravure in accelerated research and dense multi-layer applications.
Long-term, Serenius said that intelligent packaging will become common-place, incorporating technologies such as self-powering photovoltaics, sensors for quality monitoring, displays for information and advertising and RFID.
“Gravure is well suited for these and many other similar applications,” Serenius added.
“Due to high cost of the active materials in printed electronics, gravure printing has a strong advantage over other printing methods such as flexographic printing or screen printing,” Dr. Menon said. “Material use efficiency over 90% is easily achievable with gravure. Also, AVI and its partners are developing pilot scale equipment specifically for printed electronics. This will enable large manufacturers to build pilot scale production facilities.
“There will be large publishing firms entering the printed electronics world to use existing infrastructure to create electronic applications within traditional printing,” Dr. Menon added. “This may be signage, labeling, advertisements, packaging, etc. There will be consumer electronics firms from traditional information displays manufacturing, who realize the advantages of using thin, flexible low cost devices in their applications gaining advantage on form factor and power consumption. This will trigger a whole new application space for printed electronic devices such as Add-Vision OLEDs.”