Dawn Skinner, process development manager, Fusion UV Systems, looks at the potential for UV curing in the field of organic and printed electronics
Organic or printed electronics is an innovative method of producing electronic devices that combine the characteristics of being thin, lightweight and flexible, with processes that deliver cost effective manufacturing of high volume products on substrates such as paper, plastics and fabrics.
It also enables a wide range of electrical components to be produced and directly integrated into products in roll-to-roll processes. This creates many new opportunities to expand the use of electronics into a wide range of new applications such as flexible solar cells, RFID (radio frequency identification) tags, flexible displays, lighting, and flexible thin film batteries.
Market analysts have predicted a strong growth for organic electronics over the next 10 years or so. IDTechEx expects the market to grow to $57 billion by 2019. In the longer term, by 2025, the potential is for a $300 billion market – comparable to the current silicon electronics industry.
Meeting the growth expectations for many of the applications relies on being able to produce large quantities of devices, efficiently and with lower costs. To achieve these targets there is great interest in using UV curing technology in the various printing and coating applications in the manufacturing processes.
Offering many advantages over traditional drying methods, UV curing has been shown to increase production speed, reduce reject rates, improve scratch and solvent resistance, and facilitate superior bonding. In UV curing, there is no solvent to evaporate, no environmental pollutants, no loss of coating thickness, and no loss of volume. This results in higher productivity in less time, with a reduction in waste, energy use and pollutant emissions.
To meet the demands of high volume production with lower manufacturing costs, the processes for many organic electronics must be automated, and in many cases they are moving towards roll-to-roll applications.
In addition to this, many of the substrates used in printed electronics are heat sensitive films, so low temperature curing of the coatings and inks is required to prevent distortion of the substrate.
The rapid cure of UV inks and coatings and the low heat impact of the process are key motivating factors in encouraging the interest in UV curing from the printed electronics manufacturers; with opportunities for UV curing in applications including, encapsulants, barrier coatings, conductive inks and coatings, as well as anti-reflective coatings.
Optimising the process
However, there are challenges in developing UV curable inks, coatings and adhesives for use in organic electronic applications. For example, curing conductive inks that contain metallic pigments, or coatings with high levels of UV absorbers to ensure long term weatherability of scratch resistant barrier coatings requires optimisation of the interaction between the chemistry and the UV lamp system. This means matching the UV spectral output from the bulb to the absorption profile of the ink or coating.
High irradiance UV light, as delivered from a microwave powered UV lamp system, can be used to ensure a rapid and effective cross-linking process that allows a high speed process to reduce the impact of heat on the substrates. Dichroic reflectors may also be added to the UV lamp system to further reduce the effect of IR (infra-red) energy on the substrate.
UV curing is already being used in a number of applications in the production of organic electronic products. With further development work and continued co-operation between the coating formulators, UV lamp manufacturers and the end-users, UV curing will unquestionably play a significant role in the rapidly developing market for organic electronics.
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