Apr. 30, 2020
Toray Industries, Inc.
Toray Wins Top Award in Japan for New Organic EL Insulating Film Coating

Tokyo, Japan, April 30, 2020 – Toray Industries, Inc., announced today that has won the 2020 Commendation for Science and Technology from the Minister of Education, Culture, Sports, Science and Technology for developing a polyimide coating for organic electroluminescent (EL) insulating films. The award recognizes Toray’s efforts over the years to deepen its photosensitive polyimide technology capabilities, developing a positive photosensitive polyimide that dramatically enhances the luminous reliability and productivity of organic EL displays. The adoption of these displays is expanding rapidly among television sets, smartphones, and other electronic devices because they are incredibly thin and light and deliver excellent video display performance. Organic EL layers in these displays can easily deteriorate because they are very sensitive to water and impure gases. Pixel division layers in insulating films are therefore vital because they ensure minimal outgassing, for outstanding long-term reliability. The mass production of organic EL displays employs slit-die coating (see glossary note 1) to apply insulating film in small quantities in flat panel manufacturing processes. Conventional polyimide coatings are uneven and unattractive. The challenge became to develop a polyimide coating that could leverage slit -die coating to form polyimide coating films that look excellent. Toray accordingly set about exploring the potential of its polyimide materials technology, which offers exceptional chemical stability and thermal resistance. It applied a new solvent design in which it blended a polyimide coating, comprising a polyimide precursor resin, photosensitizer, and solvent, with a specific ratio of low- and high-boiling-point solvents. This resulted in a polyimide coating for organic EL insulating films that is both highly reliable and is suitable for mass production. This technique made it possible to apply coatings with just one-tenth the amount of polyimide coating used with spin coating (note 2). The ability to form polyimide coatings that appear attractive led Toray to become the first in the world to commercialize a photosensitive polyimide for commercial slit-die coating, which has been widely adopted. Toray’s coating technology has contributed to the mass production and broader adoption of organic EL displays. It has also helped significantly reduce coating waste losses, thereby lowering environmental impact. Another key benefit of Toray’s technology is that it offers considerable market expansion potential by enabling a range of curved designs in foldable devices, wearables, and automotive and other applications. Toray will continue to cultivate its photosensitive polyimide technology and foster the adoption of organic EL displays, thereby contributing to social progress.

1.Slit-die coating
This technique is suitable for coating glass and other rectangular substrates. It entails using a slot-die nozzle whose length is the same as the long or short side of a rectangular substrate, positioning the nozzle near the substrate to deliver a coating fluid. Substrates can be up to around 10 square meters.
2.Spin coating
This technique is for coating circular substrates, silicon wafers being representative examples. It entails dripping a coating fluid onto the center of a substrate, spreading as the substrate spins. Substrates for this process are generally smaller than 0.5 square meters.