Sumitomo Corp. Exhibits Transparent Electroconductive Film Formed from Coating Technology

Feb 25, 2007
Satoshi Ookubo, Nikkei Electronics
Plastic substrate on which a transparent electroconductive film was formed by coating and role-to-role technologies.
Plastic substrate on which a transparent electroconductive film was formed by coating and role-to-role technologies.
[Click to enlarge image]

Sumitomo Corporation displayed a transparent electroconductive film that can be formed with coating technology at the "International Nanotechnology Exhibition and Conference (nano tech 2007)" held at Tokyo Big Sight from February 21 through February 23, 2007. Sumitomo used a special ink technology developed by U.S. Cambrios Technologies Corp., thereby enabling the transparent electroconductive film manufacturing process to utilize a solution. The process enables not only to provide plastic or glass substrates in their state where a transparent electroconductive film has been applied on the substrate surface, but also to ship transparent electroconductive ink. Supposed applications include touch and liquid crystal panels and thin-film solar cells. Sample shipment has already started for touch panel purposes along with alleged well-preparedness for quantity production. According to Sumitomo, it recently signed an agency contract with Cambrios.

Sumitomo attributes merits of the transparent electroconductive film-applied sheet to its low price and the substrate's strong resistance to its bending. The sheet can be fabricated at lower cost than an ITO film-based counterpart since its manufacturing process can dispense with any vacuum equipment, the company explains. Bending strengths were compared with those when a transparent electroconductive film was formed on the plastic substrate. The sheet was bent and stretched 50 times from straight to a curvature radius of 8mm, which resulted in no fluctuation or deterioration in sheet resistance.

The sheet resistance as a function of the transmission factor is exemplified by some 60Ω/square for the transmission factor of 90%. According to the explanation by a clerk in charge of Sumitomo Corp., the sheet resistance is below 100-200Ω/square at the transmission factor of 92-92%, satisfying touch panel manufacturers' demand. The transmission factor and the sheet resistance have continued to improve, so further increase of the transmission factor and decrease of the sheet resistance are expected to achieve in the future.