Tanaka Holdings Co., Ltd (a company of Tanaka Precious Metals) today announced that Tanaka Kikinzoku Kogyo K.K., which operates the Tanaka Precious Metals' manufacturing business, had commercialized the world's first conductive silver ink capable of forming electronic circuits using only hardening by ultraviolet (UV) light without the need for hardening by heating, and will begin selling the product on January 18.

After printing a circuit on base material using this ink and,exposing it to UV light for approximately 0.3 seconds, the user can instantly harden the printed film even at room temperature to form a circuit that carries current. At a film thickness of five micrometers or more (one micrometer is one millionth of a meter), it is possible to form wiring on the same level as the conductive material generally used at present, with electrical resistivity of 10-3Ωcm (10-3Ω per 1 centimeter).

By using this ink, it is possible to perform wiring not only on glass base material and substrates, but also flexible base material such as polyvinyl chloride film (PVC film) and polyester film (PET film) on which it was previously difficult to form electronic circuits due to their susceptibility to heat. In particular, because it is possible to form wiring on all types of film base material by attaching this silver ink using flexographic printing that transfers ink by making it adhere to protrusions on a rubber plate, this ink is very effective wiring material for
printed electronics which produces electronic components by printing. It is expected to be applied to electronic circuits in a wide range of products including solar cells (silicon, dye sensitized, etc.) and organic EL (electroluminescence) lighting, in addition to touch panel displays, electronic books, RFID (radio-frequency identification) tags and electronic packaging for use in drug therapy monitoring.

Challenge in Thermal Hardening
A variety of technologies are currently being developed to enable popularization of printed electronics on a practical level as a next generation technology able to produce electronic equipment that is thin, lightweight and difficult to break at a low cost. Wiring materials such as materials enabling current to be carried in a circuit by heating printed metal nanoparticles are being developed, but it is necessary to form circuits without heating in order to form circuits on all types of base material such as PET film susceptible to heat. Heating conditions for ink hardening have been an issue in wiring materials because they all required a heating process such as materials requiring heating at 50 degrees Celsius to 100 degrees Celsius for several minutes, and materials requiring heating to supplement hardening by UV
irradiation.

World's First Commercial Product
This conductive silver ink commercialized by Tanaka Kikinzoku Kogyo for the first time in the world is a wiring material able to instantly form electronic circuits simply by being irradiated with UV light under room temperature conditions without heating due to optimization of the
composition and mixture of resin containing silver nanoparticles and reaction initiator. As there is no need for the large equipment or thermal processing time required in thermal hardening, it is possible to significantly improve production speed per unit of area using an overwhelmingly small device space. A total of three silver inks using different types of resin and reaction initiator will be available, and users can select the materials according to their manufacturing equipment and application.

Tanaka Kikinzoku Kogyo will sell the product for some time as a sample for solar cell manufacturers, display manufacturers and
printer manufacturers. The company will also work on technological improvements such as improving the electrical resistance of products while continuing to monitor trends in the industry aimed at the full-scale implementation of printed electronics expected to take place in the future.
 

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