Japanese Showa Denko (SDK) and Microwave Chemical have developed a technology to mass produce silver nanowire ink that forms transparent electro-conductive patterns through utilization of printing technology. In 2012, SDK developed printable silver nanowire ink to form transparent electro-conductive patterns on flexible films jointly with Professor Katsuaki Suganuma of National University Corporation Osaka University. In order to form conductive patterns with high transparency and high electro-conductivity, it is very important to raise the aspect ratio (ratio of length to diameter) of silver nanowire, a metallic nanomaterial. Since the conventional method to synthesize silver nanowires tends to allow silver nanoparticles to have crystal growth on all of their surfaces, it is not easy to have silver nanoparticles grow to be nanowires. Therefore, establishment of technology that realizes stable mass production of silver nanowires was a problem.

This time, SDK and Microwave Chemical jointly developed a method to synthesize silver nanowires with microwave heating, a technology to selectively heat materials. If microwave is irradiated on silver nanoparticles in their growth process to be silver nanowires, only the growing ends absorb energy and generate heat. In order to utilize this property, SDK made silver nanoparticles selectively absorb capping agent that interferes crystal growth, and successfully produced slender nanowires with great efficiency.

After printing, silver nanowire ink expresses electro-conductivity after application of Photonic CuringTM process technology. This time, SDK has developed undercoating agent that enhances adhesion of silver nanowire patterns to the surfaces of substrates or films and minimizes damage to substrates or films caused by curing. SDK is also developing overcoating agent that prevents deterioration of silver nanowires which are said to be weak against heat.

SDK will start to offer samples of the ink and related materials in July 2015.

The company will exhibit a touch sensor and a 7-inch touch panel made with the ink and related materials on experimental basis at the SDK?s booth in "JPCA Show 2015" which is to be held at Tokyo Big Sight from June 3 to 5, 2015.