Sony Corp developed a machine that produces graphene, which is two-dimensionally connected carbon atoms, by using a roll-to-roll method and made a graphene sheet with a width of 23cm and a length of 100m.

It is the largest area of graphene sheet in the world. Sony will deliver a lecture on the technologies used to realize the sheet and the results of the production at the 73rd JSAP Autumn Meeting, 2012, which the Japan Society of Applied Physics (JSAP) will organize at Ehime University from Sept 11 to 14, 2012 (lecture number: 14a-C1-11).

Thus far, South Korea-based manufacturers and research institutes have been leading the development of large-area graphene. But, due to the use of a high-temperature (1,000°C) manufacturing process for a chemical vapor deposition (CVD) method, they have not yet succeeded in using a roll-to-roll method to make a large-area graphene.

On the other hand, Japan's National Institute of Advanced Industrial Science and Technology (AIST) developed a CVD method that uses 300-400°C plasma, enabling to apply a roll-to-roll method to the manufacturing of graphene. However, the method does not always produce a single-layer graphene, and what is produced is an accumulation of graphene pieces with very small diameters. The sheet resistance of the graphene sheet is about 1,000Ω/□.

This time, Sony developed a technology to use both a CVD method and a roll-to-roll method without changing the process temperature of 1,000°C. Specifically, the company directly applied a current to a copper (Cu) foil that is the catalyst of graphene and a substrate for the CVD method so that only the Cu foil is heated. As a result, the thermal load on the entire machine was drastically reduced.

Furthermore, Sony made a transparent conductive film by transcribing a graphene sheet formed on the Cu foil to a PET (polyethylene terephthalate) film. The sheet resistance of the film is as low as 200Ω/□, and its optical absorptance is 2.9%, the company said.