April 8, 2011
Toray Advanced Film Co., Ltd.
Toray Advanced Film Developed New Transparent Conductive Material Using Silver Nanowire Ink
- Best in the world in transparency and conductivity, superior flexibility, natural color, durability and workability; to be mass-produced for use in touch panels -
Toray Advanced Film Co., Ltd. (head office: Chuo-ku, Tokyo; President: Susumu Yamaguchi; hereinafter referred to as "the Company") today announced that it has succeeded in developing a silver nano-wire based transparent conductive film with the world’s best transparency and conductivity -light transmittance of 90% or above and surface resistivity*1, which is a measure of conductivity, between 150 and 250 Ω/sq- using wet coating method. The material also boasts superior flexibility, natural coloration, durability and workability, and the Company expects to begin its mass production in the near future.
Transparent conductive films are generally ITO films*2 by use of vapor deposition or sputtering methods, making them not much suitable for bending as they are thin and brittle inorganic material, and they sometimes affect the flexibility of the final product. Furthermore, the primary raw material Indium being a rare metal, there is also the issue of depletion of resources. On the other hand, wet coating films using organic conducting materials, while superior in flexibility tend to be susceptible to discoloration*3 when conductivity is improved. They also have issues on durability under high heat and higher moisture circumstance though some products using such materials are available in the market. At the same time, in touch panel and display applications, it is necessary to not only have durability and reliability but also compatibility with pattern processing and other peripheral technologies without losing optical characteristics.
Against this background, the Company recently entered into a strategic partnership with Cambrios Technologies Corporation (head office: Sunnyvale, California; CEO: Michael Knapp), a U.S.-based electronic materials manufacturer, to develop a new product that addresses the above issues by bringing together high transparency, high conductivity nanowire ink technology of Cambrios with the Company’s superior film processing technology.
Key technological points of the transparent conductive film developed this time using silver nanowire ink are as follows: (1) nano-level coating thickness control technology, (2) wet-method multilayer laminating technology, and (3) product design proposals that suit the fabrication process of the user. The product is considered better suited for mass production in comparison with ITO films which require sputtering or other such vacuum process. Also, given its superior flexibility and invisible patterning properties*4 in addition to high transparency and conductivity, the new film is expected to find application in touch panels used in cellular phones, smart phones and tablet PCs. The material can also address the need for lower resistance required by larger-sized touch panels and therefore the Company expects it to contribute to the display technology revolution in the future. Going forward, the Company hopes the film would eventually be used in 3-D touch panels, solar cells and organic EL electrodes.
The Company intends to further grow its touch panel-related business centered on business expansion of transparent conductive materials widely used in smart phones and tablet PCs.
The Company will display the new products at the 2nd Highly-functional Film Technology Expo to be held at the Tokyo Big Sight Japan from April 13 (Wed) to April 15 (Fri), 2011.
*1 Surface resistivity
Surface resistivity is one of the yardsticks for measuring antistatic performance (or conductivity). It denotes the resistance per unit area and is measured in Ohms per square (Ω/sq). As long as the sample being measured is square, the surface resistivity will be the same regardless of the size of the sample (e.g. the value is same for 1mm2, 1 m2 or 1 km2).
Indium tin oxide, or ITO, is a type of inorganic compositions with transparency and conductivity, used as a primer after nano-atomization and in sputtering-based ITO films.
Organic conducting agents are generally prone to specific coloration. While coloration is barely noticeable in thin films, the thicker the films are made to boost conductivity, the more prominent it becomes. For example, in the case of polythiophene series the color becomes dark blue and for polypyrrole it becomes dark brown.
*4 Invisible patterning properties
When using conductive films in touch panels for smart phones, etc. it is necessary to carry out patterning. This patterning has been found to generate patterns with differences in degree of transmission and reflection, coloration and other optical properties. It is necessary to keep these differences in optical properties to the minimum in order to carry out patterning that is invisible to human eyes.