LCD coating material by Toray
One of the materials used in manufacturing of a LCD panel is “retarder”. Retarder is used to increase the viewing angle of LCD panel and it is normally a thin film that is attached to a glass substrate but due to expansion and contraction of this thin film especially in a large panel there has been a drive to form a retarder inside an LCD panel. But success in formation process using the existing coating material for retarder requires more than six preliminary steps which includes the coating of alignment film, orientation processing and exposure.
Toray Industries Inc. has developed a new coating material that replaces the existing retardation film and as a result manages to reduce the formation process to only two steps which requires that material to be applied to color filters and then the coating will go through thermal coating eliminating a need for orientation processing and other steps. This new material was designed in such a way to optimize the electron migration occurs between two constituents of the polyimide to provide transparency. The alignment film has a thickness of several micron with equal or higher viewing angle properties of VA LCD panels. According to Toray given surface irregularity of color filter of within 0.3 micro meter a render can be formed on an as-is basis without any need in performing the planarization such as over coating. According to company the retardation properties stays unaffected after the thermal treatment of about 230 degrees Celsius being a requirement in LDC panel production. In addition to this the new retarder provides an adequate resistance to a high polarity solvent which is used to form an alignment film on the retarder. This new coating material has been optimized for vertical alignment LCD panels but it can also be used for Twisted Nematic panels as well.