It can take as long as a year to get a mixture correct. Merck assumes the responsibility of meeting a manufacturer's specifications. Often the specs are tightened on the next order. Mixtures have involved as many as several hundred compounds. Some customers remix materials or change mixtures supplied by Merck.
Purity is always an important issue.
TN and STN Display Materials Table 2.2 outlines the physical properties of a nematic material that is desired for an STN display, along with values typically provided by manufacturers. These data were graciously supplied by Dr. H. Takatsu of Dainippon Ink and Dr. B. Rieger of Merck-Japan. Uniformity may be an issue that alters the value of the pretilt used, but not without a compromise in speed. High resistivity, approx. This parameter is controlled by ionic impurities, hence the demand for highly purified materials.