page_title: Dichroic dyes, electronic dyes, liquid crystalline dyes
hierarchical_section_title: Dichroic dyes, electronic dyes, liquid crystalline dyes
context_page_description: During the 20th century, dichroic dyes had been used as electric field responsive colorants for rugged avionics and armored vehicle electronic displays. In general, dichroic dye displays had more predictable performance than twisted nematic liquid crystal displays or plasma displays, until technological advances in nematic displays surpassed the performance of dichroic dyes.
  These displays were used in early Boeing 757 and 767 models, and the displays were manufactured by Litton, Stanley Electric, Racal, AEG and Crystalloid, amongst others.
  In the Sovient Union, dye research was extensively performed by Niopik. Currently dichroic displays for avionics is manufactured in the USA by Transicoil and Polytronix. Dichroic displays are also manufactured by AlphaMicron, amongst others.
  Many dyes exhibit dichroism. Some of these dyes are soluble in commercial liquid crystals.
  Dyes which are effective for use in liquid crystal displays:
  Azomethine,
  Indigoid and Thioindigoid,
  Merocyanine,
  Azulenes,
  Quinophthalonic,
  Perylene,
  Phthaloperine,
  Triphenodioxazines,
  Quinoxalines,
  Triazine,
  Tertrazine,
  Azo dyes, and
  Anthraquinone.
context_section_description: During the 20th century, dichroic dyes had been used as electric field responsive colorants for rugged avionics and armored vehicle electronic displays.  In general, dichroic dye displays had more predictable performance than twisted nematic liquid crystal displays or plasma displays, until technological advances in nematic displays surpassed the performance of dichroic dyes.
  These displays were used in early Boeing 757 and 767 models, and the displays were manufactured by Litton, Stanley Electric, Racal, AEG and Crystalloid, amongst others.
  In the Sovient Union, dye research was extensively performed by Niopik.  Currently dichroic displays for avionics is manufactured in the USA by Transicoil and Polytronix.   Dichroic displays are also manufactured by AlphaMicron, amongst others.
  Many dyes exhibit dichroism.  Some of these dyes are soluble in commercial liquid crystals.
  Dyes which are effective for use in liquid crystal displays:
  Azomethine,
  Indigoid and Thioindigoid,
  Merocyanine,
  Azulenes,
  Quinophthalonic,
  Perylene,
  Phthaloperine,
  Triphenodioxazines,
  Quinoxalines,
  Triazine,
  Tertrazine,
  Azo dyes, and
  Anthraquinone.
  After considerable research, scientists and engineers have identified dyes have proven suitable for use for liquid crystal displays.  The dyes need adequate lightfastness, suitable wavelength bands, and sufficient order parameter in a liquid crystal host to function as display ingredients.
  Obtaining dyes with sufficient order parameter in the liquid crystal host has been one of the primary challenges to the adoption of dichroic dyes by industry.  Although some dyes exhibit some dichroic qualities, most dyes do not have sufficient dichroic order parameter to function as display ingredients.
  In order to achieve dyes with sufficient order parameter, researchers have synthesized novel dyes which themselves are liquid crystalline in character to function as display ingredients.  The challenges that researchers face are : (1) high purity (2) small quantities and (3) high efficiency. A few companies have overcome these challenges, such as Mitsui Toatsu in Japan and Merck in the U.K.
  In most cases novel dyes were engineered specifically for use with liquid crystals.  The dyes were synthesized from common non-toxic dyes, and substituents with liquid crystalline characteristics were purposely attached to the dyes, not unlike tinker toys.
  Dichroic dyes differ from electrophoretic charged particle displays, commonly called E-ink.
  Suitable dyes are available across the visible spectrum, although there are few, if none, green colored dyes with sufficient order parameter for display use.
  Currently dichroic dyes are used in switchable windows and in some special purpose displays and consumer novelty goods.
caption: Twisted Nematic LCD Schematic
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