Minnesota Mining and Manufacturing Company

Harvey A Brown

William A Huffman

Alan G Miller

Louis M Leichter

Jack E Reece

Thermographic composition comprising a leuco dye, a nitrate salt, and, optionally, an acid and stabilizing compound. The leuco dye contains a phenazine nucleus with naphthoyl substitutents on the 10-position and, optionally on one or both of the 3- and 7-positions through an amino group. In their oxidized form, the leuco dyes of this invention provide access to a range of red and magenta colors which exhibit greater stability when subjected to light and temperatures characteristic of the stage of overhead projectors than that exhibited by previously available leuco dyes of this color range.

Thermographic system using naphthoylated leuco phenazine dyes

A composition for use in thermally-addressable liquid crystal display devices, comprising a smectic liquid crystal material and a helichromic compound possessing both a chromophoric moiety and an optically-active moiety. The helichromic compound is a circularly dichroic dye capable of propagating incident visible light in a circularly polarized manner so that all polarizations of the incident light are absorbed. The composition comprising the helichromic compound can be utilized in thermally-addressable liquid crystal display devices to provide a display which operates at lower voltages, with faster response times, and higher contrast ratios.

Helichromic-smectic liquid crystal compositions and display cells

A composition for use in liquid crystal display devices, consisting essentially of a nematic liquid crystal material and a helichromic compound possessing both a chromophoric moiety and a helical ordering moiety. The helical ordering moiety is capable of helically ordering the mixture of liquid crystal material and helichromic compound. The helichromic compound can be utilized in conventional 'guest-host' and 'twist nematic' displays as well as in unique helichromic displays. When used in helichromic displays, the helichromic compounds eliminate after-image scattering and enable the display to be operated at reduced voltages.

Helichromic compounds and displays

A particular class of novel nitro-substituted dyes has been found to act as effective, heat labile acutance dyes for photothermographic emulsions.

Thermolabile acutance dyes

Photothermographic emulsions containing thermolabile acutance dyes

Methine 4-nitro-arylidene dyes having certain substituents in the 2 position of the arylidene group are found to be pleochroic and to form guest-host combinations with dielectrically positive anisotropic nematic liquid crystals. These combinations are employed in electro-optical display devices.

Electro-optical devices containing methine arylidene dyes

Certain members of the class of odd-numbered methine arylidene dye bases are found to be of use in thermally-developable photosensitive compositions and thermally-developable photosensitive elements containing such agents. These compounds are acutance agents which are relatively stable against photo-bleaching but undergo thermochemical bleaching on heating in silver salt-containing thermally-developable photosensitive compositions.

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Lake Elmo, MN, United States of America

Harvey A Brown