Electro-optical composition of the guest-host type

An electro-optical composition comprising a host liquid crystal admixed with a linear, noncondensed aromatic guest dichroic dye of the formula:

• ##STR16## were Ar.sub.1 and Ar.sub.2 can be the same or different mono or polycylic aromatic radical selected from:
• ##STR17## or (i) combinations of two or more of (a)-(h) joined together in a linear, noncondensed structure, with the proviso that when Ar.sub.1 or Ar.sub.2 comprise only one of (a)-(h), the radical is joined to the quinonoid ring at a 1(para) type ring position in the case of (a) and at 2 ring position in the of (b)-(h) and that when Ar.sub.1 or Ar.sub.2 comprise the combination of two or more of (a)-(h), radical (a) is linked to adjacent radicals at 1,4 type ring positions, radicals (b), (c) and (d) at 2,5 type ring positions and radicals (e)-(h), when present, are terminal radicals at the end of the dye molecule and are linked to adjacent (a), (b), (c) or (d) radicals at a 2 ring position, and with the further proviso that the terminal radical of the dye molecule may include a generally linear, nonionic substituent at a 4-type terminal ring position in the case of (a), at a 5-type terminal ring position in the case of (b), (c) and (d), at the 4 or 5 terminal ring position in the case of (e) and (f) and at the 5 or 6 terminal ring position in the case of (g) and (h), and where X is a monovalent blocking substituent which is not fused to the adjacent aromatic radical so as to ensure the linear, noncondensed, molecular structure.

An electro-optical composition comprising a host liquid crystal admixed with a linear, noncondensed aromatic guest dichroic dye of the formula:

• ##STR19## where Ar.sub.1 and Ar.sub.2 can be the same or a different mono or polycyclic aromatic radical selected from:
• ##STR20## or (i) combinations of two or more (a)-(h) joined together in a linear, noncondensed structure, with the proviso that when Ar.sub.1 or Ar.sub.2 comprise only one of (a)-(h), the radical is joined to the quinonoid ring at a 1 (para) type ring position in the case of (a) and at a 2 ring position in the case of (b)-(h) and that when Ar.sub.1 or Ar.sub.2 comprise the combination of two or more of (a)-(h), radical (a) is linked to adjacent radicals at 1, 4 type ring positions, radicals (b), (c) or (d) at 2, 5 type ring positions and radicals (e)-(h), when present, are terminal radicals at the end of the dye molecule and are linked to adjacent (a), (b), (c) or (d) radicals at a 2 ring position, and with the further proviso that the terminal radical of the dye molecule may include a generally linear, nonionic substituent at a 4 type terminal ring position in the case of (a), at a 5 type terminal position in the case of (b), (c) or (d) at the 4 or 5 terminal ring positions in the case of (e) and (f) and at the 5 or 6 terminal ring positions in the case of (g) and (h), and where X is monovalent blocking substituent which is not fused to the adjacent aromatic radical so as to ensure that linear, noncondensed molecular structure.

In an electro-optical display device comprising two spaced transparent substrates whose facing surfaces have been coated with transparent electrodes, the improvement comprising an electro-optical composition disposed between the substrates comprising a host liquid crystal admixed with a linear, non-condensed aromatic guest dichroic dye of the formula:

• ##STR23## where Ar.sub.1 and Ar.sub.2 can be the same or a different mono or polycyclic aromatic radical selected from:
• ##STR24## or (j) combinations of two or more of (a)-(i) joined together in a linear, noncondensed structure, with the proviso that when Ar.sub.1 or Ar.sub.2 comprise only one of (a)-(i), the radical is joined to the quinonoid ring at a 1 (para) type ring position in the case of (a) and at a 2 type ring position in the case of (b)-(i) and that when Ar.sub.1 or Ar.sub.2 comprise the combination of two or more of (a)-(i), radical (a) is linked to adjacent radicals at 1, 4 type ring positions, radicals (b), (c), (d) and (e) are linked to adjacent radicals at 2, 5 type ring positions and radicals (f)-(i), when present, are terminal radicals at the end of the dye molecule and are linked to adjacent (a), (b), (c), (d), or (e) radical at a 2 ring position, and with further proviso that the terminal radical of the dye molecule may include a generally linear, nonionic substituent at a 4 type terminal ring position in the case of (a), at a 5 type terminal ring position in the case (b), (c), (d) and (e) at a 4 or 5 terminal ring position in the case (f) and (g) and at 5 or 6 terminal ring position in the case of (h) and (i), and where X is a monovalent blocking substituent which is not fused to the adjacent aromatic radical so as to ensure the linear, noncondensed molecular structure.