Benzpyrylium squarylium and croconylium dyes, and processes for their preparation and use

摘要

Dyes comprising an inner salt of a compound of the formula: P PQ.sup.1 =Z-Q.sup.2PPwherein:P PQ. sup.1 is a 4-(benz[b]-4H-pyrylium)methylidene, 4-(benz[b]-4H- thiopyrylium) methylidene or 4-(benz[b]-4H-selenopyrylium)methylidene grouping;P PZ is a 1,3-(2-hydroxy-4-oxo-2-cyclobutylidene) hydroxide or 1,3- (2-hydroxy-4,5-dioxo-2-cyclopentylidene) hydroxide ring; andP PQ.sup.2 is a 4-(benz[b]-4H-pyran-4-ylidene) methyl, 4-(benz[b]-4H- thiopyran-4-ylidene)methyl or 4-(benz[b]-4H- selenopyran-4-ylidene)methyl grouping;PPwherein at least one of the groupings Q.sup.1 and Q.sup.2 carries at its 2-position a substituent in which a non- aromatic carbon atom is bonded directly to the benzpyrylium, benzthiopyrylium or benzselenopyrylium nucleus, subject to the proviso that if this 2-substituent contains an aromatic nucleus, this aromatic nucleus is not conjugated with the benzpyrylium, benzthiopyrylium or benzselenopyrylium nucleus to which it is attached, are useful as visible and near infra-red absorbers, having high extinction coefficients and improved solubility in polymeric media.