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;PPZ is a 1,3-(2- hydroxy-4-oxo-2-cyclobutylidene) hydroxide or 1,3-(2-hydroxy-4,5-dioxo-2- cyclopentylidene) hydroxide ring; andPPQ.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.