A
phthalocyanine dye of formula (I) is provided: wherein M is a
metal group or is absent; Ar1, Ar2, Ar3, Ar4, Ar5, Ar6, Ar7 and Ar8 are selected from phenyl, naphthyl, pyridyl, furanyl, pyrollyl or thiophenyl, each of Ar1, Ar2, Ar3, Ar4, Ar5, Ar6, Ar7 and Ar8 being optionally substituted with 1, 2, 3, 4 or 5 groups, the or each group being independently selected from C1-12
alkyl, C1-12alkoxy, C1-12arylalkyl, C1-12 arylalkoxy, —(OCH2CH2)dORd, cyano,
halogen, amino, hydroxyl,
thiol, —SRv, —NRuRv, nitro, phenyl, phenoxy, —CO2Rv, —C(O)Rv, —OCORv, —SO2Rv, —OSO2Rv, —NHC(O)Rv, —CONRuRv, —CONRuRv,
sulfonic acid,
sulfonic acid salt and sulfonamide; d is an integer from 2 to 5000; Rd is H, C1-8
alkyl or C(O)C1-8
alkyl; Ru and Rv are independently selected from
hydrogen, C1-12alkyl, phenyl or phenyl-C1-8alkyl; wherein at least one of Ar1, Ar2, Ar3, Ar4, Ar5, Ar6, Ar7 and Ar8 is substituted with a
sulfonic acid, a sulfonic
acid salt or a sulfonamide group. Dyes of this type are especially suitable for use in netpage and Hyperlabel™ systems.