A
naphthalocyanine dye of formula (I) is provided: wherein M is a
metal group or is absent; R1 and R2 are independently selected from
hydrogen or C1-12 alkoxy; X is selected from O, S or —NH—; Ar1, Ar2, Ar3, Ar4, Ar5, Ar6, Ar7 and Ar8 are selected from phenyl, naphthyl, pyridyl, furanyl, pyrollyl, 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, C1-12 alkoxy, C1-12 arylalkyl, 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; and Ru and Rv are independently selected from
hydrogen, C1-12 alkyl, phenyl or phenyl-C1-8 alkyl. Dyes of this type are especially suitable for use in netpage and Hyperlabel™ systems.