abstract |
There is provided an IR-absorbing naphthalocyanine dye of formula (I): n nwhereinn M is Ga(A 1 ); A 1 is an axial ligand selected from —OH, halogen, —OR 3 , —OC(O)R 4 or —O(CH 2 CH 2 O) e R e wherein e is an integer from 2 to 10 and R e is H, C 1-8 alkyl or C(O)C 1-8 alkyl; R 1 and R 2 may be the same or different and are selected from hydrogen or C 1-12 alkoxy; R 3 is selected from C 1-12 alkyl, C 5-12 aryl, C 5-12 arylalkyl or Si(R x )(R y )(R z ); R 4 is selected from C 1-12 alkyl, C 5-12 aryl or C 5-12 arylalkyl; R x , R y and R z may be the same or different and are selected from C 1-12 alkyl, C 5-12 aryl, C 5-12 arylalkyl, C 1-12 alkoxy, C 5-12 aryloxy or C 5-12 arylalkoxy; and each B is independently selected from a base, wherein BH + has a pK a of between 4 and 9. The dye is suitable for use in IR-absorbing inkjet inks, providing compatibility with known CMYK inks together with an optimally red-shifted λ max . |