Ink formulations comprising gallium naphthalocyanines
There is provided an aqueous formulation comprising an IR-absorbing naphthalocyanine dye of formula (II): or a salt form thereof, wherein: 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; and 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; The formulation has a pH in the range of 3.5 to 7 and is particularly suitable for use as an IR-absorbing inkjet ink, providing compatibility with known CMYK inks together with an optimally red-shifted λ max .
1. An aqueous formulation comprising an IR-absorbing naphthalocyanine dye of formula (II):
or a salt form thereof, wherein:
Mis 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; and
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;
said formulation having a pH in the range of 4 to 6.5.
2. The formulation of claim 1 , wherein said formulation is buffered.
3. The formulation of claim 1 further comprising at least one base B, wherein a conjugate acid BH + of said at least one base B has a pK a of between 4 and 9.
4. The formulation of claim 3 , wherein a conjugate acid BH + of said at least one base B has a PK a of between 4.5 and 8.
5. The formulation of claim 3 comprising a nitrogen base, an oxyanion base or mixtures thereof.
6. The formulation of claim 5 , wherein said nitrogen base is a nitrogen-containing C 5-12 heteroaryl base.
7. The formulation of claim 6 , said nitrogen base is imidazole or pyridine.
8. The formulation of claim 5 , wherein said oxyanion base is a carboxylate base.
9. The formulation of claim 8 , wherein said carboxylate base is of formula R 5 C(O)0 − , wherein R 5 is selected from C 1-12 alkyl, C 5-12 aryl or C 5-12 arylalkyl.
10. The formulation of claim 3 comprising a nitrogen base and an oxyanion base.
11. The formulation of claim 1 , wherein R 1 and R 2 are both H.
12. The formulation of claim 1 , wherein M is Ga(OH).
13. An inkjet ink comprising a formulation according to claim 1 .
14. An inkjet ink comprising a dye according to claim 1 , wherein said ink has a max of 800 nm or more.
15. A substrate having an ink according to claim 13 disposed thereon.