Method of minimizing absorption of visible light in ink compositions comprising infrared metal-dithiolene dyes

A method of minimizing absorption of visible light in an ink composition comprising an IR-absorbing metal-dithiolene dye, wherein the dye is preselected from a metal-dithiolene of formula (II):

• wherein:
• M is selected from Ni, Pd or Pt (preferably Ni);
• j is selected from 1, 2, 3 or 4;
• k is selected from 1, 2, 3 or 4;
• n is 0, 1, 2 or 3;
• W is selected from:
• a substituent comprising an ammonium group;
• a substituent comprising an acid group, including salts thereof, or a substituent comprising a sulfonamide group;
• up to three −(CH2)— groups in the carbocycle are optionally replaced by a group independently selected from —C(O)—, —NH—, —S—, —O—;
• up to three —CH— groups in the carbocycle may be optionally replaced by —N—;
• and
• up to four H atoms in the carbocycle may be optionally replace by a group independently selected from C1-6 alkyl, C1-6 alkoxy, C5-12 aryl, C5-12 arylalkyl, halogen, hydroxyl or amino.