METHOD OF MINIMIZING VISIBLE COLORATION OF SUBSTRATE
A method of minimizing visible coloration of a substrate having an IR-absorbing dye disposed thereon. The method includes preselecting the dye such that it includes a moiety for reducing intermolecular interactions between adjacent dye molecules.
1 . A method of minimizing visible coloration of a substrate having an IR-absorbing dye disposed thereon, said method comprising preselecting said dye such that it includes a moiety for reducing intermolecular interactions between adjacent dye molecules.
2 . The method of claim 1 , wherein said dye is disposed in the form of a coded data pattern.
3 . The method of claim 1 , wherein said coded data pattern is a position-coding pattern.
4 . The method of claim 1 , wherein said substrate comprises an interface surface and wherein the coded data is disposed over a substantial portion of said interface surface.
5 . The method claim 1 , wherein said substrate is a paper sheet, a label, a tag, a packaging material or a product item.
6 . The method of claim 1 , wherein said dye is an IR-absorbing metal-dithiolene dye 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 —(CH 2 )— 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 replaced by a group independently selected from C 1-6 alkyl, C 1-6 alkoxy, C 5-12 aryl, C 5-12 arylalkyl, halogen, hydroxyl or amino.
7 . The method of claim 6 , wherein M is Ni.
8 . The method of claim 6 , wherein j is 1 and k is 2.
9 . The method of claim 6 , wherein n is 1.
10 . The method of claim 9 , wherein W is a substituent comprising a group of formula —CO 2 Z, —SO 3 Z, —OSO 3 Z, —PO 3 Z or —OPO 3 Z, wherein Z is H or a water-soluble cation.
11 . The method of claim 9 , wherein W is of formula —(CH 2 ) t —SO 3 Z, wherein t is 0 or an integer from 1 to 6, and Z is H or a water-soluble cation.
12 . The method of claim 9 , wherein W is of formula —CH 2 SO 3 H, —CH 2 SO 3 Na or —CH 2 SO 3 K.