Invisible ink structure

Claim 1

-1i- 1 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: s i. A developable surface comprising a carrier layer having deposits of two or more invisible inks printed 1 thereon in adjacent relationship, the inks in the developed P state exhibiting at least two colours and the deposits in the developed state not being optically resolvable. 1 0] I, es a S2. A deve-",.ble surface according to Claim 1 wherein 0° said invisible inks are selected from a group thereof which 00o0c in the developed state displays primary colours. "oo o oi 1 o i S* 3. A developable surface according tn Claim 1 wherein o~ o os the invisible inks are selected from a group of 2 [bis (4 hydroxyphenyl.) methyl] benzoic acid, 3,3 bis [4 hydroxy 2 1 methyl 5 (1 methylethyl) phenyl] 1 3H isobenzofuranone and si 4 nitro phenol. 0 Q I 1 1 09 ao 4. A developable surface according to Claim 3 wherein c said group also includes quinoline blue, quinaldine red, a6? s S.4 dinitro phenol, 2,5 dinitro phenol, ethyl bis (2,4 dinitro phenol) acetate, cresolphthalein, nitramine and 0 s 1,3,5 trinitrobenzene. .O A developable surface according to any one of Claims 1 to 4 wherein said carrier layer is a paper product resistant to attack from aqueous alkali and having a pH o' between 4 and 6. 1! 6. A developable surface according to any one of Claims 1 to 5 wherein said invisible ink also includes a solvent. 7. A developable surface according to Claim 6 wherein said solvent is an alcohol or glycol ether, aliphatic ester, pyrolidone or ketone. 8. A developable surface according to any one of Claims 1 to 7 wherein all the invisible inkz. are developable by a single developer compound. 9. A developable surface according to any one of Claims 1 to 7 wherein the invisible inks are developable with a plurality of developer compounds. A developable surface according to either Claims 8 or 9 wherein said developer is an alkali. zom 11. A developable surface according to either Claims 8 or 9 wherein said developer contains a colourless metal -D0 ion. 12. A developable surface according to Claim 11 wherein said metal ion is Fe or Cu POGO 13. An article for producing a coloured representation comprising a surface, a representation associated with said surface and at least partially invisible, said invisible portion comprising a plurality of discreet deposits of two or more invisible inks, which deposits in the developed state are individually visually u. resolvable, and one or more developer means. 14. An article according to Claim 13 wherein two or more of said invisible inks are used. An article according to Claim 14 wherein said invisible inks are selected from a group thereof which in the developed state displays primary colours. 16. An article according to Claim 14 wherein the invisible inks are selected from a group of 2 Ebis (4 hydroxyphenyl) methyl] benzoic acid, 3,3 bis [4 hydroxy 2 methyl 5 (1 methhylethyl) phenyll 1 3H isobenzofuranone and ND AU 2 13 105'15/48 R I -13- 4 nitro phenol. 17. An article according to Claim 16 wherein said group also includes quinoline blue, quanalidine red, 2,4 dinitro phenol, 2, 5 dinitro phenol, ethyl bis (2,4 dinitro phenol) acetate, cresolphthalein, nitramine and 1,3,5 trinitrobenzene. 18. An article according to Claim 13 wherein said developer means is a pen containing a developer medium. 0 *oo a a 19. An article accordina to Claim 18 wherein said Soo developer medium is an alkali. 0 a a S 20. An article according to Claim 18 wherein said developer medium contains a colourless metal ion. S 21. An article according to Claim 20 wherein said metal ion is Cu or Fe+. 'DATED THIS 22ND DAY OF DECEMBER 1983 GRAHAM CHARLES BARRY, NORMAN JOHN FIELD and LOCKLEY SERVICES PTV. LTD. 4 a o EDWD. WATERS SONS PATENT ATTORNEYS QUEEN STREET MELBOURNE VICTORIA AUSTRALIA