Invisible ink

• US 20050075420A1
• Filed: 09/15/2004
• Published: 04/07/2005
• Est. Priority Date: 10/06/2003
• Status: Abandoned Application

• Current Assignee: Nocopi Technologies, Inc.
• Original Assignee: Nocopi Technologies, Inc.
• Inventors: Stovold, Terry
• Application Number:
  US10/942,246
• Publication Number:
  US 20050075420A1
• Time in Patent Office: Days
• US Class Current: 523/161
• CPC Class Codes: B41M 3/142 using chemical colour-formers or chemical reactions, e.g. leuco-dye/acid, photochromes
• CPC Class Codes: B41M 5/124 using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
• CPC Class Codes: B41M 5/155 Colour-developing components, e.g. acidic compounds; Additives or binders therefor; Layers containing such colour-developing components, additives or binders
• CPC Class Codes: B41M 5/1555 Inorganic mineral developers, e.g. clays
• CPC Class Codes: B41M 5/30 using chemical colour formers B41M5/34 takes precedence
• CPC Class Codes: B41M 5/3335 Compounds containing phenolic or carboxylic acid groups or metal salts thereof
• CPC Class Codes: B41M 5/3338 Inorganic compounds
• CPC Class Codes: B41M 5/34 Multicolour thermography
• CPC Class Codes: B42D 2035/24 Colours
• CPC Class Codes: B42D 25/29 Securities; Bank notes
• CPC Class Codes: B42D 25/378 Special inks
• CPC Class Codes: B44F 1/08 characterised by colour effects
• CPC Class Codes: C09D 11/50 Sympathetic, colour changing or similar inks

Abstract

A method of invisible ink fabrication. A first ink having an activator without a leucodye is prepared. A second ink having a leucodye is prepared without an activator, which is combined with the first ink prior to color development and prior to printing. Preferably, the combined ink is printed immediately after being created. Further disclosed are items created using the ink such as toys, puzzles, stickers, coloring books, tags, labels and security devices.

Claims

1. A method of ink fabrication comprising:

preparing a first ink having a color developer activator without a color former leucodye;

preparing a second ink having a color former leucodye without a color developer activator;

combining the first and second inks prior to a color development.

2. The method of claim 1 wherein the first and second inks are prepared within five hours of printing.

3. The method of claim 1 wherein the activator is selected from the group consisting of phenolic resin, zinc chloride bisphenol and hydroxybenzoate.

4. The method of claim 1 further comprising grinding one or more of the activator and leucodye to a particle size of less than 30 microns.

5. The method of claim 4 comprising grinding the leucodye to a particle size of between 5 and 10 microns.

6. The method of claim 4 comprising grinding the activator to a particle size of between 5 and 15 microns.

7. The method of claim 1 further comprising combining at least one of the activator and leucodye with a binder.

8. The method of claim 7 wherein the binder is a polyvinyl alcohol.

9. The method of claim 1 wherein the ratio of activator to leucodye is greater than 1:

1.

10. The method of claim 9 wherein the ratio of activator to leucodye is about 2:

1.

11. The method of claim 1 further comprising printing the combined first and second inks onto a substrate.

12. The method of claim 11 wherein printing is performed by a process selected from the group consisting of flexographic, gravure, stamping, coating, tint unit and lithographic.

13. The method of claim 12 wherein printing is performed by a four or six color flexographic printing process.

14. The method of claim 11 further comprising printing a plurality of combined inks onto a single substrate, each having a different leucodye.

15. The method of claim 1 further comprising applying heat to develop the combined ink.

16. The method of claim 15 wherein heat is generated by friction.

17. The method of claim 1 further comprising adding an ingredient to protect against one or more environmental factors to one or more of the inks selected from the group consisting of first ink, second ink and combined ink.

18. The method of claim 17 wherein the protecting ingredient is a wax.

19. The method of claim 17 wherein the protecting ingredient comprises between 8% and 12% by weight of the combined ink.

20. The method of claim 1 wherein the first and second inks are water-based inks.

21. The method of claim 1 wherein the first and second inks are oil-based inks.

22. The method of claim 1 wherein the leucodye is a synthetic organic color former.

23. The method of claim 1 further comprising combining the activator with one or more components selected from the group consisting of binder, surfactant, defoamer and grinding agent.

24. The method of claim 1 further comprising printing the combined ink on a coated or treated substrate to reduce or eliminate ink absorption into the substrate.

25. The method of claim 1 further comprising printing the combined ink on a substrate to create an item selected from the group consisting of toy, puzzle, art product, educational product, customer verification product, game, book, sticker, ticket, placemat, card, tag and label.

26. The method of claim 1 further comprising wet micronizing the first ink in water and one or more components selected from the group consisting of polyvinyl alcohol, surfactant and grinding aid.

27. The method of claim 1 further comprising wet micronizing the second ink in water and one or more components selected from the group consisting of polyvinyl alcohol, surfactant and grinding aid.

28. The method of claim 1 wherein the activator is between 30% and 40% of the first ink.

29. The method of claim 1 wherein the leucodye is between 30% and 40% of the second ink.

30. The method of claim 1 further comprising printing the combined ink onto an item a security device.

31. The method of claim 1 further comprising adjusting the pH to about 7.

32. An ink formed by the method of claim 1.

33. An item selected from the group consisting of toy, puzzle, art product, educational product, customer verification product or game, book, sticker, ticket, placemat, card, tag and label having applied to it an ink formed by the method of claim 1.

40. A game comprising an ink fabricated according to claim 1.

41. A sticker comprising an ink fabricated according to claim 1.

42. A coloring book comprising an ink fabricated according to claim 1.

43. A label comprising an ink fabricated according to claim 1.

44. A tag comprising an ink fabricated according to claim 1.

45. A security device comprising an ink fabricated according to claim 1.

34. An ink mixed from a first ink and a second ink wherein:

the first ink comprises a leucodye without an activator; and

the second ink comprises an activator without a leucodye.

35. The ink of claim 34 wherein the first ink further comprises one or more components selected from the group consisting of polyvinyl alcohol, surfactant and grinding aid.

36. The ink of claim 34 wherein the second ink further comprises one or more components selected from the group consisting of polyvinyl alcohol, surfactant and grinding aid.

37. The ink of claim 34 further comprising a wax.

38. The ink of claim 34 wherein the activator is selected from the group consisting of phenolic resin, zinc chloride bisphenol and hydroxybenzoate.

39. The ink of claim 34 further comprising a pH adjuster.

46. An art item comprising:

a substrate; and

one or more mixtures of a carrier, a leuco dye and an activator;

wherein the activator is at least one selected from the group consisting of amidophenol, anilides with hydroxyl groups and benzoamides with hydroxyl groups; and

wherein the one or more mixtures are applied to the substrate so that when subjected to heat one or more colors appear.

47. The art item of claim 46 wherein the one or more mixtures are applied to the substrate to form an image.

48. The art item of claim 46 further comprising a visible ink applied to the substrate to form an image.

49. The art item of claim 46 further comprising a plurality of substrates having the one or more mixtures applied thereto, wherein the substrates are in the form of a book.

50. A method of forming an item comprising:

providing a substrate for an art item or game item;

providing a composition comprising one or more mixtures of a carrier, a leuco dye and an activator on the substrate to form an invisible image;

wherein the activator is at least one selected from the group consisting of amidophenol, anilides with hydroxyl groups and benzoamides with hydroxyl groups.

51. The method of claim 50 further comprising:

providing a plurality of substrates having the one or more mixtures applied thereto wherein the substrates are formed into a book.

52. The method of claim 50 further comprising applying a visible ink to the substrate to form an image.

53. A method for forming a product comprising the steps of:

providing a background color on a substrate for an art item or game item having an average reflectance value; and

printing an image on the background color with one or more contrast colors, each having a spectral characteristic which modulates the average reflectance value by no more than 5% and has an average value equal to the average reflectance value by applying a printing medium including a binder and further consisting of a mixture of micronized color former leuco dye and micronized activator material and wherein at least one of the micronized color former leuco dye and activator is non-soluble in the printing medium.

54. The method according to claim 53, wherein the step of applying a printing medium comprises applying an oil based printing ink.

55. The method according to claim 54, wherein the oil based printing ink is an offset printing ink.

56. The method according to claim 53, further comprising activating the color former leuco dye and the activator material to change the color of the printing medium by simultaneously applying a rubbing action on the printing medium.

57. The method of claim 53 further comprising applying a visible ink to the substrate to form an image.

58. The method of claim 53 further comprising compiling a plurality of the printed substrates to form a book.

61. An art or game item fabricated at least in part by the method of claim 53.

62. The art or game item of claim 61 selected from the group comprising coloring book, game and placemat.

59. A method for forming a product with scratch ink, comprising the steps of:

providing a background color on a substrate for an art item or game item having an average reflectance value; and

printing an image on the background color with one or more contrast colors, each having a spectral characteristic which modulates the average reflectance value by microencapsulating at least one of a micronized color former leuco dye and a micronized activator material with a colorless continuous coating of a barrier material and applying a printing medium including a binder and further consisting of the microcapsules and the other of micronized color former leuco dye and micronized activating phenolic resin.

60. The method according to claim 59 further comprising activating the color former leuco dye and the activator material to change the color of the printing medium by applying a rubbing action on the printing medium.