Leach resistant ink for protecting documents from alteration and document protected thereby

• US 5,058,925 A
• Filed: 12/13/1989
• Issued: 10/22/1991
• Est. Priority Date: 12/13/1989
• Status: Expired due to Term

• Current Assignee: The Standard Register Company (Middleby Corporation)
• Original Assignee: The Standard Register Company (Middleby Corporation)
• Inventors: Dotson, Mark
• Primary Examiner(s): Dixon, Jr., William R.
• Assistant Examiner(s): KLEMANSKI, HELENE G
• Application Number:
  US07/450,214
• Time in Patent Office: 678 Days
• Field of Search: 106/21, 106/25, 106/162, 428/29, 428/916, 283/95, 162/140
• US Class Current: 283/95
• CPC Class Codes: C09D 11/50 Sympathetic, colour changing or similar inks
• CPC Class Codes: Y10S 428/916 Fraud or tamper detecting

Abstract

An initially colorless, chemically sensitive protective ink which can be readily printed or applied onto a document substrate and which reacts upon contact with an oxidizing agent to form a noticeable color change is provided. The protective ink, when printed onto a document, resists leaching by water for an extended period of time, both before and after contact with oxidizing agents, and provides visible evidence of any attempted tampering. The leach-resistant ink includes a colorless material which becomes colored upon contact with an oxidizing agent and a complexing agent which reacts to form a complex with the colorless material. A fixing agent which promotes insolubilization and fixing of the complex to the document substrate is also provided.

Claims

1. A leach-resistant ink for protecting documents from alteration by oxidizing agents comprising diphenyl guanidine which becomes colored upon contact with an oxidizing agent and a complexing agent selected from the group consisting of glucose, sucrose, sorbitol, methyl glucoside, and mixtures thereof, which forms a complex with said diphenyl guanidine.

2. The leach-resistant ink of claim 1 wherein said complexing agent is methyl glucoside.

3. A document protected against alteration by oxidizing agents comprising a document substrate and a leach-resistant ink printed thereon, said ink comprising a colorless material which becomes colored upon contact with an oxidizing agent, a complexing agent which forms a complex with said colorless material, and a fixing agent which promotes insolubilization and fixing of said complex to said document substrate.

4. The document of claim 3 wherein said colorless material is diphenyl guanidine.

5. The document of claim 3 wherein said complexing agent is selected from the group consisting of glucose, sucrose, sorbitol, methyl glucoside, and mixtures thereof.

6. The document of claim 3 wherein said fixing agent is a mixture of condensation products from aryloxysulfonic acid derivatives.

7. The document of claim 3 wherein said colorless material is diphenyl guanidine, said complexing agent is methyl glucoside, and said fixing agent is a mixture of condensation products from aryloxysulfonic acid derivatives.

8. The document of claim 3 wherein said ink is printed in the form of tamper-indicating indicia.