Thermally-transferable polyester image-protecting layer

• US 7,026,092 B1
• Filed: 07/20/2000
• Issued: 04/11/2006
• Est. Priority Date: 08/14/1999
• Status: Expired due to Term

• Current Assignee: Illinois Tool Works Inc.
• Original Assignee: Imperial Chemical Industries PLC (IMPERIAL CHEMICAL INDUSTRIES)
• Inventors: Double, Julie C., Clifton, Andrew, Butters, Alan
• Primary Examiner(s): Schilling, Richard L.
• Application Number:
  US10/049,610
• Time in Patent Office: 2,091 Days
• Field of Search: 430/200, 430/262, 430/961, 430/10, 430/14, 428/480, 428/32.6, 428/32.84, 428/32.86, 428/32.87, 156/230, 156/235
• US Class Current: 430/200
• CPC Class Codes: B41M 5/345 by thermal transfer of dyes or pigments
• CPC Class Codes: B41M 5/52 Macromolecular coatings
• CPC Class Codes: B41M 7/0027 using protective coatings or layers by lamination or by fusion of the coatings or layers
• CPC Class Codes: Y10S 430/162 Protective or antiabrasion layer
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]

Abstract

A thermal transfer medium for use in mass transfer printing comprises a substrate bearing on at least part of one surface thereof a coating of an overlay material comprising polyester having a glass transition greater than 50° C. (preferably at least 75° C.) and a molecular weight in the range 6,000 to 10,000. The overlay material combines good transfer characteristics, barrier properties and durability and is highly transparent.

Claims

1. A thermal transfer medium comprising a substrate bearing on at least part of one surface thereof a coating layer of a thermally transferable overlay material for transfer onto a thermal transfer image formed on a receiver material, wherein the coating layer comprises a hydroxy-terminated polyester having a Tg of at least 75°

C. and a molecular weight ranging from 6,000 to 10,000, and wherein a cross-linked acrylic subcoat is present between the substrate and coating.

2. A thermal transfer medium according to claim 1, wherein the polyester has a Tg of about 80°

C. and a molecular weight ranging from about 7,000 to 10,000.

3. A thermal transfer medium according to claim 1, wherein the polyester has a Tg of about 77°

C. and a molecular weight ranging from about 7,500 to 10,000.

4. A thermal transfer medium according to claim 1, wherein the coating further comprises filler material.

5. A thermal transfer medium according to claim 1, wherein the coating further comprises one or more ultra-violet light absorbers.

6. A thermal transfer medium according to claim 1, wherein the coating further comprises one or more optical brighteners.

7. A thermal transfer medium according to claim 1, wherein the substrate comprises a film of heat-resistant material selected from polyesters, polyamides, polyimides, polycarbonates, polysulphones, polypropylene and cellophane.

8. A thermal transfer medium according to claim 1, wherein the coating has a thickness ranging from 0.5 to 5.0 μ

m.

9. A thermal transfer medium according to claim 1, wherein the other surface of the substrate has a heat-resistant backcoat.

11. A method of forming an overlay on a receiver material, comprising the steps of

superposing a thermal transfer medium in accordance with claim 1 and a receiver material;

applying localized heating to the thermal transfer medium to form an overlay on the receiver material.

12. A method according to claim 11, further comprising the step of producing a printed image on the receiver material by thermal transfer printing prior to formation of the overlay.

13. A method according to claim 11, wherein the receiver material comprises a card of polyvinyl chloride.

14. A method according to claim 11, wherein the receiver material has an image-receiving surface comprising vinyl chloride/vinyl acetate copolymer.

15. A method according to claim 11, wherein the receiver is in the form of an identification card bearing a full color image produced by thermal transfer printing and text and/or a bar code produced by mass transfer printing of colorant.

10. A thermal transfer medium, comprising an elongate strip of substrate material having on one surface thereof a plurality of similar sets of thermally transferable dye coats and mass transfer layers, each set comprising a respective coat of dye colors, yellow, magenta and cyan, and a respective mass transfer layer for colorant and overlay, each coat or layer being in the form of a discrete stripe extending transverse to the length of the substrate, wherein each overlay material mass transfer layer comprises a coating of an overlay material comprising a hydroxy-terminated polyester having a glass transition temperature (Tg) greater than 50°

C. and a molecular weight ranging from 6,000 to 10,000, and wherein a cross-linked acrylic subcoat is present between the substrate and coating.

16. The combination of a receiver material having an image-receiving surface comprising vinyl chloride/inyl acetate copolymer and a thermal transfer medium comprising a substrate bearing on at least part of one surface thereof a coating layer of a thermally transferable overlay material for transfer onto a thermal transfer image formed on the receiver material, wherein the coating layer comprises a hydroxy-terminated polyester having a Tg greater than 50°

C. and a molecular weight ranging from 6,000 to 10,000, and wherein a cross-linked acrylic subcoat is present between the substrate and coating.

17. A combination according to claim 16, wherein the receiver material comprises a card of polyvinyl chloride.

18. A method of forming an overlay on a receiver material having an image-receiving surface comprising vinyl chloride/vinyl acetate copolymer, comprising the steps of

superimposing a thermal transfer medium comprising a substrate bearing on at least part of one surface thereof a coating layer of a thermally transferable overlay material for transfer onto a thermal transfer image formed on a receiver material, wherein the coating layer comprises a hydroxy-terminated polyester having a Tg greater than 50°

C. and a molecular weight ranging from 6,000 to 10,000, and wherein a cross-linked acrylic subcoat is present between the substrate and coating; and

applying localized heating to the thermal transfer medium to form an overlay on the receiver material.