WO1995013926A1

WO1995013926A1 - Heat-transferable ink laminate and method of manufacture thereof

Info

Publication number: WO1995013926A1
Application number: PCT/CA1994/000639
Authority: WO
Inventors: Ronald W. Lowther
Original assignee: Lowther Ronald W
Priority date: 1993-11-19
Filing date: 1994-11-21
Publication date: 1995-05-26
Also published as: CA2176807A1; GB9323842D0; AU8137794A

Abstract

A substrate, e.g. a vinyl sign, is made with heat transferable inked colours thereon. A composite structure comprising a thin polyester film, a release coating and a heat transferable ink is used for transferring the ink onto the substrate. The coating is sandwiched between the film and the ink, and is adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable ink sufficiently that upon heat transference of the ink to the substrate, the coating transfers with the ink. A design element of the composite structure, with a first colour thereon is placed in contact with the substrate and heated sufficiently for the ink to adhere to the substrate but not permit the coating to release from the polyester film. Any paper backing on the composite is stripped off and then a background composite, with a second colour thereon, is laid on top of the substrate and the design elements. The substrate, design elements and background element are heated to a temperature sufficient for the inks to adhere to the substrate and for the coating to release from the polyester films.

Description

HEAT-TRANSFERABLE INK LAMINATE AND METHOD OF MANUFACTURE THEREOF

The present invention relates to the transfer of heat transferrable inks onto substrates. It has application in the sign and awning industry and has particular importance in the manufacture and use of back-lit signs. Background In the manufacture of signs, heat transferrable inks are transferred onto sign substrates from a paint- on-paper composite. Prior art paint-on-paper composites generally are three-layer structures of paper, waxy polyethylene and ink. The paper is coated ^' with the waxy polyethylene, and a heat transferable ink is coated onto the waxy polyethylene. This composite is expensive to produce and takes many "passes" in the coating operation in order to make a product, suitable for the sign and awning industry. Signs are most often made on vinyl substrates, e.g. vinyl sheet. The printed sign is made by applying coloured design elements and a coloured background to the vinyl. The process involves first cutting out design elements in the appropriate colour of a paint- on-paper composite. These design elements are placed on the vinyl sheet with the heat transferable ink in contact with the vinyl. The design elements are held in place temporarily by taping the edges of the design element to the vinyl. After taping the design elements to the vinyl sheet, the vinyl sheet is moved to a heat transfer machine. The design elements and vinyl sheet are heated sufficiently to lightly adhere the ink to the vinyl, thus allowing the tape to be removed. A paint-on-paper composite sheet suitable for the background colour is taken and laid on top of the vinyl sheet and design elements, thus trapping the design elements between the background composite sheet and the SUBSTITUTESHEET vinyl sheet. Because of the stiffness of the paper, the background sheet cannot sit snugly on the vinyl sheet immediately adjacent the edges of the design elements. Even with vacuum assist there is still a gap 5 of about 1.5 mm around the design elements. The vinyl, design element and background sheets are then heated. The ink on the design element adheres more firmly to the vinyl substrate. Where the ink on the background sheet is in contact with the vinyl, the ink adheres

10 firmly to the vinyl. Where the ink on the background sheet is in contact with the paper of the design element, the ink adheres to the paper. The sheets are then removed from the heat transfer machine and the paper is stripped from the structure, leaving the inked

15 vinyl sheet.

A major drawback of the prior art process is that the waxy polyethylene oozes around the design element sheets into the gap around the elements, leaving an uninked surround to the design elements. These need

20. ■ touching up, which requires a high degree of manual skill and additionally takes a long time to do. For many manufacturers, touching up has been a major irritation, from the cost and time standpoints, as well as from the necessity to provide training for touch-up

25 technicians. It is a problem worldwide and to applicant's knowledge, known processes for avoiding the requirement for touch up are very labour intensive. For example one method requires manual preparation and insertion of an inlay of the design element into the

30 background. Another method requires an extra step of cooling the heat transfer machine, followed by manual removal of the ooze with lacquer thinners. Both of these methods are very labour intensive and therefore costly.

35 A further drawback to the prior art processes is that the inks require a protective film or coating to cover the ink in order to keep them clean. Without a

SUBSTITUTESHEET protective film or coating, the inks are subject to dust, grit, fumes and the like. Migration of chemicals from the vinyl, through the ink, exacerbates the situation. Commonly, the inked vinyl is adhesively laminated to a clear protective film such as a polyvinylfluoride film, in order to protect the inks. Addition of the protective film adds to the cost of the signs, both in terms of the additional film cost and in terms of the added cost for lamination. Clearly, it would be desirable if the lamination step or coating step could be eliminated.

The present invention seeks to provide a mechanised process which removes the need for touch up. Preferred embodiments of the invention seek to remove the need for an additional laminating or coating step to protect the inks. Description of the Invention ^'

The present invention provides a composite structure comprising a thin polyester film, a release coating and a heat transferable ink, said coating being sandwiched between the film and the ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink.

In one embodiment the polyester film is a polyethylene terephthalate film. In a further embodiment the polyester film has a thickness of from 10 to 30 μm, especially 10 to 20 μm. In yet another embodiment the release coating is selected from a) an acrylic coating containing at least one plasticizer, b) a urethane coating, and c) mixtures of said acrylic and urethane coatings, said coatings having glass transition temperatures (T_g) above 20°C. The coatings may be acrylic copolymers or urethane

SUBSTTTUTESHEET copolymers.

In a further embodiment the heat transferable ink contains a urethane polymer to act as a tie layer between the substrate and the ink and between the ink and the release coating. The urethane may be a urethane/ethylene vinyl acetate copolymer, or may be a mixture of urethane and acrylic polymers.

In yet another embodiment the substrate is a vinyl sheet. In another embodiment the release coating is also adapted to adhere to the polyester film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyester film while the polyester film remains adhered to the substrate by means of the ink and the release, coating.

In another embodiment the polyester film is strippably adhered to a backing paper.

In a further embodiment the ink is an acrylic ink, preferably a latex acrylic ink, especially a translucent acrylic ink.

The present invention further provides a composite structure comprising a backing paper, a thin polyester film strippably adhered thereto and a release coating on the polyester film, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating is adherable to a heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink.

In one embodiment the release coating is also adapted to adhere to the polyester film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyester film while the polyester film remains adhered to the substrate by means of the ink and the release coating.

SUBSTITUTESHEET The invention also provides a process for making a composite structure of a thin polyester film, a release coating and a heat transferable ink, said process comprising: i) coating the polyester film with the release coating, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink, and ii) coating the release coating with the heat transferable ink, which adheres to the release coating at room temperature and at elevated temperatures. In one embodiment the polyester film is strippably adhered to a backing paper, prior to. step i) .

In another embodiment the polyester film is a polyethylene terephthalate film.

In a further embodiment the polyester film has a thickness of from 10 to 30 μm, especially 10 to 20 μm. In yet another embodiment the release coating is selected from a) an acrylic coating containing at least one plasticizer, b) a urethane coating, and c) mixtures of said acrylic and urethane coatings, said coatings having glass transition temperatures (T_g) above 20°C. The coatings may be acrylic copolymers or urethane copolymers.

In another embodiment, in step i) the polyester film is coated with a latex release coating. In another embodiment the release coating is also adapted to adhere to the polyester film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyester film while the polyester film remains adhered to the substrate by means of the ink and the release coating.

In a further embodiment the heat transferable ink

SUBSTITUTESHEET contains a urethane polymer to act as a tie layer between the substrate and the ink and between the ink and the release coating. The urethane may be a urethane/ethylene vinyl acetate copolymer, or may be a mixture of urethane and acrylic polymers.

In another embodiment the urethane in the ink is a urethane latex.

In yet another embodiment the substrate is a vinyl sheet. In a further embodiment the ink is an acrylic ink, preferably a latex acrylic ink, especially a translucent acrylic ink.

The invention further provides a process for making a substrate with inked colours thereon, comprising heat transferring a heat transferable ink from a composite structure to the substrate, said composite structure comprising a thin polyester film, a release coating and a heat transferable ink, said coating being sandwiched between the film and the ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink.

In one embodiment the polyester film is a polyethylene terephthalate film.

In a further embodiment the polyester film has a thickness of from 10 to 30 μm, especially 10 to 20 μm. In yet another embodiment the release coating is selected from a) an acrylic coating containing at least one plasticizer, b) a urethane coating, and c) a mixture of said acrylic and urethane coatings, said coatings having glass transition temperatures (T_g) above 20°C. The coatings may also be acrylic copolymers or urethane copolymers.

In another embodiment the composite structure has

SUBSTITUTESHEET a paper backing on the polyester film and the release coating is also adapted to adhere to the polyester film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyester film while the polyester film remains adhered to the substrate by means of the ink and the release coating; the process also having the steps of a) heating the substrate and composite structure to a temperature such that the ink lightly adheres to the substrate and the release coating remains adhered to the polyester film, b) stripping off the backing paper and c) heating the substrate, polyester film, coating and ink laminate to a temperature sufficient to release the release coating from the polyester, and to firmly adhere the ink to the substrate.

In yet another embodiment the substrate is a vinyl sheet.

In a further embodiment the ink is an acrylic ink, preferably a latex acrylic ink especially a translucent ink.

In one embodiment the process comprises: i) laying at least one paint-on-polyester design element on a substrate, said paint-on-polyester design element comprising a thin polyester film, a release coating and a heat transferable ink, said ink being of a first colour and said coating being sandwiched between the film and the first-colour ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable first-colour ink sufficiently that upon

SUBSTITUTESHEET heat transference of the first colour ink to the substrate, the coating transfers with the first-colour ink, and laying the element on the substrate such that the first-colour ink is in contact with the substrate; ii) laying a paint-on-polyester background film on top of the substrate and the paint-on-polyester design elements such that the paint-on-polyester design elements are sandwiched between the substrate and the paint-on-polyester background element, said paint-on- polyester background element comprising a thin polyester film, a release coating and a heat transferable ink, said ink being of a second colour and said coating being sandwiched between the film and the second-colour ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating. and b) the coating adheres to the heat transferable second-colour ink sufficiently that upon heat transference of the second-colour ink to the substrate, the coating transfers with the second-colour ink, and laying the element on the substrate such that the second-colour ink is in contact with the substrate or the polyester film of the design element; and iii) heating the substrate, paint-on-polyester design element and paint-on-polyester background element to a temperature sufficient for the inks to adhere to the substrate and for the coating to release from the polyester films .

In another embodiment the polyester film for the design element has a strippable backing paper which is stripped off the polyester film prior to step ii) .

In a further embodiment the polyester film for the background element has a strippable backing paper thereon which is stripped off after step iii). In another embodiment the polyester film is a polyethylene terephthalate film.

In a further embodiment the polyester film has a

SUBSTITUTESHEET thickness of from 10 to 30 μm, especially 10 to 20 μm. In yet another embodiment the release coating is selected from a) an acrylic coating containing at least one plasticizer and b) a urethane coating, said coatings having glass transition temperatures (T_g) above 20°C. The coatings may be acrylic copolymers or urethane copolymers .

In another embodiment, in step i) the polyester film is coated with a latex release coating. In yet another embodiment the release coating for at least the design element is also adapted to adhere to the polyester film at a temperature where the first- colour ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyester film while the polyester film remains adhered to the substrate by means of the first-colour ink and the release coating.

In a further ^'embodiment the heat transferable ink contains a urethane to act as a tie layer between the substrate and the ink and between the ink and the release coating. The urethane may be a urethane/ethylene vinyl acetate copolymer.

In another embodiment the urethane in the ink is urethane latex. In yet another embodiment the substrate is a vinyl sheet.

In a further embodiment the ink is an acrylic ink, preferably a latex acrylic ink, especially a translucent ink. The invention further provides a sign comprising a substrate having a plurality of heat transferred ink colours adhered thereto, wherein at edges of adjacently adhered inks, the inks cleanly abut one another without touch-up therebetween. In one embodiment the substrate is a vinyl sheet.

In another embodiment the inks are acrylic inks, preferably a latex acrylic ink, especially a

SUBSTITUTESHEET . translucent acrylic ink.

In a further embodiment the plurality of inks is at least two.

Detailed Description of the Invention The invention is now described in reference to specific embodiments. It is for illustration purposes and is not intended to be limiting.

The paint-on-polyester laminate is formed from base paper, a thin polyester film, a release coating and a heat transferable ink. The polyester film, which is preferably about 12.5 μm thick, is adhered to the base paper, which is preferably about 102 μm thick, using a so-called static lamination process or an adhesive lamination process. This polyester-on-paper laminate is then coated with the release coating, preferably using an acrylic-based latex. The acrylic- based latex may be a mixture of acrylic and urethane latexes. The release coating is then coated with a heat transferable ink. The heat transferable inks are available commercially and often contain urethane polymers in order to enable the ink to be heat transferable. The urethane polymers may be mixed with acrylic polymers, as is known in the art.

The coating and ink may be applied using a variety of processes, depending on the evenness of distribution of the coating and ink, for a particular end-use. For example, back-lit signs are extremely critical in terms of the evenness of the application of ink and coating. For such an end-use, a rotary web rotary silk screen process is the best process known to the applicant. An apparatus suitable for carrying out such a process is a Stork rotary screen machine, available form Stork X-cel B.V. in the Netherlands. For less critical end- uses, other coating methods may be used, e.g. gravure, flatbed screen printing processes.

The release coating and ink are preferably applied from water-based latexes.

SUBSTITUTESHEET Each of the steps in making the so-called paint- on-polyester laminate may be carried out separately from the other steps, e.g. by different manufacturers. However, it is particularly preferred that the release coating and ink be applied in a single continuous process.

The type of ink will determine, of course the colour and density of the colour which is to be applied to the sign or other substrate. For back-lit signs, the inks should be translucent inks and the release coating should be a clear coating. For commercial purposes it is desirable to make rolls of paint-on- polyester laminates about 100 to 200 cm wide, e.g. 152 cm wide by up to 900-1000 metres long. For convenience, customers may buy pieces of laminate about 30 metres long.

In order to make a back-lit sign on a vinyl substrate, for example, letters, designs or the like are cut out from one colour, e.g. yellow paint-on- polyester laminate. Such designs, letters and the like are sometimes referred to herein as design elements. The paint-on-polyester design elements are placed on the vinyl sheet, with the heat transferable translucent ink in contact with the vinyl. The design elements are held in place with masking tape or the like. The vinyl sheet, with paint-on-polyester design elements in contact therewith are transferred to a heat transfer machine, in a manner known in the art. The machine is heated to a temperature sufficient for the ink to lightly adhere to the vinyl, e.g. to about 40-45°C. The masking tape is then removed. In addition, the backing paper is stripped from the polyester film of the design elements.

A sheet of paint-on-polyester laminate, of a second colour, e.g. red, and of the same dimension as the vinyl sheet is taken, for use as a background colour. Such laminate is sometimes referred to herein

SUBSTITUTESHEET as the background element. The paint-on-polyester background element is laid on top of the vinyl sheet, with the heat transferrable translucent ink in contact with the vinyl. In so doing, the paint-on-polyester design elements are trapped between the vinyl sheet and the background element. The vinyl sheet, with design elements and background element in contact therewith are transferred to the heat transfer machine. The machine is heated to a temperature sufficient for the ink to firmly adhere to the vinyl, e.g. to about 110°C. At such a temperature the release coating on the polyester releases cleanly and the polyester film may be stripped away, leaving the ink firmly adhered to the vinyl and the release coating adhered to the ink. Because the polyester film of the design elements is so thin, e.g 10 to 20 μm, the backing element is able to fit snugly around the edges of the design elements. The ink, e.g. yellow ink, from the design elements lays cleanly onto vinyl. The release coating adheres to the yellow ink and does not have an opportunity or tendency to ooze adjacent to the yellow ink. At the same time that the yellow ink from the design elements is being transferred to the vinyl, the ink, e.g. red ink, from the backing element is also being transferred to the vinyl. The snug fit of the backing element around the edges of the design elements allows the red ink to butt right up to the edge of the yellow ink. As already indicated there is no ooze of the coating to prevent the inks from abutting one another. Accordingly there is no need for touch-up around the yellow ink. This is a great stride in the sign and awning industry and those skilled in the art will be able to tell easily whether a sign has been touched up or not. It will be understood that where the backing element covers the design element, the red ink will transfer to the back of the polyester film of the

SUBSTITUTESHEET design element. However, as the polyester film of the design element is peeled off, there will be no red ink on top of the yellow ink, thus allowing the back-lit sign to clearly show the yellow and red colours. The present process is adapted to making signs, awnings and the like with a background colour having design elements, e.g. letters and numbers, in one colour, with a different surrounding colour. For example, a sign may be made with a green background and a blue design element consisting of a letter J, with a red surround to the letter J. In order to make such a sign, red, green and blue paint-on-polyester laminates are first formed according to the process of the present invention. A letter J is cut out of the blue laminate to form a first design element, and a slightly larger letter J is cut out of the red laminate to form a second design element. The blue first design element is placed on a substrate, e.g. vinyl, and^' the blue ink is lightly tacked to the vinyl by heating the vinyl and ■ laminate. The backing paper is stripped off the blue design element. The red second design element is then placed over the blue first design element, so that the larger red design extends beyond the margins of the first element. The vinyl and the design elements are again heated so that the red ink is lightly tacked to the vinyl. In so doing the red ink surrounds the blue ink on the face of the vinyl. The backing paper is stripped off the red laminate. Finally, the yellow (background) laminate is place over the design elements and vinyl and the whole is heated so that all of the inks firmly adhere to the vinyl. As a result of such heating the polyester film, e.g. polyethylene terephthalate film, is able to be stripped away from the dirt resistant acrylic coating, thus leaving the vinyl with a blue letter J with a red surround, on a yellow background.

The release coating has the added value of - SUBSTITUTESHEET providing environmental protection for the ink. For example it provides protection from ultraviolet light degradation and also minimizes adhesion of environmental dirt contamination. The substrate may be flat, as in a sign or similar and may be contoured as in a bottle or an automobile. The substrate may be a natural or synthetic fabric, a synthetic film or sheet material, among other materials. The inks may be translucent or opaque, depending on the end-use.

It will be understood by those skilled in the art that the release coatings and inks may contain plasticizers, ultraviolet stabilizers and the like. Example A 157.5 cm wide web of latex impregnated paper with a thickness of about 0.117 mm, was laminated to one side of a 157.5 cm wide and 12.5 μm thick polyethylene terephthalate film with a light tack pressure sensitive adhesive, to form a polyester-on- paper laminate. A coating of 983 water-based dirt resistant acrylic coating from Lyons Coatings Inc. in Massachusetts was then applied to the free side of the polyethylene terephthalate film. In a separate step, a CD-545 yellow heat transferable solvent-based translucent acrylic ink from Ink Dezyne International Inc. of Ontario was applied to the coating, using a continuous rotary screen printing process, to form a yellow paint-on-polyester laminate.

A red paint-on-polyester laminate was formed in a similar manner to the yellow laminate except that a red translucent ink was used. A black paint-on-polyester laminate was also formed in a similar manner to the yellow laminate except that a black ink was used.

Letters were cut out of the red and black paint- on-polyester laminates to form design elements. The design elements were placed on a vinyl substrate and held in place using masking tape. The red and black

SUBSTITUTESHEET heat transferable inks were lightly adhered to the vinyl substrate by heating the vinyl and design elements to about 43°C. The masking tape and backing paper were stripped off the design elements and the yellow paint-on-polyester laminate was placed over the red and black design elements and the remainder of the vinyl substrate (which was not covered by design elements). The vinyl substrate and the laminates were heated to about 110°C. The inks which were in contact with the vinyl firmly adhered to the vinyl substrate and the bond between the polyethylene terephthalate film and the coating allowed the film to be stripped from the coating.

Upon inspection of the resulting inked substrate, the yellow ink abutted the red and black inks and there was no need for any touch-up.

SUBSTITUTESHEET

Claims

CLAIMS :

1. A composite structure comprising a backing paper, a thin polyester film strippably adhered thereto and a release coating on the polyester film, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating is adherable to a heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink.

2. A composite structure according to Claim 1 wherein the polyester film is a polyethylene terephthalate.

3. A composite structure according to Claim 1 wherein the release coating is selected from a) an acrylic coating containing at least one plasticizer, b) a urethane coating, and c) mixtures of said acrylic and urethane coatings, said coatings having glass transition temperatures (T_g) above 20°C.

4. A composite structure according to Claim 3 wherein the release coating is also adapted to adhere to the polyester film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyester film while the polyester film remains adhered to the substrate by means of the ink and the release coating.

5. A composite structure according to Claim 4 wherein the heat transferable ink contains a urethane polymer to act as a tie layer between the substrate and the ink and between the ink and the release coating.

6. A composite structure according to any one of Claims 1, 4 or 6 wherein the polyester film has a thickness of from 10 to 30 μm.

7. A composite structure according to Claim 2 wherein the release coating is selected from a) an acrylic coating containing at least one plasticizer, b) a urethane coating, and c) mixtures of said acrylic and

SUBSTITUTESHEET urethane coatings, said coatings having glass transition temperatures (T_g) above 20°C.

8. A composite structure according to Claim 7 wherein the release coating is also adapted to adhere to the polyester film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyethylene terephthalate film while the polyethylene terephthalate film remains . adhered to the substrate by means of the ink and the release coating.

9. A composite structure according to Claim 8 wherein the heat transferable ink contains a urethane polymer to act as a tie layer between the substrate and the ink and between the ink and the release coating.

10. A composite structure according to any one of Claims 2, 8 or 9 wherein the polyester film has a thickness of from 10 to 30 μm.

11. A composite structure comprising a thin polyester film, a release coating and a heat transferable ink, said coating being sandwiched between the film and the ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink.

12. A process for making a composite structure of a thin polyester film, a release coating and a heat transferable ink, said process comprising: i) coating the polyester film with the release coating, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink, ii) coating the release coating with the heat

SUBSTITUTE SHEET . transferable ink, which adheres to the release coating at room temperature and at elevated temperatures.

13. A process according to Claim 12 wherein the polyester film is a polyethylene terephthalate.

14. A process according to Claim 12 wherein the release coating is selected from a) an acrylic coating containing at least one plasticizer, b) a urethane coating, and c) mixtures of said acrylic and urethane coatings, said coatings having glass transition temperatures (T_g) above 20°C.

15. A process according to Claim 14 wherein the release coating is also adapted to adhere to the polyester film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off^* the polyester film while the polyester .film remains adhered to the substrate by means of the ink and the release coating.

16. A process according to Claim 15 wherein the heat transferable ink contains a urethane polymer to act as a tie layer between the substrate and the ink and between the ink and the release coating.

17. A process according to any one of Claims 12, 15 or 16 wherein the polyester film has a thickness of from 10 to 30 μm.

18. A process according to Claim 13 wherein the release coating is selected from a) an acrylic coating containing at least one plasticizer, b) a urethane coating, and c) mixtures of said acrylic and urethane coatings, said coatings having glass transition temperatures (T_g) above 20°C.

19. A process according to Claim 18 wherein the release coating is also adapted to adhere to the polyethylene terephthalate film at a temperature where the ink lightly adheres to the substrate, such that the backing paper may be stripped off the polyethylene terephthalate film while the polyethylene terephthalate film remains adhered to the substrate by means of the

SUBSTITUTESHEET ink and the release coating.

20. A process according to Claim 19 wherein the heat transferable ink contains a urethane polymer to act as a tie layer between the substrate and the ink and between the ink and the release coating.

21. A process according to any one of Claims 13, 19 or 20 wherein the polyethylene terephthalate film has a thickness of from 10 to 30 μm.

22. A process for making a substrate with inked colours thereon, comprising heat transferring a heat transferable ink from a composite structure to a substrate, said composite structure comprising a thin polyester film, a release coating and a heat transferable ink, said coating being sandwiched between the film and the ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable ink sufficiently that upon heat transference of the ink to a substrate, the coating transfers with the ink.

23. A process for making a substrate with inked colours thereon, wherein said process comprises: i) laying at least one paint-on-polyester design element on a substrate, said paint-on-polyester design element comprising a thin polyester film, a release coating and a heat transferable ink, said ink being of a first colour and said coating being sandwiched between the film and the first-colour ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable first-colour ink sufficiently that upon heat transference of the first colour ink to the substrate, the coating transfers with the first-colour ink, and laying the element on the substrate such that the first-colour ink is in contact with the substrate; ii) laying a paint-on-polyester background film on

SUBSTITUTESHEET top of the substrate and the paint-on-polyester design elements such that the paint-on-polyester design elements are sandwiched between the substrate and the paint-on-polyester background element, said paint-on- polyester background element comprising a thin polyester film, a release coating and a heat transferable ink, said ink being of a second colour and said coating being sandwiched between the film and the second-colour ink, said coating being adapted so that a) it adheres to the polyester film at room temperature and releases from the film upon heating and b) the coating adheres to the heat transferable second-colour ink sufficiently that upon heat transference of the second-colour ink to the substrate, the coating transfers with the second-colour ink, and laying the element on the substrate such that the second-colour ink is in contact with the substrate or the polyester film of the design element; and iii) heating the substrate, paint-on-polyester design element and paint-on-polyester background element to a temperature sufficient for the inks to adhere to the substrate and for the coating to release from the polyester films.

24. A sign comprising a substrate having a plurality of heat transferred ink colours adhered thereto, wherein at edges of adjacently adhered inks, the inks cleanly abut one another without touch-up therebetween.

SUBSTITUTESHEET