TRANSFER PRINTING

Abstract: A composition for use in printing, including sublimatic transfer printing, comprises an adhesive component chosen to be receptive to dye transferred thereto, and to be adherable to a surface to be printed, thereby binding the dye to the surface to form an image thereon.

Description: Transfer Printing The present invention relates to the printing of images, and in particular, but not exclusively to sublimatic transfer printing. Previously proposed sublimatic transfers are used on man-made fabrics, in particular polyester. They are formed by printing an image in sublimatic dye on to a paper carrier or substrate. The image may be formed on the substrate by screen printing, for instance. In order to transfer the image to the fabric, the face of the substrate which bears the image is placed against the fabric surface. Pressure is then applied at elevated temperature, for instance by means of a heated press. This causes the dye on the substrate to undergo sublimation, changing to a gas which impregnates the fabric fibres, where the dye solidifies on cooling. The resultant image is extremely durable by virtue of the impregnation of the dye into the fibres, and is vivid. The results obtained from sublimatic transfers on natural fibres and man-made fabrics other than polyester are found to be inferior, and in many cases unsatisfactory. Natural fibres have a structure which prevents impregnation by sublimatic dyes in a gaseous state, and in consequence only a faint image is produced and the image is easily removed by washing. Many manufacturers provide ranges of standard transfer images from which the consumer may choose, or may provide a service in which an image supplied by the consumer is converted into a transfer. The use of a standard range limits the choice of the consumer, and manufacturing transfers to special order increases the cost and delays involved. Conventional transfers are constructed in various ways for application to various types of article, and it is necessary to choose an appropriate form of transfer, according to the article to which the transfer is to be applied. Thus, a customer .may find that an image from a standard range is not " available as a transfer of appropriate form. The present invention seeks to obviate or mitigate these and other disadvantages of the prior art. The invention provides a coating composition for use in coating an image to be printed, and comprising a solvent, a resin, a mineral oil and a powder material. There is also provided a composition for use in sublimatic transfer printing, the composition comprising an adhesive component and the material or materials of the composition being so chosen as to be receptive to sublimatic dye transferred thereto by sublimation, and to be adherable to a surface to be printed, thereby binding the dye to the surface to form an image thereon. The composition may comprise a thermoplastic resin such as a polyurethane or acrylic resin. The resin may be n-butyl methacrylate. The composition may also include a solvent. The solvent may be a mineral spirit. The mineral spirit may be a dilute benzene based solvent. The solvent may comprise white spirit, cyclohexanone and/or 1 -methoxy-2-propanol . The composition preferably also includes a plasticizer. The plasticizer may be a phthalate such as butyl benzyl phthalate. Preferably, when the image is to be formed on a fabric, the composition includes a lubricant for affecting the feel of- the transfer after application to the fabric. The lubricant may comprise oleine. The aforesaid powder material may be copolyester, polypropylene, polyethylene or copolyamide . The composition may comprise between 20 and 40?ό solvent; between 20 and 0 % n-butyl methacrylate; between 5 and 20?ό mineral oil and between 20 and 35?ό powder m a t e r i a l . The composition may include 30 to 50?o of adhesive component, 1 to 35?<_ of plasticizer, 10 to 40?ό of mineral spirit and 1 to 1 % of lubricant. The composition may comprise xylene. The invention also provides a sublimatic transfer . comprising a substrate, an image formed by sublimatic dye, and a coating, the coating and the dye being so selected that on heating to a predetermined temperature the dye transfers the image to the coating by sublimation, the resulting transfer being capable of adherence to a surface to be printed, whereby the coating binds the dye to the surface to form an image thereon. The dye image is preferably located between the coating and the substrate. Where a solvent is included the coating includes sufficient solvent for the adhesive - component to allow removal of the substrate at a temperature in the range 10 to 200 G C. The coating is preferably a composition as set out above ' . In a further aspect, the invention provides a method of manufacturing a sublimatic dye transfer, in which an image is formed by sublimatic dye on a substrate, and a coating is applied over the image, the coating being receptive to sublimatic dye transferred thereto by sublimation, and being adherable to a surface to be printed. Sublimation of the dye into the coating may be effected during manufacture. Preferably sublimation of the dye is effected by heating. The dye may be heated to a temperature in the range 185 to 215 D C to transfer the image to the coating. The dye is preferably heated for a period of at least ten seconds to transfer the image to the coating. The coating may be applied to said surface at an elevated temperature to cause the coating to adhere to said surface. The elevated temperature may be in the region of 180 to 220 °C preferably around 190 °C. The coating is preferably applied to said surface under pressure to cause the coating to adhere to the surface. The application pressure may be in the region of 7 to 30 psi, preferably around 20 psi. Preferably the elevated temperature and pressure are applied for a period of 7 to 25 seconds, preferably around 10 seconds. The coating is preferably a composition as set out above. The invention also provides a method of printing an image on an article, in which the image is copied by a photocopying process onto a backing member, a coating compound is applied over the image on the backing member, the coated surface of the backing member is placed against the article, and conditions are created to cause the image to transfer to the article, the compound being chosen to enhance or permit the transfer of the image from the backing member to the article. The backing member may be a paper sheet. The photocopying process creates an image which is reversed on the backing member in relation to the image. The photocopying process may include a first step in which an original is copied onto an intermediate carrier, and a second step in which the image on the intermediate carrier is copied in reverse onto the backing member. The intermediate member may be transparent, the second step including scanning the image on the intermediate member by viewing the image through the intermediate member. The intermediate member may be a clear acetate sheet. Preferably the image to be printed is in colour. The image to be printed may be formed by dyes. The dyes may be sublimatic dyes, for instance. Coatings according to the invention and methods of using them will now be described in more detail, by way of example only, and with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic section through a transfer incorporating the coating; and Fig. 2 is a highly schematic diagram showing the process of Example 3. Example 1 The coating to be described is intended for use in sublimatic transfer printing on natural fibres such as cotton and cotton mixtures, for example poly/cotton (polyester/cotton). The coating material consists of four components. An acrylic resin, preferably n-butyl methacrylate is used as an adhesive component. (Alternatively, a polyurethane or other thermoplastic resin could be used). A mineral spirit is incorporated as a solvent for the n-butyl methacrylate which is normally a solid. Other suitable solvents include ethers, fluorocarbons, hydrocarbons, ketones and nitroparaffins. A plasticizer, preferably a phthalate such as butyl benzyl phthalate is incorporated to improve the handling properties of the coating. Finally the material also includes a lubricant such as oleine or another animal fat derivative, or a mineral oil derivative, or a mixture of such components. This serves to improve the feel ("handle") of the transfer on the fabric . Preferably the composition includes 30 to 50?o of n-butyl methacrylate, 1 to 35 % of plasticizer, 10 to 40 % of mineral spirit and 1 to 1 % of lubricant. A composition found to produce acceptable results comprises: n-butyl methacrylate - 48 c butyl benzyl phthalate - 8% ineral spirit - 30?ό lubricant - 14?ό The formulation of the coating begins by allowing the n-butyl methacrylate to soak in mineral spirit until it softens and dissolves. Gentle stirring at this stage results in a viscous liquid. The plasticizer and lubricant are then added and the resulting mixture is again stirred to an even consistency. The whole formulation process may take place at room temperature. When the coating has been prepared, it may be applied to a sublimatic transfer 10 which consists of a paper substrate 12A on which an image 12B has been printed in reverse, using sublimatic dyes and a silk screen or other printing process. The coating -14 is then applied, for instance by roller, over the sublimatic dye image 12B which is therefore trapped between the coating 14 and the paper substrate 12A. Once the transfer has been coated, the image may be transferred to the coating by heating the transfer. Raising the temperature into the range 185 to 215°C for a period of ten seconds is sufficient to cause the dyes to penetrate the coating by sublimation so that when the transfer is returned-to room temperature, the image is permanently fixed in the coating. To apply the transfer the substrate 12A and dyed coating 14, 12B are placed against the fabric to be printed with the coating 14 in contact with the fabric. Elevated temperature and pressure are then applied. The elevated temperature (preferably in the range 180 to 220°C, for example 190°C) softens the coating enhancing its adhesive properties and flow characteristics. The applied pressure (preferably in the range 7 to 30 psi, for example 20 psi) forces the dyed coating between the fibres of the fabric. When room temperature and pressure are restored, the coating performs an adhesive function which adheres the dye to the fabric fibres, thereby binding the image to the fabric. Thus the durability and vivid colours of sublimatic transfer images can be achieved on fabrics whose fibres are not in themselves suitable for impregnation by sublimatic dye. The formulation described above has the further advantage that, by varying the quantity of solvent included in the coating, the adhesive properties can be varied as may be required to apply the method to different fabrics. The adhesiveness is preferably reduced sufficiently to allo the backing paper to be readily removed at room temperature, or at a temperature in the range 10 to 200°C. Room temperature removal is expected to provide significant advantages when the transfers are used in presses for simultaneously printing a plurality of articles. Previously proposed sublimatic transfers required the backing paper to b.e removed before the transfer had cooled, so that a press operator may only have a period of a few seconds in which to remove the backing sheets from all of the transfers which have simultaneously been printed. This may prove to be impossible, especially if any difficulties are experienced with one or more backing sheets, and the resultant loss of production caused by failure to remove backing sheets can be unac ' ceptably high. By contrast, when the backing sheets can be removed at lower emperatures, it ceases to be necessary to remove all backing sheets within a .few seconds of the press opening. The coating formulation described above has also been found to increase the shelf-life of sublimatic transfers to which it has been applied. Untreated transfers which tend to degrade as the dyes in the image leach into one another. The presence of the coating is believed to inhibit leaching. The use of the coating to bind the sublimatic dye to the surface to be printed allows sublimatic transfer printing to be extended to surfaces which are wholly inpenetrable by sublimatic dyes. Example 2 A composition for use as a coating composition is formulated from a solvent, a resin (preferably n-butyl methacrylate), mineral oil and a powder material. The powder may be copolyester, polypropylene, polyethylene or copolyamide. The preferred solvent is based on white spirit and consists of 50 % or more b weight of white spirit. The balance of the solvent mix may substantially wholly comprise cyclohexanone and/or 1-methoxy-2- propanol. In formulating the composition, the solvent ingredients are first mixed together. The n-butyl methacrylate (a thermoplastic acrylic resin) is then added to the solvent. The solvent causes the resin to soften. The resin and solvent may be mixed in weight ratios between 1:1 and 2:3 approximately. The remaining ingredients are then added to the softened resin. In this example, the final formulation consists of approximately 60 softened resin: approximately 13 % mineral oil and 27 % copolyester powder. Other powders, such as polypropylene, polyethylene and copolyamide, could be used. These proportions may be varied widely in order to control the properties of the final compound, and in accordance with the intended application. Xylene may be incorporated as an additional ingredient. The compound can be used by coating onto an image to be printed, such as a conventional sublimatic dye transfer. Usually the image is formed on a backing member such as paper. The image may be printed on the paper, for instance by dyed inks or otherwise. The coated image is then placed against the article to which the image is to be transferred, and appropriate conditions are then created, usually including the application of heat and/or pressure, to cause the compound and the image to transfer to the article. When using the composition of Example 2 above, it is preferred to apply heat and pressure and then to remove the paper or other backing member immediately after heating, while the materials are still hot. After application, the coating provides ad esion between the image dyes and the article. When the coating is to be used with conventional transfers, the coating may be applied to the transfer during manufacture. The dyes may be encouraged to adhere to coating immediately. The process is them divided into two stages, in which the user completes the second by causing the coating to adhere to the article. Example 3 A particularly preferred method according to the invention can be used with the composition of Example 1, but preferably the composition of Example 2. The composition is coated on an image formed on paper by a photocopying process, preferably a colour photocopying process. The composition is applied over the image on the colour copy which is then placed in contact with an article. The image is transferred to the article by- applying heat and pressure. The composition described above has been found to allow an image to be transferred from a colour photocopy onto various materials, including synthetic, natural and mixed fibre fabrics. The use of a colour photocopy as the basis for printing gives the present invention wide application because any image which can be copied by a colour photocopying process can then be transferred to an article in the way described. Furthermore, the eas availability of colour photocopying machines represents a substantial improvement over techniques involving pre-printed transfers etc. which must be manufactured or ordered in advance. When applying the image from the photocopy to an article, the image is reversed from left to right. This effect is well known in the field of transfer printing. In that field, it is dealt with by preparing transfers which are themselves reversed in relation to the required final image, so that the final image is correctly produced after the image on the transfer is reversed. However, a photocopying machine is designed to reproduce an original without any reversal of the image. A reversed image can be produced by using a two stage photocopying process. This is schematically indicated in Fig. 2. In a first stage, the image 20 on an original 22 is copied onto a transparent intermediate carrier 24 such as a sheet of clear acetate. The image 20 is shown as an asymmetric image, for clarity. The acetate sheet 24 is then used in place of the original 22 in a second photocopying stage in which the image 20 on the acetate sheet 24 is copied onto paper 26. The acetate sheet 24 is placed on the photocopying machine in reverse as indicated by the arrows 28. That is, the machine scans the image 20 through -the acetate sheet 24 rather than directly. This results in a reversal of the image 20 but the transparency of the acetate removes or minimises any degradation of the image. The result of the second copying stage is a colour photocopy 26 of the original, but with the image 20 reversed. After coating and printing as described above, the final image produced by the process on an article 30 is a reproduction of the original, without reversal, as indicated at 32. The action of the coating compositions described above when used on photocopies is not fully understood. However, the composition has been found useful with a wide range of types of image, including colour photocopies from various copying processes and other colour images such as those produced by wax crayons. We believe that the compositions are usable with sublimatic dyes and other types of dye and colouring. One possible explanation of the action of the composition on photocopied images is as follows. When heat is applied in order to transfer the image from the photocopy to the article, it is believed that the composition may attack binders in the photocopied image, to cause dyes to be released from the backing member. Pressure causes the composition and at least some of the released dyes to remain on the article when the backing member is removed, and the composition then performs an adhesive function to adhere the dyes to the article. The description above relates mainly to compositions which include the acrylic resin n-butyl methacrylate. However, other acrylic resins could be substituted. Polyurethane resins or other thermoplastic resins could also be substituted. It will be appreciated that many modifications and variations to the formulation described above can be made without departing from the spirit and scope of the present invention. In particular, the choice of adhesive will depend on the surface which is to be printed, and will be made to ensure that the adhesive can adhere to the surface but can also take an image by sublimation. Other components such as lubricant, softeners, solvents, and plasticizers will be included or omitted according to the characteristics of the coating which are required for particular applications. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims: C L A I MS 1. A coating composition for use in coating an image to be printed, and comprising a solvent, a resin, a mineral oil and a powder material. 2. A composition for use in sublimatic transfer printing, the composition comprising an adhesive component and the material or materials of the composition being so chosen as to be receptive to sublimatic dye transferred thereto by sublimation, and to be adherable to a surface to be printed, thereby binding the dye to the surface to form an image thereon. 3. A composition according to claim 1 or 2, comprising a thermoplastic resin as an adhesive component. 4. A composition according to claim 3, wherein the thermoplastic resin is a polyurethane resin. 5. A composition according to claim 3, wherein the thermoplastic resin is an acrylic resin. 6. A composition according to claim 5, wherein the acrylic resin is n-butyl methacrylate. 7. A composition according to claim 2 or any claim dependent on claim 2, and including a solvent. 8. A composition according to claim 1 or 7, wherein the solvent is a mineral spirit. 9. A composition according to claim 8, wherein the mineral spirit is a dilute benzene based solvent. 10. A composition according to claim 1 or 7, wherein the solvent comprises white spirit. 11. A composition according to claim 1, 7 or 10, wherein the solvent comprises cyclohexanone and/or 1-methoxy-2-propanol. 12. A composition according to any preceding claim, and including a plasticizer. 13. A composition according to claim 12, wherein the plasticizer is a phthalate. 14. A composition according to claim 13, wherein the- phthalate is butyl benzyl phthalate. 15. A composition according to any preceding claim, and including a lubricant for affecting the feel of a transfer after application to a fabric. 16. A composition according to claim 15, wherein the lubricant comprises oleine. 17. A composition according to claim 1 or any claim dependent on claim 1 , wherein the powder material is copolyester, polypropylene, polyethylene or copolyamide. 18. A composition according to claim 1 or any claim dependent on claim 1, the composition comprising between - 20 and 40?ό solvent; between 20 and 40?o n-butyl methacrylate; between 5 and 20?o mineral oil and between 20 and 35?ό powder material. 19. A composition according to claim 2 or any claim dependent on claim 2, and including 30 to 50 % of adhesive component, 1 to 35?ό of plasticizer, 10 to 40?ό of mineral spirit and 1 to 19?ό of lubricant. 20. A composition according to any preceding claim, and further comprising xylene. 21. A sublimatic transfer comprising a substrate, an image formed by sublimatic dye, and a coating, the coating and the dye being so selected that on heating to a predetermined temperature the dye transfers the image to the coating by sublimation, the resulting transfer being capable of adherence to a surface to be printed, whereby the coating binds the dye to the surface to form an image thereon. 22. A transfer according to claim 21, wherein the dye image is located between the coating and the substrate. 23. A transfer according to claim 21 or 22, the coating including sufficient solvent' for the adhesive component to allow removal of the substrate at a temperature in the range 10 to 200°C. 24. A transfer according to claims 21, 22 or 23, wherein the coating is a composition according to any of claims 1 to 12. 25. A method of manufacturing a sublimatic dye transfer, in which an image is formed by sublimatic dye on a substrate, and a coating is applied over the image, the coating being receptive to sublimatic dye transferred thereto by sublimation, and being adherable to a surface to be printed. 26. A method according to claim 25, wherein sublimation of the dye into the coating is effected during manufacture. 27. A method according to claim 26, wherein sublimation of the dye is effected by heating. 28. A method according to claim 27, wherein the dye is heated to a temperature in the range 185 to 215°C to transfer the image to the coating. 29. A method according to claim 27 or 28, wherein the dye is heated for a period of at least ten seconds to transfer the image to the coating. 30. A method of transfer printing using a transfer manufactured according to any of claims 25 to 29, wherein the coating is applied to the surface to be printed at an* elevated temperature to cause the coating to adhere to said surface. 31. A method according to claim 30, wherein the elevated temperature is in the region of 180 to 220°C. 32. A method according to claim 31, wherein the temperature is about 190°C. 33. A method according to any of claims 30 to 32, wherein the coating is applied to said surface under pressure to cause the coating to adhere to the surface. 34. A method according to claim 33, wherein the application pressure is in the region of 7 to 30 psi. 35. A method according to claim 34, wherein the application pressure is about 20 psi. 36. A method according to any of claims 30 to 32 and any of claims 33 to 35, wherein the elevated temperature and pressure are applied for a period of 7 to 25 seconds. 37. A method according to claim 36, wherein the elevated temperature and pressure are applied for a period of about ten seconds. 38. A method according to any of claims 35 to 37, wherein the coating is a composition according to any of claims 1 to 20. 39. A method of printing an image on an article, in which the image is copied by a photocopying process onto a backing member, a coating compound is applied over the image on the backing member, the coated surface of the backing member is placed against the article, and conditions are created to cause the image to transfer to the article, the compound being chosen to enhance or permit the transfer of the image from the backing member to the article. 40. A method according to claim 39, wherein the backing member is a paper sheet. 41. A method according to claim 39 or 40, wherein the photocopying process creates an image which is reversed on the backing member in relation to the original image. 42. A method according to claim 41, wherein the photocopying process includes a first step in which an original is copied onto an intermediate carrier, and a second step in which the image on the intermediate carrier is copied in reverse onto the backing member. 43. A method according to claim 42, wherein the intermediate member is transparent, the second step including scanning the image on the intermediate carrier by viewing the image through the intermediate carrier. 44. A method according to claim 43, wherein the intermediate carrier is a clear acetate sheet. 45. A method according to any of claims 39 to 44, wherein the image to be printed is in colour. 46. A method according to any of claims 39 to 45, wherein the image to be printed is formed by dyes. 47. A method according to claim 46, wherein the dyes are sublimatic dyes.

Inventors: WALTERS DAVID GEORGE, WALTERS, DAVID, GEORGE
Applicants: BRANDYWINE MOTIFS LTD, BRANDYWINE MOTIFS LIMITED
Application year: 1990
Main classification: B41M5
IPC codes: B41M7, D06P5