GB2131966A - Manufacture of transfer materials - Google Patents

Abstract

Dry transfer materials can be produced using electrophotographic copying machines and multilayer sensitised materials. The multilayer materials consist of a base sheet 2 with image-accepting layer 1, capable of accepting an electrophotographic toner image. In addition, the sheet has one or more thermographically sensitised layers 4, 5 thereon so that a thermographic image may be produced in register with the electrophotographic toner image, conveniently at the same time as that toner image is fused. Layer 5 is a low-tack pressure adhesive composition containing metal salts, e.g. Ag behenate, and 3 is a release coat. The toner image and or thermographic image may be on the same or opposite sides of the base sheet. Transfers of high optical density may be produced quickly and easily in this way. <IMAGE>

Description

SPECIFICATION Manufacture of transfer materials This invention relates to the manufacture of transfer materials.

Transfer materials, particularly for graphic arts purposes, have become widely popular in recent years in many fields. Conventionally, in order to produce such materials, screen printing methods have been used. These, whiie they can be used to produce transfers of excellent quality, are cumbersome and require substantial investment in time and equipment. The methods accordingly do not lend themselves to the production of short runs or one-off transfers.

Various photographic methods of manufacturing dry transfers have been proposed in the literature but these likewise require investment in time and equipment in order to be able to carry them out.

Following the spread of electrophotographic copying machines in recent years, attempts have been made to utilise these for the production of transfers. These attempts have not been conspicuously successful. Some require the use of a specific toner material which has to be substituted for the material normally used in a copying machine and this is clearly impractical unless a copying machine is to be dedicated to transfer manufacture. Another approach described in United States Patent Specification No. 4,171,398 relies for its success on the application of toner to an adhesive layer which is subsequently stuck down to a receptor surface.

The fact that the adhesive layer has to pass through the electrophotographic copying apparatus limits its effectiveness, which is further diminished by the application of toner thereto. This in turn limits the optical density of images which can be obtained by this method, since the more optically dense the image, the less the adhesiveness in the image areas. In addition, the image formed is, when transferred, not right reading compared to the original exposed in the electrophotographic copying apparatus. If a right reading transfer is required, the original legend must be reversed, or the transfer-making process must be carried out twice, the first transfer made serving as an original for the second, which gives rise to a loss in definition.

We have now found that transfer materials of good quality may be produced using an electrophotographic copying machine in what is effectively a two-stage process, albeit that many electrophotographic copying machines are automatically capable of carrying out both stages.

The first of these stages is the production of a toner image on a sheet material which is fed into the electrophotographic copying apparatus in conventional fashion. The second of these is to use the toner image formed in the electrophotographic copying apparatus as a master image for contact thermographic printing.

Thus, according to the present invention there is provided a method of producing a dry transfer material bearing one or more transferable images which comprises depositing, by the electrophotographic copying process, a toner image corresponding to a desired original on a sheet of material having, on the side on which the toner image is deposited or on the opposite side, at least one removable thermographically.sensitised layer, and subsequently subjecting the sheet to infrared radiation whereby to heat the sheet preferentially in the areas carrying a deposit of toner and thereby cause the formation of a transferable, visible image in the thermographically sensitised layer or layers.

Such a method may be effected using a suitable thermographically sensitised sheet material and an electrophotographic copier in which a toner image is conventionally fixed on plain paper by fusing. In such apparatus, the electrophotographically deposited toner image is simultaneously fixed and used as a contact master. Where the toner is present, heat is absorbed which both fuses the toner and by conduction heats the thermographically sensitised layer(s) in those areas to produce a corresponding image thermographically.

As noted above, the toner image and the thermographically sensitised layer(s) may be on the same side of the basic sheet of material which is fed into the machine or on opposite sides. If they are on the same side, then the images formed electrophotographically and thermographically and then transferred from the base sheet and e.g. adhere to a suitable substrate will be reverse images. The material fed into the electrophotographic copying apparatus in such a case may consist of a base sheet having a surface having release properties allowing subsequent layers to be stripped therefrom, at least one non-adhesive layer on the release surface and a layer of pressure sensitive adhesive coating, whereby the non-adhesive layer(s) alone or together with the pressure sensitive layer are thermographically sensitized.The outermost layer which is the pressure sensitive layer must also be capable of accepting a toner image. Transfers produced in this way may have very substantial optical densities, the optical density being composed of the density of the electrophotographic image itself and that of the thermographic image.

However it can be disadvantageous to have the adhesive layer outermost as the sheet material passes through the electrophotographic copying apparatus and also the adhesive properties of the final transfer may be impaired by the toner image formed on the adhesive layer. Thus it may be preferred to provide over the pressure sensitive adhesive layer a release sheet which is capable of accepting a toner image. This release sheet, and the toner image it will then bear, can be removed after the electrophotographic and thermographic imaging steps to expose the pressure sensitive adhesive layer and give a dry transfer wherein the optical density corresponds to that of the thermographic image thereon.Alternatively the material fed into the electrophotographic copying apparatus in such a case may consist of a base sheet having a release surface, a layer of pressure sensitive adhesive coating on the release surface, and at least one nonadhesive layer on the layer of pressure sensitive adhesive, whereby the non-adhesive layer(s) alone or together with the pressure sensitive adhesive layer are thermographically sensitized, the or at least the outermost non-adhesive layer being of appropriate characteristics to accept a toner image. Transfers produced in this way again may have very substantial optical densities, optical density being composed of the density of the electrophotographic image itself and that of the thermographic image.

In the alternative, which is preferred for many uses, the thermographically sensitised layer(s) lies on the side of the base sheet opposite that on which the toner is deposited. This gives rise to a number of advantages, in particular that the transfer sheet produced from the copying apparatus can be used in conventional fashion by laying it down on a desired substrate (possibly after the removal of a protective sheet from the then lower side thereof) and the base sheet rubbed over in the area of the images or images it is desired to transfer, e.g. using a ball point pen. These images are then transferred to the desired substrate and the base sheet then peeled away with the electrophotographic image leaving the thermographically imaged layer(s) on the substrate where desired.It will be observed that using appropriate thermographically sensitised material, the colour of the so transferred image need not be black, although the electrophotographic toner image would normally be black and, indeed, would preferably be black to give good heat absorption.

Materials for feeding into electrophotographic copying apparatus for use in this way could accordingly consist of a base sheet having on one side one or more coatings designed to accept electrophotographic toner and to give a sharp clear image and having, on its other side, a release surface allowing subsequent layers to be stripped cleanly therefrom, then at least one non-adhesive layer and a layer of pressure sensitive adhesive coating, whereby the non-adhesive layer(s) alone or together with the pressure sensitive adhesive layer are thermographically sensitized. The non-adhesive and adhesive layers thus constitute layers which are transferred together when the final transfer material is used, so leaving the non-adhesive layer outermost on the desired substrate.

The adhesive and non-adhesive layers may be so formulated and coated that they may be simply transferred to the desired substrate by adhering thereto using pressure from the other side of the sheet and will shear cleanly from the remainder of the layers when the sheet is pulled away. Alternatively, they may be somewhat thicker and it may be necessary or desirable to scribe round the desired image area before adhering it to the desired final receptor surface.

The individual components of the stock material for feeding into the electrophotographic copier will now be individually considered.

First, the material fed in must have a dimensionally stable substrate which will withstand the mechanical and thermal stresses of passing through the electrophotographic copying machine.

In addition, where the thermographically sensitized layer(s) and the toner image receiving layer are on opposite sides of the base sheet, the sheet itself is preferably transparent or translucent, and must be so if the electrophotographic toner image is to be removed before the transfer material so-produced is to be used. The preferred material for use as a base sheet is a heat stable polymeric film material, most preferably a polyethylene terephthalate film.

The release properties of polyethylene terephthalate film are generally inadequate to allow clean positive release of applied coatings therefrom, for which reason it is generally preferred to coat one or both sides of the film with a release layer. The exact nature of the release layer will naturally be chosen depending on the nature of the next layer to be applied. However, a wide variety of release layers is known in the transfer manufacturing art and most can be used without difficulty.

The side of the base sheet which is to receive the toner image must be appropriately receptive thereto. The toner image receiving layer or layers may remain as part of the transfer material produced or may be removable from the base sheet leaving the base sheet with thermographically imaged non-adhesive and adhesive coatings thereon as the transfer material. In the latter case, the electrophotographically imageable layers may consist, for example, of a thin layer of polymeric film material adhered via a thin layer of an adhesive, e.g. an acrylic adhesive, to the base sheet, the polymeric material being adapted to receive a toner image. In order for the surface to accept a toner image properly it needs to be electrically non-conductive. However, it need not be transparent or translucent. Reflective non-conductive coatings can be used to enhance the temperature difference achieved on irradiation between image and non-image areas and increase the efficiency of the thermographic reaction.

The removable thermographically sensitized layer or layers may likewise be applied to a release coated base sheet. Where they lie on the side of the base sheet opposite that bearing the toner-receiving layer, the layer adjacent the base sheet is generally non-adhesive and the layer most remote adhesive in order that the assembly of layers functions as a transfer material.

Conveniently and preferably, two layers are used, each containing one component which, with the component in the other layer, is thermographically reactive. Thus the sheet material fed to the electrophotographic copying apparatus may comprise a non-adhesive layer comprising the first thermographic co-reactant and adjacent thereto the pressure sensitive adhesive layer containing the second thermographic co-reactant. If particularly optically dense images are required, three layers may be employed, first and second non-adhesive and a third adhesive layer, the first non-adhesive layer and the adhesive layer containing one thermographic coreactant and the second non-adhesive layer containing the other. In another form, there may be used a conventional pressure sensitive adhesive layer.In such a form the sheet material may comprise first and second non-adhesive layers containing first and second thermographic coreactants respectively and a pressure sensitive adhesive layer free from thermographic reactant.

The particular materials used for such a system may vary widely and may be chosen from those conventional in the dry transfer art. A particularly preferred set of materials are nitrocellulose based coatings for the non-adhesive layers and a polyisobutylene based low tack pressure sensitive adhesive for the adhesive layer. The nitro-cellulose based non-adhesive layers are preferably coated on to a release layer on the base sheet, a particularly preferred release layer being one based on a polystyrene resin, with which the nitro-cellulose layer is compatible.

The thicknesses or coating weights of the applied layers may vary widely dependent upon the precise properties desired in the final material. If the transferable coatings are desired to transfer merely being rubbed down on to the desired final receptor surface, shearing around the area where pressure was applied, then the coating weights should be low. If, on the other hand, the imaged area is to be scribed round prior to transfer, which gives a more robust transferable image, somewhat higher coating weights are desirable. Preferably the coating weight of the nonadhesive layer or layers is within the range 1 to 10 g.s.m. and the adhesive coat weight between 1 and 5 g.s.m.

As noted above, these transferable layers are thermographically imageable, these being preferably achieved by incorporating in adjacent layers co-reactants which, under the action of heat, form a visible image. There is a large body of patent literature to which recourse may be had for examples of such thermographic coatings. Purely by way of example, attention is drawn to United States Patent Specifications 3,031,329, 3,080,254 and 3,682,684 and British Patent Specifications 1,439,478 and 1,517,578. The United States Specifications disclose as thermographic reactants noble metal salts on the one hand and organic reducing agents.on the other. This reactant system is preferred for use in the present invention.The noble metal salt is preferably a silver salt of a long chain organic acid, particularly silver behenate but also silver stearate, and silver oleate, and silver phthalate can be used. Ferric and mercuric long chain organic acid salts, such as ferric stearate and mercuric behenate may be advantageously incorporated as disclosed in these specifications.

Typical reducing agents which may be used as co-reactants are methyl gal late, 3,4-dihydroxybenzoic acid, gallic acid, pyrogallol, catechol and hydroquinone. These are, however, merely examples since many cyclic, preferably aromatic, compounds having an active hydrogen atom attached to an oxygen, nitrogen or carbon atom directly attached to an atom of the cyclic ring will act as reducing agents for the noble metal ion in the co-reactant.

As is known, numerous materials may be added to the simple thermographic reactant system in order to improve the thermographic image colour and density. Thus phthalizone, barbituric acid and 1 -acetyl-2-thio-hydantoin are described as useful additives in United States Patent Specification 3,080,254. The coatings may also include stabilizers such as highly halogenated aromatic polycarboxylic acids and anhydrides, e.g. tetrachlorophthalic anhydride, as described in United States Patent Specification 3,031,329.

We have found it convenient, and it is accordingly preferred, to locate the reducing agents of the thermographic composition in the non-adhesive layer and to disperse the metal salt in the adhesive layer, when only two layers are used. When three layers are used, a non-adhesive layer containing the reducing agent is sandwiched between a non-adhesive layer containing a metal salt and an adhesive layer with or without a metal salt. Techniques of this sort enable high optical densities to be produced in the thermographically produced image without the concentration of thermographic reactants in any layer being so great as adversely to affect the mechanical performance of that layer.

The coated sheet materials used in the method of the present invention, which of themselves constitute a further feature of the invention, may be produced in any convenient fashion. We have found simple Meyer bar coating to be an adequate technique, though more sophisticated coating techniques may be used if desired. Care must, of course, be taken to ensure that the application of a subsequent coating does not adversely affect any previously applied coating. In particular, as soon as the coated material contains the thermographic reactants, it must be dried using a cold drying method in order to prevent the thermographic reaction taking place.

As noted above, in some of the ways of putting the present invention into effect, the outermost layer is an adhesive layer, e.g. a low tack pressure sensitive adhesive. This may be protected, if desired, using, e.g. a conventional release paper or film which may either be adhered to the adhesive layer or which may be, e.g. affixed along one edge to the multi-layer thermographically sensitised sheet material, that being the leading edge as the sheet is fed through electrophotographic copying apparatus. Protecting the adhesive layer serves on the one hand to preserve it from contamination with dust and dirt and from becoming less adhesive.On the other hand, it stops the sheet material adhering to parts of the electrophotographic apparatus such as rollers and feed belts, and enables sheets of material in a stack to be fed successively through electrophotographic copying apparatus where a plurality of sheets of transfer material are to be produced from the same original. As previously described this release paper/film, if chosen to be suitably electrically nonconductive, can also be used to receive the electrophotographic image if required.

The material of the present invention is used by feeding it through an electrophotographic copying apparatus in standard fashion. This first deposits a toner image corresponding to the image of an original on the sheet material. This toner image is then fixed, normally by radiant heat fusing. In any case in which the toner image is not fixed by heat fusing, the sheet is subsequently subjected to infrared radiation to effect the thermographic reaction and image the transferable layers. Thereafter, the transferable layers may be applied to the desired substrate, optionally after removal of the electrophotographically produced image.

The following Examples will serve to illustrate the invention. In each case, the layered construction of each particular Example is indicated in the accompanying sheet of drawings, each of which shows in diagrammatic section on a very greatly enlarged scale the layer construction. The layers are all identified by reference numbers, the key to which is as follows: 1. Image-accepting layer.

2. Polyethylene terephthalate film.

3. Release coat.

4. Shearable non-adhesive coating containing reducing agent.

5. Low tack pressure sensitive adhesive composition containing metal salts.

6. Image formed of electrophotographic toner.

7. Image formed thermographically.

8. Non-shearable, non-adhesive layer containing a reducing agent.

9. Non-shearable, non-adhesive layer containing metal salts.

10. Cellulose acetate film.

11. Permanently tacky pressure sensitive adhesive layer.

12. Low tack pressure sensitive adhesive layer.

EXAMPLE 1 As base sheet there was used a sheet of polyethylene terephthalate film 75 ym thick (Melinex 542 ex l.C.I.). This was coated on one side with a layer designed to accept a toner image using a coating composition formulated as follows (per cent by weight): Acrylic resin (Paraloid A10 solution, 30% by weight solution in Oxitol, ex Rohm 8 Haas) 78.3 Anti-static agent (ASA3 ex Shell Chemicals) 0.3 Precipitated calcium carbonate (Calopake F ex Sturge Chemicals) 6.6 Wax (Epolene N.11 10% by weight dispersion in toluene, ex Eastman Kodak 7.6 Oxitol 7.2 This coating composition was mixed and milled to Hegman gauge greater than 7 and finally diluted to coating viscosity of 60 seconds (Zahn Cup No. 2) with pure oxitol. The coating was applied using a Meyer bar and subsequently dried in an oven at 60"C for one minute to give a dry coat weight of 7.0 g.s.m.

The other side of the polyethylene terephthalate sheet was then coated with a release coat based on polystyrene resin. The basic coating composition had the following formulation (per cent by weight): Polystyrene resin (Type LX4300, NAW 1000 ex Monsanto) 20.2 Precipitated calcium carbonate (as above) 4.9 Anti-static agent (as above) 0.2 Ethyl acetate 34.6 Xylene 34.6 Oxitol 5.5 This coating composition was likewise mixed and milled to a Hegman greater than 7 and adjusted to a coating viscosity of 60 seconds (Zahn Cup No. 2) using a mixture of ethyl acetate, xylene and oxitol in the proportions given in the basic coating composition formulation. This was likewise Meyer bar coated, and dried in an oven at 60"C for one minute to give a dry coat weight of 7.0 g.s.m.

A non-adhesive coating was then applied from a coating composition consisting of (parts by weight): Plasticised nitro-cellulose solution 50 parts Finely divided silica (Aerosil R972 ex Degussa) 2 parts Methyl gallate 3 parts Oxitol 50 parts *The plasticised nitro-cellulose solution used comprised Butanol damped nitro-cellulose (DHX 30/50 ex l.C.I.), 21% non volatiles content in oxitol 41 parts Oil modified azaleic alkyd plasticiser (Paraplex RGA2 ex Rohm and Haas) 5 parts Butyl oxitol 4 parts This coating composition was coated using a Meyer bar and dried in an oven at 60"C for one minute to give a dry coat weight of 1.0 g.s.m.

An adhesive coating composition was formulated as follows (parts by weight): Polyisobutylene resin (Oppanol B50 ex BASF, 20% by weight solution in aliphatic solvent (Exsol 145/160, ex Esso)) 15.7 Polybutene resin (Hyvis 200 ex BP Chemicals) 6.9 Polyethylene wax (ACP6 ex Allied Chemicals, 10% by weight dispersion in aliphatic solvent (as above)) 49.6 Finely divided silica (as above) 4.0 Silver behenate (20% by weight dispersion in aliphatic solvent, as above) 24.0 Ferric stearate (20% dispersion in aliphatic solvent, as above) 16.0 Aliphatic solvent (as above) 11 3.8 Oxitol 9.0 This coating composition was applied using a Meyer bar and subsequently dried using a cold air dryer to give a dry coat weight of 2.0 g.s.m.

The so-manufactured coated sheet material was then placed together with an interleaving sheet of release paper to which it was attached at its leading edge in the infeed tray of an electrophotographic copier (Xerox (Registered Trade Mark) 3100). The coating first applied to the base sheet was placed so that it received the toner image. An original was then placed on the platen of the copier and the copier operated. The sheet was removed from the delivery tray of the copier and the interleaving sheet removed. The sheet was then laid adhesive coating side down on a sheet of Bristol board and the toner image 6 burnished over using a spatula. On peeling away the carrier sheet it was found that the thermographic image 7 had transferred to the sheet of Bristol board. The black image had an optical density of 0.3.

EXAMPLE 2 Sheets of polyethylene terephthalate, as in Example 1, were coated with the first two coating compositions set out in that Example, as in that Example. Then the release coat was supercoated with a non-adhesive layer from a coating composition consisting of (parts by weight): Plasticised nitro-cellulose solution (as in Example 1) 50.0 parts 3,4-dihydroxybenzoic acid 4.0 parts Tetrachlorophthalic anhydride (stabiliser) 1.0 parts Methylated spirit, 74 OP 37.5 parts Ethyl acetate 12.5 parts This coating composition was coated using a Meyer bar and the wet coating composition dried in an oven at 60"C for 1 minute to give a dry coat weight of 5.9 g.s.m.

A coating of adhesive as in Example 1 was then applied over this nitro-cellulose based layer as in Example 1, the final coat weight of the adhesive being 4.7 g.s.m.

Sheets so produced were imaged on their adhesive side using a photocopying machine as in Example 1. The image produced on the adhesive side was then scribed round using a scalpel and the sheet inverted to apply the image to a desired receptor surface. The applied image accordingly consisted of a thermographically produced image and the toner image and had an optical density of 1.9.

Comparison samples were made up exactly as just set out save that the reducing agent (3,4dihydroxybenzoic acid) was omitted from the plasticised nitro-cellulose based coating and the noble metal salt omitted from the adhesive. The optical density of transfers made in this way (which are similar to those disclosed in United States Specification No. 4,1 71 ,398) was only 0.9.

EXAMPLE 3 Sheets of polyethylene terephthalate as in Example 1 were coated with an image-receiving coating and a release coating on the opposite side, as in Example 1.

The release coating was then overcoated with a first non-adhesive layer from a coating composition consisting of (parts by weight): Plasticised nitro-cellulose (as in Example 1) 25.0 parts Silver behenate dispersion (20% by weight in methylated spirit, 74 OP) 30.0 parts Ferric stearate dispersion (20% by weight in methylated spirit, 74 4DP) 20.0 parts Methylated spirit 74 OP 37.5 parts Ethyle acetate 12.up parts After application using a Meyer bar and drying at 60"C for 1 minute the dry coat weight of this first non-adhesive layer was 3.8 g.s.m.

This non-adhesive layer was overcoated with a second non-adhesive layer from the coating composition set out in full in Example 2. Coating was by Meyer bar followed by cold air drying to give a dry coat weight of 7.5 g.s.m.

Finally, the two non-adhesive coats were over-coated with a pressure sensitive adhesive coating composition as set out in Example 1. Coating was by Meyer bar and after cold air drying, the outer adhesive coating had a coat weight of 4.2 g.s.m.

Sheets so produced were imaged in an electrophotographic copier as set out in Example 1.

After removing the interleaved sheet, and scribing round the area of the desired image to be transferred, the image could be transferred to a desired substrate as set out in that Example. The optical density of such images was approximately 1.4.

EXAMPLE 4 Cellulose acetate film (33 m thick ex Lonza) was coated using conventional coating machinery with a low tack acrylic pressure sensitive adhesive coating. The coating composition was a commercially available adhesive (National 030-1028 ex National Adhesives a Resins) diluted to 20% by weight solids content using ethyl acetate. The dry coat weight was 6.0 g.s.m.

This adhesive film was then hand laminated to the non-adhesive side of the multi-layer coated material produced in Example 3 and the laminate so produced then fed together with an interleaving sheet as in Example 1 through a photocopying machine. After the image material had been recovered from the delivery tray of the machine, the electrophotographically produced toner image 6 was removed by peeling away the adhesive coated cellulose acetate film 1 0. This left a sheet of transfer material which could be used in the normal way. The optical density of the transferred images was 1.25.

EXAMPLE 5 Example 3 was repeated but with the omission of the silver behenate and ferric stearate dispersion from the first non-adhesive coating. The dry coat weight of the first non-adhesive coating was 1.6 g.s.m. Such sheets were then imaged as in Example 3 and the images transferred from the dry transfer material. The optical density of those images was 0.8.

Claims (20)

1. A method of producing a dry transfer material bearing one or more transferable images which method comprises depositing, by the electrophotographic copying process, a toner image corresponding to a desired original on a sheet of material having, on the side on which the toner image is deposited or on the opposite side, at least one removable thermographically sensitised layer, and subsequently subjecting the sheet to infrared radiation whereby to heat the sheet preferentially in the areas carrying a deposit of toner and thereby cause the formation of a transferable, visible image in the thermographically sensitised layers or layers.

2. A method according to claim 1 wherein the electrophotographically deposited toner image is simultaneously fixed and used as a contact master, whereby, where the toner is present, heat is absorbed which both fuses the toner and by conduction heats the thermographically sensitised layer(s) to produce a corresponding image thermographically.

3. A method according to claim 1 or 2 wherein the toner image and removable thermographically sensitised layer(s) are on the same side of the said sheet of material.

4. A method according to claim 3 wherein the sheet of material fed to the electrophotographic copying apparatus comprises a base sheet having a release surface, at least one nonadhesive layer on the release surface and a layer of pressure sensitive adhesive coating thereon, whereby the non-adhesive layer(s) alone or together with the pressure-sensitive adhesive layer are thermographically sensitised and the pressure sensitive adhesive layer or a removable sheet thereover is capable of accepting a toner image.

5. A method according to claim 1 or 2 wherein the toner image and thermographically sensitised layer(s) are on opposite sides of the said sheet of material.

6. A method according to claim 5 wherein the sheet of material fed to the electrophotographic copying apparatus comprises a base sheet having on one side a coating capable of accepting a toner image and having on its other side a release surface and in order thereon at least one non-adhesive layer and a layer of pressure sensitive adhesive coating, whereby the non-adhesive layer(s) alone or together with the pressure sensitive adhesive layer are thermographically sensitised.

7. A method according to claim 6 wherein the coating capable of accepting a toner image is provided on a film removably adhered to the base sheet, which film, and the toner image formed thereon, is removed from the base sheet to leave the final dry transfer material.

8. A method according to any one of claims 2 to 7 wherein, in the sheet of material fed to the electrophotographic copying apparatus, the non-adhesive layer contains a first thermographic co-reactant and the adhesive layer contains a thermographic co-reactant therefor.

9. A method according to any one of claims 2 to 7 wherein, in the sheet of material fed to the electrophotographic copying apparatus, a first non-adhesive layer contains a first thermographic co-reactant and a second non-adhesive layer adjacent thereto contains a thermographic coreactant therefor.

10. A method according to claim 9 wherein, in the sheet of material fed to the electrophotographic copying apparatus, the adhesive layer adjacent said second non-adhesive layer also contains said first thermographic co-reactant.

11. A method for producing a dry transfer material substantially as described with reference to any one of the accompanying diagrams and/or Examples.

1 2. Dry transfer material produced by the method claimed in any one of claims 1 to 11.

1 3. Sheet material for use in the method claimed in claim 1 which sheet material comprises a base sheet having thereon at least one removable thermographically sensitised layer wherein the outermost removable thermographically sensitised layer is or is provided with a removable coating which is capable of accepting an electrophotographic toner image or the base sheet on the side opposite the removable thermographic layer or layers is or is provided with a coating which is capable of accepting an electrophotographic toner image.

14. Sheet material according to claim 1 3 which comprises a base sheet having a release surface, at least one non-adhesive layer on the release surface and a layer of pressure sensitive adhesive coating thereon, the non-adhesive layer(s) alone or together with the pressure-sensitive adhesive layer being thermographically sensitised and the pressure sensitive adhesive layer or a removable sheet thereover being capable of accepting a toner image.

1 5. Sheet material according to claim 1 3 which comprises a base sheet having on one side a coating capable of accepting a toner image and having on its other side a release surface and in order thereon at least one non-adhesive layer and a layer of pressure sensitive adhesive coating, the non-adhesive layer(s) alone or together with the pressure sensitive adhesive layer being thermographically sensitised.

1 6. Sheet material according to claim 1 5 wherein the coating capable of accepting a toner image is provided on a film removably adhered to the base sheet.

1 7. Sheet material according to any one of claims 14 to 16 wherein the non-adhesive layer contains a first thermographic co-reactant and the adhesive layer contains a thermographic coreactant therefor.

1 8. Sheet material according to any one of claims 1 4 to 1 6 wherein a first non-adhesive layer contains a first thermographic co-reactant and a second non-adhesive layer adjacent thereto contains a thermographic co-reactant therefor.

1 9. Sheet material according to claim 1 8 wherein the adhesive layer adjacent said second non-adhesive layer also contains said first thermographic co-reactant.

20. Sheet material for producing a dry transfer material substantially as described with reference to any one of the accompanying diagrams and/or Examples.