GB2126950A - Coloured dry transfers - Google Patents

Abstract

Coloured dry transfers are produced by applying colouring from a colouring sheet to a dry transfer sheet bearing transparent or almost transparent indicia covered by a layer of adhesive. The colouring sheet has at least two layers thereon which are transferred to the adhesive on the indicia, the then outermost layer over the indicium being an adhesive layer which can act to adhere the indicium itself, its original adhesive layer and the other layer of the two (which is preferably not adhesive and which was outermost on the colouring sheet) to a desired receptor surface when the coloured dry transfer is used. The application of colour to the transfer sheet is preferably effected by bringing the colouring sheet into contact with the transfer sheet and pressing in the area of the desired indicium with a furnishing tool.

Description

SPECIFICATION Coloured dry transfers This invention relates to the manufacture of coloured dry transfers.

Dry transfers are conventionally produced by screen printing. It is not economic to produce dry transfers, particularly dry transfer lettering sheets, in a wide range of colours save in respect of a few very widely used typefaces. However, graphic artists and others working with such materials often want to apply coloured lettering to artwork.

Masking and solvent techniques are known for effecting this but they are cumbersome.

British Patent Specification 1347011 describes one solution to the problem. It discloses use of a basic dry transfer sheet where the transferable indicia are colourless or substantially so and wherein those indicia are effectively given colour prior to transfer e.g. by the application thereover of a coloured adhesive layer applied from a suitable application sheet which works rather like "carbon paper".

While the system described in Specification 1347011 can be made to work in practice, it has disadvantages. Firstly it is not practically possible to restrict the application of the colouring material to the exact outline of the transferable indicium while that is on its original carrier sheet.

Accordingly, extra coloured material is applied to the dry transfer sheet outside the area of the indicium and there is a tendency for this to be transferred when the indicium is transferred to the desired receptor surface. The extra coloured material is of course undesired and needs to be removed. Secondly, the coloured adhesive layer is difficult to handle and tends to transfer accidentally to undesired locations.

We have now found that these difficulties can be avoided and a workable system produced by applying the colour from the multilayer colour application sheet and by formulating the dry transfer sheet and colour application sheet relative to one another to enable easy production of the coloured indicium on the dry transfer sheet and reliable subsequent transfer.

According to the present invention there is provided a method of making coloured dry transfer which comprises providing a dry transfer material comprising a base sheet, indicia thereon in colourless or substantially colourless filmforming material and a layer of adhesive over the indicia and the areas of the base sheet between them, bringing into contact with the indicia bearing side thereof, under pressure in the area of the indicia, the coated side of a second base sheet, the second base sheet bearing at least two transferable coatings, of which at least one is coloured, the adhesive over the indicia and the coatings on the second base sheet being so selected that, on peeling apart the two base sheets subsequent to the application of such pressure, the coatings are retained on the selected indicium, with the then outermost coating being an adhesive coating of sufficient adhesive power to enable dry transfer of the indicium to a desired receptor surface to take place if the desired base sheet is subsequently placed, coloured indicium side down, on the desired receptor surface, pressure is applied thereto in the area of the indicium and the base sheet is then removed.

Preferably, the surface tack of the adhesive over the indicia is greater than the surface tack of the adhesive in the areas between the indicia.

This allows the coatings retained on the selected indicium to be in register therewith, so minimising the risk of coloured contamination outside the area of the indicium.

Preferably the second carrier sheet bears two transferable layers, a first shearable adhesive layer and an outer shearable coloured nonadhesive layer. The non-adhesive layer adheres to the areas of adhesive overlying the colourless indicium sufficiently that on peeling apart the two sheets both transferable layers on the second carrier sheet remain on the indicium. However, outside the exact area of the indicium, in the preferred case referred to above, the surface tack of the adhesive on the first base sheet is insufficient to adhere to the outer of the two layers on the second carrier sheet, so no such transfer takes place in those areas.

Because of the relatively reduced or substantially zero tack of the adhesive between the colourless or substantially colourless indicia, coloured contamination of the receptor surface when such dry transfer material is used is avoided.

The dry transfer sheet bearing colourless or substantially colourless film forming material indicia, where the surface tack of the adhesive tack of the adhesive between them, may be produced by the method disclosed in British Patent Specification 954459 but is preferably produced by the method disclosed in British Patent Specification 1577617.

The base sheet, indicia forming material and adhesive may be those conventionally used in the dry transfer art with the exception, of course, that pigment or dyestuff in the indicia is omitted.

Appropriate minor changes in formulation to compensate for that omission may easily be made by those skilled in the art of manufacturing dry transfer inks.

The preferred construction of the second carrier sheet as noted above is that of a flexible plastics film e.g. of the same nature as that used for the carrier sheet supporting the indicia, bearing first a layer of adhesive and secondly a non-adhesive layer. One of these layers, and if desired both, are coloured by the inclusion therein of one or more dyes or pigments. The respective thickness of the layers should be selected having regard to the formulation to give adequate colour density but at the same time to enable the layers to be removed with clean shear from the second carrier sheet which supports them. In order to assist such removal the surface of the second carrier sheet, if not inherently possessed of release properties, may be coated with a suitable release layer of which a wide variety is known in the art.In order to enhance the shearability of the applied layers and accordingly to enhance the edge definition of the coloured indicia formed when the two sheets are brought together and separated, one or both layers may include a shearing agent, preferably finely divided silica.

The outer non-adhesive layer renders the "colouring sheet" easy to handle while the adhesive layer acts ultimately to adhere the indicium to the desired receptor surface. The adhesive layer may accordingly be a low tack adhesive of the type conventionally used in dry transfer manufacture.

Transfer sheets bearing colourless or substantially colourless indicia may be produced in a wide range of type styles and type sizes.

Likewise colouring sheets may be produced in a wide variety of colours and the two sheets then used in combination to produce coloured lettering easily and conveniently.

The following Example will serve to illustrate the invention: Example A colouring sheet was manufactured as follows: A sheet of polyethylene terephthalate 75 microns thick (Melinex 377 ex l.C.I.) was coated on a standard laboratory coating machine with a chlorinated rubber key coat. The coating composition consisted of (by weight): Chlorinated rubber (Alloprene R90, ex l.C.I.) 20% Xylene 79.7% Anti-static agent (ASA3 ex Shell) 0.3% After coating and drying at 600C for 45 seconds the sheet had a dried down chlorinated rubber key coat on it of coat weight 3.5 to 4.0 g.s.m.

A further silicone coating was then applied at a dry coat weight of 0.3 g.s.m. following drying at 1200C in a heated drier with a residence time of about 55 seconds. The silicone coating solution was a proprietary type manufactured by l.C.I. and diluted, the actual coating composition used being as follows (by weight): Silicone polymer precursor (Silolease 425 ex 1.0.1.) 9.90% Catalyst solution type 70A (6.25% by weight solution in white spirit) 0.40% Catalyst 70B solution (20% by weight solution in white spirit) 2.60% White spirit 87.10% The release coated sheet so-formed was then super-coated with an adhesive coating composition consisting of (by weight):: Polyisobutylene resin (Oppanol B50 ex BASF, 20% by weight solution in Exsol 145/160 ex Esso) 15.7% Polybutylene resin (Hyvis 220 ex B.P. Chemicals) 6.9% Polyethylene wax (ACP6 ex Allied Chemicals, 10% by weight dispersion in Exsol 145/160) 49.6% Finely divided silica (Aerosil R972 ex Degussa) 4.0% Solvent (Exsol 145/1 60 ex Esso) 13.8% Oxitol 9.0% The adhesive was applied using a Meyer bar and dried at a temperature of 650C for 35 seconds to give a dry coat weight of 2.0 g.s.m.

A final layer was applied to the colouring sheet using a Meyer bar and the final layer dried in an oven at 600C for one minute to give a bright red colouring sheet. The composition of the red nonadhesive coating was as follows (by weight): Nitrocellulose solution (30% by weight grade E650 ex Wolff Walsrode in Oxitol) 30.9% Polyethylene was (ACP6 as above) 22.5% Azelaic acid modified alkyd plasticiser (Paraplex RGA2 ex Rohm & Ha Haas) 3.9% Dye (Orasol Red G ex Ciba-Geigy) 2.3% Silicone (1% by weight solution of MS200, ex Dow Corning, in white spirit) 0.1% Oxitol 37.6% Butyloxitol 2.7% Dry transfer sheets were manufactured as follows: : Sheets of high density polyethylene, 1 50 thick, were screen printed with an array of letters using an ink of the following composition (by weight): Nitrocellulose solution (51.5% by weight solution of grade E330 ex Wolff Walsrode in oxitol acetate) 68.95% Azelaic acid modified alkyd resin (Uralac 923/68 ex Synthetic Resins) 14.18% Dimethyl cyclohexyl phthalate 1.75% Silica (Aerosil 130V, ex Degussa) 1.32% Oxitol acetate 13.80% After drying the printed sheets with a hot air drier (650C, residence time 35 seconds) they were over-printed with an adhesive applied as a single rectangular area covering the letter array.

The adhesive formulation was as set out as Adhesive 5 of British Patent Specification 1577617, and the adhesive was dried as set out in that Specification to give a coating of adhesive tackier over the ink letters than in the spaced between them.

In order to produce red coloured lettering the two sheets so-produced were laid coated face to coated face and pressed together using a burnisher in the areas of selected indicia. The sheets were then pulled apart and it was found that the area of the indicium only had, in each selected area, picked off the red coating from the colouring sheet, exactly in register with the printed transparent indicium. The selected letters were then transferred in the desired order from the dry transfer sheet in the usual way on to a desired receptor surface to give the desired legend in bright red letters.

Claims (5)

Claims

1. A method of making a coloured dry transfer which comprises providing a dry transfer material comprising a base sheet, indicia thereon in colourless or substantially colourless film-forming material and a layer of adhesive over the indicia and the areas of the base sheet between them, bringing into contact with the indicia bearing side thereof, under pressure in the area of the indicia, the coated side of the second base sheet, the second base sheet bearing at least two transferable coatings of which at least one is coloured, the adhesive over the indicia and the coatings on the second base sheet being so selected that, on peeling apart the two base sheets subsequent to the application of such pressure the coatings are retained on the selected indicium, with the then outermost coating being an adhesive coating of insufficient adhesive power to enable dry transfer of the indicium to a desired receptor surface to take place if the base sheet is subsequently placed, coloured indicium side down, on the desired receptor surface, pressure is applied thereto in the area of the indicium and the base sheet then removed.

2. A method according to claim 1 wherein the surface tack of the adhesive over the indicia on the dry transfer material is greater than the surface tack of the adhesive in the areas between the indicia, the difference being such that in the areas between the indicia, subsequent to the application of pressure to contact the dry transfer material with the coated second base sheet, on peeling apart the two materiais the coatings on the second base sheet are retained on the second base sheet in the non-indicium areas.

3. A method according to claim 2 wherein the dry transfer material is manufactured in accordance with the method disclosed in British Patent Specification No. 1,577,617.

4. A method of making a coloured dry transfer substantially as hereinbefore described with reference to the foregoing specific Example.

5. A coloured dry transfer image formed by the method of any of claims 1 to 4.