GB2301693A - Transferable signs - Google Patents

Abstract

A process is disclosed for the production of transferable sins wherein a transferable layer is deposited on a carrier sheet, and a desired shape or pattern is scribed in the transferable layer without cutting through the carrier sheet and discarding the unwanted parts of the transferable layer. The carrier sheet is suitably a polyester sheet. The pattern or shape is suitably cut with a computer-controlled knife. In an alternative process, a base layer of a clear or pigmented ink is coated on to a surface having a release layer and a pattern printed on to the base layer using a colour photocopier or a laser printer.

Description

TRANSFERABLE SIGNS This invention relates to a process for the production of transferable signs.

Signs or displays for rapidly presenting a message or announcement e.g. on a shop window can be formed using pre-printed transfers.

UK Patent No. 1488487 describes a transfer system in which very durable transfer lettering can be printed onto a carrier sheet and subsequently transferred onto a final surface. The prior art processes do not lend themselves to the production of custom-made signs since the indicia are pre-printed onto a backing sheet, usually by screen printing.

It is an object of the present invention to provide a process by which individual signs can be produced using widely available equipment.

According to one aspect of the present invention, there is provided a process for the production of a transferable sign, which comprises forming a transferable layer on a carrier surface, scribing a desired shape or pattern in or through said layer without cutting through the carrier and discarding unwanted parts of the transferable layer. The shape or pattern may be scribed by using an electronically- controlled scribing tool and discarding unwanted parts of the transferable layer, by layer, by die-cutting or by laser cutting the transferable layer.

Computer-controlled cutting plotters are now widely available and may be used to form the desired shape or pattern in the transferable layer which can be readily altered by modifying the programmed instructions to the computer.

In order that the carrier sheet can be used with a computer-controlled cutting tool, it is necessary for the carrier to maintain its dimensions without undue shrinkage or stretching so that the cut portions retain their shape and integrity. It is also important that the carrier sheet should be substantially smooth and flat, so that the cutting tool can cut through the transferable layer or layers completely without cutting through the carrier or backing sheets which it is desired to retain.

The design may be formed in the transferable layer by cutting through the layer from its open side without cutting through the carrier sheet. After the design has been cut or scribed, unwanted parts of the transferable layer are stripped off and discarded. An adhesive such as a pressure sensitive adhesive or activatable adhesive is then applied over the design as a continuous coating or as an array of dots. Finally, a protective release sheet may be applied to the adhesive layer until the design is to be used.

An alternative method of producing the transfer is to apply the transferable layer face down onto the surface to which the design is to be transferred or an intermediate carrier sheet, scribe the design by cutting through the backing sheet and the transferable layer and discarding the undesired parts of the transferable layer and backing sheet.

A further alternative employs a continuous clear or pigmented base layer in which the design is formed by printing onto the base layer. In this modification, no scribing operation is necessary because the design is produced by a direct copying method. This variation involves the steps of coating a carrier sheet having a release surface with a transferable layer of a strong pigmented or clear ink. The ink layer is printed with the described design using a colour photocopier or laser printer. A double-sided adhesive sheet, e.g. of thin plastic such as polypropylene having an adhesive coated on both sides, is then applied over the entire transferable layer and can be used to lift the transferable layer off the carrier sheet. The double sided adhesive sheet can be clear or pigmented or coated or metallised or include glass reflective beads.The transferable layer can then be secured permanently to the final surface by means of an adhesive applied to the final surface or to the underside of the transferable layer.

When cutting through a backing sheet laminated to a transferable layer, it is important that the backing sheet should be as thin as possible and also bonded as firmly as possible to the transferable layer. Thin polypropylene backing sheets having a thickness in the range of 10-15 microns are suitable for this purpose.

The transferable layer can be made up from one or more layers of coherent material. The layer is applied as a continuous layer to the carrier sheet and it should have sufficient thickness and inherent strength so that the unwanted areas can be stripped from the desired shape or pattern and the desired shape or pattern transferred as a whole to the desired final surface. Colours or patterns can be formed by printing a multiplicity of different coloured or non-coloured layers. Not all of the layers need be pigmented or coloured. For example, it is possible to deposit a non-coloured high strength layer onto the carrier sheet and produce a coloured or patterned effect by over-printing coloured layers, which need not themselves be of high strength since they are supported by the high strength non-coloured layer to which they are bonded.

The transferable layer should bond sufficiently to the carrier sheet such that the transferable layer does not delaminate during the cutting process but the excess or undesired material can be stripped away without difficulty. Furthermore, the desired pattern or shape should be releasable from the. carrier sheet so that it can be easily transferred to the final supporting surface.

In order that the transferable layer can be bonded to the final supporting surface, it should either be sufficiently adhesive itself to effect such a bond or, alternatively, a separate adhesive layer can be applied.

Such adhesive layer may be a permanently pressuresensitive adhesive or it could be heat or solventactivated. If a permanently pressure-sensitive adhesive is applied, then a protective release film may be applied over the transferable layer. The adhesive need not be pressure sensitive but can be heat or solvent-activated or can be a delayed tack pressure sensitive adhesive layer.

In these cases, a protective paper layer may not be necessary.

Whilst the accuracy with which cutting knives can be set is usually within 25 microns in depth of cut, cutting and scribing tools are continually improving in accuracy.

It is, nevertheless, important that sufficient latitude is allowed so that the depth of cut will be sufficient to cut through into the transferable layer together with any protective outer sheet material, but without substantially distorting or tearing the underlying carrier sheet.

Bearing in mind the present accuracy of scribing tools, the carrier sheet should preferably exceed 25 microns in thickness, so that there is no danger that during the cutting operation the carrier sheet will be severed. In general, the carrier sheet will be at least about 40 microns in thickness, e.g. about 50-60 microns.

Depending on the rigidity of the carrier sheet material and the need to use it either in the form of a sheet or reel, the thickness of the carrier sheet should generally not be less than about 50 microns. For some uses, it is preferred that the temporary support is transparent or translucent in order that after cutting and stripping away the excess material, the desired shaped sign or pattern can be accurately placed on the final supporting surface. This is not absolutely necessary since the position of a particular design relative to the edge of the carrier sheet might be sufficient for some applications. For the sake of cost saving where transparency of the carrier sheet is not essential, then various types of supporting paper surfaces can be used.

If paper is to be used as the carrier sheet, then the selection of the paper depends on the requirement of relative transparency in which case highly unbeaten papers such as glassine can be used or chemically treated papers such as vegetable parchment. Where the requirement is not for transparency or translucency, then there is a wide choice, but any paper must have the ability to resist the penetration of the colour layer when applied. The gloss of the transferred layer is determined to a large extent on the surface from which it has been transferred. A matt paper will result in a matt transfer and a gloss paper will equally give a relatively glossy transfer.

The ease of release from a paper substrate is determined by: (a) the lack of penetration of the transferable layer ensuring no mechanical key with the paper; (b) the smoothness and surface finish of the paper; (c) the use of a coating to provide a surface free from paper fibres; and (d) the use of a coating to provide release properties to the surface.

Certain highly beaten and chemically treated papers such as vegetable parchment have excellent hold out to penetration of liquid colour coatings and also have a fair degree of release without further coating.

Less highly beaten papers with longer fibres need to be coated with polymers of resinous materials to provide sufficient hold out to liquid colours particularly if a glossy transfer is required.

Some coatings giving the property of hold out to liquid inks may have release properties but most usually require a pre-treatment to provide the right degree of release property for the colour or transferable layer.

The sort of treatment which will provide a satisfactory release layer for the transfer of the colour layer is, for example, given by silicone resins which can be modified to vary the degree of release or "Quillon" or waxes which is a chemically reactive chrome complex bonded through the chromium to negatively charged surfaces leaving the fatty acid chains orientated away from the surface which provide some degree of repellency and release to the colour liquid deposits.

If the release is to be accomplished with a hot application technique, then the release coating may simply be a wax which is molten at the temperature of application.

When a high degree of transparency is required then the choice of substrate is usually a plastic material in the form of a sheet or web.

The selection of the plastic is determined by: 1. The degree of gloss required in the transferred layer in which case the gloss of the surface of the plastic will give in general the same gloss to the transferred layer.

2. The release characteristics of the surface of the plastic which are to a degree determined by the surface tension of the material. Polyolefins such as polythene and polypropylene being high molecular weight waxy materials have high surface tension and are difficult to wet and provide a high degree of release to colour layers. Normally these materials are treated by corona discharge or by heating to render them acceptable for most printing processes where the demand is for good adhesion of colour layers. In this case it is important that the polyolefins are not treated in order to make use of the excellent release characteristics of these films. The polyolefins are, however, naturally rather soft and lack rigidity and thicker sheets may be necessary to give a handleable product. Films in excess of 75 micron can have sufficient rigidity.

Polystyrene films particularly those modified with butadiene also have the ability to provide surfaces from which coloured coats can be easily formulated to release without the use of a release coating. Butadiene modified polystyrene has a matt surface so cannot be used when a gloss finish is required. Biaxially oriented polystyrene gives excellent gloss but has more difficult release characteristics, but cannot be used with plastisol inks.

Preferred films are polyester films due to their great strength, rigidity and hardness. Their resilience gives ideal properties as a backing film against which the plotter knife can cut the coloured layer. Release is difficult from the untreated material but release levels from extremely easy to achieve as will be described below.

Of very considerable importance in the use of polyester films is its resistance to temperatures of up to about 160-1800C, which enables inks to be applied hot or subsequently heat-cured.

Many other plastics films can be used including nylon, cellulose acetate and polyvinyl chloride, the properties of which are intermediate between paper and polyester.

The choice of release coatings depend: 1. on the type of temporary carrier, 2. the type of colour coating and the wetting characteristics of the liquid coating, 3. the thickness and rigidity of the colour coating, and 4. the ease of release required.

In general, water-based liquid colour coatings cannot be used on silicone release treatments and therefore an alternative such as a chrome complex which allows waterborne coating to wet the surface needs to be used.

In some cases, release agents which are fairly specific to some colour coating can be used and this is further described in this specification. Of specific importance in this specification is the use of an epoxy polyamide coating in conjunction with p.v.c. plastisols.

This particular combination enables controlled release of thick films to be obtained from polyester temporary carrier.

Whilst, for the sake of clarity, the transferable layer forming the design, words, or figures is referred to as coloured, it is quite possible that under normal viewing circumstances the layer is not coloured but transparent, and it may also be possible that in the situation where the transferable layer consists of a number of coloured or other layers, there may be a clear film deposited whose purpose is to provide strength to carry non-continuous or very thin weak design images.

Any continuous film-forming layer may be used but the formulation of this layer is important to the working properties of the product, since the requirement to achieve easy stripping of the excess material, fine definition of cutting, and easy release of the cut film onto the final support needs very careful manipulation and control.

In general terms, the thicker the colour layer the easier are the release properties, the more rigid the layer, the easier is the release. However, it is important to note that for ease of release it is necessary to avoid the inclusion of solvents in the liquid colour layer which would dissolve or swell the temporary support or coatings on the temporary support, also some materials may have good intrinsic adhesion to the support.

The strength and rigidity are enhanced if the liquid colour is of high solids content or even preferably 100% non-volatile. This is illustrated in examples showing the use of p.v.c. plastisol colour layers cured by heating and of ultra-violet cured layers.

The colour layer can itself be precast, extruded or blown into a thin film before being lightly laminated to the temporary support. This colour layer can then be coated with adhesive.

Preferably, the transferable layer comprises a relatively thick, robust plastics material, e.g. a heatfused plastisol ink coating such as those described in UK Patent No. 1488487. The carrier surface on which the transferable layer is formed may be a web of paper or plastics material. When using plastisol ink, the carrier sheet should be capable of withstanding temperatures reached during the heat-fusing operation, e.g. about 160 to 1800C and, for this purpose, paper webs or polyester sheets are generally suitable.

Other types of ink compositions which are suitable for the purpose of this invention include nitrocellulose/polyurethane inks which are curable at room temperatures and inks curable by U.V. radiation such as light curable epoxy acrylate compositions. Such inks should be applied as transferable coatings of at least 6 microns in thickness.

Particularly of interest are thin films of orientated polypropylene, polyethylene or polyester. These films can also be decorated prior to lamination, and can be metallised using vacuum metal deposition, printed with diffraction patterns or holograms.

The use for the invention lies primarily in the production of designs, words and numerals required in single unique configurations or perhaps in very limited numbers. These requirements find uses in the production of number plates for vehicles where the car number is unique, in street names, for exhibition purposes, in shops, factories, offices and on vehicles. The substrates may be metal, wood, glass or plastic and include, bicycles, street road signs, vehicles and white goods. A further use is for the decoration of fabrics and particularly T-shirts. The end user can be supplied with a kit including carrier sheets having continuous coatings of transferable layers of different colours, reflective beads, fluorescent colours and photoluminescent colours.A suitable computer programme can also be included in the kit so that the end user can select a desired design to be cut from the sheets using a computer controlled scribing tool. After cutting the desired shape and discarding unwanted material, the resulting sign or design can be transferred to the final surface. If the transferable layer does not embody an adhesive, an adhesive coating can be applied to the design by suitable means, such as a spray, brush, screen or blade. The sign can then be transferred onto the final surface by pressing the adhesive layer into contact with the final surface and then releasing the carrier sheet.

In such uses, the designs can either be transferred directly onto the final substrate without requiring protection, or where additional protection or support is required, they can be transferred onto the final support which is then itself over-laminated with clear plastic.

The designs can be transferred onto the final support and over-lacquered or protected with powder spray in which case the heat of coalescing the powder spray requires that the formulations must be heat-resistant to stand heat of coalescing.

If large numbers of the same design are required this can be accomplished using the same formulations as in the plotter cut examples, but the colour layer or multi layers can be printed in discrete areas.

It will be appreciated that one advantage of the invention is that a customised transfer is produced directly in which the various letters or other indicia in the message or registration number are supported in the correct size and spacing on a carrier sheet. They can, therefore, be transferred directly to the final surface and in the case of vehicle registration plates, laminated to form the final product.

The following Examples (in which all parts are by weight) will illustrate the invention: Example 1 Black plotter cuttable material for car number plates.

Temporary support 75 micron mat polyester film Release coating Parts Ethyl glycol 98.88 Epoxy resin 0.66 Modified Polyamide resin 0.33 Dimethyl amino methyl phenol 0.026 The release coating is coated onto the polyester film using reverse roll-coating or a Meyer Bar at a rate of about 5-10 grams per metre wet. The coating was then dried and cured for 20 seconds at 1600C.

Black colour coating Parts Vinyl chloride homopolymer 51.384 Hexanediol diacrylate 36.371 octyl tin mercaptide 1.746 2(2-hydroxy-5-methyl phenyl) benzo triazole 0.161 Aliphatic hydrocarbon solvent 8.96 Aerosil 1.978 Carbon black 4.00 The above formulation of black ink can be coated onto the release treated polyester using a Meyer Bar or by screen printing. The layer was cured by heating to 1600C for 30 seconds to 1 minute.

Adhesive Parts Polyvinyl isobutyl ether 15 Staybelite Ester (Hercules) 10 Solvent 75 The above adhesive was screen printed onto the cured ink and dried.

A siliconised 25-50 micron orientated polypropylene was then applied over the dried adhesive.

The assembly is cut from the protective film side using a plotter cutter. The excess material is stripped away and the release paper removed from the letters and numerals. The assembly is then transferred onto the usual reflective, self-adhesive base sheet used for number plates and over-laminated with an acrylic plastic.

Example 2 Substrate (90 gsm) Glassine paper The substrate was surface treated with a Werner complex in which a C14-C18 fatty acid is co-ordinated with trivalent chromium in a 2% solution in isopropyl alcohol.

Ink Coating Coated layer providing strong cuttable transferable layer was made from polyvinylchloride homopolymer ... 45 to 55 pts Do iso octophthalate ... 15 to 25 pts Paraffinic hydrocarbon ... 4 to 8 pts A coating was formed by application to the substrate as described in Example 1 and is then cured by passing through a heated conveyor at between 160-1800C for up to 1 minute.

Colour or design was then imparted to the layer by colour copying using a laser toner system in a standard colour photocopier.

The resulting assembly is laminated with a double sided adhesive consisting of 20 micron polypropylene film coated on both sides with a crosslinking acrylic pressure sensitive adhesive and protected on both sides with silicone paper.

Example 3 For the manufacture of one off signs such as car number plates or street names.

The plastisol black coating on the release coated polyester was prepared as in Example 1. The cured black ink coating was cut on a plotter into the desired combination of letters and numerals and the excess black plastisol stripped away. Adhesive is then screen printed in a fine dot pattern over the assembly as in Example 1, prior to application to a reflective base sheet as in Example 1.

Example 4 Carrier film of highly transparent paper is coated with a dispersion of polyethylene wax in a hydrocarbon solvent such as white spirit to give a dry coating weight of 1-2 gsm.

The treated paper is then coated with a strong black coating consisting of: Carbon black ... 3 pts Nitrocellulose solution (20% in ethyl acetate) ... 45-50 pts Polyurethane resin (80% in aromatic hydrocarbon ... 45-55 pts After evaporation of solvent, the desired design was cut in the resulting black coating using a laser and undesired parts stripped off and discarded.

Adhesive. Pressure sensitive adhesive coating consisting of a water based dispersion of crosslinking plasticiser free acrylic copolymer. This adhesive was applied to the exposed surface of the laser cut design.

Example 5 Temporary support of matt styrene butadiene film.

White U.V. cured cuttable coating consisting of: 60% Zinc sulphide 40% BaSO4 ... 30 pts Titanium dioxide ... 20 pts Epoxy acrylate ... 12 pts Tripropyleneglycol triacrylate ... 9 pts Propylated glycerol triacrylate ... 20 pts Methyl dimethyl amine ... 2 pts Benzildimethylketal ... 2 pts Benzophenone ... 5 pts Coated to give 15-30 gsm and cured by exposure to U.V. light. The cured coating was scribed using a computer controlled plotter and unwanted parts stripped off and discarded.

Adhesive Coating was prepared as described in Example 1 and screen printed onto the transferable layer.

Example 6 A carrier film of 50 micron thick polyester film was laminated using a fine coating of an ethylene vinyl acetate copolymer resin with a thin film (12.5 micron) of polyester.

A design was applied to the laminated carrier by printing with an ink jet printer. A double-sided coated adhesive film and a protective release coated sheet was then applied over the design. Individual shapes were then formed by differential die punching through the protective sheet and stripping away unwanted excess so that the desired designs remain on the carrier sheet.

The desired designs are then applied to a substrate by removing the protective sheet from the individual punched shapes and presenting the designs to the substrate. The carrier and lightly laminated thin polyester is then peeled away.

Example 7 A carrier film consisting of 75 microns polyester was coated with the following composition to give a dry coating weight of between 0.2 and 0.5 gram per square metre: High viscosity nitrocellulose solution comprising 3% of nitrocellulose in ethyl acetate 99 parts by weight Polyurethane resin (80t solution in aromatic hydrocarbon) 1 part by weight After drying,the coated film was printed with a design using a photocopier, inkjet printer or metallised, spray coated or printed by a conventional printing process.

A double-sided adhesive film was prepared by applying an adhesive as described in Example 1 to both sides of a polypropylene film of 20 microns thickness. A protective release film was applied to one adhesive surface and a laminate was formed by passing the adhesive coated film and coated carrier sheet together through the nip between laminating rollers. A design is then cut in the laminate using a suitable scribing tool, by cutting through the design layer from the adhesive side and discarding unwanted parts of the design. The design can then be transferred to a substrate and bonded thereto using the adhesive coated film.

Alternatively, after the scribing step, the protective paper can be removed from the areas of the design to be transferred. By pressing these areas into contact with the substrate, these areas are bonded to the substrate, while the remaining parts remain on the carrier sheet protected by the protective release paper.

The transferable signs of this invention have various end uses. In some applications, an adhesive is unnecessary, for example, in manufacturing magnetic or magnetically susceptible signs. The inks employed to form the transferable layer may be modified to include ferrous or other magnetisable metallic particles and the resulting designs can be removably attached to a magnetised backing board. This system is particularly suitable for embodiments of the kind described in Example 2, in which an iron oxide can be incorporated in the continuous transferable ink layer and the design produced by photocopying onto the cured ink layer.

Claims (15)

CLAIMS:- 1. A process for the production of a transferable sign, which comprises forming a transferable layer on a carrier sheet, scribing a desired shape or pattern in or through said layer without cutting through the carrier and discarding unwanted parts of the transferable layer. 2. A process as claimed in claim 1 wherein the transferable layer is coated or cast onto a substantially flat carrier sheet. 3. A process as claimed in claim 2 wherein the carrier sheet is a polyester sheet. 4. A process as claimed in claim 3 wherein the polyester sheet is at least about 40 microns thick. 5. A process as claimed in any one of the preceding claims in which the transferable layer is formed by coating the carrier surface with a pvc plastisol or organosol and heating the coating to form a plasticised pvc layer. 6. A process as claimed in claim 5 in which the plastisol or organosol comprises a dispersion of pvc in a plasticiser, the plasticiser being present in an amount of up to 40% by weight of the pvc. 7. A process as claimed in any one of the preceding claims wherein the pattern or shape in the transferable layer is cut with a computer-controlled tool. 8. A process as claimed in claim 7 wherein the tool is a knife. 9. A process as claimed in any one of the preceding claims wherein the carrier sheet has a release surface. 10. A process as claimed in claim 9 wherein after discarding unwanted parts of the transferable layer, an adhesive layer is applied to the desired shape or pattern to enable it to be bonded to a final substrate. 11. A process for the production of a customised transfer for a sign which comprises coating a base layer of a clear or pigmented ink onto a surface having a release layer and printing a designed pattern onto the base layer using a colour photocopier or laser printer. Amendments to the claims have been filed as follows CLAIMS:

1. A process for the production of a transferable sign, which comprises forming a transferable layer on a carrier sheet, scribing a desired shape or pattern in or through said layer without cutting through the carrier and discarding unwanted parts of the transferable layer.

2. A process as claimed in claim 1 wherein the transferable layer is coated or cast onto a substantially flat carrier sheet.

3. A process as claimed in claim 2 wherein the carrier sheet is a polyester film or sheet.

4. A process as claimed in any one of the preceding claims wherein the polyester sheet is at least about 40 microns thick.

5. A process as claimed in any one of the preceding claims in which the transferable layer is formed by coating the carrier surface with a PVC plastisol or organosol and heating the coating to form a plasticised PVC layer.

6. A process as claimed in claim S in which the plastisol or organosol comprises a dispersion of PVC in a plasticiser, the plasticiser being present in an amount of up to 40% by weight ofthe PVC.

7. A process as claimed in any one of claims 1 to 5 wherein the transferable layer is a polyester.

8. A process as claimed in any one of the preceding claims wherein the pattern or shape in the transferable layer is cut with a computer-controlled tool.

9. A process as claimed in claim 8 wherein the tool is a knife.

10. A process as claimed in any one of the preceding claims wherein the carrier sheet has a release surface.

11. A process as claimed in claim 10 wherein after discarding unwanted parts of the transferable layer, an adhesive layer is applied to the desired shape or pattern to enable it to be bonded to a final substrate.

12. A process for the production of a customised transfer for a sign which comprises coating a base layer of a clear or pigmented ink onto a surface having a release layer and printing a designed pattern onto the base layer using a colour photocopier or laser printer.

13. A process according to any one of the preceding claim 12 wherein the ink comprises magnetisable particles.

14. A process as claimed in claim 12 or 13 wherein said coating is applied to both sides of the carrier sheet.

15. Transferable signs whenever produced by the process claimed in any one of the preceding claims.