GB2189433A - Dry transfer film materials for sign making - Google Patents

Abstract

Dry transfer films which may be used on conventional vinyl laminate sign cutting equipment to produce cut out legends which can then be directly applied where desired thereby avoiding the use of a pre-mask tape have a multi-layer construction for the cuttable layer consisting of a) in either order 1, a film layer peelable from the carrier sheet 2. a dye- and/or pigment containing layer and b) an adhesive layer.

Description

SPECIFICATION Dry transfer film materials This invention relates to drytransferfilm materials particularly useful in sign-making applications.

Dry transfer materials have been known for many years. They consist essentially of a transparent or translucent backing sheet, a design releasably adheredto such backing sheet, and overlaying at least the design, a layer of an adhesive which will serve to adhere the design to a desired receptor surface. Such transfer materials are conventionally made by printing processes, with the transferrable design being applied to the carrier sheet by printing and subsequently over-printed or over-coated with adhesive. Because of the way they are made, it is not common to manufacture "one off" drytransfers.

Instead, dry transfers are usually produced in large runs, and if to be used e.g. for making a signfrom individual letters, the user has to transfer individual letters sequentially from a dry transfer sheet. Such sequential transfer takes time, and requires skill to do it satisfactorily, particularly in order to achieve optically satisfactory alignment and spacing.

An alternative approach to manufacturing signs is to cut the desired sign legend from a film stock material.

A number of commercially available machines for doing this have come on to the market in recent years, most notably the "Graphix" machines made by Gerber Scienfific Instruments. Such machines selectively cut through a plastics film layer held via a permanently tacky adhesive to a release coated backing, the cutting being effected under computer control. Such machines enable a complete legend to be cut on such stock material, whereafterthe waste plastics film, i.e. that not constituting part of the legend, is removed, and the legend then applied where desired.

The standard stock material consists of a release coated backing sheet having adhered thereto by a permanently tacky pressure sensitive adhesive a thin vinyl film. Once cut and waste stripped,the user is provided with a right reading legend (i.e. it is not in mirror writing as viewed) which mustthen be picked off the release coated backing and readhered in its desired final position. In orderto achieve this without disturbing the relative positions ofthe individual components ofthe legend, a so-called pre-masktape may be used. This is a strip oftransparent ortranslucentfilm material bearing a coating of pressure sensitive adhesive.The pressure sensitive adhesive is of such a kind that it will stick to the vinyl film and pull the vinyl portions forming the legend away from the release coated backing sheet, but will not stick to receptor surfaces as well as the adhesive destined to stickthe pieces of vinyl film to those receptor surfaces. The legend may accordingly be applied to the receptor surface by positioning the pre-masktape bearing the legend over the receptor surface, pressing the whole ofthe pre-masktape and the legend which it bears into contact with the receptor surface and then peeling awaythe pre-masktape, whereon the individual elements of the legend are left on the surface, asthey adherethereto more stronglythan the pre-masktape adheresto the vinyl film.

The use of pre-masktape is cumbersome and inconvenient, and it would be more convenient if this step could be avoided. This can of course be done by cutting the legend in the stock material in a mirror image fashion i.e. so that it is not right reading, with the stock material having an adhesive coating on its outside enabling the cut out legend to be directly adhered to the desired receptor surface. Products of this nature have been commercially offered, but they do notworkwell.

We have now found that considerably improved results may be obtained by using as the stock material fed through such a computer controlled cutting machine, a material in which the cut goes through several layers, all ofwhich may be cleanly removed from the carrier.

Thus according to the present invention there is provided a drytransferfilm material consisting of a carrier sheet carrying successively: a) in either order 1. a film layer of sufficient strength that it may be peeled from the carrier sheet 2. a dye- and/or pigment-containing layer and b) an adhesive layer.

Such a material may be used in a cutting machine with the cutter set to cut through all three layers. Once cutting has been achieved, because the first layer is sufficiently strong to enable itto be peeled from the carrier sheet, peeling may take place to leave the individual cut out elements of the legend on the carrier sheet, each with its adhesive surface outward. The carrier sheet may then be located where desired overthe receptor which is to receivethe legend, the individual elements ofthe legend brought into contacttherewith, adequate pressure applied to make them stick more firmly to the receptorthan the removable layer is stuckto the carrier sheet, and the carrier sheet may then simply be peeled away to leave the legend on the surface where desired.This is the preferred way of working, though it is possible in certain cases to formulatethe material such that it is not necessary to waste strip the legend first. However, such an approach is generally not preferred as the presence of waste material means that the user cannot see the receptorthrough the stock material, and this makes positioning the legend where desired more difficult.

With the general configuration described above, much variation may be made. It is convenient to consider the individual components separately: Carrier sheet Any flexible carrier material may be used consistentwith practicality. Is should desirably be dimensionally stable, to facilitate handling, and in web form if it is to be used on a commercially available machine ofthe type described above. Conveniently it is in the form of a strip or a roll of paper orfilm stock having suitable perforations or sprocket holes along its edges, for engagement with the drive mechanism ofthe machine in question.Papers are convenient and inexpensive materials, although they are less preferred as they do not generally have adequate transparency ortranslucency to enable the positioning ofthe legend by looking through the carrier. The most preferred material is accordingly a dimensionally stable plastics film, for example, a polyethylene terephthalate or polystyrene butadiene film. A convenient thickness is 50 to 100 microns.

The surface of the carrier must be chosen relative to the first of the three layers applied thereon such asto enable clean peeling of the layers from it. Although this may be achieved with certain systems where the carrier is a plastics film without any particular treatmentofthe plastics film, it is more reliable to coatthe surface of the carrierwith an appropriate release coating. Numerous release coatings for both paper and plastics films are available in commerce and are widely used. An appropriate release coating may be chosen without difficulty from the variety available.

Film layer This layer is preferably a thin tough cured polymeric film. It has to be peelable away from the carrier sheet, and accordingly must possess the necessary film strength to enablethatto occur. In addition, since it will be the outermost layer in the transferred legend, it is preferably appropriately resistant to environmental attack.

In particular, it is desirably a fairly abrasion-resistant layer and a weather resistant layer. The material of choice is a UVcured polymeric film, either based on a composition comprising an ethylenically unsaturated monomer and appropriate curing agents or a cured epoxy type system. Such curable film layers are available in commerce as clear UV curable lacquers; the layer is desirably a clear layer since this assists total cure, but it need not be clear. Specificformulations are also described in British Patent specifications 2142279 and 1580076. UV cured layers are the preferred type as these can be deposited and cured very fast, so enabling the production of drytransferfilm materials in web form.

The film layer can beformulated from other materialsthat are capable of providing tough films, for example plastisols, organosols, polyurethanes and epoxy-polyamide resin systems. In the case of polyurethane and epoxy-polyamide systems, these are not easily adapted to production in web form to facilitate supply on a roll. It is however possible to screen print products in sheet forum and allowtimefor curing priorto stacking, and then make up product for supply in strip form.

Dye- orpigment-containing layer This layer is the layer which imparts visibility to the legend. It consists generally of an appropriate polymericfilm-forming vehicle into which has been incorporated a pigment and/or dye to give visibility.

Various film forming materials may be used as basisforthis layer. The layer must of course be compatible ,th, and adhere appropriately to,thefilm layer. Oneway of ensuring this isto use a UV curable system.An alternative approach is to use some other ink system, for example, a nitrocellulose based lacquer, either formulated to bond adequately to the film layer or applied (if the film layer is applied first) after an appropriate treatment has been effected onthefilm layerto ensure adequate bonding. For example, following the application of a first film layer, its surface may be corona dischargetreated in orderto enablea subsequently applied ink layerto adhere firmlyto it.Otherfilm-forming bases which can be used are acrylic resins, polyamide resins, alcohol soluble propionate resins, cellulose acetate butyrate, polyvinyl butyrals, epoxy resins, vinyl copolymers, cellulose ethers and chlorinated rubbers.

Adhesive layer The adhesive layer may varyverywidely in composition and properties. It is of course necessary thatthe adhesive is of sufficient strength to enable itto pull itself and layers 1 and 2 from the carrier sheet. However, this can be achieved using quite low adhesive power or low tack adhesives if the release properties ofthe surface of the carrier sheet are high.

Much will depend on the final desired use of the material. For example, ifthe material is to be used to produce legends which are to be adhered externally, e.g. to a conventional painted surface on the exterior of a building, a relatively strong and weather resistant adhesive is desirable. Avariety of such adhesives is known, for example acrylic polymer based adhesives of high tack. Alternatively, systems designed for internal use, e.g. for display boards for exhibitions, presentation artwork or the like, may use a relatively low tack adhesive, e.g. a low tack polybutene based adhesive.

It should be born in mind that the adhesive layer is outward on the stock material, and that the stock material is usually conveniently supplied in form of rolls.

Because of the first of these considerations, it is usual to waste strip high tack adhesive types before attempting to transfer the desired legend.

The second consideration requires eitherthatthe carrier sheet surface remote from the cuttable set of layers is appropriately treated, or that the stock material is rolled up together with a release paper. This is the preferred approach in either case. In the case of low tack adhesive systems, a relatively light release coating on the surface in contact with the adhesive is usually sufficient. However, in the case of high tack adhesives, the rear side of the carrier or the release paper may need to be provided with a high quality very high release property coating.

The following examples will serve to illustrate the invention.

Example 1 A roll of polyethylene terephthalate film having on both faces an adhesion-promoting layer (MELINEX 542 ex ICI, 75 microns thick) was taken and coated with a polystyrene based release composition consisting of (parts by weight): High-impact polystyrene resin (Lustrex 4300, ex BP chemicals) 21.2 Ethyl Acetate 36.4 Xylene 36.4 Oxitol 5.8 Calcium/chromium salts in xylene antistatic agent (ASA 3 ex Shell) 0.2 The coating was carried out using a Meyer bar to give a dry coating weight of 7-8 grams per square metre after drying atabout700Cforabout25seconds.

This coating can, if desired, be matted with a suitable matting agent such as calcium carbonate to provide a matt finish to the transferred layers.

The other side of the polyethylene terephthalate film is coated with a slip promoting coat to aid the movement of graphic art applicators acrossthe surface during the application of the product.

The slip promoting coat consisted of: parts by weight Cellulose acetate butyrate (CAB 551-0.2, ex Eastman Kodak) 35% byweight solution in oxitol acetate 80.3 Oxitol 15.0 Silicone oil and surfactant in butyl oxitol (BykVP 341, ex Byk Mallinckrodt) 0.5 Ethoxylated amino salt in water/ alcohol (Byk ES 72, ex Mallinckrodt) 0.2 Anti-static agent in solution (10% by weight in 74 OP methylated apirit) (Cyastat LS, exAmerican Cyanamid) 4.0 100.0 This coating is deposited using a Meyer bar and dried at about 70"C for approximately 25 seconds to give a dry coating weight of between 7-8 gsm.

After this, a clear ultraviolet cured film was deposited on the release coating by coating or by screen printing.

Various ultravioletcurablefilm compositions may be used, for example, those based on cationiccuring of cyclo-aliphatic epoxy systems or those based on ethylenically unsaturated monomers.

Acoating composition consisting of the following ingredients in the following proportions by weight can be used as a cationic cured layer: Parts by weight Epoxy based flexibilising agent for cyclo-aliphatic epoxies (Cyracure 6351, ex Union Carbide) 45.00 Cycio-aliphatic epoxide (Cyracure 6110, ex Union Carbide) 48.50 Photoinitiator (UV1 6990, ex Union Carbide) 6.10 Fluorocarbon su rfactant (FC430, ex 3M) 0.40 The photoinitiator used yields highly acidic species on exposure to UV light. This coating composition can be used in continuous reel coating and after cure, the coating weight may be e.g. around 20 grams per square metre.

Asilkscreen printing composition can be used to produce the clear curable layer in strips or on sheets. A typical composition is: Parts by weight Aliphatic urethane acrylate (Photomer 6019, ex Diamond Shamrock) 58.50 Oligotriacrylate (OTA 480, ex UCB) 23.30 Iso butyl methyl acrylamide (Synocure 3165, ex Cray Valley Products) 14.00 Isopropyl thioxanthone (Quantacure lTX,(exWard Blenkinsop) 0.20 Hydroxy aryl Ketone (Daurocur 1173, ex Merck) 2.80 2-Dimethylamino ethyl benzoate (Quantacure DMB, exWard Blenkinsop) 0.20 2-Ethyl hexyl acrylate oligomer (Modaflow, ex Monsanto) 1.00 A dye- or pigment-containing layer was then deposited, optionally after subjecting the UV cured layerto corona discharge treatment, the coating composition being as follows:: Parts by weight Nitrocellulosesolution (33.3% by weight in solution oxitol acetate, E330, ex WolffWalstrode) 53.60 Dimethylcyclohexyl phthalate 1.35 Sebacicacid modified alkyd 12.17 Graphite (2 micron particle size) 2.80 Carbon black 3.18 Ethyl acetate 20.00 Oxitol acetate 6.90 This composition was coated onto the UV cured layer and dried at about 60"C for about 25 seconds. This gave a dry coating weight of about 6.0 grams per square metre. If desired, the UV cured layer may be coated afterthe nitrocellulose based layer rather than as described above. Again, the UV cured layer may if desired be treated to improve the adherence, this time of the adhesive layer to it. Corona discharge treatment is the treatment of choice.

Onto the outer of the two layers so coated, a layer of adhesive was then applied consisting ofthefollowing components in the following parts by weight: Parts by weight Finely divided Silica (Aerosil R972, ex Degussa) 4.50 Aliphatic hydrocarbon solvent (Exsol 145/160,exESSO) 15.30 Polyisobutylene (Molecular mass viscosity average 380,000) (Oppanol B.50, ex BASF) (20% by weight solution in the aliphatic hydrocarbon solvent) 17.50 Polybutene (Molecular mass number average 2400) (Hyvis 200, ex BP Chemical) 7.70 Polyethylene wax dispersion, Number average molecular mass 2000, melting point 104 108 C (10% byweight in above solvent) (ACP6, exAllied Chemicals) 55.00 This adhesive was coated onto the already coated film and the assembly dried at about 65for about 25 seconds to give a dry coating weightforthe adhesive of2to 2 grams per square metre.

In place of this adhesive, other adhesives as described in British Patent Specification 1 577617 may be used.

The finally coated film was slit into 8.6 wide strips, provided with standard perforations on the edges of each strip and the perforated strips rolled up.

The final product so produced could be used in conventional fashion in a Gerber Scientific Instrument Graphix 2 machine which was set to cut a legend in the applied layers. Viewed from the adhesive side, the legend reads in mirror fashion. Once the legend has been produced, the excess material can easily be hand stripped from the carrier film, any letter centres or islands likewise stripped, and the carrierthen turned over, positioned appropriately, and the legend applied to the desired receptor surface by simply rubbing gently down e.g. with a squeegee or burnisher. The provision of the slip promoting coat materially assists this operation. After the cut out legend has been rubbed down, the carrier sheet can simply be pulled away to leave the individual elements of the legend appropriately positioned and spaced on the desired receptor surface.

The adhesive formulation given above produces a fairly low tack adhesive in a product therefore suitable for general graphic art applications, but not suitable for external exposure.

Example2 Example 1 was repeated but using as the film material 125 micron thick polystyrene butadienefilm.

However, the slip promoting coat was not applied. Instead, a much stronger adhesive was used.

The product in this example is designed to have high weather resistance and accordingly the UVcured layer is put outwards i.e. applied first and applied by multipass application, e.g. two orthree coating passes in orderto provide a heavy, easily strippable final dry film on the surface of the polyethyleneterephthalate film. The dry coating weightofthe cured film is 60 grams per square metre after two or three passes.

The dye-or pigment-containing layer was applied as in example 1 and dried to give a layer of dry coating weight of about 6 grams per square metre.

Directly on to the dye- or pigment-containing layer a coating composition was applied by Meyer bar coating from a coating composition consisting of equal parts byweight of a non cross-linking solvent-base acrylic copolymer pressure sensitive adhesive (35% by weight solution in isopropyl acetate/isopropanol (Berger 5650, ex Resinuous Chemicals)) and ethyl acetate.

After carrying out coating with a Meyer bar and drying for about 25 seconds at 60"C, the adhesive was a high strength permanently tacky pressure sensitive adhesive with a dry coatweig ht of about 4.5 grams per square metre.

This product may be used in the same way as that of example 1. Sign legends made using it are particularly weather resistant.

Claims (12)

CLAIMS 1. A drytransferfilm material consisting of a carrier sheet carrying successively: a) in either order

1. a film layer of sufficient strength that it may be peeled from the carrier sheet

2. a dye- and/or pigment-containing layer and b) an adhesive layer.

2. A drytransferfilm material according to claim 1 wherein the carrier sheet is a dimensionally stable plastics film.

3. Adn/transferfilm according to claim 2 wherethedimensionally stable plasticsfilm is a polyethylene terephthalate or polystyrene butadiene film of thickness 50 to 100 microns.

4. A drytransferfilm according to any one of claims 1 to 3wherein thefilm layer is a thin tough cured polymericfiim.

5. Adry transferfilm according to claim 4wherein the film layer is a UVcured polymeric film, either based on a composition comprising an ethylenically unsaturated monomer and appropriate curing agent or a cured epoxy type system.

6. A drytransferfilm according to claim 5 where the dye- or pigment-containing layer consists of an appropriate polymericfil m-forming vehicle into which has been incorporated a pigment and/or dye to give visibility.

7. A drytransferfilm accordingly to claim 6 wherein the film-forming vehicle is a UV curable system, ora nitrocellulose based lacquer.

8. A drytransferfilm according to any one of claims 1 to 7 wherein the adhesive layer is of relatively low tack and based on a polyisobutylene resin.

9. A drytransferfilm according to any one of claims 1 to 7 wherein the adhesive layer is of relatively high tack and based on an acrylic resin.

10. A drytransferfilm substantially as herein before described with reference to the foregoing specific examples.

11. A method of making a sign which comprises passing a drytransferfilm according to any one ofthe preceding claims through a machine capable of cutting through all three layers thereon, adhering the legend so formed to a substrate by means of the adhesive layer and peeling away the carrier sheet.

12. Asign made bythe method ofclaim 11.