WO2008091148A2

WO2008091148A2 - Improved decalcomania transfers and methods and uses related thereto

Info

Publication number: WO2008091148A2
Application number: PCT/NL2008/050041
Authority: WO
Inventors: Jan Soeten
Original assignee: F.T. Niemeijer Beheer B.V.
Priority date: 2007-01-23
Filing date: 2008-01-23
Publication date: 2008-07-31
Also published as: WO2008091148A3

Abstract

The invention relates to decorative transfers and to methods for preparing and using them. More in particular it relates to pressure-sensitive transfers for decorating a surface which is subsequently provided with a top coating. Provided is a transfer for decorating a receiving surface with a decoration in a predetermined pattern, comprising: a) a temporary carrier film provided with a transparent release coating; b) a decoration printed onto said release coating; and c) an adhesive layer overlaying said decoration, wherein the adherence of the release coating to the decoration is higher than for the carrier film such that upon application of the transfer to said receiving surface the release coating overlays said decoration.

Description

Title: Improved decalcomania transfers and methods and uses related thereto.

The invention relates to decorative transfers or decalcomania transfers (decals) and to methods for preparing and using them. More in particular it relates to pressure-sensitive transfers for decorating a surface which is subsequently provided with a top coating. Decalcomania refers to the process of transferring pictures or designs printed on a specially prepared carrier to materials such as glass or metal. Thus, the decoration or design is formed independent of the surface to be decorated, usually on a transfer paper or other type of temporary carrier. Various types of decals are known in the art. The three main types of decals are water-release, heat-release and pressure- or cold-release.

A decal can be regarded as a 'sandwich' of several distinct layers. One type of standard decal typically comprises a temporary carrier film which is coated on one surface with a release layer or release coating. A desired pattern or decoration is printed onto the exposed surface of the release layer using conventional (multi-color) ink printing equipment including letter press, rotogravure, silkscreen,. or flexographic presses. The decal is completed by applying an adhesive layer as a discrete area entirely overlaying the ink design. In case the adhesive layer is a pressure-sensitive adhesive, a peelable protective sheet is applied .on top of the adhesive layer to protect it until use. To use the decal for decorating a surface, the protective sheet is removed and the adhesive layer is pressed against the surface to be decorated. If necessary, e.g. in case of a heat-sensitive decal, sufficient heat is used to activate the adhesive and/or release coating and leave the ink design bonded to the receiving surface. Following bonding of the design to the receiving surface, the temporary carrier film together with the release coating is removed from the adhered decaL to result in an ink design bonded via an adhesive layer to the surface.

Conventional release coatings include silicone coatings and wax or resin coatings. For heat-release decalcomania, wax or resins meltable between about 90 and 250°C are often used. For pressure- or cold-release decalcomania, the release layer is typically silicone.

The materials used for conventional release coatings have a number of drawbacks. It is known in the art that the silicone layer deteriorates physically over time which can cause a variable degree of adhesion between a) the release layer and the ink design and/or b) the release layer and the carrier film. This can result in an "incomplete" or "overcomplete" transfer to the surface to be decorated. For instance, if the adhesion of the ink to the release coating is too strong, the ink design fails to transfer completely. Also, if the adhesion of the release coating to the .carrier film is .too weak or too low, it will not stay behind with the carrier film but instead stick to the ink design and become part of the surface to be decorated.

The latter is especially problematic in case the decorated surface requires a finishing lacquer or top coating. Often, e.g. in case of decorating a metal object such as a bicycle frame, decalcomania involves application of a transfer to the surface being decorated followed by the application of a finishing lacquer or top coating which is then thermally fused onto the surface by heating at elevated temperatures, generally between 140 and 180 ⁰C.

Any residual silicone (or other type of conventional release layer material) will cause highly undesirable pinholes in the top coating of the finished product. Conventional release coatings made of meltable waxes or resins have a similar problem; they are greasy components and the top coating can not flow correctly on them.. The result is the formation of shall pinholes in the top coating. It is an object of the invention to provide improved decals which do not suffer from one or more of the above problems. Further objects include the provision of a method for the rapid and economical manufacture of decals.

The present inventors surprisingly found that these objects are met by the provision of a decal comprising a new type of release coating. The release coating of the invention is characterized in that it adheres more strongly to the printed decoration than to the temporary carrier film. Thus, in contrast to release layer materials known in the art (silicone, wax, resins), the release layer sticks with the decoration instead of with the carrier film. It has a sufficient cohesive strength to essentially completely detach from the temporary carrier film upon application of the transfer to said receiving surface. As a result, the release coating overlays said decoration. This type of release layer provides for a highly predictable and efficient transfer of the decoration. Also, it avoids the formation of pinholes and related undesirable irregularities in the coated top. surface caused by residual silicone reacting with the top coating. Herewith, the invention provides an attractive alternative for silicone in pressure- or cold-release decals.

In one embodiment, there is provided a transfer for decorating a receiving surface with a decoration in a predetermined pattern, comprising a) a temporary carrier film provided with a transparent release coating; b) a decoration printed onto said release coating; and c) an adhesive layer overlaying said decoration, wherein the adherence of the release coating to the decoration is higher than for the carrier film such that upon application of the transfer to said receiving surface the release coating overlays said decoration. Because the release layer will cover the printed ink design on the end product, it must be transparent. Also, it allows to receive a print design using conventional inks. The release layer material in a decal of the invention has a good thermal stability. Preferably, it is resistant against elevated temperatures, for instance up to 200⁰C. For .reasons given, above, it will be understood that a release coating of the invention is preferably free of any silicone.

The adhesive layer preferably comprises a pressure-sensitive adhesive.

These are known in the art. The adhesive is preferably transparent and colourless. For example, a conventional acrylic printable adhesive is suitably used. The adhesive layer overlays said ink design and is preferably applied as a discrete region having the same shape as the design.

Optionally, a decal of the invention further comprising a protective sheet overlaying said adhesive layer to prevent premature or unwanted adhesion and to protect the adhesive layer. It will be understood that additional layers and/or decorations may be present as well.

Following application of a decal according to the invention to a receiving surface, the release layer becomes the exposed surface of the decorated region.

As described herein above it is common practice to provide the decorated surface with a top coating. The release coating is preferably capable of crosslinking with the material used for the top coating, for example with a top coating based on acrylic or polyester powders. In general the powder is a compound of thermoplastic or thermosetting polyurethane or polyester resin and a binding agent. It contains also additives, for example, a flow agent. According to the invention, the release layer forms a layer between the ink design and the top coating. This is particularly advantageous if conventional inks are used for the ink design since these inks contain a small yet significant amount of silicone as rheology-controlling additive. As described above, any silicone which becomes in contact with the top coating causes unwanted pinholes upon heating. According to the invention, this problem is avoided because the release layer acts as an insulating layer between the

(silicone-containing) ink and the top coating.

Any type of ink can be used which is compatible with the release coating.

Conventional, solvent-based inks may be used, including those which contain silicone. For example, urethane and polyester based inks. The temporary carrier film can be made of any smooth material. It is sufficiently flexible to allow for transfer to a rounded or cornered surface. It is stable enough for receiving a multi-color ink design, which involves several rounds of printing. Preferably, it is suitable for silk-screen processing. The carrier film is for instance a smooth plastic film of (regenerated) cellulose or polyester. Polyester film is preferred.

A further aspect of the invention relates to a method for the manufacturing of an improved transfer according to the invention. Said method involves the stepwise assembly of the decal "sandwich". It comprising at least the steps of a) applying said release coating onto said carrier film to provide a coated carrier film; b) printing onto the exposed surface of said release coating a decoration in a predetermined manner; and c) providing an adhesive layer onto said decoration such that it overlays said decoration. Optionally, it furthermore comprises providing a protective sheet onto said adhesive layer.

The step of applying a release coating according to the invention to a carrier film results in a coated carrier film, for instance a polyester sheet coated with a release coating of the invention. The application can be continuous or discontinuous, i.e. as discrete regions. Application of the release coating in a continuous fashion is preferred because it is difficult in practice to ensure that all individual layers of the decal have precisely the same shape and location. If the coating layer is present over the whole area of the carrier film, this avoids any mismatch between the region having release coating and the subsequent layers applied onto it, In one embodiment, the release coating is applied to the carrier film, by rolling e.g. "using a rolling mill. This allows for the application of a release coating which is much thinner as compared to conventional release coatings. For example, a release coating according to the invention can be as thin as 3 to 4 microns, versus at least 6 to 8 microns encountered in the state of the art which are typically applied using other techniques such as silk screen printing. Since it is an overall aim in the field to minimize total thickness of the transfer, the reduction in the thickness of the release coating is a further advantage of the present invention. The invention also provides the coated carrier film obtainable by coating a carrier film with a release coating according to the invention. The coated carrier film can be prepared as a continuous roll, ready to be further processed into a transfer according to the invention.

As a next step, the exposed surface of the release coating is provided with a decoration, e.g. printed with a pattern of ink to provide the coated carrier film with a decoration in a predetermined manner. Conventional printing techniques may be used, in particular silk screen printing. The decoration may be in monocolor or in multicolor. Also, decorations other than ink patterns may be applied in additional to the ink pattern or as an alternative, for example thin metal films or other suitable materials.

Following the application of the decoration, an adhesive layer is applied, preferably by printing, in a predetermined pattern using a conventional adhesive composition instead of the ink (or other type of decorative material). A pressure-sensitive adhesive is preferred. Thus, the adhesive is applied as a discrete area having essentially the same shape as the decoration and covering at least the decoration such that the decoration will come off completely upon application of the adhesive layer to the surface to be decorated. It may be slightly larger than the area of the decoration (e.g. extending 0.5 mm) to ensure that the decoration is fully overlaid with adhesive even in case certain small irregularities may arise during the manufacturing process. The latter may include shrinkage of the carrier film and/or small deviations in the setting of the printing press used for application of decoration and adhesive.

To protect an adhesive layer against damage and/or premature adhesion to an unwanted surface it can be provided with a peelable temporary protective sheet. This is of particular relevance if a pressure-sensitive adhesive is used. In case of a heat-activatable adhesive that is non-tacky at room temperature, such as a well-known polyamide lacquer, the use of a protective sheet is not required.

A method of the invention is rapid and economical to carry out as compared to conventional transfers, in particular those transfers that are suitable for use under a top coating. The latter typically comprise two adhesive foils which require separate punching out and manual peeling. Furthermore, a method of the invention produces less 'waste, not only because more material is effectively used but also because the transfer of the invention is much thinner (approximately 50% of a conventional transfer). Preferably, the total thickness of the transfer is less than 15 microns, for example 10 or even 8 micron. Also provided is a transfer obtainable by a method according to the invention.

In a further aspect, the invention relates to a method for decorating an object or surface comprising the use of a transfer as provided herein. It typically involves adhering the adhesive layer of the transfer to said surface and exerting a force that is sufficient to leave the decoration bonded to the receiving surface. The decorating method may further comprise the step of providing at least one layer of top coating over the decorated surface, optionally further comprising heating the decorated surface. The receiving surface can be part of a any type of object. In one embodiment, it is a metal object, for example selected from the group consisting of bicycles, automotive objects, motor bikes, (industrial) furniture, machines, (industrial) equipment, nameplates, scaffolds, toys and rigid plastics.

The transfer is for example a pressure-sensitive transfer which can be applied by exerting sufficient pressure onto the transfer after it has been contacted with the surface to be decorated via the pressure-sensitive adhesive layer. Any type of object or surface may be decorated. In one embodiment it is a smooth, rigid surface, for example a metal surface. As indicated above, a transfer of the invention is especially advantageous to decorate an object which is thereafter provided with a finishing lacquer or other type of top coating. Because the carrier film is flexible, the transfer can be applied to curved or cornered surfaces. In a specific aspect, the transfer is used to decorate a bicycle, for instance the frame of a bicycle is provided with a decoration carrying the logo of the bicycle's manufacturer. Other possible applications are (metallic) products and machines such as (industrial) furniture, machines, industrial equipment, scaffolds and toys.

Also provided herein is an object decorated with a transfer according to the invention or an object obtainable by the decorating method described above. Said decorated object is distinguished from known decorated objects on the basis of the unique type of release coating according to the invention.

The invention will now be exemplified on the basis of a representative but non- limiting embodiment.

In the drawings, Figure 1 is a schematic drawing showing the stepwise assembly of a transfer according to the invention. Shown are views in section. Fig. IA shows a carrier film 1 provided with a thin, continuous layer of release coating 2. In Fig. IB the coated carrier film is provided with a decoration 3 in a predetermined pattern. For example, it is a logo printed in conventional ink comprising a trace of silicone as flow agent. For example, it is a logo printed in conventional ink comprising a trace of silicone as flow agent Fig.1C shows the transfer after application of an adhesive layer 4 in the shape of the decoration 3. Preferably, it is a pressure- sensitive adhesive. In this embodiment the adhesive layer is slightly larger than the decoration and sticks out on each side, e.g. by only a few millimetres. The adhesive layer 4 is protected with a protective sheet 5.

Figure 2 is a schematic view of the transfer shown in Figure 1 after the protective sheet 5 has been peeled off the transfer, followed by application of the transfer with its adhesive layer 4 to a surface 6 to be decorated of rigid object 7. The adhesive layer 4 is in direct contact with the surface 6. The carrier film 1 is detached from the applied transfer, leaving behind a portion 2A of the release coating on the transfer commensurate or co-extensive in area with the pattern of the adhesive layer 4. As a result, decoration 3 is sandwiched in between adhesive layer 4 and release coating 2. The remaining portion 2B of the release coating which was not overlaid with adhesive remains with the carrier film and is carried off the transfer together with the carrier film and can be discarded. The protective sheet 5 is not shown.

Figure 3 shows the decorated object as in Figure 2 after it has been provided with a finishing top coating 8, for instance an acrylic lacquer or powder coating. Clearly, the release coating 2 acts as insulating layer between the top coating 8 and decoration 3, avoiding direct contact between components in the decoration (e.g. silicone) and the material used for the top coating.

Claims

1. A transfer decalcomania for decorating a receiving surface with a decoration in a predetermined pattern, comprising: a) a temporary carrier film provided with a transparent release coating; b) a decoration printed onto said release coating; and c) an adhesive layer overlaying said decoration, wherein the adherence of the release coating to the decoration is higher than for the carrier film such that upon application of the transfer to said receiving surface the release coating overlays said decoration.

2. Transfer according to claim 1, wherein said adhesive layer comprises a pressure-sensitive adhesive.

3. Transfer according to claim 1 or 2, further comprising d) a protective sheet overlaying said adhesive layer.

4. Transfer according to any one of the above claims, wherein the design is an ink design, preferably made using urethane- or polyester- based ink.

5. Transfer according to any one of the above claims, wherein said release coating does not comprise silicone.

6. Transfer according to any one of the above claims, wherein said release coating is capable of cross linking with cover-coat lacquer typically used to thermally fuse the transfer onto the surface.

7. Transfer according to any one of the above claims, having a thickness of less than 15 microns, preferably less than 10 microns.

8. Transfer according to any one of the above claims, wherein said decoration comprises ink which contains silicone.

9. Transfer according to any one of the above claims, wherein the carrier film is polyester.

10. Method for manufacturing a transfer according to any one of claims 1 to 9, comprising the steps of: a) applying said release coating onto said carrier film to provide a coated carrier film; b) printing onto the exposed surface of said release coating a decoration in a predetermined manner; c) providing an adhesive layer onto said decoration such that it overlays said decoration; and optionally d) providing a protective sheet onto said adhesive layer.

11. Method according to claim 10, wherein step a) comprises applying the release coating onto said carrier film by rolling.

12. Carrier film provided with release coating obtainable by step a) of the method according to claim 10 or 11.

13. Method for decorating a receiving surface comprising adhering the adhesive layer of a transfer according to any one of claims 1-9 to said surface and exerting a force that is sufficient to leave the decoration bonded to the receiving surface.

14. Method according to claim 13, further comprising the step of providing at least one layer of top coating over the decorated surface, optionally further comprising heating the decorated surface.

15. Method according to claim 14, wherein said top coating is an acrylic or polyester powder, preferably wherein the coating comprises a thermoplastic or thermosetting polyurethane or polyester resin, a binding agent and one or more additives, for example, a flow agent.

16. Method according to any one of claims 13 to 15, wherein said receiving surface is part of a metal object, for example selected from the group consisting of bicycles, automotive objects, (industrial) furniture, nameplates, (industrial) machines and equipment scaffolds, toys and rigid plastics.

17. An object decorated with a transfer according to any one of claims 1-9 or obtainable by a method according to any one of claims 13-16.