EP0726170B1 - Method of coating articles and transfer film for coating articles - Google Patents

Abstract

The transfer consists of a backing film (1) which is softened by the effect of a liquid, and a number of layers (2, 3, 4, 5) which are applied to the backing film just before the articles to be decorated are immersed in a bath. At least one of the layers is reticulable, with the reticulation initiated prior to transfer, and the backing layer has a primary layer with reactivatable penetrating inks, and another layer which is an activator for the inks and is applied at the moment the film is immersed. After the article has been immersed and the decoration transferred to it is rinsed to get rid of any backing layer residues and protected by an impermeable film layer. The different layers can be made from composition materials, e.g. containing micro-capsules which are opened before or after application e.g. by laser radiation, electron treatment or thermal shock.

Description

The present invention relates to a method of coating of articles and a transfer film for coating of articles.

We know, in particular from document FR-A-2,281,833 a method and a device for decorating articles consisting in printing a design on a transfer film such than a polyvinyl alcohol film which is deposited on a bath, the articles to be decorated being immersed so as to press the film on the surface of the article and transfer thus the drawing on the surface of the article.

This process is effective for decoration articles with very curvilinear surfaces varied. However, given the diversity of materials that are used to make up the items, it is common that the ink with which the drawing is achieved does not have a satisfactory adhesion to the material constituting the article and it is then necessary to plan a preliminary stage of coating the article with a primer. In addition, the inks constituting the design applied to the surface of an item are usually fragile, i.e. they are sensitive to shocks, abrasion, solvents that are used for cleaning of the article, as well as any other attack outside. To ensure the longevity of the deposited decoration on the article it is therefore necessary to cover it with a varnish.

To date coating an article with a primer and protecting the decor with a varnish are usually sprayed followed by drying. The spraying and drying operations must be performed at positions different from the immersion of the article in the bath covered with a transfer film so that the decoration of the items cannot be performed continuously. In addition, spraying techniques necessarily involve a loss of great part of the sprayed material which does not reach the article. This loss of sprayed material does not constitute only a financial loss due to the cost of pulverized matter, but also pollution against which it is necessary to set up facilities expensive to save the environment.

• à un poste d'immersion, déposer sur un bain de liquide un film transfert comprenant un film support qui est ramollisable par l'action d'un liquide, ce film support étant recouvert sur une face supérieure par des couches successives d'un revêtement comprenant une première couche de matière réticulable dans un état non réticulé ou partiellement réticulé en contact avec le film support, et au moins une seconde couche en contact avec la première couche,
• mettre au moins un article en contact avec le film transfert et immerger cet article dans le bain de liquide pour transférer les couches de revêtement sur l'article, et
• assurer une réticulation complète du matériau réticulable après que celui-ci a été appliqué sur l'article.

According to the invention, a method for coating articles is proposed, characterized in that it comprises the steps of:

• at an immersion station, deposit on a liquid bath a transfer film comprising a support film which can be softened by the action of a liquid, this support film being covered on an upper face by successive layers of a coating comprising a first layer of crosslinkable material in an uncrosslinked or partially crosslinked state in contact with the support film, and at least one second layer in contact with the first layer,
• bringing at least one article into contact with the transfer film and immersing this article in the liquid bath to transfer the coating layers onto the article, and
• ensure complete crosslinking of the crosslinkable material after it has been applied to the article.

So applying the different layers on the items is done in one operation which can be performed continuously so that it results in a gain considerable time for the installation of the coating on articles. In addition, the different layers constituting the coating can be applied to the film while it is placed on a flat support so product losses are very low even when these are applied by spraying. Finally, the depositing a first layer in a non-state crosslinked or partially crosslinked and to only perform the crosslinking only after application on an article allows keep this layer all its flexibility before application and nevertheless obtain a layer of very hard finish.

The method according to the invention therefore allows significant cost reductions both in terms of operation as investments by removing facilities heavy paint, varnish or treatment of area.

According to an advantageous version of the invention, the successive layers are projected onto the transfer film just upstream of an article dumping station. We thus obtains maximum adhesion of the layers to each other and the longevity of the decorative coating of the articles finds increased.

According to the invention, a film is also provided. transfer comprising a support film which is softenable by the action of a liquid, this film being covered on a face by successive layers of a coating comprising a first layer of crosslinkable material in a non-state crosslinked or partially crosslinked in contact with the film support, and at least one second layer in contact with the first layer. From US-A-3,791,841, a transfer film (decal) is known, comprising a layer of crosslinkable material in an uncrosslinked or partially crosslinked state, said film also comprising a release layer between the support and the crosslinkable layer .

Other characteristics and advantages of the invention will appear on reading the description which follows a particular non-limiting embodiment of the invention, with reference to the attached single figure which is an enlarged sectional view of a transfer film according to the invention.

Referring to the figure, the transfer film according to the invention comprises a support film 1, a first layer 2, which will subsequently be called a top coat, in contact with the support film, a second layer 3 which will be subsequently called a decorative layer in contact with finishing layer 2, a third layer 4, called base layer, in contact with the decoration layer and a fourth layer 5, called a primer or promoter layer adhesion, in contact with the base layer 4. The support film is made of any material suitable for removed after depositing the decorative coating on a article, for example a polyvinyl alcohol or any other softenable material by the action of a liquid.

The finishing layer is made up of all material providing the final coating with resistance to external attacks of a mechanical, chemical type ... as well as the desired appearance. The top coat is by example a gloss or satin varnish preferably applied on the support by low-emission techniques such as roller or curtain printing. The top coat is of crosslinkable material in an uncrosslinked state or partially crosslinked before transfer and crosslinking complementary is ensured after application coating on the article to be decorated.

The decorative layer is obtained by application a drawing on the top coat. The realization drawing can be done by applying ink or any material using application techniques known. In the case of a crosslinkable top coat, we can also plan to apply the decorative layer before crosslinking the top coat, the material constituting the finishing layer which can then serve as a binder for the material constituting the layer of decoration, in particular in the case where it is made with solid inks applied in the form powdery. the decoration layer can also be a uniform layer of color if the decoration of the article is precisely to color this one so uniform, or a layer containing additives or fillers giving the decorative layer an appearance visual, tactile or olfactory final which can be modified after transfer by revelation techniques such as for example laser revelation ... In the case of a decoration comprising a pattern one can foresee to cancel or reduce the deformations due to the shape of the article by performing an upstream anamorphosis.

The base layer is useful when you want achieve a uniform background color that appears more or less through a decorative layer of thickness not uniform as illustrated in Figure 2. This layer of base may be a paint applied by spray gun or by any other means of application such as switching between application rollers. In the event that there is no risk of migration of the decorative layer in the base coat, base coat can be applied over the decoration layer while it is not yet dries to ensure better adhesion between the decoration layer and base layer.

The primer 5 is applied when the decorative layer or base layer have adhesion insufficient on the material constituting the articles to decorate, or even when the material constituting the layer of decoration or the base coat is a material that does not cannot be reactivated after drying.

The transfer film according to the invention can be carried out in situ just before immersion of the articles in decorate. In this case the different layers can be made on the film upstream of the bath or while the latter is arranged on the upper surface of a bath so to scroll the film continuously, with regard to the means application of the different layers. Between these means application you can insert drying ramps to hot air or irradiation to ensure crosslinking or initialize it, crosslinking may continue during the application of the other coats, during the transfer, or after transfer.

In case the transfer film has to be stored, at least the layer of the coating which is furthest from the support film, i.e. the primer layer 5 in the example illustrated, ie in a stable material under storage conditions but nevertheless reactivable. By reactivable material is meant a material whose structure can be modified after storage so that this material regains power adhesion on the articles to be decorated.

Of course, the invention is not limited to embodiment described and we can add variant embodiments without departing from the scope of the invention as defined by the claims.

In particular, although the film transfers according to the invention has been described with four superimposed layers on the support film, it can of course be produced with a different number of layers depending on the application to achieve. In this regard, it should be noted that the film transfers according to the invention can be used not only for decorate articles properly speaking, that is to say for make a drawing on the surface of an article, but also to ensure uniform color coverage intended to protect the surface of the article under consideration or to hide defects in appearance of the article under consideration, by example in the case where this is carried out from a molded plastic that does not show a color uniform.

The composition of the different layers, particular of the base layer and the layer of decoration can be made with compositions any for example with compositions comprising additives, or fillers such as microcapsules, allowing delayed differentiations revealable after application on the support film. The corresponding revelation can be performed before or after the transfer to the object using known techniques such as laser radiation, electron bombardment, shock thermal,...

We can also provide a layer of ink penetrating that is to say a layer of ink which diffuses in the adjacent layer, for example by sublimation. This layer is for example arranged between the finishing layer 2 and the decorative layer 3. After transfer of the coating multilayer on an article it is passed in a oven to allow the action of penetrating inks. We note in this regard that the top coat 2 can then play the role of the elastomeric membrane or the shell which is usually used to cover the substrate on which sublimable inks have been deposited, before proceed to the temperature rise. We can also use a top coat instead of the top coat can be eliminated after or during the ascent temperature.

According to a preferred embodiment of this aspect of the invention the transfer film comprises a first layer comprising penetrating inks in the state stable, this first layer being reactivable. Inks penetrating can be integrated into a top coat. When the transfer film is deposited on the bath, that is to say just upstream of the bath or when the film is already deposited on the bath, a second layer comprising a activator of penetrating inks, and preferably a adhesion promoting agent, is deposited on the film. So penetrating inks are activated by the layer comprising the activator of penetrating inks so this last layer retains penetrating inks inside of the coating with which the article is covered.

Before heating the article to distribute penetrating inks, it is possible to rinse it to remove residue from backing film.

To further improve the appearance of the coating obtained we can also plan to wrap the article in a waterproof sheet, for example a sheet aluminum before heating the item.

You can also apply a uncrosslinked or partially crosslinked layer which is cross-linked at the same time as the decorative layer after transfer of it on the article. The adhesion of the decorative layer is thus reinforced.

The multilayer technique according to the invention can be used not only for decorating an item as explained above but also to modify the physical or chemical characteristics of the surface of a article, for example by applying an anti-fog coating, anti-ultraviolet, anti-abrasion, improving sliding.

The first layer 2 can in this case be a primer intended to subsequently receive a decoration, for example in the case of a decoration performed retrospectively. We can also make reserves in one or more layers by placing on the film, in the reserve areas, a removable material after transfer, for example by removal or dissolution so that the outer surface of the coated article contains these reservations.

According to the invention a material having poor attachment characteristics and a poor mechanical resistance can be deposited on an article in sandwiching it between a top coat and a coat of primer.

In the case of a continuous process it is not the support film 1 must be in the solid state. he can on the contrary be a gel deposited on the bath and receiving successive layers before transfer to a article. It is also possible to use a film support intended to remain in place after transfer to a article.

The application system for each of the layers is preferably controlled by a computer system associated with image databases, parameters printing, multi-sensory data, sets, as well as a digital image analyzer, a device synthesizing images and decor, and a device for visualization to display in three dimensions the article obtained after coating according to a rendering realistic and readjust some print settings before starting the actual print. It will easily the establishment of intermediate stages of sampling. This system could be of expert type evolving by itself according to the results actually obtained. Through elsewhere, the decor database may allow interactivity with users. She will be able to receive different evolutionary elements linked to trends.

Claims (7)

1. A method of coating articles characterized in that it comprises the steps of :

   at an immersion station, placing on a bath of liquid a transfer film comprising a support film that is softenable by the action of a liquid, this support film being coated on an upper face by successive layers of a coating comprising a first layer of curable material that is not cured or that is partially cured and is in direct contact with the support film, and at least a second layer that is in direct contact with the first layer,

   putting at least one article in contact with the transfer film and immersing this article in the bath of liquid for transferring the coating layers onto the article, and

   performing a complete curing of the curable material after it has been applied on the article.
2. A method according to claim 1, characterized in that the successive layers are applied on the support film immediately before immersing the article.
3. A method according to claim 1, characterized in that the last layer applied on the film includes penetrating inks that are reactivable, and in that a layer that includes an activator for the penetrating inks is applied at the moment when the film is deposited on the bath.
4. A method according to claim 1, characterized in that the first layer includes penetrating inks in a stable state and the second layer includes an activator of the penetrating inks, and in that the method includes a step of heating the article after transfer of the coating layers onto said article.
5. A method according to claim 4, characterized in that it further includes the step of washing the article before heating the same.
6. A method according to claim 4 or claim 5, characterized in that the second layer includes an agent for promoting adhesion.
7. A transfer film for use when carrying out the method of claims 1 to 6 comprising a support film that is softenable by the action of a liquid, this film being coated on one face by successive layers of a coating comprising a first layer that is not cured or that is partially cured and is in direct contact with the support film, and at least a second layer in contact with the first layer.

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