EP3122571B2 - Gilding method and system - Google Patents

Description

The present invention relates to the field of substrate customization devices. Thus, the invention relates in particular to a method and/or a system for customizing a substrate, according to claims 1 and 6, by depositing an additional coating (or material), generally called "gilding" of a substrate. In particular, the present invention relates in particular to a printing method comprising a step of printing a substrate by inkjet followed by a step of "gilding" by contact between the areas of the substrate to be gilded and a device for depositing "gilding", such as a gilding sheet.

Techniques for gilding printed substrates are well known to those skilled in the art. The basic principle of this technique is based on depositing an additional coating (i.e., gilding or material) on the substrate, by a "gilding" deposition device, for example by applying/pressing a foil (carrying said coating or gilding) on selected areas of the substrate so as to adhere the desired part of the foil to the selected areas. This technique may for example involve depositing an adhesive on the substrate in a predetermined pattern before depositing the personalization coating (for example the gilding foil) on the adhesive deposited on the substrate. The deposition of the adhesive may be done using one or more techniques, such as for example inkjet printing, toner-based printing, screen printing or offset printing.

The present invention relates in particular to relief inkjet printing techniques, for example using piezoelectric print heads, adapted according to the printing ink and/or varnish used.

• une pellicule optionnelle d'adhésif,
• au moins une pellicule de dorure,
• une pellicule optionnelle de protection,
• une pellicule optionnelle de décollement, et
• au moins une couche dite de transport qui permet le transport de la feuille de dorure.

The gilding leaves used in the context of the present invention consist of several superimposed films including, by way of non-limiting example:

• an optional adhesive film,
• at least one layer of gilding,
• an optional protective film,
• an optional release film, and
• at least one so-called transport layer which allows the transport of the gilding leaf.

Various solutions for customizing substrates by gilding are known from the prior art, in particular the request WO2011110956 which, in its embodiment represented by its figure 2 , describes a cold foil stamping system comprising a pressing system 200 and, upstream of this pressing system, a printing section comprising a printing device 210 (for example, an inkjet printer) for depositing a deposit pattern consisting of a layer of adhesive 222, on a substrate 220. After pressing a sheet onto the substrate, the adhesive is hardened and becomes tacky, which allows the sheet to adhere to the pre-established pattern. The pressing is carried out by means of one or more pinch rollers (260) also called pressure cylinders. This pressurization is carried out on the entire sheet of foil.

The gilding technique is generally optimized so as to promote better adhesion performance of the gilding leaf on the substrate while improving the visual quality of the gilding deposit on the substrate. Despite the evolution and precision of gilding techniques, the Applicant has found that it is very difficult to reconcile these two conditions with the known gilding techniques. One of the objectives of the present invention is therefore to provide a gilding technique which promotes better adhesion performance of the gilding leaf on the substrate while improving the visual quality of the gilding deposit on the substrate.

The present invention therefore aims at least to overcome this major drawback of the prior art.

This aim is achieved by a method of gilding a substrate, according to claim 1,
by applying pressure between the areas of the substrate to be gilded and a gilding sheet comprising a gilding film and a transport layer, characterized in that the step of applying pressure and depositing the gilding film is followed by a step of applying pressure to the areas of the substrate covered with the gilding film. This additional and consecutive step of applying pressure is therefore carried out after separation of the gilding film from the transport layer of the sheet.

THE Figures 1 and 2 illustrate a gilding technique according to the prior art.

There figure. 3 illustrates a gilding technique according to a certain embodiment of the present invention.

• d'un ou plusieurs ensembles de rouleaux de pincement tels que décrits dans la figure 1 ;
• d'un ou plusieurs rouleaux de pression tels que décrits dans la figure 2.

The pressure between the areas of the substrate to be gilded and a gilding sheet comprising a gilding film and a transport layer can be carried out by any suitable method. As an illustration, the use of

• of one or more sets of pinch rollers as described in the figure 1 ;
• of one or more pressure rollers as described in the figure 2 .

• d'un ou plusieurs ensembles de rouleaux de pincement tels que décrits dans la figure 1 ;
• d'un ou plusieurs rouleaux de pression tels que décrits dans la figure 2.

Then, when the gilding foil has been pressed onto the substrate and the gilding film has been deposited on the substrate and thus detached from the transport layer, a second step is carried out of pressurizing the areas of the substrate covered with gilding film using any suitable method. As an illustration, the use of

• of one or more sets of pinch rollers as described in the figure 1 ;
• of one or more pressure rollers as described in the figure 2 .

The fundamental advantage of the present invention is that the preferred focusing parameters of the first pressurization step can be independently adjusted relative to those of the second pressurization step. The Applicant has unexpectedly discovered that this makes it possible to optimize both the adhesion performance of the gold leaf on the substrate while improving the visual quality of the gold leaf deposit on the substrate.

The present invention is described in an illustrative manner and according to one of its embodiments in the figure 3 . On the left side of the figure, we can see a pressure group according to the present invention and which is located downstream of the gilding group shown on the right side of the figure. The substrate therefore moves from right to left.

The pressure group consists of at least two motorized rollers, installed opposite each other, rotating in opposite directions, and whose distance is adjustable so as to adapt to different substrate thicknesses; according to a preferred embodiment of the present invention, this adjustment will take into account not only the thickness of the substrate but also the thickness of the ink and/or varnish previously printed on the substrate as well as optionally all the thicknesses added to the substrate during substrate treatment steps preceding the gilding and also optionally taking into account the thicknesses of the films of the gilding leaf deposited by the gilding group(s).

According to a particular embodiment of the present invention, the spacing between the facing rollers can be motorized and dynamically controlled.

According to a particular and preferred embodiment of the present invention, the surface of the upper roller is different from that of the lower roller; in particular, the surface of the upper roller is more compressible than that of the lower roller. By way of illustration, the upper roller has a compressible material on its surface allowing it to conform to the shape of the gilding deposit while the lower roller will be made of a harder material, for example incompressible.

According to a particular embodiment of the present invention, the upper roller comprises a heating device which improves the hold of the gilding; for example, this heating device can be advantageously used when the gilding film is covered with varnish because the heating allows the softening of said varnish.

According to a particular embodiment of the present invention, the pressure group operates with a linear speed (on the surface of the rollers) greater than or equal to that of the gilding group so as not to slow down the machine.

According to a particular embodiment of the present invention, the distance between the gilding group and the pressure group is greater than the maximum length of the treated substrates.

A feature of the present invention is that it allows a step of treating the gilding film to be carried out by the pressure group which controls this step independently of the deposition step which is controlled by the gilding group; this therefore allows both the adhesion performance of the gilding sheet on the substrate to be optimized while improving the visual quality of the gilding deposit on the substrate.

The control characteristics of the pressure group are given below for illustrative purposes: adjustable pressure (e.g. from 1 to 10 bar, preferably with an operating pressure greater than 1 bar), and/or adjustable speed; and/or adjustable temperature (e.g. an operating temperature of maximum 250°C, for example between 50 and 240°C, preferably between 140 and 220°C, for example 180°C); and/or hardness of the upper roller coating between 50 and 95 Shore A.

The improvement provided by the present invention has been demonstrated in the laboratory by the Applicant through tests carried out on the quality of the gilding and by making direct visual comparisons between various samples. The quality of the gilding was carried out using the “scotch tape” test: the deposited gilding is first scarified using a cutter, a piece of tape is pressed onto the gilding and then quickly torn off; if the adhesive does not remove the gilding, its adhesion is considered satisfactory.

The substrate may be selected from a large number of materials and not be considered limited to materials frequently used in standard printing and/or personalization devices such as paper, cardboard and plastic substrates. Non-limiting examples include metal, paper, non-woven fabric, plastic, for example a methacrylic copolymer resin, polyester, polycarbonate, polyethylene, polypropylene, polystyrene and/or polyvinyl chloride, or even cellulosic-type materials such as, for example, wood, plywood, or crystalline materials such as glass or ceramics, for example. The invention therefore also applies to any combination of these materials, such as, for example, complex materials comprising one or more of these components such as, for example, milk cartons.

According to the present invention, the substrate (sheet, card, etc.) is generally in a rectangular or square shape. This sheet moves, generally by means of a substrate transport system in a printing machine, along a transport path oriented along a longitudinal axis from at least one input magazine providing the printable substrates and/or customizable, up to at least one output magazine receiving the printed and/or customized substrates. The “side edges” of the substrate are therefore the two edges located on either side of this longitudinal axis; the front and/or rear edges are its transverse edges.

The present invention relates to a method and/or a system for gilding. The present invention also relates to a method and/or a printing system comprising gilding the substrate. Any gilding technique suitable for the method of the present invention may be used. However, according to certain preferred embodiments of the present invention, the cold foil transfer technique is used.

Thus, according to certain embodiments of the present invention, a gilding sheet (which is therefore part of the gilding device) is pressed against the printed areas of the substrate requiring the deposition of said gilding. This contact between the gilding sheet and the substrate is generally carried out by means of two rollers between which the substrate and the gilding sheet are brought into contact.

In order to ensure optimum detachment of the gilding film and its adhesion to the printed areas of the substrate, an adhesive will preferably be used. This adhesive may either be positioned on the printed areas (before applying the gilding) or be an integral part of the gilding leaf itself. In certain embodiments adapted to the present invention, a gilding leaf is used which incorporates an adhesive film (which will be pressed against the areas to be gilded) and an adhesive (the same or different) is previously applied to the printed areas (before applying the gilding). In other embodiments of the present invention, an ink and/or varnish used for printing make it possible to already give the areas intended to be covered with gilding an adhesive property; this latter option is particularly advantageous because it makes it possible to avoid adding glue to the areas to be gilded and/or to use gilding leaves without an adhesive film.

Finally, according to certain embodiments of the present invention, the gilding technique may also comprise an activation step (for example by means of UV rays) making it possible to crosslink the ink and/or the varnish and/or the glue and thus improve the adhesion between the gilding sheet and the raised areas of the substrate.

It will be obvious to those skilled in the art that the words "gilding" and "gilding" used in the present invention are not limited to the use of gold leaf and that any "gilding" device may be used. These terms of course cover all types of decorative foils (sometimes also called metal foils) among which we can cite, as illustrative and non-limiting examples, aluminum, chrome, gold, silver, copper or even salts of optically active metals. In general, a gilding foil pressed against the substrate to be personalized is used, and the present application therefore designates by this term the general use of a gilding device.

The gilding sheets used in the present invention are generally supplied in the form of a roll of width substantially equivalent to the transverse dimension of the substrate.

• une pellicule d'adhésif (optionnelle mais préférée). Cette pellicule peut comprendre tout type de résine et/ou de cire et/ou de charge et peut aussi transiter vers un état collant sous l'effet de traitement thermique. Elle peut avoir une épaisseur qui est généralement comprise entre 0.5 et 5 microns ; et/ou
• au moins une pellicule de dorure, et
• une pellicule de protection (optionnelle mais préférée) aussi appelée de laquage et/ou de couleur (qui peut aussi comprendre tout type de colorant et/ou pigment et/ou agent de matage ou brillant). Cette pellicule de protection peut être caractérisée par de nombreuses propriétés en fonction de l'utilisation recherchée, que ce soit des propriétés de résistance chimique et/ou physique ; et/ou
• une pellicule de décollement (optionnelle mais préférée) aussi appelée de libération (« release layer »). Cette pellicule est généralement très fine (d'une épaisseur habituellement inferieure a 0.1 micron) et elle peut être constituée à titre d'exemple à partir de résines et/ou de cires solubles dans des solvants ; et/ou
• une couche dite de transport qui permet le transport de la feuille de dorure. Cette couche a une épaisseur qui est généralement comprise entre 5 et 50 microns. Elle est généralement constituée de films de polyester.

The gilding leaves used in the context of the present invention are generally made up of several superimposed films. As a non-limiting, non-exhaustive example in the order of attachment to the substrate to be gilded, the following will be cited:

• an adhesive film (optional but preferred). This film may comprise any type of resin and/or wax and/or filler and may also transition to a tacky state under the effect of heat treatment. It may have a thickness which is generally between 0.5 and 5 microns; and/or
• at least one layer of gilding, and
• a protective film (optional but preferred) also called lacquering and/or color (which can also include any type of dye and/or pigment and/or matting or gloss agent). This protective film can be characterized by many properties depending on the intended use, whether chemical and/or physical resistance properties; and/or
• a release layer (optional but preferred). This layer is generally very thin (usually less than 0.1 micron thick) and may be made, for example, from resins and/or waxes soluble in solvents; and/or
• a so-called transport layer which allows the transport of the gilding leaf. This layer has a thickness which is generally between 5 and 50 microns. It is generally made of polyester films.

The printing method according to the present invention generally relates to inkjet printing of a substrate which highlights areas intended to be covered with a gold foil. Inkjet printing is well known to those skilled in the art.

The areas can be any shape, for example dots, letters and/or any other geometric shapes. They can be made of different materials, for example inks and/or varnishes. They can also be covered with a layer of material, for example covered with glue, before the gilding step; however, according to certain embodiments of the present invention, the gilding step is carried out directly on the ink and/or varnish deposited by inkjet.

The relief of said areas intended to be covered with a gilding leaf preferably represents a thickness of the order of a micron, preferably greater than five microns, or even greater than ten microns. This thickness - of whatever material previously deposited on the substrate; for example varnish and/or ink - is generally less than a millimeter for relief printing. However, the present invention could also be applied to substrates that have been printed by 3D technology using inkjet printing (and/or varnish) in successive layers and thus have thicknesses of up to several centimeters, for example less than 2 cm.

It is understood from the above that the present invention also relates to at least one printing and/or personalization device (or system) comprising means for implementing at least one of the methods described in the present application. Thanks to the functional considerations provided in the present application, it is understood that such systems or devices comprise means for performing the functions described with reference to the method and that it is not necessary to detail these means.

The present application describes various technical features and advantages with reference to the figures and/or to various embodiments. The skilled person will understand that the technical features of a given embodiment can in fact be combined with features of another embodiment unless the opposite is explicitly mentioned or it is obvious that these features are incompatible or that the combination does not provide a solution to at least one of the technical problems mentioned in the present application. Furthermore, the technical features described in a given embodiment can be isolated from the other features of this embodiment unless the opposite is explicitly mentioned.

It should be apparent to those skilled in the art that the present invention permits embodiments in many other specific forms without departing from the scope of the invention as claimed. Accordingly, the present embodiments are to be considered illustrative, but may be modified within the scope defined by the scope of the appended claims, and the invention is not to be limited to the details given above.

Claims (9)

1. Process for printing a substrate and customization of said substrate by gilding comprising an ink jet printing step for the substrate that prints in relief on areas on the substrate, areas that are then coated with a gilding foil by applying pressure between the areas of the substrate to be gilded and a gilding foil comprising a gilding film and a transport layer characterized in that the step to apply the pressure and place the gilding film and the step to separate the gilding film from the foil transport layer is followed by an additional and consecutive step of applying pressure to the areas of the gilding film-coated substrate and of increase in the temperature of the gilding film.
2. Process in accordance with the foregoing Claim characterized in that the gilding foil consists of several superposed films comprising

   a an optional adhesive film,

   b at least one gilding film,

   c. one optional protective film,

   d. a release film, and

   e. at least one transfer layer that allows transporting the gilding foil.
3. Process in accordance with any of the foregoing Claims characterized in that the pressure of the pressure step application to the areas of the substrate covered by the gilding film is adjustable and preferably falls between 1 and 10 bars, for example a pressure above 1 bar and below 10 bars.
4. Process in accordance with any of the foregoing Claims characterized in that the temperature is adjustable and is preferably comprised between 50 and 240°C, for example, comprised between 140 and 220°C.
5. Process according to any of the foregoing Claims characterized in that the relief of said printed areas on the substrate has a thickness greater than one micron, preferably greater than five microns.
6. System for printing a substrate and customization of said substrate by gilding comprising an ink jet printing group adapted to print in relief areas by means of ink and/or varnish and system for gilding a substrate comprising at least one group to apply pressure and place the gilding film suitable for applying pressure between the areas of the substrate to be gilded and a gilding foil comprising a gilding film and a transport layer characterized in that it comprises at least one pressure group comprising a heating device located downstream from the group to apply pressure and place the gilding film and the means to separate the gilding foil from the foil transport layer, and adapted to apply pressure to the areas of the substrate covered with gilding film.
7. System according to the foregoing Claim characterized in that the pressure group is made up of a minimum of two motorized rollers, installed opposite each other, rotating in opposite directions, and whose distance is adjustable so as to adapt to the different thicknesses of the substrate.
8. System according to Claim 7, characterized in that the heating device is integrated into the upper motorized roller.
9. System according to any of Claims 7 to 8, characterized in that the hardness of the upper roller coating is between 50 and 95 Shore A.

Images