EP0271941A1 - Method for manufacturing a transfer product with a protection layer, and product obtained for the protection of documents or other produce - Google Patents

Abstract

1. Process for bringing about a protective product with a protective film capable of being transferred in the cold state by simple pressure, which can be used for covering end protecting on the surface a document or other object, characterised in that it consists in producing on a non-adhesive support foil (1) an imprint (2) by means of a liquid polymerisable two-component mixture containing a hydroxylated polyol and an isocyanate or polhisocyanate so as to cause polymerisation of the mixture in situ, leading to a thin transparent polyurethane film, and in covering said film with a transparent adhesive layer (3).

Description

The invention relates to a method for producing a protective product with a transferable protective film, which can be used to cover and protect a document or other element on the surface. It extends to the protection product obtained.

It is often desirable to protect documents, in particular paper, either to protect them from external aggression factors such as humidity (maps, plans used outside ...), or to avoid that they are falsified and make them inviolable (identity papers, administrative documents ...).

Currently, such protection is obtained by hot plasticization (see for example patent FR 1,549,724); such a process requires professional equipment and its implementation is reserved for specialists. These conditions of implementation and the cost of this process limit their applications to specific narrow areas (important or valuable documents, small areas to be covered ...) and exclude a generalization to current documents. In addition, the plasticization leads to covering the document with a relatively thick layer (based on polyvinyl) and modifies the characteristics of the document which loses a large part of its flexibility and is no longer foldable or easy to handle as before.

Furthermore, in the field of decalcomation, cellulosic or nitrocellulosic transfer films are known (see for example patent FR 2 427 208) or films obtained by alkyd-urethane deposition (see for example patent US 4 308 310), which are used to fill a surface with a pattern. However, these marking films cannot be used to meet the protection objectives targeted by the invention, because they are very fragile and do not resist light solvents and, a fortiori, more powerful solvents such as cellulose diluents; in particular, these films can be easily removed without alter the support and therefore cannot constitute protection against falsification.

The present invention proposes to provide a new protection product which can be used cold by simple pressure, in the manner of a transfer film by any person without any particular material.

The essential objective of the invention is to provide a product which gives very safe protection both with regard to external stressors and against forgery; in particular, the invention aims to provide a product having a transferable protective film which is resistant to light solvents as well as to cellulosic solvents and whose elimination or attempted elimination is necessarily accompanied by destruction or very apparent alteration of the document, for most of the constituent materials and in particular for paper documents.

Another objective is to make it possible to personalize the document, by adding to it patterns or a screen, either directly visible, or invisible in sunlight but detectable under ultraviolet radiation.

Another objective is to avoid significantly modifying the physical characteristics of the protected document and in particular to preserve it with flexibility and folding possibilities similar to those which it initially possessed.

Another objective of the invention is to indicate a process for producing the targeted protection product benefiting from a low cost price, this cost, combined with the ease of implementation of the product, making it possible to generalize the use of the produced to the most common documents.

Another objective is to indicate a process suitable for obtaining transferable protective films, of various shapes depending on the envisaged end use.

To this end, the process targeted by the invention, for producing a protective product with a protective film transferable cold by simple pressure, uses as a base a layer obtained by printing using a two-component polymerizable liquid mixture containing a polyol. hydroxylated and an isocyanate or polyisocyanate, mixture capable of polymerizing in situ to result in a thin transparent layer of polyurethane.

In its simplest form of implementation, the process according to the invention for the manufacture of the protective product consists in producing a single impression on a non-stick support sheet by means of a polymerizable liquid mixture as shown below. above defined so as to obtain, after in situ polymerization, a thin transparent film of polyurethane on said support sheet, and to cover said film with a transparent adhesive layer.

In another form of implementation suitable for manufacturing a protection product making it possible to personalize a document or other element, the method according to the invention consists:
. to carry out a first continuous impression on a non-stick support sheet by means of a polymerizable liquid mixture as defined above, so as to generate the in situ polymerization of the mixture leading to a first transparent layer of polyurethane,
. before complete polymerization of this first impression, to carry out at least one intermediate impression according to a pattern or weft by means of a liquid polymerizable mixture as defined above, with the addition of a colored substance from the following group: fluorescent substance under radiation, in particular ultraviolet, invisible to light, fluorescent substance under radiation, in particular ultraviolet, visible to light, or opaque pigment, so as to cause in situ polymerization of said mixture leading to a discontinuous interlayer of polyurethane,
. before complete polymerization of the interlayer printing, to carry out a second continuous printing by means of a polymerizable liquid mixture as defined above, so as to generate the in situ polymerization of the mixture leading to a second transparent layer of polyurethane,
. finally cover the second impression with a transparent adhesive layer.

Thus, the method of the invention leads to coating by printing the support sheet with a thin polyurethane film, monolayer in the first case, multilayer in the second. Each printing can be carried out by any printing process known per se and in particular by screen printing or rotogravure. The liquid mixture used for printing is prepared beforehand in particular in a proportion of 1.8 to 2.2 doses of hydroxylated polyol for a dose of isocyanate or polyisocyanate. For example, it is possible to use a mixture of hydroxylated polyacrylic resin or hydroxylated polyester resin or hydroxylated polyether resin, and aliphatic or aromatic polyisocyanate.

This technique makes it possible to obtain watertight, extremely thin and resistant polyurethane films, the thickness of which can be adjusted in practice between 5 and 50 microns. In the case of a multilayer film obtained by several prints, the various layers adhere intimately to each other due to their simultaneous polymerization which leads to interpenetration of the polymer molecules at the interfaces: the film obtained is in reality, not a complex, but a real composite where the layers are more separable. The intermediate layer is thus strictly inaccessible.

The adhesive layer covering this film can in turn be produced, before complete polymerization of the last layer of the film, by printing the latter by means of transparent adhesive material, in particular by serigraphy or rotogravure. The adhesive material used is for example of the acrylic type known per se.

To allow subsequent use of the product by use, a silicone protective sheet (or similarly treated) is then placed over the adhesive layer to protect it until use.

A protective product is thus obtained which is in sheet form, which can be distributed to the end user and whose implementation by the latter is extremely simple and requires no equipment. To protect a document or any similar surface, just remove the silicone sheet, apply the cold product to the surface to be protected so that the adhesive layer covers this surface, exert pressure on the surface of the support sheet in order to generate the transfer, and detach said support sheet. Such a process, carried out cold without any particular precautions, can be carried out by any person without any particular skill.

Tests have shown that extremely effective document protection is achieved. Even very thin polyurethane film shields documents from external influences and is insensitive to most common solvents. The rare solvents that attack it, such as acetone, also destroy paper and similar materials, so that any attempt to alter the film to access the surface of a document thus protected leaves very visible traces.

In addition, in the case of a multilayer film, the intermediate layer located in an inaccessible position between the other two allows the documents to be protected to be tamper-proof. The colored substance placed in the polymerizable mixture of this intermediate layer will depend on the applications: invisible substance reacting to ultraviolet (or possibly infrared), visible substance undergoing a color change under radiation (ultraviolet ...), opaque substance forming a pattern or an opaque frame on the document or parts of it.

The protective film according to the invention can be easily adapted to cover and protect one or more surfaces of determined shapes; it suffices that the impression (s) by means of the polymerizable liquid mixture (s), then the impression by means of the adhesive material are carried out on one or portions of the support sheet of shapes corresponding to those of the surfaces to be protected. It should be noted that the process of the invention makes it possible to produce protective products suitable for covering large areas, and this, at a reduced cost taking into account the extreme thinness of the polyurethane film and therefore the low quantities of materials. first used.

Furthermore, it is possible where appropriate assaying the tackiness of the adhesive layer by carrying out the printing thereof on a plurality of separate areas according to the method described in patent application FR ^No. 86.05039 in the name of applicants. An adhesive screen is then obtained, the adhesive power of which is easily adjustable by adjusting the density and / or the extent of the printed adhesive zones.

• - les figures 1a, 1b, 1c illustrent, à échelle très dilatée, les étapes du procédé de réalisation d'un produit de protection conforme à l'invention, à film monocouche,
• - les figures 2a, 2b et 2c illustrent l'utilisation de ce produit,
• - les figures 3a, 3b, 3c, 3d et 3e illustrent, à échelle très dilatée, les étapes du procédé de fabrication d'un produit de protection à film multicouche.

Examples of embodiments of the invention are described in the description which follows with reference to the accompanying drawings; on these drawings:

• FIGS. 1a, 1b, 1c illustrate, on a very expanded scale, the steps of the process for producing a protection product according to the invention, with a monolayer film,
• - Figures 2a, 2b and 2c illustrate the use of this product,
• - Figures 3a, 3b, 3c, 3d and 3e illustrate, on a very expanded scale, the steps of the manufacturing process for a multilayer film protection product.

The method illustrated by way of example is implemented on screen printing machines, in particular on traditional snap-on machines (hinged screen) or on machines with a full lift screen (screen movable in translation). In the case described below where the prints have a thickness of the order of 5 to 10 microns, the two types of machine can be used interchangeably. In the case where greater thicknesses are desired (between 10 and 50 microns), we prefer to use the second type of machine which allows thicker prints to be obtained in a single pass; of course, the first type can also be used in several passes.

The monolayer film product referred to in Figures (1a-1c) comprises a transparent support sheet 1 (Figure 1a) of the so-called non-adherent type, that is to say capable of developing only weak bonding forces with most polymers. For example, this support sheet can be a polystyrene sheet with a grammage of the order of 120 g / m².

This support sheet 1 is chosen to be larger than that of the surface to be protected.

It is placed on the plate of the screen printing machine, and the screen thereof is filled with a liquid mixture previously prepared from a hydroxylated polyol and an isocyanate.

This mixture can in particular be prepared by adding two doses of hydroxylated polyacrylic resin or hydroxylated polyester resin, or of low molecular weight hydroxylated polyether resin, and a dose of aliphatic or aromatic trifunctional polyisocyanate (for example, polyacrylic resin "ref. U8560" and trimerized hexamethylene diisocyanate "ref. U8580", sold by the "CHIMITEC Laboratory").

The quantity of mixture spread on the screen printing screen is adjusted to correspond to a thickness of 8 to 10 microns.

After printing on the support sheet 1, the mixture polymerizes and gives a thin transparent polyurethane film 2. The printing is carried out in a shape corresponding to that of the surface to be protected, for example rectangular in the case shown diagrammatically in FIGS. 2a, 2b, 2c for the protection of identity cards.

During serial production, the screen printing machine is cleaned every hour to prevent screen clogging.

The support sheet 1 and its polyurethane print 2 are then left in the open air in order to allow the polymerization to start. The total duration of this is several days (of the order of 8 to 10 days).

Before reaching this complete polymerization, the assembly is replaced on the screen printing machine to make a new impression above the film 2 by means of a transparent adhesive material. Depending on the temperature conditions, the film will be allowed to polymerize between 3 and 36 hours and preferably approximately 4 or 5 hours. These periods make it possible to guarantee that the film is sufficiently dry and consistent to undergo a printing but with a polymerization still incomplete to allow better adhesion of the new printing. This will be for example performed using an acrylic adhesive material of the type sold by "TIFLEX" under the reference "acrylic adhesive". This printing is carried out on the entire surface of the film 2 in order to coat it with a transparent adhesive layer 3 (FIG. 1b) whose thickness is similar to that of the film (between 5 and 50 microns and, in the example of 8 to 10 microns).

The whole is then covered by a silicone protective sheet 4 (FIG. 1c), the grammage of which can be of the order of 145 gr / m².

The protection product thus obtained can be stored and distributed without special precautions.

In FIGS. 2a, 2b and 2c, an application of the invention has been shown diagrammatically for the protection of identity cards. This protection may be carried out by the administration responsible for establishing these cards, after the holder has affixed his signature and, where appropriate, fingerprints, at the same time as the identity card is given to him.

The protection product is shown diagrammatically in perspective in FIG. 2a, the silicone protective sheet 4 being removed.

After removing this protective sheet, the product is applied to the identity card (FIG. 2b), the impressions 2 and 3 of polyurethane and adhesive material having the shape of a rectangle of size corresponding to that of this card. These prints are matched to the surface of the card and the operator applies pressure which causes the adhesive layer 3 to adhere to the card with simultaneous transfer of the film 2.

Then just detach the support sheet 1 (Figure 2c) and the identity card is protected.

The tests are shown that the thin film 2, once it has adhered to the document thanks to the adhesive layer 3, is impossible to separate from it. Due to its excellent mechanical resistance, it cannot be locally scratched without damaging the document. In addition, tests with solvents or diluents did not make it possible to find one capable of attacking the film without damaging the document in paper. This produces a document that is extremely difficult to forge.

It should be noted that the protective film is not very visible and does not significantly modify the flexibility of the card.

Furthermore, FIGS. 3a-3e illustrate (on a larger scale) the manufacture of a protection product with a multilayer polyurethane film.

The first step (FIGS. 3a) is similar to the first step of the process already described and consists in printing on a polystyrene support sheet 5 a transparent layer of polyurethane 6 by means of a polymerizable mixture identical to that already described.

Before the polymerization of this mixture has ended, that is to say within a period of between 3 and 36 hours after this printing, a discontinuous intermediate printing 7 of drawings, patterns or screens is carried out on the first printing (FIG. 3b ). A delay of the order of 4 to 5 hours gives good results (initial printing sufficiently consistent to allow intermediate printing, while allowing close adhesion of the layers due to the simultaneous polymerization phenomena at their interface).

This intermediate printing 7 is carried out with a similar base resin to which has been added a colored substance between 2 and 50% by weight, the polyisocyanate then being mixed. For example, depending on the desired effects, one of the following substances can be added in the form of a fine powder:
- substance based on rare earths and metals, sold by "CHIMITEC" under the reference "Lumiton fluo UV codes" (between 2 and 25% by weight), in order to provide patterns invisible to sunlight, becoming fluorescent under ultraviolet radiation ,
- substance based on fluorescent organic dyes having a long series of double bonds in cyclic or benzene form, sold by "CHIMITEC" under the reference "Lumiton fluo LJ" (between 25% and 50% by weight), in order to provide patterns fluorescent in sunlight, having intense fluorescence under ultraviolet radiation with color change,
- opaque pigments based on titanium oxide or carbon black (from 5% to 25% by weight),
- transparent organic pigments based on ophthalocyanine (blue) or yellow "HANSA" (between 5% and 25% by weight).

Before complete polymerization of this intermediate printing, a second printing 8 is carried out identical to printing 6 in order to obtain a new transparent layer of polyurethane (FIG. 3c). This printing is carried out in the same time as previously (between 3 and 36 hours and preferably 4 to 5 hours after the interlayer printing).

At the end of the polymerization of the three layers 6, 7 and 8, a polyurethane composite film is obtained with an integrated pattern or weft, the layers no longer being separable. This multilayer film may in particular have a thickness of the order of 8 to 20 microns.

Printing of transparent adhesive material 9 is then carried out as previously (FIG. 3d). This impression is preferably made having complete polymerization of the layer 8 within a period of between 3 and 36 hours and preferably of the order of 4 to 5 hours.

The assembly is then covered by a silicone protective sheet 10 similar to that of the product previously described.

The protection product thus obtained can be stored and distributed without special precautions. Its use is similar to that already described for the product with a single-layer polyurethane film. It should be noted that, if necessary, several intermediate prints can be superimposed by successive passes on the machine (with a delay between passes of between 3 and 36 hours and preferably of the order of 4 to 5 hours).

Claims (16)

1 / - Method for producing a protection product with a protective film which can be cold transferred by simple pressure, which can be used to cover and protect a document or other element on the surface, characterized in that it consists in producing on an anti-support sheet -adherent (1) an impression (2) by means of a polymerizable bicomponent liquid mixture containing a hydroxylated polyol and an isocyanate or polyisocyanate so as to generate the in situ polymerization of the mixture, leading to a thin transparent film of polyurethane and to cover said film of a transparent adhesive layer (3). 2 / - Method for producing a protection product with a protective film which can be cold transferred by simple pressure, usable for covering and protecting a document or other element on the surface, characterized in that it consists:
. to carry out on a non-stick support sheet a first continuous impression by means of a polymerizable bicomponent liquid mixture containing a hydroxylated polyol and an isocyanate or polyisocyanate, so as to generate the in situ polymerization of the mixture leading to a first transparent layer of polyurethane,
. before complete polymerization of said first impression, to carry out at least one intermediate impression according to a pattern or weft by means of a polymerizable two-component liquid mixture containing a hydroxylated polyol and an isocyanate or polyisocyanate with the addition of a colored substance from the following group : fluorescent substance under radiation, in particular ultraviolet radiation, invisible to light, fluorescent substance under radiation, especially ultraviolet radiation, visible to light, or opaque pigment, so as to cause in situ polymerization of said mixture leading to a discontinuous interlayer of polyurethane,
. before complete polymerization of the interlayer printing, to carry out a second continuous printing by means of a bicomponent liquid polymerizable mixture based on hydroxylated polyol and isocyanate or polyisocyanate, so as to generate polymerization in situ of the mixture leading to a second transparent polyurethane layer,
. and covering the second impression with a transparent adhesive layer. 3 / - Method according to claim 2, in which:
. interlayer printing is carried out between 3 and 36 hours after the first printing,
. the second printing is carried out between 3 and 36 hours after the interlayer printing. 4 / - Method according to one of claims 1, 2 or 3, wherein the liquid polymerizable mixture used for each printing is a mixture of hydroxylated polyacrylic resin or hydroxylated polyester resin or hydroxylated polyether resin and aliphatic or aromatic polyisocyanate. 5 / - Method according to claim 4, wherein the polymerizable liquid mixture used for each printing is prepared by mixing between 1.8 and 2.2 doses of resin for a dose of isocyanate or polyisocyanate. 6 / - Method according to claims 2 and 5 taken together, wherein the polymerizable liquid mixture used for each interlayer printing contains between 2 and 50% of colored substance relative to the weight of resin. 7 / - Method according to one of claims 1, 2, 3, 4, 5 or 6, characeterized in that each impression by means of the polymerizable liquid mixture is carried out by screen printing or rotogravure. 8 / - Method according to claim 4, characterized in that the printing or screen printing or gravure printing are carried out so as to obtain on the support sheet (1) a film (2) having an overall thickness between 5 and 50 microns . 9 / - Method according to one of claims 7 or 8, characterized in that the transparent adhesive layer is made between 3 and 36 hours after the last printing, by printing the film in particular by screen printing or gravure printing, by means of transparent adhesive material. 10 / - Method according to claim 9, wherein the adhesive material used is of acrylic type. 11 / - Method according to one of claims 9 or 10, wherein the printing by means of adhesive material is carried out on a plurality of separate areas in order to obtain a discontinuous adhesive layer, of adjustable tackiness. 12 / - Method according to one of the preceding claims, wherein a silicone protective sheet (4) is disposed above the adhesive layer (3). 13 / - Protective product to allow a document or other element to be covered and protected on the surface, characterized in that it comprises, on the one hand, a thin polyurethane film (2), printed on an anti-support sheet adherent (1), on the other hand, a transparent adhesive layer (3) covering said film and surmounted by a silicone protective sheet (4). 14 / - Protection product according to claim 13, wherein the thin film is a transparent monolayer film. 15 / - Protective product according to claim 13, wherein the thin film is a multilayer film, comprising two transparent layers of polyurethane located on either side of a polyurethane layer containing a colored substance. 16 / - Protective product according to one of claims 13, 14 or 15, wherein the adhesive layer is an acrylic layer printed on the polyurethane film.

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