WO2000047423A1

WO2000047423A1 - Transfer-sublimation method for decorating a plastic film and product thus obtained

Info

Publication number: WO2000047423A1
Application number: PCT/FR2000/000255
Authority: WO
Inventors: Michel Baquie; Florence Baquie
Original assignee: Michel Baquie; Florence Baquie
Priority date: 1999-02-08
Filing date: 2000-02-03
Publication date: 2000-08-17
Also published as: FR2789346A1; AU2445300A; FR2789346B1; EP1173335A1

Abstract

The invention relates to a method for printing a plastic film using subliming dyes wherein a) a plastic film that is to be printed is brought into contact with transfer paper and a slight amount of pressure is exerted. The transfer paper comprises a set of subliming dyes that form a coloured decoration and b) said items are heated to enable the subliming dyes to be transferred onto the thickness of the plastic film by sublimation. The invention is characterized by placing a transparent anti-adhesive screen for the sublimated gases between the plastic film and the transfer paper before the contact phase. The invention also relates to a decorated plastic material object.

Description

PROCESS FOR DECORATING A PLASTIC FILM BY TRANSFER- SUBLIMATION, AND PRODUCT THUS OBTAINED

The present invention relates to the general technical field of printing and / or decoration processes by transfer-sublimation of films or plastic products with a view to obtaining a plastic product decorated in its thickness.

The present invention relates to a process for decorating and / or printing a plastic film with sublimable dyes in which:

- a Dlastic film to be printed is brought into contact with a light pressure, with a transfer paper comprising a set of sublimable dyes forming a colored decoration,

- The whole is heated to allow, by sublimation, the transfer of sublimable dyes in the thickness of the plastic film.

It is already known to provide printing and / or decoration by transfer-sublimation of polyester and polyamide fabrics or textiles.

These synthetic fabrics or textiles, the fiber thickness of which does not exceed eight to twelve microns, are printed in a traditional manner by the also known transfer-sublimation technique consisting, from a transfer paper printed with a decoration containing in its thickness a colored decoration produced by a series of sublimable dispersed dyes, to subject the textile and the transfer paper to a slight compression simultaneously with a sublimation heat treatment taking place at a temperature between 200 ° and 230 ° C. Beforehand, the printing of the transfer paper was obtained by other known printing methods, of the offset, heliography, serigraphy, flexography, inkjet type, with inks prepared on the basis of dispersed dyes which are capable of to sublimate at the appropriate processing temperature.

During the heat treatment of a duration of the order of twenty to thirty seconds, the sublimable dyes contained on the transfer paper generate a gas flow penetrating into the mass of the textile fibers placed against the printed paper. The gas flow can then be fixed in the mass of? textile fibers by reproducing the motif or decoration previously printed on the transfer paper.

Such a process, if it turns out, will give good results. in its particular application to synthetic textiles, cannot be generalized to all types of plastic materials or films, and is limited to the printing of plastic films or materials of limited thickness.

Indeed, it turns out that such a process cannot be transposed to the decoration and / or deep printing of plastic materials of all types. In particular, this known technique is not applicable to thermosensitive plastic materials which, on the one hand, are particularly deformable at the sublimation temperature, which makes their handling extremely delicate in the context of an industrial process, and which, on the other hand, behave as a "thermal accumulator" to the detriment of the transfer paper, which influences, in a negative way, the sublimation of the dyes as well as their transfer in the plastic material.

In an attempt to solve this problem, it has already been proposed to try to decorate and / or print in depth heat-sensitive plastic materials by transfer-sublimation by operating under vacuum in order to lower the sublimation temperature. Furthermore, it has already been attempted, in order precisely to alleviate the effects of degradations and deformations of plastic materials, to carry out the sublimation transfer step at very low temperature, for example at a maximum temperature of 160 ° C., which involves prolonging, thoughtlessly, the contact time between the transfer paper and the plastic material, since the total duration of the cycle was of the order of six or seven hours.

Obviously, such practices turn out to be incompatible with a conventional industrial process due in particular to the investments and the time required. Furthermore, it turns out that the transfer of dyes is imperfect or incomplete.

The object of the present invention therefore aims to remedy the various drawbacks listed above and to propose a new printing and / or decoration process by transfer-sublimation capable of being applied to the decoration of all heat-sensitive plastic materials. , whatever their shape, composition or thickness.

Another object of the invention is to propose a new printing process particularly suitable for the deep printing of a decoration in a heat-sensitive plastic material.

Another object of the invention is to propose a new printing process which is particularly simple to implement and capable of industrial development. Another object of the invention is to propose a new printing method allowing subsequent treatment of the decorated plastic material, and in particular its conformation in space.

Another object of the invention is to propose a new printing process compatible with other treatments of the plastic material.

Another object of the invention is to propose a new decorated plastic product in which the decorated pattern obtained by sublimation transfer is printed in depth.

• The objects assigned to the invention are achieved using a process for printing a plastic film with sublimable dyes in which:

a plastic film to be printed is brought into contact with a light pressure with a transfer paper comprising a set of sublimable dyes forming a colored decoration,

the whole is heated to allow, by sublimation, the transfer of sublimable dyes in the thickness of the plastic film,

characterized in that an anti-adhesive and transparent screen is interposed with the sublimed gases between the plastic film and the transfer paper before the contacting step.

The objects assigned to the invention are achieved using a decorated plastic product capable of being obtained according to one of the steps of. process, comprising a plastic film decorated in its thickness by transfer-sublimation of dyes forming a decoration, characterized in that the decoration is printed up to a depth at least equal to 13 microns, and which can go up to a depth between 60 and 100 microns.

Other details and advantages of the invention will be described in detail in the light of the description and the illustrative examples which follow below, given by way of nonlimiting example, in which:

- Figure 1 shows, in a partial cross section, a first alternative embodiment of a printing process according to the invention.

- Figure 2 shows, in a partial cross-sectional view, a second alternative embodiment of a printing process according to the invention.

The process for printing and / or decorating a plastic film with sublimable dyes consists, according to the invention, in contacting, with slight pressure, a plastic film to be printed with a transfer paper comprising a set of dyes sublimable forming a colorful decor.

To carry out this in-depth printing step, the printing method according to the invention uses the conventional transfer-sublimation technique consisting in operating, at a temperature between approximately 200 ° and 230 ° C., the transfer of the inks sublimables contained in the transfer paper to and in the plastic film to be decorated.

Within the meaning of the invention, it will be understood under the name of “plastic film”, all types of heat-sensitive plastic compounds known to date, whatever their form and / or composition, of the type for example, polyamides, polyesters, fluorinated plastic films of the PVDF type, flocked or non-flocked plastics of all kinds, plastisols, PVC, PS and copolymers, polyvinyl acetates, polyvinyl alcohols, polybutyrols, polycarbonates, cellulose resins, pheπoplasts, UF and MF aminoplasts, polyepoxy ^' des, polypropylenes, polyethylene, resins of all kinds, without this list being exhaustive.

Generally, the plastic film to be printed or decorated will be in the form of a flat surface 1 as shown in FIG. 1, of any thickness, which can range from ten to fifteen microns up to several millimeters thick.

According to the invention, the transfer paper 2 used can be obtained by all known techniques allowing the printing of said transfer paper 2 with sublimable coloring inks forming a decoration printed on the transfer paper 2, said decoration being intended to be reproduced in the plastic film thickness 1.

In particular, transfer paper 2 can be obtained by screen printing, offset, flexography, rotogravure, etc.

According to the invention, it is necessary, to allow the sublimation transfer of the sublimable dyes 3 into the mass and thickness of the plastic film to be printed 1, to heat the assembly formed by the plastic film 1 and by the transfer paper 2 at a temperature between 200 ° and 230 ° C approximately, and this for a sufficient time, of the order of 20 to 30 seconds _.

Indeed, below the temperatures stated above, the transfer-sublimation process is carried out poorly or incompletely. Likewise, heating times greater than those stated above are incompatible with an industrial process. Furthermore, most of the known plastics are heat-sensitive and have a tendency to modify their state and physical structure, for example by softening, as soon as a temperature level close to 100 ° C. is reached. In addition, heat-sensitive plastics have the specificity of becoming particularly soft and sticky, at temperatures in the region of 200 ° to 230 ° C, which inevitably leads to sticking of the transfer paper 2 on the plastic film 1 to be decorated.

This is the reason why, according to an important characteristic of the invention, provision is made to interpose, before the step of bringing the transfer paper 2 into contact with the plastic film to be decorated 1, and before the step of heats, a non-stick, transparent screen 4 to the sublimated gas.

The interposition of a screen 4, non-stick and transparent to the sublimated gas between the plastic film 1 and the transfer paper 2 consequently makes it possible to avoid sticking of the transfer paper 2 on the plastic film to be decorated 1. while allowing optimal passage of the gas flow, since due to the heating temperature, the sublimation temperature is optimal and the opening of the pores of the plastic film 1 is also complete. This in total promotes optimal and deep penetration of sublimable inks 3.

According to an advantageous feature of the invention, the screen 4 is formed by a film of siloxane polymer.

Silicone resins (or polyorganosyloxane) have a chemical structure based on an alternation of silicon, oxygen, hydrogen, phenyl and methyl The possible formulas are therefore extremely varied and come in three forms:

- in solvent,

- as an emulsion,

- solvent-free. (WITH OR WITHOUT UV).

Each resin is composed of a base resin and a crosslinker which functions with a catalyst according to the mode of thermal condensation (tin salt catalyst) or thermal addition (platinum catalyst).

Without limitation, the following DOW CORNING (registered trademark) products can be used as siloxaπé polymer:

- emulsion: ^• Syli-off System VII 7900 range: 7921 and 7922

DOW CORNING emulsion 24

- solvent phase: Syll off System II and VI: 7046/7048

- solvent-free: Syll off System 1/600 range: 7603 and Q2 7673.

According to an alternative embodiment, the siloxane polymer film forming the screen 4 is deposited on the transfer paper 2, in the form of a thin layer, and for example of the order of 0.2 to 2 microns.

According to another alternative embodiment, it is obviously possible to deposit the siloxane polymer film forming the protective screen 4 on the plastic film to be decorated 1, also preferably in the form of a thin layer, of the from 0.2 to 2 microns, for example. The siloxane polymer can be used in the form of 100% dry matter or else can be used in the solvent phase.

In the latter case, the solvent must be chosen from among the lighter and less aggressive solvents, such as white spirit.

The siloxane polymers can optionally be used in the aqueous phase (emulsion) although this form of polymer is not particularly desirable because of the risks of deformation run by the transfer paper.

In all cases, the thickness of the siloxane polymer film must not exceed a thickness of the order of 2 microns.

As shown in Figure 1, the printing and decoration process according to the invention can be implemented in a conventional flat lay or pressing machine comprising an upper pressing part 5, and a lower part pressing 6. These pressing (and heating) elements are always positioned horizontally and thus participate in the dimensional stability of the plastic films. Each of the parts includes one or more heating elements 7. In the example shown in FIG. 1, the transfer paper 4 is positioned under the plastic film 1 to be decorated. In this way, and in particular due to the presence of a heating element 7 under the transfer paper 4, it is possible to accelerate and facilitate the phenomenon of sublimation as well as the passage of the colored inks 3 through the plastic film 1 by promoting the natural displacement of the gas flow from bottom to top. In the embodiment shown in FIG. 2, the upper and lower pressing parts 5, 6 can advantageously be covered with an anti-sticking coating 10, for example based on teflon.

As shown in FIG. 2, it is also possible, as an alternative embodiment, to arrange the plastic film to be decorated 1 under the transfer paper 2 opposite the siloxane polymer film forming the screen 4. Such an arrangement is more particularly suitable for thin plastic films 1.

As an alternative embodiment not shown in the figures, it is obviously conceivable to use so-called transfer machines commonly used for example in 'tissue transfer processing. Such machines use heated metal cylinders which provide both heating and traction and conveying of the plastic film 1 - transfer paper 2 assembly.

Whatever the type of machine used, the printing process according to the invention must make it possible to reach a heating temperature of between 200 ° and 230 ° C, such a temperature being kept within these limits for a period of between 20 and about 30 seconds.

Furthermore, the contact pressure between the plastic film 1 and the transfer paper 2 will advantageously be of the order of 1 to 2 kg / cm ² .

As a variant, it is also possible to vary the heating temperature between the upper pressing part 5 and the lower pressing part 6. Advantageously, it will be preferred to provide simultaneous heating between the upper and lower pressing parts 5, 6 in order to reduce the duration of the gas transfer while maintaining its intensity and depth.

As previously presented, all of the heat-sensitive plastic materials can be printed by sublimation-transfer using the method described. Thus, flocked or non-flocked plastic materials, plastisols, fluorinated films, of the PVDF type can be treated according to the process. However, in the case of plastisols, for example, compounds based on flexible PVC incorporating a certain amount of plasticizers, a certain number of limitations are necessary. Thus, it turns out that only plastisols comprising a plasticizer content of less than 25%, and preferably less than 20%, can be treated correctly according to the method. Indeed, a higher rate of plasticizer in PVC has the consequence of migrating the dyes and thus gradually destroying the contours of the image on the surface of the PVC, which constitutes a barrier limiting the transfer of the gaseous flow of the sublimable dyes.

In a particularly advantageous manner, it is also possible to subject the plastic film to be decorated, not simultaneously, to the heating step, to a thermoforming step.

Due to the significant penetration of the printed decoration into the plastic film 1, and for example up to a depth at least equal to 13 microns, and possibly up to a depth between 60 and 100 microns, or even more, the film plastic can be thermoformed, that is to say shaped in space. In fact, the printing depth refers to the decorated plastic product capable of being obtained according to one of the steps of the process, a particular aptitude to be thermoformed or embossed without phenomena of decoration ruptures appearing.

The method according to the invention makes it possible in particular to decorate PVDF films while allowing them to be fused (plastering) with PMMA films (polymethyl methacrylate) or with PET films C and A (polyester).

In a particularly advantageous manner, the printing method according to the invention also makes it possible, before printing, to subject the plastic film 1 to be decorated to an anti-UV surface treatment, preferably based on titanium.

The method according to the invention also advantageously makes it possible, simultaneously or not with decoration or printing, to laminate a second plastic film 12 (FIG. 1) to the face of the plastic film 1. not coming into contact with the transfer paper 4.

It turns out that due to the heating temperature reached when the transfer paper 4 and the plastic film 1 to be decorated are brought into contact, the laminating of a second plastic film 12 is preferably possible. simultaneously or by the conventional technique of heat-sealing (plaxage), _c _'are t ie without the addition of glue, or on the contrary by bonding with added adhesive.

Obviously, instead of bonding a second plastic film 12, it is also possible to attach to the plastic film 1 another material, such as a foam (polyurethane, polyethylene, etc.) or another compatible material. such as paper, cardboard, fabric, sheet metal, etc. In the particular case of printing so-called flocked plastic films, that is to say comprising a PVC film of the order of 500 microns for example, on which an adhesive is attached as well as a series of fibers, a a distinction must be made between flocked plastics based on heat-sensitive plastics and flocked films of polyamide or polyester type. Thus, in the case of flocked films based on heat-sensitive plastic, the decoration process requires the presence of a siloxane film.

On the other hand, in the case of flocked films based on polyamide or polyester, the thickness of the acrylic adhesive as well as that of the fibers is sufficient to constitute in itself a non-stick screen 4.

According to the invention, the decorated plastic product and capable of being obtained according to one of process steps comprises a heat-sensitive plastic film in its thickness decorated by sublimation dye transfer-forming -a ^• decoration, said decoration being embedded and extending from the surface to the depth of the film over a thickness of the order of 60 to 100 microns, depending on the plastic material involved.

The product thus obtained consequently presents a decoration which is protected both physically and chemically in the thickness of the plastic film 1

, which allows its thermoforming to obtain various forms, such as masks, chests, boxes, images in various three dimensions, without risk of rupture of decoration.

On the other hand, in the case of flocked films based on polyamide or polyester flock, the thickness of the fibers is sufficient to constitute in themselves a non-stick screen 4. If the flocked product is on the contrary rather flat or of the polyurethane type, it is necessary to maintain a non-stick screen 4.

In both cases, it is the flocked product that is decorated as a priority.

Claims

- Process for printing a plastic film with sublimable dyes in which:

- Printing process according to claim 1 characterized in that the screen is formed by a film of siloxane polymer.

- Printing process according to claim 2 characterized in that the siloxane polymer film is deposited on the transfer paper in the form of a layer.

- Printing process according to claim 2 characterized in that the siloxaπé polymer film is deposited on the plastic film in the form of a layer.

- Printing process according to one of claims 1 to 4 characterized in that the heating temperature is between 200 ° and 230 ° C, and is kept within these limits for a period of between approximately 20 and 30 seconds.

- Printing process according to one of claims 1 to 5 characterized in that the contact pressure between the plastic film and the transfer paper is of the order of 1 kg / cm ² to 2 kg / cm ² .

- Printing process according to one of claims 1 to 6 characterized in that the plastic film to be printed is chosen from: flocked or non-flocked plastic materials, plastisols, fluorinated films, PVDF type.

- Printing process according to claim 7 characterized in that the plastisols chosen comprise a plasticizer content of less than 25%, and preferably less than 20%.

- Printing process according to one of claims 1 to 8 characterized in that the decorated plastic film is subjected, simultaneously or not to the heating step, to a thermoforming step.

-Printing process according to one of claims 1 to 9 characterized in that prior to printing, the plastic film to be printed is subjected to an anti-UV surface treatment, preferably based on titanium.

-Printing process according to one of claims 1 to 10 characterized in that, simultaneously or not with decoration, it provides the laminating of a second plastic film on the face of the plastic film to be decorated coming from not in contact with the transfer paper. -Decorated plastic product likely to be obtained according to one of the stages of. process according to one of claims 1 to 11, comprising a plastic film decorated in its thickness by transfer-sublimation of dyes forming a decoration, characterized in that the decoration is printed to a depth at least equal to 13 microns, and up to a depth of between 60 and 100 microns.

-Decorated plastic product according to claim 12 characterized in that it is thermoformed.