WO2007128781A1

WO2007128781A1 - Information printing method by means of transfer to a printing medium

Info

Publication number: WO2007128781A1
Application number: PCT/EP2007/054315
Authority: WO
Inventors: Paul Morgavi; Philippe Sarra-Bournet
Original assignee: Impika
Priority date: 2006-05-04
Filing date: 2007-05-03
Publication date: 2007-11-15
Also published as: EP2051858B1; FR2900594B1; PT2051858E; FR2900594A1; ES2395852T3; EP2051858A1

Abstract

The invention relates to a printing method by means of transfer to a printing medium comprising the application (20) of ink to a surface of a blanket and the transfer (40) to the printing medium of the ink applied to the surface of the blanket by means of direct contact between the blanket and the printing medium, the surface (12) of the blanket (13) comprising a liquid reception layer (11) to encapsulate the ink applied to the surface (12) of the blanket (13) during the application step (20), said liquid reception layer (11) being transferred with the ink, to the printing medium (41), during the transfer step. The invention is particularly applicable to ink jet printing and printing using digital data.

Description

METHOD FOR PRINTING INFORMATION BY TRANSFERRING ON A PRINTING MEDIUM

The present invention relates to the general technical field of printing information, variable or identical from one printing to the next, on a print medium. The print medium may for example be an object to decorate.

The present invention applies in particular to the field of printing using ink jet printing. More particularly, the invention relates to the field of transfer printing on a printing medium.

It is particularly suitable for printing print media that can not be directly printed because of their non-regular shape and / or surface condition, such as containers such as bottles, glasses, cases.

GENERAL PRESENTATION OF THE PRIOR ART

The printing or decorating of complex shapes or objects is generally based to date on various conventional printing processes such as flexography, offset (double offset printing) or pad printing. These processes based on the transfer of ink previously deposited on a blanket, are intended for the printing of constant patterns reproduced in large numbers (several hundreds of thousands of copies).

The principle of these methods is to use a plate engraved with the pattern to be reproduced. At first, this plate is coated with ink. Then, in a second step, the ink-coated plate is applied to the blanket which collects the ink on its surface. Thirdly, the ink collected on the surface of the blanket is transferred on the print media by calibrating the blank on the print media.

Although these technologies are well adapted to the printing of constant patterns at high volume, they do not allow the printing of variable patterns from one impression to another, typically based on digital or digital data.

The same problem arises for an impression using a screen printing technique.

Indeed, with each change of pattern, these technologies require changing the engraved plate with the pattern to reproduce or screen printing, and clean the blanket.

Direct printing methods on the print medium have therefore been implemented. These processes are more flexible and allow the printing of variable data at speeds compatible with the industrial market.

In particular, inkjet printing processes are known which make it possible to project drops of ink of different colors onto the printing medium without direct contact with it.

However, these methods do not allow the printing of printing media having a too complex form factor or a too irregular surface condition.

Indeed, if the inkjet printing processes make it possible to dispense with direct contact with the printing medium, a maximum distance between the print head and the print medium must, however, be respected. to ensure print quality compatible with the needs of the markets.

Depending on the level of quality required, the distance between the print head and the print medium should generally be between 1 and 10 millimeters. This has the disadvantage of not allowing the printing of many print media, especially containers such as vials, glasses, cases, or vacuum plastic packaging, and any printing medium having complex and / or non-linear shapes.

Other hybrid methods, to benefit from the advantages of transfer printing and inkjet printing processes, have been implemented. For example, there is known a method comprising an ink jet application on the blanket and the transfer onto the printing medium of the ink applied to the blanket by direct contact between the blanket and the printing medium.

However, these methods are very difficult to implement. Indeed, the characteristics of the inks that may be used depend on the nature of the print medium and must be in adequacy with inkjet processes and blanket transfer processes.

The general object of the invention is to provide a transfer printing method to overcome the disadvantages of existing printing processes.

In particular, an object of the present invention is to provide a printing method for printing printing media of complex and / or non-linear form, easier to implement than existing methods.

PRESENTATION OF THE INVENTION

For this purpose, according to the present invention, there is provided a method of printing by transfer on a printing medium, comprising the application of ink to a surface of a blanket and the transfer onto the printing medium of the ink. applied to the blanket surface by direct contact between the blanket and the printing medium, the blanket surface including a liquid receiving layer for encapsulating the ink applied to the blanket surface during the application step, which liquid receiving layer is transferred with the ink to the print medium during the transfer step.

Thus, the printing method according to the invention uses a blanket on a surface of which is disposed a liquid receiving layer. The liquid receiving layer allows: the encapsulation of the ink projected during the ink application step on the surface of the blanket, the easier transfer on the printing medium, the receiving layer and the the ink applied due to the liquid nature of the receiving layer, the printing medium printing of simple or complex and / or non-linear form, the protection of the printed pattern.

In the context of the present invention, provision is first and foremost to arrange the liquid receiving layer on the blanket before spraying the ink onto the blanket. In this case, the ink is more accurately projected onto or into the liquid receiving layer. However, as will be mentioned hereinafter, it is possible in the context of the present invention to envisage, first of all, arranging the ink on the blanket and then, in a second step, applying the liquid receiving layer on the blanket. same surface of the blanket, to encapsulate the ink, before effecting the transfer of the liquid receiving layer and the ink encapsulated by it, on the print medium.

In the context of the present invention, the term "liquid" means a fluid having a viscosity typically of between 20 centipoises and

15,000 centipoise, preferably between 30 centipoise and 8,000 centipoise at a temperature of 25 ° C. The liquid can be a gel.

Preferred but non-limiting aspects of the process according to the invention are the following, taken alone or in combination: the ink-applying step on the surface of the blanket uses an ink projection technique; the receiving layer is made of a material capable of picking up the drops of ink in the receiving layer during the application step, and preventing the different captured drops from mixing; the receiving layer is of UV base type (Ultra Violet application drying) or solvent base (solvent evaporation drying by application of Infra Red);

the method comprises a step of depositing the receiving layer on the surface of the blanket; the step of depositing the receiving layer on the surface of the blanket is a step of depositing by spraying, pressure spraying or transfer by contact;

the process comprises a fixing or drying step, for example by heating or UV application; the fixing step is carried out at least partially on the blanket;

the fixing step is carried out at least partially on the printing medium;

the fixing step is carried out before and / or after the transfer step;

the fixing step is a step of fixing the ink and / or the receiving layer;

the receiving layer and the ink applied to the surface of the blanket are of different natures; the fixing steps, respectively of the receiving layer and the ink, implement different processes or technologies, for example and without limitation infrared heating drying for the ink and crosslinking or polymerization by applying ultraviolet for the receiving liquid layer, or vice versa. The invention also relates to a blanket for transfer printing on a printing medium, the blanket comprising a liquid receiving layer as described above.

The invention also relates to a printing medium obtained by the method described above.

PRESENTATION OF FIGURES

Other features, objects and advantages of the present invention will become apparent from the description which follows, which is purely illustrative and not limiting and should be read with reference to the accompanying drawings, in which: FIG. 1 illustrates the various steps of the process according to the invention; FIG. 2 illustrates a step of depositing a liquid receiving layer on a surface of a blanket,

FIGS. 3, 4 and 5 illustrate ink-jet ink application steps on the surface of the blanket previously coated with the reception layer, FIG. 6 illustrates a step of transferring the reception layer and projected ink on the print media,

- Figure 7 illustrates an alternative embodiment in which the liquid receiving layer is deposited on the surface of the blanket, after the ink.

DESCRIPTION OF THE INVENTION

Referring to Figure 1, there is illustrated the various steps of the method according to an implementation of the invention. The method according to the invention is a transfer printing method on a printing medium 41. This "print medium" 41 corresponds to the object to be printed.

The print medium 41 may be any type of medium to be printed. The print medium 41 may be of any shape and of any complexity. For example, the printing medium 41 may be a container such as a bottle, glass or case or any other type of packaging, for example plastic.

The printing process comprises the steps of: - applying ink to a surface 12 of a blanket 13 and

- Transfer 40 on the printing medium 41, the ink previously applied to the surface 12 of the blanket 13, by direct contact between the blanket 13 and the printing medium 41. The main feature of the method according to the invention illustrated in Figure 1 is that the surface 12 of the blanket 13 comprises a liquid layer

11 to receive the ink applied during the application step 20.

More precisely, the printing method illustrated in FIG. 1 comprises, prior to the ink application step, a step 10 of depositing the liquid receiving layer 11 on the surface 12 of the blanket 13.

Thus, the receiving liquid layer 11 receives the ink during the ink application step.

However, alternatively, as mentioned above, the ink can be applied to the surface 12 of the blanket 13, before the liquid receiving layer 11.

Furthermore, the method may comprise a step 30 involved in fixing or drying the ink, prior to the transfer step 40, to at least partially dry the ink. This step 30 may implement for example a heating or ultraviolet application. After the transfer step 40 of the receiving layer 11 and the applied ink, the method may comprise an ultimate step of fixation 50, for example by heating or ultraviolet application, the receiving layer and the ink applied.

The method according to the invention uses a liquid intermediate layer 11 for receiving the ink typically applied by inkjet, so that the ink is transferred onto the printing medium at the same time as the liquid receiving layer 11. As previously described, in the context of the present invention, the liquid intermediate layer 11 may be deposited on a blanket before or after the ink. Once transferred, the receiving layer 11 and the applied ink are fixed, for example by heating or ultraviolet application, on the printing medium.

This method is advantageous when the direct printing on the print medium is impossible for geometric, mechanical or other reasons (impossibility of placing the printing device sufficiently close to the print medium, non-plane print medium, etc. .). According to a nonlimiting, but advantageous, implementation of the present invention, the liquid receiving layer 11 and the ink are of different chemical nature so that their attachment or drying can be operated using different respective processes. Thus fixing or drying one does not affect the other. In particular, it is possible to fix the ink before fixing the liquid receiving layer. In this case the fixing of the ink is performed in a receiving layer still in the liquid state. Such a method makes it possible to control a certain diffusion of the ink within the receiving layer. In particular, it allows a good final print resolution, a good color rendering and a printing constant over time.

As a variant, however, and in particular depending on the desired final printing result, it is conceivable to fix the ink after the liquid receiving layer.

The different steps of the process according to the invention will now be described in more detail. Step 10 of depositing the receiving layer on the surface of the blanket

With reference to FIG. 2, the deposition step 10 of the receiving layer 11 on the surface 12 of the blanket 13 is illustrated. The blanket 13 is for example an element made of elastomer material intended for the transfer of the ink onto the print media.

The shape of the blanket 13 is any at once as to its contour and the geometry of its surface. This form depends on the form of the print media to be printed. For example, in one embodiment, the blanket 13 is planar, i.e. two-dimensional as shown in FIGS. 2, 3, 5 and 6. In another embodiment, the blanket 13 is three-dimensional shape, for example in sphere portion as illustrated in Figure 4.

The deposition step 10 of the receiving layer 11 can be performed using different techniques.

For example, in some embodiments, the deposit 10 is made by screen printing or transfer by contact, in particular by offset (double offset printing process).

In another embodiment, the deposition step 10 is performed using pressurized spray technology (or spray technology).

In yet another embodiment, the deposition step 10 is performed by projection using inkjet technology.

The liquid material constituting the receiving layer 11 is introduced into means for projecting a liquid material. These means project the liquid material onto the surface 12 of the blanket 13: the receiving layer 11 is formed.

The use of ink jet technology (ie inkjet technology) for the deposition of the receiving layer 11 makes it possible to better control the quantity of liquid material projected onto the surface 12 of the blanket 13. This allows better control of the thickness of the receiving layer 11 and thus optimize the final result.

The thickness of the receiving layer to be deposited is typically but not limited to between 5 and 80 μm. It will be noted that, preferably, the thickness of the receiving layer is greater than the diameter of the drops of ink applied. Alternatively, however, it can be envisaged that the thickness of the receiving layer is equal to or of the same order of magnitude as the diameter of these drops.

In some embodiments, the receiving layer 11 is transparent. In other embodiments, the receiving layer is translucent. In any case, when the ink is applied to the receiving layer 11 after application of the receiving layer 11 itself to the blanket 13, care will be taken that the receiving layer 11 is not opaque, especially in controlling the thickness of the receiving layer 11, since the latter ultimately covers the ink, on the object to be printed or decorated.

The receiving layer 11 may be identical in nature or different from the ink applied to the surface 12 of the blanket 13, as mentioned above. This makes it possible to create various graphic rendering effects.

The receiving layer 11 may typically have a viscosity of between 20 centipoise and 15,000 centipoise, preferably between 30 centipoise and 8,000 centipoise, a density of between 0.8 and 1.5, a surface tension between 25 and 72 dyne / cm. Moreover, in the context of the present invention, in order to correctly control the kinetic energy of the ink drops, during the application thereof, and consequently the depth of penetration of the ink into the receiving layer 11, the speed of the drops of ink during their application is preferably and not limited to between 3 and 15 m / sec. The material constituting the receiving layer 11 is for example of UV base type (drying by crosslinking or polymerization by application of Ultra Violet), solvent base (drying by solvent evaporation by application of Infra Red), water base or oil base . It may for example be based on acrylate or epoxide.

It is the same for the ink.

Step 20 of applying the ink to the blanket 13

With reference to FIGS. 3 to 5, process ink step 20 is illustrated.

The ink-applying step 20 is, for example, a jet ink-applying step of projecting ink (s) onto the blanket 13 by means of printing heads 21. During this step, the image to be reproduced on the print medium is applied to the blanket 13.

More specifically, as indicated above, the ink application step 20 can be performed either on the receiving layer 11 previously applied to the surface 12 of the blanket 13, or directly on the surface 12 of the blanket 13. , before application of the receiving layer

11 on the latter, in which case the receiving layer 11 is subsequently deposited on the blanket 13 to ensure the encapsulation of the ink and its transfer to the object to be printed or decorated.

According to the physical properties of the receiving layer 11, when the ink is projected onto the receiving layer 11 previously applied to the blanket 13, the ink drops projected on the surface 12 of the blanket 13 will either:

remain on the surface of the receiving layer 11,

- be captured in the receiving layer 11. It will therefore be understood in the context of the present description that the expression "applying an ink to the surface 12 of the blanket 13" encompasses all the above variants.

The image to be reproduced can be a motif and / or text. This image can be monochromatic or in color.

Care should be taken to treat the print image (negative) so that it appears in the correct reading direction when transferred to the print medium (mirror effect).

The ink application step 20 may implement different application techniques depending on the size of the print medium to be printed.

In an embodiment illustrated in FIG. 3, the application technique used is a single-pass application technique.

In this case, the blanket 13 passes once under the printing heads 21. The blanket 13 is for example arranged on a conveyor

22, a portion of the conveyor 22 being disposed under the printing heads 21.

The conveyor 22 moves in a direction of displacement D so that the surface 12 of the blanket 13 (previously comprising the receiving layer 11 or intended to subsequently receive this receiving layer 11) passes under the print heads 21.

The printheads 21 project ink (or inks) on the surface 12 of the blanket 13 (more precisely as the case on the receiving layer 11 or directly on the surface 12 itself): the image to transfer on the print medium is applied to the surface 12 of the blanket 13.

In another embodiment illustrated in FIG. 4, the application technique used is a multi-pass application technique.

In this case, the blanket 13 must pass several times under the print heads 21 so that the image is applied completely on the surface

12 blanket 13. The blanket 13 is for example disposed on a face of a cylinder 23, a portion of which is disposed under the printing heads 21. The cylinder 23 is rotated R around a shaft extending along the axis of symmetry of the cylinder 23, so that the surface 12 of the blanket 13 comprising the receiving layer 11 passes several times under the printing heads 21.

In the embodiment illustrated in FIG. 5, the material constituting the receiving layer 11 is able to capture the ink drops 24 projected onto the surface 12 of the blanket 13 during the application step 20 by virtue of the physical properties. of viscosity, density and surface tension mentioned above and this in combination with the control of the speed of ink drops as also mentioned above.

These physical properties make the receiving layer 11 capable of preventing two different drops from mixing.

This allows the encapsulation of projected ink drops 24, either directly on the surface or in the receiving layer 11, or on the bare surface 12 of the blanket 13 before integration into the receiving layer.

11 formed later, which facilitates the transfer of the image on the print medium 41.

The receiving layer 11 capable of receiving, on its surface or inside thereof, the applied ink, allows the protection of the printed pattern once the decoration is fixed on the printing medium.

Transfer step 40 on the print medium, the receiving layer and the ink applied

When the surface or the inside of the receiving layer 11 disposed at the surface 12 of the blanket 13 has been entirely decorated by the printing heads 21, it is necessary to postpone, on the support 41, the assembly consisting of the receiving layer 11 and the ink applied.

The transfer step 40 comprises the application of a pressure P on the printing medium 41 thanks to the blanket 13. The application of a pressure P makes it possible to ensure that the contact between the blanket 13 and the support printing 41 is sufficient for the entire receiving layer 11 including the applied ink to be transferred (ie transferred) onto the printing medium 41.

The pressure P exerted must be precise and constant to ensure a good and uniform print quality on the print medium 41.

In the case where the transfer step 40, on the printing medium 41, the receiving layer 11 and the ink applied, requires the displacement of both the blanket 13 and the printing medium 41, such as that the embodiment illustrated in Figure 6, these movements are perfectly synchronized.

In other words, the speeds V1 and V2 of displacement of the print medium 41 and the blanket 13 are equal. This makes it possible to prevent the blanket 13 from sliding with respect to the printing medium 41, a slippage which would cause a deformation of the printed image.

Step (30, 50) for fixing the receiving layer and the ink on the printing medium

In some embodiments, the method includes a step of fixing the ink and / or the receiving layer. Such a fixing step, essentially intended to dry the ink and / or the receiving layer can implement different technologies, for example a solvent evaporation by heating or a crosslinking or polymerization by ultraviolet application. The fixing step makes it possible to harden the receiving layer 11 and / or the ink applied to the printing medium 41. This has the advantage of ensuring a great durability for the printing performed.

The fixing, in particular of the ink, may comprise a single step, carried out either on the printing medium 41 or upstream on the blanket 13.

It may also comprise two successive steps: a preliminary step, preferably carried out on the blanket, prefixing or partial fixing, followed by a final fixing step, preferably performed on the printing medium 41. Moreover, according to the technology used, the fixing can be performed either by application of a treatment, for example ultraviolet application, directly on the receiving layer 11 and / or the ink, or by application of a treatment, for example a heating, on a support of the receiving layer 11 and / or the ink, namely the blanket 13 or the printing medium 41 (in the latter case the printing medium 41 may be heated before, during and / or after the transfer).

Thus, in certain embodiments, the fixing step, at least of the ink, is carried out only before the transfer step.

In this case, the fixing step 30 can be carried out by heating the blanket 13 or the printing medium, or ultraviolet application on the receiving layer 11 and / or the ink.

In the case where the fixing step is performed by heating the blanket, this step allows to partially dry the receiving layer 11 and / or the ink applied. In the case where the fixing step is performed by heating the printing medium 41, this step allows, during the transfer step 40 or after this transfer step, to partially dry the ink and / or the layer reception 11.

Furthermore, if the ink has remained on the surface of the receiving layer 11 previously applied to the blanket 13, the method may comprise a step of removing the receiving layer 11 after the step 40 so that only the applied ink is printed on the print medium 41.

In some embodiments, the fixing step 50 is performed only after the transfer step 40, for example when the ink applied is in the receiving layer 11. This step is carried out for example by heating the support of 41 printing or ultraviolet application.

Finally, in some embodiments, the fixing step is carried out before and after the transfer step 40. In this case, the prefixing step 30 performed before the transfer step 40 allows for example fixing at least partial of the ink applied, and the fixing step 50 performed after the transfer step 40 essentially allows the attachment of the receiving layer 11.

In a particularly advantageous embodiment of the invention, the chemical natures of the receiving layer 11 and the applied ink are different, so that the treatment to be applied to the receiving layer 11 to fix it is different from the treatment. to be applied to the ink to fix it (for example, the fixing temperatures or the UV wavelengths for a crosslinking, respectively of the ink and of the receiving layer, are different).

In this case, the fixing of the assembly consisting of the receiving layer 11 and the ink is achieved by two different types of means, for example a means for the emission of radiation

UV for effecting a crosslinking or polymerization and means for heating for example by emitting infrared radiation.

As a result, the print can be frozen in the receiving layer 11 without cross-linking thereof.

In this way, it is possible to carry out a fixing operation of the ink applied before the transfer step 40, then a step of fixing the receiving layer 11 after the transfer step on the printing medium

41. It should be noted that when the applied ink is located on the surface or in the receiving layer 11 previously deposited on the blanket 13, this receiving layer 11 also acts as a protective layer, after transfer onto the support of impression. In addition, this makes it possible to increase the quality of the aesthetic appearance of the impression made on the printing medium 41.

The process described above has many advantages. It makes it possible in particular to produce variable data prints at industrially acceptable rates, contrary, for example, to conventional ink transfer printing methods previously deposited on a blanket, since the method according to the invention does not require changing a plate. engraved with the pattern to be reproduced, unlike conventional methods of transfer printing.

The surface step, and in particular the surface tension, of the blanket is chosen / adapted according to any technique known to those skilled in the art to facilitate the transfer of the protective layer and the ink towards the object to decorate.

REFERENCES

Depositing a liquid receiving layer on a surface of a blanket, applying ink to the surface of a blanket (comprising the receiving layer or alternatively for subsequently receiving such a receiving layer),

Fixing step or prefixation,

Transfer on a printing medium of the liquid reception layer and the ink applied,

50 Fixing the receiving layer and / or the ink applied to the printing medium,

11 receiving layer, 12 surface of the blanket,

13 blanket,

21 print head,

22 conveyor 23 cylinder

24 ink droplet 41 print medium, D direction of movement, R direction of rotation, P pressure.

Claims

A method of transfer printing on a print medium (41) comprising applying ink (20) to a surface (12) of a blanket (13) and transferring (40) to the carrier printing (41) the ink applied to the surface (12) of the blanket (13) by direct contact between the blanket (13) and the printing medium (41), characterized in that the surface (12) of the blanket (13) comprises a liquid receiving layer (11) for encapsulating the ink applied to the surface (12) of the blanket (13) during the application step (20), which liquid receiving layer (11) is transferred with the ink to the print medium (41) during the transfer step.

2. Printing method according to the preceding claim, characterized in that the ink application step (20) on the surface (12) of the blanket (13) uses an ink projection technique.

3. Printing method according to one of the preceding claims, characterized in that the method comprises a step of depositing (10) the receiving layer (11) on the surface (12) of the blanket (13).

4. Printing method according to one of the preceding claims, characterized in that the method comprises a step of depositing (10) the receiving layer (11) on the surface (12) of the blanket (13) before the ink application (20).

5. Printing method according to one of claims 1 to 3, characterized in that the method comprises a step of deposition (10) of the layer receiving (11) on the surface (12) of the blanket (13) after the application (20) of ink.

6. Printing method according to one of the preceding claims, characterized in that the receiving layer (11) and the ink are of different nature.

7. Method according to one of the preceding claims, characterized in that the method comprises a step of fixing (30, 50) the ink and / or the receiving layer (11).

8. Method according to one of the preceding claims, characterized in that the method comprises separate fixing steps (30, 50) of the ink and the receiving layer (11).

9. Method according to one of the preceding claims, characterized in that the method comprises a step of fixing (30, 50) the ink and / or the receiving layer (11) which is divided into two sub-steps: a step of prefixing and a final fixing step.

10. Method according to one of the preceding claims, characterized in that the method comprises a step of fixing (30, 50) the ink and / or the receiving layer (11) by applying a treatment on the ink and / or on the receiving layer or by application of a treatment on a support (13, 41) of that (s) -ci.

11. Method according to one of the preceding claims, characterized in that a fixing step (30, 50) is performed at least partially on the blanket (13).

12. Method according to one of the preceding claims, characterized in that a fixing step (30, 50) is performed at least partially on the printing medium (41).

13. Method according to one of the preceding claims, characterized in that a fixing step (30, 50) is performed before and / or after the transfer step (40).

14. Method according to one of the preceding claims, characterized in that it comprises a fixing step (30, 50) performed by heating, for example by infrared application, or by crosslinking, for example by ultraviolet application. .

15. Printing method according to one of the preceding claims, characterized in that the receiving layer (11) is of a material adapted to prevent the different ink drops are mixed.

Printing method according to one of the preceding claims, characterized in that the receiving layer (11) and / or the ink is selected from the group comprising a UV base type, solvent base, water base or oil base. .

17. Printing method according to one of the preceding claims, characterized in that it comprises a step of depositing (10) the receiving layer (11) on the surface (12) of the blanket (13) selected in the group comprising a projection, a pressure spray or a contact transfer.

Blanchet (13) for transfer printing on a print medium (41), characterized in that the blanket (13) comprises a liquid receiving layer (11) according to one of the preceding claims.

19. Printed print medium (41), characterized in that it is obtained by the method according to one of the preceding claims.