Membrane and method for transferring a decoration by sublimation using such a membrane

Abstract

The invention relates to a membrane suitable for decorating a substrate by a sublimation process, the membrane comprising a flexible film (11) and a seal (12), the flexible film extending in a main plane and being bordered at the periphery by the seal extending in a direction perpendicular to the main plane. The invention also relates to a system and a method for decorating a substrate by sublimation. Figure 1

Description

Title of the invention: Membrane and method for transferring a decoration by sublimation using such a membrane Technical field of the invention

[0001] The technical field of the invention relates to the decoration of objects by transferring a decoration onto the surface of the object by a sublimation process. The invention finds particular application for the decoration of objects of large dimensions and / or having three-dimensional surfaces. State of the art

[0002] In a known manner, decorating an object by sublimation consists of transferring a decoration onto a suitable surface of the object, which will subsequently be called a “substrate”. A suitable surface (or a substrate) is a surface covered with a varnish, a porous surface (for example the surface of an object made of an organic material such as wood or leather), etc. The decoration is printed on a transfer support sheet with heat-sensitive inks. The transfer is then carried out by applying the sheet to the substrate, heating the transfer support sheet to sublimate the inks and applying pressure to the support sheet to press it onto the substrate and facilitate the transfer of the sublimated inks to the substrate to be decorated.To apply uniform pressure over the entire surface of the decoration to be transferred, DI = WO0196123 proposes using a mold in the shape of the object to be decorated and a press to apply the necessary pressure while heating. However, the production of a mold is quite expensive, so that such a process is interesting for the production of large series of identical objects, but such a process is not suitable for the decoration of small series of objects or for the decoration of objects of various shapes and sizes. In addition, the size of a mold (and the associated press) that can be produced at a reasonable price is necessarily physically limited, so that this process is not relevant for the decoration of large objects, of dimensions greater than 100 cm for example.

[0003] In document D2 = WO2004106082, the transfer sheet is shaped into a pocket inside which the object to be decorated is positioned; the pocket is sealed and a vacuum is created inside the pocket so that atmospheric pressure mechanically presses the transfer support onto the outer surface of the object to be decorated during a heating step following the vacuum step, heating carried out in a closed enclosure. After transfer, the transfer support sheet is torn and discarded. This solution is advantageous for the decoration of small objects which can be enclosed in a pocket and then in an enclosure reasonable dimensions, of the order of a few centimeters or tens of centimeters, but is not suitable for decorating large objects. Statement of the invention

[0004] The invention proposes a technical solution to overcome all or part of the drawbacks set out above.

[0005] The invention firstly proposes a membrane suitable for decorating a substrate by a sublimation process, the membrane comprising a flexible film (11) and a seal (12), the flexible film extending in a main plane and being bordered at the periphery by the seal extending in a direction perpendicular to the main plane. The invention also proposes a system suitable for transferring a decoration onto a substrate by a sublimation process, the system comprising: - a sheet (20) on which the decoration to be transferred is printed with sublimable inks, - the membrane (10) of which a surface, in the main plane, is of sufficient dimensions to cover the printed sheet and of dimensions smaller than the dimensions of the substrate to be decorated with the object, - a vacuum pump (30) having a suction inlet connected to the membrane, and - a heating means (40a, 40b) adapted to apply to the sheet, at least locally, a temperature sufficient to sublimate the inks and to cause the transfer of the sublimated inks to the surface to be decorated of the object. The invention finally proposes a method for decorating a substrate, a method using a system adapted for transferring a decoration such as that described above, and a method comprising the following steps: - the decoration to be transferred is printed on the sheet (20) with sublimable inks, - the printed sheet is applied to the substrate to be decorated (50) and is covered by the membrane (10), - a vacuum is created between the membrane and the substrate to be decorated, and - the sheet is heated. The flexibility of the membrane allows you to decorate objects with a three-dimensional decorative surface, of any shape. The membrane is reusable, including for decorating objects of different shapes and / or different dimensions.

[0006] The method according to the invention does not require the use of a press to apply pressure and does not require significant means to create a vacuum under the membrane. Its implementation is therefore quite simple and inexpensive. Presentation of figures

[0007] The invention will be better understood, and other characteristics and advantages of the invention will appear in the light of the following description of examples of implementation work of the invention. These examples are given without limitation. The description should be read in conjunction with the appended drawings in which: • [Fig.l] is a perspective view of a membrane according to the invention, • [Fig.2] shows a cross-sectional diagram of a detail of the membrane of the [Fig.l], • [Fig.3] shows schematically a transfer system comprising a membrane such as that of [Fig.l], • [Fig.4] schematically shows a step of the transfer method according to the invention.

[0008] In the various figures, identical or similar elements are referenced with the same references. Detailed description

[0009] As stated above, the invention provides a membrane suitable for decorating a substrate by a sublimation process. By substrate is meant throughout the description a surface suitable for implementing a sublimation decoration process.

[0010] The membrane 10 according to the invention comprises [Fig.l] a flexible film 11 and a seal 12; the flexible film extends in a main plane and is bordered at the periphery by the seal extending in a direction perpendicular to the main plane.

[0011] The seal may have a distal end 12a rounded at least locally [Fig.2], preferably on the inner side of the membrane. Such a rounding facilitates the rotation and crushing of the seal [Fig.4] when creating a vacuum between the membrane and the substrate to be decorated, to ensure the sealing of the membrane.

[0012] The membrane also comprises a vent 14a allowing the suction of air under the membrane to create a vacuum. According to one embodiment, the vent is made in the flexible film [Fig.l]. According to another embodiment [Fig.2], [R3] the membrane comprises a pipe 14 taken in the seal 12 and opening onto an internal face of the membrane, an opening of the pipe forming the vent 14a.

[0013] The membrane is used with a system comprising [Fig.4]: - a sheet 20 on which the decoration to be transferred is printed with sublimable inks, - the membrane 10, one surface of which, in the main plane, is of sufficient dimensions to cover the printed sheet and of dimensions smaller than the dimensions of the substrate to be decorated, - a vacuum pump 30, a suction inlet of which is connected to the membrane, and - a heating means 40a, 40b adapted to apply to the sheet, at least locally, a temperature sufficient to sublimate the inks and to cause the transfer of the sublimated inks to the substrate to be decorated.

[0014] The vacuum pump is connected to the membrane by the vent 14a.

[0015] The membrane according to the invention is used to print a decoration on a substrate, with the following steps: - the decoration to be transferred is printed on the sheet 20 with sublimable inks, - the printed sheet is applied to the substrate 50 to be decorated and is covered by the membrane 10, - a vacuum is created between the membrane and the substrate to be decorated, and - the sheet is heated.

[0016] The flexible film of the membrane is for example made of a polyaddition silicone elastomer material conventionally used for prototyping. The material is chosen so that the membrane withstands a temperature of the order of 100 to 140°C and can be reused several times. Also, the material is chosen to be gas-tight to allow a vacuum to be created between the membrane and the substrate to be decorated. As a concrete example, the flexible film of the membrane can be made of polymethylvinylsiloxane.

[0017] The flexible film preferably has a thickness of between 0.5 and 4 mm. The thickness of the flexible film is chosen so that the membrane has, on the one hand, flexibility allowing it to cover three-dimensional substrates of various shapes, including substrates with significant curvatures, and on the other hand has mechanical strength allowing the same membrane to be reused to carry out several transfers. A thickness of around 2 mm is a good compromise for various applications.

[0018] The seal is preferably made of a material whose hardness is between 20 and 40 Shore A, the choice of hardness being a compromise between elasticity and mechanical strength of the seal, as for the flexible film of the membrane. The tests carried out have shown that a hardness of 30 Shore A is a good compromise for various applications.

[0019] The seal has, in a plane parallel to the main plane of the membrane, a width L [Fig.2] of between 5 and 15 mm, and preferably between 5 and 10 mm. The seal has, in a direction perpendicular to the flexible film, a height H [Fig.2] of between 5 and 17 mm and preferably between 8 and 12 mm. Preferably, the seal is a lip seal for better airtightness.

[0020] In [Fig. 1], the membrane shown has a generally rectangular shape and a prototype of such a membrane has been produced with dimensions of the order of 30 cm * 50 cm. Other shapes and other dimensions can of course be envisaged. For example, other tests have been carried out with a substantially square membrane and of dimensions of the order of 2m by 2m. The surface and dimensions of the membrane must be sufficient for the membrane to cover the sheet [Fig.3], [Fig.4] on which the decoration to be transferred is printed, said sheet having a shape and dimensions themselves adjusted according to the decoration to be transferred. And the shape and dimensions of the membrane must be adapted so that the membrane can be well pressed against the substrate to be decorated and that the vacuum can be created between the membrane and the substrate. Preferably, the shape and dimensions of the membrane are also chosen so that the edge of the membrane, and therefore the joint, [R8] have, in the main plane, a radius of curvature R [Fig.l] greater than 1mm [Fig. 1 ]. This makes it possible to minimize the risk of the joint detaching when the vacuum is created between the membrane and the substrate to be decorated.

[0021] As mentioned above, in addition to a membrane 10 such as that described above, a transfer system according to the invention comprises [Fig.4]: - a sheet 20 on which the decoration to be transferred is printed with sublimable inks, - a vacuum pump 30, a suction inlet of which is connected to the membrane, and - a heating means 40a, 40b adapted to apply to the sheet, at least locally, a temperature sufficient to sublimate the inks and to cause the transfer of the sublimated inks to the substrate to be decorated.

[0022] The transfer support sheet 20 and the sublimable inks with which the sheet is printed are elements known elsewhere for the implementation of conventional sublimation techniques; the sheet is made of a material impermeable to liquids and gases. Thus, when printing the decoration on the sheet, the liquid inks do not migrate inside the material of the sheet and, when heating the sheet, the sublimated, gaseous inks migrate towards the substrate to be decorated, without penetrating into the sheet. The sheet is placed on the object to be decorated and is covered by the membrane.

[0023] The vacuum pump 30 is also known elsewhere. It makes it possible to create a vacuum between the membrane and the substrate to be decorated so that the air located outside the membrane applies a pressure of the order of 1 bar (atmospheric pressure) uniformly over the entire membrane. The membrane thus molds itself to the shape of the substrate to be decorated, with the printed sheet pinched between the two. In [Fig. 4], the membrane 10 is shown schematically before (4a) and after (4b) having created the vacuum. The vacuum pump as well as the pipe which connects it to the membrane are in the open air and thus only undergo atmospheric pressure and a relatively low temperature, in all cases lower than the temperature applied by the heating means.

[0024] The heating means used in the context of the invention is suitable for heating, at least locally, the printed sheet to carry out the transfer by sublimation of the inks. The heating causes the transformation of the sublimable inks into gas, gases which then penetrate into the substrate to be decorated and solidify again by incorporating themselves into the structure of said substrate. The duration of the heating is of the order of 15s to 5 min, depending on the quantity of inks to be sublimated and the heating temperature.

[0025] According to one embodiment, the heating means is a heating element 40a, for example an electrical resistance in the form of a plate [Fig. 4] or in the form of a serpentine ribbon (not shown), positioned between the membrane 10 and the sheet 20; preferably, the electrical wiring elements of the ends of the heating element are also integrated between the membrane and the sheet so that the seal can be maintained during vacuum application. Heating directly at the core of the membrane has the advantage of ensuring uniform distribution of heat over the entire surface covered with the substrate to be decorated, which makes it possible to obtain an excellent, homogeneous and high-quality transfer.

[0026] This method of implementation, however, has limitations, mainly related to the dependence between the membrane and the heating element. Indeed, the flexibility and suppleness of the membrane / heating element assembly are reduced so that the assembly may have difficulty adapting to substrates with abrupt changes in angle or very pronounced curves, especially if the angle exceeds 30°. The relative rigidity of the membrane / heating element assembly may cause difficulties in maintaining close and uniform contact between the membrane and the substrate to be decorated; this may result in poorly printed areas or deformations of the transferred decoration on substrates with complex shapes.

[0027] According to another embodiment, the heating means 40b [Fig. 4] is adapted to produce a blast of hot air applied to the outer surface of the membrane, which has several advantages. First of all, the design and production of the membrane itself are simplified because it is not necessary to integrate a heating element and the associated electrical wiring in or under the membrane. The membrane is more flexible and more flexible than a membrane / heating element assembly; handling of the membrane and its installation are made possible even on substrates whose surface has greater changes in angles, up to 180°. The membrane is thus more adaptable to complex substrates to be decorated, such as substrates having curved shapes or having reliefs.Then, the use of a blast of hot air allows the creation of a thermal flow between the heat source and the membrane with very little inertia. This thermal flow allows the heating and then cooling phases to be managed much more precisely. cooling throughout the transfer. By controlling the cooling, the solidification of the sublimated inks can be influenced. This can improve the quality of the transfer, ensure optimal fixation of the inks in the target material and avoid possible defects linked to improper cooling. Finally, it is possible to optimally and easily adjust the heated area of the membrane, thus making it possible to transfer both small and larger decorations with the same membrane. The hot air flow can be applied, for example, with a heat gun carried by a cobot; the gun can thus be moved to transfer large decorations step by step, in the order of 50 cm to 5 m for example, onto large objects such as motor vehicles or even building walls.

[0028] Preferably, the heating is carried out so that a temperature of the substrate to be decorated is less than 120°C and a temperature of the printed sheet is greater than a sublimation temperature of the sublimable inks.

[0029] Since such a temperature of the substrate to be decorated is not very high, the heating and cooling phases are thus rapid and easy to control. Also, with such a temperature, it is possible to decorate more fragile substrates, such as polyamide substrates. It is also possible to decorate objects covered with varnish or paint, such as automobile body parts. In this case, the sublimated inks become embedded in the varnish and / or paint, which constitute a suitable substrate for a transfer of decoration by sublimation. Finally, the inks, in particular inks without a compound capable of creating a positive azeotrope with water, are less heated and age better.Of course, the invention can also be used to transfer a decoration onto an object made of a material more usual for such a transfer, such as for example porous materials such as leather, wood, porous aluminas, etc.

[0030] In a practical implementation, it is preferable to work with a high temperature and a low quantity of heat by adjusting the temperature and the flow of hot air so as to have a temperature difference between the printed sheet and the substrate to be decorated of the order of 30°C to 60°C and preferably between 45 and 55°C. The sublimation of the inks is thus rapid.

[0031] In summary, the invention proposes a new means for decorating objects by a sublimation process, which notably provides the following technical and economic benefits: • an easy to produce and inexpensive membrane, • a versatile membrane, usable for decorating objects of various sizes and shapes, • a membrane for decorating objects with three-dimensional surfaces, including complex shapes and shapes with significant angles or curvatures, • a membrane for decorating large, even very large, objects, • an installation that does not require expensive and fixed technical means, such as pressure • a transportable installation • excellent transfer quality

[0032] Nomenclature • 10 Membrane • 11 films • 12 seals • 12a distal end • 14 pipe • 14a vent • 20 sheets • 30 vacuum pump • 40a heating element • 40b medium suitable for producing a blast of hot air • 50 substrates to decorate

Claims

Claims

1. Membrane suitable for decorating a substrate by a sublimation process, membrane comprising a flexible film (11) and a seal (12), the flexible film extending in a main plane and being bordered at the periphery by the seal extending in a direction perpendicular to the main plane.

2. A membrane according to claim 1 wherein the seal has a rounded distal end (12a).

3. Membrane according to one of the preceding claims, also comprising a pipe (14) taken in the joint and opening onto an internal face of the membrane.

4. Membrane according to one of the preceding claims in which the flexible film is made of a polyaddition silicone elastomer material, for example polymethylvinylsiloxane.

5. Membrane according to one of the preceding claims in which the film has a thickness of between 0.5 and 4 mm and preferably equal to 2 mm.

6. Membrane according to one of the preceding claims in which the seal has, in a plane parallel to the main plane of the membrane, a width (L) of between 5 and 15 mm, and preferably between 5 and 10 mm.

7. Membrane according to one of the preceding claims in which the seal has, in a direction perpendicular to the flexible film, a height (H) of between 5 and 17 mm and preferably of between 8 and 12 mm.

8. Membrane according to one of the preceding claims in which the seal has, in the main plane, a radius of curvature R greater than 70°

9. Membrane according to one of the preceding claims in which the seal is a lip seal.

10. Membrane according to one of the preceding claims in which the seal is made of a polyaddition silicone elastomer material, for example polymethylvinylsiloxane.

11. System suitable for transferring a decoration onto a substrate by a sublimation process, system comprising: - a sheet (20) on which the decoration to be transferred is printed with sublimable inks, - the membrane (10) according to one of claims 1 to 10, a membrane of which a surface, in the main plane, is of sufficient dimensions to cover the printed sheet and of dimensions smaller than the dimensions of the substrate to be decorated, - a vacuum pump (30) of which a suction inlet is connected to the membrane, and - a heating means (40a, 40b) adapted to apply to the sheet, at least locally, a temperature sufficient to sublimate the inks and to cause the transfer of the sublimated inks onto the substrate to be decorated.

12. The system of claim 11 wherein the heating means is a heating element (40a) positioned between the sheet and the membrane.

13. A system according to claim 11 wherein the heating means (40b) is adapted to produce a blast of hot air applied to an outer surface of the membrane.

14. Method for decorating a substrate, method using a system according to one of claims 11 to 13 and comprising the following steps: - the decoration to be transferred is printed on the sheet (20) with sublimable inks, - the printed sheet is applied to the substrate to be decorated (50) and is covered by the membrane (10), - a vacuum is created between the membrane and the substrate to be decorated, and - the sheet is heated.

15. A method according to claim 14 wherein the heating is carried out so that a temperature of the substrate to be decorated is less than 120°C and a temperature of the printed sheet is greater than a sublimation temperature of the sublimable inks.

16. A method according to either of claims 14 or 15, in combination with claim 13, wherein a temperature and a flow rate of the hot air are adjusted so that a temperature difference between the printed sheet and the substrate to be decorated is between 30 and 60°C, and preferably between 45 and 55°C.

17. A method according to any one of claims 14 to 16 wherein the vacuum is maintained while the sheet is being heated.

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