Sublimation on lacquered automotive parts

Abstract

The invention provides a method for decorating the exterior surface of a motor vehicle body panel, such as a bumper skin. The decoration method comprises the following steps: a) supplying or manufacturing (100) a body panel; b) applying (102) a layer of opaque lacquer to the body panel to form the exterior surface, said opaque lacquer comprising a polymer and pigments; c) printing (104) a decoration by ink sublimation onto the body panel; in step c) printing (104), the decoration is printed onto the exterior surface formed by the opaque lacquer layer. Figure to be published with the abstract: Figure 1

Description

Title of the invention: Sublimation on lacquered automotive parts

[0001] The invention relates to the personalized decoration of visible parts of a motor vehicle. More specifically, the invention relates to a method for decorating a body panel of a motor vehicle.

[0002] In order to personalize a motor vehicle in a specific and potentially unique way, it is advantageous to add local decoration. This enhances the perceived quality of the motor vehicle. However, decoration produced in small batches must be integrated into a large-scale production process to optimize costs.

[0003] There are various techniques for customizing the appearance of a motor vehicle. These include applying paint using a stencil and applying adhesives. However, these techniques require the application of protective coatings, which are then removed. Furthermore, they can create localized areas of excess thickness, which detracts from the overall appearance. In addition, they require further heat treatment. Finally, certain body geometries are inherently incompatible. Resistance to ultraviolet radiation and abrasion reduces the lifespan of a decoration.

[0004] To meet certain constraints, the sublimation printing process is known. This method reduces labor time and is quickly implementable.

[0005] Document FR2962941B1 describes a method for printing any type of design on a motor vehicle convertible top in order to personalize it according to the owner's choice. The method consists of printing a design onto transfer paper, then sublimating said design onto a coated high-tenacity polyester fabric, which is itself laminated to a polyamide fabric by inserting a technical foam.

[0006] The invention aims to address at least one of the problems or drawbacks encountered in the prior art. In particular, the invention aims to improve the durability of a printed decoration on a vehicle body panel. The invention also aims to optimize the resistance, cost, and gloss of a decoration for a vehicle body panel.

[0007] According to a first aspect, the invention proposes a method for decorating an external surface of a part of a motor vehicle body, the decoration method comprising the following steps: a) supplying or making a part of the body; c) printing a decoration by ink sublimation on the part of the body; remarkable in that prior to step c) printing, the process includes a step: b) application of a layer of opaque lacquer on the envelope piece in order to form the outer surface, said opaque lacquer comprising a polymer and pigments; in step c) printing, the decoration is printed on the outer surface formed by the layer of opaque lacquer.

[0008] The invention combines a decorative element with a lacquer layer that supports said element. This improves the adhesion of the element. The element becomes embedded in the lacquer layer, which strengthens and protects it. Consequently, the element becomes more durable against abrasion and detachment. Furthermore, the arrangement of the element within the lacquer layer helps maintain the smooth appearance of the outer surface, thus contributing to the perceived quality.

[0009] Document DE102007017444B4 describes a radiator grille with a support and several strips individually inserted into the substrate. Each strip is formed by an overmolded film. The coating is alternately decorated by sublimation or coated with a polymer. However, this document does not consider the combination of a lacquer coating with a sublimation-applied decoration.

[0010] US patent 11453202B2 describes a thermoformable decorative material for automotive interiors comprising: a decorative layer including a textile substrate; a digitally printed design disposed on at least one side of the textile substrate and comprising a dispersion ink and / or a pigment ink; and a superimposed adhesive coating applied to the digitally printed design. The superimposed adhesive coating includes an adhesive that comprises polyurethane and / or polyacrylate. This patent does not relate to coatings in the lacquer family.

[0011] Document WO9962722A8 describes a method for applying a decoration to the surface of an object by sublimation printing. The method uses, as an ink support or transfer sheet, a heat-shrink film printed with a sublimation ink decoration. This document does not specify a lacquer-type coating.

[0012] Document EP1439094B1 describes an exterior vehicle part comprising a decorative film. The external component consists of an injection-molded skin of a transparent or translucent thermoplastic material extending in two perpendicular directions, with a thinner layer of decorative film applied to its inner surface and attached by adhesive. This document does not provide a solution using a lacquer coating.

[0013] Document US9446599B2 describes an automated product sublimation process enabling point-of-sale customization of parameters Sublimation in a retail environment. A thermal sublimation transfer printing system is configured to print one or more images onto a transfer medium, then position the medium onto a substrate A. This document does not cover parts with a lacquer coating.

[0014] Document EP0722843B1 describes a method for decorating an article using sublimation printing. The method consists of preparing a decorated composite (5) which includes a first step in which a design is transferred by sublimation onto the first surface of a first layer of plastic material. A contrasting lacquer undercoat is added only after the sublimation transfer of the design. This document applies to skis, surfboards, and skateboards; it does not provide a solution specific to a motor vehicle.

[0015] Document WO200437555A1 describes a process for obtaining a decorative marking with good adhesion, and therefore durability. It essentially consists of pre-varnishing the surface to be decorated, then applying a thermal printing process to the varnished surface using sublimation paper pre-printed with the chosen design. The application of successive layers creates a visual effect of "Chinese lacquer" produced by the sublimation process. This process is applicable to the decorative marking of school and office supplies, for example, to decorate scissor blades. It does not involve sublimation printing on an actual layer of lacquer. This document does not relate to the automotive field.

[0016] Preferably, the opaque lacquer layer comprises a first layer against the envelope piece, a second layer opposite the first layer; the decoration being in the thickness of the second layer.

[0017] Preferably, the decoration is at a distance from the first layer.

[0018] Preferably, during step c) printing, an inflated bag exerts pressure against the envelope piece.

[0019] Preferably, step c) printing includes applying a pressure of 100 g / m2 to 200 g / m2 to the envelope piece.

[0020] Preferably, in step c) printing, the ink includes a sublimation temperature, step c) printing being carried out at a temperature between 100% and 130% of said sublimation temperature.

[0021] Preferably, step c) printing includes a temperature between 80°C and 120°.

[0022] Preferably, the envelope piece includes an edge with two opposite faces, a slice connecting the opposite faces, in step c) printing, the decoration covers the slice and the opposite faces.

[0023] Preferably, the envelope piece includes a rib; in step c) printing, the decoration covers said rib.

[0024] Preferably, following step b) application, the opaque lacquer layer has a first thickness; the decoration process further includes a step d) application of a varnish film with a second thickness less than the first thickness.

[0025] Preferably, step c) printing the decoration includes a substep c1) supplying a transfer sheet; a substep c2) printing a pattern on the transfer sheet; a substep c4) applying the transfer sheet to the envelope piece; a substep c5) heating the transfer sheet against the envelope piece; a substep c6) removing the transfer sheet.

[0026] Preferably, step c) printing of the decoration includes a substep c3) treatment of the transfer sheet in order to dry the ink.

[0027] Preferably, substep c3) treatment includes heating, exposure to ultraviolet radiation, or placement under vacuum.

[0028] Preferably, in step c) printing the decoration by sublimation, said decoration comprises several colors.

[0029] Preferably, step c) sublimation decoration printing is repeated in order to implement several decorations stacked one on top of the other.

[0030] Preferably, the envelope part is a motor vehicle bumper skin.

[0031] Preferably, the envelope piece comprises metal, plastic, wood or ceramic.

[0032] Preferably, prior to step c) printing the decoration by sublimation, the decoration process includes a substep of drying and degassing the lacquer film.

[0033] Preferably, step c) printing is carried out under vacuum.

[0034] Preferably, following step c) printing, the decoration is in the thickness of the lacquer layer.

[0035] Preferably, in step c) printing, the envelope piece includes a rib and / or a rebate covered by the decoration.

[0036] Preferably, following step c) printing, the decoration process further includes a step e) polishing of the opaque lacquer layer and / or varnish film.

[0037] Preferably, the envelope part is an inner envelope part or an outer envelope part.

[0038] According to another aspect, the invention proposes a method for decorating a body part with an exterior surface of a motor vehicle; the decoration method comprising the following steps: • a) supply or production of the envelope part; • b) application of a layer of opaque lacquer on the envelope piece in order to form an outer surface, said opaque lacquer comprising a polymer and pigments; remarkable in that, following step b) application, the decoration process includes a step • c) printing of a decoration by sublimation of ink against the outer surface of the opaque lacquer layer obtained following step b) application.

[0039] According to another aspect, the invention proposes a motor vehicle comprising a body panel with an outer surface and a decoration impregnated into the outer surface; notable in that the motor vehicle further comprises an opaque lacquer layer covering the body panel and forming the outer surface, said opaque lacquer comprising a polymer and pigments, the decoration being impregnated into the opaque lacquer layer by sublimation. Adding the coating to the lacquer mutually enhances the appearance of both the decoration and the lacquer layer.

[0040] Each feature introduced by the expression "preferably" given in relation to one of the aspects of the invention applies to all other aspects of the invention.

[0041] The invention will be well understood and other aspects and advantages will become clear upon reading the following description, given with reference to the attached figures listed below.

[0042] Fig. 1 illustrates a diagram of a method for decorating a part of the bodywork of a motor vehicle according to the invention.

[0043] The [Fig.2] is a cross-section of a piece of wrap during a printing step of a decorative element for a motor vehicle according to an embodiment of the invention.

[0044] The [Fig.3] is a cross-section of a piece of wrap with a decorative element for a motor vehicle according to an embodiment of the invention.

[0045] In the following description, the term "include" is synonymous with "include" and is not limiting in that it permits the presence of other elements in the motor vehicle or other steps in the decoration process to which it relates. It is understood that the term "include" includes the terms "consist of".

[0046] In this description, the ranges of values ​​include the bounds that delimit them.

[0047] In the present description, equality between values ​​is not to be understood in the strict sense insofar as each equality allows a variation of at most 10%, preferably at most 5%, more preferably at most 2%, between these values.

[0048] In this description, the terms "vertical" and "horizontal" are not to be understood in their strict sense. Indeed, they allow an inclination of at most 20°, preferably at most 10°, more preferably at most 5°, and even more preferably at most 2°; with respect to the strict meaning of these terms.

[0049] Throughout the description, the different figures use the same reference signs to designate identical or similar entities.

[0050] Figure 1 shows a diagram of a method for decorating a body panel of a motor vehicle, according to an embodiment of the invention. The motor vehicle includes energy storage means and at least one motor (not shown) adapted to power said motor vehicle. The motor vehicle includes a structure forming an outer body, or the main frame of the motor vehicle. The structure is formed from an assembly of stamped and welded sheet metal panels. The structure receives rotating, movable openings and front and rear bumper skins. The structure locally forms the body of the motor vehicle. Its precision and homogeneity enhance the perceived quality.

[0051] The motor vehicle can, for example, be a private motor vehicle or a commercial motor vehicle.

[0052] The decoration process comprises the following steps, carried out in the following order:

[0053] a) supply or production 100 of an envelope part;

[0054] b) application 102 of a layer of opaque lacquer on the envelope piece in order to form an outer surface;

[0055] c) printing 104 of a decoration by ink sublimation on the outer surface of the opaque lacquer layer;

[0056] d) application 106 of a varnish film on the opaque lacquer layer covering the decoration;

[0057] e) polishing 108 of the opaque lacquer layer or the optional varnish film, at the decoration level.

[0058] Step a) supply or production 100 may include cutting, stamping, or spot welding of sheet metal. Other assembly methods, such as bonding, are considered. It notably includes a cataphoresis substep.

[0059] The casing piece comprises metal, plastic, wood or ceramic. It may comprise a composite material with reinforcing fibers and a polymer resin.

[0060] Before step b) application 102 of the opaque lacquer layer, the decoration process includes cleaning the envelope part. Step b) application 102 may include a substep of drying the opaque lacquer layer as well applied. In step b) application 102 said opaque lacquer comprises a polymer resin and pigments mixed, dispersed in the polymer resin.

[0061] In step c) printing 104, the ink mixes with the pigments. It becomes embedded in the opaque lacquer layer. Step c) printing 104 is a pigment transfer step. Step c) printing 104 includes holding the ink at a specific temperature for 15 to 20 minutes. The ink is of a sublimation-specific type. The formulation of a sublimation ink replaces the pigments with dyes. These dyes are transformed into gaseous elements necessary for the sublimation transfer.

[0062] Following step c) printing 104, the decoration is embedded within the thickness of the opaque lacquer layer. It is encapsulated between the opaque lacquer layer and the varnish film. Following step c) printing 104, the coating is concentrated in an undercoat, or an outer film of the opaque lacquer layer. The thickness of the opaque lacquer layer remains constant at the edges of the decoration.

[0063] According to one embodiment, the envelope piece comprises an edge with two opposing faces and a slice connecting the opposing faces. The edge forms a ridge, or a rebate, between two sheets. In step c) printing 104, the decoration covers the slice and the opposing faces. This optimizes the perceived quality.

[0064] According to one option of the invention, the envelope piece further comprises a rib. The rib forms a raised line, set back from the edges of the envelope piece. It may correspond to a style line. In step c) printing 104, the decoration covers said rib. It extends over opposite faces.

[0065] During step c) printing 104, an inflated bag exerts pressure against the envelope piece. Step c) printing 104 comprises applying pressure of 100 g / m² to 200 g / m² to the envelope piece, directed from the decoration towards the envelope piece.

[0066] In step c) printing 104, the ink used has a sublimation temperature. Step c) printing 104 is carried out at a temperature between 100% and 150%, preferably between 100% and 130%, of said sublimation temperature. Step c) printing 104 involves a temperature between 80°C and 120°C. The temperature increase is ensured by an additional heat source. Step c) printing 104 is optionally carried out under vacuum.

[0067] Prior to step c) printing 104, the decoration process includes a drying and degassing step of the opaque lacquer layer. This step limits the occurrence of blistering of the coating and the risk of corrosion. It contributes to the perceived quality.

[0068] This step c) printing 104 can be iterated. It is then repeated in order to implement several decorative layers stacked one on top of the other. These stacked layers can be of equal thickness; and / or of the same color(s). This The finish is improved thanks to thinner decorative layers. In step c) printing 104, the decoration includes several colors. This allows for the creation of polychrome designs.

[0069] Step c) printing 104 comprises substep c1) supplying 110 a transfer sheet; substep c2) printing 112 a decoration onto the transfer sheet; substep c3) processing 114 the transfer sheet to dry the ink; substep c4) applying 116 the transfer sheet to the envelope piece; substep c5) heating 118 the transfer sheet against the envelope piece; and substep c6) removing 120 the transfer sheet. The transfer sheet is also referred to as the medium or temporary support.

[0070] In substep c2) printing 112, the decoration is printed symmetrically with respect to the final version on the envelope piece. In other words, during step c) printing, a selected image is printed in reverse on heat-resistant sublimation paper. Once printed, the image is transferred under heat onto the opaque lacquer layer. Under the effect of the high temperature and pressure, the boiling inks cool instantly upon contact with the opaque lacquer material. They transform into a gas and migrate permanently onto the envelope piece. The texture of the lacquer layer is preserved.

[0071] Substep c3) treatment 114 of the transfer sheet remains optional. It includes heating, exposure to ultraviolet radiation, or vacuum treatment.

[0072] Generally, step b) application 102 of the opaque lacquer layer is a first application step. Step d) application 106 of the varnish film remains optional. In step d) application 106 of the varnish film, the opaque lacquer layer has a first thickness, and the varnish film has a second thickness that is thinner than the first. The varnish film is in contact with the decoration, or at least with the layer on which it is placed. The varnish film forms a protective barrier for the decoration. It contributes to its durability. Its presence improves resistance to ultraviolet radiation.

[0073] Step d) application 106 includes applying the varnish with a sprayer; preferably mounted on a robot. This varnish includes a hardener. The hardener limits scratches and abrasion.

[0074] Step e) polishing 108 comprises polishing the opaque lacquer layer or the optional varnish film. Step e) polishing 108 is preferably automated by robot to ensure homogeneity. Alternatively, it can be performed manually. Step e) polishing 108 is also referred to as buffing or post-treatment.

[0075] The body panel is an inner or outer body panel of the motor vehicle. It forms the outer skin of the motor vehicle, or the surface delimiting the interior of the vehicle, such as the passenger compartment.

[0076] Figure 2 shows a motor vehicle body panel during a sublimation printing step, according to an embodiment of the invention. The motor vehicle may correspond to the one shown in relation to Figure 1. The body panel and the printing step correspond to those shown in relation to Figure 1.

[0077] The body panel 10 is the general support for the decoration 16. The body panel 10 can be an interior panel within the passenger compartment, or an exterior panel representing the bodywork. It can form the structure of the motor vehicle. The body panel 10 is a finishing part. It is a visible part, from the inside and / or outside of the vehicle. The body panel 10 comprises metal, wood, or ceramic such as glass. The metal is steel or aluminum.

[0078] The outer casing 10, or more precisely the opaque lacquer layer 14, has an outer surface 12. The outer surface 12 is treated. The outer surface 12 is a support surface. It is essentially smooth due to the presence of the opaque lacquer layer 14. The opaque lacquer layer 14 covers the outer casing 10. It forms a coating, preferably a watertight one. The opaque lacquer layer 14 comprises a polymer tinted with pigments. The pigments form grains. They are added in powder form to the polymer. They are insoluble. The pigments are, for example, metallic or mineral.

[0079] The decoration 16 is temporarily supported by a transfer sheet 18, or temporary backing sheet. The transfer sheet 18 is waterproof. The decoration 16 is printed onto the transfer sheet 18 before being applied to the envelope piece 10. The transfer sheet 18 conforms to the geometry of the outer surface 12. The transfer sheet 18 is waterproof to control the sublimation of the ink of the decoration 16. It is stacked vertically on the envelope piece 10.

[0080] During the sublimation printing step, an inflatable bag 20 exerts pressure against the envelope piece 10. The pressure is maintained for a predetermined time. The inflatable bag 20 is advantageously inflated with a gas. Other fluids are also possible. The inflatable bag 20 forms a template for applying the transfer sheet. Its geometry is complementary to that of the envelope piece 10. The inflatable bag 20 replicates the ribs and slanted edges of the envelope piece 10. It conforms to the shape of the envelope piece 10.

[0081] The inflated bag 20 allows for the application of homogeneous pressure to the decoration 16. It exerts a pressure of 100 g / m2 to 200 g / m2 on the envelope piece 10, in particular on the outer surface 12 through the opaque lacquer layer 14, the decoration 16 and the transfer sheet 18. For example, the pressure is 150 g / m2.

[0082] Figure 3 shows a cross-section of the body panel 10 of a motor vehicle, according to one embodiment of the invention. The motor vehicle may correspond to the one shown in relation to one of Figures 1 to 2. The body panel 10 generally corresponds to that shown in Figure 2. According to one option, a varnish film 22 covers the opaque lacquer layer 14, at the level of the decoration 16 and beyond.

[0083] The wrap-around piece 10 is an exterior bodywork element, or an interior element that delimits the passenger compartment of the motor vehicle. Preferably, the wrap-around piece 10 is a motor vehicle bumper skin. Alternatively, the wrap-around piece is a wooden decorative panel mounted on the dashboard or a side door trim, delimiting the passenger compartment.

[0084] Following sublimation printing, the decoration 16 is embedded within the thickness of the coating 24 of the envelope part 10. The coating 24 comprises the opaque lacquer layer 14 and the varnish film 22. The coating 24 forms a stack. The decoration 16 is located at the core of the coating 24. The decoration 16 is at the interface between the varnish film 22 and the opaque lacquer layer 14. The varnish film 22 enhances the glossy appearance for perceived quality.

[0085] The opaque lacquer layer 14 has a thickness of between 0.01 mm and 0.1 mm; preferably between 40 µm and 60 µm. The thickness is average. The thickness is preferably constant. The decoration 16 is thinner than the opaque lacquer layer 14.

[0086] The opaque lacquer layer 14 comprises a first layer 26 against the outer casing 10, a second layer 28 opposite the first layer 26 and towards the outer surface 12. The decoration 16 remains within the thickness of the second layer 28. The decoration 16 is at a distance from the first layer 26. According to one option of the invention, the opaque lacquer layer comprises a third layer between the first and second. Thus, the presence of the decoration 16 does not weaken the opaque lacquer layer 14.

[0087] The outer surface 12 is here formed by the varnish film 22. In the absence of varnish film, the outer surface is directly formed by the opaque lacquer layer 14.

[0088] The precursor material of the varnish used is of the mono- or two-component type, namely a resin and possibly a hardener, which are mixed just before application. and made up of acrylic-melamine type polymer resins, polyesters, and hardeners of type HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate) or a mixture of both.

[0089] The envelope piece 10 is first coated with the opaque lacquer layer 14 in a first layer. This forms an interlayer. Then the varnish film 22 is added. The varnish film 22 has a second layer that is thinner than the first. The varnish film 22 is an outer film, or a finishing film. The decoration 16 is at the edge of the opaque lacquer layer 14. The presence of the varnish film 22 improves the finish, particularly after dye-sublimation printing. The varnish film 22 can be multilayered. It can comprise several varnish films applied successively.

[0090] The varnish film 22 undergoes polishing. The polishing is carried out with a polishing tool 30. The polishing tool 30 comprises a felt pad rubbing against the varnish film 22 in order to reduce its roughness, and thus further improve its gloss.

[0091] According to one embodiment, the casing is made of a plastic or composite material. The plastic material may include a thermoplastic or thermosetting material. According to a preferred embodiment, the plastic material is selected from the group comprising polypropylene, polyamide, polyphthalamide, polyetheretherketone, polyphenylene sulfide, polyamide-imide, polyetherimide, polyarylamide, polyepoxide, unsaturated polyester, vinyl ester, or polyester-vinylester resins. For example, the composite material comprises a matrix of a plastic material as described above with reinforcement. For example, the reinforcement comprises glass or carbon fibers.

[0092] The outer casing 10 comprises at least 10% by weight of recycled plastic material based on the total weight of the plastic material; preferably from 10 to 80% by weight; more preferably from 20 to 60% by weight or from 30 to 40% by weight. The use of recycled plastic material reduces the vehicle's environmental footprint.

[0093] The invention comprises the combination of all the embodiments illustrated by all the figures.

Claims

Demands

1. A method for decorating an exterior surface (12) of a motor vehicle body part (10), the decoration method comprising the following steps: • a) supplying or producing (100) a body part (10); • c) printing (104) a decoration (16) by ink sublimation onto the body part (10); characterized in that prior to step c) printing (104), the method comprises a step: • b) applying (102) a layer of opaque lacquer (14) onto the body part (10) to form the exterior surface (12), said opaque lacquer comprising a polymer and pigments; at step c) printing (104), the decoration (16) is printed onto the exterior surface (12) formed by the layer of opaque lacquer (14).

2. Method according to claim 1, characterized in that the opaque lacquer layer (14) comprises a first layer (26) against the envelope piece (10), a second layer (28) opposite the first layer (26); the decoration (16) being in the thickness of the second layer (28); preferably, the decoration (16) is at a distance from the first layer (26).

3. A method according to any one of claims 1 to 2, characterized in that during step c) printing (104), an inflated bag (20) exerts pressure against the envelope piece (10); and / or step c) printing (104) includes applying a pressure of 100 g / m2 to 200 g / m2 on the envelope piece (10).

4. A method according to any one of claims 1 to 3, characterized in that in step c) printing (104), the ink comprises a sublimation temperature, step c) printing (104) being carried out at a temperature between 100% and 130% of said sublimation temperature; preferably, step c) printing (104) comprises a temperature between 80°C and 120°C.

5. A method according to any one of claims 1 to 4, characterized in that the envelope piece (10) comprises an edge with two opposite faces, a slice connecting the opposite faces, at step c) printing (104), the decoration (16) covers the edge and opposite faces; and / or the envelope piece (10) includes a rib, in step c) printing (104), the decoration (16) covers said rib.

6. A method according to any one of claims 1 to 5, characterized in that following step b) application (102), the opaque lacquer layer (14) has a first thickness; the decoration method further comprises a step d) application (106) of a varnish film with a second thickness less than the first thickness.

7. A method according to any one of claims 1 to 6, characterized in that step c) printing (104) of the decoration (16) comprises a substep c1) supplying (110) of a transfer sheet (18); a substep c2) printing (112) of a pattern on the transfer sheet (18); a substep c4) application (116) of the transfer sheet (18) onto the envelope piece (10); a substep c5) heating (118) of the transfer sheet (18) against the envelope piece (10); a substep c6) removal (120) of the transfer sheet (18).

8. A method according to claim 7, characterized in that step c) printing (104) of the decoration (16) includes a substep c3) treatment (114) of the transfer sheet (18) in order to dry the ink; preferably, substep c3) treatment includes heating, exposure to ultraviolet radiation, or placement under vacuum.

9. A method according to any one of claims 1 to 8, characterized in that in step c) printing (104) of the decoration (16) by sublimation, said decoration (16) comprises several colors; and / or step c) printing (104) of decoration by sublimation is repeated in order to implement several decorations stacked one on top of the other.

10. A method according to any one of claims 1 to 9, characterized in that the envelope piece (10) is a motor vehicle bumper skin, preferably, the envelope piece (10) comprises metal, plastic, wood or ceramic.

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