EP3991982B1 - Process for decorating a sliding board and sliding board including a decorated composite material on its visible surface - Google Patents

Description

Technical area

The invention relates to the field of boards for sliding on snow or water, and in particular alpine, cross-country or touring skis, or even snowboards or wakeboards.

The invention relates more particularly to a gliding board including on its visible face a decorated composite material as well as the associated manufacturing process.

The invention has the advantage of allowing the production of a decoration on the gliding board without integrating an additional layer supporting the decoration. In the case of gliding boards, this realization notably allows an interesting weight saving.

Previous techniques

Generally speaking, a ski is identified by the different markings and patterns present on the visible side of the ski. For example, it is possible to identify the brand of the ski, its model as well as various information relating to the size of the ski and the adjustment of the shoe retaining members. Furthermore, the decor makes it possible to give an advantageous aesthetic appearance.

The choice of decor is decisive for the Applicant since it draws the attention of the user and the public to his product. Furthermore, it is also necessary to take into account the wear constraints (friction, UV, temperature, etc.) that the decoration undergoes, in order to ensure that it does not disappear over time.

In addition, the production of numerous models with different dimensions and properties involves finding a decoration process that allows the pattern and markings of the decoration to be easily modified without creating additional costs.

Among the existing methods, we know the transfer of a pattern by ink sublimation.

For example, the document EP 0 774 365 proposes a process for decorating a sliding board made of hardened composite material. A layer of transparent plastic material is previously decorated on its underside by transfer of sublimable inks, then is glued to the surface of the composite material. However, the product obtained includes an additional layer which adds to the overall weight of the board. However, this is not sought after in the context of gliding boards, which must be ever lighter to improve their behavior on snow.

The document US 6,004,900 describes a sporting article, typically a hockey stick, comprising an outer layer of hardened composite material, the resin of which contains light-colored pigments. The decoration is printed on the article by sublimation of an ink into the surface layer of the composite material. Sublimation takes place upon the application of certain pressure and temperature conditions of around 160 to 180°C, allowing the ink to temporarily pass into the gaseous state. However, during its sublimation, the ink in the gaseous state diffuses into the resin so that the contours of the decoration obtained are not clear. An example of ink diffusion is shown in figure 1 below, on which we observe a continuous sheet of ink 31, which gradually melts into the resin 23, a sign that the ink 31 diffuses into the resin 23. In addition, the process requires previously mixing color pigments clear with resin, otherwise the sublimated ink lacks contrast. However, this additional step complicates the process. It is also impossible to obtain white solid areas directly by sublimation.

The document US 5,718,792 presents a process for decorating a ski pole made of hardened composite material. To do this, a pre-printed decoration sheet with sublimable ink is applied to the surface of the stick. The assembly is heated, for example, to a temperature of approximately 210°C for 60 to 80 seconds, to allow the ink to pass directly into the gaseous state. by sublimation of the decoration into the stick. However, the transferred decoration does not have a clear appearance, because the ink diffuses into the resin, particularly in the case of a curved surface, since positioning the pre-printed decoration sheet on the stick is a delicate step and not very reproducible. The high temperatures applied in processes using sublimation are incompatible with applications on articles including materials sensitive to heat, such as for example the polyethylene sliding soles on a ski.

Furthermore, there is another method for decorating the surface of a gliding board, namely screen printing. This method consists of directly printing the pattern on the surface of the gliding board using stencils mounted on frames. However, the pattern remains on the surface of the item and is therefore very fragile in the face of external aggression. To prevent the pattern from disappearing too quickly, it is known to cover the printed surface of the gliding board with a layer of varnish. This layer, however, forms an extra thickness which contributes to increasing the overall weight of the board.

The documents EP1829699 And DE102 49 223 describe methods of decorating rigid substrates such as walls or the like, in which the substrate is covered with a layer of resin which receives the application of a support sheet including ink particles. This ink is transferred to the resin by application of pressure, before peeling off the support sheet

The technical problem that the invention proposes to solve is therefore to develop a process for manufacturing a gliding board for which the decoration printed on the composite material of the gliding board forms the least excess thickness possible and is clear. and does not diffuse into the resin, while being resistant to wear and external aggression.

Presentation of the invention

• préparation d'un film de transfert comprenant une face recouverte d'un motif constitué d'un arrangement de grains d'au moins un type d'encre, ladite encre comportant des colorants et un polymère réticulé,
• positionnement de la face du film de transfert recouverte du motif sur tout ou partie de la surface externe du matériau composite,
• application de conditions de pression et de température générant le ramollissement ou/puis le durcissement de la résine de manière à incruster au moins partiellement les grains du motif dans la couche superficielle du matériau composite tout en conservant l'arrangement des grains préparés sur le film de transfert, et
• pelage du film de transfert.

To solve this problem, the Applicant has developed a process for decorating a sliding board including on its visible part a composite material formed of a fibrous layer coated with curable resin, said process comprising the following steps:

• preparation of a transfer film comprising a face covered with a pattern consisting of an arrangement of grains of at least one type of ink, said ink comprising dyes and a crosslinked polymer,
• positioning of the side of the transfer film covered with the pattern on all or part of the external surface of the composite material,
• application of pressure and temperature conditions generating the softening and/or hardening of the resin so as to at least partially embed the grains of the pattern in the surface layer of the composite material while retaining the arrangement of the grains prepared on the film of transfer, and
• peeling of the transfer film.

For the purposes of the invention, the “curable” resin can be a resin commonly described as thermosetting, that is to say which hardens by crosslinking when the temperature and pressure conditions are applied. Alternatively, the resin may be a thermoplastic resin, which hardens upon cooling, after having been softened by application of appropriate pressure and temperature conditions.

The resin therefore has a dual function of stiffening the composite and receiving the decoration. It is therefore no longer necessary to add additional layers of decoration, which allows for an interesting gain in thickness and weight.

In other words, the process makes it possible to transfer a pattern onto a gliding board without changing the state of the ink and therefore without diffusion, and without deformation or loss of sharpness of the pattern. To do this, the pattern to be transferred to the gliding board is printed on a transfer film using screen printing or inkjet printing. Preferably, the ink used is initially in the liquid state.

More precisely, the process therefore comprises a step of crosslinking the polymer composing the ink. Crosslinking is initiated by an external energy supply. For example, the energy supply can come from contact with ambient humidity, from an increase in temperature or from exposure to UV light.

Advantageously, the ink in solid form obtained has a structure which has no melting point, does not soften but is degraded or carbonized when it is heated above a certain temperature. This degradation or carbonization temperature is higher than the conditions of the sliding board manufacturing process.

Advantageously, the transfer film ideally has at least one of the following properties.

Preferably, the transfer film is deformable, that is to say it can bend and/or stretch to adapt to the three-dimensional geometry of the external surface of the composite material. In practice, the printed transfer film is positioned by folding it to fit the three-dimensional external surface of the composite material.

For example, the transfer film is made from a material chosen from polyolefins. This family of materials has good properties of lightness and resistance to cracking and tearing.

According to a preferred embodiment, the adhesion force between the grains and the film is sufficiently significant so that the pattern does not move on the film during the movement and positioning of the transfer film in contact with the resin. Conversely, the adhesion force between the ink grains and the resin is preferentially greater than the adhesion force between the ink grains and the transfer film. Thus, the ink grains detach from the film during peeling and remain embedded in the resin.

In practice, the aforementioned adhesion forces are obtained thanks to the roughness present on the surface of the transfer film.

Furthermore, the softening temperature of the transfer film is advantageously higher than the temperature generating the softening and/or hardening of the resin to avoid deformation of the pattern or the encrustation of a portion of the transfer film in the resin.

In practice, the sliding board decoration process can be carried out in two ways. The method may include a step of positioning the composite material in a mold, the pressure and temperature conditions generating the softening and/or hardening of the resin which are then applied to said mold.

The mold corresponds, for example, to the mold in which the gliding board is assembled. In this case, the temperature generating the softening and/or hardening of the resin applied during molding is less than or equal to 120°C, so as not to degrade the heat-sensitive elements, such as for example polyethylene ski soles.

Alternatively, the pressure and temperature conditions are applied only to the layer of composite material, then assembly in a mold is carried out in a second step.

According to a second aspect, the invention relates to a gliding board obtained by the method according to the first aspect of the invention. The gliding board includes on its visible side a decorated composite material, formed of a fibrous layer coated with hardened resin.

Such a gliding board is characterized in that said decorated composite material comprises a pattern composed of an arrangement of grains of at least one type of ink, said ink comprising dyes and a crosslinked polymer, these grains being encrusted in the surface layer of the hardened resin of the composite material.

More specifically, a composite material is composed of a fibrous layer coated with hardened resin. Depending on the technology used to make the composite material, the resin may be a thermoplastic resin, which hardens when it cools, or a thermosetting resin which hardens through chemical reaction phenomena. In practice, before hardening, a thin layer of the resin remains supernatant in relation to the fibrous layer and constitutes the surface layer in which the grains can become embedded.

For the purposes of the invention, “encrusted” means that a portion of the volume of the ink grain is encompassed by the resin. In other words, a significant portion, ideally a majority, of the external surface of the grain is in contact with the resin. For example, the grain can be completely embedded and isolated in the resin or its upper surface can protrude into the open air or at least one of its lateral zones can be contiguous with another grain. In all cases, there is always a certain continuity of the resin, from the fibrous layer of the composite material, to the exterior surface, in order to properly block the ink grains. In addition, the ink grains do not enter inside the fibrous layer, which makes it possible to maintain the mechanical resistance properties of the composite material.

Thus, the embedded ink grains are point elements and not diffuse, like pixels, and it is possible to distinguish them under a microscope. They then appear in isolated form or in the form of aggregates of grains embedded in resin.

The decoration is inlaid in a very thin thickness of resin. Thus, in the case where the ink grains are completely covered by the resin, they remain clearly visible through transparency and have clear and precise contours. In addition, the decor is protected by the resin which surrounds it and resists mechanical and chemical attacks. This also provides better resistance to abrasion and tearing.

Furthermore, the gliding board does not have any extra thickness linked to the addition of the decoration, which makes it possible to gain in lightness compared to state-of-the-art gliding boards.

In practice, the polymer constituting the ink is chosen from the group including polyacrylates, polyacrylics and polyurethanes. Inside the decoration affixed to the gliding board, these polymers are in reticulated form, so that the ink grains are in a solid state and adopt a three-dimensional configuration. Unlike state-of-the-art gliding boards, all dye colors can be used, even white, while maintaining sufficient contrast with the resin to clearly distinguish the decor.

According to one characteristic of the invention, the number of grains present per unit area of the surface of the decorated composite is between 387.5 and 99,200 points per cm ² (2500 and 640,000 dots per square inch), preferably between 1550 and 24800 dots per cm ² (10000 and 160000 dots per square inch)

Which corresponds to a linear resolution of between 50 and 800 dpi or dots per inch and 100 and 400 dpi or dots per inch respectively.

The appropriate unit of area may be a square with a side of 2.54 cm. This resolution value can also be expressed in "dpsi" or number of dots per square inch, which is derived from the unit of measurement dpi or "dots per inch", commonly used to define the resolution of a printer or scanner. In practice, the number of grains present per unit area of the surface of the decorated composite is linked to the resolution of the device used to create the decoration on the gliding board, since the printing of the decoration is carried out with grains at the same time. solid state, which cannot pass either into the liquid state or into the gaseous state. Consequently, there is no diffusion of the grains in the resin, which contributes to the clean appearance of the decoration.

According to a second characteristic of the invention, the ratio of the surface occupied by the grains to a unit surface is between 20 and 75%, advantageously between 25% and 50%. This coverage ratio guarantees sufficient retention of the grains within the surface layer of hardened resin as well as good protection of the grains against external aggression. The greater the coverage ratio, the more concentrated the color and appears with more intensity and contrast. Conversely, the ink grains are more firmly embedded when this ratio does not exceed a maximum value.

According to a third characteristic of the invention, an ink grain has a diameter, or generally a larger dimension, of between 10 and 100 µm. These dimensions are chosen so that the grain thickness is ideally smaller than the supernatant resin thickness, in order to be properly encompassed by the resin. The diameter is also chosen so that the grain is large enough to be properly distinguished through the resin layer. Furthermore, the dimensions are also chosen to guarantee the aesthetic appearance of the decor and to obtain the best possible resolution within the limits of the constraints mentioned above.

In practice, the pattern can be printed on the three-dimensional external surface of the composite material. Thus, for a gliding board, the pattern covers the upper face of the gliding board. Alternatively, the pattern is not limited to the upper composite material of the gliding board, but may also cover the side surfaces of the composite material of the gliding board, which helps to improve the overall aesthetic appearance. Furthermore, the gliding board can have raised shapes on its upper surface, where the pattern can be affixed without difficulty.

Summary description of the figures

• La figure 1 est une photographie, prise au microscope, de la portion supérieure d'une planche de glisse de l'art antérieur, décorée par sublimation d'une encre dans la résine.
• La figure 2 est une coupe transversale médiane de la portion supérieure d'une planche de glisse incluant sur sa face visible un matériau composite décoré comportant un seul type de grain d'encre.
• La figure 3 est une coupe transversale médiane de la portion supérieure d'une planche de glisse incluant sur sa face visible un matériau composite décoré comportant deux types de grain d'encre.
• La figure 4 est une photographie prise au microscope, avec un grossissement comparable au grossissement de la figure 3, de la surface d'une planche de glisse selon l'invention.
• La figure 5 est un organigramme de l'enchainement des étapes du procédé de l'invention.
• La figure 6 est une représentation en coupe du film de transfert imprimé lors de la première étape du procédé de la figure 3, selon un premier mode de réalisation.
• La figure 7 est une représentation analogue à la figure 6, selon un second mode de réalisation.
• La figure 8 est une représentation en coupe du film appliqué à la surface de la résine, lors de la deuxième étape du procédé de la figure 3.
• La figure 9 est une représentation en coupe du film positionné à la surface de la résine, après application des conditions de pression et de température lors de la troisième étape du procédé de la figure 3.
• La figure 10 est une représentation en coupe de la portion supérieure de la planche de glisse une fois le film de transfert pelé lors de la quatrième étape du procédé de la figure 3.

The manner of carrying out the invention, as well as the advantages which result therefrom, will emerge clearly from the description of the embodiments which follow, in support of the appended figures in which:

• There figure 1 is a photograph, taken under a microscope, of the upper portion of a prior art sliding board, decorated by sublimation of ink in resin.
• There figure 2 is a median cross section of the upper portion of a gliding board including on its visible face a decorated composite material comprising a single type of ink grain.
• There Figure 3 is a median cross section of the upper portion of a gliding board including on its visible face a decorated composite material comprising two types of ink grain.
• There Figure 4 is a photograph taken under a microscope, with a magnification comparable to the magnification of the Figure 3 , of the surface of a gliding board according to the invention.
• There figure 5 is a flowchart of the sequence of steps of the process of the invention.
• There Figure 6 is a cross-sectional representation of the transfer film printed in the first step of the transfer process. Figure 3 , according to a first embodiment.
• There Figure 7 is a representation analogous to the Figure 6 , according to a second embodiment.
• There figure 8 is a cross-sectional representation of the film applied to the surface of the resin, during the second step of the process of Figure 3 .
• There Figure 9 is a cross-sectional representation of the film positioned on the surface of the resin, after application of the pressure and temperature conditions during the third step of the process of the Figure 3 .
• There Figure 10 is a cross-sectional representation of the upper portion of the gliding board once the transfer film has been peeled off during the fourth step of the process. Figure 3 .

Way of making the invention

THE figures 2, 3 And 6-10 are not represented to scale to facilitate the reader's understanding. In particular, the thickness of the supernatant layer of resin 13 is exaggerated to illustrate the phenomena which take place within this layer. In particular, the shape of the ink grains 11 , 21 is schematized by a generally rectangular shape, which is not necessarily representative of the real shape of the grains 11 , 21 .

THE figures 2 and 3 illustrate a median cross section of the upper portion of a gliding board including on its visible face a decorated composite material 15 . Such a composite material 15 is for example found on the upper portion of a gliding board, as reinforcement. The upper face of the composite material 15 is visible and therefore appears decorated.

A composite material 15 is typically formed of a fibrous layer 14 of glass, carbon, basalt fibers or natural fibers, long or short, unidirectional or oriented or even made of a non-woven, for example based on threads polyester. In all cases, the fibrous layer 14 is impregnated with thermosetting resin 13 , for example an epoxy resin, or thermoplastic, such as a polyamide resin. The resin 13 has a supernatant portion above the fibrous layer 14 . This supernatant portion of resin 13 has a thickness of a few micrometers.

The decoration is in the form of an arrangement of ink grains 11 , 21 embedded in the resin 13 to a thickness of less than 10 μm. The decoration may have one or more layers of one or more types of grains 11 , 21 .

As an example, the figure 2 has only one type of grain 11 , distributed over two superimposed layers, corresponding to an ink of a single given color. There Figure 3 also has two superimposed layers. The first layer is composed of a first type of grains 21 and the second layer is composed of another type of grains 11 , typically of different colors.

As illustrated on the Figure 4 , the grains 11 , 21 have a substantially rounded appearance, of a solidified and/or dried droplet.

They can be isolated and completely enclosed in the resin or contiguous with one or more other grains 11 , 21 of the same layer or of a higher or lower layer. The upper portion of grain 11 can also emerge partially or completely into the open air. Generally speaking, the decoration does not appear extra thick to the touch because the resin is predominant on the surface, so that the surface remains smooth and relatively homogeneous.

In the case where several layers have been superimposed, it is difficult to perceive the spaces between the particles, but with sufficient magnification, for example obtained under a microscope, as on the figure 4 , we can highlight the distinctive shape of the grains 11 , 21 . It is also easier to visualize these grains 11 , 21 at the edge of the decoration, because at this location there are often fewer superimposed decoration passes.

The type of a grain 11 , 21 varies depending on the ink used, typically the nature of the polymer or the dye can vary. In all cases, the ink used is an ink in solid and non-sublimable form, which does not change to a liquid state or to gaseous state when heated. On the contrary, if we heat the ink composing a grain 11 , 21 , it is irremediably degraded, or even burns and carbonizes. In particular, the ink is for example composed of a crosslinked polyurethane, polyacrylate or polyacrylic polymer.

This type of ink can integrate all types of dyes, even white, unlike state-of-the-art sublimable inks where white does not exist.

The decoration obtained is precise and clean, since the grains 11 , 21 do not diffuse into the resin. THE figures 1 And 4 make it possible to compare a product obtained thanks to the principle of the invention, visible on the figure 4 , and a product obtained by sublimation of ink in the resin, visible on the figure 1 .

On the figure 4 , we can see the clear contours of the grain arrangement 11 , 21 encompassed by the resin 13 . While on the figure 1 , we do not observe grains, but a continuous sheet of ink 31 , which gradually melts into the resin, a sign that the ink 31 diffuses into the resin 13 .

The sliding board can be decorated in this way on all its sides and even on surfaces with particular geometries, such as curved surfaces. For example, in the case where the composite reinforcement extends laterally on the edges of the ski, it is possible to decorate the top and the edges of a ski continuously, without loss of precision or deformation of the decoration at the angles or curves.

Advantageously, a gain of 40g on a 550g cross-country ski was achieved by the Applicant by replacing a decoration by adding material with the decoration method of the invention.

The process for obtaining such a gliding board is illustrated in Figure 5 and comprises four successive stages.

The first step 210 , illustrated on the figures 6 and 7 , is the preparation of a transfer film 12 . The transfer film 12 is a thin sheet, made of a flexible and deformable material, typically belonging to the polyolefin family.

The decoration pattern is printed on the transfer film 12 , with the film flat.

Advantageously, the transfer film 12 is chosen to be able to deform without breaking during transport and placement in the mold.

For three-dimensional sliding boards whose surface includes edges delimiting distinct zones, not necessarily coplanar, there is an advantage in using a transfer film 12 which has a stretching capacity. Typically, the transfer film 12 has an elongation upon cracking of between 60 and 100% of its initial surface area. Otherwise formulated, the transfer film 12 can extend up to twice its initial size before cracking.

In addition, the transfer film 12 has at least one face having a roughness intended to mechanically retain the grains 11 , 21 of the decoration. The roughness is chosen to allow the pattern to be held in place on the transfer film 12 , without migration during the movement and positioning of the transfer film 12 on the surface of the resin, especially since the decorated face of the film transfer 12 is oriented downwards during molding of the board.

In addition, the roughness is also chosen to limit the contact surface with the grains 11 , 21 , so that these transfer into the resin 13 when a predetermined pressure is applied to the transfer film 12 . Typically, the average roughness Ra is between 2 and 5 μm, preferably close to 3 μm. The average roughness Ra is obtained by calculating the average difference between the peaks and valleys of the roughness profile of the transfer film 12 . The maximum roughness Rz corresponds to the absolute vertical difference between the maximum height of the peaks and the maximum depth of the valleys over a predetermined length. Preferably, the maximum roughness Rz is between 15 and 30 µm, typically close to 23 µm.

Two different techniques can be used to print the pattern: inkjet printing or screen printing.

Inkjet printing is carried out by a printer comprising print heads allowing drops of liquid ink to be deposited on the surface of the transfer film 12 with a linear resolution of between 200 and 500 dpi, typically 360dpi, or approximately 130,000 drops per square of 2.54 cm side, or approximately 20,000 drops per cm ² . The diameter of the drops deposited is between 10 and 100µm, typically 24µm. The dimensions of the drops and grains can be measured by traditional image analysis techniques, from images similar to that of the figure 4 .

The ink usually contains a light polymerizer. After depositing the drops of ink on the transfer film 12, they are exposed to UV light making it possible to initiate the polymerization and/or crosslinking of the ink. Thus, the ink is frozen and in a solid, stable and irreversible state. For example, the inks from the ALTAMIRA DESIGN DP ^® range, marketed by the AGFA Company, or the inks from the UVIJET KO ^® range from the FUJIFILM Company can be used for inkjet printing. The ink chosen also has a certain malleability after polymerization, as well as a chemical nature which allows it not to crack during deformation of the transfer film 12 and not to be denatured in contact with the resin 13 .

In the case of screen printing, screens comprising holes with a diameter of between 10 and 100 μm, typically 40 μm, are arranged facing the transfer film 12 . The linear resolution is between 50 and 150 dpi, typically 120dpi, or approximately 15,000 drops per square of 2.54 cm side, or approximately 2300 drops per cm ² .

The liquid ink passes through the holes and flows slightly when arriving on the transfer film 12 . The ink contains a solvent which can evaporate either at room temperature or in an oven. The ink polymerizes and/or crosslinks by the addition of external energy, typically under the effect of ambient humidity, exposure to light or under the effect of an increase in temperature, to become irreversibly into a stable solid state.

In principle, the thickness of the ink layer deposited by inkjet is around 5 to 6 µm while the thickness of the ink layer deposited by screen printing is a little thicker, around 10 µm .

It is generally easier to create large, uniformly decorated surfaces with screen printing than with inkjet. With inkjet printing, it will be necessary to apply several layers of ink to obtain a similar result.

As illustrated on the Figure 6 , the ink layer can be composed of a single pass of ink grains 11 of a first type. The ink grains 11 are generally deposited evenly on the surface of the transfer film 12 .

As illustrated on the Figure 7 , the ink layer can be composed of several passes of ink grains 11 , 21 of several types.

In all cases, the ink and the surface condition, that is to say the roughness of the transfer film 12 , are chosen to have a mutual adhesion force making it possible to hold the pattern in place on the transfer film. transfer 12 , without migration during movement and positioning of the transfer film 12 on the surface of the resin, especially since the decorated face of the transfer film 12 is oriented downwards during molding of the board. However, the adhesion force between the ink and the transfer film 12 is preferably weaker than the adhesion force between the ink and the resin 13 impregnating the composite to facilitate the separation of the grains 11, 21 from the transfer film 12 and their attachment to the resin 13. As illustrated on the figure 8 , step 220 of the method consists of depositing the transfer film 12 on the surface of the resin 13 of the composite 15 . In principle, the pattern is printed in mirror on the transfer film 12 so that, when the transfer film 12 is returned to the resin 13 , the pattern is in the desired orientation, for example readable in the case of writing. .

As illustrated on the Figure 9 , in step 230 , pressure and temperature conditions, typically between 3 and 10 bars and 80 and 120°C, are applied to the composite 15 covered with the printed transfer film 12 . In the case of a simple transfer of decoration onto a composite 15 , without the problem of bonding different elements together, a pressure greater than or equal to 3 bars is sufficient. This can apply for example when the composite 15 is decorated before assembling the ski in a mold.

In addition, the transfer temperatures described above are compatible with the use of polyethylene type materials, generally constituting the sliding soles of skis. In the extreme, the temperature can even be room temperature, but the curing time of the resin is then much longer.

For a thermoplastic resin 13 , it is in the solid state before the pressure and temperature conditions are applied to the gliding board. The increase in pressure and temperature makes it possible to soften the thermoplastic resin 13 . It is in this phase that the grains 11 in the solid state composing the decoration will become embedded in the softened resin 13 . Then, the cooling phase allows the return of the assembly formed by the resin 13 encrusted with grains 11 to the solid state.

In the case of a thermosetting resin 13 , it is in the liquid state. It is in this phase that the grains 11 in the solid state composing the decoration will become embedded in the liquid resin 13 . The increase in pressure and temperature makes it possible to harden the thermosetting resin 13 around the grains 11 .

In all cases, the resin 13 in the liquid state during molding fills all the free spaces left by the grains 11 of ink from the fibrous reinforcement 14 , to the surface of the gliding board, before hardening, either by crosslinking or by cooling, depending on the nature of the resin used.

There Figure 10 illustrates step 240 of the method in which the transfer film 12 is peeled from the solid surface of the composite 15 .

In the case of manufacturing a ski, the composite 15 is generally impregnated beforehand, then transferred to the mold with the other constituent components of the ski. The application of pressure and temperature conditions makes it possible to agglomerate the different constituent layers of the ski as well as to harden the resin. In this case, 6 to 10 bars, and preferably 8 bars are preferably applied to the mold. This pressure also makes it possible to expel the excess resin and to obtain a composite 15 having a resin content of between 15 and 30%, typically 20%. Alternatively, the composite 15 can also be impregnated with resin directly in the mold.

Furthermore, the transfer of the pattern into the composite 15 can be carried out in several ways. A first method consists of applying the transfer film 12 to the composite 15 after its placement in the mold. A second method consists of first applying the transfer film 12 to the composite 15 , then transferring the assembly formed by the impregnated composite 15 and the transfer film 12 into the mold. The pressure and temperature conditions applied to the mold then allow the transfer of the pattern from the transfer film 12 to the surface layer of resin 13 .

In the case of a thermoplastic resin, one can also imagine transferring the pattern into the composite 15 before molding. To do this, pressure and temperature conditions allowing the softening of the thermoplastic resin must be previously applied to the assembly formed by the impregnated composite 15 and the transfer film 12 . Subsequently, during molding, the thermoplastic resin may still soften, while retaining the pattern as transferred.

To conclude, the invention advantageously makes it possible to obtain a gliding board with a clean decoration, exhibiting little or no deformation and which is resistant to external aggression. The manufacturing process for such a board is versatile and allows multiple decorations to be obtained with lots of contrast and without limitation in terms of colors. Furthermore, depending on the ink grain coverage rate of the resin, the feel can be modified to improve the grip of the gliding board.

Claims (16)

1. Method for decorating a sliding board including on its visible part, a composite material (15) formed of a fibrous layer (14) coated with hardenable resin (13), characterized in that said method comprises the following steps:

   - preparing a transfer film (12) comprising a face covered with a pattern constituted of an arrangement of grains (11, 21) of at least one type of ink, said ink comprising colourants and a crosslinked polymer,

   - positioning the face of the transfer film (12) covered with the pattern on all or some of the external surface of the composite material (15),

   - applying pressure and temperature conditions generating the softening or/then hardening of the resin (13) to as to incrust at least partially the grains (11, 21) of the pattern in the superficial layer of the composite material (15) while conserving the arrangement of the grains (11, 21) prepared on the transfer film (12), and

   - peeling the transfer film (12).
2. Decoration method according to claim 1, characterised in that it comprises a step of positioning the composite material (15) in a mould, the pressure and temperature conditions generating the softening or/then the hardening of the resin (13) being applied on said mould.
3. Decoration method according to claim 1, characterised in that the method further comprises a step of crosslinking the polymer composing the ink.
4. Decoration method according to claim 1, characterised in that the temperature generating the softening or/then the hardening of the resin (13) is less than or equal to 120°C.
5. Decoration method according to claim 1, characterised in that the transfer film (12) is deformable, i.e. that it can be folded and/or stretched to be adapted to the three-dimensional geometry of the external surface of the composite material (15).
6. Decoration method according to claim 1, characterised in that the transfer film (12) is made of a material chosen from among polyolefins.
7. Decoration method according to claim 1, characterised in that the adhesion force between the ink grains (11, 21) and the resin (13) is greater than the adhesion force between the ink grains (11, 21) and the transfer film (12).
8. Decoration method according to claim 1, characterised in that the softening temperature of the transfer film (12) is greater than the temperature generating the softening or/then the hardening of the resin (13).
9. Sliding board having been the subject of the method according to one of claims 1 to 8, characterised in that said decorated composite material (15) comprises a pattern composed of an arrangement of grains (11, 21) of at least one type of ink, said ink comprising colourants and a crosslinked polymer, the grains (11, 21) being incrusted in the superficial layer of the hardened resin (13) of the composite material (15).
10. Sliding board according to claim 9, characterised in that the resin (13) is a thermoplastic resin or a thermosetting resin.
11. Sliding board according to claim 9, characterised in that the polymer is chosen from among the group including polyacrylates, polyacrylics, polyurethanes.
12. Sliding board according to claim 9, characterised in that the number of grains (11, 21) present per surface unit of the decorated composite material is comprised between 2500 and 640000 dots per square inch, preferably between 10000 and 160000 dots per square inch.
13. Sliding board according to claim 9, characterised in that the ratio of the surface occupied by the grains (11, 21) on a unit surface is comprised between 20% and 75%.
14. Sliding board according to claim 9, characterised in that an ink grain (11, 21) has a larger dimension comprised between 10 and 100µm.
15. Sliding board according to claim 9, characterised in that the pattern is printed on the three-dimensional external surface of the composite material (15).
16. Sliding board according to claim 9, characterised in that the pattern covers the upper face of the sliding board.

Images