SLIDING BOARD INCLUDING ON ITS VISIBLE FACE A DECORATED COMPOSITE MATERIAL AND ASSOCIATED METHOD

Abstract

A method for decorating a sliding board including on its visible part, a composite material formed of a fibrous layer coated with hardenable resin, includes preparing a transfer film that includes a face covered with a pattern constituted of an arrangement of grains of at least one type of ink. The ink includes colourants and a crosslinked polymer. The method also includes positioning the face of the transfer film covered with the pattern on all or some of the external surface of the composite material, applying pressure and temperature conditions generating the softening or/then hardening of the resin to as to incrust the grains of the pattern in the superficial layer of the composite material while conserving the arrangement of the grains, and peeling the transfer film.

Claims

1. A method for decorating a sliding board including on a visible part of the sliding board, a composite material formed of a fibrous layer coated with hardenable resin, said method comprising the following steps: preparing a transfer film comprising a face covered with a pattern constituted of an arrangement of grains of at least one type of ink, said ink comprising colourants and a crosslinked polymer, positioning the face of the transfer film covered with the pattern on all or some of the external surface of the composite material, applying pressure and temperature conditions generating the softening or/then hardening of the resin to as to incrust at least partially the grains of the pattern in the superficial layer of the composite material while conserving the arrangement of the grains prepared on the transfer film, and peeling the transfer film.

2. A decoration method according to claim 1, further comprising a step of positioning the composite material in a mould, the pressure and temperature conditions generating the softening or/then the hardening of the resin being applied on said mould.

3. A decoration method according to claim 1, wherein the method further comprises a step of crosslinking the polymer composing the ink.

4. A decoration method according to claim 1, wherein the temperature generating the softening or/then the hardening of the resin is less than or equal to 120° C.

5. A decoration method according to claim 1, wherein the transfer film is deformable such that the transfer film can be folded and/or stretched to be adapted to the three-dimensional geometry of the external surface of the composite material.

6. A decoration method according to claim 1, wherein the transfer film is made of a material chosen from among polyolefins.

7. A decoration method according to claim 1, wherein the adhesion force between the ink grains and the resin is greater than the adhesion force between the ink grains and the transfer film.

8. A decoration method according to claim 1, wherein the softening temperature of the transfer film is greater than the temperature generating the softening or/then the hardening of the resin.

9. A sliding board having been the subject of the method according to claim 1, wherein said decorated composite material comprises a pattern composed of an arrangement of grains of at least one type of ink, said ink comprising colourants and a crosslinked polymer, the grains being incrusted in the superficial layer of the hardened resin of the composite material.

10. A sliding board according to claim 9, wherein the resin is a thermoplastic resin or a thermosetting resin.

11. A sliding board according to claim 9, wherein the polymer is chosen from among the group including polyacrylates, polyacrylics, polyurethanes.

12. A sliding board according to claim 9, wherein the number of grains present per surface unit of the decorated composite material is comprised between 2500 and 640000 dots per square inch.

13. A sliding board according to claim 9, wherein the ratio of the surface occupied by the grains on a unit surface is comprised between 20% and 75%.

14. A sliding board according to claim 9, wherein an ink grain has a larger dimension comprised between 10 and 100 μm.

15. A sliding board according to claim 9, wherein the pattern is printed on the three-dimensional external surface of the composite material.

16. A sliding board according to claim 9, wherein the pattern covers the upper face of the sliding board.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0045] As the way to implement the disclosed embodiments, as well as the advantages which arise from it, will emerge from the description of the embodiments below, in accordance with the appended figures in which:

[0046] FIG. 1 is a photograph, taken with a microscope, of the upper portion of a sliding board of the prior art, decorated by sublimation of an ink in the resin.

[0047] FIG. 2 is a median transverse cross-section of the upper portion of the sliding board including on its visible face, a decorated composite material comprising one single type of ink grain.

[0048] FIG. 3 is a median transverse cross-section of the upper portion of a sliding board including on its visible face, a decorated composite material comprising two types of ink grain.

[0049] FIG. 4 is a photograph taken with a microscope, with a magnification comparable to the magnification of FIG. 3, of the surface of a sliding board.

[0050] FIG. 5 is a flowchart of the chain of the steps of the methods described herein.

[0051] FIG. 6 is a cross-sectional representation of the printed transfer film during the first step of the method of FIG. 3, according to a first embodiment.

[0052] FIG. 7 is a representation similar to FIG. 6, according to a second embodiment.

[0053] FIG. 8 is a cross-sectional representation of the film applied to the surface of the resin, during the second step of the method of FIG. 3.

[0054] FIG. 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 method of FIG. 3.

[0055] FIG. 10 is a cross-sectional representation of the upper portion of the sliding board once the transfer film is peeled during the fourth step of the method of FIG. 3.

DETAILED DESCRIPTION

[0056] FIGS. 2, 3 and 6-10 are not represented to scale to facilitate the understanding of the reader. In particular, the thickness of the supernatant resin layer 13 is exaggerated to illustrate the phenomena which occur within this layer. In particular, the form of the ink grains 11, 21 is schematised by a mainly rectangular form, which is not necessarily representative of the actual form of the grains 11, 21.

[0057] FIGS. 2 and 3 illustrate a median transverse cross-section of the upper portion of a sliding 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 sliding board, as a reinforcement. The upper face of the composite material 15 is visible and therefore appears decorated.

[0058] A composite material 15 is typically formed of a fibrous layer 14 made of glass fibre, carbon, basalt or long or short, one-directional or oriented natural fibres, or also constituted of a non-woven material, for example polyester thread-based. In any case, the fibrous layer 14 is impregnated with thermosetting resin 13, for example an epoxy, or thermoplastic resin, like a polyamide resin. The resin 13 has a supernatant portion above the fibrous layer 14. This supernatant resin portion 13 has a thickness of a few micrometres.

[0059] The decor is presented in the form of an arrangement of ink grains 11, 21 embedded in the resin 13 on a thickness less than 10 μm. The decor can have one or more layers of one or more types of grains 11, 21.

[0060] As an example, FIG. 2 only presents one single type of grains 11, distributed over two superposed layers, corresponding to an ink of one single given colour. FIG. 3 also presents two superposed 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 colours.

[0061] Such as illustrated in FIG. 4, the grains 11, 21 have a substantially rounded, solidified and/or dried droplet appearance.

[0062] They can be isolated and completely surrounded in the resin or contiguous with one or more other grains 11, 21 of the same layer or of an upper or lower layer. The upper portion of the grain 11 can also emerge partially or totally to open air. Generally, the decor does not appear as an excess thickness by touch as the resin is predominant on the surface, such that the surface remains smooth and relatively homogenous.

[0063] In the case where several layers have been superposed, it is difficult to perceive the spaces between the particles, but with a sufficient magnification, for example obtained with a microscope, like in FIG. 4, the distinctive form of the grains 11, 21 can be highlighted. It is also easier to see these grains 11, 21 at the edge of the decor, as in this place there are often less superposed decorated passes.

[0064] The type of a grain 11, 21 varies according to the ink used, typically the nature of the polymer or of the colourant can vary. In any case, the ink used is an ink in solid and non-sublimable form, which does not pass to the liquid state, nor to the gaseous state when it is heated. On the contrary, if the ink composing a grain 11, 21 is heated, this is irremediably degraded, it even burns and carbonises. In particular, the ink is, for example, composed of a crosslinked polyurethane, polyacrylate or polyacrylic polymer.

[0065] This type of ink can integrate all types of colourants, even white, contrary to the sublimable inks of the state of the art where there is no white.

[0066] The decor obtained is precise and clean, since the grains 11, 21 do not diffuse in the resin. FIGS. 1 and 4 allow to compare a product obtained thanks to the principle of the disclosed embodiments, which can be seen in FIG. 4, and a product obtained by sublimation of ink in the resin, which can be seen in FIG. 1.

[0067] In FIG. 4, the clean contours of the grain arrangement 11, 21 surrounded by the resin 13 is distinguished. While in FIG. 1, no grains are observed, but a continuous layer of ink 31, which gradually melts in the resins, a sign that the ink 31 diffuses in the resin 13.

[0068] The sliding board can thus be decorated on all its faces and even on surfaces at particular geometries, like curved surfaces. For example, in the case where the composite reinforcement is extended laterally on the ski flanks, it is possible to decorate the top and the flanks of a ski continuously, without losing precision or deformation of the decor at the level of the angles or curves.

[0069] Advantageously, an increase of 40 g on a 550 g cross-country ski, has been achieved by the Applicant by replacing a decor by inputting material by the decoration method of the disclosed embodiments.

[0070] The method allowing to obtain such a sliding board is illustrated in FIG. 5 and comprises four successive steps.

[0071] The first step 210, illustrated in FIGS. 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.

[0072] The pattern of the decor is printed on the transfer film 12, with the film flat.

[0073] Advantageously, the transfer film 12 is chosen to be able to deform without breaking during transport and implementation in the mould.

[0074] For three-dimensional sliding boards the surface of which includes edges delimiting separate 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 to cracking comprised between 60 and 100% of its initial surface. Otherwise formulated, the transfer film 12 can be extended up to twice its initial size before cracking.

[0075] Furthermore, the transfer film 12 comprises at least one face having a roughness intended to mechanically retain the grains 11, 21 of the decor. The roughness is chosen to allow to hold the pattern in place on the transfer film 12, without migration during the movement and the positioning of the transfer film 12 on the surface of the resin, all the more so the decorated face of the transfer film 12 is oriented downwards during the moulding of the board.

[0076] In addition, the roughness is also chosen to limit the contact surface with the grains 11, 21, such that these transfer into the resin 13 when a predetermined pressure is applied on the transfer film 12. Typically, the average roughness Ra is comprised 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 the troughs 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 troughs over a predetermined length. Preferably, the maximum roughness Rz is comprised between 15 and 30 μm, typically close to 23 μm.

[0077] Two different techniques can be used to perform the printing of the pattern: printing by inkjet or screen printing.

[0078] Printing by inkjet is performed by a printer comprising printing heads allowing to deposit liquid ink drops on the surface of the transfer film 12 with a linear resolution comprised between 200 and 500 dpi, typically 360 dpi, that is around 130000 drops per square, of which the sides are 2.54 cm, that is around 20000 drops per cm.sup.2. The diameter of the drops deposited is comprised between 10 and 100 μm, typically 24 μm. The dimensions of the drops and of the grains can be measured by traditional image analysis techniques from images similar to that of FIG. 4.

[0079] The ink generally contains a photopolymerising agent. After deposition of ink drops on the transfer film 12, these are exposed to UV light allowing to initiate the polymerisation and/or the crosslinking of the ink. Thus, the ink is fixed and in a solid, stable and irreversible state. As an example, inks of the ALTAMIRA DESIGN DP® range, commercialised by the Company AGFA, or inks of the UVIJET KO® range of the Company FUJIFILM can be used for printing by inkjet. The ink chosen also has a certain malleability after polymerisation, as well as a chemical nature allowing to both not crack during the deformation of the transfer film 12 and to not be denatured in contact with the resin 13.

[0080] In the case of screen printing, screens comprising holes of a diameter comprised between 10 and 100 μm, typically 40 μm, are disposed facing the transfer film 12. The linear resolution is comprised between 50 and 150 dpi, typically 120 dpi, that is around 15000 drops per square, of which the sides are 2.54 cm, that is around 2300 drops per cm.sup.2.

[0081] The liquid ink passes through the holes and creeps lightly arriving on the transfer film 12. The ink contains a solvent which can evaporate either at ambient temperature, or in an oven. The ink polymerises and/or is crosslinked by inputting external energy, typically under the effect of ambient humidity, of exposure to light or under the effect of an increase in temperature, to be found irreversibly in a stable, solid state.

[0082] 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, that is around 10 μm.

[0083] It is generally easier to create large surfaces evenly decorated with screen printing than with inkjet. With a printing by inkjet, it will be necessary to affix several ink layers to obtain a similar result.

[0084] Such as illustrated in FIG. 6, the ink layer can be composed of one single pass of ink grains 11 of a first type. The ink grains 11 are generally deposited regularly on the surface of the transfer film 12.

[0085] Such as illustrated in FIG. 7, the ink layer can be composed of several passes of ink grains 11, 21 of several types.

[0086] In any case, the ink and the surface state, i.e. the roughness of the transfer film 12 are chosen for having a mutual adhesion force allowing to hold the pattern 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, all the more so the decorated face of the transfer film 12 is oriented downwards during the moulding 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 for impregnating the composite to facilitate the detachment of the grains 11, 21 from the transfer film 12 and their attachment to the resin 13. Such as illustrated in FIG. 8, step 220 of the method consists of depositing the transfer film 12 to the surface of the resin 13 of the composite 15. In principle, the pattern is mirror-printed on the transfer film 12 such that, when the transfer film 12 is returned on the resin 13, the pattern is in the desired orientation, for example legible in the case of a written document.

[0087] Such as illustrated in FIG. 9, in step 230, pressure and temperature conditions, typically comprised between 3 and 10 bars and 80 and 120° C., are applied on the composite 15 covered with the printed transfer film 12. In the case of a simple transfer of decor on a composite 15, without problems with gluing different elements together, a pressure greater than or equal to 3 bars is sufficient. This can be applied for example when the composite 15 is decorated prior to the assembly of the ski in a mould.

[0088] Furthermore, the transfer temperatures described above are compatible with the use of polyethylene-type materials, generally constituting the sliding soles of the skis. In the extreme, the temperature can even be ambient temperature, but the hardening time of the resin is thus a lot longer.

[0089] For a thermoplastic resin 13, this is in the solid state before the pressure and temperature conditions are applied on the sliding board. The increase in pressure and in temperature allows to soften the thermoplastic resin 13. It is in this phase that the grains 11 in the solid state composing the decor will be incrusted in the softened resin 13. Then, the cooling phase allows the return of the assembly formed by the resin 13 incrusted with grains 11 in the solid state.

[0090] In the case of a thermosetting resin 13, this is in the liquid state. It is in this phase that the grains 11 in the solid state composing the decor will be incrusted in the liquid resin 13. The increase in pressure and in temperature allows to harden the thermosetting resin 13 around the grains 11.

[0091] In any case, the resin 13 in the liquid state during the moulding fills all the free spaces left by the ink grains 11 from the fibrous reinforcement 14, to the surface of the sliding board, before hardening, either by crosslinking, or by cooling, according to the nature of resin used.

[0092] FIG. 10 illustrates step 240 of the method in which the transfer film 12 is peeled from the solid surface of the composite 15.

[0093] In the case of manufacturing a ski, the composite 15 is generally impregnated beforehand, then transferred into the mould with the other components constituting the ski. The application of the pressure and temperature conditions allows to agglomerate the different constitutive layers of the ski, as well as hardening the resin. In this case, 6 to 10 bars, and preferably 8 bars are preferably applied on the mould. This pressure further allows to repel the excess resin and to obtain a composite 15 having a resin rate comprised between 15 and 30%, typically 20%. In a variant, the composite 15 can also be impregnated with resin directly in the mould.

[0094] Moreover, the transfer of the pattern in the composite 15 can be done in several ways. A first method consists of applying the transfer film 12 on the composite 15 after its placement in the mould. A second method consists of applying the transfer film 12 beforehand on the composite 15, then to transfer the assembly formed by the impregnated composite 15 and the transfer film 12 in the mould. The pressure and temperature conditions applied to the mould then allowing the transfer of the pattern from the transfer film 12 to the superficial resin layer 13.

[0095] In the case of a thermoplastic resin, it can also be devised to perform the transfer of the pattern into the composite 15 before moulding. To do this, pressure and temperature conditions allowing the softening of the thermoplastic resin must be applied beforehand on the assembly formed by the impregnated composite 15 and the transfer film 12. Subsequently, during moulding, the thermoplastic resin can nonetheless be softened, while conserving the pattern such as transferred.

[0096] To conclude, the disclosed embodiments advantageously allow to obtain a sliding board with a clean decor, not having any or few deformations and which resists external aggressions. The method for manufacturing such a sliding board is versatile and allows to obtain multiple decors with a lot of contrast and without limitation in terms of colours. Moreover, according to the ink grain coverage rate of the resin, the touch can be modified to improve the gripping of the sliding board.