Method for producing a decorative surface

Abstract

A method for producing a decorative surface comprises the step of providing a carrier comprising a coating layer (21) having a macrostructure. The macrostructure comprises embossments (25). The method comprises the step of applying a lacquer layer (50) onto the coating layer (21). The lacquer layer (50) comprises at least components comprising radiation curable double bonds. The method comprises the step of submitting the lacquer layer (50) to excimer radiation (52), thereby providing the decorative surface with a microstructure. The microstructure is provided by a wrinkled surface of the lacquer layer (50), while maintaining a macrostructure provided by the embossments (25).

Description

[0001] Method for producing a decorative surface

[0002] The invention relates to a method for producing a decorative surface and to such decorative surfaces.

[0003] It is known to provide boards, e.g. wood fiber boards, with a decorative surface in the production of decorative panels. The decoration can comprise a printed decor and a textured surface. A very realistic impression of e.g. a wood decor can be obtained when the surface is provided by embossing with a wood texture in register with a printed wood decor.

[0004] It is known to provide wood fiber panels with decorative surfaces using melamine formaldehyde resins. Such approach is e.g. known from WO97 / 47834.

[0005] Acrylate coating compositions and methods for applying a protective acrylate coating layer onto a substrate for the production of a decorative panel are disclosed in W02020 / 095196A1.

[0006] WO202 1 / 224843 Al relates to a partially cured coated sheet and discloses a sheet that comprises a support layer and a coating layer on a side of the support layer. The coating layer is partially cured. The coating layer comprises carbon-carbon double bonds, wherein the relative amount of carbon-carbon double bonds is higher at the surface of the coating layer than at the contact surface of the coating layer with the support layer. Methods are disclosed to manufacture such sheets; and to produce a decorative panel using such sheets.

[0007] EP3725519A1 discloses a method for producing a decorative panel. The method comprises the steps of coating a carrier web with a first liquid coating mass, drying the coated carrier web, further coating the carrier web with a second liquid polymerizable coating composition - which is either a one-component coating system or a two- component coating system - to obtain a coated film, irradiating the coated film with UV radiation of a certain wavelength to thereby form a microstructure on the surface, followed by a step of producing a multilayer structure comprising the coated carrier web and at least one core layer, followed by a step of pressing the multilayer structure.

[0008] Especially in the field of furniture panels, there is a requirement for anti-finger print decorative surfaces as well as for very mat surfaces.

[0009] Therefore, it is an object of the invention to provide a method to provide appealing decorative panels with anti-finger print properties.

[0010] The first aspect of the invention is a method for producing a decorative surface. The method comprises the step of providing a carrier comprising a coating layer having a macrostructure. The macrostructure comprises embossments. The method is characterized in that it comprises the step of applying a lacquer layer onto the coating layer, wherein the lacquer layer comprises at least components comprising radiation curable double bonds; and the step of submitting the lacquer layer to excimer radiation. The decorative surface is thereby provided with a microstructure, wherein the microstructure is provided by a wrinkled surface of the lacquer layer, while maintaining a macrostructure provided by embossments.

[0011] The method provides the decorative surface with a combination of an embossed macrostructure which provides the visual appealing effect of the decorative surface and a microstructure provided by the wrinkled surface of the lacquer layer.

[0012] The method can be used with macrostructures comprising deep embossments, e.g. embossments having at least a depth of at least 100 micrometer, preferably at least 200 micrometer, more preferably at least 300 micrometer, more preferably at least 400 micrometer, more preferably at least 500 micrometer, more preferably at least 600 micrometer, more preferably at least 700 micrometer, even more preferably at least 800 micrometer. Embossments are defined as textures in the decorative surfaces, e.g. simulations of wood pores, but exclude bevels or other chamfers at the edge or edges. The wrinkled surface provides a soft touch and anti-finger print properties of the decorative surface. These functionalities cannot be achieved by introducing matting agents in a coating or lacquer layer, nor by a microstructure obtained by copying a structured press element.

[0013] The wrinkled surface is created by the use of examiner radiation to cure the surface of the lacquer layer. The excimer curing ensures a thorough curing of the surface of the lacquer layer during which tensions occur in the surface of the lacquer layer. These tensions create the wrinkled surface.

[0014] The wrinkled surface preferably shows elongated peaks; and valleys between elongated peaks. Preferably, the valleys comprise elongated valleys.

[0015] The excimer radiation used preferably has a wavelength of 172 nm. Such excimer radiation has shown to provide the lacquer layer with an appropriate wrinkled surface.

[0016] A xenon excimer light source can be used to emit excimer radiation of 172 nm wavelength.

[0017] The macrostructure can comprise a pressed bevel on one or on a multiple number of edges of the decorative surface. The pressed bevel is also covered by the coating layer and by the lacquer layer, wherein in the method the surface of the pressed bevel is also provided by a wrinkled surface of the lacquer layer. Such bevel can have a highest depth of at least 500 micrometer, or even of at least 800 micrometer, or even of at least 1200 micrometer, or even of at least 1500 micrometer. Such bevel can be straight or curved.

[0018] Preferably, the wrinkled surface is a randomly wrinkled surface. The wrinkled surface is a wrinkled surface when the wrinkles of the wrinkled surface are obtained in an unpredictable way. This can be obtained by not taking actions which would position the wrinkles specifically on the surface of the lacquer layer or which would cause the wrinkles to be created in a predetermined pattern. A preferred method is characterized in that in every square surface of 100 micrometer by 100 micrometer of the decorative surface, the first diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N1 of peaks of wrinkles, and the second diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N2 of peaks of wrinkles, wherein the sum of the numbers N1 and N2 is at least 10.

[0019] The numbers N1 and N2 can be determined by analyzing Scanning Electron Microscope pictures of the decorative surface.

[0020] The wrinkled surface of the lacquer layer preferably comprises wrinkles having a length between 50 and 100 micrometer. The wrinkles can be seen and their size measured using Scanning Electron Microscopy (SEM) or using Atomic Force Microscopy. As an example, magnification 300 or 1000 could be used. Such wrinkled surface provides a soft touch and anti-finger print properties to the decorative surface.

[0021] Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a length between 50 and 100 micrometer. Such embodiments are particularly beneficial for providing the decorative surface with a soft touch and anti-finger print properties.

[0022] The wrinkled surface of the lacquer layer preferably comprises wrinkles having a width between 2 and 15 micrometer.

[0023] Preferably, the wrinkled surface of the lacquer layer comprises wrinkles having a width of more than 5 micrometer.

[0024] Preferably, the wrinkled surface of the lacquer layer comprises wrinkles having a width of less than 10 micrometer.

[0025] Such specifications for the width of the wrinkles of the wrinkled surface of the decorative surface are favorable for achieving the targeted performance and properties of the decorative surface.

[0026] Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a width between 2 and 15 micrometer. Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a width of more than 5 micrometer.

[0027] Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a width of less than 10 micrometer.

[0028] Such specifications for the width of the wrinkles of the wrinkled surface of the decorative surface are favorable for achieving the targeted performance and properties of the decorative surface.

[0029] A preferred method is characterized in that the microstructure which is obtained in the method is a uniform microstructure over the full surface of the decorative panel.

[0030] Such embodiments provide the decorative surface with uniform surface properties over its full surface.

[0031] A preferred method is characterized in that the microstructure does not comprise cracks.

[0032] The inventors have noticed that a disturbance of the microstructure occurs if first an excimer curing is applied to a coating or lacquer layer followed by a pressing operation in which the coating or lacquer layer is embossed. The excimer curing results in a brittle surface, which is damaged in the pressing operation in which the coating layer is embossed. The damage takes the form of cracks being formed in the coating or lacquer layer. Of course, it could be possible to drastically limit the curing of the surface in the excimer step, however this would not result in the claimed wrinkled surface.

[0033] Preferably, the lacquer layer reduces the depth of the embossments of the macrostructure with less than 50%. Meant is that when the depth of an embossment is measured before applying the lacquer layer and the depth of the same embossment is measured after the step of submitting the lacquer layer to excimer radiation, the reduction of the depth - thus compared to the depth before applying the lacquer layer - is less than 50%. Preferably, the gloss value of the obtained decorative surface is less than 6 points when measured at an angle of 60°.

[0034] The gloss value can be measured according to ISO 2813:2014 with a micro-TRI-gloss measuring device, for example provided by BYK-Gamer.

[0035] Preferably, the gloss value of the obtained decorative surface when measured at an angle of 60° is substantially uniform over the full decorative surface.

[0036] Preferably, the variation of gloss value measured at an angle of 60° over the obtained decorative surface is less than 3.5 points, and more preferably less than 3 points, even more preferably less than 2 points.

[0037] The coating layer preferably is an acrylate coating layer. Such coating layers are preferred as they allow to obtain excellent adhesion between the coating layer and the lacquer layer.

[0038] Preferably, the coating layer weighs between 20 and 300 gram per square meter.

[0039] The excimer radiation step may be followed by a UV- curing step or by a thermal curing step.

[0040] The UV-curing step or the thermal curing step is beneficial to cure the lacquer layer through its entire thickness, as well as to enhance the adhesion of the lacquer layer to the coating layer. The adhesion of the lacquer layer to the coating layer can be enhanced by the creation of covalent bonds between the lacquer layer and the coating layer in the UV- curing step or in the thermal curing step.

[0041] A UV-curing step or a thermal curing step after the excimer radiation step is of interest as the excimer curing step focusses on curing the surface of the lacquer layer. A preferred lacquer layer has between 10 and 30 (and preferably less than 20) gram per square meter solid weight. More preferably, the lacquer layer has less than 20 gram per square meter solid weight.

[0042] Such values for the solid weight of the lacquer layer are beneficial, as it prevents that embossments of the macrostructure of the coating layer are filled excessively with lacquer.

[0043] Furthermore, a thin lacquer layer can be sufficient, as it is only applied to provide the decorative surface with the microstructure, which is a real surface effect, meaning it does not require a large thickness of the lacquer layer for the wrinkled surface of the lacquer layer to be created by the excimer radiation.

[0044] With “solid weight” is meant the weight of the lacquer layer after its curing.

[0045] The lacquer layer can be applied in more than one lacquer application steps, wherein the lacquer applied in the more than one lacquer application steps are the same or differ from each other.

[0046] The lacquer layer can be applied in two lacquer application steps. The lacquer of the first lacquer application can be the same - meaning having the same composition - as the lacquer of the second lacquer application step, or the composition of the lacquer of the first lacquer application can differ from the composition of the lacquer of the second lacquer application step.

[0047] It is a benefit of the application of the lacquer layer in a first lacquer application followed by a second lacquer application that a more homogeneous lacquer layer can be obtained. A more homogeneous lacquer layer is beneficial for the homogeneity of the wrinkled surface obtained in the excimer curing step, and for the resulting soft touch and antifinger print properties. In embodiments wherein the lacquer layer is applied in at least two steps, e.g. in two steps, a first lacquer can be applied for improving the adhesion with the coating layer, and a second lacquer can differ in composition from the first lacquer layer. The second lacquer may be a lacquer which, if applied directly on the coating layer, provides less adhesion to the coating layer than the first lacquer.

[0048] The lacquer layer can be obtained by applying a lacquer comprising oligomers having a molecular mass higher than 800 gram / mol and reactive diluents, wherein the reactive diluents have a molecular mass lower than 800 gram / mol. The reactive diluents can be reactive diluents having reactive acrylate groups.

[0049] In embodiments wherein the lacquer layer is applied in at least two steps, e.g. in two steps, the lacquer of a or the first lacquer application preferably has a higher mass percentage of reactive diluent than the lacquer of a or the second lacquer application. Such embodiments are preferred as adhesion with the coating layer is improved.

[0050] Prior to the step of applying the lacquer layer onto the coating layer on the carrier, a primer - preferably between 5 and 10 gram per square meter dry weight - can be applied onto the coating layer.

[0051] The primer is beneficial for improving the adhesion of the lacquer layer.

[0052] After applying the primer, a drying or partial curing step may be performed.

[0053] A primer may comprise a higher percentage by weight of reactive diluents having a number based molecular mass less than 800 gram per mol than the lacquer that is applied. The higher amount of such reactive diluents provide better penetration and better adhesion with the coating layer.

[0054] The step of applying the lacquer layer is preferably performed when the coating layer still comprises reactive carbon - carbon double bonds, e.g. reactive acrylate groups. It is a benefit of such embodiment that an improved adhesion can be obtained between the lacquer layer and the coating layer via formation of covalent bonds. This is especially the case when the lacquer comprises reactive carbon - carbon double bonds, e.g. reactive acrylate groups, and / or when the lacquer comprises reactive groups that can react with the reactive carbon - carbon double bonds, e.g. reactive acrylate groups, of the coating layer.

[0055] A preferred method is characterized in that the step of applying the lacquer layer is followed by the step of brushing the lacquer layer before the step of submitting the lacquer layer to excimer radiation.

[0056] The brushing operation has the benefit that excessive amount of lacquer is removed from deep embossments, such as from deep pores of wood simulation surfaces. This way, a deeper depth of deep embossments is maintained in the final product, i.e. after the excimer radiation step. The brushing operation can be performed with brushes comprising bristles, with brushes comprising a felt type surface, or with brushes comprising a foam surface, or with any other brush type that has as an effect that the amount of lacquer that is applied is reduced.

[0057] Furthermore, the brushing operation provides a more uniform amount of lacquer that is applied.

[0058] The step of applying the lacquer layer is preferably performed in line with the step of embossing the coating layer in a thermal pressing operation.

[0059] The step of embossing the coating layer can be performed using a structured press element, e.g. in a short cycle press, in a multistage press element or using an embossing roller. In the pressing operation, the texture of the structured press element can be copied to the coating layer.

[0060] The step of embossing the coating layer can also be performed using a texturing foil in which the texture of the texturing foil is pressed into the coating layer. The thermal pressing operation can be performed such that the coating layer flows, thereby embossing the coating layer.

[0061] The thermal pressing operation can combine the provision of the embossments - and optionally also one or more bevels - in the coating layer with a partial or full curing of the coating layer in the embossed state.

[0062] In the thermal pressing operation, addition reactions can occur between double carbon - carbon bonds in the coating layer to such an extent that at the moment of applying the lacquer layer reactive carbon - carbon double bonds are still present in the coating layer.

[0063] Such embodiment has the advantage that good adhesion is obtained between the lacquer layer and the coating layer, certainly when a lacquer is applied to form the lacquer layer which comprise reactive carbon - carbon double bonds, e.g. reactive acrylate groups.

[0064] The conversion rate of the carbon - carbon double bonds in the thermal pressing operation is preferably less than 85%. This way, an appropriate number of carbon - carbon double bonds remain available for creating excellent adhesion between the lacquer layer and the coating layer.

[0065] The conversion rate of the carbon - carbon double bonds in the thermal pressing operation is preferably more than 60%. This way, the permanency of the embossments is ensured.

[0066] The lacquer applied to provide the lacquer layer can be selected from an acrylate lacquer, an unsaturated polyester lacquer, a polyurethane acrylate lacquer, or combinations thereof.

[0067] Preferred acrylate lacquers, preferred unsaturated polyester lacquers, and preferred polyurethane acrylate lacquer can comprise reactive acrylate groups. The lacquer applied to provide the lacquer layer preferably comprises a photo-initiator; and more preferably at least two different photo-initiators.

[0068] The lacquer layer can comprise a photo-initiator which is activated by the excimer radiation.

[0069] The lacquer layer can comprise a photo-initiator which is less activated by the excimer radiation, but is activated by an optional UV-curing step performed after the excimer radiation step. Such UV-curing step can be performed to cure the lacquer layer throughout its full thickness, and for creating adhesion between the lacquer layer and the coating layer.

[0070] The lacquer layer can comprise a thermo-initiator. A lacquer layer comprising a thermoinitiator can be useful in embodiments wherein the excimer radiation step is followed by a thermal curing step to cure the lacquer layer throughout its full depth. Furthermore, the thermal curing step can be beneficial to enhance the adhesion between the coating layer and the lacquer layer.

[0071] The coating layer can comprise - still at the excimer radiation step - a thermo-initiator. This thermo-initiator can be activated in a thermal curing step after the excimer radiation step. This way, available reactive carbon - carbon double bonds (e.g. reactive acrylate groups) in the coating layer can react, between themselves thereby curing the coating layer further, but also with reactive carbon - carbon double bonds (e.g. with reactive acrylate groups) of the lacquer layer still present after the excimer radiation step thereby enhancing the adhesion between the coating layer and the lacquer layer.

[0072] The lacquer layer can be devoid of a thermo-initiator. For instance in embodiments wherein the excimer radiation step is followed by a UV-curing step, the lacquer can be devoid of a thermo-initiator.

[0073] The carrier preferably comprises a printed decor. The embossments are preferably provided in register with the printed decor. The printed decor can simulate a wood decor or a natural stone decor.

[0074] The macrostructure can simulate a wood texture or a natural stone texture.

[0075] The lacquer applied to provide the lacquer layer may comprise

[0076] - one or more acrylate and / or methacrylate oligomers, preferably wherein said oligomers have a molar mass equal to or higher than 800 g / mol;

[0077] - one or more acrylate reactive diluent and / or methacrylate reactive diluent and / or (meth)acrylamide reactive diluents; wherein the reactive diluents have a molar mass lower than 800 g / mol, and preferably lower than 500 g / mol;

[0078] - at least one photo-initiator; and optionally at least two different photo-initiators;

[0079] - optionally an unsaturated polyester resin.

[0080] Such lacquers are well suited for use in the method according to the invention, as they result in an appropriate wrinkled surface of the lacquer layer.

[0081] Preferred photo-initiators of the acrylate lacquer may comprise or consist of Norrish type I photo-initiators.

[0082] The lacquer layer may optionally comprise at least one thermo-initiator; or no thermoinitiator.

[0083] The lacquer layer may comprise silicone based additives or fluor based additives, or combinations thereof.

[0084] Such embodiments provide the surface of the decorative panel with enhanced soil repelling properties. It is preferred that silicone based additives are used and that the lacquer layer does not comprise fluor based additives.

[0085] The second aspect of the invention is a decorative panel. The decorative panel comprises a carrier, a coating layer and a lacquer layer. The lacquer layer provides the surface of the decorative panel. The coating layer has a macrostructure, wherein the macrostructure is provided by embossments;. The surface of the decorative panel comprises a macrostructure and a microstructure, wherein the macrostructure is provided by embossments of the coating layer. The microstructure is provided by a wrinkled surface of the lacquer layer.

[0086] The microstructure of the decorative panel provides the decorative panel with a soft touch and with anti-finger print properties. These functionalities cannot be achieved by introducing matting agents in a coating or lacquer layer, nor by a microstructure obtained by copying a structured press element.

[0087] A decorative panel according to the second aspect of the invention can be obtained via a method of the first aspect of the invention, and has the benefits mentioned in the description of the method of the first aspect of the invention.

[0088] The wrinkled surface preferably is a randomly wrinkled surface.

[0089] A preferred decorative panel is characterized in that in every square surface of 100 micrometer by 100 micrometer of the decorative surface, the first diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N1 of peaks of wrinkles, and the second diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N2 of peaks of wrinkles, wherein the sum of the numbers N1 and N2 is at least 10.

[0090] The wrinkled surface of the lacquer layer of the decorative panel preferably comprises wrinkles having a length between 50 and 100 micrometer. The wrinkles can be seen and their size measured using Scanning Electron Microscopy (SEM) or using Atomic Force Microscopy. As an example, magnification 300 or 1000 could be used. Such wrinkled surface provides a soft touch and anti-finger print properties of the decorative surface.

[0091] Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer of the decorative panel have a length between 50 and 100 micrometer. Such embodiments are particularly beneficial for providing the decorative surface with a soft touch and anti- finger print properties.

[0092] The wrinkled surface of the lacquer layer of the decorative panel preferably comprises wrinkles having a width between 2 and 15 micrometer.

[0093] Preferably, the wrinkled surface of the lacquer layer of the decorative panel comprises wrinkles having a width of more than 5 micrometer.

[0094] Preferably, the wrinkled surface of the lacquer layer of the decorative panel comprises wrinkles having a width of less than 10 micrometer.

[0095] Such specifications for the width of the wrinkles of the wrinkled surface of the decorative panel are favorable for achieving the targeted performance and properties of the decorative surface.

[0096] Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer of the decorative panel have a width between 2 and 15 micrometer.

[0097] Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer of the decorative panel have a width of more than 5 micrometer.

[0098] Preferably, at least 50% of the wrinkles of the wrinkled surface of the lacquer layer of the decorative panel have a width of less than 10 micrometer.

[0099] Such specifications for the width of the wrinkles of the wrinkled surface of the decorative surface of the decorative panel are favorable for achieving the targeted performance and properties of the decorative surface of the decorative panel.

[0100] A preferred decorative panel is characterized in that the microstructure is a uniform microstructure over the full surface of the decorative surface of the decorative panel. Such embodiments provide the decorative surface of the decorative panel with uniform surface properties over its full surface.

[0101] The microstructure preferably does not comprise cracks.

[0102] Cracks - if large - could disturb the visual appearance of the surface of the decorative panel. Even if small, cracks could disturb the properties and performance of the surface of the decorative panel.

[0103] The coating layer can be an acrylate coating layer, preferably a coating layer of between 20 and 300 gram per square meter.

[0104] The lacquer layer of a preferred decorative panel reduces the depth of the embossments of the macrostructure for less than 50%.

[0105] Preferably, the gloss value of the decorative surface is less than 6 points when measured at an angle of 60°.

[0106] The lacquer layer preferably has a mass between 10 and 30 gram per square meter. More preferably, the lacquer layer has a mass less than 20 gram per square meter.

[0107] The lacquer layer can comprise or consist of two layers. The lacquer of the two layers can be the same or be different.

[0108] A primer coating can be provided between the coating layer and the lacquer layer. The primer coating can have a weight between 5 and 10 gram per square meter.

[0109] Such primer can be an acrylate primer, a polyurethane primer or a polyurethane acrylate primer. The lacquer layer can preferably be selected from an acrylate lacquer layer, a polyester lacquer layer obtained from an unsaturated polyester lacquer, or a polyurethane acrylate lacquer layer.

[0110] A primer coating can be provided between the coating layer and the lacquer layer. The primer coating can have a weight between 5 and 10 gram per square meter.

[0111] Such primer can be an acrylate primer, a polyurethane primer or a polyurethane acrylate primer.

[0112] The lacquer layer of the decorative panel can comprise silicone based additives or fluor based additives, or combinations thereof.

[0113] This way, the surface of the decorative panel is provided with soil repelling properties. It is preferred that silicone based additives are used and that the lacquer layer does not comprise fluor based additives.

[0114] The carrier of the decorative panel preferably comprises a printed decor. The embossments are preferably provided in register with the printed decor.

[0115] The printed decor can simulate a wood decor or a natural stone decor. This way, the decorative panel can simulate a wood panel or a natural stone panel.

[0116] The macrostructure can simulate a wood texture or a natural stone texture.

[0117] A preferred decorative panel according to the second aspect of the invention comprises at its bottom a balancing layer, preferably provided by or comprising a resin impregnated sheet of paper laminated at the bottom of the decorative panel, or a coating layer at the bottom of the decorative panel.

[0118] The third aspect of the invention is a piece for furniture. The piece of furniture comprises a decorative panel as in any embodiment of the second aspect of the invention. The fourth aspect of the invention is a floor covering. The floor covering comprises a plurality of decorative panels as in any embodiment of the second aspect of the invention.

[0119] Such floor coverings can e.g. beneficially comprise decorative panels comprising a whether or not filled polyvinyl chloride based board.

[0120] In the different aspects of the invention, the carrier can be provided by a board. The board can be a board provided with a printed decor, wherein the printed decor is printed on the board, preferably on a primer applied on the board. The printed decor can be provided by analog printing or by digital printing, e.g. by digital ink-jet printing.

[0121] The carrier can be provided by a sheet of paper provided with a printed decor. The sheet of paper is preferably impregnated with a resin, preferably with a thermoset resin.

[0122] The sheet of paper can be laminated to a board. The sheet of paper can be laminated to the board in the same thermal pressing operation in which the coating layer on the sheet of paper has been provided with an embossed surface by using a textured press element of by using a texturing foil.

[0123] The board may in the different embodiments of the invention be provided by a woodbased board, a mineral board or a whether or not filled synthetic board.

[0124] Examples of wood-based boards that can be used in the invention include wood fiber boards, wood particle boards, solid wood boards, engineered wood boards and plywood boards.

[0125] Examples of mineral boards that can be used in the invention include cement based boards, magnesium oxide based boards and gypsum boards. Examples of synthetic boards that can be used in the invention include whether or not filled polyvinyl chloride based boards, whether or not filled polyester based boards and whether or not filled polypropylene based boards.

[0126] The molar mass of a compound is the calculated molar mass. The calculated molar mass is obtained by adding the atomic masses of all atoms present in the structural formula of a compound. When the exact structural formula of a compound is not known, the molar mass of the compound is the number average molecular weight determined using Triple Detection Size Exclusion Chromatography using tetrahydrofuran as eluent.

[0127] With the intention of better showing the characteristics of the invention, hereafter, as an example without any limitative character, several preferred embodiments are described, with reference to the accompanying drawings, wherein:

[0128] Figure 1 shows an embodiment of a method according to the invention;

[0129] Figure 2 shows a decorative panel according to the invention;

[0130] Figure 3 a detail of a decorative panel according to the invention; and

[0131] Figure 4 shows a detail of a section of the microstructure of the decorative surface of a decorative panel according to the invention.

[0132] Figure 1 shows an embodiment of a method according to the invention. Figure 1 shows an embodiment wherein the step of applying the lacquer layer is performed in line with the step of embossing the coating layer in a thermal pressing operation. It is however also possible to perform that step of applying the lacquer layer off line from the step of embossing the coating layer in a thermal pressing operation.

[0133] A stack comprising a balancing layer 13, a wood fiber board 11, and a resin impregnated printed sheet of paper 12 is positioned in a short cycle press 10. The printed sheet of paper can be printed with a wood decor. The balancing layer 13 is provided by a resin impregnated sheet of paper. The resin of the balancing layer 13 and of the resin impregnated printed sheet of paper 12 is partially cured.

[0134] The short cycle press 10 comprises a structured press element 16. A thermal pressing operation is performed in the short cycle press 10. In the thermal pressing operation, the resin impregnated printed sheet of paper 12 and the balancing layer 13 are laminated onto the wood fiber board 11 in which the resins of the resin impregnated printed sheet of paper 12 and of the balancing layer 13 are cured.

[0135] The resin impregnated printed sheet of paper 12 comprises a coating layer 21. The coating layer can be a partially cured acrylate coating layer, meaning that the coating layer still comprises reactive carbon - carbon double bonds, e.g. reactive acrylate groups. In the thermal pressing operation, the texture of the structured press element 16 is copied into the coating layer 21. The pressure and the temperature in the thermal pressing operation causes the partially cured acrylate coating layer to flow, whereby the texture of the structured press element 16 is copied into the coating layer, creating embossments 25 in the coating layer. The increase of temperature results in a curing of the coating layer. To this end, the coating layer can comprise a thermo-initiator which is activated in the thermal pressing operation. However, it is preferred that the coating layer 21 is not fully cured in the thermal pressing operation, e.g. that a carbon - carbon double bond conversion of less than 85% - and preferably at least 60% - is obtained in the thermal pressing operation.

[0136] The texture of the structured press element 16 can be a wood texture, which can be pressed in the coating layer 21 in register with the printed wood decor.

[0137] In the thermal pressing operation, a decorative panel is obtained having a decorative surface. At the same time, and in a same manner, bevels can be pressed at one or several edges of the board; or at sections of the board which will form edges of decorative panels cut from the board in a later processing operation.

[0138] In line with the thermal pressing operation, a first lacquer 30 is applied on the embossed coating layer 21 using a lacquer application unit 31. The application of the first lacquer 30 can optionally be followed by a brushing operation 33 using a brush 34 to remove excess of first lacquer that has been applied. This way, excessive filling of embossments - especially of deep embossments - with the first lacquer can be avoided.

[0139] A second lacquer 40 can then be applied on top of the first lacquer using a second lacquer application unit 41. The application of the second lacquer 40 can optionally be followed by a second brushing operation 43 using a brush 44 to remove excess of second lacquer that has been applied. This way, excessive filling of embossments - especially of deep embossments - with the second lacquer can be avoided.

[0140] The combination of the first lacquer 30 and the second lacquer 40 provide a lacquer layer 50 onto the coating layer 21.

[0141] Although figure 1 shows the application of the lacquer layer 50 by applying a first lacquer 30 and a second lacquer 40, it is also possible to apply the lacquer in just one lacquer application operation. It is also possible to apply a primer coating before applying one or more than one lacquers to provide the lacquer layer.

[0142] The lacquer layer 50 comprises components comprising radiation curable double bonds, e.g. reactive acrylate groups or unsaturated polyester components.

[0143] The lacquer layer 50 is then submitted to excimer radiation 52, e.g. with excimer radiation of 172 nanometer wavelength. The decorative surface is thereby provided with a microstructure. The microstructure is provided by a wrinkled surface of the lacquer layer, while maintaining a macrostructure provided by embossments. The method can comprise a UV-curing step 54 in which the lacquer layer 50 is cured throughout its depth. The coating layer 21 is also cured. Adhesion is created between the lacquer layer 50 and the coating layer 21. Instead of a UV-curing step - or in combination with a UV-curing step - it is possible to perform a thermal curing step.

[0144] The result is a decorative panel 60 comprising a microstructure provided by a wrinkled surface of the lacquer layer, while a macrostructure provided by embossments obtained in the thermal pressing operation is maintained.

[0145] Figure 2 shows a view according to II-II of the decorative panel 60 shown in figure 1. The decorative panel 60 comprises a balancing layer 13, a wood fiber board 11, a resin impregnated printed sheet of paper 12, an embossed coating layer 21 and a lacquer layer 50. The lacquer layer 50 has a microstructure provided by a wrinkled surface of the lacquer layer. The microstructure is not visible in figure 2. The embossments of the coating layer 21 show a wood texture, in register with the printed wood decor of the resin impregnated printed sheet of paper 12.

[0146] Figure 3 shows a detail of the decorative panel of figure 2. The detail is a Scanning Electron Microscopy picture taken at magnification 1000. Figure 3 shows the wrinkled surface of the microstructure. The wrinkled surface is a randomly wrinkled surface. The wrinkled surface is a uniform wrinkled surface over the full surface of the decorative panel, without cracks in the lacquer layer. The wrinkles of the wrinkled surface comprise peaks and valleys.

[0147] Figure 4 shows a detail of a section of the microstructure of the decorative surface of a decorative panel according to the invention. Figure 4 shows a square surface of D 100 micrometer by D 100 micrometer at magnification 1000. A first diagonal DI and a second diagonal D2 are drawn in this square surface. The number N1 of peaks of wrinkles crossed by the first diagonal DI can be counted and the number N2 of peaks of wrinkles crossed by the second diagonal can be counted. In a preferred embodiment of the invention, the sum of the numbers N1 and N2 is for every square surface of 100 by 100 micrometer of the decorative surface higher at least 10. An example of a recipe that can be used for the lacquer of the lacquer layer is:

[0148] 35 parts by weight of an aliphatic urethane acrylate oligomer having acrylate functionality equal to four;

[0149] 20 parts by weight of a polyester acrylate oligomer having acrylate functionality three;

[0150] 20 parts by weight of glyceryl propoxy triacrylate (GPTA), a trifunctional acrylate reactive diluent;

[0151] 5 parts by weight of dipropylene glycol diacrylate (DPGDA), a difunctional acrylate reactive diluent;

[0152] 20 parts by weight of tripropylene glycol diacrylate (TPGDA), a difunctional acrylate reactive diluent;

[0153] 0.2 parts by weight of photo-initiator activated by radiation having 172 nm wavelength; and

[0154] 0.2 parts by weight of photo-initiator activated by UV-A or UV-B radiation.

[0155] The lacquer layer of the decorative panel can additionally comprise silicone based additives or fluor based additives, or combinations thereof.

[0156] The present invention is in no way limited to the embodiments described as examples and represented in the figures, on the contrary it can be realized in various forms and dimensions, without leaving the scope of the invention.

Claims

Claims1.- Method for producing a decorative surface, wherein the method comprises the step of providing a carrier (12) comprising a coating layer (21) having a macrostructure, wherein the macrostructure comprises embossments; characterized in that the method comprises the step of applying a lacquer layer (50) onto the coating layer (21), wherein the lacquer layer comprises at least components comprising radiation curable double bonds; and the step of submitting the lacquer layer to excimer radiation, thereby providing the decorative surface with a microstructure, wherein the microstructure is provided by a wrinkled surface of the lacquer layer, while maintaining a macrostructure provided by the embossments.2.- Method as in claim 1, characterized in that the wrinkled surface is a randomly wrinkled surface.3.- Method as in any of the preceding claims, characterized in that in every square surface of 100 micrometer by 100 micrometer of the decorative surface, the first diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N1 of peaks of wrinkles, wherein the second diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N2 of peaks of wrinkles; wherein the sum of the numbers N1 and N2 is at least 10.4.- Method as in any of the preceding claims, characterized in that the wrinkled surface of the lacquer layer comprises wrinkles having a length between 50 and 100 micrometer.5.- Method as in claim 4, characterized in that at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a length between 50 and 100 micrometer.6.- Method as in any of the preceding claims, characterized in that the wrinkled surface of the lacquer layer comprises wrinkles having a width between 2 and 15 micrometer.7.- Method as in claim 6, characterized in that at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a width between 2 and 15 micrometer.8.- Method as in any of the preceding claims, characterized in that the microstructure is a uniform microstructure over the surface of the decorative surface; and / or that the microstructure does not comprise cracks.9.- Method as in any of the preceding claims, characterized in that the lacquer layer reduces the depth of the embossments of the macrostructure for less than 50%.10.- Method as in any of the preceding claims, characterized in that the gloss value of the obtained decorative surface is less than 6 points when measured at an angle of 60°.11.- Method as in any of the preceding claims, characterized in that the coating layer is an acrylate coating layer, preferably a coating layer of between 20 and 300 gram per square meter.12.- Method as in any of the preceding claims, characterized in that the excimer radiation is followed by a UV- curing step or by a thermal curing step.13.- Method as in any of the preceding claims, characterized in that the lacquer layer has between 10 and 30 - and preferably less than 20 - gram per square meter solid weight.14.- Method as in any of the preceding claims, characterized in that the lacquer layer is applied in two lacquer application steps, wherein the lacquer of the first lacquer application is the same as the lacquer of the second lacquer application step, or wherein the composition of the lacquer of the first lacquer application differs from the composition of the lacquer of the second lacquer application step.15.- Method as in any of the preceding claims, characterized in that prior to the step of applying the lacquer layer onto the coating layer on the carrier, a primer - preferably between 5 and 10 gram per square meter dry weight - is applied onto the coating layer.16.- Method as in any of the preceding claims, characterized in that the lacquer layer (50) is applied when the coating layer (21) still comprises reactive carbon - carbon double bonds, e.g. reactive acrylate groups.17.- Method as in any of the preceding claims, characterized in that the step of applying the lacquer layer is followed by the step of brushing the lacquer layer before the step of submitting the lacquer layer to excimer radiation.18.- Method as in any of the preceding claims, characterized in that the step of applying the lacquer layer is performed in line with the step of embossing the coating layer in a thermal pressing operation.19.- Method as in claim 18, characterized in that in the thermal pressing operation addition reactions occur between double carbon - carbon bonds in the coating layer to such an extent that at the moment of applying the lacquer layer reactive carbon - carbon double bonds are still present in the coating layer, preferably wherein in the thermal pressing operation, the conversion rate of the carbon - carbon double bonds is less than 85%.20.- Method as in any of the preceding claims, characterized in that the lacquer applied to provide the lacquer layer (50) is selected from an acrylate lacquer, an unsaturated polyester lacquer, a polyurethane acrylate lacquer, or combinations thereof.21.- Method as in any of the preceding claims, characterized in that the lacquer applied to provide the lacquer layer (50) comprises a photo-initiator, and optionally a thermoinitiator or no thermo-initiator.22.- Method as in any of the preceding claims, characterized in that the carrier comprises a printed decor, preferably wherein the embossments are provided in register with the printed decor.23.- Method as in any of the preceding claims, characterized in that the macrostructure simulates a wood texture or a natural stone texture.24.- Method as in any of the preceding claims, characterized in that the lacquer applied to provide the lacquer layer comprises- one or more acrylate and / or methacrylate oligomers, preferably wherein said oligomers have a molar mass equal to or higher than 800 g / mol;- one or more acrylate reactive diluent and / or methacrylate reactive diluent and / or (meth)acrylamide reactive diluents; wherein said reactive diluents have a molar mass lower than 800 g / mol, and preferably lower than 500 g / mol;- at least one photo-initiator; and- optionally at least one thermo-initiator; or no thermo-initiator.25.- Method as in any of the preceding claims, characterized in that the lacquer layer comprises silicone based additives or fluor based additives, or combinations thereof.26.- Decorative panel (60), comprising a carrier (12), a coating layer (21) and a lacquer layer (50); wherein the lacquer layer provides the surface of the decorative panel; wherein the coating layer has a macro structure, wherein the macrostructure is provided by embossments; wherein the surface of the decorative panel comprises a macrostructure and a microstructure, wherein the macrostructure is provided by embossments of the coating layer; wherein the microstructure is provided by a wrinkled surface of the lacquer layer.27.- Decorative panel as in claim 26, characterized in that the wrinkled surface is a randomly wrinkled surface.28.- Decorative panel as in any of the preceding claims 26 - 27, characterized in that in every square surface of 100 micrometer by 100 micrometer of the decorative surface, the first diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N1 of peaks of wrinkles, wherein the second diagonal of the square surface of 100 micrometer by 100 micrometer crosses a number N2 of peaks of wrinkles; wherein the sum of the numbers N1 and N2 is at least 10.29.- Decorative panel as in any of the preceding claims 26 - 28, characterized in that the wrinkled surface of the lacquer layer comprises wrinkles having a length between 50 and 100 micrometer.30.- Decorative panel as in claim 29, characterized in that at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a length between 50 and 100 micrometer.31.- Decorative panel as in any of the preceding claims 26 - 30, characterized in that the wrinkled surface of the lacquer layer comprises wrinkles having a width between 2 and 15 micrometer.32.- Decorative panel as in claim 31, characterized in that at least 50% of the wrinkles of the wrinkled surface of the lacquer layer have a width between 2 and 15 micrometer.33.- Decorative panel as in any of the preceding claims 26 - 32, characterized in that the microstructure is a uniform microstructure over the full surface of the decorative surface.34.- Decorative panel as in any of the preceding claims 26 - 33, characterized in that the microstructure does not comprise cracks.35.- Decorative panel as in any of the preceding claims 26 - 34, characterized in that the coating layer is an acrylate coating layer, preferably a coating layer of between 20 and 300 gram per square meter.36.- Decorative panel as in any of the preceding claims 26 - 35, characterized in that the lacquer layer reduces the depth of the embossments of the macrostructure for less than 50%.37.- Decorative panel as in any of the preceding claims 26 - 36, characterized in that the gloss value of the decorative surface is less than 6 points when measured at an angle of 60°.38.- Decorative panel as in any of the preceding claims 26 - 37, characterized in that the lacquer layer has a mass between 10 and 30 - and preferably less than 20 - gram per square meter.39.- Decorative panel as in any of the preceding claims 26 - 38, characterized in that the lacquer layer is selected from an acrylate lacquer layer, a polyester lacquer layer obtained from an unsaturated polyester lacquer, or a polyurethane acrylate lacquer layer.40.- Decorative panel as in any of the preceding claims 26 - 39, characterized in that a primer coating - preferably between 5 and 10 gram per square meter - is provided between the coating layer and the lacquer layer.41.- Decorative panel as in any of the preceding claims 26 - 40, characterized in that the lacquer layer comprises silicone based additives or fluor based additives, or combinations thereof.42.- Decorative panel as in any of the preceding claims 26 - 41, characterized in that the carrier comprises a printed decor, preferably wherein the embossments are provided in register with the printed decor.43.- Decorative panel as in any of the preceding claims 26 - 42 - characterized in that the macrostructure simulates a wood texture or a natural stone texture.44.- Piece for furniture, characterized in that the piece of furniture comprises a decorative panel as in any of the preceding claims 26 - 43.45.- Floor covering, characterized in that the floor covering comprises a plurality of decorative panels as in any of the preceding claims 26 - 43.

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