Method for making a decorative panel

Abstract

A method is disclosed for producing a transfer sheet. The transfer sheet comprises a release liner and a partially cured coating layer. The method comprises the steps of providing a release liner; applying a coating to the release liner; and partially curing the coating on the release liner, thereby obtaining a partially cured coating layer on the release liner. The partially cured coating layer comprises a thermo-initiator and unsaturated carbon – carbon bonds, preferably at least partially provided by reactive acrylate groups. The transfer sheet can be used in the production of decorative panels.

Description

[0001] Method for making a decorative panel

[0002] The invention relates to a method for producing a transfer sheet. The transfer sheet can be used in the production of decorative panels. The invention also relates to a method for producing a decorative panel having a decorative surface and a wear layer.

[0003] W02020 / 095196A1 discloses a coated panel and a method for manufacturing a coated panel. The coated panel comprises at least a substrate and a top layer applied on the substrate. The top layer comprises at least a decor layer and a translucent or transparent wear layer. The wear layer comprises a thermally cured acrylate resin or a thermally cured unsaturated polyester resin.

[0004] WO2018 / 176128A1 discloses a membrane covered panel and a membrane covered panel production method. An elastomeric membrane, preferably an aqueous elastomeric resinbased membrane, is applied to a finished panel, prior to pressing of the membrane covered panel. The method is used to produce panels which can be used in the production of flooring materials, wall panels, furniture, countertops, and the like. The membrane is applied to a transfer film, which transfer film can be removed at any time prior to, or after the pressing operation. The panels produced have a durable but elastic surface which can protect the surfaces of the panel. The elastomeric covering on the panel also preferably provides a surface which is abrasion resistant, and provides better acoustical properties while providing a soft touch haptic surface.

[0005] It is an object of the invention to provide improvements over the prior art.

[0006] The first aspect of the invention is a method for producing a transfer sheet. The produced transfer sheet comprises a release liner and a partially cured coating layer. The method comprises the steps of providing a release liner; applying a coating to the release liner; and partially curing the coating on the release liner, thereby obtaining a partially cured coating layer on the release liner. The partially cured coating layer comprises a thermoinitiator and unsaturated carbon - carbon bonds.The transfer sheet obtained in the method of the first aspect of the invention can be used to apply a wear layer onto a substrate in the production of a decorative panel. The partially cured coating layer can be transferred to the substrate and cured in a thermal pressing operation in which the coating layer is laminated to the substrate. In the same thermal pressing operation, the coating layer - which provides the wear layer - can be provided with a texture. Providing the coating layer with the texture is made possible thanks to the partially cured state of the coating layer on the release liner.

[0007] The transfer sheet of the inventive method has the benefit that it can be used to apply a very effective wear layer in an effective way in the production of small batches of decorative panels. The wear layers obtained this way are very effective, as they will have very high wear and scratch resistance, thanks to the curing of the unsaturated carbon -carbon bonds when applying the wear layer to the decorative panel.

[0008] Small batches of decorative panels can be provided with a wear layer as it is easy to use the standard transfer sheet and transfer its coating layer to small volumes of decorative panels, e.g. decorative panels having different printed decors.

[0009] The partially cured coating layer is preferably not tacky. It is a benefit of such embodiments that the transfer sheet can be rolled or stacked without the need of a liner between layers of the transfer sheet.

[0010] The unsaturated carbon - carbon bonds are preferably at least partially - and preferably fully - provided by reactive acrylate groups. This is an efficient and effective way to provide the coating layer with the required ability to be textured in a thermal pressing operation and to obtain a very wear and scratch resistant wear layer as the thermal pressing operation will cause addition reactions between the unsaturated carbon - carbon double bonds initiated by thermal dissociation of the thermo-initiator.

[0011] The unsaturated carbon - carbon bonds can in part of fully be provided by the use of an unsaturated polyester resin in the coating.The release liner can have a textured surface. It is a benefit of release liners having a textured surface that in a thermal pression operation for laminating the coating layer onto a substrate, the coating layer can be textured by copying the texture of the textured surface of the release liner.

[0012] The release liner can have a flat surface onto which the coating is applied. Transfer sheets made this way can be used in a method in which the coating is applied from the transfer sheet onto a substrate wherein the release liner is removed before the pressing operation or after the pressing operation, at will. By using different textured press surfaces (or pressure foil with different textured surfaces), coating layers applied from a same transfer sheet can be provided with different textures.

[0013] The release liner can be or can comprise a polymer film. Polymer films that can be used in the invention include polyethylene films, polypropylene films, polyethylene terephthalate films, polycarbonate films, polyester film and polytetrafluorethylene films.

[0014] The release liner can be or comprise a sheet of paper, e.g. covered by a polymer. The release liner can be or comprise a siliconized sheet of paper or a waxed sheet of paper.

[0015] The release liner can be or can comprise a metal-based foil, such as a steel foil or an aluminum foil.

[0016] The partial curing can at least be performed using UV-radiation. UV-lamps, UV-excimer radiation, UV-emitting light emission diodes (UV-LEDs) can be used to this end.

[0017] Partial curing using UV-radiation has the benefit that it can be done in an easy, efficient and controllable manner.

[0018] When partial curing using UV-radiation is performed, it is preferred that the coating comprises at least a photo-initiator. The photo-initiator can be activated using the UV-radiation and initiate addition reactions of unsaturated carbon - carbon bonds in thecoating. The amount of photo-initiator and the duration and intensity of the UV-radiation can be selected such that only a partial curing is performed, resulting in the presence of unsaturated carbon - carbon bonds in the partially cured coating layer.

[0019] Partial curing of the coating can be performed using electron beam radiation or direct cure radiation. Partial curing using electron beam or using direct cure radiation has the benefit that it can be done in an easy, efficient and controllable manner and without the need of a photo-initiator

[0020] Preferably, direct cure radiation is performed using one or a plurality of doped UV-lamps emitting UV-light between 190 and 220 nm wavelength. More preferably, direct cure radiation is performed on coatings which do not comprise a photo-initiator.

[0021] Partial curing of the coating can be performed using thermal curing, initiating addition reactions between unsaturated carbon - carbon bonds and / or creating urethane bonds.

[0022] When partial curing is performed involving thermal curing, the coating preferably comprises a first thermo-initiator which is selected such that it dissociates in the partial thermal curing and initiates addition reactions of unsaturated carbon - carbon bonds in the coating. The amount of the first thermo-initiator in the coating and the duration and intensity of the thermal curing can be selected such that only a partial curing is performed, resulting in the presence of unsaturated carbon - carbon bonds in the partially cured coating layer.

[0023] Therefore, a preferred method is characterized in that the partial curing comprises or consists of a thermal curing involving dissociation of a first thermo-initiator of the coating applied onto the release liner.

[0024] The partial curing preferably involves reactions in the coating between isocyanate groups and hydroxyl groups.When the partial curing involves urethane bond formation, the coating preferably comprises at least one isocyanate functional component and at least one hydroxyl functional component.

[0025] The at least one isocyanate functional component can be provided by a urethane acrylate oligomer having isocyanate functionality and having acrylate functionality. Preferably, such urethane acrylate oligomer has molar mass less than 800 g / mol.

[0026] It is a benefit of such embodiment that dual curing is possible, on the one hand by urethane bond formation and on the other hand by addition reactions between acrylate groups. The urethane bond formation can be used in the partial curing and the addition reaction curing method can be used in a final thermal pressing operation when the partially cured coating layer is transferred from the transfer sheet onto a substrate and laminated and cured in a thermal pressing operation. The result is efficient processing in combination with high wear and high scratch resistance of the substrate onto which the coating layer is applied as wear layer.

[0027] The at least one hydroxyl functional component can be provided by a component having acrylate functionality and having hydroxyl functionality, preferable wherein the component has molar mass less than 800 g / mol, and more preferably less than 500 g / mol.

[0028] It is a benefit of such embodiment that dual curing is possible, on the one hand curing by urethane bond formation and on the other hand curing by addition reactions between acrylate groups. The urethane bond formation can be used in the partial curing and the addition reaction curing method can be used in a final thermal pressing operation when the partially cured coating layer is transferred from the transfer sheet onto a substrate and laminated and cured in a thermal pressing operation. The result is efficient processing in combination with high wear and scratch resistance of the substrate onto which the coating layer is applied as wear layer.A preferred method is characterized in that the partially cured coating layer comprises a second thermo-initiator having a 60 seconds half time dissociation temperature at least 8°C higher than the 60 seconds half time dissociation temperature of the thermo-initiator.

[0029] It is a benefit that both the thermo-initiator and the second thermo-initiator can be activated in a thermal pressing operation in which the partially cured coating layer is textured and cured. The difference in dissociation temperature between the thermoinitiator and the second thermo-initiator allows more gradual thermal curing during the pressing operation, facilitating the creation of the texture in the coating layer, as the coating layer can flow longer and better. This is especially beneficial for thick coating layers and deep textures, e.g. for textures deeper than 200 micrometer.

[0030] The mass of the partially cured coating layer on the transfer sheet is preferably more than 70 gram per square meter, and more preferably more than 200 gram per square meter.

[0031] Preferably in the partial curing, less than 75% (and more preferably less than 60%) of the unsaturated carbon - carbon bonds of the coating are converted. Such embodiments are preferred, as sufficient flow in the coating will be possible in a thermal pressing operation for texturing and curing the coating layer.

[0032] The coating can be applied by first applying a first coating to the release liner and by applying a second coating onto the first coating.

[0033] Such embodiments provide opportunities for optimizing the cost, processing and properties (e.g. more consistent layer thickness) of the coating layer in the final product.

[0034] The first coating is preferably partially cured before applying the second coating.

[0035] The composition of the first coating can be the same as the composition of the second coating. Such embodiments have the benefit that the regularity of the coating layer can be better controlled by a two-step application of the coating than when applying the full amount of coating in only one single step.The composition of the first coating can differ from the composition of the second coating. Such embodiments provide optimization of the coating.

[0036] It is e.g. possible to apply a second coating which has a cheap composition, and a first coating which has higher performance but which is more expensive. The first coating will provide the top layer in a decorative panel onto which the coating layer is applied via transfer from the transfer sheet.

[0037] Preferably, the composition of the first coating comprises a higher functionality -expressed in number of reactive groups per unit of weight of the coating composition -than the composition of the second coating.

[0038] Such embodiments provide a transfer sheet that, when used to provide a wear layer on a substrate, has higher scratch resistance, thanks to the higher crosslinking density at the surface layer of the wear layer.

[0039] The reactive groups can be provided by unsaturated carbon - carbon bonds (e.g. acrylate groups); and / or by a combination of isocyanate and hydroxyl groups.

[0040] A preferred method is characterized in that the coating applied to the release liner comprises

[0041] - one or more (meth)acrylate oligomers, preferably wherein the oligomers have a molar mass equal to or higher than 800 g / mol;

[0042] - one or more (meth)acrylate reactive diluent and / or (meth)acrylamide reactive diluent; wherein the reactive diluents have a molar mass lower than 800 g / mol, and preferably lower than 500 g / mol; and

[0043] - a thermo-initiator.

[0044] The combination of the one or more (meth)acrylate oligomers and the one or more (meth)acrylate reactive diluent and / or (meth)acrylamide reactive diluents provides a coating of low viscosity meaning that it can be applied easily, while having a highfunctionality per unit of mass. The high functionality per unit of mass will create after full cure a high crosslinking density resulting in a high wear and high scratch resistance of the wear layer obtained from the coating.

[0045] It is a further benefit that the coating comprises no or only very little volatile organic compounds.

[0046] The coating optionally comprises a first thermo-initiator and / or a second thermoinitiator.

[0047] The coating optionally comprises an unsaturated polyester resin. Unsaturated polyester resins are cheap and provide an interesting ability to include unsaturated carbon - carbon double bonds in the coating.

[0048] The coating optionally comprises a photo-initiator. Such embodiments are preferred as they allow partial curing of the coating with UV-radiation which can dissociate the photo-initiator and initiating addition reactions of unsaturated carbon - carbon bonds, e.g. of acrylate groups.

[0049] The coating optionally comprises at least one isocyanate functional component.

[0050] The coating optionally comprises at least one hydroxyl functional component.

[0051] The presence in the coating of at least one isocyanate functional component and at least one hydroxyl functional component has the benefit that urethane bonds can be formed in the partial curing or in a thermal pressing operation. It is a benefit that the urethane bonds increase the performance.

[0052] The coating optionally comprises abrasion resistant particles, such as aluminum oxide particles, carbon nitride particles, silicon carbide particles or diamond particles.The coating optionally comprises a matting agent, preferably amorphous silica, preferably having S50 particle size according to volume between 3 and 20 micrometer and / or preferably between 2 and 14 wt% - and more preferably between 3 and 10 wt% -of the coating.

[0053] Such embodiments are preferred as it allows to obtain in the final product a wear layer having a matte surface in combination with a texture provided by a press element, without requiring a pressing element in the thermal pressing operation with a very fine texture which could result in processing difficulties. The texture provided by the press element can e.g. be a wood texture.

[0054] The S50 particle size is the particle size in the particle size distribution according to volume as determined using laser diffraction at which 50% of the particles are smaller than the S50.

[0055] The one or more (meth)acrylate oligomers preferably comprise at least a urethane (meth)acrylate oligomer, more preferably an aliphatic urethane (meth)acrylate oligomer.

[0056] 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.

[0057] The one or more (meth)acrylate reactive diluent and / or (meth)acrylamide reactive diluent preferably comprise at least a (meth)acrylate reactive diluent having acrylate functionality at least 2, and more preferably at least 3, and even more preferably at least 4.

[0058] Such embodiments are preferred as obtaining a partially cured coating layer which is not tacky is facilitated.Furthermore, the use of such reactive diluents results in a highly crosslinked wear layer after the thermal pressing operation. The result is high wear and high scratch resistance of the wear layer.

[0059] The one or more (meth)acrylate oligomers preferably comprise at least an oligomer having acrylate functionality 2, 3 or 4.

[0060] Such embodiments are beneficial as they result in a wear layer having high crosslinking density, and therefore high wear resistance and high scratch resistance.

[0061] The method can comprise the step of applying an adhesion layer for providing adhesion with a substrate onto which the partially cured coating layer is transferred from the release liner. Such embodiments are favored, as an improved adhesion of the wear layer to the substrate results in excellent wear resistance.

[0062] The adhesion layer preferably is a polyurethane adhesion layer or an acrylate adhesion layer.

[0063] The second aspect of the invention is a transfer sheet. The transfer sheet is obtained by or is obtainable by a method of the first aspect of the invention. The transfer sheet comprises a release liner and a partially cured coating layer. The partially cured coating layer comprises a thermo-initiator and unsaturated carbon - carbon bonds, preferably at least partially - and preferably fully - provided by reactive acrylate groups.

[0064] The release liner can have a textured surface comprising the partially cured coating layer.

[0065] The release liner can have a flat surface comprising the partially cured coating layer.

[0066] The transfer sheet can be provided on a roll. Such embodiments are beneficial as the transfer sheets can be unwound from the roll when needed in a subsequent production process.The transfer sheet can be provided on a roll without interlining.

[0067] The transfer sheet can be provided on a roll with interlining.

[0068] The transfer sheet can be provided as a flat sheet, and more preferably as a stack - with our without interlining - of such transfer sheets.

[0069] The release liner of the transfer sheet can be or can comprise a polymer film. Polymer films that can be used in the invention include polyethylene films, polypropylene films, polyethylene terephthalate films, polycarbonate films, polyester film and polytetrafluorethylene films.

[0070] The release liner of the transfer sheet can be or comprise a sheet of paper, e.g. covered by a polymer. The release liner can be or comprise a siliconized sheet of paper or a waxed sheet of paper.

[0071] The release liner of the transfer sheet can be or can comprise a metal-based foil, such as a steel foil or an aluminum foil.

[0072] The third aspect of the invention is a method for producing a decorative panel. The method comprises the steps of

[0073] - providing a transfer sheet as in any embodiments of the second aspect of the invention, or obtained in a method as in any embodiment of the first aspect of the invention; - providing a substrate;

[0074] - applying the partially cured coating layer from the transfer sheet onto the substrate; and - performing a thermal pressing operation onto the partially cured coating layer on the substrate, thereby thermally curing the coating layer and providing it with a texture, and laminating the coating layer to the substrate.

[0075] The thermally cured coating layer can provide the substrate with a very effective wear layer.It is a benefit that a decorative panel can be obtained having excellent wear resistance and excellent scratch resistance.

[0076] Small batches of decorative panels can be made in an efficient and effective manner as panels with different decoration can be provided with the transfer sheet.

[0077] The thermal curing can be initiated by the decomposition of the thermo-initiator and can involve addition reactions between the unsaturated carbon - carbon bonds.

[0078] A preferred method for producing a decorative panel is characterized in that in the step of applying the partially cured coating layer from the transfer sheet onto the substrate, the transfer sheet is stacked on the substrate with the partially cured coating layer contacting the substrate, wherein the release liner is removed before the thermal pressing operation.

[0079] Such embodiments have the benefit that a structured press element can be used effectively for providing the resulting wear layer with a texture.

[0080] A preferred method for producing a decorative panel is characterized in that in the step of applying the partially cured coating layer from the transfer sheet onto the substrate, the transfer sheet is stacked on the substrate with the partially cured coating layer contacting the substrate, wherein the release liner is removed after the thermal pressing operation.

[0081] Such embodiments have the benefit that when using a release liner having a flat surface, it is prevented that the coating layer sticks to the press plate.

[0082] Such embodiments have the benefit that when using a textured release liner, the texture of the textured release liner is copied into the coating layer in the thermal pressing operation, thereby providing the substrate with a wear layer having a texture.Therefore, a preferred embodiment is characterized in that the release liner is removed after the thermal pressing operation and that the surface of the release liner comprising the partially cured coating layer has a textured surface.

[0083] The thermal pressing operation can be performed using a structured press element for providing the coating layer with a texture. The structured press element can comprise a textured press plate or a textured roll.

[0084] The substrate can comprise a board and a decorative sheet of paper, wherein the step of applying the partially cured coating layer from the transfer sheet onto the substrate involves applying the partially cured coating layer from the transfer sheet onto the decorative sheet of paper before or after stacking or laminating the decorative sheet of paper onto the board.

[0085] The decorative sheet of paper can comprise a printed decor.

[0086] The decorative sheet of paper can provide a decor to the decorative panel wherein the board provides the core of the decorative panel.

[0087] The release liner can be removed before the thermal pressing operation; and after removal of the release liner and before the thermal pressing operation, the decorative sheet of paper with the partially cured coating layer on it is perforated.

[0088] Such embodiments have the benefit that air trapped in the thermal pressing operation between the press element - e.g. a structured press plate in a single daylight press - and the coating layer can escape through the decorative sheet of paper and into and through the board. Preferably, the board is a porous board, such that the texture of the press element is correctly copied into the coating layer forming the wear layer of the decorative panel.

[0089] The decorative sheet of paper can be impregnated with a thermosetting resin, preferably with an aminoplast resin (e.g. with a melamine formaldehyde resin), with a polyurethaneresin, with an acrylate resin, with a polyurethane resin comprising reactive acrylate groups; or combinations thereof.

[0090] The substrate can comprise a board comprising a decoration printed onto the board, preferably a decoration printed onto a primer layer provided on the board.

[0091] The partially cured coating layer can be applied on the decoration printed on the board.

[0092] The decoration printed on the board can be a digitally printed decoration.

[0093] A preferred substrate comprises a board. The board can be a wood-based board. Examples of wood based boards that can be used in the invention include wood fiber boards (e.g. medium density wood fiber boards or high density wood fiber boards), wood particle boards, oriented strand boards and plywood.

[0094] The board can be a mineral based board, e.g. a Portland cement based board, a magnesium oxide based board, a gypsum board, or a geopolymer based board.

[0095] The substrate can comprise a wood veneer onto which the partially cured coating layer is applied. The coating layer - after curing - provides the wood veneer with increased wear and scratch resistance.

[0096] The substrate can comprise a polymer foil - whether or not printed - onto which the partially cured coating layer is applied.

[0097] The polymer foil can be an unprinted transparent foil.

[0098] The polymer foil can be a printed foil.

[0099] The polymer foil can be a thermoplastic foil, e.g. a polyvinyl chloride foil, a polypropylene foil or a polyester foil (e.g. a polyethylene terephthalate foil).The substrate can comprise an adhesion layer onto which the partially cured coating layer is applied. It is a benefit that excellent adhesion is obtained of the wear layer to the substrate, improving the wear resistance of the decorative panel that is obtained.

[0100] The adhesion layer can be a polyurethane adhesion layer or can be an acrylate adhesion layer.

[0101] A balancing layer can be applied in the thermal pressing operation onto the side of the substrate opposite to the side onto which the partially cured coating layer is applied. Preferably, the balancing layer comprises a - whether printed or not printed - sheet of paper (which may be a decorative sheet of paper, e.g. a printed sheet of paper) impregnated with a thermosetting resin, preferably with an aminoplast resin (e.g. with a melamine formaldehyde resin), with a polyurethane resin, with an acrylate resin, with a polyurethane resin comprising reactive acrylate groups; or combinations thereof.

[0102] The balancing layer can balance tensions in the decorative panel originating from laminating the wear layer onto the substrate.

[0103] Preferably, the balancing layer applied is transferred from a release liner and preferably is an acrylate balancing layer.

[0104] Preferably, the balancing layer is at least partially obtained by transferring and curing in the thermal pressing operation a partially cured coating layer from a transfer sheet as in any embodiment of the second aspect of the invention.

[0105] In an embodiment of the invention, the transferring and curing for at least partially obtaining the balancing layer is performed onto a decorative sheet of paper (e.g. a printed sheet of paper) which may be or may not be impregnated with a thermosetting resin. The decorative sheet of paper can be impregnated with a thermosetting resin, more preferably with an aminoplast resin (e.g. with a melamine formaldehyde resin), with a polyurethane resin, with an acrylate resin, with a polyurethane resin comprising reactive acrylategroups; or combinations thereof. Such embodiments are beneficial for manufacturing furniture panels requiring a decor on both sides of the panel.

[0106] 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:

[0107] figure 1 illustrates a method for producing a transfer sheet according to the invention;

[0108] figure 2 shows a transfer sheet according to the invention obtained in the method shown in figure 1 ;

[0109] figure 3 shows an example of a transfer sheet according to the invention; figure 4 shows a method according to the invention for producing a decorative panel using a transfer sheet; and

[0110] figure 5 shows the decorative panel made in the method shown in figure 4.

[0111] The reference numerals have the same meaning in the different figures.

[0112] Figure 1 illustrates a method for producing a transfer sheet according to the invention. A release liner 1 is unrolled from a roll 2.

[0113] In the example shown, a coating layer is applied in two steps. A first coating 10 is applied to the release liner 1 by a roller coater 11 and followed by partial curing of this first coating by means of UV-radiation in a UV-treatment unit 12 using UV-lamps. As an alternative, electron beam curing can be used for performing the partial curing of this first coating.

[0114] A second coating 14 is applied onto the first coating by a roller coater 15 and the second coating is partially cured by means of UV-radiation in a UV-treatment 16 unit using UV-lamps.Although figure 1 shows an example in which a first coating and a second coating is applied, it is possible that the coating layer is applied in one single step.

[0115] Although the first coating and the second coating have the same composition as in the example shown, the composition of the first coating and the second coating can differ, e.g. for optimizing cost and performance.

[0116] In the example shown in figure 1, a water-based polyurethane dispersion 18 is applied by a roller coater 19 onto second coating for providing a polyurethane adhesion layer, and dried in an oven 20. The temperature in the oven 20 is selected such that the polyurethane adhesion layer is dried without activating the thermo-initiator of the coating. The polyurethane adhesion layer is optional, and can improve adhesion when transferring the coating layer from the release liner to a substrate.

[0117] The following recipe 1 provides an example for the coating that can be applied as first coating and as second coating:

[0118] 35 parts by weight of an aliphatic urethane acrylate oligomer having acrylate functionality equal to four;

[0119] 10 parts by weight of a polyester acrylate oligomer having acrylate functionality three;

[0120] 10 parts by weight of an unsaturated polyester resin;

[0121] 20 parts by weight of glyceryl propoxy triacrylate (GPTA), a trifunctional acrylate reactive diluent;

[0122] 5 parts by weight of dipropylene glycol diacrylate (DPGDA), a difunctional acrylate reactive diluent;

[0123] 20 parts by weight of tripropylene glycol diacrylate (TPGDA), a difunctional acrylate reactive diluent;

[0124] 0.2 parts by weight of tert-butyl 3,5,5-trimethylperoxyhexanoaat (TBPIN) as thermoinitiator; and

[0125] 0.0.05 parts by weight of photo-initiator.The photo-initiator is used to initiate addition reactions in the UV-radiation induced partial curing performed on the first coating and on the second coating.

[0126] The transfer sheet obtained 25 is wound on a roll 26. Alternatively (not shown in figure 1), the transfer sheet can be cut to length and the cut transfer sheets can be stacked.

[0127] Figure 2 shows the transfer sheet 25 obtained in the method shown in figure 1. The transfer sheet 25 comprises a release liner 1, which can have a flat surface or a textured surface onto which the coating has been applied. The first coating layer 31 contacts the release liner 1. The first coating layer 3 lis obtained from the first coating. A second coating layer 32 contacts the first coating layer 31. The second coating layer 32 is obtained from the second coating. Although figure 2 shows the first coating layer 31 and the second coating layer 32 as distinct coating layers, especially when the first coating and the second coating are the same, it will not be possible or at least very difficult to distinguish these two coating layers. As in figure 1 an optional polyurethane adhesion layer has been applied, the transfer sheet of figure 2 comprises an optional polyurethane adhesion layer 33. The combination of the first coating layer 31 and the second coating 32 provides a partially cured coating layer 36 on the release liner 1. The partially cured coating layer 36 comprises a thermo-initiator and unsaturated carbon - carbon bonds provided by the acrylate groups and by unsaturated carbon - carbon bonds of the unsaturated polyester resin when the coating of recipe 1 has been used.

[0128] Figure 3 shows an example of a transfer sheet 25 according to the invention. The transfer sheet comprises a release liner 1 and a partially cured coating layer 36. The partially cured coating layer comprises a thermo-initiator and unsaturated carbon - carbon bonds, preferably at least partially provided by reactive acrylate groups.

[0129] Figure 4 shows a method according to the invention for producing a decorative panel using a transfer sheet. A single daylight press 40 comprising a structured press element 41 is used. A stack 42 is made in the single daylight press 40. The stack 42 comprises a resin impregnated sheet of paper 43, a board 44 (in the example shown a high density wood fiberboard), a resin impregnated printed sheet of paper 45 that will form a printeddecor in the decorative panel, and the transfer sheet 25 with the partially cured coating layer 36 oriented towards the resin impregnated printed sheet of paper 45 and the release liner 1 oriented towards the structured press element 1.

[0130] The single-daylight press performs a thermal pressing operation on the stack 42. In the thermal pressing operation, the resin impregnated sheet of paper 43 is laminated to the board 44 and will provide a balancing layer. The resin impregnated printed sheet of paper 45 is laminated to the board and provides a printed decor. The partially cured coating layer 36 of the transfer sheet 25 is laminated onto the resin impregnated printed sheet of paper 45; is textured by the structured press element 41 of the single daylight press 40; and is cured by addition reactions of the unsaturated carbon - carbon bonds of the coating layer initiated by the dissociation of the thermo-initiator caused by the increased temperature of the thermal pressing operation. After opening of the press 40 the release liner 1 is removed.

[0131] As an alternative, the release liner 1 can be removed after positioning the partially cured coating layer 36 onto the resin impregnated printed sheet of paper 45 (positioning operation which can even be performed before placing the resin impregnated printed sheet of paper 45 in the single daylight press 40).

[0132] Figure 5 shows the decorative panel 50 made in the method shown in figure 4. The decorative panel 50 comprises a balancing layer 53, a board 44 (in the example shown a high density wood fiberboard), a resin impregnated printed sheet of paper 45 providing the printed decor of the decorative panel 50, and a wear layer 46 obtained by thermally curing the partially cured coating layer 36 in the thermal pressing operation shown in figure 4.

[0133] 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 transfer sheet, wherein the transfer sheet comprises a release liner and a partially cured coating layer, wherein the method comprises the steps of- providing a release liner;- applying a coating to the release liner;- partially curing the coating on the release liner, thereby obtaining a partially cured coating layer on the release liner;wherein the partially cured coating layer comprises a thermo-initiator and unsaturated carbon - carbon bonds, preferably at least partially provided by reactive acrylate groups.2.- Method as in claim 1, characterized in that the release liner has a textured surface or a flat surface onto which the coating is applied.3.- Method as in any of the preceding claims, characterized in that the release liner is of comprises a polymer film, a sheet of paper preferably covered by a polymer, a siliconized sheet of paper, or a waxed sheet of paper.4.- Method as in any of the preceding claims, characterized in that the partial curing is at least performed by UV-radiation or via electron beam radiation or via thermal curing or via direct cure radiation; initiating addition reactions between unsaturated carbon -carbon bonds and / or urethane bond formation.5.- Method as in any of the preceding claims, characterized in that the partial curing involves reactions in the coating between isocyanate groups and hydroxyl groups.6.- Method as in any of the preceding claims, characterized in that the partial curing comprises or consists of a thermal curing involving dissociation of a first thermo-initiator of the coating applied onto the release liner.7.- Method as in any of the preceding claims, characterized in that the partially cured coating layer comprises a second thermo-initiator having a 60 seconds half time dissociation temperature at least 8°C higher than the 60 seconds half time dissociation temperature of the thermo-initiator.8.- Method as in any of the preceding claims, characterized in that the coating is applied by first applying a first coating to the release liner and by applying a second coating onto the first coating; preferably wherein before applying the second coating, the first coating is partially cured.9.- Method as in claim 8, characterized in that the composition of the first coating differs from the composition of the second coating; or that the composition of the first coating is the same as the composition of the second coating.10.- Method as in claim 9, characterized in that the composition of the first coating comprises a higher functionality - expressed in number of reactive groups per unit of weight of the coating composition - than the composition of the second coating.11.- Method as in any of the preceding claims, characterized in that the coating applied to the release liner comprises- one or more (meth)acrylate oligomers, preferably wherein said oligomers have a molar mass equal to or higher than 800 g / mol;- one or more (meth)acrylate reactive diluent and / or (meth)acrylamide reactive diluent; wherein said reactive diluents have a molar mass lower than 800 g / mol, and preferably lower than 500 g / mol;- a thermo-initiator, and optionally a first thermo-initiator and / or a second thermoinitiator;- optionally an unsaturated polyester resin;- optionally a photo-initiator;- optionally at least one isocyanate functional component;- optionally at least one hydroxyl functional component;- optionally abrasion resistant particles, such as aluminum oxide particles, carbon nitrideparticles, silicon carbide particles or diamond particles,- optionally a matting agent, preferably amorphous silica, preferably having S50 particle size according to volume between 3 and 20 micrometer and / or preferably between 2 and 14 wt% - and more preferably between 3 and 10 wt% - of the coating;optionally wherein the one or more (meth)acrylate oligomers comprises at least a urethane (meth)acrylate oligomer.12.- Method as in claim 11, characterized in that the one or more (meth)acrylate reactive diluent and / or (meth)acrylamide reactive diluent comprises at least a (meth)acrylate reactive diluent having acrylate functionality at least 2, and preferably at least 3, and more preferably at least 4.13.- Method as in any of the preceding claims, characterized in that an adhesion layer is applied for providing adhesion with a substrate onto which the partially cured coating layer is transferred from the release liner, preferably wherein the adhesion layer is a polyurethane adhesion layer or an acrylate adhesion layer.14.- Transfer sheet, preferably a transfer sheet obtained by or obtainable by a method as in any of the preceding claims, characterized in that the transfer sheet comprises a release liner and a partially cured coating layer, wherein the partially cured coating layer comprises a thermo-initiator and unsaturated carbon - carbon bonds, preferably at least partially provided by reactive acrylate groups.15.- Transfer sheet as in claim 14, characterized in that the release liner has a textured surface or a flat surface comprising the partially cured coating layer.16.- Transfer sheet as in any of the preceding claims 14 - 15, characterized in that the transfer sheet is provided on a roll or is provided as a flat sheet.17.- Transfer sheet as in any of the preceding claims 14 - 16, characterized in that the release liner is of comprises a polymer film, a sheet of paper preferably covered by a polymer, a siliconized sheet of paper, or a waxed sheet of paper.18.- Method for producing a decorative panel, wherein the method comprises the steps of- providing a transfer sheet as in any of the preceding claims 14 - 17 or obtained in a method as in any of the claims 1 - 13;- providing a substrate;- applying the partially cured coating layer from the transfer sheet onto the substrate; and - performing a thermal pressing operation onto the partially cured coating layer on the substrate, thereby thermally curing the coating layer and providing it with a texture, and laminating the coating layer to the substrate.19.- Method as in claim 18, characterized in that the thermal curing is initiated by the decomposition of the thermo-initiator and involves addition reactions between the unsaturated carbon - carbon bonds.20.- Method as in any of the preceding claims 18 - 19, characterized in that in the step of applying the partially cured coating layer from the transfer sheet onto the substrate, the transfer sheet is stacked on the substrate with the partially cured coating layer contacting the substrate, wherein the release liner is removed before or after the thermal pressing operation.21.- Method as in claim 20, characterized in that the release liner is removed after the thermal pressing operation and that the surface of the release liner comprising the partially cured coating layer has a textured surface.22.- Method as in any of the preceding claims 18 -20, characterized in that the thermal pressing operation is performed using a structured press element for providing the coating layer with a texture.23.- Method as in any of the preceding claims 18 - 22, characterized in that the substrate comprises a board and a decorative sheet of paper, wherein the step of applying the partially cured coating layer from the transfer sheet onto the substrate involvesapplying the partially cured coating layer from the transfer sheet onto the decorative sheet of paper before or after stacking or laminating the decorative sheet of paper onto the board.24.- Method as in claim 23, characterized in that the release liner is removed before the thermal pressing operation and wherein after removal of the release liner and before the thermal pressing operation the decorative sheet of paper with the partially cured coating layer on it is perforated.25.- Method as in any of the preceding claim 23 - 24, characterized in that the decorative sheet of paper is impregnated with a thermosetting resin, preferably an aminoplast resin, a polyurethane resin, an acrylate resin, a polyurethane resin comprising reactive acrylate groups, or combinations thereof.26.- Method as in any of the preceding claims 18 - 22, characterized in that the substrate comprises a board comprising a decoration printed onto the board, preferably a decoration printed onto a primer layer provided on the board.27.- Method as in any of the preceding claims 18 - 26, characterized in that the substrate comprises a board and that the board is a wood-based board or in that the board is a mineral based board.28.- Method as in any of the preceding claims 18 - 27, characterized in that the substrate comprises a wood veneer onto which the partially cured coating layer is applied.29.- Method as in any of the preceding claims 18 - 28, characterized in that the substrate comprises a polymer foil - whether or not printed - onto which the partially cured coating layer is applied.30.- Method as in any of the preceding claims 18 - 29, characterized in that the substrate comprises an adhesion layer - preferably a polyurethane or an acrylate adhesion layer - onto which the partially cured coating layer is applied.31.- Method as in any of the preceding claims 18 - 30, characterized in that in the thermal pressing operation a balancing layer is applied onto the side of the substrate opposite to the side onto which the partially cured coating layer is applied.

Images