EP4124467A1

EP4124467A1 - A method of manufacturing a panel

Info

Publication number: EP4124467A1
Application number: EP21188714.6A
Authority: EP
Inventors: Bruno Vermeulen
Original assignee: Flooring Industries Ltd SARL
Current assignee: Unilin BV
Priority date: 2021-07-30
Filing date: 2021-07-30
Publication date: 2023-02-01

Abstract

A method of manufacturing a panel, comprising the steps of supplying a substrate (1), applying a layer of curable substance (3) onto the substrate (1), applying a substantially air-tight foil (6) onto the layer of curable substance (3) such that the layer of curable substance (3) is sandwiched between the substrate (1) and the foil (6), subsequently curing (8) at least a part of the layer of curable substance (3) by means of radiation through the foil (6) resulting in a layer of at least partly cured substance (3', 3"), characterized in that the method comprises a step of applying discrete quantities of an additional substance (5) at a side of the curable substance (3) which is directed away from the substrate (1) and in that after the step of curing (8) the foil (6) and the discrete quantities of an additional substance (5) are removed from the layer of at least partly cured substance (3', 3") so as to form the panel.

Description

Known methods for manufacturing said panels comprise the step of providing said top layer in the form of a sheet, normally a thermoplastic sheet or a melamine impregnated sheet. Said sheet can comprise a pre-formed surface structure for providing the surface of the panel of a three-dimensional relief.
Such a method is known from EP 2 927 017 . The curable substance forms a layer between the substrate and the air-tight foil. Due to its air-tightness the foil functions as a barrier against oxygen transfer through the foil. This means that local inert conditions at the curable substance are created. In the known method the foil comprises discrete quantities of an additional substance in the form of anti-wear particles. The final product contains the foil including the anti-wear particles.
The structure on the sheet is obtained by embossing plates or rollers that have to be previously prepared. Such an embossing technique is so expensive that is convenient only for high volume production batches and is also quite rigid and limited in the variety of the design.
An object of the invention is to provide an improved method of manufacturing a panel for covering a floor, a wall, a ceiling or furniture.
This object is accomplished by the invention with a method comprising the steps of supplying a substrate, applying a layer of curable substance onto the substrate, applying a substantially air-tight foil onto the layer of curable substance such that the layer of curable substance is sandwiched between the substrate and the foil, subsequently curing at least a part of the layer of curable substance by means of radiation through the foil resulting in a layer of at least partly cured substance, wherein the method comprises a step of applying discrete quantities of an additional substance at a side of the curable substance which is directed away from the substrate and in that after the step of curing the foil and the discrete quantities of an additional substance are removed from the layer of at least partly cured substance so as to form the panel.
The presence of the discrete quantities of an additional substance at a side of the curable substance where the air-tight foil is located before the step of curing advantageously provides the opportunity to create a surprising three-dimensional surface structure at the layer of curable substance, which three-dimensional surface structure is exposed after removing the foil and the discrete quantities of an additional substance. Due to creating inert conditions during the step of curing the layer of at least partly cured substance becomes a strong coating. The strong coating may have such characteristics that anti-wear particles as applied in the above-mentioned prior art may be omitted.
The curable substance may comprise a synthetic resin which is polymerized during the radiation treatment, more specifically via free radical polymerization. Radiation generates radicals in the curable substance. Since the chemical affinity between a radical and oxygen is higher than the affinity of the radicals with each other inert conditions are advantageous. The radiation may be UV radiation, X-ray radiation, laser radiation, electron beam radiation, visible light, infrared, or the like. If curing is performed by means of UV light the curable substance may contain photo initiators for initiating free radical polymerization. In particular, mercury-free UV LEDs appear to be appropriate because of their advantageous penetration characteristics into the curable substance. In case of using electron beam radiation photo initiators are not required.
The curable substance may be applied by means of inkjet printing, screen printing, roller printing, spraying, curtain coating or the like. In the preferred embodiment the curable substance is applied by means of coating techniques, preferably roller coating, in order to apply higher quantities of curable substance than those applicable through printing technique. To higher quantities of curable substance, generally correspond higher thicknesses of the top layer. In practice, the curable substance may be a liquid, or a pasty substance.
Preferably the curable substance, after curing, may the uppermost of layer of the panel and has to exert good surface performances. Preferably, after curing, said curable substance forms a layer having a thickness of at least 100 µm, more preferably at least 300 µm. For example, after curing, said curable substance may form a layer having a thickness comprised between 100 and 1500 µm, more preferably between 300 and 1000 µm. To thicker layer correspond a generally higher abrasion resistance. Moreover in a thicker layer it may be possible to obtain a deeper and more realistic relief.
The characteristics of the air-tight foil correspond to the type of radiation that is used. The foil may be transparent, wherein transparent means that it is transparent for the radiation used for curing, for example in case of UV curing it is transparent for UV radiation, but may be opaque for visible light. In case of applying electron beam radiation the foil should be transparent for electron beam radiation. Since the foil is removed after the step of curing the colour of the foil is of less relevance for the esthetical properties of the final product. The foil may be made of thermoplastic material, for example PVC.
The discrete quantities of an additional substance may be solid particles or the additional substance may be a liquid or a pasty substance, for example droplets. The liquid or the pasty substance may be solidified afterwards, for example via curing, preferably together with curing the curable substance. Since they are removed from the layer of at least partly cured substance the discrete quantities of an additional substance do not need to have anti-wear properties. It is noted that the discrete quantities of an additional substance may also be called placeholders, which remain at the same location with respect to the layer of curable substance during the step of curing.
The substrate may be rigid or flexible such that the resulting panel is rigid or flexible, respectively. It may be made of wood-based material like MDF, HDF, or thermoplastic, preferably vinyl, for example WPC, SPC or LVT, metal, glass, stone, ceramic, textile, non-woven fabric, polymeric composite, mineral-based material like MgO, or the like. Furthermore, although less preferred, the substrate may be a flexible thin sheet such that the resulting product itself can be an intermediate product that can be attached to a second substrate.
The resulting panel may be suitable for a floor, wall or ceiling covering or alternative coverings. The product may also be a panel that is suitable for furniture, or the like.
In a preferred embodiment the discrete quantities of an additional substance are applied onto the layer of curable substance before applying the foil onto the layer of curable substance including the discrete quantities of an additional substance, wherein attractive force between the discrete quantities of an additional substance and the foil is greater than between the discrete quantities of an additional substance and the layer of at least partly cured substance. This means that the discrete quantities of an additional substance tend to be attached to the foil rather than to the layer of at least partly cured substance such that the discrete quantities of an additional substance are automatically removed from the layer of at least partly cured substance when removing the foil. Consequently, a separate step of removing the discrete quantities of an additional substance can be omitted.
In a more specific embodiment a surface of the foil that is directed to the layer of at least partly cured substance is sticky to which surface the discrete quantities of an additional substance adhere. The surface may already be sticky before the step of curing, but it is also conceivable that it becomes sticky during the step of curing.
At least a part of the discrete quantities of an additional substance may partly penetrate into the layer of curable substance upon applying the discrete quantities of an additional substance onto the layer of curable substance. This provides the opportunity to create a rough surface structure of the layer of at least partly cured substance. The discrete quantities of an additional substance may be applied in a certain pattern such that the resulting textured upper surface has the same pattern.
The step of applying the discrete quantities of an additional substance may comprise a digital printing technique, for example inkjet printing. This provides the opportunity to print the discrete quantities of an additional substance in numerous different possible patterns and to control the penetration depth of the discrete quantities of an additional substance into the layer of curable substance.
In an alternative embodiment the discrete quantities of an additional substance are applied to the foil. This provides the opportunity to apply the discrete quantities of an additional substance to the foil before or after applying the foil onto the layer of curable substance.
In a particular embodiment the discrete quantities of an additional substance are applied onto the foil after applying the foil onto the layer of curable substance, wherein the discrete quantities of an additional substance allow less transmission of the radiation than the foil. In this case the discrete quantities of an additional substance do not penetrate into the layer of curable substance, but portions of the layer of curable substance located directly below the respective discrete quantities of an additional substance remain uncured or become partly cured. This provides the opportunity to treat these portions separately after removing the foil and the discrete quantities of an additional substance from the layer of at least partly cured substance in order to create a different appearance at these portions.
The discrete quantities of an additional substance may be applied to the foil by means of digital printing, for example by means of inkjet printing. In this case the discrete quantities of an additional substance are fixed to the foil.
In a particular embodiment the layer of curable substance is partly cured during the step of curing, wherein after the step of removing the foil and the discrete quantities of an additional substance the layer of partly cured substance is treated by means of a step of additional radiation curing. Consequently, the whole layer of curable substance including the mentioned uncured portions is cured by means of radiation resulting in a layer of cured substance.
More specifically, after the step of curing the curable substance may still be uncured at portions located below the respective discrete quantities of an additional substance, wherein the uncured portions are cured during the step of additional radiation curing. In this case the discrete quantities of an additional substance may be opaque for the radiation or only partly allow transmission of the radiation such that the radiation does not reach or insufficiently reaches the surface of the layer of curable substance below the discrete quantities of an additional substance.
The uncured portions may only be upper portions of the layer of partly cured substance at a surface thereof which is directed away from the substrate, wherein the depths of the upper portions in the layer of partly cured substance are smaller than half of the thickness thereof. Hence, the uncured upper portions are relatively shallow.
The step of additional radiation curing may comprise radiation by means of an excimer lamp. An excimer lamp has a low penetration depth of UV radiation such that a polymerization process in shallow uncured regions can be performed at a relatively low energy consumption level. This leads to a superficial polymerization, which causes a volume shrinkage, which in turn manifests itself in surface folds of varying degrees. This deformed "skin" leads to a diffuse reflection of the light, which is perceived as a matt effect. The mentioned low penetration depth is particularly advantageous in case of the presence of shallow uncured portions of the layer of partly cured substance.
The method may comprise the step of providing the panel with a decorative layer. The decorative layer can be preferably provided between the substrate and the curable substance so that the curable substance forms a protective layer, also called wear layer, on top of said decorative layer. Said decorative layer may comprise a pattern, for example imitating a wood, a stone or a cement material. In the preferred embodiment, the decorative pattern is printed directly onto the substrate by means of inkjet printing. More preferably, it is printed with an inkjet printer that is disposed upstream to a device for providing the curable substance. With the expression "printed directly" it is meant that the printing operation is performed on the substrate instead of being performed on a separate material, like a sheet, that is afterward provided on the substrate. Therefore, the expression "printed directly" doesn't exclude that intermediate layers, like primers or ink receiver layers, are interposed between the surface of the substrate and the decorative layer. In alternative embodiments is possible that the decorative layer is in form a separate layer, for example a decor sheet, that is attached on top of the substrate for example by gluing, thermal lamination or lamination. The decorative layer can be printed using water-based inks, solvent based inks, oil based inks or, preferably, UV curable inks.
In case the decorative pattern is directly printed on the substrate it is preferable that the said printing operation is performed in line with the steps of providing the curable substance and/or of providing the discrete quantities of additional material.
In the most preferred embodiment, the discrete quantities of an additional substance can be applied in a pattern which is in register with the decorative pattern. This results in a surface texture which is in register with the decorative pattern. Thanks to the fact that the structure is not preformed on a separate sheet, it is possible to obtain an extremely precise synchronization of the decorative pattern and of the relief. Moreover, this high precision synchronization can be obtained for an increased variety of the decor, without the need of a huge stock of preformed structured sheets.
In the most preferred embodiment, the curable substance can be transparent or translucent, in particular after the curing step. The transparency of the curable substance is preferably refereed to the visible radiation so that the curable substance may be visibly transparent and the decorative layer is visible through the curable substance.
In a preferred embodiment, the curable substance is a waterbased substance. Alternatively, the curable substance may comprise acrylic acid esters or methacrylic acid esters which can be polymerized by a free radical mechanism by actinic radiation and which are present, on their own or together, in a polymerizable mixture. A component may be a mono- or polyfunctional prepolymer, i.e. a mono- or polyunsaturated prepolymer. In addition to this predominant component, the copolymerizable mixture contains, if appropriate, a further component having a diluting action, which is described as a diluent monomer or diluent oligomer. The proportion in the mixture of the polyfunctional prepolymer may be 20 to 100%, in particular 60 to 90%, by weight of the total weight of copolymerizable components. Prepolymers of a low viscosity, less than 100 poise at 20° C may be employed without the monomers or oligomers producing dilution.
Preferably, the components used have a strong tendency to polymerize by a free radical mechanism under the action of actinic radiation. Suitable actinic radiation is a light in the near UV region or high-energy radiation, for example electron, particle or x-ray radiation. A prepolymer which can be polymerized by free radical mechanism is a polyfunctional, unsaturated aliphatic or aromatic acrylate or methacrylate, preferably an unsaturated polyester acrylate oligomer and especially an aliphatic urethane acrylate oligomer or aromatic urethane acrylate oligomers.
In addition to the prepolymer, a mono-, di-, tri-, tetra-, penta- or hexaacrylate or - methacrylate, preferably a diacrylate or triacrylate, may be used as an additional suitable monomer or oligomer in the mixture which can be copolymerized by a free radical mechanism. These mono- to hexaacrylates or mono- to hexamethacrylates are esters of polyols having 1 to 6 OH groups with acrylic acid or methacrylic acid, respectively, and are therefore also known as polyol acrylates or polyol methacrylates, respectively. Suitable diacrylates are esters of acrylic acid with aliphatic, dihydric alcohols, in particular ethylene glycol, 1,2-propylene glycol, 1,3-propyleneglycol, butane diols, 1,6-hexane diol or neopentylglycol, with aliphatic ether-alcohols, in particular diethylene glycol, dipropylene glycol, dibutylene glycol, polyethylene glycols or polypropylene glycols, with oxyalkylated compounds of the above-mentioned aliphatic alcohols and ether-alcohols or with aromatic dihydroxy compounds, in particular bisphenol A, pyrocatechol, resorcinol, hydroquinone, p-xylyleneglycol or p-hydroxybenzyl alcohol. Preferred diacrylates are 1,6-hexanediol diacrylate, dipropyleneglycol diacrylate, acrylic acid 2-(2-vinyloxy-ethoxy)-ethyl ester, propoxylated neopentylglycol diacrylate, isobornyl acrylate, mono-2acrryloyloxyethyl phtalate, tricyclodecane dimethanol diacrylate, 2-carboxyethyl acrylate, Benzyl acrylate, tripropylene glycol diacrylate and 1,4-butanediol diacrylate. Preferred triacrylates are trimethylolpropane triacrylate and pentaerythritol triacrylate.
In addition to the urethane acrylate oligomers and unsaturated polyester acrylate oligomers already mentioned, suitable polyfunctional prepolymers are also epoxyacrylate and silicone-acrylate oligomers, which are preferably used together with the diacrylates or triacrylates mentioned in the mixture which can be copolymerized by a free radical mechanism.
The prepolymers are compounds known per se and are prepared, for example, from hydroxylated copolymers in which the hydroxyl groups are distributed statistically along the copolymer chain. Statistically unsaturated acrylic copolymers are obtained from this copolymer by esterifying the hydroxyl groups with acrylic acid. Semi-terminal unsaturated acrylic copolymers are prepared by having the hydroxyl group at the end of the chain in the preparation of the hydroxylated copolymers. Urethane acrylate oligomers are prepared by reacting (meth)acrylic acid esters containing hydroxyl groups, for example, hydroxyethyl methacrylate, with polyfunctional isocyanates, preferably diisocyanates. The diisocyanates or polyisocyanates can preferably be reaction products of diols, polyether-diols or polyester-diols containing a stoichiometric excess of monomeric diisocyanate or polyisocyanate.
If the polyfunctional prepolymer preponderates in the polymerizable mixture, as the base resin, by virtue of its chemical nature, it determines the properties of the cured surface layer. The monoacrylate to hexaacrylate or monomethacrylate to hexamethacrylate added makes it possible as a diluent monomer or oligomer, to adjust the viscosity of the mixture to be cured, which is normally within a viscosity range from 20 to 100 poise at 20° C, and entirely takes part in the free radical polymerization. When irradiated, the coating is cured through free radical polymerization between the double bonds of the prepolymer and of the diluent monomer or oligomer which may be present.
The invention will hereafter be elucidated with reference to schematic drawings illustrating embodiments of the invention by way of example.

Fig. 1 is an illustrative view, illustrating an embodiment of the method according to the invention.
Fig. 2 is a similar view as Fig. 1, but illustrating an alternative embodiment.

Fig. 1 illustrates an embodiment of a method of manufacturing a panel for covering a floor, a wall, a ceiling or furniture by means of covering a substrate 1 according to the invention. The substrate 1 is placed on a conveyor belt 2 and moved from the left to the right as indicated by arrows in Fig. 1. The substrate may be MDF, HDF, particleboard, multi-layer wood, cellulose-based materials such as paper or cardboard, metals, plastic material (PVC, polyester, polyolefins), stone, glass, ceramic and compounds thereof, but numerous alternative materials are conceivable.
In the illustrated example the substrate 1 is conveyed to a first digital printing station 4', preferably comprising an inkjet printer, for printing a decorative pattern directly on top of the substrate 1.
In a next step a layer of curable substance 3 is applied on top of the substrate 1, in particular on top of the decorative pattern. In this case the curable substance 3 comprises a resin in the form of a pasty liquid which cures through polymerization when irradiated by UV radiation.
Then, the substrate 1 and the layer of curable substance 3 pass a second digital printing station 4, e.g. an inkjet printer, which prints a pattern of discrete quantities of an additional substance 5, for example in the form of solid additional substance 5 or pasty substance, on top of the layer of curable substance 3, hence at a side of the layer of curable substance 3 which is directed away from the substrate 1. At this stage the layer of curable substance 3 is still uncured or only partly cured. This means that the additional substance 5 may partly penetrate into the layer of curable substance 3, depending on the material characteristics of the layer of curable substance 3 and the additional substance 5 and on velocity of the additional substance 5 when arriving on the layer of curable substance 3.
In the most preferred embodiment, in said second digital printing station 4 the discrete quantities of the additional substance 5 are printed according to a pattern that is in register with the decorative pattern printed in the first digital printing station 4'.
Subsequently, a substantially air-tight foil 6 is applied on top of the layer of curable substance 3 such that it contacts both the additional substance 5 and an upper surface of the layer of curable substance 3 around the additional substance 5. The foil 6 is adapted such that it allows transmission of UV radiation. Fig. 1 shows that the layer of curable substance 3 including the additional substance 5 are sandwiched between the substrate 1 and the foil 6. The foil 6 is pressed at a low pressure level on the layer of curable substance 3 by means of a calander 7.
In a next step the substrate 1, the layer of curable substance 3 including the additional substance 5 and the foil 6 pass a UV radiator 8 which irradiates the layer of curable substance 3 through the foil 6. Consequently, the layer of curable substance 3 is cured into a layer of cured substance 3'.
Fig. 1 further illustrates that after the step of curing at the UV radiator 8, the foil 6 is removed from the layer of cured substance 3'. A lower surface of the foil 6 that is directed to the layer of cured substance 3' is sticky such that attractive force between the additional substance 5 and the foil 6 is greater than between the additional substance 5 and the layer of cured substance 3'. Consequently, the additional substance 5 are removed from the layer of cured substance 3' together with the foil 6.
An upper surface of the layer of cured substance 3' of the resulting product has a three-dimensional structure in the form of the pattern of additional substance 5 that were applied on top of the layer of curable substance 3 in a previous step.
In this case the layer of cured substance 3' is fully cured at the UV radiator 8, which may be achieved by using relatively small particles or particles which allow transmission of UV radiation. It is also conceivable that the upper surface of the layer of curable substance 3 is not fully cured at portions directly below the particles. These portions may be cured in an additional radiation curing step.
The resulting panel may be cut in separate boards of which edges may be provided with locking means, for example tongues and grooves, in order to create a covering by locking similar boards to each other.
Fig. 2 illustrates an alternative embodiment of the method according to the invention. Elements which correspond to elements in Fig. 1 and which have the same function have the same reference numbers.
The substrate 1 is also placed on the conveyor belt 2 and moved from the left to the right as indicated by arrows in Fig. 2. In this case the air-tight foil 6 is applied onto the layer of curable substance 3 before a pattern of additional substance 5 is printed onto the foil 6 at the printing station 4. In this case the additional substance 5 are adapted such that they allow less transmission of the radiation than the foil 6.
Then, the substrate 1, the layer of curable substance 3 and the foil 6 including the additional substance 5 pass the UV radiator which irradiates the layer of curable substance 3 through the foil 6. Consequently, the layer of curable substance 3 is partly cured into a layer of partly cured substance 3". Since the radiation cannot or can only partly pass through the additional substance 5 the layer of curable substance 3 remains uncured at shallow upper portions 9 thereof which are located directly below the respective additional substance 5. The uncured upper portions 9 are exposed after removing the foil 6 including the additional substance 5 from the layer of partly cured substance 3", as illustrated in Fig. 2.
Subsequently, substrate 1 and the layer of partly cured substance 3" are moved to an excimer lamp station 10 where a step of additional radiation curing is performed. The UV radiation of the excimer lamp station 10 has a limited penetration depth in the layer of partly cured substance 10, but the penetration depth is sufficient to cure the shallow uncured upper portions 9. This results in cured upper portions 9' within the layer of cured substance 3'. The upper surface of the upper portions 9' and their surrounding upper surface of the layer of cured substance 3' have a different texture, which reveals in different gloss level.
The invention is not limited to the embodiments shown in the drawings and described hereinbefore, which may be varied in different manners within the scope of the claims and their technical equivalents. For example, the discrete quantities of an additional substance may be droplets of a liquid or a pasty substance, which may be solidified afterwards, for example via curing, preferably together with curing the curable substance.
The invention is further disclosed by the following item list as defined by the below numbered items.

1. A method of manufacturing a panel, comprising the steps of supplying a substrate (1), applying a layer of curable substance (3) onto the substrate (1), applying a substantially air-tight foil (6) onto the layer of curable substance (3) such that the layer of curable substance (3) is sandwiched between the substrate (1) and the foil (6), subsequently curing (8) at least a part of the layer of curable substance (3) by means of radiation through the foil (6) resulting in a layer of at least partly cured substance (3', 3"), wherein the method comprises a step of applying discrete quantities of an additional substance (5) at a side of the curable substance (3) which is directed away from the substrate (1) and in that after the step of curing (8) the foil (6) and the discrete quantities of an additional substance (5) are removed from the layer of at least partly cured substance (3', 3") so as to form the panel.
2. The method according to item 1, wherein the discrete quantities of an additional substance (5) are applied onto the layer of curable substance (3) before applying the foil (6) onto the layer of curable substance (3) including the discrete quantities of an additional substance (5) and wherein attractive force between the discrete quantities of an additional substance (5) and the foil (6) is greater than between the discrete quantities of an additional substance (5) and the layer of at least partly cured substance (3').
3. The method according to item 2, wherein a surface of the foil (6) that is directed to the layer of at least partly cured substance (3') is sticky to which surface the discrete quantities of an additional substance (5) adhere.
4. The method according to item 2 or 3, wherein at least a part of the discrete quantities of an additional substance (5) partly penetrate into the layer of curable substance (3) upon applying the discrete quantities of an additional substance (5) onto the layer of curable substance (3).
5. The method according to any one of the preceding items, wherein the step of applying the discrete quantities of an additional substance (5) comprises a digital printing (4) technique.
6. The method according to item 1, wherein the discrete quantities of an additional substance (5) are applied to the foil (6).
7. The method according to item 6, wherein the discrete quantities of an additional substance (5) are applied onto the foil (6) after applying the foil (6) onto the layer of curable substance (3) and wherein the discrete quantities of an additional substance (5) allow less transmission of the radiation than the foil (6).
8. The method according to item 6 or 7, wherein the discrete quantities of an additional substance (5) are applied to the foil (6) by means of digital printing (4).
9. The method according to any one of the preceding items, wherein the layer of curable substance (3) is partly cured during the step of curing (8), wherein after the step of removing the foil (6) and the discrete quantities of an additional substance (5) the layer of partly cured substance (3") is treated by means of a step of additional radiation curing (10).
10. The method according to item 9, wherein after the step of curing, the curable substance (3) is still uncured at portions (9) located below the respective discrete quantities of an additional substance (5), wherein the uncured portions (9) are cured during the step of additional radiation curing (10).
11. The method according to item 10, wherein the uncured portions (9) are only upper portions of the layer of partly cured substance (3) at a surface thereof which is directed away from the substrate (1), wherein the depths of the upper portions in the layer of partly cured substance (3") are smaller than half of the thickness thereof.
12. The method according to any one of the items 9-11, wherein the step of additional radiation curing comprises radiation by means of an excimer lamp (10).
13. The method according to any one of the preceding items, wherein the supplied substrate (1) has a decorative pattern on its surface which is directed to the layer of curable substance (3), wherein the discrete quantities of an additional substance (5) are applied in a pattern which is in register with the decorative pattern.
14. The method according to any one of the preceding items, wherein it comprises the step of providing a decorative pattern on a top surface of the substrate (1), preferably by inkjet printing.
15. The method according to item 14, wherein said step of providing the decorative pattern is performed in line with the step of providing the curable substance (3) and/or with the step of providing the discrete quantities of an additional substance (5).
16. The method according to any one of the preceding claims, wherein the discrete quantities of an additional substance are solid particles (5) or the additional substance is a liquid or a pasty substance.
17. The method according to any of the preceding items wherein the panel is a floor, wall, ceiling or furniture panel.
18. The method according to any of the preceding items, wherein the cured substance (3') forms the uppermost layer of the final panel.The present invention relates to a method of manufacturing a panel, for example of the type having a substrate and a top layer, said top layer preferably comprising a decorative layer and/or a wear layer. In particular, the present invention relates to a method for manufacturing a panel of type used for covering a floor, a wall, a ceiling or furniture.

Claims

A method of manufacturing a panel, comprising the steps of supplying a substrate (1), applying a layer of curable substance (3) onto the substrate (1), applying a substantially air-tight foil (6) onto the layer of curable substance (3) such that the layer of curable substance (3) is sandwiched between the substrate (1) and the foil (6), subsequently curing (8) at least a part of the layer of curable substance (3) by means of radiation through the foil (6) resulting in a layer of at least partly cured substance (3', 3"), characterized in that the method comprises a step of applying discrete quantities of an additional substance (5) at a side of the curable substance (3) which is directed away from the substrate (1) and in that after the step of curing (8) the foil (6) and the discrete quantities of an additional substance (5) are removed from the layer of at least partly cured substance (3', 3") so as to form the panel.
The method according to claim 1, wherein the discrete quantities of an additional substance (5) are applied onto the layer of curable substance (3) before applying the foil (6) onto the layer of curable substance (3) including the discrete quantities of an additional substance (5) and wherein attractive force between the discrete quantities of an additional substance (5) and the foil (6) is greater than between the discrete quantities of an additional substance (5) and the layer of at least partly cured substance (3').
The method according to claim 2, wherein a surface of the foil (6) that is directed to the layer of at least partly cured substance (3') is sticky to which surface the discrete quantities of an additional substance (5) adhere.
The method according to claim 2 or 3, wherein at least a part of the discrete quantities of an additional substance (5) partly penetrate into the layer of curable substance (3) upon applying the discrete quantities of an additional substance (5) onto the layer of curable substance (3).
The method according to any one of the preceding claims, wherein the discrete quantities of an additional substance (5) are applied by means of digital printing (4).
The method according to claim 1, wherein the discrete quantities of an additional substance (5) are applied to the foil (6).
The method according to claim 6, wherein the discrete quantities of an additional substance (5) are applied onto the foil (6) after applying the foil (6) onto the layer of curable substance (3) and wherein the discrete quantities of an additional substance (5) allow less transmission of the radiation than the foil (6).
The method according to claim 6 or 7, wherein the discrete quantities of an additional substance (5) are applied to the foil (6) by means of digital printing (4).
The method according to any one of the preceding claims, wherein the layer of curable substance (3) is partly cured during the step of curing (8), wherein after the step of removing the foil (6) and the discrete quantities of an additional substance (5) the layer of partly cured substance (3") is treated by means of a step of additional radiation curing (10).
The method according to claim 9, wherein after the step of curing, the curable substance (3) is still uncured at portions (9) located below the respective discrete quantities of an additional substance (5), wherein the uncured portions (9) are cured during the step of additional radiation curing (10).
The method according to claim 10, wherein the uncured portions (9) are only upper portions of the layer of partly cured substance (3) at a surface thereof which is directed away from the substrate (1), wherein the depths of the upper portions in the layer of partly cured substance (3") are smaller than half of the thickness thereof.
The method according to any one of the claims 9-11, wherein the step of additional radiation curing comprises radiation by means of an excimer lamp (10).
The method according to any one of the preceding claims, wherein the supplied substrate (1) has a decorative pattern on its surface which is directed to the layer of curable substance (3), wherein the discrete quantities of an additional substance (5) are applied in a pattern which is in register with the decorative pattern.
The method according to any one of the preceding claims, characterized in that it comprises the step of providing a decorative pattern on a top surface of the substrate (1), preferably by inkjet printing.
The method according to any one of the preceding claims, wherein the discrete quantities of an additional substance are solid particles (5) or the additional substance is a liquid or a pasty substance.