Method for producing a decorative surface on a panel, panel and a panel covering

Abstract

The invention relates to a method for producing a decorative surface on a panel or other workpiece. The invention also relates to panels or other workpieces produced according to the method of the invention. The invention further relates to a panel covering comprising a plurality of interconnected panels according to the invention.

Description

Technical Field

[0001] This invention relates to a method for manufacturing decorative surfaces on panels or other workpieces. The invention also relates to panels or other workpieces manufactured according to the method of the invention. Furthermore, the invention relates to a panel cover comprising a plurality of interconnected panels according to the invention. Additionally, the invention relates to a system for implementing the method according to the invention. Background Technology

[0002] The purpose of decorative or coated surfaces is to achieve a realistic appearance. This is typically achieved by applying a three-dimensional (3D) embossed structure to a substrate such as particleboard, MDF board, HDF board, or a polymer substrate that mimics natural materials such as wood or stone.

[0003] This embossed structure, also known as tactile feedback, is typically synchronized with the underlying decorative image. For example, in wooden replicas, printed knot holes align with corresponding recesses in the embossed structure. This synchronized embossing, known as synchronized holes, can be similarly created using an embossed matrix that matches the decorative image.

[0004] Ideally, both the tactile and visual elements of decorative and printed images should be perceptible. This involves achieving variations in gloss between recessed areas (holes) and the remaining areas to enhance the 3D effect. Gloss is determined according to the method outlined in DIN EN ISO 2813:2015-02. Gloss measurement involves quantifying the amount of light reflected from the surface compared to a polished glass reference standard, measured in gloss units (GU). The amount of reflected light depends on the angle of incidence and surface characteristics. Gloss measurements can be performed at various angles of incidence (20°, 60°, and 85°), with 60° being preferred. Alternatively, the average of measurements from these three angles can be used. Reflectivity is measured as the percentage of light energy emitted and received by a gloss meter at a specified angle of incidence.

[0005] EP3928880A1 discloses a method for manufacturing matte panels, in which a liquid-curable layer to be structured is first semi-cured by a low-energy long-wave ultraviolet (UV) lamp, and then irradiated with a high-energy UV excimer lamp in an inert gas atmosphere to create micro-wrinkles in the layer, thereby structuring the layer and resulting in a matte finish. However, this method has several drawbacks. One drawback is that this method produces a completely matte panel, whereas in practice, location-selective glossy and matte areas are required. Furthermore, the excimer technology used results in relatively high initial costs, complex maintenance, safety concerns (the high-energy UV light emitted by the excimer lamp (especially at shorter wavelengths, such as 172 nm) can be harmful to human skin and eyes), complexity in managing the heat generated during operation, undesirable cooling requirements, a relatively slow curing process, and limited penetration depth, which does not allow for the curing of thicker layers. Moreover, this technology is not suitable for creating the tactile effects desired by consumers, for example, in mimicking wood (texture) patterns. Summary of the Invention

[0006] Therefore, the first objective of this invention is to develop an improved method and system for providing tactile decorative surfaces for panels or other workpieces.

[0007] Therefore, a second objective of the present invention is to develop an improved method and system for providing tactile decorative surfaces and position-selective glossy and matte areas for panels or other workpieces.

[0008] Therefore, the present invention provides a method for manufacturing decorative surfaces on panels, comprising the following steps: A) Apply a curable liquid layer to be structured onto the top surface of the panel (or other workpiece), wherein the liquid layer is preferably substantially immiscible with water. B) In a liquid state, water-based structured ink droplets are selectively printed onto a portion of the top surface of the liquid layer to be structured, wherein, preferably, the density of the structured ink droplets is equal to or greater than the density of the liquid layer to be structured, to allow the water-based structured ink droplets to sink, preferably partially sink, into the liquid structured layer, wherein the structured ink droplets are configured as follows: At least partially absorb the electromagnetic radiation irradiated in step C), and / or Upon contact with the liquid layer, at least one reaction product is generated, which is capable of at least partially absorbing the electromagnetic radiation irradiated in step C), and / or During the electromagnetic radiation irradiation in step C), the curing properties are poorer compared to the liquid layer, and / or In step C), when irradiated with electromagnetic radiation, especially in the UV region, it is not curable; C) Irradiating the surface of the liquid layer and the applied structured ink droplets with electromagnetic radiation, particularly in the UV region, wherein the liquid layer will be at least partially cured, and wherein at least a portion of the water present in the water-based structured ink will evaporate, resulting in at least one recessed diffractive microstructure forming in the at least partially cured structured layer at one or more locations of the structured ink printed in step B). D) Removal, particularly mechanical removal, of at least a portion of the remaining structured ink from the at least partially cured structured layer to at least partially expose at least one recessed diffraction microstructure. E) Applying a curable liquid top coating to at least partially cured unstructured portions of the structured layer, while the structured portions of the at least partially cured structured layer defined by the diffraction microstructure of the at least one recess are substantially not covered by the top coating, and F) Irradiate the surface of the top coating with electromagnetic radiation at least once, especially in the UV region, to cure the top coating.

[0009] This method utilizes a water-based structured ink that, due to the preferred immiscibility of the two liquids, cannot properly mix with the surrounding liquid layer (in step B). This results in a relatively clear interface between the liquid layer and the ink droplets that sink (preferably partially sink) into the liquid layer, which preferably creates one or more relatively well-defined recessed microstructures in the liquid layer. For this purpose, the liquid layer may comprise, for example, a polymerizable acrylate mixture and / or may comprise or be formed from a non-aqueous and / or non-polar solvent-based varnish system.

[0010] Secondly, by using water-based inks, the water in the ink will evaporate at least partially, typically instantaneously, in step C), resulting in a sudden and significant increase in volume, or even a vapor explosion, which typically alters the interfacial shape between the liquid layer and the structured ink. For example, in the case of a single ink droplet, the initial shape of the interface can be substantially hemispherical and can become wider and / or deeper and / or pouch-like and / or pit-like during the irradiation step according to step C). The resulting interfacial surface will be rough and microstructured, and optionally even nanostructured. This micro / nanostructured surface will ultimately reflect and scatter light in various directions, producing an optically matte finish, while also creating the desired tactile effect that the end user can perceive. This matte effect can be ensured because a topcoat is preferably not applied within the microstructure. The unprinted portions of the liquid layer (where the structured ink is not printed) will be covered by a topcoat, preferably a relatively smooth topcoat. The end user of the panel according to the invention will see and appreciate the optical contrast between the glossy topcoat and the matte microstructure. The depth of the microstructure can vary and depends on the volume of the ink droplets used and the amount of ink droplets used in the same location, but it is typically between 0.03 and 1.5 mm.

[0011] The density of the liquid-structured ink droplet and the density of the liquid layer to be structured can be between 1 and 1.2. This ensures that the droplet will fully and / or partially penetrate into the liquid layer. Preferably, the droplet will be held at the top of the liquid layer, more preferably at the top surface, to allow for the proper formation of one or more recessed microstructures.

[0012] Preferably, the surface tension of the liquid-structured ink droplet is substantially equal to the surface tension of the liquid layer to be structured. Typically, this surface tension is between 65 and 80 mN / m, for example, 72-73 mN / m.

[0013] In step B), at least a small fraction of the applied ink droplets partially reside (penetrate) within the liquid layer, such that 40% to 60% of the outer surface of each of these droplets is covered by the liquid layer. In step B), the remaining surface area is typically left uncovered. It is conceivable that in step B), one or more ink droplets completely penetrate the liquid layer and will be completely surrounded by it. Alternatively, it is conceivable that in step B), a small fraction of the ink droplets completely penetrate the liquid layer and will be completely surrounded by it, while another small fraction of the ink droplets partially penetrate the liquid layer and will be partially surrounded by it.

[0014] The water-based ink droplets applied in step B) can be fine droplets and / or larger droplets. Preferably, the volume of fine droplets is 0.1 μl to 1 μl, more preferably 0.3 μl to 0.8 μl, and particularly 0.5 to 0.6 μl. The volume of larger droplets is 1 μl to 80 μl, more preferably 3 μl to 12 μl, and particularly preferably 5 μl to 10 μl. Preferably, the average diameter of the ink droplets is between 50 and 500 μm.

[0015] The velocity of droplets and / or fine droplets is particularly between 0.5 m / s and 12 m / s, preferably between 3 m / s and 7 m / s, and especially preferably between 5 m / s and 6 m / s. This printing speed also typically determines the extent to which droplets penetrate into the liquid layer.

[0016] To ensure accurate, flexible, and positionally selective application of water-based ink droplets as a mask (or mask ink), it is preferably achieved by digital printing in step B).

[0017] In step C), the liquid layer may be partially cured. The structured ink droplets may also be partially cured in step C), although it is conceivable that the structured ink droplets may not cure at all in step C). This facilitates the removal of any remaining droplets in step D). In step F), the liquid layer and (if any) traces of structured ink droplets may undergo final curing.

[0018] In a preferred embodiment, the electromagnetic radiation used in step C) has a wavelength below 300 nm, wherein at least one LED UV radiation source is preferably used. It is conceivable that the electromagnetic radiation used in step C) has a wavelength adjusted during the execution of step C). To improve the curing process, electromagnetic radiation of different wavelengths at different time intervals can be used in step C) (and / or optionally in step F). For example, a wavelength below 200 nm can be used first, then a wavelength below 250 nm, and finally a wavelength below 300 nm.

[0019] In step C), it can be envisioned that each part of the liquid layer and ink droplet is irradiated with electromagnetic radiation at least multiple times. For successive irradiation steps, the same and / or intentionally different wavelengths can be used.

[0020] In step D), preferably, at least a portion of the residual structured ink from the at least partially cured structured layer is removed by at least one (rotating) brush roller, particularly at least one fabric brush roller (with fabric brush fibers) and / or at least one nylon brush roller (with nylon (polyamide) brush fibers) and / or at least one polypropylene-based brush roller (with acrylic brush fibers) and / or at least one metal (particularly steel)-based roller (with metal fibers, particularly steel fibers). The fibers of the brush roller should be sufficiently hard and / or stiff to (preferably substantially completely) remove the residual (uncured or semi-cured) portions of the structured ink. For this purpose, it may be advantageous if the axial rotational speed of the brush roller is between 1000 and 2000 rpm. It may also be advantageous if the brush roller moves laterally (also) alternately along its axial direction, wherein the lateral movement speed is preferably between 2 and 3 meters per minute. This provides movement of the fibers of the brush roller in both the length and width directions, thereby providing movement in the XY plane. In this way, the residue of structured ink in the recessed microstructure can be removed in a relatively accurate and efficient manner.

[0021] In step E), a top coating is applied by digital printing and / or by rolling. The top coating may comprise a single layer or multiple layers applied on top of each other. Traditionally, (preferably transparent) top coatings are applied by one or more rollers. However, this conventional technique may be less suitable if the panel has one or more bevels or grout lines. In the latter case, digital printing may be more suitable for applying the top coating. Furthermore, if digital printing is used to apply the top coating, the printed pattern is preferably completely complementary to the printed pattern of the structured ink.

[0022] In step F), the top coating and optionally the lower semi-cured layer can be cured by using electromagnetic radiation with a wavelength greater than 300 nm, wherein at least one Hg (mercury) UV radiation source is preferably used, but other suitable UV radiation sources are not excluded.

[0023] The structured layer and top coating formed in step C) are preferably transparent and / or translucent (at least after step F), which allows optional decorative images carried by the panel to remain visible.

[0024] As described above, the structured ink droplets preferably do not mix with the liquid layer to ensure and maintain a substantially clear interface between the two liquids. Water-based structured inks include water. Alternatively, water-based structured inks may include another polar solvent, such as ethanol. Typically, the presence of water is required due to its beneficial volatility, vapor formation during curing, and safety and cost reasons, which provides feasible time for application and processing.

[0025] It is conceivable that water-based structured inks consist solely of water. It is also conceivable that, in addition to water comprising 10-99% of the total content, such structured inks also contain at least one of the following components at the concentrations shown (volume %): (i) a substance from the hindered amine group at a concentration of 0-20%, and / or (ii) a substance from the N,N'-diphenylisoamide group at a concentration of 0-20%.

[0026] It is conceivable that structured inks contain solvents such as ethanol, and / or ethylene glycol, and / or water, and / or mixtures of two or more of these liquids. The solvent content in the ink is preferably 10-99% by volume. In addition to this solvent, the structured ink preferably contains at least one of the following components at the concentrations shown (volume %): (i) a substance from the hindered amine group at a concentration of 0-20%, and / or (ii) a substance from the N,N'-diphenylisoamide group at a concentration of 0-20%.

[0027] The curable liquid layer initially applied in step A) preferably comprises a (curable) polymerizable acrylate mixture. Alternatively or additionally, the liquid layer may comprise a solvent, preferably a nonpolar solvent, such as hexane, cyclohexane, toluene, xylene, heptane, and / or mineral oil. Mineral oil is a mixture of aliphatic and alicyclic C7 to C12 hydrocarbons.

[0028] In one specific embodiment, the liquid layer comprises or is composed of an acrylic varnish containing 25-35% by weight of HDDA diacrylate, and / or 35-45% by weight of DPGDA diacrylate, and / or 5-15% by weight of TM PTA crosslinking agent, and / or 1-5% by weight of industrial photoinitiator and / or 15-19% by weight of other components. If applied, the acrylic varnish preferably has a viscosity of 80-500 mPa·s, more preferably 150-400 mPa·s, as measured by a rheometer at 25°C and atmospheric pressure.

[0029] As mentioned above, gloss is preferably determined according to the method of DIN EN ISO 2813:2015-02. For gloss measurement, the amount of light reflected from the surface relative to a polished glass reference standard is measured. The unit of measurement used is GU (gloss unit). The amount of light reflected from the surface depends on the angle of incidence and the properties of the surface. For gloss measurement, reflectance can be measured using different angles of incidence (20°, 60°, and 85°), with a 60° angle of incidence being preferred. Alternatively, the average of measurements from three angles of incidence can be used. Reflectance is a comparison of the percentage of light energy emitted and received by the gloss meter at a specific angle of incidence.

[0030] According to the standard, when measured with a gloss meter, a panel is defined as "matte" if all surface portions reach less than 20 gloss units, and as "glossy" if any surface portion reaches more than 60 gloss units.

[0031] The recessed microstructures, as determined according to the method of DIN EN ISO 2813:2015-02, preferably have a gloss level of 0 to 20 gloss units (GU). Preferably, multiple microstructures are formed in step C). Typically, the collection of microstructures preferably displays as and / or represents a wood grain pattern, which is preferably at least partially aligned and / or synchronized with the printed wood image (including printed wood grain) of the decorative layer of the panel located beneath the structured layer.

[0032] As described above, the top coating preferably has a higher gloss than the microstructure of at least one depression. Preferably, the top coating has a gloss of at least 60 gloss units (GU) as determined according to the method of DIN EN ISO 2813:2015-02.

[0033] The top coating preferably has a smooth upper surface, but it is not excluded that the top coating has a structured top surface, for example, in step E) and / or step F).

[0034] The thickness of the structured layer can vary, but it is preferably thicker than half the thickness of the maximum ink droplet. From an economic perspective and for curing reasons, an excessively thick structured layer is undesirable. In practice, the thickness of the structured layer is preferably between 1 and 2 mm.

[0035] The present invention also relates to panels manufactured by the method of the present invention, particularly decorative panels.

[0036] The panel preferably comprises: The core, which can be a single core layer and / or multiple core layers, A decorative printed layer applied directly or indirectly to the top of the core. A structured layer applied directly or indirectly on top of the decorative printed layer, and A top coating applied on top of the structured layer.

[0037] Preferably, at least one transparent and / or translucent abrasion-resistant layer is located between the decorative layer and the structured layer. This will protect the decorative printed layer during normal use. The thickness of the abrasion-resistant layer is preferably less than the thickness of the structured layer. In the panel according to the invention, the thickness of each abrasion-resistant layer is preferably between 0.2 and 0.3 mm for residential use and between 0.4 and 0.7 mm for commercial use.

[0038] The decorative printed layer comprises and / or consists of printed decorative images, preferably achieved through digital printing. The latter also facilitates at least partial synchronization between the microstructure of at least one recess in the structured layer and the image represented by the decorative printed layer. This synchronization effect is also known as embossing-in-register (EIR). The decorative printed layer may include a carrier layer, such as a preferably white polymer film (e.g., PVC or PU film) and / or preferably white paper film, on which the decorative image is printed. The carrier layer may be melted and / or bonded to the core. The carrier layer may also be a primer layer, preferably a white primer layer, applied directly to the core on which the decorative image is directly printed.

[0039] The core may comprise MDF or HDF. However, alternatively, the substrate may comprise one or more other materials. For example, the core may comprise magnesium oxide (MgO) or other mineral-based materials. Examples of other mineral-based cores include gypsum-based substrates, cement-based substrates, etc. Furthermore, one or more edges of the core, which is at least partially composed of one or more of these materials, may be treated with one or more water-resistant agents. Alternatively, it is conceivable that the core comprises at least one thermoplastic material, such as polypropylene (PP), polyurethane (PU), thermoplastic polyurethane (TPU), polystyrene (PS), polyethylene (PE), polyethylene terephthalate (PET) and / or polyvinyl chloride (PVC), polylactic acid (PLA), and / or polyvinyl butyral (PVB). If one or more of these thermoplastic materials are used to manufacture the substrate, such thermoplastic material may be virgin, recyclable, or a mixture thereof.

[0040] The total thickness of the core can vary, with the thickness preferably between 5 and 12 mm, and even more preferably between 6.5 and 9.5 mm.

[0041] The panels according to the invention can be used and / or configured as floor panels, wall panels, ceiling panels and / or furniture panels.

[0042] It is conceivable that the panel includes at least one grout line or bevel at at least one panel edge, wherein at least one recessed microstructure of the structured layer is located on the grout line or the bevel, such that at least a portion of the upper surface of the grout line or the bevel is defined by the at least one recessed microstructure. This results in a textured upper surface of at least one bevel and / or at least one grout line. This can further improve the appearance and feel of the panel according to the invention.

[0043] The panels may include connecting profiles, preferably complementary, at at least a pair of opposing panel edges to allow mechanical interconnection between adjacent panels. Complementary connecting profiles may, for example, include tongues and / or grooves. Preferably, the complementary connecting profiles are configured to interlock the panels in both the horizontal and vertical directions. It is generally preferred that at least one connecting profile be included at each edge of the panel.

[0044] The present invention also relates to a panel covering comprising a plurality of mechanically interconnected panels according to the present invention.

[0045] Furthermore, the present invention also relates to a system for implementing the method according to the present invention, comprising: At least one coating station is used to coat the panel with a liquid layer to be structured. At least one structured ink printing station is used to selectively print, preferably digitally print, ink droplet positions onto the liquid layer to be structured. At least one first curing station is configured to irradiate the liquid layer to be structured with electromagnetic radiation and apply the liquid layer to the panel, preferably in the UV region, to at least partially cure and microstructure the layer. At least one scrubbing station is used to remove at least a portion of the residual structured ink from the structured layer. At least one top coating station for applying a top coating to the brushed structured layer. At least one second curing station is configured to irradiate at least the top coating to cure the top coating, and At least one conveyor is used to continuously move the panel along each station. Attached Figure Description

[0046] The invention will be further illustrated by means of several illustrative examples and with reference to the accompanying non-limiting drawings, wherein:

[0047] Figure 1-7 The sequential process steps of the method for manufacturing a decorative surface on a panel according to the present invention are illustrated schematically.

[0048] Figure 8 It shows the relationship with Figure 1-7 Compared to the panel shown, the panel according to the invention has another edge finishing, and

[0049] Figure 9 An exploded perspective view of a panel according to the invention is shown, the panel being... Figure 7 The panel shown. Detailed Implementation

[0050] Figure 1 The panel 1 according to the invention is shown schematically. Panel 1 will... Figure 7 The details are shown in more detail. A decorative 3D structure will be applied to the top of the panel 1, thus becoming an integral part of the panel 1. The first step is as follows: Figure 1 As shown, a curable liquid layer 2 (preferably acrylate-based) is applied to the top surface of the panel 1. The application of the liquid layer 2 can be achieved, for example, by rolling and / or spraying in a coating station and / or printing, particularly digital printing, in a printing station. Typically, but not necessarily, the entire top surface of the panel 1 is covered by the liquid layer 2. The thickness of layer 2 is less than the thickness of the panel 1 located beneath it and is typically in the range of 1-3 mm. The panel 1 with the liquid layer 2 is transported along a series of stations in the direction indicated by arrow (A) by at least one conveyor (not shown), first arriving at printing station 20, preferably a digital printing station, to print (preferably digitally printed) water-based structured ink droplets 3 onto the stationary liquid layer 2. Figure 3 As shown, water-based structured ink droplets 3 partially penetrate into liquid layer 2 and partially float on top of liquid layer 2, as... Figure 3a As shown. This can be achieved by adjusting the physical (and chemical) properties of the liquid layer 2 and the structured ink droplets 3. Preferably, the density of the ink droplets 3 is equal to or slightly higher (up to 20%) than the density of the liquid layer 2 to promote partial penetration of the ink droplets 3. Preferably, the surface tensions of the two liquids 2 and 3 are more or less the same (+ / - 20%). The ink droplets 3 are preferably partially or completely immiscible with the liquid layer 2, which hinders penetration and ensures and temporarily maintains a substantially transparent interface between the two liquids 2 and 3. The droplets 3 are positionally selectively printed at / on one or more depressions where the microstructure will be produced.

[0051] Subsequently, as Figure 4As shown, a panel 1, comprising a liquid layer 2 and partially permeated water-based structured ink droplets 3, moves along a first curing station 21, which has at least one first radiation source 22 for emitting electromagnetic radiation in the UV region. This first radiation source is preferably configured to emit electromagnetic radiation in the mid-ultraviolet (MUV) region (200-300 nm). Preferably, the first irradiation source is formed by an LED UV lamp, preferably with an emission wavelength of 254 nm, and / or 265 nm, and / or 280 nm. It is conceivable that the wavelength will be adjusted during lamp use, particularly during the (partial) curing of the liquid layer 2 and the ink droplets 3. In this (first) curing step, the liquid layer 2 typically cures more than the droplets 3 (achieving a higher level of curing). The heat generated by the first radiation source will force at least a portion of the water (H2O) in the water-based ink droplets 3 to evaporate. This evaporation may be accompanied by micro-explosions of water molecules within the droplets 3, which may deform the interface between the droplets 3 and the surrounding layer 2. The evaporation of water from droplet 3 will dry the droplet and—depending on the exact composition of droplet 3—may make the remaining dry portion of droplet 3 relatively brittle. For example... Figure 4 The curing steps shown can be achieved at relatively high speeds, such as 30 meters per minute, which is also known as rapid curing.

[0052] In the next step, such as Figure 5 As shown, the top surface of panel 1 (including the applied decorative top structures 2, 3) will be brushed in brushing station 22 using one or more axially rotating (or rotatable) brushes 23. Preferably, the brushes rotate in the opposite direction to the direction of movement of panel 1 to enhance the brushing action. The brush rollers may include fibers made at least partially of metal (such as steel) and / or polymer (such as nylon) and / or fabric and / or animal hair and / or natural fibers. In this embodiment, the brushes rotate at a speed of 1460 rpm. Preferably, the brushes also move alternately in a lateral (sideways) direction, more preferably at a speed of about 2.5 m / min. This brushing action removes at least a portion, preferably all, of the residual ink droplets 3, thereby creating partially or completely empty recessed microstructures 4 (microbags) and / or nanostructures 5 (nanobags), such as... Figure 5a This is shown in more detail below. Due to the recessed microstructures (and / or the nanostructures) and their nanostructures (textures), diffuse reflection will occur on the surface, resulting in an optically matte finish. This is advantageous, for example, in the case where the structured layer 2 is used to mimic a 3D wood grain pattern. As indicated by arrow B, dust can be removed by using vacuum evacuation at the scrubbing station 22.

[0053] In another step, such as Figure 6As shown, panel 1 is guided along second coating station 24 to apply top coating 6 (in liquid form) on top of (preferably only on) the non-recessed portions (unstructured portions) of structured layer 2. Top coating 6 may consist of a single layer or multiple layers. Top coating 6 may be applied, for example, by spraying and / or rolling and / or by printing (preferably digital printing).

[0054] In the subsequent steps ( Figure 7 In this curing process, the top coating 6 is cured by exposing it to one or more radiation sources, such as a mercury lamp (Hg-UV lamp) of the second curing station 25, which preferably exposes the top coating 6 (and the layers beneath it) to wavelengths between 300 and 400 nm. During this curing step, the top coating is preferably fully cured. During this curing step, the semi-cured structured layer 2 may also become more cured, or even fully cured. The top coating is transparent, at least after curing. The same applies to the structured layer 2.

[0055] like Figure 8 As shown, at least one panel edge may be provided with a bevel 7 and / or a grout line, which may be caused by a recessed edge portion of the panel, which may be a compressed edge portion and / or a portion where material has been removed. The bevel and / or grout line may have inclined planes and / or inclined curved surfaces and / or inclined corner surfaces. The structured layer 2 will follow the shape of the panel 1 (a portion) located below. The bevel 6 and / or grout line may be provided with one or more microstructures to give the bevel 6 and / or grout line a matte appearance.

[0056] Figure 9 The diagram schematically shows a perspective view of a panel according to the invention, which may be... Figure 7 The panel 1 shown is an example. Panel 1 includes a core 8, a backing layer 9 attached (e.g., glued or fused) to the underside of the core, and a decorative printed layer (2D) 10 attached directly or indirectly to the upper side of the core. Preferably, the decorative printed layer contains a digitally printed image. Preferably, the decorative printed layer is covered by one or more transparent abrasion-resistant layers (not shown), such as... Figure 7As shown, the structured layer 2 and the (discontinuous or interrupted) top coating 6 are applied over the transparent abrasion-resistant layer. The core 7 also includes complementary connecting profiles 11 at at least one pair, preferably each pair, of opposing panel edges. The connecting profiles 11 enable the decorative panels 1 to interlock with each other to form floor coverings, wall coverings, ceiling coverings, or furniture coverings. Preferably, the connecting profiles 11 are configured to interlock with adjacent decorative panels in a direction parallel to and / or perpendicular to the plane defined by the panel 1. The backing layer may be, for example, a polymer base layer and / or a cork layer. One or more abrasion-resistant layers are preferably UV-cured coatings. Preferably, the decorative image of the decorative layer 10 is embodied in a wood pattern, tile pattern, marble pattern, natural stone pattern, or concrete pattern. Preferably, the embossing of the structured layer 2, defined by recessed structures (microstructures and / or nanostructures), is at least partially and possibly completely aligned (synchronized) with the decorative image to create a realistic texture that closely matches the visual pattern of the panel 1. Panel 1 can be used, for example, as a floor panel or a wall panel. The panel may have at least one bevel and / or grout line along at least one edge, such as... Figure 8 As shown.

[0057] The verb “including” and its variations used in this patent disclosure should be understood not only to mean “including”, but also to mean the phrases “containing”, “consistently composed of”, “formed by”, and their variations.

[0058] The serial numbers used herein, such as "first" and "second," are for identification purposes only. "Horizontal" refers to a direction extending parallel to the plane defined by the panel, and this direction may intersect with the core of the panel. "Vertical" refers to a direction perpendicular to the plane defined by the panel. The term "complementary" connection means that these connection portions of adjacent panels can mate with each other. However, for this purpose, complementary connection portions do not necessarily have to have a completely complementary form (reverse design). In this disclosure, the term "panel" can be replaced by the term "workpiece," since other workpieces besides panels can also be processed using the method of the invention. "Water-based structured ink" includes a water component, although it is conceivable that water can be replaced by another polar solvent, such as ethanol, isopropanol, ethylene glycol ether, ethylene glycol, acetone, and dimethyl sulfoxide; therefore, the term "water-based structured ink" can be replaced by the more general expression "polar solvent-based structured ink."

Claims

1. A method for creating a decorative surface on a panel, comprising the following steps: A) A curable liquid layer to be structured is applied to the top surface of the panel, wherein the liquid layer is substantially immiscible with water. B) Selectively printing water-based structured ink droplets onto a portion of the top surface of the liquid layer to be structured in a liquid state, wherein the density of the structured ink droplets is equal to or greater than the density of the liquid layer to be structured, to allow the water-based structured ink droplets to be partially submerged in the liquid structured layer, wherein the structured ink droplets are configured to at least partially absorb electromagnetic radiation or to contact the liquid layer to generate at least one reaction product, the reaction product being capable of at least partially absorbing the electromagnetic radiation irradiated in step C), and / or the structured ink droplets having lower curability compared to the liquid layer in step C), and / or the structured ink droplets not curing when irradiated with electromagnetic radiation in step C), particularly in the UV region; C) Irradiating the surface of the liquid layer and the applied structured ink droplets with electromagnetic radiation, particularly in the UV region, wherein the liquid layer will be at least partially cured, and wherein at least a portion of the water present in the water-based structured ink will evaporate, resulting in the formation of at least one recessed diffractive microstructure in the at least partially cured structured layer at one or more locations of the structured ink printed in step B). D) Removal, particularly mechanical removal, of at least a portion of the remaining structured ink from the at least partially cured structured layer to at least partially expose at least one recessed diffraction microstructure. E) Applying a curable liquid top coating to at least partially cured unstructured portions of the structured layer, while the structured portions of the at least partially cured structured layer defined by the diffraction microstructure of the at least one recess are substantially not covered by the top coating, and F) Irradiate the surface of the top coating with electromagnetic radiation at least once, especially in the UV region, to cure the top coating.

2. The method according to claim 1, wherein, The ratio of the density of the liquid structured ink droplet to the density of the liquid layer to be structured is between 1 and 1.

2.

3. The method according to claim 1 or 2, wherein, The surface tension of the liquid structured ink droplet is approximately equal to the surface tension of the liquid layer to be structured.

4. The method according to any one of the preceding claims, wherein, In step B), at least a portion of the applied ink droplets are partially located within the liquid layer, such that 40% to 60% of the outer surface of each of these droplets is covered by the liquid layer.

5. The method according to any one of the preceding claims, wherein, In step B), the volume of the ink droplet is from 0.1 μl to 80 μl, and / or the average diameter of the ink droplet is from 50 to 500 μm.

6. The method according to any one of the preceding claims, wherein, In step B), ink droplets are applied at a speed between 0.5 m / s and 12 m / s, preferably between 3 m / s and 7 m / s, and more preferably between 5 m / s and 6 m / s.

7. The method according to any one of the preceding claims, wherein, In step B), the structured ink droplets are applied by digital printing.

8. The method according to any one of the preceding claims, wherein, In step C), the diffraction microstructure of the at least one recess formed in the structured layer has at least a partially nanostructured surface.

9. The method according to any one of the preceding claims, wherein, In step C), the liquid layer is partially solidified, and the structured ink droplets are preferably also partially solidified.

10. The method according to any one of the preceding claims, wherein, The electromagnetic radiation used in step C) has a wavelength of less than 300 nm, wherein at least one LED UV radiation source is preferably used.

11. The method according to any one of the preceding claims, wherein, The electromagnetic radiation used in step C) has a wavelength that is adjusted during the execution of step C).

12. The method according to any one of the preceding claims, wherein, In step C), each part of the liquid layer and the ink droplet is irradiated by the electromagnetic radiation at least multiple times.

13. The method according to any one of the preceding claims, wherein, In step D), at least a portion of the residual structured ink is removed from the at least partially cured structured layer by at least one brush roller, particularly at least one fabric brush roller and / or at least one nylon brush roller.

14. The method according to claim 13, wherein, In step D), the rotational speed of the brush roller is between 1000 and 2000 rpm.

15. The method according to claim 13 or 14, wherein, In step D), the brush roller moves laterally alternately in the axial direction of the brush roller, wherein the speed of the lateral movement is preferably between 2 and 3 meters per minute.

16. The method according to any one of the preceding claims, wherein, In step E), the top coating is applied by digital printing and / or by rolling.

17. The method according to any one of the preceding claims, wherein, The electromagnetic radiation used in step F) has a wavelength greater than 300 nm, wherein at least one mercury UV radiation source is preferably used.

18. The method according to any one of the preceding claims, wherein, The structured layer formed in step C) is transparent and / or translucent.

19. The method according to any one of the preceding claims, wherein, The at least concave microstructure scatters and reflects light, thereby producing an optically matte finish.

20. The method according to any one of the preceding claims, wherein, The at least recessed microstructure has a gloss level of 0 to 20 gloss units (GU) as determined according to the method of DIN EN ISO 2813:2015-02.

21. The method according to any one of the preceding claims, wherein, In step C), multiple microstructures are formed, which are preferably displayed together as a wood grain pattern.

22. The method according to any one of the preceding claims, wherein, The top coating has a higher gloss than the microstructure of the at least one recess.

23. The method according to any one of the preceding claims, wherein, The top coating has a gloss level of at least 60 gloss units (GU) as determined according to the method of DIN EN ISO2813:2015-02.

24. The method according to any one of the preceding claims, wherein, The top coating has a smooth upper surface.

25. A panel, particularly a decorative panel, manufactured by the method according to any one of the preceding claims, wherein the panel comprises: -Core, - A decorative printed layer applied directly or indirectly to the top of the core. - A structured layer applied directly or indirectly on top of the decorative printed layer, and - A top coating applied on top of the structured layer.

26. The panel according to claim 25, wherein, The panel includes at least one transparent and / or translucent abrasion-resistant layer located between the decorative layer and the structured layer.

27. The panel according to claim 25 or 26, wherein, The microstructure of at least one recess in the structured layer is at least partially synchronized with the image represented by the decorative printing layer.

28. The panel according to any one of claims 25 to 27, wherein, The panel includes at least one grout line or ramp at at least one edge, wherein at least one recessed microstructure of the structured layer is located on the grout line or ramp such that at least a portion of the upper surface of the grout line or ramp is defined by the at least one recessed microstructure.

29. The panel according to any one of claims 25 to 28, wherein, The panel includes a connecting profile at at least one pair of opposing panel edges to allow for mechanical interconnection between adjacent panels.

30. A panel covering comprising a plurality of mechanically interconnected panels as claimed in claim 29.

31. A system for performing the method according to any one of claims 1 to 24, comprising: - At least one coating station for coating the panel with the liquid layer to be structured. - At least one structured ink printing station for selectively printing, preferably digitally printing, ink droplet positions onto the liquid layer to be structured. - At least one first curing station configured to irradiate the liquid layer to be structured with electromagnetic radiation and apply the liquid layer to the panel, preferably in the UV region, to at least partially cure and microstructure the layer. - At least one scrubbing station for removing at least a portion of the residual structured ink from the structured layer. - At least one top coating station for applying a top coating to the brushed structured layer. - At least one second curing station, configured to irradiate at least the top coating to cure the top coating, and - At least one conveyor for continuously moving the panel along each station.

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