Method for producing inkjet printable paper for use as a decor paper

Abstract

1. A method for producing a printable paper, printable by inkjet printers and / or analogue printing, preferably by gravure printing, for use as decor paper in laminate panels, comprising the steps of: The method comprises: - providing a paper layer; - coating at least one surface of said paper layer with an ink-receptive coating; wherein the method includes the step of providing the paper with an ink adhesion promoter.

Description

[Technical field]

[0001] The present invention relates to a method for producing panels with a decorative surface, so-called decorative panels. The invention also relates to a method for producing an inkjet printable paper for use as a decor paper in such panels. The invention further relates to a printed decor paper for use in such panels and to a method for producing such a paper. In one variant, the resulting decor paper may not be used as a panel but as a laminated assembly, such as a so-called CPL (compact laminate) or HPL (high pressure laminate). [Background technology]

[0002] In particular, the present invention relates to a method for manufacturing a laminated panel, the panel comprising at least one substrate material and a top layer provided thereon with a printed decor, the top layer being formed from a thermosetting resin and one or more paper layers, the paper layers comprising a decor paper with a printed pattern. The panels of the present invention may also relate to furniture panels, ceiling panels, flooring panels or the like, these panels preferably comprising a wood-based substrate such as a substrate of MDF (Medium Density Fiberboard) or HDF (High Density Fiberboard) or a substrate material consisting of or made essentially of wood particle board. [Prior art documents] [Patent documents]

[0003] Traditionally, the decor or patterns of such panels are printed on the surface of the paper by rotogravure printing. The paper obtained is used as a decorative paper in so-called laminate panels. To manufacture the panels of the first possibility above, the DPL (Direct Pressure Laminate) process can be carried out. According to the DPL process, the already printed paper or decorative paper is provided with melamine resin to form a decorative layer. Then, a stack is provided, forming at least one layer, comprising the substrate, the decorative layer and possibly a protective layer on the top surface of the decorative layer, where the protective layer or overlay is based on the resin and / or on the surface of the paper. The stack is compressed, and as a result of the compression process, a mutual connection or adhesion of the decorative paper, the substrate and the protective layer occurs, as well as a hardening due to the presence of the resin in the stack. As a result of the pressing operation, a decorative panel is provided with a highly wear-resistant melamine surface. A counter layer or a balancing layer can be applied to the bottom side of the flat-shaped substrate or, alternatively, in particular in the case of laminate panels for furniture, a decorative layer may be attached to the bottom side. Such a counter layer or balancing layer or other layer on the bottom side of the laminate panel inhibits or prevents possible bending of the decorative panel and is applied in the same pressing operation as, for example, the provision of a paper layer with resin as the bottommost layer of the stack on the side of the stack facing the decorative layer. As an example of a DPL process, reference is made to EP 290290, where it is seen that a relief is provided during the same pressing operation or pressing operation, i.e. the melamine surface is brought into contact with a pressing component, e.g. a structured pressing plate.

[0004] Instead of analogue printing techniques, digital printing techniques, especially inkjet printing techniques, are rapidly becoming more and more popular for the production of decors and patterns, which are applied directly on paper or, possibly, on a flat substrate between prepared layers. Such digital techniques allow a great deal of flexibility in the printing of decors. [Patent Document 1] EP290290 [Patent Document 2] WO2011 / 124503 [Patent Document 3] EP1872959 [Patent Document 4] EP1857511 [Patent Document 5] EP2431190 [Patent Document 6] EP2293946 [Patent Document 7] WO2014 / 084787 [Patent Document 8] WO2015 / 140682 [Patent Document 9] WO2015 / 118451 discloses techniques referenced by these patent documents. Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, prior to being laminated to a substrate, the printed decor paper is dipped into a resin bath to soak it in. This immersion causes the ink to bleed into the bath, thereby degrading the quality of the decor paper. Subsequent immersion in the contaminated bath further contaminates the bath and the decor paper.

[0006] [Patent Document 10] EP2132041 This patent document is a method which includes at least a step of providing a paper layer with a thermosetting resin before a step of providing a resin-provided paper layer with at least a part of a digitally printed pattern. However, it is very difficult to further reliably process such printed paper to produce laminated panels in a DPL process, since compression defects start to appear on the resin surface and milling, drilling or sawing through the laminate surface or at the edges of the laminate surface often leads to splitting in the upper layer. Furthermore, the inks or dyes of EP2132041 wet the paper layer very much, which leads to wrinkling or further handling of the printed paper leads to an unstable and / or slow production process. To solve this problem, EP2132041 proposes to dry the printed paper layer quickly.

[0007] The present invention is aimed primarily at an alternative method for producing panels with a decorative surface or decorative paper for use in such panels, and, together with its preferred embodiments, at solving one or more problems arising from the state of the art. [Means for solving the problem]

[0008] Therefore, according to a first independent aspect, the present invention relates to a method for producing a paper printable by means of an inkjet printer and / or a paper printable by means of analogue printing, preferably gravure printing, for use in a laminate panel as a decor paper, said method comprising at least the following steps: (1) Providing a paper layer (2) coating at least one surface of the paper layer with an ink-receptive coating; The method characteristically includes the step of providing the paper with an ink adhesion promoter. The inventors have found that such an adhesion promoter can substantially reduce the risk of ink seepage, thereby improving the quality of the Decor paper after immersion. Preferably, the ink adhesion promoter is provided in the ink-receiving layer, e.g., the ink adhesion promoter can be part of the composition of the ink-receiving layer. Furthermore, the inclusion of the adhesion promoter in the ink-receiving layer avoids the need to perform an extra step in the manufacturing process.

[0009] Preferably, the ink adhesion promoter comprises a urea-based promoter, a polyurethane-based promoter, a casein-based promoter, an acrylic-based promoter and / or mixtures thereof. The inventors have found that these substances substantially improve the adhesion of the ink to the paper and preferably to the ink-receptive coating during immersion of the paper. The inventors have found that the adhesion of the ink is sufficiently improved if the ink adhesion promoter is selected based on the ink to be printed, and in particular if the ink adhesion promoter is sufficiently identical to the binder contained in the ink. Sufficiently identical means that the ink adhesion promoter can be the same material as the binder of the ink or belongs to the same family of materials. Examples of suitable adhesion promoters include urea-based accelerators, polyurethane-based accelerators, casein-based accelerators, styrene-based accelerators, polyester-based accelerators, polyvinyl-based accelerators, alkyd-based accelerators, ketone-based accelerators, cellulose-based accelerators, gum-based accelerators, acrylic-based accelerators, or mixtures or copolymers thereof.

[0010] In a preferred embodiment, the ink adhesion promoter is provided in an amount of 0.2 g / m2 or more, more preferably 0.5 g / m2 or more, even more preferably 1 g / m2 or more. This minimum amount was found to be the ideal value for maximizing the adhesion of the ink to the paper when the amount of ink is 15 milliliters per square meter XXXXX g / m2 or more. The ink adhesion agent may be provided in an amount of 10 g / m2 or less, more preferably 5 g / m2 or less. This maximum amount was found to be the ideal value for maximizing the adhesion effect without affecting the performance of the ink receiving layer.

[0011] The ink-receiving layer may contain a pigment. In a preferred embodiment, at least or mainly silica particles are used as pigments. Preferably, the silica particles are silane treated. Silane treatment of the pigments generally improves the dust release capacity of the ink-receiving layer obtained and of the paper or thermoplastic foil thus treated. Silane treatment refers to treatment with binding agents such as amino-organo-silanes, hydroxysilanes, dipodal silanes and / or other silanes. Preferably, the binding agents are selected so that there is a low risk of yellowing of the ink-receiving layer obtained over time. Preferably, the binding agents represent 0.1-10% of the total wet weight of the ink-receiving layer.

[0012] According to another embodiment, the pigment of the ink receiving layer is at least or mainly particulate and is selected from the list consisting of calcium carbonate, alumina, aluminosilicates, ordered mesoporous materials, modified silica, organosilica, modified organosilica, organoalumina, modified alumina, aluminates, modified aluminates, auger aluminates, modified organoaluminates, zeolites, metal organic frameworks and porous polar polymers.

[0013] Preferably, the pigment has a BET surface area of ​​10-1600 m2 / g, preferably 15-500 m2 / g.

[0014] The ink receiving layer preferably includes a binder, in a preferred embodiment of which at least or mainly polyvinyl alcohol is used.

[0015] According to another embodiment, the ink receptive coating comprises as a binder a copolymer selected from the group consisting of hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, methyl cellulose, sodium carboxymethyl cellulose, sodium carboxymethyl hydroxyethyl cellulose, water soluble ethyl hydroxyethyl cellulose, cellulose sulfide, vinyl alcohol copolymers, polyvinyl acetate, polyvinyl acetal, polyvinyl pyrolylone, polyacrylamide, acrylamide / acrylic acid copolymers, poly(2-acrylamido-2-methyl propane sulfide, poly(diethylene triamine-co-adipic acid), polyvinyl pyridine, polyvinyl imidazole, polyethylene imine epichlorohydrin variants, polyethylene imine ethyloxylate, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), and polyvinyl The binder is selected from the group consisting of ethyl bond-containing polymers such as polyvinyl ethyl (PVE); polyurethanes; melamine resins; gelatin; carrageenan; dextran; gum arabic; casein; pectin; albumin; chitins; chitosan; starch; collagen derivatives; collodion and agar. The most preferred variations of the binder are polyvinyl acetate, ethyl vinyl acetate; block copolymers based on polyvinyl acetate, block copolymers based on polyvinyl alcohol, acrylates, latexes, polyvinyl derivatives, VCVAC derivatives, polyurethanes based on polyols and isocyanates, polyurethanes based on polycarbamate or polyaldehydes, for example in water dispersions / emulsions or aqueous or solvent solutions. As mentioned above, the preferred binder of the ink-receiving layer comprises polyvinyl alcohol (PVA), but according to variations, vinyl alcohol copolymers or modified polyvinyl alcohols can be applied.The modified polyvinyl alcohol may be a cationic type polyvinyl alcohol such as Nippon Synthetic's POVAL C506 or POVAL C118, or Kuraray's cationic polyvinyl alcohol grades.

[0016] Preferably the paper is provided with a dry coating weight of the ink receiving layer of 0.2-10 g / m2.

[0017] Preferably, the ink receptive coating may contain a crosslinking agent for the crosslinking reaction of the binder, the crosslinking agent being selected from the group including aldehydes, polyaldehydes, dialdehydes, alcohols, boronic acids, borax, polyalcohols, carbamates, polycarbamates, carboxylic acids, glyoxal-based agents, zirconium-based agents, titanates and polycarbonic acids.

[0018] The ink receptive coating may further comprise a dispersant, which is an oligomer or polymer that stabilizes the liquid dispersion of the pigment against flocculation. The dispersant may comprise a polycarboxylate, a polyphosphate, a polyionic polymer, preferably polyDADMAC (polydiallyldimethylammonium chloride), a polyamine or an alumina salt.

[0019] Preferably, the ink receptive coating is provided with no more than 10% by dry coat weight of dispersant, more preferably no more than 5%, illustratively between 5% and 0.1%.

[0020] The ink receptive coating may also include a flocculant, preferably a metal salt, preferably a cationic metal salt. Preferably, the metal salt is selected from the list consisting of CaCl2, MgCl2, CaBr2, MgBr2, CMA (calcium magnesium acetate), NH4Cl, calcium acetate, ZrCl4, calcium nitrate and magnesium acetate. The cations of the dissolved metal salts tend to neutralize the electrosteric stabilizing function of the pigment. The most preferred cationic metal salts are CaCl2, MgCl2, CMA, calcium acetate, calcium nitrate and magnesium acetate, as the inventors have obtained the best results with these ink reactants. The flocculant is selected from the list consisting of sodium aluminate, double sulfate salts such as alum, polyaluminum chloride, polyacrylates, dicyandiamide (e.g., SNF's Flocquat D15) and polyacrylamides. The flocculating agent draws the ink pigment out of the ink dispersant. This prevents the pigment from concentrating in the ink-receptive coating, where primarily the ink medium, e.g., water in the case of water-based inks, is absorbed into the ink-receptive coating.

[0021] Preferably, the ink receptive coating is provided with 20-70% by dry coating weight of the flocculating agent, especially in the case of metal salts.

[0022] In a particular embodiment, the ink receptive coating may be an acid. In a particular embodiment, the ink receptive coating may include one or more acid components. The acid components may be organic or inorganic. Preferred examples of acid components are citric acid, formic acid, lactic acid, propionic acid, or combinations thereof. Preferably, the acid component has a pH of 5, more preferably a pH of 4.5 or less. The acid component acts to destabilize the ink dispersion and is generally used as a variation of the metal salts described above.

[0023] The ink receptive coating may also include one or more of the following agents: - an agent for modifying the pH of the ink receptive coating, in particular an agent for lowering the pH. Preferably, the pH of the ink receptive coating composition is lowered to pH 5, or even lowered by choosing the amount and type of substance according to the choice within the skill of the art. Preferably, the substance is selected from the list consisting of formic acid, tartaric acid, acetic acid, hydrochloric acid, citric acid, phosphoric acid, sulfuric acid, AlCl3 and boronic acid. Adjusting the pH, more preferably lowering the pH, in particular below pH 5, increases the chemical affinity of the ink to the ink receptive coating and interferes with the electrostatic stabilizing effect on the pigment, such that the dispersion of the pigment in the ink becomes rapidly unstable. - Particle surface modifiers or binders: 0.05-5g / m2, preferably 0.2-2g / m2, selected from the non-limiting list consisting of amino silanes, ureido silanes, aldehyde silanes, tetraethylorthosilatosilanes, siliazanes, organically modified silanes, organically modified siliazanes, chlorosilanes, organically modified chlorosilanes, bisilanes, organobisilanes, silsesquioxanes, potosylsequioxanes, silane oligomers, organically modified silane oligomers, bisilane oligomers, organically modified bisilane oligomers, oligomeric silsequioxanes and oligomeric polysilsequioxanes. - Additives: 0.05-0.5g / m2 moisturizer and / or 0.05-0.5g / m2 deformation agent and / or 0.05-0.5g / m2 mildew inhibitor.

[0024] Preferably, the paper or foil is provided with a dry weight of ink receptive coating of 0.2-10 g / m2, preferably 0.5-5 g / m2.

[0025] The paper layer over the ink receptive coating is preferably provided with a basis weight of 40-130 g / m2, more preferably with a basis weight of 60-90 g / m2.

[0026] The side of the paper layer on which the ink-receptive coating is provided is preferably smoothed, preferably during manufacture. Smoothing reduces the amount of binder penetrating into the core of the paper, so that the pigments contained therein are better bound by the available binder material, and the deformation due to absorption is reduced. The paper obtained using the method of the present invention, i.e. the paper comprising the ink-receptive coating, has a Gurley value of 10-60 seconds, preferably a Gurley value of 12-50 seconds. Preferably, based on the initial Gurley value of the uncoated paper layer, the paper layer after providing the ink-receptive coating shows an increase in Gurley value of not more than 30%, more preferably an increase in Gurley value of not more than 20%. Such a paper layer allows for superior print quality, since the deposited ink is less likely to bleed into the paper, and the so-called register or registration between the patterns printed with different inkjet heads is more easily obtained and more easily maintained. It should be noted that the above Gurley values ​​of the coated paper layer are significantly lower than other coated paper layers, especially those coated with coating materials containing silica and binders, especially those with highly cross-linked binders. Such Gurley values ​​improve the resin penetration ability of the paper layer, making the paper layer particularly suitable for use in panel decoration, such as for furniture and floor panels, where the decorative paper is saturated with melamine resin before being laminated onto a support board. The paper layer containing the ink-receptive coating has a resin penetration time of less than 3 seconds.

[0027] Preferably, the paper layer of the present invention is opaque and / or contains titanium oxide as a whitening agent.

[0028] Preferably, in the method of the invention, the paper is intended to be printed with water-based inks or UV-curing inks or hydro-UV inks, in particular pigmented inks. Firstly, the paper obtained by the method of the first aspect is intended to be printed with an inkjet printing device. However, the inventors have found that the paper thus treated also gives good print quality with analogue printing devices.

[0029] In the most preferred embodiment, the ink receptive coating is formed in one step to form a distinct layer with the inkjet receptive coating components, without excluding that the ink receptive coating is formed in at least two partial steps, with a first layer formed by the first component and then a second layer formed by the second component, respectively, the first and second components being the same or different components.

[0030] Preferably, the paper obtained by the method of the invention is provided after being provided with a pattern printed, preferably by inkjet printing, using a thermosetting resin such as melamine resin. For this, the paper layer is only provided with an ink-receptive layer on one side, i.e. the side to be printed. The other side, or the opposite side, is preferably not treated so that the opposite side shows the original nature of the paper layer from the start. The resin is provided into the paper core substantially from the bottom side. To allow sufficient impregnation into the paper with the inkjet receptive coating, the impregnation path speed may be slowed, the resin may be made less viscous, the impregnation may be pressurized and / or the resin may be heated, for example to 30-50°C.

[0031] ° Although the paper obtained by the method of the present invention is printable with an inkjet printer, typically the paper or foil is actually printed using other techniques, such as rotogravure or flexo printing.

[0032] Preferably, the ink receptive coating is a liquid material that is applied onto the paper layer and is preferably force dried, for example in a hot air oven, or by infrared or near infrared, or by microwave drying. Preferably, the liquid material is a water-based suspension of at least a binder and possibly a pigment. Preferably, the liquid material composition has a dry matter content of 4-65% by weight of the liquid material.

[0033] The application of the liquid substance to the ink-receptive coating is carried out by printing, for example inkjet printing, but preferably by application techniques, such as roller coating, for example with one or more gravure rollers, spray coating, metering roller coating, bead coating, scattering coating, slot die coating. In the latter case, the coating is preferably applied so as to cover at least 80% of the surface of the paper or foil. To manipulate and control the weight of the ink-receptive coating, an in-line measuring system is desirable. Such techniques reduce the risk of non-coated areas of the paper, which could lead to local defects in the printed pattern. A preferred device for applying the liquid substance is a rotogravure or anilox coating device.

[0034] The application of the liquid substance to the ink-receptive coating may be carried out in a roto-bravia application line or alternatively in a printing apparatus just before the printing process. The latter solves the problem of limited shelf life of the ink-receptive coating. Preferably, the application of the liquid substance is carried out while the paper or foil is in an endless form, as it were, pulled from the roll without being cut. This technique allows a more uniform application to the ink-receptive coating. If all or part of the application is carried out in a printing apparatus, the printing apparatus is preferably a roll-to-roll or roll-to-sheet press and includes an application device upstream of the print head, for example a gravure coater and / or an additional print head, suitable for printing the liquid substance on each sub-layer of the ink-receptive coat. The additional print head, for example an additional row of the print head, is equipped with nozzles having a larger diameter than the nozzles used for the actual printing of the pattern. A resolution of 1-100 dots per inch, or even 1-25 dots per inch, is satisfied by these nozzles.

[0035] The ink receptive coating may be applied directly, in-line, by a printing press equipped with a size press, or more preferably, a film press.

[0036] The liquid material for the ink receptive coating preferably has a viscosity of 10-75 seconds in Din cup 4 at 20° C. This property allows the liquid material to be applied directly to the surface of the paper layer or foil. In experiments it was found that a solids content of about 12% and a viscosity of about 20 seconds is sufficient to be applied uniformly to previously untreated paper, for example by a roller coater.

[0037] It should be noted that the present invention also relates to a composition of an ink-receptive coating having the characteristics described in relation to the first independent aspect. According to a second independent aspect, having the same object as in the first independent aspect, the present invention also relates to a composition of an ink-receptive coating for a printing paper, at least a composition of an ink adhesion promoter. The composition of the second independent aspect comprises one or more of the characteristics described in relation to the first independent aspect.

[0038] It should be noted that the invention also relates to a paper layer obtainable using the method of the first aspect of the invention. With the same objective as the first aspect, according to a third independent aspect, the invention also relates to a paper for inkjet printing, characterised in that the paper is provided on at least one side with an ink-receptive coating, the ink-receptive coating being provided with an ink adhesion promoter.

[0039] It is noted that the paper may include one or more of the features described above in relation to the first independent aspect.

[0040] The invention further relates to a method for producing a printed decor paper for laminate panels, the paper being provided with the ink adhesion promoter. And the invention in a fourth independent aspect relates to a method for producing a printed decor paper for laminate panels, the method comprising the steps of providing a printable paper and printing decor on the paper. The method comprises the step of providing an ink adhesion promoter to the paper. The ink adhesion promoter is provided by two main alternatives described below.

[0041] According to a first alternative of the fourth aspect, the ink adhesion promoter is provided prior to the printing step.

[0042] In a first preferred possibility of the first alternative, this is obtained by providing a printable paper according to the third aspect or produced by the method of the first aspect. The first possibility of the first alternative provides the advantage that the method of producing the decor paper does not require any further steps or modifications to existing decor paper producing lines.

[0043] In a second, less preferred possibility of the first alternative, the step of providing the ink adhesion promoter can be performed after the step of providing the printable paper. The ink adhesion promoter is provided in the form of a coating on the top surface of the printable paper, for example in the form of a coating on top of its ink receptive coating. In this way, the method of producing printed paper can start with any printable paper.

[0044] According to a second alternative of the method of the fourth aspect, the ink adhesion promoter is provided after the printing step. The ink adhesion promoter is provided in the form of a coating on the top surface of the printed paper, more particularly above the printed pattern provided on the paper. The method for producing printed paper in this way can start with any printable paper and, after printing, the ink adhesion promoter is provided, such that the ink adhesion promoter does not affect the printing performance and print quality of the printable paper.

[0045] Preferably, in the second alternative, the ink adhesion promoter is transparent or translucent. The ink adhesion promoter coating comprises a binder, preferably polyvinyl alcohol, which has one or more of the characteristics described above in relation to the binder of the ink receiving layer.

[0046] The ink adhesion promoter may be applied in liquid form to the top surface of the paper in both the first and second alternatives. The application of the ink adhesion promoter may be obtained in various ways, but by printing, such as inkjet printing, or by application techniques, such as roller coating, for example by one or more gravure rollers, spray application, metering rollers, bead coating, scattering, slot die coating.

[0047] After the ink adhesion promoter is provided, the coating may be dried, preferably by forced drying, for example, in a hot air oven, or by infrared or near infrared, or by microwave drying. In various embodiments, the ink adhesion promoter and / or binder in the ink adhesion promoter coating may be cured, preferably by radiation curing, such as, for example, UV or EB curing. In such a case, the method may preferably include the step of curing the ink adhesion promoter coating by irradiation.

[0048] Preferably, in the fourth aspect above, the paper is printed by an inkjet printer, preferably operating on a water-based ink, preferably an inkjet printer of a single pass type and / or an inkjet printer operating in a single pass mode.

[0049] Preferably, the printed pattern applied to the paper layer of the present invention covers most, and preferably 50% or more, of the surface of the paper layer.

[0050] Preferably, the ink comprises a binder. In a most preferred embodiment, the binder in the ink and the binder in the ink adhesion promoter are substantially identical. Being substantially identical, the ink adhesion promoter may be the same material as the binder of the ink. Preferably, the binder of the ink may comprise a urea-based binder, a polyurethane-based binder, a casein-based binder, a styrene-based binder, a polyester-based binder, a polyvinyl-based binder, an alkyd-based binder, a ketone-based binder, a melamine-based binder, a silicone-based binder, a cellulose-based binder, a gum-based binder, an acrylic-based binder, or mixtures or copolymers thereof.

[0051] Preferably, for use in printing printed patterns, the printed ink is made with a pigmented ink, for which a water-based ink or a so-called aqueous ink is used. The total amount of pigmented ink applied on the paper layer is made with a dry weight of 12 g / m2 or less, preferably 3-4 g / m2 or less. The limit of the dry weight of the applied ink leads to an ink layer that reduces the risk of compression defects and splitting of the top layer. Possible interference between the ink layer and the thermosetting resin during the compression run is much reduced. Since the ink load is limited to a maximum of 12 g / m2, the wrinkling and stretching of the paper due to the ink is brought to an acceptable level, ensuring a stable subsequent processing step. The pigments in the pigmented ink have an average particle size of 300 μm or less. The printed pattern is entirely formed with such a pigmented ink, or at least essentially formed with such a pigmented ink. The total amount of pigmented ink applied is made with 15 ml / m2 or less, more preferably 10 ml / m2 or less, even more preferably 5 ml / m2 or less.

[0052] Preferably, for printing the paper layer or foil of the invention, a digital inkjet printer is applied, which digital inkjet printer is capable of jetting droplets of ink with a volume of 50 picolitres or less. The inventor has found that working with droplets of a volume of 10 picolitres or less, such as 15 picolitres, offers a considerable advantage in terms of the limit of the dry weight of the ink applied. Preferably, the digital inkjet printer is applied so that it is possible to work with droplets of ink of various volumes in one or the same print, or as so-called halftone or greyscale. Since halftone or greyscale printing is possible, the dry weight of the ink applied can be much reduced while maintaining an excellent print definition. Preferably, the digital inkjet printer is applied so that a resolution of at least 200 dpi (dots per inch) can be obtained, preferably a resolution of 300 dpi or more.

[0053] The decor paper obtained according to the fourth aspect of the invention is suitable for use as decor paper in a method for producing floor, furniture, ceiling and / or wall panels, comprising at least one substrate material and a top layer on which a printed decor is provided, the top layer comprising a thermosetting resin and one or more paper layers, the paper layers comprising decor paper according to the third independent aspect and / or decor paper obtainable by a method according to the first independent aspect and / or decor paper according to preferred embodiments of these aspects.

[0054] Preferably, after printing, the DECOR paper is provided with an amount of thermosetting resin equal to 40-250% of the dry weight of the thermosetting resin relative to the weight of the paper. Experiments have shown that providing this amount of thermosetting resin allows the thermosetting resin to fully permeate the paper and avoids any significant degree of splitting, while maintaining a high degree of paper quality.

[0055] Preferably, after printing, the decor paper is provided with such an amount of thermosetting resin that at least the paper core is saturated with resin, which is achieved when a large amount of resin is provided such that the amount of resin corresponds to at least 1.5 times the weight of the paper, or alternatively at least twice the weight of the paper.

[0056] Preferably, the resulting resin applied to the paper layer, i.e. after application of the thermosetting resin, has a relative humidity of 15% or less, more preferably 10% or less by weight.

[0057] Generally, the paper and ink receptive coating, whether provided with resin or not, should be kept at a relative humidity of not more than 15%, and preferably not more than 8% by weight.

[0058] Preferably, the step of providing the paper layer with a thermosetting resin includes applying a mixture of water and resin onto the paper layer, which may include immersing the paper layer in a bath of the mixture and / or spraying, jetting, or other processes for applying the mixture onto the paper. The resin is set, for example, using one or more squeeze rollers and / or doctor blades to determine the amount of resin to be applied to the DECOR paper.

[0059] Thermosetting resins are melamine-based resins, specifically melamine-formaldehyde resins with a melamine to formaldehyde ratio of 1.4-2. The melamine-based resins are polycondensed during exposure to heat in compression runs. The polycondensation reaction produces water as a by-product.

[0060] The paper layer is saturated after applying the ink adhesion promoter by resin printing, thus preventing the ink from bleeding by the ink adhesion promoter.

[0061] The method of the fourth aspect of the invention preferably comprises the step of thermocompressing the printed and resin-provided decor paper and at least curing the resin of the resulting decor paper. The method of the invention forms the aforementioned DPL process, in which the printed and resin-provided paper layers of the invention are stacked in one pile and compressed as a decorative layer. The method of the invention forms part of the HPL (Compact Laminate) or HPL (High Pressure Laminate) process, in which the decorative layer is thermocompressed together with a resin-impregnated core paper layer, so-called Kraft paper, to form a substrate directly beneath the decorative layer, which is then compressed and cured, and the resulting laminate or laminated board is then glued to a further substrate in the case of HPL, resulting in a particle board or MDF board or HDF board.

[0062] The method also includes the step of providing an abrasion-resistant layer on the top surface of the laminated panel. Preferably, after printing, a further resin layer is applied on the decor paper, for example as a topcoat, i.e. the resin is provided and a carrier layer or liquid coating is applied while the decor paper is loosely attached or already attached to the substrate. In this case, the ink adhesion promoter reduces the risk of the ink bleeding during the lamination of the abrasion-resistant layer.

[0063] The method of the fifth aspect of the invention further comprises the step of applying a counter or balancing layer to a surface of the substrate opposite the top layer, the counter or balancing layer preferably comprising a thermosetting resin, preferably the same resin as the top layer, and a paper layer.

[0064] Preferably, the interconnection of the substrate, the possible counter layer and the possible transparent or semi-transparent layer is obtained in one and the same compression operation. According to a most preferred embodiment of the fifth aspect, these steps are carried out in a DPL process.

[0065] The decor paper, the substrate, said paper layers may be divided during the process of the invention in order to obtain their final dimensions. The panels obtained by the DPL pressing process or a similar process are preferably sawn or divided in other ways. Other processing of the obtained panels is of course not excluded.

[0066] In order to better illustrate the characteristics of the present invention, by way of example and not of limiting character, embodiments will now be described with reference to the accompanying drawings, in which: [Brief description of the drawings] [Figure 1] 1 shows diagrammatically an embodiment of a paper layer provided with an inkjet receptive coating according to a preferred embodiment of the method of the first aspect of the present invention; [Diagram 2] The F2 region in FIG. 1 is shown in an enlarged view. [Diagram 3] 5 illustrates various steps of a method according to a fourth aspect of the invention. [Figure 4] FIG. 4 is a perspective view of a panel obtained by the method of FIG. [Diagram 5] 5 is a cross-sectional view taken along line VV in FIG. 4. [Figure 6] 1 shows a small number of devices that may be used in the first aspect of the invention; [Figure 7] 1 shows a schematic side view of the printer operated in single-pass mode on the central cylinder. [Figure 8] A table showing an example of ranking according to DIN EN ISO2409 is shown below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] Figure 1 shows diagrammatically a printable paper 1. The printable paper 1 comprises a paper sheet 2 provided with an ink receptive coating 3. In this case, the paper sheet 2 is a base printing paper having a weight of about 70 g / m2 and an average air resistance expressed in Gurley values ​​of 10-30 seconds.

[0068] It should be noted that the dimensions representing the paper sheet 2 and the ink receptive coating 3 have been drawn to scale in the accompanying drawings in order to better illustrate the invention.

[0069] 2 shows that the ink receptive coating 3 comprises a binder 4 and a pigment 5. In a preferred embodiment, the pigment comprises silica particles. According to a first aspect of the invention, the ink receptive coating 3 further comprises an ink-reactive composition, in particular a flocculating agent and / or a dispersing agent. It is noted that various aspects of the invention are also depicted in the accompanying drawings where no flocculating agent, such as a cationic metal salt, is applied, but an ink-reactive composition, in particular an ink destabilizing agent, is applied.

[0070] The exemplary ink receptive coating 3 preferably comprises an ink adhesion promoter selected from the group consisting of urea-based accelerators, polyurethane-based accelerators, casein-based accelerators, styrene-based accelerators, polyester-based accelerators, polyvinyl-based accelerators, alkyd-based accelerators, ketone-based accelerators, melamine-based accelerators, silicone-based accelerators, cellulose-based accelerators, gum-based accelerators, alkyl ric-based accelerators, or mixtures or copolymers thereof.

[0071] The ink adhesion promoter is present on the printable paper 1 in an amount of 4 g / m2 on a dry basis.

[0072] FIG. 3 shows that according to a preferred embodiment of the first aspect of the invention, an ink-receptive coating 3 is obtained by applying a liquid substance 6 to a paper sheet 2. A device 7 is applied, which includes a reversing metering roller 8. This device 7 first applies an excess of the liquid substance 6, which is then squeezed off by the roller 8 to the desired weight and to obtain a smooth coated surface. Preferably, the semi-finished product 9 obtained is then dried, for example by a hot air oven, to a residual moisture level preferably below 10%, or even 7%. This is not shown here, but is carried out in a very similar manner. As an alternative to the device 7, it is obvious to use other application techniques, such as application by one or more reversing gravure rollers, preferably provided in the paper machine, or application by a size press, application by a film press. By paper machine here is meant the line which produces paper. For example, the device 7 may be a film press which applies the ink-receptive coating 3 between two drying steps in the paper machine.

[0073] Fig. 4 illustrates one step in a method for producing a decor paper according to a first alternative of the fourth independent aspect of the invention. The printable paper layer 1 with the ink-receptive coating 3 obtained according to the first aspect of the invention may be printed by an inkjet printer 10, which comprises, for example, one central cylinder 11, around which the printable paper layer 1 is partially wrapped, and various printing units 12, each including one or more print heads, which are arranged radially around the central cylinder 11 and above the area of ​​the paper layer 1 to be printed. For example, the central cylinder 11 of the inkjet printer 10 has a radius of 800-950 mm, for example about 880 mm, and a web angle of 270° or more, for example 300°, preferably 320°. The printer 10 relates, for example, to a printer of the single pass type, and the supply of the printed pattern comprises a relative movement of the printable paper 1 to the inkjet printer 10, in particular to the printing units 12, during printing in the printing direction D. In this case, the printing unit 12 and multiple print heads are stationary and the paper layer 1 is moving while ink is ejected onto the paper layer 1, more specifically onto an ink-receptive coating 3 that includes an ink adhesion promoter that is applied to the paper layer 12. During a single continuous movement of the paper layer 1 relative to the printer 10, the paper layer 1 is printed. The resulting decor paper 13 includes a pattern or ink layer 14 printed onto the top surface of the ink-receptive coating 3.

[0074] Figures 5 and 6 show a printed decor paper 15 obtained by a second alternative of the method of the fourth aspect of the invention. The decor paper 15 comprises a paper sheet 2 and an ink-receptive coating 3. In this case, the ink-receptive coating preferably does not contain an ink adhesion promoter, although this does not exclude that the ink-receptive coating contains an ink adhesion promoter. The decor paper 15 further comprises a printed pattern or ink layer 14 on the top surface of the ink-receptive coating 3.

[0075] A decor paper 15 is provided on the top surface of the printed pattern or ink layer 14 and includes an ink adhesion promoter 16, preferably transparent. The ink adhesion promoter coating 16 preferably includes an ink adhesion promoter selected from the group consisting of urea-based accelerators, polyurethane-based accelerators, casein-based accelerators, styrene-based accelerators, polyester-based accelerators, polyvinyl-based accelerators, alkyd-based accelerators, ketone-based accelerators, melamine-based accelerators, silicone-based accelerators, cellulose-based accelerators, gum-based accelerators, alkyl lic-based accelerators, or mixtures or copolymers thereof. The ink adhesion promoter coating 16 also includes a binder, preferably polyvinyl alcohol.

[0076] The various steps of a second alternative method for obtaining the printed decor paper 15 of Figs. 5 and 6 are illustrated in Fig. 7. This exemplary method includes at least a step S1 of feeding the printable paper 1 with the inkjet receptive layer 3 from a first roller 17 to an inkjet printer 10. The inkjet printer 10 performs a step S2 of printing a printed pattern on the top surface of the printable paper 1, preferably in the same manner as described in relation to Fig. 4. The method further includes a step S3 of applying an ink adhesion promoter coating 16 on the top surface of the printed pattern 14. In the illustrated embodiment, the ink adhesion promoter coating 16 is provided in the form of a liquid substance and is provided using the same device 7 as described in relation to Fig. 3. The method illustrated in Fig. 7 includes a step S4 of drying the decor paper. In the embodiment, a hot air oven 18 is used, but other alternative heating devices, such as microwave or infrared drying devices, can also be used. The resulting decor paper 15 is then wound onto a second roll 19 and is ready to be used in the method of manufacturing panels, as illustrated in FIG.

[0077] Figure 8 illustrates various steps of a method for manufacturing a laminate panel 20 of the type shown in Figure 9. This method forms an illustration of a fifth independent aspect of the invention, as described in the introduction to this patent application.

[0078] The resulting decorative panel 20 comprises at least a substrate 21 and a top layer 22. The top layer 22 comprises a decor paper 15 produced according to the fourth aspect of the invention and is provided with a printed pattern 13, in this case representing a wood pattern. The decor paper 15 comprises an ink adhesion promoter in the ink receptive coating 3 or alternatively in the ink adhesion promoter coating 16.

[0079] The method of the illustrated embodiment includes at least a step S1' of providing the decor paper 15 with a thermosetting resin 23. Here, the decor paper 15 is removed from a roll 24 and transported to a first dipping station 25 where the decor paper 15 is dipped into a bath 26 of resin 23, more specifically into a bath 26 of a mixture of water and resin 23. The decor paper 15 is then rested and, in this case, transported upwards. This resting allows the resin 23 to penetrate into the paper core. The decor paper 15 then enters a second dipping station 27 and is again dipped into a bath 26 of resin 23, more specifically into a bath 26 of a mixture of water and resin 23. A pair of squeeze rollers 28 allows the addition of a specific amount of resin 23 to be applied to the decor paper 15. In this embodiment, various doctor blades 29 can remove portions of the resin 23 at the surface of the decor paper 15 that has been provided with the resin.

[0080] In a second step S2', the resin-provided decor paper is dried so that the residual humidity level is below 10%. Although a hot air oven 18 is used in the embodiment, other heating devices such as microwave or infrared dryers can be used instead.

[0081] FIG. 8 illustrates that the continuous decor paper 15 is cut into sheets 30 and stacked in step S3'.

[0082] FIG. 8 illustrates that in the following step S4', the obtained sheets 30 or decor paper 15 are stacked in a stack to be compressed in a short daylight press 31 between upper and lower compression plates 32-33. This stack comprises, from bottom to top, a counter layer 34, a plate-like substrate 21, said decor paper 15 and a protective layer 35, where both the counter layer 34 and the protective layer 35 comprise a paper layer 2 and a resin 23. The stack is then compressed and this compression process results in mutual adhesion between the constituent layers 15-21-34-35 in the stack, including the substrate 21, and likewise the resin 23 used is solidified or cured. Here, in particular, a polycondensation reaction of melamine-formaldehyde-resin 23 takes place, obtaining water as a by-product.

[0083] The upper compression plate 32 is a structured compression plate which provides relief to the melamine surface of the panel 20 during the compression process of step S4', and the structured surface 36 of the upper compression plate 32 is in contact with the melamine of the protective layer 35.

[0084] Figure 9 shows the shape of a rectangular laminate floor panel with an HDF or MDF substrate 11, in which the resulting decorative or laminate panel 20 is rectangular in shape and has a pair of long sides 37 and a pair of short sides 38. In this case, the panel 20 is provided with a joint means 39 on its long side 37, which allows locking each long side 37 together with the side of the similar panel in a direction R1 perpendicular to the combined panel and in a direction R2 perpendicular to the joined side and in the plane of the combined panel. As shown in Figure 10, this joint means or joint part basically has the shape of a tongue 40 and groove 41, and additional cooperating locking means 42 are provided which allow locking in the R2 direction.

[0085] The present invention is further disclosed by the paragraph listing defined by the following numbered clauses:

[0086] 1.- A method for producing a printable paper by analog printing, in particular gravure printing, for use as decor paper in inkjet printers and / or laminate panels, said method comprising at least the following steps: (1) providing a paper layer; (2) applying an ink receptive coating to at least one surface of the paper layer; Here, the method includes the step of providing an ink adhesion promoter to the paper layer.

[0087] 2.- The method of item 1, wherein the ink adhesion promoter is provided in an ink-receiving layer.

[0088] 3.- The method of item 1 or 2, wherein the ink adhesion promoter comprises a urea-based accelerator, a polyurethane-based accelerator, a casein-based accelerator, a styrene-based accelerator, a polyester-based accelerator, a polyvinyl-based accelerator, an alkyd-based accelerator, a ketone-based accelerator, a melamine-based accelerator, a silicone-based accelerator, a cellulose-based accelerator, a gum-based accelerator, an alkylric-based accelerator or mixtures or copolymers thereof.

[0089] 4.- The method of any one of the preceding items, wherein the ink adhesion promoter is provided in an amount of 0.2 g / m2 or more, more preferably in an amount of 1 g / m2 or more.

[0090] 5.- The method of any one of the preceding items, wherein the ink adhesion promoter is provided in an amount of less than or equal to 10 g / m2, more preferably in an amount of less than or equal to 5 g / m2.

[0091] 6.- The method of any one of the preceding items, wherein the ink-receiving layer comprises at least a pigment and / or a binder.

[0092] 7.- The method of item 6, wherein the pigment comprises silica.

[0093] 8.- The method according to item 6 or 7, wherein the binder comprises polyvinyl alcohol.

[0094] 9.- A printable paper comprising a paper layer and an ink-receptive coating, said paper comprising an ink adhesion promoter preferably obtained by the method of any one of the previous items.

[0095] 10.- The printable paper of item 9, wherein the ink adhesion promoter is provided in the ink-receiving layer.

[0096] 11. - The printable paper of item 9 or 10, wherein the ink adhesion promoter comprises a urea-based accelerator, a polyurethane-based accelerator, a casein-based accelerator, a styrene-based accelerator, a polyester-based accelerator, a polyvinyl-based accelerator, an alkyd-based accelerator, a ketone-based accelerator, a melamine-based accelerator, a silicone-based accelerator, a cellulose-based accelerator, a gum-based accelerator, an alkylric-based accelerator or mixtures or copolymers thereof.

[0097] 12. - Decor paper used in a laminate panel, comprising the paper layers of items 9 to 11 and printed decor.

[0098] 13. - A decor paper for use in a laminate panel, comprising a paper layer, preferably an ink-receiving layer, a printed decor, and an ink adhesion promoter applied over the printed decor.

[0099] 14. - A method for producing a decor paper for use in a laminate panel, comprising: - providing a printable paper layer; - providing a printed décor on the top surface of said printable paper layer, preferably by inkjet printing; and the printable paper layer is according to any one of items 9 to 11, or the method includes the step of providing an ink adhesion promoter coating on the top surface of the printed décor.

[0100] 15. - The method according to item 14, wherein the decor is obtained by printing an ink, the ink comprising a binder, the binder and the ink adhesion promoter being substantially the same.

[0101] 16. - The method according to item 15, wherein the binder of the ink is a urea-based binder, a polyurethane-based binder, a casein-based binder, a styrene-based binder, a polyester-based binder, a polyvinyl-based binder, an alkyd-based binder, a ketone-based binder, a melamine-based binder, a silicone-based binder, a cellulose-based binder, a gum-based binder, an alkylric-based binder or mixtures or copolymers thereof.

[0102] 17. - A method for producing a laminate panel, preferably a floor panel, a wall panel, a furniture panel or a ceiling panel, comprising a substrate and a top layer, said top layer comprising at least a decorative layer having a decor paper, - providing a decor paper according to item 12 or 13, - impregnating said decor paper with resin, preferably with a thermosetting resin; - laminating, preferably by heat and pressure, the saturated decor paper onto a top surface of a substrate, preferably onto a top surface of a base made of a wood-based material; Includes.

[0103] 18. - The composition of the ink receiving layer for printable decor paper comprises at least an ink adhesion promoter, preferably selected from the group consisting of urea based accelerators, polyurethane based accelerators, casein based accelerators, styrene based accelerators, polyester based accelerators, polyvinyl based accelerators, alkyd based accelerators, ketone based accelerators, melamine based accelerators, silicone based accelerators, cellulose based accelerators, gum based accelerators, alkylric based accelerators or mixtures or copolymers thereof.

[0104] 19. - An ink receiving layer composition according to item 18, said composition comprising at least a pigment and / or a binder.

[0105] The present invention is not limited to the above-described embodiments, but can be realized by various alternatives without departing from the scope of the present invention. [Explanation of symbols]

[0106] 1 Paper 2 Paper Sheets 3. Ink-receptive coating 4. Binder 5. Pigments 6 liquid substances 7 Equipment 8. Roller 9 Semi-finished products 10 Printers 11 Central Cylinder 12 Printing unit, paper layer 13 Decorative paper, printed patterns 14 Ink layer, printed pattern 15 Decorative Paper 16 Ink adhesion promoter coating 17 First Roller 18 Hot air furnace 19 Second Roll 20 Panel 21 Substrate 22 Top Tier 23 Resin 24 rolls 25 First Dipping Station 26 Bath 27 Second Dipping Station 28 Roller 29 Doctor Blade 30 sheets 31 Short Daylight Press 32 Compression Plate 33 Compression Plate 34 Counter Layer 35 Protective layer 36 Surface 37 Long side, long side 38 Short side 39 Joining means 40 Tongue 41 Groove 42 Locking means D Print direction S1 Step S2 Step S3 Step S4 Step S1' Step S2' Step S3' Step S4' Step

Claims

1. A method for producing paper (1) printable with an inkjet printer (10) and / or analogue printing and used as a decor paper (15) in a laminate panel (20), comprising the steps of: The method comprises: - providing a paper layer (2), - applying an ink-receiving layer (3) to at least one side of said paper layer (2); wherein the method comprises the step of providing the paper layer (2) with an ink adhesion promoter.

2. 2. A method according to claim 1, characterized in that an ink adhesion promoter is provided in the ink receiving layer (3).

3. 2. The method of claim 1, wherein the ink adhesion promoter comprises a urea-based accelerator, a polyurethane-based accelerator, a casein-based accelerator, a styrene-based accelerator, a polyester-based accelerator, a polyvinyl-based accelerator, an alkyd-based accelerator, a ketone-based accelerator, a melamine-based accelerator, a silicone-based accelerator, a cellulose-based accelerator, a gum-based accelerator, an alkylric-based accelerator, or mixtures or copolymers thereof.

4. 4. The method according to claim 1, wherein the ink adhesion promoter is present in an amount of 0.2 g / m ２ The method according to claim 1, wherein the compound is provided in an amount of 0.1 or more.

5. 2. A method according to claim 1, characterized in that the ink receiving layer (3) comprises at least a pigment (5) and / or a binder (4).

6. 6. The method according to claim 5, characterized in that the pigment comprises silica (5).

7. A method according to claim 5 or 6, characterized in that the binder (4) comprises poly-vinyl alcohol.

8. A printable paper (1) comprising a paper layer (2) and / or an ink receiving layer (3), characterized in that the paper comprises an ink adhesion promoter.

9. A printable paper (1) according to claim 8, characterized in that the ink adhesion promoter is provided in an ink receiving layer (3).

10. 9. A printable paper (1) according to claim 8, characterized in that the ink adhesion promoter comprises a urea-based accelerator, a polyurethane-based accelerator, a casein-based accelerator, a styrene-based accelerator, a polyester-based accelerator, a polyvinyl-based accelerator, an alkyd-based accelerator, a ketone-based accelerator, a melamine-based accelerator, a silicone-based accelerator, a cellulose-based accelerator, a gum-based accelerator, an alkylric-based accelerator or mixtures or copolymers thereof.

11. A decor paper (15) for use in a laminate panel (20) comprising the printable paper (1) of claim 8 and a printed decor (14).

12. A decor paper (15) used in a laminate panel (20) comprising a paper layer (2), a printed decor (3), and an ink adhesion promoter applied over the printed decor.

13. - providing a printable paper layer (1), - providing a printed decor (14) on the top surface of the printable paper layer (1); A method for producing a decor paper (15) for use in a laminate panel, comprising:

13. The method according to claim 12, further comprising the step (S3) of providing an ink adhesion promoter coating (16) on a top surface of the printed decor (14).

14. 14. The method according to claim 13, wherein said decor (14) is obtained by printing an ink, said ink comprising a binder, and said binder and said ink adhesion promoter being substantially the same.

15. A method for manufacturing a laminate panel of the type comprising a substrate (21) and a top layer (22), comprising the steps of: The top layer includes at least a decorative layer having a decor paper (15), - providing a decor paper (15) according to claim 11 or 12, - impregnating said decor paper (15) with a resin (23); - laminating the saturated decor paper onto the top surface of the substrate; The method includes:

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