EP2977219B1 - Method for adapting decorative prints and device for carrying out said method - Google Patents

Description

The present invention relates to a method for adjusting decorative prints according to claim 1 and an apparatus for carrying out this method according to claim 11.

Decorated backing materials, e.g. Engineered wood panels are typically used as floor coverings or to cover walls and ceilings. For this purpose, the wood-based panels used as support materials were usually coated in the past with a decorative paper, the variety of differently patterned decorative papers were no limits or are.

As an alternative to the use of decorative papers on wood-based panels in the past, the direct printing of wood-based panels has developed as support materials, as a printing of paper and its subsequent lamination or direct coating accounts for the wood-based panel.

The printing techniques mainly used here are gravure printing and digital printing. The gravure printing process is a printing technique in which the elements to be imaged are in the form of depressions in a printing form which is inked before printing. The ink is primarily in the recesses and is due to contact pressure of the printing plate and adhesive forces on the object to be printed such. transfer a carrier material. In digital printing, on the other hand, the print image is transferred directly from a computer to a press such as: transferred to a laser printer or inkjet printer. This eliminates the use of a static printing form.

However, in the context of the technical development of printing technology for a wide variety of substrates, digital printing is becoming more and more important. While digital printing processes were initially used mainly in the graphics industry, such as advertising agencies, advertising manufacturers or printers, it is now becoming apparent that digital printing processes are also more common in other industries. There are many reasons for this, but two major arguments can be identified. Thus, the digital printing allows the production of a printed image with a special high quality through a higher resolution and also allows a broader range of applications with high flexibility.

Digital printing today is performed almost exclusively using the CMYK color system. The CMYK color model is a subtractive color model, where the abbreviation CMYK stands for the three color components cyan, magenta, yellow and the black component Key as color depth. With this color system, a color space (gamut) can be reproduced, which satisfies many requirements from various areas.

Furthermore, products should be cheaper on the one hand through mass production and on the other hand customers expect a greater diversity, which is reflected, for example, in an almost infinite variety of décor. A significant problem is a prediction that a manufacturer z. B. has to make of decorative surfaces for everyday objects such as laminate flooring, as to the question of which new decors are accepted by customers and which are not.

When redesigning a collection, a decorative board manufacturer must remove a minimum amount of printed decor paper or printed finish film from each decor. The minimum amount of paper is usually about one ton, which is about 15,000 m ² . This decor paper must then be impregnated, pressed onto carrier plates and further processed. If exactly this décor does not succeed on the market, residual amounts are created at all stages of the value chain that can no longer be used. The resulting economic damage is significant. In addition, the color of the decor was set for at least one ton of paper.

One way to solve this problem would be to produce all decors exclusively by digital printing. However, this then has the serious disadvantage that these decors are considerably more expensive in terms of printing costs. In addition, the higher quality level of the decors could be devalued by the higher resolution of digital printing other, not digitally printed decors and thus lead to a loss of sales of conventional printed substrates.

A further increasing trend is the ever smaller lot sizes. In principle, digital printing technology can also take this trend into account. Due to the high flexibility of digital printing, it is not only possible to print on paper or film webs, but also directly on carrier plates, such as wood fiber boards. With that you can On the way to further finishing to semi-finished or finished products, such as furniture panels, laminate floors or facade panels some value-added levels are skipped, resulting in a further flexibilization and simplification of manufacturing processes.

In particular, in the wood-based panel industry has been almost exclusively decorative surfaces on the indirect gravure on decorative papers produced and thus had increasingly struggling with lot size problems.

A way out here is digital printing. This is currently almost exclusively used, such as indirect gravure, on decorative paper or prepregs, such as e.g. reserved papers, propagated. In this case, mainly water-based inks are used, which still have a certain water solubility even after the printing and the subsequent drying. Since in the subsequent production of the decorative surfaces at least in the decor papers still impregnation with water-soluble resins must be made, followed by a compression in a short-cycle press, the high resolution is partially degraded or destroyed by the dissolution of the colors.

The direct printing on a, if necessary pre-primed, support plate, preferably a wood-based panel, by means of digital printing would therefore be a desirable solution.

In the realization of this solution but several obstacles are overcome.

The decor papers used for indirect gravure have good opacity due to their relatively high pigment loading. This should largely eliminate the inherent color of the carrier. Alternatively, a primer can be applied directly to a carrier plate. If a primer is applied directly to a support plate, preferably a wood-based panel, the primer on the support plate must not be made too thick, otherwise the later applied protective layers, preferably synthetic resins, the primer can not penetrate and thus after a compression in the Short-cycle press delaminations or bubbles may occur.

On the other hand, the primer should not be too thin. There is then the danger that the carrier is not completely covered, which has a negative effect on the overall color impression of the decor.

Another problem is that individual batches of the support materials may be subject to variations in composition, which may result in differences in the brightness and / or the color of the support plates. As a result, after the decals have been printed, visible differences, in particular color deviations, between the individual product batches can occur.

EP-A-2 452 829 discloses a method of applying a decor to a wood-based panel, wherein a second, digitally-printed decor is applied to a first decor produced by gravure printing (see the claims with paragraphs [0007], [0008] and [0017] of the document) ).

EP-A-2 636 531 also discloses a method for digital printing of wood-based panels (see Figure 1 and the claims).

The technical problem underlying the invention was therefore to offer a method for adapting decorative prints on carrier materials.

This object is achieved by a method having the features of claim 1 and an apparatus for performing this method with the features of claim 11.

Accordingly, a method for the production of decorative prints of the same quality is provided on substrates whose brightness and or color are subject to fluctuations, with a consistent quality, especially color, the decorative prints is achieved regardless of fluctuations in the brightness and / or the color of the substrates ,

Color deviations in the print motif of decors printed by means of digital printing occur in the production process, in particular after the change from one batch of the carrier material to a new batch of the carrier material. However, color deviations can also occur between individual or several carrier plates of the same batch of carrier material.

To correct color deviations between the carrier plates of different batches of the carrier material, the color values of the carrier plates of at least a first batch of the carrier material are first measured continuously in the method according to the invention and passed on to a computer program. When changing the charge of the carrier material, the color values of the carrier plates of at least one further batch of the carrier material are continuously measured and also passed on to the computer program. The color values of the carrier plates of the at least one first batch and the at least one further batch of carrier material are processed in the computer program. If color deviations occur between the carrier plates of the at least one first batch and at least one further batch of carrier material, the color values of the digital printing for the decors of at least one further batch and / or the at least one first batch of the carrier material customized. This ensures that no color deviations occur between the printed decors of the at least one first batch of carrier material and each further batch of carrier material.

The carrier material used in the present process can be selected from a group comprising paper, glass, metal, films, wood materials, in particular MDF or HDF boards, veneers, paint layers, plastic plates and inorganic support plates, such as. Cement, cement fiber and gypsum fiber boards.

Preferably wood-based panels, in particular wood fiber panels are used.

1. a) Messen der Farbwerte der Holzwerkstoffplatten mindestens einer ersten Charge und Weitergabe der Farbwerte an ein Computerprogramm;
2. b) Messen der Farbwerte der Holzwerkstoffplatten mindestens einer weiteren Charge und Weitergabe der Farbwerte an das Computerprogramm;
3. c) Verarbeitung der Farbwerte der Holzwerkstoffplatten der mindestens einen ersten Charge und der mindestens einen weiteren Charge in dem Computerprogramm und Anpassung der Farbwerte des Digitaldrucks für die mindestens eine erste Charge und/oder mindestens eine weiteren Charge;
4. d) Bedrucken mindestens einer Seite der Holzwerkstoffplatten mittels Digitaldrucktechnik unter Ausbildung einer Dekorschicht derart, dass keine Farbabweichungen zwischen den gedruckten Dekoren der Holzwerkstoffplatten der mindestens einen ersten Charge und jeder weiteren Charge auftreten.

According to the invention, therefore, a method is provided for printing wood-based panels, in particular wood-based panels, by means of a digital printing method,
comprising the steps

1. a) measuring the color values of the wood-based panels of at least a first batch and passing the color values to a computer program;
2. b) measuring the color values of the wood-based panels of at least one further batch and passing on the color values to the computer program;
3. c) processing the color values of the wood-based panels of the at least one first batch and the at least one further batch in the computer program and adjusting the color values of the digital printing for the at least one first batch and / or at least one further batch;
4. d) printing at least one side of the wood-based panels by means of digital printing technology to form a decorative layer such that no color deviations between the printed decors of the wood-based panels of at least a first batch and each additional batch occur.

The same procedure can be used if color deviations occur between individual plates within a batch of carrier material, preferably wood-based panels.

1. a) Messen der Farbwerte mindestens einer ersten Holzwerkstoffplatte und Weitergabe der Farbwerte an ein Computerprogramm;
2. b) Messen der Farbwerte mindestens einer weiteren Holzwerkstoffplatte und Weitergabe der Farbwerte an das Computerprogramm;
3. c) Verarbeitung der Farbwerte der mindestens einen ersten Holzwerkstoffplatte und der mindestens einen weiteren Holzwerkstoffplatte in dem Computerprogramm und Anpassung der Farbwerte des Digitaldrucks für die mindestens eine erste Holzwerkstoffplatte und/oder mindestens eine weitere Holzwerkstoffplatte;
4. d) Bedrucken mindestens einer Seite der Holzwerkstoffplatten mittels Digitaldrucktechnik unter Ausbildung einer Dekorschicht derart, dass nur tolerierbare Farbabweichungen zwischen den gedruckten Dekoren der mindestens einen ersten Holzwerkstoffplatte und jeder weiteren Holzwerkstoffplatte auftreten.

The method according to the invention then comprises the steps:

1. a) measuring the color values of at least one first wood-based panel and passing the color values to a computer program;
2. b) measuring the color values of at least one further wood-based panel and passing the color values to the computer program;
3. c) processing the color values of the at least one first wood-based panel and the at least one further wood-based panel in the computer program and adjusting the color values of the digital print for the at least one first wood-based panel and / or at least one further wood-based panel;
4. d) printing on at least one side of the wood-based panels by means of digital printing technology to form a decorative layer such that only tolerable color deviations between the printed decors of at least one first wood-based panel and any other wood-based panel occur.

The color values are preferably measured continuously in the method according to the invention.

In one embodiment of the present method, at least one primer layer comprising at least one resin and / or at least one varnish which is subsequently dried and / or cured is applied to the side of the wood-based panel to be printed prior to printing.

Preferably, the side to be printed of the wood-based panel is sanded before applying the primer.

For priming, an aqueous resin solution and / or a radiation-curable filler may be applied to the side of the substrate to be printed. As a primer, e.g. aqueous resin solutions such as melamine-formaldehyde resin, urea-formaldehyde resin or melamine-urea-formaldehyde resin can be used. It is also possible to pre-coat or prime the support material with 1K / 2K acrylate, UV and / or ESH filler and then cure this primer layer accordingly.

Preferably, an aqueous resin solution comprising an aqueous resin solution, in particular an aqueous solution of a melamine-formaldehyde resin, urea-formaldehyde resin or melamine-urea-formaldehyde resin is used for the precoating or priming of the wood-based panel.

The amount of liquid resin solution applied to the primer may be between 10 and 80 g / m ² , preferably 20 and 50 g / m ² . The solids content of the aqueous resin solution is between 30 and 80%, preferably 40 and 60%, particularly preferably 55%. The liquid resin may additionally comprise suitable wetting agents, hardeners, release agents and defoamers.

After applying the aqueous resin solution to the wood-based panel for precoating the same, the liquid resin is brought to a humidity of 10%, preferably 6% e.g. dried in a convection oven or near-infrared oven.

In another embodiment of the present method, the wood-based panel can be precoated or primed with 1K / 2K acrylate, and / or ESH filler. A UV filler preferably consists essentially of UV-curable coating components, pigments, reactive diluents and radical formers as chain starters.

The application rate of the filler may in this case be 50 to 150 g / m ² , preferably 50 to 100 g / m ² . The quantities are based on a 100% filler.

It is also possible that the putty used for the primer is pigmented, whereby the printing result can be varied or improved.

Particularly preferred according to the invention is the precoating of the wood-based panel with a transparent primer.

In a further embodiment of the present method, at least one layer of a pigmented primer, which is preferably water-based, is applied to the side of the wood-based panel to be printed prior to printing the at least one side of the wood-based panel. The pigmented primer can be applied either directly on the untreated surface of the material plate or on the previous, preferably transparent primer.

The water-based pigmented primer can also be applied in more than one layer (eg 3 to 10 layers, preferably 5 to 8 layers, more preferably 7 layers), wherein after each layer application, the pigmented primer, for example: dried in a convection dryer or a near-infrared dryer becomes. The Water-based pigmented primer preferably contains at least one pigment of a light color, more preferably at least one white pigment.

White pigments are achromatic inorganic pigments with a high refractive index (greater than 1.8), which are mainly used to produce optical whiteness in paints or as a filler in z. As plastics are used. White pigments according to the invention may be selected from the group comprising titanium dioxide, lithopone, barium sulfate, zinc oxide, zinc sulfide and calcium sulfate. Lithopone is a white pigment that contains barium sulfate and zinc sulfide.

The process of the invention is particularly environmentally friendly, since no compounds containing toxic heavy metals are used as white pigments.

According to the invention, titanium dioxide is preferably used as a white pigment in the water-based pigmented primer, since titanium dioxide has the highest refractive index and thus the highest hiding power among the known white pigments.

For the determination of color differences of the color difference (Δ E) is used. The color difference (Δ E) indicates the difference between two colors. Mathematically, the color difference is the shortest connection between two color loci present in the CIE color space (DIN 5033-2, 1992). A color location can be assigned to any color using the standard color chart and a color measurement system. If the color difference is known, a clear statement can be made as to how strongly two colors differ from each other. The color difference can be determined by conventional physical methods. But it depends mainly on the perceivability of color differences by humans.

Preferably, the method according to the invention is carried out in such a way that only tolerable color deviations occur between the printed decors of the wood-based panels of the at least one first batch and each further batch or the at least one first wood-based panel and each further wooden panel.

According to the present invention are then tolerable color deviations between the printed designs of the wood-based panels of at least a first batch, and each additional charge or at least a first wood material plate and each other engineered wood board, when the color difference (Δ E) of people do not consider is perceived differently or is very low. Preferably, the color deviations are in an area that is not perceived by humans. In a further preferred embodiment, the method according to the invention is thus carried out so that no color deviations occur between the printed decors of the wood-based panels of the at least one first batch and each further batch or the at least one first wood-based panel and each further wood-based panel.

Not tolerable according to the invention are color deviations that are perceived by humans at least as significant or strong.

Color deviations can be determined, for example, with the equality method. In this method, by a technical device or visually with the eye, the examination pattern is compared with a series of known standard patterns until the equality is determined securely. It is also possible to offer the selected primary colors proportionately. Technical implementations are the color gyro or the Maxwellian view. In the first case, the temporal resolution of the measuring device or of the eye is undershot by a rapid change, in the second case, a spatial distribution of the primary colors is brought to an apparently common surface by a defocusing and thus perceived by the eye as a uniform color impression. Usually, this method uses the equality judgment of the normal-sighted eye.

1. a) Auftragen einer Grundierung auf Holzwerkstoffplatten von mindestens einer ersten Charge und mindestens einer weiteren Charge,
2. b) Auftragen einer pigmentierten Grundierung auf die Holzwerkstoffplatten der mindestens einen ersten Charge und der mindestens einen weiteren Charge,
3. c) Messen der Farbwerte der Holzwerkstoffplatten der mindestens einen ersten Charge und Weitergabe der Farbwerte an ein Computerprogramm;
4. d) Messen der Farbwerte der Holzwerkstoffplatten der mindestens einen weiteren Charge und Weitergabe der Farbwerte an das Computerprogramm;
5. e) Verarbeitung der Farbwerte der Holzwerkstoffplatten der mindestens einen ersten Charge und der mindestens einen weiteren Charge in dem Computerprogramm und Anpassung der Farbwerte des Digitaldrucks für die mindestens eine erste Charge und/oder mindestens eine weiteren Charge;
6. f) Bedrucken mindestens einer Seite der Holzwerkstoffplatten mittels Digitaldrucktechnik unter Ausbildung einer Dekorschicht derart, dass keine Farbabweichungen zwischen den gedruckten Dekoren der Holzwerkstoffplatten der mindestens einen ersten Charge und jeder weiteren Charge auftreten;

In a preferred embodiment, the method according to the invention comprises the steps:

1. a) applying a primer to wood-based panels of at least a first batch and at least one further batch,
2. b) applying a pigmented primer to the wood-based panels of the at least one first batch and the at least one further batch,
3. c) measuring the color values of the wood-based panels of the at least one first batch and passing the color values to a computer program;
4. d) measuring the color values of the wood-based panels of the at least one further batch and forwarding the color values to the computer program;
5. e) processing the color values of the wood-based panels of the at least one first batch and the at least one further batch in the computer program and adjusting the color values of the digital printing for the at least one first batch and / or at least one further batch;
6. f) printing at least one side of the wood-based panels by means of digital printing technology to form a decorative layer such that no color deviations between the printed decors of the wood-based panels of at least a first batch and each additional batch occur;

According to one embodiment, the method according to the invention may comprise the continuous measurement of the brightness of the support plate coated with the, preferably water-based, pigmented primer.

Depending on the brightness determined, the application quantity of the water-based pigmented primer, which preferably contains titanium dioxide as white pigment, can then be adjusted in order to maintain the most uniform possible brightness level of the carrier material. The adjustment of the order quantity can either be done automatically by a control unit, such as a control computer or a process computer, or manually.

The color and brightness measurement can be performed with conventional colorimeters. Preferably, the color and brightness measurement is carried out with an online colorimeter.

However, between the individual batches of the carrier materials, not only the brightness of the carrier plates usually changes, but often also their color. Due to the only relatively imprecise adjustable rollers in the application units for the primers of the support plates, the adjustment of the exact order quantity of water-based pigmented ink is limited and leads to a commute to the desired brightness value. In addition, the influence of the color of the carrier plates by the white pigments containing primer is only very limited possible.

This problem is solved by a continuous color measurement on the pre-primed light, preferably white, support plates for determining the color values and the subsequent processing and use of the color data obtained to adjust the color values of the decor print. In the color measurement, the L *, a * and b * values are preferably determined in the so-called L * a * b * color space.

The L * a * b * color space is a color space covering the range of perceptible colors. The L * a * b * color space is described by a three-dimensional coordinate system. The L * axis describes the brightness (luminance) of the color with values of 0 (Black) to 100 (white). The a * axis describes the green or red portion of a color, with negative values for green and positive values for red. The b * axis describes the blue or yellow part of a color, with negative values for blue and positive values for yellow. The scales of the a * axis and the b * axis include a number range of -150 to +100 and -100 to +150.

In the method according to the invention, the value for the brightness L * should be at least> 50,> 60 or> 70. Preferably, L *> 80. In a particularly preferred embodiment, L *> 85 or> 90.

In the method according to the invention, the values for a * and / or b * are in a range between -100 and +100, -80 and +80, -60 and +60, -40 and +40 or -20 and +20. Preferably, the values for a * and / or b * are in a range between -10 and +10. In a preferred embodiment, the values for a * and / or b * are in a range between -5 and +5. In a particularly preferred embodiment of the invention, the values for a * and / or b * are close to zero.

The color measurement is carried out by means of a conventional colorimeter, preferably by means of an online colorimeter. Subsequently, the profiling of the color data of the pre-primed carrier plate is carried out by processing the L *, a * and b * values determined during the continuous measurement with a computer program. As a computer program preferably a so-called RIP software is used.

RIP (raster imaging process) software is a software for calculating color values. In the method according to the invention, when the color data is adapted by means of the RIP software, taking into account the brightness and / or color of the primer, the measured color values are converted into the standard color system CYMK for digital printing.

Adjusting the color values for digital printing means that the proportions of the individual components of the CYMK standard color system are changed. Preferably, the proportions of the individual components of the CYMK standard color system are changed so that, taking into account the determined brightness or the determined color values of the carrier material after the decor pressure no color deviations between the printed decorations of the carrier plates of the at least one first batch and each additional batch occur.

In a further embodiment, the method according to the invention optionally comprises the quality control of the colors of the decors after digital printing. During this quality control, it is checked whether color deviations occur in the decor between the carrier plates provided with printed decors of a carrier material. This can be done for example by visual inspection.

As print motifs for digital printing, various decors such as e.g. Wood, tile, fantasy decors or Parkettimitate be used.

In digital printing, a water-based digital printing ink is preferably used for printing the at least one side of the wood-based panel. Digital printing can be accomplished using a digital printer with a water based digital ink, UV or solvent based ink. Preference is given to the use of a water-based digital printing ink. The amount of digital printing ink used may be between 5 and 15 g / m ² , preferably 6 and 8 g / m ² .

According to a further embodiment, the present method provides a protective layer on a digitally printed wood-based panel which at the same time acts as a mediator, so-called primer, between layers which are not compatible per se, such as the decorative printing or the decorative layer on the one hand and a subsequent wear protection or other finishing layers on the other hand is arranged.

The digital printing herein may be either a resin, preferably a water-compatible resin, a radiation-curable, typically non-water-compatible, varnish, e.g. selected from the group of acrylates, modified acrylates and / or epoxides; or polyurethanes which have good adhesion properties are applied directly. After hardening or setting the protective layer, intermediate storage of the printed plates is possible without risk of surface damage or contamination of the decorative layer. Thus, even at undefined time intervals between a processing step digital printing and a further processing step no problems, such as contamination of plates or abrasion and / or detachment of the decoration can be expected. This also ensures that in the event of a business interruption in further processing, the digital printer does not have to stop his work.

In one embodiment, the protective layer to be applied to the decorative layer of the wood-based panel comprises at least one water-compatible resin, preferably a formaldehyde-containing resin, particularly preferably melamine-formaldehyde resin, urea-formaldehyde resin and / or melamine-urea-formaldehyde resin. The resin can therefore be applied in liquid form or else in solid form, the use of a liquid resin being preferred.

Subsequently, the protective layer comprising the at least one water-compatible resin is predried until the resin is still flowable and crosslinkable. The drying of the water-compatible resin-containing protective layer is typically carried out in a continuous drying oven, as are known from wood-based panel manufacturing. Depending on the amount applied, the process of pre-drying may take 5 to 15 seconds, preferably 5 to 10 seconds.

When a radiation-curable varnish is used as a protective layer, the protective layer may be subsequently gelled onto the protective layer using UV radiation (e.g., at 320-400 nm), ESH radiation, and / or NIR radiation. After setting, the paint preferably has a degree of polymerization between 20-60%, preferably 30-50%.

In a further variant of the present method, the protective layer to be applied to the printed side of the wood-based panel is applied in an amount between 5 and 50 g / m ² , preferably 8 and 30 g / m ² , particularly preferably 10 and 20 g / m ² .

It is also possible to apply to the decor or decors at least one protective layer, in particular a layer comprising abrasion-resistant particles, natural fibers, synthetic fibers and / or other additives, wherein resins such as melamine-formaldehyde resin, or urea-formaldehyde resin , Acrylate resins and polyurethane resins can be used as suitable binders.

In a further embodiment of the method according to the invention several protective layers are applied to the decor or decors, which may include different additives.

• Aufbringen einer ersten Harzschicht, die abriebfeste Partikel enthält, auf die mit dem Dekor versehene Seite der Holzwerkstoffplatte,
• Trocknen der ersten Harzschicht auf eine Restfeuchte von 3 % bis 6 %; und/oder
• Aufbringen einer zweiten Harzschicht auf die mit dem Dekor versehene Seite der Holzwerkstoffplatte, die Fasern enthält,
• Trocknen der zweiten Harzschicht auf eine Restfeuchte von 3 % bis 6 %; und/oder
• Aufbringen einer mindestens dritten Harzschicht, die Glaspartikel enthält, auf die mit dem Dekor versehene Seite der Holzwerkstoffplatte,
• Trocknen der dritten Harzschicht auf eine Restfeuchte von 3% bis 6%; und
• Verpressen des Schichtaufbaus unter Druck- und Temperatureinfluss zur Ausbildung eines Laminats.

In a preferred embodiment, the method according to the invention therefore comprises the steps:

• Applying a first resin layer containing abrasion-resistant particles, on the provided with the decor side of the wood-based panel,
• Drying the first resin layer to a residual moisture of 3% to 6%; and or
• Applying a second resin layer to the decorated side of the wood-based panel containing fibers,
• Drying the second resin layer to a residual moisture of 3% to 6%; and or
• Applying an at least third resin layer containing glass particles to the decorative side of the wood-based panel,
• Drying the third resin layer to a residual moisture of 3% to 6%; and
• Pressing the layer structure under pressure and temperature influence to form a laminate.

The abrasion-resistant particles are preferably selected from the group consisting of aluminum oxides, corundum, boron carbides, silicon dioxides, silicon carbides and glass particles. As natural and / or synthetic fibers in particular fibers are selected from the group containing wood fibers, cellulose fibers, wool fibers, hemp fibers and organic or inorganic polymer fibers are used.

As additives, conductive substances, flame retardants, luminescent substances and metals may be added. In this case, the conductive substances may be selected from the group comprising carbon black, carbon fibers, metal powder and nanoparticles, in particular carbon nanotubes. It is also possible to use combinations of these substances. As flame retardants phosphates, borates, in particular ammonium polyphosphate, tris (tri-bromneopentyl) phosphate, zinc borate or boric acid complexes of polyhydric alcohols are preferably used. As luminescent substances are preferably fluorescent and / or phosphorescent substances on an inorganic or organic basis, in particular zinc sulfide and alkaline earth aluminates.

Corundum particles are preferably contained in the first resin layer to increase the abrasion resistance. This is particularly important when used as a floor panel to withstand the high loads that a floor panel is exposed to. For example, corundum is a mixture of conventional silanized corundums of different grain sizes. The corundum can easily be added to the resin before application.

As fibers in the second resin layer, cellulose fibers are preferably used. These commercially available fibers can be used, which can also be added to the applied resin layers.

The glass particles contained in the third resin layer are, for example, commercially available glass microspheres. These can also be easily introduced into the resin layer to be applied.

The third resin layer preferably contains 20% glass particles. For the second resin layer about 5% cellulose have been found to be advantageous. The first resin layer contains in particular 20% corundum particles.

In a further embodiment of the method according to the invention, one or more resin layers can also be applied to the underside of the wood-based panel. As a result, in particular, the forces acting on the top of the wood-based panel applied resin layers tensile forces are compensated. In a particularly preferred embodiment, the respectively applied on the top and bottom resin layers are applied in the same amount or applied to the underside of the wood-based panel counter-train corresponds in the layer structure and the respective layer thickness exactly applied to the top layer sequence.

The resin layers applied to the underside of the wood-based panel may be colored.

All resin layers can be added with additives such as hardeners, wetting agents and release agents.

The resin layers on the top and bottom of the wood-based panel may contain a 60% resin solution.

Drying to a residual moisture of 3% to 6% serves to prevent the crosslinking process of the applied resin layers.

In a further embodiment of the present method, the printed and possibly provided with one or more protective layer (s) carrier material is further processed or finished in a short-cycle press. Under pressure and temperature influence in a short-cycle press, the resin layers melt again. The networking process continues through this. The individual resin layers are thus crosslinked not only in themselves but also with each other. As a result, the applied melamine resin layers can be crosslinked to include the decoration and cured into a laminate. Conventional short-cycle presses operate, for example, at a pressure of 30 to 60 kg / cm ² , one Temperature at the wood material surface of about 165 ° C and a pressing time of 6 to 12 seconds.

During further processing in the short-cycle press surface structures in at least one surface, preferably at least the top of the support material such as a wood-based panel can be produced using a structured press plate, which can optionally be designed to match the decor (so-called decorsynchronous structure). Preferably, the surface structures are formed largely congruent to the decor. In this case, one speaks of embossed-in-register structures In the case of wood decors, the structures may be in the form of pore structures that follow the grain. For tile decors, the structures may be depressions in the area of joint fill lines enclosed by the decor.

1. a) Auftragen einer Grundierung auf Holzwerkstoffplatten von mindestens einer ersten Charge und mindestens einer weiteren Charge,
2. b) Auftragen einer pigmentierten Grundierung auf die Holzwerkstoffplatten der mindestens einer ersten Charge und mindestens einer weiteren Charge,
3. c) Messen der Farbwerte der Holzwerkstoffplatten mindestens einer ersten Charge und Weitergabe der Farbwerte an ein Computerprogramm;
4. d) Messen der Farbwerte der Holzwerkstoffplatten mindestens einer weiteren Charge und Weitergabe der Farbwerte an das Computerprogramm;
5. e) Verarbeitung der Farbwerte der Holzwerkstoffplatten der mindestens einen ersten Charge und/oder der mindestens einen weiteren Charge in dem Computerprogramm und Anpassung der Farbwerte des Digitaldrucks;
6. f) Bedrucken mindestens einer Seite der Holzwerkstoffplatten mittels Digitaldrucktechnik unter Ausbildung einer Dekorschicht derart, dass keine Farbabweichungen zwischen den gedruckten Dekoren der Holzwerkstoffplatten der mindestens einen ersten Charge und jeder weiteren Charge auftreten;
7. g) Auftragen mindestens einer Schutzschicht enthaltend mindestens ein Harz, mindestens einen strahlenhärtbaren Lack und/oder mindestens ein Polyurethan auf die Dekorschicht; und
8. h) Antrocknen und/oder Angelieren der auf der Dekorschicht aufgetragenen Schutzschicht;
   und optional
9. i) Qualitätskontrolle der Farben der Dekore nach dem Digitaldruck.

In a particularly preferred embodiment, the method according to the invention comprises the steps:

1. a) applying a primer to wood-based panels of at least a first batch and at least one further batch,
2. b) applying a pigmented primer to the wood-based panels of the at least one first batch and at least one further batch,
3. c) measuring the color values of the wood-based panels of at least a first batch and passing the color values to a computer program;
4. d) measuring the color values of the wood-based panels of at least one further batch and passing the color values to the computer program;
5. e) processing the color values of the wood-based panels of the at least one first batch and / or the at least one further batch in the computer program and adjusting the color values of the digital printing;
6. f) printing at least one side of the wood-based panels by means of digital printing technology to form a decorative layer such that no color deviations between the printed decors of the wood-based panels of at least a first batch and each additional batch occur;
7. g) applying at least one protective layer containing at least one resin, at least one radiation-curable lacquer and / or at least one polyurethane to the decorative layer; and
8. h) drying and / or gelling the protective layer applied to the decorative layer;
   and optional
9. i) Quality control of the colors of decors after digital printing.

• Mindestens ein Mittel zum Messen der Farbwerte des Trägermaterials,
• mindestens ein Mittel zum Anpassen der Farbdaten,
• mindestens eine Druckstraße mit mindestens einem Digitaldrucker zum Bedrucken mindestens einer Seite des Trägermaterials mittels Digitaldrucktechnik unter Ausbildung einer Dekorschicht derart, dass keine Farbabweichungen zwischen den gedruckten Dekoren des Trägermaterials der mindestens einen ersten Charge und jeder weiteren Charge auftreten.

The present method is carried out in a device for adapting decorative prints to substrates of at least a first batch and at least one further batch, the apparatus comprising the following elements:

• At least one means for measuring the color values of the carrier material,
• at least one means for adjusting the color data,
• at least one printing line with at least one digital printer for printing at least one side of the carrier material by means of digital printing technology to form a decorative layer such that no color deviations between the printed decors of the carrier material of at least a first batch and each additional batch occur.

In a further variant, the present device comprises at least one means or device for applying a primer to the carrier material.

In a preferred variant, the device according to the invention comprises at least one means or device for applying a pigmented primer, which is preferably water-based, to the carrier material.

In a further preferred embodiment, the device comprises at least one means for measuring the brightness of the carrier material coated with the pigmented primer, which is preferably water-based.

The means for applying the primer and / or the pigmented primer and measuring the brightness of the support material are preferably in front of the at least one means for measuring the color values of the support material, i. of the L * a * b * color values.

In a further variant, the present device comprises at least one means for applying at least one protective layer to the carrier material provided with the respective printing decor. This means or device for applying a Protective layer is preferably arranged after the at least one printing line.

The device preferably contains a plurality of means for applying a plurality of protective layers to the carrier material provided with the respective printing decor. In a particularly preferred embodiment, the device comprises two, three or four means for applying two, three or four protective layers to the carrier material provided with the respective printing decor.

The device of the invention may additionally comprise one or more means for applying one or more resin layers to the underside of the substrate. If the top and bottom of the substrate are to be provided with protective layers, the means for applying the protective layers can be embodied, for example, as double application devices.

In a further embodiment, the present device comprises at least one means for measuring the color values of the substrate provided with the printing decor for quality control.

In a preferred embodiment, the present device comprises at least one short-cycle press for pressing the carrier material provided with the printing decor and the protective layer arranged thereon.

The method described here has the advantage that rapid provision of color-matched products is possible which, despite color variations of the carrier material or in the primer of the carrier material, have no significant color deviations. Even the slightest color variations of the carrier material or in the primer of the carrier material can be determined and corrected directly in the process. The method described herein is a self-regulating system in that respect. The method also leads to a cost reduction in the manufacturing process by minimizing the production of defective products or products with undesirable color variations in the digital print produced decoration, the color variations of the substrate or in the primer The carrier material is already taken into account in advance of the printing and the digital printing is thus already carried out with adapted and optimized color values. The present invention further provides a wood-based panel, preferably a fiberboard, which has been produced by the method according to the invention.

The invention will be explained in more detail below with reference to an embodiment.

embodiment

• Vereinzelung der HDF-Platten von einem Lagerstapel,
• Anschliff der HDF-Platten auf der Oberseite,
• Auftragen einer transparenten Grundierung bestehend aus Melaminharz,
• Trocknung der Grundierung,
• Auftrag einer mit Titandioxid pigmentierten Grundierung mit Zwischentrocknung (bis zu 7x),
• Farbmessung mit Weitergabe der Daten an RIP-Software,
• Digitaldruck mit angepassten Farbdaten,
• Auftrag eines Transportschutzes bestehend aus Melaminharz,
• Trocknung

In production, a batch of HDF plates (batch I) is processed, which is to be provided with a digital print. The procedure is as follows:

• Singulation of HDF plates from a stock pile,
• Polished HDF plates on top,
• Applying a transparent primer consisting of melamine resin,
• Drying the primer,
• Application of a titanium dioxide pigmented primer with intermediate drying (up to 7x),
• Color measurement with transfer of the data to RIP software,
• Digital printing with adjusted color data,
• Order of a transport protection consisting of melamine resin,
• desiccation

Charge I had the following color values after priming with the titania-containing primer:

Batch I, L * a * b * values:

• Measurement 1 88.51 / -0.66 / -0.75
• Measurement 2 86.54 / -0.57 / -0.54
• Measurement 3 87.30 / -0.63 / -0.67

• Average: 87.45 / -0.62 / -0.65

These color values were used to profile the primer in the RIP software and resulted in the following color values when printing a decoration on the plate:

L * a * b * - Colors of the decoration on Charge I plates:

• Dark color: 60 / 10.5 / 11.7
• Medium color: 73.2 / 6.0 / 25.8
• Light color: 79.5 / 4.0 / 23.8

Subsequently, a new batch of HDF plates (batch II) was processed, which had the following color values after priming:

Lot II, L * a * b * values:

• Measurement 1 89.11 / -0.79 / -0.90
• Measurement 2 88.19 / -0.69 / -0.74
• Measurement 3 88.37 / -0.63 / -0.75

• Average: 88.68 / -0.70 / -0.80

After printing, a visible difference, i. E., Between the pressure on the Charge I plates and on the Charge II plates, could be discerned. a color deviation can be determined. This occurred even though the color values of the primed panels did not differ very much. To correct the color deviation, the color values of the Charge II plates were processed in the RIP software and the digital printing was carried out with the following color values:

L * a * b * - colors of decoration after adjustment on lot II:

• Dark color: 60 / 10.5 / 11.7
• Medium color: 73.5 / 6.0 / 25.8
• Light color: 79.7 / 4.0 / 23.8

When comparing the decors of batch I and the decors of batch II, no significant color deviation was observed.

The plates of charge I and charge II were then coated on the printed side with a first layer of melamine resin containing 20% corundum particles and then dried in a drying oven to a residual moisture content of 4%.

Thereafter, all the panels on the printed side were coated with a second layer of melamine resin containing 5% cellulose fibers and then dried in a drying oven to a residual moisture of 4%.

Thereafter, all panels on the printed side were coated with a third melamine resin layer containing 20% glass microspheres and dried in a drying oven also to a residual moisture content of 4%.

Finally, the three melamine resin layers were cured to a laminate in a short cycle press at a pressure of 50 kg / cm ² , a temperature at the wood material surface of about 165 ° C and a pressing time of 10 seconds.

The decals of the Charge I and Charge II plates were compared after each coating step and after compression in the short-cycle press. No significant color deviations were observed after application of the individual melamine resin layers and also after passing through the short-cycle press.

Claims (15)

1. Method for printing wood material boards, in particular wood fiber material boards, by means of a digital printing process,
   comprising the steps

   a) continuously measuring the color values of the wood material boards from at least one first batch and forwarding the color values to a computer program;

   b) continuously measuring the color values of the wood material boards from at least one further batch and forwarding the color values to the computer program;

   c) processing the color values of the wood material boards from the at least one first batch and the at least one further batch in the computer program and continuously adapting the color values of the digital print for the at least one first batch and/or at least one further batch;

   d) printing at least one side of the wood material boards by means of digital printing technology, forming a decorative layer in such a way that no color deviations occur between the printed decorations of the wood material boards from the at least one first batch and each further batch.
2. Method according to Claim 1, characterized in that the method is used within a batch of wood material boards,
   comprising the steps:

   a) continuously measuring the color values of at least one first wood material board and forwarding the color values to a computer program;

   b) continuously measuring the color values of at least one further wood material board and forwarding the color values to the computer program;

   c) processing the color values of the at least one first wood material board and the at least one further wood material board in the computer program and continuously adapting the color values of the digital print for the at least one first wood material board and/or at least one further wood material board;

   d) printing at least one side of the wood material boards by means of digital printing technology, forming a decorative layer in such a way that only tolerable color deviations occur between the printed decorations of the at least one first wood material board and each further wood material board.
3. Method according to Claim 1 or 2, characterized in that, before the printing, at least one primer layer comprising at least one resin and/or at least one coating, which is subsequently dried and/or cured, is applied to the side of the wood material board that is to be printed.
4. Method according to Claim 3, characterized in that, for the priming, an aqueous resin solution and/or a radiation-curable filler compound is applied to the side of the wood material board that is to be printed.
5. Method according to one of the preceding claims, characterized in that, before the printing of the at least one side of the wood material board, at least one layer of a pigmented primer is applied to the side of the wood material board that is to be printed.
6. Method according to Claim 5, characterized in that the application quantity of the pigmented primer, which preferably contains at least one white pigment, is adapted in order to obtain the most uniform possible brightness level of the carrier material.
7. Method according to one of the preceding claims, characterized in that a water-based, UV-based or solvent-based digital printing ink is used to print the at least one side of the wood material board.
8. Method according to one of the preceding claims, characterized in that, after the printing, at least one protective layer which comprises at least one water-compatible resin, preferably a formaldehyde-containing resin, in particular preferably melamine formaldehyde resin, urea formaldehyde resin and/or melamine urea formaldehyde resin, is applied to the decorative layer of the wood material board.
9. Method according to one of the preceding claims, characterized in that the at least one protective layer to be applied to the decorative layer of the wood material board comprises at least one radiation-curable coating selected from the group comprising acrylates, modified acrylates and/or epoxides, or comprises at least one polyurethane selected from the group containing aliphatic urethanes or a mixture of at least one radiation-curable coating and at least one polyurethane.
10. Method according to one of Claims 1 to 8, characterized in that following the printing, a plurality of protective layers of a water-compatible resin are applied to the decorative layer of the wood material board, further comprising the steps:

    - applying a first resin layer, which contains abrasion-resistant particles,

    - drying the first resin layer to a residual moisture content of 3% to 6%; and/or

    - applying a second resin layer, which contains fibers,

    - drying the second resin layer to a residual moisture content of 3% to 6%; and/or

    - applying an at least third resin layer, which contains glass particles,

    - drying the third resin layer to a residual moisture content of 3% to 6%; and

    - pressing the layer structure under the influence of pressure and temperature in a short cycle press in order to form a laminate,

    wherein the pressing of the layer structure in the short-cycle press is optionally carried out with the simultaneous formation of a structure which is preferably matched to the decoration of the wood material board, at least on the upper side of the laminate.
11. Apparatus for producing decorative prints of identical quality on carrier materials from at least one first batch and/or at least one further batch, wherein the apparatus comprises the following elements:

    - at least one means for continuously measuring the color values of the carrier material,

    - at least one means for adapting the color data,

    - at least one printing line having at least one digital printer for printing at least one side of the carrier material by means of digital printing technology, forming a decorative layer in such a way that no color deviations occur between the printed decorations of the carrier material from the at least one first batch and/or each further batch.
12. Apparatus according to Claim 11, characterized by at least one means for applying a primer to the carrier material.
13. Apparatus according to Claim 11 or 12, characterized by at least one means for applying a pigmented primer.
14. Apparatus according to one of Claims 11 to 13, characterized by at least one means for continuously measuring the brightness of the carrier material after the application of a pigmented primer.
15. Apparatus according to one of Claims 11 to 14, characterized by at least one means for applying a protective layer to the carrier material provided with the respective printed decoration and by at least one short-cycle press for pressing the carrier material provided with the decoration and the protective layer arranged thereon.