EP1645339B1 - Process and apparatus for making a structured surface and manufactured object with stuctured surface - Google Patents

Description

The invention relates to a method and a device for producing a structured surface on a plate-shaped workpiece made of wood material for use as a floor covering or furniture part and a plate-shaped workpiece made of wood material for use as a floor covering or furniture part with a structured surface.

The invention finds application in plate-shaped workpieces made of wood-based materials, in particular made of chipboard, medium density fiberboard (MDF), high density fibreboard (HDF), hardboard and Oriented Strand Board plates (OSB boards).

The thickness of the plate-shaped workpiece made of wood material is not a limiting feature. On the one hand, the plate-shaped workpiece may be formed as a thin, a few millimeters thick MDF board. On the other hand, the plate-shaped workpiece made of wood material can be several centimeters thick. The condition is in each case only that a coating can be applied and the plate-shaped workpiece is manageable.

A structured lacquer surface is thus used for plate-shaped workpieces made of wood-based material, which are used in the area of floors or furniture parts. For this purpose, the surface to be painted is initially primed in a cost effective manner after appropriate pretreatment, then printed with a wood decor and finally provided with a transparent sealing layer. The angry Depending on the requirements, layers can be composed of several layers, for example to realize a multi-color printing or a particularly strong sealing layer. Preferably, the sealing layer consists of a curable lacquer, in this case is referred to below by a sealing lacquer.

Between the processing steps for applying the various layers, the plate-shaped workpiece made of wood-based material usually passes through so-called drying tunnels, in which an at least partial crosslinking of the layers is brought about by the action of heat and / or radiation energy. The curing and possibly drying is carried out in the usual way by means of UV radiation or by electron radiation. In addition, heat radiation techniques are also known.

To give the surfaces thus produced a more authentic appearance, the sealant layer is patterned. These structures are matched to the wood decor.

For this purpose, two methods are known in the prior art:

The process referred to as "chemical pore" uses printing inks or release agents which, due to their wetting properties, cause sealing layers applied to them to tend to flow out, forming a less thick or no sealing layer and thus forming a coating in the cured state of the coating Structure yields. The release agent may even displace the subsequently applied Sealer effect, which bursts on subsequent hardening, so that the desired pore structure forms as cracks in the surface.

A "mechanical pore" is obtained by only partially crosslinking after application of the sealing layer and then pressing in the desired structure before the final curing of the layer with the aid of an embossing roller or a structured press belt.

With both of these methods, however, only unsatisfactory structures in coated surfaces can be achieved optically and haptically.

• ein Trägermaterial mit einem aufgedruckten Holzdekor, welches eine Druckschicht umfasst, deren Farbe und Kontur derjenigen von Tracheen ähnelt;
• eine erste aufgedruckte transparente oder halbtransparente, mattierende Schicht, welche zumindest das Tracheenmuster abdeckt; und
• eine zweite aufgedruckte Schicht, die transparent oder halbtransparent, jedoch glänzend ausgebildet ist und die erste Schicht mit Ausnahme der Tracheenbereiche abdeckt, so dass oberhalb der abgebildeten Tracheen jeweils eine Vertiefung in der Oberfläche des Dekormaterials ausgebildet ist.

The US 5,178,928 discloses decorative materials intended as surface materials for furniture, household items, wall materials and the like, which have three-dimensional wood grain patterns whose appearance closely resembles the wood grain of natural trees. These decor materials include:

• a substrate having a printed wood decor comprising a print layer whose color and contour resembles that of tracheae;
• a first printed transparent or semitransparent matting layer covering at least the tracheal pattern; and
• a second printed layer which is transparent or semitransparent but shiny and covers the first layer with the exception of the tracheal areas, so that in each case one depression is formed in the surface of the decorative material above the depicted trachea.

The Tracheenabschnitte are so deepened, which corresponds to the appearance of real wood flooring, because in real wood planks, the recesses of the grain are formed by the trachea defined by the tubes (ie, cut tubes in the form of pores and grooves). The decorative material thus has a positive surface structure as a result. In all in the US 5,178,928 In the embodiments shown, the carrier material is made of tissue paper.

The present invention is based on the technical problem of providing a method with which an improved structure in a coated surface of a plate-shaped workpiece made of wood material for use as a floor covering or furniture part can be achieved in an economical manner. Likewise, the technical problem underlying providing a plate-shaped workpiece made of wood material for use as a floor covering or furniture part with a corresponding surface structure.

The above-indicated technical problem is first solved by a method having the features of claim 1.

According to the invention, it has been shown that the structure need not be introduced into an existing layer, in particular an at least partially cured layer, but rather that the surface structure can be produced by a specifically varying application of a second coating. Due to the varying application rate of the second coating, a surface structure is created which haptically and / or visually gives the viewer an impression that corresponds to a surface texture to be imitated.

For this purpose, the first coating and the second coating are at least partially optically transparent.

Spatially varying application quantity generally means that the application quantity of the second coating is not uniformly distributed over the surface to be coated, but that zones or areas with a higher order quantity and zones or areas with less or no application quantity are provided. Since the application of the method is not limited to two-dimensional surfaces, it is generally understood to be spatial, i. spoken three-dimensional distribution.

Not necessary, but preferably it is further preferred that the first coating is a full-surface coating, which thus also has, in particular, sealing properties for the surface of the carrier material of the workpiece arranged underneath.

In the following, the description of the embodiments of the invention will be referred to in each case by a first coating and a second coating. It is emphasized that the first coating and also the second coating can themselves consist of at least two separately applied layers or partial layers. In particular, a second coating may consist of two or more partial layers whose structurings overlap and / or supplement one another.

As a typical application of the method, for example, a wooden surface is arranged by a correspondingly colored decoration one below the first and second coating Printed layer and mimicked or imitated by an adapted to the wood decor structuring of the second coating.

For this purpose, the varying distribution of the application quantity of the second coating preferably has a linear structure, which is particularly typical of the surface structure of a wooden surface.

There are two ways to design the surface structure. On the one hand, the surface structure of the second coating can be produced according to the invention as a negative surface structure. In this case, the surface structures which are actually to be reproduced as a depression, for example pores, are formed as elevations. This structure, whose sublimity is, for example, below 1 mm, in particular below 0.5 mm, can be distinguished from a human hand and / or optically not from a structure with depressions. A negative surface structure is generated in particular by a line structure.

An advantage of the negative, ie raised pore lies in the better hygienic properties of the surfaces compared to a recessed pore-containing surface. Because of the raised structures much worse impurities can accumulate, as it is the case with depressions. In particular, because of the small size of the pores recessed pore structures, as they are known in laminate flooring panels, very poor or not cleaned. Therefore, plates with negative, raised pores are very suitable for use in rooms with special hygiene requirements.

Preferably, the thickness of the structures of the second coating is below 0.1 mm. Depending on the application quantity, thicknesses in the range of less than 0.01 mm or even 0.005 mm are possible. Even these small thicknesses are recognized as a textured surface. The smaller the structure thickness can be, the lower the order quantity can be set. Not least for cost reasons, the smallest possible thickness is usually advantageous.

On the other hand, the surface structure can be configured positively, wherein raised surface parts actually represent surface elevations to be imitated. In this case, which is not claimed here, the surface structure is produced with a flat surface structure which leaves open linear interstices, which then appear as pores.

It is also advantageous if the spatially varying distribution of the application amount is designed so that in the areas in which a survey is to be formed, a maximum coating amount is applied, while in the areas where no survey is to be formed, no coating is applied. This type of order is particularly suitable for a replica of a wooden surface.

In order to avoid complete flow of the structure, the second coating is preferably at least partially cured after application. It is further preferred to minimize the time interval between application of the second coating and curing. If, however, the second coating in the form of a predominantly solid material, for example in the form of a dispersion applied, so the step of curing can be omitted and, for example, only one drying step may be required.

According to the invention, the second coating is applied as a lacquer. In this case, in particular, a lacquer otherwise used otherwise as a sealing lacquer can be used.

A preferred property of the varnish is that the varnish is easy to process and also constitutes a layer-forming material.

For this purpose, a so-called high-solid paint is furthermore preferably used. A high solid paint has a high proportion of solids or solids, the volume fraction can be between 75 and 100%. The solvent content is for example in the range of 3-25%. Partly also the designation 100% high solid lacquer is used, although before the application of the lacquer a small amount of solvent has to be contained. Because of the high proportion of solids produced after curing, so after evaporation of the solvent, a noticeable layer of these solids. Because of the low solvent content, the high solid paints are more viscous than other paints and can be cured faster. Since only a small proportion evaporates, a lower shrinkage of the applied structure can be expected during curing, which benefits the exact definition of the structuring. In addition, it is preferable to use the same varnish as in the underlying layer because it provides problem-free performance because of the same application properties Processing is possible. It is precisely these properties that make the use of high-solids paints advantageous in the construction of the second coating.

Another advantage of using high-solids paints is that little or no solvent problems are to be expected during processing, and that almost all of the applied material remains on the workpiece and not a significant portion is removed during drying. Another advantage of high-solids paints is that the viscosity is adjustable within wide limits. Likewise, it is advantageous that when curing the high-solids coatings, a high degree of crosslinking is produced, the second coating thus becomes very stable. Overall, when using high-solids paints, a second coating can be produced which forms a durable and durable textured surface of the workpiece.

In particular, the paint can be provided with nanoparticles in order to have a particularly good sealing property. The abrasion resistance of the lacquer layer, which results from the addition of the nanoparticles, is particularly beneficial for surfaces which are exposed to heavy loads. This applies in particular to floor panels.

In a further preferred manner, the first coating is applied as a sealing lacquer. The sealing coat of the first coating is cured between 65% and 95%, in particular 85%, before the second coating is applied. On the one hand, this degree of curing makes it possible for the second lacquer layer to bond well with the first sealing lacquer layer. On the other hand, a good resistance of the applied structure of the second coating is achieved so that it does not melt.

There are several ways to highlight the optical effect of the structure of the second coating. On the one hand, an adjustment of a different gloss level of the second coating can be selected in comparison with the gloss level of the first coating. It has been shown that regions with increased layer application on the finished workpiece surface achieve a higher gloss level, whereas areas with reduced layer application cause a reduced degree of gloss on the finished workpiece surface.

On the other hand, the color of the second coating may be chosen differently than the color of the first coating in order to emphasize the visual impression of the structured surface. This means that the coatings can be either transparent or partially opaque.

In particular, there is the possibility that the second coating is applied as a pigmented UV-curable lacquer to adjust the gloss level and / or the color of the second coating. For this purpose, although a UV light source is required for suitable curing, particularly good effects are achieved in this embodiment of the method.

For carrying out the method, it has proved to be advantageous that the second coating is applied by a roller having a structured, in particular embossed or stitched surface. Thus, you can Techniques are used, which have already been established in other applications. According to the viscosity of the paint used and the time between application and curing, no or only partial deliquescence of the applied paint layer will take place, which then deepens zones with a lower application rate and zones with a higher application amount raised in the finished surface.

The surface of the workpiece below the two described coatings can be coated in many ways.

• eine mindestens eine Schicht aufweisende Haftvermittlerschicht,
• eine mindestens eine Schicht aufweisende Grundierungsschicht,
• eine mindestens eine Schicht aufweisende Walzgrundschicht,
• eine mindestens eine Schicht aufweisende und das Dekor darstellende Druckschicht,
• eine mindestens eine Schicht aufweisende korundhaltige Lackschicht und
• eine mindestens eine Schicht aufweisende Schleiflackschicht.

In a further refinement of the method, therefore, one or more of the following coatings of the surface can be applied, for example under the first coating, which in particular determine the optical structure (decoration) of the surface of the workpiece:

• a bonding agent layer having at least one layer,
• a primer layer having at least one layer,
• a rolling base layer having at least one layer,
• a printing layer comprising at least one layer and representing the decor,
• a corundum lacquer layer having at least one layer and
• an at least one layer having abrasive paint layer.

As can be seen from the above description of the method, it has been found that it is possible, by a quantitatively coordinated application of a second coating, in particular a sealing medium with subsequent hardening to obtain a high-quality structuring of the coated surface.

If the different application quantities in the sealing layer are chosen in coordination with the wood decor, a structure can be achieved which corresponds to the wood decor. For example, it is thus possible to provide a surface which has a wood decor with a coordinated pore structure. The material to be represented by the decor is thereby imitated improved. One can also speak of a so-called synchronous pore. In this case, it is provided according to the invention that the first coating and the second coating are at least partially transparent so that the underlying decoration remains recognizable by the two coatings.

In a preferred manner, UV-curing lacquers are used for the lacquer coating described above. But there are also all other coatings for the application of the method according to the invention applicable, as far as with these the requirements placed on the finished workpiece surface such. Scratch resistance, abrasion resistance or adhesion can be achieved.

To improve the properties of the coating materials used, they can be provided with various additives and fillers. For example, hard particles may be provided to improve the scratch and abrasion resistance, or so-called UV absorbers, which prevent premature yellowing of the surface.

The above-indicated technical problem is inventively further solved by a plate-shaped workpiece having the features of claim 13. The plate-shaped workpiece according to the invention for use as a floor covering or furniture part comprises a plate-shaped carrier material made of wood material, a wood decor printed on the carrier material, an on the wood decor following, at least partially optically transparent first coating of lacquer and a lacquer formed, at least partially optically transparent second coating , which is applied with a spatially varying distribution of the application amount to the first coating by means of a direct printing process or an indirect printing process and forms a negative surface structure, are actually formed as wells to be imitated surface structures of the wood decor as elevations.

Further embodiments of the workpiece according to the invention are specified in the subclaims, which in each case give the same properties and advantages as have been described with reference to the method described above.

• mindestens eine eine Auftragswalze aufweisende Bearbeitungsstation (18, 20) zum Aufdrucken eines Holzdekors,
• eine eine Auftragswalze (10) aufweisende Bearbeitungsstation (6) zum Aufbringen einer auf das Holzdekor folgenden zumindest teilweise optisch transparenten ersten Beschichtung (22) aus Lack auf die Oberfläche des plattenförmigen Werkstückes (2) und
• eine Bearbeitungsstation (8), die eine eine strukturierte Mantelfläche aufweisende Auftragswalze (14) zum direkten oder indirekten Aufdrucken einer zumindest teilweise optisch transparenten zweiten Beschichtung (24) aus Lack auf die erste Beschichtung (22) aufweist und die zweite Beschichtung (24) mit einer räumlich variierenden Verteilung der Auftragsmenge auf die erste Beschichtung (22) aufbringt, wobei die strukturierte Mantelfläche der Auftragswalze (14) eine Oberflächenstruktur zum Erzeugen einer negativen Oberflächenstruktur auf dem plattenförmigen Werkstück (2) definiert, so dass die zweite Beschichtung (24) eine negative Oberflächenstruktur bildet, in der eigentlich als Vertiefungen nachzubildende Oberflächenstrukturen des Holzdekors als Erhebungen (28) ausgebildet sind.

The above-indicated technical problem is inventively achieved by a device having the features of claim 22. The device according to the invention for producing a structured surface on a plate-shaped workpiece made of wood material for use as a floor covering or furniture part comprises:

• at least one processing roller (18, 20) having an applicator roll for printing a wood decor,
• a processing station (6) having an applicator roll (10) for applying a first coating (22) of lacquer to the surface of the plate-shaped workpiece (2) and following at least partially optically transparent on the wood decor
• a processing station (8) having a structured surface having an application roller (14) for directly or indirectly printing an at least partially optically transparent second coating (24) of lacquer on the first coating (22) and the second coating (24) with a spatially varying distribution of the application amount on the first coating (22), wherein the structured lateral surface of the applicator roll (14) defines a surface structure for generating a negative surface structure on the plate-shaped workpiece (2), so that the second coating (24) has a negative surface structure forms, are formed in the actually as depressions nachzubildende surface structures of the wood decor as elevations (28).

Further embodiments of the device according to the invention are specified in the subclaims, which are also explained in more detail in the following description of the preferred embodiments.

Fig. 1

eine schematische Darstellung einer Vorrichtung zum Herstellen einer strukturierten Oberfläche auf plattenförmigen Werkstücken mit einer Auftragswalzenanordnung,

Fig. 2

eine schematische Darstellung einer Auftragswalze für ein direktes Aufbringen einer zweiten Beschichtung,

Fig. 3

eine schematische Darstellung einer Auftragswalze für ein indirektes Aufbringen einer zweiten Beschichtung,

Fig. 4

eine schematische Darstellung einer Auftragswalze mit einem profilierten Rakel für ein direktes Aufbringen einer linienförmigen zweiten Beschichtung,

Fig. 5

eine schematische Darstellung einer Vorrichtung zum Herstellen einer strukturierten Oberfläche auf plattenförmigen Werkstücken mit einer digitalen Auftragsvorrichtung,

Fig. 6a,b

eine schematische Darstellung einer strukturierten Oberfläche,

Fig. 7a-c

eine schematische Darstellung einer erfindungsgemäßen Ausführungsform einer strukturierten Oberfläche und

Fig. 8

eine schematische Darstellung einer weiteren Ausführungsform einer strukturierten Oberfläche.

In the following the invention will be explained in more detail by means of embodiments, reference being made to the accompanying drawings. In the drawing show

Fig. 1

a schematic representation of an apparatus for producing a structured surface on plate-shaped workpieces with an applicator roll arrangement,

Fig. 2

a schematic representation of an applicator roll for a direct application of a second coating,

Fig. 3

a schematic representation of an applicator roll for an indirect application of a second coating,

Fig. 4

a schematic representation of an applicator roll with a profiled doctor blade for a direct application of a line-shaped second coating,

Fig. 5

a schematic representation of an apparatus for producing a structured surface on plate-shaped workpieces with a digital application device,

Fig. 6a, b

a schematic representation of a structured surface,

Fig. 7a-c

a schematic representation of an embodiment of the invention, a structured surface and

Fig. 8

a schematic representation of another embodiment of a structured surface.

Fig. 1 shows in a schematic form an apparatus for producing a structured surface on a workpiece, which in the present case is designed as a plate 2.

A plurality of plates 2 are arranged on a conveyor belt 4, which are individually fed sequentially to different processing stations. The conveying direction is in Fig. 1 indicated by an arrow and runs from left to right. Instead of a plurality of individual plates 2, a large-area workpiece or an endlessly produced workpiece can be processed, which is divided into individual plates 2 after the processing described below.

In the Fig. 1 shown processing stations 6 and 8 have in common that with them in each case a coating is applied. In the present embodiment, the two coatings consist of a same paint. However, the invention is not limited thereto, so it can also be applied by the processing stations coatings of different materials.

In the processing station 6, a first substantially full-surface coating is applied from a lacquer. For this purpose, the processing station on an applicator roll 10, which applies a uniform layer of paint on the surface of the plates 2. In the downstream finishing device 12, the applied coating is at least partially dried and cured. The post-processing device 12 can cause the drying and curing, for example by means of a hot air flow or by means of electromagnetic radiation, in particular UV radiation. For this purpose, the post-processing device 12 corresponding means for generating the hot air flow or the radiation.

In the processing station 8, a coating of a paint is applied directly by means of an applicator roll 14, wherein the order quantity varies spatially. This leads to an intended structuring of the upper lacquer layer. The spatial structuring of the lacquer layer is produced in particular by a gravure roll, in the surface of which different sections having different levels are formed.

Usually, the surface of a gravure roll is processed by means of pricking or engraving in order to produce individual recesses, so-called wells, usually in diamond form, with different depths. During printing, a paint or varnish is applied which is received in the cavities to be partially dispensed from the cavities onto the surface of the medium during transfer to another medium.

In the downstream post-processing device 16 then the last applied coating is then at least partially cured, so that the spatially different structuring is fixed before it compensates again due to bleeding. In this curing step, it may also come to a possibly incomplete curing of the arranged underneath, applied in the first processing station 6 coating.

It has proved to be advantageous if the two paint layers consist of the same paint, as this facilitates the bonding of the two coatings. In contrast, however, different compositions of the two coatings can be selected to For example, to highlight and enhance the surface effects of structuring. The differences may be, for example, in the color of the two coatings or in the degree of gloss.

Fig. 2 shows an applicator roll 14, which applies the paint on the surface of the plate 2 in a direct printing process. The arrow again indicates the direction of movement of the plate 2. The structured lateral surface 15 of the applicator roll 14 (the structuring can not be seen in detail) takes up the lacquer, wherein the amount of the lacquer L is set by a doctor 17. By a rotation of the applicator roll 14 of the paint is then structured, so transmitted with a spatially varying distribution on the surface of the plate 2 directly. Therefore, this method is also called direct printing method.

Fig. 3 shows the same roller 14, which is not used in this embodiment as a direct application roller, but first transfers the adhering paint on a separate applicator roll 19, which preferably has an elastic, preferably rubberized roll surface. From the applicator roller 19, the paint transferred from the roller 14 is then applied to the surface of the plate 2. The remainder of the lacquer L is doctored during the further rotation of the applicator roll 19 with the aid of a further doctor blade 21, before lacquer is again transferred from the roll 14. This process is also called indirect printing process.

Fig. 4 shows a further embodiment of the applicator roll arrangement. In this case, an applicator roll 14 with a smooth surface by means of a profiled doctor 17 applied separate paint strands. After application to the surface of the plate 2 then results in a line structure. The density of the lacquer strands, their distances and their diameter can be freely selected by setting the profiling. In addition, by a preferably oscillating movement of the doctor blade transversely to the direction of movement of the plate 2, it is possible to generate a wave-like arrangement of the lacquer strands on the plate surface.

A further embodiment of the doctor blade arrangement is that instead of the one profiled doctor blade 17, two identically profiled doctor blades are provided. If both doctor blades are aligned, the lacquer strands are applied to the roll surface. If the two squeegees are shifted against each other, the order of the paint strands is interrupted. By a selective shifting against each other interrupted structures can be created.

Fig. 5 shows an embodiment of an apparatus for producing a structured surface on a plate 2, in which instead of the applicator roll arrangement described above, a digital application device 30 is provided for applying the second coating. In the present example, a jet printing technique is used, which is particularly widespread in so-called inkjet printers. In Fig. 5 below the applicator a short dash is drawn in which indicates the row of droplet jets. In this case, it is assumed that the applicator device applies the paint line by line transversely to the direction of movement of the plate 2. Likewise it is also possible, in each case a surface with droplets to apply, so as to increase the speed of application.

Furthermore, a computer 31 as a means for generating a dot distribution for controlling the digital application device is connected to the application device 30. The computer 31 prepares digital control information and transmits it to the application device.

As with the other application devices, the post-processing device 32 adjoins the digital application device in order to dry and at least partially cure the previously applied second coating.

Furthermore, an optical scanning device 34 is advantageously provided to detect the surface pattern of the first coating. During operation, the optical pickup detects the surface and transmits the detected data to the computer 31. The computer 31 then calculates a dot distribution to be generated from the readings of the optical pickup 34. This is then applied with the digital applicator 30 as a second coating.

The optical scanning device can be designed as a scanner, as a line camera or as an area camera. In any case, the aim is that the optical scanning device detects the surface with a resolution or evaluates the recorded data with a resolution with which the digital application device is to apply the structured second coating.

By a time delay dependent on the conveying speed of the plate 2 and on the distance between the optical scanning device 34 and the digital application device 30, it can also be achieved that the digital application device 30 applies the structured second coating to the surface in such a way that the surface structure coincides with the optical pattern at least partially matches. In other words, a synchronous haptic and optical surface design of the plate 2 can be achieved in this way.

In Fig. 1 is further shown that the surface of the plates 2 is provided before applying the two coatings described above by means of the processing stations 6 and 8 by means of two further processing stations 18 and 20, each with a coating. This can be in particular lacquer layers with which a two-tone surface, a decor is produced. The processing stations 18 and 20, in a similar manner as previously described, have applicators and finishing devices without further description herein.

The pre-painting represents a particularly preferred embodiment, because the surfaces produced therewith are completely painted and can thus be produced in a plant.

The two processing stations 18 and 20 apply a surface varying pattern, namely a wood decor. For this purpose, the two applicator rollers of the processing stations 18 and 20 synchronized to apply matching and complementary color patterns. In addition, the gravure roller 14 is provided with a surface engraving whose image also coincides with the applied by the processing stations 18 and 20 printed images. Furthermore, the rotation of the gravure roller 14 is synchronized with the rotation of the applicator rollers of the processing stations 18 and 20 such that the spatially varying distribution of the second coating coincides with the printed image applied by the processing stations 18 and 20. Thus, a synchronized with the printed pattern varying distribution of the uppermost lacquer layer, namely a pore structure suitable for wood decor can be achieved.

Of course, further processing stations can be added to the described processing stations 18 and 20.

Fig. 6a and 6b show an embodiment of a structured surface of a plate 2. On the material of the plate 2, a first coating 22 of a paint has been applied over the entire surface. On the first coating 22, a second coating 24 has also been applied, which has a spatially varying distribution of the application amount. The variation in this case means a pore structure that is intended to imitate a wood decor. The pores are formed as elongated recesses 26, as can be seen in particular from the magnification in Fig. 6b results. The second coating 24 thus consists of the areas that are not formed as a recess.

The pores 26 are shown in this schematic representation substantially rectangular in cross-section with slightly rounded edges. In practice, however, a distribution which differs more clearly from the rectangular shape may occur, since the regions of the second coating 24 in the edge regions of the recesses 26 partially dissolve before being cured. Rounded corners are therefore to be expected at real recesses 26.

In the Fig. 6a shown spatial distribution of the order amount of the second coating results in a pore structure in which the pores actually represent depressions in the coating 24. Such a structure can also be called a positive surface structure.

The Fig. 7a to 7c show a similar surface structure of a second coating 24, in which the pores are formed as elevations 28. Such a surface structure may therefore be referred to as a negative surface structure. Because the actually to be expected as a depression pores are formed as elevations. As has already been mentioned above, the size of the structures is so small that in a normal viewing by a user the negative surface structure can not be distinguished from a positive surface structure.

The second coating 24 thus consists of the areas that have been applied as elevations, that is, for example, as negative pores. The area coverage of the second coating is therefore considerably lower than in the surface structure according to Fig. 6a and 6b ,

Especially Fig. 7b shows in an enlargement the cross-sectional shape of the negative pore. As already to the cross section of the positive pore after Fig. 6a and 6b has been described here, the cross-sectional shape of the pore is shown with rounded edges. This form is to be expected if the applied paint partially dissolves before curing to the forming edges.

Fig. 7b shows a continuous course of the survey or the negative pore 28th Fig. 7c In contrast, shows a present within the applied negative pore 28 substructure. This substructure consists of individual spaced individual elevations 29, which arise due to the application techniques described above.

On the one hand, this substructure may arise during application by means of an embossed or engraved roll shell surface, that is to say if the surface has individual wells which in each case emit the adhering lacquer. Because the wells are spaced, the dispensed droplets of paint are also spaced on the first coating 22, thus leading to the substructure.

On the other hand, such a structure can arise when using a digital application device. For here, too, the paint is applied in droplet form on the first coating 22, so that depending on the distance of the droplets on the surface of the first coating 22 forms a more or less pronounced substructure.

In Fig. 7c The individual surveys have been shown rectangular. However, here too, the above-mentioned effect of the occurring partial deliquescence before hardening applies, so that it can be assumed that the individual elevations will at least partially dissolve one another. This effect is all the more so as that the individual surveys are arranged much closer together than for the previously described entire pore structure after Fig. 7b the case is.

Fig. 8 shows by way of example a geometric pattern of the spatially varying distribution of the application amount of the second coating. The illustrated pattern is a diamond pattern that has recessed and raised diamonds. In this form of spatial distribution, no distinction can be made between a negative or a positive structure, since there are as many raised and recessed areas.

The following is a possible investigation method, with which a surface structure of the previously described can be examined. It is important to be able to resolve and recognize structures in the range of 0.01 mm.

The method is based on the principle of the known light-section method with optical triangulation, whereby a relative movement of measuring cell and measuring object is assumed. The mode of operation consists of illuminating the surface area to be measured with a suitable light source (laser) and using a surface camera to capture the light stripe imaged on the object. there the surface normals of the illumination and the camera are tilted at a triangulation angle to each other. The camera then sees the projection line as a contour line reproducing the contour of the test object, from whose coordinates and the associated positions a three-dimensional profile can be calculated. The resolution of the known techniques achieves an accuracy in the vertical direction of less than 0.1 μm.

With the aid of such a method, the structured surface of the second coating can be examined and analyzed.

Likewise, an analysis of the surface structures by means of microscopes is possible.

Claims (24)

1. Method for producing a textured surface on a panel-shaped workpiece (2) made of wood-based material for use as floor covering or a furniture part,

   - in which a wood imitating decoration is printed onto a surface of the workpiece (2) by means of applicator rollers, wherein the wood imitating decoration comprises regions which are to be understood as recesses;

   - in which a first coating (22) of varnish, which is optically transparent, at least in part, is applied to the surface of the workpiece following the wood imitating decoration; and

   - in which a second coating (24) of varnish, which is optically transparent, at least in part, is applied, in a direct printing process or an indirect printing process by means of an applicator roller (14) having a textured outer surface, to the first coating (22), with spatially varying distribution of the amount applied, such that regions having higher amounts applied and regions having lower or no amounts applied are provided, and such that the second coating (24) forms a negative surface structure, so that surface structures of the wood imitating decoration which are actually intended to replicate recesses are formed as raised portions (28).
2. Method according to claim 1, wherein the raised portions (28) of the negative surface structure are formed so as to be linear.
3. Method according to either claim 1 or claim 2, wherein the second coating (24), provided with nanoparticles, is applied.
4. Method according to any of claims 1 to 3, wherein the first coating (22) is applied as a sealing varnish provided with nanoparticles.
5. Method according to any of claims 1 to 4, wherein the varnish is formed as high-solids varnish.
6. Method according to any of claims 1 to 5, wherein the varnish of the first coating (22) is cured to between 65 % and 95 %, in particular to 85 %, before the second coating (24) is applied.
7. Method according to any of claims 1 to 6, wherein the gloss level of the second coating is formed so as to be different from the gloss level of the first coating (22).
8. Method according to any of claims 1 to 7,
   wherein the second coating (24) is applied as a pigmented UV-curable knot varnish in order to adjust the gloss level and/or the colour of the second coating.
9. Method according to any of claims 1 to 8, wherein the second coating (24) is cured after application.
10. Method according to any of claims 1 to 9, wherein one or more of the following coatings are applied to the surface prior to the application of the first coating (22):

    - an adhesion-promoting coat comprising at least one coat;

    - a primer coat comprising at least one coat;

    - a roll base coat comprising at least one coat;

    - a printed coat comprising at least one coat and showing a decoration;

    - a corundum-containing varnish coat comprising at least one coat; and

    - a rubbing varnish comprising at least one coat.
11. Method according to any of claims 1 to 10, wherein the amount applied for the second coating (24) is adjusted in such a way that the thickness of the structures of the second coating is less than 0.1 mm.
12. Method according to any of claims 1 to 10, wherein the second coating (24) is applied in a distribution which is adapted to the printed wood imitating decoration.
13. Panel-shaped workpiece made of wood-based material for use as floor covering or a furniture part, comprising a textured surface, in particular produced according to a method according to any of claims 1 to 12, comprising

    - a panel-shaped substrate material (2) made of wood-based material;

    - a wood imitating decoration which is printed on the substrate material (2) and comprises regions to be understood as recesses;

    - a first coating (22) of varnish which follows the wood imitating decoration and is optically transparent, at least in part; and

    - a second coating (24) which is optically transparent, at least in part, and is formed of varnish, and which is applied, by means of a direct printing process or an indirect printing process, to the first coating (22), with spatially varying distribution of the amount applied, such that regions having higher amounts applied and regions having lower or no amounts applied are provided, and such that said second coating forms a negative surface structure, so that surface structures of the wood imitating decoration which are actually intended to replicate recesses are formed as raised portions (28).
14. Workpiece according to claim 13, characterised in that the varying distribution of the amount of the second coating (24) applied forms a linear texture (26, 28).
15. Workpiece according to either claim 13 or claim 14, characterised in that the raised portions (28) of the second coating (24) comprise a sub-structure consisting of individual spaced-apart raised portions (29).
16. Workpiece according to any of claims 13 to 15, characterised in that the second coating (24) comprises nanoparticles.
17. Workpiece according to any of claims 13 to 16, characterised in that the first coating (24) consists of a sealing varnish having nanoparticles.
18. Workpiece according to any of claims 13 to 17, characterised in that the gloss level of the second coating (24) is different from the gloss level of the first coating.
19. Workpiece according to any of claims 13 to 18, characterised in that one or more of the following surface coatings are provided underneath the first coating (22):

    - an adhesion-promoter layer comprising at least one layer;

    - a primer layer comprising at least one layer;

    - a printed layer which has a decoration and comprises at least one layer;

    - a roller base-layer comprising at least one layer;

    - a varnish layer containing corundum and comprising at least one layer; and

    - a rubbing varnish layer comprising at least one layer.
20. Workpiece according to any of claims 13 to 19, characterised in that the thickness of the textures of the second coating (24) is below 0.1 mm.
21. Workpiece according to any of claims 13 to 20, characterised in that the second coating (24) is applied by being distributed in a manner adapted to the printed wood imitating decoration.
22. Device for producing a textured surface on a panel-shaped workpiece (2) made of wood-based material for use as floor covering or a furniture part, comprising

    - at least one processing station (18, 20) having an applicator roller for printing a wood imitating decoration which has regions to be understood as recesses,

    - a processing station (6) having an applicator roller (10) for applying a first coating (22) of varnish, which is optically transparent, at least in part, to the surface of the panel-shaped workpiece (2) following the wood imitating decoration, and

    - a processing station (8) which has an application roller (14) having a textured outer surface for directly or indirectly applying a second coating (24) of varnish, which is optically transparent, at least in part, to the first coating (22), and applies the second coating (24) with spatially varying distribution of the amount applied, to the first coating (22), so that regions having higher amounts applied and regions having lower or no amounts applied are provided, wherein the textured outer surface of the applicator roller (14) defines a surface structure for producing a negative surface structure on the panel-shaped workpiece (2) so that the second coating (24) forms a negative surface structure, so that surface structures of the wood imitating decoration which are actually intended to replicate recesses are formed as raised portions (28).
23. Device according to claim 22, characterised in that the processing station (8) for applying the second coating (24) comprises a finishing device (16) for drying and/or curing the second coating.
24. Device according to either claim 22 or 23, characterised in that the processing station (6) for applying the first coating comprises a finishing device (12) for drying and/or curing the first coating (22).

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