EP3090882B1 - Plate-shaped workpiece with a surface with gloss degree differences and method for creating such a surface - Google Patents

Description

The invention relates to a method for producing a surface with differences in gloss levels on a panel-shaped workpiece according to the preamble of patent claim 1, and a panel-shaped workpiece with a surface with differences in gloss levels according to the preamble of claim 8.

In a method of the present type, a carrier board, in particular a wood-based material carrier board, is first printed with a decorative layer. This can be done directly, for example by means of a digital printing device or a printing roller, or indirectly, for example on a decorative paper that is applied to the carrier board, or on an additional stabilization layer. In the simplest case, the decorative layer can be a single-color lacquer layer, but a wooden decoration to imitate a natural wood surface, a decorative print to imitate a stone surface, a decorative print with artistic motifs and the like are also often used. This is also the case within the scope of the present invention.

An at least partially transparent sealing layer is applied to the entire surface of this decorative layer, the sealing layer consisting of a sealing lacquer which has a first degree of gloss after it has hardened. In particular, this can be a transparent glossy lacquer or a translucent matt lacquer. This can be freely selected depending on the desired visual effect in conjunction with the decorative layer.

After the sealing layer has at least partially cured, it is conventionally printed directly with a design print, which is formed with an at least partially transparent design varnish which, after it has cured, has a second degree of gloss.

The interaction of the different degrees of gloss of the design print and the sealing layer usually serves to optically approximate a panel-shaped workpiece with a decorative layer that imitates the natural surface of wood or another natural material to the model, because the sealing layer, which the decorative layer protects against abrasion, causes an artificial appearance of the surface, especially when the surface has a uniform degree of gloss.

One way to change the uniform gloss level of a full-surface sealing layer without printing a design is in the EP-A-1 980 418 disclosed. There, a wood-based panel is provided with a decorative layer and a lacquer layer that seals it. After this sealing layer has fully cured, a structure is embossed into its surface, which optically modifies the degree of gloss accordingly.

Another approach to vary the degree of gloss of the surface of a panel-shaped workpiece with a decorative layer and a sealing layer is in EP-A-1 645 339 described. It is proposed there to apply a design print with a spatially varying application quantity to the sealing layer in order to print a three-dimensional structure that is also haptically perceptible. This structure is produced with a varnish that does not necessarily have a different degree of gloss than the sealing layer. Nevertheless, due to the three-dimensional printing and the associated sublimity of the printed structures, a varying degree of gloss is achieved on the finished surface. In particular, in the case of panel-shaped workpieces that are provided with a wood decor, the natural pores of a wood surface are preferably imitated on the surface of the sealing layer in such a way that they can be perceived optically and haptically that the design print on those Places where the decorative layer depicts a wood pore, which actually means a depression in the wood surface, a three-dimensional raised paint application takes place, which interrupts the shine of the sealing layer at this point and is also haptically perceptible.

A development of this prior art is in EP-A-2 376 292 disclosed. It is also proposed there to apply a design print with a three-dimensional structure to the sealing layer in order to make the structure particularly haptically perceptible. In addition, the optical effect of a surface with different gloss levels should be created by using paints with different gloss levels.

The present invention is based on the approach of varying the uniform degree of gloss of the sealing layer by printing a design print, without pursuing the goal of providing the design print with perceptible three-dimensional properties. Because by using a design varnish for the design print, which has a degree of gloss that differs greatly from the sealing varnish, the resulting surface, which is formed partly by the printed image of the design print and partly by the exposed surface of the sealing layer, can also have three-dimensional structures with varying degrees of gloss be provided.

Compared to the known embossing of a structure in the sealing layer and also compared to the known application of a three-dimensional structure, the simple printing of a design print offers the advantage of significantly easier handling, since conventional printing techniques that have been tried and tested for decades can be used. In addition, the simple design print can be used to produce large-area variations in the degree of gloss on the surface of the panel-shaped workpiece without having to use correspondingly large amounts of structured paint to form a three-dimensional structure, which also takes an extremely long time and requires a lot of energy to harden. This is of particular importance in applications in which the distribution of the part surfaces with different gloss levels do not necessarily match the underlying one

Decorative layer should correspond or generally imitate a surface of a natural material, but can also be a design pressure formed with completely independent motifs in order to achieve optical effects that are not related to the decorative layer.

However, it has been found that the differences in gloss level that can be achieved by simply printing a design print onto the sealing layer are in need of improvement, even if varnishes are used as the sealing varnish and as the design varnish that have very different levels of gloss after curing.

The present invention is therefore based on the object of further developing a method of the type mentioned at the outset and a plate-shaped workpiece of the type mentioned at the outset in such a way that surfaces with particularly large differences in the degree of gloss or jumps in the degree of gloss can be produced. This object is achieved by a method having the features of patent claim 1 and by a panel-shaped workpiece having the features of patent claim 8.

Preferred developments of the method according to the invention are defined in claims 2 to 7; advantageous configurations of the plate-shaped workpiece according to the invention can be found in patent claims 9 to 10.

The method according to the invention is accordingly modified in that after the at least partial curing of the sealing layer, an at least partially transparent intermediate layer is applied over the entire surface of the sealing layer, and in that the design paint is printed wet-on-wet onto the intermediate layer before this intermediate layer is cured. In this case, the intermediate layer is produced with an intermediate lacquer, which consists of the same material as the sealing lacquer, or else of a material which has the same degree of gloss as the sealing lacquer after it has hardened.

The plate-shaped workpiece produced in this way has a surface that has a second degree of gloss within the printed image of the design print and a first degree of gloss of the sealing layer outside of the printed image of the design print, with these two degrees of gloss measured according to DIN EN ISO 2813 at an angle of 60° differ by at least 50 gloss level units (GU), preferably by at least 70 GU.

According to the invention, it has been recognized that when the design print is printed, particularly if this is done by means of indirect gravure printing, a thin residual film is inevitably printed on the surface of the plate-shaped workpiece where no print image is provided. In the case of indirect gravure printing, this is largely due to the fact that the gravure roller cannot be scraped off so residue-free after the depressions have been filled with the design lacquer that no design lacquer remains outside the depressions of the gravure roller. Rather, there always remains a mostly wafer-thin residual film, which ultimately reaches the entire surface of the sealing layer on the surface of the plate-shaped workpiece via the transfer cylinder.

It has also been recognized according to the invention that this residual film significantly changes the degree of gloss of the sealing layer, namely in the direction of the degree of gloss of the design paint. This reduces the difference in gloss level between the gloss level of the design varnish that prevails in the printed image of the design print and the gloss level outside of the printed image, which is then no longer the gloss level of the sealing varnish due to the residual film, but has changed in the direction of the gloss level of the design varnish.

The effect of the residual film is particularly disturbing if a sealing layer with a particularly high degree of gloss is used and a design print with a lower degree of gloss is printed on it. Even if the gloss level of the design print is only slightly lower than the gloss level of the sealing layer, it decreases the gloss level of the sealing layer through the residual film. The same can be observed if a sealing layer with a particularly low gloss level is used and a design print with only a slightly higher gloss level is printed on it.

The reason for the sometimes unsatisfactory jumps in gloss level in the surface of a panel-shaped workpiece of the present type, which has become apparent as a result of these findings according to the invention, is rendered harmless according to the invention in that the design print is not printed directly on the at least partially cured sealing layer, but first an intermediate layer on which wet -in-wet, before the intermediate layer hardens, the design varnish is printed on. The intermediate lacquer for the production of this full-surface intermediate layer can be an additional layer of the sealing lacquer, or an intermediate lacquer that differs from this and has the same degree of gloss as the sealing lacquer after it has cured.

If the layer thickness or application quantity of the intermediate layer is selected appropriately, the unavoidable residual film of design paint, which is applied to the surface of the workpiece outside of the actual print image of the design print, is absorbed by the still wet intermediate layer, so that after curing it increases the gloss level of the Sealing varnish not or only slightly changed. At the same time, the application quantity of the intermediate layer should be selected in such a way that the design varnish in the actual print image, despite the wet-on-wet printing, only mixes to an insignificant extent with the intermediate layer and, in particular, remains essentially unaffected on its surface, i.e. after curing its typical, has substantially unadulterated gloss level.

It has been found here that the surface-specific application quantity of the design coating in the printed image should typically correspond to at least 1.5 times, preferably 1.5 to 15 times the surface-specific application quantity of the intermediate layer. Alternatively, or possibly also cumulatively, the surface-specific application quantity of the intermediate layer, i.e. the material quantity of the intermediate coat applied per unit area, should correspond to at least 5 times, preferably 5 to 50 times the surface-specific application quantity of the residual film of the design coating printed outside the printed image of the design print. Depending on the printing machine used, the application quantity of the (actually unwanted) residual film is so significant that it can be measured.

This measure according to the invention makes it possible to use a method of the present type to produce a panel-shaped workpiece with a carrier panel, a decorative layer, an at least partially transparent sealing layer and an at least partially transparent design print applied thereto, in which between the printed image of the design print and the rest surface a difference in gloss level of at least 50 gloss level units (GU), preferably at least 70 GU, measured according to DIN EN ISO 2813 at an angle of 60° and at a distance of 20 mm. This enables amazing optical effects, independent of the reproduction of a natural material surface, as they come into their own when using the panel-shaped workpiece according to the invention as a piece of furniture or for cladding floors, walls or ceilings. In this case, the design print can have a printed image that is completely independent of the decorative layer.

The printed image of the design print can have a higher degree of gloss than the surface of the sealing layer or the intermediate layer; within the scope of the present invention, however, it can also be the other way around, i.e. the sealing layer is formed, for example, from a transparent high-gloss lacquer, with the printed image of the design print having a matt surface.

Since the intermediate layer used according to the invention hardly changes the gloss level of the surface of the sealing layer, a sealing varnish and a design varnish can be used to produce the plate-shaped workpiece according to the invention, the gloss levels of which are measured according to DIN EN ISO 2813 at an angle of 60°, in the cured state differ by at least 50 gloss units (GU), preferably by at least 70 GU.

However, the present invention also offers advantages when a sealing varnish with a high degree of gloss, preferably above 75 GU, is used and the design print has an only slightly lower degree of gloss. Because of the intermediate layer used according to the invention, there is little or no change in the gloss level of the surface of the sealing layer when printing with the design paint.

In order to fully ensure the inventive effects of the intermediate layer onto which the design paint is printed wet-on-wet, it is advantageous if the sealing layer is gelled before the intermediate layer is applied, or is already essentially cured. In the latter case, it is useful if the hardened sealing layer is sanded before the intermediate layer is applied, in order to ensure good adhesion of the various layers of paint to one another.

Figur 1

eine schematische Schnittdarstellung eines erfindungsgemäß bedruckten plattenförmigen Werkstücks;

Figur 2

eine Ansicht der Oberfläche des Werkstücks aus Figur 1

Figur 3

eine schematische Schnittdarstellung einer Anlage zur Durchführung des erfindungsgemäßen Verfahrens;

Figur 4

eine schematische Schnittdarstellung einer Druckeinrichtung zum Drucken des Designdrucks.

An exemplary embodiment of a plate-shaped workpiece according to the invention and an exemplary embodiment of a system for carrying out the method according to the invention are described with reference to the accompanying drawings. Show it:

figure 1

a schematic sectional view of an inventively printed plate-shaped workpiece;

figure 2

a view of the surface of the workpiece figure 1

figure 3

a schematic sectional view of a system for carrying out the method according to the invention;

figure 4

a schematic sectional view of a printing device to print the design print.

figure 1 shows a schematic, not to scale, sectional representation of a plate-shaped workpiece printed according to the invention. This is made up of a carrier board 1 made of wood-based material, a basic structure 2 applied thereto, a decorative layer 3, a sealing layer 4, an intermediate layer 5 and a design print 6.

This in figure 1 The plate-shaped workpiece shown is intended for use as a floor panel. Accordingly, the carrier plate 1 consists of a wood fiber board, which is laminated with a basic structure 2 made of an adhesive paper impregnated with melamine resin, which increases the resistance to indentation. The decorative layer 3 is a color print of an image of a sawn wood surface, in which case basically all possible prints can be applied, such as geometric shapes, artistic representations, or a single-color layer of paint.

In the present case, the design print 6 does not correspond to the appearance of the decorative layer 3, but forms an artistic pattern independent of it; How figure 2 shows, these are tendrils of flowers. The design varnish used for design print 6 is a matt varnish that has a gloss level of approx. 10 GU after it has hardened. This is in contrast to the sealing lacquer that forms the sealing layer 4: This is a gloss lacquer that has a gloss level of approx. 90 GU after it has cured.

The intermediate layer 5, which consists of an additional layer of the same sealing lacquer, and to which the design print 6 was applied wet-on-wet according to the invention, has absorbed the residual film of design lacquer applied to the intermediate layer 5 outside of the printed image 7, which is unavoidable during design printing, in such a way that the surface of the intermediate layer 5 that is visible outside of the printed image 7 has an almost unchanged degree of gloss of approximately 90 GU after it has cured.

As a result, this leads to a hitherto unachieved jump in gloss level between the printed image of the design print 6 and the surface of the plate-shaped workpiece lying outside the printed image of 80 GU in the present case. The resulting optical effect is in figure 2 to recognize: If you look at the panel-shaped workpiece at a steep angle, the visual impression is determined by the decorative print 3, which represents the surface of a sawn wooden board. From this viewing angle, both the sealing layer 4 with the intermediate layer 5 and the design print 6 appear transparent. The reflective components increase as the viewing angle becomes flatter, and the surface of the sealing layer 4 or the intermediate layer 5 becomes highly glossy, so that the decorative layer 3 is covered by the glossy reflections. Due to the very high difference between the high-gloss surface of the sealing layer 4 or the intermediate layer 5 on the one hand and the design print 6 on the other hand, the latter can be seen very clearly as a flower tendril when viewed from a flat angle, although both the sealing varnish and the design varnish are transparent.

A comparative test by the applicant confirmed the effect according to the invention:
In a first attempt, this was figures 1 and 2 illustrated panel-shaped workpiece produced, namely by a wood-based panel was provided with a basic structure and a decorative print. A sealing layer of a high-gloss sealing lacquer was then applied. After it had cured, the degree of gloss was measured according to DIN EN ISO 2813 at an angle of 60° and a distance of 20 mm; it was 86 GU. According to the invention, a thin layer of the same sealing lacquer was then applied over the entire surface as an intermediate layer and a design print was applied to this wet-on-wet, the design lacquer having a gloss level of approximately 10 GU after curing. The design print was applied using the indirect gravure printing process with a gravure roller and a rubber blanket cylinder as a transfer cylinder. also on a squeegee was placed on the rubber blanket cylinder in order to squeegee off print image residues after the print image had been transferred to the workpiece. For this purpose, the surface of the rubber blanket cylinder was rinsed with design paint immediately in front of the squeegee. Both when scraping off the gravure roller and when scraping off the rubber blanket cylinder, a residual film of design paint was created, which covered the rubber blanket roller extremely thinly outside of the actual print image and was therefore also transferred to the workpiece. The intermediate layer of not yet hardened sealing lacquer previously applied to the workpiece according to the invention was applied in an area-specific application amount which corresponded to 10 to 20 times the area-specific application amount of the residual film. As the measurement results show, this was sufficient to absorb the residual film wet-on-wet into the intermediate layer in such a way that its degree of gloss remained essentially unchanged after curing. The design print was applied in an area-specific application amount that corresponded to about 2 to 3 times the area-specific application amount of the intermediate layer (based on the printed image), so that there, despite the wet-on-wet application, there was no mixing of the design varnish and the intermediate layer took place, which would have changed the degree of gloss of the design paint.

A final measurement resulted in a gloss level of approx. 10 GU in the printed image and a gloss level of approx. 86 GU outside the printed image.

A comparative measurement was carried out by preparing a wood-based material base board with a basic structure and decorative layer using the same materials and in the same way, after which the same sealing lacquer was applied over the entire surface and cured. Here, too, a gloss level measurement according to DIN EN ISO 2813 at an angle of 60° and at a distance of 20 mm resulted in a gloss level of approx. 86 GU. Thereafter, the same design paint as in the first experiment was printed directly onto the sealing layer with the same print image, without applying the intermediate layer according to the invention. The residual film of design varnish printed on the sealing layer outside of the print image of the design print decisively changed the gloss level of the surface: the comparative measurement showed a gloss level outside of the printed image of the design print of only 57 GU. Attempts to optimize the two squeegees in the printing device used to apply the design print more sharply in order to minimize the area-specific application quantity of the residual film resulted in optimal gloss level values outside the print image of the design print of 64 to 68 GU.

Despite the in figure 2 illustrated, strong jumps in gloss level between the printed image of the design print and the surfaces of the sealing layer or intermediate layer that remain free of it, the design print is not haptically perceptible; it is therefore merely an optical effect which, unlike in the prior art, was produced in a purely conventional, two-dimensional print.

figure 3 shows a schematic lateral sectional view of an embodiment of a system for the production of in the figures 1 and 2 shown workpiece is used.

This system includes a feed device for the carrier plate 1, the feed device not being shown here, but merely being symbolized by means of a conveying device 8 and the conveying direction 9 visualized. Since the system processes the carrier plate 1 in line with the finished workpiece, several conveyor devices 8 are shown one behind the other in the conveying direction 9 .

The system also includes a decorative printing device 10, a sealing device 11, a hardening device 12, an intermediate coating device 13, a printing device 14 and a curing device 15, through which the workpiece passes successively. The carrier plate 1 is printed with the decorative layer 3 in the decorative printing device 10 . It is a simple paint application machine to apply a uniform coloring of the carrier plate 1 as a decorative layer 3. In the sealing device 11, the sealing layer is applied to the entire surface of the workpiece, after which it is gelled in the hardening device 12 by means of UV radiation. After gelling, the workpiece passes through the intermediate coating device 13, where According to the invention, the intermediate layer 5 is applied over the entire surface to the sealing layer. The design paint is then printed wet-on-wet onto the intermediate layer 5 in the subsequent printing device 14 . Finally, all paint layers are cured in the curing device 15, which in turn contains a UV radiator.

The printing device 14 is shown enlarged in FIG. It can be seen here that the printing device 14 consists of an engraved cylinder 16 and a transfer cylinder 17, with the transfer cylinder 17 being designed as a blanket cylinder. A workpiece that is moved in the conveying direction 9 on the conveying device 8 is printed on by the transfer cylinder 17 .

Squeegees 18 , 19 are attached both to the gravure roller 16 and to the transfer cylinder 17 , each forming a reservoir for design paint 20 . On the gravure roller 16, the squeegee 18 ensures that design paint 20 is brushed into the recesses of the gravure roller and is stripped off the roller surface outside of the recesses. On the transfer cylinder 17, the reservoir formed by the squeegee 19 there serves to rinse the surface of the transfer cylinder 17 with design paint 20. At the same time, the squeegee 19 ensures that as little design paint as possible remains on the surface of the transfer cylinder 18 after the rinsing process - apart from the unavoidable residual film, which was recognized as problematic according to the invention and whose disadvantageous effects were eliminated according to the invention.

Claims (10)

1. Method for producing a surface with differences in gloss on a panel-shaped workpiece, comprising the method steps of:

   - providing a carrier panel (1), in particular a wood-based material carrier panel,

   - indirectly or directly printing a decorative layer (3) on the carrier panel (1), applying an at least partially transparent sealing layer (4) over the entire surface of the decorative layer (3), wherein the sealing layer (4) consists of a sealing lacquer which has a first gloss after it has cured,

   - at least partially curing the sealing layer (4),

   - printing, on the at least partially cured sealing layer (4), a design print (6) formed with an at least partially transparent design lacquer which has a second gloss after it has cured,
   characterised in that

   - after the sealing layer (4) has at least partially cured, an at least partially transparent intermediate layer (5) is applied over the entire surface of the sealing layer (4), wherein the intermediate layer (5) is produced using an intermediate lacquer which consists of the same material as the sealing lacquer or of a material which, after it has cured, has the same gloss as the sealing lacquer,

   - and in that the design lacquer is printed wet-on-wet onto the intermediate layer (5) before the intermediate layer (5) has cured.
2. Method according to claim 1,
   characterised in that
   the design print (6) is made using an area-specific application quantity of the design lacquer in the printed image, which quantity corresponds to at least 1.5 times, preferably 1.5 to 15 times, the area-specific application quantity of the intermediate layer (5).
3. Method according to any of claims 1 or 2,
   characterised in that
   the design print (6) is made by an indirect intaglio printing method using an engraving roller and a transfer cylinder, and in that the area-specific application quantity of the intermediate layer (5) corresponds to at least 5 times, preferably 5 to 50 times, the area-specific application quantity of a residual film of the design lacquer printed outside the printed image of the design print.
4. Method according to at least one of claims 1 to 3,
   characterised in that
   the sealing layer (4) is gelled on before the intermediate layer (5) is applied, or is cured and smoothed before the intermediate layer (5) is applied.
5. Method according to at least one of claims 1 to 4,
   characterised in that
   a sealing lacquer and a design lacquer are used whose glosses, measured according to DIN EN ISO 2813 at an angle of 60°, differ by at least 50 gloss units (GU), preferably by at least 70 GU, in the cured state in each case.
6. Method according to at least one of claims 1 to 4,
   characterised in that
   a sealing lacquer is used whose gloss, measured according to DIN EN ISO 2813 at an angle of 60°, is at least 75 gloss units (GU) in the cured state, wherein a design lacquer is used whose gloss, measured according to DIN EN ISO 2813 at an angle of 60°, is only slightly smaller, in particular about 10 GU to 30 GU smaller.
7. Method according to at least one of claims 1 to 6,
   characterised in that
   the design print (6) is made by an indirect intaglio printing method using an engraving roller and a blanket cylinder, and in that the blanket cylinder is doctored after the printed image has been transferred in order to avoid ghost images in further cycles, wherein the blanket cylinder is rinsed with design lacquer before the doctoring.
8. Panel-shaped workpiece produced by a method according to at least one of claims 1 to 7, having a carrier panel (1), in particular a wood-based material carrier panel, on which a decorative layer (3) is printed directly or indirectly, having an at least partially transparent sealing layer (4) of a sealing lacquer which has a first gloss in its cured state, said sealing layer being applied over the entire surface of the decorative layer (3), and having an at least partially transparent design print (6) which is applied to the sealing layer (4) and has a second gloss,
   wherein the first and second gloss, measured according to ISO 2813 at an angle of 60°, differ by at least 50 gloss units (GU), preferably by at least 70 GU, and characterised in that between the sealing layer (4) and the design print (6) there is an at least partially transparent intermediate layer (5) which has a gloss equal to the first gloss.
9. Panel-shaped workpiece according to claim 8,
   characterised in that
   the design print (6) has a layer thickness which corresponds to at least 1.5 times, preferably 1.5 to 15 times, the layer thickness of the intermediate layer (5).
10. Panel-shaped workpiece according to any of claims 8 or 9,
    characterised in that
    the design print (6) has a printed image that is independent of the decorative layer (3).

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