Method and apparatus for producing a decorative surface

Abstract

A method for producing a decorative and structured surface with different gloss levels by feeding of a workpiece to a lacquer application device, application of a first liquid lacquer layer over an entire surface with a coarse structure in which a difference in thickness between thicker areas and thinner areas is at least 50 μm, in order to apply a second lacquer layer on the first lacquer layer wherein after curing the second lacquer layer has a different gloss level than the first lacquer layer.

Claims

1. A method for producing a decorative and structured surface element having different gloss levels, the method comprising: feeding of a workpiece (1.0) to a lacquer application device, applying of a first liquid lacquer layer (1.4) over an entire surface of the decorative and structured surface element with a coarse structure in which a difference in thickness between thicker areas and thinner areas is at least 50 μm, spraying of droplets on partial areas of the first lacquer layer (1.4) on the workpiece (1.0), with a lacquer in order to apply a second lacquer layer (1.5) on the first lacquer layer (1.4), wherein after curing the second lacquer layer (1.5) has a different gloss level than the first lacquer layer (1.4) wherein the first lacquer layer (1.4) is applied with at least one printing roller which unrolls on a surface of the workpiece (1.0) or on a layer applied to the workpiece (1.0).

2. The method according to claim 1, further comprising: coating of the workpiece (1.0) with at least one base layer (1.1, 1.2), and/or structuring of at least one base layer (1.1, 1.2), and/or at least partial curing of the first lacquer layer (1.4) applied, and/or at least partial application of a third liquid lacquer layer (1.3) in order to create a fine structure in certain areas.

3. The method according to claim 1, comprising: feeding of the workpiece (1.0) to a digital printing station, and/or providing digital control data for the digital printing station, and/or curing of the applied first lacquer layers (1.4) and the second lacquer layer (1.5).

4. The method according to claim 2, wherein the workpiece (1.0) is printed with a decorative image before the method is carried out, and/or the at least one base layer (1.1, 1.2) or the first lacquer layer (1.4) has a coarse structure with a difference in thickness between thicker areas and thinner areas of at least 50 μm.

5. The method according to claim 1, comprising: printing at least one of the applied first lacquer layer or second lacquer layer and/or the workpiece (1.0) with a decorative image.

6. The method according to claim 5, wherein digital print data available for the decorative image is used as a basis for digital control data provided for a digital printing station used for printing on the workpiece (1.0).

7. The method according to claim 1, wherein second lacquer layer (1.5) and/or a third lacquer layer (1.3) is applied by at least one digital print head.

8. The method according to claim 2, wherein to produce the third lacquer layer (1.3), liquid material is first applied and then droplets of the liquid material are sprayed over the entire surface to produce a fine structure.

9. The method according to claim 8, wherein the lacquer droplets applied consist of another material than the liquid lacquer, and/or after impact, undergo a chemical reaction with the liquid lacquer, which changes the surface optically and/or haptically at respective areas, and/or volatilise according to a physical reaction by evaporation within less than five minutes by impact with the liquid lacquer.

10. The method according to claim 1, wherein at least one of the first and second lacquer layers (1.4, 1.5) is applied from an at least partially transparent lacquer, so that a decorative image is optically recognizable through the lacquer layers (1.4, 1.5).

11. The method according to claim 1, wherein an intermediate layer is applied between the workpiece (1.0) and the first lacquer layer (1.4).

12. The method according to claim 1, wherein drying and/or curing is applied by: an electromagnetic radiation source with a wavelength of 172 nm, and/or a UV light source, and/or an IR light source, and/or an electron beam source, and/or a fan that blows air onto the workpiece (1.0) or its lacquer layers.

13. An apparatus for carrying out the method according to claim 1, comprising: a coating station and a device for feeding the workpiece (1.0) to the coating station; a first printing station for applying a first liquid layer (1.4) over an entire surface onto the workpiece (1.0) with a coarse structure; a second printing device for applying the second lacquer layer (1.5) to the first lacquer layer (1.4).

14. The apparatus according to claim 13, further comprising: at least one station for at least partial curing of the first and second lacquer layers (1.4, 1.5) a station for applying a third, liquid, at least partially transparent, lacquer layer in order to produce a fine structure in certain areas, and/or at least one printing roller that unrolls on a surface of the workpiece, and/or a station configured to apply at least one liquid base layer (1.1, 1.2), and/or a station configured to structure at least one base layer (1.1, 1.2), a station for drying and/or curing of at least an applied lacquer.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Below is a description of preferred embodiments of the invention with the aid of the accompanying drawings. In detail:

(2) FIG. 1 is a schematic cross-sectional view of a plate-shaped workpiece produced by means of the method of the invention.

(3) FIG. 2 is another schematic illustration of a plate-shaped workpiece produced by means of the method according to the invention with an indicated wood pore in plan view.

(4) FIG. 3 is a surface of a printed workpiece.

(5) FIG. 4 is a view of a workpiece according to the invention having several layers.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(6) FIG. 1 shows a plate-shaped workpiece 1.0 on which an optional first base layer 1.1 is provided on one surface. In addition, a decorative image, e.g. a wood reproduction or a tile image, is optionally printed on the workpiece 1.0 before the first base layer 1.1 is applied.

(7) In an alternative embodiment, a decorative image can also be printed on after application of the first base layer 1.1 or after application of a structured second base layer 1.2, for example using a single or multi-colour digital printer. Alternatively, the first base layer 1.1 can also be provided with a decorative image with several colours.

(8) A second liquid base layer 1.2 is applied to the first base layer 1.1. This second base layer 1.2 has been structured with digitally sprayed droplets 1.3, so that the surface is no longer flat, but has a structure and forms a first lacquer layer with a coarse structuring. Then a first lacquer layer 1.4 is applied, which has a first gloss level.

(9) A second lacquer layer 1.5 is then applied to the first lacquer layer 1.4 by droplet delivery via digital print heads to produce a fine structuring, whereby the second lacquer layer 1.5 only partially covers the surface of the first lacquer layer 1.4.

(10) Coatings 1.4 and 1.5 are cured one after the other or together, for example by UV radiation. After curing, the second lacquer layer 1.5 has a different gloss level than the first lacquer layer.

(11) Instead of structuring the second base layer 1.2 with digitally sprayed droplets 1.3, it is also possible to structure a base layer using other methods, for example by applying it only in certain areas or using embossing matrices, or using structured rollers that apply variable layer thicknesses. It is also possible to apply the decorative image to a structured surface instead of a flat surface.

(12) FIG. 2 shows a plan view of the plate-shaped workpiece 1.0 of FIG. 1 and it can be seen that the decorative image comprises a wood pore 2.5 and grained wood areas 2.4.

(13) The different areas of the wood pore 2.5 and the grained wood areas 2.4 can also have a different gloss level due to the second lacquer layer 1.5, whereby the decorative areas of the image and the different gloss areas are preferably congruent due to the lacquer application.

(14) In a further embodiment, a carrier plate made of a wood material, or a plastic plate, or a plate made of another material with a thickness of at least 4 mm, preferably 8 to 16 mm and external dimensions of at least 200 mm width and at least 400 mm length is first coated with a UV-curing, white base lacquer, for example with a quantity of about 20 g/qm. This white base lacquer is then cured under UV irradiation.

(15) The carrier plate is then fed to a digital printing device in which a printed image, for example a reproduction of small tiles as mosaics, a wood decor or another pattern, for example with a four-colour CMYK print, is applied.

(16) FIG. 3 shows an example of a printed image with two mosaic tiles in different colours printed on a plate-like workpiece 3.0, whereby bright mosaic tiles 3.1 and darker mosaic tiles 3.2 are provided.

(17) A variety of other colours of tiles or mosaics with pictorial representations can also be used in an alternative embodiment.

(18) Then a thin base lacquer layer 1.1 of 5 to 15 g/sqm of a UV-curing lacquer is applied to the workpiece 3.0 printed in this way and (partially) cured with UV light. In an alternative embodiment, this base lacquer layer can be completely omitted or replaced by a solvent lacquer or an aqueous acrylate lacquer, which is then dried, for example physically.

(19) A second base layer 1.2 is then applied to the first base layer 1.1 or alternatively directly to the printed image as a radiation-curing lacquer layer with coarse structuring, which is produced as described above, preferably on an acrylate basis, in a layer thickness of 100 to 500 μm. The base layer 1.2 can be applied by digital print heads or by printing rollers or other processes.

(20) Directly after the application of this second base layer 1.2, a transparent lacquer layer consisting of droplets 1.3 is applied to the still liquid layer, optionally by means of a digital print template with digital print heads, before curing.

(21) When applying these droplets 1.3 the droplet size can vary between 1 pL and 100 pL. The digital printing template used is the one that was also used to print the tile mosaic described above. This printing template is electronically modified beforehand so that only the interspaces 3.3 of the mosaic tiles 3.1 and 3.2 are printed so that recesses corresponding to a joint pattern are made in the second base lacquer layer 1.2. Then the radiation-curing base lacquer layer 1.2 is cured together with the droplets 1.3 by a UV lamp. In an alternative embodiment, curing can also be performed using electron radiation.

(22) The result is a carrier plate printed with a tile mosaic in which the interspaces 3.3 are recessed by 10 μm to 60 μm as joints between the mosaic tiles 3.1 and 3.2.

(23) Subsequently, the gloss level of at least parts of the entire surface is adjusted to the desired value by at least partial application of a first lacquer layer 1.4 with subsequent drying, whereby the gloss level of the sprayed droplets 1.3 deviates from the gloss level of the second lacquer layer 1.4.

(24) In an alternative embodiment, the additional application of a third lacquer layer 1.5 can also be carried out before or after the second lacquer layer 1.4 has cured, whereby the third lacquer layer 1.5 also consists of a large number of droplets with a size of 3 to 100 pL dispensed onto the surface. With this third lacquer layer, both the gloss level can be changed again in some areas and the surface structure depth of the uncured lacquer layer 1.4 can be influenced.

(25) The lacquer layers 1.4 and 1.5 can also be completely omitted if the gloss level is changed by applying the first lacquer layer 1.3 concomittantly with application of the second base lacquer layer 1.2 for structuring.

(26) The surface of the mosaic tiles 3.1 and 3.2 now has a value of 60 to 90 gloss units, for example, while the gloss level at the interspaces 3.3 is only 20 to 40 gloss units, for example.

(27) Optionally, the gloss level at the interspaces 3.3 can also be reduced by a further lacquer layer, which is subsequently printed into the recessed interspaces by a further digital printing device with a transparent, UV-curing lacquer. Then more than just two lacquer layers are applied to adjust the gloss level.

(28) For printing a rather matte lacquer layer, droplet sizes of 3 to 6 pL are used, which are cured within 0.5 to 2 seconds after impact on the surface by means of UV LED radiation to such an extent that they can no longer flow. This creates a surface structure in these areas that no longer reflects the incident light in a straight line. The gloss level is thereby reduced to values of 30 gloss units or less, preferably to 15 gloss units or less.

(29) In the method of the invention, the second lacquer layer can have either a higher or lower gloss level than the first lacquer layer. The gloss level can be adjusted using the following methods, for example:

(30) Option 1:

(31) Matte areas through the first lacquer layer consist of previously (analog or digital) applied matte lacquer, for example with matting agents or by an excimer matting.

(32) Glossy areas of the second lacquer layer consist of lacquer applied by digital print heads, which lacquer is formed from a plurality of individual droplets, which results in a very smooth surface in certain areas and thus a high gloss level.

(33) The droplets have a size of at least 6 pL, and curing only takes place after a progression phase of at least 1 sec, preferably after more than 5 sec.

(34) Option 2:

(35) The glossy areas of the first lacquer layer consist of previously (analog or digital) applied glossy lacquer.

(36) Matte areas of the second lacquer layer consist of digitally applied lacquer consisting of a plurality of smallest droplets having a droplet size of less than 8 pL, preferably less than 3 pL, which are at least partially cured within less than 3 seconds after application, preferably less than one second after application.

(37) Both options preferably employ curing by a UV-LED lamp, which is arranged in the direction of throughput, for example within less than 100 mm after the digital print heads, which apply the plurality of droplets to the surface.

(38) Matting agents, such as PE waxes or silicas, can be added to the lacquer to produce a matte lacquer layer. The proportion of matting agents in the lacquer can be between 2% to 6%, in particular 3% to 5% (weight percent).

(39) The different Examples of FIGS. 1 to 3 can be combined with one another as desired with regard to the application and structuring of a layer. The number of layers on the workpiece can also be freely selected, depending on the surface structure to be created with the method.

(40) In alternative embodiments of the method according to the invention, acrylate-containing, UV-curing lacquers used as the lacquers can be replaced by aqueous or solvent-based lacquers. In this case, the steps for UV drying by means of UV LED or UV arc lamp are replaced by physical drying by means of hot air or IR lamps or a combination of both.

(41) FIG. 4 shows another example of a coated plate-shaped workpiece 4.1.

(42) A workpiece 4.1, for example a panel made of a wood-based material with a width of 200 to 2000 mm and a length between 500 and 3000 mm as well as a thickness between 8 mm and 18 mm, is fed to a coating station. The workpiece 4.1 is already printed with a decorative image, such as a wood reproduction, e.g. an oak decor.

(43) Alternatively, a plastic plate, a plate made of WPC, HDF, MDF, metal, in particular as coil material, can also be used as workpiece 4.1.

(44) In the coating station, a smooth intermediate lacquer layer 4.2, such as an adhesive base or primer, is optionally applied. Subsequently, by means of a laser-engraved rubber roller, a radiation-curing, transparent first lacquer layer 4.3 of 100 to 200 g/m2 is applied to the workpiece 4.1, whereby the engraving in the rubber roller creates, for example, the structure of a coarse wood pore on the surface. Other structures are also possible, such as a tile finish.

(45) The height differences between the “pore valleys” and the elevations, i.e. the thickness differences of the first lacquer layer 4.3, are between 50 μm and 300 μm (micrometers) and form a coarse structure. The applied lacquer is then cured with a UV lamp.

(46) In an alternative embodiment, a decorative image 4.4 can be printed on the thus structured surface after curing using a digital printer with four-colour printing if no image was on the workpiece before the coating. In this case, the lacquer layer 4.3 may also be coloured, for example white. Otherwise, an existing image can be added or changed.

(47) A further liquid lacquer layer 4.5 is applied to the now cured lacquer layer 4.3 with or without the coloured decorative printing layer 4.4 in a further coating station by means of a smooth rubber roller.

(48) Then the workpiece 4.1 is fed to a digital printing station 4.6, where a plurality of droplets 4.7 are applied into the still liquid lacquer layer 4.5 according to a digital image template, which provide the still liquid lacquer layer 4.5 with a fine structure. The digital image template is matched to the previously printed decorative image, for example rustic oak, in such a way that the optically recognizable image details, such as a knot hole or a black printed crack in the wood, exactly spatially match the structure printed into the liquid pore. This allows the end user to feel the optically printed knothole. At the same time, the very deep and coarse structure of the lacquer layer 4.3, which emphasizes the rustic character of the oak reproduction, is located above.

(49) Further aspects are explained below.

(50) A first aspect is a method of producing a decorative surface with different gloss levels, comprising the following steps: Feeding of a workpiece 1.0 to a lacquer application device; Coating of the workpiece 1.0 with at least a first lacquer layer 1.4; Feeding of the workpiece to a digital printing station; Provision of digital control data for the digital printing station; Digital spraying of droplets on partial areas of the first lacquer layer 1.4 on the workpiece 1.0 with an at least partially transparent lacquer in order to apply a second lacquer layer 1.5 to the first lacquer layer 1.4, the second lacquer layer 1.5 having a different gloss level than the first lacquer layer 1.4 after the curing, and physical drying and/or chemical curing of the applied lacquer layers 1.4, 1.5.

(51) A second aspect of the method described above is that the workpiece 1.0 is already printed with a decorative image before being fed to a lacquer application device, or that the workpiece 1.0 is printed with at least two different colours using a digital printer after being fed to a lacquer application device and before being coated with at least a first lacquer layer 1.4.

(52) A third aspect of the method according to one of the two preceding aspects is that the digital print data available for the decorative image on the workpiece is used in identical form or in a form modified by a digital manipulation method as a basis for the digital data provided.

(53) A fourth aspect of the method according to one of the three preceding aspects is that the lacquer layer 1.4 applied to coat the workpiece 1.0 is at least partially cured before the digital spraying of droplets by an additional method step.

(54) A fifth aspect of the method according to one of the four preceding aspects is that the gloss level of the first lacquer layer 1.4 deviates by at least 10 gloss units, preferably at least 20 gloss units, from the gloss level of the second lacquer layer 1.5, wherein the gloss units are measured according to DIN EN ISO 2813:2015-02 at an angle of 60°.

(55) A sixth aspect of the method according to one of the five preceding aspects is that during the digital spraying of the droplets, droplets with a droplet size smaller than 10 pL, in particular smaller than 6 pL, are sprayed.

(56) A seventh aspect of the method according to one of the six preceding aspects is that the surface of the workpiece 1.0 has a structure with a structure depth of 5 to 300 μm (micrometer), preferably 10 to 90 μm (micrometer), before the second lacquer layer is applied.

(57) An eighth aspect of the method according to one of the seven preceding aspects is that a transparent lacquer layer is applied to an existing decorative image with the first lacquer layer 1.4.

(58) A ninth aspect of the method according to one of the eight preceding aspects is that a liquid base layer 1.2 is applied to a surface of the coated or uncoated workpiece 1.0 and a structure is introduced into the still liquid base layer 1.2 by means of digital print heads, which structure is subsequently fixed, wherein the structured base layer is the first lacquer layer 1.4 or the first lacquer layer 1.4 is applied to the structured base layer.

(59) A tenth aspect of the method according to the ninth aspect is that only the areas provided with a structure or only the areas without a structure are printed with the second lacquer layer 1.5.

(60) An eleventh aspect of the method according to one of the ten preceding aspects is that the two lacquer layers 1.4, 1.5 are applied from an at least partially transparent lacquer, so that a decorative image arranged below the two lacquer layers 1.4, 1.5 can be optically recognized therethrough.

(61) A twelfth aspect of the method according to one of the eleven preceding aspects is that the second lacquer layer 1.5 produces a glossy or high-gloss surface or a matte or less glossy surface.

(62) A thirteenth aspect of the method according to one of the twelve preceding aspects is that the first and/or second lacquer contains matting agents, preferably in a weight proportion between 2% and 6%, in particular between 3% and 5%.

(63) A fourteenth aspect of the invention is an apparatus for carrying out the method according to one of the aspects described above, comprising a first printing device for applying a first lacquer layer 1.4 and a second digital printing device for applying a second lacquer layer 1.5 onto the first lacquer layer 1.4, wherein after curing the second lacquer layer 1.5 has a different gloss level than the first lacquer layer 1.4.

(64) A fifteenth aspect is a method of producing a decorative work piece with a structured surface comprising the following steps: Feeding of the workpiece to a coating station; Application of a first liquid lacquer with a coarse structure, in which a difference in thickness between thicker areas and thinner areas is at least 50 μm, in particular at least 100 μm, over the entire surface; at least partial hardening of the applied first lacquer; Application of a decorative image by multicolour printing before the application of the first liquid lacquer or after at least partial curing of the applied first lacquer; Application of a second liquid, at least partially transparent, lacquer to create a fine structure in certain areas; Curing of the second lacquer, wherein the difference in thickness in the area of fine structuring on the second lacquer layer is less than 50 μm, in particular less than 30 μm.

(65) A sixteenth aspect of the method according to the fifteenth aspect is that the gloss level in the area of fine structuring is different by at least 10 gloss units as compared to that of coarse structuring.

(66) A seventeenth aspect of the method according to the fifteenth or sixteenth aspect is that the first lacquer is applied with at least one printing roller that unrolls on a surface of the workpiece.

(67) An eighteenth aspect of the method according to any one of the fifteenth to seventeenth aspects is that the second lacquer is applied by at least one digital print head.

(68) A nineteenth aspect of the method according to any one of the fifteenth to eighteenth aspects is that the material for the first and second lacquers is identical.

(69) A twentieth aspect of the method according to one of the fifteenth to nineteenth aspects is that a liquid lacquer is first applied to produce the second lacquer layer and then droplets of the second lacquer layer are sprayed into the still liquid material to produce a fine structure.

(70) A twenty-first aspect of the method described in the previous paragraph is that the lacquer droplets are made of the same material as the liquid layer and/or that a plurality of lacquer droplets are applied to the still liquid lacquer layer with digital print heads, wherein each lacquer droplet has a volume of less than 10 pL, and the speed of each lacquer droplet upon impingement on the still liquid lacquer layer is greater than 1 m/s.

(71) An alternative aspect to the method described in the previous paragraph is that the lacquer droplets are made of a material other than the liquid lacquer and, after impact, undergo a chemical reaction with the liquid lacquer which changes the surface optically or haptically at the respective areas and/or volatilise according to a physical reaction by evaporation within less than five minutes after impact with the liquid lacquer.

(72) Another aspect of the method according to one of the previous eight paragraphs is that at least one intermediate layer is applied between the workpiece and the first lacquer layer.

(73) Another aspect of the invention is an apparatus for carrying out the method according to one of the preceding aspects, comprising: a coating station and a device for feeding the workpiece to the coating station; a first printing station for applying a first liquid lacquer over the entire surface of the workpiece with a coarse structuring, in which a difference in thickness between thicker areas and thinner areas is at least 50 μm, in particular at least 100 μm; a station for at least partial curing of the first lacquer; a station for applying a second liquid, at least partially transparent, lacquer for producing a fine structure in certain areas, and a station for curing the second lacquer, wherein the thickness difference in the area of the fine structuring on the second lacquer layer is less than 50 μm, in particular less than 30 μm.

(74) The aspects and embodiments of the invention described herein do not restrict the subject matter of the invention. Rather, further subject-matter, which also fall within the scope of protection of this application, can be obtained by combining individual features of the embodiments and aspects.

LIST OF REFERENCE SIGNS

(75) 1.0 Workpiece 1.1 First base layer 1.2 Second base layer 1.3 Digitally sprayed droplets (third lacquer layer) 1.4 First lacquer layer 1.5 Digitally sprayed droplets (second lacquer layer) 2.4 Grained wood areas 2.5 Wood pore 3.0 Workpiece 3.1 Light-coloured mosaic tiles 3.2 Darker mosaic tiles 3.3 Interspaces 4.1 Workpiece 4.2 Intermediate lacquer layer, e.g. adhesive base/primer 4.3 Analogously applied structured lacquer 4.4 Digital decor printing 4.5 Liquid lacquer layer 4.6 Digital printing station 4.7 Droplets