Method for producing a directly printed panel

Abstract

The present invention relates to a panel as well as a method for producing a panel, in particular a wall- ceiling- or floor panel. The method according to the invention provides that a layer of liquid radiation curing acrylate with a low Martens hardness is applied on a support layer in a first step. This is followed by an application of an intermediate layer in a second step and thereafter the application of a further layer wet-on-wet, which as a Martens hardness after curing which is larger than the Martens hardness of the first applied layer. The resulting panel has an intermediate layer with an inhomogeneous hardness profile due to the wet-on-wet application which leads to particularly advantageous properties.

Claims

1. A method for producing a panel, in particular a wall, ceilingor floor panel, comprising the following steps in the indicated order: (a) providing a support plate having a front side; (a1) applying a primer layer on the front side of the support plate and printing with a printing ink a decorative layer on the primer layer; (b) applying a layer of liquid radiation-curing acrylate on the decorative layer, which has a Martens hardness M.sub.S1 0.5 to 120 N/mm.sup.2 after curing; (c) at least partially curing of the applied layer of liquid radiation-curing acrylate by radiation in step (b); (d) repeating the steps (b) and (c) until a first elastic layer S.sub.1 with a thickness of 10 to 600 ?m is available; (e) applying an intermediate layer of liquid radiation-curing acrylate on the at least partially cured layer; (f) applying a second layer S2 of liquid radiation-curing acrylate by means of a film on the previously applied uncured intermediate layer, so that a partial mixing of the layers takes place, wherein the second layer is an acrylate, which comprises a Martens hardness M.sub.S2 after curing, wherein M.sub.S2>M.sub.S1; (g) curing together of at least the applied layers of steps (e) and (f) by means of radiation; and wherein a third elastic layer S3 having a thickness of 30 to 150 ?m is provided between the front side of the support plate and the decorative layer, which third elastic layer after curing has a Martens hardness M.sub.s3 with M.sub.S3?M.sub.S1; and wherein, after curing, the hardness of the elastic layer S1 is essentially constant over the entire thickness and the hardness differences within the layer is less than 20 N/mm.sup.2.

2. The method according to claim 1, wherein the printing ink is a polymerizable printing ink.

3. The method according to claim 2, wherein the printing ink and at least the first applied layer of liquid radiation-curing acrylate are cured together by radiation.

4. The method according to claim 1, wherein after curing M.sub.S1 is of 2 to 50 N/mm.sup.2.

5. The method according to claim 1, wherein after curing, M.sub.S2 is of 5 to 300 N/mm.sup.2.

6. The method according to claim 1, wherein the steps (b) and (c) are repeated until the first elastic layer S1 has a thickness of 40 to 500 ?m.

7. The method according to claim 1, wherein the applying in steps (b) and (e) takes place via rollers.

8. The method according to claim 1, wherein the film for applying the second layer of liquid radiation-curing acrylate is a structuring film.

9. The method according to claim 1, wherein the applied intermediate layer in step (e) is an acrylate, which comprises a Martens hardness M.sub.Z after curing, wherein
M.sub.S2 is >M.sub.Z?M.sub.S1.

10. The method according to claim 1, wherein the support plate is a MDF-plate, HDF-plate, PVC-plate, cement fiberboard, WPC-plate (Wood Powder Composite), thermoplastic recycling board, wood panel, wood veneer plate or parquet plate.

11. The method according to claim 1, wherein the acrylates are aliphatic acrylates.

12. A panel, in particular a wall, ceiling, or floor panel, comprising: a support plate with a front side and a back side, and a layer system at least on the front side of the support plate, wherein the layer system starting from the front side comprises: a first elastic layer S1 of an aliphatic polymer, which has a thickness from 40 to 600 ?m and a Martens hardness M.sub.S1 of 0.5 to 120 N/mm.sup.2; a second layer made of a polymer, which has a thickness of 10 to 180 ?m and a Martens hardness M.sub.S2, wherein
M.sub.S2 is >M.sub.S1; an intermediate area between the first elastic layer and the second layer, the intermediate area having a Martens hardness M.sub.ZB, wherein
M.sub.S2 is >M.sub.ZB?M.sub.S1; and wherein the first elastic layer S1 is at least partially cured by UV radiation before the intermediate area ZB and the second layer S2 are formed on the first elastic layer S1, and a decorative layer between the front side of the support plate and the first elastic layer, the decorative layer consisting of printing ink, wherein a third elastic layer S3 is provided between the front side and the decorative layer, which has a Martens hardness M.sub.S3 with M.sub.S3?.sub.MS1; wherein the third elastic layer S3 has a thickness of 30 to 150 ?m; and wherein the hardness of the first elastic layer S1 is essentially constant over the entire thickness and the hardness differences within the layer is less than 20 N/mm.sup.2.

13. The panel according to claim 12, wherein M.sub.S1 is between 2 and 50 N/mm.sup.2.

14. The panel according to claim 12, wherein M.sub.S2 is between 5 and 300 N/mm.sup.2.

15. The panel according to claim 12, wherein the first elastic layer has a thickness of 40 to 500 ?m.

16. The panel according to claim 12, wherein the support plate comprises nut- and spring elements at it sides, which allow a connection of several similar panels in directions parallel to the front side as well as perpendicular to the front side by a form fit.

17. The panel according to claim 12, wherein the polymer of the first elastic layer is based on an aliphatic urethane acrylate.

18. The panel according to claim 12, wherein the third elastic layer has a thickness of 60 to 120 ?m.

19. The panel according to claim 12, wherein the printing ink is based on a polymerizable acrylate and/or N-vinylcaprolactam.

20. The panel according to claim 12, wherein the printing ink of the decorative layer and at least a part of the first elastic layer were cured together.

21. The panel according to claim 12, wherein the decorative layer has been applied by digital printing.

22. The panel according to claim 12, wherein the polymer of the second layer is based on one or more of the following acrylates: 1,6-hexanediol diacrylate, polyester acrylate, polyurethane acrylic acid ester and dipropylene glycol diacrylate.

23. The panel according to claim 12, wherein the support plate has a thickness between 3 and 20 mm.

24. The panel according to claim 12, wherein the support plate is a MDF-plate, HDF-plate, PVC-plate, cement fiberboard, WPC-plate (Wood Powder Composite), thermoplastic recycling plate, wood plate, wood veneer plate or parquet plate.

25. The panel according to claim 12, wherein no paper or plastic foil is provided at the front side of the panel.

26. The panel according to claim 12, wherein the first elastic layer, second layer and third elastic layer were radiation cured.

27. The panel according to claim 12, wherein the panel is not provided with abrasion-resistant particles.

28. The panel according to claim 12, wherein the layer system has a damping effect of at least 5 dB compared to the uncoated support plate as measured by EPLF standard.

29. The panel according to claim 12, wherein the hardness differences within the first elastic layer are less than 15 N/mm.sup.2.

Description

4. DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) In the following, the present invention is explained in more detail with reference to the accompanying figures.

(2) FIGS. 1a and 1 b are exemplary layer structures in a schematic representation; and

(3) FIG. 2 is an exemplary system for the production of the panel according to the invention in a schematic view.

(4) A schematic layer structure of a panel 10 according to the invention is shown in FIG. 1a. The representation is purely schematic and not scaled. In particular, the support plate 11 is considerably thicker than the further layers 12-18 which are in the range of a few hundred ?m. In addition, the individual layers are partially shown in an exploded view for ease of understanding and are all directly adjacent to each other or arranged in direct succession in the real case.

(5) In the example as shown, a support plate 11 with a thickness of about 8 mm of HDF material is shown. A moisture barrier 13 is glued in the form of a suitable plastic film at the back side of the support plate 11. This moisture barrier is optional and depends on the material for the support plate 11 and the desired application. The support plate 11 additionally comprises coupling means in the form of nut-15 and spring elements 14 which are, however, only indicated schematically in FIGS. 1a (and b). Suitable coupling means in the form of nut- and spring elements are known to the person skilled in the art which allow connecting a plurality of similar panels in the directions parallel to the front side as well as perpendicular to the front side by a form fit. Usually, herefore, respective complementary connecting means opposite to each other are provided at the four sides of a rectangular or square support plate. Details for such as connecting means or locking profiles are known to the person skilled in the art from the technology of production of laminate floors, such as e.g. from WO 0188306 or WO 0148332 of the same applicant, which are incorporated by reference herein.

(6) A primer layer 16 with a thickness of for example 50-200 ?m is provided in the shown structure system which is based on an aqueous acrylate system. Further very thin primer layers and/or also filler layers are applied below the primer, as are known to the person skilled in the art in the field of directly printed panels. A decorative layer or a decor 18 is printed on the primer. The decor 18 or the decorative layer 18 is applied for example by means of polymerizable printing ink in the digital four-color printing. A first elastic layer S1 with a thickness of 200 ?m and a Martens hardness M.sub.S1 of about 15 N/mm.sup.2 is provided above the decorative layer 18. A second layer S2 is applied on the first elastic layer S1 which has a thickness of 80 ?m and a Martens hardness of about 25 N/mm.sup.2. An intermediate area ZB is provided between the two layers S1 and S2, which is generated by the fact that the intermediate layer and the layer S2 were applied wet-on-wet, leading to a partial mixing of liquid starting material at the boundary layer of the two layers (Lagen) or layers (Schichten). This is visualized schematically by different density of points in the figures.

(7) The example of FIG. 1b corresponds to the example of FIG. 1a with the difference that here a further elastic layer S3 is provided between the primer layer 16 and the decorative layer 18. Thereby, preferably, the layer S3 has a Martens hardness M.sub.S3 which is less than the Martens hardness of the layer S1, so M.sub.S3?M.sub.81. The first layer S1 can be designed slightly thinner than in the example of FIG. 1a, in example of FIG. 1b which is schematically indicated by different thicknesses in the figures.

(8) In the following, the production of a panel according to the invention is intended to be described exemplary with reference to FIG. 2. FIG. 2 schematically shows a coating system for coating of support layers 100. The support plates are cut in a separate profiling line (not shown) and are profiled after coating. For example, the support plates 100 have a thickness between 3 and 20 mm, a length (as seen in the transport direction of the system of FIG. 2) of 150-200 cm and a width of 125-210 cm. However, any other panel dimensions can be used for the support plates, which are cut in the desired shape and size at the end of the process. The stations of the system which are shown in FIG. 2 are not intended to be exhaustive, but serve only as an example to explain the method according to the invention. Further processing stations can be provided before, behind and between the shown stations, such as for example additional drying stations, stations for applying primers, stations for applying filler, control and monitoring devices, etc. The support plates 100 are transported by roller conveyors 20 through the coating system.

(9) In the first depicted station 30 a primer is applied by means of a fluid curtain 31 of the coating material on the front side (main side) of the support plates 100. The liquid curtain 31 extends over the entire panel width and the plates are transported through this curtain and coated thereby. A collecting container 32 is provided below the device 30 to output the curtain into which the liquid curtain falls when no plate is passed through the curtain, as for example in the gap between two consecutive plates. Preferably, an aqueous acrylic dispersion is used as a coating material for the primer. The applied primer is dried with hot air in a subsequent drying station 40, that is water is removed from the acrylic dispersion. A decorative layer is printed on the primer by means of a digital printing system 45 after the drying of the primer. This decorative layer can for example imitate a real wood, however the digital printing systems commercially available today are able to practically print any desired decor or pattern on the plates. Preferably, a printing ink is used in the printing system 45, which is polymerizable by means of radiation, that is a printing ink, which is based on a polymerizable acrylate and/or N-Vinylcaprolactam. It is clear to the person skilled in the art that the illustration of the digital printing system 45 is purely schematic and that such printing systems usually consist of several stations. A first layer of liquid radiation-curing aliphatic acrylate is applied in a first coating system 50 after the printing of the desired decor. The material is selected such that it comprises a Martens hardness M.sub.S1 of 0.5 of 120 N/mm.sup.2 after curing. The system 50 is a roller application system and is capable of applying a layer of layer thickness of about 40-100 ?m applied in one operation. The applied layer of liquid radiation-curing aliphatic acrylate is partially cured by means of UV-radiation in the subsequent station 60. This is followed by a second system 50 for applying a second layer of the same liquid radiation-curing acrylate as the first layer. Again, the station 50 is a roller application station which is usually capable of applying layer thicknesses of 30-100 ?m. This second layer is cured by UV radiation at least partially in station 60. The two cured layers form the layer S1.

(10) Subsequently, an intermediate layer made of the same liquid radiation-curing acrylate is applied in a third coating system 70 as applied in the stations 50 and 60. However this intermediate layer is not cured, but fed to a film calender 80 wet. It is clear to the person skilled in the art that the film calender 80 is only schematically outlined in FIG. 2 to illustrate the individual method steps. In the film calender 80 a structure film 82 is guided around rollers 81. The support plates 100 are guided through below the film 82, so that the film 82 lies on the upper side of the plates 100. If desired, the film 82 can additionally also be pressed against the upper sides of the plates 100 by pressure rollers. A coating material 84 is fed to the film 82 by a coating station 83 which should be applied on the upper side of the plates 100 or on the still wet or moist applied intermediate layer at the station 70, so that it comes to a partial mixing of the two layers at the boundary layer. By this mixing, the later product comprises an intermediate area, during which the hardness M.sub.ZB is not constant, but increases from the layer S1 to layer S2. In station 90, both layers are possibly completely cured by UV-radiation. For this purpose, the film 82 is UV-permeable, so thatas shown in FIG. 2 shown schematicallythe curing of the layers takes place, while the film is still arranged thereon. Since the film preferably comprises a three-dimensional structure, the negative image of this structure in the cured layers or the hardened layer S2 is impregnated and fixed. Thus, it is possible for example to give the finished panels a three-dimensional wooden structure in order to achieve a realistic imitation of a real wood surface. At the output of the film calender 80 the foil 82 is removed from the surface of the plates and the coating material 84 remains as a hardened layer S2 on the plates.