Method and device for producing a structured varnish surface

Abstract

The invention relates to a method for producing a structured, at least partly optically transparent varnish surface on a surface of a substrate board, preferably of a wood material board, having a decoration. The steps of the method include applying a transparent or at least partly transparent varnish to an applicator roll thereby producing a structured varnish surface and transferring the structured varnish surface to a substrate board having a decoration. The varnish is applied to the applicator roll by a plurality of digitally controlled nozzles in a distribution defining a structure and/or is transformed on the applicator roll into a distribution defining a structure. Furthermore, a device for carrying out the method is described.

Claims

1. A method for producing a structured, at least partly optically transparent varnish surface on a surface of a substrate board comprising the steps of: applying a transparent or at least partly transparent varnish as a film of varnish to an applicator roll, transforming the film of varnish on the applicator roll, by a plurality of digitally controlled nozzles, into a distribution defining a three dimensional structure, and transferring the structured varnished surface by the applicator roll to the substrate board having a decoration.

2. The method according to claim 1, wherein the varnish is transformed into such a distribution on the applicator roll that the structure resulting from the distribution of the structured varnish surface produced on the surface of the substrate board defines pores which match a decor image of the decoration.

3. The method according to claim 1, wherein before the varnish is transferred to the substrate board a decor image of the decoration or a guide mark placed on the substrate board is detected by an optical scanner, and measuring signals generated by the optical scanner are used to control the digitally controlled nozzles.

4. The method according to claim 1, wherein the varnish applied to the applicator roll is pre-dried or pre-cured on the applicator roll.

5. The method according to claim 1, wherein the varnish is applied as the film of varnish to the applicator roll by a metering roll and/or by a doctor.

6. The method according to claim 1, wherein the applicator roll comprises a substantially smooth applicator roll varnish-receiving lateral surface region.

7. The method according to claim 1, wherein the applicator roll is a rubberised and/or bowed applicator roll.

8. The method according to claim 1, wherein the varnish contains hard particles.

9. A device for producing a structured, at least partly optically transparent varnish surface on a surface of a substrate board, comprising: an applicator roll for transferring a structured varnish surface to a surface of a substrate board having a decoration; and a plurality of digitally controlled nozzles wherein the nozzles are configured to transform on the applicator roll a transparent or at least partly transparent varnish, which has been applied to the applicator roll as a film of varnish, into a distribution defining a three-dimensional structure.

10. The device according to claim 9, wherein the digitally controlled nozzles are arranged in at least one row along the rotational axis of the applicator roll.

11. The device according to claim 9 wherein the device further comprises an optical scanner, wherein the optical scanner is arranged upstream of the applicator roll in a feed direction of the substrate board to detect a decor image of the decoration or a guide mark placed on the substrate board, wherein the optical scanner is connected to a controller, and wherein the controller digitally controls the nozzles, subject to the measuring signals generated by the scanner.

12. The device according to claim 9, wherein the digitally controlled nozzles are formed as gas nozzles.

13. The device according to claim 9, further comprising a radiation emitter or a heater, wherein the radiation emitter or the heater is associated with the applicator roll and configured to pre-dry or pre-cure the varnish applied and structured on the applicator roll.

14. The device according to claim 9, wherein a metering roll and/or a doctor, are associated with the applicator roll to produce the film of varnish on the applicator roll.

15. The device according to claim 9, wherein the applicator roll comprises a substantially smooth varnish-receiving lateral surface region.

16. The device according to claim 9, wherein the applicator roll is rubberised and/or bowed.

17. The method according to claim 1, wherein the digitally controlled nozzles are formed as digitally controlled gas nozzles.

18. A device for producing a structured, at least partly optically transparent varnish surface on a surface of a substrate board, comprising: an applicator roll for transferring a structured varnish surface to a surface of a substrate board having a decoration; and a plurality of digitally controlled nozzles wherein the nozzles are configured to transform on the applicator roll a transparent or at least partly transparent varnish, which has been applied to the applicator roll as a film of varnish, into a distribution defining a structure, wherein the device further comprises an optical scanner, wherein the optical scanner is arranged upstream of the applicator roll in a feed direction of the substrate board to detect a decor image of the decoration or a guide mark placed on the substrate board, wherein the optical scanner is connected to a controller, and wherein the controller digitally controls the nozzles, subject to the measuring signals generated by the scanner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a side view of a device or installation having a plurality of print stations for producing board-shaped products having a decorated surface;

(2) FIG. 2 shows a first embodiment of an applicator device according to the invention; and

(3) FIG. 3 shows a second embodiment of an applicator device according to the invention.

DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a device or installation for producing board-shaped products, for example furniture construction boards or floor, wall or ceiling panels, having a decorated surface.

(5) A plurality of board-shaped workpieces 1 are arranged on a conveyor belt 2 and are individually fed successively to various processing stations 3, 4, 5 and 6. The feed direction of the workpieces 2 is indicated by an arrow and runs from left to right. Instead of a plurality of single workpieces 1, one large-area workpiece or a continuously produced workpiece can also be processed, which is divided into individual boards (blanks) after being processed as described in the following. The conveyor belt speed or feed rate of the workpieces 1 is, for example, within a range of from 1 to 120 m/min.

(6) The board-shaped workpiece 1 acts as a substrate and can therefore also be called a substrate board.

(7) The workpiece or substrate board 1 is produced from wood material, from laminate and/or from at least one compact board. Compact boards are produced from resin-impregnated cellulose webs which are pressed in laminate presses under high pressure and at elevated temperatures. However, the substrate boards 1 are preferably ground wood material boards, for example chipboard, medium-density fibreboard (MDF), high-density fibreboard (HDF) or hardboard.

(8) After an optional brushing station (not shown) which removes impurities or grinding dust which may be present, fillers are applied in several stages, preferably by applicator rolls (not shown), an intermediate drying procedure being carried out after each stage. A primer coat kept in the basic colour of a subsequently printed-on decoration is then applied, again in several stages, to the thus present substrate board 1 by rolls (not shown) and here again a partial drying is carried out after each application.

(9) The primed substrate board 1 is then preferably smoothed. This is performed, for example, using heated polished steel rolls (not shown) which are operated over the width of the substrate board 1 and pressed against said substrate board 1 at a peripheral rotational speed greater than or less than the feed rate of the substrate boards 1. Thereafter, the substrate board 1 processed thus exhibits over its entire upper side a surface which is even and uniform in colour, gloss level and structure.

(10) Directly following the optional smoothing device (not shown), a decoration (decor image), for example a wood, natural stone or tile decoration, is printed onto the substrate board 1. The decor image is preferably printed onto said board 1 by one or more print roll assemblies 3.1, 4.1. The respective print roll assembly 3.1, 4.1 is typically constructed from an engraved print roll (print cylinder) 3.11, 4.11 with inking and dampening rolls and a blanket cylinder 3.12, 4.12 with a counter-pressure cylinder. This printing method is also known as indirect gravure printing.

(11) Instead of one or more print roll assemblies 3.1, 4.1, according to the invention it is also possible to use a digital printer device (not shown), in particular an ink-jet printer device, to print a desired decor image onto the substrate boards 1. The digital printer device is preferably controlled such that the decor image is varied so that no substrate boards 1 or practically no substrate boards 1 are produced with identical decor images. For this purpose, the digital printer device is connected, for example, to a computer which varies the size, shape and/or position of one or more decor image elements, for example the image of a wood grain, of heartwood and sapwood, of a knot (knot cross section), resin galls, burrs, age rings, burrows (for example woodworm holes/passages), nail heads, screw heads, etc, according to the random principle and controls the digital print heads of the printer device accordingly.

(12) Post-processing devices 3.2, 4.2 are arranged downstream of the digital printer device or print roll assemblies 3.1, 4.1. The respective post-processing device 3.2, 4.2 can carry out a drying or partial drying of the printed decor image, for example by a stream of hot air or by high-energy and/or electromagnetic radiation, in particular UV radiation.

(13) Following the digital printer device or print roll assembly 4.1 or the post-processing device 4.2 is optionally at least one processing station 5 which applies a sealing layer (wear-protection layer) to the decoration.

(14) A transparent UV-curable varnish coating is preferably applied in at least two stages as the sealing of the decoration. The sealing varnish can contain corundum particles and/or other particles which increase the wear resistance. If the decorative boards 1 to be produced are boards which are not exposed to a high abrasive stress, for example furniture parts, particularly back walls of cupboards, then the sealing varnish can also be free from corundum particles or other particles which increase wear resistance. Alternatively or in addition to wear-resistance-increasing particles, the sealing varnish can contain further additives, for example scratch-resistance-increasing additives and/or antistatic agents.

(15) In processing station 5, a substantially full-surface coating of a UV-curable, transparent sealing varnish is applied. For this purpose, processing station 5 has an applicator roll 5.1 which applies a uniform layer of varnish to the upper side of the substrate board 1 printed with the decoration. The applied coating is at least partly dried and cured in the post-processing device 5.2 connected downstream.

(16) In a further processing station 6, an at least partly optically transparent, three-dimensionally structured layer of varnish 1.1 is applied to the surface, having the decoration, of the substrate board 1, the decor image of which has preferably been coated with a transparent sealing layer. According to the invention, this is performed indirectly by a plurality of digitally controlled nozzles 6.1 combined with an applicator roll 6.2. The varnish used for this purpose is preferably a UV-curable varnish.

(17) By means of a post-processing device 6.3, following applicator roll 6.2, then the last applied varnish layer 1.1 is at least partly cured, so that the three-dimensional structure is fixed. Reference numeral 1′ denotes the ready coated substrate board. Processing station 6 for producing the structured, at least partly optically transparent varnish surface 1.1 can be realised in different embodiments.

(18) In the embodiment shown in FIG. 2, a plurality of digitally controlled nozzles 6.1 as print heads (varnish jet nozzles) is associated with applicator roll 6.2. The nozzles or print heads 6.1 are arranged in at least one row and preferably cover the entire roll width (axial roll length). Depending on the desired print speed, a plurality of rows of print heads can also be provided, which is indicated in FIGS. 1 and 2 by a dotted row of print heads. In this respect, the print heads 6.1 of one row are preferably arranged offset to the print heads 6.1′ of the row of print heads running parallel thereto, i.e. they are arranged in the gaps between the print heads of the parallel row of print heads. The print heads 6.1, 6.1′ are positioned at a short distance above the applicator roll 6.2, whereas the applicator roll 6.2 delivers the printed-on structure varnish to the substrate board 1 by contact therewith. The lateral surface of applicator roll 6.2 is substantially smooth or slightly structured. Furthermore, applicator roll 6.2 is preferably rubberised and bowed. The bowing, i.e. the specifically barrel-shaped bulge of applicator roll 6.2 towards the centre thereof, compensates the deflection of roll 6.2 which, in the case of a purely cylindrically shaped roll, would result in an application thickness which would not be uniform over the width.

(19) Analogously to the indirect gravure printing of the decor image, the three-dimensional structure is thus not printed directly onto the substrate board 1, but is printed digitally onto applicator roll 6.2 which then transfers the printed-on structure to substrate board 1.

(20) The digital control commands for producing the structure and matching the decor image can be provided in a data record or are calculated or generated using the decor image read in by an optical scanning device (not shown). For this purpose, the decor image is localised on the substrate board 1, for example by a camera system (not shown), and the zero point is calculated or determined for printing the sleeve of the applicator roll 6.2. In this way, it can be ensured that the three-dimensional varnish surface 1.1 with its varnish pores present therein, which is produced, matches the decor image, for example a wood decor image, on substrate board 1. Specialists also call this a “synchronous varnish pore” or a “synchronous surface structure”.

(21) FIG. 3 is a sketch of a second embodiment of the device according to the invention. In this embodiment, the varnish for producing the surface structure is not applied to applicator roll 6.2 by varnish jet print heads (varnish jet nozzles), but by a metering roll 6.4 and/or by a doctor (not shown). The metering roll 6.4 or doctor produces a film of varnish 6.5 of a defined layer thickness on applicator roll 6.2.

(22) The varnish film 6.5 is then partly displaced on applicator roll 6.2 by streams of gas, preferably by streams of compressed air, and is thereby transformed into a three-dimensional structure. For this purpose, digitally controlled gas nozzles or compressed air nozzles 6.1 are arranged above and/or at applicator roll 6.2. The nozzles 6.1 are arranged in at least one row which extends over the roll width, i.e. along the rotational axis of the applicator roll. A plurality of rows of nozzles is preferably provided (cf. FIG. 1; 6.1, 6.1′), which define a digitally switchable nozzle pattern.

(23) Here again, the lateral surface region of applicator roll 6.2 receiving the varnish is substantially smooth or slightly structured. The applicator roll is also preferably rubberised and/or bowed.

(24) Arranged upstream of applicator roll 6.2 in the feed direction of the substrate board 1 is an optical scanning device (not shown) which detects the decor image or a guide mark placed on the substrate board 1. The scanning device is connected to a control device (not shown) which digitally controls the nozzles 6.1, 6.1′, subject to the measuring signals generated by the scanning device.

(25) The applicator roll 6.2 can be allocated a radiation source or a heating device 6.6, which is configured to pre-dry or pre-cure the varnish, applied and structured on the applicator roll 6.2, on said applicator roll 6.2.

(26) The realisation of the invention is not restricted to the above-described embodiments. In fact, numerous variants are possible, which use the invention set out in the accompanying claims, even in a fundamentally different form. Thus for example, it also lies within the scope of the invention to realise the application of the decoration (decor image) to the substrate board 1 by pressing on resin-impregnated decor paper. In particular, it lies within the scope of the invention to combine different features of the described embodiments with one another.