EP3892388B1 - Method and device for forming a structured surface of a plate-like material - Google Patents

Description

The invention relates to a method for producing a structured surface of a panel-shaped material, in particular a wood-based panel, in which a layer of lacquer is applied to the surface of the panel-shaped material, in which a film that is at least partially transparent to radiation is placed on the lacquer layer, in which before or After the film has been laid on, a structured absorber layer is applied to the film by means of an absorber material that is at least partially impermeable to the radiation, in the course of which radiation is then applied through the film to the lacquer layer in a first curing step, depending on the permeability of the structured absorber layer of the Foil the paint layer is cured at least in sections and at least partially, and in which the film is lifted from the paint layer and in a second curing step the paint layer is preferably completely cured by means of radiation.

The invention also relates to a device for producing a structured surface of a panel-shaped material, in particular a wood-based panel, with a painting device for applying a layer of varnish to the panel-shaped material, with a feed device for a film that is at least partially transparent to radiation, with a first hardening device for the passage a first curing step, with a lifting device for lifting the film from the paint layer and a second curing device for carrying out a second curing step,

The invention therefore relates to a method which is also known as the Calander Coating Inert (CCI) method and with which surface coatings of high quality combined with visual and haptic properties can be produced.

In this industrial coating process for the panel industry, UV coatings are applied in a rolling process. Then a foil or tape applied, whereby the still liquid paint surface is smoothed. Curing takes place through the film by means of UV radiation with direct surface contact. In principle, other types of electromagnetic radiation or particle radiation are also possible. In this way, oxygen-free or inert conditions are created underneath the foil, which significantly influence the quality of the curing process.

Boards of different carrier types such as medium-density fibreboard (MDF), high-density fibreboard (HDF), raw chipboard, veneer, paper, materials coated with melamine resin can be coated with low process costs as panel-shaped materials. For example, high-gloss surfaces can be achieved with much less effort than with conventional painting, since sanding effort, drying times and paint consumption can be significantly reduced.

The surfaces finished with the inert technology are characterized by high scratch resistance and durability. The surfaces can be produced in high gloss and dull matt. CCI is used in particular by panel manufacturers who produce coated (decor) panels for kitchen and furniture fronts.

A particular challenge is structuring the surface to be cured. A known measure is that the surface of the film facing the paint layer to be cured is itself provided with a negative surface structure. After curing by means of radiation, this structure remains in the lacquer layer as a positive surface structure. In addition, the structure can be embossed into the surface of the lacquer layer before, during or after partial curing.

However, the variability of the structuring is limited, especially if a frequent change of the geometry of the structuring is required for small lot sizes.

A method mentioned at the outset and a corresponding device for carrying out the method according to the preamble of the independent claims is from U.S. 2016/0114619 A1 known. The uncured or only partially cured sections of the paint layer are then removed, resulting in a surface structure. The removed sections of the paint layer lead to a loss of material in the paint layer.

The present invention is therefore based on the technical problem of further simplifying the method and the corresponding device for producing a structured surface of a sheet-like material.

The technical problem mentioned above is solved according to the invention by a method according to claim 1 for producing a structured surface of a panel-shaped material, in particular a wood-based panel, in which the lacquer layer is cured, preferably completely, by means of radiation in a second curing step.

The method according to the invention is therefore a modification of the Calander Coating Inert (CCI) method, in which, in particular, curing takes place in two steps.

With the described two-stage method, a structuring of the paint layer can be produced, with the structuring being able to have indentations, elevations and/or differences in the degree of gloss.

The method is preferably carried out with an unfilled and highly transparent lacquer, so that a smooth surface is basically formed, which is then matted and/or structured in a structured form by the measures described here.

Through the contact of the film provided with an absorber material with the surface of the paint layer is during the first curing step by the penetrating radiation produces a superficial hardening in the areas where the absorber layer is sufficiently permeable to the radiation due to a small layer thickness or lack of layer thickness. A crosslinking reaction is thus initiated in these areas in the paint layer adjacent to the film. In those areas where the film has a sufficient amount of absorber material, less or no radiation passes through and there is little or no crosslinking reaction. Thus, the areas of the structured absorber layer that have a maximum layer thickness for the given application can still let some of the radiation through or represent a completely opaque absorber layer. As a result, a structured superficial skin forms on the side of the lacquer layer facing the film.

During the first curing step, the paint cures to different depths, depending on the intensity of the radiation, the thickness of the absorber layer, the thickness of the foil, and the duration of the radiation. With a suitable selection of the parameters, complete curing can occur in the unstructured areas of the absorber layer, ie the areas that are transparent to the radiation. It is also possible that only partial curing occurs in the transparent areas in the first curing step. In this case, these areas of the lacquer layer to be cured are also only gelled and the above-mentioned skin forms on the surface of the lacquer layer.

All at least partially opaque materials such as lacquers, inks or the like can be used as the absorber material. In this context, preference is given to using dark-colored, preferably black, pigments.

The absorber material, i.e. generally a coating that has pigments that block the radiation in the first curing step, can consist of various substances, for example an ink such as UV ink, PUR ink, solvent-based ink, hybrid ink or a varnish, in particular UV curable varnish. The pigments applied are decisive.

The surface lacquer can be a radiation-curing film former (UV or ESH lacquer). The most important classes of film formers include unsaturated polyesters, epoxy acrylates, polyester acrylates, polyether acrylates, amine-modified polyether acrylates, as well as urethane and polyurethane acrylates. The film former contains functional groups that polymerize under the influence of UV light or ionizing radiation (ESH). This creates a three-dimensional insoluble polymer network. In the case of UV curing, additional photoinitiator additions are necessary in order to start radical or ionic polymerization.

Further possibilities for influencing the curing in sections are also possible through the application of UV blockers. In addition, structuring for the transmission of the film can also be used with a varying film thickness, at least supporting the structure of the absorber layer.

If a shrink lacquer is used for the lacquer layer, then an additional structure can be created in the surface of the lacquer layer due to the curing that takes place at different times.

Furthermore, the image sharpness of the structure of the absorber layer in the paint layer depends on the paint viscosity. If there is no curing after the first curing step, depending on the viscosity of the paint layer, there may be more or less deliquescence.

After the initial curing step, the film is stripped away, leaving the partially cured and skinning portions of the paint layer intact. The uncured or only slightly cured sections are still liquid, run and have an unstructured, smooth and preferably glossy surface.

In addition, a depth of structure is achieved on the surface of the hardened paint layer, because matt areas of the paint layer when the structuring agent is lifted off be raised. Paint from areas that have not been hardened continues to flow, resulting in indentations in sections.

If, on the other hand, a foil is used on which the paint adheres to the paint layer, a further structural depth can be achieved because the paint that has not hardened sticks and is pulled off, i.e. lifted. This creates a further effect in which the non-gelled sections are raised compared to the fused sections.

The structured surface in the paint layer that is present after the film has been lifted off is then hardened and fixed in the second hardening step. The second curing step takes place in the shortest possible time interval after the lifting of the film, in order to fix this structure through the final curing of the lacquer layer.

The time until the second hardening step should be kept short so that the running is stopped as early as possible. A typical duration is less than 60 seconds, but durations between 1 and 5 minutes are also possible.

The film to be applied to the paint layer can already be provided with the absorber layer before it is applied. In this case the structure is predetermined and the foil can possibly be reused if the existing structure is to be produced multiple times on a panel surface.

However, the film can also be provided with the absorber material, in particular printed, in a direct temporal connection shortly before or after it is placed on the lacquer layer. In this way, a structure matched to the already existing colored decor can be created on the foil.

The film is therefore preferably provided with the structured absorber layer consisting of the absorber material on the side facing away from the lacquer layer. Thus, contamination of the paint layer is avoided, in particular if the absorber layer itself has not yet hardened when the film comes into contact with the paint layer.

Furthermore, the film can have a smooth surface on the side facing the paint layer, so that the surface of the film does not result in any further structuring of the paint layer to be cured. This is particularly advantageous when it is not clear in advance on which sections a matt or a smooth surface is to be produced.

The lacquer layer can preferably consist of a transparent lacquer, with at least one further layer with a colored decoration being applied under the transparent lacquer layer. A two-layer paint structure is thus produced and only the upper transparent paint layer is structured using the method described.

It is known from the prior art to create a haptic structuring of the surface synchronously with the colored decoration. For the process described, this means the step in which the foil is provided with a structure that runs synchronously with the decoration of the lacquer layer. Thus, the structure formed by the absorber layer, which is transferred to the surface of the lacquer layer by the first curing step, is applied synchronously with a colored structure. For example, in the case of a colored wood decor, a surface structure with alternating glossy and matt sections can be produced synchronously with the wood grain, which improves the overall impression of the decor.

In a preferred embodiment of the method described, an unstructured film can be applied to the paint layer and the. structured film can be applied to the unstructured film, preferably by means of the absorber layer. For this purpose, the second film can preferably be doubled onto the first film, or the second film is fed in via a second roll unwind.

The method in which the lacquer layer consists of a glossy lacquer and a structure of glossy and matt sections is produced has been described above. Furthermore, a matte lacquer can also be applied, so that a structure can be produced from raised and non-raised sections or from more or less matte sections.

The layer of lacquer applied to the surface of the sheet-like material can, for example, also consist of a colored lacquer instead of a transparent lacquer, the surface of the colored lacquer layer being structured by the method. A surface structure is thus created directly on top of the colored coating of the sheet-like material.

The technical problem outlined above is also solved by a device mentioned at the outset according to claim 9 for producing a structured surface of a panel-shaped material, in particular a wood-based panel, in that a second hardening device (30) is provided for carrying out a second hardening step.

The method described above can be carried out with such a device and the advantages described in this context can be achieved. The curing devices each have a radiation source that serves to cure the lacquer layer. A UV source, preferably in the form of a light-emitting diode (LED), is used if the lacquer layer consists of a UV-curable lacquer. Radiation sources with other electromagnetic radiation or particle radiation are also conceivable for curing corresponding paint materials.

A device is preferably provided for applying absorber material to the film in order to produce a structured absorber layer which is at least partially impermeable to the radiation. The structure of the absorber layer can be produced on the film with this device, which can be designed in particular as a printing device. The device or the pressure device thus enables the film to be placed on the surface to be cured in a timely manner close to the point in time Lacquer layer application or printing of the film with the absorber material.

Furthermore, the device described can be designed with a feed device for feeding two films. Thus, a conventional film can first be placed on the paint layer to be cured, which has either a smooth surface or a surface that is already surface-structured, which faces the paint layer. The further foil is then already provided with the structure of the absorber material or is provided with an absorber material after it has been applied.

Fig. 1

ein erstes Beispiel einer Vorrichtung zur Herstellung einer strukturierten Oberfläche eines plattenförmigen Materials,

Fig. 2

ein zweites Beispiel einer Vorrichtung zur Herstellung einer strukturierten Oberfläche eines plattenförmigen Materials und

Fig. 3

ein drittes Beispiel einer Vorrichtung zur Herstellung einer strukturierten Oberfläche eines plattenförmigen Materials.

The invention is explained below using exemplary embodiments with reference to the drawing. Show in the drawing

1

a first example of a device for producing a structured surface of a plate-shaped material,

2

a second example of a device for producing a structured surface of a plate-shaped material and

3

a third example of a device for producing a structured surface of a plate-shaped material.

In the following description of the various exemplary embodiments according to the invention, components and elements with the same function and the same mode of operation are provided with the same reference symbols, even if the components and elements in the various exemplary embodiments can have different dimensions or shapes.

1 shows a first embodiment of a device 2 for producing a structured surface of a plate-shaped material 4, which is present as Wood-based panel is formed and in the 1 fed from left to right. The material may be in an elongate form to be subsequently divided into smaller units. In addition, it is possible that the wood-based panel already has its final shape and is not further divided after the structured surface has been produced.

A coating layer 12 is applied to the wood-based panel 4 with a coating device 6 which has a reservoir 8 for the coating and a metering roller 10 . Optionally, squeegee devices can also be provided for leveling out the still liquid paint layer 12 or other conventional devices.

A feed device 14 with a supply roll 16 is provided for feeding in a film 18 that is at least partially transparent to radiation. The film 18 is placed on the lacquer layer 12 in the area of a deflection roller 20 . At the in 1 In the embodiment shown, the film is already provided with an absorber material in the form of a structured coating before it is rolled up onto the supply roll 16, which produces a structured absorber layer on the film 18 that is at least partially impermeable to the radiation applied later.

A first hardening step is carried out with a first hardening device 22, which is arranged above the film 18 in an area in which the film 18 is in contact with the lacquer layer 12. For this purpose, radiation, for example UV radiation, is applied through the film 18 to the lacquer layer 12 . Since the film 18 is provided with the absorber layer made of structured paint, the paint layer 12 is hardened to different extents in sections, so that a superficial structure is formed on the surface of the paint layer 12 .

Further to the right in the direction of transport 1 After the first hardening device 22, a lifting device 24 with a deflection roller 26 and a take-up roller 28 is provided, with which the film 18 is lifted from the lacquer layer 12. After that is a surface structure corresponding to the structure of the absorber layer on the film is present on the only partially cured lacquer layer 12 .

Finally, a second hardening device 30 is provided, which is designed to carry out a second hardening step and emits radiation, in particular UV radiation.

For example, a UV lamp with high radiation intensity or an excimer emitter can be used for the first hardening device 22 and the second hardening device 30 .

2 shows a further exemplary embodiment of a device 2 for producing a structured surface of a wood-based panel 4, the same reference numbers being the same elements as in FIG 1 mark.

In addition to the in 1 Device 2 shown is a printing device 32 for printing the film 12 with the structure paint to produce a radiation at least partially impermeable structured absorber layer is provided. Thus, the film is provided with a structured absorber layer made of a structured lacquer only after it has been placed on the lacquer layer 12 . The absorber layer then causes the lacquer layer 12 to harden differently in sections in the region of the first hardening device 22.

3 shows a further exemplary embodiment of a device 2 for producing a structured surface of a wood-based panel 4, with the same reference numbers being the same elements as in FIGS 1 and 2 mark.

In addition, a second feed device 34 for feeding a second film 36 is provided here, which has a supply roll 38 and a deflection roller 40 with which the second film 36 is placed on the first film 12 . Likewise is a second Lifting device 42 is provided with a deflection roller 44 and a take-up roller 46 .

In this configuration, the first film 12 has no structure, while the second film 36 is printed with a structured paint by means of the printing device 32 . The first hardening device 22 then hardens the paint layer 12 partially and in sections through the second film 36 and the first film 18 .

Claims (11)

1. Method for producing a structured surface of a plate-shaped material, in particular a wood-based panel,

   - in which a lacquer layer is applied to the surface of the plate-shaped material,

   - in which a foil which is at least partially permeable to radiation is applied to the lacquer layer,

   - in which a structured absorber layer is applied to the foil by means of an absorber material which is at least partially impermeable to the radiation, before or after the foil is applied,

   - in which subsequently, in a first curing step, radiation is applied through the film to the lacquer layer, the lacquer layer being cured at least in sections and at least partially as a function of the permeability of the structured absorber layer of the film, and

   - in which the film is lifted off the lacquer layer,

   characterized in

   - that in a second curing step the lacquer layer is cured by means of radiation, preferably completely.
2. Process according to claim 1,
   wherein the foil is provided with the structured absorber layer on the side facing away from the lacquer layer.
3. Process according to claim 1 or 2,
   wherein the film has an even surface on the side facing the lacquer layer.
4. Process according to any one of claims 1 to 3,
   wherein the lacquer layer consists of a transparent lacquer and at least one further layer with a coloured decoration is applied under the lacquer layer.
5. Process according to claim 4,
   wherein the film is provided with a textured absorber layer running synchronously with the decoration.
6. Process according to any one of claims 1 to 5,

   - wherein an unstructured film is applied to the lacquer layer and

   - wherein the foil structured by means of absorber material is applied to the unstructured foil.
7. Process according to any one of claims 1 to 3,
   wherein the lacquer layer comprises a coloured lacquer.
8. Process according to any one of claims 1 to 7,
   wherein the lacquer layer is applied from a glossy lacquer.
9. Device for producing a structured surface of a panel-shaped material (4), in particular a wood-based material panel,

   - having a lacquering device (6) for applying a lacquer layer (12) to the plate-shaped material (4),

   - having a feed device (14) for a film (18) which is at least partially permeable to radiation,

   - with a first curing device (22) for carrying out a first curing step and

   - with a lifting device (24) for lifting the foil (18) off the lacquer layer (12), characterized in

   - that a second curing device (30) is provided for carrying out a second curing step.
10. Device according to claim 9,
    characterized in
    that a device (32) is provided for applying absorber material to the film (18) for producing a structured absorber layer which is at least partially impermeable to the radiation.
11. Device according to claim 9 or 10,
    characterized in
    that the feeding device (14, 34) is designed for feeding two foils (18, 36).

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