EP2060658B1 - Method for processing a structured surface - Google Patents

Abstract

The method for treating a surface of an embossing tool such as a press plate (1) or an endless belt, comprises applying a first mask on the surface for fine structuring, chemically treating the surface provided with the first mask for obtaining a surface structure, applying a second mask on the chemically treated surface for pore structuring, chemically treating the surface provided with the second mask for obtaining the surface structure, applying a third mask on the chemically treated surface, and chemically treating the surface provided with the third mask. The method for treating a surface of an embossing tool such as a press plate (1) or an endless belt, comprises applying a first mask on the surface for fine structuring, chemically treating the surface provided with the first mask for obtaining a surface structure, applying a second mask on the chemically treated surface for pore structuring, chemically treating the surface provided with the second mask for obtaining the surface structure, applying a third mask on the chemically treated surface, chemically treating the surface provided with the third mask, polishing the chemically treated surface, activating the polished surface, cleaning the activated surface, chrome-plating the cleaned surface, applying a fourth mask on the chrome-plated surface, and chrome-plating the surface chrome-plated with the fourth mask. The masks are applied by the digital printing technique. Independent claims are included for: (1) a method for treating a structured surface of an embossing tool; and (2) an embossing tool.

Description

The invention relates to a method for processing a structured surface of a stamping tool, in which the surface is provided over its entire surface with a first metallic coating.

In the coating of wood-based panels with thermoset resins, one tries again and again to reproduce surfaces from nature as far as possible true to nature. The thermoset resins used include the melamine, phenolic or melamine / urea resins. The surface design of, for example melamine resin films is done under pressure and temperature in hydraulic heating presses. As a surface donor, for example, a structured metallic press plate is used as a stamping tool, for example a steel sheet. In order to improve the wear resistance and release properties of the metal surface, the stamping tools are additionally provided with a coating. During the pressing process, the melamine resin becomes liquid under pressure and temperature, and another polycondensation takes place. Press time and temperature determine the degree of crosslinking of the melamine resins and their surface quality. After the pressing time, the melamine resin has reached the desired degree of crosslinking and has entered the solid phase. In this process, the melamine resin surface also faithfully adopts the surface of the embossing tool.

According to the state of the art embossing tools in the form of press plates and endless belts made of steel sheets, which receive a surface structure by appropriate processing. For this purpose, a pretreated sheet is provided with a matrix, which is applied for example by means of a screen printing process, so that subsequently an etching of the sheet can take place in order to achieve a surface structure. The sheets used in this case have a very large format, so that it depends on a very precise processing and especially a congruent processing, as far as several steps are necessary. Here are all areas which the raised surface structure to form later, covered by the mask, so that a surface etching takes place only in the areas that can be attacked directly by the etching liquid. The etched areas then form the profile valleys of the desired structure, after completion of the etching process the surface is cleaned and in particular the mask is removed.

Alternatively, it is possible first to apply a photo layer, which is then subjected to an exposure in order to subject the press plates or endless belts to a rinsing process after the final development of the photo layer, so that only the parts of the photo layer remain which form the mask for the later etching process. The reproducibility of the masks produced in this way is very difficult and problematic because the negative or positive used to expose the photosensitive layer must always be positioned exactly in the same position relative to the existing structuring, for example if more than one exposure and etching operation is to take place Thus, to apply complicated three-dimensional structures on the surface of the press plate or the endless belt. It should also be noted that these are extremely large-size press plates, so that the slightest deviations can already lead to significant shifts of the structures. The reproducibility of the application of the mask is therefore associated, in particular in the photographic process to achieve a high imaging accuracy with considerable difficulties. The difficulties may increase if a three-dimensional structure is to be achieved by several successive exposure and etching processes and for this purpose a plurality of masks must be applied, with an etching process taking place between each mask application. Due to the exact positioning and the required number of corresponding masks, the production of the press plates or endless belts is thus very complicated and cost-intensive. The achievable resolution is also very much dependent on the method used. Furthermore, a considerable number of steps are required, which require a complicated handling, in particular by the size of the press plates or endless belts.

Furthermore, it is known from the prior art, instead of a screen printing process to produce a mask by a wax coating, which is chemically resistant to the etchant used and thus allows etching in those areas in which the surface is not covered by the wax. In this method, a spray head, which sprays the wax onto the surface, is moved along an X and Y axis to apply the required structure. When using a wax job, however, has proved to be disadvantageous in that the wax is very difficult to remove from the surface again and is very expensive. Thus, although tremendous progress has been made in this process, it has been found in practice that the removal of the wax layer is very problematic because the wax can not be removed with a chemical treatment and thus the cleaning of the sheets after the etching process is extremely difficult, for example, can only be performed with a high-pressure cleaner.

For the above-mentioned reason, it is therefore necessary to either apply the mask directly to the press plate or endless belt by means of a digitized printing technique or to partially expose an existing photographic layer, in order subsequently to be able to carry out the etching after cleaning. The particular advantage of the digitized printing technique is that the structure is detected very accurately by the use of identical files and thus several etching processes, for example, to achieve a deep structure, can be performed successively fit.

From the DE 102 24 128 A1 a method for applying coatings on surfaces is known, wherein the device used comprises a nozzle head, which has at least one controllable by a control signal nozzle. Here, the method alternatively provides for the movement of the surface to be coated or the movement of the nozzle head. A fluid coating material is applied to the surface through the nozzle, whereby a selective coating of selected areas with liquid or gaseous materials is provided, which may also be viscous, for example. An example becomes among other things called the use of UV varnishes. The method can be used, inter alia, for etching surfaces, wherein chemical reagents are applied to the surface.

After structuring the surfaces, the press plates and endless belts are subjected to a plurality of cleaning processes and can additionally be coated with a nickel layer, which is then refined by further metallic coatings such that the surface obtains a desired degree of gloss and a necessary surface hardness. This degree of gloss is responsible for the fact that after compression of the materials to be processed with the help of the press plates or the endless belts, the structure pressed here receives different shades and color reflections.

Based on this prior art, the object of the present invention is to further increase the design possibilities of the surface structure and to adapt the synthetic resin surface as far as possible to a lacquered real wood surface.

According to the invention, it is provided for the solution of the method task that at least one further metallic coating is arranged on the first coating in predetermined regions, wherein the degree of gloss of the first coating differs from that of the further coating. Further advantageous embodiments of the method emerge from the dependent claims.

Compared to the prior art, it is provided that after application of the structuring and a first metallic coating partially a further coating is applied, wherein the gloss level of the first coating differs from that of the further coating. Thus, the gloss level of an embossing tool, in particular a press plate or an endless belt, at least partially differ from each other in partial areas. By this measure, it is possible to provide raised structures or optionally underlying structures with a different degree of gloss, for example, the structure particularly emphasized. As a result of this measure, the visual impression is sustainably improved and leads to a surface which is congruently executable as a result of the precisely fitting print templates and accurately applied matrix and thus not only a different depth structure can be achieved, but also a different degree of gloss in order to highlight certain structural areas. This gloss difference can be optionally provided, for example, the raised areas may have a higher gloss level than the lower areas or vice versa.

For example, a lacquered real wood surface can be modeled, wherein the raised surfaces have a certain degree of matt and the deeper wood pore, due to the light reflection, show a shiny area.

For this purpose, the wood pore structures, which match in register with the wood decor print, are produced according to the known etching technology.

For this purpose, a tailor-made protective layer is applied for this purpose, which allows in a subsequent operation, a further partial coating in the areas that are not covered by the protective layer. In order to achieve the high accuracy which is required to achieve a precisely fitting arrangement and coverage of the respective structure, a digital printing technique is used, so that exactly on an already existing structure a post-structuring can be done on the one hand and also made a gloss level change after applying a protective layer can.

Preferably, as a metallic coating, a chromium plating is performed, which may be a high-gloss chrome plating or a matte chrome plating. However, this method is not limited to the chrome plating of the surface, but other metal coatings can be made. It is imperative, for example, as far as a chromium plating takes place, that the protective layer used in this case of a chromic acid-resistant material so that the protective layer is not affected during the chrome plating.

For better adhesion of the protective layer on the existing chromium plating can be provided as a further intermediate processing step, a baking of the protective layer, wherein after the second metallic coating, the protective layer is completely removed. For the production of the surface structure, a deep etching is usually carried out first and then a circular etching in order to emphasize the shape of the pore structure. After that, a mechanical polish can be done before the surface is cleaned and degreased. For better adhesion of the metallic layers, in particular the chromium layer, the structured surface can be additionally activated before the application of the coatings, or other coatings which ensure better adhesion, for example a nickel layer, can be applied.

• Auftragen einer ersten Maske auf die Oberfläche mittels einer digitalen Drucktechnik,
• chemisches Bearbeiten der mit der Maske versehenen Oberfläche zur Erzielung einer Oberflächenstruktur,
• erneutes Auftragen einer zweiten passgenauen Maske auf die chemisch bearbeitete Oberfläche mittels einer digitalen Drucktechnik,
• erneutes chemisches Bearbeiten der mit der zweiten Maske versehenen Oberfläche,
• Polieren der chemisch bearbeiteten Oberfläche,
• Aktivieren der polierten Oberfläche,
• Reinigen der aktivierten Oberfläche,
• Verchromen der gereinigten Oberfläche,
• erneutes Auftragen einer dritten passgenauen Maske auf die verchromte Oberfläche und
• erneutes Verchromen der mit der Maske versehenen verchromten Oberfläche,

wobei die durch die Verchromungen erzeugten Beschichtungen der strukturierten Oberfläche einen unterschiedlichen Glanzgrad aufweisen.According to the invention, in order to achieve a higher degree of gloss, a method is provided which is composed of the following steps:

• Applying a first mask to the surface by means of a digital printing technique,
• chemically processing the masked surface to provide a surface texture;
• reapplying a second tailored mask to the chemically processed surface using a digital printing technique;
• retreating the surface provided with the second mask,
• Polishing the chemically treated surface,
• Activate the polished surface,
• Cleaning the activated surface,
• Chrome plating the cleaned surface,
• reapplying a third accurate mask on the chromed surface and
• re-chrome the masked chrome finish,

wherein the coatings of the structured surface produced by the chromium plating have a different degree of gloss.

The aforesaid method describes machining the surface of an embossing tool, for example a press plate or an endless belt, by applying the first mask to the surface by means of a digital printing technique and the subsequent chemical processing to obtain the surface structure, this patterning by repeated application of a mask and an etching process can be repeated before the finished structured surface is subjected to a cleaning step by polishing and activating and then a first coating is applied by a chrome plating, after which a mask in the form of the protective layer is applied again, so that in a final process step a renewed chrome plating can be done with a different degree of gloss.

• Auftragen einer ersten Maske auf die Oberfläche mittels einer digitalen Drucktechnik zur Feinstrukturierung,
• chemisches Bearbeiten der mit der Maske versehenen Oberfläche zur Erzielung einer Oberflächenstruktur,
• Auftragen einer zweiten passgenauen Maske auf die Oberfläche mittels einer digitalen Drucktechnik zur Porenstrukturierung,
• chemisches Bearbeiten der mit der Maske versehenen Oberfläche zur Erzielung einer Oberflächenstruktur,
• erneutes Auftragen einer dritten passgenauen Maske auf die chemisch bearbeitete Oberfläche mittels einer digitalen Drucktechnik,
• erneutes chemisches Bearbeiten der mit der dritten Maske versehenen Oberfläche,
• Polieren der chemisch bearbeiteten Oberfläche,
• Aktivieren der polierten Oberfläche,
• Reinigen der aktivierten Oberfläche,
• Verchromen der gereinigten Oberfläche,
• erneutes Auftragen einer vierten passgenauen Maske auf die verchromte Oberfläche und
• erneutes Verchromen der mit der Maske versehenen verchromten Oberfläche,

wobei die durch die Verchromungen erzeugten Beschichtungen der strukturierten Oberfläche einen unterschiedlichen Glanzgrad aufweisen.Alternatively, it is possible to supplement the method by further steps which provide a multiple application of a mask and a treatment of the surface to achieve the surface structure, namely

• Applying a first mask to the surface by means of a digital printing technique for fine structuring,
• chemically processing the masked surface to provide a surface texture;
• Applying a second tailored mask to the surface by means of a digital printing technique for pore structuring,
• chemically processing the masked surface to provide a surface texture;
• re-applying a third accurate mask to the chemically processed surface by means of a digital printing technique,
• retreating the surface provided with the third mask,
• Polishing the chemically treated surface,
• Activate the polished surface,
• Cleaning the activated surface,
• Chrome plating the cleaned surface,
• reapply a fourth accurate mask to the chrome surface and
• re-chrome the masked chrome finish,

wherein the coatings of the structured surface produced by the chromium plating have a different degree of gloss.

An essential point for achieving the precise arrangement of the structures and the subsequent degree of gloss is that the first, second and third mask and the last applied protective layer with the aid of a digitizing printing technique is applied accurately, so that a structurally conformal coverage is present and over the entire surface of the Press plates or endless belts give no deviations from the structure.

For this purpose, the method according to the invention leads to an embossing tool having at least one structured surface, wherein a metallic coating of a first material and partially a metallic coating of a second material is arranged over the entire surface of the structured surface, the degree of gloss of the coatings differing. Preferably, the material coatings used are chromium, since this is particularly hard and thus suitable for the pressing operations to be carried out. However, depending on the purpose of use, it is readily possible, for example, if materials are compacted which do not have a particularly high degree of hardness or whose surface is elastic and soft, likewise to achieve particular effects by corresponding partial chromium plating with different firmness gloss.

The particular advantage of the method according to the invention and the embossing tools produced thereby is that the structure specified there is imaged identically on the materials to be machined with the aid of the embossing tools, whereby at the same time the present degree of gloss, at least in two gradations, directly on the materials to be processed is recognizable. Due to the different degree of gloss, certain areas, for example raised areas or even lower areas, can additionally be provided with a different degree of gloss, so that the structure emerges very succinctly and produces an optical effect which leads to a material surface which hardly differs from, for example, grown wood is. According to this method, other, lifelike surfaces can be simulated accordingly.

The invention will be explained again with reference to the figures.

Fig. 1

in einer perspektivischen Ansicht ein erfindungsgemäßes Press- blech und

Fig. 2

in einer vergrößerten Seitenansicht die vorhandene Struktur auf der Pressblechoberfläche.

It shows

Fig. 1

in a perspective view of an inventive press sheet and

Fig. 2

in an enlarged side view of the existing structure on the press plate surface.

FIG. 1 shows a perspective view of an inventive press plate 1, which is flat in the embodiment shown. In the case of an endless belt, however, this embossing tool can also be curved. The press plate 1 shows a grain 2 which is modeled on the shape of a wood structure. However, it is conceivable that other grains or other surface textures are produced in this way by the method according to the invention and the etching process required for this purpose.

FIG. 2 shows in an enlarged side view a part of the front edge region of the press plate 1 and the structure thereon 3, which has a mountain-like surface with valleys 4 and heights 5. In this case, the surface is produced by one or more etching processes, after which a matrix has previously been applied in a standard process or a digitized printing technique, the regions which are not to be subjected to the etching processes being covered by the mask. With the aid of the etching process, it is possible, for example, to produce fine surface structures and deep structures which are subsequently optionally rounded off by mechanical processing. After the surface has been etched, the surface structure is completed by further chemical processing, polishing and optionally activation of the polished surface, so that subsequent cleaning is performed before a first chromium plating layer 6 having a certain degree of gloss is applied, followed by another Mask covered a portion of these chrome-plated surfaces, so that subsequently the uncovered areas can be chrome-plated again with a chromium plating layer 7, with a deviating from the first chromium plating 6 degree of gloss.

In some cases, other surface finishes may sometimes be used instead of chromium plating, wherein the surface is partially provided with different degrees of gloss using the method according to the invention. Insofar as a wood structure is to be reproduced on the press sheet 1 by the etching methods used, it is possible, for example, to provide the raised surfaces 6 with a matt degree of gloss, while the deeper areas forming the wood pores are to be provided with a higher degree of gloss. By this measure, the wood pore structures that match in register with the wood decor print are highlighted and give the products produced with the press plates the appearance of a real wood character of the natural product comes very close.

LIST OF REFERENCE NUMBERS

1

press plate

2

Grain

3

structure

4

valley

5

height

6

chromium plating

7

chromium plating

Claims (11)

1. Method for processing a structured surface of a stamping tool, wherein the surface is provided with a first metallic coating (6) all-over the surface,
   characterized in that
   on the first coating (6), at least one further metallic coating (7) is disposed in predetermined areas, the degree of gloss of the first coating (6) differing from that of the further coating (7).
2. Method according to claim 1,
   characterized in that
   a protective layer is partially applied onto the first coating (6).
3. Method according to claim 2,
   characterized in that
   the protective layer is applied by means of a digital printing technique.
4. Method according to one of the preceding claims,
   characterized in that
   the coatings (6, 7) are generated by chromium-plating.
5. Method according to one of claims 2 to 4,
   characterized in that
   a material resistant to chromic acid is used for the protective layer.
6. Method according to one of claims 2 to 5,
   characterized in that
   the protective layer is burnt into the first coating (6).
7. Method according to one of the preceding claims,
   characterized in that
   the structured surface is activated prior to the application of the coatings (6, 7).
8. Method for processing a surface of a stamping tool, comprising the steps of:

   - applying a first mask onto the surface by means of a digital printing technique,

   - chemically processing the surface provided with the mask for achieving a surface structure,

   - again applying a second, accurately fitting mask onto the chemically processed surface by means of a digital technique,

   - again chemically processing the surface provided with the second mask,

   - polishing the chemically processed surface,

   - activating the polished surface,

   - cleaning the activated surface,

   - chromium-plating the cleaned surface,

   - again applying a third, accurately fitting mask onto the chromium-plated surface, and

   - again chromium-plating the chromium-plated surface provided with the mask, wherein the coatings (6, 7) of the structured surfaces generated by chromium-plating have different degrees of gloss.
9. Method for processing a surface of a stamping tool, comprising the steps of:

   - applying a first mask onto the surface by means of a digital printing technique for fine structuring,

   - chemically processing the surface provided with the mask for achieving a surface structure,

   - applying a second, accurately fitting mask onto the surface by means of a digital printing technique for pore structuring,

   - chemically processing the surface provided with the mask for achieving a surface structure,

   - again applying a third, accurately fitting mask onto the chemically processed surface by means of a digital technique,

   - again chemically processing the surface provided with the third mask,

   - polishing the chemically processed surface,

   - activating the polished surface,

   - cleaning the activated surface,

   - chromium-plating the cleaned surface,

   - again applying a fourth, accurately fitting mask onto the chromium-plated surface, and

   - again chromium-plating the chromium-plated surface provided with the mask, wherein the coatings (6, 7) of the structured surfaces generated by chromium-plating have different degrees of gloss.
10. Method according to one of the preceding claims,
    characterized in that
    the first, second and third mask as well as the protective layer are applied to fit accurately by means of a digitalized printing technique.
11. Stamping tool with at least one structured surface,
    characterized in that
    a metallic coating (6) of a first material is disposed all-over on the structured surface, and a metallic coating (7) of a second material is partially disposed thereon, where the degrees of gloss of the coatings (6, 7) differ.

Images