EP3415317A1 - Method and device for producing a decorative surface - Google Patents

Abstract

A method for producing a decorative surface with different degrees of gloss preferably comprises the following steps:
(A) feeding a with workpiece (1.0) to a device for paint application;
(B) coating the workpiece (1.0) with at least one first lacquer layer (1.4);
(C) feeding the workpiece to a digital printing station;
(D) providing digital control data to the digital printing station;
(E) digital spraying of droplets on partial surfaces of the first lacquer layer (1.4) on the workpiece (1.0) with an at least partially transparent lacquer for applying a second lacquer layer (1.5) on the first lacquer layer (1.4), wherein the second lacquer layer (1.5) after curing has a different gloss level than the first lacquer layer (1.4), and
(F) physical drying and / or chemical curing of the applied lacquer layers (1.4, 1.5).

In addition, an apparatus for carrying out the method is provided.

Description

The present invention relates to a method and apparatus for producing a decorative surface.

A decorative surface for furniture, floor panels or wall panels is state of the art. Thereby, surfaces of workpieces, such as e.g. Chipboard or MDF boards, coated with a decorative printed paper or printed directly after applying a white primer and provided with a protective varnish. The surfaces are often replicas of real wood surfaces, stones or tiles. In doing so, both the image (decoration) of the wood surface and the tangible "haptic" structure (tangible pores and knotholes) are reproduced. However, the surfaces which are coated can also be rolled goods such as printed paper or printed plastic films (for the purposes of the present invention).

The optical reproduction of decorative images is produced according to the prior art both with analog printing methods and with digital printing methods according to a digital image master. To produce the haptic, tactile structure with a structure depth of usually 5-500 .mu.m, preferably 10-100 .mu.m, an analogous process, such as embossing with structured embossing plates ("matrices"), is used according to the prior art. It is also known to produce such structures with digital methods, as shown in the DE 10 2015 110 236 A1 and DE 10 2009 044 802 A1 is shown.

The DE 10 2007 055 053 A1 discloses a method of processing a textured surface of a stamping die ("die"), wherein the gloss level of a first coating differs from that of a second coating, for example, to better emulate wood pores. With subsequent use of such embossing tool for the production of a finished product, such as a Floor panels, consisting of an HDF support plate and a printed, melamine-impregnated paper as a decorative layer, after pressing with the embossing tool at an optical viewing angle of less than 45 degrees in the backlight decorative paper pores printed in the paper also by gloss level differences of the hardened melamine surface, Molded from the differently machined surface of the die, visible. The production of such embossing tool is an expensive process. In addition, the embossing tools are usually used in short-cycle presses, where the change from one embossing tool to another takes a long time, at least about 15 - 30 min.

It is therefore the object of the present invention to produce an optically and haptically pleasing surface while achieving a rapid change from one surface to the next, without wasting time and without the high cost of producing a special embossing tool.

This object is achieved with features of the independent claims. Advantageous developments are the subject of the dependent claims.

In the method according to the invention for producing a decorative surface having different degrees of gloss, first a workpiece which is coated with at least one first lacquer layer is fed to a digital printing station, at which digital control data are provided which at least partially reference an optional decorative image on the Workpiece can be tuned. Then, a digital spraying of droplets on partial surfaces of the first lacquer layer on the workpiece with an at least partially transparent lacquer for applying a second lacquer layer on the first lacquer layer, wherein the second lacquer layer has a different gloss level after curing than the first lacquer layer.

Due to the second lacquer layer, the surface of the workpiece is provided with different degrees of gloss, so that the degree of gloss can preferably be adapted to the optionally underlying decorative image. Through the digital application The second paint view can be adjusted individually depending on the digital artwork, the gloss level on the surface, with successive workpieces can be printed with a different gloss level at different locations without the need to replace a die or other tool is required.

Preferably, the workpiece is previously supplied to a device for paint application and coated with at least a first coating layer. Subsequently, the workpiece is preferably fed to the digital printing station.

In particular, physical drying and / or chemical curing of the applied lacquer layers preferably takes place in particular.

The gloss level of the first lacquer layer differs preferably by at least 10 gloss units, preferably at least 20 gloss units, from the gloss level of the second lacquer layer, the gloss units being measured according to DIN EN ISO 2813: 2015-02 at an angle of 60 °. As a result, an optically clearly perceivable gloss effect can be recognized. Adjusting the level of gloss can be varied in printing by droplet size and / or number of droplets per area, or by the use of matting agents.

The gloss measurement is carried out according to DIN EN ISO 2813: 2015-02. For gloss measurement, the amount of light that reflects a surface relative to a reference standard of polished glass is measured. The unit of measure used is GU (Gloss Units). The amount of light reflected on the surface depends on the angle of incidence and the properties of the surface. In the gloss measurement, different angles of incidence (20 °, 60 ° and 85 °) can be used to detect the reflectance, preferably measured at the angle of incidence of 60 °. Alternatively, the average of measurements at the three angles of incidence can also be used. The reflectance compares the light energy emitted and received by a gloss meter in percent at a certain angle of incidence.

All surfaces or sections of surfaces that achieve less than 20 gloss units by measurement when using a glossmeter are defined as "dull", and any surfaces or sections of surfaces that achieve more than 60 gloss units are considered "glossy". designated. One of the two layers of paint can be dull and the other glossy.

The surfaces on the first and second lacquer layer can be smooth or structured. In the case of a structured surface, the gloss measurement and the definition used here of distinguishing into "matt" and "glossy" subregions takes place just as in the case of non-structured surfaces. For example, a structured surface of the workpiece may have a texture depth of 5 to 300 μm (microns), preferably 10 to 90 μm (microns).

For a fine adjustment of the degree of gloss, the droplets of the second lacquer layer having a droplet size of preferably less than 100 pL, in particular less than 10 pL, are sprayed on. Optionally, different degrees of gloss can also be set on the second lacquer layer so that gloss differences can also be present within the second lacquer layer.

With the first lacquer layer, a colored decorative image can be printed in the analogous method, for example via pressure rollers, or by means of digital print heads. Alternatively, a transparent lacquer layer can be applied to an already existing decorative image with the first lacquer layer.

To produce a structured surface in a production line, a liquid base layer can be applied to a surface of a coated or uncoated workpiece and a structure can be introduced into the still liquid base layer by means of digital printheads or other structuring means in order subsequently to fix the structured base layer. Optionally, the structured base layer may then form the first lacquer layer or it will then a first lacquer layer is applied to the structured base layer. For an optically special effect, only the regions provided with a structure or only the regions without structure can be printed with the second lacquer layer. As a result, a substantially congruent arrangement of structured areas and glossy or matt areas can take place.

Figur 1

eine schematische Darstellung eines mit Hilfe des erfindungsgemäßen Verfahrens hergestellten, plattenförmigen Werkstückes im Querschnitt,

Figur 2

eine weitere schematische Darstellung eines mit Hilfe des erfindungsgemäßen Verfahrens hergestellten, plattenförmigen Werkstückes mit einer angedeuteten Holzpore in der Draufsicht, und

Figur 3

eine Oberfläche eines bedruckten Werkstückes.

The invention will be explained in more detail with reference to embodiments in detail with reference to the accompanying figures. They show:

FIG. 1

a schematic representation of a plate-shaped workpiece produced by means of the method according to the invention, in cross-section,

FIG. 2

a further schematic representation of a plate-shaped workpiece produced by means of the method according to the invention with an indicated Holzpore in plan view, and

FIG. 3

a surface of a printed workpiece.

In FIG. 1 a plate-shaped workpiece 1.0 is shown, on which an optional first base layer 1.1 is applied to a surface. In addition, optional on the workpiece 1.0 even before the application of the first base layer 1.1 a decorative image printed, such as a wood reproduction or a tile display. In an alternative embodiment, even after the application of the first base layer 1.1, or after the application of a (structured) second base layer 1.2, a decorative image can be printed, for example using a 4-color digital printer. On the first base layer 1.1, a second liquid base layer 1.2 is applied. This second base layer 1.2 has been structured by digitally sprayed droplets 1.3, so that the surface is no longer flat, but has a structure. Subsequently, a first lacquer layer 1.4 is applied, which has a first degree of gloss. On the first lacquer layer 1.4, a second lacquer layer 1.5 is applied via digital print heads, wherein the second lacquer layer 1.5, the surface of the first Lacquer layer 1.4 only partially covered. The lacquer layers 1.4 and 1.5 are cured successively or jointly, for example via UV radiation. The second lacquer layer 1.5 after hardening has a different degree of gloss than the first lacquer layer.

Instead of structuring the second base layer 1.2 by means of digitally sprayed-on droplets, it is also possible to structure a base layer by other methods, for example using only area-wise application or embossing matrices. It is also possible to apply the decor image on a structured surface instead of on a flat surface.

In FIG. 2 is a plan view of the plate-shaped workpiece 1.0 of FIG. 1 and it can be seen that the decorative image includes a wooden pore 2.5 and wooded areas 2.4. The different areas of the wooden pore 2.5 and the wood grain areas 2.4 can also have a different degree of gloss due to the second paint view 1.5, wherein the decor areas of the image and the different gloss areas are preferably congruent due to the paint application.

In a further embodiment, on a support plate of a wood material or a plate of another material having a thickness of at least 4 mm, preferably 8 to 16 mm and outer dimensions of at least 200 mm wide and at least 400 mm in length, first with a UV-curing coated white basecoat, for example, in an amount of about 20 g / qm. This white basecoat is then cured under UV irradiation.

Subsequently, the carrier plate is fed to a digital printing device in which a printed image, such as a replica of small tiles as a mosaic, a wood decor or other pattern, is applied with a 4-color printing as CMYK.

In FIG. 3 For example, for a printed image, a pattern with two differently colored mosaic tiles is shown, with bright mosaic tiles 3.1 and darker mosaic tiles 3.2 being provided. In an alternative embodiment, a variety of other colors of tiles or mosaics with pictorial representations may also be used.

Subsequently, a thin basecoat layer of 5-15 g / qm of a likewise UV-curing lacquer is applied to the thus printed backing plate and (partially) cured with UV light. In an alternative embodiment, this basecoat layer can also be completely eliminated, or replaced by a solvent-based lacquer or an aqueous acrylate lacquer, which is then physically dried.

On the first basecoat layer or alternatively directly on the printed image, a further basecoat layer 1.2 is then applied as a radiation-curing lacquer layer, preferably based on acrylate, in a layer thickness of 10 - 100 microns.

Both basecoat layers can be applied by digital printheads or by pressure rollers or other methods. Immediately after the application of this second basecoat layer 1.2, a further transparent resist layer 1.3 is optionally printed by means of a digital print master with digital print heads prior to curing in the still liquid layer. When applying this lacquer layer 1.3, the droplet size can vary between 1 pL and 100 pL. The digital artwork used is that which was also used to print the tile mosaic described above. This artwork is previously electronically modified so that only in the spaces 3.3 of the mosaic tiles 3.1 and 3.2 is printed. Subsequently, the radiation-curing basecoat 1.2 is cured together with the resist layer 1.3 with a UV lamp. In an alternative embodiment, the curing can also be effected by means of electron radiation.

The result is a printed with a tile mosaic support plate in which the interstices 3.3 are deepened as joints between the mosaic tiles 3.1 and 3.2 by 10 - 60 microns.

Subsequently, the degree of gloss of at least parts of the entire surface is adjusted to the desired value by the at least partial application of a second lacquer layer 1.4 with subsequent drying, the degree of gloss of the first lacquer layer 1.3 deviating from the gloss level of the second lacquer layer.

In an alternative embodiment, the additional application of a third lacquer layer 1.5 can also be carried out before or after curing of the second lacquer layer 1.4, wherein the third lacquer layer 1.5 likewise consists of a multiplicity of droplets having a size of 3-100 .mu.l being dispensed onto the surface. With this third lacquer layer, both the gloss level in partial areas can be changed again, and the surface texture depth of the not yet cured lacquer layer 1.4 can be influenced.

The lacquer layers 1.4 and 1.5 can also be completely eliminated if the degree of gloss is also changed by applying the first lacquer layer 1.3 at the same time as the second base lacquer layer 1.2 applied for structuring.

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

Optionally, the gloss level at the interstices 3.3 can also be lowered by a further lacquer layer, which is finally printed by a further digital printing device with a transparent, UV-curing lacquer in the lowered spaces. Then more than just two layers of paint are applied to adjust the gloss level.

To print a rather dull lacquer layer, droplet sizes of 3 - 6 pL are used, which are cured to within 0.5 - 2 sec after impact on the surface by UV-LED radiation so far that they can no longer flow. This creates a surface structure in these areas, the the incident light no longer reflects straight. The gloss level is thus lowered to values of 30 gloss units and less.

In the method according to the invention, the second lacquer layer may optionally have a higher or lower degree of gloss than the first lacquer layer. The setting of the gloss level can be carried out, for example, by the following methods:

Version 1:

Matte areas through the first lacquer layer consist of previously (analog or digital) applied matt lacquer, for example, with matting agents or by an excimer matting. Glossy areas of the second lacquer layer consist of lacquer applied by digital print heads, which is formed from a large number of individual droplets, resulting in a sectionally very smooth surface and thus a high degree of gloss. The droplets have a size of at least 6 pL, and the curing takes place only after a course of at least 1 sec, preferably after more than 5 sec.

Variant 2:

The glossy areas of the first lacquer layer consist of glossy lacquer previously applied (analog or digital), matt areas of the second lacquer layer consist of digitally applied lacquer of a multiplicity of smallest droplets with a droplet size smaller than 8 pL, preferably smaller than 3 pL, inside less than 3 seconds after application, preferably less than 1 second after application, at least partially cured.

Curing in both variants is preferably carried out by a UV-LED lamp, which is arranged in the direction of passage within less than 100 mm after the digital print heads, which apply the plurality of droplets to the surface.

For the preparation of a matt lacquer coating matting agents may be added to the paint, for example PE waxes or silicic acids. The proportion of matting agents in the paint can be between 2% to 6%, in particular 3% to 5% (percent by weight).

The different embodiments of the FIGS. 1 and 3 can be combined with each other in terms of the order and the structuring of a layer. The number of layers on the workpiece can also be freely selected, depending on which surface structure is to be produced by the method.

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

Finally, the description will be made of several aspects of the present invention.

1. A Zuführung eines mit Werkstückes 1.0 zu einer Vorrichtung zum Lackauftrag;
2. B Beschichtung des Werkstückes 1.0 mit mindestens einer ersten Lackschicht 1.4;
3. C Zuführung des Werkstückes zu einer digitalen Druckstation;
4. D Bereitstellung von digitalen Steuerungsdaten für die digitale Druckstation;
5. E digitales Aufspritzen von Tröpfchen auf Teilflächen der ersten Lackschicht 1.4 auf dem Werkstück 1.0 mit einem zumindest teilweise transparenten Lack zum Aufbringen einer zweiten Lackschicht 1.5 auf die erste Lackschicht 1.4, wobei die zweite Lackschicht 1.5 nach der Aushärtung einen anderen Glanzgrad als die erste Lackschicht 1.4 hat, und
6. F physikalische Trocknung und/oder chemische Aushärtung der aufgebrachten Lackschichten 1.4, 1.5.

A first aspect of the invention is a method for producing a decorative surface with different gloss levels, comprising the following steps:

1. A supply of a workpiece with 1.0 to a device for paint application;
2. B coating of the workpiece 1.0 with at least a first lacquer layer 1.4;
3. C feeding the workpiece to a digital printing station;
4. D providing digital control data to the digital printing station;
5. E digital spraying of droplets on partial surfaces of the first lacquer layer 1.4 on the workpiece 1.0 with an at least partially transparent lacquer for applying a second lacquer layer 1.5 to the first lacquer layer 1.4, wherein the second lacquer layer 1.5 after curing has a different gloss level than the first lacquer layer 1.4 , and
6. F physical drying and / or chemical curing of the applied lacquer layers 1.4, 1.5.

A second aspect of the method according to the preceding paragraph is that the workpiece 1.0 is already printed before the method step A with a decorative image, or that the workpiece 1.0 after the method step A and before the method step B printed with a digital printer with at least two different colors becomes.

A third aspect of the method according to one of the two preceding paragraphs is that the digital printing data for the decorative image on the workpiece, in identical form or modified by a digital manipulation method, are used as a basis for the digital data provided in step D.

A fourth aspect of the method according to one of the three preceding paragraphs is that the lacquer layer 1.4 applied in step B is already at least partially cured before step E in an additional process step.

A fifth aspect of the method according to one of the four preceding paragraphs is that the degree of gloss 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 according to DIN EN ISO 2813: 2015- 02 measured at an angle of 60 °.

A sixth aspect of the method according to any one of the previous five paragraphs is that in step E the droplets are sprayed with a droplet size smaller than 10 pL, in particular smaller than 6 pL.

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

An eighth aspect of the method according to the first, second or third aspect is that with the first lacquer layer 1.4 in step B, a transparent lacquer layer is applied to an already existing decorative image.

A ninth aspect of the method according to one of the eight preceding paragraphs is that a liquid base layer 1.2 is applied to a surface of the coated or uncoated workpiece 1.0 and in the still liquid base layer 1.2 a structure is introduced by means of digital printheads, which is subsequently fixed, and 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.

A tenth aspect of the method according to the ninth aspect is that only the regions provided with a texture or only the regions without structure are printed with the second resist layer 1.5.

An eleventh aspect of the method, which has one of the previous aspects, is that the two lacquer layers 1.4, 1.5 are applied from an at least partially transparent lacquer, so that a decor image arranged underneath can be optically recognized by the two lacquer layers 1.4, 1.5.

A twelfth aspect of the method, which has one of the previous aspects, is that a glossy or high-gloss surface is produced by the second lacquer layer 1.5, or that a matt or less glossy surface is produced by the second lacquer layer 1.5.

A thirteenth aspect of the method, which has one of the previous aspects, is that the first and / or second lacquer contains matting agents, preferably in a proportion by weight of between 2% and 6%, in particular between 3% and 5%.

• einer ersten Druckvorrichtung zum Aufbringen einer ersten Lackschicht 1.4 und einer zweiten digitalen Druckvorrichtung zum Aufbringen einer zweiten Lackschicht 1.5 auf die erste Lackschicht 1.4, wobei
• die zweite Lackschicht 1.5 nach der Aushärtung einen anderen Glanzgrad als die erste Lackschicht 1.4 hat.

A further aspect of the invention is an apparatus for carrying out the method according to one of the above claims, 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 to the first lacquer layer 1.4, wherein
• the second lacquer layer 1.5 after hardening has a different degree of gloss than the first lacquer layer 1.4.

LIST OF REFERENCE NUMBERS

1.0

workpiece

1.1

first base layer

1.2

second base layer

1.3

digitally sprayed droplets

1.4

first varnish layer

1.5

second lacquer layer

2.4

grained wood areas

2.5

wood pore

3.1

bright mosaic tiles

3.2

darker mosaic tiles

3.3

interspaces

Claims (16)

Method for producing a decorative surface with different degrees of gloss, comprising the following steps: (C) feeding a workpiece (1.0), which is coated with at least one first lacquer layer (1.4), to a digital printing station; (D) providing digital control data to the digital printing station; (E) digital spraying of droplets on partial surfaces of the first lacquer layer (1.4) on the workpiece (1.0) with an at least partially transparent lacquer for applying a second lacquer layer (1.5) to the first lacquer layer (1.4), wherein the second lacquer layer (1.5) after curing has a different gloss level than the first lacquer layer (1.4). Method according to claim 1, characterized in that
a further step (A) is provided, in which a supply of the workpiece (1.0) is performed to a device for paint application, and
a further step (B) is provided, in which a coating of the workpiece (1.0) is carried out with at least the first lacquer layer (1.4). A method according to claim 1 or 2, characterized in that
a further step (F) is provided, in which a physical drying and / or chemical curing of the applied lacquer layers (1.4, 1.5) is carried out. A method according to claim 2 or 3, characterized in that
the workpiece (1.0) is already printed with a decorative image before the method step (A), and / or that
the workpiece (1.0) after the method step (A) and before the method step (B) is printed with a digital printer having at least two different colors. Method according to one of the preceding claims, characterized in that
the digital printing data 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 in step (D). Method according to one of claims 2 to 5, characterized in that
the lacquer layer (1.4) applied in step (B) is at least partially cured already before step (E) in an additional process step. Method according to one of the above claims, characterized in that
the degree of gloss 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), the gloss units being measured according to DIN EN ISO 2813: 2015-02 at an angle of 60 °. Method according to one of the above claims, characterized in that
in step (E), the droplets are sprayed with a droplet size smaller than 10 pL, in particular smaller than 6 pL. Method according to one of the preceding claims, characterized in that
the surface of the workpiece (1.0) before the application of the second lacquer layer has a structure with a structure depth of 5 - 300 microns (microns), preferably 10 - 90 microns (microns). Method according to one of claims 2 to 9, characterized in that
with the first lacquer layer (1.4) in step (B), a transparent lacquer layer is applied to an already existing decorative image. Method according to one of the preceding claims, characterized in that
On a surface of the coated or uncoated workpiece (1.0) a liquid base layer (1.2) is applied and in the still liquid base layer (1.2) a structure by means of digital printheads is introduced, which is subsequently fixed, and the structured base layer, the first lacquer layer (1.4 ) or the first lacquer layer (1.4) is applied to the structured base layer. A method according to claim 11, characterized in that
only the areas provided with a structure or only the areas without structure with the second lacquer layer (1.5) are printed. Method according to one of the preceding claims, characterized in that
the two lacquer layers (1.4, 1.5) are applied from an at least partially transparent lacquer, so that a decor image arranged underneath can be optically recognized by the two lacquer layers (1.4, 1.5). Method according to one of the preceding claims, characterized in that
a glossy or high-gloss surface is produced by the second lacquer layer (1.5), or that
a matt or less shiny surface is produced by the second lacquer layer (1.5). Method according to one of the above claims, characterized in that
the first and / or second varnish contains matting agents, preferably in a proportion by weight of between 2% and 6%, in particular between 3% and 5%. Apparatus for carrying out the method according to one of the above claims, 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) to the first lacquer layer (1.4), wherein the second lacquer layer (1.5) after hardening has a different degree of gloss than the first lacquer layer (1.4).

Images