DE102016120878A1 - Method for producing surface effects, in particular in UV-curable layers, apparatus for producing the same and articles obtained according to the invention - Google Patents

Abstract

The invention relates to a method for producing surface effects in a coating which is curable by high-energy particle radiation, in particular by UV radiation, the method comprising the following steps: application of a coating fluid, for example a lacquer which is free-radically curable, in particular UV is curable on a substrate, wherein the coating fluid is designed so that the reactivity at the surface of the applied coating film specifically differs from the reactivity in the volume of the applied coating film, irradiating the coating with high-energy particle radiation and devices, in particular for performing this method.

Description

Field of the invention

The invention relates to a method for producing surface effects, in particular in UV-curable layers, by micro-folding, and also to a device for producing such layers and an article obtained according to the invention.

A further aspect of the invention relates to the provision of energy-rich particle radiation, for example UV radiation, curable coating fluids which can be processed by the method according to the invention.

Background of the invention

The curing of organic polymerizable coatings by means of high-energy particle radiation, such as UV radiation, has been an industrially controlled process for many years. In particular, it is also known how a dull or glossy surface can be produced by the choice of a suitable coating system.

In the context of the present invention, the indication of the gloss of a lacquer or of a lacquered surface takes place in accordance with FIG DIN 67 530 respectively. ISO 2813 , Wherein the indication of the gloss units taking into account the corresponding surface at an angle of 60 °. A high-gloss surface is correspondingly referred to as a surface which has between 70 and 100 GE (GE = gloss units), as a silk-gloss surface with 45 to 70 GE, as a satin finish a surface between 20 to 45 GE. A matte surface has less than 20 GE.

Difficulties arise, however, when using a coating system both matt and shiny areas are to be generated simultaneously, for example, to identify specific functional areas of a surface. It is also known to produce surfaces which have certain structures or a specific feel, that is to say a special tactile sensory impression. Even with these effects, however, the simultaneous production of areas with different visual or structural expression with one and the same coating system is currently only possible with a high expenditure on equipment.

The generation of different haptic and / or visual properties, such as matt / gloss effects with one and the same coating system can be done in different ways. A simple possibility consists in the coating on a partially differently pretreated substrate. An example of this is the UV coating of a substrate which has been previously pretreated with a poorly wettable oil pressure varnish or a special ink. The subsequent coating produces in this case on the pretreated areas a repulsion of the coating and thus a matte finish.

This effect is known in Asia as "chemical embossing". In Europe, this method is referred to as "drip-off painting".

On the subsequent regionally different treatment of a homogeneous film by means of a template is known.

In the application usually undesirable, but the expert is quite familiar and the variation of the degree of matting within matt-coated surfaces as a function of the layer thickness. For example, matting agent particles sometimes no longer appear on the surface in thicker lacquer layers, whereby the film appears less dull in these areas. This effect can also be used specifically.

Also known are processes in which coatings are matted by acting on the surface of the resulting coating film after the order has been completed. In the simplest case, this can be done by etching or sandblasting. Again, a pattern on the surface can be generated by means of a template.

A similar effect can also be produced in a still liquid coating before hardening, if the (partial) generation of a roughness succeeds with the help of high-energy radiation.

This is how the German patent application describes DE 10 2006 042 063 A1 a method of adjusting the gloss level of surfaces obtained by coating with UV or electron beam curable lacquers. In this case, initially short-wave monochromatic UV radiation acts on a coating applied to a substrate, so that polymerization and crosslinking occur only in the surface layer of the coating. In a second step, electromagnetic radiation of a different, higher wavelength acts on the coating, with the result that crosslinking occurs over the entire thickness of the applied coating and the layer cures accordingly. In this way, in the surface layer caused by the thus induced cross-linking a microcirculation, which is fixed by the subsequent curing of the entire layer. By suitable choice of the curing parameters can be produced in this way by means of a coating system both high gloss and matte surfaces.

In the context of the present invention, the term "microfolding" is understood to mean the following phenomenon: The surface layer of a coating fluid applied is hardened to a skin-like layer in a first step, which means a layer having a harder or tougher surface near the surface. Due to the shrinkage during curing, this surface layer contracts during curing. This leads to a structuring, which requires that at least in a partial region of the coating surface there is a local change in the coating thickness, so that the thickness fluctuations are at least in the single-digit micrometre range. In particular, the surface layer may be present folded. In a second step, the applied coating fluid is cured over the entire volume.

As sources of monochromatic radiation, which is able to cause the microstructure by crosslinking of the surface layer, find it excimer radiators use.

In particular, monochromatic radiation of the wavelengths 172 or 222 nm is used.

A disadvantage of the use of excimer emitters for the microfolding, however, is that in order to ensure a uniform matting, the irradiation must be carried out under an inert gas atmosphere, since known for free-radically curable coatings oxygen inhibition impairs the desired reaction at the surface. For example, the international patent application describes WO 2007/068322 A1 a device which is suitable for carrying out a process for microfolding of UV-curable coatings, in which the irradiation conditions remain stable. For this purpose, the beam sources are designed so that a stable inert gas atmosphere is ensured and the inert gas is used simultaneously for cooling the radiator, so that the life of the excimer lamps is extended.

A further development of the aforementioned methods describes the European patent application EP 2 418 091 A1 , Here, a method is described in which it comes only in some areas of the paint surface to a micro-mapping, while in other areas of the paint surface is obtained a smooth surface. For this purpose, the paint surface is acted upon only in the appropriately selected subregions with the necessary for micro-short-wave electromagnetic radiation, for which the beam source is provided with a template or mask, so that it comes only to the desired only partial exposure of the surface. In this way, a coating is obtained which has at least one area with a matt or micro-folded surface and at least one area with a smooth surface, wherein the areas do not differ or only insignificantly with regard to their layer thickness.

Also for that in the EP 2 418 019 A1 described method is used to generate the micromolding excimer radiation.

The mechanism of the microplating described in the abovementioned industrial property applications is based on the combination of a low penetration depth of the radiation and thus a near-surface action with the property of the free-radically curable system to undergo a curing shrinkage in the polymerization reaction. These two effects produce a film which floats on still liquid coating material and which folds through the hardening shrinkage. In the subsequently performed second curing step, the still liquid intermediate region is also cured and combines with the substrate and the folded surface film.

The known methods for producing micro-folded matte surfaces or surfaces which have special optical effects or a certain tactile sensory impression thus have the overall disadvantage that an excimer emitter must necessarily be used to produce the micro-folded structure. Even if, as in the EP 2 418 019 A1 Although light up to 300 nm could possibly also be used to generate the microfill, a monochromatic light source is nevertheless always required, which furthermore also differs from the second light source, which is necessary for complete curing of the coating. This is due to the fact that the excimer radiation is strongly absorbed in coating solutions or paints, so that it comes only to the curing of a thin film, for example, only a few micrometers in thickness. If the lacquer layer is thicker overall than corresponds to the penetration depth of the laser radiation, the use of a second radiator with a different wavelength for this volume hardening is therefore necessary for hardening the lacquer layer over its entire thickness. This leads to complex procedures with a lot of equipment.

Thus, there is a need for a low-cost, simplified process for producing surface effects in coatings by micro-compaction, in particular for processes with which these surface effects are only partially introduced into the coating. Furthermore, different optical and / or tactile sensory effects are to be achieved in different areas of a surface of a coating.

Object of the invention

The object of the invention is to provide a method for simplified, cost-effective matting of paint surfaces by micro-finishing, in particular a method with which only partial areas of a surface can be purposefully matted or provided with optical or tactile sensory properties. In one development of the invention, different surface effects in different areas of a coating can be addressed, wherein the layer thickness of the coating between the individual areas can be different.

Further aspects of the invention relate to devices for carrying out the method according to the invention and also to products produced in this way and to coating fluids which are accessible to such a method.

Summary of the invention

The invention is solved in a surprisingly simple manner by a method according to claim 1, devices according to independent claims 19 and 23, and a coating fluid according to claim 24. Another aspect relates to products with micro-folded surfaces according to claim 29 produced in this way. Preferred embodiments can be found in the respective subclaims.

• – In einem ersten Schritt erfolgt das Auftragen eines Beschichtungsfluids, beispielsweise eines Lackes, welcher radikalisch härtbar, insbesondere UV-härtbar, ist, auf eine Unterlage. Hierbei ist das Beschichtungsfluid so ausgestaltet, dass die Reaktivität an der Oberfläche des aufgetragenen Beschichtungsfilms sich von der Reaktivität im Volumen des aufgetragenen Beschichtungsfilms gezielt unterscheidet.
• – In einem zweiten Schritt erfolgt das Bestrahlen der Beschichtung, wobei vorzugsweise UV-C-Strahlung mit einer Wellenlänge von 240 nm und mehr in die Oberflächenschicht der Beschichtung eingebracht wird.

The method for producing surface effects in a coating which is curable by high-energy particle radiation, in particular by UV radiation, comprises the following steps:

• In a first step, the application of a coating fluid, for example a lacquer which is free-radically curable, in particular UV-curable, is applied to a support. Here, the coating fluid is designed so that the reactivity at the surface of the applied coating film is specifically different from the reactivity in the volume of the applied coating film.
• - In a second step, the irradiation of the coating takes place, wherein preferably UV-C radiation having a wavelength of 240 nm and more is introduced into the surface layer of the coating.

The method is thus based on the same principle of micro-folding, as it is achieved by excimer radiation and subsequent post-curing by longer-wave UV radiation or electron radiation. The advantage of the method according to the invention, however, is that the surface reactivity is deliberately set differently to the volume reactivity. In this way it is possible, with longer-wave UV radiation than the above-mentioned excimer radiation, for example UV-C radiation of a commercially available medium-pressure mercury radiator, to produce a microfilling on the surface. The specifically differently set reactivity of the surface of the applied coating film to that of the volume furthermore leads to the effect being dependent on the thickness of the layer. Thus, thin layers remain shiny in the process of the invention, whereas thicker layers are matted.

A further advantage of the method according to the invention is that the hardening reaction of the surface and the volume is initiated with the medium-pressure mercury lamps customary in industry. As a result, the user does not have to make additional investments or make modifications to his system.

The effect according to the process is based on adapting the composition of the coating fluid such that the reactivity on the surface of the applied coating film differs specifically from the reactivity in the interior of the applied coating film.

This is achieved by adding to the coating fluid two different photoinitiators which act differently, especially in the form that one photoinitiator increases the reactivity in a near-surface zone of the applied coating film and another photoinitiator increases the reactivity inside the applied coating film.

In the prior art UV curing processes, photoinitiators have been used to date. However, up to now the problem has arisen that in a processing of such UV-curing lacquers or coating fluids under normal conditions, ie not under inert gas, the chain reaction started by the photoinitiators is inhibited by oxygen. As a result, a near-surface zone of the applied coating film hardens less than the latter Volume and according to the surface of the paint layer has only a low hardness or possibly still completely liquid.

• – Eine Prozessierung unter Inertbedingungen, um so das Problem der konkurrierenden Reaktion der gebildeten Radikale mit Sauerstoff zu vermeiden, oder
• – Eine Erhöhung des Gehalts an Photoinitiator.

To overcome these difficulties, the prior art proposes two solutions:

• - Processing under inert conditions, so as to avoid the problem of competing reaction of the radicals formed with oxygen, or
• - An increase in the content of photoinitiator.

Both solutions have disadvantages. For example, curing under inert conditions leads to increased expenditure on equipment. If, on the other hand, the content of photoinitiator is increased, the risk of migration of this photoinitiator from the cured coating increases at the same time, which is particularly critical in the case of food packaging. The increased migration is due to the fact that experience has shown that not the entire photoinitiator is reacted, but always remain unreacted components. Since the photoinitiators used are usually small, mobile molecules, these particles remaining in the cured film can migrate out of the film and, in the case of packaging, pass over to the contents.

Furthermore, in this way it is merely ensured that the near-surface zone and the interior of the applied lacquer layer are substantially uniformly cured, ie the near-surface zone has almost the same degree of crosslinking as in the interior of the lacquer layer. On the other hand, a stronger and earlier crosslinking of the near-surface zone compared to the interior of the lacquer layer, which causes a microfolding, is not possible with the abovementioned solutions.

In order to achieve earlier curing of the near-surface zone of the applied paint film, so far the use of an excimer radiator is necessary. The surface reaction, which is achieved using excimer radiation, is based on the fact that, for example, the reactivity of the polymerizable acrylate monomer is directly addressed by this radiation. However, the absorption of the excimer radiation decreases exponentially with increasing penetration depth, so that only the near-surface zone can be cured in this way. For a reaction in the interior of the applied lacquer layer, however, the irradiation with UV light of higher wavelength is still necessary. Thus, with the known methods of the prior art, which proceed in two stages using excimer radiation and a second, beam source of higher wavelength, although a targeted hardening of the near-surface zone to form micro-folding possible. As already described above, however, these methods also lead to an increased outlay on equipment.

The method according to the invention thus differs from the methods of the prior art in that considerably lower-energy radiation is required to date for the micro-clipping of the surface layer of the coating and thus for the production of surface effects. For example, UV radiation with a wavelength of 240 nm and more is already sufficient for the production of the microfolding, while heretofore excimer radiators with the wavelengths 172 nm and 222 nm were used, whereby only the wavelength of 172 nm is suitable without the use from photoinitiators to generate radicals. Such complex devices are no longer needed in the process of the invention. Rather, it is possible with the method according to the invention to use other beam sources.

According to one embodiment of the invention, the surface layer comprises thicknesses between 10 nm and 1 μm.

According to one embodiment of the invention, the irradiation is carried out in two steps in the form that in the first step a smaller UV dose is irradiated, the micro-generation generates, and in a second step, the film is completely through-hardened, for both curing steps longer-wave UV radiation, for example that of a medium pressure UV radiator is used.

According to a further embodiment of the invention, however, it is also possible for both the micro-aging and the curing of the film to be achieved in an irradiation step. For this purpose, the coating material is designed accordingly, in particular by the absorption of UV radiation over the layer thickness of the coating agent varies.

According to one embodiment of the invention, both the generation of the micro-cladding in the surface layer and the irradiation for curing the coating are effected in each case by means of a medium-pressure mercury radiator.

In a further embodiment of the invention, a, preferably the same, medium pressure mercury radiator is used both for the irradiation of the surface layer and for the curing of the coating. In this case, the adjustment of the dose of UV radiation by adjusting the power of the medium-pressure mercury radiator takes place.

According to a further embodiment of the invention, the coating in the mold take place, that a coating film is obtained, which has different layer thicknesses in certain areas. In these areas, each with different layer thickness different effects can be obtained.

This is advantageous, for example, if the feel of the coating is important, for example, if certain areas of the coating should already be recognizable by contact. Also, it is advantageously possible to realize very attractive optical configurations of a coated product.

According to yet another embodiment of the invention, the application of the coating takes place only on parts of the substrate, so that at least one area of the substrate is uncoated and at least one other area of the substrate is coated.

According to a further embodiment of the invention, the application of the coating takes place over the entire surface of the substrate, wherein furthermore the layer thickness can be different in different areas.

The irradiation of the surface layer preferably takes place over the entire surface. The generation of locally different effects in terms of gloss and feel is achieved by the previous generation of different layer thicknesses in the different areas. Thus, in areas of layer thicknesses between 1 .mu.m and 10 .mu.m, for example, a smooth surface without microplating is obtained, whereas in areas with layer thicknesses above 12 .mu.m the microplating takes place.

According to a further embodiment, the irradiation takes place in at least one subarea such that surface effects due to micro-clipping are achieved only in this subarea treated in this way, while in the at least one untreated subregion of the surface there is a smooth, non-micro-folded surface.

According to a preferred embodiment of the invention, the only local irradiation of the surface layer for microfilling takes place in at least one subregion through a mask or stencil which shades regions of the emitter, or by means of a spatially resolved scanning of the coating surface.

Preferably, the scanning is carried out by scanning the surface line by line and further the line is divided into individual pixels or pixels and each line is associated with each feed of the scan head.

According to yet another embodiment of the invention, there are various surface effects in different subregions of the coating.

The irradiation is preferably carried out by UV radiation under an inert gas atmosphere, preferably a nitrogen atmosphere. In this case, the residual oxygen content is preferably less than 5000 ppm, particularly preferably less than 1000 ppm or very particularly preferably less than 500 ppm.

Preferably, the application of the coating fluid by means of a printing process, for example by gravure, flexographic printing, screen printing, pad printing or inkjet printing, or by rolling, flooding, knife coating, casting, such as curtain or slot casting, dipping spraying and / or spin.

Particularly preferably, the coating agent inkjet technology is made. With this method, it is particularly easy to produce different layer thickness of the coating material in different areas on the surface in one pass. For example, by appropriate screening and the application only very small layer thicknesses, preferably less than 2 microns, and taking into account that the applied droplets do not converge, take place a coating order with a matte surface. In areas with layer thicknesses in which the drops combine to form a film but the layer thickness is below a critical threshold, the surface appears shiny and in areas above this critical threshold a matte effect is again achieved by the microstructure. At the same time, all these three different areas have a different feel. The haptic is not only differentiated by the different layer thicknesses (relief effect, Braille structures, replacement of blind embossing by coating application), but also by a changed frictional resistance of the different areas. Micro-folded areas are characterized, for example, by a very low frictional resistance, whereas very smooth areas can be almost tacky when passing by hand. In contrast, very thin matte structures, in turn, have a low frictional resistance, but, in contrast to the areas with a microplate, are rather rough, whereas microfolded areas feel very smooth and soft.

According to a further embodiment of the invention, the gloss level of the coating is at a viewing angle according to DIN EN ISO 2813 in the areas in which the surface layer is exposed to the microplating, after hardening of the entire layer between 0.1 GE and 80 GE. The degree of gloss is preferably between 0.1 GE and 50 GE, more preferably between 0.1 GE and 20 GE and most preferably between 0.1 GE and 10 GE, this gloss level corresponding to DIN EN ISO 2813 is determined.

The invention further relates to a device for curing coating fluids, for example paints, which are curable by high-energy particle radiation, in particular by UV radiation. The curing takes place in two steps and, furthermore, the power introduced into the coating by means of the curing device is adjusted so that in a first step only the surface layer of the coating is treated, and in a second step the coating can be cured over the entire layer is.

Preferably, the curing device comprises a medium pressure mercury radiator.

A possible embodiment of the invention includes the design of the curing device so that the curing takes place in an inert gas atmosphere via the microfilling by means of excimer radiators. The inert gas is preferably nitrogen. The inert gas atmosphere may help to aid in less well suited coating solutions since the abovementioned oxygen inhibition, even with appropriate formulation, interferes with the reaction at the surface. If this impairment is reduced under inert gas, the surface reaction can proceed more efficiently and thus the micro-folding can be supported.

According to one embodiment of the invention, the device for curing the layer is formed so that initially only in a partial region of the coating, the surface layer is exposed and further, the curing of the coating over the entire surface of the coating takes place. In this way, only at least one subregion of the coating is present with a micro-clipping of the surface, while at least one other region of the coating has a non-micro-folded, smooth surface.

Preferably, the apparatus comprises a computerized means for controlling the curing of the coating. In particular, the informatic means is designed to determine the performance, dose and / or location of the cure.

• – Vorzugsweise eine Vorrichtung zur Aufnahme der Unterlage,
• – ein Mittel zum Transport der Unterlage zwischen den einzelnen Arbeitsstationen,
• – eine Vorrichtung zum Aufbringen des Beschichtungsfluids auf die Unterlage, wobei die Vorrichtung dergestalt ausgestaltet sein kann, dass das Beschichtungsfluid über den gesamten Bereich Oberfläche der der Unterlage oder nur über einen Teilbereich derselben aufgetragen wird,
• – eine Vorrichtung (6) zum Aushärten der Beschichtung, wobei sich das Aushärten in zwei Schritten vollzieht und die mittels der Vorrichtung zum Aushärten in die Beschichtung eingebrachte Leistung vorzugsweise so einstellbar ist, dass in einem ersten Schritt nur die Oberflächenschicht der Beschichtung behandelt wird, wobei die Oberflächenschicht vorzugsweise eine Dicke zwischen 10 nm und 1 µm aufweist, und in einem zweiten Schritt die Beschichtung über die gesamte Dicke aushärtbar ist,
• – vorzugsweise eine Vorrichtung zur Entnahme der Unterlage, sowie
• – vorzugsweise eine Anlagensteuerung, beispielsweise in Form eines informatischen Mittels wie beispielsweise eines Computers, zur Steuerung der Arbeitsschritte der Anlage, welches die Parameter über alle Verfahrensschritte steuert und deren Zusammenwirken sicherstellt.

Yet another aspect of the invention relates to a device for producing surface effects on at least a portion of a substrate coated with a coating which is curable by high-energy particle radiation, in particular by UV radiation, which describes a device according to the invention for curing coating fluids as described above includes. The device comprises:

• Preferably a device for receiving the base,
• A means for transporting the support between the individual workstations,
• A device for applying the coating fluid to the substrate, wherein the device may be designed in such a way that the coating fluid is applied over the entire area of the surface of the substrate or only over a partial area thereof,
• A device ( 6 ) for curing the coating, wherein the curing takes place in two steps and the power introduced into the coating by means of the curing device is preferably adjustable so that in a first step only the surface layer of the coating is treated, the surface layer preferably having a thickness between 10 nm and 1 μm, and in a second step, the coating is curable over the entire thickness,
• - Preferably, a device for removing the pad, as well
• - Preferably a system control, for example in the form of an informational means such as a computer, for controlling the operations of the system, which controls the parameters on all process steps and ensures their interaction.

The plant controller also preferably includes means to read out parameters in an informational format commonly used in the printing industry, for example JDF (Job Definition Format), and to translate them into process steps. By way of example, such a means may comprise a parameterization file stored in a memory.

According to a further embodiment of the invention, the device comprises at least one sensor as well as an encoder and actuators in order to detect the respective method steps by sensors and to implement them in a controlled manner by the computer by means of corresponding actuators.

Yet another aspect of the invention relates to a coating fluid suitable for carrying out the method according to the invention. This is a coating fluid which is accessible by high-energy particle radiation, in particular by UV radiation, curable, in particular by free-radical polymerization, and a micro-folding process. In this case, the microfolding is carried out by irradiation of the surface layer of an applied coating, for example by irradiation with UV-C radiation having a wavelength of more than 240 nm.

Generally, a coating fluid suitable for carrying out the process of the present invention comprises a composition in which 100 parts of a liquid binder comes to 13 parts of a mixture of photoinitiators and / or crosslinking agents and / or activators for curing.

In the context of the present invention, photoinitiators are substances which decompose by absorption of light, in particular UV light, and thus form reactive species, for example radicals or cations.

According to one embodiment of the invention, photoinitiators are used which form radicals.

In the context of the present invention, crosslinking agents and / or activators are substances which make polymerization reactions particularly efficient, for example by being suitable for forming particularly effective starting radicals. Another example of an increase in efficiency is the transfer of an oxygen-inactive radical into a re-start radical. In the context of this disclosure, the activator is also a synergist in each case and can also be referred to as such.

According to one embodiment of the invention, at least one tertiary amine is used as crosslinking agent or activator. According to another embodiment of the invention, this is preferably done when a so-called type II photoinitiator is used as the photoinitiator. Radicals are formed in a type II photoinitiator in that the photoinitiator, for example benzophenone, extracts a hydrogen atom from an adjacent molecule. In contrast, in type I photoinitiators, the radicals are formed directly by the decomposition of the initiator molecule. An example of a type I photoinitiator is available under the trade names Irgacure 1173 and Darocur 1173, respectively, and includes 1-phenyl-2-hydroxy-2-methyl-1-propanone.

Preferably, an acrylate-based binder is used.

Further preferably, the mixture of photoinitiators and / or crosslinking agents and / or activators is composed so that one part of a type I photoinitiator, 6 parts of a type II photoinitiator and 6 parts of an activator are added.

The synergist (or activator), together with type II photoinitiators, each overcome oxygen inhibition and are particularly useful in crosslinking under atmospheric conditions to facilitate and / or enhance surface reactivity.

According to one embodiment of the invention, the coating fluid has the following composition:
40 parts HDDA (hexanediol diacrylate)
10 parts of TMPTA (trimethylolpropane triacrylate)
50 parts DPGDA (dipropylene glycol diacrylate)
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine

The fact that the reactivity at the surface of the applied coating film specifically differs from the reactivity in the volume of the applied coating film is thus achieved by dissolving 1 part of a type I photoinitiator, here 1-phenyl-2-hydroxy-2-methyl-1. Propanone, 6 parts of a photoinitiator type II, here benzophenone, and 6 parts of an activator, here N-methyldiethanolamine, are used per 100 parts of a liquid binder mixture (here comprising HDDA, TMPTA and DPGDA). By varying the proportions of the Type I photoinitiator relative to the proportions of the Type II photoinitiator, further targeted discrimination of the reactivity at the surface of the coated coating film can be achieved from the reactivity in the volume of coating film applied.

The term parts in the context of this disclosure in each case by weight.

According to a further embodiment of the invention, the coating fluid has the following composition:
80 parts HDDA (hexanediol diacrylate)
20 parts of TMPTA (trimethylolpropane triacrylate)
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine

The fact that the reactivity at the surface of the applied coating film specifically differs from the reactivity in the volume of the applied coating film is thus achieved by dissolving 1 part of a type I photoinitiator, here 1-phenyl-2-hydroxy-2-methyl-1. Propanone, 6 parts of a photoinitiator type II, here benzophenone, and 6 parts of an activator, here N-methyldiethanolamine, per 100 parts of a liquid binder mixture (here comprising HDDA and TMPTA) are used and in contrast to the previous example, a more reactive binder mixture is used. By varying the proportions of the Type I photoinitiator relative to the proportions of the Type II photoinitiator, further targeted discrimination of the reactivity at the surface of the coated coating film can be achieved from the reactivity in the volume of coating film applied.

Another example of a product that can be microfilled by the radiation of a medium pressure mercury radiator is coated with the following formulation:
100 parts DPGDA (dipropylene glycol diacrylate)
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine

The fact that the reactivity at the surface of the applied coating film specifically differs from the reactivity in the volume of the applied coating film is thus achieved by dissolving 1 part of a type I photoinitiator, here 1-phenyl-2-hydroxy-2-methyl-1. Propanone, 6 parts of a photoinitiator type II, here benzophenone, and 6 parts of an activator, here N-methyldiethanolamine, are used per 100 parts of a liquid binder (here comprising DPGDA). The DPGDA used as difunctional binder forms a relatively soft film. The volume shrinkage is less pronounced compared to TMPTA-containing formulations. By varying the proportions of the Type I photoinitiator relative to the proportions of the Type II photoinitiator, further targeted discrimination of the reactivity at the surface of the coated coating film can be achieved from the reactivity in the volume of coating film applied.

In a further embodiment, the microfolding succeeds in only one curing step. For this purpose, for example, elastic aliphatic urethane acrylates must be added to the coating formulation. A very good reactivity with a very pronounced effect is achieved with the following formulation:
80 parts DPGDA (dipropylene glycol diacrylate)
20 parts of Ebecryl 4491 from Allnex
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine

The fact that the reactivity at the surface of the applied coating film specifically differs from the reactivity in the volume of the applied coating film is thus achieved by dissolving 1 part of a type I photoinitiator, here 1-phenyl-2-hydroxy-2-methyl-1. Propanone, 6 parts of a photoinitiator type II, here benzophenone, and 6 parts of an activator, here N-methyldiethanolamine, are used per 100 parts of a liquid binder mixture (here comprising DPGDA and Ebecryl 4491). By varying the proportions of the Type I photoinitiator relative to the proportions of the Type II photoinitiator, further targeted discrimination of the reactivity at the surface of the coated coating film can be achieved from the reactivity in the volume of coating film applied.

Even with AC Resin 250 from BASF similar effects can be achieved.

All of the formulations mentioned are basic formulations which, in order to achieve processability, can be supplemented with corresponding flow and wetting additives. However, this additive has no influence on the achievement of the desired effects. In addition, a layer thickness of at least 12 μm is necessary to achieve the micro-folding. In a range between 10 and 12 microns, the microfolding is formed only irregularly (s. ). Below 10 μm the surface remains shiny.

The aforementioned formulations are all characterized by a very low processing viscosity (of 70-120 s in the DIN 2 flow cup), which allows their use in inkjet printheads. In this case, advantageously, a method can be used which allows the simultaneous generation of areas of greatly varying layer thicknesses.

However, the effect of microfiltration is in no way dependent on the viscosity. It is also possible to produce much higher viscosity formulations that can be applied by other methods. It is important to obtain a relatively higher reactivity at the surface than in the volume. The photoinitiators used here must have their absorption maximum in the UV-C range.

The effect of microfolding can be prevented by adding higher concentrations of volume-hardening photoinitiators to the formulation (e.g.,> 2% Irgacure 1173 with otherwise equal concentrations of photoinitiators and co-initiators in the formulation can prevent the effect). The same applies if, for volume hardening, photoinitiators with a higher absorption wavelength are used in suitable concentrations. Thus, by adding 1% TPO (triphenylphosphine oxide) in the above-mentioned formulations, the micro-folding can be prevented. The percentages in each case relate to percent by weight.

Yet another aspect of the invention relates to a product which consists of a base and a coating applied thereto. In this case, the coating has a surface layer with a micro-cladding at least in a partial region and the coating is formed
40 parts HDDA (hexanediol diacrylate)
10 parts of TMPTA (trimethylolpropane triacrylate)
50 parts DPGDA (dipropylene glycol diacrylate)
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine

and or

80 parts HDDA (hexanediol diacrylate)
20 parts of TMPTA (trimethylolpropane triacrylate)
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine

and or

100 parts DPGDA (dipropylene glycol diacrylate)
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine

and or

80 parts DPGDA (dipropylene glycol diacrylate)
20 parts of Ebecryl 4491 from Allnex
1 part Irgacure 1173 (or Darocur 1173)
6 parts benzophenone
6 parts of N-methyldiethanolamine.

Suitable substrate materials as a backing for the coating may be conventional materials used in the graphic arts industry, e.g. Paper, cardboard, laminated paper or laminated board, plastic films and corrugated cardboard substrates. Polyolefin films but also PET, acetate and similar films are preferably used for the lamination.

Especially the change in haptics by the micro-folding, which can cause a reduction of the sliding friction by preventing the so-called glass plate effect, makes the method but also for completely different applications outside the graphic industry interesting. These include coatings with low frictional resistance for aviation but also for watercraft. The adhesion of dirt, lime and bacteria on such surfaces is reduced compared to smooth surfaces.

The micro-folding in combination with specially flexible or even elastic binders can be used for the production of so-called soft-touch paint surfaces.

Further preferably, the degree of gloss in the at least one region which has a microfolding is between 0.1 and 80 GE, preferably between 0.1 GE and 50 GE, more preferably between 0.1 GE and 20 GE, and very particularly preferably between 0 , 1 GE and 10 GE, at a viewing angle according to DIN EN ISO 2813 is.

By a suitable choice of the coating materials, it is also possible to produce an ice-flower-like effect or the appearance of a broken safety glass pane instead of microfilling by the method according to the invention.

Description of the drawings

Show it

1 to 3 different photographic images of samples with different degrees of microfolding,

4 and 5 Devices for producing surface effects of substrates according to embodiments of the invention,

6 a product obtained according to the method, as well as

7 to 13 Photographic representations of coatings according to embodiments of the invention.

Detailed description of preferred embodiments

In the following detailed description of preferred embodiments, for the sake of clarity, not all features of a particular device are disclosed in FIG 4 . 5 and 6 shown to scale. Furthermore, the term high-energy particle radiation is also used in general form for photons. Especially in the ultraviolet spectral range and in general towards shorter wavelengths, photons show increasing particulate character.

1 shows here by way of example a photographic image of a sample in which a coating material which is accessible to the microplate was applied only with a layer thickness of 10 μm. It can be seen that the microfolding is only irregular. Thus, in the left-hand section of the figure, a microfolding is clearly recognizable, whereas this microfolding in the right-hand region of the sample is only slightly or not at all pronounced.

2 shows an example of a photographic representation of the surface of a sample, which was obtained by the method according to the invention. The layer thickness is here 30 microns. The microfolding is very pronounced here.

3 shows a large increase in a surface area of the sample 2 , Here, too, the structures created by microfolding are very clearly recognizable.

4 shows a schematic representation of an embodiment of a device 1 for producing surface effects on at least one subregion of a substrate coated with a coating which is curable by high-energy particle radiation, in particular by UV radiation, the device comprising:
It is in 4 a means for transporting the pad 3 to recognize between the individual workstations. This means of transport is in the device 1 through the parts 21 . 22 and 23 exemplified and includes a first roller or roller 21 on which a pad or a substrate 3 , for example formed from paper, cardboard, laminated paper or laminated cardboard, plastic films and corrugated cardboard substrates, or polyolefin film or PET or acetate film, is rolled up.

The underlay 3 becomes in the direction of the arrow 25 , the transport direction, through the device 1 moves, taking the surface 31 of the printing substrate or of the substrate or the substrate 3 , which should be printed in 4 is directed upward. The roller 22 is another part of the means of transport.

Furthermore, the device comprises 1 a device 4 for applying the coating fluid to the substrate 3 , A device for applying coating fluid is for example in the WO 2009/012996 Although the disclosure of which is incorporated by reference into the subject matter of the present disclosure is described as a coating unit, according to the present invention the device described therein for smoothing the film applied to the substrate surface by means of the coating unit is advantageously usable, but represents an optional unit which does not mandatory for the implementation of the invention must be used.

The device 4 can be designed so that the coating fluid over the entire area of the surface 31 the underlay 3 or only over a portion of the same is applied. An order over the entire area of the surface 31 the underlay 3 is advantageous if a coating fluid is applied, which also performs a protective function in the cured state, for example, has anti-scratch properties. In contrast, a merely partial application, that is to say an application of the coating fluid, is only over a partial area of the surface 31 the underlay 3 , Of advantage, for example, highlight specific area of the pad or mark. In this way it is also possible to generate images, for example in the form of images or texts.

The device 1 further comprises a device 7 for curing the coating. The curing of the coating takes place in two steps. The means of the device 7 power applied to the coating for curing is preferably adjustable so that in a first step only the surface layer of the coating is treated. In this case, the surface layer preferably has a thickness of between 10 nm and 1 μm. In a second step, the coating is curable over the entire thickness. The device preferably comprises 7 a computerized means for controlling the curing of the coating. In particular, the informatic means is designed to determine the performance, dose and / or location of the cure

Furthermore, in 4 a device 6 to dry the coating. By means of this device, it is possible in a first step to remove volatile constituents of the coating fluid before curing. Such a device 6 however, is only optional of the device 1 includes. Furthermore, the device 1 a device 8th for cooling the coated substrate after curing.

The device 1 may further according to a preferred embodiment of the invention, a system control 5 comprise, for example in the form of an informational means such as a computer, for controlling the operations of the system, which preferably sensory detects the relevant parameters in all process steps and preferably controls with each associated actuators and thus ensures their interaction.

The plant control 5 preferably also comprises a means for reading out parameters in an informative format, which is generally used in the printing industry, for example, JDF (Job Definition Format) and converting them into process steps. By way of example, such a means may comprise a parameterization file stored in a memory.

Also, it is possible that the device 1 In general, without being limited to the exemplary embodiment illustrated here, a plurality of system controls comprises, which selectively drive individual devices in each case.

According to a further embodiment of the invention, the device comprises at least one sensor as well as an encoder and actuators in order to detect the respective method steps by sensors and to implement them in a controlled manner by the computer by means of corresponding actuators.

The plant control 5 is in one embodiment preferably via suitable interfaces, for example the interfaces 54 . 55 . 56 . 57 with devices coming from the device 1 are included, as an example, the devices 4 . 5 . 6 . 7 , connected.

5 shows a further schematic representation of a device 1 according to another preferred embodiment. The device 1 in this case comprises a device for receiving the pad 301 , in which various documents 3 , which for the sake of clarity are not all designated, are included. From the device 301 for receiving the pad 3 become individual documents 3 , which may comprise, for example, paper, cardboard, laminated paper or laminated board, plastic films and corrugated cardboard substrates, or polyolefin film or PET or acetate film, by means of the means for transporting the substrate 3 between the individual workstations through the device 1 emotional.

The means for transporting the base 3 includes a first roller 21 , a second roller 23 as well as an additional roller 22 , where are still several other rolls 22 may be included by the means of transport. Furthermore, the means for transport comprises a conveyor belt 24 which are the two rollers 21 and 23 connects together, so that by the rotation of at least one of the rollers 21 . 23 a movement of documents 3 through the device 1 in the direction of the arrow 25 he follows.

Again, the device includes 1 the device 4 for applying the coating fluid to the substrate 3 and a device for curing the coating 7 ,

Furthermore, the devices 6 and 8th shown, which can serve the drying of the coating fluid or a cooling of the printed substrate after curing and are merely optional in the present case. The devices 4 . 5 . 6 . 7 can each have an interface 54 . 55 . 56 . 57 with a system control 5 be connected. Also such a system control 5 with the appropriate interfaces is only optional of the device 1 includes.

Furthermore, it is generally possible, without limitation to the embodiment shown here, that several system controls 5 from a device 1 are included, which each individual devices 4 . 5 . 6 . 7 Taxes.

In addition, the device includes 1 this embodiment, a device 302 for removing the pad 3 ,

In 6 are schematic and not to scale two products 300 shown, which each have a base 3 include, on the surface 31 (not labeled) a coating 32 was applied. The coating 32 has a surface layer with a microfolding at least in a partial area.

In the upper area of 6 is a product 300 pictured, which is a full-surface coating 32 on the (not designated) surface 31 includes. In the lower part of the 6 is the coating 32 only on partial areas of the (not designated) surface 31 the underlay 3 applied.

The invention thus relates to a method for producing surface effects in a coating which is curable by high-energy particle radiation, in particular by UV radiation, the method comprising the following steps: application of a coating fluid, for example a lacquer, which is free-radically curable, in particular UV curable on a substrate, wherein the coating fluid is designed such that the reactivity at the surface of the applied coating film is specifically different from the reactivity in the volume of the applied coating film,
Irradiating the coating with high-energy particle radiation and devices, in particular for carrying out this method.

7 shows a photographic representation of coatings according to embodiments of the invention. These are a total of eight coatings, which were applied to a black base. The individual coatings differ from one another with regard to the exact formulation of the coating fluid and / or the layer thickness. While in the upper area of 7 are obtained rather matte coatings, so coatings with a rather low gloss, are in the lower part of the 7 Coatings shown, which have a rather high gloss level. The degree of gloss is in this case a function of the microfolding, so that, for example, in the case of a very strong microfolding at a certain viewing angle, a rather dull appearance can result.

To better illustrate the different effects which coatings can exhibit according to embodiments of the present invention, FIGS 8th to 13 each record of individual coated samples.

In 8th a coating is shown in which the microplating results in a larger-area structure, comparable to what are known as "dry cracks" which form, for example, during the drying of originally moist soils. The coating has a relatively high gloss in addition to the described structuring.

In 9 is a coating to see in which the microfolding results in finer structures and overall results in a rather dull appearance.

In 10 is a further coating according to yet another embodiment of the invention to see. Again, a matte appearance has been obtained, in which case the coating appears even more dull than the coating 9 ,

In contrast, in 11 to see a coating which has a very high degree of gloss, so that only a very low microcold was obtained.

In 12 and 13 You can see two samples, each of which has an ice-flower-like effect, which resembles the appearance of ice-covered glass. This effect is already in the coating, which in 12 can be seen, recognizable, even more pronounced but in 13 to see.

Thus, overall, it should be noted that with a method according to embodiments of the invention, very different optical appearances in a coating can be realized by micro-plating in a lacquer surface.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006042063 A1 [0012]
• WO 2007/068322 A1 [0016]
• EP 2418091 A1 [0017]
• EP 2418019 A1 [0018, 0020]
• WO 2009/012996 [0102]

Cited non-patent literature

• DIN 67 530 [0004]
• ISO 2813 [0004]
• DIN EN ISO 2813 [0053]
• DIN EN ISO 2813 [0053]
• DIN EN ISO 2813 [0089]

Claims (33)

Method for producing surface effects in a coating ( 32 ), which is curable by high-energy particle radiation, in particular by UV radiation, the method comprising the following steps: application of a coating fluid, for example a lacquer which is free-radically curable, in particular UV-curable, to a support ( 3 ), wherein the coating fluid is designed so that the reactivity at the surface of the applied coating film is specifically different from the reactivity in the volume of the applied coating film, - irradiation of the coating ( 32 ) with high-energy particle radiation.  The method of claim 1, wherein for irradiating the coating UV-C radiation having a wavelength of 240 nm and more is introduced into the surface layer of the coating.  The method of claim 1 or 2, wherein the irradiation is carried out in two steps in the form that in the first step, a smaller UV dose is irradiated, the micro-generation generates, and in a second step, the film is completely through-hardened, wherein for both curing steps longer-wave UV Radiation, for example, that of a UV medium-pressure radiator, is used.  The method of claim 1, 2 or 3, wherein both the micro-setting and the curing are achieved in an irradiation step, and wherein the coating material is further preferably designed so that the absorption of UV radiation over the layer thickness of the coating agent varies.  Method according to one of claims 1 to 4, wherein the irradiation of both the surface layer as well as the irradiation for curing the coating in each case by means of a medium-pressure mercury radiator. A method according to claim 5, wherein a, preferably the same medium pressure mercury radiator both for the irradiation of the surface layer and for the curing of the coating ( 32 ), wherein the adjustment of the dose of UV radiation is effected by adjusting the power of the medium pressure mercury radiator.  Method according to one of claims 1 to 6, wherein the coating is carried out in the form that a coating film is obtained, which has different layer thicknesses in certain areas. Method according to one or more of claims 1 to 6, wherein the application of the coating ( 32 ) only on parts of the base ( 3 ), so that at least a portion of the pad ( 3 ) uncoated and at least one other area of the substrate ( 3 ) coated. Method according to one or more of claims 1 to 6, wherein the application of the coating ( 32 ) over the entire surface of the pad ( 3 ), wherein further the layer thickness may be different in different areas.  Method according to one of claims 1 to 9, wherein the irradiation of the surface layer takes place over the entire surface.  Method according to one or more of claims 1 to 9, wherein the irradiation of the surface layer takes place only in at least one subregion such that only in the at least one subarea treated in this way surface effects due to microplating are achieved while in the at least one untreated subregion of the surface a smooth, not micro-folded surface is present.  The method of claim 11, wherein the only local irradiation of the surface layer for microfilling in at least a partial area by a mask or stencil which shadows areas of the radiator, or by means of a spatially resolved scanning of the coating surface.  The method of claim 12, wherein the scanning is carried out by scanning the surface line by line and further, the line is divided into individual pixels or pixels and each line is associated with an advance of the scan head. Method according to one or more of claims 1 to 13, wherein different surface effects in different subregions of the coating ( 32 ) are present.  Method according to one of the preceding claims 1 to 14 wherein the irradiation is effected by UV radiation under inert gas, preferably nitrogen atmosphere.  The method of claim 15, wherein the residual oxygen content is less than 5000 ppm, preferably less than 1000 ppm or more preferably less than 500 ppm. Method according to one or more of claims 1 to 16, wherein the application of the coating fluid by means of a printing process, for example by gravure, flexographic printing, screen printing, Pad printing or inkjet printing, or by rolling, flooding, knife coating, pouring, for example, curtain or slot casting, dipping, spraying and / or spinning takes place. Method according to one or more of claims 1 to 17, wherein the gloss level of the coating ( 32 ) at a viewing angle according to DIN EN ISO 2813 in the areas in which an exposure of the surface layer for micro-folding, after curing of the entire layer between 0.1 GE and 80 GE, preferably between 0.1 GE and 50 GE, particularly preferred between 0.1 and 20 GE and most preferably between 0.1 and 10 GE. Contraption ( 6 ) for curing coating fluids, which are curable by high-energy particle radiation, in particular by UV radiation, wherein the curing takes place in two steps and by means of the device for curing in the coating ( 32 ) is adjustable in such a way that in a first step, only the surface layer of the coating is treated and in a second step, the coating over the entire thickness is curable. Contraption ( 6 ) according to claim 19, comprising a medium pressure mercury radiator. Contraption ( 6 ) according to one or both of claims 19 and 20, wherein the device ( 6 ) is formed for curing the layer so that only in a partial region of the coating ( 32 ) the surface layer is exposed and further the curing of the coating ( 32 ) over the entire surface of the coating ( 32 ) he follows. Contraption ( 6 ) according to one or more of claims 19 to 21, wherein the device ( 6 ) a computerized means for controlling the curing of the coating, in particular so that the informative agent determines the power, the dose and / or the location of the curing. Contraption ( 1 ) for producing surface effects on at least a portion of one with a coating ( 32 ), which is curable by high-energy particle radiation, in particular by UV radiation, coated substrate ( 3 ), the device comprising: - preferably a device ( 301 ) for receiving the pad, - a means for transporting the pad ( 3 ) between the individual workstations, - a device ( 4 ) for applying the coating fluid to the substrate ( 3 ), the device ( 4 ) in such a way that the coating fluid can be applied over the entire area of the surface ( 31 ) of the document ( 3 ) or only over a sub-area of the same, - a device ( 6 ) for curing the coating, wherein the curing takes place in two steps and the power introduced into the coating by means of the curing device is preferably adjustable so that in a first step only the surface layer of the coating is treated, the surface layer preferably having a thickness between 10 nm and 1 μm, and in a second step the coating can be cured over the entire thickness, preferably a device ( 302 ) for removing the pad ( 3 ), and - preferably a plant control ( 5 ), the device ( 6 ) for curing the coating ( 32 ) is preferably configured according to one or more of claims 19 to 22.  Coating fluid which is accessible by high-energy particle radiation, in particular by UV radiation, curable, in particular by free-radical polymerization, and a micro-folding process, wherein the micro-exposure by irradiation of the surface layer of an applied coating, for example by irradiation with UV-C radiation having a wavelength of more than 240 nm.  Coating fluid according to claim 24 having a composition of from 100 parts of a liquid binder to 13 parts of a mixture of photoinitiators and / or crosslinking agents and / or activators.  Coating fluid according to one of claims 24 or 25, comprising photoinitiators which form radicals.  Coating fluid according to one of Claims 24 to 26, comprising a tertiary amine, preferably N-methyldiethanolamine or an amine-modified acrylate.  Coating fluid according to one of Claims 24 to 26 with an acrylate-based binder. Product ( 300 ), which is a base ( 3 ) and a coating applied thereto ( 32 ), wherein the coating ( 32 ) comprises a surface layer with a microfolding at least in a partial area. Product ( 300 ) according to claim 29, wherein the backing ( 3 ) Comprises paper, cardboard, laminated paper or laminated board, plastic films and corrugated cardboard substrates, or polyolefin film or PET or acetate film. Product ( 300 ) according to one or more of claims 29 to 30, wherein the degree of gloss in the at least one region which has a microfolding, between 0.1 GE and 80 GE, preferably between 0.1 GE and 50 GE, more preferably between 0.1 GE and 20 GE, and most preferably between 0.1 GE and 10 GE, at a viewing angle according to DIN EN ISO 2813. Product ( 300 ) according to one or more of claims 29 to 31, which has at least one area with a first surface effect as a result of microplating and at least one further area with a second surface effect as a result of microplating and at least one area without microplating, wherein the layer thickness of the coating ( 32 ) differs between the individual regions by no more than 10% from a nominal layer thickness which corresponds to the thickness of the coating in the non-micro-folded state. Product ( 300 ) according to one or more of claims 29 to 32, can be produced, in particular produced, in a method according to one or more of claims 1 to 18.

Images