Method and device for curing UV varnish

Abstract

The invention relates to a method for curing a UV varnish (3) applied to a surface of a substrate (2) using a roller (7), the roller core (8) of which holds at least one source (10) for emitting UV radiation, in which method the UV radiation penetrates a roller coating (9) around the periphery and strikes the surface coated with the UV varnish (3).

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for curing UV varnish using a roller. Background Art

[0002] In painting technology or lacquering technology, the use of ultraviolet (UV) radiation to cure varnishes is becoming increasingly important. UV-curing paint systems (hereinafter also referred to as UV varnishes) have relatively high mechanical and chemical resistance and can be cured in a relatively short time (e.g., within a few seconds). In addition, the energy required for curing of UV-curing paint systems is significantly lower than that required for thermally curing paint systems, and UV-curing paint systems can be easily formulated without solvents.

[0003] Thanks to these properties, UV varnishes have begun to develop successfully, for example in the furniture industry and on belly-type substrates or components. UV varnishes are also increasingly used to coat metals.

[0004] Since the uniform irradiation of UV light is very beneficial for the curing of UV varnishes, the application is currently basically limited to coating flat substrates and / or substrates with relatively simple geometries. The substrate or component can be, for example, a sheet or plate made of metal, wood, stone, cardboard or other material to be coated.

[0005] When a UV varnish is cured, the UV light splits the photoinitiator of the UV varnish into free radicals, which in turn polymerize double bonds in a chain reaction. The reaction proceeds rapidly but is disrupted at the interface with the ambient air by oxygen molecules which act as free radical scavengers. To counteract this, relatively strong doses of UV light and photoinitiator are used so that the varnish is fully crosslinked and "tack-free" even on the surface.

[0006] Mercury vapor lamps are usually used as UV sources, their spectrum can be adapted to the requirements by doping. Electron beam machines and X-ray machines have not been widely adopted due to occupational health reasons and high acquisition costs. For many years, UV LED emitters have also been used, which have a low energy requirement and work without the use of mercury. The disadvantage of UV LED emitters is that they generate UV light with a longer wavelength and oxygen inhibition is currently a problem. Only reactive varnish systems can be cured with LED emitters, or curing takes place under inert gas or at very short distances.

[0007] In particular, it would be highly advantageous to increasingly switch the curing process from mercury vapor lamps to LED emitters from the point of view of possible energy savings. Mercury vapor lamps generate a broad spectrum of electromagnetic radiation, only a small part of which is needed to activate the photoinitiator. LED emitters can generate radiation of the desired wavelength more selectively. While conventional curing processes usually require 100W to 200W per centimeter of lamp length, with LED lamps, 4W to 8W of radiation per centimeter may be sufficient. This is particularly the case if the curing reaction can take place in the absence of oxygen. For a curing system with a typical working width of 130cm, the energy required using conventional lamp technology is 13kW to 26kW. In this example, the energy required to generate the radiation is 0.5kW to 1kW.

[0008] DE 10 2013 215 739 A1 and GB 2 576 922 A each disclose a roller formed by a rotatable, transparent and hollow cylinder, inside which the actual light source is fixed.

[0009] DE 101 44 579 C2 discloses a method for producing fine to microscopic structures and / or complex microsystems by layer-by-layer construction in and from a photocurable liquid between two boundary surfaces, wherein the individual layers are formed by exposing the liquid through a mask corresponding to the layer morphology, and the distance between the boundary surfaces increases continuously by the corresponding layer thickness, and an apparatus for carrying out the method. The individual layers of the structure to be accumulated are generated between two opposite counter-rotating rollers in a roller pair that form the boundary surfaces, and the roller spacing of the rollers in the respective roller pair is determined by the thickness of the layer to be formed and the thickness of the existing layer, wherein the first layer is applied to a base carrier film passing between the rollers. Each roller in the roller pair is designed as an exposure roller and is composed of a material that is transparent to electromagnetic waves, wherein an electromagnetic wave emitting source in the form of a light source is arranged in the exposure roller, and wherein the surface of the exposure roller is non-sticky. In particular, the arrangement of the light source in the rotating exposure roller is relatively complex to implement in practice.

[0010] Furthermore, document EP 1 667 836 B1 describes a tool and a method for producing a microstructured surface, wherein there is a mold having a negative mold of the microstructure to be produced and a pressure roller that can be moved on the surface to press the mold onto the surface. The mold is arranged in such a way that when the roller moves on the surface, the mold rolls between the roller and the surface so that the negative mold of the mold faces the surface. A device for accelerating the curing of a curable material (including a light and / or heat source for irradiating and / or heating a microstructured surface) is arranged so that when the pressure roller moves on the surface, the device accompanies the movement of the roller and acts on a part of the surface. The light and / or heat source is located inside the pressure roller and is installed in such a way that the energy emitted by it can be transferred to the mold (in the case of heat) through the pressure roller material or can be radiated through the mold (in the case of light). In the latter case, the roller material must have a high transmittance to the wavelength emitted by the light source.

[0011] EP 1 951 436 B1 discloses a "calendering process" which is carried out by full curing of the film in order to produce a structured surface. The problem here is the edge area of ​​the coated plate, which must be trimmed. Summary of the invention

[0012] The invention solves the problem of creating a method and a device of the type mentioned at the outset which ensure reliable curing of UV varnishes on substrates with a relatively low outlay on equipment.

[0013] According to the invention, this object is achieved by the features of the independent claims.

[0014] The dependent claims represent advantageous embodiments of the invention.

[0015] In a method for curing a UV varnish applied to a substrate surface using a roller, the roller core of the roller holds at least one UV radiation emitting source, wherein the UV radiation penetrates the roller coating around the periphery and strikes the surface coated with the UV varnish.

[0016] An apparatus for performing the method comprises a roller comprising a central roller core and a peripheral roller coating, wherein the roller core holds a plurality of uV sources distributed on a circumference, the uV radiation emitted by the plurality of uV sources penetrating the roller coating transparent to the uV radiation and striking the surface of a substrate coated with a uV varnish so as to cure the uV varnish.

[0017] In the first step, the UV varnish is applied to the substrate or component surface. The coating can be carried out in one or more steps during a rolling process, a casting process, a spraying process, with a scraper, etc. A suitable conveying device is used to convey or transport the substrate. For example, a roller or a pair of rollers arranged opposite to the roller can be driven to convey the substrate. The movement direction of the substrate and the roller can be the same, wherein the speed of the substrate and the roller can be the same or different.

[0018] Due to the contact pressure of the roller or roller coating on the substrate surface, the roller coating forms a surface parallel to the substrate on its rolling line, the so-called roller gap. The initial uncured UV varnish is located between the substrate and the roller coating. Smaller liquid UV varnish beads are formed and grown at the inlet edge between the substrate and the roller coating until the amount of varnish delivered with the substrate corresponds to the amount of varnish delivered under the roller coating surface. The size of the resulting varnish beads depends substantially on the viscosity of the UV varnish, the contact pressure of the roller or roller coating on the substrate surface, and the speed gradient between the roller and the substrate. In addition, the properties of the roller coating and the substrate have an influence on bead formation.

[0019] The UV varnish located between the substrate and the roller coating is cured with UV radiation during the substrate transport. To this end, the UV radiation source or the UV radiation is aligned with the roller core, preferably attached to the peripheral circumferential surface of the roller core, that is, the UV radiation penetrates the roller coating and strikes the UV varnish to cure the UV varnish. Of course, optical elements can be arranged for focusing or orienting the UV radiation emitted from the UV source, wherein these optical elements can be assigned to the roller core and / or the roller coating without departing from the scope of the present invention.

[0020] Since the curing process is carried out without contact with oxygen in the ambient air, i.e. there is no oxygen inhibition, the degree of crosslinking on the surface is relatively high, which enables the varnish surface to achieve good mechanical and chemical properties. After UV-induced polymerization, the workpiece (i.e., the substrate with the cured varnish) is released again by conveying, thus leaving the area of ​​the roller, and the excess varnish accumulated in small amounts on the sides of the substrate edge and on the run-out edge in the direction of travel remains attached to the workpiece as burrs. Due to the return movement of the roller coating, the varnish is relatively easily separated from the roller surface. This is achieved by selecting a suitable coating material (e.g., silicone with an E modulus of about 8 MPa) and, if necessary, surface treating the roller. If a high-quality optical and very uniform surface structure is to be achieved on the substrate, it is important that no hardened varnish material adheres to the roller. If necessary, a scraper can be provided to remove such adhered varnish residues from the roller coating.

[0021] Currently commercially available LED emitters with a radiation spectrum range between 365 nm and 390 nm can be used as UV light sources. Other wavelength ranges are also possible. At 365 nm and 390 nm, the radiation penetrates deeper into the cured varnish material. The person skilled in the art selects the preferred emitter according to the formulation of the UV varnish. The LED UV emitters are conveniently arranged to be distributed over the length and periphery of the roller core.

[0022] When coating rigid sheet materials, the method described here has the advantage that, for example, defects in the edge area (which are common in methods using calendering processes known from the prior art) do not occur or at least occur to a reduced extent, since a uniform pressure is applied to the polymer mixture (i.e., UV varnish) over the entire width of the roller and the film does not "slip" in the edge area, thereby avoiding defects.

[0023] The roll core must have sufficient mechanical stability to allow contact pressure on the counterroller or conveyor belt and to be able to absorb the forces required to rotate the roll. In addition, the roll core should advantageously have reflective properties in order to reflect scattered light onto the roll surface, i.e. onto the surface of the roll coating. The roll core can be made of metal such as iron, steel, aluminum or metal alloys such as brass. For more pressure-sensitive substrates and small rollers, plastics can also be used to manufacture the roll core.

[0024] The roller coating should have good permeability to the UV radiation necessary to initiate the polymerization reaction. A low optical density of the material can have a positive effect, since it can be advantageous if the radiation transfer from the roller coating to the polymerization mixture takes place in a medium with a greater optical density. In addition, the roller coating must have a certain elasticity that allows the formation of a roller gap below which the crosslinking reaction can take place. Good mechanical deformability and a rapid return to the original shape are also advantageous in order to allow easy detachment of the cured varnish from the roller surface. Adhesion of the varnish material to the roller leads to a reduction in the quality of the coating.

[0025] The UV emitters can be arranged as an intermediate layer between the roll core and the roll coating. These emitters can also be integrated into the roll core or the roll coating. The UV emitters should be distributed as evenly as possible across both the circumference and the width of the roll. If an uneven radiation distribution is required for technical reasons, deviations from this description are possible.

[0026] In their design, the UV emitters or UV sources are switchable and are only supplied with voltage when the emitted radiation takes a direct path from the UV emitters through the roller coating into the polymerizing mixture located below the roller gap. For position-dependent voltage supply: an electronic controller switches the voltage supply of certain UV sources on and off depending on signals from position detection sensors; or the current paths of the UV sources arranged in a row and interconnected are connected to contacts assigned to the end faces of the rollers, which act on voltage-carrying contact segments to open and close the circuit.

[0027] Preferably, a row of UV sources extending across the width of the roll core is integrated into a light segment that can be replaceably attached to the roll core. After reaching the end of their useful life or if they are otherwise damaged, the individual light segments can be replaced, especially after the roll coating has been removed.

[0028] The rolls are provided with cooling devices to dissipate process heat. For example, the roll core may have cooling holes through which coolant flows.

[0029] Preferably, the roller coating of the roller is elastic. Depending on the contact pressure of the roller on the substrate coated with the UV varnish, a more or less large contact surface is formed. Ideally, the Shore A hardness of the roller coating is between 30 and 60. Therefore, the roller coating is designed to be relatively soft. In addition, the roller coating can be replaceably, in particular reversibly replaceably arranged on the roller core. This means that different structures of the cured UV varnish can be produced using different roller coatings, and if the roller coating is worn, it can be replaced. To form a surface effect on the painted surface, the roller coating is smooth or has a surface structure. The surface properties of the roller coating are used to form the surface structure of the varnish coating because the surface structure of the roller is reflected on the varnish surface. For example, the smooth surface of the roller coating forms a high gloss surface of the finished part (i.e., coating or UV varnish), and according to the surface structure, different degrees of gloss, structure or effect (such as anti-fingerprint performance) can be achieved.

[0030] The thickness of the roller coating may be 2% to 80%, preferably 10% to 20%, of the roller radius.

[0031] In order to convey the substrate and determine the layer thickness of the UV varnish on the substrate, according to a refinement of the invention, an adjustable counter-roller is assigned to the roller, between which the substrate coated with the UV varnish can be conveyed. Of course, the roller and the counter-roller are mounted in a frame and, if necessary, connected to drives that enable both a rotational movement and a linear feed movement of the counter-roller relative to the roller. The counter-roller ensures that the substrate coated with the UV varnish is pressed against the roller with the necessary pressure. Compared to the distance between the substrate and the unloaded roller, the distance between the substrate and the roller must be set so that the roller coated with the roller coating is at least 1% of the roller coating thickness and at most 20% of the roller coating thickness, preferably between 3% and 10% of the roller coating thickness.

[0032] The pressure of the roller is evenly distributed over the entire surface of the substrate and does not detach from the substrate even in the edge area, which reduces the risk of defects in the painted surface. In addition, there is no need to remove defective edge areas. Thus, already formatted substrates can be coated.

[0033] By pressing in the curing rollers, the edges or at least the curves at the edges are coated to a minimum. This offers advantages when coating panels with glued edges. Such panels are often used in the furniture industry. Since the adhesive seams are sealed from above with the topcoat, workpieces painted in this way are better protected against moisture penetration. Any protruding burrs of the coating material on vertical edges can be easily removed mechanically using a device.

[0034] Conveniently, the UV source is designed as an LED UV emitter. LED UV emitters are energy-efficient and ensure that the system generates relatively little heat. Of course, other radiation sources for UV light may also be used without departing from the scope of the present invention.

[0035] Furthermore, for deep curing or post-crosslinking of the UV varnish, a light source is provided which emits optical radiation, the optical radiation of which can be directed onto a substrate, the surface of which is coated with the cured UV varnish.

[0036] If the UV sources or LED UV emitters are located on the surface of the roller (i.e. the peripheral circumferential surface of the roller core directly below the roller coating), most of the radiation is directed towards the UV varnish to be cured and the intensity loss is relatively low compared to a rod-shaped or point-shaped radiation source mounted in the center of the roller. Furthermore, the heat is dissipated from the UV sources via the roller core and each of the UV sources is active only for a certain time, during which it occupies a position where the radiation strikes the UV varnish and can cool down during the remaining inactive time. Any roller circumference is possible, since the radiation sources can be mounted relatively close to the roller surface.

[0037] It is to be understood that the features mentioned above and yet to be explained below can be used not only in the respectively specified combination but also in other combinations. The scope of the present invention is limited only by the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be described in detail below based on exemplary embodiments with reference to the relevant drawings.

[0039] In the attached picture:

[0040] Figure 1 is a schematic representation of an apparatus for coating a surface of a substrate with a UV varnish, i.e. for performing a painting process,

[0041] Figure 2 is based on Figure 1 Detail II of a schematic side view of an alternative roller,

[0042] Figure 3 is based on Figure 2 A schematic perspective view of a roller,

[0043] Figure 4 is based on Figure 2 Another side view of the roller,

[0044] Figure 5 is based on Figure 4 A schematic front view of a roller, and

[0045] Figure 6 is based on Figure 2 Another side view of the roller. DETAILED DESCRIPTION

[0046] The apparatus basically comprises a conveyor belt 1, which can also be replaced by one or more pairs of rollers and is basically used to support and convey a substrate 2, wherein the substrate is a basically plate-shaped or belt-shaped component or workpiece, the surface of which is to be coated with a UV varnish 3. In a first step, the UV varnish 3 is applied from a storage container 6 to the surface of the substrate 2 at a coating station 4 by means of a rotating coating roller 5.

[0047] In a second step, UV varnish 3 is cured using UV radiation. For this purpose, roller core 8 of roller 7 is equipped with UV source 10 designed as LED UV emitter 11, the roller also comprising UV radiation transparent peripheral roller coating 9.

[0048] In a third step, the UV varnish 3 cured on the surface of the substrate 2 is deep-cured using a conventional emitter 12, which in the present case can be designed as an energy-saving LED emitter 13, which radiates in the spectral range between 365nm and 390nm. Such deep curing is not necessary in every case, but depends on the UV source 10 used, the UV varnish 3 used and other manufacturing or process parameters, such as in particular the process speed.

[0049] The LED UV emitters 11 may be distributed over the circumference of the roller core 8 of the roller 7 and may extend over the circumferential surface, for example, in a mesh-like manner, such as Figure 1 and Figure 3 As indicated in .

[0050] Alternatively, the UV source 10 designed as an LED UV emitter 11 can be inserted into a groove-like recess 16 extending on the circumference of the roll core 8 and across the width of the roll 7. The recess 16 can have a reflective surface and a geometry that focuses the UV radiation, such as Figure 2 and Figure 3 As shown. In this case, the LED UV emitters 11 can be integrated into, for example, a casting compound and combined together to form a light segment 17, wherein the light segment 17 is replaceably fixed in an associated recess 16. The channel-shaped recess 16 can be filled with various media (e.g., liquids or gases), wherein these media must be as transparent to UV radiation as possible and should have a favorable optical density. In addition, the medium can act as a heat carrier and dissipate unwanted process heat.

[0051] If the LED UV emitters 11 are arranged on the surface of the roll core 8 or in the recesses 16 of the roll core 8, the heat generated during the radiation emission can be dissipated via the metal roll core 8 or the medium present in the recesses 16 via the rear side of the LED UV emitters 11. The roll core 8 can also be equipped with cooling holes for a water cooling system, which is connected to the cooling device in a manner familiar to a person skilled in the art. By dissipating the heat of the LED UV emitters 11, heating in the LED UV emitters 11 that would lead to functional limitations is avoided, and a relatively high radiation output or low-wavelength UV radiation can also be achieved, wherein lower wavelengths can be advantageous due to the higher energy content when curing the UV varnish 3.

[0052] like Figure 4 and Figure 5 As indicated in FIG. 1 , the cooling medium flows through an annular line 18 which is sealed on the roller 7 by means of an end-face sliding ring seal 19 in order to provide an inlet and an outlet.

[0053] The control of the UV sources 10 (which are advantageously supplied with voltage only when they are aligned in the direction of the substrate 2, i.e. provide a relatively direct radiation path) is performed by an electronic controller (with which the position can be detected) or Figure 6 The arrangement of the voltage-carrying contact sections 20 shown, which are acted upon by the LED UV emitters 11 or the contacts 21 assigned to the light segments 17 in order to close the circuit depending on the rotational position of the roller 7, is performed. Only when the light segment 17 with the associated contacts 21 is located in the region of the arc-shaped contact sections 20, the circuit is closed to supply energy to the LED UV emitters 11. This makes it possible to sequentially switch the LED UV emitters 11 on and off, which saves electrical energy and reduces heat generation.

[0054] The roller coating 9 of the roller 7 , which is transparent to UV radiation, has a thickness of approximately 2% to 80%, preferably between 10% and 20%, of the radius of the roller 7 and is elastic, for example with a hardness between 30 Shore A and 60 Shore A.

[0055] The roller coating 9 can consist of various materials transparent to UV radiation, wherein a low extinction coefficient is advantageous in order to achieve a high radiation intensity. For example, elastic polyurethane materials, silicone rubber or other transparent elastic rubbers can be used, which preferably do not contain any fillers that increase the extinction coefficient.

[0056] The LED UV emitters 11 assigned to the roller core 8 can be directly surrounded by the roller coating 9. The beam path can then go directly from the LED UV emitters 11 into the roller coating 9 without additional material transfer. This structure can be easily realized by fixing the LED UV emitters 11 to the roller core 8 and casting the roller coating 9 around these emitters.

[0057] Alternatively, a roller coating 9 consisting of a silicone rubber mixture can be applied to the roller core 8 in a multilayer manner, for example, wherein a relatively elastic layer with very good adhesion to the roller core 8 is applied during the coating process, and the roller 7 pre-coated in this way is then transferred to a casting mold and the majority of the silicone rubber is cast into a type with favorable mechanical properties in terms of elasticity and durability. In order to minimize the adhesion of the UV varnish 3 to the roller coating 9, the roller coating can be surface treated or a release agent can be used during the manufacture of the roller 7.

[0058] In another alternative embodiment, the roller coating 9 can also be formed in a completely or partially replaceable manner. This means that different surface structures can be produced as required without having to have different available rollers 7. In addition, worn roller coatings 9 can be replaced without having to manufacture completely new rollers 7.

[0059] The roller coating 9 can be formed in such a way that after removal, the individual LED UV emitters 11 or light segments 17 can be accessed for replacement if necessary. For example, the roller coating 9 can be formed as a type of cover that can be pushed on the roller core 8. The axial fixation of the roller coating 9 can preferably be carried out on the end face of the roller 7 with suitable retaining means. For radial fixation, the roller coating 9 can be provided with protrusions or extensions or the like, which engage in corresponding recesses in the roller core 8. When the roller coating 9 is pulled onto the roller core 8, the roller coating 9 can be elastically stretched so that it also rests against the roller core 8 in a pre-tensioned manner.

[0060] Of course, the roller coating 9 can be provided with a structure on its peripheral surface 14 which is produced by subsequent treatment or by a casting process in which the structure of the die opening is incorporated into the casting mold.

[0061] For optimal functioning of the system, a radiation intensity as high as possible during curing of the UV varnish 3 is advantageous, since this allows a high processing speed and / or a low reactivity of the UV varnish 3. For this purpose, it is advantageous if the radiation of the UV source 10 is focused with optics to avoid unproductive scattered light.

[0062] All types of electromagnetic radiation suitable for activating photoinitiators or for initiating free radical reactions by another process can be used for curing the UV varnish 3. Care must be taken to ensure that the radiation is not absorbed by the roller coating 9. The feed rate of the substrate 2 is 5 m / min or 10 m / min. Good curing of the UV varnish 3 is achieved. The edge areas of the substrate 2 have good optical quality. There is no sign of roller unwinding and subsequent post-curing is not absolutely necessary.

[0063] The UV varnish 3 used contains polyether acrylate as reactive resin component, which enables a high-quality and light-resistant varnish for interior use. TMPO3TA is used as reactive diluent, which is advantageous in terms of marking. TPO-L is used as photoinitiator, which works very well at the radiation wavelength used. Airex 901W is used as defoamer and Tego Rad 2650 is used as leveling agent.

[0064] The following recipe is based on 100T:

[0065] 75T Laromer PO 84F(BASF)

[0066] 19.5T TMPO3TA (eg, Miwon)

[0067] 5T TPO-L(BASF)

[0068] 0.3T Tego RAD 2650 (Evonik)

[0069] 0.2T Tego Airex 901W(Evonik)

[0070] The formulations shown are examples only. Many other combinations are possible depending on the coating requirements.

[0071] Reference numerals

[0072] 1. Conveyor Belt

[0073] 2. Base

[0074] 3.UV varnish

[0075] 4. Coating station

[0076] 5. Coating roller

[0077] 6. Storage Container

[0078] 7. Roller

[0079] 8. Roller core

[0080] 9. Roller coating

[0081] 10.UV source

[0082] 11.LED UV emitter

[0083] 12. Transmitter

[0084] 13.LED Transmitter

[0085] 14.9 Surface

[0086] 15. Components

[0087] 16. Concave part

[0088] 17.Light segment

[0089] 18. Pipeline

[0090] 19. Slide ring seal

[0091] 20. Contact section

[0092] 21. Contact Department

Claims

1. A method for curing a UV varnish (3) applied to the surface of a substrate (2) using a roller (7), characterized in that The roller core (8) of the roller holds at least one UV radiation emitting source (10), wherein the UV radiation penetrates the roller coating (9) around the periphery and strikes the surface coated with the UV varnish (3).

2. The method according to claim 1, characterized in that: The position of the voltage supply of the at least one UV source (10) depends on the orientation of the at least one UV source relative to the substrate (2).

3. The method according to claim 1 or 2, characterized in that: The roller (7) is unfolded relative to the substrate (2).

4. The method according to any one of claims 1 to 3, characterized in that The substrate (2) is conveyed between the roller (7) and a counter roller opposite to the roller (7) or between the roller and a conveyor belt (1).

5. The method according to any one of claims 1 to 4, characterized in that The UV varnish (3) cured on the surface of the substrate (2) is then deep cured using a conventional emitter.

6. A device for carrying out the method according to claim 1 using a roller (7), characterized in that The roller comprises a central roller core (8) and a peripheral roller coating (9), wherein the roller core (9) holds a plurality of UV sources (10) distributed on the periphery, the UV radiation emitted by the plurality of UV sources penetrating the UV radiation-transmissive roller coating (8) and striking the surface of the substrate (2) coated with the UV varnish (3) so as to cure the UV varnish (3).

7. The device according to claim 6, characterized in that The UV source (10) is linearly oriented and extends across the width of the roller core (8).

8. The device according to claim 7, characterized in that A plurality of UV sources (10) arranged in a row can be supplied with a voltage depending on the position of the plurality of UV sources relative to the substrate (2).

9. The device according to claim 8, characterized in that For the position-dependent voltage supply: an electronic controller switches the voltage supply of certain UV sources (10) on and off according to signals from position detection sensors; or the current paths of the UV sources (10) arranged in a row and interconnected are connected to contacts (21) assigned to the end faces of the rollers (7), which act on voltage-carrying contact sections (20) to open and close the circuit.

10. The device according to any one of claims 6 to 9, characterized in that A row of UV sources (10) extending across the width of the roller core (8) is integrated into a light segment (17) which can be replaceably attached to the roller core (8).

11. The device according to any one of claims 6 to 10, characterized in that Cooling means are associated with said roller (7).

12. The device according to claim 6, characterized in that The roller coating (9) of the roller (7) is elastic.

13. The device according to any one of claims 6 to 12, characterized in that The roller (7) is assigned a counter-roller or a conveyor belt (1), wherein the roller (7) and / or the counter-roller and / or the conveyor belt (1) can be adjusted relative to each other, and the substrate (2) coated with the UV varnish (3) can be conveyed between the roller (7) and the counter-roller or between the roller and the conveyor belt.

14. The device according to claim 6, characterized in that The UV source (10) is designed as an LED UV emitter (11).

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