AT510217A1 - PROCESS FOR PARTIAL MATTING OF UV VARNISH LAYERS - Google Patents

Description

Method for partial matting of UV lacquer layers

The invention relates to a method for the partial matting of UV lacquer layers by means of an excimer radiator. 5 UV lacquer coatings generally have high resistance and resistance to mechanical, physical and chemical influences, in particular high scratch resistance. The surface of such lacquer layers usually appears shiny or matt after curing, depending on the composition of the lacquer used.

However, especially for decorative purposes only partially matted products with consistently high scratch resistance are desired. 15 methods for matting UV lacquer layers are known.

Thus, for example, EP 0 338 221 A discloses a film web consisting of at least two layers which, inter alia, has an acrylate lacquer layer produced by co-using at least one monomeric, di-20 and / or trimeric acrylate Matt varnish on the basis of an acrylate mixture, which is prepared by reacting at least one prepolymeric acrylate with at least one monomeric, di- and / or trimeric acrylate, wherein the varnish per 100 parts by weight of the acrylate varnish (calculated without any additive, 25 processing aids or blowing agent), 20-60 parts by weight of a

Matting agent or Mattierungsmittelgemisches, 1-10 parts by weight of a UV initiator or UV initiator mixture, 0-10 parts by weight of a blowing agent or blowing agent mixture contains or consists thereof. The impression of matting results from the addition of a matting agent in the paint formulation. This achieves a so-called volume matting, i. the matting agent is more or less homogeneous 2 in the paint matrix

distributes and generates there a Lichtatreuung, which is perceived as Mattierung.

EP 0 706 834 A discloses a process for the production of UV-curable lacquer-coated sheet-like support materials having a matt or glossy surface, the degree of matting of the UV lacquer being adjusted by adding mono- and / or difunctional monomers, and US Pat UV curing multiple radiation sources with defined

Wavelength range can be used. The matting that results here is due to the special shape of the surface during curing. The remaining lacquer layer is not changed. In this case one speaks of a surface matting.

Furthermore, DE 44 39 350 C discloses a process for the production of UV-curable lacquer-coated sheet-like support materials with a matt or glossy surface, wherein the degree of matting of the UV lacquer is adjusted by adding mono- and / or difunctional monomers, and for the UV curing multiple radiation sources with defined

Wavelength range can be used, wherein the first UV radiator has a monochromatic UV light with a wavelength of 172 nm and the second or the subsequent UV emitters generated or generate a light spectrum whose or their wavelength range between 210 and 900 nm. Also in this case there is a surface matting.

WO 2007/068322 discloses an apparatus for carrying out a method for modifying the surface of radiation-curable lacquers by means of photochemical micromolding with stable irradiation and inerting conditions for producing reproducible structures and textures using 172 nm excimer UV systems comprising a quartz emitter highest quartz quality with an exposed with high-frequency high voltage inner electrode and an outer ground electrode, which for the inerting of the channel to * · «:

Irradiation of the coating material used gas is fed through the ceiling of the lamp housing axially above the radiator tube and distributed at optimal pressure loss in the distributor element so that the device realizes: • a uniformly low oxygen content for optimal homogeneous UV dose rate over the entire irradiation length without significant losses Absorption, • a uniform lamp cooling to increase the UV emission efficiency and to avoid the burning of a net-shaped ground electrode, • a lamp flushing against radiation contamination and a reduction of the oxidation of the ground electrode, • that inside water-cooled excimer radiators the internal cooling and at the same time the UV output larger radiator diameters can be improved and • the lamp must be operated in an optimum frequency and power range with regard to the efficiency and service life of the radiant tube.

From DE 198 42 510 is a process for the production of decorative and functional surfaces of electron beam or UV-curing dye and varnish layers, which consist of acrylates, epoxies, vinyl ethers, styrene, or other radiation-curable components or hybrid systems derived therefrom, to rigid or flexible substrates by irradiation of monochromatic short-wave UV light, which is able to produce in the consisting of monomers or oligomers or a monomer / oligomer system on an aforementioned substrate wet layer polymer radicals, whereby at the surface and in the near-surface layers of a Polymerization and crosslinking is triggered, which leads via shrinkage to the microfolding, the Mikrofaltungsbild for a radiation-curable varnish and its composition by the choice of processing and technological parameters such as UV wavelength, photon dose = UV lamp output / Trans port speed

• the lacquer layer, oxygen concentration in the irradiation zone, coating thickness, viscosity, substrate, pigmentation, additives, coating technique, irradiation sequence and time interval is set and, when these defined parameters are implemented, the microstructure image is reproducible.

All of these methods provide full-surface, frosted lacquer coatings. A partial matting can be achieved at most when already the UV coating is partially applied, in which case the carrier substrate appears at the non-printed areas. However, this also means that at the unprinted areas, the scratch resistance of the film surface is significantly lower than that of the UV lacquer layer. Alternatively, the carrier film can first be coated over the whole area with a scratch-resistant UV lacquer layer and then partially coated with a matt UV lacquer layer. However, two steps are necessary and there is a difference in thickness between the frosted and glossy spots.

The object of the invention was to provide a method in which no full-surface, but a partial matting of UV lacquer layers in a single operation is possible.

The invention therefore relates to a process for the partial matting of UV coating layers, wherein a UV coating layer is applied to a carrier substrate and this is subsequently treated with an excimer radiator, characterized in that the excimer radiator within a template, the for the excimer radiation permeable and impermeable to the excimer radiation regions, is located, and the UV lacquer layer is partially exposed through the template with the excimer radiator.

To carry out the method, a UV lacquer layer is first applied to a carrier substrate. 5

As carrier substrates, for example carrier films are preferably flexible plastic films, for example of PI, PP, MOPP, PE, PPS, PEEK, PEK, PEI, PSU, PAEK, LCP, PEN, PBT, PET, PA, PC, COC, POM, ABS, PVC , PTFE, ETFE (ethylene tetrafluoroethylene), PFA (tetrafluoroethylene)

Perfluoropropyl vinyl ether fluorocopolymer), MFA (tetrafluoromethylene-perfluoropropyl vinyl ether fluorocopolymer), PTFE (polytetrafluoroethylene), PVF (polyvinyl fluoride), PVDF (polyvinylidene fluoride), and EFEP (ethylene-tetrafluoroethylene-hexafluoropropylene fluoropolymer).

The carrier films preferably have a thickness of 5 to 700 μm, preferably 5 to 200 μm, more preferably 5 to 50 μm.

Furthermore, metal foils, for example Al, Cu, Sn, Ni, Fe or stainless steel foils having a thickness of 5 to 200 μm, preferably 10 to 80 μm, particularly preferably 20 to 50 μm, may also serve as the carrier substrate. The films can also be surface-treated, coated or laminated, for example, with plastics or painted.

Further, as carrier substrates and pulp-free or cellulose-containing paper, thermally activated paper or composites with paper, for example composites with plastics having a basis weight of 20 - 500 g / m2, preferably 40 - 200 g / m2. be used.

Furthermore, woven or nonwovens, such as continuous fiber webs, staple fiber webs and the like, which may optionally be needled or calendered, may be used as the carrier substrates. Preferably such fabrics or webs of plastics, such as PP, PET, PA, PPS and the like, but it can also be woven or nonwovens made of natural, optionally treated fibers, such as viscose fibers are used. The webs or fabrics used have a basis weight of about 20 g / m2 to 500 g / m2. If necessary, the nonwovens or fabrics must be surface-treated.

All carrier substrates can be present as web-shaped substrates or as piece goods. * * * · «· · ·» * · :: 6 :::

The piece goods may, for example in the form of plates, tiles or other formats of optionally coated wood, plastic, metal, ceramic and the like procure, the thickness of these substrates is usually a few mm or cm.

First layers may already be applied to the carrier substrate, e.g. Lacquer or metal layers which cause an optical effect (color, color effects, gloss, reflection) or have functional properties (adhesion, wetting of the UV lacquer layer, electrical conductivity, optically active, in particular diffractive optical or optical properties, magnetic properties).

The UV varnish can be applied by known application methods, e.g. Roller application method, printing (gravure, flexo, offset or

Digital printing), casting or spraying, using slot die coating or curtain coating. The selection of the application method is basically irrelevant, but the person skilled in the art will prefer to choose such a method which produces a layer on the substrate with as homogeneous a thickness as possible and as smooth a surface as possible. However, an interesting, visually appealing contrast can also be created by the characteristic surface structure of the respective coating application in conjunction with the partial matting.

The UV coating is present as a mixture of monomers or oligomers with one or more photoinitiators and optionally other ingredients such as pigments, additives or solvents.

In principle, all radiation-curable UV coating compositions are suitable, but in particular the compositions which are known from DE 44 39 350 and which react to the curing with an excimer radiation with the formation of a micro-rough or -folded surface. 7

The thickness of the applied lacquer layer is usually between 1 and 1000 μιτι. For film substrates, the layer thickness is usually in the range of 1-20 μη, for plates whose thickness is generally much larger, the layer thickness is more in the range of 50-1000 pm.

The coated carrier substrate is then optionally pre-dried in a thermal dryer, whereby any volatile components present in the layer, such as e.g. Solvent, to be removed.

Thereafter, the coated carrier substrate is supplied to the excimer irradiation. The excimer radiator is oriented transversely to the transport direction of the carrier substrate and positioned relative to the web so that the generated UV radiation strikes the coated side of the carrier substrate and initiates a crosslinking reaction on the surface of the UV varnish there.

The actual excimer radiator, ie the lamp which generates the excimer radiation, is thereby positioned within a circumferential template which rotates around the radiator. The length of the lamp is sized to be wider than the support substrate to ensure homogeneous radiation performance across the entire width. The stencil has UV-transmissive and UV-opaque areas corresponding to the desired matted structures.

Such a template may, in one embodiment, be shaped like a rotary screenprinting stencil, i. consist of a cylindrical mesh or fabric-like framework, which is partially sealed with a UV-impermeable layer, such as a plastic layer, and thus is no longer transparent at these sealed locations. At locations where the mesh or fabric is not coated, the template is at least partially transparent. The permeability of the template is the diameter of the mesh or fabric fibers and the mesh size of the network t

t I 8 :: or tissue determined and can also be influenced by a suitable choice of materials. The production of such a template is carried out in the same process that is used for the production of rotary printing screens. The structures that can be created with it are identical to those that can also be generated by rotary screen printing. The net or fabric-like framework can also consist of metal.

In another embodiment, the template is formed from a metal cylinder having open recesses in which the excimer radiation can pass through the template completely unhindered. The recesses can thereby be mechanically, i. be introduced by a drilling or milling process or by laser cutting in the cylinder. With regard to the structures that can be produced with such a template, however, there are restrictions, since the template still has to have sufficient mechanical stability after processing in order to withstand the forces occurring during assembly or during rotation.

Another embodiment may be such that the stencil is made of a material such as e.g. Quartz, MgF 2, or the like, which is transparent to the wavelength of the excimer radiation. A cylinder is made of this material and areas are masked on its surface so that excimer radiation no longer penetrates these areas. For this purpose, for example, the surface of the cylinder with a metal layer, e.g. is made of chrome or aluminum and is thick enough not to let the excimer radiation pass. The coating can be applied by a vacuum coating method or by electroplating. The structuring takes place, for example, with a photolithographic process or with the aid of a laser by ablation. Likewise, it is conceivable that an absorber layer only partially at the sites to be masked, e.g. by printing or by glued, impermeable to the excimer radiation, covers is applied. Also in the case of 9 of this embodiment, arbitrary structures can be produced, since the cylinder per se constitutes a continuous supporting structure.

The template is driven by a motor directly or by means of a toothed or V-belt or gear. The rotational speed of the template is adjusted so that the tangential velocity of the cylinder in the plane of the masking layer is identical to the transport speed of the substrate. This ensures that no relative movement between the template and the carrier substrate is formed and the structures of the template are sharp-edged imaged on the surface of the paint.

To achieve a precise edge sharpness, the distance between the stencil and the lacquer surface is chosen as small as possible, but a small gap must remain, since otherwise the danger of adhesion of the lacquer to the stencil exists. The distance is approximately in the range of 0.1 to 10 mm.

A change in this distance would inevitably lead to fluctuations in the edge sharpness, which is why, in a preferred embodiment, a film in the region of the template is guided over a counter roller, whose distance from the template can be precisely controlled. The film is thereby stabilized such that the distance to the radiator can be kept constant within a small tolerance.

In another embodiment, the template itself consists of an endless, web-shaped fabric tape which, like one of the templates described above, consists of a reticulated or web-shaped substrate, which is partially coated with an excimer-impermeable material. The endless belt is guided over several guide rollers around the excimer radiator, wherein the web speed is selected to be identical to the transport speed of the carrier substrate. Instead of a net or tissue-shaped substrate and a metal foil can be used with openings. m

By irradiating the paint surface with the excimer radiation, a micro-rough surface forms locally at the exposed areas. On the one hand, this surface structure produces a matt optical impression because the surface diffuses light diffusely. On the other hand, the micro-folding and the resulting surface finish create a haptic that is clearly different from a smooth paint surface. In the unexposed areas, the paint surface is not modified, i. The surface is in the same condition as after applying the paint. Preferably, the paint is applied so that the surface has a very high smoothness and thus a very high gloss. The contrast between the frosted and glossy areas is then particularly high.

The wavelength of the excimer radiation is in the range of 110-300 nm, but mostly at 172 nm.

Due to the low penetration depth of the excimer radiation into the lacquer layer, it is cured only on the surface, that is to say in the first approximately 10 nm to 1 μm. The remaining lacquer layer under the hardened surface still remains in a liquid or viscous state.

The entire unit consisting of excimer lamp and template and possibly a guide roller for adjusting the distance is located in an enclosure within which a controlled, inert atmosphere, for example, by continuous purging with argon, nitrogen or other noble gas, can be adjusted. The inerting is imperative in order to avoid absorption of the excimer radiation by components of the ambient air (CO2, water vapor) on the one hand, and to prevent the oxygen inhibition of the crosslinking reaction on the paint surface on the other hand. The oxygen-inhibition causes the radicals or chain parts of the UV varnish to be terminated by incorporation of oxygen and thus can not polymerize further. This effect occurs especially with thin layers (less than 1 gm) and is therefore particularly relevant for the surface hardening of paint layers.

The partially exposed carrier substrate now passes to a second UV emitter, which, however, operates with radiation of a longer wavelength, typically in the range of 300-500 nm. This ensures that the surface relief produced in the matte areas by the excimer treatment is frozen, so to speak is fixed and the entire coating layer in all areas simultaneously cured or fully crosslinked. If necessary, an enclosure for inerting with noble gases or nitrogen may also be provided around the second UV radiator.

As a result, UV coating layers with matt and glossy areas are produced in a single operation, wherein the carrier substrate on the entire surface an excellent scratch resistance and a substantially flat surface, so no height difference between smooth and frosted areas has.

The substrates produced in this way with a partially matted UV lacquer layer can be used as decorative films or sheets or for decorative surface finishing for furniture surfaces, household appliances, in interior design, the interior of motor vehicles and the like.

Depending on the carrier substrate used, they can be applied to surfaces of different types, for example plastic, wood, composite material or metal substrates, or used as piece goods themselves.

The biggest advantage of the method described here is that it runs continuously and does not have to stop the transport of the carrier substrate during the exposure. This enables an efficient, cost-effective and large-volume production of decorative functional parts. • Φ * Ψ * * t »ι

FIG. 1 shows a carrier substrate with a partially matted UV lacquer layer, which was produced by a method of the prior art.

FIG. 2 shows a carrier substrate with a partially matted UV lacquer layer, which was produced by the process according to the invention.

In the figures 3 to 5 embodiments of the method according to the invention are shown.

In the figures, 1 denotes the carrier substrate, 2 a glossy UV lacquer layer, 3 a matt UV lacquer layer, 4 a UV lacquer layer according to the invention, 4a an UV lacquer layer according to the invention before curing, 5a matt and 5b glossy areas of the lacquer surface, 6 the screen printing stencil with regions 6a permeable to the excimer radiation and regions 6b, 7 impermeable to the excimer radiation, the excimer emitter, 8 the UV emitter for curing the UV lacquer layer, 9 the housings of the excimer or UV emitters, 10 the coater, 11 the unwinder, 12 the rewinder, 13 pulleys, 14 the dryer, 15 the excimer unit with rotating template and housing, 16 the UV dryer unit with housing, 17 the general purpose storage container, 18 the container ready coated piece goods, 19 the piece goods to be coated, 20 a device for applying the UV varnish and 21 the conveyor belt for transporting the piece goods.

FIG. 1 shows the cross section of a carrier substrate coated with a partially matted UV varnish according to the prior art. The carrier substrate 1 is first coated over its entire surface with a glossy UV lacquer layer 2. On these, a matted UV varnish 3 is partially printed with a printing process. In the areas where the matted UV lacquer is printed, the layer thickness is greater than in the areas where only the glossy UV lacquer is applied. FIG. 2 shows the cross-section of a carrier substrate 1 produced by the method according to the invention, which has a UV lacquer layer 4 with matted areas 5a and shiny areas 5b of the lacquer surface. Between the frosted and glossy areas, no difference in thickness is visible in the paint layer.

FIG. 3 shows schematically the arrangement for carrying out the essential method steps of the method according to the invention.

The carrier substrate 1 coated with a UV-curable lacquer layer 4 is continuously guided past the excimer radiator 7. The excimer emitter 7 is situated in a template 6 which has regions 6a permeable to the excimer radiation and regions 6b impermeable to the excimer radiation. In turn, the excimer radiator and stencil are located in an enclosure 9, which is placed under inert gas (Ar or N2). The drive unit for the template is not shown in FIG. 3 for reasons of clarity.

The radiation of the excimer radiator 7 passes through the regions 6a of the template 6 permeable to the excimer radiation, strikes the surface of the UV lacquer layer and generates a micro-cladding there, whereby a matt surface 5a is formed. In the non-transmissive regions 6b, no crosslinking of the UV lacquer layer takes place, resulting in a glossy lacquer surface 5b. Subsequently, the carrier substrate is guided to a UV radiator 8 and irradiated so that a continuously crosslinked UV lacquer layer 4 is produced. The UV emitter 8 is optionally located in a housing 9, which may also be under inert gas.

FIG. 4 shows schematically the method according to the invention for the production of web-shaped carrier substrates with a partially matted UV lacquer layer. In this case, the carrier substrate 1 is guided by an unwinding roller 11 via a deflection roller 13 to the Lackauftragswerk 10, then via a further deflection roller 13 by a dryer 14, in which optionally a solvent present in the UV coating solvent is evaporated. In the next step, the carrier substrate coated with UV varnish is passed through the excimer unit 15 consisting of excimer radiator 7, template 6 and housing 9 (see FIG. 3) and partially frosted the varnish surface. In the next step, the UV lacquer layer is cured by a UV radiator unit 16 consisting of UV radiator 8 and possibly an enclosure 9 (see FIG. 3). After complete curing, the coated carrier substrate is guided over a deflection roller 13 to 5 of a winding station 12 and wound up.

Fig. 5 shows schematically the inventive method for the production of cargo with a partially frosted UV lacquer layer.

From the reservoir 17, the cargo 19 is applied to a conveyor belt 21 10 and coated by a device 20 with UV varnish. Subsequently, the piece goods 19 is passed through an excimer unit 15 and thus partially matt the paint surface. In the next step, the UV lacquer layer is completely cured by a UV radiator unit 16. The finished piece goods are stacked in a container 18. 15

Claims (14)

• ♦ ♦ * * · · · * * * * * * * * I t IC IC IC »* · IC IC IC» * * * * * * * * **** **** **** **** 1) Process for the partial matting of UV lacquer layers, wherein a UV lacquer layer is applied to a carrier substrate and this is subsequently treated with an excimer emitter, characterized in that the excimer emitter within a template, for the excimer Radiation permeable and impermeable to the excimer radiation regions, is located, and the UV lacquer layer is partially exposed through the template with the excimer radiator. 2) A method according to claim 1, characterized in that the template consists of a cylindrical mesh or fabric-like framework, which is partially sealed with an impermeable to the excimer radiation layer, such as a plastic layer. 3) Method according to claim 1, characterized in that the template is formed from a metal cylinder having open recesses, 4) A method according to claim 1, characterized in that the stencil of a cylinder of a material which is transparent to the wavelength of the excimer radiation, such as quartz or MgF2, and whose surface partially with a impermeable to the excimer radiation Layer is provided. 5) Method according to one of claims 2 to 4, characterized in that the tangential velocity of the cylinder in the plane of the masking layer is identical to the web speed, 6) Method according to claim 1, characterized in that the template consists of an endless belt of a net or: .1¾. % · Fabric-like material partially provided with an excimer-radiation-impermeable layer. 7) Method according to claim 1, characterized in that the template consists of an endless metal strip having recesses. 8) A method according to claim 7 or 8, characterized in that the speed of the endless belt is identical to the web speed. 9) Method according to one of claims 1 to 8, characterized in that the template via a motor directly, by means of a toothed or V-belt or gear or driven by a drive roller. 10) Method according to one of claims 1 to 9, characterized in that the wavelength of the radiation of the excimer radiator in the range of 110 - 300 nm. 11) Method according to one of claims 1 to 10, characterized in that the UV lacquer layer is micro-folded by the partial treatment with the excimer radiator on the surface and thus a partial matting effect is achieved. 12) Method according to one of claims 1 to 11, characterized in that the partially treated with the excimer radiation UV coating layer is then completely cured by means of UV radiation. 13) Method according to claim 12, characterized in that the wavelength of the radiation of the UV radiator is in the range of 300-500 nm. η 14) Web-shaped carrier substrates or general cargo, produced by a process according to claims 1 to 13. 5