DE102006030870A1 - Structural component,especially a plastic automobile exterior component, has a protective coating comprising a scratch protection layer over a thick UV protection layer containing an organic UV absorber - Google Patents

Abstract

Structural component has a protective coating comprising a scratch protection layer over a UV protection layer that contains an organic UV absorber and is more than 10 mu m thick. An independent claim is also included for coating a structural component by applying a UV protection layer as above and applying a scratch protection layer as above over the UV protection layer.

Description

The The present invention relates to the coating of components, in particular of intended use of the weather exposed components, for UV protection and scratch protection. Especially the invention relates to a component, in particular a transparent plastic component, with a protective coating comprising a UV protective layer and an overlying Scratch-resistant layer and a corresponding coating method.

Such a component and such a method are for example from the DE 100 18 429 A1 known. In this prior art, a protective layer structure of an initially applied zinc oxide-containing layer for UV protection and a subsequently applied abrasion-resistant layer is provided. This layer structure has a number of disadvantages. For example, it is relatively expensive to form the UV protective layer with the smallest possible and evenly distributed zinc oxide particles, which is required for a good UV protection effect. In addition, over the entire visible spectral range relatively large reflectivity of zinc oxide particles complicates the creation of a transparent protective coating, as in practice in particular z. B. then may be required if the component itself is transparent.

In order to protect transparent plastics from the effects of the weather, in particular against UV components in sunlight, and to provide a high surface hardness or abrasion resistance (scratch protection), it is also known and z. B. in the field of production of plastic components for the exterior of a vehicle (eg., Glazing of a motor vehicle) currently common to apply on the component a thermosetting polysiloxane containing an organic UV absorber. In this regard, for example, on the DE 197 24 396 A1 to refer in which various organic UV absorbers are described for siloxane coating systems. This single-layer paint system can, for. B. by dipping, flooding, pouring, spinning, spraying or brushing in a layer thickness of more preferably 5 to 15 microns, z. B. on a polycarbonate component, are applied. In such a protective coating, however, results in a very disadvantageous target conflict in practice between a good UV protection on the one hand and a good resistance or scratch resistance on the other. The hardness of the polysiloxane lacquer decreases with increasing UV absorber content and vice versa. Another problem that is currently emerging is the fact that the commercially available polysiloxane paints must be baked at temperatures of at least about 130 ° C (typically one hour), which may have a detrimental effect, in particular for many plastic components (e.g. Delay, etc.). If the UV absorber content in the coating is kept low in favor of a greater hardness of the coating and a large layer thickness of more than 10 μm is selected to improve the UV protection effect, the coating becomes extremely brittle and subsequently breaks off slightly.

It It is an object of the present invention to provide UV and scratch protection for components the aforementioned To provide a type in which the above-mentioned disadvantages are avoided.

These Task is solved by a component having the features of claim 1 or a coating method with the features of claim 6. The dependent claims relate to advantageous developments of the invention.

at the component according to the invention contains the UV protective layer is an organic UV absorber and has the UV protective layer a layer thickness of more than 10 microns, preferably even more than 20 μm.

By the relatively large layer thickness of the UV protection layer in the invention in combination with the above applied scratch protection layer is advantageous in use Organic UV absorber in the prior art existing conflict of objectives between UV protection and scratch protection solved. Surprisingly, it has become pointed out that despite such a large layer thickness of the UV protective layer a reliable and over longer periods stable coating can be created. The mechanism of action is not very clear. Presumably, the scratch-resistant layer causes next the provision of a hard or abrasion resistant coating surface as well a mechanical stabilization of the underlying UV protective layer and / or a barrier effect, which is a degradation and a loss of the UV absorber prevented by migration and washing out.

The Protective layers provided in the invention can be particularly simple Way z. B. as paint layers separated from each other and successively be applied to the relevant substrate (component). each then this protective layers fulfilled a specific task (UV protection or scratch protection) and can accordingly be optimized in terms of their composition and layer thickness. The above explained Synergy effect between UV protection layer and scratch protection layer allows this the combination of a high UV protection with a high scratch resistance and surface quality.

A particularly preferred use of the invention results for components made of plastic, in particular thermoplastic materials such. B. Polycarbonate (including polycarbonate blends). In a particularly preferred embodiment, it is an injection-molded component for the exterior of a vehicle, in particular z. B. an injection molded polycarbonate component for vehicle glazing ("glazing").

Especially interesting is the coating of the invention z. B. for large format (eg maximum extension greater than 1m) disc-shaped Verscheibungsbauteile how they z. B. in the automotive industry (eg front, rear or side windows, transparent sunroof covers, panoramic roofs Etc.). With regard to such large-sized components, it should be noted that that in practice a big one desire after easy to handle and inexpensive coating process Therefore, in principle for UV protection and scratch protection also eligible complex coating methods such as a Deposition from the gas phase, plasma coating, etc., as z. B. are used for coating of spectacle lenses, in here particularly interesting area of use in the rule would be too expensive.

For the formulation The organic UV absorber used in the invention may be advantageous in itself recourse to known substances and substance combinations become, how they z. B. as additives in spray paints or sunscreens are known. For example only z. Benzophenones, oxybenzone, Called triazoles and trazine. Also, the UV protective layer may also be called HALS (Hindered Amine Light Stabilizers) which may be present in the UV protective layer reactions of aggressive Photooxidationsprodukte suppress. Especially with a comparatively large layer thickness of the UV protective layer can such reactions in near-surface Areas of the UV protective layer otherwise pose a problem. In this regard, it should be noted that the UV protective layer at the invention certainly with layer thicknesses of advantageous to about 40 μm without problems can be provided long-term stable. Of course you can Such a UV protective coating also known additives Art included.

Of the UV absorber is preferred for both UVA and UVB radiation effective. This can also be achieved by using UV absorbers which are known per se be ensured in the invention readily.

Regarding the quality of UV protection is according to a embodiment provided that by the UV protective layer at least 90%, preferably at least 95% of the solar radiation power in the wavelength range be absorbed from 100 to 350 nm.

In a particularly preferred embodiment the UV protective layer is an acrylic-based or PUR-based paint. Such paints are diverse known and particularly easy to handle in practice.

Also for the Scratch protective layer can be known per se in the context of the invention Formulations and / or application method used become. It is essential that with the UV protective layer and the scratch-resistant coating two separately on top of each other on a component surface arranged layers are formed, each of which has its specific Task completed.

Prefers the layer thickness of the scratch-resistant layer is at least one Factor 2, more preferably at least a factor of 3 smaller as the layer thickness of the UV protective layer.

With regard to the quality of the scratch protection is provided according to an embodiment that this in the DE 100 18 429 A1 , Page 2, lines 40 to 43, specified criterion met.

In a preferred embodiment the scratch protection layer is formed by a nanolack, which is the surface the protective coating is provided by nanoparticles (eg of ceramic). This can not only a relatively high scratch resistance, but also a dirt-repellent effect can be achieved, as z. B. for outdoor use Of vehicles is particularly interesting. The nanoparticles can z. B. be involved in an organic matrix and next to her Effect for scratch protection and / or self-cleaning advantageous Provide a "self-healing", in which Scratches in the paint can be automatically "cured" by self-organizing nanoparticles. In addition, can by such a nano-layer (as a scratch-proofing layer or possibly as additional on a scratch-resistant coating applied layer) a good Barrier effect of the type already mentioned above are realized, in which the UV absorber substance (s) escape (eg out-diffusion) is prevented from the UV protective layer. In addition, can through one over the UV protective layer applied nanolack the attack of the UV protective layer be contained by oxygen from the air.

In the simplest case, the protective coating consists of the UV protective layer and the scratch protection layer arranged directly above it. However, it should by no means be excluded that the protective coating comprises further layers, for example a so-called primer layer between the component surface and the UV protective layer to improve the adhesion of the protective coating on the component and / or an intermediate layer between the UV protective layer and the Scratch protection layer. With such an intermediate layer (eg lacquer layer), z. B. the adhesion of the scratch-resistant layer can be improved and / or a barrier for the UV absorber can be accomplished.

The Formation of a barrier for the organic UV absorber provided layer above the UV protective layer, z. B. between the UV protective layer and the scratch-resistant layer and / or on the surface the protective coating is according to a embodiment as deposition from the gas phase (eg CVD, PECVD or the like) intended. Regarding in this case, in particular for large-area coatings It should be noted that the cost of application comparatively thinner Barrier layers can be kept low. Such as a barrier serving layer therefore preferably has a layer thickness, a comparatively small proportion (eg less than 20%, in particular less than 10%) of the total thickness of the protective coating accounts.

• – Aufbringen einer UV-Schutzschicht auf das Bauteil, und
• – Aufbringen einer Kratzschutzschicht (direkt oder indirekt) über der UV-Schutzschicht,

wobei die UV-Schutzschicht einen organischen UV-Absorber enthält und mit einer Schichtdicke von mehr als 10 μm aufgebracht wird.The component according to the invention, with or without the peculiarities explained above, can advantageously be produced by a coating method, comprising the steps:

• - Applying a UV protective layer on the component, and
• Applying a scratch-resistant layer (directly or indirectly) over the UV protective layer,

wherein the UV protective layer contains an organic UV absorber and is applied with a layer thickness of more than 10 microns.

Either for the UV-protective layer as well as the scratch-resistant layer can on itself known methods of application (eg diving, flooding, pouring, spinning, Spraying or painting) become.

In a particularly preferred embodiment Both the UV protective layer and the scratch-resistant layer (and optionally provided additional layers at least in part) in liquid or pasty Shape separately from each other and applied one after another and each Hardened, in particular For example, thermally and / or by irradiation (eg UV irradiation). After applying a respective layer, this can before the Applying a subsequent layer here completely or even partially cured become. In the latter case, a subsequent full curing of relevant layer even after application of a subsequent layer take place (eg as a final curing the entire protective layer structure).

Especially when used for a thermoplastic plastic component is very advantageous if a maximum occurring in the coating process curing temperature is at most 120 ° C, preferably even well below 120 ° C. at a curing By means of UV irradiation, for example, a maximum curing temperature in the range of 70-90 ° C, and with purely thermal curing in the range of about 80-110 ° C possible.

As already mentioned above may as nonskack coating nanolack system or another, in particular commercial Scratch protection system can be applied.

The Invention will be described below with reference to an embodiment with reference to the attached Drawings closer explained. They represent schematically:

1 an injection-molded transparent plastic component for use as a glazing component on a motor vehicle,

2 the component of 1 after application of a UV protective varnish, and

3 the component of 2 after application of a scratch protection layer.

1 illustrates (in cross-section) a plate-shaped plastic component 10 , which was injection-molded in the illustrated embodiment of polycarbonate with a mean component thickness d0. The transparent plastic component 10 is intended for glazing on a motor vehicle (eg as a rear window, transparent roof plate, etc.) and is extremely scratch-sensitive due to the use of polycarbonate. That's why, and because the component 10 as such would be clouded and embrittled by weather conditions and in particular by the sunlight, the component becomes 10 in the manner described below before installation on the vehicle on a (in the figures upper) flat side with a protective coating 12 (see. 3 ) Mistake.

How out 2 can be seen, this is first an acrylic coating 14 containing organic UV absorbers on the component 10 applied and at least partially cured. The acrylic lacquer layer 14 forms a UV protection, which in the illustrated embodiment has a uniform layer thickness d1 of about 30 microns (The layer thicknesses are not shown to scale in the figures).

How out 3 can be seen, over the acrylic lacquer layer 14 then another nanolack layer 16 (with ceramic nanoparticles) applied and together with the acrylic lacquer layer 14 thermal completely cured at a curing temperature of less than 120 ° C. In the illustrated embodiment, the nanolack layer 16 directly, ie without a further intermediate layer painted. The nanoparticles of the layer, for example, incorporated into an organic matrix 16 can provide on the surface for a largely inert layer with very high scratch resistance. The nanolack can also z. B. by UV irradiation at 80 ° C already cured well.

All protective layers used are transparent, so that through the coating of the component 10 whose transparency is not significantly reduced.

In the described coating method complex and expensive processes are advantageously avoided. Nevertheless, the protective coating offers 12 excellent UV protection and high scratch resistance. The use of separate layers of lacquer allows for easier and cheaper processing (systems and process) with at the same time a low defect or reject rate. In contrast to conventional polysiloxane lacquers, high firing temperatures, which are critical for many plastic substrates, can be avoided in the invention. Depending on the specific formulation of the UV protective varnish, it is also possible to avoid stress cracks in the polycarbonate which are often caused by common polysiloxane varnishes or their primers. In particular, when using a nano-layer as the nanolack layer described as the outermost cover layer repairability or even a "self-healing" effect can be achieved in addition to the invention (today's polysiloxane coatings are neither reworkable nor repairable). The paint systems used for the UV protective layer and / or the scratch-resistant layer can be water-based or even based on solvents which attack the plastic in question less or not at all.

In summary can with the invention an increase the component quality achieved while reducing the cost of manufacturing be, especially for Polycarbonate glazing components for the automotive sector of great Meaning is.

10

Plastic component

12

protective coating

14

Acrylic paint layer

16

Nano paint coating

d0

component thickness

d1

layer thickness the acrylic lacquer layer

d2

layer thickness the nanolack layer

Claims (7)

Component, in particular plastic component for the exterior of a vehicle, with a protective coating ( 12 ) comprising a UV protective layer ( 14 ) and a scratch protection layer ( 16 ), characterized in that the UV protective layer ( 14 ) contains an organic UV absorber and has a layer thickness (d1) of more than 10 microns. Component according to claim 1, designed as injection-molded Polycarbonate component for the Glazing of a motor vehicle. Component according to one of the preceding claims, wherein the UV protective layer ( 14 ) also contains HALS stabilizers. Component according to one of the preceding claims, wherein the UV protective layer ( 14 ) is an acrylic-based or PUR-based paint. Component according to one of the preceding claims, wherein the scratch-resistant layer ( 16 ) is formed by a nanolack. Method for coating a component ( 10 ), in particular a plastic component for the exterior of a vehicle, comprising the steps: - applying a UV protective layer ( 14 ) on the component, and - applying a scratch-resistant coating ( 16 ) over the UV protective layer ( 14 ), characterized in that the UV protective layer ( 14 ) containing an organic UV absorber having a layer thickness (d1) of more than 10 microns is applied. The method of claim 6, wherein a maximum curing temperature while of the procedure at most 120 ° C is.