WO2012167865A1

WO2012167865A1 - Wavelength-selective reflective coating

Info

Publication number: WO2012167865A1
Application number: PCT/EP2012/002079
Authority: WO
Inventors: Adalbert Huber
Original assignee: Merck Patent Gmbh
Priority date: 2011-06-07
Filing date: 2012-05-15
Publication date: 2012-12-13
Also published as: DE102011103425A1

Abstract

The invention relates to a wavelength-selective reflective coating for transparent or translucent substrates, as are used in particular for greenhouses, polytunnels, preferably those for agricultural purposes and the cultivation of plants, for roof coverings and canopies, for roof-lights, conservatories and aviaries. The invention also relates to a method for producing such a coating and to the use thereof.

Description

Wavelength selective reflective coating

The present invention relates to a wavelength-selective reflective coating for transparent or translucent substrates, as used in particular for greenhouses, film structures, preferably those for agricultural purposes and the cultivation of plants, for roofing and roofing, for skylights, conservatories and aviaries. Rooms enclosed or covered with transparent or translucent surfaces generally have the problem of excessive heat radiation in summer and a high room temperature associated therewith. There have therefore been several solutions for coating or modification of such surfaces, which are usually made of glass or suitable polymer plates or films, proposed to avoid too high a permeability of existing in the solar spectrum heat radiation. As a rule, such solutions are then designed to reflect the radiated heat in the near infrared range (NIR). Thus, for example, DE-OS 25 44 245 describes a glazing material which consists of polymethyl methacrylate disks in which pearlescent pigments are incorporated in a very low concentration, the pigments consisting of mica with a titanium dioxide layer of specific thickness. The stated thickness of the titanium dioxide layer of about 20 nm gives a red interference color of the pigments used. Such a glazing material is intended to effectively reflect the NIR portion of the incident solar light.

Similar pigments, which likewise have a red interference color, are described in EP 548 822 B1 in a coating on an amorphous Plastic plate used, which is also the IR portion of the solar

To reflect radiation.

In buildings that are used in the agricultural sector, in particular for plant breeding, for example in greenhouses, however, not only a high irradiation in the NIR range leads to possible burns or other heat damage to the plants, but also a high proportion of green radiation in the solar spectrum, as this has a particularly high energy density. In addition, green light can be used by the plant for a compact plant and fruit growth little. There are therefore already several technical solutions for the coating of greenhouses and the like, which also absorb or reflect the green light of the solar spectrum in addition to the NIR radiation.

From DE 42 30 023 A1 and EP 659 198 B1, a composite material for shielding radiation is known which comprises a transparent polymer and a green interference pigment. The green interference pigment is composed of a platelet-shaped carrier material and a 120 to 160 nm thick layer of titanium dioxide. This reflects a high proportion of NIR radiation and green light.

For insect pollinating insects, it is difficult due to their different from human color perception (insects in the UV range shifted, therefore no red perception), with an opacity of the greenhouse surrounding areas for green light, the flowers of the remaining plant components many of these surfaces are also protected against the transmission of UV light. In the latter case, only the blue color is perceived by the insect, so that the flowers of the plants are usually not found because of their color, but only because of their smell or rather random. In view of the diverse conditions for successful plant growth in greenhouses or similar plants, it would therefore be advantageous to be able to coat or equip the transparent or translucent surfaces surrounding or covering these buildings in such a way that both the entire light that is required and usable for plant growth grows the interior of the buildings can reach and insects can find the flowers of the plants comparatively effortlessly due to their colourfulness, as well as that if possible high-energy radiation can not penetrate into the enclosed spaces.

It is therefore an object of the present invention to provide a wavelength-selective reflective coating for transparent or translucent substrates, which equally fulfills as many and, ideally, all of the stated requirements so that plant growth in the spaces enclosed by the coated substrates is advantageous can be influenced.

Another object of the invention is to provide a method for producing such a coating.

In addition, it is also an object of the invention to show the use of said coating.

The object of the present invention is achieved by a wavelength-selectively reflective, interference pigments and polymeric

Binder or interference pigments and polymer component-containing, solid coating for transparent or translucent substrates, wherein the coating under the action of solar radiation for at least 60% of the incident blue light, based on the wavelength of 470 nm, and at least 60% of the incident red Light, based on the wavelength of 680 nm, is permeable. In addition, the object of the invention is also achieved by a process for the preparation of the abovementioned coating, wherein an interference pigment with green interference color and an interference pigment with yellow interference color, individually or as a mixture, with a polymeric binder or a polymer or polymerizable component, optionally additives and optionally mixed with a solvent and

a) to a polymeric molding, or

b) to a coating composition

is processed, is applied flat on a transparent or translucent substrate or represents one, and, if a coating composition is present, dried and optionally additionally cured.

Furthermore, the object of the invention is also achieved by the use of the coating described above for the production of greenhouses and film structures, especially for agricultural purposes or the cultivation of plants, and for skylights, roofing and roofing, skylights, gardens, aviaries and conservatories.

According to the invention, the wavelength-selective reflective coating is a solid coating on a transparent or translucent substrate which contains either interference pigments and at least one suitable polymeric binder, or interference pigments and at least one polymer component.

The coating according to the invention is on exposure to solar radiation (undiminished radiation over the entire solar spectrum) for at least 60% of the incident blue light, based on the wavelength of 470 nm, as well as for at least 60% of the incident red light, based on the wavelength of 680 nm, transmissive, ie transmits the said percentage of the incident light at the given wavelengths. Maximum transmission in the In each case mentioned areas in the coating according to the invention each amount to about 80% of the incident light.

Preferably, the transmission is 65 to 75% of the incident blue light and 65 to 75% of the incident red light, based on the above-mentioned respective wavelengths.

Naturally, since reflection or transmission values of the coatings according to the invention do not change stepwise but wave-like, the transmission values in the entire red and blue wavelength range, even outside the reference wavelengths, are high overall and only slightly below the maximum values mentioned. The determination of the transreflection and reflection measured values can be carried out according to the invention by means of a UV-Vis-NIR spectrometer Lambda 900 from Perkin Elmer or another suitable UV-Vis-NIR spectrometer. To record the reflection and transreflection spectra, free coating films to be measured are positioned in front of or behind an integrating sphere at variable angles of incidence of the measuring beam (15 °, 25 °, 45 °, 75 °, 90 °).

The determination of the transmission values (permeability) takes place according to the invention as follows:

The corresponding free paint films are prepared by coating paint samples onto a PVF film by knife coating a coating composition (interference pigments in an appropriate concentration, stirred in a conventional paint-forming binder using a dispermat), drying and stripping from the PVF film, and as free paint films with a suitable dry film thickness (for example 20 ± 1 pm) for spectroscopic investigations be used. When taking the reflection spectra with the Ulbricht sphere (conditions and measuring device as mentioned above), the back side of the free lacquer film is covered with a light trap. The light trap is a thin sheet metal with a matt, black side facing the varnish and a diffusely reflecting white back. The transreflection measurements of the free coating films are carried out without Lichtfalie. The transmission spectra are mathematically derived from the reflection and transreflection spectra. The measurements are carried out in each case against a blank sample of a non-pigmented coating film of the same layer thickness. The difference between the two measurements is evaluated.

According to the invention, the transmission values given in the present description and the claims are for the calculated transmission of the sample, integrated over the measured values at all the aforementioned angles of the measuring beam.

Corresponding reflection values and transreflection values can be taken directly from the reflectance spectra or reflection spectra created at each angle of the measuring beam and then integrated over the entire measuring range (integrated values via the

Measured values under all angles of the measuring beam). All reflection values and transreflection values given in the present description, as well as the transmission values calculated therefrom, refer to such integrated measurement values, unless stated otherwise.

The above-described transmission property (permeability) of the coating according to the invention ensures sufficiently large proportions of red and blue light which strike the interior of buildings, buildings, building parts, etc., through the coating, from transparent or translucent substrates provided with the coating are converted, for example, greenhouses. This high proportion of transmitted red and blue light can be well utilized for a compact growth of stems and fruits of plants. Of particular advantage for the desired plant growth is when the proportions of transmitted red and blue light have approximately the same order of magnitude. According to the invention therefore in the coating according to the invention the ratio of transmitted red and blue light to each other is 0.9: 1 to 1, 1: 1. These figures relate to the percentage transmission both at the wavelengths of 470 nm for blue light and 680 nm for red light, and integrated into the percent transmission over the entire wavelength ranges for blue light (about 430 to 490 nm) and red Light (about 630 to 780 nm).

In addition, the coating of the invention is permeable to at least 25% of the total, in the wavelength range between 280 and 420 nm incident light. Preferably, 30 to 70%, in particular 45 to 60% of the total light incident in the wavelength range between 280 and 420 nm is transmitted.

This is light from the near UV range. The light absorption spectrum of the photoreceptors of the honeybee, as well as that of other insects with complex eyes (compound eyes) has, among other things, a maximum at about 340 nm. Light of this wavelength and the adjacent UV range can therefore be well perceived by the honeybee, for example. If such light enters a greenhouse or other enclosed space through a transparent or translucent cover, the insect can see flowers within the remodeled area which reflect this UV light, for example also white blossoms. On the other hand, if the enclosure is completely protected against the penetration of UV light, the insect is only blue and the green area of the incident light is available for viewing. However, green light, as already explained above, a carrier of high energy, so that the heat radiation thus registered would have a negative effect on plant growth. It is therefore advantageous for plant growth to absorb or reflect the green area of the incident light at a conversion.

However, absorption of green light is ruled out for various reasons, since the greenhouses converted with such elements would have a strong red inherent color, which would not correspond either aesthetically or otherwise with the requirements placed on greenhouses.

According to the invention, therefore, the coating according to the present invention reflects at least 35% and preferably 37 to 50% of the irradiated green light, based on a wavelength of 530 nm. This reflection, as well as the total reflection in the green region (light of approx. 490 nm to 550 nm wavelength), preferably higher than the reflection at any other wavelength and therefore any other color. It follows that the coating of the invention when viewed directly near the glancing angle (range at a distance of about 1 ° to 25 ° adjacent to the glancing angle) a green color

(Reflection color). In addition, the coating according to the invention also preferably reflects at least 15%, preferably at least 20%, and in particular 30 to 40%, of the total light incident in the wavelength range from 780 nm to 2250 nm. This is light in the

Infrared. In particular, light is reflected in the NIR (near infrared, 780 to 100 nm). This wavelength range is also a carrier of high light energy and known as thermal radiation. The reflection of a large part of this heat radiation therefore leads, together with the above described reflection in the green wavelength range, to the fact that a large part of high-energy radiation of the solar spectrum is reflected by the coating of the invention and thus can not penetrate into the interior of the enclosed spaces.

According to the invention, the coating contains at least one interference pigment (one type). This may be an interference pigment which has the aforementioned reflection and transmission properties for blue, red and green light, and advantageously also the aforementioned reflection and transmission properties for NIR and UV light.

However, it is particularly advantageous if the mentioned and required reflection and transmission properties are adjusted with suitable mixtures of interference pigments.

It has been found, in particular, that mixtures of interference pigments with green interference color and interference pigments with yellow interference color are very suitable for setting the required spectral properties for the coating according to the invention. Therefore, in a particularly preferred embodiment, the coating according to the invention contains at least one interference pigment with green interference color and at least one interference pigment with yellow interference color.

Interference pigments are pearlescent pigments which, in addition to having a characteristic pearlescent effect which occurs by multiple reflection of transparent platelets of high refractive index (pearlescent pigments) in their parallel orientation in the application medium, also have interference colors. Whereas classic pearlescent pigments consist only of pigment platelets of high refractive index materials, according to the invention interference pigments are used which are based on a platelet-shaped, non-metallic, inorganic, transparent carrier have at least one high-index layer.

The interference color of the interference pigments is the color of the pigment in the otherwise transparent and colorless application medium, for example in a coating, with nearly parallel alignment of the majority of the individual pigment particles with respect to the (planar) surface of the application medium and viewed at an angle just outside of the Gloss angle (in the measuring angle of 15 ° or at a viewing angle in the range of about 1 ° to about 25 ° on both sides of

Gloss angle).

According to the invention, the interference pigment with green interference color and the interference pigment with yellow interference color in a ratio of 60:40 to 85:15 are preferably used in the coating.

The ratio is preferably 65:35 to 80:20, in particular 70:30 to 75:25, in each case based on the weight of the pigments.

According to the invention, in particular interference pigments with green and yellow interference colors are used, each of which consists of a platelet-shaped, transparent, colorless carrier material and of a high-index, colorless layer.

As a platelet-shaped transparent support material usually used for interference pigments inorganic platelet-like support materials are used, such as natural or synthetic mica, talc, kaolin, but also SiO ₂ platelets, Al ₂ O ₃ platelets, glass platelets or borosilicate platelets. Preference is given to using natural or synthetic mica.

The high refractive colorless layer is conventional high refractive index layers of interference pigments, for example Layers consisting of TiO ₂ , ZrO ₂ or BiOCl, the oxide hydrates of TiO ₂ or ZrO ₂ , or mixtures of the oxide hydrates and the respective oxides, or the TiO ₂ , ZrO ₂ or the corresponding oxide hydrates in a proportion of at least 80 wt %, based on the weight of the layer.

.Other components of the high-index transparent layer may be the oxides or oxide hydrates of Sn, Si, Ce, Al, Ca or Zn, but at most in a proportion of 20 wt.%, Based on the weight of the high refractive index layer, in this and the optical properties, in particular the interference color, which do not significantly determine interference pigments.

Preferably, according to the invention, a high-index layer is used both for the interference pigment with green interference color and for the interference pigment with yellow interference color, which consists either of TiO ₂ or TiO ₂ with a proportion of at least 80% by weight, based on the weight of the high-index layer, contains. Both variants of the high-index transparent layer are referred to below as the TiO ₂ layer. In this case, the TiO ₂ in the TiO ₂ layer according to the invention can be present both in the anatase and in the rutile modification. Preferably, TiO _{2 is present} in the rutile modification.

Particularly advantageous is the use of interference pigments, which are composed of a platelet-shaped carrier, which consists of natural or synthetic mica, and a TiO ₂ layer located directly on the carrier, in the coating according to the invention.

The optical properties of the pigments used according to the invention are essentially determined by the refractive index of the layer located on the platelet-shaped carrier and the thickness of this high-index layer. In this case, the refractive index, due to the content of the above-mentioned foreign oxides, but also by trapped pores or

Crystal modification of the metal oxides, possibly deviate from the ideal refractive index of the pure high refractive index metal oxides, so that the geometric layer thickness of the high refractive index layer must be adjusted accordingly to achieve the desired interference color.

Preferably, the high refractive index transparent layer completely envelops the platy support.

The size of the platelet-shaped carrier is not particularly critical per se. It usually platelets are used with a thickness between 0.01 and 5 m, in particular between 0.05 and 4.5 pm, and preferably between 0.1 and 2 pm. The extension in length or width is usually between 1 and 250 μm, preferably between 2 and 200 μm and in particular between 2 and 100 μm. However, support plates are preferred which have a narrow particle size distribution and wholly or predominantly have particle sizes which lie in the range between 5 and 60 μm. In particular, a reduced

Fine fraction advantageous. The latter lead to interference pigments with higher color intensity.

The form factor of the carrier platelets, ie the ratio of length or width to thickness, is generally from 2: 1 to 10,000: 1, in particular from 5: 1 to 2000: 1 and very particularly preferably from 20: 1 to 250: 1.

Since the layer thickness of the high-index layer is rather low in comparison to the carrier, the size ratios given above for the carrier material, in particular especially with regard to the particle size and the shape factor, essentially also apply to the coated interference pigments. The thickness of the high refractive index layer (geometrical layer thickness), with a given interference color, is, of course, predominantly dependent on the high refractive colorless material on which the layer is to exist.

If, as is preferably the case, a TiO ₂ layer is used, then the thickness of the resulting TiO ₂ layer for the yellow interference pigment is between 60 and 110 nm, preferably between 70 and 100 nm, and the thickness of the TiO ₂ Layer for the green interference pigment between 240 and 310 nm, preferably between 250 and 300 nm.

Green interference pigments with a Ti0 ₂ layer thickness in the range indicated above have a particularly high color strength. This can be further improved if used for this purpose

Carrier material has a narrow particle size distribution. Accordingly, the mica preferably used for the green interference pigment used according to the invention, as well as the coated interference pigment, advantageously has a particle size in the range from 5 to 60 μm with a narrow particle size distribution and preferably also with low fines content.

The interference pigments with green and yellow interference color used according to the invention may, in addition to the high-indexing coating described above, also be provided on their outer surface with an inorganic and / or organic, so-called post-coating. This customary applied secondary coating is used, for example, to simplify the incorporation into the application medium, to improve the weather resistance, to

Reduction of yellowing tendency or better distribution of the interference pigments in the application medium. Secondary coatings change the optical properties (colouristics) of the interference pigments practically not and with extremely low layer thicknesses, which are usually only in the range of molecule monolayers up to about 15 nm, preferably up to about 5 nm, present on the pigment surface. According to the invention, customary commercially available interference pigments with green and yellow interference color can be used in the coating, for example those sold under the name Iriodin® or Pyrisma® by Merck KGaA, as long as the respective interference color has interference effects and not additionally

Absorption effects of the materials for high-index coating and carrier of the interference pigments is due.

The preparation of such interference pigments is generally carried out by the customary wet-chemical methods for coating the platelet-shaped carrier particles with metal oxide layers of inorganic starting materials. By way of example, customary production methods, as described in the patents DE 14 67 468, DE 19 59 988, DE 20 09 566, DE 22 14, 545, DE 22 15 191, DE 22 44 298, DE 23 13 331, DE 25 22 572, DE 31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE 32 1 602 or DE 32 35 017 are described.

Particularly suitable for use in the coating according to the invention are interference pigments of the Iriodin® series with yellow or golden yellow interference color and green interference pigments of the Pyrisma® T40-24 Green type from Merck KGaA.

The total amount of the interference pigments with yellow and green interference color used in the coating according to the invention is between 0.5 and 30% by weight, preferably between 5 and 20% by weight, based on the weight of the (solid) coating.

Provided that the transmission properties of the coating according to the invention in the blue and red wavelength area of the visible light, as described above, remain in the coating according to the invention in addition to the interference pigments with green and yellow interference color also be included further interference pigments. These are preferably transparent interference pigments which have uniformly high transmission values in the visible wavelength range of the light and neither self-absorption nor selective reflection. For example, these may be silver-white interference pigments or interference pigments whose selective reflection in the UV and / or IR range may influence the optical behavior of the coating according to the invention in this area.

According to the invention, these additional interference pigments are included, if at all, only in such small proportions in the coating that the transmission behavior of the coating according to the invention is not adversely affected. Preferably, in addition to interference pigments with green and yellow interference color, no further interference pigments are contained in the coating according to the invention. The wavelength-selective reflection or wavelength-selective transmission (light transmission) of the coating according to the present invention is based on the corresponding optical effect of the interference pigments contained and not on the optical effect of the binders, polymer components or any additives present.

Polymeric binders, polymer components and any other additives and auxiliaries which may be present are therefore selected so that they are translucent or preferably transparent to light of the solar after drying, curing and / or polymerizing the coating

Spectrum, but at least in the visible wavelength range, and also white or colorless. The corresponding polymeric binders, polymer components and additives are commercially available and known in the art and are tailored to the particular application and the specific embodiment of the coating according to the invention out.

In principle, the coating according to the invention can be present as a temporary or permanent coating on a transparent or translucent substrate.

For both variants mentioned above, a coating in the form of a polymeric film, which is optionally firmly bonded to the underlying transparent or translucent substrate, for example by gluing or laminating, or loosely adhering thereto by pure adhesion forces in question. In such a case, the interference pigments are present in combination with a polymer component which has been polymerized in film form and / or crosslinked as a coating.

The coating according to the invention can also be present on the substrate as an uncured paint, cured paint or in the form of a dried and optionally cured coating composition. These coating forms are suitable as temporary, but also as

permanent coating on a transparent or translucent substrate. The interference pigments are here in the coating with a conventional polymeric binder, which may also be crosslinkable.

Preferably, the coating of the invention is present as a temporary coating on the substrate, in the form of a dried coating composition. Depending on the seasonal or climatic conditions, such a coating can easily be applied to an already established greenhouse or other building and after any period of use, for example over several months in the hot weather period, residue-free with the use of solvents, for example, from various alkalis, and / or mechanical forces just as easily removed and reapplied at any time if necessary.

The polymeric binders used are conventional binders which are known from coating technology. These are usually organic polymeric or copolymeric binders such as alkyd resins, vinyl resins, epoxy resins, polyurethanes, acrylates, chlorinated rubber, polycarbonates, polyesters, polyethylene glycol and copolymers thereof. These are usually in commercially available Lackfirnissen, Druckfarbenfirnissen or other prefabricated, pigment-free binder compositions already in mixtures with other conventional auxiliaries and additives (additives), but can also be used without any further additives.

These auxiliaries and additives are, in particular, thickeners, dispersing aids, wetting agents, plasticizers, leveling agents, defoamers, if appropriate also crosslinking agents, and optionally also solvents, such as, for example, As water, ketones, alcohols, esters, or aromatics.

In addition, conventional fillers such as, for example, lime, kaolin or talc may be added in small amounts as further additives, provided that the transmission properties of the coating thereof are not impaired.

If the coating according to the invention is to be present in the form of a polymeric film on the transparent or translucent substrate, the film is preferably made of polyethylene, ethylene / vinyl acetate copolymer, polyvinylidene chloride, polyvinyl chloride, polycarbonate, polymethacrylate or mixtures thereof. The interference pigments are then converted into the corresponding polymerizable monomers or prepolymerized polyols. mers of the type mentioned (ie in the polymerizable or polymeric components, also referred to as polymer components according to the present invention) and processed with these, for example by extrusion, to form a polymeric film.

The above coating compositions are applied to the transparent or translucent substrates by conventional application methods such as printing, spraying, knife coating, rolling, brushing, etc., dried and optionally additionally cured or crosslinked.

Suitable transparent (opaque and translucent) or translucent (translucent) substrates are the roofing materials commonly used for greenhouses, foil tents, skylights, aviaries, etc., such as colorless polymeric films, colorless fabrics, colorless polymeric plates, or colorless glasses. These may be in the form of plates, discs, shaped articles, profiles or flexible or reinforced films.

The present invention also provides a process for the preparation of the coating according to the invention, in which an interference pigment with green interference color and an interference pigment with yellow interference color, individually or as a mixture, with a polymeric binder or a polymerizable or polymeric component, optionally additives and optionally mixed with a solvent and

a. to a polymeric molding, or

b. to a coating composition

In addition to the interference pigments used according to the invention with green and yellow interference colors, those already described above polymeric binder or polymer components (the latter are polymerizable or polymeric components), each optionally with the addition of further interference pigments, fillers, solvents and / or auxiliaries and additives, mixed together and with conventional methods either to a coating ready coating composition or to a polymeric molding , which is preferably a polymeric film processed.

When coating compositions are prepared, they may also each contain only the green or yellow interference pigment and sequentially coated onto the transparent or translucent substrate, i. in the form of a double-layered coating. However, this method is not given due to the technical overhead.

The same applies to the production of polymeric films, which, of course, also each have only one type of said interference pigments and can then be applied to the corresponding substrate in double layers.

The green and the yellow interference pigments are used in a weight ratio of 60:40 to 85:15, preferably from 65:35 to 80:20, in particular from 70:30 to 75:25, based on the total amount of the green and yellow interference pigments used, introduced into the coating composition or the polymeric molded body.

If the correspondingly resulting coating is to have a double-layered structure, as described above, the individual layers each contain the corresponding proportions of yellow or green interference pigment.

Overall, the proportion of green and yellow interference pigments in the coating of the invention 0.5 to 30 wt.%, Based on the Weight of the (solid) coating. While in the case of polymeric molded articles, for example in the case of films, a weight fraction of from 0.5 to about 10% by weight is generally sufficient, this can be up to 30% by weight, in particular from about 5 to 30, when using coating compositions % By weight, and more preferably from 5 to 20% by weight.

The coating according to the invention is applied to the transparent or translucent substrate with a (dry) layer thickness of from 10 to 2000 .mu.m, preferably from 15 to 50 .mu.m in coating compositions and from 300 to 1000 .mu.m in the case of polymeric shaped articles (films).

It must be ensured that the coating has a thickness at which the light transmission of the coating can be ensured in conjunction with the content of interference pigments. In this respect, it is necessary to match the layer thickness and content of interference pigments to one another. A high layer thickness tends to require a low percentage of interference pigments.

The present invention also relates to the use of a coating according to the invention for the production of greenhouses and film structures, in particular for agricultural purposes or the cultivation of plants, and for skylights, roofing and roofing, skylights, gardens, aviaries and conservatories.

Constructed spaces that contain the mentioned components, are considered or represent, also regularly accommodate plants whose growth, propagation or fruit yield can be advantageously controlled and influenced by the coating according to the invention. Therefore, the various advantages of the invention already described in the introduction may come into play in all of the stated fields of application.

The subject of the present invention are therefore also greenhouses, film buildings, skylights, roofing or canopies, skylights, Gardens, aviaries or conservatories, which have the coating according to the invention.

The invention relates to a coating for transparent or translucent substrates, which can be used in a particularly positive manner for influencing a desired plant growth due to their special wavelength-selectively reflecting and simultaneously wavelength-selective transmitting properties. Fig. 1 shows the transmission, reflection and absorption spectra of a coating according to the invention containing a pigment mixture of green and yellow interference pigment with a concentration of 12 wt.%, Based on solid binder, in a conventional NC lacquer at a coating film thickness of 20 ± 1 pm and at a measuring angle of 90 °.

2 shows the transmission and reflection spectra of a coating according to the invention comprising a pigment mixture of green and yellow interference pigment with a concentration of 12% by weight, based on solid binder, in a customary NC lacquer and in a conventional aqueous PU lacquer in one Paint film thickness of each 24 ± 1 pm under a measuring angle of 90 °.

The invention will be explained in more detail with reference to an example, but not limited to this.

Invention Example:

A mixture of a green interference pigment (Pyrisma T 40-24 SW Green, TiO ₂ rutile on mica, particle size 5 to 35 pm, Merck KGaA, Darmstadt, Germany) and a golden yellow interference pigment (TiO ₂ rutile on mica, thickness The Ti0 ₂ layer about 100 pm, particle size 10 to 60 pm, Merck KGaA, Darmstadt, Germany) in a weight ratio of 70:30, hereinafter referred to as pigment 1, in a concentration of 12 wt.%, Based on the solids content , in an aqueous polyurethane binder (Bayhydrol XP 2637, Fa. Bayer, Leverkusen, Germany) einispergiert. The pigment-containing polyurethane dispersion is sprayed onto a commercially available PET greenhouse film having a film thickness of 200 μm. After drying under ambient conditions, a dry layer thickness of the coating of about 20 μm is obtained. The coated greenhouse film is used to cover greenhouses for the cultivation of vegetables, flowers or fruit. In the cultivated plants, the desired compact plant growth and a high fruit yield can be achieved over the entire growing season.

To determine the reflection and transmission values of said coating, the procedure is as follows:

The transreflection and reflection measured values are determined by means of a Lambda 900 UV-Vis-NIR spectrometer from Perkin Elmer.

Free paint films are produced, which are pigmented with a mixture according to the invention of green and yellow interference pigment (Pigment 1, see Example 1). These paint films are prepared by coating paint samples by knife coating a coating composition [interference pigments (pigment 1) in a suitable concentration, based on solid binder, in a conventional binder for the coating Position using a Dispermat at a peripheral speed of 7 m / s 15 min. stirred] on a PVF film and dried. The resulting paint films are stripped from the PVF film and used as free paint films with a suitable dry film thickness for the spectroscopic investigations. To record the reflection and transreflection spectra, the free coating films to be measured are positioned in front of or behind an integrating sphere at variable angles of incidence of the measuring beam (15 °, 25 °, 45 °, 75 °, 90 °). When recording the reflection spectra with the Ulbricht sphere (measuring device as mentioned above), the back of the free coating film is covered with a light trap. The light trap is a thin sheet metal with a matt black side facing the varnish and a diffusely reflecting white back. The transreflection measurements of the free coating films are carried out without light trap. From the reflection and the

Transreflection spectra are mathematically derived the transmission spectra. The transmission values given in the present description and claims represent the calculated transmission of the sample, integrated over the measured values at all the aforementioned angles of the measuring beam, unless stated otherwise.

The measurements are carried out in each case against a blank sample of a non-pigmented coating film of the same layer thickness. The difference between the two measurements is evaluated. 1 shows the transmission, reflection and absorption spectra of the pigment 1 at a concentration of 12% by weight, based on solid binder, in a customary NC lacquer (from Merck KGaA), with a dry film thickness of the coating of 20 ± 1 pm (corresponds to the thickness of the free paint film) and at a measuring angle of 90 °.

To check the dependence of the reflection and transmission properties of the coating of the invention used Binders free paint films are again prepared, and first from the above-mentioned nitrocellulose paint binder from. Merck with a proportion of pigment 1 of 12 wt.%, Based on the solids content of the binder, and having a dry film thickness of the free paint film of 24 ± 1 μιη. The dispersion time is 15 min. at a peripheral speed of 1, 3 m / s.

For comparison, another free paint film is prepared based on an aqueous polyurethane clearcoat (Bayhydrol U XP 2750 Fa. Bayer, Leverkusen, Germany), which has a concentration of pigment 1 of also 12 wt.%, Based on the solids content of the binder , And has a layer thickness of 24 ± 1 μηι.

The superimposed transmission and reflection curves of the last two samples (angle of incidence of the measuring beam of 90 °) are shown in FIG. There are no noticeable differences in the respective reflection and transmission curves as a function of the binder used.

Claims

claims

Wavelength-selectively reflecting, interference pigments and polymeric binder or interference pigments and polymer component-containing, solid coating for transparent or translucent substrates, characterized in that the coating under the action of solar radiation for at least 60% of the incident blue light, based on the wavelength of 470 nm, and for at least 60% of the incident red light, relative to the wavelength of 680 nm, is permeable.

A coating according to claim 1, characterized in that the red and blue light transmitted through the coating have a ratio of 0.9: 1 to 1, 1: 1 to each other.

Coating according to claim 1 or 2, characterized in that the coating is additionally permeable to at least 25% of the light incident in the wavelength range between 280 and 420 nm.

Coating according to one or more of claims 1 to 3, characterized in that the coating is a green

Reflection color has.

Coating according to one or more of claims 1 to 4, characterized in that the coating additionally reflects at least 15% of the total, in the wavelength range of 780 to 2250 nm incident light.

Coating according to one or more of claims 1 to 5, characterized in that the coating at least one Interference pigment with green interference color and at least one interference pigment with yellow interference color contains.

Coating according to Claim 6, characterized in that the interference pigment with green interference color and the interference pigment with yellow interference color are present in a weight ratio of 60:40 to 85:15 in the coating.

Coating according to one or more of Claims 6 or 7, characterized in that the interference pigment with green interference color has a transparent platelet-shaped support and a TiO 2 layer with a thickness in the range from 240 to 310 nm, and the interference pigment with yellow interference color has a transparent platelet-shaped support and a TiO ₂ layer having a thickness in the range of 60 to 110 nm.

Coating according to one or more of Claims 1 to 8, characterized in that the total amount of interference pigments with green and yellow interference color in the coating is from 0.5 to 30% by weight, based on the weight of the coating.

Coating according to one or more of claims 1 to 9, characterized in that additional additives are additionally contained.

Coating according to one or more of claims 1 to 10, characterized in that the transparent or translucent substrate is a colorless polymeric film, a colorless fabric, a colorless polymeric plate or a colorless glass.

12. Coating according to one or more of claims 1 to 11, characterized in that it is present in the form of a polymeric film, an uncured lacquer, a cured lacquer or in the form of a dried and optionally cured coating composition on the substrate.

13. Coating according to one or more of claims 1 to 12, characterized in that it is present as a temporary coating on the substrate.

14. A method for producing a coating according to one or more of claims 1 to 13, characterized in that an interference pigment with green interference color and an interference with yellow interference color, individually or as a mixture, with a polymeric binder or a polymerizable or polymeric component, optionally Additives and possibly one

Solvent mixed and a. to a polymeric molding, or

b. is applied to a coating composition, is applied flat on a transparent or translucent substrate or represents one, and, if a coating composition is present, dried and optionally additionally cured.

15. The method according to claim 14, characterized in that the interference pigment with green interference color and the interference pigment with yellow interference color in a weight ratio of 60:40 to 85:15 in the polymeric molding or the coating composition are introduced.

16. The method according to claim 14 or 15, characterized in that the interference pigments in a proportion of 0.5 to 30 wt.%, Based on the solids content of the coating composition, are introduced into the coating composition or the polymeric molded body.

17. Use of a coating according to one or more of claims 1 to 13 for the production of greenhouses and film structures, especially for agricultural purposes or the cultivation of plants, and for skylights, roofing and roofing, skylights, gardens, aviaries and conservatories.

18. Greenhouse, film building, skylight dome, roofing or roofing, roof window, garden, aviary or conservatory, containing a coating or a shaped body according to one or more of claims 1 to 13.