BR112021014034B1 - SCREEN FOR GREENHOUSE WITH ENERGY SAVING - Google Patents

Abstract

The present application describes a greenhouse fabric comprising strips (11) of film material which are interconnected by a structure of threads, of transverse threads (12, 14, 18) and longitudinal threads (13a; 13b; 15; 19), by means of a knitting, warping or weaving process to form a continuous product. The film material comprises a highly transparent, biaxially oriented, UV and flame stable polyester film which is provided on at least one side with a coating which reduces the reflection of visible light. The greenhouse screen is particularly suitable for growing plants with high light requirements.

Description

Technical Field

[001] The present invention relates to a greenhouse screen of the type comprising a plurality of flexible strips of film material interconnected by a yarn structure by creating a mesh, warp or weaving process to form a product continuous. More specifically, the invention relates to an energy-saving greenhouse screen for growing crops with a high demand for light transmission. The screen has specific transparency properties, high UV stability and good flame retardancy. The invention additionally relates to a method of producing polyester films and greenhouse fabric, in addition to their use in greenhouses.

Fundamentals of the Invention

[002] The objective of protected cultivation in greenhouses is, among others, to modify the natural environment to increase yield, improve product quality, conserve resources, and extend production areas and planting cycles. Depending on the location of the greenhouse and the crop sown in it, the crop needs to be protected for all or part of the year to avoid damaging stress that will reduce production.

[003] A known type of greenhouse screens comprises a plurality of flexible strips of film material which extend in parallel and which, by means of a mesh, warp or weaving process and a system of threads are interconnected to form a continuous product, where the strips form a major part of the surface area of the product. Such greenhouse fabric is known, for example, from EP 0 109 951. Other examples of such fabrics are illustrated in FR 2 071 064, EP 1 342 824 and WO 2008/091192. The strips of flexible material can be made from selected film materials providing the desired properties with respect to the transmission and reflection of light and/or heat.

[004] Greenhouse screens are often used to save energy, create shade, and control temperature when growing crops in a greenhouse environment. Such screens must correspond to a number of requirements. On the one hand, a sufficient amount of light must be able to pass through the screens and reach the plants to promote photosynthetic activity during daylight hours. On the other hand, during the night and early morning, the greenhouse screen must retain the heat that rises from the ground due to convection within the greenhouse, by reflection as well as by new radiation. Without a greenhouse screen energy consumption increases in the greenhouse and setting an ideal climate becomes difficult.

[005] The greenhouse screen is especially important during the first hours of the day due to the need to quickly reach the ideal temperature for plant growth, while simultaneously providing the maximum amount of light to ensure high photosynthetic activity without using excessive amounts of energy for heating. However, during the morning period the sun is at a low angle, close to the horizon, and therefore the reflection of light from the surface of the screen is much greater than later on, when the sun is higher above the horizon. To solve this problem, the films used in the screens are advantageously provided with an anti-glare/anti-reflection coating that will allow the sun's rays to enter the greenhouse at lower angles of incidence and, in this way, improve photosynthetic activity even during the first hours of the day. .

[006] The greenhouse screen must also have good UV stability, guaranteeing at least 5 years of use in a greenhouse environment without yellowing, embrittlement, formation of significant surface cracks or without a serious decrease in transparency or mechanical properties. Additionally, fire in greenhouses represents a potential danger and can cause great economic losses if an accident occurs. Therefore, an additional important property of greenhouse fabric is its high resistance to flammability in order to prevent fires from starting and spreading too quickly.

[007] EP 3064549 describes a flame retardant biaxially oriented polyester film comprising aluminum dimethyl phosphinate/diethyl phosphinate particles as the flame retardant. The particles are incorporated into the extruded layers and have an average particle size of 2 to 3 µm. However, these particles tend to reduce transparency and increase the film's milky appearance.

[008] EP 1368405 describes various phosphorus-based flame retardants such as DOPO (CAS 35948-35-5) and derivatives thereof, for use in biaxially oriented polyester films. Additives result in a transparent film. DOPO derivatives that are polymerized onto the polyester structure are preferred for the polyester extrusion process, but on such stabilized films, the application of an anti-glare coating on one or both sides can significantly impair the flame retardancy of the entire fabric. structure.

[009] In EP 1441001, a separate flame retardant layer is applied on top of a polyester film coated on both sides to improve the flame retardancy of the laminate. Said flame retardant layer consists of a gas generating material such as magnesium hydroxide. Magnesium hydroxide is also applied as a coating to a polyester film in EP 1527110, but a layer of material with magnesium hydroxide (aluminum hydroxide) is only effective at a certain thickness and is incompatible with in-line production processes which are limited in coating thickness.

[010] Furthermore, magnesium hydroxide is not compatible with PET extrusion, as it breaks the polymer stream and significantly reduces the viscosity of PET. A stable process cannot be achieved in this way.

[011] EP 3251841 describes a multilayer, UV stabilized, biaxial oriented polyester film with a transparency of at least 93.5% and an anti-reflective/anti-glare coating on at least one side. Flame retardant additives are included in the polyester base film, but it is implied that below a certain particle concentration, there is no need to use a flame retardant. However, based on experience, when suitable anti-glare coatings such as acrylic, polyurethane or silicone coatings are applied to at least one side of such a film, the flame retardancy of the film is drastically reduced.

[012] The films described in the prior art above do not meet the optical requirements of at least 93.5% transparency and a milky effect of less than 8% and/or flame retardancy requirements. Systems containing particles tend to stain the final laminate and reduce its transparency. Furthermore, known anti-glare coatings impair the flame retardancy of the entire structure, noticeably when applied to both sides of the film. Surprisingly, flame stabilization of the base film only, but not the coating, or a low total particle concentration in the base film does not combat the negative burn characteristics of the anti-gloss coating.

Summary of the Invention

[013] The objective of the present invention has been to overcome the disadvantages of the prior art and to provide a greenhouse screen provided with an anti-glare / anti-reflection coating that will allow the sun's rays to enter the greenhouse and improve photosynthetic activity also during the first hours in the morning or when sunlight radiates at a low angle of incidence. However, the film must have a transparency of at least 93.5%, a milky effect of no more than 8%, and it must meet the requirements for burning behavior (meaning reduced flammability compared to polyester films). unstabilized and coated). It is additionally important that the film does not deteriorate or lose its flame retardant properties during its life cycle in the greenhouse.

[014] This objective is achieved by a greenhouse screen comprising strips of film material that are interconnected by a system of threads, of transverse and longitudinal threads, through the knitting, warping or weaving process to form a product continuous. At least some of said strips comprise a film material in the form of a single-layer or multi-layer base film which is provided with at least a first anti-glare/anti-reflection coating on a first surface of the base film. The film material has a transparency of at least 93.5%, measured in accordance with ASTM-D1003-61, and contains a total amount of <0.5% by weight of particles, as calculated on the total weight of the film.

[015] The at least first anti-glare/anti-reflection coating - has a dry thickness of between 60 and 130 nm; and - comprises at least one polymer based on acrylic acid and/or methacrylic acid; and - comprises at least one phosphonate alkylphosphonate and/or oligo-alkyl phosphonate flame retardant; and - contains phosphorus in an amount of between 2% by weight and 18% by weight as calculated based on the total weight of the film.

[016] The greenhouse screen, as described here, has a milky effect of less than 8% and a satisfactory burning behavior in 3 or less samples out of 5 in the burning test conducted in accordance with EN ISO 9773:1998/A1:2003 , before, in addition to after, weathering.

Brief Description of the Drawings

[017] Illustrative arrangements of greenhouse screens are described later with reference to the attached drawings.

[018] Figure 1 illustrates, on an enlarged scale, a part of the fabric with woven mesh, according to one embodiment;

[019] Figure 2 illustrates a part of a fabric with woven mesh, according to another embodiment;

[020] Figure 3 illustrates, on an enlarged scale, a part of a woven fabric.

[021] Figure 4 illustrates a part of a woven fabric, according to an additional embodiment.

Detailed Description

[022] The greenhouse fabrics described here comprise strips of film material that are interconnected by a system of threads, transverse threads and longitudinal threads, through knitting, warping or weaving process to form a continuous product, such as will be further described below. The film strips constituting the web material consist of a single-layer or multi-layer polyester film (hereinafter also referred to as base film), supplied with additives, and a coating (hereinafter also referred to as an anti-glare coating). /anti-glare) that is applied to at least one surface, preferably both surfaces of the base film.

[023] The terms "layers" and "coatings" will be used later, but it is important to note that there is a distinction between "layers" and "coating", where by a "layer" is meant an extruded or co-extruded layer of polyester film consisting primarily of polyester (e.g., a basecoat, midcoat, or topcoat), while a "coat" is applied to one or both surfaces of the basefilm (where the basefilm is optionally a polyester film). single-ply or multi-ply polyester) as a solution or dispersion and then dried in place; Coatings can be applied "inline", ie during the actual film production process, or "offline", ie after film production.

Base Film

[024] The total thickness of the film is at least 10 μm and a maximum of 40 μm. The total film thickness is preferably at least 11, 12, 13 or 14 µm and at most 35, 30, 29, 28, 27, 26, 25, 24 or 23 µm and ideally at least 14.5 µm μm and a maximum of 20 μm. If the total thickness of the film is below 10 μm, the mechanical strength of the film is no longer sufficient to withstand, without excessive tensile stress, the stresses that arise during use of the screen in a greenhouse environment. Above 40 μm, the film becomes very rigid, and when the screen is not in use and is rolled up, the resulting "screen roll" is excessively large and correspondingly creates an excessively large shadow.

[025] The film comprises a base layer B. Single layer films are composed only of that base layer B, while, in the case of a multilayer embodiment, the base film is composed of the base layer B and at least one additional layer which, according to its position on the film, is called the middle layer (where there is at least one additional layer on each of the two surfaces), or the outer layer (where the layer forms an outer layer of the film). In the case of the multilayer embodiment, the base layer thickness B is at least as great as the sum of the other layer thicknesses. It is preferred that the thickness of the basecoat B is at least 55% of the total film thickness and ideally at least 63% of the total film thickness.

[026] The thickness of the other layers, preferably the outer layers, is at least 0.5 μm, preferably at least 0.6 μm and, ideally, at least 0.7 μm. The thickness of the outer layers is less than 3 µm and preferably less than 2.5 µm and ideally less than 1.5 µm. Below 0.5 μm, process stability is reduced, and may affect the uniformity of outer layer thickness. Achieving very good processing stability starts at 0.7 µm. Such additional layers are also referred to as coextrusion layers.

[027] If the outer layers are too thick, the savings are reduced since, in order to ensure that the properties (in particular, UV resistance) remain optimal, regeneration elements must be added only to the base layer B, and if the basecoat thickness is too low compared to the total film thickness, then the percentage of regeneration elements that must be added to this layer in order to complete the regeneration cycle is then excessive. It can also, due to the composition of the base layer, have an adverse effect on properties such as UV resistance and transparency, as the outer layers often contain particles in order to improve gliding properties (enhancement of windability). Such particles can result in loss of transparency through backscattering, and if the proportion of such particles becomes excessive in the outer layers, it becomes increasingly difficult to achieve the high transparency properties of the film.

Base film UV stabilization

[028] A film to be used in a greenhouse must have a low light transmission in the wavelength range from below 370 nm to 300 nm. It is preferable that the transmission is less than 40%, preferably less than 30%, and ideally less than 15% at each wavelength in the mentioned range. However, the transparency to light in the wavelength range 389 nm to 400 nm should be greater than 20%, preferably greater than 30%, and ideally greater than 40% as this wavelength range is significantly efficient for photosynthesis, and excessive filtering in this wavelength range would adversely affect plant growth.

[029] Low UV light permeability is achieved by adding an organic UV stabilizer. The low UV permeability also protects the optionally present flame retardant against rapid destruction and severe yellowing. The organic UV stabilizer, as used in the film described here, is selected from the group consisting of triazines, benzotriazoles or benzoxazinones. Particular preference is given here to triazines, since, among other things, they show good thermal stability at conventional PET processing temperatures of 275 to 310°C, and exhibit little loss due to film gas evolution. 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-(hexyl)oxyphenol (TINUVIN® 1577) is particularly suitable. A greater preference is given here to 2-(240-hydroxyphenyl)-4,6-bis(4-phenylphenyl) triazines as sold by way of example by BASF under the trademark TINUVIN 1600™. If these compounds are used, the preferred low transparencies in light below 370 nm can be achieved even with relatively low concentrations of the stabilizer, with simultaneous achievement of relatively high transparency at wavelengths above 390 nm.

[030] The base film, that is, the base layer B, or in the case of a multilayer film, at least one outer layer, preferably both outer layers, therefore, comprises at least one organic UV stabilizer. The amounts of UV stabilizers added to the outer layers or monolayer film are from 0.3 to 3%, preferably from 0.75 to 2.8% by weight, based on the weight of the respective layer. The outer layers ideally comprise from 1.2 to 2.5% by weight of the UV stabilizer. In a multilayer film, it is preferred that a UV stabilizer is also present in the base layer along with the outer layers. The content of the UV stabilizer in % by weight in said base layer is in that case preferably lower than in the outer layers. The content mentioned above in the outer layers refers to triazine derivatives. If a UV stabilizer from the benzotriazole or benzoxazinones group is used to some extent, or wholly, in place of a triazine derivative, the substituted ratio for the triazine component should be replaced by 1.5 times the amount of a benzotriazole component or a benzoxazinone component. The film is thus protected against embrittlement and yellowing, and the plants as well as the equipment in the greenhouse are thus also protected against UV light.

Additives to improve fabric windability.

[031] The base layer, in addition to the outer layers, may comprise particles to improve windability. Such inorganic or organic particles are, by way of example, calcium carbonate, apatite, silica, alumina, silicon dioxides, aluminum oxide, cross-linked polystyrene, cross-linked polymethyl methacrylate (PMMA), zeolites and other silicates, such as silicate aluminium, polydimethyl siloxane (PDMS) or compatible white pigments such as TiO2 or BaSO4.

[032] However, many whitening polymers, in addition to certain polyesters, such as, for example, polypropylene, cycloolefin copolymers (COCs), polyethylene, non-crosslinked polystyrene, etc., are incompatible with the main constituent of the film, and should preferably be present in amounts of less than 0.1% by weight (based on the weight of the film) and ideally completely absent (i.e. 0% by weight), as these particles seriously reduce transparency and can have a negative effect. serious adverse effect on film burning behavior. Furthermore, they have a tendency to cause severe yellowing upon UV exposure, and would therefore require considerable additional amounts of UV stabilizer, thus significantly harming the economy.

[033] Due to the negative effect of whitening particles, frosted particles such as silicon dioxide particles are preferably added to the outer layers in order to improve the windability of the film. The advantage of using silicon dioxide particles is that they have a very small haze reduction effect. The proportion of these or other particles in any layer must not exceed 3% by weight, and preferably less than 1% by weight, and ideally less than 0.2% by weight in each layer, based, in each case, on the total weight of the relevant layer. In the case of a multilayer embodiment, it is preferable that these particles are only added to one or both of the outer layers and that only a small proportion pass into the base layer through the addition of regenerating elements. The reduction in transparency, due to the presence of particles necessary for winding, is therefore minimal. In a preferred embodiment with good windability, the at least one outer layer comprises at least 0.07% by weight matte particles.

[034] Additional particles such as whitening particles or matting agents can impair the flame retardant properties of the biaxially oriented film in general. Depending on the compatibility of the particle with the polymeric matrix, cavities can form around the particles during film stretching. The less compatible the particles are with the polymeric matrix, the more cavities will be formed. Air can migrate into such cavities and, in the event of a fire, supply oxygen to the fire and make it worse. For this reason, it is advantageous to minimize the use of added particles to films where burning properties are important. Exceptions are flame retardant particles such as those described in the prior art. That is why the proportion of particles such as whitening particles (ZnO, TiO2, BaSO4), or matting agents (PMMA, SiO2, polydimethyl siloxane (PDMSQ) is preferably limited to a maximum of 0.5% in weight (when calculated based on total film weight).

Anti-Glare/Anti-Reflection Coatings

[035] The transparency of the film is achieved if raw materials, additives and/or particles, as described here, are used in the proportions described. However, increased transparency is primarily achieved through anti-glare/anti-reflective coatings present on one or both outer sides of the film.

[036] The film material of the invention has, at least on one surface, a coating of a material that has a lower refractive index than the base polyester film (that is, the singular base layer B or the polyester film of multiple layers). The refractive index of the coating is below 1.64, preferably below 1.60, and ideally below 1.58 at a wavelength of 589 nm in the machine direction of the film.

[037] The coating according to the invention contains at least two components, specifically at least one acrylic component and a component that serves to stabilize the flame. The components are described below.

[038] Suitable acrylic components are described, for example, in EP-A-0144948. Acrylate-based coatings are preferred as they do not show a tendency for coating components to bleed or delaminate parts of the coating in the kiln. Particularly suitable are polyacrylates. To achieve good optical properties, silicones, polyurethanes or polyvinyl acetates can also be used as an anti-glare/anti-reflective coating. However, it is illustrated that the burning characteristics of acrylates were the best and thus acrylates were chosen as the coating material to further improve the flame retardancy of the film.

[039] The acrylic component according to the invention consists essentially of at least 50% by weight of one or more polymerized acrylic and/or methacrylic monomers.

[040] The acrylic component preferably consists of an ester of acrylic or methacrylic acid, in particular, alkyl ester, the alkyl group which contains up to ten carbon atoms, for example, methyl, ethyl, n-propyl, isopropyl, n -butyl, isobutyl, tertiary butyl, hexyl, 2-ethylhexyl, heptyl and n-octyl. Most preferred are adhesion-promoting copolymers of an alkyl acrylate, for example ethyl acrylate or butyl acrylate, together with an alkyl methacrylate, for example methyl methacrylate, in particular in equal molar proportions and in a total amount of 70 to 95 % by weight used. The acrylate comonomer of such acrylic/methacrylic combinations is preferably present at a level of 15 to 65 mol%, and the methacrylate comonomer is preferably present at a level generally greater by 5 to 20 mol% than the proportion of acrylate comonomer . The methacrylate is preferably included in a proportion of 35 to 85 mol% in the acrylic/methacrylic combination.

[041] In an additional embodiment, the acrylic component may comprise additional comonomers in a proportion of 0 to 15% by weight, and are suitable for forming an intermolecular crosslink under the action of elevated temperature.

[042] Suitable comonomers capable of forming crosslinks are, for example, N-methylolacrylamide, N-methylolmethacrylamide and the corresponding ethers; epoxy materials, such as, for example, glycidyl acrylate, glycidyl methacrylate and alkyl glycidyl ether; monomers containing the carboxyl group, such as, for example, crotonic acid, itaconic acid or acrylic acid; anhydrides, for example maleic anhydride or itaconic anhydride; hydroxyl-containing monomers, such as, for example, hydroxyethyl alkyl alcohol or hydroxypropyl acrylate or methacrylate; amides, such as, for example, acrylamide, methacrylamide or maleic acid amide and isocyanates, such as, for example, vinyl isocyanate or allyl isocyanate.

[043] Of the comonomers mentioned above, preference is given to N-methylolacrylamide and N-methylolmethacrylamide, basically because the streams of copolymers containing one of these monomers can, under the action of high temperatures, condense with each other and, in this way, form the desired intermolecular crosslinks. For copolymers containing the other functional monomers, it is necessary to prepare mixtures of at least two copolymers with different functional comonomer in order to achieve the desired cross-linking, for example, mixing an acrylic/crotonic acid copolymer with an acrylic copolymer containing, as functional groups, isocyanate, epoxide or N-methylol groups capable of reacting with acidic functional groups.

[044] Other specific combinations of such mixed acrylic copolymers include copolymers with monomers containing epoxy groups as functional groups, in combination with copolymers with monomers containing as functional groups, amino, anhydric acid, carboxyl, hydroxyl or N-methylol groups; copolymers with monomers containing, as functional groups, N-methylol or N-methylol ether groups, in combination with copolymers with monomers containing, as functional groups, carboxylic, hydroxyl or amino groups; copolymers having monomers containing isocyanate groups as functional groups in association with copolymers having monomers containing carboxylic or hydroxyl groups as functional groups, etc. Preferably, the functional monomers contained in the mixed copolymer systems are present in approximately equimolar amounts.

[045] Acrylic copolymers can also be interpolymerized with up to 49% by weight of one or more halogen-free monomers, non-acrylic, monoethylically unsaturated. Suitable comonomers are, for example, dialkyl maleates, such as, for example, dioctyl maleate, diisooctyl maleate and dibutyl maleate, vinyl ester of a versatic acid, vinyl acetate, styrene, acrylonitrile and the like.

[046] The preferred crosslinkable mixed copolymer compositions for the purposes of this invention are mixtures in a ratio of about 50:50 (% by weight) of an ethyl acrylate/methyl methacrylate/crotonic acid copolymer with an ethyl acrylate/ methyl methacrylate/glycidyl acrylate copolymer; mixtures of an ethyl acrylate/methyl methacrylate/methacrylamide copolymer with an ethyl acrylate/methyl methacrylate/N-methylol acrylamide copolymer; or compositions based on ethyl acrylate/methyl methacrylate/N-methylol acrylamide copolymers, for example, copolymers containing from 50 to 99% by weight of acrylic and/or methacrylic monomers, from 0 to 49% by weight of unsaturated monomer monoethylically and from 1 to 15% by weight of N-methylacrylamide. Particular preference is given to the use of copolymers which contain 70 to 95% by weight of acrylic and/or methacrylic monomers, 0 to 25% by weight of monoethyl unsaturated monomer and from 5 to 10% by weight of N-methylolacrylamide.

[047] Additionally, in addition to the acrylate component, an additional crosslinking agent, such as: a melamine or urea-formaldehyde condensation product can be used. However, they must be contained in the coating in a concentration of not more than 3% by weight (in terms of dry coating composition), especially since additional crosslinkers, having a high nitrogen content (e.g. melamine) after regeneration, can cause the PET film to yellow.

[048] In a preferred embodiment, the dry acrylate coating contains less than 10% by weight, more preferably less than 5% by weight, and ideally less than 1% by weight of repeating units containing an aromatic structural element. Above 10% by weight of repeating units having an aromatic structural element, there is a marked deterioration in the weatherability of the coating.

Coating Flame Stabilization

[049] As discussed above, the application of known anti-glare coatings to the outer surfaces of a polyester film appears to impair the flame retardancy of the entire film structure. One would expect that an obvious solution to this problem would, in this case, be to add flame retardant particles as well to the base film to reduce the flammability of the entire laminate. However, it turns out that a flame stabilized single or multi-layer film coated with known anti-glare/anti-reflective coatings will not compensate for the negative burn behavior of the coatings.

[050] Furthermore, while an unworn specimen, where only the base film but not the anti-glare/anti-reflective coatings were flame stabilized, initially passed the flame test, the same specimen surprisingly fails the same test after weathering. The negative effect of anti-glare/anti-reflective coatings on flammability appears to strengthen after exposure to light (UV) and water.

[051] Additionally, as discussed above, the addition of flame retardant additives such as particles to polyester films tends to cause a milky effect and reduce light transmission and is therefore not an adequate solution to solve the problem of flammability.

[052] Surprisingly, the addition of a flame retardant, as described here, to the anti-glare/anti-reflective coatings alone will stabilize the entire laminate structure, so additional flame stabilization of the film is not required. Coating components as described herein are suitable for anti-glare/anti-glare application, and can be applied to at least one surface, but preferably are applied to both surfaces of the base film. Additionally, coatings that include at least one of the flame retardants, as described below, are relatively thin compared to the base film, but detract from the flammability of the entire laminate compared to an uncoated base film. Enhanced flame retardancy is true for both unworn and weathered film.

[053] It should be noted that, in principle, flame retardant can also be added to the base film, while anti-glare/anti-reflective coatings are also stabilized by a flame retardant. However, this approach does not improve the laminate's flame retardancy in a way that offsets the economics.

[054] Film specimens manufactured in accordance with the description presented here, where at least one, preferably both surfaces of the base film, were coated with an anti-glare / anti-reflective coating containing at least one flame retardant as described below, passed the test of flame before and after the weather. Such a specimen burns in less than 3 out of 5 specimens at the 125 mm mark after the first ignition (see test methods below). The base film itself may or may not contain a flame retardant.

[055] The anti-glare/anti-reflective coating contains one or more flame retardants that will improve the burn test of any polyester base film.

[056] A flame retardant according to the invention advantageously has the following structures (I) and/or (II).

[057] Where, R1, R2, R3 and R4, independently of each other, may represent the following radical groups: H; linear alkyl with -(CH2)n-CH3 (n = 0-7); isopropyl; that or tertbutyl; linear alkyl alcohols with —(CH2)n-CH2-OH (n = 0.3); isopropyl alcohol or linear alkyl acids/alkyl acid esters with structure -(CH2)n-COOR5 (with R5 = H; -(CH2)n-CH3 (n = 0-3)); where at least one residual group (R1-R4) is not H.

[058] Z represents a residue of the following H groups; linear alkyl with -(CH2)n-CH3 (n = 0-10); isopropyl; iso or tert-butyl, linear alkyl alcohols with -(CH2)-CH2-OH (n = 0-5); isopropyl alcohols or linear alkyl acids/alkyl acid esters with structure -(CH2)n-COOR5 (with R5 = H; -(CH2)n-CH3 (n = 0-3)).

[059] Especially preferred flame retardants comprise compounds based on organophosphoric compounds. However, substituted phenyl phosphate compounds such as triphenylphosphate, bisphenol A bis(diphenylphosphate) (CAS 5945-33-5) or oligomeric hexaphenoxycyclotriphosphazene compounds (CAS 28212-48-8) may cause problems during manufacturing as the phenol can separate during the PET extrusion process and therefore not be compatible.

[060] Therefore, compounds of oligo and/or alkyl esters of phosphonic acid or phosphoric acid are preferred. These components can dissolve into the polymeric matrix of the anti-glare/anti-reflection coating and, unlike embedded particles, will not cause reflection or refraction of light. The refractive index of the resulting coating is, after addition of such flame retardants, in the preferred range. Additionally, they are compatible with the production process. The nD refractive index of the alkyl phosphonate is less than 1500, preferably less than 1480, and especially preferably less than 1470. If the refractive index of the alkyl phosphonate used is too high, the anti-reflective effect of the entire coating will be reduced and the transparency of the film will become very low.

[061] Preferred compounds are alkyl phosphonates and/or oligoalkyl phosphonates (preferably with a molecular weight < 1000 g/mol). However, polyalkylphosphonate is ineffective as a flame retardant as it does not sufficiently migrate into the polymeric matrix of the anti-gloss/anti-reflective coating during process conditions. As such, it does not adhere properly enough to the polymeric matrix and can be removed from the film surface.

[062] A preferred alkyl phosphonate is Rucocoat FR2200 from Rudolf Chemie.

[063] The proportion of phosphorus in the anti-glare/anti-reflective coating is between 2% by weight and 18% by weight, preferably between 3% by weight and 17% by weight, and more preferably between 4% by weight and 16% by weight as calculated based on the total weight of each coating. If the ratio of flame retardant to anti-glare/anti-glare component is below the limits mentioned above, the flame retardancy of the entire laminate becomes very slow. If the ratio is too high, the flame retardant does not dissolve well enough into the polymeric matrix of the anti-glare/anti-reflective coating and may bleed during production and/or during application. This can additionally cause friction of the surface coating.

[064] It should be noted that compounds such as ammonium phosphate, aluminum hydroxide or magnesium hydroxide can also improve the flame retardant characteristics of the laminated structure, but tend to have a negative effect on the optical properties of the film and , therefore preferably not used.

[065] Depending on the particle size of the added compounds, the milky effect may increase and the transparency may decrease. Aluminum and magnesium hydroxide, which are described in EP 1441001, act by generating water and, therefore, need a certain concentration to become efficient. Films that include high amounts of said particles also tend to be very milky and have low transparency to light. Additionally, a direct extrusion with polyester is difficult since the hydrolytic degradation of the polymer is promoted by such compounds. If the film is produced with regeneration elements, particles that are only present in the coatings will also end up in the extrusion with the polyester. The described hydrolytic degradation reduces the viscosity of the polyester which will be difficult to produce. In a production process regeneration elements are also being used and one or both film surfaces are coated in-line with the coating according to the invention in order to be able to produce films cost-effectively.

Additional Coating Components

[066] Additionally, up to 10% by weight of additives can be added to the coating. These include surfactants (ionic, nonionic and amphoteric), protective colloids, UV stabilizers, antifoams and biocides. Particularly suitable as surfactants are SDS (sodium dodecyl sulfate), polyethylene glycol based surfactants with a C8-C20 acyl end (branched or unbranched) and a polar head with nR-(CH2-O) units (where n = 8 -100 and R = -OH, -CH3 or -CH2-CH3) such as Lutensol AT50 or Tergitol.

[067] In a particularly preferred embodiment, the coating contains at least 1% by weight, based on dry weight, of a UV stabilizer, particular preference being given to Tinuvin 479 or Tinuvin 5333-DW (BASF, Ludwigshafen, Germany). Less preferred are HALS (impaired amine light stabilizers) as during regeneration (recycling of production film waste) they result in a distinct yellowing of the material and thus a reduction in transparency.

Coating Thickness

[068] The dry thickness of the anti-glare/anti-reflection coatings is in each case at least 60 nm, preferably at least 70 nm and in particular at least 78 nm, and at most 130 nm, preferably at most 115 nm nm and ideally a maximum of 110 nm. An optimal increase in transparency in the desired wavelength range is thus achieved. Advantageously, the thickness of the coating is greater than 87 nm, and particularly greater than 95 nm. In that preferred embodiment, the coating thickness is preferably less than 115 nm and ideally less than 110 nm.

[069] Within this narrow thickness range, not only is the increase in transparency close to ideal, but at the same time, the UV reflection and blue region of light are increased compared to the rest of the visible spectrum. On the one hand, this saves UV stabilizer, but in particular it also results in a shift of the blue/red ratio towards red. This achieves improved plant growth, increases flowering and fruiting, and reduces the incidence of stunted plant growth due to inadequate lighting.

[070] The surface of the film, opposite the first anti-glare / anti-reflection coating described above, is also advantageously provided with an anti-reflection modification. In a preferred embodiment, this is likewise an anti-reflective coating applied to the second surface of the film, opposite the first surface of the film. This second coating corresponds to the description of the coating applied to the first surface and, in a preferred embodiment, is the same as the first coating with respect to material and coating thickness.

[071] The coatings are preferably applied to the film in line before transverse stretching by known processes (eg reverse gravure roller or Meyer bar), preferably from aqueous dispersion.

[072] To prepare the anti-reflective coating, all components can be presented dry or pure (that is, in an undissolved or undispersed state) and then dispersed (or dissolved) in an aqueous medium, or each individually pre-dispersed or dissolved in an aqueous medium and subsequently loaded, mixed and diluted with water if necessary. If the components are each dispersed individually, or used in the solution, it has proven advantageous if the resulting mixture (the anti-reflective coating) is homogenized with a mixer for at least 10 minutes before use. If the components are used in their pure form (ie in the undissolved or undispersed state), it has proven to be particularly advantageous if, during dispersion, high shear forces are applied by using suitable homogenization methods.

[073] Depending on the type of application/method of application, i.e. in line (eg reverse engraving, Mayerbar, etc.) or offline (eg forward engraving)), the non-aqueous fraction of the dispersion is preferably in the range of 5 to 35% by weight, and more preferably in the range of 10 to 30% by weight.

[074] Transparency values of > 95.3%, which are particularly preferred according to the invention, can be achieved with an anti-reflective coating applied to both surfaces of the film.

Production process

[075] The polyester polymers of the individual layers are produced by the polycondensation of dicarboxylic acids and diol or esters of dicarboxylic acids, preferably dimethyl esters, and diol. Useful polyesters preferably have a standard viscosity (SV) value in the range of 500 to 1300, where individual values are less important, but the average SV value of the raw materials used should be greater than 700 and is preferably greater than 750.

[076] The particles, and also the UV stabilizers, can be added before the polyester production is completed. For this purpose, the particles are dispersed in the diol, optionally ground, decanted and/or filtered, and added to the reactor, in the (trans)esterification step or in the polycondensation step. In a preferred procedure, a polyester masterbatch containing concentrated particles, or containing additives, can be produced by using a twin-screw extruder and diluted with particulate-free polyester during film extrusion. It has been found here that masterbatches comprising less than 30% polyester by weight are advantageously avoided. In particular, masterbatches comprising SiO2 particles should comprise no more than 20% SiO2 by weight (due to the risk of gelling). Another possibility is to add particles and additives directly during film extrusion in a twin pin extruder.

[077] When single-pin extruders are used, it has been found that polyesters are advantageously pre-dried. When a twin pin extruder with a degassing zone is used, the drying step can be omitted.

[078] The polyester or polyester blend of the layer, or of the individual layers in the case of multilayer films, is first compressed and liquefied in the extruders. The melts are then formed into flat cast films in a mono- or co-extrusion die, forced through a slotted die and withdrawn into a quench cylinder and one or more withdrawal cylinders, where the material cools and solidifies.

[079] The film of the invention is biaxial oriented, that is, stretched biaxial. Biaxial film orientation is most often performed sequentially. The orientation here is preferably carried out first in the longitudinal direction (ie in the machine direction = MD) and then in the transverse direction (TD), that is perpendicular to the machine direction. Orientation in the longitudinal direction can be carried out with the aid of two cylinders that rotate at different speeds corresponding to the desired stretching ratio. The transverse orientation process usually uses a suitable tension structure.

[080] The temperature at which stretching is performed can vary within a relatively wide range, and depends on the desired properties of the film. Stretching in the longitudinal direction is usually carried out in the temperature range 80 to 130 C (heating temperature 80 to 130 C) and stretching in the transverse direction is generally carried out in the temperature range 90 C (start of stretching) to 140 C (end of stretching). The longitudinal stretch ratio is in the range of 2.5:1 to 4.5:1, preferably 2.8:1 to 3.4:1. A stretch ratio above 4.5 results in significantly reduced manufacturability (breakage). The transverse stretch ratio is generally in the range of 2.5:1 to 5.0:1, preferably 3.2:1 to 4:1. A transverse stretch ratio greater than 4.8 results in significantly reduced manufacturability (breakage) and should therefore preferably be avoided. To obtain the desired film properties it has been found that the stretching temperature (in MD and TD) is advantageously below 125°C and preferably below 118°C.

[081] Before transverse stretching, one or both surfaces of the film can be coated in line by processes known per se. The in-line coating can preferably serve to apply a coating in order to increase transparency (anti-glare). During the thermal setting that follows, the film is held at a temperature of 150 to 250 C for a period of about 0.1 to 10 seconds under tension and, in order to achieve the preferred shrinkage values and elongation values, relaxed in the transverse direction by at least 1%, preferably at least 3% and particularly preferably at least 4%. This relaxation preferably occurs in the temperature range of 150 to 190°C.

[082] In order to reduce the arc of transparency, the temperature in the first laying zone is preferably less than 220°C, and particularly, preferably, less than 190°C. For the same reason, additionally, at least 1%, preferably at least At least 2% of the total transverse stretching ratio should preferably refer to the first settlement zone, where no further stretching normally occurs. The film is then rolled up in a conventional manner.

[083] An especially economical production method of polyester film uses recovered/regenerated material in a portion of up to 70% by weight with respect to the total weight of the film. The recovered material can be added to the polymer extrusion without adversely affecting the physical properties of the film.

[084] In one embodiment, the film is coated by off-line technology in an additional process step that occurs after film production. In this case, an advance gravure cylinder can be used to apply the anti-glare/anti-reflection coating to a surface of the film. The upper limits (ie maximum wet application) are determined by process conditions and the viscosity of the coating dispersion and find their upper limit in the processability of the coating dispersion.

Application

[085] Films as described herein are highly transparent, UV and flame stabilized and on at least one side provided with a coating that reduces reflection of visible light. With these characteristics, they are excellently suited as high-transparency convection shields, in particular for the production of energy-saving laminated materials in greenhouses. The film material as described here is, for this purpose, cut into narrow strips from which, in combination with the polyester yarn (which must also be UV resistant), a woven fabric web, as described below, is then produced and suspended in an oven. Strips made from film as described here can be combined with strips made from other films (in particular films with a light scattering effect). Alternatively, the film itself (without the fabric) can be installed in a greenhouse.

[086] Figures 1 to 14 depict greenhouse fabrics 10 which, according to the invention, comprise a plurality of narrow film strips 11 held together by a structure of threads 12, 13a, 13b; 14, 15; 18, 19. The strips are preferably arranged close together, edge to edge, so that they form a substantially continuous surface. In all embodiments, the distance between the strips has been exaggerated for the sake of clarity to make the wire system visible in the figures. The web has a longitudinal direction y, and a transverse direction x, where the strips 11 extend in the longitudinal direction y. In some embodiments, strips 11' may also extend in the transverse x direction. A typical width of the strips is between 2 mm and 10 mm.

[087] In Figure 1, the film strips are interconnected by a warping procedure, as described in EP 0 109 951. The yarn working structure comprises warp yarns 12 forming loops, or stitches, and extending basically in the direction longitudinal y. The warp threads 12 are connected to each other by weft threads 13a and 13b extending across the film strips.

[088] Figure 1 illustrates an example of an interwoven pattern for a fabric manufactured through a warping process in which four guide bars are used, one for the strips 11, two for the connecting threads 13a and 13b, extending from transverse shape in the direction of the film strips, and one for the longitudinal warp threads 12.

[089] The space between film strips 11 has been heavily exaggerated in order to make the interlacing pattern clearer. Typically, the film strips 11 are located close together, end to end. Longitudinal warp threads 12 are arranged on one side of the fabric, on the underside, while transverse connecting threads 13a and 13b are located on both sides of the fabric, the top and bottom side. The term "transverse" in this respect is not restricted to a direction perpendicular to the longitudinal direction, but means that connecting threads 13a and 13b extend across film strips 11 as illustrated in the drawings. The connection between the longitudinal weft threads and the transverse threads is carried out on the underside of the fabric. The film strips can thus be arranged close together, edge to edge, without being constrained by the longitudinal weft threads.

[090] The longitudinal weft threads 12 in Figure 1 extend continuously in an uninterrupted fashion along opposite edges of adjacent film strips, in a series of knit stitches, in an open pillar-type stitch formation.

[091] The transverse threads 13a and 13b pass above and below the film strips at the same location, that is, opposite each other to securely trap the film strips. Each stitch knitted in the longitudinal weft threads 12 has two transverse threads 13a and 13b engaging therewith.

[092] Figure 2 illustrates another example of a pattern of interlacing a fabric, similar to that illustrated in Figure 1. The difference is that the transverse threads 13a and 13b pass over one and two strips of film 11 in an alternating manner.

[093] Figure 3 illustrates a woven fabric in which the film strips 11 are interconnected by warp threads 14 that extend in the y longitudinal direction, and interwoven with the weft threads 15 that extend across the film strips basically in the transverse direction x.

[094] Figure 4 illustrates another embodiment of a woven fabric as described in US 5,288,545 comprising film strips 11 (warp strips) that extend in the y-longitudinal direction, and film strips 11' (weft strips) that extend in the transverse x direction. The weft strips 11' in the transverse direction can, as illustrated in figure 4, always be on the same side as the warp strips 11 in the longitudinal direction, or they can alternate on the upper and lower side of the longitudinal warp strips 11. The warp strips and weft 11 and 11' are held together by a yarn work frame comprising longitudinal and transverse yarns 18 and 19. The fabric may comprise open areas that are clear of the strips to reduce heat build-up under the fabric.

Description of Test Methods

[095] The following test methods were used to characterize the raw materials and films: UV/Vis Spectra and Wavelength Transmission x

[096] The transmission of films at certain wavelengths was tested on a dual-beam LAMBDA® 12 or 35 UV/Vis spectrometer from PerkinElmer USA. A film sample approximately 3 x 5 cm long is placed on a flat sample holder perpendicular to the measurement beam in the beam path. The measurement beam passes through a 50 mm integrating sphere to the detector, where the intensity of film transparency at a desired wavelength is determined. Air is used as background.

Transparency and Milky Effect

[097] The transparency and milky effect of the film were measured according to ASTM-D1003-61 by means of a Hazergard XL 21 1 nephelometer from BYK-Gardner (Wesel, Germany).

UV stability

[098] The UV stability was determined as described on page 8 in DE 69731750 (DE of WO9806575), the weathering time being 2000 hours instead of 1000 hours, and the ultimate tensile strength value (UTS) was mentioned in % of initial value.

SV value (standard viscosity)

[099] The standard viscosity (SV) in dilute solution was measured by a method based on DIN 53728 Part 3 in an Ubbelohde viscometer at (25 +/0 0.05) C. Dichloroacetic acid (DCA) was used as solvent. The concentration of dissolved polymer was 1 g of polymer/100 ml of pure solvent. Dissolving the polymer required 1 hour at 60°C. After that time, if the samples were not fully dissolved until two dissolution attempts had been made, in each case for 40 minutes at 80°C, the solutions were then centrifuged for 1 hour at a rotation speed of 4100 rpm. The dimensionless SV value is determined as follows from the relative viscosity (^rel = ^/^s):

[100] The proportion of particles in the film or polymer was determined by incineration and corrected by appropriately increasing the input weight, that is:

Determination of Refractive Index as a Function of Wavelength

[101] The refractive index of a film substrate and an applied coating was determined as a function of wavelength by spectroscopic ellipsometry. ALREADY. Woollam et al., Overview of variableangle spectroscopic ellipsometry (VASE): I. Basic theory and typical applications, Proc. SPIE Vol. CR72, p. 3-28, Optical Metrology, Ghanim A. Al-Jumaily; Ed.

[102] The uncoated base film or modified co-extruded side is analyzed first. Backside flare is suppressed by using an abrasive paper with the smallest possible particle diameter (eg P1000) to roughen the opposite side of the film. The film is then subjected to measurement by a spectroscopic ellipsometer, in this case an M-2000 from J.A. Woollam Co., Inc., equipped with a roll compensator. The machine direction (MD) of the sample is parallel to the light beam. The wavelength used for measurement is in the range of 370 to 1000 nm; the measurement angles are 65, 70 and 75 .

[103] A model is then used to simulate the T and Δ ellipsometric data. The Cauchyn model n(X) = A + B/X2 + C/X4 (wavelength X in μm) is suitable for this purpose in the present case.

[104] Parameters A, B, and C vary such that the data provide the best possible fit with T and Δ in the measured spectrum. The validity of the model can be verified by using the mean square error value (MSE), which compares the model with measured data (T(À) and Δ(k)) and should be as small as possible. n= number of wavelengths, m = number of fitting parameters N = cos(2T), C = sin(2X) cos(Δ), S = sin(2T) sin(Δ) [1]

[105] The Cauchy A, B and C parameters obtained for the base film allow the calculation of the refractive index x as a function of the wavelength, with validity in the measurement range from 370 to 1000 nm.

[106] The coating, or a modified co-extruded layer, can be analyzed analogously. The film base parameters are now known, and must be kept constant in the modeling procedure. Determining the coating of the coextruded layer also requires increasing the roughness of the reverse side of the film, as described above. The Cauchy model can likewise be used here to describe refractive index as a function of wavelength. However, the respective layer is now present on the known substrate, and this is taken into account in the relevant evaluation software (CompleteEASE or WVase). The layer thickness influences the obtained spectrum, and must be taken into account in the modeling procedure.

Refractive Index nD of a Liquid Material

[107] To determine the refractive index of a liquid, an Abbe refractometer is used.

[108] The instrument must have a temperature of 23°C. The liquid is applied to the well-cleaned prism using a pipette. The entire prism area is covered by the liquid. The second prism is then bent down and pressed down firmly. The upper knurled screw is adjusted while looking through the refractometer eyepiece until a precise transition from light to dark can be observed. The precise transition line is then shifted by the second knurled screw until it is in the attenuation area of the eyepiece. You can now read the index of refraction from the indicator scale.

Burn Test

[109] The burn test is conducted according to the test method described in Plastics - Determination of burning behavior of thin flexible vertical specimens in contact with a small-flame ignition source - Amendment 1 Speciments (EN ISO 9773:1998/Amd 1:2003). The samples are conditioned for one day at (23 +/- 2) C and a relative humidity of (50 +/-5)%. With regard to this invention, it is of particular concern whether the specimen burns at a 125mm mark or not. The test result also contains information on whether the specimen reached the mark after the first or second ignition, or if it did not at all. For each film the test is conducted on five specimens.

Examples

[110] The Examples and Comparative Examples as described herein utilize the raw materials: PET1 = polyethylene terephthalate manufactured from ethylene glycol and terephthalic acid with a SV of 820 and a DEG content of 0.9% by weight (diethylene content glycol as a monomer). PET2 = polyethylene terephthalate with a SV value of 730, containing (6-oxodibenzo [c,e] — [1,2]oxaphosphorin-6-ylmethyl)succinic acid bis(2-hydroxyethyl)ester (Eg the compound is a flame stabilizer which is typically added to the extrusion in the form of a masterbatch, as per EP 1368405) as a comonomer, where the resulting phosphorus content in the polymer is 18,000 ppm. PET3 = polyethylene terephthalate of ethylene glycol and dimethyl terephthalate with a SV value of 820 and a DEG content of 0.9% by weight (content of diethylene glycol as monomer) and 1.5% by weight of Sylobloc 46 with a d50 of 2 .5 µm. Manufactured by a Purified Terephthalic Acid (PTA) process. Potassium titanyl oxalate catalyst with 18 ppm of titanium. Transesterification catalyst zinc acetate. PET4 = polyethylene terephthalate with a SV value of 700, comprising 20% by weight of TINUVIN® 1577. The composition of the UV stabilizer is as follows: 2-(4,6-diphenyl-1,3,5-triazine-2- yl)-5-(hexyl)oxyphenol (TINUVIN® 1577 from BASF, Ludwigshafen, Germany), TINUVIN® 1577 has a melting point of 149 C and is thermally stable at 330 C. Example 1 Coating layers (A) and ( C) Polyester film: Mixture of 10% PET4, 7.2% PET3 and 82.8% PET1 Base layer (B) Polyester film: Mixture of 90% PET1 and 10% PET4 Coating ( applied to the coextruded cover layers (A) and (C) of the polyester film):

[111] As a flame retardant 13% by weight of alkylphosphonate (RUCO-COAT FR2200, Rudolf Chemie) is dissolved in water. The pH is adjusted by adding ammonia solution to 7.5 to 8.0. While mixing 10% by weight of an aqueous dispersion of acrylate (EP-A-0144948, Ex. 1 with SDS surfactant and Tergitol 15-S-40) was added.

[112] The listed raw materials were cast in each case in a layer extruder at 292°C and extruded through a three-layer partition die into a stripping cylinder at 50°C. The resulting amorphous prefilm was then first stretched lengthwise. The elongated film was corona treated and then coated by the reverse gravure coating with the described coating formulation on a first surface of the film. With a second reverse engraving cylinder, the second surface of the film can be treated. The film is thereafter dried at 100°C and stretched in transverse direction. After that, thermal settling takes place and the film is rolled up. The final film thickness is 19 µm (cover layers A and C each having a thickness of 1 µm).

[113] The conditions of the individual steps can be seen in Table 1. Table 1: PET production process parameters for Example 1

[114] The thickness of the coating, which is applied to one or two surfaces of the film, is 80 nm each. The film properties are described in Table 3.

Examples 2 to 4 and Comparative Examples 1 to 10

[115] The production process of other examples and comparative examples are the same as those described in Example 1. The recipes for base film, coextruded layers and coatings are listed in Table 2.

Comparative Example 4

[116] The coating dispersion of Comparative Example 4 consists of 7.5% by weight of Neorez R600 polyurethane from DSM and 7.5% by weight of oxazoline crosslinker Epocros WS-700 from Sumitomo.

Comparative Example 5

[117] The coating dispersion of Comparative Example 5 consists of a silicone coating described in Example 1 of EP-A-0769540.

Comparative Examples 6 and 7

[118] The coating dispersions of Comparative Examples 6 and 7 consist of an acrylate described in EP-A-0144948 and ammonium phosphate (Exolit AP420 from Clariant, 45% by weight, aqueous dispersion). Table 2: Recipes for Examples and Comparative Examples Table 3: Characteristics for Examples and Comparative Examples

Claims (17)

1. Greenhouse fabric comprising strips (11) of film material which are interconnected by a thread system of transverse lines (12, 14, 18) and longitudinal lines (13a, 13b; 15; 19), by means of a process knitted, warp-knitted or woven to form a continuous product, and at least some of said strips (11) comprise a film material, in the form of a single-layer or multi-layer polyester base film, provided with at least one anti-glare/anti-reflective coating on a first surface of the base film, said film material having a transparency of at least 93.5%, and comprising a total amount of particles of <0.5% by weight, calculated on the total weight of the film material, wherein said at least first anti-glare/anti-reflection coating: - has a dry thickness of between 60 and 130 nm; and - comprises at least one polymer based on acrylic acid and/or methacrylic acid; characterized in that said at least first anti-glare/anti-reflection coating additionally: - comprises at least one alkyl phosphonate and/or oligoalkyl phosphonate flame retardant; and - contains phosphorus in an amount of between 2% by weight and 18% by weight, as calculated based on the total weight of the coating. 2. Greenhouse screen according to claim 1, characterized in that said base film is provided with a second anti-glare/anti-reflection coating on a second surface of the film. 3. Greenhouse screen, according to claim 2, characterized by the fact that the refractive index of the anti-glare/anti-reflective coating(s) is lower than the refractive index of the base film and is less than 1.64 , preferably less than 1.60, and most preferably less than 1.58 at a wavelength of 589 nm when measured in the machine direction (MD) of the film. 4. Greenhouse screen, according to claim 1, characterized in that said acrylic component consists of at least 50% by weight of one or more polymerized acrylic and/or methacrylic monomers. 5. Greenhouse screen, according to claim 4, characterized in that said acrylic component consists of an acrylic or methacrylic acid ester, preferably an alkyl ester whose alkyl group contains up to ten carbon atoms, more preferably of one alkyl acrylate together with an alkyl methacrylate. 6. Greenhouse screen, according to claim 4 or 5, characterized in that said acrylic component further comprises co-monomers in a proportion of 0 to 15% by weight, adapted to form an intermolecular crosslink under the action of elevated temperature. 7. Greenhouse fabric, according to any one of the preceding claims, characterized in that the dry anti-glare/anti-reflective coating(s) comprises less than 10% by weight of repeating units containing an aromatic structural element. 8. Greenhouse screen, according to any one of the preceding claims, characterized in that the anti-glare/anti-reflective coating(s) comprises a flame retardant with the following structure (I) and/or (II). wherein R1, R2, R3 and R4 are independent of each other and can be: H; linear alkyl with -(CH2)n-CH3 (n=07); isopropyl; iso- or tert-butyl; linear alkyl alcohols with -(CH2)n-CH2-OH (n = 0-3), isopropyl alcohol or linear alkyl acids/alkyl acid esters with -(CH2)n-COOR5 structure (with R5 = H; -(CH2 )n-CH3 (n = 0-3)); wherein at least one residual group (R1-R4) is not H; and Z can be from the group H; linear alkyl with -(CH2)n-CH3 (n=0-10); isopropyl; iso- or tert-butyl; linear alkyl alcohols with -(CH2)n-CH2-OH (n = 0-5); isopropyl alcohols or linear alkyl acids/alkyl acid esters with structure -(CH2)n-COOR5 (with R5 = H; -(CH2)n-CH3 (n = 0-3)). 9. Greenhouse screen, according to claim 8, characterized in that the flame retardant is an oligo- and/or alkyl ester of phosphoric acid or phosphonic acid. 10. Greenhouse screen, according to claim 8 or 9, characterized in that the proportion of phosphorus in the anti-glare/anti-reflection coating(s) is between 3% by weight and 17% by weight, preferably between 4 % by weight and 16% by weight when calculated based on the total weight of the anti-glare/anti-reflective coating. 11. Greenhouse fabric, according to any one of the preceding claims, characterized in that the thickness of the anti-glare/anti-reflection coating(s) in each case is at least 70 nm, and preferably at least 78 nm, and is at most 115 nm, and ideally at most 110 nm. 12. Screen for greenhouse, according to any of the preceding claims, characterized in that the total thickness of the film is at least 10 μm and at most 40 μm, preferably the total thickness of the film is at least 11, 12, 13 or 14 μm and a maximum of 35, 30, 29, 28, 27, 26, 25, 24, or 23 μm. 13. Greenhouse fabric, according to any one of the preceding claims, characterized in that the base film comprises a base layer B and one or more additional layers, said additional layers having a thickness of at least 0.5 μm , preferably at least 0.6 µm, and even more preferably 0.7 µm, said thickness is less than 3 µm, preferably less than 2.5 µm, and even more preferably less than 1.5 µm. 14. Greenhouse fabric, according to any one of the preceding claims, characterized in that said base film comprises a UV stabilizer selected from the group consisting of triazines, benzotriazoles or benzoxazinones in at least one layer of the greenhouse film. based on a concentration of 0.3 to 3% by weight, based on the weight of the respective layer. 15. Screen for greenhouse, according to any one of the preceding claims, characterized in that the base film comprises matting particles selected from the group consisting of cross-linked polymethylmethacrylate (PMMA), SiO2 and dimethyl polysiloxane (PDMSQ) in a concentration of less than 3% by weight as calculated based on the total weight of each layer to improve the windability of the film. 16. Greenhouse fabric according to claim 15, characterized in that at least one outer layer of the base film comprises at least 0.07% by weight of the matting particles. 17. Use of the greenhouse screen, as defined in any one of claims 1 to 16, characterized in that it is in a greenhouse environment to enhance photosynthetic activity also during the early hours of the morning or when sunlight radiates at an angle of low incidence.