EP1506140A1

EP1506140A1 - Method and use of a device for coating plate-shaped substrates

Info

Publication number: EP1506140A1
Application number: EP03720078A
Authority: EP
Inventors: Stefan Walheim; Jürgen STEPS; Martin Holzbecher
Original assignee: INTERFLOAT Corp
Current assignee: INTERFLOAT Corp
Priority date: 2002-05-21
Filing date: 2003-05-21
Publication date: 2005-02-16
Also published as: AU2003223826A1; WO2003097547A1

Abstract

The invention relates to a coating method which is used to coat plate-shaped, especially transparent large-surface substrates, such as flat glass, wherein a low-viscous coating solution containing a solvent is applied in a gravitational direction to a lower substrate (21) from an extrusion wide-slotted caster (15). Thin layers can be produced in a continuous manner with high productivity according to the inventive method.

Description

Method and use of a device for coating plate-shaped substrates

The invention relates to a method and the use of a device for applying solvent-containing coating solutions to plate-shaped substrates.

State of the art

State of the art is the production of thin layers in the submicron range

(hereinafter referred to as the “nanometer range”), for example heat protection or sun protection layers, in continuous production processes by means of vacuum technology or plasma-assisted processes. In these processes, a coating material is deposited from the gas phase onto flat glass or other flat substrates. The vacuum-technology and plasma-assisted processes mentioned are suitable For the production of hard and also abrasion-resistant anti-reflective coatings on small-area, transparent substrates, preferably made of glass materials, for example glasses or optical glasses. The increases in the use properties achieved in these applications justify the high coating and system costs. For example, in heated rooms when using windows With heat protection-coated flat glass, annual heating cost savings of 3 to 4 euros per m2 of window area - depending on the oil price.

For other applications, for example the application of anti-reflective layers on large flat glass, the achievable increases in utility value are limited for physical and optical reasons. The application of the multilayer systems required for effective anti-reflective layers is technically very complex using vacuum technology processes and is far too expensive. The application of, for example, hydrophobic, ultraphobic or hydrophilic layers cannot be achieved a priori with vacuum technology processes.

There are worldwide efforts to carry out such functional coatings with nanotechnological sol-gel techniques based on organometallic compounds or in combination with organic polymers or with hybrid polymers or even only in combinations with various high polymers. It is characteristic of most of these production processes known according to the prior art that a liquid phase (hereinafter referred to as coating solution) must first be applied to the substrates. This is followed by a chemical, chemophysical, thermochemical reaction, evaporation of the solvents, reaction products etc. and the conversion into the final desired functional layer or layer system on the substrate.

Transparent, optically effective, thin layers in the nanometer range (approx. 50 to approx. 600 nin) must be used because of the required visual uniformity as well

Color uniformity can be produced both very homogeneously in the layer thickness and in the material homogeneity per unit area. Similar to the layer homogeneity and precision achieved with vacuum technology on flat glass, the coating solution must be applied to large flat glass sheets or other transparent substrates at and from the front edge in the direction of transport as well as across the entire surface with a thickness accuracy of less than 5% - regardless of technologically-related distances between successive flat glass sheets or substrates. The same accuracies are also placed on the material homogeneity of the final desired functional layer or the layer system (the solid layer). In large-scale technical systems, this visual uniformity must continue to be guaranteed from substrate to substrate over any length of production.

The way in which a coating solution is applied in connection with the substrate geometry essentially determines the extent to which a given production process can be designed continuously and with what productivity. The production process, the individual production parameters and the quality requirements for the final, functional layer are of course all integrated into such production objectives.

Despite the many application objectives for the coating of large flat glass - larger than I m ² - only in the glass industry

Liquid coating technologies can be introduced sustainably as large-scale production technologies if processes for the continuous application of Coating solutions and overall for continuous layer production can be provided.

For example, solar technology is constantly working on increasing the maximum energy yield. Large flat glass with maximum solar transmission is required both for the devices for generating solar heat and for photovoltaics. According to the physico-optical laws, the increase in solar transmission by applying antireflection layers on flat glass can only be a maximum of 4% with one-sided coating or only a maximum of 8% with double-sided coating. There are a large number of manufacturing methods for anti-reflective layers in the prior art.

Suitable continuous coating processes are an essential prerequisite for the fact that the achievable solar energy permeability and the overall achievable increase in use value of antireflection-coated flat glasses lead to comparatively lower coating and system costs. Of course, such continuous coating processes are also required for the application of other functional layers to large-area flat glass, for example for transparent hydrophilic and hydrophobic or else for other optically effective layers. A number of coating methods for applying coating solutions to glass and to other transparent substrates are known in the prior art.

In US 4,271,210, the application of the coating solution in the immersion process is proposed as part of the manufacturing process. US Pat. No. 4,830,879 uses either immersion processes, centrifugal processes or

Spray method suggested. According to DE-A-19916811, DE-A-19708776 Cl, EP-A-0835849 and WO 00/64830, the coating solution is applied in an immersion process to produce antireflection-coated flat glass and then the flat glass coated in this way is dried over several minutes. The proposed coating process is not suitable for large-scale application in the glass industry. In addition, a one-sided coating can only be achieved by covering one side in a complex manner. In WO 00/00854 and EP-A-1 092164 it is proposed to apply the coating solution described there to the flat glass by spin coating. It is known that on an industrial scale up to round glasses or on display carriers a diameter of max. 1 m coating solutions can be applied in a centrifugal process. However, this coating method is not suitable for large-scale continuous coating.

According to DE-A-3 835 078, linear structures have been applied to flat glass surfaces, for example, by ejecting an application agent from an opening in the form of a thread that is not in contact with the substrate. We explicitly point out the need to prevent spraying. EP-A-0 765 694 describes a similar coating method and a corresponding device with a round nozzle located perpendicularly above the flat substrate and perpendicular to the substrate movement. EP-A-0 775 669 describes the production of nanoporous aerogels on glass or other plate-shaped substrates. The liquid brine should be applied by spray coating, dip coating or spin coating. In principle, spraying processes can be an option for continuously moving substrates in at a constant speed

To coat transport clearing in narrow bands. A related technical solution for large-area application is not described.

According to DE-A-19 619 545, aqueous polyurethane solutions are applied to glass, preferably to bottles, in an air pressure spraying process. To the

Layer thickness constancy is not a high requirement. According to DE-A-19719 948, the coating solution (called coating lacquer there) for the production of nanostructured layers on glass or on transparent plastics is applied to the substrate in a defined manner by spin coating. DE-A-43 25 760 describes a production process for band-shaped, also meandering, electrically conductive webs on glass. A technical solution for the coating is not described.

The coating of wide plastic films with highly viscous coating solutions has been carried out on the industrial measuring stick for around 6 decades for the production of photo films. According to the prior art, the application of viscous or highly viscous coating solutions to flexible material webs is also carried out by extrusion from wide-slot nozzles of very different designs. The wide slot nozzles are usually arranged perpendicular to the direction of transport and to the material web being passed. The material webs are opened or closed between supply rolls unwound. Complicated transport and drive devices, precisely manufactured in the micrometer range, in conjunction with roller guides and calender roller systems enable thin layers down to the range of less than about 10 nm to be applied with specially designed extruders.

Methods and devices for the uniform application of coating solutions to flexible, band-shaped, uniformly moving material webs by means of extrusion processes are described, for example, in the documents DE-A-4000405, DE-A-3126795, DE-A-3639027, DE-A-10133582, EP-A -1080866, DE-A-3014816 (EP-A-0038526).

According to DE-A-210220, wet layer thicknesses of less than 10 nm to about 5 nm can be achieved on tape-like support materials by applying low-viscosity coating solutions with viscosities less than about 50 mPas by combining extrusion and bead coating processes. The coating bead is a geometric shape made of coating solution which, viewed in cross section, bridges the narrow gap between the extrusion die and the material web that is being passed in the form of a drop that forms. The coating solution is optionally supplied to the bead via a sliding plane or a slot-shaped channel. Under the action of earth's gravity and the direction of transport of the material web, which is preferably directed against earth's gravity, the bead is virtually in suspension. Additional blowing should stabilize the bead. According to DD-A-22413, wet-film thicknesses of up to about 10 nm can be achieved on tape-like carrier materials with slight fluctuations in the layer thickness by applying magnetizable, binder-containing coating solutions (in the manner of suspensions) by a process of delirium extrusion coating. The extrusion pourer opening and the straight edge of a magnet are arranged in contact-free spacing. The material web to be coated is guided from below over a sliding surface at high speeds up to approximately 100 m / min over this straight edge into a plane sliding plane inclined against gravity. The magnet is used for additional stabilization of the coating process. After striking, the extruded coating solution is stretched by the drag effect of the material web in the direction of the sliding plane, which is inclined against gravity. According to DD-A-227624, wet layer thicknesses of about 0.5 nm can be achieved on tape-like carrier materials by applying preparation liquids by extruding such liquids a wick pressed against the material web, which consists of organic, porous materials, such as felt, paper.

EP-A-0 876 848 discloses a method and an apparatus for applying a photoresist to a glass substrate. The application device has a slot nozzle which is connected via a line to a container containing the coating solution. A plurality of horizontal channels open into the slot nozzle, through which the solution is fed into a central collecting channel. A vertical slot with an outlet opening connects to the collecting duct. EP-A-0 876 848 teaches, among other things, how to determine the viscosity and surface tension of the coating solution

Coating speed and the desired layer thickness, the distance between the outlet opening of the nozzle and the substrate surface can be calculated so that a stable and continuous meniscus between the nozzle and the substrate surface is maintained during the coating. According to the exemplary embodiment, the photoresist used has a viscosity of 60 mPas (milli-Pascal seconds) and a surface tension of 30 * 10 " ³ N / m. With a desired

Coating speed of 10 mm / s and a layer thickness of 10 μm, the distance between the application device and the substrate surface can vary between 16 and 66 μm.

US 5,622,747 discloses dispenser for wafer coating with a photoresist. The dispensing device is formed by a housing with an inlet opening and an outlet opening. The photoresist flows from the inlet opening into a reservoir, from which an elongated channel leads to the outlet opening. The outlet opening has a gap width of 0.075 mm (75 μm). When coating the

Dispenser moved over a wafer at a speed of 4.5 cm / s and approximately 2 mm. An overpressure is applied to the nozzle for coating.

The processes for the coating of wafers have in common that substrates with relatively small uneven areas are coated with a photo residue with a viscosity greater than 50 mPas. The coating speeds of up to 3 m / min are low and, for example, too low for the industrial coating of large-area substrates. task

The aim of the present invention is to provide an improved coating method and a coating device for the continuous production of optical coatings and other transparent surface coatings on plate-shaped, preferably transparent substrates, in particular flat glass (float glass or cast glass). The aim is to propose a method and a device with which large-area, plate-shaped substrates can be provided with a coating solution which can be cured. Another objective is to apply a method and a device to large and preferably transparent substrates to apply homogeneous optical and other transparent surface finishes provided with great visual uniformity and color uniformity. It is also a goal that the methods and apparatus provided make it possible to produce constant coatings for optically effective reflective and antireflective layers and for other transparent surface coatings in a cost-effective manner and in any desired time period. A further objective is that the method and the device optionally enable both single and multiple coatings as well as one- or two-sided coatings of plate-shaped, preferably transparent substrates. It is also the aim that the method and the device can be used to coat roughened or uniformly structured or also stochastically structured substrate surfaces. A further aim is to provide a method and a coating produced by the method, with which an increase in the integral solar transmission of flat glass by at least approximately 2.5% per coated glass surface is achieved. One aim is to provide antireflection coatings with a refractive index n less than 1.3, preferably about 1.23. Another goal is to provide tempered coated glass which still has properties comparable to those of the glass material.

description

According to the invention, the goal is achieved in that low-viscosity coating solutions with a viscosity of less than 10 mPas are used. to

The inventor's surprise was found to be that slot die casters are also suitable for coating rigid, large-area plate-shaped substrates with unevenness of up to ± 50 μm if coating solutions with a viscosity of less than 10 mPas be used. The coating of flat, plate-shaped substrates with a slot slitter has the advantage that the process can be operated continuously.

According to a preferred embodiment variant, the substrate is moved relative to the extrusion wide slot caster at a speed such that

The coating solution is additionally stretched on the substrate surface in the direction of transport. This enables uniform thin layers with layer thicknesses <1 μm to be obtained. The delivery rate and the speed of the substrate are expediently set in such a way that a coherent coating solution curtain forms from the extrusion wide-slot caster towards the moving substrate. It can help stabilize a coherent

Coating solution curtain, depending on the properties of the coating solution, at least part of the distance between the opening of the slot slot and the substrate surface can be bridged with a doctor blade. Depending on the type and properties of the coating solution used in each case, the elongation of the

Coating solution on the substrate surface can be adjusted by adjusting the angle of the extrusion slotted die with respect to the direction of gravity.

The theological fluid properties (viscosity and internal

Normal tension), the pH value, the delivery rate and delivery pressure, solids concentration and transport speed (relative speed between the slot die and the substrate) are adjusted so that a uniform wetting of the substrate surface, preferably from the front edge of the substrate, is achieved with the coating solution. This is important for a uniform coating of the substrates.

In particular, a corresponding wetting of the above-mentioned parameters such as fluid properties, delivery quantity and pressure, etc. is intended to achieve a uniform wetting of the substrate surface with the coating solution. Another aim of the appropriate observance of the above-mentioned process parameters is that a uniform liquid bridge is established between the extrusion wide-contact protector and the substrate surface.

The coating solution is advantageously of low viscosity with a viscosity of less than 20 mPas (milli Pascal seconds), preferably less than 10 mPas, and is particularly preferred less than 5 mPas. Surprisingly, and contrary to the previous opinion, such low-viscosity solutions can very well be applied uniformly to flat substrates with a slot die caster. The internal normal stress (perpendicular to the shear stress) of the coating solution is expediently greater than 2 Pascals.

According to a preferred variant of the method, the proportion by weight of solids in the coating solution is less than 20%, preferably less than 10%. Solutions with a low solids content are suitable for application to plate-shaped substrate surfaces by means of a slot die caster.

The substrate is expediently passed at a constant speed in the range between 2.0 to 30.0 m / min, preferably in the range between 4.0 to 15.0 m / min, under the slot slitter and coated with a liquid layer of the coating solution. At these speeds, there is a large production capacity. In addition, in contrast to the immersion process, the process can be carried out continuously.

The distance between the lower edge of the wide-slot caster and the substrate surface is preferably set via a height adjustment device of the wide-slot caster or optionally of the support. This can be achieved inexpensively, and different substrate thicknesses can then be coated. The distance between the lower edge of the extrusion slot die and the substrate surface is advantageously set to a value of less than 2 mm, preferably between 0.1 mm and 1.0 mm and very particularly preferably between 0.1 mm and 0.4 mm. The distance between the lower edge of the slot die and the substrate surface is expediently set with an accuracy of better than approximately 0.03 mm.

In contrast to the method of US Pat. No. 6,177,131 (Frauenhof er), it is advantageous not to use colloidally disperse solutions, but rather to use essentially genuine and homogeneous coating solutions. Agglomerates or solid components are expediently only contained in such a size, shape and amount that the coating solution curtain remains coherent and the delivery rate is homogeneously transferred to the substrate. Homogeneous solutions can be applied well with a wide-slot caster. The coating solutions are preferably degassed. With - lo ¬

The solid layer thicknesses produced in the coating process are preferably less than 1 μm.

An easily volatilized, preferably organic solvent or solvent mixture in which the layer-forming solids are soluble can be used as the solvent. Examples of suitable solvents are those which already have a high vapor pressure at room temperature. Preferred solvents have a boiling point <100 ° C, preferably <80 ° C.

The coating is preferably carried out in a specific working or

Process gas atmosphere carried out. The process gases can be used at least temporarily during the process to deliberately delay and accelerate the condensation and polymerization reactions etc. and solidify to form a solid layer. In addition, an even layer thickness is supported by the use of the process gases.

Preferably, the area of the extrusion wide-contact caster is flushed during the coating process by a first process gas with a gas composition adapted to the composition of the coating solution, optionally as a protective gas or gas with reactive constituents. This has the advantage of being constant

Coating conditions prevail and the liquid film does not break off. Through reactive gas components in the process gas, the condensation process of, for example, metal alkoxy compounds can be controlled in a targeted manner during the coating. The applied coating solution is expediently surrounded or washed around by further different process gases in successive working steps. The choice and composition of the process gases can be chosen according to the chemical and chemical-physical necessity and in the order of a given manufacturing process. To this end, it may be necessary to separate the individual working gas areas from one another by simple constructive measures. The preferably volatile solvent of the coating solution can be evaporated by means of one or more process gases and further volatile reaction and decomposition products can be taken up and removed. The process gases used preferably consist of one or more inert or inert carrier gases, preferably nitrogen, and optionally of admixed reactive vapors and gases. Conveniently, the concentrations of the reactive vapors and gases are admixed as a function of the process-technical reaction conditions, preferably in a total concentration of less than 15%. The solidification of the solid layer can be accelerated by adding components which react with the coating solution. In the case of organometallic compounds, for example organosiloxanes, the solidification of the layer can be accelerated by adding, for example, water vapor in the gaseous state in a concentration in the range of, for example, 20 to 80% relative humidity. For example, the alkoxy metal compounds of the coating solution can react with reactive components of the process gas, for example H ₂ O, and solidify. In addition, the process gas can contain acid gases, acids and other suitable compounds in concentrations of less than approximately 10% by volume, optionally in gaseous form. For example, but not limited to, chlorine, sulfur dioxide, HC1, H ₂ SO ₄ , H2SO3, HNO3, CHsCOOH, water-soluble chlorides, hydrogen sulfates and sulfites can be contained. The desired composition of the process gas atmospheres can be produced by mixing using a mixing device and directed to the desired location via corresponding lines. The process gases can be discharged after contact with the applied liquid layer and their composition can be measured for control.

Expediently, IR and UV radiation sources become radiation-inducing ones

Substance reactions used in the coating. By irradiation, e.g. with a UV source, the condensation of the metal alkoxy compound can be accelerated.

The substrate is preferably coated in a continuous process. The costs of the coating process can thus be kept low. After applying a first layer, further layers can also be applied. It is conceivable to apply one or two sides to plate-shaped substrates both simply and with two or more layers one above the other, each with the same or different solid layer thicknesses. Preferably, the substrates for the multiple coating within an automated production line are optionally coated in succession by the sequence of two or more slot die casters or returned or returned to the one slot die caster in a technically and logistically adapted bypass. circulated .. Flat glass, plastic glass or other transparent plates can be used as substrates. Examples of flat glass are float glass, cast glass with any regular and / or stochastically structured surfaces, for example with finely hammered surfaces, smooth or polished plate-shaped metals, mineral substances or other transparent plates. However, translucent plastic plates, preferably made of polymethyl methacrylate, polycarbonate, polystyrene and the like, can also be used as substrates. Like., Are used. By coating antique glass, which is irregular due to the manufacturing process, with nanoporous antireflection layers - as with the coating of flat glass surfaces (float glass) - an increase in the integral solar transmission can be obtained.

According to a preferred process variant, a solution is used as coating solution containing at least one metal-alkoxy compound and an essentially non-polar polymer, which is preferably chemically inert compared to the metal-alkoxy compound used. Coating solutions composed in this way can be used to produce nanoporous layers with significantly increased integral solar transmission.

The polymers are preferably derived from one of the following groups: polyacrylate, polycarbonate, polyethylene oxide, polymethylacrylate, polymethylmetaacrylate, polystyrene, polyvinylchloride, polyvinylpyridine (P2VP and P4VP), Teflon AF etc.

According to a particularly preferred process variant, the polymer used is removed from the solid layer applied to the plate-shaped substrates. This can be done, for example, by detaching with a suitable, e.g. alcoholic, ethereal or aromatic solvents happen. Alternatively, the polymer can be evaporated by the application of heat. The solvent is expediently vaporized by a process gas stream. This process can be used to obtain nanoporous layers with anti-reflective properties. The integral solar transmission can thus be increased by at least approx. 2.5%.

According to another independent aspect, the subject matter of the present invention is a coating method according to the preamble of claim 26, which is characterized in that the extrusion slurry protector and, if appropriate, the substrate passed under the extrusion slit pourer, at least in the region of the Outlet opening of the slot slot is washed with a process gas atmosphere. The process gas can ensure that the liquid curtain does not break and that a thin layer is formed within seconds as the solvent is removed. After the solvent has been removed, the layer can already be solidified to such an extent that it can be handled. Further advantageous aspects of the method are defined in the subclaims.

The present invention also relates to the use of a device according to claim 28 for the continuous coating of transparent, large-area plate-shaped substrates, in particular substrates such as flat glass, with low-viscosity coating solutions with a viscosity of <10 mPas (milliPascal seconds). Up to now, wide-slot casters have only been used for the coating of plastic sheets, etc. used with viscous coating compositions, but not for the coating of large-area plate-shaped substrates, such as glass plates. In general, the experts were convinced that slot die casters were not suitable for coating plate-shaped substrates with low-viscosity coating solutions. Surface coatings of large-area glass plates were therefore mainly carried out in the past using the immersion process. To the surprise of experts, it has now been found according to the invention that wide-slot casters are very well suited for the application of low-viscosity coating solutions.

The extrusion wide-contact protection castor is preferably arranged under a hood or in a chamber which is largely sealed off from the ambient atmosphere. As a result, the coating can be carried out in a defined process gas atmosphere. At least one connected to the chamber is advantageous

Gas processing device for mixing inert and / or reactive gas components available. This allows different atmospheres to be used. At least two connections for supplying and discharging a process gas or gas mixture can be provided on the chamber. A metering and / or pressure-maintaining device is expediently provided, which is in contact with the extrusion wide protection castor

Connection is established. The chamber in which the extrusion sluice pourer is arranged can be divided into at least two reaction spaces. Furthermore, gas guiding devices, for example baffles or lines with baffles, can be provided in order to guide or suck off the gases in a targeted manner onto the substrate surface. The transport device advantageously has a preferably movable support on which the substrates can be fixed. The substrates can be fixed to the support on this support by means of a suitable device, for example by means of a negative pressure, for example in the manner of a chuck. On the other hand, the substrates can be made movable relative to the substrate surface by means of overpressure, for example in the manner of an air cushion. It is also conceivable to arrange the support movably on a support frame by means of an air cushion.

Surface emitters in the chamber at a distance from the transport device are advantageous, e.g. IR and / or UV radiation queues arranged. The hardening of the layer can be accelerated by means of the radiation sources.

Advantageously, the extrusion wide-contact mold has a long, wide wide-contact gap, preferably at least the width of the substrate to be coated.

The gap width of the wide slot gap is expediently adjustable depending on the properties of the coating solution. The gap width or the slot width of the slot-shaped opening can preferably be set to a value less than 1.2 mm, preferably between 0.02 mm and 0.8 mm. Small slot widths are advantageous when using low-viscosity coating solutions. In addition, depending on the properties of the coating solution, a doctor blade can be connected to the wide slot gap according to known constructional designs.

According to a preferred embodiment, the slot die caster is arranged in a plane which is essentially both perpendicular to the conveying direction of the substrate and perpendicular to the support surface. This is important if low-viscosity coating solutions are to be applied. Advantageously, the slot slitter is above the support, respectively. of the substrate to be coated.

According to a preferred embodiment, the wide slot caster is pivotable about an axis running parallel to the wide slot. As a result, the coating curtain that arises during the coating process can be influenced. The distance between the transport device or. Support and the bottom edge of the Breitschlitzgiessers adjustable or adjustable. This makes it possible to coat substrates of different thicknesses with the same device. Preferably, the distance between the surface to be coated and the extrusion slotted caster can be set with an accuracy better than 0.03 mm. It is also an advantage if the support in the area under the broad contactor can be adjusted with a height accuracy better than 0.01 mm.

The transport device expediently has adjustable drive means so that the substrate can be transported at an adjustable, specific speed - preferably between 2.0 to 15 m / min. A high throughput can be achieved at these speeds. To produce a desired optically effective coating, the applied solid layer can be exposed in a final process step, preferably a thermochemical or a pyrolytic treatment. For this purpose, a hardening or annealing furnace can be provided in the transport direction of the chamber.

The invention is described in more detail below by way of example with reference to the figures. It shows:

1 schematically shows an apparatus for coating glass substances;

Figure 2 shows a slot die caster in more detail. and

Fig. 3 shows the transmission spectra of different glasses between 300 and 2500 nm, which were coated according to the inventive method, in comparison.

The coating device 11 shown in FIG. 1 has a transport device 13 and a slot die caster 15 arranged above the transport device 13. The transport device 13 comprises a support 19 movable in a conveying direction 17, on which plate-shaped substrates 21, in particular flat glass, can be arranged for the purpose of coating. The support 19 rests on a substructure 23 (not shown in more detail) and is movable relative to the latter. The support 19 can also be adjusted in height by means of a height adjustment device 25, so that substrates 21 of different thicknesses can be coated.

According to the preferred embodiment, the wide-slot caster 15 is an extrusion wide-contact caster with one that extends transversely to the conveying direction 17 Slot 27. The slot has a width between 0.02 and 1.0 mm, preferably between 0.08 and 0.3 mm. The extrusion wide protection castor 15 is arranged on a frame 28 and can be pivoted about a horizontal pivot axis 30 running transversely to the transport direction. Furthermore, the extrusion wide contactor 15 is connected to a storage container 31 via a feed line 29. The storage container 31 serves to hold a coating solution 33. A metering pump 35 allows the amount of liquid fed into the extrusion wide-contact protection caster 15 to be metered precisely. It is basically conceivable to control the metering of the amount of liquid via the hydrostatic pressure.

The extrusion wide protection casting 15 is arranged in a hood or chamber 37. The chamber 37 covers the transport device 13 in width and is apart from one between support 19 and. Transport device 13 existing slot 39 closed. Preferably, the chamber 37 is at least in a coating chamber 44, in which the extrusion slug casting 15 is arranged, and an conveying direction 17 in the

Reaction chamber 44 adjoining drying chamber 45 divided. A first working or process gas, in particular reactive gas, can be fed into the coating chamber 44 via a line 41. A first gas treatment device 63, to which the line 41 is connected, is used to mix different gases. Excess gas can be removed or extracted through an outlet opening 43 provided in the coating chamber 44.

Like the coating chamber 44, the drying chamber 45 covers the transport device 13 in width, so that substrates 21 arranged on the support 19 have a specific second, different from the first, in the conveying direction

Process gas atmosphere can be contacted. A feed line 47 is used to feed a second process gas or process gas mixture, in particular a drying gas, into the drying chamber 45. A second gas treatment device 65, to which the feed line 47 is connected, is used to mix different gases. The gas can escape again or be sucked out via an outlet opening 49 provided on the chamber 45.

Before resp. after the coating device 11, a support loading station 51 and a support unloading station 53 are provided. These stations 51, 53 are used for loading and Unloading the support 19 with the plate-shaped substrates 21. Swivel stackers 55, 57 allow uncoated substrates to be loaded onto the support 19, respectively. unload coated substrates.

A hardening furnace 59 can be provided in the conveying direction 17 after the swivel stacker 57. In the hardening furnace, for example, glass coated beforehand in the coating device 11 can be thermally tempered. The tempering of the glass and the final treatment of the applied layer (e.g. pyrolytic removal of organic components) can take place at the same time. Upstream of the coating device 11 can be a known surface cleaning system 61, not shown.

Figure 2 shows the lower part of a slot die caster 15 in more detail. The wide slot caster has a wide contactor gap 27 with a certain slot width and slot height. The slot height can be used to even out the pressure conditions in the slot slot caster and thus the delivery rate per unit of time. The liquid curtain 67 is stretched in the transport direction 17 by the selected transport speed of the substrate 21.

The coating method according to the invention is described below using the production of an antireflection coating as an example:

The flat glass surfaces must first be cleaned and provided free of chemical contaminants and dusty deposits. In an organic solvent that has a high vapor pressure at room temperature, a monomeric, preferably quadruple-crosslinking alkoxy compound of silicon or that of another metal (for example Al, Ce, Ga, In, Nd, Sn, Ti, Th, Tl, and / or Zr) solved. The coating solution further contains at least one polymer with a molecular weight of less than 10,000, but preferably greater than 500,000, which preferably has no -OH and / or -NH groups. However, the use of oligomers as precursors for precursors which react in situ to give polymers is conceivable. The polymer compound used is said to be largely chemically inert to the monomeric alkoxy compound. Furthermore, the polymer compound and the alkoxy compound should not be miscible with one another. Using polymers or oligomers which meet the above-mentioned restrictions in the context of the process according to the invention, examples include polyacrylate, Polycarbonate, polyethylene oxide, polymethyl acrylate, polymethyl methacrylate, polystyrene, polyvinyl chloride, polyvinyl pyridine (P2VP and P4VP) or Teflon AF. Coating solutions consisting of one or more of the aforementioned polymers and one or more alkoxy metal compounds are characterized in that in the process of the desired rapid, shock-like evaporation of the solvent under the chemical influence of the process gases, the applied liquid layer solidifies to form a solid layer. This solid layer consists of statistically distributed, alternating three-dimensional areas of the two solid components; from areas of the crosslinked polymer - the size and size distribution of which determines the statistical distribution of the porosity in the nanoporous antireflection layer after pyrolysis - and from areas of a chain-like crosslinked solid gel of the alkoxy compound used.

The coating solution is preferably adjusted to a pH <7. A little water and an acid (e.g. HC1, H2SO ₄ ) can be added to the organic solvent. The amount of water is added in a substoichiometric ratio to the amount of the monomeric, four-crosslinking alkoxy compound in order to specifically achieve an uneven size distribution of the primary particles in the sol. For this chemical intermediate process, the addition of an acid in a small amount is necessary to precisely set a suitable pH in the range from 1 to 6, preferably 2 to 6.

In order to achieve a thickness within the range of approximately 100 to 400 11 m for the applied solid layer before the high-temperature hardening process, the solids content in the solution should be less than 15% by weight. Within this total solid content, the quantitative ratio between the two macromolecular components can be within one

Range from 1: 5 to 5: 1. The ratio of the two components essentially depends on the type of substance and the molecular weight of the substances used.

Coating solutions whose internal liquid composition - measured perpendicular to the shear stress - is characterized by a normal stress greater than approx. 2 Pa (Pascal) are particularly suitable.

The coating of plate-shaped, large-area substrates, which also include flat glass panes, can be carried out continuously by a vertical or inclined one Free-falling liquid film takes place: After striking the coating solution on the front edge (front edge as seen in the conveying direction), the coating solution immediately spreads as a liquid curtain across the entire substrate width perpendicular to the transport speed. This ensures an even coating and layer thickness in the edge areas. Preferably the one used

Coating solution a low viscosity, especially one <20 mPas.

According to the present invention, coating solutions produced and provided with an extrusion caster with a wide slot gap of this type are now applied to the flat glass or other plate-shaped substrates which are passed underneath - also referred to collectively as substrates - in the combined expansion layer and free-fall process. In coating operation, a free-hanging liquid film bridges the distance from the bottom slot die edge to the substrate surface. Furthermore, the liquid film is additionally stretched in the direction of transport by a corresponding feed rate of the substrate on the substrate surface.

The wide slot gap preferably has a slot ü of width between 0.02 and 0.8 mm, preferably between 0.05 and 1.0 mm, and very particularly preferably between 0.05 and 0.35 mm. The distance between the surface of the substrate and the lower edge of the slot die can vary in the range between 0.1 and 1.0 mm, preferably 0.2 and 0.8 mm. The

The length of the slot slot can preferably be greater than 1 m without interruption. The aforementioned parameters are selected or selected in accordance with the properties of the coating solution and the production technology requirements. customized.

In order to ensure sufficient accuracy of the applied solid layer thickness, vibration-free support is preferably used. The support can have a vacuum suction or other means for fixing substrates of different sizes. The height of the transport plane can expediently be set with high accuracy, preferably to ± 0.02 mm, with respect to the lower edge of the caster. The transport speed should be adjustable to less than 1%.

In the immediate vicinity of the lower edge of the slot die caster, a protective gas envelope, for example nitrogen, optionally containing reactive gases in a low concentration, can preferably be provided. This helps that despite the quasi-continuous Working principle of the extrusion wide protection casters is in permanent operational readiness and substrates fed in succession are coated evenly from their front edge.

After the applied liquid layer has been made uniform, the coated substrate surface section reaches a subsequent drying chamber into which a second process gas, preferably designed as a drying gas, can absorb the evaporated solvent and other gaseous reaction products. The quality of the solidification and the drying speed and the applied layer are controlled by the special composition of the individual gas components of the second process gas and optionally in combination with an IR / UV radiation bed. In this process, a solid layer forms, the thickness of which on the substrate - depending on the thickness of the applied liquid layer and the solids content brought into solution - can be from about 20 nm, preferably in the range from 100 to 400 nm.

The solid layer thus produced consists of alternating dense areas of the two

Substance components, the crosslinked polymer and the chain-like crosslinked gel of the original alkoxy metal compound, preferably alkoxy silane compound. These areas of material exist incompatible side by side as three-dimensional areas with statistically distributed different sizes in the Naometer range.

In a next step of the process, the polymer is removed from the three-dimensional solid matrix by a pyrolytic process using a high-temperature shock treatment in the glass hardening process. A porous, highly cross-linked antireflective layer is thus formed from the original alkoxy compound. The antireflection layer produced in this way then has the property of increasing the integral solar transmission of the flat glass coated in this way by at least 2.5%.

In the event that the solid layer produced is applied to other plate-shaped, transparent materials which are temperature-resistant from approximately 250 ° C., the polymer selected for this purpose can be removed without residue by a pyrolysis process which is gentle on the substrate. The integral transmission of the substrate coated in this way can be increased by at least 2%. For substrates which have a lower temperature resistance, process gases containing gaseous solvents can be prepared in the course of this method. Especially selected and Polymers and oligomers used can be selectively removed from the three-dimensional matrix of the applied solid layer with the help of such process gases.

According to the present invention, plate-shaped metallic and other mineral, non-transparent substrates are also coated by the method and the solid layers applied in this way are likewise converted into antireflection layers with high-temperature shock treatment, and substrates are provided in this way, for example with anti-reflective surfaces and / or surfaces designed with interference color effects.

embodiments

1. Example: Production of an anti-reflective layer coated on one side

Flat glass pane to increase the integral solar transmission.

In a suitable sequence and mixture, all substances are effective

Solvent with a high vapor pressure at room temperature, a fourfold cross-linking silane, polymethacrylate with a molecular weight of 996O00, H ₂ SO ₄ and water, and a suitable ratio between the two macromolecular substances is adjusted and mixed. The total solids content in the coating solution is 5%.

The following values of the theological properties were measured: viscosity = 0.60 mPas, normal stress = 8.5 Pa

The coating speed is 7.0 m / min. The solid thickness is approximately 330 nm. Due to the high-temperature shock treatment in the glass hardening process, an average increase of 2.8% in the integral solar transmission is achieved in the spectral range from 450 to 1500 nm (measured with the integrating sphere).

2. Example: Production as in Example 1 with a solids content reduced by 50%

In comparison to example 1, the solids content in the coating solution is only 2.3

%. The proportion of the polymethacrylate was compared to 1 in a third The addition of H2SO4 and water has been reduced in proportion to the reduction in silane.

The following values were measured for the rheological properties of the coating solution:

Viscosity = 0.43 mPas

Normal tension = 2.8 Pa

The coating speed is 7.0 m / min. The solid thickness is 240 nm.

The high-temperature shock treatment in the glass hardening process results in an average increase in the integral solar transmission of 1.8% in the spectral range from 450 to 1500 nm - compared to the uncoated flat glass (measured with the integrating sphere). The anti-reflective coating was visually uneven.

In comparison to example 1, example 2 shows that the proportion by weight of the solids and the proportion by weight among themselves have a significant influence on the quality of the antireflection layer.

3. Example: Production of flat glass panes coated on one and / or two sides with single or multiple coating

For the multiple coating of flat glass panes, the simply coated flat glass panes or other substrates are returned in a new technological bypass or coated with a subsequent second slot die caster. The applied solid layer is mechanically stable after leaving the coating chamber so that substrates coated on one side can also be moved on the coated side using the automated transport technology customary for glass processing companies. For example, there are process engineering options available to coat the back of the substrates with the same coating solution and the same coating conditions before the glass hardening process, or to coat the substrates again on one or both sides for double coating.

The layer thicknesses can be changed by changing the substrate speed or the delivery rates, and multiple layers can be realized with differently applied layer thicknesses and layer structures. The solid layers are on the flat glass is converted into nanoporous anti-reflective layers by the subsequent high-temperature thermal shock. Such a coated flat glass achieves a refractive index n up to approx. 1.1 compared to the adjacent air and, when coated on one side, leads to an increase in the integral solar transmission by more than 3%.

FIG. 4 shows the transmission in the spectral range between 300 nm and 2500 nm for different glasses. Curve 1 corresponds to a non-coated reference glass (cast glass pane). The transmission in the range between approximately 400 nm and 2000 nm is just under 92%. The curves denoted by 2 and 3 show the transmission after coating the glass pane with an anti-reflection layer according to the invention. The measurement curves were obtained by measuring the transmission at widely spaced locations on the same coated cast glass pane. The integral transmission is approximately the same for both curves. Curve 4 shows the transmission of a coated cast glass pane whose antireflection layer is 20% thicker than the antireflection layer belonging to curves 2 and 3. It can clearly be seen that the maximum of curve 4 is shifted to longer wavelengths.

The design of the pore structure - pore sizes and pore size distribution - and the adjustment of the layer thickness can even achieve a higher integral solar transmission of more than 3% in this regard if the total transmission is maintained for predetermined spectral ranges.

Legend:

11 coating device

13 Transport device

15 extrusion slotted casters

17 Direction of conveyance

19 support

21 plate-shaped substrates, especially flat glass

23 substructure

25 height adjustment device

27 wide contactor gap

28 frames

29 supply line

30 swivel axis of the wide-slot caster

31 storage containers

33 coating solution

35 dosing and pressure line device, e.g. metering

37 chamber

39 slot between transport device and chamber 37

41 line

43 outlet opening

44 coating chamber

45 drying chamber

47 supply line

49 outlet opening

51 loading device

53 Unloading device

55.57 swivel tab

59 hardening furnace

61 surface cleaning system

63 first gas processing device

65 second gas treatment device

67 Liquid curtain

Claims

Patent claims

1. Coating process for coating plate-shaped, in particular transparent, preferably large-area substrates, such as flat glass or plastic glass, preferably with thin, transparent layers for optical purposes

Coating and other transparent surface coatings, by applying a solvent-containing coating solution to a substrate, in which process the coating solution is poured from an extrusion slot molder (15) in the direction of earth's gravity onto the substrate (21) underneath and the substrate and

Extrusion slot casters are moved relative to one another in a specific transport direction, characterized in that low-viscosity coating solutions with a viscosity of less than 10 mPas are used.

2. The method according to claim 1, characterized in that the delivery rate and the speed of the substrate (21) are adjusted so that a continuous curtain of coating solution is formed from the extrusion wide gun caster (15) towards the moving substrate.

3. The method according to claim 1 or 2, characterized in that the substrate (21) is moved relative to the extrusion slot caster (15) in such a way that the coating solution on the substrate surface is additionally stretched in the transport direction by dragging.

4. The method according to one of claims 1 to 3, characterized in that in order to stabilize a coherent coating solution curtain, depending on the properties of the coating solution, at least part of the distance between the opening of the wide protection gap (27) and the

Substrate surface can be bridged with a squeegee.

5. The method according to any one of claims 1 to 4, characterized in that the internal normal stress of the coating solution is set to a value greater than 2 Pa becomes.

6. The method according to any one of claims 1 to 5, characterized in that the solids proportion by weight in the coating solution is less than 20%, preferably less than 10%.

7. The method according to one of claims 1 to 6, characterized in that, depending on the type and properties of the coating solution used, the distance between the lower edge of the extrusion slot molder (15) and the substrate surface is set to a value of less than 2 mm, preferably between 0.1 mm and

1.0 mm is set.

8. The method according to any one of claims 1 to 7, characterized in that the substrate is moved at a constant speed in the range between 2.0 to 30.0 m/min, preferably in the range between 4.0 to 15.0 m/min below

Extrusion wide gun caster (15) is passed.

9. The method according to any one of claims 1 to 8, characterized in that a highly volatile, preferably organic solvent is preferably used in the coating solution.

10. The method according to one of claims 1 to 9, characterized in that the coating of the substrates is carried out in a specific process gas atmosphere formed from at least one process gas, for example in a closed chamber (37) with the exclusion of the natural ambient atmosphere.

11. The method according to one of claims 1 to 10, characterized in that during the coating process, process gases are used at least temporarily for the targeted delay or acceleration of condensation, polymerization reactions, etc. in the coating solution and for solidification

solid layer.

12. The method according to any one of claims 1 to 11, characterized in that the area of the lower edge of the extrusion slot molder is supplied by a first process gas is flushed with a gas composition adapted to the coating solution, either as a protective gas or gas with reactive components.

13. The method according to any one of claims 1 to 12, characterized in that the applied coating solution is surrounded or flushed around in successive work steps by further process gases that are different from the first process gas.

14. The method according to any one of claims 1 to 13, characterized in that the solvent of the coating solution is evaporated by means of one or more process gases and other volatile reaction and decomposition products are absorbed and removed.

15. The method according to any one of claims 10 to 14, characterized in that the process gases used consist of one or more inert or inert

Carrier gases, preferably nitrogen, and optionally consist of mixed reactive vapors and gases.

16. The method according to any one of claims 10 to 15, characterized in that gaseous water vapor is present in the process gases in a concentration of the relative

Process gas density is contained in the range of approximately 20% to 90%, preferably 20% to 80%.

17. The method according to one of claims 10 to 16, characterized in that the concentrations of the reactive vapors and gases are mixed in the process gases depending on the process engineering reaction requirements, preferably in a total concentration of less than 20%, preferably less than 15% (percentage by volume).

18. The method according to any one of claims 10 to 17, characterized in that the process gases are discharged after contact with the applied liquid layer and their composition is measured for control purposes.

19. The method according to one of claims 1 to 18, characterized in that in the area of application of the process gases, optionally IR and UV radiation sources are also used to produce radiation-inducing material reactions in the coating.

20. The method according to any one of claims 1 to 9, characterized in that the coating of the substrate takes place in a continuous process.

21. The method according to any one of claims 1 to 20, characterized in that the coating process produces simple solid layers with layer thicknesses preferably less than 1 μm for optical coatings and other surface coatings.

22. The method according to claim 21, characterized in that the applied solid layer undergoes a final process in accordance with the manufacturing process

Process step, preferably subjected to a thermochemical or pyrolytic treatment to produce a desired optically effective or other desired surface finish.

23. The method according to any one of claims 1 to 22, characterized in that plate-shaped substituents are applied to plate-shaped substituents on one or two sides, both simply and with two or more layers one above the other, each with the same or different solid layer thicknesses.

24. The method according to one of claims 1 to 23, characterized in that as

The substrate is a flat glass, e.g. float glass, cast glass with any regular and/or stochastically structured surfaces, e.g. with finely hammered surfaces, or smooth or polished plate-shaped metal, plates made of mineral materials or other transparent or non-transparent plates.

25. The method according to one of claims 1 to 24, characterized in that

Substrates translucent plate-shaped substrates made of plastic, preferably made of polymethyl methacrylate, polycarbonate, polystyrene can be used.

26. Coating process for coating plate-shaped, in particular transparent, preferably large-area substrates, such as flat glass or plastic glass, preferably with thin, transparent layers for optical coating and other transparent surface coatings, by applying a solvent-based coating solution to a substrate, in which process the coating solution from a

Extrusion wide slot caster (15) is poured in the direction of gravity onto the substrate (21) underneath and the substrate and extrusion wide slot caster are moved relative to one another in a specific transport direction, characterized in that the extrusion wide slot caster is surrounded by a process gas atmosphere at least in the area of the outlet opening.

27. The method according to claim 26 and at least one of claims 1 to 25.

28. Using a device (11).

- A support on which a substrate to be coated can be arranged

- an extrusion wide gun caster (15) with a preferably uninterrupted gap-shaped outlet opening, which is arranged above the support,

- a reservoir for holding a coating solution,

- at least one connection line and optionally a metering pump (35) between the reservoir and the extrusion slot molder,

- a transport device (13) for effecting a relative movement of the support and the coating tool in a transport direction (17), for the continuous coating of transparent, large-area plate-shaped substrates (21), in particular substrates such as flat glass, with low-viscosity coating solutions with a viscosity <10 mPas (MUUPascalseconds).

29. Use according to claim 28, characterized in that at least one

Device is provided to flush the extrusion wide gun caster with a process gas atmosphere at least in the area of the outlet opening.

30. Use according to claim 28 or 29, characterized in that a metering and / or pressure maintaining device (35) is provided, which is connected to the extrusion wide gun caster (15).

31. Use according to one of claims 28 to 30, characterized in that at least one gas processing device (63) connected to the chamber (37) via a line is provided for mixing inert and / or reactive gas components.

32. Use according to one of claims 28 to 31, characterized in that at least two connections are provided on the chamber for supplying and discharging a process gas or gas mixture, at least one of which is connected to the gas processing device (63).

33. Use according to one of claims 28 to 32, characterized in that the chamber (37) is divided into at least two reaction spaces, a coating chamber (44) and a drying chamber (45).

34. Use according to one of claims 28 to 33, characterized in that surface emitters, e.g. IR and/or UN radiation sources, are arranged in the chamber (37) at a distance from the transport device.

35. Use according to one of claims 28 to 34, characterized in that the extrusion wide gun caster (15) has a long, preferably continuous and approximately the width of the substrate to be coated

Has wide slot gap (27).

36. Use according to one of claims 28 to 35, characterized in that the gap width of the wide slot gap (27) can be adjusted depending on the properties of the coating solution.

37. Use according to one of claims 28 to 36, characterized in that the transport device (13) has a preferably movable support (19). to which the substrates (21) can be fixed.

38. Use according to one of claims 28 to 37, characterized in that the slot width of the extrusion slot molder (15) can be adjusted to a value of less than 1.2 mm, preferably between approximately 0.02 and 0.8 mm.

39. Use according to one of claims 28 to 38, characterized in that the distance between the transport device (13) or. Support (19) and the lower edge of the extrusion slot molder (15) adjust. is adjustable.

40. Use according to one of claims 28 to 39, characterized in that the extrusion wide gun caster (15) is arranged in a plane which is essentially perpendicular to both the conveying direction (17) of the substrate (21) and perpendicular to the support surface.

41. Use according to one of claims 28 to 40, characterized in that the extrusion wide gun caster (15) is above the transport device (13) or. of the support (19) is arranged.

42. Use according to one of claims 28 to 41, characterized in that the extrusion wide gun caster (15) is arranged to be pivotable about an axis (30) running parallel to the wide slot.

43. Use according to one of claims 28 to 42, characterized in that the transport device has adjustable drive means in order to transport the substrate at a specific, constantly adjustable speed - preferably between 2.0 to 30.0 m / min.

44. Use according to one of claims 28 to 43, characterized in that a hardening oven (59) or

Final treatment device for the coating of the plate-shaped substituents is arranged.