METHOD FOR PRODUCING A LOW-EMISSIVITY SYSTEM

Abstract

A method for producing a low-emissivity layer system on at least one side of the substrate includes the steps of providing the substrate, forming at least one low-emissivity layer on at least one side of the substrate by a deposition process and briefly tempering at least one deposited layer. The electromagnetic radiation used for briefly tempering a low-emissivity layer is adjusted in such a manner that the tempered layer has layer properties comparable to those of a conventionally heat-treated low-emissivity layer of a safety glass.

Description

The invention relates to a method for producing a low-emissivity layer system on at least one side of the substrate in accordance with the preamble of claim 1.

The invention relates to the production, in particular to the tempering, of low-emissivity, thin layers, e.g. silver layers, which are used in the field of thermal insulation of window and façade glasses. The specific low-emissivity coatings, also called low-e coatings for short, are used for producing heat transfer. The low-e coating is distinguished by the fact that it has a low thermal emissivity and the coating is moreover largely transparent in the visible spectral range. With the thermally insulating coatings the aim is to ensure, on the one hand, that the solar radiation can pass through the pane and heat the building, while only little heat at room temperature is emitted from the building to the environment. In a further application, the low-e coating is intended to prevent an energy input from the outside toward the inside.

The coatings used for this purpose comprise for example transparent, metallic systems, in particular silver-based multilayer systems, which have a low emissivity and thus a high reflection in the infrared range of light, in conjunction with a high transmissivity of the entire layer system in the visible spectral range. The transparent metallic layers are generally designated as IR reflection layers, for differentiation.

By contrast, glass and other nonmetallic substrate materials generally have a high emissivity in the infrared spectral range. This means that they absorb a high proportion of the thermal radiation from the environment and at the same time, according to their temperature, also emit a large amount of heat to the environment.

The method used for producing a low-e coating of the substrate is generally a vacuum method, such as evaporation methods or sputtering technology. Depending on safety specifications, in addition to the low-e coating the glasses used also have to be processed further to form safety glass. As is known, for this purpose they are thermally prestressed by heating and cooling being conducted in a specific way. However, since this means additional costs, the sheets processed to form safety glass are generally only those for which this is prescribed for their use. A large proportion of the sheets remain untreated in this regard.

The customary procedure for this purpose, in a so-called tempering process, is for the already coated glasses to be greatly heated above their softening point, typically to 680-720° C., and then rapidly cooled. The stresses specifically frozen in this way in the glass bring about—in the case of breaking—shattering into many tiny glass fragments without sharp edges.

In the course of this heat treatment, however, the optical properties of the multilayer system, such as e.g. the reflection color or transmission, in particular in the visible range of the electromagnetic spectral, also change as a result of temperature-dictated diffusion processes and chemical reactions. These changes are disadvantageous, however, since untreated and treated sheets are installed alongside one another for cost reasons, optical differences being extremely disturbing. According to the prior art, therefore, attempts are made to fashion the low-e layer systems in such a way that the changes in the optical and thermal layer properties on account of the heat treatment of the coated substrate remain minimal, at least in a range such that visually no difference can be ascertained.

Furthermore, in the course of thermal treatments per se annealing processes take place in the active layers. These extremely thin layers usually cannot be deposited ideally conformally and tend toward dewetting, which results in a corrugated, i.e. nonuniform, layer thickness distribution. However, this energetic limitation of growth is partly compensated for by the top layers, with the result that diffusion processes and the leveling of the silver layers occur during a downstream temperature increase. This results from the shift in the surface energy equilibrium in favor of a wetted configuration. These layers having a homogeneous thickness are distinguished by a corresponding decrease in the sheet resistance and afford the advantage of increased reflection in the infrared range of light and thus a reduced emissivity.

However, the thermally prestressed substrates are no longer configurable. That means that, in contrast to what is customary for glass, they can no longer be shaped by means of scribing and breaking or mechanically processed in some other way. Furthermore, microscopic defects such as microcracks in thermally prestressed sheets can lead to spontaneous cracking In order to prevent this risk, such sheets for specific applications have to be subjected to a heat soak test, i.e. a test involving the heat soak process for single-pane safety glass.

In order to ensure the configurability of the glass, endeavors are made, in RTP, to heat only the functional layer, i.e. the low-e layer, alone, without changing the substrate. The term “RTP” (“rapid thermal processing”) is taken to mean a rapid thermal treatment. The prior art discloses in this respect experiments with lasers, for example from the document WO 2010/142926 A1, which operate in the near infrared range, called IR range below. In the infrared range, however, the absorption coefficient of the low-e layers is relatively low, with the result that higher power densities of the electromagnetic radiation are required in order to obtain a sufficient temperature in the low-e layers.

The invention is therefore based on the object of providing an efficient method for producing a low-emissivity layer system on at least one side of the substrate, which reduces the sheet resistance and thus the emissivity of the low-emissivity coating. Furthermore, the intention is to reduce the use of costly IR-reflecting coating material, such as silver, for the same thermal and optical properties without expensive heat treatment of the entire low-e coated substrate and with the configurability thereof being maintained. In this case, the optical and thermal properties of untempered layer systems are intended to be matched to tempered systems without the risk of spontaneous glass breaking

This object is achieved according to the invention by means of the characterizing features of claim 1. Further embodiments of the invention are evident from the associated dependent claims.

According to the invention, after the deposition of the at least one low-emissivity layer on at least one side of the substrate, at least one transparent metallic IR reflection layer of a low-emissivity layer system, designated here as low-emissivity layer, is briefly heated by means of electromagnetic radiation while avoiding immediate heating of the entire substrate, in a brief tempering step. In this case, the electromagnetic radiation for brief tempering is set in such a way that the low-emissivity layer which is tempered by electromagnetic radiation has layer properties, in particular optical and/or thermal layer properties, comparable or identical to those of the conventionally heat-treated low-emissivity layer of a safety glass. The wording “the conventionally heat-treated low-emissivity layer of a safety glass” is taken to mean a heat treatment for thermal prestress in the process for processing a glass to form the safety glass.

It has been found that in the case of subsequent tempering of a low-e layer deposited on the substrate, by means of the electromagnetic radiation adapted to the material properties of the low-e layer, it is possible to achieve a significant reduction in the sheet resistance of the coating and, in a manner correlating therewith, a decrease in the emissivity, i.e. the heat emission, by approximately 20-30%. The optical properties, such as reflection colors and transmission, also change in the manner that would also be the case in a conventional thermal treatment. It is thus possible for low-e layer systems on simple glazing to be adapted in a targeted manner in terms of their visible appearance and their emission properties to those of heat-treated low-e layer systems on thermally prestressed safety glass, such that both can be used alongside one another without any discernible difference and at the same time the requirement for the production of safety glass can be numerically reduced to a significant extent.

One advantage of the brief tempering of the low-emissivity layer is, moreover, that, on account of the low heat capacity of the low-emissivity coating and the relatively short time of action, separate cooling of the coated substrate does not become necessary and the substrate is not processed to form safety glass during the brief tempering step. Preferably, the coated layer is irradiated from the layer side, in order to avoid absorption of the electromagnetic radiation for brief tempering, in particular in the UV range, by the substrate and thus heating of the substrate. That results in a substrate which is processable and conventionally configurable.

In one advantageous embodiment of the invention, the step of briefly tempering the low-emissivity layer by means of electromagnetic radiation is carried out at an emission wavelength of the electromagnetic radiation at which the electromagnetic radiation is at least partly absorbed by the deposited low-e layer and converted into heat. As a result of the at least partial absorption of the electromagnetic radiation, the low-emissivity coating is tempered to a specific temperature and thus restructured in such a way that its thermal and/or electrical and/or optical properties change, wherein for example in comparison with the low-emissivity layer before the brief tempering, its sheet resistance decreases and, if appropriate, its transmission in the visible range or reflection in the infrared also increases. Preferably, the emission wavelength of the electromagnetic radiation in the brief tempering step is set or adapted to the material of the low-emissivity layer in such a way that the emission wavelength of the electromagnetic radiation is realized in an absorption range of the low-e layer. A targeted increase in temperature of the irradiated low-emissivity layer can be achieved as a reuslt.

In one advantageous embodiment of the invention, the low-emissivity layer is thermally treated in the brief tempering step at an emission wavelength of the electromagnetic radiation in the range of 250 nm to 1000 nm, advantageously at an emission wavelength of the electromagnetic radiation in the range of 250 nm to less than 500 nm and/or in the range of 500 nm to 1000 nm. In this case, the tempering of the low-emissivity layer is preferably carried out in the range of the emission wavelength of the electromagnetic radiation of 250 nm to 350 nm and/or in the range of 650 nm to 850 nm.

These emission wavelength ranges of the electromagnetic radiation correspond to the ranges of the absorption maxima of the low-emissivity layer, which are in the range of approximately 250 to 350 nm and 650 to 850 nm. The thermal treatment of the coated low-emissivity layer by irradiation with emission waves in these ranges makes it possible to reduce the emissivity and/or the sheet resistance in comparison with the low-emissivity layer before the brief tempering step. In this case, the range of 250 nm to less than 500 nm is advantageous since in this range the low-e layer absorbs significantly more radiation, approximately by a factor of 2, than in the range of 650 nm to 850 nm. It is thereby possible to achieve activation with lower power densities. The range of 250 nm to less than 500 nm can likewise be implemented better from a technological standpoint.

Preferably, the electromagnetic radiation for the brief tempering step is set in such a way that the deposited layer will receive or absorb a predefinable energy input in the irradiation region. A predefinable final temperature of the low-emissivity layer in the irradiation region is achieved as a result of the predefinable energy input. In this case, the final temperature corresponds to the temperature of the deposited layer which leads to the annealing of the structural defects that arose either owing to the fluctuations in the coating conditions and/or in the temperature insufficient for the production of stable layers, and which does not cause damage to the deposited layer. The energy input is therefore set taking account of the respective highest possible layer temperature, i.e. maximum temperature of the deposited layers. A predefined crystal structure and morphology of the deposited low-e layer is thus possible as a result.

The energy input of the irradiation is preferably set taking account of the parameters of the laser radiation, such as its wavelength, energy density and area of action, and the temperature of the deposited layer, or from the temperature of the deposited layer and of the substrate. This is particularly important during irradiation of an emission wavelength of the radiation in or near the UV range. In this wavelength range, the radiation is also absorbed well by the substrate, for example composed of glass, which can result in heating of the substrate. By taking account of the temperature of the substrate and the wavelength of the radiation when setting the energy input of the radiation, it is possible to minimize the heating of the substrate when setting the layer properties of the deposited layer. The low-e layers treated in this way in the brief tempering step afford the advantage of increased reflection in the infrared range of light and hence a reduced emissivity.

In one advantageous embodiment of the invention, the energy input is set by means of the energy density, i.e. power, area of action of the electromagnetic radiation and the transport speed of the coated substrate at which the latter is guided across below the device which generates the electromagnetic radiation. Since the brief tempering step is carried out in the deposited low-e layer, the latter can be treated in a targeted manner with a significantly higher energy input, i.e. can be heated to significantly higher temperatures, while the actual substrate material, on account of its low thermal conductivity, heats up only slightly or to a significantly lower temperature with a distinct temporal delay.

In a further advantageous embodiment of the invention, the electromagnetic radiation for brief tempering is set in such a way that it has a linear intensity distribution perpendicular to the transport direction of the substrate. In this case, the length of the linear intensity distribution of the electromagnetic radiation for brief tempering corresponds at least to the width of the layer deposited on the substrate in the direction of the longitudinal extent of the linear intensity distribution of the electromagnetic radiation. As a result, regions of the low-emissivity layer system are simultaneously briefly irradiated and cooled in the longitudinal extent of the linear intensity distribution, which leads to a homogeneous structuring of the low-e coating in the irradiated region. Consequently, the method according to the invention enables targeted, selective heating and influencing of the layer properties of the low-emissivity coating in one method step.

A further advantageous is the avoidance of relatively expensive beam deflecting devices or x, y substrate manipulation, which would be necessary if the line width of the intensity distribution were smaller than the width of the layer deposited on the substrate in the direction of the longitudinal extent of the linear intensity distribution of the electromagnetic radiation or were smaller than the overlap regions at the interfaces of the sequentially activated regions. Preferably, both the length and the power density of the linear intensity distribution of the electromagnetic radiation for brief tempering are variable.

In accordance with the advantageous embodiment of the invention, the electromagnetic irradiation of the low-e layer is carried out by a linear laser. This has the advantage that a linear intensity distribution is achieved by means of a linear laser in a simple manner.

On the basis of one advantageous embodiment of the invention, the electromagnetic irradiation of the low-e layer is carried out by means of a plurality of lasers, preferably two linear lasers. In this case, the low-emissivity layer can be subjected to thermal aftertreatment by means of two linear lasers at an identical emission wavelength of the radiation or at two different wavelengths of the radiation.

This makes it possible to adapt the energy input to the process parameters, such as, for example, the absorption, maximum temperature of the low-emissivity layer, energy density of the laser and transport speed of the substrate, and to regulate them. As a result, the absorptance of the radiation absorbed by the substrate, for example in or near the UV range, can be regulated by the arrangement of a second laser having a different emission wavelength of the laser radiation, with the result that heating or excessively high heating of the substrate is avoided. In this regard, the low-emissivity layer can be treated by a laser at a wavelength from the wavelength range of 250 nm to less than 500 nm, preferably in the range of 250 nm to 350 nm, and by a second laser at a wavelength in the range of 650 nm to 850 nm. In this case, the irradiation takes place simultaneously or successively, independently in terms of the order.

In one embodiment of the invention, two linear lasers are aligned on a line perpendicular to the transport direction. A first linear laser is focused onto a planar substrate plane on the side of the low-emissivity coating, and the second linear laser is defocused. During transport of a substrate through the installation, the distance between the laser and the substrate surface to be treated varies on account of the transport itself or on account of the bending of the substrate. This leads to an inhomogeneous treatment of the substrate surface and thus to the differing color appearance of the coated substrate. This arrangement of the two linear lasers enables the energy density of the radiation and thus the energy input to be kept as constant as possible in the case of small and also in the case of larger variations of the distance up to +/−5 mm. An arrangement of more than two linear lasers, which are in part focused and in part defocused, is also conceivable.

In a further embodiment of the invention, the linear laser is constructed from a plurality of lasers with a corresponding optical system. As a result, the individual lasers can be in part focused and in part defocused in order to compensate for a distance variation between the laser and the substrate surface to be treated, with the result that the energy input remains constant during irradiation.

In accordance with an alternative embodiment of the invention, the electromagnetic irradiation of the low-e layer is carried out by continuously emitting diode or diodes. This affords the advantage of a high efficiency and of directional emission, which enables focusing along a line with very low losses at a processing speed of approximately 10 m/min for laser powers of 500 W/cm. A further positive aspect is the capability of regulating the power of said diodes for the purpose of rapid adaptation to the respective process.

In accordance with a further alternative embodiment of the invention, the electromagnetic irradiation of the low-e layers is carried out by movement past a CW gas discharge lamp (CW—continuous wave).

In accordance with a further alternative embodiment of the invention, the electromagnetic irradiation of the low-e layers is carried out by means of an electron beam.

In accordance with one embodiment of the invention, at least one low-e layer contains silver or consists thereof. Thin silver films in a wetted configuration are transparent in the solar and/or visible spectral range and at the same time highly reflective in the infrared wavelength range. In the production method, conventionally, thin silver layers usually cannot be deposited ideally conformally and tend toward dewetting. This results in a corrugated, not ideally uniform layer thickness distribution, which is highly disadvantageous for thermally insulating coatings. According to the invention, whole-area wetting and thus smoothing of the silver layers already takes place as a result of the subsequent thermal treatment of the layer in the brief tempering step by means of electromagnetic radiation and thus independently of the deposition of further layers on account of the diffusion processes caused by the temperature increase.

It is conceivable, however, that the low-emissivity layer comprises or consists of other materials, provided that the latter have a low thermal emissivity—deemed to be acceptable for low-e layer systems—in the infrared range in conjunction with a high transmittance in the visible spectrum.

In accordance with one advantageous embodiment of the invention, the substrate is composed of glass as the principally used substrate of low-e layer systems. Its high absorption in the IR range becomes less important on account of the process implementation as brief tempering with limitation and, if appropriate, with monitoring of the layer temperature and thus substrate temperature, since temporally dictated heating of the substrate can thus be ruled out to the greatest possible extent.

In a further advantageous embodiment of the invention, the method comprises, in the step of forming at least one low-emissivity layer, a plurality of layers for forming a low-emissivity layer system. In this case, the layers can be thermally treated by means of electromagnetic radiation in the brief tempering step of the low-emissivity layer or/and in a further brief tempering step. Preferably, the low-emissivity layer system comprises at least two dielectric layers. A low-e silver layer is preferably arranged between at least two dielectric layers.

In one advantageous embodiment of the invention, both the coating and the brief tempering step of the deposited low-e layer are carried out by means of electromagnetic radiation in an inline vacuum coating installation. With regard to the present invention, an “inline process implementation” means that the substrate is physically transported from a coating station to the further processing station, in order to be able to apply and treat layers, the substrate also being transported further during the coating process and/or laser irradiation. In this case, the substrate is preferably moved at a transport speed such that it does not heat up all that much. The method can be operated in continuous installations with a continuously transporting substrate belt, either an endless substrate and roll-to-roll coating or a quasi-continuous sequence of synchronously moved, successive planar at package-type substrates.

The invention will be explained in greater detail below on the basis of the exemplary embodiment. In the associated drawings:

FIG. 1 shows a schematic illustration of the installation system for combined coating and subsequent thermal treatment by means of a laser system;

FIG. 2 shows transmission (T) and reflection (R) spectra from the layer side (Rf) and glass side (Rg), in each case before (ac) and after (laser) the thermal treatment of the low-e layer, and

FIG. 3 shows a table 1 having a quantitative analysis of the results.

The specific process steps and apparatuses described in detail below should be understood merely as illustrative examples. Therefore, the invention is not restricted to the process parameters, apparatuses and materials mentioned here.

FIG. 1 shows the schematic construction of the installation system 1 for combined coating and subsequent thermal treatment by means of a laser system 50. It consists of a longitudinally extended vacuum installation 1 comprising a substrate transport system 11, by means of which the large-area substrates 10 are moved through in a transport direction below various processing stations, inter alia coating modules 30. In a coating module 30, a low-e layer system 20 comprising at least one low-e layer is applied to the substrate 10. A plurality of low-e layers are also conceivable.

After coating has been carried out, the substrate 10 provided with the layer system 20 is brought into a position for treatment by a laser system 50. In this case, the laser system 50 consists of a linear laser, such that a linear intensity distribution perpendicular to the transport direction of the substrate is achieved in a simple manner. In this case, the length of the linear intensity distribution of the electromagnetic radiation of the laser corresponds to the width of the layer deposited on the substrate in the direction of the longitudinal extent of the linear intensity distribution of the electromagnetic radiation. After the thermal treatment has been carried out, the deposited substrate 10 can subsequently be transported to a further processing station 31 or the thermal treatment can be repeated.

Optionally, the installation 1 has a regulation 41 of the energy input of the brief tempering of the low-e layer system. In this case, the regulating variable corresponds to an energy input required for obtaining a predefinable final temperature of the low-e layer system in the subsequent step of thermal treatment. In this case, it is necessary to attain the final temperature of the deposited layer system 20 within specific limits, by carrying out a setting and thus the improvement of its layer properties, such as, for example, transmission, reflection and resistance, rather than a destruction of the structure, such as embrittlement, caused on account of the maximum temperature of the deposited layer being exceeded.

In this regard, the setting of the energy input of the irradiation can be carried out taking account both of the parameters of the laser radiation, such as its wavelength, energy density and area of action, and of the temperature of the deposited layer, or from the temperature of the deposited layer and of the substrate. For this purpose, an arrangement of the temperature measuring means 40 in the installation 1 and a temperature measurement before the brief tempering step are conceivable.

The determined value of the energy input is communicated to the laser system 50 via the control device 41 and serves as a regulating variable for determining the parameters of the brief tempering step and for carrying out the subsequent brief tempering step. That means that the parameters of the brief tempering step, such as wavelength, duration, type and manner of the electromagnetic radiation, are adapted in such a way that the layer system to be treated receives the determined energy input and, as a result, the low-e layer attains the predefinable final temperature.

Exemplary Embodiment

A glass substrate having dimensions of 10×10 cm² is introduced into a vacuum chamber and coated with a temperable single-low-e layer stack having a silver layer between two dielectric cover layers. The sample constitutes a commercially available layer system. In order to improve the optical properties, the low-e layer stack is irradiated by a linear laser system at a wavelength of 980 nm, with a focus of 100 μm and a power density of 375 W/mm². Its scanning speed is set at 9.5 m/min. An exposure duration of 570 μs and an energy input of 0.21 J/mm² of the laser irradiation are achieved from this. The sheet resistance of the low-e layer stack before and after irradiation is determined by an eddy current measuring device, since direct contact cannot be made with the silver layer through the dielectric cover layers. The irradiation of the low-e layer stack results in a reduction of the sheet resistance of the low-e layer from 7.5 ohms to 5.6 ohms. The reduction of the sheet resistance indicates a densification and homogenization of the silver layer, which constitutes the characteristic feature of the expected improvement in the emissivity.

FIG. 2 illustrates the respective transmission and reflection spectra of the sample. In this case, the letter “T” corresponds to the transmission spectrum of the sample before (ac) and after irradiation (laser), and the letter “R” corresponds to the reflection spectrum before the layer side (Rf) and the glass side (Rg) before (ac) and after irradiation (laser). The comparison of the given spectra reveals a significant increase in transmission in the visual spectral range and an advantageous higher reflection in the infrared wavelength range.

The quantitative analysis of the results is illustrated in table 1. The analysis is based on the CIE Lab color model, which is known in the prior art and which is used for color determination and according to which the values L*, a*, b* correspondingly denote the brightness value, the red-green value and the yellow-blue value. The value ΔE* indicates the distance between L_ac*, a_ac*, b_ac* and L_laser*, a_laser*, b_laser* by virtue of the fact that ΔE*=((ΔL*)²+(Δa*)²+(Δb*)²)^1/2, wherein ΔL*=L_laser*−L_ac*, Δa*La_laser*−a_ac*, Δb*=b_laser*−b_ac*.

In this case, the index “ac”, in accordance with FIG. 2, denotes the determined values of the coating or the coated article before irradiation, i.e. before the brief tempering step, and the index “laser” denotes the values of the coating or the coated article after the brief tempering step. The numbers used are those which are calculated by means of the CIE LAB L*, a*, b* coordinate technique. The value “Y” corresponds to the green (and lightness) value in the XYZ color space.

As illustrated in table 1, the resistance improvement leads to a reduction of the emissivity extrapolated from the spectra from 9% to 7%, which results in a reduction of the emissivity by 27%. In this case, the simultaneous shift in the color values is comparable with the values which result from a convection tempering process. Therefore, the optical impression can be matched, independently of whether or not the panes were tempered to form safety glass. A major advantage besides purely saving costs is in this case the maintenance of the configurability of the laser-tempered pane and thus the significantly easier processability.

The method according to the invention is thus more energy-efficient and associated with fewer breaking losses in comparison with conventional convection furnaces. The color shift achieved by the method in the low-emissivity layer system is congruent with the values observed for conventional heat treatments for thermally prestressing substrates, which equalizes optical differences and enables parallel mounting of both panes.

LIST OF REFERENCE SIGNS

• 1 Coating installation system
• 2 Vacuum installation
• 10 Substrate
• 11 Transport system
• 20 Coating system/layer
• 30 Coating module/coating station
• 31 Processing module/processing station
• 40 Means for temperature measurement
• 41 Means for regulating the energy input of the device for brief tempering
• 50 Laser system

Claims

1. A method for producing a low-emissivity layer system on at least one side of a substrate, comprising the steps of

providing the substrate,

forming at least one transparent metallic IR reflection layer of the low-emissivity layer system on at least one side of the substrate by deposition,

subsequently briefly tempering at least one deposited layer by electromagnetic radiation while avoiding immediate heating of the entire substrate,

wherein the at least one transparent metallic IR reflection layer is briefly tempered, wherein the electromagnetic radiation for brief tempering is set in such a way that sheet resistance and thus absorption in an infrared spectral range and/or a transmission in a visible spectral range and/or spectral reflection of the low-emissivity layer system are set to values such as those of a conventionally heat-treated low-emissivity layer system of a safety glass.

2. The method as claimed in claim 1, wherein the step of briefly tempering the transparent metallic IR reflection layer by electromagnetic radiation is carried out at an emission wavelength of the electromagnetic radiation at which the electromagnetic radiation is at least partly absorbed by the deposited transparent metallic IR reflection layer.

3. The method as claimed in claim 1, wherein the step of briefly tempering the transparent metallic IR reflection layer is carried out at an emission wavelength of the electromagnetic radiation in the range of 250 nm to less than 500 nm and/or in the range of greater than 500 to 1000 nm.

4. The method as claimed in claim 1 wherein the electromagnetic radiation for brief tempering is set in such a way that the transparent metallic IR reflection layer receives a predefinable energy input in the irradiation region.

5. The method as claimed in claim 1, wherein the electromagnetic radiation for brief tempering is set in such a way that it has a linear intensity distribution perpendicular to the transport direction of the substrate.

6. The method as claimed in claim 1, wherein length of a linear intensity distribution of the electromagnetic radiation for brief tempering corresponds at least to a width of the transparent metallic IR reflection layer deposited on the substrate in a direction of a longitudinal extent of the linear intensity distribution of the electromagnetic radiation.

7. The method as claimed in claim 6, wherein both the length and power density of the linear intensity distribution of the electromagnetic radiation for brief tempering are variable.

8. The method as claimed in claim 1, wherein the electromagnetic irradiation of the low-emissivity layer is carried out by one or more lasers.

9. The method as claimed in claim 8, wherein energy input received by the low-emissivity layer in the irradiation region is regulated by ratio of energy density of the one or more lasers involved in the irradiation.

10. The method as claimed in claim 8, wherein at least one laser is focused onto a planar substrate plane, on the side of the transparent metallic IR reflection layer, and at least one laser is defocused.

11. The method as claimed in claim 1, wherein the electromagnetic irradiation of the transparent metallic IR reflection layer is carried out by continuously emitting diodes, by a CW gas discharge lamp or by an electron beam.

12. The method as claimed in claim 1, wherein the step of forming at least one low-emissivity layer comprises forming a plurality of layers for forming a low-emissivity layer system.

13. The method as claimed in claim 1, wherein the at least one transparent metallic IR reflection layer comprises silver.

14. The method as claimed in claim 1, carried out in an inline vacuum coating installation.

15. A low-emissivity layer system produced according to the method as claimed in claim 1.

16. The method as claimed in claim 3, wherein the emission wavelength of the electromagnetic radiation lies in a range of 250 nm to 350 nm and/or in a range of 650 nm to 850 nm.

17. The method as claimed in claim 8, wherein the one or more lasers comprise linear lasers.

18. The method as claimed in claim 1, wherein the at least one transparent metallic IR reflection layer comprises consists of silver.