CH645604A5 - HEAT REFLECTING, TITANIUM DIOXIDE COATED DISC AND METHOD FOR THE PRODUCTION THEREOF. - Google Patents

Description

The invention relates to a heat-reflecting pane according to the preamble of claim 1 and to a method for producing such a pane according to the preamble of claim 6.

Heat-reflecting panes, in which a heat-reflecting TiO 2 layer is applied by vapor deposition of a titanium layer in vacuo and subsequent oxidation of this layer at higher temperatures in air, are known and are, for example, in a publication by G. Hass with the title “Preparation, Properties and Optical Applications of Thin Films of Titanium Dioxide »(G. Hass, Vacuum, Vol. 11, No. 4, pages 331-345 [1952]). Depending on the conditions under which the Ti layer is evaporated in a vacuum, the subsequent oxidation of the Ti layer in air produces two Ti02 modifications. If the titanium is quickly vapor-deposited in a good vacuum, that is to say at a vacuum of = 1.333 · 10 ~ 3 Pa or better, the rutile modification is formed, while in the case of relatively slow evaporation with a poorer vacuum, for example about 1.333 • 10 ~ 2 Pa, the anatase modification arises. TiOz layers produced in this way have found various optical applications for coating glass panes, for example as a light splitter and as a coating reflecting solar radiation, the layer thickness for achieving the highest possible reflection as a quarter-wavelength interference layer - based on that spectral range in which a modification of the reflection properties of the substrate is desired - trained.

A special application for heat-reflecting panes of the type mentioned at the outset is that panes of this type can be used in facade elements or parapet panels. With such parapet panels, Ti02-coated glass panes are desired, which are characterized by a high, color-neutral reflection - possibly with a light blue or yellow tone - in the visible spectral range. In such parapet panels, the TÌO2 interference layer is generally arranged on the outside of the building, while the rear of the glass pane is provided with an opaque enamel or a varnish to prevent the view of parts of the building behind the parapet panel.

In particular for the latter application s

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TiCh layers with a rutile structure are of considerable advantage because TiCh layers of the rutile modification have a higher refractive index than anatase layers, which means that higher reflection values can be achieved with facade elements or parapet panels. In addition, it has been shown that rutile layers have much higher hardness and abrasion resistance than anatase layers. Therefore, panes in which the TiCh interference layer arranged on the outside of the building has a rutile modification can be exposed to the outside atmosphere for a long time without damage. In addition, the cleaning agents generally used for glass outer surfaces can be used to clean such panes or parapet panels.

In various applications of TiCh-coated panes of the type mentioned, in particular when used as a facade element or parapet panel, it is necessary to toughen the glass to comply with the safety regulations. This type of tempering is necessary if the parapet panels provided with rutile layers are enamelled on the back: In this case, the glass can heat up so strongly when exposed to sunlight through the radiation-opaque enamel layer that heat jumps occur without prestressing the glass substrate. The tempering of the glass is then carried out in a known manner by heating the glass above the transformation temperature to softening temperatures and subsequent shock-like cooling. For soda-lime-silicate glasses with the chemical composition of conventional flat glasses, temperatures of 570 to 620 ° C are required for this.

In the production of heat-reflecting panes of the type mentioned at the outset, the pretensioning can in principle be carried out in two different ways. On the one hand, it is possible to advantageously combine the tempering process with the oxidation of the Ti layer which has been vacuum-deposited. However, it is of course also possible to first oxidize the vapor-deposited Ti layer at the temperatures sufficient for this, for example 400 to 500 ° C, then to cool the glass pane provided with the TiO: layer and finally only in a further process step in a further oven heating to the temperature required for tempering - in the case of soda-lime-silicate glasses - 570 ° to 620 ° C.

In principle, it is of course desirable to be able to carry out the oxidation of the Ti layer to TiO: in a rutile modification in the shortest possible time. It is known - G. Hass, Vacuum, Vol. 11, No. 4, page 335, Fig. 3 - that the higher the oxidation temperature, the faster the oxidation takes place. However, if the oxidation temperature in the known method is increased to the values required for a rapid oxidation process, namely above about 550 ° C., layer changes occur in the rutile layers. The layers become dull and cloudy and scatter light both in transmission and in reflection to such a considerable extent that panes produced in this way can no longer be used for the applications mentioned, in particular as parapet panels or as facade elements. Oddly enough, the above-mentioned layer changes only occur with rutile layers. If other vacuum evaporation conditions are used, in particular a poorer vacuum and / or slower evaporation speed, the oxidation in the manner already described leading to TÌO2 layers with anatase structure, panes coated in this way can also be used at higher temperatures, such as 550 ° C and more, heat up without causing the described layer changes. The same difficulties, namely that the rutile layers undergo layer changes, naturally also occur whenever the panes are to be thermally tempered in the manner described above, since temperatures above about 550 ° C., in In the case of soda-lime silicate glasses, preferably 570 ° to 620 ° C, are required. These disadvantageous layer changes occur when the panes are heated to the temperatures required for thermal tempering, irrespective of whether the oxidation of the Ti layers to TiO2 layers and the heating to the tempering temperature take place in one step or the Ti layers initially at one Relatively low, below 550 ° C temperature oxidized and only then, if necessary after further processing, the panes are heated to the temperatures required for thermal tempering.

To solve the problem of creating heat-reflecting panes of the type mentioned at the outset, which are particularly suitable as parapet panels or facade elements, and a method for their production in which the TiO 2 layers have at least predominantly a rutile structure and in which the occurrence of the disruptive layer changes when heated DE-AS 26 46 513 proposes that temperatures of above 550 ° C, which are necessary for rapid oxidation of the Ti layer, in particular for thermal tempering, be effectively prevented that between the glass pane and the TÌO2- A vapor-deposited silicon oxide layer which does not cause interference is arranged, the method according to DE-AS 26 46 513 being characterized in that a silicon oxide layer which does not cause interference is vapor-deposited onto the glass pane before the Ti layer is vapor-deposited; and that the glass pane coated in this way is heated in air for oxidation.

As an alternative to this, the object defined above according to DE-OS 27 57 750 is achieved by the generic heat-reflecting pane and by the generic method for its production. DE-OS 27 57 750 is therefore based on the knowledge that it is possible to avoid the disadvantageous layer changes of the TiO 2 layer with a rutile structure when heated to temperatures above 550 ° C., as are required in particular for thermal tempering, if between an intermediate layer of T1O2 in anatase modification is arranged on the glass pane and the rutile layer. The two layers are produced in accordance with DE-OS 27 57 750 in such a way that a first Ti layer is first applied relatively slowly to the glass pane in a relatively poor vacuum and then a second Ti layer is then applied relatively quickly in a relatively good vacuum , then the subsequent oxidation by heating in air leads to the fact that the anatase intermediate layer is formed on the glass pane from the first Ti layer and the rutile layer from the second Ti layer. Further advantages of the generic heat-reflecting pane and of the generic method for its production as well as its relationship to the prior art can be seen from DE-OS 27 57 750, the description of which in this respect reference is made to avoid repetition.

In principle, the heat-reflecting disc and the method according to DE-OS 27 57 750 as well as the heat-reflecting disc and the method according to DE-AS 26 46 513 have proven themselves. However, in both cases, in the procedure according to DE-AS 26 46 513 stronger, if the teaching of the main patent is followed weaker, but still annoying, problems

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result when the heat-reflecting panes produced in this way have considerable optically disturbing deformations after the tempering process. Obviously, the tensions between the glass pane and the rutile layer are so strong, even with the generic heat-reflecting pane, that in the area where softening of soda-lime-silicate glass begins, the temperature of which is necessary for the thermal tempering, the pane is already considerably deformed. This resulted in deviations in flatness in the range of 3 to 5 mm per running meter edge length when prestressing such panes. Planarity deviations of this order of magnitude are generally not tolerable for parapet panels or facade elements, for which larger pane formats are almost exclusively required, since the distortions when reflecting buildings, for example, are too strong. Rather, flatness deviations of about 1 mm per running meter edge length are required as the highest tolerance limit for this purpose.

The invention is therefore based on the object of further developing the heat-reflecting pane and the method of the generic type in such a way that the usability of the heat-reflecting panes to be produced is improved in particular as parapet panels or facade elements by reducing the flatness deviations which occur during rapid oxidation or during prestressing.

According to the invention, this object is achieved by the measures mentioned in the characterizing part of patent claims 1 and 6. Particularly preferred embodiments of the heat-reflecting pane and of the method according to the invention result from the corresponding dependent claims.

In particular, it has proven useful to vapor-deposit the entire Ti coating without interrupting the coating process, if necessary using one and the same titanium-filled evaporator devices, with the desired and claimed inhomogeneous layer structure then being obtained by appropriate control of the vacuum conditions.

The invention is based on the surprising finding that, just as in DE-OS 27 57 750, it is not only the disadvantageous changes in the layer of the TiO 2 layer with a rutile structure that are achieved when heated to temperatures above 550 ° C., in particular for thermal tempering are to be avoided if the vapor deposition conditions are continuously changed during the vapor deposition of the titanium coating in such a way that the buildup of the TiO 2 layer formed in air after the oxidation changes - viewed from the glass pane - from the anatase modification to the rutile modification, that the portions of the TiO: layer adjoining the glass pane always have anatase structure, but with a density that is constantly increasing from the glass pane, and the portions adjoining the side of the TiOz layer facing away from the glass pane always have a rutile structure, but also that of the Heating to temperatures above 550 ° C occurring flatness deviations g egenüber heat-reflecting discs that are made according to the teaching of DE-OS 27 57 750 can be significantly reduced. The increasing density of the intermediate layer that assumes anatase modification during the later oxidation from the glass pane to the rutile layer can be determined, for example, by appropriate measurements of the refractive index and / or the layer hardness. It should be noted that the continuous increase in density according to the invention in the anatase intermediate layer continues from the glass pane into the rutile layer and can even extend over a large part of the total thickness of the rutile layer.

To produce the heat-reflecting pane according to the invention, as already mentioned, the procedure is as described in the characterizing part of patent claim 6. The titanium can then be evaporated at such a rate, while maintaining the set oxygen supply rate, that the total pressure during evaporation of the titanium layer drops into the 1.333-10 ~ 3 Pa range via the getter effect during evaporation. The conditions are chosen so that the layer formation begins under vacuum conditions, which lead to anatase modification in the subsequent oxidation of the titanium layer in air, and ends under such vacuum conditions that a rutile layer results.

The inhomogeneous layers obtained in this way, consisting of the intermediate layer with a continuous increase in density in the specified direction and the rutile layer, have practically the same surface hardness as layers produced according to the teaching of DE-AS 26 46 513 or DE-OS 27 57 750 if only the top layers with an exclusive rutile structure have a thickness of at least 8-10-9 m. The Ti02 layer systems produced according to the invention show no crack formation when soda-lime-silicate glasses coated in this way are heated to temperatures> 550 ° C., as are required for the rapid oxidation of the titanium layer or titanium layers or for tempering the glass.

Further details and advantages of the invention will become apparent from the following description, in which two exemplary embodiments, with respective comparison tests, are explained in detail with reference to the schematic drawing. The drawing shows:

Fig. 1 The structure of a first embodiment of a heat reflecting disc according to the invention in section; and

Fig. 2 shows a second embodiment of a heat reflecting pane according to the invention, also in section perpendicular to the plane of the pane.

As can be seen in FIG. 1, the heat-reflecting pane shown there has a glass pane 10, in particular made of soda-lime-silicate glass, on which, as in DE-OS 27 57 750, a Ti02 layer system is arranged, which has one on the glass pane 10 adjoining intermediate layer 12 made of TiO 2 in anatase modification and a TiO 2 layer 14 in rutile modification arranged on the side of the TiO 2 layer 12 facing away from the glass pane in anatase modification. The density, which can be determined, for example, by measurements of the refractive index and / or the layer hardness, of the intermediate layer 12 increases substantially continuously from the glass pane 10 in the direction of the rutile layer 14, this increase in density possibly also continuing into the rutile layer. It can even be assumed that between the two layers there is a “flowing” transition, in which the proportion of crystallites in anatase modification in the transition zone continuously decreases from the glass pane in the direction of rutile layer 14 and that of crystallites in rutile modification increases continuously, whereby both modifications could coexist in the transition zone. It is essential, however, that there is always a layer in anatase modification on the glass pane 10 and always a layer with a pure rutile modification on the side of the Ti coating facing away from the glass pane 10.

The exemplary embodiment shown in FIG. 2 differs from that according to FIG. 1 in that here a “Dop5

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pel-layer system »is provided, namely in that a second intermediate layer 18 and a second rutile layer 22 with the layers 12 and 14 having a corresponding structure are arranged after a first intermediate layer 12 and a first rutile layer 14. The heat-reflecting pane according to the exemplary embodiment shown in FIG. 1 is preferably produced using the method described below in Example 1, while a heat-reflecting pane according to the exemplary embodiment shown in FIG. 2 results from the procedure according to Example 2.

example 1

In a vacuum evaporation system, a float glass pane with a thickness of 8 mm and external dimensions of 210 cm x 140 cm was first cleaned in a conventional manner by glow discharge at a pressure of 4 Pa. Then the pressure was reduced to 6.665 • 10 ~ 3 Pa by further pumping. Oxygen was then admitted via a needle valve until a pressure of 4-10 ~ 2 Pa had been established in equilibrium with the inflowing oxygen. Then the evaporation of the titanium layer was started and the layer was evaporated onto the float glass pane at an evaporation rate of 4 IO-111 m per second. During the vapor deposition process, the pressure in the vapor deposition system dropped continuously to 6.665 • 10 ~ 3 Pa. The pane coated in this way was then hung horizontally in air on one of the two long edges for the oxidation of the layer and the tempering, heated in a tempering oven to 615 ° C and then quenched by cold air in a blow box and thus thermally tempered. The resulting TÌO2 layer had a thickness of 3.2-10 ~ 8 m and was completely free of turbidity after the pane had cooled. When viewed from the coated side, the pane had a slightly bluish appearance. The reflectivity of the pane produced according to the invention in this way, based on the sensitivity to brightness of the human eye, was 32.5%. The flatness deviations of the discs were on all edges as well as above the diagonals below 1 mm per running meter edge length or per running meter diagonal.

In a comparative experiment, under otherwise identical conditions, a 130 À thick SÌ2O3 layer was subsequently applied to a pane of the same dimensions at a pressure of 1.733 • 10 ~ 2 Pa using the process known from DE-AS 26 46 513 by reactive evaporation of silicon monoxide and then at a pressure of 5.333 • 10 ~ 3 Pa, a titanium layer of the same thickness as in the example described is evaporated. The disc was then heated in the same way in the tempering furnace and then quenched.

The comparison disk produced in this way according to the prior art showed a slightly bluish appearance when viewed from the coated side. The visual reflectance was 34%. The rutile layer was completely opaque. However, the flatness deviations were 3 mm per running meter on a short edge and 3 mm per running meter on one of the two diagonals.

Example 2

Using a float glass pane with the thickness and the outer dimensions of example 1, after the glow cleaning of the glass surface, the pressure in the vapor deposition system was also first reduced to 6.665 • 10-3 Pa and then adjusted to 4 • 10-2 Pa via inflowing oxygen. Then, in contrast to Example 1,

First, a first titanium layer was evaporated, the pressure dropping continuously to 6.665 • 10 ~ 3 Pa due to the getter effect of the evaporating titanium. The evaporation rate was 5 · 10 "10 m per second. After the getter effect subsided and the pressure rose again to 4-10 ~ 2 Pa, a second titanium layer of the same thickness was then evaporated in the same way.

After the oxidation and tempering process carried out as in Example 1, the pane, when viewed from the coated side, showed a silvery appearance with a visual reflection of 37%. The 5.2-10 "8 m thick Ti02 layer was completely free of turbidity. The disc showed maximum plantity deviations of 1 mm per running meter at the edges and across the diagonals.

On the other hand, a disk produced with an Svers2O3 intermediate layer and a rutile layer of 5.2 • 10 "8 m thickness produced in a comparative test under otherwise the same conditions as in Example 1 showed deviations in planarity per running meter of 3 mm on one of the two short edges and of 4.5 mm on one of the two diagonals and the visual reflection was 41%.

Also showed a disk produced in a further comparison test, in which according to the teaching of DE-OS 27 57 750 a two-layer system consisting of anatase intermediate layer and rutile layer, also 5.2-10 "8 m thick, had been applied 2.0 mm on one of the two short edges and 3.0 mm on one of the two diagonals The visual reflection was 40%.

The above examples show that in the method according to the invention with an “inhomogeneous” layer structure of the TiO 2 layer, the visual reflectivity is only slightly below the value that results with a pure rutile layer of the same thickness. The proportion of rutile in the layer (rutile has a higher refractive index than anatase) can therefore be chosen to be quite high by appropriate selection of the coating conditions, without the formation of cracks and disruptive optical deformations during the tempering process. Studies on such layers showed that the ratio of rutile to anatase was about 3: 1. Naturally, these investigations on such inhomogeneous layers can only approximately determine the two phase fractions. The high reflection values of the inhomogeneous layers in connection with the studies mentioned show, however, that with the inhomogeneous structure of the layer system according to the invention, the rutile component can be significantly higher than the anatase component, without causing critical tensions between the layer and the glass panes, which trigger crack formation and / or impair the flatness during the tempering process.

The features of the invention disclosed in the above description, in the drawing and in the following claims can be essential both individually and in any combination for realizing the invention in its various embodiments.

Compared to the method previously known from DE-AS 26 46 513, the method according to the invention has a number of advantages: A first advantage is that the TiO 2 layer is present directly on the glass surface, which, just as if the teaching of the DE is followed -OS 27 57 750, results in particularly good adhesion. In addition, as in DE-OS 27 57 750, the as yet unoxidized titanium layers also have very good adhesion to glass, which makes handling of the Ti-coated disks easier until the Ti layers are oxidized. Likewise, as in DE-OS 27 57 750, in contrast to DE-AS 26 46 513, only one type of evaporator device is required. This is

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From the point of view of the coating costs, it is particularly important because titanium is available as a coating material in wire form, while silicon monoxide, as used in DE-AS 26 46 513, is used as a coating material in granular form, so that the weighing of the material for the loading of the Evaporator devices required amounts of material is facilitated.

It is of crucial importance, however, that both the DE-AS 26 46 513 and the DE-OS 27 57 750 significantly reduce the deviations in planarity when prestressing the disks. Such flatness deviations generally increase with increasing layer thickness of the Ti02 layer. In the panes produced according to the invention, they are less than one millimeter per running meter edge length for layer thicknesses of up to approximately 4-10 ~ 8 m. In the thickness range above 4 * 10 ~ 8 m up to the layer thicknesses of about 6-10 ~ 8 m, which are mainly of interest for the application, somewhat larger deviations occur up to a maximum of about 1.5 mm per running meter edge length in some cases.

In the latter case, if layer thicknesses of approximately 6 • 10-8 m are desired, it is possible to achieve a further improvement by modifying the vapor deposition process as a special embodiment according to the invention, and also in this case deviations in flatness of less than 1 mm per running meter Edge length reproducible. This modification consists in that the evaporation of the titanium takes place in two steps. After approximately half the amount of material has been evaporated using the method according to the invention, the evaporation process is interrupted. After the getter effect has subsided, the pressure rises again to the initial value that was present at the start of the first partial evaporation. If this value is reached, the second partial coating system is evaporated on in a corresponding manner. These inhomogeneously constructed “double layers” surprisingly have obviously lower stresses than the glass pane than an inhomogeneous single layer of the same overall thickness according to the invention. In this way, according to the invention, the tempering deviations can be kept reproducibly below 1 mm per running meter edge length when the glass is tempered even with the thicker TiO: layers.

The improvement in the flatness of the heat-reflecting panes produced according to the invention during the tempering process could not have been foreseen by the person skilled in the art. A possible explanation could lie in the following: It is known that in the pressure range above approximately 1.333 • 10-2 Pa, the hardness and density of vapor deposition layers s decrease with increasing pressure in the coating chamber. The reason for this is assumed that the energy of the vapor deposition material atoms striking the substrate to be vaporized decreases due to the higher likelihood of collisions with the residual gas molecules and thus make short-range processes more difficult when the layers are formed. For the procedure according to the invention with continuous vacuum improvement during the vapor deposition process, it follows that, in particular in the area of the intermediate layer with an anatos modification after the oxidation after the oxidation of the mentioned Ti coating, there is a continuous transition from soft to harder layer areas, from the glass pane in Seen towards the rutile layer, is present. This inhomogeneous layer structure could be the reason 20 that the stresses between the glass pane and the TiO 2 layer are significantly lower and thus the deformations during tempering are also considerably weaker. This reduction of the voltages is probably also the reason for a further advantage of the heat-reflecting panes produced according to the invention over those panes which are manufactured according to DE-AS 26 46 513 or DE-OS 27 57 750: it has been shown that In the latter two cases, the optical turbidity in the 30 Ti02 layer when the panes are tempered or when the titanium-coated panes are heated to high temperatures for the purpose of rapid oxidation can only be prevented if the glass surface is carefully cleaned before coating and only fresh glass is used 35 will. The latter requirement in particular is difficult to meet in practice. In contrast, when using the method according to the invention, the sensitivity limit with regard to the cleaning and aging of the glass panes is considerably higher, which results in considerable cost savings in large-scale manufacturing processes. It can be assumed that the presumably decisive reduction in the stresses between the Ti02 layer and the glass 45 layer, which is decisive for the improved quality of the heat-reflecting panes according to the invention, also reduces the occurrence of haze phenomena due to crack formation in the Ti02 layer.

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Claims (12)

645 604 1. Heat-reflecting pane, consisting of a glass pane, in particular of soda-lime-silicate glass, with a TiO: layer in rutile modification and an intermediate layer made of TiO: in anatase modification arranged between the glass pane and the rutile layer, characterized in that the density of the intermediate layer (12) increases substantially continuously from the glass pane (10) to the rutile layer (14). 2. Heat-reflecting pane according to claim 1, characterized in that on the side of the rutile layer (14) facing away from the glass pane (10), a further intermediate layer (18) in anatase modification with an essentially continuously increasing density from the rutile layer (14) to its side facing away from the rutile layer (14), and one further rutile layer (22) are arranged. 2nd PATENT CLAIMS 3. Heat reflecting panes according to claim 1 or 2, characterized in that the total thickness of the TiCh coating is 3 • 10 ~ 8 to 6 • 10 ~ 8 m. 4. Heat-reflecting pane according to one of the preceding claims, characterized in that the rutile layer (14) or, in the case of several rutile layers, at least the rutile layer (22) most distant from the glass pane (10) has a thickness of at least 5. Heat-reflecting pane according to one of the preceding claims, characterized in that the glass pane (10) is thermally toughened. 6. A method for producing a heat-reflecting pane according to one of the preceding claims, in which on a glass pane, in particular made of soda-lime-silicate glass, first under such vacuum conditions that a later oxidation of the layer leads to anatase modification, a first Ti layer and then under such vacuum conditions that subsequent oxidation of the layer leads to rutile modification, a second Ti layer is evaporated, whereupon the glass pane coated in this way for oxidizing the first Ti layer to an intermediate layer made of TiO: in anatase modification and simultaneously oxidizing the second Ti Layer to a TiOz layer in rutile modification (rutile layer) is heated in air, characterized in that the vapor deposition of the Ti coating is reactive in an atmosphere at a total pressure> 1.333 • 10 ~ 2 Pa and an oxygen partial pressure of at least 1.333 • 10 ~ 2 Pa started and the titanium is evaporated so quickly that the get Interaction of the evaporating titanium, the pressure drops at least in the 10 ~ 3 range, whereby during the later oxidation of the titanium layer an inhomogeneous layer structure with a continuous increase in density of the intermediate layer adjacent to the glass pane in anatase modification from the glass pane in the direction of those facing away from the glass pane Rutile layer arranged on the outside of the layer structure is formed. 7. The method according to claim 6, characterized in that the oxygen partial pressure before the start of the reactive vapor deposition by supplying oxygen, preferably via an inlet valve, to the increased value of at least 1.333 • 10 ~ 2 Pa compared to a normal residual gas atmosphere, whereupon during the the set oxygen rate is maintained throughout the vapor deposition process. 8. The method according to claim 6 or 7, characterized in that first the total pressure is reduced to about 6.665 • 10 ~ 3 Pa, then such a quantity of oxygen is supplied through a valve that the total pressure rises to 4-10 ~ 2 Pa, and then the vapor deposition of the Ti coating takes place with a vapor deposition rate of approximately 5 • 10 "10 m / s. 8-10-5mhat. 9. The method according to any one of claims 6 to 8, characterized in that a further inhomogeneous Ti two-layer system is evaporated subsequent to the first inhomogeneous layer structure under the evaporation of the conditions corresponding to the first layer structure. 10. The method according to any one of claims 6 to 9, characterized in that the Ti-coated glass pane for oxidizing the Ti coating and / or for thermal tempering in air to a temperature of at least 550 ° C, preferably by heating and subsequent quenching 570 to 620 ° C, is heated. 11. The method according to claim 10, characterized in that the glass sheet is quenched after heating to the oxidation temperature for thermal tempering. 12. The method according to claim 10, characterized in that the Ti-coated glass pane is first heated to a temperature sufficient to oxidize the Ti coating, then optionally further processed and only in a further heating step for thermal tempering to the temperature of at least 550 ° C, preferably 570 to 620 ° C, heated and then quenched.