System of transparent layers for substrates

Description of the invention

The present invention relates to a layer system for transparent substrates, a method for producing a layer system, a transparent substrate, and the use of a transparent substrate. The layer system for transparent substrates, especially for glass panes, has at least one metal oxide composite layer produced by reactive sputtering of a target made of a Zn and Sn containing metal alloy. The substrates on which these layers are applied can also be made of transparent organic polymers and can be rigid or flexible. Rigid polymeric substrates can be selected from the group of polycarbonates or from the group of certain polyurethanes. The polymer can also be poly (methyl methacrylate). For example, polyethylene terephthalate (PET) in the form of a film can be chosen as flexible substrates, which is then laminated to two thermoplastic sheets (e.g., polyvinyl butyral PVB) sandwiched between two glass panes.

Patent applications EP 0183052 and EP 0226993 disclose low E value transparent sandwich systems in which a functional metal layer, in particular a thin silver layer, is sandwiched between two dielectric antireflection layers which are the oxidation product of a Zn / Sn alloy. Depending on the Zn: Sn ratio, the composite layer thus produced contains a greater or lesser amount of zinc tinate Zn2SnO4, which gives the layer particularly advantageous properties, in particular mechanical and chemical stability. Preferably used as the target are Zn: Sn alloys with a Zn: Sn weight ratio from 46:54 to 50:50.

In the technical sputtering method using industrial coating systems, sputtering Zn2SnO4 layers from Zn / Sn alloy targets is more difficult than sputtering pure ZnO or SnO layers. This is due to the fact that, especially at the beginning of the spraying, the material on the target and on the parts of the spraying chamber produces insulation effects which consequently result in defective products and production rejects. Moreover, alloy wheels of this type must operate at reduced sputter rates, i.e. with a reduced electrical power, since the target alloy has a melting point lower than the melting point of these two components, especially in the area of ​​the eutectic composition. For this reason, the cooling of such discs must be particularly intense. This, in turn, can only be achieved by using specially shaped discs, the manufacture of which is relatively expensive.

The invention aims, on the one hand, to further improve the mechanical and chemical properties of dielectric layers containing zinc tinate and, on the other hand, to reduce the difficulties encountered when sputtering Zn / Sn alloys.

The present invention relates to a layer system for transparent substrates, in particular for glass panes, with at least one composite metal oxide layer containing Zn and Sn mixed oxide produced by reactive sputtering of a target made of a Zn and Sn containing metal alloy, characterized in that the composite metal oxide layer contains one or more elements such as Ga, In, B, Y, La, Ge, P, As, Sb, Bi, Ce, Zr, Nb and Ta, the amount of the elements Ga, In, B, Y, La, Ge, P, As, Sb, Bi, Ce, Zr, Nb and / or Ta in the composite metal oxide layer with respect to the total amount of metal ranges from 0.5 wt% to 6.5 wt% and wherein the thickness of the composite metal oxide layer is from 2 to 6 nm or from 7 to 50 nm.

Preferably, in the layered system according to the invention, the composite metal oxide layer comprises from 35% by weight to 70% by weight of Zn and from 29% by weight to 64.5% by weight of Sn, based in each case on the total amount of metal.

Preferably, in the tier system according to the invention, the composite metal oxide layer comprises from 66 wt% to 69 wt% Zn, from 29 wt% to 32 wt% Sn, and from 1 wt% to 4 wt% Sb.

Preferably, in the layer system according to the invention, the composite metal oxide layer is a lower and / or upper antireflection layer of a layer system comprising one or more functional layers made of a metal such as silver.

Preferably, in the layer system according to the invention, the composite metal oxide layer is a diffusion barrier layer in a multilayer system.

Preferably, in the layer system according to the invention, the composite metal oxide layer is a sublayer of the upper and / or lower antireflection layer.

Preferably, in the layer system according to the invention, the sequence of the layers is as follows:

SnO2 / ZnO / Ag / optionally blocking layer / SnO2 / ZnSnO: Sb; or the order is as follows:

SnO2 / ZnO / Al / optionally blocking layer / SnO2 / SiO2 / SnO2 / SnZnO: Sb.

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Preferably, the layer system according to the invention comprises at least one functional layer of a metal such as Ag, NiCr, steel or a nitride such as TiN or ZrN.

Preferably, the layer system according to the invention performs the function of a solar control system, a low emission system, an anti-reflection system or an electrical system.

Preferably, in the layer system according to the invention, the composite layer has a spinel structure.

The subject of the invention is a transparent substrate of glass or polymeric material, rigid or flexible, which according to the invention is coated on at least one of its surfaces with the above-defined layer system.

The invention relates to the use of the above-defined transparent substrate for the production of monolithic, laminated or multiple glazing units.

The subject of the invention is a method for the production of the above-defined layer system by sputtering, which according to the invention consists in that the composite layer is applied by reactive sputtering from a metal target which contains Zn, Sn and at least one of the following elements: Ga, In, B, La, Ge, P, As, Bi, Ce, Zr, Nb, Ta.

The composite metal oxide layer includes one or more elements such as Al, Ga, In, B, Y, La, Ge, Si, P, As, Sb, Bi, Ce, Ti, Zr, Nb and Ta.

It was found that the introduction of the mentioned elements, which without exception belong to the elements of the main group and to subgroups III, IV and V of the periodic table of elements, gives a significant improvement in all important properties of the layer, as well as an improvement in sputtering efficiency.

The mixed oxides produced by the elements introduced, for example by introducing Sb, have a qualitative composition of ZnO · ZnSnO3 · Zn2SnO4 · ZnAl2O4 · ZnSb2O6 depending on the choice of Zn and Sn metals. During crystallization, some of these oxides form spinel structures that crystallize by themselves with a particularly dense packing of atoms. The resulting improvements in the properties of the layers may perhaps be explained by the particularly high packing density of the spinel structures obtained by the incorporation of the said additional elements, while the beneficial effect of the sputtering may perhaps be attributed to the increase in the electrical conductivity of the mixed oxides by the addition of additional elements. Due to the dense crystal structure, the layers not only have particularly good mechanical and chemical stability properties, but also hinder diffusion processes into and through this layer. This reduces the risk of changes in said layer or in any other layer of the system that can be attributed to water, oxygen and Na molecules.⁺ and, if applicable (ie, when the system comprises Ag layer or layers), Ag⁺ diffusing into the layer, especially during annealing and storage.

In order to obtain the most dense spinel structure it is particularly advantageous if the ionic radius of the added element does not differ much from the Zn ionic radius.²⁺ and Sn⁴⁺which have ion radii of 8.3 × 10, respectively^-11 m [0.83 A] (Zn²+) and 7.4 · 10^-11 m [0.74 A] (Sn⁴+). This condition is met especially for the elements Al and Sb, the ionic radius Al³+ = 5,7·10^-11 m [0.57 A] and Sb⁵+ = = 6,2·10^-11 m [0.62 Å]. On the other hand, as already mentioned, the introduction of said additional elements into the at least partially crystalline layer increases the electrical conductivity of the oxide layers on the faces and walls of the coating chambers, and also on the surface of the target itself. As a result, in turn, the operating times of the target in the sputtering method are significantly improved, thanks to which not only the properties of the layer are improved, but also the sputtering itself is improved.

The amount of elements incorporated according to the invention into the composite metal oxide layer is preferably from 0.5% by weight to 6.5% by weight, based on the total amount of metal.

Compositions of the metal oxide composite layer have been found to be particularly advantageous in which the amount of Zn is from 35% by weight to 70% by weight and the amount of Sn is from 29% by weight to 64.5% by weight, based in each case on the total amount of metal. For the production of this composite metal oxide layer, alloy wheels are used which preferably contain from 50 wt% to 70 wt%, more preferably from 66 wt% to 69 wt% Zn, preferably from 29 wt% to 50 wt%, more preferably from 29 wt% to 32 wt%. % by weight of Sn and preferably from 1% by weight to 4% by weight, more preferably from 1.5% by weight to 3% by weight of Al or Sb.

The metal composite layers according to the invention can in particular advantageously be used in partially reflecting layer systems with a metal functional layer made of silver. In such layer systems, they can be used both as a binding or antireflection layer, as a condensation layer for surface silver layers, as a blocking layer under or above the silver layers, and as a sublayer in the region of the lower and / or upper layer of the layer system.

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Exemplary layer systems are described below, the properties obtained being compared with those of the corresponding layer system according to the prior art.

In order to evaluate the properties of the layers, 10 different tests were performed on the samples, namely:

A. Hardness when scratched

In this case, it is pulled at a predetermined speed over the loaded needle layer. The load causing visible scratch marks is a measure of the scratch hardness.

B. Scratch hardness after water storage

Procedure as in A, but after storing the samples for 30 minutes in water at 20 ° C.

C. Erichsen wash test in accordance with ASTM 2486

Visual assessment.

D. Water condensation test (WCI)

The samples are tested for 140 h at the mb temperature of 60 ° C and 100%. relative humidity. Visual assessment.

E. Washout of Zn²⁺

The measurement is performed by the plate method according to Kimel et al., Z. Glastechnische Berichte 59 (1986), page 252 et seq. The test shows the resistance to hydrolysis of Zn-containing layer systems.

F. Washout of Ag⁺

The measurement is also made by the plate method of Kimel et al., Used to determine Zn leaching²⁺. The measurement result gives an analytical assessment of the density of the dielectric layers above the Ag layer.

G. Hydrochloric acid test

In this case, the glass sample is immersed in 0.01 N HCl at 38 ° C for 8 minutes and the percentage loss in emissivity is assessed.

H. Hydrochloric acid test, visual inspection

The glass sample is immersed in hydrochloric acid as in the test

G. The evaluation criterion is the appearance of the dipped edge.

I. EMF test

The test is described in Z. Silikattechnik 32 (1981), p. 216, "Untersuchungen zur elektrochemischen

Prijfung dϋnner Metallschichten (Electrochemical studies of metal thin films). The test informs about the passivation properties of the surface layer above the silver layer and about the corrosion resistance of the Ag layer. The smaller the potential difference, in mV, between the layer system and the reference electrode, the better the layer quality.

K. Water layer test

The layered side of the samples is brought into contact with a thin layer of water for 24 h. The test gives information on the storage stability of stacked coated glass panes if there are traces of water between the panes. The assessment is done visually.

Comparative example 1

Using the same coating system and comparable coating conditions, the following prior art layer system was reapplied onto panes of 6 mm thick float glass:

glass pane - 40 nm SnO2 - 2 nm CrNi - 10 nm Ag - 4 nm CrNi - 34 nm SnO2 - 4 nm Zn2SnO4 - 4.5 nm TiO2.

The Zn2SnO4 layer was reactive sputtered from a metal alloy target that consisted of 52.4 wt% Zn and 47.6 wt% Sn. Sputtering the Zn2SnO4 layer again resulted in undesirable electric arcs causing defects in the coatings. The TiO2 layer was reactive sputtered from a titanium metal target using a DMS cathode and an Ar / O2 / N2 mixture working gas.

The tests listed under A to K were performed again on samples of the coated glass panes. The test results are summarized in Table 2, along with the test results for the samples prepared according to Example 1.

Example 1

Under the same coating conditions and for the same coating system, the layered system according to the invention was applied to panes of flotation glass with a thickness of 6 mm in the following order of layers:

glass pane - 40 nm SnO2 - 2 nm CrNi - 10 nm Ag - 4 nm CrNi - 34 nm SnO2 - 4 nm ZnxSnySbzOn - 4.5 nm TiO2.

The only difference to the comparative example was that to produce the sublayer containing the mixed Zn / Sn oxide, the disk was made of an alloy containing

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68% by weight Zn, 30% by weight Sn and 2% by weight Sb. No undesirable arcs were found when spraying this alloy.

The coated glass samples were subjected to the tests mentioned under letters A to K. The results are summarized in Table 2 below, together with the results obtained for the samples of Comparative Example 1:

Table 1

<td>Attempt</td><td>Comparative example 1</td><td>Example 1</td>

<td>A, g</td><td> 30</td><td> 45 - 50</td>

<td>B, g</td><td> 35</td><td> 55</td>

<td>C, 1000 strokes</td><td>1 medium scratch</td><td>1 small scratch</td>

<td>D, 140 h</td><td>slight reddening</td><td>without defects even after 400 h</td>

<td>E, mg / 25 ml</td><td> 0,19</td><td> 0,15</td>

<td>F, mg / 25 ml</td><td> 0,35</td><td> 0,01</td>

<td>G, ΔE in%</td><td> 1</td><td> 0</td>

<td>H.</td><td>red streaks</td><td>Flawless</td>

<td>I, mV</td><td> 80</td><td> 30</td>

<td>K.</td><td>Flawless</td><td>Flawless</td>

The test results show that the cover TiO2 layer has better miscibility with the composite layer according to the invention than with the zinc tinate layer of the comparative example. This is manifested in the further improvement of the test results, especially the much better results in test D (condensation water test) and in a clearly better result in the EMF test. The leaching result was Ag⁺ it is also clearly superior, so this layering has an overall excellent quality.

As a conclusion, the composite layers according to the invention allow both the simplification of the application and the improvement of the chemical and mechanical stability of the systems containing them, especially when the layer according to the invention is the last layer or the direct layer before the last layer of the system (i.e. the penultimate layer). This type of layer makes it possible to obtain more resistant layer systems using metal oxide as dielectric layers, which brings their durability closer to that of systems using instead dielectric layers made of nitrides, such as silicon nitride. It appears that the improvement in durability is even greater when using Sb instead of Al in the composite oxide layer.

The invention can be applied to glass substrates or to any other transparent substrate, preferably made of organic polymers, as mentioned in the introductory part of the application.

The layers according to the invention can be used as a thin protective surface layer or as a "blocking" layer (this term means that this layer protects a functional layer of metal such as Ag from deterioration caused by the application of another metal oxide layer by reactive sputtering in the presence of oxygen. ), for example in the thickness range of about 2 nm to about 6 nm. The thickness may be greater, for example from about 7 nm to about 50 nm, if the layer is to perform a significant optical role.

The layers of the invention may be incorporated into many thin interference layer systems, especially systems comprising transparent functional layers with sun protection or low emission properties, such as Ag layer (s). The system may include one or more Ag layers as set out in the following descriptions: EP 638528, EP 718250, EP 844219, EP 847965, FR2784984 and FR2784985. The system may also include a functional layer of another type, for example a metal such as a Ni-Cr alloy or steel as described in EP 511 901, or a nitride such as TiN or ZrN.

The dielectric layer according to the invention may be part of the antireflection layer system described in EP 728712 or WO 97/43244, part of any other layer system having a thermal, optical or electrical function and using dielectric / oxide layers with a refractive index value of about 2.

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The substrates can also be used to make monolithic (single-backed), laminated or multiple glazing (double glazing, car windshields, and the like). They can also be placed in buildings, vehicles, billboards and the like.

By way of example, certain ml layer systems comprising a layer according to the invention are given below: transparent substrate / SnO2 / ZnO / Ag / optionally a blocking layer such as NiCr / SnO2 / ZnSnO: Al or Sb;

transparent substrate / SnO2 / ZnO / Al / optionally a blocking layer such as NiCr or Ti / SnO2 / SiO2 / SnO2 / ZnSnO: Al or Sb.

The systems may contain two Ag layers.

It should also be emphasized that the amounts of metal, such as Al or Sb, incorporated into the metal target are approximately the same as in the layers obtained from the target.

The systems may of course comprise several layers according to the invention, in particular a blocking layer and a surface layer.