WO2007042687A1 - Low emissivity ('low-e') thin coating stacks - Google Patents

Abstract

The invention concerns a system of low emissivity ("Low-E") coatings with high thermal resistance for transparent substrates, in particular for glass panes, comprising a lower antireflection coating, consisting of one layer or several partial layers, a silver-based functional layer, a barrier layer arranged above the functional layer, an upper antireflection coating consisting of one layer or several partial layers and an overlapping coating consisting of one layer or several partial layers, the layers being deposited by vacuum spraying, the barrier layer including a barrier layer arranged above the functional layer which is a metallic layer or slightly nitrided with a titanium alloy consisting of 50 to 97 wt. % of Ti and 3 to 50 wt. % of one or several among Cr, Fe, Zr and Hf, said barrier layer being at least partly oxidized after being optionally heat-treated.

Description

 STACK OF THIN LAYERS WITH LOW EMISSIVITY

( "LOW-E")

The invention relates to a low-E (low-E) and high thermal resistance layer system for transparent substrates, in particular for windows, which has in the order a lower antireflection coating, consisting of a layer or a plurality of partial layers, a silver-based functional layer, a barrier coating above the functional layer, an upper antireflection coating consisting of one or more partial layers, and a covering layer consisting of a layer or several partial layers, the layers being deposited by vacuum spraying.

By high thermal resistance layer systems is meant layer systems that resist without being destroyed at the temperatures of about 600 to 750 ⁰ C required for bending or tempering the glass and without their essential properties, namely high transmission in the visible range of the spectrum, high reflection in the range of thermal radiation, low dispersion, high color neutrality, high mechanical strength and high chemical resistance are compromised.

Different embodiments of high heat resistance layer systems are known. In a first group of high thermal resistance layer systems, the antireflection layers consist of Si ₃ N ₄ which are separated from the silver functional layer by a thin layer of NiCr sacrificed metal. Systems of layers which have these structures are described for example in the documents EP 0 567 735 B1, EP 0 717 014 B1, EP 0 771 766 B1, EP 0 646 551 B1 and EP 0 796 825 B1. These layer systems are very thermally stable, but their manufacture is made very expensive by the known problems of spraying.

Since most oxidized layers can be sprayed with less problem than the nitrided layers and their manufacture is more economical, layer systems consisting at least in part of oxidized layers are advantageous. Among the layer systems of this type, various layer systems are known in which at least one antireflection layer or a partial layer of an antireflection coating consists of mixed oxides of a titanium alloy. This oxidized antireflection layer is generally performed by reactive sputtering of a target made of a titanium alloy.

EP 0 718 250 B1 discloses dipping layer systems which have oxide, nitride or carbide antireflection layers in which a barrier metal layer is arranged on the functional layer. silver and may consist of Nb, Ta, Ti, Cr or Ni or an alloy of at least two of these metals. In this case, however, the barrier layer will preferably consist of NbTa, NbCr, TaCr or NiCr.

A system of high thermal resistance layers of the type indicated at the beginning, which has a barrier layer based on a titanium alloy, is also disclosed in DE 10 235 154 B4. In this layer system, the barrier layer located above the silver layer contains chemically bonded hydrogen and is made of Ti or an alloy of Ti and Zn and / or Al. In this system, the covering coating consists of ZnO: Al / TiO ₂ , ZnO: Al / Ti, Zn _x Sn _y O _z / TiO ₂ , Zn _x Sn _y O _z / Ti, Zn _x Ti _y Al _z O _r , Ti _x Al _y O _z , Ti _x Al _y , Ti _x Al _y N _z , Ti _x Al _y O _z N _r , TiN, Ti, Zn _x Sn _y Sb _z O _r / TiO ₂ , Zn _x Sn _y Sb _z O _r Or Ti or Zn _x Sn _y Al _z O _r / TiO ₂ .

A system of layers with high thermal resistance is also described in EP 1 060 140 B1. As a layer system, the functional layer contains a silver alloy which contains, as components Al, Ti, W, Ta, Zr, Hf, Ce, V, Ni, Cr, Zn or Nb, or a mixture of these metals. Above this functional layer is disposed a barrier layer made of Nb or an alloy or mixture of Ni and Cr.

DE 196 40 800 A1 (= EP 0 834 483) describes a thermally insulating and high thermal resistance layer system in which a metallic barrier layer, for example of Al, CrNi, Ti or Ta, is placed on the functional layer. a dielectric intermediate layer consisting of an oxide, nitride or oxynitride of a metal other than that of the barrier layer, in particular Ti, Ta, Zr, Al or Si or a mixture of these metals, being disposed on this barrier layer; .

DE 101 05 199 discloses a high thermal resistance layer structure in which a metal nitride layer, for example Si ₃ N ₄ or AlN, is arranged between the silver functional layer and the Cr-barrier metal layer. , Ni, Al, Ti, Mg, Mn, Si, Zn or Cu or an alloy of these metals.

Among the layer systems which are not of high heat resistance, that is to say which are unsuitable for glass substrates which have to be baked at high temperature and / or thermally tempered with their coating, we know who have one or more individual layers of an oxidized titanium alloy. For example DE 101 52 211 C1 discloses a layer structure which contains a mixed oxide layer which is prepared by reactive sputtering of a metal alloy target of 10 to 60 wt. 40% by weight of Zn and 0.5 to 8% by weight of one or more of metals Al, Ga and Sb. This mixed oxide layer may be a lower and / or upper antireflection layer or a partial layer of antireflection coating lower and / or higher, but also the covering layer itself.

EP 0 304 234 B1 discloses a layer structure which does not have a high thermal resistance, for a window, in which the barrier layer is made of titanium and in which several layers of metal oxide are arranged at above the barrier metal layer, a layer consisting of an oxide of Ti, Zr, Hf or a mixture thereof being disposed between two layers of an oxide of Zn, Sn, In or Bi or a mixture of these metals.

DE 195 20 843 A1 discloses a layer system which can not be tempered and in which a titanium alloy can be placed on the silver layer as a barrier layer. In this case, the barrier layer is a metal layer or a sub-stoichiometric oxide layer of a mixture of Ti, Cr and Nb.

The layer system described in DE 103 33 619 B3 is also part of diaper systems which can not be dipped. In this known layer system, the cover layer is a mixed oxide layer of TiZrHfO _x . The mixed oxide layer is deposited by reactive sputtering in a working gas atmosphere of Ar and O 2. As barrier layers, layers of CrNi are used.

The invention is based on a system of layers with high thermal resistance which has the fundamental structure indicated at the beginning. The problem underlying the invention is to further improve the properties of this layer system and in particular to further increase the transmission in the visible range, to further reduce the surface resistance and therefore the emission values and achieve reflection values as high as possible in the range of thermal radiation. According to the invention, this problem is solved with the features mentioned in claim 1.

The barrier coating thus comprises, according to the invention, a barrier layer disposed above and in contact with the functional layer which is a metal or slightly nitrided layer of a titanium alloy consisting of 50 to 97% by weight of Ti and of 3 at 50% by weight of one or more of the metals Cr, Fe, Zr and Hf and which comprises in particular chromium.

If the carrier substrate of the layer system undergoes a thermal treatment of the bending or quenching type after the deposition of the system, the barrier layer according to the invention then becomes at least partially oxidized.

It has been found that the barrier layer according to the invention allows a notable improvement of the properties, in particular transmission values in the visible range of the spectrum, while retaining high values of reflection in the range of thermal radiation.

These advantages are achieved particularly when the lower antireflection coating comprises a wetting layer consisting essentially of ZnO to which the functional layer is connected.

Obviously, during a heat treatment, the barrier layer is transformed into a particularly regular mixed oxide or mixed oxynitride layer. This is probably due to the fact that the titanium which constitutes the main component of the alloy and the Cr, Fe, Zr, Al and Hf alloy additives have quite similar formation enthalpies during the oxidation and possibly ionic rays. comparable for the oxidation stages present. Thus, based on the main valences of these alloying components, the formation enthalpies are from -940 to -1 145 kJ / mole and the ionic radii of the various oxides are from 0.63 to 0.75 Å. To prepare the barrier layer, titanium alloys consisting of 55 to 60% by weight of Ti, 35 to 45% by weight of Zr and 1 to 5% by weight of Hf are preferably used. The Hf can thus be considered as a dopant.

The barrier layer according to the invention preferably has a thickness of 1 to 5 nm. An advantageous development of the invention consists in placing on the metallic or slightly nitrided barrier layer an additional sub-oxidized barrier layer with a thickness of 1 to 3 nm deposited by sputtering a titanium alloy.

In a variant, the barrier coating thus comprises an additional sub-oxidized layer of a titanium alloy and of a thickness of 1 to 3 nm disposed above the metallic or weakly nitrided barrier layer.

The titanium alloy used for the barrier layer in contact with the silver-based functional layer can also be used particularly advantageously for the top layer or the upper partial layer of the covering layer of the layer system. in a nitrided or oxynitrided compound and regardless of the use or otherwise of the barrier coating according to the invention. In this case we can also use the AI as another alloy metal. During the prestressing or quenching operation, the strongly absorbing nitride layer is converted into a weakly absorbing layer and thus free from visible defects. The main component of the TiN is indeed completely oxidized to TiO ₂ , and the other nitrided components, for example CrN, ZrN or AlN, are transformed into less strongly absorbing oxynitride structures. This nitrided cover layer therefore acts as an oxygen trap in the heat treatment operation, so that less oxygen diffuses into the layer system and the barrier layer itself can thus be thinner. These provisions allow to improve other properties of the layers, such as their hardness and stresses in the layer system according to the preamble of claim 1.

The covering coating may thus comprise a nitrided or oxynitrided layer of a titanium alloy consisting of 50 to 97% by weight of Ti and 3 to 50% by weight of one or more of the metals Cr, Fe, Zr, Al and Hf.

In a particular variant the system of low emissivity and high thermal resistance layers for transparent substrates, in particular for windows, according to the invention comprises a lower antireflection layer, oxidized, possibly consisting of several partial layers, a layer consisting essentially of ZnO to which is connected a silver functional layer, a substantially metallic barrier layer of a titanium alloy disposed above the silver layer, an upper antireflection layer optionally consisting of several partial layers and a covering layer possibly consisting of several partial layers, the layers being applied by vacuum spraying, the barrier layer disposed above the functional layer being a metal or slightly nitrided layer of a titanium alloy consisting of 50 to 97% by weight of Ti and of 3 50% by weight of one or more Cr, Fe, Zr and Hf metals.

The layer system according to the invention can in particular have the following advantageous structures: glass / SnO ₂ / ZnO: Al / Zn / Ag / TiZrHfN ₇ / ZnO: Al / Si ₃ N ₄ / ZnSnSbO _x / Zn ₂ TiO ₄ .

glass / SnO ₂ / ZnO: Al / Zn / Ag / TiZrHfN ₇ / ZnO: Al / Si ₃ N ₄ / TiZrHfN _y .

glass / SnO ₂ / ZnO: Al / Zn / Ag / TiZrHfN ₇ / TiCrO _x / ZnO: Al / Si ₃ N ₄ / ZnSnSbO _x / Zn ₂ TiO ₄ . The present invention also relates, of course, to the transparent substrate, flat or curved, provided with the layer system according to the invention, in particular when the substrate has the form of a glass tempered thermally after the deposition of the layer system.

Preferred compositions of the layer system as well as the preferred thickness ranges of the individual layers are apparent from the dependent claims and the following exemplary embodiments.

The invention is described in more detail with the aid of two exemplary embodiments which are compared with two comparative examples of the state of the art. Since the arrangements according to the invention optimize the optical and energetic properties in particular, the assessment of the quality of the layers is based essentially on the measurements of the scattered light, the surface resistance and the emissivity. Therefore, to evaluate the properties of the layers, the measurements and tests given below are carried out on the coated panes.

A. Measurement of the thickness (d) of the silver layer by X-ray fluorescence analysis.

B. Measurement of the scattered light (H) in% using the Gardner scattered light meter.

C. Transmission measurement (T) in% using the Gardner measuring instrument.

D. Measurement of the surface electrical resistance (R) in Ω / D using FPP 5000 Veeco Instr. and the SQOHM-I manual measuring device.

E. Measurement of the emissivity (E _n ) in% with the MK2 measuring instrument from Sten Lofring. After measuring 1 emissivity is calculated emissivity values d ¹ using the surface resistance values by the formula E = 0.0106 x _n R (see H.-J. Glaser. "Dunnfilmtechnologie auf Flachglas" Verlag Karl Hofmann 1999, p. 144) and the measured values E _n are compared with the calculated values E ^* _n . The smaller the difference between the measured values E _n and the calculated values E ^* _n , the better the thermal stability of the layer system.

For each of the measurements, specimens 40 x 50 cm cut in the central portion of coated glass with a thickness of 4 mm are used. The test pieces are heated to a temperature of 720 to 730 ^° C. in a quenching furnace of the EFKO firm, type 47067, and then quenched thermally by sudden cooling in air. In this way, all the specimens undergo the same thermal stress.

It should also be pointed out that the layer system according to the invention achieves its best values in terms of thermal insulation, infrared reflection and transmission of light on windows after the heat treatment of the substrates. on which it is deposited (quenching). The diffusion barrier layer also plays a key role in heat treatments. However, the layer system described here can be used commercially with slight thermal insulation defects and light transmission even without having been heat treated, and therefore particularly on non-tempered glass, on plastic windows and also on movies. The following embodiments, however, all relate to the use of the layer system on substrates made of thermally hardened glass panes.

In the compositional data of the individual layers which follow, when oxygen contents are denoted by O _x and nitrogen by N _y , are meant compounds whose degree Oxidation or nitriding is not clearly defined because the corresponding layers are not completely oxidized or nitrided. These contents are established in a manner known per se during production in vacuum coating plants via the ratio between argon and oxygen or between argon and nitrogen. For example, a layer is completely oxidized or completely nitrided at a content of> 50% O ₂ or N ₂ in the working gas (with Ar), partially oxidized or partially nitrided at 30% C> 2 or N ₂ in the working gas. A layer is weakly oxidized or nitrided at about 5% C> 2 or N ₂ in the working gas.

Thus, in the same stack, the values designated by x and y are not necessarily identical from one layer to the other.

Comparative Example 1

In an industrial continuous coating plant, using the magnetic field-assisted reactive sputtering method, a low-emissivity layer system is deposited which corresponds to the state of the art (DE 102 35 154 B4) on float glass panes of 4 mm thickness, the figures which precede the chemical symbols indicating for each layer the thickness in nm:

glass / 25 SnO _2/9 ZnO: Al / Zn 1.5 / 11.5 Ag / TiAl 2 (tihi) / 5 ZnO: Al / 30 Si ₃ N _4/3 ZnSnSbO _x / 2 Zn ₂ TiO ₄

The ZnO: Al layers are obtained by sputtering a metal target of ZnAl at 2% Al. The thin layer of metallic Zn is deposited by sputtering the same target material but under nonreactive conditions. The barrier layer disposed on the silver layer is deposited by sputtering a metal target which contains 64% by weight of Ti and 36% by weight of Al in a gas mixture. Ar / H _{2 work} (90/10% by volume). In TiHi, 1 can be between 1 and 2, including these limits.

The upper antireflection layer is deposited by reactive sputtering of an Si target in a working gas mixture of Ar / N ₂ .

The lower cover layer is made by sputtering a metal target of a ZnSnSb alloy containing 68% by weight of Zn, 30% by weight of Sn and 2% by weight of Sb in an Ar / O ₂ working gas. and the upper overcoat layer (final layer) is deposited by reactive sputtering of a metal target into a ZnTi alloy at 73% by weight of Zn and 27% by weight of Ti.

After quenching, the test pieces are optically transparent, but a slightly white edge is observed on the edges. On the quenched test pieces of this comparative example, the following values are determined:

Thickness d of the silver layer 11.6 nm

Scattered light H 0.30%

Transmission T 88.3%

Surface resistance R 4.28 Ω / D

Emissivity E _n measured 5.5%

so-Emissivity E * _n calculated 4.5%

so-

Comparative Example 2

To continue the comparison, we study a window obtained on the market and also tempered thermally, whose layer system has the following structure:

glass / 12 TiO _2/12 SnO _2/8 Zn: Al / CrNiO 2 _x / 2 CrNiN _y / 11 Ag / CrNiN 2 _y / _x 2 CrNiO / 10 SnO _2/24 Si ₃ N _4/2 SiON _y The measurements made on the thermally hardened test pieces under the same conditions as in Comparative Example 1 give the following values:

Thickness d of the silver layer 11.5 nm Diffused light H 0.25%

Transmission T 87.2%

Surface resistance R 4.3 Ω / D

Emissivity E _n measured 5.5%

Emissivity E * _n calculated 4.6%

E _n - E * _n 0.9%

The quenched specimens are optically transparent, but these specimens also have a white edge on their edges. As in Comparative Example 1, the difference between the calculated emissivity and the measured emissivity of 0.9% is relatively high.

Exemplary embodiment 1

On the same coating plant as for Comparative Example 1, a modified layer system according to the invention is prepared which has the following structure:

glass / 25 SnO _2/9 ZnO: Al / Zn 1.5 / 11.7 Ag / 2.5 TiZrN _y Hf / 5 ZnO: Al / 30 Si ₃ N _4/3 ZnSnSbO _x / 2 Zn ₂ TiO ₄

The modification compared with Comparative Example 1 is that instead of the barrier layer which contains hydrogen, a nitrided barrier layer according to the invention is used. The metal target for producing the barrier layer consists of an alloy of 57.6% by weight of Ti, 41.4% by weight of Zr and 1.0% by weight of Hf. The barrier layer is deposited by sputtering in a working gas of Ar / N _2, the N ₂ content is only 5% by volume, whereby a low nitriding.

The test pieces are quenched in the same manner as the test pieces of the comparative examples. Measurements made on the coated and quenched specimens give the following values:

Thickness d of the silver layer 11.7 nm

Light scattered H 0.17%

T transmission 89.0%

Surface resistance R 3.23 Ω / D

Emissivity E _n measured 3.6% (3.2 to 3.8)

so-Emissivity E * _n calculated 3.4%

so-

The specimens are optically transparent over their entire surface and without defects even in their borders. The good visual appearance corresponds to the measured proportion of scattered light, which is only 0.17%. For the same thickness of the Ag layer, the emissivity decreases by 5.5% for the two comparative examples to 3.6%. The difference E _n - E * _n , which is a measure of the thermal stability of the layer system, is much smaller. In the barrier layer oxidized by the heating operation, nitrogen (N) can be detected by the SIMS method.

Exemplary example 2

On the same coating plant as for Comparative Example 1, a modified layer system according to the invention, which has the following structure:

glass / 25 SnO _2/9 ZnO: Al / Zn 1.5 / 11.7 Ag / 2.5 TiZrHfN _y / 7 ZnO: Al / 30 Si ₃ N _4/2 TiZrHfN ₇

Compared to the embodiment example 1, the covering coating consisting of the 3n ZnSnSbO _x overlap layer and the 2nm Zn ₂ TiO ₄ top cover layer is replaced by a covering layer according to the invention, in mixed nitride

TiZrHfN _y . This mixed nitride is sputter deposited in a 50/50 Ar / N ₂ working gas mixture, resulting in a high degree of nitriding. After the heating and quenching treatment which takes place under the same conditions as for the preceding examples, the following values are determined on the test pieces:

Thickness d of the silver layer 11.7 nm Diffused light H 0.30%

Transmission T 88.3%

Surface resistance R 3.6 Ω / D

Emissivity E _n measured 4.3% (4.0 to 4.6)

Emissivity E * _n calculated 3.8%

E _n - E * _n 0.5%

The specimens are again optically transparent over their entire surface and flawless, even in their borders. The difference E _n - E * _n , which is a measure of the thermal stability of the layer system, is significantly smaller than the values obtained for the comparative examples. The slight decrease in transmission can be explained by residues of the ZrN and HfN absorbent components in the cover layer.

Example of realization 3

This layer system corresponds to the layer system of the embodiment example 1, but here, there is disposed directly on the barrier metal layer an additional barrier layer deposited under partially oxidizing conditions from a titanium alloy. For this purpose, a target of a titanium alloy which contains 10% by weight of Cr has been found to be particularly suitable. The layer system has the following structure:

glass / 25 SnO _2/9 ZnO: Al / Zn 1.5 / 11.5 Ag / 2.5 TiZrHfN _y / 2 TiCrO _x / 5 ZnO: Al / 30 Si ₃ N _4/3 ZnSnSbO _x / Zn ₂ TiO 2 ₄

The measurements made on the quenched specimens give the same values as in the embodiment example 1. The dispersion of the emissivity values is significantly improved; whereas in the embodiment example 1, measuring values between 3.2 and 3.8%, the values measured in this embodiment 3 are 3.5% and 3.6%.

Claims

A low emissivity and high thermal resistance layer system for transparent substrates, in particular for windows, comprising in the following order a lower antireflection coating consisting of one or more partial layers, a functional layer based on silver, a barrier coating disposed above the functional layer, an upper antireflection coating consisting of one or more partial layers and a covering layer consisting of one or more partial layers, characterized in that the coating barrier comprises a barrier layer disposed above the functional layer which is a metal or slightly nitrided layer of a titanium alloy consisting of 50 to 97% by weight of Ti and 3 to 50% by weight of one or several metals Cr, Fe, Zr and Hf, this barrier layer being at least partially oxidized after a possible heat treatment. 2. A layer system according to claim 1, characterized in that the barrier layer is a metal or slightly nitrided layer of an alloy consisting of 55 to 60% by weight of Ti, 35 to 45% by weight of Zr and 1 to 5% by weight of Hf. 3. Layer system according to claim 1 or 2, characterized in that the barrier coating comprises an additional sub-oxidized layer of a titanium alloy and a thickness of 1 to 3 nm disposed above the barrier layer. metallic or weakly nitrided. 4. System of layers according to the preceding claim, characterized in that the titanium alloy comprises chromium. 5. System of layers according to one of claims 1 to 4, characterized in that the lower antireflection coating comprises a wetting layer consisting essentially of ZnO to which the functional layer is connected. 6. A layer system according to one of claims 1 to 5, characterized in that the covering coating comprises a nitrided or oxynitrided layer of a titanium alloy consisting of 50 to 97% by weight of Ti and from 3 to 50 % by weight of one or more of Cr, Fe, Zr, Al and Hf metals. 7. A layer system according to one of claims 1 to 5, characterized by the following structure: glass / SnO ₂ / ZnO: Al / Zn / Ag / TiZrHfN ₇ / ZnO: Al / Si ₃ N ₄ / ZnSnSbO _x / Zn ₂ TiO ₄ . 8. Layer system according to one of claims 1 to 6, characterized by the following layer structure: glass / SnO ₂ / ZnO: Al / Zn / Ag / TiZrHfN ₇ / ZnO: Al / Si ₃ N ₄ / TiZrHfN _y . 9. System of layers according to one of claims 1 to 5, characterized by the following layer structure: glass / SnO ₂ / ZnO: Al / Zn / Ag / TiZrHfN ₇ / TiCrO _x / ZnO: Al / Si ₃ N ₄ / ZnSnSbO _x / Zn ₂ TiO ₄ . 10. Transparent substrate with a layer system according to one of the preceding claims. The substrate of claim 10 which is in the form of a thermally toughened pane after the deposition of the layer system.