EP1366001A2

EP1366001A2 - Prestressable low-e layer systems for window panes

Info

Publication number: EP1366001A2
Application number: EP02700382A
Authority: EP
Inventors: Heinz Schicht; Herbert Schindler; Lars Ihlo; Uwe Schmidt
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2001-02-06
Filing date: 2002-01-23
Publication date: 2003-12-03
Also published as: US7211328B2; US20040126591A1; DE10105199C1; TR200301214T2; CZ20032116A3; WO2002062713A3; CA2435811A1; PL369996A1; JP2004526650A; AU2002233460A1; BR0206938A; CN1501896A; WO2002062713A2; CN1289428C; KR20030075170A

Abstract

The invention relates to a stack of layers capable of resisting a strong thermal stress, comprising silver as a functional layer, a sacrificial metal layer disposed on top of the silver layer and anti-reflection dielectric layers. The inventive system comprises a layer of metal nitride between the silver layer and the sacrificial metal layer. Said metal nitride layer comprises, in particular, Si3 N4 and/or AlN and constitutes an effective barrier against diffusion. As a result, the optical and energy properties of the silver layer remain essentially unchanged even after a strong thermal stress (for example, bending-type prestressing and/or curvature, tempering of glass provided with the stack of layers).

Description

Low E preloading layer systems for window panes

The invention relates to a stack of layers with low E, capable of withstanding high thermal stress, for glazing (intended to equip buildings or vehicles), having the characteristics of the preamble of claim 1. The glazing, provided of a stack of layers with low E (low E means "low emissivity", therefore, low emissivity or strong reflection of waves in the infrared spectrum), are used in particular to improve thermal insulation in windows of buildings and vehicles. The actual thermal insulation function is carried out in this case, most of the time, using one or more layer (s) of silver (what is called the "functional layer"). In the case of insulating glazing for example, it is possible to almost completely block the radiative exchange between the glasses using glazing of the double-glazing type having an emissivity of E <0.1 on the side facing the space between the two glasses. It is thus possible to manufacture insulating glazing units with a k value of 1.1 / m ² K.

Glazing provided with optimum low E layer stacks must also have the highest possible overall energy transparency (a g value as high as possible), in order to be able to use the incident solar energy for the balance energy of a building. The transmission must ultimately be as high as possible in the visible range of the spectrum. The reflection color of coated glazing must be neutral, as is the case with conventional insulating glazing. In certain cases, it is necessary or appropriate to subject glazings (at least one of the glasses which compose them) provided with a stack of low E layers of this kind, to a curvature or prestressing treatment, of the bending type or tempering. To this end, the glasses are heated, before the actual bending or prestressing treatment, at a temperature of approximately 550 ° to 650 ° C. During this thermal stress, structural changes in the silver layer often occur due to oxidation and diffusion processes. These modifications of the silver layer manifest themselves, even if they are not recognizable to the naked eye, by a deterioration of the energy values, in particular of the transmission and of the emissivity. When, for example, insulating glazing made of two 4 mm thick glasses and an intermediate space filled with argon with a thickness of 16 mm, must have a k value of 1.1 / m ² K, the emissivity of the layer system of glass panes must not be more than 5%. This corresponds to an electrical resistance of maximum 4.5 Ohm per unit area.

There is a high demand for stacks of layers of this kind, capable of withstanding high thermal stress, the emissivity and diffuse dispersion (haze) are very low, even after heat treatment (prestressing), with preservation optical properties, without affecting other layer quality criteria, such as hardness, color and corrosion resistance.

Various suggestions have already been made with a view to improving the layer stacks Of this genre. The desired optical and energy values of the coated panes must therefore be substantially maintained, even in the case of glass panes, which are subjected, after having been coated with the layers, to a bending or prestressing operation. Deterioration of the properties of the layers as a result of the heat treatment must be prevented or at least limited.

Document DE-A1-196 32 788 discloses a stack of layers capable of prestressing of the aforementioned type, for which the anti-reflection dielectric layers consist of an oxide of the metals Sn, Zn, Ti, Si or Bi, or SiN or AIN, and the metallic sacrifice layer of an AlMgMn alloy. The metallic sacrifice layer has a thickness of 5 to 10 nm. The term “capable of prestressing” denotes here stacks of layers of this kind which withstand without significant degradation the high temperatures of the bending and / or quenching operations.

Document DE-A1-196 40 800 describes a stack of layers based on silver, according to which there is, between the metallic sacrifice layer and the upper anti-reflection layer, an intermediate layer made of an oxide, a nitride or oxynitride of the metal of the metallic sacrifice layer. The upper anti-reflection treatment layer consists of an oxide, a nitride or an oxynitride of a metal other than the metal of the metallic sacrifice layer. It can also be the superposition of at least two such layers. The term "upper" means that the layer or layers in question are above the or at least one of the functional layers of the stack, as opposed to the term "lower". From documents EP-B1-0 567 735, EP-B1-0 717 014, EP-B1-0 771 766, EP-B1-0 646 551 and EP-A2-0 796 825, layers of layers are known, capable of prestressed, having a silver layer as a functional layer, with two anti-reflection layers each consisting of Si ₃ N ₄ , and the metallic sacrifice layer of Ni or NiCr. The stack of layers, capable of prestressing, described in document EP-B1-0 883 584, has anti-reflection layers preferably made of Si ₃ N ₄ , the metallic sacrifice layer consisting, however, in this case of silicon. A stack of layers, capable of prestressing, known from document DE-A1-198 50 023, is characterized in that a sub-oxidized layer of NiCrO _x , with a thickness of between 0.1 and 0.2 nm, is embedded in the surrounded silver layer disposed between a lower metal sacrifice layer and an upper metal sacrifice layer. The metal layers of sacrifice consist of NiCrO _x sub-oxidised or NiCrO _x and Ti0 ₂ sub-oxidized. This known stack of layers must make possible a prestress and a curvature of coated glass panes, without any notable modification of the optical properties of stacking layers. The diffuse dispersion (haze) after the heat treatment must, in particular, be less than 5%. Document DE-CI-198 52 358 describes a stack of layers with low E, capable of withstanding high thermal stress, having a sequence of glass layers-MeO-ZnO-Zn-Ag-AlMe-MeO-Zn _x Me _y Y _n . The metallic sacrifice layer AlMe is in this case, as a constituent of the alloy above the silver layer, an aluminum alloy with one or more of the elements Si, Mg, Mn, Cu and Zn.

None of the known layer stacks fulfills all the essential properties in an optimal manner. In most cases, the layers of layers have, after the heat treatment, too high an emissivity and a diffuse dispersion (strong) relatively strong.

The object of the invention is to further improve a stack of layers with a low E, capable of withstanding a high thermal stress, as mentioned above.

According to the invention, this object is achieved thanks to the features of claim 1. It is understood that stacks of layers of this kind are not necessarily used exclusively on glass substrates, that these can also be used / judiciously deposited on substrates made of other transparent materials (synthetic material) (for example polycarbonates, poly methyl etacrylate PMMA, polyethylene terephthalate PET, etc.). Synthetic (polymer-based) materials are of course not able to withstand temperatures as high as glass.

It has been found that a metal nitride layer between the silver layer and the metallic sacrifice layer represents an effective barrier. It prevents or greatly reduces the diffusion of atoms of the sacrifice metal in the silver layer and vice versa. Metal nitrides are in fact relatively stable compounds, which, for their part, show no tendency to diffusion movements towards the interior of the silver layer. The silver layer thus retains its original structure (to a large extent) on its particularly threatened upper boundary surface, even after high thermal stress. All in all, therefore, its good optical and energy properties are preserved.

The metallic sacrifice layer preferably consists of Cr, Ni, Al, Ti, Mg, Mn, Si, Zn or Cu, or an alloy of these metals.

It is also possible to provide a metallic layer of sacrifice below the silver layer. This metallic sacrificial layer preferably also consists of one of the metals mentioned or of an alloy of these metals. There is also, in this case, a layer of metallic nitride between the metallic sacrificial layer and the silver layer.

In the case of layer stacks, for which the silver layer is deposited on a partially crystalline ZnO layer, the use of a metal nitride layer below the silver layer is not necessary.

The lower anti-reflection layer and the upper anti-reflection layer may consist of an individual layer of oxide (s) and / or nitride (s) and / or of oxynitride (s), or of the superposition of several individual layers like this.

The selection and the thickness of the individual layers are carried out within the framework described so that the optical values, such as the transmission and the reflection color of the coated (glass) substrate, change significantly and reproducible during heat treatment. The light transmission is, in particular, markedly increased, and the reflection color undergoes, after the heat treatment, a change in “color box”. Under the term "change of color box", specialists designate a modification of the coloring or of the tint (reflection color) of a layer or of a stack of layers. The possible colors can be described in the context of a special coordinate system, for example, the L, a *, b * colorimetry system. Because layer colors cannot be reproduced absolutely precisely in this stack of coordinates, areas of color tolerance are established between suppliers and customers, who are then referred to as "boxes of color ”(“ color box ”in English). By change of color box, we mean a change in color or tint such that it goes beyond the limits of a first color box (starting state) in another color box (target state or setpoint state).

After the heat treatment, the diffuse dispersion is at most 0.3% and the emissivity at most 5%. The stack of layers must, of course, also fulfill all the other requirements concerning the properties of use and chemical resistance, which are usually required for layers of this kind.

This is why the stacking of layers according to the invention can also be used entirely without any post-deposition heat treatment being involved, in particular on suitable plastic substrates (for example polycarbonate), because its very good thermal insulation properties are not substantially modified by the heat treatment.

The invention is described below in more detail with reference to two exemplary embodiments, which are opposed in each case to a comparative example in accordance with the state of the art. In this case, the following measurements and tests are carried out, with a view to evaluating the layer properties, on the coated glasses:

A. Measurement of the light transmission T at 550 nm;

B. Measurement of the color parameters in reflection in the system L, a *, b *;

C. Measurement of surface electrical resistance;

D. Measurement of emissivity E using the Sten Lôfving MK2 device; E. Condensation water test in accordance with DIN 50017 with visual evaluation;

F. Measurement of electrochemical resistance (EMK test); this test is described in Z. Silikattechnik 32 (1981), page 216. The test makes it possible to evaluate the passivation resistance of the upper layer above the silver layer as well as the corrosion behavior of the layer of Ag;

G. Erichsen wash test in accordance with ASTM 2486, with visual evaluation;

H. Measurement of scratch resistance; in this case, a loaded needle is drawn at a defined speed on the layer. The weight in g, for which the scratch marks become visible, is used as a measure of the scratch hardness.

I. Measurement of the light scattered in% using the light scattering measurement device from Gardner.

Comparative example 1

On an industrial installation for coating layers by sputtering, the following stack of layers is applied to float glass, in accordance with the state of the art, using the reactive sputtering process assisted by magnetic field. The thickness of the individual layers is indicated in nm each time:

Glass / 25 Sn0 _2/9 ZnO: Al / ll, 6 Ag / 6 AlMgMn / 38 Sn0 _2/2 _x ZnSnSbO.

The layer of ZnO: Al is reactively applied by spraying from a metal target ZnAl at 2% by weight of Al. The metallic sacrifice layer is applied by spraying from a metal target, which contains 94% by weight of Al, 4.5% by weight of Mg and 1% by weight of Mn. The topmost partial layer of the top anti-reflection layer is deposited by reactive sputtering from a metal target, which consists of 68% by weight of Zn, 30% by weight of Sn and 2% by weight of Sb .

The results of the above tests, on several samples, before the heat treatment, provided the following values:

A. T550 transmission = 76 - 77%

B. Color parameters a ^* = 4, 06 b ^* = - 7, 17

C. Electrical resistance R = 6, 8 - 6, 9

Ohm / area

D. Emissivity E = 1, 1 '-

E. Condensation test Red spots

F. EM 132 mV test

G. Wash test 350 back and forth movements with a medium scratch

H. Scratch hardness 65 - 132 g I. Light scattered 0.17%

Several samples of the coated glass were heated to 650 ° C and subjected to prestressing by means of sudden cooling (quenching). Tests or measurements carried out on pre-stressed glasses have led to the following results:

A. Transmission ₅₀ - 88, 9 "S

B. Color parameters a ^* = 1.0 b ^* = -5.1

C. Electrical resistance R = 4.3

Ohm / area D. Emissivity E = 5.3%

H. Scratch hardness 64 - 208 g

I. Diffused light 0.35%

The significant differences in the color coordinates a ^* and b ^* from the pre-stressed state to the pre-stressed state of the glasses show the change in “color box” in question of the stacking of layers.

Example 1

The stack of layers according to the invention is produced on the same coating installation as in the case of the comparative example:

Glass / 25 Sn0 _2/9 ZnO: Al / ll, 5 Ag / 3 Si ₃ N _4/5 AlMgMn / 38 Sn0 _2/2 _x ZnSnSbO.

Measurements and tests on coated glasses before heat treatment provided the following values:

A. Transmission T ₅₅ o = 75.5%

B. Color parameters as for the comparative example

C. Electrical resistance R = 6.7

Ohm / area

D. Emissivity E = 7.5%

E. Condensation test Error free

F. EMK 44 mV test

G. Washing test After 350 back and forth movements, no scratches

H. Scratch hardness 64 - 218 g I. Diffused light 0.14% After prestressing, we carried out on several samples, the same measurements and tests as in the case of the comparative example, and this with the following results:

A. Transmission T ₅₅₀ = 88%

B. Color parameters as for the comparative example

C. Electrical resistance R = 3.6

Ohm / area D. Emissivity E = 4.0%

H. Scratch hardness 70 - 200 g I. Diffused light 0.25%

The light transmission of the stack of layers or coated glasses increases very considerably during the heat treatment, the emissivity being even lower than in the comparative example. The color values change in a similar manner to that of the comparative example, which means that the "target color box" is also reached in a safe manner by virtue of the stacking of layers according to the invention.

Comparative Example 2 The following stack of layers was produced on the same coating installation as in the previous examples, corresponding to the state of the art:

Glass / 25 Sn0 _2/9 ZnO: Al / ll, 5 Ag / 3ZnAl / 38 Sn0 _2/2 _x ZnSnSbO.

The metallic sacrificial layer was deposited by spraying from a metallic target having 98% by weight of Zn and 2% by weight of Al. The EMK test was carried out on the coated glass samples using this layer system, which gave a value of 120 mV. We then submitted the samples to a prestressing treatment. After prestressing, the layer had a slight haze. Measurements were made on the prestressed glass samples for the three most important parameters, namely the measurement of emissivity E, surface electrical resistance and scattered light. The measurements provided the following values:

C. Electrical resistance R = 3.2

Ohm / area D. Emissivity E = 7.3%

I. Diffused light 0.46%

Example 2

Glass was also produced on the same coating installation as in the previous examples, with the stack of layers according to

The following invention:

Glass / 25 Sn0 _2/9 ZnO: Al / ll, 5 Ag / 3 Si ₃ N _4/3 ZnAl / 38 Sn0 ₂ /

2 ZnSnSbO _x .

Performing the EMK test before prestressing provided a value of 8 mV. The visual evaluation also revealed, after prestressing, a layer free of optical defects. The same tests were carried out on the prestressed glasses as in the case of the comparative example. They provided the following values:

C. Electrical resistance R = 3.27

Ohm / area

D. Emissivity E = 4.2% I. Diffused light 0.29%

If we compare the properties of coated glasses according to the invention after prestressing with those of the comparative examples, it is clear that a clear improvement is obtained in both cases, by insertion of the layer of Si ₃ N ₄ , 3 nm thick, between the silver layer and the metallic sacrifice layer. This is particularly the case with regard to corrosion resistance, emissivity and scattered light.

The invention also applies to stacks which have several functional layers, in particular two silver layers: in this case, the nitride layer according to the invention is inserted on one of the silver layers at least, especially on both or only one of them.

Claims

claims

1. Stack of layers with low E emissivity, capable of withstanding high thermal stress, for glazing, in particular glass, as a substrate, with a functional layer (s) based on silver , a metallic sacrifice layer placed above the silver layer, an anti-reflection lower dielectric layer, close to the surface of the substrate, and an upper anti-reflection layer, characterized in that, between the silver layer and the metallic sacrifice layer placed above the silver layer, a layer based on metallic nitride (s), in particular on the base Si ₃ N ₄ and / or AlN.

2. A stack of low E emissivity layers according to claim 1, characterized in that the layer based on metallic nitride (s) has a thickness of 0.5 to 5 nm, in particular 1 to 4 mm.

3. A stack of low E layers according to claim 1 or 2, characterized in that the layer based on metallic nitride (s) has an at least approximately stoichiometric composition.

4. Stack of low E emissivity layers according to any one of claims 1 to 3, characterized in that the metallic sacrificial upper layer consists of Cr, Ni, Al, Ti, Mg, Mn, Si, Zn or Cu , or an alloy of these metals.

5. A stack of low E emissivity layers according to any one of claims 1 to 4, characterized in that the silver layer is deposited on a partially crystalline ZnO: Al layer.

6. A stack of low E emissivity layers according to any one of claims 1 to 4, characterized in that there is, also below the silver layer, a metallic sacrifice layer which is composed of Cr, Ni, Al, Ti, Mg, Mn, Si or Cu, or an alloy of these metals, and which is separated from the silver layer by a layer based on metallic nitride (s).

7. A stack of low E emissivity layers according to any one of claims 1 to 5, characterized by the following layer structure:

Substrate / Sn0 ₂ / ZnO: Al / Ag / Si ₃ N ₄ / AlMgMn / Sn0 ₂ / ZnSnSbOx.

8. A stack of low E emissivity layers according to any one of claims 1 to 5, characterized by the following layer structure:

Substrate / 25 Sn0 ₂ / 9ZnO: Al / ll, 5 Ag / 3 Si ₃ N _4/3 ZnAl / 38 Sn0 _2/2 ZnSnSbOx.

9. Transparent glazing coated with a stack of low E emissivity layers according to any one of claims 1 to 8, in particular made of glass or based on polymer (s), characterized in that it has a T550 transmission of 84 to 88%, and / or a diffuse dispersion of 0.2 to 0.35%, and / or on the layer side, an emissivity E of 4.0 to 5.0%.