FR2676047A1 - Glass substrate covered with thin metal multilayers for solar protection - Google Patents

Abstract

Glass substrate (1) comprising a functional layer (3) of metal alloy based on chromium and nickel, deposited over a layer (2) based on titanium oxide and optionally covered with a layer (4) of metal compound such as titanium oxide or nitride or tantalum oxide. The invention also relates to the application of such a coated substrate to a windowpane for solar protection.

Description

GLASS SUBSTRATE COATED WITH METAL NINCES HULTICOUCEES
FOR SUN PROTECTION.

 The invention relates to the field of glazing for thermal insulation and / or sun protection, and more particularly a glass substrate provided with functional thin layers deposited under vacuum.

 This type of multilayer substrate is here intended more particularly for the equipment of buildings. Indeed, by acting on the amount of energy of the solar radiation, it makes it possible to avoid, inside the premises, an excessive heating particularly uncomfortable in summer, and thus helps to limit the energy consumption necessary for the air conditioning of said premises. This point is all the more crucial since the current trend is to increase the proportion of glazed surfaces on the facades of buildings.

 However, there are other requirements for such layer substrates to be used in building, and first of all a requirement for the durability of thin layers, especially in the case where they are intended to be used as monolithic glazing.

 It is indeed important that this coated substrate can be used optionally in monolithic glazing. This means that the thin layers must prove to be resistant over time, even without these being protected as would be the case inside laminated glazing or multiple glazing type double glazing. monolithic, the thin layers, used on face 2, that is to say on the interior side to the room, are directly subjected to aggressions as well of mechanical order, for example by friction creating scratches causing appearance defects seen both in transmission and in reflection, as well as chemical aggressions, for example in contact with humidity and / or pollution of the ambient atmosphere or when cleaning the glazing with chemicals .

 Neither should one neglect an aesthetic requirement: it is desirable that the glazing in reflection on the glass side can have diversified and in particular rather soft, pastel shades.

 It is not usually necessary to have, for the building, glazing with very high light transmission as can be the case for the automobile, for windshields for example, but it is nevertheless advantageous to be able to offer glazing with different levels of light transmission.

 As for the process for obtaining thin layers, vacuum deposition techniques, in particular using sputtering, are well known and allow the optical performance of the layers obtained to be well controlled. We know in particular those which are carried out in the presence of a magnetic field which multiplies the shocks of the ions on the target and accelerates the deposition. One can quote for example the patent DE-24 63 431 C2, which presents such a process using a planar magnetron, and the patent US-4 116 806, which uses a target in the form of belt, known as belt-track.

 Likewise, reactive sputtering techniques are known which make it possible to obtain a thin layer by reacting the target material with a plasma gas, US Pat. No. 3,907,660 thus presents such a method for the deposition of oxide. metallic on glass.

Among the metallic thin layers and others acting on solar radiation, in particular by reducing the energy transmission Tz both by absorption and by reflection, layers based on chromium-nickel alloy or iron-chromium-nickel are known. So the patent
US-4,022,947 more particularly presents a glass substrate provided with a layer made from one of these alloys and with a layer of oxide corresponding to said alloy. This oxide layer is placed either on the metal layer, itself deposited on the substrate, or between the substrate and said metal layer. In the first case, it has an essentially protective role, but without this protection being encrypted. In the second case, it has an essentially interference role in modifying the coloring on the glass side, but without the patent indicating its intensity.

 The object of the invention is therefore to obtain a substrate with thin multilayers, effectively fulfilling a sun protection function, very resistant on the side of these layers both mechanically and chemically, and possibly offering a palette of colors and purities. shade in reflection on the diversified glass side.

 According to the invention, the glass substrate comprises a functional layer of metallic alloy essentially based on chromium and nickel. The alloy may also contain in particular iron and thus belong to the family of stainless steels. Preferably, said alloy is nitrided, which gives it greater mechanical strength. Its thickness is variable, between 10 and 100 nm. Indeed, it is this layer which gives the final glazing its sun protection properties, by reducing the value of T.

 It should be noted that with this type of layer, it is impossible to act on this factor Tz without also acting on the light transmittance factor TL, since more than 50% of the solar energy is in the range of wavelengths between 0.38 and 0.78 nm, that is to say in the visible range. This leads, depending on the thickness of the alloy layer used, to proposing glazings having different "pairs" of value TL and Tz, each corresponding to a judicious compromise between visibility in sufficient transmission for acceptable thermal comfort, would not be - depending on the latitude of the countries for which the final glazing is intended.

 Advantageously, a nickel-chromium alloy is chosen because it is easy to implement and of moderate cost.

The mass ratio of nickel and chromium is preferably of the order of 55/45 in the case where the alloy contains essentially nickel and chromium.

 This layer based on metal and metal compounds according to the invention is placed on a layer of metal oxide which will be designated by the term of "sublayer" which, for its part, is deposited directly on the glass substrate. It is more preferably coated with another layer of metallic compound which will be designated by the term "over-layer".

 The sub-layer is advantageously based on titanium oxide Tin2, its thickness is between 10 and 220 nm.

It has a triple function: in addition to the fact that it promotes the adhesion of the metal layer to the substrate, its thickness when it is significant gives it an interference role to act on the appearance in light reflection of the glazing, but also a primordial role as regards the physico-chemical behavior of the entire stack of layers. Indeed, surprisingly, the authors of the present invention have highlighted, as cited in the example below, the fact that the nature of the underlay is not indifferent with respect to behavior in the face of aggressions, in particular of 'chemical order, of the whole stack.

 Thus, if the undercoat is not chosen adequately, chemical corrosion may appear at the undercoat, and more particularly at the glass / undercoat interface, said corrosion resulting in destruction. localized underlayment and thereby causing the upper layers to peel off. Now very advantageously, titanium oxide is particularly chemically resistant both to humidity and to pollution and is therefore perfectly capable of fulfilling this function.

 ta overcoat when it is present is a metallic compound, in particular oxide or nitride, and preferably in titanium oxide or nitride TiO2 or TIN or in tantalum oxide Ta205. The overlay has a primary mechanical and chemical protective function for the functional layer it covers. Depending on its thickness and that of the functional layer, it can also have an interference role and thus contribute to the reflection aspect of the glazing. Its thickness is at most 50 nm and preferably at least 5 nm. However, depending on the spectrophotometric characteristics sought and the minimum performance required for the application, one can also consider removing this overcoat and therefore having a stack limited to two thin layers: the sublayer and the functional layer.

 The substrate provided with these two or three thin layers can therefore be used both in monolithic glazing and associated with another substrate. It is advantageously used in the building and in the automobile for glazed surfaces which do not require very high T1.

The details of advantageous characteristics of the invention appear from the detailed description of the thin film substrate according to the invention, made with reference to the attached drawing which represents
- Figure 1: a simplified diagram of a glass substrate with thin layers according to the invention.

 For the sake of clarity, the thickness ratios have not been respected.

 It is specified that all of these thin layer deposits are made one by one on the substrate preferably by the magnetron sputtering technique in a reactive atmosphere, but could be carried out by any vacuum deposition technique allowing good control of the thicknesses of the layers. filed.

 The substrates 1 made of soda-lime-silica glass, in particular floats, are introduced by an airlock system into the spraying chamber of the deposition installation. This spray chamber is equipped with cathodes with targets made of materials corresponding to the deposits to be made.

 In the case where the sub-layer 2 is made of titanium oxide Tin2, the functional layer 3 is made of an alloy based on nitrided nickel-chromium and the over-layer 4 is also made of titanium oxide Tin2, the three deposits are made by successive passages of the substrate under a titanium target in a controlled atmosphere consisting essentially of argon and oxygen, then under a nickel-chromium alloy target in a controlled atmosphere consisting essentially of argon and nitrogen, then again under a titanium target again in a controlled atmosphere of argon and oxygen.

 For the deposition of the functional layer 3, the control of the percentage of argon relative to that of the nitrogen makes it possible to control the nitriding rate of the deposited layer.

 In known manner, the powers applied to each of the cathodes as well as the running speed of the substrate are adjusted so as to obtain the thicknesses desired for the layers.

First of all, it is specified that the appearance in external reflection of the substrate provided with the layers according to the invention is appreciated by three values: the value of the external light reflection, glass side, R1L given by the configuration of the spectrum in reflection in the visible of said substrate taking into account the sensitivity of the eye and a standardized light source designated by the term illuminant Ds5, the value of the dominant wavelength
J dom (R1L} in nanometers indicating the color in reflection, and the excitation purity pe (RlL) indicating the "saturation" of this color.

 The value of the light reflection on the interior side, on the side of the thinned layers, for its part, is noted below RzL.

In addition, the tests used to assess the mechanical resistance of the stack of thin layers according to the invention are now specified - the abrasion tests used to assess the mechanical resistance of the layers are carried out using grinding wheels made of abrasive powder embedded in an elastomer. The machine is manufactured by the Taber Instrument Cor poration Company in the United States. This is model 174, "Standard
Abrasion Tester ", the grinding wheels are of the CS1OF type loaded with 500 grams. Each sample is subjected to 300 rotations, its overall light transmission t is measured at a wavelength of 550 nm before (l) and after (# 1300) abrasion .

Abrasion wear is measured by the quantity U
T300 - To
U = -------
100
The standardized chemical resistance tests carried out are as follows - the resistance tests in contact with neutral saline and cuproacetic saline mists comply with standard DIN 50021. They consist notably in measuring the time that elapses (in days) until the moment where the first defect appears in the stack of thin layers, when this is subjected to the normalized atmospheres corresponding to the two tests.

- the SOz sulfur dioxide resistance test meets the DIN 50018 standard. On the same principle as the two previous tests, it determines the duration (in 8-hour cycles) that elapses until the appearance of the first default.

EXAMPLES IA 4
The series of nonlimiting examples 1 to 3 relates to a thin film substrate having a reflection in the visible from the side of the glass colored in bronze.

 The metal target used to obtain the functional layer 3 is made of INCONEL 671 for Examples 1 and 2, that is to say essentially based on Ni-Cr according to the ASES standard. A sintered target is preferably chosen here, obtained from nickel and chromium powders in the appropriate proportions. In this way, "grains" of diameters small enough to obtain uniform spraying are obtained.

 A homogeneous fusion ban between the two powders must also be carried out in order to obtain a non-magnetic target.

 In Example 3, layer (3) also contains iron and the target is made of SST 316 steel, A.I.S.I.

 The substrate 1 is made of clear float-soda-lime silica glass 6 mm thick.

 The thickness of layer 3 is adapted in each example in order to obtain the desired light transmission value TL. Here, it is between 10 and 100 nm.

The thicknesses in nanometers of the sublayer 2 in
TiO2 of the functional layer 3, of the overlay 4 in Tin2, as well as the light transmission T1 of the substrate / multilayer assembly are indicated below
EXAMPLES | (2) TiOz (3) NiCrNx (4) TiO2
1 1 15 15 10 35%
2 1 15 28 10 21%
3 1 15 28 10 21%
It can be seen that by varying the thickness of the functional layer 3 within the range of values previously indicated, it is possible to obtain a wide range of light transmission TT.
In order to demonstrate the good performance against mechanical and chemical corrosion of the substrates covered according to the invention, these 3 examples were compared, and more particularly Examples 2 and 3, with Example 4 consisting of a similar stack of three metal oxide-nitrided metal alloy-metal oxide layers on the same substrate, the characteristics of which are as follows
undercoat (2): mixture of zinc and tin oxides,
10 nm
layer (3): stainless steel 316 AISI standard,
20 nm
overlay (4): titanium oxide, 10 nm.

The photometric characteristics of Examples 2, 3 on the one hand and 4 on the other hand are close, knowing that the last column of the following table indicates the color in reflection on the side of the substrate: EX.! T, R1L R2L Tz rtdom (R1L) pe (R, L) coul (RlL) --- I
2 I 21% 26% 32% 18% 493 2.1% light bronze
3 1 21% 25% 30% 17% 504 0.8% light bronze
4 1 20% 25% 35% 17% 490 2.1% light bronze
In all three cases, we obtain in R1L a color in a very pastel bronze tone.

Corrosion tests of the three coated monolithic substrates, however, give very different results EX. abrasion fog fog sulfur dioxide
I cupro-acetic saline --- I
2 1 2.5>78>90> 20
3 1 1.5>78> 90 5
4 1 2.1 14 1 1
The weakness of the results in the chemical tests of Example 4 seems to exclude its use in monolithic glazing under extreme conditions of humidity and / or pollution.

 On the other hand, the stacks of Examples 2 and 3, and more particularly of Example 2 according to the invention have excellent chemical resistance, which highlights the surprising combined effect of a TiO2 undercoat and of a nitrided metal layer, which makes it possible to use a substrate with this type of stack in monolithic glazing, whatever the conditions of use and / or climatic conditions to which said glazing is normally subjected.

 In these examples, we have chosen a thin thickness for the Tio2 sub-layer 2, which makes it possible to obtain a glazing whose color in reflection R1L bronze is fairly appreciated aesthetically in the building. It is clear, however, that by playing on this thickness, and in particular by increasing it appreciably, an interference effect is obtained making it possible to modify this tone. This then makes it possible to be able to offer glazings having different values of TL, and, for each of these values, different colors in reflection R1L.

Claims (13)

 1. Glass substrate (1) with thin multilayers comprising a functional layer (3) based on chromium and nickel, characterized in that this layer (3) is deposited on a layer (2) based on titanium oxide .  2. Substrate according to claim 1, characterized in that the functional layer (3) is covered with a layer (4) of metallic compound made of tantalum oxide.  3. Substrate according to claim 1, characterized in that the functional layer (3) is covered with a layer (4) of metallic compound made of titanium oxide.  4. Substrate according to claim 1, characterized in that the functional layer (3) is covered with a layer (4) of metallic compound made of titanium nitride.  5. Substrate according to one of claims 1 to 4, characterized in that the functional layer (3) is nitrided.  6. Substrate according to one of claims 1 to 5, characterized in that the functional layer (3) is based on nickel-chromium in mass proportion of the order of 55/45.  7. Substrate according to one of claims 1 to 5, characterized in that the functional layer (3) also contains iron and belongs to the family of stainless steels.  8. Substrate according to one of claims 1 to 7, characterized in that the thickness of the functional layer (3) is between 10 and 100 nm.  9. Substrate according to one of claims 1 to 8, characterized in that the thickness of the layer (2) of titanium oxide is between 10 and 220 nm.  10. Substrate according to claim 2, 3 or 4 and one of claims 5 to 9, characterized in that the thickness of the layer (4) of metal oxide placed on the functional layer (3) is between 5 and 50 nm.  11. Substrate according to claim 3 and one of claims 5 to 10, characterized in that are deposited on the substrate (1) in clear float glass of 6 mm respectively a layer (2) of TiO2 15 nm thick then a layer (3) of nickel-chromium nitrided 55145 in mass proportion, then a layer (4) of titanium oxide 10 nm thick, the thickness of the layer (3) of nitrided NiCr being adapted so that the substrate provided with these three layers has a light transmission of approximately 21%.  12. Substrate according to one of claims 1 to 11, characterized in that the non-purely metallic layers are obtained by reactive sputtering under vacuum assisted by magnetic field, metallic oxides in the presence of oxygen, and nitrided and / or metallic alloys nitrides in the presence of nitrogen.  13. Application of the substrate according to one of claims 1 to 12 to a sun protection glazing intended for the building or the automobile.