Thermally insulating glazing with a low emissivity

The invention relates to a thermally insulating glazing having a set of layers which have a low emissivity, preferably a high transmission in the visible range of the light spectrum, as well as neutral appearance in transparency and reflection, these successive layers respectively composed of the following materials and arranged in the order Next: tin oxide - zinc oxide - silver - sacrificial metal - oxide tin.

Glazing provided with a stack of thin layers and heat insulation with a low emissivity are all particularly used as thermal insulation glazing. For a given insulating glass structure, the heat transfer coefficient is essentially determined by the emissivity of the two inner surfaces glasses, which arranged facing each other, delimit the gap present in the glazing. This emissivity, also known as emissivity and designated by the letter ε, is relatively high for a glass surface devoid of any coating. It mounts in effect to about 0.85. The use of glazing with a low-emission coating and having an emissivity ε less than or equal to 0.7 on the side facing the gas-filled gap allows almost completely stop the trade between radiation glass surfaces. It thus becomes possible to produce in this manner insulating glass whose coefficient K (heat transfer coefficient calculated according to ISO 10292) is equal or less than 1.3 W / m²K, which allows for significant energy savings. Apart low K value, insulating glass with optimum qualities must also have a transmission capacity of overall energy (or g-value) as high as possible so that the passive use of solar energy is important and so that the energy balance of a building to be favorable. In addition, the color reflection of this glazing to the outside must be neutral as to the conventional insulating glass.

Such a glazing having a layer sequence such as that mentioned above is already in DE-A1-39 41 027. This glazing known contains, in order, the following layers: 15 nm of SnO₂ ; 14 nm ZnO; 12 nm Ag - 10 nm stainless steel to be converted into oxide; 14 nm SnO₂ ; 10 nm of TiO₂. This glazing is intended to be used as glazing Motor vehicle provided with an electric heater. The combination of layers should therefore have a high electrical conductivity and high thermal resistance in order to support the process of bending and / or tempering glass substrates. During the heating of glass substrates heated to a temperature enabling them to be bent / toughened, before this heating process bending / toughening, the sacrificial metal layer is converted to a large measurement in a metal oxide layer which protects the silver layer oxygen may seep. On the upper layer of tin oxide been disposed another layer consisting of titanium dioxide, supposed allow to increase the resistance of glazing to abrasion. this combination known between layers requires further that the zinc oxide layer located under the silver layer has a thickness of 15 nm maximum.

A glazing provided with this layer structure has been advantageous properties for the intended use as a heating glazing motor vehicle. However, for use as glazing thermally insulation in the building sector, it has neither the high transmission desired in the visible range of the spectrum or optimum emissivity.

The invention aims to improve the structure of the stack layers mentioned above, so as to produce a glazing thermally insulating provided with particularly favorable properties for its use in the building sector, glazed with a high light transmission greater than 80%, a high color neutrality transmission and in reflection, a low emissivity of less than or equal to 0.05, and a high transmission capacity of overall energy.

This can be achieved in accordance with the invention, in the Since the multiple layer has, starting from the surface of glass substrate type, the structure below with the sequence of layers whose thicknesses are as follows:<tables><table><tgroup cols="2"><tbody><row><entry align="left">SnO₂</entry><entry align="right">10 to 30 nm, especially from 18 to 22 nm</entry></row><row><entry align="left">ZnO</entry><entry align="right">16-30 nm, especially 16-22 nm</entry></row><row><entry align="left">Ag</entry><entry align="right">7 to 15 nm, preferably 10 to 13 nm</entry></row><row><entry align="left">Ni-Cr (80/20)</entry><entry align="right">0.5 to 5 nm, in particular 2 to 5 nm</entry></row><row><entry align="left">SnO₂</entry><entry align="right">30-50 nm, especially 38-42 nm</entry></row></tbody></tgroup></table></tables>

More generally, the invention relates to a stack of layers comprising at least one layer of infrared reflective type silver layer disposed between two coatings based material dielectric, with preferably at least between said layer and the coating upper dielectric matérieu (furthest from the substrate surface bearer of the stack), a sacrificial layer << >> deposited as metal and capable of at least partially oxidizing during the deposition of superior dielectric materials, especially when they are based oxide.

Under the reflective layer is advantageously provided a coating of dielectric material multilayer << >> comprising the sequence SnO₂/ ZnO or Nb₂O / ZnO or Ta₂O₅/ ZnO or WO₃/ ZnO or Sb₂O₅/ ZnO. Advantageously, the invention provides a significant thickness in ZnO, which have a particularly beneficial effect on the quality of deposition of the reflective layer. The thickness of ZnO may thus be at least 16 nm, especially 16 to 30 nm. The thickness of the layered material or dielectric in the ZnO layer is adjusted so that the thickness geometric total of the bottom coating << >> (between reflective layer and carrier substrate) is for example between 30 and 70 nm. this coating << >> Lower may also include a base layer of Si₃NOT₄, In addition to or in instead of the underlying layers of oxide ZnO.

If using a deposited layer under said metallic form << >> Sécrificielle on money, it can be selected from at least one of the following metals: nickel, chromium, nickel-chromium alloy, tantalum, niobium, zinc, palladium, zirconium. Its thickness is adjustable, in particular between 0.5 nm and 5 nm. It is generally about 1 to 2 nm.

The upper dielectric coating << >> can be monolayer or multilayer, and in particular comprise at least one layer of one of the following oxides: SnO₂, ZnO, Ta₂O₅, Nb₂O₅, WO₃, Sb₂O₅, TiO₂. each of layers or layer, if it is unique, may also be a mixture of at least two of these oxides. The coating may also include materials If dielectric type₃NOT₄. The total geometrical thickness of the coating << >> Upper may be selected from the same range as for the coating <<inferior>>.

One can also choose to split << >> the above stacks in using not one, but two layers of silver, << >> topcoat of the reflective layer closest to the carrier substrate constituting the << >> lower coating of the second, in particular.

The or each reflective layers of silver type has a thickness preferably selected between 7 and 15 nm, especially around 10-12 nm.

thus the invention is applied mainly to the manufacture of glazings multiple type double or triple glazing. Advantageously, at least one of the faces of one of the transparent substrates of the glass type constituting the Glazing is provided with the stack described above. In effect optimum, it is expected that all sides of the glass-type substrates turned on the side of (the) blade (s) of intermediate gas (s) are equipped with, type of stack.

With the invention, one can achieve multiple glazing, e.g. double glazing whose T_L exceeds 75 or even 80%, and whose emissivity is and even less than 0.1 to 0.05: the glazing according to the invention combine high transparency and high performance thermally.

The invention will be described below in more detail with the aid of a specific non-limiting embodiment illustrated by Figure 1 showing in cutting a substrate provided with the stack of layers (the proportions are not respected for easier reading.

A layered structure having these advantageous properties present for each of the following thicknesses layers:<tables><table><tgroup cols="2"><tbody><row><entry align="left">SnO₂</entry><entry align="right">20 nm</entry></row><row><entry align="left">ZnO</entry><entry align="right">17 nm</entry></row><row><entry align="left">Ag</entry><entry align="right">11 nm</entry></row><row><entry align="left">Ni-Cr (80/20)</entry><entry align="right">4 nm</entry></row><row><entry align="left">SnO₂</entry><entry align="right">40 nm</entry></row></tbody></tgroup></table></tables>

A glazing panel having this layer structure is shown in attached figure. The glazing 1 is, for example, consisting of float glass and has a thickness of 4 mm. All available first on one of the faces float glass 1 the dielectric layer 2 consisting of tin oxide and thickness of 20 nm, the dielectric layer 3 of zinc oxide of 17 nm thick is placed on this layer of tin oxide. The silver layer 4, a thickness of 11 nm, is directly on the zinc oxide layer. Sure this silver layer is disposed the sacrificial metal layer, Ni-Cr, 4 nm thick, on which is in turn deposited the dielectric layer 6 tin oxide, the thickness is 40 nm.

The achievement of this stack of layers is done in known manner, according to the sputtering process assisted by a magnetic field, in an industrial plant for continuous production, with a number corresponding cathodic areas, the oxide layers are obtained, as is usually used by reactive sputtering, with a gas containing oxygen and from metal targets. he also be ensured during the execution of the deposition process, that the latter parameters are identified and addressed in order to achieve the desired layer thicknesses. an alloy is used nickel / chromium, in the following proportions by respective weight:<sl><li>Ni = 80% </li><li>Cr = 20%,</li></sl>for the sacrificial metal layer. (The amount of Cr may be more important and up to 80% by weight of the alloy).

Optical measurements on a float glass having a thickness of 4 nm and having a coating of a structure advantageous layers of the invention have yielded values following:<sl><li>ε (emissivity): 0.04 (less than 0.1, preferably less than 0.05)</li><li>T_L (Transmittance of visible light) to DIN 67 507: 82.5% (from preferably between 75 and 85%).</li></sl>

An insulating glazing made from two float glass sheets and and provided with coatings having a wide gap of 16 mm filled with Argon gas, for glazing which glass surfaces provided with coatings are facing the gap containing the gas has a value g according to the DIN 67507 standard of 58% and a K value according to DIN 52612 of 1.1 W / m²K.