ITTO940482A1 - TRANSPARENT GLASS PANELS TO CONTROL SOLAR LIGHT. - Google Patents

Description

DESCRIPTION

of the industrial invention entitled:

"TRANSPARENT GLASS PANELS TO CONTROL THE SUNLIGHT"

Background of the invention

The present invention relates to transparent glazing panels for controlling sunlight.

Transparent and reflective glazing panels to control sunlight have become a useful material for architects to be used on the exterior facades of buildings. Such panels have aesthetic qualities, as they reflect the surrounding environment and, being available in various colors, provide the possibility of decoration. Such panels also have technical advantages, as they protect the occupants of a building from solar radiation by reflecting and / or absorbing and eliminating the glaring effects of intense sunlight, allow effective shielding against glare, improve visual comfort and reduce fatigue. Of the eyes.

From a technical point of view, it is desirable that the glazing panel does not let an excessively large percentage of the total incident solar radiation pass through, so that the interior of the building does not become overheated on sunny days. The total incident solar radiation transmission can be expressed in terms of "solar factor". As used herein, the term "solar factor" means the sum of the total energy transmitted directly and the energy that is absorbed and again radiated on the opposite side of the energy source, as a percentage of the total incident radiant energy of the coated glass . It is also desirable that the glazing panel transmit a reasonable proportion of visible light to allow natural illumination of the interior of the building and to allow its inhabitants to see outside. Visible light transmission can be expressed in terms of the "transmission factor", as a percentage of the incident light falling on the coated substrate. Thus it is desirable to increase the selectivity of the coating, i.e. to increase the ratio of the transmission factor to the solar factor.

There are a number of documents describing glazing panels having a coating that provides protection against solar radiation. For example, U.S. Patent US 4,902,081 (Viracon) promises a low-emissivity, low-shading, low-reflection window, in which one substrate is coated with a first metal oxide layer, a second silver layer, a third layer consisting of a metal such as titanium, a fourth layer of metal oxide and a fifth outer layer of titanium nitride. We have found that a glazing panel constructed in accordance with the teaching of US 4,902,081 has a low purity gray color when viewed in reflection. Although the person skilled in the art might consider depositing additional coating layers to modify the properties of known glazing panels, such an approach would clearly increase the cost and difficulty of fabrication.

From an aesthetic point of view, it is preferred to improve the color purity of the glazing panels when viewed in reflection, particularly so that the entire glass facade of a building has a uniform appearance when viewed from the outside. It has been found that it is particularly difficult to achieve color purity simultaneously with a relatively high ratio of transmission factor to solar factor, in particular with blue colored glazing panels.

Therefore, an object of the present invention is to provide a glazing panel with a high transmission factor, a low solar factor and a high purity of reflected color. A further preferred object of the invention is to provide a glazing panel of this type which uses relatively low cost components and can be formed in a simple manner.

Summary of the invention

According to the present invention, a transparent glazing panel is provided for controlling sunlight comprising a substrate coated with:

(i) a first layer comprising a non-absorbent material;

(ii) a second layer chosen from materials for which, in the wavelength range (λ) from 380 to 780 nm, the spectral absorption index k (λ) is greater than the refractive index n (λ) and, at the wavelength (λ) of 550 nm, the spectral absorption index k (λ) is greater than 1.67 times the refractive index n (λ);

(ii) a third layer comprising an absorbent material for which the spectral absorption index k (λ), in the wavelength range (λ) from 380 to 780 nm, is between 0.3 and 1.0 times the refractive index η (λ) of the material, said third layer having such a thickness that, when applied as a single coating on a 6 mm thick sodium glass substrate, its light transmission factor is reduced by at least 30% ; And

(iv) a fourth layer comprising a non-absorbent material.

The glazing panel according to the invention allows to obtain the joint objectives of high selectivity with a high purity of color in reflection for a low manufacturing cost and a simple structure for the multiple coating. The achievement of a high purity of color is surprising since a layer of absorbent material applied on a multiple coating according to US patent 4,902,081 gives a gray color, seen from the uncoated side of the substrate. The reason for this difference is not fully understood, however it seems possible that the benefit of the present invention derives from the interface between the absorbent material of the third layer and the material of the second layer. We have found, however, that the benefits of the invention are not obtained either if the order of the second and third layers are inverted, when viewed from the same uncoated side, nor if these layers are not surrounded by the first and fourth layers of material. absorbent.

The substrate may be in the form of a film, such as a plastic film, but preferably it is in the form of a sheet of glassy material, such as glass or some other transparent rigid material available in the form of a sheet. It is particularly useful to use tempered or thermally strengthened glass, although laminated glass can also be used. Taking into account the proportion of incident solar radiation that is absorbed by the glazing panel, particularly in environments where the panel is exposed to intense or prolonged solar radiation, there is a heating effect on the glass panel, which means that it is preferably the use of non-strengthened glass as substrate should be avoided.

wavelengths from 380 to 780 nm. The non-absorbent material of the first and fourth layers can be independently selected from zinc sulphide, silicon carbide, lithium, sodium and thorium fluorides, zinc selenide, silicon and aluminum nitrides, aluminum oxynitride, barium titanates and strontium , aluminum oxides, beryllium, bismuth, magnesium, silicon (both SiO and SiO2), tin, titanium, yttrium and zinc, and their mixtures. The non-absorbent material of the first and fourth layers is more preferably selected from Si3N4, AlN, ZnO, SnO2 and TiO2. The table below shows the refractive index n (X) and the spectral absorption index k (λ) of a number of suitable non-absorbent materials, in the range from 380 nm to 780 nm.

Note: 0 *

means less than 10 <-3>

It is particularly preferred that the material of the first and fourth layers be the same material, at least for ease of manufacture, and ideally this material is zinc oxide and / or stannic oxide, while titanium oxide is advantageous if a greater resistance to abrasion. These layers of non-absorbent material act respectively as a basis for the further coating layers and as protection against the external environment. It is usual for the layers of non-absorbent material to have a refractive index which is greater than that of the substrate. It will be noted that, in the layers of non-absorbent metal oxide or nitride material, it is not essential that the metal and oxygen or nitrogen be present in stoichiometric proportions.

The second layer is the layer primarily responsible for the selectivity of the coating. In particular, these materials have a spectral absorption index k (λ) which is greater than the refractive index n (λ) in the visible spectrum region, and at least 1.67 times greater at a wavelength of 550 nm. Suitable materials of this type include metals selected from aluminum, copper, gold, nickel, iridium, platinum, palladium, rhodium, zinc and silver and their mixtures, in particular silver. Lithium, sodium and potassium also have the necessary characteristics, but being reactive they must be used in doped form or in the form of alloys. The table below shows the refractive index n (λ) and the spectral absorption index k (λ) of a number of suitable materials in the range / 380 nm / 550 nm / 780 nm.

When a blue reflected color is required, we prefer to use silver both for cost reasons and for its ease of deposition. In the following description, for the sake of simplicity, this layer is referred to as the silver layer.

The absorbent material of the third layer is a material for which the spectral absorption index k (λ) is comprised between 0.3 and 1.0 times the refractive index of the material. In particular, the material of the third layer can be chosen from tungsten, stainless steel (SS) (for example containing at least 12% chromium), titanium nitrides, chromium alloys or aluminum / titanium, the "nitride" of stainless steel ( SSN), and their mixtures. The table below shows the refractive index n (λ) and the spectral absorption index k (λ) of a number of suitable absorbent materials in the range from 380 nm to 780 nm.

Note: #SSN = stainless steel nitride obtained by cathode spraying using a stainless steel cathode in a nitrogen atmosphere.

Titanium nitride and stainless steel "nitride" are particularly preferred. The nitride layer can also comprise elemental or oxidized metal and in particular it is not necessary that the metal and nitrogen be present in stoichiometric percentages. The absorbent material forms an absorbent layer and its interface with the second layer is responsible for reducing the light transmission factor of the coated glass panel against total solar radiation. The layer of absorbent material also plays an important role in obtaining the desired color thanks to the beneficial effect that derives from its combination with the first, second and fourth layer.

An intermediate layer comprising a sacrifice metal can be arranged between the second and third layers, this intermediate layer having a thickness of less than 10 nm. This sacrificial metal acts to protect the silver layer, in particular from alterations that could result from coating the silver layer with the absorbent material layer and which could lead to loss of panel performance. In addition, a thin layer of sacrifice metal can also be placed between the first and second layers. Preferably, the sacrificial metal is selected from aluminum, bismuth, chromium, nickel-chromium alloy, tin, titanium, zinc and their mixtures. Ideally, the nitride of the third layer comprises a nitride of the same metal used as the sacrifice metal of the intermediate layer. The presence of the intermediate layer can modify the emissivity characteristics of the panel, without significantly changing the reflected color as long as its thickness is relatively small. Advantageously, the intermediate layer has a thickness not greater than 6 nm, preferably not greater than 3 nm. Regardless of whether this intermediate layer becomes totally transparent in the final product, or remains wholly or partially metallic, or is in the form of a nitride, preferably it will be as thin as possible so as not to change the reflected color that the coating would have in the absence of this intermediate layer, except that, if it fulfills the conditions of the third layer, then in this case it forms part of the third layer.

A thin layer of sacrifice metal may also be placed between the third and fourth layers to protect the absorbent layer from alterations that could result from coating that layer with the fourth layer.

The thickness of the various layers applied to the panel is important to obtain optimum performance. We prefer that the optical thickness (measured in transmission) of the first layer is between 10 and 280 nm (the optical thickness is the product of the effective, i.e. geometric, thickness and the refractive index). It is highly preferred that the optical thickness of the first layer is at least 100 nm, while the total optical thickness of the first layer (non-absorbent material) and of the fourth (non-absorbent material) is between 180 and 270 nm, the optical thickness of the first layer being higher than that of the fourth layer, for example about 1.1 to 1.7 times higher. Thus a preferred optical thickness for the first layer (non-absorbent material) is between 110 and 160 nm and that of the fourth layer (non-absorbent material) is between 70 and 120 nm.

Preferably the geometric thickness of the second layer is comprised between 3 and 18 nm, more preferably between 5 and 15 nm.

The geometric thickness of the third layer must be sufficient for the layer to act as an absorbent in the finished product. We have found that the third layer must have the ability, when applied as a single coating on a 6 mm thick sodium glass substrate, to reduce its light transmission factor by at least 30%, i.e. for example TL is reduced from 90% to less than 60%. Preferably the thickness of the third layer is such that, when applied as a single coating on a 6 mm thick sodium glass substrate, the light transmission factor of the substrate is reduced by a maximum of 65%, i.e. for example TL is reduced by 90% to more than 25%. More preferably, the light transmission factor TL is reduced by at least 35% and by a maximum of 60%, i.e. for example it is reduced from 90% to a value between 55% and 30%.

More preferably the thickness of the third layer is such that, when applied as a single coating on a 6 mm thick sodium glass substrate, the light transmission factor TL of the substrate is reduced by a maximum of 54.5%, i.e. for example TL is reduced from 90% to more than 35.5 Z.

The table below shows the translucency (light transmission factor) obtained with various coatings on a 6 mm sodium glass substrate

* It should be noted that stainless steel (SS) will need to be in non-oxidized form to achieve these results. If a coating layer of stainless steel oxidizes, for example during the deposition of a subsequent oxide layer, the thickness of the non-oxidized stainless steel will have to be as given by these figures to obtain the reported transmissivity. Stainless steel oxide is neither suitable as a first layer nor as a third layer.

Therefore, when the third layer material is titanium nitride, we prefer to use a thickness of 12 to 25 nm; when the material of the third layer is stainless steel we prefer to use a thickness of 3 to 6 nm, and when the material of the third layer is stainless steel "nitride" we prefer to use a thickness of 3 to 8 nm.

An increase in the thickness of this layer will decrease the total energy transmission and at the same time decrease the light transmissivity. The thickness of the absorbent material layer will also affect the reflected color.

When an intermediate layer of sacrificial metal is present, then to obtain optimal results this layer preferably has a thickness of 0 to 10 nm, for example not more than 6 nm, ideally not more than 3 nm, in order to maintain a low emissivity of the silver layer without substantially altering the reflected color.

There will usually be no other coating layers present. Thus the first layer is applied directly to the substrate and the fourth layer is an exposed layer. Alternatively, the order of the layers is reversed, so that the fourth layer is applied directly to the substrate and the first is an exposed layer. In this case (inverted order), the advantages of the invention and especially the purity of color, are obtained by observing the panel from its coated side.

The glazing panels according to the invention can be produced with generally known methods, in particular by subsequent deposition under vacuum. One proven technique for applying these layers is cathode spraying. This is performed at very low pressure, typically on the order of 0.3 Pa, to give a layer of the coating material over the entire surface of the glazing panel. The process can be carried out under inert conditions, for example in the presence of argon, but alternatively it can be carried out as reactive spraying in the presence of a reactive gas. Thus, in the manufacture of the glazing panels according to the invention, when the first and fourth layers (non-absorbent material) are in the form of oxides, these layers can be applied in the presence of oxygen. When the first and fourth layers (non-absorbent material) are in the form of nitrides, they can be applied in the presence of nitrogen. The second layer must be applied in the presence of an inert gas such as argon. Especially in the case of silver, one can optionally use a mixture of argon and nitrogen or even nitrogen alone. The reaction between silver and nitrogen is not sufficient to form a nitride in the true sense of the word, but it is sufficient to modify the mechanical properties of this layer. If a metal nitride is used for the third layer, it can be applied in the presence of nitrogen which, for reasons of convenience, can be the same atmosphere used for the application of the second layer (silver).

The particular advantages of the panels according to the invention are that, under preferred conditions, the light transmission factor (TL) is higher than 30%, preferably between 30% and 65%, if measured for a panel thickness of 6. mm, or is an equivalent factor for other thicknesses. Furthermore, the ratio between the transmission factor (TL) and the solar factor (FS) is at least 1.0, for example between about 1.2 and about 1.3. A special advantage of the panels according to the invention is that they have a blue color in reflection from the side opposite to the coated one, this blue color having a wavelength of maximum intensity in the range between 440 and 490 nm, preferably in the range between 470 and 485 nm, ideally about 477 nm. Preferably, the reflectivity of the visible light from this side is between 13% and 33%. Furthermore, the purity of the reflected blue color is higher than 15%, preferably higher than 30%, and is advantageously comprised between 30% and 40%. The purity of a color is defined according to a linear scale where a light source defined as white has a purity of 0 and the pure color has 100% purity. By the term "purity of color", as used herein, we mean the purity of excitation measured with illuminant C as defined in the International Lighting Vocabulary, published by the International Commission on Illumination (CIE), 1987, pages 87 and 89 With the solar panels of the known art it was not possible, with the same manufacturing methods and costs, to obtain such high reflected color purities as those obtained with the panels according to the present invention. As another preferred embodiment of the invention, a green reflected color is produced, having a wavelength of maximum intensity between 490 nm and 520 nm.

The panels according to the invention can be installed in single glazed or multiple glazed structures. In both cases, the benefits of the invention are best obtained when the coated surface of the panel is the inner surface of the outer glazing panel. In this case the coated surface is not exposed to environmental atmospheric conditions which could otherwise reduce its life more quickly due to dirt, physical damage and / or oxidation. The panels according to the invention can be usefully used in laminated glass structures, where the coated surface is the internal surface of the external laminate.

Brief description of the drawings

The present invention will now be further described, simply by way of example, with reference to the attached drawings, in which:

Figure 1 is a schematic cross section of a first glazing panel according to the invention; And

Figure 2 is a schematic cross section of a second glazing panel according to the invention.

Detailed description of the represented embodiments and examples

Referring to Figure 1, a glazing panel 10 comprises a tempered glass substrate 12 having a thickness of 6 mm. The glass substrate has an outer surface 11 intended, in use, to be exposed to ambient atmospheric conditions. A first coating layer 14 of zinc oxide having a thickness of 65 nm is applied directly to the inner surface 13 of the glass substrate. This layer is deposited by reactive cathode spraying of zinc metal in an oxygen atmosphere at a pressure of 0.3 Pa. A silver metal layer 16 having a thickness of 12 nm is applied directly on the oxide layer 14. zinc. This layer is applied by cathodic spraying of silver metal in an argon atmosphere at a pressure of 0.3 Pa. A layer 18 of titanium nitride having a thickness of 20 nm is applied directly on the silver layer 16. This layer is applied by reactive cathode spraying of titanium metal in a nitrogen atmosphere at a pressure of 0.3 Pa. Finally, a second outer layer 20, of zinc oxide having a thickness of 34 nm is applied directly on the layer 18 of titanium nitride. This layer is applied by reactive cathode spraying of zinc metal in an oxygen atmosphere at a pressure of 0.3 Pa.

The glazing panel described above has an intense blue color In reflection from the uncoated side. It was incorporated into a double glazing unit with a clear glass sheet having a thickness of 6 min and a distance between the sheets of 12 min. The covered surface was placed on the inner surface of the outer part of the two glazing panels. The characteristics of the panel as such (Example 1), and of the double glazing unit (Example 2) were as follows.

The results in Example 1 can be compared with the results obtained with a structure according to US patent 4,902,081 above (Example C), as follows.

It will be noted that the panel according to the American patent US 4,902,081 has a low purity of color. The reflected color was a grayish yellow. Examples 3 to 11

According to the procedure of Examples 1 and 2, other panels were prepared according to the invention and it was found that, in the form of simple plates, they had the following characteristics in reflection from the uncoated side.

Table VI

* - Sn02 was used instead of ZnO in Example 8. - A single layer of TiN with a thickness of 36 nm on a 6 mm glass substrate would have reduced from 90% to 33%.

In Examples 4 and 5, the solar factor (FS) was also measured and the sheets were incorporated into a double glazing unit with an uncoated glass sheet having a structure as described above. The results were the following.

With reference to Figure 2, a glazing panel similar to that shown in Figure 1 is shown, except that an intermediate layer 17 of titanium is disposed between the second layer 16 and the third layer 18. The thickness of the intermediate layer is 2 nm. The intermediate layer 17 is deposited by cathodic spraying of titanium in an argon atmosphere at 0.3 Pa. The titanium metallic layer 17 acts as a sacrificial intermediate metallic layer to protect the silver layer 16, in particular by reacting with any oxygen. which can diffuse through this layer, forming titanium oxide and preventing a surface alteration of the silver layer 16 which could lead to performance losses of the panel.

Examples 12 to 18

According to the procedure described with reference to Examples 1 and 2, other panels according to the invention were prepared from a single 4 mm thick glass substrate, the layer (i) being applied to the substrate and the layer (iv) being an exposed layer. The products were found to have the following characteristics when viewed in reflection from the uncoated side of the substrate.

Notes to table VIII:

* SS = "316" (18/10) stainless steel having composition: 18% Cr, 10% Ni, 2-3% Mo, and at most 0.08% C, 2% Mn, 0.045% P, 0.030% S and 1% Si. It should be noted that stainless steel (SS) must be in non-oxidized form to achieve these results. Stainless steel oxide is neither suitable as a first layer nor as a third layer. If a coating layer of stainless steel oxidizes, for example during the deposition of a subsequent oxide layer, the thickness of the non-oxidized stainless steel must be as given by these figures, to obtain the reported transmissivity. The thickness given in the Villa table for example 15 (5.5 nm) is the non-oxidized thickness that is actually found in the final product. To achieve the structure according to this example, it is necessary to deposit a thin zinc barrier, as a sacrificial metal, on the stainless steel coating. When zinc oxide is deposited, the sacrificial zinc oxidizes to form ZnO which merges with the deposited ZnO and at the same time protects the stainless steel from oxidation. The thickness of the stainless steel as such is determined in the product.

SSN = nitride of the stainless steel mentioned above obtained by cathodic spraying using a stainless steel cathode in a nitrogen atmosphere. The exact composition of the resulting nitride is not known.

A single layer of TiN with a thickness of 12 nm on a 6mm glass substrate would reduce 90% to 60%, a single layer of TiN with a thickness of 12.5mm on a glass substrate of 6mm would reduce TL from 90% to 58%, a single layer of SSN with a thickness of 7mm on a glass substrate of 6mm would reduce 90% to 35%, and a single layer of SSN with a thickness of 5.5 mm on a 6 mm glass substrate would reduce 90% to 32%.

Claims (1)

R IV EN D ICA Z ION I 1. - Transparent glazing panel for controlling sunlight, comprising a substrate coated with: (i) a first layer comprising a non-absorbent material; (li) a second layer chosen from materials for which, in the wavelength range (λ) from 380 to 780 nm, the spectral absorption index k (λ) is greater than the refractive index n (λ) and, at the wavelength (λ) of 550 nm, the spectral absorption index k (λ) is greater than 1.67 times the refractive index n (λ); (ili) a third layer comprising an absorbent material for which the spectral absorption index k (λ), in the wavelength range from 380 to 780 nm, is comprised between 0.3 and 1.0 times the refractive index n (λ) of the material, said third layer having a thickness such that, when applied as a single coating on a 6 mm thick sodium glass substrate, its light transmission factor TL is reduced by at least 30%; And (iv) a fourth layer comprising a non-absorbent material. 2. - Transparent glazing panel to control the sunlight according to riv. 1, wherein the non-absorbent material of the first and fourth layers has a refractive index greater than 10 times the spectral absorption index of the material in the wavelength range from 380 to 780 nm. 3. - Transparent glazing panel to control the sunlight according to riv. 1 or 2, in which the non-absorbent material of the first and fourth layers is independently selected from silicon and aluminum nitrides, aluminum oxynitride, aluminum oxides, bismuth, silicon (both SiO and SiO2), tin, titanium and zinc, and their mixtures. 4. - Transparent glazing panel to control the sunlight according to riv. 3, in which the non-absorbent material of the first and fourth layers is selected from Si3N4, AlN, ZnO, SnO2 and TiO2. 5. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, in which the material of the second layer is selected from aluminum, copper, gold, nickel and silver and their mixtures. 6. - Transparent glazing panel to control the sunlight according to riv. 5, where the material of the second layer is silver. 7. - Transparent glazing panel for controlling sunlight according to any one of the preceding claims, in which the absorbent material of the third layer is selected from stainless steel, titanium nitrides, chromium, aluminum / titanium alloys, stainless steel "nitrides" and their mixtures. 8. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, wherein the optical thickness of the first layer is at least 100 nm. 9. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, wherein the total optical thickness of the first and fourth layers is comprised between 180 and 270 nm. 10. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, in which the thickness of the first layer is greater than that of the fourth layer. 11. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, in which the thickness of the second layer is comprised between 3 and 18 nm. 12. - Transparent glazing panel for controlling sunlight according to claim 11, in which the thickness of the second layer is comprised between 5 and 15 nm. 13. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, wherein the thickness of the third layer is such that, when applied as a single coating on a 6 mm thick sodium glass substrate, the transmission factor luminous TL of this is reduced to a maximum of 65%. 14. - Transparent glazing panel for controlling the sunlight according to claim 13, in which the thickness of the third layer is such that, when applied as a single coating on a 6 mm thick sodium glass substrate, the light transmission factor of this is reduced by at least 35% and at most 60%. 15. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, wherein the first layer is applied directly to the substrate and the fourth layer is an exposed layer. 16. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, having a light transmission factor (TL) between 30% and 65%, measured for a panel thickness of 6 min. 17. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, wherein the ratio between the light transmission factor (TL) and the solar factor (FS) is at least 1.0. 18. - Transparent glazing panel for controlling sunlight according to any one of the preceding claims, which has a blue color in reflection from the side opposite to the coated one, this blue color having a wavelength of maximum intensity in the range from 440 at 490 nm. 19. - Transparent glazing panel for controlling sunlight according to claim 18, wherein said blue color has a wavelength of maximum intensity in the range from 470 to 485 nm. 20. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, which has a reflectivity in visible light, on the side opposite to the coated one, of between 13% and 33%. 21. A transparent glazing panel for controlling sunlight according to any one of the preceding claims, wherein the purity of the reflected color is greater than 15%. 22. - Transparent glazing panel for controlling sunlight according to claim 21, in which the purity of the reflected color is greater than 30%.