NL9401030A - Transparent glazing panels for sunlight control. - Google Patents

Description

Transparent glazing panels for sunlight control.

This invention relates to transparent glazing panels for sunlight control.

Reflective transparent glazing panels for sunlight control have become a useful material for architects to use as an exterior facade for buildings. Such panels have aesthetic qualities by reflecting the immediate surroundings and, by the availability in a number of colors, offering design possibilities. Such panels also have technical advantages by providing solar radiation protection from reflections and / or absorption to those present in a building and eliminating the blinding effects of intense sunlight, providing an effective filter against bright light, increasing visual comfort and reduces eye fatigue.

From a technical point of view it is desirable that the glazing panel does not let in too much of the total incident solar radiation so that the interior of the building does not get too hot during sunny weather. The transmission of the total incident solar radiation can be expressed in terms of the "solar factor". As used herein, the term "solar factor" means the sum of the total energy that is directly transmitted and the energy that is absorbed and radiated back on the side facing away from the energy source, relative to the total amount of radiant energy applied to the coated glass falls. It is also desirable that the glazing panel also transmit a reasonable portion of the visible light to allow natural illumination of the interior of the building and allow those present to look outside. The transmission of visible light can be expressed in terms of the "transmission factor" as part of the incident light that falls on the coated substrate. It is therefore desirable to increase the selectivity of the coating, that is, to increase the ratio of the transmission factor to the solar factor.

A number of documents exist describing glazing panels with a coating that provides protection from solar radiation. For example, U.S. Patent 4,902,081 (Viracon) promises a window with low emissivity, low dimming coefficient and low reflection, in which a substrate is coated with a first layer of metal oxide, a second layer of silver, a third layer consisting of a metal such as titanium, a fourth layer of metal oxide and an outer fifth layer of titanium nitride. We have found that a glazing panel manufactured according to the teachings of US 4,902,081 has a low purity gray color when viewed in reflection. While those skilled in the art would consider depositing further layers to modify the properties of known glazing panels, such an approach would clearly increase the cost and manufacturing difficulty.

From an aesthetic point of view, it is preferable to improve the purity of the color of the glazed panels viewed in reflection, in particular such that the whole glazed facade of a building has a uniform appearance when viewed from the outside. The color purity has been found to be particularly difficult to achieve simultaneously with a relatively high transmission factor to solar factor ratio, especially for blue glazing panels.

It is therefore an object of this invention to provide a glazing panel with a high transmission factor, a low solar factor and a high purity of the reflected color. It is preferably a further object of the invention to provide such a glazing panel that uses relatively inexpensive components and can be formed in a simple manner.

According to the present invention, a transparent glazing panel for sunlight control is provided comprising a substrate coated with: (i) a first layer comprising a non-absorbent material (ii) a second layer selected from materials for which the wavelength (λ) range of 380 to 780 nm the spectral absorption index k (A) is greater than the refractive index n (X), and at the wavelength (λ) of 550 nm the spectral absorption index k () is more than 1.67 times greater than the refractive index n (A); (iii) a third layer comprising an absorbent material for which the spectral absorption index k () over the wavelength (λ) range of 380 to 780 nm is between 0.3 and 1.0 times the refractive index η (χ) of the material, said third layer having a thickness such that, when applied as the sole coating on a 6 mm thick sodium glass substrate, its light transmission factor TL is decreased by at least 30%; and (iv) a fourth layer comprising a non-absorbent material.

The glazing panel according to the invention makes it possible to achieve the common goals of high selectivity with high color purity in reflection with low manufacturing costs and a simple structure for the multiple coating. Achieving high color purity is surprising since a layer of absorbent material applied to a multi-coating according to US 4902081 gives a gray color when viewed from the uncoated side of the substrate. The reason for this difference is not fully understood, but it seems that the advantage of the present invention may be due to the interface between the absorbent material of the third layer and the material of the second layer. However, we have found that the benefits of the invention are not achieved if the order of the second and third layers are reversed when viewed from the same uncoated side, nor if these layers are not surrounded by the first and fourth layers. absorbent material.

The substrate is preferably in the form of a film, such as a plastic material film, but is preferably in the form of a sheet of glassy material, such as glass or another transparent rigid material available in sheet form. It is particularly advantageous to use tempered or heat-strengthened glass, although laminated glass can also be used. In view of the proportion of incident solar radiation absorbed by the glazing panel, especially in environments where the panel is exposed to strong or prolonged solar radiation, there is a heating effect on the glass panel which means the use of toughened glass as the substrate preferably should be avoided. However, the high selectivity of the glazing panels of the invention limits the energy absorption of the panel at a given light transmission, reducing the need to toughen the glass.

The different layers of the coated glazing panel work together advantageously to achieve the object of the invention. The precise properties obtained can be varied by the choice of the materials forming each layer and by its thickness.

By the term "nonabsorbent material" as used herein, we mean materials that have a "refractive index" η (λ) greater than, preferably substantially greater than, the value of the "spectral absorption index" k (^) over the total visible spectrum (380 to 780 nm). Refractive index and spectral absorption index definitions can be found in International Lighting Vocabulary, published by the International Commission on Illumination (CIE), 1987, pp. 127, 138 and 139. In particular, we have benefited from choosing a material of which the refractive index η (λ) is greater than 10 times the spectral absorption index k (^) over the wavelength range of 380 to 780 nm. The first and fourth layers nonabsorbent material can be independently selected from zinc sulfide, silicon carbide, lithium, sodium and thorium fluoride, zinc selenide, silicon and aluminum nitrides, aluminum oxynitride, barium and strontium titanates, oxides of aluminum, beryllium, bismuth, magnesium, silicon (both SiO and SiO2), tin, titanium, yttrium and zinc, and mixtures thereof. The non-absorbent material of the first and fourth layers is most preferably selected from Si3N4, AlN, ZnO, SnO2 and TiC> 2. The following table gives the refractive index η (λ) and the spectral absorption index kQO of a number of suitable non-absorbent materials in the range from 380 nm to 780 nm.

Table A

Note: 0 means less than 10 ".

It is particularly preferred if the material of the first and fourth layers is the same material, at least for ease of production, and ideally this material is zinc oxide and / or tin (IV) oxide while titanium oxide is beneficial if it is more resistant to attrition is required. These non-absorbent layers act as a basis for the further coatings and as a protection against the environment, respectively. It is common for the layers of non-absorbent material to have a refractive index greater than that of the substrate. It should be noted that in the non-absorbent metal oxide or nitride material layers, it is not essential that the material and the oxygen or nitrogen be present in stoichiometric amounts.

The second layer is the layer primarily responsible for the selectivity of the coating. In particular, such materials have a spectral absorption index k (^) over the visible light range that is greater than the refractive index n (/ \), and is at least 1.67 times greater at a wavelength of 550 nm. Suitable such materials include metals selected from aluminum, copper, gold, nickel, iridium, platinum, palladium, rhodium, zinc and silver, and mixtures thereof, especially silver. Lithium, sodium and potassium also have the necessary properties, but since they are reactive they must be used in a doped form or in the form of alloys. The following table gives the refractive index n (X) and the spectral absorption index k (A) of some suitable materials over the range 380 nm / 550 nm / 780 nm.

Table B

When a blue color is required in reflection, we prefer the use of silver, both for cost reasons and for the ease with which it can be sold. In the following description, this layer is simply referred to as the silver layer.

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

Table C

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

Titanium nitride and the "nitride" of stainless steel are particularly preferred. The nitride layer may also contain elemental or oxidized metal, and in particular the metal and nitrogen need not be in stoichiometric proportions. 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 relative to the total solar radiation. The absorbent material also plays an important role in obtaining the desired color due to the beneficial effect resulting from the combination thereof with the first, second and fourth layers.

An intermediate layer comprising a sacrificial metal can be placed between said second and third layers, said intermediate layer having a thickness of less than 10 nm. This sacrificial material acts to protect the silver layer, in particular from its change which may result from coating the silver layer with the layer of absorbent material which would result in a loss of performance of the panel.

In addition, a thin layer of sacrificial metal can also be applied between the first and second layers. The sacrificial metal is preferably selected from aluminum, bismuth, chromium, nickel-chromium alloy, tin, titanium, zinc and mixtures thereof. Ideally, the third layer nitride comprises a nitride of the same metal as the sacrificial metal of the intermediate layer. The presence of the intermediate layer can change the emissivity characteristics of the panel without significantly changing the reflected color, provided that its thickness is relatively small. Advantageously, the intermediate layer has a thickness of no more than 6 mm, preferably no more than 3 nm. Whether this intermediate layer becomes completely transparent in the final product, or whether it remains wholly or partly metallic, or in the form of a nitride, it will preferably be as thin as possible so as not to reflect the reflected color that the coating would have without this intermediate layer. to be modified, with the difference that if it satisfies the conditions of the third layer, in that case it is part of the third layer.

A thin layer of sacrificial material may also be placed between said third and fourth layers to protect the absorbent layer from change thereof which could result from the coating of that layer with the fourth layer.

The thickness of the different layers applied to this panel are important for optimal performance. We prefer that the optical thickness (measured by transmission) of the first layer is from 10 to 280 nm (the optical thickness being the product of its real, i.e., geometric thickness, and its refractive index). Most preferably, the optical thickness of the first layer is at least 100 nm, while the total optical thickness of the first (non-absorbent material) and fourth (non-absorbent material) layers is between 180 and 270 mm, the optical thickness of the first layer is greater than that of the fourth layer, for example 1.1 to 1.7 times greater. Therefore, the optical thickness for the first (non-absorbent material) layer is preferred from 110 to 160 nm and that of the fourth (non-absorbent material) layer is from 70 to 120 nm.

The geometric thickness of the second layer is preferably 3 to 18 nm, most preferably 5 to 15 nm.

The geometric layer of the third layer must be sufficient for the layer to absorb in the finished product. We have found that the third layer should have the ability, when applied as the only coating thereon, to reduce the light transmission factor of a 6 mm thick sodium glass substrate by at least 30%, for example, the TL from 90% to less than 60 % is returned. The thickness of the third layer is preferably such that, when applied as the sole coating to a 6mm thick sodium glass substrate, its light transmission factor is reduced by up to 65%, i.e., the TL is reduced from 90% to over 25%. Most preferably, the light transmission factor TL is decreased by at least 35% and at most 60%, that is, for example, the TL is decreased from 90% to between 55% and 30%.

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

The following table shows the transmittance (light transmission factor) TL obtained with the different coatings on a 6 mm sodium glass substrate.

Table D

* It should be noted that the stainless steel (SS) must be in a non-oxidized form to achieve these results. If a stainless steel cladding layer becomes oxidized, for example during the deposition of a subsequent oxide layer, the thickness of the non-oxidized stainless steel must be as indicated by these numbers, in order to obtain the stated permeability. Stainless steel oxide is neither suitable as the first layer nor as the third layer.

We prefer, therefore, when the material of the third layer is titanium nitride, to use a thickness of 12 to 27 nm, when the material of the third layer is stainless steel to use a thickness of 3 to 6 nm, and when the material of the third layer is the "nitride" of stainless steel to use a thickness of 3 to 8 nm.

Increasing the thickness of this layer will decrease the total energy transmittance and, at the same time, will decrease the light transmittance. The thickness of the absorbent layer will therefore also have an effect on the reflected color.

When an intermediate layer of sacrificial metal is present, for optimal results this layer preferably has a thickness of 0 to 10 nm, such as no more than 6 nm, ideally no more than 3 nm, to maintain the low emissivity of the silver layer without the change reflected color substantially.

Usually no other coatings will be present. Therefore, the first layer is applied directly to the substrate and the fourth layer is an exposed layer. Alternatively, the order of the layers can be reversed, with the glass substrate coated directly with the fourth layer and the first layer being an exposed layer. In this case (reverse order), the advantages of the invention, in particular the purity of the color, are obtained by viewing the panel of the coated side.

The glazing panels according to the invention can be manufactured by generally known methods, in particular by successive vacuum deposition. A proven technique for applying such layers is cathode sputtering. This is performed at very low pressure, typically of the order of 0.3 Pa, to yield a layer of coating material over the glazing panel surface. The process can be carried out under inert conditions, for example in the presence of argon, but can instead be carried out as a reactive spray in the presence of a reactive gas. For example, in the manufacture of the glazing panels of the invention, when the first and fourth (non-absorbent material) layers are in the form of oxides, these layers can be applied in the presence of oxygen. When the first and fourth (non-absorbent material) layers are in the form of nitrides, these layers can be applied in the presence of nitrogen. The second coat must be applied in the presence of an inert gas such as argon. Particularly in the case of silver, a mixture of argon and nitrogen, or optionally only nitrogen, may optionally be used. The reaction between silver and nitrogen is not sufficient to form a nitride in the true meanings of the word, but it is sufficient to change 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 convenience may be the same atmosphere as that used for applying the second (silver) layer.

The particular advantages of the panels according to the invention are that under the preferred conditions the light transmission factor (TL) is more than 30%, preferably between 30% and 65% measured at a panel thickness of 6 nm or an equal factor at other thicknesses. Furthermore, the light transmission factor (TL) to the solar factor (FS) is at least 1.0, such as from about 1.2 to about 1.3. It is a particular advantage of the panels according to the invention that they show a blue color when reflected against the side opposite the coated side, said blue color having a maximum intensity wavelength in the range of 440 to 490 nm, preferably in the range from 470 to 485 nm, ideally approx. 477 nm. The reflectivity for visible light from this side is preferably 13 to 33%. In addition, the purity of the reflected blue color is greater than 15%, preferably greater than 30%, and advantageously between 30% and 40%. The purity of a color is defined on a linear scale where a defined white light source has a purity of 0 and the pure color has a purity of 100%. By the term "color purity" as used herein, we mean the excitation purity measured with light source 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 According to the prior art, it has not been possible, with the same manufacturing methods and at the same cost, to achieve reflected color purities as high as can be achieved with the panels of the present invention. According to another preferred embodiment of the invention, a green reflected color is produced, with a maximum intensity wavelength ranging from 490 nm to 520 nm.

The panels according to the invention can be mounted in single or multiple glazing assemblies. In either case, the advantages of the invention are best achieved when the coated surface of the panel is the inner surface of the outer glazing panel. In this way, the coated surface is not exposed to the prevailing weather conditions, which would otherwise be able to reduce its life more quickly through soiling, physical damage and / or oxidation. The panels according to the invention can advantageously be used in laminated glass structures, the coated surface being the inner surface of the laminate exterior.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic section through a first glazing panel according to the invention, and Fig. 2 is a schematic section through a second glazing panel according to the invention .

Referring to Fig. 1, glazing panel 10 includes a tempered glass substrate 12 6mm thick. The glass substrate has an outer surface 11 which is intended to be exposed to the prevailing weather conditions during use. A first zinc oxide coating layer 14, having a thickness of 65 nm, is applied directly to the inner surface 13 of the glass substrate. This layer was applied by reactive sputtering of zinc metal in an oxygen atmosphere at a pressure of 0.3 Pa. A layer 16 of silver metal with a thickness of 12 mm is applied directly to the zinc oxide layer 14. This layer was applied by sputtering silver metal in an argon atmosphere at a pressure of 0.3 Pa. Directly on the silver layer 16 is a layer 18 of titanium nitride with a thickness of 20 nm. This layer was applied by reactive sputtering of titanium metal in a nitrogen atmosphere at a pressure of 0.3 Pa. Finally, a second and outer layer 20 of zinc oxide having a thickness of 34 mm is applied directly to the titanium nitride layer 18. This layer was applied by reactive sputtering of zinc metal in an oxygen atmosphere at a pressure of 0.3 Pa.

The glazing panel described above has an intense blue color when reflected against the uncoated side. It was incorporated in a double glazing unit with a 6 mm thick clear glass pane and 12 mm pane spacing. The coated surface was placed on the inner surface of the outer of the two glazing panels. The characteristics of the panel as such (example I) and of the double glazing unit (example II) are as follows.

Table El

The results of Example I can be compared with the results obtained with a structure according to US 4902081 referred to above (Example C) as follows.

Table E2

* Comparative example

It is noted that the panel according to US 4 902 081 has a low color purity. The reflected color was grayish-yellow.

Examples III to XI

According to the method described in connection with Examples I and II, further panels according to the invention were manufactured and, in the form of simple panes, were found to have the following reflection properties when reflected from the uncoated side.

Table F y Ί * - In Example VIII, SnO 2 was used instead of ZnO.

+ - A single TiN layer with a thickness of 36 nm on a 6 mm glass substrate would reduce the TL from 90% to 33%.

In Examples IV and V, the solar factor (FS) was also measured and the panes were incorporated into double glazing units with an uncoated glass pane having a structure as described above. The results were as follows.

Table G

Referring to Fig. 2, where a glazing panel similar to that shown in Fig. 1 is shown, except that an intermediate layer 17 of titanium is interposed between the second layer 16 and the third layer 18. The thickness of the intermediate layer is 2 ηπι. The intermediate layer 17 is deposited by sputtering titanium in an argon atmosphere at 0.3 Pa. The titanium metal layer 17 acts as an intermediate sacrificial metal layer to protect the silver layer 16, in particular by reacting with all the oxygen that would diffuse through this layer to form titanium oxide and change the surface of the silver layer 16, otherwise would result in loss of performance of the panel.

Examples XII to XVIII

Using the method described in connection with Examples I and II, further panels of the invention were prepared with a single 4 mm thick glass substrate, layer (i) being applied to the substrate layer and layer (iv) being an exposed layer. The products were found to have the following characteristics when viewed upon reflection from the uncoated side of the substrate.

Table Hl

Table H2

Notes to Table H: * SS = "316" (18/10) stainless steel with the 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 the stainless steel (SS) must be in the non-oxidized form to achieve these results. Stainless steel oxide is not suitable as the first layer or as the third layer. If a stainless steel cladding layer becomes oxidized, for example during the deposition of a subsequent oxide layer, the thickness of the non-oxidized stainless steel must be as given by these numbers, in order to obtain the stated permeability. The thickness given in Table III for Example XV (5.5 nm) is the non-oxidized thickness actually found in the final product. In order to obtain the structure of this example, it is necessary to deposit a thin barrier of zinc, as a sacrificial metal, on the stainless steel coating. When the zinc is deposited, the sacrificial zinc becomes oxidized to form ZnO, which mixes with the co-deposited ZnO to protect the stainless steel from oxidation. The thickness of the stainless steel as such is determined in the product.

#SSN = the nitride of the above-mentioned stainless steel obtained by sputtering using a stainless steel cathode in a nitrogen atmosphere. The exact composition of the resulting nitride is unknown.

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

from 90% to 35%, and a single layer of SS with a thickness of 5.5 nm on a 6 mm glass substrate would reduce the TL from 90% to 32%.

Claims (22)

A transparent sunlight control glazing panel comprising a substrate and applied thereon: (i) a first layer comprising a non-absorbent material (ii) a second layer selected from materials for which the wavelength (λ) range from 3 SO0 to 780 nm the spectral absorption index k (X) is greater than the refractive index n (/ \), and at the wavelength (X) of 550 nm the spectral absorption index k (X) is more than 1.67 times greater than the refractive index n (X); (iii) a third layer comprising an absorbent material for which the spectral absorption index k (X) over the wavelength (Λ) range of 380 to 780 nm is between 0.3 and 1.0 times the refractive index η (χ) of the material, said third layer having a thickness such that, when applied as the sole 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. The transparent sunlight control glazing panel of claim 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 over the wavelength range of 380 to 780 nm. The transparent glazing panel for sunlight control according to claim 1 or 2, wherein the non-absorbent material of the first and fourth layers is independently selected from nitrides of silicon and aluminum, aluminum oxynitride, oxides of aluminum, bismuth, silicon (both SiO as SiO2), tin, titanium and zinc, and mixtures thereof. The transparent sunlight control glazing panel of claim 3, wherein the non-absorbent material of the first and fourth layers is independently selected from Si3N4, A1N, ZnO, SnO2 and TiO2. The transparent sunlight control glazing panel of any preceding claim, wherein the second layer material is selected from aluminum, copper, gold, nickel and silver, and mixtures thereof. The transparent sunlight control glazing panel of claim 5, wherein the material of the second layer is silver. The transparent sunlight control glazing panel according to any one of the preceding claims, wherein the absorbent material of the third layer is selected from stainless steel, nitrides of titanium, chromium, and aluminum / titanium alloys, "nitrides" of stainless steel and mixtures thereof . A transparent sunlight control glazing panel according to any preceding claim, wherein the optical thickness of the first layer is at least 100 nm. A transparent sunlight control glazing panel according to any one of the preceding claims, wherein the total optical thickness of the first and fourth layers is between 180 and 270 nm. A transparent sunlight control glazing panel according to any one of the preceding claims, wherein the thickness of the first layer is greater than that of the fourth layer. A transparent sunlight control glazing panel according to any preceding claim, wherein the thickness of the second layer is 3 to 18 nm. The transparent glazing panel for sunlight control according to any one of the preceding claims, wherein the thickness of the second layer is 5 to 15 nm. The transparent glazing panel for sunlight control according to any of the preceding claims, wherein the thickness of the third layer is such that when applied as the sole coating on a 6 mm thick sodium glass substrate, its light transmission factor TL is at most 65% reduced. The transparent sunlight control glazing panel of claim 13, wherein the thickness of the third layer is such that, when applied as the sole cladding on a 6 mm thick sodium glass substrate, its light transmission factor TL by at least 35% and at most 60% is reduced. A transparent sunlight control glazing panel according to any preceding claim, wherein the first layer is applied directly to the substrate and the fourth layer is an exposed layer. A transparent glazing panel for sunlight control according to any one of the preceding claims, with a light transmission factor (TL) between 30% and 65%, measured at a panel thickness of 6 mm. The transparent glazing panel for sunlight control according to any one of the preceding claims, wherein the ratio of the light transmission factor (TL) to the solar factor (FS) is at least 1.0. A transparent sunlight control glazing panel as claimed in any one of the preceding claims, which exhibits a blue color upon reflection against the sides opposite the coated side, said blue color having a maximum intensity wavelength in the range of 440 to 490 nm. The transparent sunlight control glazing panel of claim 18, wherein said blue color has a maximum intensity wavelength in the range of 470 to 485 nm. A transparent sunlight control glazing panel according to any one of the preceding claims, which exhibits a visible light reflectivity from the opposite side of the coated side, from 13 to 33%. A transparent sunlight control glazing panel according to any one of the preceding claims, wherein the purity of the reflected color is greater than 15%. The transparent sunlight control glazing panel of claim 21, wherein the purity of the reflected color is greater than 30%.