LU88748A1 - Substrate bearing a coating with high light transmission with low solar factor and having a neutral aspect in reflection - Google Patents

Description

Substrate with a coating with high light transmission, low solar factor and having a neutral aspect in reflection

The present invention relates to a coated substrate, in particular to a coated substrate having a high light transmission, a low solar factor and a neutral aspect in reflection.

Coated substrates find their use in different fields for different uses. Thus, for example, glass bearing a coating is used in low-emissivity or solar protection glazing intended for buildings and vehicles.

In order to impart the desired specific properties to the coated substrate, the coating may include different layers, each of which meets specific requirements of the coating. The constituents of the layers and their thicknesses are usually defined precisely to ensure that the specific requirements of the coated substrate as a whole are obtained.

US Patent 4,985,312 describes a glass sheet carrying a multi-layer coating giving it heat reflection properties. A base layer of indium / tin oxide or AIN is deposited on the sheet, followed alternately by heat reflective layers of silver or copper with a thickness of 40 to 200 Å (4 to 20 nm), metallic zinc screen layers with a thickness of 20 to 200 Å, and protective layers of the same material as the base layer.

EP-B1-0 277 228 describes a glass panel transmitting light in the visible spectrum while stopping solar radiation outside this spectrum. This panel comprises a glass substrate carrying, sequentially from the substrate, a stack of coating layers comprising a first layer of dielectric material, a second layer of reflective material, third and fourth layers of dielectric material, a fifth layer of reflective material and a sixth layer of dielectric material, thanks to which the light transmission under illuminant A of the panel is at least 70% and its total solar factor is less than 55%.

WO 90/05 439 similarly describes transparent glazing units having stacks of transparent layers intended to reduce the solar transmission and increase the solar reflection of these glazing units. The layers include electrically conductive components which allow the glazing to be heated if desired. In its widest aspect, the claimed stack comprises at least two layers of 80 to 180 Å of metallic silver interposed between layers of dielectric material and a transparent protective layer, thanks to which the glazing has a light transmission under illuminant A d ' at least 70%, a reflection under illuminant C not exceeding 12.5%, a total solar reflection of at least 29% and a total solar transmission not exceeding 42%. The dielectric layers located outside the silver layers are 200-500 Å thick and those located between the silver layers are 400-1500 Å thick.

The present invention relates to specific components and ranges of particularly selected layer thicknesses, used in a stack of layers intended to provide the desired combination of high light transmission, low solar factor and neutral appearance in reflection to a substrate coated with such a stack.

For coated substrates intended for use in windows of buildings or vehicles, it is desirable that the product of which the coated substrate forms part does not transmit too large a proportion of the total incident solar radiation, so that the interior of the building or the vehicle is not overheated in sunny weather. The transmission of total incident solar radiation can be expressed in terms of "solar factor" (Fs in the present description). As used in the present description, the expression "solar factor" designates the sum of the solar energy transmitted directly through the glazing and that absorbed by it and re-radiated by the opposite face. at the energy source. This sum is a fraction of the total incident energy radiation on the coated substrate. The data relating to the solar factor included here are measured according to Document No. 20 of 1972 of the CIE (International Commission on Lighting).

International patent application WO 93/19936 (CARDINAL 1 G COMPANY) describes a coating for transparent substrate which has a neutral color in transmission, under a wide range of angles of incidence of light. The coating comprises a base layer adjacent to the transparent substrate having a thickness not exceeding approximately 27.5 nm and optionally two reflective metallic layers separated by an anti-reflective intermediate layer of metal oxide and surmounted by an external anti-reflective layer of metal oxide placed above the second reflective metal layer. Such a substrate coated in this way has a light transmission of only 60% and a strong blue color in reflection. However, it is desirable that a coated substrate offers a high transmission of visible light so that the occupants of a building equipped with glazing made of said coated substrates can for example look outside and that enough light enters the building to allow occupants to work there without excessive use of artificial light. As used in the present description, the term "light transmission" (TLC below) designates the percentage of the incident light flux emitted by the standard illuminant C (CIE) transmitted through the coated substrate.

Commercially available sun protection products are glass sheets with a coating of one or more layers.

It is desirable that the coated substrates are substantially neutral in reflection from the face opposite the coating (the "opposite" face in the present description), that is to say that the reflected color purity is low. It has been found that low color purity is particularly difficult to achieve simultaneously with a low solar factor and high light transmission. The purity of a color is established on a linear scale in which a defined source of white light has a purity of 0% and the pure color a purity of 100%. The term "color purity" used below means the excitation purity measured by means of illuminant C as defined in the International Vocabulary of Lighting, published by the International Commission on Lighting (CIE), 1987, pages 87 and 89. "Color purity" is measured from the opposite side of the product.

With substrates coated according to prior techniques, the dominant wavelength (λ0) in reflection and the color purity tend to vary depending on the angle from which they are viewed and in particular have a pink appearance when viewed under an angle of 45 ° on the opposite surface.

It has been discovered that this objective can be achieved and other advantages obtained, thanks to a substrate carrying a multi-layer coating in which the layers are made of specific materials and are present within specific thickness limits.

Therefore, the present invention relates to a substrate carrying a coating with high light transmission, low solar factor and having a neutral appearance in reflection, characterized in that it comprises a surface carrying the different layers of the coating in order following: (i) a first layer of transparent non-absorbent dielectric material adjacent to the substrate and having an optical thickness of between 60 and 75 nm; (ii) a first layer of silver or of silver alloy having a geometric thickness of between 9 and 11 nm; (iii) a second layer of transparent non-absorbent dielectric material having an optical thickness of between 135 and 170 nm; (iv) a second layer of silver or of silver alloy having a geometric thickness of between 12 and 15 nm; (v) a third layer of transparent non-absorbent dielectric material having an optical thickness of between 45 and 65 nm, such that the coated substrate has the following properties; a light transmission under Illuminant C greater than 70%, preferably at least 75%; a solar factor of less than 47%, preferably less than 46%, more preferably still less than 45% and a color purity in normal reflection at the opposite surface less than 12%, preferably less than 10%, more preferably still less at 9%.

The cited properties of the coated substrate are considered on the basis of a single sheet of ordinary soda-lime clear glass 6 mm thick observed from the face opposite to the coated face, that is to say from the glass side. It should be noted in this regard that the opposite side will usually not be coated.

The relationship between the thicknesses of the different layers of non-absorbent material and the optical properties of the coated substrate is not fully understood, but it is clear that the thickness of these layers is decisive in this relationship.

In a preferred embodiment of the present invention, the layers have the following thicknesses: (i) the first layer of transparent non-absorbent dielectric material adjacent to the substrate has an optical thickness of between 63 and 72 nm; (ii) the first layer of silver or of silver alloy has a geometric thickness of between 9.5 and 10.5 nm; (iii) the second layer of non-absorbent transparent dielectric material has an optical thickness of between 144 and 160 nm; (iv) the second layer of silver or silver alloy has a geometric thickness of between 13 and 14 nm; (v) the third layer of non-absorbent transparent dielectric material has an optical thickness of between 50 and 58 nm.

With the arrangement and thicknesses of the coating layers defined and claimed here, the coated substrate offers a high light transmission, a low solar factor and a neutral color in reflection on the opposite face. In addition, the color stability of the product is high. This means that in the case of a limited variation in the thickness of one of the layers (due for example to a lack of uniformity of thickness between one point of the substrate and another), there is no significant variation in color and the color remains close to neutral when the angle of observation tends to be normal to the opposite face.

On the other hand, the coated substrate according to the invention exhibits in reflection when observed from the opposite face an aesthetically pleasing color, which is neither yellow nor pink. This is particularly noteworthy since even when the purity of the reflection is low, a yellow or pink tint is clearly visible. The color of the product according to the invention remains aesthetically pleasing even when viewed obliquely on the surface, that is to say that the reflected color becomes neither yellow nor pink when the angle of observation decreases. This is a very important factor when considering glazing incorporated in a large building. In fact, the angle of observation of the facade of a building, for example, is different when a stationary observer looks at the ground floor, an intermediate floor, and the upper floor of the building. It is important that if the windows on the ground floor appear blue-green, those on an intermediate floor do not appear pink. Similarly, if the observer moves, the angle of observation will change but the color should remain within the preferred standards of aesthetics.

On the other hand, the particular arrangement of the layers makes it possible to obtain a low light reflection (Rl below) close to the light reflection obtained for an uncoated substrate.

In the coated substrates according to the invention, the nature and the thicknesses of the coating layers can be such that the direct energy transmission TED (defined as the fraction of the solar energy which is transmitted through the coated substrate without change in length d (wave) is preferably between 34 and 40%, advantageously between 36 and 39%.

The nature and the thicknesses of the coating layers can be such that the color purity remains neutral when the viewing angle changes, in particular such that the coated substrate has a color purity at an angle of 45 ° on the opposite face. in reflection less than 9%, preferably less than 6%.

At an angle of 60 ° on the opposite face (conventionally the normal to the surface is considered as 0 °), the reflected color purity is preferably less than 1%.

When the coated substrate is a single glazing consisting of a single sheet of clear glass 6 mm thick, the TLC light transmission is preferably between 70 and 81%, advantageously between 75 and 79%, the solar factor is de preferably between 41 and 46% and the light reflection RL is preferably less than 8%. The color in reflection on the opposite face is neutral with a purity preferably less than 10%, advantageously less than 9%. The dominant wavelength of the reflection is preferably between 485 and 505 nm. Above this range, a yellow color is observed, below this range, a pink color is observed when the angle of observation varies. When the color purity in normal reflection on the opposite face is at least 3%, it is easier to prevent the color from turning pink when the angle of observation varies from normal, in particular if the length dominant wave is at the lower limit of the preferred range. In fact, when the color purity is around 1-2% and the dominant wavelength is less than 495 nm, the color effectively tends to pink when the angle of observation varies from normal, and this is particularly noticeable by the eye, despite the very low purity.

The metal layers comprise silver or a silver alloy, such as for example alloys of silver with platinum or palladium.

The coated substrate according to the invention may also comprise a layer of sacrificial material placed above (that is to say deposited subsequently) and in contact with each metal layer. The purpose of the sacrificial layer is to protect the silver or silver alloy during the deposition of the next non-absorbent layer.

The coating layers are preferably deposited by sputtering. For reasons related to the sputtering process, each metal layer is deposited with a thin layer of sacrificial metal (a "screen" layer) which is converted into oxide during the coating process. This sacrificial metal is preferably titanium, although zinc, copper, a nickel / chromium alloy or aluminum may alternatively be used. A similar screen layer can, if desired, be placed below each metal layer. The sacrificial material is preferably substantially fully oxidized, since the non-oxidized material can have the effect of reducing the light emission. The sacrificial material oxidizes during the deposition of the next layer, when the latter is deposited in a reactive atmosphere (for example 02). The term "sacrificial material" is used here to embrace not only the sacrificial metal as it is deposited on the layers of silver or of silver alloy, but also the oxide or the sub-oxide in which this metal sacrificial is converted during the later process. Although these sacrificial layers constitute a protection of the silver layer against oxidation, by improving its chemical durability, increasing their thickness reduces the light transmission of the products. The thicknesses of the layers of sacrificial material, when they are present, are therefore critical for the present invention.

Preferably, a first layer of sacrificial material (iia) having a geometric thickness of between 2.5 and 5 nm is disposed between the first metallic layer (ii) and b second non-absorbent layer (iii), and a second layer of material sacrificial (iva) having a geometric thickness between 3 and 6 nm is arranged between the second metallic layer (iv) and the third non-absorbent layer (v).

If the next layer of non-absorbent material consists of a nitride (e.g. Si3N4) rather than an oxide, it is deposited in a nitrogen atmosphere. In this case, a layer of sacrificial material should not be provided above the layer of silver or silver alloy.

The coating layers can be supplemented by a protective layer, such as a thin layer (3 geometric nm) of SiO 2, which does not significantly modify the optical properties of the product (see British patent application No. 94 17 112.1 filed August 24, 1994 -Glaverbel). Otherwise, the third non-absorbent layer will usually be exposed.

Preferably, the exposed thin protective complementary layer is chosen from oxides, nitrides and oxynitrides of silicon. This layer provides the coated substrate with improved chemical and / or mechanical durability, while minimizing the changes that result from its optical properties. Advantageously, said additional protective protective layer consists of SiO 2, preferably with a geometric thickness of between 2 and 5 nm.

Particularly when the thickness of the protective layer is small, the effect of this on the optical properties of the product will be minimal.

The products according to the invention can be incorporated in particular in single or multiple glazing for buildings, especially in double glazing, and also in laminated glazing such as vehicle windshields.

A multiple glazing unit may comprise at least two sheets of transparent vitreous material arranged on either side of an intermediate gas volume delimited by a spacer extending peripherally, in which at least one of the sheets carries a coating according to the invention on its face directed towards the gas volume.

A laminated glazing can comprise at least two sheets of transparent vitreous material secured to each other by means of an intermediate film of adhesive polymeric material, in which at least one of the sheets carries a coating according to the invention on its face directed towards the polymeric material.

In the preferred embodiments of the invention in which the coated substrate is incorporated in a double glazing consisting of two sheets of clear glass 6 mm thick, with an intermediate space of 15 mm filled with argon, the TLC of the glazing is between 62 and 72%, advantageously between 66 and 70%, its Fs is between 34 and 40%, advantageously between 36 and 39%, its color purity in normal reflection on the opposite face is less than 8%, advantageously less than 7% and its light reflection is less than 12%. To determine the properties of such embodiments, the glazing is considered to be installed with the coating in position "2", (the opposite face being in position "1"), that is to say that the coated sheet is arranged outwards with its coated side facing the internal gas space of the double glazing.

The non-absorbent layers may consist of a single non-absorbent material such as zinc oxide, titanium oxide or silicon nitride, of a mixture or of a complex of non-absorbent materials such as Zn ^ nC ^ or several successive sublayers.

The term "non-absorbent material" as used in the present description describes materials having a "refractive index" η (λ) greater, preferably substantially, than the value of ["'spectral absorption index" k (X) across the entire visible spectrum (380 to 780 nm). Definitions of the refractive index and the spectral absorption index can be found in the International Vocabulary on Lighting, published by the International Lighting Commission (CIE), 1987, pages 127, 138 and 139 In particular, it has been found advantageous to choose a material whose refractive index η (λ) is greater than ten times the spectral absorption index k (X) over a range of wavelengths from 380 to 780. nm. Preferably, the material of the non-absorbent layers is chosen from aluminum nitride, silicon nitride, stannic oxide, zinc oxide, zirconium oxide and their mixtures. It should be noted that the silicon nitride is deposited by means of a silicon cathode doped, for example, with aluminum, nickel, boron, phosphorus and / or tin in order to facilitate the process of deposit. As a result, these doping elements may be present in the layer of non-absorbent material. Preferably, the non-absorbent material has a refractive index, measured at 550 nm, between 1.85 and 2.2, advantageously between 1.9 and 2.1. Zinc oxide is a particularly preferred material because of its high deposition rate, its refractive index well suited to the purpose of the invention and its advantageous effect on the passivation of the silver layer, but because its relatively high porosity in thick layers and its low chemical resistance, it is preferred to separate the zinc oxide layer into two or more layers by another material, placed between them, such as stannic oxide for example. Consequently, one or more of said layers of non-absorbent material is / are one / several composite layer (s), that is to say containing two or more non-absorbent materials deposited simultaneously and / or successively. Advantageously, one or more of said layers of non-absorbent material is / are formed of alternating zinc oxide and stannic oxide, such as for example ZnO / SnO ^ ZnO or Zn0 / Sn02 / Zn0 / Sn02 / Zn0 .. .etc.

In certain embodiments such as those intended in the field of vehicle windows, for example laminated windscreens, silicon nitride (Si3N4) is particularly preferred as a non-absorbent material, especially because of its chemical durability. In this case, a layer of sacrificial material is not really advantageous and therefore not implicitly necessary, between the layer of silver and the non-absorbent layer deposited on the latter. It should be noted that, in the non-absorbent layer of metal oxide or nitride, it is not essential that the metal and the oxygen or nitrogen are present in stoichiometric proportions.

Other layers can still be used, but it has been found that they can have the effect of reducing light transmission. Only two or three layers of metal are therefore preferred.

The substrate is preferably a sheet of glassy material, such as glass or any other transparent rigid material.

Preferably, the substrate consists of clear glass, although the invention extends to the use of a colored glass substrate, since the coating according to the invention does not significantly modify the inherent color of the substrate.

The process for forming the products according to the invention can be implemented by introducing the substrate into a treatment enclosure containing a magnetron sputtering source, provided with gas inlet and outlet closures, a conveyor of substrate, power sources, spray gas inlet pipes and an outlet pipe. The substrate is moved under the activated spray source and sprayed cold under an appropriate atmosphere (gaseous oxygen in the case of an oxide coating) to form the desired layer on the substrate. This operation is repeated for each layer of the coating.

EXAMPLE 1.

A glass sheet is introduced into a treatment enclosure containing several plane magnetron spray sources, provided with gas inlet shutters, a substrate conveyor, power sources, spray gas conduits and '' an exhaust duct. The deposit is obtained by several passages of the substrate under the same cathodes. The online deposit system includes two deposit boxes and an entry airlock. The first enclosure is intended for the deposition of oxides (or nitrides) in a reactive atmosphere (oxygen or nitrogen) and comprises several cathodes whose targets are formed of zinc and tin, which are necessary for the deposition of the coating. The second enclosure is intended for the deposition of metals in an inert atmosphere (Ar) and comprises a silver cathode and a titanium cathode. The substrate performs several back and forth, under the activated cathodes if necessary, in order to obtain the desired succession of coating layers. The pressure in each enclosure is reduced to 0.3 Pa.

The coated product has the following composition and optical properties:

Substrate: 6mm clear glass

Layer (i) zinc oxide 35 nm

Layer (ii) silver 9.5 nm

Titanium (iia) layer 3 nm

Layer (iii) zinc oxide 75 nm

Layer (iv) silver 13.5 nm

5.5 nm titanium (iva) layer

Zinc oxide layer (v) 26 nm

Single glass sheet:

Transmission (TLC) 76%

Solar factor (Fs) 43.5%

Direct energy transmission (TED) 37% Light reflection 7-8%

Reflected color purity (normal) 6.6%

Outer sheet of double glazing:

Transmission (TLC) 67%

Solar factor (Fs) 37% Light reflection 10-11%

Dominant wavelength λ0 (normal) 490 nm

Color purity (normal) 6.3%

Dominant wavelength λ0 (45 °) 490 nm

Color purity (45 °) 4.5% EXAMPLE 2

In a first variant of Example 1, the zinc oxide layers are subdivided into sublayers of ZnO / SnO ^ ZnO in the proportions of 3A ZnO and: A Sn02- So as to keep the same optical thickness as the layers of ZnO alone in Example 1, the total geometric thickness of these sublayers is greater than that of said layers of ZnO alone, taking into account the difference between the refractive indices of ZnO (approximately 2.0) and Sn02 (about 1.9). The properties observed are identical, but the coating is more resistant to corrosion.

EXAMPLES 3 AND 4

In variants of Example 2, a thin (3 nm) SiO 2 protective layer is deposited on the final layer without modifying the optical properties of the coated substrate, while providing improved chemical and / or mechanical durability of the substrate in the case of the two examples 3 and 4; it is also fully compatible with a PVB (polyvinyl butyral) interlayer film in the case of Example 4.

EXAMPLES 5 TO 9

In other variants of Example 1, coatings of compositions indicated in Table A1 are deposited on the glass substrate. According to the definitions in the claims, the thicknesses of the ZnO layers are optical thicknesses and those of silver and titanium are geometric thicknesses to aid in the comparison of optical and geometric thicknesses, it is mentioned here that the refractive index of ZnO is 2.0 and the refractive index of Ti02 is approximately 2.5 (optical thickness = geometric thickness X refractive index).

The coated product has optical properties indicated in Table A2. It will be seen that the layers of layers according to the invention provide very effective combinations of light transmission, solar factor and color purity. Perhaps the most remarkable is the weakness of the solar factors, mainly that of example 6, as low as 42%.

Table Al

Table A2

Claims (19)

1. Substrate carrying a coating with high light transmission, with low solar factor and having a neutral appearance in reflection, characterized in that it comprises a surface carrying the various layers of the coating in the following order: (i) a first layer non-absorbent transparent dielectric material adjacent to the substrate and having an optical thickness between 60 and 75 nm; (ii) a first layer of silver or of silver alloy having a geometric thickness of between 9 and 11 nm; (iii) a second layer of transparent non-absorbent dielectric material having an optical thickness of between 135 and 170 nm; (iv) a second layer of silver or of silver alloy having a geometric thickness of between 12 and 15 nm; (v) a third layer of transparent non-absorbent dielectric material having an optical thickness of between 45 and 65 nm, such that the coated substrate has the following properties; a light transmission under Illuminant C greater than 70%; a solar factor of less than 47% and a color purity under normal reflection on the opposite surface of less than 12%. 2. Substrate carrying a coating according to claim 1, characterized in that the nature and the thickness of the coating layers are such that the coated substrate has a direct energy transmission of between 34% and 40%. 3. Substrate carrying a coating according to one of claims 1 or 2, characterized in that the nature and the thickness of the coating layers are such that the light transmission under Illuminant C is not less than 75%. 4. Substrate carrying a coating according to one of claims 1 to 3, characterized in that the nature and the thickness of the coating layers are such that the solar factor does not exceed 46%, preferably not 45%. 5. Substrate carrying a coating according to one of claims 1 to 4, characterized in that the nature and the thickness of the coating layers are such that the color purity in normal reflection at the opposite surface does not exceed 10%, preferably not 9%. 6. Substrate carrying a coating according to one of claims 1 to 5, characterized in that the nature and the thickness of the coating layers are such that the color purity in normal reflection at the opposite surface is at least 3 %. 7. Substrate carrying a coating according to one of claims 1 to 6, characterized in that the nature and the thickness of the coating layers are such that the coated substrate has a purity of color in reflection at an angle of 45 °: on the opposite surface which does not exceed 9%. 8. Substrate carrying a coating according to one of claims 1 to 7, characterized in that: (i) the first layer of non-absorbent transparent dielectric material adjacent to the substrate has an optical thickness between 63 and 72 nra; (ii) the first layer of silver or silver alloy has a geometric thickness of between 9.5 and 10.5 nm; (iii) the second layer of non-absorbent transparent dielectric material has an optical thickness of between 144 and 160 nm; (iv) the second layer of silver or silver alloy has a geometric thickness of between 13 and 14 nm; (v) the third layer of non-absorbent transparent dielectric material has an optical thickness of between 50 and 58 nm. 9. Substrate carrying a coating according to one of claims 1 to 8, characterized in that it further comprises a layer of sacrificial material in contact with the top of each metal layer. 10. Substrate carrying a coating according to claim 9, characterized in that said sacrificial material is titanium. 11. Substrate carrying a coating according to one of claims 9 or 10, characterized in that said sacrificial material is substantially completely oxidized. 12. Substrate carrying a coating according to one of claims 9 to 11, characterized in that it comprises: (iia) a first layer of sacrificial material having a geometric thickness between 2.5 and 5 nm, disposed between the first layer of silver or silver alloy and the second layer of non-absorbent material; (iva) a second layer of sacrificial material having a geometric thickness of between 3 and 6 nm, disposed between the second layer of silver or of silver alloy and the third layer of non-absorbent material. 13. Substrate carrying a coating according to one of claims 1 to 12, characterized in that said non-absorbent material is chosen from zinc oxide, tin oxide, silicon nitride and their mixtures. 14. Substrate carrying a coating according to one of claims 1 to 13, characterized in that said non-absorbent material has a refractive index measured at 550 nm between 1.85 and 2.2. 15. Substrate carrying a coating according to claim 14, characterized in that said non-absorbent material has a refractive index measured at 550 nm between 1.9 and 2.1. 16. Substrate carrying a coating according to one of claims 1 to 15, characterized in that one or more of said layers of non-absorbent material are composite layers. 17. Substrate carrying a coating according to one of claims 1 to 16, characterized in that the dominant wavelength of the light reflected by the opposite surface is between 485 and 505 nm. 18. Multiple glazing comprising at least two sheets of transparent vitreous material arranged on either side of an intermediate gas volume delimited by a spacer extending peripherally, characterized in that at least one of said sheets carries a coating according to l 'one of claims 1 to 17, on its face directed towards said gas volume. 19. Multiple glazing according to claim 18, characterized in that the color purity in normal reflection at the opposite surface does not exceed 8%, preferably not 7%.