FR2722775A1 - GLAZING WITH PYROLYTIC COATING - Google Patents

Abstract

The present invention relates to a glazing having a pyrolytic coating.The glazing comprises a substrate, an underlayer comprising a nitride selected from nitrides of titanium, zirconium, niobium and mixtures of two or more thereof and an exposed upper transparent layer comprising an oxide adjacent to said underlayer. The total geometric thickness of the coating is between 20 nm and 55 nm. The reflected color remains substantially constant when the relative thicknesses of the layers of the coating are modified to optimize the optical properties.

Description

Pyrolytically coated glass The present invention is

  relates to transparent sun protection glazing. In particular. the invention relates to a glazing having a pyrolytic coating comprising a substrate, an undercoat comprising a

  nitride and an exposed upper transparent layer adjacent to said

  layer comprising a metal oxide. Pyrolysis generally has the advantage of producing a hard coating. which does not require a protective layer. Coatings formed by

  pyrolysis have durable properties of resistance to abrasion and corrosion.

  This is believed to be due in particular to the fact that the method comprises depositing coating forming material on a substrate which is hot. Pyrolysis is also generally cheaper than other coating processes such as sputtering. particularly with regard to the investment of the installation. The deposition of coating by other methods, for example by sputtering. leads to products with very different properties. in particular less resistance to abrasion and

  sometimes a different refractive index.

  Transparent reflective solar protection glazing has become a useful product for architects for the exterior façades of buildings. Such glazings have aesthetic qualities of reflection of the immediate environment and. being available in several shades, they provide a design opportunity. Such glazing also has technical advantages in providing the occupants of a building protection against solar radiation by reflection and absorption by eliminating the annoying effects of intense sunlight. which gives effective protection against glare. improves visual comfort and reduces eye strain. There are several documents describing glazing having a coating providing protection against solar radiation. Thus, EP-A-239280 (Gordon) discloses transparent glass sheets comprising a layer of titanium nitride at least 30 nm thick as the main sun protection layer for reducing near-infrared transmission and Above. a tin oxide layer about 30 to 80 nm thick. The tin oxide serves to protect the titanium nitride from oxidation and

  increases the resistance to abrasion.

  It is known that the change in the relative thicknesses of

  layers of the coating causes changes in optical properties.

  So. to optimize the optical properties. it is desirable to use particular relative thicknesses of the layers of the coating. However, it is generally expected that. for a given choice of coating materials, changes in the thickness of the layers cause changes in the dominant wavelength (i.e., color) of the reflected light. For example, in a solar pane comprising a first layer of titanium nitride and a layer of iron oxides. of cobalt and chromium, a change in the color of the reflected light is observed when the thickness of the oxide layer is changed. Therefore, measurements of the properties of samples of such glazings carrying coatings formed by chemical vapor deposition on

  4 mm glass are listed in the following Table 1.

TABLE 1

  Sample A B Nitride TiN TiN Thickness (nm) 45 45 Oxide s Thickness 32.5 45

TL () 14 12

FS (%) '26 26

RL (%) I 28 24

TL FS1 0.53 0.45

  Color reflected by blue gray coated face Purity (% O) 5 15

  Notes = measured from the uncoated side.

  s = mixture of iron oxides. cobalt and chromium in

  weight proportions of 26-61-13.

  It is an object of the present invention to provide pyrolytically coated glazings in which the reflected color remains substantially constant when changing the relative thicknesses of the layers.

  coating to optimize optical properties.

  It has been surprisingly found that this can be achieved for specific coating materials applied in a specific total thickness. In a first aspect. the present invention provides a glazing having a pyrolytic coating comprising a substrate. an underlayer comprising a nitride selected from titanium nitrides. of zirconium, niobium and mixtures of two or more thereof and an exposed upper transparent layer comprising an oxide adjacent to said underlayer, characterized in that the total geometrical thickness of the underlayer and

  of the upper layer is between 20 nm and 55 nm.

  The substrate is preferably in the form of a ribbon of vitreous material, such as glass or other transparent rigid material. Given the proportion of incident solar radiation that is absorbed by the glazing, especially in environments where the glazing is exposed to intense solar radiation and / or long-term. there is a heating effect of the glazing which may require subjecting the glass substrate to a subsequent quenching treatment. However. the durability of the coating makes it possible to mount the glazing with its coated face facing outwards. which reduces the heating effect. Preferably. the substrate is made of clear glass, although

  the invention extends to the use of colored glass as a substrate.

  Preferably. the geometrical thickness of the underlayer is between 10 and 50 nm. This range of thickness is particularly suitable for industrial manufacture. and provides an effective sunscreen effect while maintaining a sufficient level of light transmittance of the glazing. Preferably. the geometric thickness of the upper layer is between 9 and 35 nm. preferably between 15 and 35 nm. The refractive index of the upper layer is preferably between 1.8 and 2.7. The material of the transparent topcoat comprises materials which have a "refractive index" n (i '> which is greater than, preferably substantially greater than the value of the "spectral absorption index" k (k) over 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 of Illumination published by the International Commission on Illumination (CIE), 1987, p. 127. 138 and 139. In particular we have found that it is advantageous to choose a material for which the refractive index n (k) is greater than 10 times the spectral absorption index kkA1 over the entire wavelength range between 380 and 780 nm The upper layer is preferably an oxide layer The transparent material of the upper layer may be independently selected from aluminum oxides of bismuth , from

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  magnesium. of niobium. of silicon ISiOx and SiO2). tin, titanium (rutile and anatase). zinc and mixtures of two or more thereof. The following table shows the refractive index n) /) and the spectral absorption index k (X) of

  several suitable transparent materials in the range of 380 to 780 nm.

TABLE 2

  Material n (X) k () MgO 1.77-1. 73 0 * TiO; 2.9 - 2.3 0 Bi: 03 2.92 - 2.48 0.1 - 0 * TiOoa 2.64 - 2.31 0 ZnO 2.3 - 2.02 0.08 - 0.001 SnOo 1.94- 1.85 0 *

AI203 1.79- 1.76 0 *

  SiO0 1.47 - 1.45 0 ZrOo 2.1 0 * SiOx 1.7 0 * Notes: r = rutile form a = anatase form 0 * means less than 10-3 It is particularly preferred that the material of the transparent layer be made of titanium oxide and or of stannic oxide. The transparent layer is an outer layer, and for this reason the stannic oxide is advantageous if a higher abrasion resistance is required, as is the

  case for a glazing which is arranged with its coated surface on the outside.

  In preferred embodiments of the invention, the nitride of the underlayer comprises titanium nitride and the oxide of the layer.

  upper comprises tin oxide.

  It should be noted that in layers of oxide or nitride, it is not essential that the metal and the oxygen or the nitrogen are present in proportions

stoichiometric.

  From the technical point of view. it is desired that the glazing does not allow too much of the total incident solar radiation to pass so that the interior of the building does not become overheated in sunny weather. The transmission of total incident solar radiation can be expressed in terms

  of "solar factor". As used in this description, the term

  "solar factor" means the sum of the total energy directly transmitted and the energy that is absorbed and re-radiated by the far side of the energy source. as a proportion of the total radiated energy reaching the

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  coated glazing. The glazings according to the invention have a solar factor (FS) less than

  %. preferably less than 60%.

  It is also hoped that the glazing transmits a reasonable proportion of visible light to allow natural lighting of the interior of the building and to allow its occupants to see outside. Visible light transmission may be expressed in terms of "transmission factor" as a proportion of the incident light reaching the coated substrate. It is therefore desirable to increase the selectivity of the coating, that is to say to increase the ratio of the transmission factor on the solar factor. Preferably. the light transmittance (TL) of the

  glazing according to the invention is between 30% and 65%.

  Preferably. the glazing has a mean transmission of the ultra-

  purple (You,). on the ultraviolet spectrum [280 nm at 380 nm]. less than or equal to% o. preferably less than or equal to 20%. this may be advantageous by reducing damage to light-sensitive materials inside the building. Preferably the composition and thickness of the underlayer and the top layer are such that the dominant wavelength reflected by the uncoated side of the glazing in the visible spectrum is between 470 and 490 nm (blue). From the aesthetic point of view. it is preferred that the glazings have a blue color in reflection. When buildings have a relatively large glazed area and in the case of tall buildings, a blue reflected color gives the observer a more discreet appearance. In other forms

  of realization. the glazings have a neutral hue.

  The reflection of visible light (RL) by the uncoated side is preferably between 10% and 30%. Preferably, the purity of color reflected by said uncoated surface is greater than 5%, preferably at least 8% o. or better still at least 15%. as for example between 19% and 22% o. The purity of a color is defined on a linear scale where a defined source of white light has a purity of zero and the pure color has a purity of 100% o. By the term "purity of color" as used herein is meant the average excitation purity measured with Illuminant C as defined by the International Vocabulary of Lighting. published by the International Commission

  of Lighting t (CIE). 1987. pages 87 and 89.

  The upper layer can be chosen to increase the purity of color reflected by the uncoated side of the glazing, by comparison

  with similar glazing that is not provided with the top layer of oxide.

  So, for example. glazing with a 40 nm thick coating of titanium nitride has a gray-blue color (purity = 5%) in reflection from the uncoated side, while. if a top layer of 10 nm thick tin oxide is applied, the glazing takes on a blue appearance from the uncoated side and the color purity increases to 8%. In the case of a TiN layer 20 nm thick. an upper layer of SnO2 of 20 nm increases the

purity of color from 15% o to 21%.

  In one embodiment of the invention, there is no other

  layers. So. the first layer is deposited directly on the substrate.

  However. in an alternative embodiment of the invention, the glazing may comprise an additional layer disposed between said sub-layer and said substrate. In particular, in order to reduce the interaction between the reactants and the substrate during the formation of the nitride layer, a layer of silicon oxide can be applied. as described in GB 2234264 and GB 2247691 (Glaverbel!) The geometrical thickness of said layer

  additional can be between 50 and 100 nm.

  In a second aspect. the present invention provides a method of forming a coated glazing comprising the steps of: (i) forming on a sub-layer substrate by pyrolysis, said underlayer comprising a nitride selected from titanium nitrides. zirconium, niobium, and mixtures of two or more thereof; and (ii) pyrolytically forming an exposed upper transparent layer adjacent to said underlayer, said upper layer comprising an oxide; characterized in that the coating consisting of said sub-layer and said upper layer is such that its total geometric thickness is between

20 nm and 55 nm.

  Glazing according to the invention can be installed as single glazing or as multiple glazing. The coated face of the glazing may be the inner surface of the outer sheet of the glazing. In this way, the coated face is not exposed to ambient atmospheric conditions which could in other cases reduce its service life by soiling, physical damage and / or oxidation. The coatings produced by pyrolysis generally have higher mechanical strength than coatings produced by other processes and they can be exposed to the atmosphere. Glazing according to the invention can be usefully used in laminated structures. for example, or the coated surface constitutes the face

internal of the outer sheet.

  Glazing according to the invention can be manufactured in the following manner. Each pyrolytic coating step can be performed at a

  temperature between 550-C and 750-C.

  The coatings can be formed on a sheet of glass that travels through a tunnel or glass ribbon during its formation while it is hot. Coatings can be formed inside the gallery that follows the glass ribbon forming equipment or inside the float tank on the top side of the glass ribbon as it floats on a glass ribbon.

molten tin bath.

  The layers of the coating are preferably applied to the substrate by chemical vapor deposition. Chemical vapor deposition is particularly preferred because it tends to produce coatings of uniform thickness and composition. the uniformity of the product being particularly important when the glazing must be used on important surfaces. With the use of liquid reactive materials, one can not act on the vaporization process. In addition. chemical vapor deposition is more economical from the point of view of the use of materials

  first. which leads to less waste.

  To form each coating. the substrate is contacted in a coating chamber. with a gaseous medium comprising one or more substances in the gas phase. The coating chamber is supplied with reactive gas by one or more nozzles (s). whose length is at least equal to the width to be coated. Depending on the type of coating to be formed and the reactivity of the substances used. if more than one substance is to be used, it is distributed either as a mixture in a single ejection nozzle in the coating chamber or separately in

several ejection nozzles.

  Methods and devices for forming such a coating are described for example in French Patent No. 2348166 (BFG Glassgroup) or in French Patent Application No. 2648453 A1 (Glaverbel). These methods and devices lead to the formation of particularly resistant coatings

  which have advantageous optical properties.

  To form tin oxide SnO2 or TiO2 titanium dioxide coatings. two successive nozzles are used. The reagent carrying the metal (Sn or Ti). routed to a first nozzle. is a tetrachloride. liquid at room temperature. vaporized in a stream of anhydrous carrier gas at elevated temperature. The vaporization is favored by the atomization of these reagents in the carrier gas. To produce oxide, the molecules of tetrachloride are

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  placed in the presence of water vapor conveyed by the second nozzle. The water vapor is superheated and is then injected into a carrier gas. SnO2 can for example be formed using the proportions of SnCl4 and H20 given by

  British Patent GB 2026454 I Glaverbel).

  If desired, a dopant such as HF can be added to the steam

  of water to form a conductive coating of tin oxide.

  SiO2 or SiOx silicon oxide coatings can be

  formed from SiH4 silane and oxygen according to the patent specifications

  British GB 2234264 and GB 2247691. quoted above.

  The invention will now be described in more detail, with reference to

  to the following non-limiting examples.

EXAMPLE 1

  A substrate consisting of a 4 mm thick clear soda-lime glass sheet is pyrolytically coated in the following manner. A device comprising two successive nozzles is used. A reagent comprising TiCl4, vaporized in a stream of anhydrous nitrogen gas at about 600 ° C is fed to the first nozzle. Spraying is favored by the atomization of these reagents

  in the carrier gas. Ammonia gas is fed to the second nozzle.

  The ammonia is heated to about 600 ° C and is also injected into a carrier gas. which is air heated to about 600'-C. The gas flow (carrier gas + reagent) of each nozzle is 1 m3 cm of substrate width / hour, at the

working temperature.

  The deposition process is continued until the geometric thickness of the layer formed on the substrate is 11 nm. The substrate is then subjected to a second layer deposition. A stannic oxide reagent. vaporized in a stream of anhydrous nitrogen gas at about 600 ° C is fed to the first nozzle. Water vapor is supplied to the second nozzle. The water vapor is superheated at about 600 ° C and is also injected into a carrier gas. which is air heated to about 600 C. The gas flow (carrier + reagent gas) of each nozzle is 1 m3 cm of substrate width / hour, at the

working temperature.

  The second deposition process is continued until the geometric thickness of the tin oxide coating formed on the substrate, superimposed on the

  layer of titanium nitride. that is 30 nm.

  As an alternative to Example 1, a silicon oxide layer is formed on the substrate before the formation of the TiN layer. This makes it possible to reduce the interaction between TiCl4 and the substrate. The glass is coated in a coating station disposed at a location along the float chamber where the glass is

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  at a temperature of about 700 ° C. The supply line is supplied with nitrogen and silane is introduced under a partial pressure of 0.25%, and oxygen under a partial pressure of 0.5%. The formed layer is constituted

  of silicon dioxide with a thickness of about 70 nm.

  The glazing described above has an intense blue color in reflection from its uncoated side. Different properties of the glazing are measured and the

  The results are shown in Table 3 below.

EXAMPLES 2 TO 7

  Other samples are prepared by a method similar to that described in Example 1. Details of coatings and properties of

  glazings thus formed are shown in Table 3 below.

TABLE 3

EXAMPLE 1 2 3 4 5 6 7

  Nitride TiN TiN TiN TiN TiN TiN TiN Thickness (nm) 11 15 20 25 31 40 31 Tolerance (+%) 15 6 12 8 10 4 4 Oxide SnO2 SnO: SnO2 SnO2 SnO2 SnO2 TiO2a Thickness 30 27.5 20 17.5 10 10 10 Tolerance ( +%) 7 3 12 9 15 16 15

TL%) 52 45 37 31 25 19 25

FS (%) 1 55 49 42 38 34 29 34

RPL (%) 15 17 17 20 21 25 21

  TL FS I 0.96 0.93 0.86 0.81 0.73 0.65 0.73

  TLv (%) 39.5 24.8 19.8 9.9 Reflected color <--------- neutral on the coated side / blue on the uncoated side ------------------> Purity (% O) 2a = anatase = measured on the uncoated side 2 "purity" means the purity of the color measured in reflection on the uncoated side. The tolerances shown in Table 3 above are the variations in the thickness of the layers that are possible without having a noticeable effect on the

properties of the finished product.

  Examples 1 to 6 above demonstrate that for a substantially constant total coating thickness. changes in the optical properties can be obtained by variations in the relative thicknesses of the nitride and oxide layers while the reflected color remains

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  substantially constant. Example 7 shows the properties that we can

  obtain when the tin oxide of Examples 1 to 6 is replaced by anatase.

  Similar results can be obtained if the titanium nitride is replaced by

  zirconium nitride or niobium nitride.

EXAMPLE 8

  In another example. we manufacture a solar glazing having a neutral appearance. The coating layers are the same as in Example 1, but the glazing is seen from its coated side instead of being seen from its uncoated side. The measured properties are TL 52% o FS 53% o

RL 14%

TL FS 0.98

  You,; 39.5% The dominant wavelength in reflection from the coated side

  is 491 nm. with a purity of 3.9% 'neutral appearance).

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Claims (14)

  1. Glazing having a pyrolytic coating comprising a substrate. an underlayer comprising a nitride selected from titanium nitrides. of zirconium. niobium and mixtures of two or more thereof and an exposed upper transparent layer comprising an oxide adjacent to said underlayer. characterized in that the total geometric thickness of the underlayer and the top layer is between 20 nm and nm. 2. Glazing according to claim 1, characterized in that   the geometrical thickness of the underlayer is between 10 nm and 50 nm.   3. Glazing according to one of claims 1 or 2. characterized in that   that the geometrical thickness of the upper layer is between 9 nm and   nm. preferably between 15 and 35 nm.   4. Glazing according to one of claims 1 to 3, characterized in that   that the refractive index of the upper layer is between 1.8 and 2.7.   5. Glazing according to one of claims 1 to 4, characterized in that   that the oxide of the upper layer is chosen from oxides of aluminum, silicon and magnesium. tin. of zinc. of zirconium, titanium, bismuth,   niobium. and mixtures of two or more thereof.   6. Glazing according to one of claims 1 to 5, characterized in that   that the upper layer is chosen so as to provide an increase of   the purity of color reflected by the uncoated side of the glazing.   7. Glazing according to claim 6. characterized in that the nitride of the underlayer comprises titanium nitride and the oxide of the layer   upper comprises tin oxide.   8. Glazing according to one of claims 1 to 7. characterized in that   that the composition and thickness of the underlayer and the top layer are such that the dominant wavelength reflected by the uncoated side of the   Glazing in the visible spectrum is between 470 and 490 nm.   9. Glazing according to claim 8, characterized in that the purity   of color reflected by the uncoated side of the glazing is greater than 5%.   10. Glazing according to one of claims 1 to 9, characterized in that   it comprises an additional layer disposed between the said sub-layer and said substrate. 12 2722775   11. Glazing according to claim 10. characterized in that the geometric thickness of said additional layer is between 50 and nm.   12. Glazing according to one of claims 10 or 11, characterized in   what said additional layer consists of an oxide. 13. Glazing according to claim 12, characterized in that the said   additional layer consists of silicon oxide.   14. A method of forming a coated glazing comprising the steps of: (i) forming on a substrate of a sub-layer by pyrolysis, said sublayer comprising a nitride selected from nitrides of titanium, zirconium, niobium. and mixtures of two or more thereof; and (ii) pyrolytically forming an exposed upper transparent layer adjacent to said underlayer, said upper layer comprising an oxide; characterized in that the coating consisting of said sub-layer and said upper layer is such that its total geometric thickness is between nm and 55 nm.