Method for reducing the emissivity of a coated glass article

Abstract

A method for reducing the emissivity of a coated glass article (10) is provided, the method comprising the steps of: (a) forming a coated glass article (10), the coated glass article (10) comprising a glass substrate (12) and a coating (14) formed on the glass substrate (12), the coating (14) having a first layer (20) and a second layer (22) deposited above the glass substrate (12), the second layer (22) being provided between the first layer (20) and the glass substrate (12), the coated glass article (10) exhibiting a first emissivity; and (b) heating the coated glass article (10) in an environment set at a predetermined temperature for a predetermined time, wherein after step (b), the coated glass article (10) exhibits a second emissivity, the second emissivity being less than the first emissivity.

Description

Technical Field

[0001] The present invention relates to a method for controlling the emissivity of a coated glass article.

Background Art

[0002] Coatings on glass can be formed from a wide variety of materials to achieve a variety of functions. As an example, a coating can be formed on glass to reduce the emissivity exhibited by the glass. Under certain conditions, the emissivity-reducing coating can be damaged. Damage to such a coating can increase the emissivity exhibited by the coated glass article, which can render the coated glass article inappropriate for its intended use.

[0003] Therefore, it would be desirable to provide a method capable of reducing the emissivity of a glass article when the emissivity-reducing coating formed on the glass article is damaged.

Brief Description of the Drawings

[0004] The above and other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, considered in light of the accompanying drawings.

Figure 1

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Figure 3

Summary of the Invention

[0005] It should be understood that, unless otherwise explicitly specified, various alternative orientations and step sequences can be envisioned. It should also be understood that the specific articles, devices, methods, and features illustrated in the accompanying drawings and described below in the specification are merely exemplary embodiments of the concepts of the present invention. Accordingly, specific dimensions, orientations, or other physical characteristics associated with the disclosed embodiments should not be considered limiting, unless otherwise expressly stated. Also, although it may not always be the case, similar elements found in the foregoing embodiments may be referenced by similar identifiers within this portion of the application.

[0006] A method for reducing the emissivity of a coated glass article is described herein and comprises the following steps, namely, (a) forming a coated glass article 10, the coated glass article 10 comprising a glass substrate 12 and a coating 14 formed on the glass substrate 12, the coating 14 having a first layer 20 deposited above the glass substrate 12 and a second layer 22, the second layer 22 being provided between the first layer 20 and the glass substrate 12, the coated glass article 10 exhibiting a first emissivity, the step of forming the coated glass article 10; (b) heating the coated glass article 10 in an environment set to a predetermined temperature for a predetermined period of time; in that order, wherein, after step (b), the coated glass article 10 exhibits a second emissivity, the second emissivity being less than the first emissivity.

[0007] This method is carried out using the coated glass article 10. An embodiment of the coated glass article 10 is shown in FIG. 1. It should be understood that this method can also be carried out using coated glass articles not shown in FIG. 1 or described below.

[0008] The coated glass article 10 can be used for the window of a vehicle (not shown). Those skilled in the art will understand that the coated glass articles described herein can be applied to on-highway vehicles and off-highway vehicles. Also, the coated glass article can be used for commercial or residential glazing, or can have applications in, for example, architecture, photovoltaics, industry, locomotives, ships, and aerospace.

[0009] When the coated glass article 10 is used for the window of a vehicle, the coated glass article 10 can be mounted in any suitable body opening of the vehicle. In some embodiments, the coated glass article 10 can be used in the front glass, side window, or rear window of the vehicle. In other embodiments, the window can be used in another body opening within the vehicle. For example, the window having the coated glass article 10 can be mounted in an opening within the roof inside the vehicle. In this embodiment, the coated glass article 10 can be used as roof glazing for sunroof or moonroof applications.

[0010] As shown in FIG. 1, the coated glass article 10 includes a glass substrate 12. In some embodiments, the glass substrate 12 is not limited to a specific thickness. However, in certain embodiments, the glass substrate 12 can have a thickness of 20.0 millimeters (mm) or less. Preferably, the glass substrate 12 has a thickness of 0.5 to 20.0 mm. In some embodiments, the glass substrate 12 can have a thickness of 0.5 to 10.0 mm. More preferably, the glass substrate 12 has a thickness of 0.5 to 5.0 mm. In some embodiments, the glass substrate 12 has a thickness of 1.5 to 5.0 mm.

[0011] The glass substrate 12 can be any conventional glass composition known in the art. Preferably, the glass substrate 12 is soda-lime-silica glass. When the glass substrate 12 is soda-lime-silica glass, the glass substrate 12 contains 68 to 74 wt% of SiO2 , 0 to 3 wt% Al 2 O 3 , 0-6 wt% MgO, 5-14 wt% CaO, 10-16 wt% Na 2 O, 0-2 wt% SO 3 , 0.005 to 4.0 wt% Fe 2 O 3 (total iron) and 0-5 wt% K 2 As used herein, the phrase "total iron" refers to the total iron content in the glass. 2 O 3 Iron oxide (FeO+Fe 2 O 3 ) by weight. The glass may also contain other additives, such as refining agents, which will typically be present in amounts up to 2%. In this embodiment, the glass substrate 12 may be provided as part of a float glass ribbon. When the glass substrate 12 is formed as part of a float glass ribbon, the glass substrate 12 may be clear float glass. In some of these embodiments, clear float glass may refer to glass having a composition defined in relevant standards, such as BS EN 572-1:2012+A1:2016 and BS EN 572-2:2012. However, the glass substrate 12 may be of another composition, such as, for example, a borosilicate or aluminosilicate composition.

[0012] The color of the glass substrate 12 may vary among embodiments of the coated glass article 10. In some embodiments, the glass substrate 12 may be transparent. In these embodiments, the glass substrate 12 may exhibit a total visible light transmittance of 88% or greater when measured in the CIELAB color scale system (Illuminant C, 10 degree observer) at a reference thickness of 2.1 mm. In one such embodiment, the glass substrate 12 has a low iron content, which allows for a high visible light transmittance. For example, the glass substrate 12 may have 0.20 wt. % or less Fe. 2 O 3 (total iron). More preferably, in this embodiment, the glass substrate 12 may comprise 0.1 wt. % or less of Fe. 2 O3 (Total iron), more preferably, Fe of 0.02 wt% or less 2 O 3 comprises (total iron). In yet other embodiments, the glass substrate 12 can be thinly colored or can be colored.

[0013] When the glass substrate 12 is thinly colored, the glass substrate 12 comprises 0.1 to 4.0 wt% of Fe 2 O 3 (total iron). Preferably, when the glass substrate 12 is thinly colored, the glass substrate 12 comprises 0.5 to 4.0 wt% of Fe 2 O 3 (total iron). In some of these embodiments, the glass substrate 12 can comprise 0.05 to 1.6 wt of ferrous oxide (calculated as FeO). Further, when the glass substrate 12 is thinly colored, the glass substrate 12 can comprise a specific colorant. For example, the glass substrate 12 can comprise one or more of up to 600 ppm of the glass weight of cobalt oxide (calculated as Co 3 O 4 calculated as), up to 500 ppm of the glass weight of nickel oxide (calculated as NiO), and up to 50 ppm of the glass weight of selenium. In one embodiment, the glass substrate 12 comprises 100 to 500 ppm of nickel oxide (calculated as NiO). When the glass substrate 12 is thinly colored, the glass substrate 12 is preferably, for example, gray, grayish blue, green, blue - green, or bronze.

[0014] When the glass substrate 12 is gray, the glass substrate 12 can comprise 0.1 to 4.0 wt% of Fe 2 O 3 (total iron). Preferably, when the glass substrate 12 is gray, the glass substrate 12 comprises 1.2 to 3.0 wt% of Fe 2 O 3 (total iron). Also, in these embodiments, the glass substrate 12 has an a * value of - 5 ± 5, preferably - 4 ± 3, and a b *a value of 50 ± 10, preferably 50 ± 5 for L * It may have values. In these embodiments, the gray glass substrate has a visible light transmittance of 50% or less when the glass substrate 12 has a nominal thickness of 6 mm. Preferably, the gray glass substrate has a visible light transmittance of 7 - 11% when the glass substrate 12 has a nominal thickness of 6 mm. The gray glass plate may be sold under the Galaxsee trademark and may be manufactured by Pilkington. In other embodiments, the glass substrate 12 may be gray glass having optical properties similar to Galaxsee by Pilkington, or gray glass having lower light transmittance properties than Galaxsee by Pilkington at the nominal thickness.

[0015] When the glass substrate 12 is green, the glass substrate 12 may comprise 0.2 - 2.0 wt% Fe 2 O 3 (total iron). In some embodiments, when the glass substrate 12 is green, the glass substrate 12 comprises 0.3 - 1.2 wt% Fe 2 O 3 (total iron). In other embodiments where the glass substrate 12 is green, the glass substrate 12 may comprise more than 1.2 wt% Fe 2 O 3 (total iron). Also, in these embodiments, the glass substrate 12 may comprise 0 - 2.0% TiO 2 . In some embodiments, the glass substrate 12 may have an a * value of -11 to -1, a b * value of -2 to 8, and an L * value of 60 or more in the CIELAB color scale system. In these embodiments, the green glass substrate has a visible light transmittance of 50% or more when the glass substrate 12 has a nominal thickness of 6 mm.

[0016] Coating 14 is formed on the glass substrate 12. Preferably, coating 14 is formed on the first major surface 16 of glass substrate 12. When coating 14 is formed directly on glass substrate 12, there is no intervening coating between coating 14 and glass substrate 12. Preferably, the second major surface 18 of glass substrate 12 and the opposite side of the coated glass article 10 are uncoated. When the coated glass article is used as a vehicle window, the first major surface 16 of glass substrate 12 and coating 14 preferably face the passenger compartment of the vehicle.

[0017] Coating 14 comprises one or more layers 20-24. In one embodiment, coating 14 comprises a first layer 20 and a second layer 22. In other embodiments, coating 14 may comprise a first layer 20, a second layer 22, and an iridescence suppressing intermediate layer 24. In the embodiment shown in FIG. 1, coating 14 may consist of a first layer 20, a second layer 22, and an iridescence suppressing intermediate layer 24. Coating 14 is provided to reduce the emissivity exhibited by the coated glass article 10. In some embodiments, coating 14 may be configured to reduce the visible light reflectance exhibited by the coated glass article 10.

[0018] In one embodiment, coating 14 is pyrolytic. As used herein, the term "pyrolytic" may refer to a coating or layer that is chemically bonded to a glass substrate or another layer. Preferably, each of the layers 20-24 is pyrolytic. One or more of coating 14 and its layers 20-24 may be formed in connection with the manufacture of glass substrate 12. Preferably, in these embodiments, glass substrate 12 is formed using a known float glass manufacturing process. In embodiments where glass substrate 12 is provided as part of a float glass ribbon, one or more of coating 14 or its layers 20-24 may be formed within the heating zone of the float glass manufacturing process.

[0019] Coating 14 is deposited on the glass substrate 12. The coating layers 20-24 can be deposited by any suitable method. However, in some embodiments, at least one of the layers 20-24 is deposited by atmospheric pressure chemical vapor deposition (APCVD). In these embodiments, one or more of the layers 20-24 can be deposited by another known deposition method, such as sol-gel technology or sputtering technology, for example.

[0020] The first layer 20 is deposited above the glass substrate 12. The first layer 20 is deposited above the second layer 22. Preferably, the first layer 20 is deposited directly on the second layer 22. When the first layer 20 is deposited directly on the second layer 22, there is no intervening layer between the second layer 22 and the first layer 20. In some embodiments, the first layer 20 can be the outermost layer of the coating 14. When the first layer 20 is the outermost layer of the coating 14, the first layer 20 forms the outer surface 26 of the coated glass article 10. When the coated glass article 10 is included in a vehicle window, the outer surface 26 preferably faces the passenger compartment of the vehicle.

[0021] Preferably, the first layer 20 has a refractive index smaller than that of the second layer 22. In some embodiments, the first layer 20 has a refractive index of 1.7 or less. Preferably, the refractive index of the first layer 20 is between 1.4 and 1.7. In one embodiment, the refractive index of the first layer 20 can be between 1.5 and 1.7. In another embodiment, the refractive index of the first layer 20 can be between 1.4 and 1.5. It should be noted that the refractive index values described herein are shown as average values over the 400-780 nm of the electromagnetic spectrum.

[0022] Preferably, the first layer 20 comprises a dielectric material. Preferred dielectric materials include oxides of silicon. In one embodiment, the first layer 20 is silicon dioxide (SiO 2or another suitable silicon oxide. The first layer 20 may also include one or more additional components in trace amounts, such as carbon, for example. Thus, in certain embodiments, the first layer 20 may consist essentially of silicon dioxide. However, in other embodiments, the first layer 20 may comprise an oxide of silicon and one or more additional materials, which are provided to make the refractive index of the first layer 20 greater than 1.5. In such an embodiment, the first layer 20 may also include aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), zirconium oxide (ZrO 2 ), boron oxide (B 2 O 3 ), phosphorus oxide (P 2 O 5 ) or tin oxide. In addition, other dielectric materials may be suitable for use in the first layer 20. For example, in some embodiments, the oxide of silicon may be replaced with a metal oxide. Suitable metal oxides include aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), zirconium oxide (ZrO 2 ), undoped tin oxide (SnO 2 ) and mixtures thereof.

[0023] In certain embodiments, the first layer 20 is deposited on the second layer 22 with a thickness of 100 nanometers (nm) or less. Preferably, the first layer 20 is deposited with a thickness of 40 - 100 nm. In some embodiments, the thickness of the first layer 20 may preferably be 70 - 100 nm. In other embodiments, the thickness of the first layer 20 may preferably be 40 - 70 nm. For example, the thickness of the first layer 20 is preferably at least 45 nm, more preferably at least 50 nm, but preferably at most 65 nm, more preferably at most 60 nm.

[0024] In certain embodiments, the first layer 20 is pyrolyzable. When the first layer 20 is pyrolyzable, the first layer 20 can be deposited by an APCVD process. In other embodiments, the first layer 20 may not be pyrolyzable. In these embodiments, the first layer 20 can be deposited using a liquid that provides a sol-gel species layer. Conventional liquids for forming a sol-gel layer comprising silicon dioxide can be utilized to deposit the first layer 20. Preferably, in these embodiments, the liquid can comprise a hydrolyzable silicon compound that undergoes hydrolysis and condensation. Preferred silicon compounds are, for example, silicon alkoxides such as tetraethoxysilane (TEOS). In certain embodiments, the liquid can also comprise silica particles. In embodiments where the liquid contains a metal oxide additive, the liquid can contain a halide, alkoxide, nitrate, or acetylacetonate compound of aluminum, titanium, zirconium, or tin.

[0025] When the first layer 20 is deposited using the liquid, the liquid is dried. Drying can be performed by heating the coated glass article 10 after the liquid has been applied over the second layer 22. The heating can be at a temperature of 250 °C or less. Preferably, drying occurs at a temperature of 200 °C or less. After drying, the first layer can be cured. Curing can be done by ultraviolet irradiation, heating, or another method. When the curing step includes heating, the first layer 20 can be heated to a temperature of 90 - 720 °C. After curing, the coated glass article 10 is cooled over a predetermined period of time.

[0026] The second layer 22 is deposited above the glass substrate 12. More specifically, the second layer 22 is deposited above the first major surface 16 of the glass substrate 12. In one embodiment (not shown), the second layer may be deposited directly on the first major surface of the glass substrate. When the second layer 22 is deposited directly on the first major surface 16 of the glass substrate 12, there is no intervening layer between the second layer 22 and the first major surface 16 of the glass substrate 12. In other embodiments, as shown in FIG. 1, the second layer 22 is deposited above the first major surface 16 of the glass substrate 12 and the anti-iridescence intermediate layer 24. The second layer 22 is provided between the first layer 20 and the glass substrate 12. In this position, the second layer 22 separates the first layer 20 from the glass substrate 12. When provided, the anti-iridescence intermediate layer 24 also separates the first layer 20 from the glass substrate 12.

[0027] The second layer 22 comprises a low emissivity material. Thus, the second layer 22 may also be referred to herein as a low emissivity layer. In certain embodiments, the low emissivity material comprises a transparent conductive metal oxide. A preferred transparent conductive metal oxide is fluorine-doped tin oxide (SnO 2 :F). Thus, in some embodiments, the second layer 22 comprises fluorine-doped tin oxide. In other embodiments, the second layer 22 may consist essentially of fluorine-doped tin oxide. Due to the presence of the fluorine dopant, the second layer 22 is preferably conductive and imparts a reduction in emissivity to the coated glass article 10 when compared to a layer comprising undoped tin oxide (SnO 2 ) of the same thickness. However, other transparent conductive metal oxides may be suitable for use in the second layer 22. For example, in some embodiments, the second layer 22 may comprise antimony-doped tin oxide (SnO 2 :Sb) or another doped tin oxide. In these embodiments, the second layer 22 may consist essentially of antimony-doped tin oxide or another doped tin oxide.

[0028] Preferably, the second layer 22 is pyrolytic and has a thickness of 1000 nm or less. When the second layer 22 comprises fluorine-doped tin oxide, the second layer 22 preferably has a thickness of less than 500 nm. In one embodiment, the second layer 22 has a thickness of 200 to 450 nm. Preferably, the second layer 22 has a thickness of at least 250 nm, more preferably at least 290 nm, even more preferably at least 300 nm, but preferably at most 380 nm, more preferably at most 340 nm, and even more preferably at most 330 nm. However, the second layer 22 can have other thicknesses.

[0029] In some embodiments, the second layer 22 has a refractive index greater than that of the first layer 20. Preferably, the second layer 22 has a refractive index of 1.6 or more. In certain embodiments, the refractive index of the second layer 22 is 1.8 or more. In such an embodiment, the refractive index of the second layer 22 is between 1.8 and 2.4. Preferably, the refractive index of the second layer 22 is between 1.8 and 2.0.

[0030] In some embodiments, the iridescence-suppressing intermediate layer 24 is provided between the glass substrate 12 and the second layer 22. As the thicknesses of the first layer 20 and the second layer 22 increase within the range of 100 nm to 1,000 nm, it is desirable to use the iridescence-suppressing intermediate layer to reduce the reflected color or iridescence of the coated glass article 10.

[0031] In certain embodiments, the anti-iridescence intermediate layer 24 is a two-layer system. In other embodiments (not shown), the anti-iridescence intermediate layer may be provided as a single coating layer. In these embodiments, the coated glass article may comprise only three layers. In the embodiment where the anti-iridescence intermediate layer 24 is a two-layer system as shown in FIG. 1, the coated glass article 10 comprises a third layer 28 deposited above the fourth layer 30, preferably directly on the fourth layer 30, and a fourth layer 30 deposited above the first major surface 16 of the glass substrate 12, preferably directly on the first major surface 16 of the glass substrate 12. In this embodiment, the second layer 22 is deposited above the third layer 28, preferably directly on the third layer 28.

[0032] In some embodiments, the third layer 28 may be formed from an inorganic metal oxide. In other embodiments, the third layer 28 may comprise an oxide of silicon. In these embodiments, it is preferred that the third layer 28 comprises silicon dioxide (SiO 2 ). Preferably, the third layer 28 is deposited with a thickness of 10 to 40 nm. Preferably, the thickness of the third layer 28 is 15 to 30 nm. More preferably, the thickness of the third layer 28 is about 20 nm.

[0033] In some embodiments, the fourth layer 30 is formed of an inorganic metal oxide. Preferably, the fourth layer 30 comprises undoped tin oxide (SnO 2 ). In one embodiment, the fourth layer 30 is deposited with a thickness of 10 to 40 nm. Preferably, the thickness of the fourth layer 30 is 15 to 35 nm. More preferably, the thickness of the fourth layer 30 is about 25 nm.

[0034] After step (a) and before step (b), the coated glass article 10 can be cooled to ambient temperature, preferably to a temperature below 35 °C, more preferably to a temperature below 30 °C, and even more preferably to a temperature below 25 °C. When the coated glass article 10 is formed in connection with a float glass manufacturing process, the coated glass article 10 can be cooled on an annealing rail (not shown). In some embodiments, the coated glass article 10 can be flat. In other embodiments, after cooling, the coated glass article 10 can be curved by a forming process. Additionally, the coated glass article 10 can be heat-strengthened, thermoset, or chemically strengthened, which can occur before or after the deposition of the coating 14.

[0035] After forming the coated glass article 10, the coated glass article 10 can exhibit certain desirable properties. For example, the coated glass article 10 can exhibit a desirable total visible light transmittance. To describe the coated glass article 10, the total visible light transmittance is the percentage of visible light passing through the coated glass article 10 measured at a 90-degree angle of incidence from the side 32 (the coated side) of the coated glass article 10 having the coating 14 formed on the surface of the glass substrate 12 to the coated glass article 10. In addition, the criteria and arrangement of the coating layers 20-24 are such that an anti-reflection effect is provided and a desirable total visible light reflectance is exhibited by the coated glass article 10. To describe the coated glass article 10, the total visible light reflectance is the percentage of visible light reflected from the coated glass article 10 measured at a 90-degree angle of incidence from the coated side 32 of the coated glass article 10 to the coated glass article 10. Further, the total visible light transmittance and the total visible light reflectance are described herein in accordance with the CIELAB color scale system using an A light source and a 2-degree field of view and can be measured using a commercially available spectrophotometer such as a Perkin Elmer Lambda 950.

[0036] In some embodiments, the coated glass article 10 exhibits a total visible light transmittance (A light source, 2° field of view) of greater than 70.0%. In these embodiments, the coated glass article 10 can be used in the front windshield, side window, or rear window of a vehicle. In other embodiments, the coated glass article 10 exhibits a total visible light transmittance (A light source, 2° field of view) of less than 70.0%. In certain embodiments, the coated glass article 10 can exhibit a total visible light transmittance (A light source, 2° field of view) of less than 20.0%. In these embodiments, the coated glass article 10 can be used in the roof glazing, side window, or rear window of a vehicle. In some embodiments, the total visible light transmittance (A light source, 2° field of view) is 10.0% or less. In other embodiments, the total visible light transmittance (A light source, 2° field of view) is 5.0% or less. In this embodiment, the total visible light transmittance (A light source, 2° field of view) can be 2.0 - 5.0%. Additionally, in the above embodiments, the coated glass article 10 preferably exhibits a total visible light reflectance (A light source, 2° field of view) of 5.0% or less. In one embodiment, the total visible light reflectance (A light source, 2° field of view) is 1.0 - 5.0%. More preferably, the total visible light reflectance (A light source, 2° field of view) is 4.0% or less. In some embodiments, the total visible light reflectance (A light source, 2° field of view) of the coated glass article 10 is 3.5% or less. In such an embodiment, the total visible light reflectance (A light source, 2° field of view) is 1.0 - 3.5%.

[0037] The coated glass article 10 may also exhibit other advantageous properties. For example, when the anti-iridescence intermediate layer 24 is provided, the coated glass article 10 may exhibit an intermediate color with respect to visible light reflected from the coated side 32 of the coated glass article 10 when viewed at an angle of incidence of 90 degrees to the coated glass article 10. The color of the visible light reflected from the coated side 32 of the glass article 10 may be referred to herein as the "reflection color". The reflection color is described herein according to the A light source, 2-degree field of view CIELAB color scale system. The reflection color may be measured using a commercially available spectrophotometer such as a Perkin Elmer Lambda 950. Also, for the purpose of describing the embodiments of the coated glass article 10 disclosed herein, the intermediate color of the visible light reflected from the coated side 32 of the coated glass article 10 has an a* value (A light source, 2-degree field of view) in the range of -6 to 6 and a b* value (A light source, 2-degree field of view) in the range of -6 to 6.

[0038] The coated glass article 10 may exhibit a low total solar energy transmittance.

[0039] As used herein, total solar transmittance (TTS) is defined to include solar energy that passes directly through the window assembly and is absorbed by the assembly and then convected and thermally radiated and integrated inward over the wavelength range of 300 - 2500 nm according to the relative solar spectral distribution for air mass 1.5. The total solar transmittance can be determined according to an approved standard such as ISO 13837:2008 and at a wind speed of 14 kilometers per hour. In one embodiment, the coated glass article 10 exhibits a total solar energy transmittance of 35.0 or less. Preferably, the total solar energy transmittance exhibited by the coated glass article 10 is 30.0 or less. More preferably, the total solar energy transmittance exhibited by the coated glass article 10 is 25.0 or less. Even more preferably, the total solar energy transmittance exhibited by the coated glass article 10 is 20.0 or less.

[0040] In some embodiments, the coated glass article 10 can exhibit low transmitted energy (TE), which reduces the amount of heat that passes through the article 10. As used herein, transmitted energy or direct solar heat transmittance (DSHT) is measured at air mass 2 (simulating light rays from the sun incident at an angle of 30° to the horizontal) over the wavelength range of 350 - 2100 nm at 50 nm intervals. In one embodiment, the coated glass article 10 can exhibit a transmitted energy of 30% or less when measured at air mass 2, ISO 9050. Preferably, the coated glass article 10 can exhibit a transmitted energy of less than 20%, more preferably less than 10%.

[0041] Unfortunately, the second layer 22 of the coating 14 can be damaged during manufacturing. More specifically, hydrogen (H in the heating zone of the float glass manufacturing process 2) It is considered that the ability of the second layer 22 to reflect infrared light gradually decreases, increasing the emissivity of the coated glass article 10. Therefore, when the second layer 22 is damaged and the coated glass article 10 is used as a vehicle window, the coated glass article 10 will not provide a very good heat insulation effect in the vehicle cabin.

[0042] The emissivity of the coated glass article 10 can be measured using a commercially available spectrometer such as a Perkin Elmer FTIR. In embodiments where the ability of the second layer 22 to reflect infrared light gradually decreases, the coated glass article 10 will exhibit a first emissivity. In some embodiments, the first emissivity can exceed 0.19. In such an embodiment, the first emissivity can be between 0.19 and 0.21. In other embodiments, the first emissivity can be 0.16 or more. In these embodiments, the first emissivity can be between 0.16 and 0.21.

[0043] Advantageously, it has been discovered that the ability of the second layer 22 to reflect infrared light can be at least partially restored, and the emissivity of the coated glass article 10 can be reduced from the first emissivity. In these embodiments, the coated glass article 10 will exhibit a second emissivity. The second emissivity is smaller than the first emissivity. In some embodiments, the second emissivity can be 0.19 or less. In such an embodiment, the second emissivity can be between 0.10 and 0.19. Therefore, when the coated glass article 10 is used as a vehicle window, the coated glass article 10 will provide a better heat insulation effect in the vehicle cabin.

[0044] In order for the coated glass article 10 to exhibit a second emissivity, the coated glass article 10 can be delivered to the apparatus 40 shown in FIG. 2. The apparatus 40 can be opened and can include an atmosphere containing air. The apparatus 40 can be utilized to heat the coated glass article 10 after cooling. In one embodiment, the apparatus 40 includes a furnace 42. In this embodiment, the coated glass article 10 can enter the furnace 42 on rollers 44. The furnace 42 can include one or more heating elements (not shown). The coated glass article 10 is preferably heated to a predetermined temperature for a predetermined time within the furnace 42.

[0045] Preferably, step (b) is carried out in an environment set to a predetermined temperature of 400 °C or higher. More preferably, step (b) is carried out in an environment set to a predetermined temperature of 500 - 700 °C. Even more preferably, step (b) is carried out in an environment set to a predetermined temperature of 550 - 675 °C, more preferably 550 - 650 °C, even more preferably 575 - 650 °C, and most preferably 600 - 650 °C.

[0046] Preferably, the coated glass article 10 is heated to a predetermined temperature of 400 °C or higher. More preferably, the coated glass article 10 is heated to a predetermined temperature of 500 - 700 °C. Even more preferably, the coated glass article 10 is heated to a predetermined temperature of 530 - 675 °C, more preferably 550 - 650 °C, even more preferably 560 - 635 °C, and most preferably 585 - 635 °C.

[0047] Preferably, the predetermined time for heating the coated glass article 10 is 1 to 10 minutes. More preferably, the predetermined time for heating the coated glass article 10 is 3 to 8 minutes. Even more preferably, the predetermined time for heating the coated glass article 10 can be about 4 to 6 minutes. If the predetermined time for heating the coated glass article 10 is too short, reduction of emissivity may not occur, or cracks may occur in the coated glass article 10 during cooling. If the predetermined time for heating the coated glass article 10 is too long, the coated glass article 10 may undergo undesirable deformation.

[0048] Preferably, following the predetermined time for heating the coated glass article 10, the article can be cooled to ambient temperature by being placed in an environment set to less than 30°C, more preferably less than 25°C, but preferably more than 15°C, more preferably more than 20°C.

[0049] Advantageously, this method may enable an increase in conductivity and a reduction in sheet resistance as exhibited by the coated glass article 10. As should be understood, in certain applications, it may be desirable to have a coated glass article 10 that exhibits a higher conductivity and a lower sheet resistance. In some embodiments and prior to delivering the coated glass article 10 to the apparatus 40, the coated glass article 10 may exhibit a first sheet resistance. For example, the coated glass article 10 may exhibit a first sheet resistance greater than 16 ohms per square (Ω / sq). In this embodiment, the initial sheet resistance as exhibited by the coated glass article 10 may be between 16 and 20 Ω / sq. However, when entering the apparatus 40 and being heated as described above, the sheet resistance of the coated glass article 10 may change due to changes in the electron mobility and carrier concentration of the second layer 22. Preferably, when the coated glass article 10 is heated, the sheet resistance of the coated glass article 10 decreases due to an increase in the carrier concentration of the second layer 22.

[0050] In embodiments, the coated glass article 10 will exhibit a second sheet resistance. In these embodiments, the second sheet resistance will be less than the first sheet resistance. For example, the coated glass article 10 may exhibit a second sheet resistance of 16 Ω / sq or less after being heated to a predetermined temperature for a predetermined time.

[0051] After being heated for a predetermined time, the coated glass article 10 may be removed from the apparatus onto the take-up roller 46.

[0052] After heating the coated glass article to a predetermined temperature for a predetermined time, the article may be laminated to a second glass article, preferably a second coated glass article, to form a laminated glass article. In one embodiment, the second coated glass article is glass / SnO 2 / SiO 2 / SnO 2:F or other suitable arrangements. The laminated glass article can be curved and / or bent by a forming process. The method of the present invention enables better matching of the emissivity of the coated glass articles that are laminated together and then curved and / or bent. This is important because if there is a mismatch between the emissivities of two coated glass articles, subsequent forming is likely to render the article unusable.

[0053] The present invention also provides for the use of the method according to the foregoing aspect for reducing the emissivity of a coated glass article 10.

[0054] Figure 3 shows the infrared reflection spectra from 5 to 25 micrometers for separate coated glass articles before and after implementing an embodiment of the above method. As shown, before implementing this method, each coated glass article 10 exhibits a reflectivity shown by the solid line, which provides a first emissivity. After implementing this method, each coated glass article exhibits a reflectivity shown by the dashed line, which provides a second emissivity. As shown, the infrared reflectivity of each coated glass article increases, and the second emissivity of each coated glass article is less than the first emissivity. Thus, by implementing this method, the infrared reflectivity and emissivity exhibited by each coated glass article are improved.

Examples

[0055] The following examples are presented for the purpose of further illustrating and disclosing embodiments of the method. Examples of coated glass articles within the scope of the present invention are described below and shown in Tables 1 and 2. In Tables 1 and 2, the coated glass articles within the scope of the present invention are Ex1 to Ex4. Ex1 to Ex4 were obtained by depositing a coating on a 3.2 mm thick transparent glass substrate, measuring the optical spectrum of the resulting coated glass article, and then predicting the optical properties of a coated glass article having the same coating on a gray glass substrate.

[0056] Each glass substrate is a soda-lime-silica composition and is formed as part of a float glass ribbon. As it moves, a thermal decomposition coating is deposited on each glass substrate, and the coating is deposited on the substrate within the heating zone of the float glass manufacturing process.

[0057] Each coating comprises a first layer, a second layer, and an anti-iridescence intermediate layer. The first layer is deposited above the glass substrate and on the second layer. The second layer is provided between the first layer and the glass substrate and on the anti-iridescence intermediate layer. For each of Ex1 to Ex4, the first layer comprises silicon dioxide. In the case of Ex1, the thickness of the first layer is 55 nm and the first layer has a refractive index of 1.46. In the case of Ex2, the thickness of the first layer is 90 nm and the first layer has a refractive index of 1.46. In the case of Ex3, the thickness of the first layer is 45 nm and the first layer has a refractive index of 1.46. In the case of Ex4, the thickness of the first layer is 80 nm and the first layer has a refractive index of 1.46. For each of Ex1 to Ex4, the second layer comprises fluorine-doped tin oxide. In the cases of Ex1 and Ex3, the thickness of the second layer was 310 nm. In the cases of Ex2 and Ex4, the thickness of the second layer was 410 nm. An anti-iridescence intermediate layer is provided between the glass substrate and the second layer. The anti-iridescence intermediate layer is a two-layer system. The anti-iridescence intermediate layer comprises a third layer directly deposited on the fourth layer, and the fourth layer is directly deposited on the first major surface of the glass substrate. Each third layer comprises silicon dioxide. In the cases of Ex1 and Ex3, the thickness of the third layer was 30 nm. In the cases of Ex2 and Ex4, the thickness of the third layer was 16 nm. Each fourth layer comprises undoped tin oxide. In the cases of Ex1 and Ex3, the thickness of the fourth layer was 20 nm. In the cases of Ex2 and Ex4, the thickness of the fourth layer was 30 nm. Thus, each of the coated glass articles of Ex1 to Ex4 is a glass / SnO 2 / SiO 2 / SnO 2 :F / SiO 2 arrangement.

[0058] After forming the coated glass articles of Ex1 to Ex4, each coated glass article was cooled to an ambient temperature of 20 - 25 °C within an annealing rail. To enable testing at three different temperatures, each coated glass article was cut into three smaller coated glass articles. Then, the articles were delivered to a furnace for reheating. Depending on the articles to be tested, the furnace was set to a temperature of 650 °C, 625 °C or 600 °C. Each coated glass article was held in the furnace for 5 minutes.

[0059] Before entering the furnace, the first emissivity (ε1) and the first sheet resistance (SR1) of the coated glass articles of Ex1 to Ex4 were measured (SR1 was measured only for the articles heated in a furnace set to a temperature of 650 °C). After heating, the second emissivity (ε2) and the second sheet resistance (SR2) of each coated glass article were measured (SR2 was measured only for the articles heated in a furnace set to a temperature of 650 °C). The emissivities (ε1, ε2) and sheet resistances (SR1, SR2) of the coated glass articles of Ex1 to Ex4 are shown in Table 2. The emissivities of the coated glass articles of Ex1 to Ex4 were measured using a Perkin Elmer FTIR spectrometer. The sheet resistances of the coated glass articles of Ex1 to Ex4 are shown in Ω / sq and were measured using a four-point probe.

[0060] Also, the total visible light transmittance (Tvis), the total visible light reflectance (Rf), the reflected color (Rfa * , Rfb *) And the total solar energy transmittance (TTS) is shown in Table 1. For the coated glass articles of Ex1 to Ex4, the total visible light transmittance, total visible light reflectance, reflection color, and total solar energy transmittance were calculated by modeling and according to the CIELAB color scale system using an A light source and a 2-degree field of view. For the coated glass articles of Ex1 to Ex4, the total visible light transmittance refers to the percentage of visible light passing through the article, measured from the side facing the coating. The total visible light reflectance is shown for the coated side of the coated glass article. The visible light reflectance refers to the percentage of visible light reflected from the coated glass article, measured from the side of the article facing the coating. The total visible light reflectance and total visible light transmittance are expressed as percentages. The reflection color is shown for the coated side of the coated glass articles of Ex1 to Ex4. Also, the total solar energy transmittance shown below is expressed as a percentage.

[0061]

Table 1

[0062]

Table 2

[0063] As shown in Table 2, each of the coated glass articles of Ex1 to Ex4 showed a first emissivity and a second emissivity. In each of Examples 1 to 4, the emissivity shown by the coated glass article decreased after this method was implemented. Therefore, the second emissivity shown by each coated glass article was smaller than the first emissivity shown by the coated glass article. Therefore, after this method was implemented, each of the coated glass articles of Ex1 to Ex4 would provide a better heat insulation effect in the passenger compartment when the coated glass article is used for a vehicle window.

[0064] Furthermore, each of the coated glass articles of Ex1 to Ex4 exhibits a first sheet resistance and a second sheet resistance. In each of Ex1 to Ex4, the sheet resistance of the coated glass article decreased after implementing this method. Thus, the second sheet resistance exhibited by each coated glass article was less than the first sheet resistance exhibited by the coated glass article. Thus, after implementing this method, each of the coated glass articles of Ex1 to Ex4 was more conductive.

[0065] In addition, as shown in Table 1, each of the coated glass articles of Ex1 to Ex4 exhibits a total visible light transmittance of less than 5.0% (A light source, 2-degree field of view) and a total visible light reflectance of less than 4.0% (A light source, 2-degree field of view). Also, the coated glass articles of Ex1 and Ex3, Ex4 exhibit an intermediate reflection color at a vertical incident angle. Thus, if one of these coated glass articles is used for a vehicle window, the coated glass article will have an aesthetically pleasing appearance. It should also be noted that the coated glass articles of Ex1 to Ex4 exhibited a direct solar energy transmittance of less than 20.0%. Thus, during summer, if one of the coated glass articles of Ex1 to Ex4 is used for a vehicle window, the coated glass article will help prevent overheating of the passenger compartment.

[0066] From the foregoing detailed description, it will be apparent that various modifications, additions, and other alternative embodiments are possible without departing from the original scope and spirit. The embodiments discussed herein are selected and described to provide the best illustration of the principles of the invention and its actual application, thereby enabling those skilled in the art to use the invention with various modifications suitable for the particular uses contemplated in various embodiments. As should be understood, all such modifications and variations are within the scope of the invention.

Claims

**Claim 1** A method for reducing the emissivity of a coated glass article 10, comprising: (a) forming a coated glass article 10, the coated glass article 10 comprising a glass substrate 12 and a coating 14 formed on the glass substrate 12, the coating 14 being formed in a heating zone of a float glass manufacturing process and deposited above the glass substrate 12 and having a first layer 20 and a second layer 22, the second layer 22 comprising fluorine-doped tin oxide (SnO₂:F) and being provided between the first layer 20 and the glass substrate 12, the coated glass article 10 exhibiting a first emissivity; forming the coated glass article 10; (b) heating the coated glass article 10 in an environment set at a predetermined temperature for a predetermined time; in sequence, after step (b), the coated glass article 10 exhibits a second emissivity, and the second emissivity is smaller than the first emissivity. A method for reducing the emissivity of a coated glass article 10. **Claim 2** The method according to claim 1, wherein the coating 14 is formed on a first major surface 16 of the glass substrate 12, and a second major surface 18 of the glass substrate 12 and the opposite side of the coated glass article 10 are not coated. **Claim 3** The method according to claim 1 or 2, wherein the coating 14 further comprises an iridescence suppressing intermediate layer 24 provided between the second layer 22 and the glass substrate 12. **Claim 4** The method according to any one of claims 1 to 3, wherein the coating 14 is thermally decomposable. **Claim 5** The method according to any one of claims 1 to 4, wherein the coating 14 is formed in conjunction with the manufacture of the glass substrate 12, and the glass substrate 12 is preferably formed using a known float glass manufacturing process. **Claim 6** The method according to any one of claims 1 to 5, wherein at least one of the layers 20 to 24 of the coating 14 is deposited on the glass substrate 12 by atmospheric pressure chemical vapor deposition (APCVD). **Claim 7** The first layer 20 comprises silicon dioxide (SiO ２ ) or another suitable oxide of silicon, the method according to any one of claims 1 to 6. **Claim 8** The method according to any one of claims 1 to 7, wherein the thickness of the first layer 20 is 40 to 70 nm. **Claim 9** The second layer (22) has a thickness of at least 250 nm, preferably at least 290 nm, even more preferably at least 300 nm, but at most 380 nm, more preferably at most 340 nm, even more preferably at most 330 nm, according to the method of any one of claims 1 to 8.

10. After step (a) and before step (b), the coated glass article 10 is cooled to a temperature below 35 °C, preferably to a temperature below 30 °C, more preferably to a temperature below 25 °C, according to the method of any one of claims 1 to 9.

11. Step (b) is carried out in an environment set to a predetermined temperature of 550 to 675 °C, preferably 550 to 650 °C, more preferably 575 to 650 °C, most preferably 600 to 650 °C, according to the method of any one of claims 1 to 10.

12. The predetermined time for heating the coated glass article 10 is 3 to 8 minutes, preferably 4 to 6 minutes, according to the method of any one of claims 1 to 11.

13. After step (b), the article 10 is laminated to a second glass article, preferably a second coated glass article, to form a laminated glass article, and the laminated glass article is bent by a forming process, according to the method of any one of claims 1 to 12.

14. The coated glass article 10 is used for a window of a vehicle, and preferably the first main surface 16 of the glass substrate 12 and the coating 14 face the passenger compartment of the vehicle, according to the method of any one of claims 1 to 13.

15. Use of the method of any one of claims 1 to 14 for reducing the emissivity of a coated glass article 10.

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