Patent Description:
Coatings on glass can be formed from a wide variety of materials to accomplish a variety of functions. As an example, a coating may be formed on glass to decrease the emissivity exhibited by the glass. <CIT> describes a multi-layer pyrolytic coating stack deposited on a tinted glass substrate to form a coated glass article exhibiting a desired combination of emissivity, visible light transmittance and solar heat gain coefficient. <CIT> describes a laminated glass unit having at least two sheets of glass separated and bonded by a polymeric interlayer material, and further having multi-layer thin film coatings on each of the unbonded surfaces of the at least two glass sheets. The thin films deposited on the unbonded glass surfaces have anti-reflective, iridescence-suppressing and solar control properties when suitable configurations, materials and layer thicknesses are chosen.

Under certain conditions, the emissivity decreasing coating may be damaged. Damage to such a coating may increase the emissivity exhibited by the coated glass article, which may make the coated glass article unsuitable for its intended use.

Thus, it would be desirable to provide a method that allows the emissivity of a glass article to be reduced if an emissivity decreasing coating formed thereon has been damaged.

The above, as well as other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:.

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific articles, apparatuses, methods, and features illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts. Hence, specific dimensions, directions, or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. Also, although they may not be, like elements found in the aforementioned embodiments may be referred to with like identifiers within this section of the application.

A method of reducing the emissivity of a coated glass article is described herein, as set out in claim <NUM>.

The method is practiced using a coated glass article <NUM>. Embodiments of the coated glass article <NUM> are illustrated in <FIG>. It should be appreciated that the method can also be practiced using coated glass articles that are not depicted in <FIG> or described below.

The coated glass article <NUM> may be utilized in a window for a vehicle (not depicted). It would be understood by one of ordinary skill in the art that the coated glass article described herein may have applications to on-highway and off-highway vehicles. Also, the coated glass article could be utilized in a commercial or residential glazing or have, for example, architectural, photovoltaic, industrial, locomotive, naval, and aerospace applications.

When the coated glass article <NUM> is utilized in a vehicle window, the coated glass article <NUM> may be installed in any appropriate body opening of the vehicle. In some embodiments, the coated glass article <NUM> may be utilized in a windshield, side window, or rear window of the vehicle. In other embodiments, the window could be utilized in another body opening in the vehicle. For example, a window having the coated glass article <NUM> could be installed in an opening in the roof of the vehicle. In this embodiment, the coated glass article <NUM> may be utilized as a roof glazing in a sunroof or moonroof application.

As illustrated in <FIG>, the coated glass article <NUM> comprises a glass substrate <NUM>. In some embodiments, the glass substrate <NUM> is not limited to a particular thickness. However, in certain embodiments, the glass substrate <NUM> may have a thickness of <NUM> millimeters (mm) or less. Preferably, the glass substrate <NUM> has a thickness of <NUM>-<NUM>. In some embodiments, the glass substrate <NUM> may have a thickness of <NUM>-<NUM>. More preferably, the glass substrate <NUM> has a thickness of <NUM>-<NUM>. In some embodiments, the glass substrate <NUM> has a thickness of <NUM>-<NUM>.

The glass substrate <NUM> may be of any of the conventional glass compositions known in the art. Preferably, the glass substrate <NUM> is a soda-lime-silica glass. When the glass substrate <NUM> is a soda-lime-silica glass, the glass substrate <NUM> may comprise <NUM>-<NUM> weight % SiO<NUM>, <NUM>-<NUM> weight % Al<NUM>O<NUM>, <NUM>-<NUM> weight % MgO, <NUM>-<NUM> weight % CaO, <NUM>-<NUM> weight % Na<NUM>O, <NUM>-<NUM> weight % SO<NUM>, <NUM>-<NUM> weight % Fe<NUM>O<NUM> (total iron), and <NUM>-<NUM> weight % K<NUM>O. As used herein, the phrase "total iron" refers to the total weight of iron oxide (FeO + Fe<NUM>O<NUM>) contained in the glass calculated as Fe<NUM>O<NUM>. The glass may also contain other additives, for example, refining agents, which would normally be present in an amount of up to <NUM>%. In this embodiment, the glass substrate <NUM> may be provided as a portion of a float glass ribbon. When the glass substrate <NUM> is formed as a portion of a float glass ribbon, the glass substrate <NUM> may be clear float glass. In some of these embodiments, clear float glass may mean a glass having a composition as defined in a related standard such as BS EN <NUM>-<NUM>:<NUM>+A1:<NUM> and BS EN <NUM>-<NUM>:<NUM>. However, the glass substrate <NUM> may be of another composition such as, for example, a borosilicate or aluminosilicate composition.

The color of the glass substrate <NUM> can vary between embodiments of the coated glass article <NUM>. In some embodiments, the glass substrate <NUM> may be clear. In these embodiments, the glass substrate <NUM> may exhibit a total visible light transmittance of <NUM>% or more when measured at a reference thickness of <NUM> in the CIELAB color scale system (Illuminant C, <NUM> degree observer). In one such embodiment, the glass substrate <NUM> has a low iron content, which allows for the high visible light transmittance. For example, the glass substrate <NUM> may comprise <NUM> weight % Fe<NUM>O<NUM> (total iron) or less. More preferably, in this embodiment, the glass substrate <NUM> comprises <NUM> weight % Fe<NUM>O<NUM> (total iron) or less, and, even more preferably, a <NUM> weight % Fe<NUM>O<NUM> (total iron) or less. In still other embodiments, the glass substrate <NUM> may be tinted or colored.

When the glass substrate <NUM> is tinted, the glass substrate <NUM> may comprise <NUM>-<NUM> weight % Fe<NUM>O<NUM> (total iron). Preferably, when the glass substrate <NUM> is tinted, the glass substrate <NUM> comprises <NUM>-<NUM> weight % Fe<NUM>O<NUM> (total iron). In some of these embodiments, the glass substrate <NUM> may comprise <NUM>-<NUM> by weight of ferrous oxide (calculated as FeO). Further, when the glass substrate <NUM> is tinted, the glass substrate <NUM> may comprise certain colorants. For example, the glass substrate <NUM> may comprise one or more of cobalt oxide (calculated as Co<NUM>O<NUM>) in an amount up to <NUM> ppm by weight of glass, nickel oxide (calculated as NiO) in an amount up to <NUM> ppm by weight of glass, and selenium in an amount up to <NUM> ppm by weight of glass. In an embodiment, the glass substrate <NUM> comprises nickel oxide (calculated as NiO) of <NUM>-<NUM> ppm. When the glass substrate <NUM> is tinted, it is preferred that the glass substrate <NUM> is of, for example, a grey, grey-blue, green, blue-green, or bronze color.

When the glass substrate <NUM> is of a grey color, the glass substrate <NUM> may comprise <NUM>-<NUM> weight % Fe<NUM>O<NUM> (total iron). Preferably, when the glass substrate <NUM> is of a grey color, the glass substrate <NUM> comprises <NUM>-<NUM> weight % Fe<NUM>O<NUM> (total iron). Also, in these embodiments, the glass substrate <NUM> may have an a* value of -5t5, preferably -<NUM>±<NUM>, a b* value of <NUM>±<NUM>, preferably 4t1 and an L* of <NUM>±<NUM>, preferably <NUM>±<NUM> in the CIELAB color scale system. In these embodiments, the grey glass substrate has a visible light transmission of <NUM>% or less when the glass substrate <NUM> has a nominal thickness of <NUM>. Preferably, the grey glass substrate has a visible light transmission of <NUM>-<NUM> % when the glass substrate <NUM> has a nominal thickness of <NUM>. The grey glass pane may be sold under the trademark Galaxsee and manufactured by Pilkington. In other embodiments, the glass substrate <NUM> may be a grey glass having similar optical properties to Galaxsee by Pilkington or a grey glass having lower light transmission properties than Galaxsee by Pilkington at a nominal thickness.

When the glass substrate <NUM> is of a green color, the glass substrate <NUM> may comprise <NUM>-<NUM> weight % Fe<NUM>O<NUM> (total iron). In some embodiments, when the glass substrate <NUM> is of a green color, the glass substrate <NUM> comprises <NUM>-<NUM> weight % Fe<NUM>O<NUM> (total iron). In other embodiments where the glass substrate <NUM> is of a green color, the glass substrate <NUM> may comprise greater than <NUM> weight % Fe<NUM>O<NUM> (total iron). Also, in these embodiments, the glass substrate <NUM> may comprise <NUM>-<NUM>% TiO<NUM>. In some embodiments, the glass substrate <NUM> may have an a* value of -<NUM> to -<NUM>, a b* value of -<NUM> to <NUM>, and an L* of <NUM> or more in the CIELAB color scale system. In these embodiments, the green glass substrate has a visible light transmission of <NUM>% or more when the glass substrate <NUM> has a nominal thickness of <NUM>.

A coating <NUM> is formed on the glass substrate <NUM>. Preferably, the coating <NUM> is formed on a first major surface <NUM> of the glass substrate <NUM>. When the coating <NUM> is formed directly on the glass substrate <NUM>, there are no intervening coatings between the coating <NUM> and the glass substrate <NUM>. Preferably, a second major surface <NUM> of the glass substrate <NUM> and an opposite side of the coated glass article <NUM> is uncoated. It is preferred that when the coated glass article is utilized in a vehicle window, the first major surface <NUM> of the glass substrate <NUM> and the coating <NUM> face into the passenger cabin of the vehicle.

The coating <NUM> comprises more than one layer <NUM>-<NUM>. The coating <NUM> comprises a first layer <NUM> and a second layer <NUM>. In other embodiments, the coating <NUM> may comprise a first layer <NUM>, second layer <NUM>, and an iridescence-suppressing interlayer <NUM>. In the embodiment illustrated in <FIG>, the coating <NUM> may consist of the first layer <NUM>, second layer <NUM>, and iridescence-suppressing interlayer <NUM>. The coating <NUM> is provided to reduce the emissivity exhibited by the coated glass article <NUM>. In some embodiments, the coating <NUM> may be configured to reduce the visible light reflection exhibited by the coated glass article <NUM>.

In an embodiment, the coating <NUM> is pyrolytic. As used herein, the term "pyrolytic" may refer to the coating or a layer thereof being chemically bonded to the glass substrate or another layer. Preferably, each layer <NUM>-<NUM> is pyrolytic. The coating <NUM> and one or more of its layers <NUM>-<NUM> may be formed in conjunction with the manufacture of the glass substrate <NUM>. Preferably, in these embodiments, the glass substrate <NUM> is formed utilizing the well-known float glass manufacturing process. In embodiments where the glass substrate <NUM> is provided as a portion of a float glass ribbon, the coating <NUM> or one or more of its layers <NUM>-<NUM> may be formed in the heated zone of the float glass manufacturing process.

The coating <NUM> is deposited on the glass substrate <NUM>. The coating layers <NUM>-<NUM> may be deposited by any suitable method. However, in some embodiments, at least one layer <NUM>-<NUM> is deposited by atmospheric pressure chemical vapor deposition (APCVD). In these embodiments, one or more layers <NUM>-<NUM> may be deposited by another known deposition method such as, for example, a sol-gel technique or a sputter technique.

The first layer <NUM> is deposited over the glass substrate <NUM>. The first layer <NUM> is deposited over the second layer <NUM>. Preferably, the first layer <NUM> is deposited directly on the second layer <NUM>. When the first layer <NUM> is deposited directly on the second layer <NUM>, there are no intervening layers between the second layer <NUM> and the first layer <NUM>. In some embodiments, the first layer <NUM> may be the outermost layer of the coating <NUM>. When the first layer <NUM> is the outermost layer of the coating <NUM>, the first layer <NUM> forms an outer surface <NUM> of the coated glass article <NUM>. When the coated glass article <NUM> is included in a vehicle window, it is preferred that the outer surface <NUM> faces into the passenger cabin of the vehicle.

Preferably, the first layer <NUM> has a refractive index that is less than the refractive index of the second layer <NUM>. In some embodiments, the first layer <NUM> has a refractive index that is <NUM> or less. Preferably, the refractive index of the first layer <NUM> is <NUM>-<NUM>. In an embodiment, the refractive index of the first layer <NUM> may be between <NUM> and <NUM>. In another embodiment, the refractive index of the first layer <NUM> may be between <NUM> and <NUM>. It should be noted that the refractive index values described herein are reported as an average value across <NUM>-<NUM> of the electromagnetic spectrum.

The first layer <NUM> comprises silicon dioxide (SiO<NUM>) or another suitable oxide of silicon. The first layer <NUM> may also include a trace amount of one or more additional constituents such as, for example, carbon. Thus, in certain embodiments, the first layer <NUM> may consist essentially of silicon dioxide. However, in other embodiments, the first layer <NUM> may comprise an oxide of silicon and one or more additional materials, which are provided to increase the refractive index of the first layer <NUM> above <NUM>. In one such embodiment, the first layer <NUM> may also comprise aluminum oxide (Al<NUM>O<NUM>), titanium dioxide (TiO<NUM>), zirconium oxide (ZrO<NUM>), boron oxide (B<NUM>O<NUM>), phosphorus oxide (P<NUM>O<NUM>), or tin oxide. Additionally, other materials that are dielectric may be suitable for use in the first layer <NUM>.

In certain embodiments, the first layer <NUM> is deposited on the second layer <NUM> at a thickness of <NUM> nanometers (nm) or less. Preferably, the first layer <NUM> is deposited at a thickness of <NUM>-<NUM>. In some embodiments, it may be preferred that the thickness of the first layer <NUM> is <NUM>-<NUM>. In other embodiments, it may be preferred that the thickness of the first layer <NUM> is <NUM>-<NUM>, e.g. the thickness of the first layer <NUM> is preferably at least <NUM>, more preferably at least <NUM>, but preferably at most <NUM>, more preferably at most <NUM>.

In certain embodiments, the first layer <NUM> is pyrolytic. When the first layer <NUM> is pyrolytic, the first layer <NUM> may be deposited by an APCVD process. In other embodiments, the first layer <NUM> may not be pyrolytic. In these embodiments, the first layer <NUM> may be deposited utilizing a liquid, which provides a layer of the sol-gel variety. Conventional liquids for forming a sol-gel layer comprising silicon dioxide may be utilized to deposit the first layer <NUM>. Preferably, in these embodiments, the liquid may comprise a hydrolysable silicon compound that undergoes hydrolysis and condensation. Preferred silicon compounds are silicon alkoxides such as, for example, tetraethoxysilane (TEOS). In certain embodiments, the liquid may also comprise silica particles. In embodiments where the liquid includes a metal oxide additive, the liquid may include halides, alkoxides, nitrates, or acetylacetonate compounds of aluminum, titanium, zirconium, or tin.

When the first layer <NUM> is deposited utilizing a liquid, the liquid is dried. Drying may be performed by heating the coated glass article <NUM> after the liquid has been applied over the second layer <NUM>. Heating may be to a temperature of <NUM> or less. Preferably, drying occurs at a temperature of <NUM> or less. After drying, the first layer may be cured. Curing may be performed by irradiation with ultraviolet radiation, heating, or by another method. When the curing step comprises heating, the first layer <NUM> may be heated to a temperature of <NUM>-<NUM>. After curing, the coated glass article <NUM> is cooled over a predetermined period of time.

The second layer <NUM> is deposited over the glass substrate <NUM>. More particularly, the second layer <NUM> is deposited over the first major surface <NUM> of the glass substrate <NUM>. In an embodiment (not depicted), the second layer may be deposited directly on the first major surface of the glass substrate. When the second layer <NUM> is deposited directly on the first major surface <NUM> of the glass substrate <NUM>, there are no intervening layers between the second layer <NUM> and the first major surface <NUM> of the glass substrate <NUM>. In other embodiments, like the one illustrated in <FIG>, the second layer <NUM> is deposited over the first major surface <NUM> of the glass substrate <NUM> and the iridescence-suppressing interlayer <NUM>. The second layer <NUM> is provided between the first layer <NUM> and the glass substrate <NUM>. In this position, the second layer <NUM> separates the first layer <NUM> from the glass substrate <NUM>. If provided, the iridescence-suppressing interlayer <NUM> also separates the first layer <NUM> from the glass substrate <NUM>.

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

Preferably, the second layer <NUM> is pyrolytic and has a thickness of <NUM>,<NUM> or less. When the second layer <NUM> comprises fluorine doped tin oxide, the second layer <NUM> preferably has a thickness of less than <NUM>. In an embodiment, the second layer <NUM> has a thickness of <NUM>-<NUM>. Preferably the second layer <NUM> has a thickness of at least <NUM>, more preferably at least <NUM>, even more preferably at least <NUM>, but preferably at most <NUM>, more preferably at most <NUM>, even more preferably at most <NUM>. However, the second layer <NUM> may be of other thicknesses.

In some embodiments, the second layer <NUM> has a refractive index that is greater than the refractive index of the first layer <NUM>. Preferably, the second layer <NUM> has a refractive index that is <NUM> or more. In certain embodiments, the refractive index of the second layer <NUM> is <NUM> or more. In one such embodiment, the refractive index of the second layer <NUM> is between <NUM> and <NUM>. Preferably, the refractive index of the second layer <NUM> is between <NUM> and <NUM>.

In some embodiments, an iridescence-suppressing interlayer <NUM> is provided between the glass substrate <NUM> and the second layer <NUM>. The use of an iridescence-suppressing interlayer is desirable to reduce the reflected color or iridescence of the coated glass article <NUM> as the thickness of the first layer <NUM> and the second layer <NUM> increase within the range of <NUM> to <NUM>,<NUM>.

In certain embodiments, the iridescence-suppressing interlayer <NUM> is of a two-layer system. In other embodiments (not depicted), the iridescence-suppressing interlayer may be provided as a single coating layer. In these embodiments, the coated glass article may comprise only three layers. In the embodiments where the iridescence-suppressing interlayer <NUM> is a two-layer system, which is illustrated in <FIG>, the coated glass article <NUM> comprises a third layer <NUM> deposited over and, preferably, directly on a fourth layer <NUM> and the fourth layer <NUM> deposited over and, preferably, directly on the first major surface <NUM> of the glass substrate <NUM>. In this embodiment, the second layer <NUM> is deposited over and, preferably, directly on the third layer <NUM>.

In some embodiments, the third layer <NUM> may be formed of an inorganic metal oxide. In other embodiments, the third layer <NUM> may comprise an oxide of silicon. In these embodiments, it is preferred that the third layer <NUM> comprise silicon dioxide (SiO<NUM>). Preferably, the third layer <NUM> is deposited at a thickness of <NUM>-<NUM>. Preferably, the thickness of the third layer <NUM> is <NUM>-<NUM>. More preferably, the thickness of the third layer <NUM> is about <NUM>.

In some embodiments, the fourth layer <NUM> is formed of an inorganic metal oxide. Preferably, the fourth layer <NUM> comprises undoped tin oxide (SnO<NUM>). In an embodiment, the fourth layer <NUM> is deposited at a thickness of <NUM>-<NUM>. Preferably, the thickness of the fourth layer <NUM> is <NUM>-<NUM>. More preferably, the thickness of the fourth layer <NUM> is about <NUM>.

After step (a) and before step (b), the coated glass article <NUM> is cooled to a temperature of less than <NUM>, preferably cooled to a temperature of less than <NUM>, more preferably cooled to a temperature of less than <NUM>. When the coated glass article <NUM> is formed in conjunction with the float glass manufacturing process, the coated glass article <NUM> may be cooled in an annealing lehr (not depicted). In some embodiments, the coated glass article <NUM> may be flat. In other embodiments, after cooling, the coated glass article <NUM> may be curved by way of a shaping process. Additionally, the coated glass article <NUM> may be heat strengthened, thermally toughened, or chemically strengthened, which may occur before or after deposition of the coating <NUM>.

After forming the coated glass article <NUM>, the coated glass article <NUM> may exhibit certain desirable properties. For example, the coated glass article <NUM> may exhibit a desirable total visible light transmittance. For describing the coated glass article <NUM>, total visible light transmittance will refer to the percentage of visible light passing through the coated glass article <NUM> as measured at a <NUM> degree angle incident to the coated glass article <NUM> from the side <NUM> of the coated glass article <NUM> that has the coating <NUM> formed on the surface of the glass substrate <NUM> (coated side). Additionally, the criteria for and arrangement of the coating layers <NUM>-<NUM> is such that an anti-reflective effect is provided and a desirable total visible light reflectance is exhibited by the coated glass article <NUM>. For describing the coated glass article <NUM>, total visible light reflectance will refer to the percentage of visible light reflected from the coated glass article <NUM> as measured at a <NUM> degree angle incident to the coated glass article <NUM> from the coated side <NUM> of the coated glass article <NUM>. Further, the total visible light transmittance and total visible light reflectance will be described herein according to the CIELAB color scale system using Illuminant A, <NUM> degree observer and can be measured using a commercially available spectrophotometer such as the Perkin Elmer Lambda <NUM>.

In some embodiments, the coated glass article <NUM> exhibits a total visible light transmittance (Illuminant A, <NUM> degree observer) of more than <NUM>%. In these embodiments, the coated glass article <NUM> may be utilized in a windshield, side window, or rear window of the vehicle. In other embodiments, the coated glass article <NUM> exhibits a total visible light transmittance (Illuminant A, <NUM> degree observer) of less than <NUM>%. In certain embodiments, the coated glass article <NUM> may exhibit a total visible light transmittance (Illuminant A, <NUM> degree observer) of less than <NUM>%. In these embodiments, the coated glass article <NUM> may be utilized in a roof glazing, side window, or rear window of the vehicle. In some embodiments, the total visible light transmittance (Illuminant A, <NUM> degree observer) is <NUM>% or less. In other embodiments, the total visible light transmittance (Illuminant A, <NUM> degree observer) is <NUM>% or less. In this embodiment, the total visible light transmittance (Illuminant A, <NUM> degree observer) may be <NUM>-<NUM>%. Additionally, it is preferred that, in the embodiments described above, the coated glass article <NUM> exhibits a total visible light reflectance (Illuminant A, <NUM> degree observer) of <NUM>% or less. In an embodiment, the total visible light reflectance (Illuminant A, <NUM> degree observer) is <NUM>-<NUM>%. More preferably, the total visible light reflectance (Illuminant A, <NUM> degree observer) is <NUM>% or less. In some embodiments, the total visible light reflectance (Illuminant A, <NUM> degree observer) of the coated glass article <NUM> is <NUM>% or less. In one such embodiment, the total visible light reflectance (Illuminant A, <NUM> degree observer) is <NUM>-<NUM>%.

The coated glass article <NUM> may also exhibit other properties that are advantageous. For example, when the iridescence-suppressing interlayer <NUM> is provided, the coated glass article <NUM> may exhibit a neutral color for the visible light reflected from the coated side <NUM> of the coated glass article <NUM> when viewed at a <NUM> degree angle incident to the coated glass article <NUM>. The color of the visible light reflected from the coated side <NUM> of the glass article <NUM> may be referred to herein as "reflected color. " The reflected color will be described herein according to the CIELAB color scale system using Illuminant A, <NUM> degree observer. Reflected color can be measured using a commercially available spectrophotometer such as the Perkin Elmer Lambda <NUM>. Also, for the purpose of describing the embodiments of the coated glass article <NUM> disclosed herein, a neutral color for the visible light reflected from the coated side <NUM> of the coated glass article <NUM> has an a* value (Illuminant A, <NUM> degree observer) in the range of -<NUM> to <NUM> and a b* value (Illuminant A, <NUM> degree observer) in the range of -<NUM> to <NUM>.

The coated glass article <NUM> may exhibit a low total solar energy transmittance. As used herein, total solar transmittance (TTS) is defined as including solar energy transmitted directly through the window assembly and the solar energy absorbed by the assembly, and subsequently convected and thermally radiated inwardly integrated over the wavelength range <NUM> to <NUM> according to the relative solar spectral distribution for air mass <NUM>. The total solar transmittance may be determined according to a recognized standard such as ISO <NUM>:<NUM> convention A and at a wind speed of <NUM> kilometers per hour. In an embodiment, the coated glass article <NUM> exhibits a total solar energy transmittance of <NUM> or less. Preferably, the total solar energy transmittance exhibited by the coated glass article <NUM> is <NUM> or less. More preferably, the total solar energy transmittance exhibited by the coated glass article <NUM> is <NUM> or less. Even more preferably, the total solar energy transmittance exhibited by the coated glass article <NUM> is <NUM> or less.

In some embodiments, the coated glass article <NUM> may exhibit a low transmitted energy (TE), which reduces the amount of heat transmitted through the article <NUM>. As used herein, transmitted energy or direct solar heat transmission (DSHT) is measured at Air Mass <NUM> (simulated rays from the sun incident at an angle of <NUM>° to the horizontal) over the wavelength range <NUM> to <NUM> at <NUM> intervals. In an embodiment, the coated glass article <NUM> may exhibit a transmitted energy of <NUM>% or less, when measured at Air Mass <NUM>, ISO <NUM>. Preferably, the coated glass article <NUM> may exhibit a transmitted energy of less than <NUM>% and more preferably less than <NUM>%.

Unfortunately, the second layer <NUM> of the coating <NUM> may be damaged during manufacturing. More particularly, it is believed that hydrogen (H<NUM>) in the heated zone of the float glass manufacturing process diminishes the ability of the second layer <NUM> to reflect infrared light, which increases the emissivity of the coated glass article <NUM>. Thus, when the second layer <NUM> is damaged and the coated glass article <NUM> is utilized in a window for a vehicle, the coated glass article <NUM> will not provide as good of an insulating effect for the passenger cabin of the vehicle.

The emissivity of the coated glass article <NUM> can be measured using a commercially available spectrometer such as the Perkin Elmer FTIR. In embodiments where the ability of the second layer <NUM> to reflect infrared light has been diminished, the coated glass article <NUM> will exhibit a first emissivity. In some embodiments, the first emissivity may be more than <NUM>. In one such embodiment, the first emissivity may be <NUM>-<NUM>. In other embodiments, the first emissivity may be <NUM> or more. In these embodiments, the first emissivity may be <NUM>-<NUM>.

Advantageously, it has been discovered that the ability of the second layer <NUM> to reflect infrared light can be at least partially restored and the emissivity of the coated glass article <NUM> can be reduced from the first emissivity. In these embodiments, the coated glass article <NUM> will exhibit a second emissivity. The second emissivity is less than the first emissivity. In some embodiments, the second emissivity may be <NUM> or less. In one such embodiment, the second emissivity may be <NUM>-<NUM>. Thus, when the coated glass article <NUM> is utilized in a window for a vehicle, the coated glass article <NUM> will provide a better insulating effect for the passenger cabin of the vehicle.

In order for the coated glass article <NUM> to exhibit a second emissivity, the coated glass article <NUM> may be delivered to an apparatus <NUM>, which is illustrated in <FIG>. The apparatus <NUM> may be open and include an atmosphere comprising air. The apparatus <NUM> may be utilized to heat the coated glass article <NUM> after cooling. In an embodiment, the apparatus <NUM> comprises a furnace <NUM>. In this embodiment, the coated glass article <NUM> may enter the furnace <NUM> on rollers <NUM>. The furnace <NUM> may comprise one or more heating elements (not depicted). The coated glass article <NUM> is preferably heated to a predetermined temperature and for a predetermined period of time in the furnace <NUM>.

Step (b) is carried out in an environment set to a predetermined temperature of <NUM>-<NUM>, preferably <NUM>-<NUM>, more preferably <NUM>-<NUM>, most preferably <NUM>-<NUM>.

Preferably, the coated glass article <NUM> is heated to a predetermined temperature of <NUM> or more. More preferably, the coated glass article <NUM> is heated to a predetermined temperature of <NUM>-<NUM>. More preferably, the coated glass article <NUM> is heated to a predetermined temperature of <NUM>-<NUM>, even more preferably <NUM>-<NUM>, even more preferably <NUM>-<NUM>, most preferably <NUM>-<NUM>.

The predetermined period of time for heating the coated glass article <NUM> is <NUM>-<NUM> minutes. Preferably, the predetermined period of time for heating the coated glass article <NUM> is <NUM>-<NUM> minutes. Even more preferably, the predetermined period of time for heating the coated glass article <NUM> may be about <NUM>-<NUM> minutes. If the predetermined period of time for heating the coated glass article <NUM> is too short the reduction is emissivity will not occur or the coated glass article <NUM> may crack while cooling. If the predetermined period of time for heating the coated glass article <NUM> is too long the coated glass article <NUM> may undesirably deform.

Preferably, following the predetermined period of time for heating the coated glass article <NUM>, said article is allowed to cool to ambient temperature by being placed in an environment set to less than <NUM>, more preferably less than <NUM>, but preferably more than <NUM>, more preferably more than <NUM>.

Advantageously, the method may allow for an increase in the conductivity and a reduction in the sheet resistance exhibited by the coated glass article <NUM>. As should be appreciated, it may be desirable in certain applications to have a coated glass article <NUM> that exhibits higher conductivity and a lower sheet resistance. In some embodiments and prior to delivering the coated glass article <NUM> to the apparatus <NUM>, the coated glass article <NUM> may exhibit a first sheet resistance. For example, the coated glass article <NUM> may exhibit a first sheet resistance of more than <NUM> Ohms per square (Ω/sq. In this embodiment, the initial sheet resistance exhibited by the coated glass article <NUM> may be <NUM>-<NUM>Ω/sq. However, upon entering the apparatus <NUM> and being heated as described above, the sheet resistance of the coated glass article <NUM> may change due to changes in the electron mobility and carrier concentration of the second layer <NUM>. Preferably, the sheet resistance of the coated glass article <NUM> decreases due to an increase in the carrier concentration of the second layer <NUM> when the coated glass article <NUM> is heated.

In embodiments where the sheet resistance exhibited by the coated glass article <NUM> has been decreased, the coated glass article <NUM> 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 <NUM> may exhibit a second sheet resistance of <NUM>Ω/sq. or less after being heated to a predetermined temperature and for a predetermined period of time.

After being heated for a predetermined period of time, the coated glass article <NUM> may be removed from the apparatus on take-away rollers <NUM>.

After heating the coated glass article to a predetermined temperature and for a predetermined period of time the article may be laminated to a second glass article, preferably a second coated glass article, to form a laminated glass article. In an embodiment, the second coated glass article may be of a glass/SnO<NUM>/SiO<NUM>/SnO<NUM>:F or other suitable arrangement. The laminated glass article may be curved/bent by way of a shaping process. The method of the present invention enables better matching of the emissivity of coated glass articles that are to be laminated together and then curved/bent. This is important because if there is a mismatch between the emissivities of the two coated glass articles then the shaping is more likely to result in an unusable product.

The present invention also provides the use of the method according to the preceding aspect to reduce the emissivity of a coated glass article (<NUM>).

<FIG> illustrates the infrared radiation reflectance spectrum from <NUM>-<NUM> micrometers for separate coated glass articles before and after practicing embodiments of the method described above. As illustrated, before practicing the method, each coated glass article <NUM> exhibits a reflectance, indicated by the solid lines, that provides a first emissivity. After practicing the method, each coated glass article exhibits a reflectance, indicated by the dashed lines, that provides a second emissivity. As shown, the reflectance of infrared radiation for each coated glass article increases and the second emissivity of each coated glass article is less than the first emissivity. Thus, the reflectance of infrared radiation and emissivity exhibited by each coated glass article is improved by practicing the method.

The following examples are presented solely for the purpose of further illustrating and disclosing the embodiments of the method. Examples of the coated glass article within the scope of the invention are described below and illustrated in TABLES <NUM> and <NUM>. In TABLES <NUM> and <NUM>, the coated glass articles within the scope of the invention are Ex <NUM>-Ex <NUM>. Ex <NUM>-Ex <NUM> were derived from depositing coatings on <NUM> clear glass substrates, measuring the optical spectra of the resulting coated glass articles, and then predicting the optical properties of coated glass articles having the same coatings on grey glass substrates.

Each glass substrate was of a soda-lime-silica composition and formed as a portion of a float glass ribbon. A pyrolytic coating was deposited on each glass substrate as it was moving and the coating was deposited on the substrate in the heated zone of the float glass manufacturing process.

Each coating comprised a first layer, second layer, and an iridescence-suppressing interlayer. The first layer was deposited over the glass substrate and on the second layer. The second layer was provided between the first layer and the glass substrate and on the iridescence-suppressing interlayer. For each of Ex1-Ex <NUM>, the first layer comprised silicon dioxide. For Ex <NUM>, the thickness of the first layer was <NUM> and the first layer has a refractive index of <NUM>. For Ex <NUM>, the thickness of the first layer was <NUM> and the first layer has a refractive index of <NUM>. For Ex <NUM>, the thickness of the first layer was <NUM> and the first layer has a refractive index of <NUM>. For Ex <NUM>, the thickness of the first layer was <NUM> and the first layer has a refractive index of <NUM>. For each of Ex1-Ex <NUM>, the second layer comprised fluorine doped tin oxide. For Ex <NUM> and Ex <NUM>, the thickness of the second layer was <NUM>. For Ex <NUM> and Ex <NUM>, the thickness of the second layer was <NUM>. The iridescence-suppressing interlayer was provided between the glass substrate and the second layer. The iridescence-suppressing interlayer was a two-layer system. The iridescence-suppressing interlayer comprised a third layer deposited directly on a fourth layer and the fourth layer was deposited directly on the first major surface of the glass substrate. Each third layer comprised silicon dioxide. For Ex <NUM> and Ex <NUM>, the thickness of the third layer was <NUM>. For Ex <NUM> and Ex <NUM>, the thickness of the third layer was <NUM>. Each fourth layer comprised undoped tin oxide. For Ex <NUM> and Ex <NUM>, the thickness of the fourth layer was <NUM>. For Ex <NUM> and Ex <NUM>, the thickness of the fourth layer was <NUM>. Thus, the coated glass articles of Ex <NUM>-Ex <NUM> are each of a glass/SnO<NUM>/SiO<NUM>/SnO<NUM>:F/SiO<NUM> arrangement.

After forming the coated glass articles of Ex <NUM>-Ex <NUM>, each coated glass article was cooled to an ambient temperature of from <NUM> to <NUM> in an annealing lehr. Each coated glass article was cut into three smaller coated glass articles to enable testing at three different temperatures. The articles were then delivered to a furnace for reheating. The furnace was set to a temperature of <NUM>, <NUM> or <NUM> depending on which article was to be tested. Each coated glass article was held in the furnace for <NUM> minutes.

Prior to entering the furnace, the first emissivity (ε1) and first sheet resistance (SR1) of the coated glass articles of Ex <NUM>-Ex <NUM> were measured (SR1 was only measured for the articles to be heated in the furnace set to a temperature of <NUM>). After heating, the second emissivity (ε2) and second sheet resistance (SR2) of each coated glass article was measured (SR2 was only measured for the articles heated in the furnace set to a temperature of <NUM>). The emissivities (ε1, ε2) and sheet resistances (SR1, SR2) of the coated glass articles of Ex <NUM>-Ex <NUM> are reported in TABLE <NUM>. The emissivities of the coated glass articles of Ex <NUM>-Ex <NUM> were measured using a Perkin Elmer FTIR spectrometer. The sheet resistances of the coated glass articles of Ex <NUM>-Ex <NUM> are reported in Ω/sq. and were measured using a four-point probe. Also, the total visible light transmittance (Tvis), total visible light reflectance (Rf), reflected color (Rfa*, Rfb*), and total solar energy transmittance (TTS) are reported in TABLE <NUM>. For the coated glass articles of Ex <NUM>-Ex <NUM>, the total visible light transmittance, total visible light reflectance, reflected color, and total solar energy transmittance were calculated by modeling and according to the CIELAB color scale system using illuminant A, <NUM> degree observer. For the coated glass articles of Ex <NUM>-Ex <NUM>, the total visible light transmittance refers to the percentage of visible light passing through the article that would be measured from the side facing the coating. The total visible light reflectance is reported 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 that would be measured from the side of the article that faces the coating. The total visible light reflectance and the total visible light transmittance are expressed as percentages. The reflected color is reported for the coated side of the coated glass articles of Ex <NUM>-Ex <NUM>. Also, the total solar energy transmittance reported below is expressed as a percentage.

As illustrated in TABLE <NUM>, the coated glass articles of Ex <NUM>-Ex <NUM> each exhibited a first emissivity and a second emissivity. In each of Ex <NUM>-Ex <NUM>, the emissivity exhibited by the coated glass article was reduced after practicing the method. Thus, the second emissivity exhibited by each coated glass article was less than the first emissivity exhibited by the coated glass article. As such, after practicing the method, each of the coated glass articles of Ex <NUM>-Ex <NUM> would provide a better insulating effect for the passenger cabin when the coated glass article is utilized in a window for a vehicle.

Additionally, the coated glass articles of Ex <NUM>-Ex <NUM> each exhibit a first sheet resistance and a second sheet resistance. In each of Ex <NUM>-Ex <NUM>, the sheet resistance of the coated glass article decreased after practicing the 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. As such, after practicing the method, each of the coated glass articles of Ex <NUM>-Ex <NUM> was more conductive.

Claim 1:
A method of reducing the emissivity of a coated glass article (<NUM>), comprising the following steps in sequence:
(a) forming a coated glass article (<NUM>), the coated glass article (<NUM>) comprising a glass substrate (<NUM>) and a coating (<NUM>) formed on the glass substrate (<NUM>), the coating (<NUM>) having a first layer (<NUM>) deposited over the glass substrate (<NUM>) and a second layer (<NUM>), the second layer (<NUM>) being provided between the first layer (<NUM>) and the glass substrate (<NUM>), wherein the coated glass article (<NUM>) exhibits a first emissivity; and
(b) heating the coated glass article (<NUM>) in an environment set to a predetermined temperature and for a predetermined period of time,
wherein, after step (b), the coated glass article (<NUM>) exhibits a second emissivity, the second emissivity being less than the first emissivity,
wherein after step (a) and before step (b) the coated glass article (<NUM>) is cooled to a temperature of less than <NUM>,
wherein the first layer (<NUM>) comprises silicon dioxide (SiO<NUM>) or another suitable oxide of silicon,
wherein the second layer (<NUM>) comprises a transparent conductive metal oxide, preferably fluorine doped tin oxide (SnO<NUM>:F),
wherein step (b) is carried out in an environment set to a predetermined temperature of <NUM>-<NUM>, preferably <NUM>-<NUM>, more preferably <NUM>-<NUM>, most preferably <NUM>-<NUM>, and
wherein the predetermined period of time for heating the coated glass article <NUM> is <NUM>-<NUM> minutes.