Solar control coated glass

Details Solar control coated glass Solar control coated glass

1999-10-12

2002-07-09

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S702000, C428S469000, C428S472000, C428S698000, C428S697000, C428S428000, C428S432000, C428S448000, C427S585000, C427S166000, C427S167000, C427S168000, C427S255120, C427S427000

Reexamination Certificate

active

06416890

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sheets of solar control glass and to a method for their preparation.
Transparent solar control sheets are much in demand for use in exterior glazing panels for buildings. In addition to having aesthetic appeal they offer advantages in providing protection against the heating and dazzling effects of solar radiation. A similar demand exists for glass sheets used for vehicle windows.
The solar control sheets, typically of soda-lime glass, carry a coating to provide the specific properties required. They may be employed as a single sheet or in a glazing panel incorporating other sheets of glass and possibly also non-vitreous laminating materials. The solar control requirement is that the sheet, or the panel of which it forms a part, shall not pass too great a proportion of total incident solar radiation, thereby resisting overheating of the building or vehicle interior.
Properties of the coated glass sheet discussed herein are based on the standard definitions of the International Commission on Illumination—Commission Internationale de l'Eclairage (“CIE”).
The “luminous transmittance” (TL) is the luminous flux transmitted through the sheet as a percentage of the incident luminous flux.
The “luminous reflectance” (RL) is the luminous flux reflected from the sheet as a percentage of the incident luminous flux. For a sheet with a coating on one face, the reflectance may be measured from the coated side (RLc) or from the uncoated glass side (RLg).
The transmission of total incident solar radiation may be expressed as the “solar factor” (FS) of the sheet, which as used herein means the sum of the total energy directly transmitted and the energy which is absorbed and re-radiated on the side away from the energy source, as a percentage of the total radiant energy incident on the sheet.
The “selectivity” of the sheet is the ratio of the luminous transmittance to the solar factor (TL/FS). glass sheet, including pyrolysis. Pyrolysis generally has the advantage of producing a hard coating with durable abrasion- and corrosion-resistant properties. This is believed to be due in particular to the glass sheet being hot during the deposition of the coating material. Pyrolysis is also generally cheaper than alternative coating processes such as sputtering, particularly in terms of the investment in plant.
A wide variety of coating materials have been proposed for modifying the optical properties of glazing panels. Tin oxide (SnO
2
) has been widely used, often in combination with other materials such as other metal oxides.
2. Description of the Related Art
Our GB patent 1455148 is an early example of a method for pyrolytically forming a coating of one or more oxides (e.g. SnO
2
, Co
3
O
4
, Cr
2
O
3
, Sb
2
O
3
, SiO
2
, TiO
2
or ZrO
2
) on a glass sheet, primarily by spraying compounds of a metal or silicon, so as to modify its light transmission and/or light reflection.
U.S. Pat. No. 5385751 relates to the formation of a fluorine-doped film of tungsten oxide on a glass substrate surface so as to improve the solar and optical properties of the glass. The doped oxide is obtained by reaction at the said surface of a tungsten alkoxide, an oxygen-containing compound and a fluorine-containing compound.
WO 98/11031 relates to solar control coated glass in which the coating comprises a heat-absorbing layer of a metal oxide such as chromium oxide, cobalt oxide, iron oxide, molybdenum oxide, niobium oxide, vanadium oxide or doped or undoped tungsten oxide, and a low emissivity layer of a metal compound, for example a semiconductor metal oxide such as doped tin oxide or doped indium oxide.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a pyrolytically formed coated glass sheet with significant solar screening properties.
We have discovered that this and other useful objectives can be achieved by applying to the sheet a pyrolytic coating which includes a conductive or semi-conductive layer of a defined thickness of certain metal oxides containing a conductive dopant material. (References herein to numerical limits of layer thicknesses are in all cases to geometric thicknesses.)
Thus, according to the present invention, there is provided a transparent glass sheet carrying a coating of at least two pyrolytically-formed layers, characterised by the presence in the coating of a conductive or semi-conductive layer having a thickness in the range 15 to 500 nm and formed of a material comprising a metal oxide containing a dopant in an amount of from 1 to 100 moles per 100 moles of the metal oxide, the said metal oxide being selected from one or more of tungsten trioxide (WO
3
), molybdenum trioxide (MoO
3
), niobium pentoxide (Nb
2
O
5
), tantalum pentoxide (Ta
2
O
5
), vanadium pentoxide (V
2
O
5
) and vanadium dioxide (VO
2
), whereby the so-coated sheet has a neutral or blue tint in transmission and in reflection, a luminous transmittance (TL) which is in the range 30 to 85% and a selectivity of greater than 1.
The invention also provides a method of producing a transparent glass sheet carrying a coating of at least two pyrolytically-formed layers, characterised by applying to the sheet a conductive or semi-conductive layer having a thickness in the range 15 to 500 nm and formed of a material comprising a metal oxide and introducing into the said metal oxide a dopant in an amount of from 1 to 100 moles per 100 moles of the metal oxide, the said metal oxide being selected from one or more of tungsten trioxide (WO
3
), molybdenum trioxide (MoO
3
), niobium pentoxide (Nb
2
O
5
), tantalum pentoxide (Ta
2
O
5
), vanadium pentoxide (V
2
O
5
) and vanadium dioxide (VO
2
), whereby the so-coated sheet has a neutral or blue tint in transmission and in reflection, a luminous transmittance (TL) which is in the range 30 to 85% and a selectivity of greater than 1.
A particular benefit of the above-defined conductive or semi-conductive layer is that it imparts to the coated sheet a greater reflection in the near infra-red than in the visible range, thereby improving the solar protection while retaining high luminous transmission.
The coating comprises a layer, generally transparent, which interferes with the conductive or semi-conductive layer so as to confer to the coated glass sheet the neutral or blue tint in transmission and in reflection.
Doped tungsten oxide is a preferred material for the conductive or semi-conductive layer. Among its useful properties is a naturally low emissivity (E) i.e. the ratio of the energy emitted by a given surface at a given temperature to that of a perfect emitter (a black body with emissivity of 1.0) at the same temperature.
The metal oxide is formed from a suitable precursor. For example, for molybdenum oxide suitable precursors include molybdenum carbonyl [Mo(CO)
6
], molybdenum acetyl acetonate, a molybdenum chloride (MoCl
3
or MoCl
5
), molybdenum fluoride (MoF
6
), an organic molybdenum compound such as MoO
2
(2,2,6,6-tetramethylheptane-3,5-dione)
2
, and a molybdenum oxychloride (MoO
2
Cl
2
or MoOCl
4
) For vanadium oxide a suitable precursor is vanadium acetyl acetonate. For niobium oxide suitable precursors include niobium ethoxide [Nb(OC
2
H
5
)
5
], niobium chloride (NbCl
5
), niobium fluoride (NbF
5
) and niobium dipivaloylmethanatochloride (Nb(2,2,6,6-tetramethylheptane-3,5-dione)
2
Cl
3
). To form tantalum oxide, suitable precursors include tantalum fluoride or chloride (TaF
5
or TaCl
5
) or an alkoxy tantalum [e.g. Ta(OR)
5
in which R═CH
3
, C
2
H
5
or C
4
H
9
]. To form tungsten oxide, suitable precursors include tungsten hexachloride (WCl
6
), tungsten oxytetrachloride (WOC14), tungsten carbonyl [W(CO)
6
], tungsten cyclopentadienyl chloride [W(C
5
H
5
)
2
Cl
2
], tungsten fluoride (WF
6
), or a tungsten ethoxide [W(OC
2
H
5
)
5
or W(OC
2
H
5
)
6
].
The dopant provides the conductive properties of the conductive or semi-conductive layer. The dopant is present in the layer in an amoun

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