FR3097543A1 - Colored glass sheet - Google Patents

Abstract

The invention relates to a glass sheet, the chemical composition of which is free of selenium and comprises the following constituents, within the limits defined below expressed in percentages by weight: SiO2 64-75% Al2O3 0-4% CaO 5-15% MgO 0-5% Na2O 9-18% K2O 0-4% Fe2O3 (total iron) 0.09-0.17% CoO 20-40 ppmNiO 110-230 ppm with a NiO / CoO ratio ranging from 4.5 to 8.0 , the glass exhibiting a redox, defined as the ratio between the ferrous iron content, expressed in the FeO form, and the total iron content, expressed in the Fe2O3 form, between 0.24 and 0.46, said composition being such that the glass sheet has, for a thickness of 6 mm, colorimetric transmission coordinates a * and b * such that (a * ² + b * ²) 1/2 <5.0.

Description

colored glass sheet

The invention relates to the field of colored glass sheets. It relates more particularly to sheets of glass which can be incorporated into building or automobile glazing.

Coatings, in particular in the form of stacks of thin layers, are frequently deposited on glass sheets in order to confer various properties on the glazings which contain them. This may in particular be so-called solar control coatings, the purpose of which is to reflect and/or absorb part of the solar radiation, in particular in the near infrared but also in the visible, in order to reduce heating in dwellings. or vehicle interiors and therefore energy consumption related to air conditioning. Solar control coatings are often chosen for the aesthetics they give to buildings, in particular their reflection and transmission aspects, both seen from the side of the coating (layer side) and from the opposite side (glass side). Certain stacks have, for example, a neutral or bluish reflection, or even silver or gold.

Depending on the intended application, the glass sheets can be thermally tempered or not. Thermal toughening, which consists of heating the glass and then suddenly cooling it, creates superficial compressive stresses on the surface of the glass which will mechanically strengthen the glass sheet.

The object of the invention is to provide glass sheets which do not substantially modify the appearance in reflection and in transmission of any solar control coatings. Another object of the invention is to provide sheets of glass whose appearance is little modified by thermal toughening.

To this end, the subject of the invention is a sheet of glass whose chemical composition is free of selenium and comprises the following constituents, within the limits defined below, expressed in percentages by weight:
_SiO2 64-75%
Al ₂ O ₃ 0-4%
CaO 5-15%
MgO 0-5%
Na ₂ O 9-18%
_K2O 0-4%
Fe ₂ O ₃ (total iron) 0.09-0.17%
CoO 20-40ppm
NiO 110-230ppm
with a NiO/CoO ratio ranging from 4.5 to 8.0,
the glass having a redox, defined as the ratio between the ferrous iron content, expressed in the FeO form, and the total iron content, expressed in the Fe ₂ O ₃ form, between 0.24 and 0.46,
said composition being such that the glass sheet has, for a thickness of 6 mm, colorimetric coordinates in transmission a* and b* such that (a*²+b*²) ^1/2 <5.0.

The choice of such a composition makes it possible in particular to meet the aforementioned objectives, by making it possible to obtain a neutral glass whose tint varies little due to tempering and which does not modify the appearance of any coatings, in particular for solar control. , which would be deposited on the glass. Other advantages of the invention will appear on reading this text.

The glass sheet includes:
- a basic matrix of the silico-sodo-lime type, which comprises silica (SiO ₂ ), lime (CaO), soda (Na ₂ O), and possibly alumina (Al ₂ O ₃ ), magnesia (MgO) and potash (K ₂ O), and
- a coloring composition, which includes oxides of iron, cobalt and nickel.

Silica (SiO ₂ ) is a glass-forming element. Its content is between 64 and 75%, preferably between 66 and 73%. High contents lead to an increase in the viscosity of the glass at high temperature and its tendency to devitrify, whereas low contents will reduce the hydrolytic resistance of the glass.

Alumina (Al ₂ O ₃ ) is also a glass-forming element, and improves its hydrolytic resistance. Its content is between 0 and 4%, preferably between 0.3 and 3%.

Lime (CaO) and magnesia (MgO) aid in glass melting by decreasing viscosity at high temperatures. They also improve the hydrolytic resistance of the glass but increase the tendency to devitrification. The CaO content is between 5 and 15%, preferably between 8 and 13%. The MgO content is between 0 and 5%, preferably between 1 and 3%.

Soda (Na ₂ O) and potash (K ₂ O) reduce the viscosity of the glass and facilitate melting, but to the detriment of hydrolytic resistance. The Na ₂ O content is between 9 and 18%, in particular between 12 and 15%. The K ₂ O content is between 0 and 4%, in particular between 0 and 2%, or even between 0 and 1%. The potash is generally provided by the alumina carrier (for example feldspars).

Preferably, the sum of the SiO ₂ , Al ₂ O ₃ , CaO, MgO, Na ₂ O and K ₂ O contents is at least 95%, in particular at least 97% and even at least 98% or at least 99%.

The basic matrix can also comprise other oxides, for example refining agents such as sulphate (SO ₃ ), or various impurities introduced by the raw materials or due to the corrosion of the refractories. Oxides such as BaO, SrO, Li ₂ O or B ₂ O ₃ are preferably absent from the composition, or at best as impurities. The SO ₃ content is preferably between 0.1 and 0.5%.

Throughout this text, the contents are expressed in percentages by weight.

The coloring composition, incorporated into the base matrix during fusion, makes it possible to obtain the desired optical and energy properties.

The coloring composition is free of selenium. This element is indeed toxic, requires perfect control of the oxidation-reduction conditions in the glass bath to control the tint of the glass, and has a strong tendency to fly off, requiring expensive filtration systems.

The coloring composition includes iron, cobalt and nickel oxides. It preferably consists of these three oxides, to which titanium oxide is optionally added, the presence of which in the form of impurities is difficult to avoid.

Iron is present in glass in the ferrous (FeO) and ferric (Fe ₂ O ₃ ) form. Ferrous iron absorbs in the near infrared and gives a blue color while ferric iron absorbs in the ultraviolet and gives a yellow color. Thus, not only the total iron content (expressed by convention in the form Fe ₂ O ₃ ) but also the redox, are important for obtaining the desired optical and energetic properties.

The Fe ₂ O ₃ (total iron) content is between 0.09 and 0.17%, preferably between 0.10 and 0.16%, especially between 0.11 and 0.15%. Lower contents require the use of expensive raw materials. Higher contents confer an undesirable coloration liable to modify the appearance of any coatings deposited on the glass.

The redox is between 0.24 and 0.46, preferably at least 0.30, and in particular between 0.31 and 0.36. The redox can be regulated in a known manner by adding reducing agents (such as coke) and oxidants (such as sodium sulphate) to the vitrifiable mixture. In the case of fusion by flame furnace, the stoichiometry of the burners can also influence the redox.

The ferrous iron (FeO) content can in particular be determined by an optical method, from the measurement of the transmission at a wavelength of 1000 nm.

To do this, the transmission T at 1000 nm is measured using a spectrophotometer, making it possible to calculate the internal reflection R _inside the glass, then the FeO content.

The following formulas are applied.

with _R0 = 0.041775.

e being the thickness of the glass (in millimeters).

The choice of the CoO and NiO contents as well as the ratio between these contents makes it possible to obtain the desired optical properties. The CoO content is preferably between 21 and 35 ppm, especially between 24 and 32 ppm. The NiO content is between 140 and 185 ppm, in particular between 150 and 180 ppm. The NiO/CoO ratio is preferably between 5.0 and 6.5, especially between 5.2 and 6.3.

The coloring composition can optionally, but not preferably, comprise other oxides or coloring elements.

Titanium oxide (TiO ₂ ) is generally present as impurities in certain raw materials, in particular sands. Due to the yellow color that it imparts, the TiO ₂ content is preferably at most 0.10%, in particular at most 0.05%, or even at most 0.04%.

Chromium oxide (Cr ₂ O ₃ ) confers a green coloration. Its content is preferably at most 100 ppm (0.01%), or even at most 50 ppm. It will usually be present, if any, as impurities. The same is true for vanadium oxide, which also imparts a green coloration.

Copper oxide (CuO, Cu ₂ O) imparts a blue coloration. Its content is preferably zero.

Erbium oxide (Er ₂ O ₃ ), sometimes used for the production of gray glass, is however very expensive, and its content will generally be zero. Cerium oxide (CeO ₂ ) absorbs ultraviolet radiation. Its content is generally at most 0.5%, and preferably zero. The content of other lanthanide oxides is also preferably zero.

The coloring composition is normally free of sulphides and particles of silver, copper and gold, which are extremely strong colorants and generally do not achieve the desired properties.

The coloring composition is preferably free of manganese oxide.

The composition is such that the glass sheet has, for a thickness of 6 mm, colorimetric coordinates in transmission a* and b* such that c*=(a*²+b*²) ^1/2 <5.0. This parameter c* is preferably at most 4.0, even at most 3.5 and even at most 3.0. The value of c* will most often be at least 0.5, or even at least 1.0.

The colorimetric coordinates in transmission are calculated for a reference thickness of 6 mm, from an experimental spectrum produced by spectrophotometry, taking into account the reference illuminant D65 and the CIE 1964 reference observer (10°).

The glass sheet preferably has, for a thickness of 6 mm, a light transmission factor (TL) within the meaning of standard EN 410 of between 50 and 70%, in particular between 55 and 65%. The glass sheet preferably has, for a thickness of 6 mm, a direct solar energy transmission factor (TE) within the meaning of standard EN 410 of between 45 and 70%, in particular between 40 and 65%.

The glass sheet can be thermally tempered. It then presents surface stresses in compression. The choice of the aforementioned dyes makes it possible to obtain a coloring after quenching very close to that before quenching. The values of c* mentioned above are therefore also obtained after thermal quenching.

The glass sheet preferably has a thickness of between 1 and 19 mm, in particular between 3 and 10 mm, or even between 4 and 8 mm. The glass sheet preferably has at least one dimension greater than 1 m.

The glass sheet is preferably obtained by floating. Floating is a process in which molten glass is poured onto a bath of molten tin. The composition of the glass sheet is advantageously free of arsenic and antimony, which are not compatible with this process. In terms of melting, the glass can be melted by any known process, flame and/or electric melting.

The glass sheet according to the invention is advantageously provided on at least one of its faces with a solar control coating. The coating is in particular in the form of a stack of thin layers, in particular obtained by sputtering assisted by magnetic field (magnetron process). Other deposition techniques such as chemical vapor deposition (CVD) are also possible.

The solar control coating preferably comprises at least one functional thin layer based or even consisting of:
- of a metal, in particular silver, niobium or an alloy of nickel and chromium, or
- a metal nitride, in particular niobium nitride, titanium nitride or nickel and chromium nitride, or
- titanium oxide.

The functional thin layer is capable of reflecting and/or absorbing part of the solar radiation, in particular in the near infrared. The or each thin functional layer is preferably surrounded by at least two dielectric layers based on oxides, nitrides or oxynitrides.

As a preferred example, the solar control coating comprises one, two, or three thin layers of silver, each being individually surrounded by at least two dielectric layers based on oxides, nitrides or oxynitrides.

The combination of the glass sheet having the aforementioned composition with such a coating makes it possible to improve the solar control properties, due to the absorption of the colored glass, without however substantially modifying the appearance of the coating, whether in reflection or in transmission, and both on the layer side and on the glass side.

Alternatively or cumulatively, the glass sheet can be provided with other types of coatings, for example low-emissivity, self-cleaning, anti-reflective coatings, etc.

The invention also relates to a glazing comprising at least one sheet of glass according to the invention.

It may be in particular a glazing intended to equip buildings or transport vehicles, in particular automobiles.

The glazing may be laminated glazing, in which the glass sheet is adhesively bonded to another glass sheet, for example clear glass, by means of a thermoplastic lamination interlayer, for example polyvinyl butyral (PVB). The glazing may also be monolithic glazing or multiple glazing. In the latter case, the glass sheet according to the invention is associated by means of an intermediate frame with at least one other glass sheet, so as to create a space filled with air or a rare gas.

The glazing, when it comes to automotive glazing, can be used as a windshield as well as a side glazing, roof or rear window.

The glass sheet can also be used as a decorative or furnishing element (glass slabs, table top, etc.).

The following examples illustrate the invention without limiting it.

Glass sheets were obtained in a known manner by melting and floating, then their optical properties were characterized by spectrophotometry.

Each of the compositions in Table 1 below was produced from a glass matrix having the following composition:
_SiO2 72.6%
Al ₂ O ₃ 0.7%
CaO 10.5%
MgO 2.2%
Na ₂ O 13.5%
K ₂ O 0.05%.

Some glass sheets have been tempered in a known way by cooling using air nozzles

Table 1 summarizes for each of the examples the content by weight of total iron (denoted Fe ₂ O ₃ ), expressed in percentage by weight, the redox, the contents of CoO and NiO, expressed in ppm, the NiO/CoO ratio, and the properties following optics, for a reference thickness of 6 mm: the light transmission factor within the meaning of standard EN 410 (noted TL), the direct transmittance factor of solar energy within the meaning of standard EN 410 (noted TE) , as well as the c* parameter.

The FeO content, and hence the redox, was determined by the optical method and calculations mentioned above.

The glass sheets of the examples are not tempered, with the exception of the examples having the index “t”. For examples 12, 22 to 25 and 27, the table indicates the properties obtained before and after quenching.

Fe ₂ O ₃ ORP CoO NiO NiO/CoO TL YOU vs* 1 0.129 0.31 39 220 5.6 58.5 61.4 2.5 2 0.123 0.32 38 203 5.4 59.2 62.4 2.5 3 0.106 0.32 28 160 5.7 64.5 66.0 2.1 4 0.161 0.31 40 210 5.3 58.2 58.3 3.3 5 0.157 0.32 39 201 5.2 58.9 58.8 3.2 6 0.154 0.32 37 190 5.2 59.6 59.4 3.2 7 0.151 0.32 35 184 5.3 59.8 59.7 3.1 8 0.147 0.32 35 183 5.2 60.4 60.0 3.2 9 0.147 0.32 34 180 5.2 60.8 60.4 3.2 10 0.143 0.33 34 173 5.0 61.5 60.9 3.2 11 0.145 0.32 33 172 5.3 61.9 61.3 3.2 12 0.143 0.32 34 169 5.0 62.2 3.2 12t 61.2 3.3 13 0.139 0.32 32 160 4.9 62.8 62.0 3.2 14 0.137 0.32 30 156 5.2 63.2 62.4 3.2 15 0.134 0.33 31 152 4.9 63.7 62.6 3.1 16 0.133 0.32 31 150 4.9 64.5 63.3 3.1 17 0.129 0.32 29 139 4.9 65.3 63.9 3.0 18 0.106 0.36 21 115 5.4 64.4 65.3 2.6 19 0.119 0.37 28 151 5.4 58.0 60.8 3.3 20 0.134 0.33 33 200 6.0 58.8 60.3 2.4 21 0.126 0.32 28 166 6.0 63.4 63.6 2.2 22 0.159 0.40 25 156 6.2 64.1 55.0 4.7 22t 63.6 54.5 4.0 23 0.141 0.45 21 162 7.7 61.1 53.5 4.6 23t 56.1 50.5 3.1 24 0.125 0.25 31 170 5.5 63.9 64.4 2.9 24t 62.3 63.9 1.9 25 0.123 0.37 31 160 5.2 64.6 59.7 4.0 25t 62.8 60.4 3.2 26 0.126 0.30 30 178 5.9 64.3 63.3 3.0 27 0.133 0.33 29 148 5.1 64.1 3.2 27t 63.1 3.2

Claims (10)

Sheet of glass whose chemical composition is free of selenium and comprises the following constituents, within the limits defined below, expressed in weight percentages:
_SiO2 64-75%
Al ₂ O ₃ 0-4%
CaO 5-15%
MgO 0-5%
Na ₂ O 9-18%
_K2O 0-4%
Fe ₂ O ₃ (total iron) 0.09-0.17%
CoO 20-40ppm
NiO 110-230ppm
with a NiO/CoO ratio ranging from 4.5 to 8.0,
the glass having a redox, defined as the ratio between the ferrous iron content, expressed in the FeO form, and the total iron content, expressed in the Fe ₂ O ₃ form, between 0.24 and 0.46,
said composition being such that the glass sheet has, for a thickness of 6 mm, colorimetric coordinates in transmission a* and b* such that (a*²+b*²) ^1/2 <5.0. Glass sheet according to Claim 1, such that the Fe ₂ O ₃ (total iron) content is between 0.10 and 0.16%. Glass sheet according to one of the preceding claims, such that the redox is at least 0.30, in particular between 0.31 and 0.36. Glass sheet according to one of the preceding claims, such that the CoO content is between 21 and 35 ppm. Glass sheet according to one of the preceding claims, such that the NiO content is between 140 and 185 ppm. Glass sheet according to one of the preceding claims, such that the NiO/CoO ratio is between 5.0 and 6.5. Glass sheet according to one of the preceding claims, the composition of which is such that the glass sheet has, for a thickness of 6 mm, colorimetric coordinates in transmission a* and b* such that (a*²+b*² ) ^1/2 < 4.0. Glass sheet according to one of the preceding claims, which is thermally toughened. Glass sheet according to one of the preceding claims, provided on at least one of its faces with a solar control coating. Glazing comprising at least one sheet of glass according to one of the preceding claims.