Very dark grey soda-lime glass

ES 2 149 646 B1

DESCRIPTION

Very dark gray Sodo-lime glass.

The present invention relates to a very dark gray colored glass of lime and caustic soda composed of glass-forming constituents and coloring agents.

The expression "lime and caustic soda glass" is used in the present invention in a broad sense and refers to any glass composed of the following constituents (percentages by weight):

SiO2 60 to 75%

Na2O 10 to 20%

CaO 0 to 16%

K2O0a10%

MgO 0 to 10%

Al2O3 0a5%

BaO 0 to 2%

BaO + CaO + MgO 10 to 20%

K2O + Na2O10a20%

This type of glass is very widely used in the field of glazing for buildings or motor vehicles. It is generally manufactured in the form of a ribbon by means of drawing or floating procedures. Tapes of this type can be cut into sheets which can then be bent or subjected to a treatment, for example a thermic treatment, to reinforce the mechanical properties.

When talking about the oaptic properties of a sheet of glass, it is generally necessary to relate these properties to a standard illuminant. In this description, two standard illuminants are used; Illuminant C and Illuminant A follow the definition of the International Commission on Illumination (CIE). Illuminant C represents the average daylight that has a color temperature of 6700 K. This illuminant is used especially to assess the optic properties of glass for buildings. Illuminant A represents the radiation of a Planck radiator at a temperature of approximately 2856 K. This illuminant represents the light emitted by a car headlight and is especially intended for evaluating the oaptic properties of glass intended for motor vehicles. The International Commission on Illumination has also published a document entitled "Colorimetry, Official Recommendations of the CIE" (May 1970) that describes a theory according to which the colorimetric coordinates of light of each wavelength of the visible spectrum are defined in such a way. They are represented in a diagram (known as the CIE trichromatic diagram) that presents orthogonal x and y axes. This trichromatic diagram shows the position that represents the light of each wavelength (expressed in nano-meters) of the visible spectrum. This position is called "spectral geometric place" and the light whose coordinates are located in this spectral locus is said to have 100% excitation purity for the appropriate wavelength. The spectral locus is closed by a line called the purple boundary that joins the points of the spectral locus, whose coordinates correspond to wavelengths of 380 nm (violet) and 780 nm (red). The area included in the spectral geometrical location and the purple boundary is that available for the trichromatic coordinates of any visible light. The coordinates of the light emitted by Illuminant C, for example, correspond to x = 0.3101 and y = 0.3163. This point C is considered representative of white light and therefore has an excitation purity equal to zero for any wavelength. Lines can be drawn from point C to the spectral geometrical location at any desired wavelength and any point on these lines can be defined not only by its x and y coordinates, but also as a function of the wavelength that corresponds to the line in the one that is located and the distance from point C with respect to the total length of the wavelength line. From this, the light transmitted by a colored glass sheet can be described by its dominant wavelength and its excitation purity expressed as a percentage.

In fact, the CIE coordinates of the light transmitted by a colored glass sheet will depend not only on the composition of the glass but also on its thickness. In the present description and claims, all the values ​​of the trichromatic coordinates (x, y), the purity of excitation (P), the dominant wavelength) of the transmitted light and the transmittance of the glass light (TL ) are calculated from the specific internal transmission (SITa) of a 5 mm thick glass sheet. The specific internal transmission of a glass sheet depends solely on the absorption

ES 2 149 646 B1 of glass and can be expressed by the Beer-Lambert law; SITA = e^{-E AX} where Αλ is the glass absorption coefficient (in cm^-1) at the given wavelength and E is the thickness of the glass (in cm). As a first approximation, SITA can also be represented by the formula (I3A + R2A) / (I1A - R1A) where I1A is the intensity of the visible light incident on the first face of the glass sheet, R1A is the intensity of the visible light reflected by this face, I3A is the intensity of the visible light transmitted from the second face of the glass sheet and R2A is the intensity of the visible light reflected towards the inside of the sheet by this second face.

In the present description and claims, the following are used.

The total light transmission of Illuminant A, measured for a thickness of 4 mm (TLA4). This total transmission is the result of integrating the expression:

£ TA.EA.SA / £ EA.SA between wavelengths 380 and 780 nm, where TA is the transmission at wavelength A, EA is the spectral distribution of illuminant A and SA is the sensitivity of the normal human eye in function of wavelength A.

The total energy transmission, measured for a thickness of 4 mm (TE4). This total transmission is the result of integrating the expression:

TA.EA / EA between wavelengths 300 and 2150 nm, where EA is the spectral energy distribution of the sun at 30 above the horizon (Moon distribution).

Total transmission in ultraviolet, measured for a thickness of 4 mm (TUVT4). This total transmission is the result of integrating the expression:

£ TA.UA / £ UA between wavelengths 280 and 380 nm, where UA is the spectral distribution of ultraviolet radiation that has passed through the atmosphere, as determined according to DIN 67507.

When the transmission curve of a transparent substance does not vary as a function of the visible wavelength, this substance is considered "neutral gray". In the CIE system, it does not have a dominant wavelength and its excitation purity is zero. By extension, a body can be considered gray when the spectral curve is relatively flat in the visible region but nevertheless shows weak absorption bands, allowing a dominant wavelength to be defined and a purity that is low but not zero. The gray glass according to the present invention preferably has an excitation purity that does not exceed 12%, and a dominant wavelength between 460 and 490 nm, corresponding to a bluish tone. The glass according to the present invention has a very dark gray color that corresponds to a total light transmission according to illuminant A, measured for a thickness of 4 mm (TA4) less than 20%.

Gray glasses are generally selected for their protection properties against the sun's rays and their use in buildings is known, especially in countries with a lot of sun. Gray glass is also used in balcony balustrades or stairways as well as for partial glazing in certain motor vehicles or train cars, to prevent the contents from being seen.

The present invention relates to a very dark gray glass especially suitable for installation on vehicle roofs, for example for a sunroof on a car or a complete solar panel.

The present invention provides a very dark gray colored glass of lime and caoustic soda composed of glass-forming constituents and coloring agents, characterized in that the elements iron, cobalt and selenium are present as coloring agents in the following proportions (expressed in the form indicated as percentages by weight of the glass):

Fe2O3 1.00 to 1.65%

Co 0.017 to 0.030%

It 0.001 to 0.010%

ES 2 149 646 B1 being the proportions of the coloring agents such that the glass has a total light transmission, measured for illuminant A for a glass thickness of 4 mm (TLA4), less than 20%, and a total energy transmission , measured for a glass thickness of 4 mm (TE4), less than 20%.

Such a colored glass has a very dark gray appearance and exhibits low light transmission and energy transmission properties that make it particularly suitable to be used as protection against solar radiation, especially for vehicle sunroofs or roof panels. .

In fact, a gray colored glass can be made using nickel as the main coloring agent. However, the presence of nickel has certain drawbacks, especially when the glass has to be obtained by the floating process. In the floating process, a ribbon of hot glass is driven along the surface of a bath of molten tin so that its faces are flat and parallel. In order to avoid oxidation of the tin on the surface of the bath, which would lead to the entrainment of tin oxide by this belt, a reducing atmosphere is maintained above the bath. When the glass contains nickel, it is partially reduced due to the atmosphere above the tin bath, which leads to the appearance of a haze in the glass produced. Also, nickel in glass can form nickel sulfide NiS. This sulfide exists in various crystalline forms, which are stable in different temperature ranges, creating the transformation from one to the other problems when the glass has to be hardened with a thermic tempering treatment, as is the case in the automotive and automotive field. also for certain glazing used in buildings (balconies, icebergs, etc.). Therefore, the glass according to the invention, which does not contain nickel, is especially suitable for being manufactured by the floating process as well as for use in architecture or in the field of motor or other vehicles.

The combined presence of iron, cobalt and selenium as coloring agents allows to control the ooptic and energetic properties of the gray glass according to the invention. The effects of different coloring agents considered individually for the preparation of a glass are the following (as described in the German manual "Glas" by H. Scholtze, - translated by J. Le Du - Glass Institute Paris):

Iron: Iron was, in fact, present in most glasses on the market, either as an impurity or deliberately introduced as a coloring agent. The presence of ferric ions (Fe³⁺), provides the glass with a slight absorption of visible light that has a short wavelength (410 and 440 nm) and a very strong absorption band in ultraviolet (absorption band centered at 380 nm), while the presence of ferrous ions (Faith²⁺) causes strong absorption in infrared (absorption band centered at 1050 nm). The ferric ions give the glass a light yellow color, while the ferrous ions give a more accentuated blue-green color.

Selenium: The cation Se⁴⁺ It has practically no coloring effect, whereas the uncharged element Se⁰ provides a pinkish coloration. The year was^2- It forms a chromophore with the ferric ions present and because of this it gives a red-brown color to the glass.

Cobalt: The Co group^IIO4 produces an intense blue coloration with a dominant wavelength practically opposite to that given by the iron-selenium chromophore.

The energetic and optic properties of glass containing the coloring agents iron and selenium, therefore, are the result of a complex interaction between them, each of these coloring agents exhibiting a behavior that closely depends on the redox state and therefore on the presence of other elements that can influence this state.

According to a first preferred embodiment of the invention, the coloring agents are present in an amount corresponding to the following proportions (expressed as a percentage by weight of the glass):

Fe2O3 1.05 to 1.35%

Co 0.0195 to 0.0225%

It 0.003 to 0.006%

According to another preferred embodiment of the invention, the coloring agents are present in an amount corresponding to the following proportions (expressed as a percentage by weight of the glass):

ES 2 149 646 B1

Fe2O3 1.35 to 1.65%

Co 0.0175 to 0.0205%

It 0.0015 to 0.0045%

The first preferred embodiment of the invention allows easily the formation, given the limited amount of iron present in the composition, of a glass with the desired optical and energetic characteristics: light transmission, measured for Illuminant A for a glass thickness of 4 mm (TLA4), less than 20%, and energy transmission, measured for a glass thickness of 4 mm (TE4), less than 20%. The other preferred embodiment of the invention facilitates the formation of a very dark gray glass that has high selectivity (selectivity being defined as the ratio of light transmission to energy transmission), as a result of the higher iron content.

The total energy transmission of the colored glass according to the present invention, measured for a glass thickness of 4 mm (TE4), is preferably greater than 10%. This limits the heating of the glass by absorption of solar radiation in the case of strong sunlight.

The total energy transmission of colored glass, measured for a glass thickness of 4 mm (TE4), is preferably less than 15%. This total energy transmission is particularly suitable for the intended applications, especially solar panels for vehicles or glazing panels for buildings in warm countries.

It is desirable that the total light transmission of glass, measured for Illuminant A for a glass thickness of 4 mm (TLA4), is greater than 12%, preferably greater than 15%. These common values ​​of light transmission provide sufficient vision through the glass.

The presence of iron and selenium as coloring agents in the limits defined above make it possible to achieve strong absorption in the ultraviolet band. The glass according to the invention preferably has a total transmission in the ultraviolet band (TUVT4) of less than 10%, or even less than 5%. This property is particularly advantageous in the automotive field. The low transmission of ultraviolet radiation prevents aging and discoloration of the interior upholstery of motor vehicles.

Colored glass may contain cerium, if necessary, to further decrease the total transmission of the glass in the ultraviolet band (TUVT4).

The excitation purity of the very dark gray glass according to the present invention is preferably less than 12%. According to its dominant wavelength, the very dark gray glass according to the present invention can have a colored tone, for example yellow or green or, preferably, bluish.

This glass is preferably used in the form of sheets, for example sheets with a thickness of 4-5mm for the manufacture of roof panels for motor vehicles or with a thickness of more than 4mm in panels for buildings.

The very dark gray glass can carry a coating formed by at least one metal oxide, for example a coating formed by titanium oxide, tin oxide, iron oxide, cobalt oxide, chromium oxide or a mixture thereof. This coated glass has very low light transmission and energy properties. In addition, the coatings allow limiting the heating of the glass with intense sunlight.

The glass according to the present invention can be manufactured by traditional procedures. As raw material, natural materials, recycled glass, slag or a combination thereof can be used. The addition of the coloring agents in the indicated form is not necessary, but this way of giving the amounts of added coloring agents, in equivalents in the indicated forms, corresponds to current practice. In practice, iron is added in the form of polishing red, cobalt is added in the form of a hydrated sulfate, such as CoSO.₄.7H₂O or CoSO₄.6H₂Or, and selenium is added in its elemental form or in the form of a selenite, such as Na2SeO3 or ZnSeO3. Other elements such as impurities may be present in the raw material used in the manufacture of the glass according to the invention (for example, manganese oxide in proportions of the order of 50 ppm, or small proportions of vanadium or chromium), which may come from the materials recycled glass or slag, but when the presence of these impurities does not give the glass properties outside the previously defined limits, glass is considered to be in accordance with the present invention.

ES 2 149 646 B1

The present invention is illustrated from the following specific composition examples: Examples 1 to 12

Table I provides the base composition of the glass, as well as the constituents of the vitrifiable batch to be melted in order to produce glasses according to the invention (the amounts being expressed in kilograms per ton of the vitrifiable batch). Tables lia, Ilb and Ilc provide the colorants to be added to the batch (the amounts being expressed in kilograms per ton of vitrifiable raw material), and the proportions by weight of colorant agents in the glass produced. These ratios are determined by glass X-ray fluorescence and converted to the indicated molecular species. Tables IIIa, IIIb and IIIc provide the optical and energetic properties corresponding to the definitions given in the present description.

Example 10 refers to a glass according to example 6 on which a layer of titanium dioxide was deposited with a thickness between 45 and 50 nm. This layer was deposited by pyrolysis of an organic titanium compound on hot glass.

Example 11 refers to a glass according to example 6 on which a layer of iron, cobalt and chromium ioxides was deposited. This layer has a thickness of between 35 and 45 nm. It contains, in proportions by weight, 62% of cobalt oxide, 26% of iron oxide and 12% of chromium oxide. This layer is easily obtained by pyrolysis of organometallic reagents, such as acetylacetonates, on the glass strip, when it is still at a very high temperature, at the outlet of a float tank.

TABLE I

Base Glass

<td colspan="2">Base glass analysis</td>

<td>SiO2 ACO3 CaO MgO Na₂OR K2O</td><td> 72,0% 0,8% 8,8% 4,2% 14,1% 0,1%</td>

<td colspan="2">Base glass constituents</td>

<td>Sand</td><td> 571,3</td>

<td>Feldspar</td><td> 29,6</td>

<td>Limestone</td><td> 35,7</td>

<td>Dolomite</td><td> 162,1</td>

<td>W2CO3</td><td> 181,1</td>

<td>Sulfate</td><td> 5,0</td>

<td>Nitrate</td><td> 15,2</td>

ES 2 149 646 B1

TABLE IIa

N ° Example 1 2 3 4 5

Coloring agents (kg) calculated in the form of:

<td>^Faith2^OR3</td><td> 10,48</td><td> 10,90</td><td> 10,31</td><td> 10,57</td><td> 9,56</td>

<td>CoO</td><td> 0,301</td><td> 0,251</td><td> 0,251</td><td> 0,194</td><td> 0,209</td>

<td>I know Coloring agents (quantity by weight in glass) calculated in the form of:</td><td> 0,086</td><td> 0,115</td><td> 0,100</td><td> 0,078</td><td> 0,105</td>

<td>Fe2O3 (%)</td><td> 1,32</td><td> 1,37</td><td> 1,30</td><td> 1,33</td><td> 1,21</td>

<td>Co (ppm)</td><td> 288</td><td> 240</td><td> 240</td><td> 186</td><td> 200</td>

<td>Se (ppm)</td><td> 42</td><td> 56</td><td> 49</td><td> 38</td><td> 51</td>

TABLE IIb

<td>N ° Example</td><td> 6</td><td> 7</td><td> 8</td><td> 9</td><td> 10</td>

Coloring agents (kg) calculated in the form of:

<td>^Faith2^OR3</td><td> 9,73</td><td> 10,90</td><td> 10,48</td><td> 10,9</td><td> 9,73</td>

<td>CoO</td><td> 0,217</td><td> 0,212</td><td> 0,240</td><td> 0,191</td><td> 0,217</td>

<td>I know Coloring agents (quantity by weight in the glass) calculated in the form of:</td><td> 0,068</td><td> 0,074</td><td> 0,078</td><td> 0,082</td><td> 0,068</td>

<td>Fe2O3 (%)</td><td> 1,23</td><td> 1,35</td><td> 1,32</td><td> 1,37</td><td> 1,23</td>

<td>Co (ppm)</td><td> 208</td><td> 203</td><td> 230</td><td> 183</td><td> 208</td>

<td>Se (ppm)</td><td> 33</td><td> 36</td><td> 38</td><td> 40</td><td> 33</td>

TABLE IIc

<td>N ° Example</td><td> 11</td><td> 12</td>

<td>Coloring agents (kg) calculated in the form of: Fe 2O3</td><td> 9,73</td><td> 12,00</td>

<td>CoO</td><td> 0,217</td><td> 0,199</td>

<td>I know</td><td> 0,068</td><td> 0,062</td>

<td>Coloring agents (quantity by weight in the glass) calculated in the form of: Fe2O3 (%)</td><td> 1,23</td><td> 1,50</td>

<td>Co (ppm)</td><td> 208</td><td> 190</td>

<td>Se (ppm)</td><td> 33</td><td> 30</td>

ES 2 149 646 B1

TABLE IIIa

<td>N ° Example</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td>Glass properties</td><td></td><td></td><td></td><td></td><td></td>

<td>TL (%)</td><td> 6,8</td><td> 9,2</td><td> 7,8</td><td> 13,1</td><td> 10,3</td>

<td>TLA4 (%)</td><td> 10,7</td><td> 13,8</td><td> 12,2</td><td> 18,1</td><td> 15,2</td>

<td>TE4 (%)</td><td> 15,8</td><td> 18,8</td><td> 15,0</td><td> 19,2</td><td> 18,3</td>

<td>P (%)</td><td> 11,2</td><td> 9,6</td><td> 4,6</td><td> 9,8</td><td> 9,7</td>

<td>λD (nm)</td><td> 476,2</td><td> 581,0</td><td> 580,6</td><td> 574,1</td><td> 578,0</td>

<td>TUVT4 (%)</td><td> 2,1</td><td> 1,9</td><td> 2,4</td><td> 2,5</td><td> 2,2</td>

TABLE IIIb

<td>N ° Example</td><td> 6</td><td> 7</td><td> 8</td><td> 9</td><td> 10</td>

<td>Glass properties</td><td></td><td></td><td></td><td></td><td></td>

<td>TL (%)</td><td> 13,4</td><td> 10,9</td><td> 9,1</td><td> 11,2</td><td></td>

<td>TLA4 (%)</td><td> 17,8</td><td> 15,4</td><td> 13,2</td><td> 16,0</td><td> 14,1</td>

<td>TE4 (%)</td><td> 17,4</td><td> 13,1</td><td> 11,9</td><td> 14,4</td><td> 15,1</td>

<td>P (%)</td><td> 7,1</td><td> 2,1</td><td> 5,3</td><td> 11,2</td><td></td>

<td>λD (nm)</td><td> 486,2</td><td> 533,4</td><td> 487,8</td><td> 570,1</td><td></td>

<td>TUVT4 (%)</td><td> 2,6</td><td> 2,1</td><td> 2,3</td><td> 2,5</td><td> 1,7</td>

TABLE IIIc

<td>N ° Example</td><td> 11</td><td> 12</td>

<td>Glass properties</td><td></td><td></td>

<td>TL (%)</td><td></td><td> 11,4</td>

<td>TLA4 (%)</td><td> 9,5</td><td> 15,8</td>

<td>TE4 (%)</td><td> 12,1</td><td> 13,1</td>

<td>P (%)</td><td></td><td> 4,3</td>

<td>λD (nm)</td><td></td><td> 513,0</td>

<td>TUVT4 (%)</td><td> &lt;1</td><td> &lt;2</td>