GB2304710A - Clear grey soda-lime glass - Google Patents

Description

2304710 1 Clear grey soda-lime glass The present invention relates to a

dear grey coloured soda-lime glass composed of glass-fon-ning constituents and colouring agents. It also relates to a vitrifiable composition for forming such glass.

lhe expression "soda-lime ' is used here in a wide sense and concerns any glass composed of the following constituents (percentages by weight):

Si02 60 to 75% Na20 10 to 20% CaO 0 to 16% K20 0 to 10% M90 0 to 10% AJ203 0 to 5% BaO 0 to 2% BaO + CaO + MgO 10 to 20% K20 + Na20 10 to 20%.

This type of glass is used very widely in the field of glazing for buildings or motor vehicles. It is generally manufactured in the form of a ribbon by a drawing or float process. A ribbon of this type may be cut up in the form of sheets which may then be made curved or subjected to a treatment, for example heat treatment, to reinforce the mechanical properties.

When spealdng of the optical properties of a sheet of glass, it is generally necessary to relate these properties to a standard illuminant. In the present description, two standard illuminants are used; Illuminant C and

Illuminant A as defined by the International Commission on Illumination (C.I.E.). Illuminant C represents average daylight having a colour temperature of 6700 K 'This illuminant is especially useful for evaluating the optical properties of glasses intended for buildings. Illuminant A represents the radiation of a Plarick radiator at a temperature of about 2856 K 7his illuminant represents the light emitted by car headlamps and is essentially intended to evaluate the optical properties of glass intended for motor vehicles. The International Commission on Illumination has also published a document entitled Tolorimetry, Official Recommendations of the C.I.E." (May 1970) which describes a theory according to which the colorimetric 2 coordinates for the fight of each wavelength of the visible spectrum are defined in such a way as to be represented on a diagram (known as the C.I. E.

trichromatic diagram) having orthogonal axes x and y. This trichromatic diagram shows the location representing the light for each wavelength (expressed in nanometres) of the visible spectrum. This location is called the 09 spectrum locus" and the light whose coordinates are situated on this spectrum locus is said to possess a 100% excitation purity for the appropriate wavelength. 7he spectrum locus is closed off by a line called the purple boundary which joins the points of the spectrum locus, the coordinates of which correspond to wavelengths of 380 run (violet) and 780 ran (red). The area included within the spectrum locus and the purple boundary is that available for the trichrornatic 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 as representing white light and on account of this has an excitation purity equal to zero for any wavelength.

Lines may be drawn from the point C to the spec locus at any desired wavelength and any point situated on these fines may be defined not only by its coordinates x and y, but also as a function of the wavelength corresponding to the line on which it is situated and its distance from the point C with respect to the total length of the wavelength line. From this, fight transmitted by a coloured sheet of glass may be described by its dominant wavelength and its excitation purity (P) expressed in percent.

In fact the C.I.E. coordinates of fight transmitted by a coloured 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), of the excitation purity (P), of the dominant wavelength XD of the transmitted light, and of the fight transmittance of the glass (TL) are calculated from the specific internal transmission (SITJ of a 5 nim thick glass sheet. 'The specific internal transmission of a glass sheet is governed solely by the absorption of the glass and may be expressed by the Beer-Larnbert law; SIT), = J-A', where AX is the absorption coefficient of the glass (in cm-1) at the wavelength in question and E is the thickness of the glass (in cm). As a first approximation, S1Tx may also be represented by the formula:

(13X + R21) / OP - Rlx) where 11x is the intensity of the visible light on the first face of the glass sheet, R,, is the intensity of the visible light reflected by this face, I3x is the intensity of the visible light transmitted from the second face of the glass 3 sheet and R2X 15 the intensity of the visible light reflected to the interior of the sheet by this second face.

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

The total luminous transmission for illuminant A, measured for a thickness of 4 mm CrL.A4). This total transmission is the result of integrating the expression:

IT.x.E;..Sx,ú.Ex.Sx between the wavelengths 380 and 780 rim, in which T;, is the transmission at wavelength 1, E, is the spectral distribution of illuminant A and S, is the sensitivity of the normal human eye as a function of the wavelength 1.

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

1Ti.Ea.Ex between the wavelengths 300 and 2150 rim, in which Ex is the spectral energy distribution of the sun at W above the horizon (Moon's distribution).

The selectivity, measured for a thickness of 4 mm (SE4) is defined by the ratio CrIA4/TE4).

7he total transmission in the ultra-violet, measured for a thickness of 4 nun 4). This total transmission is the result of integrating the expression:

1TX.UX/LUX between the wavelengths 280 and 380 rim, in which Ux is the spectral distribution of ultra-violet radiation having passed through the atmosphere, as determined as in DIN standard 67507.

The present invention concerns in particular grey glasses with a shade varying from greenish to bluish. When the transmission curve of a transparent substance does not in practice vary as a function of the visible wavelength, this substance is described as "neutral grey'. In the C.I.E. system, it does not possess a dominant wavelength and its excitation purity is zero. By extension, a body may be considered as grey for which the spectral curve is relatively flat in the visible region but nevertheless exhibits weak absorption bands, enabling a dominant wavelength to be defined and a purity that is low but not zero. Grey glass according to the present invention preferably has an excitation purity of less than 6%.

Grey glasses are. generally selected for their protecting 4 properties against the rays of the sun and their use in buildings is known, especially in very sunny countries. Grey glasses are also used in balcony balustrades or staircases as well as for partial glazing in certain motor vehicles or railway compartments. 5 As regards the automobile sector, there is a tendency to choose grey glass for the manufacture of rear windows and rear side windows. The standards of minimum luminous transmission imposed on the materials for vehicle windscreens and front side windows, as well as the need for these windows to have low energy transmission to avoid excessive heating of the 70 vehicle interior, have hitherto required the manufacturers to use greencoloured glass for the windscreens and front side windows, since only glass of this tint enabled the achievement of a high selectivity while satisfying the legal standards for luminous transmission. 7he present invention relates to a clear grey glass especially 75 appropriate for use as vehicle windows, particularly as windscreens and front side windows. This glass has optical and energy properties hitherto offered only by green glass, while advantageously permitting the colour of the windscreen and front side windows to be matched to those of other windows of the vehicle. 1he invention provides a clear grey coloured soda-lime glass composed of glass-fom-dng constituents and colouring agents, characterised in that the elements iron, cobalt and selenium are present as colouring agents in the following proportions (expressed in the form indicated as percentages by weight of the glass):

Fe203 co se 0.25 to 0.60% 0.0010 to 0.0040% 0.0005 to 0.0030% the proportions of colouring agents being such that the glass has a total luminous transmission measured for Illuminant A for a glass thickness of 4 mm CrLA4) of greater than 62%, a selectivity measured for a glass thickness of 4nim (SE4) of greater than 1.1, and an excitation purity (P) of less than 6%.

The present invention enables the achievement of a glass with a selectivity of more than 1.1, which is very high for grey glass, with good luminous transmission corresponding to the standards imposed in the automobile sector on materials for windscreens and front side windows.

In fact, a glass having an almost similar coloration can be produced by using nickel as the main colouring agent. The presence of nickel however presents certain disadvantages, especially when the glass has to be produced by the float process. In the float process, a ribbon of hot glass is led along the surface of a bath of molten tin so that its faces are plane and parallel. In order to avoid oxidation of the tin at the surface of the bath, which would lead to entrainment of tin oxide by this ribbon, a reducing atmosphere is maintained above the bath. When the glass contains nickel, this is partially reduced by the atmosphere above the tin bath giving rise to a haze in the glass produced. 7his element is also harmful in achieving a high selectivity since it does not absorb radiation in the infra-red range, which hinders the attainment of a low energy transmission. In addition, nickel present in the glass may form nickel sulphide MS. 7his sulphide exists in various crystalline forms, which are stable within different temperature ranges, transformation from one to the other creating problems when the glass has to be reinforced by a heat tempering treatment, as is the case in the automotive field and also for certain glazing used in buildings (balconies, spandrels, etc.). Glass according to the invention, which does not contain nickel, is thus particularly well suited to manufacture by the float process as well as to architectural use or in the field of motor or other vehicles.

The combined presence of iron, selenium and cobalt colouring agents and a reducing agent enables the optical and energy properties of grey glass according to the invention to be controlled. The effects of different colouring agents considered individually for the preparation of a glass are as follows (as described in the German handbook "Glas" by H. Scholtze, - translated by J. Le DC1 - Glass Institute - Paris):

Iron: Iron is in fact present in most glasses existing on the market, either as an impurity or introduced deliberately as a colouring agent.

The presence of ferric ions (Fe 3+), gives glass a slight absorption of visible light having a short wavelength (410 and 440 nm) and a very strong absorption band in the ultra-violet (absorption band centred on 380 rim), whereas the presence of ferrous (Fe 2+) ions causes a strong absorption in the infra- red (absorption band centred on 1050 rim). Ferric ions give glass a slight yellow colour whereas ferrous ions give a more pronounced blue-green coloration.

Selenium: 7he Se4+ cation has practically no colouring effect, whereas the uncharged element Seo gives a pink coloration. The Se2 anion forms a chromophore with ferric ions present and on account of this gives a brownish red colour to the glass.

6 Cobalt: 'The CO R 04 group produces an intense blue coloration with a dominant wavelength virtually opposite to that given by the ironselenium chromophore.

The energy and optical properties of glass containing the colouring agents iron and selenium thus results from a complex interaction between them. In effect, each of these colouring agents having a behaviour which depends strongly on the redox state and thus, on the presence of other elements likely to influence this state.

The combination of colouring agents and their proportions confer to the glass according to the invention a total luminous transmission C17LA4) of greater than 62%, which enable it to satisfy the standards of minimum luminous transmission at the front of a vehicle when the glass is used in the form of windscreens and front side windows.

The total energy transmission of the glass (TE4) attainable by the present invention is preferably less than 65%. This property is particularly advantageous in the automotive field.

Grey glass according to the invention preferably has a dominant wavelength between 460 and 550 rim, corresponding to a shade varying between greenish and bluish, which is essentially linked to the combination of 20 the agents cobalt and selenium.

According to a particularly preferred embodiment of the invention, the glass is characterised by the colouring agents being present in a quantity corresponding to the following proportions (expressed in the form indicated as percentages by weight of the glass):

Fe203 Co Se 0.35 to 0.50% 0.0020 to 0.0030% 0.0005 to 0.0015% Within the above-defined preferred limits, it is possible to form glass with a total luminous transmission for Illuminant A C17LA4) of greater than 70%.

Glass corresponding to the more limited concentration range defined above for the colouring agents performs particularly well since it has energy transmission properties sufficiently low to avoid undue heating of a vehicle interior, and good light transmission properties completely satisfying the standards of minimum transmission at the front of the vehicle. These properties render the glass which has them fully adequate to be used in a 7 vehicle windscreen as well as front side windows.

Such a glass is preferably used in the form of sheets having a thickness of 2 mm for windscreen laminates, 3 mm for front side windows and more than 4 nim for rear windows and in buildings.

Among the colouring agents employed, ferrous iron (Fe 2+) is the only absorbent in the infra-red range. In normal melting conditions for glass, the quantities of colouring agents are limited in respect of the standards of minimum luminous transmission at the front of the vehicle, and do not allow a sufficient concentration of Fe2+ to be attained for the absorption in the infra- red range to impose a satisfactory Emit on the heating of the vehicle interior. To increase the rate of absorption in the infra-red range, i.e. to lessen the energy transmission of the glass, a reducing agent such as coke is included in the vitrifiable batch and the amount of sodium sulphate, used to refine the glass, is adapted so as to limit its oxidising effect. Ferrous ions, and the resulting infra-red absorption, are thus favoured over ferric ions (Fe 3+ ). Apart from coke, other reducing agents or materials containing reducing agents, may be used, for example slag (sulphides).

The vitrifiable composition which enables the formation of glass according to the present invention includes sand and most or all of feldspar, limestone, dolomite, Na2C03, coke, nitrate, slag, sulphate and sulphide. When coke is included the composition contains coke in a quantity corresponding to the following proportions (expressed as a percentage by weight of the sand):

coke 0 to 0.30% and sulphate in a quantity corresponding to the following proportions (expressed as a percentage by weight of the vitrifiable composition):

sulphate 0.5 to 1.0%.

Glass according to the present invention can be manufactured by traditional methods. As raw materials there can be used natural materials, recycled glass, slag or a combination thereof. The colouring agents are not necessarily added in the form indicated, but this way of giving the quantities of added colouring agents, in equivalents in the forms indicated, corresponds to current practice. In practice, iron is added in the form of rouge, cobalt is added in the form of a hydrated sulphate, such as COS04.71-120 or 8 C'0S04.6H20 and selenium is added in the elementary form or in the form of a selenite such as Na2Se03 or ZnSe03. Other elements may be present as impurities in the raw materials used in the manufacture of glass according to the invention (for example manganese oxide in proportions of the order of 50 ppm), which may be from the natural materials, the recycled glass or the slag, but when the presence of these impurities does not impart to the glass any properties beyond the above-defined limits the glass is taken as conforming to the present invention.

The present invention is illustrated by the following specific examples of compositions.

EXAMPLES 1 to 72 Table 1 gives the base composition of glass as well as the 75 constituents of the vitrifiable batch to be melted in order to produce glasses according to the invention (the quantities being expressed in kilogrammes per tonne of the vitrifiable batch). Table Ila gives the proportions by weight of the colouring agents in the glass produced. These proportions are determined by X-ray fluorescence of the glass and converted into the molecular species indicated. Table 1Ib gives the proportions by weight of the reducing agents in the vitrifiable raw material. Table H] gives the optical and energy properties corresponding to the definitions given in the present description.

TABLE 1: BASE

Analuis of the base glass Si02 A1203 CaO M90 Na20 K20 S03 Constituents of the base 91 Sand 577.0 71.5 to 71.9% 0.8% 8.8% 4.2% 14.1% 0.1% 0.1 to 0.5% 9 Feldspar 30.0 Umestone 36.0 Dolomite 163.3 Na2C03 183.5 Nitrate 10.2 Coke Sulphate As shown in the examples Slag i TABLE H

Example No. 1 2 3 4 5 6 7 Fe203 (%) 0.451 0.510 0.510 0.466 0.461 0.452 0.448 co (PPM) 37 26 26 30 28 22 2D Se (ppm) 6 5 8 6 7 5 8 Example No. 8 9 10 11 12 13 14 Fe203 (%) 0.450 0.451 0.410 0.457 0.405 0.421 0.419 co (PPM) 24 25 36 26 25 23 23 Se (PPM) 4 5 25 23 10 8 10 Example No. 15 16 17 18 19 20 21 Fe203 (%) 0.402 0.403 0.401 0.412 0.438 0.444 0.440 co (PPM) 24 24 24 25 21 22 23 Se (PPM) 9 6 7 9 5 7 6 Example No. 22 23 24 25 26 27 28 Fe203 (%) 0.445 0.426 0.427 0.450 0.472 0.429 0.443 co (PPM) 23 23 22 22 22 22 22 Se (ppm) 7 9 9 7 8 7 8 Example No. 29 30 31 32 33 34 35 Fe203 (%) 0.431 0.410 0.434 0.424 0.501 0.501 0.480 Co (pprn) 19 22 23 21 25 24 25 Se (ppm) 8 7 9 9 7 8 5 Exwnple No. 36 37 38 39 40 41 42 Fe203 (%) 0.506 0.352 0.340 0.310 0.308 0.367 0.3% co (PPM) 24 24 26 26 30 30 25 Se (ppm) 6 6 8 8 8 10 8 TABLE IiL(ú2atbZJ1 43 44 45 46 47 48 49 0.399 0.396 0.3% 0.368 0.376 0.372 0.386 25 Z7 27 32 32 33 8 8 7 9 9 10 10 51 52 53 54 55 56 0.381 0.439 0.426 0.413 0.410 0.414 0.410 34 31 31 27 28 29 29 8 5 7 4 6 6 6 57 58 59 60 61 62 63 64 Example No. Fe203 (%) CO (ppm) Se (ppm) Example No. Fe203 (%) CO (ppm) Se (ppm) Example No. Fe203 (%) CO (ppm) Se (ppm) Example No. Fe203 (%) CO (ppm) Se (ppm) 0.412 0.475 0.472 0.506 0.499 0.493 0.495 0.397 26 31 29 28 28 28 29 29 6 6 8 8 8 6 8 8 66 67 68 69 70 71 72 0.61 0.61 0.61 0.61 0.61 0.65 0.408 0.406 28 26 31 31 35 25 30 27 8 7 8 9 7 9 9 9 TABLE

Example No. 1 2 3 4 5 6 7 Sulphate/compm (%) 0.50 0.77 0.77 0.77 0.77 0.77 0.77 Coke/sand (%) 0.11 0.11 0.11 0.11 0.11 0.11 Example No. 8 9 10 11 12 13 14 Sulphatelcompsn.(%) 0.77 0.77 0.77 0.77 0.77 0.77 0.77 Coke/sand (%) 0.15 0.15 0.11 0.11 0.11 0.11 Example No. is 16 17 is 19 20 21 Sulphatelcompsn.(%) 0.77 0.77 0.77 0.77 0.77 0.77 0.61 Coke/sand (%) 0.13 0.13 0.13 0.13 0,11 0.11 0.11 Example No. 22 23 24 25 26 27 28 Sulphatelcompsa.(%) 0.61 0.61 0.61 0.61 0,61 0.61 0.61 Coke/sand (%) 0.11 0.13 0.13 0.11 0.11 0.13 0.13 Example No. 29 30 31 32 33 34 35 Sulphate/compsn.(%) 0.61 0.61 0.81 0.81 0.61 0.61 0.61 Coke/sand (%) 0.11 0.13 0.11 0.13 0.11 0.11 0.16 TABLE 102 (QQntinlAgd) 36 37 38 39 40 41 42 0.61 0.61 0.61 0.61 0.61 0.61 0.61 0.16 0.16 0.016 0.013 0.013 0.011 0.011 43 44 45 46 47 48 49 0.61 0.61 0.61 0.61 0.61 0.61 0.61 0.11 0.13 0.13 0.11 0.11 0.11 0.11 so 51 52 53 54 55 56 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.11 0.07 0.07 6.50 6.50 6.50 6.50 6.50 6.50 57 58 59 60 61 62 63 64 0.73 0.70 0.70 0.70 0.70 0.70 0.70 0.61 0.10 0.11 0.11 0.10 0.10 0.09 0.09 0.07 6.50 6.50 66 67 68 69 70 71 72 0.61 0.61 0.61 0.61 0.61 0.65 0.65 0.65 0.07 0.08 6.50 6.50 Example No. Sulphatelcompsn.(%) Coke/sand (%) Example No. Sulphatelcompsn. (%) Coke/sand (%) Example No. Sulphatelcompsn.(%) Coke/sand Slag/sand (%) Example No. Sulphatelcompsn.(%) Coke/sand Slag/sand (%) Example No. Sulphate/compsn.(%) Coke/sand Slag/sand (%) 6.50 6.50 6.50 6.50 6.50 6.50 TABLE H

Example No. 1 2 3 4 5 6 7 TL (%) 66.3 69.0 67.0 71.5 72.6 74.2 72.4 XD (run) 496.1 494.4 552.0 493.3 496.5 501.2 552 Purity (%) 1.8 2.9 1.9 2.2 1.7 1.4 1.8 Fe2+/Fe tot (%) 19.5 23.5 19.8 18.4 17.1 19.4 18.8 TLA4 65.5 67.3 66.4 69.5 70.4 71.7 70.6 TE4 (%) 56.6 52.3 54.6 59.5 61.1 59.7 59.7 TUVm4 22.6 25.6 23.5 26.0 25.9 27.7 26.3 SE4 1.16 1.29 1.22 1.17 1.15 1.20 1.18 12 TABLE III (úgrLti :m Example No. 8 9 10 11 12 13 14 TL (%) 74.0 71.3 67.8 70.2 72.0 72.6 73.4 ID (run) 491.6 496.3 546.8 506.1 544.9 530.3 544.0 Purity (%) 3.0 1.9 0.6 0.9 1.1 0.9 1.1 Fe2+1Fe tot (%) 21.3 21.6 15.0 18.4 19.5 19.4 17.5 TLA4 71.3 69.4 67.1 68.8 70.4 70.7 71.4 TE4 (%) 58.4 57.0 63.6 59.3 61.0 60.6 62.6 TMot4 (%) 29.4 27.6 26.0 26.1 28.3 27.9 27.3 SE4 1.22 1.22 1.06 1.16 1.15 1.17 1.14 Example No. 15 16 17 18 19 20 21 TL (%) 71.5 74.6 74.5 73.8 76.4 75.1 73.8 XD (nin) 552.0 494.6 497.2 499.0 497.2 506.1 504.3 Purity (%) 1.3 1.7 1.4 1.2 1.7 1.1 1.2 Fe2+/Fe tot (%) 19.9 19.0 19.5 17.7 18.7 18.1 19.1 TLA4 70.0 72.1 72.0 71.5 73.4 72.6 71.5 TE4 (%) 60.6 62.6 62.1 62.9 61.9 61.7 60.4 TUVm4 27.9 29.1 29.6 28.5 28.8 28.3 27.4 SE4 1.15 1.15 1.16 1.14 1.19 1.18 1.18 Example No. 22 23 24 25 26 27 28 TL (%) 71.9 70.9 70.5 74.1 72.1 71.3 71.8 XD (m) 536.0 531.3 525.9 501.8 512.5 507.9 507.5 Purity (%) 1.1 1.0 0.9 1.3 1.0 0.9 1.0 Fe2+1Fe tot (%) 19.2 21.2 21.5 19.0 19.2 21.9 20.5 TLA4 70.1 69.4 69.1 71.7 70.2 69.6 70.0 TE4 (%) 59.4 58.2 57.9 60.2 58.4 57.8 58.4 TUVm4 26.9 Z7.4 27.7 27.1 25.9 27.9 27.1 SE4 1.18 1.19 1.19 1.19 1.20 1.20 1.20 Example No. 29 30 31 32 33 34 35 TL (%) 73.4 72.6 72.5 72.4 70.3 70.1 69.0 ID (nm) 239.2 516.3 539.5 541.3 509.3 521.3 492.2 Purity (%) 1.3 0.9 1.1 1.2 1.2 1.1 3.5 FJ'7Fe tot (%) 20.1 20.5 18.7 2U 19.3 19.1 25.9 TLA4 (%) 71.3 70.6 70.6 70.6 68.7 68.6 67.3 TE4 (%) 59.6 59.9 60.5 59.7 56.5 56.6 54.6 TUVm4 27.9 28.8 27.1 27.7 24.4 25.1 27.1 SE4 1.20 1.18 1.17 1.18 1.22 1.21 1.30 13 TABLE M (continued) 36 37 38 39 40 41 42 68.3 71.7 70.6 73.6 72.2 68.1 73.1 497.6 493.2 491.6 500.3 490.7 545.0 525.1 2.4 24.9 66.8 51.0 26.2 1.31 Example No. TL (%) ID (nm) Purity (%) Fe2+/Fe tot (%) TLA4 TE4 (%) TWtot4 SE4 Example No. T L (o/11) ID (run) Purity (%) Fe2+/Fe tot TLA4 TE4 (%) TWtot4 SE4 Example No. TL (%) XD (nm) Purity (%) Fe2+/Fe tot TLA4 TE4 (%) TUVtot4 SE4 Example No. TL (%) ID (rim) Purity (%) 1.7 2.1 0.8 1.6 0.8 0.8 24.6 28.4 21.7 99.3 20.7 19.1 69.9 68.9 71.5 70.4 67.3 71.1 59.6 57.2 64.3 63.6 60.3 61.9 32.1 32.7 32.9 33.3 28.4 29.2 1.17 1.20 1.11 1.11 1.12 1.15 43 44 45 46 47 48 49 72.1 70.1 69.7 70.3 67.7 67.3 67.8 542.1 542.1 502.3 544.9 491.2 494.5 495.7 1.1 1.2 1.1 19.3 21.0 22.6 70.4 68.8 68.4 61.2 59.2 57.9 28.7 27.1 28.0 0.7 19.1 69.1 62.4 30.1 1.6 21.3 66.8 59.4 28.9 1.1 21.5 66.5 59.3 28.6 1.1 20.6 66.9 59.4 28.5 1.15 1.16 1.18 1.11 1.12 1.12 1.13 51 52 53 54 55 56 68.0 74.6 74.2 492.2 489.2 489.1 1.4 3.8 3.4 20.3 17.4 67.1 71.7 60.0 62.5 28.8 27.8 1.12 1.15 57 58 59 60 61 62 63 64 68.9 73.5 71.8 73.1 68.8 71.2 71.2 69.3 489.1 490.4 491.5 497.8 497.8 490.5 491.9 498.9 4.7 Fe2+/Fe tot 30.1 TLA4 67.0 TE4 (%) 51.7 TUVtot4 30.2 SE4 1.30 17.0 71.5 63.2 28.6 1.13 76.1 73.6 72.9 71.3 489.8 491.6 489.9 491.3 3.5 18.4 72.9 63.0 29.3 1.16 2.5 18.5 71.1 62.2 28.2 1.14 3.5 21.4 70.4 59.3 29.2 1.19 2.8 22.6 69.2 57.9 28.6 1.20 3.5 17.8 70.9 60.3 26.9 1.18 2.9 18.4 69.6 59.2 26.5 1.18 1.4 16.1 70.9 60.6 28.7 1.17 1.7 3.5 19.3 19.3 67.5 69.0 56.1 57.4 25.2 26.7 1.20 1.20 2.9 18.8 69.2 57.7 26.6 1.20 1.3 22.7 67.9 57.6 27.9 1.18 14 TABLE 111 contingú Example No. 65 66 67 68 69 70 71 72 TL (%) 68.8 71.1 68.4 69.0 71.5 73.0 70.6 72.1 XD (nM) 507.8 497.8 491.1 495.4 488.1 512.9 502.3 531.8 Purity (%) 0.9 1.5 2.8 1.6 3.5 0.7 0.9 0.9 Fe2+/Fe tot (%) 23.2 23.2 25.4 19.0 18.1 18.5 18.1 17.6 TLA4 (%) 67.7 69.3 67.0 67.5 69.4 71.0 69.1 70.4 TE4 (%) 56.7 58.2 55.3 59.3 61.6 62.1 61.7 62.4 TUVm4 27.6 29.1 28.7 25.7 27.7 27.6 26.7 26.5 SE4 1.19 1.19 1.21 1.14 1.13 1.14 1.12 1.13

Claims (8)

1. A clear grey coloured soda-lime glass composed of glass-fonning constituents and colouring agents, characterised in that the elements iron, cobalt and selenium are present as colouring agents in the following proportions (expressed in the form indicated as percentages by weight of the glass):

Fe203 0.25 to 0.60% CO 0.0010 to 0.0040% Se 0.0005 to 0.00300/6 the proportions of colouring agents being such that the glass has a total luminous transmission measured for Illuminant A for a glass thickness of 4 rnm CrLA4) of greater than 620A, a selectivity measured for a glass thickness of 4 nun (SE4) of greater than 1.1, and an excitation purity (P) of less than 6%.

2. Coloured glass according to claim 1, characterised in that the total energy transmission, measured for a thickness of 4 mm (TE4), is greater than 65%.

3. Coloured glass according to eJairn 1 or claim 2, characterised in that it has a dominant wavelength (XD) of between 460 and 550 run.

4. Coloured glass according to any one of claims 1 to 3, characterised in that the colouring agents are present in a quantity corresponding to the following proportions (expressed in the form indicated as percentages by weight of the glass):

Fe203 0.35 to 0.50% CO 0.0020 to 0.0030% se 0.0005 to 0.0015%.

5. Coloured glass according to claim 4, characterised in that the total luminous transmission, measured for Illuminant A for a thickness of 4 nim ffIA4), is greater than 70%.

6. Coloured glass according to any one of claims 1 to 5, characterised in that it is in the form of a sheet.

7. Coloured glass according to claim 6, characterised in that it forms an automobile window.

8. A vitrifiable composition to form glass according to claim 1, characterised in that it comprises glass-forming constituents 17 including sand and further includes both coke, in a quantity corresponding to the following proportions (expressed as a percentage by weight of the sand):

coke 0 to 0.30%, and of sulphate in a quantity corresponding to the following proportions (expressed as a percentage by weight of the composition):

sulphate 0.5 to 1.0%.

8. A vitrifiable composition to form glass according to claim 1, characterised in that it comprises glass-forming constituents 1 t--) Amendments to the claims have been filed as follows CLAIMS 1. A clear grey coloured soda-lime glass composed of glass-forming constituents and colouring agents, characterised in that the elements iron, cobalt and selenium are present as colouring agents in the following proportions (expressed in the form indicated as percentages by weight of the glass):

Fe203 Co Se 0.25 to 0.60% 0.0010 to 0.0040% 0.0005 to 0.0030% the proportions of colouring agents being such that the glass has a total luminous transmission measured for Illuminant A for a glass thickness of 4 mm (TLA4) of greater than 62%, a selectivity measured for a glass thickness of 4 mm (SE4) of greater than 1. 1, and an excitation purity (P) of less than 6%.

2. Coloured glass according to claim 1, characterised is in that the total energy transmission, measured for a thickness of 4 mm (TE4), is less than 65%.

3. Coloured glass according to claim 1 or claim 2, characterised in that it has a dominant wavelength (XD) of between 460 and 550 rim.

4. Coloured glass according to any one of claims 1 to 3, characterised in that the colouring agents are present in a quantity corresponding to the following proportions (expressed in the form indicated as percentages by weight of the glass):

Fe203 0.35 to 0.50% Co 0.0020 to 0.0030% Se 0.0005 to 0.0015%.

5. Coloured glass according to claim 4, characterised in that the total luminous transmission, measured for Illuminant A for a thickness of 4 mm (TLA4), is greater than 70%.

6. Coloured glass according to any one of claims 1 to 5, characterised in that it is in the form of a sheet.

7. Coloured glass according to claim 6, characterised in that it forms an automobile window.