Glass sheet with a high luminous transmittance and with warm-toned to neutral colored edges

Abstract

The invention relates to a glass sheet having a luminous transmission LTD4≥87% and having a composition free of antimony and arsenic, comprising total iron (expressed in the form of Fe.sub.2O.sub.3) from 0.002-0.04% and erbium (expressed in the form of Er.sub.2O.sub.3) from 0.003-0.1%. The glass sheet composition further having a redox ratio ≤32% and satisfying the formula 1.3*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co≤2.6*Fe.sub.2O.sub.3. Such a glass sheet has a high luminous transmittance and has warm-toned to neutral colored edges and is particularly suitable due to its aesthetics as building glass or interior glass, as well as in furniture applications, as automotive glass, or as cover glass in electronic devices/displays.

Claims

1. A glass sheet having a composition comprising in weight percentage with respect to a total weight of the glass: TABLE-US-00016 SiO.sub.2 40-78%; Al.sub.2O.sub.3  0-18%; B.sub.2O.sub.3  0-18%; Na.sub.2O  0-20%; CaO  0-15%; MgO  0-12%; K.sub.2O  0-12%; BaO  0-5%; total iron (expressed in the form of Fe.sub.2O.sub.3) 0.002-0.04 wt %; and erbium (expressed in the form of Er.sub.2O.sub.3) 0.003-0.1 wt %, wherein the glass sheet composition has a redox ratio ≤32%, wherein 1.3*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3-53.12*Co≤2.6*Fe.sub.2O.sub.3, wherein the glass sheet composition is free of antimony and arsenic, wherein the glass sheet has a luminous transmission LTD4 ≥87%, and wherein the glass sheet has a* ≥0 and b* ≥0, a* and b* being measured for a sheet thickness of 4 mm in transmission with illuminant D65, 10°, SCI.

2. The glass sheet according to claim 1, wherein the composition comprises total iron from 0.002-0.03 wt %.

3. The glass sheet according to claim 1, wherein the composition comprises total iron from 0.002-0.02 wt %.

4. The glass sheet according to claim 1, wherein the composition has a redox ratio ≤30%.

5. The glass sheet according to claim 1, wherein the composition comprises Er.sub.2O.sub.3≤0.08 wt %.

6. The glass sheet according to claim 1, wherein the composition comprises Er.sub.2O.sub.3≥0.01 wt %.

7. The glass sheet according to claim 1, wherein the composition comprises Er.sub.2O.sub.3≥0.015 wt %.

8. The glass sheet according to claim 1, wherein the composition comprises a cerium content (expressed as CeO.sub.2)≤0.05 wt %.

9. The glass sheet according to claim 1, wherein the glass sheet has a luminous transmission LTD4 ≥89%.

10. The glass sheet according to claim 1, wherein the composition comprises 1.5*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3-53.12*Co.

11. The glass sheet according to claim 1, wherein the composition comprises 1.8*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3-53.12*Co.

12. The glass sheet according to claim 1, wherein the composition comprises Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3-53.12*Co≤2.4*Fe.sub.2O.sub.3.

13. The glass sheet according to claim 1, wherein the composition comprises Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3-53.12*Co≤2*Fe.sub.2O.sub.3.

14. A glass sheet having a composition comprising, in weight percentage with respect to a total weight of the glass: TABLE-US-00017 SiO.sub.2 60-78%; Al.sub.2O.sub.3  0-8%; B.sub.2O.sub.3  0-4%; Na.sub.2O  5-20%; CaO  0-15%; MgO  0-12%; K.sub.2O  0-12%; BaO  0-5%; total iron (expressed in the form of Fe.sub.2O.sub.3) 0.002-0.04 wt %; and erbium (expressed in the form of Er.sub.2O.sub.3) 0.003-0.1 wt %, wherein the glass sheet composition has a redox ratio ≤32%, wherein 1.3*Fe.sub.2O.sub.3<Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3-53.12*Co≤2.6*Fe.sub.2O.sub.3, wherein the glass sheet composition is free of antimony and arsenic, wherein the glass sheet has a luminous transmission LTD4 ≥87%, and wherein the glass sheet has a* ≥0 and b* ≥0, a* and b* being measured for a sheet thickness of 4 mm in transmission with illuminant D65, 10°, SCI.

15. The glass sheet according to claim 14, wherein the composition comprises total iron from 0.002-0.03 wt %.

16. The glass sheet according to claim 14, wherein the composition comprises total iron from 0.002-0.02 wt %.

17. The glass sheet according to claim 14, wherein the composition has a redox ratio ≤30%.

18. The glass sheet according to claim 14, wherein the composition comprises Er.sub.2O.sub.3≤0.08 wt %.

19. The glass sheet according to claim 14, wherein the composition comprises Er.sub.2O.sub.3≥0.01 wt %.

20. The glass sheet according to claim 14, wherein the composition comprises 1.8*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3-53.12*Co.

Description

4. DETAILED DESCRIPTION OF THE INVENTION

(1) The invention relates to a glass sheet having a luminous transmission LTD4≥87% and having a composition free of antimony and arsenic comprising the following: total iron (expressed in the form of Fe.sub.2O.sub.3): 0.002-0.04 wt % erbium (expressed in the form of Er.sub.2O.sub.3): 0.003-0.1 wt % redox ratio ≤32% 1.3*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co≤2.6*Fe.sub.2O.sub.3.

(2) Hence, the invention lies on a novel and inventive approach since it enables to find a solution for the disadvantages of prior art. The inventors have indeed found that, surprisingly, combining in an antimony- and arsenic-free low-iron glass matrix:

(3) (i) erbium in specific amounts (significantly higher amounts than for selenium in known glasses with wood-toned edges);

(4) (ii) a relatively low redox ratio, and

(5) (ii) a link between the iron content and the contents in erbium (and in chromium and cobalt if present), as follows: 1.3*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co≤2.6*Fe.sub.2O.sub.3

(6) allows to reach a glass sheet with a high luminous transmittance and with edges which are warm-toned (positive a*b* coordinates) to neutral, the glass being producible without major issues of color stability and substantially not subjected to solarization.

(7) In present description and claims, to quantify the luminous transmittance of the glass sheet, one considers the total light transmission with illuminant D65 (LTD) for a sheet thickness of 4 mm (LTD4) at a solid angle of observation of 2° (according to standard ISO9050). The light transmission represents the percentage of light flux emitted between wavelengths 380 nm and 780 nm which is transmitted through the glass sheet.

(8) In present description and claims and otherwise specified, to evaluate the color of the glass sheet, one considers CIELab values: a* and b*, measured for a sheet thickness of 4 mm, in transmission with illuminant D65, 10°, SCI.

(9) Other features and advantages of the invention will be made clearer from reading the following description of preferred embodiments, given by way of simple illustrative and non-restrictive examples.

(10) Throughout the present text, when a range is indicated, the extremities are included, except if explicitly described in another way. In addition, all the integral and subdomain values in the numerical range are expressly included as if explicitly written. Also, throughout the present text, the values of content are in percentage, except if explicitly described in another way (i.e. in ppm). Moreover, throughout the present text also, values of content in percentages are by weight (also mentioned as wt %) expressed with respect to the total weight of the glass. Moreover, when a glass composition is given, this relates to the bulk composition of the glass.

(11) According to the invention, the glass sheet has an antimony-free composition. This means that the element antimony is not intentionally added in the glass batch/raw materials and that, if it is present, Sb.sub.2O.sub.3 content in the composition of the glass sheet reaches only level of an impurity unavoidably included in the production. Preferably, the composition of the glass sheet comprises Sb.sub.2O.sub.3 in a content lower than 0.01 wt %. Preferably, the composition of the glass sheet comprises Sb.sub.2O.sub.3 in a content lower than 0.005 wt %. More preferably, the composition of the glass sheet comprises Sb.sub.2O.sub.3 in a content lower than 0.002 wt %. Sb.sub.2O.sub.3 is harmful to the environment and health, so its use is prohibited or at least strictly controlled and should therefore be avoided. In addition, if the glass sheet is floated, an unwanted reduction reaction occurs at the contact with the tin, giving a very unpleasant coloration, which is averse for the objective of the invention.

(12) According to the invention, the glass sheet has an arsenic-free composition. This means that the element arsenic is not intentionally added in the glass batch/raw materials and that, if it is present, As.sub.2O.sub.3 content in the composition of the glass sheet reaches only level of an impurity unavoidably included in the production. Preferably, the composition of the glass sheet comprises As.sub.2O.sub.3 in a content lower than 0.01 wt %. Preferably, the composition of the glass sheet comprises As.sub.2O.sub.3 in a content lower than 0.005 wt %. More preferably, the composition of the glass sheet comprises As.sub.2O.sub.3 in a content lower than 0.002 wt %. As.sub.2O.sub.3 is harmful to the environment and health, so its use is prohibited or at least strictly controlled and should therefore be avoided. In addition, if the glass sheet is floated, an unwanted reduction reaction occurs at the contact with the tin, giving a very unpleasant coloration, which is averse for the objective of the invention.

(13) Preferably, the glass sheet according to the invention has advantageously a LTD4≥88%, 89%, or even ≥90%, or better ≥90.5%, ≥90.75% or even more better ≥91%, ≥91.15, ≥91.2%, ≥91.3%.

(14) The glass sheet according to the invention has a*≥0 and b*≥0, a* and b* being measured for a sheet thickness of 4 mm in transmission with illuminant D65, 10°, SCI.

(15) The glass sheet according to the invention may have varied and relatively large sizes. It can, for example, have sizes ranging up to 3.21 m×6 m or 3.21 m×5.50 m or 3.21 m×5.10 m or 3.21 m×4.50 m (“PLF” glass sheet) or also, for example, 3.21 m×2.55 m or 3.21 m×2.25 m (“DLF” glass sheet).

(16) The glass sheet according to the invention can have a thickness of from 0.1 to 30 mm. Advantageously, in the case of the touch panels application, the glass sheet according to the invention can have a thickness of from 0.1 to 6 mm. Preferably, in the case of the touchscreens application, for reasons of weight, the thickness of the glass sheet according to the invention is of from 0.1 to 2.2 mm. Alternatively, preferably, for any application other than the screen application, essentially for reasons of mechanical strength, the thickness of the glass sheet according to the invention is of from 4 to 12 mm.

(17) Preferably, the glass of the invention is completely amorphous material, thereby excluding any crystalline material, even partially crystalline material (such as, for example, glass-crystalline or glass-ceramic materials).

(18) The glass sheet according to the invention can be a glass sheet obtained by a floating process, a drawing process, a rolling process or any other process known to manufacture a glass sheet starting from a molten glass composition. According to a preferred embodiment according to the invention, the glass sheet is a float glass sheet. The term “float glass sheet” is understood to mean a glass sheet formed by the float glass process, which consists in pouring the molten glass onto a bath of molten tin, under reducing conditions. A float glass sheet comprises, in a known way, a “tin face”, that is to say a face enriched in tin in the body of the glass close to the surface of the sheet. The term “enrichment in tin” is understood to mean an increase in the concentration of tin with respect to the composition of the glass at the core, which may or may not be substantially zero (devoid of tin).

(19) According to the invention, the composition of the invention comprises total iron (expressed in terms of Fe.sub.2O.sub.3) as follows: 0.002-0.04 wt %. In present description, when talking about total iron content in glass composition, “total iron” and “Fe.sub.2O.sub.3” are used as well. According to an embodiment, the composition comprises total iron ≥0.004 wt %. Preferably, the composition comprises total iron ≥0.005 wt %. More preferably, the composition comprises total iron ≥0.006 wt % or even, ≥0.007 wt %. These increasing minimum values make it possible not to excessively damage the cost of the glass as such low iron values often require expensive, very pure, starting materials and also their purification. Preferably, the composition comprises total iron ≥0.03 wt %. More preferably, the composition comprises total iron ≥0.02 wt % or even, ≤0.015 wt % or even better, ≥0.01 wt %. These decreasing maximum values in total iron allow to reach higher and higher values of luminous transmittance. To avoid any doubt herein, each embodiment concerning lower limits in Fe.sub.2O.sub.3 is of course combinable independently with any possible embodiment concerning higher limits in Fe.sub.2O.sub.3.

(20) According to the invention, the composition of the invention comprises erbium (expressed in the form of Er.sub.2O.sub.3) as follows: 0.003-0.1 wt %. Preferably, the composition comprises Er.sub.2O.sub.3≥0.005 wt %. More preferably, the composition comprises Er.sub.2O.sub.3≥0.01 wt % or even, ≥0.015 wt % or even better, ≥0.02 wt %. These minimum values allow to better target the desired color. Preferably, the composition comprises Er.sub.2O.sub.3≤0.08 wt % or better, ≤0.06 wt % or even better, ≤0.05 wt %. These decreasing maximum values make possible (i) not to excessively damage the cost of the glass as erbium raw materials are very expensive, (ii) not to excessively damage the luminous transmission, and (iii) avoid a too excessive dichroism phenomenon. To avoid any doubt herein, each embodiment concerning lower limits in Er.sub.2O.sub.3 is of course combinable independently with any possible embodiment concerning higher limits in Er.sub.2O.sub.3.

(21) According to the invention, the composition of the invention comprises: 1.3*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co≤2.6*Fe.sub.2O.sub.3. In the invention, it is understood that chromium and cobalt are components that are only optional. In this formula, all amounts must be expressed with the same unit (wt % or ppm).

(22) Preferably, the composition comprises: 1.4*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co. More preferably, the composition comprises: 1.5*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co or even, 1.7*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co, or even better, 1.8*Fe.sub.2O.sub.3≤Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co. These minimum values allow to better target the desired color and high luminous transmittance. Preferably, the composition comprises: Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co≤2.4*Fe.sub.2O.sub.3. More preferably, the composition comprises: Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co≤2.2*Fe.sub.2O.sub.3 or even, Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co≤2*Fe.sub.2O.sub.3. These maximum values also allow to better target the desired color and high luminous transmittance. To avoid any doubt herein, each embodiment concerning lower limits is of course combinable independently with any possible embodiment concerning higher limits.

(23) According to the invention, the composition of the invention has a redox ratio ≤32%. The redox ratio in present invention is in accordance with what is generally acknowledged in the art of glass composition and is defined as the ratio of the Fe.sup.3+ content (as calculated as Fe.sub.2O.sub.3) to the total iron content (expressed as Fe.sub.2O.sub.3). According to an embodiment of the invention, the composition of the invention has a redox ratio ≤30%. Preferably, the composition of the invention has a redox ratio ≤28%, or even ≤26%, or even better ≤25%. Such low redox values allows to reach higher level of luminous transmission and make easier to reach the “first dial” (positive a*b*) by using Er.sub.2O.sub.3 according to the invention.

(24) For reasons already mentioned above (to avoid the phenomenon of solarization) and according to a preferred embodiment, the composition of the glass sheet includes a cerium content (expressed as CeO.sub.2)≤0.05 wt %. Preferably, the composition of the glass sheet comprises a cerium content (expressed as CeO.sub.2)≤0.03 wt % or even ≤0.01 wt %. More preferably, the composition of the glass sheet is free of CeO.sub.2. This means that the element cerium is not intentionally added in the glass batch/raw materials and that, if it is present, its content in the composition of the glass sheet reaches only level of an impurity unavoidably included in the production.

(25) According to another embodiment, the composition of the glass sheet comprises ZnO in a content lower than 0.1 wt %. Preferably, the composition of the glass sheet comprises ZnO in a content lower than 0.01 wt %. More preferably, the composition of the glass sheet is free of ZnO. This means that the element zinc is not intentionally added in the glass batch/raw materials and that, if it is present, ZnO content in the composition of the glass sheet reaches only level of an impurity unavoidably included in the production.

(26) According to still another embodiment, the composition of the glass sheet comprises SrO in a content lower than 0.1 wt %. Preferably, the composition of the glass sheet comprises SrO in a content lower than 0.01 wt %. More preferably, the composition of the glass sheet is free of SrO. This means that the element strontium is not intentionally added in the glass batch/raw materials and that, if it is present, SrO content in the composition of the glass sheet reaches only level of an impurity unavoidably included in the production.

(27) According to still another embodiment, the composition of the glass sheet comprises SnO.sub.2 in a content lower than 0.1 wt %. The SnO.sub.2 content herein means the SnO.sub.2 content in the bulk of the glass sheet, excluding the so-called “tin face” in the case of a float glass sheet. Preferably, the composition of the glass sheet comprises SnO.sub.2 in a content lower than 0.03 wt %. More preferably, the composition of the glass sheet comprises SnO.sub.2 in a content lower than 0.01 wt %. In the most preferred embodiment, the composition of the glass sheet is free of SnO.sub.2. This means that the element tin is not intentionally added in the glass batch/raw materials and that, if it is present, SnO.sub.2 content in the composition of the glass sheet reaches only level of an impurity unavoidably included in the production. If present, SnO.sub.2 will tend to increase redox ratio, hence decreasing luminous transmittance and promoting cold tints in the glass.

(28) The glass sheet according to the invention is made of glass which may belong to various categories. The glass can thus be a glass of soda-lime-silica, aluminosilicate or borosilicate type, and the like. Preferably, the composition of the glass sheet comprises the following in weight percentage, expressed with respect to the total weight of glass:

(29) TABLE-US-00001 SiO.sub.2 40-78%  Al.sub.2O.sub.3 0-18% B.sub.2O.sub.3 0-18% Na.sub.2O 0-20% CaO 0-15% MgO 0-10% K.sub.2O 0-10% BaO 0-5%. 

(30) More preferably, notably for low production costs reasons, the glass composition is a soda-lime-silicate-type glass. According to this embodiment, by “soda-lime-silicate-type glass”, it is meant that the base glass matrix of the composition comprises the following in weight percentage, expressed with respect to the total weight of glass:

(31) TABLE-US-00002 SiO.sub.2 60-78 wt % Al.sub.2O.sub.3 0-8 wt % B.sub.2O.sub.3 0-4 wt % CaO 0-15 wt % MgO 0-10 wt % Na.sub.2O 5-20 wt % K.sub.2O 0-10 wt % BaO 0-5 wt %.

(32) According to this embodiment, preferably, the base glass matrix of the composition comprises the following in weight percentage, expressed with respect to the total weight of glass:

(33) TABLE-US-00003 SiO.sub.2 60-78 wt % Al.sub.2O.sub.3 0-6 wt % B.sub.2O.sub.3 0-1 wt % CaO 5-15 wt % MgO 0-8 wt % Na.sub.2O 10-20 wt % K.sub.2O 0-10 wt % BaO 0-1 wt %.

(34) In a preferred embodiment of the invention, the composition comprises the following in weight percentage, expressed with respect to the total weight of glass:
65≤SiO.sub.2≤78 wt %
5≤Na.sub.2O≤20 wt %
0≤K.sub.2O<5 wt %
1≤Al.sub.2O.sub.3<6 wt %
0≤CaO<4.5 wt %
4≤MgO≤12 wt %
(MgO/(MgO+CaO))≥0.5.

(35) In another preferred embodiment of the invention, the composition comprises the following in weight percentage, expressed with respect to the total weight of glass:
65≤SiO.sub.2≤78%
5≤Na.sub.2O≤20%
0≤K.sub.2O<5%
3<Al.sub.2O.sub.3≤5%
0<CaO<4.5%
4≤MgO≤12%;
0.88≤[MgO/(MgO+CaO)]<1.

(36) In another preferred embodiment of the invention, the composition comprises the following in weight percentage, expressed with respect to the total weight of glass:
60≤SiO.sub.2≤78%
5≤Na.sub.2O≤20%
0.9<K.sub.2O≤12%
4.9≤Al.sub.2O.sub.3≤8%
0.4<CaO<2%
4<MgO≤12%

(37) In another preferred embodiment of the invention, the composition comprises the following in weight percentage, expressed with respect to the total weight of glass:
65≤SiO.sub.2≤78 wt %
5≤Na.sub.2O≤20 wt %
1≤K.sub.2O<8 wt %
1≤Al.sub.2O.sub.3<6 wt %
2≤CaO<10 wt %
0≤MgO≤8 wt %
K.sub.2O/(K.sub.2O+Na.sub.2O): 0.1-0.7.

(38) In particular, examples of base glass matrixes for the composition according to the invention are described published PCT patent applications WO2015/150207A1 and WO2015/150403A1, in filed PCT patent applications PCT/EP2015/078305 and PCT/EP2016/058090, and in EP patent application no 16176447.7.

(39) The above mentioned compositions with high MgO are especially well-suited as they allow to increase light transmission by decreasing the proportion of 6-folded Fe.sup.2+ ions in the glass matrix, hence decreasing the strong absorption peak of Fe.sup.2+ in the end of visible/near-IR range. In the same way, it has been shown (for example, in US20100304949A1) that glass compositions with higher K.sub.2O amount allows to increase luminous transmittance, which makes the above compositions containing K.sub.2O especially well-suited for the purpose of the invention.

(40) Advantageously, the glass sheet of the invention may be tempered, mechanically or chemically. It may also be bended/curved, or in a general manner, deformed to reach any desired configuration (by cold-bending, thermoforming, . . . ). It may also be laminated.

(41) According to an embodiment of the invention, the glass sheet is coated with at least one transparent and electrically conducting thin layer. A transparent and conducting thin layer according to the invention can, for example, be a layer based on SnO.sub.2:F, SnO.sub.2:Sb or ITO (indium tin oxide), ZnO:Al or also ZnO:Ga.

(42) According to another advantageous embodiment of the invention, the glass sheet is coated with at least one antireflection layer. This embodiment is obviously advantageous in the case of use of the glass sheet of the invention as front face of a screen. An antireflection layer according to the invention can, for example, be a layer based on porous silica having a low refractive index or it can be composed of several layers (stack), in particular a stack of layers of dielectric material alternating layers having low and high refractive indexes and terminating in a layer having a low refractive index.

(43) According to another embodiment, the glass sheet is coated with at least one anti-fingerprint layer or has been treated so as to reduce or prevent fingerprints from registering. This embodiment is also advantageous in the case of use of the glass sheet of the invention as front face of a touchscreen. Such a layer or such a treatment can be combined with a transparent and electrically conducting thin layer deposited on the opposite face. Such a layer can be combined with an antireflection layer deposited on the same face, the anti-fingerprint layer being on the outside of the stack and thus covering the antireflection layer.

(44) According to still another embodiment, the glass sheet is coated with at least one layer or has been treated so as to reduce or prevent glaring and/or sparkling. This embodiment is of course advantageous in the case of use of the glass sheet of the invention as front face of a display device. Such an anti-glare or anti-sparkling treatment is for example an acid-etching producing a specific roughness of the treated face of the glass sheet.

(45) According to still another embodiment, the glass sheet has been treated so as to gain antibacterial properties (i.e. through a known silver treatment). Such a treatment is also advantageous in the case of use of the glass sheet of the invention as front face of a display device.

(46) According to still another embodiment, the glass sheet is coated with at least one paint layer including enamel, organic paint, lacquer, . . . . This paint layer may advantageously be colored or white. According to this embodiment, the glass sheet may be coated on at least one face in its entire surface or only partially.

(47) According to the applications and/or properties desired, other layer(s)/treatment(s) can be deposited/done on one and/or the other face of the glass sheet according to the invention.

(48) The glass sheets of the invention is of particular interest if integrated in/associated with/used as objects as diversified as: furniture (tables, shelves, chairs, doors, . . . ), electronic devices, appliances, white boards, credencies, shower doors, wall panels, façades, interior partitions, lighting, . . . .

(49) Embodiments of the invention will now be further described, by way of examples only, together with some comparative examples, not in accordance with the invention. The following examples are provided for illustrative purposes, and are not intended to limit the scope of this invention.

EXAMPLES

(50) Different glass sheets, according to the invention or comparative, were either (i) produced industrially (“ind”) or (ii) prepared in the lab (“lab”), or (iii) calculated/simulated (“simu”), with variable amounts of total iron, erbium, chromium, cobalt and redox, and with different base glass matrixes.

(51) For the lab preparation of glass sheets (EX9.x, EX10.x): Powder raw materials were mixed together, in amounts according to the targeted composition: a base glass matrix to which it has been added raw materials comprising erbium, iron and optionally cobalt and chromium (note that iron is already at least partly present in the raw materials of the base composition as an impurity). The raw material mixture was then heated up in an electrical furnace to a temperature allowing complete melting of the raw material.

(52) For glass sheets produced industrially (EX11.x): they were produced in a classical manner on a mass production float furnace.

(53) The optical properties of each glass sheet prepared in the lab or industrially were measured on a Perkin Elmer Lambda 950 spectrophotometer fitted with an integrating sphere of 150 mm in diameter, and in particular: The luminous transmittance LTD4 was determined according to the ISO9050 standard to a thickness of 4 mm with a solid viewing angle of 2° (D65 illuminant) and for a wavelength range between 380 and 780 nm; The CIE L* a*b* parameters were determined in transmission with the following parameters: Illuminant D65, 10°, 4 mm thickness.

(54) For the simulation/computation of glass sheets (EX1.x, EX2.x, EX3.x, EX4.x, EX5.x, EX6.x and EX7.x): the optical properties were computed on the basis of optical properties of different glass colorants (using linear absorption coefficient, determined for the concerned base glass matrix, to build the complete optical spectra and compute the parameters of interest). The base glass matrix considered in computation is the following, corresponding to a glass matrix according to EP patent application no 16176447.7:

(55) TABLE-US-00004 Amount [wt %] SiO.sub.2 66.5 CaO 1.1 K.sub.2O 1.0 Na.sub.2O 16.2 SO.sub.3 0.4 Al.sub.2O.sub.3 5.6 MgO 9.4

(56) Some classical soda-lime glass sheets from the state-of-the-art and commercially available were also evaluated in terms of optical properties, as comparative examples (EX8.1, EX8.2, EX8.3). EX8.3 corresponds to a classical low-iron solar glass sheet from the state-of-the-art (Sunmax® glass from AGC Glass Europe).

(57) Results:

(58) Compositions and optical properties for comparative examples (“comp”) as well as examples according to the invention (“inv”) are shows in Tables 1-11.

(59) TABLE-US-00005 TABLE 1 EX1.1 EX1.2 EX1.3 EX1.4 EX1.5 comp comp inv inv comp simu Fe.sub.2O.sub.3 (ppm) 100 100 100 100 100 Er.sub.2O.sub.3 (ppm) 0 75 130 250 500 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 0 Co (ppm) 0 0 0 0 0 Redox (%) 20 20 20 20 20 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 0.00 0.75 1.30 2.50 5.00 [Er.sub.2O.sub.3—21.87 * 0.00 0.75 1.30 2.50 5.00 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.06 −0.02 0.02 0.10 0.26 b* (4 mm, D65, 10°) 0.13 0.11 0.10 0.06 −0.01 L* (4 mm, D65, 10°) 96.70 96.68 96.67 96.65 96.60 LTD4 (%, D65, 2°) 91.71 91.67 91.65 91.59 91.47

(60) TABLE-US-00006 TABLE 2 EX2.1 EX2.2 EX2.3 EX2.4 EX2.5 comp comp inv inv comp simu Fe.sub.2O.sub.3 (ppm) 100 100 100 100 100 Er.sub.2O.sub.3 (ppm) 0 100 150 250 300 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 0 Co (ppm) 0 0 0 0 0 Redox (%) 30 30 30 30 30 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 0.00 1.00 1.50 2.50 3.00 [Er.sub.2O.sub.3—21.87 * 0.00 1.00 1.50 2.50 3.00 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.09 −0.03 0.01 0.07 0.10 b* (4 mm, D65, 10°) 0.08 0.05 0.03 0.00 −0.01 L* (4 mm, D65, 10°) 96.68 96.66 96.65 96.63 96.62 LTD4 (%, D65, 2°) 91.65 91.60 91.58 91.53 91.51

(61) TABLE-US-00007 TABLE 3 EX3.1 EX3.2 EX3.3 EX3.4 comp comp inv comp simu Fe.sub.2O.sub.3 (ppm) 400 400 400 400 Er.sub.2O.sub.3 (ppm) 0 400 800 1200 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 Co (ppm) 0 0 0 0 Redox (%) 22 22 22 22 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 0.00 1.00 2.00 3.00 [Er.sub.2O.sub.3—21.87 * 0.00 1.00 2.00 3.00 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.38 −0.12 0.14 0.39 b* (4 mm, D65, 10°) 0.26 0.14 0.03 −0.08 L* (4 mm, D65, 10°) 96.46 96.39 96.31 96.23 LTD4 (%, D65, 2°) 91.14 90.95 90.76 90.57

(62) TABLE-US-00008 TABLE 4 EX4.1 EX4.2 EX4.3 EX4.4 comp comp inv comp simu Fe.sub.2O.sub.3 (ppm) 200 200 200 200 Er.sub.2O.sub.3 (ppm) 0 200 350 600 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 Co (ppm) 0 0 0 0 Redox (%) 27 27 27 27 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 0.00 1.00 1.75 3.00 [Er.sub.2O.sub.3—21.87 * 0.00 1.00 1.75 3.00 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.20 −0.07 0.03 0.19 b* (4 mm, D65, 10°) 0.11 0.05 0.01 −0.06 L* (4 mm, D65, 10°) 96.60 96.56 96.53 96.48 LTD4 (%, D65, 2°) 91.45 91.36 91.28 91.16

(63) TABLE-US-00009 TABLE 5 EX5.1 EX5.2 EX5.3 EX5.4 comp comp inv comp simu Fe.sub.2O.sub.3 (ppm) 80 80 80 80 Er.sub.2O.sub.3 (ppm) 0 40 200 400 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 Co (ppm) 0 0 0 0 Redox (%) 25 25 25 25 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 0.00 0.50 2.50 5.00 [Er.sub.2O.sub.3—21.87 * 0.00 0.50 2.50 5.00 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.06 −0.03 0.07 0.20 b* (4 mm, D65, 10°) 0.10 0.09 0.04 −0.02 L* (4 mm, D65, 10°) 96.70 96.70 96.66 96.63 LTD4 (%, D65, 2°) 91.72 91.70 91.63 91.53

(64) TABLE-US-00010 TABLE 6 EX6.1 EX6.2 EX6.3 EX6.4 EX6.5 EX6.6 EX6.7 EX6.8 EX6.9 comp comp inv comp comp inv comp comp inv simu Fe.sub.2O.sub.3 (ppm) 150 150 150 150 150 150 150 150 150 Er.sub.2O.sub.3 (ppm) 0 150 200 600 200 637.5 200 418.7 466.6 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 20 20 10 10 10 Co (ppm) 0 0 0 0 0 0 0.9 0.9 0.9 Redox (%) 20 20 20 20 20 20 20 20 20 Er.sub.2O.sub.3/ 0.00 1.00 1.33 4.00 1.33 4.25 1.33 2.79 3.11 Fe.sub.2O.sub.3 [Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3- 0.00 1.00 1.33 4.00 −1.59 1.33 −0.45 1.01 1.33 53.12*Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.11 −0.02 0.02 0.27 −0.26 0.02 −0.15 −0.01 0.02 b* (4 mm, D65, 10°) 0.16 0.12 0.11 −0.01 0.41 0.29 0.08 0.02 0.00 L* (4 mm, D65, 10°) 96.66 96.63 96.62 96.55 96.44 96.35 96.40 96.36 96.35 LTD4 (%, D65, 2°) 91.62 91.55 91.53 91.33 91.10 90.89 90.98 90.88 90.85

(65) TABLE-US-00011 TABLE 7 EX7.1 EX7.2 EX7.3 EX7.4 EX7.5 inv inv inv comp comp simu Fe.sub.2O.sub.3 (ppm) 100 100 100 100 100 Er.sub.2O.sub.3 (ppm) 200 200 200 200 200 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 0 Co (ppm) 0 0 0 0 0 Redox (%) 10 20 30 40 50 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 2.00 2.00 2.00 2.00 2.00 [Er.sub.2O.sub.3—21.87 * 2.00 2.00 2.00 2.00 2.00 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) 0.11 0.07 0.04 0.00 −0.03 b* (4 mm, D65, 10°) 0.15 0.08 0.00 −0.07 −0.14 L* (4 mm, D65, 10°) 96.66 96.63 96.60 96.58 96.55 LTD4 (%, D65, 2°) 91.62 91.55 91.47 91.40 91.32

(66) TABLE-US-00012 TABLE 8 EX8.1 EX8.2 EX8.3 comp comp comp Glass sheets commercially available SiO.sub.2 (wt %) 71.9 72.2 72.0 CaO (wt %) 9.2 9.1 7.9 K.sub.2O (wt %) 0.4 0.0 0.0 Na.sub.2O (wt %) 13.5 13.8 13.9 SO.sub.3 (wt %) 0.2 0.2 0.4 Al.sub.2O.sub.3 (wt %) 0.4 0.7 1.3 MgO (wt %) 4.3 4.0 4.5 Fe.sub.2O.sub.3 (ppm) 100 94 119 Er.sub.2O.sub.3 (ppm) 100 100 0 Cr.sub.2O.sub.3 (ppm) 0 0 0 Co (ppm) 0 0 0 Redox (%) 42.0 32.1 22.8 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 1.00 1.06 0 [Er.sub.2O.sub.3—21.87 * Cr.sub.2O.sub.3 − 1.00 1.06 0 53.12 * Co]/Fe.sub.2O.sub.353.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.14 −0.09 −0.14 b* (4 mm, D65, 10°) 0.02 0.07 0.15 L* (4 mm, D65, 10°) 96.50 96.54 96.64 LTD4 (%, D65, 2°) 91.22 91.32 91.56

(67) TABLE-US-00013 TABLE 9 EX9.1 EX9.2 EX9.3 EX9.4 comp comp inv comp lab SiO.sub.2 (wt %) 71.8 71.8 71.8 71.8 CaO (wt %) 9.0 9.0 9.0 9.0 K.sub.2O (wt %) 0.1 0.1 0.1 0.1 Na.sub.2O (wt %) 13.8 13.8 13.8 13.8 SO.sub.3 (wt %) 0.2 0.2 0.2 0.2 Al.sub.2O.sub.3 (wt %) 0.8 0.8 0.8 0.8 MgO (wt %) 4.3 4.3 4.3 4.3 Fe.sub.2O.sub.3 (ppm) 118 119 119 116 Er.sub.2O.sub.3 (ppm) 0 90 240 1380 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 Co (ppm) 0 0 0 0 Redox (%) 19.3 15.6 18.2 21.5 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 0.00 0.76 2.02 11.90 [Er.sub.2O.sub.3—21.87 * 0.00 0.76 2.02 11.90 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.11 −0.05 0.00 0.45 b* (4 mm, D65, 10°) 0.13 0.17 0.11 −0.09 L* (4 mm, D65, 10°) 96.45 96.44 96.43 96.28 LTD4 (%, D65, 2°) 91.10 91.10 91.10 90.70

(68) TABLE-US-00014 TABLE 10 EX10.1 EX10.2 EX10.3 EX10.4 EX10.5 EX10.6 comp inv comp comp inv comp lab SiO.sub.2 (wt %) 66.5 66.6 66.6 67.2 67.2 67.3 CaO (wt %) 1.1 1.1 1.1 1.1 1.1 1.1 K.sub.2O (wt %) 1.0 1.0 1.0 1.0 1.0 0.9 Na.sub.2O (wt %) 16.2 16.2 16.2 16.2 16.2 16.2 SO.sub.3 (wt %) 0.4 0.3 0.2 0.3 0.3 0.2 Al.sub.2O.sub.3 (wt %) 5.6 5.6 5.5 4.7 4.7 4.7 MgO (wt %) 9.4 9.4 9.4 9.6 9.6 9.6 Fe.sub.2O.sub.3 (ppm) 90 90 90 92 92 92 Er.sub.2O.sub.3 (ppm) 100 229 1009 97 231 1006 Cr.sub.2O.sub.3 (ppm) 0 0 0 0 0 0 Co (ppm) 0 0 0 0 0 0 Redox (%) 16.2 15.4 20.8 18.1 18.3 19.1 Er.sub.2O.sub.3/ 1.11 2.54 11.21 1.05 2.51 10.93 Fe.sub.2O.sub.3 [Er.sub.2O.sub.3-21.87*Cr.sub.2O.sub.3- 1.11 2.54 11.21 1.05 2.51 10.93 53.12*Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.08 0.02 0.53 −0.09 0.00 0.51 b* (4 mm, D65, 10°) 0.22 0.17 −0.11 0.19 0.15 −0.07 L* (4 mm, D65, 10°) 96.60 96.60 96.50 96.68 96.66 96.49 LTD4 (%, D65, 2°) 91.47 91.49 91.22 91.67 91.61 91.19

(69) TABLE-US-00015 TABLE 11 EX11.1 EX11.2 EX11.3 EX11.4 comp inv inv comp ind SiO.sub.2 (wt %) 66.7 66.6 66.5 69.4 CaO (wt %) 1.3 1.0 1.0 5.0 K.sub.2O (wt %) 1.0 1.0 1.1 0.6 Na.sub.2O (wt %) 15.7 15.8 15.8 14.7 SO.sub.3 (wt %) 0.2 0.3 0.3 0.3 Al.sub.2O.sub.3 (wt %) 5.6 5.7 5.8 3.3 MgO (wt %) 9.5 9.5 9.5 6.7 Fe.sub.2O.sub.3 (ppm) 198 136 116 257 Er.sub.2O.sub.3 (ppm) 226 384 481 229 Cr.sub.2O.sub.3 (ppm) 0 1.7 6.5 3.8 Co (ppm) 0.29 0.35 0.75 0.38 Redox (%) 17.6 10.6 10.4 18.7 Er.sub.2O.sub.3/Fe.sub.2O.sub.3 1.14 2.83 4.15 0.89 [Er.sub.2O.sub.3—21.87 * 1.06 2.42 2.58 0.49 Cr.sub.2O.sub.3—53.12 * Co]/Fe.sub.2O.sub.3 a* (4 mm, D65, 10°) −0.14 0.01 0.04 −0.20 b* (4 mm, D65, 10°) 0.19 0.23 0.12 0.24 L* (4 mm, D65, 10°) 96.61 96.72 96.62 96.35 LTD4 (%, D65, 2°) 91.48 91.76 91.53 90.86

(70) Those results proofs in a very clear manner that combining, in a low-iron glass matrix, a specific erbium content according to the invention together with a relatively low redox (≤32%) and a ratio [Er.sub.2O.sub.3−21.87*Cr.sub.2O.sub.3−53.12*Co]/Fe.sub.2O.sub.3 between 1.3 and 2.6 allows to reach the objective of the invention, namely a glass sheet with a high luminous transmittance and which lies in the first dial of the a*b* diagram (positive a*b* coordinates).