Low ir and low uv transmittance green glass composition and laminated windshields and automotive glass made from such glass

BACKGROUND OF THE INVENTION The present invention relates to green glass for infrared energy and ultraviolet radiation, and to laminated windscreen and automotive glass made of such glass.

It has long been known that soda / limestone / silica glasses can change color to green if different amounts of iron are added to the portion. In this respect, the total iron content is usually Fe₂SHE₃ is expressed in% by weight, although iron may be present in the glass in various valencies. However, it is also known that iron (II) oxide (FeO) and iron (III) oxide (Fe₂SHE₃) can cause significant differences in the resulting shade of green and other properties of the glass. In general, the FeO concentration is Fe₂SHE₃with increasing concentration compared to yellow glass, the color of the glass shifts from dark green to dark green or blue green with a lower transmittance.

FeO: Fe₂SHE₃ [ie iron (II) content / iron (III) content] shifts other properties of glass. Among other things, iron (FeO) with oxidation number +2 is known to absorb infrared energy in glass. The increase in FeO content at the expense of Fe2O3 content adversely reduces the absorption of ultraviolet energy, since Fe₂SHE₃ UV absorbers. It has also been disclosed that although relatively high concentrations of FeO are desirable due to high infrared absorption, they significantly limit the penetration of heat into the glass melt and require special melting and purifying equipment to achieve homogeneous glass.

Prior to the present invention, the person skilled in the art, having regard to the state of the art and the related knowledge in the field of glass having a relatively high transmittance, low ultraviolet and low infrared transmittance, iron-based soda / limestone / silica glass, is described in Nos. 4,792,536 and 5,077,133. U.S. Patents and the state of the art cited and discussed in them.

The glasses, which represent the preferred versions of the two patents, have attempted in various ways to balance the iron (III) and iron (II) contents. To do this, while retaining the necessary transmittance in the visible range, to achieve a selected level of infrared absorption, the relative proportions of the above iron components are shifted by changing the oxidation state. Both patents teach that cerium oxide (CeO₂) are added to the composition to provide an adequate amount of ultraviolet absorption and thus a sufficient level of total sunlight transmittance. U.S. Patent No. 4,792,536 discloses certain other CeO₂ UV-absorbing additives, which may be TiO₂, V₂SHE₅ and MoO₃. However, U.S. Patent No. 5,077,133 discloses that, in the practice of the present invention, CeO₂ use is critical, but CeO₂part of it may be added as a mixture with TiO₂using.

All of these UV-absorbing additives, in particular CeO₂ costly. In addition, their use causes difficulties in the formulation. CeO₂other than additives have been reported to adversely affect transmittance in the visible range. On the other hand, besides being expensive and adversely affecting transmittance in the visible range, CeO₂ inhibited by Fe₂SHE₃reduction to FeO [i.e., reduction of iron (III) ions to iron (II) ions],

CeO is also used for the glass of European Patent No. 469,446₂ of the invention to achieve a glass transmittance of at least 70% in the visible range. Although the glass of Example 4 described herein does not contain CeO₂however, to ensure proper properties, the total iron content exceeds 1% by weight, which causes production difficulties.

Also expensive CeO₂ International Patent Publication No. WO 91/07356.

A further difficulty in producing acceptable green glasses is described in U.S. Patent No. 4,792,536, whereby the presence of sulfur in the glass inhibits Fe₂SHE₃ reduction to FeO. Advantageously, sulfur, such as sodium sulfate ("crude" Na₂SALT₄) known, inexpensive and valuable refining material for soda / limestone / silica glass, especially in the traditional "float" process for the manufacture of flat glass for architecture and / or automobiles. The Fe₂SHE₃ Due to its inhibitory effect on the reduction to FeO, the process described in U.S. Patent No. 4,792,536 is intended to severely limit the₃). According to the teachings of this patent, in order to achieve the stated general goal (to preserve the transmittance in the visible range), the total iron content is kept to a minimum, preferably 0.45-0.65% by weight of the total composition of the glass, and under glass reducing conditions. is formed such that at least 35, most preferably at least 50% by weight of this average iron content is present in the iron (II) state (in the form of FeO) for the total iron content. Infrared transmittance up to 15% is reported to have been achieved.

According to the examples described in the latter patent, when the glasses were reduced to the desired degree to achieve this IR transmittance, and because of the low iron content, the UV transmittance increased due to the small amount of iron (III) remaining. This in turn is additives such as CeO₂ and the like has been required to absorb UV. Thus, in most of the examples, the transmittance (LT_THE) rarely approach 70%, which is considered a desirable, sometimes necessary measure of transmittance in the visible range for automotive glasses. The glasses of the compositions described in the tables of the above-mentioned patent use special UV absorbing additives (such as CeO).₂), the transmittance of composition 14 alone is greater than or equal to 70% of the visible range. (The glass of Example All also fulfills this criterion, however, since it has not been sufficiently reduced, it contains 1.0% by weight of cerium oxide.)

EN 213 955 Β does not contain CeO₂ or other aforementioned UV absorbing oxide (such as TiO₂, MoO₃ or V2O5), the UV transmittance, even at a thickness of 5 mm, is 51.3%, which is very high. The latter value renders these glasses unacceptable for use in certain vehicles. In addition, in some cases, due to certain user demands, many of these compositions become undesirable due to the change of hue to bluish-green.

The latter patent describes four prior art glass compositions. Formulation 1 is a conventional green glass that has little inhibitory effect on the passage of sunlight. Figures 2-4. Although the iron content is slightly closer to the iron content of the glasses according to the invention, even with a thickness of less than 5 mm, the compositions are disadvantageous in one or more aspects with respect to the sun rays. In that regard, Article 2 (2) provides:. composition large A1₂SHE₃- and K₂Because of its O content, it differs from the glass according to the invention, which additives make it difficult to produce float glass, which is a preferred method for carrying out the invention. Composition 3 is also significantly different from SO₃The content of the glasses according to the invention is as follows, in the range of 0.20-0.25% by weight, in a rather narrow and critical range₃content, which makes it difficult to clean the 3rd glass formulation. Compared to the glass according to the invention, it is FeO / Fe₂SHE₃it also has a high content, which results in relatively high UV transmittance at thicknesses less than 5 mm. Composition 4 is reduced to such an extent that it exhibits very high UV transmittance relative to the glasses of the invention. In addition, this composition can only be obtained by special processes and therefore cannot be used in the manufacture of float glass. In contrast to the compositions described in U.S. Patent No. 4,792,536, which contains a minimum amount of iron and a small amount of sulfur, the compositions of U.S. Patent No. 5,077,133 are intended to provide green glasses with relatively high total iron content. For cleaning purposes, portions of these glasses also contain conventional crude sodium sulfate, and as described herein require only conventional melting and purifying equipment. The color of these glasses is generally yellow-green, as opposed to the blue-green tones of the glasses described in U.S. Patent No. 4,792,536.

U.S. Patent No. 5,077,133 attempts to differentiate from the above-mentioned U.S. Patent No. 4,792,536 (see Column 2, line 40 et seq.). They emphasize the relatively small amounts of iron used in the solution of the latter patent and the characteristic properties of the resulting glass end product. On the other hand, U.S. Patent No. 5,027,133 states that the corresponding glasses use a higher total iron content and that FeO / (Fe₂SHE₃ Formula), and in certain specific concentrations (alone or in TiO₂CeO)₂ has achieved excellent color and transmittance characteristics through its critical use.

Specifically, U.S. Patent No. 5,077,133 states that, within certain limits, a specific ratio of FeO to total iron content, as well as a defined amount of CeO,₂The transmittance in the visible range of the light source is greater than 70%, the transmittance for total solar energy is less than 46%, and the transmittance for ultraviolet radiation is less than 38%, preferably less than 34%. The cited patent further states that the dominant wavelength for light source C is between 498 and 525 nm, compared to 10% for blue glass according to U.S. Patent 4,792,536, with a purity of 2 to 4%. Of course, at least some of these properties are thickness dependent, and it is stated that these combined results are achieved with 3-5 mm full thickness (single or multiple layers) glasses.

U.S. Patent No. 5,077,133 discloses low transmittance for "infrared energy" (column 7, rows 1 and 2), but does not disclose the value or range of values. Using the formula described in U.S. Patent No. 4,792,536 (line 13 of column 13), it can be calculated that said IR transmittance (TSIR) is in the 17-33% range in U.S. Patent 5,077,133. .

Desirably desirable properties for transmittance, clarity, and hue as described in U.S. Patent 5,077,133, particularly for automotive windshields, side and rear windows, and other automotive glass. However, for the purposes of the invention cited above and prior U.S. Patent 4,792,536, CeO₂ use alone or TiO₂ additive undesirable and disadvantages.

From the foregoing, there is clearly a need for a glass composition which generally achieves the transmittance and color properties of the product described in U.S. Patent 5,077,133 without the need for special UV absorbing additives such as CeO.₂should be applied, which is considered necessary in the prior art to achieve adequate UV absorption.

It is an object of the present invention to meet this need, as well as other needs that will be apparent to those skilled in the art from the disclosure.

The invention relates to infrared energy and ultraviolet radiation absorbing green glass having a transmittance of greater than 70%, a transmittance of ultraviolet radiation of less than 38%, and SiO₂, So₂O and CaO 0.20-0.25% by weight SO₃, Fe₂SHE₃ in the form of 0.7-0.95% by weight of total iron and in the form of FeO 0.19-0.24% by weight of divalent iron, the total transmittance of the sun being less than 44.5%.

HU 213 955 Β

In preferred embodiments of the present invention, at a thickness of 3.7 to 4.8 mm, a dominant wavelength of 495-510 nm, most preferably 500-502 nm, is obtained in excess of the above transmittance and 2-4% color purity and C light source. Together with a purity of 2-4%, this wavelength represents a very favorable and aesthetic green, which shifts slightly towards the yellow rather than the blue towards the spectrum. thus, it is possible for the product to meet the specific requirements of users in the automotive industry.

Further variants of the glasses of the invention may be prepared under reducing conditions such that the ratio of FeO (Fe₂SHE₃ ), 0.24-0.27 for the total iron content calculated using the method described in U.S. Patent No. 4,792,536 and calculated as% of FeO calculated according to the method of U.S. Patent 5,077,133. rate of 25-29%.

The method for calculating the percentage reduction in total iron content is disclosed in U.S. Patent 5,077,133, column 4, pp. 28-44. lines. The cited description and method are incorporated herein by reference, as well as the calculation method described in U.S. Patent No. 4,792,536 for FeO: total iron content. Unless otherwise stated, the percentage reduction of total iron content to FeO by the optical density formula obtained by the process of the above-mentioned patent refers to the ratio of FeO to total iron content calculated using the method of the above patent.

In all versions of the product of the invention, the composition of the glass is free of CeO₂, TiO₂, MoO₃ or V7O5 in an effective amount sufficient to significantly absorb UV radiation (i.e., they may only be present in trace amounts than the natural impurities in the dose, generally less than 0.1% by weight).₂(e.g., 0.02%). In fact, the specific object and feature of the invention is to avoid the use of such additives. The term "substantially" used to determine the composition of the glasses of the invention refers to this object and characteristic of the invention.

It is understood that the terms IR, UV, and total transmittance as used in the above patents and the present invention refer to the transmittance of rays. Throughout this specification (except for the transmittance for the visible range), the transmittance of sunlight energy is determined by the standard Simpson parabolic integration method for accuracy. This procedure is described in basic literature (Gillet, Calculus and Analytical Geometry DC Health & Co., Chapter 10, page 440]. The transmittance of infrared radiation in this regard can be determined either by the Simpson rule or by knowing the other values ​​using the following formula:

TSET = 0.44 LT_the + 0.53 TSIR + 0.03 TSUV where TSET is the transmittance of total sunlight energy,

LT_the j is the transmittance for the visible range,

TSIR stands for Infrared Transmittance, and

TSUV stands for ultraviolet transmittance.

Determined by these formulas or measurements, the preferred glasses of the present invention have an infrared transmittance of 18-21% for a thickness of 3.7 to 4.8 mm. For the discussed features, the transmittance for the visible range is measured by the light source method (in the range 380-770 nm); determining the transmittance of total sunlight energy according to the Simpson rule (in the range 300-2100 nm); UV transmittance is also determined by the Simpson rule (in the range 300-400 nm), while IR transmittance is determined by the Simpson rule or by the calculation described above (in the range 800-2100 nm). The color is denoted by the dominant wavelength and color purity, and with respect to the C and / or D-65 light source. The purity of color and the dominant wavelength are determined by a standard light source C using a procedure using the x, y color chart. The foregoing are conventional markings known to those skilled in the art.

It is further true that the aforementioned features are thickness dependent. Therefore, the ranges of characteristic properties are given for glasses of 3.7 to 4.8 nm thickness. This does not necessarily mean that it is the thickness of a single sheet of glass. This merely means that if the total thickness of the glass in the structure were within this range, it would exhibit such properties. As automotive glass, glass sheets are sometimes 4 mm thick, but they often combine two 2 mm thick glass panes (for windscreens and other automotive glass). As another example, slightly thicker windscreens require two sheets of glass 2.3 mm thick. Of course, it is also known and frequently claimed to use about 0.8 mm plastic laminate (such as Butecite brand Du Pont) or vinyl laminate brand Sekisui Corp. Japan) having a refractive index similar to that of glass and having properties that can be designed in the sense of having their own UV absorbing curve]. In the case of glass panes having a thickness of 2 mm, the total thickness of the laminated windscreen is approximately 4.8 mm (although the total thickness of the glass is 4 mm). When the thickness of the glass panes is 2.3 mm, the overall thickness of the windscreen is approximately 5.1 mm (although the total thickness of the glass is 4.6 mm). All of these products are within the scope of the invention.

The invention will now be described with reference to certain embodiments and figures.

Figure 1 is a schematic plan view of a conventional melting and cleaning apparatus for use in the manufacture of the glasses of the present invention.

Figure 2 is a schematic side elevational view of a device with a conventional loading ditch in their presentations in Figure 1.

Bottles according to the invention may be prepared using conventional ingredients known in the art

EN 213 955 Β. These portions of the portions may be thawed and purified using standard equipment and procedures. Special equipment such as that described, inter alia, in U.S. Patent No. 4,792,536 is not necessary in this regard.

Figures 1 and 2 show schematically a typical (conventional) glass manufacturing apparatus, the various parts and operation of which are known to those skilled in the art. Such an apparatus can be used to produce the glasses of the invention. In this respect, Figure 1 shows the three successive zones of glass production. The liquid glass flows in the direction of the X arrows. Zone A is the melting zone. Zone B is commonly referred to as a tapering mid section. Zone C is the action zone. The glass is cleaned between the opening 4 and the tapering center portion B. This part of the equipment is usually designated by R. From the C operating zone, the liquid glass flows to a forming unit, where it solidifies to the desired shape. For the purposes of the present invention, as a forming operation, a floating operation is preferably carried out according to the known glass floating process to produce a flat glass. However, the invention is obviously not limited to this or any other glass making process. Embossed, hollow or other shapes can also be produced using the glass of the invention.

Fig. 2 is a side view of the apparatus of Fig. 1, except that it also shows a conventional loading hopper 7 and a dispensing device 9 of known design for feeding the unmelted portion into the melting zone. The melting zone A is heated in conventional manner by means of 4, orifice, openings 1, 2, 3 and 4 using a gas / air mixture. This produces a glass melt of T thickness. Typically, 11 "hot spots" are formed in the glass melt between and around the burner openings 3 and 4. Melting zone A is usually provided with 13 supernatant troughs upstream of zone B. The tapered center portion B is provided with a belt cooler 15 and mixers 17. In the practice of the present invention, it has been found that proper mixing and convection currents can be maintained by batch cooling 15 and proper operation of the mixture 17 in batch mode. Thus, the difficulty described in U.S. Patent No. 4,792,536, which is related to the penetration of heat due to the increasing amount of FeO under molten reducing conditions and is excellent in terms of flow and consistency of the glass melt. This, in turn, eliminates the need for the special melting and purifying device described in that patent.

In zone C, standard operations are performed with the glass melt to prepare the glass for the subsequent forming operation. From the C zone, the glass passes through the conventional 19 channels for forming.

The present invention does not require special atmospheric reducing conditions beyond the conventional operation of the apparatus described above. This is due to the reduction of iron to FeO by reducing and oxidizing components in the bath, such as carbon or crude sodium sulfate (Na₂SO4). In this context, adjusting the S03 content in the glass end product to a range of 0.20-0.25% by weight, in the rather narrow range of transmittances and color, as described above, has proved to be quite critical to the practice of the invention. This rather narrow SO3 content reflects the control of the oxidation state in the glass during its production, which is favorable for the desired properties.

Ingredients of portions useful in the practice of the invention include sand, calcined soda, dolomite, limestone, (crude) sodium sulfate, industrial grade iron oxide, and carbon (such as conventional glass-making coal). Iron oxide is a commonly used material that is substantially completely Fe₂SHE₃ form. A typical dose for use in the present invention for producing flat glass of approximately 2.3 mm thickness is as follows:

<td>material</td><td>kg / batch</td><td>crowd%</td>

<td>sand</td><td> 1099</td><td> 59,66</td>

<td>calcined soda</td><td> 344</td><td> 18,68</td>

<td>dolomite</td><td> 268</td><td> 14,57</td>

<td>limestone</td><td> 89,6</td><td> 4,86</td>

<td>crude sodium sulfate</td><td> 28,6</td><td> 1,55</td>

<td>Iron Oxide *</td><td> 11,44</td><td> 0,62</td>

<td>carbon</td><td> 1,4</td><td> 0,06</td>

100.00 * This iron oxide is the conventional iron (III) oxide which, according to the analysis, is the following (expressed as percentage by weight)

<td colspan="2">Components: 97.39% Fe₂SHE₃; 0.51% MgO; 0.11% CaO; 0.070% TiO₂; 1.13% SiO₂ and 1.24% A1₂SHE₃.</td>

<td colspan="2">The composition of this glass, written in the form of oxides,</td>

<td>air is as follows:</td><td></td>

<td>material</td><td>crowd%</td>

<td>So₂SHE</td><td> 13,75</td>

<td>MgO</td><td> 3,90</td>

<td>A1₂SHE₃</td><td> 0,15</td>

<td>salt₃</td><td> 0,23</td>

<td>K₂SHE</td><td> 0,04</td>

<td>CaO</td><td> 8,72</td>

<td>all iron Fe₂SHE₃ shape</td><td> 0,78</td>

<td>SiO₂</td><td> 72,41</td>

<td>FeO</td><td> 0,19</td>

Made with the thickness of 3.7-4.8mm discussed above, this glass is a

It is within the ranges provided by the present invention with respect to dominant wavelengths and color purity characteristics.

Other typical inserts useful for the invention, in particular for the manufacture of flat glass having a thickness of 2-4 mm, are as follows:

<td>material</td><td>kg / batch</td><td>crowd%</td>

<td>sand</td><td> 1099</td><td> 59,60</td>

<td>calcined soda</td><td> 344</td><td> 18,66</td>

<td>dolomite</td><td> 268</td><td> 14,56</td>

<td>limestone</td><td> 89,6</td><td> 4,86</td>

<td>crude sodium sulfate</td><td> 28,6</td><td> 1,55</td>

<td>Iron Oxide *</td><td> 13</td><td> 0,71</td>

<td>carbon</td><td> 1,4</td><td> 0,06</td>

100.00 * ferric oxide as described above

This portion is thawed and cleaned using conventional melting techniques in the apparatus described above, and then formed into a flat glass of 2 mm or 4 mm thickness by a conventional floating process to achieve the following characteristics:

material weight%

<td>ai₂She₃</td><td> 0,17</td>

<td>SALT₃</td><td> 0,21</td>

<td>K₂SHE</td><td> 0,04</td>

<td>CaO</td><td> 8,70</td>

<td>all iron Fe₂SHE₃ shape</td><td> 0,889</td>

<td>SiO₂</td><td> 72,41</td>

<td>FeO</td><td> 0,22.</td>

The above - described glass having the composition of FeO (Fe₂SHE₃ ratio to total iron content of 0.2475, expressed as% Fe (expressed as total iron content) (calculated by the method of U.S. Patent 5,077,133), 27% - converted to flat glass of various thicknesses, then to C light source we determined the dominant wavelength and color purity. Studies show the influence of thickness on color purity, and that thickness does not substantially affect the value of the dominant wavelength. The results of the tests are as follows:

<td></td><td>2 mm</td><td>4 mm</td>

<td>Light source (%)</td><td> 80,9</td><td> 71,1</td>

<td>UV Transmittance (%)</td><td> 53,1</td><td> 36,6</td>

<td>full of sunlight</td><td></td><td></td>

<td>transmittance (%)</td><td> 60,6</td><td> 42,9</td>

<td>IR Transmittance (%)</td><td> 47,0</td><td> 19,8</td>

<td>D-65 Light Source L</td><td> 92,65</td><td> 88,5</td>

<td>(mean value) a</td><td>R 35</td><td> -8,31</td>

<td>b</td><td> 0,89</td><td> 1,55</td>

<td>C light source</td><td></td><td></td>

<td>dominant wavelength</td><td> 501</td><td> 501</td>

<td>(mean) x</td><td> 0,3050</td><td> 0,2996</td>

<td>y</td><td> 0,3207</td><td> 0,3245</td>

<td>color purity (%)</td><td> 1,6</td><td> 3,3</td>

<td>FeO / total iron content</td><td> 0,2475</td><td> (24,75%)</td>

(Fe₂SHE₃ form)

Fe₂SHE₃ % reduction

FeO (relative to total iron content) * 27% * calculated by the method described in U.S. Patent 5,077,133.

Analysis of the glass showed the following composition expressed as oxides:

<td>material</td><td>crowd%</td>

<td>So₂SHE</td><td> 13,67</td>

<td>MgO</td><td> 3,91</td>

<td>thickness (Mm)</td><td>dominant wavelength (nm)</td><td>optical purity</td>

<td> 5,7*</td><td> 500,8</td><td> 4,6</td>

<td> 3,9</td><td> 501,5</td><td> 3,3</td>

<td> 4,0</td><td> 502,0</td><td> 3,3</td>

<td> 4,0</td><td> 501,5</td><td> 3,3</td>

<td> 4,0</td><td> 500,9</td><td> 3,3</td>

<td> 4,75</td><td> 502,5</td><td> 3,8</td>

<td> 4,2</td><td> 500,7</td><td> 3,5</td>

<td> 2,9</td><td> 500,5</td><td> 2,6</td>

<td> 4,5**</td><td> 501,2</td><td> 3,7</td>

<td> 2,8</td><td> 500,9</td><td> 2,3</td>

<td> 4,2***</td><td> 500,5</td><td> 3,5</td>

<td>4 i ***</td><td> 501,2</td><td> 3,3</td>

<td> 4 2***</td><td> 500,5</td><td> 3,5</td>

<td> 2,06</td><td> 501,2</td><td> 1,6</td>

<td> 2,15</td><td> 501,5</td><td> 1,7</td>

* oil with the same refractive index between two 2.85 mm thick glass panes, ** oil with the same refractive index between two glass panes with a thickness of 2.26 mm each, *** oil with the same refractive index between two glass panes of the same thickness.

The above two glasses, representing two preferred embodiments of the invention, illustrate the feasibility of the invention within a relatively narrow range of soda / limestone / silica type glasses, the preferred form of which is characterized by the following data:

EN 213 955% by weight of substance

<td>So₂SHE</td><td> 12-20</td>

<td>MgO</td><td> 3-5</td>

<td>A1₂SHE₃</td><td> 0,10-0,30</td>

<td>salt₃</td><td> 0,20-0,25</td>

<td>K₂SHE</td><td> 0-0,1</td>

<td>CaO</td><td> 8-10</td>

<td>all iron Fe₂SHE₃ shape</td><td> 0,7-0,95</td>

<td>SiO₂</td><td> 71,0-74,0</td>

<td>FeO</td><td> 0,20-0,24</td>

<td colspan="2">(preferably 0.20-0.24)</td>

<td>FeO / total iron content Fe₂SHE₃ shape Fe₂SHE₃ % reduction to FeO (U.S. Pat. No. 5,077,133)</td><td> 0,24-0,27</td>

<td>calculated by method)</td><td> 25-29%.</td>

<td colspan="2">These glasses are formulated in accordance with the present invention without the addition of CeO, TiO as UV-absorbing additives.₂, MoO₃ or V₂SHE₃ we would use additives - a</td>

<td>In the range of 3.7-4.8mm thickness, they show the following characteristics:</td><td>next wish-</td>

<td>quality</td><td>province</td>

<td>The light source (transmittance in the visible range)</td><td> &gt;70%</td>

<td>UV transmittance</td><td> &lt;38%</td>

<td>total transmittance for sunlight</td><td> &lt;44,5%</td>

<td>IR transmittance</td><td> 18-21%</td>

<td>C light source dominant wavelength</td><td>495-510 nm</td>

<td>D-65 Light Source L</td><td> 87-91%</td>

<td>the</td><td> -8±3</td>

<td>b</td><td> 2±2</td>

<td>color purity</td><td> 2-4%.</td>

Transmission density less than 38%, characterized by 0.20-0.25% by weight of SO₃and 0.19-0.24% by weight of divalent iron, expressed as FeO, with a total solar transmittance of less than 44.5% at 3.7 to 4.8 mm.

Second Glass according to Claim 1, characterized in that it consists of the following constituents, expressed as oxide:

<td>material</td><td>crowd%</td>

<td>So₂SHE</td><td> 12-20</td>

<td>MgO</td><td> 3-5</td>

<td>A1₂SHE₃</td><td> 0,10-0,30</td>

<td>SALT₃</td><td> 0,20-0,25</td>

<td>K₂SHE</td><td> 0-0,1</td>

<td>CaO</td><td> 8-10</td>

<td>all iron Fe₂SHE₃ shape</td><td> 0,7-0,95</td>

<td>SiO₂</td><td> 71,0-74,0</td>

<td>FeO</td><td> 0,20-0,24</td>

<td>% FeO reduction</td><td> 25-29%</td>

<td>FeO / total iron Fe₂SHE₃ shape</td><td> 0,24-0,27.</td>

<td colspan="2">Glass according to claim 2, characterized in that, at a thickness of 3.7 to 4.8 mm, it has the following properties:</td>

<td>quality</td><td>province</td>

<td>The light source (transmittance a</td><td></td>

<td>visible range)</td><td> &gt;70%</td>

<td>UV transmittance</td><td> &lt;38%</td>

<td>for sunlight</td><td></td>

<td>total transmittance</td><td> &lt;44,5%</td>

<td>IR transmittance</td><td> 18-21%</td>

<td>C light source</td><td></td>

<td>dominant wavelength</td><td>495-510 nm</td>

<td>D-65 Light Source L</td><td> 87-91%</td>

<td>the</td><td> -8±3</td>

<td>b</td><td> 2±2</td>

<td>color purity</td><td> 2-1%.</td>

From the above description, many other features, modifications and improvements will be apparent to those skilled in the art. These further features, modifications and improved versions are therefore to be considered as part of the invention, the scope of which is defined by the following claims.