Clear glass composition

p00001Clear glass composition

p00002This invention relates to glass compositions and the manufacturing processes thereof. More particularly, this invention relates to glass having a high light transmittance in the visible spectrum and / or rather neutral color. Such glass compositions are useful, for example, in architectural windows, printed glass applications, solar cells, and / or automobile windows.

Background of the invention

p00003Glass that is quite clear in color and highly transmissive to visible light (for example, at least 75% transmission, or even more preferably transmissible at least 80%) is sometimes desirable. One way to achieve such as glass is to use very pure glass-based materials (for example, substantially free of dyes, such as iron). However, base materials with a high degree of purity are expensive and therefore not always desirable and / or convenient. In other words, for example, the removal of iron from glass raw materials has certain practical and / or economic limits.

p00004WO 95/13993 describes a lead-free glass glass with high light transmittance, which is suitable for decoration by cutting, engraving and other decorating techniques. The glass suggested in this document contains a weight percentage of 50 to 75 silicon dioxide SiO2, 0.05 to 10 aluminum oxide Al2O3, 0.05 to 15 zirconium dioxide ZrO2, 0.001 to 2 , 5 hafnium dioxide etc.

p00005US 5,264,400 also refers to a glass for applications in vehicles comprising from 65 to 80% by weight of SiO2, from 0 to 5% by weight of Al2O3, from 0 to 5% by weight of B2O3, from 0 to 10% by weight of MgO, from 0 to 15% by weight of CaO, from 10 to 18% by weight of Na2O, from 0 to 5% by weight of K2O, from 5 to 15% by weight in total of MgO and CaO, of 10 to 20% by weight in total of Na2O and K2O, from 0.1 to 1% by weight of cerium oxide in terms of CeO2, from 0.2 to 0.6% by weight of iron oxide in terms of Fe2O3, from 0 to 0.005% by weight of CoO, from 0 to 0.01% by weight of NiO, from 0.2 to 3% in Er2O4 weight and from 0.0003 to 0.004% by weight of Se. The glass assumes bronze while exhibiting excellent absorption of ultraviolet and heat.

p00006JP H11-60269 (1999) discloses a colorless transparent ultraviolet absorbent glass. This glass is provided by incorporating 0.02 to 0.07% by weight of erbium oxide as a color loss agent in a soda-lime glass containing 0.3 to 0.6% by weight of cerium y: 0.05% by weight of iron oxide. The incorporation of cerium oxide provides this crystal with ultraviolet light absorption effect. Yellowish color due to iron oxide and cerium oxide can be corrected due to the pale pink color of erbium oxide, becoming practically colorless.

p00007As can be seen, raw glass materials (for example, silica, soda ash, dolomite and / or limestone) typically include certain impurities such as iron. The total amount of iron present herein is expressed in terms of Fe2O3 in accordance with standard practice. However, typically not, all iron is in that of Fe2O3. Instead, iron is normally present in both the ferrous state (Fe2 +; expressed herein as FeO, even though all iron in the ferrous state the crystal cannot be in the form of FeO) and the ferric state (Fe3 +) . Iron in the ferrous state (Fe2 +; FeO) is a greenish blue dye, while iron in the ferric state (Fe3 +) is a yellow-green dye. The blue-green ferrous iron dye (Fe2 +; FeO) is of particular concern when it comes to achieving a fairly clear or neutral colored glass, since as a strong dye a significant color is introduced into the glass. Although iron in the ferric state (Fe3 +) is also a dye, it is of less concern when it comes to achieving a fairly light colored glass since iron in the ferric state tends to be weaker as a dye than its ferrous state counterpart .

p00008In view of the above, it is evident that there is a need in the art for a new glass composition that allows a glass to have a fairly clear color and / or a high visible transmission, without resorting to extremely pure glass raw materials. (that is, iron free).

Summary of the Invention

p00009An object of this invention is to provide a glass that has a fairly clear color and / or high visible transmission.

p00010Certain exemplary embodiments of the invention fulfill one or more of the aforementioned objects and / or needs by providing a glass manufacturing process according to claim 11.

p00011Certain exemplary embodiments of this invention fulfill one or more of the aforementioned objects and / or needs by providing a glass according to claim 1.

Detailed description of certain embodiments of this invention

p00012Glasses according to different embodiments of this invention can be used, for example, in the automotive industry (for example, windshields, rear windows, side windows, etc.), in architectural applications, for patterned glass applications, applications of solar cells, and / or in other appropriate applications.

p00013Certain glasses according to this invention use flat glass of soda-lime-silica as their base composition / glass. In addition to the base composition / glass, a single coloring portion is provided in order to achieve a glass that is quite clear in color and / or has a high visible transmission. An example sosacal-silica base glass according to certain embodiments of this invention, on a weight percent basis, includes the following basic ingredients:

TABLE 1: BASE GLASS EXAMPLE

p00015Ingredient% by weight

p00016SiO2 67 to 5%

p00017Na2O 10 to 20%

p00018CaO 5 to 15%

p000190-5% MgO

p00020Al2O3 0a5%

p00021K2O 0a5%

p00022BaO 0 to 1%

p00023Other minor ingredients, including several conventional refining aids, such as SO3, Carbon, and the like can also be included in the base glass. In certain embodiments, for example, herein, glass may be made from the raw materials of silica sand, soda ash, dolomite, limestone, with the use of salt cake (SO3) and / or Epsom salts (for example, approximately a 1: 1 combination of the two) as refining agents. Preferably, soda-lime-silica-based glass herein includes about 10 to 15% Na2O by weight and from about 6 to 12% CaO. While a soda-lime-silica base glass as set forth above is preferred in certain embodiments of this invention, this invention is not as limited. Therefore, other base glasses (for example, borosilicate glass) can be used instead in alternative embodiments of the present invention.

p00024In addition to the base glass (for example, see Table 1 above), in the manufacture of glass according to the present invention the glass batch includes materials (including dyes and / or oxidizers) that make the resulting glass quite neutral in color and / or have a high visible light transmission. These materials may be present in either the raw materials (for example, small amounts of iron), or may be added to the base glass materials in the batch (for example, cerium, erbium, etc.) In certain forms of Preferred embodiments, the resulting glass has visible transmission of at least 75%, more preferably at least 80%, and most preferably at least 85%.

p00025In certain embodiments of this invention, in addition to the base glass, the glass batch includes materials as set forth in Table 2 below (in terms of percentage by weight of the total glass composition):

p00026Table 2: EXAMPLE GLASS LOT OF THE FIRST FORM OF EMBODIMENT

<dl><dt>Ingredient </dt><dd>General (% by weight) Most preferred Most preferred </dd></dl>

<dl><dt>Total iron (expressed as Fe2O3): </dt><dd>0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.15% </dd></dl>

<dl><dt>erbium oxide (for example, Er2O3): </dt><dd>0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.13% </dd></dl>

<dl><dt>cerium oxide (for example, CeO2): </dt><dd>0.005 to 0.30% 0.01-0.18% 0.03 to 0.12% </dd></dl>

p00027The batch melts and glass is formed by the known flotation process. Optionally, in exemplary embodiments of the invention, neodymium oxide (eg, Nd2O3) can be added to the batch, as exemplified below in Table 3 according to a second exemplary embodiment of the present invention (the material listed in Table 3 is added to the base glass described above).

TABLE 3: EXAMPLE GLASS LOTS OF THE SECOND FORM OF EMBODIMENT

p00029General Ingredient (% by weight) Most preferred Most preferred

p00030Total iron (expressed as Fe2O3): 0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.15%

p00031Erbium oxide (for example, Er2O3): 0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.13%

<dl><dt>Ingredient </dt><dd>General (% by weight) Most preferred Most preferred </dd></dl>

<dl><dt>cerium oxide (CeO2): </dt><dd>0.005 to 0.30% 0.01 to 0.18% 0.03 to 0.12% </dd></dl>

<dl><dt>Neodymium oxide (e.g., Nd2O3): </dt><dd>0.005 to 0.15% 0.010 to 0.050% 0.010 to 0.030% </dd></dl>

p00032In certain embodiments of the present invention (for example, first and / or second above embodiments), the dye portion is substantially free of other dyes (other than potentially trace amounts). However, it should be appreciated that the amounts of other materials (for example, refining aids, melting aids, dyes and / or impurities) may be present in the glass in certain other embodiments of this invention without removing the (from the) purpose (s) and / or objective (s) of the present invention. It is noted that while the presence of cerium oxide is preferred in many embodiments of this invention, it is not required in all embodiments. In addition, it is possible to use little or no Er in certain embodiments of this invention.

p00033In comparative embodiments not in accordance with this invention, cerium oxide (eg, CeO2) can be replaced by NaNO3 in the glass batch; see the third, fourth and fifth embodiments below (the batch materials in Tables 4 to 6 below are added to the raw base glass materials described above).

p00034TABLE 4: GLASS BATCH of Comparative Example

p00035General Ingredient (% by weight) Most preferred Most preferred

p00036Total iron (expressed as Fe2O3): 0.01 to 0.30 0.02% to 0.20% 0.03 to 0.15%

p00037Erbium oxide (for example, Er2O3): 0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.13%

p00038sodium nitrate (NaNO3): 0.1 to 2.0% 0.2 to 1.5% 0.3 to 1.2%

p00039TABLE 5: GLASS BATCH of Comparative Example

p00040General Ingredient (% by weight) Most preferred Most preferred

p00041Total iron (expressed as Fe2O3): 0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.15%

p00042Erbium oxide (for example, Er2O3): 0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.13%

p00043sodium nitrate (NaNO3): 0.1 to 2.0% 0.2 to 1.5% 0.3 to 1.2%

p00044neodymium oxide (e.g., Nd2O3): 0.005 to 0.15% 0.010 to 0.050% 0.010 to 0.030%

TABLE 6: EXAMPLE GLASS LOT OF THE THIRD FORM OF EMBODIMENT

p00046General Ingredient (% by weight) Most preferred Most preferred

p00047Total iron (expressed as Fe2O3): 0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.15%

p00048Erbium oxide (for example, Er2O3): 0.01 to 0.30% 0.02 to 0.20% 0.03 to 0.13%

p00049cerium oxide (for example, CeO2): 0 to 0.30% 0 to 0.18% 0 to 0.12%

p00050sodium nitrate (NaNO3): 0 to 2.0% 0.2 to 1.5% 0.3 to 1.2%

p00051In the third embodiment (see Table 6), cerium oxide (for example, CeO2) and sodium nitrate (NaNO3) can be combined as oxidants, in order to cause the effects of equations (1) and (2 ) then. Accordingly, both cerium oxide and / or sodium nitrate can be provided in this embodiment.

p00052It is noted that in certain embodiments of the present specification, the amount of total iron may even be less than 0.10%.

p00053The above batches are melted and the flotation process is used to form glass (for example, silica lime soda glass) in a known manner.

p00054The total amount of iron present in the glass batch and in the resulting glass, that is, in the coloring portion thereof, is expressed herein in terms of Fe2O3 in accordance with standard practice. This, however, does not imply that all iron is actually in the form of Fe2O3 (see previous analysis in this regard). Also, the amount of iron in the ferrous state (Fe2 +) is given herein as FeO, although all iron in the ferrous state in the glass or glass batch cannot be in the form of FeO. As mentioned earlier, iron in the ferrous state (Fe2 +; FeO) is a greenish blue dye, while iron in the ferric state (Fe3 +) is a yellow-green dye, and the blue-green ferrous iron dye is particularly interest, since as a strong dye that introduces significant color in the glass that sometimes may not be desirable when it comes to achieving a neutral or clear color.

p00055According to exemplary embodiments of this invention, the presence of cerium oxide (eg, CeO2) as an oxidant in the glass batch acts as a chemical bleach since during melting the glass batch causes iron in the ferrous state (Fe2 +; FeO) it is oxidized to the ferric state (Fe3 +) as illustrated by the following equation:

p00056Fe2 ++ Ce4 + = Fe3 ++ Ce3 + (1)

p00057Equation (1) shows that the presence of cerium oxide in the glass batch causes an amount of the strong blue-green ferrous iron dye (Fe2 +; FeO) to oxidize to the weakest ferric iron dye (Fe3 +) in color yellow-green during the melting of glass (note: some iron in the ferrous state will generally remain in the resulting glass, as can some Ce4 + potentially). Consequently, an important part of the CeO2 added to the original glass batch before melting is transformed during melting into Ce2O3 which is present in the resulting glass. The above-mentioned oxidation of iron tends to reduce the coloration of the glass, and does not significantly decrease the visible light transmission of the resulting glass (in certain cases, this may even cause the visible transmission to increase). However, those skilled in the art will appreciate that there is still significant coloration in the glass due to ferric iron if only iron and cerium oxide are provided. In other words, it has been found that the addition of cerium oxide to glass containing only iron is not sufficient to achieve a desired color quite clear or neutral.

p00058It is noted that, as Fe2O3, the phrase "cerium oxide" as used herein, refers to the total cerium oxide (ie, including cerium oxide in both the state of Ce4 + and Ce3 +).

p00059As mentioned above, cerium oxide can be supplemented with sodium nitrate in exemplary embodiments of this invention. In embodiments in which sodium nitrate (NaNO3) is supplied to glass (for example, see Table 6 above), it works in a similar way to cerium oxide, as shown in the following equation (but have consider the potential of oxygen bubbles). In particular, such as cerium oxide, sodium nitrate can be added to the glass batch as an oxidant to cause an amount of the strong blue-green ferrous iron dye (Fe2 +; FeO) to oxidize to the weakest yellow dye. Ferric iron green (Fe3 +) during glass melting (note: some iron in the ferrous state will generally remain in the resulting glass):

p00060Fe2 ++ NO3 = Fe3 ++ NO3 + ½ O2 (2)

p00061Those skilled in the art will recognize that most of the nitrate (for example, sodium nitrate) that is added to the glass batch decomposes during melting so that something burns like NOx while other parts of it end up in the glass as Na2O. While sodium nitrate (NaNO3) is used as an oxidant in Tables 4-6 above, the present invention is not so limited. For example, KNO3 can be used instead of or in addition to sodium nitrate in alternative embodiments of the present invention.

p00062In order to compensate for the color caused by ferric iron resulting from the addition of cerium oxide and / or sodium nitrate, it has been found that the addition of erbium oxide (eg, Er2O3 or any other suitable stoichiometric form da) and / or neodymium oxide (eg, Nd2O3 in any suitable stoichiometric shape) makes the resulting glass color lighter (i.e., more neutral as the color value (s) a * and / or * move towards 0 neutral). Erbium oxide acts as a pink dye, while neodymium oxide acts as a purple dye. One or both of Er and / or Nd apparently acts to physically compensate for the iron color, making the color of the glass more neutral than is desirable in certain embodiments of this invention, while allowing the glass to still maintain visible transmission high.

p00063It will be appreciated by those skilled in the art that the addition of cerium oxide and / or sodium nitrate (see equations (1) and (2) above) results in a glass with a lower "redox" value (ie, less iron in the ferrous state FeO). In this regard, the proportion of total iron in the ferrous state (FeO) is used to determine the redox state of the glass, and redox is expressed as the ratio of FeO / Fe2O3, which is the percentage by weight (%) of iron in Ferrous state (FeO) divided by the percentage by weight (%) of total iron (expressed as Fe2O3) in the resulting glass. Due to the presence of cerium oxide and / or sodium nitrate, the redox of the glass according to exemplary embodiments of this invention is quite low; in particular, glass according to exemplary embodiments of this invention may have a redox value (ie, FeO / Fe2O3) of less than or equal to 0.25, more preferably less than or equal to 0.20, and even more preferably less than or equal to 0.15, and most preferably less than or equal to 0.13. In addition, resulting glass according to exemplary embodiments of this invention may include iron in the ferrous state (FeO) in an amount (% by weight) of less than or equal to 0.020%, more preferably less than or equal to 0.015 %, and more preferably less than or equal to 0.011%.

p00064It is noted that the glass according to the present invention is often made through the known flotation process in which a tin bath is used. Thus, it will be appreciated by those skilled in the art that, as a result of forming molten tin glass in certain exemplary embodiments, small amounts of tin or tin oxide can migrate to the surface areas of the glass on the face I was in contact with

p00065the tin bath during manufacturing (i.e. typically float glass may have a tin oxide concentration of 0.05% or more (by weight) in the first few microns below the surface that was in contact with tin bath)

p00066In view of the foregoing, glass according to exemplary embodiments of this invention achieves a neutral or substantially clear color and / or high visible transmission. In certain embodiments, resulting glass according to exemplary embodiments of this invention can be characterized by one or more of the following optical or color characteristics when measured at a thickness of about 1 mm to 6 mm (more preferably a thickness of about 5.5 to 5.6 mm (0.219 inches), which is a non-limiting thickness used for reference purposes only) (Lta is% of visible transmission):

TABLE 7: CHARACTERISTICS OF SOME EXEMPLARY EMBODIMENTS

p00068General Feature Most preferred Most preferred

p00069Lta (III. C, 2 gr.):> = 75%> = 80%> = 85%

p00070% UV (III. C. 2 gr.): &lt;= 85% &lt;= 80% &lt;= 75%

p00071% TS (III. C. 2 gr.): &lt;; = 90% &lt;= 87% &lt;= 85%

p00072% FeO (% by weight): &lt;= 0.020% &lt;= 0.015% &lt;= 0.011%

p00073L * (III.D65, 10 gr.): 90 to 100 n / an / a

p00074a * (III. D65, 10 gr.): -1.0 to +1.0 -0.60 to +0.60 -0.30 to +0.50

p00075b * (III. D65, 10 gr.): -1.0 to +1.5 -0.70 to +1.0 -0.30 to +0.40

p00076As can be seen in Table 7 above, glass of certain embodiments of this invention achieve desired characteristics of fairly clear color and / or high visible transmission, while not requiring the removal of iron from the glass composition. This can be achieved by providing the combinations of unique materials described herein.

EXAMPLES

p00077Example glass of this invention can be prepared from batch ingredients by well known glass melting and refining techniques. The following approximate batch of base glass was used for the Examples herein (note: the following ingredients in the listed batch add up to 100% by weight once the oxides thereof are justified; therefore they do not need to add up to one hundred as raw material):

p00078Batch ingredient for Base Glass Parts by weight

p00079sand 71.5

p00080soda ash 23.7

p00081dolomite 18.32

p00082limestone 6.1

p00083Epsom salt 0.9

p00084In addition to the above base glass batch materials, the materials indicated below were present in the original batch (s) for the Examples (compound amounts given% by weight). It is noted that Examples 1 to 5 and 7 to 8 are in accordance with examples of different embodiments of this invention, while CA, CB EX-6 and CC are comparative examples provided for comparison purposes. In particular, Comparative Example A (CA) should be compared with Examples 1 to 3 of the present invention, since they all have the same amount of total iron, while Comparative Example B (CB) must be compared with Examples 4 to 5 of the present invention, and they all have the same total amount of iron, and Comparative Example C (CC) should be compared with Examples 7 to 8 of the present invention, since they all have the same amount of iron total.

p00085Batch materials in Examples 1 to 8 (IN ADDITION TO THE BASE LOT)

<dl><dt>Compound </dt><dd>CA 1 Ex. Ex 2 Ex 3 CB Ex.4 Ex 5 DC Comp. Ex 6 Ex 7 Ex 8 </dd></dl>

<dl><dt>Fe2O3: </dt><dd> 0,102 0,102 0,102 0,102 0,09 0,09 0,09 0,033 0,033 0,033 0,033 </dd></dl>

<dl><dt>Er2O3: </dt><dd> 0 0,06 0,08 0,11 0 0,086 0,08 0 0 0,10 0,09 </dd></dl>

<dl><dt>CeO2: </dt><dd> 0 0,035 0,035 0,035 0 0,066 0,06 0 0,08 0,10 0,09 </dd></dl>

<dl><dt>Nd2O3: </dt><dd> 0 0 0 0 0 0 0 0,02 0,02 0,03 0,025 </dd></dl>

p00086The batches were melted and glass was formed using known techniques. Solar characteristics for the resulting Example glasses were as follows in the following table, with the measurements taken after the melting and formation of the glass. It is observed that Lta (% of visible transmission),% of UV transmission, and% TS were measured using III. C, observer 2 degrees, while the transmissive color coordinates L *, a * and b * (CIE) were measured using III. D65, 10 degree observer. On the other hand, Dom. A stands for dominant wavelength, and Pe means excitation purity. All glass samples were approximately 0.219 inches thick (about 5.5 to 5.6 mm thick).

p00087CHARACTERISTICS OF GLASSES Examples 1 to 8

<dl><dt>Characteristic </dt><dd>AC Ex. 1 Ex 2 Ex. 3 CB Ex 4 Ex 5 DC Comp. Ex 6 Ex 7 Ex 8 </dd></dl>

<dl><dt>Lta% </dt><dd> 88,4 88,0 87,7 86,2 88,8 89,7 89,4 88,0 89,6 89,0 88,5 </dd></dl>

<dl><dt>% UV </dt><dd> 74,5 68,9 74,8 73,6 76,9 65,9 66,4 76,2 65,9 63,2 63,6 </dd></dl>

<dl><dt>% TS </dt><dd> 79,6 83,1 81,3 79,8 79,2 84,5 84,0 79,5 84,9 86,0 84,9 </dd></dl>

<dl><dt>FeO (% by weight) </dt><dd> ,0232 ,011 ,0177 ,0191 ,0254 ,009 ,0104 ,023 ,0079 ,0042 ,0065 </dd></dl>

<dl><dt>Dom. A (nm) </dt><dd> 498 562 487 487 493 573 564 492 537 566 581 </dd></dl>

<dl><dt>Pe% </dt><dd> 0,64 0,37 0,24 0,22 0,9 0,48 0,27 0,96 0,25 0,07 0,07 </dd></dl>

<dl><dt>L * </dt><dd> 95,5 95,2 95,1 94,4 95,7 95,8 95,7 93,6 95,9 95,6 95,4 </dd></dl>

<dl><dt>to* </dt><dd> -1,54 -0,34 -0,18 -0,15 -1,49 -0,1 -0,21 -1,41 -0,72 0,09 -0,05 </dd></dl>

<dl><dt>b * </dt><dd> 0,24 0,51 -0,12 -0,11 -0,15 0,58 0,39 -0,29 0,47 0,11 0,14 </dd></dl>

p00088It can be seen from the foregoing that glasses according to different embodiments of the present invention (Examples 1 to 5 and 7 to 8) have one or more of the following example advantages over comparative examples (CA, CB and CC): (i) glasses according to Examples 1 to 5 and 7 to 8 had a more neutral color than the respective Comparative Examples CA, CB and CC (it is noted that the comparative examples do not include erbium or cerium), (ii) the glasses according to Examples 1 to 5 7 to 8 had less FeO (i.e. less iron in a ferrous state) than the respective examples (CA, CB and CC), although the respective examples and comparative examples for comparison therewith had the same amount of total iron; and / or (iii) the glasses according to Examples 1 to 5 and 7 to 8 had a lower excitation purity (Pe) than the respective Comparative Examples CA, CB and CC. High visible transmission (Lta) was maintained in Examples 1 to 5 and 7 to 8.

p00089With respect to color, it can be observed for example that Example 1 was characterized by a color a * much more neutral than CA (ie, a * was closer to zero in Example 1 than in CA); compare a * = -0.34 of Example 1 with an a * of Comparative Example A (CA). Similarly, it can be seen for example that Example 4 had a color a * much more neutral than CB (ie, a * was closer to zero in Example 4 than in CB); compare a * = -0.1 of Example 4 with a * = 1.49 of Comparative Example B (CB). In a similar manner, it can be seen for example that Example 7 had a color a * much more neutral than CC (ie, a * closer to zero in Example 7 than in CC); compare a * = 0.09 of Example 7 with an a * = -1.41 of Comparative Example C (CC). The improved neutral color of exemplary embodiments of this invention is the result of the unique material combinations used in glasses according to exemplary embodiments of this invention.

p00090Certain examples according to other embodiments of this invention are set forth below (the same base glass above for other examples), where examples 10 to 11 are comparative using sodium nitrate and instead of or in addition to cerium. It is noted that Examples 9 to 11 differed from Examples 1 to 8 above in that for Examples 9 to 11 each glass sample was only 4.1 mm (0.161 inches) thick.

Batch materials in Examples 9 to 11 (IN ADDITION TO THE BASE LOT)

p00091Compound Ex. 9 Comp. Ex. 10 Comp. Ex.11

p00092Fe2O3: 0.054 0.055 0.048

p00093Er2O3: 0.06 0 0

p00094CeO2: 0.06 0.09 0

p00095NaNO3: 0 0.5 0.78

p00096Nd2O3: 00 0

p00097The above lots were melted and glass formed using known techniques. Solar characteristics for the resulting Example glasses were as follows in the following table, with the measurements taken after the melting and formation of the glass.

CHARACTERISTICS OF THE GLASSES OF EXAMPLES 9 to 11

p00098Feature Ex. 9 Comp. Ex. 10 Comp. Ex 11

p00099Lta% 90.43 91.32 90.75

p00100UV% 71.81 72.63 77.73

p00101% TS 87.78 90.54 88.14

p00102FeO (% by weight) 0.0031 0.0007 0.0048

p00103Dom. A (nm) 578 570 566

p00104Pe% 0.63 0.41 0.53

p00105L * 96.11 96.52 96.29

p00106a * 0.09 -0.18 -0.36

p00107b * 0.67 0.5 0.67

p00108As in the previous examples, it can be seen that Examples 9 to 11 have an improved color (more neutral) and high visible transmission relative to the comparative examples, although of smaller thickness. It is observed that the

p001095 Examples 9 to 11 used a smaller amount of total iron than Examples 1 to 8. Example illustrates that according to exemplary embodiments of this invention, the glass may even have a visible transmission of at least 90% when it has a thickness reference of approximately 4.1 mm (0.161 inches.

p00110The terms and characteristics of ultraviolet light transmittance (% UV), dominant wavelength and

p0011110 excitation purity (ie,% of "purity", or Pe) are in terms of the technique well understood, as are their measurement techniques. Such terms are used herein, in accordance with their well-known meaning, for example, see US Patent No. 5,308,805. In particular, ultraviolet transmittance (% UV) is measured herein using Parry Moon air mass = 2 (300 to 400 nm inclusive, integrated using Simpson's rule with 10 nm intervals). Dominant Wavelength (DW) is calculated and conventionally measured from

p00112fifteen agreement with the aforementioned publication CIE 15.2 (1986) and ASTM: E 308-90. The term "dominant wavelength" includes both the actual measured wavelength and, where applicable, its calculated complement. Excitation purity (Pe or% "purity") is measured conventionally in accordance with CIE Publication 15.2 (1986) and ASTM: E 308-90.

p00113twenty Once the previous disclosure has been given, many other features, modifications and improvements will be apparent to the person skilled in the art. Said characteristics, modifications and improvements are therefore considered a part of this invention, the scope of which must be determined by the following claims: