Coloured glass batch composition for making window glass

The present invention relates to a colored glass composition intended for the production of glass useful in particular for installation in motor vehicles. In particular, the invention relates to a glass composition from which windscreens suitable for use as side rear windows and rear windows in motor vehicles can be manufactured.

Car designers propose to their clients glazed glass panes not only because of their aesthetic value, but also because of the functions that they can perform, in particular the improvement of visibility in critical lighting conditions and / or greater passenger comfort.

In addition, as the share of glazed areas increases every year in new models, the greenhouse effect is becoming an increasingly important factor that must be taken into account when designing vehicle air conditioning. One way to reduce this effect is the use of low-transmittance glazing in the near infrared area, in which the transmittance in the visible area, although lower than that of ordinary windshields, is acceptable to passengers.

United States Patent No. 4104 076 describes glasses based on iron, cobalt, chromium and / or uranium oxides, optionally also containing selenium. These glasses can be divided into two categories: brown glasses with a light transmission coefficient of 40 to 55%, and gray glasses, for which this ratio is from 35 to 45%. These glasses intended for the production of window glass in buildings have a conventional total energy transfer coefficient below 50% at a thickness of 6.2 mm.

In turn, European Patent Application No. 0 349 909 describes glasses in gray shade based on iron and cobalt oxides, to which at least 30 ppm of selenium has been added. These glasses have, at a thickness of 5.56 mm, a light transmission factor of 5 to 20% and a total energy transfer coefficient below 40%. For all glasses given as examples, the energy transfer coefficient is greater than the light transmission coefficient.

The essence of a colored glass composition according to the invention, containing basic oxide components in an amount of 64-75% by weight S1O2, 0-5% by weight Al2O3.0-5% by weight B2O3, 5-15% by weight CaO, 0-5% by weight MgO, 10- 18% by weight Na2O and 0-5% by weight K2O, and coloring components in an amount of 0.5-1.5% by weight Fe2O3 (total iron) with an equivalent FeO content of 16-55% by weight, 0.003-0.015% by weight CoO and 0-0.0025% by weight Se, consists in that it additionally contains 0.025-0.09% by weight of Ώ2Ο3 as a coloring agent.

The compositions of the invention may further contain other ingredients in very small amounts, derived from compounds added to the glass mixture to

170 583 to facilitate refining of glass. This is the case, for example, with SO3, resulting from the decomposition of the sulphate added to the mixture.

The glass according to the composition obtained according to the invention can be produced in conventional furnaces and formed into a continuous strip or ribbon, by a well-known method of pouring glass onto a molten tin bath.

The resulting glass has low excitation purity at C illuminator. It is usually below 15%, and most often below 12%. The glass transmission characteristics and the dominant wavelength at C illuminator depend on the oxyreductive state. In the composition of the invention, 16-55% by weight of the total amount of iron expressed as Fe2O3 may be in the form of ferrous oxide. Even more often, 20-40% by weight of the total amount of iron is in the form of ferrous oxide.

The glasses obtained from the composition of the invention show shades of gray and a more or less neutral color, which can vary from blue / green to green / yellow, passing through all intermediate shades, corresponding to the prevailing wavelengths at C illuminator, in the range from 490 to 560 nm . They also show the desired permeability characteristics, due to the use of iron and cobalt oxides as coloring components, optionally with the addition of selenium, while the latter component reduces the excitation purity.

Glasses obtained from the compositions of the present invention may contain only part of the specified coloring components or all coloring components, in proportions chosen depending on the required characteristics. Thus, glasses may contain as the coloring component iron and cobalt oxides, chromium and possibly selenium. The weight proportions of the coloring ingredients can be changed depending on the properties required.

The content of the coloring components in the glasses obtained from the compositions of the invention is defined by the following limits given in weight percent:

Fe2C> 3 (total amount of iron)

CaO

Cr2O3

Se

0,5-1,5% 0,003-0,015% 0,025-0,09% 0 -0,0025%

In order to make glasses, the basic glass composition used in the flat glass industry is used as the basic composition, adding to it the coloring components in proportions ensuring obtaining the required optical characteristics and appearance at a given thickness. The composition of the selected primary glass is as follows:

SiO2

Al2O3

CaO

MgO

Na 2 O

K2O

SO3

72,10%

0,74%

8,90%

3,79%

14,16%

0,11%

0,20%

Coloring components are added to this glass at the expense of silica.

The attached table gives a number of examples of glass compositions illustrating the invention. The content of coloring components is expressed in weight percent. The values ​​of the different characteristics of the glasses were determined using 3.85 mm thick glass. The level of purity obtained with some glasses is significant given the very low selenium content of these glasses. For all glasses, the ratio of Fe2O3 (total iron) to Se is greater than 200.

170 583

As noted earlier, the glass is obtained by casting in the form of a continuous tape. Sheets of glass obtained by cutting such a tape have a thickness in the range of 2 to 8 mm. Such glass sheets can be used, alone or in combination with a glass of sheet glass, to produce windshields that can be fitted to motor vehicles as rear side windows and a rear window.

Such windows can be adjusted by combining them in a set of glass with other glass forming the windscreen and front side windows. In this way, the glazing of a motor vehicle can be made of windows whose total light transmittance coefficient at A illuminator will gradually decrease for a given thickness from the windscreen to the rear window. Windows made of glass can be successfully used in the windshield of a car. And so the side windows of the rear windows, regardless of whether they are openable or fixed, can be made of glasses with a thickness of 3.85 mm with a total light transmittance factor of about 30-60%. They can be combined with a rear window made of glass, in which, for the same thickness, the factor of total light transmission at illuminator A is about 20-45%.

Table

<td>Example</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td><td> 6</td>

<td>Fe203 (total iron)</td><td> 0,90</td><td> 0,96</td><td> 1,27</td><td> 1,10</td><td> 0,99</td><td> 0,95</td>

<td>CaO</td><td> 0,0130</td><td> 0,0099</td><td> 0,0093</td><td> 0,0093</td><td> 0,0103</td><td> 0,0104</td>

<td>Se</td><td> 0,0010</td><td> 0,0005</td><td> -</td><td> -</td><td> 0,0003</td><td> -</td>

<td>Cr2O3</td><td> 0,0480</td><td> 0,0350</td><td> 0,0780</td><td> 0,0880</td><td> 0,0450</td><td> 0,0600</td>

<td>Redox system</td><td> 0,31</td><td> 0,35</td><td> 0,21</td><td> 0,29</td><td> 0,25</td><td> 0,35</td>

<td>TL (A) (%)</td><td> 32,5</td><td> 37,8</td><td> 40,0</td><td> 39,2</td><td> 30,2</td><td> 38,8</td>

<td>THESE(%)</td><td> 24,8</td><td> 24,7</td><td> 29,8</td><td> 16,5</td><td> 29,8</td><td> 24,7</td>

<td>ADj (C) (nm)</td><td> 501</td><td> 495</td><td> 497</td><td> 495</td><td> 502</td><td> 497</td>

<td>PC (%)</td><td> 5,61</td><td> 8,81</td><td> 11,5</td><td> 14,0</td><td> 6,49</td><td> 12,21</td>

UP Department of Publications. Circulation of 90 copies

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