Arsenic and antimony free, titanium oxide containing borosilicate glass and methods for the production thereof

Abstract

Titanium oxide containing borosilicate glasses, which have been produced without the use of arsenic and antimony compounds, are provided. An environmentally friendly refining method for providing titanium oxide containing borosilicate glass is also provided. The method includes using oxygen containing selenium compounds as refining agents to provide glasses with good transmittance values in the infrared range and show no disturbing discolorations. The glasses of the present disclosure are particularly suitable for the production of IR light conductors, cover glasses for photo sensors, and UV filters.

Claims

1. An arsenic- and antimony-free colorless borosilicate glass, consisting essentially of the following oxides, in % by weight, based on the total amount of glass: TABLE-US-00002 SiO.sub.2 30 to 85; B.sub.2O.sub.3 3 to 20; Al.sub.2O.sub.3 0 to 15; Na.sub.2O 3 to 15; K.sub.2O 3 to 15; ZnO 0 to 12; TiO.sub.2 0.5 to 10; CaO 0 to 0.1 at least one oxygen containing selenium compound 0.001 to 0.1; and a sulfate content of at least 150 ppm (m/m), wherein the oxygen containing selenium compound is selected from the group consisting of salts of selenious acid, salts of selenic acid, selenium dioxide (SeO.sub.2), selenium trioxide (SeO.sub.3), and mixtures thereof.

2. The glass according to claim 1, consisting essentially of the following oxides, in % by weight, based on the total amount of glass: TABLE-US-00003 SiO.sub.2 40 to 70; B.sub.2O.sub.3 3 to 15; Al.sub.2O.sub.3 0 to 10; Na.sub.2O 3 to 12; K.sub.2O 3 to 12; ZnO 0 to 8; TiO.sub.2 0.5 to 6; CaO 0 to 0.1; and at least one oxygen containing selenium compound 0.001 to 0.1.

3. The glass according to claim 1, consisting essentially of the following oxides, in % by weight, based on the total amount of glass: TABLE-US-00004 SiO.sub.2 30 to 85; B.sub.2O.sub.3 3 to 20; Al.sub.2O.sub.3 0 to 15; Na.sub.2O 3 to 15; K.sub.2O 3 to 15; ZnO 0 to 12; TiO.sub.2 0.5 to 10; CaO 0 to 0.1; and at least one oxygen containing selenium compound 0.001 to 0.1.

4. The glass according to claim 1, wherein the glass is usable as an IR light conductor, a cover glass for a photo sensor, or a filter glass.

5. The glass according to claim 1, wherein the sulfate content is not higher than 450 ppm (m/m).

6. An arsenic- and antimony-free borosilicate glass, consisting of the following oxides, in % by weight, based on the total amount of glass: TABLE-US-00005 SiO.sub.2 35 to 70; B.sub.2O.sub.3 3 to 17; Al.sub.2O.sub.3 0 to 12; Na.sub.2O 3 to 12; K.sub.2O 3 to 12; ZnO 0 to 10; TiO.sub.2 0.5 to 8; CaO 0 to 0.1; and at least one oxygen containing selenium compound 0.001 to 0.1, wherein the oxygen containing selenium compound is selected from the group consisting of salts of selenious acid, salts of selenic acid, selenium dioxide (SeO.sub.2), selenium trioxide (SeO.sub.3), and mixtures thereof.

7. An arsenic- and antimony-free colorless borosilicate glass, comprising the following oxides, in % by weight, based on the total amount of glass: ##STR00001## at least one oxygen containing selenium compound 0.001 to 0.1; and sulfate, wherein the oxygen containing selenium compound is selected from the group consisting of salts of selenious acid, salts of selenic acid, selenium dioxide (SeO.sub.2), selenium trioxide (SeO.sub.3), and mixtures thereof.

8. The glass according to claim 7, wherein the sulfate has a content that is not higher than 450 ppm (m/m).

9. The glass according to claim 7, wherein the sulfate has a content that is not higher than 350 ppm (m/m).

10. The glass according to claim 7, wherein the sulfate has a content that is not higher than 250 ppm (m/m).

11. The glass according to claim 7, wherein the sulfate has a content that is at least 150 ppm (m/m).

12. The glass according to claim 7, wherein the sulfate is selected from the group consisting of alkali sulfates, alkaline earth sulfates, and mixtures of alkali sulfates and alkaline earth sulfates.

13. The glass according to claim 7, wherein the sulfate is selected from the group consisting of Na.sub.2SO.sub.4, CaSO.sub.4, and mixtures of Na.sub.2SO.sub.4 and CaSO.sub.4.

14. The glass according to claim 7, wherein the sulfate comprises SO.sub.3 with a content that is at least 150 ppm (m/m) and not higher than 250 ppm (m/m).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The single FIGURE illustrates the transmittance spectra of the glasses of the comparative examples as well as the glass according to the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Comparative Example 1

(2) A TiO.sub.2 containing borosilicate glass was prepared using a standard refining process with antimony oxide and halides. The glass obtained in this manner had the following composition, in % by weight, based on the total amount of glass: SiO.sub.2 64.0; B.sub.2O.sub.3 8.3; Al.sub.2O.sub.3 4.0; Na.sub.2O 6.5; K.sub.2O 7.0; ZnO 5.5; TiO.sub.2 4.0 Sb.sub.2O.sub.3 0.6; and Cl.sup. 0.1.

(3) The glass was colorless and without any undesirable shades of color. The glass was tested with regard to its transmission properties in the range of visible light as well as near UV and IR region. The transmittance spectrum obtained in this test is shown in the single FIGURE.

Comparative Example 2

(4) A glass having the below mentioned composition was prepared by heating a mixture of the raw materials of the glass to about 1450 C. and subsequently keeping it at 1500 C. for about four hours. As a refining agent sulfate was used. Prior to the steps of cooling the glass melt and the subsequent shaping the glass was subjected to a homogenization step. The sand used had a proportion of 70 ppm Fe.sub.2O.sub.3 which was contained therein as an impurity. The glass obtained in this manner had with regard to its main components (undesirable impurities not considered) the following composition, in % by weight, based on the total amount of the glass: SiO.sub.2 64.1; B.sub.2O.sub.3 8.36; Al.sub.2O.sub.3 4.18; Na.sub.2O 6.32; K.sub.2O 6.85; ZnO 5.38; and TiO.sub.2 4.18.

(5) The glass was tested with regard to its transmission properties in the range of visible light as well as near UV and IR region. The transmittance spectrum obtained in this test is shown in the single FIGURE.

Example 1

According to the Present Disclosure

(6) A glass having the below mentioned composition was prepared by heating a mixture of the raw materials of the glass to about 1450 C. and subsequently keeping it at 1500 C. for about four hours. As a refining agent sodium selenite in combination with sulfate was used. Prior to steps of cooling and subsequent shaping the glass melt the glass was subjected to a homogenization step. The sand used had a proportion of 70 ppm Fe.sub.2O.sub.3 which was contained therein as an impurity. The glass obtained in this manner had with regard to its main components (undesirable impurities not considered) the following composition, in % by weight, based on the total amount of the glass: SiO.sub.2 64.1; B.sub.2O.sub.3 8.36; Al.sub.2O.sub.3 4.18; Na.sub.2O 6.32; K.sub.2O 6.85; ZnO 5.38; TiO.sub.2 4.18; and SeO.sub.2 0.025.

(7) The glass was completely colorless. With the naked eye in comparison to the glass which had the composition of comparative example 1 and had been subjected to the refining process described there no differences could be determined. The glass was tested with regard to its transmission properties in the range of visible light as well as near UV and IR region. The transmittance spectrum obtained in this test is shown in the single FIGURE.

(8) Surprisingly it was found that the transmission properties of the glass which had a composition according to the present disclosure and had been subjected to the refining process according to the present disclosure were as good as the transmission properties in the near IR of the comparison specimen.