GLASS MATERIAL

Abstract

Provided is a glass material having a high light transmittance in a short wavelength range and easily producible. A glass material contains, in terms of % by mole, 5 to less than 30% Pr.sub.2O.sub.3 and 0.1 to 95% B.sub.2O.sub.3.

Claims

1. A glass material containing, in terms of % by mole, 5 to less than 30% Pr.sub.2O.sub.3 and 0.1 to 95% B.sub.2O.sub.3.

2. The glass material according to claim 1, further containing, in terms of % by mole, 0 to 90% SiO.sub.2 and 0 to 90% P.sub.2O.sub.5.

3. The glass material according to claim 1, further containing, in terms of % by mole, 0 to 50% Al.sub.2O.sub.3.

4. The glass material according to claim 1, wherein B.sub.2O.sub.3+SiO.sub.2+P.sub.2O.sub.5 is 20% or more.

5. The glass material according to claim 1, having a light transmittance of 50% or more at a thickness of 1 mm and a wavelength of 355 nm.

6. The glass material according to claim 1, being used as a magneto-optical element.

7. The glass material according to claim 6, being used as a Faraday rotator.

Description

EXAMPLES

[0042] The present invention will be described below with reference to examples, but the present invention is not at all limited by the following examples.

[0043] Tables 1 to 3 show examples of the present invention and comparative examples.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 8 Pr.sub.2O.sub.3 6 11 16 21 19 25 29 26 B.sub.2O.sub.3 80 53 69 71 59 65 27 29 SiO.sub.2 4 15 10 11 5 26 25 Al.sub.2O.sub.3 10 20 5 8 11 5 16 15 P.sub.2O.sub.5 1 2 5 B.sub.2O.sub.3 + SiO.sub.2 + P.sub.2O.sub.5 84 69 79 71 70 70 55 59 Verdet Constant @355 nm (min/Oe .Math. cm) 0.255 0.675 1.115 1.371 1.266 1.579 1.668 1.549 Transmittance @355 nm (%) 71.1 69.8 68.8 66.6 65.3 61.2 59.6 55.3

TABLE-US-00002 TABLE 2 Comparative Example 1 2 3 Pr.sub.2O.sub.3 50 50 Tb.sub.2O.sub.3 25 B.sub.2O.sub.3 30 30 30 SiO.sub.2 25 Al.sub.2O.sub.3 20 20 20 p.sub.2O.sub.5 B.sub.2O.sub.3 + SiO.sub.2 + P.sub.2O.sub.5 30 30 55 Verdet Constant @355 nm (min/Oe .Math. cm) not 2.233 3.68 Transmittance @355 nm (%) vitrified 45.2 39.6

TABLE-US-00003 TABLE 3 Comparative Example Example 1 2 3 4 5 7 8 2 Tg (° C.) unmeasured unmeasured unmeasured 660 665 712 705 751 Tc (° C.) unmeasured unmeasured unmeasured 882 928 893 899 863 ΔT (° C.) unmeasured unmeasured unmeasured 222 263 181 194 112

[0044] Examples 1 to 8 and Comparative Examples 1 and 3 were produced in the following manner. First, raw material powders were weighed to give a pertinent glass composition shown in the tables and well mixed, thus forming a glass raw material. Next, approximately 100 g of glass raw material was put into a platinum crucible and stirred with a platinum stirring rod while melted at 1200° C. to 1500° C. in an electric furnace, thus clarifying and homogenizing it. Finally, the molten glass was formed into shape by pouring it onto a carbon plate, thus forming a glass material.

[0045] Comparative Example 2 was produced in the following manner. First, raw material powders were weighed to give a pertinent glass composition shown in the tables and well mixed, thus forming a glass raw material. Next, approximately 0.5 g of glass raw material was press-formed and sintered at 800° C. for six hours, thus producing a block of glass raw material. Finally, the block of glass raw material was placed in a containerless levitation apparatus, levitated using nitrogen gas, melted by irradiation with CO.sub.2 laser, and then cooled, thus producing a glass material.

[0046] The obtained glass materials were measured in terms of the Verdet constant at a wavelength of 355 nm and the light transmittance at a wavelength of 355 nm. Furthermore, as for Examples 1 to 8 and Comparative Example 2, the glass materials were measured in terms of glass transition temperature (Tg) and crystallization temperature (Tc). The measurements were conducted in the following manners.

[0047] The Verdet constant at a wavelength of 355 nm was measured with a Faraday rotation measurement device (manufactured by JASCO Corporation). Specifically, each obtained glass material was polished to have a thickness of 1 mm, the obtained piece was measured in terms of Faraday rotation angle at a wavelength of 355 nm in a magnetic field of 12.5 kOe, and the Verdet constant was then calculated.

[0048] The light transmittance at a wavelength of 355 nm was measured with a spectro-photometer (UV-3100 manufactured by Shimadzu Corporation). Specifically, each obtained glass material was polished to have a thickness of 1 mm, the obtained piece was measured in terms of light transmittance at a wavelength of 300 to 400 nm to obtain a light transmittance curve, and the light transmittance at a wavelength of 355 nm was read from the light transmittance curve. The light transmittance is the external light transmittance including reflection.

[0049] The glass transition temperature (Tg) and the crystallization temperature (Tc) were measured with a macro differential thermal analyzer. Specifically, in a chart obtained by measuring each glass material up to 1100° C. with the macro differential thermal analyzer, the value of a first inflection point was considered as the glass transition point and a strong exothermic peak was considered as the crystallization temperature. The difference between the glass transition point and the crystallization temperature was represented by ΔT and used as an index of ease of vitrification. A larger ΔT means a higher ease of vitrification.

[0050] As seen from Tables 1 and 2, the glass materials in Examples 1 to 8 exhibited a Verdet constant of 0.255 to 1.668 at a wavelength of 355 nm and their light transmittance at a wavelength of 355 nm was as high as more than 50%. On the other hand, the glass material in Comparative Example 1 was not vitrified by the molding method including melting in the platinum crucible and pouring of the melt onto the plate. The glass material in Comparative Example 2 was vitrified by the containerless levitation method, but exhibited a light transmittance as low as 45.2% at a wavelength of 355 nm, that is, its low light transmittance in a short wavelength range was low. The glass material in Comparative Example 3 exhibited a light transmittance as low as 39.6% at a wavelength of 355 nm, that is, its light transmittance in a short wavelength range was low.

[0051] Furthermore, as seen from Table 3, the glasses in Examples 4, 5, 7, and 8 exhibited ΔT as high as 181 to 263° C. In contrast, the glass in Comparative Example 2 exhibited ΔT as low as 112° C.

INDUSTRIAL APPLICABILITY

[0052] The glass material according to the present invention is suitable as a material for a magneto-optical element making up part of a magnetic device, such as an optical isolator, an optical circulator or a magnetic sensor, a material for a magnetic glass lens for use in a digital camera or the like, and a material for a glass sheet for use in a bandpass filter.