JPH062595B2 - How to suppress glass coloring and fluorescence - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for suppressing coloring / fluorescence of glass.

[Conventional technology]

Conventionally, for example, in silica glass used in an optical system utilizing ultraviolet light, coloring and fluorescence have been a problem due to point defects existing in the glass. For this reason, there has been adopted a method of heat-treating glass in a gas such as hydrogen or fluorine, or mixing fluoride or the like into a raw material to reduce absorption or fluorescence induced by defects.

Also, in other glasses, coloring was reduced by doping with antimony, arsenic, rare earth elements and the like.

[Problems to be Solved by the Invention]

In the method of heat-treating glass in a gas such as hydrogen or fluorine or mixing a fluoride or the like into the raw material, the additive gas is desorbed from the glass surface during the heat treatment process, resulting in non-uniform additive concentration. Further, the effect of reducing the coloring and fluorescence did not last for long-term use, and a recovery treatment such as heat treatment had to be performed. Also, antimony, arsenic,
In the method of doping rare earth or the like, the wavelength range that can be used is limited because of the intrinsic absorption and fluorescence of the dopant.

An object of the present invention is to solve the problems of these conventional techniques and to provide a method for suppressing glass coloring / fluorescence.

[Means for Solving the Problems]

The method for suppressing absorption and fluorescence of the present invention which achieves the above object,
While heating the glass under the conditions shown in the following formula (I),
It consists of pressing the glass with a pressure that causes distortion in the structure of the glass but does not break the bonds of the glass.

0.9 ≦ Tp / Tg ≦ 1.3 (I) However, in the formula (I), Tp represents the heating temperature (K) of the glass, and Tg represents the glass transition temperature (K) of the glass.

In the present invention, the glass is pressure-treated using a high-pressure apparatus such as an anvil type or a belt type or a hot isostatic pressing (HIP) apparatus.

The glass to be treated is preferably one that is hard to crystallize by heat treatment, such as optical glass and silica glass. Further, the shape of the glass to be treated is not particularly limited, and it is necessary to uniformly apply pressure from the surroundings so that the glass to be treated is not broken depending on the shape of the glass to be treated.

The pressure range is not so high that the glass bond is broken, and may be a pressure that causes strain in the glass structure. For example, in silica glass, the bond is broken at a pressure of 8 GPa or more, so it is desirable to perform the treatment at a pressure lower than this.

What is important in the present invention is that the temperature of the glass to be treated at the time of pressure treatment is near or above the glass transition point.

The temperature near the glass transition point or above the glass transition point is 0.9 ≦ Tp / Tg ≦ 1.3 when the treatment temperature is Tp (K) and the glass transition point is Tg (K). Is preferred. If Tp / Tg is smaller than 0.9,
The glass to be treated has a high viscosity, and a pressure difference is generated between the inside and the outside, so that a very long holding time is required to obtain a uniform glass to be treated. Furthermore, the temperature range that can be used stably becomes narrow. Further, if Tp / Tg is larger than 1.3, crystal precipitation may occur during pressure treatment and transparency may decrease, depending on the type of glass.

That is, in the present invention, the glass sample pressurized by the high-pressure device is heated to a temperature near or above the glass transition point and kept in this temperature range for a certain period of time.

Although the glass to be treated is distorted by the pressure treatment, the pressure effectively acts on the defective portion of the glass structure that causes coloring and fluorescence, and the coloring and fluorescence are suppressed. Although the treatment pressure depends on the type and temperature of the glass, the higher the treatment pressure is, the greater the effect of suppressing the coloring / absorption on the point defects is. However, on the other hand, the strain of the glass structure also becomes large, and the stability of the glass structure under light irradiation is lowered. Therefore, the pressure must actually be lower than the pressure at which the bond is broken. For example, in the case of silica glass, 1 to 2 GPa or less is preferable.

Further, the larger the glass, the longer the heat treatment time is required.
For example, with a 4 cm square block of silica glass, a uniform glass to be treated can be obtained by treatment at 1200 ° C. for 2 hours under a pressure of 100 MPa. The lower the processing temperature, the longer the holding time is required.

Coloring and fluorescence are suppressed in the glass treated according to the present invention. Furthermore, since the treatment temperature is high, the effect of the pressure treatment is not attenuated for long-term use at room temperature.

Examples of the present invention will be described below.

〔Example〕

A 2 × 2 × 0.4 cm quartz glass plate was subjected to hot isostatic pressing (HIP) treatment at 150 MPa and 1200 ° C. for 2 hours to obtain a homogeneous treated glass. Moreover, in order to show the effect of the present invention, untreated quartz glass of the same size was also prepared. Optically polished untreated glass and treated glass were irradiated with high-energy light for a certain period of time under the same conditions. First in untreated glass
The coloration shown in Figure 1 was measured. However, in the glass obtained by the present invention shown in FIG. 2B, coloring near 4 to 5 eV is suppressed by the effect of the present invention.

Further, the untreated glass and the glass obtained by the present invention were measured for fluorescence by the emission spectrum by photoexcitation of 5.0 eV. Results are shown in FIG. In the untreated quartz glass shown in 1 of FIG. 2, fluorescence was observed near 1.9 eV. However, the quartz glass treated with the present invention is 1.
The fluorescence of 9 eV is suppressed by more than half.

〔The invention's effect〕

As described above, according to the present invention, coloring of glass and fluorescence can be suppressed.

That is, because the viscosity of the treated glass is high, there is a difference in pressure between the inside and the outside of the glass, which requires a very long time to obtain a uniform glass to be treated, and a temperature range in which it can be used stably. It is possible to avoid the narrowing by setting Tp / Tg to 0.9 or more.

Also, by setting Tp / Tg to be 1.3 or less, it is possible to avoid precipitation of crystals or deterioration of transparency during the pressure treatment, depending on the type of glass.

Further, the pressure range is set so that the pressurization condition causes distortion in the glass structure but does not break the glass bond, thereby preventing the deterioration of the stability of the glass structure while increasing the effect of suppressing coloring and fluorescence. be able to.

Therefore, according to the present invention, it is possible to obtain a homogeneous glass-treated product in which the coloring and fluorescence are suppressed, and it is possible to eliminate the difference in the suppression effect depending on the location, which is impossible by the conventional fluorine doping method.

Further, the effect of the present invention is stable at room temperature and does not require heat treatment or the like for recovering the coloring / fluorescence suppressing effect as in the prior art.

[Brief description of drawings]

FIG. 1 is a diagram showing absorption spectra of quartz glass and untreated glass obtained by the present invention, and FIG.
5.Glass obtained by the present invention and untreated glass
It is a figure which shows the emission spectrum by optical excitation of 0 eV. 1 ... Untreated glass, 2 ... Glass obtained by the present invention.

Claims (1)

[Claims] 1. The glass is heated under the condition represented by the following formula (I), and the glass is pressed with a pressure that causes distortion in the structure of the glass but does not break the bond of the glass. A method for suppressing glass coloring and fluorescence. 0.9 ≦ Tp / Tg ≦ 1.3 (I) However, in the formula (I), Tp represents the heating temperature (K) of the glass, and Tg represents the glass transition temperature (K) of the glass.