JPH11106233A - Low fluorescent optical glass and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical glass reduced in the strength of fluorescent light generated by the excitation of UV light by controlling the amount of platinum contained in the glass to a specific value or less. SOLUTION: This low fluorescent optical glass does preferably substantially not contain arsenic and/or antimony, and contains platinum in an amount of <=10 ppm in the glass. The optical glass can be produced by melting raw materials in a crucible. Therein, the contamination of platinum from a gas phase and from the interface between a platinum crucible and a melted glass liquid is inhibited. The contamination of the platinum from the gas phase is dominantly caused by the gas of platinum oxide (PtO2 ), and can be reduced by lowering a melting temperature or by reducing the fraction of oxygen in a melting atmosphere by the introduction of an inactive gas or the like. The contamination of the platinum from the interface between a platinum tank and a melted glass is dominated by the contact area of the platinum with the melted glass liquid and by a melting temperature, and can be reduced by the improvement of the design of the platinum-melting tank, the melting of the glass at a low temperature, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical glass having a low fluorescence intensity due to ultraviolet excitation and particularly useful for an optical system such as a fluorescence microscope in which fluorescence from the optical glass is problematic, and a method for producing the same.

[0002]

2. Description of the Related Art In the fields of biology, medicine, etc., a specimen is irradiated with excitation light such as ultraviolet light to observe biological tissues, cells, bacteria, etc., and the fluorescence emitted from the observation object is observed and measured. The method is often used. In recent years, techniques for detecting weak fluorescence from very small amounts of bacteria and cells have been actively studied, and the optical glass used in the objective lens of a fluorescence microscope emits fluorescent light when excited by ultraviolet light. It has begun to be viewed as a problem. Therefore,
With respect to these optical glasses, there is an increasing demand for reducing the fluorescence intensity of the glass due to ultraviolet excitation, which causes noise during observation and measurement.

[0003] For optical glass with low fluorescence intensity,
Many studies have been made on the effect of the glass composition main component on the fluorescence characteristics due to ultraviolet excitation, and various reports and inventions on optical glass compositions having low fluorescence intensity have already been made.

[0004]

However, in the conventional optical glass or low-fluorescent optical glass, sufficient consideration has not been given to the instability of the fluorescence intensity due to the excitation of ultraviolet light due to the manufacturing method. It is hardly enough to stably supply an optical glass suitable for an optical system for observing weak fluorescence from a specimen due to the excitation light.

The present invention has been made in view of the above-mentioned problems of the optical glass. An object of the present invention is to provide an optical glass which has a low fluorescence intensity by ultraviolet excitation and is particularly useful for an optical system such as a fluorescence microscope in which fluorescence from the optical glass is a problem, and which can be stably supplied, and a method for manufacturing the same. is there.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that platinum contained as impurities in optical glass and arsenic and antimony contained as defoaming agents are excited by ultraviolet light. Have been found to deteriorate the fluorescent properties of the optical glass, and the present invention has been accomplished by limiting the content thereof.

[0007] Platinum, which is generally used as a crucible material for melting when producing high-quality optical glass, is mixed into the glass during melting of the optical glass composition, and has various optical properties, particularly, spectral transmittance. Influencing is already known. Investigations to improve the amount of platinum mixed in during melting and its condition have been made energetically and various reports have been made. The impact has not been studied. Further, the effects of arsenic and antimony, which are contained in the optical glass composition in trace amounts as defoaming agents, on the fluorescence properties of the optical glass due to ultraviolet excitation caused by platinum in the glass have not been sufficiently studied.
Therefore, impurities and trace components in these glasses have become unstable factors in the production of low-fluorescence optical glass.

That is, the present invention has a platinum content of 10 ppm or less in the glass, has a low fluorescence intensity upon excitation with ultraviolet light, and is particularly useful for an optical system such as a fluorescence microscope in which fluorescence from an optical glass is a problem. Provide an optical glass that can be supplied stably. Further, the optical glass in the present invention preferably contains substantially no arsenic as a defoaming agent, substantially no antimony, and further substantially no arsenic and antimony components. Having.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention according to the present application will be described in detail, but the present invention is not limited thereto. First, the reduction of the amount of platinum will be described. In the usual melting and production of optical glass, first use the corresponding oxide, carbonate, nitrate, metaphosphate, orthophosphoric acid, etc. as the raw materials of each component, weigh them in a desired ratio, and powder or liquid And mix well to make the mixture. This is put into, for example, a quartz crucible or a platinum crucible in a heated electric furnace, melted and refined, homogenized by stirring, cast into a pre-heated iron mold, and gradually cooled to produce. Alternatively, continuous production using a continuous dissolution apparatus is performed. To prevent the contamination of platinum, it is desirable to dissolve using a crucible material other than platinum, such as a quartz crucible, but to produce optically homogeneous high-quality optical glass, melting using a platinum crucible is required. It has become mainstream. In the glass production process using such platinum, the amount of platinum mixed into the glass in the vitrification reaction process requiring a high temperature and the fining process for removing bubbles in the molten glass is extremely large.

The mixing of platinum can be roughly classified into mixing from the gas phase and mixing from the interface between the platinum tank and the glass melt. In the case of the same glass composition, the following can be said. That is, contamination from the gas phase is caused by platinum oxide gas (Pt
O ₂ ) is dominant and can be reduced by lowering the melting temperature or reducing the oxygen partial pressure in the melting atmosphere. This can be realized by introducing an inert gas such as nitrogen or argon, or by dissolving at a low temperature. Contamination from the interface between the platinum tank and the glass melt is governed by the contact area of the platinum and the glass melt and the melting temperature, and the amount of contamination can be reduced by improving the design of the platinum melting tank and melting at a low temperature. Regarding low-temperature melting that is common to both, it is possible to realize platinum melting at a lower temperature by sufficiently promoting vitrification by coarse melting using a quartz crucible or the like.

The low-fluorescence optical glass according to the present invention can be realized by using these techniques to reduce the amount of platinum in the glass to 10 ppm or less. In addition, by analyzing the platinum mixed in the glass during melting, it can be easily controlled, and stable results can be obtained by reflecting the results in the manufacturing conditions. Next, arsenic and antimony, which are defoamers, will be described. Arsenic and antimony added in the composition to remove bubbles in the glass do not themselves fluoresce, but impart the energy of absorbed ultraviolet radiation to the platinum, increasing the fluorescence intensity from the platinum. Therefore, with respect to a glass composition in which it is difficult to reduce the incorporation of platinum in production, it is possible to reduce the fluorescence intensity by ultraviolet excitation even without adding these elements. In addition, even when the amount of platinum can be suppressed to 10 ppm or less, an effect of reducing the fluorescence intensity by ultraviolet excitation by not adding these elements is recognized. If the addition of these components is unavoidable to remove bubbles in the glass, antimony has a smaller contribution to the increase in the fluorescence intensity due to platinum than arsenic, so priority is given to not adding arsenic. You.

[0012]

EXAMPLES Next, examples according to the present invention will be described with reference to the content of arsenous acid.
Table 1 shows the content of antimony oxide, the content of platinum, and the fluorescence intensity.

[0013]

[Table 1]

In the examples, a P-Ta-Nb-based optical glass composition (nd = 1.62) disclosed in Japanese Patent Application No. 8-315146 was used. The glass sample to be subjected to each evaluation is weighed to a desired ratio using a corresponding oxide, carbonate, nitrate, metaphosphate, orthophosphoric acid, etc. as a raw material of each composition component, and sufficiently weighed in powder or liquid. Mix to form a blended raw material, put into a quartz crucible or platinum crucible in an electric furnace heated to, for example, 900-1350 ° C., melt and clarify, stir and homogenize and cast into a preheated iron mold. , And slowly manufactured. In order to change the amount of platinum in the glass, the temperature and time conditions during melting using a platinum crucible were changed to obtain a glass for evaluation. If necessary, a standard solution for atomic absorption analysis (P
(t = 1000 ppm) was added to the glass raw material to change the amount of platinum in the glass.

The amount of platinum in the glass was analyzed by the following method. First, a glass sample was acid-decomposed into a decomposition solution. Next, the platinum in the decomposition solution was extracted into an organic solvent, and the platinum in the extract was subjected to quantitative analysis using an atomic absorption spectrophotometer. To measure the fluorescence intensity, use the "Method for measuring the fluorescence of optical glass" (JOGIS03-19
75) ", the flint glass used as a standard sample was used as a reference. The optical glass prepared with the above working composition, the optical glass of the comparative example and the standard sample were 12 × 12
It was set to a size of × 20 mm, and three surfaces out of 12 × 20 mm were polished to obtain a fluorescence intensity measurement sample. Excitation light was incident on the opposing polished surfaces of these measurement samples, and the fluorescence emitted from the polished surface in a direction perpendicular to the excitation light was measured using a commercially available fluorescence spectrophotometer. The measurement sample was excited at a wavelength of 365 nm, a fluorescence spectrum in a wavelength range of 400 to 700 nm was measured, and the height of the highest fluorescence peak in this wavelength range was defined as the peak height of each glass. The evaluation was performed at a relative intensity ratio where 1/50 of the peak height of the standard sample was set to 1 because the fluorescence intensity of the standard sample excited by 365 nm was very large.

From the results shown in Table 1, it can be seen that in the optical glasses having the same composition, the fluorescence intensity by excitation with ultraviolet rays is controlled by reducing the amount of platinum contained. And
It can be seen that when the content is 10 ppm or less, the fluorescence intensity by ultraviolet excitation can be kept low. It is also clear that the effect is affected by arsenic or antimony contained as a defoaming agent. Therefore, by controlling or managing these contents, low-fluorescence optical glass can be stably dissolved and produced.

[0017]

According to the present invention, it is possible to provide an optical glass capable of being supplied stably, characterized in that the fluorescence intensity upon excitation by ultraviolet light is small, and a method for producing the same. Moreover, since the optical glass according to the present invention has a low fluorescence intensity due to ultraviolet excitation,
In particular, it is extremely useful for an optical system such as a fluorescence microscope which has a problem of fluorescence from optical glass.

Claims (9)

[Claims] 1. An optical glass wherein the amount of platinum contained in the glass is 10 ppm or less, and the intensity of fluorescence upon excitation by ultraviolet light is reduced. 2. An optical glass comprising substantially no arsenic and having a reduced fluorescence intensity upon excitation by ultraviolet light. 3. An optical glass comprising substantially no antimony and having a reduced fluorescence intensity upon excitation by ultraviolet light. (4) substantially free of arsenic and antimony;
An optical glass characterized in that the fluorescence intensity by ultraviolet excitation is reduced. 5. The optical glass according to claim 1, which does not substantially contain arsenic. 6. The method according to claim 1, wherein the antimony is not substantially contained.
The optical glass as described. 7. The optical glass according to claim 1, wherein the optical glass is substantially free of arsenic and antimony. 8. The optical glass according to claim 1, which is used for an optical system of a fluorescence microscope. 9. A method for producing an optical glass obtained by melting a raw material in a crucible, wherein mixing of platinum from the gas phase and mixing of platinum from the interface between the platinum crucible and the glass melt are prevented. Manufacturing method of optical glass.