JP2955463B2 - Silica glass having good ultraviolet absorption and high visible light transmission and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bulb material for an illumination lamp, and a silica glass useful as a bulb material and a protective tube material for a laser excitation lamp.

[0002]

2. Description of the Related Art Conventionally, silica glass is not only excellent in light transmittance, but also excellent in chemical durability, rapid heat quenching resistance, and gas encapsulation.
It has been used as a bulb material for a solid laser excitation lamp and the like (hereinafter referred to as a bulb material). However, due to its high light transmittance, ultraviolet light generated by the light source decomposes oxygen in the air to generate ozone harmful to the human body, or causes ultraviolet damage to the laser element, thereby lowering the laser oscillation efficiency. However, there is a drawback that the silica glass itself may be damaged by ultraviolet rays and the strength of the bulb material may be reduced or solarization may occur. In order to solve this drawback, a method for producing silica glass doped with a transition metal element that absorbs ultraviolet light has been proposed, for example, in Japanese Patent Publication No. 46-42114. However, in this method for producing silica glass, melting of glass raw materials,
During molding and processing, the transition metal element compound impregnated in the melting vessel and molding jig is vaporized and the transition metal element is diffused in the silica glass. No glass was obtained.
Therefore, a method for producing a UV-absorbing silica glass in which a transition metal element compound is mixed with a silica raw material and the mixture is melted and vitrified has been generally studied. Only a silica glass in which a transition metal element is uniformly dispersed can be obtained. In addition, each silica glass absorbs ultraviolet rays with higher efficiency as the dope concentration increases, but has a disadvantage that the transmittance of visible light decreases and the ultraviolet rays are easily damaged. In particular, the tendency is that the transition metal element concentration is about 1,0.
When it exceeded 00 wtppm, it was remarkable.

[0003]

In view of the current situation,
The present inventors have conducted intensive studies on the development of silica glass which has good ultraviolet absorption and is hardly subjected to ultraviolet damage, and has high visible light transmittance. As a result, the transition metal element is doped in the silica glass. In doing so, it has been found that the above-mentioned disadvantage can be solved by coexisting an aluminum compound and adding water so that the OH group concentration is in a specific range. Furthermore, it has been found that when the above-mentioned silica glass is subjected to a specific virtual temperature setting process and the virtual temperature is set in a specific range, ultraviolet damage is further reduced, and the strength of the silica glass is reduced and the occurrence of solarization is reduced. . The present invention has been completed based on these findings. That is,

[0004] It is an object of the present invention to provide a silica glass for a valve material having less ultraviolet damage.

It is an object of the present invention to provide a silica glass which has less solarization and lower strength even when irradiated with ultraviolet rays for a long time.

[0006] The present invention is also applicable to ultraviolet light, particularly about 400 n.
It is an object of the present invention to provide a silica glass which has a high absorbance of ultraviolet light of m or less and a high visible light transmittance.

Another object of the present invention is to provide a novel method for producing the above silica glass.

[0008]

In order to achieve the above object, the present invention provides a transition metal element having a content of 100 wtppm to 10 wtppm.
000wtppm, aluminum content is 100wtp
pm to 10,000wtppm, OH group concentration is 30wt
The present invention relates to silica glass having a concentration of from ppm to 2,000 wtppm.

As the transition metal element contained in the silica glass, 3A, 4A, 5A, 6A, 7A,
At least one member selected from the group of groups 8 and 1B, and the content thereof is 100 wtppm to 10,000.
wtppm range. In particular, Fe, Ce, Ti, V,
Transition metal elements of Cr and U are preferred. These transition metal elements are used as oxides, chlorides, iodides, nitrates or carbonates, water-soluble compounds are mixed with silica raw materials in aqueous solutions, and water-insoluble powders are mixed with silica raw materials in powder. Is done. When the content of the transition metal element is less than 100 wtppm, the ultraviolet absorption is low. Conversely, 10,000wtp
At pm or more, the decrease in transmittance of visible light is increased, and the ultraviolet light resistance is significantly reduced.

The aluminum element is compounded as a compound of an oxide, a chloride, an iodide, a nitrate or a carbonate together with the above-mentioned transition metal element compound in a silica raw material, and is transparently vitrified. By the blending of the aluminum element, the phase separation of the transition metal element does not occur and the transition metal element is uniformly contained. Aluminum content in silica glass is 100w
tppm to 10,000 wtppm. Below the above range, the effect of uniformly dispersing the transition metal element is small.
If it exceeds 000 wtppm, the transmittance of visible light is sharply reduced. As a method of compounding the aluminum compound, an aqueous solution is used for a water-soluble compound, and a powder is used as a powder for a water-insoluble powder, which is mixed with a silica raw material.

As the silica raw material, natural quartz powder, natural quartz powder, synthetic quartz powder, synthetic cristobalite powder and synthetic silica glass powder are used. Particularly, in order to obtain transparent silica glass with few bubbles, silica having an α-crystal structure is used. Good powder.

The main control method of the OH group concentration in the silica glass will be described below. (1) In the case where the vitrification is performed by the electric heating and melting method using the powder raw material, control is performed by heating at 100 to 200 ° C. before melting, and further performing heat treatment at about 1,000 ° C. as necessary. I do. (2) In the case of using a powdery raw material and performing vitrification by an oxyhydrogen flame Bernoulli method, control is performed by adjusting the gas ratio of the oxyhydrogen flame to the raw material powder during melting by the Bernoulli method. (3) When a soot body is prepared by a oxyhydrogen flame hydrolysis method using a liquid raw material such as silicon tetrachloride, and the soot body is subsequently made into a transparent glass by an electric heating and melting method, a soot body is used.
After doping a transition metal element compound and an aluminum compound in an aqueous solution with an aqueous solution, the temperature is controlled by heating at 100 ° C. to 200 ° C. before melting and, if necessary, at about 1,000 ° C. .

The OH groups contained in the silica glass serve as a terminator for the silica network, thereby reducing distortion in the silica glass and making it less susceptible to ultraviolet damage. OH group concentration is 30wtpp
m, there is no such effect, and conversely, 2,000 wtppm
If the ratio exceeds the above range, the glass becomes a glass having many air bubbles at the time of transparent vitrification, and the transmittance of visible light is reduced.

The vitrification of the silica raw material is preferably carried out by an electric heat melting method or a flame Bernoulli method for a powder raw material. For liquid raw materials such as silicon tetrachloride, an oxyhydrogen flame hydrolysis method is an appropriate synthesis method. In other methods such as a plasma flame fusion method, a predetermined amount of OH groups is not present in silica glass, which is not preferable.

As described above, the transparent silica glass containing a metal element has a virtual temperature of 1,400 ° C. to 1,800.
° C. 900 ℃ to 1,300 ℃
When the fictive temperature setting process of heating for 10 to 100 hours is performed, the fictive temperature of the silica glass becomes 900 ° C. to 1,300 ° C.
And the UV resistance is further improved.

The silica glass of the present invention has a thickness of 2 m.
m when the sample is a double-sided mirror-finished plate sample.
The transmittance of light of 00 nm is set to 1% or less, and the wavelength of 600 n
m has a transmittance of 85% or more for visible light. Therefore,
General lighting lamps, headlight lamps for automobiles, lamps for projectors, xenon lamps for exciting solid lasers, krypton lamps, argon lamps, protective tubes, and the like made of this silica glass are made of plastic members around the lamps. There is no deterioration of the glass or ultraviolet damage of the laser element, and there is no reduction in strength or solarization of the silica glass itself.

The silica glass of the present invention is most easily and inexpensively manufactured by the following method. That is, a powder or an aqueous solution of a transition metal element compound and an aluminum compound is mixed with natural or synthetic silica raw material powder, and dried at 100 ° C. to 200 ° C. as necessary, and further 1,000 ° C.
After adjusting the water content by heat treatment, a transparent vitrification is performed by an electric heating melting method or a flame Bernoulli method. After the above silica glass is further cooled,
A virtual temperature setting process is performed at 1,300 ° C. for 10 to 100 hours.

The terms used in the present invention have the following meanings, and the physical properties of the silica glass were measured by the following measuring methods.

1) The OH group concentration means that a silica glass sample having a thickness of 2 mm is immersed in a vacuum of 1 Torr or less for 1,000 hours.
O present after heat treatment at 0 ° C. for 10 hours or more
Refers to H group concentration.

2) The fictive temperature is a temperature at which it is assumed that physical properties such as the density and refractive index of silica glass at room temperature are set, and differs depending on the heat history of the silica glass (R. Bruckner (1970)). Journal
of Non-Crystalline Solid
s, Vol. 5 p123-175).

3) Measurement of OH group concentration: Infrared absorption spectrophotometry (DM Dodd, DB Frase)
r, Journal of Applied Physi
cs, Vol. 37 (1966) p3911).

4) Virtual temperature measurement: Raman scattering spectrophotometry (AE Geissberger, Physi)
calReview B, Vol. 28, no. 6 (1
983) p. 3266-3271).

6) Transmittance: According to ultraviolet spectrophotometry. The sample had a thickness of 2 mm and was mirror-polished on both sides.

[0024]

【Example】

Examples 1 to 4 Natural quartz powder was put in an atmosphere containing chlorine gas at 1,000 ° C. and 10 ° C.
Time purification treatment, then reduce the particle size from 10 μm to 100 μm
m. Fine powder of cesium oxide CeO ₂ and / or titanium oxide TiO ₂ having a particle size of about 1 μm was added to the silica raw material powder, and uniformly mixed with a V-type mixer. An aqueous solution of aluminum chloride was mixed with the obtained mixed raw material powder,
After drying at -200 ° C, the mixture was further heat-treated at 1,000 ° C for 10 hours to adjust the amount of water in the mixture. This silica glass raw material is made into a transparent glass by an electric heating and melting method in a vacuum of 1 Torr or less, cooled, and then cooled to 1,150 ° C.
Performed a virtual temperature setting process for 100 hours. Physical properties of the contained components and silica glass were measured. Table 1 shows the results.
Shown in

Example 5 A white soot body of silica glass was prepared from silicon tetrachloride as a raw material by an oxyhydrogen flame hydrolysis method. To this white soot body, an aqueous solution of titanium chloride and cerium chloride having a predetermined concentration and aluminum chloride are added, and the soot body in which the metal element compound is immersed is heated and dried at 100 ° C. to 200 ° C., and then at a degree of vacuum of 1 Torr or less. It was heated to about 1,700 ° C. to form a transparent glass. After cooling the silica glass, 10
A virtual temperature setting process for 0 hours was performed. The content and physical properties of each component of the obtained silica glass were measured, and the results are shown in Table 1.

Example 6 A silica glass having a higher OH group content was produced in the same manner as in Example 5, and its components and physical properties were measured. The results are shown in Table 1.

Comparative Examples 1 to 3 Comparative Example 1 is a silica glass containing no aluminum in the production method of Example 1. Ti and Ce were not uniformly dispersed in the obtained silica glass, and it was a cloudy translucent body.

Comparative Example 2 is also a silica glass containing no aluminum. It was a translucent white turbid body as in Comparative Example 1.

Comparative Example 3 is the silica glass of Example 1 with OH
It is a silica glass having a group concentration of less than 1 wtppm. The fictive temperature of this silica glass was 1,650 ° C.

[0030]

[Table 1]Note): Vacuum melting method^aIs the vacuum electric heating and melting method The flame decomposition
Law^bRefers to the oxyhydrogen flame hydrolysis method.

For the silica glass of Example 1 and Comparative Example 3 in Table 1 above, a KrF excimer laser (2
48 nm), and the bending strength before and after the irradiation was measured.
Table 2 shows the results. As is clear from this table, the silica glass of the present invention hardly changed in strength before and after laser irradiation.

[0032]

[Table 2] (MPa)

The laser irradiation conditions are as follows: energy density 1
00mJ / cm ・ Pulse, frequency 100Hz, irradiation
Number of pulses 1 × 10⁶pulses. Also, bending strength
The degree was measured according to JIS R-1601. Strength
The order is MPa.

[0034]

Industrial Applicability The silica glass of the present invention is a silica glass having a low transmittance of ultraviolet rays, no reduction in strength due to ultraviolet rays and no occurrence of solarization, and a high transmittance of visible light. Illumination lamps and laser excitation lamps made of this silica glass are excellent lamp materials that do not degrade the plastics of the members and do not lower the luminous efficiency of the laser oscillator.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C03C 3/06 C03C 3/06

Claims (7)

(57) [Claims] (1) a transition metal element content of 100 wtppm or more;
10,000wtppm, aluminum content 100
wtppm to 10,000 wtppm, OH group concentration is 3
Ultraviolet-absorbing and visible-light-transmitting silica glass having a content of 0 wtppm to 2,000 wtppm. 2. The ultraviolet-absorbing and visible-light-transmitting silica glass according to claim 1, wherein the transmittance of ultraviolet light having a wavelength of 200 nm is 1% or less, and the transmittance of visible light having a wavelength of 600 nm is 85% or more. . 3. The silica glass according to claim 1, wherein the fictive temperature is 900 ° C. to 1,300 ° C. 4. A process for producing a silica glass having a UV-absorbing and visible-light-transmitting property, which comprises subjecting a mixture comprising a silica raw material, a transition metal element compound and an aluminum compound to heat treatment to adjust the water content thereof, followed by melt vitrification. Method. 5. The method of claim 4, wherein the silica raw material is a soot body of silica obtained by flame hydrolysis of a silicon compound raw material. Method. 6. The method of claim 4, wherein the silica raw material is a silica obtained by subjecting a crystalline silica powder to a highly purified treatment. 7. A process for producing a silica glass having a UV-absorbing and visible-light transmittance, further comprising the step of setting a fictive temperature at 900 ° C. to 1,300 ° C. on the silica glass after the melt vitrification according to claim 4. .