JPH0769671A - Ultraviolet ray absorbing silica glass and production thereof - Google Patents

Abstract

PURPOSE:To obtain silica glass for a discharge tube having excellent UV absorbing property and devitrification resistance. CONSTITUTION:This silica glass has <=200 wt.ppm concn. of OH groups and <=5X10<17>molecules/cm<3> concn. of hydrogen molecules and contains at least one kind of transition metal having controlled valency.

Description

Detailed Description of the Invention

FIELD OF THE INVENTION The present invention is excellent in ultraviolet absorption,
The present invention also relates to silica glass having excellent devitrification resistance, and particularly to silica glass for discharge tubes and high brightness discharge lamp bulb materials.

[0002]

2. Description of the Related Art Conventionally, in the field of lighting industry, silica glass, in particular, so-called "fused silica glass" obtained by electromelting natural quartz has been used as a material for various discharge tubes. However, this fused silica glass has a high transmittance of ultraviolet rays, and a discharge tube made of this fused silica glass has a drawback in that oxygen in the air generates harmful ozone which is harmful to the human body because it transmits ultraviolet rays well. Therefore, Ti, V, Cr, M
An ultraviolet absorbing silica glass doped with n, Fe, Co, Ni, Cu or Ce has been developed, which is disclosed, for example, in Japanese Patent Publication No. 39-21056 and Japanese Patent Publication No. 46-42114.
JP-A-52-89280 and JP-A-5-89280.
No. 4-79978.

However, although the silica glass described in the above publication absorbs ultraviolet rays having a wavelength of about 220 nm or less, it has poor absorption of ultraviolet rays having a longer wavelength, and, for example, an automobile headlight made of this silica glass is There are drawbacks that the long-wavelength ultraviolet light generated at the time of light emission damages the naked eye of human beings and significantly deteriorates the plastics member constituting the automobile headlight. In addition, the silica glass has a high concentration of OH groups and hydrogen molecules,
In the high-intensity discharge lamp thus created, the luminescent gas enclosed in the bulb material reacts with oxygen generated from the OH group to cause black devitrification, or hydrogen molecules increase the operating voltage of the lamp, or The crystallization by the alkali metal element in the silica glass and the chemical etching by the enclosed gas were promoted to generate white devitrification, and the life was short.

[0004]

In view of these circumstances, the present inventors have found that the silica glass for discharge tubes has about 4
We have earnestly researched the development of silica glass that absorbs UV rays of less than 00 nm and prevents ozone generation, adverse effects on the human body, and deterioration of plastics, and has little deterioration in luminous efficiency as a bulb material for high-intensity discharge lamps. As a result of stacking, while limiting the OH group concentration and the hydrogen molecule concentration in the silica glass to a specific range, the transition metal element is contained, and by controlling the ionic valence of the transition metal element, it is possible to achieve the above object. Heading, completes the present invention.

It is an object of the present invention to provide a silica glass which has excellent ultraviolet absorption and does not adversely affect the human body and deteriorate the plastics member.

It is an object of the present invention to provide a silica glass which does not cause devitrification even when used as a bulb material for a high intensity discharge lamp such as a high pressure mercury lamp or a metal halide lamp.

Another object of the present invention is to provide a silica glass which has high heat resistance and is not thermally deformed as a bulb material for a high-intensity discharge lamp. A further object of the present invention is to provide a new production method for producing the above silica glass.

[0008]

The present invention, which achieves the above object, provides an ultraviolet absorbing silica glass for a discharge tube,
The OH group concentration is 200 wt. TECHNICAL FIELD The present invention relates to a silica glass containing ppm or less, a hydrogen molecule concentration of 5 × 10 ¹⁷ molecules / cm ³ or less, and containing at least one transition metal element having a controlled ionic valence, and a method for producing the same.

Further, according to the present invention, in the case of the ultraviolet absorbing silica glass for a high-intensity discharge lamp bulb material, its OH group concentration is 20 wt. ppm or less, hydrogen molecule concentration 5 × 10
^The present invention relates to silica glass containing at least one transition metal element having a controlled ionic valence of ¹⁶ molecules / cm ³ or less, and a method for producing the same.

The above-mentioned transition metal elements include Ti, V, Cr,
Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo,
Tc, Ru, Ce, Pr, Nd, Pm, Sm and Eu
Of the atomic numbers 22 to 29, 40 to 44, and 58 to 63. Particularly preferable transition metal elements are titanium, chromium and cerium. The content of the transition metal element is 10
~ 10,000 wt. ppm range, and the range is 10 wt. If it is less than ppm, the effect of absorbing ultraviolet rays having a wavelength of about 400 nm or less is not observed even if the ion valence control treatment is properly selected. When the content is more than ppm, the transparency of the silica glass in the visible region is deteriorated and the light output when used as a bulb material is lowered.

The silica glass of the present invention is obtained by subjecting silica glass containing a transition metal element to an ionic valence control treatment,
It is a silica glass that is controlled so that the ionic valence of the transition metal element is changed to absorb ultraviolet rays of about 400 nm or less. The ionic valence control treatment is performed by changing the transition metal element-containing silica glass in an oxidizing atmosphere or a reducing atmosphere from 800 to
Heat treatment at 1300 ℃, or UV, X-ray, γ
It refers to a treatment of irradiating a ray to oxidize or reduce.

The control of the ionic valence is to change the ionic valence so that the light transmission spectrum of silica glass in the ultraviolet region is about 400 nm or more. For example, when cerium-containing silica glass is oxidized at 800 to 1300 ° C. in an oxidizing atmosphere, it absorbs about 400 or less ultraviolet rays. Higher transmittance, 22
A part of 0 to 300 nm is transmitted. As described above, it is important to appropriately select the ion valence control treatment in order to improve the absorption of ultraviolet rays having a wavelength of about 400 nm or less.

Furthermore, when the absorption of ultraviolet rays increases, the temperature of the discharge lamp bulb material rises, and the luminous efficiency of the lamp increases. In addition, since the transition metal element is contained in the silica glass, the heat resistance of the silica glass is improved, and the surface temperature of the silica glass rises to about 1000 ° C during light emission. However, it does not cause thermal deformation.

By the way, O contained in silica glass
The H group is decomposed during the light emission of the high-intensity discharge lamp to generate oxygen, which reacts with the enclosed metal gas and the metal tungsten of the electrode to cause black devitrification. Further, it is said that generation of hydrogen molecules causes generation of re-ignition spike voltage and increase in operating voltage (Matsuno Hiromitsu et al. (1981) Mechanism of lowering luminous flux maintenance rate in metal halide lamp, Journal of Illuminating Engineering, Vol. 65). , No. 4, pp. 176-181). further,
It is presumed that white devitrification occurs due to crystallization promotion by alkali metal elements and alkaline earth metal elements in silica glass and chemical etching with a sealing gas. When the black devitrification and the white devitrification and the increase of the operating voltage occur, the luminous efficiency of the lamp is remarkably reduced, but the black devitrification and the increase of the operating voltage reduce the OH group concentration and the hydrogen molecule concentration in the silica glass. By doing so, it can be solved to some extent. However, in order to sufficiently solve these problems including white devitrification, specifically, the OH group concentration in silica glass should be 20%.
0 wt. ppm or less, hydrogen molecule concentration of 5 × 10 ¹⁷ mol
It is necessary to improve the heat resistance by incorporating a transition metal element in the number of ecules / cm ³ or less.

Further, when the discharge tube is a high-intensity discharge lamp, the OH group concentration is 20 wt. The concentration of hydrogen molecule should be 5 ppm or less, the hydrogen molecule concentration should be 5 × 10 ¹⁶ molecules / cm ³ or less, and the transition metal element should be contained.

The above-mentioned OH group concentration is measured by D. M. Dod
d, D. B. Fraser (1960), Optica
l Determinations of OH in
Fused Silica, J.M. Applied P
hysics, Vol. 37, p. 3911 (196
According to the method of 6) and the measurement of the hydrogen molecule concentration, V.
S. Khotimchenko, et al. (19
87) Determining the Conte
nt of Hydrogen Dissolved
in Quartz Glass Using the the
Methodof Raman Scatterin
g and Mass Spectrometry,
J. Appl. Spectrosc. , Vol. 46,
No. 6, pp632-635.

The silica glass of the present invention which absorbs ultraviolet rays of about 400 mm or less and has excellent devitrification resistance is manufactured by the following means. That is, crystal powder and a transition metal compound such as chloride, iodide, carbonate,
A compound such as a nitrate is mixed and the mixed raw material is vitrified by a vacuum electric melting method, or a mixture of the transition metal element compound and silicon tetrachloride is subjected to the oxyhydrogen flame hydrolysis method.
Vitrification by the gating method and then subjecting this silica glass to an ionic valence control treatment to control the ionic valence of the transition metal element in the silica glass to the required value.

In the above production, the transition metal element is mixed with quartz powder which is a silica glass raw material in the form of an aqueous solution if the transition metal compound is water-soluble, and if it is an insoluble solid particle, the particle size is adjusted to form a powder mixture. To do. In particular, when vitrifying by a vacuum electric melting method, when the transition metal compound is mixed with an aqueous solution, it is preferable to perform a pretreatment of drying at about 200 ° C. and calcining at about 1000 ° C.

On the other hand, in the case of vitrification by the soot method of oxyhydrogen flame hydrolysis method, the OH group and hydrogen molecule concentration can be arbitrarily changed by dehydration treatment in a chlorine or hydrogen chloride gas atmosphere.

Hereinafter, the present invention will be described in more detail with reference to Examples.

【Example】

(1) Preparation of silica glass For Examples 1 to 5, natural quartz powder having a particle size of 10 to 100 was used.
was adjusted to [mu] m, performs a high-purity treatment of heating in a chlorine gas atmosphere, 99.999wt the SiO ₂ purity. %. Next, the crystal powder was added with a purity of 99.99 wt. % Titanium, cerium, and chromium oxide powders were mixed. If necessary, the mixed powder is kept at 200 ° C., and further 100
After maintaining at 0 ° C and adjusting the water content, transparent vitrification was performed by a vacuum electric melting method. The obtained transition metal element-containing silica glass was subjected to an ionic valence control treatment by a heating oxidation treatment at 1100 ° C. for 100 hours in the air, or a γ-ray irradiation treatment using Co-60. Physical properties of the silica glass subjected to the ionic valence control treatment were evaluated, and the results are shown in Table 1.

Regarding Example 6, the mixed powder prepared in the same manner as in the above Example was subjected to transparent vitrification by the oxyhydrogen flame Bernoulli method. The obtained transition metal element-containing silica glass was subjected to γ-ray irradiation with Co-60 to perform an ionic valence control treatment. Physical properties of the silica glass subjected to the ionic valence control treatment were evaluated, and the results are shown in Table 1.

In Examples 7 and 8, high purity silicon tetrachloride as a silica raw material was mixed with chlorides of cerium and titanium. Next, a soot body was prepared from this mixed raw material by the soot method of the oxyhydrogen flame hydrolysis method. This soot body was heat-treated in a chlorine gas atmosphere to reduce water content. Next, this dehydrated soot body was heat-treated in vacuum to obtain transparent glass. Further, the obtained transition metal element-containing silica glass was subjected to a heat oxidation treatment at 1100 ° C. for 100 hours in the atmosphere to perform an ionic valence control treatment. Physical properties of the silica glass subjected to the ionic valence control treatment were evaluated, and the results are shown in Table 1.

For comparison, the silica glass of the present invention which is not properly subjected to the ion valence control treatment, and Shin-Etsu Quartz Co., Ltd.
Manufactured M-382 was measured, and the results were compared with Comparative Examples 1 to 1.
4 is shown in Table 1.

(2) Measurement of physical properties-Measurement of OH group concentration; Measurement by infrared absorption spectrophotometry (DM Dodd, et al. (1987))
reference). -Measurement of hydrogen molecule concentration; Raman scattering method (V.S.
Khotim-chenko, et al. (198
7)).・ Measurement of transition metal element concentration; measured by atomic absorption photometry.・ Measurement of light transmission wavelength range; thickness of 2 mm, double-sided mirror polished sample with light transmittance meter 190-900 nm
Measuring light in the range. Ampoule test: A tube having a diameter of 10 mm, a thickness of 2 mm, and a length of 100 mm was prepared, and one end of the tube was sealed in a circle to form a test tube. Next, DyI ₃ particles were charged in the dried globe box. The tube was evacuated, and the other end was also sealed into a round ampoule. After heating this at 100 ° C. for 100 hours, it was taken out of the furnace and the degree of white devitrification on the inner wall of the ampoule was visually observed.

[0025]

[Table 1]

As shown in Table 1 above, the silica glass of the present invention well absorbs ultraviolet rays having a wavelength of about 400 nm or less, and hardly causes white devitrification.

[0027]

EFFECT OF THE INVENTION The silica glass of the present invention is excellent in ultraviolet absorption and also in devitrification resistance, so that it is particularly useful as a discharge tube material for automobile headlights, projectors and general lighting. Silica glass is also excellent as a bulb material for high-intensity discharge lamps such as metal halide lamps.

Front Page Continuation (72) Inventor Mitsuha Kuriyama Kanayama, Koriyama City, Fukushima Prefecture Kawakubo 88 Shin-Etsu Quartz Co., Ltd., Quartz Technology Laboratory (72) Inventor Wolfgang English Gerkline Helderlein Strasse 54

Claims (9)

[Claims] 1. An ultraviolet absorbing silica glass for a discharge tube, the OH group concentration of which is 200 wt. Silica glass characterized in that it contains at least one transition metal element having a hydrogen ion concentration of 5 ppm or less, a hydrogen molecule concentration of 5 × 10 ¹⁷ molecules / cm ³ or less, and a controlled ionic valence. 2. An ultraviolet absorbing silica glass for a high-intensity discharge lamp bulb material, the OH group concentration of which is 20 wt. p
pm or less, hydrogen molecule concentration is 5 × 10 ¹⁶ molecule
A silica glass containing at least one transition metal element having a controlled ionic valence of s / cm ³ or less. 3. The content of transition metal element is 10 to 10,0.
00 wt. It is ppm, The silica glass of Claim 1 or 2 characterized by the above-mentioned. 4. The silica glass according to claim 1 or 2, wherein a mixture of crystal powder and a transition metal element compound is vitrified by a vacuum electric melting method. 5. The silica glass according to claim 1, wherein a mixture of silicon tetrachloride and a transition metal element compound is vitrified by a soot method of an oxyhydrogen flame hydrolysis method. 6. The silica glass according to claim 1, wherein the transition metal element is at least one element selected from titanium, chromium and cerium. 7. A mixture of a raw material of silica glass and at least one kind of transition metal element is melted and vitrified to obtain transparent silica glass, and then an ion valence control treatment of the transition metal element contained in the silica glass is performed. A method for producing silica glass, comprising: 8. The method for producing silica glass according to claim 7, wherein the ionic valence control treatment of the transition metal element is a heat treatment in an oxidizing atmosphere or a reducing atmosphere. 9. The method for producing silica glass according to claim 7, wherein the ionic valence control treatment of the transition metal element is a radiation irradiation treatment. [0001]