JP2000185924A - Production of glass material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nitrogen-incorporated silica glass material, capable of introducing high-concentration nitrogen gas into a silica glass porous form and easily setting nitrogen incorporation level as well. SOLUTION: This method for producing a nitrogen-incorporated glass material comprises treating a silica glass porous form under heating in an ammonia- contg. atmosphere to introduce nitrogen into the porous form which is then vitrified; wherein the porous form is heat-treated in an atmosphere containing a silicon halide gas followed by heat treatment of the resulting halogen- incorporated porous form in the ammonia-contg. atmosphere and then further heat treatment of the resultant nitrogen-incorporated porous form to effect vitrification thereof to obtain transparent glass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glass material to which nitrogen is added, which is widely used for various containers and other optical materials in the semiconductor industry.

[0002]

2. Description of the Related Art Silica glass bodies are materials widely used in heat treatment vessels, various jigs, various chemical reaction instruments, various optical materials such as optical fibers, lenses, and waveguides in the semiconductor industry. Nitrogen is added (doped) for the purpose of imparting resistance to devitrification or deformation at the high temperature, adjusting the refractive index when used in an optical fiber or the like. As a method of adding nitrogen, a method of heat-treating a porous glass body in an ammonia-containing atmosphere is known, and various improvements have been proposed. For example, Japanese Patent Application Laid-Open No. H5-279049 discloses that the effect of foaming due to decomposition of NH ₃ is reduced by slowing the rate of temperature rise when sintering by heating the glass porous body after ammonia treatment, thereby reducing Although a method of obtaining quartz glass doped with nitrogen has been proposed, the introduction amount of nitrogen is described as being 0.15 wt% or more. .2 wt%, the amount introduced after sintering is not described. In addition, 7-6458
No. 0 and 64581 disclose a method of subjecting a nitrogen-containing porous body after ammonia treatment to heat treatment in an oxygen gas or water vapor-containing atmosphere to partially denitrify, thereby eliminating the difference in nitrogen concentration between the surface portion and the central portion. Although disclosed, the amount of nitrogen introduced is as low as 4000 ppm even on highly concentrated surfaces.

Further, Japanese Patent Application Laid-Open No. 10-502324 discloses that a porous silica preform is provided with a hydroxyl or halogen group and then reacted with ammonia to improve the physical properties of nitrogen containing chemically bonded nitrogen. Although a method for obtaining a glass product is disclosed, the amount of nitrogen introduced is at least about 150 ppm, about 150 to 250 pp.
There is no numerical value of a specific example only with the description of m, etc., and there is also a description of a hydroxyl group in the method of introducing a reactive group, but the halogen group is not described at all and its effect is not clear. . In addition, JP
No. 313341 discloses that after sintering an optical fiber preform in an atmosphere containing a fluorine compound, it is drawn in an atmosphere containing nitrogen gas to improve the fatigue strength of the optical fiber on the surface,
In addition, a method for manufacturing an optical fiber having a silicon oxynitride layer serving as a barrier layer for preventing H ₂ O and H ₂ from penetrating is disclosed. However, nitrogen is introduced only on the surface, and the nitrogen source is not ammonia. This is a treatment at a high temperature (about 2000 ° C.) at the time of drawing. JP-A-56-155036 discloses that a porous glass body is subjected to a heat treatment in a nitrogen gas and an ammonium halide gas or a decomposition gas thereof, and co-doped with nitrogen and halogen to thereby reduce the viscosity during spinning. When used as a core glass, a method for producing a high silicate glass has been proposed in which the corresponding clad glass is melted during spinning so that the strength of the fiber itself can be increased. This is a method of simultaneously doping nitrogen and halogen. Chlorine gas is known as an additive other than nitrogen to increase the refractive index of silica glass. For example, Japanese Patent Application Laid-Open No. Hei 10-53423 discloses heating a porous glass body obtained by depositing silica glass fine particles. In a method for producing a synthetic silica glass which is treated to be transparent vitrified, said transparent vitrification is performed by using an inert gas and silicon tetrachloride (Si).
By performing in Cl ₄₎ composed of a mixed gas of a gas atmosphere, but efficient way to achieve flattening of the refractive index distribution and effective to index raising the introduction of chlorine is disclosed, nitrogen No relevance to the introduction method is described.

[0004]

As a method for obtaining a silica glass material having improved physical properties by adding nitrogen as described above, various methods have been proposed by heat treatment in an atmosphere containing ammonia. However, none of these conventional methods introduces a small amount of nitrogen, and a nitrogen addition amount required particularly for optical applications has not been obtained. Further, it takes a long time to introduce nitrogen, and there is a problem in productivity of glass. The nitrogen addition reaction to the porous silica glass body is considered as in the equations (1) and (2).

Embedded image SiO ₂ + NH ₃ = OSi [NH] + H ₂ O (1) SiOH + NH ₃ = SiNH ₂ + H ₂ O (2) The H ₂ O to be produced is important for the above reaction equilibrium, and the H ₂ O concentration is high. When this happens, the above reaction proceeds to the left and a nitrogen desorption reaction occurs, making it difficult to add a high concentration of nitrogen. Also,
According to these reactions, if the addition is carried out while replacing the gas for a very long time, the removal of H ₂ O, which is a generated gas, from the atmosphere proceeds, so that the addition of nitrogen proceeds. However, in order to efficiently promote gas replacement, the only option is to reduce the volume of the heated reaction vessel or increase the flow rate of the gas. In the former, the productivity is reduced due to the limitation of the size of the porous body that can be treated, and the latter is reduced. In this case, an increase in the amount of gas used causes an increase in the price of the gas and the cost of treating the exhaust gas. The present invention has been made in view of such conventional techniques, and provides a method for producing a silica glass material to which nitrogen can be easily added at a high concentration, and the amount of nitrogen to be introduced can be easily set. Aim.

[0005]

According to the present invention, there is provided (1) a method for producing a glass material in which nitrogen is introduced by heating a porous silica glass body in an ammonia-containing atmosphere to introduce nitrogen, and then adding vitrification to the glass. In the above, the silica glass porous body is heat-treated in an atmosphere containing a silicon halide gas, and the obtained silica glass porous body to which a halogen element is added is heat-treated in an ammonia-containing atmosphere to form a nitrogen-containing porous body. A method for producing a glass material to which nitrogen is added, wherein the nitrogen-containing porous body is further heat-treated to be vitrified, and (2) the halogen element constituting the silicon halide is fluorine or chlorine. (1) the method for producing a glass material to which nitrogen is added as described in (1), (3) heat treatment in an atmosphere containing a silicon halide gas, and heat treatment in an ammonia-containing atmosphere. (1) The method for producing a glass material to which nitrogen is added as described in (1) or (2) above, wherein the oxygen concentration is less than 100 ppm, and (4) the vitrification of the nitrogen-containing porous body. (1) wherein the heat treatment is performed in a mixed gas atmosphere of nitrogen gas, an inert gas other than nitrogen gas, and oxygen gas.
A method for producing a glass material to which any one of (3) to (3) is added.

According to the method of the present invention, a halogen element is added to a porous silica glass body in advance, and a heat treatment is performed in an ammonia-containing atmosphere, whereby the halogen element is replaced with ammonia as shown in formula (3). Nitrogen can be efficiently added to the silica glass.

Embedded image SiO _1.5 X + NH ₃ ＳｉＯSiO _1.5 [NH ₂ ] + HX (3) (X: F, Cl, Br, I) The advantages of this reaction are as follows: (1) Oxygen that inhibits the production reaction due to reaction equilibrium Almost 100% because there are no gaseous products
(2) The generated hydrogen halide is:
The point is that the gas can be quickly discharged out of the furnace in accordance with the gas replacement. By performing this reaction, the reaction rate is increased as compared with the conventional method, so that nitrogen can be added in a short time, and nitrogen can be added in accordance with the amount of halogen added in advance. Thus, there is an effect that the control of the amount of added nitrogen becomes easy.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, first, a porous silica glass body is heated in an atmosphere containing a silicon halide gas to introduce a halogen element into the porous body (halogen addition step). As the porous silica glass, for example, a gas phase synthesis of a VAD method or an OVD method is performed by synthesizing glass fine particles from a silicon compound as a glass raw material by a gas phase oxidation reaction or a flame hydrolysis reaction to form a soot-like deposit. By sol-gel method,
Pressure-molded glass fine particles (fine powder) can be used. The bulk specific gravity of 0.2-0.
Since the porous body in the region of 5 g / cm ³ can have continuous pores, it is desirable for adding a halogen element and nitrogen in a gas phase.

As a method for adding a halogen element to a porous silica glass body, a method already known as a method for treating a glass base material for optical fibers can be applied. That is, by subjecting the porous silica glass body to heat treatment in a halogen compound-containing atmosphere, a halogen element is added with a dehydration step and a halogen addition step. The halogen compound used in the halogen addition step is C
chlorides such as l ₂ , SiCl ₄ , CCl ₄ , SiF ₄ ,
In addition to fluorides such as CF ₄ and SF ₆ , Br ₂ and I _2, their carbides and silicides are effective. The halogen compounds used in the method of the present invention include SiCl ₄ , S
Silicon halides such as iF ₄ are preferred. The reason is,
This is because the addition of the halogen element to SiO ₂ proceeds according to the chemical reaction equilibrium of the formula (4), so that no by-product is generated, and the halogen element can be added efficiently and at a high concentration.

Embedded image 3SiO ₂ + SiX ₄ = 4SiO _1.5 X (4) (X: F, Cl, Br, I)

As the silicon halide, silicon chloride such as SiCl ₄ is most suitable. Even when silicon fluoride is used, fluorine can be added at a high concentration, but the reaction product when ammonia is reacted is hydrogen fluoride, and the etching of the porous silica glass body may proceed. .
In addition, when silicon bromide or silicon iodide is used, it is difficult to maintain the temperature of the raw material supply system at a high temperature (100 ° C. or higher) in order to supply the raw materials. Increases, the saturation concentration in the silica glass decreases.

In the halogen addition step, the porous silica glass body is heated at 800 to 1300 ° C., preferably 11 ° C., in an atmosphere of an inert gas containing silicon halide gas such as He or N _2.
The heat treatment is performed at 00 to 1200 ° C. for 30 to 100 minutes. The concentration of the silicon halide gas is 0.1 to 1
Within the range of 00%. If the temperature is lower than 800 ° C., the rate of addition of the halogen becomes slow, and if the temperature exceeds 1300 ° C., the addition becomes difficult due to shrinkage of the glass. The oxygen concentration in the halogen compound-containing atmosphere is preferably less than 100 ppm. An oxygen concentration is 100ppm or more, there is a possibility that the formation of SiO ₂ particles in the reaction between oxygen and a halogen compound occurs (However, in the case of compound F SiO ₂
SiO ₂ is not generated because the bond of Si—F is stronger than that of Si—F). 0.1 to 3 wt% in this halogen addition step
Some halogen elements can be added.

Next, the porous silica glass to which the halogen element added in the halogen addition step is added is made of He, N ₂
Heat treatment is performed in an ammonia-containing atmosphere containing 1 to 20% ammonia gas in an inert gas such as nitrogen to introduce nitrogen (nitrogen addition step). Heat treatment temperature is 800 ~
1200 ° C., preferably in the range of 900 to 1000 ° C. If the temperature is lower than 800 ° C., the rate of addition of nitrogen becomes slow. If the temperature exceeds 1200 ° C., ammonia gas is decomposed and dissociated into N ₂ and H ₂ , making it difficult for the addition of nitrogen to proceed. On the other hand, if the concentration of ammonia gas exceeds 20%, handling becomes difficult, which is not preferable. The heat treatment time is 10 to 300 minutes. If the treatment time is less than 10 minutes, the replacement of the halogen element with nitrogen becomes insufficient, and if it exceeds 300 minutes, there is a problem in terms of productivity. When the oxygen concentration in the ammonia-containing atmosphere is high, the generated Si—N bond is replaced by oxygen, and the amount of added nitrogen decreases. Substitution of nitrogen with oxygen occurs almost 100% on the reaction equilibrium, so the oxygen concentration in the atmosphere needs to be sufficiently smaller than the ammonia concentration. As described above, since the reaction is performed with the ammonia gas partial pressure in the range of 1 to 20%, it is desirable that the oxygen concentration in the atmosphere be less than 100 ppm from the viewpoint of adding nitrogen. In this nitrogen addition step, nitrogen of 0.2 to 3 wt% can be added corresponding to the halogen element addition amount in the previous step.

Next, the nitrogen-containing porous body obtained in the nitrogen addition step is further subjected to a heat treatment to form a transparent vitrification (a transparent vitrification step). Transparent vitrification is performed by heating the nitrogen-containing porous body to 1450 to 1650 ° C. in an inert atmosphere. When the temperature is lower than 1450 ° C., the transparency is insufficient, and when the temperature is higher than 1650 ° C., the furnace tube may be deformed. The processing time is about 10 to 100 minutes, depending on the temperature. By the heat treatment in the transparent vitrification step, a transparent silica glass body to which 0.2 to 3 wt% of nitrogen is added corresponding to the amount of the halogen element added can be obtained.

In this transparent vitrification step, the heat treatment atmosphere is changed to an inert gas other than nitrogen gas (for example, He, A
A rare gas element such as r or Ne) is mixed with 1 to 10% of nitrogen gas and 0.1 to 5% of oxygen gas to cause a partial denitrification reaction to cause a refractive index. It is also possible to form a distribution.

[0014]

The following examples further illustrate the method of the present invention.
Explain physically. (Example 1) As a porous silica glass, SiCl_Four
Glass granules synthesized by flame hydrolysis
Ratio produced by the VAD method in which the elements are deposited in the axial direction
Weight 0.25g / cm^ThreeWas used. Made
Place the porous silica glass body in an electric resistance heating furnace,
The temperature was raised to 200 ° C. at a rate of 10 ° C./min.
_FourGas flow rate 0.2 liter / min, helium gas flow rate 10
In an atmosphere of liter / min (oxygen concentration less than 100 ppm)
At 1200 ° C. for 30 minutes.
Chlorine was added to the Kagurasu porous body. Heating for 30 minutes
After treatment, SiCl _FourTurn off gas supply and cool down at 5 ° C per minute
The furnace temperature is lowered to 1000 ° C at a_Three
Gas flow rate 1 liter / min, nitrogen gas flow rate 10 liter / minute
For 60 minutes in an atmosphere of less than 100 minutes (oxygen concentration less than 100 ppm)
Heat treatment to reduce the chlorine introduced into the porous silica glass
Was replaced with a prime. NH_ThreeEnd of heat treatment in containing atmosphere
Thereafter, the supply gas was supplied at a helium gas flow rate of 10 L / min.
Switch to elemental gas flow rate 1 liter / min (oxygen concentration in atmosphere
Less than 100 ppm) at a rate of 5 ° C./min.
℃, hold at the same temperature for 10 minutes, then up to 1000 ℃
And the silica glass body was taken out. Got
The glass body is transparent with visible light, and the hydroxyl concentration is determined by infrared absorption.
When the degree was measured, the concentration was less than 0.1 ppm.
The amount of nitrogen added to this glass body was 2 wt% by chemical analysis.
And the residual amount of chlorine was 0.05 wt% or less.

(Example 2) A porous silica glass body produced in the same manner as in Example 1 was used. The prepared porous silica glass body was placed in an electric resistance heating furnace, and the temperature was adjusted to 12 ° C.
The temperature was raised to 00 ° C. at a rate of 10 ° C./minute, and the flow rate of SiF ₄ gas was 1 liter / minute, and the flow rate of helium gas was 1 liter / minute.
1200 minutes in an atmosphere (oxygen concentration less than 100 ppm)
A heating atmosphere treatment was performed at 30 ° C. for 30 minutes, and fluorine was added to the porous silica glass body. After heat treatment for 30 minutes, S
iF ₄ the supply of gas is stopped, lowered at a cooling rate per minute 5 ° C. the furnace temperature to 1000 ° C., NH ₃ gas flow rate 2 at 1000 ° C.
Heat treatment was performed for 60 minutes in an atmosphere (oxygen concentration less than 100 ppm) in an atmosphere (oxygen concentration less than 100 ppm) at a rate of 10 liters / minute with a nitrogen gas flow rate to replace the fluorine introduced into the silica glass porous body with nitrogen. After the completion of the heat treatment in the NH ₃ -containing atmosphere, the supply gas is switched to a helium gas flow rate of 10 L / min and a nitrogen gas flow rate of 1 L / min (oxygen concentration in the atmosphere is 100 p.
pm), the temperature was raised to 1550 ° C. at a rate of 5 ° C. per minute, and held at the same temperature for 10 minutes, the furnace temperature was lowered to 1000 ° C., and the silica glass body was taken out. The obtained glass body was transparent with visible light, and the hydroxyl group concentration was measured by an infrared absorption method. The concentration was less than 0.1 ppm. The amount of nitrogen added to this glass body was 3 wt% according to a chemical analysis method, and the remaining amount of fluorine was 0.3 wt%.

Comparative Example A porous silica glass body produced by the same method as in Example 1 was used. The prepared silica glass porous body was placed in an electric resistance heating furnace, and the temperature was set to 120.
The temperature was raised to 0 ° C. at a rate of 2 ° C./min.
H ₃ gas flow rate 2 liter / min, nitrogen gas flow rate 10 liter / min atmosphere (oxygen concentration less than 100 ppm)
Heat treatment was performed for 0 minutes to add nitrogen to the porous silica glass body. After the completion of the heat treatment in the NH ₃ -containing atmosphere, the supply gas is switched to a helium gas flow rate of 10 liter / minute and a nitrogen gas flow rate of 1 liter / minute (oxygen concentration in the atmosphere is 100 ppm).
), The temperature was raised to 1550 ° C. at a rate of 1.5 ° C. per minute, and the temperature was maintained at the same temperature for 10 minutes, and then the furnace temperature was lowered to 1000 ° C. to take out the silica glass body. The obtained glass body was transparent with visible light, and the hydroxyl group concentration was measured by an infrared absorption method. The concentration was less than 0.1 ppm. The amount of nitrogen added to this glass body was 0.5 wt% according to a chemical analysis method. In addition, when the heating rate after the nitrogen addition treatment was set to 2 ° C./min or more, a phenomenon of foaming on the surface of the glass body occurred. Therefore, a long time was required for the heat treatment.

[0017]

According to the method of the present invention, a silica glass body to which a high concentration of nitrogen is added can be easily produced in a short time as compared with the conventional method. Also, the amount of nitrogen added can be controlled by controlling the amount of halogen element introduced.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Takagi 1st Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Taku Yamazaki 1st Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Ki Kogyo Co., Ltd. Yokohama Works F-term (reference) 4G014 AH00 4G021 CA14

Claims (4)

[Claims] 1. A method for producing a glass material in which nitrogen is introduced by heat-treating a porous silica glass body in an ammonia-containing atmosphere to introduce nitrogen and then adding vitrified nitrogen to the glass material. A heat treatment is performed in an atmosphere containing gas, and the obtained silica glass porous body to which the halogen element is added is heat-treated in an ammonia-containing atmosphere to obtain a nitrogen-containing porous body, and the nitrogen-containing porous body is further heat-treated. And producing a glass material to which nitrogen is added. 2. The method for producing a glass material to which nitrogen is added according to claim 1, wherein the halogen element constituting the silicon halide is fluorine or chlorine. 3. A heat treatment in an atmosphere containing a silicon halide gas and a heat treatment in an atmosphere containing ammonia.
The method for producing a glass material to which nitrogen is added according to claim 1, wherein the method is performed in an atmosphere having an oxygen concentration of less than 100 ppm. 4. The method according to claim 1, wherein the heat treatment for vitrifying the nitrogen-containing porous body is performed in a mixed gas atmosphere of nitrogen gas, an inert gas other than nitrogen gas, and oxygen gas. A method for producing a glass material to which nitrogen is added according to any one of the preceding claims.