JPS61186235A - Method for manufacturing base material for optical fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a base material for a silica-based optical fiber.

[Conventional technology]

The main manufacturing method for conventional silica-based optical fiber base materials is described below.

(1) VAD method (Electric Corporation, etc.) Gaseous raw materials such as SiC14, GeC1, etc. are fed into an oxyhydrogen burner, and glass fine particles made by a chemical reaction are sprayed onto the tip of a seed rod and deposited, allowing them to grow in the axial direction. A method of making a porous base material by heating it and making it a transparent base material.

(2) M CV D method (Pell Lab et al.) A raw material gas such as Sic 14 r G e C1i is sent into a quartz glass tube together with oxygen gas, heated with a burner from outside the quartz tube, and reacted inside the tube. , a method in which the glass particles produced by the reaction are placed inside a tube to create a hollow tube, and the tube is heated to collapse the hollow part to create a transparent base material.

Currently, the above two methods are mainly used for manufacturing the base material for silica-based optical fibers, but other methods for manufacturing the base materials for silica-based optical fibers include the OVD method, POD method, and sol-gel method. There is.

[Problem that the invention seeks to solve]

However, the above VAD method, MCVD method, OVD method, POD method
The method is a gas phase method that utilizes chemical reactions of gaseous raw materials.
There are problems in that the reaction yield is low, the mass productivity is low, it is difficult to realize a desired refractive index distribution, and the X production equipment is expensive, resulting in high costs. In addition, although the sol-gel method has the potential to be significantly cheaper than the above-mentioned vapor phase method, it has the problem that it is difficult to obtain glass of a size that is generally used as a base material for optical fibers. was there. (Hitachi Unexamined Patent Publication No. 55-100231) The present invention solves the above problems, and its purpose is to produce a high-quality quartz-based optical fiber base material of sufficient size using the conventional vapor phase method. The purpose is to provide a method that can be manufactured at a lower cost.

[Failure to solve the problem]

In the method for producing an optical fiber base material of the present invention, an appropriate metal alkoxide (M(OR )x.

An acidic alkyl silica-1-(Si (OR),) hydrolyzed solution containing 0% or more of molar ratio (M is a metal, R is an alkyl μ group) and ultrafine powdered silica are uniformly dispersed. Two or more types of zo/l' solution obtained by mixing fine powder silica dispersed dissolved acid are prepared by changing the dopant concentration in the sol solution, and the sol solution OPH value and effective glass component concentration are set to predetermined values. Step of adjusting and preparing a prepared sol solution, transferring the prepared sol solution to a cylindrical rotating container 200-5
00QC] At least once, the sol is gelled while rotating at a predetermined rotational speed in the range of rpm to form a tubular wet gel, and if necessary, the charged sol is poured into the central hole formed in the process of forming the tubular wet gel. a step of producing a wet gel with concentric composition changes (refractive index changes), a step of drying the wet gel to produce a dry gel, and a step of sintering the dry gel to make it transparent vitrified. It is characterized by

Examples of dopants used in the present invention include tetraalkoxyaluminum (Al(oa)a), tetraalkoxytitanium (Ti(OR)4), and tetraalkoxytitanium (Ti(OR)4), which change the refractive index when incorporated into quartz glass. Alkoxygermanium (Ge(OR)4) and tetraalkoxyzirconium metal alkoxide are selected, but tetraalkoxygermanium is preferred because it can be easily manufactured into large-sized optical fiber base materials with good transparency without cracking. Particularly desirable.

Among the steps of preparing an acidic alkyl silicate hydrolyzed solution containing 0% or more of a dopant in molar ratio, which is included in the method for producing an optical fiber preform of the present invention,
In the process of preparing an acidic alkyl silicate hydrolyzed solution (excluding %), after the argyl silicate is added with water, the required amount of the metal alkoxide is added and reacted, and then water is added to dissolve the remaining alkoxide groups (alcohol) in the solution. (excluding the alkoxide group). At this time, the amount of water added when partially hydrolyzing the alkyl silicate is preferably in a molar ratio of 1 to 5 with respect to the alkyl silicate. This is because if an alkyl silicate is partially hydrolyzed with water with a molar ratio of 1 or less, the reaction solution will gel as soon as the hydrolysis reaction occurs, and the alkyl silicate will be partially hydrolyzed with water with a molar ratio of 3 or more. When decomposed, a small amount of water is likely to be present in the reaction solution, and when a metal alkoxide is added, the metal alkoxide reacts with water, producing microparticles that are thought to be metal oxides, which may cause transparency during sintering. In this step, it is desirable to keep the reaction solution at a temperature of 10° C. or lower. This is because unless the reaction solution is kept at 10° C. or lower, the viscosity of the reaction solution increases or gelation occurs.

In addition, in this step, if water is added to a solution containing 20% or more, preferably 40%, of alcohol by volume relative to the alkyl silicate and a partial hydrolysis reaction is performed, the reaction becomes more uniform. The resulting hydrolysis solution has low viscosity and good stability, and the reaction solution is heated at 10°C.
The amount of water added during partial hydrolysis does not need to be kept below 0. However, the range of the amount of water added during partial hydrolysis is also wide. The content is a little high, so you need to dry it carefully.

In the method for manufacturing an optical fiber preform of the present invention, the ultrafine powder silica dispersion solution has an average particle size of 0.01 to 1.0.
It is desirable that ultrafine silica powder in the μm range be contained in an amount of 0.15 g/ml or more.

If the average particle size of ultrafine powder silica is small, the viscosity of the ultrafine powder silica dispersion solution increases and it becomes difficult to contain ultrafine powder silica to a practical concentration. Therefore, the average particle size of ultrafine powder silica is 0. The lower limit is .01 μmn. In addition, if the average particle size is large, sedimentation of the superacid powder silica will occur during gelation while rotating in a cylindrical container, resulting in distribution of M911 powder silica in the radial direction of the wet gel, resulting in the drying process of the wet gel. The average particle size of the ultrafine silica powder is at most 1.0 μm since the particles will crack inside.

In addition, if the concentration of ultrafine powder silica in the ultrafine silica dispersion solution is low, the wet gel made using the solution will shrink when it becomes a dry pull and will be prone to cracking during the process of drying the wet gel. The concentration of silica is preferably 0.1597ml or more. As a result of further investigation into the conditions for producing quartz glass with a good yield, the average particle size of the ultrafine powder silica contained in the ultrafine powder silica dispersion solution was 0.04 to Q, and the 471m% concentration was 0.25. 9/m
It was found that KW-* is more than 75f.

In the method for manufacturing an optical fiber base material of the present invention, when the prepared sol solution is transferred to a cylindrical rotating container and gelled while being rotated, the ultrafine powder silica contained in the sol is affected by centrifugal force due to the rotation of the cylindrical rotating container. In order to remove the opening point, which causes sedimentation and distribution of ultrafine powdered silica in the radial direction of the wet gel and cracks during the drying process of the wet gel, the average particle size of the ultrafine powdered silica described earlier is In addition to setting limits on the number of rotations of the cylindrical rotating container and gelation time, it is also necessary to set certain limits on the rotation speed of the cylindrical rotating container and the gelling time. That is, the rotation speed of the cylindrical rotating container was set to 5000 rpm or less, and the gelation time was set to 6.
It is necessary to keep the time to 00 minutes or less. Although this depends on the size of the cylindrical rotating container used, a rotation speed of 5000 rpm or less is more desirable in order to produce a practical size optical fiber preform (diameter of 10 mm or more).

If the cylindrical rotating container is rotated at 200 rpm or less, it will be difficult to obtain a tubular wet gel with a clean inner surface for one axis of rotation, so in the process of making the tubular wet gel, the cylindrical rotating container is rotated at 20 rpm. It is necessary to rotate at a rotation speed higher than that. In the present invention, this operation is repeated 9 times as necessary to produce a wet gel with a compositional change, but if necessary, the charged sol may be poured into the pores of the obtained tubular wet gel and the pores closed. good.

In the method for producing optical fiber preforms of the present invention, when wet gel shrinks to become dry gel or transparent glass, if the shrinkage rate is extremely large, it will easily break during the drying and sintering processes, and the optical fiber preforms can be manufactured with good yield. Difficult to manufacture. Therefore, it is desirable that the concentration of the effective glass component in the sol solution used when making a wet gel is high. However, increasing the effective glass component is not practical because it increases the viscosity of the sol solution, making it difficult to operate, and requires a special operation to increase the effective glass component. . After examining the conditions in detail, we found that if the composition of the sol solution is selected so that when the wet gel is dried and sintered to become transparent glass, the volume of the transparent glass is in the range of 5 to 15% of the volume of the wet gel. I knew it was a good thing.

In the method for manufacturing an optical fiber preform of the present invention, there are certain conditions that must be met in order to obtain transparent glass from wet gel with a good yield.

That is, the wet gel component at any dopant concentration must have the same shrinkage rate to form a transparent glass. That is, when the wet gel is dried and sintered to form transparent glass, the sol solution must be adjusted so that the ratio of the volume of the transparent glass to the volume of the wet gel remains constant regardless of the dopant concentration of the sol solution. Must be.

In the method for manufacturing optical fiber preforms of the present invention, the drying process from wet gel to dry gel is the most important process that affects the yield, but drying is a condition for wet gel to shrink without cracking. It is necessary to proceed uniformly inside the wet gel. To achieve this, it is best to dry as slowly as possible, but after considering productivity, etc.
If the temperature is raised to a temperature of 40 to 160°C at an aperture ratio of 10% or less and a heating rate of 120°C/hr or less, and dried at a temperature within that temperature range, a dry gel can be obtained with a high yield in a relatively short period of time. . Drying the gelatinized cylindrical rotating container with a lid of the above-mentioned aperture ratio is a good way to obtain a dry gel with relatively little effort and high yield. If you use the method of transferring it to a container and drying it inside,
In addition, it is possible to obtain 0 Vf with better yield.
At this time, a method of transferring a plurality of wet gels into the container and drying them therein is desirable as a method of increasing productivity without affecting yield.

In the method for manufacturing an optical fiber preform of the present invention, the step of sintering the dry gel consists of the following seven steps.

1) Process of desorption water treatment 2) Process of decarbonization 6) Process of promoting dehydration condensation reaction 4) DeOH
Base treatment step 5) Dechlorination treatment or defluorination treatment step 6) Pore closing treatment step 7) Transparent vitrification treatment step (1) Deadsorbed water treatment step is the sintering step. Physically adsorbed water, which has the greatest effect on the yield in the process, can be removed by heat treatment at approximately 400°C, which is adsorbed in large amounts on the dry gel. However, if the temperature is raised rapidly at this time, cracks are likely to occur, resulting in a decrease in yield. However, if the temperature increase rate is too low, the processing will take too much time and the manufacturing cost will increase. As a result of detailed investigation, the upper limit of desorption water treatment without reducing yield is approximately 400℃/hr.
Therefore, it is desirable to carry out an operation of holding at a predetermined temperature of 400° C. for at least one hour at least once. This is because holding the gel at a predetermined temperature for at least one hour creates a condition in which the desorbed water reaction occurs more uniformly within the gel, which helps improve the yield.

In the step (2) of decarbonizing, the decarbonizing treatment is performed by heat treatment in the range of 400 to 900°C.

At this time, ammonia and acid salts (ammonium salts) present inside the gel can also be removed. As with the previous desorption water treatment, the temperature increase rate affects the yield, but a temperature increase rate of 50 to 50 b/hr is practical. Further, when performing this treatment, the presence of 0□Ganu is required in the atmosphere.

In the step of promoting the dehydration bonding reaction (6),
The dehydration condensation reaction is accelerated at a heating rate of 30 to 400°C/
hr to the specified temperature within the range of 90 to 1200℃!
+ Warming and holding at that temperature for at least 30 minutes at least once. The purpose of this step is to accelerate the dehydration condensation reaction inside the gel and reduce unreacted OR groups.If you proceed to the next step without going through this step, during the OH group removal treatment, In the 0-piece process, a large amount of the base material is consumed, which often results in foaming during the transparent vitrification process.The heating rate also affects the yield, but the above range is practical. .

The purpose of the OH group removal process (4) is to remove OH groups that have a particularly serious effect on the transmission loss of the optical fiber. In this step, a carrier gas such as He that does not contain moisture or other impurities and a deOH base at a flow rate of 1 to 40% of the carrier gas are fed into a sintering furnace at temperatures ranging from 700 to 1100°C. By heating at a temperature of In order to completely remove the OH group, it is necessary to use the OH removing base in an amount of 1% or more based on the gear gas, but it is preferably in the range of 1 to 40%. ! ! The zero-removal base used in the damoto process is (yo5t-
OH) to react with (3Si C1) or (yo5i-
A reagent that gives F) is selected, but CI is used for reasons such as economic efficiency and ease of handling.

5OCI 2. SF,,cF4. C2F6. C2F8 is practical.

The purpose of the dechlorination or defluorination treatment (5) is to remove chlorine or fluorine present in the gel after the OIN removal treatment. If this step is omitted and the sintering step is proceeded, the chlorine or fluorine remaining in the glass tends to cause foaming when the transparent vitrified υ wire is drawn to make an optical fiber. Dechlorination or defluorination treatment is 800-1
The sintering is carried out at a temperature range of 200° C. while feeding O2 in a range of 1 to 100% with respect to a carrier gas such as He into a sintering furnace.

The pore-forming process (6) is carried out by making the inside of the furnace a vacuum or by raising the temperature while feeding He gas into the furnace. If the pores are opened without going through the above operations, atmospheric gas will be trapped in the closed pores, and bubbling will likely occur during transparent vitrification. Although the rising rate still affects the yield, it is only for 60~b. The temperature at which pore closure occurs in glass depends on the ratio of effective glass components contained in the hydrolysis solution and ultrafine powder dispersion solution mixed when preparing the sol, the average particle size of ultrafine powder silica, and the ultrafine powder silica. It is necessary to investigate the sample to be subjected to pore-closing treatment in advance because it varies depending on the particle size distribution, type of dopant, concentration of dopant, pore size distribution in the gel, water content in the gel, heating speed, etc.

In the examples of the present invention, the temperature was in the range of 900 to 1350°C.

After performing the pore-closing treatment, the material is heated to a predetermined temperature in the range of 1,200 to 1,600°C, held at that temperature for a predetermined period of time, and subjected to the transparent vitrification treatment to obtain an optical fiber matrix. .

Regarding the manufacturing method of the optical fiber preform of the present invention, the optimum temperature program under each sintering condition is determined by the ratio of the effective glass component contained in the hydrolysis solution and the ultrafine powder silica dispersion solution mixed when preparing the sol, Average particle size of ultrafine powder silica, particle size distribution of ultrafine powder silica, type of dopant,
It varies depending on the concentration of the dopant, the pore size distribution in the gel, the water content in the gel, etc., and is selected from the above-mentioned temperature range and heating speed.

By the above-described operations, a high-quality silica-based optical fiber preform having a sufficient size can be manufactured with good yield.The present invention will be described in detail based on the following examples.

[Example 1] ■ Preparation of hydrolysis solution Add 0.0 to 576.6 g of purified commercially available ethyl silicate.
199.5 g of 2N hydrochloric acid was added, and the mixture was hydrolyzed with vigorous stirring to obtain a hydrolyzed solution Hh.

Purified commercially available ethyl silicone) 134.0 to 19
．． 17.49 g of 2N hydrochloric acid was added, and the reaction solution was stirred vigorously while keeping the temperature below 5° C. After about 30 minutes, the reaction solution became a uniform transparent solution. Tetraethoxygermanium 11.6J9 is added little by little to this transparent bath solution while maintaining the temperature below 5°C, and the reaction is allowed to proceed with thorough stirring. After reacting for 20 minutes, while maintaining the reaction solution at 95° C. or lower, 32.3 f/ of water was added and reacted with thorough stirring to obtain hydrolyzed solution B.

■ Preparation of ultrafine powder silica dispersion solution 500 g of ultrafine powder silica with an average particle size of 0.15 μm synthesized by vapor phase method was mixed with 10100O! of water and stirred thoroughly. Further, this solution was irradiated with ultrasonic waves for 4 hours to achieve more uniform dispersion.

Clumpy foreign matter from the ultrafine silica powder is removed by centrifugation and filtration to obtain an ultrafine silica dispersion solution.

■ Preparation of sol solution and gelation 609 of the solution containing hydrolyzed solution A and ultrafine powdered silica,
89 was mixed to prepare a sol solution A. Similarly, 152.5 of a solution containing hydrolyzed solution B and ultrafine powdered silica. ! i+ was mixed to prepare sol solution B.

Next, the PR value was adjusted to 5.0 using 0.2N aqueous ammonia and water to the sol solution A, and the volume was adjusted to 1600 ml. Active glass component a, 231o9/ml.

Calculated value 1206.4 ml of this solution was transferred to a cylindrical rotating vessel made of vinyl chloride (inner diameter 40 mm, length 102071 mm, internal volume 12 s 66 mQ) whose inner surface was coated with silicone.A lid was placed on this cylindrical rotating vessel. After 60 minutes of adjusting the pH value to 5.0, I started rotating at 11,000 rpm.Gel formation occurred 20 minutes after I started rotating, but I kept rotating it for 10 minutes. Outer diameter 40m7M, inner diameter 80mm, length 1100mm
A tubular wet gel with dimensions of 0i was obtained. (The tubular wet gel is in a cylindrical rotating container.) In parallel, the pH value of the sol solution B was adjusted to 4.2 using 0.2N ammonia water and water, and the volume was adjusted to 400ml. A solution adjusted to (effective glass component concentration 0.2555
9 iml, calculated value) After removing the lid from the cylindrical rotating container that had been removed from the rotating device and standing still, the solution was poured into the tubular wet gel after 15 minutes of gelation, and the pH value was 4. 20 minutes after the adjustment, this solution also gelled, and a wet gel with a coaxial structure was obtained.

(Outer diameter: 40 m, length: 101,000 ta■ Wet gel made using the same method as drying) 10 v. Transfer to a drying container made of dry polypropylene. Next, this drying container was placed in a dryer at 60℃ and the wet gel was dried for 14 days.
Stable dry gel that does not crack even when left at room temperature (outer diameter 27
．． 0mm, length 675mm - average value) yield is 9100%
I got 10 pieces.

■ Sintering Next, this drive) V was placed in a quartz tubular sintering furnace and heated from 60°C to 200°C at a temperature increase rate of 30°C/hr.
Maintain this temperature for 5 hours, then increase the temperature by 1 degree to 30℃/
Heat from 200℃ to 300℃ with hr.
Desorption of water was carried out by holding for a certain period of time. Next, heating rate 3
Heating from 300°C to 1100°C at 0°C/hr,
This temperature was maintained for 60 minutes to perform decarbonization, dechlorination ammonium treatment, and acceleration treatment of dehydration condensation reaction. Subsequently, the temperature was lowered to 700℃, He 21/min, C120,2
It was held for 30 minutes while flowing a mixed gas of 1/min, and then heated to 80°C at a heating rate of 60°C/hr while flowing only He.
Heated to 0°C. He2. g/min
Hold for 1 hour while flowing a mixed gas of C1□0.21/min, then increase the temperature to 60℃ while flowing only He.
/ 11 r and heated to 900 °C.

He21/min, C1□0.21/rni at 900℃
The mixture was maintained for 1 hour while flowing a mixed gas of n to perform OH group removal treatment. Next, while flowing a mixed gas of 020.4 II /min against He 2 l/min K, the mixture was heated to 1050°C at a heating rate of 60°C/hr and held at this temperature for 1 hour to perform dechlorination treatment. Ta.

Next, without flowing only H'e, the temperature increase rate was 60℃/hr.
The sample was heated to 1250° C. and held at this temperature for 60 minutes to perform a pore-closing treatment. Next, the sample was heated at a rate of 60℃/
When heated to 1650° C. for 1 hour and held at this temperature for 1 hour, it became non-porous and a transparent optical fiber base material was obtained. In addition, cracking occurred frequently during the sintering process, and the yield was 100%. The size of this optical fiber base material is 1a8mm in diameter,
The length was 470 mm, and the diameter of the portion corresponding to the core was 6.7 mm. (The loss is less than 1%) When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption peak in the infrared region, there was no absorption peak at 2.7 μm. Not recognized, lp
It was confirmed that it was below pm. Furthermore, when the glass body was fused by covering it with a quartz jacket tube and drawn, no foaming occurred, and a high-quality single-mode optical fiber was obtained.

[Example 2] Hydrolyzed solution g! When preparing A, 0.02N nitric acid was used instead of 0.02N hydrochloric acid, and when preparing hydrolysis solution B, 0.2N nitric acid was used instead of 0.2N hydrochloric acid. A hydrolyzed solution was prepared in the same manner as in Example 1, except that .

This hydrolyzed solution was mixed with an ultrafine powder silica dispersion solution prepared in the same manner as in Example 1, and then a sol solution was prepared, gelled, dried, and
After sintering, the yield was 90%, and the motherboard for optical fiber could be manufactured. However, even if the hydrolysis solution was prepared using sulfuric acid or acetic acid instead of hydrochloric acid or nitric acid, the optical fiber base material could be manufactured in the same way.

[Example 3] The same operation as in Example 1 was performed except that methyl silicate was used as the alkyl silicate when preparing the hydrolyzed solution, and an optical fiber preform was manufactured with a yield of 90%. However, the amount of methyl silicate used was 421.1 g when preparing hydrolysis solution A, and 97.9 g when preparing hydrolysis solution B.

[Example 4] 0.0 to 576.6 g of purified commercially available ethyl silicate
Hydrolysis solution A was obtained by adding 199.59% of 2N hydrochloric acid and stirring vigorously for hydrolysis.

02 to 134.1 g of purified commercially available ethyl silicate
Add 11.6 g of specified hydrochloric acid and stir vigorously while keeping the reaction solution below 5°C. After about 50 minutes, the reaction solution becomes transparent, but gelation occurs immediately and a homogeneous solution is obtained. I couldn't do it. As a result of detailed experiments, it was found that even if ethyl silicate is partially hydrolyzed with water having a molar ratio of 1 or less to ethyl silicate, a homogeneous solution cannot be obtained.

[Example 5] 0.0 to purified commercially available ethyl silicate 576.69
Hydrolysis solution A was obtained by adding 199.59% of 2N hydrochloric acid and stirring vigorously for hydrolysis.

Purified commercially available ethyl silicate 154.19 to 0.2
Add 40.6 g of specified hydrochloric acid and stir vigorously while keeping the reaction solution below 5℃. After about 25 minutes, the reaction solution becomes a homogeneous and transparent solution.The transparent solution here becomes a homogeneous transparent solution while keeping the temperature below 5℃. When 11.65 g of tetraethoxygermanium was added little by little, the reaction solution became cloudy and did not become a homogeneous solution. As a result of detailed experiments, we found that when ethyl silicate is partially hydrolyzed with water at a molar ratio of 6 or more to ethyl silicate, the reaction solution becomes cloudy when tetraethoxygermanium is added later, and the distribution of germanium and silicon becomes cloudy. It turns out that the results are not uniform.

[Example 6] Purified commercially available ethyl silica) 134.19 to 02
Add 17.4 g of specified hydrochloric acid and stir vigorously to obtain 60
After about a minute, the reaction solution started to gel. As a result of detailed experiments, it was found that gelation tends to occur if the reaction solution is kept at a temperature below 10°C. Also, during the subsequent steps of adding tetraalkoxygermanium and total hydrolysis, gelation tends to occur unless the reaction solution is kept below 10°C, so it is desirable to keep the reaction solution below 10°C. I understand.

[Example 7] (1) Preparation of hydrolysis solution Anhydrous ethanol-tLy21Brnl was added to purified commercially available ethyl silicate 549.19 and stirred thoroughly. Subsequently, 190.0 g of 0.02N hydrochloric acid was added, and the mixture was hydrolyzed by vigorous stirring to obtain a hydrolyzed solution A.

Purified commercially available ethyl silicate 127.7. ! Add 55 ml of anhydrous ethanol/l to 9 and stir well.
Subsequently, 0.02N hydrochloric acid ii,og was added and stirred vigorously for 60 minutes. 11.10 g of tetraethoxygermanium was added little by little to this reaction solution and stirred well. 2
After reacting for 0 minutes, 36.3 g of 0.02N hydrochloric acid was added to this reaction solution and reacted with thorough stirring to obtain hydrolysis solution B. 0 ■ Preparation of ultrafine powder silica dispersion solution Synthesis by vapor phase method 500 g of the obtained ultrafine powder silica having an average particle size of 0.15 μm was gradually added to 10,001 nl of water and thoroughly stirred. Further, this solution was irradiated with ultrasonic waves for 4 hours to ensure uniform dispersion.

Clumpy foreign matter from the ultrafine powdered silica was removed (by centrifugation and filtration) to obtain an ultrafine powdered silica dispersion solution.

580 of a solution containing hydrolysis solution A and ultrafine powdered silica,
89 was mixed to prepare a sol solution A. Similarly, hydrolysis solution B and solution containing ultrafine powder silica 145 and 29 were mixed to make sol solution B. Next, 02 normal ammonia water and water were added to sol solution A to adjust the pH value to 5.5. and the volume was adjusted to 1600ml. (Effective glass component concentration 0, 22097ml, calculated value) 1206.4 of the solution of
ml in a cylindrical rotating container made of vinyl chloride (inner diameter 40 mm, length 1020 mm) whose inner surface is coated with silicone.

(inner volume 1.256.6 ml). This cylindrical rotating container was capped and attached to a rotating device, and 30 minutes after adjusting the pH value to 5.5,
Gelation occurred 15 minutes after the rotation started at 0 rpm, but the tube was rotated for 10 minutes and a tubular wet gel 7 with dimensions of outer diameter 4.0 mm, inner diameter 80 mm, and length 10 QQis was formed. Obtained. (The tubular wet gel is in a cylindrical rotating container.) In parallel, the pH value of sol solution B was adjusted to 5.1 using 0.2N ammonia water and water, and the volume was adjusted to 4.
To prepare a solution adjusted to 0.00ml (effective glass component concentration: 0.2243 g/ml, calculated value), remove it from the rotating device, remove the lid of the cylindrical rotating container that has been left standing, and let it gel for 10 minutes. When this solution was poured into the subsequent tubular wet gel, the solution also gelled 22 minutes after adjusting the pH value to 5.1, and a wet gel with a coaxial structure was obtained. (Outer diameter 407
1M, length 1000mm) ■Drying 20 wet gels prepared in the same manner as above were aged in a cylindrical rotating container in a closed state at 30°C for 2 days, and 10 of them were aged with an aperture of 0.1%. The remaining 10 bottles were placed in a polypropylene drying container with an opening ratio of 0.1% at both ends of the cylindrical rotating container. Next, I put these in a dryer at 60℃ to dry the wet gel, and after 17 days it turned out to be a stable drive that would not break even if left at room temperature (outer diameter 26.5 mm, length 663 mm - average value). Obtained. When the former method was selected as the drying method, the yield was 90%, and when the latter method was selected, the yield was 80%.

(2) Sintering When one drive/liter was sintered using the same method as in Example 1, an optical fiber base material was obtained with a yield of 100%. The size of this optical fiber base material is 18.5 in diameter.
The length was 463 mm, and the diameter of the portion corresponding to the core was 3.7 mm.

When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption spectrum in the infrared region, no absorption peak was observed at 2.7 μm, and lppm It was confirmed that: Furthermore, a high-quality optical fiber was obtained without foaming when drawn.

As shown in this example, using alcohol when preparing a hydrolysis solution saves the effort of cooling compared to not using alcohol, which is more practical. In addition, the viscosity of the sol solution mixed with the hydrolyzed solution or the solution containing ultrafine powdered silica was low, and the workability was good.

[Example 8] (1) Preparation of hydrolyzed solution 549.1 g of purified commercially available ethyl silicate (2,18 ml of K anhydrous ethanol) was added and stirred thoroughly. Subsequently, 190.09 g of 0.02 N hydrochloric acid was added, and the mixture was hydrolyzed by vigorous stirring to obtain a hydrolyzed solution A.

55 ml of absolute ethanol was added to 127.717 purified commercially available ethyl silicate and stirred well. followed by 0
．． 02N hydrochloric acid 11.0.9 was added and stirred vigorously for 60 minutes. 5.54 g of tetraisopropoxygermanium 1' was added little by little to this reaction solution and stirred well. 2
After reacting for 0 minutes, add 002N hydrochloric acid 3 to this reaction solution.
6.3 g was added and reacted with thorough stirring to obtain a hydrolyzed solution B.

■ Preparation of ultrafine powder silica dispersion solution 500 g of ultrafine powder silica with an average particle size of 007 μm synthesized by vapor phase method was gradually added to 10100 O water.
Stir thoroughly. Further, this solution was exposed to ultrasonic waves for 4 hours to achieve more uniform dispersion.

Clumpy foreign matter from the ultrafine powdered silica was removed by centrifugation and filtration to obtain a dispersion solution of ultrafine powdered silica.

■ Preparation of sol solution and gelation Hydrolysis solution A and ultrafine powder silica dispersion solution 580, 8
A sol solution A was prepared by mixing the silica powder with the following ingredients and further applying ultrasonic vibration to disperse the ultrafine powder silica.

Similarly, hydrolysis solution B and solution 1 containing ultrafine powder silica
45.2 g were mixed, and ultrasonic vibration was similarly applied to disperse the ultrafine powdered silica to obtain sol solution B.

Next, the pH value of the sol solution A was adjusted to 5'5 using 0.2N aqueous ammonia and water, and the volume was adjusted to 1600ml. (Calculated value of effective glass component 0.220 g/ml) 1206.4 ml of this solution was transferred to a metal cylindrical rotating container (inner diameter 40 mm, length 1020 mm, internal volume 1256.6 m1) whose inner surface was coated with Silicoten. .

Put a lid on this cylindrical rotating container and attach it to the rotating device,
1 after 60 minutes after adjusting the pH value to 5.5.
Rotation started at 500 rpm. 21 years since I started spinning
After a few minutes, gelation occurred, and the machine was rotated for 20 minutes, and the outer diameter was 40m7rLs, the inner diameter was ao, m, and the length was 1.
A tubular wet gel with dimensions of 1000i was obtained. (The tubular wet gel = 68- is in a cylindrical rotating container.) In parallel, the PR value was adjusted to 5.2 using 0.2N aqueous ammonia and water in the sol solution B, and A solution whose volume was adjusted to 400 ml (effective glass content: 0,2243 fl/ml, calculated value) was prepared, and the lid of the cylindrical rotating container, which had been removed from the rotating device and left standing, was removed and gelatinized for 23 minutes. When this solution was poured into the subsequent tubular wet gel, P
Eighteen minutes after the H value was adjusted to 5.2, this solution also gelled, and a wet gel with a coaxial structure was obtained.

(Outer diameter 40'mNs Length 1000.)■Drying 10 wet gels prepared in the same manner were aged in a closed cylindrical rotating container at 30°C for 2 days.
Thereafter, it was transferred to a drying container with an open area ratio of 0.1%. Next, this drying container was placed in a dryer at 58°C to dry the wet gel. After 17 days, it became a stable dry gel that did not break even when left at room temperature (outer diameter 26.2 mm, length 65 mm).
8-average value) were obtained with a yield of 9100%.

(2) Sintering Ten drykels were sintered in the same manner as in Example 1, and an optical fiber base material was obtained with a yield of 100%. The size of this optical fiber base material is 1 a 5 mm in diameter and 4 mm in length.
There are 66 lines, of which the diameter of the part corresponding to the core is 3
．． There were seven strikes.

When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption spectrum in the infrared region, no absorption peak was observed at 2.7 μm, and it was below lppm. This was confirmed. Furthermore, a high-quality optical fiber was obtained without foaming when drawn.

[Example 9] (1) Preparation of hydrolyzed solution 218 ml of absolute ethanol was added to purified commercially available ethyl silica 549.19 and stirred thoroughly. followed by 0
, 190.0 g of 02 N hydrochloric acid was added thereto, and the mixture was hydrolyzed with vigorous stirring to obtain a hydrolyzed solution A.

55 ml of absolute ethanol was added to purified commercially available ethyl silicate 127.7.9 and stirred thoroughly.
11.0 g of 02N hydrochloric acid was added and stirred vigorously for 60 minutes. Tetraethoxygermanium 11 is added to this reaction solution.
．． 10 g was added little by little and stirred well. After reacting for 20 minutes, 363 g of 002N hydrochloric acid was added to this reaction solution and reacted with thorough stirring to obtain a hydrolyzed solution B.

(2) Preparation of ultrafine powder silica dispersion solution Ultrafine powder silica 500I with an average particle size of 0.15 μm synthesized by a vapor phase method was gradually added to 3066 TLl of water and thoroughly stirred. Further, this solution was irradiated with ultrasonic waves for 4 hours to achieve more uniform dispersion.

Clumpy foreign matter from the ultrafine powdered silica was removed by centrifugation M, if'' to obtain a dispersion solution of ultrafine powdered silica.

■ Hydrolyzed solution A and ultrafine powder silica (dispersion) solution 1
380.8g were mixed to form sol solution A.

Similarly, hydrolysis solution B and solution 3 containing ultrafine powder silica
45.29 were mixed to prepare a sol solution B.

Next, the pH value of the sol solution A was adjusted to 5.60 using 0.2N aqueous ammonia and water, and the volume was adjusted to 2400 m.
Adjusted to l. (Effective glass component 0.15.9/ml,
Calculated value) 1206.4 ml of this solution was placed in a cylindrical rotating container made of vinyl chloride (inner diameter 40
The tube was transferred to a container (mm5, length 1020 mm, internal volume 1256.6 ml). This cylindrical rotating container was capped and attached to a rotating device, and 30 minutes after adjusting the pH value to 560, it started rotating at 150 rpm. Gelation occurred 25 minutes after the start of rotation, but after 20 minutes of rotation, the outer diameter was 40 mm, the inner diameter was 807 nm, and the length was 100 mm.
A tubular wet gel with dimensions of 0 rhyme was obtained. (The tubular wet cell is in a cylindrical rotating container.) In parallel, 0.2N ammonia water and water are added to the sol solution B.
Prepared sol solution with H value adjusted to 5.6 and volume adjusted to 6ooml (effective glass component 0.115397ml)
1, calculated value), removed from the rotating device, removed the lid of the cylindrical rotating container that was standing still, and poured this solution into the tubular wet gel after 30 minutes of gelation. Thirty minutes after the value was adjusted to 5.3, this solution also gelled, and a wet gel with a coaxial tooth structure was obtained. (Outer diameter: 40 mm, length: 100 mm
100O■ Drying 10 wet gels prepared in the same manner are sealed in a cylindrical rotating container. The sample was aged at 60°C for 2 days until 200°C, and then transferred to a drying container with an open area of 0.1%. Next, put this drying container in a dryer at 60℃,
After drying the wet gel for 17 days, it turned out to be a stable dry gel that does not crack even when left at room temperature (outer diameter 23.211 m).
5 length: 584 mm, average value), 3 pieces were obtained at a yield of 30 inches.

(2) Sintering When three pieces of dry gel were sintered in the same manner as in Example 1, an optical fiber base material was obtained with a yield of 100%. The size of this optical fiber base material is 16.0 mm in diameter and 4 mm in length.
01, and the diameter of the part corresponding to the core is 3
．． There were 2 friends.

When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption spectrum in the infrared region, no absorption peak was observed at 327 μm, and it was confirmed that it was below 1 ppm. It was done. Furthermore, a high-quality optical fiber was obtained without foaming when drawn.

As in this example, a solution containing ultrafine powdered silica with a silica concentration of about 0.15g7ml (or as a result, when the wet gel is dried and sintered to become transparent glass, the volume of the transparent glass becomes wet) Although a high-quality optical fiber preform can be obtained by producing an optical fiber preform using gel (66% of the gel volume), the yield in the drying process was low at 30%, making it uneconomical. . In addition, it was not practical because the shrinkage was large and it was necessary to make a thicker wet gel. .

[Example 10] (1) Preparation of hydrolysis solution 155 ml of absolute ethanol was added to purified commercially available ethyl silica 427.29 and stirred well. followed by 0
．． 147.8 g of 0.2N hydrochloric acid was added thereto, and the mixture was hydrolyzed with vigorous stirring to obtain a 1-water decomposition solution A.

sqml of absolute ethanol was added to 97.1 g of purified commercially available ethyl silica, and the mixture was thoroughly stirred. Followed by 0.
02N hydrochloric acid (a) (4 g) was added, and the mixture was vigorously stirred for 60 minutes. Tetraethoxygermanium 11.0% was added to this reaction solution.
g was added little by little and stirred well.

After reacting for 20 minutes, 0.02N hydrochloric acid 28.4.9 was added to the reaction solution and the reaction was carried out with thorough stirring to obtain a hydrolyzed solution B.

(2) Preparation of ultrafine powder silica dispersion solution 500 g of ultrafine powder silica with an average particle size of 0.15 μm synthesized by the vapor phase method was gradually added to 10,100 O water and thoroughly stirred. Further, this solution was irradiated with ultrasonic waves for 4 hours to ensure uniform dispersion.

Clumpy foreign matter from the ultrafine powdered silica was removed by centrifugation and r-filtration to obtain an ultrafine powdered silica dispersion solution.

■ Preparation and gelation of sol solution 686 of the solution containing hydrolyzed solution A and ultrafine powdered silica,
4 g were mixed to prepare sol solution A. Similarly, hydrolysis solution B and solutions 171 and 69 containing ultrafine powdered silica were mixed to prepare sol solution B.

Next, the pH value of the sol solution A was adjusted to 5.3 using 0.2N aqueous ammonia and water, and the volume was adjusted to 1600 ml. (Effective glass component concentration CL 2209/ml
, calculated value) 12,064 ml of this preparation solution was placed in a cylindrical rotating container made of vinyl chloride whose inner surface was coated with silicone (
Inner diameter 40mm5 length 1020mm, internal volume 1256.6
rnl).

Put a lid on this cylindrical rotating container and attach it to the rotating device.
1 after 30 minutes after adjusting the pH value to 5.6
It started rotating at 200 rpm. (Constant speed rotation) Gelation occurred 15 minutes after the start of rotation, but after 10 minutes of rotation, the outer diameter was 40 m, the inner diameter was 8711 m, and the length was 110 m.
A tubular wet gel with dimensions 00i was obtained. In parallel with this, a prepared sol solution was prepared by adjusting the pH value of sol solution B to 5.0 using 0.2N aqueous ammonia and water, and adjusting the volume to 400ml.The effective glass component concentration was 0. 2243 g7ml (calculated value), removed from the rotating device, removed the lid of the cylindrical rotating container that was standing still, and poured this solution into the tubular wet gel after 12 minutes of gelation, and the pH value was 50. After 20 minutes of adjustment, this solution also gelled, and a wet gel with a cylindrical structure was obtained. (Outer diameter 40 mm, length 1000 m 1fL) ■ Drying 10 wet gels prepared in the same manner were aged in a closed cylindrical rotating container at 60°C for 2 days.
When transferred to a drying container made of polypropylene with an open area ratio of 0.01% and placed in a dryer at 65°C,
Nine dry gels (outer diameter 27.0 nm, length 675 mm, average value) that remained stable even after being left at room temperature for several days were obtained at a yield of 90%.

■ Sintering Next, this dry gel was placed in a quartz tubular sintering furnace and heated from 30°C to 200°C at a heating rate of 30°C/hr, held at this temperature for 5 hours, and then heated from 200°C to 600°C.
Heating at a heating rate of 60°C/hr until 50°C at this temperature.
Desorption of water was carried out by holding for a certain period of time. Next, heating rate 6
Heating from 600 °C to 1050 °C at 0 °C/hr,
This temperature was maintained for 60 minutes to perform decarbonization, dechlorination ammonium treatment, and acceleration treatment of dehydration network reaction. Subsequently, the temperature was lowered to 700°C and He 2 l/min, c
3 while flowing a mixed gas of 120.2 l/min.
The temperature was maintained for 0 minutes, and then the temperature was heated to 800°C at a temperature increase rate of 60°C/hr without flowing only He gas. He 2 l/min at 800°C.

The mixture was maintained for 1 hour while flowing a mixed gas of 20.2 l/min, and then heated in a trench at 900°C at a heating rate of 60°C/hr without flowing only He gas. 90
He 2 l/min at 0°C, cl 20.2
Hold for 1 hour while flowing mixed gas at l/min.
OH group removal treatment was performed. Next is He21/rrun
Heating to 1000°C at a rate of 60°C/hr while flowing a mixed gas at a rate of 020.41/min.
This temperature was maintained for 1 hour to perform dechlorination treatment. Next, I (without flowing only e gas, the temperature increase rate was 30℃/h.
The sample was heated to 1250° C. using r and held at this temperature for 60 minutes to perform a pore-closing treatment. Four of the samples subjected to the above treatment were heated from 1250°C to 1550°C at a heating rate of 60°C/hr and held at this temperature for 1 hour. Obtained with 100 pieces. Furthermore, when five of the samples subjected to the pore-closing treatment were passed through a ring heater at 1600° C. to render them pore-free, a transparent optical fiber base material was obtained at a yield of 100%. The size of this optical fiber base material is 18.5 in diameter.
The length was 461 m, and the diameter of the portion corresponding to the core was 6.7 m.

The OH groups contained in the optical fiber base material obtained in this example were quantified by measuring absorption spectra in the infrared region.
No absorption peak at μm was observed, and it was confirmed that the absorption peak was at 1 ppm or less.

Furthermore, a high-quality optical fiber was obtained without foaming when drawn.

When preparing the charged sol solution in this way, the ratio of the effective glass component from the acidic alkyl silicate hydrolysis solution to the effective glass component from the solution containing ultrafine powder silica is 3.
Although the optimum sintering conditions were slightly different in both the case of 5:65 and the case of 45:55 in Example 7, high-quality optical fiber preforms were obtained. As a result of detailed experiments, this ratio is 20:80 to 80.
A range of 20 was found to be practical.

[Example 11] ■ Preparation of hydrolysis solution Purified commercially available ethyl silica) 549.1,! i
+ [218 ml of absolute ethanol was added and stirred well. Subsequently, 190.0 g of 0.02N hydrochloric acid was added, and the mixture was hydrolyzed by vigorous stirring to obtain a hydrolyzed solution A.

55 ml of absolute ethanol was added to 127.79 g of purified commercially available ethyl silicate and stirred thoroughly. followed by 0.0
2N hydrochloric acid 11. C1p was added and stirred vigorously for 60 minutes. Tetraethoxygermanium 11 is added to this reaction solution.
．． 10p was added little by little and stirred well. After reacting for 20 minutes, 36.39 g of 002N hydrochloric acid was added to this reaction solution and reacted with thorough stirring to obtain a hydrolyzed solution B.

(2) Preparation of ultrafine powder silica dispersion solution 500 g of ultrafine powder silica with an average particle size of 0.65 μm synthesized by the vapor phase method was gradually added to 10,100 O water and thoroughly stirred. Further, this solution was irradiated with ultrasonic waves for 4 hours to achieve more uniform dispersion.

Clumpy foreign matter from the ultrafine silica powder was removed by centrifugation and filtering to obtain an ultrafine silica dispersion solution.

■ Preparation of sol solution and gelation 580 of the solution containing hydrolyzed solution A and ultrafine powdered silica,
8 g were mixed to prepare sol solution A. Similarly, 145.2 of a solution containing hydrolyzed solution B and ultrafine powdered silica. ! 9 was mixed to prepare sol solution B.

Next, the pH value was adjusted to 5.6 using 0.2N aqueous ammonia and water to the sol solution A, and the volume was adjusted to 160.0++.
Adjusted to +l. (Effective glass component concentration 0, 220 g
/ml, planned value) 1206.4 ml, liter of this solution was placed in a cylindrical rotating container made of vinyl chloride whose inner surface was coated with silicone (inner diameter 40 mm, length IC 120 mm).

It was transferred to a container with an internal volume of 1256.6 m1). This cylindrical rotating container was capped and attached to the rotating container, and the PI (value was adjusted to 5.42 and 60 minutes later, the temperature was 150 O.
It started rotating at rpm. Gelation occurred 18 minutes after starting the rotation, but-! The gel was rotated for 15 minutes to obtain a tubular wet gel having dimensions of an outer diameter of 40 mvts, an inner diameter of aomm, and a length of 1000 mm. In parallel with this, sol solution i
The pH value of B was adjusted to 5.0 using 02N ammonia water and water.
Make a solution whose volume is adjusted to 2 and the volume is adjusted to 4 ooml.The effective glass component is 0.2243 ji/me.
, calculated value), removed from the rotating device, removed the lid of the cylindrical rotating container that was standing still, and gelled.
When this solution was poured into the tubular wet gel after 8 minutes, the solution also gelled 15 minutes after adjusting the pH value to 52, and a wet gel with a coaxial structure was obtained. (Outer diameter: 40 mm, length: 101,000 i) 10 wet gels prepared in a similar manner were aged in a cylindrical rotating container for 2 days at 30°C in a sealed state.
Thereafter, it was transferred to a drying container with an open area ratio of 0.1%. Next, this drying container was placed in a dryer at 65°C to dry the wet gel. After 15 days, a stable dry gel (outer diameter 28.0 mm, length 7
00m, m, average value) were obtained with a yield of 70 inches.

(2) Sintering When seven pieces of dry gel were sintered in the same manner as in Example 1, seven pieces of optical fiber base material were obtained with a yield of 100%.

The thickness of this optical fiber preform was 18.4 mm in diameter and 462 mm in length, of which the diameter of the portion corresponding to the core was 3.6 mm.

When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption spectrum in the infrared region, no absorption peak was observed at 2.7 μm, and it was found to be less than 1 ppm. confirmed. Furthermore, a high-quality optical fiber was obtained without foaming when drawn.

As shown in this example, an optical fiber base material could be manufactured even when ultrafine powdered silica having an average particle size of 0.35 μm was used. As a result of detailed experiments, it was found that when ultrafine powdered silica having an average particle size exceeding 1 μm was used, it was difficult to prepare a dry gel due to sedimentation of the particles during rotational gelation.

[Example 12] ■ Preparation of hydrolysis solution -531 The same method as in Example 7 was used.

■ Preparation of solution containing ultrafine powdered silica The same method as in Example 7 was used.

■ Preparation of sol solution and gelation Rotation When the same method as in Example 7 was carried out except that the rotation speed during gelation was 50,000 rpm, fine powder silica sedimented due to the strong centrifugal force generated by rotation. happens,
(You can see it with your eyes) All of the wet gels fell apart during the drying process.

As a result of detailed experiments, the inner diameter was 40. When using a cylindrical rotating container of m, the rotation speed during rotational gelation is 5000 rpm.
It was necessary that it be less than m.

However, if the cylindrical rotating container was much smaller in size, for example with an inner diameter of 5 mm, it was possible to produce dry gel without cracking even at 5000 El r pm if the rotating time was shortened.

[Example 16] ■ Preparation of hydrolysis solution The same method as in Example 7 was used.

■ Preparation of ultrafine powder silica dispersion solution This was carried out in the same manner as in Example 7.

(2) Preparation and gelation of sol solutions Sol solutions A and B were prepared in the same manner as in Example 7.

Next, the pH value of the sol solution A was adjusted to 5.5 using 0.2N aqueous ammonia and water, and the volume was adjusted to 1600 ml. (Effective glass component concentration 0, 220 g/ml
, calculated value) 1 ml of 115a containing this prepared sol solution,
A metal cylindrical rotating container with silicone coating on the inside (
Inner diameter 40 mm, length 1020 mm, content fi 1256.6 m
I moved it to J). Put a lid on this cylindrical rotating container, attach it to the rotating device, adjust the pH value to 5.5, and then
After a minute, it started rotating at 1500 rpm. Although gelation occurred 15 minutes after the start of rotation, the gel was continued to rotate for 10 minutes to obtain a tubular wet gel having dimensions of an outer diameter of 40 mm, an inner diameter of 11.2 mm, and a length of 1000 mm.

In parallel, the pH value of sol solution B was adjusted to 5.1 using 0.2N aqueous ammonia and water, and the volume was adjusted to 40%.
Prepare the sol solution B adjusted to 0 ml (effective glass component: 0.2243 g/ml, calculated value), remove from the rotating device [-1] Remove the lid of the cylindrical rotating container that is standing still, After 12 minutes of gelation, 48.25 ml of this prepared sol solution B was poured into the tubular wet gel. After that, this cylindrical rotating container was capped and reattached to the rotating device and immediately started rotating at 150 rpm, and 18 minutes after adjusting the pH value to 51, this prepared sol solution B also gelled. Part 1″iJ,
When rotated for 10 minutes, the outer diameter is 40TIms and the inner diameter is 8.0
mm, length 1000. , a tubular wet gel was obtained.

■Drying 10 wet gels prepared in the same manner were aged in a cylindrical rotating container in a sealed state at 60°C for 2 days.
Subsequently, it was transferred to a polypropylene drying container with an open area ratio of 0.1%. When this drying container was placed in a dryer at 60°C and the wet gel was dried, the dry gel (outer diameter 26.5
．． , , inner diameter 56 lines, length 665 nm - average value) were obtained with a yield of 0.

(2) Sintering When nine pieces of dry gel were sintered using the same method as in Example 7, nine pieces of optical fiber base material were obtained with a yield of 100 inches. The size of this optical fiber base material is 1a5 mm in outer diameter.
It had an inner diameter of 57 mm and a length of 463 mm, of which the outer diameter of the portion corresponding to the core was 52 mm. Further, an optical fiber was obtained by making the optical fiber preform into a solid material by evacuating the central hole and then drawing it.

When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption spectrum in the infrared region, no absorption peak was observed at 2.7 μm, and it was below lppm. was confirmed. Furthermore, even when the fiber was drawn after solidification, no foaming occurred and a high-quality optical fiber was obtained.

[Example 14] (1) Preparation of hydrolysis solution 218 ml of absolute ethanol was added to purified commercially available ethyl silica 549.2.9 and stirred thoroughly. Subsequently, 190.0 g of 0.02N hydrochloric acid was added, and the mixture was hydrolyzed by vigorous stirring to obtain a hydrolyzed solution A.

55 ml of absolute ethanol was added to purified commercially available ethyl silica) 105.4.9 and stirred well. Followed by 0.
11.7 g of 2N hydrochloric acid was added and stirred vigorously for 60 minutes. Add 36% of tetraethoxygermanium to this reaction solution.
84.9 was added little by little and stirred well. After reacting for 20 minutes, 35.2 g of 02N hydrochloric acid was added to the reaction solution and the reaction was carried out with thorough stirring to obtain a hydrolyzed solution B.

■ Preparation of ultrafine powder silica dispersion solution Gradually add 500 g of ultrafine powder silica with an average particle size of 015 μm synthesized by vapor phase method to 10100O water.
Stir thoroughly. Furthermore, this solution was irradiated with ultrasonic waves for 4 hours to uniformly disperse it.

Clumpy foreign matter from the ultrafine silica powder was removed by centrifugation and filtration to obtain an ultrafine silica dispersion solution.

■ Preparation of sol solution and gelation 580 of the solution containing hydrolyzed solution A and ultrafine powdered silica,
89 was mixed to prepare a sol solution A. Similarly, 145.2 of a solution containing hydrolyzed solution B and ultrafine powdered silica. Sol solution B was prepared by adding a small amount of 2N hydrochloric acid to jQ to lower the pH.

Next, the pH value of the sol solution A was adjusted to 5.5 using 0.2N aqueous ammonia and water, and the volume was adjusted to 1600 ml. (Effective glass component concentration 0, 220 g7ml
, calculated value) 5278 ml of this solution was placed in a cylindrical rotating container made of vinyl chloride (inner diameter 40
17H, length 520m, content at 628.3ml
). This cylindrical rotating container was capped and attached to a rotating device, and 60 minutes after adjusting the pH value to 5.5, rotation was started at 180 rpm. Gel formation occurred 15 minutes after starting the rotation, but the
Rotate for 0 minutes, outer diameter 40mrls inner diameter 16g1 length 5
A tubular wet gel with dimensions of 00 m was obtained. In parallel, a solution was prepared in which the pH value of sol solution B was adjusted to 3.0 using 02N ammonia water and water, and the volume was adjusted to 400ml.The effective glass component was 0.2344.
g7m11 calculated value), removed from the rotating device, opened the lid of the cylindrical rotating container that was standing still, and poured this solution into the tubular wet gel after 15 minutes of gelation, resulting in a pH value of 60. After 22 minutes of adjustment, this solution also gelled, and a wet gel with a coaxial structure was obtained. (Outer diameter 40mm, length 500ii)■
Ten wet gels prepared in the same manner as drying were aged in a cylindrical rotating container in a sealed state at 60°C for 2 days.
Subsequently, it was transferred to a drying container made of polypropylene having an aperture ratio of 0.1. When this drying container was placed in a dryer at 60°C and the wet gel was dried, a stable dry gel (outer diameter 26.5
mm5 inner diameter 10, 67nrn, length 662 lines, average value)
Seven pieces were obtained with a yield of 70 cm.

(2) Sintering When seven pieces of dry gel were sintered using the same method as in Example 7, seven base materials for optical fibers were obtained with a yield of 100%. The size of this optical fiber base material is 1a5m in diameter.
The diameter of the portion corresponding to the core was 7.4 m.

When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption spectrum in the infrared region, no absorption peak was observed at 2.7 μm, and it was below lppm. was confirmed. Furthermore, a high-quality optical fiber was obtained without foaming when drawn.

As shown in this example, a base material for a multimode step-index optical fiber was fabricated by doping Ge with 10 molti.

[Example 15] (1) Preparation of hydrolysis solution A 218 d of absolute ethanol was added to 549.2 g of purified commercially available ethyl silicate and stirred thoroughly.

Subsequently, 190.0 g of 002N hydrochloric acid was added, and the mixture was hydrolyzed with vigorous stirring to obtain a hydrolyzed solution A.

B Purified commercially available ethyl silica) 119.5I was added with 55 ml of absolute ethanol and stirred well.

Add 11.7 g of 0.2 N hydrochloric acid to -61 one by one, and vigorously 6
Stirred for 0 minutes. 20.59 g of tetraethoxygermanium was added little by little to this reaction solution and stirred well. After reacting for 20 minutes, 35% of 0.2N hydrochloric acid was added to the reaction solution.
517 was added and reacted with thorough stirring to obtain a hydrolyzed solution B.

55 ml of absolute ethanol was added to 108.9 g of purified commercially available ethyl silica and stirred well.

Subsequently, 11.7.9% of 0.2N hydrochloric acid was added and stirred vigorously for 60 minutes. To this reaction solution, 32.779 g of tetraethoxygermanium was added little by little and stirred well. 2
After reacting for 0 minutes, 0.2N hydrochloric acid 5 was added to the reaction solution.
5.3 g was added and reacted with thorough stirring to obtain a hydrolyzed solution C.

D. 55 ml of absolute ethanol was added to 105.4 g of purified commercially available ethyl silica, and the mixture was thoroughly stirred.

Next, add 11.7 g of 02N hydrochloric acid and
Stir for a minute. 36.8 g of tetraethoxygermanium was added little by little to this reaction solution and stirred well. After reacting for 20 minutes, 35% of 0.2N hydrochloric acid was added to the reaction solution.
29 was added and reacted with thorough stirring to obtain a hydrolyzed solution.

(2) Preparation of fine powder silica dispersion solution 500 g of ultrafine powder silica with an average particle size of 0.15 μm synthesized by a vapor phase method was gradually added to 10,007 nl of water and thoroughly stirred. Further, this solution was irradiated with ultrasonic waves for 4 hours to ensure uniform dispersion.

Clumpy foreign matter from the ultrafine powdered silica was removed by centrifugation and Δ4 filtration to obtain an ultrafine powdered silica dispersion solution.

■ Preparation of sol solution and 580, 8 of kelization hydrolysis solution A and ultrafine powder silica dispersion solution
9 was mixed to obtain sol solution A.

Similarly, hydrolysis solution B and solution 1 containing ultrafine powder silica
A solution obtained by adding 2N hydrochloric acid to 45.2 g to lower the pH value was mixed to obtain sol solution B.

Similarly, hydrolysis solution C and solution 1 containing ultrafine powder silica
A solution obtained by adding 2N hydrochloric acid to 45.29 to lower the pH value was mixed, and a sol solution C was obtained.

Similarly, one of the solutions containing hydrolyzed solution and ultrafine powdered silica
45. Add 2N hydrochloric acid to 2.9 to lower the P value. The solutions were mixed to form a sol solution.

Next, 0.2N ammonia water and water were used in the sol solution A to adjust the P I-I value to 5.5 and the volume to 1600 ml to prepare a charged sol solution A. (Effective glass component concentration 0.220 g/ml!, calculated value) 471.23 TL of this prepared sol solution A was placed in a cylindrical rotating container made of vinyl chloride (inner diameter 40F1) whose inner surface was coated with silicone.
71 hours long, 520 meters long, internal volume 628.3 m1). Put a lid on this cylindrical rotating container and attach it to the rotating device.
30 minutes after the pH value was adjusted to 5.5, rotation was started at 1500 rpm. Gelation occurred 15 minutes after the start of rotation, but by continuing to rotate for 10 minutes, a tubular wet gel having dimensions of 40 mm in outer diameter, 20 mm in inner diameter, and 500 m in length was obtained.

In parallel, the sol solution B was adjusted to a pH value of 4.2 using 0.2N ammonia water and water, and the volume was adjusted to 400ml.
Prepare the sol solution B (effective glass component concentration: 2.280 g/ml, calculated value), remove it from the rotating device, and remove the lid of the cylindrical rotating container that has been left standing standing still. After 12 minutes of gelation, 100.53 ml of this prepared sol solution B was poured into the tubular wet gel. This man's cylindrical rotating container was capped and reattached to the rotating device and immediately started rotating at 150 rpm, and after 15 minutes after adjusting the pH value to 4.2, this prepared sol solution B also gelled. However, if you keep rotating it for 10 minutes, the outer diameter will be 40mm, the inner diameter will be 12mm,
Length 500. m tubular wet gels were obtained.

In parallel with this, the PH value of the sol solution C was adjusted to Δ2 using 0.2N aqueous ammonia and water, and the volume was adjusted to 400ml to prepare a charged sol solution C (effective glass component concentration 2. 328 fl/ml) Next, remove the lid from the cylindrical rotating container that was left standing standing still after removing it from the rotating device, and add 50.26 ml of this prepared sol solution C to the tubular wet gel that has been gelatinized for 10 minutes. ml was poured. I put a lid on this man's cylindrical rotating container and attached it to the rotating device again and immediately started rotating at 1500 rpm'm, and after 15 minutes after adjusting the value to PH-65 = 3.2, this prepared sol solution C also gelled, but when rotated for 10 minutes, the outer diameter was 40 mm and the inner diameter was 4 mm.

A tubular wet gel with a length of 500 m was obtained.

In parallel with this, the sol solution was adjusted to a pH value of 3.10 using 02N ammonia water and water, and the volume was 400ml.
The effective glass component concentration was adjusted to 2.344 fi/ml s (calculated value), and the lid of the cylindrical rotating container, which had been left standing standing still, was removed. After 10 minutes of gelation, this prepared sol solution was poured into a tubular wet gel, and after 12 minutes after adjusting the pH value to 3.1, this prepared sol solution also gelled and had a coaxial structure. A wet gel was obtained. (Outer diameter 40., Length 500.
10 wet gels prepared in the same manner as drying were aged in a closed cylindrical rotating container at 60°C for 2 days.
Subsequently, it was transferred to a polypropylene drying container with an open area ratio of 0.1%. When this drying container was placed in a dryer at 60°C and the wet gel was dried, the dry gel (diameter 26.5
mm, length 633 [gamma]m - average value) and a yield of 70t16.

(2) Sintering When seven pieces of dry gel were sintered using the same method as in Example 7, seven pieces of transparent glass bodies were obtained with a yield υ of 100%. The size of this transparent glass body is 1115 mm in diameter and 2 mm in length.
31. , among which the diameter of the component doped with 10 moles of Ge is 1.85 mm, and Ge has an EL of 89
The outer diameter of the molti-doped component is 5.55 mm, the m% inner diameter is 1.85 m, and the outer diameter of the 5,56 Ge-doped component is 9.25 m, and the inner diameter is 5.55 m.
, and the outer diameter of the Ge non-doped component was 1a5m, and the inner diameter was 9.25m.

Next, this transparent glass body was placed in a sintering furnace and heated to 1490°C.
A preform for a graded-index multimode optical fiber in which the refractive index changes gently in the radial direction was obtained by holding the sample at 100° C. for 1 hour.

When the OH groups contained in the optical fiber base material obtained in this example were quantified by measuring the absorption spectrum in the infrared region, no absorption peak was observed at 2.7 μm, and it was below 1 ppm. This was confirmed. Furthermore, a high-quality optical fiber was obtained without foaming when drawn.

As shown in this example, four types of sol solutions were prepared, a transparent glass body with a coaxial structure was made using them, and the refractive index was changed approximately in the radial direction by heat treatment at a high temperature for a predetermined time. Although it is possible to fabricate a graded index multimode optical fiber base material with a square distribution, it is possible to prepare a larger number of sol solutions and use them to fabricate a transparent glass body with an even finer coaxial structure.
By subsequently heat-treating at a high temperature, a graded index multimode optical fiber base material with even better band characteristics can be produced.

[Example 16] The lengths shown in the above examples are 520 mm, 1020 mm.
In this example, an optical fiber base material was produced using a cylindrical rotating container with a length of 40 mm and an inner diameter of 40 mm, but Example 7 could also be produced using a cylindrical rotating container with a length of 2020 mm and an inner diameter of 60 mm. A dry gel was produced with a yield margin of 0% using the same method (the amount of preparation was different). Since there is currently no sintering furnace for sintering this dry gel, transparent vitrification is only partially possible and a base material for optical fibers has not been obtained. From a good perspective, it is considered that it is easy to produce an optical fiber preform having a length of 1 m or more at an industrially practical yield using the method for producing an optical fiber preform of the present invention.

It was confirmed that optical fiber base materials can be produced using various methods such as titanium, aluminum, and zirconium in a similar manner.

However, ultrafine powdered silica can be synthesized using methods other than the vapor phase method, such as wet methods, ammonia synthesis methods, etc., and is selected according to the grade and price of the optical fiber to be manufactured.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to produce a high-quality preform for a silica-based optical fiber of a practical size at a lower cost than by the conventional vapor phase method. Further, according to the present invention, preforms for single mode optical fibers, preforms for multimode graded index optical fibers, preforms for multimode step index optical fibers, preforms for large diameter high NA step index optical fibers, etc. Can be manufactured. Therefore, it will be applied to various applications using optical fibers, including optical fiber communications.

that's all

Claims (1)

[Scope of Claims] (1) A suitable metal alkoxide (M(OR)_4
, M is a metal, R is an alkyl group) by mixing an acidic alkyl silicate hydrolyzed solution containing 0% or more in molar ratio and an ultrafine powder silica dispersion solution in which powdered ultrafine powder silica is uniformly dispersed. a step of preparing two or more types of sol solutions obtained by changing the dopant concentration of the sol solution, adjusting the pH value and effective glass component concentration in the sol solution to predetermined values, and preparing the sol solution; It includes at least one operation of transferring the prepared sol solution to a cylindrical rotating container and gelling it while rotating at a predetermined rotation speed in the range of 200 to 50,000 rpm to form a tubular wet gel, and if necessary, the operation of forming the tubular wet gel. Composition changes (
1. A preform for an optical fiber, comprising: a step of making a wet gel with a change in refractive index), a step of drying the wet gel to make a dry gel, and a step of sintering the dry gel to make it into transparent glass. manufacturing method. (2) The general formula of the metal alkoxide is Ge(OR
)_4 The method for manufacturing an optical fiber preform according to claim 1, characterized in that tetraalkoxygermanium represented by _4 is used. (5) In the step of producing an acidic alkyl silicate hydrolyzed solution containing the dopant in a molar ratio of 0% or more, in the step of producing an acidic alkyl silicate hydrolyzed solution containing the dopant (excluding 0%), The alkyl silicate is partially hydrolyzed with water in a molar ratio of 1 to 3 to the silicate, then the required amount of the metal alkoxide is added and reacted, and then water is added to form a solution remaining in the solution. 3. The method for producing an optical fiber preform according to claim 1 or 2, wherein the alkoxide group is hydrolyzed to obtain the hydrolyzed solution. (4) The method for manufacturing an optical fiber preform according to claim 3, characterized in that in the step of preparing the hydrolysis solution, the reaction solution is kept at a temperature of 10° C. or lower. (5) In the step of producing an acidic alkyl silicate hydrolysis solution containing the dopant in a molar ratio of 0% or more, the step of producing an acidic alkyl silicate hydrolysis bath solution containing the dopant (excluding 0%), alkyl silicate and a volume ratio of 2 to the alkyl silicate.
Water is added in a molar ratio of 0.1 to 3.9 to the alkyl silicate to a mixed solution of 0% or more alcohol to partially hydrolyze the alkyl silicate, and then the metal alkoxide is required. The optical fiber according to claim 1 or 2, characterized in that the alkoxide group remaining in the solution is hydrolyzed by adding a large amount of the solution and reacting, and then water is added to hydrolyze the alkoxide group remaining in the solution. Method of manufacturing base material. (6) The ultrafine powder silica dispersion solution has an average particle size of 0.
Ultrafine powder silica in the range of 0.01 to 1.0 μm is 0.1
6. The method for manufacturing an optical fiber preform according to claim 1, wherein the preform contains 5 g/ml or more. (7) In the step of gelling, the sol solution is gelled in a time period of 600 minutes or less by adjusting the temperature and pH of the sol solution. A method for manufacturing the optical fiber base material described above. (8) Adjust the composition of the sol bath solution so that when the wet gel is dried and sintered to become transparent glass, the volume of the transparent glass is in the range of 5 to 15% of the volume of the wet gel. A method for manufacturing an optical fiber preform as claimed in any one of claims 1 to 7. (9) When the wet gel is dried and sintered into transparent glass, the sol solution is adjusted so that the ratio of the volume of the transparent glass to the volume of the wet gel is constant regardless of the dopant concentration of the sol solution. A method for manufacturing an optical fiber preform according to any one of claims 1 to 8, characterized in that: (10) In the drying step, the wet gel is dried by forming lids with an opening ratio of 10% or less on both ends of the cylindrical rotating container.
9. The method for manufacturing an optical fiber preform according to item 9. (11) In the drying process, the wet gel is taken out from the cylindrical rotating container, and the wet gel is
Claims 1 to 10, characterized in that the product is transferred to a container having the following opening ratio and dried in said container.
A method for producing an optical fiber base material as described in . (12) After gelling at a temperature in the range of 5 to 60°C, the temperature is raised to a temperature of 40 to 160°C at a heating rate of 120°C/hr or less, and dried by shrinkage to create a dry gel. A method for manufacturing an optical fiber preform according to claims 1 to 11. (13) The step of sintering the dry gel consists of the following seven steps.
13. A method for manufacturing an optical fiber preform according to item 12. 1) Process of desorption water treatment 2) Process of decarbonization 3) Process of promoting dehydration condensation reaction 4) Process of removing OH group 5) Process of dechlorination or defluorination 6 ) Step of pore closing treatment 7) Step of transparent vitrification treatment (14) 20 to 400°C at a temperature increase rate of 400°C/hr or less
14. The optical fiber according to claim 13, wherein the deadsorbed water treatment is performed at least once by raising the temperature to a predetermined temperature in the range of and holding it at that temperature for one hour or more. Method of manufacturing base material. (15) 400-90 at a heating rate of 30-400℃/hr
15. The method for manufacturing an optical fiber preform according to claim 13 or 14, wherein the decarbonization treatment is performed by increasing the temperature to a predetermined temperature within a range of 0°C. (16) 900-12 at a heating rate of 30-400℃/hr
Raise the temperature to a predetermined temperature within the range of 00℃, and at that temperature
16. The method of manufacturing an optical fiber preform according to claim 13, wherein the dehydration condensation reaction is accelerated by performing a holding process for at least one minute. (17) At a temperature in the range of 700 to 1100°C, the flow rate ratio for He gas, O_2 gas, N_2 gas, Ar gas, or a mixture thereof is 1 to 1.
De-O while feeding 40% range of de-OH base into the furnace.
Claim 1 characterized in that H group treatment is performed.
A method for manufacturing an optical fiber preform according to items 3 to 16. (18) Cl_2, SOCL, S as the OH removing base
19. The method for manufacturing an optical fiber preform according to claim 18, wherein the OH group removal treatment is performed using any one of F_6, CF_4, C_2F_6, and C_2F_8. (19) After the OH group removal treatment, He gas or Ar gas or N
_2 gases or a mixture thereof with a flow rate ratio of 1
The method for manufacturing an optical fiber preform according to claims 13 to 18, characterized in that the dechlorination treatment or defluorination treatment is performed by sending O_2 in the range of ~100% into the furnace. . (20) Make the inside of the furnace a vacuum or feed He gas into the furnace at a heating rate of 30 to 400°C/hr to 900°C.
Claim 13, characterized in that the pore-closing treatment is performed by performing at least once a process of raising the temperature to a predetermined temperature within the range of ~1350°C and holding it at that temperature for 1 hour or more. 20. The method for manufacturing an optical fiber preform according to item 19. (21) After pore closing treatment, 1200 to 1600
The optical fiber motherboard according to claims 13 to 20, characterized in that the transparent vitrification treatment is performed by raising the temperature to a predetermined temperature in the range of °C and holding at that temperature for a predetermined time. Method of manufacturing wood.