JP2611684B2 - Manufacturing method of quartz glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for the production of quartz glass that had use of the sol-gel method.

[0002]

2. Description of the Related Art Quartz glass is used in various fields such as photomask substrates, glass wafers, semiconductor industrial materials, optical materials, preforms for optical fibers, and support tubes. It is expected that the demand will continue to increase in the future. .

The sol-gel method has been proposed as a method for producing quartz glass at low cost, and various methods are known.

[0004] For example, Nogami et al. "Journal
of Non-Crystalline Solid
s "Vo 1.37. No (l980), Rabinov
Itch et al. "Journal of Non-
Crystalline Solids "Vol.4
7. No. 435 (1982); S.
Patent Application Serial
No. 642, 606, and Matsuo et al.

[0005] The difference between the above methods lies in the components of the sol solution as a raw material, and can be classified into the following four types. 1) An alkyl silicate, water, alcohol and a suitable catalyst such as hydrochloric acid or ammonia are mixed and hydrolyzed, and a sol solution is used (the method of Nogami et al.). 2) A sol solution obtained by mixing a solution obtained by hydrolyzing an alkyl silicate with an acidic reagent and a solution containing silica fine particles obtained by hydrolyzing an alkyl silicate keto basic reagent at a predetermined ratio (Matsuo et al.) the method of). 3) A sol solution obtained by mixing a solution obtained by hydrolysis with an alkylsilicate acidic reagent and ultrafine powdered silica at a predetermined ratio is used (the method of Toki et al.). 4) Use a sol solution in which ultrafine silica powder is dispersed in water or an organic solvent at a predetermined ratio (Rabinovitc)
h et al.).

[0006] The sol solutions prepared by the above various methods are gelled in a container having an appropriate shape and then dried to form a dry gel. By sintering the dry gel, quartz glass can be produced. Each has its strengths and weaknesses, so the features are summarized in Table 1.

[0007]

[Table 1]

From Table 1, it can be said that the Toki et al. Method is superior when productivity is emphasized, and the Matsuo et al. Method is superior when high purity substances are emphasized.

However, even if the sol solution is used as a raw material and the sol solution is simply dried and sintered, many inclusions are present in the manufactured quartz glass. In order to improve the quality, Matsuo et al. Work in a clean environment, irradiating the sol solution with ultrasonic waves to increase the dispersibility, and remove particles larger than the standard by filtration and centrifugation. doing.

[0010] In addition, the formation of bubbles is prevented by closing the dry gel by sintering in a helium atmosphere or under reduced pressure.

[0011]

By the above method, inclusions in quartz glass were significantly reduced. However, quartz glass free of crystals, foreign matter, microcracks, bubbles and the like has not yet been obtained. At present, it cannot be used in fields requiring extremely high quality, such as photomask substrates and optical fiber preforms.

An object of the present invention is to introduce a new method to the sol-gel method and to provide a method for producing optically extremely high-quality quartz glass that can be used as a photomask substrate or a preform for an optical fiber. . In addition, a method for improving mass productivity and a method for forming quartz glass are provided.

One of the advantages of the sol-gel method is that a high-melting glass can be synthesized at a low temperature. In fact, when quartz glass is produced by a melting method, a difficult production step is required in a high temperature range of 1700 ° C. or higher, whereas when a sol-gel method is used, it can be easily produced at around 1200 ° C.

The vitrification temperature differs depending on the components of the sol solution as a raw material, and 900 ° C. when the alkyl silicate is hydrolyzed with an acidic reagent, and 120 ° C. when the alkyl silicate is hydrolyzed with a basic reagent.
It is about 0 ° C. When the silica silicate is mixed with the solution obtained by hydrolyzing the alkyl silicate with the basic reagent, or the silica fine particles obtained by hydrolyzing the alkyl silicate with the basic reagent are mixed or the ultrafine powder silica is mixed, the vitrification temperature varies depending on the mixing ratio. However, vitrification ends at 1400 ° C. or lower. The highest temperature is required when ultrafine non-silica is dispersed in the solution, but the vitrification ends at 1470 ° C. or lower.

By using the sol-gel method, quartz glass can be synthesized with less energy than the melting method. However, the following inclusions, defects, and the like exist in quartz glass manufactured by the sol-gel method regardless of the components of the sol solution.

(1) Inorganic proboscis mixed in raw materials and sols (2) Voids caused by burning of organic contaminants (3) Micro cracks generated during shrinkage (4) Incorporation during gelation or generated in sintering process (5) Crystals generated in the sintering process (mainly cristobalite) (6) Insufficient sintering silica

[0017]

The present invention overturns the common sense of the sol-gel method. It is characterized by the idea of processing at high temperatures. The material was heated to near the melting temperature, and the glass or glass precursor produced by the conventional sol-gel method was temporarily placed in a semi-molten state. This process has produced a revolutionary effect. The crystal of (5) and the silica lump of (6) were naturally melted at a temperature higher than the melting temperature of quartz, and disappeared even at a temperature lower than the melting temperature, resulting in uniform quartz glass. Further, if the dry gel is closed in a helium atmosphere or under reduced pressure, the sintering proceeds by heating to a high temperature for the microcracks in the space (3), the bubbles in the space (3), and the like in (2). Disappeared.

Even if the inorganic substance (1) has a melting point lower than that of quartz and a high-melting inorganic substance, the interface disappears when heated to a temperature close to the melting temperature of quartz, and the homogenization proceeds. However, if extremely large particles or inorganic substances that are difficult to vitrify are mixed in, it will not be completely homogeneous. It is preferable to perform the sol treatment in a clean environment and remove particles having a size larger than the standard by filtration or centrifugation.

Since the melting temperature of quartz is 1713 ° C.,
If the temperature is maintained at or above this temperature, high quality quartz glass can be reliably produced. From the point of quality improvement, l500
If the temperature is higher than ℃, the effect appears sufficiently. The high processing temperature may be determined in consideration of desired quality and energy consumption. Conversely, if the temperature is too high, the volatilization of quartz will increase,
The upper limit is about 200 ° C.

As described above, the method for producing high quality quartz glass by heating to 1500 to 2200 ° C. and holding for a certain period of time does not select the components of the sol solution. However, if the dry gel is not closed using any of the following methods, the closed holes grow into huge bubbles by increasing the temperature.

1) Sintering is performed in a helium atmosphere to form pores. 2) Sinter under reduced pressure to make pores. 3) After a helium atmosphere, sintering is performed under reduced pressure to form pores. The pore closing step does not need to be a completely transparent glass body, but may be a translucent glass precursor.

Various methods are conceivable for heating the closed glass or glass precursor to 1500 to 2200 ° C. First, a method using a gas burner such as hydrogen or acetylene is used. Although it is easily available and easy to operate, it has the disadvantage that the temperature control is difficult and the temperature difference between the sample surface and the inside is large. It is not suitable for mass production.

Next, a method using a high-temperature furnace using graphite, tungsten, molybdenum or the like as a heating element can be used.
Although the apparatus is expensive and difficult to operate, for example, when used in an atmosphere where oxygen does not exist, temperature control can be reliably performed, and high-quality quartz glass can be stably manufactured. A high-temperature continuous heat treatment furnace can be used by assembling the equipment. Mass production is easy. In addition, there is a method using a high-temperature gas furnace using combustion of hydrogen or hydrocarbon gas as a heat source.

Considering application to a photomask substrate, in addition to stable quality assurance , 5 × 5 × 0.09 inch,
A large area such as 6 × 6 × 0.12 inch is required. Graphite or tungsten, to achieve it
A method using a high-temperature furnace using molybdenum or the like as a heating element is suitable. However, since the sample is in a semi-molten state, the sample is fused to the furnace material and cracks and deformations occur. To prevent this, it is necessary to provide a separation layer between the furnace material and the sample.

The carbonaceous material is chemically stable in an inert atmosphere, does not react with quartz glass, and a high-purity product can be easily obtained. When the separation layer is provided with powder or fiber, the difference in the expansion coefficient between the sample and the furnace material is absorbed by the movement of the separation layer, and no cracking or deformation occurs. Even if it adheres partially to the sample, it can be easily removed by washing or burning. When the carbonaceous material processed into the shape of paper or cloth is used, the operability is improved, and the contact surface becomes better. The same separation effect can be obtained even when provided between samples, and high-density processing can be performed, and mass productivity is improved.

In the case of a high-temperature furnace using tungsten, molybdenum or the like as a heating element, the heating element is carbonized when carbon is present, and
to degrade. Therefore, it is appropriate to use a hard-to-sinter powder such as alumina, zirconia, or silicon nitride as the separation layer. However, it is difficult to remove the powder attached to the sample.

The glass or glass precursor is mixed with
When heated to 2200 ° C., the sample is easily deformed due to softening. As an advantage of the sol-gel method, moldability at the time of gelation is mentioned, but it is possible to form again at the time of high temperature treatment. For example, when manufacturing a large-area quartz glass flat plate, even if it is gelled in a container serving as a mold of the flat plate, the flatness is not necessarily maintained during vitrification. When the sample is placed on a furnace jig having a flat surface and heated to a high temperature, the sample is flattened by its own weight. This is very advantageous in view of the subsequent grinding process.

Not only a flat plate but also a very high-precision molding can be achieved by using an in-furnace jig which is a mold having a desired shape. It is also possible to adopt a method in which a press device is incorporated in a furnace and pressurized without depending on its own weight.

When manufacturing a quartz glass rod or tube , it is more efficient to use a ring burner or a ring heater. When fixing both ends of the rod or tube and heating the center at a high temperature, the straightness can be improved by applying tension from both ends. This is very important when applied to optical fiber preforms and support tubes .

When heated to 1500 to 2200 ° C. and quenched, internal stress remains in the quartz glass. Therefore, it is necessary to perform slow cooling after high-temperature treatment or slow cooling after annealing after rapid cooling. 120 at least once
Cooling from 0 ° C. to room temperature must be done gradually.

The high temperature treatment of the present invention is fundamentally different from the melting method. First, the bulk of quartz glass itself has already been formed by the conventional sol-gel method, the retention time of high-temperature treatment is extremely shorter than that of the melting method, and there is almost no work during high-temperature treatment. Is a major difference. It is conceptually close to an annealing process for removing distortion in glass, and can be positioned as a process for eliminating inclusions in glass.

As described above, the use of the production method of the present invention makes it possible to produce high-quality quartz glass, which was impossible with the conventional sol-gel method, and to improve the formability. Quartz glass can be provided at a much lower price than before.

Further, when applying the manufacturing method of the present invention, other component glass, for example, Si O ₂ -ZrO ₂ based alkali resistant glass or Si O ₂ -TiO ₂ based high quality, low expansion glass of Can be manufactured at a low price.

According to the present invention, very high quality optically usable quartz glass which can be used as a photomask substrate or a briform for an optical fiber can be supplied to the market in large quantities at a low price.

[0035]

EXAMPLES Example 1 440 ml of ethyl silicate and 360 ml of a 0.05 N aqueous hydrochloric acid solution were vigorously stirred to obtain a colorless and transparent homogeneous solution. After adjusting the pH to 4.2 with 0.1N ammonia water, the solution was passed through a 1 μm filter, and placed in a polypropylene container (width 20 cm × 20 cm × height 10 cm) for 500 m.
1 was injected. Close the lid with an opening ratio of 0.5%.
After drying for days, a colorless and transparent dry gel was produced.

Place the dry gel in a gas displacement furnace,
/ Hr at a rate of / hr. From 700 ° C., pure helium gas was introduced into the furnace at a flow rate of 1 l / min, the temperature was increased to 900 ° C. at a rate of 10 ° C./hr, and 900 ° C.
C. for 1 hour. The specific gravity was 2.20, and it was vitrified.

The size was 8 cm × 8 cm × 0.5 cm. Slight inclusions of several microns in diameter were detected.

An oxyhydrogen flame was applied from both sides of the obtained quartz glass plate using a gas burner. Surface temperature 180
The temperature was maintained at 0 ° C. or higher for 10 seconds or longer, and the entire surface was heated under substantially uniform conditions. Although inclusions could not be detected with a 100 × microscope, distortion occurred on the entire surface.

After holding at 1200 ° C. for 1 hour, 100 ° C. /
The temperature was lowered at a rate of hr to remove strain. The mirror was polished to a thickness of 2 mm, and a condenser lamp was applied so that the illuminance was 50,000 lux in a dark room. However, no light spot was detected.

(Example 2) 440 m of ethyl silicate
l, ethanol 900ml, 0.1N ammonia water 3
60 ml were mixed uniformly and left at room temperature for 1 day. Using a rotary evaporator, the turbid sol is 400 m
and concentrated to 1.

After passing through a 1 μm filter,
m, 400ml in a 30cm deep polypropylene container
It was injected and a lid having an opening ratio of 2% was provided. After drying at 60 ° C. for 10 days, a white dry gel was produced.

The dry gel is placed in a vacuum furnace, and the temperature is 60 ° C./h.
The temperature was raised to 900 ° C. at a rate of r.

1T using a rotary pump at 900 ° C.
orr, and then maintain the degree of vacuum at 10
The temperature was raised to 1200 ° C. at a rate of 0 ° C./hr. 1200
After holding at 1 ° C. for 1 hour, it was vitrified, and the specific gravity was 2.20. The size is 2cm in diameter and 10cm in length
Swearing. When a laser beam having a wavelength of 0.633 μm was irradiated into the quartz glass rod, scattering was observed everywhere.

The rod was fixed on a glass lathe and heated with an oxyhydrogen flame while rotating. After maintaining the surface temperature at 2000 ° C. or higher for 30 seconds or more, the burner was slid and the whole was heated uniformly. When the laser beam was irradiated again, no scattering was observed.

(Example 3) 440 m of ethyl silicate
l, ethanol 900ml, 0.1N ammonia water 3
60 ml were mixed uniformly and left at room temperature for 1 day. Using a rotary evaporator, the turbid sol is 400 m
and then add 1N aqueous hydrochloric acid and add
It was adjusted to 4.0.

Separately, 440 ml of ethyl silicate
And 360 ml of 0.05N hydrochloric acid aqueous solution are vigorously stirred,
A colorless and transparent homogeneous solution was obtained. After uniformly mixing with the above sol, the mixture was passed through a 1 μm filter. After adjusting the pH to 4.8 with 0.1 N aqueous ammonia, 1000 ml of the solution was poured into a Teflon container having an inner diameter of 6 cm and a length of 40 cm, and the container was sealed. The rotation speed is 500 r.
p. m, and allowed to stand for 2 days.

The gel was taken out by removing the stopper, transferred to a polypropylene container (W10 × D45 × H15 cm), and covered with a lid having an opening ratio of 1%. After drying at 60 ° C. for 10 days, a tube-shaped dry gel was produced.

The dry gel is placed in a vacuum furnace at 60 ° C./h
The temperature was raised to 800 ° C. at a rate of r. 1 Torr at 800 ° C
After reducing the pressure to r or less, pure helium gas was introduced into the furnace. Thereafter, the pressure was reduced again to 1 Torr or less, and thereafter, at a rate of 100 ° C./hr, 1200
The temperature was raised to ° C. When it was kept at 1200 ° C. for 1 hour, it was vitrified, and the specific gravity was 2.20. The size was 3 cm in outer diameter, 1 cm in inner diameter, and 20 cm in length. Wavelength 0.
When a 633 μm laser beam was irradiated into the quartz tube, scattering was observed everywhere.

A quartz glass tube was placed vertically in a graphite heating furnace, and was replaced with nitrogen gas.
The temperature was raised to ° C. and maintained for 10 minutes. 10 to 1200 ° C
The temperature was lowered at a rate of 00 ° C./hr,
The temperature was lowered at a rate of ° C / hr. When again irradiated with laser light, scattering was only slightly observed.

Example 4 440 ml of ethyl silicate and 360 ml of a 0.05 N hydrochloric acid aqueous solution were vigorously stirred to obtain a colorless and transparent homogeneous solution. There, ultrafine silica (AerosilOX-5)
0) 150 g was added slowly and stirred thoroughly. The sol was irradiated with ultrasonic waves of 28 kHz for 2 hours while maintaining the temperature at 20 ° C., and centrifugal force of 1500 G was further removed for 10 minutes to remove lumps, and then passed through a 1 μm filter.

The obtained sol having a high degree of homogeneity was adjusted to pH 4.2 with 0.1N ammonia water, and then placed in a polypropylene container (width 20 cm × 20 cm × height 10 cm).
00 ml was injected. Cover with 1% opening ratio, 7 ℃ at 60 ℃
After drying for days, a white and porous dry gel was produced.

Dry gel is placed in a gas replacement furnace,
/ Hr at a rate of / hr. From 1000 ° C., pure helium gas began to flow into the furnace at a flow rate of 1 l / min, and was heated to 1300 ° C. at a rate of 30 ° C./hr.
It was kept at 1300 ° C. for 1 hour. Vitrification was completed, and the specific gravity was 2.20. The size is 10cm x
It was 10 cm x 0.5 cm. An inclusion having a diameter of about 10 μm and a β-cristobalite type crystal were slightly detected.

A carbon powder was evenly spread on a 15 cm × 15 cm × 1 cm graphite flat plate so as to have a thickness of about 1 mm. A quartz glass plate was placed thereon, and set in a graphite heating furnace.

After replacing with nitrogen gas, 1800
The temperature was raised to ° C. and maintained for 10 minutes. 10 to 1200 ° C
The temperature was lowered at a rate of 00 ° C./hr,
The temperature was lowered at a rate of ° C / hr.

The graphite flat plate and the quartz glass plate were not fused, and the flatness of the quartz glass plate was good. The mirror was polished to a thickness of 2 mm, and a condenser lamp was applied so that the illuminance was 50,000 lux in a dark room. However, no light spot was detected. There were no crystals or strains, and the optical quality was extremely high.

(Example 5) Ultrafine powdered silica (Aerosil 2) was added to 500 ml of pure water.
00) Disperse 250 g and keep 28 k
Hz ultrasonic waves were irradiated for 2 hours. Put the viscous slurry in a polypropylene container with an inner diameter of 5 cm and a depth of 30 cm.
00 ml was injected, and a lid having an opening ratio of 2% was provided. 1 at 60 ° C
After drying for days, a white and porous dry gel was produced.

Place the dry gel in a gas replacement furnace,
/ Hr at a rate of 1100 ° C. From 1100 ° C., pure helium gas began to flow into the furnace at a flow rate of 1 l / min, and the temperature was raised to 1400 ° C. at a rate of 30 ° C./hr.
It was kept at 1400 ° C. for 1 hour. Although it was translucent, the specific gravity was almost 2.20.

The quartz glass precursor rod thus obtained was placed vertically in a high-temperature gas furnace, and heated at 1800 ° C. with a propane gas flame.
And held for 10 minutes. 1000 up to 1200 ° C
The temperature was lowered at a rate of 100 ° C / hr.
The temperature dropped at a rate of r.

A transparent quartz glass rod was obtained without generating bubbles. The size is 4cm in diameter and 24 in length
cm.

When a laser beam having a wavelength of 0.633 μm was irradiated, no scattering was observed .

Example 6 15 cm × 15 cm × 0.2
zirconia powder on a 1 cm tungsten plate
It was spread evenly to a thickness of A quartz glass plate closed in the same manner as in Example 4 was placed thereon, and set in a stainless steel heating furnace. After purging with nitrogen gas, the temperature was raised to 1800 ° C. in 2 hours and maintained for 10 minutes. 120
The temperature was lowered to 0 ° C. at a rate of 1000 ° C./hr, and then to room temperature at a rate of 100 ° C./hr.

The Tandasten flat plate and the quartz glass plate were not fused, and the flatness of the quartz glass plate was good. Thickness 2
mm, and a condensing lamp was applied to the illuminance of 50,000 lux in a dark room, but no light spot was detected. There was no crystal or strain, and the optical quality was very high.

1,760 ml of ethyl silicate, 2,690 ml of ethanol, and 670 ml of 1N ammonia water were uniformly mixed and allowed to stand at room temperature for 5 days. 400 ml of pure water was added to the cloudy sol, and then concentrated to 1000 ml using a rotary evaporator. Further, a 2N hydrochloric acid aqueous solution was added to adjust the pH to 4.0.

Separately, 760 ml of ethyl silicate
And 250 ml of 0.02 N hydrochloric acid aqueous solution are vigorously stirred,
A colorless and transparent homogeneous solution was obtained. After uniformly mixing with the above sol, the mixture was passed through a 1 μm filter. After adjusting the pH to 4.2 with 0.1 N aqueous ammonia, centrifugal force of 1500 G was applied for 10 minutes to remove lumps, and then 1 μm
Passed through the filter.

The obtained sol having a high degree of homogeneity was placed in a polypropylene container (30 cm × 30 cm × 15 cm in height).
100 ml was injected. Cover with 0.5% opening rate, 60
After drying at 20 ° C. for 20 days, a white and porous dry gel (22 cm × 22 cm × 0.9 cm) was produced.

The dry gel was placed in the gas replacement furnace, and dry air was flowed into the furnace at a flow rate of 2 l / min. 60 ° C / h
The temperature was raised to 700 ° C. at a rate of r, and maintained at 700 ° C. for 20 hours.

Switching the incoming gas to helium, 2 l / m
in at a flow rate of 900 ° C., 1000 ° C., 1100
And 1200 ° C. for 10 hours. Vitrification has been completed and the size is 15.5 cm x 5.5
cm × 0.6 cm, and flatness was 2 mm.

A carbon paper (Kureha carbon fiber paper) having a thickness of 0.3 mm is laid on a flat graphite sheet of 20 cm × 20 cm × 1 cm, and a quartz glass plate is placed thereon.
It was set in a graphite heating furnace.

After replacing with nitrogen gas, 1850
The temperature was raised to ° C. and maintained for 5 minutes. 100 to 1200 ° C
The temperature is lowered at a rate of 0 ° C./hr, and thereafter the temperature is lowered to room temperature at 100 ° C.
/ Hr.

The graphite flat plate and the quartz glass plate were not fused, and the flatness of the quartz glass plate was 0.1 mm or less.

Mirror polishing to 6 × 6 × 0.12 inch,
A condensing lamp was applied so that the light intensity was 50,000 lux in a dark room, but no light spot could be detected. When the transmittance in the ultraviolet region was measured, the transmittance was maintained at 90% or more up to 200 mm, and no specific absorption was observed.

Example 8 1150 ml of ethyl silicate and 620 ml of a 0.01 N hydrochloric acid aqueous solution were vigorously stirred to obtain a colorless and transparent homogeneous solution. There, ultra fine powder silica (ReolosiQS-10)
2) 300 g was gradually added, followed by sufficient stirring. The sol was irradiated with ultrasonic waves of 28 kHz for 2 hours while maintaining the temperature at 20 ° C., and centrifugal force of 1500 G was further removed for 10 minutes to remove lumps, and then passed through a 1 μm filter.
After adjusting the pH to 4.2 with 0.1N aqueous ammonia,
Again, a centrifugal force of 1500 G was applied for 10 minutes to pass through a 1 μm filter.

The obtained sol having a high degree of homogeneity was placed in a polypropylene container (width 30 cm × 30 m × height 15 cm).
00 ml was injected. Cover with 0.5% opening rate, 60 ℃
After drying for 20 days, a white and porous dry gel was produced.

The dry gel was placed in a gas replacement furnace, and dry air was flowed into the furnace at a flow rate of 2 l / min. 60 ° C / h
r, 200 ° C, 30 ° C
It was kept at each of 0 ° C. and 500 ° C. for 3 hours. The inflow gas is switched to helium and flows in at a flow rate of 2 l / min, 700 ° C, 900 ° C, 1000 ° C, 1100 ° C, 1
Each temperature was kept at 200 ° C. for 10 hours.

The vitrification has been completed, and the specific gravity is 2.20.
Had become.

A 0.3 mm thick carbon paper was spread on a 20 cm × 20 cm × 1 cm graphite flat plate, and the obtained quartz glass plate was placed on the plate and put into a graphite heating furnace at 1800 ° C., and held for 10 minutes. It moved to a cooling room and cooled to room temperature for 30 minutes. Because distortion occurred, 1200
After holding at 1 ° C. for 1 hour, the temperature was lowered at a rate of 100 ° C./hr to remove strain. Flatness was less than 0.1 mm.

A mirror was polished to 6 × 6 × 12 inches and a condensing lamp was applied so that the illuminance was 50,000 lux in a dark room, but no light spot could be detected. When the transmittance in the ultraviolet region was measured, the transmittance was maintained at 85% or more up to 200 nm, and no specific absorption was observed.

(Example 9) White and porous dry gel (22 cm x 22 cm x
0.9 cm) in a dregs replacement furnace, and dry air at 2 l /
It flowed into the furnace at a flow rate of min. The temperature was raised to 700 ° C. at a rate of 60 ° C./hr and maintained at 700 ° C. for 20 hours. The inflow gas was switched to helium, flowed in at a flow rate of 2 l / min, and maintained at 800 ° C., 900 ° C., and 1000 ° C. for 5 hours. After cooling to room temperature, the size is 1
It was 8 cm × 18 cm × 0.7 cm, white and porous.

A 0.3 mm thick carbon paper was spread on a graphite plate of 20 cm × 20 cm × 1 cm,
The sintered gel heated to 0 ° C was placed and set in a graphite heating furnace.

Using a rotary pump, the temperature was rapidly raised to 1000 ° C. for 10 minutes while maintaining a reduced pressure of 1 Torr or less. Subsequently, the temperature was raised to 1300 ° C. at a rate of 300 ° C./hr and maintained at 1300 ° C. for 1 hour. Nitrogen gas was flown into the furnace to return to normal pressure, then the temperature was raised to 1750 ° C. at a rate of 600 ° C./hr and held for 30 minutes.

It was moved to a cooling room and cooled to room temperature for 30 minutes.

15.5 cm × 15.5 cm × 0.6 cm
A transparent quartz glass with a size of was produced, and no cracks or cracks occurred. Because distortion occurred, 1
After maintaining at 200 ° C. for 1 hour, the temperature was lowered at a rate of 100 ° C./hr to remove strain.

Mirror polishing to 6 × 6 × 0.12 inch,
A condensing lamp was applied so that the light intensity was 50,000 lux in a dark room, but no light spot could be detected. There was no crystal or strain, and the optical quality was extremely high. When the transmittance in the ultraviolet region was measured, the transmittance was maintained at 90% or more up to 200 nm, and no specific absorption was observed.

(Example 10) Quartz glass (15.5 cm x 15.5 cm x
0.6 cm) were prepared. 20cm x 2cm x 1
17cm × 17cm × 0.03cm on a black graphite flat plate
Of carbon paper and 5 pieces of quartz glass were alternately stacked. Four graphite pillars having a height of 4 cm were erected and a graphite flat plate was placed thereon. On top of this, five quartz glass plates were stacked on top of each other in the same manner as in the first stage via a carbon paper. Hereinafter, 20 sheets were set in the same manner.

After purging with nitrogen gas, the mixture was charged into a graphite heating furnace at 1800 ° C. and maintained for 15 minutes. It moved to a cooling room and cooled to room temperature for 30 minutes. The graphite plate, the quartz glass plate, and the quartz glass plates were not fused together, and the flatness of the quartz glass plate was 0.2 cm or less.

Since strain was generated, the temperature was kept at 1200 ° C. for 1 hour, and then the temperature was lowered at a rate of 100 ° C./hr to remove the strain.

Mirror polishing to 6 × 6 × 0.12 inch,
The condenser lamp was turned on so that the illuminance was 50.000lux in a dark room, but no light spot could be detected. There were no crystals or strains, and the optical quality was extremely high. When the transmittance in the ultraviolet region was measured, the transmittance was maintained at 90% or more up to 200 nm, and no specific absorption was observed.

Example 11 2200 ml of ethyl silicate and 1600 ml of a 0.02 N aqueous hydrochloric acid solution were vigorously stirred to obtain a colorless and transparent homogeneous solution. There, ultrafine silica (AerosilOX-5)
0) 600 g was added slowly and stirred thoroughly. The sol was irradiated with 28 kHz ultrasonic waves for 2 hours while maintaining the sol at 20 ° C., and centrifugal force of 1500 G was further applied for 10 minutes to remove lumps, and then passed through a 1 μm filter.
After adjusting the pH to 4.8 with 0.1N ammonia water,
It was passed again through a 1 μm filter.

3,770 ml of the obtained sol having a high degree of homogeneity was poured into a Teflon-coated container (circular diameter: 6 cm, length: 150 cm) in an aluminum tube and sealed.

The tube was mounted on a rotating device and rotated at a rotation speed of 500 rpm for 1 hour around the central axis of the tube.

After leaving at room temperature for 4 days, the stopper was removed.
The gel was transferred into a polypropylene container (10 cm × 17 cm × height 20 cm). Cover with 0.5% opening rate, 6
After drying at 0 ° C. for 30 days, a tube-shaped dry gel was produced.

Dry gel was placed in a gas replacement furnace, and dry air was flowed into the furnace at a flow rate of 2 l / min. 60 ° C / h
The temperature was raised to 700 ° C. at a rate of r and kept for 10 hours. The incoming gas was helium (1.8 l / min) and chlorine (0.2
1 / min) and the temperature was raised to 1000 ° C. at a rate of 30 ° C./hr. Oxygen (0.2
1 / min) and maintained at 1000 ° C. and 1050 ° C. for 10 hours.

Finally, the inflow gas was changed to helium (2 l / mi).
Switch to n), 1050 ° C, 110 ° C, 1200 ° C
At each temperature for 10 hours.

The product was translucent, but had a specific gravity of about 2.20.
Had become. The size was 3 cm in outer diameter, 1 cm in inner diameter, and 75 cm in height. Roundness is 16 μm, straightness is 2.0c
m.

The obtained quartz glass precursor was moved inside a graphite ring-shaped heater while holding both ends of the precursor so as to be vertical. Ring heater maintained at 2000 ° C. under a stream of argon gas around, 3c the upper moving vertically downward
The lower end was performed at a speed of 4 cm / min at a speed of m / min. Next, it was placed in an electric furnace, kept at 1200 ° C. for 1 hour, and then cooled at a rate of 100 ° C./hr to remove strain.

The size is 26 cm outside diameter and 0.87 c inside diameter.
m, 1 m in length. The roundness was unchanged at 16 μm, and the straightness was improved to 0.1 mm.

When the film was irradiated with a laser beam having a wavelength of 0.633 μm, no scattering was observed. Also, 272
The water content was measured by absorption at μm and found to be 1 ppm or less.

440 ml of ethyl silicate and 360 ml of a 0.05 N hydrochloric acid aqueous solution were vigorously stirred to obtain a colorless and transparent homogeneous solution. There, ultra fine powder silica (Aerosil
(OX- 50) 150 g was gradually added, followed by sufficient stirring. The sol was irradiated with ultrasonic waves of 28 kHz for 2 hours while maintaining the temperature at 20 ° C., and centrifugal force of 1500 G was further removed for 10 minutes to remove lumps, and then passed through a 1 μm filter.

The obtained sol having a high degree of homogeneity was adjusted to pH 4.2 with 0.1 N ammonia water, and then 700 ml was placed in a polypropylene container (inner diameter 30 cm × height 10 cm).
Injected.

When the lid having an opening ratio of 1% was covered and dried at 60 ° C. for 7 days, a white and porous dry gel was produced.

Dry gel is placed in a vacuum furnace,
The temperature was raised to 1000 ° C. at a rate of r.

Using a rotary pump at 1000 ° C.
The pressure was reduced to 1300 ° C. or less at a rate of 100 ° C./hr while maintaining this degree of vacuum.
It was kept at 0 ° C. for 1 hour. Vitrification was completed, and the size was 15 cm in diameter × 0.5 cm in thickness.

A quartz glass plate was placed on a concavely curved graphite jig having a radius of curvature of 30 cm and set in a graphite heating furnace.
After purging with nitrogen gas, the temperature was raised to 1800 ° C. in 2 hours and maintained for 10 minutes. 1000 ° C / h up to 1200 ° C
Then, the temperature was lowered at a rate of 100 ° C./hr to room temperature. A quartz glass having a watch glass shape with a uniform thickness of 0.5 cm was produced. There were no bubbles and the quality was extremely high.

Example 13 A quartz glass plate (diameter 15 cm × thickness 0.5) vacuum-sintered in the same manner as in Example 12
cm) between the graphite jigs serving as crucible-shaped molds,
It was set in a graphite heating furnace having a hot press mechanism.
After purging with nitrogen gas, the temperature was raised to 1850 ° C. in 2 hours and maintained for 5 minutes. 10kg / cm via graphite jig
After pressing at a pressure of ² , 1000 ° C /
The temperature dropped at a rate of hr. Very high quality quartz glass with a crucible shape could be manufactured.

Example 14 Using the same method as that of Example 7, a glass body closed in a helium atmosphere (15.
(5 cm × 15.5 cm × 0.6 cm) was placed in an electric furnace and kept at 1600 ° C. for 30 minutes. 100 to 1200 ° C
The temperature is lowered at a rate of 0 ° C./hr, and thereafter the temperature is lowered to room temperature at 100 ° C.
/ Hr.

Mirror polishing to 6 × 6 × 0.12 inch,
When a condensing lamp was applied so that the illuminance was 50,000 lux in a dark room, spots were observable.
In addition, small light spots could be detected with the naked eye at several places in the plane.

(Example 15) Using the same method as in Example 7, the glass body (15.
(5 cm × 15.5 cm × 0.6 cm) was set in a graphite heating furnace. After replacing with argon gas, 21 hours in 2 hours
The temperature was raised to 00 ° C. and maintained for 1 minute. 1 to 1200 ° C
Temperature at a rate of 000 ° C./hr,
The temperature was lowered at a rate of 0 ° C./hr.

The size is 14 cm × 14 cm × 0.5 cm
And had decreased. Mirror-polished to a thickness of 2 mm, 5 in a dark room
The condenser lamp was turned on so that the illuminance became 000 lux, but no light spot was detected.

(Comparative Example 1) A glass body (15.5) closed in a helium atmosphere using the same method as in Example 7.
cm × 15.5 cm × 0.6 cm) in an electric furnace.
It was kept at 450 ° C. for 30 minutes. Upon cooling to room temperature, the quartz glass surface turned white due to crystallization.

Mirror polishing to 6 × 6 × 0.12 inch,
When a condensing lamp was applied so as to have an illuminance of 50,000 lux in a dark room, a spot clearly appeared. Also, there were many light spots of various sizes in the plane.

Comparative Example 2 Using the same method as in Example 7, a glass body (15.5) closed in a helium atmosphere was used.
cm × 15.1 cm × 0.6 cm) was set in a graphite heating furnace. After purging with argon gas, the temperature was rapidly raised to 2300 ° C. and then lowered to room temperature. Only a small amount of quartz glass remained in the furnace.

Comparative Example 3 A white, porous dry gel dried in the same manner as in Example 4 was heated to 1300 ° C. in the air to obtain a glass body. The size was 10 cm × 10 cm × 0.5 cm, and inclusions and bubbles with a diameter of about 10 μm were detected. It was set in a graphite heating furnace, replaced with nitrogen gas, and kept at 1800 ° C. for 10 minutes. The glass body was swollen to about three times the volume due to foaming, and the appearance was white.

[0113]

As described above, according to the first aspect of the present invention, in a method for producing quartz glass by a sol-gel method, glass or a glass precursor is used in an amount of 1500 to 22%.
When heating to 00 ° C., between the heating means and the glass body or glass precursor or between a plurality of the glass bodies or glass precursors, because it is allowed to stand through the separation means,
For example, it is possible to prevent "cracking" or "deformation" caused by fusion of a sample (glass or glass precursor) to a furnace material.
According to the invention described in claim 3, in the method for producing quartz glass by the sol-gel method, when the glass or the glass precursor is heated to 1500 to 2200 ° C., an external pressure is applied to the glass body or the glass precursor. Since it is additionally formed into a desired shape, not only a flat plate but also an arbitrary shape such as a crucible shape can be formed with high precision. According to the fifth aspect of the present invention, in the method for producing quartz glass by the sol-gel method, the glass or the glass precursor is used for 15 times.
When the glass body or the glass precursor is heated to 00 to 2200 ° C., the glass body or the glass precursor is placed on a jig having a flat surface. The glass precursor) is planarized by its own weight. This facilitates the subsequent grinding process. According to the invention described in claim 7, 1
After heating to 500 to 2200 ° C. to form quartz glass, it is rapidly cooled, then annealed, and then gradually cooled, so that quartz glass of good optical quality can be obtained as described above.

In order to prevent foaming, it is necessary to close the holes in a helium atmosphere or under reduced pressure, but the method for preparing the sol and the method for heating are not limited. Further, it can correspond to products of various shapes.

According to the present invention, quartz glass by the sol-gel method can be applied to a quartz substrate for an IC mask, a support tube for an optical communication fiber, and a mother rod for an optical communication fiber.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuhiko Takeuchi 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (72) Inventor Hirohito Kitabayashi 3-3-5, Yamato, Suwa-shi, Nagano, Say (56) References JP-A-62-86563 (JP, A) JP-A-60-239328 (JP, A) JP-A-63-129028 (JP, A) JP-A-57-22137 ( JP, A)

Claims (7)

(57) [Claims] 1. A After gelling the sol solution containing a silicon compound, a process of forming a dry gel is dried, forming a glass body or glass precursor and closed porosity of the dry gel, the glass body or 1500-220 glass precursor
A step of heating at 0 ° C. and holding for a certain period of time to form quartz glass, wherein when heating the glass body or the glass precursor, a heating means and the glass body or the glass precursor or a plurality of the glass A method for producing quartz glass, comprising standing still between a body or a glass precursor via a separating means. 2. The method according to claim 1 , wherein the quartz glass is cooled after the step of forming the quartz glass.
The method for producing quartz glass described above. 3. A step of gelling and drying a sol solution containing a silicon compound to produce a dry gel; a step of closing the dry gel to form a glass body or a glass precursor; 1500-220 glass precursor
Heating at 0 ° C. and holding for a certain period of time to form quartz glass; and when heating the glass body or the glass precursor, applying pressure from the outside to the glass body or the glass precursor, A method for producing quartz glass, characterized by being formed into a shape. Claim 3, characterized in that cooling the quartz glass thereafter the step of forming the quartz glass
The method for producing quartz glass described above. 5. After gelation the sol solution containing a silicon compound, a process of forming a dry gel is dried, forming a glass body or glass precursor and closed porosity of the dry gel, the glass body or 1500-220 glass precursor
A step of heating at 0 ° C. and holding for a predetermined time to form quartz glass; and, when heating the glass body or the glass precursor, placing the glass body or the glass precursor on a jig having a flat surface. Characteristic method for producing quartz glass. 6. A claim, characterized in that cooling the quartz glass thereafter the step of forming the silica glass 5
The method for producing quartz glass described above. 7. A step of gelling a sol solution containing a silicon compound, followed by drying to produce a dry gel; a step of closing the dry gel to form a glass body or a glass precursor; 1500-220 glass precursor
A step of heating at 0 ° C. and holding for a predetermined time to form quartz glass; a step of rapidly cooling the quartz glass; a step of annealing the quartz glass that has been quenched; and a step of gradually cooling after the annealing treatment And a method for producing quartz glass.