JPS5925738B2 - Optical glass fiber manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing optical glass fibers that has low transmission loss and transmission signal distortion and eliminates drawbacks caused by flame hydrolysis.

A conventional optical glass fiber manufacturing method that reduces transmission loss and transmission signal distortion involves, for example, causing a combustion reaction in a flame of a glass-forming raw material gas such as silicon to produce an optical glass powder. The powder of the optical glass is laminated on a starting member, and then the powder of the optical glass is heated and fired in a controlled gas atmosphere to produce vitrified optical glass, and the optical glass is spun. A method of manufacturing optical glass fiber by flame hydrolysis, or a method of laminating optical glass using a high-frequency plasma flame, etc. by supplying a raw material gas to the inside or outside of a quartz tube, etc.
A CVD method was used in which optical glass fibers were produced by spinning the optical glass.

However, in conventional methods, especially those using flame hydrolysis, the waste gas generated by hydrolysis is difficult to dispose of as water vapor containing corrosive hydrochloric acid is generated, and it is also easy to dehydrate. Not.

Therefore, since it contains many OH groups that have an absorption peak at a wavelength of 0.95 μm in the wavelength range used for optical transmission, it has the disadvantage of increasing transmission loss. The present invention is a new invention that eliminates the above-mentioned drawbacks, and its purpose is to produce optical glass that does not generate corrosive gas during combustion reactions, has few OH groups, and at a relatively low temperature. The present invention provides a method for manufacturing optical glass fiber that can produce optical glass fiber with low optical transmission loss.

In order to achieve this object, the manufacturing method of the present invention involves producing an optical glass powder by subjecting silicon and other element hydrides or organic compounds to a combustion reaction using oxygen gas. a step of laminating the optical glass powder on a starting member; a step of vitrifying the optical glass powder by heating it at a predetermined temperature and time in an inert gas atmosphere with low moisture containing halogen gas and oxygen gas; The method is characterized by comprising a step of spinning the optical glass produced by the method.

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 4A and 4B.

FIG. 1 is an explanatory diagram of an embodiment of the present invention, in which 1 is a SiH
4 or a tank for diluted SiH4 gas, 2 a tank for raw material gas for dope, 3 and 4 each flowmeter, 5 and 6 a flow rate adjustment device, 7 a mixer, 8 a raw material gas feed pipe, 9 10 is a carrier gas inlet pipe, 10 is a cutoff gas inlet pipe, 11 is a burner, 12 is an optical glass product, 13 is a starting member, and 14 is a laminated optical glass.

13A is an arrow indicating the direction of rotation, and 13B is an arrow indicating the direction of movement.

First, B2H6 (diborane), NH3 (ammonia),
Hydrides that easily become a gas near room temperature, such as SiH4 (silane), PH3 (phosphine or hydrogen phosphate), GeH4 (germanium tetrahydride), AsH3 (arsine), SnH4 (tin tetrahydride), and SbH3 (stipine), Alternatively, an oxide optical glass product is produced by mixing an organic compound with oxygen and burning it in a burner made of quartz glass or a refractory metal. Here, in comparison with flame hydrolysis, for example, the main reaction between SlH4, GeH4 and oxygen is shown.
The main reaction in hydride combustion is SiH4+202=SiO2+2H20 GeH4+202-GeO2+2H20 The main reaction in flame hydrolysis is SiCl4+2H2+02=SiO2+4HCIGeC
114+2H2+02=GeO2+4HC1 In this case, SiC24 (silicon tetrachloride) used in the flame hydrolysis method,
Since halides such as GeCl4 (germanium tetrachloride) are stable as compounds, they must be converted to oxides at higher temperatures (by the heat of an oxyhydrogen flame).

On the other hand, SiH4. Since hydrides such as GeH4 or organic compounds are more unstable as compounds, they can be converted into oxides at relatively low temperatures. Note that Si is used as a raw material.
H4 mixed with other hydrides produces oxide-doped SiO2 optical glass products.

As shown in FIG. 1, the SiH4 gas to be used as the optical glass product of the oxide, or the SiH4 gas diluted with an inert gas such as Ar, He, N2, or H2 gas, is supplied from a tank 1 to a flowmeter. 3, the gas is adjusted to a predetermined flow rate by a flow rate regulator 5, and sent to a gas mixer 7.

In addition, the raw material gas (for example, GeH4) as a dopant or the diluted raw material gas as a dopant passes from the tank 2 through the flow meter 4, is adjusted to a predetermined flow rate by the flow regulator 6, and is sent to the gas mixer 7. sent. The mixed gas mixed in the mixer 7 is sent to the burner 11 from the feed pipe 8, and the 02 gas for combustion is sent from the feed pipe 9, respectively.
In the burner 11, at the same time, Ar, He,
An inert gas such as N2 or H2 gas is fed into the burner 11 from the feed pipe 10. Figures 2A and b show the case where the burner has triple nozzles, a is a longitudinal cross-section, b is a cross-sectional view, and Figures 3A and b are the same five-nozzle configuration, and a is the longitudinal cross-section. 4A and 4B are cross-sectional views, and FIGS. 4A and 4B are cross-sectional views in which two types of nozzles are arranged so that the outflow gas intersects near the outlet, where a is a longitudinal cross-sectional view and FIG. 4 b is a cross-sectional view.

In each figure, 15 is the inner raw material gas outlet, 16 is the cutoff gas outlet, 17 is the oxygen gas outlet, 18 is the inner oxygen gas outlet, 19 is the inner cutoff gas outlet, and 20 is the raw material gas flow. 21 is an outer blocking gas outlet, 22 is an outer oxygen gas outlet, 23 is an M nozzle, 24 is a raw material gas outlet,
25 is a cutoff gas outlet, 26 is an N nozzle, and 27 is an oxygen gas outlet. For example, if a nozzle as shown in FIGS. 2A and 2B is used, near the outlet, the raw material gas flowing out from the inner raw material gas outlet 15 and the oxygen gas flowing out from the outer oxygen gas outlet 17 are separated by an intermediate barrier. The gas flows out while being blocked by the blocking gas flowing out from the gas outlet 16, and the oxidation reaction is prevented near the outlet.

Therefore, no optical glass is deposited at the outlet. Similarly, when using a nozzle as shown in FIGS. 3A and 3B, layers of oxygen gas, raw material gas, and oxygen gas are discharged from the outlet ports 18, 20, and 22 in order from the inside to the outside, but the intermediate layer The oxidation reaction is blocked in the vicinity of the outlets by being shielded by the blocking gas layers flowing out from the outlets 19 and 21, so that optical glass is not deposited at the outlet of the nozzle. In addition, when using nozzles such as those shown in Figure 4 A and b, M
The raw material gas flowing out from the outlet 24 of the nozzle 23 is covered with the blocking gas flowing out from the outlet 25, and intersects with the oxygen gas flowing out from the outlet 27 of the N nozzle 26 at a place slightly away from the outlet. Therefore, no optical glass is deposited at the outlets of both nozzles 23 and 26, as a combustion reaction occurs. Therefore, since the size of the outlet of each nozzle can be kept constant, it is possible to produce a product with constant performance from beginning to end. In addition to the nozzles described above, those shown in FIGS. 2A and 2B to 4A and 4B can be used in various combinations.

Then, at a position away from the vicinity of the outlet of the burner 11, the respective gases undergo a mixing reaction to form an optical SiO2 glass product doped with a predetermined oxide.

The optical glass product is uniformly laminated onto a starting member 13 rotating in the direction 13A and reciprocating in the direction 13B shown in FIG. 1 to form a layer 14 of optical glass powder. To go. As the starting member 13, a rod or tube made of a refractory material such as quartz glass, carbon, or silicon carbide, or a refractory metal such as W, MO, or r can be used.

The starting member 13 is removed from the optical glass rod or tube 14 stacked on the starting member 13, or the starting member 13 is adsorbed onto the optical glass in a high temperature region with a temperature gradient, for example, while the starting member 13 is attached. The gas is melted and vitrified while being expelled in a certain direction. If the atmosphere at this time is vacuum, moisture and OH groups can also be reduced. In this case, it is also possible to use a dry oxygen atmosphere as the atmosphere. To remove the 0H group more actively, an inert gas such as He gas containing a small amount of oxygen gas and a very low moisture content containing a halogen gas that reacts with the 0H group is used to suppress the decomposition of the dopant. It's okay. In particular, when F2 is used as a halogen gas, F2 gas molecules are smaller than other halogen gases and easily enter optical glass or its particles, and also have strong reactivity with OH groups in optical glass, so 0H groups It is effective in removing. However, in the reaction at this time, it is necessary to feed F2 in an amount corresponding to the 0H groups in the optical glass.

Further, since HF (hydrogen fluoride) reacts with optical glass, it is preferable that the mixed gas for sintering be flowed in and out so as to be removed as quickly as possible. As the F2 gas raw material, a fluorine compound gas such as SF6 or CF4, which is extremely stable in the atmosphere, may be used and thermally decomposed at a high temperature during sintering. In addition, in the conventional method using chlorine gas, bubbles tend to remain in the glass after sintering, the piping materials of the raw material supply system are likely to be contaminated, the loss value of the obtained glass fiber is high, and the waste generated is Gases such as Cl2 and HCI are more difficult to reduce in concentration than fluorine-based gases, and are difficult to process. Next, when the starting member 13 is removed before or after sintering, the inner surface of the tube hole in the optical glass created by the removal is cleaned with hydrofluoric acid water. In addition to cleaning, the inner surface of the hole is scraped off with hydrofluoric acid water to obtain an optical glass tube. Next, the optical glass tube is heated to a high temperature to soften it, and stretched so that the inner surface of the hole collapses due to surface tension to form a rod-shaped body. The method is, for example, by placing the optical glass tube in a glass lathe, heating it from the outside to a high temperature with an oxyhydrogen flame, plasma flame, electric heater, etc. while rotating it, and crushing the holes in the optical glass tube to make it solid. The heating source or tube is further moved in the axial direction. In this case, reducing the pressure inside the hole will facilitate the operation of crushing the hole. It is also possible to provide a heating source inside the hole and heat the optical glass tube from the inside to make it into a solid rod shape. The rod-shaped optical glass thus formed is inserted into a tube made of glass with a relatively low refractive index such as quartz glass or Vycor to form a composite, and the composite is melt-spun to form an optical glass fiber. It manufactures pipes. It is also possible to make an optical glass fiber by melting and heating an optical glass tube as it is and spinning it. Specific examples of the present invention will be described below.

Example 1 In FIG. 1, Ar gas containing 20% SiH4 (referred to as the first gas) and 50! ) is mixed with Ar gas (second gas) containing GeH4 and used as a raw material gas.
Then, the second gas was closed and only the first gas was fed into the burner 11 for 150 minutes at a flow rate of 2.01/min.

This raw material gas flows out from the outlet 15, and at the same time as this raw material gas, H2 gas is fed into the burner 11 as a shutoff gas from the feed pipe 10 at a flow rate of 21/min.
6, and 02 gas is also used as combustion gas at 31.
It was sent into the burner 11 from the sending pipe 9 at a flow rate of /Min, and was discharged from the outlet 17. Then, a starting member 13 made of a carbon tube with an outer diameter of 10 mm was placed at 60 mm with the axis as the center.
While rotating at rpm and reciprocating in the axial direction at a speed of 200 mu7/min, optical glass powder produced by the reaction of the gas discharged from the burner 11 was laminated on the outer periphery of the starting member 13. . As a result, starting member 13
A tube of optical glass powder was produced having a 7.5 mm thick layer of GeO2-SiO2 and a further 7.5 mm thick layer of SiO2 thereon. The tubular body is 0.1
The starting member (carbon tube) of the tubular body was heated by energizing it while placed in a flow of dry He gas containing % F2 and 0.20 t)02.

First, in order to remove the moisture adsorbed on the tubular part of the optical glass powder, the starting member was heated gradually, and after the temperature of the starting member exceeded 1000°C, the inside of the pores of the starting member was uniformly heated for 3 hours. The temperature was increased to 1750° C. while burning and thinning the starting material. During this time, a lumina tube that sucks in the waste gas generated as the carbon in the starting material burns,
An alumina tube through which pure oxygen was introduced into the tube of the starting member was inserted into the tube of the starting member, and gas was introduced and sucked out. Inner diameter 10mm and outer diameter 20m7! The inner surface of an L optical glass tube was cleaned with hydrofluoric acid, and heated to approximately 2000°C in a high-frequency induction heating furnace while melt-spun to obtain an outer diameter of 15.
A 0 μm optical glass fiber was used. As a result of measurement, the transmission loss of this optical glass fiber is λ=0.84.
In the case of μm, it is 8 dB/Km, and even in the part where the 0H group absorbs at λ-0.95 μm, it is 12 dB/Km, making it possible to create a clad optical glass fiber with extremely low transmission loss. Example 2 As described above, the first gas, the second gas, the shutoff gas, the combustion gas, and the nozzle structure of the burner 11 were the same as in Example 1, and the starting member 13 was made of quartz with an outer diameter of 101 mm and an inner diameter of 9 mm. A tube covered with a carbon rod was used, and the rotational speed was 60 rpm and the reciprocating speed was 300 mm/min.

Then, the first gas is kept constant at a flow rate of 1.51/Min, and the second gas is allowed to flow from 1.51/Min to a flow rate of zero over 3 hours. Further, when only the first gas was allowed to flow for 1 hour at a flow rate of 21/Min, GeO2-SiO was formed on the outer periphery of the starting member 13 to a thickness of 13 mu.
Optical glass powder bodies consisting of SiO2 and SiO2 were laminated. Next, the carbon rod is removed from the starting member on which the optical glass powder is laminated, and the optical glass tubular powder is gradually lowered from above into a vertical furnace with a temperature gradient. , 3 in the temperature range where the adsorbed gas escapes.
The mixture was heated for about 15 minutes in a temperature range of 1400° C. or higher where melting begins. During this heating time, dry and moisture-free gas is used, for example, F2 at 0.2 (!), 02 at 2
% He gas was continued to flow. The optical glass tube vitrified in this manner had an outer diameter of 20 mm and an inner diameter of 9 mm, but the inner surface of the hole was etched with hydrofluoric acid water and scraped off until the inner diameter was 20 mm. This step scrapes away the quartz portion of the starting member. Then, the optical glass tube was melt-spun to produce an optical glass fiber having an outer diameter of 150 μm. As a result of measurement, the transmission loss of the above-mentioned optical glass fiber is 7 dB/ at λ-0.84 μm.
Km, it was confirmed that it has extremely low transmission loss and has a graded index type refractive index distribution in which the refractive index is large in the center and gradually decreases toward the outside.

Note that the sintering conditions of Example 1 and Example 2 described above are He: 99.7%, 02: 0.2%, F2: 0.1%.
, temperature condition 100 "C x 3 hr and He: 97.8%
, 02:2%, F2:0.2(f), temperature condition 140'
For C×15 minutes, He: 930 as comparative example 1 using conventional Cl2 gas! ), 02:2%, Cl2:5%
, glass fiber manufactured under temperature conditions of 1000°C x 3 hr, and Comparative Example 2: He: 97.8%, 02:2
%, CZ2:0.2 (:L1 temperature condition 1000'CX3
An evaluation of the losses measured on glass fibers produced at hr.

As a result, in Comparative Example 1, bubbles were generated in the glass after sintering,
The fiber cannot be evaluated, and in Comparative Example 2, the loss was 0.9.
8dB/Km. at 5μm wavelength. O. 10 at 84 μm wavelength
In terms of dB/Km, the case using F2 of the present invention is excellent. As detailed above, the present invention produces an optical glass powder by subjecting silicon and hydrides or organic compounds of other elements to a combustion reaction using oxygen gas, and uses the optical glass powder as a starting member. a step of laminating the laminated optical glass powder, a step of vitrifying the laminated optical glass powder by heating it at a predetermined temperature and time in an inert gas atmosphere with low moisture containing halogen gas and oxygen gas, and vitrifying the vitrified optical glass. The manufacturing method for optical glass fiber consists of heating the glass to the drawing temperature and spinning it, so the raw materials for the synthesis reaction are hydrides or organic compounds rather than halides, and fluorine-based fibers are used during sintering. Since gas is used, it is possible to prevent equipment from being corroded by the corrosive hydrochloric acid in the waste gas in the reaction part, and combustion can be carried out at a relatively low temperature, so it is possible to prevent irregularly shaped optical materials due to softening of starting materials. It can prevent it from becoming glass.

Furthermore, since an appropriate sintering method can be adopted, optical glasses with extremely low 0H groups can be produced. In addition, since the raw material gases hydrides and organic compounds have low boiling points, raw materials with extremely low impurities can be easily obtained by distillation, so the optical glass fiber produced by this process has low impurities and low optical transmission loss. becomes. Furthermore, since the combustion reaction was shut off using a blocking gas near the outlet of the burner, it was possible to prevent optical glass powder from forming at the outlet. As a result, a product with constant performance can be obtained without any change in flow rate. Furthermore, since the composition and type of the raw material gas can be easily controlled by controlling the flow rate using a mass flow controller or the like, it is possible to stack layers while producing optical glass having a predetermined composition. As a result, it is possible to produce a desired optical glass having a different refractive index distribution by changing the composition in the radial direction, and thus a desired optical glass fiber. Furthermore, a process of vitrifying an optical glass powder by heating it in a heating region with a temperature gradient and in a gas atmosphere mainly consisting of helium containing a small amount of fluorine in order to suppress the decomposition of the dopant. As a result, it was possible to create an optical glass fiber with low photoconductive loss from which the 0H group was removed.

[Brief explanation of the drawing]

Fig. 1 is a process explanatory diagram of one embodiment of the present invention, Fig. 2 A, b
4A to 4B are a longitudinal cross-sectional view and a cross-sectional view of each nozzle of the burner in each embodiment. 1 and 2 are tanks for optical glass product gas and dope raw material gas, respectively, 3 and 4 are flow meters, 5 and 6 are flow rate regulators, 7 is a mixer, 8 is a raw material gas feed pipe, and 9 is a combustion 10 is a gas supply pipe for shutoff, 11 is a burner, 12 is a flame (frame) for producing optical glass powder, 13 is a starting member, 13A is its rotation direction, 13B
14 is the stacked optical glass powder layer; 15, 20 and 24 are raw material gas outlet ports; 16, 1 are the moving directions;
9, 21 and 25 are gas outlet ports for shutoff, 17, 18, 2
2 and 27 are oxygen gas outlet ports, and 23 and 26 are intersecting M and N nozzles.

Claims (1)

[Claims] 1. A step of producing a glass powder by subjecting a vaporizable compound of silicon and other elements to a combustion reaction, and laminating the glass powder on a starting member; and a step of laminating the glass powder on a starting member; A step of vitrifying the body by heating it at a predetermined temperature and time in an atmosphere containing at least fluorine gas, and after the vitrification,
1. A method for producing optical glass fiber, comprising a heating and spinning step. 2. The optical glass fiber manufacturing method according to claim 1, wherein oxygen gas is added to the atmosphere containing fluorine gas.