JP2003238166A - Method for producing glass particulate deposition body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of stably producing, by a VAD (vapor phase axial deposition) method, a glass particulate deposition body which is added with Ge and has a GI (graded index) type refractive index distribution without disturbance of the refractive index distribution, occurrence of burner clogging during deposition, and soot cracking. <P>SOLUTION: This method comprises using a burner for synthesizing a glass particulate having the ports protruded from the central ports at the outside of a concentric multiplex tube, using the glass raw material gas-feeding ports having a cross-sectional area of 4π-25π mm<SP>2</SP>, and performing a deposition operation by the VAD method so as to satisfy T<SB>1</SB>≥45 ms and T<SB>2</SB>≤45 ms when defining the in-tube flying time of a Ge compound gas in a port α through which the most volume thereof is passed as T<SB>1</SB>(ms) and that of a glass raw material gas in a port β through which the most volume thereof is passed as T<SB>2</SB>(ms). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a VA type glass particle deposit having a GI type refractive index distribution to which Ge is added.
The present invention relates to a method capable of improving the refractive index controllability by the D (gas phase axis attachment) method.

[0002]

2. Description of the Related Art Optical fibers are classified by their refractive index structure.
Sometimes, the Graded Index
Index: GI) type fiber.
The refractive index of the fiber gradually decreases from the center of the core to the periphery.
It ’s a little bit, and it ’s used for multimode fiber cores.
There is. The GI type core member is a dispersion compensating fiber core or high N
It is also used as the core of A fiber. In Figure 3, GI
As an example of the refractive index distribution of the core of the
The core profile is shown. GI type optical fiber glass
As the composition, Ge is a dopant that raises the refractive index.
SiO added with ₂Is used for the core part and S for the clad part.
iO₂Alternatively, F, which is a dopant that lowers the refractive index,
Added SiO₂Is used, and also contains F (fluorine)
Resin with SiO₂2% lower refractive index due to the relative refractive index difference with
In some cases, a material having a is used as a clad material.

To manufacture such a GI type core glass by the VAD (vapor phase axis attachment) method, as shown in FIG.
In the reaction vessel 9, a glass fine particle synthesis burner 10 having a plurality of gas ejection ports (hereinafter, may be simply referred to as a burner) 10, a glass raw material gas such as SiCl ₄ ,
Compounds containing Ge as a dopant, eg GeC
A flame 11 formed in the burner 10 by introducing a Ge raw material gas such as l ₄ or the like, a combustible gas such as H ₂ or hydrocarbon, a supporting gas such as O ₂ and an inert gas such as Ar if necessary. In the glass raw material and Ge raw material gas, flame hydrolysis reaction and /
Alternatively, fine glass particles are generated by an oxidation reaction, and the fine glass particles are sprayed onto a starting material (target) 12 that moves upward relative to the burner 10 while rotating,
Glass fine particles are deposited in the axial direction from the end portion of the starting material 12 to form a glass fine particle deposit body 13. The obtained glass fine particle deposit 13 is made transparent by heating and sintering, and becomes a glass body (core base material).

GeCl_FourUndergoes hydrolysis reaction in a flame, oxidation
GeO generated by reacting ₂Is the reaction in the flame
As it easily volatilizes depending on the condition and the temperature of the deposition surface, the temperature in the flame
It is necessary to control the temperature and the temperature of the deposition surface. GI type
The formation of the glass particulate deposits for use as the core base material is
Always use one burner. Outside the glass particle deposit
On the side, Ge easily volatilizes, so
It is difficult to control the folding rate distribution. GI type core
As a profile, from the center to the periphery as shown in Fig. 3.
It is desirable to have a smooth parabolic shape over
For example, as shown in FIG.
The shape may be unfavorable. Also the bar
It is advantageous in terms of glass particle deposition efficiency
Therefore, as shown in Fig. 1, the port on the outer peripheral side of the center port is
Sometimes a multi-tube burner of the type with a protruding
However, during deposition, SiO near the point B on the burner protrusion₂Fine particles
Place where burner port clogging occurs due to accumulation of soot
If there is a clogging and clogging occurs, glass particulates will no longer accumulate
Will not be possible.

[0005]

DISCLOSURE OF THE INVENTION The present invention improves the controllability of the refractive index distribution by the VAD method and stabilizes and collects a Ge-containing glass fine particle deposit for a GI type core. It is an object of the present invention to provide a novel method that can be efficiently manufactured.

[0006]

The present invention includes the following (1) and (2)
The above problem can be solved by the above configuration. (1) Glass raw material gas and Ge compound gas are used as glass particles
Produced by introducing into the flame of a synthesis burner
Glass particles move relative to the burner while rotating
Containing Ge by depositing from one end of the starting material
To form a glass particulate deposit with a GI type refractive index profile
In the manufacturing method, the burner for synthesizing the glass fine particles is used.
The concentric multi-tube structure,
Port on the outside to supply glass source gas
Cross-sectional area is 4πmm²~ 25πmm ²For burner
And at the port where the most Ge compound gas flows
T between₁(Ms), the port that flows the most glass source gas
T is the flight time₂(Ms), T₁And T
₂Is the number 3

## EQU00003 ## A method for producing a glass particle deposit, which is performed so as to satisfy the expressions T ₁ ≧ 45 ms and T ₂ ≦ 45 ms. (2) The distance r from the center of the multi-tube burner to the tube of the protruding portion and the protruding length L are several 4

## EQU4 ## The method for producing a glass particle deposit according to (1) above, wherein 0.04≤r / L≤0.4 is satisfied. In the present invention, π means the circular constant.

[0007]

DETAILED DESCRIPTION OF THE INVENTION First, the background of the present invention will be described. The present invention forms a glass particle deposit having a GI type refractive index distribution containing Ge by the so-called VAD method (gas phase axis attaching method) described with reference to FIG. In order to produce the glass fine particles without clogging, the dope raw material (Ge) from the burner for synthesizing the glass particle deposit to the deposition surface is used.
Consider that the reaction of Cl ₄ ) and the reaction of the glass raw material (SiCl ₄ ) are different, especially that it takes time for GeCl ₄ to react in a burner flame and become stable as GeO _2. The present inventors have realized that there is a need.

As a result of various experiments conducted from this viewpoint, G
The flight time T ₁ of the Ge raw material from the tip of the port through which the e compound gas (Ge raw material) flows most to the deposition surface is 4
It was found that sufficient reactivity can be obtained by setting the time to 5 ms or more. Also, regarding the clogging of the burner,
The time (in-flight time) T ₂ for which the glass raw material flies at the distance between the tip position of the outer port protruding from the center port and the tip position of the port through which the largest amount of raw material gas flows is 45 ms.
It turns out that the following is better. Within the range where these conditions can be satisfied (T ₁ ≧ 45 ms and T ₂ ≦ 45 ms), deposition of Ge-doped glass fine particles having stable GI type refractive index distribution without burner clogging and good yield is achieved. It is possible to manufacture the body.

In the present invention, G which is a dopant is used.
The flight time T ₁ of the Ge raw material at the port α where the largest amount of the e raw material (GeCl ₄ ) flows is given by the equation (5).

[Equation 5]

In the present invention, glass raw material (SiCl ₄ )
The in-tube flight time T ₂ of the glass raw material at the port β at which the largest amount of the gas flows is represented by the formula (6).

[Equation 6] Here, the protrusion length L is A at the tip of the port β through which the raw material flows most, and B at the tip of the outer port of the port closest to the port β through which the flammable gas flows and outside the combustible gas. Is the distance between A and B along the burner axis.

The present invention will be described below with reference to the drawings.
FIG. 1 shows the ejection of a multi-tube burner used in one embodiment of the present invention.
Schematic cross-sectional view schematically showing the vicinity of the mouth and the glass particulate deposit
And multiple ports (spouts) are
Port 2), 2nd port 2, 3rd port 3,
4th port 4 ... Multiplexed concentrically with nth port n
Has been. In the center port 1, for example, a Ge raw material (GeC
l_FourEtc.), glass raw material (SiCl _Four) And flammable gas
(H₂Etc.), flammable gas (H₂), The first
Inert gas (Ar) for 3 port 3 and auxiliary gas for 4th port
Flammable gas (O₂Etc.) but is limited to this way
There is no place to be. Also, from port 5 to port n
Is the gas ejection direction (burner axial direction) from the 1st to 4th ports
)). Further, in the illustrated example, the first to fourth
Ports 1 to 4 form a set to form a flame, and the 5th port
After that, another flame is formed.

In the example of FIG. 1, since the center port 1 is the port α and the port β, when the tip position of the center port is A and the deposition surface position is C, the distance between A and C Is D. The tip position of the fifth port is B, and the distance between A and B is the protrusion length L.

Therefore, when the flow rate of the Ge material gas at the port where the largest amount of Ge material flows is Vα and the flow rate of the glass material gas at the port where the largest amount of glass material gas flows is Vβ, several 7

## EQU00007 ## The flow velocity and D, L satisfy the flight time T ₁ = D / Vα ≧ 45 ms and the flight time T ₂ = L / Vβ ≦ 45 ms. In the case of FIG. 1, Vα
= Vβ, it is only necessary to satisfy L ≦ 45V ≦ D (V = Vα = Vβ).

As described above, T ₁ according to the present invention is 45 ms.
However, it is more preferable that T ₁ ≦ 70 ms.
The reason for this is that if T ₁ exceeds 70 ms, the raw material flow spreads too much and the deposition efficiency decreases. Further, T _{2 according} to the present invention is set to 45 ms or less, and more preferably T ₂ ≧ 20 ms. The reason is that T ₂ is 20m
This is because if it is less than s, the flight time after passing through the protruding portion becomes long and the raw material flow spreads to lower the deposition efficiency.

Examples of the multi-tube burner used in the present invention include, but are not limited to, an inner quadruple tube having an outer quadruple tube and an inner quintuple tube having an outer quadruple tube. There is no place.

If the flow rate (flow velocity) satisfying these conditions is satisfied with the size of the port for supplying the raw material of the burner used in the present invention being too large, the size of the glass particle deposit will become too large, and soot (glass particles) The problem is that the deposits become soft and crack easily, so the cross-sectional area of the port that supplies the glass raw material is 4π mm ²
To 25πmm ² (π is the circular constant),
In addition, especially 5πmm ² to 16πmm ² , or even 6
πmm ² to 12πmm ² is preferable.

The form of the burner is 0.04≤, where r is the distance from the center of the burner to the tube of the protruding portion and L is the protruding length.
It is preferable to use a burner structure in which r / L ≦ 0.4. A more preferable range is 0.1 ≦ r / L ≦ 0.3, and a further preferable range is 0.15 ≦ r / L ≦ 0.25. If r / L is less than 0.04, it is difficult to suppress the adhesion of fine glass particles to the protruding portion of the burner even if the gas flow rate at the port supplying the raw material is increased.
When L exceeds 0.4, the spread of the glass fine particles becomes too large, so that the shape of the glass fine particle deposit obtained by deposition becomes too thick, and soot cracking easily occurs.

In the present invention, the glass raw material gas, the Ge raw material gas, the combustible gas, the supporting gas, and the inert gas introduced into the multi-tube burner are not particularly limited in flowing manner. The flowing method shown in (A) and (B) can be adopted.

In the present invention, except that the flight times T ₁ and T ₂ are within the range of the present invention, the conventionally known V
A technique for forming a glass particulate deposit having a Ge-containing GI type refractive index distribution by the AD method can be applied. As the glass source gas, for example, SiCl ₄ , SiHCl ₃ or the like can be used. As the Ge raw material, for example, GeCl
₄ etc. can be used. The flammable gas is, for example, H ₂ , CH ₄ , C ₂ H ₆ or the like, the combustible gas is, for example, O ₂ or the like, and the inert gas is, for example, N ₂ , Ar, or He.
Etc. can be used.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Examples 1 to 5 and Comparative Examples 1 to 3) FIG.
A glass particle deposit having a GI type refractive index distribution to which Ge was added was manufactured by the VAD method with the structure shown in FIG. The glass fine particle synthesizing burner 10 is a concentric octuple tube burner, and the jet outlet cross-sectional structure is the same as that shown in FIG. 1, and the fifth port 5 to the eighth port 8 forming the outer flame form the inner flame. It has a shape that protrudes from the 1st port in the ejection direction more than the 4th port. L in the figure is 69 to 73 mm, r is 1
A 1 mm one was used. The distance (D) from the tip of the first port to the deposition surface C was 160 mm, and the cross-sectional area of the port for supplying the glass raw material was 4π mm ² . S to this burner
iCl ₄ : 2.5 SLM, GeCl ₄ : 0.3 SLM,
Assuming that H _{2 is} 1.0 SLM and Ar is 0.5 SLM, FIG.
As shown in (A), the gas was supplied to each port, and the flow rate was changed so that the flow rate became the value shown in Table 1 while maintaining the above ratio of each gas. The obtained glass base material has an outer diameter of 16
0mm, pulling length is 500mm, average pulling speed is 90
It was mm / hr. Whether or not the burner was clogged during the production and the obtained glass fine particle deposits (Examples 1 to 5,
For Comparative Examples 1 to 3), the profile of the sintered and transparent glass body was measured, and as a result, the yield (definition: weight of deposited Si / weight of Si supplied to the burner) was determined as shown in Table 1.
Shown in.

[0022]

[Table 1]

From Table 1, the profile is not good when T ₁ <45 ms (Comparative Example 1), but a good profile is obtained when T ₁ ≧ 45 ms (Examples 1 to 5), and T ₂ > 4.
It can be seen that burner clogging occurs at 5 ms (Comparative Examples 2 and 3), but there is no burner clogging at T ₂ ≦ 45 ms (Examples 1 to 5). In Comparative Examples 2 and 3, since the burner was clogged, the shape of the glass particulate deposits became abnormal, and sintering could not be performed, so that the profile could not be measured. If T ₁ ≦ 70 ms and T ₂ ≧ 20 ms, the yield exceeds 50%, but T ₁ > 70 ms or T ₂ <20.
If it is ms, the yield decreases. This is because the raw material gas flow is too wide.

(Examples 6 to 8 and Comparative Examples 3 and 4) Eight tube
Using a burner, connect G to the first port as shown in Fig. 2 (B).
eCl_Four: 0.3SLM, H₂: 0.6 SLM, Ar:
Flow 0.6 SLM and SiCl 2 in the second port_Four: 2.5
SLM, H₂: Run 5.0 SLM, other ports
Flowing in the same manner as in Examples 1 to 5 to prepare glass particulate deposits
did. L is 50 mm, r is 12 mm, distance to the deposition surface
Is 120 mm, GeCl_FourSection of the port (first) through which the water flows
Product is 4πmm², SiCl_FourThe port that washed away (the second port
G)) cross-sectional area is 24πmm ²(Examples 6-8,
Comparative Examples 3 and 4). The conditions and results at this time are shown in Example 1.
As in the case, it is shown in Table 2.

[0025]

[Table 2]

As shown in Examples 6 to 8, even if the port for flowing the Ge raw material gas and the port for flowing the glass raw material gas are different, if T ₁ ≧ 45 ms and T ₂ ≦ 45 ms, a good profile is obtained. A glass body can be manufactured.

(Example 9 and Comparative Examples 5 to 7) GeCl ₄
And SiCl ₄ are both supplied to the first port, the cross-sectional area of the first port is changed as shown in Table 3, and SiCl ₄ :
1.0 SLM, GeCl ₄ : 0.1 SLM, H ₂ 0.2
The flow rate was changed so that the flow rate had the values shown in Table 3 while maintaining the ratio of SLM and Ar0.2SLM. The conditions and results at this time are shown in Table 3 as in the case of Example 1.

[0028]

[Table 3]

As shown in Table 3, burner clogging occurs when the cross-sectional area of the port for supplying the raw material is less than 4πmm ² (Comparative Examples 5 and 7), and when the cross-sectional area exceeds 25πmm ² , the glass fine particle flow spreads and the soot flows. Cracking occurs (Comparative Example 6). In Comparative Example 7, r / L <0.04 is another cause of burner clogging.

(Examples 10 and 11, and Comparative Example 8)
A 9-tube burner (cross-sectional area of the first port 6.3 π mm ² ) was used, and SiCl ₄ , GeC was used for the first port (center port).
l ₄ : 0.2 and O ₂ , Ar at the _2nd port, H _{2 at} the 3rd port, Ar at the 4th port, O _{2 at} the 5th port, Ar at the 6th port, H _{2 at} the 7th port, Each gas was supplied in the order of Ar to the 8th port and O _{2 to} the 9th port. In Example 10, SiCl ₄ : 2.0SLM, GeC was used for the first port.
l ₄ : 0.2 SLM and O ₂ : 0.75 SLM were supplied to prepare a glass fine particle deposit. Further, the mixing ratio of each gas was changed in the same manner as in Example 10 and the flow rate was changed as shown in Table 4 to prepare a glass particulate deposit (Example 11).
And Comparative Example 8). The conditions and results at this time are shown in Table 4 as in the case of Example 1.

[0031]

[Table 4]

As shown in Table 4, T ₁ ≧ 45 ms and T ₂ ≦ 45 ms even when the nine-tube burner is used, and the cross-sectional area S of the port for supplying the raw material is 4π mm ² ≦
By virtue of the range limitation of the present invention in which S ≦ 25 π mm ² is satisfied, and at the same time, the Ge-containing glass fine particle deposit can be manufactured with good profile without clogging of the burner or soot cracking. It can be seen that burner clogging occurs when T ₂ exceeds 45 ms (Comparative Example 8). The yield of Example 11 in which T ₁ exceeds 70 ms is lower than that of Example 10.

[0033] In the above embodiment shows an example using GeCl ₄ as SiCl _4, Ge raw material as a glass material, for example, SiHCl ₃ as a glass raw material, Si
The effects of the present invention can be obtained by using H ₂ Cl ₂ or the like and using, as the combustible gas, a short-chain hydrocarbon such as CH ₄ or C ₂ H _{6 in} addition to H ₂ . Further, the supply of SiCl ₄ and GeCl ₄ uses the direct delivery method, but the same effect can be obtained by supplying by bubbling.

[0034]

INDUSTRIAL APPLICABILITY In producing a glass fine particle deposit having a GI type refractive index distribution containing Ge by the VAD method, a multi-tube type glass fine particle synthesizing burner is used and flight is carried out at a port α through which the Ge raw material gas flows most. Time T
_1, and the in-tube flight time T ₂ of the port β through which the glass raw material gas flows most is set within a specific range, the burner is not clogged stably, and the controllability of the GI type refractive index distribution is improved to improve the Ge-containing GI. It is possible to manufacture a glass fine particle deposit having a type refractive index distribution.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view illustrating a structure of a burner for synthesizing glass fine particles used in one embodiment of the present invention and a gas flow method.

FIG. 2 is a cross-sectional view showing a cross-sectional structure of a jet outlet portion of a burner for synthesizing glass particles used in an example of the present invention and a flow method of gas species.

FIG. 3 is a diagram showing an example of a GI type refractive index distribution containing Ge.

FIG. 4 is a schematic diagram for explaining the production of a glass particulate deposit having a Ge-added GI type refractive index distribution according to the present invention and the conventional VAD method.

FIG. 5 contains Ge, but has a recess in the center, etc.
It is a refractive index distribution map explaining various unfavorable profiles.

[Explanation of symbols]

1 1st port (center port), 2 2nd port,
3 3rd port, 4th 4th port, 5 5th port, 6 6th port, 7 7th port, 8 8th port, 9 reaction vessel, 10 glass particle synthesis burner, 11 flame, 12 target (starting material) , 13 Glass fine particle deposit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuichi Oga             Sumitomoden 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa             Ki Industry Co., Ltd. Yokohama Works F-term (reference) 2H050 AC05                 4G014 AH16                 4G021 EA01 EB15

Claims (2)

[Claims] 1. Glass fine particles produced by introducing a glass raw material gas and a Ge compound gas into the flame of a burner for synthesizing glass fine particles, from one end of a starting material that moves relative to the burner while rotating. In a manufacturing method for forming a GI-type refractive index distribution glass fine particle deposit containing Ge, the burner for synthesizing glass fine particles has, as a burner for synthesizing glass fine particles, a port having a concentric multi-tube structure and protruding from a central port on the outside. However, a burner having a cross-sectional area of the port for supplying the glass raw material gas of 4πmm ^{2 to} 25πmm ² is used, and the flight time of the port for flowing the most Ge compound gas is T ₁ (ms), and the most glass raw material gas is flown. When the in-flight time of the port is T ₂ (ms),
A method for producing a glass fine particle deposit, characterized in that T ₁ and T ₂ are satisfied so as to satisfy the equations: T ₁ ≧ 45 ms and T ₂ ≦ 45 ms. 2. The radial distance r from the center of the multi-tube burner to the tube of the projecting portion and the projecting length L satisfy the following equation (2): 0.04 ≦ r / L ≦ 0.4. The method for producing a glass fine particle deposit according to claim 1, wherein