JPH0459626A - Formation of porous glass - 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 "Field of Industrial Application" The present invention relates to a method for forming porous glass used in the fields of communications and optics.

"Prior Art" In the fields of communications and optics, optical fibers, image guides, light guides, rod lenses, etc. are representative examples of quartz-based products manufactured by glass synthesis.

When producing the base material for such products, glass raw material scraps, tope raw material scraps, etc. are chemically reacted at high temperatures to produce soot-like glass fine particles, and the glass fine particles are deposited in a desired shape to form porous glass. Generally, the porous glass is sintered and made transparent in a high temperature atmosphere to obtain a transparent glass base material.

By the way, in an example of forming a porous glass for an optical fiber by the OVD method using a multi-tube structure, a glass rod for the core or a glass rod with glass for the core/cladding is used as the target. This is rotated and raw material gas is supplied to the burner kept in a burning state to generate glass particles, which are injected together with the burner flame onto the outer peripheral surface (deposition surface) of the target and deposited. I'm letting you do it.

"Problems to be Solved by the Invention" When forming porous glass through the above-mentioned glass particle deposition means, the size of the porous glass and the size of the eight flame containing the glass particles are determined by the size of the glass particles. Deposition efficiency has a significant impact on the yield of porous glass.

For example, under conditions where the raw material gas supply amount to the heather and the flow rate of the heather flame are kept constant, when the outer diameter of the porous glass is relatively small and the burner flame is large, the porous glass More glass particles are discarded without colliding and adhering to the outer peripheral surface (deposition surface) of the glass. Conversely, when the outer diameter of the porous glass is large and the burner flame is small, most of the glass particles are Collision and adhesion to the outer circumferential surface of the

From this point of view, it can be said that when the outer diameter of the porous glass is larger than the eight flame, the deposition efficiency of glass particles increases.

However, the small burner flame locally heats the large porous glass and induces cracking, thereby reducing the yield of the porous glass.

Taking these circumstances into consideration, it seems best for the porous glass and the burner flame to maintain appropriate sizes and remain constant from beginning to end. When forming porous glass, as fine glass particles are deposited, the porous glass becomes larger, so that at a certain point the balance between the two is lost.

Therefore, either the deposition efficiency of glass particles or the yield of porous glass must be sacrificed.

In addition, by increasing the amount of raw material gas supplied to the burner and speeding up the burner flame, it is possible to increase the amount of glass particles deposited per unit time. reaches the deposition surface, making it impossible to obtain good quality porous glass.

In view of these technical problems, the present invention aims to provide a method for forming porous glass that is capable of reducing the deposition efficiency and speed of glass fine particles, and that can yield high-quality porous glass at a high yield. be.

"Means for Solving the Problems" In order to achieve the intended purpose, the present invention makes use of the fluidity of flame to inject glass particles contained in the flame onto a rotating deposition surface. The method of forming porous glass by deposition is characterized in that the flame is increased in size in accordance with the growth of porous glass due to the deposition of the glass particles.

[Operation] In the method of the present invention, when forming porous glass, glass particles contained in a flame are injected and deposited on a predetermined deposition surface.

As is obvious, the porous glass thus formed grows as glass fine particles are deposited, and its outer diameter increases.

In the method of the present invention, when forming such porous glass, the flame is enlarged according to the growth of the porous glass, so that the flame size is always kept in an appropriate state for porous glass whose outer diameter changes. can be retained.

As a result, the deposition efficiency of glass particles increases.

There is no localized heating of the porous glass, which can cause cracks.
It is possible to sufficiently improve quality, yield, productivity, etc. when forming porous glass.

Example J A method for forming porous glass according to the present invention will be described with reference to the illustrated example.

In FIG. 1, 10 indicates a quartz-based glass rod, 11 indicates a deposition surface (outer peripheral surface) of the glass rod 10, and 12 indicates a quartz-based porous glass formed on the deposition surface 11 of the glass rod 10. Reference numeral 20 indicates a burner having a multi-tube structure that is movable in the length direction of the glass rod 10, and reference numeral 30 indicates an exhaust duct arranged corresponding to the burner 20.

The quartz-based glass rod 10 is used as a rod-shaped material for, for example, optical fibers, image guides, light guides, and lenses. cladding glass with a relatively low refractive index.

In FIG. 1, such glass $10 is rotatably supported at both ends via chucks (not shown) of a glass lathe.

The silica-based porous glass 12 formed on the deposition surface 11 of the glass s10 is used, for example, as the above-mentioned cladding glass.

As shown in Fig. 2, the multi-tube structure burner 20 is constructed by concentrically combining a large number (10) of quartz pipes with different outer diameters, and the axis From the center to the outer periphery, the first flow path 21. Second flow path 22, third flow path 23, fourth flow path 24, fifth flow path 25, sixth flow path 28, seventh flow path 27, eighth flow path 28, ninth flow path 2
9 is formed.

At the base end of the burner 20, frit gas (SiGIa), hydrogen gas (H2), and oxygen gas (02
), and these piping systems are connected to a predetermined gas supply source (not shown).

Incidentally, in the case of the burner 20 to which these piping systems are connected, frit gas is supplied to each of the first, fourth, and seventh channels 21, 24, and 27, and each of the second, fifth, and Channel 22
．． Hydrogen gas is supplied to channels 25, 28, and oxygen scum is further supplied to each of the third, sixth, and ninth channels 23, 26, and 29.

The exhaust duct 30 is connected to an intake type exhaust gas processing means (not shown).

In the embodiment shown in FIG. 1, after the glass rod 10 is rotated at a predetermined speed, the burner 20, which is in a combustion state while being supplied with raw material gas, hydrogen gas, and oxygen gas, is moved along the length of the glass rod 10. When the glass rod 10 is reciprocated, the soot-like glass particles generated through the burner 20 are blown from the tip of the burner onto the deposition surface ll of the glass rod 10 along with the flame.
In addition, the particles are deposited on the deposition surface 11 to become porous glass 12, and as the glass particles are deposited, the porous glass 12 grows and becomes larger in outer diameter.

In the above, after the glass particles are deposited on the deposition surface ll of the glass rod 10 and the porous glass 12 is formed,
The outer peripheral surface of the porous glass 12 becomes a new deposition surface.

In this manner, when forming the porous glass 12, the burner flame containing the glass particles is increased in size according to the outer diameter of the growing porous glass at the initial stage, middle stage, and final stage.

That is, in the initial stage, only the first flow path 21: glass raw material, the second flow path 22: hydrogen gas, and the third flow path 23: oxygen gas are used, and in the middle stage, the fourth flow path 24: glass raw material is used. gas, fifth flow path 25: hydrogen gas, sixth flow path 26: oxygen gas, and in the final stage, seventh flow path 27
: Glass raw material gas, Eighth flow path 28: Hydrogen gas, Ninth flow path 29: # Raw scum is also used together.

In this way, by increasing the number of channels used in the burner 20 in a timely manner, the outer diameter of the porous glass 12 and the flame (size) of the burner 20 can be maintained in an appropriate relationship at all times. High quality glass can be advantageously formed without wasting raw materials.

The size of the burner flame relative to the outer diameter of the porous glass (the diameter of the cross section of the flame at the part that reaches the deposition surface) should be within the appropriate range of 0.3 to 3.0 times the outer diameter of the porous glass. However, when the eight flames are outside this range, the problems described above arise.

Therefore, when forming a porous glass, the number of channels used in the burner 20 may be increased as described above based on this range.

Next, specific examples of the method of the present invention and comparative examples thereof will be explained.

[Specific Example] When forming the porous glass 12 by the technical means described with reference to FIGS. 1 and 2, the glass rod 10 is made of a silica-based optical fiber base material (
The outer diameter ratio of core glass to cladding glass was 1:4), and each gas was supplied to each flow path of the eighth 20 as shown in the vestibule.

Table (In the table, 5iC1a is indicated by weight, but burner 2
The high temperature gas is introduced into each of the 0 passages. Furthermore, S
iC:14 contains l of argon gas Ar for dilution.
Only 1% of Oma is added. ) When implementing the specific example as described above, the glass rod IO
Porous glass 12 with an outer diameter of 20rxtmφ is placed on the deposition surface 11 of
Only the first flow path 21 to third flow path 23 are used until the porous glass 12 is formed, and then the first flow path 21 to the sixth flow path 26 are used until the porous glass 12 grows to an outer diameter of 5 mφ. After that, all of the first flow path 21 to the ninth flow path 29 were used to finish the outer diameter of the porous glass 12 to 120I1 mφ.

[Comparative Examples 1 to 3] In the case of Comparative Example 1, the same glass rod 10 as in the specific example was used, and the porous glass 12 was formed using only the first flow path 21 to the third flow path 23 from beginning to end. did.

In the case of Comparative Example 2, the same glass rod IO as in the specific example was used, and the porous glass 12 was formed using the first channel 21 to the sixth wave channel 2B from beginning to end.

In the case of Comparative Example 3, the same glass rod 10 as in the specific example was used, and the porous glass 12 was formed using the first flow path 21 to the ninth flow path 29 from beginning to end.

In addition, in the case of Comparative Example 3, the outer diameter of the porous glass 12 is 5h.
At the time when +mφ is exceeded, 24g/win is applied to the fourth flow path 24.
of SiC:Ia was introduced.

[Evaluation] Figure 3 shows the relationship between the outer diameter of the porous glass and the glass particle deposition rate for each of the above, and Figure 4 shows the relationship between the outer diameter of the porous glass and the glass particle deposition efficiency.

As is clear from these figures, in the case of the specific example, both the deposition rate and the deposition efficiency (4 oz or more) were good, and no cracking of the porous glass occurred.

On the other hand, in the case of Comparative Example 1, although the deposition rate is partially better than that of the specific example, the deposition efficiency is significantly low when the outer diameter of the porous glass is small.

In the case of Comparative Example 2, the deposition efficiency is maintained at the same level as the specific example, such as 6 oz or more, but the deposition rate is slow, and moreover, when the outer diameter of the porous glass exceeds 75 mmφ, the porous glass A crack occurred.

Furthermore, in the case of Comparative Example 3, the deposition efficiency was decreased at the initial stage and at the final stage of forming the porous glass.

This is because the surface on which the glass particles are deposited is small in the initial stage.
The flow rate of the frit gas was high during the binding period, and it is thought that this was the reason why the fine glass particles did not adhere well.

The porous glass formed on the outer periphery of the glass rod in the above specific example and comparative example 1.3 was sintered and made transparent in a high-temperature atmosphere containing helium (He) to obtain a transparent glass base material. The outer diameter ratio of core glass to cladding glass was 1:13.

Further, each of these base materials was spun using a well-known heating drawing means to obtain optical fibers each having an outer diameter of 125 gmφ.

All of these optical fibers had good transmission losses of 0 and 19 dB/ at a wavelength of 1.55 pm.

"Effects of the Invention" As explained above, the method for forming porous glass according to the present invention, when forming porous glass by depositing glass fine particles contained in a flame on a predetermined deposition head, Since the flame is enlarged according to the growth of crow, the deposition efficiency of crow fine particles is high, the deposition rate of glass fine particles is also fast, and moreover, high quality porous glass without cracking can be obtained with a high yield. I can do it.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing an embodiment of the method of the present invention, and FIG.
The figure is a plan view schematically showing the tip surface of the burner used in the method of the present invention, Figure 3 is an explanatory diagram showing the relationship between the outer diameter of the porous glass and the glass particle deposition rate, and Figure 4 is the outer diameter of the porous glass. FIG. 3 is an explanatory diagram showing the relationship between the diameter and the glass particle deposition efficiency. 10...Glass rod 11...Deposition surface of glass rod 12...
・・・・・・Porous glass 20・・・・・・・・・
Burners 21 to 29...Each flow path 30 of the burner...
... Exhaust duct agent Patent attorney Yoshio Saifuji Figure (e, on in the snow) Porous Pttr lath rice bowl (fresh)

Claims (1)

[Claims] In a method of forming porous glass by injecting and depositing glass particles contained in the flame onto a rotating deposition surface by utilizing the fluidity of the flame, the porous glass is formed by depositing the glass particles. A method for forming porous glass, the method comprising increasing the size of the flame according to the growth of the porous glass.