JP2008050203A - Glass dehydration method, optical glass manufacturing method, and optical fiber manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass dehydration method by which occurrence of structural defects is suppressed. <P>SOLUTION: Dehydration of quartz-based glass is carried out under a condition that the reaction progresses to the right side of formula (1) and the left side of formula (2). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a glass dehydrating method, an optical glass manufacturing method using the glass dehydrating method, and an optical fiber manufacturing method using the optical glass manufacturing method.

  Since porous glass produced using a hydrolysis reaction contains a large amount of moisture, when it is sintered as it is, an optical glass containing moisture or OH groups is formed. Moisture and OH groups in the optical glass give absorption loss. For example, an optical fiber formed of optical glass containing moisture or OH groups has an absorption loss in the communication wavelength region.

Therefore, there is a method of dehydrating the porous glass by heat-treating the porous glass in an inert gas atmosphere to which a chlorine-based gas is added (see Patent Document 1 below).
Japanese Patent Laid-Open No. 5-24873

  However, in the dehydration method described in Patent Document 1, it is necessary to prepare and maintain an equipment environment in which toxic chlorine gas can be used, and this requires costs.

  It is an object of the present invention to provide a glass dehydration method, an optical glass manufacturing method, and an optical fiber manufacturing method that are not costly to arrange and maintain equipment for using chlorine.

の右辺に反応が進み、且つ、化学反応式（２）

の左辺に反応が進む条件下で石英系ガラスの脱水を行うことを特徴とする。 The glass dehydration method of the present invention comprises a chemical reaction formula (1)

The reaction proceeds to the right side of the chemical reaction formula (2)

The silica glass is dehydrated under the condition that the reaction proceeds to the left side of the glass.

In the glass dehydration method of the present invention, the treatment is performed under the condition that the reaction proceeds to the right side of the chemical reaction formula (1). Therefore, the reaction in which H ₂ O physically attached to the quartz-based glass is decomposed into H ₂ and O ₂ proceeds and chemically bonded to SiO ₂ which is the main component of the quartz-based glass. The OH group is removed. That is, it is possible to perform dehydration treatment of the quartz glass without using chlorine. Accordingly, it is possible to dehydrate the quartz glass while suppressing the occurrence of structural defects. Further, since the process under conditions that the reaction proceeds to the left side of the chemical equation (2), it is possible to suppress the reduction of SiO ₂ occurs maintain the state of the silica-based glass.

  The optical glass production method of the present invention includes a dehydration step of dehydrating the porous glass under conditions where the reaction proceeds to the right side of the chemical reaction formula (1) and the reaction proceeds to the left side of the chemical reaction formula (2); And a sintering step of producing an optical glass by sintering the porous glass after the dehydration step.

In the optical glass manufacturing method of this invention, it processes on the conditions which reaction advances to the right side of Chemical Reaction Formula (1) in a dehydration process. Therefore, a reaction in which H ₂ O physically attached to the porous glass is decomposed into H ₂ and O ₂ proceeds and chemically bonded to SiO ₂ which is the main component of the porous glass. The OH group is removed. That is, the porous glass can be dehydrated without using chlorine. Therefore, the porous glass can be dehydrated while suppressing the occurrence of structural defects. Further, since the process under conditions that the reaction proceeds to the left side of the chemical equation (2), it is possible to suppress the reduction of SiO ₂ occurs maintain the state of the porous glass. Moreover, since the optical glass is manufactured by sintering the porous glass thus dehydrated, the optical glass can be manufactured while suppressing the occurrence of structural defects.

  The optical glass is also preferably an optical fiber preform. By doing in this way, generation | occurrence | production of a structural defect can be suppressed and an optical fiber preform | base_material can be formed.

  The optical fiber manufacturing method of the present invention includes a dehydration step of dehydrating the porous glass under a condition that the reaction proceeds to the right side of the chemical reaction formula (1) and the reaction proceeds to the left side of the chemical reaction formula (2); It includes a sintering step in which porous glass is sintered after the dehydration step to form an optical fiber preform, and a drawing step in which the optical fiber preform is drawn to produce an optical fiber.

In the optical fiber manufacturing method of the present invention, the dehydration process is performed under conditions where the reaction proceeds to the right side of the chemical reaction formula (1). Therefore, a reaction in which H ₂ O physically attached to the porous glass is decomposed into H ₂ and O ₂ proceeds and chemically bonded to SiO ₂ which is the main component of the porous glass. The OH group is removed. That is, the porous glass can be dehydrated without using chlorine. Therefore, the porous glass can be dehydrated while suppressing the occurrence of structural defects. Further, since the process under conditions that the reaction proceeds to the left side of the chemical equation (2), it is possible to suppress the reduction of SiO ₂ occurs maintain the state of the porous glass. Since the porous glass thus dehydrated is sintered to form an optical fiber preform, and the optical fiber is manufactured by drawing, the optical fiber can be manufactured while suppressing the occurrence of structural defects.

  ADVANTAGE OF THE INVENTION According to this invention, the glass dehydration method, optical glass manufacturing method, and optical fiber manufacturing method which do not require the cost which arranges and maintains the installation for using chlorine can be provided.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are assigned to the same elements, and duplicate descriptions are omitted.

  FIG. 1 is a flowchart for explaining an optical fiber manufacturing method according to this embodiment. The optical fiber manufacturing method according to the present embodiment is a method of manufacturing an optical fiber using the glass dehydration method and the optical glass manufacturing method of the present invention.

First, in the forming step S1, porous glass is formed. Porous glass is formed, for example, by OVD method, SiO ₂ fine particles to produce the a SiCl ₄ was hydrolyzed, the resulting SiO ₂ particles are deposited on the rod-shaped base material formed. Next, the porous glass formed in the dehydration step S2 is dehydrated. Subsequently, in the sintering step S3, the dehydrated porous glass is sintered at a temperature of about 1650 ° C. to 1800 ° C., for example, to form an optical fiber preform. Thereafter, in the drawing step S4, the formed optical fiber preform is drawn to form an optical fiber.

  Subsequently, the dehydration step S2 will be described in detail. FIG. 2 is a configuration diagram of the ultra-low oxygen dehydration apparatus used in the dehydration step S2. The extremely low oxygen dehydration apparatus 10 includes a low oxygen apparatus 11 that generates a low oxygen gas having a low oxygen partial pressure, and a low oxygen chamber 13 that is connected to the low oxygen apparatus 11 via a valve 12.

  As indicated by an arrow Y, the low oxygen gas generated in the low oxygen device 11 is supplied to the low oxygen chamber 13, dehydration is performed in the low oxygen chamber 13, and exhaust gas is exhausted from the low oxygen chamber 13. . The ultra-low oxygen dehydration apparatus 10 includes an oxygen sensor 14 that measures an oxygen partial pressure of a supply gas supplied to the low oxygen chamber 13 and an oxygen sensor 15 that measures an oxygen partial pressure of exhaust gas exhausted from the low oxygen chamber 13. And further comprising. The low oxygen chamber 13 is provided with a temperature sensor 16 for measuring the temperature in the low oxygen chamber 13.

  The low oxygen device 11 includes an oxygen pump that lowers the oxygen partial pressure in a rare gas such as He, Ne, Ar, or Xe or nitrogen gas, and generates a low oxygen gas having a low oxygen partial pressure. As the oxygen pump, for example, the oxygen pumps described in JP-A-2005-331339 and JP-A-2004-250283 can be used.

  The low oxygen chamber 13 is set to a predetermined temperature range and a predetermined oxygen partial pressure atmosphere based on the oxygen partial pressure values and temperatures output from the oxygen sensors 14 and 15 and the temperature sensor 16. The predetermined temperature range and the predetermined oxygen partial pressure atmosphere are ranges shown in a region A of FIG.

FIG. 3 is a H ₂ O / SiO ₂ thermodynamic state diagram. A curve 21 in FIG. 3 shows a thermodynamic equilibrium condition of the chemical reaction shown in the chemical reaction formula (3). A curve 22 in FIG. 3 shows a thermodynamic equilibrium condition of the chemical reaction shown in the chemical reaction formula (4).

  Region A is at least a higher temperature side or a lower oxygen partial pressure side than the equilibrium condition of the chemical reaction represented by the chemical reaction formula (3), and at least a lower temperature side than the equilibrium condition of the chemical reaction represented by the chemical reaction formula (4). Alternatively, the oxygen partial pressure is a region on the high pressure side. In the dehydration step S2, the porous glass is placed in the low oxygen chamber 13 set to the predetermined temperature range and the predetermined oxygen partial pressure atmosphere, and the dehydration process is performed in an extremely low oxygen partial pressure atmosphere. That is, the dehydration step S2 is performed under conditions where the reaction proceeds to the right side of the chemical reaction formula (3) and the reaction proceeds to the left side of the chemical reaction formula (4).

As described above, in the dehydration step S2 of the present embodiment, the process is performed under the condition that the reaction proceeds to the right side of the chemical reaction formula (3). Therefore, a reaction in which H ₂ O physically attached to the porous glass is decomposed into H ₂ and O ₂ proceeds and chemically bonded to SiO ₂ which is the main component of the porous glass. The OH group is removed. That is, the porous glass can be dehydrated without using chlorine. Therefore, the porous glass can be dehydrated while suppressing the occurrence of structural defects. Further, since the process under conditions that the reaction proceeds to the left side of the chemical equation (4), it is possible to suppress the reduction of SiO ₂ occurs maintain the state of the porous glass.

The dehydration treatment is preferably performed at a temperature at which the porous glass is not sintered. That is, the region A preferably has a temperature of 1400 ° C. or lower. In other words, the region A preferably has an oxygen partial pressure of 10 ⁻³⁰ to 10 ⁻¹⁰ . In this case, by performing dehydration treatment of the porous glass at a temperature of 1400 ° C. or lower, the dehydration treatment can be performed before the porous glass is sintered.

  As described above, since the porous glass is sintered after the porous glass is dehydrated while suppressing the occurrence of structural defects, the optical fiber preform can be formed while suppressing the generation of structural defects. Furthermore, since an optical fiber is manufactured by drawing an optical fiber preform formed by suppressing the occurrence of structural defects, it is possible to manufacture an optical fiber while suppressing the occurrence of structural defects.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, the ultra-low oxygen dehydration apparatus 10 is not limited to the above configuration as long as it constitutes a low oxygen chamber that satisfies the conditions shown in the region A of FIG. For example, the oxygen partial pressure may be set so as to satisfy the conditions shown in the region A of FIG. 3 by letting out oxygen in the low oxygen chamber from the sealed low oxygen chamber by an oxygen pump.

Moreover, in the said embodiment, although the porous glass was dehydrated, it is not restricted to porous glass. For example, the sintered optical glass may be dehydrated. For example, a sintered glass lump, a glass rod, or a glass tube may be dehydrated under the conditions shown in the region A. In this case, H ₂ O physically attached to the surface of the glass block, glass rod, or glass tube can be mainly removed. In this case, the temperature condition during the dehydration process satisfies the condition shown in the region A and is set to be equal to or lower than the melting point of the optical glass.

  Further, after the dehydration step S2, the porous glass may be sintered by raising the low oxygen chamber 13 to a sintering temperature in a state where the porous glass is placed in the low oxygen chamber 13. By doing in this way, a porous glass can be sintered more reliably in the state which dehydrated the porous glass.

It is a flowchart explaining the manufacturing method of the optical fiber which concerns on this embodiment. It is a block diagram of the dehydration apparatus used in a dehydration process. A H ₂ O / SiO ₂ thermodynamic phase diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Extremely low oxygen dehydration device, 11 ... Low oxygen device, 12 ... Valve, 13 ... Low oxygen chamber, 14, 15 ... Oxygen sensor, 16 ... Temperature sensor

Claims (4)

Chemical reaction formula (1)

The reaction proceeds to the right side of the chemical reaction formula (2)

A glass dehydration method comprising dehydrating quartz glass under a condition in which the reaction proceeds to the left side of the glass. Chemical reaction formula (3)

The reaction proceeds to the right side of and the chemical reaction formula (4)

A dehydration step of dehydrating the porous glass under conditions where the reaction proceeds to the left side of
A sintering step of producing optical glass by sintering the porous glass after the dehydration step;
An optical glass manufacturing method comprising:   The optical glass manufacturing method according to claim 2, wherein the optical glass is an optical fiber preform. Chemical reaction formula (5)

The reaction proceeds to the right side of and the chemical reaction formula (6)

A dehydration step of dehydrating the porous glass under conditions where the reaction proceeds to the left side of
A sintering step of forming the optical fiber preform by sintering the porous glass after the dehydration step;
A drawing step of drawing an optical fiber by drawing the optical fiber preform;
An optical fiber manufacturing method comprising:

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