JP2006036601A - Method of manufacturing quartz-based glass body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a quartz-based glass body having a desired shape and composition distribution, prevented from the occurrence of crack by enhancing bonding strength in the manufacturing process and capable of being made large-scaled. <P>SOLUTION: The method of manufacturing the quartz-based glass body is carried out by preparing silicon dioxide powder coated with silicon carbide and germanium dioxide powder coated with silicon carbide (step S10, S11), mixing each with water to make clay-like carbides respectively for a core and a clad (step 11-14), integrally combining the clay-like carbides to form a shape (step S15), drying the clay-like carbide (step S16), heating under an oxygen atmosphere to form a porous glass body (step S17), further heating the porous glass body under a chlorine atmosphere to dehydrate (S18) and after that, heating the porous glass body to sinter and to vitrify it (step S19). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a silica-based glass body, in which a transparent quartz-based glass body is produced using a powder that is a raw material for the silica-based glass.

  Various methods are known for producing quartz glass bodies by producing fine particles of quartz glass oxide particles and sintering them to form a porous body, and are widely used in gas phase synthesis methods and liquid phase synthesis methods. (For example, refer nonpatent literature 1).

  Known vapor phase synthesis methods include VAD (Vapor phase Axial Deposition), OVD (Outside Vapor Deposition), and MCVD (Modified Chemical Vapor Deposition). In the VAD method, a starting rod as a substrate is arranged in the vertical direction, and while rotating around its axis and moving in the axial direction, glass particles (silica) are deposited on its outer periphery by a burner for generating glass particles. This is a method of growing a glass particulate deposit in the axial direction of the starting bar. The OVD method (external method) is a method in which a glass fine particle deposit is grown in a radial direction with respect to a starting rod. The porous glass particulate deposit is then made into a transparent glass by dehydration and sintering.

  In the MCVD method (internal method), a raw material gas for generating glass fine particles is introduced inside a glass pipe serving as an internal substrate, and a heat source provided outside the glass pipe is used in the longitudinal direction of the glass pipe. The glass pipe is heated by traversing along. By heating the glass pipe in this manner, the raw material gas introduced into the inside of the glass pipe undergoes an oxidation reaction to generate glass particles. The fine glass particles adhere to and accumulate on the inner peripheral surface of the glass pipe on the downstream side of the flow of the source gas. Thereafter, the deposited glass particles are heated and transparentized by traversing the heat source, and a glass film is sequentially formed.

  Colloidal silica methods and alkoxide methods are known as liquid phase synthesis methods (sol-gel methods) in which fine particles are synthesized and gelled (solidified) in the liquid phase. In the colloidal silica method, glass fine particles are generated in a gas phase, and this is mixed with water to form a suspension and gelled. And this is dried to obtain a porous dry gel, which is then made into a transparent glass by dehydration and sintering in the same manner as in the VAD method or the like. In the alkoxide method, silicon alkoxide is mixed with alcohol to be gelled. In the case of the alkoxide method, the glass fine particles are also synthesized in the liquid phase, and more kinds of dopants can be added than in the colloidal silica method.

Shuichi Shibata, “Ceramics Basic Course <8> Glass for Optical Fibers Made from Fine Particles” Uchida Otsukuru, September 25, 1997

  By the way, in the VAD method and the OVD method, glass fine particles are deposited so as to be sprayed on the substrate, so that it is difficult to obtain a fine and highly accurate composition distribution and shape. Further, the MCVD method has lower productivity than the VAD method and the OVD method. Furthermore, in general gas phase synthesis methods, the glass body to be produced has an axisymmetric structure due to the characteristics of the manufacturing method in which glass particles are deposited on a rotating substrate, so that the degree of freedom in designing the glass body becomes low. On the other hand, in the liquid phase synthesis method, it is possible to obtain the desired composition distribution and shape by shaping in a gelled state, but the bonding between glass particles in a low temperature environment compared to the gas phase synthesis method. The bond strength is weak. Therefore, it is easy to generate | occur | produce a crack and needs to dry and sinter slowly over time. Moreover, since the bonding force is weak, it is difficult to make a large glass body.

  An object of the present invention is to provide a method for producing a quartz-based glass body having a desired shape and composition distribution, strengthening bonding in the production process to prevent cracks, and capable of increasing the size.

  The method for producing a silica-based glass body of the present invention capable of achieving the above object is to form a clay-like carbide by mixing a powder having silicon carbide on the surface with a solvent, and shape the shape of the clay-like carbide. Heating the clay-like carbide in an oxygen-containing atmosphere to oxidize the silicon carbide to form a porous glass body, heating the porous glass body to make it transparent, To do.

  In the method for producing a quartz-based glass body according to the present invention, it is preferable that a plurality of kinds of powders having silicon carbide on the surface are blended and mixed with the solvent to make the clay-like carbide.

  Moreover, in the manufacturing method of the quartz type glass body of this invention, it is preferable to shape by combining the said multiple types of said clay-like carbide | carbonized_materials from which mixing | blending differs integrally.

  In the method for producing a quartz glass body according to the present invention, it is preferable that the porous glass body is heated in an atmosphere containing chlorine and then transparentized.

  Moreover, in the manufacturing method of the quartz type glass body of this invention, it is preferable to dry the said clay-like carbide | carbonized_material before forming the said porous glass body.

  According to the method for producing a silica-based glass body of the present invention, a clay-like carbide obtained by mixing a powder and a solvent is strongly bonded between the powders by bonding between the silicon carbides on the surface as compared with the gel of the conventional manufacturing method. Therefore, cracks are unlikely to occur and the size is likely to increase. Further, by heating and oxidizing silicon carbide bonded between powders, bonds between glass particles can be formed in a high temperature environment, and bonding between particles can be strengthened. In addition, a desired shape can be obtained with high accuracy by adjusting the shape by putting or extruding a moldable clay-like carbide. Moreover, a desired composition can be obtained easily and accurately by blending a plurality of types of powders having silicon carbide on the surface to make a clay-like carbide. Moreover, a desired composition distribution can be easily obtained by combining clay-like carbides having a desired composition.

Embodiments of a method for producing a quartz glass body according to the present invention will be described below in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a flowchart showing a first embodiment of a method for producing a silica-based glass body according to the present invention.
In the present embodiment, an example of a method for producing a silica-based glass preform for an optical fiber having a core / cladding structure will be described.
First, a powder in which silicon carbide (SiC) is coated on silicon dioxide (SiO ₂ ) glass fine particles and a powder in which silicon carbide (SiC) is coated on germanium dioxide (GeO ₂ ) are prepared (steps S10 and S11). . The powder prepared in step S11 is for adjusting the refractive index of the glass constituting the core of the optical fiber, and a substance other than germanium dioxide may be used.

In step S10, SiC powder made only of silicon carbide or silicon oxycarbide (SiO _X C _Y ) powder may be used instead of the powder obtained by coating silicon carbide on silica.
The powder obtained by coating silicon dioxide on silicon dioxide can be produced by, for example, a plasma CVD method in which SiO ₂ fine particles, SiCl ₄ gas, and CH ₄ gas are introduced into a plasma jet.
The SiC powder can be produced, for example, by a plasma CVD method in which a SiCl ₄ gas and a CH ₄ gas are introduced into a plasma jet. SiH ₄ may be used instead of SiCl ₄ .
Silicon oxycarbide (SiO _{X CY} ) powder is, for example, “Porous silicon oxycarbide ceramics by foaming a polymer liquid and compression molding (Journal of the Ceramic Society of Japan 111 [11] 863- 864 (2003)) ”can be obtained by processing into a powder. It can also be produced by a plasma CVD method.

The powder prepared by coating silicon carbide on germanium dioxide prepared in step S11 can be manufactured by, for example, a plasma CVD method in which fine particles of GeO ₂ , SiCl ₄ gas, and CH ₄ gas are introduced into a plasma jet. .

  Next, a solvent is added to and mixed with the powder prepared in Step S10 to produce a clay-like carbide for cladding (Step S12). As the solvent used here, pure water from which alkali ions have been removed can be suitably used. Alcohol may also be used.

  On the other hand, the powder prepared in step S11 is appropriately blended with the powder prepared in step S10 so as to have a desired composition for making glass for the core (step S13). And this is mixed with solvents, such as a pure water, similarly to step S12, and the clay-like carbide | carbonized_material for cores is made (step S14).

  Then, in order to obtain a cross-sectional refractive index distribution to be an optical fiber, the cladding clay-like carbide made in step S12 and the core-like clay-like carbide made in step S14 are respectively shaped and combined integrally. (Step S15). Since the clay-like carbide can be shaped freely, a desired shape can be obtained with high accuracy. The shaping of the clay-like carbide can be performed easily and with high accuracy by performing extrusion processing, as in the case of molding plastics, or by performing press processing in a mold. In the present embodiment, the optical fiber preform may be shaped by extruding it into a columnar shape or putting it in a cylindrical mold.

  The clay-like carbide shaped in step S15 is naturally dried in a clean atmosphere such as in a clean room (step S16). Thereby, silicon carbide existing on the surface of the powder is bonded to each other, and a porous carbide having appropriate pores corresponding to the particle diameter of the powder is formed. That is, the shape of the clay-like carbide is determined stably. In this porous carbide, the powders are strongly bonded to each other as compared with the dry gel of silica obtained by the conventional liquid phase synthesis method due to bonding between silicon carbides, and damage such as cracks is hardly generated.

  The porous carbide obtained by drying is taken out of the mold and placed in a heating furnace. When heated to a temperature of, for example, about 500 ° C. to 1000 ° C. in an oxygen atmosphere, silicon carbide is oxidized, and carbon is converted into carbon dioxide and vaporized. A porous glass body made of germanium is formed (step S17). Since this porous glass body forms bonds between glass particles in a heated high-temperature environment, the bonding force is relatively strong.

  Then, in order to dehydrate the porous glass body and remove impurities, the porous glass body is heated in a mixed gas atmosphere of helium and chlorine (step S18). Thereby, OH groups and impurities contained in the porous glass body are removed.

  Further, the porous glass body is heated and sintered at a temperature of about 1400 ° C. to 1700 ° C., for example, in a helium gas atmosphere or a vacuum to make it transparent (step S19). As a result, a solidified transparent silica-based glass base material for optical fibers is obtained. Note that the chlorine remaining in the pores of the porous glass body in step S17 escapes during this sintering.

  As described above, according to the first embodiment of the method for producing a silica-based glass body of the present invention, by making a clay-like carbide by blending a plurality of types of powders, the desired glass portion as a core is desired. Can be obtained. In addition, a desired refractive index distribution as an optical fiber preform can be easily obtained by integrally combining clay-like carbides having desired compositions for the core and the cladding. Moreover, since the clay-like carbide can be shaped with high accuracy, the shape of the quartz glass body can be obtained accurately. Moreover, the porous carbide obtained by drying the clay-like carbide and the clay-like carbide is strongly bonded between the powders by silicon carbide existing on the surface of the powder. And since glass fine particles are combined in a high temperature environment to form a porous glass body, the strength of the porous glass body is also stronger than that of the conventional liquid phase synthesis method. Therefore, damage such as cracks is unlikely to occur, and the size can be increased easily.

(Second Embodiment)
FIG. 2 is a flowchart showing a second embodiment of a method for producing a silica-based glass body according to the present invention.
In the present embodiment, an example of a method for producing a quartz glass body used as a PDP (Plasma Display Panel) substrate will be described.
First, SiC powder consisting only of silicon carbide is prepared (step S20).
In step S20, instead of SiC powder, silica-coated silicon carbide powder or silicon oxycarbide powder may be used.

  Next, a solvent is added to and mixed with the powder prepared in step S20 to produce a clay-like carbide for cladding (step S21). The solvent used here is the same as in the first embodiment.

  Then, the clay-like carbide produced in step S21 is put into a flat mold so as to obtain a desired shape (step S22). Next, the shaped clay-like carbide is naturally dried in a clean atmosphere such as in a clean room (step S23). Thereby, silicon carbide existing on the surface of the powder is bonded to each other, and a porous carbide having appropriate pores corresponding to the particle diameter of the powder is formed.

  The porous carbide obtained by drying is taken out of the mold and placed in a heating furnace. When heated to a temperature of, for example, about 500 ° C. to 1000 ° C. in an oxygen atmosphere, the silicon carbide is oxidized, the carbon becomes carbon dioxide, vaporizes and escapes, and a porous glass body made of silicon dioxide by oxygen bonding. Is formed (step S24).

  Then, the porous glass body is heated to a temperature of, for example, about 1400 ° C. to 1700 ° C. to be sintered and transparentized (step S25). Thus, a solidified transparent quartz glass body for a PDP substrate is obtained.

  Also in the second embodiment, since the clay-like carbide can be shaped with high accuracy, the shape of the quartz glass body for the PDP substrate can be obtained accurately. In addition, the strength of the porous carbide or the porous glass body can be increased as compared with the conventional liquid phase synthesis method, and damage during the manufacturing process hardly occurs.

It is a flowchart which shows 1st Embodiment of the manufacturing method of the quartz type glass body which concerns on this invention. It is a flowchart which shows 2nd Embodiment of the manufacturing method of the quartz type glass body which concerns on this invention.

Claims (5)

Mixing powder with silicon carbide on the surface with a solvent to make clay-like carbide,
After shaping the clay-like carbide,
Heating the clay-like carbide in an atmosphere containing oxygen to oxidize the silicon carbide to form a porous glass body;
A method for producing a silica-based glass body, wherein the porous glass body is heated to be transparent to obtain a silica-based glass body.   The method for producing a quartz-based glass body according to claim 1, wherein a plurality of types of powders having silicon carbide on the surface are blended and mixed with the solvent to produce the clay-like carbide.   The method for producing a quartz-based glass body according to claim 1 or 2, wherein a plurality of types of clay-like carbides having different blending are integrally combined and shaped.   The method for producing a quartz-based glass body according to any one of claims 1 to 3, wherein the porous glass body is heated in an atmosphere containing chlorine and then made transparent.   The method for producing a quartz-based glass body according to any one of claims 1 to 4, wherein the clay-like carbide is dried before forming the porous glass body.

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