JP2002182068A - Quartz glass ferrule and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrule of an optical fiber connector which prevents the irregular reflection of light incident on the ferrule end surface. SOLUTION: At least part or the entire part of the ferrule is constituted of a quartz glass sintered compact. The density of the sintered compact is 95% or greater than the theoretical value, and the average pore diameter is equal to or smaller than 10 μm. The ferrule is obtained by steps in which one or more kinds of silicic powders having an average particle diameter of at least 10 μm or less are mixed, and a molded body of a green density of 50% or greater is prepared and sintered at >=1000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member used in the optical communication industry, and more particularly to a ferrule of an optical fiber connector for interconnecting optical fibers.

[0002]

2. Description of the Related Art When interconnecting optical fibers, optical fiber connectors are used. There is a ferrule as a member constituting the optical fiber connector. Conventionally, ceramics such as alumina and zirconia have been used as ferrule materials. These ceramics are materials having high hardness and high modulus of elasticity, and can satisfy the high precision and dimensional stability required for ferrules.

However, the ferrule made of alumina or zirconia ceramics is opaque because it is a polycrystalline material, and a part of the light incident on the end face around the fiber insertion hole of the ferrule (hereinafter referred to as the ferrule end face) is irregularly reflected, and the ferrule inside the ferrule is formed. There is a fatal drawback that the optical communication function is hindered by re-entering the optical fiber. The optical fiber is made of quartz glass, whereas the ferrule is a ceramic with high hardness and high elastic modulus,
In the step of polishing the end face of the ferrule at the time of connecting the optical fiber and the ferrule, there is a problem that it takes a long time to flatten the end face due to the difference in polishing characteristics between the two materials.

Further, the coefficient of linear thermal expansion of alumina ceramics is about 8 × 10 ⁻⁶ / ° C., and that of zirconia is about 10 × 10 ⁻⁶ / ° C.
10 ⁻⁶ / ° C., whereas that of quartz glass is 0.5
× 10 ⁻⁶ / ° C., an order of magnitude lower. This means that the dimensional deviation between the ferrule and the optical fiber may occur depending on the long-term use and use environment of the optical fiber connector, and optical communication may actually be hindered in a cold area or a high temperature area.

As means for solving this problem, Japanese Patent Application No. 8-67 is disclosed.
No. 749 and Japanese Patent Application No. 8-53545 describe a ferrule made of quartz glass and a manufacturing method thereof. These use a general manufacturing method of quartz glass in which quartz glass is once melted to give a ferrule form.

However, when quartz glass is melt-molded, the melting point of quartz is as high as 1700 ° C. or higher,
Further, since the viscosity of the quartz melt is much higher than that of other glasses, it is necessary to perform melt forming at an extremely high temperature of 2000 ° C. or more. In addition, it is very difficult to obtain dimensional accuracy that satisfies ultra-high precision such as ferrule in products such as ferrules by the melt molding method, and it is necessary to obtain dimensions by performing precision polishing after melt molding. . That is, the quartz glass ferrule formed by the melting method has a basic problem that the processing cost is high.

[0007]

It is ideal that a quartz glass ferrule is theoretically combined with a quartz glass optical fiber. However, there is a problem in terms of dimensional accuracy and cost, and the fact is that it has not been put to practical use yet. An object of the present invention is to provide a ferrule that can sufficiently cope with practical costs while using quartz glass as a ferrule material.

[0008]

Means for Solving the Problems As a result of intensive studies on the above-mentioned problems, the following solutions have been found. That is, a ferrule of an optical fiber connector, wherein at least a part or the whole of the ferrule is made of a quartz glass sintered body. The sintered density of the quartz glass sintered body is 95% of the theoretical value
The ferrule described in the above, wherein the average pore diameter is 10 μm or less. The ferrule according to claim 1, wherein the quartz glass sintered body has a bending strength value of 60 MPa or more. A step of producing a compact having a green density of 50% or more, comprising at least one powder having an average particle diameter of 10 μm or less, and a step of sintering the compact at 1000 ° C. or higher. Manufacturing method of the described ferrule. The powder contains at least 50 mass of amorphous silica.
% Or more.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ferrule of the present invention comprises a quartz glass sintered body. The greatest feature of the present invention lies in the quartz glass sintered body. The density of the quartz glass sintered body needs to be 95% or more when the theoretical density of the quartz glass is 100%. That is, when the sintered body density is less than 95%, in the case of the quartz glass sintered body, opacity becomes remarkable. The progress of the opacity of the sintered body lowers the light transmission performance at the ferrule end face. The cause of the opacity is due to insufficient density, that is, remaining pores. When light collides with the residual pores, diffuse reflection occurs, and a part is radiated again from the end face of the ferrule, and this is mixed into the optical fiber passing through the center hole of the ferrule, leading to a decrease in optical communication performance. When the density of the quartz glass sintered body is at least 95% of the theoretical density, it is possible to suppress irregular reflection of light due to the residual pores. Here, the theoretical density of the quartz glass sintered body is 2.20 Mg / m ³
It is.

At the same time, the size of the residual pores in the quartz glass sintered body is a very important factor from the viewpoint of the above-mentioned irregular reflection of light. That is, in the present invention, which is completely different from the molten glass forming method and the manufacturing method, it is very difficult to completely eliminate voids by sintering. In the ferrule made of the quartz glass sintered body of the present invention, the average pore diameter remaining in the sintered body needs to be 15 μm or less, preferably 10 μm or less. If the average pore diameter exceeds 15 μm, large scattering of light occurs due to the size effect of the pores themselves, and light incident from the ferrule end face is again irradiated from the end face. It is known that the strength of the sintered body greatly depends on the pore diameter. Particularly, in a product of an extremely small size such as a ferrule, pores are a major factor in the product strength. That is, if the average pore diameter exceeds 15 μm, the mechanical strength of the ferrule decreases, and the ferrule cannot be damaged during assembly of the optical fiber connector or cannot be used for a long time.
The present invention is to provide a high-precision quartz glass sintered body ferrule by an inexpensive sintering method, but in some cases, after sintering the formed body, heat and pressure treatment (hot isostatic pressing) ) Can substantially eliminate residual pores.

The average pore diameter of the ferrule made of the quartz glass sintered body specified in the present invention is determined by cutting an arbitrary point of the ferrule perpendicular to the longitudinal axis direction, obtaining a smooth surface by polishing, and then using a scanning electron microscope. The total number of pores and pore diameters are counted in. In addition, all pore diameters are regarded as circles, and pore diameter =
All pore diameters are calculated by the formula of (maximum diameter + minimum diameter) / 2, calculated by the formula of average pore diameter = (sum of all pore diameters) / number, and rounded to one decimal place. The average pore diameter of a ferrule made of a quartz glass sintered body can be measured by measuring three points on an arbitrary surface by this method and employing the average value.

The mechanical strength of the ferrule made of the quartz glass sintered body of the present invention is desirably as high as possible, but it is sufficient if the ferrule has sufficient strength to withstand practical use. That is, although it is difficult to measure the bending strength of the quartz glass ferrule of the present invention, it is difficult to measure the bending strength of the quartz glass ferrule using the same raw material and the same manufacturing process and a polished test piece. Regarded as strength. The test piece is J
The bending strength is measured according to the bending test method described in IS R1601. The bending strength of the ferrule made of the quartz glass sintered body of the present invention needs to be 60 MPa or more. If the flexural strength is less than this, the ferrule may be broken by some factor in the work for assembling into the optical fiber connector or in long-term use.

The ferrule made of the quartz glass sintered body of the present invention is manufactured by the following manufacturing method. First, the average particle size of the raw material powder is important. The average particle diameter of the raw material powder needs to be 10 μm or less on average. If it is larger than this, although the green density after powder compaction is high, the sintering characteristics are reduced due to the coarse grain effect, the sintering temperature is increased, and the production cost is increased. The average particle size of the raw material powder is 10 μm
If it is at most, a sintering temperature of about 1600 ° C. or less can be achieved, and a molding density of 50% or more of the theoretical density can be achieved by adjusting the molding conditions. Conversely, the average particle size is 1
Even if the thickness is 0 μm or less, the density of the compact is 50% of the theoretical density.
If it is less than 1, the sintering characteristics are reduced, the residual pore diameter is coarsened, and the number of pores is increased, so that the characteristics of the quartz glass ferrule, which is the object of the present invention, cannot be exhibited. The density of the green body referred to here is the ferrule shape or the volume of the test piece obtained by the same method as the molding process for obtaining the ferrule, and a measurement calculated assuming that the powder used has become vitrified after sintering. It is calculated from the weight of the material and the theoretical density of quartz glass.

As described above, the higher the density of the compact is, the more effective the reduction of residual pores is, but practically it is at least 50% or more, more preferably 60% or more. As a means for achieving this, a method of mixing two or more types of raw material powders having an average particle diameter of 10 μm or less and blending the particle sizes is effective in obtaining the quartz glass sintered body of the present invention. In this case, regardless of whether the raw material powder is in the form of a plate, a square shape, or a sphere, the powder is formed so that the green density of the above-mentioned powder compact becomes approximately 50% or more, preferably 60% or more of the theoretical value. Select

The powder used in the present invention includes amorphous silica (including quartz glass), powder having a precursor structure of amorphous silica, and powder having an organic structure as a part of the powder. It falls into the category of powder. The powder for molding the quartz glass sintered body of the present invention preferably contains at least 50 mass% or more of amorphous silica powder. In addition, liquids, sols, etc.
A gel substance may be added to the compact to improve the density of the compact or the strength of the compact. In this case, the green density in the case of a molded article containing a substance that changes into quartz glass or siliceous substance by a reaction such as thermal decomposition is calculated by converting them into the theoretical density of quartz glass.

A general manufacturing method can be applied to the powder molding method, and specific examples include extrusion molding, injection molding, press molding, in-mold casting molding, and self-curing casting molding. In particular, when the inner diameter of the ferrule is one hole, extrusion and injection molding are useful, and for a multi-hole ferrule, a fill-in type or a self-hardening type casting is useful. Regardless of the molding method, the density of the molded body is required to be approximately 50% or more, preferably 60% or more in order to realize the present invention.

In the step of sintering the compact, a binder,
Alternatively, when there is moisture attached, hydroxyl groups on the surface of the powder, etc., it is important to incinerate and remove by heating before sintering (degreasing step). If this is neglected, the density, average pore diameter and bending strength of the sintered body, which are essential requirements of the present invention, may not be satisfied. Therefore, the processing conditions are slightly different depending on the molding method. In order to obtain a ferrule made of a high-purity quartz glass sintered body, an acid treatment of a molded body or a degreased body is appropriately used.

In the sintering step, sintering under reduced pressure, so-called vacuum sintering, is preferable in order to reduce the number of residual pores and the pore diameter of the sintered body. The degree of pressure reduction needs to be at least 10 ⁻² Pa or more. The sintering temperature varies depending on the sinterability of the powder used and the density of the compact, but is generally 1100 ° C. or higher, preferably 1
The upper limit is 300 ° C or higher and the upper limit is 1700 ° C or lower. The retention time is a factor that affects the number of residual pores and the pore diameter. When powder having excellent sintering characteristics is used, the retention time can be 0 minute, but generally 0.5 to 1 hour. It is a guide. The dimensional accuracy of the ferrule formed of the obtained quartz glass sintered body is high within a range of about ± 2% or less.

The sintered body is subjected to the same precision polishing finish as the usual alumina and zirconia ferrules, but the working time can be shortened because quartz glass has a lower hardness than both. Further, in the case of the powder sintering method, since the sintering is performed at a melting temperature of quartz glass or less, the dimensional deformation rate is extremely high at 5% or less. This is effective for shortening the polishing time and cost.

[0020]

EXAMPLES (Example 1) Amorphous silica having an average particle diameter of 1 μm 100 mass% distilled water 20 mass% (outside of powder) Dispersant (amine) 0.8 mass% Binder (PVA) 0.5 mass % After wet-mixing the amorphous silica powder, distilled water, dispersant, and binder in a ball mill for 16 hours, take out the slip from the ball mill, put the slip in a reduced pressure container, and stir the coarse bubbles in the slip by 30%. Degassed for a minute to make a slip for casting. Next, a slip was cast into a porous resin mold having a metal pin corresponding to the inner diameter of the ferrule, and inlay molding was performed. After completion of the inking, the core pin was removed, and the ferrule molded body was taken out of the mold. 140 μm at the center of the compact
Formed through holes. This was dried at room temperature for 5 hours, heated to 600 ° C. in an electric furnace at a rate of 2 ° C./min, kept for 1 hour, and cooled in a furnace to obtain a degreased body. Next, the degreased body was heated to 1400 ° C. under a reduced pressure at a rate of temperature increase of 5 ° C./min, held for 30 minutes, cooled in a furnace, and taken out of the sintered body. This was polished and used as a ferrule to measure the sintered body density and the average pore diameter, and then an optical transmission evaluation test was performed. Table 1 shows the results of this operation. Each test data of Nos. 1 to 5 represents an average value of 10 test pieces.

[0021]

[Table 1]

In Table 1, when the green density of the ferrule compact was 43% (No. 1), the density of the ferrule sintered body obtained by sintering was only 90%, and the average pore diameter was 22 μm. . In an optical transmission test using this ferrule, irregular reflection of light due to residual pores of the ferrule was observed. Similarly, in the ferrule of the number 2, the number 1
Although the irregular reflection characteristics were reduced, the bending strength value of the test piece manufactured by the same method was 55 MPa, but one out of ten pieces was damaged at the time of assembling the optical fiber connector, and did not reach practical characteristics. Green density 50 of molded product of No. 3
%, The sintered body density was 95%, and the average pore diameter was 10 μm, the diffuse reflection characteristics were remarkably reduced as compared with Nos. 1 and 2.

The bending strength of the test piece obtained by the same manufacturing process as that of the ferrule was 60 MPa, and no problem such as breakage occurred in all of the ten test pieces subjected to the assembling process.
When the green density of the molded body was 57%, the sintered body density was 97%, and the average pore diameter was 8 μm (No. 4), diffuse reflection at the ferrule end surface remained slightly, but it was found that it was not a problem in practical use. Furthermore, the cases of Nos. 5 and 6 were higher than those of Nos. 1 to 3, and diffused reflection at the obtained ferrule end face was hardly detected. At this time, the residual average pore diameter was 10 μm or less, and the density of the molded body obtained from this was approximately 60% or more, and the density of the sintered body was 99% or more. Numbers 5 and 6
The bending strength values of the test pieces were 65 and 70 MPa, respectively.

Reference numeral 7 denotes a quartz glass ferrule manufactured by a melt molding method, and reference numeral 9 denotes a zirconia ferrule. In the case of a zirconia sintered body, the green density, the sintered body density, and the average pore diameter fall within the category of the quartz glass sintered body of the present invention, but irregular reflection occurs because zirconia is a polycrystalline and opaque. ing. As described above, the ferrule made of the quartz glass sintered body by the powder sintering method of Nos. 3 to 6 which is within the scope of the present invention has a light at the end face of the ferrule compared with the conventional ferrule made of the alumina and zirconia sintered bodies. It is clear that the diffuse reflection has been greatly reduced.

(Example 2) A curable resin, a dispersion medium, and a dispersant were added to a mixed powder obtained by adding 40 mass% of the same powder having an average particle diameter of 0.5 µm to the same powder as in Example 1, and the mixture was subjected to a ball mill for 12 hours. The primary slip was made by wet mixing. Add a curing agent for the curable resin to this, and about 15 minutes
After performing the vacuum degassing operation, a slip was poured into a mold having a core pin for the inner diameter of the ferrule, and self-cured at about 50 ° C. When the slip was cured, the cured product was released from the mold and dried at room temperature for 5 hours and at 80 ° C. for 5 hours.
A 5% compact was obtained. This was heated in an electric furnace at a heating rate of 2 ° C./min, kept at 550 ° C. for 1 hour, and then cooled in the furnace. Next, the degreased body was heated at 1400 ° C. under reduced pressure (10 ⁻³ Pa) for 30 minutes.
After holding for one minute, the furnace was cooled. The density of the obtained ferrule sintered body was 99%, the remaining average pore diameter was 5 μm, and irregular reflection of light on the end face of the ferrule was not detected.

[0026]

As described above, the ferrule made of the quartz glass sintered body according to the present invention has the following industrial advantages. 1) Irregular reflection of light at the end face of the ferrule can be reduced. 2) Dimensional accuracy of the ferrule is high. 3) Polishing time of the ferrule can be reduced. 4) Ferrules having various shapes can be manufactured by powder sintering.

Claims (5)

[Claims] 1. A ferrule for an optical fiber connector, wherein at least a part or the whole of the ferrule is made of a quartz glass sintered body. 2. The ferrule according to claim 1, wherein a sintered density of the quartz glass sintered body is 95% or more of a theoretical value and an average pore diameter is 10 μm or less. 3. The quartz glass sintered body has a bending strength of 6
The ferrule according to claim 1, wherein the ferrule is 0 MPa or more. 4. A method for producing a compact having a green density of 50% or more comprising at least one kind of powder having an average particle diameter of 10 μm or less, and sintering the compact at 1000 ° C. or more. The method for producing a ferrule according to claim 1, wherein the ferrule is provided. 5. The method of claim 1, wherein the powder comprises at least 5 amorphous silica.
The method according to claim 4, wherein the content is 0 mass% or more.