JP2001240468A - Zirconia sintered body for optical connector and manufacturing method thereof - Google Patents

Abstract

(57) [Problem] To provide a zirconia sintered body for an optical connector which is excellent in polishing properties of a ferrule tip surface and excellent in durability in a high temperature atmosphere where water is present. SOLUTION: ZrO ₂ is a main component, and Y ₂ O ₃ is 5.5 to 5.5%.
6.5% by weight, 0.1 to 0.5% by weight of Al ₂ O ₃ , 0.001 to 0.1% by weight of SiO ₂ , and Zr
The average crystal grain size of O ₂ was set to 0.28 to 0.4 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zirconia sintered body suitable for optical connector members such as ferrules and sleeves.

[0002]

2. Description of the Related Art In recent years, with an increase in the amount of information in communication, optical communication using optical fibers has been used. In this optical communication, an optical connector is used for connection between optical fibers or connection between an optical fiber and various optical elements.

For example, in the case of an optical connector for connecting optical fibers, an end of the optical fiber is held in a through hole formed in a ferrule, a pair of ferrules are inserted from both ends of a sleeve, and a convex spherical shape is formed inside. It has a structure in which the end faces machined to make contact with each other.

Various materials such as ceramics, metals, plastics and glass have been produced as materials for the ferrules and sleeves, but most are now made of ceramics. The reason is that ceramics have high processing accuracy and the tolerance of inner diameter and outer diameter can be as high as 1 μm or less, and ceramics have low friction coefficient, so they have excellent optical fiber insertion properties, high rigidity and high thermal expansion. The coefficient is low, so it is stable against external stress and temperature changes.
This is because they have excellent corrosion resistance.

Further, in recent years, most ceramics have been replaced with zirconia from alumina. Since this zirconia sintered body has a Young's modulus as low as about half that of alumina, when the tip surfaces of two ferrules come into contact with each other, it is possible to increase the adhesion with a small stress and to have high strength and toughness. Therefore, the reliability can be improved (see Japanese Patent Publication No. 8-30775).

The zirconia sintered body for an optical connector includes ZrO ₂ as a main component and a stabilizer of 2.5 to 2.5%.
About 3.5 mol% (about 4.5 to 6.2 wt%) of Y ₂ O ₃
Is formed and fired to obtain an average grain size of 0.4
A zirconia sintered body mainly composed of a tetragonal crystal phase having a thickness of about 0.6 μm has been proposed (JP-A-6-337327).
Reference).

A raw material containing ZrO ₂ as a main component and Y ₂ O ₃ as a stabilizer and 0.2 to 0.3% by weight of Al ₂ O ₃ added to the raw material is molded and fired. A zirconia for an optical connector mainly composed of the above crystal phase has been proposed (see JP-A-10-260336).

Further, in a zirconia sintered body for an optical connector containing ZrO ₂ as a main component and Y ₂ O ₃ as a stabilizer, the concentration of Y ₂ O ₃ in the tetragonal phase is 3.0 mol% (about 10 mol%). 5.4% by weight or more of zirconia has been proposed (Journal of the Ceramic Society of Japan, 19).
(See the September 1999 issue).

[0009]

However, after the optical fiber is bonded and fixed to the ferrule formed of the zirconia sintered body of the prior art, a great amount of polishing time is required when polishing the tip surface of the ferrule. As fiber connectors have been required to be reduced in price, there has been a major problem in that the cost is greatly impeded.

Furthermore, when exposed to a high-temperature atmosphere in which water is present, there is a problem that a surface roughening phenomenon that causes irregularities on the polished surface is likely to occur.

[0011] Further, depending on the intended use, the ferrule may be used for a long time in a bad environment. Therefore, as an accelerated test, a pair of ferrules are inserted from both ends of a sleeve, and the tip surface is processed into a convex spherical shape inside. A test may be performed in which the optical connectors in a state where they are in contact with each other are exposed to hot water at 85 ° C. At this time, the optical connector member such as a ferrule made of a zirconia sintered body has a flattening phenomenon in which the connected surface is deformed and the radius of curvature of the convex spherical surface at the end surface of the ferrule becomes large. There has been a problem that a defect or excessive connection loss occurs.

[0012]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and a zirconia sintered body for an optical connector has ZrO ₂ as a main component and Y ₂ O ₃ of 5.5. ~ 6.5 wt% (about 3.0-3.7 mol%), A
l ₂ O ₃ 0.1 to 0.5 wt%, and the SiO ₂ 0.0
It is characterized by containing 0.1 to 0.1% by weight and having an average crystal grain size of ZrO ₂ of 0.28 to 0.4 μm.

Further, in a zirconia sintered body for an optical connector, starting materials such as ZrO ₂ and Y ₂ O ₃ are purified to obtain Y ₂ O ₃
Was mixed so as to be 5.5 to 6.5% by weight, 0.1 to 0.5% by weight of Al ₂ O ₃ , and 0.001 to 0.1% by weight of SiO ₂ , and the obtained raw material was mixed. After molding into a predetermined shape,
It is characterized by the step of firing at 1350 to 1550 ° C.

That is, as a result of various experiments performed by the present inventors, 5.5 to 6.5% by weight of Y ₂ O ₃ was
l ₂ O ₃ 0.1 to 0.5 wt%, and the SiO ₂ 0.0
In a zirconia sintered body containing 0.01 to 0.1% by weight, by setting the average crystal grain size to 0.28 to 0.4 μm, the polishing property of the tip surface of the ferrule is improved and a high-temperature atmosphere in which moisture is present. It was found that the durability in the interior was improved.

[0015]

Embodiments of the present invention will be described below.

As shown in FIG. 1A, a ferrule 1 for an optical connector has a through hole 1 for inserting an optical fiber in the center.
The rear end of the through hole 1a is provided with a conical portion 1b for facilitating insertion of an optical fiber, and the outer periphery of the distal end is provided with a guide portion 1c serving as a guide surface when the sleeve is inserted.

As shown in FIG. 1 (b), the sleeve 2 is a cylindrical body, and has a slit 2a in its axial direction, thereby holding the ferrule 1 elastically. May not be required. Further, about three convex portions may be formed on the inner peripheral surface, and the ferrule 1 may be supported by these convex portions.

The ferrule 1 is formed of a zirconia sintered body which will be described in detail later. As shown in FIG. 2, the rear side thereof is joined to a metal support 3 and an optical fiber 4 is inserted into the through hole 1a. After joining, the tip surface 1d has a radius of curvature of 1
Polish to a convex spherical shape of about 0 to 25 mm. The optical fibers 4 can be connected to each other by inserting such a pair of ferrules 1 from both ends of the sleeve 2 and pressing them with a spring or the like to bring the tip surfaces 1d into contact with each other.

The zirconia sintered body forming the ferrule 1 and the sleeve 2 contains ZrO ₂ as a main component and contains Y ₂ O _{3 in an amount} of 5%.
5 to 6.5% by weight (about 3.0 to 3.7 mol%), Al ₂
0.1 to 0.5% by weight of O ₃ and 0.001 of SiO ₂
And the average crystal grain size of ZrO ₂ is set to 0.28 to 0.4 μm. By doing so, the polishing property of the tip end face 1d of the ferrule 1 is improved, and the water content is improved. Can be prevented from deteriorating in a high temperature atmosphere where

The zirconia sintered body of the present invention has a tetragonal phase as a main component, so that when subjected to stress, the tetragonal crystal is transformed into a monoclinic crystal and expands in volume to prevent the crack from developing. The strength and toughness of the sintered body can be improved by the mechanism of the stress-induced transformation of preventing. Further, the zirconia sintered body of the present invention does not contain a monoclinic phase,
By containing a cubic crystal that is stable to phase transformation in addition to the main tetragonal phase, the durability in a high-temperature atmosphere in which moisture is present is substantially improved without substantially impairing the mechanism of the stress-induced transformation. Can be.

Where Y_TwoO_ThreeContent of 5.5% by weight or more
Is less than 5.5% by weight of Y in the tetragonal phase._TwoO_Three
High temperature atmosphere with moisture due to reduced amount
Degradation of the ferrule tip 1d
Necessary characteristics cannot be obtained, such as increasing the radius of curvature of the convex spherical surface.
This is because On the other hand, the reason why the content is set to 6.5% by weight or less is that Y _Two
O_ThreeIncreases the thermal stability, but the strength, toughness, etc.
This is because the decrease becomes remarkable. This is Y_TwoO_ThreeIncrease
In the cubic phase ratio in zirconia is too large,
The strength and toughness of zirconia by stress-induced transformation of zirconia
This is probably because the proportion of the tetragonal phase that appears is reduced.
You.

Further, Al_TwoO_ThreeContent of 0.1 to 0.5
The weight percentage is Al_TwoO_ThreeActs as a sintering aid
Therefore, if it is less than 0.1% by weight, it is difficult to fire at a low temperature.
If the content exceeds 0.5% by weight, over-firing occurs.
You. In addition, Al_TwoO_ThreeIs the above ZrO _TwoIncluded in the starting materials such as
Although it is rare, it can be added to the final
What is necessary is just to make it fall within the said range.

Next, the content of SiO ₂ is set to 0.001 to
The reason for setting the content to 0.1% by weight is that if the content exceeds 0.1% by weight, the composition is liable to be deteriorated in a high-temperature atmosphere where moisture is present. This makes the Y ₂ O ₃ around the SiO ₂ particles tend to segregate as a solid solution, Y ₂ O ₃ in the zirconia unevenly distributed, in particular from the water portion of a small content of Y ₂ O ₃ This is because deterioration easily occurs in a high-temperature atmosphere. or,
The reason why the content is set to 0.001% by weight or more is that it is difficult to make the content less than 0.001% by weight in the current production method. SiO ₂ is usually present as an impurity in a starting material powder such as ZrO ₂ or Y ₂ O ₃ as 0.1% by weight or more. These impurities may be removed in advance.

In the zirconia sintered body, the content of each of TiO ₂ , CaO, Na ₂ O, and Fe ₂ O ₃ is preferably set to 0.1% by weight or less. This is because these impurities degrade the durability in a high-temperature atmosphere where moisture exists.

Further, in the zirconia sintered body of the present invention, the average crystal grain size is set to 0.28 to 0.4 μm.
If the thickness exceeds 0.4 μm, the strength of the zirconia sintered body is reduced, and deterioration in high-temperature water is liable to occur. Also, if it is less than 0.28 μm, deterioration in high-temperature water is unlikely to occur, but after bonding and fixing the optical fiber to the ferrule, if the tip surface is polished, the average crystal grain size is too small and the crystal is too dense, This is because the polishing property is deteriorated, and the polishing time is greatly increased, and the cost is greatly hindered in the case where the price of the optical fiber connector is required to be reduced. For the above reasons, the average crystal grain size was set to 0.28 to 0.4 μm.

As described above, if importance is placed on durability in a high-temperature atmosphere in which water is present, a finer and smaller average crystal grain size is required, but the abrasion of the tip surface of the ferrule deteriorates. Conversely, if the abrasiveness is emphasized, a larger average crystal grain size is required, but the durability in a high-temperature atmosphere in which water exists is deteriorated.

The present invention relates to a zirconia sintered body for an optical connector.
As a result, the durability and
As a condition for satisfying both the polishing properties of the ferrule tip surface, Z
rO _Two, And Y_TwoO_Three5.5 to 6.5% by weight
(About 3.0 to 3.7 mol%), Al_TwoO_ThreeFrom 0.1 to 0.
5% by weight and SiO_Two0.001 to 0.1% by weight
And ZrO_TwoAverage grain size of 0.28 to 0.4
They found the range of each parameter of μm.

Next, a method of manufacturing the ferrule 1 and the sleeve 2 will be described.

First, ZrO _{2 as} a starting material contains Al ₂ O ₃ , SiO ₂ , TiO ₂ , or CaO, Na as impurities.
_Although it contains ₂ O, Fe ₂ O _3, etc., this raw material is treated with a chemical such as acid or alkali, or purified by a method such as gravity separation utilizing a specific gravity difference to increase the purity. And
Y a ₂ O ₃ added to and mixed 5.5-6.5% by weight ZrO _2,
The reaction and solid solution are performed by a method such as neutralization coprecipitation or hydrolysis.

Next, the obtained raw material is formed into a predetermined shape by extrusion molding, press molding, injection molding, or the like, and if necessary, cut and the like, and then fired in the air atmosphere.

At this time, in order to obtain a small average crystal grain size of 0.28 to 0.4 μm or less, 1350 to 1550
It must be fired at a low temperature of ℃ and be a dense sintered body, which can be achieved by reducing the primary particle diameter of the raw material and increasing the specific surface area. The ferrule 1 and the sleeve 2 can be obtained by further polishing and grinding this sintered body.

Here, the firing temperature and the average crystal grain size are in a proportional relationship, and the higher the firing temperature, the larger the average crystal grain size. The zirconia sintered body of the present invention has an average crystal grain size of about 0.28 μm,
About 0.34 µm at 450 ° C, about 0.4 µm at 1550 ° C
Becomes

Although FIG. 2 shows an optical connector for connecting the optical fibers 4 to each other, the ferrule 1 and the sleeve 2 are used in an optical module for connecting an optical element such as a laser diode or a photodiode to the optical fiber. It can also be used.

The zirconia sintered body for an optical connector according to the present invention can be applied to various members used for connecting the optical fibers described above or between the optical fibers and various optical elements. It is not limited to the sleeve 2. For example, the present invention can be applied to a splice used for completely connecting optical fibers, a dummy ferrule used for an optical module, and the like.

[0035]

Embodiments of the present invention will be described below.

Zr containing about 0.3% by weight of Al ₂ O ₃ and about 0.07% by weight of SiO ₂ as starting materials
Zirconia raw materials having various compositions were prepared by changing the amount of Y ₂ O ₃ added to O ₂ .

Each of the final products has an outer diameter of 2.5 m.
m, and extruded into a ferrule shape shown in FIG.
It was fired at 00 ° C., and the average crystal grain size of the zirconia sintered body was measured.

A ferrule 1 was prepared for each composition, an optical fiber 4 was bonded, and the tip surface 1d was polished using a 1 μm diamond polishing sheet so that the radius of curvature of the convex spherical surface was about 15 mm on average. After measuring the polishing time until the mirror finished to a mirror surface, it was left in hot water at 85 ° C. for 14 days with the pair of ferrules 1 connected inside the sleeve 2 as shown in FIG. Then, the amount of change (increase) in the radius of curvature of the tip surface 1d of the ferrule 1 before and after the test was examined by a shape measuring instrument. Table 1 shows the change in the radius of curvature and the polishing time under each condition.

From these results, those having a Y ₂ O ₃ content of less than 5.5% by weight (Nos. 1 to 5) and those having a Y ₂ O ₃ content of more than 6.5% by weight (Nos. 21 to 25) have a variation in the radius of curvature. Is about 10 mm, and the average crystal grain size exceeds 0.4 μm even when the Y ₂ O ₃ content is in the range of 5.5 to 6.5% by weight (Nos. 10, 15, 20). ) Also has a slightly larger radius of curvature variation, whereas the Y ₂ O ₃ content is 5.5 to 5.5.
In the range of 6.5% by weight and an average grain size of 0.4
μm or less (Nos. 6 to 9, 11 to 14, 16 to 1)
In 9), the rate of change in the radius of curvature is 5 mm or less, and it can be seen that there is little deterioration in a high-temperature atmosphere where moisture exists.

The polishing time was such that the average crystal grain size was 0.28 μm.
m (No. 1, 6, 11, 16, 21) 40
Seconds or more, while those with 0.28 μm or more (Nos. 2 to 5, 7 to 10, 12 to 15, 17 to 20,
22 to 25) indicate that the polishing time is shorter than 30 seconds.

As described above, when the change in the radius of curvature is small and the polishing time is short, the Y ₂ O ₃ content is 5.5 to 6.5.
Wt% and the average grain size is 0.28
(No. 7-9, 12-14, 1)
7 to 19).

[0042]

[Table 1]

[0043]

As described above, according to the present invention, ZrO ₂
Was the main component, Y ₂ O ₃ and 5.5 to 6.5 wt%, Al ₂
0.1 to 0.5% by weight of O ₃ and 0.001 of SiO ₂
0.1% by weight and an average crystal grain size of ZrO ₂ of 0.28 to 0.4 μm makes the ferrule tip surface excellent in polishing properties and durable in a high temperature atmosphere where moisture is present. A zirconia sintered body for an optical connector having excellent properties can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing a member for an optical connector using a zirconia sintered body of the present invention.

FIG. 2 is a sectional view showing an optical connector using an optical connector member made of a zirconia sintered body of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ferrule 1a Through-hole 1b Conical part 1c Guide part 1d Tip surface 2 Sleeve 2a Slit 3 Support 4 Optical fiber

Claims (2)

[Claims] 1. ZrO ₂ as a main component and Y ₂ O _{3 in a range} of 5.5 to 5.5.
6.5% by weight, 0.1 to 0.5% by weight of Al ₂ O ₃ , 0.001 to 0.1% by weight of SiO ₂ , and Zr
A zirconia sintered body for an optical connector, characterized in that the average crystal grain size of O ₂ is 0.28 to 0.4 μm. 2. A purified starting materials, such as ZrO _2, Y ₂ O _3, a Y ₂ O ₃ 5.5 to 6.5 wt%, the Al ₂ O ₃ 0.1
0.5 wt%, and SiO ₂ were mixed so that 0.001 to 0.1 wt%, after forming the resulting material into a predetermined shape, the light comprising a step of firing at 1,350 to 1,550 ° C. A method for producing a zirconia sintered body for a connector.