JP2003238253A - Method of producing ceramic sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of a warp in a tubular ceramic sintered compact. <P>SOLUTION: A raw material to be molded, obtained by mixing a starting material with a sintering aid or the like and adding a binder to the resulting mixture, is molded into a tubular form, and then the formed body having the tubular form is sintered after being dried until the content of water becomes ≤1.5 wt.% in a drying process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a tubular or rod-shaped ceramic sintered body which requires precise dimensional accuracy.

[0002]

2. Description of the Related Art In recent years, ceramics sintered bodies have high strength,
Utilizing properties such as wear resistance, high rigidity, low thermal expansion, heat resistance, and high hardness, it is used as a machine material for machine tool parts, measuring devices, engines, blowers, bearings, tools, lubricants, or optical communication. It has been used for parts and the like. In addition, it has been attempted to be applied to a chemical device utilizing chemical stability and a device utilizing heat insulating property or heat transfer property.

Among these, ceramics sintered bodies have come to be used for important element parts of precision instruments such as precision instruments and precision measuring instruments used in a normal temperature environment. In the background, ultra-precision electronic parts represented by semiconductors,
This is because miniaturization has progressed rapidly, and processing machines and measuring instruments for manufacturing them are required to have accuracy of submicron or less. Conventionally, stainless steel, aluminum-based alloys, rust-prevented iron-based materials and stone materials have been used as structural members for these precision instruments.

However, in the field of ultra-precision and ultra-fine processing, where the processing accuracy is required to be less than micron, the required specifications are so strict that the deformation due to the self-weight of the structure and the minute deformation due to temperature and humidity changes are strict and more efficient. Therefore, there is a strong demand for faster and lighter machines. In order to meet such high performance quality requirements, various problems have been pointed out in conventional materials, and ceramics sintered bodies have begun to be used.

Further, in recent years, with the increase in the amount of information in communication, optical communication using an optical fiber is used. In this optical communication, an optical connector is used for connecting optical fibers to each other or connecting optical fibers to various optical elements.

For example, in the case of a connector for connecting optical fibers to each other, an end portion of the optical fiber 3 is held in a through hole 1a formed in the ferrule 1 shown in FIGS. The structure is such that the tip surfaces 1d, which are inserted from both ends and processed into a convex spherical shape inside, are brought into contact with each other.

Various materials such as ceramics sintered bodies, metals, plastics, and glasses have been experimentally produced as materials for the ferrule 1, but most of them are currently made of ceramics. The reason for this is that ceramics can be processed with high accuracy, so the tolerance of the inner and outer diameters can be as high as 1 μm or less, and because ceramics sintered bodies have a low coefficient of friction, they can be inserted into optical fibers. This is because it has excellent properties, has high rigidity, and has a low coefficient of thermal expansion, so that it is stable against external stress and temperature changes, and has excellent corrosion resistance.

Further, in recent years, as the ceramic sintered body of the ferrule 1, most of alumina has been replaced by zirconia. Since this zirconia sintered body has a Young's modulus as low as about half that of alumina, it is possible to enhance the adhesion with a small stress when the tip faces of two ferrules are brought into contact with each other, and have high strength and toughness. Therefore, the reliability can be improved (see Japanese Patent Publication No. 8-30775).

As shown in FIG. 1, the above-mentioned method for producing a ceramics sintered body is performed by removing impurities from a starting material, mixing a sintering aid and the like, and adding a binder to the raw material before molding to obtain a ceramics sintered body. A molding die was selected so that a specific part of the body had a desired size, molding, drying and firing were performed, and a necessary portion was subjected to mechanical finishing such as grinding and polishing to commercialize it. The general moisture content of the ceramic molded body after drying is about 2 to 18% (JP-A-200)
0-264716).

[0010]

However, in the above-mentioned conventional manufacturing method, a warp occurs in the drying and firing stages in a molded body having a large slenderness ratio, which is a ratio of the length to the outer shape, such as a tubular shape or a rod shape. However, there has been a problem that a specific portion of the molded and fired ceramics sintered body does not fall within a desired dimensional tolerance of micron or less including cylindricity.

If the ceramic sintered body has a cutting allowance with respect to a desired size, it must be finished to a desired size by polishing or the like, which requires a great amount of work time and increases the manufacturing cost. It was a factor.

Further, the ceramic sintered body cannot be used unless it has a cutting allowance for a desired size, and therefore it must be discarded. The average shrinkage ratio was shifted to the side having a large cutting allowance so that the allowance remains.

For this reason, the machining allowance is further increased, and it is necessary to finish the product to a desired size by grinding or polishing, which requires a much longer working time and is a factor of increasing the manufacturing cost.

[0014]

In view of the above-mentioned problems, the present invention forms a pre-forming raw material obtained by mixing a starting material with a sintering aid or the like and adding a binder into a tubular or rod-like shape having an elongated ratio of 10 or more. In the drying step, drying is performed until the water content becomes 1.5% by weight or less, and then firing is performed.

Further, the above-mentioned ceramics sintered body is used for a connector member for optical communication.

That is, according to the present invention, it is possible to substantially eliminate the warpage of the ceramic sintered body by controlling the residual water content when the ceramic molded body is dried.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a flow chart showing a method for manufacturing a tubular ceramics sintered body of the present invention.

In the above ceramic sintered body, the raw material before forming is formed into a tubular or rod shape having a slenderness ratio of 10 or more, which is the ratio of the length to the outer shape, and the water content is reduced to 1.5% by weight or less in the drying step. After drying until it becomes calcined,
After that, necessary parts are subjected to mechanical finishing such as grinding or polishing to commercialize.

At this time, since the deformation of the sled or the like is greatly affected by the water content after drying, the water content after drying is 1.
If it exceeds 5% by weight, the deformation such as sled becomes large,
When dried until the water content is less than 1.5% by weight,
Deformation such as warpage after firing is significantly reduced and stable. Also,
Even if the slenderness ratio is less than 10, the water content after drying is 1.
If it is 5% by weight or less, it is effective against deformation such as warpage, but if the slenderness ratio is 10 or more, preferably 30 or more, the difference becomes remarkable.

The molding step and the drying step will be described with reference to FIGS. 2 (a) and 2 (b).

First, regarding the molding step, as an example, the concept of extrusion molding is shown in FIG. 2 (a). The raw material 15 before molding is charged into the charging port 14 of the molding machine 13 and mixed by the screw 16 over several stages. Then, it is passed through the mold 17 to obtain a tubular ceramics molded body 11 having an elongated ratio of 10 or more.

Next, in the drying step, as shown in FIG. 2 (b), the ceramic molded body 11 aligned in the drying jig 12 is put into the drying furnace 20, and the moisture content is 1.5% by weight. Dry until:

The present invention relates to, among the ceramics sintered bodies, a tubular ceramics sintered body having a long overall length with respect to the outer dimensions and a large so-called slenderness ratio.

A specific example of the tubular ceramics sintered body of the present invention will be described using a ferrule for an optical connector.

As shown in FIG. 5, the ferrule 1 for an optical connector has a through hole 1a for inserting an optical fiber in the center, and facilitates the insertion of the optical fiber at the rear end side of the through hole 1a. Therefore, a conical portion 1b is provided, and a C surface portion 1c which serves as a guide surface when the sleeve is inserted is provided on the outer circumference of the tip.

The ferrule 1 is formed of a zirconia sintered body, the details of which will be described later. As shown in FIG. 6, the rear side of the ferrule 1 is joined to a metallic support 2 and the optical fiber 3 is inserted into the through hole 1a. Then, the tip surface 1d is bent to a radius of curvature of 1
Polish to a convex spherical shape of about 0 to 25 mm. The optical fibers 3 can be connected to each other by inserting the pair of ferrules 1 from both ends of the sleeve 4 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 contains ZrO ₂ as a main component, Y ₂ O ₃ as a stabilizer, a tetragonal crystal phase as a main component, and an average crystal grain size of 0.3. ~ 0.5 μm, Vickers hardness 1240-13
00, and by doing so, the polishability of the tip surface 1d of the ferrule 1 is improved.

The zirconia sintered body of the present invention is mainly composed of a tetragonal phase, so that when the stress is applied, the tetragonal crystal transforms into a monoclinic crystal and expands in volume, and cracks develop. The strength and toughness of the sintered body can be improved by the mechanism of stress-induced transformation to prevent it, and it is called partially stabilized zirconia.

Further, the zirconia sintered body of the present invention does not contain a monoclinic phase, but contains a cubic crystal stable to a phase transformation in addition to a tetragonal phase as a main component, so that the stress-induced transformation The phase transformation characteristics in high temperature water can be greatly improved without impairing the mechanism.

Next, a method for manufacturing the ferrule 1 will be described.

First, ZrO _{2 as} a starting material contains Al ₂ O ₃ , SiO ₂ , TiO ₂ , or CaO as impurities.
Although Na ₂ O, Fe ₂ O _{3 and the} like are contained, the raw material is treated with a chemical such as acid or alkali, or purified by a method such as gravity separation utilizing the difference in specific gravity to increase the purity. Then, ₃ to 5 mol% of Y ₂ O ₃ is added to ZrO ₂ and mixed,
Reaction and solid solution are carried out by a method such as neutralization coprecipitation or hydrolysis.

Next, a binder such as an aqueous system, a resin system, or an emulsion system is mixed with the obtained raw material to facilitate molding, to prepare a raw material before molding, and a slenderness ratio of 10 is used by using a predetermined die. The above tubular shape is formed.

Next, after drying in a drying process until the water content becomes 1.5% by weight or less, firing is performed, and then a necessary portion is subjected to mechanical finishing such as grinding or polishing to obtain a product. The drying here means a step of reducing the water content of the ceramic molded body at 50 ° C or lower, and the firing means a step of removing the water content and the binder of the ceramic molded body at 50 ° C or higher and further sintering.

The drying method is not particularly limited, and examples thereof include hot air drying, drying by radiant heat utilizing infrared rays, microwave drying and the like. The drying conditions are not particularly limited, and it is sufficient to finally achieve a water content of 1.5% by weight or less. As an example, in order to prevent cracking of the ceramic molded body, a state of normal temperature and high humidity immediately after molding is used. For example, the drying is started from the stage of holding at 20 ° C. and 80% for about 5 hours, and finally left at a temperature of 20 to 50 ° C. and a humidity of 5 to 30% for 5 hours or more to make the water content of the ceramic molded body 1 0.5% by weight or less.

The moisture content referred to here is defined by the moisture content = (A−B) / A × 100, where A is the weight of the dried ceramic compact,
B represents the weight after the dried ceramics compact is further kept at 100 ° C. under normal pressure for 20 hours. As described above, the drying temperature of the present invention is preferably in the range of 20 to 50 ° C. If the temperature is lower than 20 ° C., the progress of drying will be slow, and it will take too much time to reduce the water content to 1.5% by weight or less, resulting in low productivity. Further, if the temperature exceeds 50 ° C. before the water content falls below 1.5% by weight, deformation such as large warpage occurs in the drying process.
A temperature of ~ 50 ° C is desirable.

The dry humidity of the present invention is preferably within the range of 5 to 30%. If it exceeds 30%, the progress of drying becomes slow, and it takes too much time to reduce the water content to 1.5% by weight or less, resulting in low productivity. Further, if the substrate is placed in an environment with a humidity of less than 5% before the water content becomes 1.5% by weight or less, deformation such as large warpage occurs in the drying step, so 5-30% is desirable.

The drying time of the present invention is not particularly limited, but is preferably in the range of 2 to 48 hours. If the water content is 1.5% by weight or less within 2 hours, deformation such as warpage becomes large during the drying process. Further, it takes 2 hours to 48 hours, since there is no particular advantage even if it takes more than 48 hours and productivity is lowered.

As described above, in the present invention, the generation of warpage can be suppressed by setting the water content to 1.5% by weight or less in the step of drying the ceramic sintered body.

Here, when the ceramic molded body of the present invention is dried, the outer peripheral surface 11a of the tubular ceramic molded body 11 is brought into contact with the drying jig 12 having the V groove 12a as shown in FIG. 4 (a). There is a method of placing it in such a manner that it is put into a drying furnace, and this is sufficient if the external dimension is 5 mm or less.

However, if higher dimensional accuracy is required even if the external dimensions are large or the external dimensions are small, as shown in FIG. 4B, two tubular ceramic molded bodies 11 are provided. Ceramic molded body 11 on rod 22
There is a method of mounting the outer peripheral surface 11a so that the outer peripheral surface 11a is held, and promoting evaporation of water from two directions, an upper direction and a lower direction.

Further, as shown in FIG. 4 (c), the two rotating rollers 23 are placed so that the outer peripheral surface 11a of the ceramic molded body 11 is held, and the two rotating rollers 23 are rotated. Even if the direction is eliminated by doing so,
The same effect as that of (b) can be obtained.

According to the manufacturing method of the present invention, the same effect can be obtained even if various firing methods such as a batch furnace and a continuous furnace are used as the firing method.

Although FIG. 6 shows an optical connector for connecting the optical fibers 3 to each other, the ferrule 1 has
It can also be used in an optical module for connecting an optical fiber to an optical element such as a laser diode or a photodiode.

The zirconia sintered body according to the present invention can be applied to various members used for connecting the above-mentioned optical fibers or connecting the optical fibers to various optical elements, and is not limited to the above-mentioned ferrule 1. For example, it can be applied to a splicer used for completely connecting optical fibers, a dummy ferrule used for an optical module, and the like.

Further, the ceramic sintered body according to the present invention is not limited to the optical communication connector member, but a tubular ceramic sintered body which has been difficult to suppress the deformation such as a warp in the past while requiring precise dimensional accuracy. It can be applied to a precision machine such as a gas turbine member using a body, a nozzle for fluid, a precision measuring instrument, and the like.

[0047]

EXAMPLES Examples of the present invention will be described below.

A partially stabilized zirconia obtained by adding Y ₂ O ₃ to ZrO ₂ was used as a raw material, and each was made into a ferrule sintered body having an outer diameter of φ2.500 mm and a length of 640 mm after sintering. Then, a sample was prepared by the manufacturing method shown in FIG.

Outer diameter φ based on average shrinkage of 77.8%
3.2 Mold using a molding die of 134 mm, and adjust the temperature, humidity, and time in the drying step to prepare seven types of samples having a water content of 1.5 wt% or less, and after firing, sample No. The warpage of each of 20 sintered bodies was measured.
As an example, the sample No. 1 is 5 at 20 ° C and 80%
After holding for a period of time, it was dried at 30 ° C. and 10% for 7 hours, the moisture content was adjusted to 0.6%, and then the calcination warpage was measured. As a result, the size of the warpage was 0.03 mm.

As a comparative example, the water content after drying was 1.
Seven kinds of samples were prepared under the same conditions as those in the examples except that the content was more than 5% by weight, and after firing, the warpage of 20 sintered bodies was measured for each sample No.

The warpage was measured by placing the ceramic sintered body 32 on the surface plate 31 in such a direction that the gap between the surface plate 31 and the ceramic sintered body 32 was maximized as shown in FIG. The gap height 30 was used as the measured value of the sled. The average value of the water content and the size of the warpage of each sample is shown in Table 1, and a graph showing the relationship between the water content and the average value of the size of the warpage is shown in FIG.

[0052]

[Table 1]

As described above, in the sample manufactured by the conventional manufacturing method, the range of warpage is 0.09 to 0.70 mm, and the variation which is the difference between the maximum value and the minimum value of each value is as large as 0.17 mm. However, according to the manufacturing method of the present invention, it was possible to obtain a sintered body in which warpage was 0.029 mm and variation was 0.008 mm, and there was almost no warpage.

[0054]

As described above, according to the present invention, a pre-molding raw material obtained by mixing a sintering aid or the like with a starting raw material and adding a binder is molded into a tubular or rod shape having an elongated ratio of 10 or more, and is subjected to a drying step. Then, the product was dried until the water content became 1.5% by weight or less, and then fired, whereby generation of warpage could be substantially eliminated.

[Brief description of drawings]

FIG. 1 is a flow chart showing a method for producing a ceramics sintered body of the present invention.

2 (a) and 2 (b) are schematic views showing a forming step and a drying step in the method for producing a ceramics sintered body of the present invention.

FIG. 3 is a graph showing the relationship between the water content of the tubular ceramics molded body of the present invention and the size of warpage.

4 (a) to 4 (c) are schematic views showing a drying method in the method for producing a ceramics sintered body of the present invention.

FIG. 5 is a view showing an optical connector member using the ceramic sintered body of the present invention.

FIG. 6 is a sectional view showing an optical connector using an optical connector member made of the ceramic sintered body of the present invention.

FIG. 7 is a schematic diagram showing a method of measuring warpage.

[Explanation of symbols]

1: Ferrule 1a: Through hole 1b: conical part 1c: C surface part 1d: Tip surface 2: Support 3: Optical fiber 4: Sleeve 11: Ceramic molded body 11a: outer peripheral surface 12: Drying jig 12a: V groove 13: Molding machine 14: Input port 15: Raw material before molding 16: Screw 17: Mold 20: Drying oven 21: Infrared generator 22: Bar material 23: rotating roller 30: Gap height 31: surface plate 32: Ceramics sintered body

Claims (2)

[Claims] 1. A raw material, which is obtained by mixing a starting material with a sintering aid or the like and adding a binder, is formed into a tubular or rod shape having an elongated ratio of 10 or more, and has a water content of 1.5% by weight in a drying step.
A method for producing a ceramics sintered body, which is characterized by performing drying until the following, and then firing. 2. The method for producing a ceramics sintered body according to claim 1, wherein the ceramics sintered body is used for an optical communication connector member.