JP2013252978A - Translucent ceramic joined body and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a translucent ceramic joined body with enhanced joining which exerts a high intensity even when used as small and thin parts, e.g. portable electronic devices and watch members and its manufacturing method.SOLUTION: A translucent ceramic joined body includes a translucent ceramic and a frame in contact with at least a part of the outer periphery of the ceramic, and a compression stress produced on joining of the frame enhances the ceramic. The frame is preferably composed of a zirconia type sintered material.

Description

  The present invention relates to a light-transmitting ceramic joined body having a light-transmitting ceramic with enhanced bonding and a method for producing the same.

  Ceramics are widely used in industrial member applications because of their excellent heat resistance, wear resistance, and corrosion resistance. Furthermore, since translucent ceramics with added transparency have light transmissivity and wear resistance, applications such as electronic device members such as mobile phones, watch members, and jewelry are being studied. With such expansion of applications, there is an increasing demand for higher strength of translucent ceramics.

  For glass, which is a general transparent material, tempering methods such as an air cooling tempering method and an ion exchange method are widely used. In the air-cooling strengthening method, a density difference is created between the surface layer and the inside by heat treatment, and compressive stress is generated near the surface. In the ion exchange method, potassium having a large ion radius is ion exchanged with glass, and a compressive stress is formed in the vicinity of the surface. Both methods are strengthened by inhibiting the progress of scratches by the compressive stress present on the glass surface. On the other hand, in the case of opaque ceramics, a material in which scratches do not easily progress has been developed by introducing a second phase (for example, Patent Document 1), improving a fine structure (for example, Patent Document 2), and the like.

  When using ceramics as a portable electronic device or watch member, it is essential to have high strength with a thickness of several millimeters and high transparency. However, in translucent ceramics, transparency decreases due to the introduction of the second phase and the improvement of the microstructure. In addition, the heat strengthening method and the chemical strengthening method widely used for glass materials cannot be applied to materials other than glass because they utilize properties inherent to glass. Therefore, until now, in transparent ceramics, there has been no translucent ceramic having improved strength without decreasing transparency and a method for producing the same.

Japanese Patent Laid-Open No. 3-80153 Japanese Patent Laid-Open No. 11-1365

  In increasing the strength by introducing the second phase and improving the structure, the transparency due to the increase of the heterogeneous interface and residual pores is lowered, and it is extremely difficult to increase the strength while maintaining high transparency. Conventionally, a method of improving the strength by changing the shape such as increasing the thickness of the member has been common.

  Since the glass strengthening method, which is a general transparent material, uses a phenomenon inherent to glass, it cannot be applied to crystalline translucent ceramics. The present invention provides a bonded and strengthened transparent ceramic that solves these problems and a method for producing the same.

  In view of the above-mentioned problems, the present inventors have intensively studied and found that compressive stress is generated by thermally expanding the frame by heating and shrink-fitting the transparent ceramic, and the translucent ceramic is strengthened. .

  That is, the present invention is a translucent ceramic comprising a translucent ceramic and a frame in contact with at least a part of the outer periphery of the ceramic, wherein the ceramic is reinforced by compressive stress generated when the frames are joined. The present invention relates to a joined body and a manufacturing method thereof.

  Hereinafter, the translucent ceramic joined body of the present invention will be described in detail.

  The compressive stress is generated in the translucent ceramic by compressing the translucent ceramic by the fitting force on the translucent ceramic side by the frame. The translucent ceramic and the frame in contact with at least a part of the outer periphery of the ceramic are mechanically firmly bonded by compressive stress, and there is no bonding layer. In this respect, it is different from a metallized bonded body bonded with a bonded body or a bonding layer bonded with an adhesive.

  There are shrinking and chilling technologies for joining metals / ceramics using thermal expansion and cooling shrinkage of metals, but these are aimed at obtaining mechanical joining by utilizing thermal expansion and thermal shrinkage of metal members. Is. On the other hand, the translucent ceramic joined body of the present invention is intended to apply a compressive stress to the translucent ceramic by utilizing the thermal expansion of the frame. It is different from the body.

  The material used for the frame may be a metal such as SUS as long as it has a large thermal expansion coefficient and high mechanical strength, but ceramics are preferable from the viewpoint of design. Examples of the ceramic used as the frame include zirconia, sapphire, alumina, and silicon nitride, but a zirconia sintered body having a large thermal expansion coefficient and high strength and toughness is particularly preferable.

Examples of the translucent ceramic include translucent zirconia sintered body, yttria (yttrium oxide, Y ₂ O ₃ ) sintered body, spinel (MgAl ₂ O ₄ ) sintered body, yttria-alumina-garnet (YAG; Y ₃ Examples thereof include polycrystalline bodies such as Al ₅ O ₁₂ ) sintered bodies, translucent alumina sintered bodies, aluminum oxynitride (AlON), silica glass, sapphire, and blue plate glass.

  Among these, the translucent zirconia sintered body is preferably a zirconia sintered body containing a cubic fluorite structure in its crystal structure, and the crystal structure is a single phase of the cubic fluorite structure. It is more preferable.

As the translucent zirconia sintered body, it can be exemplified and yttria-containing zirconia sintered body, titania (titanium oxide, TiO ₂₎ to and yttria-containing zirconia sintered body.

  The amount of yttria contained in the yttria-containing translucent zirconia sintered body is preferably 6 mol% or more and 15 mol% or less with respect to zirconia in the translucent zirconia sintered body, and is 7 mol% or more and 12 mol% or less. Is more preferable, and it is still more preferable that they are 8 mol% or more and 10 mol% or less.

  The amount of titania in the titania- and yttria-containing translucent zirconia sintered body is preferably 3 mol% or more and 20 mol% or less with respect to the total of zirconia and yttria in the translucent zirconia sintered body. % Or less, more preferably 8 mol% or more and 12 mol% or less. By containing titania in this range, the transparency of the translucent zirconia sintered body is likely to be high.

  The translucent ceramic joined body of the present invention is formed by mechanically sandwiching a translucent ceramic with a frame that contacts at least a part of the outer periphery of the ceramic, preferably a frame made of a sintered body. Compressive stress is generated on the side. Therefore, the progress of scratches at the time of destruction is hindered by the compressive stress, and the strength of the light-transmitting ceramic that has been strengthened by bonding increases. As the compressive stress is higher, the progress of flaws is inhibited. Therefore, if the average value of the compressive stress is 10 MPa or more, a sufficient effect can be obtained. The compressive stress can be evaluated by measuring the strain by the Senarmon method for an optically isotropic substance. It can also be evaluated by measuring the amount of deformation of the base material due to bonding.

  Furthermore, the ceramic joined body of the present invention may be formed by joining the frame and a part of the translucent ceramic, but the sintered body is joined so as to surround the entire outer periphery of the translucent ceramic. Is preferred.

  The shape of the ceramic joined body of the present invention is not particularly limited as long as the translucent ceramic and a frame that contacts at least a part of the outer periphery of the ceramic are in a joined state. For example, examples of the shape of the translucent ceramic contained in the ceramic joined body of the present invention include a plate shape such as a circular shape, an elliptical shape, a rectangular shape, or a square shape. A plurality of translucent ceramics can also be fitted.

  Next, the manufacturing method of the translucent ceramic joined body of this invention is demonstrated in detail.

  In the manufacturing method of the present invention, the frame is thermally expanded by heating, the translucent ceramic is sandwiched in the expanded frame, the frame and the translucent ceramic are fitted by thermal contraction by cooling, and compressive stress is applied to the transparent ceramic. It is a manufacturing method characterized by doing.

  The translucent ceramics to be reinforced are mechanically fitted using a frame having a smaller fitting dimension, preferably a frame made of a sintered body. It is preferable to use thermal expansion by heating for fitting the frame. The fitting size that expands by heating is larger than that of the translucent ceramic to be strengthened, the translucent ceramic is placed in the expanded frame, and the translucent ceramic is fitted by thermal contraction by cooling.

  When the thermal expansion of the frame due to heating is considered in fitting by heating, the fitting size L (mm) of the frame and the size a (mm) of the transparent base material can be expressed by the following relationship.

L × (1 + α × ΔT)> a (1)
Here, α is a thermal expansion coefficient (1 / ° C.), and ΔT is a temperature difference (° C.) between room temperature and the fitting temperature. If the conditions satisfy the expression (1), the transparent ceramics are sandwiched between the outer frames, and a joined body in which compressive stress is generated in the transparent ceramics can be obtained. For example, when the fitting dimension L is 30 mm in a zirconia sintered body (thermal expansion coefficient 10.6 × 10 ⁻⁶ / ° C.) at room temperature: 30 ° C., the expansion amount at 300 ° C. is about 86 μm. By adjusting the fitting size (a-L), the compressive stress applied to the transparent ceramic can be adjusted.

  The fitting can also be performed by cooling the translucent ceramic and making it smaller than the fitting size of the frame.

  It is also possible to form a thin film of alumina, silica, zirconia or the like on both surfaces and one surface of the joined body. Examples of the method for forming a thin film include ion plating, sputtering, CVD, and a slurry DIP method. Forming a thin film has the effect of reducing the reflectance and increasing the strength.

1 is a view showing an overview of a ceramic joined body obtained in Example 1. FIG. FIG. 3 is a diagram showing a stress distribution in the ceramic joined body obtained in Example 1.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Relative density)
The density of the sample was measured using the Archimedes method. The obtained density was determined as a relative density with respect to the true density. The true density of the black zirconia sintered body was 6.06 g / cm ^3, and the true density of the yttria- and titania-containing translucent zirconia sintered body was 5.83 g / cm ³ .

(Impact strength measurement)
The impact strength of the translucent ceramic joined body was evaluated using a steel ball drop test. For the steel ball drop test, a method similar to ISO14368-3 of the “Watch Glass Dimensions, Test Method” standard was applied. That is, the height at which a 25 mm SUS steel ball was dropped and dropped at the center position of the translucent ceramic was measured. The sample was supported on a fulcrum for a three-point bending strength test, and the span between the fulcrums was 3 cm. The measurement sample used was a mirror polished on both sides with a surface roughness Ra = 0.02 μm or less.
(Linear transmittance)
A translucent ceramic joined body in which the surface roughness Ra of the transparent ceramic portion was mirror-polished to 0.02 μm or less was used as a measurement sample. The linear transmittance was measured using a haze meter (trade name “NDH5000” manufactured by Nippon Denshoku). The light source used was D65 light.
(Compressive stress measurement)
The compressive stress of the isotropic translucent ceramic was measured using a strain tester (manufactured by Luceo, trade name “LSM-3002”) by the Senarmont method. As the photoelastic constant used for the calculation, translucent zirconia: −1.2 nm / cm / 10 ⁵ Pa and blue plate glass: 2.6 nm / cm / 10 ⁵ Pa were used. The longitudinal stress of the joined body was evaluated for the compressive stress (σ1) and the compressive stress (σ2) in the short direction.
(Measurement of L)
For sapphire with optical anisotropy, compressive stress was evaluated by measuring the deformation of the base material. The calculation of stress assumes a plane stress model (ceramics fracture mechanics, Uchida Otsukuru, page 15). went. The elastic constant of sapphire used for the calculation was 400 GPa.
(Vickers measurement)
About the translucent zirconia sintered compact, the fracture toughness value before and behind reinforcement | strengthening was evaluated using the Vickers indentation test. The indentation load was set to 10 kgf, and evaluation was performed in accordance with JIS R1607. Here, the elastic modulus of zirconia was set to 205 GPa.

Example 1-3
(Preparation of sintered zirconia)
Black zirconia powder (manufactured by Tosoh, trade name “TZ-Black”) was molded at a pressure of 50 MPa by a mold press. The black zirconia powder after molding was molded by a cold isostatic press (CIP) with a pressure of 200 MPa to obtain a plate-shaped molded body having a length of 70 mm and a width of 70 mm. The obtained molded body was sintered under normal pressure to obtain a black zirconia sintered body having a relative density of 99%.

  This zirconia sintered body is machined to obtain a rectangular black zirconia sintered body having a rectangular hollow portion of 30 mm in length, 25 mm in width, and 1.1 mm in thickness, and 50 mm in length, 45 mm in width, and 1.1 mm in thickness. It was.

(Production of translucent zirconia sintered body)
10 mol% yttria-containing zirconia powder (manufactured by Tosoh, trade name “TZ-10YS”) and high-purity titania powder were added at 10 mol% with respect to zirconia, and ball mill mixed for 72 hours with zirconia balls having a diameter of 10 mm in an ethanol solvent. Thereafter, it was dried to obtain a raw material powder.

  The raw material powder was molded at a pressure of 50 MPa by a die press and then molded at a pressure of 200 MPa by a cold isostatic press to obtain a plate-like molded body having a length of 50 mm, a width of 40 mm, and a thickness of 2 mm.

  The obtained plate-like molded body was primarily sintered in the atmosphere at a temperature rising rate of 100 ° C./h, a sintering temperature of 1350 ° C., and a sintering time of 2 hours to obtain a primary sintered body. The obtained primary sintered body had a relative density of 94%, an average particle size of 3 μm or less, and the crystal phase was a cubic phase and a tetragonal phase.

  Next, this primary sintered body was subjected to a hot isostatic pressing (HIP) treatment at a temperature of 1500 ° C., a pressure of 150 MPa, and a holding time of 1 hour to obtain a translucent zirconia sintered body. The density of the translucent zirconia sintered body was 100%. Note that argon gas having a purity of 99.9% was used as a pressure medium, and the primary sintered body was placed in a carbon container with a lid, and HIP treatment was performed.

  The crystal phase of the obtained translucent zirconia sintered body was a single phase having a cubic fluorite structure. This translucent zirconia sintered body was machined so as to have a size obtained by adding the fitting white as shown in Table 1 to the above-mentioned hollow size of black zirconia.

(Production of ceramic joined body)
The frame-type zirconia sintered body was heated to 300 ° C. with a heater, and the translucent zirconia sintered body was placed in the hollow portion and cooled to prepare a joined body. An overview of the obtained bonded body is shown in FIG. 1 (Example 1). The state of compressive stress obtained by using the Senalmon method is shown in FIG. 2 (Example 1). It can be seen that due to the shrinkage of the frame-type zirconia sintered body, the zirconia sintered body and the translucent zirconia sintered body are joined, and compressive stress is applied to the transparent zirconia side. Table 1 shows the results of the strength evaluation. The strengthened translucent zirconia sintered body was found to provide high strength. Moreover, the linear transmittance | permeability of the translucent zirconia sintered compact is 70% or more, and it turned out that it has high transparency.

Example 4-6
A ceramic joined body was obtained in the same manner as in Example 1 except that a commercially available blue plate glass was used as the translucent ceramic. The results are shown in Table 1. It has been found that tempered blue glass provides high strength.

Example 7
A ceramic joined body was obtained in the same manner as in Example 1 except that a commercially available sapphire was used as the translucent ceramic. The results are shown in Table 1. Enhanced sapphire has been found to provide high strength.

Example 8
The fracture toughness value of the translucent zirconia sintered body of Example 1 was evaluated by the Vickers indentation method. In the reinforced product, it was 2.7 MPam ^0.5 .

Comparative Examples 1 and 2
The steel ball drop measurement was performed about the translucent zirconia sintered compact and blue plate glass which have not been strengthened. The dimensions of the test piece were 50 mm long, 45 mm wide, and 1.1 mm thick. The breaking heights were 2 cm and 5 cm, respectively.

Comparative Example 3
Fracture toughness was measured by a Vickers indentation method for a translucent zirconia sintered body that had not been strengthened. The fracture toughness value of the untreated transparent zirconia sintered body was 1.4 MPam ^0.5 .

  The translucent ceramic joined body of the present invention can be suitably used for small and thin parts such as portable electronic devices and watch members.

Claims (7)

  A translucent ceramic joined body comprising a translucent ceramic and a frame in contact with at least a part of an outer periphery of the ceramic, and the ceramic is reinforced by compressive stress generated when the frames are joined. The joined body according to claim 1, wherein the frame is made of a zirconia sintered body.   The joined body according to claim 1 or 2, wherein the translucent ceramics comprises a transparent zirconia sintered body.   The bonded body according to any one of claims 1 to 3, wherein an average value of compressive stress of the translucent ceramic is 10 MPa or more.   The frame is thermally expanded by heating, placed so that the translucent ceramic is sandwiched in the expanded frame, the frame and the translucent ceramic are fitted by heat shrinkage by cooling, and compressive stress is applied to the translucent ceramic A method for producing a translucent ceramic joined body characterized by the above.   The portable electronic device using the conjugate | zygote in any one of Claims 1-4.   A timepiece member using the joined body according to claim 1.

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