JP5829563B2 - Silicon nitride-based sintered body and decorative part using the same - Google Patents

Description

  The present invention relates to a silicon nitride-based sintered body, and particularly to a silicon nitride-based sintered body that can be suitably used for a wristwatch case, a wristwatch band piece, and the like to produce a beautiful color tone, and a decoration using the same. Regarding parts.

  A silicon nitride sintered body was produced when a sintered body was obtained using a powder mainly composed of α-type silicon nitride powder as a raw material, as well as phase transfer from α-type to β-type occurred in the sintering process. It is known that β-type silicon nitride crystal grains are columnar and have a structure in which these crystal grains are entangled with each other, and mechanical properties are improved compared to a structure made of isotropic crystals.

  As a silicon nitride-based sintered body having such high mechanical properties, in Patent Document 1, in a silicon nitride-based ceramic made of a silicon nitride-additive sintered body, β-type silicon nitride columnar crystals are in one plane. Ratio of (101) plane strength (I101) and (210) plane strength (I210) of β-silicon nitride obtained by X-ray diffraction of the parallel plane. Silicon nitride ceramics having (I101 / I210) of 0.4 or less have been proposed.

Japanese Patent No. 2563392

  However, although the silicon nitride ceramics described in Patent Document 1 have high temperature strength and high fracture toughness, the processing efficiency is not considered, and the surface is intended to be polished using a lapping device, a barrel device, or the like. Then, there was a problem that processing efficiency was low.

  The present invention has been devised to solve the above-described problems, and an object of the present invention is to provide a silicon nitride sintered body having high processing efficiency and a decorative part using the same.

The silicon nitride sintered material of the present invention, beta-made silicon nitride as a main component, obtained using X-ray diffraction method, the beta-nitride of silicon (101) plane and (210) each diffraction plane the intensity I (101), when the I (210), the ratio of the diffraction intensity arithmetic average roughness Ra of that obtained when irradiated with X-rays to the polished surface below 0.25μm or 0.06μm I (101)
/ I (210) is much larger than the 1, inside falls deeper than the surface, the ratio of the diffraction intensity obtained when X-rays were irradiated in a plane substantially parallel to said surface I (101) / I ( 210) is less than one.

  The decorative part of the present invention is characterized by using the above-mentioned silicon nitride sintered body.

According to the silicon nitride sintered body of the present invention, beta-made silicon nitride as a main component, obtained using X-ray diffraction method, the beta-nitride (101) silicon surface and (210) plane of each the diffraction intensity of the I (101), when the I (210), the diffraction intensity arithmetic average roughness Ra of that obtained when irradiated with X-rays to the polished surface below 0.25μm or 0.06μm the ratio I (101) / I (210 ) is much larger than the 1, ratio of the diffraction intensity obtained when inside falls deeper than the surface was irradiated with X-rays in a plane substantially parallel to the surface I Since (101) / I (210) is smaller than 1 , the orientation of the crystal changes from the inside toward the surface, so the ratio of the diffraction intensities in the inside and the surface I (101) / I ( 210) is less than 1 compared to Fracture toughness in the surface is lowered, the processing efficiency is increased.

  In addition, according to the decorative part of the present invention, since the silicon nitride sintered body of the present invention is used, the production efficiency can be increased by increasing the processing efficiency. Can be a part.

(A) is obtained by irradiating the silicon nitride-based sintered body of the present embodiment with X-rays, (b) is an example of a diagram showing a result of X-ray diffraction of a polished surface. (A)-(f) is the schematic diagram which looked at the decorative surface planarly, which shows an example of the decorative component using the silicon nitride sintered body of this embodiment, respectively. An example of a watch case which is a decorative part for a watch using the silicon nitride sintered body of the present embodiment is shown, (a) is a perspective view of the watch case as viewed from the front side, and (b) is (a) FIG. It is a perspective view which shows the other example of the case for timepieces which is a decorative component for timepieces using the silicon nitride sintered body of this embodiment. It is a bottom view which shows an example of the back cover for timepieces which is a decorative part for timepieces using the silicon nitride based sintered body of this embodiment. It is a schematic diagram which shows an example of a structure of the timepiece band which is a decorative part for timepieces using the silicon nitride sintered body of this embodiment.

  Hereinafter, an example of this embodiment will be described in detail with reference to the drawings.

  The silicon nitride sintered body of the present embodiment is a silicon nitride sintered body containing β-silicon nitride as a main component, and includes, for example, at least one oxide of aluminum, calcium, magnesium, and rare earth elements. It is preferable to contain at least one of chromium, manganese, iron, cobalt, nickel, molybdenum and tungsten silicides.

Here, each oxide of aluminum, calcium, magnesium and rare earth elements acts as a sintering aid for promoting the sintering. More specifically, the composition formula is a component represented by, for example, Al ₂ O ₃ , CaO, MgO, and RE ₂ O ₃ (hereinafter, RE represents a rare earth element). In addition, each silicide of chromium, manganese, iron, cobalt, nickel, molybdenum, and tungsten controls the solidification of the grain boundary phase to increase the high temperature strength, and also blackens the color of the sintered body. It works to reduce the color difference from the surface. More specifically, composition formula, for _example, a component represented as _{CrSi 2, MnSi 2, FeSi,} FeSi 2, CoSi 2, NiSi 3, MoSi 2, WSi 2 and _W 5 Si ₃ and the like.

The silicon nitride-based sintered body of the present embodiment has a β-silicon nitride content of 81.8% by mass or more, for example, the balance includes calcium oxide, aluminum oxide, and rare earth element oxide as a sintering aid. The content of calcium oxide, aluminum oxide and rare earth element oxide is 0.3% by mass to 1.5% by mass and 14.2% by mass, respectively, with respect to 100% by mass of the total of calcium oxide, aluminum oxide and rare earth element oxide. The content is 48.8% by mass or less, and the balance is made of a rare earth element oxide. Further, the silicide is, for example, iron silicide and tungsten silicide, and the content of these silicides is 0.2 mass% to 10 mass% in terms of Fe and 0.1 mass% to 3 mass% in terms of W, respectively. It is. In the silicon nitride sintered body of this embodiment, there is no problem even if unavoidable impurities are contained in an amount of 1% by mass or less with respect to 100% by mass of the silicon nitride sintered body.

Further, as another example of the silicon nitride sintered body of the present embodiment, the content of β-silicon nitride is 81.8% by mass or more, for example, the balance is aluminum oxide, magnesium oxide and Containing calcium oxide, the total content of aluminum oxide, magnesium oxide and calcium oxide is 100 for aluminum oxide, magnesium oxide and calcium oxide.
12% by mass or more and 22% by mass or less and 20% by mass or more and 33% by mass or less, respectively, and the balance is made of calcium oxide. Further, the silicide is, for example, iron silicide and tungsten silicide, and the content of these silicides is 0.2 mass% to 10 mass% in terms of Fe and 0.1 mass% to 3 mass% in terms of W, respectively. It is.

  Here, what is necessary is just to obtain | require content about the component which comprises a silicon nitride sintered compact by a fluorescent X ray analysis method or an ICP (Inductively Coupled Plasma) emission spectroscopy analysis method. The specific content of the ICP emission spectroscopic analysis method is as follows. First, as a pretreatment, a part of a silicon nitride sintered body is pulverized in a cemented mortar, and then boric acid and sodium carbonate are added and melted. . Then, after cooling, the solution is dissolved in a hydrochloric acid solution, and the solution is transferred to a flask, diluted to the standard line with water to obtain a constant volume, and measured with an ICP emission spectrometer together with a calibration curve solution. Each content of the metal element of the component which comprises a sintered compact can be calculated | required.

Based on this value, components other than Si, for example, Al, Ca, Mg, and RE (rare earth elements) are converted into oxides to obtain aluminum oxide (Al ₂ O ₃ ), calcium oxide (CaO), respectively. , Magnesium oxide (MgO) and rare earth element oxide (RE ₂ O ₃ ) can be determined. In addition, Cr, Mn, Fe, Co, Ni, Mo and W are converted into silicides, respectively, thereby providing chromium silicide (CrSi ₂ ), manganese silicide (MnSi ₂ ), iron silicide (FeSi ₂ ), cobalt silicide. Each content of (CoSi ₂ ), nickel silicide (NiSi ₂ ), molybdenum silicide (MoSi ₂ ), and tungsten silicide (WSi ₂ ) can be determined.

In addition, the silicon nitride content is determined by measuring the content of Al, Ca, Mg, RE, Cr, Mn, Fe, Co, Ni, Mo and W, respectively, aluminum oxide, calcium oxide, magnesium oxide and rare earth. Element oxides and chromium oxides, manganese silicides, iron silicides, cobalt silicides, nickel silicides, molybdenum silicides, and tungsten silicides, each containing 100% by mass of oxides of aluminum oxide, calcium oxide, magnesium oxide, and rare earth elements The value obtained by subtracting the sum of the amount and each content of iron silicide, cobalt silicide, nickel silicide, molybdenum silicide, and tungsten silicide may be the silicon nitride content.

  FIG. 1 is an example of a diagram obtained by irradiating a silicon nitride based sintered body of this embodiment with X-rays, (a) is an inside, and (b) is a result of X-ray diffraction of a polished surface. It is.

  1 are the diffraction intensities I (101) and I (210) of the (101) plane and (210) plane of β-silicon nitride, respectively.

As in the example shown in FIG. 1, the silicon nitride sintered body according to this embodiment is obtained by using the (101) plane and the (210) plane of β-silicon nitride obtained by using the X-ray diffraction method. The diffraction intensity is I (101
), I (210), the internal diffraction intensity ratio I (101) / I (210) is smaller than 1, and the diffraction intensity ratio I (101) / I (210) on the polished surface is It is important that it is greater than 1. When the diffraction intensity ratio I (101) / I (210) is in such a relationship, the crystal orientation changes from the inside to the surface, and therefore the diffraction intensity ratio I (101) / I at the inside and the surface. Compared with the case where (210) is smaller than 1, the fracture toughness on the surface is low, and the processing efficiency tends to be high. Here, the polished surface is preferably a surface formed by polishing the surface of a sintered silicon nitride-based sintered body in the depth direction by 10 μm or more and 60 μm or less.

In particular, the diffraction intensity ratio I (101) / I (210) is the ratio of the diffraction intensity ratio I (101) / I (210) in the interior to the diffraction intensity ratio on the polished surface while maintaining the above relationship. Ratio I (101)
/ I (210) is 0.65 or more, and the ratio of the diffraction intensity inside I (101) / I (210)
Is preferably 0.45 or less. By doing so, the fracture toughness inside becomes high, the fracture toughness on the polished surface becomes lower than the internal fracture toughness, and it becomes easy to obtain a sintered body having both high processing efficiency and mechanical properties.

  In addition, what is necessary is just to collate with the card | curd shown by PDF (trademark) Number: 00-033-1160 using the X-ray-diffraction method about identification of (beta) -silicon nitride which comprises a silicon nitride sintered body.

Further, the polished surface, for example, lapping, polishing abrasive, Ru surface der obtained by barrel polishing and buffing.

Further, the silicon nitride sintered body of this embodiment has a carbon content of 0.3 on the polished surface.
It is preferable that it is less than or equal to mass% (excluding 0 mass%). When the carbon content is 0.3% by mass or less, the carbon diffuses into silicon nitride to form a solid solution and promotes sintering, so that the hardness can be increased and the black color of the carbon causes an achromatic color. When the silicon nitride sintered body is used, for example, as a decorative part, the chromaticness index a * and b * and the following formula (A The color difference (ΔE * ab), which is the difference in color tone defined by (1), can be reduced, so that it is possible to obtain a preferable extremely black color that hardly feels the color difference generated between decorative parts. In particular, from the viewpoint that mechanical properties such as fracture toughness and hardness can be sufficiently increased, the carbon content in the polished surface is preferably 0.1% by mass or more.
ΔE * ab = ((ΔL *) ² + (Δa *) ² + (Δb *) ² )) ^1/2 (A)
In addition, the silicon nitride sintered body of this embodiment preferably has an open porosity of 0.5% or less on the polished surface. When the open porosity is 0.5% or less, the color unevenness due to the contour formed by the pores is reduced and the color tone on the surface is deepened. Therefore, the value of the lightness index L * is reduced, and the silicon nitride sintered body is, for example, When used as a decorative part, since the texture is further increased, high aesthetic satisfaction is easily obtained.

The open porosity on the polished surface is calculated as follows. First, using an optical microscope, the magnification is set to 200 times, and an image of the decorative surface is captured by a CCD camera. Next, using an image analyzer (LUZEX-FS manufactured by Nireco Corporation), the measurement area of one visual field in the image is 2.25 × 10 ⁻² mm ² , the number of measurement visual fields is 20, that is, the total measurement area is 4.5 × 10. ^The area of open pores in the measured total area is determined as ⁻¹ mm ² . The area of the open pores is divided by the total measurement area, and the ratio of the area of the open pores in the total measurement area is defined as the surface open porosity. Thereby, the open porosity on the surface can be calculated.

  In the silicon nitride sintered body of this embodiment, it is preferable that the maximum opening diameter of the open pores on the polished surface is 0.1 mm or less. If the maximum opening diameter of the open pores on the surface is 0.1 mm or less, uneven color due to differences from other parts is reduced due to the contour formed by the open pores. For example, this silicon nitride sintered body is used as a wristwatch band. When used as a piece, there is almost no difference in color tone between adjacent band pieces, so that the sense of discomfort can be reduced even if parts are replaced.

  In particular, the maximum opening diameter of the open pores on the polished surface is more preferably 0.05 mm or less.

  The maximum opening diameter of the open pores can be measured using an optical microscope.

Specifically, the magnification was set to 100 times, and five areas where the area per area was set to 1235 μm × 926 μm were extracted from the polished surface of the silicon nitride sintered body, and the diameter of the largest open pore among them was extracted. It is calculated | required by measuring.

  The silicon nitride sintered body of this embodiment preferably has a surface arithmetic average roughness Ra of 0.06 μm or more and 0.25 μm or less.

  In such a surface state, the entire surface is appropriately roughened, and even when the open pores are partially concentrated, it is possible to suppress the appearance of the contours of the open pores and the occurrence of uneven color. Further, in such a surface state, the hydrophilicity of the silicon nitride sintered body is further improved, so that dirt of oil components derived from sebum is less likely to adhere, and a clean feeling is easily maintained.

  Furthermore, the silicon nitride sintered body of this embodiment preferably has a kurtosis (Rku) determined from a surface roughness curve of 2.5 or more and 4.5 or less.

  If it is such a surface state, because the tip portion that is a mountain or valley in the contour formed by the open pores is dispersed in a moderately rounded and pointed one, It becomes a state where the boundary of the contour is further thinned, and color unevenness can be further suppressed.

The arithmetic average roughness Ra and kurtosis (Rku) of the surface is JIS B 0601-2001 (ISO
4287-1997), and the measurement length and cutoff value are 5m each.
m and 0.8 mm, and when measuring using a stylus type surface roughness meter, for example, a stylus having a stylus tip radius of 2 μm is applied to the polished surface of a silicon nitride sintered body. The scanning speed of the stylus is set to 0.5 mm / second, and the average values of the five locations obtained by this measurement are the values of arithmetic average roughness Ra and kurtosis (Rku).

Further, silicon nitride, which is a constituent component of the silicon nitride-based sintered body of the present embodiment, has a composition formula represented by Si _6-Z Al _Z O _Z N _8-Z (z = 0.1 to 1). -Sialon is preferred. The represented β- SiAlON a composition formula _{Si 6-Z Al Z O Z} N 8-Z (z = 0.1~1), Al, O, is N components in solid solution in the _β-Si 3 _{N 4} When it is β-sialon that is composed of crystals and the value of the solid solution amount z is within the above range, the number of abnormally grown columnar crystals decreases, so that the strength hardly decreases, and β− Since the crystal symmetry of Si ₃ N ₄ is hardly impaired, the thermal conductivity is unlikely to decrease, and when used as a decorative part with sliding, the local temperature rise due to the generation of frictional heat is suppressed. can do. In particular, the solid solution amount z is more preferably 0.35 or more and 0.70 or less.

Here, the solid solution amount z can be calculated as follows. First, a sample is pulverized until it passes through a mesh having a particle size number of 200 described in ASTM E 11-61, and the obtained powder is a high-purity α which is a sample for correcting an angle of diffraction in a powder X-ray diffraction method. -Add 60 mass% of silicon nitride powder (Ebe grade made by Ube Industries, aluminum content is 20 mass ppm or less) and mix it uniformly in a mortar, and set the analysis range 2θ by powder X-ray diffraction method. The profile intensity is measured with a Cu-Kα line (λ = 1.40556 mm) with a scanning step width of 0.002 ° at 33 to 37 °. Note that the angle is corrected using the maximum peak value obtained from the angle correction sample.

Then, the difference (Δ2θ ₁ ) between the average 2θ of the top 10 peak intensities obtained every 0.002 ° of α (102) appearing near 2θ = 34.565 ° and 34.565 °, and α appearing near 2θ = 35.333 °
The difference (Δ2θ ₂ ) between the average 2θ of the top 10 peak intensities obtained every 0.002 ° of (210) and 35.333 ° is obtained, and the average (Δ2θ ₁ + Δ2θ ₂ ) / 2 of the difference is set as the corrected Δ2θ. .

Next, the angle obtained by correcting the average 2θ of the top 10 peak intensities obtained every 0.002 ° of β (210) appearing in the vicinity of 2θ = 36.055 ° by the correction Δ2θ is the peak position (2 of the sample β (210)
θ _β ). Then, the lattice constant a (Å) is calculated by substituting the peak position (2θ _β ), λ = 1.40556Å, and (hkl) = (210) into the following equation.
sin ² θ _β = λ ² (h ² + hk + k ² ) / (3a ² ) + λ ² l ² / (4c ² )
In this equation, the calculated lattice constant a (Å) and the lattice constant a (Å) −solid solution amount z described in KH Jack, J. Mater. Sci., 11 (1976) 1135-1158, FIG. From this graph, the solid solution amount z can be determined.

  In addition, the silicon nitride sintered body of the present embodiment has a reflectance of 13.6% or less in the visible light region of the polished surface, which is required to have a decorative property (hereinafter referred to as a decorative surface). Is preferred. When the reflectance in the visible light region is 13.6% or less, since the reflection with respect to the visible light is suppressed, it can be used as a decorative part that is required to suppress the reflection with respect to the visible light.

Further, in the silicon nitride sintered body of the present embodiment, the chromaticness index a * and b * in the CIE1976L * a * b * color space of the decorative surface is −0.5 or more and +0.5 or less and −1.0 or more and +1.0, respectively. It is preferable that: If the chromaticness indices a * and b * are within this range, the decorative surface can create a refined impression. Therefore, when the silicon nitride sintered body of the present embodiment is used as a decorative part, it is visually high-class. A feeling, aesthetic satisfaction and mental comfort can be obtained.

  In addition, the silicon nitride sintered body of this embodiment preferably has a lightness index L * of 40 to 45 in the CIE1976 L * a * b * color space of the decorative surface. If the lightness index L * is within this range, a moderate brightness can be achieved in the color tone of extremely black, so a gorgeous black color is obtained, which increases the sense of quality, increases aesthetic satisfaction, and makes it more spiritual. You can get peace.

  The reflectance of the decorative surface in the visible light region, the value of the lightness index L * and the value of the chromaticness index a *, b * in the CIE1976 L * a * b * color space are measured in accordance with JIS Z 8722-2000. It is required by that. For example, a spectrocolorimeter (such as CM-3700d manufactured by Konica Minolta Holdings Co., Ltd.) can be used, and the light source can be measured with a CIE standard light source D65, the viewing angle set to 10 °, and the measurement range set to 5 mm × 7 mm. .

In the silicon nitride sintered body of the present embodiment, the rare earth element (RE) constituting the oxide of the rare earth element is a lanthanoid element (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb). , Dy, Ho, Er, Tm, Yb, Lu), and in order to obtain a ceramic having high thermal conductivity, among these, at least erbium (Er), ytterbium (Yb), and lutetium (Lu). One type is preferred. The reason is that erbium (Er), ytterbium (Yb) and lutetium (Lu) are elements having a small ionic radius among the Group 3 elements of the periodic table, and therefore the composition formula is Si _{6 -Z} Al _Z O _Z. Since the bond with Si, O, and N which are elements constituting β-sialon represented by N ₈ -Z (z = 0.1 to 1) is strong, the transmission of phonons is good and the thermal conductivity is increased. Because it can. In addition, erbium (Er), ytterbium (Yb), and lutetium (Lu) have a strong bond with Si, O, and N, so that lattice vibration due to thermal energy is small and volume expansion due to temperature change is small. This is because the coefficient can be reduced and the thermal shock resistance can be improved.

  FIGS. 2A to 2F are schematic views of an example of a decorative part using the silicon nitride sintered body of the present embodiment, as viewed from above.

  The decorative component 3 shown in FIGS. 2A to 2F is different from the decorative member 1 and the decorative member 1 made of the silicon nitride-based sintered body of the present embodiment that exhibits an extremely black color when the decorative surface is viewed in plan view. It is an example of what is arrange | positioned along with the decorative member 2 which has a decorative surface of a color tone. As the shapes of the decorative member 1 and the decorative member 2, FIG. 2 (a) is a triangular shape, (b) is a quadrangular shape, (c) is a parallelogram shape, and (d) Is a combination of a hexagonal shape and a triangular shape, (e) is a combination of an octagonal shape and a quadrangular shape, and (f) is a quadrilateral decorative member 1 and a decorative member 2 surrounding the decorative member 1 and It is a combination.

  Further, if the color tone of the decorative member 2 is golden, the combination with the extremely black color tone exhibited by the decorative member 1 enhances the visibility, and uses for which visual recognition from a distance is required, for example, display components such as a guide plate Can be suitably used. Furthermore, if the color tone of the decorative member 2 is silver, it is possible to enhance the decorativeness that is more luxurious.

  The decorative member 2 may be any material that enhances the decorativeness with a color tone different from that of the decorative member 1. Therefore, the material is not limited, and the shapes and combinations of the decorative member 1 and the decorative member 2 are those shown in FIG. Needless to say, the present invention is not limited to (a) to (f).

  Moreover, a decorative part for a watch which is another example of the decorative part of the present embodiment is characterized by using the silicon nitride sintered body of the present embodiment having the above-described configuration, and examples thereof include a watch case and There is a watch band piece.

  FIG. 3 shows an example of a watch case that is a decorative part for a watch using the silicon nitride sintered body of the present embodiment, and (a) is a perspective view of the watch case as viewed from the front side. (b) is the perspective view which looked at the case for timepieces of (a) from the back side. FIG. 4 is a perspective view showing another example of a watch case which is a decorative part for a watch using the silicon nitride sintered body of the present embodiment. FIG. 5 is a bottom view showing an example of a watch back cover, which is a watch decorative part using the silicon nitride sintered body of the present embodiment. FIG. 6 is a schematic view showing an example of the configuration of a watch band that is a decorative part for a watch using the silicon nitride sintered body of the present embodiment. In addition, when showing the same site | part in these figures, the same code | symbol is attached | subjected.

  A watch case 10A shown in FIGS. 3 (a) and 3 (b) has a recess 11 for housing a movement (drive mechanism) (not shown), and a foot for fixing a watch band (not shown) for mounting the watch on an arm. The concave portion 11 includes a thin bottom portion 13 and a thick trunk portion 14. The watch case 10B shown in FIG. 4 fixes a hole 15 for receiving a movement (drive mechanism) (not shown) and a watch band (not shown) for attaching the watch to the arm formed on the body 14. And a foot 12 to be provided.

  A watch case back cover 17 shown in FIG. 5 is attached to a plurality of attachment holes 18 provided on the peripheral side through screws (not shown), for example, from the back side of the watch case 10B shown in FIG.

  The band piece constituting the watch band 50 shown in FIG. 6 has a middle piece 20 having a through hole 21 into which the pin 40 is inserted, and a pin hole 31 into which the both ends of the pin 40 are inserted. The pin 40 is inserted into the through hole 21 of the middle piece 20, and both ends of the inserted pin 40 are inserted into the pin holes 31 of the outer piece 30, thereby And the outer piece 30 are sequentially connected to form a watch band 50.

The decorative parts of the present embodiment used as the band pieces constituting the watch cases 10A and 10B, the watch back cover 17 and the watch band 50 are made of the silicon nitride sintered body of the present embodiment. Therefore, it is possible to obtain a high-class feeling and aesthetic satisfaction as a watch, to obtain mental comfort through vision and to increase production efficiency by increasing processing efficiency. It can be a decorative component with high added value.

  The watch decorative part of the present embodiment includes a heart rate monitor and a pulse meter decorative part of the type attached to the wrist.

  In the silicon nitride sintered body of this embodiment, the Vickers hardness (Hv) of the decorative surface is one of the factors affecting the long-term reliability, and the Vickers hardness (Hv) is preferably 13 GPa or more. When the Vickers hardness (Hv) is in this range, the decorative surface is difficult to be damaged, so that the decorative surface is not easily damaged even when it comes into contact with a substance having high hardness such as dust made of glass or metal. Because. The Vickers hardness (Hv) of this decorative surface can be measured according to JIS R 1610-2003.

Further, the fracture toughness affects the processing characteristics and the wear resistance of the decorative surface. In order to obtain a sintered body having both characteristics, the silicon nitride-based sintered body of the present embodiment has 6.5 MPa · m ^{1/2. 2} or more 8MP
a · m ^½ or less is preferable. This fracture toughness can be measured in accordance with the indenter press-in method (IF method) defined in JIS R 1607-1995.

In the case where the silicon nitride sintered body is worn and used, the lighter one is preferred. Therefore, in the silicon nitride sintered body of this embodiment, the apparent density is 3.4 g / cm ³ or less. (0g
/ Cm ³ is preferable to be the exception), the apparent density is measured according to JIS R 1634-1998. In addition, allergens such as mercury, nickel, tin, zinc, and palladium may cause irritation to the skin if they are exposed to the skin for a long time. Each content is 0.1% by mass or less with respect to 100% by mass of the sintered body, and is preferably 0.5% by mass or less in total. The content of such allergic metals can be measured by ICP (Inductively Coupled Plasma) emission spectroscopy.

  Next, an example of each manufacturing method of the silicon nitride sintered body and the decorative part of the present embodiment will be described.

First, the β conversion rate is 40% or less, the composition formula is represented by Si _6-Z Al _Z O _Z N _8-Z , the solid solution amount z is 0.5 or less, and the average value of the aspect ratio is 1.4. The above silicon nitride powder and calcium oxide, aluminum oxide and rare earth oxide powders as a sintering aid are wet mixed using a barrel mill, rotary mill, vibration mill, bead mill or attritor. Pulverize into a slurry. In order to obtain a columnar crystal mainly composed of silicon nitride which is β-sialon represented by a composition formula of Si _6-Z Al _Z O _Z N _8-Z (z = 0.1 to 1),
A silicon nitride powder having a solid solution amount z of 0.05 or more and 0.5 or less may be used.

Here, the total of the powders of calcium oxide, aluminum oxide and rare earth element oxides, which are sintering aids, is 100% by mass of the sum of the silicon nitride powder and the sum of these sintering aid powders.
3 mass% or more and 18.2 mass% or less, and the content of each sintering aid is based on the total of 100 mass% of calcium oxide, aluminum oxide and rare earth element oxide. The contents of calcium oxide and aluminum oxide are 0.3% by mass or more and 1.5% by mass or less and 14.2% by mass or more and 48.8% by mass or less, respectively, and the remainder may be an oxide of a rare earth element. Further, with respect to the total of the silicon nitride powder and the sintering aid powder, each of the ferric oxide and tungsten oxide powders is 0.2% by mass to 3% by mass in terms of Fe, and 0.1% by mass in terms of W. More than 3 mass% may be added.

  The added ferric oxide and tungsten oxide powders react with silicon nitride, which is the main phase in the firing described later, to release oxygen and produce iron and tungsten silicides, respectively.

As another example, the content of the sintering aid is 100% by mass of aluminum oxide, magnesium oxide and calcium oxide, and the content of aluminum oxide and magnesium oxide is 12% by mass or more and 22% by mass, respectively. % Or less, 20 mass% or more and 33 mass% or less, with the balance being calcium oxide.

By the way, there are two types of silicon nitride, α-type and β-type, due to the difference in crystal structure of silicon nitride. The α type is stable at low temperatures, the β type is stable at high temperatures, and the phase transition from α type to β type occurs irreversibly at 1400 ° C or higher. Here, the β conversion rate is α (102 obtained by the X-ray diffraction method.
) The sum of the peak intensities of the diffraction lines and α (210) diffraction lines is I _α , β (101) diffraction lines and β (210)
This is a value calculated by the following equation, where I _β is the sum of peak intensities with diffraction lines. β conversion rate = {I _β / (I _α + I _β )} × 100 (%)
The β conversion rate of the silicon nitride powder affects the strength and fracture toughness values of ceramics mainly composed of silicon nitride. The reason why silicon nitride powder having a β conversion ratio of 40% or less is used is that both strength and fracture toughness values can be increased. Silicon nitride powder having a β conversion ratio of more than 40% becomes a nucleus of grain growth in the firing step, tends to be coarse and crystals having a small aspect ratio, and there is a risk that strength and fracture toughness values are lowered. Therefore, it is particularly preferable to use a silicon nitride powder having a β conversion rate of 10% or less, whereby the solid solution amount z can be 0.05 or more.

Further, the solid solution amount z affects the thermal conductivity of the silicon nitride sintered body of the present embodiment, and the use of powder having a solid solution amount z of 0.5 or less is a columnar shape having an aspect ratio of 5 or more after sintering. This is because crystals are obtained and both the strength and thermal conductivity of the silicon nitride sintered body can be increased.

  As balls used for pulverizing silicon nitride powder, balls made of various sintered bodies such as silicon nitride, zirconia, and alumina can be used. However, a material that does not easily contain impurities, or silicon nitride having the same material composition. A ball made of a sintered material is suitable.

It should be noted that the silicon nitride powder is pulverized until the particle size (D ₉₀ ) at which the cumulative volume is 90% when the sum of the cumulative volume of the particle size distribution curve is 100% is 3 μm or less. It is preferable from the viewpoint of improving the cohesiveness and making the crystal structure columnar. The particle size distribution obtained by pulverization can be adjusted by the outer diameter of the ball, the amount of the ball, the viscosity of the slurry, the pulverization time, and the like.

Then, the ground in a short time, the particle diameter (D ₅₀₎ in advance at a cumulative 50% volume it is preferable to use the following powder 1 [mu] m.

Next, the slurry is passed through a mesh having a particle size number of 200 described in ASTM E 11-61 or a sieve having a finer mesh than this mesh to remove foreign matters, and then the slurry is spray-dried using a spray dryer. Granulate.

Then, the obtained granules and the plastic resin are put into a kneader, and the clay obtained by kneading while heating is put into a pelletizer to obtain pellets as a raw material for injection molding. In addition, as a thermoplastic resin thrown into the kneader, ethylene vinyl acetate copolymer, polystyrene, acrylic resin, etc. are 10% by mass with respect to 100 parts by mass of the obtained granules.
It may be added at 35% by mass or less. As the kneader kneading conditions, the heating temperature is 140.
What is necessary is just to set to 180 degreeC or more, and what is necessary is just to set suitably other conditions, such as a pressure, according to the raw material of the ceramic to be used, the kind of thermoplastic resin, or an additive. The obtained pellet-shaped kneaded body is melted by heating the cylinder attached to the injection molding machine to about 150 ° C. using an injection molding machine equipped with a mold having a predetermined shape. The desired molded product can be obtained by molding the pressing force, pressurizing time, and injection speed at 50 MPa to 200 MPa, 10 seconds to 180 seconds, and 50 cm ³ / second to 1000 cm ³ / second, respectively.

  Here, in order to make the diffraction intensity ratio I (101) / I (210) on the polished surface of the silicon nitride-based sintered body greater than 1, the surface in contact with the melted kneaded body is previously subjected to electric discharge machining. By using a mold having a controlled arithmetic average roughness Ra, by changing the orientation of the crystal grains constituting the kneaded body in the vicinity of the surface of the mold, the silicon nitride crystals inside the silicon nitride-based sintered body It is preferable to make the direction of the particles different from the polished silicon nitride sintered body on the surface. More preferably, if the value of the kurtosis Rku on the surface is larger than 3, the orientation of crystal grains constituting the kneaded body can be easily changed.

Moreover, in order to obtain a silicon nitride sintered body having an open porosity of 0.5% or less on the surface, a silicon nitride powder having a particle size (D ₅₀ ) of 1 μm or less with a cumulative volume of 50% may be used in advance.

In order to obtain a silicon nitride sintered body having a maximum opening diameter of open pores on the surface of 0.1 mm or less, for example, the pressure may be set to 120 MPa or more.

The obtained molded body is degreased in a nitrogen atmosphere or a vacuum atmosphere, for example, with a holding time of 15 hours to 48 hours. The degreasing temperature varies depending on the kind of the added organic binder, but it is preferably 900 ° C. or lower, and particularly preferably 500 ° C. or higher and 800 ° C. or lower. Further, the content on the surface of the silicon nitride-based sintered body can be controlled by the retention time in degreasing. To make the carbon content 0.3 mass% or less, the retention time is, for example, 24 hours or more 48 It should be less than the time.

Next, the compact is placed in a firing furnace in which a graphite resistance heating element used for firing a general silicon nitride shaped compact is placed and fired. About temperature, it heats up in a vacuum atmosphere from room temperature to 300-1000 degreeC, Then, nitrogen gas is introduce | transduced and nitrogen partial pressure is maintained at 10-2000 kPa. At this time, since the open porosity of the compact is about 40 to 55%, the compact is sufficiently filled with nitrogen gas. When the temperature is continued to rise, the above-mentioned components undergo a solid phase reaction in the vicinity of 1000 to 1400 ° C. to form a liquid phase component, and β-sialon is precipitated in a temperature range of about 1400 ° C. or higher. In order to obtain a fine crystal structure, the temperature should be further increased and the firing temperature may be set to 1700 ° C. or higher and lower than 1800 ° C. and held for 10 to 15 hours.

  Further, if a method of embedding the compact in a powder mainly composed of silicon nitride or silicon carbide is used as a method for arranging the compact, it can be fired in the air in an electric furnace. When such a method is used, since the molded body is embedded in the powder, oxygen gas in the atmosphere is shut off, and the firing atmosphere is substantially a nitrogen atmosphere.

  And the decorative part of this embodiment can be obtained by carrying out the barrel grinding | polishing, after lapping the surface of the obtained sintered compact as needed.

Here, in order to adjust the arithmetic average roughness Ra of the surface to be a decorative surface to 0.06 μm or more and 0.25 μm or less, diamond abrasive grains having an average particle diameter of 1.5 μm or more and 3 μm or less, for example, using a tin lapping machine And the lapping time may be 2 hours or more and 6 hours or less. In order to make the arithmetic average roughness Ra 0.03 μm or less, diamond abrasive grains having an average particle diameter of 1 μm or less may be used, and the lapping time may be 4 hours or more and 15 hours or less.

In addition, when the arithmetic average roughness Ra of the surface is 0.06 μm or more and 0.25 μm or less and the kurtosis (Rku) obtained from the surface roughness curve is 2.5 or more and 4.5 or less, it is processed using a rotating barrel polishing machine. do it. For example, the medium is selected from spherical, triangular, rhomboid, cylindrical, and slanted cylinders having a size of 5 to 10 mm, and the abrasive grains are green carborundum (# 80 to # 8000). GC) may be put into a rotary barrel grinder and performed wet for 10 hours or more. In order to make the arithmetic average roughness Ra 0.03 μm or less, the count of the abrasive grains may be set to # 3000 to # 8000. In addition, in order to make the arithmetic average roughness Ra of the surface 0.06 μm or more and 0.25 μm or less, the number of abrasive grains is set to # 120 to # 2000, and the kurtosis (Rku) obtained from the surface roughness curve is 2.5 or more. In order to make it 4.5 or less, the barrel time may be 14 hours or more and 30 hours or less.

  The decorative part of the present embodiment obtained as described above exhibits extremely black color, which is highly evaluated as a particularly beautiful color tone, has a high-class feeling, and can obtain aesthetic satisfaction. As described above, the watch case, the watch decorative piece such as the watch band piece, the mobile phone, the notebook personal computer, the decorative part for the mobile terminal such as the smartphone, the soap case, Coffee cup set, knife, fork, toothbrush, razor handle, earpick, scissors, decorative parts for daily parts such as stamps and business cards, vehicle decorative parts such as emblems and corner poles of manufacturers and car models, golf Decorative parts for sports equipment to decorate clubs and spiked shoes, decorative parts for musical instruments to decorate guitars, etc. And artificial dental crowns, eyeglasses, brooches, necklaces, earrings, rings, bracelets, anklets, tie pins, tie tacks, medals, buttons and other accessories for audio equipment such as headphones or hearing aid casings, floors It can be suitably used as a decorative part for building materials such as tiles for decorating walls and ceilings or grips for door handles. In addition, a watch and a mobile phone are combined, and can be suitably used as a decorative part for a wristwatch type mobile phone having both functions.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

First, 85% by mass of silicon nitride powder having an average particle diameter of 0.6 μm and an average aspect ratio of 1.4, and the balance as powders of calcium oxide, aluminum oxide, and yttrium oxide as sintering aids. Prepared. And each content of calcium oxide, aluminum oxide and yttrium oxide in the silicon nitride sintered body is 0.9% by mass, 31.5% by mass, and the balance with respect to 100% by mass in total of calcium oxide, aluminum oxide and yttrium oxide, respectively. The mixed powder weighed so as to be composed of oxides of rare earth elements was placed in a vibration mill together with water as a solvent and a ball of silicon nitride, and pulverized and mixed for 72 hours using the vibration mill to prepare a slurry. Note that the silicon nitride powder has a β conversion ratio of 10%, and all samples are silicon nitride powders having a solid solution amount z of 0.05 in the composition formula Si _6-Z Al _Z O _Z N _8-Z . Using.

  Next, these slurries were spray-dried using a spray dryer to produce granules.

And with respect to 100 mass% of obtained granules, acrylic resin, polystyrene, ethylene-
By adding 25% by mass of vinyl acetate copolymer, stearic acid, and butyl phthalate (DBP) to the kneader, and adding the clay obtained by kneading while heating to 150 ° C. to the pelletizer Then, a pellet was obtained as a raw material for injection molding. The obtained pellet-shaped kneaded body was molded using a cylinder attached to the injection molding machine using an injection molding machine equipped with a molding die for molding the middle piece 20 of the wristwatch band shown in FIG. The kneaded body is melted by heating the temperature to 150 ° C., and the pressure, pressurization time and injection speed are 100 MPa, 100 seconds, 50
A molded body having a predetermined shape was obtained by molding at 0 cm ³ / sec.

  The molding die was changed for each sample, and the molding die processed so that the arithmetic average roughness Ra of the surface of the molding die in contact with the melted kneaded body was a value shown in Table 1 was used.

Next, in a nitrogen atmosphere at 600 ° C., the holding time is 20 hours, and polyvinyl alcohol (PV
After degreasing A), it is placed in a firing furnace in which a graphite resistance heating element is installed, and the nitrogen partial pressure is 110 kP.
While maintaining a, nitrogen partial pressure, firing temperature and holding time are 200 kPa and 1780 ° C, respectively.
, And fired for 10 hours to obtain a sintered body. Here, the arithmetic average roughness Ra of the surface of each sintered body was measured, and the value is shown in Table 1. The arithmetic average roughness Ra is measured in accordance with JIS B 0601-2001 (ISO 4287-1997). The measurement length and the cut-off value are 5 mm and 0.8 mm, respectively. A stylus having a tip radius of 2 μm was applied, the scanning speed of the stylus was set to 0.5 mm / sec, and the average value of the five locations obtained by this measurement was used as the value of arithmetic average roughness Ra.

  Then, the surface of the obtained sintered body was barrel-polished, and the sample No. 1-4 were obtained. In all samples, the arithmetic average roughness Ra of the decorative surface was 0.03 μm or less. The arithmetic average roughness Ra of the decorative surface was measured by the same method as described above.

Then, the diffraction intensities I (101) and I (210) of the (101) plane and the (210) plane of β-silicon nitride in each sample and on the polished surface are obtained by using an X-ray diffraction method. Measurement was performed to calculate the diffraction intensity ratio I (101) / I (210).

Further, the fracture toughness of each sample was measured in accordance with an indenter press-in method (IF method) defined by JIS JIS R 1607-2010 (ISO 15732-2003 (MOD)).
These values are shown in Table 1.

As can be seen from the results shown in Table 1, Sample No. 2 to 4, the internal diffraction intensity ratio I (101) / I (210) is smaller than 1, and the diffraction intensity ratio I (101) on the polished surface.
/ I (210) is larger than 1, sample No. 1 having a diffraction intensity ratio I (101) / I (210) smaller than 1 in the inside and the surface. Compared to 1, the fracture toughness at the surface is low, and it can be said that the processing efficiency is high.

  A molded body was produced by the same method as shown in Example 1. In each sample, an injection molding machine provided with a mold having an arithmetic average roughness Ra of 0.12 μm on the surface in contact with the melted kneaded body was used.

Next, polyvinyl alcohol (PVA) with a retention time shown in Table 2 in a nitrogen atmosphere at 600 ° C.
After degreasing, the nitrogen partial pressure, the firing temperature and the holding time were respectively set to 200 kPa, 1780 ° C., 10 in a state where the graphite resistance heating element was installed and the nitrogen partial pressure was maintained at 110 kPa.
It baked as time and the sintered compact was obtained.

  Then, the surface of the obtained sintered body was barrel-polished to obtain a sample No. which is the middle piece 20 of the wristwatch band in the example shown in FIG. 5-8 were obtained. Note that the arithmetic mean roughness Ra of the surface of each sample was 0.03 μm or less, and was measured by the same method as that shown in Example 1.

  Also, according to JIS Z 8722-2000, the light source of the spectrocolorimeter (CM-3700d manufactured by Konica Minolta Holdings, Inc.) is set to CIE standard light source D65, the viewing angle is set to 10 °, and the measurement range is set to 3 × 5 mm. Then, the brightness index and chromaticness index on the decorative surface of each sample were measured. And sample no. Sample No. 8 with 8 as the standard sample. The color difference of each sample with respect to 8 was calculated using the above-described formula (A).

  The results are shown in Table 2.

As can be seen from the results shown in Table 2, the sample No. Nos. 6 and 7 have a carbon content of 0.3% by mass or less on the surface, so that carbon diffuses into silicon nitride to form a solid solution and promotes sintering. It seems that the coloration tendency appears slightly and color unevenness is suppressed, and the color difference (ΔE * ab), which is the difference in color tone, can be reduced, so that the color tone generated between decorative parts It can be said that there is almost no difference in feeling.

  A molded body was produced by the same method as shown in Example 1, and fired under the firing conditions shown in Example 2 to obtain a sintered body.

  Then, the surface of the obtained sintered body was barrel-polished, and the sample No. 9-12 were obtained. In any sample, the arithmetic average roughness Ra of the decorative surface was 0.03 μm or less, and was measured by the same method as that shown in Example 1.

  Further, the brightness index and chromaticness index of each sample were measured using the same method as that shown in Example 2.

  As can be seen from the results shown in Table 3, Sample No. In Nos. 9 to 11, since the open porosity on the surface is 0.5% or less, the color unevenness due to the outline formed by the pores is reduced and the color tone on the surface becomes dark, so the value of the lightness index L * becomes small. When the silicon nitride sintered body is used as a decorative part, it can be said that a higher aesthetic satisfaction can be obtained because the texture is further increased.

A molded body was produced by the same method as shown in Example 1. In addition, for molding, each sample was subjected to a pressing time and a pressing time using an injection molding machine provided with a molding die having an arithmetic average roughness Ra of 0.14 μm on the surface in contact with the melted kneaded body. A molded body was obtained by molding at a pressure of 100 seconds and 500 cm ³ / second and with a pressing force shown in Table 4.

Next, in a nitrogen atmosphere at 600 ° C., the holding time is 20 hours, and polyvinyl alcohol (PVA
) Is degreased and placed in a firing furnace in which a graphite resistance heating element is installed, and the nitrogen partial pressure is 110 kPa.
In this state, firing was performed at a partial pressure of nitrogen, a firing temperature and a holding time of 200 kPa, 1780 ° C. and 10 hours, respectively, to obtain a sintered body.

  Then, the surface of the obtained sintered body was barrel-polished, and the sample No. 13-16 were obtained. In any sample, the arithmetic average roughness Ra of the decorative surface was 0.03 μm or less, and was measured by the same method as that shown in Example 1.

As can be seen from the results shown in Table 4, sample No. 13 to 15, since the maximum opening diameter of the open pores on the surface is 0.1 mm or less, the color unevenness due to the difference from other parts is reduced by the contour formed by the open pores, and this silicon nitride sintered body When used as a watch band piece, the color difference (ΔE * ab), which is the difference in color tone, can be reduced, so there is almost no difference in color tone between adjacent band pieces. It can be said that there is no such thing as feeling uncomfortable.

1: decorative member 2: decorative member 3: decorative part
10A, 10B: Watch case
11: Recess
12: Foot
13: Bottom
14: Torso
15: Hole
17: Back cover for watch
20: Nakakoma
21: Through hole
30: Outer piece
31: Pin hole
40: Pin
50: Watch band

Claims (6)

it as a main component β- silicon nitride, obtained using X-ray diffraction method, each of the diffraction intensity of the (101) plane and the (210) plane of the β- silicon nitride I (101), I (210) when the the ratio of the diffraction intensity that is obtained when the arithmetic average roughness Ra was irradiated with X-rays to the polished surface below 0.25μm or 0.06μm I (101) / I ( 210) 1 much larger than the, inside falls deeper than the surface, the ratio of the diffraction intensity obtained when X-rays were irradiated in a plane substantially parallel to said surface I (101) / I (210 ) is less than 1 A silicon nitride-based sintered body characterized by the above.   2. The silicon nitride based sintered body according to claim 1, wherein a content of carbon on the surface is 0.3 mass% or less (excluding 0 mass%).   The silicon nitride based sintered body according to claim 1 or 2, wherein an open porosity on the surface is 0.5% or less.   The silicon nitride based sintered body according to any one of claims 1 to 3, wherein a maximum opening diameter of the open pores on the surface is 0.1 mm or less. The silicon nitride based sintered body according to any one of claims 1 to 4 , wherein a kurtosis (Rku) determined from the roughness curve of the surface is 2.5 or more and 4.5 or less. A decorative part using the silicon nitride sintered body according to any one of claims 1 to 5 .

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