JP2007313749A - Manufacturing method of composite structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a composite structure in which each dielectric has a high Q value and the contrast of the dielectric constants is large. <P>SOLUTION: The composite structure, in which a titanium oxide sintered structure and an alumina sintered structure are periodically three-dimensionally arranged, is obtained by mixing alumina powders permeable to UV and a photocurable resin, by obtaining from the mixture of the photocurable resin and the alumina powders a structure of the above mixture by a photofabrication method, by sintering, in the structure of the above mixture, the alumina powders and at the same time removing the photocurable resin to obtain the alumina sintered structure, by putting a slurry containing titanium oxide and not containing an organic binder into a mold holding the alumina sintered structure, and by sintering in the mold the titanium oxide below the sintering temperature of the alumina. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a composite structure in which a plurality of materials having different refractive indexes or dielectric constants are periodically arranged in three dimensions.

  A three-dimensional structure having a complicated shape whose refractive index or dielectric constant changes periodically exhibits an electromagnetic interference effect and a resonance effect, and can be used as an element for an electromagnetic wave in a specific frequency region. In particular, a three-dimensional structure having no defect in the crystal structure is known to exhibit an electromagnetic interference effect and a resonance effect regardless of the irradiation direction of the electromagnetic wave.

  Further, a composite structure in which three-dimensional structures having different dielectric constants are combined is known to have a firm structure because there is no void portion.

Such a composite structure is disclosed in Patent Document 1. In FIG. 1, the structure of the composite structure shown by patent document 1 is shown.
The composite structure 50 is configured by alternately and periodically arranging a high dielectric constant three-dimensional structure 51A and a low dielectric constant three-dimensional structure 51B. The high-dielectric-constant three-dimensional structure 51A and the low-dielectric-constant three-dimensional structure 51B are three-dimensional structures made of dielectric materials having greatly different bending rates or dielectric constants. Has been. Each cube 52 has a side of several hundred to several hundreds of nanometers, and is set to a half wavelength of an electromagnetic wave in a specific frequency region of interest.

  The composite structure 50 having such a configuration blocks electromagnetic waves in a specific frequency region (specific wavelength) in all directions when there is no defect in the crystal structure. When there is a defect in a part of the crystal structure, an electromagnetic wave in a specific frequency region is propagated only in a specific direction with a low loss or bent with a low loss. Thus, the composite structure 50 expresses various electromagnetic wave propagation characteristics with respect to electromagnetic waves in a specific frequency region according to the crystal structure.

Since microfabrication is necessary for the manufacture of such a composite structure, it has been attempted to manufacture the composite structure by combining an optical modeling method and a casting method (see Patent Document 2). In the method disclosed in Patent Document 2, first, low dielectric constant material powder having translucency to ultraviolet rays is mixed (kneaded) with a photocurable resin that is cured by light. Next, the mixture of the photocurable resin and the low dielectric constant material powder is cured by an optical modeling apparatus to form a low dielectric constant three-dimensional structure having a predetermined gap. Next, using this low dielectric constant three-dimensional structure as a mold, a high dielectric constant three-dimensional structure in which a high dielectric constant material powder and a resin are mixed in the gap is cast. In this way, a composite structure is manufactured.
JP 2002-169052 A JP-T-2001-502256

  As described above, the composite structure is configured by combining a high dielectric constant three-dimensional structure and a low dielectric constant three-dimensional structure. In such a composite structure (photonic crystal), the contrast of the dielectric constant is important together with the crystal structure, and by increasing the contrast of the dielectric constant, the electromagnetic wave propagation characteristics caused by the crystal structure can be made remarkable. .

  However, in the conventional composite structure manufacturing method, both the high dielectric constant three-dimensional structure and the low dielectric constant three-dimensional structure are configured to contain a large amount of resin. There is an upper limit, and therefore, the dielectric constant of the high dielectric constant three-dimensional structure cannot be increased, and there is a limit to the remarkable propagation characteristics caused by the crystal structure. In addition, each dielectric has a low Q value, and there is a problem in that a large dielectric loss occurs during use.

  Accordingly, an object of the present invention is to provide a method of manufacturing a composite structure in which each dielectric has a high Q value and a large dielectric constant contrast.

  (1) The composite structure of the present invention includes a step of mixing a powder of a first material that is transparent to ultraviolet light and a photocurable resin, and a powder of the photocurable resin and the first material. Obtaining the structure of the mixture from the mixture by stereolithography, sintering the first material and removing the photocurable resin in the structure of the mixture, and firing the first material. A step of obtaining a bonded structure, a step of injecting a slurry containing a powder of the second material into a mold containing the sintered structure of the first material, and a sintering of the first material in the mold. Sintering the second material at a temperature lower than the temperature to obtain a composite structure in which the sintered structure of the second material and the sintered structure of the first material are periodically arranged in three dimensions To manufacture.

  (2) The second material of the composite structure of the present invention includes any of titanium oxide, barium titanate, strontium titanate, and calcium titanate.

  (3) The first material of the composite structure of the present invention includes any one of alumina, zirconium oxide, magnesium oxide, quartz glass, and hafnium oxide.

  (4) The slurry containing the powder of the second material of the composite structure of the present invention is a slurry containing no organic binder.

  (1) When a powder of a first material that is transparent to ultraviolet rays is kneaded with a photocurable resin, the mixture transmits ultraviolet rays. Therefore, it is possible to create a structure of the mixture from the mixture of the powder of the first material and the photocurable resin by an optical modeling method.

  By heat-treating the structure of the mixture, the photocurable resin is burned and removed, and the first material is sintered. Therefore, a sintered structure of the first material that does not contain a photocurable resin can be obtained.

  Further, a slurry containing the powder of the second material is injected into the mold containing the sintered structure of the first material, and the first material is sintered in the mold containing the slurry and the sintered structure of the first material. Sinter the two materials. Thereby, the sintered structure by the second material can be provided in a space other than the sintered structure of the first material in the mold.

  In the second material sintering step, the second material is sintered at a temperature equal to or lower than the sintering temperature of the first material. However, at such a temperature, almost no thermal deformation occurs in the sintered structure of the first material. Therefore, the shape accuracy of the sintered structure of the second material that is sintered using the sintered structure of the first material as a mold can be increased.

  In this way, a composite structure that does not include a resin can be formed in each of the sintered structure of the first material and the sintered structure of the second material. This composite structure is a photonic crystal containing no resin, and the contrast of the dielectric constant of each sintered structure is large. Moreover, since each sintered structure can be manufactured with high accuracy, the electromagnetic wave propagation characteristics according to the crystal structure can be made remarkable.

  (2) The second material contains any one of titanium oxide, barium titanate, strontium titanate, and calcium titanate. These materials have extremely high dielectric constants, and dielectric loss does not increase even when sintered. Therefore, by using such a material, a sintered structure of the second material having a very high dielectric constant can be obtained, and a composite structure having remarkable electromagnetic wave propagation characteristics can be obtained. If titanium oxide is used as the second material, the sintered structure of the second material having a higher dielectric constant than that of other titanium oxide compounds in the high frequency band of the millimeter wave band or terahertz band to be used. And a composite structure in which the propagation characteristic according to the crystal structure is further remarkable is obtained.

  (3) The first material includes any of alumina, zirconium oxide, magnesium oxide, quartz glass, and hafnium oxide. These materials have translucency with respect to ultraviolet rays. Moreover, it has a sintering temperature characteristic higher than the disappearance temperature of the photocurable resin and the sintering temperature of the second material (for example, titanium oxide, barium titanate, strontium titanate, calcium titanate, etc.). Also, it has a lower dielectric constant than the second material. Further, the material hardly reacts with the second material. In addition, the material does not increase dielectric loss due to sintering. Therefore, a composite structure with more remarkable electromagnetic wave propagation characteristics can be obtained.

(4) The slurry containing the second material is preferably a slurry containing no organic binder. When this slurry is used, the organic binder and its carbon component do not remain when the second material is sintered. In addition, the organic binder has the property of causing large shrinkage due to heating, but by not using the organic binder, the shrinkage can be reduced and a highly accurate crystal structure can be obtained. Therefore, a composite structure with more remarkable electromagnetic wave propagation characteristics can be obtained.

The manufacturing method of the composite structure of this invention is demonstrated with reference to FIG.
FIG. 2 illustrates the appearance of the structure in a part of each process for manufacturing the composite structure.

The procedure for manufacturing this composite structure is as follows.
13 g of a photocurable resin having a specific gravity of 1.1 is added to 64 g of alumina powder (first material powder) made of spherical alumina having an average particle size of 10 μm and a specific gravity of 4.0, and the mixture is stirred for 10 minutes in a stirring deaerator. By defoaming, an alumina mixed stereolithography resin having an alumina powder content of about 57.5 vol% is obtained. In addition, since the precision as a type | mold at the time of sintering of a titanium oxide is decided by the particle size of the alumina powder to be used, it is desirable to determine the particle diameter of an alumina powder according to the precision of the composite structure to be obtained. For example, when a composite structure having an inner diameter of the gap portion of about 1 to 10 mm is manufactured, the particle size is preferably several tens of μm or less.

  Next, titanium oxide powder (second material powder) having an average particle diameter of 1.5 μm, water, and a dispersing agent are mixed at a ratio of 100 g of powder, 14 g of water, and 1 g of dispersing agent, and pulverized and dispersed and mixed for 24 hours by a ball mill. And vacuum defoaming to obtain an emulsion slurry. The slurry containing the powder of the second material is a slurry containing no organic binder.

  Next, an alumina mixed optical modeling resin structure 1 shown in FIG. 2A is created by an optical modeling apparatus using an alumina mixed optical modeling resin. The shape and dimensions of the alumina mixed stereolithography resin structure 1 are designed by CAD. For example, a plurality of tetrapot-like voids each having a radius of 1 mmφ and a height of 3 mm are provided in a three-dimensional manner. And having a diamond-type crystal structure arranged periodically. This crystal structure may be any structure and is determined according to the required electromagnetic wave transmission characteristics.

  Next, this alumina mixed stereolithographic resin structure 1 is put into a pressure degreasing furnace and degreased. First, the furnace is filled with nitrogen pressurized to a pressure of 0.5 MPa. Then, the alumina mixed optical modeling resin structure 1 is heated to 380 ° C. in a furnace. Thereby, the resin component of the photocurable resin is removed (disappeared) by oxidation (combustion / vaporization). Next, this structure is transferred to a sintering furnace and sintered. The structure is heated to 1700 ° C. while air is supplied to the sintering furnace at a flow rate of 1 liter / min, and the temperature is maintained for 2 hours after reaching 1700 ° C. Thereby, the alumina powder is sintered. In this way, an alumina sintered structure (sintered structure of the first material) 2 is obtained from the alumina mixed optical modeling resin structure 1. Alumina has a melting point of about 2000 ° C., and its powder is a high-temperature sintered material that is sintered at about 1700 ° C. This sintering temperature has the most influence on the sintering conditions of the alumina powder. In addition to the sintering temperature, the sintering atmosphere, particle size, and alumina content are also related. For example, the higher the purity of alumina, the higher the temperature required for sintering. Conversely, the lower the purity of alumina, the lower the temperature required for sintering. Therefore, it is desirable to use high-purity alumina when sintering titanium oxide described later at a high temperature. On the other hand, when sintering titanium oxide at a low temperature, it is desirable to use low-purity alumina.

  Next, as shown in FIG. 2 (b), the alumina sintered structure 2 is put inside the outer frame 3 made of alumina or resin, and inside the outer frame and in the void portion of the alumina sintered structure 2. The emulsion slurry is impregnated with a dehydration molding machine. The alumina sintered structure 2 impregnated with the emulsion slurry is dried to form a titanium oxide injection body 4 shown in FIG. Since this emulsion slurry does not contain an organic binder other than the dispersant, the titanium oxide injector 4 does not contain an organic binder, and the titanium oxide content of the titanium oxide injector 4 is increased.

  Next, the dried titanium oxide injection body 4 is taken out from the outer frame 3, put into an electric furnace, heated at 350 ° C. for 4 hours in an air atmosphere, and further heated at 700 ° C. for 4 hours to perform degreasing. As a result, the dispersant component is oxidized (combusted and vaporized) and removed (disappeared). This process can also remove most of the residual carbon of the resin. Subsequently, main baking is performed at 1250 ° C. for 4 hours. Thereby, the titanium oxide is sintered, and a sintered structure of the second material is obtained. Alumina hardly undergoes thermal deformation at about 1250 ° C. Titanium oxide and alumina do not react at about 1250 ° C.

  Through the above steps, a composite structure obtained by combining the alumina sintered structure 2 and the titanium oxide sintered structure 5 is obtained as shown in FIG. The composite structure manufactured by such a method can have a desired dielectric constant contrast, and can have a desired strength of electromagnetic wave propagation characteristics due to the crystal structure. Further, there is no void portion and it is difficult to be influenced by the atmosphere.

  In the embodiment described above, titanium oxide is used as the second material. In addition, the composite structure of the present invention is manufactured using a titanium oxide compound such as barium titanate, strontium titanate, or calcium titanate. And can be configured.

  Further, although alumina is used as the first material, the composite structure of the present invention can be manufactured and configured by using zirconium oxide, magnesium oxide, quartz glass, and hafnium oxide.

  The inventors conducted experiments on electromagnetic wave transmission characteristics as a photonic crystal of the composite structure of alumina and titanium oxide manufactured as described above. The following experiments were used: a composite structure of a diamond structure having a lattice constant of 7 mm made of alumina and titanium oxide produced by the above production method, and a diamond structure having a lattice constant of 7 mm made only of alumina produced by a conventional method as a comparison object. This is a three-dimensional structure.

  FIG. 3A shows the electromagnetic wave transmission characteristics of the alumina-titanium oxide composite structure, and FIG. 3B shows the electromagnetic wave transmission characteristics of the alumina three-dimensional structure. In the figure, the vertical axis represents attenuation, and the horizontal axis represents frequency.

  In the case of the alumina-titanium oxide composite structure of the present invention, a cutoff performance exceeding 10 dB from a low frequency of about 0.6 GHz to a high frequency of about 7 GHz, and 30 dB from a low frequency of about 1.2 GHz to a high frequency of about 6 GHz. Exceeded the blocking performance. On the other hand, in the case of the conventional alumina three-dimensional structure, the cutoff performance exceeding 10 dB was shown from the low frequency of about 2.0 GHz to the high frequency of about 6.5 GHz, but the cutoff performance exceeding 30 dB can be stably obtained. There wasn't.

  As described above, the alumina-titanium oxide composite structure of the present invention has a high dielectric constant due to the high dielectric constant three-dimensional structure made of titanium oxide having a very high dielectric constant and the alumina three-dimensional structure having a relatively low dielectric constant. This is to realize the contrast of rate. This configuration makes the electromagnetic wave propagation characteristics caused by the crystal structure, in this case, the electromagnetic wave blocking performance remarkable, and exhibits a stronger electromagnetic wave passage characteristic than before for a wider frequency band.

It is a figure which shows the structure of the composite structure shown by patent document 1. FIG. It is a figure which shows the external appearance of the structure in a part of process of manufacturing the composite structure which concerns on embodiment of this invention. It is a figure which shows the electromagnetic wave shielding characteristic of each experimental result of the composite structure of this invention, and the conventional three-dimensional structure.

Explanation of symbols

1-Alumina mixed optical modeling resin structure 2-alumina sintered structure 3-outer frame 4-titanium oxide injection body 5-titanium oxide sintered structure

Claims (4)

A step of mixing a powder of a first material that is transparent to ultraviolet rays and a photocurable resin;
Obtaining a structure of the mixture by stereolithography from a mixture of the photocurable resin and the powder of the first material;
In the structure of the mixture, sintering the first material and removing the photocurable resin to obtain a sintered structure of the first material;
Injecting slurry containing powder of the second material into a mold containing the sintered structure of the first material;
In the mold, the second material is sintered at a temperature equal to or lower than the sintering temperature of the first material, and the sintered structure of the second material and the sintered structure of the first material are periodically three-dimensionally. Obtaining a composite structure that is arranged in a mechanical manner.   The method for producing a composite structure according to claim 1, wherein the second material includes any one of titanium oxide, barium titanate, strontium titanate, and calcium titanate.   3. The method of manufacturing a composite structure according to claim 1, wherein the first material includes any one of alumina, zirconium oxide, magnesium oxide, quartz glass, and hafnium oxide.   The method for producing a composite structure according to any one of claims 1 to 3, wherein the slurry containing the powder of the second material is a slurry not containing an organic binder.

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