JP4915772B2 - Manufacturing method of ceramic sintered body - Google Patents

Description

  The present invention relates to a method for producing a ceramic sintered body.

  In order to improve the brightness of the high-pressure discharge lamp, the light emission of the luminescent material inside the discharge tube is released to the outside of the discharge tube without being absorbed by ceramics by improving the translucency of the discharge tube. Should be done. From this point of view, at present, it is often formed of translucent alumina having high translucency. And it is usual to make the translucency of a discharge tube high by making the thickness of the discharge tube which consists of translucent alumina as thin as possible.

Examples of such an arc tube for a high-pressure discharge lamp include those described in Patent Documents 1, 2, and 3. Patent Document 4 describes a technique for manufacturing a deformed arc tube made of translucent alumina using a gel cast method.
JP 2002-141021 A JP 2002-164019 A JP 2002-141022 A WO 02/85590

Further, in Non-Patent Document 1, a slurry is prepared using α-alumina fine powder (purity = 99.99%) having an average particle size of 0.24 μm, and an alumina molded body is produced by a slip casting method. . By sintering this alumina molded body, a high-strength translucent alumina sintered body has been successfully produced. In this sintering step, in order to remove fine pores remaining in the sintered body, the sintered body is subjected to hot isostatic pressing for 6 hours at an absolute temperature of 1523K.
“Resources and Materials” 115 (1999) No. 6 pp. 471-474 “Effect of crystal grain size on translucency of sintered alumina

Based on Patent Documents 1 to 4, the applicant of the present application has disclosed, in Patent Document 5, a slurry containing a raw material powder having an average particle size of 0.3 μm or less, a dispersion medium, and a gelling agent. A molded body was obtained by casting and gelling the slurry, and a method was disclosed in which the molded body was sintered (filed on May 10, 2004, unpublished).
Japanese Patent Application No. 2005-154945

  An object of the present invention is to cast a slurry containing a ceramic raw material powder, a dispersion medium, a gelling agent and a dispersing agent, and to obtain a ceramic sintered body by a sintering method. It is to make it possible to promote the conversion and to obtain better translucency.

The present invention relates to a slurry concentration comprising ceramic raw material powder having an average particle size of 0.5 μm or less, a dispersion medium, a gelling agent, a maleic acid copolymer, and a nonionic dispersant having an HLB value of 3 or more and 12 or less. A ceramic sintered body characterized by casting a slurry of 25 to 75% by volume, gelling the slurry to obtain a molded body, and sintering the molded body to obtain a ceramic sintered body. This relates to the manufacturing method.

In the process of continuing to study the method for producing a translucent ceramic sintered body by such a gel cast method, the present inventor uses a maleic acid copolymer and a nonionic dispersant in combination as a dispersant in a slurry. As a result, a molded body with less powder agglomeration and a high filling rate can be obtained. As a result, it was found that the densification was sufficiently promoted at a lower temperature during sintering, and the translucency was thereby significantly improved, and the present invention was achieved. Furthermore, by using a nonionic dispersant having an HLB value of 3 or more and 12 or less, there is a very remarkable effect in terms of short crushing time (ease of crushing) at the time of slurry production.

  Hereinafter, the present invention will be described in more detail, but the present invention is not limited to these specific embodiments, and various modifications are possible.

(Ceramic raw material powder)
The material which can be used by the ceramic sintered compact of this invention is not limited, The following can be illustrated.
Alumina, aluminum nitride, yttria, YAG, Si3N4

  The ceramic sintered body of the present invention is particularly preferably used as a translucent ceramic. Such a material is not limited, but alumina, yttria, YAG (yttrium / aluminum garnet) and quartz are preferable, and translucent alumina is particularly preferable. For example, a raw material obtained by adding an auxiliary of 150 to 1000 ppm to a high-purity alumina powder having a purity of 99.9% or more (preferably 99.95% or more) is preferable.

  As such high-purity alumina powder, high-purity alumina powders “Tymicron TM-D”, “Tymicron TM-DR”, “Tymicron TM-DA”, “Tymicron TM-DAR” manufactured by Daimei Chemical Co., Ltd. “Tymicron TM-5D” can be exemplified.

As the above-mentioned auxiliary agent, magnesium oxide is preferable, but ZrO ₂ , Y ₂ O ₃ , La ₂ O ₃ ,
Sc ₂ O ₃ can also be exemplified.

The average particle diameter of the ceramic raw material powder is set to 0.5 μm or less, and more preferably 0.4 μm or less , from the viewpoint of densification during low temperature sintering and improvement of translucency. More preferably, the average particle size of the ceramic raw material powder is 0.3 μm or less (primary particle size). The lower limit of the average particle size is not particularly limited. The average particle diameter of the raw material powder can be determined by direct observation of the raw material powder by SEM (scanning electron microscope).
The average particle diameter here is n = the value of (longest axis length + shortest axis length) / 2 of primary particles excluding secondary agglomerated particles on an SEM photograph (magnification: X30000, arbitrary two fields of view). It is an average value of 500.

In order to improve the dispersibility and dispersion stability of the ultrafine powder by molding such an ultrafine ceramic powder having an average particle size of 0.3 μm or less by the gel casting method, the sintered body is sintered. There are hardly any pores or defects in the body, and the translucency of the sintered body is remarkably improved.
In particular, even when the molded body is sintered at normal pressure, no pores or defects are observed in the sintered body, and the translucency of the sintered body is remarkably improved. That is, in the past, by employing pressure sintering such as the HIP method, fine pores and defects were prevented from remaining, but without using such a special method, a fine pore and defects were not retained. It becomes possible to obtain a ligation. Such a sintered body has fine particles and is not pressure-sintered at a low temperature, thereby reducing the room for grain growth. For example, even if it is used for a long time at a high temperature of about 1200 ° C. There is no grain growth.

  The gel casting method is a powder in which a slurry containing a ceramic powder, a dispersion medium, and a gelling agent is cast, and then the slurry is solidified by gelation by addition of a temperature condition or a cross-linking agent to obtain a compact. It is a manufacturing method of a molded object.

Examples of the gel casting method include the following methods.
(1) A slurry is prepared by dispersing prepolymers such as polyvinyl alcohol, epoxy resin, phenol resin and the like as a gelling agent together with an inorganic powder in a dispersion medium together with a maleic acid copolymer and a nonionic dispersant. After the casting, the slurry is solidified by three-dimensionally crosslinking with a crosslinking agent and gelling.
(2) The slurry is solidified by chemically bonding an organic dispersion medium having a reactive functional group and a gelling agent. This method is described in Japanese Patent Application Laid-Open No. 2001-335371 and Patent Document 4 of the present applicant. In accordance with the present invention, a maleic acid copolymer and a nonionic dispersant are further mixed in the slurry.

  In the method (2), it is preferable to use an organic dispersion medium having two or more reactive functional groups. Further, 60% by mass or more of the total dispersion medium is preferably an organic dispersion medium having a reactive functional group.

  The viscosity of the organic dispersion medium having a reactive functional group at 20 ° C. is preferably 20 cps or less, and the viscosity of the gelling agent at 20 ° C. is preferably 3000 cps or less. Specifically, it is preferable to solidify the slurry by chemically bonding an organic dispersion medium having two or more ester groups and a gelling agent having an isocyanate group and / or an isothiocyanate group.

  The organic dispersion medium satisfies the two conditions of being a liquid substance capable of solidifying the slurry by chemical bonding with the gelling agent and a liquid substance capable of forming a highly fluid slurry that is easy to cast. is required.

  In order to chemically bond with the gelling agent and solidify the slurry, it has a reactive functional group, that is, a functional group that can form a chemical bond with the gelling agent such as a hydroxyl group, a carboxyl group, or an amino group in the molecule. It is necessary to be.

  The organic dispersion medium need only have at least one reactive functional group, but in order to obtain a more solidified state, it is preferable to use an organic dispersion medium having two or more reactive functional groups. .

  Examples of liquid substances having two or more reactive functional groups include polyhydric alcohols (diols such as ethylene glycol, triols such as glycerin) and polybasic acids (dicarboxylic acids and the like).

  In addition, the reactive functional group in a molecule | numerator does not necessarily need to be the same kind of functional group, and a different functional group may be sufficient as it. Moreover, there may be many reactive functional groups like polyethylene glycol.

  On the other hand, in order to form a highly fluid slurry that is easy to cast, it is preferable to use a liquid material having a viscosity as low as possible, and in particular, it is preferable to use a material having a viscosity at 20 ° C. of 20 cps or less. .

  Since the polyhydric alcohol and polybasic acid described above may have high viscosity due to the formation of hydrogen bonds, even if the slurry can be solidified, it may not be preferable as a reactive dispersion medium. Accordingly, it is preferable to use esters having two or more ester groups such as polybasic acid esters (for example, dimethyl glutarate) and polyhydric alcohol acid esters (for example, triacetin) as the organic dispersion medium. In addition, it is effective to use polyhydric alcohol and polybasic acid for strength reinforcement as long as they do not greatly thicken the slurry.

  This is because esters are relatively stable, but can be sufficiently reacted with a highly reactive gelling agent and have low viscosity, so that the above two conditions are satisfied. In particular, an ester having a total carbon number of 20 or less can be suitably used as a reactive dispersion medium because of its low viscosity.

  In this embodiment, a non-reactive dispersion medium can be used in combination. As the dispersion medium, ether, hydrocarbon, toluene and the like are preferable.

  Further, even when an organic compound is used as the non-reactive dispersion medium, from the viewpoint of ensuring reaction efficiency with the gelling agent, 60% by mass or more of the reactive dispersion medium is included in the total dispersion medium. Is more preferable, and 85% by mass or more is more preferable. Examples of the reactive gelling agent are described in JP-A No. 2001-335371 and Patent Document 4.

  Specifically, this reactive gelling agent is a substance that can chemically bond with the dispersion medium and solidify the slurry. Therefore, the gelling agent in the present invention is not particularly limited as long as it has a reactive functional group capable of chemically reacting with the dispersion medium in the molecule. Any of prepolymers (for example, polyvinyl alcohol, epoxy resin, phenol resin, etc.) may be used.

  However, from the viewpoint of ensuring the fluidity of the slurry, the reactive gelling agent is preferably a material having a low viscosity, specifically, a material having a viscosity at 20 ° C. of 3000 cps or less.

  In general, prepolymers and polymers having a large average molecular weight have high viscosity. Therefore, in the present invention, a monomer or oligomer having a molecular weight smaller than these, specifically, an average molecular weight (by GPC method) of 2000 or less may be used. preferable. Here, “viscosity” means the viscosity of the gelling agent itself (viscosity when the gelling agent is 100%), and a commercially available gelling agent diluted solution (for example, an aqueous solution of the gelling agent). It does not mean the viscosity of.

  The reactive functional group of the gelling agent is preferably selected as appropriate in consideration of the reactivity with the reactive dispersion medium. For example, when an ester having a relatively low reactivity is used as the reactive dispersion medium, a highly reactive isocyanate group (—N═C═O) and / or an isothiocyanate group (—N═C═S). It is preferred to select a gelling agent having

  Isocyanates are generally reacted with diols and diamines, but diols are often highly viscous as described above, and diamines are too reactive to solidify the slurry before casting. May end up.

  Also from such a viewpoint, it is preferable to solidify the slurry by a reaction between a reactive dispersion medium composed of an ester and a gelling agent having an isocyanate group and / or an isothiocyanate group. In order to obtain it, it is preferable to solidify the slurry by a reaction between a reactive dispersion medium having two or more ester groups and a gelling agent having an isocyanate group and / or an isothiocyanate group. In addition, it is effective to use diols and diamines for reinforcing the strength as long as they do not greatly increase the viscosity of the slurry.

  Examples of the gelling agent having an isocyanate group and / or an isothiocyanate group include MDI (4,4′-diphenylmethane diisocyanate) -based isocyanate (resin) and HDI (hexamethylene diisocyanate) -based isocyanate. (Resin), TDI (tolylene diisocyanate) isocyanate (resin), IPDI (isophorone diisocyanate) isocyanate (resin), isothiocyanate (resin) and the like.

  In consideration of chemical characteristics such as compatibility with the reactive dispersion medium, it is preferable to introduce another functional group into the basic chemical structure described above. For example, when making it react with the reactive dispersion medium which consists of ester, it is preferable to introduce a hydrophilic functional group from the point which improves the compatibility with ester and improves the homogeneity at the time of mixing.

  The gelling agent molecule may contain a reactive functional group other than an isocyanate group or an isothiocyanate group, or an isocyanate group and an isothiocyanate group may be mixed. Furthermore, a large number of reactive functional groups may be present, such as polyisocyanate.

In the present invention, a maleic acid copolymer and a nonionic dispersant are mixed in the slurry. (Maleic acid copolymer)
It is a copolymer of a maleic acid compound and other monomers. It is preferable to further modify the copolymer of the maleic acid compound and other monomers with the polymer.

  Examples of maleic acid compound monomers include maleic anhydride, maleic acid and / or maleate. Maleates include alkali metal salts of maleic acid such as monolithium maleate, dilithium maleate, monosodium maleate, disodium maleate, monopotassium maleate, dipotassium maleate, calcium maleate, magnesium maleate, etc. Alkaline earth metal salt of maleic acid, ammonium salt of maleic acid such as monoammonium maleate, diammonium maleate, monomethylammonium maleate, bismonomethylammonium maleate, monodimethylammonium maleate, bisdimethylammonium maleate Alkylamine salt of maleic acid, 2-hydroxyethylammonium maleate, bis-2-hydroxyethylammonium maleate, di (2-hydroxyethyl maleate) And alkanolamine salts of maleic acid such as ammonium) and bisdi (2-hydroxyethyl) ammonium maleate.

  Examples of the monomer to be copolymerized with the maleic acid compound include styrene, vinyl acetate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, acrylic acid, methacrylic acid, methyl acrylate, and methyl methacrylate.

  Examples of the monomer to be copolymerized with the maleic acid compound further include alcohols having a carbon-carbon double bond (eg, allyl alcohol).

  Further, polyoxyalkylene monoalkyl ether and polyoxyalkylene monoallyl ether can be grafted onto the copolymer. As the oxyalkylene group constituting these compounds, an oxyalkylene group having 2 to 18 carbon atoms is preferable, and an oxyethylene group, an oxypropylene group, an oxybutylene group, an oxytetramethylene group, an oxide decylene group, an oxytetradecylene group. Group, oxyhexadecylene group and oxyoctadecylene group are more preferable. Two or more oxyalkylene groups may be present in the same compound, and in that case, either random addition or block addition may be used.

  Moreover, it is preferable that the alkyl group couple | bonded with the ether part of polyoxyalkylene monoalkyl ether and the allyl group couple | bonded with the ether part of polyoxyalkylene monoallyl ether are C1-C24 alkyl groups.

  In the present invention, the nonionic dispersant is not particularly limited as long as it is a nonionic dispersant. Specifically, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block polymers, polyethylene glycol dispersants, polyhydric alcohol partial ester dispersants, Ester ether dispersants, special nonionic dispersants, polyoxyethylene alkyl ester dispersants, polyoxyethylene alkyl ether dispersants, polyoxyethylene alkyl phenol ether dispersants, sorbitan alkyl ester dispersants, polyoxyethylene Sorbitan alkyl ester dispersants are preferred.

  In a preferred embodiment, the nonionic dispersant is an ester of a polyhydric alcohol and a fatty acid. Examples of such polyhydric alcohols include mannitol, sorbitol, and xylitol. As a fatty acid, a C1-C24 fatty acid is preferable and a C1-C18 fatty acid is especially preferable. Further, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, sesquioleic acid, trioleic acid, and behenic acid are preferable.

The HLB value of the nonionic dispersant is 3 or more and 12 or less. It has been found that this does not affect so much densification and translucency at low temperatures, but has a remarkable effect in terms of short crushing time (ease of crushing) during slurry production. .

  From the viewpoint of the present invention, the total amount of the dispersant is preferably 3 parts by weight or more when the weight of the raw material powder is 100 parts by weight. However, since the effect does not increase so much if too much dispersant is added, the total amount of the dispersant is preferably 6 parts by weight or less from the economical viewpoint.

  From the viewpoint of the present invention, the weight ratio of the nonionic dispersant to the total amount of the nonionic dispersant and the maleic acid copolymer dispersant is preferably 5% by weight or more and 40% by weight or less.

  The specific trade name of the maleic acid copolymer is not limited, but “Marialim AKM-053” (allyl alcohol / maleic anhydride, grafted product of styrene copolymer and polyoxyalkylene monoalkyl ether) (Japan) Oil and fat Co., Ltd.) and "Floren G700" (Kyoeisha Chemical) are particularly preferred.

Although it is not limited as a specific brand name of a nonionic dispersing agent, the following can be illustrated.
Polyethylene glycol dispersant (Nissan Nonion S-15, L-2, P-208, NS-210, NS-208.5, HS-210 )
Polyhydric alcohol partial ester dispersant (Nissan Nonion SP-60R, OP-80R, OP-83RAT, PP-40R, LP-20R)
Special nonionic dispersants (Nissan Nonion MN-609, NM-811, A-10R, A-13P, Unilube 34S-32, 10MS-250KB, UNIOX HC-10, HC-40, HC-50, HC- 60)
Polyoxyethylene alkyl ester dispersants (Nissan Nonion L-2, P-6, S-2, S-4, S-6, S-10, S-15, O-2, O-3, O-4 )
Polyoxyethylene alkyl ether dispersants (Nissan Nonion K-201, K-204, K-208, K-210, K-213, K-223)
Polyoxyethylene alkylphenol ether dispersants (Nissan Nonion E-202S, E-205S, E-212, E-206, E-207, S-206, S-207, S-211, S-230)
Polyoxyethylene alkylphenol ether dispersants (Nissan Nonion HS-204.5, HS-206, HS-208, HS-210, HS-215, HS-220, HS-240, NS-204.5, NS-206 NS-208.5, NS-210, NS-212, NS-215, NS-220, NS-230, NS-240, NS-270)
Sorbitan alkyl ester dispersants (CP-08R, LP-20R, MP-30R, PP-40R, SP-60R, OP-80R, OP-83RAT, OP-85R, BP-70R)
Special nonionic dispersant (A-10R, A-13P, MN-811, Unilube 34S-23, 10MS-250KB)
Polyoxyethylene hydrogenated castor oil (Uniox HC-40, HC-60)

The molding slurry can be produced as follows.
(1) A raw material powder and a dispersant are dispersed in a dispersion medium to form a slurry, and then a gelling agent is added.
(2) A slurry is produced by simultaneously adding and dispersing the raw material powder, the dispersant and the gelling agent to the dispersion medium.

  The viscosity of the slurry at 20 ° C. is preferably lower than 600 cps. According to the present invention, the viscosity of the slurry can be remarkably decreased, and the sintering temperature required for densification can be lowered. From this viewpoint, the viscosity of the slurry at 20 ° C. is more preferably 500 cps or less, and most preferably 450 cps or less.

However, if the slurry concentration is too low, the density of the molded body is lowered, which is not preferable in that the strength of the molded body is reduced, cracks are generated during drying / firing, and deformation due to an increase in shrinkage rate is caused. Accordingly, considering that the slurry concentration is 25 to 75% by volume and cracks due to drying shrinkage are reduced, it is more preferably 35 to 75% by volume.

  In addition, various additives such as a catalyst for accelerating the reaction between the dispersion medium and the gelling agent, other dispersants, antifoaming agents, and surfactants for facilitating slurry preparation are included in the molding slurry. Alternatively, it is possible to add a sintering aid or the like for improving the sintered body characteristics.

  In a preferred embodiment, the compact is sintered in a reducing atmosphere. The reducing atmosphere is typically hydrogen and may contain an inert gas.

  The sintering temperature is determined by the material. However, in a preferred embodiment, the maximum temperature during sintering may be 1750 ° C. or lower.

  There is no particular lower limit for the firing temperature, and it is selected depending on the material. Moreover, according to the color tone of a sintered body, you may humidify suitably (dew point -10 + 10 degreeC).

  In a preferred embodiment, the molded body can be degreased at a temperature of 1000 ° C. or higher and 1200 ° C. or lower and then sintered. Degreasing is preferably performed in an air atmosphere. At this time, air or oxygen may be appropriately supplied so that the inside of the furnace does not lack oxygen.

  This degreasing process is effective in promoting the decomposition of organic components, because the organic components in gel casts are less prone to degradation than the organic components in molded products obtained by normal molding (powder press and extrusion). It is effective for suppressing blackening of the sintered body. The degreasing time is not limited, but is preferably 30 hours or longer, and more preferably 60 hours or longer.

  Moreover, you may anneal in air | atmosphere at 1000-1500 degreeC according to a sintered body color tone. At this time, air or oxygen may be appropriately supplied so that the inside of the furnace does not become deficient in oxygen.

  The average particle size of the fired product produced by the method of the present invention is not particularly limited, but is preferably 0.8 μm or more, more preferably 0.9 μm or more, and even more preferably 1.0 μm or more. The average particle size is preferably 5.0 μm or less, more preferably 3.5 μm or less, and even more preferably 3.0 μm or less.

  FIG. 1 is a longitudinal sectional view schematically showing an example of a discharge tube 1A that can be manufactured according to the present invention. FIG. 2 is a longitudinal sectional view schematically showing a high-pressure discharge lamp using the discharge tube 1A of FIG.

  The discharge tube 1A includes a circular tube-shaped central light emitting portion 2A, a pair of tubular end portions 3 provided on both sides of the central light emitting portion 2A, and a pair of connecting portions 4 that connect the central light emitting portion 2A and the end portions 3 to each other. And. The internal space 5 of the central light emitting unit 2A communicates with the internal space 6 of the end 3. 2a is an outer peripheral surface of the central light emitting portion 2A, 2b is an inner peripheral surface of the central light emitting portion 2A, 3a is an outer peripheral surface of the end portion 3, and 3b is an inner peripheral surface of the end portion 3.

  FIG. 2 is a longitudinal sectional view schematically showing a design example of a high pressure discharge lamp using the discharge tube of FIG. In the vicinity of the opening 3c of the end 3 of the discharge tube 1A, a conductive member 8 is fixed with a sealing glass 7, and an electrode device 9 is attached to the end of the conductive member. Then, the internal spaces 5 and 6 are filled with an ionized luminescent material and a starting gas, and arc discharge is generated between the pair of electrode members 9.

  The material of the conductive member was selected from one or more metals selected from the group consisting of molybdenum, tungsten, rhenium, niobium, and tantalum, or one or more metals selected from the group consisting of alumina, yttria, and quartz. A conductive cermet made of ceramic is preferred. Among them, the conductive cermet is advantageous because the difference in thermal expansion from the ceramic discharge tube to be sealed can be reduced, and generation of thermal stress can be suppressed.

  The sealing glass is preferably a mixture of two or more ceramics selected from the group consisting of alumina, yttria, quartz, and rare earth oxides.

  In the case of a metal halide high-pressure discharge lamp, an inert gas such as argon and a metal halide are sealed in the internal space of the ceramic discharge tube, and mercury is sealed as necessary.

  These high-pressure discharge lamps can be applied to various lighting devices such as automobile headlamps, OHP (overhead projector), and liquid crystal projectors.

Moreover, the translucent ceramics of this invention are applicable to the following uses, for example.
Structures in thermal cycle engines that require thermal shock resistance Visual windows in high-temperature furnaces, etc.

(Experiment 1)
500 ppm magnesium oxide powder was added to high-purity alumina powder having a purity of 99.99% or more, a BET surface area of 9 to 15 m ² / g, and a tap density of 0.9 to 1.0 g / cm ³ . This raw material powder was molded by a gel cast method.

  Specifically, 100 parts by weight of this powder, 40 parts by weight of a dispersion medium (dimethyl malonate), 8 parts by weight of a gelling agent (4,4′-diphenylmethane diisocyanate modified product), 0.1 parts of a reaction catalyst (triethylamine) ~ 0.3 parts by weight, maleic acid copolymer and nonionic dispersant were mixed. The total amount of maleic acid copolymer and nonionic dispersant was 3 parts by weight. Table 1 shows the respective weight ratios (parts by weight) when the total amount of the maleic acid copolymer and the nonionic dispersant is 100 parts by weight.

  At 20 ° C., the raw material powder and the dispersant were added and dispersed in the dispersion medium, then the gelling agent was added and dispersed, and finally the reaction catalyst was added to prepare a slurry. The viscosity of this slurry is shown in Table 1.

  This slurry was poured into a mold and left to gel for 2 hours. The gelled molded body was taken out from the mold and dried at 60 to 100 ° C. Subsequently, the molded body was degreased at 1100 ° C. for 2 hours. Firing was performed in 100% Dry hydrogen under the maximum temperature condition such that the bulk density of the sintered body was 99.8% under each condition. Then, annealing was performed in the atmosphere at 1200 ° C. for 5 hours. The slurry viscosity, densification degree (maximum temperature during sintering), and linear transmittance are shown in Tables 1 and 2.

  The obtained ceramic was subjected to double-sided lapping with a thickness of 0.3 mm and measured at a measurement wavelength of 650 nm.

  As can be seen from Tables 1 and 2, when the maleic acid copolymer and the nonionic dispersant are used in combination, the slurry viscosity decreases, that is, the degree of powder aggregation decreases, and the sintering temperature required for densification decreases. Thus, it can be seen that the translucency of the ceramic obtained thereby is remarkably improved. Separately, only 4 parts by weight and 5 parts by weight of slurry were prepared for the total amount of the dispersant, and a fired body was obtained, but the transmittance was almost the same as that of 3 parts by weight.

(Experiment 2)
A slurry was prepared in the same manner as in Experiment 1. However, “Marialim AKM-053” was used as the maleic acid copolymer, and the nonionic dispersant was variously changed as shown in Table 3. The time required for the final viscosity of the slurry to be approximately constant (slurry time) was measured and is shown in Table 3.

  As can be seen from Table 3, by setting the HLB value of the nonionic dispersant to 3 or more and 12 or less, the slurrying time could be shortened to 1 hour or less. However, the HLB value was calculated by the Griffin equation.

It is a longitudinal section showing roughly an example of arc tube 1A which can be manufactured with the method of the present invention. It is a longitudinal cross-sectional view which shows typically the example of the high pressure discharge lamp produced using the arc tube 1A of FIG.

Explanation of symbols

  1A arc tube: 2A light emission part: 7 glass for sealing: 9 electrode member

Claims (11)

A slurry concentration of 25 to 75 volumes containing ceramic raw material powder having an average particle size of 0.5 μm or less, a dispersion medium, a gelling agent, a maleic acid copolymer and a nonionic dispersant having an HLB value of 3 or more and 12 or less. %, A molded body is obtained by gelling the slurry, and a ceramic sintered body is obtained by sintering the molded body.   The method for producing a ceramic sintered body according to claim 1, wherein the ceramic sintered body is a translucent ceramic. The method for producing a ceramic sintered body according to claim 1 or 2 , wherein the molded body is sintered under normal pressure. The method for producing a ceramic sintered body according to any one of claims 1 to 3 , wherein the slurry has a viscosity lower than 600 cps. The method for producing a ceramic sintered body according to any one of claims 1 to 4 , wherein the ceramic sintered body is alumina. The method for producing a ceramic sintered body according to any one of claims 1 to 5 , wherein the sintering is performed in a reducing atmosphere. The dispersion medium is an organic dispersing medium having a reactive functional group, wherein the gelling said slurry by chemically coupling the organic dispersion medium and the gelling agent, according to claim 1 to 6 A method for producing a ceramic sintered body according to any one of the preceding claims. The method for producing a ceramic sintered body according to any one of claims 1 to 7 , wherein the nonionic dispersant is an ester of a polyhydric alcohol and a fatty acid. The method for producing a ceramic sintered body according to claim 8 , wherein the nonionic dispersant is a sorbitan fatty acid ester dispersant. Wherein when the weight of the ceramic raw material powder is 100 parts by weight, wherein the total amount of the dispersing agent is 3 parts by weight or more, the ceramic sintered according to any one of claims 1-9 A method for producing a knot. The weight ratio of the nonionic dispersant is 5% by weight or more and 40% by weight or less when the total weight of the maleic acid copolymer and the nonionic dispersant is 100% by weight. The method for producing a ceramic sintered body according to any one of claims 1 to 10 .

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