Slurry, compact, and sintered compact

Abstract

To provide a slurry that can be sintered at low temperatures and in a short time to obtain a densified sintered body.SOLUTION: The slurry contains zirconia powder, glass powder, and polymerizable monomer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to slurries, compacts, and sintered bodies.

Background Art

[0002] As sintering aids for zirconia powder, alumina, silica, aluminum silicate, transition metal oxides, etc. are known (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional zirconia powder requires high temperature and long time during sintering, and the obtained sintered body contains many pores or voids.

[0005] An object of the present invention is to provide a slurry that can be sintered at low temperature and in a short time to obtain a densified sintered body.

Means for Solving the Problems

[0006] The slurry of the present disclosure contains zirconia powder, glass powder, and a polymerizable monomer.

Effects of the Invention

[0007] According to the present disclosure, it is possible to provide a slurry that can be sintered at low temperature and in a short time to obtain a densified sintered body.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0009] Next, the mode for carrying out the present invention will be described.

[0010] <Slurry> The slurry of the present embodiment contains zirconia powder, glass powder, and a polymerizable monomer.

[0011] The zirconia powder is a granule or powder of zirconia (ZrO2).

[0012] Zirconia (ZrO2) is monoclinic at room temperature, but as the temperature rises, its crystal structure undergoes a phase transition to tetragonal and cubic crystals. Since this phase transition is accompanied by a volume change, the sintered body will be destroyed by repeating heating and cooling. Therefore, it is preferable to use partially stabilized zirconia in which a rare earth oxide or the like is solid-solved as a stabilizer in zirconia to form oxygen vacancies in the crystal structure and suppress the destruction due to heating and cooling.

[0013] Examples of such stabilizers include yttria (Y2O3), scandia (Sc2O3), calcia (CaO), magnesia (MgO), ceria (CeO2), praseodymia (Pr2O3), neodymia (Nd2O3), thoria (ThO2), urania (UO2), titania (TiO2), manganese oxide (MnO2), strontia (SrO), barium oxide (BaO), nickel oxide (NiO), cobalt oxide (Co2O4), chromium oxide (Cr2O3, CrO3), etc. Among these, yttria (Y2O3) is preferable as the stabilizer.

[0014] The content of the stabilizer is not particularly limited, but is preferably 1 mol% or more and 8 mol% or less, more preferably 1.5 mol% or more and 6 mol% or less, and still more preferably 2 mol% or more and 5 mol% or less in the zirconia powder. By containing 1 mol% or more and 8 mol% or less of the stabilizer in the zirconia powder, the obtained zirconia sintered body contains tetragonal zirconia particles and becomes excellent in toughness due to stress-induced phase transition.

[0015] The particle size of the zirconia powder is not particularly limited, but is preferably 0.01 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.9 μm or less, and still more preferably 0.2 μm or more and 0.7 μm or less. Here, the particle size means the average particle size defined by the median diameter (d50). When the particle size of the zirconia powder is 0.01 μm or more and 1.0 μm or less, the zirconia powder is easily dispersed in the slurry and a uniform slurry can be obtained.

[0016] The glass powder is glass granules or powder.

[0017] The type of glass is not particularly limited. For example, lithium silicate glass, lithium disilicate glass, lithium metasilicate glass, strontium glass, strontium borosilicate glass, strontium fluoroaluminosilicate glass, barium glass, barium borosilicate glass, barium fluoroaluminosilicate glass, lanthanum glass, lanthanum borosilicate glass, lanthanum fluoroaluminosilicate glass, zinc silicate glass, zinc borosilicate glass, zinc fluorosilicate glass, zinc borate glass, potassium feldspar glass, soda feldspar glass, aluminum fluoride-zirconium fluoride glass, zirconium fluoride (ZBLAN: ZrF4-BaF2-LaF3-AlF3-NaF) glass, etc. may be mentioned. These may be used alone or in combination of two or more. Among these, lithium disilicate glass, barium glass, and zinc fluorosilicate glass are preferable.

[0018] The particle size of the glass powder is not particularly limited, but is preferably 0.01 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.9 μm or less, and still more preferably 0.2 μm or more and 0.7 μm or less. When the particle size of the glass powder is 0.01 μm or more and 1.0 μm or less, the glass powder is easily dispersed in the slurry, and a uniform slurry can be obtained.

[0019] The content of the glass powder is not particularly limited, but is preferably 0.01% by mass or more and 5% by mass or less, preferably 0.05% by mass or more and 3% by mass or less, and still more preferably 0.08% by mass or more and 1% by mass or less in the slurry. By containing 0.01% by mass or more and 5% by mass or less of the glass powder in the slurry, the densification of the sintered body during sintering of the slurry can be efficiently promoted.

[0020] The glass powder preferably further contains silicon dioxide (SiO2). The silicon dioxide may be present as a glass compound in the glass powder or may be present as a solid solution of the glass.

[0021] The content of the silicon dioxide is not particularly limited, but is preferably 10% by mass or more and 85% by mass or less in the glass powder, more preferably 15% by mass or more and 80% by mass or less, and still more preferably 20% by mass or more and 75% by mass or less. By including the glass powder having a silicon dioxide content of 10% by mass or more and 85% by mass or less in the slurry, the densification of the sintered body during sintering of the slurry can be promoted.

[0022] The polymerizable monomer is a compound that polymerizes and cures by heat or light.

[0023] The polymerizable monomer is not particularly limited, and for example, various polymerizable monomers applied in the dental field or the like can be used. Among them, radical polymerizable monomers can be used. The polymerizable monomer may have one functional group or two or more functional groups.

[0024] The specific substances of the polymerizable monomers are not particularly limited. For example, esters such as α-cyanoacrylic acid, (meth)acrylic acid, α-haloacrylic acid, crotonic acid, cinnamic acid, sorbic acid, maleic acid, itaconic acid, etc., (meth)acrylamide, (meth)acrylamide derivatives, vinyl esters, vinyl ethers, mono-N-vinyl derivatives, styrene derivatives, etc. can be mentioned. These polymerizable monomers may be used alone or in combination of two or more. Among them, (meth)acrylate esters and (meth)acrylamide derivatives can be used, and preferably (meth)acrylate esters are used.

[0025] Here, (meth)acrylate ester means acrylate ester (acrylate) or methacrylate ester (methacrylate). Also, (meth)acrylamide means acrylamide or methacrylamide.

[0026] Examples of monofunctional (meth)acrylate esters and (meth)acrylamide derivatives include methyl (meth)acrylate, isobutyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, 2,3-dibromopropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, propylene glycol mono(meth)acrylate, glycerin mono(meth)acrylate, erythritol mono(meth)acrylate, N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-(dihydroxyethyl) (meth)acrylamide, (meth)acryloyloxide decylpyridinium bromide, (meth)acryloyloxide decylpyridinium chloride, (meth)acryloyloxyhexadecylpyridinium chloride, (meth)acryloyloxide decylammonium chloride, etc.

[0027] Examples of the bifunctional (meth)acrylate esters include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6 - hexanediol di(meth)acrylate, 1,10 - decanediol di(meth)acrylate, 2,2 - bis[4 - [3 - (meth)acryloyloxy - 2 - hydroxypropoxy]phenyl]propane, 2,2 - bis[4 - (2 - (meth)acryloyloxyethoxy)phenyl]propane, 2,2 - bis[4 - (meth)acryloyloxypolyethoxyphenyl]propane, 1,2 - bis[3 - (meth)acryloyloxy - 2 - hydroxypropoxy]ethane, pentaerythritol di(meth)acrylate, [2,2,4 - trimethylhexamethylenebis(2 - carbamoyloxyethyl)]di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, and the like.

[0028] Examples of the trifunctional or higher functional (meth)acrylate esters include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, N,N´-(2,2,4 - trimethylhexamethylene)bis[2 - (aminocarboxy)propane - 1,3 - diol]tetramethacrylate, 1,7 - diacryloyloxy - 2,2,6,6 - tetraacryloyloxymethyl - 4 - oxyheptane, and the like.

[0029] Among these, the bifunctional (meth)acrylate esters are preferred as the (meth)acrylate ester, more preferably neopentyl glycol di(meth)acrylate and ethoxylated bisphenol A di(meth)acrylate, and still more preferably neopentyl glycol diacrylate and ethoxylated bisphenol A diacrylate.

[0030] The content of the polymerizable monomer is not particularly limited, but is preferably 2% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less, and still more preferably 10% by mass or more and 20% by mass or less in the slurry. When the content of the polymerizable monomer is 2% by mass or more and 40% by mass, the kneadability of the slurry is improved, and high mechanical strength in the sintered body obtained by sintering or firing the slurry can be maintained.

[0031] The slurry of the present disclosure may contain other components as long as the object of the present invention is not impaired. Examples of other components contained in the slurry include a polymerization initiator, a polymerization inhibitor, a plasticizer, a dispersant, a filler (excluding zirconia powder and glass powder), a colorant, a fluorescent agent, and the like.

[0032] Examples of the polymerization initiator include a chemical polymerization initiator and a photopolymerization initiator.

[0033] The chemical polymerization initiator is not particularly limited, and for example, a thiourea derivative, a vanadium compound, a tertiary amine, and an organic peroxide can be used.

[0034] The thiourea derivative functions as a reducing agent among the chemical polymerization initiators.

[0035] The thiourea derivative is not particularly limited. For example, it includes ethylene thiourea, N-methylthiourea, N-ethylthiourea, N-propylthiourea, N-butylthiourea, N-laurylthiourea, N-phenylthiourea, N-cyclohexylthiourea, N,N-dimethylthiourea, N,N-diethylthiourea, N,N-dipropylthiourea, N,N-dibutylthiourea, N,N-dilaurylthiourea, N,N-diphenylthiourea, N,N-dicyclohexylthiourea, trimethylthiourea, tetramethylthiourea, N-acetylthiourea, N-benzoylthiourea, 1-allyl-3-(2-hydroxyethyl)-2-thiourea, 1-(2-tetrahydrofurfuryl)-2-thiourea, N-tert-butyl-N'-isopropylthiourea, 2-pyridylthiourea, and the like. Among these, N-benzoylthiourea is preferable in terms of improving the curability of the slurry.

[0036] The vanadium compound functions as a reducing agent among chemical polymerization initiators.

[0037] The vanadium compound is not particularly limited. For example, it includes oxovanadium oxalate, vanadyl acetylacetonate, vanadium acetylacetonate, vanadyl stearate, vanadium naphthenate, vanadium benzoylacetonate, and the like. Among these, vanadyl acetylacetonate is preferable in terms of the curability of the slurry.

[0038] The tertiary amine functions as a reducing agent among chemical polymerization initiators. The tertiary amine is not particularly limited. For example, it includes tertiary aliphatic amines and tertiary aromatic amines.

[0039] Examples of the tertiary aliphatic amine include N,N-dimethylaminoethyl methacrylate, triethanolamine, and the like.

[0040] Examples of the tertiary aromatic amine include alkyl p-dialkylaminobenzoate, 7-dimethylamino-4-methylcoumarin, N,N-dimethylaniline, N,N-dibenzylaniline, N,N-dimethyl-p-toluidine, N,N-diethyl-p-toluidine, N,N-bis(2-hydroxyethyl)-p-toluidine, N,N,2,4,6-pentamethylaniline, N,N,2,4-tetramethylaniline, N,N-diethyl-2,4,6-trimethylaniline, and the like. Among these tertiary amines, tertiary aromatic amines are preferred, and alkyl p-dialkylaminobenzoate is more preferred.

[0041] Examples of the alkyl p-dialkylaminobenzoate include methyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, propyl p-dimethylaminobenzoate, amyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethyl p-diethylaminobenzoate, propyl p-diethylaminobenzoate, and the like.

[0042] Among chemical polymerization initiators, organic peroxides function as oxidizing agents.

[0043] Examples of the organic peroxide include benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-amyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethyl-2,5-di(hydroperoxy)hexane, p-diisopropylbenzene monohydroperoxide, p-methane hydroperoxide, pinane hydroperoxide, and the like. Among these, cumene hydroperoxide is preferred in terms of the curability of the slurry.

[0044] The photoinitiator is not particularly limited. For example, camphorquinone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, benzyl ketal, diacetyl ketal, benzyldimethyl ketal, benzyldiethyl ketal, benzylbis(2-methoxyethyl) ketal, 4,4'-dimethyl(benzyldimethyl ketal), anthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 1,2-benzanthraquinone, 1-hydroxyanthraquinone, 1-methylanthraquinone, 2-ethylanthraquinone, 1-bromoanthraquinone, thioxanthone, 2-isopropylthioxanthone, 2-nitrothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chloro-7-trifluoromethylthioxanthone, thioxanthone-10,10-dioxide, thioxanthone-10-oxide, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, bis(4-dimethylaminophenyl) ketone, 4,4'-bis(diethylamino)benzophenone, etc. may be mentioned. Among these, camphorquinone and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide are preferable in terms of improving the curability of the slurry molded body.

[0045] These polymerization initiators may be used alone or in combination of two or more.

[0046] The content of the polymerization initiator in the slurry is not particularly limited. For example, it is 0.001% by mass or more and 10% by mass or less, preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.01% by mass or more and 0.1% by mass or less. When the content of the polymerization initiator in the slurry is 0.001% by mass or more, the curability of the slurry is further improved. When it is 10% by mass or less, the storage stability of the slurry is improved, and the polymerization efficiency when curing the slurry is also improved.

[0047] Examples of the polymerization inhibitor include dibutylhydroxytoluene (2,6-di-tert-butyl-p-cresol), 6-tert-butyl-2,4-xylenol, hydroquinone, 4-methoxyphenol, 4-tert-butylpyrocatechol, tert-butylhydroquinone, and the like. These polymerization inhibitors may be used alone or in combination of two or more. Among these, dibutylhydroxytoluene is preferable in terms of improving the curability of the slurry.

[0048] The content of the polymerization inhibitor in the slurry is not particularly limited. However, when it is contained, it may be 0.0005% by mass or more and 5% by mass or less, preferably 0.001% by mass or more and 1% by mass or less, and more preferably 0.005% by mass or more and 0.1% by mass or less. When the content of the polymerization inhibitor in the slurry is 0.0005% by mass or more and 5% by mass or less, the storage stability of the slurry is improved.

[0049] Examples of the plasticizer include polyethylene glycol, glycerin, propylene glycol, polypropylene glycol, dimethyl phthalate, diethyl phthalate, di-2-ethylhexyl phthalate, dibutyl phthalate, and the like.

[0050] Among these, polypropylene glycol is preferable as the plasticizer. The average molecular weight of polypropylene glycol is preferably 200 or more and 600 or less, more preferably 300 or more and 500 or less, and still more preferably 380 to 420.

[0051] Examples of the dispersant include commercially available dispersants such as polyacrylic acid, sodium polyacrylate, ammonium polyacrylate, formalin-condensed naphthalenesulfonic acid, partially alkyl-esterified polycarboxylic acid, polyether, polyalkylene polyamine, sodium polyphosphate, alkylamine salt of polycarboxylic acid, linear alkylbenzene sulfonic acid, α-sulfofatty acid methyl ester salt, α-olefin sulfonic acid, dialkyl sulfosuccinic acid, alkyl sulfate ester salt, polyoxyethylene alkyl acid ester salt, Disperbyk-110, 162, 180 (manufactured by BYK Chemie GmbH, "Disperbyk" is a registered trademark), and the like.

[0052] Examples of the filler include inorganic fillers other than zirconia powder and glass powder, organic-inorganic composite fillers, cluster fillers, and the like. Hydrophobized fillers may be used. For the hydrophobization treatment of the filler, for example, a silane coupling agent such as γ-methacryloyloxypropyltrimethoxysilane can be used.

[0053] Examples of the colorant include ZrSiO4-Fe2O3, ZrSiO4-V2O5, ZrSiO4-NiO-CoO, CoO-ZnO-Al2O3, MnO-SiO2-Al2O3, NiO, CoO, iron oxide, neodymium oxide, erbium oxide, praseodymium oxide, titanium oxide, alumina, silica, and the like.

[0054] Examples of the fluorescent agent include europium oxide, gallium oxide, gadolinium oxide, neodymium oxide, thulium oxide, bismuth oxide, and the like.

[0055] <Method for manufacturing the slurry> The method for manufacturing the slurry is not particularly limited. For example, the slurry of the present disclosure can be obtained by mixing zirconia powder, glass powder, and a polymerizable monomer and uniformly dispersing them.

[0056] <Formed body> The molded article of the present disclosure is obtained using the slurry of the present disclosure. The method for molding the molded article is not particularly limited, and for example, a method of putting the slurry into a mold and solidifying it (slip casting method, gel casting method, etc.), a layer manufacturing method (active manufacturing, 3D printing, etc.) can be used. Among these, it is preferable to use 3D printing capable of precise molding.

[0057] In 3D printing, a known 3D printer can be used. Examples of the 3D printer method include, for example, stereolithography (SLA) method, digital light processing (DLP) method, etc., and the DLP method is preferable. Examples of commercially available DLP method 3D printers include, for example, MAX UV (manufactured by Asiga), etc.

[0058] Examples of the method of laminating by 3D printing include, for example, a method of irradiating light from above (free liquid surface method), a method of irradiating light from below (regulated liquid surface method), etc. to a container in which the laminated molded article is accommodated. Among these, the regulated liquid surface method is preferable.

[0059] When manufacturing a molded article using the regulated liquid surface method, the lower surface of the container has light transmissibility, and the light emitted from below the container passes through the lower surface of the container and irradiates the molded article. Examples of the irradiated light include, for example, ultraviolet rays with a wavelength of 380 to 450 nm, visible light, etc. Examples of the light source of the irradiated light include, for example, an LED laser, an LED lamp, an LED projector, etc.

[0060] Note that the method for manufacturing the molded article may further include a step of washing the molded article, a step of post-polymerizing the molded article, etc.

[0061] <Sintered body> The sintered body of the present disclosure is obtained by sintering or firing the molded body of the present disclosure. The sintering conditions of the sintered body are not particularly limited. For example, the heating temperature during sintering is 700°C or higher and 2500°C or lower, preferably 900°C or higher and 2000°C or lower, more preferably 1100°C or higher and 1700°C or lower. By setting the heating temperature during sintering to 700°C or higher and 2500°C or lower, a sufficiently degreased and sintered sintered body can be obtained.

[0062] Note that the heating temperature during sintering may be increased stepwise. For example, the molded body may be sintered while increasing the temperature from 1000°C to 1500°C at a rate of 100°C / min. Further, when heating during sintering is increased, each temperature may or may not be held.

[0063] The heating time during sintering is not particularly limited. For example, the heating time during sintering is 10 seconds or longer and 2 hours or shorter, preferably 30 seconds or longer and 1 hour or shorter, more preferably 1 minute or longer and 30 minutes or shorter. By setting the heating time during sintering to 10 seconds or longer and 2 hours or shorter, a degreased and sintered sintered body can be obtained.

[0064] In the slurry of the present disclosure, as described above, by including zirconia powder, glass powder, and a polymerizable monomer, a slurry in which the zirconia powder and the glass powder are uniformly mixed can be molded and cured. Further, the obtained molded body can be sintered by liquid phase sintering. Therefore, the slurry of the present disclosure can be sintered at a low temperature and in a short time. Further, by sintering the slurry of the present disclosure, a densified sintered body can be obtained.

[0065] In the slurry of the present disclosure, as described above, since the glass powder becomes a liquid phase during sintering, it can be sintered at a lower temperature and in a shorter time. Further, the wettability of zirconia with respect to the glass that has become a liquid phase during sintering is improved, and the molded body is likely to shrink due to capillary force, so a more densified sintered body can be obtained.

[0066] In the molded body of the present disclosure, as described above, by being obtained using the slurry of the present disclosure, the effects of the slurry of the present disclosure can be obtained.

[0067] That is, the molded body of the present disclosure is obtained by molding and curing a slurry in which zirconia powder, glass powder, and a polymerizable monomer are uniformly mixed by using a slurry containing zirconia powder, glass powder, and a polymerizable monomer. Further, the molded body of the present disclosure can be sintered by liquid phase sintering. Therefore, the molded body of the present disclosure can be sintered at a low temperature for a short time. Further, by sintering the molded body of the present disclosure, a sintered body that is densified while maintaining the shape of the molded body is obtained.

[0068] In the sintered body of the present disclosure, as described above, by further sintering the molded body obtained by using the slurry of the present disclosure, the effect of the slurry of the present disclosure can be obtained.

[0069] That is, the sintered body of the present disclosure can sinter the molded body obtained by molding and curing a slurry in which zirconia powder and glass powder are uniformly mixed by using a slurry containing zirconia powder, glass powder, and a polymerizable monomer by liquid phase sintering. Therefore, the sintered body of the present disclosure can be obtained by sintering at a low temperature for a short time. Further, the sintered body of the present disclosure is densified while maintaining the shape of the molded body.

[0070] As described above, the sintered body of the present disclosure is obtained by sintering the slurry of the present disclosure at a low temperature for a short time and is densified. Therefore, the slurry of the present disclosure that can obtain such a sintered body can be used for various dental materials. Examples of such dental materials include dental prostheses, dental correction devices, dental surgical guides, dental implants, and the like.

Examples

[0071] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the examples.

[0072] <Production of glass powder> The glass raw materials were thoroughly mixed and stirred using a mortar or a nylon ball mill. The resulting mixture was placed in a platinum crucible and placed in an electric furnace. The electric furnace was heated to 1300°C, melted, thoroughly homogenized, and then poured into water to form lump glass. The lump glass obtained was pulverized for 20 hours using an alumina ball mill, and then passed through a 120 mesh sieve to obtain glass powder. The glass powder was further wet-pulverized for 50 to 70 hours using an alumina ball mill to obtain barium glass powder and zinc fluorosilicate glass powder with a median diameter of 0.4 μm. Upon checking the composition, the zinc fluorosilicate glass powder was found to be 26.4 mass% zinc oxide, 6.5 mass% fluorine, 24.7 mass% silicon dioxide, 9.6 mass% calcium oxide, and 32.5 mass% lanthanum oxide, while the barium glass was 45.0 mass% silicon dioxide, 12.0 mass% boron oxide, 8.9 mass% aluminum oxide, 1.8 mass% fluorine, and 32.3 mass% barium oxide.

[0073] The lithium disilicate glass ceramics was produced by obtaining a lump of glass, and then heating it at 650°C for 60 minutes and then at 850°C for 10 minutes. The composition was confirmed to be 69.8 mass% silicon dioxide, 11.7 mass% lithium oxide, 5.6 mass% aluminum oxide, 5.6 mass% diphosphorus pentoxide, 2.4 mass% potassium oxide, 1.2 mass% sodium oxide, 1.9 mass% zirconium oxide, 1.4 mass% strontium oxide, and 0.4 mass% titanium oxide. The obtained glass ceramics was wet-ground for 15 hours using an alumina ball mill and zirconia media to obtain a glass ceramic powder. The glass powder was further elutriated to obtain a lithium disilicate glass ceramic powder with a median diameter of 0.4 μm.

[0074] <Preparation of slurry> Using a rotation-revolution mixer, 3 mol% yttria-containing zirconia powder was mixed with neopentyl glycol diacrylate and ethoxylated bisphenol A diacrylate as photopolymerizable monomers, polypropylene 400 (polypropylene with an average molecular weight of about 400) as a plasticizer, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as a photopolymerization initiator to obtain a uniform slurry. To this, the above-mentioned glass powder (lithium disilicate glass ceramics powder, barium glass powder, or zinc fluorosilicate glass powder) was added so as to be 0.2% by mass, and the mixture was mixed in a mortar to obtain a slurry that was uniformly dispersed. Examples and comparative examples of the obtained slurries are shown in Tables 1 to 3.

[0075] <Fabrication of Molded Body> The obtained slurry was made into a 50-micrometer thin layer by a film applicator and laminated while irradiating it with light to produce a cured body having a thickness of 1.5 mm. The cured body was cut with a precision cutting machine to obtain a molded body having a length of 5 mm, a width of 5 mm, and a thickness of 1.5 mm.

[0076] <Fabrication of Sintered Body> The obtained molded body was placed in a furnace and degreased and sintered to obtain a sintered body. At this time, the heating rate after the degreasing process was 100 °C / min, and after heating to 1300 °C (without holding), 1400 °C (without holding), 1500 °C (without holding), and 1500 °C·2 hours holding, respectively, it was allowed to cool.

[0077] <Relative Density of Sintered Body> The relative density of the obtained sintered body was measured by the Archimedes method. The relative density was determined from the measured value of the sintered body density obtained by the Archimedes method, the density of 3 mol% yttria-containing zirconia of 6.09 g / cm 3 , and the densities of each sintering aid, lithium disilicate glass ceramics of 2.50 g / cm 3 , barium glass of 2.95 g / cm 3 , and zinc fluorosilicate glass of 3.60 g / cm 3 The relative densities of the respective sintered bodies are shown in Tables 1 to 3.

[0078] <Fracture toughness value> The fracture toughness value was measured using a Vickers hardness tester (FV-700, manufactured by Future-Tech Corporation) in accordance with the IF method described in JIS R1607 "Test Method for Fracture Toughness of Fine Ceramics". The unit of the fracture toughness value is MPa·m 1 / 2 It is. The fracture toughness values of each sintered body are shown in Tables 1 to 3.

[0079] <SEM observation of the material structure> The obtained sintered body was polished using a polydiamond (final polishing grit size 1000), subjected to thermal etching, and then observed with a scanning electron microscope (SEM: Scanning Electron Microscope). An field emission scanning electron microscope (FE-SEM SU-70, manufactured by Hitachi, Ltd.) was used for the SEM. Note that Fig. 1 shows an SEM photograph of the cross-section of the sintered body of Example 19, and Fig. 2 shows an SEM photograph of the cross-section of the sintered body of Comparative Example 4.

[0080]

Table 1

[0081]

Table 2

[0082]

Table 3

[0083] From Tables 1 to 3, the slurries of Examples 1 to 21 had a higher relative density of the obtained sintered body compared to the slurries of the corresponding Comparative Examples 1 to 3. Also, from the results of the SEM observations shown in Figs. 1 and 2, the sintered body of Example 19 was denser compared to the sintered body of Comparative Example 4. From these facts, it was found that a slurry containing glass powder in addition to zirconia powder and a polymerizable monomer can obtain a densified sintered body.

[0084] In addition, the slurries of Examples 3, 6, 9, 12, 15, and 18 had a higher relative density of the sintered body obtained compared to the slurries of Examples 2, 5, 8, 11, 14, and 17. From this, it was found that the slurry to which zinc fluorosilicate glass powder with a low melting point was added as the glass powder had a higher effect of promoting densification of the sintered body obtained than the slurry to which barium glass powder with a high melting point was added as the glass powder.

[0085] Also, from Tables 2 and 3, the sintered bodies in which no tethering was performed in Examples 16 to 18 had the same relative density of the sintered body obtained as compared to the sintered body in which tethering was performed in Comparative Example 4. From this, it was found that the slurry containing zirconia powder, a polymerizable monomer, and further containing glass powder can shorten the sintering time at the same sintering temperature.

[0086] Also, the sintered bodies in which no tethering was performed in Examples 16 to 18 had the same relative density of the sintered body obtained as compared to the sintered bodies in which tethering was performed in Examples 19 to 21. From this, it was found that a sintered body with a densified structure can be obtained even without providing a tethering time during sintering for the slurry containing zirconia powder, glass powder, and a polymerizable monomer.

[0087] Furthermore, the sintered bodies in Examples 16 to 18 had the same fracture toughness value as the sintered body in Comparative Example 4. From this, it was found that a sintered body with high mechanical strength and maintained density can be obtained even when the sintering time is shortened for the slurry containing zirconia powder, glass powder, and a polymerizable monomer.

[0088] The embodiments disclosed above are appended as follows.

[0089] <1> A slurry containing zirconia powder, glass powder, and a polymerizable monomer.

[0090] <2> The slurry according to <1> above, wherein the glass powder contains silicon dioxide.

[0091] <3> The slurry according to <1> or <2> above, which is for dental use.

[0092] <4> A molded body obtained by using the slurry according to any one of <1> to <3> above.

[0093] <5> A sintered body obtained by sintering the molded body according to <4> above.

[0094] The embodiments of the present invention have been described above. However, the present invention is not limited to specific embodiments, and various modifications and changes are possible within the scope of the invention described in the claims.

Claims

**Claim 1** A slurry comprising zirconia powder, glass powder, and a polymerizable monomer. **Claim 2** The slurry according to claim 1, wherein the glass powder contains silicon dioxide. **Claim 3** The slurry according to claim 1, which is for dental use. **Claim 4** A molded body obtained by using the slurry according to any one of claims 1 to 3. **Claim 5** A sintered body obtained by sintering the molded body according to claim 4.

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