Slurry composition for electrode for multilayer ceramic capacitor, electrode layer for multilayer ceramic capacitor, and multilayer ceramic capacitor

Abstract

The purpose of the present invention is to provide a slurry composition for an electrode for a multilayer ceramic capacitor which is capable of forming an electrode layer for a multilayer ceramic capacitor, the electrode layer being capable of imparting excellent sheet attack resistance to a multilayer body for a multilayer ceramic capacitor and reducing hygroscopicity of the multilayer body for a multilayer ceramic capacitor. A slurry composition for an electrode for a multilayer ceramic capacitor according to the present invention contains conductive metal particles, a water-soluble polymer, and a solvent, the water-soluble polymer containing a crosslinkable monomer unit.

Description

Slurry composition for electrodes of multilayer ceramic capacitors, electrode layer for multilayer ceramic capacitors, and multilayer ceramic capacitors

[0001] The present invention relates to a slurry composition for electrodes in multilayer ceramic capacitors, an electrode layer for multilayer ceramic capacitors, and a multilayer ceramic capacitor.

[0002] With the miniaturization and increased performance of electronic devices such as mobile phones and digital equipment, there is a demand for smaller and higher-capacitance electronic components, including multilayer ceramic capacitors. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and miniaturization and increased capacitance can be achieved by thinning these dielectric layers and internal electrode layers.

[0003] Multilayer ceramic capacitors can be manufactured, for example, as follows: First, barium titanate (BaTiO) ３ A slurry composition for electrodes containing conductive metal particles, binder resin, and organic solvent is printed or otherwise applied to the surface of a dielectric layer such as a ceramic green sheet containing powdered dielectric material and binder resin to form a desired electrode pattern. The coated film is then dried to form a dried film (internal electrode layer) to obtain a laminate for a multilayer ceramic capacitor (hereinafter sometimes simply referred to as "laminated body"). Next, the laminates are further stacked so that the internal electrode layer and dielectric layer are alternately stacked, and then heated and compressed to integrate them and form a compressed body. This compressed body is cut, subjected to a de-organic binder treatment in an oxidizing or inert atmosphere, and then sintered to obtain a sintered chip. Subsequently, the slurry composition for electrodes is applied to both ends of the sintered chip, and after sintering, nickel plating or the like is applied to the external electrode surface to obtain a multilayer ceramic capacitor (for example, Patent Document 1, etc.).

[0004] International Publication No. 2019 / 107501

[0005] As mentioned above, when manufacturing multilayer ceramic capacitors, an electrode slurry composition is applied to the surface of the dielectric layer, the applied film is dried, and a dried film (internal electrode layer) is formed to obtain a laminate. However, it is known that during this process, a phenomenon called sheet attack may occur, in which the organic solvent in the electrode slurry composition dissolves the binder resin in the dielectric layer. When sheet attack occurs in the laminate, the dielectric layer becomes less dense, which can degrade the performance of the resulting multilayer ceramic capacitor. Therefore, the development of laminates with excellent resistance to sheet attack is desired.

[0006] Furthermore, laminates can absorb moisture from the external atmosphere during storage, potentially increasing their moisture content. Since increased moisture content can negatively impact the performance of multilayer ceramic capacitors, reducing the hygroscopic properties of the laminate is essential.

[0007] Therefore, the present invention aims to provide a slurry composition for electrodes for multilayer ceramic capacitors that can form an electrode layer for multilayer ceramic capacitors that can impart excellent sheet attack resistance to the laminate for multilayer ceramic capacitors and reduce the moisture absorption of the laminate for multilayer ceramic capacitors. The present invention also aims to provide an electrode layer for multilayer ceramic capacitors that can impart excellent sheet attack resistance to the laminate for multilayer ceramic capacitors and reduce the moisture absorption of the laminate for multilayer ceramic capacitors. Furthermore, the present invention aims to provide a multilayer ceramic capacitor in which at least one of the internal electrode and the external electrode is formed by sintering the above-mentioned electrode layer for multilayer ceramic capacitors.

[0008] The inventors diligently conducted research with the aim of solving the above problems. As a result, the inventors newly discovered that the above problems can be solved with a slurry composition for electrodes of multilayer ceramic capacitors containing conductive metal particles, a water-soluble polymer containing crosslinkable monomer units, and a solvent, and thus completed the present invention.

[0009] In other words, the present invention aims to advantageously solve the above problems, and according to the present invention, slurry compositions for electrodes for multilayer ceramic capacitors described in [1] to [7] below, an electrode layer for a multilayer ceramic capacitor described in [8] below, and a multilayer ceramic capacitor described in [9] below are provided.

[0010] [1] A slurry composition for electrodes for multilayer ceramic capacitors, comprising conductive metal particles, a water-soluble polymer, and a solvent, wherein the water-soluble polymer contains crosslinkable monomer units. In this invention, "contains monomer units" means that "the polymer obtained using those monomers contains repeating units derived from the monomers."

[0011] [2] The slurry composition for electrodes for multilayer ceramic capacitors according to [1] above, wherein the proportion of water in the solvent is 50% by mass or more.

[0012] [3] A slurry composition for electrodes for multilayer ceramic capacitors according to [1] or [2], preferably [2], wherein the content ratio of the crosslinkable monomer units in the water-soluble polymer is 0.1% by mass or more and 10% by mass or less. In this invention, the "content ratio (mass%)" of each monomer unit (each repeating unit) contained in the polymer is, １ H-NMR and １３ It can be measured using nuclear magnetic resonance (NMR) methods such as C-NMR.

[0013] [4] A slurry composition for electrodes for multilayer ceramic capacitors according to any of [1] to [3] above, preferably according to [2] or [3] above, wherein the weight-average molecular weight of the water-soluble polymer is 200,000 or more and 2,000,000 or less. In the present invention, the "weight-average molecular weight" of the water-soluble polymer can be measured using the method described in the examples of this specification.

[0014] [5] A slurry composition for electrodes for multilayer ceramic capacitors according to any of [1] to [4] above, preferably any of [2] to [4] above, wherein the glass transition temperature of the water-soluble polymer is 30°C or more and 100°C or less. In the present invention, the "glass transition temperature" of the water-soluble polymer can be measured using the method described in the examples of this specification.

[0015] [6] A slurry composition for electrodes for multilayer ceramic capacitors according to any of [1] to [5] above, preferably any of [2] to [5] above, further comprising a particulate polymer, wherein the volume average particle diameter of the particulate polymer is 0.01 μm or more and 0.5 μm or less. In the present invention, the "volume average particle diameter" of the particulate polymer means "the particle diameter (D50) at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured by laser diffraction method becomes 50%", and can be measured using the method described in the examples of this specification.

[0016] [7] The slurry composition for electrodes for multilayer ceramic capacitors according to [6] above, wherein the glass transition temperature of the particulate polymer is -60°C or higher and 20°C or lower. In this invention, the "glass transition temperature" of the particulate polymer can be measured using the method described in the examples of this specification.

[0017] [8] An electrode layer for a multilayer ceramic capacitor, obtained by drying a coating film made of any of the slurry compositions for electrodes for multilayer ceramic capacitors described in any of [1] to [7] above, preferably any of [2] to [7] above.

[0018] [9] A multilayer ceramic capacitor comprising an internal electrode, an external electrode, and a dielectric layer, wherein at least one of the internal electrode and the external electrode is formed by sintering the electrode layer for multilayer ceramic capacitors described in [8] above.

[0019] According to the present invention, it is possible to provide a slurry composition for electrodes for multilayer ceramic capacitors that can form an electrode layer for a multilayer ceramic capacitor that can impart excellent sheet attack resistance to the laminate for the multilayer ceramic capacitor and reduce the moisture absorption of the laminate for the multilayer ceramic capacitor. Furthermore, according to the present invention, it is possible to provide an electrode layer for a multilayer ceramic capacitor that can impart excellent sheet attack resistance to the laminate for the multilayer ceramic capacitor and reduce the moisture absorption of the laminate for the multilayer ceramic capacitor. And according to the present invention, it is possible to provide a multilayer ceramic capacitor in which at least one of the internal electrode and the external electrode is formed by sintering the above-mentioned electrode layer for a multilayer ceramic capacitor.

[0020] This is a schematic cross-sectional view showing an example of a multilayer ceramic capacitor of the present invention.

[0021] Embodiments of the present invention will now be described in detail. Herein, the electrode slurry composition for multilayer ceramic capacitors of the present invention (hereinafter sometimes simply referred to as "electrode slurry composition") can be used to form an electrode layer for multilayer ceramic capacitors of the present invention (hereinafter sometimes simply referred to as "electrode layer"). The electrode layer of the present invention is formed by drying a coating film made of the electrode slurry composition of the present invention. The multilayer ceramic capacitor of the present invention uses an electrode formed by sintering the electrode layer of the present invention as at least one of the internal electrode and the external electrode. Each component disclosed herein, as well as preferred embodiments, numerical ranges, and thresholds defining such numerical ranges shown with respect to each component, can be independently combined with each other in any manner.

[0022] (Electrode slurry composition for multilayer ceramic capacitors) The electrode slurry composition of the present invention comprises conductive metal particles, a water-soluble polymer, and a solvent, and optionally further comprises other components. Herein, the electrode slurry composition of the present invention is characterized in that the water-soluble polymer contains crosslinkable monomer units. Furthermore, because the electrode slurry composition of the present invention contains conductive metal particles and a water-soluble polymer containing crosslinkable monomer units in the solvent, it can impart excellent sheet attack resistance to the laminate and reduce the hygroscopicity of the laminate.

[0023] Furthermore, since the electrode slurry composition of the present invention contains conductive metal particles and a water-soluble polymer containing crosslinkable monomer units in the solvent, it is possible to manufacture laminates with excellent sheet attack resistance and reduced hygroscopicity by using this electrode slurry composition. The reason why the above effects are obtained by using the electrode slurry composition of the present invention is not clear, but it is presumed to be as follows.

[0024] The electrode slurry composition of the present invention contains a water-soluble polymer containing crosslinkable monomer units. Because the water-soluble polymer in the electrode slurry composition of the present invention contains crosslinkable monomer units, when forming an electrode layer on a dielectric layer using the electrode slurry composition of the present invention, the solvent contained in the electrode slurry composition can suppress erosion of the dielectric layer. Combined, these effects make it possible to suppress sheet attack in laminates by using the electrode slurry composition of the present invention. Furthermore, because the water-soluble polymer in the electrode slurry composition of the present invention contains crosslinkable monomer units, the water-soluble polymer is prevented from absorbing moisture and expanding in the electrode layer formed using the electrode slurry composition, resulting in a reduction in the hygroscopicity of the laminate. For these reasons, using the electrode slurry composition of the present invention makes it possible to manufacture laminates with excellent sheet attack resistance and reduced hygroscopicity.

[0025] <Conductive Metal Particles> Conductive metal particles are not particularly limited and can include, for example, particles of fourth-period conductive transition metals or their alloys such as vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu); particles of fifth-period conductive transition metals or their alloys such as niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), and silver (Ag); particles of sixth-period conductive transition metals or their alloys such as tantalum (Ta), platinum (Pt), gold (Au), tungsten (W), and iridium (Ir); and particles of other conductive metals or their alloys such as aluminum (Al), sodium (Na), magnesium (Mg), zinc (Zn), potassium (K), lithium (Li), tin (Sn), beryllium (Be), and rhenium (Re). These can be used individually or in combination of two or more. Among these, from the viewpoint of conductivity, corrosion resistance, and cost, particles of conductive transition metals or alloys of the 4th to 5th period are preferred, particles of conductive transition metals or alloys of the 4th period are more preferred, and particles of Ni, Cu, or alloys thereof are even more preferred.

[0026] As the Ni alloy, for example, an alloy of Ni with at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd can be used. The Ni content in the Ni alloy is usually 50% by mass or more, and preferably 80% by mass or more. In addition, the Ni particles may contain several hundred ppm of S (sulfur).

[0027] When the electrode slurry composition of the present invention is used to form the internal electrodes of a multilayer ceramic capacitor, it is preferable to use Pd, Ni, Cu, or an alloy thereof as the conductive metal particles, and more preferably Ni or an alloy thereof. On the other hand, when the electrode slurry composition of the present invention is used to form the external electrodes of a multilayer ceramic capacitor, it is preferable to use Cu or an alloy thereof as the conductive metal particles.

[0028] The average aspect ratio of conductive metal particles is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2. The average aspect ratio of conductive metal particles can be determined, for example, by measuring the major and minor axes of 100 conductive metal particles and calculating the average value of the ratio of major to minor axes (major axis / minor axis).

[0029] The volume-average particle diameter of the conductive metal particles is preferably 0.01 μm or more, more preferably 0.1 μm or more, and preferably 0.5 μm or less. If the volume-average particle diameter of the conductive metal particles is above the lower limit, good dispersibility of the conductive metal particles in the electrode slurry composition can be ensured. On the other hand, if the volume-average particle diameter of the conductive metal particles is below the upper limit, the electrode layer can be uniformly thinned. In this invention, the "volume-average particle diameter" of the conductive metal particles can be measured using the method described in the examples of this specification.

[0030] <Water-soluble polymer> In the electrode slurry composition of the present invention, the water-soluble polymer is a component that can function as a viscosity modifier. Furthermore, in the electrode layer formed using the electrode slurry composition, the water-soluble polymer is a component that can function as a binder, similar to the particulate polymer described later. The water-soluble polymer imparts adhesion to the electrode layer formed using the electrode slurry composition and can hold conductive metal particles contained in the electrode layer so that they do not detach from the electrode layer. In the present invention, a polymer is said to be "water-soluble" if, when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25°C, the insoluble content is less than 1.0% by mass.

[0031] The water-soluble polymer contains at least crosslinkable monomer units and may optionally further contain ethylenically unsaturated acid monomer units and (meth)acrylic acid ester monomer units. If the water-soluble polymer does not contain crosslinkable monomer units, the water-soluble polymer is more likely to absorb moisture and swell in the electrode layer formed using the electrode slurry composition, thus reducing the hygroscopicity of the laminate. Furthermore, if the water-soluble polymer does not contain crosslinkable monomer units, the sheet attack resistance of the laminate decreases. In addition, the water-soluble polymer may contain monomer units other than crosslinkable monomer units, ethylenically unsaturated acid monomer units, and (meth)acrylic acid ester monomer units (hereinafter sometimes referred to as "other monomer units A"). In this invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0032] <<Cross-linkable monomer units>> Cross-linkable monomers that can form cross-linkable monomer units are not particularly limited and include monomers that can form a cross-linked structure by polymerization. Examples of cross-linkable monomers usually include monomers that have thermal cross-linkability. More specifically, examples include cross-linkable monomers having a thermally cross-linkable cross-linkable group and one olefinic double bond per molecule; and cross-linkable monomers having two or more olefinic double bonds per molecule.

[0033] Examples of thermally crosslinkable groups include epoxy groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, and combinations thereof. Among these, epoxy groups are more preferred because they allow for easy adjustment of crosslinking and crosslinking density.

[0034] Furthermore, examples of crosslinkable monomers having an epoxy group as a thermally crosslinkable crosslinkable group and having an olefinic double bond include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allylphenyl glycidyl ether; monoepoxides of dienes or polyenes such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, and 1,2-epoxy-5,9-cyclododecadiene; 3,4 Examples include alkenyl epoxides such as epoxy-1-butene, 1,2-epoxy-5-hexene, and 1,2-epoxy-9-decene; as well as glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl esters of 3-cyclohexenecarboxylic acid, and glycidyl esters of 4-methyl-3-cyclohexenecarboxylic acid.

[0035] Furthermore, examples of crosslinkable monomers having an N-methylolamide group as a thermally crosslinkable crosslinkable group and also possessing an olefinic double bond include (meth)acrylamides having a methylol group, such as N-methylol(meth)acrylamide.

[0036] Furthermore, examples of crosslinkable monomers having an oxetanyl group as a thermally crosslinkable crosslinkable group and having an olefinic double bond include 3-((meth)acryloyloxymethyl)oxetane, 3-((meth)acryloyloxymethyl)-2-trifluoromethyloxetane, 3-((meth)acryloyloxymethyl)-2-phenyloxetane, 2-((meth)acryloyloxymethyl)oxetane, and 2-((meth)acryloyloxymethyl)-4-trifluoromethyloxetane. In this invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0037] Further, examples of the crosslinkable monomer having an oxazoline group as a thermally crosslinkable crosslinkable group and having an olefinic double bond include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

[0038] Further, examples of the crosslinkable monomer having two or more olefinic double bonds per molecule include allyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane-tri(meth)acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, trimethylolpropane-diallyl ether, allyl or vinyl ethers of polyfunctional alcohols other than those described above, triallylamine, methylene bisacrylamide, and divinylbenzene. In the present invention, “(meth)acrylate” means acrylate and / or methacrylate.

[0039] The crosslinkable monomer may be used alone or in combination of two or more kinds. Among these, ethylene glycol dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate are preferable, and ethylene glycol dimethacrylate and allyl glycidyl ether are more preferable.

[0040] The proportion of the crosslinkable monomer unit contained in the water-soluble polymer is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.5% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 5% by mass or less, and particularly preferably 3% by mass or less, with respect to 100% by mass of all repeating units (all monomer units and all structural units) contained in the water-soluble polymer. If the proportion of the crosslinkable monomer unit in the water-soluble polymer is at least the above lower limit, swelling due to moisture absorption of the water-soluble polymer can be suppressed, and the hygroscopicity of the laminate can be further reduced. Also, if the proportion of the crosslinkable monomer unit in the water-soluble polymer is at least the above lower limit, the sheet attack resistance of the laminate can be further improved. On the other hand, if the proportion of the crosslinkable monomer unit in the water-soluble polymer is at most the above upper limit, excessive increase in the hydrophilicity of the water-soluble polymer can be suppressed, and the hygroscopicity of the laminate can be further reduced.

[0041] <Ethylenically unsaturated acid monomer unit> Examples of the ethylenically unsaturated acid monomer that can form an ethylenically unsaturated acid monomer unit include carboxylic acid group-containing ethylenically unsaturated monomers, sulfonic acid group-containing ethylenically unsaturated monomers, phosphoric acid group-containing ethylenically unsaturated monomers, and the like. These may be used singly or in combination of two or more.

[0042] Examples of ethylenically unsaturated monomers containing carboxylic acid groups that can form ethylenically unsaturated monomer units include ethylenically unsaturated monocarboxylic acids and their derivatives, ethylenically unsaturated dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of ethylenically unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of ethylenically unsaturated monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro-β-E-methoxyacrylic acid. Examples of ethylenically unsaturated dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of ethylenically unsaturated dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid monoesters such as nonyl maleic acid, decyl maleic acid, dodecyl maleic acid, octadecyl maleic acid, and fluoroalkyl maleic acid. Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. In addition, as ethylenically unsaturated monomers containing carboxylic acid groups, acid anhydrides that generate carboxylic acid groups by hydrolysis can also be used.

[0043] Examples of sulfonic acid group-containing ethylenically unsaturated monomers that can form sulfonic acid group-containing ethylenically unsaturated monomer units include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, ethyl (meth)acrylic acid-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-alyloxy-2-hydroxypropanesulfonic acid. In this specification, "(meth)allyl" means allyl and / or methallyl.

[0044] Examples of phosphate-containing ethylenically unsaturated monomers that can form phosphate-containing ethylenically unsaturated monomer units include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, ethyl-(meth)acryloyloxyethyl phosphate, and vinylphosphonic acid.

[0045] Among these, ethylenically unsaturated monomers containing a carboxylic acid group are preferred, ethylenically unsaturated monocarboxylic acids are more preferred, acrylic acid and methacrylic acid are even more preferred, and methacrylic acid is particularly preferred.

[0046] Furthermore, the proportion of ethylenically unsaturated acid monomer units contained in the water-soluble polymer is preferably 20% by mass or more, more preferably 25% by mass or more, preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, based on 100% by mass of all repeating units (total monomer units and total structural units) contained in the water-soluble polymer. If the proportion of ethylenically unsaturated acid monomer units in the water-soluble polymer is above the lower limit, the solubility of the water-soluble polymer in the electrode slurry composition can be ensured well. On the other hand, if the proportion of ethylenically unsaturated acid monomer units in the water-soluble polymer is below the upper limit, the hygroscopicity of the laminate can be further reduced.

[0047] <(meth)acrylic acid ester monomer units> Examples of (meth)acrylic acid ester monomers that can form (meth)acrylic acid ester monomer units include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate. Examples include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, and glycidyl methacrylate. These may be used individually or in combination. Among these, ethyl acrylate and n-butyl acrylate are preferred. In this invention, the (meth)acrylic acid ester monomer does not include monomers having two or more olefinic double bonds per molecule, such as allyl (meth)acrylate.

[0048] The proportion of (meth)acrylic acid ester monomer units contained in the water-soluble polymer is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, particularly preferably 62% by mass or more, preferably 80% by mass or less, more preferably 78% by mass or less, and even more preferably 75% by mass or less, based on 100% by mass of all repeating units (total monomer units and total structural units) contained in the water-soluble polymer. If the proportion of (meth)acrylic acid ester monomer units in the water-soluble polymer is above the lower limit above, cracking and chipping of the resulting electrode layer can be suppressed. On the other hand, if the proportion of (meth)acrylic acid ester monomer units in the water-soluble polymer is below the upper limit above, the solubility of the water-soluble polymer in the electrode slurry composition can be ensured well.

[0049] <<Other Monomer Units A>> Other monomer units A are monomer units that can be formed by other monomer units A. Other monomer units A are not particularly limited as long as they are monomers copolymerizable with the monomers that can form the above-mentioned water-soluble polymers. Examples of other monomer units A include aromatic monovinyl monomers such as styrene; olefins such as ethylene and propylene; halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; heterocyclic vinyl compounds such as N-vinylpyrrolidone, vinylpyridine, and vinylimidazole; amino group-containing monomers such as aminoethyl vinyl ether and dimethylaminoethyl vinyl ether; and the like. These other monomer units A may be used individually or in combination of two or more types.

[0050] The content of other monomer units A in a water-soluble polymer is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass (i.e., the water-soluble polymer does not contain other monomer units A), when the total repeating units (total monomer units and total structural units) contained in the water-soluble polymer are taken as 100% by mass.

[0051] <<Properties of Water-Soluble Polymers>> [Weight-Average Molecular Weight] The weight-average molecular weight of the water-soluble polymer is preferably 200,000 or more, more preferably 250,000 or more, even more preferably 300,000 or more, particularly preferably 780,000 or more, preferably 2,000,000 or less, more preferably 1,500,000 or less, even more preferably 1,000,000 or less, and particularly preferably 860,000 or less. If the weight-average molecular weight of the water-soluble polymer is above the lower limit above, the hygroscopicity of the laminate can be further reduced. On the other hand, if the weight-average molecular weight of the water-soluble polymer is below the upper limit above, the adhesion between electrode layers and between the dielectric layer and the electrode layer in the laminate (i.e., the lamination of the electrode layers) can be improved. The weight-average molecular weight of the water-soluble polymer can be adjusted, for example, by changing the amount of molecular weight adjusting agent used in the polymerization of the water-soluble polymer or the polymerization conditions (e.g., polymerization temperature).

[0052] [Glass Transition Temperature] The glass transition temperature of the water-soluble polymer is preferably 30°C or higher, more preferably 35°C or higher, even more preferably 40°C or higher, preferably 100°C or lower, more preferably 80°C or lower, even more preferably 70°C or lower, even more preferably 50°C or lower, and particularly preferably 43°C or lower. If the glass transition temperature of the water-soluble polymer is above the lower limit above, the lamination properties of the electrode layer can be improved. On the other hand, if the glass transition temperature of the water-soluble polymer is below the upper limit above, the hygroscopicity of the laminate can be further reduced. The "glass transition temperature" of the water-soluble polymer can be adjusted, for example, by changing the type and proportion of monomers used in the preparation of the water-soluble polymer.

[0053] <<Content of water-soluble polymer>> The content of water-soluble polymer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less, based on 100 parts by mass of conductive metal particles in the electrode slurry composition. If the content of water-soluble polymer is above the lower limit per 100 parts by mass of conductive metal particles, the hygroscopicity of the laminate can be further reduced. Also, if the content of water-soluble polymer is below the upper limit per 100 parts by mass of conductive metal particles, the lamination properties of the electrode layer can be improved.

[0054] <<Method for Preparing Water-Soluble Polymers>> Water-soluble polymers can be obtained, for example, by polymerizing monomer compositions obtained by mixing each of the above-mentioned monomers with any polymerization solvent in a known manner, using any polymerization method. Here, the polymerization method for water-soluble polymers is not limited, and any of the following methods may be used, for example, solution polymerization methods such as aqueous solution polymerization, slurry polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. Addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used as the polymerization reaction. Additives such as polymerization initiators, polymerization accelerators, emulsifiers, dispersants, and molecular weight modifiers used in polymerization can be those that are commonly used, and the amount used can also be the amount commonly used. Among these, aqueous solution polymerization using water as the polymerization solvent is preferred because it does not require solvent removal and the solvent is highly safe.

[0055] <Solvent> The solvent contained in the electrode slurry composition of the present invention preferably contains water in a proportion of 50% by mass or more, with the total amount of solvent being 100% by mass. Furthermore, the proportion of water in the solvent is more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 99% by mass or more, and most preferably 100% by mass (i.e., the electrode slurry composition of the present invention contains only water as the solvent). It is presumed that an aqueous slurry composition in which the proportion of water in the solvent is 50% by mass or more is less likely to dissolve the binder resin in the dielectric layer compared to a slurry composition containing a large amount of organic solvent, but if the proportion of water in the solvent is above the lower limit mentioned above, the sheet attack resistance of the laminate can be further improved.

[0056] The electrode slurry composition of the present invention may contain organic solvents (e.g., esters, ketones, alcohols). The electrode slurry composition of the present invention may contain one organic solvent or two or more organic solvents.

[0057] <Particulate Polymer> The electrode slurry composition of the present invention preferably further contains a particulate polymer. If the electrode slurry composition further contains a particulate polymer, the lamination properties of the electrode layer can be improved.

[0058] Here, the particulate polymer is a component that can function as a binder, providing adhesion to the electrode layer formed using the electrode slurry composition, and also holding the material contained in the electrode layer (e.g., conductive metal particles) so that it does not detach from the electrode layer. The particulate polymer has a particle shape in the electrode slurry composition, but in the electrode layer, it may exist while maintaining its particle shape or in any non-particle shape.

[0059] Particulate polymers are typically water-insoluble. Therefore, when the solvent in the electrode slurry composition of the present invention is water, the particulate polymers are present in particulate form in the electrode slurry composition of the present invention. Hereinafter, in this specification, a polymer is said to be "water-insoluble" if, when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25°C, the insoluble content is 90% by mass or more. Particulate polymers and water-soluble polymers can be distinguished in that the former are water-insoluble, while the latter are water-soluble.

[0060] The particulate polymer is not particularly limited, and any polymer can be used, for example, conjugated diene polymers, acrylic polymers, etc. Among these, acrylic polymers are preferred. The particulate polymer may be used alone, or two or more types may be used in any ratio.

[0061] <<Conjugated Diene Polymers>> Conjugated diene polymers refer to polymers that contain conjugated diene monomer units. Examples of conjugated diene polymers include polymers containing aromatic monovinyl monomer units and aliphatic conjugated diene monomer units, such as styrene-butadiene polymers (SBR, polymers containing at least styrene units and 1,3-butadiene units) and styrene-isoprene-styrene block copolymers (SIS); polymers consisting only of aliphatic conjugated diene monomer units, such as polybutadiene; and acrylic rubber (NBR) (polymers containing at least acrylonitrile units and 1,3-butadiene units).

[0062] <<Acrylic Polymers>> Acrylic polymers are polymers containing (meth)acrylic acid ester monomer units. Acrylic polymers may optionally contain aromatic monovinyl monomer units, ethylenically unsaturated acid monomer units, and nitrogen-containing monomer units. Furthermore, acrylic polymers may contain monomer units other than (meth)acrylic acid ester monomer units, aromatic monovinyl monomer units, ethylenically unsaturated acid monomer units, and nitrogen-containing monomer units (hereinafter sometimes referred to as "other monomer units B").

[0063] [(meth)acrylic acid monomer units] (meth)acrylic acid monomer units are monomer units that can be formed by (meth)acrylic acid monomers. Examples of (meth)acrylic acid monomers that can be used in the preparation of acrylic polymers include the same monomers as those described above in the "Water-soluble polymers" section. Among these, 2-ethylhexyl acrylate is preferred. (meth)acrylic acid monomers may be used individually or in combination of two or more types.

[0064] The content of (meth)acrylic acid ester monomer units in an acrylic polymer is preferably 35% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, preferably 98% by mass or less, and more preferably 95% by mass or less, when the total repeating units (total monomer units and total structural units) contained in the acrylic polymer are taken as 100% by mass.

[0065] [Aromatic Monovinyl Monomer Units] Aromatic monovinyl monomer units are monomer units that can be formed from aromatic monovinyl monomers. Examples of aromatic monovinyl monomers that can be used in the preparation of acrylic polymers include aromatic monovinyl compounds such as styrene, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. Among these, styrene is preferred. Aromatic monovinyl monomers may be used individually or in combination of two or more types.

[0066] The content of aromatic monovinyl monomer units in an acrylic polymer is preferably 1% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, preferably 60% by mass or less, and more preferably 50% by mass or less, when the total repeating units (total monomer units and total structural units) contained in the acrylic polymer are taken as 100% by mass.

[0067] [Ethylene-Unsaturated Acid Monomer Units] Ethylene-unsaturated acid monomer units are monomer units that can be formed from ethylenically unsaturated acid monomers. Examples of ethylenically unsaturated acid monomers that can be used in the preparation of acrylic polymers include monomers similar to those described above in the "Water-Soluble Polymers" section. Among these, carboxylic acid group-containing ethylenically unsaturated monomers are preferred, itaconic acid and methacrylic acid are more preferred, and itaconic acid is even more preferred. Ethylene-unsaturated acid monomers may be used individually or in combination of two or more types.

[0068] The content of ethylenically unsaturated acid monomer units in an acrylic polymer is preferably 0.1% by mass or more, more preferably 1% by mass or more, preferably 10% by mass or less, and more preferably 5% by mass or less, when the total repeating units (total monomer units and total structural units) contained in the acrylic polymer are taken as 100% by mass.

[0069] [Nitrogen-containing monomer units] Nitrogen-containing monomer units are monomer units that can be formed from nitrogen-containing monomers. Examples of nitrogen-containing monomers that can be used in the preparation of acrylic polymers include unsaturated nitrile compounds such as (meth)acrylonitrile; (meth)acrylamide, N-methylol(meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, N-phenyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, 4-acroylmorpholine, diacetone(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, 2-(meth)acrylamide-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone, and other amide-containing unsaturated compounds. Among these, acrylonitrile and acrylamide are preferred as nitrogen-containing monomers, with acrylonitrile being more preferred. The nitrogen-containing monomers mentioned above may be used individually or in combination of two or more types.

[0070] The content of nitrogen-containing monomer units in an acrylic polymer is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, preferably 40% by mass or less, and more preferably 30% by mass or less, when the total repeating units (total monomer units and total structural units) contained in the acrylic polymer are taken as 100% by mass.

[0071] [Other Monomer Units B] Other monomer units B are monomer units that can be formed by other monomer units B. Other monomer units B are not particularly limited as long as they are monomers copolymerizable with the monomers that can form the acrylic polymers described above. Examples of other monomer units B include the crosslinkable monomers described in the "Water-soluble Polymers" section; olefins such as ethylene and propylene; halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; heterocyclic vinyl compounds such as N-vinylpyrrolidone, vinylpyridine and vinylimidazole; and the like. These may be used individually or in combination of two or more types.

[0072] The content of other monomer units B in the acrylic polymer is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass (i.e., the acrylic polymer does not contain other monomer units B), when the total repeating units (total monomer units and total structural units) contained in the acrylic polymer are taken as 100% by mass.

[0073] <<Properties of Particulate Polymers>> [Volume Average Particle Diameter] The volume average particle diameter of the particulate polymer is preferably 0.01 μm or more, more preferably 0.02 μm or more, even more preferably 0.05 μm or more, preferably 0.5 μm or less, more preferably 0.4 μm or less, and even more preferably 0.3 μm or less. If the volume average particle diameter of the particulate polymer is above the lower limit above, the sheet attack resistance of the laminate can be further improved. On the other hand, if the volume average particle diameter of the particulate polymer is below the upper limit above, the lamination properties of the electrode layer can be improved. Note that the "volume average particle diameter" of the particulate polymer can be adjusted, for example, by changing the polymerization conditions of the particulate polymer (for example, the amount of emulsifier used).

[0074] [Glass Transition Temperature] The glass transition temperature of the particulate polymer is preferably -60°C or higher, more preferably -50°C or higher, even more preferably -40°C or higher, preferably 20°C or lower, more preferably 10°C or lower, and even more preferably 0°C or lower. If the glass transition temperature of the particulate polymer is above the lower limit above, the sheet attack resistance of the laminate can be further improved. On the other hand, if the glass transition temperature of the particulate polymer is below the upper limit above, the lamination properties of the electrode layer can be improved. The "glass transition temperature" of the particulate polymer can be adjusted, for example, by changing the type and proportion of monomers used in the preparation of the particulate polymer.

[0075] <<Content of particulate polymer>> The content of particulate polymer in the electrode slurry composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less, based on 100 parts by mass of conductive metal particles.

[0076] The content of particulate polymer in the electrode slurry composition is preferably 25 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, preferably 400 parts by mass or less, more preferably 300 parts by mass or less, and even more preferably 200 parts by mass or less, based on 100 parts by mass of water-soluble polymer.

[0077] <<Method for Preparing Particulate Polymers>> The polymerization method for particulate polymers is not particularly limited, and any of the following methods may be used, for example, solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. Addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used as the polymerization reaction. The polymerization solvents and additives such as emulsifiers, dispersants, polymerization initiators, and molecular weight modifiers that can be used in polymerization can be general-purpose materials, and the amounts used can also be general-purpose amounts.

[0078] <Other Components> The electrode slurry composition of the present invention may optionally contain other components. Examples of other components include polymer components other than the water-soluble polymer and particulate polymer described above; the additives used when polymerizing the water-soluble polymer and any particulate polymer; dielectric materials; and so on.

[0079] Furthermore, the electrode slurry composition of the present invention preferably contains a dielectric material as another component. The dielectric material is not particularly limited as long as it is a material that has dielectric properties, but it is preferable to use a ceramic material. Examples of ceramic materials include zirconia, aluminum silicate, titanium oxide, zinc oxide, barium titanate, calcium zirconate, calcium titanate, strontium titanate, magnesia, sialon, spinemulite, silicon carbide, silicon nitride, and aluminum nitride. Among these, barium titanate is preferred. These ceramic materials may be used individually or in combination of two or more.

[0080] The content of dielectric material in the electrode slurry composition is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less, based on 100 parts by mass of conductive metal particles.

[0081] <Solid content concentration of electrode slurry composition> The solid content concentration of the electrode slurry composition is preferably 50% by mass or more, more preferably 55% by mass or more, preferably 80% by mass or less, and more preferably 75% by mass or less.

[0082] <Method for preparing electrode slurry composition> The electrode slurry composition described above can be prepared by mixing the conductive metal particles, water-soluble polymer, solvent, and any particulate polymer and other components by known methods. Specifically, the electrode slurry composition can be prepared by mixing the above components using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, lye crusher, ultrasonic disperser, homogenizer, planetary mixer, film mixer, or rotational mixer.

[0083] (Electrode layer for multilayer ceramic capacitors) The electrode layer of the present invention is obtained by drying a coating film made of the electrode slurry composition of the present invention described above. The electrode layer of the present invention is usually a dried film obtained by partially or completely removing the solvent from a coating film made of the electrode slurry composition of the present invention. That is, the electrode layer of the present invention contains the predetermined water-soluble polymer described above and conductive metal particles, and optionally contains particulate polymer, solvent, and other components. Here, since the electrode layer of the present invention is obtained by drying a coating film made of the electrode slurry composition of the present invention, the hygroscopicity of the laminate can be reduced and excellent sheet attack resistance can be imparted to the laminate.

[0084] Furthermore, the components contained in the electrode layer are those contained in the electrode slurry composition described above, and the preferred ratio of each component is the same as the preferred ratio of each component in the electrode slurry composition.

[0085] The thickness of the electrode layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, preferably 10 μm or less, and more preferably 5 μm or less.

[0086] The electrode layer of the present invention has two embodiments: an internal electrode layer and an external electrode layer. The internal electrode layer forms the internal electrodes of a multilayer ceramic capacitor after sintering, and the external electrode layer forms the external electrodes of a multilayer ceramic capacitor after sintering. In the following description, the case in which the electrode layer is an internal electrode layer will be explained as an example, but the present invention is not limited to the example below.

[0087] <Internal Electrode Layer> The internal electrode layer, which serves as the electrode layer in this invention, is typically formed on top of the dielectric layer.

[0088] <<Dielectric Layer>> A dielectric layer can be prepared by applying a slurry composition for dielectric layers onto a release substrate and drying the formed coating film. The slurry composition for dielectric layers can be prepared by conventionally known methods, for example, by mixing dielectric materials, binders, solvents, etc.

[0089] In this process, it is preferable that the release substrate used to produce the dielectric layer is made of a flexible resin. By using a flexible resin as the release substrate, the dielectric layer slurry composition for the dielectric layer can be applied to the release substrate, dried, and the resulting release substrate (laminated film) with the dielectric layer formed on it can be stored in a rolled state and supplied as needed. The release substrate is not particularly limited and examples include substrates containing resins such as polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, and polyvinyl chloride.

[0090] The release substrate preferably has a surface treatment applied to the side on which the dielectric layer is formed to improve its release properties. The surface treatment is not particularly limited and includes, for example, surface treatment using a release agent such as a silicone-based release agent, a fluorine-based release agent, or a wax-based release agent.

[0091] The thickness of the release agent is not particularly limited, but is usually between 20 μm and 100 μm.

[0092] The method for applying the slurry composition for the dielectric layer onto a release substrate is not particularly limited, and known application methods include, for example, using an applicator or various roll coaters such as gravure coaters and comma coaters (registered trademarks).

[0093] The drying method for the coating film formed on the release substrate is not particularly limited, and a known drying method using a hot air dryer can be cited as an example. The drying conditions can be appropriately set according to the solvent content in the coating film, the thickness of the coating film, etc., but the drying temperature is usually 80°C to 150°C, and the drying time is usually 3 minutes to 60 minutes.

[0094] <Method for manufacturing the internal electrode layer> The internal electrode layer, as the electrode layer of the present invention, can be formed by applying the electrode slurry composition of the present invention onto a dielectric layer in a manner that typically results in a desired electrode pattern, and then drying the applied film.

[0095] Various printing methods such as screen printing, gravure printing, stamp printing, inkjet printing, and offset printing using patterns formed by these methods, as well as vacuum deposition methods for forming metal vapor-deposited films, can be applied to form the internal electrode layer.

[0096] The drying method for a coating film formed on a dielectric layer is not particularly limited, and for example, the same method as for drying a coating film formed on a release substrate can be used. The drying conditions can be appropriately set according to the solvent content in the coating film, the thickness of the coating film, etc. The drying temperature is usually 80°C to 150°C, and the drying time is usually 3 minutes to 60 minutes.

[0097] (Multilayer ceramic capacitor) The multilayer ceramic capacitor of the present invention comprises an internal electrode, an external electrode, and a dielectric layer, wherein at least one of the internal electrode and the external electrode is formed by sintering the electrode layer of the present invention described above.

[0098] As described above, an electrode formed by sintering the electrode layer of the present invention can be used as at least one of an internal electrode and an external electrode. That is, the internal electrode of a multilayer ceramic capacitor may be an electrode formed by sintering the electrode layer of the present invention, and the external electrode may be another known external electrode; or the external electrode of a multilayer ceramic capacitor may be an electrode formed by sintering the electrode layer of the present invention, and the internal electrode may be another known internal electrode; or both the internal and external electrodes of a multilayer ceramic capacitor may be electrodes formed by sintering the electrode layer of the present invention.

[0099] Here, the electrodes other than those obtained by sintering the electrode layer of the present invention described above, which can be used in the multilayer ceramic capacitor of the present invention, are not particularly limited, and known electrodes used in the manufacture of multilayer ceramic capacitors can be used.

[0100] Specifically, electrodes other than those formed by sintering the electrodes for the multilayer ceramic capacitor of the present invention can be internal electrodes formed using known internal electrode materials (e.g., conductive paste containing conductive materials, organic solvents, etc.) or external electrodes formed using known external electrode materials (e.g., Cu paste containing glass frit). An example of the multilayer ceramic capacitor of the present invention will be described below with reference to Figure 1, but the multilayer ceramic capacitor of the present invention is not limited thereto.

[0101] Figure 1 is a schematic cross-sectional view showing an example of a multilayer ceramic capacitor of the present invention. The multilayer ceramic capacitor 10 shown in Figure 1 comprises alternately stacked layered dielectrics 11 and layered internal electrodes 12, and a pair of external electrodes 13 are provided on the outside of the dielectrics 11 and internal electrodes 12. One of a pair of internal electrodes 12 adjacent to each other along the stacking direction, with the dielectric 11 in between, is electrically connected to one of a pair of external electrodes 13 inside the multilayer ceramic capacitor 10, and the other of a pair of internal electrodes 12 adjacent to each other along the stacking direction, with the dielectric 11 in between, is electrically connected to the other of a pair of external electrodes 13 inside the multilayer ceramic capacitor 10. As a result, the space between a pair of external electrodes 13 has a structure in which multiple capacitor elements are electrically connected in parallel. Note that the interface between dielectric layers that may be formed when the stacked bodies are stacked is not shown in Figure 1 because the dielectric layers may merge and disappear due to sintering.

[0102] Multilayer ceramic capacitors are not particularly limited and can be manufactured by conventionally known methods. For example, a multilayer ceramic capacitor can be manufactured by optionally peeling off the dielectric layer and internal electrode layer from the release substrate, stacking the laminates so that the dielectric layer and internal electrode layer are alternate, heating and pressing them together, thermally decomposing and removing the binder components (such as the water-soluble polymer and particulate polymer mentioned above) contained in the dielectric layer and internal electrode layer (degreasing treatment), further sintering the laminate, and then forming external electrodes on the end faces of the sintered ceramic product.

[0103] Degreasing is typically performed in a nitrogen atmosphere at a temperature between 300°C and 500°C. The degreasing time is typically between 1 and 5 hours. The content of binder components (such as the water-soluble polymer and particulate polymer mentioned above) in the dielectric layer and internal electrode layer after degreasing is typically 50 ppm or less in total.

[0104] Sintering of degreased laminates typically occurs at an oxygen partial pressure of 10 －９ ~10 －１２ MPa H ２ -N ２ -H ２The process is carried out in a reducing atmosphere such as O gas at a temperature between 1000°C and 1500°C. The sintering time for the laminate is usually between 1 hour and 30 hours.

[0105] External electrodes can be formed by applying an external electrode material to the end face of a sintered ceramic product and then baking it. This allows for the production of a multilayer ceramic capacitor, such as the one shown in Figure 1. Baking is typically performed in a nitrogen atmosphere at a temperature of 500°C to 1500°C. The surface of the external electrodes can also be plated with Ni, Sn, or the like. By using the electrode slurry composition of the present invention described above as the external electrode material applied to the end face of the sintered ceramic product, a multilayer ceramic capacitor of the present invention can be manufactured in which the external electrodes are electrodes formed by sintering the electrode layers of the present invention described above.

[0106] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing quantities refer to mass unless otherwise specified. In addition, in polymers produced by polymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer is usually equal to the ratio of that monomer to the total monomers used in the polymerization of that polymer (starting ratio), unless otherwise specified. Furthermore, various measurements and evaluations were performed using the following methods.

[0107] <Glass Transition Temperature of Water-Soluble Polymers and Particulate Polymers> An aqueous solution of a water-soluble polymer or an aqueous dispersion containing a particulate polymer was dried for 3 days at 50% humidity and 25°C to obtain a film with a thickness of 1.0 mm. This film was dried in a vacuum dryer at 60°C for 10 hours. Subsequently, the dried film was used as a sample, and the glass transition temperature (°C) was measured using a differential scanning calorimetry analyzer (Nanotechnology Inc., product name "DSC6220SII") in accordance with JIS K7121, under conditions of measurement temperature of -100°C to 180°C and heating rate of 5°C / min. <Weight-Average Molecular Weight of Water-Soluble Polymers> The weight-average molecular weight of water-soluble polymers was measured by gel permeation chromatography (GPC). Specifically, first, the water-soluble polymer was added to approximately 5 mL of eluent so that the solid content concentration of the polymer was approximately 0.5 g / L, and slowly dissolved at room temperature. After visually confirming the dissolution of the water-soluble polymer, the sample was gently filtered through a 0.45 μm filter to prepare the sample for measurement. The obtained sample was then used for measurement. A calibration curve was created using standard substances, and the weight-average molecular weight was calculated as a value converted to the standard substance. The measurement conditions were as follows. <<Measurement Conditions>> ・Column: Showa Denko Co., Ltd., product name Shodex OHpak (SB-G, SB-807HQ, SB-806MHQ) ・Eluent: 0.1 M Tris buffer (with 0.1 M potassium chloride added) ・Flow rate: 0.5 mL / min ・Sample concentration: 0.05 g / L (solid content concentration) ・Injection volume: 200 μL ・Column temperature: 40°C ・Detector: Differential refractive index detector RI (Tosoh Corporation, product name "RI-8020") ・Standard substance: Monodisperse pullulan (Showa Denko Co., Ltd.) <<Volume average particle diameter of particulate polymer>> The volume average particle diameter of particulate polymer was measured by laser diffraction. Specifically, aqueous dispersions containing particulate polymer prepared in the examples and comparative examples (adjusted to a solid content concentration of 0.1%) were used as samples. Then, the particle size distribution (volume-based) measured using a laser diffraction particle size distribution analyzer (Beckman Coulter, product name "LS-230") was defined as the volume-average particle size, where the cumulative volume calculated from the smallest diameter side reached 50%, with particle size D50 being the volume-average particle size. <Volume-average particle size of conductive metal particles> 500 parts of deionized water were added to 100 parts of conductive metal particles, and the dispersion was performed using an ultrasonic disperser for 5 minutes to obtain a dispersion.Next, the obtained dispersion was measured using a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation, product name "SALD-2300"). In the measured particle size distribution (volume basis), the particle size D50 at which the cumulative volume calculated from the small-diameter side was 50% was taken as the volume average particle size of the conductive metal particles. <Sheet attack resistance> The release base materials with dielectric layers prepared in the examples and comparative examples were cut into pieces with a width of 1 cm × a length of 10 cm to obtain test pieces. A cellophane tape (specified in JIS Z1522) was attached to the dielectric layer side of this test piece. The cellophane tape was fixed flat on the horizontal plane of the test bench, and one end of the release base material was peeled off at a pulling speed of 10 mm / min in the vertical direction with respect to the cellophane tape surface, and the stress at that time was measured as the adhesion strength n1 between the release base material and the dielectric layer. Next, the laminates prepared in the examples and comparative examples were cut into pieces with a width of 1 cm × a length of 10 cm to obtain test pieces. A cellophane tape (specified in JIS Z1522) was attached to the internal electrode layer side of this test piece. The cellophane tape was fixed flat on the horizontal plane of the test bench, and one end of the release base material was peeled off at a pulling speed of 10 mm / min in the vertical direction with respect to the cellophane tape surface, and the stress at that time was measured as the adhesion strength n2 between the release base material and the dielectric layer and the internal electrode layer. The change in adhesion strength (Δn) was calculated according to the following formula (1). Δn (%) = (n2 / n1) × 100 (1) Using the above Δn, the sheet attack resistance of the laminate was evaluated according to the following criteria. The larger Δn is, the more excellent the sheet attack resistance of the laminate is. A: Δn exceeds 80% B: Δn is 60% or more and 80% or less C: Δn is less than 60% <Laminability> The laminates manufactured in the examples and comparative examples were cut into squares with a width of 5 cm × a length of 5 cm, and the release base material was peeled off to obtain test pieces. Two of these test pieces were prepared, and after overlapping the two test pieces so that the internal electrode layer of one test piece faced the dielectric layer of the other test piece, it was heated at 80°C under 5 kg / cm². ２Under pressure, the laminate was pressed for 60 seconds to obtain an evaluation laminate. The evaluation laminate was then cut with a cutter, and the cross-sections of the laminated internal electrode layer and dielectric layer were visually inspected and evaluated according to the following criteria: A: The internal electrode layer and dielectric layer are bonded, and no powder fallout occurs on the cut surface. B: The internal electrode layer and dielectric layer are bonded, but powder fallout occurs on the cut surface. C: The internal electrode layer and dielectric layer are not bonded, and powder fallout occurs on the cut surface. <Hygroscopicity> Laminates prepared in the examples and comparative examples were cut to a size of 10 cm x 10 cm to be used as test specimens. These test specimens were left at a temperature of 25°C and a humidity of 50% for 24 hours, and then the moisture content (W) of the test specimen was measured using a coulometric titration moisture meter by the Karl Fischer method (JIS K-0068 (2001) moisture vaporization method, vaporization temperature 150°C). ０ The moisture content (W) of the test specimen was measured. After that, the test specimen was stored in an environment of 25°C, 80% humidity for 12 hours, and then measured using a coulometric titration moisture meter. １ The moisture content was measured using the Karl Fischer method described above. Then, the change in moisture content (ΔW) was calculated according to the following formula (2). ΔW (%) = (W １ / W ０ ) × 100 (2) Using the above ΔW, the hygroscopicity of the laminate was evaluated according to the following criteria. The smaller ΔW, the lower the hygroscopicity of the laminate. A: ΔW is 100% or more and 120% or less B: ΔW is greater than 120% and 150% or less C: ΔW is greater than 150%

[0108] (Example 1) <Synthesis of water-soluble polymer> In a 5 MPa pressure vessel equipped with a stirrer, 30 parts of methacrylic acid (ethylenically unsaturated acid monomer), 57 parts of ethyl acrylate ((meth)acrylic acid ester monomer), 12 parts of n-butyl acrylate ((meth)acrylic acid ester monomer), 1 part of ethylene glycol dimethacrylate (crosslinkable monomer), 0.3 parts of tert-dodecyl mercaptan as a molecular weight adjuster, 0.6 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 1 part of potassium persulfate as a polymerization initiator were added as monomer composition, and after thorough stirring, the mixture was heated to 60°C to start polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling, and an aqueous sodium hydroxide solution was added to adjust the pH to 4. 0.08 parts of benzoisothiazolin-3-one (manufactured by Katsuyama Chemical Co., Ltd., product name "Naviside P-40") were added as a preservative to obtain an aqueous solution of the water-soluble polymer (solid content concentration 10%). The weight-average molecular weight and glass transition temperature of the water-soluble polymer were measured using the obtained aqueous solution of the water-soluble polymer. The results are shown in Table 1. <Synthesis of particulate polymer> 74 parts of deionized water, 0.2 parts of sodium dodecyldiphenyl ethersulfonate, 1.0 part of ammonium persulfate as a polymerization initiator, and 9.7 parts of deionized water were added to a 5 MPa pressure vessel A equipped with a stirrer, and the mixture was heated to 70°C and stirred for 30 minutes. Next, in a separate 5 MPa pressure vessel B equipped with a stirrer, 78.0 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, 20.0 parts of acrylonitrile as a nitrogen-containing monomer, 2.0 parts of itaconic acid as an ethylenically unsaturated acid monomer, 0.8 parts of sodium dodecyldiphenyl ethersulfonate as an emulsifier, and 74 parts of deionized water were added and stirred to prepare an emulsion. The prepared emulsion was sequentially added from pressure vessel B to pressure vessel A over approximately 200 minutes, and then stirred for approximately 180 minutes. When the polymerization conversion rate reached 97% or higher, the reaction was cooled to terminate. After that, the pH was adjusted with a 4% NaOH aqueous solution, and unreacted monomers were removed by heated vacuum distillation to obtain an aqueous dispersion (pH 8.0, solid content concentration 40%) containing an acrylic particulate polymer.The volume-average particle size and glass transition temperature of the particulate polymer were measured using an aqueous dispersion containing the obtained particulate polymer. The results are shown in Table 1. <Preparation of electrode slurry composition> 100 parts of Ni particles (manufactured by Toho Titanium Co., Ltd.) with a volume-average particle size of 0.18 μm as conductive metal particles, 20 parts of barium titanate (manufactured by Toda Kogyo Co., Ltd.) with an average particle size of 0.1 μm as a dielectric material, and 5 parts of the water-soluble polymer obtained above (solid content; 50 parts in aqueous solution) were stirred at 50 rpm for 2 hours using a planetary mixer (manufactured by Primix Co., Ltd., product name "T.K. Hibiscus Mix"). Furthermore, 5 parts of the particulate polymer obtained above (solid content, 12.5 parts as an aqueous dispersion) and 40 parts of water as a solvent were added, and the mixture was stirred at 50 rpm for 2 hours to obtain an electrode slurry composition. <Preparation of Slurry Composition for Dielectric Layer> 100 parts of barium titanate (manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-01") with a volume-average particle size of 0.1 μm as the dielectric material, 5 parts of polyvinyl alcohol (manufactured by Denka Co., Ltd., product name "B-33") as the water-soluble polymer (50 parts as aqueous solution), and 20 parts of water as the solvent were mixed together with 100 parts of zirconia beads with a particle size of 0.1 mm (manufactured by Nikkatoh Co., Ltd.) using a bead mill (manufactured by AIMEX Co., Ltd., product name "RMB-01") at 500 rpm for 2 hours. Then, another 20 parts of water were added and the mixture was stirred at 500 rpm for 1 hour. The zirconia beads were filtered off to obtain a dispersion of barium titanate. To 190 parts of this dispersion (containing 100 parts of barium titanate), 5 parts of the particulate polymer obtained above (12.5 parts as an aqueous dispersion) were added, and the mixture was stirred at 1000 rpm for 3 minutes using a rotary-orbit mixer to prepare a slurry composition for the dielectric layer. <Preparation of Laminate> The slurry composition for the dielectric layer obtained above was applied to a release-treated film (Lintec Corporation, product name "PET38AL-5") measuring 100 mm in width and 100 mm in length using a gravure coater so that the film thickness of the dielectric layer after drying was approximately 1.0 μm, and dried in an oven at 100°C for 5 minutes to form a dielectric layer on the release substrate, thereby obtaining a release substrate with a dielectric layer. The adhesive strength n1 between the release substrate and the dielectric layer was measured using the obtained release substrate with a dielectric layer.Next, the electrode slurry composition obtained above was printed onto the dielectric layer of the release substrate with dielectric layer obtained above using a screen printing machine so that the thickness of the resulting internal electrode layer was 1 μm. Then, it was dried in an oven at 100°C for 10 minutes to form the internal electrode layer on the dielectric layer (ceramic green sheet method). That is, a laminate was prepared in which the release substrate, dielectric layer, and internal electrode layer were stacked in this order. Using the obtained laminate, the adhesive strength n2 between the release substrate, dielectric layer, and internal electrode layer was measured to evaluate the sheet attack resistance. The results are shown in Table 1.

[0109] (Examples 2-4, 7-8) Except for changing the types and proportions of monomers used in the synthesis of the water-soluble polymer as shown in Table 1, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. Measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0110] (Example 5) In the synthesis of the water-soluble polymer, the amount of tert-dodecyl mercaptan added was changed to 0.6 parts, but the various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0111] (Example 6) In synthesizing the water-soluble polymer, the polymerization temperature was changed to 40°C and tert-dodecyl mercaptan was not added. Except for these differences, the various operations, measurements, and evaluations were carried out in the same manner as in Example 1. Measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0112] (Example 9) In the synthesis of particulate polymers, the amount of sodium dodecyldiphenyl ethersulfonate added was changed to 0.2 parts, but the various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0113] (Example 10) In the synthesis of particulate polymer, the amount of sodium dodecyldiphenyl ethersulfonate added was changed to 1.2 parts, but the various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0114] (Examples 11-12) Except for changing the types and proportions of monomers used in the synthesis of particulate polymers as shown in Table 2, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0115] (Example 13) In preparing the electrode slurry composition, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that no particulate polymer was added. Measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2.

[0116] (Example 14) In preparing the electrode slurry composition, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that Cu particles (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "1030Y"; volume average particle size: 0.42 μm) were used instead of Ni particles as conductive metal particles. Measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2.

[0117] (Comparative Example 1) In the synthesis of the water-soluble polymer, the types and proportions of monomers used were changed as shown in Table 2. In addition, no particulate polymer was added when preparing the electrode slurry composition. Otherwise, measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0118] (Example 15) Measurement and evaluation were performed in the same manner as in Example 13, except that 15 parts water and 25 parts ethanol were used instead of 40 parts water as the solvent when preparing the electrode slurry composition. The results are shown in Table 2.

[0119] In Tables 1 and 2 below, "Ni" represents Ni particles, "Cu" represents Cu particles, "MAA" represents methacrylic acid units, "EDMA" represents ethylene glycol dimethacrylate units, "AGE" represents allyl glycidyl ether units, "EA" represents ethyl acrylate units, "BA" represents n-butyl acrylate units, "MMA" represents methyl methacrylate units, "IA" represents itaconic acid units, "2-EHA" represents 2-ethylhexyl acrylate units, "AN" represents acrylonitrile units, "ST" represents styrene units, "D50" represents the volume-average particle size, "Mw" represents the weight-average molecular weight, and "Tg" represents the glass transition temperature.

[0120]

[0121]

[0122] According to the present invention, it is possible to provide a slurry composition for electrodes for multilayer ceramic capacitors that can form an electrode layer for a multilayer ceramic capacitor that can impart excellent sheet attack resistance to the laminate for the multilayer ceramic capacitor and reduce the moisture absorption of the laminate for the multilayer ceramic capacitor. Furthermore, according to the present invention, it is possible to provide an electrode layer for a multilayer ceramic capacitor that can impart excellent sheet attack resistance to the laminate for the multilayer ceramic capacitor and reduce the moisture absorption of the laminate for the multilayer ceramic capacitor. And according to the present invention, it is possible to provide a multilayer ceramic capacitor in which at least one of the internal electrode and the external electrode is formed by sintering the above-mentioned electrode layer for a multilayer ceramic capacitor.

[0123] 10: Multilayer ceramic capacitor 11: Dielectric 12: Internal electrode 13: External electrode

Claims

1. A slurry composition for electrodes of multilayer ceramic capacitors, comprising conductive metal particles, a water-soluble polymer, and a solvent, wherein the water-soluble polymer contains crosslinkable monomer units.

2. The slurry composition for electrodes for multilayer ceramic capacitors according to claim 1, wherein the proportion of water in the solvent is 50% by mass or more.

3. The slurry composition for electrodes for multilayer ceramic capacitors according to claim 2, wherein the content ratio of the crosslinkable monomer units in the water-soluble polymer is 0.1% by mass or more and 10% by mass or less.

4. The slurry composition for electrodes for multilayer ceramic capacitors according to claim 2, wherein the weight-average molecular weight of the water-soluble polymer is 200,000 or more and 2,000,000 or less.

5. The slurry composition for electrodes for multilayer ceramic capacitors according to claim 2, wherein the glass transition temperature of the water-soluble polymer is 30°C or higher and 100°C or lower.

6. The slurry composition for electrodes for multilayer ceramic capacitors according to claim 2, further comprising a particulate polymer, wherein the volume-average particle diameter of the particulate polymer is 0.01 μm or more and 0.5 μm or less.

7. The slurry composition for electrodes for multilayer ceramic capacitors according to claim 6, wherein the glass transition temperature of the particulate polymer is -60°C or higher and 20°C or lower.

8. An electrode layer for a multilayer ceramic capacitor, obtained by drying a coating film made of the slurry composition for electrodes of a multilayer ceramic capacitor according to any one of claims 1 to 7.

9. A multilayer ceramic capacitor comprising an internal electrode, an external electrode, and a dielectric layer, wherein at least one of the internal electrode and the external electrode is formed by sintering an electrode layer for a multilayer ceramic capacitor as described in claim 8.

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