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

Abstract

To provide a slurry composition for a dielectric layer which is capable of imparting excellent crack resistance and stackability to the dielectric layer, and is excellent in dispersion stability.SOLUTION: A slurry composition for a dielectric layer includes a dielectric material having perovskite structure, a water-soluble polymer having a hydrophilic group, a cross-linking agent, and water. A content of the cross-linking agent is 0.001-1 pt.mass with respect to 100 pts.mass of the water-soluble polymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a slurry composition for a dielectric layer, a dielectric layer, and a multilayer ceramic capacitor. [Background technology]

[0002] Multilayer ceramic capacitors are generally manufactured using dielectric layers such as ceramic green sheets. The dielectric layer can be obtained, for example, by first preparing a slurry composition containing a binder, a dielectric material, and a solvent, then applying the slurry composition to a release substrate and drying it. The obtained dielectric layers are then stacked, optionally subjected to a degreasing treatment (binder removal treatment), and sintered to obtain a multilayer ceramic capacitor.

[0003] In recent years, in order to impart excellent properties to multilayer ceramic capacitors, development of slurry compositions to be used in the production of dielectric layers has been progressing. For example, Patent Document 1 proposes a slurry composition that contains a dispersion medium made of an organic solvent, ceramic powder having a predetermined average particle size, and a binder made of a predetermined (meth)acrylate copolymer, as a slurry composition that can produce ceramic green sheets that leave little unburned binder during binder removal processing and have excellent smoothness and ceramic particle density after binder removal processing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6337628 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, in dielectric layers such as ceramic green sheets, further improvements are required in terms of suppressing cracks that may occur during the production of sintered bodies (hereinafter, this may be referred to as "crack resistance").

[0006] Furthermore, in the manufacture of multilayer ceramic capacitors, dielectric layers are typically stacked on top of each other and then pressed to obtain a laminate, and it is desirable that the dielectric layers in the obtained laminate are well bonded to each other (hereinafter, this may be referred to as "laminability").

[0007] Furthermore, since the slurry composition can be stored for a certain period of time (e.g., 7 days) after preparation, it is desirable that the slurry composition has little change in viscosity when comparing the viscosity after storage for a certain period of time with the viscosity immediately after preparation, and has excellent dispersion stability, in order to enable uniform application and suppress variations in the performance of the resulting multilayer ceramic capacitor.

[0008] Therefore, an object of the present invention is to provide a slurry composition for a dielectric layer that can impart excellent crack resistance and lamination properties to a dielectric layer and also has excellent dispersion stability. Another object of the present invention is to provide a dielectric layer obtained by drying a coating film made of the above-mentioned slurry composition for a dielectric layer. Another object of the present invention is to provide a multilayer ceramic capacitor obtained by sintering a laminate in which the above-mentioned dielectric layers are stacked one on top of the other. [Means for solving the problem]

[0009] The present inventors have conducted extensive research with the aim of solving the above-mentioned problems, and have newly discovered that the above-mentioned problems can be solved by a slurry composition for a dielectric layer, the slurry composition including a dielectric material having a perovskite structure, a water-soluble polymer having a hydrophilic group, a predetermined amount of a crosslinking agent, and water, and have thus completed the present invention.

[0010] That is, the present invention aims to advantageously solve the above-mentioned problems, and [1] the present invention is a slurry composition for a dielectric layer, which contains a dielectric material having a perovskite structure, a water-soluble polymer having a hydrophilic group, a crosslinking agent, and water, wherein the content of the crosslinking agent is 0.001 parts by mass or more and 1 part by mass or less, when the water-soluble polymer is taken as 100 parts by mass. The above-mentioned dielectric layer slurry composition can impart excellent crack resistance and lamination properties to the dielectric layer, and also has excellent dispersion stability.

[0011] [2] In the slurry composition for a dielectric layer described in [1] above, the weight average molecular weight of the water-soluble polymer is preferably 5,000 or more and 2,000,000 or less. When the weight average molecular weight of the water-soluble polymer is at least the above lower limit, the crack resistance and lamination properties of the resulting dielectric layer can be improved. On the other hand, if the weight average molecular weight of the water-soluble polymer is equal to or less than the above upper limit, the dispersion stability of the dielectric layer slurry composition can be improved. In this specification, the "weight average molecular weight" of the water-soluble polymer can be measured by the method described in the examples of this specification.

[0012] [3] In the dielectric layer slurry composition of the above [1] or [2], the hydrophilic group of the water-soluble polymer is preferably at least one of a carboxylic acid group and a hydroxyl group. When the hydrophilic group of the water-soluble polymer is at least one of a carboxylic acid group and a hydroxyl group, the dispersion stability of the dielectric layer slurry composition can be improved, and the crack resistance of the resulting dielectric layer can be improved.

[0013] [4] In the slurry composition for a dielectric layer according to any one of the above [1] to [3], the content of the water-soluble polymer is preferably 0.1 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of the dielectric material. When the content of the water-soluble polymer is equal to or greater than the above lower limit, the crack resistance and lamination properties of the resulting dielectric layer can be improved. On the other hand, if the content of the water-soluble polymer is equal to or less than the above upper limit, the dispersion stability of the dielectric layer slurry composition can be improved.

[0014] [5] In the slurry composition for a dielectric layer according to any one of the above [1] to [4], the crosslinking agent preferably contains a metal atom. If the crosslinking agent contains a metal atom, the dispersion stability of the dielectric layer slurry composition can be improved, and the crack resistance of the resulting dielectric layer can be improved.

[0015] [6] In the slurry composition for a dielectric layer according to any one of the above [1] to [5], the crosslinking agent preferably has an amino group. If the crosslinking agent has an amino group, the dispersion stability of the dielectric layer slurry composition can be further improved, and the crack resistance of the resulting dielectric layer can be further improved.

[0016] [7] The above slurry compositions for dielectric layers [1] to [6] preferably further contain a particulate polymer. If the dielectric layer slurry composition further contains a particulate polymer, the dispersion stability of the dielectric layer slurry composition can be improved, and the crack resistance and lamination properties of the resulting dielectric layer can be improved.

[0017] [8] In the above slurry compositions for dielectric layer [1] to [7], the solid content concentration is preferably 30% by mass or more and 70% by mass or less. When the solid content is equal to or higher than the lower limit, the crack resistance and lamination properties of the resulting dielectric layer can be improved. On the other hand, if the solid content concentration is equal to or less than the above upper limit, the dispersion stability of the dielectric layer slurry composition can be improved.

[0018] The present invention also aims to advantageously solve the above problems, and [9] the present invention is a dielectric layer formed by drying a coating film made of a slurry composition for a dielectric layer according to any one of [1] to [8] above. The dielectric layer as described above has excellent uniformity in film thickness. Furthermore, the dielectric layer as described above has excellent crack resistance and lamination properties.

[0019] Another object of the present invention is to advantageously solve the above problems, and

[10] the present invention is a multilayer ceramic capacitor obtained by sintering a laminate in which the dielectric layers according to [9] above are stacked. The above-described multilayer ceramic capacitor has reduced variations in performance. Furthermore, the multilayer ceramic capacitor described above has excellent performance. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a slurry composition for a dielectric layer that can impart excellent crack resistance and lamination properties to a dielectric layer and has excellent dispersion stability. Furthermore, according to the present invention, it is possible to provide a dielectric layer obtained by drying a coating film made of the above-mentioned slurry composition for a dielectric layer. Furthermore, according to the present invention, it is possible to provide a multilayer ceramic capacitor obtained by sintering a laminate in which the above-mentioned dielectric layers are stacked. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view showing an example of a multilayer ceramic capacitor of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail. Here, the dielectric layer slurry composition of the present invention (hereinafter sometimes simply referred to as "slurry composition") can be used to form a dielectric layer used in the manufacture of a multilayer ceramic capacitor or the like. The dielectric layer of the present invention is formed by drying a coating film made of the slurry composition of the present invention. The multilayer ceramic capacitor of the present invention is formed by stacking dielectric layers formed using the slurry composition of the present invention and sintering the resulting laminate.

[0023] The slurry composition for a dielectric layer of the present invention contains a dielectric material having a perovskite structure, a water-soluble polymer having a hydrophilic group, a crosslinking agent, and water, and may optionally contain a particulate polymer. The slurry composition of the present invention has a crosslinking agent content of 0.001 parts by mass or more and 1 part by mass or less, relative to 100 parts by mass of the water-soluble polymer. The above-described slurry composition can impart excellent crack resistance and lamination properties to the dielectric layer, and also has excellent dispersion stability. The reason for this is presumably that the content of the crosslinking agent within a predetermined range allows the dielectric material and the water-soluble polymer in the slurry composition to be effectively crosslinked.

[0024] The slurry composition of the present invention may optionally further contain components other than the dielectric material, water-soluble polymer, crosslinking agent, water, and particulate polymer (hereinafter, sometimes referred to as "other components").

[0025] <Dielectric materials> In the slurry composition of the present invention, the dielectric material has a perovskite structure. Here, "perovskite structure" means a structure represented by the general formula ABO3, and "the dielectric material has a perovskite structure" means that the structure represented by the general formula ABO3 is present in at least a part of the dielectric material. The slurry composition may optionally further contain a dielectric material other than the dielectric material having a perovskite structure.

[0026] As a dielectric material having a perovskite structure, a ceramic material having a perovskite structure as a main phase is preferable. Examples of the ceramic material include barium titanate (BaTiO3), calcium zirconate (CaZrO3), calcium titanate (CaTiO3), strontium titanate (SrTiO3), and BaTiO3, which form a perovskite structure. 1-x-y Ca x Sr y Ti 1-z Zr zO3 (0≦x≦1, 0≦y≦1, 0≦z≦1), etc. Among these, barium titanate and calcium zirconate are preferred as ceramic materials having a perovskite structure as the main phase.

[0027] The average particle size of the dielectric material is preferably 0.01 μm or more, more preferably 0.02 μm or more, even more preferably 0.05 μm or more, even more preferably 0.08 μm or more, and is preferably 1 μm or less, more preferably 0.8 μm or less, even more preferably 0.5 μm or less, even more preferably 0.3 μm or less, and even more preferably 0.2 μm or less. When the volume average particle size of the dielectric material is within the above range, the dispersion stability of the dielectric material in the slurry composition can be improved, and as a result, a dielectric layer in which the dielectric material is uniformly dispersed can be produced. In this specification, the average particle size of a dielectric material means the particle size at which the cumulative volume calculated from the smallest diameter side is 50% in the particle size distribution (volume basis) obtained by measurement using a laser diffraction method.

[0028] The content of the dielectric material in the slurry composition is preferably 40% by mass or more, more preferably 50% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, when all components in the slurry composition (including the solvent) are taken as 100% by mass.

[0029] <Water-soluble polymer> In the slurry composition of the present invention, the water-soluble polymer has a hydrophilic group and is a component that can function as a viscosity modifier and a binder.

[0030] Examples of the hydrophilic group possessed by the water-soluble polymer include acid groups such as a carboxylic acid group, a sulfonic acid group, and a phosphate group; a hydroxyl group; an amide group; etc. Among these, the hydrophilic group is preferably at least one of an acid group and a hydroxyl group, more preferably at least one of a carboxylic acid group and a hydroxyl group, and even more preferably a carboxylic acid group, because this can improve the dispersion stability of the slurry composition and the crack resistance of the resulting dielectric layer.

[0031] A water-soluble polymer having a hydrophilic group usually contains a structural unit having a hydrophilic group (hereinafter, sometimes referred to as a "hydrophilic group-containing structural unit"). The water-soluble polymer may also contain a (meth)acrylic acid alkyl ester monomer unit in addition to the hydrophilic group-containing structural unit. The water-soluble polymer may also contain a monomer unit other than the hydrophilic group-containing structural unit and the (meth)acrylic acid alkyl ester monomer unit (hereinafter, sometimes referred to as an "other monomer unit A"). In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0032] <<Structural units having hydrophilic groups>> The structural unit having a hydrophilic group (hydrophilic group-containing structural unit) may be a structural unit that can be formed from a monomer having a hydrophilic group (hereinafter, may be referred to as a "hydrophilic group-containing monomer"), or may be a structural unit obtained by obtaining a water-soluble polymer using a monomer composition containing a monomer having a predetermined functional group, and then modifying or converting the functional group into a hydrophilic group.

[0033] Examples of carboxylic acid group-containing monomers that can form structural units having a carboxylic acid group as a hydrophilic group (hereinafter, sometimes referred to as "carboxylic acid group-containing structural units") include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, and crotonic acid. Examples of the monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid esters such as methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Examples of the acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Furthermore, as the carboxylic acid group-containing monomer, an acid anhydride that generates a carboxylic acid group upon hydrolysis can also be used. Other examples include monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate. Among the above, acrylic acid and methacrylic acid are preferred as the carboxylic acid group-containing monomer.

[0034] Examples of sulfonic acid group-containing monomers that can form structural units having a sulfonic acid group as a hydrophilic group (hereinafter, sometimes referred to as "sulfonic acid group-containing structural units") include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid. In this specification, "(meth)allyl" means allyl and / or methallyl.

[0035] Examples of phosphate group-containing monomers that can form structural units having a phosphate group as a hydrophilic group (hereinafter, sometimes referred to as "phosphate group-containing structural units") include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, ethyl-(meth)acryloyloxyethyl phosphate, vinylphosphonic acid, and dimethyl vinylphosphonate. In this specification, the term "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0036] Examples of amide group-containing monomers that can form structural units having amide groups as hydrophilic groups (hereinafter, sometimes referred to as "amide group-containing structural units") include acrylamide and methacrylamide.

[0037] The structure of the structural unit having a hydroxyl group as a hydrophilic group (hereinafter, sometimes referred to as a "hydroxyl group-containing structural unit") is not particularly limited as long as it is a repeating unit having a hydroxyl group. The method for introducing the hydroxyl group-containing structural unit into the water-soluble polymer may be, for example, the following method (1) or (2): (1) A method for preparing a water-soluble polymer containing a hydroxyl group-containing structural unit from a monomer composition containing a hydroxyl group-containing monomer. (2) A method for preparing a water-soluble polymer containing vinyl alcohol units and, optionally, vinyl carboxylic acid ester monomer units, by preparing a polymer from a monomer composition containing a vinyl carboxylic acid ester monomer represented by the general formula: R-CO-O-CH=CH2 (wherein R is any structure, but is preferably an alkyl group having 1 to 19 carbon atoms), and saponifying the polymer to convert all or part of the "R-CO-O-" of the vinyl carboxylic acid ester monomer units into hydroxyl groups. Examples include:

[0038] Examples of the hydroxyl group-containing monomer used in the above method (1) include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-butene-1-ol, and 5-hexene-1-ol; alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate (2-hydroxyethyl methacrylate), 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconate; and alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconate; 1 -COO-(C q H 2q O) p -H (wherein p is an integer of 2 to 9, q is an integer of 2 to 4, R 1represents hydrogen or a methyl group) and (meth)acrylic acid esters; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; mono(meth)allyl alkylene glycols such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, and (meth)allyl-6-hydroxyhexyl ether. ethers; polyoxyalkylene glycol mono(meth)allyl ethers such as diethylene glycol mono(meth)allyl ether and dipropylene glycol mono(meth)allyl ether; mono(meth)allyl ethers of halogen- and hydroxy-substituted (poly)alkylene glycols such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether and (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyhydric phenols such as eugenol and isoeugenol and halogen-substituted products thereof; (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether; 2-hydroxyethyl(meth)acrylamide, N-methylolacrylamide; etc. These may be used alone or in combination of two or more. Among these, alkanol esters of ethylenically unsaturated carboxylic acids are preferred, and 2-hydroxyethyl methacrylate (2-hydroxyethyl methacrylate) is more preferred.

[0039] Examples of the vinyl carboxylate monomer used in the above method (2) include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, and vinyl stearate. These can be used alone or in combination of two or more. Among these, vinyl acetate is preferred. Examples of the water-soluble polymer obtained by the above method (2) include polyvinyl alcohol.

[0040] When preparing a water-soluble polymer by the above method (2), some of the hydroxyl groups of the obtained water-soluble polymer may be acetalized. Examples of such water-soluble polymers include polyvinyl butyral, in which the hydroxyl groups of the water-soluble polymer are acetalized with butyraldehyde.

[0041] The content of the hydrophilic group-containing structural unit in the water-soluble polymer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less, when all repeating units (all monomer units and all structural units) contained in the water-soluble polymer are taken as 100% by mass. When the content of the hydrophilic group-containing structural unit is equal to or greater than the lower limit above, assuming that all monomer units and all structural units contained in the water-soluble polymer are 100% by mass, the dispersion stability of the slurry composition can be improved. On the other hand, when the content ratio of the hydrophilic group-containing structural unit is equal to or less than the above upper limit when all the monomer units and all the structural units contained in the water-soluble polymer are taken as 100% by mass, for example, when a release substrate with a dielectric layer obtained by forming a dielectric layer on a release substrate is wound into a roll, the dielectric layer adheres closely to the surface of the release substrate on the side on which the dielectric layer is not formed (hereinafter, may be referred to as the "rear surface of the release substrate"), and adhesion of the dielectric layer to the rear surface of the release substrate (so-called blocking) is suppressed, thereby improving blocking resistance. In this specification, the content ratio of various repeating units (monomer units and structural units) in the polymer is expressed as follows: 1 It can be measured using nuclear magnetic resonance (NMR) techniques such as H-NMR.

[0042] <<(Meth)acrylic acid alkyl ester monomer unit>> The (meth)acrylic acid alkyl ester monomer unit that the water-soluble polymer may contain is a monomer unit that may be formed from a (meth)acrylic acid alkyl ester monomer.

[0043] Examples of (meth)acrylic acid alkyl ester monomers that can form (meth)acrylic acid alkyl ester monomer units include 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. and 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, and stearyl methacrylate. These may be used alone or in combination of two or more. Among these, ethyl acrylate and n-butyl acrylate are preferred. That is, the water-soluble polymer preferably contains at least one of an ethyl acrylate unit and an n-butyl acrylate unit. And, the water-soluble polymer more preferably contains an ethyl acrylate unit and an n-butyl acrylate unit.

[0044] The content of (meth)acrylic acid alkyl ester monomer units in the water-soluble polymer is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and even more preferably 70% by mass or less, when all repeating units (all monomer units and all structural units) contained in the water-soluble polymer are taken as 100% by mass.

[0045] <<Other Monomer Unit A>> The other monomer unit A is a monomer unit that can be formed by another monomer A. The other monomer A is not particularly limited as long as it is a monomer that can be copolymerized with the above-mentioned monomer that can form the water-soluble polymer. Examples of the other monomer A include crosslinkable monomers (crosslinkable monomers) such as polyfunctional ethylenically unsaturated carboxylic acid ester monomers having two or more ethylenically unsaturated bonds (C=C) in the molecule, such as allyl glycidyl ether, allyl (meth)acrylate, and ethoxylated pentaerythritol tetraacrylate; 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; and amino group-containing monomers such as aminoethyl vinyl ether and dimethylaminoethyl vinyl ether. These other monomers A may be used alone or in combination of two or more.

[0046] The content of the other monomer units A in the water-soluble polymer is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0% by mass, i.e., the water-soluble polymer does not contain any other monomer units A, when all repeating units (all monomer units and all structural units) contained in the water-soluble polymer are taken as 100% by mass.

[0047] <<Characteristics of water-soluble polymers>> The water-soluble polymer preferably has a weight average molecular weight of 5,000 or more, more preferably 200 or more, and preferably 2,000,000 or less, more preferably 1,500,000 or less. When the weight average molecular weight of the water-soluble polymer is at least the above lower limit, the crack resistance and lamination properties of the resulting dielectric layer can be improved. On the other hand, if the weight average molecular weight of the water-soluble polymer is equal to or less than the upper limit, the dispersion stability of the slurry composition can be improved.

[0048] The water-soluble polymer preferably has a glass transition temperature of 0°C or higher, more preferably 5°C or higher, and preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 50°C or lower. In this specification, the glass transition temperature of a polymer can be measured according to the method described in the examples.

[0049] <<Water-soluble polymer content>> The content of the water-soluble polymer in the slurry composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the dielectric material. When the content of the water-soluble polymer is equal to or greater than the above lower limit, the crack resistance and lamination properties of the resulting dielectric layer can be improved. On the other hand, if the content of the water-soluble polymer is equal to or less than the upper limit, the dispersion stability of the slurry composition can be improved.

[0050] <<Method for preparing water-soluble polymers>> The water-soluble polymer can be obtained, for example, by mixing the above-mentioned monomers with an arbitrary polymerization solvent by a known method to obtain a monomer composition, polymerizing the resulting monomer composition by an arbitrary polymerization method, and optionally subjecting the resulting polymer to a treatment such as saponification. Here, the polymerization method for the water-soluble polymer is not limited, and any method may be used, for example, a solution polymerization method such as aqueous solution polymerization, a slurry polymerization method, a suspension polymerization method, a bulk polymerization method, an emulsion polymerization method, etc. Furthermore, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization may be used as the polymerization reaction. Furthermore, additives used in the polymerization, such as a polymerization initiator, a polymerization accelerator, an emulsifier, a dispersant, and a chain transfer agent, may be those generally used, and the amounts used may also be the amounts generally used. Among these, aqueous solution polymerization using water as the polymerization solvent is preferred because it does not require a solvent removal operation and the solvent is highly safe.

[0051] When water is used as a polymerization solvent and the above-mentioned monomer composition is polymerized in water to prepare an aqueous solution containing a water-soluble polymer, it is preferable to adjust the pH of the aqueous solution to 7 or more and 9 or less after polymerization.

[0052] Here, the polymerization initiator that can be used in preparing the water-soluble polymer is not particularly limited, and includes known polymerization initiators such as sodium persulfate, ammonium persulfate, and potassium persulfate. Among them, potassium persulfate is preferably used. The polymerization initiator may be used alone or in combination of two or more types in any ratio.

[0053] The polymerization accelerator is not particularly limited, and a known reducing polymerization accelerator, such as tetramethylethylenediamine, can be used. One type of polymerization accelerator may be used alone, or two or more types may be used in combination at any ratio.

[0054] <Crosslinking agent> In the slurry composition of the present invention, the crosslinking agent is capable of crosslinking the dielectric material and the water-soluble polymer.

[0055] Here, the content of the crosslinking agent in the slurry composition is 0.001 parts by mass or more, preferably 0.01 parts by mass or more, and 1 part by mass or less, preferably 0.1 parts by mass or less, based on 100 parts by mass of the dielectric material. When the content of the crosslinking agent is equal to or greater than the above lower limit, the crack resistance and lamination properties of the resulting dielectric layer can be improved. On the other hand, if the content of the crosslinking agent is equal to or less than the upper limit, the dispersion stability of the slurry composition can be improved.

[0056] The crosslinking agent is not particularly limited as long as it can crosslink the dielectric material and the water-soluble polymer, but preferably contains a metal atom. If the crosslinking agent contains a metal atom, effective interaction occurs between the crosslinking agent and the dielectric material, improving the dispersion stability of the slurry composition. In addition, the crack resistance of the resulting dielectric layer can be improved.

[0057] Examples of metal atoms that can be contained in the crosslinking agent include silicon, titanium, aluminum, etc. Among these, silicon and titanium are preferred. Specific examples of the crosslinking agent containing a metal atom include a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent.

[0058] The crosslinking agent is not particularly limited as long as it can crosslink the dielectric material and the water-soluble polymer, but it is preferable that the crosslinking agent has a hydrophilic group. If the crosslinking agent has a hydrophilic group, effective interaction occurs between the crosslinking agent and the water-soluble polymer, improving the dispersion stability of the slurry composition. In addition, the crack resistance of the resulting dielectric layer can be improved.

[0059] Examples of hydrophilic groups that the crosslinking agent may have include basic groups such as amino groups, hydroxyl groups, etc. Among these, basic groups are preferred, and amino groups are more preferred, since they can further improve the dispersion stability of the slurry composition and further improve the crack resistance of the resulting dielectric layer.

[0060] In one embodiment, when the above-mentioned water-soluble polymer has an acid group as a hydrophilic group, the crosslinking agent and the water-soluble polymer interact more effectively, and the dispersion stability of the slurry composition and the crack resistance of the resulting dielectric layer can be particularly improved. Therefore, the hydrophilic group that the crosslinking agent may have is preferably a basic group, and more preferably an amino group. It is particularly preferable that the combination of the hydrophilic groups of the water-soluble polymer and the crosslinking agent be a carboxylic acid group in the water-soluble polymer and an amino group in the crosslinking agent.

[0061] <Water> The slurry composition of the present invention contains water as a solvent. Note that the slurry composition of the present invention may contain a solvent other than water as long as the object of the present invention is not impaired. However, from the viewpoint of reducing the environmental load and safety, it is preferable that the slurry composition of the present invention contains only water as a solvent.

[0062] <Particulate polymer> The slurry composition of the present invention further preferably contains a particulate polymer. When the slurry composition further contains a particulate polymer, the dispersion stability of the slurry composition can be improved. In addition, the crack resistance and lamination properties of the resulting dielectric layer can be improved.

[0063] Here, the particulate polymer is a component that can function as a binder, imparting adhesiveness to the dielectric layer formed using the slurry composition and retaining materials (e.g., dielectric materials) contained in the dielectric layer so that they do not detach from the dielectric layer. The particulate polymer has a particulate shape in the slurry composition, but in the dielectric layer, it may be present while maintaining its particulate shape or may be present in any non-particulate shape.

[0064] The particulate polymer is preferably water-insoluble. In this specification, the term "water-insoluble" means that when 0.5 g of the polymer is dissolved in 100 g of water at 25°C, the insoluble content is 90 mass % or more.

[0065] The particulate polymer is not particularly limited, and any polymer such as a conjugated diene polymer or an acrylic polymer can be used.

[0066] <<Conjugated diene polymer>> A conjugated diene polymer is a polymer containing a conjugated diene monomer unit. The conjugated diene polymer may optionally contain an aromatic vinyl monomer unit, a hydrophilic group-containing structural unit, and a cyano group-containing monomer unit. The conjugated diene polymer may also contain a monomer unit other than the conjugated diene monomer unit, the aromatic vinyl monomer unit, the hydrophilic group-containing structural unit, and the cyano group-containing monomer unit (hereinafter, sometimes referred to as "other monomer unit B").

[0067] Examples of the conjugated diene polymer include copolymers containing aromatic vinyl monomer units and conjugated diene monomer units, such as styrene-butadiene copolymer (SBR), butadiene rubber (BR), isoprene rubber, acrylic rubber (NBR) (copolymers containing cyano group-containing monomer units and conjugated diene monomer units), and hydrogenated products thereof.

[0068] [Conjugated diene monomer unit] The conjugated diene monomer unit is a monomer unit that can be formed by a conjugated diene monomer. Examples of conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, and substituted and side-chain conjugated hexadienes. These may be used alone or in combination of two or more. Among these, 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene) are preferred as the conjugated diene monomer, and 1,3-butadiene is more preferred.

[0069] The content of conjugated diene monomer units in the conjugated diene polymer is preferably 20% by mass or more, more preferably 25% by mass or more, and is preferably 60% by mass or less, more preferably 55% by mass or less, when all repeating units (all monomer units and all structural units) contained in the conjugated diene polymer are taken as 100% by mass.

[0070] [Aromatic vinyl monomer unit] The aromatic vinyl monomer unit is a monomer unit that can be formed by an aromatic vinyl monomer. Examples of aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These may be used alone or in combination of two or more. Among these, styrene is preferred as the aromatic vinyl monomer.

[0071] The content of aromatic vinyl monomer units in the conjugated diene polymer is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more, and is preferably 70% by mass or less, and more preferably 65% by mass or less, when all repeating units (all monomer units and all structural units) contained in the conjugated diene polymer are taken as 100% by mass.

[0072] [Hydrophilic group-containing structural unit] In a conjugated diene polymer, the hydrophilic group-containing structural unit may be a structural unit that can be formed from a hydrophilic group-containing monomer, or may be a structural unit obtained by obtaining a water-soluble polymer using a monomer composition containing a monomer having a predetermined functional group and then modifying or converting the functional group into a hydrophilic group. However, when the hydrophilic group-containing structural unit is a hydroxyl group-containing structural unit, the hydrophilic group-containing structural unit in the conjugated diene polymer is usually a hydrophilic group-containing structural unit introduced into the polymer by the above method (1). Examples of hydrophilic group-containing monomers that can be used to prepare the conjugated diene polymer include the same monomers as those described above in the section "Hydrophilic Group-Containing Structural Unit." These may be used alone or in combination of two or more. Among these, acid group-containing monomers are preferred as the hydrophilic group-containing monomer. Furthermore, as the acid group-containing monomer, carboxylic acid group-containing monomers are preferred, with acrylic acid, methacrylic acid, itaconic acid, and vinyl sulfonic acid being more preferred, and acrylic acid, methacrylic acid, and itaconic acid being even more preferred.

[0073] The content of the hydrophilic group-containing structural unit in the conjugated diene polymer is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, when all repeating units (all monomer units and all structural units) contained in the conjugated diene polymer are taken as 100% by mass.

[0074] [Cyano group-containing monomer unit] The cyano group-containing monomer unit is a monomer unit that can be formed by a cyano group-containing monomer. Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile. These may be used alone or in combination of two or more in any ratio. Among these, acrylonitrile is preferred as the cyano group-containing monomer.

[0075] The cyano group-containing monomer units in the conjugated diene polymer preferably account for 5% by mass or more, more preferably 10% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less, when all repeating units (all monomer units and all structural units) contained in the conjugated diene polymer are taken as 100% by mass.

[0076] [Other monomer units B] The other monomer unit B is a monomer unit that can be formed by the other monomer B. The other monomer B is not particularly limited as long as it is a monomer that can copolymerize with the above-mentioned monomer that can form the conjugated diene polymer. Examples of the other monomer B include amide group-containing monomers such as acrylamide and methacrylamide; crosslinkable monomers (crosslinkable monomers) such as allyl glycidyl ether and allyl (meth)acrylate; 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; and N-vinylpyrrolidone. Examples of the other monomers B include heterocyclic ring-containing vinyl compounds such as vinylpyridine and vinylimidazole; amino group-containing monomers such as aminoethyl vinyl ether and dimethylaminoethyl vinyl ether; and (meth)acrylic acid alkyl ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, and octyl (meth)acrylate such as 2-ethylhexyl (meth)acrylate. These other monomers B may be used singly or in combination of two or more.

[0077] The content of the other monomer units B in the conjugated diene polymer is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0% by mass, i.e., the conjugated diene polymer does not contain the other monomer units B, when all repeating units (all monomer units and all structural units) contained in the conjugated diene polymer are taken as 100% by mass.

[0078] When a (meth)acrylic acid alkyl ester monomer is used to prepare the conjugated diene polymer, the content of the (meth)acrylic acid alkyl ester monomer unit is less than 50 mass % when the total repeating units (total monomer units and total structural units) contained in the conjugated diene polymer is 100 mass %.

[0079] <<Acrylic polymer>> An acrylic polymer (ACL) is a polymer containing (meth)acrylic acid alkyl ester monomer units. The acrylic polymer may optionally contain hydrophilic group-containing structural units and cyano group-containing monomer units. The acrylic polymer may also contain monomer units other than (meth)acrylic acid alkyl ester monomer units, hydrophilic group-containing structural units, and cyano group-containing monomer units (hereinafter, sometimes referred to as "other monomer units C"). The acrylic polymer is typically a polymer containing 50% by mass or more of (meth)acrylic acid alkyl ester monomer units, with the total repeating units (total monomer units and total structural units) contained in the acrylic polymer being 100% by mass, and is different from the above-mentioned conjugated diene polymer.

[0080] [(Meth)acrylic acid alkyl ester monomer unit] The (meth)acrylic acid alkyl ester monomer unit is a monomer unit that can be formed from a (meth)acrylic acid alkyl ester monomer. Examples of the (meth)acrylic acid alkyl ester monomer that can be used to prepare the acrylic polymer include the same monomers as those explained in the above section "(meth)acrylic acid alkyl ester monomer unit." These may be used alone or in combination of two or more.

[0081] The content of (meth)acrylic acid alkyl ester monomer units in the acrylic polymer is usually 50% by mass or more, preferably 55% by mass or more, and preferably 98% by mass or less, and more preferably 95% by mass or less, when all repeating units (all monomer units and all structural units) contained in the acrylic polymer are taken as 100% by mass.

[0082] [Hydrophilic group-containing structural unit] In the acrylic polymer, the hydrophilic group-containing structural unit may be a structural unit that can be formed from a hydrophilic group-containing monomer, or may be a structural unit obtained by obtaining a water-soluble polymer using a monomer composition containing a monomer having a predetermined functional group and then modifying or converting the functional group into a hydrophilic group. However, when the hydrophilic group-containing structural unit is a hydroxyl group-containing structural unit, the hydrophilic group-containing structural unit in the acrylic polymer is usually a hydrophilic group-containing structural unit introduced into the polymer by the above method (1). Examples of hydrophilic group-containing monomers that can be used to prepare acrylic polymers include the same monomers as those described in the section "Hydrophilic Group-Containing Structural Unit" above. These may be used alone or in combination of two or more. Among these, acid group-containing monomers are preferred as hydrophilic group-containing monomers. Preferred acid group-containing monomers are acrylic acid, methacrylic acid, itaconic acid, and vinyl sulfonic acid.

[0083] The content of the hydrophilic group-containing structural unit in the acrylic polymer is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, when all repeating units (all monomer units and all structural units) contained in the acrylic polymer are taken as 100% by mass.

[0084] [Cyano group-containing monomer unit] The cyano group-containing monomer unit is a monomer unit that can be formed by a cyano group-containing monomer. Examples of the cyano group-containing monomer that can be used to prepare the acrylic polymer include the same monomers as those described in the above section "Cyano group-containing monomer unit." These may be used alone or in combination of two or more types in any ratio.

[0085] The content of the cyano group-containing monomer units in the acrylic polymer is preferably 10% by mass or more, more preferably 15% by mass or more, and is preferably 45% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, when all repeating units (all monomer units and all structural units) contained in the acrylic polymer are taken as 100% by mass.

[0086] [Other monomer units C] The other monomer unit C is a monomer unit that can be formed by another monomer C. The other monomer C is not particularly limited as long as it is a monomer that can be copolymerized with the above-mentioned monomer that can form the acrylic polymer. Examples of other monomers C include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and divinylbenzene; amide group-containing monomers such as acrylamide and methacrylamide; crosslinkable monomers (crosslinkable monomers) such as allyl glycidyl ether and allyl (meth)acrylate; 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 amino group-containing monomers such as aminoethyl vinyl ether and dimethylaminoethyl vinyl ether. These may be used alone or in combination of two or more.

[0087] The content of the other monomer units C 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 even more preferably 0% by mass, i.e., the acrylic polymer does not contain any other monomer units C, when all repeating units (all monomer units and all structural units) contained in the acrylic polymer are taken as 100% by mass.

[0088] <<Glass transition temperature of particulate polymers>> The glass transition temperature of the particulate polymer is preferably −60° C. or higher, more preferably −50° C. or higher, and is preferably −5° C. or lower, more preferably −10° C. or lower.

[0089] <<Volume average particle size of particulate polymer>> The volume average particle size of the particulate polymer is preferably 10 nm or more, more preferably 20 nm or more, and is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 500 nm or less. In this specification, the average particle size of the particulate polymer can be measured according to the method described in the Examples.

[0090] <<Particulate polymer content>> The content of the particulate polymer in the slurry composition is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, based on 100 parts by mass of the dielectric material.

[0091] <<Method for preparing particulate polymer>> The polymerization method for the particulate polymer is not particularly limited, and any method such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. may be used. Furthermore, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization may be used as the polymerization reaction. Furthermore, polymerization solvents and additives such as emulsifiers, dispersants, polymerization initiators, and chain transfer agents that can be used in the polymerization may be commonly used ones, and the amounts used may also be commonly used amounts.

[0092] <Other ingredients> The slurry composition of the present invention may contain other component A. Examples of other component A include the above-mentioned additives used when polymerizing the water-soluble polymer and any particulate polymer.

[0093] <Solid Content Concentration of Slurry Composition for Dielectric Layer> The solid content concentration of the slurry composition is preferably 30% by mass or more, more preferably 35% by mass or more, and is preferably 70% by mass or less, more preferably 65% by mass or less. When the solid content concentration of the slurry composition is equal to or higher than the lower limit, the crack resistance and lamination properties of the resulting dielectric layer can be improved. On the other hand, if the solid content concentration of the slurry composition is equal to or less than the upper limit, the dispersion stability of the slurry composition can be improved.

[0094] <Method for preparing a slurry composition for a dielectric layer> The above-mentioned slurry composition can be prepared by a known method by mixing the above-mentioned dielectric material, water-soluble polymer, crosslinking agent, water, any particulate polymer, and other component A. Specifically, the slurry composition can be prepared by mixing the above-mentioned components using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, Filmix, or planetary / revolution mixer.

[0095] (dielectric layer) The dielectric layer of the present invention is obtained by drying a coating film made from the above-mentioned slurry composition of the present invention. The dielectric layer of the present invention is usually a dried film obtained by partially or completely removing the solvent from a coating film made from the above-mentioned slurry composition. That is, the dielectric layer of the present invention contains the above-mentioned predetermined dielectric material, a water-soluble polymer, and a crosslinking agent, and optionally contains a particulate polymer, water, and other components A. The dielectric layer of the present invention is obtained by drying a coating film made of the slurry composition of the present invention, which has excellent dispersion stability, and therefore has excellent film thickness uniformity.Furthermore, the dielectric layer of the present invention is obtained by drying a coating film made of the slurry composition of the present invention, which can impart excellent crack resistance and lamination properties to the dielectric layer, and therefore has excellent crack resistance and lamination properties.

[0096] The content of the dielectric material in the dielectric layer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, and is preferably 98% by mass or less, and more preferably 95% by mass or less, when all components in the dielectric layer are taken as 100% by mass.

[0097] The content of the water-soluble polymer in the dielectric layer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the dielectric material in the dielectric layer.

[0098] The content of the crosslinking agent in the dielectric layer is usually 0.001 parts by mass or more, preferably 0.01 parts by mass or more, and usually 1 part by mass or less, preferably 0.1 parts by mass or less, based on 100 parts by mass of the dielectric material in the dielectric layer.

[0099] The content of any particulate polymer in the dielectric layer is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, based on 100 parts by mass of the dielectric material in the dielectric layer.

[0100] The thickness of the dielectric layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less.

[0101] The dielectric layer of the present invention may have a conductor layer formed thereon. The conductor layer can be formed by various printing methods such as screen printing, gravure printing, stamp printing, inkjet printing, and offset printing using a pattern formed by these methods, or by vacuum deposition for forming a metal deposition film. When forming the conductor layer by printing, a conductive paste can be used. The conductive paste can be prepared by a conventionally known method, for example, by mixing a polyvinyl acetal resin with a conductive powder such as a metal, a dispersant, a plasticizer, a solvent, and the like.

[0102] <Method for producing dielectric layer> The dielectric layer can be produced by applying the slurry composition of the present invention to a release substrate and drying the resulting coating film.

[0103] Here, the release substrate used in producing the dielectric layer is preferably made of a flexible resin. By using a release substrate made of a flexible resin, the release substrate (laminated film) on which the dielectric layer is formed, obtained by applying the slurry composition to the release substrate and drying it, can be stored in a rolled state and supplied as needed. The release substrate is not particularly limited, and examples thereof include substrates containing polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, and other resins.

[0104] The release substrate is preferably subjected to a surface treatment to improve releasability on the side on which the dielectric layer of the present invention is formed. The surface treatment is not particularly limited, and examples thereof include surface treatments using a release agent such as a silicone-based release agent, a fluorine-based release agent, or a wax-based release agent.

[0105] The thickness of the release substrate is not particularly limited, but is usually 20 μm or more and 100 μm or less.

[0106] The method for applying the slurry composition to the release substrate is not particularly limited, and examples thereof include known application methods using an applicator or various roll coaters such as a gravure coater and a comma coater (registered trademark).

[0107] The method for drying the coating film formed on the release substrate is not particularly limited, and for example, a known drying method using a hot air dryer can be mentioned. The drying conditions can be appropriately set depending on the content of the solvent in the coating film, the thickness of the coating film, etc., but the drying temperature is usually 80°C or higher and 150°C or lower, and the drying time is usually 3 minutes or higher and 60 minutes or lower.

[0108] When the dielectric layer of the present invention is used in the production of a multilayer ceramic capacitor or the like, a plurality of dielectric layers may be superimposed on one another and then thermocompression bonded. However, the dielectric layer may be peeled off from the release substrate either before or after the superposition and thermocompression bonding of the dielectric layers.

[0109] (multilayer ceramic capacitors) The multilayer ceramic capacitor of the present invention is a sintered product obtained by sintering a laminate in which the dielectric layers of the present invention described above are stacked. The multilayer ceramic capacitor of the present invention is obtained by sintering a laminate in which the dielectric layers of the present invention, which have excellent film thickness uniformity, are stacked, and therefore performance variations are suppressed. Furthermore, the multilayer ceramic capacitor of the present invention is obtained by sintering a laminate in which the dielectric layers of the present invention, which have excellent crack resistance and stackability, are stacked, and therefore has excellent performance. An example of the multilayer ceramic capacitor of the present invention will be described below with reference to FIG. 1, but the multilayer ceramic capacitor of the present invention is not limited to this.

[0110] FIG. 1 is a schematic cross-sectional view showing an example of a multilayer ceramic capacitor according to the present invention. The multilayer ceramic capacitor 10 shown in FIG. 1 includes layered dielectrics 11 and layered internal electrodes 12 that are alternately stacked. A pair of external electrodes 13 is provided on the outer sides of the dielectrics 11 and the internal electrodes 12. One of the pair of internal electrodes 12 that are adjacent to each other along the stacking direction, sandwiching the dielectric 11 therebetween, is electrically connected to one of the pair of external electrodes 13 within the multilayer ceramic capacitor 10. The other of the pair of internal electrodes 12 that are adjacent to each other along the stacking direction, sandwiching the dielectric 11 therebetween, is electrically connected to the other of the pair of external electrodes 13 within the multilayer ceramic capacitor 10. This results in a structure in which multiple capacitor elements are electrically connected in parallel between the pair of external electrodes 13. Note that the interface between the dielectric layers of the present invention that may be formed when the dielectric layers are stacked is not shown in FIG. 1 because it may disappear when the dielectric layers are integrated by sintering.

[0111] The multilayer ceramic capacitor is not particularly limited and can be produced by a conventionally known method. For example, the multilayer ceramic capacitor can be produced by stacking a plurality of dielectric layers of the present invention, each having a conductive layer that can serve as an internal electrode, so that the dielectric layers and the conductive layers alternate, heat-pressing the stack to form a laminate, thermally decomposing and removing binder components (water-soluble polymer, crosslinking agent, any particulate polymer, etc.) contained in the laminate (degreasing treatment), sintering the stack, and then forming external electrodes on the end faces of the sintered ceramic product obtained by sintering.

[0112] The degreasing treatment is usually carried out in a nitrogen atmosphere at a temperature of 300° C. to 500° C. The degreasing treatment time is usually 1 hour to 5 hours. The binder content of the laminate after degreasing is usually 50 ppm or less.

[0113] The degreasing process is usually carried out under an oxygen partial pressure of 10 -9 ~10 -12 The sintering is carried out in a reducing atmosphere such as H2-N2-H2O gas at 1000° C. to 1500° C. The sintering time for the laminate is usually 1 hour to 30 hours.

[0114] The external electrodes can be formed by applying an external electrode material to the end faces of the sintered ceramic body and then baking it, thereby obtaining, for example, the multilayer ceramic capacitor shown in Figure 1. Examples of materials for the external electrodes include Cu paste containing glass frit. Baking is usually performed in a nitrogen atmosphere at a temperature of 500°C to 1500°C. The surfaces of the external electrodes can also be plated with Ni, Sn, or the like. [Example]

[0115] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a polymer produced by polymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that monomer to all the monomers used in the polymerization of the polymer, unless otherwise specified. The glass transition temperatures of the water-soluble polymer and the particulate polymer, the volume average particle size of the particulate polymer, the weight average molecular weight of the water-soluble polymer, the dispersion stability, the lamination property, and the crack resistance were measured and evaluated by the following procedures.

[0116] <Method for measuring the glass transition temperature of water-soluble polymers and particulate polymers> Aqueous solutions containing the water-soluble polymers or aqueous dispersions containing the particulate polymers of the Examples and Comparative Examples were dried for 3 days at 50% humidity and 25°C to obtain films with a thickness of 1.0 mm. These films were then dried for 10 hours in a vacuum dryer at 60°C. The glass transition temperatures (°C) of the dried films were then measured using a differential scanning calorimeter (DSC6220, manufactured by SII NanoTechnology Inc.) in accordance with JIS K7121 at temperatures ranging from -100°C to 180°C and a heating rate of 5°C / min.

[0117] <Method for measuring volume average particle size of particulate polymer> The volume-average particle diameter of the particulate polymers in the examples and comparative examples was measured by a laser diffraction method. Specifically, an aqueous dispersion containing the prepared particulate polymer (adjusted to a solids concentration of 0.1%) was used as a sample. Then, in the particle size distribution (volume basis) measured using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc., product name "LS-230"), the particle diameter D50 at which the cumulative volume calculated from the smallest diameter side reached 50% was taken as the volume-average particle diameter.

[0118] <Method for measuring weight-average molecular weight of water-soluble polymer> The weight average molecular weight of the water-soluble polymer was measured by gel permeation chromatography (GPC). Specifically, the water-soluble polymer was first added to approximately 5 mL of eluent so that the solid concentration was approximately 0.5 g / L, and slowly dissolved at room temperature. After visually confirming the dissolution of the water-soluble polymer, the solution was gently filtered through a 0.45 μm filter to prepare a measurement sample, which was then used for measurement. A calibration curve was then created using a standard substance, and the weight-average molecular weight was calculated as a value converted from 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: 0.1M Tris buffer (with 0.1M potassium chloride) ·Flow rate: 0.5mL / min Sample concentration: 0.05g / L (solids concentration) ·Injection volume: 200μL Column temperature: 40℃ Detector: Differential refractive index detector RI (manufactured by Tosoh Corporation, product name "RI-8020") Standard substance: Monodisperse pullulan (Showa Denko Co., Ltd.)

[0119] <Dispersion stability> The viscosity η0 of the slurry compositions produced in the examples and comparative examples was measured at 25°C and 60 rpm using a Brookfield viscometer. The slurry compositions were then allowed to stand at 25°C for 7 days, and the viscosity η1 was measured again in the same manner as above. The viscosity change rate α was calculated using the measured viscosities η0 and η1 according to the following formula (2). Viscosity change rate α(%)=(η1 / η0)×100 (2) The dispersion stability was evaluated according to the following criteria: The greater the viscosity change rate α is, and the closer it is to 100%, the less the viscosity of the slurry composition is likely to change over time, indicating that the slurry composition has excellent dispersion stability. A: Viscosity change rate α is 100% or more but less than 150% B: Viscosity change rate α is 150% or more but less than 200% C: Viscosity change rate α is 200% or more

[0120] <Stackability> The release substrate with a dielectric layer (the release substrate with a dielectric layer) produced in the examples and comparative examples was cut into a square with a width of 5 cm and a length of 5 cm, and the release substrate was peeled off to prepare a test piece. Two such test pieces were prepared, stacked on top of each other, and then heated at 80°C and 5 kg / cm 2 The laminated dielectric layers were then cut with a cutter, and the cross section of the laminated dielectric layers was visually inspected and evaluated according to the following criteria. A: The dielectric layers are bonded together and no powder falls off at the cut surface. B: The dielectric layers are bonded together, but powder is falling off at the cut surface. C: The dielectric layers are not bonded together, and powder is falling off the cut surface.

[0121] <Crack resistance> In the examples and comparative examples, the dielectric layer formed on the release substrate (the release substrate with the dielectric layer) was cut into a square with a width of 5 cm and a length of 5 cm, and the release substrate was peeled off to prepare a test piece. Two such test pieces were prepared, stacked on top of each other, and then heated at 80°C and 5 kg / cm 2 The laminate was pressed for 60 seconds under a pressure of 1000°C, and then fired at 1000°C for 5 hours and at 1200°C for 5 hours. The dielectric layer was visually inspected and the crack resistance was evaluated according to the following criteria. A: No cracks at both 1000℃ and 1200℃ B: No cracks occurred at 1000℃, but cracks occurred at 1200℃ C: Cracks occurred at both 1000℃ and 1200℃

[0122] Example 1 <Preparation of Water-Soluble Polymer> A 5 MPa pressure vessel equipped with a stirrer was charged with 35 parts of methacrylic acid (hydrophilic group-containing monomer), 52 parts of ethyl acrylate ((meth)acrylic acid alkyl ester monomer), and 13 parts of n-butyl acrylate ((meth)acrylic acid alkyl ester monomer) as a monomer composition, 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. After thorough stirring, the mixture was heated to 60°C to initiate 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, yielding an aqueous solution of water-soluble polymer A (solids concentration 10%). The glass transition temperature and weight-average molecular weight of the resulting aqueous solution were measured. The results are shown in Table 1.

[0123] <Preparation of particulate polymer> 74 parts of ion-exchanged water, 0.2 parts of sodium dodecyl diphenyl ether sulfonate, 1.0 parts of ammonium persulfate as a polymerization initiator, and 9.7 parts of ion-exchanged water were added to a 5 MPa pressure vessel A equipped with a stirrer, heated to 70°C, and stirred for 30 minutes. Next, 75.0 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid alkyl ester monomer, 22.0 parts of acrylonitrile as a cyano group-containing monomer, 2.0 parts of itaconic acid as a hydrophilic group-containing structural unit, 1.0 parts of 2-hydroxyethyl acrylate, 0.8 parts of sodium dodecyl diphenyl ether sulfonate as an emulsifier, and 74 parts of ion-exchanged water were added to a separate 5 MPa pressure vessel B equipped with a stirrer, and stirred to produce an emulsion. The resulting emulsion was gradually added from pressure vessel B to pressure vessel A over approximately 200 minutes, then stirred for approximately 180 minutes. The reaction was terminated by cooling when the monomer conversion reached 97% or higher. Thereafter, the pH was adjusted with a 4% NaOH aqueous solution, and unreacted monomers were removed by heating and vacuum distillation to obtain an aqueous dispersion of particulate polymer (ACL) (solid concentration: 40%). The pH of the obtained aqueous dispersion was 8.0. The glass transition temperature and volume average particle size of the particulate polymer were measured using the obtained aqueous dispersion. The results are shown in Table 1.

[0124] <Preparation of Slurry Composition> 100 parts of barium titanate (BT-01, manufactured by Sakai Chemical Industry Co., Ltd.) with an average particle size (d50) of 0.1 μm as the dielectric material, 1 part of the water-soluble polymer A prepared above (10 parts as an aqueous solution) in terms of solids, and 20 parts of water as the solvent were mixed with 100 parts of zirconia beads (manufactured by Nikkato Corporation) with a particle size of 0.1 mm as mixing beads using a bead mill (RMB-01, manufactured by Imex Co., Ltd.) at 500 rpm for 2 hours. 44 parts of water was then added, and 0.05 parts of a silane coupling agent (KBP-90, manufactured by Shin-Etsu Silicone Co., Ltd.) with an amino group was added as a crosslinking agent. The mixture was stirred at 500 rpm for 1 hour. The zirconia beads were filtered off to prepare a dispersion of barium titanate. To 174 parts of this dispersion (100 parts of barium titanate), 9 parts of particulate polymer (22.5 parts as aqueous dispersion) was added, and then the mixture was stirred at 1000 rpm for 3 minutes in a planetary centrifugal mixer to prepare a slurry composition with a solids concentration of 56%.

[0125] <Creating the dielectric layer> The slurry composition obtained above was applied to a release-treated film (PET38AL-5, manufactured by Lintec Corporation) measuring 100 mm in width and 100 mm in length using a gravure coater so that the thickness of the dried green sheet (dry film) would be approximately 1.0 μm, and the film was dried in an oven at 100°C for 5 minutes to obtain a dielectric layer on the release substrate (ceramic green sheet method).

[0126] Example 2 In preparing the slurry composition, the amount of crosslinking agent added was changed from 0.05 part to 0.005 part, and a slurry composition with a solid content of 56.5% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0127] Example 3 In preparing the slurry composition, the amount of crosslinking agent added was changed from 0.05 parts to 0.2 parts, and a slurry composition with a solid content of 55% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0128] Example 4 In preparing the slurry composition, the crosslinking agent was changed from a silane coupling agent having an amino group (KBP-90, manufactured by Shin-Etsu Silicones Co., Ltd.) to a titanate coupling agent having an amino group (Plenact (registered trademark) 44, manufactured by Ajinomoto Fine-Techno Co., Ltd.), and a slurry composition with a solids concentration of 56% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0129] Example 5 In preparing the slurry composition, the amount of the water-soluble polymer A added as a solid component was changed from 1 part to 0.2 parts, and a slurry composition having a solid component concentration of 61% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0130] Example 6 In preparing the slurry composition, the amount of the water-soluble polymer A added as a solid component was changed from 1 part to 8 parts, and a slurry composition having a solid component concentration of 48% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0131] Example 7 In preparing the slurry composition, various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that a slurry composition with a solid content concentration of 57% was obtained without adding a particulate polymer. The results are shown in Table 1.

[0132] Example 8 In preparing the slurry composition, barium titanate was replaced with calcium zirconate (Sakai Chemical Industry Co., Ltd., CZ-03) having an average particle size (d50) of 0.3 μm, and a slurry composition with a solid content of 56% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0133] Example 9 Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the preparation of the water-soluble polymer, the amount of potassium persulfate added was changed from 1 part to 2 parts to prepare water-soluble polymer B, and in the preparation of the slurry composition, water-soluble polymer A was changed to water-soluble polymer B to obtain a slurry composition with a solids concentration of 59%. The results are shown in Table 1.

[0134] Example 10 Various operations, measurements, and evaluations were carried out in the same manner as in Example 1, except that in the preparation of the water-soluble polymer, the amount of potassium persulfate added was changed from 1 part to 0.5 parts to prepare water-soluble polymer C, and in the preparation of the slurry composition, water-soluble polymer A was changed to water-soluble polymer C to obtain a slurry composition with a solids concentration of 48%. The results are shown in Table 1.

[0135] Example 11 In preparing the slurry composition, the water-soluble polymer A was changed to the water-soluble polymer D prepared by the following method, and a slurry composition having a solids concentration of 48% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0136] <Preparation of aqueous solution of water-soluble polymer> Polyvinyl alcohol (Denka Poval (registered trademark) B-33, manufactured by Denka Co., Ltd.) was prepared as a water-soluble polymer D having a hydroxyl group as a hydrophilic group. The polyvinyl alcohol and ion-exchanged water were mixed to a solids concentration of 10%, to obtain an aqueous solution of the water-soluble polymer D.

[0137] Example 12 In preparing the slurry composition, the crosslinking agent was changed from a silane coupling agent having an amino group (KBP-90, manufactured by Shin-Etsu Silicones Co., Ltd.) to a silane coupling agent having a hydroxyl group (X-12-1098, manufactured by Shin-Etsu Silicones Co., Ltd.), and a slurry composition with a solid content of 52% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 11. The results are shown in Table 1.

[0138] (Comparative Example 1) In preparing the slurry composition, various operations, measurements, and evaluations were carried out in the same manner as in Example 11, except that a slurry composition with a solids concentration of 57% was obtained without adding a crosslinking agent. The results are shown in Table 1.

[0139] (Comparative Example 2) In preparing the slurry composition, the amount of crosslinking agent added was changed from 0.05 part to 0.0005 part, and a slurry composition with a solids concentration of 41% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 12. The results are shown in Table 1.

[0140] (Comparative Example 3) In preparing the slurry composition, the amount of crosslinking agent added was changed from 0.05 parts to 1.5 parts, and a slurry composition with a solids concentration of 41% was obtained. Except for this, various operations, measurements, and evaluations were carried out in the same manner as in Example 12. The results are shown in Table 1.

[0141] In addition, in Table 1 shown below, "BaTiO3" indicates barium titanate, "CaZrO3" refers to calcium zirconate.

[0142] [Table 1]

[0143] As is clear from Table 1, the slurry compositions of the examples are capable of imparting excellent crack resistance and lamination properties to the dielectric layer, and are also excellent in dispersion stability. [Industrial Applicability]

[0144] According to the present invention, it is possible to provide a slurry composition for a dielectric layer that can impart excellent crack resistance and lamination properties to a dielectric layer and has excellent dispersion stability. Furthermore, according to the present invention, it is possible to provide a dielectric layer obtained by drying a coating film made of the above-mentioned slurry composition for a dielectric layer. Furthermore, according to the present invention, it is possible to provide a multilayer ceramic capacitor obtained by sintering a laminate in which the above-mentioned dielectric layers are stacked. [Explanation of symbols]

[0145] 10: Multilayer ceramic capacitor 11: Dielectric 12: Internal electrode 13: External electrode

Claims

1. A slurry composition for a dielectric layer, comprising a dielectric material having a perovskite structure, a water-soluble polymer having a hydrophilic group, a crosslinking agent, and water, The slurry composition for a dielectric layer, wherein the content of the crosslinking agent is 0.001 parts by mass or more and 1 part by mass or less, relative to 100 parts by mass of the water-soluble polymer.

2. 2. The slurry composition for a dielectric layer according to claim 1, wherein the water-soluble polymer has a weight average molecular weight of 5,000 or more and 2,000,000 or less.

3. 2. The slurry composition for a dielectric layer according to claim 1, wherein the hydrophilic group of the water-soluble polymer is at least one of a carboxylic acid group and a hydroxyl group.

4. 2. The slurry composition for a dielectric layer according to claim 1, wherein the content of the water-soluble polymer is 0.1 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of the dielectric material.

5. The dielectric layer slurry composition according to claim 1 , wherein the cross-linking agent comprises a metal atom.

6. The slurry composition for a dielectric layer according to claim 1 , wherein the crosslinking agent has an amino group.

7. The dielectric layer slurry composition according to claim 1 , further comprising a particulate polymer.

8. 2. The slurry composition for a dielectric layer according to claim 1, wherein the solid content concentration is 30% by mass or more and 70% by mass or less.

9. A dielectric layer obtained by drying a coating film made of the slurry composition for a dielectric layer according to any one of claims 1 to 8.

10. A multilayer ceramic capacitor obtained by sintering a laminate in which the dielectric layers according to claim 9 are stacked.

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