Binder for producing ceramic green sheet, slurry composition, ceramic green sheet, and method for producing multilayer ceramic capacitor

Abstract

To provide a binder for producing ceramic green sheets, which can obtain ceramic green sheets having high strength and excellent thermal decomposition properties while keeping the viscosity of a slurry composition low. [Solution] The binder for producing ceramic green sheets includes a block copolymer mainly composed of structural units derived from vinyl monomers, substantially free of polyvinyl acetal structures, and having hydrogen-bonding functional groups. The slurry composition includes a binder for producing ceramic green sheets including a block copolymer mainly composed of structural units derived from vinyl monomers, substantially free of polyvinyl acetal structures, and having hydrogen-bonding functional groups, and ceramic powder. The ceramic green sheets are formed using the slurry composition.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2020-088217, filed on May 20, 2020, the contents of which are incorporated herein by reference. [Technical Field]

[0002] The present disclosure relates to a binder for producing a ceramic green sheet, a slurry composition, a ceramic green sheet, and a method for producing a multilayer ceramic capacitor. [Background technology]

[0003] Multilayer ceramic capacitors are generally manufactured by stacking ceramic green sheets formed using a slurry composition containing ceramic powder and a binder. To manufacture a multilayer ceramic capacitor, a metal paste that will become the internal electrodes is first printed on ceramic green sheets, and the green sheets are then stacked and heated and pressed to produce a laminate. The laminate is then subjected to a heat treatment (degreasing treatment) to pyrolyze the binder resin contained in the laminate, and then sintered at a high temperature. External electrodes are formed on the resulting ceramic sintered body to produce a multilayer ceramic capacitor.

[0004] Polyvinyl acetal resins and (meth)acrylic resins are commonly used as binders for ceramic green sheets (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses a slurry composition for ceramic green sheets that contains a polyvinyl acetal resin of a specific composition as a binder. Patent Document 2 also discloses a slurry composition for ceramic green sheets that contains a (meth)acrylic resin of a specific composition as a binder. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-089354 [Patent Document 2] International Publication No. 2018 / 235907 Summary of the Invention [Problem to be solved by the invention]

[0006] When polyvinyl acetal resin is used as a binder, a ceramic green sheet with relatively high strength can be obtained. However, polyvinyl acetal resin does not have sufficiently high thermal decomposition properties, and there is a concern that binder residue may be generated after degreasing treatment.

[0007] In contrast, (meth)acrylic resins exhibit good thermal decomposition properties, but the strength of the resulting ceramic green sheets is not sufficiently high. Therefore, there is a concern that cracks may occur in the ceramic green sheets due to the load acting on the ceramic green sheets during the manufacturing process of the multilayer ceramic capacitor. Such cracks in the ceramic green sheets are more likely to occur as the ceramic green sheets become thinner and more multi-layered due to the increasing performance of electronic devices.

[0008] One method for increasing the strength of a ceramic green sheet is to use a binder with a high molecular weight. However, the use of a high-molecular-weight binder increases the viscosity of the slurry composition for a ceramic green sheet, which may reduce the applicability to a support.

[0009] The present disclosure has been made in view of the above circumstances, and a main object of the present disclosure is to provide a binder for producing ceramic green sheets that can obtain ceramic green sheets with high strength and excellent thermal decomposition properties while keeping the viscosity of the slurry composition low. [Means for solving the problem]

[0010] As a result of intensive research into solving the above problems, the present inventors have completed the present disclosure by using a specific block copolymer. The present disclosure provides the following means.

[0011] [1] A binder for producing a ceramic green sheet, comprising a block copolymer, the block copolymer mainly comprising structural units derived from vinyl monomers, substantially free of a polyvinyl acetal structure, and having a hydrogen-bonding functional group. [2] The binder for producing a ceramic green sheet according to [1], wherein the block copolymer has structural units derived from a (meth)acrylic monomer in an amount of 70 mass % or more based on the total structural units. [3] The binder for producing a ceramic green sheet according to [1] or [2], wherein the block copolymer has a structural unit derived from an aromatic vinyl monomer and a structural unit derived from an imide group-containing vinyl monomer. [4] The binder for producing a ceramic green sheet according to any one of [1] to [3], wherein the block copolymer has structural units derived from a methacrylic acid ester compound in an amount of 5% by mass to 70% by mass based on all structural units. [5] The binder for producing a ceramic green sheet according to any one of [1] to [4], wherein the block copolymer has a polymer block having a glass transition temperature of 30°C or higher and a polymer block having a glass transition temperature of lower than 30°C.

[0012] [6] The binder for producing a ceramic green sheet according to any one of [1] to [5], wherein the block copolymer has structural units derived from a vinyl monomer having a hydrogen-bonding functional group in an amount of 5% by mass or more and 25% by mass or less based on the total structural units. [7] The binder for producing a ceramic green sheet according to any one of [1] to [6], wherein the block copolymer has a molecular weight distribution (Mw / Mn) expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 3.0 or less. [8] A slurry composition comprising the binder for producing a ceramic green sheet according to any one of [1] to [7] above and ceramic powder. [9] A ceramic green sheet formed using the slurry composition of [8] above.

[10] A method for manufacturing a multilayer ceramic capacitor using the ceramic green sheet according to [9] above. [Effects of the Invention]

[0013] According to the binder for producing a ceramic green sheet of the present disclosure, it is possible to obtain a ceramic green sheet that has high strength and excellent thermal decomposition properties while keeping the viscosity of the slurry composition low. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present disclosure will be described in detail below. In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0015] <Binder for ceramic green sheet manufacturing> The binder for producing a ceramic green sheet of the present disclosure is used to mold ceramic powder to produce a laminated ceramic green sheet. The binder for producing a ceramic green sheet of the present disclosure contains a block copolymer (hereinafter also referred to as "block copolymer (P)") that is mainly composed of structural units derived from vinyl monomers, is substantially free of a polyvinyl acetal structure, and has a hydrogen-bonding functional group.

[0016] (vinyl monomer) The block copolymer (P) has structural units derived from a vinyl monomer, such as a (meth)acrylic monomer, an aromatic vinyl monomer, or an imide group-containing vinyl monomer.

[0017] In this specification, "mainly composed of structural units derived from vinyl monomers" means that the content of structural units derived from vinyl monomers in the block copolymer (P) is 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 99% by mass or more, based on the total structural units of the block copolymer (P).

[0018] Examples of the (meth)acrylic monomer include (meth)acrylic acid, (meth)acrylic acid alkyl ester compounds, (meth)acrylic acid aliphatic cyclic ester compounds, (meth)acrylic acid aromatic ester compounds, (meth)acrylic acid alkoxyalkyl compounds, (meth)acrylic acid hydroxyalkyl compounds, (di)alkylaminoalkyl (meth)acrylate compounds, epoxy group-containing (meth)acrylic acid ester compounds, and polyoxyalkylene (meth)acrylate compounds.

[0019] Specific examples of these include (meth)acrylic acid alkyl ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, amyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-decyl (meth)acrylate; Examples of aliphatic cyclic ester compounds of (meth)acrylic acid include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; Examples of aromatic ester compounds of (meth)acrylic acid include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and 3-phenoxypropyl (meth)acrylate; Examples of the alkoxyalkyl (meth)acrylate compounds include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, n-propoxyethyl (meth)acrylate, n-butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, and ethoxypropyl (meth)acrylate; Examples of hydroxyalkyl (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; (Di)alkylaminoalkyl(meth)acrylate compounds include N-[2-(methylamino)ethyl](meth)acrylate, N-[2-(dimethylamino)ethyl](meth)acrylate, N-[2-(ethylamino)ethyl](meth)acrylate, and N-[2-(diethylamino)ethyl](meth)acrylate; Epoxy group-containing (meth)acrylic acid ester compounds include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate; Examples of polyoxyalkylene (meth)acrylate compounds include polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate, etc. As the (meth)acrylic monomer, one of these compounds can be used alone or two or more of them can be used in combination.

[0020] Among the above, the (meth)acrylic monomer used for producing the block copolymer (P) is preferably a compound represented by the following formula (1), because when used as a binder for producing a ceramic green sheet, it has high thermal decomposition property during firing and can reduce binder residue. CH2=CR 1 -C(=O)-O-(R 2 O)nR 3 …(1) (In formula (1), R 1 is a hydrogen atom or a methyl group, and R2 is a linear or branched alkylene group having 2 to 6 carbon atoms, and R 3 is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. n is an integer of 0 to 50. When n is 2 or more, multiple R 2 may be the same or different.)

[0021] In order to further improve the dispersion stability of the ceramic powder, the (meth)acrylic monomer used in producing the block copolymer (P) preferably contains a (meth)acrylic acid alkyl ester compound, and particularly preferably contains at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0022] The block copolymer (P) is preferably a polymer mainly composed of structural units derived from a (meth)acrylic monomer (hereinafter also referred to as "(meth)acrylic units"). The content of (meth)acrylic units in the block copolymer (P) is preferably 70% by mass or more, based on the total structural units of the block copolymer (P). When the block copolymer (P) contains 70% by mass or more of (meth)acrylic units, it is advantageous in that it can be used as a binder resin with excellent thermal decomposition properties during firing. From this viewpoint, the content of (meth)acrylic units is more preferably 80% by mass or more, even more preferably 85% by mass or more, and particularly preferably 87% by mass or more, based on the total structural units of the block copolymer (P).

[0023] The block copolymer (P) preferably has a structural unit derived from a methacrylic acid ester compound (hereinafter also referred to as a "methacrylic acid ester unit"). The block copolymer (P) preferably has a methacrylic acid ester unit, which is advantageous in that it can further enhance the thermal decomposition property of the binder. The methacrylic acid ester unit is preferably a structural unit derived from a compound represented by the following formula (2): CH2=C(CH3)-C(=O)-O-(R 4 O) m -R 5 …(2) (In formula (2), R 4 is a linear or branched alkylene group having 2 to 6 carbon atoms, and R 5 is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. m is an integer of 0 to 50. When m is 2 or more, multiple R 4 may be the same or different.)

[0024] Specific examples of the compound represented by the above formula (2) include alkyl methacrylate compounds, aliphatic cyclic ester compounds of methacrylic acid, aromatic ester compounds of methacrylic acid, alkoxyalkyl methacrylate compounds, hydroxyalkyl methacrylate compounds, and polyoxyalkylene methacrylate compounds, which are exemplified as vinyl monomers constituting the block copolymer (P).

[0025] The methacrylic acid ester unit contained in the block copolymer (P) is preferably a structural unit derived from at least one selected from the group consisting of alkyl methacrylate compounds, alkoxyalkyl methacrylate compounds, hydroxyalkyl methacrylate compounds, and polyoxyalkylene methacrylate compounds, and more preferably a structural unit derived from at least one selected from the group consisting of alkyl methacrylate compounds, alkoxyalkyl methacrylate compounds, and hydroxyalkyl methacrylate compounds. Among these, it is particularly preferred that the block copolymer (P) contains a structural unit derived from at least one selected from the group consisting of alkyl methacrylate compounds and alkoxyalkyl methacrylate compounds.

[0026] The content of the methacrylic acid ester units in the block copolymer (P) is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on the total structural units of the block copolymer (P). The upper limit of the content of the methacrylic acid ester units is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less, based on the total structural units of the block copolymer (P), in order to prevent a decrease in the strength and flexibility of the ceramic green sheet. The methacrylic acid ester compounds may be used singly or in combination of two or more.

[0027] When the block copolymer (P) has a structural unit derived from an aromatic vinyl monomer (hereinafter also referred to as an "aromatic vinyl unit") and a structural unit derived from an imide group-containing vinyl monomer (hereinafter also referred to as an "imide group-containing vinyl unit"), it is preferable in that the strength of the ceramic green sheet produced using the block copolymer (P) can be increased.

[0028] The aromatic vinyl monomer is a monomer having a structure in which a polymerizable carbon-carbon double bond is bonded to an aromatic ring. Specific examples of aromatic vinyl monomers include styrene, α-methylstyrene, β-methylstyrene, vinylxylene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, pn-butylstyrene, p-isobutylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, o-isopropenylphenol, o-vinylbenzoic acid, m-vinylbenzoic acid, p-vinylbenzoic acid, and styrene-based monomers such as divinylbenzene, as well as vinylnaphthalene. As the aromatic vinyl monomer, styrene-based monomers can be preferably used. As the aromatic vinyl monomer, one or more of these can be used.

[0029] Examples of imide group-containing vinyl monomers include maleimide compounds such as maleimide and N-substituted maleimide compounds; itaconimide compounds such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-2-ethylhexylitaconimide, and N-cyclohexylitaconimide; citraconimide compounds such as N-methylcitraconimide, N-ethylcitraconimide, N-butylcitraconimide, N-2-ethylhexylcitraconimide, and N-cyclohexylcitraconimide; and (meth)acrylimide compounds such as N-(2-(meth)acryloyloxyethyl)succinimide, N-(2-(meth)acryloyloxyethyl)maleimide, N-(2-(meth)acryloyloxyethyl)phthalimide, and N-(4-(meth)acryloyloxybutyl)phthalimide. Among these, maleimide compounds are preferred because they exhibit high copolymerizability with styrene-based monomers.

[0030] As the maleimide compound, maleimide and N-substituted maleimide compounds can be preferably used. Examples of the N-substituted maleimide compound include N-alkyl-substituted maleimide compounds such as N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, and N-stearylmaleimide; N-cyclopentyl ... Examples of such compounds include N-cycloalkyl-substituted maleimide compounds such as hexylmaleimide, N-aralkyl-substituted maleimide compounds such as N-benzylmaleimide, and N-aryl-substituted maleimide compounds such as N-phenylmaleimide, N-(4-hydroxyphenyl)maleimide, N-(4-acetylphenyl)maleimide, N-(4-methoxyphenyl)maleimide, N-(4-ethoxyphenyl)maleimide, N-(4-chlorophenyl)maleimide, and N-(4-bromophenyl)maleimide. One or more of these compounds may be used as the imide group-containing vinyl monomer.

[0031] Of the above, the imide group-containing vinyl monomer used to produce the block copolymer (P) is preferably a compound represented by the following formula (3). [ka] (In formula (3), R 6 represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a cyclohexyl group, a phenyl group, or a substituted phenyl group in which a hydroxy group, an alkoxy group having 1 to 2 carbon atoms, an acetyl group, or a halogen atom is bonded to any position of the phenyl group.

[0032] When the block copolymer (P) has aromatic vinyl units, the content of the aromatic vinyl units is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, based on the total structural units of the block copolymer (P). The upper limit of the aromatic vinyl units is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on the total structural units of the block copolymer (P).

[0033] When the block copolymer (P) has imide group-containing vinyl units, the content of the imide group-containing vinyl units is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, based on the total structural units of the block copolymer (P). The upper limit of the imide group-containing vinyl units is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on the total structural units of the block copolymer (P). When an aromatic vinyl monomer and an imide group-containing vinyl monomer are used in combination in producing the block copolymer (P), the proportion of the aromatic vinyl monomer used per mole of the imide group-containing vinyl monomer is preferably 0.01 to 20 moles, more preferably 0.1 to 10 moles, and even more preferably 0.2 to 5 moles.

[0034] The block copolymer (P) may contain structural units derived from vinyl monomers other than (meth)acrylic monomers, aromatic vinyl monomers, and imide group-containing vinyl monomers (hereinafter also referred to as "other vinyl monomers"), as long as the effects achieved by the present disclosure are not impaired. Examples of other vinyl monomers include (meth)acrylamide compounds such as (meth)acrylamide, tert-butyl(meth)acrylamide, and N-methylolacrylamide; vinyl acetate; and vinyl benzoate. The content of structural units derived from other vinyl monomers in the block copolymer (P) is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less, based on the total structural units of the block copolymer (P).

[0035] (Hydrogen-bonding functional group) The block copolymer (P) has a hydrogen-bonding functional group. Examples of the hydrogen-bonding functional group that the block copolymer (P) has include a hydroxyl group, an amino group (including a primary amino group, a secondary amino group, and a tertiary amino group), a carboxyl group, an amide group, a thiol group, and a sulfonyl group. Among these, the hydroxyl group, the amino group, and the carboxyl group are preferred, and the hydroxyl group is particularly preferred, because they have high adsorption to ceramic powder and can increase the dispersion stability of the ceramic powder.

[0036] The block copolymer (P) is preferably produced using a vinyl monomer having a hydrogen-bonding functional group (hereinafter also referred to as a "hydrogen-bonding group-containing vinyl monomer"), since it is easy to adjust the amount of hydrogen-bonding functional groups in the block copolymer (P) and it is easy to produce a block copolymer having a hydrogen-bonding functional group. The hydrogen-bonding group-containing vinyl monomer preferably has a hydroxyl group, and specific examples thereof include (meth)acrylate hydroxyalkyl compounds such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; mono(meth)acrylic acid ester compounds of polyalkylene glycols (polyethylene glycol, polypropylene glycol, etc.); hydroxystyrene compounds such as p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, and o-isopropenylphenol; and hydroxy-substituted maleimide compounds such as N-(4-hydroxyphenyl)maleimide. Among the above, it is particularly preferred to use a (meth)acrylate hydroxyalkyl compound as the hydrogen-bonding group-containing vinyl monomer.

[0037] In the block copolymer (P), the content of structural units derived from hydrogen-bonding group-containing vinyl monomers is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more, based on the total structural units of the block copolymer (P), from the viewpoint of sufficiently increasing the dispersion stability of the inorganic particles. The upper limit of the content of structural units derived from hydrogen-bonding group-containing vinyl monomers is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on the total structural units of the block copolymer (P), from the viewpoint of ensuring solubility in the solvent component of the slurry composition. The hydrogen-bonding group-containing vinyl monomers may be used alone or in combination of two or more.

[0038] The block copolymer (P) is a polymer primarily composed of (meth)acrylic units and is substantially free of a polyvinyl acetal structure. In this specification, "substantially free of a polyvinyl acetal structure" means that the block copolymer (P) does not exhibit properties derived from the polyvinyl acetal structure. However, it is acceptable for the block copolymer (P) to contain a trace amount of polyvinyl acetal structure to the extent that it does not impair the effects of the present disclosure. Specifically, the proportion of polyvinyl acetal structure in the block copolymer (P) is typically 2% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. It is particularly preferred that the block copolymer (P) contains no polyvinyl acetal structure.

[0039] (Structure of block copolymer (P)) The block copolymer (P) is not particularly limited in the number or sequence of polymer blocks in one molecule, as long as it has two or more polymer blocks. Specific examples of the block copolymer (P) include an (AB) diblock copolymer consisting of polymer block (A) and polymer block (B), an (ABA) triblock copolymer consisting of polymer block (A) / polymer block (B) / polymer block (A), and an (ABC) triblock copolymer consisting of polymer block (A), polymer block (B), and polymer block (C). The block copolymer (P) may also be a polyblock copolymer having four or more polymer blocks. Among these, the number of polymer blocks per molecule of the block copolymer (P) is preferably 2 to 7, more preferably 2 to 5, and even more preferably 2 or 3, in order to efficiently produce a slurry composition having high dispersion stability of the ceramic powder and sufficiently low viscosity.

[0040] All of the at least two polymer blocks contained in the block copolymer (P) may have hydrogen-bonding functional groups, or only some of the two or more polymer blocks may have hydrogen-bonding functional groups. From the viewpoint of sufficiently increasing the dispersion stability of the ceramic powder, it is preferable that the at least two polymer blocks contained in the block copolymer (P) satisfy the following [i] or [ii]: [i] Of the two or more polymer blocks, some of the blocks have hydrogen-bonding functional groups, and the remaining blocks do not have hydrogen-bonding functional groups. [ii] Two or more polymer blocks have hydrogen-bonding functional groups, and the content of structural units derived from hydrogen-bonding group-containing vinyl monomers differs between the polymer blocks.

[0041] Each polymer block of the block copolymer (P) is mainly composed of structural units derived from a vinyl monomer. In one preferred embodiment, the block copolymer (P) has a polymer block (hereinafter also referred to as a "hard segment") having a glass transition temperature (Tg) of 30°C or higher and a polymer block (hereinafter also referred to as a "soft segment") having a Tg of less than 30°C. This embodiment makes it possible to obtain a polymer capable of forming a pseudo-crosslinked structure by forming a microphase-separated structure, for example, as the block copolymer (P). Furthermore, a ceramic green sheet produced using such a block copolymer (P) is advantageous in that it can increase the breaking energy while maintaining a low slurry viscosity, thereby improving mechanical properties.

[0042] The Tg of the hard segment is preferably 50°C or higher, more preferably 75°C or higher, and even more preferably 100°C or higher. Due to restrictions on the raw material monomers, the Tg of the hard segment is generally 250°C or lower. The Tg range of the hard segment is preferably 50°C or higher and 250°C or lower, more preferably 75°C or higher and 250°C or lower, and even more preferably 100°C or higher and 250°C or lower. In this specification, the glass transition temperature (Tg) of the polymer block is a value calculated using the Fox formula, as described in the Examples below.

[0043] The Tg of the soft segment is preferably 25° C. or lower, more preferably 20° C. or lower, and even more preferably 10° C. or lower. The Tg of the soft segment is preferably −50° C. or higher, more preferably −30° C. or higher, and even more preferably −20° C. or higher. The Tg range of the soft segment is preferably −50° C. or higher and lower than 30° C., more preferably −30° C. or higher and lower than 30° C., and even more preferably −20° C. or higher and lower than 30° C.

[0044] The mass ratio of the hard segment in the block copolymer (P) is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of forming a pseudo-crosslinked structure by forming a microphase-separated structure, etc. The upper limit of this mass ratio is preferably 50% by mass or less, more preferably 35% by mass or less, and even more preferably 20% by mass or less, in order to suppress an increase in the viscosity of the slurry composition and to suppress a decrease in the flexibility of the ceramic green sheet. The mass ratio of the hard segment in the block copolymer (P) is a value calculated from the charge ratio of each block when producing the block copolymer (P) (hereinafter also referred to as the "charge block ratio"; unit: mass ratio) and the polymerization rate (%) of each monomer.

[0045] When the block copolymer (P) has hard segments and soft segments, it preferably contains a polymer block having an aromatic vinyl unit and an imide group-containing vinyl unit as the hard segment. A polymer block having an aromatic vinyl unit and an imide group-containing vinyl unit is preferred in that it can form a segment with a sufficiently high glass transition temperature and can easily produce a polymer capable of forming a pseudo-crosslinked structure by forming a microphase-separated structure, for example. This polymer block is preferably a polymer block having an aromatic vinyl unit and a structural unit derived from a maleimide compound, and more preferably a polymer block having a structural unit derived from a styrene-based monomer and a structural unit derived from a maleimide compound. In this polymer block, the total content of the aromatic vinyl unit and the imide group-containing vinyl unit is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more.

[0046] Preferred embodiments of the block structure of the block copolymer (P) include the following embodiments [1] and [2]. [1] A block copolymer comprising a first block mainly composed of (meth)acrylic units and a second block mainly composed of (meth)acrylic units and having a different monomer composition from that of the first block. [2] A block copolymer comprising a polymer block mainly composed of (meth)acrylic units and a polymer block having aromatic vinyl units and imide group-containing vinyl units.

[0047] In the case of the above [1], more specific examples include the following [1-1] and [1-2]. [1-1] A block copolymer comprising a first block mainly composed of (meth)acrylic units and a second block mainly composed of (meth)acrylic units, one of which has a hydrogen-bonding functional group and the other of which does not have a hydrogen-bonding functional group. [1-2] A block copolymer comprising a first block mainly composed of (meth)acrylic units and a second block mainly composed of (meth)acrylic units, wherein both the first block and the second block have hydrogen-bonding functional groups, and the content of structural units derived from hydrogen-bonding group-containing vinyl monomers differs between the polymer blocks.

[0048] In the case of the above [2], more specific examples include the following [2-1] and [2-2]. [2-1] A block copolymer comprising a polymer block mainly composed of (meth)acrylic units and a polymer block having aromatic vinyl units and imide group-containing vinyl units, one of which has a hydrogen-bonding functional group and the other of which does not have a hydrogen-bonding functional group. [2-2] A block copolymer comprising a polymer block mainly composed of (meth)acrylic units and a polymer block having aromatic vinyl units and imide group-containing vinyl units, wherein both of these polymer blocks have hydrogen-bonding functional groups, and the content of structural units derived from hydrogen-bonding group-containing vinyl monomers differs between the polymer blocks.

[0049] The block copolymer (P) preferably has a polystyrene-equivalent number average molecular weight (Mn) in the range of 10,000 to 500,000, as measured by gel permeation chromatography (GPC). An Mn of 10,000 or more is preferred because it allows the strength of the ceramic green sheet produced using the block copolymer (P) to be sufficiently high. An Mn of 500,000 or less is preferred because it prevents the viscosity of the slurry composition from becoming too high, ensuring sufficient coatability and handleability. The Mn of the block copolymer (P) is more preferably 20,000 or more, even more preferably 30,000 or more, and particularly preferably 50,000 or more. The Mn of the block copolymer (P) is more preferably 300,000 or less, even more preferably 250,000 or less, and particularly preferably 150,000 or less.

[0050] The weight average molecular weight (Mw) of the block copolymer (P) measured by GPC in terms of polystyrene is preferably in the range of 30,000 to 700,000. The Mw of the block copolymer (P) is more preferably 40,000 or more, even more preferably 50,000 or more, and particularly preferably 70,000 or more. The Mw of the block copolymer (P) is more preferably 500,000 or less, even more preferably 300,000 or less, and particularly preferably 250,000 or less.

[0051] The molecular weight distribution (Mw / Mn) of the block copolymer (P), expressed as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn), is preferably 3.0 or less, since this prevents the viscosity of a slurry composition containing the block copolymer (P) from becoming too high. Furthermore, when Mw / Mn is 3.0 or less, the amount of high-molecular-weight components that significantly increase the viscosity of the slurry composition is small, and the viscosity of the slurry composition can be sufficiently reduced, thereby increasing the molecular weight of the block copolymer (P). This increases the strength of ceramic green sheets obtained using the slurry composition. Mw / Mn is more preferably 2.8 or less, even more preferably 2.5 or less, and particularly preferably 2.2 or less. From the viewpoint of ease of production, the lower limit of Mw / Mn is preferably 1.1 or more.

[0052] <Production of Block Copolymer (P)> The block copolymer (P) is preferably produced by polymerizing the above-mentioned monomers by living radical polymerization, since this allows the production of a block copolymer (P) with a sufficiently narrow molecular weight distribution. For example, in the case of solution polymerization, an organic solvent and monomers are charged into a reactor, a polymerization inhibitor and a radical polymerization initiator are added, and the copolymerization is preferably carried out by heating to produce the desired block copolymer (P). The method for charging each raw material may be a batch-type initial lump-sum charge in which all raw materials are charged at once, a semi-continuous charge in which at least some of the raw materials are continuously fed into the reactor, or a continuous polymerization method in which all raw materials are continuously fed and the product is continuously withdrawn from the reactor at the same time.

[0053] When producing the block copolymer (P), known polymerization methods can be used as living radical polymerization. Specific examples of living radical polymerization methods include living radical polymerization using an exchange chain transfer mechanism, living radical polymerization using a bond-dissociation mechanism, and living radical polymerization using an atom transfer mechanism. Specific examples of these living radical polymerization methods using an exchange chain transfer mechanism include reversible addition-fragmentation chain transfer polymerization (RAFT), iodine transfer polymerization, polymerization using organotellurium compounds (TERP), polymerization using organoantimony compounds (SBRP), and polymerization using organobismuth compounds (BIRP); living radical polymerization using a bond-dissociation mechanism includes the nitroxy radical method (NMP); and atom transfer mechanism includes atom transfer radical polymerization (ATRP). Among these, living radical polymerization using an exchange chain transfer mechanism is preferred because it can be applied to the widest range of vinyl monomers and has excellent polymerization controllability. The RAFT method is particularly preferred from the viewpoint of ease of implementation.

[0054] In the RAFT method, polymerization proceeds via a reversible chain transfer reaction in the presence of a polymerization control agent (RAFT agent) and a free-radical polymerization initiator. Various known RAFT agents, such as dithioester compounds, xanthate compounds, trithiocarbonate compounds, and dithiocarbamate compounds, can be used as RAFT agents. The RAFT agent may be a monofunctional compound having only one active site, or a multifunctional compound having two or more active sites. When producing a block copolymer having an A-(BA)n structure, a B-(AB)n structure, or an (AB)mC-(BA)n structure (where n and m are integers of 1 or greater), a bifunctional RAFT agent is preferred because it allows for efficient production of the block copolymer. The amount of RAFT agent used is adjusted appropriately depending on the target number-average molecular weight (Mn) of the block copolymer.

[0055] The polymerization initiator used in the RAFT polymerization can be a known radical polymerization initiator such as an azo compound, organic peroxide, or persulfate. Among these, azo compounds are preferred because they are safe to handle and less likely to cause side reactions during radical polymerization. Specific examples of azo compounds include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], and 2,2'-azobis(N-butyl-2-methylpropionamide). The radical polymerization initiator may be used alone or in combination of two or more kinds.

[0056] The amount of radical polymerization initiator used is not particularly limited, but from the viewpoint of obtaining a polymer with a narrower molecular weight distribution, it is preferably 1 part by mass or less, more preferably 0.8 parts by mass or less, per 1 part by mass of the RAFT agent. From the viewpoint of stably carrying out the polymerization reaction, the lower limit of the amount of radical polymerization initiator used is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, per 1 part by mass of the RAFT agent. The amount of radical polymerization initiator used per 1 part by mass of the RAFT agent is preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.8 parts by mass.

[0057] In the polymerization reaction using the RAFT method, the reaction temperature is preferably 40°C or higher and 100°C or lower, more preferably 45°C or higher and 90°C or lower, and even more preferably 50°C or higher and 80°C or lower. A reaction temperature of 40°C or higher is preferred because it allows the polymerization reaction to proceed smoothly, while a reaction temperature of 100°C or lower is preferred because it can suppress side reactions and alleviates restrictions on the initiators and solvents that can be used. The reaction time can be appropriately set depending on the monomers used, etc., but is preferably 1 hour or higher and 48 hours or lower, and more preferably 3 hours or higher and 24 hours or lower. The polymerization reaction may be carried out in the presence of a chain transfer agent (e.g., an alkylthiol compound having 2 to 20 carbon atoms, etc.) as needed.

[0058] For example, when a diblock copolymer consisting of polymer block (A) and polymer block (B) is obtained by RAFT polymerization, a specific polymerization method is to produce the desired diblock copolymer by sequentially polymerizing each block using a monofunctional RAFT agent. In this method, in the first polymerization step, monomers are polymerized in the presence of a monofunctional RAFT agent and a radical polymerization initiator to obtain polymer block (A). Next, in the second polymerization step, monomers are polymerized in the presence of polymer block (A) to obtain polymer block (A) and polymer block (B). In this way, a block copolymer (P) having two blocks can be obtained. Furthermore, by repeating the above polymerization steps, a block copolymer (P) having three or more blocks can be produced. For example, after polymer block (A)-polymer block (B) are obtained by the first polymerization step and the second production step, a triblock copolymer consisting of polymer block (A)-polymer block (B)-polymer block (C) or a triblock copolymer consisting of polymer block (A)-polymer block (B)-polymer block (A) can be obtained by polymerizing monomers in the presence of polymer block (A)-polymer block (B).

[0059] Furthermore, when a pentablock copolymer having five blocks is obtained by RAFT polymerization, the copolymer consists of polymer block (A), polymer block (B), polymer block (C), polymer block (B), and polymer block (A). The production method includes sequentially polymerizing each block using a monofunctional RAFT agent as described above, as well as a three-stage polymerization method using a bifunctional RAFT agent to produce the desired pentablock copolymer. In this method, the first polymerization step involves polymerizing monomers in the presence of a bifunctional RAFT agent (e.g., 1,4-bis(n-dodecylsulfanylthiocarbonylsulfanylmethyl)benzene or S,S-dibenzyltrithiocarbonate) and a radical polymerization initiator to obtain polymer block (A). The second polymerization step involves polymerizing monomers in the presence of polymer block (A) to obtain polymer block (A), polymer block (B), and polymer block (A). Furthermore, in the third polymerization step, monomers are polymerized in the presence of polymer block (A)-polymer block (B)-polymer block (A), thereby obtaining a pentablock copolymer consisting of polymer block (A)-polymer block (B)-polymer block (C)-polymer block (B)-polymer block (A). The method using a bifunctional RAFT agent is advantageous in that it can simplify the production process and improve production efficiency.

[0060] When producing the block copolymer (P), a polymerization solvent known in living radical polymerization can be used. Specific examples include aromatic compounds such as benzene, toluene, xylene, and anisole; ester compounds such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone compounds such as acetone and methyl ethyl ketone; dimethylformamide, acetonitrile, dimethyl sulfoxide, alcohol, and water. When the block copolymer (P) is produced by solution polymerization, the block copolymer (P) dissolved in the polymerization solvent can be isolated by known desolvation methods such as reprecipitation, or drying methods such as heat treatment. Alternatively, bulk polymerization or other methods may be used without using a polymerization solvent.

[0061] Slurry Composition The slurry composition of the present disclosure is a polymer composition used in producing a ceramic green sheet, and contains a block copolymer (P) and ceramic powder. The ceramic powder may be any known material for constituting the dielectric layer of a ceramic capacitor, such as barium titanate, titanium oxide, alumina, zirconia, zinc oxide, aluminum silicate, or silicon nitride. The content of the block copolymer (P) in the slurry composition is preferably 1 to 70 parts by mass, and more preferably 3 to 50 parts by mass, per 100 parts by mass of the ceramic powder.

[0062] A solvent is blended into the above-mentioned slurry composition as needed. As the solvent, an organic solvent is preferably used, and examples thereof include hydrocarbons such as toluene, xylene, methylcyclohexane, and terpineol; alcohols such as ethanol, n-propanol, isopropanol, and n-butanol; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether; and esters such as ethyl acetate, butyl acetate, isobutyl acetate, and propylene glycol monomethyl ether acetate. The solvent may be used alone or in combination of two or more. The content of the solvent in the slurry composition is preferably 10 to 500 parts by mass, more preferably 30 to 200 parts by mass, per 100 parts by mass of the ceramic powder.

[0063] In addition to the block copolymer (P), ceramic powder, and solvent, the slurry composition may contain known additives such as plasticizers, dispersants, leveling agents, and antifoaming agents. The blending ratios of these additives can be appropriately set depending on the additives, as long as the effects of the present disclosure are not impaired. The slurry composition can be prepared, for example, by mixing the ceramic powder with a binder and, if necessary, a solvent, using a bead mill or the like.

[0064] The viscosity of the slurry composition is preferably 80 mPa·s or more, more preferably 100 mPa·s or more. By setting the slurry viscosity to 80 mPa·s or more, it is possible to ensure a thin film shape when the slurry composition is applied to a support. From the viewpoint of ensuring coatability, the upper limit of the slurry viscosity is preferably 3000 mPa·s or less, more preferably 2000 mPa·s or less. The viscosity of the slurry composition is a value measured at 25°C using a Brookfield viscometer with a rotor rotation speed set to 6 rpm.

[0065] <Ceramic green sheet and multilayer ceramic capacitor> The ceramic green sheet of the present disclosure is produced using a slurry composition containing a block copolymer (P) and ceramic powder. Furthermore, by laminating the obtained ceramic green sheets, a multilayer ceramic capacitor having a dielectric layer formed from the above-mentioned slurry composition can be produced. The method for producing the ceramic green sheet and the multilayer ceramic capacitor is not particularly limited, and can be performed by a known method.

[0066] Specifically, a slurry composition containing a block copolymer (P) and ceramic powder is first applied to a support such as a release-treated PET sheet. Subsequently, a drying process is performed to remove volatile components from the slurry composition on the support, forming a film, and obtaining a ceramic green sheet. A metal paste that will become the internal electrodes is printed on this ceramic green sheet and dried, and the ceramic green sheet with electrodes is peeled off from the support. A laminate is produced by stacking multiple sheets of this material and thermocompression bonding, and the laminate is then cut into a predetermined shape to obtain a ceramic green chip. The resulting ceramic green chip is then heat-treated to degrease it (thermal decomposition of the binder), and the ceramic is then sintered at high temperature. This results in a multilayer ceramic capacitor. [Example]

[0067] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified. The polymers obtained in the production examples and comparative production examples were analyzed as follows.

[0068] <Molecular weight measurement> The resulting polymer was subjected to gel permeation chromatography (GPC) under the following conditions to obtain the polystyrene-equivalent number average molecular weight (Mn) and weight average molecular weight (Mw). The molecular weight distribution (Mw / Mn) was calculated from the obtained Mn and Mw values. Measurement conditions Column: Tosoh Corporation TSKgel SuperMultiporeHZ-M x 4 Solvent: tetrahydrofuran Temperature: 40℃ Detector: RI Flow rate: 600μL / min

[0069] <Glass transition temperature (Tg)> The glass transition temperature (Tg) of the polymer block was calculated by Fox's formula represented by the following mathematical formula (4) based on the glass transition temperature of the homopolymer of each monomer constituting the polymer block. 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+····+(W n / Tg n ) …(4) Formula (4) is a calculation formula for when the polymer for which Tg is to be calculated is a copolymer consisting of monomer 1, monomer 2, ..., and monomer n (n is an integer). In formula (4), W1, W2, ..., and W n indicates the mass fraction of each monomer in the polymer block, and Tg1, Tg2, ... and Tg n indicates the glass transition temperature (unit: K) of the homopolymer of each monomer.

[0070] 1. Preparation of Block Copolymers <Production Example 1> Production of Polymer A First polymerization step (production of polymer block (A)) A flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 19.5 parts of methyl acrylate (hereinafter also referred to as "MA"), 10.5 parts of n-butyl acrylate (hereinafter also referred to as "BA"), 70 parts of 2-hydroxyethyl acrylate (hereinafter also referred to as "HEA"), 1.60 parts of 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid (hereinafter also referred to as "CBSTSP"), 0.14 parts of 2,2'-azobis(2-methylbutyronitrile) (hereinafter also referred to as "ABN-E"), and 184 parts of acetonitrile, and thoroughly degassed with nitrogen bubbling. Polymerization was initiated in a constant temperature bath at 70 ° C. After 5 hours, the mixture was cooled to room temperature to terminate the polymerization. The amount of residual monomer was measured by gas chromatography (GC) and the monomer polymerization rate and block composition were calculated. The monomer polymerization rates were 38% for MA, 33% for BA, and 42% for HEA, and the block composition was as shown in Table 2. The block composition was calculated from the monomer polymerization rate (the same applies below). The molecular weight of the polymer was measured by GPC (polystyrene equivalent) and was found to be Mn 5,600, Mw 6,100, and Mw / Mn 1.08.

[0071] Second polymerization step (production of polymer block (B)) Next, 90 parts of MA, 210 parts of BA, 300 parts of methyl methacrylate (hereinafter also referred to as "MMA"), 1.20 parts of ABN-E, and 280 parts of acetonitrile were charged, thoroughly degassed by nitrogen bubbling, and polymerization was restarted in a thermostatic bath at 80 °C. After 5 hours, the polymerization was stopped by cooling to room temperature, and a solution containing a block copolymer (referred to as "Polymer A") was obtained. The amount of residual monomer was measured by gas chromatography (GC) measurement, and the monomer polymerization rate and block composition were calculated. The polymerization rates of each monomer were 88% for MA (residual fraction from the first polymerization step and additional fraction from the second polymerization step), 87% for BA (residual fraction from the first polymerization step and additional fraction from the second polymerization step), >99% for MMA, and 90% for HEA (residual fraction from the first polymerization step). The block composition was as shown in Table 2. The molecular weight of the block copolymer was measured by GPC (polystyrene equivalent) to find that Mn was 60,000, Mw was 114,800, and Mw / Mn was 1.91.

[0072] The resulting polymerization solution was purified by reprecipitation from a methanol / water mixed solvent and vacuum dried to obtain block copolymer A. The molecular weight of the resulting block copolymer A was Mn 67,100, Mw 119,700, and Mw / Mn 1.78, as determined by GPC measurement (polystyrene equivalent). Table 1 also shows the charged block ratio (% by mass). In Production Example 1, the amount of monomer charged in each polymerization step was set so that the ratio of each block contained in the polymer obtained in the first polymerization step and the second polymerization step was polymer block (A):polymer block (B) = 14:86 (mass ratio).

[0073] <Production Examples 2, 5 to 7 and Comparative Production Examples 1 and 2> Production of Polymers B, E to G, I, and J The same operations as in Production Example 1 were carried out except that the types and amounts of raw materials charged into the flask were changed as shown in Table 1 and the polymerization temperature was appropriately adjusted, thereby obtaining block copolymers, Polymers B, E to G, I, and J. The analysis results of the block compositions and molecular weights of Polymers B, E to G, I, and J are shown in Table 2.

[0074] <Production Example 3> Production of Polymer C First polymerization step (production of polymer block (A)) A flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 61.5 parts of N-phenylmaleimide (hereinafter also referred to as "PhMI"), 38.5 parts of styrene (hereinafter also referred to as "St"), 2.29 parts of CBSTSP, 0.15 parts of ABN-E, and 268 parts of acetonitrile. The mixture was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 70 °C. After 5 hours, the mixture was cooled to room temperature and terminated. The residual monomer amount was measured by gas chromatography (GC) and the monomer polymerization rate and block composition were calculated. The polymerization rates of each monomer were PhMI > 98% and St > 98%, and the block composition was as shown in Table 2. The molecular weight of the polymer was measured by GPC (polystyrene equivalent) to find Mn 7,900, Mw 9,200, and Mw / Mn 1.17.

[0075] Second polymerization step (production of polymer block (B)) Next, 114 parts of MA, 266 parts of BA, 328 parts of MMA, 1.40 parts of ABN-E, and 267 parts of acetonitrile were added, thoroughly degassed by nitrogen bubbling, and polymerization was restarted in a thermostatic bath at 80 °C. After 5 hours, the mixture was cooled to room temperature and polymerization was terminated. The residual monomer amount was measured by gas chromatography (GC) and the monomer polymerization rate and block composition were calculated. The monomer polymerization rates were 85% for MA, 85% for BA, and >99% for MMA. The block composition is shown in Table 2. The molecular weight of the block copolymer was measured by GPC (polystyrene equivalent) to find Mn 46,300, Mw 82,600, and Mw / Mn 1.78.

[0076] Third polymerization step (production of polymer block (C)) Next, 7.41 parts of MA, 17.3 parts of BA, 115 parts of HEA, 0.46 parts of ABN-E, and 236 parts of acetonitrile were added, thoroughly degassed by nitrogen bubbling, and polymerization was restarted in a constant-temperature bath at 70 °C. After 5 hours, the mixture was cooled to room temperature to terminate the polymerization, yielding a solution containing a block copolymer (referred to as "Polymer C"). The amount of residual monomer was measured by gas chromatography (GC) and the monomer polymerization rate and block composition were calculated. The monomer polymerization rates were 83% for MA (residual fraction from the second polymerization step and additional fraction from the third polymerization step), 76% for BA (residual fraction from the second polymerization step and additional fraction from the third polymerization step), and 87% for HEA. The block composition was as shown in Table 2. The molecular weight of the block copolymer was measured by GPC (polystyrene equivalent) to find Mn 55,400, Mw 119,200, and Mw / Mn 2.15.

[0077] The obtained polymerization solution was purified by reprecipitation from a methanol / water mixed solvent and dried in vacuum to obtain Polymer C. The molecular weight of the obtained Polymer C was Mn 70,300, Mw 132,100, and Mw / Mn 1.88, as determined by GPC measurement (polystyrene equivalent).

[0078] <Production Examples 4 and 8> Production of Polymers D and H The same operations as in Production Example 3 were carried out except that the types and amounts of raw materials charged into the flask were changed as shown in Table 1 and the polymerization temperature was appropriately adjusted, thereby obtaining block copolymers, Polymers D and H. The analysis results of the block composition and molecular weight of Polymers D and H are shown in Table 2.

[0079] [Table 1]

[0080] [Table 2]

[0081] Details of the compounds (monomers, control agents, initiators, and solvents) shown in Tables 1 and 2 are as follows. For each monomer, the Tg of the homopolymer produced from that monomer is shown in parentheses. The Tg of the homopolymer was taken from the Materials Database (https: / / polymer.nims.go.jp / ) of the National Institute for Materials Science, National Research and Development Agency. The Tg of the N-phenylmaleimide homopolymer was calculated using the Fox equation using the Tg (221°C) of the N-phenylmaleimide / styrene alternating copolymer (62.4 / 37.6 wt%) and the Tg (98°C) of the styrene homopolymer. MA: Methyl acrylate (10°C) BA: n-butyl acrylate (-48°C) EA: Ethyl acrylate (-21°C) MMA: methyl methacrylate (108°C) HEA: 2-hydroxyethyl acrylate (-15°C) PhMI: N-phenylmaleimide (344°C) St: styrene (98°C) ABN-E: 2,2'-azobis(2-methylbutyronitrile) CBSTSP: 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid DBTTC: S,S-Dibenzyltrithiocarbonate

[0082] 2. Evaluation <Examples 1 to 8 and Comparative Examples 1 and 2> Each of the block copolymers (polymers A to J) prepared above was used as a binder resin to prepare a slurry composition. Furthermore, ceramic green sheets were produced using the prepared slurry compositions and evaluated. The methods for preparing the slurry compositions and the evaluation items in the examples and comparative examples are as follows:

[0083] <Preparation of Slurry Composition> 100 parts of ceramic powder containing barium titanate (product of Sakai Chemical Industry Co., Ltd., "BT-01") having a particle size of 0.1 μm, 1 part of dispersant (product of NOF Corporation, "Marialim SC-0505K"), and 56 parts of toluene and 14 parts of ethanol as solvents were mixed with 100 parts of zirconia beads having a particle size of 0.1 mm using a bead mill (product of Imex Co., Ltd., "Easy Nano RMB") at 500 rpm for 5 hours, and the zirconia beads were then filtered off to prepare a barium titanate dispersion. 171 parts of this dispersion was mixed with 10 parts of binder resin and the amounts of toluene and ethanol listed in Table 3, and the mixture was stirred for 5 minutes at 2000 rpm using a planetary centrifugal mixer to prepare a slurry composition.

[0084] <Thermal decomposition of binder resin> Regarding the thermal decomposition of the binder resin, each binder resin was used as a sample, and the sample was heated to a predetermined temperature and the mass residue was evaluated when the temperature reached 500°C. Specifically, using a thermal analyzer (TGDTA6300 manufactured by Hitachi High-Tech Science Corporation), 5 to 8 mg of the sample was heated from 30°C to 600°C at a heating rate of 10°C / min under a nitrogen gas flow, and the change in mass during this period was measured, and the mass residue when the temperature reached 500°C was determined.

[0085] <Viscosity measurement of slurry composition> The slurry composition obtained above was adjusted to 25°C, and then the viscosity was measured at a rotor rotation speed of 6 rpm using a Brookfield viscometer.

[0086] <Tensile properties of ceramic green sheets> The slurry composition obtained above was applied to a release-treated PET film using a variable applicator so that the dried green sheet would have a thickness of 100 μm, and then dried in a forced-air dryer at 100°C for 15 minutes to produce a ceramic green sheet. 4 cm x 1 cm test pieces were cut out from the produced ceramic green sheet, and the tensile properties of the ceramic green sheet were measured in a tensile tester at a pulling rate of 10 mm / min in the normal state (25°C) to determine the elongation at break (%), maximum strength (MPa), and tensile product (elongation at break (%) x maximum strength (MPa)).

[0087] Table 3 shows the block ratios and Tg of each block of polymers A to J, as well as the evaluation results of Examples 1 to 8 and Comparative Examples 1 and 2.

[0088] [Table 3]

[0089] As shown in Table 3, the slurry compositions of Examples 1 to 8 containing the block copolymer (P) exhibited low slurry viscosities of 1200 mPa·s or less. Furthermore, the resulting ceramic green sheets exhibited high strengths of 1.3 MPa or more, as well as sufficiently high values ​​for elongation at break and tensile product. In particular, in Examples 1, 2, 5, 6, and 8, ceramic green sheets with high strength, elongation at break, and tensile product were obtained despite the low slurry viscosity of 500 mPa·s or less. Furthermore, in Examples 2 to 5, the tensile product was high at 150 MPa·% or more, demonstrating excellent toughness. Furthermore, in Examples 1 to 3, in which a methacrylic acid ester compound was introduced into the block copolymer (P), the thermal decomposition properties of the binder resin were also good.

[0090] In contrast, in Comparative Examples 1 and 2, in which a (meth)acrylic block copolymer having no hydrogen-bonding functional group was used instead of block copolymer (P), the viscosity of the slurry composition was as high as 3000 mPa s or more. Furthermore, the strength and tensile product of the obtained ceramic green sheets were lower than those of Examples 1 to 8.

[0091] From the above results, it became clear that by using the block copolymer (P), it is possible to produce ceramic green sheets with high strength and excellent thermal decomposition properties while keeping the viscosity of the ceramic slurry low.

[0092] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A binder for producing a ceramic green sheet, comprising a block copolymer, the block copolymer is mainly composed of structural units derived from vinyl monomers, is substantially free of a polyvinyl acetal structure, has a hydrogen-bonding functional group, and contains structural units derived from vinyl monomers having a hydrogen-bonding functional group in an amount of 7% by mass or more and 25% by mass or less based on the total structural units; The binder for producing ceramic green sheets, wherein the block copolymer has a number average molecular weight (Mn) of 10,000 to 500,000.

2. 2. The binder for producing a ceramic green sheet according to claim 1, wherein the block copolymer contains structural units derived from a (meth)acrylic monomer in an amount of 70 mass % or more based on all structural units.

3. 3. The binder for producing a ceramic green sheet according to claim 1, wherein the block copolymer has a structural unit derived from an aromatic vinyl monomer and a structural unit derived from an imide group-containing vinyl monomer.

4. The binder for producing a ceramic green sheet according to any one of claims 1 to 3, wherein the block copolymer has structural units derived from a methacrylic acid ester compound in an amount of 5% by mass to 70% by mass, based on all structural units.

5. The binder for producing a ceramic green sheet according to any one of claims 1 to 4, wherein the block copolymer has a polymer block having a glass transition temperature of 30°C or higher and a polymer block having a glass transition temperature of lower than 30°C.

6. The binder for producing a ceramic green sheet according to any one of claims 1 to 5, wherein the block copolymer has a molecular weight distribution (Mw / Mn) expressed as a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) of 3.0 or less.

7. The binder for producing a ceramic green sheet according to any one of claims 1 to 6, wherein the block copolymer has a weight average molecular weight (Mw) of 30,000 to 700,000.

8. A slurry composition comprising the binder for producing a ceramic green sheet according to any one of claims 1 to 7 and ceramic powder.

9. A ceramic green sheet formed using the slurry composition according to claim 8.

10. A method for producing a multilayer ceramic capacitor, using the ceramic green sheet according to claim 9.

Images