Binder resin composition for baking, metallic paste, inorganic sintered body, electronic device and solar panel

Abstract

To provide a binder resin composition for baking which is excellent in baking property, has high viscosity, and has high thixotropy property and thread breakage property, a metallic paste, an inorganic sintered body, an electronic device, and a solar panel.SOLUTION: A binder resin composition for baking contains a (meth)acrylic polymer (I) having a crosslinked structure, wherein when solid content concentration of the binder resin composition for baking is 7 mass%, viscosity (η1) at 23°C measured at a shear rate of 1(1 / s) is 10 Pa s or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a binder resin composition for firing, a metal paste containing the binder resin composition for firing, an inorganic sintered body obtained by firing the metal paste, and an electronic device and a solar panel containing the inorganic sintered body. [Background technology]

[0002] Inorganic molded bodies and patterns formed by such molded bodies (e.g., wiring patterns, insulating patterns, etc.) are sometimes used for internal and external electrodes of multilayer electronic components such as multilayer ceramic capacitors, solar cell electrodes, etc. A known method for obtaining such molded bodies is to mix an inorganic compound such as a metal powder, a metal oxide powder, a fluorescent powder, or glass frit with a binder resin composition for firing containing a binder resin and a solvent to prepare a metal paste, which is then molded into a predetermined shape to obtain a molded body. It is also known that when a pattern is formed using the obtained molded body, the binder resin is thermally decomposed and fired after the pattern is formed.

[0003] The binder resin contained in the binder resin composition for firing serves to improve the processability of the metal paste when it is molded and to bind the inorganic compounds so that they are not damaged during movement. The binder resin is removed by thermal decomposition before the final product is produced, specifically when the metal paste is fired and the inorganic compounds are sintered. Therefore, the binder resin is required to have high thermal decomposition properties (hereinafter also referred to as "fireability") and excellent workability during each processing.

[0004] Known methods for forming a pattern using a metal paste include screen printing of the metal paste, gravure printing of the metal paste, forming the metal paste into a sheet using a doctor blade or the like, dipping, dispensing, etc. When using screen printing, the metal paste is required to have screen printability, i.e., properties such as thixotropy, resistance to thread breakage, and high viscosity.

[0005] In recent years, as electronic devices have become smaller and more powerful, there has been a demand for smaller, larger-capacity multilayer ceramic capacitors.To achieve this, the ceramic green sheets and conductive layers that make up the capacitors have been made thinner and more multilayered, thereby achieving smaller size and larger capacitance. When making the layers thinner, there is a problem that defects caused by even small amounts of firing residue during firing can lead to reduced insulation, circuit breaks, and cracks in the laminate, so there is a demand for binder resins with excellent firing properties. Furthermore, because the final layer thickness depends on the film thickness during printing and the solids concentration of the paste to be printed, achieving thin layers requires an extremely low solids concentration in the metal paste. Therefore, binder resins are required to exhibit high viscosity even with low solids concentrations. Low viscosity binder resins can lead to reduced conductivity due to sagging and bleeding after printing. Increasing the binder resin content in the metal paste can increase viscosity. However, increasing the binder resin content can lead to problems such as residual sintering when the metal paste is fired, larger voids where the binder resin has evaporated, and significant shrinkage during curing, which can easily cause cracks.

[0006] For example, Patent Document 1 discloses a conductive paste containing ethyl cellulose as a binder resin. Patent Document 2 discloses a conductive paste containing an acrylic polymer having a hydroxyurethane skeleton as a binder resin. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-231828 [Patent Document 2] Japanese Patent Application Publication No. 2019-196446 Summary of the Invention [Problem to be solved by the invention]

[0008] However, although ethyl cellulose is said to have excellent resistance to thread breakage during printing, high viscosity, and excellent thixotropy, it has problems such as poor sinterability, which can cause a decrease in insulation, circuit breakage, and cracks in laminates, thereby reducing yields in the production of electronic devices and solar panels. The binder resin described in Patent Document 2 is an acrylic polymer that is generally considered to have good baking properties, and improves printability by imparting thixotropy through interactions of the hydroxyurethane skeleton. However, the viscosity is extremely low, making it difficult to form desired electrodes.

[0009] An object of the present invention is to provide a binder resin composition for firing that has excellent firing properties, high viscosity, and high thixotropy and thread breakage resistance, as well as a metal paste, an inorganic sintered body, an electronic device, and a solar panel. [Means for solving the problem]

[0010] The present invention has the following aspects. [1] A binder resin composition for baking containing a (meth)acrylic polymer (I) having a crosslinked structure, A binder resin composition for baking, wherein the viscosity (η1) at 23°C measured at a shear rate of 1 (1 / s) when the solid content concentration of the binder resin composition for baking is 7% by mass is 10 Pa·s or more. [2] Further containing an organic solvent (S), The binder resin composition for baking according to [1] above, wherein the content of the organic solvent (S) is 900 parts by mass or more and 10,000 parts by mass or less relative to 100 parts by mass of the (meth)acrylic polymer (I). [3] The binder resin composition for baking according to [2] above, wherein the boiling point of the organic solvent (S) is 180°C or higher. [4] The binder resin composition for baking according to [2] or [3], wherein the organic solvent (S) has active hydrogen. [5] The binder resin composition for baking according to any one of [1] to [4] above, wherein the crosslinked structure is a crosslinked structure formed by a crosslinking reaction between a (meth)acrylic polymer (A) containing a structural unit derived from a (meth)acrylic acid ester (a1) having a reactive functional group (x) and a functional group (y) that reacts with the reactive functional group (x). [6] The binder resin composition for baking according to [5], wherein the reactive functional group (x) is one or more selected from a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, a glycidyl group, and precursors thereof. [7] The binder resin composition for baking according to [5] or [6], wherein the functional group (y) is one or more selected from a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, a glycidyl group, and precursors thereof. [8] A metal paste comprising the binder resin composition for firing according to any one of [1] to [7] above and an inorganic compound (D). [9] An inorganic sintered body obtained by firing the metal paste of [8].

[10] An electronic device containing the inorganic sintered body according to [9].

[11] A solar panel containing the inorganic sintered body according to [9]. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a binder resin composition for firing, a metal paste, an inorganic sintered body, an electronic device, and a solar panel, which have excellent firing properties, high viscosity, and high thixotropy and thread breakage resistance. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in further detail below by presenting preferred embodiments of the invention. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to the contents of the following description as long as it does not go beyond the gist of the invention. In this specification, unless otherwise specified, the symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. Additionally, "(meth)acrylate" is a general term for "acrylate" and "methacrylate." "(meth)acrylic" is a general term for "acrylic" and "methacrylic." "(meth)acryloyl" is a general term for "acryloyl" and "methacryloyl." Furthermore, the term "polymer" is a general term for "homopolymer" and "copolymer."

[0013] [Binder resin composition for firing] Hereinafter, one embodiment of the binder resin composition for baking (hereinafter also simply referred to as "resin composition") of the present invention will be described. The resin composition of the present embodiment contains the following (meth)acrylic polymer (I). The resin composition may consist of only the (meth)acrylic polymer (I), or may further contain an organic solvent (S) in addition to the (meth)acrylic polymer (I). The resin composition preferably does not substantially contain any components other than the (meth)acrylic polymer (I) and the organic solvent (S) (hereinafter also referred to as "optional components"). Here, "substantially does not contain" means that optional components are not intentionally blended into the resin composition, except for those that are unintentionally contained. Note that unreacted monomers, polymerization initiators, catalysts, etc. used in producing the (meth)acrylic polymer (A) and (meth)acrylic polymer (I), which will be described later, do not fall under the category of optional components.

[0014] <(Meth)acrylic polymer (I)> The (meth)acrylic polymer (I) has a crosslinked structure. The (meth)acrylic polymer (I) is a binder resin. The crosslinked structure of the (meth)acrylic polymer (I) is preferably formed by a crosslinking reaction between a reactive functional group (x) described below and a functional group (y) that reacts with the reactive functional group (x). A specific example of the crosslinked structure is a crosslinked structure formed by a crosslinking reaction between a (meth)acrylic polymer (A) containing a structural unit derived from a (meth)acrylic acid ester (a1) having a reactive functional group (x) and a functional group (y) that reacts with the reactive functional group (x).

[0015] Examples of the reactive functional group (x) include a hydroxyl group, a carboxyl group, an amino group (amide group), an isocyanate group, a glycidyl group, and precursors thereof. Examples of precursors include a blocked hydroxyl group, a blocked carboxyl group, a carboxyl anhydride group, a blocked amino group, melamine, and a blocked isocyanate group (hereinafter also referred to as a "blocked isocyanate group").

[0016] Examples of the functional group (y) include a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, a glycidyl group, and precursors thereof. Examples of the precursors include a blocked hydroxyl group, a blocked carboxyl group, a carboxyl anhydride group, a blocked amino group, melamine, and a blocked isocyanate group. The functional group (y) may also react with a reactive functional group other than the reactive functional group (x) possessed by the (meth)acrylic polymer (A), for example, when the organic solvent (S) described below has a reactive functional group, with the reactive functional group possessed by the organic solvent (S).

[0017] When an isocyanate group is selected as each of the reactive functional group (x) and the functional group (y), the isocyanate group may be a blocked isocyanate group that is activated before the reaction, or may be an unblocked isocyanate group. A blocked isocyanate group is an isocyanate group in which an unblocked isocyanate group is blocked with a blocking agent.

[0018] The crosslinking reaction between the reactive functional group (x) and the functional group (y) can be carried out by a commonly known method such as a reaction in a solution or a reaction in the absence of a solvent, but is not limited to these methods. The crosslinking reaction between the reactive functional group (x) and the functional group (y) can be carried out at any temperature.

[0019] [(Meth)acrylic polymer (A)] The (meth)acrylic polymer (A) contains a structural unit (hereinafter also referred to as "structural unit (a1)") derived from a (meth)acrylic acid ester (a1) (hereinafter also referred to as "monomer (a1)") having a reactive functional group (x). That is, the (meth)acrylic polymer (A) has a reactive functional group (x). It is preferable that the (meth)acrylic polymer (A) further contains a structural unit (hereinafter also referred to as "structural unit (a2)") derived from a (meth)acrylic acid ester (a2) (hereinafter also referred to as "monomer (a2)") that does not have a reactive functional group (x). Furthermore, the (meth)acrylic polymer (A) may further contain, if necessary, a structural unit (hereinafter also referred to as "structural unit (a3)") derived from a monomer (hereinafter also referred to as "monomer (a3)") other than the monomer (a1) and the monomer (a2). The (meth)acrylic polymer (A) may or may not have a functional group (y). That is, the (meth)acrylic polymer (A) has a reactive functional group (x), but may also have a functional group (y) that reacts with the reactive functional group (x) contained in the (meth)acrylic polymer (A).

[0020] (Monomer (a1)) The monomer (a1) is a (meth)acrylic acid ester having a reactive functional group (x). Examples of the reactive functional group (x) include those exemplified above. Among them, a hydroxyl group is preferred because it is a versatile raw material with a wide range of options and the crosslinking reaction can be easily controlled.

[0021] Specific examples of the monomer (a1) having a hydroxyl group (hereinafter also referred to as "monomer (a1-1)") include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,2-dihydroxyethyl (meth)acrylate, 1,2-dihydroxypropyl (meth)acrylate, 1,2-dihydroxybutyl (meth)acrylate, 1,2 Hydroxyalkyl (meth)acrylates such as 5-ethylhexyl dihydroxyacrylate, 1,1-dihydroxyethyl (meth)acrylate, 1,1-dihydroxypropyl (meth)acrylate, 1,1-dihydroxybutyl (meth)acrylate, 1,2,3-trihydroxypropyl (meth)acrylate, 1,2,3-trihydroxybutyl (meth)acrylate, 1,1,2-trihydroxypropyl (meth)acrylate, and 1,1,2-trihydroxybutyl (meth)acrylate acrylate; hydroxy(meth)acrylates having an aromatic ring such as 2-hydroxy-3-phenoxypropyl(meth)acrylate; hydroxypolyethylene oxide mono(meth)acrylate, hydroxypolypropylene oxide mono(meth)acrylate, hydroxy(polyethylene oxide-polypropylene oxide) mono(meth)acrylate, hydroxy(polyethylene oxide-propylene oxide) mono(meth)acrylate, hydroxy(polyethylene oxide-polytetramethylene oxide) mono(meth)acrylate, hydroxy(polyethylene oxide-tetramethylene oxide) mono(meth)acrylate, hydroxy(polypropylene oxide-polytetramethylene oxide) mono(meth)acrylate, hydroxy(polypropylene oxide-polytetramethylene oxide) mono(meth)acrylate, 1,2-dihydroxypolyethyl oxide(meth)acrylate, 1,2-dihydroxypolypropylene oxide(meth)acrylate, polyhydroxyalkyl(meth)acrylate;Examples of suitable (meth)acrylates include hydroxypolyalkylene oxide (meth)acrylates such as 1,2,3-trihydroxypropylene glycol (meth)acrylate and 1,1,2-trihydroxypropylene glycol (meth)acrylate; and polyfunctional (meth)acrylates having a hydroxy group such as 2-hydroxy-3-acryloyloxypropyl (meth)acrylate and pentaerythritol tri(meth)acrylate. Among these, 2-hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate are preferred from the viewpoint of baking properties. The monomer (a1-1) may be used alone or in combination of two or more kinds.

[0022] Specific examples of the monomer (a1) having a carboxyl group (hereinafter also referred to as "monomer (a1-2)") include (meth)acrylates having a carboxyl group, such as acrylic acid, methacrylic acid, acrylic anhydride, methacrylic anhydride, mono(2-(meth)acryloyloxyethyl) succinate, ω-carboxy-polycaprolactone mono(meth)acrylate phthalate monohydroxyethyl (meth)acrylate, p-carboxybenzyl (meth)acrylate, and ethylene oxide-modified (ethylene oxide addition mole number is 2 to 18) phthalic acid (meth)acrylate. The monomer (a1-2) may be used alone or in combination of two or more kinds.

[0023] Specific examples of the monomer (a1) having an amino group (hereinafter also referred to as "monomer (a1-3)") include (meth)acrylates having an amino group, such as N-dimethylaminoethyl (meth)acrylate and N-diethylaminoethyl (meth)acrylate. The monomer (a1-3) may be used alone or in combination of two or more kinds.

[0024] Specific examples of the monomer (a1) having an isocyanate group (hereinafter also referred to as "monomer (a1-4)") include monomers having an isocyanate group such as 2-isocyanatoethyl (meth)acrylate, 2-(2-(meth)acryloyloxyethyloxy)ethyl isocyanate, and 1,1-(bis(meth)acryloyloxymethyl)ethyl isocyanate. The monomer (a1-4) may be a blocked isocyanate that is activated before the reaction. As the blocked isocyanate, a blocked isocyanate compound, which is a compound in which the isocyanate group in the above-mentioned monomer having an isocyanate group is blocked with a blocking agent, can be used.

[0025] Examples of blocking agents include phenol-based agents such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; lactam-based agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; aliphatic alcohol-based agents such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, and lauryl alcohol; ether-based agents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate ... Alcohol-based compounds such as methyloxyethyl methacrylate; oxime-based compounds such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime; active methylene-based compounds such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, and methylthiophenol mercaptans such as ethylthiophenol; acid amides such as acetanilide, acetanisidide, acetotoluide, acrylamide, methacrylamide, acetic amide, stearic acid amide, and benzamide; imides such as succinimide, phthalic acid imide, and maleic acid imide; amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine; imidazoles such as imidazole and 2-ethylimidazole;Examples of the compounds include urea-based compounds such as urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea; carbamate-based compounds such as N-phenyl phenylcarbamate; imine-based compounds such as ethyleneimine and propyleneimine; sulfite-based compounds such as sodium bisulfite and potassium bisulfite; and azole-based compounds. Examples of the azole compounds include pyrazoles or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazoles or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline. The blocking agent may be used alone or in combination of two or more kinds.

[0026] Specific examples of the monomer (a1) having a blocked isocyanate group include monomers having a blocked isocyanate group such as 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl(meth)acrylate and 2-[0-(1'-methylpropylideneamino)carboxyamino]ethyl(meth)acrylate. The monomer (a1-4) may be used alone or in combination of two or more kinds.

[0027] Specific examples of the monomer (a1) having a glycidyl group (hereinafter also referred to as "monomer (a1-5)") include (meth)acrylic acid esters having a glycidyl group, such as glycidyl (meth)acrylate and hydroxybutyl (meth)acrylate glycidyl ether. The monomer (a1-5) may be used alone or in combination of two or more kinds.

[0028] The monomer (a1) may be used alone or in combination of two or more kinds thereof, i.e., the (meth)acrylic polymer (A) may contain one kind of structural unit (a1) or may contain two or more kinds of structural units (a1). When the (meth)acrylic polymer (A) contains two or more types of structural units (a1), the reactive functional groups (x) possessed by the respective monomers (a1) may be the same or different, i.e., the (meth)acrylic polymer (A) may have one type of reactive functional group (x) or two or more types of reactive functional groups (x).

[0029] The proportion of the structural unit (a1) in the (meth)acrylic polymer (A) is preferably 0.1% by mass or more and 99.9% by mass or less, more preferably 1% by mass or more and 70% by mass or less, and even more preferably 5% by mass or more and 50% by mass or less, based on the total mass of all structural units constituting the (meth)acrylic polymer (A) (i.e., when the sum of all structural units constituting the (meth)acrylic polymer (A) is 100% by mass). When the proportion of the structural unit (a1) is equal to or more than the lower limit, the thixotropy of the (meth)acrylic polymer (I) and the resin composition is further improved. When the proportion of the structural unit (a1) is equal to or less than the upper limit, the sinterability of the (meth)acrylic polymer (I) and the resin composition is further improved.

[0030] (Monomer (a2)) The monomer (a2) is a (meth)acrylic acid ester having no reactive functional group (x). The monomer (a2) is a monomer having at least one polymerizable double bond, specifically having at least one (meth)acryloyl group as a functional group having a polymerizable double bond. Specific examples of the monomer (a2) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, i-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl alkyl (meth)acrylates having a linear or branched hydrocarbon skeleton, such as (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and 4-t-butylcyclohexyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; Alkyl (meth)acrylates having an alicyclic skeleton; (meth)acrylic acid esters having an aromatic ring such as phenoxy (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, nonylphenol EO adduct (meth)acrylate, o-biphenyloxyethyl (meth)acrylate; (meth)acrylic acid salts such as ammonium (meth)acrylate, sodium (meth)acrylate, and potassium (meth)acrylate; (meth)acrylates having a cyclic ether such as tetrahydrofurfuryl (meth)acrylate; (meth)acrylamide derivatives such as (meth)acrylamide, (meth)acrylamide diacetone acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and (meth)acryloylmorpholine;Monomers containing a phosphate group, such as 2-(meth)acryloyloxyethyl acid phosphate, 2-(meth)acryloyloxyethyl acid phosphate monoethanolamine salt, diphenyl((meth)acryloyloxyethyl)phosphate, (meth)acryloyloxypropyl acid phosphate, 3-chloro-2-acid phosphooxypropyl (meth)acrylate, acid phosphooxypolyoxyethylene glycol mono(meth)acrylate, acid phosphooxypolyoxypropylene glycol (meth)acrylate; ethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 1,10 di(meth)acrylate. -Decanediol, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and other polyfunctional alkyl (meth)acrylates having a linear or branched hydrocarbon skeleton; polyfunctional polyalkoxylene (meth)acrylates such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and ethoxylated glycerin tri(meth)acrylate; polyfunctional (meth)acrylates having an ester skeleton such as neopentyl glycol hydroxypivalate di(meth)acrylate;Examples include polyfunctional glycerin (meth)acrylates such as glycerin tri(meth)acrylate and ethoxylated glycerin tri(meth)acrylate. Among these, alkyl (meth)acrylates having a linear or branched hydrocarbon skeleton are preferred from the viewpoint of baking properties, and among these, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate are more preferred for general versatility. The monomer (a2) may be used alone or in combination of two or more kinds thereof, i.e., the (meth)acrylic polymer (A) may contain one kind of structural unit (a2) or two or more kinds of structural units (a2).

[0031] The proportion of the structural unit (a2) in the (meth)acrylic polymer (A) is preferably 0.1% by mass or more and 99.9% by mass or less, more preferably 5% by mass or more and 99% by mass or less, and even more preferably 10% by mass or more and 95% by mass or less, based on the total mass of all structural units constituting the (meth)acrylic polymer (A). When the proportion of the structural unit (a2) is equal to or greater than the lower limit, the sinterability of the (meth)acrylic polymer (I) and the resin composition is further improved. When the proportion of the structural unit (a2) is equal to or less than the upper limit, the thixotropy of the (meth)acrylic polymer (I) and the resin composition is further improved.

[0032] (Monomer (a3)) The monomer (a3) ​​is a monomer other than the monomer (a1) and the monomer (a2). The monomer (a3) ​​is not particularly limited as long as it is copolymerizable with at least the monomer (a1). Examples of the monomer (a3) ​​include aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, 4-ethenylphenol, vinyltoluene, and chlorostyrene; cyanide vinyl monomers such as acrylonitrile, methacrylonitrile, α-cyanoacrylate, dicyanovinylidene, fumaronitrile, and 3-hydroxyacrylonitrile; crotonic acid, isocrotonic acid, cinnamic acid, itaconic acid, and maleic acid. monomers having a carboxyl group such as vinyl sulfonic acid, maleic anhydride, fumaric acid, citraconic acid, mesaconic acid, and glutaconic acid; monomers having a sulfonic acid group such as vinyl sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid; polyfunctional monomers such as divinylbenzene, divinylnaphthalene, and divinyl ether; vinyl monomers such as vinyl acetate and vinyl propionate; and conjugated diene monomers such as 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, and chloroprene. The monomer (a3) ​​may be used alone or in combination of two or more kinds, i.e., the (meth)acrylic polymer (A) may contain one kind of structural unit (a3) ​​or two or more kinds of structural units (a3).

[0033] The proportion of the structural unit (a3) ​​in the (meth)acrylic polymer (A) is preferably 30 mass% or less, more preferably 20 mass% or less, based on the total mass of all structural units constituting the (meth)acrylic polymer (A). When the proportion of the structural unit (a3) ​​is equal to or less than the upper limit, the (meth)acrylic polymer (I) and the resin composition have a better balance between thixotropy and sinterability.

[0034] (Physical Properties) The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably from 50,000 to 5,000,000, and more preferably from 80,000 to 400,000. When the weight average molecular weight of the (meth)acrylic polymer (A) is within the above range, high viscosity characteristics and resistance to thread breakage are further improved. The weight average molecular weight of the (meth)acrylic polymer (A) is a value calculated as a standard polystyrene as measured by gel permeation chromatography (GPC). The detailed measurement conditions are as described in the examples below.

[0035] The glass transition temperature (Tg) of the (meth)acrylic polymer (A) is preferably −50° C. or higher and 130° C. or lower, more preferably 10° C. or higher and 80° C. or lower. When the glass transition temperature of the (meth)acrylic polymer (A) is equal to or higher than the lower limit, deformation of a molded body obtained by molding the metal paste described below into a predetermined shape is suppressed. When the glass transition temperature of the (meth)acrylic polymer (A) is equal to or lower than the upper limit, adhesion is good when the molded body is laminated by thermocompression bonding. The glass transition temperature of the (meth)acrylic polymer (A) is a value calculated from the glass transition temperatures and mass fractions of the homopolymers of the respective monomers constituting the (meth)acrylic polymer (A) by the Fox formula represented by the following formula (1). 1 / (273+Tg)=Σ(Wi / (273+Tgi)) ···(1) (In formula (1), Wi represents the mass fraction of monomer i, and Tgi represents the glass transition temperature (°C) of the homopolymer of monomer i.) The glass transition temperature of a homopolymer of monomer i can be the value described in Polymer Handbook [Polymer Handbook, J. Brandrup, Interscience, 1989]. When a monomer whose homopolymer glass transition temperature is not described in the Polymer Handbook is used, the Tg is an actual value measured by the method described in JIS K 7121:2012 "Method for measuring glass transition temperature of plastics."

[0036] The solubility parameter (SP value) of the (meth)acrylic polymer (A) is 6.0 (J / cm 3 ) 1 / 2 More than 11.0(J / cm 3 ) 1 / 2 Preferably less than 8.0 (J / cm 3 ) 1 / 2 More than 9.0(J / cm 3 ) 1 / 2The following is more preferable: When the solubility parameter of the (meth)acrylic polymer (A) is equal to or greater than the lower limit, the viscosity of the (meth)acrylic resin (I) is high. When the solubility parameter of the (meth)acrylic polymer (A) is equal to or less than the upper limit, the solubility in the organic solvent (S) described below is improved, and the storage stability of the (meth)acrylic resin (I) is good. The solubility parameter of the (meth)acrylic polymer (A) is calculated by the method proposed by Fedors et al. Specifically, it is calculated by the following formula (2). Solubility parameter (SP value) = (ΣEcoh / ΣV) 1 / 2 ···(2) (In equation (2), ΣEcoh represents the cohesive energy (cal / mol), and ΣV represents the molar molecular volume (cm 3 / mol). It should be noted that ΣEcoh and ΣV can be publicly known values, for example, values ​​described in Robert F. FEDORS, "POLYMER ENGINEERING AND SCIENCE", February 1974, Vol. 14, No. 2, pp. 147-154.

[0037] When the solubility parameter cannot be determined from the formula (2), the solubility parameter of the (meth)acrylic polymer (A) can be measured, for example, by the following method [Reference: SUH, CLARKE [JPSA-1, 5, 1671-1681 (1967)].

[0038] A sample is prepared by weighing 0.5 g of (meth)acrylic polymer (A) into a 100 ml beaker, adding 10 ml of a good solvent using a whole pipette, and dissolving the polymer using a magnetic stirrer. The solvent used is, for example, acetone or dioxane. A poor solvent is added dropwise to the obtained sample using a 50 ml burette at a measurement temperature of 20°C, and the point at which the solution becomes cloudy (cloudy point) is recorded as the amount added. Ion-exchanged water is used as a high-SP poor solvent, and n-hexane is used as a low-SP poor solvent, and the cloudy point is measured for each poor solvent. From the following formulas (3-1) to (3-5), the SP value (δ) (unit: (J / cm 3 ) 1 / 2 ) is found. V ml =(V l ×V a ) / (φ l ×V a +φ a1 ×V l ) ···(3-1) δ ml =φ l ×δ l +φ a1 ×δ a (3-2) V mh =(V h ×V a ) / (φ h ×V a +φ a2 ×V h ) ···(3-3) δ mh =φ h ×δ h +φ a2 ×δ a (3-4) δ={(V ml ) 1 / 2 ×δ ml +(V mh ) 1 / 2 ×δ mh} / {(V ml ) 1 / 2 +(V mh ) 1 / 2} ···(3-5)

[0039] The abbreviations in formulas (3-1) to (3-5) have the following meanings. ·V l : Molar volume of n-hexane (cm 3 / mol) ·V h : Molar volume of ion-exchanged water (cm 3 / mol) ·V a : Molar volume of good solvent (cm 3 / mol) φ l: Volume fraction of n-hexane to the sum of good solvent and n-hexane at the cloudiness point = Amount of n-hexane added / (Amount of good solvent used + Amount of n-hexane added) φ h : Volume fraction of ion-exchanged water relative to the sum of good solvent and ion-exchanged water at the cloudiness point = Amount of ion-exchanged water added / (Amount of good solvent used + Amount of ion-exchanged water added) φ a1 : Volume fraction of good solvent to the sum of good solvent and n-hexane at the cloudiness point = amount of good solvent used / (amount of good solvent used + amount of n-hexane dropped) φ a2 : Volume fraction of good solvent relative to the sum of good solvent and ion-exchanged water at the cloudiness point = amount of good solvent used / (amount of good solvent used + amount of ion-exchanged water dropped) δ l : SP value of n-hexane δ h : SP value of ion-exchanged water δ a :SP value of good solvent

[0040] The hydroxyl value (OHV) of the (meth)acrylic polymer (A) is preferably 200 mgKOH / g or less, more preferably 150 mgKOH / g or less. When the hydroxyl value of the (meth)acrylic polymer (A) is the above upper limit or less, the solubility in the organic solvent (S) described below is improved, and the storage stability of the (meth)acrylic resin (I) is improved. The hydroxyl value of the (meth)acrylic polymer (A) is a value calculated by the following formula (4). Hydroxyl number (mgKOH / g) = (f × M1 / Mn / M2 × [KOH] × 1000) (4)

[0041] The abbreviations in formula (4) have the following meanings: f: the number of hydroxyl groups in the hydroxyl group-containing monomer (e.g., the above-mentioned monomer (a1-1)) constituting the (meth)acrylic polymer (A) · [KOH]: Molecular weight of KOH M1: Mass of hydroxyl group-containing monomer (g) M2: Solid mass of (meth)acrylic polymer (A) (g) Mn: Molecular weight of hydroxyl group-containing monomer (number average molecular weight)

[0042] (Method for producing (meth)acrylic polymer (A)) The (meth)acrylic polymer (A) can be obtained, for example, by polymerizing a monomer mixture containing the monomer (a1) in the presence of a polymerization initiator by a commonly known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, etc. The polymerization method is not limited to these. Furthermore, the polymerization of the monomer mixture may be carried out in the presence of a chain transfer agent, if necessary. The monomer mixture preferably contains a monomer (a2) in addition to the monomer (a1), and may further contain a monomer (a3) ​​as necessary.

[0043] [Functional group (y)] The functional group (y) may be contained in the (meth)acrylic polymer (A). When the functional group (y) is contained in the (meth)acrylic polymer (A), the functional group (y) may be contained in at least one of the monomer (a1) and the monomer (a3), or may be contained in at least one of the polymerization initiator and the chain transfer agent used in producing the (meth)acrylic polymer (A). That is, at least one of the monomer (a1), the monomer (a3), the polymerization initiator, and the chain transfer agent may have the functional group (y). Alternatively, the functional group (y) may be mixed with the (meth)acrylic polymer (A) as a compound (B) containing the functional group (y) (hereinafter simply referred to as "compound (B)") and undergo a crosslinking reaction with the reactive functional group (x) in the (meth)acrylic polymer (A). The compound (B) will be described below.

[0044] (Compound (B)) The compound (B) is a compound containing a functional group (y). Examples of the functional group (y) include those exemplified above. For example, when the reactive functional group (x) is a hydroxyl group, the functional group (y) is preferably an isocyanate group, more preferably a blocked isocyanate group.

[0045] When the functional group (y) is a hydroxyl group, the compound (B) containing a hydroxyl group (hereinafter also referred to as "compound (B1)") is preferably a polyol. The polyol is preferably a compound having two or more functional hydroxyl groups. Known compounds having two or more functional hydroxyl groups can be used. Examples of compounds having bifunctional hydroxyl groups (hereinafter also referred to as "diol compounds") include linear aliphatic saturated diols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, and 1,20-eicosanediol. Other examples of diol compounds include polypropylene glycol, polyethylene glycol, polyether diol, polyurethane diol, and polyester diol. The diol compounds may be used alone or in combination of two or more.

[0046] When the functional group (y) is a carboxyl group, the compound (B) containing a carboxyl group (hereinafter also referred to as "compound (B2)") is preferably a polycarboxylic acid. The polycarboxylic acid is preferably a compound having a bifunctional or higher carboxyl group. Known compounds can be used as the compound having a bifunctional or higher carboxyl group. Examples of compounds having a bifunctional carboxyl group (hereinafter also referred to as "dicarboxylic acid compounds") include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acid compounds may be used alone or in combination of two or more.

[0047] When the functional group (y) is an amino group, the compound (B) containing an amino group (hereinafter also referred to as "compound (B3)") is preferably a polyamine. The polyamine is preferably a compound having two or more functional amino groups. Known compounds having two or more functional amino groups can be used. Examples of compounds having two or more functional amino groups include ethylenediamine, putrescine, cadaverine, hexamethylenediamine, ethambutol, phenylenediamine, melamine, monomethylolmelamine, dimethylolmelamine, and hexamethylolmelamine. The compound having two or more functional amino groups may be used alone or in combination of two or more.

[0048] When the functional group (y) is a glycidyl group, the compound (B) containing a glycidyl group (hereinafter also referred to as "compound (B4)") is preferably a polyepoxy compound. The polyepoxy compound is preferably a compound having a difunctional or higher glycidyl group. Known compounds can be used as the compound having a difunctional or higher glycidyl group. Examples of the compound having a difunctional or higher glycidyl group include poly(ethylene glycol) diglycidyl ether, 1,7-octadiene diepoxide, 1,3-butadiene diepoxide, and epoxy resins having two or more epoxy groups. The compound having two or more functional glycidyl groups may be used alone or in combination of two or more.

[0049] When the functional group (y) is an isocyanate group, the compound (B) containing an isocyanate group (hereinafter also referred to as "compound (B5)") is preferably a polyisocyanate. The polyisocyanate is preferably a bifunctional or higher functional isocyanate compound, and known bifunctional or higher functional isocyanate compounds can be used. Examples of bifunctional isocyanate compounds (hereinafter also referred to as "diisocyanate compounds") include hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, pentamethylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane 4,4-dicyclohexyl diisocyanate. The diisocyanate compounds may be used alone or in combination of two or more.

[0050] Tri- or higher functional isocyanate compounds are synthesized using the above-mentioned diisocyanate compounds as starting materials, and examples thereof include biuret compounds, trimethylolpropane adduct compounds, isocyanurate compounds, and allophanate compounds. Specific examples of tri- or higher functional isocyanate compounds include biuret compounds of hexamethylene diisocyanate (trade name "Duranate 24A-100" manufactured by Asahi Kasei Corporation), adduct compounds of hexamethylene diisocyanate (trade name "Duranate P-301-75E" manufactured by Asahi Kasei Corporation), isocyanurate compounds of hexamethylene diisocyanate (trade name "Duranate TPA-100" manufactured by Asahi Kasei Corporation), blocked isocyanates (trade name "Duranate MF-K60X" manufactured by Asahi Kasei Corporation); 1,3-bis(isocyanatomethylene) Examples of suitable isocyanurates include a trimethylolpropane adduct of 1,3-bis(isocyanatomethyl)cyclohexane (manufactured by Mitsui Chemicals, Inc. under the trade name "Takenate D-120N"), a trimethylolpropane adduct of 1,3-bis(isocyanatomethyl)cyclohexane (manufactured by Mitsui Chemicals, Inc. under the trade name "Takenate D-127N"), a trimethylolpropane adduct of isophorone diisocyanate (manufactured by Mitsui Chemicals, Inc. under the trade name "Takenate D-140N"); and an allophanate of hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd. under the trade name "Desmodur XP2679"). The tri- or higher functional isocyanate compounds may be used alone or in combination of two or more.

[0051] The compound (B5) may be a blocked isocyanate that is activated before the reaction, or may be an unblocked isocyanate. As the blocked isocyanate, a blocked isocyanate compound, which is a compound in which the isocyanate group in the above-mentioned bifunctional or higher isocyanate compound is blocked with a blocking agent, can be used. Examples of the blocking agent include those exemplified above.

[0052] The compound (B) may contain one functional group (y) or two or more functional groups (y). When compound (B) contains two or more functional groups (y), the functional groups (y) may be of the same type or different types. Examples of the compound (B) containing multiple different functional groups (y) (hereinafter also referred to as "compound (B6)") include ethanolamine, heptaminol, isoethanolamine, propanolamine, sphingosine, methanolamine, dimethylethanolamine, N-methylethanolamine, salicylic acid, glycolic acid, etc. The compound (B6) may be used alone or in combination of two or more kinds.

[0053] The compound (B) may also be a (meth)acrylic polymer having a functional group (y) (hereinafter also referred to as "(meth)acrylic polymer (B7)"). The (meth)acrylic polymer (B7) preferably contains a structural unit (hereinafter also referred to as "structural unit (b1)") derived from a (meth)acrylic acid ester (b1) (hereinafter also referred to as "monomer (b1)") having a functional group (y). The (meth)acrylic polymer (B7) may further contain a structural unit (hereinafter also referred to as "structural unit (b2)") derived from a (meth)acrylic acid ester (b2) (hereinafter also referred to as "monomer (b2)") that does not have a functional group (y). Furthermore, the (meth)acrylic polymer (B7) may further contain, as necessary, a structural unit (hereinafter also referred to as "structural unit (b3)") derived from a monomer (hereinafter also referred to as "monomer (b3)") other than the monomer (b1) and the monomer (b2). The functional group (y) may be contained in at least one of the polymerization initiator and the chain transfer agent used in producing the (meth)acrylic polymer (B7).

[0054] Examples of the monomer (b1) include the monomer (a1) exemplified above in the description of the (meth)acrylic polymer (A). Examples of the monomer (b2) include the monomer (a2) exemplified above in the description of the (meth)acrylic polymer (A). Examples of the monomer (b3) include the monomer (a3) ​​exemplified above in the description of the (meth)acrylic polymer (A).

[0055] When the (meth)acrylic polymer (B7) is used as the compound (B), the following combinations can be mentioned as examples of preferred combinations of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B7). A combination of a (meth)acrylic polymer (A) having structural units derived from the monomer (a1-1) and no structural units derived from the monomer (a1-4) and a (meth)acrylic polymer (B7) having structural units derived from the monomer (a1-4) as the monomer (b1) and no structural units derived from the monomer (a1-1). A combination of a (meth)acrylic polymer (A) having structural units derived from the monomer (a1-2) and no structural units derived from the monomer (a1-5) and a (meth)acrylic polymer (B7) having structural units derived from the monomer (a1-5) as the monomer (b1) and no structural units derived from the monomer (a1-2). A combination of a (meth)acrylic polymer (A) having structural units derived from the monomer (a1-5) but not having structural units derived from the monomer (a1-1) and a (meth)acrylic polymer (B7) having structural units derived from the monomer (a1-1) as the monomer (b1) but not having structural units derived from the monomer (a1-5). A combination of a (meth)acrylic polymer (A) having a structural unit derived from the monomer (a1-4) and a (meth)acrylic polymer (B7) having no structural unit derived from the monomer (a1-4) as the monomer (b1).

[0056] [Physical Properties of (Meth)acrylic Polymer (I)] The thermal weight loss rate of the (meth)acrylic polymer (I) is preferably 95.0% or more, more preferably 99.0% or more, even more preferably 99.8% or more, and particularly preferably 99.9% or more. A higher thermal weight loss rate indicates better sinterability (thermal decomposition property). When the thermal weight loss rate of the (meth)acrylic polymer (I) is equal to or greater than the lower limit, the amount of impurities in the inorganic sintered body obtained using the (meth)acrylic polymer (I) and the defective rate in the production of inorganic sintered bodies, electronic devices, and solar panels are suppressed. The upper limit of the thermal weight loss rate of the (meth)acrylic polymer (I) is 100%. The thermal weight loss rate of the (meth)acrylic polymer (I) can be determined under the following measurement conditions. That is, using a differential thermal balance (TG-DTA), 5 mg of a measurement sample is heated in a nitrogen atmosphere from a starting temperature of 30°C to 500°C at a rate of 10°C / min, the mass of the residue when it reaches 450°C is measured, and the thermal weight loss rate is calculated using the following formula (5). Thermal weight loss rate (%) = (mass of measurement sample (mg) - mass of residue (mg)) × 100 / mass of measurement sample (mg) (5)

[0057] The thermal weight loss rate of the (meth)acrylic polymer (I) tends to increase, for example, as the proportion of the structural unit (a2) in the (meth)acrylic polymer (A) increases, and tends to increase as the proportion of the structural unit (a3) ​​in the (meth)acrylic polymer (A) decreases. Specifically, when the proportion of the structural unit (a2) is 0.1% by mass or more relative to the total mass of all structural units constituting the (meth)acrylic polymer (A), the thermal weight loss rate of the (meth)acrylic polymer (I) tends to increase. When the proportion of the structural unit (a3) ​​is 20% by mass or less relative to the total mass of all structural units constituting the (meth)acrylic polymer (A), the thermal weight loss rate of the (meth)acrylic polymer (I) tends to increase.

[0058] The water content (moisture content) of the (meth)acrylic polymer (I) is preferably 10% by mass or less, more preferably 8.0% by mass or less, even more preferably 5.0% by mass or less, and particularly preferably 3.0% by mass or less, based on the total mass of the (meth)acrylic polymer (I). When the water content of the (meth)acrylic polymer (I) is equal to or less than the upper limit, uniform film coating properties are improved when a metal paste containing the resin composition of this embodiment is screen printed.

[0059] Resin solution (α) in which (meth)acrylic polymer (I) is dissolved in a solvent to a solids concentration of 7 mass %, i.e., resin solution (α) containing 7 mass % of (meth)acrylic polymer (I) relative to the total mass of resin solution (α), satisfies the following formula (7): Furthermore, resin solution (α) preferably satisfies one or more of the following formulas (6) and (8) to (12), and more preferably satisfies all of them. η0.1≧50 Pa·s (6) η1≧10 Pa·s (7) η10≧5Pa·s (8) η100≧1 Pa·s (9) η1000≧0.1 Pa·s (10) η1 / η100≧2.0 (11) η10 / η1000≧2.0 (12) Here, η0.1, η1, η10, η100, and η1000 are the viscosities (Pa·s) of resin solution (α) or resin solution (β) described below, measured using a viscoelasticity measuring device with a cone plate of 1.0° / 20 mm and a measurement temperature of 23°C. η0.1 is the viscosity (Pa·s) at a shear rate of 0.1 (1 / s), η1 is the viscosity (Pa·s) at a shear rate of 1 (1 / s), η10 is the viscosity (Pa·s) at a shear rate of 10 (1 / s), η100 is the viscosity (Pa·s) at a shear rate of 100 (1 / s), and η1000 is the viscosity (Pa·s) at a shear rate of 1000 (1 / s).

[0060] η1 is 10 Pa s or more. When η1 is less than 10 Pa s, even if the metal paste is prepared so that the concentration of the (meth)acrylic polymer (I) in the metal paste described below is low in order to achieve a thin film, sagging or bleeding after printing of the metal paste is unlikely to occur, and good conductivity can be maintained. There is no particular upper limit to the value of η1, but for example, η1 is preferably 300 Pa·s or less.

[0061] Each of η / η00 and η / η000 is preferably 2.0 or more, more preferably 3.5 or more, and even more preferably 5.0 or more. When the ratio is equal to or greater than the lower limit, the thixotropy is further improved when the (meth)acrylic polymer (I) is dissolved in the organic solvent (S) described below. As a result, the printability and the resistance to sagging after printing are further improved when a metal paste containing the resin composition of this embodiment is screen printed. There are no particular upper limits for η1 / η100 and η10 / η1000, but for example, η1 / η100 and η10 / η1000 are each preferably 30.0 or less, more preferably 10.0 or less.

[0062] η0.1, η1, η10, η100, and η1000, as well as η1 / η100 and η10 / η1000, can be adjusted by adjusting the proportion of the structural unit (a1) in the (meth)acrylic polymer (A). For example, as the proportion of the structural unit (a1) in the (meth)acrylic polymer (A) increases, η0.1, η1, η10, η1 / η100, and η10 / η1000 tend to increase, and η100 and η1000 tend to decrease. Conversely, as the proportion of the structural unit (a1) decreases, η0.1, η1, η10, η1 / η100, and η10 / η1000 tend to decrease, and η100 and η1000 tend to increase. Specifically, when the proportion of the structural unit (a1) relative to the total mass of all structural units constituting the (meth)acrylic polymer (A) is 0.1 mass% or more, η0.1, η1, η10, η1 / η100, and η10 / η1000 tend to increase, while η100 and η1000 tend to decrease. When the proportion of the structural unit (a1) relative to the total mass of all structural units constituting the (meth)acrylic polymer (A) is 20 mass% or less, η0.1, η1, η10, η1 / η100, and η10 / η1000 tend to decrease, while η100 and η1000 tend to increase.

[0063] The solvent used in preparing the resin solution (α) is not particularly limited, but the organic solvent (S) described below is preferred, and among these, terpineol is particularly preferred. Terpineol is a mixture of α-terpineol, which is the main component, β-terpineol, and γ-terpineol. Commercially available terpineol can be used, and examples of commercially available terpineol include "TERPINEOL PG" manufactured by Takasago International Corporation, "TERPINEOL C" manufactured by Nippon Terpene Chemical Co., Ltd., and "TERPINEOL" manufactured by Nippon Fragrance Pharmaceutical Co., Ltd.

[0064] [Method for producing (meth)acrylic polymer (I)] The (meth)acrylic polymer (I) can be obtained, for example, by reacting a (meth)acrylic polymer (A) with a compound (B) in a reaction solvent in the presence of a catalyst, specifically by crosslinking a reactive functional group (x) contained in the (meth)acrylic polymer (A) with a functional group (y) contained in the compound (B). The proportion of compound (B) is preferably 1 part by mass or more and 100 parts by mass or less, more preferably 2 parts by mass or more and 50 parts by mass or less, and even more preferably 5 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of (meth)acrylic polymer (A). When the proportion of compound (B) is equal to or greater than the lower limit, the breakability and thixotropy of the (meth)acrylic polymer (I) become better. When the proportion of compound (B) is equal to or less than the upper limit, the sinterability of the (meth)acrylic polymer (I) becomes better.

[0065] As the reaction solvent, the organic solvent (S) described below is preferred, and among these, terpineol is particularly preferred. Examples of the catalyst include tin-based catalysts such as dibutyltin dilaurate, dioctyltin dilaurate, and stannous octanoate; amine-based catalysts such as diazabicycloundecene, triethylamine, and triethylenediamine; and quaternary ammonium-based catalysts such as tetramethylammonium hydroxide, tetrabutylammonium hydroxide, tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium iodide. Among these, tin-based catalysts are preferred, and dibutyltin dilaurate is more preferred. The reaction temperature is preferably 70°C or higher and 200°C or lower, and more preferably 100°C or higher and 150°C or lower.

[0066] When the (meth)acrylic polymer (A) contains both the reactive functional group (x) and the functional group (y), the (meth)acrylic polymer (I) may be produced by crosslinking the reactive functional group (x) and the functional group (y) in the (meth)acrylic polymer (A). Examples of the (meth)acrylic polymer (A) containing the reactive functional group (x) and the functional group (y) include the (meth)acrylic polymer (A) containing a structural unit derived from the above-mentioned monomer (a1-1) and a structural unit derived from the monomer (a1-4). The crosslinking reaction between the reactive functional group (x) and the functional group (y) proceeds, for example, by heating the (meth)acrylic polymer (A) containing the reactive functional group (x) and the functional group (y) in a reaction solvent in the presence of a catalyst. Examples of the catalyst include those exemplified above. The reaction temperature is preferably 80°C or higher and 250°C or lower, and more preferably 100°C or higher and 200°C or lower.

[0067] [Content] The content of the (meth)acrylic polymer (I) is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less, based on the total mass of the solid content of the resin composition. When the resin composition contains an organic solvent (S), the content of the (meth)acrylic polymer (I) is preferably from 0.99% by mass to 10% by mass, more preferably from 1% by mass to 9% by mass, even more preferably from 2% by mass to 9% by mass, particularly preferably from 2% by mass to 8% by mass, and most preferably from 3.5% by mass to 8% by mass, relative to the total mass of the resin composition. In this specification, the solid content of the resin composition refers to the remaining components after excluding the organic solvent (S) from the resin composition.

[0068] <Organic solvent (S)> The (meth)acrylic polymer (I) is preferably dissolved or dispersed in the organic solvent (S) in the resin composition, that is, the resin composition preferably contains the organic solvent (S). The organic solvent (S) preferably has active hydrogen. When the organic solvent (S) has active hydrogen, the viscosity of the resin composition containing the (meth)acrylic polymer (I) and the organic solvent (S) increases. Examples of active hydrogen include hydrogen atoms directly bonded to oxygen atoms, nitrogen atoms, sulfur atoms, etc. Examples of such active hydrogen include hydrogen atoms in functional groups such as hydroxyl groups, amino groups, and thiol groups. In particular, hydrogen atoms in hydroxyl groups are preferred.

[0069] The boiling point of the organic solvent (S) is preferably 180° C. or higher and 300° C. or lower, more preferably 190° C. or higher and 250° C. or lower, and even more preferably 195° C. or higher and 230° C. If the boiling point of the organic solvent (S) is within the above range, the printability of the metal paste containing the resin composition of the present embodiment will be good. The boiling point of the organic solvent (S) is the temperature at which the organic solvent (S) begins to boil when heated, and is a value measured by the equilibrium reflux boiling point measurement method described in JIS K 2233:2017, for example.

[0070] Examples of the organic solvent (S) include α,β,γ-terpineol, terpineol acetate, dihydroterpineol, dihydroterpineol acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monoisobutyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, isophorone, benzyl alcohol, 1-octanol, 1-nonaol, 2-ethyl-1-hexanol, 1-decanol, 1-undecanol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butanediol. Examples of suitable solvents include ethanol, 1,4-butanediol, 1,5-pentanediol, Texanol, butyl lactate, dioctyl phthalate, dioctyl adipate, phenylpropylene glycol, cresol, dimethyl sulfoxide, N-methylpyrrolidone, toluene, xylene, ethyl acetate, n-butyl acetate, isobutyl acetate, ethyl acetate, propyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, butyl carbitol acetate, Texanol, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, diacetone alcohol, cyclohexanone, isophorone, methanol, ethanol, isopropanol, n-butanol, isobutanol, Supersol 100 (product name, manufactured by Nippon Oil Corporation), and cyclohexane. Among these, α,β,γ-terpineol, terpineol acetate, dihydroterpineol, dihydroterpineol acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monoisobutyl ether, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate are more preferred because they have a boiling point of 180° C. or higher and are widely used. Among these, organic solvents (S) having active hydrogen, i.e., α,β,γ-terpineol, dihydroterpineol, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, are more preferred, with α,β,γ-terpineol being even more preferred. The organic solvent (S) may be used alone or in combination of two or more kinds.

[0071] The content of the organic solvent (S) in the resin composition is preferably 900 parts by mass or more and 10,000 parts by mass or less, more preferably 1,000 parts by mass or more and 5,000 parts by mass or less, and even more preferably 1,100 parts by mass or more and 3,000 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (I). When the content of the organic solvent (S) is equal to or more than the lower limit, uniformity is improved when blending the metal paste. When the content of the organic solvent (S) is equal to or less than the upper limit, the thixotropy of the resin composition is improved.

[0072] <Physical properties of resin composition> The resin composition (hereinafter also referred to as "resin solution (β)") having a solid content of 7 mass % satisfies the formula (7). Furthermore, the resin solution (β) preferably satisfies one or more of the formulas (6), (8) to (12), and more preferably satisfies all of them.

[0073] When the resin composition consists of only the (meth)acrylic polymer (I), the resin composition is dissolved in a solvent to a concentration of 7 mass % to prepare a resin solution (β). The solvent used to prepare the resin solution (β) is not particularly limited, but the above-mentioned organic solvent (S) is preferred, and among them, terpineol is particularly preferred. When the resin composition contains the (meth)acrylic polymer (I) and the organic solvent (S) and the content of the (meth)acrylic polymer (I) is 7 mass % relative to the total mass of the resin composition, the resin composition may be used as is as the resin solution (β). When the resin composition contains a (meth)acrylic polymer (I) and an organic solvent (S) and the content of the (meth)acrylic polymer (I) is less than 7 mass% relative to the total mass of the resin composition, the resin composition is concentrated to a solids concentration of 7 mass% to prepare a resin solution (β). When the resin composition contains a (meth)acrylic polymer (I) and an organic solvent (S), and the content of the (meth)acrylic polymer (I) exceeds 7% by mass relative to the total mass of the resin composition, the resin composition is diluted with a dilution solvent to a solids concentration of 7% by mass to prepare a resin solution (β). The dilution solvent is not particularly limited, but the above-mentioned organic solvent (S) is preferred, with terpineol being particularly preferred. Furthermore, a solvent of the same type as the organic solvent (S) contained in the resin composition is preferred. The resin solution (β) is preferably prepared by diluting or concentrating the resin composition as necessary with an organic solvent (S) or the like so that the content of the (meth)acrylic polymer (I) relative to the total mass of the resin solution (β) is 7 mass%.

[0074] <Method of manufacturing resin composition> In the above-mentioned method for producing the (meth)acrylic polymer (I), the (meth)acrylic polymer (I) is obtained in a state of being dissolved or dispersed in a reaction solvent. The (meth)acrylic polymer (I) dissolved or dispersed in the reaction solvent may be used as a resin composition as is, or may be concentrated or further diluted with an organic solvent (S) as necessary to have a desired solid content concentration and then used as a resin composition.

[0075] <Action and effect> The resin composition of the present embodiment described above contains a (meth)acrylic polymer (I) having a crosslinked structure as a binder resin, and therefore has excellent sinterability, high thixotropy, and resistance to thread breakage. In addition, even if the solids concentration of the resin composition is low, specifically, when the solids concentration is 7% by mass, the viscosity (η1) is 10 Pa s or more. Therefore, the resin composition of the present embodiment has a high viscosity, which makes it less likely to sag or bleed after printing and maintains good conductivity.

[0076] <Application> The resin composition can be used, for example, as a raw material for internal electrode layers or external electrode layers of multilayer electronic components such as multilayer ceramic capacitors, or as a paste raw material for solar cell electrodes.

[0077] [Metal paste] Hereinafter, one embodiment of the metal paste of the present invention will be described. The metal paste of this embodiment contains the resin composition of the present invention described above and an inorganic compound (D). When the resin composition of the present invention does not contain an organic solvent (S), the metal paste preferably further contains an organic solvent in addition to the resin composition of the present invention and the inorganic compound (D). That is, the metal paste preferably contains a (meth)acrylic polymer (I), an inorganic compound (D), and an organic solvent. The metal paste may further contain components other than the (meth)acrylic polymer (I), the inorganic compound (D), and the organic solvent (hereinafter also referred to as "optional components"), as necessary, within a range that does not impair the effects of the present invention.

[0078] <(Meth)acrylic polymer (I)> The content of the (meth)acrylic polymer (I) is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, based on the total mass of the metal paste. If the content of the (meth)acrylic polymer (I) is equal to or more than the lower limit, the formability of the metal paste is improved. If the content of the (meth)acrylic polymer (I) is equal to or less than the upper limit, the amount of organic residue after firing the metal paste is reduced.

[0079] <Inorganic compounds (D)> The inorganic compound (D) is not particularly limited, but examples thereof include oxides such as alumina, zirconia, titanium oxide, barium titanate, and calcium oxide; nitrides such as alumina nitride, silicon nitride, and boron nitride; metals such as copper, silver, and nickel; silica-based powders such as low-melting-point glass powder; carbon-based powders such as carbon black; and various phosphors. The inorganic compounds may be used alone or in combination of two or more.

[0080] The content of the inorganic compound (D) is preferably 30% by mass or more and 90% by mass or less relative to the total mass of the metal paste. If the content of the inorganic compound (D) is equal to or more than the lower limit, the molding efficiency of the metal paste is improved. If the content of the inorganic compound (D) is equal to or less than the upper limit, the moldability of the metal paste is improved.

[0081] <Organic solvents> Examples of the organic solvent include the organic solvents (S) exemplified above in the description of the resin composition of the present invention, among which terpineol is particularly preferred. The organic solvents may be used alone or in combination of two or more.

[0082] The content of the organic solvent is preferably 9.9% by mass or more and 69.9% by mass or less relative to the total mass of the metal paste. If the content of the organic solvent is equal to or more than the lower limit, the formability of the metal paste is improved. If the content of the organic solvent is equal to or less than the upper limit, the solid content of the metal paste is improved.

[0083] <Optional ingredients> Examples of the optional components include a plasticizer, a dispersing agent, an antifoaming agent, and a binder resin other than the (meth)acrylic polymer (I). The optional components may be used alone or in combination of two or more.

[0084] <Metal paste manufacturing method> The metal paste can be obtained, for example, by mixing the resin composition of the present invention, the inorganic compound (D), and, if necessary, optional components. When the resin composition of the present invention contains an organic solvent (S), an organic solvent may be further mixed as needed to achieve a desired solid content concentration. When the resin composition of the present invention does not contain an organic solvent (S), the metal paste can be obtained by mixing the resin composition of the present invention, an inorganic compound (D), an organic solvent, and, if necessary, optional components.

[0085] <Action and effect> The metal paste of the present embodiment described above contains the resin composition of the present invention, and therefore has high thixotropy and resistance to thread breakage, and is excellent in both printability when the metal paste is screen-printed and leveling property after printing.

[0086] Since the metal paste of this embodiment has high thixotropy and thread breakage resistance and is excellent in printability by screen printing, it is preferable to use screen printing when forming a pattern on a substrate using the metal paste of this embodiment, but methods other than screen printing may also be used. For example, if the viscosity of the metal paste is high, dip coating or dispense coating can be used, and if the viscosity is low, doctor blade coating, cast coating, gravure printing, etc. can be used. The substrate onto which the metal paste is printed or applied is not particularly limited, but examples thereof include ceramic substrates and capacitors.

[0087] [Inorganic sintered body] Hereinafter, one embodiment of the inorganic sintered body of the present invention will be described. The inorganic sintered body of this embodiment is obtained by firing the metal paste of the present invention described above. The firing method is not particularly limited, but may be, for example, a method in which the substrate on which the metal paste is printed or applied is placed in a high-temperature atmosphere. During the firing process, organic substances such as binder resin contained in the metal paste are decomposed and removed, and inorganic compounds contained in the metal paste are melted and sintered, thereby obtaining an inorganic sintered body. The firing temperature can be determined appropriately depending on the melting temperature of the substrate, the type of inorganic powder, and the organic substance contained in the metal paste, but is usually about 200°C or higher and 1500°C or lower, and preferably 300°C or higher and 1000°C or lower.

[0088] [Electronic devices and solar panels] From the viewpoint of current collection performance, the electronic device of the present invention preferably contains the inorganic sintered body of the present invention described above. Examples of the electronic device include semiconductors such as logic circuits, memory circuits, and analog circuits, lithium ion batteries, capacitors, printed circuits, and current collection circuits for solar panels. From the viewpoint of photovoltaic power generation, the solar panel of the present invention preferably contains the inorganic sintered body of the present invention described above. [Example]

[0089] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these. In the following description, unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass".

[0090] [Measurement and evaluation method] <Calculation of glass transition temperature (Tg)> The glass transition temperature of the (meth)acrylic polymer (A) was calculated by the Fox formula represented by the following formula (1). 1 / (273+Tg)=Σ(Wi / (273+Tgi)) ···(1) (In formula (1), Wi represents the mass fraction of monomer i, and Tgi represents the glass transition temperature (°C) of the homopolymer of monomer i.)

[0091] <Calculation of solubility parameter (SP value)> The solubility parameter of the (meth)acrylic polymer (A) was calculated by the following formula (2). Solubility parameter (SP value) = (ΣEcoh / ΣV) 1 / 2 ···(2) (In equation (2), ΣEcoh represents cohesive energy (cal / mol), and ΣV represents molar volume (cm3 / mol).)

[0092] <Hydroxyl value (OHV) measurement> The hydroxyl value of the (meth)acrylic polymer (A) was calculated by the following formula (4). Hydroxyl number (mgKOH / g) = (f × M1 / Mn / M2 × [KOH] × 1000) (4) The abbreviations in formula (4) have the following meanings: f: the number of hydroxyl groups in the hydroxyl group-containing monomer (e.g., the above-mentioned monomer (a1-1)) constituting the (meth)acrylic polymer (A) · [KOH]: Molecular weight of KOH M1: Mass of hydroxyl group-containing monomer (g) M2: Solid mass of (meth)acrylic polymer (A) (g) Mn: Molecular weight of hydroxyl group-containing monomer (number average molecular weight)

[0093] <Measurement of weight average molecular weight (Mw)> The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) was measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value using a calibration curve of standard polystyrene. The GPC measurement conditions were as follows: (GPC measurement conditions) -Device: Tosoh Corporation product name "HLC-8220GPC". Column: Two columns, manufactured by Tosoh Corporation, named "TSKgel SuperHZM-H (4.6mmφ×150mm)", connected in series. Eluent: tetrahydrofuran. Sample concentration: 0.27% by mass. ·Measurement temperature: 40℃. ·Injection volume: 10μL. ·Flow rate: 0.5mL / min. Detectors: RI (built-in), UV (product name "UV-8220" manufactured by Tosoh Corporation).

[0094] <Viscosity measurement and thixotropy evaluation> The viscosity (Pa·s) of the resin composition was measured using a viscoelasticity measuring device (Thermo Fisher Scientific, product name "HAAKE MARS") with a cone plate of 1.0° / 20 mm and a measurement temperature of 23°C. The viscosity (Pa·s) of the resin composition at a shear rate of 0.1 (1 / s) was defined as η0.1, the viscosity (Pa·s) at a shear rate of 1 (1 / s) as η1, the viscosity (Pa·s) at a shear rate of 10 (1 / s) as η10, the viscosity (Pa·s) at a shear rate of 100 (1 / s) as η100, and the viscosity (Pa·s) at a shear rate of 1000 (1 / s) as η1000, and the viscosity was evaluated according to the following criteria.

[0095] (η1 evaluation) A: The value of η1 is 50 Pa·s or more. B: The value of η1 is 30 Pa·s or more and less than 50 Pa·s. C: The value of η1 is 10 Pa·s or more and less than 30 Pa·s. D: The value of η1 is less than 10 Pa·s.

[0096] (η10 rating) A: The value of η10 is 30 Pa·s or more. B: The value of η10 is 10 Pa·s or more and less than 30 Pa·s. C: The value of η10 is 5 Pa·s or more and less than 10 Pa·s. D: The value of η10 is less than 5 Pa·s.

[0097] (η100 rating) A: The value of η100 is 10 Pa·s or more. B: The value of η100 is 5 Pa·s or more and less than 10 Pa·s. C: The value of η100 is 0.5 Pa·s or more and less than 5 Pa·s. D: The value of η100 is less than 0.5 Pa·s.

[0098] (η1000 rating) A: The value of η1000 is 5 Pa·s or more. B: The value of η1000 is 1 Pa·s or more and less than 5 Pa·s. C: The value of η1000 is 0.1 Pa·s or more and less than 1 Pa·s. D: The value of η1000 is less than 0.1 Pa·s.

[0099] The thixotropy was evaluated according to the following criteria: the higher the values ​​of η1 / η100 and η10 / η1000, the better the thixotropy. (η1 / η100 evaluation) A: The value of η1 / η100 is 5.0 or more. B: The value of η1 / η100 is 3.5 or more and less than 5.0. C: The value of η1 / η100 is 2.0 or more and less than 3.5. D: The value of η1 / η100 is less than 2.0.

[0100] (η10 / η1000 rating) A: The value of η10 / η1000 is 5.0 or more. B: The value of η10 / η1000 is 3.5 or more and less than 5.0. C: The value of η10 / η1000 is 2.0 or more and less than 3.5. D: The value of η10 / η1000 is less than 2.0.

[0101] <Evaluation of baking properties> The organic solvent was removed from the resin composition, and the dried resin composition was used as a measurement sample. Using a differential thermobalance (TG-DTA) (Rigaku Corporation, product name "Thermo plus EVO"), 5 mg of a measurement sample was heated from an initial temperature of 30°C to 500°C at a heating rate of 15°C / min in an oxygen or nitrogen atmosphere. The mass of the residue when it reached 500°C was measured, and the thermal weight loss rate (%) was calculated using the following formula (5), and the sinterability was evaluated according to the following evaluation criteria. A higher value for the thermal weight loss rate indicates better sinterability (thermal decomposition property). Thermal weight loss rate (%) = (mass of measurement sample (mg) - mass of residue (mg)) × 100 / mass of measurement sample (mg) (5)

[0102] (Evaluation criteria for baking properties) A: The thermal weight loss rate (%) is 99.9% or more. B: The thermal weight loss rate (%) is 99.5% or more and less than 99.9%. C: The thermal weight loss rate (%) is 99.0% or more and less than 99.5%. D: The thermal weight loss rate (%) is less than 99.0%.

[0103] <Evaluation of thread breakage> Using a viscoelasticity measuring device (manufactured by Thermo Fisher Scientific, product name "HAAKE MARS"), the resin composition was applied to a thickness of 0.053 μm with a cone plate at 1.0° / 20 mm at a measurement temperature of 23° C., and the cone plate was then pulled up at a speed of 4 cm / sec. The height to which the resin composition was pulled up until threads broke was measured, and thread breakage resistance was evaluated according to the evaluation criteria. The lower (shorter) the height to which the resin composition was pulled up until thread breakage occurred, the better the thread breakage resistance. (Evaluation of thread breakage) A: The lifting height is less than 3cm. B: The lifting height is 3cm or more but less than 8cm. C: The lifting height is 8 cm or more but less than 15 cm. D: The lifting height is 15cm or more.

[0104] [Production of (meth)acrylic polymer] <Production Example 1> A reaction vessel equipped with a thermometer, temperature controller, stirrer, reflux condenser, nitrogen gas inlet tube, and dropping device was charged with 40 parts of terpineol, 90 parts of i-butyl methacrylate, and 10 parts of 2-hydroxyethyl methacrylate, and stirred until uniform. The atmosphere in the reaction vessel was then replaced with nitrogen while stirring for 1 hour to remove oxygen. Subsequently, 5 parts of terpineol and 0.05 parts of t-butylperoxy-2-ethylhexanoate were added, and the mixture was heated to 90°C over 1 hour with stirring and then aged for 1 hour. Next, a solution of 40 parts of terpineol and 0.2 parts of 2,2'-azobis(2-methylbutyronitrile) was added dropwise to the reaction vessel over 2.5 hours. After the dropwise addition, 10 parts of terpineol was rapidly added dropwise, followed by aging for 45 minutes. Next, a solution prepared by uniformly mixing 10 parts of terpineol and 0.5 parts of 2,2'-azobis(2-methylbutyronitrile) was added, and after 30 minutes, a solution of the same composition was further added. After another 30 minutes, a solution prepared by uniformly mixing 10 parts of terpineol and 0.5 parts of t-butylperoxy-2-ethylhexanoate was added, and the mixture was aged for 1.5 hours. Next, 165 parts of terpineol was added as a dilution solvent, and the mixture was cooled to room temperature to obtain a polymer solution containing a (meth)acrylic polymer (A-1) (hereinafter also referred to as "polymer solution (A-1)"). The content of the (meth)acrylic polymer (A-1) relative to the total mass of the polymer solution (A-1) was 25.6%. The glass transition temperature, SP value, hydroxyl value, and weight average molecular weight of the obtained (meth)acrylic polymer (A-1) were calculated or measured. The results are shown in Table 1.

[0105] <Production Examples 2 to 12> Polymer solutions containing (meth)acrylic polymers (A-2) to (A-11) (hereinafter also referred to as "polymer solutions (A-2)" to "polymer solutions (A-11)") and a polymer solution containing (meth)acrylic polymer (B-1) (hereinafter also referred to as "polymer solution (B-1)") were produced in the same manner as in Production Example 1, except that the monomer mixtures having the formulations shown in Tables 1 and 2 were used. The glass transition temperatures and SP values ​​were calculated, and the hydroxyl values ​​and weight average molecular weights were measured. The results are shown in Tables 1 and 2. The (meth)acrylic polymer (B-1) was used as the (meth)acrylic polymer (B7) which is the compound (B).

[0106] [Table 1]

[0107] [Table 2]

[0108] The abbreviations in Tables 1 and 2 have the following meanings. The amount (unit: parts by mass) of each monomer and polymerization initiator charged in the tables corresponds to the content (unit: % by mass) of each structural unit and chemical structure relative to the total mass of the (meth)acrylic polymer (A). A blank space in the tables indicates that the component was not blended (amount blended: 0 parts). IBMA: i-butyl methacrylate (corresponding to monomer (a2), Tg of homopolymer: 48°C). HEMA: 2-hydroxyethyl methacrylate (corresponding to monomer (a1-1), Tg of homopolymer: 55°C). HOMS: Mono(2-methacryloyloxyethyl) succinate (corresponding to monomer (a1-2)). ·DM: N-dimethylaminoethyl methacrylate (corresponding to monomer (a1-3), Tg of homopolymer: 18°C). MOI-BM: 2-[0-(1'-methylpropylideneamino)carboxyamino]ethyl (meth)acrylate (manufactured by Resonac Corporation, product name "Karenz MOI-BM", equivalent to monomer (a1-4)). GMA: Glycidyl methacrylate (corresponding to monomer (a1-5)). ·MAH: Maleic anhydride (corresponding to monomer (a3)). · Perbutyl O: t-butylperoxy-2-ethylhexanoate. ·AMBN: 2,2'-Azobis(2-methylbutyronitrile).

[0109] [Example 1] A reaction vessel equipped with a thermometer, temperature controller, stirrer, reflux condenser, nitrogen gas inlet tube, and dropping device was charged with 390 parts of polymer solution (A-1), 400 parts of terpineol, and 0.022 parts of dibutyltin dilaurate, and the temperature was raised to 110°C while stirring and mixing. Next, a solution prepared by uniformly mixing 100 parts of terpineol and 8.7 parts of isophorone diisocyanate as compound (B) was added dropwise to the reaction vessel over 30 minutes and aged for 1 hour. Next, 650 parts of terpineol was added, and the mixture was aged for another 1 hour. The mixture was then cooled to room temperature to obtain a resin composition containing a (meth)acrylic polymer (I-1) and an organic solvent (S). The content of the (meth)acrylic polymer (I-1) relative to the total mass of the resin composition was 7.0%. The viscosity of the resulting resin composition was measured, and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Table 3.

[0110] [Examples 2 to 7] Resin compositions containing any of the (meth)acrylic polymers (I-2) to (I-7) and an organic solvent (S) were obtained in the same manner as in Example 1, except that the type of polymer solution (A-1) and the amount of compound (B) were changed as shown in Tables 3 and 4. The viscosity of the resulting resin composition was measured, and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Tables 3 and 4.

[0111] [Examples 8 and 9] A reaction vessel equipped with a thermometer, temperature controller, stirrer, reflux condenser, nitrogen gas inlet tube, and dropping device was charged with 390 parts of polymer solution (A-8) or polymer solution (A-9), 400 parts of terpineol, and 0.022 parts of dibutyltin dilaurate. The mixture was heated to 110°C with stirring and aged for 1 hour. Next, 640 parts of terpineol was added, and the mixture was aged for another 1 hour. After that, the mixture was cooled to room temperature to obtain a resin composition containing (meth)acrylic polymer (I-8) or (meth)acrylic polymer (I-9) and an organic solvent (S). The viscosity of the resulting resin composition was measured, and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Table 4.

[0112] [Examples 10 and 11] A reaction vessel equipped with a thermometer, temperature controller, stirrer, reflux condenser, nitrogen gas inlet tube, and dropping device was charged with 390 parts of polymer solution (A-2) or polymer solution (A-3), 400 parts of terpineol, and 0.022 parts of dibutyltin dilaurate, and the temperature was raised to 110 ° C. while stirring and mixing. Next, a solution obtained by uniformly mixing 100 parts of terpineol and 6.1 parts of pentamethylene diisocyanate as compound (B) was added dropwise to the reaction vessel over 30 minutes and aged for 1 hour. Next, 610 parts of terpineol was added, and the mixture was aged for another 1 hour. After that, the mixture was cooled to room temperature to obtain a resin composition containing (meth)acrylic polymer (I-10) or (meth)acrylic polymer (I-11) and an organic solvent (S). The viscosity of the resulting resin composition was measured, and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Table 4.

[0113] [Example 12] A reaction vessel equipped with a thermometer, temperature controller, stirrer, reflux condenser, nitrogen gas inlet tube, and dropping device was charged with 234 parts of polymer solution (A-10), 156 parts of polymer solution (B-1) as compound (B), and 390 parts of terpineol, and the temperature was raised to 110°C while stirring and mixing. Next, 0.5 parts of tetrabutylammonium bromide was added, and the mixture was aged for 1 hour. Next, 650 parts of terpineol was added, and the mixture was aged for another 1 hour. After that, the mixture was cooled to room temperature to obtain a resin composition containing (meth)acrylic polymer (I-12) and organic solvent (S). The viscosity of the resulting resin composition was measured, and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Table 4.

[0114] [Example 13] A reaction vessel equipped with a thermometer, temperature controller, stirrer, reflux condenser, nitrogen gas inlet tube, and dropping device was charged with 253.5 parts of polymer solution (A-11), 136.5 parts of polymer solution (A-3) as compound (B), and 390 parts of terpineol, and the temperature was raised to 110 ° C. while stirring and mixing. Next, 0.03 parts of dibutyltin dilaurate was added, and the mixture was aged for 1 hour. Next, 650 parts of terpineol was added, and the mixture was aged for another 1 hour. After that, the mixture was cooled to room temperature to obtain a resin composition containing (meth)acrylic polymer (I-13) and organic solvent (S). The viscosity of the resulting resin composition was measured, and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Table 4. In Table 4, the polymer solution (A-3) used as the compound (B) is represented as "B-2."

[0115] [Comparative Examples 1 to 3] A mixture of 390 parts of polymer solution (A-1), polymer solution (A-8), or polymer solution (A-9) and 1,040 parts of terpineol was used as a resin composition, and the viscosity was measured, and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Table 5.

[0116] [Comparative Examples 4 and 5] A resin composition was prepared by mixing 100 parts of ethyl cellulose, which is commonly used as a binder for conductive pastes in multilayer ceramic capacitors, with 1,330 parts of terpineol. The viscosity was measured and the thixotropy, sinterability, and thread breakage resistance were evaluated. The results are shown in Table 5.

[0117] Comparative Example 6 A resin composition was prepared by mixing 100 parts of a general-purpose acrylic resin with excellent baking properties and 1,330 parts of terpineol, and the viscosity was measured to evaluate the thixotropy, baking properties, and thread breakage. The results are shown in Table 5.

[0118] [Table 3]

[0119] [Table 4]

[0120] [Table 5]

[0121] The abbreviations in Tables 3 to 5 have the following meanings. The amount of terpineol in the tables is the total amount (parts) of terpineol added separately as the organic solvent (S). A blank space in the tables means that the component is not added (amount added: 0 parts). IPDI: Isophorone diisocyanate (equivalent to compound (B5)). PDI: Pentamethylene diisocyanate (equivalent to compound (B5)). B-2: Polymer solution (A-3) containing the (meth)acrylic polymer (A-3) obtained in Production Example 3 (the (meth)acrylic polymer (A-3) also corresponds to the (meth)acrylic polymer (B7)). · DBTDL: Dibutyltin dilaurate. ·TBAB: Tetrabutylammonium bromide. STD45: Ethyl cellulose (manufactured by Nisshin Chemical Co., Ltd., product name: "Ethocel STD45"). STD300: Ethyl cellulose (manufactured by Nisshin Chemical Co., Ltd., product name: "Ethocel STD300"). EMB-003: Solid acrylic resin (manufactured by Mitsubishi Chemical Corporation, product name: "EMB-003").

[0122] As is clear from Tables 3 and 4, the resin compositions obtained in each example had high viscosity, good resistance to thread breakage and sintering properties, and high thixotropy, and were therefore highly suitable for screen printing. On the other hand, in the case of Comparative Examples 1 to 3, the (meth)acrylic polymer in the resin composition did not have a crosslinked structure, so the thixotropy was low and it was not suitable for screen printing. In addition, the viscosity was extremely low and it was not suitable for thinning of electronic components. Comparative Examples 4 and 5 were examples using ethyl cellulose, which has traditionally been used as a paste binder, but they left a large amount of firing residue and had poor firing properties. In particular, Comparative Example 4, which used STD45, had a lower η1 viscosity than Comparative Example 5, which used STD300, and was not suitable for thin film formation. Comparative Example 6 is an example in which a general-purpose solid acrylic resin with good baking properties was used, but it had low thixotropy and poor thread breakage resistance, making it unsuitable for screen printing. Furthermore, its viscosity was extremely low, making it unsuitable for thinning electronic components. [Industrial Applicability]

[0123] The resin composition of the present invention has excellent sinterability, high viscosity, and high thixotropy and resistance to thread breakage. For example, it can be used as a raw material for internal electrode layers or external electrodes of multilayer electronic components such as multilayer ceramic capacitors, or as a paste raw material for solar cell electrodes, and is therefore extremely important from an industrial perspective.

Claims

1. A binder resin composition for baking containing a (meth)acrylic polymer (I) having a crosslinked structure, A binder resin composition for baking, wherein the binder resin composition for baking has a viscosity (η1) of 10 Pa·s or more at 23°C measured at a shear rate of 1 (1 / s) when the solid content concentration of the binder resin composition for baking is 7% by mass.

2. Further containing an organic solvent (S), 2. The binder resin composition for baking according to claim 1, wherein the content of the organic solvent (S) is 900 parts by mass or more and 10,000 parts by mass or less relative to 100 parts by mass of the (meth)acrylic polymer (I).

3. 3. The binder resin composition for baking according to claim 2, wherein the organic solvent (S) has a boiling point of 180°C or higher.

4. 3. The binder resin composition for baking according to claim 2, wherein the organic solvent (S) has active hydrogen.

5. 2. The binder resin composition for baking according to claim 1, wherein the crosslinked structure is a crosslinked structure formed by a crosslinking reaction between a (meth)acrylic polymer (A) containing a structural unit derived from a (meth)acrylic acid ester (a1) having a reactive functional group (x) and a functional group (y) that reacts with the reactive functional group (x).

6. 6. The binder resin composition for baking according to claim 5, wherein the reactive functional group (x) is at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, a glycidyl group, and precursors thereof.

7. 6. The binder resin composition for baking according to claim 5, wherein the functional group (y) is at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, a glycidyl group, and precursors thereof.

8. A metal paste comprising the binder resin composition for firing according to any one of claims 1 to 7 and an inorganic compound (D).

9. An inorganic sintered body obtained by firing the metal paste according to claim 8.

10. An electronic device comprising the inorganic sintered body according to claim 9.

11. A solar panel comprising the inorganic sintered body according to claim 9.

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