JP7544157B2 - Inorganic particle-containing paste, inorganic particle-containing film, and laminate - Google Patents

Description

The present invention relates to an inorganic particle-containing paste, an inorganic particle-containing film that can be formed using the inorganic particle-containing paste, and a laminate including the aforementioned inorganic particle-containing film.

Films containing various inorganic particles are used in a variety of applications. A known method for forming such films is to use a paste containing inorganic particles. A film containing inorganic particles can be formed by forming a film from the paste containing inorganic particles by a method such as coating or printing, and then curing or drying the formed film.

A typical application of inorganic particle-containing films is a laminate used to manufacture multilayer ceramic electronic components such as multilayer ceramic capacitors. In such laminates, a green sheet containing ceramic powder is usually laminated with a precursor film of an internal electrode layer containing metal particles.

For example, a conductive paste containing metal particles and ethyl cellulose as a binder resin has been proposed as a conductive paste for forming a conductive sheet that provides an internal electrode layer by firing (see Patent Document 1). Ethyl cellulose has excellent solubility in organic solvents and decomposability during firing, and provides a conductive paste with good printing characteristics.

JP 2018-168238 A

When manufacturing multilayer ceramic electronic components, a laminate including a conductive sheet and a green sheet that will provide an internal electrode layer when fired may be cut and divided to a predetermined size by a method such as press cutting, and then the divided laminates may be fired. However, when using a laminate including a conductive sheet formed using a conductive paste that contains ethyl cellulose as a binder resin, there is a problem that when the laminate is cut in a direction perpendicular or approximately perpendicular to the surface direction, the action of shear forces and the like applied to the cut surface can easily cause interlayer peeling or intralayer peeling due to cohesive failure.

The present invention has been made in consideration of the above problems, and aims to provide an inorganic particle-containing paste that gives an inorganic particle-containing film that is less likely to undergo interlayer delamination with other layers due to the action of shear force or intralayer delamination due to cohesive failure when a laminate obtained by laminating inorganic particle-containing films is cut into small pieces, an inorganic particle-containing film that can be formed using the inorganic particle-containing paste, and a laminate that includes the aforementioned inorganic particle-containing film.

The present inventors have found that the above problems can be solved by using in combination, in an inorganic particle-containing paste containing a binder resin, inorganic particles, and an organic solvent, a branched polymer having a molecular chain with a main chain made of a cellulose-based polymer and a branch chain made of an aliphatic polycarbonate or an aliphatic polyester, and a dispersant having at least one type selected from the group consisting of a polyether chain, a polyester chain, and a polycarbonate chain, and have completed the present invention. More specifically, the present invention provides the following (1) to (3).

(1) A dispersion medium comprising a branched polymer, inorganic particles, a dispersant, and an organic solvent;
the molecular chain of the branched polymer has a main chain made of a cellulose-based polymer and a branch chain made of an aliphatic polycarbonate or an aliphatic polyester;
The branched chain may be linear or branched.
the branch chains may be attached to two or more of said backbones to crosslink two or more of said backbones;
A paste containing inorganic particles, wherein the dispersant has at least one chain selected from the group consisting of a polyether chain, a polyester chain, and a polycarbonate chain.

(2) A dispersion medium comprising a branched polymer, inorganic particles, and a dispersant,
the molecular chain of the branched polymer has a main chain made of a cellulose-based polymer and a branch chain made of an aliphatic polycarbonate or an aliphatic polyester;
The branched chain may be linear or branched.
the branch chains may be attached to two or more of said backbones to crosslink two or more of said backbones;
An inorganic particle-containing film, wherein the dispersing agent has at least one selected from the group consisting of a polyether chain, a polyester chain, and a polycarbonate chain.

(3) A laminate in which at least one layer is made of the inorganic particle-containing film described in (2).

According to the present invention, it is possible to provide an inorganic particle-containing paste that, when laminated, gives an inorganic particle-containing film that is less likely to undergo delamination with other layers due to the action of shear force, etc., an inorganic particle-containing film that can be formed using the inorganic particle-containing paste, and a laminate that includes the aforementioned inorganic particle-containing film.

<Paste containing inorganic particles>
The inorganic particle-containing paste contains a branched polymer, inorganic particles, a dispersant, and an organic solvent.
The molecular chain of the branched polymer has a main chain and branch chains. The main chain is made of a cellulose-based polymer. The branch chain is made of an aliphatic polycarbonate or an aliphatic polyester. The branch chain may be linear or branched. The branch chain may be bonded to two or more main chains to crosslink the two or more main chains.
The dispersant has at least one chain selected from the group consisting of a polyether chain, a polyester chain, and a polycarbonate chain.

In an inorganic particle-containing paste containing inorganic particles and an organic solvent, by using a combination of a branched polymer of the above-mentioned specific structure and a dispersant having a chain of a specific structure, the inorganic particle-containing paste gives an inorganic particle-containing film that is less likely to undergo interlayer delamination with other layers due to the action of shear force, etc., or intralayer delamination due to cohesive failure, when the laminate obtained by laminating the inorganic particle-containing film is cut into small pieces.

Below, we explain the essential and optional components that the inorganic particle-containing paste may contain.

<Branched polymer>
A branched polymer has a main chain and branch chains in its molecular chain. The main chain is made of a cellulose-based polymer. The branch chains are made of an aliphatic polycarbonate or an aliphatic polyester.
The branched chains may be linear or branched. The branched chains may be bonded to two or more main chains to crosslink the two or more main chains.
By using the above-mentioned branched polymer in combination with a dispersing agent described later, an inorganic particle-containing paste can be obtained that provides an inorganic particle-containing film that is less susceptible to interlayer peeling from other layers due to the action of shear force or the like, or intralayer peeling due to cohesive failure, when a laminate obtained by laminating inorganic particle-containing films is cut into small pieces.

In the branched polymer, the graft ratio, which is the ratio of the mass of the branch chain to the mass of the main chain, is not particularly limited as long as the desired effect is not impaired. When cutting the laminate obtained by laminating the inorganic particle-containing film formed using the inorganic particle-containing paste into small pieces, the graft ratio is preferably 10% by mass or more and 400% by mass or less, more preferably 50% by mass or more and 250% by mass or less, from the viewpoint of easily suppressing the occurrence of interlayer peeling due to external forces such as shear force and intralayer peeling due to cohesive failure.
The graft ratio can be determined by nuclear magnetic resonance spectroscopy (NMR analysis).

The mass average molecular weight of the branched polymer is not particularly limited. The mass average molecular weight of the branched polymer is, for example, preferably 50,000 or more and 1,000,000 or less, and more preferably 100,000 or more and 600,000 or less. When the mass average molecular weight of the branched polymer is within this range, the branched polymer has good mechanical properties such as strength, elongation, and toughness, and good moldability.

Below, we explain the production methods for main chain, branch chain, and branched polymers.

(Main Chain)
The branched polymer has a main chain made of a cellulose-based polymer. The type of the cellulose-based polymer is not particularly limited as long as the main chain of the cellulose-based polymer has a functional group to which a branch chain can be bonded.
Specific examples of suitable cellulose-based polymers include cellulose; alkyl celluloses such as methyl cellulose, ethyl cellulose, n-propyl cellulose, isopropyl cellulose, n-butyl cellulose, tert-butyl cellulose, and n-hexyl cellulose; hydroxyalkyl celluloses such as hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxybutyl cellulose; cellulose esters such as cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose acetate propionate, and cellulose acetate butyrate; carboxyalkyl celluloses such as carboxymethyl cellulose, carboxyethyl cellulose, and carboxypropyl cellulose; and cellulose derivatives such as nitrocellulose, aldehyde cellulose, dialdehyde cellulose, and sulfonated cellulose.
The branched polymer may contain two or more types of branched polymer molecules having different types of cellulosic polymers as the backbone.

The cellulose-based polymer is preferably at least one selected from the group consisting of alkyl cellulose, hydroxyalkyl cellulose, and cellulose ester, in that the branched polymer is easy to produce and, when an inorganic particle-containing film formed using an inorganic particle-containing paste is laminated, the occurrence of delamination due to external forces is easily suppressed.
Among the above-mentioned preferred cellulose-based polymers, at least one selected from the group consisting of methyl cellulose, ethyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate is preferred.

The mass average molecular weight of the cellulose-based polymer is not particularly limited. The mass average molecular weight of the cellulose-based polymer is, for example, preferably 5,000 or more, more preferably 10,000 or more, and particularly preferably 100,000 or more. The mass average molecular weight of the cellulose-based polymer is preferably 1,000,000 or less, more preferably 750,000 or less, and even more preferably 500,000 or less.
More specifically, the molecular weight of the cellulose-based polymer is preferably 5,000 or more and 1,000,000 or less, more preferably 10,000 or more and 750,000 or less, and even more preferably 10,000 or more and 750,000 or less.

The degree of substitution of the cellulose-based polymer is not particularly limited as long as the desired effect is not impaired. The degree of substitution of the cellulose-based polymer is preferably 2 or more and 3 or less, and typically 2.5.
The degree of substitution of a cellulose-based polymer is the total number of hydroxyl groups substituted by groups other than those on branch chains, out of all hydroxyl groups in the constituent units of the cellulose-based polymer.

(Branched Chain)
The branched polymer has a branch chain attached to a main chain made of a cellulose-based polymer. The branch chain is made of an aliphatic polycarbonate or an aliphatic polyester. The branch chain may be linear or branched.
Typically, a branch chain is attached to only one backbone, however, a branch chain may be attached to two or more backbones to cross-link two or more backbones.

As long as the branch chain can be formed in a state of being bonded to the main chain or can be bonded to the main chain, the aliphatic polycarbonate or aliphatic polyester constituting the branch chain is not particularly limited.
Typical examples of aliphatic polycarbonates or aliphatic polyesters constituting branched chains will be shown in the following description of the method for producing a branched polymer.

(Method for Producing Branched Polymer)
The method for producing the branched polymer is not particularly limited. Typically, a graft polymerization method is used. The graft polymerization method can be appropriately selected from various known methods depending on the type of branch chain.

As a graft polymerization method, for example, a ring-opening polymerization method can be used. By ring-opening polymerization of a cyclic carbonate compound or a cyclic ester compound such as lactone in the presence of a cellulose-based polymer, an aliphatic polycarbonate or an aliphatic polyester is produced as a graft chain on the molecular chain of the cellulose-based polymer.

For example, propylene carbonate as a cyclic compound gives a branched chain consisting of polypropylene carbonate. Butylene carbonate as a cyclic compound gives a branched chain consisting of polybutylene carbonate. Cyclohexene carbonate as a cyclic compound gives a branched chain consisting of polycyclohexene carbonate. Trimethylene carbonate as a cyclic compound gives a branched chain consisting of polytrimethylene carbonate. 2,2-dimethyltrimethylene carbonate as a cyclic compound gives a branched chain consisting of poly(2,2-dimethyltrimethylene carbonate).

ε-caprolactone as a cyclic compound gives a branch chain made of polycaprolactone, an aliphatic polyester. L-lactide as a cyclic compound gives a branch chain made of polylactic acid in the L form, an aliphatic polyester. D-lactide as a cyclic compound gives a branch chain made of polylactic acid in the D form, an aliphatic polyester. Meso-lactide as a cyclic compound gives a branch chain made of polylactic acid in the syndiotactic form, an aliphatic polyester. β-propiolactone as a cyclic compound gives a branch chain made of poly(3-hydroxypropionic acid) in the D form, an aliphatic polyester. β-butyrolactone as a cyclic compound gives a branch chain made of poly(3-hydroxybutyric acid), an aliphatic polyester. γ-butyrolactone as a cyclic compound gives a branch chain made of poly(4-hydroxybutyric acid), an aliphatic polyester. δ-valerolactone as a cyclic compound gives a branch chain made of poly(3-hydroxyvaleric acid), an aliphatic polyester. p-Dioxanone as a cyclic compound gives poly(p-dioxanone), an aliphatic polyester, as a branched chain.

Typically, the ring-opening polymerization is carried out in the presence of a catalyst. Specific examples of catalysts that can be used in the ring-opening polymerization include alkali metals such as sodium and potassium; metal-containing catalysts such as sodium hydroxide, potassium hydroxide, triethylaluminum, aluminum triisopropoxide, n-butyllithium, titanium tetraisopropoxide, titanium tetrachloride, zirconium tetraisopropoxide, tin tetrachloride, sodium stannate, tin octanoate, and dibutyltin dilaurate diethylzinc; pyridine, 4-N,N-dimethylaminopyridine, 1,5, Examples of suitable catalysts include basic organic compounds such as 7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBT); acid catalysts such as hydrochloric acid, acetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, diphenyl phosphoric acid, and phenol; and N-heterocyclic carbenes such as 1,3-bis(2-propyl)-4,5-dimethylimidazol-2-ylidene and 1,3-diisopropylimidazol-2-ylidene.
The catalyst may be used alone or in combination of two or more kinds.

When carrying out ring-opening polymerization using a cyclic carbonate, it is also preferable to use a co-catalyst together with the catalyst. Specific examples of the co-catalyst include N-cyclohexyl-N'-phenylthiourea, N,N'-bis[3,5-bis(trifluoromethyl)phenyl]thiourea, N-[3,5-bis(trifluoromethyl)phenyl]-N'-cyclohexylthiourea, and (-)-sparteine.

The amount of catalyst that can be used for ring-opening polymerization is appropriately determined by considering the amount of catalyst used in conventionally known ring-opening polymerization reactions.Typically, the amount of catalyst used is preferably 0.001 mol or more, more preferably 0.005 mol or more, per 1 mol of cyclic compound.The amount of catalyst used is preferably 0.2 mol or less, more preferably 0.1 mol or less, per 1 mol of cyclic compound.
More specifically, the amount of the catalyst used is preferably 0.001 mol or more and 0.2 mol or less, and more preferably 0.005 mol or more and 0.1 mol or less, per 1 mol of the cyclic compound.
The amount of the cocatalyst used is similar to that of the catalyst used.

The ring-opening polymerization is preferably carried out in the presence of a solvent. The type of the solvent is not particularly limited as long as it does not inhibit the ring-opening polymerization reaction.
Specific examples of suitable solvents include aliphatic hydrocarbon solvents such as pentane, hexane, octane, decane, and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; halogenated hydrocarbon solvents such as methylene chloride, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, chlorobenzene, and bromobenzene; ether solvents such as ethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, and anisole; ester solvents such as ethyl acetate, n-propyl acetate, and isopropyl acetate; and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.

The amount of the solvent used is not particularly limited as long as the ring-opening polymerization reaction proceeds well. For example, the amount of the solvent used is preferably 100 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of the cyclic compound.

Typically, the cellulose-based resin, the cyclic compound, and the catalyst, and optionally a co-catalyst and/or a solvent, etc., are charged into a reaction vessel, and the mixture in the reaction vessel is then stirred to carry out ring-opening polymerization.

The preferred reaction temperature for ring-opening polymerization varies depending on the cyclic compound, the type of catalyst, the amount of catalyst used, etc. Typically, the reaction temperature for ring-opening polymerization is preferably −80° C. or higher, more preferably −40° C. or higher, and even more preferably 0° C. or higher. From the viewpoint of achieving both a good yield and suppression of side reactions, the reaction temperature for ring-opening polymerization is preferably 250° C. or lower, more preferably 200° C. or lower, and even more preferably 150° C. or lower.
More specifically, the reaction temperature is preferably from -80°C to 250°C, more preferably from -40°C to 200°C, and even more preferably from 0°C to 150°C.

The reaction time for ring-opening polymerization varies depending on the type of cyclic compound, the type of catalyst, the amount of catalyst used, etc. Typically, the reaction time for ring-opening polymerization is preferably 1 hour or more and 40 hours or less.

The amount of cyclic compound used in ring-opening polymerization is determined appropriately taking into account the graft ratio mentioned above.

Another preferred example of a method for producing a branched polymer is copolymerization of a cyclic ether with carbon dioxide in the presence of a cellulose-based resin. This copolymerization reaction produces branched chains made of aliphatic polycarbonate. The cellulose-based resin is as described above.

As the cyclic ether, a cyclic ether corresponding to the aliphatic polycarbonate as a branched chain is appropriately selected.
Preferred examples of cyclic ethers include ethylene oxide, propylene oxide, trimethylene oxide (oxetane), 3,3-dimethyltrimethylene oxide (3,3-dimethyloxetane), 1,2-butylene oxide, 2,3-butylene oxide, isobutylene oxide, 1-pentene oxide, 2-pentene oxide, 1-hexene oxide, 1-octene oxide, 1-dodecene oxide, cyclopentene oxide, cyclohexene oxide, styrene oxide, vinylcyclohexane oxide, 3-phenylpropylene oxide, 3,3,3-trifluoropropylene oxide, 3-naphthylpropylene oxide, 2-phenoxypropylene oxide, 3-naphthoxypropylene oxide, butadiene monoxide, 3-vinyloxypropylene oxide, and 3-trimethylsilyloxypropylene oxide.

Among the above cyclic ethers, ethylene oxide, propylene oxide, trimethylene oxide, and 1,2-butylene oxide are preferred, and ethylene oxide, propylene oxide, and trimethylene oxide are more preferred, because they have excellent polymerization reactivity and, when an inorganic particle-containing film formed using an inorganic particle-containing paste is laminated, a branched polymer is obtained that is likely to suppress the occurrence of interlayer delamination due to external forces.

Examples of aliphatic polycarbonates produced by copolymerization of cyclic ethers with carbon dioxide are shown below. Ethylene oxide gives polyethylene carbonate. Propylene oxide gives polypropylene carbonate. Trimethylene oxide gives polytrimethylene carbonate.

The copolymerization of the cyclic ether and carbon dioxide is carried out in the presence of a metal catalyst. Preferred examples of metal catalysts include zinc-based catalysts, aluminum-based catalysts, chromium-based catalysts, and cobalt-based catalysts. Among these, zinc-based catalysts and cobalt-based catalysts are preferred because of their high polymerization activity.

Specific examples of suitable zinc-based catalysts include, for example, diethylzinc-water catalyst, diethylzinc-pyrogallol catalyst, bis((2,6-diphenyl)phenoxy)zinc, N-(2,6-diisopropylphenyl)-3,5-di-tert-butylsalicylaldiminato zinc, 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)imino)-2-pentenoic acid acetate, zinc adipate, and zinc glutarate.

Specific examples of suitable cobalt-based catalysts include cobalt acetate-acetic acid-based catalysts, N,N'-bis-(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt acetate, N,N'-bis-(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt pentafluorobenzoate, N,N'-bis-(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt chloride, N,N'-bis-(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt nitrate, N,N'-bis-(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt 2,4-dinitrophenoxide, tetraphenylporphyrin cobalt chloride, tetraphenylporphyrin cobalt acetate, N,N'-bis[2-(ethoxycarbonyl)-3-oxobutylidene]-1,2-cyclohexanediaminatocobalt chloride, and N,N'-bis[2-(ethoxycarbonyl)-3-oxobutylidene]-1,2-cyclohexanediaminatocobalt pentafluorobenzoate.

Cobalt-based catalysts are preferably used together with a cocatalyst. Specific examples of cocatalysts include pyridine, 4-N,N-dimethylaminopyridine, N-methylimidazole, tetrabutylammonium chloride, tetrabutylammonium acetate, triphenylphosphine, bis(triphenylphosphoranylidene)ammonium chloride, and bis(triphenylphosphoranylidene)ammonium acetate.

The amount of catalyst that can be used for copolymerization of cyclic ether and carbon dioxide is appropriately determined in consideration of the amount of catalyst that is conventionally known for such copolymerization reaction.Typically, the amount of catalyst is preferably 0.001 mol or more, more preferably 0.005 mol or more, per 1 mol of cyclic ether.The amount of catalyst is preferably 0.2 mol or less, more preferably 0.1 mol or less, per 1 mol of cyclic ether.
More specifically, the amount of the catalyst used is preferably 0.001 mol or more and 0.2 mol or less, and more preferably 0.005 mol or more and 0.1 mol or less, per 1 mol of the cyclic ether.
The amount of the cocatalyst used is similar to that of the catalyst used.

The copolymerization of the cyclic ether with carbon dioxide is preferably carried out in the presence of a solvent. The type of the solvent is not particularly limited as long as it does not inhibit the copolymerization reaction.
Specific examples of suitable solvents include aliphatic hydrocarbon solvents such as pentane, hexane, octane, decane, and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; halogenated hydrocarbon solvents such as methylene chloride, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, chlorobenzene, and bromobenzene; ether solvents such as ethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, and anisole; ester solvents such as ethyl acetate, n-propyl acetate, and isopropyl acetate; and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.

The amount of the solvent used is not particularly limited as long as the copolymerization reaction proceeds smoothly. For example, the amount of the solvent used is preferably 100 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the cyclic ether.

Typically, the cellulose-based resin, the cyclic ether, and the catalyst, and optionally a cocatalyst and/or a solvent, are charged into a reaction vessel, carbon dioxide is injected into the reaction vessel, and the mixture in the reaction vessel is stirred to carry out the copolymerization.

The amounts of the cyclic ether and carbon dioxide used in the copolymerization are appropriately determined taking into consideration the above-mentioned graft ratio.
In terms of good reaction progress, the pressure of carbon dioxide in the reaction vessel at the time of copolymerization is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and even more preferably 0.5 MPa or more, as a gauge pressure at the reaction temperature. In terms of eliminating the need to use an expensive pressure vessel with high pressure resistance and of operational safety, the pressure of carbon dioxide in the reaction vessel is preferably 20 MPa or less, more preferably 10 MPa or less, and may be 5 MPa or less.
More specifically, the pressure of carbon dioxide in the reaction solution is preferably 0.1 MPa or more and 20 MPa or less, more preferably 0.2 MPa or more and 10 MPa or less, and even more preferably 0.5 MPa or more and 5 MPa or less, in terms of gauge pressure.
The copolymerization reaction may be carried out under supercritical conditions of carbon dioxide.

The preferred reaction temperature for copolymerization varies depending on the type of cyclic ether, the type of catalyst, the amount of catalyst used, etc. Typically, the reaction temperature for copolymerization is preferably 0° C. or higher, more preferably 20° C. or higher, and even more preferably 30° C. or higher. From the viewpoint of achieving both good yield and suppression of side reactions, the reaction temperature for copolymerization is preferably 100° C. or lower, more preferably 80° C. or lower, and even more preferably 60° C. or lower.
From the above viewpoints, the reaction temperature of the copolymerization is preferably from 0°C to 100°C, more preferably from 20°C to 80°C, and even more preferably from 30°C to 60°C.

The reaction time for copolymerization varies depending on the type of cyclic ether, the type of catalyst, the amount of catalyst used, etc. Typically, the reaction time for ring-opening polymerization is preferably 1 hour or more and 40 hours or less.

The amount of cyclic compound used in ring-opening polymerization is determined appropriately taking into account the graft ratio mentioned above.

When the branched chains consist of an aliphatic polyester formed by polycondensation of an aliphatic dicarboxylic acid and a glycol, such as polyethylene succinate, polyethylene adipate, polybutylene succinate, or polybutylene adipate, a branched polymer can also be produced by copolycondensing an aliphatic dicarboxylic acid and a glycol according to the structure of the aliphatic polyester in the presence of a cellulose-based resin according to a conventional method.

The amount of the branched polymer used in the inorganic particle-containing paste is not particularly limited as long as the desired effect is not impaired.
For example, the ratio of the volume of the branched polymer to the total volume of the branched polymer and the inorganic particles is preferably 17 vol % or more and 29 vol % or less, and more preferably 19 vol % or more and 27 vol % or less.

<Inorganic particles>
The inorganic particle-containing paste contains inorganic particles. As the inorganic particles, inorganic particles that have been conventionally added to various resin compositions can be used without any particular limitation.
As inorganic particles, typically ceramic particles and/or metal particles are preferred.

Suitable examples of inorganic particle-containing films formed using inorganic particle-containing pastes include conductive sheets that contain metal particles and provide internal electrode layers, which form laminates useful as precursors for multilayer ceramic electronic components, and green sheets that contain ceramic particles.

When a paste containing inorganic particles is used to form green sheets that provide dielectric layers in a multilayer ceramic electronic component, ceramic particles are used as the inorganic particles.
When an electrode sheet that provides an internal electrode layer in a multilayer ceramic electronic component is formed using a paste containing inorganic particles, the inorganic particles may contain a combination of metal particles and ceramic particles in terms of affinity between the green sheet and the electrode sheet and adhesion between the dielectric layer and the internal electrode layer.

The ceramic particles preferably contain at least one element selected from the group consisting of Ba, Ti, Sr, Ca, and Zr.
Preferable specific examples of the ceramic particles include barium titanate particles, calcium titanate particles, strontium titanate particles, and lead zirconate titanate particles.
The ceramic particles may be used alone or in combination of two or more kinds. For example, ceramic particles containing barium titanate particles as a main component and a component containing Ca, Zr, or Sr as a subcomponent may be used.

The particle size of the ceramic particles is not particularly limited as long as the desired effect is not impaired. The average particle size of the ceramic particles is preferably 3 nm or more and 500 nm or less as measured by the BET conversion method.

When a conductive sheet that provides an internal electrode layer in a multilayer ceramic electronic component is formed using a paste containing inorganic particles, the inorganic particles are preferably metal particles.
The metal constituting the metal particles is preferably at least one selected from the group consisting of Ni, Cu, Ag, and Au.
The average particle size of the metal particles is not particularly limited as long as the desired effect is not impaired. The average particle size of the metal particles is preferably 3000 nm or less, more preferably 30 nm or more and 1000 nm or less, as measured by SEM.
The metal particles may contain two or more kinds of metal particles. The metal particles may be particles of an alloy containing two or more kinds of metals.

When the inorganic particles contain a combination of ceramic particles and metal particles, it is preferable that the mass of the ceramic particles is 4% by mass or more and 25% by mass or less relative to the mass of the metal particles.

<Dispersant>
The paste containing inorganic particles includes a dispersant having at least one chain selected from the group consisting of a polyether chain, a polyester chain, and a polycarbonate chain.
When the dispersant has a polyether chain, a polyester chain, or a polycarbonate chain, the dispersant is easily compatible with a branched polymer having a branch chain made of an aliphatic polycarbonate or an aliphatic polyester.

The polyester chains and polycarbonate chains include those described as branch chains of a branched polymer.
The polyether chain is preferably a polyoxyalkylene chain. Preferred examples of the polyoxyalkylene chain include a polyoxyethylene chain and a polyoxypropylene chain.

From the viewpoint of dispersion effect, it is preferable that the dispersant has a hydrophobic group. Suitable examples of the hydrophobic group include a hydrocarbon group and a fluorinated hydrocarbon group, and an aliphatic hydrocarbon group and an aliphatic fluorinated hydrocarbon group are more preferable.

In terms of dispersion effect, it is preferable that the dispersant has an adsorptive group such as a carboxy group, an amino group, a phosphate group, or a sulfonic acid group that can bond to the surface of the inorganic particles.

The molecular weight of the dispersant is not particularly limited as long as the desired effect is not impaired. The dispersant may be a so-called low molecular weight compound or a polymer type dispersant. In terms of ease of molecular design to give the dispersant various functional groups as described above, a polymer type dispersant is preferred as the dispersant.
As the polymer dispersant, for example, a comb-structured (meth)acrylic resin obtained by copolymerizing a (meth)acrylic monomer having a hydrophobic chain such as a hydrocarbon chain with a (meth)acrylic monomer having a hydrophilic chain such as a polyether chain, a polyester chain, or a polycarbonate chain can be preferably used. A comb-structured (meth)acrylic resin obtained by introducing the above-mentioned hydrophobic chain and hydrophilic chain as side chains into a known (meth)acrylic resin is also preferably used as the polymer dispersant.

The amount of the dispersant used is preferably 0.5 mg/m ² to 5 mg/m ² , and more preferably 1.0 mg/m ² to 2.5 mg/m ² , relative to the surface area of the particles to be dispersed.

<Other ingredients>
The paste containing inorganic particles may contain components other than the above components as long as the desired effect is not impaired.
The other components include, for example, at least one additive selected from the group consisting of a plasticizer and an antistatic agent.
The amount of the other components used is not particularly limited as long as the desired effect is not impaired. The amount of the other components used is appropriately determined taking into consideration the amount that can be normally used depending on the type of the additive.

<Organic solvent>
The inorganic particle-containing paste contains an organic solvent. Suitable examples of the organic solvent include alkanols such as isopropanol, water-soluble carbon-based solvents such as toluene, xylene, and isophorone, terpineol-based solvents such as terpineol and dihydroterpineol, ester-based solvents such as ethyl acetate, n-butyl acetate, n-pentyl acetate, n-hexyl acetate, n-heptyl acetate, n-octyl acetate, terpineol acetate, and dihydroterpineol acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, propylene ... Examples of the solvent include glycol ether-based solvents such as glycol dimethyl ether and diethylene glycol dimethyl ether; glycol ester-based solvents such as ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; carbonate-based solvents such as dimethyl carbonate and propylene carbonate; ketone-based solvents such as acetone, methyl ethyl ketone, and cyclohexanone; and nitrogen-containing polar organic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.

Among these solvents, ester-based solvents such as ethyl acetate, n-butyl acetate, n-pentyl acetate, n-hexyl acetate, n-heptyl acetate, n-octyl acetate, terpineol acetate, and dihydroterpineol acetate, and glycol ester-based solvents such as ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate are preferred because of their good affinity with branched polymers and dispersants.

The amount of organic solvent used is not particularly limited as long as the desired effect is not impaired. The amount of organic solvent used is preferably 60% by volume or more and 97% by volume or less, and more preferably 80% by volume or more and 94% by volume or less, based on the total volume of the inorganic particle-containing paste.

<Inorganic particle-containing film>
The inorganic particle-containing film contains a branched polymer, inorganic particles, and a dispersant. The branched polymer, inorganic particles, and dispersant are all as described above for the inorganic particle-containing paste.
The inorganic particle-containing film can be formed by forming the above-mentioned inorganic particle-containing paste into a film and then removing at least a part of the organic solvent from the film made of the inorganic particle-containing paste.
The method for removing the organic solvent is not particularly limited, and for example, the organic solvent is removed by heating, exposure to a reduced pressure atmosphere, or the like.

The inorganic particle-containing film is preferably, for example, a green sheet in which the inorganic particles contain ceramic particles and which provides a dielectric layer in a multilayer ceramic electronic component when fired.
Such a green sheet can be formed by a known method such as a die coater sheet method, a doctor blade method, etc. The thickness of the green sheet is preferably 4 μm or less, and more preferably 3 μm or less.

The inorganic particle-containing film is also preferably a conductive sheet in which the inorganic particles contain metal particles and which provides an internal electrode layer in a multilayer ceramic electronic component when fired.
The method for forming the conductive sheet is not particularly limited. Preferably, the conductive sheet is formed by printing a paste containing inorganic particles on the green sheet. As the printing method, for example, gravure printing or screen printing can be used.
The thickness of the conductive sheet is preferably, for example, 1.5 μm or less.

<Laminate>
The laminate includes at least one layer made of the above-mentioned inorganic particle-containing film.
A preferred laminate is one in which a green sheet which is fired to provide a dielectric layer and a conductive sheet which is fired to provide an internal electrode layer are laminated together,
Examples of the laminate include a laminate in which the green sheet is the aforementioned inorganic particle-containing film, or a laminate in which the conductive sheet is the aforementioned inorganic particle-containing film. Such a laminate is suitably used for producing a multilayer ceramic electronic component.
After firing the laminate, the fired laminate is subjected to various known processes for producing a multilayer ceramic electronic component, thereby obtaining a multilayer ceramic electronic component.
Examples of the multilayer ceramic electronic components include multilayer ceramic capacitors, inductors, piezoelectric elements, thermistors, and the like.

The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
A conductive paste containing Ni particles as inorganic particles was prepared.
In preparing the conductive paste, Ni particles having an average SEM diameter of 200 nm and barium titanate particles having a BET diameter of 20 nm were used as inorganic particles.
As the branched polymer, a resin having a main chain made of ethyl cellulose and branch chains made of polypropylene carbonate, which is an aliphatic polycarbonate, was used.
As the dispersant, a polymer dispersant having a carboxy group as an adsorptive functional group, a chain aliphatic hydrocarbon group as a hydrophobic group, and a polyoxyethylene group (polyether chain) was used.
As the organic solvent, dihydroterpineol acetate, an ester-based solvent, was used.

(Conductive Paste Preparation)
40 parts by mass of Ni particles, 4 parts by mass of barium titanate particles, 2 parts by mass of a branched polymer, 0.7 parts by mass of a dispersant, and 53.3 parts by mass of an organic solvent were uniformly mixed. The mixture was dispersed with a roll to obtain a conductive paste.

(Dielectric Paste Preparation)
7.2 parts by mass of polypropylene carbonate, which is an aliphatic polycarbonate, was dissolved in 26 parts by mass of n-butyl acetate and 26 parts by mass of dimethyl carbonate. The polypropylene carbonate has a carboxylic acid modified site in the repeating structure. The ratio of the carboxylic acid modified site is 0.8 mol% in the entire structure. 40 parts by mass of barium titanate particles (BET equivalent diameter 0.2 μm) as ceramic particles, 0.7 parts by mass of polyethylene glycol as a plasticizer, and 0.1 parts by mass of an antistatic agent were added to the obtained solution. Next, the obtained suspension was dispersed in a ball mill for a predetermined time to obtain a dielectric paste.

(Preparation of green sheets)
The dielectric paste was applied onto a PET (polyethylene terephthalate) film by a doctor blade method. The applied film was then dried to obtain a green sheet containing ceramic particles. The thickness of the green sheet was adjusted so that the thickness of the dielectric layer after firing would be 1.7 μm.

(Preparation of conductive sheet)
A conductive paste was screen-printed on the green sheet. The printed conductive paste was dried to obtain a conductive sheet. The conductive paste was printed on the green sheet so as to form a pattern such that the planar dimensions of the cut and fired chip-shaped laminate were 3.2 mm x 1.6 mm. The thickness of the conductive sheet, as the thickness of only the metal components, measured by XRF was 0.4 μm. The thickness of the conductive sheet immediately after drying was 0.8 μm.

(Laminate manufacturing)
The green sheet with the conductive sheet was peeled off from the PET film. 200 of the peeled sheets were stacked, and the stacked 200 sheets were placed in a mold. The sheets in the mold were pressed and pressure-bonded to obtain a laminate. The obtained laminate was cut to a predetermined size by pressing, and a chip-shaped unfired laminate was obtained.

(Evaluation of the occurrence of structural defects)
The cut surface of each of 100 randomly selected unfired laminates on the chip was observed under an optical microscope to confirm the presence or absence of structural defects such as interlayer delamination between the conductive sheet and the green sheet, and intralayer delamination due to cohesive failure inside the conductive sheet. The number of laminates in which structural defects were observed is shown in Table 1 as the occurrence rate of structural defects. In addition, the occurrence of structural defects was evaluated according to the following criteria based on the number of laminates in which structural defects were observed.
⊚: The number of laminates in which structural defects were observed was 0 or 1.
◯: The number of laminates in which structural defects were observed was 2 or more and 10 or less.
x: The number of laminates in which structural defects were observed was 11 or more.

Example 2
Except for changing the branched polymer to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, which is an aliphatic polyester, the same test as in Example 1 was carried out. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 3
Except for changing the polyoxyethylene group (polyether chain) of the dispersant to a polycaprolactone group (polyester chain), the same test as in Example 1 was carried out. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 4
Except for changing the hydrophilic group of the dispersant to a polypropylene carbonate group (polycarbonate chain), the same test as in Example 1 was carried out. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 5
The same test as in Example 1 was carried out except that the branched polymer was changed to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, which is an aliphatic polyester, and the polyoxyethylene group (polyether chain) of the dispersant was changed to a polycaprolactone group (polyester chain). The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 6
The same test as in Example 1 was carried out except that the branched polymer was changed to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, which is an aliphatic polyester, and the hydrophilic group of the dispersant was changed to a polypropylene carbonate group (polycarbonate chain). The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 7
Except for not using ceramic particles in the preparation of the conductive paste, the same test as in Example 1 was carried out. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 8
The same test as in Example 1 was carried out except that the branched polymer was changed to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, which is an aliphatic polyester, and ceramic particles were not used in preparing the conductive paste. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 9
Except for changing the metal particles to Cu particles having an SEM diameter of 500 nm, the same test as in Example 1 was carried out. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 10
The same test as in Example 1 was carried out except that the branched polymer was changed to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, which is an aliphatic polyester, and the metal particles were changed to Cu particles having an SEM diameter of 500 nm. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 11
The same test as in Example 1 was performed except that the amount of the branched polymer and the amount of the Ni particles and the ceramic particles were adjusted to change the binder resin volume ratio, which is the ratio of the volume of the binder resin to the total volume of the binder resin and the inorganic particles in the conductive paste, to 17 volume %. The evaluation results for the occurrence of structural defects are shown in Table 1.

Example 12
The same test as in Example 1 was performed except that the binder resin volume ratio, which is the ratio of the volume of the binder resin to the total volume of the binder resin and the inorganic particles in the conductive paste, was changed to 29 volume % by adjusting the amount of the branched polymer and the amount of the Ni particles and the ceramic particles used. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 13
The branched polymer was changed to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, which is an aliphatic polyester, and the amount of the branched polymer and the amount of the Ni particles and the ceramic particles used were adjusted to change the binder resin volume ratio, which is the ratio of the volume of the binder resin to the total volume of the binder resin and the inorganic particles in the conductive paste, to 17 volume %. The same test as in Example 1 was performed. The evaluation results of the occurrence of structural defects are shown in Table 1.

Example 14
The branched polymer was changed to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, which is an aliphatic polyester, and the amount of the branched polymer and the amount of the Ni particles and the ceramic particles used were adjusted to change the binder resin volume ratio, which is the ratio of the volume of the binder resin to the total volume of the binder resin and the inorganic particles in the conductive paste, to 29 volume %. The same test as in Example 1 was performed. The evaluation results of the occurrence of structural defects are shown in Table 1.

Comparative Example 1
Except for replacing the branched polymer with ethyl cellulose, which is a linear polymer, the same test as in Example 1 was carried out. The evaluation results for the occurrence of structural defects are shown in Table 1.

Comparative Example 2
The same test as in Example 1 was carried out, except that the branched polymer was changed to ethyl cellulose, a linear polymer, and the dispersant was changed to a polymer dispersant having a carboxyl group, which is an adsorptive functional group, and a chain aliphatic hydrocarbon group, which is a hydrophobic group, but not a polyoxyethylene group (polyether chain). The evaluation results for the occurrence of structural defects are shown in Table 1.

Comparative Example 3
A test was conducted in the same manner as in Example 1, except that the dispersant was changed to a polymer dispersant having a carboxyl group, which is an adsorptive functional group, and a chain aliphatic hydrocarbon group, which is a hydrophobic group, but not a polyoxyethylene group (polyether chain). The evaluation results for the occurrence of structural defects are shown in Table 1.

Comparative Example 4
The same test as in Example 1 was carried out except that the branched polymer was changed to a resin having a main chain made of ethyl cellulose and a branch chain made of polycaprolactone, an aliphatic polyester, and the dispersant was changed to a polymer dispersant having a carboxy group, which is an adsorptive functional group, and a chain-like aliphatic hydrocarbon group, which is a hydrophobic group, but no polyoxyethylene group (polyether chain). The evaluation results for the occurrence of structural defects are shown in Table 1.

Comparative Example 5
The same test as in Example 1 was carried out, except that the branched polymer was changed to ethyl cellulose, which is a linear polymer, and the hydrophilic group of the dispersant was changed to a polycaprolactone group (polyester chain). The evaluation results of the occurrence of structural defects are shown in Table 1.

Comparative Example 6
The same test as in Example 1 was carried out except that the branched polymer was changed to ethyl cellulose, which is a linear polymer, and the hydrophilic group of the dispersant was changed to a polypropylene carbonate group (polycarbonate chain). The evaluation results of the occurrence of structural defects are shown in Table 1.

Comparative Example 7
The same test as in Example 1 was carried out, except that the branched polymer was replaced with ethyl cellulose, which is a linear polymer, and no ceramic particles were used in the preparation of the conductive paste. The evaluation results for the occurrence of structural defects are shown in Table 1.

Comparative Example 8
The same test as in Example 1 was carried out, except that the branched polymer was changed to ethyl cellulose, which is a linear polymer, and the metal particles were changed to Cu particles having an SEM diameter of 500 nm. The evaluation results of the occurrence of structural defects are shown in Table 1.

Comparative Example 9
The branched polymer was replaced with ethyl cellulose, which is a linear polymer, and the amount of ethyl cellulose, Ni particles, and ceramic particles used was adjusted to change the binder resin volume ratio, which is the ratio of the binder resin volume to the total volume of the binder resin and the inorganic particles in the conductive paste, to 17 volume %, and the same test as in Example 1 was performed. The evaluation results for the occurrence of structural defects are shown in Table 1.

Comparative Example 10
The branched polymer was replaced with ethyl cellulose, which is a linear polymer, and the amount of ethyl cellulose, Ni particles, and ceramic particles used was adjusted to change the binder resin volume ratio, which is the ratio of the binder resin volume to the total volume of the binder resin and the inorganic particles in the conductive paste, to 29 volume %. The same test as in Example 1 was performed. The evaluation results for the occurrence of structural defects are shown in Table 1.

In Table 1 below, the specific functional group is a type of functional group that corresponds to any one of a polyether chain, a polyester chain, and a polycarbonate chain.
The binder resin volume ratio is the ratio of the volume of the binder resin to the total volume of the binder resin and the inorganic particles in the conductive paste.
The abbreviations in the table below are as follows.
EC: Ethyl cellulose PCL: Polycaprolactone (aliphatic polyester)
PPC: Polypropylene carbonate (aliphatic polycarbonate)

According to the examples, when cutting a laminate including a conductive sheet formed using a conductive paste containing a combination of a branched polymer having a main chain made of a cellulose-based polymer and a branch chain made of an aliphatic polycarbonate or an aliphatic polyester, and a dispersant having a hydrophilic chain such as a polyether chain, it can be seen that even if a shear force is applied when cutting the laminate, delamination as a structural defect hardly occurs.
On the other hand, according to the comparative examples, when the binder resin contained in the conductive paste consists only of a main chain made of a cellulose-based polymer, or when the dispersant does not have a specific hydrophilic chain, it is found that delamination as a structural defect is likely to occur when the laminate is cut.

Claims (8)

The dispersion medium includes a branched polymer, inorganic particles, a dispersant, and an organic solvent,
the molecular chain of the branched polymer has a main chain made of a cellulose-based polymer and a branch chain made of an aliphatic polycarbonate or an aliphatic polyester;
The branched chain may be linear or branched,
The branch chains may be bonded to two or more of the main chains to crosslink two or more of the main chains,
the dispersant has at least one selected from the group consisting of a polyether chain, a polyester chain, and a polycarbonate chain;
The inorganic particles include metal particles, and the metal constituting the metal particles is at least one selected from the group consisting of Ni, Cu, Ag, and Au.
A paste containing inorganic particles. The inorganic particle-containing paste according to claim 1, wherein the cellulose-based polymer comprises at least one selected from the group consisting of methyl cellulose, ethyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate. The inorganic particle-containing paste according to claim 1 or 2 , further comprising ceramic particles as the inorganic particles, the material constituting the ceramic particles including at least one selected from the group consisting of Ba, Ti, Sr, Ca, and Zr. The inorganic particle-containing paste according to claim 1 , wherein the organic solvent comprises an ester-based solvent. 5. The inorganic particle-containing paste according to claim 1 , wherein a ratio of the volume of the branched polymer to the total volume of the branched polymer and the inorganic particles is 17 volume % or more and 29 volume % or less. The composition includes a branched polymer, inorganic particles, and a dispersant,
the molecular chain of the branched polymer has a main chain made of a cellulose-based polymer and a branch chain made of an aliphatic polycarbonate or an aliphatic polyester;
The branched chain may be linear or branched,
The branch chains may be bonded to two or more of the main chains to crosslink two or more of the main chains,
the dispersant has at least one selected from the group consisting of a polyether chain, a polyester chain, and a polycarbonate chain;
The inorganic particles include metal particles, and the conductive sheet provides an internal electrode layer in a multilayer ceramic electronic component by firing.
Inorganic particle-containing films. A laminate comprising at least one layer comprising the inorganic particle-containing film according to claim 6 . A green sheet which is fired to provide a dielectric layer and a conductive sheet which is fired to provide an internal electrode layer are laminated together,
The conductive sheet is the inorganic particle-containing film according to claim 6 ,
The laminate according to claim 7, which is used for producing a multilayer ceramic electronic component.