WO2024024534A1

WO2024024534A1 - Carboxy group-containing polymer dispersant, electroconductive paste, electronic component, and laminated ceramic capacitor

Info

Publication number: WO2024024534A1
Application number: PCT/JP2023/025984
Authority: WO
Inventors: 健二福田; 正剛川口; 聖也山本
Original assignee: 住友金属鉱山株式会社; 国立大学法人山形大学
Priority date: 2022-07-29
Filing date: 2023-07-14
Publication date: 2024-02-01

Abstract

The present invention provides: a low viscosity electroconductive paste that can suppress separation between electroconductive powder and ceramic powder, has good viscosity stability over time, and has good smoothness of a dry membrane surface after application; a carboxy group-containing polymer dispersant; an electronic component; and a laminated ceramic capacitor.　This carboxy group-containing polymer dispersant comprises a copolymer of at least one of an acrylic acid or methacrylic acid, and at least one of an acrylic acid ester represented by general formula (1) or a methacrylic acid ester represented by general formula (2). In the dispersant, the mass-average molecular weight is 2000 or greater and less than 30,000, for the mole ratio, the ratio of the total of the acrylic acid and the methacrylic acid to the total of the acrylic acid ester and the methacrylic acid ester is X:1–X, X is 0.1 or greater and less than 0.4, and in general formula (1) and general formula (2), R1 is a straight chain or a branched alkyl group.

Description

Carboxy group-containing polymer dispersants, conductive pastes, electronic components and multilayer ceramic capacitors

The present invention relates to a carboxy group-containing polymer dispersant, a conductive paste, an electronic component, and a multilayer ceramic capacitor.

As electronic devices such as mobile phones and digital devices become smaller and have higher performance, electronic components including multilayer ceramic capacitors are also desired to be smaller and have higher capacity. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and by making these dielectric layers and internal electrode layers thinner, they can be made smaller and have higher capacitance. can be achieved.

A multilayer ceramic capacitor is manufactured, for example, as follows. First, a paste for internal electrodes (conductive powder) containing conductive powder, binder resin, organic solvent, _etc. paste) printed with a predetermined electrode pattern and stacked in multiple layers to obtain a laminate in which internal electrodes and dielectric green sheets are stacked in multiple layers. Next, this laminate is heat-pressed and integrated to form a crimped body. This pressed body is cut, treated to remove the organic binder in an oxidizing atmosphere or an inert atmosphere, and then fired to obtain fired chips. Next, an external electrode paste is applied to both ends of the fired chip, and after firing, nickel plating or the like is applied to the external electrode surface to obtain a multilayer ceramic capacitor.

Conventionally, screen printing has been commonly used as the printing method for printing conductive paste onto dielectric green sheets, but due to demands for smaller electronic devices, thinner films, and improved productivity. There is a need to print finer electrode patterns with high productivity.

One of the methods of printing conductive paste is a continuous printing method in which the conductive paste is transferred from the plate by filling the concave portions of the plate with the conductive paste and pressing it against the surface to be printed. A gravure printing method has been proposed. Gravure printing has fast printing speed and excellent productivity. When using the gravure printing method, it is necessary to appropriately select the binder resin, dispersant, solvent, etc. in the conductive paste, and adjust the properties such as viscosity to a range suitable for gravure printing.

For example, in Patent Document 1, a conductive paste is used to form an inner conductor film by gravure printing in a laminated ceramic electronic component including a plurality of ceramic layers and an inner conductor film extending along a specific interface between the ceramic layers. 30 to 70% by weight solid component containing metal powder, 1 to 10% by weight ethyl cellulose resin component having an ethoxy group content of 49.6% or more, and 0.05 to 5% by weight dispersant. and a solvent component as the remainder, the viscosity η _0.1 at a shear rate of 0.1 (s ^-1 ) is 1 Pa·s or more, and the viscosity at a shear rate of 0.02 (s ^-1 ) A conductive paste is described that is a thixotropic fluid, satisfying the condition that η _0.02 is expressed by a specific formula.

Furthermore, Patent Document 2 discloses a conductive paste used for forming by gravure printing as in Patent Document 1, which contains 30 to 70% by weight of a solid component including metal powder and 1 to 10% by weight of a conductive paste. A thixotropic fluid containing a resin component, 0.05 to 5% by weight of a dispersant, and the remainder a solvent component, and having a viscosity of 1 Pa·s or more at a shear rate of 0.1 (s ^-1 ), A conductive paste is described that has a viscosity change rate of 50% or more at a shear rate of 10 (s ^-1 ), based on the viscosity at a shear rate of 0.1 (s ^-1 ).

According to Patent Documents 1 and 2, these conductive pastes are thixotropic fluids with a viscosity of 1 Pa·s or more at a shear rate of 0.1 (s ⁻¹ ), and are stable at high speeds in gravure printing. It is said that continuous printing can be achieved and multilayer ceramic electronic components such as multilayer ceramic capacitors can be manufactured with good production efficiency.

Further, Patent Document 3 discloses a conductive material for multilayer ceramic capacitor internal electrodes containing a conductive powder (A), an organic resin (B), an organic solvent (C), an additive (D), and a dielectric powder (E). The organic resin (B) is composed of polyvinyl butyral having a degree of polymerization of 10,000 or more and 50,000 or less, and ethyl cellulose having a weight average molecular weight of 10,000 or more and 100,000 or less, and the organic solvent (C) is propylene glycol monobutyl ether, Or, it consists of either a mixed solvent of propylene glycol monobutyl ether and propylene glycol methyl ether acetate, or a mixed solvent of propylene glycol monobutyl ether and mineral spirit, and the additive (D) consists of a separation inhibitor and a dispersant for gravure printing. A conductive paste is described. According to Patent Document 3, this conductive paste has a viscosity suitable for gravure printing and has good drying properties.

Japanese Patent Application Publication No. 2003-187638 Japanese Patent Application Publication No. 2003-242835 Japanese Patent Application Publication No. 2012-174797

As electronic components become smaller, electrodes and wiring formed by printing conductive paste are also becoming thinner. In order to apply conductive paste thinly and smoothly, lower viscosity is required. However, when a ceramic powder such as barium titanate and a conductive powder such as Ni are added to a low-viscosity conductive paste, the difference in sedimentation rate due to the difference in specific gravity of these powders affects the difference between the conductive powder and the conductive powder. Ceramic powder may separate.

For example, when a low-viscosity conductive paste is produced, a phenomenon called "white floating" (two-layer separation) may occur in which a white separation layer containing ceramic powder appears on the top. If the composition in the paste becomes non-uniform in this way, the surface of the dry film after application will not be smooth, and for example, if used for the internal electrodes of a multilayer ceramic capacitor, short circuits between the internal electrodes may occur, and the specified capacitance may be reduced. may not be obtained.

In addition, as a result of studies conducted by the present inventors, low-viscosity conductive pastes tend to thicken after long-term storage, and the viscosity increase ratio over time calculated as the ratio of the viscosity after long-term storage to the viscosity immediately after manufacture is high. I found out that it's easy to do. In order to obtain a smooth and uniform thin film, it is necessary to control the viscosity of the applied paste within a certain range, but pastes with a high viscosity increase ratio over time will not print smoothly if used for a long period of time. There are problems in that the printing process becomes complicated, such as not being able to obtain a uniform surface or requiring viscosity adjustment each time it is used for a certain period of time.

In view of these circumstances, the present invention provides a conductive paste that stably maintains a low paste viscosity over a long period of time even in a low-viscosity conductive paste, and is capable of suppressing separation of conductive powder and ceramic powder. The purpose of the present invention is to provide a conductive paste with good smoothness on the surface of a dried film after drying. Another object of the present invention is to provide a carboxy group-containing polymer dispersant that can provide such a conductive paste, and electronic components and multilayer ceramic capacitors formed using such a conductive paste.

In order to solve the above problems, the dispersant of the present invention combines at least either acrylic acid or methacrylic acid, and an acrylic ester represented by the following general formula (1) or a methacrylic ester represented by the following general formula (2). A carboxyl group-containing polymeric dispersant consisting of a copolymer with at least one of the following, which has a mass average molecular weight of 2,000 or more and less than 30,000, and has a molar ratio of the sum of the acrylic acid and the methacrylic acid to the acrylic acid. The ratio of the ester to the total of the methacrylic ester is X:1-X, where X is 0.1 or more and less than 0.4, and in the following general formula (1) and the following general formula (2), R ₁ is a dispersant which is a linear or branched alkyl group.

Furthermore, in order to solve the above problems, the conductive paste of the present invention is a conductive paste containing the carboxy group-containing polymer dispersant of the present invention.

The conductive paste of the present invention further includes a conductive powder, a ceramic powder, a binder resin, and an organic solvent, and the content of the carboxy group-containing polymer dispersant is 0.01% by mass or more and less than 2.0% by mass. There may be.

The organic solvent is from the group consisting of dihydroterpineol (DHT), dihydroterpineyl acetate (DHTA), terpineol (TPO), propylene glycol monobutyl ether (PNB), diethylene glycol monobutyl ether acetate (BCA), and diisobutyl ketone (DIBK). It may include one or more selected types.

The conductive paste of the present invention contains a dispersant other than the carboxy group-containing polymer dispersant, and the content of the carboxy group-containing polymer dispersant is 30% by mass with respect to the total amount of the dispersant in the conductive paste. It may be more than that.

The conductive paste contains an acid-based dispersant having a mass average molecular weight of less than 2000 as a dispersant other than the carboxy group-containing polymer dispersant, and the acid-based dispersant is based on the total amount of the dispersant in the conductive paste. The content may be more than 0% by mass and 70% by mass or less.

The conductive powder may include one or more metal powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.

The number average particle diameter of the conductive powder may be 0.05 μm or more and 1.0 μm or less.

The ceramic powder may include barium titanate.

The number average particle diameter of the ceramic powder may be 0.01 μm or more and 0.5 μm or less.

The content of the ceramic powder may be 1% by mass or more and 20% by mass or less.

The binder resin may include a cellulose resin.

The conductive paste of the present invention may be used for internal electrodes of laminated ceramic parts.

The conductive paste of the present invention may have a viscosity of 2.0 Pa·S or less at a shear rate of 100 sec ⁻¹ at a temperature of 25° C.

Furthermore, in order to solve the above problems, the electronic component of the present invention is an electronic component formed using the conductive paste of the present invention.

Further, in order to solve the above problems, the multilayer ceramic capacitor of the present invention has at least a laminate in which a dielectric layer and an internal electrode layer are laminated, and the internal electrode layer is formed using the conductive paste of the present invention. This is a multilayer ceramic capacitor formed by

With the present invention, even a low-viscosity conductive paste can stably maintain a low paste viscosity over a long period of time, and can suppress separation of the conductive powder and ceramic powder, and the dry film surface after application. It is possible to provide a conductive paste with good smoothness. Furthermore, it is possible to provide a carboxy group-containing polymer dispersant that can provide such a conductive paste, and electronic components and multilayer ceramic capacitors formed using such a conductive paste. In particular, the conductive paste of the present invention can suppress separation of the conductive powder and the ceramic powder even if it is a low-viscosity paste, and the dry film surface after application has good smoothness, and Good long-term viscosity stability eliminates the need for viscosity adjustment during printing, contributing to the simplification of the printing process. It is particularly effective when used in gravure printing, which performs high-speed printing with low viscosity.

FIG. 1A is a schematic diagram of a multilayer ceramic capacitor according to the present embodiment, with FIG. 1A being a perspective view and FIG. 1B being a sectional view.

Hereinafter, one embodiment of the carboxy group-containing polymer dispersant, conductive paste, electronic component, and multilayer ceramic capacitor of the present invention will be described.

[Carboxy group-containing polymer dispersant]
The carboxyl group-containing polymer dispersant of the present invention includes at least one of acrylic acid or methacrylic acid, and at least one of an acrylic ester represented by the following general formula (1) or a methacrylic ester represented by the following general formula (2). A carboxyl group-containing polymer dispersant consisting of a copolymer of methacrylic acid and methacrylic acid, which has a mass average molecular weight of 2,000 or more and less than 30,000, and has a molar ratio of the sum of the acrylic acid and the methacrylic acid, the acrylic acid ester, and the methacrylic acid. A dispersant having a ratio of X:1-X to the total amount of methacrylic acid esters, where X is 0.1 or more and less than 0.4. Here, in the following general formula (1) and the following general formula (2), R ₁ is a linear or branched alkyl group.

The present inventors have discovered that the low-viscosity conductive paste described below has a stable low viscosity with little change in viscosity over time by containing a certain amount of a carboxy group-containing polymer dispersant having a mass average molecular weight of 2000 or more. We have also found that separation of the conductive powder and ceramic powder can be suppressed, and a smooth dry film can be obtained.

A carboxyl group-containing polymer dispersant has a carboxyl group as an adsorption group to conductive powder or ceramic powder. By having a copolymer structure of at least one of acrylic acid or methacrylic acid and at least one of acrylic ester or methacrylic ester, the solubility in organic solvents and the dispersibility of the conductive powder, which will be described later, are improved. It is possible to achieve both improvement effects.

Here, the copolymers include copolymers of acrylic acid and acrylic esters, copolymers of acrylic acid and methacrylic esters, copolymers of methacrylic acid and acrylic esters, and copolymers of methacrylic acid and methacrylic acid. Copolymers with esters, copolymers with acrylic acid and methacrylic acid, and acrylic esters, copolymers with acrylic acid, methacrylic acid, and methacrylic esters, acrylic acid, acrylic esters, and methacrylic esters Copolymers of methacrylic acid, acrylic esters and methacrylic esters, and copolymers of acrylic acid and methacrylic acid and acrylic esters and methacrylic esters.

Furthermore, when acrylic acid and acrylic ester are used together, their molar ratio can be adjusted as appropriate. Moreover, when using an acrylic ester and a methacrylic ester together, the molar ratio of these can be adjusted as appropriate.

In addition, in the molar ratio during copolymerization, by adjusting the ratio of the total of acrylic acid and methacrylic acid (X) to the total of acrylic ester and methacrylic ester (1-X), dissolution in organic solvent The properties and dispersibility of the conductive powder change. If the total ratio of acrylic acid and methacrylic acid is too low, the amount of carboxy groups that act as adsorption groups for the conductive powder will be small, resulting in poor dispersibility. On the other hand, if the total ratio of acrylic acid and methacrylic acid is too high, the hydrophilicity of the carboxy group-containing polymer dispersant will increase, and the solubility in the organic solvent used in the conductive paste will deteriorate.

Therefore, in terms of molar ratio, an appropriate ratio exists between the total of acrylic acid and methacrylic acid and the total of acrylic ester and methacrylic ester. That is, when the total ratio X of acrylic acid and methacrylic acid is 0.1 or more and less than 0.4, the solubility in organic solvents and the effect of improving the dispersibility of the conductive powder are well balanced, As a result, separation of the conductive powder and ceramic powder can be suppressed, and a low-viscosity conductive paste with good viscosity stability over time and good smoothness of the dry film surface after application is provided. be able to.

Further, R ₁ of the acrylic ester and methacrylic ester shown in the general formula (1) and the general formula (2) is a linear or branched alkyl group. Here, when R ₁ is a linear alkyl group, the number of carbon chains is preferably 2 or more and 10 or less, more preferably 2 or more and 4 or less. If the number of carbon chains is 1, the carbon chain of the acrylic ester or methacrylic ester is too short, so when used as a dispersant for conductive paste, the effect of suppressing separation of the conductive paste is not sufficiently exhibited. This is not preferable because there are cases. In addition, when the number of carbon chains is 11 or more, the carbon chains of the acrylic ester or methacrylic ester are too long, so when used as a dispersant for conductive paste, the effect of suppressing separation of the conductive paste is insufficient. This is not preferable because the conductive paste may not be effective, or the surface roughness and density of the dried film after forming the conductive paste by gravure printing or the like may deteriorate.

Further, when R ₁ is a branched alkyl group, the total number of carbon atoms in R ₁ is preferably 3 or more and 14 or less, the number of carbon chains in the straight chain part is 2 or more and 10 or less, and the number of carbon chains in the branched part is 2 or more and 10 or less, and The number of carbon atoms is preferably 1 or more and 4 or less. By satisfying these conditions, there is a good balance between solubility in organic solvents and the effect of improving the dispersibility of the conductive powder, and as a result, separation of the conductive powder and the ceramic powder can be suppressed. It is possible to provide a low-viscosity conductive paste with good viscosity stability over time and good smoothness of the dry film surface after application. On the other hand, if these conditions are not met, the effect of suppressing the separation of the conductive paste may not be fully demonstrated when used as a dispersant for the conductive paste, or the The surface roughness of the dried film and the density of the dried film may deteriorate.

Further, the mass average molecular weight of the carboxyl group-containing polymer dispersant is 2,000 or more, may be 5,000 or more, or may be 10,000 or more. The mass average molecular weight of the carboxyl group-containing polymer dispersant affects the initial viscosity, time-dependent viscosity increase, separation amount, etc. of the conductive paste using the same. Therefore, when the mass average molecular weight is 2000 or more, a stable dispersion effect can be exhibited, and thickening and separation over time can be sufficiently suppressed. In addition, from the viewpoint of suppressing viscosity increase over time, the upper limit of the mass average molecular weight is not particularly limited, but if the mass average molecular weight is too large, the initial viscosity of the conductive paste itself may become high, making it unsuitable for gravure printing. Therefore, the mass average molecular weight may be 30,000 or less. Note that the mass average molecular weight of the carboxy group-containing polymer dispersant can be measured by, for example, GPC (gel permeation chromatography).

[Conductive paste]
The conductive paste of this embodiment contains the carboxyl group-containing polymer dispersant of the present invention. Further, it may further contain a conductive powder, a ceramic powder, a binder resin, and an organic solvent. Each of these components will be explained in detail below.

(conductive powder)
The conductive powder is not particularly limited, and metal powder can be used, for example, one or more powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof can be used. . Among these, powder of Ni or its alloy (Ni alloy) is preferred from the viewpoints of conductivity, corrosion resistance, and cost. As the Ni alloy, for example, an alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt and Pd can be used. can. The Ni content in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Further, the Ni powder may contain about several hundred ppm of element S in order to suppress rapid gas generation due to partial thermal decomposition of the binder resin during binder removal treatment.

The number average particle diameter of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. When the number average particle diameter of the conductive powder is within the above range, it can be suitably used as a paste for internal electrodes of thin-film multilayer ceramic capacitors (multilayer ceramic components), and can improve the smoothness and density of dry films, for example. will improve. The number average particle diameter is a value obtained from observation with a scanning electron microscope (SEM), and the particle diameter of each particle is measured from an image observed with a SEM at a magnification of 10,000 times. This is the average value (SEM average particle diameter) obtained.

The content of the conductive powder is preferably 30% by mass or more and less than 70% by mass, more preferably 40% by mass or more and 60% by mass or less, based on the entire conductive paste. When the content of the conductive powder is within the above range, the conductivity and dispersibility are excellent.

(ceramic powder)
The ceramic powder is not particularly limited, and for example, in the case of a paste for internal electrodes of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of multilayer ceramic capacitor to which it is applied. As the ceramic powder, for example, a perovskite oxide containing Ba and Ti can be used, and preferably barium titanate (BaTiO ₃ ) is used.

As the ceramic powder, a ceramic powder containing barium titanate as a main component and an oxide as a subcomponent may be used. Examples of the oxide include one or more oxides selected from Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and rare earth elements. Examples of such ceramic powders include ceramic powders of perovskite-type oxide ferroelectrics in which Ba and Ti atoms of barium titanate (BaTiO ₃ ) are replaced with other atoms, such as Sn, Pb, and Zr. Can be mentioned.

As the ceramic powder used for the conductive paste for the internal electrodes, a powder having the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor (electronic component) may be used. This suppresses the occurrence of cracks due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer during the sintering process. Examples of such ceramic powders include, in addition to the above-mentioned perovskite oxides containing Ba and Ti, ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , Examples include oxides such as TiO ₂ and Nd ₂ O ₃ . Note that one type of ceramic powder may be used, or two or more types of ceramic powder may be used.

The number average particle diameter of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, preferably 0.01 μm or more and 0.3 μm or less. Since the number average particle diameter of the ceramic powder is within the above range, when used as a conductive paste for internal electrodes, sufficiently thin and uniform internal electrodes can be formed. The number average particle diameter is a value obtained from observation with a scanning electron microscope (SEM), and the particle diameter of each particle is measured from an image observed with a SEM at a magnification of 50,000 times. This is the average value (SEM average particle diameter) obtained.

The content of the ceramic powder is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, based on the entire conductive paste. When the content of the ceramic powder is within the above range, the dispersibility and sinterability are excellent.

Further, the content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of the conductive powder. When the content of the conductive powder is within the above range, the conductivity and dispersibility are excellent.

(binder resin)
The binder resin is not particularly limited, and any known resin can be used. Examples of the binder resin include cellulose resins such as methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, and nitrocellulose, acrylic resins, and acetal resins including butyral resins such as polyvinyl butyral. Among these, from the viewpoints of solubility in solvents, combustion decomposability, etc., it is preferable that cellulose resin is included, and it is more preferable that ethyl cellulose is included. In addition, when used as a paste for internal electrodes, from the viewpoint of improving the adhesive strength with the green sheet, it may contain a butyral resin or may be used alone. When the binder resin contains an acetal resin, the viscosity can be easily adjusted to be suitable for gravure printing, and the adhesive strength with the green sheet can be further improved. The binder resin may contain, for example, 20% by mass or more, or 30% by mass or more of acetal resin based on the entire binder resin. Further, the binder resin may contain 50% by mass or less of acetal resin based on the entire binder resin.

The weight average molecular weight of the binder resin can be adjusted as appropriate within the range of 10,000 or more and 200,000 or less, depending on the required viscosity of the conductive paste.

The content of the binder resin is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7% by mass or less, based on the entire conductive paste. When the content of the binder resin is within the above range, the conductivity and dispersibility are excellent.

The content of the binder resin is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 1 part by mass or more and 14 parts by mass or less, based on 100 parts by mass of the conductive powder. When the content of the binder resin is within the above range, the conductivity and dispersibility are excellent.

(Organic solvent)
The organic solvent is not particularly limited, and any known organic solvent that can dissolve the binder resin and dispersant can be used. Examples of the organic solvent include terpene solvents, glycol ether solvents, acetate solvents, acetate ester solvents, ketone solvents, and hydrocarbon solvents. In addition, one type of organic solvent may be used, or two or more types may be used.

Examples of the terpene solvent include terpineol, dihydroterpineol (DHT), dihydroterpineyl acetate, and the like, with dihydroterpineol (DHT) being preferred.

Examples of glycol ether solvents include (di)ethylene glycol ethers such as diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, and ethylene glycol monohexyl ether, and propylene glycol. Examples include propylene glycol monoalkyl ethers such as monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether (PNB). Among them, propylene glycol monoalkyl ethers are preferred, and propylene glycol monobutyl ether (PNB) is more preferred. When the organic solvent contains a glycol ether solvent, it has excellent compatibility with the above-mentioned binder resin and has excellent drying properties.

Examples of acetate solvents include ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate (butyl carbitol acetate), dipropylene glycol methyl ether acetate, 3-methoxy 3-methylbutyl acetate, 1-methoxypropyl-2-acetate, etc. Examples include glycol ether acetates, isobornyl acetate, isobornyl propinate, isobornyl butyrate, isobornyl isobutyrate, and the like.

Examples of acetate-based solvents include ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, and the like. Examples of the ketone solvent include methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and the like.

Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as tridecane, nonane, cyclohexane, naphthenic solvents, and mineral spirits, and aromatic hydrocarbon solvents such as toluene and xylene. Hydrogen solvents are preferred, mineral spirits are more preferred. Further, the mineral spirit may contain chain saturated hydrocarbons as a main component, and may contain 20% by mass or more of chain saturated hydrocarbons based on the entire mineral spirit.

In addition, the organic solvents include dihydroterpineol (DHT), dihydroterpineyl acetate (DHTA), terpineol (TPO), propylene glycol monobutyl ether (PNB), diethylene glycol monobutyl ether acetate (BCA), and diisobutyl ketone (DIBK). It is preferable to include one or more types selected from the group. By using these solvents, it is possible to achieve both appropriate viscosity and drying speed.

For example, the organic solvent may include one or more terpene solvents (a) selected from the group consisting of dihydroterpineol (DHT), dihydroterpineyl acetate (DHTA), and terpineol (TPO), and propylene glycol monobutyl ether (PNB). , diethylene glycol monobutyl ether acetate (BCA), and a hydrocarbon solvent.

The total content of organic solvents is preferably 20% by mass or more and 50% by mass or less, more preferably 25% by mass or more and 45% by mass or less, based on the total amount of the conductive paste. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

The total content of organic solvents is preferably 50 parts by mass or more and 130 parts by mass or less, more preferably 60 parts by mass or more and 90 parts by mass or less, based on 100 parts by mass of the conductive powder. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

When the conductive paste contains a terpene solvent (a), the total content of the terpene solvent (a) may be 5% by mass or more and 40% by mass or less, and 10% by mass or less, based on the total amount of the conductive paste. It may be at least 12% by mass and at most 25% by mass, and may be at least 12% by mass and at most 25% by mass.

When the conductive paste contains a solvent (b) such as propylene glycol monobutyl ether (PNB), the total content of the solvent (b) is 3% by mass and 20% by mass or less based on the total amount of the conductive paste. It may be 5% by mass or more and 20% by mass or less.

When the conductive paste contains a hydrocarbon solvent, the total content of the hydrocarbon solvent may be 1% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, based on the total amount of the conductive paste. It may be less than or equal to 5% by mass and less than or equal to 10% by mass.

Further, when the conductive paste contains diisobutyl ketone, the total content of diisobutyl ketone is preferably 1% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, based on the total amount of the conductive paste. It may be 3% by mass or more and 10% by mass or less.

(dispersant)
The carboxyl group-containing polymer dispersant of the present invention is contained in an amount of 0.01% by mass or more and less than 2.0% by mass, preferably 0.01% by mass or more and 1.0% by mass based on 100% by mass of the entire conductive paste. The content is more preferably 0.03% by mass or more and 0.5% by mass or less. When the carboxy group-containing polymer dispersant is contained in the above range, the conductive paste can stably maintain a low viscosity state for a long period of time, and separation of the conductive powder and the ceramic powder can be suppressed.

Further, the dispersant may be composed only of the carboxyl group-containing polymer dispersant represented by the above general formula (1), but may also contain a dispersant other than the carboxyl group-containing polymer dispersant as described below. . When a dispersant other than a carboxy group-containing polymer dispersant is included, the content of the carboxy group-containing polymer dispersant may be, for example, 30% by mass or more based on the total amount of the dispersant, preferably 60% by mass. or more, and more preferably 80% by mass or more. The greater the content of the carboxyl group-containing polymer dispersant based on the total amount of the dispersant, the better the effect of suppressing separation between the conductive powder and the ceramic powder.

Furthermore, the conductive paste of the present embodiment may further contain an acid-based dispersant (a dispersant having an acidic adsorption group) other than the carboxy group-containing polymer dispersant. Examples of the acid-based dispersant (excluding the above-mentioned carboxylic acid-based polymer dispersant) include acid-based dispersants having a mass average molecular weight of less than 2,000. Note that the acidic dispersants may be used alone or in combination of two or more.

Examples of acid-based dispersants having a mass average molecular weight of less than 2000 include higher fatty acids, dicarboxylic acids, polycarboxylic acid-based dispersants, and carboxylic acid-based dispersants such as alkyl monoamine salt types. When the conductive paste contains an acid-based dispersant with a mass average molecular weight of less than 2000 together with a carboxyl group-containing polymer dispersant, the viscosity may decrease or the dispersibility of ceramic powder such as barium titanate may be further improved. There is. In addition, the mass average molecular weight of the acidic dispersant having a mass average molecular weight of less than 2,000 may be 1,000 or less.

Higher fatty acids may be unsaturated carboxylic acids or saturated carboxylic acids, and are not particularly limited to those having 11 carbon atoms such as stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid. These include the above. Among these, oleic acid or stearic acid is preferred as the higher fatty acid.

Examples of alkyl monoamine salt types include oleoyl sarcosine, which is a compound of glycine and oleic acid, stearamide, lauriloyl, which is an amide compound using a higher fatty acid such as stearic acid or lauric acid instead of oleic acid. Sarcosine is preferred.

In addition, if the content of the acid-based dispersant with an average molecular weight of less than 2000 is too large, there is a concern that it will have an adverse effect such as inhibiting the adsorption of the carboxy group-containing polymer dispersant to the metal powder material (filler). When used together, it is preferable to adjust the content appropriately.

For example, the content of the acidic dispersant having a mass average molecular weight of less than 2000 may be more than 0% by mass and 70% by mass or less, preferably 40% by mass or less, based on 100% by mass of the total amount of the dispersant. The content is more preferably 20% by mass or less.

Furthermore, the dispersant may include a dispersant other than the acid-based dispersant. Examples of dispersants other than acidic dispersants include basic dispersants, nonionic dispersants, amphoteric dispersants, and the like. These dispersants may be used alone or in combination of two or more.

Examples of the basic dispersant include aliphatic amines such as laurylamine, rosinamine, cetylamine, myristylamine, stearylamine, and oleylamine.

Furthermore, the content of the dispersant (total) is preferably less than 2.0% by mass based on the entire conductive paste. If the content of the above-mentioned carboxylic acid-based polymer dispersant or the entire dispersant is too high, the conductive paste will not be sufficiently dried during the printing process or drying process, leaving the internal electrode layer in a soft state. Lamination misalignment may occur during the lamination process. Further, the dispersant remaining during firing may vaporize, and the vaporized gas components may generate internal stress or cause structural destruction of the laminate.

(Additive)
The conductive paste of this embodiment may contain other additives other than the above-mentioned dispersant, if necessary. As other additives, conventionally known additives such as antifoaming agents, plasticizers, surfactants, and thickeners can be used.

For example, in Patent Document 3, polycarboxylic acid polymers and polycarboxylic acid salts are described as separation inhibitors that suppress separation of conductive powder and dielectric powder, but in this specification, such In a broad sense, separation inhibitors are also included in acid-based dispersants as agents that improve the dispersibility of inorganic powders.

(Method for manufacturing conductive paste)
The method for manufacturing the conductive paste according to this embodiment is not particularly limited, and conventionally known methods can be used. The conductive paste can be produced, for example, by stirring and kneading the above-mentioned components using a three-roll mill, a ball mill, a mixer, or the like. Regarding dicarboxylic acid (separation inhibitor), it is preferable to weigh and add it when stirring and kneading with a mixer, etc., as with other materials, but after stirring and kneading (dispersing) A similar effect can be obtained by adding it to the material as a separation inhibitor.

The conductive paste of the present invention preferably has a viscosity of 2.0 Pa·S or less at a shear rate of 100 sec ^-1 at a temperature of 25°C. When the viscosity at a shear rate of 100 sec ^-1 is within the above range, it is suitable for efficient coating at high speed. If it exceeds the above range, the viscosity of the conductive paste will be too high and the smoothness of the dried film surface after application may be poor. The lower limit of the viscosity at a shear rate of 100 sec ^-1 is not particularly limited, but is, for example, 0.2 Pa·S or more.

Further, in the conductive paste, it is preferable that the thickness of the white floating layer observed one week after the conductive paste is less than 8% of the total thickness of the conductive paste, and % or less, or 2% or less. The smaller the thickness of the white floating layer, the better the effect of suppressing separation between the conductive powder and the ceramic powder. In addition, the thickness of the white floating layer can be measured by the method described in Examples described later.

Furthermore, the conductive paste of this embodiment can be suitably used for electronic components such as multilayer ceramic capacitors. A multilayer ceramic capacitor has a dielectric layer and an internal electrode layer formed using a dielectric green sheet, and the conductive paste of this embodiment can be suitably applied to forming the internal electrode layer.

[Electronic parts]
Hereinafter, an example of an electronic component etc. according to the present embodiment will be described with reference to the drawings. In the drawings, the drawings may be expressed schematically or with a changed scale, as appropriate. Further, the positions and directions of the members will be explained with reference to the XYZ orthogonal coordinate system shown in FIGS. 1A and 1B as appropriate. In this XYZ orthogonal coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction (up and down direction).

1A and 1B are a perspective view and a side sectional view showing a multilayer ceramic capacitor 1, which is an example of an electronic component. The multilayer ceramic capacitor 1 includes a laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and an external electrode 20.

Hereinafter, an example of a method for manufacturing a multilayer ceramic capacitor 1 using the above conductive paste will be described. First, a conductive paste is gravure printed on a ceramic green sheet (dielectric green sheet) and dried to form a dry film. A plurality of ceramic green sheets having this dry film on the upper surface are laminated by pressure bonding to obtain a laminate, and then the laminate is baked and integrated, so that the internal electrode layer 11 and the dielectric layer 12 are alternately formed. A ceramic laminate 10 is produced in which the ceramic laminate 10 is laminated. Thereafter, a pair of external electrodes 20 are formed at both ends of the ceramic laminate 10, thereby manufacturing the multilayer ceramic capacitor 1. This will be explained in more detail below.

First, a ceramic green sheet, which is an unfired ceramic sheet, is prepared. For example, this ceramic green sheet is made of a dielectric layer paste obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a specified ceramic raw material powder such as barium titanate. Examples include those obtained by coating a sheet on a support film and drying it to remove the solvent. Note that the thickness of the ceramic green sheet is not particularly limited, but from the viewpoint of the demand for miniaturization of multilayer ceramic capacitors, it is preferably 0.05 μm or more and 3 μm or less.

Next, a plurality of ceramic green sheets are prepared in which the above-mentioned conductive paste is printed on one side of the ceramic green sheet using a gravure printing method and dried to form a dry film. Note that the thickness of the dried film is preferably 1 μm or less after drying, from the viewpoint of reducing the thickness of the internal electrode layer 11.

Next, the ceramic green sheets are peeled off from the support film, and the ceramic green sheets and the dry film formed on one side of the sheets are laminated so that they are alternately arranged, and then the laminate is formed by heating and pressurizing at the same time. get. Note that a configuration may be adopted in which protective ceramic green sheets to which no conductive paste is applied are further disposed on both sides of the laminate.

Next, after cutting the laminate into a predetermined size to form a green chip, the green chip is subjected to a binder removal treatment and fired in a reducing atmosphere to produce a fired laminate ceramic body (ceramic laminate 10). Manufacture. Note that the atmosphere in the binder removal treatment is preferably air or N ₂ gas atmosphere. The temperature during the binder removal treatment is, for example, 200°C or more and 400°C or less. Further, it is preferable that the holding time at the above temperature during the binder removal treatment is 0.5 hours or more and 24 hours or less. Further, the firing is performed in a reducing atmosphere to suppress oxidation of the metal used for the internal electrode layer, and the temperature when firing the laminate is, for example, 1000°C or more and 1350°C or less, and the firing is The temperature is maintained for a period of, for example, 0.5 hours or more and 8 hours or less.

By firing the green chip, the organic binder in the green sheet is completely removed, and the ceramic raw material powder is fired to form the ceramic dielectric layer 12. Further, the organic vehicle in the internal electrode layer 11 is removed, and the nickel powder or the alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrode, and the dielectric layer 12 and the internal electrode A laminated ceramic fired body is formed in which a plurality of layers 11 are alternately laminated. Note that from the viewpoint of increasing reliability by incorporating oxygen into the dielectric layer and suppressing re-oxidation of the internal electrodes, the fired multilayer ceramic fired body may be subjected to an annealing treatment.

Then, the multilayer ceramic capacitor 1 is manufactured by providing a pair of external electrodes 20 on the produced multilayer ceramic fired body. For example, the external electrode 20 includes an external electrode layer 21 and a plating layer 22. External electrode layer 21 is electrically connected to internal electrode layer 11 . Note that, as the material for the external electrode 20, for example, copper, nickel, or an alloy thereof can be suitably used. Note that the electronic component is not limited to the multilayer ceramic capacitor, and electronic components other than the multilayer ceramic capacitor, such as a varistor, can also be used.

Hereinafter, the present invention will be explained in detail based on Examples and Comparative Examples, but the present invention is not limited by the Examples in any way.

[Evaluation method]
(Viscosity of conductive paste)
The viscosity of the conductive paste was measured using a rheometer (Rheometer MCR302, manufactured by Anton Paar Japan Co., Ltd.). The viscosity was measured using a cone plate with a cone angle of 1° and a diameter of 25 mm at a shear rate of 100 sec ^-1 .

In addition, the viscosity of the conductive paste was measured at a temperature of 25°C at 1 day and 1 month after production, and the measured value at 1 day was taken as the initial viscosity, and the value at 1 month relative to this initial viscosity was measured. The ratio of the measured values (measured value at 1 month/measured value at 1 day x 100) was evaluated as the viscosity increase ratio over time. In Table 1, the initial viscosity was evaluated as "○" if it was 0.2 Pa·s or more and not more than 2.0 Pa·s, and "x" if it was higher than 2.0 Pa·s. Regarding the time-dependent thickening ratio, a ratio of less than 130 was evaluated as "○" (sufficient viscosity stability), and a ratio of 130 or more was evaluated as "x" (insufficient viscosity stability).

(white float)
Immediately after preparation, 20 g of the conductive paste was left standing at room temperature in a glass bottle (diameter φ30 x height 65 mm), and after one week, the appearance of the conductive paste was visually observed, and the percentage of white spots observed was determined. was measured. The white float ratio (%) is calculated as (thickness of the white float layer/thickness of the entire paste amount)*100. In Table 1, the percentage of white floatation (%) is judged as "〇" (good separation suppression effect) for less than 5%, "△" (good separation suppression effect) for 5% or more and less than 8%, and 8%. The above was evaluated as "x" (separation suppressing effect is insufficient).

(Surface roughness)
The prepared conductive paste was applied onto a glass substrate using an applicator so that the wet film thickness was 10 μm, and then a drying process was performed at 300° C. for 10 minutes in the air to produce a dry film. The average roughness of the dried film was measured using a laser microscope (VK-X130, manufactured by Keyence Corporation) within a measurement range of 200 x 250 μm, and the measurements were repeated at five random locations. The average value (arithmetic mean height Sa) of the obtained values was taken as the average roughness of the conductive paste dry film. In Table 1, the surface roughness is evaluated as "〇" (the surface of the dry film is smooth) when it is less than 0.065 μm, and "x" (the surface of the dry film is not smooth) when it is 0.065 μm or more. did.

In addition, in the overall judgment item in Table 1, if all the judgments of the tests conducted were ○, it is marked as "〇" (pass), and if even one of the tests conducted was judged as ×, it is marked as "×". ” (failed).

[Materials used]
(conductive powder)
As the conductive powder, Ni powder (SEM average particle size: 0.2 μm) was used.

(ceramic powder)
Barium titanate (BaTiO ₃ ; SEM average particle size: 0.10 μm) was used as the ceramic powder.

(binder resin)
As the binder resin, polyvinyl butyral and ethyl cellulose were used.

(dispersant)
A copolymer of acrylic acid ester (general formula (1)) having a linear or branched alkyl group and acrylic acid, and a carboxyl group-containing polymer dispersant with a mass average molecular weight of 2000 or more, and acrylic acid and acrylic acid for comparison. An acidic low-molecular dispersant containing no acrylic acid ester polymer and a carboxyl group-containing polymer dispersant having a mass average molecular weight smaller or larger than those in the examples were used. The ratio of acrylic acid in the molar ratio during copolymerization (X), the number of carbon atoms in the alkyl group, the structure of the alkyl group, the name of the acrylic ester, the mass average molecular weight, the content of the carboxy group-containing polymer dispersant in the conductive paste The amounts are shown in Table 1.

As an example of synthesis of a carboxyl group-containing polymer dispersant, the procedure for synthesizing the carboxyl group-containing polymer dispersant of Example 1 is shown below. In addition, in Examples 2 to 11, Comparative Example 1, Comparative Examples 4 and 5, the molar ratio of acrylic acid and acrylic ester was changed so that the structure of the alkyl group of the acrylic ester and the ratio (X) of acrylic acid were changed. Synthesis was carried out in the same manner as the following synthesis procedure by changing the synthesis temperature, synthesis time, and amount of chain transfer agent added.

Main raw material monomers acrylic acid (12.2 mmol) and acrylic ester (2-ethylhexyl acrylate, 48.8 mmol), polymerization initiator AIBN (0.603 mmol), chain transfer agent dodecanethiol (0.722 mmol) ), 50 mL of 1,4-dioxane as a solvent was added to a three-necked flask, and after bubbling the solvent with nitrogen in an ice bath, it was held at 65° C. for 12 hours with stirring under a nitrogen atmosphere. Thereafter, methanol was added to reprecipitate, and decantation by centrifugation was repeated three times. Finally, it was dissolved in benzene and freeze-dried to obtain a polymer dispersant. The obtained polymeric dispersant was analyzed by NMR (nuclear magnetic resonance) and SEC (size exclusion chromatography) to analyze the acrylic acid ratio (X) and mass average molecular weight. Note that 2-mercaptoethanol can also be used as the chain transfer agent.

(Organic solvent)
As the organic solvents, dihydroterpineol (DHT) was used as the main solvent, and mineral spirit and propylene glycol monobutyl ether (PNB) were used as the subsolvents.

[Example 1]
Conductive powder 50% by mass, ceramic powder 12.5% by mass, carboxy group-containing polymer dispersant (acrylic acid ratio (X) 0.1, number of carbon chains of branched alkyl group 8, mass average molecular weight approximately 25,000 ) 0.3% by mass, binder resin 2.5% by mass (breakdown: polyvinyl butyral resin 1.75% by mass, ethyl cellulose 0.75% by mass), and the remainder an organic solvent consisting of DHT, mineral spirit, and PNB ( A material was prepared by adding DHT:mineral spirit:PNB=53:20:27 (mass ratio) so that the total amount was 100% by mass. The conductive paste of Example 1 was prepared by mixing and dispersing these materials.

For the obtained conductive paste, the initial viscosity was measured, the viscosity ratio over time was calculated, white cast was observed, and the surface roughness of the dried film was measured. The evaluation results are shown in Table 1 along with the detailed conditions of the additives.

[Examples 2 to 11]
A carboxyl group-containing polymer dispersant was prepared from the carboxyl group-containing polymer dispersant of Example 1 by adjusting the acrylic acid ratio x, the number of carbon atoms in the alkyl group of the acrylic ester, the presence or absence of branching of the carbon chain of the alkyl group, and the mass average. The molecular weight was changed to a carboxy group-containing polymer dispersant shown in Table 1, and in Examples 10 and 11, the amount of the carboxy group-containing polymer dispersant added was changed so that the amount of the above-mentioned conductive paste was 100% by mass. A conductive paste was prepared and evaluated in the same manner as in Example 1, except that the amount of organic solvent added was adjusted. Table 1 shows the conditions and evaluation results for the dispersant.

[Comparative Examples 1 to 5]
Comparative Example 1 was carried out in the same manner as in Example 1, except that although it was a carboxyl group-containing polymer dispersant, the dispersant had an acrylic acid ratio (X) of 0.05, which was outside the scope of the present invention. A conductive paste was prepared. In addition, in Comparative Example 2, a dicarboxylic acid with an average molecular weight of 370 was used as an acid-based low-molecular dispersant that has been widely used conventionally, and in Comparative Example 3, male anhydride with a mass-average molecular weight of 50,000 was used as a carboxylic acid-based polymer dispersant. A conductive paste was produced in the same manner as in Example 1 except that an acid copolymer was used. As Comparative Example 4, Example 1 was prepared except that the same carboxyl group-containing polymer dispersant as used in Example 5 was added in a content (0.005% by mass) that was less than the range of the present invention. A conductive paste was prepared in the same manner. As Comparative Example 5, a conductive paste was prepared in the same manner as in Example 5 except that the mass average molecular weight of the carboxyl group-containing polymer dispersant was 1000. Comparative Examples 1 to 5 were also evaluated in the same manner as in the Examples. Table 1 shows the conditions and evaluation results for the dispersant.

(Evaluation results)
The conductive paste of the example has an aging viscosity increase ratio of 125 or less after one month, and a viscosity of 2.0 Pa·s or less after one month, so it has excellent viscosity stability over time. I know that there is. Furthermore, the percentage of white flaking that occurs after one week due to storage is sufficiently small at 5% or less, indicating that it has a separation suppressing effect.

Furthermore, from the results of Examples 1 to 3, within the scope of the present invention, the more the proportion (X) of acrylic acid in the carboxyl group-containing polymer dispersant is increased, the more viscosity increase over time and white cast can be suppressed, and the dry film surface There is a tendency for the curve to become smoother. Further, from the results of Examples 4 to 7, it can be seen that the smoothness of the dried film surface tends to be higher as the number of carbon atoms in the alkyl chain length of the acrylic ester is smaller. From the results of Examples 5 and 8 to 9, within the scope of the present invention, the larger the mass average molecular weight of the carboxyl group-containing polymer dispersant, the more the viscosity increase over time and white cast can be suppressed, and the dried film surface will be smoother. A trend can be seen. In addition, from the results of Examples 5 and 10 to 11, within the scope of the present invention, the influence of the content of the carboxy group-containing polymer dispersant of the present invention is small, but the content of the carboxy group-containing polymer dispersant is large. However, there is a tendency for the dry film surface to become smoother and to suppress thickening and whitening over time.

The conductive paste of Comparative Example 1 has the same structure as the dispersant of the present invention, but since the proportion of acrylic acid (X) is lower than the range of the present invention, the initial viscosity cannot be kept low, and after drying The roughness of the dry film surface becomes high, which is undesirable. Next, in the conductive paste of Comparative Example 2, by using a low molecular weight acidic dispersant, the viscosity is sufficiently stabilized and the dry film surface roughness after drying is also good, but the percentage of white floating is not acceptable. It has exceeded its capacity. In the conductive paste of Comparative Example 3, a carboxyl group-containing polymer dispersant was used, but it was not possible to suppress the increase in viscosity over time, and the white cast rate and dry film surface roughness after drying were also poor. Not suitable for gravure printing. In addition, in the conductive paste of Comparative Example 4, the dispersant of the present invention was used, but since the content was less than the range of the present invention, the effect of the additive was not sufficiently exhibited, the initial viscosity was high, and the dispersant after drying was This is not preferable because the surface roughness of the dried film becomes high. In the conductive paste of Comparative Example 5, the mass average molecular weight of the carboxyl group-containing polymer dispersant is small, so the dispersion performance is poor, and the surface roughness of the dry film after drying becomes high, which is not preferable.

Note that the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above embodiments etc. may be omitted. Furthermore, the requirements described in the above embodiments and the like can be combined as appropriate. In addition, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments, etc. are incorporated into the description of the main text.

The conductive paste of the present invention stably has a viscosity suitable for gravure printing over a long period of time, the separation between the conductive powder and the ceramic powder is sufficiently small, and the surface roughness of the dry film after drying is also sufficient. low. Therefore, the conductive paste of the present invention can be suitably used as a raw material for internal electrodes of multilayer ceramic capacitors, which are chip components of electronic devices that are becoming increasingly smaller, such as mobile phones and digital devices. It can be suitably used as a conductive paste.

1 Multilayer ceramic capacitor 10 Ceramic laminate 11 Internal electrode layer 12 Dielectric layer 20 External electrode 21 External electrode layer 22 Plating layer

Claims

at least one of acrylic acid or methacrylic acid;
A carboxyl group-containing polymer dispersant comprising a copolymer with at least one of an acrylic ester represented by the following general formula (1) or a methacrylic ester represented by the following general formula (2),
The mass average molecular weight is 2000 or more and less than 30000,
In terms of molar ratio, the ratio of the total of the acrylic acid and the methacrylic acid to the total of the acrylic ester and the methacrylic ester is X:1-X, and the X is 0.1 or more and less than 0.4. can be,
A dispersant in which R 1 is a linear or branched alkyl group in the following general formula (1) and the following general formula (2).
A conductive paste comprising the carboxy group-containing polymer dispersant according to claim 1.
further comprising conductive powder, ceramic powder, binder resin and organic solvent,
The conductive paste according to claim 2, wherein the content of the carboxyl group-containing polymer dispersant is 0.01% by mass or more and less than 2.0% by mass.
The organic solvent is from the group consisting of dihydroterpineol (DHT), dihydroterpineyl acetate (DHTA), terpineol (TPO), propylene glycol monobutyl ether (PNB), diethylene glycol monobutyl ether acetate (BCA), and diisobutyl ketone (DIBK). The conductive paste according to claim 3, comprising one or more selected types.
The conductive paste contains a dispersant other than the carboxy group-containing polymer dispersant,
The conductive paste according to claim 3, wherein the content of the carboxy group-containing polymer dispersant based on the total amount of the dispersant in the conductive paste is 30% by mass or more.
The conductive paste contains an acid-based dispersant having a mass average molecular weight of less than 2000 as a dispersant other than the carboxyl group-containing polymer dispersant,
The conductive paste according to claim 5, wherein the content of the acidic dispersant based on the total amount of the dispersant in the conductive paste is more than 0% by mass and 70% by mass or less.
The conductive paste according to claim 3, wherein the conductive powder contains one or more metal powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.
The conductive paste according to claim 3, wherein the conductive powder has a number average particle diameter of 0.05 μm or more and 1.0 μm or less.
The conductive paste according to claim 3, wherein the ceramic powder contains barium titanate.
The conductive paste according to claim 3, wherein the ceramic powder has a number average particle diameter of 0.01 μm or more and 0.5 μm or less.
The conductive paste according to claim 3, wherein the content of the ceramic powder is 1% by mass or more and 20% by mass or less.
The conductive paste according to claim 3, wherein the binder resin includes a cellulose resin.
The conductive paste according to claim 2, which is used for internal electrodes of laminated ceramic parts.
The conductive paste according to claim 2, having a viscosity of 2.0 Pa·S or less at a shear rate of 100 sec -1 at a temperature of 25°C.
An electronic component formed using the conductive paste according to claim 2.
It has at least a laminate including a dielectric layer and an internal electrode layer,
A multilayer ceramic capacitor in which the internal electrode layer is formed using the conductive paste according to claim 2.