Carboxy group-containing polymer dispersant, conductive paste, electronic component, and multilayer ceramic capacitor

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

Technical Field

[0001] The present invention relates to a carboxyl group-containing polymer dispersant, a conductive paste, an electronic component, and a multilayer ceramic capacitor.

Background Art

[0002] With the miniaturization and high performance of electronic devices such as mobile phones and digital devices, miniaturization and high capacitance are desired for electronic components including multilayer ceramic capacitors. A multilayer ceramic capacitor has a structure in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated, and by thinning these dielectric layers and internal electrode layers, miniaturization and high capacitance can be achieved.

[0003] A multilayer ceramic capacitor is manufactured, for example, as follows. First, an internal electrode paste (conductive paste) containing a conductive powder, a binder resin, and an organic solvent or the like is printed on the surface of a dielectric green sheet containing a dielectric powder such as barium titanate (BaTiO3) and a binder resin in a predetermined electrode pattern, and the printed materials are stacked in multiple layers to obtain a laminate in which the internal electrodes and the dielectric green sheets are stacked in multiple layers. Next, this laminate is heat-pressed and integrated to form a pressed body. This pressed body is cut, and after performing a de-organic binder treatment in an oxidizing atmosphere or an inert atmosphere, firing is performed to obtain a fired chip. Then, 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 surface of the external electrode to obtain a multilayer ceramic capacitor.

[0004] As a printing method used when printing a conductive paste on a dielectric green sheet, conventionally, the screen printing method has generally been used. However, due to the requirements for miniaturization, thinning, and productivity improvement of electronic devices, it is required to print a finer electrode pattern with high productivity.

[0005] As one of the printing methods for conductive paste, a gravure printing method has been proposed, which is a continuous printing method that fills a recess provided in a printing plate with conductive paste and transfers the conductive paste from the printing plate by pressing it against the surface to be printed. The gravure printing method has a high 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.

[0006] For example, in Patent Document 1, a conductive paste used for forming the internal conductor film in a multilayer ceramic electronic component including a plurality of ceramic layers and an internal conductor film extending along a specific interface between the ceramic layers by gravure printing, which contains a solid component of 30 to 70% by weight including metal powder, an ethyl cellulose resin component with an ethoxy group content of 49.6% or more of 1 to 10% by weight, a dispersant of 0.05 to 5% by weight, and a solvent component as the balance, and the viscosity η at a shear rate of 0.1 (s -1 ) is 1 Pa·s or more, and the viscosity η at a shear rate of 0.02 (s 0.1 ) satisfies the conditions represented by a specific formula, and is a thixotropic fluid, a conductive paste is described. -1 ) is 1 Pa·s or more, and the viscosity η at a shear rate of 0.02 (s 0.02 satisfies the conditions represented by a specific formula, and is a thixotropic fluid, a conductive paste is described.

[0007] Also, in Patent Document 2, a conductive paste used for forming by gravure printing in the same manner as Patent Document 1 above, which contains a solid component of 30 to 70% by weight including metal powder, a resin component of 1 to 10% by weight, a dispersant of 0.05 to 5% by weight, and a solvent component as the balance, and is a thixotropic fluid with a viscosity at a shear rate of 0.1 (s -1 ) of 1 Pa·s or more, and when based on the viscosity at a shear rate of 0.1 (s -1 ), the viscosity change rate at a shear rate of 10 (s -1 ) is 50% or more, a conductive paste is described.

[0008] According to the above Patent Documents 1 and 2, these conductive pastes have a shear rate of 0.1 (s -1) It is a thixotropic fluid with a viscosity of 1 Pa·s or more at [specific condition], and it is said that stable continuous printability at high speed can be obtained in gravure printing, and laminated ceramic electronic components such as laminated ceramic capacitors can be manufactured with good production efficiency.

[0009] Further, Patent Document 3 discloses a conductive paste for internal electrodes of a laminated ceramic capacitor containing conductive powder (A), organic resin (B), organic solvent (C), additive (D), and dielectric powder (E). The organic resin (B) consists of polyvinyl butyral with a degree of polymerization of 10,000 or more and 50,000 or less, and ethyl cellulose with a weight average molecular weight of 10,000 or more and 100,000 or less. The organic solvent (C) consists of propylene glycol monobutyl ether, or 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. The additive (D) consists of a separation inhibitor and a dispersant, and a gravure printing conductive paste is described. According to Patent Document 3, this conductive paste has a viscosity suitable for gravure printing and good drying properties.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] With the miniaturization of electronic components, electrodes, wiring, etc. formed by printing conductive paste are also becoming thinner. To thinly and smoothly apply the conductive paste, a lower viscosity is required. However, when ceramic powders such as barium titanate and conductive powders such as Ni are added to a low-viscosity conductive paste, the difference in sedimentation rates due to the difference in specific gravity of these powders may cause the conductive powder and the ceramic powder to separate.

[0012] For example, when producing a low-viscosity conductive paste, a phenomenon called "white floating" (two-layer separation) may occur, where a white separation layer containing ceramic powder is generated at the top. When the composition in the paste becomes non-uniform in this way, the smoothness of the surface of the dried film after coating cannot be obtained. For example, when used for the internal electrodes of a multilayer ceramic capacitor, there may be cases where short circuits between the internal electrodes or a predetermined capacitance cannot be obtained.

[0013] In addition, as a result of investigations by the present inventors, it has been found that 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 production, tends to be high. In order to obtain a smooth and uniform thin film, it is required to control the viscosity of the paste to be within a certain range. However, pastes with a high viscosity increase ratio over time have problems such as not being able to obtain a smooth printing surface during printing after long-term use, or the need for viscosity adjustment each time after a certain period of use, which complicates the printing process.

[0014] In view of such circumstances, an object of the present invention is to provide a conductive paste that has a low paste viscosity stably over a long period even in a low-viscosity conductive paste, can suppress the separation of the conductive powder and the ceramic powder, and has good smoothness of the surface of the dried film after coating. Another object is to provide a carboxy group-containing polymer dispersant capable of providing such a conductive paste, an electronic component formed using such a conductive paste, and a multilayer ceramic capacitor.

Means for Solving the Problems

[0015] To solve the above problems, the dispersant of the present invention is a carboxyl group-containing polymer dispersant composed of a copolymer of at least one of acrylic acid and methacrylic acid and at least one of an acrylate represented by the following general formula (1) and a methacrylate 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 acrylate and the methacrylate is X:1-X, where X is 0.1 or more and less than 0.4. In the following general formula (1) and the following general formula (2), R1 is a linear or branched alkyl group, and it is a dispersant.

[0016]

Chemical formula

[0017]

Chemical formula

[0018] Also, to solve the above problems, the conductive paste of the present invention is a conductive paste containing the carboxyl group-containing polymer dispersant of the present invention.

[0019] The conductive paste of the present invention further contains conductive powder, ceramic powder, binder resin, and organic solvent, and the content of the carboxyl group-containing polymer dispersant may be 0.01% by mass or more and less than 2.0% by mass.

[0020] The organic solvent may contain one or more selected from the group consisting of dihydroterpineol (DHT), dihydroterpinyl acetate (DHTA), terpineol (TPO), propylene glycol monobutyl ether (PNB), diethylene glycol monobutyl ether acetate (BCA), and diisobutyl ketone (DIBK).

[0021] The conductive paste of the present invention contains a dispersant other than the carboxyl group-containing polymer dispersant, and the content of the carboxyl group-containing polymer dispersant with respect to the total amount of the dispersants in the conductive paste may be 30% by mass or more.

[0022] The conductive paste contains, as a dispersant other than the carboxyl group-containing polymer dispersant, an acid-based dispersant having a mass average molecular weight of less than 2000, and the content of the acid-based dispersant with respect to the total amount of the dispersants in the conductive paste may be more than 0% by mass and 70% by mass or less.

[0023] The conductive powder may contain one or more metal powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.

[0024] The number average particle diameter of the conductive powder may be 0.05 μm or more and 1.0 μm or less.

[0025] The ceramic powder may contain barium titanate.

[0026] The number average particle diameter of the ceramic powder may be 0.01 μm or more and 0.5 μm or less.

[0027] The content of the ceramic powder may be 1% by mass or more and 20% by mass or less.

[0028] The binder resin may contain a cellulose-based resin.

[0029] The conductive paste of the present invention may be used for an internal electrode of a multilayer ceramic component.

[0030] The conductive paste of the present invention has a viscosity at a shear rate of 100 sec -1 at a temperature of 25 °C of 2.0 Pa·S or less.

[0031] Also, 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.

[0032] Also, 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 a multilayer ceramic capacitor formed using the conductive paste of the present invention.

Effect of the Invention

[0033] According to the present invention, even in a low-viscosity conductive paste, a low paste viscosity can be stably maintained over a long period of time, separation between the conductive powder and the ceramic powder can be suppressed, and a conductive paste having good smoothness of the surface of the dried film after coating can be provided. Further, a carboxy group-containing polymer dispersant capable of providing such a conductive paste, an electronic component and a multilayer ceramic capacitor formed using such a conductive paste can be provided. In particular, the conductive paste of the present invention can suppress separation between the conductive powder and the ceramic powder even in a low-viscosity paste, has good smoothness of the surface of the dried film after coating, and has good viscosity stability over a long period of time, so that viscosity adjustment during printing is not required, contributing to simplification of the printing process. In particular, it is effective when used for gravure printing in which low viscosity and high-speed printing are performed.

Brief Description of the Drawings

[0034]

Figure 1

Mode for Carrying Out the Invention

[0035] Hereinafter, an embodiment of the carboxy group-containing polymer dispersant, conductive paste, electronic component, and multilayer ceramic capacitor of the present invention will be described.

[0036] [Carboxy Group-Containing Polymer Dispersant] The carboxy group-containing polymer dispersant of the present invention is a carboxy group-containing polymer dispersant composed of a copolymer of at least one of acrylic acid or methacrylic acid and at least one of an acrylate represented by the following general formula (1) or a methacrylate represented by the following general formula (2), having a mass average molecular weight of 2000 or more and less than 30000, and in terms of molar ratio, the ratio of the total of the acrylic acid and the methacrylic acid to the total of the acrylate and the methacrylate is X:1-X, 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), R1 is a linear or branched alkyl group.

[0037]

Chemical formula

[0038]

Chemical formula

[0039] The inventors of the present invention have found that a low-viscosity conductive paste described later contains a certain amount of a carboxy group-containing polymer dispersant having a mass average molecular weight of 2000 or more, has a small change in viscosity over time and a stable low viscosity, and can suppress the separation of conductive powder and ceramic powder to obtain a smooth dry film.

[0040] The carboxy group-containing polymer dispersant has a carboxy group as an adsorption group to conductive powder or ceramic powder. And by having the structure of a copolymer of at least one of acrylic acid or methacrylic acid and at least one of an acrylate or a methacrylate, it is possible to achieve both solubility in an organic solvent described later and an effect of improving the dispersibility of conductive powder.

[0041] Here, examples of the copolymer include a copolymer of acrylic acid and an acrylic acid ester, a copolymer of acrylic acid and a methacrylic acid ester, a copolymer of methacrylic acid and an acrylic acid ester, a copolymer of methacrylic acid and a methacrylic acid ester, a copolymer of acrylic acid and methacrylic acid with an acrylic acid ester, a copolymer of acrylic acid and methacrylic acid with a methacrylic acid ester, a copolymer of acrylic acid with an acrylic acid ester and a methacrylic acid ester, a copolymer of methacrylic acid with an acrylic acid ester and a methacrylic acid ester, and a copolymer of acrylic acid and methacrylic acid with an acrylic acid ester and a methacrylic acid ester.

[0042] In addition, when acrylic acid and an acrylic acid ester are used in combination, their molar ratio can be adjusted as appropriate. Also, when an acrylic acid ester and a methacrylic acid ester are used in combination, their molar ratio can be adjusted as appropriate.

[0043] Further, by adjusting the ratio between the total (X) of acrylic acid and methacrylic acid and the total (1-X) of acrylic acid esters and methacrylic acid esters in the molar ratio during copolymerization, the solubility in the organic solvent and the dispersibility of the conductive powder change. If the ratio of the total of acrylic acid and methacrylic acid is too low, the amount of carboxy groups acting as adsorption groups for the conductive powder is small, resulting in a decrease in dispersibility. On the other hand, if the ratio of the total of acrylic acid and methacrylic acid is too high, the hydrophilicity of the carboxy group-containing polymer dispersant increases, and the solubility in the organic solvent used for the conductive paste deteriorates.

[0044] Therefore, in terms of molar ratio, there is an appropriate ratio between the total of acrylic acid and methacrylic acid and the total of acrylic acid esters and methacrylic acid esters. That is, when the ratio X of the total of acrylic acid and methacrylic acid is 0.1 or more and less than 0.4, the balance between the solubility in the organic solvent and the effect of improving the dispersibility of the conductive powder is good. As a result, the separation between the conductive powder and the ceramic powder can be suppressed, the viscosity stability over time is good, and a low-viscosity conductive paste with good smoothness of the surface of the dried film after coating can be provided.

[0045] In addition, R1 of the acrylic acid ester and methacrylic acid ester represented by the general formula (1) and the general formula (2) is a linear or branched alkyl group. Here, when R1 is a linear alkyl group, the number of carbon atoms in the carbon chain is preferably 2 or more and 10 or less, and more preferably 2 or more and 4 or less. When the number of carbon atoms in the carbon chain is 1, the carbon chain of the acrylic acid ester or methacrylic acid ester is too short, so when used as a dispersant for the conductive paste, the effect of suppressing the separation of the conductive paste may not be sufficiently exerted, which is not preferable. Further, when the number of carbon atoms in the carbon chain is 11 or more, the carbon chain of the acrylic acid ester or methacrylic acid ester is too long, so when used as a dispersant for the conductive paste, the effect of suppressing the separation of the conductive paste may not be sufficiently exerted, or the surface roughness and density of the dried film after forming the conductive paste into a film by gravure printing or the like may deteriorate, which is not preferable.

[0046] In addition, when R1 is a branched alkyl group, the total number of carbon atoms in R1 is preferably 3 or more and 14 or less, the number of carbon atoms in the straight-chain portion is preferably 2 or more and 10 or less, and the number of carbon atoms in the branched portion is preferably 1 or more and 4 or less. By satisfying these conditions, a good balance is achieved between the solubility in the organic solvent and the effect of improving the dispersibility of the conductive powder. As a result, the separation between the conductive powder and the ceramic powder can be suppressed, the viscosity stability over time is good, and a low-viscosity conductive paste with good smoothness of the surface of the dried film after coating can be provided. On the other hand, when these conditions are not satisfied, when used as a dispersant for the conductive paste, the effect of suppressing the separation of the conductive paste may not be sufficiently exerted, or the surface roughness and density of the dried film after forming the conductive film may deteriorate.

[0047] Further, the mass average molecular weight of the carboxy group-containing polymer dispersant is 2000 or more, and may be 5000 or more, or may be 10000 or more. The mass average molecular weight of the carboxy group-containing polymer dispersant affects the initial viscosity, viscosity increase over time, and separation amount, etc. of the conductive paste using this. Therefore, when the mass average molecular weight is 2000 or more, a stable dispersion effect can be exhibited, and the viscosity increase over time and separation can be sufficiently suppressed. From the viewpoint of suppressing the viscosity increase over time, the upper limit of the mass average molecular weight is not particularly limited, but when the mass average molecular weight is too large, the initial viscosity of the conductive paste itself may become high and it may not be suitable for gravure printing. Therefore, the mass average molecular weight may be 30000 or less. The mass average molecular weight of the carboxy group-containing polymer dispersant can be measured by, for example, GPC (gel permeation chromatography).

[0048] [Conductive Paste] The conductive paste of this embodiment contains the carboxy group-containing polymer dispersant of the present invention. It may further contain a conductive powder, a ceramic powder, a binder resin, and an organic solvent. Hereinafter, each of these components will be described in detail.

[0049] (Conductive Powder) The conductive powder is not particularly limited, and metal powders 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, from the viewpoints of conductivity, corrosion resistance, and cost, powders of Ni or its alloys (Ni alloys) are preferred. As the Ni alloy, for example, an alloy of Ni with 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. The content of Ni in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Also, 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 the debinding process.

[0050] 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 a thin-film laminated ceramic capacitor (laminated ceramic component). For example, the smoothness and density of the dried film are improved. The number average particle diameter is a value obtained from observations using a scanning electron microscope (SEM). It is the average value (SEM average particle diameter) obtained by measuring the particle diameter of each of a plurality of particles from an image observed at a magnification of 10,000 times with the SEM.

[0051] 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 total amount of the conductive paste. When the content of the conductive powder is within the above range, it is excellent in conductivity and dispersibility.

[0052] (Ceramic powder) The ceramic powder is not particularly limited. For example, when it is a paste for internal electrodes of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected according to the type of multilayer ceramic capacitor to be applied. As the ceramic powder, for example, a perovskite-type oxide containing Ba and Ti can be used, and preferably contains barium titanate (BaTiO3).

[0053] As the ceramic powder, a ceramic powder containing barium titanate as the main component and an oxide as the sub-component 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 powder include ceramic powder of a perovskite-type oxide ferroelectric in which Ba atoms or Ti atoms of barium titanate (BaTiO3) are substituted with other atoms such as Sn, Pb, Zr, etc.

[0054] As the ceramic powder used for the conductive paste for 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. Thereby, the generation of cracks due to the shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer in the sintering process is suppressed. Examples of such ceramic powder include oxides such as ZnO, ferrite, PZT, BaO, Al2O3, Bi2O3, R (rare earth element)2O3, TiO2, Nd2O3, etc., in addition to the above perovskite-type oxide containing Ba and Ti. Note that one type of ceramic powder may be used, or two or more types may be used.

[0055] The number average particle diameter of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, preferably in the range of 0.01 μm or more and 0.3 μm or less. When the number average particle diameter of the ceramic powder is within the above range, a sufficiently thin and uniform internal electrode can be formed when used as a conductive paste for an internal electrode. The number average particle diameter is a value obtained from observation by a scanning electron microscope (SEM). It is the average value (SEM average particle diameter) obtained by measuring the particle diameter of each of a plurality of particles from an image observed at a magnification of 50,000 times with an SEM.

[0056] 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 with respect to the entire conductive paste. When the content of the ceramic powder is within the above range, it has excellent dispersibility and sinterability.

[0057] Also, the content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the conductive powder. When the content of the conductive powder is within the above range, it has excellent conductivity and dispersibility.

[0058] (Binder resin) The binder resin is not particularly limited, and known resins can be used. Examples of the binder resin include cellulose resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose; acrylic resins; and acetal resins including butyral resins such as polyvinyl butyral. Among them, from the viewpoints of solubility in solvents, combustion decomposability, etc., it is preferably included cellulose resins, and more preferably included ethyl cellulose. Further, when used as a paste for internal electrodes, from the viewpoint of improving the adhesion strength to the green sheet, it may contain a butyral resin or may be used alone a butyral resin. When the binder resin contains an acetal resin, the viscosity can be easily adjusted to a viscosity suitable for gravure printing, and the adhesion strength to the green sheet can be further improved. The binder resin may contain, for example, 20% by mass or more, and may contain 30% by mass or more of the acetal resin based on the whole binder resin. Also, the binder resin may contain 50% by mass or less of the acetal resin based on the whole binder resin.

[0059] The weight average molecular weight of the binder resin can be appropriately adjusted within the range of 10,000 or more and 200,000 or less according to the required viscosity of the conductive paste.

[0060] The content of the binder resin is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 7% by mass or less based on the whole conductive paste. When the content of the binder resin is within the above range, it is excellent in conductivity and dispersibility.

[0061] The content of the binder resin is preferably 1 part by mass or more and 20 parts by mass or less, and 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, it is excellent in conductivity and dispersibility.

[0062] (Organic solvent) The organic solvent is not particularly limited, and a known organic solvent capable of dissolving the above binder resin and dispersant can be used. Examples of the organic solvent include terpene solvents, glycol ether solvents, acetate solvents, acetic acid ester solvents, ketone solvents, hydrocarbon solvents, and the like. Note that one type of organic solvent may be used, or two or more types may be used.

[0063] Examples of the terpene solvent include terpineol, dihydroterpineol (DHT), dihydroterpinyl acetate, etc. Among them, dihydroterpineol (DHT) is preferred.

[0064] Examples of the glycol ether solvent include (di)ethylene glycol ethers such as diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monhexyl ether, ethylene glycol monhexyl ether, and propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, 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-described binder resin and excellent drying properties.

[0065] Examples of the acetate solvent include glycol ether acetates such as 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, and isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, etc.

[0066] Examples of the acetate solvents include ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate and the like. Examples of the ketone solvents include methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and the like.

[0067] Examples of the hydrocarbon solvents include aliphatic hydrocarbon solvents such as tridecane, nonane, cyclohexane, naphthene solvents, and mineral spirits, and aromatic hydrocarbon solvents such as toluene and xylene. Among them, aliphatic hydrocarbon solvents are preferred, and mineral spirits are more preferred. Mineral spirits may contain a chain saturated hydrocarbon as a main component, and may contain 20% by mass or more of the chain saturated hydrocarbon based on the whole mineral spirits.

[0068] Further, the organic solvent preferably contains one or more selected from the group consisting of dihydroterpineol (DHT), dihydroterpinyl acetate (DHTA), terpineol (TPO), propylene glycol monobutyl ether (PNB), diethylene glycol monobutyl ether acetate (BCA), and diisobutyl ketone (DIBK). By using these solvents, it is possible to achieve both appropriate viscosity and drying rate.

[0069] For example, the organic solvent may contain one or more terpene solvents (a) selected from the group consisting of dihydroterpineol (DHT), dihydroterpinyl acetate (DHTA), and terpineol (TPO), one or more solvents (b) selected from the group consisting of propylene glycol monobutyl ether (PNB) and diethylene glycol monobutyl ether acetate (BCA), and a hydrocarbon solvent.

[0070] The total content of the organic solvent 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, it has excellent conductivity and dispersibility.

[0071] The total content of the 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, with respect to 100 parts by mass of the conductive powder. When the content of the organic solvents is within the above range, excellent conductivity and dispersibility are achieved.

[0072] When the conductive paste contains the terpene-based solvent (a), the total content of the terpene-based solvent (a) may be 5% by mass or more and 40% by mass or less, may be 10% by mass or more and 30% by mass or less, or may be 12% by mass or more and 25% by mass or less, with respect to the total amount of the conductive paste.

[0073] When the conductive paste contains a solvent (b) such as propylene glycol monobutyl ether (PNB), the total content of the solvent (b) may be 3% by mass or more and 20% by mass or less, or may be 5% by mass or more and 20% by mass or less, with respect to the total amount of the conductive paste.

[0074] When the conductive paste contains a hydrocarbon-based solvent, the total content of the hydrocarbon-based solvent may be 1% by mass or more and 20% by mass or less, may be 3% by mass or more and 15% by mass or less, or may be 5% by mass or more and 10% by mass or less, with respect to the total amount of the conductive paste.

[0075] 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, may be 3% by mass or more and 15% by mass or less, or may be 3% by mass or more and 10% by mass or less, with respect to the total amount of the conductive paste.

[0076] (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 or less, more preferably 0.03% by mass or more and 0.5% by mass or less, with respect to 100% by mass of the entire conductive paste. When the carboxyl group-containing polymer dispersant is contained within the above range, the conductive paste can stably have a low-viscosity state for a long period of time, and separation between the conductive powder and the ceramic powder can be suppressed.

[0077] Further, the dispersant may be composed only of the carboxy group-containing polymer dispersant represented by the above general formula (1), but may contain a dispersant other than the carboxy group-containing polymer dispersant as described below. When a dispersant other than the 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, preferably 60% by mass or more, and more preferably 80% by mass or more based on the total amount of the dispersant. The higher the content of the carboxy group-containing polymer dispersant in the total amount of the dispersant, the more the effect of suppressing the separation between the conductive powder and the ceramic powder is improved.

[0078] Also, the conductive paste of the present embodiment may further contain an acid-based dispersant (dispersant having an acidic adsorption group) other than the carboxy group-containing polymer dispersant. Examples of the acid-based dispersant (excluding the above carboxy acid-based polymer dispersant) include acid-based dispersants having a mass average molecular weight of less than 2000. Note that the acid-based dispersant may be used alone or in combination of two or more.

[0079] Examples of the acid-based dispersant having a mass average molecular weight of less than 2000 include carboxylic acid-based dispersants such as higher fatty acids, dicarboxylic acids, polycarboxylic acid-based dispersants, and alkyl monoamine salts. When the conductive paste contains an acid-based dispersant having a mass average molecular weight of less than 2000 together with the carboxy group-containing polymer dispersant, the viscosity may decrease or the dispersibility of ceramic powders such as barium titanate may be further improved. Note that the mass average molecular weight of the acid-based dispersant having a mass average molecular weight of less than 2000 may be 1000 or less.

[0080] The higher fatty acid may be an unsaturated carboxylic acid or a saturated carboxylic acid, and is not particularly limited, but examples include those having 11 or more carbon atoms such as stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid. Among them, oleic acid or stearic acid is preferable as the higher fatty acid.

[0081] Examples of the alkyl monoamine salt type include oleoyl sarcosine, which is a compound of glycine and oleic acid, and amide compounds such as stearic acid amide and lauroyl sarcosine, which use higher fatty acids such as stearic acid or lauric acid instead of oleic acid.

[0082] In addition, when the content of the acid-based dispersant with an average molecular weight of less than 2000 is too high, there is a concern that it may have an adverse effect such as inhibiting the adsorption of the carboxy group-containing polymer dispersant to the metal powder material (filler). Therefore, when used in combination, it is preferable to appropriately adjust the content.

[0083] For example, the content of the acid-based dispersant with a mass average molecular weight of less than 2000 may be more than 0% and 70% or less, preferably 40% or less, and more preferably 20% or less based on 100% by mass of the total amount of the dispersant.

[0084] The dispersant may also include a dispersant other than the acid-based dispersant. Examples of the dispersant other than the acid-based dispersant include basic dispersants, nonionic dispersants, and amphoteric dispersants. These dispersants may be used alone or in combination of two or more.

[0085] Examples of the basic dispersant include aliphatic amines such as laurylamine, rosinamine, cetylamine, myristylamine, stearylamine, and oleylamine.

[0086] In addition, the content of the dispersant (in total) is preferably less than 2.0% by mass based on the entire conductive paste. When the content of the above carboxylic acid-based polymer dispersant or the total content of the dispersant is too high, drying becomes insufficient in the printing process or drying process of the conductive paste, and the internal electrode layer becomes soft, so that lamination deviation may occur in the subsequent lamination process. In addition, the dispersant remaining during firing may vaporize, and internal stress may be generated by the vaporized gas component, or the structure of the laminate may be damaged.

[0087] (Additive) The conductive paste of this embodiment may contain other additives other than the above dispersant as necessary. As other additives, for example, conventionally known additives such as defoamers, plasticizers, surfactants, thickeners, etc. can be used.

[0088] Note that, for example, Patent Document 3 describes a polycarboxylic acid polymer and a salt of polycarboxylic acid as a separation inhibitor for suppressing the separation of conductive powder and dielectric powder. In this specification, such a separation inhibitor is also included in the acid-based dispersant as a substance for improving the dispersibility of inorganic powder in a broad sense.

[0089] (Manufacturing method of conductive paste) The manufacturing method of the conductive paste according to this embodiment is not particularly limited, and conventionally known methods can be used. The conductive paste can be manufactured, for example, by stirring and kneading the above-mentioned respective components with a three-roll mill, ball mill, mixer, etc. Regarding the dicarboxylic acid (separation inhibitor), similar to other materials, it is preferably weighed and added when stirring and kneading with a mixer or the like, but the same effect can be obtained by adding it as a separation inhibitor to the material after the completion of stirring and kneading (dispersion).

[0090] The conductive paste of the present invention has a shear rate of 100 sec at a temperature of 25°C -1 and preferably has a viscosity of 2.0 Pa·S or less. 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 is too high, and the smoothness of the surface of the dried film after coating may be inferior. 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.

[0091] Further, for the conductive paste, it is preferable that the thickness of the white floating layer observed one week after the production of the conductive paste is less than 8% of the thickness of the entire conductive paste, and it may be 5% or less, or may be 2% or less. The smaller the thickness of the white floating layer, the better the effect of suppressing the separation of the conductive powder and the ceramic powder. The thickness of the white floating layer can be measured by the method described in the examples below.

[0092] In addition, the conductive paste of the present 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 the present embodiment can be suitably used for forming the internal electrode layer.

[0093] [Electronic Component] Hereinafter, an example of an electronic component and the like according to the present embodiment will be described with reference to the drawings. In the drawings, it may be schematically represented or the scale may be changed as appropriate. Also, the position, direction, etc. of the members will be described 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 the vertical direction (up and down direction).

[0094] FIGS. 1A and 1B are a perspective view and a side cross-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 laminated, and external electrodes 20.

[0095] An example of a method for manufacturing the multilayer ceramic capacitor 1 using the above conductive paste will be described below. First, the conductive paste is gravure printed on a ceramic green sheet (dielectric green sheet) and dried to form a dry film. After obtaining a laminate by laminating a plurality of ceramic green sheets each having this dry film on the upper surface by pressure bonding, the laminate is fired and integrated to produce a ceramic laminate 10 in which the internal electrode layers 11 and the dielectric layers 12 are alternately laminated. Then, 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 described in more detail below.

[0096] First, a ceramic green sheet, which is an unfired ceramic sheet, is prepared. Examples of this ceramic green sheet include those obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a raw material powder of a predetermined ceramic such as barium titanate, coating the resulting dielectric layer paste in a sheet shape on a support film such as a PET film, and drying to remove the solvent. The thickness of the ceramic green sheet is not particularly limited, but from the viewpoint of the requirement for miniaturization of the multilayer ceramic capacitor, it is preferably 0.05 μm or more and 3 μm or less.

[0097] Next, on one side of this ceramic green sheet, using the gravure printing method, the above-mentioned conductive paste is applied by printing and dried to prepare a plurality of dry films thus formed. The thickness of the dry film is preferably 1 μm or less after drying from the viewpoint of the requirement for thinning of the internal electrode layer 11.

[0098] Next, the ceramic green sheet is peeled from the support film, and after laminating so that the ceramic green sheet and the dry film formed on one side thereof are alternately arranged, a laminate is obtained by a process of simultaneously performing heating and pressurization. A configuration in which protective ceramic green sheets on which the conductive paste is not applied are further arranged on both surfaces of the laminate may also be adopted.

[0099] Next, after cutting the laminate into a predetermined size to form a green chip, the green chip is subjected to a debinding process and fired in a reducing atmosphere to produce a laminated ceramic fired body (ceramic laminate 10). Note that the atmosphere in the debinding process is preferably air or an N2 gas atmosphere. The temperature during the debinding process is, for example, 200°C or higher and 400°C or lower. Also, it is preferable that the holding time of the above temperature during the debinding process is 0.5 hours or more and 24 hours or less. Further, firing is performed in a reducing atmosphere to suppress oxidation of the metal used for the internal electrode layer. The temperature during firing of the laminate is, for example, 1000°C or higher and 1350°C or lower, and the holding time of the temperature during firing is, for example, 0.5 hours or more and 8 hours or less.

[0100] By firing the green chip, the organic binder in the green sheet is completely removed, and the raw material powder of the ceramic is fired to form a ceramic dielectric layer 12. Also, the organic vehicle in the internal electrode layer 11 is removed, and nickel powder or an alloy powder mainly composed of nickel is sintered, melted, and integrated to form an internal electrode, and a laminated ceramic fired body in which a plurality of dielectric layers 12 and internal electrode layers 11 are alternately laminated is formed. Note that from the viewpoint of taking in oxygen into the interior of the dielectric layer to improve reliability and suppressing re-oxidation of the internal electrode, an annealing process may be performed on the laminated ceramic fired body after firing.

[0101] Then, a pair of external electrodes 20 are provided on the produced laminated ceramic fired body to manufacture a laminated ceramic capacitor 1. For example, the external electrode 20 includes an external electrode layer 21 and a plating layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. Note that as the material of the external electrode 20, for example, copper, nickel, or an alloy thereof can be preferably used. Note that the electronic component is not limited to a laminated ceramic capacitor, and electronic components other than laminated ceramic capacitors such as varistors can also be used.

Example

[0102] Hereinafter, the present invention will be described in detail based on examples and comparative examples, but the present invention is not limited by the examples at all.

[0103] [Evaluation method] (Viscosity of conductive paste) The viscosity of the conductive paste was measured using a rheometer (manufactured by Anton Paar Japan Co., Ltd.: Rheometer MCR302). The viscosity was measured using a cone plate with a cone angle of 1° and a diameter of 25 mm under the condition of a shear rate of 100 sec -1 The value measured under these conditions was used.

[0104] Also, the viscosity of the conductive paste was measured at 1 day and 1 month after production under the temperature condition of 25°C. The measured value at 1 day was used as the initial viscosity, and the ratio of the measured value at 1 month to the initial viscosity (measured value at 1 month / measured value at 1 day × 100) was evaluated as the thickening ratio over time. In Table 1, for the determination of the initial viscosity, a value of 0.2 Pa·s or more and 2.0 Pa·s or less was evaluated as "〇", and a value higher than 2.0 Pa·s was evaluated as "×". For the thickening ratio over time, a value less than 130 was evaluated as "〇" (sufficient viscosity stability), and a value of 130 or more was evaluated as "×" (insufficient viscosity stability).

[0105] (White floating) 20 g of the conductive paste immediately after production was allowed to stand at room temperature in a glass bottle (diameter φ30 × height 65 mm). After 1 week, the appearance of the conductive paste was visually observed, and the ratio of the observed white floating was measured. The ratio of white floating (%) was calculated by (thickness of the white floating layer / thickness of the entire paste amount) * 100. In Table 1, for the determination of the ratio of white floating (%), a value less than 5% was evaluated as "〇" (good separation suppression effect), a value of 5% or more and less than 8% was evaluated as "△" (there is a separation suppression effect), and a value of 8% or more was evaluated as "×" (insufficient separation suppression effect).

[0106] (Surface roughness) After applying the prepared conductive paste on a glass substrate with an applicator to a wet film thickness of 10 μm, a drying treatment was performed at 300 °C for 10 minutes in an air atmosphere to produce a dried film. The surface roughness of the produced dried film was measured with a laser microscope (VK-X130 manufactured by Keyence Corporation) to measure the average roughness of the dried film in a measurement range of 200 × 250 μm, and the measurement was repeated randomly at 5 locations. The average value of the obtained values (arithmetic mean height Sa) was taken as the average roughness of the conductive paste dried film. In Table 1, for the determination of surface roughness, less than 0.065 μm was evaluated as "〇" (the surface of the dried film is smooth), and 0.065 μm or more was evaluated as "×" (the surface of the dried film is not smooth).

[0107] In addition, in the item of comprehensive determination in Table 1, when all the determinations of the conducted tests were "〇" determinations, it was determined as "〇" (qualified), and when there was even one "×" determination among the conducted tests, it was determined as "×" (unqualified).

[0108] [Materials Used] [Conductive Powder] As the conductive powder, Ni powder (SEM average particle diameter 0.2 μm) was used.

[0109] [Ceramic Powder] As the ceramic powder, barium titanate (BaTiO3; SEM average particle diameter 0.10 μm) was used.

[0110] [Binder Resin] As the binder resin, polyvinyl butyral and ethyl cellulose were used.

[0111] [Dispersant] A copolymer of an acrylate having a linear or branched alkyl group (general formula (1)) and acrylic acid, a carboxyl group-containing polymer dispersant having a mass average molecular weight of 2000 or more, an acid-based low molecular weight dispersant not containing a polymer of acrylic acid and an acrylate for comparison, and a carboxyl group-containing polymer dispersant having a mass average molecular weight smaller or larger than that of the examples were used. The ratio (X) of acrylic acid in the molar ratio during copolymerization, the number of carbon atoms of the alkyl group, the structure of the alkyl group, the name of the acrylate, the mass average molecular weight, and the content of the carboxyl group-containing polymer dispersant in the conductive paste are shown in Table 1.

[0112] As a synthesis example of the carboxyl group-containing polymer dispersant, the synthesis procedure of the carboxyl group-containing polymer dispersant of Example 1 is shown below. For Examples 2 to 11, Comparative Example 1, Comparative Examples 4 and 5, the molar ratio of acrylic acid and acrylate was changed so that the structure of the alkyl group of the acrylate and the ratio (X) of acrylic acid were changed, and the synthesis temperature, synthesis time, and addition amount of the chain transfer agent were adjusted. Synthesized in the same manner as the following synthesis procedure.

[0113] Acrylic acid (12.2 mmol) and acrylate (2-ethylhexyl acrylate, 48.8 mmol) as the main raw material monomers, AIBN (0.603 mmol) as the polymerization initiator, dodecanethiol (0.722 mmol) as the chain transfer agent, and 50 mL of 1,4-dioxane as the solvent were added to a three-necked flask. After bubbling the solvent with nitrogen in an ice bath, it was maintained at 65 °C for 12 hours while stirring under a nitrogen atmosphere. Then, methanol was added for reprecipitation, and decantation by centrifugation was repeated three times. Finally, it was dissolved in benzene and then freeze-dried to obtain a polymer dispersant. The obtained polymer dispersant was analyzed by NMR (nuclear magnetic resonance apparatus) and SEC (size exclusion chromatography) to analyze the ratio (X) of acrylic acid and the mass average molecular weight. Note that 2-mercaptoethanol can also be used as the chain transfer agent.

[0114] (organic solvent) As the organic solvent, dihydroterpineol (DHT) was used as the main solvent, and mineral spirit and propylene glycol monobutyl ether (PNB) were used as auxiliary solvents.

[0115] [Example 1] 50% by mass of conductive powder, 12.5% by mass of ceramic powder, 0.3% by mass of a carboxy group-containing polymer dispersant (acrylic acid ratio (X) 0.1, carbon chain number of the alkyl group having a branched chain 8, mass average molecular weight about 25,000), 2.5% by mass of a binder resin (breakdown: 1.75% by mass of polyvinyl butyral resin, 0.75% by mass of ethyl cellulose), and the balance an organic solvent composed of DHT, mineral spirit and PNB (DHT:mineral spirit:PNB = 53:20:27 by mass ratio) were added and formulated so as to be 100% by mass in total. These materials were mixed and dispersed to prepare the conductive paste of Example 1.

[0116] For the obtained conductive paste, measurement of the initial viscosity, calculation of the viscosity ratio over time, observation of white blooming, and measurement of the surface roughness of the dried film were performed. Table 1 shows the evaluation results together with the detailed conditions of the additives.

[0117] [Examples 2 to 11] The carboxy group-containing polymer dispersant was changed from the carboxy group-containing polymer dispersant of Example 1 to the carboxy group-containing polymer dispersant shown in Table 1 in terms of acrylic acid ratio x, carbon number in the alkyl group of the acrylic acid ester, presence or absence of branching in the carbon chain of the alkyl group, and mass average molecular weight. In Examples 10 and 11, the addition amount of the carboxy group-containing polymer dispersant was further changed, and conductive pastes were prepared and evaluated in the same manner as in Example 1 except that the addition amount of the above organic solvent was adjusted so as to be 100% by mass as the conductive paste. Table 1 shows the conditions of the dispersant and the evaluation results.

[0118] [Comparative Examples 1 to 5] As Comparative Example 1, a conductive paste was prepared in the same manner as in Example 1, except that a dispersant having a ratio (X) of acrylic acid outside the scope of the present invention was used at 0.05 although it was a carboxy group-containing polymer dispersant. Further, in Comparative Example 2, a dicarboxylic acid having an average molecular weight of 370 was used as an acid-based low molecular weight dispersant that has been generally and widely used in the past, and in Comparative Example 3, a maleic anhydride copolymer having a mass average molecular weight of 50,000 was used as a carboxylic acid-based polymer dispersant, and a conductive paste was prepared in the same manner as in Example 1. Then, as Comparative Example 4, a conductive paste was prepared in the same manner as in Example 1, except that the same carboxy group-containing polymer dispersant used in Example 5 was added in a content (0.005% by mass) that does not meet the scope of the present invention. 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 carboxy group-containing polymer dispersant was 1000. Then, evaluations were also conducted for Comparative Examples 1 to 5 in the same manner as for the examples. The conditions of the dispersants and the evaluation results are shown in Table 1.

[0119] [Table 1]

[0120] (Evaluation Results) The conductive paste of the example has a time-dependent thickening ratio after one month of 125 or less and a viscosity after one month of 2.0 Pa·s or less, indicating that it has excellent viscosity stability over time. Also, the ratio of white floating after one week generated by storage is sufficiently small at 5% or less, indicating that it has a separation suppression effect.

[0121] Moreover, 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 carboxy group-containing polymer dispersant increases, the more the thickening over time and the white floating are suppressed, and the surface of the dried film tends to become smoother. Further, from the results of Examples 4 to 7, the shorter the carbon number of the alkyl chain length of the acrylate ester, the higher the smoothness of the surface of the dried film tends to be. And from the results of Examples 5, 8 to 9, within the scope of the present invention, the larger the mass average molecular weight of the carboxy group-containing polymer dispersant, the more the thickening over time and the white floating are suppressed, and the surface of the dried film tends to become smoother. Incidentally, from the results of Examples 5, 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 larger the content of the carboxy group-containing polymer dispersant, the more the thickening over time and the white floating are suppressed, and the surface of the dried film tends to become smoother.

[0122] The conductive paste of Comparative Example 1 has a structure equivalent to that of the dispersant of the present invention, but since the proportion (X) of acrylic acid is less than the scope of the present invention, the initial viscosity cannot be suppressed low, and the roughness of the surface of the dried film after drying becomes high, which is not preferable. Next, in the conductive paste of Comparative Example 2, by using a low molecular weight acid-based dispersant, the viscosity is sufficiently stable and the surface roughness of the dried film after drying is also good, but the proportion of white floating exceeds the allowable amount. And in the conductive paste of Comparative Example 3, although a carboxy group-containing polymer dispersant is used, the thickening over time cannot be suppressed, and the proportion of white floating and the surface roughness of the dried film after drying are also poor, and it is not suitable for gravure printing. Further, in the conductive paste of Comparative Example 4, although the dispersant of the present invention is used, since the content is less than the scope of the present invention, the effect of the additive is not sufficiently exhibited, the initial viscosity is also high, and the roughness of the surface of the dried film after drying becomes high, which is not preferable. In the conductive paste of Comparative Example 5, since the mass average molecular weight of the carboxy group-containing polymer dispersant is small, the dispersion performance is inferior, and the roughness of the surface of the dried film after drying becomes high, which is not preferable.

[0123] Note that the technical scope of the present invention is not limited to the aspects described in the above embodiments and the like. One or more of the requirements described in the above embodiments and the like may be omitted. Also, the requirements described in the above embodiments and the like can be combined as appropriate. Further, to the extent permitted by law, the disclosures of all the documents cited in the above embodiments and the like are incorporated by reference and made part of the description herein.

Industrial Applicability

[0124] The conductive paste of the present invention stably has a viscosity suitable for gravure printing over a long period of time, and the separation between the conductive powder and the ceramic powder is sufficiently small, and the roughness of the surface of the dried film after drying is also sufficiently 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 such as mobile phones and digital devices that are becoming smaller, and can be suitably used as a conductive paste for gravure printing.

Explanation of Reference Numerals

[0125] 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

1. At least one of acrylic acid and methacrylic acid, A carboxy group-containing polymer dispersant comprising a copolymer of an acrylic acid ester represented by the following general formula (1) and a methacrylic acid ester represented by the following general formula (2), The mass average molecular weight is 2,000 or more and less than 30,000, a molar ratio of the sum of the acrylic acid and the methacrylic acid to the sum of the acrylic acid ester and the methacrylic acid ester is X:1-X, where X is 0.1 or more and less than 0.4; In the following general formula (1) and the following general formula (2), R １ is a linear or branched alkyl group, a dispersant. 【Chemical 1】 [Chemical 2]

2. A conductive paste comprising the carboxy group-containing polymer dispersant according to claim 1.

3. Further comprising a conductive powder, a ceramic powder, a binder resin and an organic solvent; The conductive paste according to claim 2 , wherein the content of the carboxy group-containing polymer dispersant is 0.01% by mass or more and less than 2.0% by mass.

4. The organic solvent is selected from the group consisting of dihydroterpineol (DHT), dihydroterpineol 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 at least one selected from the group consisting of dihydroterpineol (DHT), dihydroterpineol acetate (DHTA), terpineol (TPO), propylene glycol monobutyl ether (PNB), diethylene glycol monobutyl ether acetate (BCA), and diisobutyl ketone (DIBK).

5. 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 carboxyl group-containing polymer dispersant relative to the total amount of dispersants in the conductive paste is 30 mass % or more.

6. 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, The conductive paste according to claim 5 , wherein a content of the acid-based dispersant relative to a total amount of dispersants in the conductive paste is more than 0 mass % and not more than 70 mass %.

7. The conductive paste according to claim 3 , wherein the conductive powder contains one or more metal powders selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof.

8. The conductive paste according to claim 3 , wherein the number average particle size of the conductive powder is 0.05 μm or more and 1.0 μm or less.

9. The conductive paste of claim 3 , wherein the ceramic powder comprises barium titanate.

10. The electrically conductive paste according to claim 3, wherein the number average particle diameter of the ceramic powder is 0.01 μm or more and 0.5 μm or less.

11. The electrically 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.

12. The electrically conductive paste according to claim 3, wherein the binder resin contains a cellulose-based resin.

13. The electrically conductive paste according to claim 2, which is for an internal electrode of a multilayer ceramic component.

14. The viscosity at a shear rate of 100 sec⁻¹ at a temperature of 25°C is 2.0 Pa·s or less, the conductive paste according to claim 2. －１ ​

15. An electronic component formed using the electrically conductive paste according to claim 2.

16. Having at least a laminate in which a dielectric layer and an internal electrode layer are laminated, The internal electrode layer is a multilayer ceramic capacitor formed using the electrically conductive paste according to claim 2.

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