Conductive paste for gravure printing, electronic components, and multilayer ceramic capacitors

Abstract

This invention provides a conductive paste for gravure printing that can reduce surface waviness of the dried film. [Solution] A conductive paste for gravure printing comprising conductive powder, ceramic powder, dispersant, binder resin and organic solvent, wherein the organic solvent comprises a first organic solvent, The first organic solvent is at least one selected from the group consisting of isobornyl acetate, methyl isobutyl ketone, and diisobutyl ketone, in a conductive paste for gravure printing.

Description

[Technical Field]

[0001] The present invention relates to a conductive paste for gravure printing, electronic components, and multilayer ceramic capacitors. [Background technology]

[0002] With the miniaturization and increased performance of electronic devices such as mobile phones and digital equipment, there is a demand for smaller and higher-capacitance electronic components, including multilayer ceramic capacitors. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and miniaturization and increased capacitance can be achieved by thinning these dielectric layers and internal electrode layers.

[0003] Multilayer ceramic capacitors are manufactured, for example, as follows: First, a conductive paste for internal electrodes is printed in a predetermined electrode pattern onto the surface of a ceramic green sheet containing dielectric powder such as barium titanate (BaTiO3) and a binder resin, and then dried to form a dry film. Next, the dry film and the ceramic green sheet are stacked alternately to obtain a laminate. Then, this laminate is heated and compressed to form a bonded body. This bonded body is cut, subjected to a de-organic binder treatment in an oxidizing or inert atmosphere, and then fired to obtain a fired chip. Next, paste for external electrodes 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 electrodes to obtain a multilayer ceramic capacitor.

[0004] While screen printing has traditionally been the most common printing method used to print conductive paste onto dielectric green sheets, the demands for miniaturization, thinner films, and improved productivity of electronic devices necessitate the printing of finer electrode patterns with higher productivity.

[0005] One proposed printing method for conductive paste is gravure printing, a continuous printing method in which conductive paste is filled into recesses in a printing plate and then pressed onto the surface to be printed, thereby transferring the conductive paste from the plate. Gravure printing offers high printing speed and excellent productivity. When using gravure printing, it is necessary to appropriately select the binder resin, dispersant, solvent, etc., in the conductive paste to adjust its viscosity and other properties to a range suitable for gravure printing.

[0006] For example, Patent Document 1 describes a conductive paste used for forming an internal conductive film in a multilayer ceramic electronic component comprising a plurality of ceramic layers and an internal conductive film extending along a specific interface between the ceramic layers by gravure printing, comprising 30 to 70% by weight of a solid component containing metal powder, 1 to 10% by weight of an ethylcellulose resin component with an ethoxy group content of 49.6% or more, 0.05 to 5% by weight of a dispersant, and a solvent component as the remainder, with a shear rate of 0.1 (s -1 ) viscosity η 0.1 The pressure is 1 Pa·s or greater, and the shear rate is 0.02 (s) -1 ) viscosity η 0.02 A conductive paste is described that is a thixotropic fluid satisfying the conditions expressed by a specific formula.

[0007] Furthermore, Patent Document 2 describes a conductive paste used for formation by gravure printing, similar to Patent Document 1, comprising 30 to 70% by weight of a solid component containing metal powder, 1 to 10% by weight of a resin component, 0.05 to 5% by weight of a dispersant, and a solvent component as the remainder, with a shear rate of 0.1 (s -1 A thixotropic fluid with a viscosity of 1 Pa·s or more at ) and a shear rate of 0.1 (s -1 When the viscosity at ) is used as the reference, the shear rate is 10 (s -1 A conductive paste is described in which the viscosity change rate at ) is 50% or more.

[0008] According to the above-mentioned Patent Documents 1 and 2, these conductive pastes have a shear rate of 0.1 (s -1It is a thixotropic fluid with a viscosity of 1 Pa·s or more at 3°C, and it is said that stable continuous printing at high speeds can be obtained in gravure printing, enabling the manufacture of multilayer ceramic electronic components such as multilayer ceramic capacitors with good production efficiency.

[0009] Furthermore, Patent Document 3 describes a conductive paste for internal electrodes of a multilayer ceramic capacitor, comprising a conductive powder (A), an organic resin (B), an organic solvent (C), an additive (D), and a dielectric powder (E), wherein the organic resin (B) consists of polyvinyl butyral with a degree of polymerization of 10,000 to 50,000 and ethyl cellulose with a weight-average molecular weight of 10,000 to 100,000; the organic solvent (C) consists of propylene glycol monobutyl ether, 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 spirits; and the additive (D) consists of a separation inhibitor and a dispersant, with the separation inhibitor being a polycarboxylic acid polymer or a salt of polycarboxylic acid. According to Patent Document 3, this conductive paste has a viscosity suitable for gravure printing, improved uniformity and stability of the paste, and good drying properties. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2003-187638 [Patent Document 2] Japanese Patent Publication No. 2003-242835 [Patent Document 3] Japanese Patent Publication No. 2012-174797 [Overview of the project] [Problems that the invention aims to solve]

[0011] Conductive pastes used in gravure printing require low viscosity. However, low-viscosity conductive pastes tend to exhibit greater surface waviness when dried compared to high-viscosity conductive pastes used in screen printing and other applications. When such conductive pastes are used to form the internal electrode layer of a multilayer ceramic capacitor, the resulting thickness of the internal electrode layer varies, reducing the reliability of the multilayer ceramic capacitor.

[0012] In view of these circumstances, the present invention aims to provide a conductive paste for gravure printing that exhibits minimal surface waviness on the dried film. [Means for solving the problem]

[0013] In a first aspect of the present invention, a conductive paste for gravure printing is provided, comprising conductive powder, ceramic powder, a dispersant, a binder resin, and an organic solvent, wherein the organic solvent contains at least one selected from the group consisting of isobornyl acetate, methyl isobutyl ketone, and diisobutyl ketone.

[0014] Further, the conductive paste preferably further contains a dicarboxylic acid in an amount of 0.05% by mass or more and less than 3.0% by mass based on the total amount of the conductive paste. Also, the organic solvent is preferably contained in an amount of 10% by mass or more and 60% by mass or less based on the total amount of the conductive paste. Also, the dispersant is preferably contained in an amount of 0.01% by mass or more and 3.0% by mass or less based on the total amount of the conductive paste. Also, the dispersant preferably contains an acid-based dispersant. Also, the conductive powder preferably contains at least one metal powder selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Also, the conductive powder preferably has an average particle size of 0.05 μm or more and 1.0 μm or less. Also, the ceramic powder preferably contains barium titanate. The ceramic powder preferably has an average particle size of 0.01 μm or more and 0.5 μm or less. Also, the ceramic powder is preferably contained in an amount of 1% by mass or more and 20% by mass or less based on the total amount of the conductive paste. Also, the binder resin preferably contains a cellulose-based resin. Also, the conductive paste preferably has a viscosity of 3 Pa·S or less at a shear rate of 100 sec-1 and a viscosity of 1 Pa·S or less at a shear rate of 10,000 sec-1. Also, it is preferable that the average height (Wc) of the waviness curve element of the dried film obtained by gravure printing the conductive paste under the conditions of a printing speed of 30 m / min and a film thickness of 0.50 μm or more and 2 μm or less is 0.5 μm or less.

[0015] In a second aspect of the present invention, an electronic component formed using the above conductive paste is provided.

[0016] In a third aspect of the present invention, a multilayer ceramic capacitor is provided that 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 above conductive paste for gravure printing.

Advantages of the Invention

[0017] Even when the conductive paste of the present invention is gravure printed to form a dry film, the undulation on the surface of the dry film can be reduced. Further, the internal electrode layer formed using the conductive paste of the present invention can produce a highly reliable multilayer ceramic capacitor with high productivity even when forming a thinned electrode.

Brief Description of Drawings

[0018] [Figure 1] FIG. 1 is a perspective view and a cross-sectional view showing a multilayer ceramic capacitor according to an embodiment.

Embodiments for Carrying Out the Invention

[0019] [Conductive Paste] The conductive paste of the present embodiment contains conductive powder, ceramic powder, a dispersant, a binder resin, and an organic solvent. Hereinafter, each component will be described in detail.

[0020] (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, from the viewpoints of conductivity, corrosion resistance, and cost, powder of Ni or its alloy (hereinafter sometimes referred to as "Ni powder") is preferable. As the Ni alloy, for example, an alloy of Ni with at least one or more elements 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 mass% or more, preferably 80 mass% or more. Further, the Ni powder may contain about several hundred ppm of element S in order to suppress the sudden gas generation due to the partial thermal decomposition of the binder resin during the debinding process.

[0021] The average particle size of the conductive powder is preferably 0.05 μm to 1.0 μm, and more preferably 0.1 μm to 0.5 μm. When the average particle size 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 for example, the smoothness and density of the dried film are improved. The average particle size is a value obtained from observation using a scanning electron microscope (SEM), and is the average value obtained by measuring the particle size of multiple individual particles from an image observed with an SEM at a magnification of 10,000x (SEM average particle size).

[0022] The conductive powder content is preferably 30% by mass or more and less than 70% by mass, and more preferably 40% by mass or more and 60% by mass or less, relative to the total conductive paste. When the conductive powder content is within the above range, the conductivity and dispersibility are excellent.

[0023] (Ceramic powder) The ceramic powder is not particularly limited, and for example, in the case of a paste for the internal electrodes of a multilayer ceramic capacitor, a known ceramic powder can be appropriately selected depending on the type of multilayer ceramic capacitor to be used. As the ceramic powder, for example, a perovskite-type oxide containing Ba and Ti can be used, and preferably contains barium titanate (BaTiO3).

[0024] As the ceramic powder, a ceramic powder mainly composed of barium titanate and containing oxides as minor components may be used. Examples of oxides include oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and one or more rare earth elements. Alternatively, as the ceramic powder, a perovskite-type oxide ferroelectric ceramic powder may be used, in which the Ba or Ti atoms of barium titanate (BaTiO3) are substituted with other atoms, such as Sn, Pb, or Zr.

[0025] When used as a conductive paste for internal electrodes, the ceramic powder may have the same composition as the dielectric ceramic powder that constitutes the green sheet of a multilayer ceramic capacitor (electronic component). This suppresses crack generation due to a mismatch in shrinkage at the interface between the dielectric layer and the internal electrode layer during the sintering process. Examples of such ceramic powders include oxides such as ZnO, ferrite, PZT, BaO, Al2O3, Bi2O3, R(rare earth element)2O3, TiO2, and Nd2O3. One type of ceramic powder may be used, or two or more types may be used.

[0026] The average particle size of the ceramic powder is, for example, 0.01 μm to 0.5 μm, preferably in the range of 0.01 μm to 0.3 μm. Because the average particle size of the ceramic powder is within this range, when used as a paste for internal electrodes, it is possible to form sufficiently fine, thin, and uniform internal electrodes. The average particle size is determined from observation using a scanning electron microscope (SEM), and is the average value obtained by measuring the particle size of multiple individual particles from an image observed at a magnification of 50,000x with an SEM (SEM average particle size).

[0027] The ceramic powder content is preferably 1% to 20% by mass, and more preferably 3% to 15% by mass, relative to the total conductive paste. When the ceramic powder content is within the above range, the dispersibility and sinterability are excellent.

[0028] Furthermore, the ceramic powder content is preferably 1 to 30 parts by mass, and more preferably 3 to 30 parts by mass, per 100 parts by mass of conductive powder.

[0029] (Binder resin) The binder resin is not particularly limited, and any known resin can be used. Examples of binder resins include cellulose-based resins such as methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, and nitrocellulose, acrylic resins, and butyral-based resins such as polyvinyl butyral. Among these, it is preferable to include a cellulose-based resin, and more preferably to include ethylcellulose, from the viewpoint of solubility in solvents and combustion decomposition.

[0030] Furthermore, when used as a paste for internal electrodes, the binder resin may contain a butyral resin or be used alone to improve the adhesive strength with the green sheet. When the binder resin contains a butyral resin, the viscosity can be easily adjusted to a level suitable for gravure printing, and the adhesive strength with the green sheet can be further improved. For example, the binder resin may contain 20% by mass or more, or 30% by mass or more, of the total binder resin.

[0031] When the binder resin contains cellulose-based resin and butyral-based resin, it may contain acetal resin in an amount of 20% to 80% by mass, 30% to 80% by mass, or 30% to 60% by mass, relative to the total content (100% by mass) of the cellulose-based resin and butyral-based resin.

[0032] Furthermore, the degree of polymerization and weight-average molecular weight of the binder resin can be appropriately adjusted within the above range depending on the required viscosity of the conductive paste.

[0033] For example, when a cellulose-based resin is included as the binder resin, the weight-average molecular weight (Mw) may be between 10,000 and 300,000, between 30,000 and 200,000, or between 50,000 and 150,000. When the Mw of the cellulose-based resin is within the above range, the viscosity of the conductive paste can be adjusted to a suitable range while reducing the waviness of the surface of the dried film.

[0034] Furthermore, the hydroxyl value of the cellulose resin is not particularly limited, but is preferably 0.1 mg KOH / g or more and 15 mg KOH / g or less, more preferably 0.5 mg KOH / g or more and 7 mg KOH / g or less, and even more preferably 1.5 mg KOH / g or more and 3 mg KOH / g or less. When the hydroxyl value of the cellulose resin is within the above range, it exhibits excellent dispersibility of conductive powders and ceramic powders, and is therefore suitable for use in conductive pastes for gravure printing. Note that the hydroxyl value is a value measured in accordance with JIS K 0070 and represents the number of mg of potassium hydroxide corresponding to hydroxyl groups in 1 g of sample.

[0035] Furthermore, the ethoxyl group content of the cellulose resin is not particularly limited, but may be, for example, 40% by mass or more and 55% by mass or less, 45% by mass or more and 52% by mass or less, or 48% by mass or more and 50% by mass or less.

[0036] For example, when a butyral resin is included as the binder resin, the weight-average molecular weight (Mw) may be between 30,000 and 300,000, between 50,000 and 200,000, or between 100,000 and 150,000. When the Mw of the butyral resin is within the above range, it is possible to adjust the viscosity of the conductive paste to a suitable range while reducing the waviness of the surface of the dried film.

[0037] The binder resin content is preferably 0.5% to 10% by mass, and more preferably 1% to 7% by mass, relative to the total conductive paste. When the binder resin content is within the above range, the conductivity and dispersibility are excellent.

[0038] The binder resin content is preferably 1 to 20 parts by mass, and more preferably 1 to 14 parts by mass, per 100 parts by mass of conductive powder.

[0039] (Organic solvents) The conductive paste according to this embodiment contains at least one organic solvent selected from the group consisting of isobornyl acetate (IBA), methyl isobutyl ketone (MIBK), and diisobutyl ketone (DIBK) (hereinafter referred to as the "first organic solvent"), preferably containing either isobornyl acetate and / or diisobutyl ketone, and more preferably containing isobornyl acetate. By containing the above organic solvent (hereinafter also referred to as the "first organic solvent"), the conductive paste can reduce waviness on the film surface when a dried film is formed. The first organic solvent may be one type or two or more types. Furthermore, if the first organic solvent contains two or more types, it may also contain isobornyl acetate and diisobutyl ketone.

[0040] The content of the first organic solvent may be 3% to 60% by mass, 5% to 40% by mass, 10% to 30% by mass, or 10% to 20% by mass, relative to the total amount of conductive paste. Furthermore, even if the content of the first organic solvent is 5% to 10% by mass, waviness on the surface of the dried film can be reduced.

[0041] Furthermore, if the first organic solvent contains isobornyl acetate (IBA), the isobornyl acetate content is preferably 4% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more, based on the total amount of conductive paste. When the isobornyl acetate content is within the above range, the waviness of the film surface when a dried film is formed can be further reduced. In addition, the isobornyl acetate content may be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less, based on the total amount of conductive paste.

[0042] Furthermore, when the first organic solvent contains diisobutyl ketone (DIBK), the diisobutyl ketone content is preferably 4% by mass or more, and more preferably 5% by mass or more, based on the total amount of conductive paste. When the diisobutyl ketone content is within the above range, the waviness of the film surface when a dried film is formed can be reduced, and the viscosity can be easily adjusted to one suitable for gravure printing. In addition, when diisobutyl ketone (DIBK) is included, the drying properties are excellent, and the process of applying the conductive paste onto a green sheet by gravure printing and drying it (film formation process) can be shortened. Furthermore, the diisobutyl ketone content may be 30% by mass or less, 20% by mass or less, 10% by mass or less, or 7% by mass or less, based on the total amount of conductive paste.

[0043] Furthermore, the organic solvent may include an organic solvent other than the first organic solvent. The organic solvent other than the first organic solvent (other organic solvent) is not particularly limited, and any known organic solvent that can dissolve the above-mentioned binder resin can be used. Examples of other organic solvents include glycol ether solvents, acetate solvents, ketone solvents, terpene solvents, and petroleum hydrocarbon solvents including aliphatic hydrocarbon solvents. Furthermore, one type of other organic solvent may be used, or two or more types may be used.

[0044] 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, as well as propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether (PNB).

[0045] Examples of acetate-based solvents include isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, glycol ether acetates such as ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy-3-methylbutyl acetate, and 1-methoxypropyl-2-acetate, as well as ethyl acetate, propyl acetate, isobutyl acetate, and butyl acetate.

[0046] Examples of ketone-based solvents include methyl ethyl ketone.

[0047] Examples of terpene solvents include terpineol, dihydroterpineol (DHT), and dihydroterpinyl acetate.

[0048] Examples of petroleum-based hydrocarbon solvents containing aliphatic hydrocarbon solvents include solvents containing tridecane, nonane, cyclohexane, mineral spirits (MA), and naphthenic solvents. Among these, the inclusion of mineral spirits is preferred, and mineral spirits may be included as the main component (the solvent with the highest content among the petroleum-based hydrocarbon solvents). Furthermore, the mineral spirits may contain chain-type saturated hydrocarbons as the main component, and may contain chain-type saturated hydrocarbons in an amount of 20% by mass or more relative to the total mineral spirits.

[0049] Other organic solvents may include, for example, terpene solvents and aliphatic hydrocarbon solvents, or may consist solely of terpene solvents or solely of aliphatic hydrocarbon solvents. Furthermore, if other organic solvents include, for example, terpene solvents, the content of terpene solvents may be 5% by mass or more and 40% by mass or 10% by mass or more and 25% by mass or less, based on the total amount of conductive paste. Furthermore, if other organic solvents include, for example, aliphatic hydrocarbon solvents, the content of aliphatic hydrocarbon solvents may be 5% by mass or more and 25% by mass or less, based on the total amount of conductive paste, based on the total amount of conductive paste.

[0050] The content of the organic solvent (total) is preferably 20% to 60% by mass, and more preferably 25% to 45% by mass, relative to the total amount of conductive paste. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

[0051] The content of the organic solvent is preferably 50 parts by mass to 130 parts by mass, and more preferably 60 parts by mass to 90 parts by mass, per 100 parts by mass of conductive powder. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

[0052] (Dispersant) As a dispersant, known dispersants can be used. For example, an acidic dispersant may be included as the dispersant. Furthermore, as an acidic dispersant, dispersants having carboxyl groups other than dicarboxylic acid, as described later, may also be included. In this specification, as described later, dicarboxylic acid is defined separately from dispersants, focusing on the effect of dicarboxylic acid on suppressing the separation of conductive powder and ceramic powder.

[0053] For example, when a comb-type carboxylic acid is used as a dispersant, the dispersibility of the conductive paste is improved by including the comb-type carboxylic acid. Note that one type of dispersant may be used, or two or more types may be used. The conductive paste according to this embodiment exhibits improved dispersibility due to the inclusion of a dispersant.

[0054] The dispersant may include, for example, an acidic dispersant having a hydrocarbon group. Examples of such acidic dispersants include higher fatty acids, polymeric surfactants, and phosphate-based dispersants. These dispersants may be used individually or in combination of two or more.

[0055] The higher fatty acids can be either unsaturated or saturated carboxylic acids, and are not particularly limited, but examples include those with 11 or more carbon atoms, such as stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid. Among these, oleic acid or stearic acid is preferred.

[0056] Other acidic dispersants are not particularly limited and include, for example, alkylmonoamine salts, such as monoalkylamine salts.

[0057] As for alkyl monoamine types, for example, oleoylsarcosine, which is a compound of glycine and oleic acid, and amide compounds using higher fatty acids such as stearic acid or lauric acid instead of oleic acid are preferred.

[0058] Furthermore, the dispersant may include dispersants other than acidic dispersants. Examples of dispersants other than acidic dispersants include basic dispersants, nonionic dispersants, and amphoteric dispersants. These dispersants may be used individually or in combination of two or more types.

[0059] Examples of basic dispersants include aliphatic amines such as laurylamine, rosinamine, cetylamine, myristylamine, and stearylamine. Conductive pastes containing both the above-mentioned acidic dispersant and basic dispersant exhibit superior dispersibility and viscosity stability over time.

[0060] The dispersant is preferably contained in an amount of 3% by mass or less relative to the total conductive paste. The upper limit of the dispersant content is preferably 2% by mass or less, and more preferably 1% by mass or less. The lower limit of the dispersant content is not particularly limited, but for example, it is 0.01% by mass or more, and preferably 0.05% by mass or more. When the dispersant content is within the above range, the dispersibility of the conductive paste can be improved while adjusting the paste viscosity to an appropriate range, deterioration of drying properties after printing can be prevented, and sheet attack and peeling defects of the green sheet can be suppressed.

[0061] Furthermore, the dispersant is preferably contained in an amount of 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.05 parts by mass or more and 3 parts by mass or less, and even more preferably 0.4 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of conductive powder. When the dispersant content is within the above range, the dispersibility of conductive powder and ceramic powder, the smoothness of the dry electrode surface after coating are superior, the viscosity of the conductive paste can be adjusted to an appropriate range, deterioration of drying after printing can be prevented, and sheet attack and peeling defects of green sheets can be suppressed. In addition, the dispersant may contain both an acidic dispersant and a basic dispersant. When the dispersant contains both an acidic dispersant and a basic dispersant, it is preferable that the content of the acidic dispersant is greater than the content of the basic dispersant. For example, the content of the basic dispersant relative to the content of the acidic dispersant may be 0.1 to less than 1, or 0.3 to 0.8.

[0062] (Dicarboxylic acid) The conductive paste according to this embodiment may contain dicarboxylic acid as an additive. By including a specific amount of dicarboxylic acid in a conductive paste for gravure printing, separation of conductive powder and ceramic powder can be suppressed, and the occurrence of white floating, where a white separation layer containing ceramic powder forms on top when the conductive paste is made, can be suppressed. Furthermore, when an internal electrode layer is formed using the conductive paste according to this embodiment, a high coverage rate can be obtained.

[0063] Dicarboxylic acids are carboxylic acid-based additives having two carboxyl groups (COO- groups). Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, and azelaic acid; dibasic acids produced by the dimerization of unsaturated fatty acids having 12 to 28 carbon atoms, such as dimer acids; hydrolyzed dimer acids; 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid; 4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 2-methylhexahydrophthalic anhydride; dicarboxyhydrogenated bisphenol A, dicarboxyhydrogenated bisphenol S, hydrogenated naphthalenedicarboxylic acid, tricyclodecanedicarboxylic acid, and alicyclic dicarboxylic acids, as well as their derivatives. Among these, derivatives of succinic acid are preferred.

[0064] Furthermore, the average molecular weight of the dicarboxylic acid is not particularly limited, but may be other than 1000, or it may be 500 or less, or it may be 400 or less. When the average molecular weight of the dicarboxylic acid is within the above range, a high separation inhibition effect can be obtained. The average molecular weight of the dicarboxylic acid may be, for example, 100 or more, or 200 or more.

[0065] Furthermore, in the conductive paste according to this embodiment, the dicarboxylic acid may be contained in an amount of 0.05% by mass or more and less than 3.0% by mass of the total conductive paste, and preferably in an amount of 0.1% by mass or more and 1.0% by mass or less. The upper limit of the dicarboxylic acid content may also be 0.5% by mass or less. If the dicarboxylic acid content is 3.0% by mass or more, drying may be insufficient during the printing and drying process, resulting in a soft internal electrode layer, which may cause misalignment in the subsequent lamination process, or residual dicarboxylic acid may vaporize during firing, causing internal stress due to the vaporized gas components, or structural failure of the laminate.

[0066] In addition, when the conductive paste contains a dispersant (excluding dicarboxylic acid) and a dicarboxylic acid, the total content of the dispersant and the dicarboxylic acid may be 0.05% by mass or more and 3.0% by mass or less, may be 0.1% by mass or more and 2.0% by mass or less, or may be 0.1% by mass or more and 1.0% by mass or less with respect to the entire conductive paste.

[0067] Note that the conductive paste according to the present embodiment may not contain a dicarboxylic acid. Even when the conductive paste according to the present embodiment does not contain a dicarboxylic acid, as described above, by containing a specific organic solvent, the undulation on the surface of the dry film can be reduced.

[0068] (Other additives) The conductive paste of the present embodiment may contain other additives other than the above components as necessary. As the other additives, for example, conventionally known additives such as defoamers, plasticizers, surfactants, and thickeners can be used.

[0069] (Conductive paste) The method for producing the conductive paste according to the present embodiment is not particularly limited, and a conventionally known method can be used. The conductive paste can be produced, for example, by stirring and kneading the above components with a three-roll mill, ball mill, mixer, or the like. Regarding the dicarboxylic acid (separation inhibitor), it is preferably weighed and added when stirring and kneading with a mixer or the like in the same manner as other materials, but the same separation inhibiting effect can be obtained by adding it as a separation inhibitor to the material after the completion of stirring and kneading (dispersion).

[0070] The conductive paste has a viscosity at a shear rate of 100 sec -1 preferably of 3 Pa·S or less. When the viscosity at a shear rate of 100 sec -1 is within the above range, it can be suitably used as a conductive paste for gravure printing. If it exceeds the above range, the viscosity may be too high and it may not be suitable for gravure printing. When the shear rate is 100 sec -1The lower limit of viscosity is not particularly limited, but for example, it is 0.2 Pa·S or higher.

[0071] Furthermore, the conductive paste has a shear rate of 10,000 sec. -1 The viscosity is preferably 1 Pa·s or less. Shear rate 10000 sec -1 If the viscosity is within the above range, it can be suitably used as a conductive paste for gravure printing. If it exceeds the above range, the viscosity may be too high and it may not be suitable for gravure printing. Shear speed 10000 sec -1 The lower limit of viscosity is not particularly limited, but for example, it is 0.05 Pa·S or higher.

[0072] Conductive paste can be suitably used in electronic components such as multilayer ceramic capacitors. A multilayer ceramic capacitor has a dielectric layer formed using a dielectric green sheet and an internal electrode layer formed using the conductive paste.

[0073] Conductive paste, printing speed 30 m / min, film thickness 0.50 μm or more. 2 The dried film obtained by gravure printing under conditions of μm or less preferably has an average height (Wc) of the waviness curve elements of less than 0.5 μm, more preferably 0.47 μm or less, more preferably 0.45 μm or less, more preferably 0.4 μm or less, and even more preferably 0.35 μm or less when a cutoff value (λc = 0.08 mm) is applied.

[0074] The average height (Wc) of the undulation curve element can be measured in accordance with JIS B 0601:2013. The average height (Wc) of the undulation curve element represents the average value of the height (Zti) of the undulation curve element (contour curve element) over a reference length. A contour curve element is a pair of adjacent peaks and valleys, and the height of a contour curve element is the difference in height between adjacent peaks and valleys. There are minimum height and minimum length requirements for the peaks (valleys) that make up a contour element. If the height (depth) is 10% or less of the maximum height, or the length is 1% or less of the length of the calculation interval, it is considered noise and is included as part of the valleys (peaks) that follow it.

[0075] [Electronic components] Embodiments of the electronic components of the present invention will be described below with reference to the drawings. In the drawings, schematic representations and changes in scale may be used as appropriate. The position and orientation of the components will be described with reference to the XYZ Cartesian coordinate system shown in Figure 1, etc., as appropriate. In this XYZ Cartesian coordinate system, the X and Y directions are horizontal directions, and the Z direction is vertical (up and down direction).

[0076] Figures 1A and 1B show a multilayer ceramic capacitor 1, which is an example of an electronic component according to the embodiment. The multilayer ceramic capacitor 1 comprises a ceramic laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and an external electrode 20.

[0077] The following describes a method for manufacturing a multilayer ceramic capacitor using the conductive paste described above. First, a conductive paste is printed onto a ceramic green sheet and dried to form a dried film. Multiple ceramic green sheets, each having this dried film on its upper surface, are laminated by pressing to obtain a laminate. The laminate is then fired to integrate it, thereby creating a ceramic laminate 10 in which internal electrode layers 11 and dielectric layers 12 are alternately laminated. Subsequently, a pair of external electrodes 20 are formed at both ends of the ceramic laminate 10 to manufacture a multilayer ceramic capacitor 1. A more detailed explanation follows below.

[0078] First, an unfired ceramic sheet, known as a ceramic green sheet, is prepared. Examples of this ceramic green sheet include a dielectric layer paste obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate, which is then applied in a sheet-like manner to a support film such as a PET film, dried, and the solvent removed. The thickness of the dielectric layer made of the ceramic green sheet is not particularly limited, but from the viewpoint of miniaturizing multilayer ceramic capacitors, a thickness of 0.05 μm to 3 μm is preferred.

[0079] Next, the conductive paste described above is printed and applied to one side of the ceramic green sheet using gravure printing, and then dried to form a dried film on one side of the ceramic green sheet. Multiple such sheets are prepared. The thickness of the dried film formed from the conductive paste is preferably 1 μm or less after drying, from the viewpoint of thinning the internal electrode layer 11.

[0080] Next, the ceramic green sheet is peeled off the support film, and the ceramic green sheet and the dried film formed on one side of it are laminated alternately. Then, a laminate is obtained by heating and pressurizing. Alternatively, protective ceramic green sheets without conductive paste can be placed on both sides of the laminate.

[0081] Next, the laminate is cut to a predetermined size to form green chips, and then the green chips are subjected to a debinder treatment and fired in a reducing atmosphere to produce a laminated ceramic fired body (ceramic laminate 10). The atmosphere used for the debinder treatment is preferably air or an N2 gas atmosphere. The temperature used for the debinder treatment is, for example, 200°C to 400°C. Furthermore, the holding time at the above temperature during the debinder treatment is preferably 0.5 hours to 24 hours. The firing is performed in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layer, and the firing temperature of the laminate is, for example, 1000°C to 1350°C, with a holding time at the temperature of 0.5 hours to 8 hours.

[0082] By firing the green chips, the organic binder in the ceramic green sheet is completely removed, and the ceramic raw material powder is fired to form a ceramic dielectric layer 12. In addition, the organic vehicle in the dried film is removed, and nickel powder or nickel-based alloy powder is sintered or melted and integrated to form an internal electrode layer 11, and a multilayer ceramic fired body is formed in which multiple dielectric layers 12 and internal electrode layers 11 are alternately stacked. Furthermore, from the viewpoint of incorporating oxygen into the dielectric layer to improve reliability and suppressing re-oxidation of the internal electrode, the multilayer ceramic fired body may be subjected to annealing treatment after firing.

[0083] Then, a multilayer ceramic capacitor 1 is manufactured by providing a pair of external electrodes 20 to the fabricated multilayer ceramic firing body. For example, the external electrodes 20 comprise an external electrode layer 21 and a plating layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. Suitable materials for the external electrodes 20 include, for example, copper, nickel, or alloys thereof. Electronic components other than multilayer ceramic capacitors can also be used. [Examples]

[0084] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited in any way by the examples.

[0085] [Evaluation Method] (Viscosity of conductive paste) The viscosity of the conductive paste after manufacturing was measured using a rheometer (Anton Paar Japan Co., Ltd.: Rheometer MCR302). 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 , and 10000sec -1 The values ​​used were those measured under the specified conditions.

[0086] (Evaluation of the dried film) A conductive paste was printed onto a dielectric sheet using a small gravure printing machine (Kurabo Industries Ltd., GP-10TYPEII) at a printing speed of 30 m / min, with a conductive powder (Ni powder) concentration of 0.7 mg / cm². 2 After printing with the specified coating amount, the film was dried in a box-type dryer at 80°C for 4 minutes, removed, and a dried film (2.5 mm wide x 5 mm long) for evaluation was obtained. The film thickness of the dried film was between 0.50 μm and 2 μm.

[0087] The waviness of the dried film surface was evaluated using a laser microscope (Keyence VK-100, 20x objective lens, measurement length: 2000 μm) and the average height (Wc) of the waviness curve elements when a cutoff value (λc = 0.08 mm) was applied. The average height (Wc) of the waviness curve elements was the average of multiple measurements.

[0088] [Materials used] (conductive powder) Ni powder (SEM average particle size 0.2 μm) was used as the conductive powder.

[0089] (Ceramic powder) Barium titanate (BaTiO3; SEM average particle size 0.10 μm) was used as the ceramic powder.

[0090] (Binder resin) Polyvinyl butyral resin and ethyl cellulose were used as binder resins.

[0091] (Additives) A dicarboxylic acid was used as an additive.

[0092] (Dispersant) Acidic and basic dispersants were used as dispersants. Comb-shaped carboxylic acids and phosphoric acid-based dispersants were used as acidic dispersants, and oleylamine was used as a basic dispersant.

[0093] (Organic solvents) The organic solvents used included isobornyl acetate (IBA), methyl isobutyl ketone (MIBK), diisobutyl ketone (DIBK), dihydroterpineol (DHT), propylene glycol monobutyl ether (PNB), propylene glycol monomethyl ether acetate (PMA), diethylene glycol monomethyl ether (DEGME), and mineral spirits (MA).

[0094] [Example 1] A conductive paste was prepared by mixing 50% by mass of conductive powder, 12.5% ​​by mass of ceramic powder, 0.5% by mass of dispersant (0.3% by mass of acid-based dispersant, 0.2% by mass of basic-based dispersant), 0.2% by mass of dicarboxylic acid, 2.5% by mass of binder resin (polyvinyl butyral resin:ethyl cellulose = 1:2 (mass ratio)), and 4.1% by mass of IBA, 12.0% by mass of MA, and the remainder of DHT as organic solvents, to a total of 100% by mass. The contents of the conductive paste and the evaluation results of the average waviness height Wc are shown in Table 1.

[0095] [Examples 2-18] In Examples 2 to 18, conductive pastes were prepared and evaluated in the same manner as in Example 1, except that the presence or absence of additives, the type and content ratio of organic solvents were changed as shown in Table 1. Table 1 shows the evaluation results Wc for the content of additives, etc., in the conductive paste and the average height of the waviness.

[0096] [Comparative Examples 1-4] As organic solvents, 13.7% by mass of MA and the remainder of PNB (Comparative Example 1), 13.7% by mass of MA and the remainder of DHT (Comparative Example 2), 12% by mass of MA, 5.9% by mass of PMA and the remainder of DHT (Comparative Example 3), and 12% by mass of MA, 5.9% by mass of DEGME and the remainder of DHT (Comparative Example 4). Except for the use of [specific material], a conductive paste was prepared and evaluated in the same manner as in Example 1. Table 1 shows the content of additives in the conductive paste and the evaluation results Wc for the average height of the waviness.

[0097] [Table 1]

[0098] (Evaluation results) The conductive pastes of Examples 1 to 18 had a smaller average height (Wc) of the waviness curve elements in the dried film compared to the conductive pastes of Comparative Examples 1 to 4, which did not use the first organic solvent (IBA, MIBK, DIBK).

[0099] Furthermore, in all the examples and comparative examples of conductive pastes shown in Table 1, the shear rate was 100 sec. -1 The viscosity is 3 Pa·s or less, and the shear rate is 10,000 sec. -1 The viscosity is 1 Pa·s or less, confirming that it has a viscosity suitable for gravure printing. [Industrial applicability]

[0100] When the conductive paste of the present invention is used to form the internal electrodes of a multilayer ceramic capacitor, highly reliable multilayer ceramic capacitors can be obtained with high productivity. Therefore, the conductive paste of the present invention can be suitably used as a raw material for the internal electrodes of multilayer ceramic capacitors, which are chip components of electronic devices that are becoming increasingly miniaturized, such as mobile phones and digital devices, and can also be suitably used as a conductive paste for gravure printing.

[0101] Furthermore, the technical scope of the present invention is not limited to the embodiments described above. One or more of the requirements described above may be omitted. Also, the requirements described above may be combined as appropriate. In addition, to the extent permitted by law, all disclosures of the documents cited above shall be incorporated as part of the description herein. [Explanation of symbols]

[0102] 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

[Claim 1] A conductive paste for gravure printing comprising conductive powder, ceramic powder, dispersant, binder resin and organic solvent, The organic solvent contains at least one selected from the group consisting of isobornyl acetate, methyl isobutyl ketone, and diisobutyl ketone. Conductive paste for gravure printing.

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