TW201815991A - Electrically conductive paste capable of forming an electrically conductive film having excellent adhesion to a substrate - Google Patents

Abstract

An object of the present invention is to provide an electrically conductive paste that can form an electrically conductive film having excellent adhesion to a substrate. Through the present invention an electrically conductive paste is provided which comprises an electrically conductive powder, a resin adhesive agent, an organic additive, and an organic solvent. The organic additive includes a (meth)acrylate compound having two or more (meth)acryloyl groups in one molecule and a number average molecular weight of 1,000 or less.

Description

Conductive paste

The present invention relates to a conductive paste. In particular, it relates to a conductive paste suitable for forming an internal electrode layer of a multilayer ceramic capacitor.

In the manufacture of electronic components such as a multi-layer ceramic capacitor (MLCC), a conductive paste is usually used for the formation of the electrode layer. In one example of the MLCC manufacturing method, a plurality of unfired ceramic green sheets containing ceramic powder are first prepared. In addition, a conductive paste for forming an internal electrode layer containing a conductive powder was prepared. Next, a conductive paste is applied to a plurality of ceramic green sheets by a printing method or the like. Then, the provided conductive paste is dried to prepare a green sheet with a conductive film. Next, a plurality of green sheets with a conductive film are laminated and pressure-bonded to each other, and then cut into a predetermined size. Then, it is sintered integrally by calcining it at a high temperature. In this way, an MLCC having a structure in which a ceramic-based dielectric layer and a conductive internal electrode layer are alternately laminated is manufactured. As a related art related to a conductive paste for forming an internal electrode layer, for example, Patent Document 1 discloses a conductive paste prepared by including a conductive powder, a resin binder, an organic additive, and an organic solvent. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2016-31912

[Problems to be Solved by the Invention] However, in recent years, with the further miniaturization or high performance of various electronic devices, electronic components mounted in electronic devices have been required to be further reduced in size, thickness, and density. From the viewpoint of meeting the requirements, for example, in a wafer-type MLCC, the thickness of one layer of the internal electrode layer is thinned to the sub-micron to micron level, and the number of stacked layers also exceeds several hundred layers. In the production of MLCCs that are thus promoted by multi-layering, even when an external force is applied during crimping or cutting, it is necessary to prevent the conductive film from peeling from the substrate (such as ceramic green sheet) or the multilayer structure. The laminated structure is stably maintained in a shifted state. Therefore, it is required to improve the adhesion between the substrate and the conductive film.

This invention was made in view of the said aspect, and an object of this invention is to provide the electroconductive paste which can form the electroconductive film excellent in adhesiveness with a base material. [Means for solving problems]

According to the present invention, a conductive paste for forming an electrode layer on a substrate is provided. The conductive paste includes a conductive powder, a resin binder, an organic additive, and an organic solvent. The organic additive contains a (meth) acrylic acid ester compound having two or more (meth) acrylfluorenyl groups and having a number average molecular weight of 1,000 or less in one molecule.

By using the said conductive paste, compared with the case where the conventional conductive paste is used, the adhesiveness of a base material and the conductive film before baking can be improved. Thereby, peeling of a conductive film from a base material can be suppressed, and occurrence of delamination (interlayer peeling) can be reduced. In addition, for example, in the production of MLCC, a plurality of green sheets with a conductive film can be pressure-bonded to each other with a smaller pressure. Then, when a plurality of green sheets with a conductive film are laminated and pressure-bonded, or when the laminated green sheets with a conductive film are cut, the laminated structure can be favorably maintained. In addition, handling properties of the paste and workability during the manufacture of electronic parts can be improved.

In the present specification, the term "(meth) acrylfluorenyl" refers to a group consisting of acrylfluorenyl (CH ₂ = CH-C (= O)-) and methacrylfluorenyl (CH ₂ = C (CH ₃ ) -C (= O)-). In addition, in this specification, a "(meth) acrylate compound" is a term which contains "(meth) acrylate" and "(meth) acrylate." In the present specification, the "number average molecular weight" refers to a measurement by gel chromatography (Gel Permeation Chromatography (GPC)) and conversion using a standard polystyrene calibration curve Number based on the average molecular weight. When the (meth) acrylate compound is a single monomer, it has the same meaning as the molecular weight.

The (meth) acrylate compound may have, for example, six (meth) acrylfluorenyl groups in one molecule. The number average molecular weight of the (meth) acrylate compound may be 200 or more and 800 or less.

In a preferred aspect disclosed herein, the organic additive further includes an amine-based organic additive. Thereby, the adhesiveness of a base material and a conductive film can be improved more, and the effect of this invention can be exhibited at a higher level.

In a preferred aspect disclosed herein, the (meth) acrylate compound includes a lactone-modified (meth) acrylate compound. Thereby, the adhesiveness of a base material and a conductive film can be improved more with a small addition amount, and the effect of this invention can be exhibited at a high level.

In a preferred aspect disclosed herein, when the entire conductive paste is 100% by mass, the proportion of the organic additive is 5% by mass or less. Thereby, the flexibility or adhesiveness of the conductive film can be more stably improved, and the workability at the time of manufacturing the electronic component can be improved more favorably. In addition, typically, the organic additive is completely burned when the conductive powder is sintered. Therefore, by suppressing the content ratio of the organic additive to be low, an electrode layer having excellent electrical conductivity can be preferably realized.

In a preferred aspect disclosed herein, the resin binder includes a cellulose-based resin. The cellulose-based resin is excellent in combustion decomposition properties during firing. Therefore, by using a cellulose-based resin, the electrical conductivity of the electrode layer can be more improved. In addition, the surface smoothness of the electrode layer can be improved better.

In a preferred aspect disclosed herein, when the entire conductive paste is 100% by mass, the proportion of the resin adhesive is 1% by mass or more and 5% by mass or less. Thereby, the workability | operativity at the time of manufacture of an electronic component can be improved more favorable. In addition, by suppressing the content ratio of the resin binder to be low, an electrode layer having excellent electrical conductivity can be preferably realized.

The substrate is, for example, a ceramic green sheet containing a ceramic powder and a resin binder. In such a case, the effect of the present invention can be exhibited more stably.

The conductive paste is preferably used for forming an internal electrode layer of a multilayer ceramic capacitor. By using the conductive paste, it is also possible to stably manufacture MLCCs having, for example, several hundreds of layers.

Hereinafter, preferred embodiments of the present invention will be described. Furthermore, matters other than those specifically mentioned in this specification (for example, the composition of a conductive paste) and matters required for the implementation of the present invention (for example, a method for preparing a conductive paste or a method for forming an electrode layer) may be It is grasped as a design matter for those skilled in the art based on the prior art in this field. The present invention can be implemented based on the contents disclosed in this specification and technical common sense in the field. It should be noted that the expression “A to B” in the present specification means a range from A to B.

<Conductive Paste> The conductive paste (hereinafter, sometimes referred to simply as a paste) disclosed herein is used to form an electrode layer on a substrate. The conductive paste contains a conductive powder, a resin binder, an organic additive, and an organic solvent as essential constituent components. Hereinafter, each component is demonstrated in order.

<Conductive powder> The conductive powder contained in the paste is a component for imparting electrical conductivity to the electrode layer. The conductive powder is not particularly limited, and one or two or more kinds can be appropriately selected and used from the conventionally known conductive powders depending on the use of the paste and the like. Preferred examples of the conductive powder include nickel (Ni), gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), ruthenium (Ru), and rhodium (Rhodium) Rh), iridium (Ir), osmium (Os), aluminum (Al) and other metal monomers, and mixtures or alloys of these. For example, for the purpose of forming the internal electrode layer of the MLCC, it is preferable to use a metal species whose melting temperature is sufficiently higher than the sintering temperature of the ceramic powder contained in the substrate. Examples of such a metal species include metal powders including nickel, silver, copper, platinum, and palladium. Among them, nickel is preferred because it is inexpensive and has excellent balance between electrical conductivity and cost. The average particle diameter of the conductive powder (value based on the number of electron microscope observations. The same applies hereinafter) is preferably about 0.01 μm to 10 μm, typically 0.05 μm to 5 μm, for example, 0.1 μm to 0.3 μm.

The content ratio of the conductive powder to the total mass of the paste is not particularly limited, but it is preferably approximately 30% by mass or more, typically 40% to 95% by mass, for example, 45% to 60% by mass. By satisfying the above range, it is possible to form an electrode layer with high electrical conductivity or denseness. In addition, the operability of the paste and the workability during printing of the paste can be improved.

<Resin Binder> The resin binder contained in the paste is a component that imparts adhesiveness to a non-calcined conductive film and adheres the conductive particles constituting the conductive powder and the conductive particles to the substrate. The resin adhesive is not particularly limited, and one or two or more resin adhesives may be appropriately selected from various resin adhesives known to be used in such applications. As a preferable example, cellulose resin, acrylic resin, butyral resin, epoxy resin, phenol resin, alkyd resin, rosin resin, etc. are mentioned. The resin binder may be, for example, a linear or branched aliphatic compound having no aromaticity, or an alicyclic compound having a saturated or unsaturated carbocyclic ring having no aromaticity, or may include benzene in the molecule. Aromatic compounds such as rings and the like. The "resin resin" in this specification is a polymer compound having an exponential average molecular weight of more than 1,000, and is typically a polymer (polymer).

The term “cellulose-based resin” refers to a term that includes all cellulose-derived compounds (cellulose derivatives) such as alkyl cellulose-based resins and hydroxyalkyl cellulose-based resins in this field. Examples of the cellulose-based resin include a part or all of hydrogen atoms in a hydroxyl group of cellulose as a repeating structural unit via alkyl groups such as methyl, ethyl, propyl, isopropyl, and butyl; Allyl groups such as propionyl and butylmethyl; substituted cellulose organic acid esters such as methylol, hydroxyethyl, carboxymethyl, and carboxyethyl. Specific examples of the cellulose-based resin include methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), and ethylmethyl. Cellulose (ethyl methyl cellulose, EMC), hydroxyethyl methyl cellulose (HEMC), hydroxypropyl cellulose, carboxymethyl cellulose, nitrocellulose, and the like. As a preferred example, an ethyl group having a structure in which a hydrogen atom in a hydroxyl group of cellulose as a repeating structural unit is substituted with an ethyl group (CH ₃ CH ₂ group) or a hydroxyethyl group (CH ₂ CH ₂ OH group) may be mentioned. Cellulose resin.

Examples of the acrylic resin include a homopolymer (homopolymer) of an alkyl (meth) acrylate, or an alkyl (meth) acrylate as a main monomer (50 weight of the entire monomer) % Or more of the components. The same applies hereinafter), and the main monomer includes a copolymer (copolymer) having a copolymerizable secondary monomer. As a preferred example, the general formula: CH ₂ = C (R ¹ ) COOR ² (here, R ¹ represents a hydrogen atom or a methyl group. In addition, R ² represents a carbon number of 1 to 20 A chain alkyl group.) The R ^{2 is} preferably 1 to 14 carbon atoms, more preferably 1 to 10 carbon atoms, for example, 1 to 8 carbon atoms. Specific examples of the acrylic resin include polymethyl (meth) acrylate, polyethyl (meth) acrylate, polybutyl (meth) acrylate, polymer blocks containing methacrylate, and acrylic acid. Block copolymers of polymer blocks of esters and the like.

The term "butyraldehyde-based resin" is used to include all resins called polyvinyl butyral-based resin or polyvinyl acetal-based resin in this field. Examples of the butyraldehyde-based resin include a homopolymer (homopolymer) of vinyl acetate or a copolymer of vinyl acetate as a main monomer and a copolymerizable sub-monomer included in the main monomer. (Copolymer). Specific examples of the homopolymer include polyvinyl butyral (PVB) and the like. Specific examples of the copolymer include a butyraldehyde group, a hydroxyl group, and an acetamyl group as repeating structural units in the main chain skeleton, and the degree of butyralization (the ratio of acetalization via butyl aldehyde) is About 50 mol% or more, for example, a compound of 60 mol% or more.

It is preferable that the resin binder contains a cellulose-based resin, for example, an ethyl cellulose-based resin, from the viewpoint of excellent combustion decomposability during firing or improvement of surface smoothness of the electrode layer. In a preferred aspect, when the entire resin binder is 100% by mass, the content ratio of the cellulose-based resin is approximately 50% by mass or more, and preferably 80% by mass or more. Thereby, the effects of the technology disclosed herein can be exerted at a higher level.

The number average molecular weight of the resin adhesive is preferably approximately 10,000 or more, typically 20,000 or more, for example, about 50,000 to 100,000. When the number average molecular weight is a predetermined value or more, the function as an adhesive can be exhibited with a small amount of addition, and the adhesion between the substrate and the conductive film or the integrity of the conductive film can be improved. When the number average molecular weight is equal to or less than a predetermined value, the printability or operability of the paste can be improved.

In a preferred aspect, the resin adhesive does not contain a component that can generate corrosive gas (calculus gas component) during firing. Specific examples of the corrosive gas cause component include a sulfur component, a halogen component such as fluorine or chlorine. It is particularly preferable that the molecular structure of the resin adhesive is substantially composed of carbon, oxygen, and hydrogen (inevitable mixing of impurities is allowed). With such a molecular structure, no harmful gas is generated during the firing of the conductive film, and the corrosion deterioration or environmental load of the firing equipment can be reduced.

The content ratio of the resin adhesive with respect to the conductive powder tends to be such that the more the conductive powder is finer, the higher the content ratio is. For example, when the conductive powder having an average particle size of sub-micron is used for the purpose of forming the internal electrode layer of the MLCC, etc., when the conductive powder is 100 parts by mass, the content ratio of the resin binder is preferably It is approximately 1 to 15 parts by mass, for example, 2 to 10 parts by mass. With this, even when a fine conductive powder is used, the amount of the resin adhesive can be suppressed, and the adhesion between the base material and the conductive film or the integrity of the conductive film can be better ensured.

The content ratio of the resin binder to the total mass of the paste is not particularly limited, but is preferably approximately 0.1% by mass or more, typically 0.5% to 10% by mass, for example, 1% to 5% by mass. By satisfying the above range, the adhesiveness between the base material and the conductive film or the integrity of the conductive film can be more improved. In addition, occurrence of delamination can be highly suppressed. Furthermore, it is possible to impart a moderate viscosity to the paste and improve workability during the manufacture of electronic parts (for example, when printing the paste or when laminating green sheets with conductive films in MLCC).

<Organic additive> The organic additive contained in the paste is a component for improving the adhesiveness of a base material and a conductive film. The organic additive functions, for example, as a so-called plasticizer to improve the flexibility or adhesion of the conductive film. The organic additive may, for example, play a role of better exerting the adhesiveness of the resin adhesive. The paste disclosed here contains at least a predetermined (meth) acrylate compound as an organic additive.

The (meth) acrylate compound is a polyfunctional (meth) acrylate compound having two or more (meth) acrylfluorenyl groups in one molecule. The (meth) acrylate compound typically includes a (meth) acrylate monomer. The number of (meth) acrylfluorenyl groups contained in one molecule of the (meth) acrylate compound is two or more, typically two to ten, for example two to six.

Preferred examples of the (meth) acrylate compound having two (meth) acrylfluorene groups in one molecule include hydroxytrimethylacetic acid neopentyl glycol di (meth) acrylate, and Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, butanediol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (Meth) acrylate, pentaerythritol di (meth) acrylate, dipentaerythritol di (meth) acrylate, trimethylolpropane di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di ( Meth) acrylates, bis (hydroxymethyl) tricyclodecane di (meth) acrylates, bisphenol A-di (meth) acrylates, and these via diethyl ether (EO) or cyclic Difunctional (meth) acrylates modified with lactones such as propylene oxide (PO) or cyclic lactones having a lactone ring such as caprolactone.

Preferred examples of the (meth) acrylate compound having three (meth) acrylfluorene groups in one molecule include pentaerythritol tri (meth) acrylate and dipentaerythritol tri (meth) acrylate. , Trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethyloloctane tri (meth) acrylate, tri ((meth) acrylic acid) (Oxyethyl) isocyanurate, tri (2-hydroxyethyl) isocyanurate tri (meth) acrylate, sorbitol tri (meth) acrylate, and these are EO or PO Or trifunctional (meth) acrylic acid esters which are modified with lactones such as caprolactone and cyclic lactones having a lactone ring.

Preferred examples of the (meth) acrylate compound having four or more (meth) acrylfluorene groups in one molecule include pentaerythritol tetra (meth) acrylate and dipentaerythritol penta (methyl). Acrylate, dipentaerythritol hexa (meth) acrylate, tripentaerythritol hepta (meth) acrylate, tripentaerythritol octa (meth) acrylate, tetrapentaerythritol nine (meth) acrylate, tetrapentaerythritol ten (meth) Acrylates, and (meth) acrylates modified with lactones such as cyclic lactones having a lactone ring such as EO, PO, or caprolactone.

The (meth) acrylic acid ester compound preferably has an acrylic fluorenyl group. Thereby, the effect of the technology disclosed here can be effectively exhibited with a smaller amount of addition. The (meth) acrylate compound is preferably a modified (meth) acrylate compound modified with a lactone. Thereby, the flexibility or adhesion of the conductive film can be improved better, and the adhesion between the substrate and the conductive film can be effectively improved. In addition, lactone-modified (meth) acrylate compounds have excellent compatibility with, for example, a wide range of resin adhesives such as cellulose resins. By using the one having good compatibility with the resin adhesive, it is possible to suppress a change in paste viscosity with time or to suppress separation of the resin adhesive after gelatinization. Therefore, for example, when a cellulose resin is used as the resin binder, it is preferable to use a lactone-modified (meth) acrylate compound as the (meth) acrylate compound. This makes it possible to suppress the change with time of the paste or the separation of the resin adhesive, and to use the paste well.

The number average molecular weight of the (meth) acrylate compound is 1,000 or less, typically 100 to 1,000, for example 200 to 800. In this way, for example, the molecular weight of the (meth) acrylate compound is relatively low as compared with a polymer compound generally used as an adhesive resin, thereby improving the flexibility or adhesiveness of the conductive film, and being effective. In order to improve the adhesion between the substrate and the conductive film.

The molecular structure of the (meth) acrylate compound is not particularly limited as long as it has two or more (meth) acrylfluorenyl groups in one molecule and the number average molecular weight is 1,000 or less. The (meth) acrylate compound may be, for example, a linear or branched aliphatic compound having no aromaticity, or an alicyclic compound having a saturated or unsaturated carbocyclic ring having no aromaticity, or The aromatic compound may be an aromatic compound containing a benzene ring or the like in the molecule. For example, when the resin adhesive is an aliphatic compound, the (meth) acrylate compound preferably contains an aliphatic compound. Thereby, the synergistic effect with the resin adhesive can better improve the flexibility or adhesion of the conductive film, and effectively improve the adhesion between the substrate and the conductive film. In addition, the (meth) acrylate compound may contain a functional group other than an acryl group, such as a hydroxyl group or a carboxyl group.

In a preferred aspect, the (meth) acrylate compound does not include a component (corrosive gas cause component) that can generate a corrosive gas during firing. Specific examples of the corrosive gas cause component include a sulfur component, a halogen component such as fluorine or chlorine. It is particularly preferred that the molecular structure of the (meth) acrylate compound is substantially composed of carbon, oxygen, and hydrogen (inevitable mixing of impurities is allowed). With such a molecular structure, no harmful gas is generated during the firing of the conductive film, and the corrosion deterioration or environmental load of the firing equipment can be reduced.

The glass transition point (Tg value based on Differential Scanning Calorimetry (DSC) of the (meth) acrylate compound) is preferably below room temperature (25 ° C). Thereby, the flexibility or adhesion of the conductive film can be improved better, and the adhesion between the substrate and the conductive film can be further improved.

The decomposition start temperature of the (meth) acrylate compound (value based on thermogravimetric analysis (Thermogravimetry Mass Spectrometry: TG)) is preferably about 100 ° C or higher, preferably 200 ° C or higher, For example, about 200 ° C to 400 ° C. Thereby, it is possible to preferably maintain the adhesion (adhesion to the substrate) to the extent that the conductive film can be brought into close contact with the substrate (for example, even after being dried) after the conductive film is applied to the substrate until it is fired. force). The decomposition end temperature (value based on TG.) Of the (meth) acrylate compound is preferably approximately 1000 ° C. or lower, typically 800 ° C. or lower, for example, 600 ° C. or lower. Thereby, the degreasing property can be improved, and it can be appropriately and completely burned during firing.

The solubility parameter (Solubility Parameter of the (meth) acrylate compound is calculated based on the Hildebrand method. The same applies hereinafter.) It is preferably approximately 8 (cal / cm ³ ) ^0.5 to 13 (cal / cm ³ ) ^0.5 , for example, about 9.5 (cal / cm ³ ) ^0.5 to 12 (cal / cm ³ ) about ^0.5 . From the viewpoint of improving the adhesion with the base material, when the base material contains a resin adhesive, the solubility parameter between the resin adhesive contained in the base material and the (meth) acrylate compound is preferably poor. It is approximately 5 (cal / cm ³ ) ^0.5 or less, for example, 3.5 (cal / cm ³ ) ^0.5 or less. Thereby, the affinity or integration of the base material and the conductive film can be improved, and the effect of the present invention can be exerted at a higher level.

In a preferred aspect, when the entire organic additive is 100% by mass, the content ratio of the (meth) acrylate compound is approximately 50% by mass or more, and preferably 80% by mass or more. Thereby, the effect of the technique disclosed here can be exhibited efficiently while suppressing the addition amount of an organic additive.

In addition to the (meth) acrylate compound, for example, for the purpose of improving the homogeneity or stability of the paste, or improving the self-leveling property, the organic additive may also include those previously known to be used in such pastes. Various organic additives, such as surfactants, tackifiers, defoamers, plasticizers, leveling agents, stabilizers, antioxidants, preservatives, colorants (organic pigments, dyes), etc. As a preferable example, an organic additive of an alkali type, for example, an organic additive of an amine type which has one or two or more amine groups, is mentioned. Examples of the amine-based organic additive include a higher amine having 10 or more carbon atoms or a rosin amine. In a preferred aspect, the (meth) acrylate compound and an amine-based organic additive may be contained at the same time. By using the two organic additives in combination, the effects of the technology disclosed herein can be exerted at a higher level.

Moreover, in this paste, as a plasticizer, for example, phthalates such as dibutyl phthalate (DBP) or dioctyl phthalate (DOP) are generally used. Class (phthalate). Phthalates are a general term for compounds in which phthalic acid and alcohol are ester-bonded. However, phthalates are environmentally hazardous substances, and in recent years, their use tends to be limited. Therefore, in a preferred aspect, it is preferable that the paste disclosed herein is constituted without phthalates. By including the (meth) acrylic acid ester compound, the paste disclosed here can exhibit the effect as if it contains a plasticizer even without phthalates, and can further improve the flexibility of the conductive film. Or adhesive.

The content ratio of the organic additive in the total mass of the paste can be appropriately changed depending on the use of the paste, the desired properties (flexibility, adhesion, etc.) of the conductive film, and the like. Therefore, the content ratio of the organic additive is not particularly limited, but it is preferably approximately 0.1% by mass or more, for example, 0.5% by mass or more, preferably the same as or lower than the content ratio of the resin adhesive, for example, 1 / 2 times or less. Specifically, it is preferably approximately 5% by mass or less, preferably 3% by mass or less, for example, 2% by mass or less. This makes it possible to more stably improve the flexibility or adhesiveness of the conductive film, and to improve workability during the manufacture of electronic parts (for example, when the laminated body is crimped or cut during manufacture of MLCC). In addition, typically, the organic additive is completely burned when the conductive powder is sintered. Therefore, by suppressing the content ratio of the organic additive to be low, an electrode layer having excellent electrical conductivity can be preferably realized. Furthermore, for example, even when a thin-film electrode layer is formed, it is possible to suppress the occurrence of defects such as pores and cracks in the electrode layer.

<Organic solvent> The organic solvent contained in the paste is not particularly limited as long as it can dissolve or disperse the conductive powder, the resin binder, and the organic additive. One or two of them can be appropriately selected according to the use of the paste and the like. Use more than one. From the viewpoint of improving workability during printing of paste or storage stability of paste, it is preferable to use a high-boiling organic solvent having a boiling point of approximately 200 ° C or higher, for example, 200 ° C to 300 ° C as a main component (50% by volume or more) Ingredients.). As a preferred example, alcohol solvents such as dihydroterpineol and terpineol; terpene solvents such as isobornyl acetate; glycol solvents such as ethylene glycol and diethylene glycol; diethylene glycol Glycol ether solvents such as alcohol monoethyl ether and diethylene glycol monobutyl ether (butylcarbitol); ester solvents; hydrocarbon solvents such as toluene and xylene; and organic solvents with high boiling points such as mineral spirits .

The content ratio of the organic solvent to the total mass of the paste is not particularly limited, but is preferably approximately 70% by mass or less, typically 5 to 60% by mass, for example, 30 to 55% by mass. By satisfying the above range, moderate fluidity can be imparted to the paste, and workability during manufacturing of the electronic component (for example, during printing of the paste) can be improved.

<Other Ingredients> The paste disclosed here may include other added ingredients in addition to the four ingredients as needed. Examples of the additive component include inorganic additives such as inorganic fillers. For example, in the application of forming the internal electrode layer of the MLCC, ceramic powder as a common material may be considered, and typically, barium titanate (BaTiO ₃ ) and the like are used.

The content ratio of the inorganic additive to the total mass of the paste is not particularly limited. For example, it is preferably about 1% to 20% by mass, for example, 3% to 15% by mass, for use in forming an internal electrode layer of an MLCC. When the conductive powder is 100 parts by mass, the content of the inorganic additive relative to the conductive powder is preferably approximately 5 to 30 parts by mass, for example, 7 to 25 parts by mass.

Such a paste can be prepared by weighing the material so as to have a predetermined content ratio, and stirring and mixing uniformly. The materials can be stirred and mixed using various known mixing devices such as a roll mill, a magnetic stirrer, a planetary mixer, a disperser, and the like. The application of the paste can be performed using, for example, a printing method such as screen printing, gravure printing, lithographic printing, or inkjet printing, or a spray coating method. In particular, for the purpose of forming the internal electrode layer of the MLCC, a gravure printing method capable of high-speed printing is preferred. Examples of the base material for applying the paste include ceramic green sheets, ceramic base materials, glass base materials, and amorphous silicon base materials.

<Application of Paste> The paste disclosed herein can be preferably used for applications requiring adhesion to a substrate. Typical applications include the formation of an internal electrode layer in a multilayer ceramic electronic component. Among them, it can be preferably used for the formation of internal electrode layers of MLCCs, for example, the formation of internal electrode layers of small MLCCs with sides of 5 mm or less, especially of ultra-small MLCCs with sides of 1 mm or less. In addition, in this specification, "ceramic electronic component" is the term which shows the whole electronic component which has an amorphous ceramic substrate (glass ceramic substrate) or a crystalline (that is, non-glass) ceramic substrate. For example, chip inductors with ceramic substrates, high-frequency filters, ceramic capacitors, low-temperature-fired ceramic substrates (LTCC substrates), and high-temperature-fired ceramic substrates (High Temperature Co -Fired Ceramics Substrate (HTCC substrate) is a typical example included in "ceramic electronic parts" mentioned here.

Examples of the ceramic material constituting the ceramic substrate include barium titanate (BaTiO ₃ ), zirconia (ZrO ₂ ), magnesium oxide (magnesia: MgO), alumina (alumina: Al ₂ O ₃ ), and oxidation. Oxide-based materials such as silicon (SiO ₂ ), zinc oxide (ZnO), titanium oxide (titania: TiO ₂ ), cerium oxide (ceria: CeO ₂ ), and yttria (yttria: Y ₂ O ₃ ); cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ), forsterite (2MgO · SiO ₂ ), block talc (MgO · SiO ₂ ), silicon aluminum nitride oxide (Si ₃ N ₄ -AlN-Al ₂ O ₃ ), zircon (ZrO ₂ · SiO ₂ ), ferrite (M ₂ O · Fe ₂ O ₃ ) and other composite oxide materials; silicon nitride (silicon nitride) : Si ₃ N ₄ ), aluminum nitride (aluminum nitride: AlN) and other nitride-based materials; silicon carbide (silicon carbide: SiC) and other carbide-based materials; hydroxyapatite and other hydroxide-based materials; carbon (C ), Silicon (Si) and other elemental materials; or two or more inorganic composite materials containing these; and so on.

FIG. 1 is a cross-sectional view schematically showing the MLCC 10. The MLCC 10 is a ceramic capacitor in which a plurality of dielectric layers 20 and internal electrode layers 30 are alternately laminated. The internal electrode layer 30 includes a fired body of the conductive paste disclosed herein. The MLCC 10 can be manufactured by, for example, the following procedure.

That is, the ceramic green sheet is first formed. In one example, a ceramic powder (for example, barium titanate or titanium oxide), a resin binder, an organic solvent, and the like as a dielectric material are stirred and mixed to prepare a paste for forming a dielectric layer. Then, this paste is spread on a carrier sheet by a doctor blade method or the like, thereby forming a ceramic green sheet for forming the dielectric layer 20. This ceramic green sheet is a portion that becomes a dielectric layer after firing.

Next, a conductive paste for forming an internal electrode layer as disclosed herein is prepared. That is, at least a conductive powder, a resin binder, an organic additive, and an organic solvent are prepared, and these are stirred and mixed to prepare a conductive paste. The conductive paste is applied to the formed ceramic green sheet in a predetermined pattern so as to have a desired thickness (for example, sub-micron to micron order). Thereby, a conductive film is formed on the ceramic green sheet. This conductive film is a part which becomes an internal electrode layer after firing.

The ceramic green sheet with a conductive film obtained as described above is laminated to a predetermined number (for example, several hundred pieces) and then pressure-bonded, and then cut into a predetermined size to obtain an unfired laminated wafer. The non-calcined laminated wafer is calcined under appropriate heating conditions (for example, about 1000 ° C. to 1300 ° C.) to be integrally sintered. Thereby, a laminated wafer in which a plurality of dielectric layers 20 and internal electrode layers 30 are alternately laminated can be obtained. Then, a conductive paste for external electrode formation is applied to the cross section of the fired laminated wafer and fired to form an external electrode 40. The conductive paste for forming an external electrode may be the same as the conductive paste for forming an internal electrode layer. In this way, MLCC 10 can be manufactured.

The following describes some embodiments related to the present invention, but it is not intended to limit the present invention to those shown in the embodiments.

<Preparation of conductive paste> First, the following two compounds were prepared as a resin adhesive. EC: Ethylcellulose PVB: Polyvinyl butyraldehyde In addition, nine organic compounds shown in Table 1 were prepared as organic additives. The organic additive A and the organic additive G are polyfunctional (meth) acrylate compounds having two or more (meth) acrylfluorenyl groups in one molecule. The organic additives B to organic additives F and organic additives H are A monofunctional (meth) acrylate compound having one (meth) acrylfluorenyl group in one molecule.

[Table 1]

[Chemical 1]

[Chemical 2]

Next, as shown in Table 2, conductive pastes (Examples 1 to 4 and Reference Examples 1 to 11) in which the types and addition amounts of the resin adhesives and / or organic additives were different were prepared. Regarding Reference Example 1, no organic additives were used, and the mass ratios were (1): (2): (3) = 50: 15: 2. (1) Nickel powder as a conductive powder and (2) as A barium titanate powder as a common material and ethyl cellulose (3) as a resin binder were stirred and mixed with an organic solvent so that the entire amount became 100% by mass, thereby preparing a conductive paste. Regarding Example 1 to Example 4, Reference Example 2 to Reference Example 8, one or two organic additives shown in Table 2 were added, and the whole was stirred and mixed with an organic solvent so as to become 100% by mass as a whole. 1 Similarly, a conductive paste was prepared. Regarding Reference Example 9 to Reference Example 11, two resin binders (ethyl cellulose and polyvinyl butyral) were used in combination at the ratios shown in Table 2, and they were stirred and mixed with an organic solvent so that the whole became 100% by mass. Except for the above, a conductive paste was prepared in the same manner as in Reference Example 8.

<Production of Laminate> Next, a conductive film was formed on a ceramic green sheet using the conductive paste of each example. That is, first, a ceramic green sheet mainly comprising barium titanate is prepared, and the conductive paste is applied to the surface of the ceramic green sheet by screen printing (using a plate-making stainless steel (SUS) 200). Then, it was dried with a warm air dryer at 100 ° C. for 10 minutes to obtain a green sheet with a conductive film. Eight pieces were produced, and one of them was laminated so that a ceramic green sheet and a conductive film prepared separately became inside, to produce a laminated body. Next, using a hot press, a pressure of 1 ton (ton) was applied from the lamination direction of the laminated body, and the pressure bonding was performed under conditions of 45 ° C. and 30 seconds. The pressure was gradually increased in units of 1 ton, and the lamination and compression bonding of the green sheet with a conductive film was performed repeatedly until the pressure became 8 ton. In this way, a laminated body obtained by crimping 8 green sheets with a conductive film at different pressures was obtained. Then, when the laminated body after pressure-bonding is peeled off by hand, the pressure applied when pressure-bonding the peeled part is taken as ｢adhesive pressure｣. The results are shown in Table 2. In addition, the smaller the value of the adhesion pressure, the lower the adhesion can be. It can be said that the ceramic green sheet and the conductive film are excellent in adhesion.

[Table 2]

As shown in Table 2, Reference Example 2, Reference Example 3, Reference Example 6 to Reference Example 11 have substantially the same bonding pressure as Reference Example 1 without using an organic additive. In addition, in Reference Example 4 and Reference Example 5, compared with Reference Example 1 in which no organic additive was used, the subsequent pressure was increased, and the adhesion between the ceramic green sheet and the conductive film was reduced. Compared to these reference examples, in Examples 1 to 4, compared with Reference Example 1 without using an organic additive, or Reference Example 9 to Reference Example 11 using PVB as a resin binder, the bonding pressure is also significantly smaller. The adhesion between the ceramic green sheet and the conductive film is improved.

As described above, the effect of improving the adhesion between the substrate and the conductive film cannot be obtained when a monofunctional (meth) acrylate compound having one (meth) acrylfluorene group in one molecule is used as an organic additive. Not only that, but sometimes the adhesion is reduced. In addition, as an organic additive, it is also used as a resin adhesive in the case of using only an amine-based organic additive having no (meth) acrylfluorene group in the molecule, or in addition to the (meth) acrylate compound disclosed herein In the case of butyral resin (PVB), the effect of improving the adhesion is small. That is, the (meth) acrylate compound as an organic additive disclosed here can be said to be a particularly advantageous material from the viewpoint of improving the adhesion between the substrate and the conductive film.

The present invention has been described in detail above, but these explanations are merely examples, and the present invention can be modified in various ways without departing from the spirit thereof.

10‧‧‧Multilayer Ceramic Capacitors

20‧‧‧ Dielectric layer

30‧‧‧Internal electrode layer

40‧‧‧External electrode

FIG. 1 is a cross-sectional view schematically showing a multilayer ceramic capacitor according to an embodiment of the present invention.

Claims (10)

A conductive paste for forming an electrode layer on a substrate. The conductive paste includes: a conductive powder, a resin binder, an organic additive, and an organic solvent. The organic additive is contained in a molecule and has 2 The above (meth) acrylfluorenyl group is a (meth) acrylate compound having a number average molecular weight of 1,000 or less. The conductive paste according to the first claim, wherein the organic additive further includes an amine-based organic additive. The conductive paste according to claim 1 or claim 2, wherein the (meth) acrylate compound comprises a lactone-modified (meth) acrylate compound. The conductive paste according to item 1 or 2 of the scope of patent application, wherein when the entire conductive paste is 100% by mass, the proportion of the organic additive is 5% by mass or less. The conductive paste according to claim 1 or claim 2, wherein the (meth) acrylate compound has 6 or less (meth) acrylfluorenyl groups in one molecule. The conductive paste according to item 1 or 2 of the patent application scope, wherein the number average molecular weight of the (meth) acrylate compound is 200 or more and 800 or less. The conductive paste according to item 1 or item 2 of the patent application scope, wherein the resin binder contains a cellulose-based resin. The conductive paste according to item 1 or 2 of the scope of patent application, wherein when the entire conductive paste is 100% by mass, the proportion of the resin adhesive is 1% by mass or more and 5% by mass %the following. The conductive paste according to item 1 or item 2 of the patent application scope, wherein the substrate is a ceramic green sheet containing a ceramic powder and a resin binder. The conductive paste according to item 1 or 2 of the scope of patent application, which is used for forming an internal electrode layer of a multilayer ceramic capacitor.