TWI874335B - Conductive slurries, electronic components, and multilayer ceramic capacitors - Google Patents

Abstract

The present invention provides a conductive slurry with excellent dispersibility. The conductive slurry of the present invention contains conductive powder, ceramic powder, dispersant, binder resin and organic solvent. The dispersant includes an acid dispersant and an alkaline dispersant. The average molecular weight of the acid dispersant exceeds 500 and is less than 2000, and has more than one side chain composed of hydrocarbons relative to the main chain. The binder resin includes an acetal resin, and the organic solvent includes a glycol ether solvent.

Description

Conductive slurries, electronic components, and multilayer ceramic capacitors

The present invention relates to a conductive slurry, electronic components and a multilayer ceramic capacitor.

As electronic devices such as mobile phones and digital devices become smaller and more powerful, electronic components such as multilayer ceramic capacitors are also expected to become smaller and more powerful. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked. Miniaturization and higher capacity can be achieved by thinning the dielectric layers and internal electrode layers.

For example, a laminated ceramic capacitor can be manufactured as follows. First, a conductive slurry for an internal electrode is printed (applied) in a predetermined electrode pattern on the surface of a dielectric green sheet containing a dielectric powder such as barium titanium _oxide (BaTiO 3 ) and a binder resin, and dried to form a dry film. The dry film and the dielectric green sheet are laminated in an alternating manner, and are heated and pressed to form a press-bonded body. The press-bonded body is cut, subjected to an organic binder removal treatment in an oxidizing gas environment or an inert gas environment, and then fired to obtain a fired chip (laminated body). Next, external electrode slurry is applied to both ends of the fired wafer (laminated body), and after firing, nickel or the like is plated on the surface of the external electrode to obtain a laminated ceramic capacitor.

Screen printing has been the most common printing method for printing conductive paste on dielectric green sheets. However, with the need for miniaturization, thin filmization, and improved productivity of electronic devices, there is a need to print finer electrode patterns with higher productivity.

As one of the printing methods of conductive slurry, gravure printing is proposed as a continuous printing method in which the conductive slurry is filled in the recessed part provided on the plate and the plate is pressed against the printed surface to transfer the conductive slurry from the plate. The gravure printing method has a high printing speed and excellent productivity. When using the gravure printing method, it is necessary to appropriately select the binder resin, dispersant, solvent, etc. in the conductive slurry and adjust the properties such as viscosity to a range suitable for gravure printing.

For example, Patent Document 1 describes a conductive slurry for forming an internal conductor film by gravure printing, wherein the internal conductor film is an internal conductor film in a laminated ceramic electronic component having a plurality of ceramic layers and an internal conductor film extending along a specific interface between the ceramic layers. The conductive slurry comprises 30 to 70 wt % of a solid component containing metal powder, 1 to 10 wt % of an ethyl cellulose resin component having an ethoxy content of 49.6% or more, 0.05 to 5 wt % of a dispersant and a solvent component as the remainder, and has a viscosity η _0.1 of 1 Pa at a shear rate of 0.1 (s ^-1 ). s or more and a viscosity η _0.02 at a shear rate of 0.02 (s ^-1 ) that satisfies the conditions represented by a specific formula.

In addition, Patent Document 2 describes a conductive slurry, which is also a conductive slurry for forming an internal conductive film by gravure printing, similarly to Patent Document 1, and comprises 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, and is a thixotropic fluid having a viscosity of 1 Pa.s or more at a shear rate of 0.1 (s ^-1 ), and a viscosity change rate of 50% or more at a shear rate of 10 (s ^-1 ) based on the viscosity at a shear rate of 0.1 (s ^-1 ).

According to the above-mentioned patent documents 1 and 2, the above-mentioned conductive slurry is a thixotropic fluid with a viscosity of 1 Pa.s or more at a shear rate of 0.1 (s ^-1 ), which can obtain stable continuous printing at high speed in gravure printing, and can manufacture multilayer ceramic electronic components such as multilayer ceramic capacitors with good production efficiency.

Patent document 3 discloses a conductive slurry for gravure printing, which is a conductive slurry 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) is composed of polyvinyl butyral having a degree of polymerization of 10,000 to 50,000 and a weight average molecular weight of 1. 0000 to 100000 ethyl cellulose, the organic solvent (C) is composed of any one 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) is composed of a separation inhibitor and a dispersant, and the separation inhibitor is composed of a composition containing a polycarboxylic acid polymer or a polycarboxylate. According to patent document 3, the conductive slurry has a viscosity suitable for gravure printing, can improve the uniformity and stability of the slurry, and has good drying properties.

[Prior Technical Literature]

【Patent Literature】

[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

With the thinner internal electrode layer in recent years, the conductive powder also tends to have a smaller particle size. When the particle size of the conductive powder is smaller, the specific surface area of the particle surface becomes larger, so the surface activity of the conductive powder (metal powder) becomes higher, and there is a possibility that the dispersibility of the conductive slurry decreases, thus requiring a conductive slurry with higher dispersibility.

In addition, when printing the conductive slurry using the gravure printing method, a lower slurry viscosity is required than the screen printing method, so it is considered that the conductive powder with a larger specific gravity will settle and reduce the dispersibility of the slurry. In addition, in the conductive slurry described in the above-mentioned patent documents 1 and 2, although the dispersibility of the slurry is improved by removing the lumps in the conductive slurry using a filter, a process of removing the lumps is required, so the manufacturing process tends to become complicated.

In view of such a situation, the purpose of the present invention is to provide a conductive slurry having a slurry viscosity suitable for gravure printing and excellent dispersibility and productivity.

In the first aspect of the present invention, a conductive slurry is provided, comprising conductive powder, ceramic powder, dispersant, binder resin and organic solvent, wherein the dispersant comprises an acidic dispersant and an alkaline dispersant, the average molecular weight of the acidic dispersant is greater than 500 and less than 2000, and has one or more side chains composed of hydrocarbons relative to the main chain, the binder resin comprises an acetal resin, and the organic solvent comprises a glycol ether solvent.

In addition, the acid dispersant is preferably an acid dispersant having a carboxyl group, and more preferably a hydrocarbon graft copolymer with a polycarboxylic acid as the main chain. In addition, ideally, relative to 100 parts by mass of the conductive powder, it contains 0.2 parts by mass or more and 2 parts by mass or less of the acid dispersant, and relative to 100 parts by mass of the above-mentioned conductive powder, it contains 0.02 parts by mass or more and 2 parts by mass or less of the alkali dispersant. In addition, the conductive powder is preferably a metal powder containing at least one metal selected from Ni, Pd, Pt, Au, Ag, Cu and alloys of the above elements. In addition, the average particle size of the conductive powder is preferably 0.05μm or more and 1.0μm or less. In addition, the ceramic powder is preferably a calcite-titanium-type oxide. In addition, the average particle size of the ceramic powder is preferably 0.01μm or more and 0.5μm or less. In addition, the binder resin preferably contains a butyral resin. In addition, the conductive slurry is preferably used for an internal electrode of a laminated ceramic part. In addition, the conductive slurry preferably has a viscosity of 0.8 Pa. S or less at a shear rate of 100 sec ^-1 and a viscosity of 0.18 Pa. S or less at a shear rate of 10000 sec ^-1 .

In the second aspect of the present invention, an electronic component formed using the above-mentioned conductive slurry is provided.

In the third aspect of the present invention, a multilayer ceramic capacitor is provided, which has at least a multilayer body formed by laminating a dielectric layer and an internal electrode, and the internal electrode is formed using the above-mentioned conductive slurry.

The conductive slurry of the present invention has a viscosity suitable for gravure printing, and the dispersibility and productivity of the slurry are excellent. In addition, when the electrode pattern of electronic parts such as multilayer ceramic capacitors formed using the conductive slurry of the present invention is formed into a thin film electrode, the printing performance of the conductive slurry is also excellent and has a uniform thickness.

1: Multilayer ceramic capacitors

10: Ceramic laminate

11: Internal electrode layer

12: Dielectric layer

20: External electrode

21: External electrode layer

22: Electroplating

A in [Figure 1] is a three-dimensional diagram showing a multilayer ceramic capacitor related to an implementation form, and B in Figure 1 is a cross-sectional diagram thereof.

[Conductive slurry]

The conductive slurry of this embodiment contains conductive powder, ceramic powder, dispersant, binder resin and organic solvent. The following is a detailed description of each component.

(Conductive powder)

There is no particular limitation on the conductive powder, and metal powder can be used. For example, powders of one or more selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys of the above elements can be used. Among them, from the perspective of conductivity, corrosion resistance, and cost, it is desirable to use a powder of Ni or its alloy (hereinafter, sometimes referred to as "Ni powder"). As a Ni alloy, for example, an alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd can be used. The Ni content in the Ni alloy is, for example, 50% by mass or more, and ideally 80% by mass or more. In addition, in order to suppress the violent gas generation caused by the partial thermal decomposition of the binder resin during the debonding agent treatment, the Ni powder can contain the element S of several hundred ppm.

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 slurry for internal electrodes of thin-film multilayer ceramic capacitors (multilayer ceramic parts), for example, to improve the smoothness and density of the dry film. The average particle size is a value obtained by observation based on a scanning electron microscope (SEM), and is the number average value obtained by measuring the particle sizes of multiple particles one by one from an image obtained by observation at a magnification of 10,000 times by SEM.

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

(Ceramic powder)

The ceramic powder is not particularly limited, and for example, in the case of a conductive slurry for an internal electrode of a multilayer ceramic capacitor, a known ceramic powder can be appropriately selected according to the type of multilayer ceramic capacitor to be used. Examples of the ceramic powder include a calcium titanate-type oxide containing Ba and Ti, preferably barium titanate (BaTiO ₃ ).

As the ceramic powder, a ceramic powder containing barium titanate as a main component and oxides as a subcomponent can be used. As the oxide, one or more oxides selected from Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb and rare earth elements can be listed. In addition, as the ceramic powder, for example, a calcite-titanic oxide ferroelectric ceramic powder in which Ba atoms and Ti atoms of barium titanate (BaTiO ₃ ) are replaced with other atoms such as Sn, Pb, Zr, etc. can be used.

When used as a conductive slurry for an internal electrode, the ceramic powder may have the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor (electronic component). This can suppress the generation of cracks due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer during the sintering process. _{Such ceramic powders include, in addition to the above-mentioned calcite-titanic oxides containing Ba and Ti, oxides such as ZnO, ferrite, PZT, BaO, Al2O3, Bi2O3 , R (} rare earth element) _{2O3 , TiO2} , and _Nd2O3 . In addition, the ceramic powder may be one kind or two or more _kinds .

The average particle size of the ceramic powder is, for example, 0.01 μm to 0.5 μm, and ideally 0.01 μm to 0.3 μm. By making the average particle size of the ceramic powder within the above range, when used as an internal electrode slurry, a sufficiently thin and uniform internal electrode can be formed. The average particle size is a value obtained by observation based on a scanning electron microscope (SEM), and is the number average value obtained by measuring the particle sizes of multiple particles one by one from the image obtained by observation at a magnification of 50,000 times by SEM.

Based on 100 parts by mass of the conductive powder, the content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less.

The content of ceramic powder relative to the total amount of conductive slurry is preferably 1% by mass to 20% by mass, and more preferably 3% by mass to 20% by mass. When the content of conductive powder is within the above range, the conductivity and dispersibility are excellent.

(Adhesive resin)

The binder resin contains an acetal resin. As the acetal resin, a butyral resin such as polyvinyl butyral is preferred. When the binder resin contains an acetal resin, the viscosity can be adjusted to be suitable for gravure printing, and the bonding strength with the raw sheet can be further improved. The binder resin may contain, for example, 20% or more of the acetal resin relative to the entire binder resin, or may contain 30% or more of the acetal resin, or may be composed only of the acetal resin. In addition, even if the content of the acetal resin is less than 40% by mass relative to the entire binder resin, a low slurry viscosity and sufficient bonding strength can be achieved.

Based on 100 parts by mass of the conductive powder, the content of the acetal resin is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 8 parts by mass or less.

In addition, the adhesive resin may contain other resins besides the acetal resin. There is no particular limitation on other resins, and known resins may be used. Examples of other resins include cellulose resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, and acrylic resins. Among them, ethyl cellulose is ideal from the perspective of solubility in solvents and combustion decomposition. In addition, the molecular weight of the adhesive resin is, for example, about 20,000 to 200,000.

Based on 100 parts by mass of the conductive powder, the content of the binder resin is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 8 parts by mass or less.

The content of the binder resin relative to the total amount of the conductive slurry is preferably 0.5% by mass to 10% by mass, and more preferably 0.5% by mass to 6% by mass. When the content of the binder resin is within the above range, the conductivity and dispersibility are excellent.

(Organic solvent)

The organic solvent contains glycol ether solvent.

As glycol ether solvents, for example, diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, ethylene glycol monohexyl ether and other (di)ethylene glycol ethers, and propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether (PNB) and other propylene glycol monoalkyl ethers can be listed. Among them, propylene glycol monoalkyl ethers are preferred, and propylene glycol monobutyl ether (PNB) is more preferred. When the organic solvent contains a glycol ether solvent, it has excellent compatibility with the above-mentioned adhesive resin and excellent drying properties.

The organic solvent may contain, for example, 25% by mass or more of a glycol ether solvent relative to the entire organic solvent, or may contain 50% by mass or more, or may consist only of a glycol ether solvent. In addition, a glycol ether solvent may be used alone or in combination of two or more.

The organic solvent may further contain an acetate-based solvent. Examples of the acetate-based solvent include dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy 3-methylbutyl acetate, 1-methoxypropyl-2-acetate and other glycol ether acetates.

When the organic solvent contains an acetate solvent, for example, it may contain at least one acetate solvent (A) selected from dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, and isobornyl isobutyrate. Among them, isobornyl acetate is more preferred. Relative to the entire organic solvent, the acetate solvent is contained in an amount of 0 mass% to 80 mass%, preferably 10 mass% to 60 mass%, and more preferably 20 mass% to 40 mass%.

In addition, when the organic solvent contains an acetate solvent, for example, it may contain the above-mentioned acetate solvent (A) and at least one acetate solvent (B) selected from ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate. When such a mixed solvent is used, the viscosity of the conductive slurry can be easily adjusted, and the drying speed of the conductive slurry can be accelerated.

In the case of a mixed solution containing an acetate solvent (A) and an acetate solvent (B), the organic solvent preferably contains 50% by mass or more and 90% by mass or less of the acetate solvent (A) relative to the entire organic solvent, and more preferably contains 60% by mass or more and 80% by mass or less. In the case of the above-mentioned mixed solution, the acetate solvent (B) is contained in an amount of 10% by mass or more and 50% by mass or less, and more preferably contains 20% by mass or more and 40% by mass or less, based on the entire acetate solvent being 100% by mass.

In addition, the organic solvent may contain other organic solvents other than glycol ether solvents and acetate solvents. As other organic solvents, there are no particular limitations, and known organic solvents that can dissolve the above-mentioned adhesive resin can be used. As other organic solvents, for example, acetate solvents such as ethyl acetate, propyl acetate, isobutyl acetate, and butyl acetate, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, terpene solvents such as terpineol and dihydroterpineol, aliphatic hydrocarbon solvents such as tridecane, nonane, and cyclohexane, etc. can be listed. Among them, aliphatic hydrocarbon solvents are ideal, and mineral spirits are more ideal among aliphatic hydrocarbon solvents. In addition, other organic solvents can be used alone or in combination.

The organic solvent may contain, for example, a glycol ether solvent as a main solvent and an aliphatic hydrocarbon solvent as a secondary solvent. In this case, based on 100 parts by mass of the conductive powder, it is ideal to contain 30 parts by mass to 50 parts by mass of the glycol ether solvent, and more ideally, it is ideal to contain 40 parts by mass to 50 parts by mass. Based on 100 parts by mass of the conductive powder, it is ideal to contain 20 parts by mass to 80 parts by mass of the aliphatic hydrocarbon solvent, and more ideally, it is ideal to contain 20 parts by mass to 40 parts by mass. In addition, even when the conductive powder contains more than 25 parts by mass of the aliphatic hydrocarbon solvent, the dispersibility of the conductive slurry is excellent.

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

The content of the organic solvent relative to the total amount of the conductive slurry is preferably 20% by mass to 50% by mass, and more preferably 25% by mass to 45% by mass. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

(Dispersant)

The inventors of the present invention have studied various dispersants used in conductive slurries and found that by using a dispersant containing an acidic dispersant and an alkaline dispersant having one or more, preferably multiple, side chains composed of hydroxyl groups relative to the main chain and an average molecular weight of more than 500 and less than 2000, the powder material contained in the conductive slurry, i.e., the conductive powder and ceramic powder, can be excellently dispersed, and the surface smoothness of the dried film after the conductive slurry is applied and dried can be excellent.

Although the details of the reason for this effect are not clear, it is believed that by making the acid dispersant have a side chain composed of hydrocarbons, a stereo barrier is effectively formed to prevent the aggregation of the powder material, and by containing an alkaline dispersant with good compatibility with the acid dispersant, the dispersant can be more effectively dispersed uniformly. In addition, by setting the molecular weight of the acid dispersant to a specific size, the conductive slurry can be maintained at an appropriate viscosity corresponding to the purpose. In addition, the present invention is not restricted by the above theory (reason). The following is a further detailed description of the dispersant related to this embodiment.

The acid-based dispersant has one or more side chains composed of alkyl groups relative to the main chain, and preferably has multiple side chains composed of alkyl groups. The acid-based dispersant preferably has a carboxyl group, and more preferably is a alkyl graft copolymer with a polycarboxylic acid as the main chain. In addition, the polycarboxylic acid preferably has an ester structure. In addition, the alkyl group preferably has a chain structure. In addition, the alkyl group may be an alkyl group. In addition, the alkyl group may be composed only of carbon and hydrogen, and a part of the hydrogen constituting the alkyl group may be substituted by a substituent.

The molecular weight of the acidic dispersant is greater than 500 and less than 2000, and may be greater than 1000 and less than 2000. When the molecular weight is within the above range, the dispersibility of the conductive powder and ceramic powder is excellent, and the density and smoothness of the dry electrode surface after coating are excellent. In addition, in this specification, when the molecular weight of the dispersant has a certain degree of distribution, the molecular weight of the dispersant represents the weight average molecular weight.

For example, an acid-based dispersant that satisfies the above-mentioned characteristics can be selected from commercially available products. In addition, the acid-based dispersant can also be manufactured using a conventionally known manufacturing method in a manner that satisfies the above-mentioned characteristics.

With the conductive powder as 100 parts by mass, it is ideal to contain 0.2 parts by mass or more and 2 parts by mass or less of an acidic dispersant. When the content of the acidic dispersant is within the above range, the dispersibility of the conductive powder and ceramic powder, the smoothness of the dry electrode surface after coating are excellent, and the viscosity of the conductive slurry can be adjusted to an appropriate range. In addition, sheet erosion and poor peeling of the green sheet can be suppressed. In addition, in the conductive slurry related to this embodiment, even if the content of the acidic dispersant is less than 1 part by mass, it can have a high dispersibility.

In addition, relative to the total amount of the conductive slurry, it is ideal to contain 3% by mass or less of the acidic dispersant. The upper limit of the content of the acidic dispersant is ideally 2% by mass or less, and more ideally 1% by mass or less. The lower limit of the content of the acidic dispersant is not particularly limited, for example, it is 0.01% by mass or more, ideally 0.05% by mass or more, and can also be 0.5% by mass or more. When the content of the acidic dispersant is within the above range, the viscosity of the conductive slurry can be adjusted to an appropriate range, and sheet erosion and poor peeling of the green sheet can be suppressed.

The structure of the alkaline dispersant is not particularly limited, and examples thereof include fatty amines such as lauryl amine, polyethylene glycol lauryl amine, rosin amine, cetyl amine, myristic amine, stearyl amine, oleyl amine, and polyoxyethylene lauryl amine. The alkaline dispersant can further enhance the effect of the above-mentioned acidic dispersant and can further enhance the dispersibility when forming a conductive slurry.

Based on 100 parts by mass of the conductive powder, it is ideal to contain 0.02 parts by mass or more and 2 parts by mass or less of the alkaline dispersant. When the alkaline dispersant is contained within the above range together with the acidic dispersant of the present invention, the dispersibility of the conductive powder and ceramic powder in the conductive slurry is better, the smoothness of the dry electrode surface after coating is better, and the viscosity of the conductive slurry can be adjusted to an appropriate range. In addition, sheet erosion and poor peeling of the green sheet can be suppressed. In addition, in the conductive slurry related to this embodiment, the content of the alkaline dispersant can be less than 1 part by mass, less than 0.1 part by mass, or less than 0.05 part by mass.

In addition, based on 100 parts by mass of the acidic dispersant, for example, 1 part by mass or more and 500 parts by mass or less of the alkaline dispersant may be contained, preferably 10 parts by mass or more and 300 parts by mass or less, more preferably 50 parts by mass or more and 200 parts by mass or less, and more preferably 50 parts by mass or more and 150 parts by mass or less. When the alkaline dispersant is contained in the above range, the viscosity stability of the conductive slurry is more excellent and the dry film density tends to be higher.

For example, the amount of alkaline dispersant contained in the conductive slurry as a whole is 0 mass% to 2.5 mass%, preferably 0 mass% to 1.0 mass%, more preferably 0.1 mass% to 1.0 mass%, and more preferably 0.1 mass% to 0.8 mass%. When the alkaline dispersant is contained in the above range, the viscosity stability of the slurry over time is more excellent. In addition, the alkaline dispersant can be 0.5 mass% or less, less than 0.1 mass%, or less than 0.05 mass% relative to the conductive slurry as a whole.

In addition, the conductive slurry may contain only the above-mentioned acidic dispersant and the above-mentioned alkaline dispersant as dispersants, or may contain dispersants other than the above-mentioned dispersants within the range that does not hinder the effect of the present invention. Dispersants other than the above-mentioned may include, for example, acidic dispersants containing higher fatty acids, polymeric surfactants, amphoteric surfactants, and polymeric dispersants. In addition, these dispersants may be used alone or in combination of two or more.

Taking the conductive powder as 100 parts by mass, the content (total content) of the dispersant as a whole combined with the acidic dispersant is preferably 0.01 parts by mass to 3 parts by mass, and more preferably 0.23 parts by mass to 3 parts by mass. In addition, in the conductive slurry related to this embodiment, the content (total content) of the dispersant as a whole can be 2 parts by mass or less, or 1 part by mass or less. Even if the content of the dispersant as a whole is within the above range, it can have a high dispersibility.

(Other ingredients)

The conductive slurry of this embodiment may contain other components in addition to the above components as needed. As other components, for example, conventionally known additives such as defoamers, plasticizers, and thickeners may be used.

(Conductive slurry)

There is no particular limitation on the method for producing the conductive slurry of this embodiment, and a conventionally known method can be used. For example, the conductive slurry can be produced by stirring and kneading the above-mentioned components by a three-roll mill, a ball mill, a mixer, etc. At this time, if a dispersant is pre-coated on the surface of the conductive powder, the conductive powder will not agglomerate, but can be fully dispersed, and the dispersant is spread all over its surface, and it is easy to obtain a uniform conductive slurry. In addition, the binder resin can be pre-dissolved in a part of the organic solvent, and after preparing the organic carrier, the conductive powder, ceramic powder, dispersant and organic carrier are added to the organic solvent for slurry adjustment, and then stirred and kneaded to prepare the conductive slurry.

The viscosity of the conductive slurry at a shear rate of 100 sec ^-1 is preferably 0.8 Pa. S or less, and may be 0.5 Pa. S or less, 0.4 Pa. S or less, or 0.3 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 slurry for gravure printing. If it exceeds the above range, the viscosity is too high and there is a case where it is not suitable for gravure printing. There is no particular lower limit on the viscosity of the conductive slurry of this embodiment at a shear rate of 100 sec ^-1 , for example, it is 0.1 Pa. S or more.

In addition, the viscosity of the conductive slurry at a shear rate of 10000 sec ^-1 is preferably 0.18 Pa. S or less, and may be less than 0.14 Pa. S. When the viscosity at a shear rate of 10000 sec ^-1 is within the above range, it can be suitably used as a conductive slurry for gravure printing. When it exceeds the above range, the viscosity may be too high and unsuitable for gravure printing. There is no particular lower limit for the viscosity at a shear rate of 10000 sec ^-1 , and for example, it is 0.05 Pa. S or more.

In addition, after printing the conductive slurry, the dry film density (DFD) of the dried film obtained is preferably more than 5.0 g/cm ³ , and may be more than 5.2 g/cm ³ , or may be more than 5.3 g/cm ^3. There is no particular upper limit on the dry film density, but it does not exceed 9.8 g/cm ³ , which is the true density of metallic nickel, and may be, for example, less than 6.5 g/cm ³ .

In addition, when a 20 mm square dry film with a film thickness of 1 to 3 μm is produced by printing a conductive slurry and drying it at 120°C in the atmosphere for 1 hour, the arithmetic mean roughness Sa is preferably 0.25 μm or less, more preferably 0.2 μm or less, and may be 0.16 μm or less. On the other hand, the lower limit of the arithmetic mean roughness Sa is not particularly limited, and the surface is preferably flat, and a value exceeding 0 and a smaller value is more ideal. In addition, the arithmetic mean roughness Sa is measured based on the ISO 25178 standard.

Conductive slurry can be suitably used in electronic parts such as multilayer ceramic capacitors. Multilayer ceramic capacitors have a dielectric layer formed using a dielectric green sheet and an internal electrode layer formed using a conductive slurry.

For multilayer ceramic capacitors, the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive slurry are preferably powders of the same composition. The multilayer ceramic device manufactured using the conductive slurry of this embodiment can suppress sheet erosion and green sheet peeling defects even when the thickness of the dielectric green sheet is, for example, less than 3μm.

[Electronic parts]

Hereinafter, the implementation forms of the electronic components of the present invention are described with reference to the drawings. In the drawings, the components are sometimes appropriately represented in a schematic manner or with a changed scale. In addition, the positions and directions of the components are appropriately described with reference to the XYZ orthogonal coordinate system shown in FIG. 1, etc. In the XYZ orthogonal coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction (up and down direction).

A in FIG. 1 and B in FIG. 1 are diagrams showing a multilayer ceramic capacitor 1 as an example of an electronic component related to the embodiment. The multilayer ceramic capacitor 1 has a multilayer body 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and an external electrode 20.

The following is a description of a method for manufacturing a multilayer ceramic capacitor using the above-mentioned conductive slurry. First, a conductive slurry is printed on a dielectric green sheet and dried to form a dry film, and a plurality of dielectric green sheets having the dry film on the upper surface are laminated by compression bonding, and then fired to integrate them, thereby preparing a laminated ceramic fired body (ceramic laminate 10) that becomes the main body of the ceramic capacitor. Thereafter, a pair of external electrodes 20 are formed at both ends of the laminate 10 to manufacture the multilayer ceramic capacitor 1. A more detailed description is given below.

First, a dielectric green sheet (ceramic green sheet) as an unfired ceramic sheet is prepared. As the dielectric green sheet, for example, a dielectric layer slurry obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a specified ceramic raw material powder such as barium titanium oxide is coated on a support film such as a PET film in a sheet shape and dried to remove the solvent. In addition, the thickness of the dielectric layer formed by the dielectric green sheet is not particularly limited, but from the perspective of the miniaturization of the multilayer ceramic capacitor 1, it is ideally 0.05μm or more and 3μm or less.

Next, prepare a plurality of sheets having a dry film formed by printing and applying the above-mentioned conductive slurry on one surface of the dielectric green sheet using the gravure printing method and drying. In addition, from the perspective of the requirement for thinning the internal electrode layer 11, the thickness of the conductive slurry (dry film) after printing is preferably less than 1μm after drying.

Next, the dielectric green sheet is peeled off from the supporting film, and after the dielectric green sheet and the conductive slurry (dry film) formed on one surface of the dielectric green sheet are alternately arranged, a laminate (pressed body) is obtained by heating and pressurizing. In addition, a structure in which a protective dielectric green sheet without conductive slurry is further arranged on both sides of the laminate can also be set.

Next, after the laminate is cut into pieces of a specified size to form a green chip, the green chip is subjected to a debinder treatment and fired in a reducing gas environment, thereby manufacturing a laminated ceramic fired body (laminated body 10). In addition, the gas environment in the debinder treatment is preferably an atmospheric air or an _N2 gas environment. The temperature during the debinder treatment is, for example, 200°C to 400°C. In addition, the holding time of the above temperature during the debinder treatment is preferably 0.5 hours to 24 hours. In order to suppress oxidation of the metal used in the internal electrode layer 11, the sintering is performed in a reducing gas environment. The temperature during sintering of the laminate 10 is, for example, not less than 1000°C and not more than 1350°C, and the temperature is maintained for, for example, not less than 0.5 hour and not more than 8 hours.

By firing the green wafer, the organic binder in the dielectric green sheet is completely removed, and the ceramic raw material powder is fired to form a ceramic dielectric layer 12. In addition, the organic carrier in the dry film is removed, and the nickel powder or the alloy powder with nickel as the main component is sintered or melted to form an internal electrode layer 11, and then a laminated ceramic fired body (laminated body 10) is formed in which a plurality of dielectric layers 12 and internal electrode layers 11 are alternately stacked. In addition, from the perspective of bringing oxygen into the interior of the dielectric layer 12 to improve reliability and suppress reoxidation of the internal electrode layer 11, the laminated ceramic fired body (laminate body 10) after firing can be subjected to annealing treatment.

Then, by providing a pair of external electrodes 20 to the manufactured multilayer ceramic sintered body (multilayer body 10), a multilayer ceramic capacitor 1 is manufactured. For example, the external electrode 20 has an external electrode layer 21 and an electroplated layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. In addition, as a material of the external electrode 20, for example, copper, nickel, or an alloy of the above elements can be preferably used. In addition, electronic components other than multilayer ceramic capacitors can also be used.

[Implementation Example]

The present invention is described in detail below based on embodiments and comparative examples, but the present invention is not limited to the embodiments in any way.

[Evaluation method]

(Viscosity of conductive slurry)

The viscosity of the conductive slurry after production was measured using a rheometer at shear rates of 100 sec ^-1 and 10,000 sec ^-1 .

(Dry film density)

The prepared conductive slurry was placed on a PET film and stretched to a length of about 100 mm using an applicator with a width of 50 mm and a gap of 125 μm. The obtained PET film was dried at 120°C for 40 minutes to form a dry film, which was then cut into four 2.54 cm (1 inch) squares. The thickness and weight of each of the four dry films were measured on the basis of peeling the PET film, and the dry film density (average value) was calculated.

(Surface roughness)

The prepared conductive slurry was printed on a 2.54 cm (1 inch) square heat-resistant tempered glass and dried at 120°C in the atmosphere for 1 hour to produce a 20 mm square dry film with a film thickness of 1 to 3 μm. The surface roughness Sa (arithmetic mean roughness) of the prepared dry film was measured using a device based on the ISO 25178 standard.

[Materials used]

(Conductive powder)

As the conductive powder, Ni powder (SEM average particle size: 0.3μm) was used.

(Ceramic powder)

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

(Adhesive resin)

As adhesive resins, polyvinyl butyral resin (PVB) and ethyl cellulose (EC) are used.

(Dispersant)

(1) As the acid dispersant (A), an acid dispersant having an average molecular weight of 1500 and being a hydrocarbon graft copolymer having a polycarboxylic acid as a main chain (having a side chain composed of hydrocarbon) is used.

(2) As alkaline dispersants, rosin amine (B), polyoxyethylene lauryl amine (C), and oleyl amine (D) are used.

(3) For comparison, a phosphoric acid-based dispersant (E) (molecular weight: 1400, no hydrocarbon-based side chains) used in conventional conductive slurries was used.

(Organic solvent)

As organic solvents, propylene glycol monobutyl ether (PNB), mineral spirits (MA), and terpineol (TPO) were used.

[Implementation Example 1]

With respect to 100 parts by mass of Ni powder as a conductive powder, 25 parts by mass of ceramic powder, 0.2 parts by mass of acid dispersant (A) as an acid dispersant, 1.0 parts by mass of alkaline dispersant (B) as an alkaline dispersant, 2 parts by mass of PVB and 4 parts by mass of EC as a binder resin, 41 parts by mass of PNB and 27 parts by mass of MA as an organic solvent were mixed to prepare a conductive slurry. The viscosity of the prepared conductive slurry, the dry film density of the slurry, and the surface roughness were evaluated by the above method. The content of the dispersant, etc. of the conductive slurry is shown in Table 1, and the evaluation results of the viscosity, dry film density, and surface roughness Sa of the conductive slurry are shown in Table 2.

[Example 2]

The conductive slurry was prepared and evaluated in the same manner as Example 1 except that the content of the acid dispersant (A) was set to 0.74 parts by mass. The content of the dispersant, etc. of the conductive slurry is shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Implementation Example 3]

The conductive slurry was prepared and evaluated in the same manner as Example 1 except that the content of the acid dispersant (A) was set to 2.0 parts by mass. The content of the dispersant, etc. of the conductive slurry is shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Implementation Example 4]

The conductive slurry was prepared and evaluated in the same manner as Example 2 except that the content of the alkaline dispersant (B) was set to 0.02 parts by mass. The content of the dispersant, etc. of the conductive slurry is shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Implementation Example 5]

The conductive slurry was prepared and evaluated in the same manner as Example 2 except that the content of the alkaline dispersant (B) was set to 2.0 parts by mass. The content of the dispersant, etc. of the conductive slurry is shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Implementation Example 6]

Conductive slurry was prepared and evaluated in the same manner as Example 1, except that the content of the acidic dispersant (A) was set to 0.6 parts by mass and the content of the alkaline dispersant (B) was set to 1.2 parts by mass. The content of the dispersant, etc. of the conductive slurry is shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the surface roughness evaluation results are shown in Table 2.

[Implementation Example 7]

Except for using alkaline dispersant (C) as the alkaline dispersant, the conductive slurry was prepared and evaluated in the same manner as Example 2. The content of the dispersant, etc. of the conductive slurry is shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Implementation Example 8]

The conductive slurry was prepared and evaluated in the same manner as Example 2 except that alkaline dispersant (D) was used as the alkaline dispersant. The contents of the dispersant, etc. of the conductive slurry are shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Comparison Example 1]

The conductive slurry was prepared and evaluated in the same manner as Example 1 except that only 0.8 parts by mass of a phosphoric acid-based dispersant (E) was used as the dispersant. The contents of the dispersant, etc. of the conductive slurry are shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the surface roughness evaluation results are shown in Table 2.

[Comparison Example 2]

Except for using 0.8 parts by mass of phosphoric acid-based dispersant (E) as the acid-based dispersant, the conductive slurry was prepared and evaluated in the same manner as Example 1. The contents of the dispersant, etc. of the conductive slurry are shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the surface roughness evaluation results are shown in Table 2.

[Comparison Example 3]

Conductive slurry was prepared and evaluated in the same manner as Example 2, except that 68 parts by mass of TPO was used as the main solvent and no secondary solvent was used. The contents of the dispersant, etc. of the conductive slurry are shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Comparison Example 4]

Conductive slurry was prepared and evaluated in the same manner as Example 2, except that 6 parts by mass of EC was used as the binder resin and PVB was not used. The contents of the dispersant, etc. of the conductive slurry are shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Reference Example 1]

The conductive slurry was prepared and evaluated in the same manner as Example 2 except that the alkaline dispersant (B) was not used as the dispersant. The contents of the dispersant, etc. of the conductive slurry are shown in Table 1, and the viscosity of the conductive slurry, the dry film density, and the evaluation results of the surface roughness are shown in Table 2.

[Reference Example 2]

The conductive slurry was prepared and evaluated in the same manner as Example 2 except that 0.8 parts by mass of alkaline dispersant (B) was used as the dispersant instead of the acidic dispersant (A). The contents of the dispersant and the like in the conductive slurry are shown in Table 1, and the viscosity of the conductive slurry, and the evaluation results of the dry film density and surface roughness are shown in Table 2.

(Evaluation results)

The viscosity of the conductive slurry of the embodiment is 0.21~0.31Pa.s at a shear rate of 100sec ^-1 , and is 0.10~0.14Pa.s at a shear rate of 10000sec ^-1. It stably shows a low value at any shear rate, indicating that it has a viscosity suitable for gravure printing. In addition, it can be confirmed that the dry film density of the conductive slurry of the embodiment shows a high value of 5.26~5.36g/ ^cm3 , and the surface roughness Sa of the dry film is 0.12~0.23μm, and the dispersibility is excellent.

In addition, when comparing the conductive slurries of Examples 1 to 3, it can be seen that even the conductive slurries with an acidic dispersant (A) content of 0.2 parts by mass (Example 1) and 0.74 parts by mass (Example 2) can obtain a higher dry film density and a smoother dry film surface that are comparable to the conductive slurry with an acidic dispersant (A) content of 2.0 parts by mass (Example 3). In addition, from Examples 2, 4, and 5, it can be seen that there is a tendency that the dry film density and surface roughness of the conductive slurry obtained are improved as the content of the alkaline dispersant is increased. In addition, from the comparison of the conductive slurries of Examples 1 and 4 with Example 6, it can be seen that there is a trend that the dry film density is improved when the mixing ratios of the acidic dispersant (A) and the alkaline dispersant (B) are close, compared with the case where there is a large difference in the mixing ratio. In addition, from the comparison of the conductive slurries of Examples 2, 7, and 8, it can be seen that even if the type of alkaline dispersant is changed, good dry film density and surface roughness can be obtained.

In contrast, when the conductive slurry of Comparative Example 1 was produced under the same conditions without the acid-based dispersant related to the present embodiment and only the phosphoric acid-based dispersant, the viscosity was higher than that of the conductive slurry of the embodiment, and the dry film density was not sufficiently increased.

In addition, in the conductive slurry of Comparative Example 2 in which an alkaline dispersant (B) is further added to the same phosphoric acid dispersant as Comparative Example 1, although the various properties are improved to some extent, the same dry film density as that of the example cannot be obtained. In addition, the viscosity of the conductive slurry of Comparative Example 3 using TPO, which is generally used as the main solvent, becomes very high and cannot become a viscosity suitable for gravure slurry. In addition, the surface roughness of the conductive slurry of Comparative Example 2 is also higher than that of the conductive slurry of the example. In addition, the viscosity of the conductive slurry of Comparative Example 4 in which the resin does not contain acetal resin is high, and the dry film density cannot be sufficiently improved.

In addition, it is shown that in the conductive slurry of Reference Example 1 containing only an acidic dispersant (A) as a dispersant, the dry film density is higher than that of Comparative Example 1 using a phosphoric acid dispersant (E), and the viscosity of the conductive slurry is also lower. In addition, in the conductive slurry of Reference Example 2 containing only an alkaline dispersant (B), the dry film density is slightly higher than that of Comparative Example 1 using a phosphoric acid dispersant (E), but the viscosity of the conductive slurry is higher.

From the above, it can be seen that when the conductive slurry of the embodiment of the present invention containing both the acidic dispersant (A) and the alkaline dispersant (B) is compared with the conductive slurry of the comparative example and the reference example, the dry film density is higher and the dispersibility of the conductive slurry is further improved. In addition, it can be seen that the conductive slurry of the embodiment of the present invention containing both dispersants is lower than the conductive slurry of the comparative example and the reference example in terms of the viscosity of the conductive slurry at a shear rate of 10000 sec ^-1 , and is more suitable for gravure printing.

In addition, the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments, etc. Sometimes one or more of the requirements described in the above-mentioned embodiments, etc. are omitted. In addition, the requirements described in the above-mentioned embodiments, etc. can be appropriately combined. In addition, as long as permitted by law, the disclosure contents of all documents cited in the above-mentioned embodiments, etc. are cited as part of the description of this article.

【Industrial Utilization】

The conductive slurry of the present invention has a viscosity suitable for gravure printing, and the density of the dry film after coating is relatively high, the surface smoothness of the dry film is very excellent, and the dispersibility is excellent. Therefore, the conductive slurry of the present invention is particularly suitable for use as a raw material for the internal electrode of the multilayer ceramic capacitor as a chip part of increasingly miniaturized electronic equipment such as mobile phones and digital devices, and is particularly suitable for use as a conductive slurry for gravure printing.

In addition, the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments, etc. Sometimes one or more of the requirements described in the above-mentioned embodiments, etc. are omitted. In addition, the requirements described in the above-mentioned embodiments, etc. can be appropriately combined. In addition, as long as permitted by law, the contents of Japanese Patent Application No. 2018-241706 filed in Japan and all documents cited in this specification are cited as part of the description of this article.

Claims (10)

A conductive slurry contains conductive powder, ceramic powder, dispersant, binder resin and organic solvent, wherein the slurry contains 1 to 30 parts by mass of the ceramic powder, 0.01 to 3 parts by mass of the dispersant, 1 to 10 parts by mass of the binder resin, and 50 to 130 parts by mass of the organic solvent, relative to 100 parts by mass of the conductive powder. The dispersant includes an acidic dispersant and an alkaline dispersant. The acidic dispersant has an average molecular weight of more than 500 and less than 2000 and is a hydrocarbon graft copolymer with a polycarboxylic acid as the main chain. The alkaline dispersant is an aliphatic amine. The binder resin comprises an acetal resin, the organic solvent comprises a glycol ether solvent, the acid dispersant is contained in an amount of 0.2 to 2 parts by mass relative to 100 parts by mass of the conductive powder, and the alkali dispersant is contained in an amount of 0.02 to 2 parts by mass relative to 100 parts by mass of the conductive powder; the conductive slurry has a viscosity of 0.18 Pa·S or less at a shear rate of 10000 sec ^-1 . The conductive slurry as recited in claim 1, wherein the conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu and alloys of the above elements. The conductive slurry as recited in claim 1, wherein the conductive powder has an average particle size of not less than 0.05 μm and not more than 1.0 μm. The conductive slurry as recited in claim 1, wherein the ceramic powder contains a calcium-titanium-based oxide. The conductive slurry as recited in claim 1, wherein the average particle size of the ceramic powder is greater than or equal to 0.01 μm and less than or equal to 0.5 μm. The conductive slurry as recited in claim 1, wherein the binder resin contains a butyraldehyde-based resin. The conductive slurry as recited in claim 1, wherein the viscosity of the conductive slurry at a shear rate of 100 sec ^-1 is less than 0.8 Pa·S. The conductive slurry as recited in claim 1, wherein the conductive slurry is used for an internal electrode of a laminated ceramic part. An electronic component is characterized in that it is an electronic component comprising a laminate, wherein the laminate has a dry film formed using the conductive slurry described in any one of claims 1 to 7. A multilayer ceramic capacitor is characterized in that it has at least a laminated body formed by laminating a dielectric layer and an internal electrode, wherein the internal electrode is formed using the conductive slurry described in claim 8.

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