TW201939523A - Conductive paste having stable viscosity over time - Google Patents

Abstract

Provided is a conductive paste which is suppressed in increase of the viscosity during storage, thereby having further enhanced viscosity stability. The present invention provides a conductive paste which contains a conductive powder, a binder, a thickening inhibitor and a dispersion medium. The thickening inhibitor is a secondary amine compound which is represented by general formula NHR1R2. In the formula, each of R1 and R2 independently represents a linear or cyclic aliphatic group having 4-12 carbon atoms, and carbon chains in the R1 and R2 moieties do not contain a nitrogen atom and an oxygen atom.

Description

Conductive paste with stable viscosity over time

The present invention relates to a conductive paste capable of forming a conductor layer.
This application claims priority based on Japanese Patent Application No. 2018-050965 filed on March 19, 2018, and incorporates the entire contents of this application into this specification by reference.

Along with miniaturization and weight reduction of electronic devices, miniaturization and thickness reduction of each electronic component constituting the electronic devices is also required. As an example, a multi-layer ceramic capacitor (MLCC) has a structure in which a dielectric layer including a ceramic and a plurality of internal electrode layers are laminated. In the MLCC, it is required to enlarge the electrode area by further thinning the dielectric layer and further increasing the number of layers, so that the volume of the MLCC is miniaturized and the electrostatic capacitance is increased.

The MLCC is generally manufactured using the following sequence. That is, first, a conductive paste for an internal electrode containing a conductive powder is printed on a dielectric green sheet containing a dielectric powder, a binder, and the like to form an internal electrode layer. Many dielectric green sheets having the internal electrode layer printed thereon are printed. The layers are laminated and crimped for integration. Then, the laminated body is cut into a predetermined size, and dried and fired to produce a capacitor body. The capacitor body can be made into an MLCC suitable for surface mounting by forming an external electrode for side-by-side bonding of each capacitor structure due to the end surface. In recent years, MLCCs such as 0ML size (0.25 mm × 0.125 mm) and 01005 size (0.1 mm × 0.05 mm) with a dielectric layer thickness of less than 1 μm are commercially available.

Regarding the conductive paste for forming the electronic component, in general, the reduction in the particle size of the conductive powder and the reduction in the polarity of the solvent as a dispersion medium for stably dispersing the conductive powder are being promoted. However, the reduction in the particle size of the conductive powder essentially causes agglomeration of particles, and causes deterioration in quality when the conductive paste is stored (for example, an increase in viscosity over time). Therefore, an amine-based thickening inhibitor is added to such a conductive paste in addition to a dispersant as compared with the conventional case (for example, refer to Patent Documents 1 to 4).
[Prior Art Literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2017-135058
[Patent Document 2] Japanese Patent Application Publication No. 2016-031912
[Patent Document 3] Japanese Patent Application Publication No. 2013-149457
[Patent Document 4] Japanese Patent Application Publication No. 2004-182951

[Problems to be Solved by the Invention]
Regarding the conductive powder, a conductive powder having an average particle diameter of about 0.4 μm has been previously used, and in recent years, a conductive powder of 0.2 μm or less has been used. In addition, as for the conductive paste for MLCC, in addition to the conductive powder, a coexisting material containing ceramic fine powder with a smaller particle size is also used. Therefore, the aggregation of the dispersed particles and the increase in the viscosity of the paste cannot be avoided during long-term storage of the conductive paste, and further improvement in the viscosity stability of the paste is required.

The present invention has been made in view of the above-mentioned aspects, and an object thereof is to provide a conductive paste in which viscosity increase during storage is suppressed and viscosity stability is further improved.
[Means for solving problems]

According to the conventional conductive paste, a thickening inhibitor must be used separately according to the properties of the conductive powder contained in the conductive paste. For example, it has been proposed to use a thickening inhibitor that exhibits a thickening inhibitory effect only for a conductive powder having a narrow specific particle size range, a conductive powder having a specific surface protective agent, and the like. On the other hand, the inventors of the present inventors conducted diligent research, and found that an amine compound having an extremely limited molecular structure is preferable as a thickening inhibitor in a conductive paste containing a conductive powder having a wide particle size range. The present invention has been completed. That is, the conductive paste disclosed herein includes a conductive powder, a binder, a viscosity-increasing inhibitor, and a dispersion medium. Moreover, the viscosity-increasing inhibitor is a secondary amine compound represented by the general formula: NHR ¹ R ² ; In addition, R ¹ and R ² in the formula are independently a linear or cyclic aliphatic group having 4 to 12 carbon atoms, and the carbon chain in R ¹ and R ² does not contain an oxygen atom (O). , Nitrogen atom (N) and sulfur atom (S).

By using the conductive paste, it is possible to suppress agglomeration of the conductive powder, and to suppress an increase in the viscosity of the paste with time. For example, even if it is a conductive paste containing a conductive powder having an average particle diameter of 1 μm or less, it is not limited to the specific particle diameter range, and high dispersibility of the conductive powder can be maintained well and stably for a long period of time. Further, details is not clear, but it was confirmed that even R ^1, R ² having a carbon number of 4 to 12 secondary amino compound, for example, in R ^1, R ² O contained in the carbon chain, the case of N, S of Etc., the effect of suppressing the viscosity increase cannot be obtained, but the properties of the conductive paste may be deteriorated.

In a preferred aspect of the conductive paste disclosed herein, the R ¹ and the R ² satisfy R ¹ = R ² . That is, the secondary amine compound may have symmetry in a molecular structure. Therefore, it is preferable that the conductive paste having excellent viscosity stability can be realized by a secondary amine compound that is relatively easy to obtain.

In a preferred aspect of the conductive paste disclosed herein, both R ¹ and R ² do not contain a methyl group other than a terminal. Thereby, the dispersibility of the conductive powder can be maintained and the thickening suppressing effect of the conductive paste can coexist at a higher level, which is preferable.

In a preferred aspect of the conductive paste disclosed herein, the viscosity increasing inhibitor is contained in the conductive paste at a ratio of 0.001% by mass or more and 5% by mass or less. With the addition of the small amount of a viscosity-increasing inhibitor, the effect can be exerted better, so it is preferable.

In a preferred aspect of the conductive paste disclosed herein, the conductive powder is a nickel powder. Thereby, a conductive paste having the above characteristics can be provided as a lower-cost conductive paste, which is preferable.

In a preferred aspect of the conductive paste disclosed herein, the average particle diameter of the conductive powder is 1 μm or less. The conductive paste is preferred even when it contains conductive powders with an average particle size of 0.4 μm or less, or when it contains conductive powders with an average particle size of 0.2 μm or less. To suppress viscosity rise. When the particle size of the conductive powder is 1/2 in the particle size level, not only the specific surface area thereof becomes four times, but also the activity of the surface of the particles increases, and aggregation becomes remarkable. The conductive paste disclosed herein is preferable because it can maintain the dispersibility of the conductive powder and the effect of suppressing the thickening of the conductive paste at a high level in a wide range of particle sizes.

In a preferred aspect of the conductive paste disclosed herein, a dielectric powder is further included. Thereby, the conductive paste can better adjust the sintering shrinkage characteristics during sintering. As a result, for example, a conductive paste can be preferably used for the formation of an internal electrode of the MLCC, and thus it is preferable.

A preferable aspect of the conductive paste disclosed herein further includes a first powder having a first average particle diameter and a second powder having a second average particle diameter. Here, the second average particle diameter D ₂ is within a range of 0.1 × D _{1 to} 0.4 × D ₁ based on the first average particle diameter D ₁ . The conductive powder is configured to include at least the first powder. The conductive paste disclosed herein can exert the effects of maintaining the dispersibility of the conductive powder and suppressing the viscosity increase at a high level in a wide range of particle sizes. Therefore, for example, in a range where the average particle diameter is 1 μm or less, even if the second powder having a smaller average particle diameter is included in addition to the conductive powder as the first powder, the above-mentioned effect can be exhibited better, and therefore, it is preferable. .

As described above, the conductive paste disclosed herein can better maintain the dispersibility of the conductive powder, and as a result, the increase in the viscosity of the conductive paste can be suppressed for a long period of time. Accordingly, even if the electrode formed using the conductive paste is extremely thin, for example, the surface flatness caused by the aggregation of the conductive powder is reduced or the bonding structure of the conductive particles is uneven and unstable. Viscosity caused by printing or reduction in quality stability at a mass production level is also suppressed. As a result, an electrode having excellent surface flatness and homogeneous electrode structure such as a conductive channel can be stably formed by a mass production step.

Therefore, in another aspect, the technology disclosed herein provides an MLCC in which a dielectric layer and an internal electrode are laminated. The internal electrode layer is composed of a fired product of any one of the conductive pastes. In the MLCC, further thinning and high build-up of the dielectric layer are required. The internal electrode layer disposed between the thin (for example, 1 μm or less) dielectric layers can be preferably formed by using the conductive paste disclosed herein as a surface with high flatness, electrical connection, and homogeneity. As a result, a small-sized, large-capacity, and high-quality MLCC with suppressed occurrence of short circuits, cracks, and the like of the dielectric layer can be achieved.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. Furthermore, matters other than those specifically mentioned in this specification (for example, the composition of conductive paste or its properties) are matters required for the implementation of the present invention (for example, regarding the preparation of the paste and the substrate). The specific method of the application, the composition of electronic components, etc.) can be implemented based on the technical content pointed out in this specification and the general technical common sense of practitioners in the field. In addition, the expression "A to B" which shows a numerical range in this specification means A or more and B or less.

[Conductive paste]
The conductive paste disclosed herein includes (A) a conductive powder, (B) a viscosity-increasing inhibitor, (C) a binder, and (D) a dispersion medium as main constituent components. The conductive paste is sintered, and (B) the thickening inhibitor, (C) the binder, and (D) the dispersing medium will disappear, and (A) the conductive powder is sintered to form a conductive sintered body (typically, (Layered "conductor layer"). The conductive powder (A), which is the main body of the conductive layer, is usually dispersed in a vehicle containing (C) a binder and (D) a dispersion medium to form a paste, and is imparted with moderate viscosity and fluidity. . In addition, the conductive paste can well maintain its viscosity and fluidity by the (B) viscosity increasing inhibitor.

Here, when high precision is required for properties such as the thickness and flatness of the formed conductive layer (sintered body), the conductive powder is required to exist in the dispersion medium in a highly dispersed state. The conductive paste disclosed in this article is structured such that (A) the aggregation of the conductive powder is suppressed and the dispersibility of the (A) conductive powder is reduced by the action of (B) a viscosity-increasing agent even in the case of long-term storage. The high level is maintained, and the increase in viscosity is also suppressed. Hereinafter, each constituent of the conductive paste will be described.

(A) Conductive powder Conductive powder is mainly used to form conductive objects (may be conductive layers) with high electrical conductivity (hereinafter referred to as "conductivity") such as electrodes, wires, and conductive films in electronic components and the like. material. Therefore, as the conductive powder, powders of various materials having desired conductivity can be used without particular limitation. Specific examples of the conductive material include nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu), ruthenium (Ru), and rhodium ( Rh), osmium (Os), iridium (Ir), aluminum (Al), tungsten (W) and other metals, and alloys containing these metals. The conductive powder may be used singly or in combination of two or more kinds.

In addition, although it is not particularly limited, for example, as for the conductive paste used for the purpose of forming an MLCC internal electrode layer, a metal whose melting temperature of the conductive powder is close to the sintering temperature of the dielectric layer (for example, about 1300 ° C) is preferred. Kind of use. Examples of the metal species include precious metals such as rhodium, platinum, palladium, copper, and gold, and base metals such as nickel. Among them, the use of noble metals such as platinum and palladium is preferred from the viewpoint of melting point and conductivity, but nickel is more preferably used in consideration of stability and low price.

The method for producing the conductive powder, and the properties such as the size and shape of particles constituting the conductive powder are not particularly limited. For example, in consideration of the scorch shrinkage rate, it may be included in the range of the minimum size of the target electrode (typically, the thickness and / or width of the electrode layer). For example, the average particle diameter of the conductive powder may be about several nm to several tens of μm, for example, about 10 nm to 10 μm.
Further, in this specification called "average particle diameter" unless otherwise specified, it refers to a number-based particle size distribution of electron microscopic observation based cumulative 50% particle diameter equivalent (D _50). In the present specification, the cumulative 90% particle diameter based on the equivalent number-based particle size distribution in the electron microscope called "cumulative 90% particle size (D _90)." Furthermore, it goes without saying that the cumulative value related to the particle size distribution is an accumulated (cumulative) value from the side with a smaller particle size.

In addition, for the purpose of forming an internal electrode layer of a small-capacity MLCC, for example, it is important that the average particle diameter of the conductive powder is smaller than the thickness of the internal electrode layer (size in the stacking direction). In other words, it is preferable not to contain coarse particles that actually exceed the thickness of the internal electrode layer. From the viewpoint, as an example, the conductive powder preferably has a cumulative 90% particle diameter (D ₉₀ ) of not more than 3 μm, and more preferably not more than 1 μm, for example, not more than 0.5 μm. The average particle diameter (D ₅₀ ) may be approximately 1 μm or less as a standard, and may be typically 0.5 μm or less, preferably 0.3 μm or less, more preferably 0.25 μm or less, such as 0.2 μm or less. When the average particle diameter is equal to or smaller than a predetermined value, a conductive layer can be formed stably. In addition, the surface roughness of the formed conductor layer can be preferably suppressed. For example, the arithmetic average roughness Ra can be suppressed to a level of 5 nm or less.

The lower limit of the average particle diameter of the conductive powder is also not limited, and may be, for example, 0.005 μm or more, approximately 0.01 μm or more, typically 0.05 μm or more, preferably 0.1 μm or more, such as 0.12 μm or more. By preventing the average particle diameter from being too small, the surface energy (activity) of the particles constituting the conductive powder can be suppressed, and the aggregation of the particles in the conductive paste can be suppressed. In addition, the density of the paste coating layer can be increased, and a conductive layer having high electrical conductivity and high density can be preferably formed.

The specific surface area of the conductive powder is not particularly limited, and may be approximately 10 m ² / g or less, preferably 1 m ² / g to 8 m ² / g, for example, 2 m ² / g to 6 m ² / g. Thereby, the aggregation in the paste can be better suppressed, and the homogeneity, dispersibility, and storage stability of the paste can be better improved. In addition, a conductive layer having excellent electrical conductivity can be realized more stably.

The shape of the conductive powder is not particularly limited. For example, the shape of the conductive powder in the conductive paste for a part of an electrode forming application such as an MLCC internal electrode may be a spherical shape or a substantially spherical shape. The average aspect ratio of the conductive powder may be typically 1 to 2, and preferably 1 to 1.5. Thereby, the viscosity of the paste can be kept low, and the operability of the paste or the workability during film formation for formation of a conductor layer can be improved. In addition, the homogeneity of the paste can be improved.
The "aspect ratio" in this specification is calculated based on observation with an electron microscope, and refers to the length of the long side (b) relative to the length of the short side (a) when drawing a rectangle circumscribed with the particles constituting the powder. Ratio (b / a). The average aspect ratio is an arithmetic average of the aspect ratios obtained for 100 particles.

The content ratio of the conductive powder is not particularly limited. When the entire conductive paste is 100% by mass, it may be approximately 30% by mass or more, typically 40% to 95% by mass, for example, 45% to 60% by mass. %. By satisfying the above range, a conductive layer having high electrical conductivity and high density can be preferably realized. In addition, the operability of the paste and the workability during film formation can be improved.

(A ') Dielectric Powder In addition to the (A) conductive powder, the conductive paste disclosed herein may include (A') a dielectric powder as a component mainly constituting a fired conductor layer. The dielectric powder is, for example, a component that suppresses sintering of the conductive powder from a low temperature during the sintering of the conductive paste, or can adjust the thermal shrinkage rate and the sintering shrinkage history. Dielectric powders can have multiple functions. In particular, the dielectric powder contained in the conductive paste for the internal electrode layer of the MLCC has a composition common to or similar to that of the dielectric layer, thereby serving as a coexistence of improving the sintering bonding between the dielectric layer and the internal electrode layer. Materials are preferred because they function.

The dielectric constant of the dielectric powder is not particularly limited, and may be appropriately selected depending on the intended use. As an example, the relative dielectric constant of the dielectric powder used in the conductive paste for forming an internal electrode layer of a high-dielectric-constant MLCC is typically 100 or more, preferably 1,000 or more, for example, about 1,000 to 20,000. There is no particular limitation on the composition of the dielectric powder, and one or two or more kinds can be suitably used from various inorganic materials depending on the purpose and the like. As a dielectric powder, specifically include barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconate titanate, zinc titanate, barium magnesium niobate, calcium zirconate and the like having ABO ₃ Perovskite metal oxides, titanium dioxide (rutile), titanium pentoxide, hafnium oxide, zirconia, alumina, forsterite, niobium oxide, barium neodymium titanate, rare earth oxides, etc. Other metal oxides are typical examples. In the paste for use in the internal electrode layer, the dielectric powder may be preferably composed of barium titanate (BaTiO ₃ ), calcium zirconate (CaZrO ₃ ), or the like. On the other hand, as a matter of course, a dielectric material (and thus an insulating material) having a relative dielectric constant of less than 100 may be used.

The properties of the particles constituting the dielectric powder, such as the size and shape of the particles, are not particularly limited as long as they are included in the minimum size (typically, the thickness and / or width of the electrode layer) in the cross section of the electrode layer. The average particle diameter of the dielectric powder can be appropriately selected according to, for example, the use of the paste, the size (fineness) of the electrode layer, and the like. The target conductive layer preferably has an average particle diameter of the dielectric powder that is smaller than the average particle diameter of the conductive powder, from the viewpoint of easily ensuring predetermined conductivity. When the average particle diameter of the dielectric powder is D ₂ and the average particle diameter of the conductive powder is D ₁ , D ₁ and D ₂ are usually preferably D ₁ > D ₂ , and more preferably D ₂ ≦ 0.5 × D. ₁ and further preferably D ₂ ≦ 0.4 × D ₁ , for example, D ₂ ≦ 0.3 × D ₁ . In addition, if the average particle diameter D _{2 of} the dielectric powder is too small, aggregation of the dielectric powder is likely to occur, which is not preferable. In this respect, as a rough standard, 0.05 × D ₁ ≦ D _{2 is} preferable, and 0.1 × D ₁ ≦ D _{2 is more} preferable. For example, D ₂ ≦ 0.15 × D ₁ . For example, the average particle diameter of the dielectric powder may be approximately several nm to several tens μm, for example, 10 nm to 10 μm, and preferably 0.3 μm or less. As an example, in the conductive paste for forming the internal electrode layer of the MLCC, the average particle diameter of the dielectric powder may be approximately several nm to several hundreds nm, for example, 10 nm to 100 nm.
The dielectric powder is an example of the second powder in the present invention, and the average particle diameter D ₂ of the dielectric powder is an example of the second average particle diameter.

The content ratio of the dielectric powder is not particularly limited. For example, in applications such as forming an internal electrode layer of an MLCC, when the entire conductive paste is 100% by mass, it may be approximately 1% to 20% by mass, for example, 3% to 15% by mass. The ratio of the dielectric powder to 100 parts by mass of the conductive powder may be, for example, approximately 3 to 35 parts by mass, preferably 5 to 30 parts by mass, for example, 10 to 25 parts by mass. Thereby, the low-temperature sintering of the conductive powder can be appropriately suppressed, and the electrical conductivity and the denseness of the conductive layer after the sintering can be improved.

(B) Viscosity Inhibitor In the technology disclosed herein, the conductive paste contains a viscosity increasing inhibitor that inhibits its viscosity from increasing over time. A so-called viscosity-increasing inhibitor is a component which improves the anti-agglomeration property of the said powder in a conductive paste, and contributes to the improvement of storage stability. The viscosity-increasing inhibitor is composed of a secondary amine compound having a specific molecular structure. The secondary amine compound is a compound having a general formula: NHR ¹ R ² ; the two hydrogen atoms (H) of ammonia (NH ₃ ) are substituted with functional groups R ¹ and R ² containing a hydrocarbon. Here, R ¹ and R ^{2 are} independently a linear or cyclic aliphatic group having 4 to 12 carbon atoms. R ¹ and R ^{2 are} preferably a saturated aliphatic group.

The carbon chain in R ¹ and R ² does not contain an oxygen atom (O), a nitrogen atom (N), and a sulfur atom (S). In other words, the carbon skeletons of R ¹ and R ² are constituted by direct bonding of carbon atoms (C), and do not include bonds interposing heteroatoms such as O, N, and S. As such, the secondary amine compounds disclosed herein do not contain ether or ester bonds. In addition, the secondary amine compound disclosed herein preferably does not contain a hydroxyl group, a carbonyl group, a carboxyl group, a nitro group, an amine group, a sulfo group and the like at the terminal. Although the details are not clear, when the carbon chain contains the hetero atom, the conductive paste may increase the viscosity, which is not good. In addition, although the details are not clear, regarding the secondary amine compound, R ¹ and R ² may have an alicyclic structure, but when a branched chain structure is included, it is also observed that the thickening property of the conductive paste is likely to increase Tends to be poor. Accordingly, for example, a case where R ¹ and R ² do not contain a methyl group (CH ₃ ) other than the terminal may be a preferable aspect.

Although the specific role of the thickening inhibitor is not clear, by including the thickening inhibitor containing the specific secondary amine, the conductive paste exhibits the effect of suppressing the conductive powder (and, if contained), Dielectric powder) is agglomerated in the paste, and the increase in the viscosity of the paste is preferably suppressed. According to a study by the inventors, for example, as shown in the embodiment described later, the viscosity of the conductive paste is stored even under a condition where the powder is allowed to stand for 15 days in a high-temperature environment of 40 ° C for 15 days. The rise rate can also be suppressed to approximately 50% or less, typically 30% or less, preferably 20% or less, more preferably 15% or less, still more preferably 10% or less, and even more preferably 5% or less.

Specific examples of the secondary amine compound include dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, and diamine. -Dialkylamines such as undecylamine, di-dodecylamine; butylpentylamine, butylhexylamine, butylheptylamine, butyloctylamine, butylnonylamine, butyldecylamine , Butylundecylamine, butyldodecylamine, pentylhexylamine, pentylheptylamine, pentyloctylamine, pentylnonylamine, pentyldecylamine, pentylundecyl Alkylamine, pentyldodecylamine, hexylheptylamine, hexyloctylamine, hexylnonylamine, hexyldecylamine, hexylundecylamine, hexyldodecylamine, heptyloctyl Amine, heptylnonylamine, heptyldecylamine, heptylundecylamine, heptyldodecylamine, octylnonylamine, octyldecylamine, octylundecylamine, octyl Dodecylamine, nonyldecylamine, nonylundecylamine, nonyldodecylamine, decylundecylamine, decyldodecylamine, undecyldodecylamine Alkylamines such as alkylamines; dicyclobutylamine Dicyclopentylamine, dicyclohexylamine, dicycloheptylamine, dicyclooctylamine, dicyclononylamine, dicyclodecylamine and other bicycloalkylamines; cyclohexylbutylamine, cyclohexylpentane Alkylcycloalkylamines, such as alkylamine, cyclohexylhexylamine, heptylcyclohexylamine, octylcyclohexylamine, nonylcyclohexylamine, cyclopentylcyclohexylamine, etc. In addition, the secondary amine compound may be a similar compound and a derivative of the compound. These secondary amine compounds may be contained alone, or may be contained in a combination of two or more. Thereby, the dispersion stability of the powder in a paste can be improved more.

Furthermore, the proportion of the viscosity-increasing inhibitor contained in the conductive paste also depends on the morphology, average particle size, and the like of the conductive powder, so it cannot be specified in a general manner. Since the viscosity-increasing inhibitor is contained in a small amount in the conductive paste, for example, a viscosity-increasing inhibitory effect can be exhibited. Furthermore, in order to more reliably exert the viscosity-increasing effect, for example, when the entire conductive paste is set to 100% by mass, the viscosity-increasing inhibitor may be 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably It is 0.05% by mass or more, and more preferably 0.1% by mass or more. In addition, even if the viscosity-increasing inhibitor is excessively added, it is impossible to suppress the increase in viscosity corresponding to the viscosity-increasing inhibitor, and the paste properties may be impaired. Although not particularly limited, the addition amount of the viscosity-increasing inhibitor may be, for example, 10% by mass or less as a standard, may be 5% by mass or less, and may be, for example, 3% by mass or less. Accordingly, even when the conductive paste is left to stand, aggregation of powder in the paste can be suppressed, and an increase in viscosity with time can be effectively suppressed. As a result, for example, in a case where the conductive paste is supplied onto the substrate by printing or the like, it is possible to suppress a change in the viscosity of the conductive paste in the supply device for a long period of time. In addition, even when the conductive paste is stored in a low-temperature, normal-temperature, or high-temperature environment, the viscosity change of the conductive paste can be better suppressed.

(B ') Other additives In addition, the conductive paste disclosed herein can be used in a range that does not significantly impair the effect of the technology disclosed herein, and includes a known general conductive paste in addition to the viscosity increasing inhibitor. Various organic additives. The organic additives include, for example, a dispersant, a leveling agent, an antifoaming agent, a thickener, a plasticizer, a pH adjuster, a stabilizer, an antioxidant, a preservative, and a colorant (pigment, dye, etc.). For example, if a powder such as a conductive powder or a dielectric powder that is the main body of the conductor layer is used, as long as the nano particles are not subjected to a special surface treatment or the like, aggregation occurs during and immediately after the preparation of the paste. Regarding the above-mentioned tendency, when using nano particles having an average particle size of less than about 1 μm, or ultrafine powder (for example, a powder having an average particle size of 0.5 μm or less) with a significantly improved surface activity, as a conductive powder, etc. And so on became more significant. Therefore, the conductive paste disclosed herein may preferably include a dispersant as other additives.

The dispersant is a component that suppresses agglomeration of particles constituting the powder when the powder is dispersed in a dispersion medium, and uniformly disperses the particles in the dispersion medium. The dispersant has a function of directly adsorbing on the solid surface of the particles and stabilizing the solid-liquid interface between the particles and the dispersion medium. The dispersant is preferably burned during the sintering of the conductive paste. In other words, it is preferred that the dispersant has a decomposition temperature sufficiently lower than the sintering temperature of the conductive paste (typically 600 ° C. or lower).

The type of the dispersant is not particularly limited, and one or two or more kinds can be used as needed from various known dispersants. Typically, those having sufficient compatibility with a vehicle (a mixture of a binder and a dispersion medium) described later can be appropriately selected and used. There are various methods for classifying the dispersant, and as the dispersant, any one of a so-called surfactant-type dispersant, a polymer-type dispersant, and an inorganic-type dispersant may be used. These dispersants may be any of anionic, cationic, amphoteric, and nonionic. In other words, the dispersant is a compound having at least one functional group among anionic groups, cationic groups, amphoteric groups, and nonionic groups in the molecular structure. Typically, the dispersant may be a solid in which the functional group can be directly adsorbed on particles Surface compounds. The term “surfactant” refers to an amphiphilic substance that includes a hydrophilic portion and a lipophilic portion in a molecular structure and has a chemical structure formed by covalent bonding.

As the dispersant, for example, as a surfactant dispersant, specific examples include a dispersant mainly composed of an alkyl sulfonate, a dispersant mainly composed of a quaternary ammonium salt, and a dispersion mainly composed of an alkylene oxide compound. Agents, dispersants mainly composed of polyol ester compounds, dispersants mainly composed of alkyl polyamine compounds, and the like. Examples of the polymer-based dispersant include a dispersant composed mainly of a fatty acid salt such as a carboxylic acid, a dispersant composed mainly of a polycarboxylic acid alkylamine salt, and a polymer composed of a polycarboxylic acid having an alkyl ester bond in part. Dispersant mainly composed of carboxylic acid alkyl ester compounds, and dispersion mainly composed of sulfonic acid compounds such as polystyrene sulfonate, polyisoprene sulfonate, naphthalene sulfonate, and naphthalenesulfonic acid formaldehyde condensate Dispersant mainly composed of hydrophilic polymers such as polyethylene glycol, dispersant mainly composed of poly (meth) acrylates, poly (meth) acrylamide, etc., A dispersant mainly composed of a polyether compound, a dispersant mainly composed of a polyalkylene polyamine compound, and the like. Examples of the inorganic dispersant include phosphates such as orthophosphate, metaphosphate, polyphosphate, pyrophosphate, tripolyphosphate, hexametaphosphate, and organic phosphate; ferric sulfate; ferrous sulfate; Dispersants mainly composed of iron salts such as ferric chloride and ferrous chloride, aluminum salts such as aluminum sulfate, polyaluminum chloride and sodium aluminate, and calcium salts such as calcium sulfate, calcium hydroxide, and calcium hydrogen phosphate. In addition, although not limited to this, when preparing a conductive paste containing finer powder at a higher concentration, for example, it is preferable to use a polymer-type dispersant with excellent function: the interaction between particles can be effectively reduced Function, improve dispersion stability.

In addition, the organic additives may include any one kind alone, or may include two or more kinds in combination. In addition, the content of the organic additive may be appropriately adjusted within a range that does not significantly hinder the properties of the conductive paste disclosed herein. For example, it may be contained in an appropriate ratio according to the properties of the organic additive and its purpose. Generally, for example, the dispersant is contained in a proportion of about 5 mass% or less, for example, 3 mass% or less, typically 1 mass% or less and about 0.01 mass% or more with respect to the total mass of the powder component. Furthermore, it is not preferable to contain a component that inhibits the sinterability of the conductive powder or inorganic powder or the like, or an additive that inhibits these amounts. From the viewpoint, when the organic additive is included, the total content of these components is preferably about 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

(C) Adhesive The adhesive functions as an adhesive in the conductive paste disclosed herein. The adhesive typically helps the bonding of the powder contained in the conductive paste and the substrate, and the bonding of particles constituting the powder to each other. In addition, the binder works in cooperation with a dispersion medium to be described later, and functions as a liquid phase medium (also referred to as a liquid). Thereby, the viscosity of the conductive paste is increased, and the powder component is suspended uniformly and stably in the vehicle liquid, fluidity is imparted to the powder, and workability is improved. The said adhesive is a component which presupposes that it disappears by burning. Therefore, the adhesive is preferably a compound that burns during the sintering of the conductor film. Typically, the decomposition temperature is preferably 500 ° C or lower regardless of the environment. The composition and the like of the adhesive are not particularly limited, and various known organic compounds used in such applications can be suitably used.

Examples of the binder include rosin-based resin, cellulose-based resin, polyvinyl alcohol-based resin, polyvinyl acetal-based resin, acrylic resin, urethane-based resin, epoxy-based resin, and phenol. Organic polymer compounds such as resins, polyester resins, and vinyl resins. It also depends on the combination with the solvent used, so it cannot be generalized. For example, as a binder of conductive paste containing inorganic oxide powders and a higher sintering temperature, cellulose resins, polyvinyl alcohol resins, Polyvinyl acetal resin, acrylic resin, etc.

Cellulose-based resins contribute to the improvement of the dispersibility of inorganic oxide powders. When conductive paste is used for printing, the shape characteristics of printed materials (wiring films) and the adaptability to printing operations are excellent. Better. The cellulose-based resin refers to all the polymers and their derivatives containing at least β-glucose as a repeating unit. Typically, it may be a compound obtained by substituting a part or all of the hydroxyl groups in the β-glucose structure as the repeating unit with an alkoxy group and a derivative thereof. Alkoxy (RO ^-) in the alkyl or aryl portion of the group (R) or all may be substituted by an ester group to a carboxyl group, a nitro group, a halogen, an organic group other. Specific examples of the cellulose-based resin include methyl cellulose, ethyl cellulose, propoxy cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl. Methyl cellulose, hydroxypropyl ethyl cellulose, carboxy methyl cellulose, carboxy ethyl cellulose, carboxy propyl cellulose, carboxy ethyl methyl cellulose, cellulose acetate phthalate, nitro fibers Su et al.

Polyvinyl alcohol-based resins have good dispersibility of inorganic oxide powder and are soft. Therefore, when a conductive paste is used for printing, the printed matter (wiring film) has excellent adhesion, printability, etc., and is therefore preferred. The polyvinyl alcohol-based resin refers to all the polymers and derivatives thereof that contain at least a vinyl alcohol structure as a repeating unit. Typically, it may include polyvinyl alcohol (PVA) having a structure obtained by polymerizing vinyl alcohol, a polyvinyl acetal resin obtained by acetalizing the PVA with an alcohol, and derivatives thereof. Things. Among them, a polyvinyl butyral (PVB) resin having a structure in which PVA is acetalized with butanol is more preferable because it improves the shape characteristics of a printed body. In addition, these polyethylene acetal resins may also be copolymers (including graft copolymers) and the like: a polyethylene acetal is a main monomer, and a secondary monomer having a copolymerizability with the main monomer is contained. Examples of the secondary monomer include ethylene, esters, (meth) acrylates, and vinyl acetate. The ratio of acetalization in the polyvinyl acetal resin is not particularly limited, but is preferably 50% or more.

The acrylic resin is preferable in that it is rich in adhesiveness and softness, and has fewer burnt residues regardless of the burnt environment. The acrylic resin refers to, for example, the entirety of the polymer and its derivative containing at least an alkyl (meth) acrylate as a constituent monomer component. Typically, it may be a homopolymer containing 100% by mass of alkyl (meth) acrylate as a constituent monomer component, or a copolymer (including a graft copolymer), etc. The copolymer) is mainly composed of an alkyl (meth) acrylate, and contains a sub-monomer having copolymerizability with the main monomer. Examples of the secondary monomer include 2-hydroxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, a vinyl alcohol-based monomer, a dialkylamino group, a carboxyl group, and an alkoxy group introduced. A comonomer such as a carbonyl group. Specific examples of the acrylic resin include poly (meth) acrylic acid, vinyl chloride / acrylic acid graft copolymer resin, and ethylene acetal / acrylic acid graft copolymer resin. In addition, in this specification, expressions, such as "(meth) acrylate", are used as the term which shows that acrylate and / or methacrylate are included.

Any of these adhesives can be used, or two or more of them can be used in combination. In addition, even if it is not explicitly described, the monomer components of any two or more of the resins may be copolymerized and used. The content of the binder is not particularly limited. In order to properly adjust the properties of the conductive paste and the properties of the paste printing body (including the dry film), for example, the content of the binder may be 0.5 parts by mass or more, preferably 1 part by mass or more, based on 100 parts by mass of the conductive powder. The ratio is more preferably 1.5 parts by mass or more, for example, 2 parts by mass or more. On the other hand, since the binder resin may increase the scorch residue, the excessive content is not preferable. From this viewpoint, the content of the binder may be 10 parts by mass or less, preferably 7 parts by mass or less, more preferably 5 parts by mass or less, for example 4 parts by mass or less, based on 100 parts by mass of the conductive powder.

(D) Dispersion medium The dispersion medium is a medium for making the powder contained in the conductive paste into a dispersed state, and is an element for imparting fluidity while maintaining the dispersibility. In addition, the dispersion medium and the binder work together to function as a liquid phase medium (also referred to as a vehicle liquid). The dispersion medium is also a component premised on disappearance by sintering. The dispersion medium is not particularly limited, and an organic solvent used in such a conductive paste can be suitably used. Although it also depends on the combination with, for example, a high-boiling-point organic solvent having a boiling point of about 180 ° C or higher and 300 ° C or lower, such as 200 ° C or higher and 250 ° C or lower, from the viewpoint of film formation stability and the like. The main component (component that accounts for more than 50% by volume).

Specific examples of the dispersion medium include sclareol, citronellol, phytol, geranyl linalool, texanol, benzyl alcohol, phenoxyethanol, and 1-phenoxy-2-propane Alcohol solvents such as alcohol, terpineol, dihydroterpineol, isobornyl, butylcarbitol, diethylene glycol; terpineol acetate, dihydroterpineol acetate, isobornyl acetate Ester solvents such as esters, carbitol acetate, methanol acetate, diethylene glycol monobutyl ether acetate; mineral spirits, etc. Among these, an ester-based solvent can be preferably used.

The proportion of the (C) dispersion medium in the conductive paste is not particularly limited, and when the entire paste is 100% by mass, it may be approximately 70% by mass or less, typically 5 to 60% by mass, for example, 30% by mass ～ 50% by mass. By satisfying the above range, moderate fluidity can be imparted to the paste, and workability during film formation can be improved. In addition, it is possible to improve the self-leveling property of the paste and realize a smoother surface conductor film.

The conductive paste can be prepared by blending the constituent components at a predetermined ratio and uniformly mixing and kneading. During the mixing, the respective constituent materials may be mixed at the same time, but for example, (C) a binder and (D) a dispersion medium may be mixed in advance to prepare a medium solution, and then the powder may be mixed with (A) conductive powder and the like in the medium solution. (B) Viscosity inhibitor. In addition, when other additives are added, the timing of their addition is not particularly limited. The mixing of these raw materials can be performed using a known stirring and mixing device, for example. Examples of the device include a three-roll mill, a planetary mixer, and a disperser. In addition, the conductive paste can be supplied to the substrate by a printing method such as screen printing, gravure printing, lithography, and inkjet printing, a spraying method, or a dip coating method. In particular, in the case of forming the internal electrode layer of the MLCC, a gravure printing method, a screen printing method, or the like capable of high-speed printing can be preferably used.

[use]
As described above, even if the conductive paste is stored in a thermostat at 40 ° C for 15 days and stored under conditions that easily cause powder aggregation, the viscosity increase rate can be kept low ( For example, 50% or less, typically 30% or less). In other words, the conductive paste is excellent in long-term storage after the preparation of the paste, and for example, a large amount of paste can be prepared at one time in a mass production step and used for a long time. This feature not only stabilizes the storability of the conductive layer formed using the conductive paste, but also stabilizes printability, and contributes to, for example, improvement in the uniformity of the thickness and density of the conductive layer. Therefore, the paste disclosed herein can be preferably used in applications in which the homogeneity and surface smoothness of a conductor layer are particularly required. Typical applications include formation of an electrode layer in a multilayer ceramic electronic component. The conductive paste disclosed herein can be preferably used, for example, for forming an internal electrode layer of a small MLCC with sides of 5 mm or less, such as 1 mm or less. In particular, it can be preferably used for the production of internal electrodes of small and large-capacity MLCCs with a dielectric layer thickness of 1 μm or less.

In addition, in this specification, "ceramic electronic component" means all the electronic components which have a crystalline ceramic base material or an amorphous ceramic (glass ceramic) base material. For example, chip inductors including ceramic substrates, high-frequency filters, ceramic capacitors, high temperature co-fired ceramics (HTCC) substrates, and low temperature co-fired multilayer ceramics (Low Temperature Co -Fired Ceramics (LTCC) substrates are typical examples included in "ceramic electronic components" described here.

Examples of the ceramic material constituting the ceramic substrate include barium titanate (BaTiO ₃ ), zirconia (zirconia: ZrO ₂ ), magnesium oxide (magnesium oxide: MgO), and alumina (aluminum oxide: Al ₂ O ₃ ), silicon dioxide (silicon oxide: SiO ₂ ), zinc oxide (ZnO), titanium oxide (titanium dioxide: TiO ₂ ), cerium oxide (cerium oxide: CeO ₂ ), yttrium oxide (yttrium oxide: Y ₂ O ₃ ) and other oxide-based materials; cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ), forsterite (2MgO · SiO ₂ ), block talc (MgO · SiO ₂ ), Sialon (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 oxides Materials; silicon nitride (silicon nitride: Si ₃ N ₄ ), aluminum nitride (aluminum nitride: AlN), boron nitride (boron nitride: BN), and other nitrogen Carbide-based materials; silicon carbide (monosilicon carbide: SiC), boron carbide (tetraboron carbide: B ₄ C) and other carbide-based materials; hydroxide-based materials such as hydroxyapatite. These may be contained singly, or as a mixture of two or more kinds, or in the form of a composite of two or more kinds.

[Multilayer Ceramic Capacitor]
FIG. 1 is a cross-sectional view schematically showing a multilayer ceramic capacitor (MLCC) 1. MLCC1 is a wafer-type capacitor in which a plurality of dielectric layers 20 and internal electrode layers 30 are alternately and integrally laminated. A pair of external electrodes 40 is provided on a side surface of the multilayer wafer 10 including the dielectric layer 20 and the internal electrode layer 30. As an example, the internal electrode layers 30 are alternately connected to different external electrodes 40 in a stacking order. Thereby, a small and large-capacity MLCC 1 is constructed, and a capacitor structure including a dielectric layer 20 and a pair of internal electrode layers 30 sandwiching the dielectric layer 20 is connected in parallel. The dielectric layer 20 of the MLCC1 is made of ceramic. The internal electrode layer 30 is composed of a fired body of the conductive paste disclosed herein. The MLCC1 is preferably manufactured by the following procedure, for example.

FIG. 2 is a cross-sectional view schematically showing an unfired laminated wafer 10 (unfired laminated body 10 ′). When manufacturing MLCC1, a ceramic green sheet is first prepared as a base material. Here, for example, a ceramic powder, a binder, and an organic solvent, which are dielectric materials, are mixed to prepare a dielectric layer forming paste. Next, a plurality of unfired ceramic green sheets 20 'are prepared by supplying the prepared paste in a thin layer onto a carrier sheet by a doctor blade method or the like.

Next, prepare the conductive paste disclosed herein. Specifically, at least a conductive powder (A), a viscosity-increasing inhibitor (B), a binder (C), and a dispersion medium (D) are prepared, and these are mixed at a predetermined ratio and uniformly mixed to prepare a conductive paste. . Then, the prepared paste is supplied onto the prepared ceramic green sheet 20 ′ so as to have a predetermined pattern and a desired thickness (for example, 1 μm or less) to form a conductive paste coating layer 30 ′. The increase in viscosity of the conductive paste disclosed over time is suppressed. Therefore, in mass production of MLCC, even if the formation (printing) of the conductive paste coating layer 30 ′ on the ceramic green sheet 20 ′ is continuous and elapsed over a long period of time, the properties of the conductive paste are stable, so the printing quality can be stabilized well. .

The prepared ceramic green sheet 20 'with the coating layer 30' is laminated on a plurality of sheets (for example, hundreds to thousands of sheets) and pressure-bonded. The laminated body is cut into a wafer shape as necessary. Thereby, the unfired laminated body 10 'can be obtained. Next, the produced unfired laminate 10 'is fired under appropriate heating conditions (for example, a temperature of about 1000 ° C to 1300 ° C in a nitrogen-containing environment). Thereby, the ceramic green sheet 20 'and the conductive paste coating layer 30' are simultaneously fired. The ceramic green sheet is fired to form the dielectric layer 20. The conductive paste coating layer 30 ′ is fired to become the internal electrode layer 30. The dielectric layer 20 and the electrode layer 30 are sintered integrally to obtain a sintered body (multilayer wafer 10). Furthermore, before the calcination, in order to eliminate the viscosity-increasing inhibitor, adhesive, and dispersion medium, a debinding treatment may be performed (for example, in an oxygen-containing environment, at a temperature lower than the calcination temperature: for example, about 250 ℃ ～ 700 ℃; heat treatment). Thereafter, the external electrode 40 is formed by applying an external electrode material to the side surface of the laminated wafer 10 and performing firing. Thereby, MLCC1 can be manufactured.

Hereinafter, several embodiments related to the present invention will be described, but it is not intended to limit the present invention to those shown in the embodiments.

[Embodiment 1]
Preparation Example 1 was prepared by dispersing Ni powder having an average particle size of 0.18 μm and barium titanate powder having an average particle size of 0.05 μm together with a dispersant and a viscosity-increasing inhibitor, and kneading by a three-roll mill. ~ The conductive paste of Example 13.
The vehicle solution is prepared by mixing the binder with an organic solvent and then processing the mixture while stirring at about 100 ° C. for 5 hours. Ethylcellulose was used as the binder, isobornyl acetate was used as the organic solvent, carboxylic acid-based dispersant was used as the dispersant, and the secondary amine shown in Table 1 below was used as the viscosity inhibitor. In addition, the formulation of each component in the conductive paste was determined to be Ni powder: 50% by mass, barium titanate powder: 12.5% by mass (25% by mass of Ni powder), binder: 2.0% by mass, and carboxylic acid-based dispersant: 0.64. Mass%, secondary amine: 0.5 mass%, residual solvent.

In Table 1, the secondary amine used in the conductive paste of each example is shown together with the schematic formula or structural formula, molecular weight, and other structural characteristics showing the structure. Regarding the structural characteristics, (A) the chemical structure of the secondary amine: NHR ¹ R ² ; whether R ¹ and R ² are the same (R ¹ = R ² ); (B) functional group R ¹ , functional group R ^The number of carbons N _C contained in ² ; and (C) the functional group R ¹ or the functional group R ² contains more numbers N _CH3 than the methyl group. In addition, the symbol "○" in the column (A) indicates that R ¹ and R ^{2 are the} same.

[Promote viscosity increase rate]
The conductive paste of each example was left to stand in a thermostat at 40 ° C. for 15 days and stored, and the viscosity increase rate before and after storage was investigated. A digital rotary viscometer (DV-III ULTRA manufactured by Brookfield) was used, and the spindle "SC4-14" and the sample cavity "SC4-6R" were used at room temperature (25 ° C) at a speed of 100 rpm. Measure the viscosity of the conductive paste. The viscosity increase rate is calculated based on the following formula, and the results are shown in Table 1.

Viscosity increase rate (%) = (viscosity after storage-viscosity before storage) ÷ viscosity before storage × 100

[Table 1]

As shown in Table 1, it can be seen that the viscosity increase of the conductive paste can be suppressed by using the following secondary amine as a viscosity increasing inhibitor, which is represented by the general formula: NHR ¹ R ² ; R ¹ and R ² both are linear or cyclic saturated hydrocarbon group, the carbon number of 4 or more. Specifically, for example, even when an ultrafine powder including an Ni powder having an average particle diameter of 0.18 μm and a barium titanate powder of 0.05 μm is used as a paste main material, the viscosity increase rate after 15 days at high temperature can be suppressed. It is 50% or less, typically 30% or less. From this, it can be seen that, even with long-term storage, a conductive paste having excellent dispersion stability can be obtained by the technology disclosed herein.

On the other hand, in the case of using a dipropylamine having a carbon number of R ¹ and R ² of 3 even if it is a secondary amine, it is confirmed that the effect of suppressing the increase in viscosity cannot be sufficiently obtained despite the simple structure and small molecular weight.

In addition, it can be seen that when a secondary amine having a carbon number of R ¹ and R ² is 4, that is, dibutylamine is used as a dispersant, when R ¹ and R ² are linear di-n-butylamines. The viscosity increase rate can be suppressed to be extremely low at 15.2%. In contrast, when R ¹ and R ² are branched bis (second butyl) amines, the viscosity increase rate is 52.2%, which cannot be suppressed. It is, for example, 50% or less. When bis (isobutyl) amine is used, the viscosity increase rate is 129.4%, which is the highest value in this embodiment.

Furthermore, when using a branched bis (2-ethylhexyl) amine having a carbon chain length of R ¹ and R ² , the viscosity increase rate was 117.6%, which was the second highest value in all the examples. From this, it can be seen that if R ¹ and R ² are branched chains, it is difficult to suppress the thickening of the conductive paste with time.
On the other hand, when using dicyclohexylamine containing a cyclic structure in R ¹ and R ² , it is found that the viscosity increase rate is suppressed to as low as 24.7%, and even if R ¹ and R ^{2 have} a large structure, they can be used. Obtains a viscosity-increasing effect. For example, R ¹ and R ^{2 are} expected to have fewer terminal or terminal methyl groups.

Although the details are not clear, it can be seen from the above that by properly selecting the structure of the secondary amine, the secondary amine can be used as a thickening inhibitor (viscosity stabilizer) of the conductive paste.

[Embodiment 2]
The conductive pastes of Examples 14 to 31 were prepared by dispersing Ni powder and barium titanate powder in an organic solvent together with a binder, a dispersant, and a viscosity-increasing inhibitor, and kneading with a three-roll mill.
As a binder, ethyl cellulose was used, as an organic solvent, isobornyl acetate was used, as a dispersant, a carboxylic acid-based dispersant was used, and as a viscosity-increasing inhibitor, an amine-based compound shown in Table 2 below was used. In addition, the components of the conductive paste were prepared as Ni powder: 50% by mass, barium titanate powder: 12.5% by mass (25% by mass of Ni powder), binder: 2.0% by mass, and carboxylic acid-based dispersant: 0.9. Mass%, amine-based compound: Refer to the following Table 2 and the remaining solvent.

(Examples 14 to 20)
In the conductive pastes of Examples 14 to 20, as in Embodiment 1, powders having an average particle diameter of 0.18 μm and 0.05 μm were used as Ni powder and barium titanate powder, respectively. In addition, as the amine compound, di-n-butylamine was used, and the blending amount thereof was changed from 0% by mass to 2.00% by mass as shown in Table 2 below.

(Examples 21 to 23)
As the conductive pastes of Examples 21 to 23, relatively coarse powders having average particle diameters of 0.4 μm and 0.10 μm were used as Ni powder and barium titanate powder, respectively. In addition, as the amine-based compound, di-n-butylamine was used, and the blending amount thereof was changed from 0.50% by mass to 2.00% by mass as shown in Table 2 below.

(Examples 24 to 28)
In the conductive pastes of Examples 24 to 28, as in Embodiment 1, powders having an average particle diameter of 0.18 μm and 0.05 μm were used as Ni powder and barium titanate powder, respectively. As the amine compound, bis (2-methoxyethyl) amine was used in Example 24, bis (2-ethoxyethyl) amine was used in Example 25, and tributylamine was used in Examples 26 to 28. , Set the blending amount as shown in Table 2. In addition, the compounding amount of Example 24, Example 25, Example 26, and Example 29 is marked * to indicate that the compounding amount and 0.5% by mass of dibutylamine are molar equivalents. The bis (2-methoxyethyl) amine and bis (2-ethoxyethyl) amine used in Examples 24 to 28 are amine compounds having an ether bond in R ¹ and R ² . Butylamine is a tertiary amine.

(Examples 29 to 31)
As the conductive pastes of Examples 29 to 31, relatively coarse powders having an average particle diameter of 0.4 μm and 0.10 μm were used as Ni powder and barium titanate powder, respectively. As an amine-based compound, tributylamine was used in the same manner as in Examples 26 to 28.

[Promote viscosity increase rate]
Regarding the conductive paste of each example, the rate of viscosity increase was investigated in the same manner as in the first embodiment. That is, the conductive paste of each example was left to stand in a thermostat at 40 ° C. for 15 days and stored, and the rate of increase in viscosity before and after storage was investigated. A digital rotary viscometer (DV-III ULTRA manufactured by Brookfield) was used, and the spindle "SC4-14" and the sample cavity "SC4-6R" were used at room temperature (25 ° C) at a speed of 100 rpm Measure the viscosity of the conductive paste. The viscosity increase rate is calculated based on the following formula, and the results are shown in Table 2.

Viscosity increase rate (%) = (viscosity after storage-viscosity before storage) ÷ viscosity before storage × 100

[Table 2]

As shown in Examples 14 to 20, in Example 14 without the addition of an amine-based viscosity increasing inhibitor, it was confirmed that the viscosity increase rate was as high as 74.5%; In Example 20, the viscosity increase rate can be preferably suppressed to 16.2% or less, for example, about 2.5%. As shown in Example 15, it can be seen that even if the addition amount of the amine-based viscosity increasing inhibitor is only 0.01% by mass relative to the conductive paste, a sufficient viscosity increasing effect can be obtained. In addition, it can be seen that although an error was observed in Example 17, the increase in the amount of the amine-based viscosity increasing inhibitor tended to increase the effect of suppressing the increase in viscosity. However, when the addition amount of the amine-based viscosity-increasing inhibitor is as high as about 2% by mass, it is observed that the effect of suppressing the viscosity-increasing becomes slightly saturated.

In addition, as shown in Examples 21 to 23, it was confirmed that if the average particle diameter of the powder material added to the conductive paste is made slightly coarse, the viscosity increase suppression by the amine-based viscosity increasing inhibitor can be more significantly exerted. The effect is, for example, that a slight addition of 0.50% by mass can suppress the viscosity increase rate to as low as 2.2%. Moreover, in Example 23 in which the addition amount was 2% by mass, it was confirmed that even after storage in a high-temperature environment at 40 ° C. for 15 days, no change in viscosity was observed at all, and an increase in viscosity could be completely prevented. From this, it can be seen that the addition amount of the amine-based viscosity increasing inhibitor can be approximately 2% by mass (for example, 3% by mass or less) as an upper limit standard.

On the other hand, as shown in Examples 24 and 25, it was confirmed that if a compound in which O (oxygen atom) such as methylmethoxyethyl or ethoxyethyl was introduced into R ¹ and R ² was used as the amine Series compounds, even if the other structures are almost the same, the viscosity increase rate suddenly increases. It was confirmed that amine compounds containing elements other than C and H, such as O, in R ¹ and R ² did not function as a thickening inhibitor of the conductive paste.

In addition, as shown in Examples 26 to 31, it can be seen that when a tributylamine as a tertiary amine is used as the amine-based compound, a certain degree of viscosity-increasing effect can be obtained. However, it was found that when tributylamine was used, the conductive pastes containing powders with large particle diameters in Examples 29 to 31 had a viscosity increase rate as low as, for example, 4.6% or less, but Examples 26 to The conductive paste containing fine powder of Example 28 has a viscosity increase rate of, for example, 30.4% or more, and is 6 times or more (approximately 8 times) higher than the case of using a powder having a large particle size. From this, it can be said that tributylamine exerts a viscosity-increasing effect on conductive pastes using, for example, Ni powder having an average particle size of 0.4 μm, but does not sufficiently exhibit a viscosity-increasing effect on conductive pastes containing a large amount of finer powders. . For example, this can be clearly confirmed by comparing Example 18 and Example 26, Example 21 and Example 29 using a secondary amine. In addition, it can be seen that, in other words, a thickening inhibitor containing a secondary amine that satisfies the conditions disclosed herein can of course exert an excellent thickening inhibitory effect on a conductive paste containing powder having an average particle diameter of about 0.4 μm, and containing an average particle diameter of 0.2 μm The following level of powdery conductive paste also exhibits excellent viscosity-increasing effects.

The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the patent application. The technology described in the scope of the patent application includes various modifications and changes to the specific examples illustrated above.

1‧‧‧MLCC

10‧‧‧Laminated Wafer

10'‧‧‧Unfired laminate

20‧‧‧ Dielectric layer

20'‧‧‧ceramic green sheet

30‧‧‧Internal electrode layer

30'‧‧‧ Coating

40‧‧‧External electrode

FIG. 1 is a schematic cross-sectional view illustrating the structure of the MLCC.

FIG. 2 is a schematic cross-sectional view illustrating the structure of the MLCC before sintering.

Claims (9)

A conductive paste includes: a conductive powder, a binder, a viscosity-increasing inhibitor, and a dispersion medium. The viscosity-increasing inhibitor is a secondary amine compound represented by the general formula: NHR ¹ R ² , where R ¹ And R ^{2 is} independently a linear or cyclic aliphatic group having 4 to 12 carbon atoms, and the carbon chain in R ¹ and R ² does not contain an oxygen atom, a nitrogen atom, and a sulfur atom. The conductive paste according to item 1 of the scope of patent application, wherein the R ¹ and the R ² satisfy R ¹ = R ² . The conductive paste according to item 1 or item 2 of the patent application scope, wherein both of R ¹ and R ² do not contain a methyl group other than a terminal. The conductive paste according to any one of claims 1 to 3 in the scope of the patent application, wherein the viscosity-increasing inhibitor is contained in the conductive paste at a ratio of 0.001% by mass to 5% by mass. The conductive paste according to any one of claims 1 to 4, wherein the conductive powder is a nickel powder. The conductive paste according to any one of claims 1 to 5, in which the average particle diameter of the conductive powder is 1 μm or less. The conductive paste according to any one of claims 1 to 6, further comprising a dielectric powder. The conductive paste according to any one of claims 1 to 7 of the patent application scope, which comprises a first powder having a first average particle diameter and a second powder having a second average particle diameter, and the second average The particle diameter D _{2 is} in a range of 0.1 × D _{1 to} 0.4 × D ₁ based on the first average particle diameter D ₁ , and the conductive powder includes at least the first powder. A laminated ceramic capacitor is a laminate of a dielectric layer and an internal electrode. The internal electrode layer is composed of a fired product of the conductive paste according to any one of claims 1 to 8 of the scope of patent application.