KR20220136254A - Nickel nanoparticles, paste materials and multilayer ceramic condenser - Google Patents

Abstract

The present invention provides nickel nanoparticles having a high purity of 5-100 nm, which have excellent thin film formability and excellent filling properties into extremely narrow gaps. The nickel nanoparticles have an average particle diameter of 5 nm to 100 nm. A nickel component contained in 100 parts by weight of a metal component is contained in 99.5 parts by weight or more. With respect to the average particle diameter of the nickel nanoparticles in the total 400 nickel nanoparticles captured by a scanning electron microscope having a secondary electron resolution of 1.0 nm or less at an acceleration voltage of 15 kV, the ratio of the total number of particles having a particle diameter of 1/2 or less and particles having a particle diameter of 3/2 or more is 5% or less.

Description

NICKEL NANOPARTICLES, PASTE MATERIALS AND MULTILAYER CERAMIC CONDENSER

The present invention relates to nickel nanoparticles, paste materials and multilayer ceramic capacitors.

MLCC (Multilayer Ceramic Condenser) is a product in which a ceramic dielectric layer and an internal electrode layer are alternately laminated and integrated. As the thin film is reduced, the particles used in dielectrics and electrodes are also finely divided, so the problem of particle aggregation has become a reality, and advanced dispersion technology and particle shape control technology are required.

In the particle shape, when the paste is stretched to form a thin film, if the particle size distribution is wide and large particles exist, liquid breakage occurs starting from the large particles, so that it cannot be applied with an even thickness. there is a problem that In order to apply a uniform tension to the entire paste, it is necessary to have a uniform particle diameter of the large particles and to arrange a certain amount in a balanced way.

In addition, for the purpose of forming wirings such as electromagnetic shields or touch panels, in order to prevent penetration or diffusion of wirings, filling the grooves of the nanoimprinted substrate with metal particles is being considered. It is known that the uniform size of the particles maintains the uniformity of the tension of the entire paste even when high filling is performed in a narrow groove, and high filling is easy.

As a method for producing uniform particles, a method for producing nickel particles obtained by reducing nickel hydroxide particles obtained by reacting a nickel salt with an alkali metal hydroxide in water with hydrazine (Patent Document 1) is exemplified. In the particles produced by this production method, the number of particles having a particle diameter of 1.2 times or more of the average particle diameter as observed by a scanning electron microscope (SEM) is 5% or less of the total number of particles, and 0.8 times or less of the average particle diameter Nickel particles with an average particle diameter of 0.44 to 0.51 μm have a narrow particle size distribution in which the number of particles having a particle diameter of is 5% or less of the total number of particles. In addition, the production method of Patent Document 1 cannot completely remove hydroxide because it causes a reaction in an aqueous solution. When applied to a particle size of 100 nm or less, when applied to a non-polar solvent suitably used for the above use, etc., sufficient minutes Can't get acid. Therefore, there is a problem that aggregation between particles occurs. Moreover, the point that it is difficult to synthesize|combine the particle|grains with a particle diameter of 100 nm or less and uniform particle size is also mentioned.

As a method for producing uniform particles having a size of 100 nm or less, by using 10 nm to 50 nm seed particles obtained by adding copper formate to a salt containing nickel carboxylate and reducing it with an amine, the coefficient of variation (CV) uniformity of 0.2 or less It has been reported that one particle can be obtained (Patent Document 2), but copper is used as the seed particle. Moreover, in the other Example of patent document 2, although copper formate is not used, silver nitrate uses palladium acetate, chloroplatinic acid hexahydrate, or chloroauric acid tetrahydrate, and all use a dissimilar metal other than nickel in combination. . From the viewpoint of electrical properties and cost, nickel particles with as high a purity of nickel as possible are required.

Japanese Patent No. 3280372 Publication International Publication No. WO2016/052067

SUMMARY OF THE INVENTION It is an object of the present invention to provide nickel nanoparticles with high purity of 5 to 100 nm, which are excellent in thin film formability and filling properties for very narrow gaps.

As a result of repeated research, the present inventors have found that nickel nanoparticles having a uniform particle size can be produced even when observed with high-resolution SEM by controlling the stirring power and the components of the gas generated when synthesizing nickel nanoparticles. Found and completed the present invention.

That is, the present invention is a nickel nanoparticle having an average particle diameter of 5 to 100 nm and a nickel component contained in 100 parts by weight of a metal component of 99.5 parts by weight or more, wherein the secondary electron resolution at an acceleration voltage of 15 kV is 1.0 nm or less. In all 400 nickel nanoparticles photographed with a scanning electron microscope (SEM), the ratio of the sum of the number of particles having a particle diameter of 1/2 or less and particles having a particle diameter of 3/2 or more to their average particle diameter is It relates to nickel nanoparticles, characterized in that 5% or less.

The nickel nanoparticles of the present invention preferably contain 0.00003 parts by weight to 0.5 parts by weight of lithium.

The paste material of the present invention is characterized in that it is formed by mixing the nickel nanoparticles and a resin.

The multilayer ceramic capacitor of the present invention is characterized in that the nickel nanoparticles are used as a material for electrodes.

Nickel nanoparticles of the present invention, even when observed with a high-resolution SEM having a secondary electron resolution of 1.0 nm or less at an acceleration voltage of 15 kV, particles having an average particle diameter of 1/2 or less and particles having an average particle diameter of 3/2 or more Since the ratio of the total number of particles to the total particles is 5% or less, the tension acting on the inside of the paste becomes uniform when forming the thin film. Therefore, it is easy to form a uniform ultra-thin film, and it can be suitably used for applications requiring lamination of multi-layered thin films, such as MLCC (Multilayer Ceramic Condenser).

In addition, the paste material using the nickel nanoparticles of the present invention is a material for filling the grooves formed by printing for the purpose of preventing penetration or diffusion of wiring, and can be widely used for manufacturing electromagnetic shields, touch panels, etc. have.

1 is a scanning electron microscope (SEM) image (200,000 times) of particles prepared in Example 1. FIG.
Fig. 2 is an SEM image (200,000 magnifications) of particles prepared in Comparative Example 1.
Fig. 3 is an SEM image (200,000 times) of particles prepared in Comparative Example 2.
Fig. 4 is an SEM image (100,000 times) of particles prepared in Example 2.
Fig. 5 is an SEM image (200,000 times) of particles prepared in Comparative Example 3.
Fig. 6 is an SEM image (200,000 times) of particles prepared in Example 3.
Fig. 7 is an SEM image (200,000 times) of particles prepared in Comparative Example 4.
Fig. 8 is an SEM image (200,000 times) of particles prepared in Example 4.
Fig. 9 is an SEM image (200,000 times) of particles prepared in Comparative Example 5;
Fig. 10 is an SEM image (200,000 times) of particles prepared in Example 5.
Fig. 11 is an SEM image (50,000 magnifications) of particles prepared in Comparative Example 6.

EMBODIMENT OF THE INVENTION Embodiment of this invention is described below.

The nickel nanoparticles of the present invention are nickel nanoparticles having an average particle diameter of 5 to 100 nm and a nickel component contained in 100 parts by weight of a metal component of 99.5 parts by weight or more, and have secondary electron resolution at an acceleration voltage of 15 kV. In all 400 nickel nanoparticles photographed by SEM of 1.0 nm or less, particles having a particle diameter of 1/2 or less (hereinafter sometimes referred to as "relative small particle") and a particle diameter of 3 with respect to their average particle diameter The ratio of the total number of particles of /2 or more (hereinafter, sometimes referred to as "relatively large particles") is 5% or less. As described above, by making the ratio of the sum of the number of relative small particles and relative large particles to 5% or less in the total number of particles, the particles greatly deviating from the average particle diameter in the particle size distribution. Since the particle size distribution is narrow because the abundance ratio of

In the nickel nanoparticles of the prior art, there was a problem that a large number of relatively small particles are included. In applications of adding ceramic fillers to prevent shrinkage during sintering, such as MLCC, fine particles are used to fill the gaps between nickel nanoparticles. Also, there is a problem in thin film formation and sinterability. In addition, if particles larger than twice the average particle diameter exist, there is a concern that problems such as conduction through the insulating layer may occur when thin films such as electrodes are formed in multiple layers, so the ratio of relatively large particles is small it is preferable Therefore, it is preferable that the proportion of the relatively small particles and the relatively large particles in the total particles is 3% or less, respectively, and the combined ratio of the relatively small particles and the relatively large particles is 5% or less.

The nickel nanoparticles of the present invention have a value (CV value) of 0.25 or less obtained by dividing the standard deviation of the particle diameter of 400 nickel nanoparticles photographed by SEM with a secondary electron resolution of 1.0 nm or less at an acceleration voltage of 15 kV by the average particle diameter It is preferable, and it is more preferable that it is 0.20 or less.

The nickel nanoparticles of the present invention have an average particle diameter of 5 to 100 nm, but the nucleophilic reagent to be added is expensive, For the purpose of clarifying the difference, the lower limit thereof is preferably 10 nm or more, and more preferably 15 nm or more. On the other hand, the upper limit is preferably 90 nm or less, and more preferably 80 nm or less, because the amount of the nucleating agent added becomes very small as the particle size increases, and the precision of the particle size decreases.

The nickel nanoparticles of the present invention contain 99.5 parts by weight or more of the nickel component contained in 100 parts by weight of the metal component, but 99.8 parts by weight or more is preferable from the viewpoint of expressing good electrical properties such as electrical conductivity and migration, and 99.95 parts by weight or more. More preferably not less than parts by weight.

The nickel nanoparticles of the present invention preferably contain 0.00003 parts by weight to 0.5 parts by weight of lithium from the viewpoint of easy control of the particle size. A more preferable lower limit is 0.00005 parts by weight. On the other hand, a more preferable upper limit is 0.2 parts by weight.

Further, the nickel nanoparticles of the present invention may be core-shell type particles in which the nickel nanoparticles are used as a core and other metals are used as a shell. In this case, the nickel nanoparticles of the present invention correspond to the core portion of the core-shell-type particles. That is, in the present specification, the content of lithium or alkali metal or alkaline earth metal by ICP mass spectrometry is specified in the present specification, but they define the core portion of the core-shell type particle.

Moreover, it is preferable that the said other metal is iron, cobalt, copper, palladium, platinum, gold|metal|money, or tungsten. Moreover, it is preferable that the average particle diameter of core-shell type particle|grains is 10-105 nm.

Next, the manufacturing method of the nickel nanoparticles of the present invention will be exemplified.

The manufacturing method of the nickel nanoparticle of this embodiment, the following process A and process B;

A) a step of obtaining a nickel complexing reaction solution by mixing a nickel salt and a reducing agent,

B) A step of obtaining a slurry of nickel nanoparticles by heating the nickel complexing reaction solution to reduce nickel ions in the nickel complexing reaction solution

contains And in the manufacturing method of the nickel nanoparticles of this embodiment, in the process B, while blowing in nitrogen at 0.1 to 5 L/min with respect to 100 g of the nickel complexing reaction solution, the power of the stirring device is set to 0.025 to 0.1 kW. After adjusting within the range, it is heated to 190-240° C. to produce nickel nanoparticles. Further, the organometallic compound may be added at any timing between the step A and the heating of the metal complexing reaction solution in the step B.

[Process A]

Step A is a step of obtaining a nickel complexing reaction solution by mixing a nickel salt and a reducing agent.

<Nickel salt>

As a nickel salt, a well-known nickel salt is mentioned. For example, organic acid nickel salts, such as a nickel carboxylate salt, inorganic nickel salts, such as a nickel chloride salt, a nickel sulfate salt, a nickel nitrate salt, and a nickel carbonate salt, are mentioned. Among these, a nickel carboxylate salt having 1 to 12 carbon atoms in the portion excluding the COOH group is preferable from the viewpoint of easy control of the particle diameter and particle size distribution of the nickel nanoparticles. Among these, nickel acetate is more preferable.

Although there is no restriction|limiting in particular as a reducing agent used for this embodiment, What can form a complex with nickel is preferable, For example, a primary amine is used suitably. A primary amine is preferable because it can form a complex with nickel and can exhibit effectively reducing ability with respect to a nickel complex. On the other hand, since secondary amines have a large steric hindrance, there is a risk of inhibiting good formation of nickel complexes, and tertiary amines cannot be used alone because they do not have nickel reducing ability. However, while using the primary amine, it does not matter to use them together in a range that does not interfere with the shape of the nickel nanoparticles produced.

The reducing agent may be solid or liquid at room temperature. Here, the normal temperature means 20°C±15°C. The primary amine, which is liquid at room temperature, also functions as an organic solvent for forming a nickel complex. In addition, even if it is a solid primary amine at room temperature, there is no particular problem as long as it is made into a liquid by heating at 100°C or higher or dissolved using an organic solvent.

Although an aromatic primary amine may be sufficient as a primary amine, an aliphatic primary amine is preferable from a viewpoint of the easiness of formation of the nickel complex in a reaction liquid. The aliphatic primary amine is advantageous in applications requiring dispersibility, since the dispersibility of the produced nickel nanoparticles can be controlled by, for example, adjusting the length of the carbon chain. From the viewpoint of controlling the aggregation of nickel nanoparticles, the aliphatic primary amine is preferably selected from those having about 6 to 20 carbon atoms. Examples of such amines include octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, oleylamine, myristylamine, and laurylamine. . Since oleylamine and dodecylamine exist as liquids under the temperature conditions in the production process of nickel nanoparticles, the reaction can proceed efficiently with a homogeneous solution, and thus, they are particularly preferable. Most preferred is oleylamine.

Since a primary amine functions as a surface modifier when producing|generating a nickel nanoparticle, even after removal of the said primary amine, secondary aggregation can be suppressed. In addition, primary amines are treated at room temperature after the reduction reaction in step B from the viewpoint of ease of treatment in the washing step of separating the solid component of the produced nickel nanoparticles from the solvent or unreacted primary amine. It is preferably liquid. Furthermore, the primary amine preferably has a boiling point higher than the reduction temperature from the viewpoint of easiness of reaction control when reducing the nickel complex to obtain nickel nanoparticles. The amount of primary amine is preferably used at a ratio of 2 x 1 times mol or more of nickel valence with respect to 1 mol of nickel, more preferably 2 x 1.1 times mol or more of valence, and 2 x 2 times mol or more of valence. It is more preferable to do When the amount of the primary amine is less than 2x1 times mole of valence of nickel, it becomes difficult to control the particle size of the nickel nanoparticles obtained, and the particle size becomes non-uniform. Moreover, although there is no upper limit in particular of the quantity of a primary amine, for example, from a viewpoint of productivity, it is preferable to set it as 2x10 times mol of valence of nickel or less.

The conditions for forming the nickel complex reaction solution in step A, that is, the mixing conditions of the nickel salt and the reducing agent, will be described by taking the case where nickel carboxylate is used as the nickel salt and a primary amine is used as the reducing agent. In this case, although the complex-forming reaction can proceed even at room temperature, in order to carry out the complex-forming reaction with sufficient and higher efficiency, the reaction is preferably carried out by heating, for example, at a temperature within the range of 100°C to 165°C. The heating temperature is preferably a temperature exceeding 100°C, and more preferably a temperature of 105°C or higher. By such heating temperature, the ligand substitution reaction between the coordination water coordinated with the nickel carboxylate and the primary amine can be efficiently performed, thereby dissociating the water molecule as a complex ligand, and further dissociating the water with the system (系) Since it can be sent to the outside, a complex with an amine can be formed efficiently. The heating time can be appropriately determined according to the heating temperature or the content of each raw material. There is no particular upper limit of the heating time, but unnecessary long-term heat treatment is useless from the viewpoint of saving energy consumption and process time.

The method of heating in process A is not restrict|limited in particular, For example, heating by heating medium, such as oil, may be sufficient, and heating by microwave irradiation or ultrasonic irradiation may be sufficient.

In step A, in order to more efficiently proceed the reaction by the homogeneous solution, an organic solvent separate from the primary amine may be newly added. In the case of using an organic solvent, the organic solvent may be mixed simultaneously with the nickel carboxylate and the primary amine. However, if the nickel carboxylate and the primary amine are first mixed to form a complex and then the organic solvent is added, the primary amine can be efficiently Since it coordinates to a nickel atom, it is more preferable. The organic solvent that can be used is not particularly limited as long as it does not inhibit complex formation between nickel carboxylate and primary amine and does not oxidize the nickel produced, for example, a saturated or unsaturated hydrocarbon-based organic solvent having 7 to 30 carbon atoms. A solvent, etc. can be used. In addition, from the viewpoint of enabling use under heating conditions, it is preferable that the organic solvent used has a boiling point of 170° C. or higher. As a specific example of such an organic solvent, paraffin oil is mentioned.

[Process B]

In step B, an inert gas is blown into the nickel complexing reaction solution obtained by the complexing reaction at a predetermined flow rate, and heating is performed while adjusting the power according to the liquid amount and the desired particle size to reduce nickel ions in the complexing reaction solution, A slurry of nickel nanoparticles is obtained. Specifically, while blowing in nitrogen at a rate of 0.1 to 5 L/min with respect to 100 g of the nickel complexing reaction solution, the power of the stirring device is adjusted within the range of 0.025 to 0.1 kW, and then heated to 190 to 240° C. to produce nickel nanoparticles. make it

Although the heating temperature in step B varies depending on the particle size, particle size distribution, etc. of the nickel nanoparticles to be obtained, it is preferable to maintain the temperature at which the reaction accompanied by endothermic heat occurs. When sufficiently heated beyond the reaction temperature, hydrocarbons are decomposed by the catalytic action of the nickel produced, and carbon is deposited and covered the surface of the nickel nanoparticles, thereby suppressing the generation of nickel ions on the surface of nickel. Therefore, when nickel nanoparticles are used as a paste material, etc., there is a tendency for the bonding properties between nickel nanoparticles or between nickel nanoparticles and other particles to decrease.

Here, the inert gas means a chemically stable gas that does not react with other materials used for the synthesis reaction of nickel nanoparticles in step B. For example, nitrogen and argon are mentioned. Preferably, nitrogen is mentioned from the reason that it can obtain cheaply.

As an example of the inert gas, the flow rate of nitrogen is preferably adjusted to a flow rate corresponding to the gas generated during the reaction, and since it changes according to the desired particle size and the amount of synthesis, the range of the flow rate can be appropriately selected. Preferably it is 0.1-5 L/min with respect to 100-750 g of nickel complexing reaction liquid, More preferably, 500-750 g.

More specifically, when synthesizing particles having a particle diameter of 15 nm, 2 to 4 L/min is preferable with respect to 750 g of nickel complexing reaction liquid, and more preferably 2.8 to 3.2 L/min. In addition, according to the particle diameter of the nickel nanoparticles, it is also preferable to change the nitrogen flow rate in the temperature range of 190 to 215 ℃. For example, when synthesizing particles having a particle diameter of more than 30 nm, for example, particles having a diameter of 40 nm, the nitrogen flow rate at less than 200 ° C. It is preferable to set it as 2-4 L/min, and at 200 degreeC or more, the desired particle|grains can be obtained by adjusting the nitrogen flow rate to 0.1-3.3 L/min.

There is no particular limitation on the purity of nitrogen, but if there is a lot of moisture, the complex absorbs moisture and may affect the reaction. In addition, blowing in nitrogen gas means injecting nitrogen gas directly to the reaction solution by applying a pressure higher than a certain level, not simply in a nitrogen atmosphere or under the flow of nitrogen (so-called "nitrogen flow"). In the method of blowing nitrogen gas, it may be made to flow along the reaction liquid surface, or it may be sprayed toward the reaction liquid surface with a well-known nozzle. It is more preferable to directly inject nitrogen gas into the reaction solution for bubbling. By directly "blowing" nitrogen gas into the reaction liquid, the gas (reaction product gas) generated by the reaction can be efficiently discharged. It is preferable to adjust the blowing method, flow rate, pressure, etc. according to the desired particle size. If the removal of the reaction product gas is insufficient, the generation of nuclei is inhibited, and the nuclei are generated step by step, which is not preferable because particles having a wide particle diameter are generated. However, if it is excessive to efficiently remove the reaction product gas, new nuclei are generated during the growth reaction after nucleation, and the particle diameter tends to increase.

The power for stirring the reaction solution can be appropriately selected according to the shape of the impeller, etc., but it is preferable to synthesize the power according to the amount of the liquid. As a preferable lower limit of power, it is 0.025 kW or more with respect to 100 g of nickel complexing reaction liquid in order to prevent generation|occurrence|production of coarse particle by particle-to-particle association. In addition, the upper limit of the power is 0.1 kW or less, preferably 0.07, because there is a risk of quality problems such as the formation of coarse particles due to contamination caused by splashing due to dispersion of the nickel complexing reaction solution 100 g. less than kW. In addition, since the gas emission property changes and it also causes the generation of new nuclei during the growth reaction, it is preferable to adjust the power to an appropriate value.

The heating time is not particularly limited, but the nickel concentration of the reaction solution is measured using a nickel concentration meter (for example, a nickel concentration meter Ni-5Z manufactured by Kasahara Chemical Instruments Corp.), It is preferable to heat until the time when it is not detected. If the heating time is shorter than this, it is difficult to obtain nickel nanoparticles having a desired particle size, and dispersibility is more likely to be lowered, which is not preferable. In addition, the upper limit of the heating time is not particularly limited because the heating time changes depending on the particle size. However, long-term heating after the reaction is completed causes carbon to be deposited on the surface of the nickel nanoparticles, so the use in which the avoidance of impurities is required. , for example, in applications requiring low-temperature sintering, the temperature required for sintering becomes high, which is undesirable. In addition, since the amount of gas generated during sintering increases, there is a high possibility that the shape of the sintered body is damaged, which is not preferable.

As the production process in step B, a batch method or a continuous reactor in which a stainless steel vessel is heated is used. Examples of the heating means include a heating method using a heating medium such as oil temperature control, electricity, microwave, and ultrasonic waves. From the viewpoint of production cost, a heating method using a heating medium such as oil temperature control or electricity is preferably used. Moreover, the heating by microwave irradiation or ultrasonic irradiation may be sufficient.

In step B, in order to improve the dispersibility of the nickel nanoparticles or to impart a function such as a rust preventive agent for preventing oxidation, a dispersing agent or an additive for imparting a function may be added in a range that does not impair bondability.

[Addition of organometallic compound]

The organometallic compound used in the present embodiment is not particularly limited as long as it has the same properties (nucleophilicity) as the nucleophilic reagent and acts on the metal complex. As a preferred organometallic compound, an alkali metal-based organometallic compound in which an organic group such as an alkyl group or an alkoxy group is coordinated to an alkali metal from the viewpoint of ease, safety, convenience, and productivity of controlling the particle diameter or particle size distribution of nickel nanoparticles and alkali and alkaline earth metal-based organometallic compounds in which the organic group is coordinated to an earth metal. Hereinafter, the alkali metal-based organic compound and the alkaline earth metal-based organic compound are collectively referred to as “the present organometallic compound”. The organometallic compound may be an organometallic halide containing a halide such as chlorine, bromine or iodine. In this case, they are also referred to as an alkali metal-based organometal halide and an alkaline earth metal-based organometal halide, respectively. The alkali metal-based organometal halide is one form of the alkali metal-based organometallic compound, and the alkaline earth metal-based organometallic halide is one form of the alkaline-earth metal-based organometallic compound.

Examples of the alkali metal constituting the alkali metal-based organometallic compound include lithium, sodium, potassium, rubidium, and cesium, and organolithium containing highly reactive lithium is preferably used.

Further, examples of the alkaline earth metal constituting the alkaline earth metal-based organometallic compound include beryllium, magnesium, calcium, strontium, and barium, and an organomagnesium halide containing magnesium with good reactivity is preferably used. In addition, since alkylaluminum in which an alkyl group is coordinated with aluminum has strong flammability, alkali metal-based organometallic compounds are more suitably used from the viewpoint of safety and convenience.

The present organometallic compound is preferably used as a diluted solution diluted with an organic solvent such as tetrahydrofuran, hexane, toluene, cyclohexane, butyl ether, dibutyl ether, etc. From this point, toluene and a dibutyl ether solution are especially preferable. There is no restriction on the concentration of the diluting solution, but when it affects the particle size in a small amount, a low concentration is preferable because it is easy to control.

As the alkali metal-based organometallic compound, inexpensive general-purpose n-butyllithium and phenyllithium are suitably used, and a dibutyl ether solution of phenyllithium is particularly preferable from the viewpoints of safety and convenience.

The amount of the organometallic compound to be added is not particularly limited, as it is sufficient to select the amount to be added according to the desired particle size. Specifically, the amount of the organometallic compound added is preferably in the range of 0.001 to 30 g, more preferably in the range of 0.003 to 10 g, per 100 g of the nickel complex.

The organometallic compound may be added at any timing between the process A and the heating of the complex reaction solution in the process B. For example, the present organometallic compound may be added after mixing the nickel salt and the reducing agent in step A and removing excess moisture, or may be added after preparing the complexing reaction solution. In addition, since the present organometallic compound is deactivated by moisture and loses its effect, it is difficult to control the particle size distribution, so it is preferable to add the organometallic compound immediately before heating the complexing reaction solution in step B. By adding the present organometallic compound, the particle diameter of the nickel nanoparticles can be significantly reduced. Although its mechanism of action is not yet clear, it is presumed that the present organometallic compound having nucleophilicity acts on the nickel complex to promote the formation of nickel nuclei.

The nickel nanoparticles of the present invention can be mixed with a known resin to form a paste material. For example, a resin can be used as an organic binder. The organic binder serves to maintain dispersibility by suppressing sedimentation or aggregation of nickel nanoparticles in the paste material. In addition, it contributes to the formation of a bonding layer having high bonding strength by creating a wide network structure by connecting nickel nanoparticles to each other or nickel nanoparticles to other particles.

The known resin can be used without particular limitation as long as it is a binder that can be dissolved in an organic solvent, for example, thermosetting resins such as phenol resin, epoxy resin, unsaturated polyester resin, urea resin, melamine resin, polyethylene resin, and acrylic resin. and thermoplastic resins such as resin, methacrylic resin, nylon resin, acetal resin, and polyvinyl acetal resin. Among these, a polyvinyl acetal resin is preferable, and especially a polyvinyl acetal resin provided with the unit of an acetal group, the unit of an acetyl group, and the unit of a hydroxyl group in a molecule|numerator is more preferable.

The paste material may include other particles as an optional component. That is, it may be a paste material including the nickel nanoparticles and other particles. Here, the material and shape of the other particles are not limited, but non-metals such as tin, titanium, cobalt, copper, chromium, manganese, iron, zirconium, tungsten, molybdenum, and vanadium, which have excellent thermal conductivity as a sintering material, and gold and metal elements such as noble metals such as silver, platinum, palladium, iridium, osmium, ruthenium, rhodium, and rhenium. These may be contained individually or 2 or more types. More preferably, they are cobalt, silver, copper, and pewter excellent in thermal conductivity and sintering property.

Since the paste material contains the nickel nanoparticles of the present invention as an essential component, the tension acting on the inside of the paste becomes uniform when forming the thin film, and it is easy to form a uniform ultra-thin film. Moreover, it is excellent in filling property with respect to a groove|channel etc., and linearity of a wiring. Therefore, it can be suitably used for applications requiring multi-layer thin film lamination, such as, for example, MLCC. In addition, as a material for filling a groove formed by printing with a paste for the purpose of preventing penetration or diffusion of wiring, it can be widely used for manufacturing electromagnetic shields, touch panels, and the like.

Moreover, the case where the said paste material is used for MLCC use, especially the case where nickel nanoparticles are used as an electrode material of MLCC is exemplified below.

[Internal electrode for multilayer ceramic capacitor]

The internal electrodes of the multilayer ceramic capacitor of the present embodiment (hereinafter, simply referred to as "internal electrodes") are manufactured by pasting the nickel nanoparticles of the present embodiment and printing them on a ceramic substrate.

When performing the said paste formation, you may mix well-known viscosity modifiers, such as an organic vehicle and an aqueous vehicle. By mixing the viscosity modifier, appropriate fluidity and volatility are imparted to the paste, and a smooth internal electrode can be formed on the ceramic substrate.

An organic vehicle is what melt|dissolved resin in the organic solvent, for example. The resin used for the organic vehicle is not particularly limited, and may be appropriately selected from various general resins such as ethyl cellulose and polyvinyl butyral. Also, the organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butylcarbitol, acetone and toluene depending on the method used such as a printing method or a sheet method.

Moreover, polyvinyl alcohol, a cellulose, and a water-soluble acrylic resin are mentioned, for example as an aqueous vehicle colorant.

A known ceramic dielectric is used, for example, as a perovskite dielectric, barium titanate, a dielectric in which a part of titanium is substituted with zircon, and a dielectric in which barium is partly substituted with strontium or calcium, etc. are mentioned. can

The printing method of the internal electrode is not particularly limited as long as it is a method capable of uniformly forming a layer, and examples thereof include a screen printing method, a gravure printing method, a vapor deposition method, a sputtering method, and an inkjet method.

[Multilayer Ceramic Capacitor]

The multilayer ceramic capacitor of the present embodiment is manufactured by alternately stacking the internal electrodes and the ceramic dielectric in a layered manner, pressing, firing, and integrating them. A known ceramic dielectric is used, and the said barium titanate etc. are mentioned. This is pasted to form a ceramic dielectric layer on the internal electrode. When forming into a paste, you may mix well-known viscosity modifiers, such as an organic vehicle and an aqueous vehicle. By mixing the viscosity modifier, appropriate fluidity and volatility are imparted to the paste, and a smooth internal electrode layer and a ceramic dielectric layer can be formed on the ceramic substrate. An organic vehicle is what melt|dissolved resin in the organic solvent, for example. The resin used for the organic vehicle is not particularly limited, and may be appropriately selected from various general resins such as ethyl cellulose and polyvinyl butyral. Also, the organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butylcarbitol, acetone and toluene depending on the method used such as a printing method or a sheet method.

Moreover, polyvinyl alcohol, a cellulose, and a water-soluble acrylic resin are mentioned, for example as an aqueous vehicle colorant.

The printing method of the ceramic dielectric is not particularly limited as long as it is a method capable of uniformly forming a layer, and examples thereof include a screen printing method, a gravure printing method, a vapor deposition method, a sputtering method, and an inkjet method.

Although the layers and thicknesses of the internal electrode and the ceramic dielectric are not limited, for example, several to 1000 layers, and each layer thickness is 0.1 to 2 μm.

Next, the thus obtained internal electrode and the multilayer structure of the ceramic dielectric are pressed and integrally molded, cut to a predetermined size (size of the chip), and fired to form a chip. The firing temperature is, for example, 1000°C to 1300°C. After firing, a metal paste is applied to both end surfaces of the chip, heat-treated, and the surface is plated to form an external electrode.

The multilayer ceramic capacitor according to the embodiment of the present invention manufactured in this way is mounted on a printed board or the like by soldering or the like, and is used for various electronic devices and the like.

Since these electronic devices use the nickel nanoparticles of the present invention, miniaturization and high capacity are possible, reliability and high lifespan are excellent, and the lifespan of electronic components against high temperature loads can be improved. .

(Example)

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by these Examples. In addition, in the following examples, the measurement and evaluation are based on the following unless otherwise stated.

[Measurement of particle size distribution, average particle diameter and CV value]

The particle size distribution, average particle diameter, and CV value were performed by the following method.

A photograph of the sample was taken with SEM (Scanning Electron Microscope, manufactured by Hitachi High-Tech Corporation, Regulus 8100, secondary electron resolution 0.8 nm at an acceleration voltage of 15 kV), and particle size distribution analysis software ((( (Note) Using Mounttech (Mountech Co., Ltd.), Mac-View), 400 particles of which all particles are photographed are sequentially extracted from the left side of the photo. Using the diameter of the circle (Heywood diameter) corresponding to the selected area as the individual particle diameter, the mathematical mean diameter and standard deviation are calculated. In all 400 extracted nickel nanoparticles, the ratio of particles having a particle diameter of 1/2 or less (≤ 1/2 particle diameter) to particles having a particle diameter of 3/2 or more (≥ 3/2 particle diameter) to the average particle diameter (%) was calculated.

In addition, the CV value (coefficient of variation) was calculated by (standard deviation) ÷ (mathematical mean diameter). It also indicates that the smaller the CV value, the more uniform the particle size is.

[Measurement of content of nickel component, alkali metal or alkaline earth metal contained in metal component]

The content (parts by weight) of the nickel component, alkali metal or alkaline earth metal contained in the nickel nanoparticles was measured by high-frequency inductively coupled plasma mass spectrometry (ICP mass spectrometry).

[Organic metal compound]

Organometallic compound (1): manufactured by FUJIFILM Wako Pure Chemical Corporation, about 19% dibutyl ether solution of phenyllithium (about 1.9 mol/L)

[Oleylamine]

NOF CORPORATION product, NISSANAMINE OB

(Synthesis Example 1)

600 g of oleylamine was extract|collected in a 2 L 4-necked flask, 246.8 g of nickel acetate tetrahydrates were added, and it was made to react at 140 degreeC under a nitrogen stream of 2 L/min for 3 hours, and 775 g of nickel complex reaction liquid A was obtained.

(Synthesis Example 2)

200 g of oleylamine was collected in a 2 L four-neck flask, 82.3 g of nickel acetate tetrahydrate was added, and reaction was performed at 140°C for 3 hours under a nitrogen stream of 2 L/min to obtain 258 g of nickel complex reaction solution B.

(Example 1)

To 775 g of the nickel complexing reaction solution A obtained in Synthesis Example 1, 6 g of the organometallic compound (1) was added to make a total of 781 g, and the power was adjusted to 0.034 kW while directly injecting (bubbling) nitrogen gas into the reaction solution at 3 L/min. And, the temperature was raised with a mantle heater, and the nickel nanoparticle slurry was obtained by making it react at 210 degreeC for 10 minutes. As shown in Fig. 1 and Table 1, particles exhibiting a narrow particle size distribution with an average particle diameter of 14.9 nm and a CV value of 0.12 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.85 parts by weight, and the lithium component was 0.12 parts by weight.

(Example 2)

To 775 g of nickel complexing reaction solution A obtained in Synthesis Example 1, 0.15 g of organometallic compound (1) was added to make a total of 775.15 g, and nitrogen gas was directly injected (bubbled) into the reaction solution at 1 L/min, while power was 0.033 kW was adjusted to, heated with a mantle heater, and reacted at 230°C for 10 minutes to obtain a nickel nanoparticle slurry. As shown in Fig. 4 and Table 1, particles exhibiting a narrow particle size distribution with an average particle diameter of 27.9 nm and a CV value of 0.14 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.0003 parts by weight.

(Example 3)

To 775 g of nickel complexing reaction solution A obtained in Synthesis Example 1, 0.17 g of organometallic compound (1) was added to make a total of 775.17 g, and nitrogen gas was directly injected (bubbled) into the reaction solution at 3 L/min, while power was 0.048 kW , the temperature was raised with a mantle heater, and the amount of nitrogen was changed to 0.5 L/min at the stage of reaching 200 ° C., and reacted at 230 ° C. for 10 minutes to obtain a nickel nanoparticle slurry. As shown in Fig. 6 and Table 1, particles exhibiting a narrow particle size distribution with an average particle diameter of 38.2 nm and a CV value of 0.17 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.0003 parts by weight.

(Example 4)

13.2 g of the nickel nanoparticle slurry obtained in Example 1 was added to 258 g of the nickel complexing reaction solution B obtained in Synthesis Example 2 to make a total of 271.2 g, and nitrogen gas was directly injected (bubbled) into the reaction solution at 0.5 L/min. , the power was adjusted to 0.029 kW, the temperature was raised with a mantle heater, and reacted at 230°C for 10 minutes to obtain a nickel nanoparticle slurry. As shown in Fig. 8 and Table 1, particles exhibiting a narrow particle size distribution with an average particle diameter of 41.0 nm and a CV value of 0.19 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.0006 parts by weight.

(Example 5)

5 g of the nickel nanoparticle slurry obtained in Example 1 was added to 258 g of the nickel complexing reaction solution B obtained in Synthesis Example 2 to make a total of 263 g, and nitrogen gas was directly injected (bubbled) into the reaction solution at 1 L/min, while power was 0.033 Adjusted to kW, heated with a mantle heater, and reacted at 230°C for 10 minutes to obtain a nickel nanoparticle slurry. As shown in Fig. 10 and Table 1, particles exhibiting a narrow particle size distribution with an average particle diameter of 49.8 nm and a CV value of 0.18 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.0004 parts by weight.

(Comparative Example 1)

6 g of organometallic compound (1) was added to 775 g of nickel complexing reaction solution A obtained in Synthesis Example 1 to make a total of 781 g, and while nitrogen gas was flowed at 2 L/min, the power was adjusted to 0.033 kW, and the temperature was raised with a mantle heater, By reacting at 210°C for 10 minutes, a nickel nanoparticle slurry was obtained. As shown in Fig. 2 and Table 1, particles exhibiting a wide particle size distribution with an average particle diameter of 18.4 nm and a CV value of 0.29 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.85 parts by weight, and the lithium component was 0.13 parts by weight.

(Comparative Example 2)

6 g of organometallic compound (1) was added to 775 g of nickel complexing reaction solution A obtained in Synthesis Example 1 to make a total of 781 g, and while nitrogen gas was flowed at 4 L/min, the power was adjusted to 0.033 kW, and the temperature was raised with a mantle heater, By reacting at 210°C for 10 minutes, a nickel nanoparticle slurry was obtained. As shown in Fig. 3 and Table 1, particles exhibiting a wide particle size distribution with an average particle diameter of 20.4 nm and a CV value of 0.24 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.85 parts by weight, and the lithium component was 0.12 parts by weight.

(Comparative Example 3)

To 775 g of nickel complexing reaction solution A obtained in Synthesis Example 1, 0.2 g of organometallic compound (1) was added to make a total of 775.2 g, and while nitrogen gas was flowed at 3 L/min, the power was adjusted to 0.033 kW, and the temperature was raised with a mantle heater. and reacted at 230°C for 10 minutes to obtain a nickel nanoparticle slurry. As shown in Fig. 5 and Table 1, particles exhibiting a wide particle size distribution with an average particle diameter of 27.8 nm and a CV value of 0.27 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.0007 parts by weight.

(Comparative Example 4)

To 775 g of nickel complexing reaction solution A obtained in Synthesis Example 1, 0.2 g of organometallic compound (1) was added to make a total of 775.2 g, and while nitrogen gas was flowed at 3 L/min, the power was adjusted to 0.048 kW, and the temperature was raised with a mantle heater. and reacted at 230°C for 10 minutes to obtain a nickel nanoparticle slurry. As shown in Fig. 7 and Table 1, particles having an average particle diameter of 36.6 nm, a CV value of 0.36, and a broad particle size distribution including fine particles of 10 to 20 nm were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.0006 parts by weight.

(Comparative Example 5)

13.2 g of the nickel nanoparticle slurry obtained in Example 1 was added to 258 g of the nickel complexing reaction solution B obtained in Synthesis Example 2 to make a total of 271.2 g, and the power was adjusted to 0.029 kW while flowing nitrogen gas at 3 L/min, and the mantle By heating up with a heater and making it react at 230 degreeC for 10 minutes, the nickel nanoparticle slurry was obtained. As shown in Fig. 9 and Table 1, particles exhibiting a wide particle size distribution with an average particle diameter of 36.5 nm and a CV value of 0.55 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.001 parts by weight.

(Comparative Example 6)

4.0 g of the nickel nanoparticle slurry obtained in Example 1 was added to 258 g of the nickel complexing reaction solution B obtained in Synthesis Example 2 to make a total of 262 g, and the power was adjusted to 0.018 kW while flowing nitrogen gas at 1 L/min, and a mantle heater The temperature was raised to , and by reacting at 230°C for 10 minutes, a nickel nanoparticle slurry was obtained. As shown in Fig. 11 and Table 1, particles exhibiting a wide particle size distribution with an average particle diameter of 49.3 nm and a CV value of 0.31 were obtained. In addition, the nickel component included in 100 parts by weight of the metal component was 99.99 parts by weight, and the lithium component was 0.0002 parts by weight.

As shown in Table 1, the nickel nanoparticles of the present invention of Examples 1 to 5 had a secondary electron resolution of 1.0 nm or less at an acceleration voltage of 15 kV. In all 400 nickel nanoparticles photographed by high-resolution SEM, the average The ratio of the sum of the number of particles having a particle diameter of 1/2 or less and particles having a particle diameter of 3/2 or more to the particle diameter was 5% or less. That is, in the particle size distribution, it was confirmed that the abundance ratio of the particles greatly deviating from the average particle diameter was small, and since it had a narrow particle size distribution, it was confirmed that it was excellent in thin film formation and filling properties for very narrow gaps.

In addition, as shown in Table 1, the nickel nanoparticles of the present invention had a CV value of 0.25 or less even when measured by a high-resolution SEM having a secondary electron resolution of 1.0 nm or less at an acceleration voltage of 15 kV. High-resolution SEM can sufficiently detect the presence of nickel nanoparticles with a small particle size of less than 20 nm, particularly less than 5 nm (hereinafter referred to as “small particle size nickel nanoparticles”), so that the CV value The actual situation is more accurately reflected. Since the nickel nanoparticles of the present invention have a small content of the nickel nanoparticles of small particle size compared with the nickel nanoparticles of the prior art, the CV value is 0.25 or less even when measured by high-resolution SEM.

In the above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict|limited to said embodiment.

Claims (4)

Nickel nanoparticles having an average particle diameter of 5 to 100 nm and a nickel component contained in 100 parts by weight of a metal component of 99.5 parts by weight or more, photographed with a scanning electron microscope having a secondary electron resolution of 1.0 nm or less at an acceleration voltage of 15 kV Nickel, characterized in that the ratio of the sum of the number of particles having a particle diameter of 1/2 or less and particles having a particle diameter of 3/2 or more to their average particle diameter is 5% or less in a total of 400 nickel nanoparticles nanoparticles.
The method of claim 1,
Nickel nanoparticles containing 0.00003 parts by weight to 0.5 parts by weight of lithium.
A paste material comprising a mixture of the nickel nanoparticles of claim 1 or 2 and a resin.
A multilayer ceramic capacitor comprising the nickel nanoparticles of claim 1 or 2 as a material for electrodes.

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