JP2014148750A - Metal composite superfine particle and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal composite superfine particle excellent in reactivity and method of manufacturing the metal composite superfine particle manufacturing the particle in high efficiency.SOLUTION: Metal composite superfine particles are used having an average 1.2 or more of circularity of particles photographed by a transmission electron microscope and an average particle major axis of 1 to 200 nm. There is provided a method of manufacturing the metal composite superfine particle whose metal species are gold, silver and copper, by reacting inorganic metal salts and higher alcohols with heating and stirring the inorganic metal salts and the higher alcohols, including a process of stirring at 20 to 120°C for at least 5 minutes and a process of stirring at 120°C to 300°C for at least 5 minutes, and the stirring processes satisfy a condition represented by the formula (1). 0.05≤Δt/D≤0.8 (1), where D is a radius of a swirl on a surface of a liquid during stirring and Δt is difference of the lowest point and the highest point of the swirl.

Description

  The present invention relates to a metal composite ultrafine particle, and more specifically, a metal composite ultrafine particle having a high roundness in a particle photographed with a transmission electron microscope, that is, a metal composite ultrafine particle having an irregular shape such as a polyhedron, and the like It relates to the manufacturing method.

  The metal composite ultrafine particles of the present invention are metal composite ultrafine particles in which the metal shell is modified with an organic substance (for example, alcohol, acid, amine, ketone, aldehyde, or a mixture of two or more thereof).

With the downsizing of electronic parts such as semiconductor devices, for example, the applicability of metal composite ultrafine particles having an average particle size of 100 nm or less to electronic parts is attracting attention. Application development of the above-mentioned metal composite ultrafine particles to an electronic component such as a semiconductor device is being studied as, for example, a wiring circuit forming material or a conductive paste material.
One of the typical properties of this metal composite ultrafine particle is its low-temperature sinterability such that sintering can be started at a temperature that is significantly lower than that of powders that are usually used industrially. It is done.

  In general, it is known that the metal composite ultrafine particles exhibit different properties from the metal material as the lump as the particle size becomes smaller. This is probably because the ratio of the exposed material is much larger than that of the lump. That is, it is considered that the metal composite ultrafine particles have a large solid surface, that is, a true spherical shape, from the viewpoint of the reactivity of the fine particles that contribute to low-temperature sinterability and the like.

  Various methods for producing such metal composite ultrafine particles have been studied. For example, an inorganic metal salt and an organic compound such as a higher alcohol are heated at a temperature of 100 to 230 ° C., depending on the organic compound used. Thus, a method for producing metal composite ultrafine particles in which a metal compound is coated with an organic substance has been proposed (see, for example, Patent Document 1). According to this method, for example, metal composite ultrafine particles in which the periphery of a metal nucleus composed of a metal (silver) component having an average particle diameter of about 7 to 10 nm is coated with an organic substance having a thickness of about 1.5 nm are manufactured. In addition, by holding the inorganic metal salt and the higher alcohol for a certain period of time in a low temperature range of 70 to 140 ° C., the inorganic metal salt is decomposed to generate a central part composed of a metal component, and the metal component of the inorganic metal salt There has been proposed a method for producing metal composite ultrafine particles in which the organic substance is coated around the center without reacting the organic substance to produce an organometallic compound (see Patent Document 2).

International Publication No. 01/70435 International Publication No. 05/75132

  The metal composite ultrafine particles are usually reacted in a single step at a constant temperature. However, when the reaction temperature is 120 ° C. or lower, the reaction efficiency is low and there is a problem that an unreacted inorganic metal salt remains. In addition, when the reaction temperature is higher than 120 ° C., the inorganic metal organic salt as a by-product tends to exhibit a surface active effect and foam. It has been found that the metal composite ultrafine particles obtained from such a foamed state have a shape close to a true sphere, and there is room for improvement in reactivity of the metal composite ultrafine particles described in the above-mentioned patent document having a true spherical shape.

  The present invention has been made in view of such circumstances, and provides a metal composite ultrafine particle having excellent reactivity and a method for producing a metal composite ultrafine particle capable of producing the fine particle with high efficiency. Is the purpose.

Therefore, the present inventor deviates from the conventional idea that the higher the surface area of solid, ie, spherical, the higher the reactivity of the metal composite ultrafine particles, and the ultrafine particles with rather small surface area such as polyhedrons become reactive. I found it excellent.
This is thought to be due to the fact that electrons in the ultrafine particles are more localized in the surface with a more distorted shape, and the activity at those sites increases.

  That is, the present invention is a metal composite ultrafine particle characterized in that the average value of roundness of particles taken with a transmission electron microscope is 1.1 or more.

  In addition, in producing an irregular metal composite ultrafine particle having a small surface area as described above, a step of stirring at a temperature at which the inorganic metal salt at 20 to 120 ° C. and the higher alcohol do not sufficiently react, and an inorganic metal at 120 to 300 ° C. Including the step of stirring at a temperature at which the salt and the higher alcohol sufficiently react, and by performing the stirring at a specific efficiency that is not too strong or too weak, to produce the target metal composite ultrafine particles with high efficiency Found that it would be possible.

That is, the present invention comprises a step of stirring at a temperature of 20 to 120 ° C. for at least 5 minutes in a method for producing metal composite ultrafine particles by reacting an inorganic metal salt with a higher alcohol;
And a step of stirring at a temperature of 120 ° C. to 300 ° C. for at least 5 minutes, wherein the stirring step satisfies the condition represented by the following formula (1). .
0.05 ≦ Δt / D ≦ 0.8 (1)
[In the above formula (1), D = d / 2, d represents the diameter of the vortex generated on the liquid surface during stirring, and Δt is the lowest and highest point of the vortex generated on the liquid surface during stirring. Represents the difference between points. ]

Since the metal composite ultrafine particle of the present invention has an irregular shape such as a polyhedron, the surface metal atoms in the number of constituent atoms of the particles are localized, and the electrons are localized on the surface accordingly, and thus the reactivity is excellent. ing.
The method for producing metal composite ultrafine particles of the present invention includes a step of stirring at a temperature of 20 to 120 ° C. for at least 5 minutes, a step of stirring at a temperature of 120 to 300 ° C. for at least 5 minutes, and the stirring is too strong. By carrying out with the specific efficiency which is not too weak, it becomes possible to manufacture such metal composite ultrafine particles with high efficiency.

An example of a schematic diagram showing the description of formula (1) Image taken with a transmission electron microscope in Example 1 Image taken with a transmission electron microscope in Example 2 Image taken with a transmission electron microscope in Comparative Example 1 Image taken with a transmission electron microscope in Example 3

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and is not limited to these contents.
Hereinafter, the present invention will be described in detail.

<Metal composite ultrafine particles>
The metal composite ultrafine particles of the present invention are metal composite ultrafine particles in which the outer shell is modified with an organic substance (for example, alcohol, acid, amine, ketone, aldehyde, two types).
Examples of the metal include transition metals such as gold, silver, and copper, and metals such as tin, and gold, silver, and copper are preferable.

《Inorganic metal salt》
In general, an inorganic metal salt is used as the raw material of the present invention to form the metal shell.
Such inorganic metal salts usually include transition metals such as gold, silver and copper, carbonates such as tin, hydrochlorides, nitrates and sulfates. Specific examples include silver carbonate, silver chloride, silver nitrate, silver sulfate, copper carbonate, copper chloride, copper nitrate, copper sulfate, tin carbonate, tin chloride, tin nitrate, and tin sulfate.
In the present invention, among the above inorganic metal salts, metal carbonates are preferable because they are easily compatible with non-aqueous solvents, and silver carbonate or copper carbonate is particularly preferable.

  In addition, the said inorganic metal salt is a solid powder form normally at normal temperature.

《Higher alcohol》
Examples of the higher alcohol used together with the inorganic metal salt in the present invention include aliphatic alcohols having 6 to 22 carbon atoms, preferably 8 to 18 carbon atoms, and particularly preferably 10 to 16 carbon atoms. Specific examples include octanol, decanol, dodecanol, tetradecanol, hexadecanol, and octadecanol. If the carbon number is too small, a stable coating layer tends to be difficult to obtain, and if it is too large, the metal content tends to be low. These may be used alone or in combination of two or more. Among these higher alcohols, tetradecanol is particularly preferably used because it is stable and has a high metal content. These higher alcohols are usually solid at room temperature. In addition, these higher alcohols may be mixed in a solid state, but since it is difficult to mix in a solid state, the higher alcohol may be melt-treated in advance before mixing with the inorganic metal salt. preferable.

  The higher alcohol is used in an amount of usually 40 to 500 parts by weight, preferably 50 to 400 parts by weight, particularly preferably 60 to 300 parts by weight with respect to 100 parts by weight of the inorganic metal salt. When the proportion of the higher alcohol used is too small, the inorganic metal salt tends to remain in the reaction with the inorganic metal salt, and it tends to be difficult to produce the metal composite ultrafine particles in a high yield. . Moreover, when there is too much usage-amount of the said higher alcohol, the tendency for the removal of unreacted alcohol to become difficult will be seen.

<Reaction solvent>
In the reaction of the present invention, it is usually preferable to use an excess amount of a higher alcohol, and this is also allowed to proceed as a solvent. If necessary, the reaction is carried out in the presence of an inert solvent. Also good. For example, the solvent used in that case may be a nonpolar solvent having a boiling point close to the reaction conditions, such as 1,3,5-trimethylbenzene (mesitylene), 1,2,4-trimethylbenzene ( Pseudocumene), isopropylbenzene (cumene), diethylene glycol dibenzoate, dipropylene glycol dibenzoate and the like.

《Other additives》
In the reaction of the present invention, in addition to the inorganic metal salt and higher alcohol as raw materials, a foam inhibitor may be used for the purpose of improving the reaction yield. For example, when the inorganic metal salt is carbonate-based, carbon dioxide gas is generated, and bubbles generated thereby may be a reaction inhibiting factor. In such a case, the addition of a foam inhibitor is effective. In addition to the carbonate system, it is effective when bubbles resulting from the generated gas are produced during the reaction.

  As the foaming inhibitor, those having various foaming inhibiting actions are used, and examples thereof include ionic liquids. The ionic liquid is an ionic substance having a melting point of 150 ° C. or lower and consisting of a cation portion and an anion portion, and has an effect of suppressing gas generation in the reaction system. And in this invention, if it does not contain a metal, it will not specifically limit, Various ionic liquids are used.

  The blending amount of the ionic liquid is preferably 2.5 to 100 parts by weight, more preferably 5 to 50 parts by weight, and particularly preferably 10 to 30 parts by weight with respect to 100 parts by weight of the inorganic metal salt. .

"Production method"
The method for producing metal composite ultrafine particles having specific physical properties according to the present invention is usually performed by heating and stirring the above-described inorganic metal salt and higher alcohol to cause reaction. And in the present invention, the polyhedron is manufactured by paying attention to the fact that, in such a production method, the mixture is stirred stepwise at a specific temperature, and the stirring is performed with a specific efficiency that is not too strong and not too weak. And the like can be obtained efficiently.

  First, the heating and stirring is performed at a temperature of 20 to 120 ° C. for at least 5 minutes. Preferably it is 40-70 degreeC, Most preferably, it is 50-65 degreeC. The time is usually 5 to 120 minutes, preferably 20 to 90 minutes, in particular 30 to 60 minutes. In this process, the inorganic metal salt is dispersed in the higher alcohol, and the inorganic metal salt is refined.

The temperature is then raised to 120-300 ° C. and stirred for at least 5 minutes.
Such temperature is preferably 130 to 180 ° C, more preferably 140 to 180 ° C, and particularly preferably 150 to 170 ° C. The time is usually 5 to 300 minutes, preferably 20 to 240 minutes, particularly preferably 30 to 180 minutes. In this process, the reaction between the finely divided fine particles of the inorganic metal salt and the higher alcohol proceeds with high activity.

Stirring in the above two steps is performed under conditions that satisfy the following formula (1).
0.05 ≦ Δt / D ≦ 0.8 (1)
[In the above formula (1), D = d / 2, d represents the diameter of the vortex generated on the liquid surface during stirring, and Δt is the lowest and highest point of the vortex generated on the liquid surface during stirring. Represents the difference between points. ]
Such conditions represent the state of vortices generated on the liquid surface during stirring, and indicate that stirring is intense when Δt / D is large (that is, d is smaller and Δt is larger). In addition, when Δt / D is small (that is, d is large, Δt is small), the stirring is gentle.
The lower limit value of Δt / D in the above formula is preferably 0.08, more preferably 0.1. The lower limit value of Δt / D is preferably 0.7, and more preferably 0.6.
The above formula of the present invention means that the stirring is performed at a specific efficiency that is neither too strong nor too weak.

  Examples of the stirring device used for the stirring include a mechanical stirrer and a magnetic stirrer. It is preferable to use a mechanical stirrer because it is easy to improve the stirring efficiency.

A known general shape can be used for the stirring blade in the stirring device, but a gently mixed shape is preferable. Examples include propeller blades, paddle blades, turbine blades, cone blades, and ribbon blades. Although the number of installations is arbitrary, it is usually one.
The stirring speed needs to be adjusted depending on the type of the stirring blade. Usually, it is 300-1500 rpm, preferably 350-1300 rpm. If it is too low, the reaction efficiency tends to decrease. If it is too high, the solid inorganic metal salt tends to precipitate and become non-uniform.
Note that if the stirring efficiency is too high, spherical particles tend to be obtained.

  In this process, the color tone of the inorganic metal salt changes with the progress of the previous reaction (in the case of silver, changes to brown), and also changes with the progress of the subsequent reaction (in the case of silver, changes to blue-violet).

In the step of stirring at a temperature of 20 to 120 ° C. and the step of stirring at a temperature of 120 to 300 ° C. or more, one step may be performed in another stage. Moreover, the temperature difference in these two processes is 20-250 degreeC normally, Preferably it is 40-150 degreeC.
Conventionally, there has been a problem that the reaction efficiency is low in the reaction between an inorganic metal salt and an organic substance, and an unreacted inorganic metal salt remains. In the present invention, however, the reaction efficiency is considered to increase through such a multi-step process. It is done.

  In the reaction of the present invention, water, carbonic acid and the like are by-produced by the progress of the reaction. Therefore, it is preferable to proceed the reaction while distilling off these volatiles in the subsequent reaction. The reaction in the present invention can be performed under normal pressure or under pressure, but is usually performed under normal pressure.

  By the above reaction, a reaction mixture containing metal composite ultrafine particles coated around the metal with organic residues derived from higher alcohol is obtained.

  It is presumed that irregularly shaped metal composite ultrafine particles such as polyhedrons can be obtained with high reaction efficiency by carrying out the reaction at a specific efficiency that is neither too strong nor too weak during the reaction.

"cooling"
The reaction of the present invention can be stopped by cooling the reaction mixture to usually 80 ° C. or lower, preferably 60 ° C. or lower. And after the said reaction stops, for example, by mix | blending a C1-C3 alcohol with a reaction mixture, the metal composite ultrafine particle in a reaction mixture will aggregate easily, and a metal composite ultrafine particle will precipitate easily. . As said C1-C3 aliphatic alcohol, ethanol etc. are suitable, for example.

"Washing"
By the above reaction, a reaction mixture containing metal composite ultrafine particles centered on the metal and coated with organic residues derived from a higher alcohol is obtained. After separating the metal composite ultrafine particles from the reaction mixture, this metal is separated. It is preferable to wash the composite ultrafine particles with a lower alcohol. The lower alcohol is usually an aliphatic alcohol having 1 to 3 carbon atoms, and ethanol is particularly preferable.

As a washing method, a suspension washing method such as decantation is generally used, but other methods include sprinkling washing and distribution washing.
Sprinkling washing includes a method of sprinkling the washing liquid on the fixed cake, a method of sprinkling the washing liquid while centrifuging, and the flow washing is performed by, for example, introducing metal composite ultrafine particles into the tower type washing machine from above and below. There is a method of adding more cleaning liquid.
The suspension washing method is carried out, for example, by adding a lower alcohol to the reaction mixture, stirring and mixing, allowing to stand, and then repeating the solid-liquid separation operation for separating the precipitated metal composite ultrafine particles. In this case, the lower alcohol may be added to the reaction mixture at any time as long as the temperature of the mixture becomes 50 ° C. or lower, preferably 40 ° C. or lower.

  The washing temperature is usually 20 to 40 ° C., and the amount of lower alcohol used is usually 1 to 50 times the weight of the metal composite ultrafine particles. The number of washings is repeated until the desired purity of the metal composite ultrafine particles is obtained, but is usually 2 to 10 times.

《Solid-liquid separation》
After the washing, the metal composite ultrafine particles and the washing waste liquid are usually separated by solid-liquid separation, and the washing waste liquid is removed. As said solid-liquid separation method, it can carry out by methods, such as filtration and centrifugation.

《Dry》
The metal composite ultrafine particles after washing are usually subjected to a drying treatment. The drying temperature is usually about 20 to 80 ° C. Moreover, even if the solid after drying is agglomerated, it can be easily powdered by grinding or the like.

<Metal composite ultrafine particles>
The obtained metal composite ultrafine particles of the present invention are ultrafine particles (nanoparticles) having a structure in which a metal produced by reaction decomposition of the inorganic metal salt is mainly covered with an organic residue derived from the higher alcohol. Particle).

  The metal composite ultrafine particles of the present invention are irregular ultrafine particles having a small surface area such as a polyhedron. Therefore, the metal composite ultrafine particles of the present invention have an average roundness of 1.1 or more, preferably 1.1 to 1.5, particularly preferably 1.1, in particles photographed with a transmission electron microscope. ~ 1.3.

In photographing the metal composite ultrafine particles with the transmission electron microscope, an arbitrary measurement sample is taken out from the population of the metal composite ultrafine particles to be measured, and measured using a commercially available transmission electron microscope (TEM).
As a measurement sample, a general hydrocarbon-based organic solvent in which metal composite ultrafine particles are dispersed can be used. Examples of the solvent include saturated hydrocarbons having 5 to 10 carbon atoms, and cyclohexane. A solution is preferred. It is preferable that the measurement sample penetrates with ultrasonic waves immediately before photographing.

The roundness is measured using an image of particles obtained by photographing. At this time, measurement is performed using particles whose contour can be independently confirmed. Particles that overlap each other and whose outline cannot be confirmed are excluded.
The number of particles to be measured is arbitrary, but is usually 100 or more, preferably 100 to 1000, and more preferably 150 to 500.
For measurement of roundness and average particle length, it is preferable to use image analysis software “Region Advisor” manufactured by System In Frontier.

  The average particle length of the metal composite ultrafine particles of the present invention is 1 to 200 nm. This is a numerical value which usually means a general size as a metal composite ultrafine particle. Preferably it is 2-100 nm, Most preferably, it is 3-50 nm. The average particle long diameter of the metal composite ultrafine particles can be measured with reference to a scale bar as the long diameter of particles per fixed area taken with a transmission electron microscope as described above.

  Moreover, the metal composite ultrafine particles obtained above can be identified by performing, for example, thermogravimetric analysis (TG) measurement and infrared absorption analysis (IR) measurement.

  The metal composite ultrafine particles produced in the present invention have high reactivity, and therefore, the firing temperature when firing using this is low, and a uniform and good metal surface can be obtained.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
“Teflon” in the examples is a registered trademark.

[Example 1]
In a 1 liter reactor equipped with a heating device, a reflux condenser, and a stirring blade composed of three Teflon blades with a stirring diameter of 25 mm, first, 1-tetradecanol (made by Wako Pure Chemical Industries, Ltd.) was heated to 60 ° C. and melted. ) (Melting point: 38 ° C.) (600 g) was added, and then powdered silver carbonate (dark blue) (manufactured by Nisshin Chemical Co., Ltd.) (300 g) was added.

The above contents were stirred at 60 ° C. for 40 minutes at 800 rpm, then the contents were heated, heated to 140 ° C. over 11 minutes, and kept at the same temperature for 180 minutes to continue the reaction. In addition, with the progress of the above reaction, the reaction was in a reflux state in the later stage. At this time, d (diameter of the liquid level) was 100 mm, and Δt (difference between the lowest point and the highest point of the liquid level during stirring) was 8 mm. Therefore, Δt / D in the above formula (1) was 0.16, which was a result satisfying the above formula (1).
In the preceding step, the color tone of the mixture changed to brown, and in the latter reaction step, it changed to blue-violet.

  Thereafter, the internal temperature was cooled to 80 ° C. or lower, and 50 ml of ethanol was gradually added thereto (stirring condition: 500 rpm). Further cooling was continued, the internal temperature was reduced to 50 ° C. or lower, and the solution was transferred to a 3 liter beaker. . The 1 liter reactor was also washed with ethanol and the wash was added to a 3 liter beaker.

  In the washing treatment, 1 liter of ethanol was added to the separated metal composite ultrafine particles, and the mixture was stirred with a glass rod and allowed to stand at 25 ° C. After standing for about 6 hours, the reaction mixture was separated into a yellow transparent supernatant and a dark gray sediment. Next, after draining as much of the supernatant as possible by decantation, 1 liter of ethanol was newly added to the beaker, and after stirring well with a glass rod, it was allowed to stand. After standing for about 3 hours, it was separated into an almost colorless and transparent supernatant and a slightly grayish, dark gray sediment. Next, the supernatant liquid was discharged as much as possible by decantation.

  Subsequently, the dark gray sedimentation part (solid content) which is the residue which remove | eliminated the said supernatant liquid was moved to the prepared Kiriyama funnel using fresh ethanol, and suction filtration was performed. In addition, when the filtration progressed sufficiently by suction filtration using the Kiriyama funnel, a solid (blue cake) remaining on the funnel was cracked.

  The cracked solid (blue cake) was shrunk and dried with a spatula until it cracked (about 24 hours), and further dried until it could be crushed with a glass rod (about 48 hours), the obtained cake was pulverized into powder.

<Identification>
With respect to the metal composite ultrafine particle powder obtained by drying and pulverization, thermogravimetric analysis (TG) measurement and infrared absorption analysis (IR) measurement were performed using the following apparatus. As a result of these measurements, the obtained metal composite ultrafine particles had an organic residue (mainly C ₁₄ H ₂₉ COO derived from 1-tetradecanol) around the silver produced by the reaction decomposition of the silver carbonate. - and it was confirmed that the coated metal composite ultrafine particles by C ₁₃ H ₂₇ COO-). A peak derived from unreacted silver carbonate was not detected.
Roundness and average particle length were measured based on images taken with a transmission electron microscope (TEM). The number of target particles was 211, the average value of roundness was 1.25, and the standard deviation was 0.37. The average particle major axis was 9.7 nm and the standard deviation was 2.65.

<< Thermogravimetric analysis (TG) measurement >>
Measuring device: “Thermal Analysis TG-7” manufactured by Perkin Elmer
<< Infrared absorption analysis (IR) measurement >>
Measuring instrument: “Avatar 360” manufactured by Nicolet
<< Transmission electron microscope (TEM) photography >>
Measuring equipment: “Transmission electron microscope H-7100FA type” manufactured by Hitachi, Ltd.
Acceleration voltage: 100 kv
Measurement sample: 0.1 wt% solution prepared using metal composite ultrafine particles and cyclohexane solvent Measurement conditions: Immediately before imaging, the sample was permeated with ultrasonic waves for 6 minutes, and a TEM sample stage was used. Magnification for only particles whose contours can be confirmed independently: 773,000 times Measurement of roundness and average particle length: Image analysis software “Region Advisor” manufactured by System in Frontier

<Reactivity evaluation>
A gel-like paste was obtained by dissolving 5 g of 12-hydroxystearic acid in 95 g of dipropylene glycol dibenzoate previously heated to 150 ° C. and then cooling to room temperature. A mixture of 50 g of the obtained metal composite ultrafine particles in 50 g of the paste and made uniform by three rolls is about 20 mm in diameter on a glass substrate heated on a hot stirrer heated to 200 ° C. It was applied and the time until the white color changed was measured, and the electrical resistance between 10 mm of the formed film was measured with a tester.
As a result, it took 30 minutes to turn white, and the resistance of the film was 0.5Ω.

[Example 2]
The procedure was the same as in Example 1 except for the following items.
First, 1-dodecanol was used instead of 1-tetradecanol. 1-Dodecanol (manufactured by Kishida Chemical Co., Ltd.) (melting point: 24 ° C.) was prepared, and this was heated at 50 ° C. for 5 hours to melt. Next, the above-mentioned melting was carried out in a 1 liter reactor equipped with the same heating apparatus, reflux condenser and stirring blade as in Example 1. 500 g of 1-dodecanol was supplied, and 300 g of powdered silver carbonate (dark blue) (manufactured by Nisshin Chemical Co., Ltd.) was added thereto.

As in Example 1, the contents were stirred at 60 ° C. for 40 minutes at 800 rpm, then the contents were heated, heated to 160 ° C. over 15 minutes, and held at that temperature for 120 minutes. The reaction was continued. In addition, with the progress of the above reaction, the reaction was in a reflux state in the later stage. At this time, the d value was 110 mm, and Δt was 8 mm. Therefore, Δt / D in the above formula (1) was 0.14, which was a result satisfying the above formula (1).
Thereafter, the same operation as in Example 1 was performed to obtain a metal composite ultrafine particle powder.

The obtained metal composite ultrafine particle powder was subjected to thermogravimetric analysis (TG) measurement and infrared absorption analysis (IR) measurement in the same manner as in Example 1. As a result, the silver produced by reaction decomposition of the silver carbonate was obtained. Above around the center. It was confirmed to be a metal composite ultrafine particle coated with an organic residue derived from 1-dodecanol (mainly C ₁₂ H ₂₅ COO— and C ₁₁ H ₂₃ COO—). A peak derived from unreacted silver carbonate was not detected.

  Roundness and average particle length were measured based on images taken with a transmission electron microscope (TEM). The target particles were 173, the average roundness was 1.25, and the standard deviation was 0.23. The average particle major axis was 10.8 nm and the standard deviation was 3.06.

  As a result of the reactivity evaluation, it took 25 minutes to change to white, and the resistance of the film was 0.4Ω.

Example 3
In Example 1, in the reaction of 1-tetradecanol and silver carbonate, stirring was performed using a dama dissolving stirring blade (manufactured by Chuo Rika Kogyo Co., Ltd .: simplified NCR100-CB5-D).

As in Example 1, the contents were stirred at 60 ° C. for 40 minutes at 300 rpm, then the contents were heated, heated to 200 ° C. over 30 minutes, and held at that temperature for 15 minutes. The reaction was continued. In addition, with the progress of the above reaction, the reaction was in a reflux state in the later stage. At this time, the d value was 100 mm, and Δt was 25 mm. Δt / D in the above formula (1) is 0.5, which satisfies the above formula (1).
Other than that was carried out similarly to Example 1, and manufactured the solid substance which is a sample. About the obtained sample, it carried out similarly to Example 1, and measured the roundness and average particle length.

The obtained metal composite ultrafine particle powder was subjected to thermogravimetric analysis (TG) measurement and infrared absorption analysis (IR) measurement in the same manner as in Example 1. As a result, the obtained metal composite ultrafine particle was obtained from the above silver carbonate. metal composite ultrafine particles but coated with organic residues from the 1-tetradecanol around around the silver produced by the reaction decomposition (mainly C ₁₄ H ₂₉ COO- and C ₁₃ H ₂₇ COO-) It was confirmed that. A peak derived from unreacted silver carbonate was not detected.

  Roundness and average particle length were measured based on images taken with a transmission electron microscope (TEM). The target particles were 273, the average roundness was 1.16, and the standard deviation was 0.16. The average particle length was 8.1 nm and the standard deviation was 2.30.

  As a result of the reactivity evaluation, it took 30 minutes for the color to change to white, and the resistance of the film was 0.5Ω.

[Comparative Example 1]
In Example 1, in the reaction of 1-tetradecanol and silver carbonate, stirring was performed using a dama dissolving stirring blade (manufactured by Chuo Rika Kogyo Co., Ltd .: simplified NCR100-CB5-D).

As in Example 1, the contents were stirred at 60 ° C. for 40 minutes at 500 rpm, then the contents were heated, heated to 160 ° C. over 15 minutes, and held at that temperature for 120 minutes. The reaction was continued. In addition, with the progress of the above reaction, the reaction was in a reflux state in the later stage. At this time, the d value was 95 mm, and Δt was 40 mm. Therefore, Δt / D in the above formula (1) was 0.84, which did not satisfy the above formula (1).
Other than that was carried out similarly to Example 1, and manufactured the solid substance which is a sample. About the obtained sample, it carried out similarly to Example 1, and measured the roundness and average particle length.

The obtained metal composite ultrafine particle powder was subjected to thermogravimetric analysis (TG) measurement and infrared absorption analysis (IR) measurement in the same manner as in Example 1. As a result, the obtained metal composite ultrafine particle was obtained from the above silver carbonate. metal composite ultrafine particles but coated with organic residues from the 1-tetradecanol around around the silver produced by the reaction decomposition (mainly C ₁₄ H ₂₉ COO- and C ₁₃ H ₂₇ COO-) It was confirmed that. A peak derived from unreacted silver carbonate was not detected.

  Roundness and average particle length were measured based on images taken with a transmission electron microscope (TEM). The number of target particles was 570, the average roundness was 1.07, and the standard deviation was 0.08. The average particle major axis was 5.8 nm, and the standard deviation was 0.74.

  As a result of the reactivity evaluation, it took 40 minutes for the color to change to white, and the resistance of the film was 0.7Ω.

The results of Examples and Comparative Examples are shown in Table 1.

  Based on the above results, a step of stirring under conditions satisfying the formula (1), a step of stirring at a temperature of 20 to 120 ° C. for at least 5 minutes, a step of stirring at a temperature of 120 to 300 ° C. for at least 5 minutes was adopted. In Examples 1 and 2, metal composite ultrafine particles of the present invention having a small surface area such as a polyhedron were obtained. When such a fine particle is used as a film, the resistance value is as low as 0.5Ω or 0.4Ω, and the conductivity is excellent.

  On the other hand, the comparative example 1 which employ | adopted the process stirred at least for 5 minutes at the temperature of 20-120 degreeC and the process stirred for at least 5 minutes at the temperature of 20-120 degreeC on the conditions which do not satisfy | fill Formula (1). Then, the roundness in the image image | photographed with the transmission electron microscope (TEM) was closer to 1, and the particle | grains close | similar to a perfect sphere were obtained. When such fine particles are used as a film, the resistance value is as high as 0.7Ω and the conductivity is low, so that it is clear that there is room for improvement in reactivity.

  Although silver carbonate is used as a representative example of the inorganic metal salt, an effect peculiar to the present application was confirmed with silver, which is a metal having low reactivity, and the same effect can be obtained with other inorganic metal salts. is there.

  Since the metal composite ultrafine particles of the present invention are excellent in reactivity, the firing temperature in firing can be lowered. For example, it is useful as a forming material for fine wiring of an electronic component such as a semiconductor device or a conductive material used when electrically connecting electrodes of an electronic component such as a semiconductor device.

1: Reactor 2: Liquid level

Claims (3)

Metal composite ultrafine particles characterized in that the average roundness of particles photographed with a transmission electron microscope is 1.1 or more and the average particle major axis is 1 to 200 nm. The metal composite ultrafine particle according to claim 1, wherein the metal species of the metal composite ultrafine particle is gold, silver, or copper. In the method for producing metal composite ultrafine particles by reacting an inorganic metal salt and a higher alcohol by heating and stirring the inorganic metal salt and the higher alcohol, a step of stirring at a temperature of 20 to 120 ° C. for at least 5 minutes; Stirring for at least 5 minutes at a temperature of 300 ° C.
And the stirring step satisfies the condition represented by the following formula (1).
0.05 ≦ Δt / D ≦ 0.8 (1)
[In the above formula (1), D = d / 2, d represents the diameter of the vortex generated on the liquid surface during stirring, and Δt is the lowest and highest point of the vortex generated on the liquid surface during stirring. Represents the difference between points. ]

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