JP2020174042A - Conductor forming composition, method for producing conductor, conductor and device - Google Patents

Abstract

To provide a conductor forming composition which can form a conductor having excellent adhesiveness at a low temperature, a method for producing a conductor using the same, a conductor which can be formed at a low temperature and has excellent adhesiveness, and a device having the conductor.SOLUTION: A conductor forming composition has a copper-containing particle, a dispersion medium, and a resin. The copper-containing particle has a core particle having copper, and organic matter present on at least part of the surface of the core particle. The percentage of a copper-containing particle with the major axis of 50 nm or less in length is 55% or less in number.SELECTED DRAWING: None

Description

The present invention relates to a conductor forming composition, a method for producing a conductor, a conductor and an apparatus.

As a method for forming a metal pattern, a step of applying a conductive material such as an ink containing metal particles such as copper or a paste onto a substrate by inkjet printing, screen printing or the like, and a step of heating the conductive material to fuse the metal particles. , A so-called printed electronics method including a conductor-forming step of exhibiting conductivity is known. As the metal particles contained in the conductive material, those in which an organic substance as a coating material is adhered to the surface in order to suppress the oxidation of the metal and improve the storage stability are known.

Patent Document 1 describes copper particles coated with an organic substance that can be fused at a low temperature and exhibits good conductivity, and a method for producing the same. The copper particles described in Patent Document 1 are a step of mixing a copper precursor such as copper oxalate and a reducing compound such as hydrazine to obtain a composite compound, and a step of heating the composite compound in the presence of an alkylamine. It is manufactured by a method having and. In the example of Patent Document 1, the composition containing the produced copper particles is heated to 300 ° C. at 60 ° C./min and held for 30 minutes in an argon atmosphere to achieve conductor formation. Patent Document 2 describes a method for producing copper particles using fatty acid copper as a copper precursor in the method described in Patent Document 1. In the examples of Patent Document 2, it is described that the thin film of the prepared composition containing copper particles is made into a conductor by heating at 200 ° C.

Japanese Unexamined Patent Publication No. 2012-72418 Japanese Unexamined Patent Publication No. 2014-148732

In recent years, against the background of improvement of production efficiency and diversification of types of base materials used, development of a technique for forming a conductor that can be formed at a low temperature and has good adhesion to a base material has been required. There is. For example, in the method using copper particles described in Patent Document 2, although it is possible to form a conductor at a low temperature (200 ° C.), the adhesiveness of the conductor to a base material made of glass, ceramic or the like is improved. There is room for improvement. Therefore, there is a need for the development of a technique capable of forming a conductor that can be formed at a low temperature and has good adhesiveness to a substrate.

In view of the above problems, the present invention provides a conductor forming composition capable of forming a conductor having excellent adhesiveness at a low temperature, a method for producing a conductor using the same, a conductor capable of forming at a low temperature and having excellent adhesiveness, and an apparatus including the conductor. The purpose is to provide.

The means for solving the above problems are as follows.
<1> A copper-containing particle, a dispersion medium, and a resin are contained, and the copper-containing particle has a core particle containing copper and an organic substance present at least a part of the surface of the core particle. A conductor forming composition in which the proportion of copper-containing particles having a major axis length of 50 nm or less is 55% or less.
<2> The conductor forming composition according to <1>, wherein the amount of the resin is 0.01 part by mass to 10 parts by mass with respect to 100 parts by mass of the copper-containing particles.
<3> The conductor forming composition according to <1> or <2>, wherein the copper-containing particles have a major axis length of 70 nm or more and a proportion of copper-containing particles of 30% or more.
<4> The conductor forming composition according to any one of <1> to <3>, wherein the copper-containing particles have an average value of 55 nm or more in length on the major axis.
<5> The conductor-forming composition according to any one of <1> to <4>, wherein the copper-containing particles have an average value of 500 nm or less in length on the major axis.
<6> The conductor forming composition according to any one of <1> to <5>, which contains copper-containing particles having a circularity of 0.70 to 0.99.
<7> A method for producing a conductor, which comprises a step of heating the conductor forming composition according to any one of <1> to <6>.
<8> A conductor having a structure in which copper-containing particles contained in the conductor forming composition according to any one of <1> to <6> are fused and containing a resin.
<9> A device including the conductor according to <8>.

According to the present invention, a conductor forming composition capable of forming a conductor having excellent adhesiveness at a low temperature, a method for producing a conductor using the same, a conductor capable of forming at a low temperature and having excellent adhesiveness, and an apparatus including the conductor are provided. be able to.

It is a transmission electron microscope image of a copper-containing particle satisfying the requirement of this embodiment. It is a transmission electron microscope image of a copper-containing particle which does not satisfy the requirement of this embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.

In the present specification, the term "process" includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if the process cannot be clearly distinguished from the other process. Is done.
In the numerical range indicated by using "~" in the present specification, the numerical values before and after "~" are included as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. Good. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present specification, the content of each component in the composition is the total of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means the content rate of.
In the present specification, the particle size of each component in the composition is a mixture of the plurality of particles existing in the composition unless otherwise specified, when a plurality of particles corresponding to each component are present in the composition. Means a value for.
In the present specification, the term "membrane" refers to the case where the film is formed in the entire region when the region where the membrane exists is observed, and the case where the membrane is formed only in a part of the region. Is also included.
In the present specification, "(meth) acrylic" means methacrylic or acrylic, and "(meth) acrylate" means methacrylate or acrylate, respectively.

As used herein, the term "conductor" means that metal-containing particles are fused and transformed into a conductor. The “conductor” means an object having conductivity, and more specifically, an object having a volume resistivity of 300 μΩ · cm or less. "Individual%" means a percentage based on the number of pieces.

<Conductor forming composition>
The conductor-forming composition of the present embodiment contains copper-containing particles, a dispersion medium, and a resin, and the copper-containing particles are present on the copper-containing core particles and at least a part of the surface of the core particles. The proportion of copper-containing particles having an organic substance and having a major axis length of 50 nm or less is 55% or less. Hereinafter, the copper-containing particles are also simply referred to as copper-containing particles.

The copper-containing particles contained in the conductor-forming composition are excellent in fusion property at a low temperature (for example, 150 ° C.). Therefore, the conductor can be formed at a low temperature. Further, when the conductor forming composition contains a resin, it is possible to form a conductor having excellent adhesiveness to a base material.

Specific examples of the use of the conductor forming composition include conductive paints, conductive pastes, conductive inks, and the like.

[Copper-containing particles]
The copper-containing particles include core particles containing copper and organic substances present on at least a part of the surface of the core particles, and the proportion of copper-containing particles having a major axis length of 50 nm or less is 55%. It is as follows.
The copper-containing particles have an organic substance present on at least a part of the surface of the core particles, and thus have excellent fusion property at a low temperature (for example, 150 ° C.). That is, organic substances present on at least a part of the surface of the core particles containing copper play a role as a protective material and suppress the oxidation of the core particles. Therefore, good fusion property at low temperature is maintained even after long-term storage in the atmosphere. It should be noted that this organic substance is thermally decomposed and disappears by heating when the copper-containing particles are fused to produce a conductor.
Further, since the proportion of copper-containing particles (hereinafter, also referred to as small-diameter particles) having a major axis length of 50 nm or less is 55% or less, the copper-containing particles as a whole are excellent in fusion property at low temperature. There is. Although it is not clear why the small-diameter particles in the copper-containing particles are excellent in fusion property at low temperature when the ratio is 55% or less, the present inventors consider as follows. Originally, the smaller the copper-containing particles, the easier it is to melt. However, due to some factors such as the organic substances on the particle surface being easily desorbed and being easily affected by oxidation, and the generation of substances that have high catalytic activity on the particle surface and hinder melting, the ease of melting due to the small size is offset. On the contrary, it may be difficult to melt. In the present embodiment, it is considered that the fusion property at a low temperature is well maintained by suppressing the ratio of the small-diameter particles in the copper-containing particles to 55% or less.

Patent Document 1 and Patent Document 2 describe that the average particle size of copper particles is 50 nm or less, and further, the average particle size is 20 nm. Further, Patent Document 2 describes that copper particles having a particle diameter of 10 nm or less and copper particles having a particle diameter of 100 nm to 200 nm are mixed in the copper particles obtained in Examples. However, none of the patent documents specifically describes the ratio of small-diameter particles to the total copper particles, and there is no description suggesting that the fusion property is improved when the ratio of small-diameter particles is small.

As used herein, the major axis of the copper-containing particles means the distance between the two planes circumscribing the copper-containing particles and selected so that the distance between the two planes parallel to each other is maximized. In the present specification, the proportion of copper-containing particles having a major axis length of 50 nm or less is the proportion of 200 randomly selected copper-containing particles. For example, when the number of copper-containing particles having a major axis length of 50 nm or less is 110 out of 200, the proportion of copper-containing particles having a major axis length of 50 nm or less is 55%.

From the viewpoint of fusion property at low temperature, the proportion of copper-containing particles having a major axis length of 50 nm or less is preferably 50% or less, more preferably 35% or less, and 20 particles. It is more preferably% or less.

From the viewpoint of fusion property at low temperature, the proportion of copper-containing particles having a major axis length of 70 nm or more is preferably 30% or more, more preferably 50% or more, and 60 particles. It is more preferably% or more. In the present specification, the proportion of copper-containing particles having a major axis length of 70 nm or more is a proportion of 200 randomly selected copper-containing particles.

From the viewpoint of fusion property at low temperature, the average value of the length of the major axis is preferably 55 nm or more, more preferably 70 nm or more, and further preferably 90 nm or more. In the present specification, the mean value of the length of the long axis is an arithmetic mean value of the length of the long axis measured for 200 randomly selected copper-containing particles.

From the viewpoint of fusion property at low temperature, the average value of the length of the major axis is preferably 500 nm or less, more preferably 300 nm or less, and further preferably 200 nm or less.

From the viewpoint of fusion property at low temperature, the length of the long axis of the copper-containing particles having the longest major axis (hereinafter, also referred to as the maximum diameter particles) is preferably 500 nm or less, preferably 300 nm or less. More preferably, it is more preferably 250 nm or less. In the present specification, the length of the major axis of the maximum diameter particles is the length of the major axis of the copper-containing particles having the longest major axis length among the 200 randomly selected copper-containing particles.

From the viewpoint of fusion property at low temperature, the length of the major axis of the copper-containing particles having the shortest major axis length (hereinafter, also referred to as the smallest diameter particles) is preferably 5 nm or more, preferably 8 nm or more. More preferably, it is more preferably 10 nm or more. In the present specification, the length of the major axis of the smallest diameter particles is the length of the major axis of the copper-containing particles having the shortest major axis length among the 200 randomly selected copper-containing particles.

The length of the major axis of the copper-containing particles adjusts the conditions such as the type of raw material in the method for producing copper-containing particles described later, the temperature at which the raw materials are mixed, the reaction time, the reaction temperature, the cleaning process, and the cleaning solvent. Can be done by doing.

From the viewpoint of promoting fusion at low temperatures, the copper-containing particles preferably contain copper-containing particles having irregularities on the surface, and the roundness of the copper-containing particles having irregularities on the surface is 0.70 to 0.99. More preferably, it contains certain copper-containing particles. The circularity is a value represented by 4π × S / (peripheral length) ² , where S is the area of the particle to be measured, and the perimeter is the perimeter of the particle to be measured. The circularity can be determined by analyzing the electron microscope image using image processing software.

It is not clear why the copper-containing particles contain copper-containing particles having irregularities on the surface to promote fusion at low temperatures, but the presence of irregularities on the surface of the copper-containing particles causes the melting point due to the so-called nanosize effect. It is presumed that a decrease will occur and the fusion property at low temperature will be promoted.

The shape of the copper-containing particles is not particularly limited and can be selected according to the application. For example, the aspect ratio, which is the ratio of the major axis to the minor axis (major axis / minor axis) of the copper-containing particles, can be selected from the range of 1.0 to 10.0. When a mixture of copper-containing particles with a dispersion medium or the like is applied to a substrate by a printing method, the average value of the aspect ratio, which is the ratio of the major axis to the minor axis (major axis / minor axis) of the copper-containing particles, is 1. A ratio of .5 to 8.0 is preferable because the viscosity of the mixture can be easily adjusted. The minor axis of the copper-containing particles means the distance between the two planes circumscribing the copper-containing particles and selected so that the distance between the two planes parallel to each other is minimized. The aspect ratio of the copper-containing particles can be examined by a usual method such as observation with an electron microscope.

In some embodiments, the average aspect ratio is preferably 1.0 to 8.0, more preferably 1.1 to 6.0, and even more preferably 1.2 to 3.0. preferable. In the present specification, the mean value of the aspect ratio is obtained by calculating the long-axis arithmetic mean value and the short-axis arithmetic mean value of 200 randomly selected copper-containing particles, respectively, and obtaining the long-axis arithmetic mean value. Is a value obtained by dividing by the arithmetic mean value on the short axis.

The aspect ratio of the copper-containing particles can be adjusted, for example, by adjusting conditions such as the number of carbon atoms of the fatty acid used in the method for producing copper-containing particles described later.

The length of the long axis of the copper-containing particles, the presence or absence of surface irregularities, the circularity and the aspect ratio can be measured by a known method such as observation with an electron microscope. The magnification when observing with an electron microscope is not particularly limited, but can be, for example, 20 to 50,000 times. Copper-containing particles having a particle size of less than 3.0 nm are excluded from the measurement.

In some embodiments, the organic matter present on at least a portion of the surface of the copper-containing core particles comprises a substance derived from an alkylamine. The presence of organic matter and alkylamines is confirmed by heating the copper-containing particles at a temperature equal to or higher than the temperature at which the organic matter is thermally decomposed in a nitrogen atmosphere and comparing the weights before and after heating. Examples of the alkylamine include alkylamines used in the method for producing copper-containing particles described later.

The proportion of the organic matter present on at least a part of the surface of the core particles is preferably 0.1% by mass to 20% by mass with respect to the total of the core particles and the organic matter. When the proportion of the organic substance is 0.1% by mass or more, sufficient oxidation resistance tends to be obtained. When the proportion of organic matter is 20% by mass or less, the fusion property at low temperature tends to be good. The ratio of the organic matter to the total of the core particles and the organic matter is more preferably 0.3% by mass to 10% by mass, and further preferably 0.5% by mass to 5% by mass.

The core particles contain at least metallic copper and may optionally contain other substances. Examples of substances other than copper include metals such as gold, silver, platinum, tin, and nickel, compounds containing these metal elements, fatty acid copper described later, reducing compounds, organic substances derived from alkylamines, copper oxide, copper chloride, and the like. Can be mentioned. From the viewpoint of forming a conductor having excellent conductivity, the content of metallic copper in the core particles is preferably 50% by mass or more, more preferably 60% by mass or more, and 70% by mass or more. Is more preferable.

Since organic substances are present on at least a part of the surface of the core particles of the copper-containing particles, the oxidation of copper is suppressed even when stored in the atmosphere, and the oxide content is small. For example, in one embodiment, the oxide content in the copper-containing particles is 5% by mass or less. The content of oxides in the copper-containing particles can be measured by, for example, XRD (X-ray diffraction, X-ray diffraction).

The shape of the copper-containing particles is not particularly limited. Specific examples thereof include spherical, long-granular, flat, fibrous and the like, which can be selected according to the usage mode of the conductor forming composition. For example, when the conductor forming composition is applied to a printing method, the shape of the copper-containing particles is preferably spherical or long-granular.

[Manufacturing method of copper-containing particles]
The method for producing the copper-containing particles is not particularly limited. For example, copper-containing particles are produced by a method comprising heating a composition comprising a metal salt of a fatty acid and copper, a reducing compound, and an alkylamine. The method may include steps such as a centrifugation step and a washing step after the heating step, if necessary.

The method uses a metal salt of fatty acid and copper as a copper precursor. It is considered that this makes it possible to use an alkylamine having a lower boiling point (that is, a smaller molecular weight) as a reaction medium as compared with the method described in Patent Document 1 in which silver oxalate or the like is used as a copper precursor. Be done. As a result, in the obtained copper-containing particles, the organic matter existing on the surface of the core particles becomes more easily thermally decomposed or volatilized, and it is considered that the conductor formation becomes easier at a low temperature.

(fatty acid)
The fatty acid is a monovalent carboxylic acid represented by RCOOH (R is a chain hydrocarbon group, which may be linear or branched). The fatty acid may be either a saturated fatty acid or an unsaturated fatty acid. Linear saturated fatty acids are preferable from the viewpoint of efficiently coating the core particles and suppressing oxidation. The fatty acid may be only one kind or two or more kinds.

The number of carbon atoms of the fatty acid is preferably 9 or less. Saturated fatty acids having 9 or less carbon atoms include acetic acid (2 carbon atoms), propionic acid (3 carbon atoms), butyric acid and isobutyric acid (4 carbon atoms), valeric acid and isovaleric acid (5 carbon atoms), and caproic acid. Examples thereof include acid (6 carbon atoms), enanthic acid and isoenantic acid (7 carbon atoms), capric acid, isocaprilic acid and isocaproic acid (8 carbon atoms), nonanoic acid and isononanoic acid (9 carbon atoms). Examples of the unsaturated fatty acid having 9 or less carbon atoms include those having one or more double bonds in the hydrocarbon group of the saturated fatty acid.

The type of fatty acid can affect properties such as dispersibility of copper-containing particles in a dispersion medium and fusion property. Therefore, it is preferable to select the type of fatty acid according to the use of the copper-containing particles. From the viewpoint of homogenizing the particle shape, it is preferable to use a fatty acid having 5 to 9 carbon atoms and a fatty acid having 4 or less carbon atoms in combination. For example, it is preferable to use nonanoic acid having 9 carbon atoms and acetic acid having 2 carbon atoms in combination. The ratio of the fatty acid having 5 to 9 carbon atoms and the fatty acid having 4 or less carbon atoms in combination is not particularly limited.

The method for obtaining a salt compound of fatty acid and copper (fatty acid copper) is not particularly limited. For example, it may be obtained by mixing copper hydroxide and a fatty acid in a solvent, or commercially available fatty acid copper may be used. Alternatively, by mixing copper hydroxide, a fatty acid and a reducing compound in a solvent, the formation of the fatty acid copper and the formation of the complex formed between the fatty acid copper and the reducing compound are carried out in the same step. May be good.

(Reducing compound)
It is considered that the reducing compound forms a complex compound such as a complex between the two compounds when mixed with the fatty acid copper. As a result, the reducing compound becomes a donor of electrons to the copper ions in the fatty acid copper, and the reduction of the copper ions is likely to occur, and the copper atoms are liberated by spontaneous thermal decomposition as compared with the fatty acid copper in the uncomplexed state. Is likely to occur. One type of reducing compound may be used alone, or two or more types may be used in combination.

Specifically, the reducing compound includes hydrazine, hydrazine derivative, hydrazine hydrochloride, hydrazine sulfate, hydrazine sulfate such as hydrazine hydrate, hydroxylamine compound such as hydroxylamine and hydroxylamine derivative, sodium boron hydride, sodium sulfite, hydrogen sulfite. Examples thereof include sodium compounds such as sodium, sodium thiosulfate, and sodium hypophosphate.

A reducing compound having an amino group is preferable from the viewpoints of easily forming a coordination bond with respect to a copper atom in the fatty acid copper and easily forming a complex while maintaining the structure of the fatty acid copper. Examples of the reducing compound having an amino group include hydrazine and its derivative, hydroxylamine and its derivative, and the like.

From the viewpoint of lowering the heating temperature (for example, 150 ° C. or lower) in the step of heating the composition containing the fatty acid copper, the reducing compound and the alkylamine (hereinafter, also referred to as the heating step), evaporation or decomposition of the alkylamine occurs. It is preferable to select a reducing compound capable of forming a complex that causes reduction and liberation of copper atoms in a non-temperature range. Examples of such reducing compounds include hydrazine and its derivatives, hydroxylamine and its derivatives, and the like. In these reducing compounds, the nitrogen atom forming the skeleton can form a coordination bond with the copper atom to form a complex. Further, since these reducing compounds generally have a stronger reducing power than alkylamines, the formed complex tends to spontaneously decompose under relatively mild conditions, resulting in reduction and liberation of copper atoms.

By selecting a suitable derivative from these derivatives instead of hydrazine or hydroxylamine, the reactivity with the fatty acid copper can be adjusted, and a complex that causes spontaneous decomposition can be produced under desired conditions. Examples of hydrazine derivatives include methyl hydrazine, ethyl hydrazine, n-propyl hydrazine, isopropyl hydrazine, n-butyl hydrazine, isobutyl hydrazine, sec-butyl hydrazine, t-butyl hydrazine, n-pentyl hydrazine, isopentyl hydrazine, neo-pentyl hydrazine. , T-pentyl hydrazine, n-hexyl hydrazine, isohexyl hydrazine, n-heptyl hydrazine, n-octyl hydrazine, n-nonyl hydrazine, n-decyl hydrazine, n-undecyl hydrazine, n-dodecyl hydrazine, cyclohexyl hydrazine, phenyl Examples thereof include hydrazine, 4-methylphenylhydrazine, benzylhydrazine, 2-phenylethylhydrazine, 2-hydrazinoethanol, acetohydrazine and the like. Examples of the hydroxylamine derivative include N, N-di (sulfoethyl) hydroxylamine, monomethylhydroxylamine, dimethylhydroxylamine, monoethylhydroxylamine, diethylhydroxylamine, N, N-di (carboxyethyl) hydroxylamine and the like. Can be done.

The ratio of copper to the reducing compound contained in the fatty acid copper is not particularly limited as long as the desired complex is formed. For example, the ratio (copper: reducing compound) can be in the range of 1: 1 to 1: 4 on a molar basis, preferably in the range of 1: 1 to 1: 3, and 1: 1 to 1. : It is more preferable to set the range to 2.

(Alkylamine)
The alkylamine is considered to function as a reaction medium for the decomposition reaction of the complex formed from the fatty acid copper and the reducing compound. Furthermore, it is considered that the protons generated by the reducing action of the reducing compound are captured, and the reaction solution is inclined to be acidic to suppress the oxidation of copper atoms.

Alkyl amines are primary amines represented by RNH ₂ (R is a hydrocarbon group and may be cyclic or branched), R ₁ R ₂ NH (R ₁ and R ₂ are the same but different. It is a hydrocarbon group which may be present, and may be cyclic or branched), and means a secondary amine, an alkylenediamine in which two amino groups are substituted in a hydrocarbon chain, and the like. Alkylamines may have one or more double bonds and may have atoms such as oxygen, silicon, nitrogen, sulfur and phosphorus. The alkylamine may be only one kind or two or more kinds.

The hydrocarbon group of the alkylamine preferably has 7 or less carbon atoms. When the hydrocarbon group of the alkylamine has 7 or less carbon atoms, the alkylamine is easily thermally decomposed during heating for fusing the copper-containing particles to form a conductor, and a good conductor formation tends to be achieved. It is in. The hydrocarbon group of the alkylamine preferably has 6 or less carbon atoms, and more preferably 3 or more carbon atoms.

Specifically, as primary amines, ethylamine, 2-ethoxyethylamine, propylamine, butylamine, isobutylamine, pentylamine, isopentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, Hexadecylamine, oleylamine, 3-methoxypropylamine, 3-ethoxypropylamine and the like can be mentioned.

Specific examples of the secondary amine include diethylamine, dipropylamine, dibutylamine, ethylpropylamine, ethylpentylamine, dibutylamine, dipentylamine, dihexylamine and the like.

Specifically, as alkylenediamine, ethylenediamine, N, N-dimethylethylenediamine, N, N'-dimethylethylenediamine, N, N-diethylethylenediamine, N, N'-diethylethylenediamine, 1,3-propanediamine, 2,2 -Dimethyl-1,3-propanediamine, N, N-dimethyl-1,3-diaminopropane, N, N'-dimethyl-1,3-diaminopropane, N, N-diethyl-1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, N, N'-dimethyl-1,6-diaminohexane, 1,7-diaminoheptane, 1, Examples thereof include 8-diaminooctane, 1,9-diaminononane, and 1,12-diaminododecane.

The alkylamine preferably contains at least one of the alkylamines having 7 or less carbon atoms in the hydrocarbon group. This makes it possible to produce copper-containing particles having better fusion properties at low temperatures. The alkylamine may be used alone or in combination of two or more. The alkylamine may include an alkylamine having a hydrocarbon group having 7 or less carbon atoms and an alkylamine having a hydrocarbon group having 8 or more carbon atoms. When an alkylamine having 7 or less carbon atoms in a hydrocarbon group and an alkylamine having 8 or more carbon atoms in a hydrocarbon group are used in combination, the alkylamine having 7 or less carbon atoms in the hydrocarbon group as a whole. The ratio of the above is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more.

The ratio of copper to alkylamine contained in the fatty acid copper is not particularly limited as long as the desired copper-containing particles can be obtained. For example, the ratio (copper: alkylamine) can be in the range of 1: 1 to 1: 8 on a molar basis, preferably in the range of 1: 1 to 1: 6, and 1: 1 to 1: 1. It is more preferably in the range of 4.

(Heating process)
The method for carrying out the step of heating the composition containing the fatty acid copper, the reducing compound and the alkylamine is not particularly limited. For example, a method of mixing fatty acid copper and a reducing compound in a solvent and then adding an alkylamine and heating, a method of mixing fatty acid copper and an alkylamine with a solvent and then further adding a reducing compound and heating, a method of fatty acid A method in which copper hydroxide, a fatty acid, a reducing compound and an alkylamine, which are starting materials for copper, are mixed with a solvent and heated, and a method in which fatty acid copper and an alkylamine are mixed with a solvent and then a reducing compound is added and heated. Etc. can be mentioned.

The heating step can be performed at a relatively low temperature by using fatty acid copper having 9 or less carbon atoms as the copper precursor. For example, it can be carried out at 150 ° C. or lower, preferably at 130 ° C. or lower, and more preferably at 100 ° C. or lower.

The composition containing the fatty acid copper, the reducing compound and the alkylamine may further contain a solvent. From the viewpoint of promoting the formation of a complex of the fatty acid copper and the reducing compound, it is preferable to contain a polar solvent. Here, the polar solvent means a solvent that dissolves in water at 25 ° C. The use of polar solvents tends to promote the formation of complexes. The reason is not clear, but it is considered that the contact with the water-soluble reducing compound is promoted while dissolving the solid fatty acid copper. One type of solvent may be used alone, or two or more types may be used in combination.

Examples of the polar solvent include alcohols that dissolve in water at 25 ° C. Examples of the alcohol that dissolves in water at 25 ° C. include alcohols having 1 to 8 carbon atoms and having one or more hydroxyl groups in the molecule. Examples of such alcohols include linear alkyl alcohols, phenols, and those in which the hydrogen atom of a hydrocarbon having an ether bond in the molecule is replaced with a hydroxyl group. From the viewpoint of exhibiting stronger polarity, an alcohol containing two or more hydroxyl groups in the molecule is preferably used. Further, alcohol containing sulfur atom, phosphorus atom, silicon atom and the like may be used depending on the use of the produced copper-containing particles.

Specific examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, butanol, pentanol, hexanol, heptanol, octanol, allyl alcohol, benzyl alcohol, pinacol, propylene glycol, menthol, catechol, hydroquinone, salicyl alcohol, Examples thereof include glycerin, pentaerythritol, sculose, glucose, xylitol, methoxyethanol, triethylene glycol monomethyl ether, ethylene glycol, triethylene glycol, tetraethylene glycol and pentaethylene glycol.

Of the alcohols, methanol, ethanol, 1-propanol and 2-propanol, which have extremely high solubility in water, are preferable, 1-propanol and 2-propanol are more preferable, and 1-propanol is further preferable.

〔resin〕
The type of resin is not particularly limited, and can be selected according to the type of dispersion medium, the type of base material forming the conductor, and the like.
Examples of the resin include (meth) acrylic resin, polyimide resin, polyurethane resin, polyphenylene ether resin, silicone resin, epoxy resin, phenol resin, polyolefin resin such as polyethylene, polyvinyl chloride resin, polyethylene terephthalate resin, nylon resin, and polyfluoride. Vinylidene resin, polysulfone resin, polyether sulfone resin, nitrile butadiene resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, melamine resin, urea resin (ureia resin), polycarbonate resin, polyacetal resin, silicone resin, polyether Imid resin, phenoxy resin, modified polyphenylene ether resin, polyamide resin, polyvinyl butyral resin, fluororesin, bismaleimide resin, cyanate ester resin, alkyd resin, unsaturated polyester resin, resorcinol formaldehyde resin, xylene resin, furan resin, ketone resin, Triallyl cyanurate resin, polyisocyanate resin, resin containing tris (2-hydroxyethyl) isocyanurate, resin containing triallyl trimellitate, thermosetting resin synthesized from cyclopentadiene, and aromatic disianamide. Examples thereof include thermosetting resins by quantification, copolymers of isobutylene and maleic anhydride, and various modified resins. Further, peptides having a weight average molecular weight of 5000 or more may be used, and such peptides are also included in the "resin" in the present specification. As the resin, one type may be used alone, or two or more types may be used in combination.

The conductor forming composition may contain a thermosetting resin for the purpose of suppressing flow due to heat during conductor formation. Examples of the thermosetting resin include the above-mentioned resins that undergo a cross-linking reaction due to heat. Of these, epoxy resins are preferable because they can impart an excellent effect of suppressing flow due to heat.

The conductor forming composition may contain a thermosetting compound other than the above-mentioned resin for the purpose of suppressing the flow due to heat at the time of conductor formation. Examples of the thermosetting compound include compounds that undergo a cross-linking reaction by heat, and such compounds are also included in the "resin" in the present specification.
Examples of the thermosetting compound include acid dianhydride, isocyanate compounds, polyfunctional (meth) acrylate compounds, compounds having a styryl group, diallyl bisphenol A, bisallyl nadiimide, diallyl phthalate or diallyl phthalate prepolymer, and diallyl melamine. , Triallyl isocyanurate, allyl-modified phenol novolac, 1,3-diallyl-5-glycidyl isocyanurate and the like. These thermosetting compounds may be used alone or in combination of two or more.

From the viewpoint of dispersibility, the resin is preferably a (meth) acrylic resin, an epoxy resin or a urethane resin, and more preferably a (meth) acrylic resin. The resin may have a substituent such as an epoxy group, a hydroxyl group, or an amino group.

From the viewpoint of the durability and heat resistance of the conductor, the conductor forming composition preferably contains a resin having a glass transition temperature (Tg) of 15 ° C. to 250 ° C.
When the conductor forming composition contains a resin having a Tg of 15 ° C. or higher, the surface tacking force of the formed conductor tends to increase. Further, when the conductor forming composition contains a resin having a Tg of 250 ° C. or lower, the flexibility of the formed conductor tends to be well maintained.

From the viewpoint of heat resistance, the weight average molecular weight of the resin is preferably 50,000 to 1,000,000, more preferably 300,000 to 900,000, and even more preferably 500,000 to 800,000.

From the viewpoint of obtaining sufficient adhesiveness to the base material, the amount of the resin in the conductor forming composition is preferably 0.01 part by mass or more, preferably 0.1 part by mass with respect to 100 parts by mass of the copper-containing particles. The above is more preferable.

From the viewpoint of ensuring sufficient conductivity of the conductor, the amount of the resin in the conductor forming composition is preferably 10 parts by mass or less with respect to 100 parts by mass of the copper-containing particles, and is preferably 5 parts by mass or less. Is more preferable.

[Dispersion medium]
The type of the dispersion medium is not particularly limited, and can be selected from commonly used organic solvents depending on the use of the conductor forming composition. As the dispersion medium, one type may be used alone, or two or more types may be used in combination. When the conductor forming composition is applied to a printing method, it contains at least one selected from the group consisting of terpineol, isobornylcyclohexanol, dihydroterpineol and dihydroterpineol acetate from the viewpoint of viscosity control of the conductor forming composition. Is preferable.

The viscosity of the conductor-forming composition is not particularly limited and can be selected according to the method of using the conductor-forming composition. For example, when the conductor forming composition is applied to a screen printing method, the viscosity is preferably 0.1 Pa · s to 30 Pa · s, and more preferably 1 Pa · s to 30 Pa · s. When the conductor forming composition is applied to the inkjet printing method, the viscosity is preferably 0.1 mPa · s to 30 mPa · s, and 5 mPa · s to 20 mPa · s, although it depends on the standard of the inkjet head used. More preferably.

The conductor-forming composition may contain components other than the copper-containing particles, the resin and the dispersion medium, if necessary. Examples of such a component include a silane coupling agent, a radical initiator, a reducing agent and the like.

<Conductor manufacturing method>
The method for producing a conductor of the present embodiment includes a step (heating step) of heating the conductor forming composition. In the heating step, the organic matter on the surface of the copper-containing particles contained in the conductor forming composition is thermally decomposed and the copper-containing particles are fused. Since the conductor forming composition can be made into a conductor at a low temperature, the heating step can be performed at a temperature of 200 ° C. or lower, preferably 150 ° C. or lower.

The components in the atmosphere in which the heating step is performed are not particularly limited, and can be selected from nitrogen, argon, and the like used in the normal conductor manufacturing process. Further, a reducing substance such as hydrogen or formic acid may be heated in an atmosphere saturated with nitrogen or the like. The pressure at the time of heating is not particularly limited, but the reduced pressure tends to promote the formation of a conductor at a lower temperature.

The heating step may be performed at a constant heating rate or may be changed irregularly. The time of the heating step is not particularly limited, and can be selected in consideration of the heating temperature, the heating atmosphere, the amount of copper-containing particles, and the like. The heating method is not particularly limited, and examples thereof include heating with a hot plate, heating with an infrared heater, and heating with a pulse laser.

The method for manufacturing the conductor may include other steps if necessary. Other steps include a step of applying the conductor forming composition to the substrate before the heating step, a step of removing at least a part of the volatile components in the conductor forming composition by drying or the like before the heating step, and a step of reducing after the heating step. Examples thereof include a step of reducing copper oxide generated by heating in an atmosphere, a step of performing light firing after the heating step to remove residual components, a step of applying a load to the conductor obtained after the heating step, and the like.

<Conductor>
The conductor of the present embodiment has a structure in which copper-containing particles contained in the conductor forming composition are fused, and contains a resin.
The shape of the conductor is not particularly limited, and examples thereof include a thin film shape and a pattern shape. The conductor of this embodiment can be used for forming wirings, coatings, etc. of various electronic components. In particular, since the conductor of this embodiment can be manufactured at a low temperature, it is suitably used for forming a metal foil, a wiring pattern, or the like on a base material having low heat resistance such as resin. Further, it is suitably used for applications such as decoration and printing that are not intended to be energized.

Whether or not the conductor has a structure in which the copper-containing particles contained in the conductor forming composition are fused can be confirmed by observing with, for example, a transmission electron microscope or a scanning electron microscope. The organic matter existing on the surface of the core particles in the copper-containing particles may be completely eliminated after being made into a conductor, or a part thereof may remain.
Whether or not the conductor contains a resin can be confirmed by, for example, a scanning electron microscope or an atomic force microscope.

When the conductor forming composition is applied onto the base material and heated to form the conductor, the material of the base material is not particularly limited and may or may not have conductivity. Specifically, metals such as Cu, Au, Pt, Pd, Ag, Zn, Ni, Co, Fe, Al and Sn, alloys of these metals, semiconductors such as ITO, ZnO, SnO and Si, glass and graphite. Examples include carbon materials such as graphite, resins, papers, and combinations thereof. Since the conductor of the present embodiment is obtained by heating at a low temperature, it can be suitably applied particularly when a base material made of a material having relatively low heat resistance is used. Examples of materials having relatively low heat resistance include thermoplastic resins. Examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene and polymethylpentene, and polycarbonate resins. The shape of the base material is not particularly limited, and may be a plate shape, a rod shape, a roll shape, a film shape, or the like.

The volume resistivity of the conductor is preferably 75 μΩ · cm or less, more preferably 50 μΩ · cm or less, further preferably 30 μΩ · cm or less, and particularly preferably 20 μΩ · cm or less.

The conductor of this embodiment can be used for various purposes. Specifically, it can be used as a member such as an electric wiring, a heat radiating film, and a surface coating film used for electronic parts such as a laminated board, a solar cell panel, a display, a transistor, and a semiconductor package. In particular, since the conductor included in the apparatus of the present embodiment can be formed on a base material such as resin, it is suitable for manufacturing flexible laminated plates, solar cell panels, displays and the like.

<Device>
The apparatus of this embodiment includes the conductor of this embodiment. The type of device is not particularly limited. Examples thereof include wiring made of conductors of the present embodiment, laminated plates having a coating film, solar cell panels, displays, transistors, and electronic components such as semiconductor packages. Further, electronic devices, home appliances, industrial machines, transportation machines, etc. incorporating these electronic components are also included in the apparatus of the present embodiment.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[1.1] Synthesis of copper nonanoate To 91.5 g (0.94 mol) of copper hydroxide (Kanto Chemical Co., Inc., special grade), 150 mL of 1-propanol (Kanto Chemical Co., Inc., special grade) was added and stirred. 370.9 g (2.34 mol) of nonanoic acid (Kanto Chemical Co., Inc., 90% or more) was added. The resulting mixture was heated and stirred in a separable flask at 90 ° C. for 30 minutes. The obtained solution was filtered while being heated to remove undissolved substances. After that, the mixture was allowed to cool, and the produced copper nonanoate was suction-filtered and washed with hexane until the washing liquid became transparent. The obtained powder was dried in an explosion-proof oven at 50 ° C. for 3 hours to obtain copper (II) nonanoate. The yield was 340 g (yield 96% by mass).

[1.2] Synthesis of copper-containing particles (A)
15.01 g (0.040 mol) of copper (II) nonanoate and 7.21 g (0.040 mol) of copper (II) acetate anhydride (Kanto Chemical Co., Inc., special grade) obtained above were placed in a separable flask. 22 mL of 1-propanol and 32.1 g (0.32 mol) of hexylamine (Tokyo Kasei Kogyo Co., Ltd., purity 99%) were added, and the mixture was dissolved by heating and stirring at 80 ° C. in an oil bath. After transferring to an ice bath and cooling to an internal temperature of 5 ° C., 7.72 mL (0.16 mol) of hydrazine monohydrate (Kanto Chemical Co., Inc., special grade) was stirred in the ice bath. The molar ratio of copper: hexylamine is 1: 4. Then, it was heated and stirred at 90 ° C. in an oil bath. At that time, the reduction reaction accompanied by foaming proceeded, and the reaction was completed within 30 minutes. The inner wall of the separable flask had a copper luster and the solution turned dark red. Centrifugation was performed at 9000 rpm (rotation / min) for 1 minute to obtain a solid. The step of further washing the solid material with 15 mL of hexane was repeated three times to remove the acid residue to obtain a copper cake A containing a powder of copper-containing particles having a copper luster.

When the copper-containing particles synthesized above were observed with a transmission electron microscope (manufactured by JEOL Ltd., product name: JEM-2100F), as shown in FIG. 1, many large copper-containing particles were present. The average value of the major axis of 200 randomly selected copper-containing particles is 104 nm, the proportion of copper-containing particles having a major axis length of 50 nm or less is 18%, and the major axis length is The proportion of copper-containing particles having a diameter of 70 nm or more was 67%, the length of the major axis of the maximum diameter particles was 200 nm, and the average aspect ratio was 1.2. Further, copper particles having irregularities on the surface were observed, and the circularity was 0.81.

[1.3] Synthesis of copper-containing particles (B)
Put 15.01 g (0.040 mol) of copper (II) nonanoate and 7.21 g (0.040 mol) of copper (II) acetate anhydride (Kanto Chemical Co., Inc., special grade) in a separable flask, and add 1-propanol to 15 mL. 32.1 g (0.32 mol) of hexylamine (Tokyo Kasei Kogyo Co., Ltd., purity 99%) was added, and the mixture was dissolved by heating and stirring at 80 ° C. in an oil bath. After transferring to an ice bath and cooling to an internal temperature of 5 ° C., 7.72 mL (0.16 mol) of hydrazine monohydrate (Kanto Chemical Co., Inc., special grade) was stirred in the ice bath. The molar ratio of copper: hexylamine is 1: 4. Then, it was heated and stirred at 80 ° C. in an oil bath. At that time, the reduction reaction accompanied by foaming proceeded, and the reaction was completed within 3 minutes. The inner wall of the separable flask had a copper luster and the solution turned dark red. Centrifugation was performed at 9000 rpm (rotation / min) for 1 minute to obtain a solid. The step of further washing the solid material with 15 mL of hexane was repeated three times to remove the acid residue to obtain a copper cake B containing a powder of copper-containing particles having a copper luster.

When the copper-containing particles synthesized above were observed with a transmission electron microscope (manufactured by JEOL Ltd., product name: JEM-2100F), as shown in FIG. 2, large copper-containing particles and small copper-containing particles were mixed. Was. The average value of the major axis of 200 randomly selected copper-containing particles is 54 nm, the proportion of copper-containing particles having a major axis length of 50 nm or less is 59%, and the major axis length is The proportion of copper-containing particles having a diameter of 70 nm or more was 26%, the length of the major axis of the maximum diameter particles was 120 nm, and the average aspect ratio was 1.1. Further, copper-containing particles having irregularities on the surface were observed, and the circularity was 0.80.

[1.4] Synthesis of copper-containing particles (C)
Copper in the same manner as in the synthesis of copper-containing particles (A) except that the conditions for centrifugation in the above-mentioned "[1.2] Synthesis of copper-containing particles (A)" were set at 1000 rpm (rotation / minute) for 10 seconds. A copper cake C containing a powder of glossy copper-containing particles was obtained.

When the copper-containing particles synthesized above were observed with a transmission electron microscope (manufactured by Nippon Denshi Co., Ltd., product name: JEM-2100F), the average value of the long axis of 200 randomly selected copper-containing particles was 50 nm. The proportion of copper-containing particles having a major axis length of 50 nm or less is 50%, and the proportion of copper-containing particles having a major axis length of 70 nm or more is 35%, which is the maximum diameter particles. The length of the major axis of the particle was 200 nm, and the average value of the aspect ratio was 1.2. In addition, copper particles having irregularities on the surface were observed, and the circularity was 0.84.

<Example 1>
[Preparation of conductor forming composition]
Cake A (100 parts by mass) of copper-containing particles synthesized by the above method, cyclohexanone (manufactured by Wako Pure Chemical Industries, Ltd.) (67 parts by mass), acrylic rubber containing an epoxy group (manufactured by Nagase ChemteX Corporation, product) A conductor-forming composition was prepared by mixing the name HTR-3CSP (weight average molecular weight = 800,000, Tg = 20 ° C.) (0.5 parts by mass).

[Formation of conductor]
The obtained conductor forming composition was applied onto a base material (glass plate) and heated to form a metallic copper thin film (conductor). The heating was carried out by heating to 200 ° C. at a heating rate of 40 ° C./min and holding for 60 minutes in an atmosphere where the oxygen concentration in nitrogen was 100 ppm or less. When the formed metallic copper thin film was observed with a transmission electron microscope (manufactured by JEOL Ltd., product name: JEM-2100F), it was observed that the copper-containing particles were fused to each other. The thickness of the thin film was 3 μm.

[Evaluation of volume resistivity]
The volume resistivity (unit: μΩ · cm) of the obtained metallic copper thin film was measured by a four-end needle surface resistance measuring device, and the surface resistivity value and the non-contact surface / layer cross-sectional shape measurement system (VertScan, Ryo Co., Ltd.) It was calculated from the film thickness obtained by the chemical system). The results are shown in Table 1.

[Evaluation of adhesive strength]
A cross-cut test was carried out on the obtained conductor-treated film according to JIS K5400 (width 1 mm). If there was no peeling of the film after the tape was peeled off and the number of remaining squares was 100/100, the adhesive strength was evaluated as "good (○)", and the film peeled off after the tape was peeled off. In that case, the adhesive strength was evaluated as "poor (x)".

<Examples 2 to 4>
A conductor forming composition was prepared in the same manner as in Example 1 except that the amount of acrylic rubber (parts by mass) with respect to 100 parts by mass of copper-containing particles was changed to the amount shown in Table 1, and a conductor was formed and evaluated. It was. The results are shown in Table 1.

<Examples 5 to 8>
A conductor forming composition was prepared in the same manner as in Examples 1 to 4 except that the same amount of copper-containing particle cake C was used instead of the copper-containing particle cake A, and a conductor was formed and evaluated. .. The results are shown in Table 1.

<Comparative example 1>
A conductor-forming composition was prepared in the same manner as in Example 1 except that acrylic rubber was not added, and a conductor was formed and evaluated. The results are shown in Table 1.

<Comparative example 2>
A conductor-forming composition was prepared in the same manner as in Comparative Example 1 except that the same amount of copper-containing particle cake B was used instead of the copper-containing particle cake A, and a conductor was formed and evaluated. The results are shown in Table 1.

As shown in Table 1, the conductors produced in Examples 1 to 8 are conductor-forming compositions containing copper-containing particles having a major axis length of 50 nm or less and a proportion of copper-containing particles of 59%. Compared with Comparative Example 2, the volume resistivity was low and the conductivity was excellent.
In Comparative Example 1 using the conductor-forming composition containing no resin, the volume resistivity was low and the conductivity was excellent, but the evaluation of the adhesive force to the substrate was low.

Claims (8)

Contains copper-containing particles, a dispersion medium, and a resin,
The copper-containing particles include core particles containing copper and organic substances present on at least a part of the surface of the core particles, and the proportion of copper-containing particles having a major axis length of 50 nm or less is 55. % Or less
A conductor forming composition in which the amount of the resin is 0.01 part by mass to 10 parts by mass with respect to 100 parts by mass of the copper-containing particles. The conductor-forming composition according to claim 1, wherein the copper-containing particles have a major axis length of 70 nm or more and a proportion of copper-containing particles having a length of 70 nm or more is 30% or more. The conductor-forming composition according to claim 1 or 2, wherein the copper-containing particles have an average value of 55 nm or more in length on the major axis. The conductor-forming composition according to any one of claims 1 to 3, wherein the copper-containing particles have an average value of 500 nm or less in length on the major axis. The conductor forming composition according to any one of claims 1 to 4, which comprises copper-containing particles having a circularity of 0.70 to 0.99. A method for producing a conductor, which comprises a step of heating the conductor forming composition according to any one of claims 1 to 5. A conductor having a structure in which copper-containing particles contained in the conductor-forming composition according to any one of claims 1 to 5 are fused and containing a resin. A device comprising the conductor according to claim 7.