JP2016145397A - Producing method of copper membrane and conductor obtained thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of a copper membrane in which steps are simplified and introduction of conductivity can be realized at lower temperature, and to provide a conductor using it.SOLUTION: There is provided a producing method of a copper membrane comprising a step of heating treatment of a conductive composition consisting of core particles containing copper in which at least a part of its surface is covered with organic matter and dispersion medium under reducing gas atmosphere at a temperature of 250°C or less. It is preferable that content ratio of organic matter in the core particles containing copper in which at least a part of its surface is covered with organic matter is 0.1 to 10.0 mass%. It is preferable that the organic matter is alkylamine. It is preferable that the core particles containing copper in which at least a part of its surface are copper containing particles obtained by a step of heating a mixture of a salt compound of fatty acid and copper (fatty acid copper), a reducing compound and alkylamine.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a copper film and a conductor obtained thereby.

  As a method for forming a metal pattern, a step of applying a conductive material such as ink or paste containing metal particles such as copper onto a substrate by ink jet printing, screen printing or the like, and heating the conductive material to sinter the metal particles, There is known a method including a conductor-forming step for developing conductivity.

  From the viewpoint of imparting printability to the conductive material, a binder resin or the like is generally added to the conductive material. Moreover, an organic dispersing agent may be added to a conductive material from a viewpoint of improving the dispersibility of the metal particle in conductive materials, such as a paste. Furthermore, when the metal particles are copper particles, a protective agent may be used because copper is a substance that is easily oxidized. Organic components such as a binder resin, an organic dispersant, and a protective agent are factors that inhibit the sintering of metal particles in the conductor process. Therefore, in order to obtain a conductor having a low volume resistivity, it is necessary to remove organic components, and the conductor-forming step is performed at a high temperature in an oxygen atmosphere, and these organic components are burned and removed.

  On the other hand, from the viewpoints of improving production efficiency and diversifying the types of substrates to be used, there is a need for the development of a technique that enables conductive materials to be made conductive at lower temperatures (for example, 150 ° C. or lower). Further, since copper easily becomes copper oxide by heating in an oxygen atmosphere, there is a complicated process of sintering in a reducing atmosphere after removing organic components.

  Therefore, in order to suppress the oxidation of copper and improve the storage stability, one in which an organic substance as a coating material is attached to the surface of copper particles is known. For example, Patent Document 1 describes a coated copper particle that can be sintered at a low temperature and exhibits good conductivity and a method for producing the same. The copper particles described in Patent Document 1 are obtained by mixing a copper precursor such as copper oxalate and a reducing compound such as hydrazine to obtain a composite compound, and heating the composite compound in the presence of an alkylamine. It is manufactured by the method which has these. In the example of Patent Document 1, the ink containing the produced copper particles is heated to 300 ° C. at 60 ° C./min in an argon atmosphere and held for 30 minutes to achieve a conductor.

  Patent Document 2 describes a conductive paste composition containing a conductive metal powder, an organic vehicle, and the like. In order to remove the organic binder, heat treatment is usually performed at 250 to 330 ° C. in an air atmosphere, a nitrogen atmosphere, etc., and the organic vehicle is burned, and then 850 to 1300 ° C. in a neutral or reducing atmosphere so that the metal powder is not oxidized. Sintering is described.

JP 2012-72418 A JP 2012-226865 A

  In recent years, from the viewpoint of improving production efficiency and diversifying the types of substrates to be used, there is a demand for the development of a technique that enables metal particles to be made conductive at a lower temperature (for example, 150 ° C. or lower). Moreover, the simplicity of the conductor process is required. Accordingly, there is a need for the development of a conductorization method that can be easily performed at a temperature lower than the temperatures described in Patent Documents 1 and 2.

  In view of the above problems, an object of the present invention is to provide a method of manufacturing a copper film that can be simplified and can be made into a conductor at a lower temperature, and a conductor using the same.

Means for solving the above problems are as follows.
<1> Copper including a step of heat-treating a conductive composition composed of core particles containing copper whose surface is coated with an organic substance and a dispersion medium at a temperature of 250 ° C. or lower in a reducing gas atmosphere. A method for producing a membrane.

<2> The production of the copper film according to <1>, wherein a content ratio of the organic substance in the core particle containing copper having at least a part of the surface coated with the organic substance is 0.1 to 10.0% by mass. Method.

<3> The method for producing a copper film according to <1> or <2>, wherein the organic substance is an alkylamine.
<4> The step of heating the mixture of the fatty acid and the copper salt compound (fatty acid copper), the reducing compound, and the alkylamine, wherein the core particles containing copper whose surface is covered with at least a part of the organic matter. The method for producing a copper film according to any one of <1> to <3>, wherein the copper-containing particles are obtained.

<5> The method for producing a copper film according to <4>, wherein the fatty acid has 9 or less carbon atoms.

<6> The method for producing a copper film according to <4> or <5>, wherein the reducing compound includes at least one selected from the group consisting of hydrazine, hydrazine derivatives, hydroxylamine, and hydroxylamine derivatives.

<7> The method for producing a copper film according to any one of <3> to <6>, wherein the alkylamine has 7 or less carbon atoms.
<8> A conductor obtained by the method for producing a copper film according to any one of <1> to <7>.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the copper film which can simplify a process and can be made into a conductor at lower temperature, and the conductor obtained by the manufacturing method can be provided.

  In the present specification, a numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. Further, in the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. Means.

  In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. .

  In this specification, the term “film” includes not only a configuration of a shape formed on the entire surface but also a configuration of a shape formed on a part when observed as a plan view.

  In the present specification, the term “conducting” means that the metal-containing particles are sintered to be changed into a conductive object. The “conductor (conductor)” refers to an object having conductivity. Conductivity means that the volume resistivity is 300 μΩ · cm or less.

<Manufacturing method of copper film>
In the method for producing a copper film of the present invention, a conductive composition composed of core particles containing copper whose surface is coated with an organic substance and a dispersion medium is subjected to a reducing gas atmosphere at a temperature of 250 ° C. or lower. Including a step of heat treatment. The manufacturing method of the copper film of this invention may include the other process as needed.

  The manufacturing method of the copper film of the present invention adopts the above-described configuration, thereby simplifying the process and making the conductor at a lower temperature. Thereby, a copper film can be formed even on a substrate having relatively low heat resistance. The reason is guessed as follows.

  Copper is easily oxidized. However, since at least a part of the surface of the copper-containing particles according to the present invention is coated with an organic substance, there is an advantage that oxidation is suppressed even when stored in the atmosphere.

  Moreover, conductorization can be realized at a lower heat treatment temperature by performing the heat treatment step in a reducing gas atmosphere. The reason for this is not clear, but it is presumed that the reducing gas promotes the elimination and decomposition of organic substances present on the surface of the copper-containing particles in addition to the reduction of the oxide. In the examples described in Patent Document 1, there is no specific description about the oxygen concentration in the atmosphere during heating, and heating is performed at a maximum temperature of 300 ° C. in order to sufficiently decompose the organic matter. Yes.

  In addition, since oxidation is suppressed in the copper-containing particles in the present invention, the content of copper oxide is smaller than that of conventional copper-containing particles, and even if it contains a small amount of copper oxide, it is a reducing gas. By being heat-treated in an atmosphere, the copper oxide is reduced to produce metallic copper. Therefore, a copper film (conductor) having a lower resistance can be obtained. In addition, since the pyrolysis of the organic substance and the reduction to metallic copper are performed at once, the process can be simplified.

  As described above, according to the method for producing a copper film of the present invention, conductorization at a lower temperature can be realized, and the reduction process can be omitted after the thermal decomposition process of the organic matter, thereby simplifying the process.

(substrate)
In the present invention, the conductive composition is provided on the substrate and heat-treated. The material of the substrate is not particularly limited, and may or may not have conductivity. For example, metals such as Cu, Au, Pt, Pd, Ag, Zn, Ni, Co, Fe, Al, Sn, alloys of these metals, semiconductors such as ITO, ZnO, SnO, Si, glass, graphite, graphite, etc. A carbon material, resin, paper, etc. can be mentioned.

The method for producing a copper film of the present invention can be suitably applied particularly when a substrate made of a material having relatively low heat resistance is used. An example of such a material is a thermoplastic resin. Examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate, and polyimide resins.
The shape of the substrate is not particularly limited, and may be a plate shape, a rod shape, a roll shape, a film shape, or the like.

(Conductive composition)
The conductive composition used in the method for producing a copper film of the present invention includes copper-containing particles having copper-containing core particles and organic substances disposed on at least a part of the surface of the core particles, and a dispersion medium. It may contain other components as necessary.

-Copper-containing particles-
In the copper-containing particles in the present invention, an organic substance is disposed on at least a part of the surface of the core particles containing copper. When at least a part of the surface of the core particle is coated with an organic substance, the oxidation of the copper-containing particle is suppressed, and the copper-containing particle that can be stored for a long time in the air can be obtained.

  From the viewpoint of more effectively suppressing the oxidation of the copper-containing particles, the organic content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more in the copper-containing particles. More preferably, the content is 0.3% by mass or more. From the viewpoint of achieving a conductor at a lower temperature, the content of the organic substance is preferably 10% by mass or less, more preferably 5% by mass or less in the copper-containing particles, and 3% by mass or less. Is more preferable.

  The content of the organic substance is obtained by heating the copper-containing particles at a temperature equal to or higher than the temperature at which the organic substance is thermally decomposed, and comparing the mass before and after the heating.

In one preferable embodiment of the present invention, the organic substance includes a substance having an alkyl group having 7 or less carbon atoms and derived from an alkylamine. Alkylamine is a primary amine 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 or different. Or a branched or branched hydrocarbon group), an alkylene diamine in which two amino groups are substituted on the hydrocarbon chain, and the like. The alkylamine 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 type or two or more types.

  Specific examples of the primary amine used in the method of the present invention include ethylamine, 2-ethoxyethylamine, propylamine, butylamine, isobutylamine, pentylamine, isopentylamine, hexylamine, cyclohexylamine, heptylamine, and octylamine. , Nonylamine, decylamine, dodecylamine, hexadecylamine, oleylamine, 3-methoxypropylamine, 3-ethoxypropylamine and the like.

  Specific examples of the secondary amine used in the method of the present invention include diethylamine, dipropylamine, dibutylamine, ethylpropylamine, ethylpentylamine, dibutylamine, dipentylamine, and dihexylamine.

  Specific examples of the alkylene diamine used in the method of the present invention include ethylene diamine, N, N-dimethylethylene diamine, N, N′-dimethyl ethylene diamine, N, N-diethyl ethylene diamine, N, N′-diethyl ethylene diamine, 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, , 7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,12-diaminododecane, etc. Door can be.

  The hydrocarbon group of the alkylamine preferably has 7 or less carbon atoms. Alkylamines having a carbon number of 7 or less (specific alkylamines) have a relatively low molecular weight, and therefore tend to thermally decompose even at relatively low temperatures. From the viewpoint of achieving better conductorization, the hydrocarbon group of the alkylamine preferably has 6 or less carbon atoms. Further, the hydrocarbon group of the alkylamine preferably has 4 or more carbon atoms.

  Specific examples of primary amines having 7 or less carbon atoms include ethylamine, 2-ethoxyethylamine, propylamine, butylamine, isobutylamine, pentylamine, isopentylamine, hexylamine, cyclohexylamine, heptylamine and the like. Can do.

  Specific examples of the secondary amine having 7 or less carbon atoms include diethylamine, dipropylamine, dibutylamine, ethylpropylamine, and ethylpentylamine.

  Specific examples of the alkyldiamine having 7 or less carbon atoms include 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, Examples thereof include 7-diaminoheptane.

  The shape of the copper-containing particles according to the present invention is not particularly limited. For example, a spherical shape, a long granular shape, a flat shape, and the like can be mentioned, which can be selected according to the use of the copper-containing particles. From the viewpoint of preparing a printing paste, it is preferably spherical or long granular.

  The copper-containing particles according to the present invention are copper-containing particles having an average particle diameter (average value of major axis length of 200 copper-containing particles randomly selected: average particle diameter) of 5 to 300 nm. At least one or more of the secondary structures are in close contact. Further, it has a secondary structure in which at least one copper-containing particle having an average particle diameter of 5 to 50 nm is in close contact with the copper-containing particle of 30 to 300 nm. Copper-containing particles (core particles) having an average particle diameter of 30 to 300 nm as a core mainly have a conductive function, and copper-containing particles (adhesive particles) having an average particle diameter of 5 to 50 nm adhered to the core particles are The core particles are bonded to each other by melting at a low temperature during heating. When the average particle diameter of the core particles is less than 30 nm, it is difficult to form a conductive path even if the surrounding adhesion particles are melted. When the average particle diameter is larger than 300 nm, there is a distance between the core particles. Therefore, it is difficult to form a conductive path. In addition, when the average particle diameter of the adhesion particles is less than 5 nm, it is easily affected by oxidation, and when it exceeds 50 nm, it is difficult to melt at low temperatures, so that the core particles are difficult to adhere to each other. .

  In the present invention, the length of the major axis means the distance between two planes selected so that the distance between the two planes circumscribing the particle and parallel to each other is maximized. In the present invention, the median value of the length of the major axis is the two values (100th and 101st) located at the center when the major axis length values of 200 copper-containing particles are arranged in ascending order. Means the arithmetic mean. The length of the major axis of the copper-containing particles can be measured by a usual method such as observation with an electron microscope.

  The copper-containing particles according to the present invention contain at least metallic copper (copper-containing core particles) and an organic substance on the surface thereof, and may contain other substances as necessary. The organic substance is preferably an alkylamine. Examples of other substances include metals such as gold, silver, platinum, tin, and nickel or compounds containing these metal elements, fatty acid copper, reducing compounds, copper oxides, and copper chlorides described later. From the viewpoint of forming a copper pattern with excellent conductivity, the content of metallic copper in the copper-containing particles is preferably 50% by mass or more, more preferably 60% by mass or more, and 70% by mass or more. More preferably it is.

  In the copper-containing particles in the present invention, since an organic substance having an amino group such as alkylamine is present on at least a part of the surface of the core particles, oxidation is suppressed, and the content of copper oxide is small. For example, in a certain embodiment, the content rate of the copper oxide in a core particle is 5 mass% or less. The content rate of the copper oxide in the core particle can be measured by, for example, an X-ray diffraction spectrum (XRD, X-ray diffraction). The content rate of the copper oxide in a core particle is a value when measured before conductorization.

-Method for producing copper-containing particles-
The method for producing the copper-containing particles according to the present invention is not particularly limited. In a preferred embodiment of the present invention, an alkylamine comprising a metal salt (salt compound, fatty acid copper) of a fatty acid and copper having 9 or less carbon atoms, a reducing compound, and an alkylamine having 7 or less carbon atoms. And the copper containing particle | grains which concern on this invention can be manufactured by the method which has the process of heating the composition containing these.

  The method uses a metal salt of fatty acid and copper having 9 or less carbon atoms as a copper precursor. This makes it possible to use an alkylamine having a lower boiling point (that is, a lower molecular weight) as a reaction medium as compared with the method described in Patent Document 1 using copper oxalate or the like as a copper precursor. It is done. As a result, the organic substance present on the surface of the obtained copper-containing particles is more likely to be thermally decomposed, and it is considered that the conductorization can be performed at a low temperature.

-Fatty acid-
The fatty acid used in the above method is a monovalent carboxylic acid represented by RCOOH (R is a chain hydrocarbon group, which may be linear or branched). The fatty acid used in the present invention may be either a saturated fatty acid or an unsaturated fatty acid. From the viewpoint of obtaining a good coating of the core particles, linear saturated fatty acids are preferred. Only one type or two or more types of fatty acids may be used.

  From the viewpoint of obtaining good sintering at a low temperature, the fatty acid preferably has 9 or less carbon atoms. Examples of 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), capron Examples include acids (carbon number 6), enanthic acid and isoenanthic acid (carbon number 7), caprylic acid, isocaprilic acid and isocaproic acid (carbon number 8), nonanoic acid and isononanoic acid (carbon number 9). 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 used in the production of the copper-containing particles in the present invention can affect properties such as dispersibility of the obtained copper-containing particles in a dispersion medium (solvent) and sinterability. For this reason, it is preferable to select the kind of fatty acid according to the use of copper-containing particles. From the viewpoint of achieving both dispersibility in a dispersion medium and conductorization at low temperature, 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, nonanoic acid having 9 carbon atoms and acetic acid having 2 carbon atoms are preferably used in combination.

  The ratio in the case of using together the fatty acid having 5 to 9 carbon atoms and the fatty acid having 4 or less carbon atoms is not particularly limited. In addition, when the ratio of the fatty acid having 4 or less carbon atoms in the fatty acid having 9 or less carbon atoms is less than 40 mol%, long-shaped copper-containing particles extending in one direction can be stably produced. be able to. On the other hand, when the proportion of fatty acids having 4 or less carbon atoms is 40 mol% or more, the shape tends to be controlled in a spherical shape.

  The method for obtaining a salt compound (fatty acid copper) of fatty acid and copper having 9 or less carbon atoms 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 production of fatty acid copper and the formation of a complex formed between the fatty acid copper and the reducing compound can be performed collectively. Good.

-Reducing compound-
The reducing compound used in the above method is considered to form a complex compound such as a complex between both compounds when mixed with fatty acid copper. As a result, the reducing compound becomes an electron donor to the copper ion in the fatty acid copper, and the reduction of the copper ion is likely to occur, and the liberation of copper atoms due to spontaneous pyrolysis than the fatty acid copper in a state where no complex is formed. This is likely to occur. A reducing compound may be used individually by 1 type, or may use 2 or more types together.

  Specific examples of reducing compounds include hydrazine, hydrazine derivatives, hydrazine hydrochloride, hydrazine sulfate, hydrazine hydrate and other hydrazine compounds, hydroxylamine, hydroxylamine derivatives such as hydroxylamine compounds, sodium borohydride, sodium sulfite, hydrogen sulfite. Examples thereof include sodium compounds such as sodium, sodium thiosulfate, and sodium hypophosphite.

  A reducing compound having an amino group is preferable from the viewpoints of easily forming a coordination bond to a copper atom in fatty acid copper, and easily forming a complex while maintaining the structure of fatty acid copper. Examples of the reducing compound having an amino group include hydrazine and derivatives thereof, hydroxylamine and derivatives thereof, 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 fatty acid copper, the reducing compound and the alkylamine in the method (hereinafter also referred to as the heating step), the evaporation of the alkylamine or It is preferable to select a reducing compound capable of forming a complex that causes reduction and liberation of a copper atom in a temperature range that does not cause decomposition. Examples of such reducing compounds include hydrazine and its derivatives, hydroxylamine and its derivatives, and the like. These reducing compounds can form a complex by forming a coordinate bond with a copper atom by a nitrogen atom forming a skeleton. In addition, since these reducing compounds generally have a stronger reducing power than alkylamines, the resulting complexes tend to spontaneously decompose under relatively mild conditions, and tend to reduce and release copper atoms.

  By selecting a suitable one of these derivatives instead of hydrazine or hydroxylamine, the reactivity with the fatty acid copper can be adjusted, and a complex that generates spontaneous decomposition under a desired condition can be generated. 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, and neo-pentyl hydrazine. , T-pentylhydrazine, n-hexylhydrazine, isohexylhydrazine, n-heptylhydrazine, n-octylhydrazine, n-nonylhydrazine, n-decylhydrazine, n-undecylhydrazine, n-dodecylhydrazine, cyclohexylhydrazine, phenyl Examples include hydrazine, 4-methylphenylhydrazine, benzylhydrazine, 2-phenylethylhydrazine, 2-hydrazinoethanol, and acetohydrazine. Rukoto can. Examples of hydroxylamine derivatives include N, N-di (sulfoethyl) hydroxylamine, monomethylhydroxylamine, dimethylhydroxylamine, monoethylhydroxylamine, diethylhydroxylamine, N, N-di (carboxyethyl) hydroxylamine and the like. Can do.

  The ratio of the copper and the reducing compound contained in the fatty acid copper is not particularly limited as long as a 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 : The range of 2 is more preferable.

-Alkylamine-
The alkylamine used in the above method 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 protons generated by the reducing action of the reducing compound are captured, and the reaction solution is inclined to be acidic and copper atoms are prevented from being oxidized.

  The alkylamine is similar to that described in connection with the organic matter present on the surface of the copper-containing particles of the present invention. When the alkylamine contains an alkylamine other than the specific alkylamine (alkylamine having 7 or less carbon atoms), the proportion of the specific alkylamine in the total alkylamine is preferably 50% by mass or more, and 60% by mass or more. It is more preferable that it is 70 mass% or more.

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

-Heating process-
In the said method, the method in particular for implementing the process of heating the composition containing fatty-acid copper, a reducing compound, and an alkylamine is not restrict | limited. For example, a method of heating a composition obtained by adding alkylamine after mixing fatty acid copper and a reducing compound, and a composition obtained by adding reducing compound after mixing fatty acid copper and alkylamine Examples thereof include a method of heating, a method of heating a composition obtained by mixing copper hydroxide, a fatty acid, a reducing compound and an alkylamine, which are starting materials for fatty acid copper.

  The composition containing fatty acid copper, reducing compound and alkylamine is heated at a temperature at which a complex formed from fatty acid copper and the reducing compound is decomposed. For example, the heating is preferably performed at 150 ° C. or less, more preferably at 130 ° C. or less, and further preferably at 100 ° C. or less. In the said method, a heating process can be performed at comparatively low temperature by using specific fatty acid copper as a copper precursor.

  The composition containing fatty acid copper, a reducing compound and an alkylamine may further contain a solvent. From the viewpoint of promoting the formation of a complex of fatty acid copper and a reducing compound, it is preferable to include a polar solvent. Here, the polar solvent is preferably a solvent having solubility in water at 25 ° C., and more preferably an alcohol solvent. The reason why the formation of the complex is promoted by using alcohol as the solvent 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. A solvent may be used individually by 1 type, or may use 2 or more types together.

  As alcohol which shows the solubility with respect to water at 25 degreeC, C1-C8 can be mentioned and the alcohol which has one hydroxyl group in a molecule | numerator can be mentioned. Examples of such alcohols include linear alkyl alcohols, phenols, and those obtained by replacing hydrogen atoms of hydrocarbons having an ether bond in the molecule with hydroxyl groups. From the viewpoint of expressing a stronger polarity, an alcohol having two or more hydroxyl groups in the molecule is also preferably used. Moreover, you may use alcohol containing a sulfur atom, a phosphorus atom, a silicon atom, etc. according to the use of the copper containing particle | grains manufactured.

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

  Among the alcohols, methanol, ethanol, 1-propanol and 2-propanol having a very high solubility in water are preferable, 1-propanol and 2-propanol are more preferable, and 1-propanol is still more preferable.

(Dispersion medium)
The dispersion medium (solvent) used in the conductive composition according to the present invention is not particularly limited, and can be selected from organic solvents generally used for the production of conductive inks, conductive pastes and the like according to applications. For example, terpineol, isobornylcyclohexanol, dihydroterpineol, dihydroterpineol acetate and the like are preferable from the viewpoint of viscosity control.

(Other ingredients)
In addition to the components described above, the conductive composition in the present invention can further contain other components that are usually used in the technical field, if necessary. Examples of other components include thixotropic agents, plasticizers, dispersants, surfactants, inorganic binders, metal oxides, ceramics, and organometallic compounds.

(Method for producing conductive composition)
The manufacturing method of the electrically conductive composition in this invention is not specifically limited, The method normally used in the said technical field can be used.
For example, it can prepare by disperse | distributing the copper containing particle | grains in this invention, and the other component contained as needed in a dispersion medium. Dispersion treatment includes Ishikawa-type stirrer, rotation-revolution stirrer, ultra-thin high-speed rotary disperser, roll mill, ultrasonic disperser, media disperser such as bead mill, homomixer, cavitation stirrer such as Silverson stirrer, Ultema An opposing collision method such as Iser can be used. Moreover, you may use combining these methods suitably.

  The state of the conductive composition of the present invention is not particularly limited, and can be selected according to the application. For example, when the conductive composition is applied to the screen printing method, it is preferably a conductive paste having a viscosity of 0.1 to 30 Pa · s, more preferably 1 to 30 Pa · s at the temperature used. . When the conductive composition is applied to the inkjet printing method, it is preferably a conductive ink having a viscosity of 0.1 to 30 mPa · s at the temperature used, although it depends on the standard of the inkjet head to be used. More preferably, it is 20 mPa · s.

(Method for imparting conductive composition)
The method for forming the conductive composition-containing layer by applying the conductive composition on the substrate is not particularly limited as long as the conductive composition can be formed in any shape on any location on the substrate. Absent. Examples of such methods include inkjet methods, super inkjet methods, screen printing methods, transfer printing methods, offset printing methods, jet printing methods, dispenser methods, jet dispenser methods, needle dispenser methods, comma coating methods, slit coating methods, and die coating methods. , Gravure coating method, letterpress printing method, intaglio printing method, gravure printing method, soft lithographic method, dip pen lithographic method, particle deposition method, spray coating method, spin coating method, dip coating method, electrodeposition coating method, etc. Can do. Among them, at least selected from the group consisting of an inkjet method, a super inkjet method, a screen printing method, an offset printing method, a jet printing method, a dispenser method, a needle dispenser method, a comma coating method, a slit coating method, a die coating method, and a gravure coating method. One method is preferred. For example, the paste-like conductive composition may be applied on the substrate by a screen printing method, or the ink-like conductive composition may be applied on the substrate by an inkjet printing method.

(Characteristics of copper film)
The shape of the copper film formed on the substrate is not particularly limited and can be appropriately selected according to the purpose.
The thickness of the copper film is not particularly limited and can be appropriately selected according to the purpose. For example, it can be 0.2-50 micrometers, and it is preferable that it is 0.5-20 micrometers from a viewpoint of electroconductivity and connection reliability.

<Heat treatment process>
In the heat treatment step, the conductive composition is heat-treated in a reducing gas atmosphere at a temperature range of 250 ° C. or lower, preferably 200 ° C. or lower, more preferably 150 ° C. or lower to form a copper film.

  Examples of the substance that can be introduced as the reducing gas in the heat treatment step include formic acid and hydrogen, but are not particularly limited.

  An inert gas can be used in the atmosphere in the heat treatment step. Examples of the inert gas include nitrogen gas, argon gas, and helium gas.

  As described above, the conductive composition according to the present invention can be formed into a conductor at a relatively low temperature. Specifically, for example, the conductor can be formed at 250 ° C. or lower. Therefore, for example, it can be suitably used when a copper wiring is formed on a substrate having low heat resistance such as resin. The heat treatment step may be performed at a constant rate of temperature increase or irregularly. The heat treatment time is not particularly limited, and can be selected in consideration of the heat treatment temperature, the heat treatment atmosphere, the amount of copper-containing particles, and the like. The heat treatment time is preferably 10 to 120 minutes from the viewpoint of process management.

<Other processes>
The method for producing a copper film of the present invention may include other steps as necessary. Examples of other steps include a step of reducing copper oxide after the heat treatment step, a step of removing residual components by light baking after the heat treatment step, a step of applying a load after the heat treatment step, and the like.

  Since the board | substrate with a copper layer (electric conductor) obtained by the manufacturing method of the copper film of this invention can be manufactured by heat processing lower temperature than before, there is little damage to a board | substrate. Therefore, for example, it can be suitably used when a copper wiring is formed on a substrate having low heat resistance such as resin.

  In the method for converting the conductive composition of the present invention into a conductor, the heating step may be performed at a constant rate of temperature increase or irregularly. The time for 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 can be selected from heating with a hot plate, heating with an infrared heater, heating with a pulse laser, and the like if the temperature is raised to a predetermined temperature.

  Moreover, since the conductor (copper layer) in the present invention is a sintered product of a conductive material applied on the substrate, palladium used as an additive as compared with a conductor formed by a plating method or the like The amount of impurities is small, and the volume resistivity tends to be lowered.

  The copper film (conductor) formed by the present invention can be used for, for example, electrical wiring such as a laminated plate, a solar cell panel, a display, and a transistor, a heat dissipation film, a surface coating film, and a semiconductor package.

  EXAMPLES Hereinafter, although an Example is shown and demonstrated about this invention, this invention is not limited to these Examples at all.

<Example 1>
[1.1] Synthesis of Copper Nonanoate To synthesize fatty acid and copper salt compound (fatty acid copper), 91.5 g (0.94 mol) of copper hydroxide (Kanto Chemical Co., Ltd.) and 1-propanol (Kanto Chemical) 150 mL of a special grade) was added and stirred, and 370.9 g (2.34 mol) of nonanoic acid (Kanto Chemical Co., Inc., purity 90 mass% or more) was added thereto. The obtained mixture was heated and stirred at 90 ° C. for 30 minutes in a separable flask. The obtained solution was filtered while heated to remove undissolved substances. Thereafter, 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 mass%).

[1.2] Synthesis of copper-containing core particles 21.01 g (0.056 mol) of copper nonate (II) obtained above and copper (II) acetate anhydride (Kanto Chemical Co., Ltd., special grade) 33 g (0.024 mol) was put into a separable flask, 10 mL of 1-propanol and 32.1 g (0.32 mol) of hexylamine (Tokyo Chemical Industry Co., Ltd., purity 99% by mass) as an alkylamine were added to the oil bath. It was dissolved by heating and stirring at 80 ° C. After transferring to an ice bath and cooling to an internal temperature of 5 ° C., a solution obtained by dissolving 7.72 mL (0.16 mol) of hydrazine monohydrate (Kanto Chemical Co., Ltd., special grade) in 12 mL of 1-propanol Added to the copper solution and stirred in an ice bath. The molar ratio of copper: hexylamine is 1: 4. Subsequently, it heated and stirred at 90 degreeC in the oil bath. At that time, the reduction reaction accompanied with foaming progressed, and the reaction was completed within 10 minutes. The inner wall of the separable flask had a copper luster and the solution turned dark red. Centrifugation was performed at 4000 (rev / min) for 1 minute to obtain a solid. The step of further washing the solid with 15 mL of hexane was repeated three times to remove the acid residue, thereby obtaining a copper cake containing copper particles having copper luster.

[1.3] Preparation of conductive composition Obtained copper cake (copper-containing core particles, 60 parts by mass), terpineol (20 parts by mass) as a dispersion medium, and isobornylcyclohexanol (trade name: Telsolve) MTPH, Nippon Terpene Chemical Co., Ltd.) (20 parts by mass) was mixed to prepare a conductive composition.

[1.4] Conductivity The temperature rise rate is 15 in an atmosphere in which the conductive composition is applied onto a polyethylene naphthalate (PEN) film and the concentration of formic acid in nitrogen is 5% by volume as a reducing gas atmosphere. The copper film was formed by heating at 120 ° C. to 120 ° C. and holding for 60 minutes.

[Evaluation of low-temperature conductor]
The volume resistivity was calculated from the surface resistance value and the film thickness of the obtained copper film. The film thickness of the copper film was measured with a non-contact surface / layer cross-sectional shape measurement system (VertScan, Ryoka System Co., Ltd.).
From the above results, it was evaluated that the low temperature conductorization was “good” when the volume resistivity was 300 μΩ · cm or less, and the low temperature conductorization was “defective” when the volume resistivity exceeded 300 μΩ · cm.

  The result of measuring and calculating the volume resistivity as described above was 50 μΩ · cm, and a conductor (conductor) having a sufficiently low volume resistivity was formed. From the above, it was found that the copper-containing particles of the present invention can be made into a conductor at a low temperature of 120 ° C.

[Measurement of content of organic substance having amino group in copper-containing particles]
After drying the copper cake and removing hexane in the copper cake, it is heated at a temperature equal to or higher than the temperature at which the organic matter is thermally decomposed, and by comparing the mass before and after the heating, the organic substance having an amino group in the copper-containing particles When the content rate was measured, it was 3.5 mass%.

<Example 2>
Conducting was conducted in the same manner as in Example 1 except that the treatment was performed at 250 ° C. The result of measuring and calculating the volume resistivity was 30 μΩ · cm, and a conductor that was a copper film having a sufficiently low volume resistivity was formed. As mentioned above, it turned out that the copper containing particle | grains of this invention can be conductorized at low temperature.

<Comparative Example 1>
Conductorization was performed in the same manner as in Example 1 except that formic acid was not introduced and the treatment was performed at 120 ° C. in nitrogen. As a result of measuring and calculating the volume resistivity, conduction was not obtained. When no formic acid was introduced, organic substances could not be removed by heating at 120 ° C., and a conductor having a sufficiently low volume resistivity was not formed.

<Comparative example 2>
Conductorization was performed in the same manner as in Example 1 except that formic acid was not introduced and the treatment was performed at 250 ° C. in nitrogen. The result of measuring and calculating the volume resistivity was 60 μΩ · cm, and a conductor that was a copper film having a low volume resistivity was formed. However, the resistivity was higher than when formic acid was introduced.

Claims (8)

  Production of a copper film comprising a step of heat-treating a conductive composition comprising core particles containing copper, the surface of which is coated with an organic substance, and a dispersion medium at a temperature of 250 ° C. or lower in a reducing gas atmosphere Method.   The manufacturing method of the copper film of Claim 1 whose content rate of the organic substance in the core particle containing the copper by which at least one part of the surface was coat | covered with the said organic substance is 0.1-10.0 mass%.   The method for producing a copper film according to claim 1, wherein the organic substance is an alkylamine.   Core particles containing copper, the surface of which is coated with at least a part of the organic matter, are obtained by heating a mixture of a fatty acid and copper salt compound (fatty acid copper), a reducing compound and an alkylamine. It is a copper containing particle | grain, The manufacturing method of the copper film as described in any one of Claims 1-3.   The method for producing a copper film according to claim 4, wherein the fatty acid has 9 or less carbon atoms.   The method for producing a copper film according to claim 4 or 5, wherein the reducing compound includes at least one selected from the group consisting of hydrazine, a hydrazine derivative, hydroxylamine, and a hydroxylamine derivative.   The method for producing a copper film according to any one of claims 3 to 6, wherein the alkylamine has 7 or less carbon atoms.   The electrical conductor obtained by the manufacturing method of the copper film as described in any one of Claims 1-7.