JP5736244B2 - Method for producing metal fine particles - Google Patents

Description

  The present invention relates to a method for producing metal fine particles, and more particularly to a method for producing metal fine particles used for forming a predetermined film such as a metal wiring or a transparent conductive film by an ink jet method.

  In the manufacturing process of a semiconductor device, it is conventionally known to use a so-called inkjet method for forming a predetermined film such as a metal wiring film or a transparent conductive film. In this apparatus, an in-jet type coating apparatus is used, and a dispersion liquid in which metal fine particles are dispersed is directly applied to the surface of the substrate, and the applied dispersion liquid is dried and fired. By firing the dispersion, the dispersing agent such as an organic acid or amine that covers the surface of the metal fine particles is released, and the metal fine particles are sintered together, and the predetermined film is obtained. According to this, a lithography process, an etching process, etc. can be skipped, and there exists an advantage that an installation cost and a production cost can be reduced.

  As a method for producing the metal fine particles, for example, Patent Document 1 discloses that a gas evaporation method or a chemical reduction method is used. In the gas evaporation method, a metal raw material is housed in a tank, the metal raw material is evaporated under reduced pressure, and an organic solvent vapor containing a dispersant is introduced when the evaporated metal vapor is cooled and collected. Then, the surface of the metal is brought into contact with an organic solvent at the stage of grain growth to obtain a metal fine particle-containing liquid in which the obtained metal fine particles are singly and uniformly dispersed in a colloidal form in the organic solvent. In the chemical reduction method, a reducing agent as a dispersant is added to a solution obtained by dissolving an organometallic compound in a nonpolar solvent, and heated as necessary to obtain a metal fine particle-containing liquid in which metal fine particles are dispersed. obtain.

  Then, in order to improve the dispersion stability of the metal fine particles, at least one selected from alkylamines, carboxylic acid amides, and aminocarboxylates is added to and mixed with the metal fine particle-containing liquid thus obtained. . Next, a step of adding a low molecular weight polar solvent to precipitate the metal fine particles and allowing the supernatant liquid to flow out by decantation is repeated a plurality of times to remove the organic solvent. Thereby, metal fine particles having a particle size of 100 nm or less are recovered.

  By the way, in recent years, materials having low heat resistance such as resin and paper are used as a base material in addition to a glass substrate, and further performance improvement and productivity improvement of a semiconductor device are required. For this reason, it is required to apply the above dispersion liquid to a wide range of uses, and depending on the use of the dispersion liquid, further low-temperature firing is required.

  In order to achieve low-temperature baking, metal fine particles whose surfaces are covered with fatty acids are generated, a part of the fatty acids are substituted with amines having 1 to 7 carbon atoms, and the amines are replaced with amines having 8 to 20 carbon atoms. A method for further replacement is known from Patent Document 2, for example. Since the decomposition temperature of amines having 8 to 20 carbon atoms is lower than the decomposition temperature of fatty acids, the calcination temperature can be lowered, but in this way a part of fatty acids is substituted with amines having 8 to 20 carbon atoms. However, there are cases where sufficient low-temperature firing cannot be achieved, and further, the dispersion stability of the metal fine particles is lowered, and the metal fine particles are aggregated to cause sedimentation in the dispersion.

  Here, the firing temperature of the dispersion, that is, the temperature at which the dispersant covering the surface of the metal fine particles is detached from the surface of the metal fine particles is determined by a dispersant such as carboxylic acid (fatty acid) or amine covering the surface of the metal fine particles. Depends on the molecular weight. For this reason, in order to achieve further low-temperature firing, it is conceivable to cover the surface of the metal fine particles with a dispersant having a low molecular weight. However, for example, when producing fine metal particles by gas evaporation method, if a carboxylic acid having a low molecular weight is used as a dispersant, such a carboxylic acid has a high vapor pressure. As a result, the metal material is not evaporated and the metal fine particles cannot be stably generated.

  On the other hand, for example, when metal fine particles are produced by a chemical reduction method, if a dispersing agent having a small molecular weight is used, the dispersion stability of the metal fine particles is lowered, so that there is a problem that the metal fine particles cannot be produced stably. When such a dispersion liquid in which the dispersion stability of the metal fine particles is lowered is used as an ink to be applied by, for example, an ink jet method, it is difficult to stably discharge the ink from fine nozzles of the ink jet head.

JP 2002-121606 A JP 2008-150701 A

  In view of the above points, the present invention can produce metal fine particles that can stably produce metal fine particles and can be fired at a firing temperature according to the use of the dispersion when firing a dispersion in which the metal fine particles are dispersed in an isolated state. The problem is to provide a method.

  In order to solve the above problems, the method for producing metal fine particles of the present invention includes a first step of generating metal fine particles whose surface is covered with a first carboxylic acid having 6 to 18 carbon atoms having a linear or branched structure. And the metal fine particles generated in the first step are mixed with a second carboxylic acid having 4 to 22 carbon atoms having a linear or branched structure, and the first carboxylic acid covering the surface of the metal fine particles is mixed with the second carboxylic acid. The second step of substituting with a carboxylic acid, and the metal fine particles whose surface is covered with the second carboxylic acid are mixed with a primary amine having 4 to 22 carbon atoms having a linear or branched structure, and the surface is the second And a third step of obtaining metal fine particles covered with the carboxylic acid and the primary amine.

  According to the present invention, since the first carboxylic acid having 6 to 18 carbon atoms suitable for the production of metal fine particles in the first step is used as a dispersant, high dispersion stability can be obtained when the metal fine particles are produced. It can be generated stably. Furthermore, by mixing the metal fine particles thus generated with the second carboxylic acid, the first carboxylic acid covering the surface of the metal fine particles is replaced with the second carboxylic acid. Furthermore, by mixing the metal fine particles whose surface is covered with the second carboxylic acid with the primary amine, the surface of the metal fine particles is further covered with the primary amine, thereby improving the dispersion stability of the metal fine particles. be able to. Therefore, when a dispersion of metal fine particles is prepared, if a second carboxylic acid suitable for the application is selected, a firing temperature corresponding to the use of the dispersion when the dispersion is applied to the substrate and fired. Can be fired. In the present invention, the metal fine particles mean those having a particle size of 100 nm or less (typical particle size is 1 nm to 10 nm). In the present invention, the metal fine particle dispersion includes metal fine particle ink and metal fine particle paste.

  In the present invention, the first step contains a metal raw material, a solvent containing imine obtained by dehydrating condensation of the first carboxylic acid, and the first amine and ketone in a tank, The metal raw material is heated and evaporated below, and the evaporated material is collected and brought into contact with the solvent to disperse the metal fine particles whose surface is covered with the first carboxylic acid and the first amine. It is more desirable to have a step of obtaining a liquid containing fine metal particles.

As described above, when the imine is used in the first step, the imine contacts the surface of the metal fine particles and hydrolyzes to return to the first amine, and the first amine coats the surface of the metal fine particles. As a result, the entire surface of the generated metal fine particles is covered with the first carboxylic acid and the first amine. In the second step, the first carboxylic acid is replaced with a second carboxylic acid different from the first carboxylic acid, and in the third step, the first amine is different from the first amine. If substituted with a primary amine, the entire surface of the metal fine particles is covered with the second carboxylic acid and the primary amine. As a result, the metal fine particles of the present invention are further highly dispersible, so that the dispersion stability of the metal fine particles is improved, and aggregation of the metal fine particles in the dispersion can be reliably prevented.

  In the present invention, as the first carboxylic acid, hexanoic acid, 2-methylheptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, myristic acid, palmitic acid, 2- It is preferable to use at least one selected from hexyldecanoic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and isostearic acid, and as the second carboxylic acid, butanoic acid, pentanoic acid, hexanoic acid, 2 -Methylheptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, myristic acid, palmitic acid, 2-hexyldecanoic acid, stearic acid, oleic acid, linoleic acid, linolenic acid At least selected from isostearic acid, nonadecanoic acid, arachidic acid, behenic acid One is preferably used.

  In the present invention, it is preferable to use at least one selected from butylamine, pentylamine, hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, dodecylamine, tetradecylamine and oleylamine as the primary amine. As the first amine, it is preferable to use at least one selected from butylamine, pentylamine, hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, dodecylamine, tetradecylamine and oleylamine.

  The metal used in the present invention is at least one metal selected from Ag, Au, Ni, Pd, Rh, Ru, In, Sn, Cu and Pt, or an alloy composed of at least two of these metals. It can be appropriately selected depending on the purpose and application.

The electron micrograph of Au microparticles | fine-particles obtained by embodiment of this invention. The graph which shows the calcination temperature and specific resistance of the metal film obtained by baking the metal microparticle dispersion liquid of this invention.

  Hereinafter, the manufacturing method of the metal microparticle of embodiment of this invention is demonstrated. First, in the first step, metal fine particles are produced by an evaporation method using high-frequency induction heating under a pressure of 10 Pa or less. In this first step, the metal carboxylic acid is brought into contact with the metal fine particles in the production process by evaporating the metal raw material in the tank, and then cooled and collected, so that the surface of the metal fine particles becomes the first carboxylic acid. A product liquid of metal fine particles covered with acid is obtained. A polar solvent having a low molecular weight such as acetone is added to the resulting fine metal particle production solution, stirred and allowed to settle to precipitate the fine metal particles, and then the supernatant is removed. In this way, washing of the metal fine particles using the polar solvent is repeated to obtain metal fine particles whose surface is covered with the first carboxylic acid.

  Here, as the first carboxylic acid, one suitable for stably generating metal fine particles can be used. For example, hexanoic acid, 2-methylheptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, myristic acid, palmitic acid, 2-hexyldecanoic acid, stearic acid, oleic acid It is preferable to use at least one selected from linoleic acid, linolenic acid, and isostearic acid.

  Examples of the metal raw material include at least one metal selected from Ag, Au, Ni, Pd, Rh, Ru, In, Sn, Cu, and Pt, or an alloy composed of at least two of these metals. It can select suitably according to a use. For example, Au can be selected for plating, and Ag can be selected for wiring.

  In the first step, the imine obtained by dehydrating and condensing the first amine and the ketone in advance was accommodated in the tank, and the imine was brought into contact with the fine metal particles in the generation process in the tank. Thereafter, it is more preferable to obtain a product liquid of metal fine particles whose surface is covered with the first carboxylic acid and the first amine by collecting by cooling. The imine hydrolyzes back to the first amine when coming into contact with the surface of the metal fine particles, and the first amine covers the surface of the metal fine particles.

  Examples of the first amine used as a raw material for obtaining imine include hexylamine having 6 carbon atoms, octylamine having 8 carbon atoms, 2-ethylhexylamine, nonylamine having 9 carbon atoms, decylamine having 10 carbon atoms, and 12 carbon atoms. It is preferable to use one or more selected from dodecylamine, tetradecylamine having 14 carbon atoms, and oleylamine having 18 carbon atoms. Although it does not specifically limit as a ketone for making it react with a 1st amine and obtaining imine, Acetone, methyl ethyl ketone, methyl propyl ketone, etc. can be used preferably.

  In the second step, the metal fine particles obtained in the first step are mixed with the second carboxylic acid, and the first carboxylic acid covering the surface of the metal fine particles is replaced with the second carboxylic acid. Here, as the second carboxylic acid, one that is suitable for the use of the metal fine particle dispersion and can be removed at a firing temperature corresponding to the use can be used. For example, butanoic acid, pentanoic acid, hexanoic acid, 2-methylheptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, myristic acid, palmitic acid, 2-hexyldecanoic acid Preferably, at least one selected from stearic acid, oleic acid, linoleic acid, linolenic acid, isostearic acid, nonadecanoic acid, arachidic acid and behenic acid is used. For example, it is preferable to use octanoic acid in applications where the thermal history allowed for the substrate to which the metal fine particle dispersion is applied is 200 ° C. or less, and for the substrate to which the metal fine particle dispersion is applied. For applications where the acceptable thermal history may be 230 ° C. or higher, it is preferable to use oleic acid.

  In the third step, the metal fine particles substituted with the carboxylic acid in the second step are washed using the above method, and the washed metal fine particles are further mixed with a primary amine so that the surface of the metal fine particles is the 1 Metal fine particles covered with secondary amine are obtained. When the surface of the metal fine particles obtained in the first step is covered with the first amine, the first amine covering the surface of the metal fine particles in the third step is the primary. Substituted with amine. As the primary amine, those having 4 to 22 carbon atoms are preferably used. For example, butylamine having 4 carbon atoms, pentylamine having 5 carbon atoms, hexylamine having 6 carbon atoms, octylamine having 8 carbon atoms, nonylamine having 9 carbon atoms, decylamine having 10 carbon atoms, dodecylamine having 12 carbon atoms, carbon number It is preferable to use at least one selected from 14 tetradecylamines and 18 oleylamines.

  A dispersion of metal fine particles is prepared by dispersing the metal fine particles obtained in the third step in a solvent. As the solvent for adjusting the dispersion, an organic solvent having a weak polarity and having 6 to 18 carbon atoms in the main chain is preferably used. For example, hexane, heptane, octane, decane, undecane, Long chain hydrocarbons such as dodecane, tridecane, tetradecane; cyclic hydrocarbons such as cyclohexane, cycloheptane, cyclooctane, cyclododecene; aromatic hydrocarbons such as benzene, xylene, trimethylbenzene, dodecylbenzene; and hexanol, Alcohols such as heptanol, octanol, decanol, cyclohexanol, and terpineol can be used alone or in admixture.

  Thereafter, Au fine particles whose surfaces are covered with oleic acid which is the first carboxylic acid are obtained, oleic acid which covers the surfaces of the obtained Au fine particles is substituted with octanoic acid which is the second carboxylic acid, and further 1 The method for producing metal fine particles according to the embodiment of the present invention will be described by taking as an example the case where the surface of Au fine particles is covered with octylamine which is a secondary amine.

  When producing Au fine particles by an evaporation method using high-frequency induction heating under a pressure of 10 Pa or less, 60 g of oleic acid was brought into contact with 250 g of Au fine particles in the generation process in the tank, and then cooled and collected to obtain a surface. A production solution of Au fine particles covered with oleic acid is obtained. The product liquid is taken out from the tank, acetone is added to the taken-out product liquid to precipitate Au fine particles, and the supernatant liquid is discharged by decantation or the like (hereinafter, this operation is referred to as “cleaning step”). At this time, 10 volumes of acetone are added to 1 volume of the product liquid. By repeating this washing step a plurality of times and removing the solvent by drying at room temperature, Au fine particles whose surface is covered with oleic acid are obtained.

  Au fine particles whose surface is covered with oleic acid, which is the first carboxylic acid, are mixed with 150 g of octanoic acid, which is the second carboxylic acid, and stirred. Thereby, oleic acid covering the surface of the Au fine particles is replaced with octanoic acid, and an Au fine particle-containing liquid containing Au fine particles whose surface is covered with octanoic acid is obtained. The above washing step performed by adding 10 volumes of acetone to 1 volume of the obtained Au fine particle-containing liquid is repeated a plurality of times, and the solvent is removed by drying at room temperature, so that the octane surface is the second carboxylic acid. Au fine particles covered with acid are obtained.

  The Au fine particles substituted with carboxylic acid in this way are mixed with 50 g of primary amine octylamine and stirred. Thereby, an Au fine particle-containing liquid containing Au fine particles whose surface is further covered with octylamine which is a primary amine is obtained. The above washing step performed by adding acetone to the obtained Au fine particle-containing liquid is repeated a plurality of times, and the solvent is removed by drying at room temperature, whereby the surface is octanoic acid and the first grade which are the second carboxylic acids. Au fine particles covered with octylamine, which is an amine, are obtained.

  150 g of cyclododecene for dispersion is added to Au fine particles whose surface is covered with octanoic acid as the second carboxylic acid and octylamine as the primary amine to obtain an Au fine particle dispersion. The obtained Au fine particle dispersion is heated and concentrated to a predetermined concentration (for example, 50% by weight when used as an Au fine particle ink and 80% by weight when used as an Au fine particle paste). Then, this concentrated Au fine particle dispersion is directly applied to the surface of a glass substrate as a base material by a spin coating method, and this applied dispersion is dried, and in the atmosphere, for example, at a temperature of 150 ° C. to 230 ° C. at 90 ° C. An Au film is formed by partial firing. As the substrate, in addition to the glass substrate, for example, polyimide, PEN film, polycarbonate, PET film, or a substrate in which a TFT (thin film transistor) is formed on glass can be used. In addition to the spin coating method, an inkjet method can be used as a method for applying the dispersion.

  According to the embodiment described above, Au fine particles whose surface is covered with oleic acid, which is the first carboxylic acid, are generated by a vacuum evaporation method. At this time, since oleic acid having 18 carbon atoms (relatively large molecular weight) suitable for the production of Au fine particles is used as a dispersing agent, high dispersion stability is obtained when Au fine particles are produced, and Au fine particles are stably produced. be able to. By mixing the generated Au fine particles with the second carboxylic acid octanoic acid, the first carboxylic acid oleic acid covering the surface of the Au fine particles is replaced with the second carboxylic acid octanoic acid. Is done. Further, by mixing Au fine particles whose surface is covered with octanoic acid, which is the second carboxylic acid, with the octylamine, which is the primary amine, the surface of the Au fine particles is also covered with octylamine, which is the primary amine. Therefore, the dispersion stability of Au fine particles can be further improved. By covering the surface of the Au fine particles with octanoic acid, which is the second carboxylic acid suitable for the use (low temperature firing) of the Au fine particle dispersion, and octylamine, which is the primary amine, it is dispersed at the firing temperature according to the use. The liquid can be fired. Therefore, according to the present embodiment, Au fine particles can be stably generated, and Au fine particles that can be fired at a firing temperature corresponding to the use of the dispersion liquid can be produced when the dispersion of Au fine particles is fired.

  Next, in order to confirm the effect of the above embodiment, the following experiment (Experiment 1) was performed. In this experiment 1, Au fine particles whose surface is covered with oleic acid which is the first carboxylic acid are generated, and oleic acid which is the first carboxylic acid covering the surface of the generated Au fine particles is converted with the second carboxylic acid. Au fine particles were obtained by substituting with certain octanoic acid and covered with octylamine whose surface was a primary amine (Invention 1). When a TEM photograph of the product 1 of the present invention was taken, it was confirmed that the Au fine particles were dispersed with high dispersibility without condensing as shown in FIG. This shows that Au fine particles can be generated stably.

  Inventive product 1 was dispersed in cyclododecene in an isolated state to obtain an Au fine particle dispersion. The obtained heating was concentrated to a concentration of 50% by weight, and the concentrated Au fine particle dispersion was applied to the surface of the substrate by a spin coating method, dried, and then heated at 150 ° C. by a hot plate in the air atmosphere. By baking for 90 minutes, an Au film was formed. Only the firing temperature was changed to 180 ° C., 200 ° C., and 230 ° C., and the others were formed under the same conditions. Thus, the film thickness of the Au film formed by changing the firing temperature was 0.1 to 0.3 μm, and specific resistance values as shown in Table 1 were obtained. According to this, the Au fine particle surface is covered with octanoic acid which is the second carboxylic acid suitable for the use of the dispersion and octylamine which is the primary amine, and the firing temperature of 150 to 230 ° C. according to this use. As a result, it was found that a low-resistance Au film having a specific resistance value of 20 μΩ · cm or less can be obtained (see FIG. 2).

  Next, another experiment (Experiment 2) was performed in the same manner as Experiment 1 above. In this experiment 2, Au fine particles whose surface is covered with dodecanoic acid having 12 carbon atoms, which is the first carboxylic acid, are generated, and dodecanoic acid, which is the first carboxylic acid covering the surface of the generated Au fine particles, is secondly added. The surface of the Au fine particles was covered with dodecylamine which is a primary amine. Then, similarly to Experiment 1, an Au fine particle dispersion in which the obtained Au fine particles were dispersed in cyclododecene in an isolated state was obtained, and an Au film was formed using the obtained dispersion. In this experiment 2, the firing temperature was changed to 200 ° C., 230 ° C., 250 ° C., 270 ° C., 280 ° C., 300 ° C., 350 ° C., and the firing time was 90 minutes. Thus, the film thickness of the Au film formed by changing the firing temperature was 0.1 to 0.3 μm, and specific resistance values as shown in Table 2 were obtained. According to this, the Au fine particle surface is covered with oleic acid, which is the second carboxylic acid suitable for the use of the dispersion, and dodecylamine, which is the primary amine, so that the firing temperature is 230 to 350 ° C. according to this use. As a result, it was found that an Au film having a specific resistance value of 20 μΩ · cm or less was obtained (see FIG. 2).

  Next, another experiment (Experiment 3) was performed in the same manner as Experiment 1 and Experiment 2 described above. In this experiment 3, Au fine particles whose surface is covered with dodecanoic acid having 12 carbon atoms, which is the first carboxylic acid, are generated, and dodecanoic acid, which is the first carboxylic acid covering the surface of the generated Au fine particles, is secondly added. The surface of the Au fine particles was covered with oleylamine which is a primary amine. Then, in the same manner as in Experiment 1, an Au film was formed using an Au fine particle dispersion in which Au fine particles were dispersed in cyclododecene in an isolated state. In Experiment 3, the firing temperature was changed to 250 ° C., 270 ° C., 280 ° C., 300 ° C., and 350 ° C., and the firing time was 90 minutes. The film thickness of the Au film thus formed by changing the firing temperature was 0.1 to 0.3 μm, and specific resistance values as shown in Table 3 were obtained. According to this, by covering the Au fine particle surface with oleic acid which is the first carboxylic acid suitable for the use of the dispersion and oleylamine which is the primary amine, at a firing temperature of 300 to 350 ° C. according to this use. It was found that an Au film having a specific resistance value of 20 μΩ · cm or less can be obtained by firing (see FIG. 2).

  Hereinafter, olein which is the first carboxylic acid covering the surface of the Au fine particles obtained by obtaining Au fine particles whose surfaces are covered with oleic acid which is the first carboxylic acid and dodecylamine which is the first amine In the case where the acid is substituted with octanoic acid, which is the second carboxylic acid, and dodecylamine, which is the first amine covering the surface of the Au fine particles, is substituted with octylamine, which is the primary amine. The manufacturing method of the metal microparticles of the embodiment will be described.

  Prior to the first step, imine obtained by reacting acetone with dodecylamine, which is the first amine, and dehydrating and condensing is stored in a tank. In the first step, when producing Au fine particles by an evaporation method using high frequency induction heating under a pressure of 10 Pa or less, 60 g of oleic acid and 150 g of the above imine were brought into contact with 250 g of Au fine particles in the production process. Thereafter, by collecting by cooling, an Au fine particle-containing liquid whose surface is covered with oleic acid as the first carboxylic acid and dodecylamine as the first amine is obtained. At this time, the imine is hydrolyzed when it comes into contact with the surface of the Au fine particles and returns to the first amine, dodecylamine, so that the first amine, dodecylamine, covers the surface of the Au fine particles. The Au fine particle-containing liquid is taken out from the tank, acetone is added to the taken out product solution to precipitate the Au fine particles, and the supernatant liquid is discharged by decantation or the like to wash the Au fine particles. At this time, 10 volumes of acetone are added to 1 volume of the product liquid. By repeating such cleaning of the Au fine particles a plurality of times and removing the solvent by drying at room temperature, the Au fine particles whose surface is covered with oleic acid as the first carboxylic acid and dodecylamine as the first amine are covered. Get.

  The Au fine particles thus obtained are mixed with 150 g of octanoic acid as the second carboxylic acid and stirred. As a result, oleic acid, which is the first carboxylic acid covering the surface of the Au fine particles, is replaced with octanoic acid, which is the second carboxylic acid, and the surface is octanoic acid, which is the second carboxylic acid, and the first amine. An Au fine particle-containing liquid containing Au fine particles covered with dodecylamine is obtained. The above washing performed by adding 10 volumes of acetone to 1 volume of the obtained Au fine particle-containing liquid is repeated a plurality of times, and the solvent is removed by drying at room temperature, so that the surface is octanoic acid, which is the second carboxylic acid. And Au fine particles covered with the first amine, dodecylamine, are obtained.

  The Au fine particles substituted with carboxylic acid in this way are mixed with 50 g of primary amine octylamine and stirred. As a result, dodecylamine, which is the first amine covering the surface of the Au fine particles, is replaced with octylamine, which is the primary amine, and the surface is covered with octanoic acid, which is the second carboxylic acid, and octylamine, which is the primary amine. An Au fine particle-containing liquid containing broken Au fine particles is obtained. The above washing performed by adding 10 volumes of acetone to 1 volume of the obtained Au fine particle-containing liquid is repeated a plurality of times, and the solvent is removed by drying at room temperature, so that the surface is octanoic acid, which is the second carboxylic acid. And Au fine particles covered with octylamine which is a primary amine are obtained.

  150 g of cyclododecene for dispersing Au fine particles obtained by the above method in an isolated state is added to obtain an Au fine particle dispersion. The obtained Au fine particle dispersion is heated and concentrated to a predetermined concentration (for example, 50% by weight when used as an Au fine particle ink and 80% by weight when used as an Au fine particle paste). Then, the concentrated Au fine particle dispersion is directly applied to the surface of the glass substrate by spin coating, and the applied dispersion is dried and baked in the atmosphere at a temperature of 200 ° C. for 90 minutes to form an Au film. The It was confirmed that the relationship between the firing temperature and the specific resistance of the Au film thus obtained was substantially the same as that of the Au film obtained in Experiment 1. As the base material, in addition to the glass substrate, for example, polyimide or a material in which a TFT (thin film transistor) is formed on glass can be used. In addition to the spin coating method, an inkjet method can be used as a method for applying the dispersion.

  According to the other embodiments described above, Au fine particles whose surfaces are covered with oleic acid as the first carboxylic acid and dodecylamine as the first amine are generated by vacuum evaporation. At this time, since the carboxylic acid having 18 carbon atoms, which is the first carboxylic acid suitable for the production of Au fine particles, and dodecylamine having 12 carbon atoms, which is the first amine, are used as the dispersing agent, a high dispersion is achieved when the Au fine particles are produced. Stability is obtained, and Au fine particles can be generated stably. The oleic acid that is the first carboxylic acid that covers the surface of the Au fine particles thus generated is replaced with octanoic acid that is the second carboxylic acid, and further, dodecylamine that is the first amine that covers the surface of the Au fine particles. By substituting octylamine which is a primary amine, Au fine particles whose surfaces are covered with octanoic acid and octylamine are covered. Thus, by covering the surface of the Au fine particles with octanoic acid which is the second carboxylic acid and primary amine which is suitable for the use (low temperature firing) of the Au fine particle dispersion, firing according to the use is performed. The dispersion can be fired at temperature. Therefore, according to the present embodiment, Au fine particles can be stably generated, and Au fine particles that can be fired at a firing temperature corresponding to the use of the dispersion liquid can be produced when the dispersion of Au fine particles is fired.

Moreover, in this embodiment, when producing | generating Au microparticles | fine-particles by a vacuum evaporation method, it does not contain dodecylamine which is a 1st amine in a tank, but makes a ketone and dodecylamine which is a 1st amine react. The imine dehydrated and condensed was accommodated, and the imine was brought into contact with the Au fine particles in the production process. At this time, the imine is hydrolyzed on the surface of the Au fine particles in the production process to return to the first amine, dodecylamine, and the first amine, dodecylamine, firmly covers the surface of the Au fine particles. As a result, the dispersion stability of the Au fine particles can be further improved. Thus, when the surface of the Au fine particles is covered with the first amine via the imine, the dispersion stability of the Au fine particles remains high even after the first amine is replaced with the primary amine in the subsequent step. .

Claims (4)

The tank contains a metal raw material and a solvent containing an imine obtained by dehydration condensation by reacting a first carboxylic acid having 6 to 18 carbon atoms having a linear or branched structure and a first amine with a ketone. Then, the metal raw material is heated and evaporated under reduced pressure, and the evaporated fine material is collected and brought into contact with the solvent, whereby the surface is covered with the first carboxylic acid and the first amine. A first step of generating
The metal fine particles generated in the first step are mixed with a second carboxylic acid having 4 to 22 carbon atoms having a linear or branched structure different from the first carboxylic acid to cover the surface of the metal fine particles. A second step of replacing one carboxylic acid with a second carboxylic acid;
The metal fine particles whose surface is covered with the second carboxylic acid are mixed with a primary amine having 4 to 22 carbon atoms having a linear or branched structure different from the first amine, and the surface has the second carboxylic acid. a third step of obtaining a fine metal particles covered with acid and the primary amine, only including,
The method for producing fine metal particles, wherein the first amine is at least one selected from hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, dodecylamine, tetradecylamine, and oleylamine . Before SL first carboxylic acid, hexanoic acid, 2-methyl heptanoic acid, Kishirudekan octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, myristic acid, palmitic acid, the 2- acid, stearic acid, oleic acid, linoleic acid, linolenic acid, is at least one selected or isostearic acid, et al.,
The second carboxylic acid is butanoic acid, pentanoic acid, hexanoic acid, 2-methylheptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, myristic acid, palmitic acid , Kishirudekan acid to 2-, stearic acid, No placement claim 1 Symbol for oleic acid, linoleic acid, linolenic acid, isostearic acid, nonadecanoic acid, arachidic acid, wherein the at least one selected from behenic acid A method for producing fine metal particles. The primary amine, the hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, claim 1 or claim 2, wherein the dodecylamine is at least one selected from tetradecyl amine and oleylamine The manufacturing method of the metal microparticle of description. The metal raw material is at least one metal selected from Ag, Au, Ni, Pd, Rh, Ru, In, Sn, Cu and Pt, or an alloy composed of at least two of these metals. The method for producing fine metal particles according to any one of claims 1 to 3 .