JP2012028342A - Silver paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide silver paste containing metal silver and a manufacturing method thereof.SOLUTION: Silver paste includes a heat treatment product of a mixture of silver β-ketocarboxylate represented by the following formula (1) and a polar solvent. In the heat treatment product, metal silver formed by decomposition of the silver β-ketocarboxylate is included.

Description

  The present invention relates to a silver paste containing metallic silver obtained from silver β-ketocarboxylate and a method for producing the same.

  Metallic silver is widely used as a wiring material, a printing plate material, and a highly conductive material because of its excellent conductivity. When used as the wiring material, generally, a paste in which metallic silver is dispersed in a dispersion solvent is used, a pattern is formed on a wiring substrate, and the metallic silver in the paste is sintered to form a wiring. At this time, when metal silver is used as the conductive material, it is necessary to use finer metal silver particles in order to reduce the resistance of the formed film. It is known that such fine metallic silver particles are likely to contact each other and aggregate. Therefore, in order to prevent aggregation of fine metallic silver particles, the paste needs to contain a dispersant (see, for example, Patent Document 1). However, when metallic silver particles are sintered using the paste containing the dispersant, impurities derived from the dispersant remain in the obtained wiring. It is desirable to remove such impurities as much as possible in order to increase the conductivity in the obtained wiring.

  As a general method for producing metallic silver, for example, a method of heating silver oxide which is an inorganic substance in the presence of a reducing agent can be mentioned. Specifically, for example, particulate silver oxide is dispersed in a binder, a reducing agent is added thereto to prepare a paste, and the paste is applied to a substrate or the like and heated. Thus, by heating in the presence of a reducing agent, the silver oxide is reduced, the metallic silver produced by the reduction is fused together, and a film containing metallic silver is formed.

  However, when silver oxide is used as a material for forming metallic silver, there is a problem that a reducing agent is necessary and the processing temperature is as high as about 300 ° C. Further, when metallic silver is used as the conductive material, it is necessary to use finer silver oxide particles in order to reduce the resistance of the formed film.

  On the other hand, in recent years, a method for forming metallic silver using organic acid silver instead of the inorganic material as described above has also been reported. As the organic acid silver, for example, a method of sintering a silver salt of a long-chain carboxylic acid in a nitrogen atmosphere has been reported (Patent Document 2), and silver stearate and silver α-ketocarboxylate are new. It has been reported as a material for forming metallic silver (Patent Documents 3 to 4).

Japanese Patent Laid-Open No. 2005-60824 JP 2005-298922 A Japanese Patent Laid-Open No. 10-183207 JP 2004-315374 A

  Then, this invention is a silver paste containing metallic silver, Comprising: It aims at providing the silver paste which can be manufactured by low-temperature heating, and its manufacturing method.

To solve the above problem,
The present invention includes a heat-treated product of a mixture containing a silver β-ketocarboxylate represented by the following formula (1) and a polar solvent, and the silver β-ketocarboxylate is decomposed in the heat-treated product. A silver paste containing metallic silver is provided.

前記式（１）において、Ｒは、直鎖、分枝もしくは環状の飽和もしくは不飽和Ｃ₁〜Ｃ₂₀脂肪族炭化水素基、Ｒ¹−ＣＹ₂−、ＣＹ₃−、Ｒ¹−ＣＨＹ−、Ｒ²Ｏ−、アリール基、１個もしくは複数の置換基で置換されたアリール基、ヘテロアリール基、１個もしくは複数の置換基で置換されたヘテロアリール基、Ｒ⁵Ｒ⁴Ｎ−、水酸基、アミノ基、または、（Ｒ³Ｏ）₂ＣＹ−である。
ただし、前記式中、
Ｙは、同一であるかまたは異なり、それぞれフッ素原子、塩素原子、臭素原子または水素原子であり、
Ｒ¹は直鎖、分枝または環状の飽和または不飽和Ｃ₁〜Ｃ₁₉脂肪族炭化水素基、アリール基、１個もしくは複数の置換基で置換されたアリール基、ヘテロアリール基、または１個もしくは複数の置換基で置換されたヘテロアリール基であり、
Ｒ²は直鎖、分枝または環状の飽和または不飽和Ｃ₁〜Ｃ₂₀脂肪族炭化水素基であり、
Ｒ³は直鎖、分枝または環状の飽和または不飽和Ｃ₁〜Ｃ₁₆脂肪族炭化水素基であり、
Ｒ⁴およびＲ⁵は、同一であるかまたは異なり、それぞれ直鎖、分枝または環状の飽和または不飽和Ｃ₁〜Ｃ₁₈脂肪族炭化水素基である。
前記式（１）において、Ｘは、同一であるかまたは異なり、それぞれ水素原子、直鎖、分枝または環状の飽和または不飽和Ｃ₁〜Ｃ₂₀脂肪族炭化水素基、Ｒ⁶Ｏ−、Ｒ⁶Ｓ−、Ｒ⁶−ＣＯ−、Ｒ⁶−ＣＯ−Ｏ−、ハロゲン原子、アリール基、１個もしくは複数の置換基で置換されたアリール基、ヘテロアリール基、１個もしくは複数の置換基で置換されたヘテロアリール基、アラルキル基、１個もしくは複数の置換基で置換されたアラルキル基、シアノ基、Ｎ−フタロイル−３−アミノプロピル基、２−エトキシビニル基である。
ただし、前記式中、
Ｒ⁶は直鎖、分枝もしくは環状の飽和もしくは不飽和Ｃ₁〜Ｃ₁₀脂肪族炭化水素基、アリール基、１個もしくは複数の置換基で置換されたアリール基、ヘテロアリール基、１個もしくは複数の置換基で置換されたヘテロアリール基である。

In the formula (1), R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, R ¹ -CY ₂ —, CY ₃ —, R ¹ —CHY—, R ² O—, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, a heteroaryl group substituted with one or more substituents, R ⁵ R ⁴ N—, a hydroxyl group, It is an amino group or (R ³ O) ₂ CY-.
However, in the above formula,
Y is the same or different and each is a fluorine atom, a chlorine atom, a bromine atom or a hydrogen atom;
R ¹ is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₉ aliphatic hydrocarbon group, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, or one Or a heteroaryl group substituted with a plurality of substituents,
R ² is a linear, branched or cyclic saturated or unsaturated C ₁ -C ₂₀ aliphatic hydrocarbon group;
R ³ is a linear, branched or cyclic saturated or unsaturated C ₁ -C ₁₆ aliphatic hydrocarbon group;
R ⁴ and R ⁵ are the same or different and are each a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₈ aliphatic hydrocarbon group.
In the formula (1), X is the same or different and each represents a hydrogen atom, a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, R ⁶ O—, R ⁶ S-, R ⁶ —CO—, R ⁶ —CO—O—, a halogen atom, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, one or more substituents A substituted heteroaryl group, an aralkyl group, an aralkyl group substituted with one or more substituents, a cyano group, an N-phthaloyl-3-aminopropyl group, and a 2-ethoxyvinyl group.
However, in the above formula,
R ⁶ represents a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₀ aliphatic hydrocarbon group, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, one or A heteroaryl group substituted with a plurality of substituents.

In the silver paste of the present invention, the polar solvent is preferably one or more selected from the group consisting of dodecylamine, lauryl alcohol, n-octanol, N-methylpyrrolidone, dimethylformamide, and ethylene glycol.
In the silver paste of the present invention, silver β-ketocarboxylate represented by the formula (1) is silver isobutyryl acetate, silver benzoyl acetate, silver acetoacetate, silver propionyl acetate, silver α-methylacetoacetate and silver α-ethylacetoacetate. It is preferably 1 or more selected from the group consisting of

  Since the silver paste of the present invention is obtained from the silver β-ketocarboxylate represented by the formula (1), there is an advantage that a silver paste containing metallic silver can be produced even by low-temperature heating. In addition, since the silver paste of the present invention can be produced without using a reducing agent or the like, there are few impurities contained in the silver paste, and therefore there is an advantage that a side reaction is unlikely to occur when the silver paste is fired. is there.

FIG. 1 is a graph showing the results of thermogravimetric analysis of silver isobutyryl acetate in Reference Example 1. FIG. 2 is a graph showing the results of thermogravimetric analysis of silver acetoacetate in Reference Example 2. FIG. 3 is a graph showing the results of thermogravimetric analysis of silver propionyl acetate in Reference Example 3. FIG. 4 is a graph showing measurement results of thermogravimetric analysis of silver benzoyl acetate in Reference Example 4. FIG. 5 is a graph showing measurement results of thermogravimetric analysis of silver α-methylacetoacetate in Reference Example 5. FIG. 6 is a graph showing the results of thermogravimetric analysis of silver α-ethylacetoacetate in Reference Example 6.

  In the production method of the present invention, the heating is preferably performed at a temperature of 60 ° C. or lower than the decomposition temperature of the silver β-ketocarboxylate.

  In the production method of the present invention, the heating is preferably performed under normal pressure conditions.

  In the production method of the present invention, the heating may be performed under pressurized conditions.

  In the production method of the present invention, the polar solvent is a heterocycle, an alkyl-substituted heterocycle, water, -COOH, -SH, -NH2, -OH, -COO-, -CON (-)-, -CONH. Alkane, alkene, alkyne, aromatic hydrocarbon, alkyl containing one or more selected from the group consisting of-, -CONH2, -S-, -SO-, -SO2-, -NH- and -N (-)- Preference is given to one or more polar solvents selected from the group consisting of substituted aromatic hydrocarbons, heterocycles and alkyl-substituted heterocycles.

In the production method of the present invention, in the formula (1), R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, an aryl group, or one or more a substituted aryl group substituted group, X is, which are identical or different, are each a hydrogen atom or a linear, saturated or unsaturated C ₁ branched or cyclic -C ₂₀ aliphatic hydrocarbon radical, Is preferred.

  In the production method of the present invention, the silver β-ketocarboxylate represented by the formula (1) is silver isobutyryl acetate, silver benzoyl acetate, silver acetoacetate, silver propionyl acetate, α-methyl acetoacetate silver and α-ethyl acetoacetate silver. It is preferably 1 or more selected from the group consisting of

  In the manufacturing method of this invention, it is preferable that the metallic silver contained in the said silver paste contains metallic silver of the particle size of the range of 3 nm-500 nm. When the metallic silver contained in the silver paste contains metallic silver having a particle diameter in the range of 3 nm to 20 nm, the mixture preferably further contains a dispersant in the production method of the present invention. The reason why the dispersant is included is to suppress aggregation of metallic silver having a particle diameter in the range of 3 nm to 20 nm.

  In the production method of the present invention, the content of silver β-ketocarboxylate represented by the formula (1) in the mixture is preferably 0.01 mol / L to 10 mol / L.

  The silver paste of the present invention is preferably formed by the production method of the present invention.

  The method for firing metallic silver of the present invention is characterized in that a metallic silver film is formed by applying the silver paste of the present invention on a substrate and subjecting it to a heat treatment.

  In the method for firing metallic silver according to the present invention, the metallic silver film is preferably a connection wiring on a substrate.

  In the method for firing metallic silver according to the present invention, the substrate is formed of one or more materials selected from the group consisting of thermoplastic resin, thermosetting resin, glass, paper, metal, silicon, and ceramics. Is preferred.

  The metallic silver of the present invention is metallic silver formed by the method for firing metallic silver of the present invention.

  First, as described above, the present invention is a silver paste obtained from silver β-ketocarboxylate represented by the following formula (1).

  The silver paste of the present invention is not limited as long as it is obtained from the silver β-ketocarboxylate represented by the above formula (1). Further, since the silver paste of the present invention is obtained from the silver β-ketocarboxylate represented by the formula (1), there is an advantage that it can be produced by low-temperature heating. Further, since it is obtained from the silver β-ketocarboxylate represented by the formula (1), the silver β-ketocarboxylate is decomposed by heat treatment to generate volatile ketone and carbon dioxide, and a silver paste containing metallic silver is obtained. Can be manufactured.

In the formula (1), R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, R ¹ -CY ₂ —, CY ₃ —, R ¹ —CHY—, R ² O—, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, a heteroaryl group substituted with one or more substituents, R ⁵ R ⁴ N—, a hydroxyl group, It is an amino group or (R ³ O) ₂ CY-.

In the present invention, when R is a linear, branched, or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, examples of R include an alkyl group, an alkenyl group, an alkynyl group, and a cycloalkyl group. , include such cycloalkenyl group, for _{example, -C n H 2n + 1 (} n is an integer of 1 to 20, preferably 1 to 6 _{integer), - C n H 2n-} 1 (n is 2 to 20 An integer, preferably an integer of 2 to 6), or -C _n H _2n-3 (n is an integer of 2 to 20, preferably an integer of 2 to 6).

In the present invention, examples of -C _n H _{2n +} 1 _(n is an integer of 1 to 20), methyl, ethyl, isopropyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl Tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosanyl and the like. Further, examples of -C _n H _{2n +} 1 _(n is an integer from 1 to 6), methyl, ethyl, isopropyl, propyl, butyl, pentyl, hexyl and the like.

In the present invention, examples of -C _n H _{2n-1 (n} is 2-20 integer), ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, cyclopropenyl, cyclopentyl, cyclohexyl, And cycloheptyl. Further, examples of -C _n H _{2n-1 (n} is an integer of from 2 to 6), ethenyl, propenyl, butenyl, pentenyl, hexenyl, cyclopropenyl, cyclopentyl, cyclohexyl and the like.

In the present invention, examples of —C _n H _2n-3 (n is an integer of 2 to 20) include ethynyl, propynyl, butynyl, pentynyl, hexaynyl, heptynyl, octaynyl, noninyl, decynyl, undecynyl, dodecynyl, tridecynyl, tetra Examples include decynyl, pentadecynyl, hexadecynyl, heptadecynyl, octadecynyl, nonadecynyl, icosinyl and the like. Further, examples of -C _n H _{2n-3 (n} is an integer of from 2 to 6), ethynyl, propynyl, butynyl, pentynyl, Hekisainiru and the like. In the linear, branched or cyclic saturated or unsaturated C ₁ -C ₂₀ aliphatic hydrocarbon group, one or more hydrogen groups may be substituted with a fluorine atom, a chlorine atom or a bromine atom.

  In the present invention, examples of the aryl group mean a group obtained by removing one hydrogen atom from an aromatic hydrocarbon, and examples thereof include those having 6 to 30 carbon atoms. The aryl group is preferably phenyl, pentarenyl, naphthalenyl, phenalenyl, phenanthrenyl and the like.

In the present invention, when R is an aryl group substituted with one or more substituents, examples of the substituent include R ³ —, R ³ O—, a fluorine atom, a chlorine atom, a bromine atom, a hydroxyl group ( —OH), a cyano group (—C≡N), a phenoxy group (C ₆ H ₅ —O—), an alkyl group, an aryl group, and the like, and any position of the aryl group may be substituted. Examples of the substituted aryl group are 4-phenylphenyl (biphenyl), 2,4,6 trimethylphenyl and the like.

  In the present invention, examples of the heteroaryl group include groups obtained by removing one hydrogen atom from a heterocycle, and examples include heteroaryl groups containing oxygen, sulfur, nitrogen, and the like. The heteroaryl group is preferably thiophenyl, furanyl, pyranyl, xanthenyl, pyrrolinyl, imidazolinyl, pyrazolinyl, thiazolinyl, isoxazolinyl, pyridinyl, pyrazinyl, pyrimidinyl and the like.

In the present invention, when R is a heteroaryl group substituted with one or more substituents, examples of the substituent include R ³ —, R ³ O—, a fluorine atom, a chlorine atom, a bromine atom, and a hydroxyl group. (—OH), a cyano group (—C≡N), a phenoxy group (C ₆ H ₅ —O—), an alkyl group, an aryl group and the like may be mentioned, and any position of the aryl group may be substituted. Examples of the substituted heteroaryl group include 4-phenylpyridinyl, 4-methylpyridinyl and the like.

  The “alkyl group” in the present invention is not particularly limited, but for example, an alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, Examples include sec-butyl group and tert-butyl group. The “alkenyl group” is not particularly limited, but examples thereof include alkenyl groups having 2 to 6 carbon atoms such as vinyl group, allyl group, 1-propenyl group, isopropenyl group, 1-butenyl group and 2-butenyl group. Is mentioned. The “alkynyl group” is not particularly limited, and examples thereof include an alkynyl group having 2 to 6 carbon atoms, such as an ethynyl group and a propargyl group. The “cycloalkyl group” is not particularly limited, and examples thereof include a cycloalkyl group having 3 to 8 carbon atoms, such as a cyclopentyl group and a cyclohexyl group. The “cycloalkenyl group” is not particularly limited, and examples thereof include a C 4-8 cycloalkenyl group such as a 1,3-cyclohexadienyl group, a 1,4-cyclohexadienyl group, a cyclopentadienyl group, and the like. Is mentioned. In the various hydrocarbon groups in the present invention, one or more hydrogen groups may be substituted with a fluorine atom, a chlorine atom or a bromine atom.

  In the present invention, Y in R may be the same or different and each is a fluorine atom, a chlorine atom, a bromine atom or a hydrogen atom.

In the present invention, R ¹ in R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₉ aliphatic hydrocarbon group, an aryl group, an aryl group substituted with one or more substituents A heteroaryl group, or a heteroaryl group substituted with one or more substituents. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, and the like. For example, —C _n H _{2n + 1} , —C _n H _2n−1 , or — C _n H _{2n-3 (n} is 1 to 19 integer) may be a group represented by.

In the present invention, R ² is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, and the like. For example, —C _n H _{2n + 1} , —C _n H _2n−1 , or — C _n H _{2n-3 (n} is an integer of 1 to 20) may be a group represented by.

In the present invention, R ³ is a linear, branched or cyclic saturated or unsaturated C ₁ -C ₁₆ aliphatic hydrocarbon group. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, and the like. For example, —C _n H _{2n + 1} , —C _n H _2n−1 , or — C _n H _{2n-3 (n} is 1 to 16 integer) may be a group represented by.

In the present invention, R ⁴ and R ⁵ may be the same or different and are each a linear, branched or cyclic saturated or unsaturated C ₁ -C ₁₈ aliphatic hydrocarbon group. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, and the like. For example, —C _n H _{2n + 1} , —C _n H _2n−1 , or — C _n H _{2n-3 (n} is 1 to 18 integer) may be a group represented by.

In the formula (1), Xs may be the same or different, and are a hydrogen atom, a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, R ⁶ O—, R ^6. S-, R ⁶ -CO-, R ⁶ -CO-O-, halogen atom (eg, fluorine, chlorine, bromine, iodine), aryl group, aryl group substituted with one or more substituents, heteroaryl Group, heteroaryl group substituted with one or more substituents, aralkyl group, aralkyl group substituted with one or more substituents, cyano group (—C≡N), N-phthaloyl-3-amino A propyl group and a 2-ethoxyvinyl group (C ₂ H ₅ —O—CH═CH—). Where R ⁶ is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₀ aliphatic hydrocarbon group, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, 1 A heteroaryl group substituted with one or more substituents.

When X is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, examples of X include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cyclo alkenyl groups and the like, for example, -C _n H _2n + 1, a -C _n H _2n-1 or -C _n H _2n-3 group (n is an integer of from 1 to 20) represented by, Also good.

In the present invention, in R ⁶ O—, R ⁶ S—, R ⁶ —CO—, R ⁶ —CO—O— of X, examples of R ⁶ include an alkyl group, an alkenyl group, an alkynyl group, and a cycloalkyl group. , include cycloalkenyl groups such as, for example, in _{-C n H 2n + 1, -C} n H 2n-1 or -C _n H _2n-3 group (n denotes an integer from 1 to 10) represented by, There may be. R ⁶ may be an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, a heteroaryl group substituted with one or more substituents, as described above. Good. Examples of the substituent include halogen (fluorine, chlorine, bromine, iodine)), and any position of the aryl group or heteroaryl group may be substituted.

  The “aralkyl group” in the present invention is not particularly limited, and examples thereof include groups in which an aryl group is substituted for an alkyl group having 1 to 6 carbon atoms, such as phenylmethyl (benzyl), phenethyl, naphthylmethyl and the like.

In the present invention, X is an aryl group substituted with one or more substituents, a heteroaryl group substituted with one or more substituents, or an aralkyl group substituted with one or more substituents. In this case, examples of the substituent include halogen (fluorine, chlorine, bromine, iodine), nitro group (—NO ₂ ) and the like, and any position of the aryl group or heteroaryl group may be substituted.

In the formula (1), a group in which one group X is not bonded to X and ═CH—C ₆ H ₄ —NO ₂ is bonded only to the other X may be used.

  The decomposition temperature of the silver β-ketocarboxylate can be set, for example, in the range of about 60 ° C. to 210 ° C., preferably in the range of about 60 ° C. to 200 ° C., for example, substitution of R or X in the formula (1) It can be adjusted depending on the type of group.

  The decomposition temperature depends on, for example, the electron withdrawing property of R, and the larger the value, the easier the decarboxylation reaction of β-ketocarboxylic acid occurs during heating. Therefore, if the electron withdrawing value is set to R, which is relatively large, for example, the decomposition temperature can be set relatively low. On the other hand, if the electron withdrawing value is set to R, which is relatively small, for example, the decomposition temperature can be set relatively high.

  Below, an example of the relationship between the substituent R in Formula (1) and the decomposition temperature of β-ketocarboxylate is shown. In addition, X in Formula (1) is each a hydrogen atom, and the equal sign and inequality sign in a table | surface represent an example of the relationship of each decomposition temperature.

Specific examples in the case where R is R ¹ -CY ₂ — include, for example, groups shown in the following formula, and the inequality sign in the following formula shows an example of the relationship between the decomposition temperatures of such compounds having R. ing.

Specific examples of the case where R is CY ₃ — include, for example, CF ₃ —, CCl ₃ —, etc. The relationship between the decomposition temperatures of such compounds having R is, for example, CF _3- <CCl ₃ -.

Specific examples of the case where R is R ¹ —CHY— include, for example, groups shown in the following formula, and the inequality sign in the following formula shows an example of the relationship between the decomposition temperatures of such compounds having R. Yes.

Specific examples in the case where R is a phenyl group substituted with R ³ — include, for example, groups shown in the following formula, and the inequality sign in the following formula indicates the relationship of the decomposition temperature of the compound having R. An example is shown.

Specific examples in the case where R is a phenyl group substituted with R ³ O— include, for example, groups shown in the following formula, and the inequality sign in the following formula is the relationship of the decomposition temperature of such a compound having R. An example is shown.

Specific examples in the case where R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group include, for example, groups represented by the following formulas, 1 shows an example of the relationship between the decomposition temperatures of such R-containing compounds.

Specific examples of the case where R is R ⁵ R ⁴ N— include, for example, groups shown in the following formula, and the inequality sign in the following formula shows an example of the relationship between the decomposition temperatures of such compounds having R. ing.

  Specific examples of the relationship between R and the decomposition temperature when X is a hydrogen atom are as follows. If R in Formula (1) is an isopropyl group, silver β-ketocarboxylate is silver isobutyryl acetate, and the decomposition temperature is If R is a methyl group at about 145 ° C., the silver β-ketocarboxylate becomes silver acetoacetate, and its decomposition temperature is about 110 ° C. If R in formula (1) is an ethyl group, silver β-ketocarboxylate will be silver propionyl acetate, its decomposition temperature is about 130 ° C., and if R is a phenyl group, silver β-ketocarboxylate will be silver benzoyl acetate. The decomposition temperature is about 120 ° C.

  In addition, the extremely excellent effect as described above by using silver β-ketocarboxylate was found by the present inventors, but what is the degree of electron withdrawing of various substituents? Moreover, since the relative relationship between substituents can be determined from, for example, common technical knowledge, R in Formula (1) is not limited to those listed above. That is, for example, if R is an electron withdrawing property smaller than that of an isopropyl group, the decomposition temperature can be set higher, and if the electron attracting property is larger than an isopropyl group, R is set to a lower decomposition temperature. it can.

  Further, the decomposition temperature of silver β-ketocarboxylate can also be adjusted by X in the formula (1). The greater the electron withdrawing property of X, the easier the decarboxylation reaction of β-ketocarboxylic acid occurs during heating. Therefore, if the electron withdrawing value is set to X, which is relatively large, for example, the decomposition temperature can be set relatively low. On the other hand, if the electron withdrawing value is set to X, which is relatively small, for example, the decomposition temperature can be set relatively high.

  The decomposition temperature of silver β-ketocarboxylate can be adjusted by, for example, the steric effect of X such as steric hindrance. That is, if the steric hindrance is set to relatively large X, for example, the decomposition temperature can be set relatively low, and if the steric hindrance is set to relatively small X, for example, the decomposition temperature is set relatively high. it can. For example, the degree of steric hindrance of various substituents X and the relative relationship of steric hindrance between substituents can be determined from, for example, common technical knowledge.

  The following table is based on the case where X in formula (1) is a hydrogen atom when considering the electronic effects of substituents such as electron-withdrawing and steric effects such as steric hindrance. An example of a change in decomposition temperature due to substitution of X is shown. Note that the degree of change in the decomposition temperature due to the substitution of X may be set, for example, as a value obtained by adding a temperature change due to a three-dimensional effect to a temperature change due to an electronic effect.

  Specifically, in Formula (1), for example, when R is an isopropyl group and X is a hydrogen atom, the decomposition temperature of silver isobutyryl acetate is about 145 ° C. as described above. Here, when only one X in the formula (1) is substituted with benzyl, the decomposition temperature of silver isobutyrylcarboxylate is, for example, about (145 + 5-20) ° C. about 130 ° C., When both are substituted with benzyl, it is understood that the decomposition temperature can be set to about 115 ° C., for example, (145 + 10−40) ° C.

Specific examples when X is R ⁶ O— include, for example, groups represented by the following formulae.

Specific examples of the case where X is R ⁶ S— include, for example, groups represented by the following formulae.

Specific examples of the case where X is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group include groups represented by the following formulas.

  Hereinafter, other specific examples of R and X in the formula (1) will be given, but the present invention is not limited thereto.

In the silver paste of the present invention, in the formula (1), R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, an aryl group, or one or more a substituted aryl group substituted group, X is, which are identical or different, are each a hydrogen atom or a linear, saturated or unsaturated C ₁ branched or cyclic -C ₂₀ aliphatic hydrocarbon radical, β-ketocarboxylate is preferred.

In the silver paste of the present invention, in the above formula (1), R is —C _n H _{2n + 1} (n is an integer of 1 to 20) or an aryl group, and X is the same or different, More preferable are silver β-ketocarboxylates each being a hydrogen atom or —C _n H _{2n + 1} (n = 1 to 20).

In the silver paste of the present invention, in the formula (1), R is —C _n H _{2n + 1} (n is an integer of 1 to 6) or a phenyl group, and X is the same or different, More preferred are silver β-ketocarboxylates each being a hydrogen atom or —C _n H _{2n + 1} (n = 1 to 6).

  In the silver paste of the present invention, the silver β-ketocarboxylate represented by the formula (1) is silver isobutyryl acetate, silver benzoyl acetate, silver acetoacetate, silver propionyl acetate, α-methyl acetoacetate silver and α-ethyl acetoacetate silver. It is preferably 1 or more selected from the group consisting of These silver β-ketocarboxylates are preferable because the heating temperature when producing silver paste by decomposition into metallic silver is low and the production conditions are relaxed. Further, since these silver β-ketocarboxylates are used, volatile ketones and carbon dioxide are generated by heating, and the concentration of impurities remaining in the resulting silver paste containing metallic silver can be particularly reduced. As the metallic silver has relatively few impurities, for example, the contact between the relatively precipitated silvers becomes better, the conduction becomes easier, and the resistivity is lowered.

  The method for producing the β-ketocarboxylate is not particularly limited as long as the above-described compound can be produced, and specific examples thereof include the following method for producing β-ketocarboxylate.

  The production method of silver β-ketocarboxylate includes, for example, a step of producing silver β-ketocarboxylate by reacting β-ketocarboxylic acid and a silver compound in a reaction solution having a water content of 55% by weight or less. including. An example of the manufacturing method will be described below.

  First, a β-ketocarboxylate is prepared. This β-ketocarboxylate can be produced, for example, by hydrolyzing a β-ketocarboxylic acid ester. In the hydrolysis of the ester, a base is usually used, and the type of the base is not particularly limited, and examples thereof include NaOH and KOH. The base is prepared, for example, as an aqueous solution, and the concentration thereof is, for example, 1 mol / L or more, preferably 2 mol / L to 5 mol / L.

  Specifically, for example, while stirring the aqueous solution of the base, a β-ketocarboxylic acid ester may be dropped and reacted. The addition ratio of the base is not particularly limited, but is preferably 0.8 mol to 2 mol, more preferably 0.9 mol to 1.2 mol, relative to 1 mol of the β-ketocarboxylic acid ester. Moreover, the density | concentration of (beta) -ketocarboxylic acid ester in a reaction liquid is 0.5 mol / L-6.25 mol / L, for example, Preferably it is 1 mol / L-5.6 mol / L. The reaction temperature is not particularly limited, but is preferably 50 ° C. or less, more preferably 40 ° C. or less, and particularly preferably 20 ° C. to 40 ° C. The reaction time is, for example, 0.5 hour to 48 hours, preferably 1 hour to 4 hours.

  In this step, in order to sufficiently reduce the remaining amount of the base (such as NaOH) in the reaction solution after completion of the reaction, the amount of the base used may be set smaller than the amount of β-ketocarboxylic acid ester used. Preferably, for example, 0.8 mol to 1 mol is preferable with respect to 1 mol of β-ketocarboxylic acid ester, and more preferably 0.8 mol to 0.9 mol. This condition is preferable when the β-ketocarboxylate is isolated once and then supplied to the next step. On the other hand, when the β-ketocarboxylate produced in this step is supplied to the next step as it is, for example, 1 mol to 1.3 mol of a base (more preferably 1. 1 mol to 1.2 mol) is added to form the β-ketocarboxylate. In the next step, an acid equivalent to the base used (such as sulfuric acid described later) may be added.

  The β-ketocarboxylic acid ester is not particularly limited, but can be appropriately set according to the desired structure of the silver β-ketocarboxylate. The β-ketocarboxylic acid ester is represented, for example, by the following formula (2). In the following formula (2), R and X are the same as R and X in the formula (1), and R ′ is particularly limited. Non-limiting examples include methyl, ethyl, isopropyl and benzyl. Specific compounds include, for example, methyl isobutyryl acetate, ethyl benzoyl acetate, methyl acetoacetate, methyl propionyl acetate, benzyl isobutyryl acetate, isopropyl isobutyryl acetate, ethyl 2-methylacetoacetate, ethyl 2-ethylacetoacetate and 2-n-butyl. Examples include ethyl acetate.

  Moreover, as a raw material, it is not limited to the above-mentioned (beta) -ketocarboxylic acid ester, For example, the cyclic compound which becomes said ester by ring-opening can also be used. As such a cyclic compound, for example, the following can be used.

The obtained β-ketocarboxylate is represented by the following formula (3). In the following formula (3), R and X are the same as R and X in the formula (1). R ″ is not particularly limited and is determined depending on the type of salt used, and examples thereof include Na, K, NH _{4 and the} like. Specific compounds include, for example, isobutyryl acetate Na or K, benzoyl acetate Na or K, acetoacetate Na or K, propionyl acetate Na or K, isobutyryl acetate Na or K, 2-methylacetoacetate Na or K, 2-ethylacetate Examples include Na or K acetate and Na or K 2-n-butyl acetate.

  As described above, this β-ketocarboxylate can be prepared by hydrolysis of a β-ketocarboxylate, but the obtained β-ketocarboxylate may be isolated by a conventional method or silver in the next step. It is also possible to use the hydrolyzed one as it is when mixing with the compound.

  Next, β-ketocarboxylate and silver compound are mixed to produce silver β-ketocarboxylate. The first and second methods for producing this silver β-ketocarboxylate are shown below.

  First, an acid is added to the β-ketocarboxylate represented by the formula (3), and the generated β-ketocarboxylic acid is extracted with an organic solvent. The acid is not particularly limited, and for example, sulfuric acid, hydrochloric acid, HBr, nitric acid, phosphoric acid, acetic acid and the like can be used. The amount of the acid used is not particularly limited, and for example, it is sufficient if an amount of hydrogen corresponding to R ″ of the β-ketocarboxylate salt represented by the formula (3) can be supplied. In addition, when the β-ketocarboxylate produced in the previous step is used as it is without being isolated, the acid amount may be such that an amount of hydrogen corresponding to the base used in the previous step can be supplied. By extracting with an organic solvent in this way, the purity of the β-ketocarboxylate obtained can be further improved. Moreover, after producing | generating the beta-ketocarboxylic acid obtained at this process, it is preferable to cool rapidly by ice cooling etc., and to advance to the next process, for example.

  Next, a silver compound is added to β-ketocarboxylic acid to produce silver β-ketocarboxylic acid.

  Both of the reactions are usually carried out in a solvent, but it is preferable to reduce the amount of water in the reaction solution in order to efficiently produce silver β-ketocarboxylate. That is, as the amount of water in the reaction solution is smaller, the production rate of silver β-ketocarboxylate is relatively improved. Specifically, the ratio (% by weight) of water in the reaction solution is, for example, 55% by weight or less, preferably 50% by weight or less, and more preferably 44% by weight or less. Although a minimum in particular is not restrict | limited, For example, it is about 35 weight%, Especially preferably, it is below a detection limit. Examples of the solvent in the reaction solution include an organic solvent such as ether, water, and a mixed solution thereof.

  The mixing ratio of β-ketocarboxylic acid and silver compound is not particularly limited, but 1 mol to 1.5 mol of β-ketocarboxylic acid is preferable with respect to 1 mol of silver compound, and more preferably β with respect to 1 mol of silver compound. -1 mol to 1.2 mol of ketocarboxylic acid. Each of the β-ketocarboxylic acid and the silver compound may be used at least one type, but two or more types may be used in combination.

  β-ketocarboxylic acid is usually used as a β-ketocarboxylic acid solution dissolved or dispersed in an organic solvent. The organic solvent is not particularly limited, and examples thereof include esters such as ethyl acetate and ethers such as diethyl ether. The concentration of the β-ketocarboxylic acid solution is not particularly limited, but is, for example, 0.2 mol / L or more, preferably 0.5 mol / L or more.

  The silver compound is usually added as a silver compound solution (for example, an aqueous silver compound solution), but for the purpose of reducing the amount of water in the reaction solution as described above, the concentration is, for example, 1 mol / L or more, preferably Is 2 mol / L or more, more preferably 3 mol / L or more, and the upper limit thereof is not particularly limited, and is, for example, 13 mol / L or less. Further, when the β-ketocarboxylate to be produced is unsubstituted at the α-position, the concentration of the silver compound solution is, for example, 1 mol / L or more, preferably 1.5 mol / L or more, more preferably 2 mol / L or more. In the case of substitution at the α-position, the concentration of the silver compound solution is, for example, 3 mol / L or more, preferably 4 mol / L or more, more preferably 5 mol / L or more. Specifically, in the case of silver acetoacetate, for example, it is 3 mol / L or more, preferably 4 mol / L or more, more preferably 5 mol / L or more.

  The silver compound is not particularly limited, and examples thereof include silver nitrate, silver chloride, silver carbonate, silver bromide, and silver iodide. Among them, silver nitrate is relatively high in water solubility, stability, and safety. Particularly preferred.

In the reaction of β-ketocarboxylic acid and silver compound, in order to dissociate —COOH of β-ketocarboxylic acid into carboxylate (—COO ⁻ ), for example, diethanolamine, methylaminoethanol, dimethylaminoethanol and triethanolamine An amine such as The addition ratio of the amine is not particularly limited, and is preferably, for example, 1 mol to 1.5 mol with respect to 1 mol of the silver compound, and more preferably 1 mol to 1.1 mol with respect to 1 mol of the silver compound. . By adding an amine, for example, the β-ketocarboxylic acid is transferred from the organic phase to the aqueous phase. Therefore, when adding an amine, for example, the β-ketocarboxylic acid concentration in the β-ketocarboxylic acid liquid (organic solvent) need not be considered. Further, the β-ketocarboxylic acid is transferred from the organic phase to the aqueous phase by addition of an amine, and only the aqueous phase is separated at this stage, and a β-ketocarboxylic acid aqueous solution (aqueous phase) and a silver compound solution (for example, a silver compound aqueous solution) are obtained. ) May be mixed to produce silver β-ketocarboxylate.

  The amine is usually added as an amine solution (for example, an aqueous amine solution). For the purpose of reducing the amount of water in the reaction solution as described above, the concentration of the amine solution is, for example, 2 mol / L or more, preferably Is 4 mol / L or more, more preferably 6 mol / L. Moreover, the upper limit in particular is not restrict | limited, For example, it is 8 mol / L or less.

  The concentration of β-ketocarboxylic acid in the reaction solution is, for example, 0.1 mol / L to 5 mol / L, preferably 0.3 mol / L to 3 mol / L. The concentration of amine in the reaction solution is, for example, 0.1 mol / L to 5 mol / L, preferably 0.3 mol / L to 3 mol / L. In addition, the concentration of the silver compound in the reaction solution is, for example, 0.1 mol / L or more, preferably 0.3 mol / L or more, more preferably, when the β-ketocarboxylate to be formed is α-position unsubstituted. In the case of α-position substitution, the concentration of the silver compound solution is, for example, 0.1 mol / L or more, preferably 0.5 mol / L or more, more preferably 2 mol / L or more. is there. In the case of silver acetoacetate, the concentration of the silver compound solution is, for example, 0.1 mol / L or more, preferably 0.5 mol / L or more, more preferably 2 mol / L or more, and silver isobutyryl acetate. In this case, for example, it is 0.15 mol / L or more, preferably 0.4 mol / L or more, more preferably 0.6 mol / L or more.

  The reaction conditions for the β-ketocarboxylic acid and the silver compound are not particularly limited. For example, the reaction time is preferably 0.1 hour to 0.5 hour, and the reaction temperature is preferably 0 ° C to 25 ° C.

  The silver β-ketocarboxylate thus obtained may be quickly collected and dried after the reaction, for example, and may be used as it is as a material for forming metallic silver. For example, water or alcohol such as ethanol may be used. It is preferable to use what was purified by washing.

  In addition to the above methods, for example, there is also a method in which a silver compound is directly added to a β-ketocarboxylate to produce silver β-ketocarboxylate. In this case, it is preferable to add a β-ketocarboxylate solution (for example, an aqueous solution) to the silver compound solution (for example, an aqueous silver compound solution).

  Next, the present invention is a method for producing a silver paste containing metallic silver as described above, wherein the method comprises a mixture containing silver β-ketocarboxylate represented by the formula (1) and a polar solvent. It includes a step of producing metallic silver by heating.

  In the production method of the present invention, the definitions for R and X in the formula (1) are the same as the definitions for R and X in the formula (1) in the silver paste of the present invention.

In the production method of the present invention, as described above, in the formula (1), R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, an aryl group, or a one or more substituted aryl group substituted with group, X is, or identically or differently, are each a hydrogen atom or a linear, branched or cyclic saturated or unsaturated C ₁ -C ₂₀ aliphatic, It is preferably a hydrocarbon group.

In the production method of the present invention, the β-ketocarboxylate in the formula (1), R is —C _n H _{2n + 1} (n is an integer of 1 to 20) or an aryl group, and X is More preferably, they are the same or different and each is a hydrogen atom or —C _n H _{2n + 1} (n is an integer of 1 to 20).

In the production method of the present invention, the β-ketocarboxylate in the formula (1), R is —C _n H _{2n + 1} (n is an integer of 1 to 6) or a phenyl group, and X is More preferably, they are the same or different and each is a hydrogen atom or —C _n H _{2n + 1} (n is an integer of 1 to 6).

  In the production method of the present invention, as described above, the silver β-ketocarboxylate represented by the formula (1) is silver isobutyryl acetate, silver benzoyl acetate, silver acetoacetate, silver propionyl acetate, silver α-methylacetoacetate and It is preferably 1 or more selected from the group consisting of silver α-ethylacetoacetate. These silver β-ketocarboxylates are preferable because the heating temperature when producing silver paste by decomposition into metallic silver is low and the production conditions are relaxed. Further, since these silver β-ketocarboxylates are used, volatile ketones and carbon dioxide are generated by heating, and the concentration of impurities remaining in the resulting silver paste containing metallic silver can be particularly reduced. As the metallic silver has relatively few impurities, for example, the contact between the relatively precipitated silvers becomes better, the conduction becomes easier, and the resistivity is lowered.

  First, in the production method of the present invention, a mixture containing silver β-ketocarboxylate represented by the formula (1) and a polar solvent is prepared.

  In the production method of the present invention, the content of the silver β-ketocarboxylate represented by the formula (1) in the mixture is preferably 0.01 mol / L to 10 mol / L, more preferably 0.1 mol / L. It is -3 mol / L, More preferably, it is 0.5 mol / L-2 mol / L.

In the production method of the present invention, as described above, the polar solvent is a heterocycle, an alkyl-substituted heterocycle, water, —COOH, —SH, —NH ₂ , —OH, —COO—, —CON ( -)-, -CONH-, -CONH ₂ , -S-, -SO-, -SO _2- , -NH- and -N (-)-, alkanes containing one or more, alkenes, Preference is given to one or more polar solvents selected from the group consisting of alkynes, aromatic hydrocarbons, alkyl-substituted aromatic hydrocarbons, heterocycles and alkyl-substituted heterocycles.

  The “heterocycle” moiety in the heterocycle and the alkyl-substituted heterocycle means a ring containing one or more atoms other than carbon atoms, and examples thereof include heterocycles containing oxygen, sulfur, nitrogen and the like. The heterocyclic ring and heterocyclic moiety are preferably thiophene, furan, pyran, xanthene, pyrrole, pyrrolidone, imidazole, pyrazole, thiazole, isoxazole, pyridine, pyrazine, pyrimidine and the like.

  The “aromatic hydrocarbon” part in the aromatic hydrocarbon and the alkyl-substituted aromatic hydrocarbon means an unsaturated ring hydrocarbon showing aromaticity, and examples thereof include those having 6 to 30 carbon atoms. . The aromatic hydrocarbon and aromatic hydrocarbon moiety are preferably benzene, pentalene, naphthalene, phenalene, phenanthrene and the like.

  The alkyl-substituted heterocycle means one in which one or more hydrogen atoms of the heterocycle are substituted with the alkyl group, for example, a heterocycle substituted with an alkyl group having 1 to 10 carbon atoms. Can be mentioned. The heterocycle substituted with the alkyl group is preferably methylthiophene, hexylfuran, methylpyran, butylxanthene, methylpyrrole, N-methylpyrrolidone, pentylimidazole, octylpyrazole, hexylthiazole, pentylisoxazole, butylpyridine, methyl Pyrazine, methylpyrimidine and the like.

  The alkyl-substituted aromatic hydrocarbon means a compound in which one or more hydrogen atoms of the aromatic hydrocarbon are substituted with the alkyl group, for example, substituted with an alkyl group having 1 to 10 carbon atoms. And aromatic hydrocarbons having 6 to 30 carbon atoms. Examples of the alkyl-substituted aromatic hydrocarbon include methylbenzene (toluene), propylpentalene, hexylnaphthalene, methylphenalene, ethylphenanthrene, and the like, and preferably substituted with an alkyl group having 1 to 6 carbon atoms. Aromatic hydrocarbons such as toluene, propylpentalene, hexylnaphthalene, methylphenalene, ethylphenanthrene, more preferably aromatic hydrocarbons substituted with an alkyl group having 1 to 3 carbon atoms such as toluene, propylpentalene, And ethylnaphthalene, methylphenalene, ethylphenanthrene, and the like.

Alkane means an acyclic saturated hydrocarbon represented by the formula C _n H _{2n + 2} , and examples thereof include those having 1 to 100 carbon atoms. The alkane includes a chain shape and a branched shape. The alkane is preferably an alkane having 1 to 20 carbon atoms, such as methane, ethane, propane, butane, pentane, hexane, heptane, 2,2,2,4-trimethylpentane, octane, nonane, decane, undecane, dodecane. , Tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, icosane, etc., more preferably alkanes having 5 to 15 carbon atoms, such as pentane, hexane, heptane, 2,2,2,4-trimethylpentane, octane. , Nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, etc., more preferably an alkane having 8 to 15 carbon atoms, such as 2,2,2,4-trimethylpentane, octane, nonane, decane, undecane, dodecane. The Decane, tetradecane, is pentadecane and the like.

_{-COOH, -SH, -NH 2, -OH} , -COO -, - CON (-) -, - CONH -, - CONH 2, -S -, - SO -, - SO 2 -, - NH- and - The alkane containing one or more selected from the group consisting of N (-)-means that one or more hydrogen atoms of the alkane are substituted with one or more of the substituents, for example, formic acid, acetic acid, propionic acid , Butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, etc., hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, methanesulfonic acid, methanol, Ethanol, isopropanol, 2-methyl-2-propanol, butanol, pentanol, hexanol, heptanol, octanol, nonaol, decanol, undecanol Dodecanol, tridecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, icosanol, ethylene glycol, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine , Decylamine, undecylamine, dodecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, icosanylamine, methanethiol, ethanethiol, propanethiol, butanethiol, pentanethiol, hexanethiol , Heptanethiol, octanethiol, nonanethiol, decanethiol, undecanethiol, Cantilever ol, tridecane thiol, tetra decanethiol, pentadecane thiol, hexadecane thiol, heptadecane thiol, octadecane thiol, nona decanethiol, equalizer San thiol, dimethyl sulfoxide, dimethylformamide and the like. The substituted alkane is preferably octanol, dodecanol, ethylene glycol, dodecylamine, dimethylformamide or the like.

Alkene means an acyclic unsaturated hydrocarbon represented by the formula C _n H _2n , and examples thereof include those having 2 to 100 carbon atoms. The alkene includes a chain shape and a branched shape. The alkene is preferably an alkene having 2 to 20 carbon atoms, such as ethene, propene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, tridecene, tetradecene, pentadecene, hexadecene, heptadecene, octadecene, Nonadecene, icosene and the like, more preferably alkene having 3 to 10 carbon atoms, such as propene, butene, pentene, hexene, heptene, octene, nonene, decene, etc., more preferably alkene having 3 to 5 carbon atoms, such as Propen, butene, pentene, etc.

_{-COOH, -SH, -NH 2, -OH} , -COO -, - CON (-) -, - CONH -, - CONH 2, -S -, - SO -, - SO 2 -, - NH- and - The alkene containing one or more selected from the group consisting of N (-)-means that the alkene contains one or more of the substituents, such as allyl alcohol, vinylamine, propenylamine, butenylamine, pentenylamine, hexenyl. Amine, heptenylamine, octenylamine, nonenylamine, decenylamine, undecenylamine, dodecenylamine, tridecenylamine, tetradecenylamine, pentadecenylamine, hexadecenylamine, heptadecenylamine, octadecenylamine, nonadecenylamine, Oleylamine, icocenylamine, nonacosenyl Min, ethene thiol, propene thiol (allyl mercaptan), butene thiol, pentene thiol, hexene thiol, heptene thiol, octene thiol, nonene thiol, decene thiol, undecene thiol, dodecene thiol, tridecene thiol, tetradecene thiol, Pentadecene thiol, hexadecene thiol, heptacene thiol, octadecene thiol, nonadecene thiol, icosene thiol, nonacose thiol, acrylic acid (propenoic acid), methacrylic acid (2-methylpropenoic acid), crotonic acid (Trans-but-2-enoic acid), isocrotonic acid (cis-but-2-enoic acid), hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetrade Acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, oleic acid (cis-octadeca-9-enoic acid), elaidic acid (trans-octadeca-9-enoic acid), maleic acid (cis-butenedioic acid), fumaric acid (Trans-butenedioic acid) and the like.

Alkyne means an acyclic unsaturated hydrocarbon represented by the formula C _n H _2n-2 , and examples thereof include those having 2 to 100 carbon atoms. The alkyne includes a chain shape and a branched shape. The alkyne is preferably an alkyne having 2 to 20 carbon atoms, such as ethyne, propyne, butyne, pentyne, hexaine, heptine, octaine, nonine, decaine, undecaine, dodecane, tridecane, tetradecane, pentadecane, hexadecaine, heptadecane, octadecane, Nonadecane, icosine and the like, more preferably alkyne having 3 to 10 carbon atoms, such as propyne, butyne, pentine, hexaine, heptane, octane, nonine, decaine, etc., more preferably alkene having 3 to 5 carbon atoms, such as Propin, butyne, pentyne and the like.

_{-COOH, -SH, -NH 2, -OH} , -COO -, - CON (-) -, - CONH -, - CONH 2, -S -, - SO -, - SO 2 -, - NH- and - The alkyne containing one or more selected from the group consisting of N (-)-means one containing one or more of the substituents in the alkyne, and examples thereof include ethynethiol and propyneylamine.

_{-COOH, -SH, -NH 2, -OH} , -COO -, - CON (-) -, - CONH -, - CONH 2, -S -, - SO -, - SO 2 -, - NH- and - The aromatic hydrocarbon containing one or more selected from the group consisting of N (-)-means that the aromatic hydrocarbon contains one or more of the substituents, for example, benzoic acid, benzenethiol, aniline Etc.

_{-COOH, -SH, -NH 2, -OH} , -COO -, - CON (-) -, - CONH -, - CONH 2, -S -, - SO -, - SO 2 -, - NH- and - The alkyl-substituted aromatic hydrocarbon containing one or more selected from the group consisting of N (-)-means that the alkyl-substituted aromatic hydrocarbon contains one or more of the substituents, Examples include benzyl alcohol and phenylacetic acid.

_{-COOH, -SH, -NH 2, -OH} , -COO -, - CON (-) -, - CONH -, - CONH 2, -S -, - SO -, - SO 2 -, - NH- and - The heterocyclic ring containing one or more selected from the group consisting of N (-)-means that the heterocyclic ring contains one or more of the substituents, and examples thereof include carboxyl pyridine and hydroxypyrazole.

_{-COOH, -SH, -NH 2, -OH} , -COO -, - CON (-) -, - CONH -, - CONH 2, -S -, - SO -, - SO 2 -, - NH- and - The alkyl-substituted heterocycle containing one or more selected from the group consisting of N (-)-means that the alkyl-substituted heterocycle contains one or more of the substituents, such as carboxyl pyridine, And hydroxypyrazole.

  Next, the mixture is heated. In the production method of the present invention, the heating is preferably at least 60 ° C. lower than the decomposition temperature of the silver β-ketocarboxylate, more preferably at least 55 ° C. lower than the decomposition temperature of the silver β-ketocarboxylate. More preferably, it is carried out at a temperature of 45 ° C. lower than the decomposition temperature of the silver β-ketocarboxylate. Although there is no upper limit of the heating temperature, it is, for example, 150 ° C. or lower, preferably 120 ° C. or lower, more preferably 110 ° C. or lower.

  In the production method of the present invention, the heating is preferably performed under normal pressure conditions as described above. Since the production method of the present invention can be carried out under the normal pressure conditions, it is not necessary to carry out under a special pressure, which is preferable.

  Moreover, in the manufacturing method of this invention, the said heating can be performed on pressurization conditions. The heating is performed at, for example, 1.1 to 15 atmospheres, more preferably 1.1 to 10 atmospheres, and even more preferably 1.1 to 5 atmospheres. In the case of this pressurizing condition, the heating may or may not be performed at a temperature equal to or higher than the boiling point of the polar solvent.

  In the production method of the present invention, the heating can be performed in air, in an inert gas (eg, argon, nitrogen, etc.) atmosphere, or the like. The production method of the present invention is preferable because the heating can be performed in the air, and it is not necessary to perform the heating in a special atmosphere.

  Moreover, it is preferable that the silver paste of this invention is formed by the manufacturing method of this invention as mentioned above.

As described above, since the silver paste of the present invention formed from silver β-ketocarboxylate is rapidly and sufficiently decomposed at the decomposition temperature, the formed silver paste is sintered after sintering. Excellent electrical conductivity, i.e. low resistivity, can also be realized. Specifically, the resistivity of metallic silver can be set to, for example, about 1 × 10 ⁻⁴ Ωcm to 1 × 10 ⁻⁵ Ωcm. This resistivity is a sufficiently practical value. In particular, since the resistivity on the order of 5 × 10 ⁻⁵ Ωcm is extremely excellent, it can be said that the silver paste of the present invention is very useful as a conductive material.

Furthermore, the silver paste of this invention contains the particle | grains of the metallic silver which decomposed | disassembled by heating beta-ketocarboxylate silver. When forming the metal silver particles, volatile ketone and CO ₂ derived from β-ketocarboxylic acid are generated from silver β-ketocarboxylate. CO ₂ is removed from the silver paste as a gas. Therefore, the obtained silver paste of the present invention is preferable because it contains few impurities. The volatile ketone is also removed from the silver paste as a gas under suitable conditions. The resulting silver paste of the present invention is preferable because it contains no β-ketocarboxylate-derived material other than silver particles.

  Further, the metallic silver contained in the silver paste of the present invention preferably contains metallic silver having a particle size in the range of 3 nm to 500 nm, more preferably metallic silver having a particle size in the range of 3 nm to 100 nm, It is preferable to contain metallic silver having a particle size in the range of 3 nm to 50 nm. The particle size is a particle size measured by observation using a transmission electron microscope (for example, JEM-3000F (manufactured by JEOL Ltd.)). The metallic silver may have a uniform particle size or a mixed particle size.

  In the production method of the present invention, when the metallic silver contained in the silver paste contains metallic silver having a particle size in the range of 3 nm to 20 nm, the mixture preferably further contains a dispersant as described above. This is because the metal silver having a particle size in the above range is preferably included in order to suppress aggregation of the metal silver. In the production method of the present invention, it is possible to reduce the content of the dispersant from the content of the dispersant contained in the conventional silver paste. When the dispersing agent is included in the production method of the present invention, the content of the dispersing agent is, for example, 5% by weight to 40% by weight, preferably 5% by weight to 30% by weight, and more preferably 10%. % By weight to 15% by weight.

  The dispersant is not limited as long as it can disperse metallic silver having a particle diameter in the range of 3 nm to 20 nm, and examples thereof include primary amines and secondary amines. In addition, when the metal silver particles contained in the silver paste are not fine particles having a particle diameter in the range of 3 nm to 20 nm, the silver paste can be produced without using a dispersant. Such a silver paste makes it possible to form a coating of metallic silver that does not contain a sintering residue of the dispersant.

  In the production method of the present invention, the mixture may contain an additive. Examples of the additive include acid anhydrides and polymer compounds (for example, polyvinylpyrrolidone). As said additive, what does not remain after sintering a silver paste is preferable, for example, a fatty acid anhydride etc.

  Next, the method for firing metal silver according to the present invention will be described with reference to an example in which a metal silver film is formed on a substrate, for example. In addition, the baking method of the metallic silver of this invention should just use the silver paste of this invention, and is not limited to the following methods at all.

  First, the silver paste of the present invention is prepared as described above. Next, this silver paste is apply | coated on a base material. The substrate is not particularly limited and can be appropriately determined according to the use of the metallic silver film to be formed. For example, thermoplastic resin, thermosetting resin, glass, paper, metal (for example, gold, silver, copper, etc.) , Silicon, ceramics and the like. In particular, in the metallic silver production method of the present invention, a substrate having low heat resistance that cannot be used in a conventional production method requiring high-temperature treatment can be used. For example, a resinous substrate such as polyethylene terephthalate and epoxy resin And so on. Examples of the method for applying the silver paste include screen printing, offset printing, dip method, ink jet method, dispenser method, and the like. The amount of the silver paste applied per substrate area is not particularly limited, and can be appropriately determined depending on, for example, the concentration of silver β-ketocarboxylate in the silver paste, the thickness of the metal silver film to be formed, and the like.

  Next, a metallic silver film is formed by subjecting the base material coated with the silver paste to a heat treatment. The heating can be performed by a method such as heating using an electric furnace or a method using a thermal head, and the conditions are not particularly limited. For example, the heating can be performed under atmospheric pressure.

  The heat treatment is performed, for example, at 0.01 to 1 atm, preferably 0.1 to 1 atm, and more preferably 0.8 to 1 atm. For example, in the case of 1 atm, the heat treatment is at a temperature of 50 ° C. lower than the boiling point of the polar solvent, preferably in the case of 1 atm, at a temperature of 40 ° C. lower than the boiling point of the polar solvent, more preferably 1 atm. In this case, the temperature is 30 ° C. lower than the boiling point of the polar solvent. Moreover, although there is no upper limit of the heating temperature, for example, it is below the boiling point of the polar solvent, preferably below 10 ° C. below the boiling point of the polar solvent, more preferably below 15 ° C. below the boiling point of the polar solvent. . When the atmospheric pressure is low, the heat treatment can be performed at a temperature lower than the temperature used in the case of 1 atmospheric pressure. For example, the heat treatment is, for example, at a temperature of 30 ° C. lower than the boiling point of the polar solvent at 0.1 atm, and preferably at a temperature of 25 ° C. lower than the boiling point of the polar solvent at 0.5 atm. More preferably, the pressure is 0.8 atm or more at a temperature lower by 23 ° C. than the boiling point of the polar solvent.

  Although the use as a conductive material of the silver paste of this invention is not restrict | limited at all, For example, a connection wiring, an electrode, a conductive adhesive, etc. are mentioned. In particular, since a silver paste containing metallic silver particles formed from silver β-ketocarboxylate can be sintered at a low temperature, a fine connection wiring or the like can be easily formed.

  The metallic silver of the present invention is metallic silver formed by the method for producing metallic silver of the present invention.

  First, production examples of silver β-ketocarboxylate will be described.

(Reference Example 1)
Synthesis of Silver Isobutyryl Acetate Sodium hydroxide (0.4 g) was dissolved in water (10 ml), and methyl isobutyryl acetate (1.44 g: manufactured by Fluka) was added thereto, followed by stirring at room temperature for 6 hours. The reaction product was washed with ether, 10% dilute sulfuric acid (4.9 g) was added, and the mixture was extracted with ether. Excess anhydrous sodium sulfate was added to the ether extract and dried, and the anhydrous sodium sulfate was removed by filtration. Then, the ether was removed by a rotary evaporator to obtain isobutyryl acetic acid (yield 1 g).

  Diethanolamine (0.33 g) was dissolved in water (5 ml), and an ether solution (10 ml) containing isobutyrylacetic acid (0.43 g) was added thereto. Then, stirring the said liquid mixture at 15 degreeC, the aqueous solution (5 ml) containing silver nitrate (0.51g) was dripped at this, and also it stirred for 15 minutes. The precipitated white precipitate was collected by filtration to obtain silver isobutyryl acetate (yield 0.37 g).

IR (ATR method): 1709 cm ⁻¹ , 1505 cm ⁻¹ .
¹ H-NMR (DMSO-d ₆ ) δ: 1.00 ppm (6H, d), 2.83 ppm (1H, quintet), 3.30 ppm (2H, s, J = 7 Hz).
Elemental analysis measured values C: 30.33, H: 3.65, N: 0.00, Ag: 45.42
Calculated value C: 30.41, H: 3.84, Ag: 45.51.

(Reference Example 2)
Synthesis of silver acetoacetate Sodium hydroxide (0.8 g) was dissolved in water (10 ml), methyl acetoacetate (2.2 g: manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto, and the mixture was stirred at room temperature overnight. Further, silver nitrate (3.4 g) was added and stirred at 15 ° C. for 15 minutes. The deposited precipitate was collected by filtration to obtain silver acetoacetate (yield 3.52 g).
IR (ATR method): 1709 cm ⁻¹ , 1547 cm ⁻¹ .
¹ H-NMR (DMSO-d ₆ ) δ: 2.17 ppm (3H, s), 3.25 ppm (2H, s).

(Reference Example 3)
Synthesis of silver propionyl acetate Sodium hydroxide (0.4 g) was dissolved in water (10 ml), methylpropionyl acetate (1.3 g: manufactured by Aldrich) was added thereto, and the mixture was stirred at room temperature for 3 hours. The reaction product was washed with ether, 10% dilute sulfuric acid (4.9 g) was added, and the mixture was extracted with ether. Excess anhydrous sodium sulfate was added to the ether extract and dried, and the anhydrous sodium sulfate was removed by filtration. Then, the ether was removed by a rotary evaporator to obtain propionyl acetic acid (yield 0.88 g).

Diethanolamine (0.22 g) was dissolved in water (0.5 ml), and an ether solution (3 ml) containing propionyl acetic acid (0.25 g) was added thereto. Then, stirring the said liquid mixture at 15 degreeC, the aqueous solution (1 ml) containing silver nitrate (0.34g) was dripped at this, and also it stirred for 15 minutes. The precipitated white precipitate was collected by filtration to obtain silver propionyl acetate (yield 1.89 g).
IR (ATR method): 1714 cm ⁻¹ , 1505 cm ⁻¹ .
¹ H-NMR (DMSO-d ₆ ) δ: 0.87 ppm (3H, t), 2.55 ppm (2H, q), 3.25 ppm (2H, s, J = 7 Hz).

(Reference Example 4)
Synthesis of Silver Benzoyl Acetate Sodium hydroxide (0.4 g) was dissolved in water (10 ml), and ethyl benzoyl acetate (2.14 g: purity 90%, manufactured by Aldrich) was added thereto and stirred at room temperature overnight. The reaction product was washed with ether, 10% dilute sulfuric acid (4.9 g) was added, and the mixture was extracted with ether. Excess anhydrous sodium sulfate was added to the ether extract and dried, and the anhydrous sodium sulfate was removed by filtration. Then, the ether was removed by a rotary evaporator to obtain benzoylacetic acid (yield 1.05 g).

Diethanolamine (0.33 g) was dissolved in water (5 ml), and an ether solution (20 ml) containing benzoylacetic acid (0.54 g) was added thereto. Then, stirring the said liquid mixture at 15 degreeC, the aqueous solution (5 ml) containing silver nitrate (0.51g) was dripped at this, and also it stirred for 15 minutes. The precipitated pale yellow precipitate was collected by filtration to obtain silver benzoyl acetate (yield 0.79 g).
IR (ATR method): 1687 cm ⁻¹ , 1540 cm ⁻¹ .
¹ H-NMR (DMSO-d ₆ ) δ: 3.55 ppm (2H, s), 7.45 to 8.00 ppm (5H, m).

(Reference Example 5)
Synthesis of silver α-methylacetoacetate Sodium hydroxide (1.92 g) was dissolved in water (8 ml) and ethyl 2-methylacetoacetate (5.77 g: Wako Pure Chemical Industries, Ltd.) was added dropwise while stirring at room temperature. And stirred for another 30 minutes. Thereafter, ethanol was removed by a rotary evaporator, and the remaining aqueous layer was washed with ether. Ether (20 ml) was added thereto, and a solution prepared by dissolving 2.35 g of concentrated sulfuric acid in 8 ml of water was added dropwise with stirring under ice cooling. The ether layer was separated, and the aqueous layer was salted out and extracted with ether. The ether layer was collected to obtain an ether solution of α-methylacetoacetic acid.

Diethanolamine (4.4 g) was dissolved in water (5 ml), and this solution was added to an ether solution of α-methylacetoacetic acid under ice cooling. Subsequently, a solution of silver nitrate (6.8 g) dissolved in water (8 ml) was added dropwise. Then, the precipitated white precipitate was collected by filtration, washed with ice water, followed by isopropanol, and dried to obtain α-methyl acetoacetate silver as a white precipitate (yield 4.78 g).
IR (ATR method): 1692 cm ⁻¹ , 1523 cm ⁻¹ .
¹ H-NMR (DMSO-d ₆ ) δ: 1.25 ppm (3H, d), 2.25 ppm (3H, s), 3.55 ppm (1H, q, J = 7 Hz).
Elemental analysis measurement values C: 26.49, H: 3.11, Ag: 48.91,
Theoretical value C: 26.93, H: 3.16, Ag: 48.36.

(Reference Example 6)
Synthesis of silver α-ethylacetoacetate Sodium hydroxide (1.92 g) was dissolved in water (10 ml), and ethyl 2-ethylacetoacetate (6.32 g: Wako Pure Chemical Industries, Ltd.) was added dropwise while stirring at room temperature. And stirred for another 30 minutes. Thereafter, ethanol was removed by a rotary evaporator, and the remaining aqueous layer was washed with ether. Ether (20 ml) was added thereto, and a solution prepared by dissolving 2.35 g of concentrated sulfuric acid in 8 ml of water was added dropwise with stirring under ice cooling. The ether layer was separated, and the aqueous layer was salted out and extracted with ether. The ether layer was collected to obtain an ether solution of α-ethylacetoacetic acid.

Diethanolamine (4.4 g) was dissolved in water (5 ml), and this solution was added to an ether solution of α-ethylacetoacetic acid under ice cooling. Subsequently, a solution of silver nitrate (6.8 g) dissolved in water (8 ml) was added dropwise. Then, the precipitated white precipitate was collected by filtration, washed with ice water, followed by isopropanol, and dried to obtain silver α-methylacetoacetate as a white precipitate (yield 6.7 g).
IR (Nujol): 1700 cm ⁻¹ , 1547 cm ⁻¹ .
¹ H-NMR (DMSO-d ₆ ) δ: 0.83 ppm (3H, t), 1.67 ppm (2H, quintet), 2.15 ppm (3H, s), 3.25 ppm (1H, t, J = 7 Hz).

(Reference Example 7)
(Thermogravimetric analysis)
Thermogravimetric analysis (TGA) of each β-ketocarboxylate sample synthesized in Reference Examples 1 to 6 was performed using a thermal analyzer (trade name GTA50: manufactured by Shimadzu Corporation). The measurement conditions were set to 10 ° C./min for the temperature rising rate and in an air atmosphere. The sample amounts were respectively 8.63 mg of silver isobutyryl acetate, 6.77 mg of silver acetoacetate, 5.24 mg of silver propionyl acetate, 5.35 mg of silver benzoyl acetate, 6.18 mg of silver α-methylacetoacetate, and 9.05 mg of silver α-ethylacetoacetate. It was. The TGA measurement results of β-carboxylate silver of Reference Examples 1 to 6 are shown in the graphs of FIGS. In addition, Table 3 below shows the mass change of the sample by the heat treatment obtained from the results of each TGA. In Table 3 below, the silver content (theoretical value) of the synthesized silver β-ketocarboxylate and the residual mass (experimental value) after thermal decomposition of the sample were calculated from the following formula.
Silver content (%) = (atomic weight of silver / molecular weight of silver β-ketocarboxylate) × 100
Residual mass (%) = (A / B) × 100
A: Mass of sample after pyrolysis (mg)
B: Mass of sample used for TGA measurement (mg)

  From the results of FIGS. 1 to 6, according to the β-ketocarboxylate of each reference example, it can be rapidly decomposed at a heating temperature of 210 ° C. or less to form metallic silver quickly, and further, β-ketocarbonyl group It was found that the decomposition temperature can be adjusted by changing. Further, since the residual mass after thermal decomposition of each β-ketocarboxylate showed a value close to the theoretical value of the silver content, each β-ketocarboxylate was sufficiently decomposed at the decomposition temperature, It was found that it was formed.

Example 1-1
A silver paste was produced using the silver isobutyryl acetate obtained in Reference Example 1. First, dodecylamine (1.5 g) was dissolved at normal pressure of 100 ° C., and silver isobutyryl acetate (0.47 g, 2 mmol) synthesized in Reference Example 1 was added thereto (1 M) and stirred to give a silver paste (1.7 g). ) Was manufactured. The particle size of metallic silver contained in the silver paste was 10 nm or less (TEM measurement).

Example 2-1
A silver paste was prepared using the silver α-methylacetoacetate obtained in Reference Example 5. First, silver α-methylacetoacetate (0.45 g, 2 mmol) synthesized in Reference Example 5 was dispersed in lauryl alcohol (2 ml) with stirring (1M) to obtain a mixture. The mixture was heated at 110 ° C. for 5 minutes to obtain a black paste. The black paste was cooled to room temperature, washed with acetone, and the supernatant was removed to obtain a silver paste (1.5 g) containing a fine black powder.

Example 2-2
The silver paste obtained in Example 2-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 160 ° C. for 30 minutes, and then the resistance of the coated film was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a conductivity of 0.41Ω was shown.

Example 3-1
A silver paste was prepared using the silver α-methylacetoacetate obtained in Reference Example 5. First, silver α-methylacetoacetate (0.45 g, 2 mmol) synthesized in Reference Example 5 was dispersed in n-octanol (2 ml) with stirring (1M) to obtain a mixture. The mixture was heated at a normal pressure of 100 ° C. for 3 minutes to obtain a silver paste (1.8 g).

Example 3-2
The silver paste obtained in Example 3-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 160 ° C. for 10 minutes, and then the resistance of the coated film was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a conductivity of 2.3Ω was shown. Moreover, the resistance of the coating film after the heat treatment at the same temperature for 25 minutes was 1.0Ω.

Example 4-1
A silver paste was prepared using the silver α-methylacetoacetate obtained in Reference Example 5. First, silver α-methylacetoacetate (0.45 g, 2 mmol) synthesized in Reference Example 5 was dissolved in N-methylpyrrolidone (2 ml) (1M) to obtain a mixture. The mixture was heated at an ordinary pressure of 110 ° C. for 3 minutes to obtain a silver paste (2.2 g, a mixture having a metal silver particle size of 5 nm to 50 nm (TEM measurement)).

Example 4-2
The silver paste obtained in Example 4-1 was applied onto a slide glass using a dropper under the conditions of a coating area (length 25 mm × width 5 mm) and a coating amount of 0.2 mL. The slide glass coated with the silver paste was heat-treated at 180 ° C. for 30 minutes, and then the resistivity of the coated film was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, the conductivity was 4.4 × 10 ⁻⁵ Ωcm.

Example 5-1
A silver paste was prepared using the silver α-methylacetoacetate obtained in Reference Example 5. First, silver α-methylacetoacetate (0.9 g, 4 mmol) synthesized in Reference Example 5 was dispersed in dimethylformamide (2 ml) with stirring (2M) to obtain a mixture. The mixture was heated at a normal pressure of 100 ° C. for 3 minutes to obtain a silver paste (2.2 g).

Example 5-2
The silver paste obtained in Example 5-1 was applied onto a slide glass using a dropper under the conditions of a coating area (length 25 mm × width 5 mm) and a coating amount of 0.2 mL. The slide glass coated with the silver paste was heat-treated at 130 ° C. for 30 minutes, and then the resistivity of the coated film was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, conductivity of 6.9 × 10 ⁻⁴ Ωcm was exhibited.

Comparative Example 1-1
A silver paste was produced using silver glyoxylate. First, silver glyoxylate (0.2 g, 1.1 mmol) was dispersed in dimethylformamide (1 ml) with stirring (1.1 M) to obtain a mixture. The mixture was heated at a normal pressure of 120 ° C. for 3 minutes to obtain a silver paste (1.1 g).

Comparative Example 1-2
The silver paste obtained in Comparative Example 1-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 130 ° C. for 30 minutes. The obtained metallic silver was fragile and could not keep its shape. The resistance of the metallic silver was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a resistance of 6 MΩ was shown.

Comparative Example 2-1
A silver paste was produced using silver laurate. First, silver laurate (0.2 g, 0.65 mmol) was dispersed in DMF (1 ml) with stirring (0.65 M) to obtain a mixture. The mixture was heated at a normal pressure of 150 ° C. for 5 minutes to obtain a silver paste (1.1 g).

Comparative Example 2-2
The silver paste obtained in Comparative Example 2-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 130 ° C. for 30 minutes. The obtained metallic silver was powdery, and the resistivity of the metallic silver was measured with a multimeter (trade name R6871E-DC Digital Multimeter: manufactured by Advantest). As a result, it did not show conductivity.

Comparative Example 3-1
A silver paste was produced using silver propionate. First, silver propionate (0.2 g, 1.1 mmol) was dispersed in dimethylformamide (1 ml) with stirring (1.1 M) to obtain a mixture. The mixture was heated at a normal pressure of 150 ° C. for 3 minutes to obtain a silver paste (1.1 g).

Comparative Example 3-2
The silver paste obtained in Comparative Example 3-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 130 ° C. for 30 minutes. The obtained metallic silver was powdery, and the resistance of the metallic silver was measured with a multimeter (trade name R6871E-DC Digital Multimeter: manufactured by Advantest). As a result, it did not show conductivity.

Comparative Example 4-1
A silver paste was produced using silver neodecanoate. First, silver neodecanoate (0.2 g, 0.7 mmol) was dissolved in dimethylformamide (1 ml) with stirring (0.7 M) to obtain a mixture. The mixture was heated at a normal pressure of 150 ° C. for 3 minutes to obtain a silver paste (1.1 g).

Comparative Example 4-2
The silver paste obtained in Comparative Example 4-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 130 ° C. for 30 minutes, and the resistance of the coated film was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a resistance of 100 MΩ was shown.

Example 6-1
A silver paste was prepared using the silver α-methylacetoacetate obtained in Reference Example 5. First, silver α-methylacetoacetate (0.45 g, 2 mmol) synthesized in Reference Example 5 was dispersed in ethylene glycol (2 ml) with stirring (1M) to obtain a mixture. The mixture was heated at a normal pressure of 100 ° C. for 3 minutes to obtain a silver paste (2.4 g).

Example 6-2
The silver paste obtained in Example 6-1 was applied onto a slide glass using a dropper under the conditions of a coating area (length 25 mm × width 5 mm) and a coating amount 0.2 mL. The slide glass coated with the silver paste was heat-treated at 150 ° C. for 30 minutes, and then the resistivity of the coated film was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a conductivity of 7.5 × 10 ⁻⁵ Ωcm was exhibited.

Comparative Example 5-1
A silver paste was produced using silver glyoxylate. First, silver glyoxylate (0.2 g, 1.1] mmol) was dispersed in ethylene glycol (1 ml) with stirring (1.1 M) to obtain a mixture. The mixture was heated at a normal pressure of 100 to 110 ° C. for 3 minutes to obtain a silver paste (1.3 g).

Comparative Example 5-2
The silver paste obtained in Comparative Example 5-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 150 ° C. for 30 minutes. The obtained metallic silver was powdery. The resistance of the metallic silver was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a resistance of 3.5 MΩ was shown.

Comparative Example 6-1
A silver paste was produced using silver laurate. First, silver laurate (0.2 g, 0.65 mmol) was dispersed in ethylene glycol (1 ml) with stirring (0.65 M) to obtain a mixture. The mixture was heated at a normal pressure of 180 ° C. for 3 minutes to obtain a silver paste (1.3 g).

Comparative Example 6-2
The silver paste obtained in Comparative Example 6-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 150 ° C. for 30 minutes. The obtained metallic silver was powdery. The resistance of the metallic silver was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, there was no conduction.

Comparative Example 7-1
A silver paste was produced using silver propionate. First, silver propionate (0.2 g, 1.1 mmol) was dispersed in ethylene glycol (1 ml) with stirring (1.1 M) to obtain a mixture. The mixture was heated at a normal pressure of 150 ° C. for 3 minutes to obtain a silver paste (1.3 g).

Comparative Example 7-2
The silver paste obtained in Comparative Example 7-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 150 ° C. for 30 minutes. The obtained metallic silver was powdery. The resistance of the metallic silver was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a resistance of 1000 MΩ was shown.

Comparative Example 8-1
A silver paste was produced using silver neodecanoate. First, silver neodecanoate (0.2 g, 0.7 mmol) was dispersed in ethylene glycol (1 ml) with stirring (0.7 M) to obtain a mixture. The mixture was heated at 140 ° C. for 3 minutes to obtain a silver paste (1.3 g).

Comparative Example 8-2
The silver paste obtained in Comparative Example 8-1 was applied on a slide glass. The slide glass coated with the silver paste was heat-treated at 150 ° C. for 30 minutes. The obtained metallic silver was powdery. The resistance of the metallic silver was measured with a multimeter (trade name R6871E-DC digital multimeter: manufactured by Advantest). As a result, a resistance of 1Ω was shown.

  From the examples and comparative examples, it was confirmed that the silver paste containing metallic silver can be produced from the β-ketocarboxylate represented by the formula (1) by low temperature heating by the production method of the present invention. Moreover, it was confirmed that the silver paste obtained by the production method of the present invention can form a film containing metallic silver even by low-temperature heating. Furthermore, when the silver paste of this invention was used, it has confirmed that the electrical conductivity outstanding after sintering, ie, a low resistivity, is realizable. In addition, since the silver paste of the present invention can be produced without using a reducing agent or the like, there are few impurities contained in the silver paste, and therefore there is an advantage that a side reaction is unlikely to occur when the silver paste is fired. is there.

  When the metallic silver particles contained in the silver paste are not fine particles, the silver paste can be produced without using a dispersant. Such a silver paste makes it possible to form a coating of metallic silver that does not contain a sintering residue of the dispersant. Moreover, according to the silver paste and manufacturing method of this invention, metal silver can be formed easily compared with the conventional method. In addition, since processing at low temperature is possible, it is possible to perform processing in combination with, for example, a resin having low heat resistance, and the use of metallic silver is widened, which can be said to be extremely useful.

Claims (3)

It includes a heat-treated product of a mixture containing a β-ketocarboxylate silver represented by the following formula (1) and a polar solvent. In the heat-treated product, metallic silver obtained by decomposing the silver β-ketocarboxylate contains Silver paste included.

In the formula (1), R is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, R ¹ -CY ₂ —, CY ₃ —, R ¹ —CHY—, R ² O—, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, a heteroaryl group substituted with one or more substituents, R ⁵ R ⁴ N—, a hydroxyl group, It is an amino group or (R ³ O) ₂ CY-.
However, in the above formula,
Y is the same or different and each is a fluorine atom, a chlorine atom, a bromine atom or a hydrogen atom;
R ¹ is a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₉ aliphatic hydrocarbon group, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, or one Or a heteroaryl group substituted with a plurality of substituents,
R ² is a linear, branched or cyclic saturated or unsaturated C ₁ -C ₂₀ aliphatic hydrocarbon group;
R ³ is a linear, branched or cyclic saturated or unsaturated C ₁ -C ₁₆ aliphatic hydrocarbon group;
R ⁴ and R ⁵ are the same or different and are each a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₈ aliphatic hydrocarbon group.
In the formula (1), X is the same or different and each represents a hydrogen atom, a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₂₀ aliphatic hydrocarbon group, R ⁶ O—, R ⁶ S-, R ⁶ —CO—, R ⁶ —CO—O—, a halogen atom, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, one or more substituents A substituted heteroaryl group, an aralkyl group, an aralkyl group substituted with one or more substituents, a cyano group, an N-phthaloyl-3-aminopropyl group, and a 2-ethoxyvinyl group.
However, in the above formula,
R ⁶ represents a linear, branched or cyclic saturated or unsaturated C _{1 to} C ₁₀ aliphatic hydrocarbon group, an aryl group, an aryl group substituted with one or more substituents, a heteroaryl group, one or A heteroaryl group substituted with a plurality of substituents.   The silver paste according to claim 1, wherein the polar solvent is one or more selected from the group consisting of dodecylamine, lauryl alcohol, n-octanol, N-methylpyrrolidone, dimethylformamide, and ethylene glycol.   The silver β-ketocarboxylate represented by the formula (1) is selected from the group consisting of silver isobutyryl acetate, silver benzoyl acetate, silver acetoacetate, silver propionyl acetate, silver α-methylacetoacetate and silver α-ethylacetoacetate 1 It is the above, The silver paste of Claim 1 or 2.

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