JP4050301B2 - Conductive composition, method for forming conductive film, and conductive film - Google Patents

Description

  The present invention relates to a conductive composition, a method for forming a conductive film, and a conductive film.

  Conventionally, it is composed of conductive particles such as silver particles, thermoplastic resin such as acrylic resin and vinyl acetate resin, thermosetting resin such as epoxy resin and unsaturated polyester resin, etc. on a synthetic resin substrate such as polyester film. A conductive composition such as a silver paste obtained by mixing a binder, an organic solvent, a curing agent, a catalyst, etc., is printed by a printing method such as screen printing so that a predetermined circuit pattern is obtained, and these are heated. A method of manufacturing a circuit board by forming a conductive film forming a conductor circuit is known.

For example, Patent Document 1 describes “general formula Ag _x Cu _y (0.001 ≦ x ≦ 0.4, 0.6 ≦ y ≦ 0.999 (atomic ratio)) and the silver concentration on the particle surface. Is a copper alloy powder whose average particle size is higher than the average silver concentration of the particles, the average particle size is 1 to 10 μm, and the fine particles having a particle size of 0.1 to 1 μm are 5 to 80% by weight of the total particles The binder resin contains 10 to 40 parts by weight of a binder resin with respect to 100 parts by weight of the conductive powder, and the binder resin has a weight average molecular weight of 300 to 4000 and a molar ratio of formaldehyde / phenol of 0.8. The electroconductive paste characterized by including the thermosetting phenol resin which is -2. "Is described.

Patent Document 2 describes “a conductive paste using an electrically conductive metal powder and an epoxy resin as a binder for the metal powder.”
Patent Document 3 describes "a silver compound paste characterized by containing particulate silver oxide and a tertiary fatty acid silver salt."

JP 07-331125 A JP 09-92029 A JP 2003-203522 A

However, the present inventor has found that the film obtained from the conductive paste described in Patent Documents 1 and 2 has high electrical resistance, and the silver compound paste described in Patent Document 3 requires a long heating time. The problem of low productivity of the conductive coating was found.
In order to solve such a problem, the present inventor has previously disclosed a conductive composition capable of forming a conductive film on a substrate having a short conductive film formation time and low heat resistance, and the conductive composition. A method for forming a conductive film using a conductive composition and a conductive film have been found and proposed (Japanese Patent Application No. 2006-108751).
Furthermore, when the present inventors produce a circuit pattern by a printing method such as screen printing using the conductive composition described in Japanese Patent Application No. 2006-108751 as ink, there is room for improvement in the printability of the ink. I found out. This is because the thixotropic property of the conductive composition containing silver oxide and a secondary fatty acid silver salt obtained by using a secondary fatty acid having a boiling point of 200 ° C. or lower is relatively low. Guessed.

  Therefore, the present invention provides a conductive composition that is excellent in thixotropy and can be a film having low electrical resistance even with a short heating time, a method for forming a conductive film using the conductive composition, and a conductive film having low electrical resistance. The purpose is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have found that a composition containing silver oxide, a specific secondary fatty acid silver salt, a specific fatty acid and / or a fatty acid silver salt, and a solvent, The present invention has been completed by finding that the film has excellent thixotropy and can be a conductive film having low electric resistance even with a short heating time.

That is, the present invention provides the following (1) to (7).
(1) Silver oxide, secondary fatty acid silver salt having 7 or less carbon atoms, linear or branched fatty acid having 8 or more carbon atoms and / or linear or branched chain having 8 or more carbon atoms The electrically conductive composition containing the fatty acid silver salt of and a solvent.
(2) The total mass of the silver oxide and the secondary fatty acid silver salt, the linear or branched fatty acid having 8 or more carbon atoms and / or the linear or having 8 or more carbon atoms The electrically conductive composition as described in said (1) whose ratio with the mass of branched fatty acid silver salt is 100 / 0.5-100 / 20.
(3) The conductive composition according to the above (1) or (2), wherein the secondary fatty acid silver salt is 2-methylpropanoic acid silver salt.
(4) The conductive composition according to any one of (1) to (3), wherein the solvent is α-terpineol.
(5) A coating film forming step of coating the conductive composition according to any one of the above (1) to (4) on a substrate to form a coating film, and a conductive film by heat-treating the coating film. And a heat treatment step for obtaining a conductive film.
(6) The method for forming a conductive coating film according to (5), wherein the temperature when the coating film is heat-treated in the heat treatment step is 100 to 250 ° C.
(7) The electroconductive film obtained by the formation method of the electroconductive film as described in said (5) or (6).

The conductive composition of the present invention is excellent in thixotropy and can be a conductive film having low electrical resistance even with a short heating time.
Moreover, according to the method for forming a conductive film of the present invention, a conductive film having a low electrical resistance can be obtained.

The present invention will be described in detail below.
First, the conductive composition of the present invention will be described.
The conductive composition of the present invention is
A composition comprising silver oxide, a secondary fatty acid silver salt having 7 or less carbon atoms, a fatty acid having 8 or more carbon atoms and / or a fatty acid silver salt having 8 or more carbon atoms, and a solvent.

Silver oxide will be described below.
The silver oxide contained in the conductive composition of the present invention is silver (I) oxide, that is, Ag ₂ O.
In the present invention, the shape of the silver oxide is not particularly limited, and is preferably a particle shape having a particle size of 10 μm or less, more preferably 1 μm or less. When the particle diameter is within this range, a self-reduction reaction occurs at a lower temperature, and as a result, a conductive film can be formed at a lower temperature.

The secondary fatty acid silver salt will be described below.
The secondary fatty acid silver salt contained in the conductive composition of the present invention has 7 or less carbon atoms. The secondary fatty acid silver salt can have an unsaturated bond.
Examples of the secondary fatty acid silver salt include those represented by the following formula (1).

In the formula, R ¹ and R ² represent an alkyl group having 1 to 3 carbon atoms, and the sum of the number of carbon atoms of R ^{1 and} the number of carbon atoms of R ² is 5 or less. The alkyl group may be branched.

Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.
R ¹ is preferably a methyl group or an ethyl group.
R ² is preferably a methyl group, an ethyl group, or an n-propyl group.

Examples of the secondary fatty acid silver salt include 2-methylpropanoic acid silver salt (also known as silver isobutyrate), 2-methylbutanoic acid silver salt (also known as 2-methylbutyric acid silver salt), and silver 2-methylpentanoate. Salts, silver 2-ethylbutanoate, and silver acrylate.
In particular, the conductive film formed using the resulting composition has a short formation time, specifically, conductivity having a lower electrical resistance even at a temperature of about 180 ° C. for several seconds (for example, about 5 to 60 seconds). Since it can become a film, 2-methylpropanoic acid silver salt is preferable.
The secondary fatty acid silver salt can be used alone or in combination of two or more.

  The secondary fatty acid silver salt is not particularly limited for its production, and can be obtained, for example, by reacting a secondary fatty acid having 7 or less carbon atoms with silver oxide.

The secondary fatty acid used in the production of the secondary fatty acid silver salt is not particularly limited as long as it is a secondary fatty acid having 7 or less carbon atoms. The secondary fatty acid can have an unsaturated bond.
Examples of the secondary fatty acid having 7 or less carbon atoms include those represented by the following formula (2).

In the formula, R ¹ and R ² are as defined above.
R ¹ is preferably a methyl group or an ethyl group.
R ² is preferably a methyl group, an ethyl group, or an n-propyl group.

  Examples of the secondary fatty acid include saturated secondary fatty acids such as 2-methylpropanoic acid (also known as isobutyric acid), 2-methylbutanoic acid (also known as 2-methylbutyric acid), 2-methylpentanoic acid, and 2-ethylbutanoic acid. Grade fatty acids; unsaturated secondary fatty acids such as acrylic acid.

  On the other hand, the silver oxide used in the production of the secondary fatty acid silver salt has the same meaning as the silver oxide contained in the conductive composition of the present invention.

  The reaction between the secondary fatty acid having 7 or less carbon atoms and silver oxide is not particularly limited as long as the reaction represented by the following formula (3) proceeds.

  In the production of the secondary fatty acid silver salt, preferred methods include a method of proceeding while pulverizing silver oxide and a method of reacting secondary fatty acid after pulverizing silver oxide. Specifically, as the former method, silver oxide and a solution of a secondary fatty acid in a solvent are kneaded by a ball mill or the like, and the above-mentioned silver oxide that is a solid is pulverized, and at room temperature, 1 It is preferable to react for about 24 hours, preferably 2 to 8 hours.

Examples of the solvent for dissolving the secondary fatty acid include butyl carbitol, methyl ethyl ketone, isophorone, and α-terpineol.
A solvent can be used individually or in combination of 2 types or more, respectively.
Among these, the use of isophorone and / or α-terpineol as a solvent improves the thixotropy of the conductive composition of the present invention containing the resulting secondary fatty acid silver salt.

  In the conductive composition of the present invention, the quantitative ratio of silver oxide to secondary fatty acid silver salt is the molar ratio between the number A of silver oxide and the number B of secondary fatty acid silver salt (A / B). ) Is preferably 2/1 to 15/1, and more preferably 1/1 to 10/1. When the molar ratio is within this range, the electric resistance of the conductive film formed using the obtained conductive composition is further reduced.

The fatty acid having 8 or more carbon atoms will be described below.
The fatty acid contained in the conductive composition of the present invention has 8 or more carbon atoms.
The fatty acid is a chain, may be linear or branched, and may have an unsaturated bond.
From the viewpoint that the number of carbon atoms of the fatty acid is 8 or more and is more excellent in thixotropy, 8 to 22 is preferable, and 10 to 18 is more preferable.

The fatty acid having 8 or more carbon atoms is represented as R ^3- (COOH) _m , R ³ is an aliphatic hydrocarbon group having 2 or more carbon atoms, m is an integer of 1 or more, and the carbon of R ³ The sum of the number of atoms and m is 8 or more.
m is preferably an integer of 1 to 4.

The number of carbon atoms of the aliphatic hydrocarbon group as R ³ is 2 or more, preferably 4 or more, more preferably 4 to 21, and still more preferably 6 to 21.
The aliphatic hydrocarbon group having 2 or more carbon atoms is not particularly limited. The aliphatic hydrocarbon group is a chain, may be linear or branched, and may have an unsaturated bond.

  Examples of the aliphatic hydrocarbon group having 2 or more carbon atoms include ethyl group, propyl group, butyl group, pentyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n- An undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group is mentioned.

  As the fatty acid, for example, caprylic acid (the number of carbon atoms is 8. In the following paragraph, the numbers in [] indicate the number of carbon atoms of the fatty acid), capric acid [10], lauric acid [12], myristic acid [ 14], monocarboxylic acid-containing saturated aliphatic hydrocarbon compounds such as palmitic acid [16] and stearic acid [18]; polyvalent carboxylic acid-containing saturated aliphatic carbonizations such as compounds represented by the following formula (4) Hydrogen compounds; unsaturated fatty acids such as oleic acid [18], linoleic acid [18], linolenic acid [18], arachidonic acid [20], eicosapentaenoic acid [20], docosahexaenoic acid [22].

  Of these, monocarboxylic acid-containing saturated aliphatic hydrocarbon compounds and polyvalent carboxylic acid-containing saturated aliphatic hydrocarbon compounds are preferred from the viewpoint of superior thixotropy, and capric acid, lauric acid, myristic acid, palmitic acid, stearic acid. The compound represented by formula (4) is more preferred.

The fatty acid silver salt having 8 or more carbon atoms will be described below.
The fatty acid silver salt contained in the conductive composition of the present invention has 8 or more carbon atoms.
The fatty acid silver salt is a chain, may be linear or branched, and may have an unsaturated bond.
The number of carbon atoms of the fatty acid silver salt is 8 or more, and from the viewpoint of being superior in thixotropy, 8 to 22 is preferable, and 10 to 18 is more preferable.

Fatty acid silver salt, R ⁴ - (COOAg) are those represented by _n, R ⁴ is an aliphatic hydrocarbon group having 2 or more carbon atoms, n is an integer of 1 or more, the carbon of R ⁴ The sum of the number of atoms and n is 8 or more.
n is preferably an integer of 1 to 4.

The number of carbon atoms of the aliphatic hydrocarbon group as R ⁴ is 2 or more, preferably 4 or more, more preferably 4 to 21, and more preferably 6 to 21.
The aliphatic hydrocarbon group having 2 or more carbon atoms is not particularly limited and has the same meaning as described above.

  Examples of the fatty acid silver salt having 8 or more carbon atoms include monocarboxylic acid such as silver caprylate, silver caprate, silver laurate, silver myristic acid, silver palmitate and silver stearate. Silver salt of saturated aliphatic hydrocarbon compound; Silver salt of saturated aliphatic hydrocarbon compound containing polyvalent carboxylic acid such as silver salt of compound represented by formula (4); Silver oleate, silver linoleate, Examples include unsaturated fatty acid silver salts such as silver linolenic acid, silver arachidonic acid, silver eicosapentaenoic acid, and silver docosahexaenoic acid.

  Among these, from the viewpoint of being superior in thixotropy, a silver salt of a monocarboxylic acid-containing saturated aliphatic hydrocarbon compound and a silver salt of a polyvalent carboxylic acid-containing saturated aliphatic hydrocarbon compound are preferable, and capric acid silver salt and silver laurate More preferred are salts, silver myristic acid salt, silver palmitate, silver stearate, and silver salt of the compound represented by formula (4).

The fatty acid silver salt having 8 or more carbon atoms is not particularly limited in its production, and can be obtained, for example, by reacting a fatty acid having 8 or more carbon atoms with silver oxide.
The fatty acid having 8 or more carbon atoms used in the production of the fatty acid silver salt having 8 or more carbon atoms is not particularly limited as long as it is a fatty acid having 8 or more carbon atoms.
A fatty acid having 8 or more carbon atoms has the same meaning as described above.
On the other hand, the silver oxide used in the production of the fatty acid silver salt having 8 or more carbon atoms is synonymous with the silver oxide contained in the conductive composition of the present invention.
The production of a fatty acid silver salt having 8 or more carbon atoms can be carried out in the same manner as described above using a fatty acid having 8 or more carbon atoms and silver oxide.

The fatty acid having 8 or more carbon atoms and the fatty acid silver salt having 8 or more carbon atoms can be used alone or in combination of two or more.
Among them, from the viewpoint of being excellent in thixotropy and having a lower electrical resistance, it is at least two selected from the group consisting of fatty acids having 8 or more carbon atoms and silver salts of fatty acids having 8 or more carbon atoms. Preferably, at least two of the fatty acids having 8 or more carbon atoms are more preferable, and a combination of stearic acid and lauric acid is more preferable.

  From the viewpoint that the amount of fatty acid having 8 or more carbon atoms and / or fatty acid silver salt having 8 or more carbon atoms can be a film having a lower electrical resistance, the total of 100 masses of silver oxide and secondary fatty acid silver salt. The amount is preferably 20 parts by mass or less, more preferably 0.5 to 15 parts by mass with respect to parts.

  Further, the amount of the fatty acid having 8 or more carbon atoms and / or the fatty acid silver salt having 8 or more carbon atoms is a film having a lower electric resistance, and from the viewpoint of excellent thixotropy of the ink, silver oxide, secondary grade Ratio of total mass of fatty acid silver salt and mass of fatty acid having 8 or more carbon atoms and / or fatty acid silver salt having 8 or more carbon atoms [(silver oxide + secondary fatty acid silver salt) / (number of carbon atoms 8 or more fatty acids and / or fatty acid silver salts having 8 or more carbon atoms)] is preferably 100 / 0.5 to 100/20, more preferably 100 / 0.5 to 100/15. .

The solvent will be described below.
The solvent contained in the conductive composition of the present invention is not particularly limited as long as it can dissolve the fatty acid and / or fatty acid silver salt.
For example, butyl carbitol, methyl ethyl ketone, isophorone, α-terpineol and the like can be mentioned.
Among these, α-terpineol is preferable from the viewpoint that it can be a film having lower electric resistance.
A solvent can be used individually or in combination of 2 types or more, respectively.

  The amount of the solvent is preferably 20 to 50 parts by mass, preferably 25 to 40 parts by mass with respect to 100 parts by mass of silver oxide, from the viewpoint that the film is excellent in thixotropy and can have a lower electrical resistance. Is more preferable.

The electrically conductive composition of this invention can contain additives, such as a metal powder and a reducing agent, as needed.
Specific examples of the metal powder include copper, silver, and aluminum. Among these, copper and silver are preferable. Moreover, it is preferable that it is a metal powder with a particle size of 0.01-10 micrometers.
Specific examples of the reducing agent include ethylene glycols.

The conductive composition of the present invention is not particularly limited for its production. For example, a roll, a kneader, an extruder, a universal agitator, containing silver oxide, a secondary fatty acid silver salt, a fatty acid and / or a fatty acid silver salt, a solvent, and an additive that can be contained as necessary. And the like.
In the conductive composition of the present invention, as described above, the silver oxide used in the production of the secondary fatty acid silver salt is the same as the silver oxide contained in the conductive composition of the present invention. In addition to containing a pre-synthesized secondary fatty acid silver salt when producing the conductive composition of the present invention, for example, silver oxide and secondary fatty acid are reacted in the system to produce secondary fatty acid silver salt By generating the secondary fatty acid silver salt in the conductive composition.
The same applies to fatty acid silver salts having 8 or more carbon atoms.

  The conductive composition of the present invention has a thixo index (viscosity at 1 rpm) measured with an E-type viscometer using a 3 ° cone under conditions of 23 ° C. and 65% RH (relative humidity). / 10 rpm) is preferably 4.0 or more, and more preferably 5.0 to 20.

  Examples of the use of the conductive composition of the present invention include ink for producing a circuit such as an electronic circuit or an antenna on a substrate.

Since the conductive composition of the present invention contains a secondary fatty acid silver salt, it can be a film with low electrical resistance, the formation time of the conductive film is short, specifically, a temperature of about 180 ° C. It can be formed in a few seconds to 1 minute, and a conductive film can be satisfactorily formed even on a substrate having low heat resistance. This is presumably because the secondary fatty acid silver salt is easily decomposed into silver by heat treatment, and the secondary fatty acid produced by the decomposition or a decomposition product thereof is easily volatilized. Moreover, it is clear from the result of thermogravimetry (TGA) that it is more easily reduced than the tertiary fatty acid silver salt.
Moreover, since the electrically conductive composition of this invention contains a C8 or more fatty acid and / or a C8 or more fatty acid silver salt, it is excellent in thixotropy. This is because the compatibility between the fatty acid having 8 or more carbon atoms and / or the fatty acid silver salt having 8 or more carbon atoms and the solvent is good, so that the fatty acid having 8 or more carbon atoms and / or fatty acid silver having 8 or more carbon atoms is used. The present inventors speculate that the salt acts as a silver oxide dispersant in the system and imparts thixotropic properties to the composition.
Thus, the electrically conductive composition of this invention is excellent in the reduction of the electrical resistance of a film, and the balance of thixotropy.
When the conductive composition of the present invention is used as an ink, it is easy to control the film thickness during printing, printing can be performed with precision even with fine lines, no blurring, good separation, and excellent printability.

Next, the method for forming the conductive film of the present invention will be described below.
The conductive film forming method of the present invention includes a coating film forming step of forming a coating film by applying the conductive composition of the present invention on a substrate, and heat-treating the obtained coating film to form a conductive film. And a heat treatment step for obtaining a conductive film.
Below, a coating-film formation process and a heat processing process are explained in full detail.

<Coating film formation process>
A coating-film formation process is a process of apply | coating the electrically conductive composition of this invention on a base material, and forming a coating film.
Here, examples of the base material include films such as polyethylene terephthalate (PET), polyethylene naphthalate, and polyimide; and substrates such as copper plate, copper foil, glass, and epoxy.
The conductive composition of the present invention is applied onto a substrate by a coating method such as inkjet, screen printing, gravure printing, offset printing, letterpress printing, and forms a coating film.

<Heat treatment process>
The heat treatment step is a step of obtaining a conductive film by heat-treating the coating film obtained in the coating film forming process.
In the heat treatment step, the substrate having a coating film can be used as a substrate with a conductive coating by heat-treating the coating to obtain a conductive coating.

  In the heat treatment step, the temperature at which the coating film is heat-treated is preferably 100 to 250 ° C., and about 180 ° C. from the viewpoint that a good conductive film can be formed even on a substrate having low heat resistance. More preferably, the heating is performed for several seconds. When the heat treatment temperature and time are within this range, a good conductive film can be formed even on a substrate having low heat resistance. This is because the conductive composition used in the method for forming a conductive film of the present invention contains a secondary fatty acid silver salt.

  In addition, in the formation method of the electroconductive film of this invention, the electroconductive film can be formed even when the coating film obtained at the coating-film formation process is based on irradiation of an ultraviolet-ray or infrared rays. For this reason, ultraviolet rays or infrared rays can be used in the heat treatment step.

  In the method for forming a conductive film of the present invention, the secondary fatty acid silver salt and the fatty acid silver salt having 8 or more carbon atoms contained in the coating film are decomposed by heat-treating the coating film. It becomes a secondary fatty acid, a fatty acid having 8 or more carbon atoms, or a decomposition product thereof. A part of the secondary fatty acid, fatty acid having 8 or more carbon atoms, or a decomposition product thereof generated by the decomposition is volatilized. In addition, some secondary fatty acids and fatty acids having 8 or more carbon atoms react with silver oxide to become secondary fatty acid silver salts and fatty acid silver salts having 8 or more carbon atoms, which are reduced. , Silver is produced. By repeating such a cycle, silver is efficiently generated in the system, and is formed into a film on the substrate by silver to form a conductive film (silver film), that is, the conductive film of the present invention.

The conductive film of the present invention will be described below.
The conductive film of the present invention is obtained by the method for forming a conductive film of the present invention.

The conductive film of the present invention is heat-treated at 180 ° C. for 1 minute, and its volume resistivity is preferably 12 × 10 ⁻⁶ Ω · cm or less, preferably 10 × 10 ⁻⁶ to 8 ×. More preferably, it is 10 ⁻⁶ Ω · cm.
The conductive coating of the present invention can be printed with high precision even with fine lines, has no blurring, has good release, and is excellent in printability.
Applications of the conductive coating of the present invention include, for example, electronic circuits and antenna circuits.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to this.

1. Evaluation (1) Thixo Index The obtained conductive composition was subjected to a rotation speed of 1 r. Using a 3 ° cone with an E-type viscometer under the conditions of 23 ° C. and 65% RH (relative humidity). p. m and 10r. p. The viscosity at m was measured. And 1r. p. viscosity at m and 10 r. p. The thixo index was determined from the ratio to the viscosity at m (viscosity at 1 rpm) / viscosity at 10 rpm. The results are shown in Table 1.

(2) Volume resistivity Composition obtained by screen-printing the conductive composition obtained on a 125 μm-thick PET film (trade name: Lumirror S56, manufactured by Toray Industries, Inc.) as a substrate and drying at 180 ° C. for 1 minute. A sample having a coating was prepared. Using the obtained sample, the volume resistivity of the coating was measured by a 4-terminal 4-probe method using a low resistivity meter (Lorestar GP, manufactured by Mitsubishi Chemical Corporation). The results are shown in Table 1.
In Table 1, “unmeasurable” as a result of volume resistivity indicates that the volume resistivity could not be measured because the composition did not form a film.

2. Preparation of Conductive Composition The components shown in Table 1 were charged into a ball mill in the amounts (unit: g) shown in Table 1, and mixed while grinding silver oxide for 24 hours to prepare a conductive composition.

Details of the components shown in Table 1 are as follows.
Silver oxide: manufactured by Toyo Chemical Industry Co., Ltd.
・ Secondary fatty acid silver salt: α-terpineol (manufactured by Tokyo Chemical Industry Co., Ltd.) in 60 g is added with 30.5 g of 2-methylpropanoic acid (manufactured by Kanto Chemical Co., Ltd.) and 40 g of silver oxide to form a mixture. 2-methylpropanoic acid silver salt / fatty acid silver salt obtained by kneading in a ball mill for 12 hours: in 60 g of α-terpineol (manufactured by Tokyo Chemical Industry Co., Ltd.), 97 g of stearic acid (manufactured by Kanto Chemical Co., Ltd.) and 40 g of silver oxide And stearic acid silver salt obtained by kneading for 12 hours with a ball mill, stearic acid: manufactured by Kanto Chemical Co., Ltd., palmitic acid: manufactured by Wako Pure Chemical Industries, Ltd., myristic acid: Wako Pure Chemical Industries, Ltd. Industrial company, lauric acid: manufactured by Kanto Chemical Co., Ltd., capric acid: trade name LUNAC 10-98, Kao Corporation, caprylic acid: trade name LUNAC 8-98, manufactured by Kao Corporation, fat Acid 1: Compound represented by the following formula (4), Ricacid BT-W, manufactured by Shin Nippon Chemical Co., Ltd.

・ Pentanoic acid: manufactured by Kanto Chemical Co., Ltd. ・ Fatty acid 2: Compound represented by the following formula (5), Ricacid TH-W, manufactured by Shin Nippon Rika Co., Ltd.

Fatty acid 3: Compound represented by the following formula (6), Ricacid HH-W, manufactured by Shin Nippon Rika Co., Ltd.

・ Solvent: α-terpineol, manufactured by Tokyo Chemical Industry Co., Ltd.

As is apparent from the results shown in Table 1, Comparative Example 1 containing no fatty acid having 8 or more carbon atoms and / or no fatty acid silver salt having 8 or more carbon atoms was inferior in thixotropy.
Further, Comparative Example 2 containing a fatty acid having less than 8 carbon atoms and Comparative Examples 3 and 4 containing a compound other than a fatty acid having 8 or more carbon atoms were inferior in thixotropy, and the composition did not form a film.
On the other hand, the compositions of Examples 1 to 11 were excellent in thixotropy, and the electrical resistance of the coating obtained by low-temperature and short-time heat treatment was low.

Claims (7)

Silver oxide, secondary fatty acid silver salt having 7 or less carbon atoms, linear or branched fatty acid having 8 or more carbon atoms and / or linear or branched fatty acid silver having 8 or more carbon atoms A conductive composition containing a salt and a solvent. The total mass of the silver oxide and the secondary fatty acid silver salt, the linear or branched fatty acid having 8 or more carbon atoms and / or the linear or branched fatty acid having 8 or more carbon atoms . The conductive composition according to claim 1, wherein the ratio of the fatty acid silver salt to the mass is 100 / 0.5 to 100/20.   The conductive composition according to claim 1 or 2, wherein the secondary fatty acid silver salt is 2-methylpropanoic acid silver salt.   The conductive composition according to claim 1, wherein the solvent is α-terpineol.   A coating film forming step of forming a coating film by applying the conductive composition according to any one of claims 1 to 4 on a substrate, a heat treatment step of obtaining a conductive film by heat-treating the coating film, A method for forming a conductive coating comprising:   The method for forming a conductive film according to claim 5, wherein, in the heat treatment step, a temperature when the coating film is heat-treated is 100 to 250 ° C. 6.   The electroconductive film obtained by the formation method of the electroconductive film of Claim 5 or 6.