JP2013120624A - Conductive paste and conductive thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste in which reduction in flex resistance is minimized and gas generation is suppressed, and to provide a conductive thin film formed by using this conductive paste.SOLUTION: The conductive paste contains a polyimide precursor solution or a polyimide solution, a metal capturing agent, and conductive particles. The metal capturing agent is any one kind of compound selected from a thiol compound represented by general formula (1) or a sulfide compound represented by general formula (2). Ar-SH ... (1) (In the formula (1), Ar represents a benzene ring, and may have a substituent group). (A-R'-O-R-S)... (2) (In the formula (2), R', R represents an alkylene group, and A represents a fluoroalkyl group).

Description

  The present invention relates to a conductive paste and a conductive thin film.

  The conductive paste is used, for example, when forming a conductive circuit of a printed wiring board. The conductive path is formed by a screen printing method using a conductive paste. Moreover, in a double-sided printed wiring board or a build-up multilayer printed wiring board, the through holes are filled with a conductive silver paste, and the wiring patterns of the respective layers are electrically connected. A conductive paste for forming a thick film conductor circuit on a ceramic substrate is also known.

  For example, Patent Document 1 proposes a conductive ink in which a metal powder and a metal-organic decomposition (MOD) compound are dispersed in an organic liquid vehicle. This conductive ink is used when producing a conductor to be transferred to a polymer substrate such as a printed wiring board or a flexible printed wiring board by screen printing, gravure printing or the like. When a MOD compound such as silver neodecanoate is heated, it begins to decompose and deposits a metal. Since the deposited metal has a small particle size, it has high activity and is sintered at a relatively low temperature. When this conductive ink is printed on a substrate and baked by heat treatment, the metal deposited from the MOD compound promotes the bonding between the metal powders and bonds to the substrate to form a conductive thin film.

  However, such a conductive thin film is substantially composed only of silver. For this reason, the flexibility of the obtained conductive thin film is low, and when the film is thick, the conductive thin film is cracked and the bending resistance is lowered.

  In order to improve the flexibility of the conductive thin film, for example, Patent Document 2 uses a silver-containing organic compound having a structure in which a silver atom and an organic portion are bonded via a hetero atom. However, the film thickness shown in the examples is 30 μm at the maximum, and this technique has a problem that hydrocarbon gas or carbon dioxide gas is released during firing of the silver-containing organic compound.

  In view of the above problems, the present invention is formed using a conductive paste in which a decrease in bending resistance is suppressed and gas generation is suppressed even when the thickness is formed, and the conductive paste. It is to provide a conductive thin film.

In order to solve the above problems, the present invention includes a polyimide precursor solution or a polyimide solution, a metal scavenger, and conductive particles, and the metal scavenger is represented by the following general formula (1). There is provided a conductive paste characterized by being at least one compound selected from a thiol compound or a sulfide compound represented by the following general formula (2).
Ar-SH (1)
[In the formula (1), Ar represents a benzene ring and may have a substituent. ]
(AR′—O—R—S) ₂ (2)
[In the formula (2), R ′ and R represent an alkylene group, and A represents a fluoroalkyl group. ]

  According to the present invention, even when the thickness is increased, a conductive paste in which a decrease in bending resistance is suppressed and gas generation is further suppressed, and a conductive thin film formed using the conductive paste Is realized.

  Embodiments of the present invention will be described below. The present invention is not limited to the embodiments described below.

(Conductive paste)
The conductive paste according to the present invention contains a polyimide precursor solution or a polyimide solution, a metal scavenger, and conductive particles. The conductive paste is manufactured by preparing a polyimide precursor solution or a soluble polyimide solution in advance, mixing conductive fine particles, and then adding a metal scavenger dissolved in a solvent.

  Moreover, when manufacturing the electrically conductive paste of this invention, resin, such as a polyamide imide and polyether sulfone, may be added in the range which does not impair the essence of this invention.

  In addition, in the production of the conductive paste of the present invention, the method for adding the conductive fine particles and the method for adding the metal scavenger are not particularly limited.

  In addition, in the production of the conductive paste of the present invention, the filler, pigment, pigment dispersant, solid lubricant, anti-settling agent, leveling agent, surface conditioner, moisture absorber are within the range not impairing the essence of the present invention. , Anti-gelling agent, antioxidant, UV absorber, light stabilizer, plasticizer, anti-coloring agent, anti-skinning agent, surfactant, antistatic agent, antifoaming agent, antibacterial agent, antifungal agent, Known additives such as preservatives and thickeners may be added.

  In addition, you may use together the chemical imidation method which adds the dehydrating agent and imidation catalyst more than stoichiometry to an electroconductive paste, and advances imidation. The conductive paste of the present invention is excellent in adhesiveness with a base material, and can form a strongly integrated conductive coating film or conductive thin film by completing imidization after coating on the base material.

(Conductive fine particles)
The conductive fine particles are preferably metal fine particles having high conductivity such as platinum, gold, silver, nickel and palladium. The conductive fine particles are more preferably coated with a metal shell on the core particles. Hereinafter, the conductive fine particles in which the core particles are coated with the metal shell are referred to as “core-shell type conductive fine particles”. This is because when the conductive fine particles are core-shell type conductive fine particles, the cost and weight of the paste material can be reduced.

  In the core-shell type conductive fine particles, the core particles are not particularly limited. In view of characteristics such as cost and heat resistance, inorganic fine particles such as carbon, glass and ceramics are preferred. As the inorganic fine particles, those having an arbitrary shape such as a scale shape, a needle shape, or a resin shape can be used. The inorganic fine particles are more preferably hollow or foamed fine particles from the viewpoint of dispersibility, stability and weight reduction when mixed with a polyimide precursor solution or a soluble polyimide solution.

  In the core-shell type conductive fine particles, the metal shell preferably covers 80% or more of the surface area of the inorganic fine particles that are the core particles with a metal (for example, silver). The metal shell more preferably covers 90% or more of the surface area of the inorganic fine particles that are core particles, and more preferably 95% or more. This is because when the core particle coverage of the metal shell is less than 80%, the conductivity is lowered. The metal shell may be a single layer or two or more layers. Further, the remaining surface of the core particle may be coated with another conductive metal within a range that does not impair the essence of the present invention.

  Examples of other conductive metals other than silver include noble metals such as platinum, gold, and palladium, base metals such as molybdenum, nickel, cobalt, iron, copper, zinc, tin, antimony, tungsten, manganese, titanium, vanadium, and chromium. Is mentioned.

  The average particle diameter of the core-shell type conductive fine particles is preferably 1 μm or more and less than 50 μm. This is because if the average particle diameter of the core-shell type conductive fine particles is less than 1 μm, the core-shell type conductive fine particles are likely to aggregate and become difficult to disperse. Moreover, it is because the surface roughness of the electroconductive thin film obtained will become large that the average particle diameter of core-shell type electroconductive fine particles is 50 micrometers or more. In other words, when the average particle diameter of the core-shell type conductive fine particles is 1 μm or more, the core-shell type conductive fine particles are difficult to aggregate. Further, when the average particle diameter of the core-shell type conductive fine particles is less than 50 μm, the surface roughness of the obtained conductive thin film may not be so large.

  A method for forming the inorganic fine particles as core particles with a metal shell is not particularly limited, and examples thereof include electrolytic plating, electroless plating, vacuum deposition, and sputtering.

(Metal scavenger)
In the present invention, the metal scavenger that can be suitably used is preferably a thiol compound represented by the following chemical formula (1) or a sulfide compound represented by the following chemical formula (2).
Ar-SH (1)
[In the formula (1), Ar represents a benzene ring and may have a substituent. ]
Examples of the substituent include a halogen atom.
(AR′—O—R—S) ₂ (2)
[In the formula (2), R ′ and R represent an alkylene group, and A represents a fluoroalkyl group. ]
Examples of R ′ and R include a C1-14 alkylene group, and examples of A include a C1-16 fluoroalkyl group.

  The thiol compound represented by the general formula (1) is 4-fluorobenzenethiol represented by the following formula (3),

・・・（３）

... (3)

・・・（４） Alternatively, the sulfide compound represented by the general formula (2) is at least one selected from dithiobis (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane) represented by the following formula (4): Preferably there is.

... (4)

  The addition amount of the metal scavenger is preferably 0.01% by weight or more and 10% by weight or less with respect to the solid content of the polyimide precursor solution or the soluble polyimide solution. This is because if the amount is less than 0.01% by weight, the metal scavenger cannot capture the metal. Further, if the amount is more than 10% by weight, the conductive fine particles may rarely aggregate.

(Polyimide precursor solution or soluble polyimide solution)
As the polyimide precursor solution, a solution obtained by reacting diamine or a derivative thereof with tetracarboxylic dianhydride or a derivative thereof in a polar solvent (polyamide acid solution) can be used. Further, the soluble polyimide can be dissolved in the polar solvent.
Examples of the polyimide precursor solution or soluble polyimide solution that can be suitably used in the present invention include those having a viscosity of less than 1000 poise. It is because it becomes difficult to disperse | distribute the said electroconductive fine particles uniformly as the viscosity of a solution is 1000 poise or more.

  Although the manufacturing method of a polyimide precursor solution or a soluble polyimide solution is not specifically limited, The method of making diamine and tetracarboxylic dianhydride react in a polar solvent may be simple.

(Diamine)
Examples of the diamine that can be suitably used in the present invention include paraphenylene diamine (PPD), metaphenylene diamine (MPDA), 2,5-diaminotoluene, 2,6-diaminotoluene, and 4,4′-diaminobiphenyl. 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 2,2-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane (MDA), 2,2-bis- (4-aminophenyl) propane, 3,3′-diaminodiphenylsulfone (33DDS), 4,4′- Diaminodiphenylsulfone (44DDS), 3,3′-diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfur 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether (34 ODA), 4,4′-diaminodiphenyl ether (ODA), 1,5-diaminonaphthalene, 4,4′-diaminodiphenyldiethylsilane, 4,4′-diaminodiphenylsilane, 4,4′-diaminodiphenylethylphosphine oxide, 1,3-bis (3-aminophenoxy) benzene (133APB), 1,3-bis (4-aminophenoxy) benzene (134APB) ), 1,4-bis (4-aminophenoxy) benzen, bis [4- (3-aminophenoxy) phenyl] sulfone (BAPSM), bis [4- (4-aminophenoxy) phenyl] sulfone (BAPS), 2,2-bis [4- (4-aminophenoxy) phenyl] propane ( APP), 2,2-bis (3-aminophenyl) 1,1,1,3,3,3-hexafluoropropane, 2,2-bis (4-aminophenyl) 1,1,1,3,3 , 3-hexafluoropropane, aromatic diamines such as 9,9-bis (4-aminophenyl) fluorene, aliphatic diamines such as tetramethylene diamine and hexamethylene diamine, cyclohexane diamine, isophorone diamine, norbornane diamine, bis (4 -Alicyclic diamines such as -aminocyclohexyl) methane and bis (4-amino-3-methylcyclohexyl) methane.

Note that one or more of these diamines may be mixed and used for the polymerization reaction. Among these diamines, particularly preferred diamines are paraphenylenediamine (PPD), metaphenylenediamine (MPDA), 4,4′-diaminodiphenylmethane (MDA), 3,3′-diaminodiphenylsulfone (33DDS), 4 , 4′-diaminodiphenyl sulfone (44DDS), 3,4′-diaminodiphenyl ether (34 ODA), 4,4′-diaminodiphenyl ether (ODA), 1,3-bis (3-aminophenoxy) benzene (133APB), 1 , 3-bis (4-aminophenoxy) benzene (134APB), bis [4- (3-aminophenoxy) phenyl] sulfone (BAPSM), bis [4- (4-aminophenoxy) phenyl] sulfone (BAPS), 2 , 2-bis [4- (4-aminopheno Shi) include phenyl] propane (BAPP) is.
These diamine derivatives may be used.

(Tetracarboxylic dianhydride)
Examples of tetracarboxylic dianhydrides that can be suitably used in the present invention include pyromellitic dianhydride (PMDA), 1,2,5,6-naphthalene tetracarboxylic dianhydride, 5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,3, 3'4'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2', 3,3'-benzophenone tetracarboxylic dianhydride 2,3,3 ′, 4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA), bis (3,4-dicarboxyphenyl) ) No sulfone , Bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, 2,2-bis [3,4- (dicarboxyphenoxy) phenyl] propane dianhydride (BPADA), 4,4′- (Hexafluoroisopropylidene) diphthalic anhydride, oxydiphthalic anhydride (ODPA), bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) sulfoxide dianhydride, thiodiphthalate Acid dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2, 7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride and 9,9-bis [4- (3,4'-dicarboxyphenoxy) phenyl Aromatic tetracarboxylic dianhydrides such as fluorene dianhydride, cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,4,5-tetrahi Drofurantetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,4-dicarboxy-1-cyclohexylsuccinic dianhydride, 3,4-dicarboxy-1, Examples include 2,3,4-tetrahydro-1-naphthalene succinic dianhydride.

  Moreover, these tetracarboxylic dianhydrides may be reacted with alcohols such as methanol and ethanol to form ester compounds. Note that one or more of these tetracarboxylic dianhydrides may be mixed and used for the polymerization reaction.

Among these tetracarboxylic dianhydrides, particularly preferred tetracarboxylic dianhydrides include pyromellitic dianhydride (PMDA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride ( BPDA), 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 2,2-bis [3,4- (dicarboxyphenoxy) phenyl] propane dianhydride (BPADA), oxydiphthalate An acid anhydride (ODPA) is mentioned.
In addition, you may use the derivative | guide_body of these tetracarboxylic dianhydrides.

(Polar solvent)
Examples of polar solvents that can be suitably used in the present invention include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, and 1,3-dimethyl. -2-imidazolidinone, N-methylcaprolactam, hexamethylphosphoric triamide, 1,2-dimethoxyethane, diglyme, triglyme, gamma butyl lactone, cyclohexanone and the like.

  Among these solvents, particularly preferable solvents include N, N-dimethylacetamide (DMAC) and N-methyl-2-pyrrolidone (NMP).

  In addition, these solvents may be used independently, may be used as a mixture, and may be used by mixing with other solvents, such as an aromatic hydrocarbon, for example, toluene, xylene, etc. Moreover, in order to adjust a viscosity, you may mix with the material containing many alcoholic OH groups, such as glycerol.

  In addition to manufacturing a polyimide precursor solution or a soluble polyimide by the above method, a commercially available polyimide precursor solution or a soluble polyimide solution may be used.

(Conductive thin film)
The conductive thin film of the present invention is formed by applying the conductive paste of the present invention on a substrate and then heat-treating it. In the conductive thin film formed in this way, conductive particles in a state of being captured by the metal scavenger are dispersed in the polyimide resin.

  In addition, the conductive thin film is obtained by casting (injecting) a conductive paste onto a substrate, for example, by a bar coating method, followed by heat treatment (temperature 80 to 120 ° C., 15 minutes, further temperature 200 to 300 ° C., 60 minutes). Further, it may be released from the substrate, fixed to a metal frame, and heated, for example, at a temperature of 200 to 300 ° C. for 60 minutes.

  The film thickness of the conductive thin film can be arbitrarily determined, but is usually about 1 μm to 125 μm. When the conductive paste of the present invention is used, a highly flexible conductive thin film can be obtained even when the film thickness is 50 μm to 125 μm.

The volume resistivity of the conductive thin film of the present invention is preferably 2 × 10 ⁻⁶ Ω · cm or more and 1 × 10 ² Ω · cm or less. The volume resistivity of the conductive thin film is within such a range by changing the content (5 to 40 wt%) of the conductive fine particles in the polyimide, the film thickness (10 to 30 μm) of the conductive thin film, the type, and the like. It will fit. When the conductive thin film has a volume resistivity within this range, when a conductive path is formed by screen printing or the like, or a conductive medium that actively forms electricity by forming it as a coating on the power supply terminal connection part of an electric circuit, a so-called electric wire Alternatively, excellent electrical conductivity can be maintained even when an electric circuit is formed.

(substrate)
After conducting treatment such as defoaming and filtration on the conductive paste as necessary, methods such as doctor blade, screen printing, casting, etc. on the base material (for example, heat resistant substrate, flexible heat resistant film, etc.) Apply the conductive paste. Then, the conductive paste is dried by heating, and gradually or stepwise heated to 200 ° C. to 450 ° C. to advance imidization. Alternatively, the solvent is removed.

  As a specific substrate, a plastic film, glass film, or ceramic film or plate can be used.

  Examples of materials used for plastic films and plates include polyesters, polyolefins, vinyl resins, and other resins.

  Examples of polyesters include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Examples of polyolefins include polypropylene (PP), polystyrene, polyethylene (PE), EVA and the like. Examples of the vinyl resin include polyvinyl chloride and polyvinylidene chloride. Examples of other resins include polycarbonate (PC), polysulfone (PSF), polyethersulfone (PES), polyetheretherketone (PEEK), polyamide, polyimide, acrylic resin, triacetylcellulose (TAC), and the like. Illustrated. Examples of the ceramic include alumina and silica.

  The film or plate as the substrate may be a single layer structure of the above material or a multilayer structure of two or more layers. When using a glass plate as a substrate for display applications, it is preferable to use tempered glass provided with a tempered layer. The tempered glass has a higher ability to prevent breakage than a normal glass plate, and even in the unlikely breakage, the crushed pieces are small and the end face is not sharp, and the product made by safety is high.

  The substrate used for the display is preferably a plastic film such as PET, PEN, PE, PP, polystyrene, polyvinyl chloride, polyvinylidene chloride or TAC, or a plastic plate, and particularly for light-transmitting electromagnetic wave shielding films. PET is preferable from the viewpoints of properties and processability.

  When a plastic film or a plastic plate is used as the transparent conductive thin film, the substrate is preferably highly transparent. Usually, the total visible light transmittance of the plastic film or plastic plate is preferably 70 to 100%, more preferably 85 to 100%, and particularly preferably 90 to 100%. In the present invention, the plastic film and the plastic plate may be colored so as not to interfere with the object of the present invention.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the scope of the present invention.

  The flexibility of the conductive thin film is obtained by winding a conductive thin film (or a conductive coating film) formed on a flexible substrate such as Kapton (registered trademark) film or Upilex (registered trademark) film around a cylinder having a diameter of 5 mm, Evaluation was made based on whether or not the conductive coating film or the conductive thin film had a defect such as a crack or a crack. Here, the conductive coating film is a film in a state before heating, in which a conductive paste is applied on a substrate. In the table below, those marked with “O” in the flexibility evaluation column are those where no cracks or cracks occurred, and those marked with “x” in the first place are conductive coatings. No film or conductive thin film was formed. The volume resistivity of the conductive thin film was measured by a four-short needle method.

  In the present invention, “high flexibility” means that the conductive coating film or conductive thin film formed on the flexible substrate is broken or cracked even if it is wound around a cylinder having a diameter of 5 mm. Means no.

Example 1
40 g of polyimide precursor solution (trade name CT4112: manufactured by Kyocera Chemical Co., Ltd., solid content: 17.5 wt%) and 8.77 g of silver-coated carbon powder (trade name: AG / GCM-10: manufactured by Mitsubishi Materials Corporation, average particle size) 10 μm) was added and stirred for 15 minutes.

  Subsequently, 0.018 g of 4-fluorobenzenethiol (trade name 4-fluorobenzenethiol: manufactured by Tokyo Chemical Industry Co., Ltd.) is added to 10 g of N-methyl-2-pyrrolidone solution in the polyimide precursor solution containing the silver-coated carbon powder. A solution in which was dissolved was added and stirred for 8 hours to obtain a conductive paste. Here, 4-fluorobenzenethiol is a metal scavenger. 4-Fluorobenzenethiol is added in an amount of 0.25% by weight based on the solid content of the polyimide precursor solution.

  Then, this conductive paste is applied onto the substrate by the above-described method, and further heated in a drying furnace, for example, at 120 ° C. for 30 minutes, and further at 200 ° C. for 30 minutes to provide a highly flexible conductive material. A thin film was obtained. The film thickness of the conductive thin film was 15 μm. The results are shown in Table 1.

(Example 2)
The silver-coated carbon powder (7.77 g) of Example 1 was added to 40 g of a polyimide precursor solution (trade name CT4200H: manufactured by Kyocera Chemical Co., Ltd., solid content: 15.5% by weight) and stirred for 15 minutes.

  Next, a solution in which 0.018 g of 4-fluorobenzenethiol of Example 1 was dissolved in 10 g of N-methyl-2-pyrrolidone of Example 1 was dissolved in the polyimide precursor solution containing the silver-coated carbon powder. The mixture was further stirred for 8 hours to obtain a conductive paste. 4-Fluorobenzenethiol is added in an amount of 0.25% by weight based on the solid content of the polyimide precursor solution.

  Then, this conductive paste is applied onto the substrate by the above-described method, and further heated in a drying furnace, for example, at 120 ° C. for 30 minutes, and further at 200 ° C. for 30 minutes to provide a highly flexible conductive material. A thin film was obtained. The film thickness of the conductive thin film was 16 μm. The results are shown in Table 1.

(Example 3)
The silver-coated carbon powder (8.77 g) of Example 1 was added to 40 g of a polyimide precursor solution (trade name CT4112: manufactured by Kyocera Chemical Co., Ltd., solid content: 17.5% by weight) and stirred for 15 minutes. Next, 0.0035 g of dithiobis (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane) in 10 g of N-methyl-2-pyrrolidone was added to the polyimide precursor solution containing the silver-coated carbon powder [Dithibis A solution in which (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane) (abbreviation: DFU)] (manufactured by Dojindo) was added and stirred for 8 hours to obtain a conductive paste. Here, dithiobis is a metal scavenger. Dithiobis (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane) is added in an amount of 0.25% by weight based on the solid content of the polyimide precursor solution.

  Then, this conductive paste is applied onto the substrate by the above-described method, and further heated in a drying furnace, for example, at 120 ° C. for 30 minutes, and further at 200 ° C. for 30 minutes to provide a highly flexible conductive material. A thin film was obtained. The film thickness of the conductive thin film was 16 μm. The results are shown in Table 1.

Example 4
The silver-coated carbon powder (7.77 g) of Example 1 was added to 40 g of a polyimide precursor solution (trade name CT4200H: manufactured by Kyocera Chemical Co., Ltd., solid content: 15.5% by weight) and stirred for 15 minutes. Next, 0.0031 g of dithiobis (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane) in 10 g of N-methyl-2-pyrrolidone was added to the polyimide precursor solution containing the silver-coated carbon powder [Dithibis A solution in which (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane) (abbreviation: DFU)] (manufactured by Dojindo) was added and stirred for 8 hours to obtain a conductive paste. Dithiobis (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane is added in an amount of 0.25% by weight based on the solid content of the polyimide precursor solution.

  Then, this conductive paste is applied onto the substrate by the above-described method, and further heated in a drying furnace, for example, at 120 ° C. for 30 minutes, and further at 200 ° C. for 30 minutes to provide a highly flexible conductive material. A thin film was obtained. The film thickness of the conductive thin film was 17 μm. The results are shown in Table 1.

(Example 5)
8.5 g of the silver-coated carbon powder of Example 1 was added to 40 g of a polyimide solution (trade name SN-20, manufactured by Shin Nippon Rika Co., Ltd., solid content concentration: 10%), and stirred for 15 minutes. Subsequently, 0.017 g of dithiobis (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane [Dithibis ()] was added to 10 g of N-methyl-2-pyrrolidone in the polyimide precursor solution containing the silver-coated carbon powder. 1H, 1H, 2H, 2H-perfluorodecyloxy-undecane (abbreviation: DFU)] (trade name, manufactured by Dojin Chemical Co., Ltd.) was added and stirred for 8 hours to obtain a conductive paste. 2H, 2H-perfluorodecyloxy-undecane) is added in an amount of 0.25% by weight based on the solid content of the polyimide precursor solution.

  Then, this conductive paste is applied onto the substrate by the above-described method, and further heated in a drying furnace, for example, at 120 ° C. for 30 minutes, and further at 200 ° C. for 30 minutes to provide a highly flexible conductive material. A thin film was obtained. The film thickness of the conductive thin film was 18 μm. The results are shown in Table 1.

(Comparative Example 1)
The silver-coated carbon powder (8.77 g) of Example 1 was added to 40 g of a polyimide precursor solution (trade name CT4112: manufactured by Kyocera Chemical Co., Ltd., solid content: 17.5% by weight) and stirred for 15 minutes. Next, 10 g of N-methyl-2-pyrrolidone was added to the polyimide precursor solution containing the silver-coated carbon powder and stirred for 8 hours to obtain a conductive paste. Then, this conductive paste is applied onto the substrate by the above-described method, and is further heated in a drying furnace, for example, at 120 ° C. for 30 minutes, and further at 200 ° C. for 30 minutes, thereby attempting to produce a conductive thin film. It was. However, a conductive thin film could not be obtained because of a cotton-like powder. The results are shown in Table 1.

(Comparative Example 2)
The silver-coated carbon powder (7.77 g) of Example 1 was added to 40 g of a polyimide precursor solution (trade name CT4200H: manufactured by Kyocera Chemical Co., Ltd., solid content: 15.5% by weight) and stirred for 15 minutes. Next, 10 g of N-methyl-2-pyrrolidone was added to the polyimide precursor solution containing the silver-coated carbon powder and stirred for 8 hours to obtain a conductive paste. Then, this conductive paste is applied onto the substrate by the above-described method, and is further heated in a drying furnace, for example, at 120 ° C. for 30 minutes, and further at 200 ° C. for 30 minutes, thereby attempting to produce a conductive thin film. It was. However, a conductive thin film could not be obtained because of a cotton-like powder. The results are shown in Table 1.

(Comparative Example 3)
The silver-coated carbon powder (8.52 g) of Example 1 was added to 40 g of a polyimide solution (trade name SN-20, manufactured by Shin Nippon Rika Co., Ltd., solid content concentration 10%), and stirred for 15 minutes. Next, 10 g of N-methyl-2-pyrrolidone was added to the polyimide precursor solution containing the silver-coated carbon powder and stirred for 8 hours to obtain a conductive paste. Then, this conductive paste is applied onto the substrate by the above method and further heated in a drying furnace at 120 ° C. for 30 minutes and further at 200 ° C. for 30 minutes, for example. I tried to make it. However, only severely fragile films were obtained. The results are shown in Table 1.

注）体積導電率計測：四短針法

Note) Volume conductivity measurement: Four-short needle method

  As in Comparative Examples 1 to 3, when using a polyimide precursor solution or a polyimide solution as a binder resin to produce a silver-containing conductive paste, these conductive pastes are powders such as cotton when imidization proceeds. As a result, the conductive thin film was not a conductive film.

  On the other hand, when the conductive pastes of Examples 1 to 5 are used, a conductive coating film or conductive thin film having a large thickness (specifically, a thick film of 50 μm to 125 μm) and a high flexibility can be obtained. . In these conductive pastes, a polyimide precursor solution or a polyimide solution is used as a binder resin. Therefore, if this conductive paste is used as a raw material, a smooth and tough conductive thin film having excellent heat resistance, mechanical properties and adhesion to other materials can be formed.

  In Examples 1 to 5, hydrocarbon gas and carbon dioxide gas are not released during the heat treatment of the conductive paste. Therefore, voids and defects are not easily formed in the conductive thin film. Thereby, the electroconductive thin film which concerns on this invention shows favorable electroconductivity and durability.

  Moreover, in Examples 1-5, since the thickness of an electroconductive thin film can be formed thickly, the resistance of an electroconductive thin film can be lowered | hung and the design freedom degree of an electroconductive thin film can be improved.

  Although the embodiments have been described above, the embodiments are not limited to the embodiments shown in the drawings. Other embodiments, additions, changes, deletions, and the like can be changed within a range that can be conceived by those skilled in the art. Any aspect is included in the scope of the present invention as long as the operations and effects of the embodiment are exhibited.

US Pat. No. 5,882,722 JP 2004-039379 A

Claims (7)

Including a polyimide precursor solution or a polyimide solution, a metal scavenger, and conductive particles,
The metal scavenger is at least any one compound selected from a thiol compound represented by the following general formula (1) or a sulfide compound represented by the following general formula (2). paste.
Ar-SH (1)
[In the formula (1), Ar represents a benzene ring and may have a substituent. ]
(AR′—O—R—S) ₂ (2)
[In the formula (2), R ′ and R represent an alkylene group, and A represents a fluoroalkyl group. ] The conductive paste according to claim 1, wherein the thiol compound represented by the general formula (1) is 4-fluorobenzenethiol represented by the following formula (3).

... (3) The sulfide compound represented by the general formula (2) is dithiobis (1H, 1H, 2H, 2H-perfluorodecyloxy-undecane) represented by the following formula (4). Or the electrically conductive paste of 2.

(4)   The metal capture agent is added in an amount of 0.01% by weight or more and 10% by weight or less based on the solid content of the polyimide precursor solution or the polyimide solution. The conductive paste according to claim 1.   5. A conductive thin film formed by heat-treating the conductive paste according to claim 1.   The conductive thin film according to claim 5, wherein the conductive particles are captured by the metal scavenger, and the conductive particles are dispersed in the polyimide resin. 7. The conductive thin film according to claim 5, wherein the volume resistivity is 2 × 10 ⁻⁶ Ω · cm or more and 1 × 10 ² Ω · cm or less.