CN116323749A - Conductive paste and conductive film - Google Patents

Conductive paste and conductive film Download PDF

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Publication number
CN116323749A
CN116323749A CN202180062197.XA CN202180062197A CN116323749A CN 116323749 A CN116323749 A CN 116323749A CN 202180062197 A CN202180062197 A CN 202180062197A CN 116323749 A CN116323749 A CN 116323749A
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tannic acid
equal
paste
conductive
mass
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西川哲平
滨田亘人
田中信也
酒井静雄
古贺慎也
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Goo Chemical Industries Co Ltd
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Goo Chemical Industries Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/08—Metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/38—Boron-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/09—Carboxylic acids; Metal salts thereof; Anhydrides thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/205—Compounds containing groups, e.g. carbamates
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L101/00—Compositions of unspecified macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L97/00—Compositions of lignin-containing materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
    • H01B5/14—Non-insulated conductors or conductive bodies characterised by their form comprising conductive layers or films on insulating-supports
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/08—Metals
    • C08K2003/085—Copper
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/001—Conductive additives

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Dispersion Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Conductive Materials (AREA)

Abstract

Provided is a conductive paste which has excellent initial conductivity and can maintain excellent conductivity for a long period of time. The electroconductive paste contains at least one of tannic acid and tannic acid derivatives (A), copper powder (B), a thermosetting resin (C) and a solvent (D).

Description

Conductive paste and conductive film
Technical Field
The present disclosure relates to a conductive paste and a conductive film, and in particular, to a conductive paste and a conductive film containing a cured product of the conductive paste, the conductive paste containing: a component (a) comprising at least one of tannic acid or tannic acid derivatives; copper powder (B); a thermosetting resin (C); and a solvent (D).
Background
A technique of printing a conductive paste on various types of base materials to form wirings is used. Conventionally known conductive pastes are mainly silver paste and copper paste. Silver paste has satisfactory conductivity but is expensive, and tends to migrate therein at high humidity, thus causing short circuits due to migration problems. Therefore, it is considered to use a copper paste instead of a silver paste, but the copper paste is more easily oxidized than the silver paste, which thus causes a problem that the specific resistance value increases with time and the conductivity thus tends to decrease.
Methods for suppressing such oxidation of copper paste are proposed, for example, a method of treating the surface of copper powder with an organic substance in advance and a method of mixing an additive for suppressing copper oxidation in a composition containing copper powder.
Patent document 1 discloses a method including: treating the oxidizable metal fine particles with an aqueous surface treating agent containing an organic acid in advance to effectively remove oxide films formed on the surfaces of the metal fine particles; and further adding an organic carboxylic acid as an additive for inhibiting copper oxidation to the composition containing the treated copper powder. Patent document 2 discloses a method of suppressing oxidation of copper powder by: the addition of the organic carboxylic acid compound to the conductive copper paste containing copper powder causes protons to be contributed to the oxide film on the surface of the copper powder to elute the oxide film.
The method of treating copper powder with an organic acid is effective in removing the copper oxide coating already present on the copper powder to be used as a raw material, and thus is effective in exhibiting electrical conductivity at the initial stage, but the method is insufficient to suppress oxidation over time. Furthermore, the method of adding the organic carboxylic acid compound is insufficient to suppress oxidation of the copper powder. Therefore, there is a need for materials that exhibit further effective reducing power for copper powder, and that can exhibit copper-inherent conductivity in the initial stage and can maintain conductivity for a long period of time to ensure reliability of the product.
Prior art literature
Patent literature
Patent document 1: JP 2014-01006 011006A
Patent document 2: JP 2008-130301A
Disclosure of Invention
An object of the present disclosure is to provide a conductive paste and a conductive film that have excellent conductivity in an initial stage and are capable of maintaining excellent conductivity for a long period of time.
The electroconductive paste according to one aspect of the present disclosure includes a component (a) including at least one of tannic acid or tannic acid derivative, copper powder (B), a thermosetting resin (C), and a solvent (D).
The conductive film according to one aspect of the present disclosure contains a cured product of the conductive paste.
Detailed Description
< conductive paste >
The electroconductive paste of the present embodiment (hereinafter also referred to as electroconductive paste (X)) contains a component (a) (hereinafter also referred to as component (a)), copper powder (B), a thermosetting resin (C), and a solvent (D) that contain at least one of tannic acid or tannic acid derivative. The electroconductive paste (X) is heat-curable, and thus is suitably suitable for forming an electroconductive film.
The present inventors found that when the electroconductive paste containing copper powder as the metal powder contains tannic acid or a derivative thereof, the electroconductive paste has excellent electroconductivity at the initial stage and is capable of maintaining excellent electroconductivity for a long period of time. That is, the electroconductive paste (X) can have a reduced specific resistance value at the initial stage and can be suppressed from oxidizing with time (as evaluated by a wet heat test or the like), so that the electroconductive paste (X) can maintain electroconductivity for a long period of time. The reason for this is not necessarily clear, but it can be inferred that, for example, tannic acid and tannic acid derivatives enable enhancement of dispersibility of copper powder (B) in conductive paste (X) and reducibility of tannic acid and tannic acid derivatives also enable suppression of oxidation of copper powder (B) and reduction of copper oxide generated by oxidation of copper to original copper, thereby recovering conductivity. In particular, when the thermosetting resin (C) is thermally cured, the component (a) may exhibit a high reducing ability, and the electroconductive paste (X) can exhibit a high electroconductivity in the initial stage, and furthermore, the reducing ability of the component (a) enables to maintain the high electroconductivity for a long period of time. Therefore, the electroconductive paste (X) has excellent electroconductivity at the initial stage and can maintain excellent electroconductivity for a long time.
[ component (A) ]
The component (A) is at least one of tannic acid or tannic acid derivatives. "tannic acid" includes both tannic acid in a broad sense and meta-digallic acid (m-galloylgallic acid) which is tannic acid in a narrow sense. Tannic acid in a broad sense is a general term for aromatic compounds having a large number of phenolic hydroxyl groups, and examples thereof include condensed tannins which are derivatives of flavanols and hydrolyzable tannins having one or more gallic acid and saccharide (typically glucose) bonded to each other through ester linkages. The phenolic hydroxyl number per tannic acid molecule is generally greater than or equal to 3 and less than or equal to 100, preferably greater than or equal to 10 and less than or equal to 50, and more preferably greater than or equal to 20 and less than or equal to 30. The molecular weight of tannic acid is generally 300 or more and 15000 or less, preferably 500 or more and 5000 or less, and more preferably 1000 or more and 2500 or less.
"tannic acid derivative" means a derivative obtained, for example, by substituting some or all of hydrogen atoms in phenolic hydroxyl groups of tannic acid with a substituent (hereinafter also referred to as substituent (S)). The tannic acid derivative is a derivative obtained by hydrophobizing tannic acid.
Component (a) preferably comprises tannic acid derivatives. The use of a tannic acid derivative obtained by hydrophobizing tannic acid as the component (a) further enhances the effect of suppressing oxidation of the electroconductive paste (X) with time, and in particular, in a wet heat resistance test (e.g., 85 ℃,85% rh,100 hours), an increase in specific resistance value can be further suppressed.
The tannic acid derivative preferably includes a derivative obtained by reacting some or all of phenolic hydroxyl groups of tannic acid with a compound having an isocyanate group so that a urethane bond is formed. The introduction of urethane bonds into tannic acid derivatives further improves the flexibility of the conductive film formed from the conductive paste (X), and thus, application of the conductive film to a flexible base material such as a film base material is expected.
Alternatively, the tannic acid derivative is preferably a derivative obtained by reacting some or all of phenolic hydroxyl groups of tannic acid with a silane coupling agent so that a-Si-O-bond is formed. It is expected that the incorporation of the-Si-O-bond into the tannic acid derivative further improves the dispersibility of the copper powder (B) and improves the adhesion between the conductive film formed of the conductive paste (X) and the base material.
Examples of the substituent (S) include: hydrocarbyl groups, for example, alkyl groups such as methyl, cycloalkyl groups such as cyclohexyl, aryl groups such as phenyl, and aralkyl groups such as benzyl; a group obtained by substituting some or all of hydrogen atoms of a hydrocarbon group with other substituents; -CONHR (R is a monovalent organic group having 1 to 20 carbon atoms); and-Si (OR') 2 R "(R' is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and R" is a monovalent organic group having 1 to 20 carbon atoms). "organic group" refers to a group containing at least one carbon atom.
The substituent (S) preferably includes a group having a polymerizable group. In this case, the curing shrinkage upon thermally curing the electroconductive paste (X) can be further improved, and therefore, the conductivity of the electroconductive film made of the electroconductive paste (X) can be further improved. Examples of the polymerizable group include (meth) acryl, vinyl, epoxy, glycidyl, amino, and mercapto.
the-CONHR group as the substituent (S) is formed by reacting tannic acid with a compound having an isocyanate group. Examples of the organic group represented by R include: monovalent hydrocarbon groups such as substituted or unsubstituted butyl groups; groups containing polymerizable groups such as (meth) acryl, vinyl and glycidyl groups. When R is a group containing a polymerizable group, curing shrinkage upon thermally curing the electroconductive paste (X) can be further improved, and therefore, the electroconductivity of the electroconductive film made of the electroconductive paste (X) can be further improved.
Si (OR') as substituent (S) 2 R "is formed by reacting tannic acid with a silane coupling agent. Examples of the hydrocarbon group represented by R' include alkyl groups such as methyl and ethyl. Examples of the organic group represented by R "include: substituted or unsubstituted monovalent hydrocarbon groups; and groups containing polymerizable groups such as glycidyl, epoxy, (meth) acryl, vinyl, amino, and mercapto groups. When R "is a group containing a polymerizable group, curing shrinkage upon thermally curing the conductive paste (X) can be further improved, and thus, the conductivity of the conductive film made of the conductive paste (X) can be further improved.
The substitution rate of the tannic acid derivative (ratio of the number of substituents (S) per tannic acid derivative molecule to the number of phenolic hydroxyl groups per tannic acid molecule before substitution) is preferably 10% or higher. In this case, the wet heat resistance of the electroconductive paste (X) can be further effectively improved. The substitution rate is more preferably 15% or higher, still more preferably 20% or higher, and particularly preferably 30% or higher. The substitution rate in the tannic acid derivative is preferably 65% or less. In this case, the effect of suppressing oxidation of the electroconductive paste (X) can be further improved. The substitution rate is more preferably less than or equal to 60%, still more preferably less than or equal to 55%, and particularly preferably less than or equal to 50%.
The ratio of the component (a) to 100 parts by mass of the copper powder (B) is preferably 0.05 parts by mass or more and 5.0 parts by mass or less. In this case. The conductivity and continuity of the conductive paste (X) can be further improved. The ratio of the component (a) to 100 parts by mass of the copper powder (B) is more preferably greater than or equal to 0.1 parts by mass and less than or equal to 3.0 parts by mass, still more preferably greater than or equal to 0.4 parts by mass and less than or equal to 2.0 parts by mass, and particularly preferably greater than or equal to 0.5 parts by mass and less than or equal to 1.2 parts by mass.
The ratio of the component (a) to the electroconductive paste (X) is preferably greater than or equal to 0.01 mass% and less than or equal to 10 mass%, more preferably greater than or equal to 0.05 mass% and less than or equal to 5 mass%, still more preferably greater than or equal to 0.1 mass% and less than or equal to 3 mass%, and particularly preferably greater than or equal to 0.4 mass% and less than or equal to 1.5 mass%.
[ copper powder (B) ]
Copper powder (B) is a metal particle containing copper as a main component, wherein copper is exposed on the surface of the particle.
Examples of the shape of the copper powder (B) include a spherical shape, a flat shape (a flake shape), a dendritic shape, and an amorphous shape. The copper powder (B) may be in a combination of two or more of these shapes. The excellent conductivity and oxidation resistance of the electroconductive paste (X) are attributed to the excellent reducing ability of the component (a) to copper, and the shape and particle diameter of the copper powder (B) are not particularly limited.
From the viewpoint of printing suitability, the average particle diameter of the copper powder (B) is preferably greater than or equal to 0.1 μm and less than or equal to 30 μm, more preferably greater than or equal to 0.5 μm and less than or equal to 20 μm, and still more preferably greater than or equal to 1 μm and less than or equal to 10 μm. The average particle diameter is the median diameter, the particle size distribution (volume basis) of the copper powder (B) is measured, and the particle diameter in the cumulative distribution of 50% by volume thereof is shown.
The ratio of the copper powder (B) to the electroconductive paste (X) is preferably greater than or equal to 50 mass% and less than or equal to 99 mass%, more preferably greater than or equal to 60 mass% and less than or equal to 98 mass%, still more preferably greater than or equal to 70 mass% and less than or equal to 95 mass%, and particularly preferably greater than or equal to 80 mass% and less than or equal to 90 mass%.
[ thermosetting resin (C) ]
The electroconductive paste (X) contains a thermosetting resin (C). Therefore, the heating enables the conductive paste (X) to be cured to form a conductive film.
Examples of the thermosetting resin (C) include amino resins, urethane resins, unsaturated polyester resins, epoxy resins, cyanate resins, acrylic resins, and phenolic resins such as novolac phenolic resins or resole phenolic resins. The thermosetting resin (C) contains no tannic acid or tannic acid derivative.
The thermosetting resin (C) preferably includes a resin having a phenolic hydroxyl group. In this case, the curing shrinkage due to the thermosetting of the thermosetting resin (C) can be further improved, and therefore, the conductivity of the conductive paste (X) can be further improved. Examples of the thermosetting resin (C) having a phenolic hydroxyl group include phenolic resins.
The ratio of the thermosetting resin (C) to the electroconductive paste (X) is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and still more preferably 5% by mass or more and 15% by mass or less.
Further, the electroconductive paste (X) may contain, for example, a curing agent and a curing accelerator to promote curing of the thermosetting resin (C).
As the curing agent, any curing agent may be used as long as it can cure the thermosetting resin (C), and examples of the curing agent include: a novolac resin; latent amine-based curing agents such as dicyandiamide, imidazole, BF 3 -amine complexes and guanidine derivatives; aromatic amines such as metaphenylene diamine, diaminodiphenylmethane and diaminodiphenylsulfone; nitrogen atom-containing curing agents such as cyclophosphazene oligomer; and anhydride-based curing agents such as polyamide resins, maleic anhydride, phthalic anhydride, hexahydrophthalic anhydride, and pyromellitic anhydride. The ratio of the curing agent to the thermosetting resin (C) is generally greater than or equal to 0.1 mass% and less than or equal to 10 mass%, and preferably greater than or equal to 0.5 mass% and less than or equal to 5 mass%.
Examples of the curing accelerator include tertiary amines such as benzyl dimethylamine; imidazole; an organic acid metal salt; a Lewis acid; and amine complex salts. The ratio of the curing accelerator to the thermosetting resin (C) is generally greater than or equal to 0.01 mass% and less than or equal to 10 mass%, and preferably greater than or equal to 0.1 mass% and less than or equal to 5 mass%.
[ solvent (D) ]
The electroconductive paste (X) contains a solvent (D). This enables more appropriate adjustment of the viscosity of the electroconductive paste (X), and therefore, the electroconductive paste (X) is suitably suitable for screen printing or the like.
Examples of the solvent (D) include: polyols such as diols (e.g., ethylene glycol, propylene glycol, and dipropylene glycol) and triols (e.g., glycerol); sugar alcohols; lower alcohols such as ethanol, methanol, butanol, propanol, and isopropanol; 1-methyl-1-methoxybutanol; cellosolves such as ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monoisopropyl ether (isopropyl cellosolve), ethylene glycol mono-n-butyl ether (n-butyl cellosolve) and ethylene glycol mono-tert-butyl ether (tert-butyl cellosolve); carbitol such as diethylene glycol monomethyl ether (methyl carbitol); diethylene glycol monoethyl ether (ethyl carbitol), diethylene glycol mono-n-propyl ether (n-propyl carbitol); diethylene glycol monoisopropyl ether (isopropyl carbitol), ethylene glycol mono-n-butyl ether (n-butyl carbitol), diethylene glycol mono-tert-butyl ether (tert-butyl carbitol); triethylene glycol such as triethylene glycol monoethyl ether (ethyltriethylene glycol); propylene glycol monoethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-tertiary-butyl ether, propylene glycol mono-n-propyl ether, and propylene glycol monoisopropyl ether; dipropylene glycol monoethers such as dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono n-propyl ether, and dipropylene glycol monoisopropyl ether; glycol ethers such as tripropylene glycol monoether (e.g., tripropylene glycol monomethyl ether); glycol ether carboxylates such as cellosolve (cellosolve carboxylates) (e.g., ethylene glycol monomethyl ether acetate); and alkanolamines such as ethanolamine, diethanolamine, and triethanolamine.
The solvent (D) preferably includes a solvent having an alcoholic hydroxyl group. In this case, the solvent (D) can satisfactorily dissolve the component (a), which makes it possible to further improve the oxidation inhibiting effect provided by the component (a). Further, since the solvent (D) having an alcoholic hydroxyl group exhibits reducibility when thermally cured, the solvent (D) can further improve the oxidation inhibiting effect provided by the component (a).
From the viewpoint of the solubility, printability, and the like of tannic acid, the solvent (D) preferably includes at least one selected from lower alcohols and glycol ethers, and more preferably includes at least one selected from methanol, ethanol, and ethylcarbitol.
From the viewpoint of further appropriately adjusting the viscosity of the electroconductive paste (X), the ratio of the solvent (D) to the electroconductive paste (X) is preferably greater than or equal to 0.1 mass% and less than or equal to 10 mass%, more preferably greater than or equal to 1 mass% and less than or equal to 8 mass%, and still more preferably greater than or equal to 3 mass% and less than or equal to 7 mass%.
[ boric acid ]
Except orthoboric acid (H) 3 BO 3 ) Examples of boric acid include, in addition, boric acid (H 3 BO 3 ) Metaboric acid, tetraboric acid of the condensate of (a). The electroconductive paste (X) preferably contains boric acid. This makes it possible to further reduce the specific resistance value of the electroconductive paste (X). Further, when the thermosetting resin (C) has a hydroxyl group, hydrogen bonding between the hydroxyl group and boric acid enables further reduction of the specific resistance value. In addition, since boric acid also forms hydrogen bond with the phenolic hydroxyl group of the component (a), the formation of a network of thermosetting resin (C) -boric acid-tannic acid enables further improvement of conductivity.
The ratio of boric acid to the sum of the component (a) and the thermosetting resin (C) (containing a curing agent and a curing accelerator) is preferably greater than or equal to 1.0 mass% and less than or equal to 40 mass%, more preferably greater than or equal to 2 mass% and less than or equal to 20 mass%.
The ratio of boric acid to the electroconductive paste (X) is preferably greater than or equal to 0.1 mass% and less than or equal to 4 mass%, more preferably greater than or equal to 0.2 mass% and less than or equal to 2 mass%.
[ other Components ]
The electroconductive paste (X) may contain, for example, an antirust agent, an antioxidant, an adhesion imparting agent, a dispersant, a chelating agent, a leveling agent, a thixotropic regulator (thixo adjusting agent), and an antifoaming agent as other components. The ratio of the other component to the electroconductive paste (X) is, for example, 2% by mass or less.
(viscosity)
The viscosity of the electroconductive paste (X) at 25 ℃ is preferably 5.0pa·s or more and 200pa·s or less. In this case, the electroconductive paste (X) is easily printed, workability of screen printing is not impaired, and wiring is easily formed in a satisfactory pattern. The thixotropic ratio (Ti value) of the electroconductive paste (X) is preferably 1.0 or more and 3.0 or less. In this case, the conductive paste (X) does not impair the workability of screen printing, and wiring is easily formed in a satisfactory pattern. The thixotropic ratio is expressed as the ratio of the viscosity at 25 ℃ and 0.5rpm to the viscosity at 25 ℃ and 5rpm (thixotropic ratio= (viscosity at 25 ℃,0.5 rpm)/(viscosity at 25 ℃,5 rpm)).
< conductive film >
The conductive film of the present embodiment contains the cured product of the conductive paste (X). Since the conductive film of the present embodiment is formed of the conductive paste (X), the conductive film has excellent conductivity at the initial stage and can maintain excellent conductivity for a long period of time. Further, when the electroconductive paste (X) contains boric acid and a tannic acid derivative having a urethane bond, the electroconductive film is also excellent in folding resistance.
The conductive film of the present embodiment is formed by applying the conductive paste (X) onto a base material such as a glass plate or a PET film via, for example, screen printing, and then curing the conductive paste (X) by heating. The heating temperature and the heating period are appropriately selected according to the type of the thermosetting resin (C) or the like, wherein the heating temperature is generally higher than or equal to 100 ℃ and lower than or equal to 250 ℃, and preferably higher than or equal to 130 ℃ and lower than or equal to 200 ℃. The heating period is generally longer than or equal to 1 minute and shorter than or equal to 5 hours, and preferably longer than or equal to 10 minutes and shorter than or equal to 1 hour. The shape of the conductive film is not particularly limited, and examples of the shape include a circular shape and a quadrangular shape in a plan view, in addition to a line shape or a bar shape such as a circuit pattern in a plan view. The thickness of the conductive film is, for example, 1 μm or more and 1mm or less, preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.
Examples
The present disclosure will be specifically described with reference to the following examples.
< Synthesis of tannic acid derivative >
In a four-necked flask equipped with a reflux condenser, a thermometer, a nitrogen introducing tube, and a stirrer, 100g of tannic acid (manufactured by Fuji Chemical Industries co., ltd.: trade name: tannic acid, total number of hydroxyl groups per tannic acid molecule is 25) and 100g of methyl ethyl ketone were placed and dissolved by mixing, thereby obtaining a solution. 82g of ethyl acrylate isocyanate (manufactured by Showa Denko K.K. under the trade name "Karenz AOI") as isocyanate compound was mixed with the solution and reacted at 60℃for 5 hours. Methyl ethyl ketone is evaporated from the solution and dried, whereby the tannic acid derivative (1) is obtained.
In the same manner, 141g of an isocyanate compound was reacted with the solution to obtain a tannic acid derivative (2), 24g of an isocyanate compound was reacted with the solution to obtain a tannic acid derivative (3), 160g of an isocyanate compound was reacted with the solution to obtain a tannic acid derivative (4), and 65g of butyl isocyanate as an isocyanate compound was reacted with the solution to obtain a tannic acid derivative (5), and 36g of a silane coupling agent (trade name: "Xiameter OFS-6040 silane", glycidoxypropyl trimethoxysilane manufactured by Dow Toray co., ltd.) was reacted with the solution to obtain a tannic acid derivative (6). The weight average molecular weight of the tannic acid derivative thus obtained was measured by the GPC measurement method shown below.
(measurement of weight average molecular weight)
The weight average molecular weight was determined by GPC method from standard polystyrene. The measurement conditions are shown below.
Device: prominence LC-20AD manufactured by SHIMADZU CORPORATION "
Column: a total of three columns "GPC KF-801, GPC KF-803, GPC KF-805" manufactured by Showa Denko K.K. are provided "
Protection column: "GPC-KF-G4A" manufactured by Showa Denko K.K "
Sample concentration: the concentration of tannic acid or tannic acid derivative was made 0.5 mass% by dilution with tetrahydrofuran.
Mobile phase solvent: tetrahydrofuran (THF)
Flow rate: 1.0 mL/min
Column temperature: 40 DEG C
Table 1 below collectively shows the weight average molecular weight of each of the tannic acid derivative and tannic acid thus synthesized and the substitution rate of the hydrogen atom of the phenolic hydroxyl group of each tannic acid derivative.
TABLE 1
Figure BDA0004118698350000101
< preparation of conductive paste >
Example 1
0.40g of the tannic acid derivative (1), 4.6g of an epoxy resin (manufactured by DIC Corporation, epicolin EXA 4816), 0.02g of a curing accelerator (manufactured by SHIKOKU CHEMICALS CORPORATION, CUREZOL 2 PHZ-PW), and 0.5g of boric acid were blended in 3.0g of ethyl carbitol as a solvent and dissolved, thereby obtaining a resin solution. 48.0g of copper particles (manufactured by FUKUDA METAL FOIL & POWDER CO., LTD. Trade name: cu-HWF-4 ") were blended in the resin solution, mixed by using a mixing stirrer, and then kneaded by using a roll mill, thereby obtaining conductive paste 1 (DP-1).
Example 2
Conductive paste 2 (DP-2) was obtained in the same manner as in example 1, except that boric acid was not blended.
Example 3
Conductive paste 3 (DP-3) was obtained in the same manner as in example 1 except that tannic acid was used instead of tannic acid derivative (1).
Example 4
Conductive paste 4 (DP-4) was obtained in the same manner as in example 1 except that tannic acid derivative (6) was used.
Example 5
Conductive paste 5 (DP-5) was obtained in the same manner as in example 2, except that a resol (manufactured by MEIWA PLASTIC INDUSTRIES, LTD., trade name: MWF-2620, solid content: 70 mass%) was used as a thermosetting resin instead of the epoxy resin and the curing accelerator.
Example 6
Conductive paste 6 (DP-6) was obtained in the same manner as in example 1 except that the tannic acid derivative (2) was used.
Example 7
Conductive paste 7 (DP-7) was obtained in the same manner as in example 1, except that ethyl carbitol acetate was used instead of the solvent.
Example 8
Conductive paste 8 (DP-8) was obtained in the same manner as in example 1 except that tannic acid derivative (3) was used.
Example 9
Conductive paste 9 (DP-9) was obtained in the same manner as in example 1 except that tannic acid derivative (4) was used.
Example 10
Conductive paste 10 (DP-10) was obtained in the same manner as in example 1 except that tannic acid derivative (5) was used.
Comparative example 1
Conductive paste 11 (DP-11) was obtained in the same manner as in example 1, except that tannic acid and tannic acid derivative were not added.
[ evaluation of conductive paste ]
(viscosity measurement and Ti value)
The viscosity at 25 ℃ of the conductive paste obtained in each of examples 1 to 9 and comparative example 1 was measured by a cone-plate type viscometer (manufactured by Toki Sangyo co., ltd) (at 5rpm and 0.5 rpm). Further, from these measured values, ti value (=viscosity at 0.5 rpm/viscosity at 5 rpm) was determined.
(evaluation of dispersibility of copper powder)
In order to evaluate dispersibility of the copper powder in each of the thus obtained conductive pastes, coarse particles were inspected by using a grind gauge (manufactured by Taiyu Kizai co.ltd., "GM-7470",0 μm to 25 μm) and referring to JIS K5600-2-5 (fineness of grinding).
From the test results of the coarse particles, dispersibility of the copper powder was evaluated based on the following criteria.
A: the fineness gauge determination result is less than or equal to 7.5 μm.
B: the fineness gauge was found to be 10.0 μm.
C: the fineness gauge determination result is greater than or equal to 12.5 mu m.
Table 2 below collectively shows the measured values of paste viscosity (Pa.s) (at 5rpm and 0.5 rpm) and Ti values, and the evaluation results of dispersibility of copper powder.
TABLE 2
Figure BDA0004118698350000131
< formation of conductive film >
The thus obtained electroconductive pastes 1 to 11 (DP-1 to DP-11) were applied on a PET film in a stripe-like wiring shape having a width of 1mm, a length of 50mm and a thickness of 20 μm by screen printing, and then cured by heating it at 150 ℃ for 30 minutes, thereby obtaining base materials 1 to 11 provided with the electroconductive films 1 to 11 (DM-1 to DM-11), respectively.
[ evaluation of conductive film ]
(measurement of resistance value of conductive film)
The resistance values (Ω) of the conductive films 1 to 11 (DM-1 to DM-11) thus obtained were measured by using a four-point resistance meter (manufactured by HIOKI e.e. corporation), resistance meter RM 3544-01.
(durability test)
The base materials 1 to 11 provided with the conductive films were subjected to durability test in a high-temperature and high-humidity environment. In other words, the base materials provided with the conductive films 1 to 11 (DM-1 to DM-11) were stored in a can at a high temperature of 85 ℃ and a high humidity of 85% rh for 100 hours, and then, the resistance values of the conductive films 1 to 11 (DM-1 to DM-11) were measured, thereby calculating the specific resistance values after the durability test.
(evaluation of folding resistance)
The thus obtained conductive films 1 to 11 (DM-1 to DM-11) were folded by winding around an iron core of 2mm Φ, and then unfolded by using a folding tester, after which the specific resistance values of the conductive films were measured. Folding endurance was evaluated based on the following criteria.
S: the rate of increase of the specific resistance value before and after folding is 20% or less.
A: the rate of increase of the specific resistance value before and after folding is greater than 20% and less than or equal to 40%.
B: the rate of increase of the specific resistance value before and after folding is greater than 40% and less than or equal to 100%.
C: the rate of increase of the specific resistance value before and after folding is greater than 100%.
Table 3 below collectively shows the evaluation results of the resistance value (Ω) of the conductive film, the film thickness (μm) of the conductive film, the specific resistance value (volume resistivity) (μΩ·cm) calculated from the resistance value and the film thickness, the specific resistance value (μΩ·cm) after the durability test, the durability test change rate (= (specific resistance value after the durability test/specific resistance value-1 before the durability test) ×100 (%)) and the folding resistance.
TABLE 3
Figure BDA0004118698350000151
As can be seen from the results shown in tables 2 and 3, the conductive film formed of the conductive paste of the example has excellent conductivity at the initial stage and can maintain excellent conductivity for a long period of time. In particular, the conductive pastes of examples 1 to 5 are excellent in dispersibility of copper powder, and particularly the conductive pastes of examples 1, 3, 4 and 5 have low resistivity of about 100 μΩ·cm and can provide excellent conductive films. Further, examples 1, 2, 4, 5, 6, 7, 8 and 10 using tannic acid derivatives having substitution rates of 10% to 65% can provide conductive films having excellent durability. The conductive paste of comparative example 1 has poor dispersibility of copper powder, has a high specific resistance value of the conductive film already at the initial stage, and therefore, seems to have been oxidized in the step of preparing the conductive paste, and in addition, the specific resistance value increases in the moisture resistance test.
Further, as can be seen from the results shown in table 3, the conductive films formed of the conductive pastes obtained by combining the tannic acid derivative having a urethane bond and the boric acid in examples 1, 6, 7, 9 and 10 have satisfactory folding endurance.
The conductive paste of example 9 employing the tannic acid derivative in which the substitution rate of the hydrogen atom of the phenolic hydroxyl group exceeds a certain value has an increased specific resistance value at the initial stage, a decreased dispersibility of the copper powder, and a high specific resistance value of the rising rate after the durability test, and therefore, the effect of the tannic acid derivative may be decreased. The electroconductive paste of example 7 does not use a solvent having a hydroxyl group, and therefore, it is possible to reduce the rust inhibitive effect of the tannic acid derivative at the time of preparing the paste.
(summary)
As can be seen from the foregoing, the electroconductive paste according to the first aspect of the present disclosure contains component (a) containing at least one of tannic acid or tannic acid derivative, copper powder (B), thermosetting resin (C), and solvent (D).
According to the first aspect, the electroconductive paste has excellent electroconductivity at the initial stage and can maintain excellent electroconductivity for a long time.
In the electroconductive paste relating to the second aspect of the first aspect, the component (a) contains a tannic acid derivative, and the tannic acid derivative is a derivative obtained by substituting hydrogen atoms in some phenolic hydroxyl groups of tannic acid with a substitution rate of 10% or more and 65% or less with a substituent.
The second aspect enables further enhancement of the effect of suppressing oxidation of the electroconductive paste with time, in particular, enables further suppression of an increase in specific resistance in the wet heat resistance test, and enables more effective improvement of the wet heat resistance.
In the electroconductive paste relating to the third aspect of the first aspect, the component (a) contains a tannic acid derivative, and the tannic acid derivative is a derivative obtained by reacting some or all of phenolic hydroxyl groups of tannic acid with a compound having an isocyanate group so that a urethane bond is formed.
According to the third aspect, the effect of suppressing oxidation over time is further enhanced, and in particular, the increase in specific resistance is further suppressed in the wet heat resistance test, and furthermore, the introduction of a urethane bond into a tannic acid derivative improves the flexibility of a conductive film formed of a conductive paste, so that application of the conductive film to a flexible base material such as a film base material is expected.
The electroconductive paste of the fourth aspect relating to any one of the first to third aspects further contains boric acid.
The fourth aspect enables further reduction of the specific resistance value of the electroconductive paste. Further, when the thermosetting resin (C) has a hydroxyl group, hydrogen bonding between the hydroxyl group and boric acid enables further reduction of the specific resistance value. In addition, since boric acid also forms hydrogen bond with the phenolic hydroxyl group of the component (a), the formation of a network of thermosetting resin (C) -boric acid-tannic acid enables further improvement of conductivity.
The electroconductive paste of the fifth aspect relating to any one of the first to fourth aspects further comprises a solvent (D) having an alcoholic hydroxyl group.
According to the fifth aspect, the solvent (D) can satisfactorily dissolve the component (a), which makes it possible to further improve the oxidation inhibiting effect provided by the component (a). Further, since the solvent (D) having an alcoholic hydroxyl group exhibits reducibility upon heat curing, the solvent (D) can further improve the oxidation inhibiting effect provided by the component (a).
In the electroconductive paste of the sixth aspect relating to any one of the first to fifth aspects, the thermosetting resin (C) has a phenolic hydroxyl group.
According to the sixth aspect, the curing shrinkage due to the thermosetting of the thermosetting resin (C) is further improved, and therefore, the conductivity of the electroconductive paste (X) is further improved.
The electroconductive film of the seventh aspect contains the cured product of the electroconductive paste of any one of the first to sixth aspects.
According to the seventh aspect, the conductive film has excellent conductivity at the initial stage and can maintain excellent conductivity for a long period of time.
INDUSTRIAL APPLICABILITY
According to the electroconductive paste of the present disclosure, heat curing enables formation of an electroconductive film having excellent electroconductivity at an initial stage, having excellent moisture resistance, and capable of maintaining excellent electroconductivity for a long period of time without using special equipment requiring an inert gas or the like.

Claims (7)

1. A conductive paste comprising:
a component (a) comprising at least one of tannic acid or tannic acid derivatives;
copper powder (B);
a thermosetting resin (C); and
solvent (D).
2. The electroconductive paste according to claim 1, wherein
The component (A) comprises the tannic acid derivative, and
the tannic acid derivative is a derivative obtained by substituting hydrogen atoms in some phenolic hydroxyl groups of tannic acid with a substitution rate of 10% or more and 65% or less with a substituent.
3. The electroconductive paste according to claim 1, wherein
The component (A) comprises the tannic acid derivative, and
the tannic acid derivative is a derivative obtained by reacting some or all of phenolic hydroxyl groups of tannic acid with a compound having an isocyanate group so that a urethane bond is formed.
4. The electroconductive paste according to any one of claims 1-3, further comprising boric acid.
5. The electroconductive paste according to any one of claims 1 to 4, wherein
The solvent (D) has an alcoholic hydroxyl group.
6. The electroconductive paste according to any one of claims 1 to 5, wherein
The thermosetting resin (C) has phenolic hydroxyl groups.
7. A conductive film comprising the cured product of the conductive paste according to any one of claims 1 to 6.
CN202180062197.XA 2020-09-10 2021-09-07 Conductive paste and conductive film Pending CN116323749A (en)

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CN1668460A (en) * 2002-05-14 2005-09-14 新日本制铁株式会社 Weldable coated metal material with superior corrosion resistance for formed part
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CN104123974A (en) * 2014-01-21 2014-10-29 深圳唯一科技股份有限公司 Electronic paste for mobile phone touch screen and preparation method thereof

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