CN116171286A - Conductive paste and conductive film - Google Patents

Conductive paste and conductive film Download PDF

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Publication number
CN116171286A
CN116171286A CN202180062187.6A CN202180062187A CN116171286A CN 116171286 A CN116171286 A CN 116171286A CN 202180062187 A CN202180062187 A CN 202180062187A CN 116171286 A CN116171286 A CN 116171286A
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Prior art keywords
meth
resin
equal
acrylic resin
mass
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Inventor
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
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/10—Esters
    • C08F20/26—Esters containing oxygen in addition to the carboxy oxygen
    • C08F20/28—Esters containing oxygen in addition to the carboxy oxygen containing no aromatic rings in the alcohol moiety
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/08—Epoxidation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/14—Esterification
    • 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
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • C08L33/04—Homopolymers or copolymers of esters
    • C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
    • C08L33/062—Copolymers with monomers not covered by C08L33/06
    • C08L33/066—Copolymers with monomers not covered by C08L33/06 containing -OH groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • C08L33/04—Homopolymers or copolymers of esters
    • C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
    • C08L33/062—Copolymers with monomers not covered by C08L33/06
    • C08L33/068—Copolymers with monomers not covered by C08L33/06 containing glycidyl groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • C08L33/04—Homopolymers or copolymers of esters
    • C08L33/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur, or oxygen atoms in addition to the carboxy oxygen
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
    • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09D133/062—Copolymers with monomers not covered by C09D133/06
    • C09D133/066—Copolymers with monomers not covered by C09D133/06 containing -OH groups
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
    • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09D133/062—Copolymers with monomers not covered by C09D133/06
    • C09D133/068—Copolymers with monomers not covered by C09D133/06 containing glycidyl groups
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/24—Electrically-conducting paints
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/61—Additives non-macromolecular inorganic
    • 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
    • C08K2003/0806—Silver
    • 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

Abstract

Provided is a conductive paste which achieves both good adhesion and conductivity. The electroconductive paste contains a binder (A), a metal powder (B), boric acid (C), and an organic solvent (D). The binder (a) contains a (meth) acrylic resin (a) having a hydroxyl group.

Description

Conductive paste and conductive film
Technical Field
The present disclosure relates to a conductive paste and a conductive film, and more particularly, to a conductive paste including a binder, a metal powder, boric acid, and an organic solvent, and a conductive film including a cured product of the conductive paste.
Background
A technique of printing a conductive paste on various types of base materials to form wirings is used. A conductive paste is printed on the surface of a base material by screen printing or the like to form a conductive film to be wired in a predetermined pattern.
The conductive mechanism of the conductive paste is that the metal powder particles are in contact with or in proximity to each other due to the curing shrinkage of the thermosetting resin that is the binder. Thus, the oxidation state of the metal powder surface and the curing shrinkage state of the thermosetting resin significantly affect the conductivity. The binder typically used is a resole that provides good electrical conductivity due to the magnitude of its cure shrinkage. However, resole resins are hard and brittle and have low adhesion to the substrate. Thus, a conductive paste containing a (meth) acrylic resin is proposed.
Patent document 1 discloses, as a conductive paste containing a (meth) acrylic resin, which has a glass transition point Tg in a range of-60 ℃ to 120 ℃, hydroxyl groups in a molecule in a range of 0.0 wt% to 5 wt%, an acid value in a range of 1mg KOH/g to 50mg KOH/g, and a weight average molecular weight in a range of 10000 to 350000, a conductive paste containing a (meth) acrylic resin, an organic solvent, and a metal powder as a binder resin. Patent document 2 discloses a conductive paste containing a conductive component, a thermosetting resin, and a specific cationic polymerization initiator, wherein the conductive paste contains an acrylic resin as the thermosetting resin.
The use of the (meth) acrylic resin can impart good flexibility to the electroconductive paste and can also improve the adhesion of the electroconductive paste due to the characteristics of the (meth) acrylic resin. However, since the thermal curing shrinkage of the resin is small, the conductive paste containing the conventional (meth) acrylic resin cannot exhibit satisfactory conductivity.
Prior art literature
Patent literature
Patent document 1: WO 2013/187183
Patent document 2: JP 2019-106305A
Disclosure of Invention
An object of the present disclosure is to provide a conductive paste and a conductive film having both good adhesion and conductivity.
The electroconductive paste according to one aspect of the present disclosure includes a binder (a), a metal powder (B), boric acid (C), and an organic solvent (D). The binder (a) contains a (meth) acrylic resin (a) having a hydroxyl group.
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 binder (a), a metal powder (B), boric acid (C), and an organic solvent (D). The binder (a) includes a (meth) acrylic resin (a) having a hydroxyl group. "(meth) acrylic resin" means an acrylic resin, a methacrylic resin, or both. The (meth) acrylic resin is a polymer having a building block (building block) of a monomer based on at least one of (meth) acrylic acid or (meth) acrylic acid ester.
The present inventors have found that in a conductive paste containing a (meth) acrylic resin as a thermosetting resin as a binder, a (meth) acrylic resin (a) having a hydroxyl group is used as a (meth) acrylic resin, and boric acid is further added, whereby the conductive paste can exhibit good conductivity. The reason for this is not necessarily clear, but it is inferred that, for example, the hydroxyl groups of the (meth) acrylic resin (a) and boric acid form a three-dimensional crosslinked structure through a network due to hydrogen bonding or the like, thereby increasing the cure shrinkage of the resin, which consequently improves the electrical conductivity. The inventors have also found that, in the electroconductive paste (X), the binder (a) contains the (meth) acrylic resin (a) having a hydroxyl group, and the electroconductive paste (X) contains boric acid, whereby the adhesion of the electroconductive paste (X) to various base materials can be made good. Therefore, the electroconductive paste (X) has both good adhesion and electroconductivity.
[ Binder (A) ]
The binder (a) contains a (meth) acrylic resin (a) having a hydroxyl group (hereinafter, also referred to as a (meth) acrylic resin (a)). Examples of the hydroxyl group include an alcoholic hydroxyl group and a phenolic hydroxyl group. Examples of the hydroxyl group of the (meth) acrylic resin (a) include an alcoholic hydroxyl group or a phenolic hydroxyl group in a structural unit based on a monomer having a hydroxyl group, and an alcoholic hydroxyl group generated by a reaction of an epoxy group and a carboxyl group in a modification reaction of the (meth) acrylic resin.
The hydroxyl value of the (meth) acrylic resin (a) is preferably 20mg KOH/g or more and 150mg KOH/g or less. Setting the hydroxyl value in the above range further improves the adhesion to the base material and makes the hydrogen bonding property to boric acid better, which enables further improvement of the conductivity. The hydroxyl value is more preferably greater than or equal to 30mg KOH/g and less than or equal to 130mg KOH/g, still more preferably greater than or equal to 40mg KOH/g and less than or equal to 120mg KOH/g, and particularly preferably greater than or equal to 50mg KOH/g and less than or equal to 80mg KOH/g. The hydroxyl value of the (meth) acrylic resin (a) means mg of potassium hydroxide corresponding to the hydroxyl group in 1g of the (meth) acrylic resin (a).
The acid value of the (meth) acrylic resin (a) is preferably greater than or equal to 0mg KOH/g and less than or equal to 200mg KOH/g, and more preferably greater than or equal to 50mg KOH/g and less than or equal to 150mg KOH/g. Setting the acid value within the above range allows better dispersibility of the metal powder. The acid value of the (meth) acrylic resin (a) is mg of potassium hydroxide required for neutralizing the carboxyl group in 1g of the (meth) acrylic resin (a).
The weight average molecular weight (Mw) of the (meth) acrylic resin (a) is preferably 3000 or more and 100000 or less. Setting Mw within the above range further improves adhesion and makes paste viscosity more suitable, thereby allowing better handling. When the Mw exceeds 100000, the adhesion decreases and the paste viscosity increases, which may lead to poor handling properties. The Mw is more preferably 5000 or more and 80000 or less, still more preferably 7000 or more and 50000 or less, and particularly preferably 10000 or more and 50000 or less. Mw is a value determined by GPC measurement method from standard polystyrene.
The glass transition temperature (Tg) of the resin (x) having the same main chain structure as that of the (meth) acrylic resin (a) and producing a precursor of the (meth) acrylic resin (a) is preferably 20 ℃ or higher and 100 ℃ or lower. Setting Tg within the above range enables further improvement of adhesion. The Tg is more preferably higher than or equal to 30 ℃ and lower than or equal to 95 ℃, and still more preferably higher than or equal to 40 ℃ and lower than or equal to 90 ℃. The glass transition temperature (Tg) is a value theoretically calculated from the composition ratio of monomers which are the constituent units of the resin (x), and is a value calculated by Fox formula.
Examples of the (meth) acrylic resin (a) include resins (a 1) to (a 4) shown below.
Resin (a 1): a resin obtained by modifying a polymer (x 1) having a structural unit based on a (meth) acryl-and carboxyl-containing monomer with a compound having a (meth) acryl group and an epoxy group.
Resin (a 2): a resin obtained by modifying a polymer (x 2) having a structural unit based on a (meth) acryl-and epoxy-group-containing monomer with a compound having a (meth) acryl group and a carboxyl group.
Resin (a 3): a resin obtained by further modifying the resin (a 2) with a carboxylic anhydride.
Resin (a 4): (meth) acrylic resins having structural units based on hydroxyl group-containing monomers.
(resin (a 1))
The resin (a 1) is a resin obtained by modifying a polymer (x 1) having a structural unit (hereinafter also referred to as a structural unit (u 1)) based on a (meth) acryl-and carboxyl-containing monomer with a compound having a (meth) acryl group and an epoxy group (hereinafter also referred to as a compound (c 1)). The resin (a 1) is formed by a modification reaction of a (meth) acrylic resin (x 1) having a carboxyl group and a compound (c 1) having an epoxy group. The reaction between the carboxyl group and the epoxy group produces a secondary alcohol hydroxyl group, and the hydroxyl group and boric acid form a network by, for example, hydrogen bonding. Further, the resin (a 1) has a (meth) acryloyl group at the end of the side chain of the polymer, which may contribute to heat curing, further improving curing shrinkage, and thereby further improving conductivity.
Examples of monomers having a (meth) acryloyl group and a carboxyl group include (meth) acrylic acid, crotonic acid, cinnamic acid, carboxymethyl (meth) acrylate, carboxyethyl (meth) acrylate, carboxycyclohexyl (meth) acrylate, carboxyphenyl (meth) acrylate, carboxybenzyl (meth) acrylate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl tetrahydrophthalate, 2- (meth) acryloyloxyethyl hexahydrophthalate, 2- (meth) acryloyloxyethyl succinate, and ω -carboxyl-polycaprolactone monoacrylate.
The ratio of the structural unit (u 1) in the resin (a 1) to all the structural units constituting the resin (a 1) is preferably 5% by mass or more and 100% by mass or less, and more preferably 20% by mass or more and 50% by mass or less.
Examples of the compound (c 1) having a (meth) acryloyl group and an epoxy group include glycidyl (meth) acrylate, epoxybutyl (meth) acrylate, and epoxycyclohexyl (meth) acrylate.
In the modification reaction between the polymer (x 1) and the compound (c 1), the compound (c 1) is preferably used in such an amount that the amount of the epoxy group is greater than or equal to 0.1mol and less than or equal to 0.7mol relative to 1mol of the carboxyl group of the polymer (x 1).
Optimizing the proportion of the structural unit (u 1) and the proportion of the compound (c 1) in the resin (a 1) for the modification reaction further improves the adhesion of the conductive film formed of the conductive paste (X) to the inorganic base material and the organic base material and the conductivity of the conductive film.
(resin (a 2))
The resin (a 2) is a resin obtained by modifying a polymer (x 2) having a structural unit (hereinafter also referred to as a structural unit (u 2)) based on a (meth) acryl-and epoxy-containing monomer with a compound having a (meth) acryl group and a carboxyl group (hereinafter also referred to as a compound (c 2)). The resin (a 2) is formed by a modification reaction of a (meth) acrylic resin (x 2) having an epoxy group and a compound (c 2) having a carboxyl group. The reaction between the epoxy group and the carboxyl group produces a secondary alcohol hydroxyl group, and the hydroxyl group and boric acid form a network by, for example, hydrogen bonding. Further, the resin (a 2) has a (meth) acryloyl group at the terminal of the side chain of the polymer, which may contribute to heat curing, further improving curing shrinkage, and thereby further improving conductivity.
Examples of the monomer having a (meth) acryloyl group and an epoxy group include compounds similar to those exemplified as the compound (c 1) having a (meth) acryloyl group and an epoxy group.
The ratio of the structural unit (u 2) in the resin (a 2) to all the structural units constituting the resin (a 2) is preferably greater than or equal to 10 mass% and less than or equal to 100 mass%, and more preferably greater than or equal to 30 mass% and less than or equal to 80 mass%.
Examples of the compound (c 2) having a (meth) acryloyl group and a carboxyl group include compounds similar to those exemplified as monomers having a (meth) acryloyl group and a carboxyl group.
In the modification reaction between the polymer (x 2) and the compound (c 2), the compound (c 2) is preferably used in such an amount that the amount of the carboxyl group is greater than or equal to 0.1mol and less than or equal to 1.0mol relative to 1mol of the epoxy group of the polymer (x 2).
Optimizing the proportion of the structural unit (u 2) and the proportion of the compound (c 2) in the resin (a 2) for the modification reaction further improves the adhesion of the conductive film formed of the conductive paste (X) to the inorganic base material and the organic base material and the conductivity of the conductive film.
(resin (a 3))
The resin (a 3) is a resin obtained by further modifying the resin (a 2) with a carboxylic acid anhydride. The resin (a 3) is formed by a modification reaction of the resin (a 2) having an epoxy group and a carboxylic anhydride (compound (c 3)). The use of the resin (a 3) enables further improvement of dispersibility of the metal powder.
Examples of carboxylic anhydrides include: aliphatic carboxylic anhydrides such as succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, itaconic anhydride, glutaconic anhydride and 1,2,3, 4-butanetetracarboxylic anhydride; alicyclic carboxylic anhydrides such as tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, cyclohexane tricarboxylic anhydride, cyclohexane tetracarboxylic anhydride, bicyclo [2.2.1] heptane-2, 3-dicarboxylic anhydride and methyl bicyclo [2.2.1] heptane-2, 3-dicarboxylic anhydride; and aromatic carboxylic anhydrides such as phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, naphthalene dicarboxylic anhydride, naphthalene tricarboxylic anhydride, naphthalene tetracarboxylic anhydride, biphenyl dicarboxylic anhydride, biphenyl tricarboxylic anhydride, biphenyl tetracarboxylic anhydride, and benzophenone tetracarboxylic anhydride.
The carboxylic anhydride is preferably used in such an amount that the acid value of the resin (a 3) to be obtained is preferably greater than or equal to 0mg KOH/g and less than or equal to 200mg KOH/g, and more preferably greater than or equal to 50mg KOH/g and less than or equal to 150mg KOH/g. Setting the acid value of the resin (a 3) within the above range provides good dispersibility of the metal powder.
(resin (a 4))
The resin (a 4) is a (meth) acrylic resin having a structural unit based on a hydroxyl group-containing monomer (hereinafter also referred to as a structural unit (u 4)). Examples of the hydroxyl group include an alcoholic hydroxyl group and a phenolic hydroxyl group.
Examples of the monomer having a hydroxyl group include: hydroxyl-containing esters of (meth) acrylic acid such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxycyclohexyl (meth) acrylate, hydroxyphenyl (meth) acrylate and hydroxybenzyl (meth) acrylate; and hydroxyl group-containing vinyl compounds such as allyl alcohol and vinylcyclohexanol.
The resin (a 4) preferably has a structural unit (u 1). In this case, the resin (a 4) has carboxyl groups, which may contribute to thermosetting, further enhancing curing shrinkage, and thereby further improving conductivity.
The ratio of the structural unit (u 4) in the resin (a 4) to all the structural units constituting the resin (a 4) is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.
The resins (a 1) to (a 3) may have a structural unit (u 4). Examples of monomers that produce structural units other than the structural units (u 1) to (u 4) in the resins (a 1) to (a 4) include (meth) acrylates and vinyl compounds. Examples of (meth) acrylates include: aliphatic (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate; alicyclic (meth) acrylates such as cyclohexyl (meth) acrylate; and aromatic (meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate. Examples of the vinyl compound include ethylene, propylene, 1-butene and styrene.
The ratio of the (meth) acrylic resin (a) to the binder (a) is preferably greater than or equal to 50 mass% and less than or equal to 100 mass%, and more preferably greater than or equal to 70 mass% and less than or equal to 100 mass%.
(other resins)
The binder (a) may contain, for example, other thermosetting resins as other resins in addition to the (meth) acrylic resin (a). Examples of other thermosetting resins include epoxy resins, phenolic resins, amino resins, urethane resins, unsaturated polyester resins, cyanate resins, and (meth) acrylic resins having no hydroxyl groups.
The ratio of the other resin to the binder (a) is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 45% by mass or less, and still more preferably 10% by mass or more and 40% by mass or less.
The electroconductive paste (X) may contain, for example, a curing agent and a curing accelerator to cure the thermosetting resin.
As the curing agent, any agent capable of curing the thermosetting resin may be used, and examples thereof include: a novolac resin; latent amine-based curing agents such as dicyandiamide, imidazole, BF 3 Amine complexes and guanidine derivativesThe method comprises the steps of carrying out a first treatment on the surface of the 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 is preferably greater than or equal to 0.1 mass% and less than or equal to 10 mass%, and more 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 is preferably greater than or equal to 0.1 mass% and less than or equal to 10 mass%, and more preferably greater than or equal to 0.5 mass% and less than or equal to 3 mass%.
The other thermosetting resin described above preferably includes a resin having hydroxyl groups or a resin that generates hydroxyl groups upon heat curing. Examples of such thermosetting resins include epoxy resins and phenolic resins. Other thermosetting resins have hydroxyl groups or generate hydroxyl groups, thereby forming a network of further increased number by, for example, hydrogen bonding between hydroxyl groups and boric acid, so that conductivity can be further improved.
The heat curing of the electroconductive paste (X) may be mainly performed due to occurrence of a crosslinking reaction involving radicals in the (meth) acrylic resin (a). In addition, when the (meth) acrylic resin (a) has an acidic functional group such as a carboxyl group, curing also proceeds due to a reaction of the (meth) acrylic resin (a) with an epoxy resin, a curing agent, or the like. The electroconductive paste (X) contains a compound that generates hydroxyl groups upon heat curing of an epoxy resin or the like, and thus, a more complex three-dimensional network of hydroxyl groups thus generated, hydroxyl groups of the (meth) acrylic resin (a), and boric acid is formed, thereby providing further improved electroconductivity.
[ Metal powder (B) ]
The electroconductive paste (X) contains a metal powder (B). The metal powder (B) is a particle containing a metal as a main component, wherein the metal is exposed on the surface of the particle.
Examples of the metal powder (B) include copper powder (including copper powder coated with silver), silver powder, copper-silver alloy powder, gold powder, platinum powder, palladium powder, nickel powder, and aluminum powder. Of these, copper powder (including silver-coated copper powder) is preferred. In this case, a highly conductive and inexpensive conductive paste (X) is obtained.
Examples of the shape of the metal powder (B) include a spherical shape, a flat shape (a flake shape), a dendritic shape, and an amorphous shape. The metal powder (B) may be in a combination of two or more of these shapes.
From the viewpoint of printing suitability, the average particle diameter of the metal powder (B) is preferably 0.1 μm or more and 30 μm or less, more preferably 0.5 μm or more and 20 μm or less, and still more preferably 1 μm or more and 10 μm or less. The average particle diameter is the median diameter, the particle size distribution (volume basis) of the metal powder (B) is measured, and the particle diameter in the cumulative distribution of 50% by volume thereof is shown.
The ratio of the metal 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%.
[ boric acid (C) ]
Except orthoboric acid (H) 3 BO 3 ) Examples of boric acid (C) include, in addition, boric acid (H) 3 BO 3 ) Metaboric acid, tetraboric acid of the condensate of (a).
The ratio of boric acid (C) to 100 parts by mass of the binder (a) (solid content) is preferably 1 part by mass or more and 40 parts by mass or less. In this case, the adhesiveness and conductivity of the electroconductive paste (X) can be further improved. The ratio of boric acid to 100 parts by mass of the binder (a) (solid content) is more preferably greater than or equal to 2 parts by mass and less than or equal to 20 parts by mass, and still more preferably greater than or equal to 3 parts by mass and less than or equal to 15 parts by mass.
The ratio of boric acid (C) to the electroconductive paste (X) (solid content) is preferably greater than or equal to 0.1 mass% and less than or equal to 5 mass%, more preferably greater than or equal to 0.2 mass% and less than or equal to 3 mass%, and still more preferably greater than or equal to 0.5 mass% and less than or equal to 2 mass%.
[ organic solvent (D) ]
The electroconductive paste (X) contains an organic solvent (D). This enables the viscosity of the electroconductive paste (X) to be more appropriately adjusted, and therefore, the electroconductive paste (X) is suitably suitable for screen printing or the like.
Examples of the organic solvent (D) include: polyols such as diols (e.g., ethylene glycol, propylene glycol, and dipropylene glycol) and triols (e.g., glycerol); sugar alcohols; monohydric 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.
From the viewpoint of more appropriately adjusting the viscosity of the electroconductive paste (X), the ratio of the organic solvent (D) to the electroconductive paste (X) is preferably greater than or equal to 0.1 mass% and less than or equal to 30 mass%, more preferably greater than or equal to 1 mass% and less than or equal to 25 mass%, and still more preferably greater than or equal to 3 mass% and less than or equal to 20 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 good pattern. The thixotropic ratio (Ti value) of the electroconductive paste (X) is preferably 1.0 or more and 3.0 or less. 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)). In this case, the conductive paste (X) does not impair the workability of screen printing, and wiring is easily formed in a good pattern.
< 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 both good adhesion and conductivity. Further, since the conductive film obtained by curing the conductive paste (X) has good adhesion to various types of base materials and is also excellent in terms of flexibility, the conductive film can be formed as wiring, for example, on the following materials in addition to an aluminum plate, a glass plate, a stainless steel plate, and the like: flexible base materials such as polyvinyl chloride film, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polybutylene terephthalate (PBT) film, polycarbonate film, and ABS film; and Indium Tin Oxide (ITO) films.
The conductive film of the present embodiment is formed by applying the conductive paste (X) on the base material via, for example, screen printing, and then curing the conductive paste (X) by heating. The heating temperature and the heating period may be appropriately selected in consideration of the type of the base material and 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 of base materials include: metal plates such as aluminum plates and stainless steel plates; inorganic plates such as glass plates; organic films such as polyvinyl chloride film, PET film, PEN film, PBT film, polycarbonate film, and ABS film; and transparent conductive films such as ITO films, tin oxide films, and ZnO-based films. Since the conductive film is formed by curing the conductive paste (X), the conductive film can have excellent adhesion to the above base material.
When a conductive film such as wiring is formed of a conductive paste (X) on the surface of a transparent conductive film such as an ITO film, a particularly low specific resistance value can be obtained. This is probably because the hydroxyl groups on the ITO film form a network of further increased number with the hydroxyl groups of the boric acid- (meth) acrylic resin (a). Furthermore, this further improves the adhesion of the conductive film to the ITO film.
Examples
The present disclosure will be specifically described with reference to the following examples.
Synthesis of (meth) acrylic resin (a)
[ (meth) acrylic resin (a 1) Synthesis ]
In a reactor provided with a stirrer, a condenser tube, a dropping funnel and a nitrogen-introducing tube, 300g of dipropylene glycol monomethyl ether, 70g of methacrylic acid, 130g of butyl methacrylate and 2g of azobisisobutyronitrile were blended and polymerized by a solution polymerization method at 80℃for 10 hours under atmospheric pressure and a nitrogen gas stream, thereby obtaining a solution of resin X1-1 as (meth) acrylic resin (X1). Subsequently, 0.2g of hydroquinone and 2g of triphenylphosphine were added to and dissolved in a solution of the resin X1-1 in a reactor provided with a stirrer, a condenser tube, a dropping funnel and a tube for introducing air into the liquid, and further 70g of glycidyl methacrylate was added, followed by heating at 110℃for 5 hours under air bubbling. Thus, a solution of the resin A1-1 which is the (meth) acrylic resin (A1) was obtained.
In a similar reaction, a solution of resin A1-2 was obtained, in which the blending amount of azobisisobutyronitrile was varied. Furthermore, solutions of resins A1-3, A1-4, A1-5 and A1-6 were obtained, in which different mass ratios of methacrylic acid/butyl methacrylate/glycidyl methacrylate were used.
[ (meth) acrylic resin (a 4) Synthesis ]
In a reaction similar to the above reaction, hydroxyethyl methacrylate having a hydroxyl group was further employed as a monomer and glycidyl methacrylate was not added for the reaction, thereby obtaining a solution of the resin A4-1.
[ (meth) acrylic resin (a 2) Synthesis ]
In a reactor provided with a stirrer, a condenser tube, a dropping funnel and a nitrogen-introducing tube, 300g of ethyl carbitol acetate, 130g of methyl methacrylate, 70g of glycidyl methacrylate and 5g of azobisisobutyronitrile were blended and polymerized by a solution polymerization method at 80℃for 7 hours under atmospheric pressure and a nitrogen gas stream, to thereby obtain a solution of resin X2-1 as (meth) acrylic resin (X2). Subsequently, 36g of acrylic acid and 2g of triphenylphosphine were added to and dissolved in a solution of the resin X2-1 in a reactor provided with a stirrer, a condenser tube, a dropping funnel and a tube for introducing air into the liquid, and then heated under air bubbling at 100℃for 8 hours. Thus, a solution of the resin A2-1 which is the (meth) acrylic resin (A2) was obtained.
[ (meth) acrylic resin (a 3) Synthesis ]
In a reaction similar to the above reaction, the mass ratio of methyl methacrylate/glycidyl methacrylate/acrylic acid thus used was changed, and further modified with tetrahydrophthalic anhydride as a carboxylic anhydride, to obtain a solution of resin A3-1.
The weight average molecular weight of the (meth) acrylic resin (a) 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 the (meth) acrylic resin (a) 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
Tables 1 and 2 below each collectively show the measurement results of the weight average molecular weight, acid value, and hydroxyl value of the (meth) acrylic resin (a), and the glass transition temperature (Tg) of the (meth) acrylic resin (x) ((meth) acrylic resins (x 1) and (x 2)).
TABLE 1
Figure BDA0004118677420000131
TABLE 2
Figure BDA0004118677420000141
< preparation of conductive paste >
Example 1
9.4g of a solution of resin A1-1 and 0.5g of boric acid were blended and dissolved in 2.0g of ethyl carbitol as a solvent, thereby obtaining a solution. 48.0g of copper particles (manufactured by FUKUDA METAL FOIL & POWDER CO., LTD. Trade name: cu-HWF-4 ") were blended in the 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 a similar manner to example 1, except that 9.4g of the solution of resin A1-2 was used instead of the solution of resin A1-1.
Example 3
Conductive paste 3 (DP-3) was obtained in a similar manner to example 1, except that 10.8g of the solution of resin A1-3 was used instead of the solution of resin A1-1.
Example 4
Conductive paste 4 (DP-4) was obtained in a similar manner to example 1, except that 8.5g of the solution of resin A1-6 was used instead of the solution of resin A1-1.
Example 5
Conductive paste 5 (DP-5) was obtained in a similar manner to example 1, except that 10.5g of the solution of resin A1-4 was used instead of the solution of resin A1-1.
Example 6
Conductive paste 6 (DP-6) was obtained in a similar manner to example 1, except that 8.7g of the solution of resin A1-5 was used instead of the solution of resin A1-1.
Example 7
Conductive paste 7 (DP-7) was obtained in a similar manner to example 1, except that 6.7g of a solution of resin A4-1 was used instead of the solution of resin A1-1, 1.8g of an epoxy resin (manufactured by dic corporation, epicolin EXA 4816) and 0.02g of a curing accelerator (manufactured by SHIKOKU CHEMICALS CORPORATION, CUREZOL2 PHZ-PW) were further added, and the blending amount of ethyl carbitol as a solvent was changed to 3.0g.
Example 8
Conductive paste 8 (DP-8) was obtained in a similar manner to example 1, except that 48.0g of silver-coated copper powder (manufactured by Mitsui Mining & refining co., ltd., trade name: "10% ag02 k") was used as the metal powder instead of the copper powder (Cu-HWF-4).
Example 9
Conductive paste 9 (DP-9) was obtained in a similar manner to example 1, except that the blending amount of the solution of resin A1-1 was changed to 5.8g, 1.8g of an epoxy resin (manufactured by DIC Corporation, epicolin EXA 4816) and 0.02g of a curing accelerator (manufactured by SHIKOKU CHEMICALS CORPORATION, CUREZOL2 PHZ-PW) were further added, and the blending amount of ethyl carbitol as a solvent was changed to 3.0g.
Example 10
Conductive paste 10 (DP-10) was obtained in a similar manner to example 1, except that 10.0g of the solution of resin A2-1 was used instead of the solution of resin A1-1, and the solvent was changed to 3.0g of ethylcarbitol acetate.
Example 11
Conductive paste 11 (DP-11) was obtained in a similar manner to example 10, except that 8.3g of the solution of resin A3-1 was used instead of the solution of resin A2-1.
Comparative example 1
Conductive paste 12 (DP-12) was obtained in a similar manner to example 1, except that the blending amount of the solution of resin A1-1 was changed to 10.4g and boric acid was not added.
Comparative example 2
Conductive paste 13 (DP-13) was obtained in a similar manner to example 1, except that the solution of resin A1-1 was not blended, and 4.5g of epoxy resin (EPICLON EXA 4816) and 0.05g of curing accelerator (CUREZOL 2 PHZ-PW) were blended.
[ evaluation of conductive paste ]
(viscosity measurement and Ti value)
The viscosity at 25 ℃ of the conductive pastes obtained in each of examples 1 to 10 and comparative examples 1 and 2 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 metal powder)
In order to evaluate dispersibility of the metal powder in each of the thus obtained conductive pastes, the coarse particles were inspected by using a grind gauge (manufactured by Taiyu Kizai co.ltd. Manufactured by 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 metal 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 3 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 the metal powder.
TABLE 3
Figure BDA0004118677420000171
/>
< formation of conductive film >
The thus obtained electroconductive pastes 1 to 13 (DP-1 to DP-13) were applied onto a PET film base material, a glass base material, and a transparent electroconductive film (indium tin oxide film) on the glass base material 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 them at 150 ℃ for 30 minutes, thereby obtaining the base materials 1 to 13 provided with the electroconductive films 1 to 13 (DM-1 to DM-13), respectively.
[ evaluation of conductive film ]
(measurement of resistance value of conductive film)
The resistance values (Ω) of the conductive films 1 to 13 (DM-1 to DM-13) thus obtained were measured by using a four-point resistance meter (manufactured by HIOKI e.e. corporation), resistance meter RM 3544-01.
(evaluation of adhesion)
By conforming to JIS-K5600-5-6:1999 (paint general test method (adhesion: cross-cut test)) to evaluate the adhesion of the obtained conductive films 1 to 13 (DM-1 to DM-13) to glass, PET and ITO. Specifically, the conductive film (size: 20 mm. Times.100 mm, thickness: 18 μm) formed on each base material was cut in a grid pattern of 5X 5 squares at 1mm intervals by using a cutter, and cellophane tape was stuck on a portion of the grid pattern, and then peeled off to evaluate the adhesion in 6 stages (i.e., stages 0 to 5).
(evaluation of folding resistance)
The thus obtained conductive films 1 to 13 (DM-1 to DM-13) 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.
A: the rate of increase in resistance values before and after folding is less than or equal to 20%.
B: the rate of increase in resistance values before and after folding is greater than 20% and less than or equal to 100%.
C: the rate of increase of the resistance values before and after folding is greater than 100%.
Table 4 below collectively shows the evaluation results of the resistance value (Ω) of the conductive film, the thickness (μm) of the conductive film, the specific resistance value (volume resistivity) (μΩ·cm) calculated from the resistance value and the film thickness, the evaluation results of the adhesiveness (glass, PET, ITO), and the evaluation results of the folding resistance.
TABLE 4
Figure BDA0004118677420000191
As can be seen from the results shown in table 4, the conductive paste of the example has both good adhesion and conductivity. In particular, a conductive film having a low specific resistance value of 100 μΩ·cm or less and exhibiting particularly good adhesion to various base materials can be obtained from the conductive pastes of examples 1, 6, and 7. The conductive paste of comparative example 1 has a large specific resistance value. This is probably because the curing shrinkage required for exhibiting conductivity is insufficient because boric acid is not used in comparative example 1 and hydrogen bonds are not formed. Since the electroconductive paste of comparative example 2 does not contain a (meth) acrylic resin blended therein, it has low adhesion to various types of base materials.
(summary)
As can be seen from the foregoing, the electroconductive paste according to the first aspect of the present disclosure contains a binder (a), a metal powder (B), boric acid (C), and an organic solvent (D). The binder (a) contains a (meth) acrylic resin (a) having a hydroxyl group.
According to the first aspect, the electroconductive paste has both good adhesion and electroconductivity.
In the electroconductive paste relating to the second aspect of the first aspect, the weight average molecular weight of the (meth) acrylic resin (a) is greater than or equal to 3000 and less than or equal to 100000, and the hydroxyl value of the (meth) acrylic resin (a) is greater than or equal to 20mg KOH/g and less than or equal to 150mg KOH/g.
According to the second aspect, the electroconductive paste has further improved adhesion to the base material and better hydrogen bonding characteristics to boric acid, and thus further improved electroconductivity, and furthermore, the second aspect makes the paste viscosity more suitable, thereby making the electroconductive paste better handled.
In the electroconductive paste according to the third aspect referring to the first or second aspect, the (meth) acrylic resin (a) includes a resin (a 1) obtained by modifying a polymer (x 1) having a structural unit based on a (meth) acryl-and carboxyl-containing monomer with a compound having a (meth) acryl group and an epoxy group.
According to the third aspect, the reaction between the carboxyl group and the epoxy group generates a secondary alcohol hydroxyl group, the hydroxyl group and boric acid form a network by hydrogen bonding or the like, and the (meth) acryl group is at the terminal end of the side chain of the polymer, which contributes to heat curing, further enhancing curing shrinkage, thereby further improving conductivity.
In the electroconductive paste relating to the fourth aspect of the first or second aspect, the (meth) acrylic resin (a) includes a resin (a 2) obtained by modifying a polymer (x 2) having a structural unit based on a (meth) acryl-and epoxy-containing monomer with a compound having a (meth) acryl group and a carboxyl group.
According to the fourth aspect, the reaction between the epoxy group and the carboxyl group generates a secondary alcohol hydroxyl group, the hydroxyl group and boric acid form a network by hydrogen bonding or the like, and the (meth) acryl group is at the terminal end of the side chain of the polymer, which contributes to heat curing, further enhancing curing shrinkage, thereby further improving conductivity.
In the electroconductive paste relating to the fifth aspect of the fourth aspect, the (meth) acrylic resin (a) includes a resin (a 3) obtained by further modifying the resin (a 2) with a carboxylic anhydride.
According to the fifth aspect, the use of the resin (a 3) enables further improvement of dispersibility of the metal powder.
In the electroconductive paste of the sixth aspect relating to any one of the first to fifth aspects, the metal powder (B) includes copper powder.
According to the sixth aspect, a highly conductive and inexpensive conductive paste is obtained.
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 both good adhesion and conductivity.
INDUSTRIAL APPLICABILITY
The electroconductive paste according to the present disclosure can be used for forming electroconductive films as electrodes and circuit patterns of, for example, semiconductor devices and electronic components. The conductive paste of the present disclosure contains a predetermined component and thus may be thermally cured at a low temperature (e.g., less than or equal to 250 ℃) to form an electrode. Further, the electroconductive paste of the present application can be used to obtain an electroconductive film (electrode) having a low specific resistance. The electroconductive paste of the present application can optimize the numerical range of the physical properties of the (meth) acrylic resin to obtain a coating film excellent in adhesion to both inorganic base materials and organic base materials. Thus, the electroconductive paste of the present disclosure can form such an electroconductive film: it is excellent not only in adhesion to the surfaces of inorganic base materials such as semiconductors, oxides, and ceramics, but also in adhesion to organic base materials such as PET and PEN having low heat resistance, and thus, the conductive film can be used for forming electrodes and circuit patterns of flexible devices, for example. Further, the electroconductive paste of the present disclosure can form an electroconductive film that is also excellent in adhesion to a transparent electroconductive film (e.g., an ITO film, a tin oxide film, a ZnO-based film) that is a material for a transparent electrode, and the electroconductive film can be used to form an electrode.

Claims (7)

1. A conductive paste comprising:
a binder (A);
metal powder (B);
boric acid (C); and
an organic solvent (D),
the binder (a) contains a (meth) acrylic resin (a) having a hydroxyl group.
2. The electroconductive paste according to claim 1, wherein
The (meth) acrylic resin (a) has a weight average molecular weight of 3000 or more and 100000 or less, and
the hydroxyl value of the (meth) acrylic resin (a) is greater than or equal to 20mg KOH/g and less than or equal to 150mg KOH/g.
3. The electroconductive paste according to claim 1 or 2, wherein
The (meth) acrylic resin (a) includes a resin (a 1) in which a polymer (x 1) having a structural unit based on a (meth) acryl-and carboxyl-containing monomer is modified with a compound having a (meth) acryl group and an epoxy group.
4. The electroconductive paste according to claim 1 or 2, wherein
The (meth) acrylic resin (a) includes a resin (a 2) in which a polymer (x 2) having a structural unit based on a (meth) acryl-and epoxy-group-containing monomer is modified with a compound having a (meth) acryl group and a carboxyl group.
5. The electroconductive paste according to claim 4, wherein
The (meth) acrylic resin (a) includes a resin (a 3) obtained by further modifying the resin (a 2) with carboxylic anhydride.
6. The electroconductive paste according to any one of claims 1 to 5, wherein
The metal powder (B) includes copper powder.
7. A conductive film comprising the cured product of the conductive paste according to any one of claims 1 to 6.
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