TW202217860A - Conductive paste and conductive film - Google Patents

Abstract

Provided is a conductive paste that achieves both good adhesion and conductivity. This conductive paste includes 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.

Description

Conductive paste and conductive film

The present invention relates to a conductive paste and a conductive film, and more specifically, to a conductive paste and a conductive film. The conductive paste contains: a binder, metal powder, boric acid, and an organic solvent, and the conductive film contains A hardened product of this conductive paste.

A technique has been used in which a conductive paste is printed on various substrates to form wiring. It has been carried out that a conductive paste is printed on the surface of a base material by a screen printing method or the like to form a conductive film, and the conductive film becomes a circuit of a predetermined pattern.

The conduction mechanism of the conductive paste is derived from the following: The metal powders are in contact with or approach each other due to the curing shrinkage of the binder, that is, the thermosetting resin, so the conductivity is greatly affected by the following states: The oxidation of the surface of the metal powder state, and the curing shrinkage state of the thermosetting resin. The adhesive has a large shrinkage due to hardening, so a resol-type phenol resin that can obtain good electrical conductivity has been generally used. However, resol-type phenol resins are relatively hard and brittle, and their adhesion to substrates is also low. Then, a conductive paste using a (meth)acrylic resin has been proposed.

As a conductive paste using a (meth)acrylic resin, Patent Document 1 (International Publication No. 2013/187183) discloses a conductive paste comprising: a (meth)acrylic resin as a binder resin, An organic solvent and a metal powder, and the glass transition point Tg of the (meth)acrylic resin is in the range of -60°C to 120°C, the hydroxyl group in the molecule is in the range of 0.01% by weight to 5% by weight, and the acid value is in the range of In the range of 1 mgKOH/g to 50 mgKOH/g, the weight average molecular weight is in the range of 10000 to 350000. Patent Document 2 (Japanese Laid-Open Patent Publication No. 2019-106305) discloses a conductive paste comprising a conductive component, a thermosetting resin, a specific cationic polymerization initiator, and an acrylic resin as thermosetting Sexual resin.

By using a (meth)acrylic resin, the conductive paste can have good flexibility and improved adhesiveness in terms of its properties, but since the curing shrinkage of the resin due to heating is small, the above-mentioned conventional A known conductive paste using a (meth)acrylic resin cannot express sufficient conductivity.

The problem to be solved by this application is to provide a conductive paste and a conductive film which can achieve both good adhesion and conductivity.

The conductive paste of one aspect of this application contains a binder (A), metal powder (B), boric acid (C), and an organic solvent (D). The said binder (A) contains the (meth)acrylic resin (a) which has a hydroxyl group.

The conductive film of one aspect of this invention contains the hardened|cured material of the said conductive paste.

＜Conductive paste＞

The conductive paste (hereinafter also referred to as conductive paste (X)) of the present embodiment contains a binder (A), metal powder (B), boric acid (C), and an organic solvent (D). The binder (A) contains the (meth)acrylic resin (a) having a hydroxyl group. The "(meth)acrylic resin" means an acrylic resin, a methacrylic resin, or both. (Meth)acrylic resin is a polymer having a structural unit based on at least one monomer among (meth)acrylic acid and (meth)acrylate.

The inventors of the present invention discovered the fact that by using a (meth)acrylic resin (a) having a hydroxyl group in a conductive paste of a thermosetting resin using a (meth)acrylic resin as a binder As a (meth)acrylic resin, and further adding boric acid, it can express favorable electroconductivity. The reason for this is not necessarily clear, but it is considered that, for example, a three-dimensional crosslinked structure is formed by the hydroxyl group of the (meth)acrylic resin (a) and boric acid through a network obtained by hydrogen bonding, and the curing shrinkage of the resin is increased. , resulting in improved electrical conductivity and the like. In addition, it was also found that in the conductive paste (X), by including the (meth)acrylic resin (a) having a hydroxyl group and boric acid as the binder (A), various substrates can be good adhesion. As described above, with the conductive paste (X), both good adhesion and conductivity can be achieved.

[Binder (A)] The binder (A) contains a (meth)acrylic resin (a) having a hydroxyl group (hereinafter also referred to as (meth)acrylic resin (a)). As a hydroxyl group, an alcoholic hydroxyl group and a phenolic hydroxyl group are mentioned, for example. The hydroxyl group of the (meth)acrylic resin (a) includes, for example, an alcoholic hydroxyl group or a phenolic hydroxyl group in a structural unit based on a monomer having a hydroxyl group; in the modification reaction of the (meth)acrylic resin Alcoholic hydroxyl groups and the like generated by the reaction of epoxy groups and carboxyl groups.

The hydroxyl value of the (meth)acrylic resin (a) is preferably 20 mgKOH/g or more and 150 mgKOH/g or less. By setting the hydroxyl value to the above-mentioned range, the adhesiveness with the base material is further improved, and the hydrogen bonding property with boric acid is further improved, and the electrical conductivity is further improved. The hydroxyl value is preferably more than 30 mgKOH/g and less than 130 mgKOH/g, more preferably more than 40 mgKOH/g and less than 120 mgKOH/g, and particularly preferably more than 50 mgKOH/g and less than 80 mgKOH/g. The hydroxyl value of the (meth)acrylic resin (a) means the number of mg of the hydroxyl group and the equivalent of potassium hydroxide in 1 g of the (meth)acrylic resin (a).

The acid value of the (meth)acrylic resin (a) is preferably 0 mgKOH/g or more and 200 mgKOH/g or less, and preferably 50 mgKOH/g or more and 150 mgKOH/g or less. By making the acid value into the above-mentioned range, the dispersibility of the metal powder can be made more favorable. The acid value of the (meth)acrylic resin (a) means the mg number of potassium hydroxide required to neutralize the carboxyl group of 1 g of the (meth)acrylic resin (a).

The weight average molecular weight (Mw) of the (meth)acrylic resin (a) is preferably 3,000 or more and 100,000 or less. By making Mw into the said range, adhesiveness improves more, and it becomes possible to make a paste viscosity moderate and handleability more favorable. When Mw exceeds 100000, adhesiveness may fall, and a paste viscosity may become high and handleability may become unsatisfactory. Mw is preferably 5,000 or more and 80,000 or less, more preferably 7,000 or more and 50,000 or less, and particularly preferably 10,000 or more and 50,000 or less. Mw is the value calculated|required by the standard polystyrene conversion by GPC (gel permeation chromatography) measurement method.

The main chain structure of the resin (x) is the same as that of the (meth)acrylic resin (a), and it is a precursor from which the (meth)acrylic resin (a) can be obtained. The glass transition temperature (Tg) of the resin (x) is higher than The temperature is preferably 20°C or higher and 100°C or lower. Adhesion can be further improved by making Tg into the said range. Tg is preferably 30°C or higher and 95°C or lower, and more preferably 40°C or higher and 90°C or lower. The glass transition temperature (Tg) is a value calculated theoretically from the composition ratio of a monomer, which is a constituent unit of the resin (x), and is a value calculated by Fox's formula.

The (meth)acrylic resin (a) includes, for example, the following resins (a1) to (a4). Resin (a1): a resin obtained by modifying a polymer (x1) with a compound having a (meth)acryloyl group and an epoxy group, the polymer (x1) having a (meth)propylene group A structural unit based on a monomer of an acyl group and a carboxyl group. Resin (a2): a resin obtained by modifying a polymer (x2) with a compound having a (meth)acryloyl group and a carboxyl group, the polymer (x2) having a (meth)acryloyl group and epoxy-based monomer-based structural units. Resin (a3): A resin obtained by further modifying resin (a2) with a carboxylic acid anhydride. Resin (a4): (meth)acrylic resin which has a structural unit based on the monomer which has a hydroxyl group.

(Resin (a1)) The resin (a1) is a resin obtained by modifying the polymer (x1) with a compound having a (meth)acryloyl group and an epoxy group (hereinafter also referred to as a compound (c1)), and the polymer ( x1) has a structural unit (henceforth also called structural unit (u1)) based on the monomer which has a (meth)acryloyl group and a carboxyl group. The resin (a1) is formed by subjecting the compound (c1) having an epoxy group to a reforming reaction with the (meth)acrylic resin (x1) having a carboxyl group. A secondary alcoholic hydroxyl group is generated by the reaction of the carboxyl group and the epoxy group, and the hydroxyl group and the boronic acid form a network through hydrogen bonding or the like. In addition, it is considered that the resin (a1) has a (meth)acryloyl group at the end of the side chain of the polymer, so that the (meth)acryloyl group participates in thermal hardening, and the hardening shrinkage is further increased, so that the electrical conductivity can be further improved. sex.

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, (meth)acrylate ) carboxycyclohexyl acrylate, carboxyphenyl (meth)acrylate, carboxybenzyl (meth)acrylate, 2-(meth)acryloyloxyethyl phthalate, 2-tetrahydrophthalate -(Meth)acryloyloxyethyl ester, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxyethyl succinate, ω-carboxypolyethylene Caprolactone monoacrylate, etc.

The ratio of the structural unit (u1) in the resin (a1) is preferably 5 mass % or more and 100 mass % or less, and preferably 20 mass % or more and 50 mass % or less with respect to all the structural units constituting the resin (a1). better.

As the compound (c1) having a (meth)acryloyl group and an epoxy group, for example, glycidyl (meth)acrylate, epoxybutyl (meth)acrylate, and (meth)acrylate epoxy ring Hexyl ester etc.

In the modification reaction of the polymer (x1) and the compound (c1), the compound (c1) is preferably used in an amount such that the epoxy group is 0.1 mol or more and 0.7 mol per 1 mol of the carboxyl group of the polymer (x1). the following amount.

By optimizing the ratio of the structural unit (u1) in the resin (a1) and the ratio of the compound (c1) used in the reforming reaction, the conductivity of the conductive paste (X) can be further improved. Adhesion and conductivity of films to inorganic substrates and organic substrates.

(Resin (a2)) The resin (a2) is a resin obtained by modifying the polymer (x2) with a compound having a (meth)acryloyl group and a carboxyl group (hereinafter also referred to as a compound (c2)). The polymer (x2) It has a structural unit (hereinafter also referred to as a structural unit (u2)) based on a monomer having a (meth)acryloyl group and an epoxy group. The resin (a2) is formed by subjecting the compound (c2) having a carboxyl group to a modification reaction with the (meth)acrylic resin (x2) having an epoxy group. Secondary alcoholic hydroxyl groups are generated by the reaction of epoxy groups and carboxyl groups, and the hydroxyl groups and boronic acids form a network through hydrogen bonding or the like. In addition, it is considered that the resin (a2) has a (meth)acryloyl group at the end of the side chain of the polymer, so that the (meth)acryloyl group participates in thermal hardening, and the hardening shrinkage is further increased, so that the electrical conductivity can be further improved. sex.

As a monomer which has a (meth)acryloyl group and an epoxy group, the compound etc. which are the same as the compound illustrated in the compound (c1) which has a (meth)acryloyl group and an epoxy group mentioned above are mentioned, for example.

The ratio of the structural unit (u2) in the resin (a2) is preferably 10% by mass or more and 100% by mass or less, preferably 30% by mass or more and 80% by mass or less, with respect to all the structural units constituting the resin (a2). better.

As a compound (c2) which has a (meth)acryloyl group and a carboxyl group, the compound etc. which are the same as the compound illustrated in the monomer which has a (meth)acryloyl group and a carboxyl group mentioned above are mentioned, for example.

In the modification reaction of the polymer (x2) and the compound (c2), the compound (c2) is preferably used in an amount such that the carboxyl group is 0.1 mol or more and 1.0 mol per 1 mol of the epoxy group of the polymer (x2). the following amount.

By optimizing the ratio of the structural unit (u2) in the resin (a2) and the ratio of the compound (c2) used in the reforming reaction, the conductivity of the conductive paste (X) can be further improved. Adhesion and conductivity of films to inorganic substrates and organic substrates.

(Resin (a3)) The resin (a3) is a resin obtained by further modifying the resin (a2) with a carboxylic acid anhydride. The resin (a3) is formed by subjecting the carboxylic anhydride (compound (c3)) to a reforming reaction with the epoxy group-containing resin (a2). By using the resin (a3), the dispersibility of the metal powder can be further improved.

Examples of the carboxylic anhydride include aliphatic carboxylic anhydrides such as succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, itaconic anhydride, glutaric anhydride, and 1,2,3,4-butanetetracarboxylic anhydride; Hydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, cyclohexanetricarboxylic anhydride, cyclohexanetetracarboxylic anhydride, bicyclo[2.2.1]heptane-2,3 - Alicyclic carboxylic acid anhydrides such as dicarboxylic anhydride, methylbicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride; phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, naphthalene dimethyl anhydride Aromatic carboxylic anhydrides such as acid anhydride, naphthalene tricarboxylic anhydride, naphthalene tetracarboxylic anhydride, biphthalic anhydride, biphenyl tricarboxylic anhydride, biphenyl tetracarboxylic anhydride, benzophenone tetracarboxylic anhydride, and the like.

The carboxylic acid anhydride is preferably used in an amount such that the acid value of the obtained resin (a3) is preferably 0 mgKOH/g or more and 200 mgKOH/g or less, more preferably 50 mgKOH/g or more and 150 mgKOH/g or less. quantity. By making the acid value of resin (a3) into the said range, favorable dispersibility of a metal powder can be acquired.

(Resin (a4)) Resin (a4) is a (meth)acrylic-type resin which has a structural unit (henceforth a structural unit (u4)) based on the monomer which has a hydroxyl group. As a hydroxyl group, an alcoholic hydroxyl group and a phenolic hydroxyl group are mentioned, for example.

Examples of the monomer having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxycyclohexyl (meth)acrylate, (meth)acrylate (meth)acrylic acid hydroxyl-containing esters such as hydroxyphenyl acrylate and hydroxybenzyl (meth)acrylate; hydroxyl-containing vinyl compounds such as allyl alcohol and vinylcyclohexanol, and the like.

The resin (a4) preferably has a structural unit (u1). In this case, since the resin (a4) has a carboxyl group, the carboxyl group participates in thermal curing, and the curing shrinkage is further increased, so that the conductivity can be further improved.

The ratio of the structural unit (u4) in the resin (a4) is preferably 5% by mass and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less, relative to all the structural units constituting the resin (a4). good.

Resins (a1)-(a3) may have a structural unit (u4). Examples of monomers that can obtain structural units other than the structural units (u1) to (u4) in the resins (a1) to (a4) include methyl (meth)acrylate, ethyl (meth)acrylate, and (meth)acrylate. (meth)acrylic acid aliphatic esters such as propyl acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; (meth)acrylates such as cyclohexyl (meth)acrylate Cyclic esters; (meth)acrylates such as aromatic (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; ethylene such as ethylene, propylene, 1-butene, and styrene compounds, etc.

The ratio of the (meth)acrylic resin (a) to the binder (A) is preferably 50 mass % or more and 100 mass % or less, and preferably 70 mass % or more and 100 mass % or less.

(other resins) The binder (A) may contain, for example, other thermosetting resins other than the aforementioned (meth)acrylic resin (a) as other resins. Such other thermosetting resins include, for example, epoxy resins, phenol resins, amine resins, urethane resins, unsaturated polyester resins, cyanate resins, and (meth)acrylic resins having no hydroxyl group. resin, etc.

The ratio of the other resins to the binder (A) is preferably 1% by mass or more and 50% by mass or less, preferably 5% by mass or more and 45% by mass or less, and more preferably 10% by mass or more and 40% by mass or less .

In order to harden the thermosetting resin, the conductive paste (X) may contain, for example, a hardener, a hardening accelerator, and the like.

The curing agent can be used as long as it can cure the thermosetting resin, and examples thereof include novolak resins; latent amine-based curing agents such as dicyandiamide, imidazole, BF ₃ -amine complexes, and guanidine derivatives; m-phenylene Aromatic amines such as diamine, diaminodiphenylmethane, and diaminodiphenyl benzene; hardeners containing nitrogen atoms such as cyclophosphazene oligomers; polyamide resins, maleic anhydride, phthalate Acid anhydride-based hardeners such as formic anhydride, hexahydrophthalic anhydride, and pyromellitic anhydride, etc. The ratio of the curing agent is preferably 0.1 mass % or more and 10 mass % or less, and preferably 0.5 mass % or more and 5 mass % or less with respect to the thermosetting resin.

Examples of the curing accelerator include tertiary amines such as benzyldimethylamine, imidazoles, metal salts of organic acids, Lewis acids, and amine complexes. The ratio of the curing accelerator is preferably 0.1 mass % or more and 10 mass % or less, and preferably 0.5 mass % or more and 3 mass % or less with respect to the thermosetting resin.

It is preferable that the said other thermosetting resin contains resin which has a hydroxyl group, or a resin which generates a hydroxyl group when thermosetting. As such a thermosetting resin, an epoxy resin, a phenol resin, etc. are mentioned, for example. Since other thermosetting resins have or generate hydroxyl groups, and more networks are formed by hydrogen bonds between hydroxyl groups and boric acid, etc., further improvement in electrical conductivity can be achieved.

It is considered that the thermal curing of the conductive paste (X) proceeds mainly by a crosslinking reaction in which radicals in the (meth)acrylic resin (a) are generated. Further, when the (meth)acrylic resin (a) has an acid functional group such as a carboxyl group, curing also proceeds by the reaction of the (meth)acrylic resin (a) with an epoxy resin, a curing agent, and the like. The conductive paste (X) forms a more complicated three-dimensional network of the hydroxyl group and the hydroxyl group of the (meth)acrylic resin (a) and the boric acid by containing a compound that generates a hydroxyl group when it is thermally cured, such as an epoxy resin. , that is, better electrical conductivity can be obtained.

[Metal Powder (B)] The composition (X) contains the metal powder (B). The metal powder (B) is a particle mainly composed of a metal, and the metal is exposed on the surface of the particle.

The metal powder (B) includes, for example, copper powder (including silver-plated copper powder), silver powder, copper-silver alloy powder, gold powder, platinum powder, palladium powder, nickel powder, aluminum powder, and the like. Among these, copper powder (including silver-plated copper powder) is preferable. In this case, a highly conductive and inexpensive conductive paste (X) can be obtained.

The shape of the metal powder (B) includes, for example, a spherical shape, a flat shape (scaly shape), a dendritic shape, and an amorphous shape. The metal powder (B) may be a combination of two or more of these shapes.

From the viewpoint of proper printing, 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 more preferably 1 μm or more and 10 μm or less. The mean particle diameter refers to the median diameter, and is the particle diameter at which the cumulative distribution of the metal powder (B) is 50% by volume after the particle size distribution (volume basis) of the metal powder (B) is measured.

The ratio of the metal powder (B) to the conductive paste (X) is preferably 50 mass % or more and 99 mass % or less, preferably 60 mass % or more and 98 mass % or less, and 70 mass % or more and 95 mass % or more. It is more preferable that it is 80 mass % or more and 90 mass % or less.

[Boric acid (C)] In addition to orthoboric acid (H ₃ BO ₃ ), boric acid (C) also includes metaboric acid, tetraboric acid and the like as a condensate thereof.

The ratio of boric acid (C) is preferably 1 part by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the binder (A) (solid content). In this case, the adhesiveness and conductivity of the conductive paste (X) can be further improved. The ratio of boric acid is preferably 2 parts by mass or more and 20 parts by mass or less, and preferably 3 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the binder (A) (solid content).

The ratio of boric acid (C) to the conductive paste (X) (solid content) is preferably 0.1 mass % or more and 5 mass % or less, preferably 0.2 mass % or more and 3 mass % or less, and 0.5 mass % More preferably, it is more than or equal to 2 mass %.

[Organic solvent (D)] The composition (X) contains the organic solvent (D). Thereby, the conductive paste (X) can adjust the viscosity more appropriately, and can be suitably used for screen printing or the like.

Examples of the organic solvent (D) include polyols such as glycols such as ethylene glycol, propylene glycol, and dipropylene glycol, and triols such as glycerin; sugar alcohols; and monohydric alcohols such as ethanol, methanol, butanol, propanol, and isopropanol. 1-Methyl-1-methoxybutanol; Ethylene Glycol Monomethyl Ether (Methyl Cellulose), Ethylene Glycol Monoethyl Ether (Ethyl Cellulose), Ethylene Glycol Monoiso Celluloid such as propyl ether (isopropyl cellulose), ethylene glycol mono-n-butyl ether (n-butyl cellulose), ethylene glycol monotertiary butyl ether (tertiary butyl cellulose), etc. Thres; diethylene glycol monomethyl ether (methyl carbitol), diethylene glycol monoethyl ether (ethyl carbitol), diethylene glycol mono-n-propyl ether (n-propyl carbitol) alcohol), diethylene glycol monoisopropyl ether (isopropyl carbitol), ethylene glycol mono-n-butyl ether (n-butyl carbitol), diethylene glycol mono-tertiary butyl ether (tri-butyl alcohol) Carbitols such as tertiary butyl carbitol); triethylene glycol such as triethylene glycol monoethyl ether (ethyl triethylene glycol); propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-tertiary Butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-isopropyl ether and other propylene glycol monoethers; dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol monoisopropyl ether Dipropylene glycol monoethers such as base ethers; Glycol ethers such as tripropylene glycol monoethers such as tripropylene glycol monomethyl ether; Glycol ethers such as ethylene glycol monomethyl ether acetate and other cellulocarboxylates Acid esters; alkanolamines such as ethanolamine, diethanolamine, triethanolamine, etc.

From the viewpoint of more appropriately adjusting the viscosity of the conductive paste (X), the ratio of the organic solvent (D) to the conductive paste (X) is preferably 0.1% by mass or more and 30% by mass or less, and 1 mass % or more and 25 mass % or less are preferable, and 3 mass % or more and 20 mass % or less are more preferable.

[other ingredients] The conductive paste (X) may contain, for example, a rust inhibitor, an antioxidant, an adhesion imparting agent, a dispersing agent, a caulking agent, a leveling agent, a thixotropy adjusting agent, an antifoaming agent, etc., as other components . The ratio of other components is, for example, 2 mass % or less with respect to the conductive paste (X).

(viscosity) The viscosity at 25°C of the conductive paste (X) is preferably 5.0 Pa·s or more and 200 Pa·s or less. At this time, the conductive paste (X) is easy to print without impairing the workability of screen printing, and it is easy to form a wiring having a good pattern. Further, the thixotropic ratio (Ti value) of the conductive 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°C and 0.5 rpm to the viscosity at 25°C and 5 rpm (thixotropic ratio = (viscosity at 25°C, 0.5 rpm)/(the viscosity at 25°C and 5 rpm) viscosity)). At this time, the conductive paste (X) does not impair the workability of screen printing, and it is easy to form a wiring having a good pattern.

＜Conductive film＞ The conductive film of this embodiment contains the hardened|cured material of the said conductive paste (X). Since the conductive film of the present embodiment is formed of the conductive paste (X), it is possible to achieve both good adhesion and conductivity. In addition, the conductive film obtained by curing the conductive paste (X) is excellent in flexibility in addition to good adhesion to various substrates, and can be used in the following applications in addition to aluminum plates, glass plates, stainless steel plates, and the like. Conductive films such as lines are formed on it: polyvinyl chloride film, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polybutylene terephthalate (PBT) film, Substrates with flexibility such as polycarbonate films, ABS (acrylonitrile-butadiene-styrene) films; and indium tin oxide (ITO) films.

The conductive film of the present embodiment is formed, for example, by applying it to a base material by a screen printing method or the like, and then heating and curing it. The heating temperature and the heating time are appropriately selected in consideration of the type of the base material and the like, and the heating temperature is usually 100°C or higher and 250°C or lower, preferably 130°C or higher and 200°C or lower. The heating time is usually 1 minute or more and 5 hours or less, preferably 10 minutes or more and 1 hour or less. The shape of the conductive film is not particularly limited, and other than a linear shape or a strip shape in a plan view of a circuit pattern or the like, for example, a circle, a quadrangle, or the like may be a planar shape in a plan view. The thickness of the conductive film is, for example, 1 μm or more and 1 mm or less, preferably 5 μm or more and 100 μm or less, and preferably 10 μm or more and 50 μm or less.

Examples of substrates include metal plates such as aluminum plates and stainless steel plates; inorganic plates such as glass plates; organic films such as polyvinyl chloride films, PET films, PEN films, PBT films, polycarbonate films, and ABS films; ITO films, tin oxide films, etc. film, transparent conductive films such as ZnO-based films, and the like. Since the formed conductive film is formed by hardening of the conductive paste (X), it can be made excellent in adhesion to such a wide range of base materials.

When the conductive paste (X) is used to form a conductive film such as a wiring on the surface of a transparent conductive film such as an ITO film, a particularly low resistivity value can be obtained. The reason for this is considered to be that the hydroxyl groups on the ITO film further form a network of the hydroxyl groups of the boronic acid-(meth)acrylic resin (a). In addition, by this, the adhesiveness of the conductive film to the ITO film is further improved. [Example]

Hereinafter, the present case will be specifically described by means of examples.

<Synthesis of (meth)acrylic resin (a)> [Synthesis of (meth)acrylic resin (a1)] 300 g of dipropylene glycol monomethyl ether, 70 g of methacrylic acid, 130 g of butyl methacrylate, and azobisisobutyl were prepared in a reaction apparatus equipped with a stirring device, a cooling tube, a dropping funnel, and a nitrogen gas introduction tube. 2 g of nitrile was polymerized at 80° C. for 10 hours by a solution polymerization method under normal pressure and nitrogen flow to obtain a solution of (meth)acrylic resin (x1), that is, resin X1-1. Then, 0.2 g of hydroquinone and 2 g of triphenylphosphine were added to the solution of the obtained resin X1-1 in a reaction apparatus equipped with a stirring device, a cooling tube, a dropping funnel, and a liquid introduction tube for air. This was dissolved, and 70 g of glycidyl methacrylate was further added, followed by heating at 110° C. for 5 hours under air bubbling. In the above-described manner, a solution of (meth)acrylic resin (a1), that is, resin A1-1 was obtained.

In the same reaction, the compounding quantity of azobisisobutyronitrile was changed, and the solution of resin A1-2 was obtained. Moreover, the mass ratio of the methacrylic acid/butyl methacrylate/glycidyl methacrylate used was changed, and the solution of resin A1-3, A1-4, A1-5, and resin A1-6 was obtained.

[Synthesis of (meth)acrylic resin (a4)] In the same reaction described above, a solution of resin A4-1 was obtained by further using hydroxyethyl methacrylate having a hydroxyl group as a monomer and not performing an addition reaction of glycidyl methacrylate.

[Synthesis of (meth)acrylic resin (a2)] In a reaction apparatus equipped with a stirring device, a cooling tube, a dropping funnel, and a nitrogen gas introduction tube, 300 g of ethyl carbitol acetate, 130 g of methyl methacrylate, 70 g of glycidyl methacrylate, and 5 g of azobisisobutyronitrile was carried out by solution polymerization at 80°C under normal pressure and nitrogen flow for 7 hours to obtain (meth)acrylic resin (x2), namely resin X2- 1 solution. Then, 36 g of acrylic acid and 2 g of triphenylphosphine were added to the solution of the obtained resin X2-1 in a reaction device equipped with a stirring device, a cooling tube, a dropping funnel, and a liquid introduction tube for air, and the resulting After dissolution, it was heated at 100°C for 8 hours under air bubbling. In the above-described manner, a solution of (meth)acrylic resin (a2), that is, resin A2-1 was obtained.

[Synthesis of (meth)acrylic resin (a3)] In the same reaction as described above, by changing the mass ratio of methyl methacrylate/glycidyl methacrylate/acrylic acid used, and further also by carboxylic anhydride, ie, tetrahydrophthalic anhydride. quality to obtain a solution of resin A3-1.

About the obtained (meth)acrylic-type resin (a), the weight average molecular weight was measured by the GPC measurement method shown below.

(Measurement of weight average molecular weight) The weight average molecular weight was calculated|required by standard polystyrene conversion by the GPC method. The measurement conditions are as follows. ・Installation: "Prominence LC-20AD" made by Shimadzu Corporation ・Pipe column: manufactured by Showa Denko Co., Ltd., "GPC KF-801, GPC KF-803, GPC KF-805" 3 pieces in total ・Guard column: Showa Denko Co., Ltd., "GPC-KF-G 4A" ・Sample concentration: Diluted with tetrahydrofuran so that the concentration of the (meth)acrylic resin (a) may be 0.5% by mass. ・Mobile phase solvent: Tetrahydrofuran ・Flow rate: 1.0 mL/min ・Column temperature: 40℃

The weight average molecular weight, acid value and hydroxyl value of (meth)acrylic resin (a), and (meth)acrylic resin (x) ((meth)acrylic resin) are shown together in Tables 1 and 2 below. The measurement results of the glass transition temperature (Tg) of (x1) and (x2)).

[Table 1]

[Table 2]

<Preparation of conductive paste> (Example 1) 9.4 g of a solution of resin A1-1 and 0.5 g of boric acid were prepared and dissolved in 2.0 g of ethyl carbitol as a solvent. 48.0 g of copper powder (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., trade name "Cu-HWF-4") 48.0 g was prepared in the obtained solution, mixed with a mixer, and then kneaded with a roll mill to obtain Conductive Paste 1 (DP-1).

(Example 2) A conductive paste 2 (DP-2) was obtained in the same manner as in Example 1, except that 9.4 g of the solution of the resin A1-2 was used instead of the solution of the resin A1-1.

(Example 3) A conductive paste 3 (DP-3) was obtained in the same manner as in Example 1, except that 10.8 g of the solution of the resin A1-3 was used instead of the solution of the resin A1-1.

(Example 4) A conductive paste 4 (DP-4) was obtained in the same manner as in Example 1 except that 8.5 g of the solution of the resin A1-6 was used instead of the solution of the resin A1-1.

(Example 5) A conductive paste 5 (DP-5) was obtained in the same manner as in Example 1 except that 10.5 g of the solution of the resin A1-4 was used instead of the solution of the resin A1-1.

(Example 6) A conductive paste 6 (DP-6) was obtained in the same manner as in Example 1, except that 8.7 g of the solution of the resin A1-5 was used instead of the solution of the resin A1-1.

(Example 7) In addition to using 6.7 g of the solution of the resin A4-1 in place of the solution of the resin A1-1, 1.8 g of an epoxy resin (manufactured by DIC, EPICLON EXA4816) and a curing accelerator (manufactured by Shikoku Chemicals, CUREZOL 2PHZ-PW) 0.02 g were added g, except that the compounding amount of ethyl carbitol, which is a solvent, was changed to 3.0 g, it was carried out in the same manner as in Example 1 to obtain a conductive paste 7 (DP-7).

(Example 8) The same procedure as in Example 1 was carried out, except that 48.0 g of silver-plated copper powder (manufactured by Mitsui Metal Mining Co., Ltd., trade name "10% Ag02K") was used instead of the copper powder "Cu-HWF-4" as the metal powder to obtain Conductive Paste 8 (DP-8).

(Example 9) In addition to changing the formulation amount of the solution of resin A1-1 to 5.8 g, 1.8 g of epoxy resin (manufactured by DIC Corporation, EPICLON EXA4816) and 0.02 g of hardening accelerator (manufactured by Shikoku Chemicals Co., Ltd., CUREZOL 2PHZ-PW) were further added. Except having changed the compounding quantity of ethyl carbitol as a solvent to 3.0 g, it carried out similarly to Example 1, and obtained the conductive paste 9 (DP-9).

(Example 10) A conductive paste 10 was obtained in the same manner as in Example 1 except that 10.0 g of the solution of the resin A2-1 was used in place of the solution of the resin A1-1 and the solvent was changed to 3.0 g of ethyl carbitol acetate. (DP-10).

(Example 11) A conductive paste 11 (DP-11) was obtained in the same manner as in Example 10, except that 8.3 g of the solution of the resin A3-1 was used in place of the solution of the resin A2-1.

(Comparative Example 1) Except having changed the compounding quantity of the solution of resin A1-1 to 10.4 g, and not adding boric acid, it carried out similarly to Example 1, and obtained the electroconductive paste 12 (DP-12).

(Comparative Example 2) Conductive paste 13 was obtained in the same manner as in Example 1, except that the solution of resin A1-1 was not prepared, and 4.5 g of epoxy resin (EPICLON EXA4816) and 0.05 g of curing accelerator (CUREZOL 2PHZ-PW) were prepared. (DP-13).

[Evaluation of conductive paste] (Measurement of viscosity and Ti value) The viscosity (5 rpm and 0.5 rpm) at 25 degreeC of each conductive paste obtained in Examples 1-10 and Comparative Examples 1 and 2 was measured using a cone-plate viscometer (made by Toki Sangyo Co., Ltd.). In addition, the Ti value (=viscosity at 0.5 rpm/viscosity at 5 rpm) was obtained from these measured values.

(Evaluation of Dispersibility of Metal Powder) In order to evaluate the dispersibility of the metal powder in the obtained conductive paste, a grind gauge (manufactured by Taiyu Machinery Co., Ltd., "GM-7470", 0 to 25 μm) was used, referring to JIS K5600-2-5 ( dispersity) to confirm the coarse particles.

From the confirmation result of the coarse particles, the dispersibility of the metal powder was evaluated according to the following criteria. A: The particle size analyzer judgment result is 7.5 μm or less. B: The particle size analyzer judgment result was 10.0 μm. C: The particle size analyzer judgment result is 12.5 μm or more.

In Table 3 below, the measured value of the paste viscosity (Pa·s) (5 rpm, 0.5 rpm), the Ti value, and the evaluation results of the dispersibility of the metal powder are collectively shown.

[table 3]

<Formation of conductive film> The conductive pastes 1 to 13 (DP-1 to DP-13) obtained above were applied by screen printing to the transparent conductive films (oxidized) on the PET film substrate, the glass substrate, and the glass substrate. The indium tin film) was coated in a strip-shaped line shape with a width of 1 mm, a length of 50 mm, and a thickness of 20 μm, and then heated at 150° C. for 30 minutes to harden, to obtain conductive films 1 to 13 (DM- 1 to DM-13) of the conductive film-attached substrates 1 to 13.

[Evaluation of Conductive Film] (Measurement of resistance value of conductive film) The resistance value (Ω) of the obtained conductive films 1 to 13 (DM-1 to DM-13) was measured using a four-probe resistance meter (RESISTANCE METER RM3544-01, manufactured by Hioki Co., Ltd.).

(tightness evaluation) The obtained conductive films 1 to 13 (DM-1 to DM-13) were tested by the method according to JIS-K5600-5-6:1999 (General Test Method for Paints (Adhesion: Cross-Cross Method)). Adhesion evaluation of glass, PET, and ITO. Specifically, a dicing knife was used to draw a 5×5 checkerboard-shaped cut with a width of 1 mm on the conductive film (size: 20 mm×100 mm, thickness 18 μm) formed on each substrate, and After the operation of sticking the cellophane tape to the checkerboard-shaped part and peeling it off, the adhesiveness was evaluated in 6 stages of classification 0 to classification 5.

(Bending resistance evaluation) Using a bending tester, the obtained conductive films 1 to 13 (DM-1 to DM-13) were wound around a 2 mmΦ iron core, bent, and recovered from the bending, and then the resistivity value was measured. Bending resistance was evaluated by the following criteria. A: The increase rate of the resistance value before and after bending is 20% or less. B: The increase rate of the resistance value before and after bending exceeds 20% and is 100% or less. C: The increase rate of the resistivity value before and after bending exceeds 100%.

In Table 4 below, the resistance value (Ω) of the conductive film, the film thickness (μm) of the conductive film, the resistivity value (volume resistivity) (μΩ·cm) calculated from the resistance value and the film thickness, and the adhesion are collectively shown in Table 4 below. (Glass, PET, ITO) evaluation results and bending resistance evaluation results.

[Table 4]

As can be seen from the results in Table 4, by using the conductive pastes of Examples, both good adhesion and conductivity can be achieved. In particular, from the conductive pastes of Example 1, Example 6, and Example 7, it was possible to obtain a conductive film having a low resistivity value of 100 μΩ·cm or less and showing particularly good properties for various substrates tightness. The electrical resistivity value of the conductive paste of Comparative Example 1 is large, and the reason is considered that sufficient hardening shrinkage for expressing electrical conductivity cannot be obtained because boric acid is not used and hydrogen bonds are not formed. The conductive paste of Comparative Example 2 has low adhesiveness with respect to various base materials because (meth)acrylic resin is not prepared.

(Summarize) As apparent from the above, the conductive paste of the first aspect of the present application contains a binder (A), a metal powder (B), a boric acid (C), and an organic solvent (D). The said binder (A) contains the (meth)acrylic resin (a) which has a hydroxyl group.

According to the first aspect, the conductive paste can achieve both good adhesion and conductivity.

In the conductive paste of the second aspect, in the first aspect, the weight average molecular weight of the (meth)acrylic resin (a) is 3,000 or more and 100,000 or less, and the (meth)acrylic resin (a) The hydroxyl value of 20 mgKOH/g or more and 150 mgKOH/g or less.

According to the second aspect, the adhesiveness between the conductive paste and the substrate is further improved, the hydrogen bonding between the conductive paste and the boric acid is more favorable, the conductivity is further improved, and the viscosity of the paste can be made more moderate, and the processing Sex is better.

In the conductive paste of the third aspect, in the first or second aspect, the (meth)acrylic resin (a) contains the resin (a1), and the resin (a1) is obtained by having (meth)propylene A polymer (x1) having a structural unit based on a monomer having a (meth)acryloyl group and a carboxyl group is modified with a compound of an acyl group and an epoxy group.

According to the third aspect, a secondary alcoholic hydroxyl group is generated by the reaction between a carboxyl group and an epoxy group, and the hydroxyl group and the boronic acid form a network by hydrogen bonding, etc., and since the end of the side chain of the polymer has ( Meth)acryloyl group, so the (meth)acryloyl group participates in thermal hardening, so that the hardening shrinkage is further increased, so that the electrical conductivity can be further improved.

The conductive paste of the fourth aspect is in the first or second aspect, wherein the (meth)acrylic resin (a) contains the resin (a2), and the resin (a2) is obtained by having (meth)propylene A polymer (x2) having a structural unit based on a monomer having a (meth)acryloyl group and an epoxy group is modified with a compound of an acyl group and a carboxyl group.

According to the fourth aspect, a secondary alcoholic hydroxyl group is generated by the reaction of an epoxy group and a carboxyl group, and the hydroxyl group and the boronic acid form a network by hydrogen bonding, etc., and since the end of the side chain of the polymer has ( Meth)acryloyl group, so the (meth)acryloyl group participates in thermal hardening, so that the hardening shrinkage is further increased, so that the electrical conductivity can be further improved.

In the conductive paste of the fifth aspect, in the fourth aspect, the (meth)acrylic resin (a) includes a resin (a3), and the resin (a3) is further treated with a carboxylic acid anhydride to the resin ( a2) is modified.

According to the fifth aspect, by using the resin (a3), the dispersibility of the metal powder can be further improved.

In the conductive paste of the sixth aspect, in any one of the first to fifth aspects, the metal powder (B) contains copper powder.

According to the sixth aspect, a highly conductive and inexpensive conductive paste can be obtained.

The conductive film of the seventh aspect includes a cured product of the conductive paste of any one of the first to sixth aspects.

According to the seventh aspect, both good adhesion and conductivity can be achieved in the conductive film. [Industrial Availability]

The conductive paste of the present invention can be used for the formation of electrodes for semiconductor devices, electronic components, and the like, and conductive films as circuit patterns. The conductive paste of the present invention can be thermally cured at a low temperature (for example, 250° C. or lower) by including a predetermined component to form an electrode. In addition, by using the conductive paste of the present invention, a conductive film (electrode) having a low resistivity value can be obtained. The conductive paste of the present invention can optimize the numerical range of various properties of the (meth)acrylic resin in order to obtain a coating film excellent in adhesion to both an inorganic substrate and an organic substrate. Thereby, not only the surface of inorganic substrates such as semiconductors, oxides, and ceramics, but also organic substrates with low heat resistance such as PET and PEN, a conductive film having excellent adhesion can be formed, which can be used to form flexible elements electrodes and circuit patterns. In addition, a conductive film excellent in adhesion can be formed on a transparent conductive film (ITO film, tin oxide film, ZnO-based film, etc.), which is a material of the transparent electrode, and can be used for electrode formation.

Domestic storage information (please note in the order of storage institution, date and number) none Foreign deposit information (please note in the order of deposit country, institution, date and number) none

Claims (7)

A conductive paste comprising: a binder (A), metal powder (B), boric acid (C), and an organic solvent (D), and The said binder (A) contains the (meth)acrylic resin (a) which has a hydroxyl group. The conductive paste according to claim 1, wherein the weight average molecular weight of the (meth)acrylic resin (a) is 3,000 or more and 100,000 or less, and the hydroxyl value of the (meth)acrylic resin (a) is 3,000 or more and 100,000 or less. It is 20 mgKOH/g or more and 150 mgKOH/g or less. The conductive paste according to claim 1 or 2, wherein the (meth)acrylic resin (a) contains a resin (a1) obtained by having a (meth)acryloyl group and The polymer (x1) having a structural unit based on a monomer having a (meth)acryloyl group and a carboxyl group is modified with a compound of an epoxy group. The conductive paste according to claim 1 or 2, wherein the (meth)acrylic resin (a) contains a resin (a2) obtained by having a (meth)acryloyl group and A compound of a carboxyl group is used to modify a polymer (x2) having a structural unit based on a monomer having a (meth)acryloyl group and an epoxy group. The conductive paste according to claim 4, wherein the (meth)acrylic resin (a) contains a resin (a3) obtained by further processing the resin (a2) with a carboxylic acid anhydride. Modified. The conductive paste according to claim 1 or 2, wherein the metal powder (B) contains copper powder. A conductive film comprising a cured product of the conductive paste according to any one of claims 1 to 6.