JP6780554B2 - Aqueous conductive paste and products - Google Patents

Description

The present invention relates to aqueous conductive pastes and products. In particular, the present invention relates to an aqueous conductive paste and a product that can be used for jumper wires, conductive adhesives, etc. in electronic / electrical members and the like.

Conventionally, it is a conductive member having a wiring formed by drying a conductive paste of an aqueous polyurethane dispersion and a conductive particle and a stretchable polyurethane substrate, and the aqueous polyurethane dispersion is a polyester polyol and an aliphatic. A conductive member in which a self-emulsifying anionic polyurethane composed of diisocyanate or aliphatic diisocyanate is dispersed in water is known (see, for example, Patent Document 1). In Patent Document 1, a conductive member that is bendable and has elasticity can be provided.

Japanese Patent No. 5570353

However, the conductive member described in Patent Document 1 contains a polyester-based compound, and since the polyester-based compound is hydrolyzed, it cannot be used for applications in contact with moisture, and has a problem in durability. In addition, it is difficult to stably disperse the conductive particles in the aqueous liquid, and there is a problem that the conductive particles in the conductive paste are separated after long-term storage.

Therefore, an object of the present invention is to provide an aqueous conductive paste having excellent durability of a cured or dried aqueous conductive paste and having conductive particles that are difficult to separate even after long-term storage, and a product.

In order to achieve the above object, the present invention has at least one of an ether-based or polycarbonate-based urethane resin emulsion, a conductive filler containing metal particles, and an unshared electron pair having polarity and coordinating with the metal particles. An aqueous conductive paste containing a polymer compound containing an atom having an atom is provided.

In the aqueous conductive paste, it is preferable that the polymer compound has hydrophilicity and contains a pyrrolidone group.

In the aqueous conductive paste, the polymer compound preferably contains polyvinylpyrrolidone.

In the above-mentioned aqueous conductive paste, the metal particles preferably contain silver particles.

In the above aqueous conductive paste, it is preferable that the conductive filler is not separated after being allowed to stand for 4 weeks in an environment of 40 ° C.

Further, in order to achieve the above object, the present invention provides a cured product of the aqueous conductive paste according to any one of the above.

Further, in order to achieve the above object, the present invention provides a product having a cured product of the aqueous conductive paste according to any one of the above as a component.

According to the aqueous conductive paste and the product according to the present invention, it is possible to provide the aqueous conductive paste and the product which have excellent durability of the cured or dried aqueous conductive paste and the conductive particles are difficult to separate even after long-term storage.

Conventional conductive pastes containing polyester compounds cannot be used for applications that come into contact with moisture because the polyester compounds have the property of hydrolyzing. That is, if the conventional conductive paste is dried and left in the air, the polyester compound is hydrolyzed by the moisture in the air, so that the durability of the conventional conductive paste is low. Therefore, the present inventor has studied an aqueous conductive paste using an ether-based urethane resin emulsion and / or a carbonate-based urethane resin emulsion in order to improve such a difficulty. In addition, the present inventor appropriately disperses conductive particles in an aqueous conductive paste using an ether-based urethane resin emulsion and / or a carbonate-based urethane resin emulsion, and even after long-term storage, in the aqueous conductive paste. From the viewpoint of not separating the conductive particles, it has been found that it is effective to adopt a specific water-soluble polymer compound that is easily coordinated with the conductive particles. Furthermore, the present inventor has conventionally used a film that is not durable against heat because when conductive particles (for example, silver nanoparticles) are used, the protective colloid existing around the conductive particles must be removed by firing to conduct conduction. It has been found that an aqueous conductive paste that conducts without heating such as firing can be realized by adopting a specific composition, where it cannot be used for or a substrate.

That is, the aqueous conductive paste according to the present invention has at least one of an ether-based or polycarbonate-based urethane resin emulsion, a conductive filler containing metal particles, and an unshared electron pair that has polarity and coordinates with the metal particles. Contains a water-soluble polymer compound containing an atom having.

<Urethane resin emulsion>
Examples of the ether-based or polycarbonate-based urethane resin emulsion of the present invention include polyurethane emulsions, aqueous polyurethanes, water-dispersible polyurethanes, polyurethane dispersions, and polyurethane microemulsions. The urethane resin emulsion is an emulsion in which urethane resin is dispersed and stabilized in an aqueous medium.

The urethane resin is a reaction product of an isocyanate compound and a compound having active hydrogen such as an amino group (for example, a polyol such as a polyether). In addition, the synthetically obtained isocyanate compound can be reacted with a chain extender such as a diol or a diamine to increase the molecular weight.

Examples of isocyanate compounds include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3,6-hexamethylene triisocyanate, dianisidine diisocyanate, lysine diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), tolylene diisocyanate, and xylyl. Range isocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diisocyanate-3,3-dimethylbiphenyl, triphenylmethane triisocyanate, 1,5-naphthalenediisocyanate, isophorone diisocyanate and the like, and polyisocyanates which are derivatives thereof. Prepolymer and the like can be mentioned.

In addition, examples of the compound containing active hydrogen include polyol compounds such as polyethers containing a hydroxyl group (however, in the present invention, polyester is excluded). Examples of the polyether include poly (oxyethylene) glycol, poly (oxypropylene) glycol, poly (oxyethylene) / poly (oxypropylene) glycol, poly (oxybutylene) glycol and the like, and derivatives thereof.

Further, examples of the compound containing active hydrogen include polycarbonates. Examples of polycarbonate include reaction products of carbonate and polyol. Examples of the carbonate include diaryl carbonate such as diphenyl carbonate, dialkyl carbonate such as dimethyl carbonate and diethyl carbonate, and the like. These can be used alone or in combination of two or more.

Examples of other compounds having an active hydrogen group include polyesteramides, polythioethers, acrylic polyols, hydroxyl group-containing polybutadiene and the like. Examples of chain extenders include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butylene glycol, trimethylolpropane, hydroquinone dihydroxyethyl ether, water, ethylenediamine, hexamethylenediamine, trimethylhexamethylenediamine, isophoronediamine, piperazin, and amino. Examples thereof include compounds having an active hydrogen group in the molecule such as ethyl piperazine and 2,5-dimethylpiperazine.

The urethane resin can be made into a water-dispersible emulsion by various methods shown below, and the urethane resin emulsion of the present invention can be obtained.

1) A method of making urethane resin water-soluble using a water-soluble raw material.
2) A method in which urethane resin is dissolved in an organic solvent such as toluene and mechanically forcibly emulsified in an aqueous emulsifier solution.
3) An excess amount of isocyanate compound is reacted with a polyol compound to synthesize a prepolymer having an isocyanate group at the terminal, and the mixture is treated with a blocking agent such as phenols and ketooximes to synthesize blocked isocyanate, which is then mixed in an aqueous emulsifier. A method of dropping and stirring.
4) A method of synthesizing a prepolymer having an isocyanate group at the terminal, adding the prepolymer to an aqueous emulsifier solution to which a chain extender has been added with high speed stirring, and simultaneously performing emulsification and chain extension.
5) At the time of producing a urethane resin, a compound such as diaminobenzenesulfonate, diaminobenzoate, N- (2-aminoethyl) -2-aminoethanesulfonic acid was added as a chain extender to add a sulfonic acid group to the molecule of the urethane resin. An anionic group such as a carboxyl group is introduced, or a compound such as N-methyldiethanolamine or N-ethyldiethanolamine is added to introduce a cationic group such as an amino group into the molecule of the urethane resin to make it self-emulsifying. , A method of dispersing this in water containing a neutralizing agent.

In the present invention, the urethane resin emulsion is preferably an ether-based or polycarbonate-based polyurethane dispersion from the viewpoint of durability of the aqueous conductive paste.

<Conductive filler>
The conductive filler is formed using a material having electrical conductivity. As the conductive filler, carbon particles, metal particles or alloy particles such as silver, copper, nickel, gold, tin, zinc, platinum, palladium, iron, tungsten, molybdenum, and solder, or the surface of these particles is made of metal or the like. Conductive particles such as particles prepared by covering with a conductive coating can be used. Further, for example, polymer particles which are non-conductive particles composed of polyethylene, polystyrene, phenol resin, epoxy resin, acrylic resin, or benzoguanamine resin, or inorganic particles composed of glass beads, silica, graphite, or ceramic. It is also possible to use conductive particles obtained by applying a conductive coating such as metal to the surface. In the present invention, from the viewpoint of ease of coordination by the polymer compound, it is preferable to use a conductive filler containing metal particles, and a conductive filler composed of silver particles or silver nanoparticles is used. Is more preferable.

As the shape of the conductive filler, various shapes (for example, spherical shape, ellipse, cylinder shape, flakes, flat plate, grain mass, etc.) can be adopted. The conductive filler can also have a slightly rough or jagged surface. The particle shape, size, and / or hardness of the conductive filler can be combined and used in the aqueous conductive paste of the present invention. Further, for the purpose of further improving the conductivity of the cured product of the aqueous conductive paste, a plurality of conductive fillers having different particle shapes, sizes, and / or hardnesses of the conductive fillers can be combined. The conductive filler to be combined is not limited to two types, and may be three or more types. For example, a flake-shaped conductive filler made of silver may be used in combination with other conductive fillers such as granules.

Here, the flake shape includes a shape such as a flat shape, a flaky shape, or a scale shape, and includes a shape obtained by crushing a three-dimensional silver powder such as a spherical shape or a lump shape in one direction. Further, the term “granular” means the shape of all conductive fillers having no flake shape. For example, examples of the granules include a shape in which powder is aggregated in the shape of a tuft of grapes, a spherical shape, a substantially spherical shape, a lump shape, a dendritic shape, and a mixture of silver powder having these shapes.

When silver is used as the conductive filler, the conductive filler can be produced by various methods. For example, when flaky silver powder is used as a conductive filler, it can be produced by mechanically pulverizing spherical silver powder and / or silver powder such as lump silver powder using an apparatus such as a jet mill, a roll mill, or a ball mill. When granular silver powder is used as a conductive filler, it can be produced by an electrolysis method, a pulverization method, a heat treatment method, an atomizing method, a reduction method or the like.

From the viewpoint of exhibiting good electrical conductivity, the aqueous conductive paste of the present invention preferably contains a conductive filler of 500 parts by weight or more and 800 parts by weight or less with respect to 100 parts by weight of the resin content of the urethane resin emulsion. In particular, from the viewpoint of ensuring sufficient stretchable physical properties of the cured product, it is preferable to contain a conductive filler of 800 parts by weight or less.

<Polymer compound>
The aqueous conductive paste of the present invention contains atoms having unshared electron pairs that can coordinate with the metal particles of the conductive filler, and contains a polar polymer compound. This polymer compound preferably has hydrophilicity and is preferably water-soluble. Examples of the atom having an unshared electron pair that can coordinate with the metal particle include a nitrogen atom and an oxygen atom. Then, in the present invention, it is preferable to use a polymer compound containing a pyrrolidone group containing a nitrogen atom and an oxygen atom.

Examples of the polymer compound having a pyrrolidone group include a homopolymer of N-vinyl-2-pyrrolidone (polyvinylpyrrolidone), a copolymer of N-vinyl-2-pyrrolidone and another monomer, and a copolymer of maleic anhydride. Examples thereof include a polymer obtained by reacting a coalescence with a hydroxy group-containing pyrrolidone. In the present invention, it is preferable to use a polymer compound containing polyvinylpyrrolidone from the viewpoint of ease of coordination to metal particles (particularly silver particles).

Further, the weight average molecular weight of the polymer compound of the present invention is preferably 45,000 or more, more preferably 100,000 or more, from the viewpoint of exhibiting the association behavior in water. Further, the weight average molecular weight of the polymer compound of the present invention is preferably 1.2 million or less, more preferably 1 million or less, from the viewpoint of ensuring water solubility.

<Other additives>
The aqueous conductive paste according to the present invention includes stabilizers, dispersants, defoamers, preservatives, thickeners, fillers, as necessary, as long as the functions such as conductivity and curability of the aqueous conductive paste are not impaired. , Defoamer, ion-exchanged water, surfactant, tackifier resin, bulking agent, property conditioner, reinforcing agent, colorant, flame retardant, sagging inhibitor, thixotropy agent, anti-precipitation agent, antioxidant, anti-aging agent Various additives such as agents, UV absorbers, fragrances, pigments and dyes may be added.

Examples of the stabilizer include polyoxyalkylene alkyl ethers, polyoxyethylene polyoxypropylene block copolymers and the like. Examples of the dispersant include inorganic dispersants such as tripolyphosphate and pyrophosphate, and polymer dispersants such as polycarboxylic acid salt. Examples of the defoaming agent include mineral oil-based nonionic surfactants, silicone-based defoaming agents such as polydimethylsiloxane oil, ethylene oxide or propylene oxide-modified dimethyl silicone or dimethyl silicone emulsion, mineral oil, acetylene alcohol and the like. Alcohol-based antifoaming agent and the like. Examples of the preservative include cyclic nitrogen-based compounds and cyclic nitrogen-sulfur-based compounds. Examples of the thickener include polyacrylate, hydroxyethyl cellulose, water-soluble urethane resin and the like.

(Filler)
As the filler, a resin filler (resin fine powder), an inorganic filler, and a functional filler can be used. The filler may be surface-treated with a silane coupling agent, a titanium chelating agent, an aluminum coupling agent, a fatty acid, a fatty acid ester, rosin or the like. As the resin filler, a particulate filler made of an organic resin or the like can be used. For example, as the resin filler, organic fine particles such as ethyl polyacrylate resin, polyurethane resin, polyethylene resin, polypropylene resin, urea resin, melamine resin, benzoguanamine resin, phenol resin, acrylic resin, and styrene resin can be used.

Examples of the inorganic filler include talc, clay, calcium carbonate, magnesium carbonate, silicon dioxide, hydrous silicon, calcium silicate, titanium dioxide, carbon black and the like.

Examples of the functional filler include hollow particles described in JP-A-2016-199668 and the like having excellent heat insulating properties and light weight; core-shell particles described in JP-A-2016-199669 and the like having excellent sound insulation and vibration damping properties; Layered silicates described in JP-A-2016-199670 and the like having excellent gas barriers and the like; light-reflecting fillers described in JP-A-2016-199671 etc.; ..

<Manufacturing method of aqueous conductive paste>
The aqueous conductive paste can be produced by the following procedure. First, at least one of ether-based or polycarbonate-based urethane resin emulsions, a conductive filler containing metal particles, a polymer compound containing an atom having a polarity and an unshared electron pair coordinated to the metal particles, and a polymer compound. / Or each of the other additives is weighed in a predetermined amount and prepared (preparation step). Next, at least one of an ether-based or polycarbonate-based urethane resin emulsion is put into a predetermined container and stirred for a predetermined time. Subsequently, a conductive filler containing metal particles is added to at least one of an ether-based or polycarbonate-based urethane resin emulsion, and the mixture is stirred for a predetermined time (filler addition step). Further, to at least one of the ether-based or polycarbonate-based urethane resin emulsion containing a conductive filler, a polymer compound containing an atom having an atom having an unshared electron pair coordinated with metal particles is added. Stir for a predetermined time (polymer compound addition step). As a result, the aqueous conductive paste according to the present invention can be produced. In addition, other additives may be added as appropriate in each step or any step.

<Products containing a cured product of aqueous conductive paste as a component>
The aqueous conductive paste of the present invention is applied to an object and cured by allowing it to stand or dry under normal temperature and pressure. In addition, in order to improve the drying rate, it may be heated. The cured aqueous conductive paste has conductivity. By this drying or curing, a cured product of the aqueous conductive paste is obtained. Therefore, various products such as electronic circuits, electronic parts, and automobile parts can be manufactured by using the cured product of the aqueous conductive paste as a component. For example, a product can be manufactured by applying the aqueous conductive paste according to the present invention to a predetermined adherend and drying it.

The aqueous conductive paste of the present invention can be used in various applications where conductivity is required. The aqueous conductive paste can also be used as an adhesive. For example, the aqueous conductive paste of the present invention can be used for forming jumper lines on electronic / electric circuit boards, for adhering electronic devices / electric devices where continuity is required, and the like.

<Effect of embodiment>
Since the aqueous conductive paste according to the present invention contains at least one of an ether-based or polycarbonate-based urethane resin emulsion, it does not hydrolyze, and the cured or dried aqueous conductive paste has a polyester-based durability against moisture. It is greatly improved as compared with the case where the urethane resin emulsion is used. Further, the aqueous conductive paste according to the present invention contains at least one of an ether-based or polycarbonate-based urethane resin emulsion and a conductive filler, and further contains a specific water-soluble polymer compound, and therefore, after long-term storage. It is also possible to prevent the conductive filler from separating in the aqueous conductive paste. Further, the aqueous conductive paste of the present invention has a configuration containing at least one of an ether-based or polycarbonate-based urethane resin emulsion, a conductive filler containing metal particles, and a specific water-soluble polymer compound. Therefore, since it is cured and conducted by simply leaving it in the air, heat treatment such as firing is not required as in the case of a conventional paste using silver nanoparticles.

An embodiment will be described below in more detail. Needless to say, these examples are examples and should not be construed in a limited manner.

(Examples 1 to 4, Comparative Examples 1 to 5)
Each compounding substance was added at the compounding ratio shown in Table 1 to prepare an aqueous conductive paste according to the above description of "Method for producing aqueous conductive paste". Specifically, each of the urethane resin emulsion, the conductive filler, the polymer compound, and other additives was weighed and prepared so as to have the blending ratio shown in Table 1. Next, the urethane resin emulsion, the thickener, the defoaming agent, and the ion-exchanged water were put into a planetary stirrer and stirred for 2 minutes (rotation conditions: rotation 500 rpm, revolution 1000 rpm). Subsequently, a conductive filler and a defoaming agent were added thereto, and the mixture was stirred for 2 minutes under the same rotation conditions as described above. Further, a polymer compound, a dispersant, a fluorine-based surfactant, or a surfactant was added thereto, and the mixture was stirred for 2 minutes under the same rotation conditions as described above. As a result, the aqueous conductive pastes according to Examples 1 to 4 and Comparative Examples 1 to 5 were obtained.

In Table 1, the unit of the compounding amount of each compounding substance is "part by weight". The details of the compounded substances are as follows.
(Urethane resin emulsion)
-Ether-based polyurethane dispersion (hereinafter, polyurethane dispersion is referred to as "PUD") (resin content 35-40%) (product name "Hydran WLS-207", manufactured by DIC Corporation)
-Ether-based PUD (resin content 35%) (Product name "Hydran WLS-201", manufactured by DIC Corporation)
-Polycarbonate PUD (product name "ETERNACOLL UW-5034E", manufactured by Ube Industries, Ltd.)
-Polyester PUD (Product name "Hydran HW-940", manufactured by DIC Corporation)
(Thickener)
-Product name "Adecanol UH-541VF", manufactured by ADEKA Corporation (defoamer)
-Product name "SN Deformer 777", manufactured by San Nopco Co., Ltd. (foaming agent)
-Product name "DISPER BYK-012", manufactured by Big Chemie Japan Co., Ltd. (conductive filler)
-Product name "Silcoat AgC-B", manufactured by Fukuda Metal Leaf Powder Industry Co., Ltd.-Product name "Silcoat AgC-201Z", manufactured by Fukuda Metal Leaf Powder Industry Co., Ltd. (polymer compound)
-Polyvinylpyrrolidone (polyvinylpyrrolidone K90, manufactured by Nippon Shokubai Co., Ltd.) dissolved in ion-exchanged water to a concentration of 5 wt%.
(Dispersant)
-Product name "DISPER BYK-2012", manufactured by Big Chemie Japan Co., Ltd.-Product name "DYNEWET N800", manufactured by Big Chemie Japan Co., Ltd. (fluorine-based surfactant)
-Product name "CAPSTONE FS30", made by DuPont (surfactant)
・ Surfactin sodium, manufactured by Kaneka Corporation, dissolved in ion-exchanged water to a concentration of 5 wt%.

(Volume resistivity)
The aqueous conductive paste according to Example 1 was applied on a glass plate in a size of 70 mm × 100 mm using a masking tape having a thickness of 100 μm as a spacer, and dried at 80 ° C. for 20 minutes. Then, it cooled to room temperature, and the test piece of the dried aqueous conductive paste was obtained. Then, using Lorester MCP-T360 (manufactured by Mitsubishi Analytech), the volume resistivity (volume resistivity immediately after drying) of this test piece was measured. Similar measurements were made for the aqueous conductive pastes of Examples 2-4 and Comparative Examples 1-5.

(Volume resistivity after 60 ° C. 90% RH 500 hr)
Using the aqueous conductive paste according to Example 1, the test piece prepared in the above description of "volume resistivity" was allowed to stand in a constant temperature and humidity chamber adjusted to 60 ° C. and 90% RH. This test piece was taken out after 500 hours in a constant temperature and humidity chamber, left at room temperature for 1 hour, and then the volume resistivity (volume resistivity after 500 hr elapse) was measured in the same manner as above. Similar measurements were made for the aqueous conductive pastes of Examples 2-4 and Comparative Examples 1-5.

(Confirmation of separation)
10 ml of the aqueous conductive paste according to Example 1 was filled in a syringe PSY-10E (with scale) manufactured by Musashi Engineering Co., Ltd., and MLP-B-10E was attached as a plunger and HC-10C was attached as a head cap. Then, the tip and bottom of the syringe were sealed with Teflon (registered trademark) tape, the tip of the syringe was set down on a test tube rack, and the syringe was allowed to stand in a hot air circulation dryer adjusted to 40 ° C. for 4 weeks. .. After 4 weeks, the syringe was taken out and the state of separation was observed. The evaluation criteria are as follows. Further, the same confirmation was made for the aqueous conductive pastes according to Examples 2 to 4 and Comparative Examples 1 to 5.

(Evaluation criteria for separation)
◯: No separation Δ: Separation less than 2 ml ×: Separation 2 ml or more

As can be seen from Table 1, in all of the aqueous conductive pastes according to Examples 1 to 4, the volume resistivity of the cured product immediately after the adjustment and the volume resistivity after 500 hr at 60 ° C. and 90% RH are both good. Yes, no separation of the conductive filler was substantially observed even when left at 40 ° C. for 4 weeks. Further, the rate of change in volume resistivity was confirmed using the formula | (volume resistivity after 500 hr)-(volume resistivity immediately after drying) | / (volume resistivity immediately after drying) x 100. The rate of change in volume resistivity of the aqueous conductive paste according to the example was about 40% or less.

On the other hand, in Comparative Example 1, separation of the conductive filler was not observed even after being left at 40 ° C. for 4 weeks, but the volume resistivity deteriorated by two digits or more. Further, in Comparative Example 2 and Comparative Example 4, although the separation of the conductive filler was small after being left at 40 ° C. for 4 weeks, it was not completely eliminated, the volume resistivity was poor, and practicality was not recognized. Then, in Comparative Example 3 and Comparative Example 5, separation of the conductive filler was confirmed after being left at 40 ° C. for 4 weeks. Further, the rate of change in the volume resistivity of the aqueous conductive paste according to the comparative example was 70% or more, which was a very large rate of change.

From the above, in the aqueous conductive paste according to the examples, the volume resistivity is excellent and the change in volume resistivity is small, so that the durability is excellent, and the conductive filler is separated in the aqueous conductive paste even after long-term storage. It has been shown that it can be suppressed.

Although the embodiments and examples of the present invention have been described above, the embodiments and examples described above do not limit the invention according to the claims. In addition, not all combinations of features described in the embodiments and examples are indispensable for the means for solving the problems of the invention, and various as long as they do not deviate from the technical idea of the present invention. It should be noted that it can be transformed.

Claims (7)

With at least one of ether-based or polycarbonate-based urethane resin emulsions,
Conductive filler containing metal particles and
An aqueous conductive paste containing a polymer compound having polarity and containing an atom having an unshared electron pair coordinated with the metal particles. The aqueous conductive paste according to claim 1, wherein the polymer compound has hydrophilicity and contains a pyrrolidone group. The aqueous conductive paste according to claim 1 or 2, wherein the polymer compound contains polyvinylpyrrolidone. The aqueous conductive paste according to any one of claims 1 to 3, wherein the metal particles include silver particles. The aqueous conductive paste according to any one of claims 1 to 4, which does not separate the conductive filler after being allowed to stand in an environment of 40 ° C. for 4 weeks. The cured product of the aqueous conductive paste according to any one of claims 1 to 5. A product having a cured product of the aqueous conductive paste according to any one of claims 1 to 5 as a component.