JP5927004B2 - Conductive paste and conductive circuit - Google Patents

Description

  The present invention relates to a conductive paste and a conductive circuit using the same.

  Conventionally, as a technique for forming a conductive circuit for a flat panel display (hereinafter also referred to as “FPD”) such as a plasma display panel (hereinafter also referred to as “PDP”), a conductive powder such as silver powder is used as an organic binder. The mixed conductive paste is patterned on the substrate by, for example, screen printing or photolithography, and then burned at 550 ° C. or higher to burn out organic components and fuse the conductive powder onto the substrate. A method for forming a conductive circuit composed only of an inorganic component is known (see, for example, Patent Document 1). Since this method is performed under very high temperature conditions, applicable substrates are limited.

  On the other hand, as a technique for forming a conductive circuit for flexible devices such as electronic paper using PET as a base material and devices having low heat resistance such as a touch panel, a conductive paste is patterned on the base material, and the temperature is 250 ° C. or lower. There has been proposed a method of forming a conductive circuit made of conductive powder and an organic component by curing at a temperature of (see, for example, Patent Document 2).

Japanese Patent No. 3520798 JP 2004-355933 A

  In order to obtain high conductivity in the conductive circuit formed by the conductive paste as described above, for example, the content of the conductive powder in the conductive paste is increased, or the shape such as flaky conductive powder is specified. Although studies have been made to reduce the resistance of the conductive circuit, it is still not sufficient and there is room for improvement.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a conductive paste capable of forming a low-resistance conductive circuit.

  The conductive paste according to the present embodiment is characterized by containing conductive powder, an organic binder, and at least one of thiodiglycolic acid and thiodiglycolic acid derivatives. With such a configuration, the resistance of the conductive circuit can be reduced. The resistance of the conductive circuit can be reduced regardless of whether or not the organic component is burned out.

  The conductive paste according to this embodiment is preferably non-photosensitive. Moreover, as for the electrically conductive paste which concerns on this embodiment, it is preferable that the said electroconductive powder is silver powder.

Moreover, the conductive paste according to the present embodiment has a blending amount of at least any one of the thiodiglycolic acid and the thiodiglycolic acid derivative as a solid content of 0.01 to 100 parts by mass per 100 parts by mass of the organic binder resin. It is preferably 10 parts by mass.
With such a configuration, the resistance of the conductive circuit can be further reduced.
In addition, the conductive circuit according to the present embodiment is characterized by being formed using the above conductive paste.

  According to the conductive paste of the present invention, a low resistance conductive circuit can be formed.

As a result of intensive studies on the above problems, the inventors of the present invention have found that the paste used for forming the conductive circuit includes at least one of a conductive powder, an organic binder, thiodiglycolic acid and a thiodiglycolic acid derivative. It has been found that a low resistance conductive circuit can be formed by containing one kind, and the present invention has been completed.
Hereinafter, the conductive paste of this embodiment will be described in detail.

The conductive powder in the conductive paste of the present embodiment imparts conductivity to the formed conductive circuit. Specifically, for example, Ag, Au, Pt, Pd, Ni, Cu, Al, Sn, Pb Zn, Fe, Ir, Os, Rh, W, Mo, Ru, etc. can be mentioned. These conductive powders may be used in the form of a single body, or may be any of these alloys, or a multilayer body having any of these as a core or a coating layer. Further, oxides such as tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), and ITO (Indium Tin Oxide) may be used. Among these conductive powders, Ag is preferably used.

  The shape of the conductive powder is not particularly limited, and may be various shapes such as a dentlite shape as well as a spherical shape and a flake shape.

The particle size of the conductive powder is not particularly limited. For example, when a spherical conductive powder is used, the average particle size is 0.1 to 5 μm, preferably 0.2 to 3 μm. Moreover, when using flaky conductive powder, an average particle diameter is 0.1-5 micrometers, Preferably it is 0.3-3 micrometers.
In addition, an average particle diameter is calculated | required by calculating the average which measured 10 random electroconductive powders observed using SEM (scanning electron microscope).
The flaky silver powder specifically refers to silver powder having an aspect ratio of 3 or more. The aspect ratio can be obtained by (average particle diameter / average thickness T).
Here, “average particle diameter” indicates an average long diameter L of 10 particles measured in the longitudinal direction with a scanning electron microscope, and “average thickness T” indicates particles measured in the thickness direction with a scanning electron microscope. Ten average thicknesses T are shown.

  Such conductive powder is preferably 30 to 90% by mass based on the nonvolatile component of the conductive paste (the component that does not volatilize from the paste in the drying step and remains in the film). If it is less than 30% by mass, it will be difficult to obtain sufficient electrical conductivity, and if it exceeds 90% by mass, the printability will be inferior and it will be difficult to form a coating film. More preferably, it is 50-85 mass%.

  The organic binder in the conductive paste of the present embodiment disperses the conductive powder so that it can be applied on the substrate. When the conductive paste is photosensitive, it is developed by pattern exposure to form a coating film. Used to form a pattern.

  As the organic binder, any of non-photosensitive resins and photosensitive resins can be used. As an organic binder, what contains any 1 type of a dry organic binder, a thermosetting organic binder, and a photocurable organic binder can be used. It is not always necessary to use alone, and two or more kinds can be used together.

  Among these, a dry organic binder and a thermosetting organic binder are used for the non-photosensitive conductive paste used. A dry organic binder is used with the organic solvent mentioned later, and forms a dry coating film by removing an organic solvent by heat drying. Further, the thermosetting organic binder is cured by intermolecular crosslinking under the action of heat or a catalyst to form a cured coating film.

  Examples of such dry organic binder and thermosetting organic binder include acrylic polyol, polyvinyl alcohol, polyvinyl acetal, styrene-allyl alcohol resin, olefinic hydroxyl group-containing polymer such as phenol resin, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose Cellulose derivatives such as ethylene-vinyl acetate copolymer, alkyd resin, alkyd phenol resin, butyral resin, epoxy resin, modified epoxy resin, acrylic resin, polyurethane resin, and polyester resin can be used. In particular, when a cured coating film is formed by thermosetting as the thermosetting organic binder, it is preferable to use a peroxide thermal polymerization catalyst described later in combination.

  The photocurable organic binder is used for imparting photosensitivity and is cured by intermolecular crosslinking under the action of active energy rays such as ultraviolet rays and electron beams to form a cured coating film.

  Examples of such a photocurable organic binder include a resin having a photosensitive group such as an ethylenically unsaturated bond such as a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group, or a propargyl group, for example, an ethylenically unsaturated group in a side chain. Conventionally known various photosensitive resins (photosensitive prepolymers) such as an acrylic copolymer having an unsaturated carboxylic acid, an unsaturated carboxylic acid-modified epoxy resin, or a resin further added with a polybasic acid anhydride can be used.

  These photocurable organic binders can be used in combination with a compound having one or more ethylenically unsaturated bonds in the molecule, that is, a photopolymerizable monomer described later. In addition, the photocurable organic binder is preferably used in combination with a photopolymerization initiator described later in order to allow the photopolymerization to proceed more efficiently.

  Thiodiglycolic acid is added for the purpose of imparting the stability of the metal plating solution. However, in this embodiment, a low-resistance conductive circuit is formed by adding it to the conductive paste used for forming the conductive circuit. Can be achieved. As thiodiglycolic acid, for example, thiodiglycolic acid such as deer grade 1 manufactured by Kanto Chemical Co., Inc. can be used.

In addition, formation of a low-resistance conductive circuit can be achieved using a thiodiglycolic acid derivative. A derivative refers to a compound formed by a small structural change in a compound. Generally, a compound in which a hydrogen atom or a specific atomic group in a compound is replaced by another atom or atomic group. Say.
Examples of thiodiglycolic acid derivatives include 3,3′-thiodipropionic acid, diallyl thiodiacetic acid, thiobis (butyl acetate), disodium thiodiglycolate, bis (2,2′-thiodiacetic acid bis (2- Ethylhexyl), dioctyl thiodiacetate, 2,2′-thiobis (methyl acetate), dipotassium thiodiglycolate and the like.

  The blending ratio of at least one of thiodiglycolic acid and thiodiglycolic acid derivatives is preferably 0.01 to 10 parts by mass per 100 parts by mass of the organic binder in terms of solid content. If it is less than 0.01 parts by mass, the conductivity is deteriorated, which is not preferable. On the other hand, if it exceeds 10 parts by mass, the conductivity is similarly deteriorated, which is not preferable. More preferably, it is 0.1-5 mass parts.

Moreover, when providing photosensitivity to the electrically conductive paste of this embodiment, a photopolymerizable monomer can be used.
Examples of the photopolymerizable monomer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, polyurethane diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, Pentaerythritol tetraacrylate, trimethylolpropane ethylene oxide-modified triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate and the corresponding methacrylates; phthalic acid, adipic acid, maleic acid, itaconic acid, succinic acid, Polybasic acids such as trimellitic acid and terephthalic acid and hydroxya Mono and kill (meth) acrylate -, di -, tri -, or the like more polyesters may be mentioned.

  These photopolymerizable monomers can be used alone or in combination of two or more. Among these photopolymerizable monomers, polyfunctional monomers having two or more acryloyl groups or methacryloyl groups in one molecule are preferable.

  As a compounding quantity of such a photopolymerizable monomer, 5-200 mass parts is preferable per 100 mass parts of organic binders as solid content conversion.

  In addition, a photopolymerization initiator can be used for the purpose of promoting photocuring when imparting photosensitivity to the conductive paste.

  Examples of such photopolymerization initiators include benzoin and benzoin alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2- Acetophenones such as diethoxy-2-phenylacetophenone and 1,1-dichloroacetophenone; 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino -1- (4-morpholinophenyl) -butanone-1,2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, etc. Aminoacetophenones; 2-methylanthraquinone, 2-ethylanthraquinone, 2- anthraquinones such as t-butylanthraquinone and 1-chloroanthraquinone; thioxanthones such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone and 2,4-diisopropylthioxanthone; acetophenone dimethyl ketal and benzyldimethyl Ketals such as ketals; benzophenones such as benzophenones; or xanthones; (2,6-dimethoxybenzoyl) -2,4,4-pentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide 2,4,6-trimethylbenzoyldiphenylphosphine oxide, phosphine oxides such as ethyl-2,4,6-trimethylbenzoylphenylphosphinate; 1,2-octanedione, 1- [4-phenylthio]-, 2 − (O Benzoyloxime), 2- (acetyloxyiminomethyl) thioxanthen-9-one, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-9-yl] -1- (O-acetyl) Oxime esters such as oxime) and various peroxides. Further, IRGACURE 389 manufactured by BASF Japan can also be suitably used as a photopolymerization initiator. These photopolymerization initiators can be used alone or in combination of two or more.

  Examples of commercially available products include BASF Japan's IRGACURE 184, IRGACURE 369, IRGACURE 379, IRGACURE 389, IRGACURE 819, IRGACURE 907, Lucyrin (registered trademark) TPO, CGI-325, IRGACURE (registered trademark) OXE01, IRGACURE OXE02, NCI-831 manufactured by ADEKA can be used.

  As a compounding quantity of such a photoinitiator, 0.01-50 mass parts is preferable per 100 mass parts of organic binders as solid content conversion. If it is less than 0.01 parts by mass, the photocurability becomes insufficient and the pattern tends to be chipped. Further, the surface curability is insufficient, and the surface of the coating film is damaged during development, affecting the conductivity. On the other hand, when the amount exceeds 50 parts by mass, pattern halation occurs, and the sharpness of the pattern edge portion deteriorates. In addition, the pattern releasability deteriorates and a pattern with a small space cannot be drawn.

  The photopolymerization initiator includes tertiary amines such as N, N-dimethylaminobenzoic acid ethyl ester, N, N-dimethylaminobenzoic acid isoamyl ester, pentyl-4-dimethylaminobenzoate, triethylamine, and triethanolamine. These photosensitizers can be used alone or in combination with two or more.

  Moreover, a thermal polymerization catalyst can be used as needed for the purpose of accelerating the curing of the conductive paste. The thermal polymerization catalyst can react with an uncured polymerizable component by aging at a high temperature of about several minutes to 1 hour.

  Examples of such a thermal polymerization catalyst include peroxides such as benzoyl peroxide and azo compounds such as isobutyronitrile, preferably 2,2′-azobisisobutyronitrile, 2,2′- Azobis-2-methylbutyronitrile, 2,2′-azobis-2,4-divaleronitrile, 1,1′-azobis-1-cyclohexanecarbonitrile, dimethyl-2,2′-azobisisobutyrate, 4,4′-azobis-4-cyanovaleric acid, 2-methyl-2,2′-azobispropanenitrile, 2,4-dimethyl-2,2,2 ′, 2′-azobispentanenitrile, 1 , 1'-azobis (1-acetoxy-1-phenylethane), 2,2,2 ', 2'-azobis (2-methylbutanamide oxime) dihydrochloride, and the like.

Moreover, in the conductive paste of this embodiment, an organic solvent can be used to adjust the viscosity and form a uniform coating film.
Examples of such organic solvents include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; cellosolve, methyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol Glycol ethers such as monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monoethyl ether; ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene Glycol monomethyl ether acetate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate Esters of ethanol; alcohols such as ethanol, propanol, ethylene glycol, propylene glycol, terpineol; aliphatic hydrocarbons such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha These can be used alone or in combination of two or more.

  In such a conductive paste, a stabilizer can be added in order to further improve the storage stability and suppress the deterioration of the coating workability due to the gelation or the decrease in fluidity.

  As such a stabilizer, a compound having an effect such as complex formation with the conductive powder in the conductive paste or salt formation can be used.

  Specifically, for example, various inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, boric acid; formic acid, acetic acid, acetoacetic acid, citric acid, stearic acid, maleic acid, fumaric acid, phthalic acid, benzenesulfonic acid, sulfamic acid, etc. Various organic acids; phosphoric acid, phosphorous acid, hypophosphorous acid, methyl phosphate, ethyl phosphate, butyl phosphate, phenyl phosphate, ethyl phosphite, diphenyl phosphite, mono (2-methacryloyloxyethyl) Examples thereof include acids such as various phosphate compounds (inorganic phosphoric acid and organic phosphoric acid) such as acid phosphate and di (2-methacryloyloxyethyl) acid phosphate. These stabilizers can be used alone or in combination of two or more.

  Furthermore, other additives such as a defoaming / leveling agent such as silicone or acrylic and a silane coupling agent for improving the adhesion of the coating film can be blended in the conductive paste of this embodiment. Furthermore, a known antioxidant or a thermal polymerization inhibitor for improving the thermal stability during storage may be added.

  The conductive paste configured as described above is prepared by mixing each component, and after stirring with a stirrer or the like, it can be paste-formed by kneading with a three-roll mill or the like.

  When the conductive paste thus prepared is a non-photosensitive conductive paste, a desired conductive circuit is printed on a substrate such as a glass substrate by a printing method such as screen printing or offset printing. The substrate on which the circuit is printed is dried or cured at 80 to 300 ° C. for 5 to 60 minutes to form a desired conductive circuit on the substrate.

On the other hand, in the case of a photosensitive conductive paste, a conductive circuit is formed by the following method in addition to the above method.
First, it is applied to a substrate such as a glass substrate by an appropriate application method such as a screen printing method, a bar coder, or a blade coater to form a coating film.

  Next, the obtained coating film is dried at, for example, about 70 to 120 ° C. for about 5 to 40 minutes in a hot-air circulating drying furnace, a far-infrared drying furnace or the like in order to obtain a touch-drying property. Dry film). At this time, when the conductive paste is previously formed on the film, it may be laminated on the substrate.

Then, selective exposure is performed with respect to the obtained dry coating film. As selective exposure, contact exposure and non-contact exposure using a negative mask having a predetermined exposure pattern are possible. As the exposure light source, for example, a halogen lamp, a high-pressure mercury lamp, a laser beam, a metal halide lamp, a black lamp, an electrodeless lamp, or the like is used. The exposure dose is preferably about 10 to 700 mJ / cm ² .

  Development is performed on the coating film after selective exposure. For the development, a spray method, a dipping method or the like is used. As the developer, it is sufficient that the carboxyl group contained in the organic binder contained in the conductive paste is saponified and the uncured part (unexposed part) can be removed. For example, sodium hydroxide, potassium hydroxide, A metal alkali aqueous solution such as sodium carbonate, potassium carbonate and sodium silicate, an amine aqueous solution such as monoethanolamine, diethanolamine and triethanolamine, particularly a dilute alkaline aqueous solution having a concentration of about 1.5 wt% or less is preferably used. Moreover, it is preferable to perform washing with water and acid neutralization in order to remove an unnecessary developer after development.

  Thereafter, the substrate on which a desired conductive pattern is formed by development is dried or cured at 80 to 300 ° C. for 5 to 60 minutes to form a desired conductive circuit on the base material.

  Hereinafter, although an Example and a comparative example are shown and this embodiment is demonstrated concretely, this invention is not limited to these Examples. In the following, “%” is based on weight unless otherwise specified.

<Synthesis example of organic binder>
A flask equipped with a thermometer, stirrer, dropping funnel, and reflux condenser is charged with methyl methacrylate and methacrylic acid in a molar ratio of 0.87: 0.13, dipropylene glycol monomethyl ether as a solvent, and azobisiso as a catalyst. Butyronitryl was added and stirred at 80 ° C. for 2 to 6 hours under a nitrogen atmosphere to obtain a resin solution containing an organic binder. This organic binder had a weight average molecular weight of about 10,000, an acid value of 74 mgKOH / g, and a solid content of 57%.

  For the measurement of the weight average molecular weight of the organic binder, high performance liquid chromatography using three Shimadzu pump LC-6AD and Showa Denko column Shodex (registered trademark) KF-804, KF-803, KF-802 is used. did.

<Preparation of conductive paste>
It mixes with each component and composition ratio shown in Table 1, and after stirring with a stirrer, it pastes by kneading with a 3 roll mill , and each electrically conductive paste of Examples 1-3, a reference example, and Comparative Examples 1-5 Was prepared.

＊１：平均粒径＝１．５μｍ
＊２：Ｍ−３５０（東亜合成社製）
＊３：ビス(2,4,6-トリメチルベンゾイル)-フェニルホスフィンオキサイド；ＩＲＧＡＣＵＲＥ ８１９（ＢＡＳＦジャパン社製）
＊４：２，２’−チオジグリコール酸（関東化学社製；規格 鹿１級）
＊５：３，３’−チオジプロピオン酸（関東化学社製；規格 鹿１級）
＊６：グリコール酸（関東化学社製；規格 鹿１級）
＊７：チオグリコール酸（関東化学社製；規格 鹿１級）
＊８：マロン酸（関東化学社製；規格 鹿１級）

* 1: Average particle size = 1.5 μm
* 2: M-350 (manufactured by Toa Gosei Co., Ltd.)
* 3: Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; IRGACURE 819 (manufactured by BASF Japan)
* 4: 2,2′-thiodiglycolic acid (manufactured by Kanto Chemical Co., Inc .; standard deer grade 1)
* 5: 3,3′-thiodipropionic acid (manufactured by Kanto Chemical Co., Ltd .; standard deer grade 1)
* 6: Glycolic acid (manufactured by Kanto Chemical Co., Inc .; standard deer grade 1)
* 7: Thioglycolic acid (manufactured by Kanto Chemical Co., Inc., standard deer grade 1)
* 8: Malonic acid (manufactured by Kanto Chemical Co., Inc .; standard deer grade 1)

<Evaluation of sheet resistance>
Each adjusted conductive paste was pattern-printed on a glass substrate to form a 0.5 cm × 10 cm pattern, and heat-treated at 170 ° C. for 30 minutes to form a 0.5 cm × 10 cm conductive circuit. For this conductive circuit, the sheet resistance value was measured by a four-terminal method using a milliohm high tester, and the specific resistance value was calculated.

As shown in Table 2, in Examples 1 to 3 and Reference Examples using thiodiglycolic acid or derivatives thereof, the ratio of 10 ⁻⁵ (Ω · cm) order regardless of whether it is photosensitive or non-photosensitive. A resistance value was obtained, and it was confirmed that the resistance was low. On the other hand, Comparative Examples 1 and 2, which do not use at least any one of thiodiglycolic acid and thiodiglycolic acid derivatives, glycolic acid instead of at least one of thiodiglycolic acid and thiodiglycolic acid derivatives In Comparative Examples 3, 4 and 5 using thioglycolic acid and malonic acid, respectively, specific resistance values of the order of 10 ⁻⁵ (Ω · cm) were not obtained regardless of whether they were photosensitive or non-photosensitive. As a result, it was confirmed that the specific resistance value was high.

Claims (4)

A non-photosensitive conductive paste comprising a conductive powder, an organic binder, and at least one of thiodiglycolic acid and a thiodiglycolic acid derivative, and cured at 80 to 300 ° C. The non-photosensitive conductive paste according to claim 1 , wherein the conductive powder includes silver powder. 2. The thiodiglycolic acid and / or a derivative of thiodiglycolic acid is 0.01 to 10 parts by mass per 100 parts by mass of the organic binder in terms of solid content. Or the non-photosensitive electrically conductive paste of Claim 2 . A conductive circuit formed using the non-photosensitive conductive paste according to any one of claims 1 to 3 .