KR20130056828A - Conductive paste and method for preparing conductive paste - Google Patents

Abstract

PURPOSE: Conductive paste is provided to form excellent conductive patterns with high conductivity and high reliability as a wiring substrate, by a screen printing method. CONSTITUTION: Conductive paste contains thixotropic agent which is formed by activating copper particle, resol type phenol resin, and fatty acid amide wax. The content of the thixotropic agent is 0.05-2 wt%, based on the whole conducting paste. The thixotropic agent allows the fatty acid amide wax to be swelled by xylene or mineral terpene.

Description

TECHNICAL FIELD [0001] The present invention relates to a conductive paste and a method for preparing the conductive paste,

More particularly, the present invention relates to a conductive paste for screen printing using copper as a conductive material and a method for preparing the conductive paste.

BACKGROUND ART Conventionally, a method of using a conductive paste for forming wiring conductors such as electronic parts and printed wiring boards (printed boards) has been known. As the conductive paste, a silver paste containing silver (Ag) as a main component has been mainly applied from the viewpoint of ensuring high conductivity. However, the silver paste is liable to cause ion migration (all silver stones), thereby causing a problem such as a short circuit between the wirings, which may hinder the reliability of the wiring board. Therefore, a technique of increasing the reliability of electronic parts and wiring boards by using a copper paste containing copper (Cu) as a main component which does not easily cause migration phenomenon is proposed instead of the silver paste.

On the other hand, in recent years, electronic equipment has been strongly demanded for small size, light weight, and high performance, and a conductor pattern formed by using a conductive paste is also required to have high definition. As a technique for obtaining a conductor pattern with high precision, a technique of forming a conductor pattern by a photolithography method is known, and a conductive paste for this purpose has been developed.

For example, in Patent Document 1, for the purpose of suppressing gelation by reaction with an acidic functional group in a resin in a conductive paste mainly used in a photolithography method, the surface of a conductive paste coated with a coating film and an oxide film There is disclosed a technique of mixing base metal particles containing copper as conductive particles. Patent Document 1 discloses a polyether ester type surfactant, a hydrogenated castor oil compound, a fatty acid amide wax and the like as a thixotropic property-imparting agent.

However, the conductive paste of Patent Document 1 does not have enough thixotropy to form a rigid conductive pattern by screen printing, and the thixotropic property-imparting agent described in Patent Document 1 has a problem of lowering the conductivity of the paste There was a difficulty in being easy.

Further, for example, Patent Document 2 describes a photosensitive paste composition which is excellent in printing property and developability using a silver oxide particle as a thixotropic property-providing agent and which can obtain a conductive pattern having a low electrical resistance value.

However, the conductive paste of Patent Document 2 does not have enough thixotropy to form a fine conductive pattern by screen printing. As described above, it is not known that copper paste used in the screen printing method can form a fine pattern having a line and space of a conductive pattern of 100 mu m or less, for example.

Japanese Patent No. 4466250 Japanese Laid-Open Patent Publication No. 2010-39396

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a conductive paste containing a copper powder having high reliability as a wiring board as a conductive material, Conductive paste, and a method for preparing such a conductive paste.

The present invention provides the following conductive paste and a method for preparing the conductive paste.

(1) As a conductive paste containing copper particles (A), a resol-type phenol resin (B) and a thixotropic property-imparting agent (C) obtained by activating a fatty acid amide wax,

Wherein the content of the thixotropic property-imparting agent (C) is the solid fatty acid amide wax in an amount of 0.05 to 2% by mass based on the whole conductive paste.

(2) The conductive paste according to (1), wherein the thixotropic property-imparting agent (C) is obtained by swelling the fatty acid amide wax with xylene.

(3) The conductive paste according to (1), wherein the thixotropic property-imparting agent (C) is obtained by swelling the fatty acid amide wax with a mineral terpene.

(4) A process for producing a resin composition, which comprises (a) preparing a first vehicle comprising a resol-type phenol resin (B) and a solvent (D)

(b) adding a thixotropic property-imparting agent (C), which is obtained by activating the fatty acid amide wax, to the first vehicle, stirring and mixing the same to prepare a second vehicle,

(c) adding copper particles (A) to the second vehicle and mixing them.

(5) In the step of preparing the second vehicle, the thixotropic property-imparting agent (C) is added to the solvent (D) of the first vehicle as the solid fatty acid amide wax in the solvent of the first vehicle ( D) at a shear rate of 1 sec ^{< -1 &gt}; of not less than 5 Pa < sec >, the first liquid and the thixotropic property imparting agent (C) is stirred. The method for preparing a conductive paste according to (4)

(6) The method for preparing a conductive paste according to (5), wherein the kneading means is a homogenizer.

According to the conductive paste of the present invention, it is possible to form a conductive pattern having high reliability as a wiring board, high precision, and excellent conductivity by a screen printing method.

Fig. 1 is a diagram showing a pattern shape of a screen plate (L / S = 75 占 퐉 / 75 占 퐉) used in the printability evaluation test in the embodiment.

Hereinafter, embodiments of the present invention will be described in detail.

The conductive paste of the embodiment of the present invention contains the copper particle (A), the resol-type phenol resin (B) and the thixotropic property-imparting agent (C) obtained by previously activating the fatty acid amide wax. The fatty acid amide wax having a solid content of the thixotropic property-imparting agent (C) is 0.05 to 2% by mass relative to the entire conductive paste.

In the present specification, the term " activating treatment " refers to a treatment for enhancing the thixotropic property (hereinafter also referred to as tic) of the fatty acid amide wax. For example, a swelling treatment with a specific treating agent It says.

In the conductive paste of the embodiment of the present invention, since the thixotropic property-imparting agent (C) obtained by activating the fatty acid amide wax is contained as 0.05 to 2 mass% of the entire conductive paste as the fatty acid amide wax, It is possible to form a fine three-dimensional conductive pattern having a suitable good thixotropic property, for example, both lines and spaces of 100 mu m or less by screen printing. In addition, the formed conductive pattern has a low resistivity and good conductivity.

In the present specification, the width of the line and the width of the space in the conductive pattern are expressed by L / S as required. When both the widths of the lines and spaces are 100 占 퐉, L / S is 100 占 퐉 / 100 占 퐉 or L / S = 100 占 퐉 / 100 占 퐉.

In screen printing, the conductive paste is supplied to the upper surface of the screen plate provided on the substrate, and is pressed between the meshes of the screen plate by being pressed by a squeegee or the like. Thereafter, the screen plate is removed, so that the conductive paste pushed in remains on the substrate, and the conductive pattern is printed. In order to improve the printing precision in the screen printing through such a process, the conductive paste is required to have a viscosity characteristic capable of maintaining the shape of the conductive pattern well, and a viscosity property of decreasing the viscosity at the time of printing. Specifically, in a state in which a high shearing stress is applied by a squeegee or the like, the shear stress can be sufficiently transmitted between the meshes, and the shear stress can not be applied to the screen plate, And has a high viscosity such as to separate the mold from the screen plate and to maintain the shape of the printed pattern in the papermaking state.

As a fluid showing such characteristics, for example, a thixotropic fluid or a fluid having a shear rate dependency (hereinafter also referred to as shear thinning property) may be mentioned. The viscosity of the thixotropic fluid is constantly applied with the shear rate constant shear rate, that is, the viscosity is decreased with time. On the other hand, a fluid having a shear thinning property does not show a temporal change in viscosity but shows a change in viscosity with the applied strain rate. That is, the viscosity decreases with the increase of the shear rate, and the viscosity increases reversibly with the decrease of the shear rate. At this time, the shear stress shows an increase in monotonous with increasing shear rate. Shear stress is a product of shear rate and viscosity.

Various compounds and materials have been known as additives for improving the thixotropic property and shear thinning property. The thixotropic property-imparting agent (C) obtained by activating the fatty acid amide wax, which is used in the present invention, ) Has a large effect of improving the thixotropic property and the shear thinning property of the conductive paste containing the copper particles (A) and the resol-type phenol resin (B), and is less likely to lower the conductivity.

Hereinafter, each component constituting the conductive paste of the embodiment of the present invention will be described.

Copper particles (A)

The copper particles (A) become conductive components of the conductive paste. As the copper particles (A), various kinds of copper particles can be used, and they may be metal copper particles, copper fine particles, or composite particles in which metal copper particles and copper fine particles are combined. Examples of the composite particles include those in which copper fine particles are attached or bonded to the surface of the metal copper particles.

The average particle diameter of the copper particles (A) is preferably 0.01 to 20 탆, and can be appropriately adjusted within the above range according to the shape of the copper particles (A). When the average particle diameter of the copper particles (A) is 0.01 m or more, the flowability of the conductive paste containing the copper particles becomes good. When the average particle diameter of the copper particles (A) is 20 m or less, it is easy to produce fine interconnections by the conductive paste containing the copper particles.

When the copper particles (A) contain metallic copper particles, the average particle diameter (average primary particle diameter) is preferably 0.3 to 20 탆. When the copper particles (A) consist only of copper fine particles, the average particle size (average aggregate particle size) of the aggregated particles is preferably 0.01 to 1 占 퐉.

When the average particle size (average primary particle diameter) of the copper particles (A) contains metallic copper particles of 0.3 mu m or more and when the copper particles (A) consist of only copper microparticles, the average particle size Particle diameter) of not less than 0.01 mu m, the flowability of the conductive paste containing the copper particles is improved. When the average particle size (average primary particle size) of the copper particles (A) contains metallic copper particles of 20 탆 or less and when the copper particles (A) consist of only copper microparticles, the average particle size Average aggregate particle diameter) of 1 mu m or less, it is easy to produce fine interconnections by the conductive paste containing the copper particles.

As the copper particles (A), for example, the following copper particles (A1) to (A5) can be preferably used.

(A1) A metallic copper particle having an average primary particle diameter of 0.3 to 20 탆.

(A2) metallic copper particles having an average primary particle size of 0.3 to 20 탆 and copper hydrogenated microparticles adhering to the surface of the metallic copper particles, wherein the average particle size (average size of aggregate particle size) Copper composite particles having hydrogenated copper fine particles of 400 nm.

(A3) Copper hydride fine particles having an average particle size (average aggregate particle size) of the agglomerated particles of 10 nm to 1 μm.

(A4) metal copper particles having an average primary particle diameter of 0.3 to 20 占 퐉 and copper microparticles adhered to the surface of the metallic copper particles, wherein the average particle diameter (average aggregate particle diameter) of the aggregated particles is 20 to 400 Lt; RTI ID = 0.0 > nm. ≪ / RTI >

(A5) Copper fine particles having an average particle size (average aggregate particle size) of the aggregated particles of 10 nm to 1 μm.

The composite metal copper particles (A4) are obtained by converting the copper hydrogenated copper microparticles of the copper composite particles (A2) into metal copper fine particles by a heat treatment. The copper fine particles (A5) Lt; / RTI >

In the present specification, the average particle diameter is obtained as follows.

That is, the average primary particle diameter of the metal copper microparticles is calculated by measuring the Feret diameter of 100 randomly selected particles from an image of a scanning electron microscope (hereinafter referred to as " SEM ") and averaging these particle diameters.

The average particle size (average aggregate particle size) of copper microparticles was calculated by measuring Feret diameters of 100 particles randomly selected from images of a transmission electron microscope (hereinafter referred to as " TEM ") and averaging these particle diameters .

Further, in the case of composite particles containing metal copper particles and copper hydride fine particles adhered to the surface of the metal copper particles, for example, copper composite particles (A2), the whole composite particles are observed by SEM, And the feret diameter of the whole particles containing copper fine particles was also measured and the average particle diameter obtained was averaged.

The above-mentioned copper particles (A) include, for example, " surface-modified copper particles " obtained by reducing a surface of a copper particle.

(Surface-modified copper particles)

The "surface-modified copper particles" in the present invention are obtained by reducing the surfaces of copper particles in a dispersion medium having a pH value of 3 or less. For example, (1) copper particles are dispersed in a dispersion medium to form "copper dispersion" (3) adding the reducing agent to the copper dispersion by the following wet reduction method after (2) adjusting the pH value of the copper dispersion to a predetermined value or less, and (3) following the steps of (1) to (3).

The surface-modified copper particles obtained by the steps (1) to (3) are mainly composed of metallic copper particles, and the average primary particle diameter thereof is preferably 0.3 to 20 탆 (metallic copper particles (A1)).

When the average primary particle diameter of the surface-modified copper particles is 0.3 m or more, the flowability of the conductive paste containing the copper particles is improved. If the average primary particle diameter is 20 m or less, fine wiring can be easily produced by the conductive paste containing the copper particles.

Processes (1) to (3) for producing surface-modified copper particles will be described below.

(1) Preparation of copper dispersion

Copper particles to be dispersed in the copper dispersion may be copper particles generally used as a conductive paste, and the shape of the particles may be spherical or planar.

The average particle diameter of the copper particles to be dispersed in the copper dispersion is preferably 0.3 to 20 탆, more preferably 1 to 10 탆.

If the average particle diameter of the copper particles is less than 0.3 占 퐉, the fluidity of the conductive paste may be lowered. On the other hand, when the average particle diameter of the copper particles exceeds 20 占 퐉, it becomes difficult to prepare the fine wiring in the obtained conductive paste. By setting the average particle diameter of the copper particles to 0.3 to 20 占 퐉, a conductive paste having good flowability and being suitable for the production of fine interconnections can be obtained.

The average particle diameter of the copper particles was obtained by measuring the Feret diameter of 100 metal copper particles randomly selected from SEM images and calculating the average value thereof.

The copper dispersion can be obtained by putting the copper particles in powder form into a dispersion medium. The concentration of the copper particles in the copper dispersion is preferably 0.1 to 50 mass%.

If the concentration of the copper particles is less than 0.1% by mass, the amount of the dispersion medium contained in the copper dispersion becomes excessive, and the production efficiency may not be maintained at a sufficient level. On the other hand, when the concentration of the copper particles exceeds 50 mass%, the influence of agglomeration of the particles becomes excessive, which may reduce the yield of the surface-modified copper particles. By adjusting the concentration of the copper particles in the copper dispersion to the above range, the surface-modified copper particles can be obtained in high yield.

The dispersion medium of the copper particle dispersion is not particularly limited as long as it can disperse the copper particles, but those having a high polarity can be preferably used.

Examples of the high-polarity dispersion medium include water, alcohols such as methanol, ethanol and 2-propanol, glycols such as ethylene glycol, and mixed media obtained by mixing them. .

The copper particles to be dispersed in the dispersion medium may be surface treated with the surface treatment agent to prevent oxidation of the particle surface. As the surface treatment agent, long-chain carboxylic acids such as stearic acid, palmitic acid and myristic acid can be used.

When a long chain carboxylic acid is used as the surface treatment agent, the copper particles may be provided as it is in the reduction treatment. In order to facilitate the reduction reaction described later, the long chain carboxylic acid, which is a surface treatment agent, And then dispersed in the dispersion medium. Removal of the long chain carboxylic acid can be carried out, for example, by a method such as washing with an acid.

From the viewpoint of improving the dispersibility of the copper particles to the dispersion medium, it is preferable to conduct the pre-treatment on the copper particles. By performing the pretreatment, the surface of the particles is made hydrophilic, so that the dispersibility to a high-polarity dispersion medium such as water can be enhanced.

Examples of the pretreatment agent include aliphatic monocarboxylic acids such as aliphatic monocarboxylic acids having 6 or less carbon atoms, aliphatic hydroxymonocarboxylic acids and aliphatic amino acids, and aliphatic polycarboxylic acids (for example, Of aliphatic polycarboxylic acid or aliphatic hydroxycarboxylic acid) can be preferably used. More preferred are aliphatic polycarboxylic acids having 8 or less carbon atoms, and specific examples thereof include glycine, alanine, citric acid, malic acid, maleic acid and malonic acid.

It is preferable to add a dispersant to the copper dispersion thus obtained. As the dispersant, various water-soluble compounds having adsorptivity to copper particles can be used.

Specific examples of the dispersing agent include water-soluble polymeric compounds such as polyvinyl alcohol, polyacrylic acid, polyvinylpyrrolidone, hydroxypropyl cellulose, propyl cellulose and ethyl cellulose, ethylenediaminetetraacetic acid, iminodi2 And chelate compounds such as acetic acid.

The amount of the surface treating agent, the pretreatment agent and the dispersing agent which are carried on the surface of the copper particles after subjected to the respective treatments is preferably from 0.1 to 10% by mass relative to the copper particles.

The treatment of the copper particles with a pretreatment agent or a dispersant is carried out by adding copper particles to a solution obtained by adding a pretreatment agent or the like to a solvent such as water and stirring the solution so that a pretreatment agent or the like is carried on the surface of the copper particles .

From the viewpoint of increasing the processing speed, it is preferable to carry out the pretreatment while heating the solution. The heating temperature is preferably 50 ° C or higher and the boiling point of the solvent (water or the like). When a surface treating agent such as a carboxylic acid or a dispersant is added to a solvent, it is preferable to heat the heating temperature at a temperature not higher than the boiling point of these compounds.

The time for the heat treatment is preferably from 5 minutes to 3 hours. If the heating time is less than 5 minutes, there is a possibility that the effect of increasing the processing speed may not be sufficiently obtained. On the other hand, even if the heat treatment is performed for more than 3 hours, the cost may be excessively increased, which is not preferable from the economical point of view.

When the pretreatment or the like is carried out, it is preferable that the inside of the processing vessel is replaced with an inert gas such as nitrogen gas or argon gas from the viewpoint of preventing oxidation of the surface of the copper particles. After the pretreatment, the solvent is removed, and if necessary, it is washed with water or the like to obtain copper particles to be dispersed in the dispersion.

(2) Adjustment of the pH value of the copper dispersion

The pH value of the copper dispersion obtained in (1) above is adjusted. The pH value can be adjusted by adding a pH adjuster to the copper dispersion. As the pH adjusting agent of the copper dispersion, an acid can be used, and for example, a carboxylic acid such as formic acid, citric acid, maleic acid, malonic acid, acetic acid or propionic acid, or an inorganic acid such as sulfuric acid, nitric acid, have. As the carboxylic acid, the same compound as the carboxylic acid used as the pretreatment agent described above can be used.

Among them, the carboxylic acid is adsorbed on the surface of the copper particles and remains on the surface of the surface-modified copper particles after the reduction treatment to protect the surface of the particles, so that the oxidation reaction of copper can be suppressed. have. Particularly, since formic acid has an aldehyde group (-CHO) having a reducing property, it remains on the surface of the surface-modified copper particle, so that the progress of oxidation of the particle surface can be suppressed. By using the conductive paste containing such copper particles, it is possible to form a conductive film in which an oxide film is not formed well and an increase in volume resistivity is suppressed.

In addition, the pH adjuster is not necessarily limited to acidic components. When the pH value of the dispersion is low, a base may be used as the pH adjuster.

The pH value of the copper dispersion is preferably 3 or less from the viewpoint of smoothly removing the oxide film on the surface of the particles and reducing the surface oxygen concentration of the obtained surface-modified copper particles in the subsequent reduction treatment step.

If the pH value of the dispersion exceeds 3, the effect of removing the oxide film formed on the surface of the copper particles can not be sufficiently obtained, and the oxygen concentration on the surface of the copper particles may not be sufficiently reduced. On the other hand, the pH value of the dispersion is preferably 0.5 or more. If the pH value of the dispersion is less than 0.5, copper ions are excessively eluted and the surface modification of the copper particles may not be smoothly progressed. The pH value of the dispersion is more preferably 0.5 or more and 2 or less. When the pH value of the dispersion is 3 or less, the dispersion may be subjected to reduction treatment as it is.

(3) Reduction treatment of copper dispersion

A reducing agent is added to the copper dispersion whose pH value is adjusted, and reduction treatment is performed.

As the reducing agent to be added to the copper dispersion, at least one selected from metal hydrides, hydride reducing agents, hypophosphites such as hypophosphorous acid and sodium hypophosphite, amine boranes such as dimethylamine borane, and formic acid can be used. Examples of the metal hydride include lithium hydride, potassium hydride, and calcium hydride. Examples of the hydride reducing agent include lithium aluminum hydride, lithium borohydride, and sodium borohydride. Of these, hypophosphorous acid and sodium hypophosphite are preferably used.

In addition, as described above, formic acid is also used as a pH adjusting agent. Therefore, when formic acid is added to the dispersion medium, it acts as a reducing agent and also acts as a pH adjusting agent.

The reducing agent to be added to the copper dispersion is preferably added in excess to the amount of copper atoms on the surface of the particles. Concretely, it is preferable to add a reducing agent in a molar ratio of 1 or more to the total number of moles of the copper particles contained in the dispersion. It is preferable to add a reducing agent in a molar ratio of 1.2 to 10 times the mole number of the total copper atoms of the copper particles .

When the reducing agent is added in an amount exceeding 10 times the total molar amount of copper, the cost is disadvantageously lowered and the production cost may be excessively increased. Further, the amount of the decomposition products from the reducing agent becomes excessive, and the removal thereof may become troublesome.

The reduction reaction is preferably carried out at a temperature of 5 to 60 캜, more preferably 35 to 50 캜. By setting the temperature of the dispersion liquid at 60 占 폚 or less, it is possible to reduce the influence of the concentration change of the entire dispersion liquid when the dispersion medium is removed by evaporation from the copper dispersion liquid.

The reduction of the copper particles can be carried out by adding a reducing agent to the copper dispersion as described above, or by dispersing the copper particles in a dispersion medium containing a reducing agent.

From the viewpoint of smoothly removing the oxide film on the surface of the copper particles, it is preferable that the pH value of the copper dispersion after the addition of the reducing agent is kept at 3 or less from the start of the reaction to the end of the reaction.

The redox potential of the copper dispersion can be appropriately adjusted depending on the amount and kind of the reducing agent to be added. From the viewpoint of facilitating the reduction reaction of the copper ion, the redox potential of the copper dispersion is preferably 100 to 300 mV, more preferably 100 to 220 mV with respect to the potential of the standard hydrogen electrode (SHE).

The redox potential can be obtained as a potential difference from the standard electrode. In the present specification, the redox potential is expressed as a potential difference measured using a standard hydrogen electrode as a standard electrode.

After the decomposition of the reducing agent is almost completed, the surface-modified copper particles are separated from the dispersion, washed with water or the like, if necessary, and dried to obtain the surface-modified copper particles, that is, the copper particles (A).

By performing the surface treatments of (1) to (3) above, copper oxide (Cu ₂ O, CuO) present on the surface of copper particles as a starting material can be reduced to copper atoms, The amount of copper oxide present can be reduced.

Further, since the by-products such as the decomposition product of the reducing agent are usually components soluble in the dispersion medium, they can be separated from these components by filtration or centrifugation.

On the surface of the copper particles after the surface treatments (1) to (3), a part of copper atoms is reduced by a reducing agent to generate copper hydride. Therefore, after the surface-treated copper particles are separated from the dispersion, the copper hydride may be changed to copper by heat treatment at 40 to 120 ° C.

As the copper particles (A) of the present invention, "composite metal copper particles" in which metal copper fine particles are adhered to at least a part of the surface of the metal copper particles may be used in addition to the "surface-modified copper particles" thus produced.

≪ Resoluble phenol resin (B) >

As the resol-type phenol resin (B) contained in the conductive paste of the embodiment of the present invention, a known resol-type phenol resin used as a resin binder for ordinary conductive paste can be used.

Specific examples of the resol-type phenol resin (B) include modified resol-type phenol resins prepared by adding various modifiers to unmodified resol-type phenol resins, phenols and aldehydes produced from phenols and aldehydes .

Examples of the phenol or its derivatives (phenols) include phenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol, hydroquinone, xylenol, pyrogallol, bisphenol A, bisphenol F, p-tert-butylphenol, p-tert-octylphenol,? -naphthol,? -naphthol, and the like.

Examples of the aldehydes include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, furfural, glyoxal, n-butylaldehyde, caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde , Acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like, and these may be used alone or in combination of two or more.

When a resol-type phenol resin having self-hardness is used, an acid or a curing agent may be added to the resol-type phenol resin, and a novolak-type phenol resin may be added in order to lower the degree of curing. They may be added in combination.

Commercially available resol-type phenolic resins (B) may also be used. For example, a powdery phenolic resin (trade name: RegisTop, PGA-4528, PGA-2473, PGA-4704, PGA-4504, manufactured by Sumitomo Bakelite, trade name: SUMILITE RESIN PR-UFC-504 , PR-EPN, PR-ACS-100, PR-ACS-150, PR-12687, PR-13355, PR-16382, PR-217, PR-310, PR-311, PR- -50102, PR-50252, PR-50395, PR-50590, PR-50590B, PR-50699, PR-50869, PR-51316, PR-51326B, PR-51350B, PR-51510, , PR-51820, PR-51939, PR-53153, PR-53364, PR-53497, PR-53724, PR-53769, PR-53804, PR-54364, PR-54458A, PR-54545, PR- (Trade name: SUMILITE RESIN PR-12686R, PR-13349, PR-50235A, PR-51363F, PR-FTZ-15) manufactured by Sumitomo Bakelite Co., PR-F-151G, PR-51618G, PR-53194, PR-53195, PR-54869, PR-F-110, PR- HF-6), liquid phenolic resin (Sumitomo Bakelite, trade name: SUMILITE RESIN PR-50087, PR-50607B, PR-50 PR-54135, PR-54313, PR-54562, PR-54038, PR-51138C, PR-51206, PR-51663, PR-51947A, PR-53123, PR- PL-4690, PL-3630, PL-3630), a resol type liquid phenolic resin (trade name: Regent PL-4826, PL- PR-51301, PR-53056, PR-53311, PR-53056, PR- R800, R600, R200, R100, S830, S870, S890, S895, S290, S190) manufactured by Air Water Co., Ltd., Jean- FM-010, FM-150, HF-008, HF-015, HF-075, HF-300, HF-500 and HF-1500) manufactured by Nippon Kayaku Co., Phenol resin (PS-2607, PS-2655, PS-2768, PS-2608, PS-4609, PSM-2222, PSK- .

The resolubilized phenol resin (B) used in the present invention is not particularly limited in its molecular weight, but from the viewpoint of solution viscosity upon solution, the mass average molecular weight is preferably 200 to 10000, more preferably 300 to 3000 Do. As the resol-type phenol resin (B), one type may be used alone, or two or more types may be used in combination.

The content of the resol-type phenol resin (B) in the conductive paste can be appropriately selected in accordance with the ratio of the volume of the voids existing between the volume of the copper particles (A) and the copper particles. Is preferably 5 to 50 mass%, more preferably 5 to 20 mass%, based on 100 mass% of the copper particles (A). When the content of the resol-type phenol resin (B) is 5 mass% or more, sufficient flow characteristics can be obtained as a conductive paste. On the other hand, when the content of the resol-type phenol resin (B) is 50 mass% or less, contact between the copper particles is hardly interrupted by the resin component after curing, and there is no fear of increasing the volume resistivity of the conductive film obtained from the conductive paste .

<Thixotropic property-imparting agent (C)>

The thixotropic property-imparting agent (C) contained in the conductive paste of the present invention is obtained by subjecting the fatty acid amide wax to an activation treatment for enhancing the thixotropic property-imparting function.

The fatty acid amide wax is a compound which has a long chain fatty acid group and an amide group in the molecule and has a surfactant action and is thermally and chemically stable and is solid at room temperature. Having both groups of a lipophilic long chain fatty acid group and a hydrophilic amide group in the molecule, thereby giving a thixotropic property to the resin composition. In addition, the fatty acid amide wax has an advantage that when it is added to the conductive paste, the ratio of raising the electrical resistance is small.

The molecular structure, molecular weight and the like of the fatty acid amide wax used in the present invention are not particularly limited, but it is preferable that the fatty acid amide wax has a melting point of 110 to 130 ° C. Preferable examples of the fatty acid amide wax include condensation reaction products of a hydrogenated castor oil fatty acid and a primary diamine represented by the following chemical formula.

[Chemical Formula 1]

The activation treatment of the fatty acid amide wax is not particularly limited as long as it is a treatment for enhancing the function of imparting the tack plasticity of the fatty acid amide wax, but from the viewpoint of the effect, the swelling (pre-swelling) treatment with a specific treatment agent is preferable. For example, in the swelling treatment of the condensation reaction product of the hydrogenated castor oil fatty acid and the primary diamine represented by the above formula, xylene or the like can be used for the swelling treatment of the condensation reaction product of the fatty acid amide wax and the primary diamine, Mineral terpenes are preferred. Here, the mineral terpene is one kind of a petroleum solvent which is also called mineral spirit. In addition, alcohol may be used together with xylene or mineral terpene for the swelling treatment of the fatty acid amide wax.

Examples of commercially available products of the thixotropic property imparting agent (C) that has been swollen with fatty acid amide wax by a solvent include Disperon 6900-20X, Disperon 6850-20X, and Disperon A670-30M (all trade names of Kusumoto Chemical Co., Ltd.) . Disperon 6900-20X and Disperon 6850-20X were prepared by dissolving the fatty acid amide wax represented by the above formula in a thixotropic property-imparting agent on a pre-swelling paste by a mixed solvent of xylene and ethanol and methanol, and Disperon A670-30M , And a fatty acid amide wax represented by the above formula is pre-swollen by a mixed solvent of mineral terpene and benzyl alcohol. Any thixotropic property imparting system and a vehicle containing the resol-type phenol resin (B) can impart good thixotropy to the vehicle. In addition, the swelling structure was very strong, and the heat resistance and the time-course stability were excellent.

The content (concentration) of the fatty acid amide wax in the thixotropic property-imparting agent (C) obtained by subjecting the fatty acid amide wax to swelling with a solvent is not particularly limited, but the efficiency of activation of the fatty acid amide wax by swelling treatment And from the viewpoint of ease of use, it is preferably in the range of 2 to 50 mass%.

The content of the thixotropic property-imparting agent (C) is such that the amount of fatty acid amide wax which is a solid content in the thixotropic property-imparting agent (C) accounts for 0.05 to 2% by mass of the entire conductive paste, % By mass is preferable. When the content of the thixotropic property-imparting agent (C) is 0.05% by mass or more as the total amount of the conductive paste as the fatty acid amide wax, the conductive paste has sufficient thixotropic properties and has a high fineness with an L / S of 100 m / The pattern can be formed by screen printing. On the other hand, when the amount of the fatty acid amide wax is 2% by mass or less of the entire conductive paste, the resistivity of the conductive paste is hardly increased, and a conductive pattern with good conductivity can be obtained.

&Lt; Other components >

The conductive paste of the present invention may further contain other components such as a solvent and various additives (leveling agent, coupling agent, viscosity adjuster, antioxidant, adhesion agent, etc.) in addition to the components (A) But may be contained in a range that does not impair the effects of the present invention. Particularly, in order to obtain a paste having suitable fluidity, it is preferable to contain a solvent. As such a solvent, it is preferable to include a solvent (D) capable of dissolving the resol-type phenol resin (B).

Examples of the solvent (D) capable of dissolving the resol-type phenol resin (B) include butyl acetate, 3-methoxybutyl acetate, 1-butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether , Methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone, cyclohexanol, ethylene glycol, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl Diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, terpineol, diethylene glycol, and the like can be given. One of these may be used alone, or two or more of them may be used in combination.

From the viewpoint of solubility of the solution and difficulty in drying the paste, it is preferable to use a solvent such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene Glycol monoethyl ether acetate and the like are preferable.

The solvent (D) capable of dissolving the resol-type phenol resin (B) is preferably 10 to 1000 mass%, more preferably 20 to 200 mass%, based on 100 mass% of the resol-type phenol resin (B). In the conductive paste of the embodiment of the present invention, by setting the content ratio of the solvent (D) to the resol-type phenol resin (B) within the above range, workability in screen printing is good, It becomes possible to form a pattern.

The total amount of the solvent contained in the conductive paste is preferably in the range of 1 to 10 mass% with respect to the copper particles (A) from the viewpoint of setting the viscosity range suitable for a printing paste body. This solvent also includes a solvent (D) capable of dissolving the resol-type phenol resin (B) and a solvent for swelling the fatty acid amide wax contained in the thixotropic property-imparting agent (C).

The conductive paste of the embodiment of the present invention can be obtained by mixing each of the components (A) to (C) and other components such as the solvent, for example, as shown below. That is, the method for preparing a conductive paste of the present invention comprises the steps of: (a) preparing a first vehicle comprising a resol-type phenol resin (B) and a solvent (D); (b) adding to the first vehicle a fatty acid amide wax (C) a step of adding and mixing copper particles (A) to the second vehicle, and (c) a step of mixing and adding the copper particles (A) to the second vehicle. Respectively. Each step will be described below.

< (a) Step of preparing first vehicle >

A first vehicle is prepared by dissolving the resol-type phenol resin (B) in the solvent (D) capable of dissolving the resin. The content of the solvent (D) in the first vehicle is preferably 10 to 1000% by mass, more preferably 20 to 200% by mass, based on 100% by mass of the resol-type phenol resin (B) desirable. In the conductive paste of the embodiment of the present invention, by setting the content ratio of the solvent (D) to the resol-type phenol resin (B) within the above range, workability in screen printing becomes good, It becomes possible to form a pattern.

It is preferable that the viscosity of the first vehicle at 25 캜 (hereinafter referred to as the viscosity (25 캜)) is 5 Pa · sec or less. By setting the viscosity (25 캜) of the first vehicle to 5 Pa · sec or less, a conductive paste having good thixotropy suitable for screen printing can be obtained.

< (b) Step of preparing second vehicle >

A thixotropic property-imparting agent (C) obtained by activating a fatty acid amide wax (for example, swelling treatment with a specific solvent) is added to the first vehicle obtained in the step (a). Then, the mixture is stirred, and the fatty acid amide wax is uniformly dispersed in the first vehicle to obtain the second vehicle.

The means for agitating the mixture is not particularly limited so long as it is a means capable of applying a high shear stress to the mixture and uniformly dispersing the fatty acid amide wax in the first vehicle. For example, various stirring and mixing means such as a homogenizer, a stirrer and a disper with a cowless blade (crows dispenser) can be used.

As described above, in the step of preparing the second vehicle, the stirring means of the mixture is not particularly limited, but the size of the thixotropic property imparted by the thixotropic property-imparting agent (C) varies depending on the stirring strength. The viscosity at the conditions can be measured and the magnitude of the influence of the stirring means on the tie plasticity can be evaluated using the measured viscosity (hereinafter, sometimes referred to as standard viscosity) as an index.

That is, first, a thixotropic property-imparting agent (C) is added to the same solvent (for example, ethylcarbitol) as the solvent (D) contained in the first vehicle, and the solvent (D) of fatty acid amide wax To 1% by mass, to prepare a standard solution. Then, the buffer solution a shear rate of 1 sec ^- a (standard viscosity) viscosity when stirred with a ^1, and measured for the various types of agitation means. In the present invention, it is preferable that the mixture of the first vehicle and the thixotropic property-imparting agent (C) is stirred and kneaded by using the stirring means having a standard viscosity measured in this way of 5 Pa · sec or more.

In the case of stirring and kneading using the means that the standard viscosity is equal to or higher than 5 Pa · sec, compared with the case where the standard viscosity is less than 5 Pa · sec, a better thixotropy suitable for screen printing Is obtained. As a stirring / kneading means having a standard viscosity of 5 Pa · sec or more, for example, a roll mill, a bead mill, a rotary kneader, an emulsification / dispersion testing apparatus, a three- , A rotation / revolution mixer, a homogenizer, and an ultrasonic emulsifier.

Here, the homogenizer includes various types, such as a disk rotating type, an ultrasonic wave applying method, and a method in which a blade of a special shape rotates at a high speed. Particularly, as a method of rotating the blades of a special shape at a high speed, there is an apparatus for performing a series of homogenization of high-speed dispersion to microstructure to homogenization based on the principle of Willems. There is known a homogenizer which has a high speed dispersion, a fine chain, and a homogenization effect. A common homogenizer has a rotating, sliding, and oscillating part, and a faster homogenizer is called a high-speed homogenizer.

< (c) Addition and mixing process of copper particles >

Copper particles (A) are added to the second vehicle obtained in the step (b) and mixed. The mixing means is not particularly limited, and a known stirring / mixing apparatus can be used.

In the method for preparing a conductive paste according to the embodiment of the present invention, when mixing the respective components (A) to (D), it is preferable that the temperature is set at such a temperature as not to cause curing of the resol- , While heating. The temperature at the time of mixing and stirring is preferably 10 to 40 占 폚. More preferably 20 to 30 占 폚. Particularly, in the step (c) of adding and mixing the copper particles, the viscosity of the conductive paste can be sufficiently lowered by setting the temperature to 10 ° C or higher, and the stirring can be sufficiently carried out smoothly. In addition, the copper hydride produced on the surface of the copper particles (A) can be a copper atom. On the other hand, if the temperature in the step (c) of adding and mixing the copper particles exceeds 120 캜, the curing of the resol-type phenol resin (B) in the paste may occur or fusion bonding of the copper particles (A) .

In addition, in the step (c) of adding and mixing the copper particles, it is preferable to mix them in a container substituted with an inert gas in order to prevent the copper particles (A) from being oxidized.

According to the preparation method described above, a conductive paste having good thixotropic property suitable for screen printing and excellent in conductivity can be obtained.

A conductive film such as a conductive pattern (wiring pattern) is formed on a substrate using the conductive paste of the present invention to obtain a substrate having a conductive film such as a printed wiring board. The substrate on which the conductive film is formed can be obtained by applying the conductive paste of the embodiment of the present invention to the surface of the substrate by a printing method such as screen printing to form a conductive paste film and then heating to remove volatile components such as a solvent in the conductive paste film Can be produced by curing a resol-type phenol resin.

As the substrate, a glass substrate, a polyester such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), a plastic substrate such as polycarbonate or polyimide, a glass fiber reinforced resin substrate, a ceramics substrate or the like can be used.

The conductive paste of the embodiment of the present invention is excellent in thixotropy and can be sufficiently pushed between meshes under high shear stress at the time of printing but has a viscosity low enough not to turn into the inside of the screen plate, The leveling property of the film is high, and the mold separability is good. Therefore, by screen printing the conductive paste of the present invention on the base material, it is possible to obtain a smooth wiring shape in which the generation of irregularities on the surface and the side is suppressed, particularly, the fine wiring pattern with L / S of 100 m / It is possible to efficiently form the film.

The heating temperature of the conductive paste film formed by the printing method such as screen printing is preferably 100 to 180 캜. If the heating temperature is less than 100 ° C, it is difficult to sufficiently cure the resol-type phenol resin. On the other hand, if the heating temperature exceeds 180 ° C, for example, when a base material such as a plastic film is used, there is a possibility that the base material is deformed. Examples of the heating method include hot air heating, thermal radiation, IR heating, and the like. The heating may be carried out in air or in a nitrogen atmosphere with a small amount of oxygen.

The thickness of the conductive film such as a wiring pattern formed on the substrate is preferably 1 to 200 占 퐉, more preferably 5 to 100 占 퐉, from the viewpoint of ensuring stable conductivity and facilitating the maintenance of the wiring shape. The conductive film volume resistivity is preferably not more than 1.0 × 10 ^-4 Ω㎝. If the volume resistivity of the conductive film exceeds 1.0 x 10 &lt; ^-4 &gt; [Omega] cm, there is a fear that sufficient electrical conductivity can not be obtained as a conductor for electronic devices.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples. Examples 1 to 7 are examples of the present invention, and Examples 8 to 11 are comparative examples.

(Example 1)

[Preparation of copper particles (surface-modified copper particles) (A)] [

As shown below, the copper particles were subjected to a reduction treatment to obtain copper particles (surface-modified copper particles) (A). First, 3.0 g of formic acid and 9.0 g of a 50 mass% aqueous solution of hypophosphorous acid were added to a glass beaker, and the beaker was placed in a water bath and kept at 40 캜.

Subsequently, 5.0 g of copper particles (trade name: 1400 YP, manufactured by Mitsui Mining and Mining Co., Ltd., average primary particle size: 7 mu m) was gradually added to the beaker and stirred for 30 minutes to obtain a copper dispersion. The resulting copper dispersion was centrifuged at a rotation number of 3000 rpm for 10 minutes using a centrifugal separator, and the precipitate was recovered. The precipitate was dispersed with 30 g of distilled water, and the agglomerates were again precipitated by centrifugation, and the precipitates were separated. The resulting precipitate was heated at 80 DEG C for 60 minutes under a reduced pressure of -35 DEG C, and the residual moisture was removed by volatilization to obtain copper particles (A) having modified particle surfaces.

[Preparation of phenol resin solution (first vehicle)] [

50 g of ethyl carbitol was added to 100 g of a resol type phenol resin (trade name: REGITT PL2211, methanol solution, resin solid content: about 50% by mass, manufactured by Guyi Ain Kagaku Co., Ltd.), and the autoclave was degassed under reduced pressure while being maintained at 30 캜. Thus, methanol was removed to prepare an ethylcarbitol solution of the resol-type phenol resin. Subsequently, a part of the obtained resin solution was taken out and evaporated to dryness at 200 DEG C to measure the resin solid content concentration. Based on these measured values, an ethyl carbitol solution (first vehicle) having a solids concentration of 50% by mass of the resol-type phenol resin was prepared.

[Addition of thixotropic property-imparting agent (C) and stirring / mixing)

To the first vehicle obtained above, 4.2 g of a pre-swollen product (product name: Disperon 6900-20X, solid content 20% by mass, manufactured by Kusumoto Chemical Co., Ltd.) in which fatty acid amide wax was swollen with xylene (for ethanol and methanol) And the mixture was kneaded for 1 minute at a rotational speed of 1000 to 1300 rpm using a homogenizer (manufactured by KINEMATICA, a device name: Polytron PT10 / 35 GT Benchtop Homogenizer, PTA10S shaft). Thus, the fatty acid amide wax was dispersed in the first vehicle to obtain the second vehicle.

[Preparation of conductive paste]

Then, 317 g of the copper particles (A) was added to 104.2 g of the second vehicle, and the mixture was stirred at 2000 rpm for 1 minute using a rotary mixer (manufactured by Singkis Co., Ltd., apparatus: ARE- Kneaded, and defoaming operation was performed at 2200 rpm for 0.5 minute to obtain conductive paste (1). The content ratio of the fatty acid amide wax (solid content) in the conductive paste 1 was 0.2 mass%.

(Example 2)

Disperson 6900-20X, which is a pre-swollen product of xylene of fatty acid amide wax, was added to the entire conductive paste so that the content of fatty acid amide wax was 0.8% by mass. A conductive paste 2 was obtained in the same manner as in Example 1 except for the above.

(Example 3)

In the preparation of the second vehicle, a mixture obtained by adding Disperon 6900-20X to the ethyl carbitol solution of the resol-type phenol resin was prepared by using a stirrer (manufactured by Yamato Scientific Co., Ltd., apparatus name: MG600H) in place of the homogenizer, And the mixture was stirred at a rotation speed of 100 rpm for 10 minutes. A conductive paste 3 was obtained in the same manner as in Example 1 except for the above.

(Examples 4 to 6)

Disperone 6900-20X, which is a pre-swelling product of fatty acid amide wax by xylene, was 0.4% by mass in Example 4, 0.8% by mass in Example 5, and 6% by mass in Example 6 as the content ratio of the solid fatty acid amide wax to the entire conductive paste 1.0% by mass, respectively. Other than that, conductive pastes 4 to 6 were obtained in the same manner as in Example 3.

(Example 7)

(Disperson A670-30M, solid content 30% by mass, manufactured by Kusumoto Chemical Co., Ltd.) swollen with a fatty acid amide wax with a mineral terpene (for benzyl alcohol combination) instead of Disperon 6900-20X, The content of the solid fatty acid amide wax in the paste was 1.0% by mass. A conductive paste 7 was obtained in the same manner as in Example 3 except for the above.

(Example 8)

Only the stirrer was performed without adding the fatty acid amide wax to the first vehicle. A conductive paste 8 was obtained in the same manner as in Example 3 except for the above.

(Example 9)

The fatty acid amide wax was used without any swelling treatment. Then, the fatty acid amide wax was added so as to have a content ratio of 0.2 mass% with respect to the entire conductive paste. A conductive paste 9 was obtained in the same manner as in Example 3 except for the above.

(Example 10)

(Disperon PFA131, solid content 10% by mass, manufactured by Kusumoto Chemical Co., Ltd.) in which fatty acid amide wax was swollen with alkylcyclohexane was used in place of Disperon 6900-20X, So that the content of the fatty acid amide wax was 1.0% by mass. A conductive paste 10 was obtained in the same manner as in Example 3 except for the above.

(Example 11)

(PF911, solid content 10% by mass), which is a known thixotropic property-imparting agent (manufactured by Kusumoto Chemical Co., Ltd., trade name, solid content 10% by mass), was used in place of Disperon 6900-20X in a content ratio of 1.0% by mass of polyethylene oxide . A conductive paste 11 was obtained in the same manner as in Example 3 except for the above.

Next, for the conductive pastes 1 to 11 obtained in Examples 1 to 11, the following printing evaluation test was carried out. The conductive paste (1 to 11) was applied on a glass substrate by a screen printing method, and the volume resistivity of the conductive film obtained by heating and curing the coating film was measured. These results are shown in Table 1 together with the content ratio of the fatty acid amide wax, means for stirring the vehicle, and the like.

<Printability Evaluation Test>

A screen plate (manufactured by Tokyo Process Co., Ltd.) having a pattern of L / S of 75 占 퐉 / 75 占 퐉 shown in Fig. 1 was mounted on a screen printing machine (manufactured by Microtex Co., Ltd., MT-750). Using this screen printer, the conductive paste obtained in Examples 1 to 11 was screen-printed on a glass substrate having a thickness of 1.1 mm. A wiring pattern was printed and formed with a squeegee angle of 70 degrees, a squeegee pressure of 0.25 MPa, a squeegee speed of 50 mm / min, and a clearance of 2.5 mm between the screen plate and the glass substrate.

Subsequently, the glass substrate on which the wiring pattern was printed was placed in an oven of a warm-air circulation type which was temperature-controlled at 150 DEG C, and heated for 30 minutes to cure the resol-type phenol resin and take out the resin. The wiring pattern thus obtained was observed using a laser microscope, and the line width of the wiring portion was measured at arbitrary ten points to obtain an average value. The ratio of the average value of the line width to the design value of 75 mu m as the screen plate was evaluated as the thickness ratio.

&Lt; Volume resistivity of conductor film &

Masking was carried out so that a rectangular pattern having a length of 40 mm and a width of 2 mm could be formed on a soda lime glass plate of 5 cm in length and 5 cm in thickness and using a general cellophane tape. Thereafter, the above-mentioned conductive paste (1 to 11) was applied on a glass plate, and the amount of coating was adjusted using a metal blade in accordance with the thickness of the masking tape, followed by drying at 150 DEG C for 30 minutes. The effective resistance value was measured at two points 30 mm apart in the longitudinal direction of the printed matter by using a resistance value meter (manufactured by Kaseya Co., Ltd., Millimoht Testers). In addition, the cross-sectional shape of the wiring near the center between two points separated by 30 mm was measured using a surface roughness and contour shape measuring instrument (manufactured by TOKYO CORPORATION, name: Surfcom 130A). Based on these values, the volume resistivity of the printed pattern was determined.

Examples 1 to 7 (in which the thixotropic property-imparting agent (C) obtained by swelling the fatty acid amide wax with xylene or mineral terpene is contained in the proportion of 0.05 to 2% by mass of the whole conductive paste as the fatty acid amide wax component According to the conductive paste of the embodiment of the present invention, the thickness ratio of the wiring pattern is 75% or less, and a conductive pattern with high precision can be formed by the screen printing method. Further, according to the conductive pastes of Examples 1 to 7, it is possible to form a wiring pattern having a good volume conductivity with a volume resistivity of 30 to 45 mu OMEGA cm.

On the contrary, in Example 8 in which fatty acid amide wax was not added and Example 9 in which fatty acid amide wax was used without swelling treatment, it was found that the thickness ratio of the wiring pattern was high, which is not practical. Further, in Example 10 in which a pre-swollen material obtained by swelling the fatty acid amide wax with alkylcyclohexane was blended and Example 11 in which polyethylene oxide which is a known thixotropic property-imparting agent was blended, a wiring pattern having sufficient conductivity was not obtained .

(Examples 12 to 15)

Next, with respect to various means for agitating the mixture in which the thixotropic property-imparting agent (C) is added to the first vehicle, the effect of agitation means on the tie-plasticity imparting by the thixotropic property-imparting agent (C) The standard viscosity was evaluated using the index.

First, in Examples 1 to 7 described above, 5 g of Disperon 6900-20X used as a thixotropic property-imparting agent (C) was added to 100 g of ethylcarbitol used as a solvent in the first vehicle, By weight of the fatty acid amide wax to ethyl carbitol was 1% by weight. Then, a standard solution of, for example, 12 in a homogenizer (1): using (KINEMATICA Corp., device name Polytron Homogenizer PT 10/35 GT Benchtop, PTA10S shaft), a shear rate of 1 sec ^- viscosity when stirred in ¹ (Standard viscosity) was measured. A homogenizer 2 (manufactured by NISSEI Corporation, device name: AM-7) was used in Example 13, a stirrer (MG-600H manufactured by Yamato Scientific Co., Ltd.) was used in Example 14, and a kaures disper Eiko positive article manufacture, device name: use the VMA disper mats), respectively, shear rate 1 sec ^- measured standard viscosity when stirred with ¹ each.

Measurement of the viscosity using a cone plate-type measurement jig, rheometer: a shear rate 1 sec in the standard solution by (Anton-Paar Co., Ltd., device name MCR301) ^- to measure the viscosity of a steady flow in the ^first. The measurement results are shown in Table 2.

From Table 2, it can be seen that in Examples 12 and 13 in which the stirring means is a homogenizer, the standard viscosity is 5 Pa · sec or more, whereas in Examples 14 and 15 in which the stirring means is a stirrer or a dispenser, Is less than 5 Pa · sec.

By comparing the results of the printability evaluation tests in Examples 1 and 3 and Examples 2 and 5 in which the content ratio of the fatty acid amide wax was the same and only the means for agitating the vehicle was different, the thixotropic property- From the viewpoint of realizing the effect of imparting the tie plasticity by the step (C), the stirring means having a standard viscosity of 5 Pa · sec or more is superior.

That is, in Examples 1 and 3, the content ratio of the fatty acid amide wax to the entire conductive paste is 0.2% by mass, and only the stirring means for the vehicle differs from the homogenizer and the stirrer. The thickness ratio of the wiring pattern is 69% in Example 1, whereas 75% in Example 3, and the printability of Example 1 using the homogenizer is greatly increased. Evaluation of printability in Examples 2 and 5 in which the content ratio of the fatty acid amide wax was the same as 0.8 mass% and only the stirring means of the vehicle differs between the homogenizer and the stirrer, and the thickness of the wiring pattern of Example 2 The ratio of Example 5 was 64%, while the printability of Example 2 using homogenizer was greatly increased. Thus, as means for agitating the mixture of the first vehicle and the thixotropic property-imparting agent (C), by using a means such as a homogenizer having a standard viscosity of 5 Pa · sec or more, a better thixotropic property Paste can be obtained.

While the invention has been described in detail and with reference to specific embodiments thereof, it is evident to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

This application is based on Japanese Patent Application No. 2011-255005 filed on November 22, 2011, the content of which is incorporated herein by reference.

Claims (6)

As a conductive paste containing a copper particle (A), a resol-type phenol resin (B) and a thixotropic property-imparting agent (C) obtained by activating a fatty acid amide wax,
Wherein the content of the thixotropic property-imparting agent (C) is the solid fatty acid amide wax in an amount of 0.05 to 2% by mass based on the whole conductive paste. The method according to claim 1,
Wherein the thixotropic property-imparting agent (C) is obtained by swelling the fatty acid amide wax with xylene. The method according to claim 1,
Wherein the thixotropic property-imparting agent (C) is obtained by swelling the fatty acid amide wax with a mineral terpene. (a) a step of preparing a first vehicle comprising a resol-type phenol resin (B) and a solvent (D)
(b) adding a thixotropic property-imparting agent (C), which is obtained by activating the fatty acid amide wax, to the first vehicle, stirring and mixing the same to prepare a second vehicle,
(c) adding copper particles (A) to the second vehicle and mixing them. 5. The method of claim 4,
(C) is added to the solvent (D) of the first vehicle as the solid fatty acid amide wax in the solvent of the first vehicle (D), and the thixotropic property- (C) at a shear rate of 1 sec ^{&lt; -1 &gt;} at a shear rate of 5 Pa · sec or higher is used as a standard solution, which is prepared by adding the first vehicle and the thixotropic property imparting agent (C) Is mixed with the conductive paste. 6. The method of claim 5,
Wherein the kneading means is a homogenizer.

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