TWI494389B - Electrically conductive paste and metal thin film - Google Patents

Description

Conductive paste and metal film

The present invention relates to a conductive paste which uses a specific polyester resin as a resin adhesive, a method for producing a metal thin film laminate using the same, a metal thin film, and an application thereof.

A technique of forming a conductive circuit by using a screen printing or a dispenser to draw a circuit by using a conductive paste in which conductive fine particles such as metal fine particles are dispersed in a medium is widely used. The conductive fine particles used herein generally have a sheet having a particle number of several μm or more, and the thickness of the circuit is made 10 μm or more to ensure conductivity. In recent years, conductive circuits have rapidly increased in density. The development of finer metal particles is carried out in order to form a denser circuit.

The method for producing fine particles is classified into a solid phase method, a gas phase method, and a liquid phase method depending on the phase to be formed. In the process of pulverization by the solid phase method, the particle size is about 0.1 μm. In the production of particles in which the particle diameter of the nano particles is several tens nm or less, a gas phase method and a liquid phase method which are suitable for the buildup process are suitable. Examples of the gas phase method include a physical condensation method by cooling of high-temperature steam and a particle formation method by gas phase chemical reaction.

On the other hand, the liquid phase method has the following advantages: the structural components of the particles are not only suitable for a single case, but also can be adapted to a multi-component system; the process can be diversified, the control of the particle size is easy, and the surface modification of the particles can be simplified. Various methods have been explored. In the liquid phase method, a coprecipitation method, a sol-gel method, a gel-sol method, an inverse microcell method, a hot soap method, a spray pyrolysis method, and the like have been proposed. The metal fine particles are also synthesized in a gel state by a method of reducing a metal salt in a solution in the presence of a protective polymer. For example, in Patent Document 1, a metal fine particle dispersion containing a linear aliphatic polyether has been described. Further, in Patent Document 2, a metal ultrafine particle dispersion which is stabilized by a polymer having a pyrrolidone group has been described.

Conventionally, by reducing the particle size of the metal particles, the firing temperature between the metal particles can be greatly reduced. For example, Patent Document 3 describes a method of forming a metal thin film by using a dispersion of metal fine particles having a particle diameter of 100 nm or less. Circuits or wiring can be formed by this method. However, the particles represented by the nanoparticles are extremely large in surface area and are extremely easy to aggregate. Therefore, the adhesive resin or the dispersant is required to prevent the aggregation of the fine particles by the adsorption of the metal fine particles, and to ensure the fluidity of the dispersion to stabilize the dispersion. In order to stabilize the dispersion, the finer the metal particles are, the more a large amount of the adhesive resin or dispersant will become necessary. Therefore, even if a dispersion composed of metal fine particles which can be fired at a low temperature is used, the adhesive resin or the dispersant will impede the improvement in conductivity. It is necessary to remove the adhesive resin or the dispersant by sublimation or decomposition evaporation. Further, it is also likely to deteriorate the adhesion to a substrate such as a film or glass due to firing.

After experiencing the firing step, and in order to find the adhesion of the metal thin film layer to the substrate, it is considered advantageous to use a dispersion containing a non-volatile resin adhesive, and conversely, after the resin adhesive is subjected to the firing step, The tendency to remain in the coating film and hinder the connection between the metal particles is also strong, and it is practically not easy to obtain a metal film layer having a low volume resistivity. For this reason, Patent Document 4, Patent Document 5, and the like which are used as a metal thin film which can obtain high conductivity are used in the dispersion of the metal nanoparticles. In Patent Document 4, although an unspecified resin can be used, in the examples, it has been shown that the effective one is only a specific one of the cresol type phenol resins. In Patent Document 5, a polyester resin having a branch unit and a hydroxyl group in a molecule has been described. However, in the adhesion to a substrate and the volume resistivity, sufficient performance has not been achieved so far.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-9120

Patent Document 2: Japanese Patent Laid-Open No. Hei 5-224006

Patent Document 3: Japanese Patent No. 2561537

Patent Document 4: Japanese Patent No. 4155821

Patent Document 5: Japanese Laid-Open Patent Publication No. 2009-62523

A technique of forming a conductive film by using a conductive paste or a conductive ink to form a metal thin film layered body is widely used. One of the means for achieving high density of the conductive circuit is to reduce the circuit width or the circuit thickness. In order to achieve such a change while ensuring electrical conductivity, the metal filler used is also accelerated to atomize. On the other hand, in order to ensure workability in forming a conductive circuit, it is necessary to prevent aggregation of the metal fine particle dispersion and maintain an appropriate viscosity. However, in order to stabilize the dispersed metal fine particles, it is effective to adsorb the organic substance on the surface of the metal fine particles. However, the adsorbed organic matter is reduced in electrical conductivity after film formation. In general, the stability of the dispersion is opposite to that of the film after film formation.

The problem of the present invention is to provide a conductive paste capable of imparting a dispersion stability of a conductive paste to a low volume resistivity (high conductivity, low resistance) of a metal thin film layer of a metal thin film laminate formed using the conductive paste. ) and the high adhesion to the substrate coexist. Further, the term "metal film" as used in the present invention does not mean a film composed only of a metal, but also a metal and other substances such as a branched polyester (B), an organic solvent (C), and a hardener (for example). D), a dispersant (E) and a film of a mixture of one or more selected from the mutual reaction products.

The present inventors have conducted research in order to solve the above problems, and have completed the present invention. That is, the contents of the present invention are as follows:

(1) A conductive paste comprising a conductive paste of metal fine particles (A), a branched polyester (B) and an organic solvent (C), wherein the metal fine particles (A) have an average particle diameter of 1 × 10 ^-3 μm or more and 5 × 10 ^-1 μm or less, the branched polyester (B) has a branching point derived from a trifunctional or higher polycarboxylic acid compound and/or a trifunctional or higher polyhydric alcohol compound. The branched polyester (B) has an acid value of 30 equivalents/10 ⁶ g or more and 200 equivalents/10 ⁶ g or less, and the branched polyester (B) contains an isophthalic acid residue and an phthalic acid. And at least one of a formate residue and a cyclohexanedicarboxylic acid residue, and at least a carbon atom having a carbon number of 1 to 4 substituted with a carbon atom of a linear alkanediol having 3 to 5 carbon atoms; When a compound of one hydrogen atom is used as a copolymerization component, when the total of the residues of all the polycarboxylic acid compounds constituting the branched polyester (B) and the total of the residues of all the polyol compounds is 200 mol%, isophthalic acid The total of the residue, the phthalic acid residue and the cyclohexanedicarboxylic acid residue is 70 mol% or more, and the linear alkyl group having a carbon number of 1 to 4 is substituted for the linear alkane bonded to the carbon number of 3 to 5. Glycol carbon The total of the residues of the compound of at least one hydrogen atom on the atom is 20 mol% or more, and the glass transition temperature of the branched polyester (B) is less than 40 ° C with respect to the branched polyester (B) 100 parts by weight, the metal fine particles (A) are from 600 to 1,500 parts by weight.

(2) The conductive paste according to (1), wherein the total of the residues of all the polyvalent carboxylic acid compounds constituting the branched polyester (B) and the total of the residues of all the polyol compounds are 200 mol % The total of the phthalic acid residue and the cyclohexanedicarboxylic acid residue is 20 mol% or more and 50 mol% or less.

(3) The conductive paste according to (1) or (2), wherein the content of the metal fine particles (A) is 20% by weight or more and 80% by weight or less based on the entire conductive paste.

(4) The conductive paste according to any one of (1) to (3) further comprising a curing agent (D).

(5) A method for producing a metal thin film laminated body, comprising applying a conductive paste according to any one of (1) to (4) to a substrate, and performing heat treatment and rolling The step of treating and selecting at least one of the selected treatments.

(6) The method for producing a metal thin film laminate according to (5), wherein the substrate is an insulating film.

(7) A metal thin film layered product obtained by the production method as described in (5) or (6).

(8) A device comprising an electric wiring using the metal thin film laminate according to (7) as a constituent element.

The conductive paste of the present invention can be formed into a metal thin film layer having a metal thin film layer having a low volume resistivity by being subjected to heat drying treatment by being applied to a substrate and having excellent dispersion stability. Further, in a preferred embodiment of the present invention, a metal thin film layer having higher conductivity can be obtained by performing a rolling treatment and/or a baking treatment. In a preferred embodiment of the present invention, a metal thin film layer having a volume resistivity of 1 × 10 ^-1 Ω ‧ cm or less can be obtained, and in a more preferred embodiment, 1 × 10 ^-3 Ω ‧ cm or less is displayed, and further In a preferred embodiment, 1 × 10 ^-4 Ω ‧ cm or less is displayed. In the preferred embodiment, a metal thin film layer having a volume resistivity of 1 × 10 ^-5 Ω ‧ cm or less is displayed. In addition, a metal thin film layer is formed from the conductive paste of the present invention, and a device such as a metal thin film laminated body, an electromagnetic wave shielding metal thin film, a plating conductive layer, a metal wiring, or a conductive circuit can be formed.

The conductive paste of the present invention is mainly characterized by a conductive paste composed mainly of metal fine particles (A), a branched polyester (B) and an organic solvent (C), and the average particle diameter of the metal fine particles (A) is 1. ×10 ^-3 μm or more and 5 × 10 ^-1 μm or less, the branched polyester (B) has a branching point derived from a trifunctional or higher polyvalent carboxylic acid compound and/or a trifunctional or higher polyhydric alcohol compound The branched polyester (B) is a carboxyl group having a specific range of carboxyl groups in the molecule, and is a total of residues of all the polycarboxylic acid compounds constituting the branched polyester (B) and all the polyol compound residues. When it is 200 mol%, the total of the isophthalic acid residue, the phthalic acid residue, and the cyclohexanedicarboxylic acid residue is 70 mol% or more, and the linear alkyl group having 1 to 4 carbon atoms is substituted for the bond. The total of the residues of the compound having at least one hydrogen atom on the carbon atom of the linear alkanediol having 3 to 5 carbon atoms is 20 mol% or more, and the glass transition temperature of the branched polyester (B) is Below 40 ° C, the metal fine particles (A) are contained in an amount of 600 to 1500 parts by weight based on 100 parts by weight of the branched polyester (B).

The average particle diameter of the metal fine particles (A) used in the present invention is obtained by a method of randomly selecting metal particles of five fields of view selected by an electric field radiation type scanning electron microscope, and selecting the nearest from the center of each field of view. 20 particles, a method of measuring the diameter of a total of 100 metal particles and collecting the average value. Further, in the measurement of the diameter of each of the metal fine particles, when the shape is not circular, the average of the longest portion length and the shortest portion length is defined as the diameter of the particles.

The upper limit of the average particle diameter of the metal fine particles (A) used in the present invention is 5 × 10 ^-1 μm or less, preferably 2.5 × 10 ^-1 μm or less, more preferably 1 × 10 ^-1 μm or less, further preferably 8 × 10 ^-2 μm or less. When the metal fine particles are excessively large, the metal tends to be easily deposited and adversely affects the dispersion stability of the conductive paste. In the case where the conductive paste is used to form a fine line, the fine line reproducibility may be deteriorated.

The lower limit of the average particle diameter of the metal fine particles (A) of not be particularly limited, but is preferably not less than 5 × 10 ^-3 μm, more preferably not less than 1 × 10 ^-2 μm, more preferably not less than 4 × 10 ^-2 μm . If the average particle diameter of the metal fine particles is too small, the dispersion of the metal fine particles becomes difficult, and in order to preserve the stable dispersion state, a large amount of a resin adhesive or other dispersant will become necessary, and a metal film having high conductivity will become a change. A difficult situation. When the metal fine particles used in the present invention have an average particle diameter of 5 × 10 ^-1 μm or less, it is also possible to use a mixture of particles having different particle diameters.

The metal fine particles (A) used in the present invention may be used as long as they are melted or adhered to each other by heat treatment, and are preferably used for fusion bonding. The type of metal can be exemplified by copper, nickel, cobalt, silver, platinum, gold, molybdenum, titanium, etc., and particularly preferably silver or copper. These metal fine particles can be used as a commercially available product, and can be prepared by a known method. Further, it may be a structure in which a dissimilar metal is constructed, and a metal plating is applied to an organic or inorganic substance.

The shape of the metal fine particles (A) used in the present invention is not particularly limited. The particles may be in the form of a spherical shape, a flat shape, a dendritic shape, a rod shape, or the like, or may be a mixture of any one of them or a mixture of a plurality of species or agglomerates.

The content of the metal fine particles (A) of the present invention is preferably from 20 to 80% by weight, more preferably from 35 to 55% by weight, still more preferably from 35 to 45% by weight, based on the conductive paste. When the content of the metal fine particles (A) in the conductive paste is too low, it becomes difficult to obtain the thickness of the metal thin film layer by one application drying. Further, in order to lower the viscosity of the conductive paste, the coating film overflows easily. The weight ratio of the resin adhesive (B) to the metal fine particles (A) affects the dispersion stability of the conductive paste, the adhesion between the coating film and the substrate, and the conductivity of the coating film. The weight is preferably from 600 to 1500 parts by weight, based on 100 parts by weight of the resin adhesive (B), of the metal fine particles (A), particularly preferably from 800 to 1200 parts by weight. By using the resin adhesive (B), even if it can be used in a small amount without impairing the conductivity of the coating film, it is possible to prevent aggregation of the metal fine particles (A), and to have excellent dispersion stability of the conductive paste and coating film. Adhesion to the substrate.

The branched polyester (B) of the present invention contains one or more of an isophthalic acid residue, a phthalic acid residue and a cyclohexanedicarboxylic acid residue as a copolymerization component. The cyclohexanedicarboxylic acid residue is more preferably a cyclohexane-1,2-dicarboxylic acid residue. By containing these dibasic oxygen compounds as a copolymerization component, the solvent solubility of the branched polyester resin (B) is improved, and the dispersibility and dispersion stability of the metal fine particles (A) are effectively improved.

When the total of the residue of the polyvalent carboxylic acid compound constituting the branched polyester (B) of the present invention and the total of the residues of all the polyol compounds is 200 mol%, it constitutes between the branched polyesters (B) of the present invention. The total of the phthalic acid residue, the phthalic acid residue and the cyclohexanedicarboxylic acid residue is 70 mol% or more. The total of the phthalic acid residue and the cyclohexanedicarboxylic acid residue is more preferably 20 mol% or more and 50 mol% or less. By copolymerizing the dibasic oxygen compound at such a ratio, the solvent solubility of the branched polyester resin (B) obtained is further improved, and the dispersibility and dispersion stability of the metal fine particles (A) are effectively improved. effect. The residue of the polycarboxylic acid compound other than the phthalic acid residue, the phthalic acid residue and the cyclohexanedicarboxylic acid residue constituting the branched polyester (B) of the present invention can also be used, and terephthalic acid or naphthalene can also be used. An aromatic dicarboxylic acid residue such as dicarboxylic acid; an alicyclic dicarboxylic acid such as succinic acid, adipic acid, sebacic acid, sebacic acid, dodecanedioic acid or dimer acid.

The branched polyester (B) contains at least one of a carbon atom having 1 to 4 carbon atoms as a copolymer component and a carbon atom bonded to a linear alkanediol having 3 to 5 carbon atoms. A compound of a hydrogen atom. By including these diol compounds as a copolymerization component, the solvent solubility of the branched polyester resin (B) is improved, and the dispersibility and dispersion stability of the metal fine particles (A) are effectively improved.

When the total number of residues of all the polyvalent carboxylic acid compounds constituting the branched polyester (B) and the total number of residues of all the polyol compounds is 200 mol%, the carbon number of the branched polyester (B) constituting the present invention is used. The total of the residues of the linear alkyl group of 1 to 4 and the compound of at least one hydrogen atom bonded to the carbon atom of the linear alkanediol having 3 to 5 carbon atoms is 20 mol% or more, by a total of By polymerizing these diol compounds, the solvent solubility of the branched polyester resin (B) is further improved, and the dispersibility and dispersion stability of the metal fine particles (A) are further effectively improved. A specific example of replacing at least one hydrogen atom bonded to a carbon atom of a linear alkanediol having 3 to 5 carbon atoms by using a linear alkyl group having 1 to 4 carbon atoms is preferably 2-methyl-1. 3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 3- Methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, etc., particularly preferably 2-methyl-1,3-propanediol, 2,2-dimethyl- a 1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol or the like which uses a linear alkyl group having 1 to 4 carbon atoms instead of hydrogen bonded to a 2-position carbon of 1,3-propanediol Compound residue. The residue of the polyol compound other than the compound having at least one hydrogen atom bonded to the carbon atom of the linear alkanediol having 3 to 5 carbon atoms by using a linear alkyl group having 1 to 4 carbon atoms can be used. a linear aliphatic diol such as 1,3-propanediol.

The branched polyester (B) of the present invention has a branching point derived from a trifunctional or higher polycarboxylic acid compound and/or a trifunctional or higher polyhydric alcohol compound. The polyvalent carboxylic acid having a trifunctional or higher functional group is preferably an aromatic polybasic carboxylic acid, and specific examples thereof include compounds having three or more carboxyl groups in one molecule such as trimellitic acid, trimesic acid, and pyromellitic acid. Can use multiple kinds together. On the other hand, the trifunctional or higher polyhydric alcohol compound is preferably an aliphatic polyhydric alcohol, and examples thereof include compounds having three or more hydroxyl groups in one molecule such as glycerin, trihydroxyethane, trihydroxypropane or pentaerythritol. And use a variety of species. Further, a trifunctional or higher polyvalent carboxylic acid and a trifunctional or higher polyhydric alcohol compound can also be used in combination.

When the total of all the polyvalent carboxylic acid compound residues and the total polyol compound residues constituting the branched polyester (B) is 200 mol%, the trifunctional or higher polycarboxylic acid compound and the trifunctional or higher polyhydric compound The total copolymerization ratio of the alcohol compound is preferably 0.1 mol% or more and 10 mol% or less, more preferably 0.3 to 5 mol%, still more preferably 1 to 3 mol%. If the copolymerization ratio of the branch component is too low, the number of molecular terminals of the branched polyester (B) obtained will be small, and a sufficient amount of polar groups cannot be introduced into the molecular terminal; if it is too high, The polymerization process of the branched polyester (B) tends to cause gelation and has a tendency to cause problems in production stability.

The branched polyester (B) of the present invention has an acid value of 30.sup./10 ⁶ g or more and 200 equivalents/10 ⁶ g or less, more preferably 40 equivalents/10 ⁶ g or more and 180 equivalents/10 ⁶ g. the following. The method of imparting an acid value to the branched polyester (B) is a branched polyester obtained by copolymerizing the above-mentioned trifunctional or higher polycarboxylic acid or a polyhydric alcohol compound, and then various kinds in an inert gas atmosphere. The valence carboxylic anhydride is melt mixed and can be obtained by subjecting it to ring-opening addition mainly at the molecular end. Specific polyvalent carboxylic acid anhydrides can be exemplified by trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, 3,3', 4,4'-bis(phenylhydroxy)ethylene tetracarboxylic anhydride, succinic anhydride, etc. The viewpoint of sex is preferably trimellitic anhydride. The carboxyl group introduced in these molecules has an effect of efficiently adsorbing the branched polyester molecules on the surface of the metal ultrafine particles and improving the dispersibility and dispersion stability of the metal fine particles in a paste state.

The branched polyester (B) of the present invention has a glass transition temperature of less than 40 °C. At 40 ° C or higher, it is difficult to obtain the interface adhesion between the surface of the substrate coated with the coated/dried polyimide film and the fine metal dispersion layer obtained by the metal fine particle paste. The method for setting the glass transition temperature of the branched polyester (B) to less than 40 ° C, for example, exemplified by the phthalic acid residue between the acid components constituting the branched polyester (B), phthalic acid A method or a diol component in which a polycarboxylic acid compound other than a formic acid residue and a cyclohexanedicarboxylic acid residue is copolymerized in an amount of less than 30 mol% to copolymerize an aliphatic dibasic oxygen compound having 4 or more carbon atoms A method of copolymerizing an aliphatic diol component compound having 5 or more carbon atoms. Examples of the aliphatic dibasic oxygen compound having 4 or more carbon atoms include adipic acid, sebacic acid, sebacic acid, dodecanedioic acid, and dimer acid. On the other hand, examples of the alicyclic diol compound having 5 or more carbon atoms include 1,5-pentanediol, 1,6-hexanediol, and 2,2-diethyl-1,3-propanediol. 2-ethyl-2-butyl-1,3-propanediol, 3-methyl-1,5-pentaerythritol, 2,4-diethyl-1,5-pentanediol, and the like.

The branched polyester (B) of the present invention preferably has a number average molecular weight of from 4,000 to 100,000, particularly preferably from 8,000 to 50,000, based on the dispersibility of the metal particles, the adhesion to the substrate, and the like.

The organic solvent (C) used in the conductive paste of the present invention is selected from those in which the branched polyester (B) is dissolved. The organic solvent (C) has a function of adjusting the viscosity and fluidity of the conductive paste in addition to the function of dispersing the metal fine particles (A) in the conductive paste. Examples of the organic solvent (C) are exemplified by alcohols, ethers, ketones, esters, aromatic hydrocarbons, decylamines and the like. Preferable examples are acetoacetic acid carbitol ester, butyl cellosolve acetate, methyl ethyl ketone, cyclohexanone, n-butyl alcohol, second butanol, third butanol and the like.

In the conductive paste of the present invention, the curing agent (D) may be blended if necessary. The hardener (D) which can be used in the present invention can be exemplified by a phenol resin, an amine resin, an isocyanate compound, an epoxy resin or the like. The amount of the hardener is preferably in the range of from 1 to 30% by weight of the branched polyester (B). By blending the curing agent (D), there is a case where the effect of further improving the adhesion between the substrate and the conductive layer formed by the conductive paste of the present invention is exhibited.

The conductive paste of the present invention contains, as an essential component, a branched polyester (B) having a dispersing function for the metal fine particles (A), and may further blend other dispersing agents. The dispersant may, for example, be a higher fatty acid such as stearic acid, oleic acid or myristic acid, a fatty acid guanamine, a fatty acid metal salt, a phosphate ester, a sulfonate or the like. The amount of the dispersant is preferably in the range of from 0.1 to 10% by weight based on the branched polyester (B).

The method of producing the conductive paste of the present invention can use a general method of dispersing a powder in a liquid. For example, a solution of the metal fine particles (A) and the branched polyester (B) is preferably mixed with a mixture of additional solvents as necessary, and then subjected to an ultrasonic method, a mixer method, a 3-roll method, and a ball mill method. Equal dispersion. When these dispersion means are used, it is also possible to combine a plurality of types and to perform dispersion. These dispersion treatments can be carried out at room temperature or by heating.

A general method for forming a metal thin film layer on a substrate by using the conductive paste of the present invention can be applied to a case where a liquid dispersion is applied to a substrate. For example, a screen printing method, a dip coating method, a spray coating method, a spin coating method, an inkjet method, a relief printing method, a gravure printing method, or the like can be exemplified. A metal thin film layer can be formed from a coating film formed by printing or coating by heat, decompression, air blowing, or the like, or by natural drying, by evaporating at least a portion of the solvent. .

The method of forming the metal thin film layer is a case where the viscosity of the conductive paste greatly affects the coating workability or the performance of the obtained metal thin film layer. In general, since the viscosity of the conductive paste is lowered to increase the blending ratio of the organic solvent and tend to cause sedimentation of the metal fine particles, since the dispersion medium contains the branched polyester (B), even if the viscosity is low, It is possible to suppress the tendency of the metal particles to settle.

Preferably, after the metal thin film layer is formed, the metal thin film layer is subjected to a rolling treatment (pressure treatment) without being damaged. There is a tendency to increase the conductivity of the metal thin film layer by the rolling treatment. In general, the calendering treatment is carried out between a metal roll and an elastic roll under a line pressure of the material, for example, a press treatment of 1 to 100 kg/cm. The calendering treatment is particularly preferably carried out by heating to a temperature higher than the glass transition temperature of the branched polyester (B). The calendering treatment can also be carried out in a state in which other layers are laminated on the metal thin film layer.

In the conductive metal thin film layer obtained according to the present invention, it is more preferable to carry out a baking treatment. The firing treatment tends to exhibit a particularly high effect when the particle diameter of the metal fine particles is 100 nm or less. Depending on the surface state of the metal particles such as the degree of crystallization or the degree of oxidation, in the case of so-called nanoparticles, the surface activity is large, and melting is started at a temperature far lower than a conventionally known large melting point. . Further, in the present invention, the "burning treatment" refers to a heat treatment in which at least a part of the metal fine particles (A) is melted and adhered, and the decomposition or scattering of the branched polyester (B) is not necessary.

[Examples]

The present invention is further illustrated by the following examples, which are not intended to limit the invention. Further, the measured values described in the examples were measured by the following methods. In addition, parts are parts by weight unless otherwise stated.

Hereinafter, the abbreviations of the compounds shown in the tables and tables in the examples respectively indicate the following compounds:

T: terephthalic acid

I: isophthalic acid

O: Phthalic acid

SIPA: sodium isophthalate-5-sulfonate

HOPA: hydrogenated phthalic acid

AA: adipic acid

SA: azelaic acid

TMA: trimellitic anhydride

NPG: neopentyl glycol

EG: ethylene glycol

PD: 1,5-pentanediol

HD: 1,6-hexanediol

2MD: 2-methyl-1,3-propanediol

BEPD: 2-butyl-2-ethyl-1,3-butanediol

DEG: Diethylene glycol

Resin composition: The sample was dissolved in heavy chloroform, and quantified by a ¹ H-NMR method using a 400 MHz nuclear magnetic resonance (NMR) spectrometer (manufactured by Varian). The measurement conditions were d1 = 26 s.

The number average molecular weight is such that the sample is dissolved in tetrahydrofuran so that the resin concentration is about 0.5% by weight, and the material filtered by a polytetrafluoroethylene filter having a pore diameter of 0.5 μm is used as a sample for measurement, and tetrahydrofuran is used as a mobile phase. The number average molecular weight was measured by using a differential refractometer as a gel permeation chromatograph of the detector. The flow rate was set to 1 mL/min and the temperature system was set to 30 °C. KF-802, 804L, and 806L manufactured by Showa Denko are used in the column. Monodisperse polystyrene is used in the molecular weight standard.

Specific gravity: Approximately 0.1 g of the sample is placed in an aqueous solution of calcium chloride at a water temperature of 30 ° C, and the concentration of calcium chloride is adjusted, and the specific gravity of the calcium chloride aqueous solution at the time when the resin is not precipitated is measured by a hydrometer. Set to the specific gravity of the resin.

Acid value: 0.2 g of the resin was dissolved in 20 ml of tetrahydrofuran, and then measured with a 0.1 N NaOH ethanol solution using phenolphthalein as an indicator. The measured value is represented by the equivalent of 10 ⁶ g of the resin solid matter.

Glass transition temperature: 5 mg of the sample was placed in an aluminum pan and sealed, and a micro-scanning calorimeter DSC-220 manufactured by Seiko Instruments was used, and the temperature was measured at a heating rate of 20 ° C / min until 200 ° C. The extension line of the baseline below the transfer temperature is determined from the temperature at the intersection of the line showing the maximum inclination of the transition portion.

Conductivity: Measured using a DC precision measuring device, Double Bridge 2769-10, manufactured by Yokogawa M & C. Conductivity is expressed by volume resistivity (unit: Ω ‧ cm).

Dispersion stability: The presence or absence of precipitation after standing on a conductive paste at 30 ° C for 24 hours was observed.

○ - no precipitation.

△ - A small amount of precipitate was confirmed, and the amount of precipitation was 20% by weight or less of all the metal fine particles.

╳ - has a large amount of precipitation. The amount of precipitation exceeded 20% by weight of all metal particles.

Substrate adhesion: The adhesion to the metal film layer of the substrate was evaluated by a tape peeling test at room temperature. In the peeling test, a Scotch tape made of Sumitomo 3M was attached, and the peeling state of the metal thin film layer at the time of peeling off the tape was observed.

○-No peeling.

△ - Partial peeling.

╳ - Fully stripped.

Metal particles used Silver particles (1):

It is obtained by reducing silver nitrate in hexane by ascorbic acid and dodecylamine. After washing and drying, it was observed by a transmission electron microscope to be spherical particles having an average particle diameter of 60 nm.

Silver particles (2):

It is obtained by reducing silver nitrate in hexane by sodium borohydride and dodecylamine. After washing and drying, it was observed by a transmission electron microscope to be spherical particles having an average particle diameter of 830 nm.

Silver particles (3):

It is obtained by reducing silver nitrate in hexane by ascorbic acid and octylamine. After washing and drying, it was observed by a transmission electron microscope to be spherical particles having an average particle diameter of 143 nm.

Synthesis Example 1 Synthesis of Branched Polyester (b1) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 131.9 parts of dimethyl isophthalate, 48.0 parts of neopentyl glycol, 122.0 parts of 1,6-hexanediol, and tetrabutoxy titanate were fed. 0.1 part was heated at 150 to 230 ° C for 180 minutes, and after transesterification, 43.7 parts of phthalic anhydride and 3.8 parts of trimellitic anhydride were added, and the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 1.9 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b1). The analysis results of the obtained resin are shown in Tables 1 and 2.

Synthesis Example 2 Synthesis of Branched Polyester (b2) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 131.9 parts of dimethyl isophthalate, 48.0 parts of neopentyl glycol, 122.0 parts of 1,6-hexanediol, and tetrabutoxy titanate were fed. 0.1 part was heated at 150 to 230 ° C for 180 minutes, and after transesterification, 42.9 parts of phthalic anhydride and 3.8 parts of trimellitic anhydride were added, and the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 3.8 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b2). The analysis results of the obtained resin are shown in Tables 1 and 2.

Synthesis Example 3 Synthesis of Branched Polyester (b3) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 131.9 parts of dimethyl isophthalate, 48.0 parts of neopentyl glycol, 122.0 parts of 1,6-hexanediol, and tetrabutoxy titanate were fed. 0.1 part was heated at 150 to 230 ° C for 180 minutes, and after transesterification, 44.1 parts of phthalic anhydride and 3.8 parts of trimellitic anhydride were added, and the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 1 part of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b3). The analysis results of the obtained resin are shown in Tables 1 and 2.

Synthesis Example 4 Synthesis of Branched Polyester (b4) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 97.0 parts of dimethyl isophthalate, 153.0 parts of 2-methyl-1,3-propanediol, and 2-butyl-2-ethyl-1 were fed. 48.0 parts of 3-propanediol and 0.1 part of tetrabutoxy titanate were heated at 150 to 230 ° C for 180 minutes, and after transesterification, 45.4 parts of hydrogenated phthalic acid, 26.3 parts of adipic acid, and 3.8 parts of trimellitic anhydride were added. And the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 1.9 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b4). The analysis results of the obtained resin are shown in Tables 1 and 2.

Synthesis Example 5 Synthesis of Branched Polyester (b5) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 131.9 parts of dimethyl isophthalate, 99.0 parts of 2-methyl-1,3-propanediol, 94.0 parts of 1,5-pentanediol, and 0.1 part of tetrabutyl titanate was heated at 150 to 230 ° C for 180 minutes, and after transesterification, 45.4 parts of hydrogenated phthalic acid and 3.8 parts of trimellitic anhydride were further added, and the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 1.9 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b5). The analysis results of the obtained resin are shown in Tables 1 and 2.

Comparison of the synthesis of branched polyester (b6) without synthesis of carboxyl groups in Synthesis Example 6.

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 131.9 parts of dimethyl isophthalate, 48.0 parts of neopentyl glycol, 122.0 parts of 1,6-hexanediol, and tetrabutoxy titanate were fed. 0.1 part was heated at 150 to 230 ° C for 180 minutes, and after transesterification, 44.4 parts of phthalic anhydride and 3.8 parts of trimellitic anhydride were added, and the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under the above conditions, the reaction was terminated without adding trimellitic anhydride, and a pale yellow transparent polyester (b6) was obtained. The analysis results of the obtained resin are shown in Tables 1 and 2.

Comparative Synthesis Example 7 Synthesis of Branched Polyester (b7) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 95.1 parts of dimethyl terephthalate, 94.1 parts of dimethyl isophthalate, 3.8 parts of trimellitic anhydride, and 2,2-dimethyl-1 were fed. 73.0 parts of 3-propanediol, 81.0 parts of ethylene glycol, and 0.1 part of tetrabutoxy titanate were heated at 150 to 230 ° C for 180 minutes, and after transesterification, the reaction system was heated to 250 ° C for 30 minutes, and then, The system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 1.9 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b7). The analysis results of the obtained resin are shown in Tables 1 and 2.

Comparative Synthesis Example 8 Synthesis of a Carboxyl Group-Containing Polyester (b8)

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 135.8 parts of dimethyl isophthalate, 48.0 parts of neopentyl glycol, 122.0 parts of 1,6-hexanediol, and tetrabutoxy titanate were fed. 0.1 part was heated at 150 to 230 ° C for 180 minutes, and after transesterification, 43.7 parts of phthalic anhydride was added, and the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 1.9 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b8). The analysis results of the obtained resin are shown in Tables 1 and 2.

Comparative Synthesis Example 9 Synthesis of Branched Polyester (b9) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 92.2 parts of dimethyl terephthalate, 97.0 parts of dimethyl isophthalate, 3.8 parts of trimellitic anhydride, 99.2 parts of ethylene glycol, and diethylene glycol were fed. 42.4 parts and 0.1 part of tetrabutoxy titanate were heated at 150 to 230 ° C for 180 minutes, and after transesterification, the reaction system was heated to 250 ° C for 30 minutes, and then the temperature was raised until 260 ° C and slowly The system was depressurized and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under this condition, the reaction system was returned to normal pressure in a nitrogen atmosphere, and the temperature of the system was set to 220 °C. 1.9 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b9). The analysis results of the obtained resin are shown in Tables 1 and 2.

Comparative Synthesis Example 10 Synthesis of Branched Polyester (b10) Containing Carboxyl Group

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 131.9 parts of dimethyl isophthalate, 48.0 parts of neopentyl glycol, 122.0 parts of 1,6-hexanediol, and tetrabutoxy titanate were fed. 0.1 part was heated at 150 to 230 ° C for 180 minutes, and after transesterification, 42.2 parts of phthalic anhydride and 3.8 parts of trimellitic anhydride were added, and the esterification reaction was carried out at 200 to 250 ° C for 60 minutes. Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After the reaction for 60 minutes under the above conditions, the reaction was terminated without adding trimellitic anhydride, and a pale yellow transparent polyester (b10) was obtained. The analysis results of the obtained resin are shown in Tables 1 and 2.

Comparative Synthesis Example 11 Synthesis of Polyester (b11) Containing Metal Sulfate Base

In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig cooling tube, 126.1 parts of dimethyl isophthalate, 14.8 parts of sodium isophthalate-5-sulfonate, 48.0 parts of neopentyl glycol, and 1,6- were fed. 122.0 parts of hexanediol and 0.1 part of tetrabutoxy titanate were heated at 150 to 230 ° C for 180 minutes, and after transesterification, 44.4 parts of phthalic anhydride was added and esterification was carried out at 200 to 250 ° C for 60 minutes. . Next, the system was gradually depressurized while raising the temperature to 260 ° C, and became 0.3 mmHg or less after 10 minutes. After reacting for 60 minutes under these conditions, 3.8 parts of trimellitic anhydride was added, and the mixture was stirred at 220 ° C for 45 minutes under a nitrogen atmosphere at normal pressure to obtain a pale yellow transparent polyester (b11). The analysis results of the obtained resin are shown in Tables 1 and 2.

Example 1

The following blending ratios of the composition were mixed using 3 rolls:

Polyester (b1) solution 8.3 parts

(24% by weight solution of ethyl acetate carbitol ester / butyl cellosolve acetate = 1 / 1 (weight ratio));

Silver particles (1) (average particle size 60 nm) 23.0 parts

To the obtained kneader, 9.3 parts of ethyl carbitol ketone/butyl cellosolve acetate was added, and the mixture was stirred and mixed for 10 minutes by a planetary mixer to obtain a conductive paste having a solid concentration of 50% by weight.

The obtained conductive paste was applied to a polyimide film having a thickness of 25 μm so that the thickness after drying was 2 μm, and dried at 120 ° C for 10 minutes to obtain a metal thin film layer. Next, a calender roll composed of a chrome plating roll and a rubber roll was passed at 100 ° C at a line pressure of 50 kg/cm. Further, heat treatment was performed at 180 ° C for 1 hour to carry out firing of silver fine particles. The measurement results of the dispersion stability of the conductive paste and the substrate adhesion and conductivity of the metal thin film layer are shown in Table 3. The conductivity in the case where the calcination treatment was carried out without performing the calendering treatment is also shown in Table 3.

Examples 2 to 5 and Comparative Examples 6 to 11

Conductive pastes having the blend ratios disclosed in Tables 3 and 4 were obtained in the same manner as in Example 1. Evaluation was carried out in the same manner as in Example 1. The results are shown in Tables 3 and 4.

Comparative Examples 12, 13

The metal fine particles were replaced with silver fine particles (1) by using silver fine particles (2), and a metal thin film layer was formed in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 4.

Examples 14, 15

In the metal fine particles, silver fine particles (3) were used instead of the silver fine particles (1), and a metal thin film layer was formed in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 4.

Examples 16, 17 and Comparative Examples 18 to 20

The metal fine particles were formed by using the silver fine particles (1) or (3), and the blend ratio of the silver fine particles and the branched polyester (b1) was changed as shown in Table 4, and a conductive film was formed in the same manner as in Example 1. Evaluation was carried out in the same manner as in Example 1. The results are shown in Table 4. However, in Comparative Example 19, the kneaded material obtained by the three rolls could not be formed into a paste, and it could not be thinly applied to the base material.

As shown in Tables 3 and 4, the metal fine particle dispersion system of the present invention has excellent dispersion stability of metal fine particles, and the metal thin film layer formed of the conductive paste has excellent adhesion to the substrate. In addition, it is also known to exhibit excellent electrical conductivity. Comparative Example 6 is a case where the branched polyester resin blended as an adhesive does not have an acid value, and the acid component of the branched polyester resin of Comparative Example 7 deviates from the scope of the present patent, and the glass transition temperature also becomes an application. In the case of the patent, Comparative Example 8 is a case where the polyester resin does not have a branched structure. Further, in Comparative Example 9, the acid component and the diol component were all out of the scope of the present patent, and the glass transition temperature also became the case of the patent application. Further, Comparative Example 10 is an example in which the acid value of the branched polyester resin of the present invention deviated from the scope of the present patent, and Comparative Example 11 was a polyester resin containing a metal sulfonate having excellent dispersion effect of magnetic particles. As an example of the case where the adhesive for magnetic tape is used, there is no branching structure, and the acid value is also out of the example of the scope of the patent application. The particle diameters of the comparative examples 12 and 13 are not in conformity with the scope of the patent application of the present invention. Further, the blending ratio of the silver particles to the branched polyester of Comparative Examples 18 to 20 is out of the scope of the patent application.

[Possibility of industrial use]

The conductive paste of the present invention has excellent dispersion stability, and can be applied to a substrate and subjected to heat drying treatment to form a metal having a low volume resistivity which is excellent in adhesion to the substrate on the substrate. film. The obtained metal thin film can be used for a metal/resin laminate, an electromagnetic wave shield metal film, a plating conductive layer, a metal wiring material, a conductive material, or the like.

Claims (9)

A conductive paste comprising a conductive paste of metal fine particles (A), a branched polyester (B) and an organic solvent (C), the metal fine particles (A) having an average particle diameter of 1 × 10 ^-3 μm or more and 5 × 10 ^-1 μm or less, the branched polyester (B) due to the system having the above polybasic acid compound and / or more than trifunctional branching point of the polyol compound, the branching type The acid value of the polyester (B) is 30 equivalents/10 ⁶ g or more and 200 equivalents/10 ⁶ g or less, and the branched polyester (B) contains an isophthalic acid residue and a phthalic acid residue. And one or more of the cyclohexanedicarboxylic acid residues, and at least one hydrogen atom bonded to a carbon atom of a linear alkanediol having 3 to 5 carbon atoms by using a linear alkyl group having 1 to 4 carbon atoms; The compound is a copolymerization component, and when the total of the residues of all the polyvalent carboxylic acid compounds constituting the branched polyester (B) and the total of the residues of all the polyol compounds is 200 mol%, the isophthalic acid residue, The total of the phthalic acid residue and the cyclohexanedicarboxylic acid residue is 70 mol% or more, and the linear alkyl group having a carbon number of 1 to 4 is substituted for the linear alkanediol bonded to the carbon number of 3 to 5. Carbonogen The total of the residues of the compound of at least one hydrogen atom in the substrate is 20 mol% or more, and the glass transition temperature of the branched polyester (B) is less than 40 ° C with respect to the branched polyester (B) 100 parts by weight, the metal fine particles (A) are from 600 to 1,500 parts by weight. The conductive paste according to claim 1 is characterized in that when the total of the residues of all the polyvalent carboxylic acid compounds constituting the branched polyester (B) and the total of the residues of all the polyol compounds is 200 mol%, The total of the phthalic acid residue and the cyclohexanedicarboxylic acid residue is 20 mol% or more and 50 mol% or less. The conductive paste according to claim 1 or 2, wherein the content of the metal fine particles (A) is 20% by weight or more and 80% by weight or less based on the entire conductive paste. The conductive paste of claim 1 or 2 further contains a curing agent (D). The conductive paste according to item 3 of the patent application further contains a hardener (D). A method for producing a metal thin film laminate comprising a coating film formed by applying a conductive paste according to any one of claims 1 to 5 to a substrate, and performing heat treatment, rolling treatment, and firing The step of processing the selected at least one process. The method for producing a metal thin film laminate according to claim 6, wherein the substrate is an insulating film. A metal thin film laminate produced by the production method of claim 6 or 7. A device comprising, as a constituent element, an electric wiring using a metal thin film laminate as in the eighth aspect of the patent application.