TW201829652A - Conductive paste for gravure offset printing, method for forming conductive pattern, and method for manufacturing conductive substrate wherein the conductive paste has sufficient conductivity and good adhesion to a substrate - Google Patents

Abstract

The present invention provides a conductive paste for gravure offset printing, which has sufficient conductivity and good adhesion to a substrate and is capable of performing fine line printing. The conductive paste for gravure offset printing of the present invention comprises silver fine particles, an organic solvent, and a water-soluble polymer. The average particle diameter of the silver fine particles is 1 <mu>m or less. Preferably, the water-soluble polymer comprises a polymeric compound having a cyclic structure, and more preferably, the water-soluble polymer comprises polyvinylpyrrolidone.

Description

Conductive paste for gravure transfer, method for forming conductive pattern, and method for producing conductive substrate

The present invention relates to a conductive paste for gravure transfer, a method for forming a conductive pattern using the conductive paste for gravure transfer, and a method for producing a conductive substrate using the method for forming the conductive pattern. .

In recent years, there has been a focus on printed electronics technology that uses printing technology to form electronic circuits, components, and the like. In the printed electronic technology, a printing method such as a letterpress printing method, a gravure printing method, a screen printing method, or an inkjet printing method has been studied as a method for forming a simpler and cheaper conductive pattern, and research and development are suitable for various types. A conductive ink or a conductive paste of a printing method.

For example, Patent Document 1 discloses a conductive paste which is a conductive paste for frame pattern printing by a gravure transfer method, and the conductive paste for frame pattern printing contains conductive metal particles (A). An organic compound (B) which is solid at 50 ° C and has a boiling point of more than 300 ° C at normal pressure, an organic compound (C) which is liquid at 50 ° C and has a boiling point of more than 300 ° C under normal pressure, and (B) and An organic solvent (D) having a boiling point of 170 ° C to 300 ° C which is not reactive with (B) and (C) other than (C), and has a boiling point of 170 ° C to 300 ° C under normal pressure, and is characterized by: In the total amount of A) to (D), the (B) nonvolatile content is 1.0% to 3.0% by mass, and the organic compound (B) and the organic compound (C) are used in terms of mass of the nonvolatile matter. The total amount of use is set to R, and the mass ratio R/P of both when the amount of use of the conductive metal particles (A) is P is 0.07 to 0.15.

Further, Patent Document 2 discloses a method for producing a conductive film using a conductive copper paste in which a thermosetting resin component or a glass × glass frit is not blended, and discloses a method for producing a conductive film, which is characterized in that The conductive copper paste is selected from the group consisting of copper powder selected in a range of an average particle diameter of 2 μm to 10 μm and a fine copper having an average particle diameter of 0.2 μm to 1.0 μm. a powder, a copper salt of a specific aliphatic monocarboxylic acid, a specific (dialkylamino)alkylamine, a polymer binder having a thermal decomposition temperature in a specific range, and a first boiling point and a specific functional group In the conductive copper paste of the organic solvent, the conductive copper paste is applied to the resin substrate, and then the light is allowed to be in a state where the residual amount of the first organic solvent is 0.1% by mass to 5% by mass. Irradiation and film formation.

In the formation of the conductive pattern of the conductive substrate, the gravure transfer which is one of the gravure printing methods is suitable for printing on thin lines, and therefore can be preferably used. In the gravure transfer, a conductive paste is filled in a concave portion formed on the surface of the intaglio plate, the conductive paste is temporarily transferred to the coating layer, and the conductive paste transferred to the coating layer is transferred. It is printed on the adherend, whereby the printed pattern formed on the surface of the intaglio is printed on the adherend. Therefore, the conductive paste for gravure transfer is required to have an appropriate viscosity so as to be easily filled in the concave portion of the intaglio plate, and has a degree of adhesiveness (viscosity) in a semi-solid/semi-liquid state, so that the self-gravure is made. The transfer to the coating layer and the transfer from the self-coating layer to the adherend are good. [Prior Art Document] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5610112 [Patent Document 2] Japanese Patent Laid-Open Publication No. 2014-186902

[Problems to be Solved by the Invention] In recent years, the density of electronic circuits has been increased, and wiring research has been further refined. In particular, it is required to form a conductive pattern having a line width of 10 μm or less, and further, in a precise electronic circuit, it is required to form a conductive pattern having a line width of 3 μm or less. Conventionally, as a resin material for imparting viscosity or adhesiveness to a conductive paste, an acrylic resin, a polyester resin, a urethane resin or the like has been used. Further, as the solvent, an organic solvent having a relatively low polarity is often used. However, since the combination of a resin material such as an acrylic resin, a polyester resin, and a urethane resin and an organic solvent has low adhesion in a semi-solid/semi-liquid state, it is particularly useful for performing fine line printing using a gravure transfer method. In the following, it is easy to cause poor transfer and it is extremely difficult to perform fine line printing without disconnection. Further, in the case of forming a thin line having a line width of 3 μm or less, it is very important to achieve adhesion to the adherend, and to have adhesion in a semi-solid/semi-liquid state and adhesion to the adherend. A conductive paste for gravure transfer.

The conductive paste described in Patent Document 1 is designed to be printed on a frame pattern, and there is room for further research in order to correspond to the thinning of the conductive pattern in recent years. Further, in Patent Document 2, the thinning of the conductive pattern formed by the gravure transfer has not been studied.

The present invention has been made in view of the above problems, and provides a conductive paste for gravure transfer and formation of a conductive pattern which has sufficient conductivity and good adhesion to a substrate and can form a fine conductive pattern. A method and a method of producing a conductive substrate. [Means for solving the problem]

In order to achieve the above object, the inventors of the present invention have conducted intensive studies and found that in order to realize the thinning of the conductive pattern formed by the gravure transfer method, the water-soluble polymer is added to the conductive paste. The adhesion in this semi-solid/semi-liquid state is improved and fine line printing can be performed by gravure transfer, thereby achieving the present invention.

The conductive paste for gravure transfer of the present invention is characterized by comprising silver fine particles, an organic solvent, and a water-soluble polymer, and the silver fine particles have an average particle diameter of 1 μm or less.

The water-soluble polymer preferably contains a polymerizable compound having a cyclic structure.

The water-soluble polymer preferably contains polyvinylpyrrolidone.

The content of the water-soluble polymer is preferably from 3% by weight to 8% by weight based on the total amount of the conductive paste.

The organic solvent preferably contains a first organic solvent having a hydroxyl group and having a boiling point of 200 ° C or higher at normal pressure.

The organic solvent preferably contains the second organic solvent having a coating swelling ratio of 2.0% or less in an amount of 3.0% by weight to 30% by weight based on the entire conductive paste.

In the method of forming a conductive pattern according to the present invention, the intaglio printing method using a gravure has a concave portion on a printing surface filled with a conductive paste for gravure transfer, and the width of the concave portion is 10 μm or less. The conductive paste for gravure transfer is the conductive paste for gravure transfer of the present invention.

The method for producing a conductive substrate of the present invention is characterized in that a conductive pattern is drawn on a substrate by using the method for forming a conductive pattern of the present invention. [Effects of the Invention]

Since the conductive paste for gravure transfer of the present invention has sufficient conductivity and good adhesion to a substrate, fine line printing by gravure transfer can be performed. Further, according to the method for forming a conductive pattern of the present invention, a conductive pattern having a line width of 10 μm or less can be formed, and even a conductive pattern having a line width of 3 μm or less can be formed without being broken. According to the method for producing a conductive substrate of the present invention, a conductive substrate on which a precise conductive pattern is printed can be produced.

[Conductive Paste for Gravure Transfer] The conductive paste for gravure transfer of the present invention includes silver fine particles, an organic solvent, and a water-soluble polymer, and the average particle diameter of the silver fine particles is 1 μm or less. Since the conductive paste for gravure transfer of the present invention contains an organic solvent and a water-soluble polymer, it is difficult to dehydrate and has a degree of adhesion in a semi-solid/semi-liquid state, and thus is suitable for fine line printing by a gravure transfer method. .

(Silver Fine Particles) The silver fine particles have an average particle diameter of 1 μm or less. By setting the average particle diameter of the silver fine particles to 1 μm or less, a fine conductive pattern having a line width of 3 μm or less can be formed by a gravure transfer method. The shape of the silver fine particles is not particularly limited as long as the effects of the present invention are not impaired. When coarse silver particles having an average particle diameter of more than 1 μm are used, for example, when the width of the concave portion formed on the surface of the intaglio plate is 3 μm, only a few silver particles can be filled, so that sintering of the silver particles is difficult. Moreover, a fine conductive pattern cannot be formed. Further, depending on the particle diameter of the silver particles, there is a case where the silver particles are not completely filled in the recess of the 3 μm width.

The silver fine particles preferably have an average particle diameter which causes a decrease in melting point, and more preferably, for example, silver fine particles having an average particle diameter of from 1 nm to 200 nm. By including the nano-sized silver microparticles, a large amount of silver microparticles can be densely filled in the concave portion of the intaglio plate, and the silver microparticles can be arranged in a finely overlapping manner, so that the silver microparticles are easily sintered to each other. (necked). In addition, since the particle diameter is extremely small, the influence of one silver microparticle on the printing quality can be further reduced. When the average particle diameter of the silver fine particles is 1 nm or more, the silver fine particles have excellent low-temperature sinterability and can suppress the cost associated with the production of silver fine particles, and are practical. Further, when the average particle diameter of the silver fine particles is 200 nm or less, the dispersibility of the silver fine particles is difficult to change with time. A still more preferred lower limit of the average particle diameter of the silver fine particles is 2 nm, and a more preferable upper limit is 100 nm.

The silver microparticles may also contain submicron-sized silver microparticles having an average particle diameter of more than 200 nm and 1 μm or less. When the silver microparticles of the submicron size are used, the particle diameter of the silver microparticles is large. Therefore, although the sinterability of the silver microparticles is slightly lowered, the fine line printing can be sufficiently performed.

The silver fine particles may also contain silver fine particles having an average particle diameter of 1 nm to 200 nm and submicron size silver fine particles having an average particle diameter of more than 200 nm and 1 μm or less. By using nano-sized silver particles and sub-micron-sized silver particles, the nano-sized silver particles have a lower melting point around the sub-micron-sized silver particles, and thus are compared with the case where only sub-micron-sized silver particles are used. , a better conductive path can be obtained.

The particle diameter of the silver fine particles can be measured by a dynamic light scattering method, a small-angle X-ray scattering method, or a wide-angle X-ray diffraction method. In the present specification, the "average particle diameter" means a dispersed median diameter. The dispersed median diameter can be calculated by using a dynamic light scattering method (Dynamic Light Scattering) to obtain a dispersed particle diameter on the basis of a particle diameter reference. As the measuring device of the DLS, for example, a particle diameter distribution measuring device (model: LB-550) manufactured by Horiba, Ltd. can be used. Specifically, the synthesized silver fine particle dispersion was diluted 100-fold with terpineol, and the refractive index of the solvent was measured to 1.48.

The weight ratio of the silver fine particles to the entire nonvolatile component of the conductive paste is preferably 90% by weight or more. The non-volatile component is a component other than the organic solvent, and includes, in addition to the silver fine particles, an organic component coated with silver fine particles, a water-soluble polymer contained in the conductive paste, and a polymer dispersant. Thickeners, etc. When the weight ratio of the silver fine particles is 90% by weight or more, a conductive pattern having a high silver content can be formed. Since the silver fine particles are excellent in chemical stability, it is possible to form a conductive pattern which is hard to be oxidized and whose volume resistance value is hard to be reduced, mainly by silver fine particles.

Further, in consideration of the problem of migration of the conductive pattern formed by using the conductive paste for gravure transfer of the present invention, particles of gold, copper, platinum, palladium or the like which are metals which are more inert to hydrogen than the hydrogen may be added. When the conductive paste for gravure transfer of the present invention contains metal particles other than silver, the content ratio of the silver fine particles to the total of the metal particles obtained by adding the silver fine particles to the metal particles other than silver is preferably 90% by weight. %the above.

(Organic Component) It is preferred that at least a part of the surface of the silver fine particles adhere to an organic component. The surface of the silver fine particles is more preferably coated with an organic component. The form of the coating is not particularly limited, and the organic component is a so-called dispersant and substantially constitutes the inorganic colloidal particles together with the silver fine particles. The organic component is a trace organic substance that does not contain, as originally contained as, an impurity in the silver fine particles; is added to the silver microparticles in a manufacturing process to be described later; a residual reducing agent that is not completely removed during the cleaning process, The concept of a small amount of organic matter attached to silver fine particles, such as a residual dispersant. In addition, the "minor amount" means specifically less than 1% by weight of the inorganic colloidal particles.

The organic component is an organic substance capable of coating silver fine particles to prevent aggregation of silver fine particles and forming inorganic colloidal particles, and preferably contains an amine and a carboxylic acid from the viewpoints of dispersibility, conductivity, and the like. Further, when the organic components are chemically or physically bonded to the silver fine particles, it is also considered to be changed to an anion or a cation, and ions or complexes derived from the organic components are also included in the organic In the ingredients.

The amine may be linear or branched, or may have a side chain. Specific examples thereof include N-(3-methoxypropyl)propane-1,3-diamine, 1,2-ethylenediamine, 2-methoxyethylamine, and 3-methoxypropene. a diamine such as a base amine, 3-ethoxypropylamine, 1,4-butanediamine, 1,5-pentanediamine, pentanolamine or aminoisobutanol, an alkoxyamine or an amino alcohol, Or an alkylamine such as propylamine, butylamine, pentylamine, hexylamine or hexylamine (linear alkylamine, which may also have a side chain); a cycloalkylamine such as cyclopentylamine or cyclohexylamine a primary amine such as aniline or allylamine; a secondary amine such as dipropylamine, dibutylamine, piperidine or hexamethyleneimine; tripropylamine, dimethylpropanediamine, cyclohexyldi A tertiary amine such as methylamine, pyridine or quinoline. Among them, an alkylamine or an alkoxyamine is preferred.

The amine may be, for example, a compound containing a functional group other than an amine such as a hydroxyl group, a carboxyl group, an alkoxy group, a carbonyl group, an ester group or a mercapto group. Further, the amines may be used singly or in combination of two or more. The boiling point of the amine at normal pressure is preferably 300 ° C or lower, more preferably 250 ° C or lower.

The carboxylic acid may be contained in addition to the amine insofar as it does not impair the effects of the present invention. The carboxyl group in one molecule of the carboxylic acid has a relatively high polarity, and it is easy to cause an interaction caused by hydrogen bonding, but a portion other than the functional group has a relatively low polarity. Further, the carboxyl group is liable to exhibit acidic properties.

As the carboxylic acid, a compound having at least one carboxyl group can be widely used, and examples thereof include formic acid, oxalic acid, acetic acid, caproic acid, acrylic acid, octanoic acid, and oleic acid. A part of the carboxyl group of the carboxylic acid may also form a salt with the metal ion. Further, the metal ions may contain two or more kinds of metal ions.

The carboxylic acid may be, for example, a compound containing a functional group other than a carboxyl group such as an amino group, a hydroxyl group, an alkoxy group, a carbonyl group, an ester group or a fluorenyl group. In this case, the number of carboxyl groups is preferably at least the number of functional groups other than the carboxyl group. Further, the carboxylic acids may be used alone or in combination of two or more. The boiling point of the carboxylic acid under normal pressure is preferably 300 ° C or lower, more preferably 250 ° C or lower. Further, the amine forms a guanamine group with the carboxylic acid. The guanamine group is also suitably adsorbed on the surface of the silver fine particles, and thus the amide group may be contained in the organic component.

The content of the organic component in the inorganic colloid in the conductive paste for gravure transfer of the present invention is preferably from 0.5% by weight to 50% by weight. When the content of the organic component is 0.5% by weight or more, the storage stability of the obtained conductive paste tends to be good, and when it is 50% by weight or less, the conductivity of the conductive pattern tends to be good. A more desirable content of the organic component is from 1% by weight to 30% by weight, and still more preferably from 2% by weight to 15% by weight.

In the case where the amine and the carboxylic acid are used in combination, the composition ratio (by weight) of the amine to the carboxylic acid may be arbitrarily selected within the range of from 1/99 to 99/1. It is preferred that the composition ratio of the amine to the carboxylic acid is from 20/80 to 98/2, and more preferably from 30/70 to 97/3. Further, the amine or the carboxylic acid may also use a plurality of amines or carboxylic acids, respectively.

(Organic solvent) The conductive paste for gravure transfer of the present invention contains an organic solvent as a dispersion medium of silver fine particles. By using an organic solvent as a dispersion medium, aggregation of silver fine particles can be suppressed. Further, since the boiling point is usually high and it is difficult to dry, transfer to the coating layer is easy. Further, since the surface tension is low, the intimacy with the fluorenone rubber which is usually used as a coating layer is also good. Further, when water is used as the dispersion medium, the silver fine particles are aggregated, and there is a possibility that the concave portion of the intaglio plate is blocked. Further, water is not suitable as a dispersion medium for the conductive paste used in the gravure transfer having the transfer step because of high surface tension, poor wettability with respect to the coating layer, low boiling point, and easy drying.

The organic solvent preferably contains a first organic solvent having a hydroxyl group and having a boiling point of 200 ° C or higher at normal pressure. The conductive paste for gravure transfer of the present invention can be preferably used for fine line printing having a line width of 10 μm or less, particularly a line width of 3 μm or less. Therefore, it is preferred to use a solvent which is difficult to dry. When the boiling point of the first organic solvent at normal pressure is 200 ° C or higher, the conductive paste can be prevented from being excessively dried on the intaglio plate. In addition, since the first organic solvent contains a hydroxyl group, the dispersion of the silver fine particles is good, and the polarity of the organic solvent is increased, so that the swelling of the coating layer tends to be suppressed.

As the first organic solvent, for example, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3 is preferably used. - hexanediol, tripropylene glycol, triethylene glycol, 1,2-hexanediol, 1,3-butanediol, 1,3-propanediol, dipropylene glycol, 2-butene-1,4-diol, etc. Glycol solvent.

The content of the first organic solvent with respect to the entire conductive paste is preferably 3% by weight to 30% by weight. A more preferable upper limit of the content ratio of the first organic solvent is 25% by weight, and a still more preferred upper limit is 20% by weight.

The organic solvent preferably contains a second organic solvent having a coating swelling ratio of 2.0% by weight or less of 3.0% by weight to 30% by weight. The second organic solvent having a swelling ratio of the coating layer of 2.0% or less is also referred to as a "low swelling organic solvent". The second organic solvent may also have the first organic solvent. By using the low-swelling organic solvent having a swelling ratio of the coating layer of 2.0% or less, the absorption of the organic solvent by the coating layer can be reduced, and the drying of the conductive paste on the surface of the coating layer can be greatly suppressed. When a fine line is printed using a conductive paste, the conductive paste printed in a thin line is very easy to dry, and it is difficult to form a favorable conductive pattern. On the other hand, by setting the swelling ratio of the coating layer of the organic solvent to 2.0% or less, for example, it is possible to form a fine line conductive pattern having a line width of 3 μm or less. Further, a better coating swelling ratio is 0.4% or less.

In addition, by setting the content ratio of the second organic solvent to the entire conductive paste to 3.0% by weight or more, it is possible to impart appropriate coatability (fluidity) to the conductive paste, and further, for example, Drying of fine lines with a line width of 3 μm or less can be suppressed. By setting the content ratio to 30% by weight or less, expansion at the time of printing can be prevented. Further, the upper limit of the content of the low-swelling organic solvent is more preferably 25.0% by weight, and still more preferably the upper limit is 20.0% by weight.

In general, the outermost surface of the printing plate used for the gravure transfer is made of fluorenone rubber, and the "coating swelling ratio" in the present invention means the swelling ratio when the fluorenone rubber is immersed in the organic solvent. Here, the "coating swelling ratio" is the same as the weight change rate of the coating layer (anthrone rubber) before and after the immersion when the coating layer (anthrone rubber) is immersed in the organic solvent. Specifically, the test layer (anthrone rubber) was cut into 1 cm squares to prepare a test piece, and the test piece was immersed in an organic solvent at room temperature (25 ° C ± 5 ° C), and taken out after 10 hours. The weight increase rate before and after the immersion was determined, and the "coating swelling ratio" was evaluated. It has been experimentally proved that if it is used as a standard for the fluorenone coating in the printing of conductive paste, the swelling ratio measured with respect to a specific organic solvent is not greatly deteriorated.

As the low-swelling organic solvent having a coating swelling ratio of 2.0% or less, a plurality of solvents can be used as long as the effects of the present invention are not impaired. Among them, a solvent having a hydroxyl group as a functional group is preferable, and examples thereof include a polyol having a plurality of hydroxyl groups or another monool solvent. Further, by using a solvent having a high polarity such as a diol having a very low swelling ratio of the coating layer, drying of the fine line pattern on the coating layer can be more effectively suppressed. These solvents may be used alone or in combination of two or more.

(Organic solvent having a coating swelling ratio of 2.0% or less) Examples of the polyol having two to three hydroxyl groups include glycerin, 1,2,4-butanetriol, and 1,2,6-hexane. Alcohol, ethylene glycol, diethylene glycol, 1,2-butanediol, propylene glycol, 2-methylpentane-2,4-diol, and the like.

Examples of the monohydric alcohol include butyl triethylene glycol, isobutyl diethylene glycol, 2-butoxyethanol, 3-methoxy-3-methylbutanol, and 2-(2-methyl). Oxyethoxyethyl)ethanol, 2-(2-hexyloxyethoxy)ethanol, and the like.

Further, although it is repeated with the first organic solvent, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-ethyl group can also be used. -1,3-hexanediol, tripropylene glycol, triethylene glycol, 1,2-hexanediol, 1,3-butanediol, 1,3-propanediol, dipropylene glycol, 2-butene-1,4 a diol solvent such as a diol.

The organic solvent may use a plurality of organic solvents in a range that does not impair the effects of the present invention, and may be used in combination with the first organic solvent and the second organic solvent to adjust the drying property and the like. A solvent having a swelling ratio of more than 2.0% and a high swelling ratio. Further, the number and combination of the solvents to be mixed are not particularly limited.

(Organic solvent having a coating swelling ratio of more than 2.0%) Examples of the organic solvent having a coating swelling ratio of more than 2.0% include glycol ether, ethylene glycol ester, terpene-based solvent, hydrocarbon solvent, and alcohol solvent. These solvents may be used singly or in combination of two or more. Further, when the concentration of the terpene solvent in the organic solvent is too high, the amount of the solvent absorbed by the coating layer increases, and the coating layer in the middle of the transfer printing is likely to be easily dried. Therefore, it is preferable to mix the two in a well-balanced manner. An alcohol solvent and a terpene solvent.

Specific examples of the organic solvent in which the coating layer has a swelling ratio of more than 2.0% include tripropylene glycol n-butyl ether, butyl carbitol, diethylene glycol monomethyl ether, tripropylene glycol methyl ether, and Ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, triethylene glycol dimethyl ether, dipropylene glycol methyl ether acetate, ethylene glycol monohexyl ether, dipropylene glycol Methyl ether, propylene glycol diacetate, 1,4-butanediol divinyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, and the like.

The hydrocarbon solvent may be an aliphatic hydrocarbon-containing compound, a cyclic hydrocarbon compound, or an alicyclic hydrocarbon compound.

Examples of the aliphatic hydrocarbon compound include tetradecane, octadecane, heptamethylnonane, tetramethylpentadecane, hexane, heptane, octane, decane, decane, and thirteen. A saturated or unsaturated aliphatic hydrocarbon compound such as an alkane, a methylpentane, a normal paraffin or an isoparaffin.

Examples of the cyclic hydrocarbon compound include toluene, xylene, and the like.

Examples of the alicyclic hydrocarbon compound include limonene, dipentene, terpinene, terpinene (also known as terpinene), nesol, and cinene. , orange flavor, terpinolene, terpinolene (also known as terpinolene), hydrocelene, menthadiene, mucene, dihydrocymene ), Moslene, isodecene, terpinolene (also known as isodecene), crithmene, kautschin, cajeputene, oilimene, Pinene, turpentine, menthane, pinane, terpene, cyclohexane, and the like.

The alcohol solvent is a compound containing one or more hydroxyl groups in its molecular structure, and examples thereof include an aliphatic alcohol, a cyclic alcohol, and an alicyclic alcohol. These alcohols may be used singly or in combination of two or more. Further, a part of the hydroxyl group may be derived from an ethoxy group or the like within a range not impairing the effects of the present invention.

Examples of the aliphatic alcohol include heptanol, octanol (1-octanol, 2-octanol, 3-octanol, etc.), decyl alcohol (1-nonanol, etc.), lauryl alcohol, and tetradecyl alcohol. A saturated or unsaturated aliphatic alcohol having 6 to 30 carbon atoms such as cetyl alcohol, 2-ethyl-1-hexanol, stearyl alcohol, cetyl alcohol or oleyl alcohol.

Examples of the cyclic alcohol include cresol and eugenol.

Examples of the alicyclic alcohol include a cycloalkanol such as cyclohexanol, terpineol (terpineol containing an α, β, γ isomer or any mixture thereof), and dihydroterpineol. Isoenol (monoterpene alcohol, etc.), dihydroterenol, myrtenol, sobrerol, menthol, carveol, perilla Perillyl alcohol, pinocarveol, sobresol, verbenol, and the like. The alicyclic alcohol may also be repeated with the terpene solvent.

(Water-Soluble Polymer) The conductive paste for gravure transfer of the present invention contains a water-soluble polymer. Since the adsorption of the coating layer and the adherend interface is improved by the inclusion of the water-soluble polymer, the gravure transfer method can be used, for example, even if the conductive pattern has a line width of 3 μm or less. In the present specification, the term "water-soluble" means a solubility of 1 g or more with respect to 1 L of water.

The water-soluble polymer is preferably a polymer which is soluble in both an organic solvent and water. Further, the water-soluble polymer is required to have adhesion to a substrate, transfer property to a substrate, and difficulty in occurrence of expansion on a coating layer. When the adherend (substrate) of the conductive paste is, for example, polyethylene terephthalate (PET), it is preferred that the adhesion to PET is good.

The water-soluble polymer preferably contains a polymerizable compound having a cyclic structure. Although the solubility in an organic solvent is limited, polyvinyl alcohol can also be used. The cyclic structure is preferably γ-endoamine, and further preferably has a vinyl group. Among them, the water-soluble polymer more preferably contains polyvinylpyrrolidone. Polyvinylpyrrolidone is a polymer represented by the following chemical formula (1).

[Chemical 1] (where n is a natural number)

Polyvinylpyrrolidone has high solubility in a highly polar polyol (especially a diol solvent), and can be well dissolved in a solvent such as an ester or a ketone, so that silver fine particles can be made with respect to the organic solvent. Well dispersed. In particular, it is well dissolved in a first organic solvent having a hydroxyl group and having a boiling point of 200 ° C or higher under normal pressure.

In addition, polyvinylpyrrolidone can also be dissolved in water, so that the adsorption to the interface of the substrate can be remarkably improved. Further, as a feature of gravure transfer, a semi-solid/semi-liquid paste is transferred onto a coating, but polyvinylpyrrolidone has high viscosity (adhesion) in a semi-solid/semi-liquid state. Therefore, the transfer from the coating layer to the substrate is very excellent. Therefore, it is possible to further improve the printability in fine line printing in which the line width which cannot be printed, for example, is 3 μm or less, with respect to the conventional conductive paste.

The polyvinylpyrrolidone preferably has an average molecular weight of 100,000 or less. When the average molecular weight is 100,000 or less, the viscosity of the conductive paste can be prevented from being excessively increased, and the transfer property to the coating layer or the substrate can be improved. Examples of such a polyvinylpyrrolidone include polyvinylpyrrolidone K25 (average molecular weight: 25,000) and polyvinylpyrrolidone K30 (average molecular weight: 40,000) (all manufactured by Wako Pure Chemical Industries, Ltd.). The average molecular weight is a weight average molecular weight and is determined by liquid chromatography. In the measurement of the weight average molecular weight, a LC-6AD pump manufactured by Shimadzu Corporation, a RID-10A RI detector, a CLASS-LC10 Chromatopac data processor, and a DGU- were used. 20A3 degasser. Further, as a column, TSK-GEL G1000H, G2000H, and G2500H were used, the oven temperature was set to 40 ° C, and tetrahydrofuran (THF) was flowed at a flow rate of 1.0 mL/min. The weight average molecular weight is calculated by calibration using polystyrene as a standard.

The content of the water-soluble polymer is preferably from 3% by weight to 8% by weight based on the total amount of the conductive paste. When the content of the water-soluble polymer is less than 3% by weight, the adhesion to the adherend may be lowered. On the other hand, when the content of the water-soluble polymer is more than 8% by weight, the volume resistivity of the conductive pattern formed by the conductive paste of the present invention may increase. A more preferable upper limit of the content of the water-soluble polymer is 7% by weight.

In addition to the above-mentioned components, the conductive paste for gravure transfer of the present invention may be provided with appropriate viscosity, adhesion, and drying in accordance with the purpose of use without impairing the effects of the present invention. An optional component such as a polymer dispersant, an oligomer component, a surfactant, a thickener, or a surface tension adjuster is added to functions such as properties or printability. The optional component is not particularly limited.

As the polymer dispersant, a commercially available polymer dispersant can be used. As a commercially available polymer dispersant, for example, SOLSPERSE 11200, SOLSPERSE 13940, SOLSPERSE 16000, SONOSPERSE 17000, cable SOLSPERSE 18000, SOSOLPERSE 20000, SOLSPERS 24000, SOLSPERS 26000, SOSOLERS 27000, SONOSPERSE 28000 (made by Lubrizol, Japan); DISPERBYK-102, DISPERBYK-110, DISPERBYK-111, Dispa DISPERBYK-170, DISPERBYK-190, DISPERBYK-194N, DISPERBYK-2015, DISPERBYK- 2090, DISPERBYK-2096 (made by BYK-Chemie Japan); EFKA-46, EFKA-47, EFKA )-48, EFKA-49 (manufactured by EFKA Chemical); Polymer 100, Polymer 120, Polymer 150, Polymer 400, Polymer 401, Polymer 402, Polymer 403, Polymerization Polymer 450, Polymer 451, Polymer 452, Polymer 453 (made by EFKA Chemical); AJISPER PB711, Aji AJISPER PA111, AJISPER PB811, AJISPER PW911 (made by Ajinomoto Co., Ltd.); FLOWLEN DOPA-15B, FLOWLEN DOPA- 22, FLOWLEN DOPA-17, FLOWLEN TG-730W, FLOWLEN G-700, FLOWLEN TG-720W (manufactured by Kyoeisha Chemical Industry Co., Ltd.) , the DISPERBYK series manufactured by BYK-Chemie, etc., and the TEGO Dispers series manufactured by Evonik can list 610, 610S, 630, 651, 655, 750W, 755W, etc., Di Siba manufactured by Nanben Chemical Company Examples of the Disparlon series include DA-375 and DA-1200. From the viewpoint of low-temperature sinterability and dispersion stability, it is preferred to use DISPERBYK-102, Sonupas ( SOLSPERSE) 11200, SOLSPERS 13940, SOSOLERS 16000, SOLSPERSE 17000, SOSOLERS 18000, SOLSPERS 28000, etc.

The content of the polymer dispersant is preferably from 0.1% by weight to 15% by weight based on the total amount of the conductive paste. When the content of the polymer dispersant in the entire conductive paste is 0.1% by weight or more, the dispersion stability of the obtained conductive paste is good, but when the content is too large, the dispersion stability is lowered. Case. From such a viewpoint, a more preferable content of the polymer dispersant is from 0.3% by weight to 3% by weight, and more preferably from 0.5% by weight to 2% by weight.

Examples of the thickener include clay minerals such as clay, bentonite, or hectorite; polyester latex resin, acrylic latex resin, and polyurethane latex. Latex such as resin or block isocyanate; cellulose derivative such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose; xanthan gum Or a polysaccharide such as guar gum or the like, and these may be used alone or in combination of two or more.

In addition to the organic component, a surfactant may be further added. In the inorganic colloidal dispersion liquid of the multicomponent solvent system, the roughness of the surface of the coating film and the variation of the solid content due to the difference in the volatilization speed at the time of drying are likely to occur. By adding a surfactant to the conductive paste of the present embodiment, it is possible to suppress the disadvantages and form a uniform conductive film.

The surfactant is not particularly limited, and an anionic surfactant, a cationic surfactant, a nonionic surfactant, or the like can be used. Specifically, an alkylbenzenesulfonate, a quaternary ammonium salt, etc. are mentioned. From the viewpoint of obtaining an effect in a small amount of addition, a fluorine-based surfactant is more preferable.

The conductive paste preferably has a viscosity of from 500 cP to 10,000 cP. When the viscosity of the conductive paste is in the above range, it is easy to be filled in the concave portion of the intaglio plate, and after the transfer to the adherend, the conductive paste is hard to permeate, so that fine line printing can be performed. The viscosity can be measured by a cone-and-plate type viscometer (for example, a rheometer MCR301 manufactured by Anton Paar Co., Ltd.). The measurement was carried out at a temperature of 25 ° C, and the viscosity at a cone rotation speed of 50 rpm was used. The viscosity may also be expressed by shear viscosity, preferably at a shear rate of 1 s ^-1 and a paste viscosity of 0.5 Pa x s to 20 Pa x s. Further, it is more preferable that the viscosity of the paste at a shear rate of 1 s ^-1 is 10 Pa × s or less and the viscosity of the paste at a shear rate of 100 s ^-1 is 0.5 Pa × s or more.

Further, in the printing of the conductive pattern, screen printing is usually also used, but the screen printing is stencil printing. Therefore, if the viscosity is low, the paste flows and it is difficult to print as a pattern, so that it is used for gravure transfer. A conductive paste with a higher viscosity than a conductive paste. Usually, the conductive paste used in screen printing is often in a viscosity range of about 50,000 cP to 100,000 cP. When the conductive paste for screen printing is filled in the intaglio plate of the gravure transfer, the viscosity is too high, and it is difficult to transfer to the coating layer, and clogging occurs in the concave portion of the intaglio plate.

[Method for Producing Conductive Paste for Gravure Transfer] The method for producing the conductive paste for gravure transfer of the present invention is not particularly limited. First, a silver fine particle dispersion is prepared, and the silver fine particle dispersion is organic. The conductive paste for gravure transfer of the present invention can be obtained by mixing a solvent, a water-soluble polymer, and optionally the above various components.

As a method of preparing the silver fine particle dispersion, a method comprising the steps of: preparing a silver compound which can be decomposed to form silver by reduction, and a mixed solution with an amine; and a second step, by The silver compound in the mixed solution is reduced to form silver fine particles in which at least a part of the surface is attached with the amine.

In the first step, it is preferred to add 2 mol or more of an amine to 1 mol of silver. By setting the amount of the amine added to 2 mol or more with respect to 1 mol of silver, an appropriate amount of the amine can be attached to the surface of the silver fine particles formed by reduction, and the silver fine particles can be given a relative Excellent dispersibility and low temperature sinterability in a variety of dispersion media.

Further, it is preferable that the composition of the mixed liquid in the first step and the reducing conditions (for example, heating temperature and heating time) in the second step are such that the particle diameter of the obtained silver fine particles becomes The way the nano size is adjusted. The reason is that the particle diameter of the silver fine particles is set to a nanometer size, thereby causing a decrease in melting point and calcination at a low temperature. The particle diameter of the obtained silver fine particles is more preferably set to 1 nm to 200 nm. Micron sized particles may also be included as needed. The method of taking out the silver fine particles from the silver fine particle dispersion obtained in the second step is not particularly limited, and examples thereof include a method of washing the silver fine particle dispersion.

As the starting material for obtaining the silver fine particles of at least a part of the surface of the organic component coating, various well-known silver compounds can be used, for example, a hydrate of a silver salt or a silver salt can be used. Specific examples thereof include silver salts such as silver nitrate, silver sulfate, silver chloride, silver oxide, silver acetate, silver oxalate, silver formate, silver nitrite, silver chlorate, and silver sulfide. These are not particularly limited as long as they can be reduced, and they can be dissolved in a suitable solvent or used in a state of being dispersed in a solvent. In addition, these may be used alone or in combination. Among them, silver oxalate is preferred. Silver oxalate is the simplest silver dicarboxylate, and the silver oxalate amine complex synthesized by using silver oxalate is promoted at a low temperature for a short period of time, and thus is suitable for the synthesis of silver fine particles having a nanometer size. Further, when silver oxalate is used, only by-products are generated during the synthesis, and only carbon dioxide derived from oxalate ions is generated outside the system, so that the amount of purification is small after the synthesis.

As a method of reducing the silver compound, heating is preferred. The method of heating is not particularly limited. As a method of reducing the silver compound by the heating, for example, a method of heating a wrong compound produced by a silver compound such as silver oxalate or an organic component such as an amine may be mentioned. The metal compound such as the oxalate ion contained therein decomposes and agglomerates the generated atomic silver. According to the method, silver fine particles coated with a protective film of an organic component such as an amine can be produced.

As described above, in the metal amine complex decomposition method of producing silver fine particles coated with amine by thermally decomposing a compound of a silver compound in the presence of an amine, silveramine is used as a single molecule. Since the atomic silver is formed by the decomposition reaction of the compound, atomic silver can be uniformly formed in the reaction system, and the composition of the components constituting the reaction is shaken compared with the case where silver atoms are formed by the reaction between the various components. The resulting unevenness of the reaction is suppressed, especially when a large amount of silver powder is produced on an industrial scale.

Further, in the metal amine complex decomposition method, it is presumed that an amine molecule is coordinately bonded to the generated silver atom, and silver is formed by the action of an amine molecule located on the silver atom. The movement of the atom is controlled by the person. As a result, according to the metal amine complex decomposition method, metal particles having a very fine particle size and a narrow particle size distribution can be produced.

Further, on the surface of the produced silver microparticles, a large amount of amine molecules also generate a relatively weak force coordination bond, and these surfaces form a dense protective film on the surface of the silver microparticles, thereby producing a surface excellent in storage stability. Clean organic coated silver particles. Further, the amine molecules forming the coating film can be easily separated by heating or the like, so that silver fine particles which can be sintered at a very low temperature can be produced.

In addition, when a solid silver compound is mixed with an amine to form a composite compound such as a erroneous compound, the amine is mixed with a dispersant having an acid value with respect to the coating film constituting the silver fine particles, thereby compounding a compound such as a wrong compound. The formation of the compound becomes easy, and the compound can be produced by mixing for a short period of time. Further, by using the amine in combination, it is possible to produce coated silver fine particles having characteristics suitable for various uses.

In the dispersion liquid containing silver fine particles coated with an amine or a protective dispersant having an acid value obtained in the above manner, in addition to the silver fine particles, a counter ion of a metal salt, a dispersant, a residue of a reducing agent, and the like are also present. There is a tendency that the electrolyte concentration or the organic matter concentration of the liquid as a whole is high. The liquid in such a state is likely to cause segregation of metal particles and precipitation due to high electrical conductivity and the like. Alternatively, even if it does not precipitate, if the counter ion of the metal salt or the excess dispersant or the residue of the reducing agent required for the dispersion remains, the conductivity is deteriorated. Therefore, by washing the solution containing the silver fine particles to remove excess residue, silver fine particles coated with the organic component can be surely obtained.

As the cleaning method, for example, a method in which the following steps are repeated several times is carried out: a dispersion containing silver fine particles covering at least a part of the surface of the organic component is allowed to stand for a predetermined period of time, and after removing the supernatant, silver fine particles are added. The precipitated solvent (for example, water, methanol, methanol/water mixed solvent, etc.) is stirred, and allowed to stand for a certain period of time and the supernatant is removed. As another method, a method of performing centrifugation instead of the standing, a method of performing desalination by an ultrafiltration apparatus, an ion exchange apparatus, etc., etc. are mentioned. By removing such excess residue by such cleaning and removing the solvent, at least a part of the silver fine particles covering the surface of the organic component can be obtained.

The method of mixing the silver fine particle dispersion, the organic solvent, and the water-soluble polymer is not particularly limited, and it can be carried out by a conventionally known method using a stirrer or a stirrer. Stirring with a spatula or the like, or using an ultrasonic mixer of appropriate power.

[Method of Forming Conductive Pattern] Since the conductive paste for gravure transfer of the present invention is used, a fine conductive pattern can be formed by a gravure transfer method using a gravure. That is, another aspect of the present invention is also a method of forming a conductive pattern by using a gravure transfer method using a gravure on a printing surface having a concave portion filled with a conductive paste for gravure transfer. The width of the concave portion is 10 μm or less, and the conductive paste for gravure transfer is the conductive paste for gravure transfer of the present invention.

Hereinafter, a method of applying a conductive paste to the substrate 60 using a gravure transfer method will be described with reference to FIG. 1 . FIG. 1 is a conceptual diagram schematically showing an example of a gravure transfer method. As shown in FIG. 1, the printing apparatus 100 for gravure transfer is provided with the intaglio 40 and the coating layer 50. The gravure transfer printing apparatus 100 preferably further includes a pickup roller 20 for applying the gravure transfer conductive paste 10 to the intaglio plate 40 and a blade 30 for removing the remaining conductive paste 10.

The intaglio plate 40 has a concave portion 41 that fills the conductive paste 10 for gravure transfer on the printing surface. The width W of the concave portion 41 is 10 μm or less. By setting the width W of the concave portion 41 to 10 μm or less, a conductive pattern having a line width of 10 μm or less can be formed. The width W of the concave portion 41 is preferably 5 μm or less, more preferably 3 μm or less. By using the conductive paste for gravure transfer of the present invention, even if the intaglio plate having the width W of the concave portion 41 of 3 μm or less is used, a fine conductive pattern having a line width of 3 μm or less can be formed without being broken. The intaglio plate 40 may have a plate shape or a cylindrical shape.

The coating 50 preferably has an anthrone rubber layer. As the coating layer 50, for example, a Silblan series manufactured by Jinyang Co., Ltd., #700-STD manufactured by Fujikura Rubber Industries Co., Ltd., or the like can be used. The coating 50 may be in the form of a plate or a cylindrical shape.

The substrate 60 is not particularly limited as long as it has at least one main surface to which the conductive paste 10 for gravure transfer can be applied and which is baked by heating and is provided with a conductive pattern. It is a substrate excellent in heat resistance. In addition, the conductive paste for gravure transfer of the present invention can be obtained by heating and baking at a low temperature, and a conductive pattern having sufficient conductivity can be obtained as compared with the conventional conductive ink and the conductive paste. Thus, a substrate having a lower heat resistant temperature than previously can be used in a temperature range higher than the low calcination temperature.

Examples of the material constituting the substrate 60 include polyamide (PA), polyimide (PI), polyamide imide (PAI), and polyphenylene terephthalate. Polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyester, polycarbonate (polycarbonate, PC) ), polyether sulfone (PES), vinyl resin, fluororesin, liquid crystal polymer, ceramic, glass or metal. Further, the base material 60 may have various shapes such as a plate shape or a stripe shape, and may be rigid or flexible. The thickness of the substrate 60 can be suitably selected. A substrate on which a surface layer is formed or a substrate subjected to surface treatment such as hydrophilization treatment may be used for the purpose of improving adhesion or adhesion or other purposes.

The method for forming the conductive pattern preferably includes: a coating step of applying the conductive paste 10 for gravure transfer to the substrate 60; and a calcining step of transferring the intaglio plate applied to the substrate 60 The conductive paste 10 is printed and fired to form a conductive pattern.

Hereinafter, an example of the coating step will be described with reference to Fig. 1 . In Fig. 1, the arrows shown in the pickup roller 20, the intaglio 40, and the cladding 50 indicate the respective directions of rotation. Further, an arrow below the substrate 60 indicates a moving direction of the substrate 60. First, the conductive paste 10 is applied to the intaglio plate 40 by the pickup roller 20, and the remaining conductive paste 10 is removed by the blade 30, whereby the conductive paste 10 is filled in the intaglio plate. In the concave portion 41 of the printing surface of 40 ((a) in Fig. 1). Then, the conductive paste 10 filled in the concave portion 41 is transferred to the cladding layer 50 ((b) in Fig. 1). Thereafter, the conductive paste 10 transferred to the semi-solid/semi-liquid state (wet state or semi-dry state) of the cladding layer 50 is transferred to a substrate (adhered body) 60 (in FIG. 1 ( c)). By the above steps, the pattern reversed with respect to the printing pattern formed on the surface of the intaglio 40 is printed on the substrate 60.

When the fine line is printed by using the conductive paste 10, when the transfer from the gravure 40 to the cladding layer 50 and from the overcoat layer 50 to the substrate 60, transfer failure is likely to occur, but this is easy. Since the conductive paste for gravure transfer of the invention contains a water-soluble polymer, the conductive paste 10 transferred onto the cladding layer 50 is difficult to expand, and has sufficient adhesion to the substrate 60 and transferability. Therefore, for example, a conductive pattern having a line width of 10 μm or less, particularly a line width of 3 μm or less, can be formed without being broken.

After the conductive paste 10 is transferred onto the surface of the cladding layer 50 and left for a short time, the low boiling point solvent is volatilized and absorbed in the cladding layer 50, whereby the viscosity of the conductive paste 10 rises. On the other hand, the organic solvent constituting the conductive paste 10 for gravure transfer contains a second organic solvent containing a hydroxyl group and having a boiling point of 200 ° C or higher at normal pressure, and/or a second swelling ratio of the coating layer of 2.0% or less. In the case of the organic solvent, the absorption of the coating layer 50 by the organic solvent is reduced, so that the drying of the conductive paste 10 on the surface of the coating layer 50 can be greatly suppressed. Therefore, for example, a fine line conductive pattern having a line width of 3 μm or less can be more preferably formed.

The calcination temperature of the conductive paste in the calcination step is preferably less than 140 ° C, more preferably 120 ° C or less. By using the conductive paste for gravure transfer of the present invention, it is possible to form a conductive pattern having excellent conductivity even when calcined at a temperature of less than 140 ° C.

The method of performing the calcination is not particularly limited, and for example, a conventionally known gear oven or the like can be used. In the method for forming a conductive pattern of the present invention, since the conductive paste for gravure transfer of the present invention is used, it can be formed even when heated at a low temperature of less than 140 ° C (preferably 120 ° C or less). A highly conductive conductive pattern is produced. The lower limit of the calcination temperature is not necessarily limited, and is preferably a temperature at which a conductive pattern can be formed on a substrate, and the organic component or the like can be evaporated or decomposed without departing from the effects of the present invention. The temperature removed. It is also possible to retain a part in the range which does not impair the effect of this invention, and it is preferable to remove all. Since the method for forming a conductive pattern of the present invention can be heat-treated at a low temperature of about 120 ° C, a conductive pattern can be formed on a substrate that is relatively heat-resistant. Further, the calcination time is not particularly limited and may be appropriately adjusted depending on the calcination temperature.

In the present invention, it is basically unnecessary, but in order to further improve the adhesion between the substrate and the conductive pattern, the surface treatment of the substrate may be performed. Examples of the surface treatment method include a method of performing dry treatment such as corona treatment, plasma treatment, ultraviolet (UV) treatment, and electron beam treatment; and a primer layer is previously provided on the substrate. Or a method in which a conductive paste receives a layer or the like.

The film thickness of the conductive pattern after the firing step is, for example, 0.1 μm to 5 μm, preferably 0.1 μm to 1 μm. In the method for forming a conductive pattern of the present invention, the conductive paste for gravure transfer of the present invention is used. Therefore, a conductive pattern having sufficient conductivity even when the film thickness is about 0.1 μm to 5 μm can be obtained.

Further, the film thickness t of the conductive pattern can be measured by a laser microscope (for example, a laser microscope VK-9510 manufactured by Keyence Corporation). Further, the film thickness t of the conductive pattern can be obtained by the following formula. Formula: t=m/(d×M×w) m: Conductive pattern weight (measurement of the weight of the conductive pattern formed on the glass slide using an electronic balance) d: Conductive pattern density (g/cm ³ ) ( In the case of silver, it is 10.5 g/cm ³ ) M: Conductive pattern length (cm) (the conductivity pattern formed on the glass slide is measured on a scale equivalent to Japanese Industrial Standards (JIS) level 1 Length) w: Conductive pattern width (cm) (measuring the width of the conductive pattern formed on the glass slide at a scale equivalent to JIS level 1)

The volume resistivity of the conductive pattern obtained by the method for forming a conductive pattern of the present invention is preferably 110 μΩ·cm or less, more preferably 100 μΩ·cm or less, and still more preferably 50 μΩ·cm or less. The volume resistance value can be measured, for example, by the following method. First, a pattern of a conductive paste having a width of 1 mm and a length of 1.5 cm was formed on a PET substrate, and baked in a gear oven at 120 ° C for 30 minutes to form a film (conductive pattern) by sintering. Thereafter, the resistance value R of the coating film and the thickness t of the coating film were measured. The resistance value R of the film can be measured, for example, using a "digital multimeter PM-3" manufactured by Sanwa Electric Co., Ltd. The thickness t of the film can be measured, for example, using a shape measuring laser microscope "VK-X100" manufactured by Keyence Corporation. Based on the obtained value, the volume resistance value was converted based on the following formula (1). Formula (1): (volume resistance value ρv) = (resistance value R) × (film width w) × (film thickness t) / (inter-terminal distance L)

Moreover, an aspect of the present invention is also a method for producing a conductive substrate, in which a conductive pattern is drawn on a substrate by using the method for forming a conductive pattern of the present invention. As the substrate, the same ones as those described in the method for forming a conductive pattern of the present invention can be used. In the method for producing a conductive substrate of the present invention, the method for forming a conductive pattern using the conductive paste for gravure transfer of the present invention can be formed, for example, to have a line width of 10 μm or less, particularly a line width of 3 Thin wire conductive pattern of μm or less. Therefore, a conductive substrate having a precise electronic circuit can be manufactured. Examples of the conductive substrate include an electronic circuit board and the like. The conductive pattern is, for example, a wiring formed on an electronic circuit board or the like. [Examples]

Hereinafter, the present invention will be described in further detail by way of examples, but the invention is not limited to the examples.

<Synthesis Example 1> (Preparation of Silver Fine Particle Dispersion) 9.0 g of 3-methoxypropylamine (carbon number: 4) and 0.2 g of DISPERBYK as a polymer dispersing agent were added. 102 was mixed and thoroughly stirred by a magnetic stirrer to form an amine mixture. Then, 3.0 g of silver oxalate was added while stirring. After the addition of silver oxalate, the stirring was continued at room temperature, whereby silver oxalate was changed to a viscous white substance, and the stirring was completed at the time when the change was confirmed to be finished (first step).

The obtained mixed liquid was transferred to an oil bath, and heated and stirred at 120 °C. The reaction accompanying the generation of carbon dioxide is started immediately after the start of the stirring, and thereafter, the stirring is performed until the generation of carbon dioxide is completed, whereby a suspension in which the silver fine particles are suspended in the amine mixed liquid is obtained (second step).

In order to replace the dispersion medium of the suspension, 10 mL of a mixed solvent of methanol and water was added and stirred, and then the silver fine particles were precipitated and separated by centrifugation. Then, 10 mL of a mixed solvent of methanol and water was added to the separated silver fine particles, and the mixture was stirred and centrifuged to precipitate and purify the silver fine particles. The separated silver fine particles were dried at room temperature for 20 minutes to obtain a silver fine particle dispersion of Synthesis Example 1 in the form of a slurry.

The average particle diameter of the silver fine particles contained in the silver fine particle dispersion obtained in Synthesis Example 1 was 32 nm. The average particle diameter was obtained by diluting the obtained silver fine particle dispersion by a factor of 100 with a dispersion solvent, and using a particle diameter distribution measuring apparatus (Model: LB-550) manufactured by Horiba, Ltd., and calculating by a dynamic light scattering method. As a dispersion solvent, terpineol was used, and the refractive index of the solvent was measured and found to be 1.383.

<Example 1> A water-soluble polymer mixed solution obtained by dissolving 3.0 parts by weight of polyvinylpyrrolidone K30 as a water-soluble polymer in an organic solvent, which is 3.0 parts by weight of 2, 4, was prepared. 2-Diethyl-1,5-pentanediol (Kyowadiol PD-9) was mixed with 14.0 parts by weight of terpineol. In the case where the water-soluble polymer is difficult to dissolve, it may be heated as needed.

20 parts by weight of the aqueous solution polymer mixed solution was added to 80.0 parts by weight of the silver fine particle dispersion (nano silver) of Synthesis Example 1, and mixed by a stirring bar, and stirred using a rotation x revolution mixer, and then stirred. Defoaming was performed to obtain the conductive paste of Example 1.

<Example 2> The amount of the water-soluble polymer to be added was changed from 3.0 parts by weight of polyvinylpyrrolidone K30 to 3.0 parts by weight of polyvinylpyrrolidone to 80 parts by weight of the silver fine particle dispersion of Synthesis Example 1. A conductive paste of Example 2 was obtained in the same manner as in Example 1 except for K25.

<Example 3> In Example 3, as the silver fine particles, submicron-sized silver fine particles (sub-micron silver) having an average particle diameter of 0.3 μm (manufactured by Rare Metal Materials Research Institute, particle size distribution of 0.2 μm to 1.0 μm) were used. . As a water-soluble polymer mixed solution, 3.0 parts by weight of 2,4-diethyl-1,5-pentanediol (Kyowadiol PD-9) and 13.0 parts by weight of terpineol were used as an organic solvent to dissolve 3.0. Percent by weight of polyvinylpyrrolidone K30 as a water-soluble polymer, 0.5 part by weight of Crystasense MP as a thickener, and 0.5 part by weight of Sonopas as a polymer dispersant (SOLSPERSE) ) 41000 mixed solution. The conductive paste of Example 3 was obtained in the same manner as in Example 1 except that 20 parts by weight of the water-soluble polymer mixed solution was added to the above-mentioned submicron-sized silver fine particles.

<Example 4> As the silver fine particles, 60.0 parts by weight of the silver fine particle dispersion of Synthesis Example 1 and 20.0 parts by weight of the submicron-sized silver fine particles used in Example 3 (manufactured by Rare Metal Materials Research Co., Ltd.) were used. The particle size distribution is 0.2 μm to 1.0 μm). The conductive paste of Example 4 was obtained in the same manner as in Example 1 except that 20.0 parts by weight of the water-soluble polymer mixed solution prepared in Example 3 was added to 80.0 parts by weight of the silver fine particles.

<Example 5> In Example 5, an organic solvent obtained by mixing 3.0 parts by weight of 2,4-diethyl-1,5-pentanediol (Kyowadiol PD-9) and 14.0 parts by weight of terpineol was mixed. An organic solvent obtained by mixing 3.0 parts by weight of a 2-ethyl-1,3-hexanediol isomer mixture with 14.0 parts by weight of terpineol was used. The conductive paste of Example 5 was obtained in the same manner as in Example 1 except that 17.0 parts by weight of the mixed organic solvent was added to the silver fine particle dispersion of Synthesis Example 1 in an amount of 80.0 parts by weight.

<Example 6> In Example 6, an organic solvent having only a mixture of 2-ethyl-1,3-hexanediol isomers which was not mixed with terpineol was used. The same procedure as in Example 1 was carried out, except that the silver fine particle dispersion of Synthesis Example 1 was added in an amount of 17.0 parts by weight of the 2-ethyl-1,3-hexanediol isomer mixture. The conductive paste of Example 6.

<Example 7> The amount of the water-soluble polymer added was changed from 3.0 parts by weight to 7.0 parts by weight, and 3.0 parts by weight of 2,4-diethyl-1,5-pentanediol (Kyowadiol PD-9) was used. The conductive paste of Example 7 was obtained in the same manner as in Example 1 except that the organic solvent was mixed with 10.0 parts by weight of terpineol.

<Example 8> The amount of the water-soluble polymer added was changed from 3.0 parts by weight to 8.0 parts by weight, and 3.0 parts by weight of 2,4-diethyl-1,5-pentanediol (Kyowadiol PD-9) was used. The conductive paste of Example 8 was obtained in the same manner as in Example 1 except that the organic solvent was mixed with 9.0 parts by weight of terpineol.

<Comparative Example 1> In place of polyvinylpyrrolidone K30, 3.0 parts by weight of a polyvinylacetate acetal resin (polyvinylacetoacetal resin) which is not water-soluble (Skiyoshi Chemical Industry Co., Ltd., S-LEC) KS was added. In the same manner as in Example 1, except that the conductive paste of Comparative Example 1 was obtained.

<Comparative Example 2> In place of polyvinylpyrrolidone K30, 3.0 parts by weight of a polyvinyl butyral resin (S-LEC BL-1) which is not water-soluble is added, except for S-LEC BL-1. The conductive paste of Comparative Example 2 was obtained in the same manner as in Example 1 except the above.

<Comparative Example 3> A conductive paste of Comparative Example 3 was obtained in the same manner as in Example 1 except that 3.0 parts by weight of polymethyl methacrylate which is not water-soluble was added instead of the polyvinylpyrrolidone K30.

<Comparative Example 4> The same procedure as in Example 1 except that 3.0 parts by weight of a vinyl chloride-vinyl acetate copolymer (SOLBIN AL) which is not water-soluble was added instead of polyvinylpyrrolidone K30 The conductive paste of Comparative Example 4 was obtained.

<Comparative Example 5> The same procedure as in Example 1 except that 3.0 parts by weight of a vinyl chloride-vinyl acetate copolymer (SOLBIN M5) which is not water-soluble was added instead of the polyvinylpyrrolidone K30 The conductive paste of Comparative Example 5 was obtained.

<Comparative Example 6> The same operation as in Example 1 was carried out except that 3.0 parts by weight of a non-aqueous amorphous polyester resin (Vylon 200) was added instead of polyvinylpyrrolidone K30. However, Vylon 200 is not dissolved in the solvent, so that a conductive paste cannot be obtained.

<Comparative Example 7> 3.0 parts by weight of 2,4-diethyl-1,5-pentanediol (Kyowadiol) was added to 80.0 parts by weight of the silver fine particle dispersion of Synthesis Example 1 without adding a water-soluble polymer. A conductive paste of Comparative Example 7 was obtained in the same manner as in Example 1 except that an organic solvent obtained by mixing PD-9) with 17.0 parts by weight of terpineol was used.

[Lamination swelling ratio of organic solvent] The coating swelling ratio of the organic solvent used in the examples and the comparative examples was measured by the following method. In the measurement of the swelling ratio of the coating layer, the fluorenone coating layer used in the examples and the comparative examples (Silblan SP11-1 manufactured by Jinyang Co., Ltd. (rubber layer 0.6 mm, PET layer 0.25 mm) was used. )).

The coating was cut into 1 cm in length and 1 cm in width, and the weight was measured. Thereafter, the cut coating layer was completely immersed in various organic solvents (20 g) and allowed to stand for 10 hours. The impregnation was carried out at room temperature (25 ° C ± 5 ° C). After 10 hours, the coating layer was taken out from each organic solvent, and the adhered solvent was wiped off, and the weight of the coating layer after the immersion was measured within 1 minute to determine the weight increase rate before and after the immersion. The obtained value was defined as the coating swelling ratio. The boiling points of the respective organic solvents and the measured swelling ratio of the coating layer are shown in Table 1 below.

[Table 1]

[Evaluation Test] For the conductive pastes obtained in the above Examples and Comparative Examples, (1) dispersibility, (2) dilutableness, (3) printability under gravure transfer, and (4) adhesion were evaluated. Sex. Further, the volume resistivity of (5) was measured for the conductive pattern formed of the conductive paste. The results of the respective evaluation tests are shown in Tables 2 and 3 below. Further, in the printing suitability of the following (3), the following (3) expansion of the conductive pattern in the printability is performed with respect to the examples and the comparative examples in which the conductive patterns having the width of 3 μm or 5 μm are formed. (4) Adhesion and (5) Evaluation of volume resistance value.

(1) Dispersibility The conductive paste was diluted twice with a dispersing solvent (terpineol) and left to stand in a container, and allowed to stand at room temperature for one day. Thereafter, the presence or absence of the precipitate and the supernatant were visually observed. The state of the liquid was used to evaluate the dispersibility of the conductive paste. The case where the sediment was not recognized substantially under the container was evaluated as "○", and the case where a small amount of sediment was recognized was evaluated as "△", and the difference in concentration between the upper and lower sides of the container was clearly observed and the sediment was clearly recognized. The evaluation is "X".

(2) Dilution The conductive paste was diluted 100-fold with a dispersion medium (terpineol), and the dispersibility immediately after the dilution (initial) and the dispersibility after leaving at room temperature for one week were visually evaluated. The case where no aggregation or silver mirror was observed was evaluated as "○", and a part of the aggregation or silver mirror was observed as "△", and the case where aggregation/precipitation occurred was evaluated as "x".

(3) Printing suitability The printing suitability evaluation was carried out by the following method using a simple gravure conversion method using a manual printing machine. As the intaglio plate, a first intaglio plate provided with a plurality of concave portions having a width of 3 μm and a depth of 5 μm, and a second intaglio plate provided with a plurality of concave portions having a width of 5 μm and a depth of 5 μm were prepared. A gravure (first intaglio) having a width of 3 μm and a gravure (2 gravure) having a width of 5 μm in the concave portion are all used in "Platar Platinum plating intaglio" manufactured by Think Laboratory Co., Ltd. "."

The conductive pastes of the examples and the comparative examples were filled in the recesses of the first intaglio and the second intaglio by a doctor blade, and then pressed against a rubber roller wound with an anthrone coating to make a desired The pattern is transferred to the coating. Thereafter, the coating film on the coating layer was pressed against a single PET film (thickness: 100 μm), transferred, and printed to produce a printed pattern (printed wiring) having a line width of about 3 μm and 5 μm. As the fluorenone coating layer, Silblan SP11-1 (rubber layer 0.6 mm, PET layer 0.25 mm) manufactured by Jinyang Co., Ltd. was used.

The linearity of the wire (conductive pattern) was particularly excellent, and the case where the wire was not broken was evaluated as "◎", and the linearity of the wire was excellent, and the one without the broken portion was evaluated as "○", and the linearity of the wire was poor but not broken. The line portion was evaluated as "△", and the line having poor linearity and the broken portion was evaluated as "x". In addition, the extension of the line (conductivity pattern) is set to "○", the extension of the slightly existing line is set to "△", and the extension of the existing line and the significant thick line are set to "×". .

(4) Adhesion test The adhesion was evaluated by a pull-off method. A tape (Cellotape) (registered trademark) was attached to the printed wiring on the PET substrate used for the printability evaluation, and was evaluated by the fracture state at the time of tearing. Specifically, the tape was strongly rubbed against the five portions of the printed wiring, and was strongly pulled in the vertical direction to be evaluated. The case where the number of pieces of the tape which has been peeled off from the printed wiring is 0 to 1 is "○", the case of 2 to 3 is "△", and the case of 4 to 5 is " X", even if it is partial peeling instead of full peeling, it is set as a peeler and counts into one piece.

(5) The volume resistivity was transferred by gravure, and the conductive paste obtained in the examples and the comparative examples was used to form a pattern of a conductive paste having a width of 1 mm and a length of 1.5 cm on the PET substrate, and The film was formed by calcination in a gear oven at 120 ° C for 30 minutes to form a film (conductive pattern). The resistance value R of both ends of the film was measured using a "digital multimeter PM-3" manufactured by Sanwa Electric Co., Ltd. Further, the thickness t of the coating film was measured using a shape measuring laser microscope "VK-X100" manufactured by Keyence Corporation. Thereafter, the volume resistance value is converted based on the distance between the measurement terminals and the thickness t of the coating film based on the following formula (1). When the volume resistance value is 50 μΩ·cm or less, it is evaluated as “◎”, and when it exceeds 50 μΩ·cm and 100 μΩ·cm or less, it is evaluated as “○”, and it is more than 100 μΩ·cm and 110 μΩ·cm or less. The case was evaluated as "△", and the case of exceeding 110 μΩ·cm was evaluated as "x". The results are shown in Tables 2 and 3. Formula (1): (volume resistance value ρv) = (resistance value R) × (film width w) × (film thickness t) / (inter-terminal distance L)

[Table 2]

[table 3]

The conductive pastes of Examples 1 to 8 were excellent in dispersibility and dilution. Further, when the conductive pastes of Examples 1 to 8 were used, a conductive pattern having a width of 3 μm can be formed by gravure transfer. Further, in the first embodiment, the second embodiment, and the fifth embodiment to the eighth embodiment, only the silver fine particles of the nanometer size were used, but the printability was high. However, according to the results of the third and fourth examples, it was found that not only the nanometer Silver microparticles of a size, and submicron-sized silver microparticles, alone or in combination with nano-sized and sub-micron-sized silver microparticles, can also be printed with a conductive pattern having a narrow line width. In Example 8, in which the amount of the water-soluble polymer added was 8 parts by weight, the volume resistance value was slightly increased, but fine line printing was possible. Further, according to the results of Example 6, it was found that, as the organic solvent, even if the terpene-based solvent is not used, the fine fibers can be formed only by the diol solvent, and therefore the number of hydroxyl groups of the organic solvent does not become a problem.

On the other hand, according to the results of Comparative Example 1 to Comparative Example 6, it was found that in the resin agent having no water solubility other than polyvinylpyrrolidone, in the thin line printing having a line width of 3 μm or less, the conductive film could not be transferred. Sex paste. Further, according to Comparative Example 7, it was found that when the resin agent was not added, the conductive pattern was remarkably generated at the time of printing, and printing was impossible even with a desired line width.

10‧‧‧ Conductive paste for gravure transfer

20‧‧‧ Pickup Roller

30‧‧‧blade

40‧‧‧gravure

41‧‧‧ recess

50‧‧‧laying

60‧‧‧Substrate (adhesive body)

100‧‧‧Gravure printing device

W‧‧‧Width

FIG. 1 is a conceptual diagram schematically showing an example of a gravure transfer method.

Claims (8)

A conductive paste for gravure transfer, comprising: silver fine particles, an organic solvent, and a water-soluble polymer, wherein the silver fine particles have an average particle diameter of 1 μm or less. The conductive paste for gravure transfer according to the first aspect of the invention, wherein the water-soluble polymer contains a polymerizable compound having a cyclic structure. The conductive paste for gravure transfer according to the first or second aspect of the invention, wherein the water-soluble polymer contains polyvinylpyrrolidone. The conductive paste for gravure transfer according to any one of claims 1 to 3, wherein the content of the water-soluble polymer is 3% by weight based on the entire conductive paste. ～8% by weight. The conductive paste for gravure transfer according to any one of claims 1 to 4, wherein the organic solvent contains a first organic solvent having a hydroxyl group and having a boiling point of 200 ° C or higher at normal pressure. . The conductive paste for gravure transfer according to any one of the items 1 to 5, wherein the organic solvent contains 3.0% by weight to 30% by weight based on the entire conductive paste. The coating layer has a swelling ratio of 2.0% or less of the second organic solvent. A method of forming a conductive pattern, wherein the intaglio plate has a concave portion filling a conductive paste for gravure transfer on a printing surface by a gravure transfer method using a gravure, and the width of the concave portion is 10 μm or less. The conductive paste for gravure transfer is a conductive paste for gravure transfer according to any one of the first to sixth aspects of the invention. A method for producing a conductive substrate, characterized in that a conductive pattern is drawn on a substrate by using a method of forming a conductive pattern according to claim 7 of the patent application.