CN101036199A - Conductive ink - Google Patents

Abstract

An object of the invention is to provide a conductive metal ink having an excellent adhesion to various kinds of substrates such as a glass substrate, and making it possible to form fine wiring or electrodes. Another object is to provide a conductive ink which can be used for ink jet printing system etc. For the purpose of achieving the objects, ''a conductive ink comprising a solvent, a metal powder, and an adhesion improver, which is characterized in that the adhesion improver is one or mixture selected from the group consisting of a silane coupling agent, a titanium coupling agent, a zirconium coupling agent, and an aluminum coupling agent.'' is adopted. Furthermore, a surface tension of the solvent is adjusted to be in the range of 15 mN/m to 50 mN/m with a surface tension adjustor to provide conductive ink suitable for ink jet printing system etc.Disclosed is a conductive metal ink which has excellent adhesion to various bases such as glass substrates and enables formation of fine wiring or electrodes. Also disclosed is a conductive ink which can be used in inkjet systems. Specifically disclosed is a conductive ink containing a solvent, a metal powder and an adhesion improver which is characterized in that the adhesion improver is composed of one or more substances selected from the group consisting of silane coupling agents, titanium coupling agents, zirconia coupling agents and aluminum coupling agents. By adjusting the surface tension of the solvent to be within the range from 15 mN/m to 50 mN/m using a surface tension regulator, the conductive ink is formed into an ink which can be suitably used in inkjet systems or the like.

Description

conductive ink

technical field

The present invention relates to a method for forming a circuit using conductive metal ink, and more specifically, to a method capable of forming a high-density metal substrate at a low temperature on a ceramic substrate, a glass substrate, and a resin substrate represented by a polyimide substrate. Metallic ink for wiring or electrodes and method for producing the same. At the same time, it relates to a conductive ink capable of forming a circuit on a substrate by drawing and curing a circuit shape by an inkjet method or the like.

Background technique

Conventionally, as methods for forming circuit patterns on various substrates, there have been photolithographic printing or etching methods or screen printing methods described in Patent Document 1 or Patent Document 2. As a conventional method, the copper foil of the copper-clad laminate is etched to form a circuit pattern, or a conductive paste is mixed with a metal powder and a solvent or resin to form a paste (paste) and printed on the surface of the substrate by screen printing. A method of directly forming wiring or electrode patterns is widely used. As described above, a method in which a metal powder is processed into a paste (hereinafter, simply referred to as conductive paste) or ink (hereinafter, simply referred to as conductive ink), and a circuit is directly formed on the surface of a substrate by transferring a technique such as a screen printing method Compared with the etching method of etching the copper foil of the copper-clad laminate to form the circuit, it has been widely used because it has fewer steps and can significantly reduce the production cost.

In addition, in recent years, the density of conductive circuit patterns inside thin displays represented by portable intelligence devices or TVs has increased year by year. Not only has the area with a wiring width of 40 μm or less been studied, but also research has been conducted on flexible resin substrates by low-temperature sintering. A technique for forming circuit patterns. In a commonly used circuit pattern formed by screen printing, the line width is about 100 μm without interruption and the wiring shape is excellent, but it is difficult to form a finer region, especially a region with a line width of 40 μm or less. Substantial wiring. In addition, as a technique for forming circuit patterns on various substrates by low-temperature sintering, there is a silver ink containing silver nanoparticles as disclosed in Patent Document 3.

On the other hand, regarding a liquid paste (hereinafter referred to as conductive metal ink) in which metal powder is mixed with a large amount of organic solvents and resins, as a coating method using a dispenser (dispenser) or as described in Patent Document 4 As a raw material for forming extremely fine circuit patterns in inkjet printing technology, various conductive metal inks have been proposed, but since the adhesion strength to various substrates depends on organic resins, they are generally used to form low-resistance wiring Or in the process of reduction sintering using hydrogen or nitrogen in the electrode, the gas generated due to the decomposition of the organic resin component tends to generate microscopic cracks, and thus the bulk density of wiring or electrodes becomes low, and as a result it is difficult to form a low resistance circuit.

In addition, as the composition of the conductive ink, Patent Document 5 discloses a water-based nickel paste, and a conductive paste containing the water-based nickel paste and a binder. The aqueous nickel slurry contains water, nickel particle powder with insoluble inorganic oxide fixed on the particle surface of each particle nickel powder, polyacrylic acid and its ester or its salt, and ammonium hydroxide substituted by organic groups. This water-based nickel paste is a water-based nickel paste in which the high-concentration nickel particle powder does not aggregate and is stably dispersed. Although there is no problem in calcining metal powder by high-temperature sintering, as represented by the internal electrodes of laminated ceramic capacitors, However, in applications where circuits are formed on various substrates at low temperatures in recent years, there has been a problem that circuits cannot be formed because the adhesion strength to the substrates is substantially zero.

In addition, when using inkjet printing technology to form a very fine circuit pattern, because it does not have the surface tension suitable for printing, when the circuit is formed by continuous printing, the ink is easy to clog the nozzle, and the phenomenon that the ink does not appear on the target printing position, so , it is substantially difficult to form circuits by industrial continuous printing. In addition, because it does not contain a binder that imparts adhesive strength to the substrate, even if it can be printed on the substrate through the printing process for a while, since the adhesive strength to the substrate is substantially zero, it is suitable for producing internal electrodes of laminated ceramic capacitors It is substantially difficult to form a circuit except for applications such as calcined metal powder, which is represented by high-temperature sintering.

Patent Document 1: JP Unexamined Patent Publication No. 9-246688

Patent Document 2: JP Unexamined Patent Publication No. 8-18190

Patent Document 3: JP Unexamined Publication No. 2002-334618

Patent Document 4: JP-A-2002-324966

Patent Document 5: JP Unexamined Publication No. 2002-317201

Contents of the invention

The problem to be solved by the invention

As can be understood from the above, in order to form the above-mentioned fine circuit at low temperature, the dispenser coating method or inkjet printing method using conductive metal ink has been studied, but there are problems of low adhesion to various substrates, Or don't get the attachment problem at all. As a result, it cannot be used in the inkjet method, either.

In conventional conductive metallic inks, organic resin components are used as binders to improve adhesion to substrates. Therefore, when circuits are printed on resin substrates such as ceramics, glass, and polyimide, at 300°C When the reduction sintering is carried out at the following low temperature, the resin components contained in it are decomposed and vaporized due to heat or the influence of reducing gas, and as a result, high adhesion strength with various substrates cannot be obtained.

As described above, the conductive ink is required to have excellent adhesion to a substrate and to be able to form fine wiring or electrodes. At the same time, the conductive ink is required to be a conductive ink that can print extremely fine wiring or electrodes on the substrate using an inkjet device and a dispenser device, and can be printed continuously when forming a circuit. Adhesion of circuits, etc. to substrates.

Solution to the problem

Therefore, as a result of earnest research, the present inventors have found that the above object can be achieved if a conductive ink containing a solvent, a metal powder, and an adhesion enhancer is used, and completed the present invention.

The basic composition of the conductive ink of the present invention is to contain solvent, metal powder, adhesion enhancer, it is characterized in that, above-mentioned adhesion enhancer is selected from the group consisting of silane coupling agent, titanium coupling agent, zirconium coupling agent, aluminum coupling agent One or more of the group.

In addition, the surface tension of the above-mentioned solvent is adjusted to a range of 15 mN/m to 50 mN/m by using a surface tension modifier to make the conductive ink suitable for use in inkjet printers.

In addition, it is preferable that the above-mentioned surface tension modifier is a surface tension modifier that is a combination of one or more selected from the group consisting of alcohols and diols having a boiling point of 100° C. to 300° C. under normal pressure.

Furthermore, in the conductive ink of the present invention, it is preferable that the above-mentioned solvent is one or two or more selected from the group consisting of water, alcohols, and saturated hydrocarbons whose boiling point under normal pressure is 300° C. or lower.

In the conductive ink of the present invention, the metal powder is preferably selected from nickel powder, silver powder, gold powder, platinum powder, copper powder, and palladium powder, and the primary particle diameter of the metal powder is 500 nm or less.

Furthermore, in consideration of the application of the conductive ink of the present invention to an inkjet printer, it is preferable that the aggregated particles contained in the above metal powder have a maximum particle diameter of 0.8 μm or less.

In the conductive ink of the present invention, it is preferable that the metal powder is an inorganic oxide-plated nickel powder having an insoluble inorganic oxide adhered to the surface of the powder particle.

In the conductive ink of the present invention, it is preferable that the above-mentioned insoluble inorganic oxide coated with inorganic oxide nickel powder is an oxide containing at least one element selected from the group consisting of silicon dioxide, aluminum oxide, zirconium oxide, and titanium oxide. .

In the conductive ink of the present invention, it is preferable to add as a dispersant ( A substance obtained by combining any one or two or more of any group of a) to (c).

In addition, considering the application of the conductive ink of the present invention to an inkjet printer, it is preferable that its viscosity at 25° C. is 60 cP or less.

The effect of the invention

The conductive ink of the present invention is excellent in adhesion to various substrates including glass substrates, and can form fine wiring or electrodes. Adhesion to circuits and the like formed of different elements Also excellent. Therefore, this conductive ink can be suitably used for forming a protective electrode or a protective coating on a glass substrate used in a TFT panel, an ITO transparent electrode surface, a circuit surface formed with a silver paste, or the like. In addition, the conductive film of the present invention is also suitable for forming accurate and fine wiring or electrodes by a dispenser coating method or an inkjet printing method.

The best solution for implementing the present invention

The conductive ink of the present invention contains a solvent, a metal powder, and an adhesion enhancer. Furthermore, the present invention is characterized in that one or a combination of two or more selected from the group consisting of silane coupling agents, titanium coupling agents, zirconium coupling agents, and aluminum coupling agents is used as the adhesion enhancer.

The adhesion enhancer mentioned here means to use a substance selected from the group consisting of a silane coupling agent, a titanium coupling agent, a zirconium coupling agent, and an aluminum coupling agent. In this case, not only one component selected from the above group may be used, but a combination of two or more components may be used. That is, by containing a plurality of components, it is possible to control the adhesiveness according to the properties of the substrate on which circuits and the like are formed.

The silane coupling agent mentioned here is preferably vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-Glycidoxypropyltrimethoxysilane, 3-Glycidoxypropylmethyldiethoxysilane, 3-Glycidoxypropyltriethoxysilane, p-Styryl Trimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyl Diethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2(aminoethyl)-3-aminopropylmethyl Dimethoxysilane, N-2(aminoethyl)-3-aminopropyltrimethoxysilane, N-2(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyl Trimethoxysilane, 3-aminotriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-amino Propyltrimethoxysilane, N-(ethylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloro Propyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyl Triethoxysilane, Tetramethoxysilane, Tetraethoxysilane, Methyltrimethoxysilane, Methyltriethoxysilane, Dimethyltriethoxysilane, Phenyltriethoxysilane, Any silane coupling agent among hexamethyldisilazane, hexyltrimethoxysilane, and decyltrimethoxysilane. Among them, it is preferable to use methyltrimethoxysilane, methyltriethoxysilane, dimethyltriethoxysilane, or the like that exhibit stable performance from the viewpoint of stable adhesion to the substrate.

The titanium coupling agent mentioned here is preferably tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetrakis (2-ethylhexyl) titanate, tetramethyl Among titanate, titanium acetylacetonate, titanium tetraacetylacetonate, titanium ethyl acetoacetate, titanium octane dioleate, titanium lactate, titanium triethanolamine compound, polyhydroxy titanium stearate Any titanium silane coupling agent. Among them, tetraisopropyl titanate, tetra-n-butyl titanate, titanium lactate, and the like that exhibit stable performance are preferably used from the viewpoint of stable adhesion to the substrate.

The zirconium coupling agent mentioned here is preferably zirconium n-propionate, zirconium n-butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium diacetylacetonate, zirconium monoethylacetoacetate Any zirconium coupling agent among zirconium esters, zirconium acetylacetonate diethylacetoacetate, zirconium acetate, and zirconium monostearate. Among them, zirconium n-propionate, zirconium n-butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium diacetylacetonate, zirconium monoethyl acetonate exhibiting stable performance are preferably used from the viewpoint of stable adhesion to the substrate. Acetoacetate, Zirconium Acetylacetonate Diethylacetoacetate, Zirconium Acetate.

The aluminum coupling agent mentioned here is preferably aluminum isopropoxide, mono-sec-butoxy aluminum diisopropionate, aluminum sec-butyrate, aluminum acetate, ethyl acetoacetate aluminum diisopropionate, aluminum tri( Ethyl Acetoacetate), Aluminum Alkyl Acetoacetate Diisopropionate, Aluminum Monoacetylacetonate Bis(Ethyl Acetoacetonate), Aluminum Tris(Acetoacetonate), Aluminum Monoisopropoxy Monooleyl Alcohol Any aluminum coupling agent among ethyl ethyl acetoacetate, cyclic aluminum oxide isopropionate, cyclic aluminum oxide octanoate, and cyclic aluminum oxide stearate. Among them, it is preferable to use ethyl acetoacetate aluminum diisopropionate, aluminum tris(ethyl acetoacetate), and alkyl acetoacetate aluminum diisopropionate, which exhibit stable performance, from the viewpoint of stable adhesion to the substrate. Propionate, Aluminum Monoacetylacetonate Bis(Ethyl Acetoacetate), Aluminum Tris(Acetylacetonate).

Next, the solvent will be described. The solvent used in the present invention can widely use water, organic solvents, etc., and is not particularly limited as long as it is compatible with at least the above-mentioned adhesion enhancer, as long as a predetermined paste viscosity can be prepared. Therefore, if it is limited, it is one or a combination of two or more of the group consisting of water, alcohols, and saturated hydrocarbons whose boiling point under normal pressure is 300° C. or lower.

Here, it is limited to "the boiling point under normal pressure is 300°C or less", because in the temperature region where the boiling point exceeds 300°C, sticking occurs in the reduction sintering process with the conductive ink using an organic resin component as the binder resin. Just like the binder resin is decomposed and vaporized, the solvent is vaporized at high temperature, so a dense electrode cannot be formed, and as a result, high adhesion strength to various substrates cannot be exhibited.

When water is used as a solvent, it is water having a degree of purity such as ion-exchanged water, distilled water, etc., and water having a degree of purity such as tap water is not included.

When alcohols are used as the solvent, it is preferable to use one selected from 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, cyclohexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-Decanol, Glycidyl Alcohol, Benzyl Alcohol, Methylcyclohexanol, 2-Methyl-1-Butanol, 3-Methyl-2-Butanol, 4-Methyl-2-Pentanol, Iso Propanol, 2-ethylbutanol, 2-ethylhexanol, 2-octanol, terpineol, dihydroterpineol, 2-methoxyethanol, 2-ethoxyethanol, 2-n-butyl One or a combination of two or more of oxyethanol, 2-phenoxyethanol, carbitol, ethyl carbitol, n-butyl carbitol and diacetone alcohol. Among them, it is more preferable to use 1-butanol, 1-octanol, terpineol, dihydroterpineol, and 2-methoxyethanol, which have a boiling point of 80° C. or higher at normal pressure and are difficult to vaporize at room temperature and normal pressure. , 2-ethoxyethanol, 2-n-butoxyethanol, diacetone alcohol.

When using saturated hydrocarbons as a solvent, it is preferable to use one selected from heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane a combination of two or more. Among them, decane, undecane, dodecane, tridecane, and tetradecane are more preferably used. This is because they have a boiling point of 300° C. or lower at normal pressure and are difficult to vaporize at room temperature where the vapor pressure is low, and thus are easy to handle.

The conductive ink as described above can be imparted with the surface tension most suitable for the inkjet method by using a surface tension modifier. That is, by adjusting the surface tension of the conductive ink of the present invention in the range of 15 mN/m to 50 mN/m, it becomes easy to form a circuit by an inkjet method or a dispenser method. Therefore, the addition amount of the surface tension regulator described later is such that the surface tension of the conductive ink is adjusted to 15 mN/m to 50 mN/m, preferably 20 mN/m to 40 mN/m by adding various additives. If the surface tension of the conductive ink exceeds the above range, the conductive ink cannot be discharged from the inkjet nozzle, or even if it can be discharged from the nozzle, it will be displaced from the target printing position, or continuous printing will not be possible. Therefore, by adjusting the surface tension of the conductive ink of the present invention within the above-mentioned range suitable for the use of the inkjet method, fine circuit wiring and the like can be formed using the inkjet device.

When considering the surface tension of the above-mentioned conductive ink, there is a problem of the combination of the solvent and the surface tension modifier. Therefore, first, a description will be given of a solvent in consideration of adjusting the surface tension. In consideration of the solvent for adjusting the surface tension, only an organic solvent may be used or water may be contained. When water is used as a solvent, water having a purity such as ion-exchanged water, distilled water, etc., but water having a purity such as tap water may be used.

In addition, the solvent is not particularly limited as long as it is compatible with at least the above-mentioned water, dispersant, and adhesion enhancer when mixed with water and an organic solvent, and a predetermined ink viscosity can be prepared. At this time, when water is 100 parts by weight, about 3 parts by weight to 5000 parts by weight of an organic solvent and the like are mixed to carefully adjust the viscosity of the conductive ink, the dispersibility of the metal powder, and the like. In particular, it is required to select and use it in consideration of the combination with the type of metal powder used. Therefore, if the organic solvent and the like are limited, it is one or a combination of two or more of the group consisting of water, alcohols, and glycols having a boiling point of 100° C. to 300° C. under normal pressure.

It is limited here to "the boiling point at normal pressure is 100°C to 300°C", because in the temperature range where the boiling point exceeds 300°C, the conductive ink using an organic resin component as a binder resin will cause damage in the reduction and sintering process. Just like the binder resin decomposes and vaporizes, the solvent vaporizes at high temperature, so a dense electrode cannot be formed, and as a result, high adhesion strength to various substrates cannot be exhibited. In addition, it is set at 100° C. or higher because this temperature is higher than the boiling point of water, and it is possible to select a heating temperature range in which the removal of water necessarily contained in the solvent is reliably possible.

When alcohols are used as solvents, it is preferred to use alcohols selected from 1-butanol, 1-pentanol, glycidyl alcohol, benzyl alcohol, 3-methyl-2-butanol, 4-methyl-2-pentanol, 2 -Methoxyethanol, 2-ethoxyethanol, 2-n-butoxyethanol, 2-phenoxyethanol, carbitol, ethyl carbitol, n-butyl carbitol, diacetone alcohol One or two or more combinations. Among them, it is more preferable to use 1-butanol, 1-pentanol, 2-methoxyethanol, 2-ethoxyethanol, 2- n-Butoxyethanol, 2-phenoxyethanol, diacetone alcohol.

When glycols are used as the solvent, it is preferable to use a solvent selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, trimethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, Alcohol, 1,3-butanediol, 1,4-butanediol, pentylene glycol, hexanediol or a combination of two or more. Among them, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and trimethylene glycol having a viscosity of 100 cp or less at room temperature are more preferably used. If the viscosity is too high, it will be difficult to adjust to a viscosity suitable for the dispenser method or the inkjet method.

In addition, as the above-mentioned surface tension modifier, an additive having a surface tension of 40 mN/m or less is used. When a surface tension modifier having the above-mentioned surface tension is used, it is easiest to adjust the surface tension to be suitable for the ink used in the inkjet device, and the viscosity adjustment conforming to the design of the inkjet device can become simple and easy. Fine wiring circuits can be formed. The surface tension modifier mentioned here is preferably one selected from the group consisting of alcohols and diols whose surface tension is 40 mN/m or less and whose viscosity at 25° C. is 100 cp or less, and which can also be used as solvents. Combination of two or more substances.

Among the surface tension modifiers, alcohols having a surface tension of 40 mN/m or less and a viscosity of 100 cp or less at 25°C include, for example, 1-butanol, 1-pentanol, 4-methyl-2- Pentanol, 2-ethoxyethanol, 2-n-butoxyethanol, n-butyl carbitol and the like. In the present invention, it is preferable to use 2-n-butoxyethanol or 1-butanol among the above-mentioned surface tension modifiers from the viewpoint of maintaining the long-term quality stability of the conductive ink.

In the conductive ink of the present invention, the amount of the surface tension regulator to be blended is not particularly limited as long as it is an amount suitable for adjusting the surface tension of the conductive ink. However, generally in conductive ink, it is usually 1% by weight to 50% by weight, preferably 3% by weight to 30% by weight. When the amount of the surface tension regulator is less than 1% by weight, the surface tension cannot be adjusted. In addition, when the addition amount of the surface tension regulator is more than 50% by weight, the dispersion form of the particulate metal powder contained in the conductive ink changes greatly before and after the addition of the surface tension regulator, and as a result, the particulate metal powder begins to agglomerate. It prevents the uniform dispersion of the most important particulate metal powder in conductive ink, so it cannot be used as conductive ink.

In addition, the metal powder mentioned here is not particularly limited in its particle size, dispersibility and other powder properties, and the powder particle shape includes all concepts of spherical shape, flake shape, and powder particles with a surface coating layer. However, the conductive ink of the present invention is mainly premised to be used for circuit formation of electronic materials. Therefore, it is conceivable to select from nickel powder, silver powder, gold powder, platinum powder, copper powder, and palladium powder that are often used in electronic material applications, and the primary particle diameter of the metal powder is 500 nm or less.

Furthermore, considering use in an inkjet method, it is preferable that the average primary particle diameter is 500 nm or less. If the average particle diameter of the primary particles exceeds 500 nm, the conductive ink is extremely likely to clog the inkjet nozzles, making continuous printing difficult. Even if printing is possible, the film thickness of the formed wiring or electrode is too thick, and the intended fine wiring cannot be achieved.

Furthermore, depending on the degree of refinement of the circuit to be formed, it is only necessary to select a fine particle metal powder having an appropriate primary particle size. However, from the concept of the fine particle metal powder, it is usually selected and used in the range of 3 nm to 500 nm, preferably 5 nm to 200 nm, more preferably 10 nm to 150 nm. When the average primary particle diameter of the fine metal powder is less than 3 nm, the production method cannot be established at present, and it cannot be verified by experiments. On the other hand, when the average primary particle size exceeds 500 nm, it is difficult to form the intended wiring or electrode with a width of 40 μm or less, and the film thickness of the formed wiring or electrode is too thick, which is not suitable. In general, the finer the average primary particle size of the fine metal powder, the less likely it is to cause clogging of inkjet nozzles, and the more suitable it is for the formation of fine circuits. The average primary particle diameter in the present invention refers to the particle diameters of at least 200 powder particles included in the observation field of view when observed with a scanning electron microscope, and the particle diameter is obtained by accumulatively averaging the above particle diameters.

Although the average primary particle size of particulate metal powder is small, it will become the basis of so-called fine powder particles. However, even if it is a fine particle, the particles in the conductive ink will also aggregate. , it is still easy to cause clogging of inkjet nozzles. Therefore, it is necessary to control the agglomerated particles, which are the secondary structure of the fine metal powder in the conductive ink, to a size that does not cause clogging of the inkjet nozzles. This size has been confirmed in experiments, that is, if the agglomerated particles When the maximum particle size is adjusted to be 0.8 μm or less, clogging of the inkjet nozzles can be almost certainly prevented. In addition, as a method of confirming the aggregated particles, a laser particle size distribution measuring device is used.

In addition, when considering the time-dependent changes and sintering characteristics of conductive inks, metal powders that have been surface-treated with oleic acid, stearic acid, etc., or plated oxide powders with predetermined oxides attached to the surface of the powder particles can be used. etc., as long as they are selected and used in consideration of the characteristics required for conductive inks. Among them, considering the use of nickel powder in the conductive ink of the present invention, inorganic oxide-plated nickel powder having an insoluble inorganic oxide attached to the surface of the powder is preferable.

In addition, among the insoluble inorganic oxides adhering to the surface of the nickel powder coated with inorganic oxide, silica, alumina, zirconia, titania, palladium titanate, calcium zirconate, etc. can be used, among which, it is preferable to use An oxide containing one or two or more elements selected from the group consisting of silica, alumina, zirconia, and titania. Among them, silica is more preferable because it is particularly easy to adhere stably to the surface of the nickel powder.

Various methods can be used to form the insoluble inorganic oxide layer on the surface of the nickel powder. For example, a method of immobilizing the insoluble inorganic oxide on the surface of the nickel powder can be adopted by putting nickel powder, powdery insoluble inorganic oxide and medium (substance similar to zirconia beads) into a mixer and stirring.

In addition, as a method for attaching insoluble inorganic oxides on the surface of nickel powder particles, after dispersing nickel powder and insoluble inorganic oxides in water, drying treatment is used to remove water, so that the insoluble inorganic oxides are deposited on the nickel powder particles. method of surface attachment. In this case, the average primary particle diameter of the insoluble inorganic oxide is preferably 0.2 times or less, preferably 0.15 times or less, the average primary particle diameter of the particles constituting the nickel powder. The adhesion of the insoluble inorganic oxide particles on the surface of the nickel powder particles tends to adhere more uniformly as the particle diameter of the insoluble inorganic oxide particles becomes smaller.

When using the oxide-plated nickel powder in the present invention, the amount of insoluble inorganic oxides attached to the surface of the nickel particles is generally 0.05% by weight to 10% by weight, preferably 0.1% by weight to 100% by weight when the weight of nickel is taken as 100% by weight. 5% by weight, more preferably 0.5% by weight to 2% by weight. When the amount of the insoluble inorganic oxide is less than 0.05% by weight, the life extension of the conductive ink in the meaning of providing an oxide plating layer cannot be obtained. In addition, when the amount of the insoluble inorganic oxide exceeds 10% by weight, the oxide coating becomes thick, forming an uneven coating on the particle surface, which loses smoothness and causes unwanted viscosity. The above-mentioned more suitable range can more reliably achieve the meanings of the above-mentioned upper limit and lower limit in the industrial production process.

As described above, the use of oxide-plated nickel powder can effectively prevent re-aggregation even if nickel powder is contained in a high concentration in the conductive ink, so that the life of the conductive ink can be extended.

Furthermore, it is preferable to add a dispersant to the conductive ink of the present invention, particularly nickel ink, if necessary. As the dispersant, it is preferable to add (a) to (c) selected from (a) polyacrylic acid, its ester or its salt; (b) ammonium hydroxide substituted with an organic group, and (c) an amine compound containing a hydroxyl group. Any combination of one or two or more substances.

As (a) polyacrylic acid, its ester or its salt used in the present invention, for example, polyacrylic acid, polymethyl acrylate, sodium polyacrylate, ammonium polyacrylate can be mentioned, wherein, because ammonium polyacrylate is on the surface of metal particles Coordination is easy, and at the same time, coordinated ammonium polyacrylate suppresses aggregation of metal particles in a solvent by electric repulsion and steric hindrance effects, so it is preferable. In (a) of the present invention, one of the above-mentioned substances may be used alone or a combination of two or more kinds thereof may be used.

Examples of the (b) organic group-substituted ammonium hydroxide used in the present invention include alkyl-substituted ammonium hydroxide such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide, and trimethylammonium hydroxide. Alkyl-substituted aryl-substituted ammonium hydroxides such as methylphenylammonium hydroxide and benzyltrimethylammonium hydroxide, among them, because the alkyl-substituted ammonium hydroxide is easy to coordinate on metal particles, and at the same time, the electric repulsion force High and preferred. (b) of the present invention may be used alone or in combination of two or more of the above-mentioned substances.

Examples of the (c) hydroxyl-containing amine compound used in the present invention include alkanolamines, among which dialkanolamines such as dimethanolamine, diethanolamine, and dipropanolamine, and metal particles Excellent wettability is preferable, and diethanolamine is more preferable because it is most likely to suppress aggregation of metal particles over time. (c) in the present invention may be used alone or in combination of two or more of the above substances.

In the present invention, re-agglomeration of nickel powder particles in the ink is prevented by adding the above-mentioned dispersant to the conductive nickel ink. The dispersant used in the present invention may be at least one of the above (a) to (c), and among them, if (a) and (c) are used together, the nickel powder can be dispersed more stably, so it is preferable .

When "polyacrylic acid, its ester or its salt" is present in the conductive ink of the present invention, the amount of "polyacrylic acid, its ester or its salt" is usually 0.05 to 5 parts by weight relative to 100 parts by weight of the metal powder , preferably 0.1 to 2 parts by weight, at this time, the adhesion of the ink to the substrate is not damaged, and the life of the ink is the longest.

When "organic group-substituted ammonium hydroxide" exists in the conductive ink of the present invention, the amount of "organic group-substituted ammonium hydroxide" is usually 0.01 to 5 parts by weight relative to 100 parts by weight of metal powder, preferably It is 0.05 parts by weight to 1 part by weight. At this time, the adhesion of the ink to the substrate is not damaged, and the life of the ink is the longest.

When the "hydroxyl-containing amine compound" exists in the conductive ink of the present invention, the amount of the "hydroxyl-containing amine compound" is usually 0.5 to 20 parts by weight, preferably 5 to 20 parts by weight, relative to 100 parts by weight of nickel. 15 parts by weight, at this time, the adhesion of the ink to the substrate is not damaged, and the life of the ink is the longest.

In the case of using a combined dispersant in the conductive ink of the present invention, in the presence of "polyacrylic acid, its ester or its salt" and "organic group-substituted ammonium hydroxide", relative to 100 parts by weight of "polyacrylic acid, its ester or its salt", ester or its salt", the amount of "organic group substituted ammonium hydroxide" is usually 1 to 30 parts by weight, preferably 5 to 20 parts by weight, at this time, the adhesion of the ink to the substrate will not be damaged, and the ink longest lifespan.

The viscosity of the conductive ink will be described. In the present invention, it is preferable that the viscosity of the conductive ink at 25° C. is 60 cp or less in order to facilitate circuit formation by the inkjet method or the dispenser method. The viscosity adjustment of the present invention is achieved by optimally blending the above-mentioned solvent, dispersant, and oxide-plated metal powder. The reason why the lower limit of the viscosity is not described in the present invention is that the places and purposes used for circuit formation of each metal conductive ink are different, and the desired size and shape of wiring and electrodes are also different. If the viscosity at 25°C exceeds 60cp, even if you want to form fine wiring or electrodes by inkjet method or dispenser method, since the viscosity of the conductive ink is higher than the energy of ejecting the conductive ink from the nozzle, therefore, It is difficult to eject conductive ink droplets stably from the nozzles. When the viscosity at 25° C. is 60 cp or less, it has been found through experiments that fine wiring or electrodes can be formed by the inkjet method or the dispenser method.

Hereinafter, although an Example is shown, this invention is not limited to this explanation. First, in Examples 1 to 4, examples mainly for evaluating the adhesion between the base material and the formed conductive film are described.

Example 1

(nickel powder)

In this example, oxide-plated nickel powder was used as the nickel powder. The production method of this oxide-plated nickel powder is as follows.

Into the container that capacity is 20L, inject 10L pure water, while stirring with the stirring speed of 200rpm, add 4000g nickel powder (manufactured by Mitsui Metal Mining Co., Ltd., NN-100, the average particle diameter of primary particle is 100nm) while slowly adding, stir After 20 minutes, 200 g, 20% by weight of colloidal silica (manufactured by Nissan Chemical Industries, Ltd., Snowtex 0, the average particle diameter of primary particles is 20 nm) was added thereto, and stirring was continued for 20 minutes to obtain a dispersion liquid.

Next, in order to uniformly blend the colloidal silica into the nickel powder in the dispersion liquid, a high-speed emulsification disperser T.K.filmix (manufactured by Tokuki Kagaku Kogyo Co., Ltd.) was used for continuous mixing treatment to obtain a uniform colloidal silica Slurry mixed with nickel. Next, using a vacuum dryer, the slurry was dried for 24 hours at a vacuum degree of 50 Torr or less and a temperature in the dryer of 120°C for 24 hours to obtain a dry powder in which silica was fixed on the particle surface of the nickel powder. Next, the dry powder was pulverized using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and then classified and sieved using a 20 μm sieve to remove coarse particles. Next, in order to improve the adhesion between the silicon dioxide present on the surface of the nickel particles of the powder passing through the 20 μm sieve and the surface of the nickel particles, a vacuum drying machine is further used under the condition that the vacuum drying degree is 10 Torr or less and the temperature inside the dryer is 150°C. The heat treatment was carried out for 24 hours to obtain silica-plated nickel powder (hereinafter referred to as "nickel powder A"). This nickel powder A is a nickel powder in which silica adheres to the particle surface of nickel fine particles.

(Dispersant)

Add 380 g of diethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.), 45.6 g of a 44% ammonium polyacrylate solution (manufactured by Wako Pure Chemical Industries, Ltd.) and 13.4 g of 15% tetramethyl An ammonium solution (manufactured by Wako Pure Chemical Industries, Ltd.) was stirred with an electromagnetic stirrer to prepare a dispersant (hereinafter referred to as dispersant A).

(preparation of conductive ink)

Add 0.7 L of pure water as a solvent to a container with a capacity of 1 L, while stirring at a stirring speed of 200 rpm, slowly add 300 g of nickel powder A, then add 40.3 g of dispersant A, and stir for 20 minutes to obtain a slurry.

Next, this slurry was subjected to continuous dispersion treatment using a high-speed emulsification disperser T.K.filmix (manufactured by Tokuki Kagaku Kogyo Co., Ltd.), and then 0.96 L of pure water was added to obtain a slurry having a nickel concentration of 15% by weight.

Next, particles of 1 μm or more contained in the slurry were removed by passing through a cartridge filter (manufactured by Advantec Toyo Co., Ltd., MCP-JX-E10S, with an average pore diameter of 1 μm or less), and further to remove particles of 0.8 μm The above particles were filtered with a mixed cellulose ester type membrane filter A065A293C (manufactured by Advantec Toyo Co., Ltd., average pore size: 0.65 μm) to obtain a filtrate (nickel paste A).

(preparation of conductive ink)

65.8 g of titanium lactate (manufactured by Matsumoto Junyaku Kogyo Co., Ltd. TC-315) was added to the nickel paste A as an adhesion enhancer, and stirred at a stirring speed of 200 rpm for 30 minutes to obtain a conductive ink (conductive ink A).

(Electrode Formation and Evaluation)

The conductive ink A was coated on a square alkali-free glass substrate OA-10 (manufactured by NEC Glass Co., Ltd.) having a length of 4 cm at a rotation speed of 2000 rpm using a spin coater. Next, the coated glass substrate was reduced and sintered at 300° C. for 2 hours in a hydrogen-helium mixed gas atmosphere with a hydrogen content of 2% by volume to form a nickel electrode film on the glass substrate. The electrode thickness measured by SEM observation was about 1 μm. The specific resistance of the nickel electrode film was measured with a four-probe resistance measuring machine Loresta GP (manufactured by Mitsubishi Chemical Corporation), and in accordance with JIS K 5600 paragraphs 5-6, the adhesion to the glass substrate was evaluated by a cross cut method. . The measured specific resistance was 3.8×10 ^-3 Ω·cm, and the evaluation of the adhesion was classified as 0, showing good adhesion. In addition, the above-mentioned nickel electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes, and as a result, peeling off of the nickel electrode film was not observed at all.

(Formation and evaluation of fine electrodes)

A dispenser coating device (manufactured by Musashi Engineering Co., Ltd.) was joined to a nozzle whose inner diameter at the tip of the nozzle was processed to be 25 μm, so that the conductive ink could be continuously coated. Using this apparatus, conductive ink A was applied to a square alkali-free glass substrate OA-10 (manufactured by NEC Glass Co., Ltd.) with a length of 4 cm to form a nickel electrode film. Next, the glass substrate was subjected to reduction sintering at 300° C. for 2 hours in a hydrogen-helium mixed gas atmosphere with a hydrogen content of 2% by volume to form a nickel electrode film on the glass substrate. The width of the electrode measured with a microscope was about 40 μm. In addition, the obtained nickel electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes, and when observed with a microscope, no peeling of the nickel electrode film was observed.

Example 2

A conductive ink (conductive ink B) was obtained in the same manner as in Example 1 except that the aminosilane coupling agent KBE-903 (manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of titanium lactate, and a nickel electrode film was obtained using a spin coater. For the nickel electrode film, the specific resistance was measured and the adhesion was evaluated in the same manner as in Example 1. The specific resistance was 4.5×10 ^-3 Ω·cm, and the evaluation of adhesion was classified as 0, showing good adhesion. In addition, the above-mentioned nickel electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes. As a result, peeling off of the nickel electrode film was not observed at all. Next, in the same manner as in Example 1, a fine nickel electrode film was formed on the glass substrate by the dispenser coating method. The width of the electrode measured with a microscope was about 40 μm. In addition, the obtained nickel electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes, and when observed with a microscope, no peeling of the nickel electrode film was observed.

Example 3

Except that the substrate on which the nickel electrode film is formed is replaced by a glass substrate with an ITO film (manufactured by Mitsui Metal Mining Co., Ltd., the thickness of the ITO film is 0.2 μm), the same operation as in Example 1 is carried out, and the coating method is applied by a dispenser. A fine nickel electrode film is formed on a glass substrate with an ITO film. The width of the electrode measured with a microscope was about 40 μm. In addition, the obtained nickel electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes, and when observed with a microscope, no peeling of the nickel electrode film was observed.

Example 4

Except that the substrate on which the nickel electrode film is formed is replaced with a copper-clad laminate (manufactured by Mitsui Metal Mining Co., Ltd., the thickness of the copper foil is 35 μm), the same operation as in Example 1 is carried out, and the copper-clad layer is coated by a dispenser coating method. A fine nickel electrode film is formed on the press plate. The width of the electrode measured with a microscope was about 40 μm. The obtained nickel electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes. When observed with a microscope, no peeling of the nickel electrode film was observed.

Hereinafter, Examples 5 to 7 in which a conductive ink is adjusted for viscosity, and a circuit is formed using an inkjet printer and evaluated are described.

Example 5

(Preparation of microparticle metal powder)

In this example, inorganic oxide fine particle nickel powder was used as the fine particle metal powder. Hereinafter, the preparation of inorganic oxide fine particle nickel powder plating is demonstrated. In the container that capacity is 20L, inject 10L pure water, on the one hand, stir with the stirring speed of 200rpm, add 4000g nickel powder (Mitsui Metal Mining Co., Ltd. manufacture, NN-100, the average particle diameter of primary particle is 100nm) on the one hand, After stirring for 20 minutes, 200 g, 20% by weight of colloidal silica (manufactured by Nissan Chemical Industries, Ltd., Snowtex 0, the average particle diameter of primary particles is 20 nm) was added thereto, and stirring was continued for 20 minutes to obtain a dispersion.

Next, in order to uniformly blend the colloidal silica into the nickel powder in the dispersion liquid, a high-speed emulsification disperser T.K.filmix (manufactured by Tokuki Kagaku Kogyo Co., Ltd.) was used for continuous mixing treatment to obtain a uniform colloidal silica Slurry mixed with nickel. Next, use a vacuum dryer to dry the slurry for 24 hours under the conditions of a vacuum degree of 50 Torr or less and a temperature in the dryer of 120°C to obtain a dry product in which silica is fixed on the particle surface of the nickel powder. powder. Next, the dry powder was pulverized using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and then classified and sieved using a 20 μm sieve to remove coarse particles. Next, in order to improve the adhesion between the silicon dioxide present on the surface of the nickel particles of the powder passing through the 20 μm sieve and the surface of the nickel particles, a vacuum drying machine is further used under the condition that the vacuum drying degree is 10 Torr or less and the temperature inside the dryer is 150°C. The heat treatment was carried out for 24 hours to obtain silica-coated nickel powder (hereinafter referred to as "nickel powder"). This nickel powder is a nickel powder in which silica adheres to the particle surface of nickel fine particles.

(Dispersant)

Add 380 g of diethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.), 45.6 g of a 44% ammonium polyacrylate solution (manufactured by Wako Pure Chemical Industries, Ltd.) and 13.4 g of 15% tetramethyl Ammonium solution (manufactured by Wako Pure Chemical Industries, Ltd.) was stirred with an electromagnetic stirrer to prepare a dispersant.

(preparation of aqueous nickel paste)

Add 0.7 L of pure water as a solvent to a container with a capacity of 1 L, and slowly add 300 g of the above-mentioned nickel powder while stirring at a stirring speed of 200 rpm, then add 40.3 g of a dispersant, and stir for 20 minutes to obtain a slurry.

Next, this slurry was subjected to continuous dispersion treatment using a high-speed emulsification disperser T.K.filmix (manufactured by Tokuki Kagaku Kogyo Co., Ltd.), and then 0.96 L of pure water was added to obtain a slurry having a nickel concentration of 15% by weight.

Next, particles of 1 μm or more contained in the slurry were removed by passing through a cartridge filter (manufactured by Advantec Toyo Co., Ltd., MCP-JX-E10S, with an average pore diameter of 1 μm or less), and further to remove particles of 0.8 μm The above particles were filtered with a mixed cellulose ester type membrane filter A065A293C (manufactured by Advantec Toyo Co., Ltd., average pore size: 0.65 μm) to obtain a filtrate (hereinafter referred to as "aqueous nickel slurry").

(preparation of conductive ink)

To the above-mentioned aqueous nickel slurry, 188.9 g of 2-n-butoxyethanol (manufactured by Kanto Chemical Co., Ltd., surface tension 28.2 mN/m) was added as a surface tension regulator to the filtrate, and stirred at a stirring speed of 200 rpm for 30 minutes , Then add 65.8g of titanium lactate (TC-315 manufactured by Matsumoto Junyaku Industries Co., Ltd.) as an adhesion enhancer, and stir with a stirring speed of 200rpm for 30 minutes to obtain a conductive ink (hereinafter referred to as "conductive ink A "). The surface tension of the conductive ink A measured with a dynamic contact angle measuring device (manufactured by EI AND DAY Co., Ltd., DCA-100W) was 32.5 mN/m, and was measured with a vibrating viscometer (manufactured by CBC Materials Co., Ltd. , VM-100A) measured viscosity at 25°C is 10.8cP.

(evaluation of printability)

For the conductive ink A, a wiring pattern (circuit width and The distance between the circuits was 100 μm and the length was 2 cm), and as a result, the conductive ink A could be printed without clogging the inkjet nozzles. Moreover, it can print more than 50 times continuously. After 50 consecutive printings, in order to check whether the nozzles were clogged, a nozzle check pattern was printed, and as a result, no clogging of the nozzles was found. In addition, when the obtained wiring pattern was observed with an optical microscope, no disconnection or ink scattering was observed on the wiring pattern, and it was a good wiring pattern.

(Evaluation of electrical conductivity)

Next, on a square glass substrate with a length of 4 cm, a square film with a length of 3 cm was produced by using the above-mentioned inkjet printer. Heat treatment was performed for 2 hours to obtain an electrode film. The specific resistance of this electrode film was measured with a four-probe resistance measuring machine Loresta GP (manufactured by Mitsubishi Chemical Corporation), and found to be 1.8×10 ^-3 Ω·cm.

(evaluation of adhesion)

Next, in accordance with JIS K 5600 paragraphs 5-6, the adhesion of the electrode film produced above to the glass substrate was evaluated by a cross cut method. As a result of the evaluation of the adhesiveness, the classification was 0, and the adhesiveness was good. In addition, the electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes. As a result, peeling off of the nickel electrode film was not observed at all. The above-mentioned performance evaluation results and the like are shown in Table 1 together with other Examples and Comparative Examples.

Example 6

In this example, except that 89.5 g of 1-butanol (manufactured by Kanto Chemical Co., Ltd., with a surface tension of 24.9 mN/m) was added as a surface tension regulator instead of 2-n-butoxyethanol, the same procedure as in Example 5 was carried out. This was carried out to obtain a conductive ink (hereinafter referred to as "conductive ink B"). The surface tension of this conductive ink B was 41.8 mN/m, and the viscosity at 25° C. was 10.5 cP.

Hereinafter, it carried out similarly to Example 5, and when producing a wiring pattern, the conductive ink B could be printed without clogging an inkjet nozzle. And it can be printed more than 50 times continuously.

In addition, when the obtained wiring pattern was observed with an optical microscope, no disconnection or ink scattering was observed on the wiring pattern, and it was a good wiring pattern. In addition, an electrode film was produced in the same manner as in Example 1, and the measured specific resistance was 2.3×10 ^-2 Ω·cm. Moreover, when the adhesiveness of the said electrode film was evaluated similarly to Example 5, classification|category 0 was obtained, and it had favorable adhesiveness. In addition, the electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes. As a result, peeling off of the electrode film was not observed at all. The above-mentioned performance evaluation results and the like are shown in Table 1 together with other Examples and Comparative Examples.

Example 7

In this example, inorganic oxide fine particle silver powder was used as the fine particle metal powder. The preparation of the inorganic oxide microparticle-plated silver powder will be described below. Inject 10L of pure water into a container with a capacity of 20L, while stirring at a stirring speed of 200rpm, slowly add 4000g of fine particle silver powder (manufactured by Mitsui Metal Mining Co., Ltd., the average primary particle diameter is 0.3 μm), after stirring for 20 minutes, 200 g, 20% by weight of colloidal silica (manufactured by Nissan Chemical Industries, Ltd., Snowtex 0, average particle diameter of primary particles: 20 nm) was added thereto, and stirring was continued for 20 minutes to obtain a dispersion liquid.

Next, in order to uniformly blend colloidal silicon dioxide into the fine particle silver powder in the dispersion liquid, a high-speed emulsification disperser T.K.filmix is used for continuous mixing treatment to obtain a slurry in which colloidal silicon dioxide is uniformly blended in the fine particle silver powder . Next, use a vacuum dryer to dry the slurry for 24 hours at a temperature of 50°C and a vacuum of 50 Torr or less in the dryer to obtain a dry powder in which silica is fixed on the particle surface of the fine-grained silver powder. . Next, the dry powder was pulverized using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and then classified and sieved using a 20 μm sieve to remove coarse particles. Next, in order to improve the adhesion between the silicon dioxide present on the surface of the silver particles of the powder passing through the 20 μm sieve and the surface of the silver particles, a vacuum dryer is further used, and the vacuum degree is 10 Torr or less, and the temperature in the dryer is 70 ° C. The heat treatment was carried out under the conditions for 24 hours to obtain silica-plated silver powder (hereinafter referred to as "silver powder"). This silver powder is the silver powder which adhered the silicon dioxide on the particle surface of silver microparticles|fine-particles.

Add 0.7 L of pure water as a solvent to a container with a capacity of 1 L, and slowly add 300 g of the above-mentioned silver powder while stirring at a stirring speed of 200 rpm, then add 40.3 g of a dispersant, and stir for 20 minutes to obtain a slurry.

Next, this slurry was continuously dispersed using a high-speed emulsification disperser T.K.filmix (manufactured by Tokuki Kagaku Kogyo Co., Ltd.), and then 0.96 L of pure water was added to obtain a slurry with a silver concentration of 15% by weight.

Next, particles of 1 μm or more contained in the slurry were removed using the same cartridge filter and mixed cellulose ester membrane filter as in Example 5 to obtain a filtrate (hereinafter referred to as "aqueous silver slurry").

Then, to the above-mentioned aqueous silver paste, add 188.9 g of 2-n-butoxyethanol as a surface tension regulator relative to the filtrate, stir for 30 minutes at a stirring speed of 200 rpm, and then add 65.8 g of titanium lactate as an adhesion enhancer , and then stirred at a stirring rate of 200 rpm for 30 minutes to obtain a conductive ink (hereinafter referred to as "conductive ink C"). The measured surface tension of the conductive ink C was 34.8 mN/m, and the viscosity at 25° C. was 10.8 cP.

Next, a wiring pattern was prepared in the same manner as in Example 5, and as a result, the conductive ink C could be printed without clogging the inkjet nozzles. Moreover, it can print more than 50 times continuously.

In addition, when the obtained wiring pattern was observed with an optical microscope, no disconnection or ink scattering was observed on the wiring pattern, and it was a good wiring pattern. In addition, an electrode film was produced in the same manner as in Example 5, and the measured specific resistance was 3.5×10 ^-4 Ω·cm. In addition, the adhesion of the electrode film was evaluated in the same manner as in Example 1, and the evaluation result of the adhesion was classified as 0, indicating good adhesion. In addition, the electrode film was ultrasonically cleaned in water for 10 minutes, and then in acetone for 10 minutes. As a result, peeling off of the electrode film was not observed at all. The above-mentioned performance evaluation results and the like are shown in Table 1 together with other Examples and Comparative Examples.

Comparative example 1

A conductive ink D (hereinafter, referred to as "conductive ink D") was obtained in the same manner as in Example 5 except that the addition of 2-n-butoxyethanol was omitted. In addition, the surface tension of the conductive ink D was 53.1 mN/m, and the viscosity at 25° C. was 10.4 cP. When the wiring pattern was prepared in the same manner as in Example 5, the inkjet nozzles were clogged after the conductive ink D was printed five times, and continuous printing was not possible. In addition, when the wiring pattern was observed with an optical microscope, disconnection was observed on the wiring pattern, and a good wiring pattern could not be obtained.

In addition, although an attempt was made to produce an electrode film in the same manner as in Example 5, the wettability to the glass substrate was poor, and the electrode film could not be formed. The above performance evaluation results and the like are shown in Table 1 together with other examples.

Table 1 Example 5 Example 6 Example 7 Comparative example 1 metal powder nickel nickel silver nickel adhesion enhancer Titanium Lactate Titanium Lactate Titanium Lactate Titanium Lactate surface tension regulator 2-n-Butoxyethanol 1-butanol 2-n-Butoxyethanol none Surface Tension mN/m 32.5 41.8 34.8 53.1 viscosity CP 10.8 10.5 10.8 10.4 Inkjet printing experiment clogging of inkjet nozzles none none none have Disconnection of wiring none none none have Electrode film characteristics Resistance value of electrode film 1.8×10 ^-3 2.3×10 ^-2 3.5×10 ^-4 Electrode film cannot be made Adhesion (JIS K5600) Category 0 Category 0 Category 0 Electrode film cannot be made

Industrial Utilization Possibility

The conductive ink of the present invention is a conductive metal ink that has excellent adhesion to various substrates and can form fine wiring or electrodes. In addition, the conductive ink of the present invention is suitable for use in forming fine wiring or electrodes on a substrate using an inkjet method or a dispenser method. This conductive metallic ink has excellent adhesion to various substrates and can form fine wiring or electrodes by using additives such as an adhesion enhancer even when an inkjet method is used. Therefore, a circuit can be formed on a glass substrate, or a wiring, an electrode, a protective circuit, or a protective film can be formed on a circuit formed using silver paste or copper paste, or a transparent electrode using ITO, or the like. Therefore, it can be used in the manufacturing process of liquid crystal displays and the like. As described above, there is no conductive ink on the market that can print fine wiring or electrodes using a dispenser device or an inkjet device, and can ensure adhesion to various substrates, so that the conductive ink of the present invention can be obtained. Widespread use by leaps and bounds.

Claims (10)

1. conductive ink, it contains solvent, metal powder, tack reinforcing agent, it is characterized in that, and above-mentioned tack reinforcing agent is to be selected from the group of being made up of silane coupling agent, titanium coupling agent, zirconium coupling agent, aluminium coupling agent one or more.

2. conductive ink according to claim 1 is characterized in that, uses surface tension modifier that the surface tension of above-mentioned solvent is adjusted into 15mN/m～50mN/m.

3. conductive ink according to claim 2, wherein, above-mentioned surface tension modifier is 100 ℃～300 ℃ alcohol, one or more surface tension modifier that combined in the group that glycol is formed for being selected from by the boiling point under the normal pressure.

4. according to any described conductive ink in the claim 1～3, it is characterized in that above-mentioned solvent is that being selected from by the boiling point under the normal pressure is in the group formed of water, alcohols, saturated hydrocarbons below 300 ℃ one or more.

5. according to any described conductive ink in the claim 1～4, wherein, above-mentioned metal powder is selected from nickel powder, silver powder, bronze, platinum powder, copper powder, palladium powder, and the primary particle diameter of this metal powder is below the 500nm.

6. conductive ink according to claim 5, wherein, the maximum particle diameter of the aggregated particle that contains in the above-mentioned metal powder is below the 0.8 μ m.

7. according to any described conductive ink in the claim 1～6, wherein, above-mentioned metal powder is for being attached with the plating inorganic oxide nickel powder of insoluble inorganic oxide on its powder surface.

8. conductive ink according to claim 7 is characterized in that, above-mentioned insoluble inorganic oxide is to contain the oxide that is selected from least a element in the group of being made up of silicon dioxide, aluminium oxide, zirconia and titanium oxide.

9. according to any described conductive ink in the claim 1～9, wherein, interpolation will be selected from (a) polyacrylic acid, its ester or its salt as dispersant; (b) one or more materials that combined of any group in (a)～(c) of the ammonium hydroxide that replaces of organic group and the amines that (c) contains hydroxyl.

10. according to any described conductive ink in the claim 1～9, wherein, the viscosity of this conductive ink in the time of 25 ℃ is below the 60cP.