JP5939386B2 - Conductive ink composition - Google Patents

Description

  The present invention relates to a conductive ink composition, and more specifically, when a conductive pattern is formed on a polymer film substrate such as PET or a transparent conductive film substrate such as ITO, a high substrate regardless of the type or surface state of the substrate. Conductive ink composition suitable for mass production of patterns having adhesion and low specific resistance, and electronic component mounting body, electric circuit wiring body, electromagnetic wave absorber, light reflection made using the conductive ink composition It is about the body.

  In recent years, portable information terminals have become widespread among electric and electronic devices, but with the increase in functionality, the weight tends to increase due to the increase in device size. For this reason, there is a strong demand from the market to reduce the weight of portable information terminals. In addition, due to weight reduction and design properties, as the portable information terminal is made thinner, glass used for a display, a sensor, or the like is broken at the time of dropping, which is a problem in terms of durability. As means for solving these problems, adoption of materials having high impact resistance has been promoted by reviewing parts constituting the portable information terminal, but it has not yet reached a fundamental solution. Therefore, conversion of conventional printed circuit boards and glass substrates to materials such as a polymer film having excellent flexibility and a light weight has been promoted among materials constituting portable information terminals.

  In order to use a polymer film substrate for a portable information terminal, it is necessary to form electrical wiring on the surface of the polymer film. The electrical wiring pattern formed on the surface of the polymer film is required to be able to form a fine circuit pattern in addition to high conductivity, adhesion to the substrate, and flexibility.

  Examples of a method for forming a conductive circuit pattern on a polymer film substrate include plating / electroless plating methods and vapor deposition methods such as sputtering. However, since the plating / electroless plating method uses a large amount of a solvent, the cost of treating the waste liquid increases. In addition, a vapor deposition method such as sputtering not only requires a large-scale apparatus, but also requires an unnecessary portion to be removed by etching after vapor deposition over the entire surface of the substrate, resulting in high costs overall.

As another pattern forming method, there is a method using a baking type or heat curing type conductive ink or paste.
The former type is a curing mechanism in which the solvent and the binder component are generally removed by heating at a high temperature of 200 ° C. or higher and the conductive fine particles are sintered or brought into contact with each other. The latter type is a curing mechanism in which a thermosetting resin is used as a binder component and is retained in a cured product, and conductive fine particles are brought into conduction by being brought into contact with each other. Since the former has only a conductive particle component in the cured product, a low specific resistance can be achieved. However, for the same reason, there is no chemical bond at the interface between the cured product and the substrate, and the adhesion tends to be low. In particular, low adhesion is remarkable for materials having a low surface tension such as ITO.

As a method for improving the adhesion at the interface, 1) Modification of the substrate surface (ultraviolet irradiation, corona discharge, plasma, sanding treatment), 2) primer coating, 3) adhesion effect by adding an additive to the conductive ink There are ways to make it appear.
However, active adoption is avoided because 1) increases the number of manufacturing processes, and 2) becomes an organic insulating layer, resulting in failure to obtain conductivity.

  Various proposals have been made for the method 3). For example, as a substance responsible for adhesion imparting, there may be mentioned a method of adding a resin such as urethane, epoxy, phenol, or a adhesion imparting agent having an acidic group or a basic group. For example, there are a method of blending an epoxy compound (Patent Document 1), a method of improving adhesion with a carboxylic acid contained in a dispersant for conductive fine particles (Patent Document 2), and the like. Further, a method of adding a silane coupling agent, a titanium coupling agent, or the like (Patent Document 3) has been proposed.

  However, in these prior examples, there is no report that it adheres to a substrate having a remarkably low surface tension such as ITO. In order to achieve adhesion to a low surface tension substrate, a technique (patent document 4) has been proposed in which the surface is modified by plasma ashing or the like to aim at the anchor effect. However, such a method has a demerit of an increase in the manufacturing process.

JP2010-168445A JP 2006-193594 A JP 2006-348160 A JP 2001-281435 A

  An object of the present invention is to provide a conductive ink composition that enables high adhesion and low specific resistance regardless of the type of transparent film, transparent conductive film, and the like.

The present invention provides a composition that solves the above problems,
A composition (A) containing conductive fine particles (a-1) and a solvent (a-2);
A conductive ink composition comprising a monomer component (B) having a functional group and having a surface tension of 29 mN / m or less,
The monomer component (B) having a functional group is 4 to 8 parts by weight with respect to 100 parts by weight of the composition (A),
Conductive ink having an absolute value of the difference in solubility parameter (SP value) between the composition (A) and the monomer component (B) having a functional group in the range of 0 to 1.7 (cal / cm ³ ) ^1/2. A composition is provided.

Item 1. A composition (A) containing conductive fine particles (a-1) and a solvent (a-2);
A conductive ink composition comprising a monomer component (B) having a functional group and having a surface tension of 29 mN / m or less,
The monomer component (B) having a functional group is 4 to 8 parts by weight with respect to 100 parts by weight of the composition (A),
The absolute value of the difference in solubility parameter (SP value) between the composition (A) and the monomer component (B) having a functional group is in the range of 0 to 1.7 (cal / cm ³ ) ^1/2 .
Item 2. The conductive ink composition according to Item 1, wherein the conductive fine particles of 1 nm or more and less than 100 nm are 50% by weight or more based on the total weight of the conductive fine particles (a-1). .
Item 3. The conductive ink composition according to Item 1 or 2, wherein the conductive fine particles (a-1) are silver or an alloy thereof.
Item 4. The conductivity according to Items 1 to 3, wherein the monomer component (B) having a functional group is one selected from compounds having any one of an amino group, an isocyanate group, a cyano group, and a mercapto group. Ink composition.
Item 5. A conductive circuit pattern for a flexible circuit board, a touch panel substrate, and a display device substrate formed using the conductive ink composition according to Item 1-4.

According to the present invention, it is possible to provide a conductive ink composition that achieves high adhesion and low specific resistance regardless of the type of polymer film, transparent conductive film, and the like.
Minimizing the difference in solubility parameter (SP value) between the composition (A) containing the conductive fine particles (a-1) and the solvent (a-2) and the monomer component (B) having a functional group; and When the monomer component (B) having a functional group is 4 to 8 parts by weight with respect to 100 parts by weight of the composition (A), the conductive particles (a-1) and the functional group in the conductive ink composition It is possible to increase the compatibility of the monomer component (B) having a high bond strength between them.
Moreover, by making the surface tension of the conductive ink composition lower than the surface tension of the substrate to be used, the penetration of the conductive ink composition into the substrate proceeds, and the adhesion to the substrate can be maintained high.

  Hereinafter, the present invention will be described in detail.

(Conductive ink composition)
The conductive ink composition of the present invention comprises a composition (A) containing conductive fine particles (a-1) and a solvent (a-2), and a monomer component (B) having a functional group. .

Specifically, the composition (A) containing the conductive fine particles (a-1) and the solvent (a-2) of the present invention and the monomer component (B) having a functional group are contained, and the surface tension is 29 mN. / m or less, a conductive ink composition,
The monomer component (B) having a functional group is 4 to 8 parts by weight with respect to 100 parts by weight of the composition (A),
The absolute value of the difference in solubility parameter (SP value) between the composition (A) and the monomer component (B) having a functional group is in the range of 0 to 1.7 (cal / cm ³ ) ^1/2 .

The conductive ink composition of the present invention is different when the solubility parameter (SP value, hereinafter referred to as SP value) of the composition (A) and the monomer component (B) having a functional group is δA and δB, respectively. The absolute value of (Δδ = | δA−δB |) must be 0 to 1.7 (cal / cm ³ ) ^1/2 . This is because the absolute value of the difference in SP value is large, and when the solubility of the composition (A) and the monomer component (B) having a functional group is poor, one of the components is easily separated, and the conductive ink composition. The bond strength between the conductive fine particles (a-1) and the monomer component (B) in the product is deteriorated, and sufficient adhesion to the substrate cannot be obtained. In terms of adhesion to the substrate, the absolute value of the difference in solubility parameter (SP value) is preferably in the range of 0 to 1.7 (cal / cm ³ ) ^1/2 , and 0 to 0.7 ( cal / cm ³ ) ^1/2 is more preferable.

  Calculation of the solubility parameter (SP value: δ) between the composition (A) and the monomer component (B) having a functional group in the present invention can be obtained by utilizing the thermodynamic relationship described below.

For example, in the case of a composition, if the type and mixing ratio of substances in the composition are clear and the value of the surface tension of the composition can be measured, ASMichaels: A. S. T. M. It can be obtained by using Equation 1 described in Technical Publications, 340, 3 (1963).
δ = 4.1 (γ / V ^1/3 ) ^0.43 (Formula 1)
(In the formula, V: molar molecular volume, γ: surface tension)

  Although the surface tension of the conductive ink composition of the present invention depends on the surface tension of the substrate used, the surface tension of the conductive ink composition is approximately equal to or less than the surface tension of the substrate. High adhesion can be achieved by allowing the monomer (B) having a functional group in the ink composition to bind to the surface of the conductive fine particles (a-1) and causing intermolecular force with the substrate surface.

  The weight ratio of the composition (A) to the monomer component (B) having a functional group in the conductive ink composition of the present invention may be within the absolute value range of the difference in solubility parameter (SP value: δ). Specifically, it may be in the range of 4 to 8 parts by weight, preferably in the range of 5 to 7 parts by weight, relative to 100 parts by weight of the composition (A). When the amount is less than 3 parts by weight, sufficient adhesion to the substrate cannot be obtained, and when the amount is more than 9 parts by weight, the specific resistance value increases.

  The conductive ink composition of the present invention can be used for forming a circuit on a substrate usually used for electronic component mounting products, electric circuit wiring bodies, electromagnetic wave absorbers, light reflectors, etc., for example, polyimide (surface tension 50 mN / m) polyester (43 mN / m), polyethylene terephthalate (43 mN / m), polycarbonate (42 mN / m), acrylic (38 mN / m), polypropylene (29 mN / m), ITO (22 mN / m) The surface tension of the conductive ink composition when used as a substrate such as m) is preferably 29 mN / m or less, and more preferably 25 mN / m or less.

The surface tension of the conductive ink composition can be easily measured by a hanging ring method or the like. As a specific measurement method, when the metal ring is submerged in the measurement substance and pulled up, the load immediately before the thin film attached to the metal ring is broken and falls down is measured with a spring balance, and Equation 2 is used. Can be obtained.
γ = F / 4πR (Formula 2)
(In the formula, F represents the load immediately before the thin film was broken and dropped, R represents the radius of the metal ring, and γ represents the surface tension.)

  In the conductive ink composition of the present invention, a viscosity adjusting agent, a conductive auxiliary agent, an anti-choking agent, an antioxidant, and a pH adjusting agent are added as necessary as long as they do not affect the effects of the present invention. Anti-drying agents, adhesion-imparting agents, preservatives, antifoaming agents, leveling agents and the like may be added. Among the above additives, various printing methods can be used by using a viscosity modifier, and higher conductivity can be obtained by adding a conductive aid.

Composition (A) containing conductive fine particles (a-1) and solvent (a-2)
The composition (A) in the conductive ink composition of the present invention contains conductive fine particles (a-1) and a solvent (a-2). The compounding ratio of the conductive fine particles (a-1) and the solvent (a-2) in the composition (A) may be (conductive fine particles: solvent) in the range of 3: 5 to 9: 1. A range of 3: 2 to 6: 1 is preferred. If it is the said range, the effect of this invention can fully be acquired.

  In the composition (A) of the present invention, as additives other than the conductive fine particles (a-1) and the solvent (a-2), for example, a viscosity adjusting agent, a conductive auxiliary agent added to the conductive ink composition, An anti-choking agent, an antioxidant, a pH adjuster, an anti-drying agent, an adhesion promoter, an antiseptic, an antifoaming agent, a leveling agent and the like may be added in advance. As an addition method, the conductive fine particles (a-1) and other additives may be added and mixed simultaneously to the solvent (a-2), and other additives may be added and mixed to the solvent (a-2). Conductive fine particles (a-1) may be added to the resulting product.

Conductive fine particles (a-1)
As the conductive fine particles (a-1) in the composition (A), any conductive material having an average particle diameter of 1 nm or more and less than 5 μm can be used without particular limitation. For example, noble metals such as gold, silver, copper, and platinum group metals, single metal particles having high conductivity such as zinc, nickel, and aluminum, or metal particles of these alloys can be exemplified. These conductive fine particles (a-1) are preferably metal fine particles of gold, silver, copper, a platinum group metal or an alloy thereof, and more preferably metal fine particles of silver or an alloy thereof in terms of conductivity.

  The average particle diameter of the conductive fine particles (a-1) may be in the range of 1 nm or more and less than 5 μm, and is preferably in the range of 5 nm or more and less than 2 μm. By using the conductive fine particles (a-1) in the above range, the effects of the present invention can be sufficiently obtained. In addition, it can measure by a laser diffraction method, a dynamic light scattering method, etc. as a general measuring method of an average particle diameter.

  The conductive fine particles (a-1) in the composition (A) may be a combination of two or more of the above metal fine particles or metal fine particles of an alloy. When two or more types of metal fine particles are used in combination, 50% or more of the total weight of the conductive fine particles (a-1) is 1 nm or more for the purpose of promoting diffusion sintering of the conductive particles from a relatively low temperature of about 100 ° C. The conductive fine particles (a-1) are preferably less than 100 nm.

  What is necessary is just to select suitably content of electroconductive fine particles (a-1) in a composition (A) according to the other component to add. Especially, it is preferable that it is the range of 60 to 900 weight part with respect to 100 weight part of solvent (a-2) at the point of the electroconductivity in a conductive pattern, and the dispersibility in a conductive ink composition. From the viewpoint of productivity, it is more preferably in the range of 150 parts by weight or more and less than 600 parts by weight.

  The shape of the conductive fine particles (a-1) is not particularly limited as long as the desired conductivity can be obtained, and examples thereof include a spherical shape, a rod shape, and a flake shape. You may mix and use things.

  When the conductive fine particles (a-1) having an average particle size of less than 100 nm are used as the conductive fine particles (a-1), aggregation is likely to occur due to the large surface energy, particularly those having an average particle size of 1 nm or more and less than 100 nm. As for, in order to prevent aggregation in the conductive ink composition, the surface of the conductive fine particles (a-1) is preferably coated with a protective layer. The protective layer on the particle surface is preferably one that can be quickly detached and removed by drying after coating on the substrate. Further, the weight of the conductive fine particles (a-1) includes the weight of the protective layer.

  The protective layer of conductive fine particles (a-1) having an average particle diameter of 1 nm or more and less than 100 nm is generally used as a protective layer for conductive fine particles (a-1) within a range that does not affect the effect of the present invention. Compounds can be included. Specifically, a compound having an amino group, a compound having a carboxyl group, a compound having a thiol group, and the like can be exemplified. A compound having an amino group is preferred in that elimination from the surface of the conductive fine particles (a-1) easily proceeds.

  Compounds having an amino group used in the protective layer include ethylamine, n-propylamine, isopropylamine, 1,2-dimethylpropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, isoamylamine, tert-amylamine 3-pentylamine, allylamine, n-amylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-octylamine, 2-ethylhexylamine, n-nonylamine, n-aminodecane, n-aminoundecane, n-dodecylamine, n-tridecylamine, 2-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-oleylamine, N-ethyl-1,3-diaminopropane, N, N-dii Examples include sopropylethylamine, N, N-dibutylaminopropane, N, N-diisobutyl-1,3-diaminopropane, N-lauryldiaminopropane and the like. Moreover, it is preferable to use suitably the compound which has a carboxyl group, and the compound which has a thiol group at the point which improves the storage stability of electroconductive particle (A), and the compound which has a carboxyl group from the point of an odor is used more suitably. . Specific examples of the compound having a carboxyl group include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and olein. Examples thereof include acids, linoleic acid, and linolenic acid.

  As the conductive fine particles (a-1), either commercially available products or manufactured products may be used. As a specific method for producing the conductive fine particles (a-1), methods disclosed in JP-A-2006-1118010 or JP-A-2009-270146 can be exemplified. The conductive fine particles (a-1) produced by the method described above can be used.

Solvent (a-2)
The solvent (a-2) in the composition (A) can be used without particular limitation as long as each component contained in the conductive ink composition is uniformly dispersed. Specifically, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, ethylene glycol, hexane, cyclohexane, cyclohexanone, heptane, octane, nonane, decane, undecane, dodecane, Hydrocarbons such as tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, benzene, toluene, ethylbenzene, xylene, styrene monomer, mineral spirit, ethyl acetate, butyl acetate, propyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, ethylene Esters such as glycol monoethyl ether acetate, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ethylene glycol Examples thereof include glycol ethers such as coal monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether, and solvents such as terpineol, pinene, limonene, menthane, cymene, and isophorone. Among these, nonpolar solvents such as hydrocarbons and ketones are preferable from the viewpoint of reducing the surface tension of the conductive ink composition, and hexane, cyclohexane, cyclohexanone, toluene, methyl ethyl ketone, and the like are more preferable. The solvent may be a liquid in the environment where the conductive ink composition is used, and may be used in a single or mixed form as long as the compatibility and surface tension targeted by the present invention are not affected. it can.

Monomer component having a functional group (B)
The monomer component (B) having a functional group in the conductive ink composition of the present invention has at least one end thereof in order to form a good bond with the conductive fine particles (a-1) in the composition (A). It must have one or more functional groups. This is because the bond generated between the surface of the conductive fine particles (a-1) and the functional group of the monomer component plays an important role in the adhesion between the conductive ink composition and the substrate. The addition of the polymer obtained by polymerizing the monomer component (B) having a functional group to the conductive ink composition means that the conductive fine particles (a-1) are dried at the time of drying after the conductive ink composition is applied to the substrate. This is not preferable because it interferes with the contact property and sintering reaction.

  Examples of the functional group of the monomer component (B) having a functional group include monomer components having a carboxyl group, a phosphino group, an isocyanate group, an amino group, a mercapto group, a cyano group, and a thiocyanate group. Similar effects can also be obtained with monomer components having a glycinato group, alkylseleno group, alkyltelluro group, silane group, alcohol group, and aldehyde group. A commercial item may be used for said monomer component, and what was synthesize | combined with the well-known synthesis | combining method may be used.

  Examples of the monomer component having a carboxyl group include acrylic acid, methacrylic acid, propionic acid, myristoleic acid, pyruvic acid, and linoleic acid.

  Examples of the monomer component having a phosphino group include triethylphosphine, tributylphosphine, aminotrimethylenephosphonic acid, 1,2-bis (dimethylphosphino) ethane, and hydroxyethanediphosphonic acid.

  Examples of the monomer component having an isocyanate group include tert-butyl isocyanate, isopropyl isocyanate, octadecyl isocyanate, 3-triethoxysilylpropyl isocyanate, 2-isocyanatoethyl methacrylate, and the like.

  Examples of monomer components having an amino group include tris (2-aminoethyl) amine, N- (3-dimethylaminopropyl) methacrylamide, N- (3-trimethoxysilylpropyl) ethylenediamine, and 3- (triethoxysilyl) propyl. Examples include amines and 1,3-bisaminomethylcyclohexane.

  Examples of the monomer component having a mercapto group include 3-mercaptopropionic acid, 3- (methyldimethoxysilyl) propane-1-thiol, 3-mercapto-1-propanol, dimercaptosuccinic acid, and 2,3-dimercapto-1-propanol. Etc. can be illustrated.

  Examples of the monomer component having a cyano group include lactonitrile, benzonitrile, cyanoacrylate, methyl 3-cyanopropionate, ethyl 2-cyanopropionate, and the like.

  Examples of the monomer component having a thiocyanate group include allyl isothiocyanate, sulforaphane, methylphenyl isothiocyanate, 4-fluorophenyl isothiocyanate, and octamethylene diisothiocyanate.

  Specific examples of the monomer component (B) having a functional group include 3- (triethoxysilylpropyl) isocyanate and 2-isocyanatoethyl methacrylate in that they form a good bond with the conductive fine particles (a-1). 3-mercaptopropionic acid, 3- (methyldimethoxysilyl) propane-1-thiol, 3-mercapto-1-propanol, 3- (triethoxysilyl) propylamine, N- (3-dimethylaminopropyl) methacrylamide, Lactonitrile, methyl 3-cyanopropionate and the like are preferable, 3- (triethoxysilylpropyl) isocyanate, 2-isocyanatoethyl methacrylate, 3-mercaptopropionic acid, 3- (methyldimethoxysilyl) propane-1-thiol, 3- (Triethoxysilyl) propylamine, cyanoacyl Rate, 3-cyano-propionic acid methyl are more preferred.

(Other additives)
In the conductive ink composition of the present invention, a viscosity adjusting agent, a conductive auxiliary agent, an anti-choking agent, an antioxidant, and a pH adjusting agent are added as necessary as long as they do not affect the effects of the present invention. Anti-drying agents, adhesion-imparting agents, preservatives, antifoaming agents, leveling agents and the like may be added. When the composition (A) containing the above additive is used, the above additive may not be added to the conductive ink composition or may be added as necessary. Among the above additives, various printing methods can be used by using a viscosity modifier, and higher conductivity can be obtained by adding a conductive aid.

(Viscosity modifier)
As the viscosity modifier used in the present invention, when high viscosity is required, various polymers such as vinyl chloride / vinyl acetate copolymer resin, polyester resin, acrylic resin, polyurethane resin, polysaccharides such as carboxymethyl cellulose, palmitic acid Sugar fatty acid esters such as dextrin, metal soaps such as zinc octylate, swelling clay minerals such as smectite, spike lavender oil, mineral petrol obtained by distilling petroleum, and the like can be used. Further, when it is necessary to reduce the viscosity, a leveling agent, a surface tension adjusting agent, a reducer, or the like can be used. In addition, since a viscosity modifier inhibits the sintering reaction of electroconductive fine particles (a-1), it is desirable that it can volatilize at the time of drying. In addition, when the viscosity adjusting agent has a high molecular weight or is used in a large amount, since sufficient volatilization cannot be expected at a drying temperature of about 100 ° C., it is necessary to keep the addition amount as small as possible according to the molecular weight. Therefore, the addition amount of the viscosity modifier in the conductive ink composition may be 7 parts by weight or less with respect to 100 parts by weight of the solvent (a-2), and is preferably 5 parts by weight or less.

(Method for preparing conductive ink composition)
The conductive ink composition of the present invention is performed by preparing a composition (A) containing conductive fine particles (a-1) and a solvent (a-2). In this case, it can prepare by adding electroconductive fine particles (a-1) to a solvent (a-2), and mixing by the stirring method used normally. In addition, you may add the additive used for a conductive ink composition as needed. Moreover, when adding a viscosity modifier to a composition (A), after adding and stirring a viscosity modifier to a solvent (a-2) previously, electroconductive fine particles (a-1) are added and it stirs and mixes. It is preferable. Subsequently, the monomer component (B) having a functional group is added to the prepared composition (A), and the mixture is stirred and mixed to obtain a conductive ink composition.

  The mixing method of each component of the conductive ink composition is not particularly limited as long as each component can be uniformly dispersed and mixed in the conductive ink composition. Specific examples include a mechanical stirrer, a magnetic stirrer, an ultrasonic disperser, a planetary mill, a ball mill, and a three roll. It is preferable to use a planetary mill from the uniformity of the obtained conductive ink composition and the simplicity of work. In addition, what is necessary is just to select and implement mixing conditions on the conditions normally used.

(Use of conductive ink composition)
By adjusting the viscosity of the conductive ink composition of the present invention, an arbitrary conductive circuit pattern can be formed on a substrate with a general general-purpose machine without using special equipment or technology. Examples of the method for forming the conductive circuit pattern include a discharge method and a printing method. Examples of the discharge method include an inkjet method and a dispensing method. Examples of the printing method include screen printing, and rotary printing such as flexographic printing, offset printing, gravure printing, and gravure offset printing. . By using the printing method, an arbitrary conductive circuit pattern can be applied on the substrate using the conductive ink composition. In addition, the protective layer on the surface of the solvent (a-2) or the conductive fine particles (a-1) is removed by drying after coating. What is necessary is just to select a drying temperature timely according to the solvent (a-2) to be used and the heat-resistant temperature of a base material.

  As a substrate used in the method for forming a conductive circuit pattern, a substrate usually used as a substrate for a conductive circuit pattern can be used. The substrate surface may be formed with partially different materials depending on the application. Examples thereof include metal films such as copper and aluminum, inorganic films such as ITO, and organic films such as hard coat. When the rotary printing method is used, for example, a polymer film made of polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyolefin, polycarbonate, polyimide, polyamide, polyvinylidene chloride, or the like can be preferably used.

  After applying to the substrate, a sintering reaction is performed to promote the sintering reaction of the conductive fine particles (a-1). This removes components other than the conductive fine particles (a-1) in the conductive ink composition applied on the substrate by volatilization or the like, while bringing the conductive fine particles (a-1) into contact with each other for sintering. This is to achieve a low specific resistance. Depending on the conductive fine particles (a-1) to be used, it is necessary to perform the sintering at a temperature at which components other than the conductive fine particles (a-1) are volatilized and the substrate is not deformed. Specifically, a range of 60 to 120 ° C is preferable. The sintering time is preferably 5 to 120 minutes. The conductive circuit pattern obtained by drying in the above range has sufficient conductivity.

  By using the conductive ink composition of the present invention, the conductive circuit pattern formed on the base material has high conductivity and adhesion to the substrate. Therefore, it can be applied to substrate materials with low heat resistance (thermoplastic temperature less than 150 ° C thermoplastic polymer film) such as polyamide, polyester, polyethylene, polyvinyl chloride, etc., and the effect of film shrinkage due to heat treatment Can be eliminated. Accordingly, the conductive ink composition of the present invention can be applied to conductive circuit patterns such as a flexible circuit board, a touch panel substrate, and a display device substrate, which are greatly affected by the positional deviation of the printed pattern. is there.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these.

(Measurement method of viscosity)
The viscosity of each composition was measured using an E-type viscometer (VISCOMETER DV-II + Pro manufactured by BROOKFIELD) with a rotation speed of 10 rpm as a reference.

Conductive ink composition The components used in Examples and Comparative Examples are as follows.

(Composition A)
Compositions (A1) to (A5) were prepared based on the blending amounts shown in Table 1 for the components described below. In the preparation method, the conductive fine particles (a-1) and the solvent (a-2) shown in Table 1 were added to the same container, and then stirred at room temperature for 1 minute with Kurabo Industries's Mazerustar KK-250S. (A) was produced. In addition, each SP value was derived from Formula 2 using the value of the surface tension measured by the above-described hanging ring method and the value of the molar molecular weight calculated from the type and ratio of the blend. In addition, the numerical value of Table 1 represents each weight, making the weight of a solvent (a-2) 100.

Conductive fine particles (a-1)
M1: Silver fine particles (average particle size 21 nm, measured with Spectris Zetasizer Nano) Manufactured based on the method described in JP-A-2009-270146. The amine compound contained in the protective layer of the conductive fine particles is oleylamine (10% by weight in the components of the protective layer), n-octylamine (30% by weight in the components of the protective layer), n-butylamine (of the protective layer). 60% by weight of ingredients)
M2: Silver powder (average particle size 1.2 μm, Fukuda Metal Foil Co., Ltd., AgC-104W)

Solvent (a-2)
S1: Hexane (SP value: 7.3)
S2: Cyclohexane (SP value: 8.3)
S3: Toluene and methyl ethyl ketone mixed at a weight ratio of 50/50 (SP value: 9.1)
S4: cyclohexanone (SP value: 9.9)

Monomer having functional group (B)
B1: 3-mercaptopropionic acid (Tokyo Chemical Industry, SP value 7.8)
B2: 3- (Triethoxysilyl) propylamine (manufactured by Tokyo Chemical Industry, SP value 8.7)
B3: 2-isocyanatoethyl methacrylate (Showa Denko Karenz, SP value 9.2)
B4: Methyl 3-cyanopropionate (manufactured by Tokyo Chemical Industry, SP value 9.4)
Table 2 shows the surface tension and SP value of each component used as the monomer component (B) having a functional group. The SP value was derived from the surface tension by the method described above.

Preparation of conductive ink composition After adding 100 parts by weight of the above composition (A) and 6 parts by weight of the monomer component (B) having a functional group to the same container, the mixture is stirred at room temperature for 1 minute with Kurabo Industries Mazerustar KK-250S. By doing so, each conductive ink composition was produced. The blending amounts of the compositions (A1) to (A5) and the monomer components (B1) to (B4) are shown in Table 3 (Examples) and Table 4 (Comparative Examples). In addition, the numerical value of Table 3 and 4 represents each weight when the weight of a composition (A) is set to 100.

  In order to confirm that the conductive fine particles are uniformly dispersed and not aggregated in each of the prepared conductive ink compositions, using a Viscometer DV-II + Pro manufactured by E-type viscometer BROOKFIELD at 25 ° C., The hysteresis curve of the shear stress value was drawn by changing the rotation speed between 0.5 rpm and 100 rpm from low rotation to high rotation (going) and from high rotation to low rotation (return). The forward and return shear stress values were the same at each rotation number, and it was confirmed that the conductive fine particles (a-1) were not aggregated in each conductive ink composition, and used for the following evaluations. .

(Physical properties of conductive ink composition)
The SP values of the composition (A) and the monomer component (B) having a functional group were set as δA and δB, respectively, and the absolute value of the difference between the SP values was obtained from the equation (Δδ = | δA−δB |). Further, the surface tension of each conductive ink composition was measured by the above-described hanging ring method. The results are shown in Table 5 (Examples) and Table 6 (Comparative Examples).

(Adhesion evaluation)
For the adhesion evaluation, an ITO sputtering-treated PET film (HK188G-AB500H manufactured by Teijin Chemicals) having a size of 50 × 50 mm was used as the adhesion. Each conductive ink composition was applied to the entire surface of these substrates with a spin coater, dried in air at 100 ° C. for 30 minutes, and a sample with a coating thickness of 1 μm was tested according to JIS K5600, and an adhesive tape was drawn. Judging from the number of cells remaining without peeling when peeled. Evaluation criteria were determined as follows. The results are shown in Table 5 (Examples) and Table 6 (Comparative Examples).
○: 23/25 or more ×: 22/25 or less

(Specific resistance evaluation)
For the resistivity evaluation, a conductive ink composition was spun on a 100 × 100 mm surface-adhesive PET film (TPE Kasei HPE-50) using a four-terminal conductivity meter (Lorestar AX manufactured by Mitsubishi Chemical Analytech). The entire surface was coated with a coater, dried in air at 100 ° C. for 30 minutes, measured at the center of the coating film of a sample having a coating thickness of 1 μm, and judged from the obtained specific resistance value. Evaluation criteria were determined as follows. The results are shown in Table 5 (Examples) and Table 6 (Comparative Examples).
○: Less than 1 × 10 ⁻⁵ Ω · cm ×: 1 × 10 ⁻⁵ Ω · cm or more

As shown in Table 5, Examples 1 to 12 showed adhesion to the ITO film, and the specific resistance was lower than 10 ⁻⁵ Ω · cm. On the other hand, as shown in Table 6, in Comparative Example 1, Δδ is 1.9 (cal / cm ³ ) ^1/2 , and it is considered that the ink compatibility is poor because of a relatively large value. There was a phenomenon in which the adhesion to the film was not perfect and partly peeled off. In Examples 3 and 8 and Comparative Example 3, Δδ was 1.7 (cal / cm ³ ) ^1/2 , but the surface tensions were different and were 20, 29, and 33 mN / m, respectively. Differences in adhesion to ITO occurred, and examples with surface tensions of 20 and 29 mN / m showed good adhesion, but in Comparative Example 3 with 33 mN / m, there was no adhesion at all, and the adhesive tape side had conductivity. All ink was transferred. From this result, the conductive ink composition has an absolute value (Δδ) of a difference in solubility parameter (SP value) between the composition (A) and the monomer component (B) having a functional group of 1.7 (cal / cm ^3). ) is ^1/2 or less, and when the surface tension of the conductive ink composition is not more than 29 mN / m, sufficient adhesion to the substrate is obtained, a low resistance value is obtained.
Further, as shown in Comparative Examples 2 to 5, when the surface tension was 33 mN / m, all the conductive ink was transferred to the tape side regardless of the magnitude of Δδ. It can be seen that ITO adhesion cannot be obtained when the surface tension is large.

  As shown in Comparative Example 6, when the amount of the functional group-containing monomer (B) is small, adhesion to the ITO film is not achieved. Moreover, when the addition amount of the monomer component (B) having a functional group is large as in Comparative Example 7, this itself inhibits the sintering and contact of the conductive particles and increases the specific resistance.

  The conductive ink composition of the present invention can be effectively used in various fields such as conductive adhesives, electric circuit wiring, electromagnetic wave absorbers, and light reflectors.

Claims (4)

A composition (A) containing conductive fine particles (a-1) and a solvent (a-2);
A conductive ink composition comprising a compound (B) having a functional group and having a surface tension of 29 mN / m or less ,
The compound (B) having a functional group is one selected from compounds having any functional group of amino group, isocyanate group, cyano group, and mercapto group,
The compound (B) having a functional group is 4 to 8 parts by weight with respect to 100 parts by weight of the composition (A),
The absolute value of the difference in the solubility parameter (SP value) between the composition (A) and the compound (B) having a functional group is in the range of 0 to 1.7 (cal / cm ³ ) ^1/2 .   2. The conductive ink composition according to claim 1, wherein the conductive fine particles of 1 nm or more and less than 100 nm are 50% by weight or more with respect to the total weight of the conductive fine particles (a-1).   The conductive ink composition according to claim 1, wherein the conductive fine particles (a-1) are silver or an alloy thereof. Flexible circuit board, a conductive circuit pattern of the substrate for a touch panel, or the display device substrate formed by using a conductive ink composition according to claim 1-3.