CN107109095B

CN107109095B - Conductive ink

Info

Publication number: CN107109095B
Application number: CN201580061233.5A
Authority: CN
Inventors: 新谷祐树
Original assignee: Bando Chemical Industries Ltd
Current assignee: Bando Chemical Industries Ltd
Priority date: 2014-11-25
Filing date: 2015-11-09
Publication date: 2021-01-26
Anticipated expiration: 2035-11-09
Also published as: WO2016084312A1; TWI686447B; TW201627422A; JPWO2016084312A1; KR20170086072A; KR102056972B1; JP6101403B2; CN107109095A

Abstract

The invention provides a conductive ink for transfer printing, which can calcine a conductive film pattern with sufficient conductivity and good adhesion with a substrate at low temperature. The conductive ink for transfer printing includes: metal particles, a solvent containing ethanol, and 0.1 to 3.0 mass% of a high boiling point solvent having a hydroxyl group.

Description

Conductive ink

Technical Field

The present invention relates to a conductive ink which is used for forming a wiring or an electrode pattern of a semiconductor integrated circuit or the like and which can form a wiring or an electrode pattern on an organic thin film transistor substrate. More specifically, the present invention relates to a conductive ink which can be suitably used for forming a wiring or an electrode pattern by a transfer printing method including a reverse printing method.

Background

The following methods are previously known: after a metal thin film is formed on the entire surface of the substrate by sputtering, vapor deposition, or the like, unnecessary portions are etched by photolithography to form a desired conductive film pattern. However, this method requires an expensive vacuum apparatus in addition to the complicated steps.

Therefore, a simpler and cheaper method for forming a conductive film pattern has been demanded, and in recent years, a method using a printing method such as a relief printing method, a gravure printing method, a screen printing method, or an inkjet printing method has been proposed. Further, as a printing method capable of forming a higher-definition pattern, a method using a reverse printing method, a micro-contact printing method, or the like has been proposed, and various inks such as a conductive ink, an insulating ink, and a resistive ink suitable for these printing methods have been developed.

Patent document 1 proposes a conductive ink for forming a fine conductive film pattern by a relief reverse printing method, and specifically discloses a conductive ink substantially not containing a binder component for forming a conductive film pattern by a relief reverse printing method, in which: the ink is characterized in that the ink contains, as essential components, conductive particles having a volume average particle diameter (Mv) of 10 to 700nm, a release agent, a surface energy adjuster, and a solvent component, wherein the solvent component is a mixture of a solvent having a surface energy of 27mN/m or more at 25 ℃ and a volatile solvent having a boiling point of 120 ℃ or less at atmospheric pressure, and the surface energy of the ink at 25 ℃ is 10 to 21 mN/m.

By using the conductive ink described in the above-mentioned patent document 1, a fine conductive film pattern can be stably formed without transfer failure by a relief reverse printing method, and for example, by firing a fine pattern formed by using silver as a conductive particle at a low temperature of 200 ℃^-5In addition to excellent conductivity of the order of Ω · cm or less, transfer property is excellent, and therefore a fine pattern can be formed by full transfer.

Patent document 2 discloses: "an ink having a dynamic surface tension of 16mN/m or more and 23mN/m or less when a dynamic surface tension at 25 ℃ determined by a maximum bubble pressure method is measured with an occurrence frequency of bubbles set to 0.05Hz, and of 20mN/m or more and 27mN/m or less when the occurrence frequency is set to 10.0 Hz".

The ink is an ink for reverse printing, which has both appropriate wettability and releasability to the surface of a silicone rubber sheet (silicone blanket) by adjusting the dynamic surface tension to an appropriate range, and which can obtain an ink pattern having a uniform thickness without unevenness or defects on the surface of a printing object such as a substrate.

Documents of the prior art

Patent document

Patent document 1: international publication No. WO2008/111484

Patent document 2: japanese patent laid-open publication No. 2011-252072

Disclosure of Invention

[ problems to be solved by the invention ]

However, although a fine pattern can be formed by using the conductive ink described in patent document 1, the conductive film pattern formed on the substrate may lack adhesiveness because the conductive ink does not substantially contain a binder. Further, a firing temperature of 180 ℃ or higher is required to exhibit conductivity, and there is a problem that an inexpensive substrate with deteriorated heat resistance cannot be used.

Further, the ink disclosed in the above-mentioned patent document 2 is an ink mainly suitable for a color filter constituting a liquid crystal display, cannot be directly used as a conductive ink suitable for a transfer printing method such as a reverse printing method, and contains a relatively large amount of a solvent for dissolving a binder, and therefore, it takes a relatively long time to dry the ink after being applied to the surface of a silicone rubber sheet, and there is a problem in that a printing operation (printing tact) is relatively long.

Accordingly, an object of the present invention is to provide a conductive ink for transfer printing, which is suitable for use in transfer printing methods including a reverse printing method and the like, and which can be used for firing a conductive film pattern having sufficient conductivity and good adhesion to a substrate at a low temperature.

[ means for solving problems ]

The present inventors have made extensive studies to achieve the above-mentioned object, and as a result, have found that, in order to obtain a conductive ink for transfer printing which is suitable for a transfer printing method including a reverse printing method and the like and which can be used for firing a conductive film pattern having sufficient conductivity and good adhesion to a substrate at a low temperature, a case where a suitable amount of metal particles and a specific high-boiling-point solvent having a hydroxyl group are contained is extremely effective in achieving the above-mentioned object, and have reached the present invention.

That is, the present invention provides a conductive ink for transfer printing, comprising:

metal particles;

a vehicle comprising ethanol; and

0.1 to 3.0 mass% of a high boiling point solvent having a hydroxyl group.

In the present invention, a representative "reverse printing method" will be described as the "transfer printing method". The "reverse printing method" is a printing method as follows: an ink-coated surface is formed by coating ink on a blanket made of silicone resin or the like, a relief plate for removing a non-image portion is pressed against the ink-coated surface, ink in a portion in contact with the relief plate is removed from the blanket, and then the ink remaining on the blanket is transferred to a printing object.

In the conductive ink for transfer printing of the present invention, the high boiling point solvent more preferably contains 1, 3-butanediol, 2, 4-diethyl-1, 5-pentanediol, or octanediol.

In addition, the conductive ink for transfer printing of the present invention preferably further contains a hydrofluoroether.

In addition, the conductive ink for transfer printing of the present invention is preferably:

the metal particles are silver microparticles; and is

The conductive ink for transfer printing contains a fine silver particle dispersion containing:

fine silver particles;

short-chain amines having a carbon number of 5 or less and a distribution coefficient logP of-1.0 to 1.4;

a highly polar solvent; and

and a dispersant having an acid value for dispersing the fine silver particles.

Further, the conductive ink for transfer printing of the present invention is preferably:

in the fine silver particle dispersion, the short-chain amine is an alkoxyamine, and further includes a protective dispersant having an acid value.

In the conductive ink for transfer printing according to the present invention, it is preferable that:

the protective dispersant has an acid value of 5-200 and has a functional group derived from phosphoric acid.

[ Effect of the invention ]

According to the conductive ink for transfer printing of the present invention, it is possible to realize a conductive ink for transfer printing which can be suitably used for a transfer printing method including a reverse printing method and can fire a conductive film pattern having sufficient conductivity and good adhesion to a substrate at a low temperature.

Detailed Description

Hereinafter, (1) a preferred embodiment of the conductive ink for transfer printing of the present invention, (2) a preferred embodiment of the method for producing the conductive ink for transfer printing of the present invention, (3) a conductive film pattern using the conductive ink for transfer printing of the present invention, and a method for producing the conductive film pattern will be described in detail. In the following description, overlapping description may be omitted.

(1) Conductive ink for transfer printing

The conductive ink for transfer printing according to the present embodiment is characterized by comprising: metal particles, a solvent containing ethanol, and 0.1 to 3.0 mass% of a high boiling point solvent having a hydroxyl group. Further, the conductive ink for transfer printing includes: a solid component containing, as a main component, metal particle dispersion (in other words, metal colloid (colloid)) particles containing metal particles and an organic component, and a dispersion medium for dispersing these solid components. In the colloidal liquid, the "dispersion medium" may dissolve a part of the solid component.

According to the metal colloid liquid, since the metal colloid liquid contains an organic component, the dispersibility of the metal colloid particles in the metal colloid liquid can be improved, and therefore, even if the content of the metal component in the metal colloid liquid is increased, the metal colloid particles are less likely to aggregate, and good dispersion stability can be maintained. The term "dispersibility" as used herein means whether or not the dispersion state of the metal particles in the metal colloid liquid is excellent (uniform) immediately after the metal colloid liquid is prepared, and the term "dispersion stability" as used herein means whether or not the dispersion state of the metal particles in the metal colloid liquid is maintained after a predetermined time has elapsed from the preparation of the metal colloid liquid, and may also be referred to as "low sedimentation aggregation".

Here, in the metal colloid liquid, the "organic component" in the metal colloid particles is an organic substance that substantially constitutes the metal colloid particles together with the metal component. The organic component does not contain a trace amount of organic matter adhering to the metal component, such as a trace amount of organic matter originally contained in the metal as impurities, an organic matter adhering to the metal component in a trace amount of organic matter mixed in a production process described later, a residual reducing agent not completely removed in a washing process, a residual dispersing agent, and the like. The "trace amount" specifically means less than 1% by mass of the metal colloidal particles.

The metal colloidal particles in the present embodiment contain an organic component, and thus have high dispersion stability in a metal colloidal fluid. Therefore, even if the content of the metal component in the metal colloid liquid is increased, the metal colloid particles are less likely to aggregate, and as a result, good dispersibility is maintained.

The "solid content" of the metal colloid liquid in the present embodiment means a solid content remaining after removing the dispersion medium from the metal colloid liquid using silica gel or the like, and dried at room temperature of, for example, 30 ℃ or lower (for example, 25 ℃) for 24 hours, and usually includes metal particles, a residual organic component, a residual reducing agent, and the like. In addition, a method of removing the dispersion medium from the metal colloid liquid using the colloidal silica can be variously employed, and for example, a method of removing the dispersion medium by coating the metal colloid liquid on a glass substrate, and leaving the glass substrate with the coated film in a closed vessel containing the colloidal silica for 24 hours or more can be employed.

In the colloidal metal solution of the present embodiment, the concentration of the solid component is preferably 1 to 60% by mass. When the concentration of the solid component is1 mass% or more, the content of the metal in the conductive ink for transfer printing can be secured, and the conductive efficiency is not lowered. When the concentration of the solid content is 60% by mass or less, the viscosity of the colloidal metal solution is not increased, the handling is easy, and the method is industrially advantageous and can form a flat film. More preferably, the concentration of the solid content is 5 to 40% by mass.

The conductive ink for transfer printing of the present invention contains 0.1 to 3.0 mass% of a high boiling point solvent having a hydroxyl group. The high boiling point solvent having a hydroxyl group is preferably selected from 1, 3-butanediol (boiling point: 203 ℃ C.), 2, 4-diethyl-1, 5-pentanediol (boiling point: 150 ℃ C./5 mmHg, 200 ℃ C. or more at 1 atmosphere) or octanediol (boiling point: 243 ℃ C.).

The "high boiling point solvent" in the present invention means a solvent having a boiling point of 200 ℃ or higher. Further, since the ink has a hydroxyl group and has a suitable affinity for water, and tends to retain moisture by absorbing or adsorbing moisture in the air, it is possible to form an ink suitable for a transfer printing method with a small amount of addition. Further, by minimizing the amount of the high boiling point solvent to be added, the following effects are exhibited: the ink applied to the silicone rubber sheet can be semidried in a short time, and the printing operation can be shortened.

The amount of the high boiling point solvent having a hydroxyl group added is 0.1 to 3.0% by mass. If the amount is less than 0.1% by mass, the amount is too small to be in an ink form suitable for the transfer printing method, and if the amount exceeds 3.0% by mass, the time to reach a semi-dry state suitable for the transfer printing method becomes long, which is disadvantageous in terms of printing work. More specifically, the amount of the high boiling point solvent having a hydroxyl group added is particularly preferably 0.3 to 2.0 mass% from the viewpoint of facilitating the formation of an ink suitable for the transfer printing method, reducing the time required to reach a semi-dry state suitable for the transfer printing method, and making the printing operation more favorable.

In the conductive ink for transfer printing of the present invention, a highly volatile solvent such as ethanol is added to improve the drying property of the ink. By adding the solvent, the viscosity of the conductive ink for transfer printing can be quickly adjusted to a viscosity suitable for printing. As the high-volatility solvent, in addition to ethanol, one or two or more low-boiling solvents selected from the group of solvents having a boiling point of less than 100 ℃, such as methanol, propanol, isopropanol, acetone, n-butanol, sec-butanol, and tert-butanol, can be used.

Further, the conductive ink for transfer printing of the present invention preferably contains a fluorine solvent such as hydrofluoroether. The fluorine solvent exhibits good wettability to the silicone adhesive sheet due to low surface tension, and can impart good drying properties due to a relatively low boiling point. Among these, hydrofluoroethers are preferable to fluorine solvents containing halogen atoms from the viewpoint of the ozone depletion coefficient.

Furthermore, hydrofluoroether has an ether bond as compared with hydrofluorocarbons, and therefore has the advantage of having a high polarity, and does not substantially swell the silicone rubber sheet, and exhibits the effects of having good compatibility with an alcohol such as ethanol, and also having excellent compatibility with metal particles dispersed in the alcohol, and therefore is more preferable.

In the conductive ink for transfer printing of the present invention, a fluorine-based surfactant having a fluorine atom may be added for the purpose of improving wettability to a silicone rubber sheet. In this case, however, if the amount of addition is too large, the conductivity of the conductive coating film produced using the conductive ink for transfer printing is reduced, and if the amount of addition is too small, the effect of improving wettability is insufficient, and therefore, 0.01 to 2 mass% is preferable.

The surface tension of the conductive ink for transfer printing of the present invention is 22mN/m or less. By sufficiently reducing the surface tension to 22mN/m or less, the wettability of the conductive ink for transfer printing to a plate made of a silicone resin or the like can be sufficiently secured. The surface tension of the conductive ink for transfer printing of the present invention can be adjusted to 22mN/m or less by adjusting the composition ratio. The lower limit of the surface tension is preferably about 13 mN/m. The surface tension in the present invention is measured based on the principle of the plate method (willemy method), and can be measured, for example, by a full-automatic surface tensiometer CBVP-Z manufactured by synghoni interfacial science.

Here, the conductive ink for transfer printing of the present embodiment preferably contains a fine silver particle dispersion (for example, colloidal) containing: fine silver particles, a short-chain amine having 5 or less carbon atoms and a distribution coefficient logP of-1.0 to 1.4, a highly polar solvent, and a dispersant having an acid value for dispersing the fine silver particles. The fine silver particle dispersion and the components thereof will be described in detail below.

The fine silver particle dispersion of the present embodiment includes: the fine silver particles, the short-chain amine having 5 or less carbon atoms, and the highly polar solvent are in the form of, for example, a colloidal solution. The form of the fine silver particles (silver colloidal particles) contained in the solid component of the fine silver particle dispersion includes, for example, silver colloidal particles formed by adhering an organic component to the surfaces of particles containing a silver component; silver colloidal particles having the particles containing a silver component as a core and having a surface coated with an organic component; the silver colloidal particles and the like, which are composed of a silver component and an organic component uniformly mixed, are not particularly limited. Preferably: silver colloidal particles having particles containing a silver component as a core and having surfaces coated with an organic component; or silver colloidal particles formed by uniformly mixing a silver component and an organic component. Further, the silver colloidal particles having the morphology can be appropriately prepared by those skilled in the art using techniques well known in the art.

(1-1) Fine silver particles

The average particle size of the fine silver particles contained in the fine silver particle dispersion in the present embodiment is not particularly limited as long as the effect of the present invention is not impaired, but is preferably an average particle size that causes a decrease in melting point, and may be, for example, 1nm to 400 nm. Particularly preferably 1nm to 70 nm. When the average particle size of the fine silver particles is 1nm or more, the fine silver particles have good low-temperature sinterability, and the cost for producing the fine silver particles does not increase, and therefore, the fine silver particles are practical. Further, it is preferably 400nm or less because the dispersibility of the fine silver particles is less likely to change with time. In the conductive ink for transfer printing obtained using the fine silver particle dispersion of the present embodiment, the average particle diameter (median particle diameter) of the silver colloidal particles (including the fine silver particles) is also substantially the same as (can be approximated to) this range.

The particle size of the fine silver particles in the fine silver particle dispersion varies depending on the solid content concentration, and is not limited to a fixed particle size, and may not be fixed. In addition, in the case where the fine silver particle dispersion contains a dispersant or the like described later as an optional component, the fine silver particle component having an average particle diameter of more than 400nm may be contained, but the fine silver particle component having an average particle diameter of more than 400nm may be contained as long as the fine silver particle component does not cause aggregation and does not significantly impair the effects of the present invention.

Here, the average particle diameter of the fine silver particles in the fine silver particle dispersion of the present embodiment is obtained by a dynamic light scattering method (doppler scattering light analysis), and is represented by a volume-based median particle diameter (D50) measured by a dynamic light scattering particle diameter distribution measuring device LB-550 manufactured by horiba ltd. Specifically, a few drops of a colloidal metal solution were dropped into 10mL of ethanol, and dispersed by hand shaking to prepare a sample for measurement. Then, 3mL of the measurement sample was put into a tank of a dynamic light scattering type particle size distribution measuring apparatus LB-550 manufactured by horiba institute of Party, and measured under the following conditions.

Measurement conditions

Data read-in times: 100 times (twice)

Temperature in the cell frame: 25 deg.C

Display conditions

Distribution form: standard of merit

The number of repetitions: 50 times

Particle size reference: volume basis

Refractive index of dispersoid: 0.200-3.900i (silver case)

Refractive index of dispersion medium: 1.36 (in the case of ethanol as the main component)

Setting of System conditions

Strength standard: dynamic (Dynamic)

Upper limit of scattering intensity range: 10000.00

Lower limit of scattering intensity range: 1.00

(1-2) short-chain amine having 5 or less carbon atoms

In the fine silver particle dispersion of the present embodiment, a short-chain amine having 5 or less carbon atoms is attached to at least a part of the surface of the fine silver particles. On the surface of the fine silver particles, a trace amount of organic matter such as a trace amount of organic matter originally contained as impurities in the raw material, a trace amount of organic matter mixed in a production process described later, a residual reducing agent not completely removed in a washing process, a residual dispersing agent, and the like may be adhered.

In the short-chain amine having 5 or less carbon atoms, the distribution coefficient logP is not particularly limited as long as it is-1.0 to 1.4, and it may be straight-chain, branched, or have a side chain. Examples of the short-chain amine include ethylamine (-0.3) propylamine (0.5), butylamine (1.0), N- (3-methoxypropyl) propane-1, 3-diamine (-0.6), 1, 2-ethylenediamine, N- (3-methoxypropyl) - (-0.9), 2-methoxyethylamine (-0.9), 3-methoxypropylamine (-0.5), 3-ethoxypropylamine (-0.1), 1, 4-butanediamine (-0.9), 1, 5-pentanediamine (-0.6) pentaolamine (-0.3), aminoisobutanol (-0.8), and the like, and alkoxyamines are preferably used.

The short-chain amine may be, for example, a compound containing a functional group other than an amine such as a hydroxyl group, a carboxyl group, an alkoxy group, a carbonyl group, an ester group, a mercapto group, or the like. The amines may be used alone or in combination of two or more. In addition, the boiling point at room temperature is preferably 300 ℃ or lower, and particularly preferably 250 ℃ or lower.

The fine silver particle dispersion of the present embodiment may contain a carboxylic acid in addition to the short-chain amine having 5 or less carbon atoms, as long as the effects of the present invention are not impaired. Carboxyl groups in one molecule of carboxylic acid have relatively high polarity and are likely to cause interaction due to hydrogen bonds, but portions other than these functional groups have relatively low polarity. Further, the carboxyl group tends to exhibit acidic properties. In addition, if the carboxylic acid is locally present (attached) to at least a part of the surface of the fine silver particles in the fine silver particle dispersion of the present embodiment (that is, if at least a part of the surface of the fine silver particles is covered), the solvent can be made to sufficiently affinity the fine silver particles, and the fine silver particles can be prevented from aggregating (the dispersibility is improved).

As the carboxylic acid, a compound having at least one carboxyl group can be widely used, and for example, there can be mentioned: formic acid, oxalic acid, acetic acid, caproic acid, acrylic acid, caprylic acid, oleic acid, and the like. The carboxyl group of a part of the carboxylic acid may also form a salt with a metal ion. The metal ion may contain two or more kinds of metal ions.

The carboxylic acid may also be a compound containing a functional group other than a carboxyl group, such as an amino group, a hydroxyl group, an alkoxy group, a carbonyl group, an ester group, a mercapto group, and the like. In this case, the number of carboxyl groups is preferably not less than the number of functional groups other than carboxyl groups. The carboxylic acids may be used alone or in combination of two or more. In addition, the boiling point at room temperature is preferably 300 ℃ or lower, and particularly preferably 250 ℃ or lower. In addition, amines form amides with carboxylic acids. Since the amide group is also appropriately adsorbed on the surface of the fine silver particles, the amide group may be attached to the surface of the fine silver particles.

When the colloid is composed of fine silver particles and an organic substance (such as the short-chain amine having 5 or less carbon atoms) attached to the surfaces of the fine silver particles, the content of the organic component in the colloid is preferably 0.5 to 50% by mass. When the organic component content is 0.5% by mass or more, the storage stability of the obtained fine silver particle dispersion tends to be good, and when it is 50% by mass or less, the conductivity of a calcined body obtained by heating the fine silver particle dispersion tends to be good. The content of the organic component is more preferably 1 to 30% by mass, and particularly preferably 2 to 15% by mass.

(1-3) highly polar solvent

The fine silver particle dispersion of the present embodiment is obtained by dispersing fine silver particles in a plurality of highly polar solvents.

As the solvent, various solvents having high polarity can be used within a range not impairing the effect of the present invention. Examples of the high-polarity solvent include: methanol, ethanol, propanol, isopropanol, butanol, isobutanol, 2-butanol, pentanol, hexanol, isoamyl alcohol, furfuryl alcohol, nitromethane, acetonitrile, pyridine, acetonesol, dimethylformamide, dioxane, ethylene glycol, glycerol, phenol, p-cresol, propyl acetate, isopropyl acetate, tert-butanol, 1-pentanol, 2-pentanol, 4-methyl-2-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 2-butanol, 1-hexanol, 2-hexanol 2-pentanone, 2-heptanone, 2- (2-ethoxyethoxy) ethyl acetate, 2-butoxyethyl acetate, 2- (2-butoxyethoxy) ethyl acetate, 2-methoxyethyl acetate, pentanol, 2-heptanone, 2-ethoxyethoxy) ethyl acetate, 2-butoxyethyl acetate, 2-hexyloxyethanol, etc., in the present invention, since the compatibility with the short chain amine having 5 or less carbon atoms is good, it is preferable to use an alcohol having 1 to 6 carbon atoms. These solvents may be used alone or in combination of two or more.

(1-4) dispersing agent

The fine silver particle dispersion of the present embodiment further includes a "dispersant having an acid value" added after the fine silver particles are synthesized in order to disperse the fine silver particles. By using the dispersant, the dispersion stability of the fine silver particles in the solvent can be improved. Here, the acid value of the dispersant is more preferably 5 to 200, and the dispersant particularly preferably has a functional group derived from phosphoric acid.

The reason is that: when the acid value of the dispersant is 5 or more, the metal compound is coordinated with the amine and starts to be adsorbed to the surface of the particle by an acid-base interaction, because: if 200 or less, adsorption sites are not excessively present, and thus adsorption is performed in a preferred form. In addition, the reason is that: since the dispersant has a functional group derived from phosphoric acid, phosphorus P interacts with metal M via oxygen O, and thus the dispersant is most effective for adsorption of metal or metal compound, and can obtain appropriate dispersibility with the minimum required adsorption amount.

Examples of the polymeric dispersant having an acid value of 5 to 200 include, for example, Sonopa (SOLSPERSE) -16000, 21000, 41000, 41090, 43000, 44000, 46000, 54000 manufactured by Lubrizol (Lubrizol), Dispalzer (DISPERBYK) manufactured by ByK-Chemie, Dispalzer (DISPERBYK) -102, 110, 111, 170, 190, 194N, 2015, 2090, 2096 manufactured by ByK, Disco (TEGO Dispers) manufactured by Wooko corporation, 610S, 630, 651, 655, 750W, 755W and the like manufactured by Rowa (Deko corporation) and Dejora (Dispron) manufactured by Wolson, and the like manufactured by Wolson, Tex-375, DA-1200, Wolff-1500, Wolff (Wolk-700, Wolk-Wolk) manufactured by Wolk-chemical corporation and the Wolff-700, Wolff-Wolk, Wolk-1200 manufactured by Wolk-Wolk and the Wolk series manufactured by Wolk-chemical corporation, GW-1640 and WK-13E.

The content of the dispersant in the fine silver particle dispersion of the present embodiment may be adjusted depending on the desired characteristics such as viscosity, and for example, when the fine silver particle dispersion is used as a silver ink, the content of the dispersant is preferably 0.5 to 20% by mass, and when the fine silver particle dispersion is used as a silver paste, the content of the dispersant is preferably 0.1 to 10% by mass.

The content of the polymeric dispersant is preferably 0.1 to 15% by mass. When the content of the polymeric dispersant is 0.1% by mass or more, the dispersion stability of the obtained fine silver particle dispersion becomes good, and when the content is too large, the low-temperature sinterability is lowered. From this viewpoint, the content of the polymeric dispersant is more preferably 0.3 to 10% by mass, and particularly preferably 0.5 to 8% by mass.

The fine silver particle dispersion of the present embodiment is preferably: the solid content has a weight loss of 10 mass% or less at 100 to 500 ℃ when subjected to thermogravimetric analysis at a temperature rise rate of 10 ℃/min. When the solid content is heated to 500 ℃, organic substances and the like are oxidized and decomposed, and most of the organic substances are gasified and disappear. Therefore, the weight loss due to heating to 500 ℃ can be substantially equivalent to the amount of organic matter in the solid content.

As the weight loss increases, the dispersion stability of the fine silver particle dispersion becomes excellent, and if the weight loss increases too much, organic matter remains as impurities in the conductive ink for transfer printing, and the conductivity decreases. In particular, in order to obtain a conductive film pattern having high conductivity by heating at a low temperature of about 100 ℃, the weight loss is preferably 20 mass% or less. On the other hand, if the weight loss is too small, the dispersion stability in a colloidal state is impaired, and therefore, it is preferably 0.1 mass% or more. More preferably, the weight loss is 0.5 to 15% by mass.

(1-5) protective agent (protective dispersant)

The fine silver particle dispersion according to the present embodiment may further include a dispersant having an acid value (protective dispersant) as a protective agent added before the synthesis of the fine silver particles. The "protective dispersant" may be the same as or different from the "dispersant having an acid value" added after the synthesis of the fine silver particles.

(1-5) other Components

In the fine silver particle dispersion of the present embodiment, in addition to the above-described components, any component such as an oligomer component, a resin component, an organic solvent (which can dissolve or disperse a part of the solid component), a surfactant, a thickener, or a surface tension adjuster, which functions as a binder, may be added in order to provide a function such as appropriate viscosity, adhesion, drying property, or printing property according to the purpose of use, within a range not to impair the effect of the present invention. The optional component is not particularly limited.

Examples of the resin component include a polyester resin, a polyurethane resin such as a blocked isocyanate, a polyacrylate resin, a polyacrylamide resin, a polyether resin, a melamine resin, and a terpene resin, and these resins may be used alone or in combination of two or more.

Examples of the thickener include clay minerals such as clay (clay), bentonite (bentonite), and hectorite (hectorite), and examples thereof include: examples of the tackifier include a latex such as a polyester latex resin, an acrylic latex resin, a polyurethane latex resin, or a blocked isocyanate, and a polysaccharide such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, a cellulose derivative of hydroxypropylmethylcellulose, xanthan gum (xanthan gum), or guar gum (guar gum).

A surfactant different from the organic component may also be added. In the inorganic colloidal dispersion liquid of the multi-component solvent system, roughness of the coating surface and variation in solid content due to a difference in volatilization rate during drying are likely to occur. By adding a surfactant to the fine silver particle dispersion of the present embodiment, these disadvantages are suppressed, and a fine silver particle dispersion capable of forming a uniform conductive coating film is obtained.

The surfactant that can be used in the present embodiment is not particularly limited, and any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used, and examples thereof include alkyl benzene sulfonate, quaternary ammonium salt, and the like. Among them, a fluorine-based surfactant and a silicone-based surfactant are preferable because an effect is obtained by a small amount of addition. If the content of the surfactant is too small, the effect cannot be obtained, and if it is too large, the surfactant becomes a residual impurity in the coating film, which may inhibit the conductivity. The content of the surfactant is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the dispersion medium of the fine silver particle dispersion.

The fine silver particles in the present embodiment are fine silver particles having alkoxyamines having a distribution coefficient logP of-1.0 to 1.4 and 5 or less carbon atoms adhered to at least a part of the surface thereof. By attaching alkoxyamines having a distribution coefficient logP of-1.0 to 1.4 and a carbon number of 5 or less to at least a part of the surface of fine silver particles, fine silver particles can be provided with excellent dispersibility in various solvents (particularly high-polarity solvents) and low-temperature sinterability.

As the solvent, various solvents can be used within a range not impairing the effect of the present invention, and a solvent having an SP value (dissolution parameter) of 7.0 to 15.0 can be used. Here, it is one of the characteristics of the fine silver particle dispersion of the present invention that fine silver particles are uniformly dispersed in a highly polar solvent, and in the present invention, it is preferable to use an alcohol having 1 to 6 carbon atoms because of good compatibility with the short chain amine having 5 or less carbon atoms. These solvents may be used alone or in combination of two or more.

Examples of the solvent having an SP value (dissolution parameter) of 7.0 to 15.0 include: hexane (7.2), triethylamine (7.3), diethyl ether (7.7), n-octane (7.8), cyclohexane (8.3), n-pentyl acetate (8.3), isobutyl acetate (8.3), methyl isopropyl ketone (8.4), pentylbenzene (8.5) butyl acetate (8.5), carbon tetrachloride (8.6), ethylbenzene (8.7), p-toluene (8.8), toluene (8.9), methyl propyl ketone (8.9) ethyl acetate (8.9), tetrahydrofuran (9.2), methyl ethyl ketone (9.3), chloroform (9.4), acetone (9.8), dioxane (10.1), pyridine (10.8), isobutanol (11.0), n-butanol (11.1), nitroethane (11.1) isopropanol (11.2), m-cresol (11.4), acetonitrile (11.9), n-propanol (12.1), furfuryl alcohol (12.5), nitromethane (12.7), ethanol (12.8), cresol (13.2), cresol (14.2), p-cresol (14.4), phenol (14.8), p-propyl acetate (14.8), phenol (14.4), phenol (14, p-propyl acetate (14.8), phenol (14.8), methyl alcohol (2), isopropyl acetate, t-butanol, 1-pentanol, 2-pentanol, 4-methyl-2-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 2-butanol, 1-hexanol, 2-hexanol-2-pentanone, 2-heptanone, 2- (2-ethoxyethoxy) ethyl acetate, 2-butoxyethyl acetate, 2- (2-butoxyethoxy) ethyl acetate, 2-methoxyethyl acetate, 2-hexyloxyethanol, and the like.

The viscosity of the fine silver particle dispersion of the present embodiment is preferably in the range of 1cps to 100cps, and more preferably in the range of 1cps to 20 cps. By setting the viscosity to this range, the fine silver particle dispersion can be uniformly applied to the silicone resin in a thin film form. The coating method may be a general coating method, and examples thereof include: applicator method, bar coater method, capillary coater method, spin coating method, and the like.

The viscosity of the fine silver particle dispersion of the present embodiment can be adjusted by adjusting the solid content concentration, adjusting the blending ratio of each component, adding a thickener, and the like. In addition, the viscosity can be measured using a vibration viscometer such as VM-100A-L manufactured by CBC (strand). The measurement is carried out by immersing the oscillator in a liquid, and the measurement temperature may be set to normal temperature (20 ℃ to 25 ℃).

(2) Method for producing conductive ink for transfer printing

In order to produce the conductive ink for transfer printing of the present embodiment, first, a fine silver particle dispersion (metal colloid liquid) is prepared. Then, the metal colloid liquid is mixed with the various components to obtain the conductive ink of the present embodiment.

The fine silver particle dispersion of the present embodiment includes: a step of generating fine silver particles; and a step of adding and mixing a dispersant having an acid value for dispersing the fine silver particles to the fine silver particles. Further, it is preferable to include: the method comprises the steps of 1, preparing a mixed solution of a silver compound which can be decomposed to generate metallic silver through reduction and short-chain amine with a distribution coefficient logP of-1.0-1.4; and a step 2 preceding that includes reducing the silver compound in the mixed solution to produce fine silver particles having short-chain amines having 5 or less carbon atoms attached to at least a part of the surface thereof.

In the step before 1, it is preferable to add 2mol or more of short-chain amine to 1mol of metallic silver. By setting the amount of the short-chain amine to 2mol or more relative to 1mol of the metallic silver, an appropriate amount of the short-chain amine can be attached to the surface of the fine silver particles produced by reduction, and the fine silver particles can be provided with excellent dispersibility in various solvents (particularly highly polar solvents) and low-temperature sinterability.

Further, the particle size of the obtained fine silver particles is preferably a nanometer size in which a decrease in melting point occurs, and more preferably 1nm to 200nm, depending on the composition of the mixed solution in the 1 st preceding step and the reduction conditions (for example, heating temperature, heating time, and the like) in the 2 nd preceding step. Here, if necessary, micron-sized particles may also be included.

The method for extracting fine silver particles from the fine silver particle dispersion obtained in the step 2 is not particularly limited, and examples thereof include a method for washing the fine silver particle dispersion.

As a starting material for obtaining fine silver particles coated with an organic substance (short-chain amine having a partition coefficient logP of-1.0 to 1.4), various known silver compounds (metal salts or hydrates thereof) can be used, and examples thereof include: silver salts such as silver nitrate, silver sulfate, silver chloride, silver oxide, silver acetate, silver oxalate, silver formate, silver nitrite, silver chlorate, and silver sulfide. These compounds are not particularly limited as long as they are reducible, and can be used in a state of being dissolved in an appropriate solvent or dispersed in a solvent. These compounds may be used alone or in combination.

The method for reducing these silver compounds in the raw material liquid is not particularly limited, and examples thereof include: a method using a reducing agent; a method of irradiating light such as ultraviolet rays, electron beams, ultrasonic waves, or thermal energy; a method of heating, and the like. Among them, a method using a reducing agent is preferable in terms of ease of handling.

The reducing agent may be exemplified by: amine compounds such as dimethylaminoethanol, methyldiethanolamine, triethanolamine, phenidone (phenidone), hydrazine (hydrazine); hydrogen compounds such as sodium borohydride, hydrogen iodide, hydrogen gas, and the like; oxides such as carbon monoxide and sulfurous acid; low-valence metal salts such as ferrous sulfate, ferric oxide, ferric fumarate, ferric lactate, ferric oxalate, ferric sulfide, tin acetate, tin chloride, tin diphosphate, tin oxalate, tin oxide, and tin sulfate; sugars such as ethylene glycol, glycerin, formaldehyde, hydroquinone, pyrogallol, tannin, tannic acid, salicylic acid, and D-glucose; the metal salt is not particularly limited as long as it is soluble in the dispersion medium and reduces the metal salt. In the case of using the reducing agent, light and/or heat may be applied to promote the reduction reaction.

Specific examples of the method for producing fine silver particles coated with an organic material using the metal salt, the organic component, the solvent and the reducing agent include the following methods: the metal salt is dissolved in an organic solvent (for example, toluene or the like) to prepare a metal salt solution, and a short-chain amine or a protective dispersant having an acid value as a protective dispersant is added to the metal salt solution, and then a solution in which a reducing agent is dissolved is slowly dropped thereto.

In the dispersion liquid containing fine silver particles coated with a short-chain amine or a protective dispersant having an acid value obtained in the above manner, in addition to the fine silver particles, counter ions of a metal salt, residues of a reducing agent, or a dispersant are present, and the electrolyte concentration or the organic matter concentration of the entire liquid tends to be high. The liquid in this state is likely to cause condensation and precipitation of metal particles due to a high electrical conductivity or the like. Alternatively, even if the metal salt does not precipitate, if a counter ion of the metal salt, a residue of the reducing agent, or an excessive dispersant in an amount not less than an amount necessary for dispersion remains, there is a concern that the conductivity may be deteriorated. Therefore, by washing the solution containing the fine silver particles to remove excess residues, fine silver particles coated with organic substances can be reliably obtained.

Examples of the washing method include: a method of repeating the following steps several times: allowing the dispersion containing the fine silver particles coated with the organic component to stand for a certain period of time, removing the resulting supernatant, adding a solvent (e.g., water, methanol, a methanol/water mixed solvent, etc.) for precipitating the fine silver particles, stirring again, and allowing the resulting mixture to stand for a certain period of time to remove the resulting supernatant; a method of performing centrifugal separation instead of the standing; a method of desalting by an ultrafiltration apparatus, an ion exchange apparatus or the like. By removing the excess residue by such washing and removing the organic solvent, the metal particles coated with the "short-chain amine or the dispersant having an acid value" of the present embodiment can be obtained.

In the present embodiment, the fine silver particle dispersion (silver colloid dispersion) is obtained by mixing the fine silver particles coated with the short-chain amine or the protective dispersant having an acid value obtained in the above-described manner with the dispersion medium described in the present embodiment. The method of mixing the metal particles coated with the "short-chain amine or the protective dispersant having an acid value" and the dispersion medium is not particularly limited, and can be carried out by a conventionally known method using a stirrer, a stirrer (sticrer), or the like. Stirring is carried out by means of a spatula or the like, or an ultrasonic homogenizer of suitable power may be used.

In the case of obtaining a fine silver particle dispersion containing a plurality of metals, the production method is not particularly limited, and for example, in the case of producing a fine silver particle dispersion containing silver and another metal, a dispersion containing fine silver particles and a dispersion containing another metal particle may be separately produced and mixed in the preparation of the metal particles coated with the organic substance, or a silver ion solution and another metal ion solution may be mixed and then reduced.

The fine silver particles can also be produced by the following steps: step 1, preparing a mixed solution of a silver compound which can be decomposed by reduction to produce metallic silver and a short-chain amine having a distribution coefficient logP of-1.0 to 1.4; and a 2 nd step of reducing the silver compound in the mixed solution to produce fine silver particles having short-chain amines having 5 or less carbon atoms attached to at least a part of the surface thereof.

For example, a complex formed by a metal compound such as silver oxalate containing silver and a short-chain amine is heated to decompose the metal compound such as oxalate ions contained in the complex and to aggregate atomic silver, thereby producing silver particles protected by a protective film of the short-chain amine.

As described above, in the decomposition method of a metal amine complex for producing metal particles coated with an amine by thermally decomposing a complex of a metal compound in the presence of an amine, since an atomic metal is produced by a decomposition reaction of a metal amine complex which is a single molecule, the atomic metal can be produced uniformly in a reaction system, and unevenness of the reaction due to fluctuation in the composition of components constituting the reaction is suppressed as compared with the case of producing a metal atom by a reaction between a plurality of components, which is advantageous particularly when a large amount of metal powder is produced on an industrial scale.

In addition, in the metal amine complex decomposition method, it is presumed that: short-chain amine molecules coordinately bound to the metal atoms to be formed, and the movement of the metal atoms when the metal atoms are aggregated by the action of the short-chain amine molecules coordinately bound to the metal atoms is controlled. The result is: according to the decomposition method of the metal amine complex, very fine metal particles having a narrow particle size distribution can be produced.

Furthermore, many short-chain amine molecules also generate relatively weak coordinate bonds on the surface of the produced metal fine particles, and these form a dense protective coating on the surface of the metal particles, so that coated metal particles having excellent storage stability and clean surfaces can be produced. In addition, since the short-chain amine molecules forming the coating film can be easily detached by heating or the like, metal particles that can be sintered at a very low temperature can be produced.

In addition, when a solid metal compound is mixed with an amine to form a composite compound such as a complex, a short-chain amine having 5 or less carbon atoms is mixed with a dispersant having an acid value constituting a coating film covering silver particles and used, whereby the composite compound such as a complex can be easily formed and can be produced by mixing in a short time. Further, by mixing and using the short-chain amine, coated silver particles having characteristics suitable for various applications can be produced.

(3) Conductive film pattern (substrate with conductive film pattern) and method for producing same

When the conductive ink for transfer printing of the present embodiment is used, a substrate with a conductive film pattern including a base material and a conductive film pattern formed on at least a part of the surface of the base material can be manufactured by a conductive ink application step of applying the conductive ink for transfer printing to a base material, and a conductive film pattern formation step of forming a conductive film pattern by baking the conductive ink for transfer printing applied to the base material at a temperature of 200 ℃.

The present inventors have conducted extensive studies and, as a result, found that: when the conductive ink for transfer printing of the present embodiment is used as the conductive ink in the conductive ink application step for transfer printing, a conductive film pattern having excellent conductivity can be reliably obtained even when the conductive ink applied to the base material is fired at a temperature of 200 ℃.

In the reverse printing method among the transfer printing methods, first, a conductive ink for transfer printing is applied to a blanket to form a conductive ink-applied surface. The glue board is preferably a silicone glue board comprising silicone. After the conductive ink coated surface is formed on the surface of the blanket, the blanket is left for a predetermined period of time, and the low boiling point solvent is volatilized and absorbed into the blanket, thereby increasing the viscosity of the conductive ink for transfer printing.

When a relief plate having a plate corresponding to a predetermined pattern is pressed against the conductive ink-applied surface, the conductive ink in the portion in contact with the relief plate is removed from the blanket. In this case, since the conductive ink has appropriate cohesive properties, the structure of the conductive ink is not destroyed, and peeling from the blanket and adhesion to the relief plate are reliably performed, so that defective residue on the blanket is suppressed. The result is: the pattern of the conductive ink conforming to the pattern of the relief is formed on the blanket by the conductive ink remaining on the blanket.

The wet or semi-dry conductive ink remaining on the blanket is transferred to a printing object. In this case, since the conductive ink has appropriate cohesive properties, peeling from the blanket and adhesion to the printing object are reliably performed, and defective residue on the blanket is suppressed. The result is: on the printing object, a conductive film pattern is formed by a pattern inverted with respect to a pattern formed on the relief plate.

The substrate usable in the present embodiment is not particularly limited as long as it has at least one main surface on which a conductive film pattern can be mounted by applying a conductive ink and heating and firing the conductive film pattern, but a substrate having excellent heat resistance is preferable. As described above, the conductive ink for transfer printing according to the present embodiment can obtain a conductive film pattern having sufficient conductivity even when heated and fired at a low temperature as compared with the conventional conductive ink, and therefore, a base material having a lower heat-resistant temperature than before can be used in a temperature range higher than the low firing temperature.

Examples of the material constituting such a substrate include: polyamide (PA), Polyimide (PI), Polyamideimide (PAI), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and other polyesters, Polycarbonate (PC), Polyethersulfone (PES), vinyl resin, fluororesin, liquid crystal polymer, ceramic, glass, or metal. The substrate may have various shapes such as a plate shape or a belt shape, and may be rigid or flexible. The thickness of the substrate may also be selected as appropriate. For the purpose of improving adhesiveness or adhesion or the like, a substrate having a surface layer formed thereon or a substrate subjected to a surface treatment such as hydrophilization treatment may be used.

The conductive film pattern (substrate with a conductive film pattern) of the present embodiment can be obtained by heating the coating film applied in this manner to a temperature of 200 ℃ or lower (preferably less than 180 ℃, and particularly preferably 150 ℃ or lower) and calcining the same.

The method of performing the firing is not particularly limited, and for example, a conductive film pattern can be formed by firing the conductive ink applied or drawn on the substrate at a temperature of 200 ℃ or less (preferably less than 180 ℃, and particularly preferably 150 ℃ or less) using a conventionally known gear oven (gear oven) or the like. The lower limit of the temperature of the calcination is not necessarily limited, and it is preferably a temperature at which the conductive film pattern can be formed on the substrate and at which the organic component and the like can be removed by evaporation or decomposition within a range not impairing the effect of the present invention (a part may remain within a range not impairing the effect of the present invention, but it is preferable to remove all of them).

According to the conductive ink of the present embodiment, since a conductive film pattern exhibiting high conductivity even in a low-temperature heating process at about 120 ℃ can be formed, the conductive film pattern can be formed also on a relatively heat-labile substrate. The firing time is not particularly limited, and a conductive film pattern can be formed on the substrate depending on the firing temperature.

In this embodiment, the surface of the base material may be treated to further improve the adhesion between the base material and the conductive film pattern. Examples of the surface treatment method include: a method of performing dry treatment such as corona treatment (corona treatment), plasma treatment, Ultraviolet (UV) treatment, and electron beam treatment; a method of providing an undercoat layer or a conductive ink receiving layer on a substrate in advance, and the like.

In this manner, the conductive film pattern (substrate with a conductive film pattern) of the present embodiment can be obtained. The conductive film pattern of the present embodiment obtained in this manner is, for example, about 0.1 to 5 μm, and more preferably about 0.1 to 1 μm. When the conductive ink of the present embodiment is used, a conductive film pattern having sufficient conductivity can be obtained even if the thickness is about 0.1 to 5 μm. The volume resistance value of the conductive film pattern of the present embodiment is 15 μ Ω · cm or less.

The thickness t of the conductive film pattern according to the present embodiment can be obtained by using the following formula, for example (the thickness t of the conductive film pattern can be measured by a laser microscope (for example, a laser microscope VK-9510 manufactured by Keyence).

Formula (II): t is M/(dXMXw)

m: conductive film pattern weight (weight of conductive film pattern formed on glass slide measured by electronic balance)

d: pattern density (g/cm) of conductive film³) (10.5 g/cm in the case of silver)³)

M: conductive film Pattern Length (cm) (the length of the conductive film pattern formed on the glass slide is measured in a scale corresponding to JIS1 level)

w: width (cm) of conductive film pattern (width of conductive film pattern formed on glass slide measured in a scale corresponding to JIS 1)

[ examples ]

The conductive ink for transfer printing and the method for producing a conductive film pattern (a substrate with a conductive film pattern) using the conductive ink of the present invention will be described below by way of examples and comparative examples, but the present invention is not limited to these examples.

< preparation example 1>

8.9g of 3-methoxypropylamine (C4, log P: -0.5, first grade reagent manufactured by Wako pure chemical industries, Ltd.) and 0.3g of Disperbek (DISPERBYK) -111 as a polymer dispersant were mixed and sufficiently stirred by a magnetic stirrer to produce an amine mixture (the molar ratio of the added amine to silver was 10). Then, 3.0g of silver acetate was added while stirring. After the addition of silver oxalate, stirring was continued at room temperature, whereby the silver oxalate was changed to a viscous white substance, and the end of the change in appearance was visually confirmed, and at that time, stirring was terminated (step 1).

The obtained mixture was transferred to an oil bath and heated and stirred at 120 ℃. Immediately after the start of the stirring, the reaction accompanied by the generation of carbon dioxide was started, and then the stirring was performed until the generation of carbon dioxide was completed, thereby obtaining a suspension in which fine silver particles were suspended in the amine mixed solution (step 2, prior).

Then, in order to replace the dispersion medium of the obtained suspension, 10mL of a mixed solvent of methanol and water was added and stirred, and then fine silver particles were separated by sedimentation by centrifugal separation. Fine silver particles thus separated were again stirred with 10mL of a mixed solvent of methanol and water, and then separated by centrifugation to precipitate fine silver particles, and 2.1g of a mixed solvent of ethanol, isobutanol and isopropanol (40: 20v/v) was added as a dispersion solvent, thereby obtaining fine silver particle dispersion a having a solid content of 48 mass%.

< preparation example 2>

8.9g of 3-methoxypropylamine (C4, log P: -0.5, first grade reagent manufactured by Wako pure chemical industries, Ltd.) and 0.3g of Disperbek (DISPERBYK) -102 as a polymer dispersant were mixed and sufficiently stirred by a magnetic stirrer to produce an amine mixture (the molar ratio of the added amine to silver was 5). Then, 3.0g of silver acetate was added while stirring. After the addition of silver oxalate, stirring was continued at room temperature, whereby the silver oxalate was changed to a viscous white substance, and the end of the change in appearance was visually confirmed, and at that time, stirring was terminated (step 1).

The obtained mixture was transferred to an oil bath and heated and stirred at 120 ℃. Immediately after the start of the stirring, the reaction accompanied by the generation of carbon dioxide was started, and then, the stirring was performed until the generation of carbon dioxide was completed, thereby obtaining a suspension in which fine silver particles were suspended in the amine mixed solution (step 2, prior).

Then, in order to replace the dispersion medium of the obtained suspension, 10mL of a mixed solvent of methanol and water was added and stirred, and then fine silver particles were separated by sedimentation by centrifugal separation. The separated fine silver particles were again stirred with 10mL of a mixed solvent of methanol and water, and then separated by centrifugation to settle the fine silver particles, and 2.1g of ethanol containing 0.06g of knoop (SOLSPERSE)41000 (manufactured by Lubrizol corporation, japan) was added to obtain a fine silver particle dispersion B having a solid content concentration of 48 mass%.

< examples and comparative examples >)

Using the fine silver particle dispersion a or the fine silver particle dispersion B obtained in the above manner, mixed with other components shown in table 1, the conductive inks 1 to 7 for transfer printing of examples 1 to 7 and the conductive inks 1 to 3 for comparative transfer printing of comparative examples 1 to 3 were prepared. The unit of the amount of the component in table 1 is "mass%".

The following evaluation tests were carried out on the fine silver particle dispersion a and the fine silver particle dispersion B, and the conductive ink 1 to 7 for transfer printing, and the conductive ink 1 to 3 for comparative transfer printing. The results are shown in table 1.

[ evaluation test ]

(1) Determination of organic Components

The content of the organic component contained in the fine silver particle dispersion was measured by thermogravimetry. Specifically, the solid content of the fine silver particle dispersion was heated at a temperature rise rate of 10 ℃/min, and the content of the specific organic component was defined as the weight loss at room temperature to 500 ℃.

(2) Dispersibility

The conductive ink for transfer printing was left to stand in a container and the presence or absence of precipitation and the state of the supernatant liquid were visually observed after 1 day at room temperature, thereby evaluating the dispersibility of the fine silver particle dispersion. The case where substantially no sediment was recognized below the vessel was evaluated as "O", the case where a small amount of sediment was recognized was evaluated as "Delta", and the case where a concentration difference was clearly present above and below the vessel and sediment was clearly recognized was evaluated as "X".

(3) Surface tension measurement of conductive ink

The surface tensions of the conductive inks 1 to 4 for transfer printing obtained in examples 1 to 4 and the conductive inks 1 to 3 for comparative transfer printing obtained in comparative examples 1 to 3 were measured by a fully automatic surface tension meter CBVP-Z (manufactured by consortium interfacial science). The measurement was performed by automatic measurement using a platinum plate. The measurement temperature was set to room temperature (20 ℃ C. to 25 ℃ C.).

(4) Evaluation of wettability of conductive ink

The conductive inks 1 to 7 for transfer printing obtained in examples 1 to 7 and the conductive inks 1 to 3 for comparative transfer printing obtained in comparative examples 1 to 3 were applied to a silicone rubber plate by a bar coater (No.7) to visually evaluate the wettability of the conductive inks for transfer printing with respect to the rubber plate. The case where the wettability was good was evaluated as "o", and the case where the wettability was poor was evaluated as "x".

(5) Evaluation of printing shape (thin line drawing Property)

The glass relief plate is pressed against a blanket coated with conductive ink for transfer printing, and the non-image portion (unnecessary portion) is transferred and removed. Further, a pattern was transferred to the base material by pressing the base material (PEN: polyethylene naphthalate) against the sheet material. The print shape was evaluated by visual observation of the obtained pattern shape. The case of good printing shape was evaluated as "o", the case of acceptable range was evaluated as "Δ", and the case of failure was evaluated as "x". The pattern was a thin line, the line width was 10 μm, 20 μm, 30 μm, 50 μm, and 100 μm, and the length was 10 mm.

(6) Evaluation of transferability

The transferability was evaluated by visually evaluating the print shape formed in (5) and the conductive ink remaining on the blanket. The case where the printing shape was good and remained substantially on the blanket was evaluated as "o", the case where the acceptable range was evaluated as "Δ", and the case where the printing shape was poor or remained significantly on the blanket was evaluated as "x".

(7) Evaluation of continuous printability

The operation of evaluating the print shape of (5) was continuously repeated 5 times to evaluate the continuous printability.

(8) Evaluation of conductivity of conductive film pattern

The pattern (line width 100 μm, length 10mm) transferred onto the substrate was calcined at 120 ℃ for 30 minutes, and the resistance value of the pattern was measured. Specifically, the volume resistivity was determined by a Double Bridge method using a portable Double Bridge (Double Bridge)2769 manufactured by Yokogawa Meters and Instruments (stockpile). The volume resistance value is converted from the measurement of the distance between the terminals and the thickness of the conductive film pattern based on the following equation.

Formula (II): (volume resistivity ρ v) ═

(resistance value R) × (coating width w) × (coating thickness t)/(inter-terminal distance L)

[ Table 1]

In Table 1, "Nobel (Novec) 7300" was manufactured by Sumitomo 3M, and "Shafu Long (Surflon) S-651" was manufactured by AGC chemistry. Further, "Forgelite (Ftergent)610 FM" is manufactured by Neos corporation.

As is clear from the results shown in table 1, the conductive ink for transfer printing of the present invention is excellent in dispersibility, wettability, printability and conductivity. Among these, examples 3 and 4 using fine silver particle dispersion B are also excellent in continuous printability, and particularly preferred.

On the other hand, comparative examples 1 and 2 show that: the transferability of the conductive ink containing no specific high boiling point solvent is deteriorated. In addition, from comparative example 3, it is clear that: when the content of the high boiling point solvent is excessive, drying is slow and transferability is deteriorated. Further, from comparative example 2, it is clear that: when only the fluorine solvent is contained, the wettability can be secured, but the transferability is deteriorated.

Claims

1. A conductive ink for transfer printing, comprising:

a fine silver particle dispersion;

a vehicle comprising ethanol; and

0.1 to 3.0 mass% of a high boiling point solvent having a boiling point of 200 ℃ or higher under 1 atmosphere of a hydroxyl group, the high boiling point solvent being 1, 3-butanediol; and is

The fine silver particle dispersion includes:

fine silver particles, a short-chain amine having 5 or less carbon atoms and a distribution coefficient logP of-1.0 to 1.4, a highly polar solvent having a dissolution parameter of 7.0 to 15.0, and a dispersant having an acid value of 5 or more for dispersing the fine silver particles.

2. The conductive ink for transfer printing according to claim 1, further comprising a hydrofluoroether.

3. The conductive ink for transfer printing according to claim 1, wherein:

in the fine silver particle dispersion, the short-chain amine is an alkoxyamine, and further includes a protective dispersant having an acid value added before the fine silver particle synthesis.

4. The conductive ink for transfer printing according to claim 3, wherein: