WO2016084312A1 - Conductive ink - Google Patents

Abstract

Provided is a conductive ink for transfer printing with which it is possible to fire at low temperature a conductive film pattern having adequate conductivity and excellent adhesiveness with a substrate. A conductive ink for transfer printing, characterized by containing metal particles, a solvent containing ethanol, and 0.1-3.0 mass% of a high-boiling-point solvent that has hydroxyl groups.

Description

Conductive ink

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

Conventionally, a method is known in which a metal thin film is formed on the entire surface of a substrate by sputtering or vapor deposition, and then an unnecessary portion is etched by photolithography to form a necessary conductive film pattern. However, this method requires complicated vacuum processes and an expensive vacuum apparatus.

For this reason, a simpler and less expensive method for forming a conductive film pattern has been demanded. In recent years, methods using printing methods such as letterpress printing, intaglio printing, screen printing, and ink jet printing have been proposed. . Furthermore, as a printing method capable of forming a higher-definition pattern, a method using a reverse printing method, a microcontact printing method, or the like has been proposed, and conductive ink, insulating ink, and resistance suitable for these printing methods are proposed. Various inks such as ink have been developed.

In Patent Document 1, a conductive ink for forming a fine conductive film pattern by a letterpress reverse printing method has been proposed. Specifically, a substantial effect for forming a conductive film pattern by a letterpress reverse printing method is proposed. Is a conductive ink which does not contain a binder component, and has a volume average particle size (Mv) of 10 to 700 nm, a conductive particle, a release agent, a surface energy adjusting agent, a solvent component as essential components, and a solvent component at 25 ° C. A mixture of a solvent having a surface energy of 27 mN / m or more and a volatile solvent having a boiling point of 120 ° C. or less under atmospheric pressure, and the surface energy of the ink at 25 ° C. is 10 to 21 mN / m An electrically conductive ink is disclosed.

By using the conductive ink described in Patent Document 1, a fine conductive film pattern can be stably formed without a transfer defect by a letterpress reverse printing method. For example, when silver is used as conductive particles In addition to providing excellent conductivity with a specific resistance of the order of 10 ⁻⁵ Ω · cm or less by firing the formed fine pattern at a low temperature of 200 ° C. or less, it is excellent in transferability. It becomes possible to form a fine pattern.

Further, in Patent Document 2, “when the dynamic surface tension at 25 ° C. determined by the maximum bubble pressure method is measured by setting the bubble generation period to 0.05 Hz, it is 16 mN / m or more and 23 mN / m or less. In addition, an ink having 20 mN / m or more and 27 mN / m or less when measured with the generation period set to 10.0 Hz is disclosed.

This ink has appropriate wettability and releasability on the surface of the silicone blanket by adjusting the dynamic surface tension to an appropriate range. This is an ink for reversal printing in which an ink pattern having a uniform thickness is obtained.

International Publication No. WO2008 / 111484 JP 2011-252072 A

However, a fine pattern can be formed by using the conductive ink described in Patent Document 1, but since the binder is substantially not included, the adhesion of the conductive film pattern formed on the substrate is low. There are scarce cases. Furthermore, in order to develop conductivity, a baking temperature of 180 ° C. or higher is necessary, and there is a problem that an inexpensive base material having poor heat resistance cannot be used.

The ink disclosed in Patent Document 2 is mainly suitable for a color filter constituting a liquid crystal display and cannot be used as it is for a conductive ink suitable for a transfer printing method such as a reverse printing method. Since a relatively large amount of the solvent for dissolving the resin is contained, it is necessary to dry the surface of the silicone blanket for a relatively long time after coating, and there is a problem in that the printing tact is relatively long.

Accordingly, an object of the present invention has been made in view of the above-described problems of the prior art, and is a conductive ink for transfer printing that can be suitably used for a transfer printing method including a reverse printing method. An object of the present invention is to provide a conductive ink for transfer printing, which can fire a conductive film pattern having good conductivity and good adhesion to a substrate at a low temperature.

As a result of intensive studies to achieve the above object, the present inventor is a conductive ink for transfer printing that can be suitably used for transfer printing methods including reversal printing methods, etc., and has sufficient conductivity and substrate. In order to obtain a conductive ink for transfer printing that can be baked at a low temperature, a conductive film pattern having good adhesiveness with a suitable amount of metal particles and a high boiling point solvent having a specific hydroxyl group may be included. The inventors have found that the present invention is extremely effective in achieving the above-described object, and have reached the present invention.

That is, the present invention
Metal particles,
A solvent comprising ethanol;
Containing 0.1 to 3.0% by mass of a high-boiling solvent having a hydroxyl group,
A conductive ink for transfer printing is provided.

In the “transfer printing method” of the present invention, a typical “reverse printing method” will be described. “Reversal printing method” is a portion in which ink is applied onto a blanket such as a silicone resin to form an ink application surface, and a relief plate for removing a non-image part is pressed on the ink application surface to contact the relief plate After the ink is removed from the blanket, the ink remaining on the blanket is transferred to a printing medium.

In the conductive ink for transfer printing of the present invention, it is more preferable that the high boiling point solvent contains 1,3-butylene glycol, 2,4-diethyl-1,5-pentanediol or octanediol.

Moreover, it is preferable that the conductive ink for transfer printing of the present invention further contains hydrofluoroether.

The conductive ink for transfer printing of the present invention is
The metal particles are silver particles;
Silver particles,
A short-chain amine having 5 or less carbon atoms and a partition coefficient log P of -1.0 to 1.4,
A highly polar solvent;
A dispersant having an acid value for dispersing the silver fine particles;
A silver fine particle dispersion containing
Is preferred.

Furthermore, the conductive ink for transfer printing of the present invention is
In the silver fine particle dispersion, the short chain amine is an alkoxyamine, and further contains a protective dispersant having an acid value.
Is preferred.

Furthermore, in the conductive ink for transfer printing of the present invention,
The protective dispersant has an acid value of 5 to 200, and has a functional group derived from phosphoric acid,
Is preferred.

The conductive ink for transfer printing according to the present invention is a conductive ink for transfer printing that can be suitably used for transfer printing methods including reversal printing methods, and has sufficient conductivity and good adhesion to a substrate. The conductive ink for transfer printing which can bake the electrically conductive film pattern which has this at low temperature is realizable.

Hereinafter, (1) one preferred embodiment of the conductive ink for transfer printing of the present invention, (2) one preferred embodiment of the method for producing the conductive ink for transfer printing of the present invention, and (3) the transfer of the present invention. A conductive film pattern using a conductive ink for printing and a manufacturing method thereof 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 this embodiment includes metal particles, a solvent containing ethanol, and 0.1 to 3.0% by mass of a high boiling point solvent having a hydroxyl group. It is characterized by that. Moreover, the solid content which has the metal particle dispersion (in other words metal colloid) particle | grains which consist of a metal particle and an organic component as a main component, and the dispersion medium which disperse | distributes these solid content are included. However, in the colloid liquid, the “dispersion medium” may dissolve a part of the solid content.

According to such a metal colloid liquid, since it contains an organic component, the dispersibility of the metal colloid particles in the metal colloid liquid can be improved. Therefore, the content of the metal component in the metal colloid liquid can be reduced. Even if it is increased, the colloidal metal particles are less likely to aggregate and good dispersion stability can be maintained. The “dispersibility” as used herein indicates whether or not the dispersion state of the metal particles in the metal colloid liquid is excellent immediately after the metal colloid liquid is prepared (whether it is uniform or not). , "Dispersion stability" indicates whether or not the dispersion state of the metal particles in the metal colloid liquid is maintained after a predetermined time has elapsed after adjusting the metal colloid liquid, It can also be said to be “low sedimentation aggregation”.

Here, in the metal colloid liquid, the “organic component” in the metal colloid particle is an organic substance that substantially constitutes the metal colloid particle together with the metal component. The organic component includes trace organic substances contained in the metal as impurities from the beginning, organic substances adhering to the metal component from trace organic substances mixed in the manufacturing process described later, residual reducing agent that could not be removed in the cleaning process, residual dispersion It does not include organic substances that adhere to trace amounts of metal components such as agents. The “trace amount” is specifically intended to be less than 1% by mass in the metal colloid particles.
Since the metal colloid particles in this embodiment contain an organic component, the dispersion stability in the metal colloid liquid is high. 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.

In addition, the “solid content” of the metal colloid liquid in the present embodiment means that after removing the dispersion medium from the metal colloid liquid using silica gel or the like, for example, it is dried at room temperature of 30 ° C. or lower (for example, 25 ° C.) for 24 hours. In general, the solid content that remains is usually contained metal particles, residual organic components, residual reducing agent, and the like. Various methods can be employed as a method of removing the dispersion medium from the metal colloid liquid using silica gel. For example, a metal colloid liquid is applied on a glass substrate and placed in a sealed container containing silica gel. What is necessary is just to remove a dispersion medium by leaving a glass substrate with a coating film for 24 hours or more.

In the metal colloid liquid of the present embodiment, the preferable solid content is 1 to 60% by mass. When the solid content concentration is 1% by mass or more, the metal content in the conductive ink for transfer printing can be secured, and the conductive efficiency does not decrease. In addition, when the solid content concentration is 60% by mass or less, the viscosity of the metal colloid liquid does not increase, the handling is easy, it is industrially advantageous, and a flat thin film can be formed. A more preferable solid content is 5 to 40% by mass.

The conductive ink for transfer printing of the present invention is characterized by containing 0.1 to 3.0% by mass of a high boiling point solvent having a hydroxyl group. The high boiling point solvent having a hydroxyl group is 1,3-butylene glycol (boiling point: 203 ° C.), 2,4-diethyl-1,5-pentanediol (boiling point: 150 ° C./5 mmHg, 200 ° C. or more at 1 atm) or octane. It is preferably selected from diols (boiling point: 243 ° C.).

In the present invention, the “high boiling point solvent” refers to a solvent having a boiling point of 200 ° C. or higher. In addition, since it has a suitable affinity for water by having a hydroxyl group and tends to absorb or absorb moisture in the air and moisturize it, an ink suitable for transfer printing with a small addition amount can be obtained. can do. Furthermore, by minimizing the amount of the high-boiling solvent added, the ink applied on the silicone blanket can be semi-dried in a short time, and the printing tact can be shortened.

The addition amount of the high boiling point solvent having a hydroxyl group is 0.1 to 3.0% by mass. If the amount is less than 0.1% by mass, the amount is too small to easily form an ink suitable for the transfer printing method. If the amount exceeds 3.0% by mass, the time to reach a semi-dry state suitable for the transfer printing method is reached. It becomes longer and disadvantageous in terms of printing tact. The addition amount of the high boiling point solvent having a hydroxyl group is 0.3 to 2.0% by mass, but it is more sure that the ink is suitable for the transfer printing method, and it is a semi-dry state suitable for the transfer printing method. This is particularly preferable from the viewpoint of shortening the time required to reach the position and being advantageous in terms of printing tact.

Further, in the conductive ink for transfer printing of the present invention, a highly volatile solvent such as ethanol is added in order to improve the drying property of the ink. By adding the solvent, the transfer printing conductive ink can be quickly adjusted to a viscosity suitable for printing. Examples of the highly volatile solvent include one or more selected from the group of solvents having a boiling point of less than 100 ° C. such as ethanol, methanol, propyl alcohol, isopropyl alcohol, acetone, n-butanol, sec-butanol, tert-butanol and the like. Low boiling solvents can be used.

Furthermore, the conductive ink for transfer printing of the present invention preferably contains a fluorine solvent such as hydrofluoroether. Since the fluorine solvent has a low surface tension, it can exhibit good wettability with respect to the silicone blanket, and since the boiling point is relatively low, it can provide good drying properties. Of these, hydrofluoroethers are more preferable than fluorine solvents containing halogen atoms from the viewpoint of the ozone depletion coefficient.

In addition, hydrofluoroether has an ether bond than hydrofluorocarbons, so it has a high polarity and has the advantage of hardly causing the silicone blanket to swell, and has good compatibility with alcohols such as ethanol, This is more preferable because it has an effect of being excellent in compatibility with metal particles dispersed in alcohol.

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 the wettability with respect to the silicone blanket. However, in this case, if the addition amount is too large, the conductivity of the conductive film produced using the conductive ink for transfer printing is lowered, and if the addition amount is too small, the effect of improving the wettability is insufficient. The content is preferably 0.01 to 2% by mass.

In the conductive ink for transfer printing of the present invention, the surface tension is 22 mN / m or less. By sufficiently lowering the surface tension to 22 mN / m or less, the wettability of the conductive ink for transfer printing onto a blanket such as a silicone resin can be sufficiently ensured. The surface tension of 22 mN / m or less can be realized by adjusting the component ratio of the conductive ink for transfer printing according to the present invention. The lower limit of the surface tension may be about 13 mN / m. The surface tension referred to in the present invention is obtained by measurement based on the principle of the plate method (Wilhelmy method). For example, the surface tension is measured by a fully automatic surface tension meter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. can do.

Here, the conductive ink for transfer printing of the present embodiment includes silver fine particles, a short-chain amine having a carbon number of 5 or less and a distribution coefficient log P of −1.0 to 1.4, a high-polarity solvent, It is preferable to be composed of a silver fine particle dispersion (for example, colloidal) containing a dispersant having an acid value for dispersing the silver fine particles. Details of the silver fine particle dispersion and each component will be described below.

The silver fine particle dispersion of the present embodiment contains silver fine particles, a short-chain amine having 5 or less carbon atoms, and a highly polar solvent, and has, for example, a colloidal colloidal liquid form. Regarding the form of silver fine particles (silver colloidal particles) contained in the solid content of the silver fine particle dispersion, for example, silver colloidal particles formed by adhering organic components to the surface of particles composed of silver components, Silver colloidal particles whose surface is coated with an organic component and silver colloidal particles that are configured by uniformly mixing a silver component and an organic component are included. Not. Silver colloidal particles having a particle composed of a silver component as a core and the surface of which is coated with an organic component, or silver colloidal particles formed by uniformly mixing a silver component and an organic component are preferable. A person skilled in the art can appropriately prepare the colloidal silver particles having the above-described form using a well-known technique in this field.

(1-1) Silver Fine Particles The average particle diameter of the silver fine particles contained in the silver fine particle dispersion in the present embodiment is not particularly limited as long as the effects of the present invention are not impaired, but a melting point drop occurs. It is preferable to have such an average particle diameter, for example, it may be 1 to 400 nm. Further, it is preferably 1 to 70 nm. If the average particle diameter of the silver fine particles is 1 nm or more, the silver fine particles have good low-temperature sinterability, and the production of silver fine particles is practical without increasing the cost. Moreover, if it is 400 nm or less, the dispersibility of a silver fine particle does not change easily over time, and it is preferable. In the conductive ink for transfer printing obtained using the silver fine particle dispersion of this embodiment, the average particle diameter (median diameter) of the silver colloid particles (including silver fine particles) is substantially the same as this range. (Can approximate)

Note that the particle size of the silver fine particles in the silver fine particle dispersion varies depending on the solid content concentration, and is not necessarily constant, and may not be constant. In addition, when the silver fine particle dispersion contains a dispersant described later as an optional component, the silver fine particle dispersion may contain a silver fine particle component having an average particle diameter of more than 400 nm. A silver fine particle component having an average particle diameter of more than 400 nm may be included as long as the component is not significantly impaired.

Here, the average particle diameter of the silver fine particles in the silver fine particle dispersion of the present embodiment is based on the dynamic light scattering method (Doppler scattered light analysis). For example, the dynamic light scattering particle diameter manufactured by Horiba, Ltd. It can be represented by a volume-based median diameter (D50) measured by the distribution measuring device LB-550. Specifically, several drops of a metal colloid solution are dropped into 10 mL of ethanol, and are shaken and dispersed by hand to prepare a measurement sample. Next, 3 mL of the measurement sample is put into a cell of a dynamic light scattering particle size distribution measuring device LB-550 manufactured by Horiba, Ltd., and measurement is performed under the following conditions.

・ Measurement condition data read count: 100 times Cell holder temperature: 25 ° C
Display condition distribution form: Standard number of repetitions: 50 times Particle size standard: Volume-based refractive index of refractive index: 0.200-3.900i (in the case of silver)
Refractive index of dispersion medium: 1.36 (when ethanol is the main component)
・ System condition setting strength criteria: Dynamic
Scattering intensity range upper limit: 10000.00
Scattering intensity range lower limit: 1.00

(1-2) Short-chain amine having 5 or less carbon atoms In the silver fine 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 silver fine particles. . In addition, on the surface of the silver fine particles, a trace amount of organic matter contained as an impurity from the beginning, a trace amount of organic matter mixed in the manufacturing process described later, a residual reducing agent that could not be removed in the cleaning process, a residual dispersant, etc. A trace amount of organic matter may be attached.

The short-chain amine having 5 or less carbon atoms is not particularly limited as long as the distribution coefficient logP is −1.0 to 1.4, and may be linear or branched. You may have a 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-ethanediamine, 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) pentanolamine (-0.3), aminoisobutanol ( -0.8), etc., among which alkoxyamine is preferably used.

The short chain amine may be a compound containing a functional group other than an amine such as a hydroxyl group, a carboxyl group, an alkoxy group, a carbonyl group, an ester group, or a mercapto group. Moreover, the said amine may be used independently, respectively and may use 2 or more types together. In addition, the boiling point at normal temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower.

The 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. The carboxyl group in one molecule of the carboxylic acid has a relatively high polarity and tends to cause an interaction due to a hydrogen bond, but a portion other than these functional groups has a relatively low polarity. Furthermore, the carboxyl group tends to exhibit acidic properties. In addition, when the carboxylic acid is localized (attached) on at least a part of the surface of the silver fine particles (that is, covers at least a part of the surface of the silver fine particles) in the silver particle dispersion of the present embodiment, the solvent. And silver fine particles can be made to sufficiently adhere to each other and aggregation of silver fine particles can be prevented (dispersibility is improved).

As the carboxylic acid, compounds having at least one carboxyl group can be widely used, and examples thereof include formic acid, oxalic acid, acetic acid, hexanoic acid, acrylic acid, octylic acid, and oleic acid. A part of carboxyl groups of the carboxylic acid may form a salt with a metal ion. In addition, about the said metal ion, 2 or more types of metal ions may be contained.

The carboxylic acid may 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, or a mercapto group. In this case, the number of carboxyl groups is preferably equal to or greater than the number of functional groups other than carboxyl groups. Moreover, the said carboxylic acid may be used independently, respectively and may use 2 or more types together. In addition, the boiling point at normal temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower. Also, amines and carboxylic acids form amides. Since the amide group also adsorbs moderately on the surface of the silver fine particles, the amide group may adhere to the surface of the silver fine particles.

When the colloid is composed of silver fine particles and organic substances (such as the short-chain amine having 5 or less carbon atoms) attached to the surface of the silver fine particles, the content of the organic component in the colloid is 0.5 to 50 It is preferable that it is mass%. If the organic component content is 0.5% by mass or more, the storage stability of the resulting silver fine particle dispersion tends to be improved, and if it is 50% by mass or less, the silver fine particle dispersion is obtained by heating. There exists a tendency for the electroconductivity of a sintered body to be good. A more preferable content of the organic component is 1 to 30% by mass, and a more preferable content is 2 to 15% by mass.

(1-3) High Polar Solvent The silver fine particle dispersion of the present embodiment is a dispersion of silver fine particles in various high polar solvents.

As the solvent, various highly polar solvents can be used as long as the effects of the present invention are not impaired. High polar solvents include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, 2-butanol, pentanol, hexanol, isoamyl alcohol, furfuryl alcohol, nitromethane, acetonitrile, pyridine, acetone cresol, dimethylformamide, dioxane, ethylene Glycol, glycerin, 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-butoxye acetate Examples include chill, 2- (2-butoxyethoxy) ethyl acetate, 2-methoxyethyl acetate, 2-hexyloxyethanol, etc., but the present invention is compatible with the short-chain amine having 5 or less carbon atoms. Therefore, 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) Dispersant The silver particle dispersion of the present embodiment further includes a “dispersant having an acid value” added after the synthesis of silver fine particles in order to disperse the silver fine particles. By using such a dispersant, the dispersion stability of the silver fine particles in the solvent can be improved. Here, the acid value of the dispersant is more preferably from 5 to 200, and it is further preferable that the dispersant has a functional group derived from phosphoric acid.

If the acid value of the dispersant is 5 or more, adsorption with an acid-base interaction starts to occur on a metal substance that coordinates with the amine and the particle surface is basic. This is because it does not have an adsorption site and adsorbs in a suitable form. In addition, since the dispersant has a functional group derived from phosphoric acid, phosphorus P interacts with and attracts the metal M through the oxygen O, and is therefore most effective for adsorption with metals and metal compounds. This is because suitable dispersibility can be obtained by the amount of adsorption.

Examples of the polymer dispersant having an acid value of 5 to 200 include SOLPERSE-16000, 21000, 41000, 41090, 43000, 44000, 46000, and 54000 in the SOLSPERSE series of Lubrizol. In the series, DISPERBYK-102, 110, 111, 170, 190.194N, 2015.2090, 2096 and the like are listed, and in Evonik's TEGO® Dispers series, 610, 610S, 630, 651, 655, 750W, 755W and the like are listed. In the Disparon series manufactured by Enomoto Kasei Co., Ltd., DA-375, DA-1200 and the like are listed. In the Floren series manufactured by Kyoei Chemical Industry Co., Ltd., WK-13E, G-700, G-9. The 0, GW-1500, GW-1640, WK-13E can be exemplified.

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

The content of the polymer dispersant is preferably 0.1 to 15% by mass. When the content of the polymer dispersant is 0.1% or more, the dispersion stability of the obtained silver fine particle dispersion is improved. However, when the content is too large, the low-temperature sinterability is lowered. From such a viewpoint, the more preferable content of the polymer dispersant is 0.3 to 10% by mass, and still more preferable content is 0.5 to 8% by mass.

The silver fine particle dispersion of this embodiment preferably has a weight loss of 10% by mass or less at 100 to 500 ° C. when thermogravimetric analysis is performed at a rate of temperature increase of 10 ° C./min with respect to the solid content. When the solid is heated to 500 ° C., organic matter and the like are oxidatively decomposed, and most of them are gasified and disappear. For this reason, the reduction | decrease by heating to 500 degreeC can correspond to the quantity of the organic substance in solid content substantially.

The greater the weight loss, the better the dispersion stability of the silver fine particle dispersion, but if it is too much, the organic matter remains as impurities in the conductive ink for transfer printing, and the conductivity is lowered. In particular, in order to obtain a conductive film pattern having high conductivity by heating at a low temperature of about 100 ° C., the weight loss is preferably 20% by mass or less. On the other hand, since the dispersion stability in a colloidal state is impaired when the weight loss is too small, the content is preferably 0.1% by mass or more. A more preferred weight loss is 0.5 to 15% by mass.

(1-5) Protective agent (protective dispersant)
The silver fine particle dispersion of this embodiment may further contain a dispersant (protective dispersant) having an acid value as a protective agent added before the synthesis of the silver fine particles. The “protective dispersant” referred to here may be of the same type or different type as the “dispersant having an acid value” added after the synthesis of the silver fine particles.

(1-5) Other components In addition to the above components, the silver fine particle dispersion of the present embodiment has an appropriate viscosity, adhesiveness, and drying property in accordance with the purpose of use within a range not impairing the effects of the present invention. Or, in order to provide functions such as printability, for example, an oligomer component that plays a role as a binder, a resin component, an organic solvent (a part of the solid content may be dissolved or dispersed), a surfactant, a thickening agent. You may add arbitrary components, such as an agent or a surface tension regulator. Such optional components are not particularly limited.

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

Examples of the thickener include clay minerals such as clay, bentonite or hectorite, for example, emulsions such as polyester emulsion resins, acrylic emulsion resins, polyurethane emulsion resins or blocked isocyanates, methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose. , Hydroxypropylcellulose, cellulose derivatives of hydroxypropylmethylcellulose, polysaccharides such as xanthan gum or guar gum, etc., and these may be used alone or in combination of two or more.

A surfactant different from the above organic components may be added. In a multi-component solvent-based inorganic colloidal dispersion, the coating surface becomes rough and the solid content tends to be uneven due to the difference in volatilization rate during drying. By adding a surfactant to the silver fine particle dispersion of this embodiment, a silver fine particle dispersion capable of suppressing these disadvantages and forming a uniform conductive film can be 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. For example, alkylbenzene sulfonic acid Salt, quaternary ammonium salt and the like. Of these, fluorine-based surfactants and silicone-based surfactants are preferred because an effect can be obtained with a small amount of addition. If the content of the surfactant is too small, the effect cannot be obtained. If the content is too large, the remaining amount of impurities in the coating becomes an impurity, so that the conductivity may be hindered. A preferable surfactant content is 0.01 to 5 parts by mass with respect to 100 parts by mass of the dispersion medium of the silver fine particle dispersion.

The silver fine particles in the present embodiment are silver fine particles in which an alkoxyamine having a distribution coefficient logP of −1.0 to 1.4 and a carbon number of 5 or less is attached to at least a part of the surface. By attaching an alkoxyamine having a partition coefficient logP of −1.0 to 1.4 and having 5 or less carbon atoms to at least a part of the surface of the silver fine particles, the silver fine particles can be used for various solvents (particularly highly polar solvents). Excellent dispersibility and low-temperature sinterability can be imparted.

As the solvent, various solvents can be used as long as the effects of the present invention are not impaired, and a solvent having an SP value (solubility parameter) of 7.0 to 15.0 can be used. Here, it is one of the characteristics of the silver fine particle dispersion of the present invention that the silver fine particles are uniformly dispersed even in a highly polar solvent. In the present invention, the phase is combined with the short-chain amine having 5 or less carbon atoms. It is preferable to use an alcohol having 1 to 6 carbon atoms because of good solubility. These solvents may be used alone or in combination of two or more.

Examples of the solvent having an SP value (solubility parameter) of 7.0 to 15.0 include hexane (7.2), triethylamine (7.3), ethyl ether (7.7), and n-octane (7. 8), cyclohexane (8.3), n-amyl acetate (8.3), isobutyl acetate (8.3), methyl isopropyl ketone (8.4), amyl benzene (8.5) butyl acetate (8.5) ), Carbon tetrachloride (8.6), ethylbenzene (8.7), p-xylene (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-bu Nord (11.1), Nitroethane (11.1) Isopropyl alcohol (11.2), m-cresol (11.4), acetonitrile (11.9), n-propanol (12.1), furfuryl alcohol ( 12.5), nitromethane (12.7), ethanol (12.8), cresol (13.3), ethylene glycol (14.2), methanol (14.8) phenol, p-cresol, propyl acetate, acetic acid Isopropyl, 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, acetic acid-2 Butoxyethyl, 2- (2-butoxyethoxy) ethyl acetate, acetic acid-2-methoxyethyl, can be exemplified 2-hexyloxy ethanol.

The viscosity of the silver fine particle dispersion of this embodiment is preferably in the viscosity range of 1 to 100 cps, and more preferably in the viscosity range of 1 to 20 cps. By setting it as the said viscosity range, a silver fine particle dispersion can be apply | coated uniformly and in thin film form on a silicone resin. A general-purpose coating method can be used as the coating method, and examples include an applicator method, a bar coater method, a capillary coater method, and a spin coating method.

The viscosity of the silver fine 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. The viscosity can be measured with a vibration viscometer (for example, VM-100A-L manufactured by CBC Corporation). The measurement is performed by immersing the liquid in the vibrator, and the measurement temperature may be normal temperature (20 to 25 ° C.).

(2) Method for Producing Transfer Printing Conductive Ink To produce the transfer printing conductive ink of the present embodiment, first, a silver fine particle dispersion (metal colloid liquid) is prepared. Subsequently, the conductive ink of this embodiment can be obtained by mixing this metal colloid liquid and the above-mentioned various components.

Among these, the silver fine particle dispersion of the present embodiment includes a step of generating silver fine particles, and a step of adding and mixing a dispersant having an acid value for dispersing the silver fine particles to the silver fine particles. Is. Furthermore, a first pre-process for preparing a mixture of a silver compound that can be decomposed by reduction to produce metallic silver and a short-chain amine having a partition coefficient log P of −1.0 to 1.4, It is preferable to include a second pre-process of reducing the silver compound in the mixed solution to generate silver fine particles having a short-chain amine having 5 or less carbon atoms attached to at least a part of the surface.

In the first pre-process, it is preferable to add 2 mol or more of short chain amine to 1 mol of metallic silver. By setting the addition amount of the short chain amine to 2 mol or more with respect to 1 mol of metallic silver, an appropriate amount of the short chain amine can be attached to the surface of the silver fine particles produced by the reduction, and various solvents (particularly, Excellent dispersibility and low-temperature sinterability with respect to a highly polar solvent) can be imparted.

It should be noted that the particle size of the silver fine particles obtained is a nanometer size that causes a melting point drop depending on the composition of the liquid mixture in the first pre-process and the reduction conditions (for example, heating temperature, heating time, etc.) in the second pre-process. Preferably, the thickness is 1 to 200 nm. Here, particles of micrometer size may be included as necessary.

The method for taking out the silver fine particles from the silver fine particle dispersion obtained in the second pre-process is not particularly limited, and examples thereof include a method for washing the silver fine particle dispersion.

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

In addition, the method for reducing these silver compounds in the raw material liquid is not particularly limited. For example, a method using a reducing agent, a method of irradiating light such as ultraviolet rays, an electron beam, ultrasonic waves or thermal energy, a method of heating, etc. Is mentioned. Among these, a method using a reducing agent is preferable from the viewpoint of easy operation.

Examples of the reducing agent include amine compounds such as dimethylaminoethanol, methyldiethanolamine, triethanolamine, phenidone, and hydrazine; for example, hydrogen compounds such as sodium borohydride, hydrogen iodide, and hydrogen gas; for example, carbon monoxide. Oxides such as sulfurous acid; for example, ferrous sulfate, iron oxide, iron fumarate, iron lactate, iron oxalate, iron sulfide, tin acetate, tin chloride, tin diphosphate, tin oxalate, tin oxide, sulfuric acid Low valent metal salts such as tin; for example, sugars such as ethylene glycol, glycerin, formaldehyde, hydroquinone, pyrogallol, tannin, tannic acid, salicylic acid, D-glucose, etc. There is no particular limitation as long as it can be reduced. When the reducing agent is used, light and / or heat may be added to promote the reduction reaction.

As a specific method for preparing silver fine particles coated with an organic substance using the above metal salt, organic component, solvent and reducing agent, for example, the above metal salt is dissolved in an organic solvent (for example, toluene) to form a metal salt. Examples include a method of preparing a solution, adding a short-chain amine as a protective dispersant or a protective dispersant having an acid value to the metal salt solution, and then gradually dropping a solution in which the reducing agent is dissolved. .

In the dispersion containing silver fine particles coated with the short-chain amine and the protective dispersant having an acid value obtained as described above, in addition to the silver fine particles, a metal ion counter ion, a reducing agent residue, There is a dispersant, and the concentration of the electrolyte and the organic matter in the whole liquid tend to be high. The liquid in such a state is likely to precipitate due to the coagulation of the metal particles due to high electrical conductivity. Alternatively, even if precipitation does not occur, the conductivity of the metal salt may deteriorate if the counter ion of the metal salt, the residue of the reducing agent, or an excessive amount of dispersant remaining in the amount necessary for dispersion remains. Therefore, by washing the solution containing silver fine particles to remove excess residues, silver fine particles coated with an organic substance can be obtained with certainty.

As the washing method, for example, a dispersion containing silver fine particles coated with an organic component is allowed to stand for a certain period of time, and after removing the resulting supernatant, a solvent for precipitating silver fine particles (for example, water, methanol, Methanol / water mixed solvent, etc.) is added and stirred again, and the method of removing the supernatant liquid after standing for a certain period of time is repeated several times, the method of performing centrifugation instead of the above standing, Examples thereof include a desalting method using a filtration device, an ion exchange device, and the like. By removing excess residues and removing the organic solvent by such washing, metal particles coated with the “short-chain amine or the dispersant having an acid value” of the present embodiment can be obtained.

Among the present embodiments, the silver fine particle dispersion (silver colloid dispersion) includes the silver fine particles coated with the short-chain amine obtained above and a protective dispersant having an acid value, and the dispersion medium described in the present embodiment. And are mixed. The mixing method of 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 may be performed by a conventionally known method using a stirrer or a stirrer. Can do. An ultrasonic homogenizer with an appropriate output may be applied by stirring with a spatula or the like.

When obtaining a silver fine particle dispersion containing a plurality of metals, the production method is not particularly limited. For example, when producing a silver fine particle dispersion composed of silver and other metals, the silver fine particle dispersion is coated with the organic substance. In the preparation of metal particles, a dispersion containing silver fine particles and a dispersion containing other metal particles may be produced separately and then mixed, or a silver ion solution and other metal ion solution may be mixed. Thereafter, reduction may be performed.

A first step of adjusting a mixed solution of a silver compound that can be decomposed by reduction to form metallic silver and a short-chain amine having a partition coefficient log P of −1.0 to 1.4; Silver fine particles may be produced by the second step of producing silver fine particles in which a short-chain amine having 5 or less carbon atoms is attached to at least a part of the surface by reducing the silver compound.

For example, atomic silver produced by heating a complex compound generated from a metal compound such as silver oxalate containing silver and a short-chain amine and decomposing the metal compound such as oxalate ion contained in the complex compound By agglomerating, silver particles protected by a short-chain amine protective film can be produced.

Thus, in the metal amine complex decomposition method for producing metal particles coated with amine by thermally decomposing a complex compound of a metal compound in the presence of amine, decomposition of the metal amine complex which is a single kind of molecule is performed. Since the atomic metal is generated by the reaction, it is possible to generate the atomic metal uniformly in the reaction system, and the reaction is configured as compared with the case where the metal atom is generated by the reaction between multiple components. Inhomogeneity of the reaction due to fluctuations in the composition of the components is suppressed, which is particularly advantageous when a large amount of metal powder is produced on an industrial scale.

In the metal amine complex decomposition method, a short chain amine molecule is coordinated to the metal atom to be generated, and the movement of the metal atom when aggregation occurs due to the action of the short chain amine molecule coordinated to the metal atom. Is assumed to be controlled. As a result, according to the metal amine complex decomposition method, it is possible to produce metal particles that are very fine and have a narrow particle size distribution.

In addition, many short-chain amine molecules also form a relatively weak coordination bond on the surface of the metal fine particles to be produced, and these form a dense protective film on the surface of the metal particles. It is possible to produce coated metal particles having a clean surface with excellent surface resistance. In addition, since the short-chain amine molecules forming the coating can be easily detached by heating or the like, it is possible to produce metal particles that can be sintered at a very low temperature.

In addition, when a solid metal compound and an amine are mixed to form a complex compound such as a complex compound, the number of carbon atoms is 5 or less with respect to the dispersant having an acid value constituting the coating of the coated silver particles. By mixing and using a short-chain amine, it becomes easy to produce a complex compound such as a complex compound, and the complex compound can be produced by mixing in a short time. Further, by mixing and using the short chain amine, it is possible to produce coated silver particles having characteristics according to various uses.

(3) Conductive ink coating step (coating substrate with conductive film pattern) and method for producing the same When using the conductive ink for transfer printing according to the present embodiment, the conductive ink applying step for applying the conductive ink for transfer printing to the base material. And a conductive film pattern forming step in which the conductive ink for transfer printing applied to the substrate is baked at a temperature of 200 ° C. or lower (preferably less than 180 ° C., more preferably 150 ° C. or lower) to form a conductive film pattern. Thus, 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.

As a result of intensive studies, the inventor used the conductive ink for transfer printing according to the present embodiment described above as the conductive ink in the conductive ink application process for transfer printing. It has been found that even when the conductive ink applied to the substrate is baked at a temperature of 200 ° C. or less, a conductive film pattern having excellent conductivity can be obtained with certainty.

In the reverse printing method of the transfer printing method, first, a conductive ink application surface is formed by applying conductive ink for transfer printing on a blanket. As the blanket, a silicone blanket made of silicone is preferable. By forming the conductive ink application surface on the surface of the blanket and leaving it for a predetermined time, the low boiling point solvent is volatilized and absorbed in 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 on the conductive ink application surface, the portion of the conductive ink that contacts the relief plate is removed from the blanket. At this time, since the conductive ink has an appropriate cohesiveness, the conductive ink is surely peeled off from the blanket and adhered to the relief plate without structural destruction, and undesirable residue on the blanket is prevented. It is suppressed. As a result, the conductive ink remaining on the blanket forms a conductive ink pattern corresponding to the relief pattern on the blanket.

Transfer the wet or semi-dried conductive ink remaining on the blanket to the substrate. At this time, since the conductive ink has appropriate cohesiveness, peeling from the blanket and adhesion to the printing medium are surely performed, and undesirable residue on the blanket is suppressed. As a result, a conductive film pattern is formed on the substrate to be printed by a pattern inverted with respect to the pattern formed on the relief plate.

The substrate that can be used in the present embodiment is not particularly limited as long as it has at least one main surface on which a conductive ink can be applied and fired by heating to mount a conductive film pattern. Although it is not, it is preferable that it is a base material excellent in heat resistance. In addition, as described above, the conductive ink for transfer printing of this embodiment has a conductive film pattern that has sufficient conductivity even when heated and baked at a lower temperature than conventional conductive inks. Since it can be obtained, it is possible to use a substrate having a lower heat-resistant temperature than the conventional one in a temperature range higher than this low firing temperature.

Examples of the material constituting such a base material include polyamide (PA), polyimide (PI), polyamideimide (PAI), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and the like. Polyester, polycarbonate (PC), polyethersulfone (PES), vinyl resin, fluororesin, liquid crystal polymer, ceramics, glass or metal can be used. Further, the substrate may have various shapes such as a plate shape or a strip shape, and may be rigid or flexible. The thickness of the substrate can also be selected as appropriate. In order to improve adhesiveness or adhesion, or for other purposes, a substrate on which a surface layer is formed or a substrate that has been subjected to a surface treatment such as a hydrophilic treatment may be used.

The coated film after coating as described above is baked by heating to a temperature of 200 ° C. or less (preferably less than 180 ° C., more preferably 150 ° C. or less), and the conductive film pattern (conductive film pattern) of this embodiment. Substrate) can be obtained.

The method for performing the baking is not particularly limited. For example, the temperature of the conductive ink applied or drawn on the substrate using a conventionally known gear oven or the like is 200 ° C. or less (preferably less than 180 ° C., More preferably, the conductive film pattern can be formed by baking to 150 ° C. or lower. The lower limit of the firing temperature is not necessarily limited, and is a temperature at which a conductive film pattern can be formed on a substrate, and a temperature at which the organic components and the like can be removed by evaporation or decomposition within a range that does not impair the effects of the present invention. (A part may remain within a range that does not impair the effects of the present invention, but it is desirable that all be removed desirably).

According to the conductive ink of the present embodiment, a conductive film pattern exhibiting high conductivity can be formed even by a low-temperature heat treatment at about 120 ° C. Therefore, the conductive film pattern is also formed on a relatively heat-sensitive substrate. Can be formed. Moreover, baking time is not specifically limited, A conductive film pattern can be formed on a base material according to baking temperature.

In this embodiment, in order to further improve the adhesion between the substrate and the conductive film pattern, the substrate may be subjected to a surface treatment. Examples of the surface treatment method include a method of performing a dry treatment such as a corona treatment, a plasma treatment, a UV treatment, and an electron beam treatment, and a method of previously providing a primer layer and a conductive ink receiving layer on a substrate.

Thus, the conductive film pattern (substrate with conductive film pattern) of this embodiment can be obtained. The conductive film pattern of the present embodiment thus obtained is, for example, about 0.1 to 5 μm, more preferably 0.1 to 1 μm. When the conductive ink of this embodiment is used, a conductive film pattern having sufficient conductivity can be obtained even when the thickness is about 0.1 to 5 μm. In addition, the volume resistance value of the electrically conductive film pattern of this embodiment is 15 microhm * cm or less.

In addition, the thickness t of the conductive film pattern of the present embodiment can be obtained using, for example, the following formula (the thickness t of the conductive film pattern is measured with a laser microscope (for example, a laser microscope VK-9510 manufactured by Keyence). It is also possible to do this.)
Formula: t = m / (d × M × w)
m: conductive film pattern weight (the weight of the conductive film pattern formed on the slide glass is measured with an electronic balance)
d: Conductive film pattern density (g / cm ³ ) (10.5 g / cm ^{3 in} the case of silver)
M: conductive film pattern length (cm) (the length of the conductive film pattern formed on the slide glass is measured on a scale equivalent to JIS class 1)
w: Conductive film pattern width (cm) (The width of the conductive film pattern formed on the slide glass is measured on a scale equivalent to JIS class 1)

Hereinafter, the conductive ink for transfer printing of the present invention and a method for producing a conductive film pattern (substrate with a conductive film pattern) using the conductive ink will be further described with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

<< Preparation Example 1 >>
8.9 g of 3-methoxypropylamine (Wako Pure Chemical Industries, Ltd., first grade reagent, carbon number: 4, log P: -0.5) and 0.3 g of DISPERBYK-111, a polymer dispersant, are mixed. Then, the mixture was thoroughly stirred with a magnetic stirrer to produce an amine mixture (molar ratio of added amine was 10 with respect to silver). Next, 3.0 g of silver oxalate was added while stirring. After the addition of silver oxalate, by continuing stirring at room temperature, the silver oxalate was changed to a viscous white substance, and it was visually confirmed that the change was apparently observed. Finished (first pre-process).
The resulting mixture was transferred to an oil bath and heated and stirred at 120 ° C. The reaction with the generation of carbon dioxide started immediately after the start of stirring, and then stirring was performed until the generation of carbon dioxide was completed, thereby obtaining a suspension in which silver fine particles were suspended in the amine mixture ( Second pre-process).
Next, in order to replace the dispersion medium of the obtained suspension, 10 mL of a mixed solvent of methanol / water was added and stirred, and then silver fine particles were precipitated and separated by centrifugation. To the separated silver fine particles, 10 mL of a mixed solvent of methanol / water was added and stirred again, and then the fine silver particles were separated by centrifugation and separated, and ethanol / isobutanol / isopropyl alcohol (40:40) was used as a dispersion solvent. : 20 v / v) By adding 2.1 g of a mixed solvent, a silver fine particle dispersion A having a solid content of 48% by mass was obtained.

<< Preparation Example 2 >>
8.9 g of 3-methoxypropylamine (Wako Pure Chemical Industries, Ltd., first grade reagent, carbon number: 4, log P: -0.5) and 0.3 g of DISPERBYK-102, a polymer dispersant, are mixed. Then, the mixture was thoroughly stirred with a magnetic stirrer to produce an amine mixture (molar ratio of added amine was 5 with respect to silver). Next, 3.0 g of silver oxalate was added while stirring. After the addition of silver oxalate, by continuing stirring at room temperature, the silver oxalate was changed to a viscous white substance, and it was visually confirmed that the change was apparently observed. Finished (first pre-process).
The resulting mixture was transferred to an oil bath and heated and stirred at 120 ° C. The reaction with the generation of carbon dioxide started immediately after the start of stirring, and then stirring was performed until the generation of carbon dioxide was completed, thereby obtaining a suspension in which silver fine particles were suspended in the amine mixture ( Second pre-process).
Next, in order to replace the dispersion medium of the obtained suspension, 10 mL of a mixed solvent of methanol / water was added and stirred, and then silver fine particles were precipitated and separated by centrifugation. To the separated silver fine particles, 10 mL of a mixed solvent of methanol / water was added and stirred again, and then the silver fine particles were settled and separated by centrifugation. By adding 2.1 g of ethanol, a silver fine particle dispersion B having a solid content concentration of 48% by mass was obtained.

<< Examples and Comparative Examples >>
Using the silver fine particle dispersion A or B obtained as described above, it was mixed with the other components shown in Table 1, and Examples 1 to 7 of the conductive inks 1 to 7 for transfer printing and Comparative Examples 1 to 3 were used. Conductive inks 1 to 3 for comparative transfer printing were prepared. The unit of the amount of the component in Table 1 was “mass%”.
In addition, the following evaluation tests were performed on the above-described silver fine particle dispersions A and B, the conductive inks 1 to 7 for the transfer printing, and the conductive inks 1 to 3 for the comparative transfer printing. The results are shown in Table 1.

[Evaluation test]
(1) Organic content measurement The content of organic components contained in the silver fine particle dispersion was measured by thermogravimetric analysis. Specifically, the solid content of the silver fine particle dispersion was heated at a heating rate of 10 ° C./min, and the content of the organic component was specified as the weight loss from room temperature to 500 ° C.
(2) Dispersibility The conductive ink for transfer printing was allowed to stand in a container, and after 1 day at room temperature, the presence or absence of precipitation and the state of the supernatant were visually observed to evaluate the dispersibility of the silver fine particle dispersion. “○” when almost no sediment is observed under the container, “△” when a small amount of sediment is observed, and “×” when there is a clear difference in concentration between the top and bottom of the container and sediment is clearly observed. It was evaluated.
(3) Measurement of surface tension of conductive ink Conductive transfer printing conductive inks 1 to 4 obtained in Examples 1 to 4 and Comparative transfer printing conductive inks 1 to 3 obtained in Comparative Examples 1 to 3 The surface tension was measured with a fully automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.). The measurement was performed by automatic measurement using a platinum plate. The measurement temperature was room temperature (20 to 25 ° C.).
(4) Conductive ink wettability evaluation Conductive transfer printing conductive inks 1 to 7 obtained in Examples 1 to 7 and Comparative transfer printing conductive inks 1 to 3 obtained in Comparative Examples 1 to 3 Was applied on a silicone blanket with a bar coater (No. 7), and the wettability of the conductive ink for transfer printing to the blanket was visually evaluated. When the wettability was good, it was evaluated as “◯”, and when it was poor, it was evaluated as “x”.
(5) Evaluation of printing shape (thin line drawing property) A glass relief was pressed on a blanket coated with conductive ink for transfer printing, and a non-image part (unnecessary part) was transferred and removed. Furthermore, the pattern was transferred to the base material by pressing the base material (PEN: polyethylene naphthalate) against the blanket material. The printed shape was evaluated by visually observing the obtained pattern shape. Evaluate as “◯” when the printed shape is good, “△” when it is acceptable, and “x” when it is defective. The pattern was a thin line, and the line width was 10, 20, 30, 50, 100 μm and the length was 10 mm.
(6) Evaluation of transferability Transferability was evaluated by visually evaluating the printed shape formed in (5) above and the conductive ink remaining on the blanket. “○” if the printed shape is good and almost not left on the blanket, “△” if it is acceptable, or “x” if the printed shape is bad or clearly left on the blanket .
(7) Evaluation of continuous printability Continuous printability was evaluated by repeating the layer of the printed shape evaluation of (5) above five times continuously.
(8) Conductivity evaluation of conductive film pattern The pattern transferred to the substrate (line width 100 μm, length 10 mm) was baked under the conditions of 120 ° C. × 30 minutes, and the resistance value of the pattern was measured. Specifically, the volume resistivity was determined by the double bridge method using a portable double bridge 2769 manufactured by Yokogawa Meter & Instruments Co., Ltd. Based on the following formula, the volume resistance value was converted from the distance between the measurement terminals and the thickness of the conductive film pattern.
Formula: (volume resistivity ρv) =
(Resistance value R) × (film width w) × (film thickness t) / (terminal distance L)

In Table 1, “Novec7300” is manufactured by Sumitomo 3M, and “Surflon S-651” is manufactured by AGC Chemical. “Factent 610FM” is manufactured by Neos.

As is apparent from the results shown in Table 1, it can be seen that the conductive ink for transfer printing of the present invention is excellent in dispersibility, wettability, printability and conductivity. Among them, Examples 3 and 4 using the silver fine particle dispersion B are particularly preferable because they are excellent in continuous printability.
On the other hand, it can be seen from Comparative Examples 1 and 2 that the conductive ink containing no specific high boiling point solvent is inferior in transferability. Further, it can be seen from Comparative Example 3 that when the content of the high boiling point solvent is excessive, drying is slow and transferability is poor. Further, it can be seen from Comparative Example 2 that even when only the fluorine solvent is included, the wettability can be ensured but the transferability is poor.

Claims (6)

1. Metal particles,
   A solvent comprising ethanol;
   Containing 0.1 to 3.0% by mass of a high-boiling solvent having a hydroxyl group,
   Conductive ink for transfer printing, characterized by
2. The conductive ink for transfer printing according to claim 1, wherein the high boiling point solvent contains 1,3-butylene glycol, 2,4-diethyl-1,5-pentanediol or octanediol.
3. The conductive ink for transfer printing according to claim 1, further comprising hydrofluoroether.
4. The metal particles are silver particles;
   Silver particles,
   A short-chain amine having 5 or less carbon atoms and a partition coefficient log P of -1.0 to 1.4,
   A highly polar solvent;
   A dispersant having an acid value for dispersing the silver fine particles;
   A silver fine particle dispersion containing
   The conductive ink for transfer printing according to any one of claims 1 to 3.
5. In the silver fine particle dispersion, the short chain amine is an alkoxyamine, and further contains a protective dispersant having an acid value.
   The conductive ink for transfer printing according to claim 4.
6. The protective dispersant has an acid value of 5 to 200, and has a functional group derived from phosphoric acid,
   The conductive ink for transfer printing according to claim 5.