JP6053246B1 - Electrode manufacturing method - Google Patents

Abstract

Provided is an electrode manufacturing method which can be applied to a substrate having low heat resistance and low heat resistance even when the baking temperature is low, and which can be suitably used for an electrode such as a TFT. The present invention includes a first step of forming a pre-firing coating by printing or applying a conductive ink mainly composed of metal nanoparticles, and a second step of firing the pre-firing coating to form a conductive coating. And a third step of cleaning by bringing an acidic solution into contact with at least a part of the conductive coating.

Description

  The present invention relates to an electrode manufacturing method, for example, an electrode manufacturing method used as an electrode for a thin film transistor (TFT) substrate.

  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 (conductive film). . However, this method requires complicated vacuum processes and an expensive vacuum apparatus.

  Therefore, a simpler and less expensive method for forming a conductive film has been demanded. In recent years, methods using printing methods such as letterpress printing, intaglio printing, screen printing, and inkjet 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.

  For example, Patent Document 1 (WO2008 / 111484) discloses a conductive ink substantially free of a binder component for forming a conductive pattern by a relief printing method, and has a volume average particle size (Mv). Conductive particles of 10 to 700 nm, a release agent, a surface energy adjusting agent, and a solvent component are essential components, and the solvent component has a solvent having a surface energy of 27 mN / m or more at 25 ° C. and a boiling point under atmospheric pressure. There has been proposed a conductive ink, which is a mixture with a volatile solvent at 120 ° C. or lower and has a surface energy of 10 to 21 mN / m at 25 ° C.

  In the conductive ink described in Patent Document 1, since transfer residue is suppressed by optimizing the ink composition, complete transfer can be realized, and formation of a high-definition fine pattern can be facilitated. While the adhesion of ink can be obtained in a short time due to the volatilization of the low boiling point solvent, the cohesiveness of the ink is maintained and the pattern is maintained due to the residual high surface energy solvent.

  Further, for example, in Patent Document 2 (WO2010 / 113931), a method for forming an organic transistor by transferring a pattern using a liquid-repellent transfer base plate, such as a microcontact printing method or a reversal printing method. Optimal ink, that is, a uniform ink coating can be formed on the surface of a liquid-repellent transfer base plate, and an ink-dried film or semi-dried film can be easily transferred onto a transfer substrate from the transfer base plate. A possible organic semiconductor ink composition has been proposed.

  In the organic semiconductor ink composition described in Patent Document 2, an organic transistor having excellent electrical characteristics can be produced while forming an organic semiconductor pattern having excellent electrical characteristics while being capable of forming a shape-selective and site-selective. It is said that an organic semiconductor pattern can be formed only in a necessary area of a circuit when manufacturing a TFT.

WO2008 / 111484 WO2010 / 113931

  However, when the methods described in Patent Document 1 and Patent Document 2 are used, the firing temperature for forming the conductive film becomes 175 ° C. or higher, and it is difficult to apply to a substrate having low heat resistance such as PET. is there.

  On the other hand, the present inventors have invented a conductive ink that can be applied to a substrate having low heat resistance and can obtain sufficient conductivity even when the baking temperature is lowered (Japanese Patent Application No. 2014). -238100 and Japanese Patent Application No. 2014-238101), when used for an electrode such as a TFT, an organic residue that does not hinder the conductivity may not be able to efficiently inject carriers into the semiconductor. There was room for.

  That is, if the firing temperature is increased, the organic residue can be reduced. However, if the firing temperature is low, the organic residue cannot be completely removed, and not a little organic matter remains. There was room for improvement in that there was a problem when using as.

  Therefore, an object of the present invention is an electrode that can be applied to a substrate having a low amount of organic residue that does not impair conductivity even at a low baking temperature, and can be applied to an electrode such as a TFT. It is in providing the manufacturing method of.

  As a result of intensive studies to achieve the above object, the present inventor can obtain an electrode with very little organic residue by bringing the electrode surface formed at a low baking temperature into contact with a specific solution. Has been found to be extremely effective in achieving the above, and the present invention has been achieved.

That is, the present invention
A first step of forming a pre-firing film by printing or applying a conductive ink mainly composed of metal nanoparticles;
A second step of firing the pre-fired coating to form a conductive coating;
A third step of cleaning by bringing an acidic solution into contact with at least a part of the conductive coating;
A method for manufacturing an electrode is provided.

  According to the method for producing an electrode of the present invention having such a configuration, an organic residue that does not impede conductivity even at a low baking temperature is obtained by washing at least a part of the conductive film with an acidic solution. Therefore, an electrode that can be suitably used for an electrode such as a TFT can be obtained.

  According to the method for producing an electrode of the present invention having the above-described configuration, the electrode is preferably an electrode for a thin film transistor (TFT). When the electrode is a TFT, as described above, the electrode obtained by the method for producing an electrode of the present invention can be used more suitably.

  In the method for producing an electrode of the present invention having the above-described configuration, it is preferable that the acidic solution contains sulfuric acid.

  According to the method for producing an electrode of the present invention having such a configuration, even an organic residue that does not inhibit conductivity can be more effectively removed.

Here, as the conductive ink in the electrode manufacturing method of the present invention, various inks can be used, but mainly those described below can be preferably used.
(1) comprising metal nanoparticles, a short-chain amine having 5 or less carbon atoms, a highly polar solvent, and a dispersant having an acid value for dispersing the metal nanoparticles, A metal nanoparticle dispersion having a partition coefficient logP of −1.0 to 1.4 is included (metal nanoparticle dispersion A).
(2) containing metal nanoparticles, a solvent containing ethanol, and 0.1 to 3.0% by mass of a high boiling point solvent having a hydroxyl group (conductive ink B).

In the metal nanoparticle dispersion A, it is preferable that the metal nanoparticle dispersion further contains a protective dispersant having an acid value.
Moreover, it is preferable that the said short chain amine is an alkoxyamine.
Moreover, it is preferable that the acid value of the said protective dispersant is 5-200.
Furthermore, it is preferable that the protective dispersant has a functional group derived from phosphoric acid.
Furthermore, it is preferable that the highly polar solvent is methanol, ethanol, isopropyl alcohol or n-propyl alcohol.

In the conductive ink B, the high boiling point solvent preferably contains 1,3-butylene glycol, 2,4-diethyl-1,5-pentanediol or octanediol.
Further, it is preferable that the conductive ink B further contains a hydrofluoroether.

  According to the method for producing an electrode of the present invention, even if the firing temperature is low, the organic matter residue is small enough not to impede conductivity, and can be applied to a substrate having low heat resistance, and is also suitable for an electrode such as a TFT. An electrode manufacturing method that can be used can be provided.

It is a schematic sectional drawing for demonstrating the structure of the top gate bottom contact type TFT produced in the Example of this invention. 4 is a graph showing output characteristics of a TFT in Example 1. 6 is a graph showing output characteristics of TFTs in Comparative Example 1. It is a graph which shows the result of having evaluated the cleaning effect of a conductive film in the electrode obtained in Example 1 and comparative example 1. FIG.

The present invention includes a first step of forming a pre-firing coating by printing or applying a conductive ink mainly composed of metal nanoparticles, and a second step of firing the pre-firing coating to form a conductive coating. And a third step of cleaning by bringing an acidic solution into contact with at least a part of the conductive film.

First Step In the first step, a pre-firing film is formed by printing or applying a conductive ink mainly composed of metal nanoparticles. Conventionally known methods can be employed for the printing and coating methods in the first step. The shape and pattern of the pre-firing film may also be a conventionally known one.

  In this embodiment, the conductive ink has silver fine particles (silver nanoparticles), a short-chain amine having 5 or less carbon atoms, a highly polar solvent, and an acid value for dispersing the silver fine particles. And a silver fine particle dispersion containing a dispersant. Especially, it is preferable that the distribution coefficient logP of the said short chain amine is -1.0-1.4 (said metal nanoparticle dispersion A).

  The above-mentioned silver fine particle dispersion is a silver fine particle dispersion having a low temperature sintering property in which silver fine particles are uniformly dispersed in various solvents (especially highly polar solvents), and a conductive film is formed by sintering the silver fine particle composite. By doing so, a conductive film having good conductivity can be formed at a low temperature. Among these, the conductive film composed of the specific silver nanoparticles described in the present embodiment is preferable because the reason is not always clear by using an amine-based dispersant described later, but an acidic solution and an amine. This is because the dispersant in the system is more likely to interact and the cleaning effect is exhibited. In particular, by using silver nanoparticles described later, an electrode that can be fired at a low temperature and can exhibit good TFT characteristics can be obtained more reliably.

  An amino group in one molecule of the amine has a relatively high polarity and is likely to cause an interaction due to hydrogen bonding, but a portion other than these functional groups has a relatively low polarity. Furthermore, each amino group tends to exhibit alkaline properties. Accordingly, when the amine is localized (attached) on at least a part of the surface of the silver fine particles (that is, when at least a part of the surface of the silver fine particles is coated), the amine and the inorganic particles can sufficiently have an affinity. And aggregation of silver fine particles can be prevented (dispersibility is improved). That is, the functional group of amine is adsorbed on the surface of the silver fine particles with an appropriate strength and prevents mutual contact between the silver fine particles, thereby contributing to the stability of the silver fine particles in the storage state. Moreover, it is thought that the fusion | melting of silver fine particles is accelerated | stimulated by moving and / or volatilizing from the surface of silver fine particles by heating.

  Further, by making the amine constituting the silver fine particle dispersion a short chain amine having 5 or less carbon atoms, the amine attached to at least a part of the surface of the silver fine particles by heating can be easily removed. Good low-temperature sinterability (for example, sinterability at 100 to 350 ° C.) of the fine particles can be ensured.

  Moreover, the distribution coefficient logP of the short-chain amine is set to -1.0 to 1.4. If the distribution coefficient logP is -1.0 or less, the polarity of the short-chain amine is too high. This is because it rapidly proceeds and it becomes difficult to control the formation of silver fine particles, and if the distribution coefficient logP is 1.5 or more, it is difficult to disperse in a highly polar solvent because the polarity of amine coordinated to silver is low.

  The partition coefficient logP means an octanol / water partition coefficient using n-octanol and water as solvents, and obtains a concentration Co in octanol and a concentration Cw in water, respectively, and a common logarithm of concentration ratio P = Co / Cw. Log P is calculated as a distribution coefficient. Therefore, the distribution coefficient logP means that it is one index that indicates whether or not a range of polar solvent can disperse the silver fine particles. The method for measuring the partition coefficient logP is not particularly limited, and can be determined by, for example, flask shaking method, high performance liquid chromatography (HPLC) method, and calculation using a quantitative structure-activity relationship algorithm. Literature values published on websites such as centers may be used.

  Further, the silver fine particle dispersion includes an acid value dispersant added after the synthesis of the silver fine particles (that is, a dispersant having an acid value for dispersing the silver fine particles). The “dispersant having an acid value” as used herein includes all dispersants that do not have an amine value or a hydroxyl value as an adsorbing group or a functional group. By using such a dispersant, the dispersion stability of the silver fine particles in the solvent can be improved. The acid value of the dispersant is preferably 5 to 200, and the dispersant preferably has a functional group derived from phosphoric acid. The reason why the “dispersant having an acid value” is preferable is not necessarily clear, but the present inventors not only adsorb metal, but also adsorb in a denser form by interacting with a short chain amine. It is thought that it exhibits high dispersibility while having low-temperature sinterability.

  When it is desired to disperse silver fine particles in a highly polar solvent described later, it is generally effective to use a highly polar dispersant. For example, it is conceivable to use a short-chain amine having a lower log P, but the short-chain amine generally exhibits reducibility and may not keep the reaction rate properly. Specifically, the reaction rate is excessively increased, and silver fine particles having excellent dispersibility may not be formed. Therefore, by adding a more polar dispersant after the synthesis of the silver fine particles, it is possible to improve only the compatibility with the dispersion medium (surface modification) while leaving the silver fine particles intact.

When the acid value of the dispersant is 5 or more, adsorption by an acid-base interaction starts to occur on a metal substance coordinated with an amine and the particle surface is basic, and if it is 200 or less, an adsorption site is excessively formed. Since it does not have, it adsorb | sucks in a suitable form, and is preferable. 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. It is preferable because suitable dispersibility can be obtained by the amount of adsorption. Here, the “acid value” is expressed in mg of potassium hydroxide required to neutralize the acidic component contained in 1 g of the sample. Examples of the acid value measurement method include an indicator method (p-naphtholbenzein indicator) and a potentiometric titration method.
ISO6618-1997: Neutralization titration method by indicator titration method → Corresponding to indicator titration method (acid value) ISO6619-1988: Corresponding to potentiometric titration method (acid value) → Potentiometric titration method (acid value)

  The silver fine particle dispersion 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” herein may be the same as the “dispersant having an acid value” added after the synthesis of the silver fine particles.

  In the silver fine particle dispersion, various solvents, particularly high polarity solvents can be used as the solvent. A highly polar solvent means a solvent that is generally incompatible with a low polarity solvent such as hexane or toluene, such as water or an alcohol having a short carbon number. In the present invention, an alcohol having 1 to 6 carbon atoms is used. More preferably, it is used. By using an alcohol having 1 to 6 carbon atoms as a high polarity solvent, it is possible to cause problems when a low polarity solvent is used, for example, when a silver fine particle dispersion is laminated on a resin, the solvent invades the underlying resin layer. Can be avoided. Here, it is preferable to use an alkoxyamine as the amine. By using alkoxyamine as the amine, the silver fine particles can be favorably dispersed in the highly polar solvent. Furthermore, although the mechanism is not necessarily clear, the alkoxy group of alkoxyamine interacts efficiently with water vapor, which is preferable in that sufficient grain growth can be promoted.

  The particle size of the silver fine particles constituting the silver fine particle dispersion is suitably a nanometer size that desirably causes a melting point drop, preferably 1 to 200 nm. However, if necessary, even if particles of a micrometer size are included. Good.

  The conductive film obtained in the present embodiment is a sintered body formed from silver fine particles and formed by external heating, and has good conductivity comparable to that inherent in the silver fine particles. The silver fine particle dispersion (conductive ink) used for forming the conductive film will be described in more detail below.

  The silver fine particle dispersion (conductive ink) used for forming the conductive film is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known silver fine particle dispersions can be used. A short chain amine having a carbon number of 5 or less, a highly polar solvent, and a dispersant having an acid value for dispersing silver fine particles, the partition coefficient log P of the short chain amine is -1.0 to 1 It is preferable to use a silver fine particle dispersion of .4.

  The above-mentioned silver fine particle dispersion is a silver fine particle dispersion having a low temperature sintering property in which silver fine particles are uniformly dispersed in various solvents (especially highly polar solvents), and a conductive film is formed by sintering the silver fine particle composite. By doing so, a conductive film having good conductivity can be formed at a low temperature.

(A) Silver fine particles The average particle size of the silver fine particles in the silver fine particle dispersion of the present embodiment is not particularly limited as long as the effect of the present invention is not impaired. It is preferable to have a diameter, for example, it may be 1 to 200 nm. Furthermore, it is preferable that it is 2-100 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 200 nm or less, the dispersibility of a silver fine particle does not change easily over time, and it is preferable.

  The silver fine particle dispersion may be added with a metal whose ionization column is more noble than hydrogen, that is, gold, copper, platinum, palladium, or the like in consideration of migration problems.

  Note that the particle size of the silver fine particles in the silver fine particle dispersion of the present embodiment may not be constant. In addition, when the silver fine particle dispersion contains a dispersant described later as an optional component, it may contain a metal particle component having an average particle size of more than 200 nm, but it does not cause aggregation, and the effect of the present invention is achieved. A metal particle component having an average particle diameter of more than 200 nm may be included as long as the component is not significantly impaired.

Here, the particle size of the silver fine particles in the silver fine particle dispersion of the present embodiment can be measured by a dynamic light scattering method, a small-angle X-ray scattering method, and a wide-angle X-ray diffraction method. In order to show the melting point drop of nano-sized silver fine particles, the crystallite diameter determined by the wide-angle X-ray diffraction method is appropriate. For example, in the wide-angle X-ray diffraction method, more specifically, Rθ-UtimaIII manufactured by Rigaku Corporation can be used to measure 2θ in the range of 30 to 80 ° by the diffraction method. In this case, the sample may be measured by extending it thinly so that the surface is flat on a glass plate having a depression of about 0.1 to 1 mm in depth at the center. The crystallite diameter (D) calculated by substituting the half width of the obtained diffraction spectrum into the following Scherrer equation using JADE manufactured by Rigaku Corporation may be used as the particle diameter.
D = Kλ / Bcos θ
Here, K: Scherrer constant (0.9), λ: wavelength of X-ray, B: half width of diffraction line, θ: Bragg angle.

(B) Short-chain amine having 5 or less carbon atoms In the silver fine particle dispersion of this 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) formamide (-0.2), 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) and the like are mentioned, 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 pressure 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 this 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 pressure 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 constituted by 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. The more preferable content of the organic component is 1 to 30% by mass, and the more preferable content is 2 to 15% by mass.

(C) High Polar Solvent The silver fine particle dispersion of the present embodiment is obtained by dispersing 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-butoxy 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. Is preferable, alcohol having 1 to 6 carbon atoms is preferably used. These solvents may be used alone or in combination of two or more.

(D) 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 5 to 200, and the dispersant further preferably 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, 54000, etc. in the SOLPERSE series of Lubrizol Corporation. 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 Dispalon 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- 900, GW-1500, GW-1640, and WK-13E.

  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 the more preferable content is 0.5 to 8% by mass.

  The dispersion of this embodiment further has a weight reduction rate of 20% by mass or less when heated from room temperature to 200 ° C. by thermal analysis, and a weight reduction rate of 10% when heated from 200 ° C. to 500 ° C. It is preferable that it is below mass%. Here, the weight reduction rate up to 200 ° C. mainly indicates the content of the short-chain amine, which is a low-temperature component contributing to low-temperature sinterability, and the weight reduction rate of the high-temperature property at 200 to 500 ° C. is mainly dispersion stability. The content of the dispersant having an acid value that contributes to If the short-chain amine or the high temperature component is excessive, the low temperature sintering property is impaired. That is, if the weight reduction rate when heated from room temperature to 200 ° C. is 20% by mass or less and the weight reduction rate when heated from 200 ° C. to 500 ° C. is 10% by mass or less, the low temperature sinterability is more excellent.

(E) 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.

(F) Other components In addition to the above components, the silver fine particle dispersion of the present embodiment has an appropriate viscosity, adhesion, drying property or printing depending on the purpose of use within a range not impairing the effects of the present invention. For example, an oligomer component, a resin component, an organic solvent (a part of the solid content may be dissolved or dispersed), a surfactant, a thickener, You may add arbitrary components, such as 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 organic component 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.

  The silver fine particles contained in the silver fine particle dispersion of the present embodiment are silver fine particles in which an alkoxyamine having a distribution coefficient log P of −1.0 to 1.4 and a carbon number of 5 or less is attached to at least a part of the surface. Preferably there is.

  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 applied to various solvents (particularly highly polar solvents). Excellent dispersibility and low-temperature sinterability can be imparted.

  As said solvent, a various solvent can be used in the range which does not impair the effect of this invention, and the solvent whose SP value (solubility parameter) is 7.0-15.0 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. Since solubility is favorable, it is preferable to use a C1-C6 alcohol. 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), methylpropylketone (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-pig (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, 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, acetic acid-2 Butoxyethyl, 2- (2-butoxyethoxy) ethyl acetate, acetic acid-2-methoxyethyl, can be exemplified 2-hexyloxy ethanol.

  The particle size of the silver fine particles of this embodiment is a nanometer size that desirably causes a melting point drop, preferably 1 to 200 nm, but may contain micrometer size particles as necessary.

  Here, when the conductive ink for transfer printing is used as the conductive ink in the present embodiment, more specifically, the conductive ink for transfer printing has a metal nanoparticle, a solvent containing ethanol, and a hydroxyl group. And 0.1 to 3.0% by mass of a high-boiling solvent (the conductive ink B). Moreover, the solid content which has the metal particle dispersion (in other words, metal colloid particle) which consists 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 preparing 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, a preferable solid content concentration 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 concentration is 5 to 40% by mass.

  The conductive ink for transfer printing contains 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.).

  “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 amount of the high-boiling solvent having a hydroxyl group added 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.

  In addition, in the conductive ink for transfer printing, a highly volatile solvent such as ethanol is added 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. As the highly volatile solvent, in addition to ethanol, one or two or more selected from the group of solvents having a boiling point of less than 100 ° C. such as methanol, propyl alcohol, isopropyl alcohol, acetone, n-butanol, sec-butanol, tert-butanol and the like Low boiling solvents can be used.

  Further, the conductive ink for transfer printing 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, 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. It is suitable that it is 0.01-2 mass%.

  In the conductive ink for transfer printing, 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), and is measured by, for example, a fully automatic surface tension meter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. can do.

  Next, the method for producing silver fine particles and the silver fine particle dispersion according to the present embodiment includes a step of producing silver fine particles, and a dispersant having an acid value for dispersing the silver fine particles is added to and mixed with the silver fine particles. 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. And a second pre-process for generating 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 in the mixed solution. And.

  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.

  Various known silver compounds (metal salts or hydrates thereof) are used as starting materials 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). 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 of the method include preparing a solution, adding a short-chain amine as a 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. In the liquid in such a state, the silver fine particles are agglomerated due to high electrical conductivity, etc., and are easily precipitated. 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 residue and removing the organic solvent by such washing, silver fine 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 metal colloid dispersion liquid is a mixture of the silver fine particles coated with the short-chain amine obtained in the above or the protective dispersant having an acid value and the dispersion medium described in the present embodiment. Is obtained. The method of mixing the silver fine particles coated with the “short-chain amine or the protective dispersant having an acid value” and the dispersion medium is not particularly limited, and is 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 metal colloid dispersion liquid containing a plurality of metals, the production method is not particularly limited. For example, when producing a metal colloid dispersion liquid composed of silver and other metals, the metal colloid dispersion liquid is coated with the above organic substance. In the preparation of silver fine 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 preparing 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 fine particles protected by a short-chain amine protective film can be produced.

  Thus, in the metal amine complex decomposition method for producing silver fine 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 producing a large amount of silver fine particles 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, it is possible to produce silver fine particles that are very fine and have a narrow particle size distribution according to the metal amine complex decomposition method.

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

  In addition, when a solid metal compound and an amine are mixed to produce 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 fine 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 fine particles having characteristics according to various uses.

  The dispersion of the present embodiment obtained as described above can be used as it is, but various inorganic components can be used as long as the dispersion stability and low-temperature sinterability of the conductive ink and conductive paste are not impaired. And organic components can be added.

Then the second step, firing the pre-fired film formed in the first step. This firing may be performed by a conventionally known method and conditions. For example, by using a conventionally known gear oven or the like, the conductive film is baked by baking the pre-fired film that has undergone the first and second steps so that the temperature is 300 ° C. or less (preferably less than 180 ° C.). (Conductive film pattern) can be formed.

  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 not impairing 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 100 ° C. Therefore, the conductive film pattern can be 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.

  The pre-firing film obtained through the first step in the present embodiment is a sintered body formed from silver fine particles and formed by external heating, and has good conductivity equivalent to the conductivity inherent to the silver fine particles. Have moderate roughness and reflectivity.

Third Step Next, a third step is performed in which at least a part of the conductive coating formed in the second step is contacted with an acidic solution for cleaning. The electrode of this embodiment is obtained by the third step.

  In this third step, an acidic solution may be brought into contact with at least a part of the conductive coating, and this “contact” is a concept including “dipping”, “spraying” and the like. Moreover, it is the concept also including dripping an acidic solution on a conductive film.

  Here, the acidic solution used in the present embodiment may contain any sulfuric acid or hydrochloric acid and can effectively wash the conductive film. For example, the acidic solution is 1 to 50% by mass, preferably 5 to 30% by mass. An acidic solution with a concentration is desirable. When the acid concentration is 1% by mass or more, a cleaning effect is obtained, and when the acid concentration is 50% by mass or less, deterioration of the film base material and other members forming the conductive film can be suppressed. Moreover, if it is 5 mass% or more, the effect of washing | cleaning will be acquired more reliably, and if it is 30 mass% or less, deterioration of the film base material and other member which form a conductive film will be suppressed more reliably. Can do.

  The acidic solution may contain a surfactant or a water-soluble solvent in order to improve the wettability to the surface of the conductive film. The surfactant is not particularly limited, and for example, any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used. For example, an alkylbenzene sulfonate, a quaternary ammonium salt, and the like. A fluorine-based surfactant that can sufficiently reduce the surface free energy with a small amount of addition can be suitably used. Examples of the water-soluble solvent include methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and the like. As a commercially available surfactant, for example, a fluorosurfactant (Surflon) manufactured by AGC Seimi Chemical Co., Ltd. can be suitably used.

  As what can be used suitably as said acidic solution, the DP clean 320 etc. by Okuno Pharmaceutical Co., Ltd. can be illustrated, for example. Moreover, the environmental temperature of the cleaning by contact in the third step may be room temperature or may be heated as necessary. In addition, after washing with an acidic solution, washing with water or a water-soluble solvent is preferable.

  Moreover, there is no restriction | limiting in particular about the thickness of the electroconductive film (namely, electrode) after passing through a 3rd process, What is necessary is just to determine suitably by the use of the obtained electrode, For example, it is 0.05-1 micrometer. It is preferable that it is 0.1 to 0.5 μm. If it is 0.05 micrometer or more, suitable conduction | electrical_connection will be obtained, and if it is 1 micrometer or less, desired performance will be obtained, and an extra material is not required and it is preferable also in terms of cost.

  In this embodiment, the electrode obtained after the cleaning of the conductive film in the third step is subjected to surface modification (post-step) by SAM (self-assembled film) for the purpose of further improving the carrier injection property of the electrode. Also good. As SAM, for example, pentafluorobenzenethiol (PFBT), phosphonic acid, or a derivative thereof can be suitably used.

  The exemplary embodiments of the present invention have been described above. However, conventionally known techniques may be used for the contents that are not particularly described, and various design changes are possible. Included in the technical scope.

  In addition, as a base material that can be used to print or apply the conductive ink, at least one main surface on which the conductive ink can be printed or applied and baked by heating to be mounted with a conductive film pattern If it has, there will be no restriction | limiting in particular, However, It is preferable that it is a base material excellent in heat resistance. In addition, as described above, the conductive ink of this embodiment can obtain a conductive film pattern having sufficient conductivity even when heated and baked at a lower temperature than the conventional conductive ink. Therefore, it is possible to use a base material 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.

  In this embodiment, in order to further improve the adhesion between the substrate and the conductive film pattern (conductive film or electrode), 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.

  Suitable primer layers include, for example, polyurethane, polyimide, polyamideimide, polyvinyl alcohol, polyvinylphenol, polyester, polyethylene, polyphenylene sulfide, unsubstituted or halogen atom-substituted polyparaxylylene, polyacrylonitrile, cyanoethyl pullulan, polymethyl methacrylate, silyl. Sesquioxane, polyvinyl butyral, and the like can be used.

Examples of the polyurethane include -COO-H, -COOR, -COO-NH ⁺ R ₂ and -COO-NH ⁴⁺ described in Japanese Patent Application No. 2015-060183, wherein R and R ₂ are respectively Independently, a linear or branched alkyl group, the same cycloalkyl group, the same alkylene group, the same oxyalkylene group, the same aryl group, the same aralkyl group, the same heterocyclic group, the same alkoxy group which may have a substituent Group, the same alkoxycarbonyl group, and the same acyl group), and a polyurethane resin having a breaking elongation of 600% or more is preferable.

  Hereinafter, although the manufacturing method of the electrode of this invention is further demonstrated with an Example and a comparative example, this invention is not limited to these Examples at all.

<< 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-102, which is a polymer dispersant, The mixture was mixed and stirred well with a magnetic stirrer to form 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, stirring was continued at room temperature to change the silver oxalate to a viscous white substance, and stirring was terminated when the change was found to be apparently finished.

  The obtained mixed solution was transferred to an oil bath and heated and stirred at 120 ° C. Immediately after the start of stirring, a reaction involving the generation of carbon dioxide started, 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.

  Next, in order to replace the dispersion medium of the suspension, 10 mL of a mixed solvent of methanol / water is added and stirred, and then silver fine particles are precipitated and separated by centrifugation, and methanol is again added to the separated silver fine particles. 10 mL of a mixed solvent of water / water is added, and silver fine particles are precipitated and separated by stirring and centrifuging, and then solidified by adding 2.1 g of ethanol containing 0.06 g of SOLPERSE 41000 (manufactured by Nippon Lubrizol Co., Ltd.). A silver fine particle dispersion a having a partial concentration of 48% by mass was obtained.

The silver fine particle dispersion a obtained as described above and other components shown in Table 1 were added and mixed to prepare a conductive ink a. In addition, the quantity of the component shown in Table 1 is shown by the mass%.

<< Preparation Example 2 >>
17 mL of trisodium citrate dihydrate and 0.36 g of tannic acid were dissolved in 50 mL of water made alkaline by adding 3 mL of 10N-NaOH aqueous solution. To the obtained solution, 3 mL of 3.87 mol / L silver nitrate aqueous solution was added and stirred for 2 hours to obtain a silver colloid aqueous solution. The obtained silver colloid aqueous solution was desalted by dialysis until the electric conductivity became 30 μS / cm or less. After dialysis, coarse silver colloidal particles were removed by centrifuging at 2100 rpm (920 G) for 10 minutes to obtain a silver fine particle dispersion b.

The silver fine particle dispersion b obtained as described above and the other components shown in Table 2 were added and mixed to prepare a conductive ink b. In addition, the quantity of the component shown in Table 2 is shown by the mass%.

Example 1
In this example, a TFT having a top gate bottom contact type structure shown in FIG. 1 was produced.
On a PEN (polyethylene naphthalate) substrate 1, “Hydran HW-312B” manufactured by DIC as a base 2 is diluted 3 times with ethanol, and a resin layer forming ink is applied on a glass substrate using a spin coater. The layer forming ink was deposited at 2000 rpm for 30 seconds. Then, the resin layer was formed by heating at 120 degreeC for 30 minutes. Next, the conductive ink a was applied on a silicone blanket with a bar coater (No. 7), the glass relief was pressed, and the non-image part (unnecessary part) was transferred and removed. Furthermore, the SD (source-drain) electrode pattern was transferred to the base 2 on the substrate 1 by pressing the substrate against the blanket material (first step).
The obtained SD electrode pattern was baked under the conditions of 120 ° C. × 30 minutes to form a conductive film laminate (1, 2, 3) (second step).
Next, the conductive film was immersed in “DP Clean 320 (100 g / 1 L of water) manufactured by Okuno Pharmaceutical Co., Ltd. for 30 seconds at 45 ° C. and then rinsed with pure water to obtain the electrode 3 of the present invention. (Third step).

Next, a semiconductor F8T2 (Poly [(9,9-dioctylfluorenyl-2,7-diyl) -co-bithiophene]) manufactured by Sigma-Aldrich is dissolved in tetralin to form an SD electrode pattern by inkjet. Application was performed between the electrodes 3. Thereafter, the semiconductor layer 4 was formed by heating in a nitrogen atmosphere under conditions of 100 ° C. × 5 minutes.
Thereafter, a fluorine-based insulating film 5 was formed using a spin coater under conditions of 3000 rpm × 30 seconds. Then, it formed on the conditions of 100 degreeC x 5 minutes.
Next, a G (gate) electrode pattern was printed in the same manner as the SD electrode pattern. The obtained G electrode pattern was baked under the conditions of 120 ° C. × 30 minutes, and the G electrode 6 was formed to produce a TFT (top gate bottom contact type) having the structure shown in FIG.

≪Comparative example 1≫
A TFT was produced in the same manner as in Example 1 except that “DP Clean 320 (100 g / 1 L of water)” manufactured by Okuno Pharmaceutical Co., Ltd. was not used.

<< Example 2 >>
Instead of “DP Clean 320 (100 g / 1 L of water)” manufactured by Okuno Pharmaceutical Co., Ltd., a 10% sulfuric acid, 10% IPA aqueous solution was used, and the sample was immersed in room temperature for 1 minute. A TFT was produced.

Example 3
As in Example 1, after cleaning the surface of the electrode 3, the substrate was immersed in an IPA solution of pentafluorobenzenethiol (PFBT) for 1 minute, then immersed and washed in IPA, and then at 60 ° C. for 1 minute. A TFT was produced in the same manner as in Example 1 except that the substrate was dried in the same manner as in Example 1.

Example 4
A TFT was produced in the same manner as in Example 1 except that the conductive ink b was used instead of the conductive ink a.
Example 5
A TFT was produced in the same manner as in Example 2 except that a 10% aqueous solution of sulfuric acid was used.

≪Comparative example 2≫
Instead of “DP Clean 320 (100 g / water 1 L)” manufactured by Okuno Pharmaceutical Industry Co., Ltd., “OPC-180 Cleaner (200 g / water 1 L)” manufactured by Okuno Pharmaceutical Industry Co., Ltd. was used. A TFT was produced in the same manner as in Example 1 except that the immersion was performed.

«Comparative Example 3»
Instead of “DP Clean 320 (100 g / water 1 L)” manufactured by Okuno Pharmaceutical Industry Co., Ltd., “OPC Clean 65 (500 g / water 1 L)” manufactured by Okuno Pharmaceutical Industry Co., Ltd. was used for 1 minute at room temperature. A TFT was produced in the same manner as in Example 1 except for the above.

[Evaluation Test 1]
The characteristics of the TFT elements obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated using B1500A manufactured by Agilent. Measure the output characteristics when the gate voltage is scanned from 0V to 80V and the drain voltage from 0V to 80V. From the relationship between the gate voltage and the drain current when the drain voltage is -80V, the mobility and the ON-OFF ratio are calculated. Calculated. The results are shown in Table 3.

  Also, a graph showing the output characteristics of the TFT in Example 1 and a graph showing the output characteristics of the TFT in Comparative Example 1 are shown in FIGS. 2 and 3, respectively.

2 and FIG. 3 and Table 1, when cleaned in Examples 1 and 2, good TFT characteristics were shown, but Comparative Example 1 (without cleaning), Comparative Example 2 (alkaline) and Comparative Example 3 (neutral) ) Shows that the TFT characteristics are relatively inferior.
In addition, it can be seen from Example 3 that the surface of the S-D electrode is appropriately modified by PFBT and exhibits good TFT characteristics. Example 4 is a relatively good result by using ink b, although the mobility and the ON-OFF ratio are slightly inferior to those of Example 1 using ink a. Furthermore, in Example 5, although the process nonuniformity on the surface of SD electrode is recognized visually, it turns out that the comparatively favorable TFT characteristic is shown.

[Evaluation Test 2]
Next, an experiment corresponding to Example 1 and Comparative Example 1 was performed and an additional evaluation test was performed on the cleaning effect of the electrode obtained using the conductive ink.
(1) The conductive ink a was applied on a silicone blanket with a bar coater (No. 7), and the solid film was transferred to the substrate by pressing the substrate against the blanket material. The obtained solid film was baked under the conditions of 120 ° C. × 30 minutes to form a conductive film. Subsequently, after being immersed in “DP Clean 320 (100 g / water 1 L)” manufactured by Okuno Pharmaceutical Co., Ltd. for 30 seconds at 45 ° C., it was rinsed with pure water. Thus, the electrode of the present invention was obtained.
(2) A comparative electrode was obtained in the same manner as in (1) above except that “DP Clean 320 (100 g / water 1 L)” manufactured by Okuno Pharmaceutical Co., Ltd. was not used.

  The work functions of the electrodes obtained in (1) and (2) above and the comparative electrode were measured using AC-2 manufactured by Riken Keiki Co., Ltd. The obtained results are shown in FIG. FIG. 4 is a graph showing the results of evaluating the cleaning effect of the conductive film in the electrodes obtained in Example 1 and Comparative Example 1.

  From FIG. 4, the work functions calculated by AC-2 are 4.4 eV (Example 1) and 4.8 eV (Comparative Example 1), respectively, and Example 1 is closer to bulk silver (4.3 eV). And the yield (vertical axis) has risen, so even if the same energy is applied, more photoelectrons are emitted, and as a result, efficient carrier injection has been determined. Is done.

Claims (14)

A first step of forming a pre-firing film by printing or applying a conductive ink mainly composed of metal nanoparticles;
A second step of firing the pre-fired coating to form a conductive coating;
A third step of cleaning by bringing an acidic solution into contact with at least a part of the conductive coating;
Including
The conductive ink is
A metal nanoparticle, a short-chain amine having 5 or less carbon atoms, a highly polar solvent, and a dispersant having an acid value for dispersing the metal nanoparticle, the partition coefficient logP of the short-chain amine Including a metal nanoparticle dispersion in which -1.0 to 1.4
An electrode manufacturing method characterized by the above. The electrode is an electrode for a thin film transistor (TFT);
The method for producing an electrode according to claim 1. The acidic solution contains sulfuric acid;
The method for producing an electrode according to claim 1 or 2. The acidic solution contains a surfactant or a water-soluble solvent;
The method for producing an electrode according to any one of claims 1 to 3.   The method for producing an electrode according to claim 1, wherein the water-soluble solvent is any one of methanol, ethanol, isopropyl alcohol, and n-propyl alcohol. The metal nanoparticles are silver nanoparticles,
The method for producing an electrode according to any one of claims 1 to 5. The metal nanoparticle dispersion further comprises a protective dispersant having an acid value;
The method for producing an electrode according to claim 6 . The short chain amine is an alkoxyamine;
The method for producing an electrode according to claim 6 or 7 . The acid value of the protective dispersant is 5 to 200,
The method for producing an electrode according to any one of claims 6 to 8 . The protective dispersant has a functional group derived from phosphoric acid,
The method for producing an electrode according to any one of claims 6 to 9 . The highly polar solvent is methanol, ethanol, isopropyl alcohol or n-propyl alcohol;
The method for producing an electrode according to any one of claims 6 to 10 . The conductive ink is
Metal nanoparticles,
A solvent comprising ethanol;
Containing 0.1 to 3.0% by mass of a high boiling point solvent having a hydroxyl group,
Method of manufacturing an electrode according to any one of claims 1 to 11, wherein. The high boiling point solvent comprises 1,3-butylene glycol, 2,4-diethyl-1,5-pentanediol or octanediol;
The method for producing an electrode according to claim 12 . The conductive ink further contains a hydrofluoroether;
The method for producing an electrode according to claim 12 or 13 , wherein: