JP6393953B2 - Silver fine particle dispersion, ink composition, silver electrode, and thin film transistor - Google Patents

Description

  The present invention relates to a silver fine particle dispersion, an ink composition, a silver electrode, and a thin film transistor.

Silver fine particles are widely used as a material for forming conductor wiring and electrodes (hereinafter referred to as “conductor wiring and the like”). By applying silver fine particles on a base material in a state dispersed in an aqueous medium, baking (sintering) the silver fine particles, and performing etching treatment as necessary, a conductor wiring or the like having a desired shape can be formed.
As a method for applying the silver fine particle dispersion onto a substrate, application by various printing methods, application by spin coating, application by a dispenser, and the like are known. When the silver fine particle dispersion is applied by printing, the silver fine particle dispersion is used as an ink, and this ink is applied to a substrate or the like by various printing methods. In particular, the use of ink jet printing is expanding because a fine pattern can be formed with high accuracy, the process is simple, and ink can be used without waste.

Ink consisting of a silver fine particle dispersion used for ink jet printing has good dispersion stability as well as good dispersibility of silver fine particles (characteristic that enables silver fine particles to be uniformly dispersed in a medium) in order to improve ejection stability. (The property that the dispersion state of the above-mentioned silver fine particles can be stably maintained over time or against external stimuli (heat, vibration, etc.)).
For example, Patent Document 1 discloses a silver colloid solution in which silver fine particles having an oxidized polymer of a phenol compound and / or an oxidized form thereof on the surface are dispersed in a solvent. It describes that it is excellent in dispersion stability and can be used for forming electrodes and circuit wiring patterns by ink jet printing.

Japanese Patent No. 4932662

In recent years, with miniaturization of electronic components, miniaturization of conductor wiring and the like has progressed. For example, in a thin film transistor, the distance between a source electrode and a drain electrode is reduced with downsizing, and part of the electrode is ionized and moves between both electrodes, and ion migration (hereinafter, referred to as “conducting between both electrodes”). Simply called “migration”). Under such circumstances, the silver fine particle dispersion used for ink jet printing is required to suppress migration of the formed conductor wiring in addition to good dispersibility and dispersion stability.
The present invention is a silver fine particle dispersion in which silver fine particles are dispersed in an aqueous medium, and is excellent in the dispersibility and dispersion stability of the silver fine particles, and further has electrical conductivity such as conductor wiring formed using this dispersion. Another object of the present invention is to provide a silver fine particle dispersion capable of effectively suppressing migration of a conductor wiring or the like formed using this dispersion. Another object of the present invention is to provide an ink composition using the silver fine particle dispersion, a silver electrode using the ink composition, and a thin film transistor having the silver electrode.

The inventors of the present invention have prepared an emulsion obtained by emulsifying and dispersing a hydrophobic organic solvent solution in which a specific antioxidant is dissolved in an aqueous medium using a nonionic surfactant, and dispersing silver fine particles in the aqueous medium. When the silver fine particle dispersion was prepared by mixing with the resulting dispersion, the silver fine particle dispersion was excellent in the dispersibility and dispersion stability of the silver fine particles, and the conductor wiring formed using this silver fine particle dispersion. Etc. showed excellent conductivity and hardly caused migration. Furthermore, it has been found that when a thin film transistor (TFT) electrode is formed using this silver fine particle dispersion, it shows good carrier mobility and functions well as a TFT electrode.
The present invention has been further studied based on these findings and has been completed.

The above-described problems of the present invention have been solved by the following means.
[1]
A silver fine particle dispersion obtained by dispersing silver fine particles in an aqueous medium,
A mixed solution of an antioxidant having an SP value of 30 or less and a hydrophobic organic solvent is emulsified and dispersed in the aqueous medium by a nonionic surfactant,
A silver fine particle dispersion, wherein the antioxidant is present in oil droplets dispersed in the aqueous medium .
[2]
The silver fine particle dispersion according to [1], wherein the antioxidant is a compound having an aromatic ring.
[3]
The silver fine particle dispersion according to [1] or [2], wherein the antioxidant is a compound having a molecular weight of 200 to 3,000.
[4]
The silver fine particle dispersion according to any one of [1] to [3], wherein the antioxidant is selected from a hindered phenol compound, a benzophenone compound, a benzotriazole compound, a salicylic acid compound, and a benzoxazole compound.
[5]
The nonionic surfactant is, in a hydrophilic site _{- (C 2 H 4 O)} n - having, (1) to the silver fine particle dispersion according to any one of [4].
However, n is an integer of 3 or more.
[6]
The silver fine particle dispersion according to any one of [1] to [5], wherein the nonionic surfactant has an aromatic ring.
[7]
An ink composition using the silver fine particle dispersion described in any one of [1] to [5].
[8]
The ink composition according to [7], which is used for inkjet printing.
[9]
The ink composition according to [7] or [8], which is used for forming a silver electrode.
[10]
A silver electrode formed using the silver fine particle dispersion according to any one of [1] to [6] or the ink composition according to any one of [7] to [9].
[11]
[10] A thin film transistor having the silver electrode according to [10].

  In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

The silver fine particle dispersion or ink composition of the present invention is excellent in both dispersibility and dispersion stability. Moreover, the conductor wiring etc. formed using this silver fine particle dispersion are excellent in electroconductivity, and generation | occurrence | production of migration is also suppressed effectively.
The silver electrode of the present invention can effectively suppress the occurrence of migration, and can be suitably used, for example, as a TFT electrode. Furthermore, the thin film transistor of the present invention has the electrode of the present invention, and migration of the electrode is suppressed, so that the insulation reliability between the electrodes is excellent and the carrier mobility is excellent.
The above and other features and advantages of the present invention will become more apparent from the following description, with reference where appropriate to the accompanying drawings.

It is a figure which shows typically the preferable structure of the thin-film transistor of this invention.

[Silver fine particle dispersion]
A preferred embodiment of the silver fine particle dispersion of the present invention will be described.
In the silver fine particle dispersion of the present invention, silver fine particles are dispersed in an aqueous medium, and the aqueous medium further contains a mixed solution of an antioxidant having an SP value of 30 or less and a hydrophobic organic solvent. It is emulsified and dispersed with a nonionic surfactant. That is, the antioxidant is present in oil droplets dispersed in an aqueous medium in the silver fine particle dispersion. In this specification, “dispersed” in an aqueous medium means a state in which the particles are in the form of fine particles and are uniformly (homogeneously) dispersed in the aqueous medium.
The silver fine particle dispersion of the present invention may contain one or more of the above antioxidants. Moreover, the silver fine particle dispersion of the present invention may contain one kind or two or more kinds of the nonionic surfactant. Moreover, the silver fine particle dispersion of the present invention may contain one or more of the above hydrophobic organic solvents.
The silver fine particle dispersion of the present invention may further contain a drying inhibitor, a penetration accelerator, an antiseptic, an antifoaming agent, a viscosity modifier, a pH adjuster, a chelating agent, metal particles other than silver, and the like.
The silver fine particle dispersion of the present invention preferably does not contain an ionic component. The ionic component means a component having ionized and charged groups in the silver fine particle dispersion.
Since the silver fine particle dispersion of the present invention does not contain an ionic component, it is possible to further increase the conductivity of a conductor wiring or the like formed using the silver fine particle dispersion, and to further suppress the occurrence of migration and to insulate. Reliability can be increased.

<Aqueous medium>
The aqueous medium (hereinafter sometimes referred to as the aqueous medium (a)) used in the silver fine particle dispersion of the present invention is water or a mixed liquid of water and a water-soluble organic solvent. In the aqueous medium contained in the silver fine particle dispersion, the content of water is preferably 30% by mass or more, more preferably 40 to 100% by mass, further preferably 50 to 100% by mass, and more preferably 60 to 100% by mass.

Examples of water include distilled water, ion exchange water, pure water, and ultrapure water.
The water-soluble organic solvent that can be contained in the aqueous medium preferably has a solubility in water at 20 ° C. of 10% by mass or more. Examples of the water-soluble organic solvent include alcohols, ketones, ether compounds, amide compounds, nitrile compounds, and sulfone compounds.

Among these, examples of alcohol include ethanol, isopropanol, 1-methoxy-2-propanol, n-butanol, t-butanol, isobutanol, diacetone alcohol, diethylene glycol, ethylene glycol, dipropylene glycol, propylene glycol, and glycerin. Can be mentioned.
Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone.
Examples of the ether compound include dibutyl ether, tetrahydrofuran, and dioxane.
Examples of the amide compound include dimethylformamide and diethylformamide.
An example of the nitrile compound is acetonitrile.
Examples of the sulfone compound include dimethyl sulfoxide, dimethyl sulfone, and sulfolane.

  10-90 mass% is preferable, as for content of the aqueous medium in the silver fine particle dispersion of this invention, 20-85 mass% is more preferable, and 30-70 mass% is further more preferable.

<Silver fine particles>
Silver fine particles contained in the silver fine particle dispersion of the present invention can be prepared by a conventional method.
For example, a silver compound such as silver nitrate (I) (AgNO ₃ ) or silver methanesulfonate (CH ₃ SO ₃ Ag) and a dispersant are dissolved in water, a reducing agent is added, and the silver is stirred for a certain time while stirring. Silver fine particles can be obtained as a dispersion by reducing the ions.

  There is no restriction | limiting in particular in the said reducing agent, The conventionally well-known reducing agent used in order to reduce | restore a silver compound and to obtain silver fine particles can be used. Among them, from the viewpoint of obtaining silver fine particles having a small particle diameter and uniform particle diameter, alcohol (preferably methanol, ethanol, 2-propanol, ethylene glycol, trimethylolpropane, N, N-diethylhydroxylamine) is used as a reducing agent. Or 3-amino-1-propanol), an amine having no hydroxy group (preferably hydrazine or phenylhydrazine), ascorbic acid, formaldehyde, saccharides and the like are preferably used.

As the silver fine particle dispersant, a conventionally known dispersant used as a silver fine particle dispersant can be widely used. The dispersant may be a dispersant having an ionic group as a hydrophilic group, but a dispersion having a nonionic group as a hydrophilic group from the viewpoint of further improving the conductivity of a conductor wiring or the like and further suppressing the occurrence of migration. Agents are preferred. The dispersant having a nonionic group as a hydrophilic group is preferably a polymer compound. For example, polyvinylpyrrolidone, polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, polyvinyl alcohol, polyallylamine, polyvinyl alcohol-polyvinyl acetate. Mention may be made of copolymers.
When the nonionic dispersant that can be used in the present invention is a polymer compound, the weight average molecular weight is preferably 2000 to 50000, and more preferably 3000 to 30000.
In this specification, the weight average molecular weight is measured by gel permeation chromatograph (GPC). GPC uses HLC-8220GPC (manufactured by Tosoh Corporation), and three columns of TSKgeL Super HZM-H, TSKgeL Super HZ4000, and TSKgeL Super HZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are connected in series. And THF (tetrahydrofuran) is used as the eluent. As conditions, the sample concentration is 0.35% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

  The primary particle size of the silver fine particles can be adjusted by appropriately adjusting the types and blending ratios of the silver compound, dispersant, and reducing agent to be used, and further adjusting the stirring speed, temperature, time, and the like.

In the silver fine particle dispersion of the present invention, the average particle size of the silver fine particles is not particularly limited as long as it can be stably dispersed in an aqueous medium, but it is 10 to 200 nm from the viewpoint of coating suitability and storage stability. Preferably, the thickness is 20 to 150 nm, more preferably 30 to 120 nm, still more preferably 40 to 100 nm, and still more preferably 50 to 100 nm. By setting the average particle diameter of the silver fine particles within the above preferred range, a sufficiently low volume resistance value can be obtained when a film, wiring, electrode, or the like is formed.
The average particle size of the silver fine particles in the present specification is measured using a concentrated particle size analyzer FPAR-1000 (product name, manufactured by Otsuka Electronics Co., Ltd.). Specifically, measurement is performed under standard measurement conditions using the above apparatus (FPAR-1000), and an average particle diameter is obtained by cumulant analysis.
Further, the particle size distribution of the silver fine particles in the silver fine particle dispersion is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution.

  The content of silver fine particles in the silver fine particle dispersion of the present invention is preferably 5 to 90% by mass, more preferably 10 to 80% by mass, and still more preferably 20 to 70% by mass. More preferably, it is 20-50 mass%, and it is further more preferable that it is 20-40 mass%. If it is in said range, the conductor wiring and electrically conductive film which have sufficient thickness and electroconductivity can be formed, and the fluid silver fine particle dispersion suitable for various printing methods can be obtained.

<Antioxidant>
In the present invention, an antioxidant is a compound that exhibits an oxidation-inhibiting action on coexisting substances. One or more antioxidants can be used in the silver fine particle dispersion of the present invention.
The antioxidant used in the present invention has an SP value (solubility parameter, unit: MPa ^1/2 ) of 30 or less. From the viewpoint of suppressing migration more effectively, the SP value of the antioxidant used in the present invention is preferably 15 to 22, and more preferably 15 to 20.
In this specification, the SP value can be determined by Hansen's method. Hansen's method is one of methods for calculating an SP value well known in the art, and the SP value is expressed by a multidimensional vector composed of a dispersion term, a polar term, and a hydrogen bond term. Hansen's SP value is Int. J. et al. Thermophys, 2008, 29, pages 568-585, and the SP value described in this specification is a value predicted by the method of this document.

  The antioxidant used in the present invention has a solubility in 100 g of water (pure water) at 20 ° C. of 0.5 g or less, and more preferably 0.2 g or less. The antioxidant used in the present invention has a solubility in 100 g of water (pure water) at 20 ° C., usually 0.001 g or more.

  The antioxidant used in the present invention constitutes oil droplets together with the hydrophobic organic solvent described later in the silver fine particle dispersion of the present invention. That is, in the present invention, the antioxidant is present in oil droplets dispersed in an aqueous medium.

The antioxidant used in the present invention is preferably a compound having an aromatic ring in its structure. When the antioxidant is a compound having an aromatic ring, good dispersion stability can be maintained.
There is no restriction | limiting in particular in the aromatic ring which antioxidant has, An aromatic hydrocarbon ring or an aromatic heterocyclic ring may be sufficient. The aromatic ring may be a single ring or a condensed polycyclic structure. From the viewpoint of the oxidation potential of the antioxidant, the aromatic ring is preferably an aromatic hydrocarbon ring, and more preferably a benzene ring. The number of benzene rings in one molecule of the antioxidant is preferably 1 to 4, more preferably 1 to 2.

  Although there is no restriction | limiting in particular in the molecular weight of antioxidant used for this invention, Usually, it is 10,000 or less, 5000 or less is more preferable, 2000 or less is further more preferable, 1500 or less is further more preferable. Further, the molecular weight of the antioxidant is preferably 200 or more, and more preferably 300 or more. By setting the molecular weight of the antioxidant within the above preferred range, volatilization during sintering can be suppressed and migration can be effectively suppressed.

  Preferred examples of the antioxidant used in the present invention include an antioxidant selected from a hindered phenol compound, a benzophenone compound, a benzotriazole compound, a salicylic acid compound, and a benzoxazole compound, and among them, a hindered phenol compound, and Antioxidants selected from benzotriazole compounds are preferred.

  In the present specification, the hindered phenol compound means a compound having a skeleton represented by the following structural formula (A). In this specification, “having a skeleton” means to include those having a structure in which part or all of the hydrogen atoms in the structural formula (A) are substituted.

Preferable specific examples of the hindered phenol compound include, for example, butylhydroxyanisole, 2,6-di-t-butyl-4-hydroxymethylphenol, 4,4′-thiobis (6-t-butyl-m-cresol) 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, 2,2′-methylenebis (6-t-butyl-p-cresol), 1, 1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 2,2′-methylenebis (6-t-butyl-4-ethylphenol), 1,3,5-tris { [4- (1,1-dimethylethyl) -3-hydroxy-2,6-dimethylphenyl] methyl} -1,3,5-triazine-2,4,6- (1H, 3H, 5H) -trione, 4,4'- Methylenebis (2,6-di-t-butylphenol), 2,2′-methylenebis [6- (1-methylcyclohexyl) -p-cresol], 2- (5-chlorobenzotriazol-2-yl) -4- Methyl-6-tert-butyl-phenol, 2- (3,5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-tert-amyl-2- Hydroxyphenyl) benzotriazole, stearyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 3,5-di-t-butyl-4-hydroxybenzoic acid 2,4-di-t -Butylphenyl, 1,3,5-tris {[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl} -1,3,5-triazine-2,4,6 (1H , 3H, 5H) -trione, {3- [3- (4-hydroxy-3,5-di-t-butyl-phenyl) propanoyloxy] -2,2-bis [3- (4-hydroxy-3, 5-di-t-butyl-phenyl) propanoyloxy] propyl} 3- (4-hydroxy-3,5-di-t-butyl-phenyl) propanoate, 2,4,6-tris (3 ′, 5 ′ -Di-t-butyl-4'-hydroxybenzyl) mesitylene, tris phosphite (2,4-di-t-butylphenyl).
In addition, even if it is a compound which has the frame | skeleton represented by following (B)-(E), the compound which has the frame | skeleton represented by said (A) is contained in a hindered phenol compound in this specification ( That is, it is not included in the benzophenone compound, benzotriazole compound, salicylic acid compound, or benzoxazole compound). Here, “having a skeleton” means to include those having a structure in which part or all of the hydrogen atoms in each structural formula are substituted, as described for the general formula (A). To do.

  In this specification, the benzophenone compound means a compound having a skeleton represented by the following structure (B).

  Preferable specific examples of the benzophenone compound include, for example, 2-hydroxy-4-n-octyloxybenzophenone.

  In this specification, the benzotriazole compound means a compound having a skeleton represented by the following structure (C).

  Preferable specific examples of the benzotriazole compound include, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole.

  In this specification, a salicylic acid compound means a compound having a skeleton represented by the following structure (D).

  Specific examples of the salicylic acid compound include 4-t-butylphenyl salicylate.

  In this specification, the benzoxazole compound means a compound having a skeleton represented by the following structure (E).

  Preferable specific examples of the benzoxazole compound include, for example, 2,5-bis (5-t-butyl-2-benzoxazolyl) thiophene.

  In the silver fine particle dispersion of the present invention, the content of the antioxidant having an SP value of 30 or less is preferably 0.1 to 20% by mass, and more preferably 1 to 10% by mass.

<Hydrophobic organic solvent>
The hydrophobic organic solvent used in the present invention dissolves the above-mentioned antioxidant and constitutes oil droplets in the silver fine particle dispersion of the present invention.
The hydrophobic organic solvent used in the present invention means an organic solvent having a solubility in 100 g of water (pure water) at 20 ° C. of 10 g or less, and a solubility in 100 g of water (pure water) at 20 ° C. of 1 g or less. Is more preferable. The hydrophobic organic solvent used in the present invention has a solubility in 100 g of water (pure water) at 20 ° C. of usually 0.001 g or more.

  Preferred examples of the hydrophobic organic solvent used in the present invention include toluene, xylene, alkylbenzene having 9 to 18 carbon atoms, hexane, cyclohexane, 2-butanone, ethyl acetate, butyl acetate, anisole, methylcyclohexane, isopropyl methyl ketone, and methyl isobutyl. Mention may be made of ketones, cyclohexanone, ditertiary butyl ether.

  In the silver fine particle dispersion of the present invention, the content of the hydrophobic organic solvent is preferably 0.0001 to 20% by mass, more preferably 0.001 to 10% by mass, and 0.01 to 1 It is more preferable that it is mass%, and it is still more preferable that it is 0.1-1 mass%.

<Nonionic surfactant>
The silver fine particle dispersion of the present invention contains a nonionic surfactant as a surfactant.
The nonionic surfactant used in the present invention is used as an emulsifier for emulsifying and dispersing a hydrophobic organic solvent solution in which an antioxidant is dissolved in an aqueous medium.
Nonionic surfactant is a non-ionic group that volatilizes easily when silver fine particle dispersion or ink composition is applied and sintered. Can be suppressed. Further, migration can be effectively suppressed as compared with the case of using an ionic surfactant. Furthermore, the dispersion stability of the silver fine particles in the dispersion can be improved as compared with the case where an ionic surfactant is used.

The nonionic surfactant used in the present invention preferably has an HLB of 9 to 15 and more preferably 10 to 14 from the viewpoint of dispersion stability of the antioxidant. HLB is a value calculated by the Griffin method (WC Griffin, J. Soc. Cosmetic. Chemist., 1, 311 (1949)).
The molecular weight of the nonionic surfactant is preferably 500 to 20000, more preferably 1000 to 10,000.

The nonionic surfactant is — (C ₂ H ₄ O) _n — (n is an integer of 3 or more, preferably 3 to 50, and more preferably 5 to 25 in the hydrophilic portion. Preferably).
The nonionic surfactant preferably has an aromatic ring (preferably a benzene ring) in its structure. By having an aromatic ring, dispersion stability can be improved.

Preferable examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylamine, polyoxyethylene polycyclic aryl ether, and polyoxyethylene sorbitan alkylate.
Preferable specific examples of the nonionic surfactant include, for example, polyoxyethylene distyrenated phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene tribenzyl phenyl ether, polyoxyethylene sorbitan trioleate, polyoxyethylene polycyclic phenyl Examples include ether and polyoxyethylene cumylphenyl ether.

  In the silver fine particle dispersion of the present invention, the content of the nonionic surfactant is preferably 1 to 20% by mass, and more preferably 2 to 15% by mass.

<Preparation of silver fine particle dispersion>
The silver fine particle dispersion of the present invention includes an oil-in-water emulsion in which a mixed solution of a hydrophobic organic solvent and an antioxidant is emulsified and dispersed in an aqueous medium by the action of a nonionic surfactant, as described above. It can be obtained by mixing with an aqueous dispersion of silver fine particles obtained by reducing a silver compound.
For the preparation of the oil-in-water emulsion, a general emulsion dispersion method can be employed. An example of the preparation of the oil-in-water emulsion will be described below.

In one preparation example of the oil-in-water emulsion, a solution (hereinafter referred to as “antioxidant solution”) in which the antioxidant, the hydrophobic organic solvent, and the nonionic surfactant are mixed is prepared. . The solution temperature for preparing the antioxidant solution is preferably 10 to 40 ° C.
The concentration of the antioxidant in the antioxidant solution is preferably 5 to 50% by mass. Moreover, it is preferable that the nonionic surfactant density | concentration in antioxidant solution shall be 5-50 mass%.
Further, the amount ratio of the antioxidant and the nonionic surfactant in the antioxidant solution is preferably antioxidant / nonionic surfactant = 1/9 to 9/1 (mass ratio). Nonionic surfactant = 2/8 to 8/2 (mass ratio) is more preferable.
Next, the above-mentioned oil-in-water emulsion can be obtained by dropping the above-mentioned antioxidant solution into water and emulsifying and dispersing the antioxidant solution in water using an ultrasonic homogenizer or the like. The ratio of the amount of the antioxidant solution to the amount of water to which the solution is dropped is preferably an antioxidant solution / water = 1/100 to 50/50 (mass ratio), and the antioxidant solution / water = 10. / 100-30 / 100 (mass ratio) is more preferable.

  In the oil-in-water emulsion or the silver fine particle dispersion of the present invention, the oil droplets preferably have a particle size of 20 to 200 nm, more preferably 30 to 150 nm, and even more preferably 40 to 120 nm. . The particle size of the oil droplets means an average particle size and can be measured by a dynamic light scattering photometer.

  In the silver fine particle dispersion of the present invention, the antioxidant is present in a dispersed state in an aqueous medium, so that the antioxidant can be present stably and homogeneously in the silver fine particle dispersion. By using the dispersed silver fine particles, it is possible to more effectively suppress the migration of the conductor wiring and the like. When a pulverized product of an antioxidant or the like is simply contained in the silver fine particle dispersion, the antioxidant cannot be stably dispersed, resulting in poor printing characteristics.

<Physical properties of silver fine particle dispersion>
The viscosity of the silver fine particle dispersion of the present invention is usually 3 to 1000 mPa · s, more preferably 5 to 500 mPa · s, and more preferably 5 to 100 mPa · s, although it depends on the content of silver fine particles and the like. More preferably, it is 5 to 50 mPa · s, more preferably 5 to 20 mPa · s. The viscosity of the silver fine particle dispersion is measured at 25 ° C. using a TV-25 viscometer (manufactured by Toki Sangyo Co., Ltd.).

  From the viewpoint of dispersion stability, the pH of the silver fine particle dispersion of the present invention is preferably from 3 to 10, more preferably from 4 to 8, and even more preferably from 5 to 7 at 25 ° C.

[Ink composition]
The ink composition of the present invention may be the silver fine particle dispersion itself of the present invention. Moreover, it may be prepared using the silver fine particle dispersion of the present invention as a raw material. More specifically, the ink composition of the present invention may be prepared by mixing at least the silver fine particle dispersion of the present invention and an aqueous medium (hereinafter referred to as an aqueous medium (b)). In some cases, the silver fine particle dispersion of the present invention can be concentrated to obtain the ink composition of the present invention. In the ink composition of the present invention, a surface tension adjusting agent, a drying inhibitor (swelling agent), a coloring inhibitor, a penetration accelerator, an ultraviolet absorber, an antiseptic, a rust inhibitor, an antifoaming agent, if necessary, You may mix additives, such as a clay regulator, a pH adjuster, and a chelating agent. The mixing method is not particularly limited, and a commonly used mixing method can be appropriately selected to obtain the ink composition of the present invention.

  An aqueous medium (b) is synonymous with an aqueous medium (a), and its preferable range is also the same. In the ink composition of the present invention, the content of the aqueous medium (the total content of the aqueous mediums (a) and (b)) is preferably 10 to 90% by mass from the viewpoint of storage stability of the silver fine particles. -85 mass% is more preferable, and 30-70 mass% is further more preferable.

In the ink composition of the present invention, the content of the silver fine particles is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, from the viewpoint of expressing high conductivity by the coating film. More preferably, it is 20-70 mass%, It is more preferable that it is 20-50 mass%, It is more preferable that it is 20-40 mass%.
The preferable range of the average particle diameter of the silver fine particles and the average particle diameter of the oil droplets dispersed in the ink composition of the present invention is the average particle diameter of the silver fine particles and the oil droplets in the silver fine particle dispersion of the present invention described above. It is the same as the average particle size.

In the ink composition of the present invention, the surface tension of the ink composition is preferably 20 to 60 mN / m, more preferably the surface tension of the ink composition, from the viewpoint of satisfactorily discharging the ink composition by an inkjet method. 20 to 45 mN / m, more preferably 25 to 40 mN / m.
The surface tension is measured under the condition of 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.). The surface tension can be appropriately adjusted by adding a surfactant or the like.

  The viscosity of the ink composition of the present invention is not particularly limited, but the viscosity at 25 ° C. is preferably 1 mPa · s or more and 500 mPa · s or less, more preferably 2 mPa · s or more and less than 100 mPa · s, Preferably it is 2.5 mPa * s or more and less than 50 mPa * s, More preferably, it is 5 mPa * s or more and less than 20 mPa * s. The viscosity of the ink composition is a value obtained by the same method as the above-described method for measuring the viscosity of the silver fine particle dispersion.

  The pH of the ink composition of the present invention is preferably pH 6 to 11, more preferably pH 7 to 10, more preferably pH 7 to 9, at 25 ° C., from the viewpoint of dispersion stability.

  The ink composition of the present invention is applied on a substrate and sintered at 100 to 250 ° C., preferably 120 to 200 ° C. in the air, thereby forming a conductor wiring, a conductive film, a silver electrode, and the like. Can be formed. There is no restriction | limiting in particular in the coating method of the ink composition of this invention, A well-known ink application | coating method can be used. For example, coating methods such as a screen printing method, a dip coating method, a spray coating method, a spin coating method, and an ink jet method can be used. Among these, it is preferable to apply the ink composition by an ink jet method from the viewpoint of efficient use of ink, downsizing of the recording apparatus, high-speed recording property, and the like.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, Either an acoustic ink jet method that converts an electrical signal into an acoustic beam, irradiates the ink with ink, and ejects the ink using radiation pressure, or a thermal ink jet method that heats the ink to form bubbles and uses the generated pressure. May be.
The ink jet head used in the ink jet method may be an on-demand method or a continuous method. Furthermore, there are no particular limitations on the ink nozzles used when recording by the ink jet method, and the ink nozzles can be appropriately selected depending on the purpose.

  In the case where the ink application is carried out by an ink jet method, the amount of droplets of the ink composition ejected by the ink jet method is preferably 1.5 to 20 pL from the viewpoint of forming a high-definition pattern. More preferably, it is 10 pL. The amount of droplets of the ejected ink composition can be adjusted by appropriately adjusting the ejection conditions.

[Silver electrode]
The silver electrode of the present invention is formed using the silver fine particle dispersion or ink composition of the present invention. More specifically, the silver electrode of the present invention can be formed by applying the above-described silver fine particle dispersion or ink composition on a substrate and subjecting to heat treatment (sintering) as necessary. . By performing the heat treatment, the silver fine particles are fused with each other to form grains, and the grains are bonded and fused to form a silver layer.
The temperature of the heat treatment is preferably 100 ° C to 250 ° C, more preferably 120 ° C to 200 ° C.
The heating time is preferably 5 minutes to 4 hours, more preferably 15 minutes to 2 hours.
By setting the temperature and time of the heat treatment within the above preferred range, the silver fine particles are sufficiently sintered and desired conductivity (volume resistance value) is easily obtained.
The volume resistance value of the silver electrode of the present invention is preferably 2 × 10 ⁻⁶ to 1 × 10 ⁻⁴ Ωcm, more preferably 2 × 10 ^{−6 to} 5 × 10 ⁻⁵ Ωcm. The volume resistance value can be measured by the method described in Examples described later.

[Thin Film Transistor (TFT)]
The TFT of the present invention has the silver electrode of the present invention. In the TFT of the present invention, the silver electrode of the present invention is used as a gate electrode, a source electrode and / or a drain electrode, and is preferably used as at least a source electrode and a drain electrode.
Preferred embodiments of the TFT of the present invention are described below, but the TFT of the present invention is not limited to these aspects, and at least one electrode uses the silver fine particle dispersion or ink composition of the present invention. If it is formed, there will be no restriction | limiting in particular.

  The TFT of the present invention is provided on a substrate, in contact with the semiconductor layer, a gate electrode, a semiconductor layer, a gate insulating layer provided between the gate electrode and the semiconductor layer, and through the semiconductor. And a source electrode and a drain electrode connected to each other. When a voltage is applied to the gate electrode, a current channel (channel) is formed at the interface between the semiconductor layer between the source electrode and the drain electrode and the adjacent layer. That is, the current flowing between the source electrode and the drain electrode is controlled according to the input voltage applied to the gate electrode.

A preferred structure of the TFT of the present invention will be described with reference to the drawings. The TFT shown in each drawing is a schematic diagram for facilitating the understanding of the present invention, and the size or relative size relationship of each member may be changed for convenience of explanation. Is not shown as it is. Moreover, it is not limited to the external shape and shape shown by these drawings except the matter prescribed | regulated by this invention. For example, in FIGS. 1A and 1B, the gate electrode does not necessarily cover the entire substrate, and a mode in which the gate electrode is provided in the central portion of the substrate is also preferable as a mode of the TFT of the present invention.
1A to 1D are longitudinal sectional views each schematically showing a typical preferable structure of a TFT of the present invention. 1A to 1D, 1 is a semiconductor layer, 2 is a gate insulating layer, 3 is a source electrode, 4 is a drain electrode, 5 is a gate electrode, and 6 is a substrate.
1A is a bottom gate / bottom contact type, FIG. 1B is a bottom gate / top contact type, FIG. 1C is a top gate / bottom contact type, and FIG. 1D is a top. A gate-top contact type TFT is shown. All of the above four forms are included in the TFT of the present invention. Although not shown, an overcoat layer may be formed on the top of each TFT in the drawing (opposite to the substrate 6).

<Board>
The substrate may be any substrate that can support the TFT and the display panel or the like produced thereon. The substrate is not particularly limited as long as the surface is insulative, has a sheet shape, and has a flat surface.

An inorganic material may be used as the material for the substrate. As a substrate made of an inorganic material, for example, various glass substrates such as soda lime glass and quartz glass, various glass substrates with an insulating film formed on the surface, a quartz substrate with an insulating film formed on the surface, and an insulating film on the surface Examples thereof include a silicon substrate, a sapphire substrate, a metal substrate made of various alloys such as stainless steel, aluminum, nickel, and various metals, metal foil, and paper.
When the substrate is made of a conductive or semiconducting material such as stainless steel sheet, aluminum foil, copper foil or silicon wafer, an insulating polymer material or metal oxide is usually applied or laminated on the surface. Used.

  Further, an organic material may be used as the material of the substrate. For example, polymethyl methacrylate (polymethyl methacrylate, PMMA), polyvinyl alcohol (PVA), polyvinyl phenol (PVP), polyethersulfone (PES), polyimide, polyamide, polyacetal, polycarbonate (PC), polyethylene terephthalate (PET), Examples thereof include a flexible plastic substrate (also referred to as a plastic film or a plastic sheet) made of an organic polymer exemplified by polyethylene naphthalate (PEN), polyethyl ether ketone, polyolefin, and polycycloolefin. Moreover, the thing formed with the mica can also be mentioned.

  The thickness of the substrate is preferably 10 mm or less, more preferably 2 mm or less, and particularly preferably 1 mm or less. On the other hand, it is preferably 0.01 mm or more, and more preferably 0.05 mm or more.

<Gate electrode>
As the gate electrode, a conventionally known electrode used as a gate electrode of a TFT can be used. It can also be formed using the silver fine particle dispersion or ink composition of the present invention.
A conductive material (also referred to as an electrode material) constituting the gate electrode is not particularly limited. For example, metals such as platinum, gold, silver, aluminum, chromium, nickel, copper, molybdenum, titanium, magnesium, calcium, barium, sodium, palladium, iron, manganese; InO ₂ , SnO ₂ , indium / tin oxide (ITO ), Fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and other conductive metal oxides; polyaniline, polypyrrole, polythiophene, polyacetylene, poly (3,4-ethylenedioxy) Conductive polymers such as thiophene) / polystyrene sulfonic acid (PEDOT / PSS); acids such as hydrochloric acid, sulfuric acid, sulfonic acid, Lewis acids such as PF ₆ , AsF ₅ , FeCl ₃ , halogen atoms such as iodine, sodium, potassium Conductivity with dopants such as metal atoms added Polymers, as well as carbon black, graphite powder, a composite material of the conductive dispersed metal fine particles and the like. These materials may be used alone or in combination of two or more in any combination and ratio.

There is no limitation on the method of forming the gate electrode. For example, a film formed by physical vapor deposition (PVD) such as vacuum vapor deposition, chemical vapor deposition (CVD), sputtering, printing (coating), transfer, sol-gel, or plating is necessary. Accordingly, there is a method of patterning into a desired shape.
Alternatively, the gate electrode can be formed by a coating method. In the coating method, a solution, paste, or dispersion of the above material can be prepared and applied, and a film can be formed or an electrode can be directly formed by drying, baking, photocuring, aging, or the like.
In addition, inkjet printing, screen printing, (reversal) offset printing, letterpress printing, intaglio printing, lithographic printing, thermal transfer printing, microcontact printing, etc. allow for desired patterning, simplifying processes, reducing costs, and speeding up It is preferable in terms of conversion.
Even when a spin coating method, a die coating method, a micro gravure coating method, or a dip coating method is adopted, patterning can be performed in combination with the following photolithography method or the like.

  Although the thickness of a gate electrode is arbitrary, 1 nm or more is preferable and 10 nm or more is especially preferable. Moreover, 500 nm or less is preferable and 200 nm or less is more preferable.

<Gate insulation layer>

The gate insulating layer is not particularly limited as long as it is an insulating layer, and may be a single layer or a multilayer.
The gate insulating layer is preferably formed of an insulating material, and preferable examples of the insulating material include organic polymers and inorganic oxides.
The organic polymer and the inorganic oxide are not particularly limited as long as they have insulating properties, and those that can form a thin film, for example, a thin film having a thickness of 1 μm or less are preferable.
Each of the organic polymer and the inorganic oxide may be used alone or in combination of two or more, or the organic polymer and the inorganic oxide may be used in combination.

  Although it does not specifically limit as an organic polymer, For example, polyvinyl phenol, polystyrene (PS), poly (meth) acrylate represented by polymethylmethacrylate, polyvinyl alcohol, polyvinyl chloride (PVC), polyfluorination Represented by vinylidene (PVDF), polytetrafluoroethylene (PTFE), cyclic fluoroalkyl polymers represented by CYTOP, polycycloolefin, polyester, polyethersulfone, polyetherketone, polyimide, epoxy resin, polydimethylsiloxane (PDMS) And polyorganosiloxane, polysilsesquioxane, butadiene rubber and the like. In addition to the above, thermosetting resins such as phenol resin, novolac resin, cinnamate resin, acrylic resin, and polyparaxylylene resin are also included.

The inorganic oxide is not particularly limited. For example, silicon oxide, silicon nitride (SiN _Y ), hafnium oxide, titanium oxide, tantalum oxide, aluminum oxide, niobium oxide, zirconium oxide, copper oxide, oxide oxides such as nickel, _{also, SrTiO 3, CaTiO 3, BaTiO} 3, MgTiO 3, SrNb perovskite such as ₂ O ₆ or a composite oxide thereof, or a mixture thereof. Here, as silicon oxide, in addition to silicon oxide (SiO _X ), BPSG, PSG, BSG, AsSG, PbSG, silicon oxynitride (SiON), SOG (spin on glass), low dielectric constant SiO ₂ based material (for example, , Polyaryl ether, cycloperfluorocarbon polymer and benzocyclobutene, cyclic fluororesin, polytetrafluoroethylene, fluorinated aryl ether, fluorinated polyimide, amorphous carbon, organic SOG).

  As a method for forming the gate insulating layer with an inorganic oxide, for example, a vacuum film formation method such as a vacuum evaporation method, a sputtering method, an ion plating method, a CVD method, or the like can be used. Assist may be performed with the plasma, ion gun, radical gun, or the like used.

<Semiconductor layer>
The semiconductor layer is a layer that exhibits semiconductor properties and can accumulate carriers. Conventionally known organic or inorganic semiconductor compounds can be widely used for the semiconductor layer.

It does not specifically limit as an organic semiconductor, An organic polymer, its derivative (s), a low molecular compound, etc. are mentioned.
In the present invention, the low molecular compound means a compound other than the organic polymer and its derivative. That is, it refers to a compound having no repeating unit. As long as the low molecular weight compound is such a compound, the molecular weight is not particularly limited.

  Examples of the low molecular compound include a condensed polycyclic aromatic compound. For example, naphthacene, pentacene (2,3,6,7-dibenzoanthracene), hexacene, heptacene, dibenzopentacene, tetrabenzopentacene and other acenes, anthradithiophene, pyrene, benzopyrene, dibenzopyrene, chrysene, perylene, coronene, terylene , Ovalene, quaterrylene, circumanthracene, and derivatives obtained by substituting a part of these carbon atoms with atoms such as N, S, O, etc., or at least one hydrogen atom bonded to the carbon atom is a functional group such as a carbonyl group Derivatives substituted with a group (perixanthenoxanthene and dioxaanthanthrene compounds including such derivatives, triphenodioxazine, triphenodithiazine, hexacene-6,15-quinone, etc.) and other functional groups of the above hydrogen atom Derivatives substituted with groups It is possible.

  Further, metal phthalocyanine represented by copper phthalocyanine, tetrathiapentalene and derivatives thereof, naphthalene-1,4,5,8-tetracarboxylic acid diimide, N, N′-bis (4-trifluoromethylbenzyl) naphthalene— 1,4,5,8-tetracarboxylic acid diimide, N, N′-bis (1H, 1H-perfluorooctyl), N, N′-bis (1H, 1H-perfluorobutyl), N, N′-dioctylnaphthalene -1,4,5,8-tetracarboxylic acid diimide derivatives, naphthalene tetracarboxylic acid diimides such as naphthalene-2,3,6,7-tetracarboxylic acid diimide, anthracene-2,3,6,7-tetracarboxylic acid Condensed ring tetracarboxylic acid diimide such as anthracene tetracarboxylic acid diimide such as diimide, C60, C70, 76, C78, C84 fullerene and derivatives thereof such as, for SWNT such as carbon nanotubes, merocyanine dyes, may be mentioned such dyes and their derivatives, such as hemicyanine dyes.

  Furthermore, polyanthracene, triphenylene, quinacridone can be mentioned.

  Examples of the low molecular weight compound include 4,4′-biphenyldithiol (BPDT), 4,4′-diisocyanobiphenyl, 4,4′-diisocyano-p-terphenyl, 2,5-bis (5 '-Thioacetyl-2'-thiophenyl) thiophene, 2,5-bis (5'-thioacetoxyl-2'-thiophenyl) thiophene, 4,4'-diisocyanophenyl, benzidine (biphenyl-4,4'- Diamine), TCNQ (tetracyanoquinodimethane), tetrathiafulvalene (TTF) and its derivatives, tetrathiafulvalene (TTF) -TCNQ complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTF-iodine complex , A charge transfer complex represented by TCNQ-iodine complex, biphenyl-4,4′-dica Boronic acid, 1,4-di (4-thiophenylacetylinyl) -2-ethylbenzene, 1,4-di (4-isocyanophenylacetylinyl) -2-ethylbenzene, 1,4-di (4- Thiophenylethynyl) -2-ethylbenzene, 2,2 ″ -dihydroxy-1,1 ′: 4 ′, 1 ″ -terphenyl, 4,4′-biphenyldiethanal, 4,4′-biphenyldiol, 4, 4′-biphenyl diisocyanate, 1,4-diacetinylbenzene, diethylbiphenyl-4,4′-dicarboxylate, benzo [1,2-c; 3,4-c ′; 5,6-c ″] tris [1,2] dithiol-1,4,7-trithione, α-sexithiophene, tetrathiatetracene, tetraselenotetracene, tetratellurtetracene, poly (3-alkylthiophene) Poly (3-thiophene-β-ethanesulfonic acid), poly (N-alkylpyrrole) poly (3-alkylpyrrole), poly (3,4-dialkylpyrrole), poly (2,2′-thienylpyrrole), Poly (dibenzothiophene sulfide) can be exemplified.

The inorganic semiconductor material for forming the semiconductor layer is not particularly limited, but a preferable example thereof is an oxide semiconductor.
The oxide semiconductor is not particularly limited as long as it is made of a metal oxide. The semiconductor layer made of an oxide semiconductor is preferably formed using an oxide semiconductor precursor, that is, a material that is converted into a semiconductor material made of a metal oxide by a conversion process such as thermal oxidation.
The oxide semiconductor is not particularly limited. For example, indium gallium zinc oxide, indium gallium oxide, indium tin zinc oxide, gallium zinc oxide, indium tin oxide, indium zinc oxide, zinc tin oxide, zinc oxide, tin oxide For example, InGaZnO _x , InGaO _x , InSnZnO _x , GaZnO _x , InSnO _x , InZnO _x , SnZnO _x (all x> 0), ZnO, and SnO ₂ can be given.

Examples of the oxide semiconductor precursor include metal nitrates, metal halides, and alkoxides. Examples of the metal contained in the oxide semiconductor precursor include Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb, Bi, Ce, Pr, Examples thereof include at least one selected from the group consisting of Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
Specific examples of the oxide semiconductor precursor include, for example, indium nitrate, zinc nitrate, gallium nitrate, tin nitrate, aluminum nitrate, indium chloride, zinc chloride, tin chloride (divalent), tin chloride (tetravalent), and gallium chloride. , Aluminum chloride, tri-i-propoxyindium, diethoxyzinc, bis (dipivaloylmethanato) zinc, tetraethoxytin, tetra-i-propoxytin, tri-i-propoxygallium, tri-i-propoxyaluminum It is done.

<Source electrode, drain electrode>
In the TFT of the present invention, the source electrode and drain electrode are preferably formed using the silver fine particle dispersion or ink composition of the present invention. In the case where the source electrode and the drain electrode are not formed using the silver fine particle dispersion or ink composition of the present invention, a conventionally known source electrode and drain electrode can be employed. For example, the conductive material described for the gate electrode can be used.
The source electrode and the drain electrode can each be formed by a method similar to the method for forming the gate electrode.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not construed as being limited thereto.

[Reference Example 1] Preparation of silver fine particles (dispersion with nonionic dispersant)
A solution a in which polyvinylpyrrolidone (weight average molecular weight 3000, manufactured by Sigma-Aldrich) (7.36 g) was dissolved in water (100 mL) as a dispersant was prepared. Further, a solution b in which 50.00 g (294.3 mmol) of silver nitrate was dissolved in water (200 mL) was prepared. Solution a and solution b were mixed and stirred. An aqueous solution (78.71 g) having an N, N-diethylhydroxylamine concentration of 85% by mass (750.5 mmol as N, N-diethylhydroxylamine) was slowly added dropwise to the resulting mixture at room temperature, and polyvinylpyrrolidone was further added. A solution prepared by dissolving (7.36 g) in water (1000 mL) was slowly added dropwise at room temperature. The obtained suspension was passed through an ultrafiltration unit (Saltrius Stedim Vivaflow 50, molecular weight cut off: 100,000, number of units: 4) and purified until about 5 L of exudate was produced from the ultrafiltration unit. Purified by passing water through. The supply of purified water was stopped and concentrated to obtain a dispersion of 30 g of silver fine particles. The solid content in the dispersion was 50% by mass. Moreover, it was 96.0 mass% when content of silver in solid content was measured in TG-DTA (differential thermogravimetric simultaneous measurement) (the SII nanotechnology Inc. make, model: STA7000). .

[Reference Example 2] Preparation of oil-in-water emulsion A solution was prepared by mixing 5 g of the antioxidant shown in Table 1 below, 5 g of toluene, 5 g of the nonionic surfactant shown in Table 1 below, or 5 g of the ionic surfactant. The solution was dropped into 50 g of water. While cooling to 20 ° C. with an ultrasonic homogenizer (500 W), dispersion was performed for 5 minutes to obtain 32 types of oil-in-water emulsions having an average particle size of oil droplets in the range of 50 nm to 200 nm. Thereafter, toluene was removed to 1% or less by distillation under reduced pressure, and pure water was added to adjust the solid content to 20%. The average particle size of the oil droplets was measured with a concentrated particle size analyzer (FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.). Moreover, as a result of measuring the content rate of toluene by high performance liquid chromatography, 0.2% was contained in the solution.

[Preparation Example] Preparation of Silver Fine Particle Dispersion (Ink Composition) 1 g of the silver fine particle dispersion obtained in Reference Example 1, 0.3 g of the oil-in-water emulsion prepared in Reference Example 2, and 1- 0.2 g of methoxy 2-propanol was added and stirred to obtain a silver fine particle dispersion (ink composition). The silver fine particle dispersion had a surface tension of 36 mN / m and a viscosity at 25 ° C. of 8.0 Pa · s. Further, in this silver fine particle dispersion, the content of silver fine particles is 32% by mass, the content of antioxidant is 4% by mass, and the content of nonionic surfactant is 4% by mass.

<Measurement of average particle diameter of silver fine particles>
The silver fine particle dispersion prepared in the above Preparation Example is diluted 20 times with ion-exchanged water and measured using a particle size analyzer FPAR-1000 (Otsuka Electronics) to determine the average particle size of the silver fine particles. It was.

[Test Example 1] Evaluation of Dispersibility of Silver Fine Particles The dispersibility of silver fine particles was evaluated by measuring the average particle diameter of silver fine particles immediately after the preparation of the silver fine particle dispersion (ink composition) and by the following evaluation criteria.
A: Average particle diameter is 50 nm or more and less than 100 nm
B: Average particle size is 100 nm or more and less than 200 nm C: Average particle size is 200 nm or more

Test Example 2 Evaluation of Dispersion Stability of Silver Fine Particles The dispersion stability of silver fine particles is determined by the average particle diameter d1 of silver fine particles immediately after preparation of the silver fine particle dispersion (ink composition) and the silver fine particle dispersion (ink composition). After the preparation, the particle diameter change rate (%) was calculated based on the following formula from the average particle diameter d2 of the silver fine particles after storage at 40 ° C. for 30 days, and evaluated based on the following evaluation criteria.
Particle size change rate (%) = 100 × (d2−d1) / d1
A: Change rate of particle size is less than 5% B: Change rate of particle size is 5% or more and less than 10% C: Change rate of particle size is 10% or more

[Test Example 3] Evaluation of Volume Resistance Value Volume resistance value was measured as a conductivity index.
Each silver fine particle dispersion prepared in the above preparation example was applied to a clean 50 mm square glass substrate by a spin coating method (500 rpm, 30 seconds), and heated in an oven at 200 ° C. for 2 hours. About each obtained coating film, the average film thickness calculated | required with the stylus-type film thickness meter was 320 nm. After standing to cool, the volume resistance value was measured by Loresta GP MCP-T610 type (trade name, manufactured by Mitsubishi Materials) and evaluated according to the following evaluation criteria.
− Evaluation criteria −
A: Less than 2 × 10 ⁻⁵ Ωcm B: 2 × 10 ⁻⁵ Ωcm or more and less than 1 × 10 ⁻⁴ Ωcm C: 1 × 10 ⁻⁴ Ωcm or more and less than 1 × 10 ⁻³ Ωcm D: 1 × 10 ⁻³ Ωcm or more

[Test Example 4] Evaluation of insulation reliability Substrate obtained by laminating ABF-GX13 (trade name, manufactured by Ajinomoto Fine-Techno Co., Ltd., interlayer insulation material) on a FR4FR-4 grade glass epoxy substrate NIKAPLEX (trade name, manufactured by Nikkan Kogyo Co., Ltd.) Above, each silver fine particle dispersion prepared in the above preparation example is applied by spray coating method using STS-200 (trade name, manufactured by WIDY Mechatronic Solutions) so that the film thickness after sintering becomes 200 nm. did. Then, it sintered using oven (210 degreeC, 1 hour), and formed the silver film on the board | substrate. The formed silver film was etched into a comb shape of L (line) / S (space) = 50/50 μm by photolithography to form a comb-shaped silver film (silver wiring). At this time, Photech H-7025 (trade name, manufactured by Hitachi Chemical Co., Ltd.) was used as the dry film resist, and Agrip 940 (trade name, manufactured by Meltex) was used as the silver etching solution. Further, Cytop CTL107MK (trade name, manufactured by AGC) was spin-coated on the silver wiring so that the film thickness after drying was 1 μm, and then dried in an oven at 140 ° C. for 20 minutes to form a sealing layer. Each wiring board for insulation reliability evaluation was produced.

Each obtained wiring board was subjected to a life test (use apparatus: EHS-221MD, manufactured by Espec Corp.) under the conditions of humidity 85%, temperature 85 ° C., pressure 1.0 atm, and voltage 60V. Specifically, the voltage was applied to adjacent silver wirings in the environment. Then, the time until the silver wiring was short-circuited by migration (time T until the resistance value between the silver wirings was 1 × 10 ⁵ Ω) was measured. The time T when using a silver fine particle dispersion to which no antioxidant was added was defined as T1 (reference), and the insulation reliability was evaluated relative to the following evaluation criteria.

− Evaluation criteria −
A: Time T is 5 times or more of T1 B: Time T is 2 times or more and less than 5 times T1 C: Time T is longer than T1 and less than 2 times T1 D: Time T is T1 or less The results are shown in Table 1 below. . The nonionic surfactants listed in Table 1 below are as follows.
Emulgen A60: Polyoxyethylene distyrenated phenyl ether Emulgen 104P: Polyoxyethylene lauryl ether manufactured by Kao Corporation Emulgen 106P: Polyoxyethylene lauryl ether manufactured by Kao Corporation Emulgen 109P: Polyoxyethylene lauryl ether manufactured by Kao Corporation Emargen B- manufactured by Kao Corporation 66: Polyoxyethylene tribenzyl phenyl ether New Coal 707 manufactured by Kao Corporation: Polyoxyethylene polycyclic phenyl ether New Coal 3-85 manufactured by Nippon Emulsifier Co., Ltd. New Coal CMP-8 manufactured by Nippon Emulsifier Co., Ltd. Oxyethylene cumylphenyl ether New Emulsion 719 manufactured by Nippon Emulsifier Co., Ltd .: Polyoxyethylene polycyclic phenyl ether manufactured by Nippon Emulsifier Co., Ltd.

[Test Example 4] Manufacture of TFT The TFT (bottom gate / bottom contact type) shown in FIG. 1 (A) was manufactured, and the mobility was evaluated.
On the glass substrate (Eagle XG: manufactured by Corning), aluminum serving as a gate electrode was deposited (thickness: 50 nm). On top of that, a composition for forming a gate insulating film (polyvinylphenol / melamine = 1 part by weight / 1 part by weight (w / w) PGMEA (propylene glycol monomethyl ether acetate) solution (solid content concentration: 2% by weight)) is spun After coating, baking was performed at 150 ° C. for 60 minutes to form a gate insulating film 2 having a thickness of 400 nm. In addition, the silver fine particle dispersion prepared in each of the above preparation examples (silver fine particle dispersion used in Examples 1 to 25) was used as a source electrode and an ink jet device DMP-2831 (manufactured by Fuji Film Dimatics). A drain electrode pattern (channel length 40 μm, channel width 200 μm) was drawn. Thereafter, baking was performed at 180 ° C. for 30 minutes in an oven and sintering was performed, whereby the source electrode 3 and the drain electrode 4 were formed. On top of that, a toluene solution of 2,8-difluoro-5,11-bis (triethylsilylethynyl) anthradithiophene (ALDRICH) is spin-coated, baked at 140 ° C. for 15 minutes, and an organic semiconductor layer having a thickness of 100 nm 1 was formed. Cytop CTL-107MK (manufactured by AGC) is spin-coated thereon, and baked at 140 ° C. for 20 minutes to form a 2 μm-thick sealing layer (the uppermost layer, not shown in FIG. 1). A type of TFT (bottom gate bottom contact type) was fabricated.

Each electrode of the obtained organic thin film transistor was connected to each terminal of a manual prober connected to a semiconductor parameter analyzer (4155C, manufactured by Agilent Technologies) to evaluate a field effect transistor (FET). Specifically, field effect mobility (cm ² / V · sec) was calculated by measuring drain current-gate voltage (Id-Vg) characteristics. As a result, it was found that the field-effect mobility in all TFTs was in the range of 0.1 to 0.3 and functioned well as TFTs.

  While this invention has been described in conjunction with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified and are contrary to the spirit and scope of the invention as set forth in the appended claims. I think it should be interpreted widely.

  This application claims priority based on Japanese Patent Application No. 2015-004538 filed in Japan on January 13, 2015, which is hereby incorporated herein by reference. Capture as part.

Claims (11)

A silver fine particle dispersion obtained by dispersing silver fine particles in an aqueous medium,
A mixed solution of an antioxidant having an SP value of 30 or less and a hydrophobic organic solvent is emulsified and dispersed in the aqueous medium by a nonionic surfactant,
A silver fine particle dispersion , wherein the antioxidant is present in oil droplets dispersed in the aqueous medium .   The silver fine particle dispersion according to claim 1, wherein the antioxidant is a compound having an aromatic ring.   The silver fine particle dispersion according to claim 1 or 2, wherein the antioxidant is a compound having a molecular weight of 200 to 3,000.   The silver fine particle dispersion according to any one of claims 1 to 3, wherein the antioxidant is selected from a hindered phenol compound, a benzophenone compound, a benzotriazole compound, a salicylic acid compound, and a benzoxazole compound. The nonionic surfactant is present in a hydrophilic site _{- (C 2 H 4 O)} n - having a silver fine particle dispersion according to any one of claims 1 to 4.
However, n is an integer of 3 or more.   The silver fine particle dispersion according to any one of claims 1 to 5, wherein the nonionic surfactant has an aromatic ring.   An ink composition using the silver fine particle dispersion according to any one of claims 1 to 6.   The ink composition according to claim 7, which is used for inkjet printing.   The ink composition according to claim 7 or 8, which is used for forming a silver electrode.   The silver electrode formed using the silver fine particle dispersion of any one of Claims 1-6, or the ink composition of any one of Claims 7-9. A thin film transistor comprising the silver electrode according to claim 10.

Images