JP2012054209A - Conductive oxide microparticle dispersion liquid and coating liquid for forming transparent conductive film, and transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a conductive oxide microparticle dispersion liquid including conductive oxide microparticles stably dispersed therein, capable of being used in forming a transparent conductive film of various display devices, such as liquid crystals, or the like through a coating method, in particular through ink jet printing; a coating liquid for forming a transparent conductive film, which is obtained by adding a binder to the conductive oxide microparticle dispersion liquid; and a transparent conductive film obtained by coating, drying, and, if necessary, curing the coating liquid for forming a transparent conductive film.SOLUTION: There are provided a conductive oxide microparticle dispersion liquid or the like. The conductive oxide microparticle dispersion liquid includes conductive oxide microparticles (A) which are surface-modified with halogen elements, have an average particle size of 1 to 500 nm and are dispersed in an organic solvent (B). In the conductive oxide microparticle dispersion liquid, the organic solvent (B) comprises a 5-membered cyclic ketone compound having a boiling point of 230°C or more and a surface tension of 40 dyn/cm or less as a main constituent, and further 2 pts.wt. or less of a dispersant (C) is contained relative to 100 pts.wt. of the conductive oxide microparticles.

Description

  The present invention relates to a conductive oxide fine particle dispersion, a coating liquid for forming a transparent conductive film, and a transparent conductive film. More specifically, the present invention relates to a method for coating a transparent conductive film such as liquid crystal or electronic paper, particularly inkjet printing. A conductive oxide fine particle dispersion in which conductive oxide fine particles are stably dispersed, a coating liquid for forming a transparent conductive film obtained by adding a binder thereto, and the same It is related with the transparent conductive film obtained by apply | coating, drying, and hardening as needed.

Conventionally, a transparent conductive film of indium-tin oxide (ITO) formed by a physical film forming method represented by sputtering, ion plating, or the like has been used for transparent electrodes of various display devices such as LCDs. Has been. Among these, a transparent conductive film obtained by sputtering (hereinafter abbreviated as a sputtering ITO film) is most widely used.
However, with the recent increase in the size of displays, there are problems such as an increase in capital investment cost for producing a sputtering ITO film and a low utilization efficiency of an ITO film material from the viewpoint of resource saving. That is, in order to form a sputtering ITO film on a large-area substrate, a large capital investment is required to make the large space into a high vacuum. Moreover, in ITO sputtering, only about 20% of the target material is used for an actual transparent conductive film, and about 70% is used for recovery of indium as scrap.

Therefore, research has been conducted to form a transparent conductive film using a coating method that does not require expensive equipment. The coating method is based on a coating liquid (coating liquid for forming a transparent conductive film) containing conductive oxide fine particles (transparent conductive filler) mainly composed of indium oxide, tin oxide, zinc oxide, and the like and a resin binder. A transparent conductive film is formed by applying to the substrate and drying and curing. Since a vacuum is not required, there is an advantage that the capital investment cost can be greatly suppressed as compared with the case of producing a sputtering ITO film. In addition, since the coating liquid only needs to be applied (printed) to the necessary portion, the coating method is also a resource-saving method that has high utilization efficiency of the transparent conductive material and can save the material.
In the coating solution (coating solution for forming a transparent conductive film), generally, when the particle diameter of the conductive oxide fine particles is reduced, the cohesive force between the particles is increased and the fine particles are easily aggregated. In the coating liquid for forming a transparent conductive film, when aggregation of conductive oxide fine particles occurs, the haze of the obtained transparent conductive film deteriorates, the transparency decreases, the film uniformity deteriorates, and the film strength and film resistance Cause problems such as worsening. Therefore, it is required that the conductive oxide fine particles have sufficient dispersibility in order to form a coating film excellent in transparency and film strength in the coating liquid for forming a transparent conductive film. Further, the coating liquid for forming a transparent conductive film is required to maintain the dispersion stability of the conductive oxide fine particles for a long time so that it can be easily stored for a long time.

In order to prevent aggregation (dispersion stabilization) of the conductive oxide fine particles, a method of applying a dispersant such as a polymer or a surfactant to a coating liquid for forming a transparent conductive film is generally used. Here, the dispersing agent is adsorbed on the surface of the fine particles while penetrating between the fine particles to be aggregated, and enables uniform dispersion in the solvent while loosening the aggregation state in the course of the dispersion treatment (see Patent Documents 1 and 2). . In Patent Document 1, an aluminum complex in which a chelate ligand is coordinated to aluminum is used as a dispersant. In Patent Document 2, an anionic surfactant having a phosphate group as a hydrophilic group in the molecular structure is used as a dispersant.
However, since the surface area increases as the microparticles become smaller, a large amount of dispersant is required for sufficient stabilization. In addition, when a large amount of a dispersant is added to the coating liquid for forming a transparent conductive film, a large amount of the dispersant is also present in the coating film formed using the coating liquid, covering the surface of the conductive oxide fine particles, Since the contact between the oxide fine particles is hindered, there is a problem that conductivity is deteriorated.

  Therefore, the present applicant, for example, as a method of obtaining a coating liquid (coating liquid for forming a transparent conductive film) excellent in dispersion stability, for example, conductive oxide fine particles having an average particle diameter of 1 to 500 nm that is surface-modified with a halogen element Without using a dispersant, cyclopentanone, cyclohexanone, 2- (1-cyclohexylinyl) cyclohexanone, 2-cyclohexylcyclohexanone, cycloheptanone, cyclooctanone, γ-butyrolactone, γ-valerolactone, γ-caprolactone, Or the electroconductive oxide fine particle dispersion liquid disperse | distributed to the organic solvent which consists of at least 1 type of cyclic ketone compound chosen from isophorone was proposed (refer patent document 3).

By the way, the application method includes ink jet printing, screen printing, spin coating, roll coating, gravure printing, offset printing, and the like, but using the ink jet printing method has an advantage that pattern printing can be performed by direct drawing. However, in addition to the dispersion stability of the conductive oxide fine particles in the coating liquid for forming a transparent conductive film, ejection stability (droplet flight stability, suppression of nozzle clogging during initial ejection and intermittent ejection) is required.
By using the conductive oxide fine particle dispersion as in Patent Document 3, the dispersion stability can be maintained for a long time, and the coating liquid for forming a transparent conductive film can be easily stored for a long time. However, since the coating liquid (coating liquid for forming a transparent conductive film) has a low boiling point of the organic solvent to be used and easily volatilizes, there is a problem that nozzle clogging gradually occurs in ink jet printing.

  Under such circumstances, there has been a demand for a coating liquid for forming a transparent conductive film that does not cause nozzle clogging in ink jet printing and can achieve both dispersion stability and ink jet printability.

Japanese Patent Laid-Open No. 5-120921 JP 2006-73300 A JP 2008-34345 A

  In view of the problems of the prior art, an object of the present invention is to provide a conductive oxide used when forming a transparent conductive film for various display devices such as liquid crystal and electronic paper by a coating method such as an ink jet printing method. Conductive oxide fine particle dispersion in which fine particles are stably dispersed, a transparent conductive film forming coating solution obtained by adding a binder thereto, and transparent conductive material obtained by coating, drying, and curing as necessary It is to provide a membrane.

  When forming a transparent conductive film using a coating liquid for forming a transparent conductive film containing conductive oxide fine particles, the inventor of the organic solvent blended with the conductive oxide fine particles whose surface is halogen-modified As a result of changing the type and preparing various coating liquids, when an organic solvent mainly composed of a specific 5-membered ring ketone compound is used, even if the amount of the dispersant added to the coating liquid is very small, the conductive oxidation It is found that fine particles can be stably dispersed, and when an ink jet printing method is used, excellent discharge stability can be secured, and a transparent conductive film can be stably obtained, thereby completing the present invention. It came to.

  That is, according to the first aspect of the present invention, the conductive oxide fine particles (A) in which the conductive oxide fine particles (A) having an average particle diameter of 1 to 500 nm, which are surface-modified with a halogen element, are dispersed in the organic solvent (B). A dispersion comprising a 5-membered ring ketone compound having an organic solvent (B) having a boiling point of 230 ° C. or higher and a surface tension of 40 dyn / cm or less as a main component, and 100 parts by weight of conductive oxide fine particles A conductive oxide fine particle dispersion containing 2 parts by weight or less of the dispersant (C) is provided.

According to the second invention of the present invention, in the first invention, the conductive oxide fine particles (A) mainly comprise at least one metal oxide selected from the group consisting of indium oxide, tin oxide and zinc oxide. There is provided a conductive oxide fine particle dispersion characterized by being fine particles contained as a component.
According to the third invention of the present invention, in the first invention, the conductive oxide fine particles (A) are metal oxide fine particles containing indium oxide doped with tin as a main component. A characteristic conductive oxide fine particle dispersion is provided.
According to a fourth aspect of the present invention, there is provided the conductive oxide fine particle dispersion liquid according to the first aspect, wherein the halogen element is chlorine.
According to the fifth invention of the present invention, in the first invention, the organic solvent (B) is selected from the group of 2-hexylcyclopentanone, 2-heptylcyclopentanone and 2-cyclopentylcyclopentanone. There is provided a conductive oxide fine particle dispersion which is at least one kind of 5-membered ring ketone compound.
According to the sixth invention of the present invention, in the first or fifth invention, the content of the 5-membered ketone compound is 50% by mass or more based on the entire organic solvent (B). A conductive oxide fine particle dispersion is provided.
Furthermore, according to the seventh invention of the present invention, in the first invention, the conductive oxidation is characterized in that the content of the organic solvent (B) is 50 to 95% by mass with respect to the whole dispersion. A fine particle dispersion is provided.
Furthermore, according to an eighth aspect of the present invention, there is provided a conductive oxide fine particle dispersion characterized in that, in the first aspect, the dispersant (C) is a phosphate ester compound.

On the other hand, according to the ninth invention of the present invention, the conductive oxide fine particle dispersion according to any one of the first to eighth inventions further comprises a binder component (D). A coating solution for film formation is provided.
Furthermore, according to the tenth aspect of the present invention, in the ninth aspect, the binder component (D) is a thermoplastic resin, a thermosetting resin, a room temperature curable resin, an ultraviolet curable resin, an electron beam curable resin. A coating solution for forming a transparent conductive film is provided, which is any organic resin selected from the group such as

According to an eleventh aspect of the present invention, according to any one of the first to eighth aspects, the conductive oxide fine particle dispersion is applied onto a plastic substrate or a ceramic substrate and dried. The resulting transparent conductive film is provided.
Furthermore, according to a twelfth aspect of the present invention, there is provided the transparent conductive film according to the eleventh aspect, wherein the conductive oxide fine particle dispersion is applied by ink jet printing.
According to the thirteenth aspect of the present invention, the transparent conductive film forming coating liquid is applied on a plastic substrate or a ceramic substrate and dried, followed by a curing treatment. A transparent conductive film obtained by applying is provided.
Furthermore, according to a fourteenth aspect of the present invention, there is provided the transparent conductive film according to the thirteenth aspect, wherein the coating liquid for forming a transparent conductive film is applied by ink jet printing.

According to the present invention, a transparent conductive film forming coating solution capable of forming a transparent conductive film by a simple and inexpensive coating method, particularly an ink jet printing method, and a conductive oxide fine particle dispersion used for the preparation thereof are provided. Can do.
Moreover, since the transparent conductive film formed by the inkjet printing method using the coating liquid for forming a transparent conductive film of the present invention can be formed into an arbitrary shape by direct drawing, the transparent conductive film of the present invention is a liquid crystal It can be suitably used as various display devices such as displays and electronic paper, and transparent electrodes such as touch panels.

1. Conductive oxide fine particle dispersion The conductive oxide fine particle dispersion of the present invention is obtained by dispersing conductive oxide fine particles (A) having an average particle diameter of 1 to 500 nm, surface-modified with a halogen element, in an organic solvent (B). A conductive oxide fine particle dispersion, the organic solvent (B) having a boiling point of 230 ° C. or more and a surface tension of 40 dyn / cm or less as a main component, and a conductive oxide 2 parts by weight or less of the dispersant (C) is contained with respect to 100 parts by weight of the fine particles.
That is, the present invention provides specific 5-membered ring ketones such as 2-hexylcyclopentanone, 2-heptylcyclopentanone, and 2-cyclopentylcyclopentanone for conductive oxide fine particles whose surface is modified with a halogen element. When an organic solvent containing a compound as a main component is used, even if the amount of the dispersing agent is extremely small, the conductive oxide fine particles can be dispersed well, and the organic solvent has a high boiling point. It is based on the fact that it is difficult to volatilize and nozzle clogging can be suppressed, and since the surface tension of the organic solvent is relatively low, it is easily discharged from the nozzle.

(A) Conductive oxide fine particles In the present invention, the conductive oxide fine particles contain at least one metal oxide selected from the group of indium oxide, tin oxide, and zinc oxide as a main component.
That is, the conductive oxide fine particles are conductive oxide fine particles mainly composed of at least one selected from the group consisting of indium oxide, tin oxide, and zinc oxide, for example, indium-tin oxide (ITO ) Fine particles, indium zinc oxide (IZO) fine particles, indium-tungsten oxide (IWO) fine particles, indium-titanium oxide (ITiO) fine particles, indium zirconium oxide fine particles, tin antimony oxide (ATO) fine particles, fluorine tin oxide (FTO) fine particles, aluminum zinc oxide (AZO) fine particles, gallium zinc oxide (GZO) fine particles, and the like may be used, but the material is not limited to these as long as it has transparency and conductivity.
However, ITO containing indium oxide doped with tin as a main component is the most preferable because it has both high visible light transmittance and excellent conductivity.

The average particle diameter of the conductive oxide fine particles is preferably 1 to 500 nm, more preferably 5 to 100 nm, and still more preferably 10 to 80 nm. When the average particle size is less than 1 nm, it becomes difficult to produce a conductive oxide fine particle dispersion or a transparent conductive film forming coating solution, and the resistance value of the obtained transparent conductive film becomes high. It is difficult to achieve high transmittance and low resistance in the transparent conductive film at the same time as the conductive oxide fine particles are liable to settle in the oxide fine particle dispersion or the coating liquid for forming the transparent conductive film. Because it becomes.
Further, 5 to 100 nm is more preferable because the characteristics (transmissivity, resistance value) of the transparent conductive film and the stability of the conductive oxide fine particle dispersion or the coating liquid for forming the transparent conductive film (precipitation of the conductive oxide fine particles). ) Etc. in a well-balanced manner.
The shape of the conductive oxide fine particles contained in the conductive oxide fine particle dispersion or the transparent conductive film forming coating liquid is generally spherical or granular. The transparent conductive film to be obtained is preferable because it has an advantage that it has little visible light scattering and excellent transparency. On the other hand, in the present invention, in addition to the spherical and granular conductive oxide fine particles, it is also possible to use a fibrous (including needles, rods, and whiskers) or a plate.

The transparent conductive film obtained by using these fibrous or plate-like conductive oxide fine particles ensures contact between the conductive oxide fine particles even if the transparent conductive film forming coating liquid contains a large amount of binder components. Therefore, there is an advantage that it is easy to achieve both film strength and conductivity. However, since the fibrous or plate-like conductive oxide fine particles are difficult to form a densely packed film structure, visible light is easily scattered at the interface between the fine particles and the binder matrix, and a haze value (indicating cloudiness) Tends to be a highly transparent conductive film. Depending on the use of the transparent conductive film, for example, there is a device that requires a transparent conductive film that does not absorb visible light, such as a transparent electrode of a dispersive electroluminescence element. What is necessary is just to select suitably according to a use.
In the present invention, the conductive oxide fine particles have a diameter of spherical or granular fine particles, and a thickness and a thickness of fibrous or plate-like fine particles, respectively.

Further, it is important that the surface of the conductive oxide fine particles is surface-modified with a halogen element. Examples of the halogen element include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), etc. Among them, it is particularly modified with chlorine because it is the easiest to handle and can be used preferably. It is preferable.
When the surface of the conductive oxide fine particles is not modified with a halogen element, it is difficult to obtain a desired dispersibility in the conductive oxide fine particle dispersion or the transparent conductive film-forming coating liquid, and the conductivity of the obtained transparent conductive film is difficult. And transparency are likely to deteriorate.
The modification method using a halogen element is not particularly limited as long as the halogen element can be introduced into the surface of the conductive oxide fine particles. The surface modification with the halogen element may be performed simultaneously in the production process of the fine particles, or may be performed after the production of the fine particles within a range not impairing the object of the present invention. That is, the surface is modified by using a halogen compound such as indium chloride, tin chloride or zinc chloride as a raw material for producing fine particles, or by surface treatment with the above indium chloride, tin chloride, zinc chloride or the like after the production of fine particles. be able to.
Alternatively, instead of directly modifying the surface of the conductive oxide fine particles with a halogen element, in the manufacturing process of the conductive oxide fine particle dispersion or the transparent conductive film forming coating liquid, a halogen compound (for example, By adding the above-mentioned indium chloride, tin chloride, zinc chloride, etc., the surface of the conductive oxide fine particles can be modified with a halogen element (so-called “integral blend method”).
Here, the amount of the halogen element that modifies the conductive oxide fine particles depends on the specific surface area (particle diameter) of the conductive oxide fine particles. It is good to set it as 0.005-0.04 mol with respect to mol, Preferably it is 0.01-0.03 mol. If it is less than 0.005 mol or exceeds 0.04 mol, good dispersion cannot be obtained, and in some cases gelation occurs, and conductive oxide fine particle dispersion or coating for forming a transparent conductive film is formed. The liquid cannot be obtained. Even if a coating liquid for forming a transparent conductive film is obtained, the formed coating film becomes an opaque film having a high haze.
As described above, the amount of the halogen element necessary for modifying the conductive oxide fine particles depends on the specific surface area of the conductive oxide fine particles. For example, if the average particle diameter is doubled, the specific surface area is 1 Therefore, the required amount of halogen element is also ½ times the above.

(B) Organic solvent In this invention, an organic solvent is a solvent which disperse | distributes electroconductive oxide microparticles | fine-particles, and uses what has a 5-membered ring ketone compound as a main component. The boiling point of the 5-membered ring ketone compound is preferably 220 to 280 ° C., and the surface tension is 40 dyn / cm [25 ° C.] or less, more preferably 36 dyn / cm [25 ° C.] or less. When the boiling point is less than 220 ° C., the drying speed of the conductive oxide fine particle dispersion or the transparent conductive film forming coating liquid becomes high, and there is a problem that nozzle clogging is likely to occur in the droplet discharge nozzle in ink jet printing. If it exceeds 280 ° C., it is not preferable in that the drying speed of the coating film after inkjet printing is remarkably reduced. In addition, when the surface tension exceeds 40 dyn / cm [25 ° C.], it becomes difficult to discharge droplets from the discharge nozzle in the inkjet printing of the conductive oxide fine particle dispersion or the transparent conductive film forming coating liquid. It is not preferable in terms. From the viewpoint of discharging droplets, it is more preferable that the surface tension is lower.

  Specifically, 2-hexylcyclopentanone represented by [Chemical Formula 1] [alias: 2-hexylcyclopentanone, 2-hexyl-1-cyclopentanone; CAS number: 13074-65-2] (boiling point 246 , Surface tension 32 dyn / cm [25 ° C.]), 2-heptylcyclopentanone represented by [Chemical Formula 2] [alias: 2-heptylcyclopentanone, 2-heptyl-1-cyclopentanone; CAS No. 137 -03-1] (boiling point 264 ° C., surface tension 36 dyn / cm [25 ° C.]), and 2-cyclopentylcyclopentanone represented by [Chemical Formula 3] [alias: 2-cyclopentylcyclopentan-1-one, 1′-bicyclopentan-2-one; CAS No .: 4884-24-6] (boiling point 233 ° C., surface tension 36 dyn / cm [25 ° C.]) Is al least one 5-membered ring ketone compounds selected.

The reason why such a 5-membered ring ketone compound stably disperses the conductive oxide fine particles is not clear, but the cyclic ketone structure has an affinity with the surface of the conductive oxide fine particles modified with a halogen element. Therefore, it is considered that the organic solvent exhibits extremely good dispersibility.
In addition to 2-hexylcyclopentanone, 2-heptylcyclopentanone, and 2-cyclopentylcyclopentanone, the conductive oxide fine particle dispersion of the present invention deteriorates dispersion for the purpose of improving film formability and the like. A small amount of various solvents can be added as long as they are not allowed. The content of the 5-membered ring ketone compound is desirably 50% or more with respect to the entire organic solvent (B). If it is less than 50%, dispersibility may deteriorate.

Examples of the organic solvent that can be used in combination with the cyclic ketone compound for the above purpose include alcohol solvents other than cyclic ketone compounds, ketone solvents, ester solvents, glycol solvents, glycol derivatives, and benzene derivatives. In order to reduce the viscosity of the coating liquid or improve the coating property, the solvent to be blended in the coating liquid for forming a transparent conductive film includes an organic indium compound, an organometallic compound for a dopant, and a cellulose derivative and / or acrylic. Those that are compatible with the solution in which the resin is dissolved are preferred.
Specifically, alcohol solvents such as methanol (MA), ethanol (EA), 1-propanol (NPA), isopropanol (IPA), butanol, pentanol, benzyl alcohol, diacetone alcohol (DAA), acetone, methyl ethyl ketone Ketone solvents such as (MEK), methyl propyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone, isophorone, ethyl acetate, butyl acetate, isobutyl acetate, amyl formate, isoamyl acetate, butyl propionate, isopropyl butyrate, ethyl butyrate, butyric acid Butyl, methyl lactate, ethyl lactate, methyl oxyacetate, ethyl oxyacetate, butyl oxyacetate, methyl methoxyacetate, ethyl methoxyacetate, butyl methoxyacetate, methyl ethoxyacetate, ethyl ethoxyacetate, 3-oxy Methyl propionate, ethyl 3-oxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl 2-oxypropionate, 2-oxypropion Acid ethyl, propyl 2-oxypropionate, methyl 2-methoxypropionate, ethyl 2-methoxypropionate, propyl 2-methoxypropionate, methyl 2-ethoxypropionate, ethyl 2-ethoxypropionate, 2-oxy-2 -Methyl methyl propionate, ethyl 2-oxy-2-methylpropionate, methyl 2-methoxy-2-methylpropionate, ethyl 2-ethoxy-2-methylpropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate Ace Esters such as methyl acetate, ethyl acetoacetate, methyl 2-oxobutanoate, ethyl 2-oxobutanoate, ethylene glycol monomethyl ether (MCS), ethylene glycol monoethyl ether (ECS), ethylene glycol isopropyl ether (IPC), ethylene Glycol monobutyl ether (BCS), ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol methyl ether (PGM), propylene glycol ethyl ether (PE), propylene glycol methyl ether acetate (PGM-AC), propylene glycol ethyl Ether acetate (PE-AC), diethylene glycol monomethyl ether, diethylene glycol mono Ethyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol Glycol derivatives such as monobutyl ether, benzene derivatives such as toluene, xylene, mesitylene, dodecylbenzene, formamide (FA), N-methylformamide, dimethylformamide (DMF), dimethylacetamide, dimethylsulfoxide (DMSO) N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butylene glycol, pentamethylene glycol, 1,3-octylene glycol, tetrahydrofuran (THF) ), Chloroform, mineral spirits, terpineol, and the like, and some mixtures thereof, but are not limited thereto.

However, some of the above solvents easily absorb moisture, and when these solvents are used, it is sufficient not to absorb moisture in the blending process into the conductive oxide fine particle dispersion or the transparent conductive film forming coating liquid. Special attention is required.
When water is contained in these solvents, it is necessary to remove them in advance for the above-described reason. For example, the solvent can be adsorbed using a dehydrating agent such as synthetic zeolite or aluminosilicate. As described above, when the amount of water in the solvent increases, even if the conductive oxide fine particles can be dispersed temporarily and satisfactorily, the structure of the dispersion is eventually destroyed and a stable dispersion can be obtained. Can not.
The content of the organic solvent (B) in the conductive oxide fine particle dispersion of the present invention is not particularly limited, but is preferably 50 to 95% by mass with respect to the entire dispersion. If the content of the organic solvent (B) is less than 50% by mass, the concentration of the conductive oxide fine particles becomes too high to maintain the liquid state as a dispersion, and gelation or solidification occurs. On the other hand, if it exceeds 95% by mass, the concentration of the conductive oxide fine particles becomes too low, and the film thickness of the formed transparent conductive film becomes too thin. A more preferable content of the organic solvent (B) is 60 to 90% by mass with respect to the entire dispersion.

(C) Dispersant In the present invention, the dispersant (C) is an additive that is blended together with the organic solvent (B) and used to disperse the conductive oxide fine particles, and has such a function. If there is no particular limitation. For example, a phosphate ester compound, a high molecular polymer, or the like can be used.
In the present invention, the preferred dispersant (C) is mainly composed of a phosphate ester-based compound such as a phosphate ester having a mono- or di-oxyalkylene substituent and a phosphate trialkyl ester. As the phosphate ester having an oxyalkylene substituent, R which is a polymerizable terminal group is oxyethyl methacryloyl-, oxyethylacryloyl-, polyoxypropylmethacryloyl-, glyceryl dimethacryloyl-, dipentaerythritol pentaacryloyl-, or The compound which is a (meth) acrylate group selected from polyoxyethyl methacryloyl- is mentioned.
Examples of the phosphoric acid trialkyl ester include phosphoric acid tributyl ester, phosphoric acid tri-2-ethylhexyl ester, phosphoric acid tricresyl ester, and phosphoric acid trixylyl ester.

Examples of the phosphate ester surfactant include an anionic surfactant having a phosphate ester group as a hydrophilic group in the molecular structure. Details thereof are described in JP-A-2006-73300.
Further, as the polymer, nonionic polymers are preferable, and among them, comb polymers are preferable.

  The content of the dispersant (C) in the conductive oxide fine particle dispersion of the present invention is 2 parts by weight or less with respect to 100 parts by weight of the conductive oxide fine particles. If the amount exceeds 2 parts by weight, the amount of the dispersant (C) interposed between the conductive oxide fine particles in the finally obtained transparent conductive film becomes too large, and the resistance value of the transparent conductive film becomes too high. It is not preferable. However, if the content of the dispersing agent (C) is less than 0.01 parts by weight, the dispersion stability of the conductive oxide fine particles deteriorates so that the liquid state as the dispersion cannot be maintained and gelation or solidification occurs. End up. The content of the dispersant (C) is preferably 0.01 to 2 parts by weight and more preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the conductive oxide fine particles.

In the present invention, the amount of water contained in the conductive oxide fine particle dispersion is preferably 1.5 parts by weight or less with respect to 100 parts by weight of the conductive oxide fine particles. 0 parts by weight or less. If the amount of water is more than 1.5 parts by weight, it is difficult to obtain a good dispersion and, in some cases, gelation (cream-like) occurs, and a good conductive oxide fine particle dispersion cannot be obtained. Moreover, even if a coating liquid for forming a transparent conductive film is obtained, a coating film formed using the same tends to be an opaque film having a high haze.
The reason why it is preferable that the water content in the conductive oxide fine particle dispersion is lower is also to ensure dispersion stability in the atmosphere in addition to obtaining good dispersion. That is, if the dispersion liquid and coating liquid are left in the atmosphere, the moisture content is gradually increased and the water content gradually increases. The smaller the water content, the longer the dispersion stability is ensured even if left in the air. It's easy to do.

2. Method for Producing Conductive Oxide Fine Particle Dispersion In the present invention, to produce a conductive oxide fine particle dispersion, conductive oxide fine particles (A) having an average particle diameter of 1 to 500 nm that are surface-modified with a halogen element are used. The organic solvent (B) mainly composed of a 5-membered ring ketone compound and the dispersant (C) in an amount of 2 parts by weight or less with respect to 100 parts by weight of the conductive oxide fine particles are mixed well by using a general-purpose method. After that, the conductive oxide fine particles (A) are dispersed.

That is, in the conductive oxide fine particle dispersion of the present invention, for example, 2 parts by weight or less of the dispersant is added to the conductive oxide fine particles whose surface is modified with a halogen element with respect to 100 parts by weight of the conductive oxide fine particles. And dispersed in an organic solvent containing at least one 5-membered ring ketone compound selected from the group of 2-hexylcyclopentanone, 2-heptylcyclopentanone and 2-cyclopentylcyclopentanone. As the dispersion treatment, general-purpose methods such as ultrasonic treatment, homogenizer, paint shaker, and bead mill can be applied.
The atmosphere of the dispersion treatment is not particularly limited, but if the treatment time is long, the container containing the treatment liquid is sealed or the space (in the treatment apparatus or treatment chamber) where the dispersion treatment is performed is dehumidified. It is preferable to prevent moisture in the air from being mixed into the treatment liquid by dehumidifying with a machine or supplying dehumidified air. The processing time varies depending on the type of raw material used, the processing amount, the type of dispersion processing apparatus, and the like. For example, in the case of ultrasonic processing, it can be several tens of seconds to several tens of minutes.

By such a dispersion treatment, for example, when the average particle diameter of the conductive oxide fine particles is 30 nm, the average dispersed particle diameter of the conductive oxide fine particles in the dispersion can be set to about 130 to 150 nm. The average particle diameter of the conductive oxide fine particles can be determined by observing the conductive oxide fine particle dispersion with a transmission electron microscope (TEM). The average dispersed particle size in the dispersion can be measured using various particle size measuring devices (for example, a laser scattering method).
Here, the average dispersed particle size measured by a particle size measuring apparatus such as a laser scattering method is generally obtained after diluting with a solvent so that the fine particle concentration is 0.01% by mass or less as a measurement sample. Not a little affected by aggregation due to solvent shock during dilution.
Therefore, for example, even when the average dispersed particle size is about 130 to 150 nm as described above, this value is a value measured by a particle size measuring device to the last, and needs to be considered as a relative value. Usually, the average dispersed particle size when measured with a special particle size measuring device that can be measured without dilution is often about 1/3 to 1/2 of the value measured by diluting the sample.

3. Transparent conductive film forming coating solution The transparent conductive film forming coating solution of the present invention further comprises a binder component (D) in the conductive oxide fine particle dispersion.
The conductive oxide fine particle dispersion of the present invention described above can be applied to a substrate as it is, dried, and fired as necessary to form a transparent conductive film. However, since the bonding between the conductive oxide fine particles is weak, the transparent conductive film often has a very low film strength as it is. For this reason, it is necessary to overcoat a coating solution containing a transparent binder component on the transparent conductive film, which complicates the film-forming process and forms a two-layer structure with the overcoat. However, it must be devised so as not to interpose an insulating overcoat layer, and is not necessarily practical. Therefore, in the present invention, it is desirable to add a binder component to the conductive oxide fine particle dispersion to obtain a coating liquid for forming a transparent conductive film.

(D) Binder component A binder component is a component which has the effect | action which raises the adhesive force of a base material and a transparent conductive film while couple | bonding electroconductive oxide fine particles and improving the electroconductivity and intensity | strength of a transparent conductive film. As the binder component, an organic and / or inorganic binder can be used, and is appropriately selected in consideration of the base material to which the transparent conductive film forming coating solution is applied and the film forming conditions so as to satisfy the above role. can do.
As an organic binder (resin binder), it can select suitably from groups, such as a thermoplastic resin, a thermosetting resin, normal temperature curable resin, an ultraviolet curable resin, and an electron beam curable resin.

  For example, since a thermoplastic resin has various glass transition points (Tg) depending on its type and structure, it is preferable to select the thermoplastic resin appropriately according to the heat resistance of the substrate. As the thermoplastic resin, generally known thermoplastic resins can be used, but those having a high glass transition point (Tg) are preferable. When the glass transition point (Tg) is high, the volume shrinkage of the binder resin can be directly converted into the bonding force between the conductive oxide fine particles in the process of cooling from the heat treatment temperature for curing to room temperature. This is because it has the effect of improving conductivity. In addition, examples of the thermoplastic resin include acrylic resins such as methacrylic resins, polyester resins, and the like.

  In addition, as the thermosetting resin, for example, epoxy resin, fluorine resin, etc., as the room temperature curable resin, two-part epoxy resin, various urethane resins, etc., as the ultraviolet curable resin, various oligomers, monomers, Examples of the resin containing the photoinitiator and the electron beam curable resin include resins containing various oligomers and monomers, but are not limited to these resins. Here, when solvent resistance is required for the transparent conductive film, the organic binder must be a crosslinkable resin, thermosetting resin, room temperature curable resin, ultraviolet curable resin, and electron beam curing. It can select suitably from groups, such as a resin.

Examples of the inorganic binder include binders mainly composed of silica sol, alumina sol, zirconia sol, titania sol and the like. For example, as the silica sol, tetraalkyl silicate is hydrolyzed by adding water or an acid catalyst, dehydration condensation polymerization is progressed, or tetraalkyl silicate has already been polymerized into a tetramer to a pentamer. A polymer obtained by further hydrolyzing and dehydrating polycondensation of the alkyl silicate solution can be used.
If the dehydration condensation polymerization proceeds too much, the solution viscosity increases and eventually solidifies. Therefore, the degree of dehydration condensation polymerization is adjusted to be equal to or lower than the upper limit viscosity that can be applied on the substrate. However, the degree of dehydration polycondensation is not particularly limited as long as it is a level equal to or lower than the above upper limit viscosity, but considering film strength, weather resistance and the like, a weight average molecular weight of about 500 to 50,000 is preferable. This alkylsilicate hydrolyzed polymer (silica sol) undergoes a dehydration condensation polymerization reaction (crosslinking reaction) almost completely upon heating after application / drying of the coating liquid for forming a transparent conductive film, and a hard silicate binder matrix (silicon oxide). A binder matrix containing as a main component.

An organic-inorganic hybrid binder can also be used as the binder. For example, a binder obtained by partially modifying the above-described silica sol with an organic functional group and a binder mainly composed of various coupling agents such as a silicon coupling agent can be given.
Transparent conductive films using the above inorganic binders and organic-inorganic hybrid binders inevitably have excellent solvent resistance. However, in consideration of adhesion to the substrate and flexibility of the transparent conductive film, etc. However, it is necessary to select appropriately.

These various binders can be used as they are, but when the viscosity is high, the same organic solvents as those described above, that is, 2-hexylcyclopentanone, 2-heptylcyclopentanone, and 2-cyclopentylcyclo It is preferably used by dissolving in an organic solvent containing at least one 5-membered ring ketone compound selected from the group of pentanone.
Moreover, the ratio of the conductive oxide fine particles and the binder component in the coating liquid for forming the transparent conductive film is assumed that the specific gravity of the conductive oxide fine particles and the binder component is about 7.2 (specific gravity of ITO), 1.2 Assuming that it is about (specific gravity of a normal organic resin binder), the conductive oxide fine particles: binder component = 70: 30 to 97: 3, preferably 75:25 to 95: 5, more preferably 80 by weight ratio. : It is good to set it as the range of 20-90: 10. The reason is that if the binder component is more than 70:30, the resistance of the transparent conductive film becomes too high, and conversely if the binder component is less than 97: 3, the strength of the transparent conductive film is lowered and at the same time sufficient with the substrate. This is because the adhesion cannot be obtained.
The coating liquid for forming a transparent conductive film of the present invention is prepared by mixing conductive oxide fine particles whose surface is modified with a halogen element in an organic solvent containing a five-membered ring ketone compound having a low water content as a main component. The conductive oxide fine particle dispersion thus prepared can be obtained by adding a binder component thereto and dispersing it in the same manner.

4). Transparent conductive film The transparent conductive film of the present invention is formed by applying the transparent conductive film-forming coating solution on a plastic substrate or a ceramic substrate and drying it. Depending on the type, the heat treatment (dry curing, thermosetting), ultraviolet irradiation treatment (ultraviolet curing), electron beam irradiation treatment (electron beam curing) or the like is performed.

  As the base material, an organic base material or an inorganic base material can be applied. Usually, transparent base materials such as various plastic base materials (plates, films) and ceramic base materials are used. Specifically, for plastic substrates, epoxy, acrylic, polycarbonate (PC), polyethersulfone (PES), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP ), Urethane, nylon resin, cycloolefin resin (Zeonor [manufactured by Zeon Corporation] or Arton [manufactured by JSR], etc.), fluorine-based resin, polyamideimide, polyimide (PI), and the like. Among these, it is preferable to use a PET film from the viewpoint of being inexpensive, excellent in transparency, strength, and flexibility. Moreover, if it is a ceramic base material, various glass, such as soda-lime glass, an alkali free glass, quartz glass, an alumina, a zirconia etc. can be used, for example.

The thickness of the substrate is not particularly limited and can be appropriately selected depending on the application. In recent years, there has been a tendency for thin substrates to be as thin as possible in response to the trend of thinning and miniaturization of various display devices, and a plastic substrate having a thickness of 100 μm or less is preferable. On the other hand, in the case of various glasses such as soda lime glass and non-alkali glass, those having a thickness of 3 mm or less, more preferably 1 mm or less are desirable.
In addition, in order to increase the adhesive force with the transparent conductive film, the plastic substrate has an easy adhesion treatment, specifically, primer treatment, plasma treatment, corona discharge treatment, short wavelength ultraviolet irradiation treatment, silicon coupling treatment, etc. Is preferably applied in advance.

  The coating liquid for forming the transparent conductive film (and the conductive oxide fine particle dispersion) can be pattern-printed by direct drawing by inkjet printing, but other printing methods include screen printing, blade coating, wire bar coating, and spraying. After coating and drying on a substrate by a method such as coating, spin coating, roll coating, die coating, slit coating, gravure printing, flexographic printing, offset printing, dispenser coating, etc., the above-mentioned curing treatment is applied, and a transparent conductive film May be obtained. Ink-jet printing enables on-demand printing that can be output as is without making a plate from digital data. Therefore, it can be printed faster and at a lower cost than screen printing. There is an advantage that can be done.

The heat treatment temperature of the substrate can be appropriately selected in consideration of its heat resistance and the boiling point of the solvent in the coating liquid for forming a transparent conductive film. For example, when a base material consists of PET films, it is preferable to heat a coating film at 150 degrees C or less for 1 to 30 minutes. More preferable is heating at 50 to 120 ° C. for 5 to 10 minutes. When the temperature exceeds 150 ° C., the film is softened and easily deformed, and at the same time, a low molecular component oligomer precipitates on the film surface and causes whitening. Further, when the substrate is made of glass, the substrate has high heat resistance. Therefore, when it is desired to further improve the conductivity of the coating film, heating at a temperature exceeding 150 ° C. is possible. Specifically, it is preferable to heat at 300 ° C. or lower for 1 to 30 minutes. Considering the versatility (price and availability) of the heating device, it is more preferable to heat at 150 to 200 ° C. for 5 to 10 minutes.
The film characteristics of the transparent conductive film thus obtained are visible light transmittance: 80% or more, preferably 85% or more, haze value: 10% or less, preferably 7% or less, surface resistance value: 5M (mega) Ω / □ or less, preferably 1 M (mega) Ω / □ or less.

Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. In the text, “%” may indicate “mass%” and “part” may indicate “part by weight”.
The average dispersed particle diameter of the conductive oxide fine particles in the dispersion was measured using a laser scattering particle size analyzer (ELS-800) manufactured by Otsuka Electronics Co., Ltd.

Moreover, the transmittance | permeability and haze value of the transparent conductive film obtained are the values only of a transparent conductive film, and were calculated | required by the following formulas 1 and 2, respectively.
[Calculation Formula 1]
Transmittance (%) of transparent conductive film = [(transmittance measured for each substrate on which transparent conductive film is formed) / transmittance of substrate] × 100
[Calculation Formula 2]
Haze value (%) of transparent conductive film = (Haze value measured for each substrate on which transparent conductive film is formed) − (Haze value of substrate)
The surface resistance of the transparent conductive film was measured using a surface resistance meter Loresta AP (MCP-T400) manufactured by Mitsubishi Chemical Corporation. The haze value and visible light transmittance were measured using a haze meter (HR-200) manufactured by Murakami Color Research Laboratory.

Example 1
Granular ITO fine particles having an average particle size of 0.03 μm and surface-modified with chlorine (Sn content = 6%, chlorine = 0.5%, ITO: Cl = 1: 0.02 [molar ratio], dust resistance [ ² -hexylcyclopentanone (water content: less than 0.1%, boiling point 246 ° C., surface tension 32 dyn / cm), which is a 5-membered ring ketone compound as a solvent, 20 g of 100 kgf / cm ² ] = 0.18 Ω · cm) [25 ° C.] 79.9 g and phosphoric acid ester-based dispersant 0.1 g were mixed and subjected to ultrasonic dispersion treatment for 3 minutes to conduct conductivity according to Example 1 in which ITO fine particles having an average dispersed particle diameter of 140 nm were dispersed. An oxide fine particle dispersion was obtained. The amount of water was less than 0.4 parts by weight with respect to 100 parts by weight of the conductive oxide fine particles. This dispersion maintained a good dispersion state for one month or more when stored at room temperature in a sealed glass container. The surface tension of this dispersion was 32.9 dyn / cm (25 ° C.).
This conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.2%). , Refractive index: 1.53), ink jet printing was performed using a printer (trade name: IJET-2000H) manufactured by Microjet Co. There was no repellency, the ink spreading property was appropriate, and sufficient ink jet printing was possible.
Next, a transparent conductive film was formed by a spin coating method, and this was used as an evaluation sample. That is, the conductive oxide fine particle dispersion liquid (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.0. 2%, refractive index: 1.53) was spin-coated on the entire surface (substrate temperature: 25 ° C., 400 rpm × 60 seconds) and dried at 120 ° C. for 10 minutes to obtain a transparent conductive film. The film characteristics of this transparent conductive film were visible light transmittance: 94.9%, haze value: 5.1%, and surface resistance value: 5M (mega) Ω / □.
In addition, since these use the same electroconductive oxide fine particle dispersion (coating liquid for transparent conductive film formation), even if it employs an ink-jet printing method or the like, it can be obtained by employing a spin coating method. There is no change in the film characteristics of the transparent conductive film.

(Example 2)
The same as in Example 1 except that 2-heptylcyclopentanone (water content: less than 0.1%, boiling point 264 ° C., surface tension 36 dyn / cm [25 ° C.]), which is a 5-membered ring ketone compound, was used as the solvent. Thus, a conductive oxide fine particle dispersion according to Example 2 in which ITO fine particles having an average dispersed particle diameter of 140 nm were dispersed was obtained. The amount of water was less than 0.4 parts by weight with respect to 100 parts by weight of the conductive oxide fine particles. This dispersion maintained a good dispersion state for one month or more when stored at room temperature in a sealed glass container. The dispersion had a surface tension of 37.4 dyn / cm (25 ° C.).
This conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.2%). , Refractive index: 1.53) When ink jet printing is performed, the nozzles are not clogged, the ink ejection property is good, the formed coating film does not repel, the ink spreading property is appropriate, and sufficient ink jet printing is possible. Met.
A transparent conductive film was produced in the same manner as in Example 1 except that the conductive oxide fine particle dispersion (transparent conductive film forming coating liquid) was used. The film characteristics of this transparent conductive film were visible light transmittance: 97.1%, haze value: 4.4%, and surface resistance value: 1M (mega) Ω / □.

(Example 3)
The same as Example 1 except that 2-cyclopentylcyclopentanone (water content: less than 0.1%, boiling point 233 ° C., surface tension 36 dyn / cm [25 ° C.]), which is a 5-membered ring ketone compound, was used as the solvent. Thus, a conductive oxide fine particle dispersion according to Example 3 in which ITO fine particles having an average dispersed particle diameter of 140 nm were dispersed was obtained. The amount of water was less than 0.4 parts by weight with respect to 100 parts by weight of the conductive oxide fine particles. This dispersion maintained a good dispersion state for one month or more when stored at room temperature in a sealed glass container. The dispersion had a surface tension of 37.4 dyn / cm (25 ° C.).
This conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.2%). , Refractive index: 1.53) When ink jet printing is performed, the nozzles are not clogged, the ink ejection property is good, the formed coating film does not repel, the ink spreading property is appropriate, and sufficient ink jet printing is possible. Met.
A transparent conductive film was produced in the same manner as in Example 1 except that the conductive oxide fine particle dispersion (transparent conductive film forming coating liquid) was used. The film characteristics of this transparent conductive film were visible light transmittance: 92.0%, haze value: 6.9%, and surface resistance value: 3M (mega) Ω / □.

Example 4
Granular ITO fine particles having an average particle diameter of 0.05 μm surface-modified with chlorine (Sn content = 8%, chlorine = 0.5%, ITO: Cl = 1: 0.02 [molar ratio]), pressure Conductive oxide fine particles according to Example 4 in which ITO fine particles having an average dispersed particle diameter of 150 nm are dispersed in the same manner as in Example 1 except that 20 g of powder resistance [100 Kgf / cm ² ] = 0.15 Ω · cm) is used. A dispersion was obtained.
This conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.2%). , Refractive index: 1.53) When ink jet printing is performed, the nozzles are not clogged, the ink ejection property is good, the formed coating film does not repel, the ink spreading property is appropriate, and sufficient ink jet printing is possible. Met.

(Example 5)
The amount of 2-hexylcyclopentanone, which is a 5-membered ring ketone compound, is reduced to 50.0 g (50 mass% with respect to the total dispersion), and isophorone (water content: less than 0.02%, boiling point 215 ° C. Conductive oxide fine particles according to Example 5 in which ITO fine particles having an average dispersed particle diameter of 140 nm were dispersed in the same manner as in Example 1 except that 29.9 g of surface tension 32.3 dyn / cm [20 ° C.] was used. A dispersion was obtained.
This conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.2%). , Refractive index: 1.53) When ink jet printing is performed, the nozzles are not clogged, the ink ejection property is good, the formed coating film does not repel, the ink spreading property is appropriate, and sufficient ink jet printing is possible. Met.

(Comparative Example 1)
Granular ITO fine particles having an average particle diameter of 0.03 μm that are not surface-modified with chlorine (Sn content = 6%, chlorine = 0.05% or less, ITO: Cl = 1: 0.002 or less [molar ratio], pressure 20 g of powder resistance [100 Kgf / cm ² ] = 0.25 Ω · cm) and ² -hexylcyclopentanone as a solvent (water content: less than 0.1%, boiling point 246 ° C., surface tension 32 dyn / cm [25 ° C]) was mixed with 79.9 g of phosphoric acid ester-based dispersant and 0.1 g of ultrasonic dispersant, and was subjected to ultrasonic dispersion treatment. However, it became creamy and a good conductive oxide fine particle dispersion could not be obtained.
Since it became creamy, it has not been evaluated as a coating liquid for forming a transparent conductive film.

(Comparative Example 2)
Granular ITO fine particles having an average particle size of 0.03 μm and surface-modified with chlorine (Sn content = 6%, chlorine = 0.5%, ITO: Cl = 1: 0.02 [molar ratio], dust resistance [ 100 kgf / cm ² ] = 0.18 Ω · cm) 20 g of cyclopentanone [also known as cyclopentan-1-one; CAS number: 120-92-3] (water content: 5 membered ring ketone compound solvent) Less than 0.1%, boiling point 130 ° C., surface tension 33.4 dyn / cm [25 ° C.]) 79.9 g, and phosphate ester dispersant 0.1 g, and subjected to ultrasonic dispersion treatment for 3 minutes, A conductive oxide fine particle dispersion according to Comparative Example 2 in which ITO fine particles having an average dispersed particle diameter of 140 nm were dispersed was obtained. This dispersion maintained a good dispersion state for one month or more when stored at room temperature. The surface tension of this dispersion was 35 dyn / cm (25 ° C.).
This conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.2%). , Refractive index: 1.53) When ink-jet printing was performed, nozzle clogging gradually occurred, resulting in poor ink ejection properties, and stable ink-jet printing was impossible.
A transparent conductive film was produced in the same manner as in Example 1 except that the conductive oxide fine particle dispersion (transparent conductive film forming coating liquid) was used. The film characteristics of this transparent conductive film were visible light transmittance: 90.5%, haze value: 4.5%, surface resistance value: 280 k (kilo) Ω / □.

(Comparative Example 3)
Comparison in which ITO fine particles having an average dispersed particle diameter of 145 nm were dispersed in the same manner as in Example 1 except that 20 g of ITO fine particles were mixed with 79 g of 2-hexylcyclopentanone as a solvent and 1 g of a phosphate ester dispersant. A conductive oxide fine particle dispersion according to Example 3 was obtained.
This conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) was used as a soda lime glass substrate (10 cm × 10 cm × 2 mm thickness, transmittance: 91.1%, haze: 0.2%). , Refractive index: 1.53) When ink jet printing is performed, the nozzles are not clogged, the ink ejection property is good, the formed coating film does not repel, the ink spreading property is appropriate, and sufficient ink jet printing is possible. Met.
A transparent conductive film was produced in the same manner as in Example 1 except that the conductive oxide fine particle dispersion (transparent conductive film forming coating liquid) was used. The film characteristics of this transparent conductive film were visible light transmittance: 94.5%, haze value: 5.2%, and surface resistance value: 5 × 10 ¹⁰ Ω / □.

"Evaluation"
When Examples 1-5 were compared with Comparative Example 1, the ITO fine particles surface-modified with chlorine were dispersed in 2-hexylcyclopentanone, 2-heptylcyclopentanone, and 2-cyclopentylcyclopentanone. The conductive oxide fine particle dispersion (coating liquid for forming a transparent conductive film) exhibits good dispersibility, whereas ITO fine particles not surface-modified with chlorine are dispersed in 2-hexylcyclopentanone. No. 1 conductive oxide fine particle dispersion is creamy and does not show good dispersibility.
Comparing Examples 1 to 3 with Comparative Example 2, conductive oxide fine particle dispersions using 2-hexylcyclopentanone, 2-heptylcyclopentanone and 2-cyclopentylcyclopentanone of each example as organic solvents The conductive oxide fine particle dispersion liquid of Comparative Example 2 using cyclopentanone having a low boiling point as an organic solvent is excellent in dispersibility and good discharge stability in ink jet printing. Although the conductive oxide fine particle dispersion exhibits good dispersibility, nozzle clogging occurs in ink jet printing, and good discharge stability is not exhibited.
On the other hand, in Comparative Example 3, since the amount of the dispersant was large, a large amount of the dispersant was present in the obtained transparent conductive film, and the conductive oxide fine particles were interposed between the conductive oxide fine particles. Since the mutual contact was inhibited, the conductivity of the transparent conductive film was significantly deteriorated.
As described above, in the present invention, the conductive oxide fine particle dispersion exhibits good dispersibility and good discharge stability in ink jet printing. However, if the constituents are out of the scope of the present invention. It can be seen that good dispersibility cannot be obtained, or nozzle clogging occurs in ink jet printing, and stable dispersibility cannot be obtained.

Claims (14)

  A conductive oxide fine particle dispersion liquid in which conductive oxide fine particles (A) having an average particle diameter of 1 to 500 nm, which is surface-modified with a halogen element, are dispersed in an organic solvent (B), wherein the organic solvent (B) has a boiling point The main component is a 5-membered ketone compound having a surface tension of 230 ° C. or more and a surface tension of 40 dyn / cm or less, and contains 2 parts by weight or less of the dispersant (C) with respect to 100 parts by weight of the conductive oxide fine particles. Conductive oxide fine particle dispersion.   The conductive oxide fine particles (A) are fine particles containing, as a main component, at least one metal oxide selected from the group of indium oxide, tin oxide, and zinc oxide. Conductive oxide fine particle dispersion.   3. The conductive oxide fine particle dispersion according to claim 2, wherein the conductive oxide fine particles (A) are metal oxide fine particles containing indium oxide doped with tin as a main component.   The conductive oxide fine particle dispersion according to claim 1, wherein the halogen element is chlorine.   The organic solvent (B) is at least one 5-membered ring ketone compound selected from the group of 2-hexylcyclopentanone, 2-heptylcyclopentanone, and 2-cyclopentylcyclopentanone. The conductive oxide fine particle dispersion liquid according to 1.   6. The conductive oxide fine particle dispersion according to claim 1, wherein the content of the five-membered ring ketone compound is 50% by mass or more based on the whole organic solvent (B).   Content of an organic solvent (B) is 50-95 mass% with respect to the whole dispersion liquid, The electroconductive oxide fine particle dispersion liquid of Claim 1 characterized by the above-mentioned.   The conductive oxide fine particle dispersion according to claim 1, wherein the dispersant (C) is a phosphate ester compound.   The conductive oxide fine particle dispersion according to any one of claims 1 to 8, further comprising a binder component (D), a coating liquid for forming a transparent conductive film.   The binder component (D) is any organic resin selected from the group of thermoplastic resins, thermosetting resins, room temperature curable resins, ultraviolet curable resins, electron beam curable resins, and the like. The coating liquid for transparent conductive film formation of Claim 9.   The transparent conductive film obtained by apply | coating the electroconductive oxide fine particle dispersion liquid in any one of Claims 1-8 on a plastic base material or a ceramic base material, and drying.   The transparent conductive film according to claim 11, wherein the conductive oxide fine particle dispersion is applied by inkjet printing.   The transparent conductive film obtained by apply | coating the coating liquid for transparent conductive film formation of Claim 9 or 10 on a plastics base material or a ceramic base material, and drying after giving.   The transparent conductive film according to claim 13, wherein the coating liquid for forming a transparent conductive film is applied by ink jet printing.