WO2019026829A1

WO2019026829A1 - Method for producing conductive film, conductive film, and metal nanowire ink

Info

Publication number: WO2019026829A1
Application number: PCT/JP2018/028412
Authority: WO
Inventors: 山木　繁
Original assignee: 昭和電工株式会社
Priority date: 2017-08-02
Filing date: 2018-07-30
Publication date: 2019-02-07
Also published as: CN110720129A; TW201920508A; JPWO2019026829A1; KR102393615B1; JP7300991B2; CN110720129B; KR20200006998A

Abstract

[Problem] Provided is a conducive film for which the amount of a metal nanowire to be used can be reduced, and which has a surface resistivity ranging from 1000 to 10000 Ω/□, and has a small degree of variation in in-plane surface resistivities. Also provided are: a method suitable for the production of a conductive film, which has excellent production efficiency; and a metal nanowire ink which can be used for the method. [Solution] A conductive film which can be produced by a production method including a step of applying a metal nanowire ink onto at least one surface of a polymer film and then drying the metal nanowire ink, wherein the metal nanowire ink contains a metal nanowire (A) having an average diameter of 1 to 100 nm, an average long axis length of 1 to 100 μm and an average aspect ratio of 100 to 2000, a binder resin (B) containing at least one of ethyl cellulose and hydroxypropyl cellulose and a solvent (C) containing diethylene glycol monoethyl ether, the content of the metal nanowire (A) in the metal nanowire ink is 0.005 to 0.05% by mass, the surface resistivity of a conductive layer in the conductive film is 1000 to 10000 Ω/□, and the degree of variation in the in-plane surface resistivity is 35% or less.

Description

Method of manufacturing conductive film, conductive film and metal nanowire ink

The present invention relates to a method of producing a conductive film, a conductive film and a metal nanowire ink.

In recent years, metal nanowires have attracted attention as a raw material of a highly transparent and highly conductive thin film as an alternative to an ITO (indium tin oxide) film used for transparent electrodes of touch panels and the like. Such metal nanowires are generally manufactured by heating a metal compound in the presence of polyvinyl pyrrolidone and a polyol such as ethylene glycol (Non-patent Document 1).

Patent Document 1 below describes a method for producing a transparent conductor, which comprises the step of drying a fluid in which metal nanowires are dispersed to form a metal nanowire network layer on a substrate, and carboxymethylcellulose and 2-hydroxyethylcellulose. Hydroxypropyl methylcellulose, methylcellulose, polyvinyl alcohol, tripropylene glycol, and xanthan gum may be included in the fluid.

In addition, Patent Document 2 below includes a coated transparent support and a random network of silver nanowires dispersed in a cellulose ester polymer (cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, or a mixture thereof) A transparent conductive article is disclosed, comprising: a transparent conductive film.

Patent Document 3 below describes metal nanowires, binders (binder (A): polysaccharides (hydroxypropyl guar gum and derivatives thereof, hydroxypropyl methylcellulose and derivatives thereof, and methylcellulose and derivatives thereof) and binders (B): aqueous A metal nanowire-containing coating film formed by a composition containing a metal nanowire containing a polyester resin, an aqueous polyurethane resin, at least one selected from an aqueous acrylic resin and an aqueous epoxy resin, a surfactant, and a solvent is on a substrate There is disclosed a transparent conductor formed in

In addition, Patent Document 4 below includes metal nanowires as conductive fibers, gelatin as a polymer, gelatin derivative, casein, agar, starch, polyvinyl alcohol, a copolymer of polyacrylic acid, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl pyrrolidone, A conductive membrane containing dextran, etc. is disclosed.

Japanese Patent Application Publication No. 2009-505358 JP 2012-533846 gazette International Publication No. 2014/196354 brochure JP 2011-233514 A

According to Patent Documents 1 to 4, it is suggested that it is intended to obtain a conductive film having a surface resistance value of 1000 Ω / □ or less. In order to obtain such a low-resistance conductive film, it is necessary to use a corresponding conductive material, which causes problems in cost and optical characteristics, and causes a problem in that anisotropy occurs in the conductivity. On the other hand, when a dilute coating solution containing metal nanowires is applied to a substrate film to obtain a conductive film having a surface resistance value not so low as 1000 Ω / □ or more, the metal nanowires are coated or coated in the coating solution. Cohesion occurs in the subsequent drying step, and as a result, a uniform coated state can not be obtained, and high and low portions of the surface resistance value are generated in the film surface, which causes a problem of increased variation.

An object of the present invention is to provide a conductive film which has a reduced amount of metal nanowires used and which has a surface resistance value in the range of 1000 to 10000 Ω / □ and which has a small variation in the surface resistance value in the plane. Another object of the present invention is to provide a method for producing a conductive film excellent in productivity and a metal nanowire ink therefor.

In order to achieve the above object, the present invention includes the following embodiments.

[1] Metal nanowire (A) having an average diameter of 1 to 100 nm, an average long axis length of 1 to 100 μm, and an average aspect ratio of 100 to 2000, and at least one of ethyl cellulose and hydroxypropyl cellulose A metal nanowires ink comprising: a binder resin (B) comprising: and a solvent (C) comprising diethylene glycol monoethyl ether, wherein the content of the metal nanowires (A) is 0.005 to 0.05% by mass, A method for producing a conductive film, comprising the steps of applying and drying on at least one side of a polymer film.

[2] The method for producing a conductive film according to [1], wherein the solvent (C) contains 10 to 50% by mass of diethylene glycol monoethyl ether.

[3] A conductive film having a conductive layer formed on at least one surface of a polymer film, wherein the conductive layer has an average diameter of 1 to 100 nm and an average length of the major axis of 1 to 100 μm, and an aspect The metal nanowires (A) having an average ratio of 100 to 2000 and a binder resin (B) containing at least one of ethyl cellulose and hydroxypropyl cellulose, and the surface resistivity of the conductive layer is 1000 to 10000 Ω / □ What is claimed is: 1. A conductive film characterized by having a variation in surface resistance value of 35% or less.

[4] The conductive film according to [3], wherein the metal nanowires (A) are silver nanowires and the occupied area ratio is in the range of 0.5 to 1.5%.

[5] The mass ratio of the metal nanowire (A) to the binder resin (B) [metal nanowire (A) / binder resin (B)] is in the range of 0.01 to 0.5, [3] or [3] 4] conductive film.

[6] The polymer film according to any one of [3] to [5], which is a film made of any polymer selected from the group consisting of polyester, polycarbonate, acrylic resin, and polycycloolefin. Conductive film.

[7] The conductive film according to any one of [3] to [6], having a total light transmittance of 80% or more and a haze value of 0.1 to 1.5%.

[8] A metal nanowire (A) having an average diameter of 1 to 100 nm, an average long axis length of 1 to 100 μm, and an average aspect ratio of 100 to 2000, and at least one of ethyl cellulose and hydroxypropyl cellulose And a solvent (C) containing diethylene glycol monoethyl ether, and the content of the metal nanowire (A) is 0.005 to 0.05% by mass. Metal nanowire ink.

[9] The metal nanowire ink according to [8], wherein the solvent (C) contains 10 to 50% by mass of diethylene glycol monoethyl ether.

According to an embodiment of the present invention, a conductive film having a small amount of metal nanowires and a surface resistance of 1000 to 10000 Ω / □, a conductive film with little in-plane variation, a method for producing the same, and metal nanowire ink used therefor are provided. You can do it. Moreover, the conductive film which concerns on embodiment of this invention can be used suitably for the conductive film use for a touch panel and electronic paper excellent in low cost and resistance value stability.

It is a figure for demonstrating the evaluation method of the dispersion | variation (in-plane uniformity) of the surface resistance value of the electroconductive film in an Example and a comparative example.

Hereinafter, each configuration of a mode for carrying out the present invention (hereinafter, referred to as an embodiment) will be described in detail.

In the conductive film according to the embodiment, a conductive layer is formed on at least one side of a polymer film as a substrate, and the conductive layer has an average diameter of 1 to 100 nm and an average major axis length of 1 to 100 μm. And a metal nanowire (A) having an average aspect ratio of 100 to 2000, and a binder resin (B) containing at least one of ethyl cellulose and hydroxypropyl cellulose, and the surface resistivity of the conductive layer is 1,000. It is characterized in that it is ̃10000 Ω / □, and the variation of the in-plane surface resistance value is 35% or less.

<Polymer film>
The polymer film is not particularly limited as long as it has sufficient adhesion to the conductive layer. As the polymer film, for example, a film made of a polymer such as polyester (polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc.), polycarbonate, acrylic resin, polycycloolefin, polysulfone, polyamide, polyimide, etc. is suitably used. I can do things. By using a film made of polyester (polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc.), polycarbonate, acrylic resin, or polycycloolefin, a conductive film having excellent transparency can be obtained. It can. The preferred polymer film is a film made of any of polycycloolefin, polyester (polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc.), and a film made of polycycloolefin, polyethylene terephthalate (PET) Is more preferred.

The thickness of the polymer film is not particularly limited and may be appropriately selected depending on the application and type, but is usually 25 to 500 μm, more preferably 38 to 400 μm from the viewpoint of mechanical strength, handling property, etc. More preferably, it is 50 to 300 μm. In addition, various additives may be added to the polymer film, for example, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, nucleating agents, etc. It may be added to an extent that does not deteriorate the characteristics.

The polymer film may be used as it is without surface treatment. In order to enhance the adhesion with the conductive layer formed on the polymer film and the uniformity of the conductive layer, the polymer film may be subjected to surface treatment such as corona treatment or plasma treatment.

<Conductive layer>
The conductive layer is obtained by applying and drying a metal nanowire ink on at least one surface of a polymer film. The metal nanowires ink comprises metal nanowires (A), a binder resin (B), and a solvent (C). The conductive layer is a conductive layer in which metal nanowires (A) are dispersed in a binder resin (B), the surface resistance value is 1000 to 10000 Ω / □, and the variation of the surface resistance value is 35% or less The conductive layer is formed on at least one side of the polymer film to constitute the conductive film of the present embodiment.

The content of the metal nanowires (A) in the conductive layer is preferably 0.5 to 1.5%, preferably 1.0 to 1.4% in terms of the occupied area ratio of the metal nanowires (A) to the conductive film. Is more preferred. In this case, when the occupied area ratio of the metal nanowires to the conductive film is 0.5% or more, a conductive film having a surface resistance value of 10000 Ω / □ or less can be obtained. Further, by setting the occupied area ratio of the metal nanowires to the conductive film at 1.5% or less, it is possible to obtain a conductive film having a high total light transmittance, a low haze, and excellent transparency. That is, by setting the occupied area ratio of the metal nanowires to the conductive film at 0.5% or more and 1.5% or less, the conductivity and transparency are excellent, and the amount of the expensive metal nanowires used is small and the economy is economical An excellent conductive film can be obtained. Here, the “occupied area ratio of the metal nanowires to the conductive film” means the ratio of the projected area of the metal nanowires observed from the direction perpendicular to the plane of the conductive layer of the conductive film.

<Metal nanowire (A)>
The metal nanowire is a metal having a diameter of nanometer order size, and is a conductive material having a wire-like or tube-like shape. In the present specification, "wire-like" and "tube-like" are both linear, but the former is intended not to be hollow in the center and the latter to be hollow in the center. The properties may be flexible or rigid. The former is referred to as "metal nanowire in a narrow sense" and the latter is referred to as "metal nanotube in a narrow sense". Hereinafter, in the present specification, "metal nanowire (A)" is used to encompass metal nanowires in a narrow sense and metal nanotubes in a narrow sense. The narrow sense metal nanowires and the narrow sense metal nanotubes may be used alone or in combination.

The average diameter (diameter) of the metal nanowires (A) is 1 to 100 nm, preferably 5 to 80 nm, more preferably 10 to 60 nm, and still more preferably 10 to 50 nm. The average length of the major axes of the metal nanowires is 1 to 100 μm, preferably 1 to 50 μm, more preferably 2 to 50 μm, and still more preferably 5 to 30 μm.

The metal nanowire (A) has an average diameter thickness and an average long axis length satisfying the above range, and an average aspect ratio of 100 to 2000, preferably 200 to 1000, and 300 to 300 It is more preferably 1000, and still more preferably 300 to 700. Here, the aspect ratio is a value obtained by a / b when the average diameter of the diameter of the metal nanowire is b and the average length of the major axis is a. a and b can be measured using a scanning electron microscope (SEM).

As the type of metal, at least one metal selected from the group consisting of gold, silver, platinum, copper, nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium, osmium, iridium and alloys combining these metals, etc. Can be mentioned. In order to obtain a transparent conductive film having low surface resistance and high total light transmittance, it is preferable to include at least one of gold, silver and copper. Since these metals have high conductivity, the density of the metal occupied on the surface can be reduced when obtaining a constant surface resistance, so that high total light transmittance can be realized.

Among these metals, it is more preferable to include at least one of gold and silver. Optimal embodiments include silver nanowires.

A well-known manufacturing method can be used as a manufacturing method of metal nanowire (A). For example, silver nanowires (in a narrow sense) can be synthesized by reducing silver nitrate in the presence of polyvinyl pyrrolidone using the polyol (Poly-ol) method (see Chem. Mater., 2002, 14, 4736). Gold nanowires (in a narrow sense) can be similarly synthesized by reducing chloroauric acid hydrate in the presence of polyvinyl pyrrolidone (see J. Am. Chem. Soc., 2007, 129, 1733). WO 2008/073143 and WO 2008/046058 provide a detailed description of large scale synthesis and purification techniques of silver nanowires and gold nanowires. Gold nanotubes (in a narrow sense) having a porous structure can be synthesized by reducing a chloroauric acid solution using silver nanowires as a template. Here, the silver nanowires used as the template are dissolved in the solution by the redox reaction with chloroauric acid, and as a result, gold nanotubes having a porous structure can be formed (J. Am. Chem. Soc., 2004, 126, 3892 -3901).

<Binder resin (B)>
The binder resin (B) used for the metal nanowire ink disperses and immobilizes the metal nanowire (A) in the conductive layer, and contains at least one of ethyl cellulose and hydroxypropyl cellulose. By using ethyl cellulose and hydroxypropyl cellulose as the binder resin (B), the metal nanowires (A) can be uniformly dispersed in the binder resin (B), and uniformly dispersed and immobilized on the polymer film. In addition to the above, transparency and the like can be provided. For the binder resin (B), a resin other than ethylcellulose and hydroxypropylcellulose can be used in combination as long as it dissolves in the solvent (C) described later, but the compounding amount thereof is 50 mass of the whole binder resin (B) The content is preferably less than%, more preferably less than 30% by mass, and still more preferably less than 20% by mass.

The mass ratio of the metal nanowires (A) to the binder resin (B) in the metal nanowires ink [metal nanowires (A) / binder resin (B)] is preferably in the range of 0.01 to 0.5, and more preferably Is from 0.03 to 0.4, more preferably from 0.05 to 0.2. When the mass ratio of the metal nanowires (A) to the binder resin (B) is 0.5 or less, a uniform coating can be formed. Moreover, various characteristics and effects of the binder resin (B) can be imparted to the conductive film. The conductivity of the metal nanowire (A) can be sufficiently expressed by setting the mass ratio of the metal nanowire (A) to the binder resin (B) to 0.01 or more.

<Solvent (C)>
The solvent (C) contained in the metal nanowires ink needs to have a composition capable of dissolving the binder resin (B), dispersing the metal nanowires (A), and capable of being favorably applied to the surface of the polymer film. Therefore, the solvent contains diethylene glycol monoethyl ether. The amount of solvent used is not particularly limited as long as it can provide a uniform conductive layer when the metal nanowires ink is applied on the polymer film. In this case, the amount of the solvent is adjusted so that the total amount of the metal nanowires (A) and the binder resin (B) contained in the metal nanowires ink is about 0.1 to 0.5% by mass with respect to the entire metal nanowires ink. It is preferable to adjust the

The solvent (C) preferably contains an alcohol other than diethylene glycol monoethyl ether. It is also preferable to use a mixed solvent with water. Examples of alcohols other than diethylene glycol monoethyl ether include methanol, ethanol, propanol, propylene glycol, propylene glycol monomethyl ether and the like, and one or more of these can be used in combination. In this case, diethylene glycol monoethyl ether is preferably contained in the range of 10 to 50% by mass in all solvents. The preferred range of alcohol in the total solvent is 90 to 100% by weight, and the preferred range of water is 0 to 10% by weight.

<Metal nanowire ink>
The metal nanowires ink may contain additives such as a surfactant, an antioxidant, and a filler as long as the performance such as printing characteristics, conductivity and optical characteristics is not adversely affected. Fillers such as fumed silica can be used to adjust the viscosity of the composition. The total amount of these components is preferably 5% by mass or less.

In the metal nanowires ink according to the embodiment, the metal nanowires (A), the binder resin (B), the solvent (C), and the additive that can be added as needed are added in the above-mentioned mixing ratio (% by mass). It mix | blends and it can stir and mix with a rotation revolution stirrer etc. The viscosity of the metal nanowires ink is preferably 1 to 50 mPa · s.

The conductive film of the embodiment is obtained by applying a metal nanowire ink to the surface of the polymer film. The content of the metal nanowires (A) in the metal nanowires ink is 0.005 to 0.05% by mass. If the amount is less than 0.005% by mass, the conductivity is too low, the sheet resistance can not be measured by the measurement method described in the examples described later, and if it exceeds 0.05% by mass, the conductivity is too high. Preferably, it is 0.01 to 0.05% by mass, more preferably 0.02 to 0.04% by mass.

The metal nanowire ink can be applied to the polymer film by any known method such as a bar coating method, a reverse coating method, a gravure coating method, a die coating method, and a blade coating method. Moreover, drying can be performed by arbitrary systems, such as a hot blast furnace and a far-infrared furnace.

According to a manufacturing method using a metal nanowire ink containing the above specific binder resin and a solvent, the conductive film is a conductive film formed on a polymer film, and has a surface resistance value of 1000 to 10000 Ω / □, and a surface It is possible to obtain a conductive film having a variation in resistance of 35% or less.

The conductive film of the present embodiment is manufactured using a metal nanowire ink in which metal nanowires are well dispersed, containing a small amount of metal nanowires (A), a specific binder resin (B), and a solvent (C). Accordingly, a conductive film having a total light transmittance of 80% or more, preferably 85% or more, and a haze value of 0.1 to 1.5%, preferably 0.3 to 1.0% can be obtained. By setting the total light transmittance to 80% or more and the haze value to 0.1 to 1.5%, it is possible to obtain a conductive film having excellent transparency and less clouding.

Examples of the present invention will be specifically described below. The following examples are provided to facilitate the understanding of the present invention, and the present invention is not limited to these examples. In each of the following examples and comparative examples, silver nanowires were used as metal nanowires.

<Observation of the shape of silver nanowires>
The shape (length and diameter) of silver nanowires is the diameter and length of 50 nanowires arbitrarily selected using Hitachi High-Technologies Corporation high-resolution field-emission scanning electron microscope SU8020 (acceleration voltage 3 to 10 kV) Were observed and their arithmetic mean value was determined. Specifically, several drops of silver nanowire dispersion were dropped onto a silicon wafer, and after drying, the shape of the silver nanowire deposited on the silicon wafer was observed by the above-mentioned scanning electron microscope. The aspect ratio (average) was calculated from [average value of length of major axis of nanowire] / [average diameter of nanowire].

In addition, a solution in which silver nanowires obtained by the synthesis of silver nanowires described later are dispersed in methanol using an ultraviolet visible near infrared spectrophotometer V-670 manufactured by JASCO Ltd. (silver nanowire content in the solution UV-visible absorption spectrum at 300-600 nm): 0.003 mass%, maximum peak value Abs (λ max) of absorbance at 370 nm-380 nm based on silver nanowires and absorbance value Abs at wavelength 450 nm based on silver spherical particles The ratio (Abs (λ450) / Abs (λmax)) to (λ450) was determined. Although depending on the shape of the silver nanowires, this ratio is preferably in the range of 0.1 to 0.5, and the smaller the ratio, the smaller the number of spherical particles generated at the time of silver nanowire synthesis. When spherical particles do not exist, it becomes about 0.1.

<Measurement of surface resistance value and variation>
The surface resistance value and the variation is a resistance value up to 5000 Ω / □, using a non-contact resistance measuring instrument EC-80P manufactured by Napson Co., Ltd., and a resistance value of 5000 Ω / □ or more, manufactured by Mitsubishi Chemical Analytic Co., Ltd. It was determined by the following method using a 4-probe contact type resistance measuring device Loresta-GP.

A sheet sample of 210 mm × 300 mm in size is divided into a total of 70 areas of 7 rows × 10 columns of 30 mm × 30 mm, and the surface resistance value near the center of the hatched area in FIG. The average value of 12 points was taken as the surface resistance value. In this case, if the surface resistance value can not be measured even at one point, that is, there is non-conduction (1 × 10 ⁷ Ω / □ or more), the surface resistance value is not calculated.

Among the surface resistance values of 12 points, the variation was calculated based on the equation (1) with Rmax as the maximum value and Rmin as the minimum value.
Variation [%] = [(Rmax−Rmin) / (Rmax + Rmin)] × 100 (1)

<Calculation of occupied area ratio of metal nanowires>
The surface of the conductive film was photographed at five places with a scanning electron microscope (S5000 manufactured by Hitachi, Ltd .; accelerating voltage 5 kV) at a magnification of 10000 from the direction perpendicular to the plane of the conductive layer, and stored as an image. The image area of one place was 6 μm × 4.5 μm. The obtained image was subjected to image analysis using Keyence's analysis application software VK-H1XA, and the average value of the area occupied by the metal nanowires in the plane of the conductive layer at the five locations was calculated.

<Measurement of optical characteristics>
As an optical characteristic of this conductive film, total light transmittance and haze were measured by Nippon Denshoku Industries Co., Ltd. make, haze meter NDH2000. The reference for optical property measurement was measured using air. Three samples having a side of 30 mm square were prepared, and the average value measured three times in total each time was taken as the total light transmittance and haze of the sample.

<Synthesis of silver nanowires>
100 g of propylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) is weighed in a 200 mL glass container, 2.3 g (13 mmol) of silver nitrate (manufactured by Toyo Kagaku Kogyo) is added as a metal salt, and the silver nitrate solution is stirred at room temperature for 2 hours Prepared. Hereinafter, this silver nitrate solution is referred to as a second solution.

In a nitrogen gas atmosphere, 600 g of propylene glycol, 0.052 g (0.32 mmol) of tetraethylammonium chloride as an ionic derivative in a 1 L four-necked flask (mechanical stirrer, dropping funnel, reflux tube, thermometer, nitrogen gas inlet tube) (Lion Specialty Chemicals Co., Ltd.) and sodium bromide 0.008 g (0.08 mmol) (Manuc Co., Ltd.), 7.2 g of polyvinyl pyrrolidone K-90 (PVP) as a structure defining agent (Wako Pure Chemical Industries, Ltd., weight average) The molecular weight was 350,000, and the mixture was completely dissolved by stirring at 150 ° C. for 1 hour at a rotational speed of 200 rpm to obtain a first solution.

The silver nitrate solution (second solution) prepared above is added to the dropping funnel, and the above first solution is maintained at a temperature of 150 ° C., so that the average supply mole number of silver nitrate is 0.087 mmol / min. Silver nanowire was synthesize | combined by dripping a 2nd solution over time. In this case, the molar ratio calculated from the number of moles of the ionic derivative and the average number of moles of silver nitrate supplied is 0.22. In addition, when the silver ion concentration in the first solution was measured during the reaction, the molar ratio of the ionic derivative to the metal salt (metal salt / ionic derivative) was in the range of 0.2 to 6.7. After completion of the dropwise addition, heating and stirring were continued for 1 hour to complete the reaction. The silver ion concentration was measured by an ammonium thiocyanate titration method using an automatic titration apparatus AUT-301 manufactured by Toa DKK.

Next, the reaction mixture (reaction solution) containing the synthetic silver nanowires is diluted 5 times with methanol (manufactured by Wako Pure Chemical Industries, Ltd.), and centrifugal force is applied for 5 minutes at a rotational speed of 6000 rpm using a centrifuge. The silver nanowires were allowed to settle. After the supernatant was removed, the operation of adding methanol and treating at 6000 rpm for 5 minutes was further repeated twice to wash and remove the PVP and the solvent remaining in the system.

The diameter and length of the obtained silver nanowires were determined from images of ultra-high resolution field emission scanning electron microscope SU8020 (acceleration voltage: 3 to 10 kV) manufactured by Hitachi High-Technologies Corp. by the above method. The length was 20.5 μm. As a result, the aspect ratio is 560.

Moreover, it was 0.21 when Abs ((lambda) 450) / Abs ((lambda) max) was calculated | required from the ultraviolet visible absorption spectrum of the obtained silver nanowire.

Example 1
<Inking>
As a binder resin, a cellulose ^{ETHOCEL TM STD100CPS (Dow Chemical Company,} Standard 100 Industrial Ethylcellulose) was used.

Water, ethanol (manufactured by Wako Pure Chemical Industries, Ltd.), diethylene glycol monoethyl ether (manufactured by Wako Pure Chemical Industries, Ltd.), to be mixed with methanol, which is a solvent for the silver nanowire dispersion, to form a water + alcohol mixed solvent Propylene glycol was prepared.

In a container with a lid, add the silver nanowire dispersion obtained above (where the solvent is methanol) and water, methanol, ethanol, diethylene glycol monoethyl ether, propylene glycol, ETHOCEL ^TM, and add lid, It mixed by the rotation revolution stirrer, and obtained the silver nanowire ink whose viscosity is 5 mPa * s.

The viscosity of the obtained silver nanowire ink was measured at 25 ° C. using a Brookfield digital viscometer DV-E (spindle: SC4-18).

The composition (mass ratio) of the solvent was water: methanol: ethanol: diethylene glycol monoethyl ether: propylene glycol = 5: 21: 34: 34: 6. The 100 parts by weight of solvent relative to the amount of 0.2 parts by weight of ETHOCEL ^TM, the amount of metallic silver supplied by silver nanowires was adjusted to 0.02 parts by weight.

<Silver content>
A sample liquid containing silver nanowires in a dispersed state is collected from the obtained silver nanowire ink, nitric acid is added to the liquid to dissolve the silver nanowires, and atomic absorption spectrophotometer (apparatus: furnace made by Agilent Technologies, Inc. The amount of silver was measured by atomic absorption spectrophotometer AA280Z). As a result, the silver content was 0.02% by mass, and the same value as the targeted 0.02% by mass was obtained. Therefore, in Table 1, the silver content is shown by the nominal value (target value) (the same in each of the following examples).

<Formation of conductive layer>
Using the above-described silver nanowire ink, using a coating machine 70F0 manufactured by Imoto Manufacturing Co., Ltd., using a bar coater with a wet film thickness of about 20 μm, at a coating speed of 100 mm / sec, a PET film as a polymer film substrate It was applied to the surface. As a PET film, a 125 μm thick film of Cosmo Shine (registered trademark) A4100 manufactured by Toyobo Co., Ltd. was used. In this case, the surface of the PET film is an untreated surface. Then, it was dried at 130 ° C. for 10 minutes with a blower drier (ETAC HS 350 manufactured by Kushimoto Chemical Co., Ltd.) to form a transparent conductive film having a transparent conductive layer.

The characteristic evaluation results of the obtained conductive film are shown in Table 1 together with the composition of the metal nanowires ink used. The occupied area ratio of the silver nanowires of the obtained conductive film was 1.02%. The average surface resistance was 2668 Ω / □, and the variation in the surface resistance was as small as 27.7%, confirming that the conductive film had a substantially uniform conductivity. In addition, it was confirmed that the total light transmittance was as high as 90%, the haze was as low as 0.4%, and the transparency was extremely excellent.

Examples 2-6.
The conductive film was obtained like Example 1 except having prepared and used the silver nanowire ink which made the compounding quantity of silver nanowire, binder resin, and the solvent as Table 1. Hydroxypropylcellulose 1000 to 5000 cP and hydroxypropyl cellulose 150 to 400 cP used in Examples 3 to 6 in Table 1 are manufactured by Wako Pure Chemical Industries, Ltd.

In the conductive films obtained in Examples 1 to 6, the occupied area ratio of silver nanowires is in the range of 1.0 to 1.4%, and the average surface resistance value is in the range of 2500 to 4000 Ω / □. Was as small as 30% or less, and it was confirmed to be a conductive film having uniform conductivity. In addition, it was confirmed that the total light transmittance was as high as 90%, the haze was as low as 0.4%, and the transparency was extremely excellent.

Comparative Example 1
The difference from Example 2 is that the solvent diethylene glycol monoethyl ether was changed to ethanol, and the amount of binder resin was changed from 0.2 parts by mass to 0.4 parts by mass. The same procedure as in Example 2 was followed except for this point.

The results are shown in Table 1. The occupied area ratio of silver nanowires of the obtained conductive film was 1.47%. The average surface resistance was 4367 Ω / □, and the variation in the surface resistance was as high as 36.7%, confirming that the film was a conductive film. In addition, it was confirmed that the haze was very high at 2.8% and the transparency was not excellent.

Comparative Example 2
The difference from Example 2 is that the solvent propylene glycol monomethyl ether (manufactured by Wako Pure Chemical Industries, Ltd.) and diethylene glycol monoethyl ether were changed to ethanol. The same procedure as in Example 2 was followed except for this point.

The results are shown in Table 1. The occupied area rate of silver nanowires of the obtained conductive film was 1.49%. It was confirmed that the average surface resistance value is 1689 Ω / □, and the variation of the surface resistance value is as high as 57.2%, which is a conductive film. In addition, it was confirmed that the haze was as high as 4.3% and the transparency was not excellent.

Comparative Example 3
The difference from Example 3 is that the solvent diethylene glycol monoethyl ether was changed to ethanol. The same procedure as in Example 3 was followed except for this point.

The results are shown in Table 1. One or more points out of 12 points could not measure the surface resistance value, and that part was a non-conducting part. Therefore, it was confirmed that it was not a conductive film which has uniform conductivity.

Comparative Example 4
The difference from Example 4 is that the solvent diethylene glycol monoethyl ether was changed to diethylene glycol monobutyl ether (manufactured by Wako Pure Chemical Industries, Ltd.). The same procedure as in Example 4 was followed except for this point.

Comparative Example 5
The difference from Example 1 is that the silver concentration was changed from 0.02 to 0.04, and the binder resin was changed to poly-N-vinylacetamide (manufactured by Showa Denko KK). The same procedure as in Example 1 was followed except for this point.

The results are shown in Table 1. Insoluble matter was deposited during preparation of the silver nanowires ink. This was because poly-N-vinylacetamide did not dissolve in diethylene glycol monoethyl ether.

Comparative Example 6
The difference from Example 1 is that the binder resin is changed to methylcellulose 4000 (manufactured by Wako Pure Chemical Industries, Ltd.). The same procedure as in Example 1 was followed except for this point.

The results are shown in Table 1. Insoluble matter was deposited during preparation of the silver nanowires ink. This was because methyl cellulose was not soluble in diethylene glycol monoethyl ether.

Comparative Example 7
The difference from Example 1 is that the binder resin is changed to cellulose acetate (manufactured by Wako Pure Chemical Industries, Ltd.). The same procedure as in Example 1 was followed except for this point.

The results are shown in Table 1. Insoluble matter was deposited during preparation of the silver nanowires ink. This was because cellulose acetate did not dissolve in diethylene glycol monoethyl ether.

Comparative Example 8
The difference from Example 1 is that the binder resin is changed to cellulose triacetate (manufactured by Wako Pure Chemical Industries, Ltd.). The same procedure as in Example 1 was followed except for this point.

The results are shown in Table 1. Insoluble matter was deposited during preparation of the silver nanowires ink. This was because cellulose triacetate was not soluble in diethylene glycol monoethyl ether.

Comparative Example 9
The difference from Example 1 is that the binder resin was changed to hydroxypropyl methylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.). The same procedure as in Example 1 was followed except for this point.

The results are shown in Table 1. Insoluble matter was deposited during preparation of the silver nanowires ink. This was because hydroxypropyl methylcellulose was not soluble in diethylene glycol monoethyl ether.

Comparative Example 10
The difference from Example 1 is that the binder resin is changed to hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd.). The same procedure as in Example 1 was followed except for this point.

The results are shown in Table 1. Insoluble matter was deposited during preparation of the silver nanowires ink. This was because hydroxyethyl cellulose did not dissolve in diethylene glycol monoethyl ether.

Comparative Example 11.
The difference from Example 1 is that the binder resin was changed to sodium carboxymethylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.). The same procedure as in Example 1 was followed except for this point.

The results are shown in Table 1. Insoluble matter was deposited during preparation of the silver nanowires ink. This was because carboxymethylcellulose was not soluble in diethylene glycol monoethyl ether.

Claims

A binder comprising metal nanowires (A) having an average diameter of 1 to 100 nm, an average long axis length of 1 to 100 μm, and an average aspect ratio of 100 to 2000, and at least one of ethyl cellulose and hydroxypropyl cellulose A polymer film of metal nanowire ink comprising a resin (B) and a solvent (C) containing diethylene glycol monoethyl ether, wherein the content of the metal nanowire (A) is 0.005 to 0.05% by mass. A method for producing a conductive film, comprising the steps of applying and drying on at least one surface of
The method for producing a conductive film according to claim 1, wherein the solvent (C) contains 10 to 50% by mass of diethylene glycol monoethyl ether.
A conductive film in which a conductive layer is formed on at least one surface of a polymer film, wherein the conductive layer has an average diameter of 1 to 100 nm, an average length of the major axis of 1 to 100 μm, and an average aspect ratio And a binder resin (B) containing at least one of ethyl cellulose and hydroxypropyl cellulose, wherein the surface resistance value of the conductive layer is 1000 to 10000 Ω / □, and A conductive film characterized in that a variation in surface resistance value in a plane is 35% or less.
The conductive film according to claim 3, wherein the metal nanowires (A) are silver nanowires, and the occupied area ratio thereof is in the range of 0.5 to 1.5%.
The mass ratio of the metal nanowire (A) to the binder resin (B) [metal nanowire (A) / binder resin (B)] is in the range of 0.01 to 0.5. Conductive film.
The conductive film according to any one of claims 3 to 5, wherein the polymer film is a film made of any polymer selected from the group consisting of polyester, polycarbonate, acrylic resin, and polycycloolefin.
The conductive film according to any one of claims 3 to 6, wherein the total light transmittance is 80% or more and the haze value is 0.1 to 1.5%.
A binder comprising metal nanowires (A) having an average diameter of 1 to 100 nm, an average long axis length of 1 to 100 μm, and an average aspect ratio of 100 to 2000, and at least one of ethyl cellulose and hydroxypropyl cellulose A metal nanowire ink comprising: a resin (B) and a solvent (C) containing diethylene glycol monoethyl ether, wherein the content of the metal nanowire (A) is 0.005 to 0.05% by mass. .
The metal nanowires ink according to claim 8, wherein the solvent (C) contains 10 to 50% by mass of diethylene glycol monoethyl ether.