TWI671766B - Conductive film and method for producing conductive film - Google Patents

Abstract

The present invention is a conductive film comprising a polymer film, a base resin layer formed on at least one side of the polymer film, and a metal containing an average diameter of 1 to 100 nm and an average of aspect ratio of 100 to 2000. The nanowire and the binder resin are formed on the conductive layer of the base resin layer. The surface resistance value of the conductive layer is 1.0 × 10 ² to 1.0 × 10 ⁶ Ω / □, and the variation of the surface resistance value is 15% or less.

Description

Conductive film and method for manufacturing conductive film

The present invention relates to a conductive film and a method for manufacturing a conductive film.

Metal nanowires have attracted attention in recent years as raw materials for highly transparent and highly conductive thin films that are used as substitutes for ITO (indium tin oxide) films used for transparent electrodes such as touch panels. Such metal nanowires are generally produced by heating a metal compound in the presence of a polyol such as polyvinylpyrrolidone and ethylene glycol (Non-Patent Document 1).

Patent Documents 1 to 3 disclose transparent conductors and the like in which a conductive layer containing a particulate metal rod coating film or a metal nanowire is directly formed on a polymer film such as polyester. In this case, the conductive layer is formed by directly applying a solution in which particulate metal rods or metal nanowires are dispersed on a polymer film such as polyester, and then removing and removing solvent components.

In addition, Patent Document 3 discloses an ink for forming a transparent conductive film containing silver nanowires, an aqueous solvent, a cellulose-based binder resin, and a surfactant. Patent Document 4 discloses a silver nanowire ink that can be used as a material for forming a transparent conductor. Patent Document 5 discloses a composition for forming a conductive layer containing metal nanowires, polyvinylacetamide, and a water / alcohol solvent. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2008-279434 [Patent Literature 2] Japanese Patent Application Publication No. 2006-111675 [Patent Literature 3] Japanese Patent Application Publication No. 2009-505358 [Patent Literature 4] Japanese Patent Application Publication No. 2015-174922 Publication [Patent Document 5] Japanese Patent Application Publication No. 2009-253016 [Non-Patent Document]

[Non-Patent Document 1] Ducamp-Sanguesa, et al., J. Solid State Chem., 1992, 100, 272

[Problems to be Solved by the Invention]

For example, according to the prior art disclosed in Patent Documents 1 to 3, it is considered that the conductive layer can be made to have a low resistance. However, it is difficult to reduce the use amount of conductive materials by such a prior art, so that there is a problem that it is difficult to improve the cost or transparency, or the conductivity exhibits heterogeneity. In addition, as in the prior art disclosed in Patent Documents 1 to 5, in the invention of applying a dilute coating solution containing rod-shaped metal particles or metal nanowires, the rod-shaped metal particles or metal nanowires are being applied. Aggregation occurs in the liquid or in the solvent drying step after coating, and as a result, there is a problem that the surface resistance value changes.

An object of the present invention is to provide a conductive film, which can suppress the amount of metal nanowires used, and can suppress variations in surface resistance values over a wide range of surface resistance values. Moreover, it aims at providing the suitable manufacturing method of the electroconductive thin film excellent in productivity. [Means for solving problems]

In order to achieve the above-mentioned object, a conductive film according to an embodiment of the present invention includes a polymer film, a base resin layer formed on at least one side of the polymer film, and a resin having an average diameter of 1 to 100 nm and an aspect ratio. A conductive layer of metal nanowires and a binder resin having an average of 100 to 2000 and formed on the aforementioned base resin layer. The surface resistance value of the conductive layer is 1.0 × 10 ² to 1.0 × 10 ⁶ Ω / □, and the variation of the surface resistance value is 15% or less.

In addition, a method for manufacturing a conductive film according to an embodiment of the present invention includes: a step of forming a base resin layer on at least one side of a polymer film; and an average containing an average diameter of 1 to 100 nm and an aspect ratio of 100-2000 metal nanowires, a metal nanowire ink of a binder resin and a solvent are coated on the base resin layer formed on the polymer film and dried. [Effect of the invention]

According to the embodiment of the present invention, it is possible to provide a conductive thin film with a small amount of metal nanowires and a small change in surface resistance, and a conductive film having a thickness of 1.0 × 10 ² to 1.0 × 10 ⁶ Ω / □ and a method for manufacturing the same. In addition, the conductive film according to the embodiment of the present invention is suitable for use in a conductive film for a touch panel or an electronic paper with low resistance and excellent resistance value stability.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the conductive film 10 according to the embodiment is composed of a polymer film 11, a base resin layer 12, and a conductive layer 13. The base resin layer 12 is provided on at least one side of the polymer film 11. The conductive layer 13 is formed by coating a metal nanowire ink on the base resin layer 12, that is, the side opposite to the polymer film 11 and drying it. The metal nanowire ink contains a metal nanowire having an average diameter of 1 to 100 nm and an average aspect ratio of 100 to 2000, a binder resin, and a solvent.

In addition, in FIG. 1, the thicknesses of the polymer film 11, the base resin layer 12, and the conductive layer 13 are exaggerated for ease of understanding and are different from actual articles. In addition, in the description of the present invention, the "metal nanowire" includes a nanometer-sized metal fiber that forms a solid line, that is, a linear shape, and a nanometer-sized metal fiber that forms a hollow line, that is, a tube. Nanotube is the concept of both. In this case, both the linear shape and the tubular shape may be collectively referred to as a metal nanofiber. Details of each component are explained below.

(1) Polymer film The polymer film 11 is not particularly limited as long as it has sufficient adhesion to the base resin layer 12. The polymer film 11 is suitably used, for example, polyester (polyethylene terephthalate [PET], polyethylene naphthalate [PEN], etc.), polycarbonate, acrylic resin, cycloolefin resin, polyfluorene, polymer Polymer films such as ether fluorene, polyfluorene, and polyfluorine. By using any polymer film of polyester (polyethylene terephthalate [PET] film, polyethylene naphthalate [PEN] film, etc.), polycarbonate, acrylic resin, or cycloolefin resin, A conductive thin film 10 having excellent transparency can be obtained.

In addition, the thickness of the polymer film 11 is not particularly limited, and may be appropriately selected depending on the application or kind. From the viewpoint of mechanical strength and operability, it is usually 25 to 500 μm, preferably 38 to 400 μm, and more preferably 50 to 300 μm. In addition, various additives such as antioxidants, heat-resistant stabilizers, weather-resistant stabilizers, ultraviolet absorbers, organic slip agents, pigments, dyes, organic or Inorganic fine particles, fillers, nucleating agents, etc.

The polymer film 11 can be used without surface treatment. In addition, in order to improve the uniformity or adhesion of the base resin layer 12 formed on the polymer film 11, a surface treatment such as corona treatment or plasma treatment may be performed on the base resin layer 12 side of the polymer film 11.

(2) Base resin layer The base resin layer 12 is a resin layer formed on a polymer film 11 as a base material. The base resin layer 12 can achieve the effects of improving the adhesion between the polymer film 11 and the conductive layer 13 or the uniformity of the conductive layer 13 formed on the polymer film 11. The resin used for the base resin layer 12, that is, the base resin, may be any resin that can be uniformly coated on the polymer film 11 and exhibits good adhesion to the polymer film 11 and the conductive layer 13. In this case, the base resin used in the base resin layer 12 may be any resin such as thermoplastic, thermosetting, or ultraviolet curable resin.

As the base resin, resins such as polyester resin, epoxy resin, acrylic resin, urethane resin, melamine resin, phenol resin, polyamide resin, and urea resin can be used alone or in combination. In this case, the polyester resin is particularly suitable as the base resin used in the base resin layer 12.

In addition, when a polyester resin is used as the base resin, it may be denatured by other components such as acrylic acid, and the base resin may have functional groups such as -COOH or -SO ₃ Na. Moreover, in order to improve the adhesion with the conductive layer 13 and at the same time to improve the thickness or the uniformity of the conductivity, the base resin preferably contains the same resin as the binder resin used in the conductive layer 13. In this case, containing the same resin as the base resin and the binder resin naturally means that the concept of the base resin and the binder resin containing completely the same component and the same grade of resin is not limited to the concept that the base resin and the binder resin completely contain Resin of the same composition and grade.

That is, in this case, either the base resin layer 12 or the conductive layer 13 is a resin containing any hydrophilic group selected from the group consisting of -SO ₃ H or a metal salt thereof, -COOH, -OH, and -NH ₂ . The component is preferably, and it is more preferably composed of a resin having -SO ₃ H or a metal salt thereof or -COOH. In addition, it is preferable that each of the base resin layer 12 and the conductive layer 13 is made of a resin having the same hydrophilic group among the above-mentioned hydrophilic groups.

In addition, the base resin may be added with, for example, antioxidants, heat-resistant stabilizers, weather-resistant stabilizers, ultraviolet absorbers, natural or petroleum waxes to such an extent that its resin properties or adhesion to polymer films and conductive layers are not deteriorated. And other organic slip agents, pigments, dyes, organic or inorganic fine particles, fillers, nucleating agents, and the like.

The thickness of the base resin layer 12 is preferably 0.1 to 10 μm, preferably 0.2 to 5 μm, and more preferably 0.3 to 3 μm. By setting the thickness of the base resin layer 12 to be 0.1 μm or more, it is possible to form the base resin layer 12 that is uniform and has no uneven coating. In addition, by setting the thickness of the base resin layer 12 to 10 μm or less, the conductive film 10 having excellent transparency and mechanical properties can be manufactured with good productivity.

The formation of the base resin layer 12 on the polymer film 11 can be performed by any method such as a wet coating method and a CVD method. In this case, a wet coating method is preferred. The wet coating method is a method of coating a resin solution of a base resin on the polymer film 11 and drying the coated resin solution to form the base resin layer 12, so it is relatively simple, and it is easy to obtain a uniform and The polymer film 11 has a good adhesion to the base resin layer 12.

In addition, the resin solution referred to here means not only a liquid in which the resin is dissolved in a solvent, but also a liquid in which the resin is dispersed in a solvent in the form of an emulsion. The solvent used for the resin solution of the base resin can be appropriately selected in consideration of factors such as the type of the base resin used and the drying temperature.

When the resin solution of the base resin is coated on the polymer film 11 by the wet coating method to form the base resin layer 12, a known coating method such as a bar coating method or a reverse coating can be used. Any of a cloth method, a gravure coating method, a die coating method, and a doctor blade coating method. In addition, drying can be performed by arbitrary methods, such as a hot-air furnace and a far-infrared furnace. When an ultraviolet curable resin is used as the base resin, the ultraviolet ray irradiation device may be used in combination with the drying oven or alone.

(3) Conductive layer The conductive layer 13 is obtained by applying a metal nanowire ink to the base resin layer 12 on the polymer film 11 forming the base resin layer 12 and drying it. The metal nanowire ink contains (A) metal nanowire, (B) a binder resin, and (C) a solvent. The conductive layer 13 is a conductive film in which metallic nanowires are dispersed in a binder resin, and the surface resistance value is 1.0 × 10 ² to 1.0 × 10 ⁵ Ω / □, and the variation of the surface resistance value is 15% or less. Conductive layer.

The content of the metal nanowires in the conductive layer 13 is preferably 1.5 to 4.5% based on the area occupancy of the metal nanowires with respect to the conductive film 10. In this case, by setting the area occupation ratio of the metal nanowires to the conductive thin film 10 to be 1.5% or more, a good conductive thin film 10 can be obtained. In addition, by setting the area occupancy ratio of the metal nanowires to the conductive film 10 to 4.5% or less, a conductive film having high total light transmittance, low haze, and excellent transparency can be obtained. That is, by setting the area occupancy ratio of the metal nanowires to the conductive thin film 10 to 1.5% or more and 4.5% or less, excellent conductivity and transparency can be obtained, and the use of expensive metal nanowires is small. The conductive film 10 is also excellent in economy.

(A) Metal nanowire Metal nanowire is a linear metal with an outer diameter, that is, a nanometer-sized diameter, and is a conductive material that forms a wire or tube. As the metal nanowire, only one of a linear shape and a tubular shape may be used, or both may be used in combination. Metal nanowires may be flexible or may be rigid. An example of a metal nanowire is, for example, a solid silver nanowire or a silver nanotube formed into a porous or non-porous tube.

The outer diameter of the metal nanowire, that is, the average value of the diameter (hereinafter referred to as the average diameter) is 1 to 100 nm, preferably 5 to 100 nm, and more preferably 10 to 100 nm. The average length of the major axis of the metal nanowires (hereinafter referred to as the average length) is preferably 1 to 100 μm, more preferably 1 to 50 μm, more preferably 2 to 50 μm, and particularly preferably 5 to 30 μm.

The average diameter and average length of the metal nanowires satisfy the above range, while the average aspect ratio is 100-2000, preferably 200-1000, 300-1000 is more preferable, and 300-700 is more preferable. The aspect ratio here is a value obtained from a / b when the average diameter of the metal nanowires is set to b and the average length is set to a. a and b can be measured using a scanning electron microscope (SEM).

The type of metal of the metal nanowire includes at least one selected from the group consisting of gold, silver, platinum, copper, nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium, osmium, and iridium, and An alloy of these metals. In order to obtain a transparent conductive film having a low surface resistance and a high total light transmittance, it is preferable to contain at least any one of gold, silver, and copper. These metals have high electrical conductivity, so when a certain surface resistance is obtained, the density of the metal occupying the surface can be reduced, so that a high total light transmittance can be achieved.

The metal nanowire preferably contains at least one of gold and silver among the above metals. The most suitable aspect includes silver nanowires.

As a method for manufacturing the metal nanowire, a known manufacturing method can be used. For example, silver nanowires can be synthesized by reducing silver nitrate in the presence of polyvinylpyrrolidone using the Polyol method (see Chem. Mater., 2002, 14, 4736). Similarly, nanometer noodles can be synthesized by reducing chloroauric acid hydrate in the presence of polyvinylpyrrolidone (see J. Am. Chem. Soc., 2007, 129, 1733).

Techniques for large-scale synthesis and purification of silver nanowires are described in detail in International Publication Gazette WO2008 / 073143 and International Publication No. 2008/046058. A gold nano tube having a porous structure can be synthesized by casting a silver nano wire and reducing a chloroauric acid solution. Here, the silver nanowire used in the mold is dissolved into the solution by the redox reaction with chloroauric acid, and as a result, a gold nanotube having a porous structure is produced (see J. Am. Chem. Soc. 2004, 126, 3892-3901).

(B) Binder Resin The binder resin used in metal nanowire inks is a substance that disperses and fixes metal nanowires in the conductive layer 13. Thermoplastic, thermosetting, or ultraviolet curing resins can be used. Arbitrary resin. As the binder resin, resins such as polyester resin, epoxy resin, acrylic resin, urethane resin, melamine resin, phenol resin, polyamide resin, and urea resin can be used alone or in combination.

In this case, in order to improve the adhesion with the base resin layer 12 and at the same time improve the thickness or the uniformity of the conductivity of the conductive layer 13, the binder resin used in the metal nanowire ink is used in combination with the base resin layer 12. The base resin is preferably the same resin. In this case, the binder resin and the base resin contain the same resin, which of course means the concept that the base resin and the binder resin contain completely the same composition and the same grade of resin, but it is not limited to the fact that the base resin and the binder resin contain the same resin. Composition, the same grade of resin. For example, if the base resin and the binder resin contain resins having the same component, the grades may be different.

The binder resin is particularly preferably a polyester resin. This is because in this case, by using the polyester resin as the binder resin, the metal nanowires can be uniformly dispersed and fixed in the binder resin layer, that is, the base resin layer 12, and not only this, but also easy It provides transparency, solvent resistance, and abrasion resistance.

As the binder resin, a resin having an ionic functional group such as -COOH or -SO ₃ Na can be used. Thereby, the solubility or dispersibility of the binder resin in the solvent is improved, and at the same time, the dispersibility of the metal nanowires can be improved. When a polyester resin is used as the binder resin, it may be denatured by other components such as acrylic acid. In addition, in order to improve the adhesion of the conductive layer 13 to the base resin layer 12 and at the same time to improve the thickness or the uniformity of the conductivity of the conductive layer 13, the binder resin preferably contains the same resin component as the base resin. To the binder resin, organic materials such as antioxidants, heat-resistant stabilizers, weather-resistant stabilizers, ultraviolet absorbers, natural or petroleum waxes can be added to such a degree that the properties of the binder resin and the dispersibility of the metal nanowires are not deteriorated. Additives such as slip agents, pigments, dyes, organic or inorganic fine particles, fillers, and core agents.

The content of the binder resin in the conductive layer 13 is preferably 1000 to 2000 parts by mass, and more preferably 1250 to 1750 parts by mass relative to 100 parts by mass of the metal nanowires in the conductive layer 13. By setting the content of the binder resin in the conductive layer 13 to 1,000 parts by mass or more, a uniform coating film can be formed, and various characteristics or effects of the binder resin can be imparted to the conductive film. In addition, by setting the binder resin in the conductive layer 13 to 2000 parts by mass or less, the conductivity of the metal nanowire can be sufficiently expressed.

(C) Solvent The solvent contained in the rhenium nanowire ink can be used alone or in combination of a plurality of solvents such as water or an organic solvent. In this case, as long as the solvent contained in the metal nanowire ink can dissolve or disperse the binder resin in the form of an emulsion and disperse the metal nanowire, any solvent can be used. The amount of the solvent to be used is not particularly limited as long as it is an amount that can produce a uniform conductive layer 13 when the metal nanowire ink is applied to the base resin layer 12 formed on the polymer film 11. In this case, it is desirable to adjust the amount of the solvent so that the solid content of the metal nanowire or the binder resin contained in the metal nanowire ink is 0.1 to 10% by mass relative to the entire metal nanowire ink.

In addition, as the solvent, a mixed solvent of an alcohol and water containing at least one of saturated monohydric alcohols (methanol, ethanol, 1-propanol, and 2-propanol) having 1 to 3 carbon atoms is suitably used. In this case, the solvent is preferably a saturated monohydric alcohol having 1 to 3 carbon atoms in a range of 1 to 50% by mass of the entire solvent. By containing a saturated monohydric alcohol having 1 to 3 carbon atoms, it is easy to dry and a uniform coating film can be formed.

Metal nanowire inks may contain additives such as surfactants, antioxidants, fillers, and the like, as long as they do not adversely affect the properties of the coating film, electrical conductivity, and optical properties. To adjust the viscosity of the composition, a filler such as fumed silica can be used. The total blending amount is preferably set to within 5 parts by mass with respect to 100 parts by mass of the solid content excluding the solvent.

The metal nanowire ink according to the embodiment is a mixture of the metal nanowires described above, a binder resin, and additives that may be added as necessary, in accordance with the above blending ratio (mass%), and mixed with a solvent. , And it is further manufactured by stirring and mixing with a revolution revolution mixer or the like. In this way, a metallic nanowire ink having a viscosity of about 1 to 50 mPa ･ s can be obtained.

The metal nanowire ink is coated on the polymer film forming the base resin layer so as to be in contact with the base resin layer, a coating film is formed, and the target conductive film is obtained by drying.

As the coating film of the metal nanowire ink, a known coating method can be used, for example, any one of a bar coating method, a reverse coating method, a gravure coating method, a die coating method, and a doctor blade coating method. In addition, drying can be performed by arbitrary methods, such as a hot-air furnace and a far-infrared furnace. When an ultraviolet curable resin is used as the base resin, an ultraviolet irradiation device may be used in combination with the above-mentioned drying furnace or alone.

<Manufacturing Procedure> An example of a method for manufacturing the conductive thin film 10 of this embodiment will be described with reference to FIG. 2. The manufacturing steps of the conductive thin film 10 include a base resin layer forming step in step S11 and a conductive layer forming step in step S12. When the manufacturing process of the conductive thin film 10 is started, in step S11, a base resin layer formation step is performed. In the base resin layer forming step, the base resin layer 12 is formed on at least one side of the polymer film 11 by any method such as a wet coating method or a CVD method.

Next, in step S12, a conductive layer forming step is performed. In the conductive layer forming step, after the metal nanowire ink is applied on the base resin layer 12 formed in step S11, the solvent component is removed by drying. Thereby, the conductive layer 13 is formed on the base resin layer 12 and the conductive thin film 10 is completed.

According to the above manufacturing method, a conductive thin film 10 having a conductive layer 13 formed on the polymer thin film 11 through the base resin layer 12 can be obtained, and has a surface resistance value of 1.0 × 10 ² to 1.0 × 10 ⁶ Ω / □ and a surface resistance value. The variation is 15% or less of the conductive film 10.

The total light transmittance of the conductive film 10 in this embodiment is preferably 80% or more, preferably 85% or more, and the haze value is preferably 0.1 to 1.5%, and preferably 0.1 to 1.0%. 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 10 having excellent transparency and less blur.

These values are measured by a method described in Examples described later. In the conductive thin film 10 of this embodiment, as needed, the conductive layer 13 formed on the base resin layer 12 or the polymer thin film 11 without the conductive layer 13 formed thereon may be formed. Functional layer like hard coating.

The present invention will be described more specifically in the following examples. The following examples are examples for easy understanding of the present invention, and the present invention is not limited by these examples.

<Observation of the shape of metal nanowires> The shape (length and diameter) of metal nanowires is measured using an ultra-high-resolution field emission scanning electron microscope SU8020 (acceleration voltage 3 to 10kV) manufactured by Hitachi High Technologies Co., Ltd. The diameter and length of the selected 50 nanowires are used to obtain the arithmetic mean. In each of the following examples and comparative examples, silver nanowires are used as the metal nanowires.

In addition, an ultraviolet / visible near-infrared spectrophotometer V-670 manufactured by Japan Spectroscopy Co., Ltd. was used to measure the ultraviolet / visible absorption spectrum at 300 to 600 nm, and the maximum peak of the absorbance at 370 to 380 nm generated by the metal nanowire was determined The ratio (Abs (λ450) / Abs (λmax)) of Abs (λmax) to the absorbance value Abs (λ450) at a wavelength of 450 nm of the spherical particles of silver. This ratio is suitable in the range of 0.1 to 0.5, but the situation will depend on the shape of the metal nanowires. The smaller the ratio, the fewer the spherical particles generated when the metal nanowires are synthesized. When no spherical particles exist, it is about 0.1.

<Synthesis of silver nanowire> In a 200 mL glass container, weigh 100 g of propylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), and add 2.3 g (13 mmol) of silver nitrate (manufactured by Toyo Chemical Industry Co., Ltd.) as a metal salt. , And stirred at room temperature for 2 hours to prepare a silver nitrate solution. This silver nitrate solution is hereinafter referred to as a second solution.

In a 1 L four-necked flask (mechanical stirrer, dropping funnel, reflux tube, thermometer, nitrogen introduction tube), 600 g of propylene glycol and 0.052 g of tetraethylammonium chloride (0.32) as an ionic derivative were charged under a nitrogen atmosphere. mmol) (manufactured by Lion Specialty Chemicals) and 0.008 g (0.08 mmol) of sodium bromide (manac), 7.2 g of polyvinylpyrrolidone K-90 (PVP) as a structure regulator (Wako Pure Chemical Industries, Ltd. The company produced a weight-average molecular weight of 350,000) and stirred at 150 ° C. for 1 hour at a speed of 200 rpm to completely dissolve it to obtain a first solution.

Next, the previously prepared silver nitrate solution (second solution) was charged into a dropping funnel, and the temperature of the first solution was maintained at 150 ° C., and the average molar supply of silver nitrate was 0.087 mmol / min. Method, it took 2.5 hours to drop into the second solution, and silver nanowires were synthesized. In this case, the molar ratio calculated from the molar number of the ionic derivative and the average molar number of silver nitrate supplied was 0.22. In addition, as a result of measuring the silver ion concentration in the first solution during the reaction, the molar ratio (metal salt / ionic derivative) of the ionic derivative to the metal salt was in the range of 0.2 to 6.7. After completion of the dropwise addition, heating and stirring were further continued for 1 hour to complete the reaction.

Next, the reaction mixture was diluted 5 times with water, and a centrifugal force was applied at 6000 rpm for 5 minutes using a centrifugal separator to settle the silver nanowire. Next, after removing the supernatant, two more operations of adding water and treating at 6000 rpm for 5 minutes were performed. After the remaining polyvinyl pyrrolidone (PVP) and the solvent were washed in the system, a predetermined amount of water was added to obtain Silver nanowire dispersion with water as dispersion medium.

With respect to the obtained silver nanowires, the diameter and length of 50 randomly selected silver nanowires were measured from a field emission scanning electron microscope (FE-SEM) image by the method described above, and the arithmetic mean value was obtained. The average diameter was 36.3 nm and the average length was 20.5 μm.

In addition, Abs (λ450) / Abs (λmax) was determined from the ultraviolet / visible absorption spectrum of the obtained silver nanowire, and it was 0.21.

Example 1 <Inkization> As the binder resin, an aqueous polyester resin dispersion having a -SO ₃ Na group was used. This polyester aqueous dispersion was made of PESRESIN A-647GEX manufactured by Takamatsu Oils and Fats Co., Ltd., and was prepared to have a solid content concentration of 5% by mass. Hereinafter, this polyester aqueous dispersion is referred to as a PESRESIN aqueous solution.

In order to mix with water as a dispersion medium of the silver nanowire dispersion liquid to prepare a water + alcohol mixed dispersion medium, methanol (MeOH) and 2-propanol (IPA) were prepared.

In a container with a lid, the above silver nanowire dispersion liquid using water as a dispersion medium and the 5 mass% aqueous solution of the above PESRESIN were added, and various solvents were added. After being covered, the mixture was mixed by a mixing rotor. In this case, the mixed composition of the solvent was set to a mass ratio of water: MeOH: IPA = 72: 18: 10. In addition, the mixing amount was adjusted such that the amount of the PESRESIN component supplied from the PESRESIN aqueous solution was 0.60% by mass and the amount of metallic silver supplied from the silver nanowire was 0.04% by mass relative to the total amount of the entire mixture. In this way, a silver nanowire ink, which is a conductive composition having a viscosity of 2.5 mPa ･ s, is obtained.

<Silver content> A sample solution of silver nanowires in a dispersed state was taken from the obtained silver nanowire inks. Nitric acid was added to the sample solution to dissolve the silver nanowires, and an atomic absorption spectrophotometer (Agilent Technology Co., Ltd.) Co., Ltd., a graphite furnace atomic absorption spectrophotometer AA280Z) was used to measure the amount of silver. As a result, the silver content was 0.04% by mass, and a value close to the target of 0.04% by mass when the ink was formed was obtained.

<Formation of Base Resin Layer> The resin solution of the base resin is a polyester resin water dispersion having a -SO ₃ Na group, that is, the aforementioned PESRESIN aqueous solution. That is, the resin solution of the base resin is prepared so that the solid content concentration becomes 5% by mass using PESRESIN A-647GEX manufactured by Takamatsu Oils and Fats Co., Ltd.

A resin solution of the base resin, that is, an aqueous solution of PESRESIN, was applied using a coater 70F0 manufactured by Imoto Manufacturing Co., Ltd. and a coating rod having a wet film thickness of about 10 μm at a coating film speed of 100 mm / sec. The surface of a PET film with a polymer film substrate. The PET film is a 100 μm-thick film using COMOSHINE A4100 manufactured by Toyobo Co., Ltd. In this case, the surface of the PET film is an easy-to-adhere surface. The size of the PET film was 21 cm × 30 cm. Then, it was dried at 100 ° C for 1 minute with a hot air dryer (ETACHS350 manufactured by Kusumoto Chemical Co., Ltd.) to form a PET film with a base resin layer.

<Formation of the conductive layer> The above silver nanowire ink was coated on a coating machine at a coating film speed of 100 mm / sec using a coating bar with a wet film thickness of about 20 μm using a coating machine 70F0 manufactured by Imoto Manufacturing Co., Ltd. The side on which the base resin layer is formed on the PET film with the base resin layer. Then, it was dried at 100 ° C for 1 minute with a hot air dryer (ETACHS350 manufactured by Kusumoto Chemical Co., Ltd.) to form a transparent conductive film having a transparent conductive layer.

<Measurement of Thickness> 调查 The thickness of the base resin layer and the conductive layer were investigated by scanning electron microscope (SEM) observation of the cross section of the conductive film.

<Measurement of surface resistance value and fluctuation> When the surface resistance value is 4.0 × 10 ³ Ω / □ or less, use a non-contact resistance tester EC-80P manufactured by Napson Corporation, or When the surface resistance value exceeds 4.0 × 10 ³ Ω / □, Loresta-GP manufactured by Mitsubishi Chemical Analytech Co., Ltd. is used, and the following method is used.

A grid having a size of 3 cm × 3 cm was prepared in 3 columns × 3 rows from the measured sheet samples, and a total of 9 grids were measured. The surface resistance value of each grid was determined, and the average value of 9 points was determined as the surface resistance value. In addition, among the surface resistance values at 9 points, the maximum value was set to Rmax, and the minimum value was set to Rmin, and the fluctuation was calculated by the formula (1). Change [%]: [(Rmax-Rmin) / (Rmax + Rmin)] × 100 (1)

<Calculation of the area occupied by metallic nanowires in the plane of the conductive layer> For the surface of the conductive film, a scanning electron microscope (S5000 manufactured by Hitachi, acceleration voltage 5kV) was used, and the direction perpendicular to the plane of the conductive layer was 10,000. Take 5 shots of the shape and save the image. The keyence analysis application software VK-H1XA was used to perform image analysis on the obtained image, and the arithmetic mean of the area occupied by the metal nanowires in the plane of the five conductive layers was calculated.

<Measurement of optical characteristics> 的 The optical characteristics of this conductive film were measured for total light transmittance and haze with a haze meter NDH2000 manufactured by Nippon Denshoku Industries. The reference material for optical property measurement is measurement using air. The samples were prepared with three samples each having a side length of 30 mm, and were measured once and three times in total. The average value was determined as the total light transmittance and haze of the sample.

The results are shown in Table 1. The silver nanowire (AgNW) occupied area of the obtained conductive film was 4.34%, the surface resistance value was 1.0 × 10 ³ Ω / □, and the variation of the surface resistance value was as low as 10%. It was confirmed that the conductive film had uniform conductivity. Conductive film. In addition, the total light transmittance was as high as 90.9%, and the haze was as low as 0.79%, and it was confirmed that the transparency was extremely excellent.

Example 2 is different from Example 1 in that the silver nano-line ink is applied so that the wet film thickness becomes about 10 μm. Other than that, it carried out similarly to Example 1. The results are shown in Table 1. The silver nanowire (AgNW) occupied area of the obtained conductive film was 3.75%, the surface resistance value was 1.8 × 10 ³ Ω / □, and the variation in surface resistance value was as low as 7%. It was confirmed that the conductive film had uniform conductivity. Conductive film. In addition, the total light transmittance was as high as 91.2%, and the haze was as low as 0.48%, which was confirmed to be extremely excellent in transparency.

Example 3 The difference from Example 1 is silver nano-line ink using a water solvent. Other than that, it carried out similarly to Example 1. The results are shown in Table 1. Compared with Example 1 using a mixed solvent of water and alcohol, the variation in surface resistance value was slightly larger, and was 15%, but it was a level that was not inconvenient in use.

Example 4: The difference from Example 1 is that the PET film before the base resin layer is formed is subjected to a plasma treatment on the side on which the base resin layer is provided. Plasma treatment was performed using a plasma treatment device (AP-TO3 manufactured by Sekisui Chemical Industry Co., Ltd.) under a nitrogen environment at a power of 1 kW for 20 seconds. Except that a plasma treatment was performed, it carried out similarly to Example 1.

The results are shown in Table 1. The occupied area of silver nanowires (AgNW) in the obtained conductive film was 4.15%, the surface resistance value was 1.3 × 10 ³ Ω / □, and the variation in surface resistance value was as low as 11%, which confirmed that it had uniform conductivity. Conductive film. In addition, the total light transmittance was as high as 91.3%, and the haze was as low as 0.69%, which was confirmed to be extremely excellent in transparency.

Example 5: The difference from Example 1 is that the polymer film substrate is different, and the polymer film substrate is subjected to a plasma treatment in the same manner as in Example 4. The polymer film substrate of Example 5 used a cyclic olefin copolymer (COP) film instead of a PET film. The COP film was ZeonorFilm ZF14, manufactured by Zeon Co., Ltd., and had a thickness of 100 μm. The plasma processing apparatus and conditions used in the plasma processing are the same as those of the fourth embodiment. A polymer film base material was treated in the same manner as in the first example, except that the polymer film base material was different, and the polymer film base material was subjected to a plasma treatment in the same manner as in Example 4.

The results are shown in Table 1. The silver nanowire (AgNW) occupied area of the obtained conductive film was 4.23%, the surface resistance value was 1.1 × 10 ³ Ω / □, and the variation in surface resistance value was as low as 11%. It was confirmed that the conductive film had uniform conductivity. Conductive film. In addition, the total light transmittance was as high as 91.3%, and the haze was as low as 0.67%, which was confirmed to be extremely excellent in transparency.

The difference between Comparative Example 1 and Example 1 is that the formation of a base resin layer using a binder resin is not performed, and a silver nanowire ink is directly coated on a PET film. Other than that, it carried out similarly to Example 1. The results are shown in Table 1. Unlike Example 1, it is difficult to form a conductive layer uniformly. Therefore, the surface resistance value is as high as 2.4 × 10 ⁶ Ω / □, and the variation in surface resistance value is as high as 79%. It is confirmed that the conductivity is not uniform. .

The difference between Comparative Example 2 and Example 1 is that the substrate treatment uses a plasma treatment device (AP-T03, manufactured by Sekisui Chemical Industry Co., Ltd.) instead of the formation of the base resin layer. Under the same conditions as in Example 4, only the Plasma treatment does not form a base resin layer, but forms a conductive layer. Other than that, it carried out similarly to Example 1. The results are shown in Table 1. Through the implementation of plasma treatment, the surface resistance value is 1.2 × 10 ³ Ω / □, but the change in surface resistance value is still as high as 38%, which is not an item that can withstand actual use.

Comparative Example 3 is different from Example 1 in that a PET film having an acrylic resin hard coat layer as a polymer film substrate is used, and a base resin layer is not formed. In this case, OPTERIA H522-125 manufactured by Lintec Co., Ltd. was used for the PET film, and the thickness was 125 μm. Other than that, it carried out similarly to Example 1. In this case, ink repellency occurs when the silver nanowire ink is applied, and it is difficult to form a uniform coating film.

10‧‧‧ conductive film

11‧‧‧ polymer film

12‧‧‧ base resin layer

13‧‧‧ conductive layer

S11‧‧‧ Formation step of base resin layer

S12‧‧‧Conductive layer forming step

FIG. 1 is a conceptual diagram showing an example of the configuration of a conductive film according to the embodiment. FIG. 2 is a flowchart showing an example of a method for manufacturing a conductive film according to the embodiment.

Claims (9)

A conductive film comprising a polymer film, a base resin layer formed on at least one side of the polymer film, and a metal nanometer having an average diameter of 1 to 100 nm and an average aspect ratio of 100 to 2000. Wire and adhesive resin and a conductive layer formed on the base resin layer, the surface resistance value of the conductive layer is 1.0 × 10 ³ to 1.0 × 10 ⁶ Ω / □, and the variation of the surface resistance value is 15% or less, The occupied area ratio of the metal nanowires in the conductive layer is in a range of 1.5 to 4.5%. For example, the conductive film of claim 1, wherein the total light transmittance is 80% or more and the haze value is 0.1 to 1.5%. The conductive film according to claim 1 or 2, wherein any one of the base resin layer and the conductive layer contains any one selected from the group consisting of -SO ₃ H or a metal salt thereof, -COOH, -OH, and -NH ₂ . Hydrophilic resin component. The conductive film according to claim 3, wherein any one of the base resin layer and the conductive layer is composed of a resin having -SO ₃ H or a metal salt thereof or any hydrophilic group of -COOH. The conductive film according to claim 3, wherein any one of the base resin layer and the conductive layer is composed of a hydrophilic group selected from -SO ₃ H or a metal salt thereof, -COOH, -OH, and -NH ₂ It consists of the same hydrophilic resin. The conductive film according to claim 3, wherein the base resin used in the base resin layer and the binder resin used in the conductive layer contain a resin having the same component. A method for manufacturing a conductive film, which is the method for manufacturing a conductive film according to any one of claims 1 to 6, comprising a step of forming a base resin layer on at least one side of a polymer film, and including an average diameter Metal nanowires having an average aspect ratio of 100 to 2000 of 1 to 100 nm, a metal nanowire ink of a binder resin, and a solvent are applied to the base resin layer formed on the polymer film, and the base resin layer is formed. In the step of drying, the content of the binder resin in the conductive layer is 1000-2000 parts by mass relative to 100 parts by mass of the metallic nanowire. The method for manufacturing a conductive thin film according to claim 7, wherein the solvent is a mixed solvent of water and alcohol, and contains a saturated monohydric alcohol having 1 to 3 carbon atoms in a range of 1 to 50% by mass in the total solvent. The method for manufacturing a conductive film according to claim 7, wherein the base resin used in the base resin layer and the binder resin used in the metal nanowire ink contain a resin having the same component.